WorldWideScience

Sample records for chemical exchange saturation

  1. Chemical Exchange Saturation Transfer (CEST) Agents: Quantum Chemistry and MRI.

    Science.gov (United States)

    Li, Jikun; Feng, Xinxin; Zhu, Wei; Oskolkov, Nikita; Zhou, Tianhui; Kim, Boo Kyung; Baig, Noman; McMahon, Michael T; Oldfield, Eric

    2016-01-04

    Diamagnetic chemical exchange saturation transfer (CEST) contrast agents offer an alternative to Gd(3+) -based contrast agents for MRI. They are characterized by containing protons that can rapidly exchange with water and it is advantageous to have these protons resonate in a spectral window that is far removed from water. Herein, we report the first results of DFT calculations of the (1) H nuclear magnetic shieldings in 41 CEST agents, finding that the experimental shifts can be well predicted (R(2) =0.882). We tested a subset of compounds with the best MRI properties for toxicity and for activity as uncouplers, then obtained mice kidney CEST MRI images for three of the most promising leads finding 16 (2,4-dihydroxybenzoic acid) to be one of the most promising CEST MRI contrast agents to date. Overall, the results are of interest since they show that (1) H NMR shifts for CEST agents-charged species-can be well predicted, and that several leads have low toxicity and yield good in vivo MR images.

  2. Spin-locking versus chemical exchange saturation transfer MRI for investigating chemical exchange process between water and labile metabolite protons.

    Science.gov (United States)

    Jin, Tao; Autio, Joonas; Obata, Takayuki; Kim, Seong-Gi

    2011-05-01

    Chemical exchange saturation transfer (CEST) and spin-locking (SL) experiments were both able to probe the exchange process between protons of nonequivalent chemical environments. To compare the characteristics of the CEST and SL approaches in the study of chemical exchange effects, we performed CEST and SL experiments at varied pH and concentrated metabolite phantoms with exchangeable amide, amine, and hydroxyl protons at 9.4 T. Our results show that: (i) on-resonance SL is most sensitive to chemical exchanges in the intermediate-exchange regime and is able to detect hydroxyl and amine protons on a millimolar concentration scale. Off-resonance SL and CEST approaches are sensitive to slow-exchanging protons when an optimal SL or saturation pulse power matches the exchanging rate, respectively. (ii) Offset frequency-dependent SL and CEST spectra are very similar and can be explained well with an SL model recently developed by Trott and Palmer (J Magn Reson 2002;154:157-160). (iii) The exchange rate and population of metabolite protons can be determined from offset-dependent SL or CEST spectra or from on-resonance SL relaxation dispersion measurements. (iv) The asymmetry of the magnetization transfer ratio (MTR(asym)) is highly dependent on the choice of saturation pulse power. In the intermediate-exchange regime, MTR(asym) becomes complicated and should be interpreted with care.

  3. Design and optimization of pulsed Chemical Exchange Saturation Transfer MRI using a multiobjective genetic algorithm.

    Science.gov (United States)

    Yoshimaru, Eriko S; Randtke, Edward A; Pagel, Mark D; Cárdenas-Rodríguez, Julio

    2016-02-01

    Pulsed Chemical Exchange Saturation Transfer (CEST) MRI experimental parameters and RF saturation pulse shapes were optimized using a multiobjective genetic algorithm. The optimization was carried out for RF saturation duty cycles of 50% and 90%, and results were compared to continuous wave saturation and Gaussian waveform. In both simulation and phantom experiments, continuous wave saturation performed the best, followed by parameters and shapes optimized by the genetic algorithm and then followed by Gaussian waveform. We have successfully demonstrated that the genetic algorithm is able to optimize pulse CEST parameters and that the results are translatable to clinical scanners.

  4. Proton Exchange in a Paramagnetic Chemical Exchange Saturation Transfer Agent from Experimental Studies and ab Initio Metadynamics Simulation.

    Science.gov (United States)

    Pollet, Rodolphe; Bonnet, Célia S; Retailleau, Pascal; Durand, Philippe; Tóth, Éva

    2017-03-27

    The proton-exchange process between water and a carbamate has been studied experimentally and theoretically in a lanthanide-based paramagnetic chemical exchange saturation transfer agent endowed with potential multimodality detection capabilities (optical imaging, or T1 MRI for the Gd(III) analogue). In addition to an in-depth structural analysis by a combined approach (using X-ray crystallography, NMR, and molecular dynamics), our ab initio simulation in aqueous solution sheds light on the reaction mechanism for this proton exchange, which involves structural Grotthuss diffusion.

  5. Simplified quantification of labile proton concentration-weighted chemical exchange rate (k(ws) ) with RF saturation time dependent ratiometric analysis (QUESTRA): normalization of relaxation and RF irradiation spillover effects for improved quantitative chemical exchange saturation transfer (CEST) MRI.

    Science.gov (United States)

    Sun, Phillip Zhe

    2012-04-01

    Chemical exchange saturation transfer MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, chemical exchange saturation transfer MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and radiofrequency (RF) irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the chemical exchange saturation transfer MRI experiments. Although methods including numerical fitting with modified Bloch-McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple-parameter non-linear fitting and accurate relaxation measurement. Our work extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono-exponentially at a rate determined by the reverse exchange rate (k(ws) ), with little dependence on bulk water T(1) , T(2) , RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue-like phantom of serially titrated pH compartments.

  6. Advantages of chemical exchange-sensitive spin-lock (CESL) over chemical exchange saturation transfer (CEST) for hydroxyl- and amine-water proton exchange studies.

    Science.gov (United States)

    Jin, Tao; Kim, Seong-Gi

    2014-11-01

    The chemical exchange (CE) rate of endogenous hydroxyl and amine protons with water is often comparable to the difference in their chemical shifts. These intermediate exchange processes have been imaged by the CE saturation transfer (CEST) approach with low-power and long-duration irradiation. However, the sensitivity is not optimal and, more importantly, the signal is contaminated by slow magnetization transfer processes. Here, the properties of CEST signals are compared with those of a CE-sensitive spin-lock (CESL) technique irradiating at the labile proton frequency. First, using a higher power and shorter irradiation in CE-MRI, we obtain: (i) an increased selectivity to faster CE rates via a higher sensitivity to faster CEs and a lower sensitivity to slower CEs and magnetization transfer processes; and (ii) a decreased in vivo asymmetric magnetization transfer contrast measured at ±15 ppm. The sensitivity gain of CESL over CEST is higher for a higher power and shorter irradiation. Unlike CESL, CEST signals oscillate at a very high power and short irradiation. Second, time-dependent CEST and CESL signals are well modeled by analytical solutions of CE-MRI with an asymmetric population approximation, which can be used for quantitative CE-MRI and validated by simulations of Bloch-McConnell equations and phantom experiments. Finally, the in vivo amine-water proton exchange contrast measured at 2.5 ppm with ω1 = 500 Hz is 18% higher in sensitivity for CESL than CEST at 9.4 T. Overall, CESL provides better exchange rate selectivity and sensitivity than CEST; therefore, CESL is more suitable for CE-MRI of intermediate exchange protons.

  7. Lactate Chemical Exchange Saturation Transfer (LATEST) Imaging in vivo A Biomarker for LDH Activity.

    Science.gov (United States)

    DeBrosse, Catherine; Nanga, Ravi Prakash Reddy; Bagga, Puneet; Nath, Kavindra; Haris, Mohammad; Marincola, Francesco; Schnall, Mitchell D; Hariharan, Hari; Reddy, Ravinder

    2016-01-22

    Non-invasive imaging of lactate is of enormous significance in cancer and metabolic disorders where glycolysis dominates. Here, for the first time, we describe a chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) method (LATEST), based on the exchange between lactate hydroxyl proton and bulk water protons to image lactate with high spatial resolution. We demonstrate the feasibility of imaging lactate with LATEST in lactate phantoms under physiological conditions, in a mouse model of lymphoma tumors, and in skeletal muscle of healthy human subjects pre- and post-exercise. The method is validated by measuring LATEST changes in lymphoma tumors pre- and post-infusion of pyruvate and correlating them with lactate determined from multiple quantum filtered proton magnetic resonance spectroscopy (SEL-MQC (1)H-MRS). Similarly, dynamic LATEST changes in exercising human skeletal muscle are correlated with lactate determined from SEL-MQC (1)H-MRS. The LATEST method does not involve injection of radioactive isotopes or labeled metabolites. It has over two orders of magnitude higher sensitivity compared to conventional (1)H-MRS. It is anticipated that this technique will have a wide range of applications including diagnosis and evaluation of therapeutic response of cancer, diabetes, cardiac, and musculoskeletal diseases. The advantages of LATEST over existing methods and its potential challenges are discussed.

  8. Chemical exchange saturation transfer MR imaging of Parkinson's disease at 3 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chunmei; Peng, Shuai; Wang, Rui; Chen, Min [Beijing Hospital, Department of Radiology, Beijing (China); Chen, Haibo; Su, Wen [Beijing Hospital, Department of Neurology, Beijing (China); Zhao, Xuna [Peking University, Center for MRI Research and Beijing City Key Lab for Medical Physics and Engineering, Beijing (China); Zhou, Jinyuan [Johns Hopkins University, Department of Radiology, Baltimore, MD (United States)

    2014-10-15

    To demonstrate the feasibility of using chemical exchange saturation transfer (CEST) imaging to detect Parkinson's disease (PD) in patients at 3 Tesla. Twenty-seven PD patients (17 men and 10 women; age range, 54-77 years) and 22 age-matched normal controls (13 men and 9 women; age range, 55-73 years) were examined on a 3-Tesla MRI system. Magnetization transfer spectra with 31 different frequency offsets (-6 to 6 ppm) were acquired at two transverse slices of the head, including the basal ganglia and midbrain. One-way analysis of variance tests was used to compare the differences in CEST imaging signals between PD patients and normal controls. Total CEST signal between the offsets of 0 and 4 ppm in the substantia nigra was significantly lower in PD patients than in normal controls (P = 0.006), which could be associated with the loss of dopaminergic neurons. Protein-based CEST imaging signals at the offset of 3.5 ppm in the globus pallidus, putamen and caudate were significantly increased in PD patients, compared to normal controls (P < 0.001, P = 0.003, P < 0.001, respectively). CEST imaging signals could potentially serve as imaging biomarkers to aid in the non-invasive molecular diagnosis of PD. (orig.)

  9. Nuclear overhauser enhancement mediated chemical exchange saturation transfer imaging at 7 Tesla in glioblastoma patients.

    Directory of Open Access Journals (Sweden)

    Daniel Paech

    Full Text Available BACKGROUND AND PURPOSE: Nuclear Overhauser Enhancement (NOE mediated chemical exchange saturation transfer (CEST is a novel magnetic resonance imaging (MRI technique on the basis of saturation transfer between exchanging protons of tissue proteins and bulk water. The purpose of this study was to evaluate and compare the information provided by three dimensional NOE mediated CEST at 7 Tesla (7T and standard MRI in glioblastoma patients. PATIENTS AND METHODS: Twelve patients with newly diagnosed histologically proven glioblastoma were enrolled in this prospective ethics committee-approved study. NOE mediated CEST contrast was acquired with a modified three-dimensional gradient-echo sequence and asymmetry analysis was conducted at 3.3 ppm (B1 = 0.7 µT to calculate the magnetization transfer ratio asymmetry (MTR(asym. Contrast enhanced T1 (CE-T1 and T2-weighted images were acquired at 3T and used for data co-registration and comparison. RESULTS: Mean NOE mediated CEST signal based on MTR(asym values over all patients was significantly increased (p<0.001 in CE-T1 tumor (-1.99 ± 1.22%, tumor necrosis (-1.36 ± 1.30% and peritumoral CEST hyperintensities (PTCH within T2 edema margins (-3.56 ± 1.24% compared to contralateral normal appearing white matter (-8.38 ± 1.19%. In CE-T1 tumor (p = 0.015 and tumor necrosis (p<0.001 mean MTR(asym values were significantly higher than in PTCH. Extent of the surrounding tumor hyperintensity was smaller in eight out of 12 patients on CEST than on T2-weighted images, while four displayed at equal size. In all patients, isolated high intensity regions (0.40 ± 2.21% displayed on CEST within the CE-T1 tumor that were not discernible on CE-T1 or T2-weighted images. CONCLUSION: NOE mediated CEST Imaging at 7 T provides additional information on the structure of peritumoral hyperintensities in glioblastoma and displays isolated high intensity regions within the CE-T1 tumor that cannot be acquired on CE-T1 or T2

  10. Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST).

    Science.gov (United States)

    Friedman, Joshua I; Xia, Ding; Regatte, Ravinder R; Jerschow, Alexej

    2015-07-01

    Chemical Exchange Saturation Transfer (CEST) magnetic resonance experiments have become valuable tools in magnetic resonance for the detection of low concentration solutes with far greater sensitivity than direct detection methods. Accurate measures of rates of chemical exchange provided by CEST are of particular interest to biomedical imaging communities where variations in chemical exchange can be related to subtle variations in biomarker concentration, temperature and pH within tissues using MRI. Despite their name, however, traditional CEST methods are not truly selective for chemical exchange and instead detect all forms of magnetization transfer including through-space NOE. This ambiguity crowds CEST spectra and greatly complicates subsequent data analysis. We have developed a Transfer Rate Edited CEST experiment (TRE-CEST) that uses two different types of solute labeling in order to selectively amplify signals of rapidly exchanging proton species while simultaneously suppressing 'slower' NOE-dominated magnetization transfer processes. This approach is demonstrated in the context of both NMR and MRI, where it is used to detect the labile amide protons of proteins undergoing chemical exchange (at rates⩾30s(-1)) while simultaneously eliminating signals originating from slower (∼5s(-1)) NOE-mediated magnetization transfer processes. TRE-CEST greatly expands the utility of CEST experiments in complex systems, and in-vivo, in particular, where it is expected to improve the quantification of chemical exchange and magnetization transfer rates while enabling new forms of imaging contrast.

  11. Quantitative chemical exchange saturation transfer (qCEST) MRI--RF spillover effect-corrected omega plot for simultaneous determination of labile proton fraction ratio and exchange rate.

    Science.gov (United States)

    Sun, Phillip Zhe; Wang, Yu; Dai, ZhuoZhi; Xiao, Gang; Wu, Renhua

    2014-01-01

    Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute proteins and peptides as well as microenvironmental properties. However, the complexity of the CEST MRI effect, which varies with the labile proton content, exchange rate and experimental conditions, underscores the need for developing quantitative CEST (qCEST) analysis. Towards this goal, it has been shown that omega plot is capable of quantifying paramagnetic CEST MRI. However, the use of the omega plot is somewhat limited for diamagnetic CEST (DIACEST) MRI because it is more susceptible to direct radio frequency (RF) saturation (spillover) owing to the relatively small chemical shift. Recently, it has been found that, for dilute DIACEST agents that undergo slow to intermediate chemical exchange, the spillover effect varies little with the labile proton ratio and exchange rate. Therefore, we postulated that the omega plot analysis can be improved if RF spillover effect could be estimated and taken into account. Specifically, simulation showed that both labile proton ratio and exchange rate derived using the spillover effect-corrected omega plot were in good agreement with simulated values. In addition, the modified omega plot was confirmed experimentally, and we showed that the derived labile proton ratio increased linearly with creatine concentration (p exchange rate (p = 0.32). In summary, our study extends the conventional omega plot for quantitative analysis of DIACEST MRI.

  12. Evaluating the use of a continuous approximation for model-based quantification of pulsed chemical exchange saturation transfer (CEST)

    Science.gov (United States)

    Tee, Y. K.; Khrapitchev, A. A.; Sibson, N. R.; Payne, S. J.; Chappell, M. A.

    2012-09-01

    Many potential clinical applications of chemical exchange saturation transfer (CEST) have been studied in recent years. However, due to various limitations such as specific absorption rate guidelines and scanner hardware constraints, most of the proposed applications have yet to be translated into routine diagnostic tools. Currently, pulsed CEST which uses multiple short pulses to perform the saturation is the only viable irradiation scheme for clinical translation. However, performing quantitative model-based analysis on pulsed CEST is time consuming because it is necessary to account for the time dependent amplitude of the saturation pulses. As a result, pulsed CEST is generally treated as continuous CEST by finding its equivalent average field or power. Nevertheless, theoretical analysis and simulations reveal that the resulting magnetization is different when the different irradiation schemes are applied. In this study, the quantification of important model parameters such as the amine proton exchange rate from a pulsed CEST experiment using quantitative model-based analyses were examined. Two model-based approaches were considered - discretized and continuous approximation to the time dependent RF irradiation pulses. The results showed that the discretized method was able to fit the experimental data substantially better than its continuous counterpart, but the smaller fitted error of the former did not translate to significantly better fit for the important model parameters. For quantification of the endogenous CEST effect, such as in amide proton transfer imaging, a model-based approach using the average power equivalent saturation can thus be used in place of the discretized approximation.

  13. Imaging in Vivo Extracellular pH with a Single Paramagnetic Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agent

    Directory of Open Access Journals (Sweden)

    Guanshu Liu

    2012-01-01

    Full Text Available The measurement of extracellular pH (pHe has potential utility for cancer diagnoses and for assessing the therapeutic effects of pH-dependent therapies. A single magnetic resonance imaging (MRI contrast agent that is detected through paramagnetic chemical exchange saturation transfer (PARACEST was designed to measure tumor pHe throughout the range of physiologic pH and with magnetic resonance saturation powers that are not harmful to a mouse model of cancer. The chemical characterization and modeling of the contrast agent Yb3+-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, 10-o-aminoanilide (Yb-DO3A-oAA suggested that the aryl amine of the agent forms an intramolecular hydrogen bond with a proximal carboxylate ligand, which was essential for generating a practical chemical exchange saturation transfer (CEST effect from an amine. A ratio of CEST effects from the aryl amine and amide was linearly correlated with pH throughout the physiologic pH range. The pH calibration was used to produce a parametric pH map of a subcutaneous flank tumor on a mouse model of MCF-7 mammary carcinoma. Although refinements in the in vivo CEST MRI methodology may improve the accuracy of pHe measurements, this study demonstrated that the PARACEST contrast agent can be used to generate parametric pH maps of in vivo tumors with saturation power levels that are not harmful to a mouse model of cancer.

  14. Bacterial spore detection and analysis using hyperpolarized (129)Xe chemical exchange saturation transfer (Hyper-CEST) NMR.

    Science.gov (United States)

    Bai, Yubin; Wang, Yanfei; Goulian, Mark; Driks, Adam; Dmochowski, Ivan J

    2014-08-01

    Previously, we reported hyperpolarized (129)Xe chemical exchange saturation transfer (Hyper-CEST) NMR techniques for the ultrasensitive (i.e., 1 picomolar) detection of xenon host molecules known as cryptophane. Here, we demonstrate a more general role for Hyper-CEST NMR as a spectroscopic method for probing nanoporous structures, without the requirement for cryptophane or engineered xenon-binding sites. Hyper-CEST (129)Xe NMR spectroscopy was employed to detect Bacillus anthracis and Bacillus subtilis spores in solution, and interrogate the layers that comprise their structures. (129)Xe-spore samples were selectively irradiated with radiofrequency pulses; the depolarized (129)Xe returned to aqueous solution and depleted the (129)Xe-water signal, providing measurable contrast. Removal of the outermost spore layers in B. anthracis and B. subtilis (the exosporium and coat, respectively) enhanced (129)Xe exchange with the spore interior. Notably, the spores were invisible to hyperpolarized (129)Xe NMR direct detection methods, highlighting the lack of high-affinity xenon-binding sites, and the potential for extending Hyper-CEST NMR structural analysis to other biological and synthetic nanoporous structures.

  15. Chemical exchange saturation transfer (CEST) MR technique for in-vivo liver imaging at 3.0 tesla

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shu-Zhong; Deng, Min; Wang, Yi-Xiang J. [Chinese University of Hong Kong, Prince of Wales Hospital, Department of Imaging and Interventional Radiology, Faculty of Medicine (China); Yuan, Jing [Hong Kong Sanatorium and Hospital, Medical Physics and Research Department, Happy Valley, Hong Kong (China); Wei, Juan [Philips Healthcare Asia, Shanghai (China); Zhou, Jinyuan [Johns Hopkins University, Department of Radiology, Baltimore, MD (United States); Kennedy Krieger Institute, F.M. Kirby Research Center for Functional Brain Imaging, Baltimore, MD (United States)

    2016-06-15

    To evaluate Chemical Exchange Saturation Transfer (CEST) MRI for liver imaging at 3.0-T. Images were acquired at offsets (n = 41, increment = 0.25 ppm) from -5 to 5 ppm using a TSE sequence with a continuous rectangular saturation pulse. Amide proton transfer-weighted (APTw) and GlycoCEST signals were quantified as the asymmetric magnetization transfer ratio (MTR{sub asym}) at 3.5 ppm and the total MTR{sub asym} integrated from 0.5 to 1.5 ppm, respectively, from the corrected Z-spectrum. Reproducibility was assessed for rats and humans. Eight rats were devoid of chow for 24 hours and scanned before and after fasting. Eleven rats were scanned before and after one-time CCl4 intoxication. For reproducibility, rat liver APTw and GlycoCEST measurements had 95 % limits of agreement of -1.49 % to 1.28 % and -0.317 % to 0.345 %. Human liver APTw and GlycoCEST measurements had 95 % limits of agreement of -0.842 % to 0.899 % and -0.344 % to 0.164 %. After 24 hours, fasting rat liver APTw and GlycoCEST signals decreased from 2.38 ± 0.86 % to 0.67 ± 1.12 % and from 0.34 ± 0.26 % to -0.18 ± 0.37 % respectively (p < 0.05). After CCl4 intoxication rat liver APTw and GlycoCEST signals decreased from 2.46 ± 0.48 % to 1.10 ± 0.77 %, and from 0.34 ± 0.23 % to -0.16 ± 0.51 % respectively (p < 0.05). CEST liver imaging at 3.0-T showed high sensitivity for fasting as well as CCl4 intoxication. (orig.)

  16. Muscle oxidative phosphorylation quantitation using creatine chemical exchange saturation transfer (CrCEST) MRI in mitochondrial disorders

    Science.gov (United States)

    DeBrosse, Catherine; Nanga, Ravi Prakash Reddy; Wilson, Neil; D’Aquilla, Kevin; Elliott, Mark; Yan, Felicia; Wade, Kristin; Nguyen, Sara; Worsley, Diana; Parris-Skeete, Chevonne; McCormick, Elizabeth; Xiao, Rui; Cunningham, Zuela Zolkipli; Fishbein, Lauren; Nathanson, Katherine L.; Lynch, David R.; Stallings, Virginia A.; Yudkoff, Marc; Falk, Marni J.; Reddy, Ravinder; McCormack, Shana E.

    2016-01-01

    Systemic mitochondrial energy deficiency is implicated in the pathophysiology of many age-related human diseases. Currently available tools to estimate mitochondrial oxidative phosphorylation (OXPHOS) capacity in skeletal muscle in vivo lack high anatomic resolution. Muscle groups vary with respect to their contractile and metabolic properties. Therefore, muscle group–specific estimates of OXPHOS would be advantageous. To address this need, a noninvasive creatine chemical exchange saturation transfer (CrCEST) MRI technique has recently been developed, which provides a measure of free creatine. After exercise, skeletal muscle can be imaged with CrCEST in order to make muscle group–specific measurements of OXPHOS capacity, reflected in the recovery rate (τCr) of free Cr. In this study, we found that individuals with genetic mitochondrial diseases had significantly (P = 0.026) prolonged postexercise τCr in the medial gastrocnemius muscle, suggestive of less OXPHOS capacity. Additionally, we observed that lower resting CrCEST was associated with prolonged τPCr, with a Pearson’s correlation coefficient of –0.42 (P = 0.046), consistent with previous hypotheses predicting that resting creatine levels may correlate with 31P magnetic resonance spectroscopy–based estimates of OXPHOS capacity. We conclude that CrCEST can noninvasively detect changes in muscle creatine content and OXPHOS capacity, with high anatomic resolution, in individuals with mitochondrial disorders. PMID:27812541

  17. A Potential Magnetic Resonance Imaging Technique Based on Chemical Exchange Saturation Transfer for In Vivo γ-Aminobutyric Acid Imaging

    Science.gov (United States)

    Yan, Gen; Zhang, Tao; Dai, Zhuozhi; Yi, Meizhi; Jia, Yanlong; Nie, Tingting; Zhang, Handi; Xiao, Gang; Wu, Renhua

    2016-01-01

    Purpose We developed a novel magnetic resonance imaging (MRI) technique based on chemical exchange saturation transfer (CEST) for GABA imaging and investigated the concentration-dependent CEST effect ofGABA in a rat model of brain tumor with blood—brain barrier (BBB) disruption. Materials and Methods All MRI studies were performed using a 7.0-T Agilent MRI scanner. Z-spectra for GABA were acquired at 7.0 T, 37°C, and a pH of 7.0 using varying B1 amplitudes. CEST images of phantoms with different concentrations of GABA solutions (pH, 7.0) and other metabolites (glutamine, myoinositol, creatinine, and choline) were collected to investigate the concentration-dependent CEST effect of GABA and the potential contribution from other brain metabolites. CEST maps for GABA in rat brains with tumors were collected at baseline and 50 min, 1.5 h, and 2.0 h after the injection of GABA solution. Results The CEST effect of GABA was observed at approximately 2.75 parts per million(ppm) downfield from bulk water, and this effect increased with an increase in the B1 amplitude and remained steady after the B1 amplitude reached 6.0 μT (255 Hz). The CEST effect of GABA was proportional to the GABA concentration in vitro. CEST imaging of GABA in a rat brain with a tumor and compromised BBB showed a gradual increase in the CEST effect after GABA injection. Conclusion The findings of this study demonstrate the feasibility and potential of CEST MRI with the optimal B1 amplitude, which exhibits excellent spatial and temporal resolutions, to map changes in GABA. PMID:27711138

  18. Biochemical imaging of cervical intervertebral discs with glycosaminoglycan chemical exchange saturation transfer magnetic resonance imaging: feasibility and initial results

    Energy Technology Data Exchange (ETDEWEB)

    Schleich, Christoph; Mueller-Lutz, Anja; Zimmermann, Lisa; Boos, Johannes; Wittsack, Hans-Joerg; Antoch, Gerald; Miese, Falk [Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, Dusseldorf (Germany); Schmitt, Benjamin [Siemens Ltd. Australia, Healthcare Sector, Macquarie Park, NSW (Australia)

    2016-01-15

    To evaluate glycosaminoglycan chemical exchange saturation transfer (gagCEST) imaging at 3T in the assessment of the GAG content of cervical IVDs in healthy volunteers. Forty-two cervical intervertebral discs of seven healthy volunteers (four females, three males; mean age: 21.4 ± 1.4 years; range: 19-24 years) were examined at a 3T MRI scanner in this prospective study. The MRI protocol comprised standard morphological, sagittal T2 weighted (T2w) images to assess the magnetic resonance imaging (MRI) based grading system for cervical intervertebral disc degeneration (IVD) and biochemical imaging with gagCEST to calculate a region-of-interest analysis of nucleus pulposus (NP) and annulus fibrosus (AF). GagCEST of cervical IVDs was technically successful at 3T with significant higher gagCEST values in NP compared to AF (1.17 % ± 1.03 % vs. 0.79 % ± 1.75 %; p = 0.005). We found topological differences of gagCEST values of the cervical spine with significant higher gagCEST effects in lower IVDs (r = 1; p = 0). We could demonstrate a significant, negative correlation between gagCEST values and cervical disc degeneration of NP (r = -0.360; p = 0.019). Non-degenerated IVDs had significantly higher gagCEST effects compared to degenerated IVDs in NP (1.76 % ± 0.92 % vs. 0.52 % ± 1.17 %; p < 0.001). Biochemical imaging of cervical IVDs is feasible at 3T. GagCEST analysis demonstrated a topological GAG distribution of the cervical spine. The depletion of GAG in the NP with increasing level of morphological degeneration can be assessed using gagCEST imaging. (orig.)

  19. Eu(III) complexes as anion-responsive luminescent sensors and paramagnetic chemical exchange saturation transfer agents.

    Science.gov (United States)

    Hammell, Jacob; Buttarazzi, Leandro; Huang, Ching-Hui; Morrow, Janet R

    2011-06-06

    The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions. Anion interactions produce changes in the luminescence emission spectrum of the Eu(III) complex, in the (1)H NMR spectrum, and correspondingly, in the PARACEST spectrum of the complex (PARACEST = paramagnetic chemical exchange saturation transfer). Direct excitation spectroscopy and luminescence lifetime studies of Eu(S-THP) give information about the speciation and nature of anion interactions including carbonate, acetate, lactate, citrate, phosphate, and methylphosphate at pH 7.2. Data is consistent with the formation of both innersphere and outersphere complexes of Eu(S-THP) with acetate, lactate, and carbonate. These anions have weak dissociation constants that range from 19 to 38 mM. Citrate binding to Eu(S-THP) is predominantly innersphere with a dissociation constant of 17 μM. Luminescence emission peak changes upon addition of anion to Eu(S-THP) show that there are two distinct binding events for phosphate and methylphosphate with dissociation constants of 0.3 mM and 3.0 mM for phosphate and 0.6 mM and 9.8 mM for methyl phosphate. Eu(THPC) contains an appended carbostyril derivative as an antenna to sensitize Eu(III) luminescence. Eu(THPC) binds phosphate and citrate with dissociation constants that are 10-fold less than that of the Eu(S-THP) parent, suggesting that functionalization through a pendent group disrupts the anion binding site. Eu(S-THP) functions as an anion responsive PARACEST agent through exchange of the alcohol protons with bulk water. The alcohol proton resonances of Eu(S-THP) shift downfield in the presence of acetate, lactate, citrate, and methylphosphate, giving rise to distinct PARACEST peaks. In contrast, phosphate binds to Eu(S-THP) to suppress the PARACEST alcohol OH peak and carbonate does not markedly change the alcohol peak at 5 mM Eu(S-THP), 15 mM carbonate at p

  20. Assessment of ischemic penumbra in patients with hyperacute stroke using amide proton transfer (APT) chemical exchange saturation transfer (CEST) MRI.

    Science.gov (United States)

    Tietze, Anna; Blicher, Jakob; Mikkelsen, Irene Klaerke; Østergaard, Leif; Strother, Megan K; Smith, Seth A; Donahue, Manus J

    2014-02-01

    Chemical exchange saturation transfer (CEST)-derived, pH-weighted, amide proton transfer (APT) MRI has shown promise in animal studies for the prediction of infarction risk in ischemic tissue. Here, APT MRI was translated to patients with acute stroke (1-24 h post-symptom onset), and assessments of APT contrast, perfusion, diffusion, disability and final infarct volume (23-92 days post-stroke) are reported. Healthy volunteers (n = 5) and patients (n = 10) with acute onset of symptoms (0-4 h, n = 7; uncertain onset diffusion- and perfusion-weighted MRI, fluid-attenuated inversion recovery (FLAIR) and CEST. Traditional asymmetry and a Lorentzian-based APT index were calculated in the infarct core, at-risk tissue (time-to-peak, TTP; lengthening) and final infarct volume. On average (mean ± standard deviation), control white matter APT values (asymmetry, 0.019 ± 0.005; Lorentzian, 0.045 ± 0.006) were not significantly different (p > 0.05) from APT values in normal-appearing white matter (NAWM) of patients (asymmetry, 0.022 ± 0.003; Lorentzian, 0.048 ± 0.003); however, ischemic regions in patients showed reduced (p = 0.03) APT effects compared with NAWM. Representative cases are presented, whereby the APT contrast is compared quantitatively with contrast from other imaging modalities. The findings vary between patients; in some patients, a trend for a reduction in the APT signal in the final infarct region compared with at-risk tissue was observed, consistent with tissue acidosis. However, in other patients, no relationship was observed in the infarct core and final infarct volume. Larger clinical studies, in combination with focused efforts on sequence development at clinically available field strengths (e.g. 3.0 T), are necessary to fully understand the potential of APT imaging for guiding the hyperacute management of patients.

  1. Improved measurement of labile proton concentration-weighted chemical exchange rate (k(ws)) with experimental factor-compensated and T(1) -normalized quantitative chemical exchange saturation transfer (CEST) MRI.

    Science.gov (United States)

    Wu, Renhua; Liu, Charng-Ming; Liu, Philip K; Sun, Phillip Zhe

    2012-01-01

    Chemical exchange saturation transfer (CEST) MRI enables measurement of dilute CEST agents and microenvironment properties such as pH and temperature, holding great promise for in vivo applications. However, because of confounding concomitant radio frequency (RF) irradiation and relaxation effects, the CEST-weighted MRI contrast may not fully characterize the underlying CEST phenomenon. We postulated that the accuracy of quantitative CEST MRI could be improved if the experimental factors (labeling efficiency and RF spillover effect) were estimated and taken into account. Specifically, the experimental factor was evaluated as a function of exchange rate and CEST agent concentration ratio, which remained relatively constant for intermediate RF irradiation power levels. Hence, the experimental factors can be calculated based on the reasonably estimated exchange rate and labile proton concentration ratio, which significantly improved quantification. The simulation was confirmed with creatine phantoms of serially varied concentration titrated to the same pH, whose reverse exchange rate (k(ws)) was found to be linearly correlated with the concentration. In summary, the proposed solution provides simplified yet reasonably accurate quantification of the underlying CEST system, which may help guide the ongoing development of quantitative CEST MRI.

  2. Quantitative chemical exchange saturation transfer (qCEST) MRI - omega plot analysis of RF-spillover-corrected inverse CEST ratio asymmetry for simultaneous determination of labile proton ratio and exchange rate.

    Science.gov (United States)

    Wu, Renhua; Xiao, Gang; Zhou, Iris Yuwen; Ran, Chongzhao; Sun, Phillip Zhe

    2015-03-01

    Chemical exchange saturation transfer (CEST) MRI is sensitive to labile proton concentration and exchange rate, thus allowing measurement of dilute CEST agent and microenvironmental properties. However, CEST measurement depends not only on the CEST agent properties but also on the experimental conditions. Quantitative CEST (qCEST) analysis has been proposed to address the limitation of the commonly used simplistic CEST-weighted calculation. Recent research has shown that the concomitant direct RF saturation (spillover) effect can be corrected using an inverse CEST ratio calculation. We postulated that a simplified qCEST analysis is feasible with omega plot analysis of the inverse CEST asymmetry calculation. Specifically, simulations showed that the numerically derived labile proton ratio and exchange rate were in good agreement with input values. In addition, the qCEST analysis was confirmed experimentally in a phantom with concurrent variation in CEST agent concentration and pH. Also, we demonstrated that the derived labile proton ratio increased linearly with creatine concentration (P exchange rate followed a dominantly base-catalyzed exchange relationship (P exchange rate in a relatively complex in vitro CEST system.

  3. Iopamidol as a responsive MRI-chemical exchange saturation transfer contrast agent for pH mapping of kidneys: In vivo studies in mice at 7 T.

    Science.gov (United States)

    Longo, Dario Livio; Dastrù, Walter; Digilio, Giuseppe; Keupp, Jochen; Langereis, Sander; Lanzardo, Stefania; Prestigio, Simone; Steinbach, Oliver; Terreno, Enzo; Uggeri, Fulvio; Aime, Silvio

    2011-01-01

    Iopamidol (Isovue®-Bracco Diagnostic Inc.) is a clinically approved X-Ray contrast agent used in the last 30 years for a wide variety of diagnostic applications with a very good clinical acceptance. Iopamidol contains two types of amide functionalities that can be exploited for the generation of chemical exchange saturation transfer effect. The exchange rate of the two amide proton pools is markedly pH-dependent. Thus, a ratiometric method for pH assessment has been set-up based on the comparison of the saturation transfer effects induced by selective irradiation of the two resonances. This ratiometric approach allows to rule out the concentration effect of the contrast agent and provides accurate pH measurements in the 5.5-7.4 range. Upon injection of Iopamidol into healthy mice, it has been possible to acquire pH maps of kidney regions. Furthermore, it has been also shown that the proposed method is able to report about pH-changes induced in control mice fed with acidified or basified water for a period of a week before image acquisition.

  4. A lanthanide complex with dual biosensing properties: CEST (chemical exchange saturation transfer) and BIRDS (biosensor imaging of redundant deviation in shifts) with europium DOTA-tetraglycinate.

    Science.gov (United States)

    Coman, Daniel; Kiefer, Garry E; Rothman, Douglas L; Sherry, A Dean; Hyder, Fahmeed

    2011-12-01

    Responsive contrast agents (RCAs) composed of lanthanide(III) ion (Ln3R) complexes with a variety of1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA4S) derivatives have shown great potential as molecular imaging agents for MR. A variety of LnDOTA–tetraamide complexes have been demonstrated as RCAs for molecular imaging using chemical exchange saturation transfer (CEST). The CEST method detects proton exchange between bulk water and any exchangeable sites on the ligand itself or an inner sphere of bound water that is shifted by a paramagnetic Ln3R ion bound in the core of the macrocycle. It has also been shown that molecular imaging is possible when the RCA itself is observed (i.e. not its effect on bulk water) using a method called biosensor imaging of redundant deviation in shifts (BIRDS). The BIRDS method utilizes redundant information stored in the nonexchangeable proton resonances emanating from the paramagnetic RCA for ambient factors such as temperature and/or pH.Thus, CEST and BIRDS rely on exchangeable and nonexchangeable protons, respectively, for biosensing. We posited that it would be feasible to combine these two biosensing features into the same RCA (i.e. dual CEST and BIRDS properties). A complex between europium(III) ion (Eu3R) and DOTA–tetraglycinate [DOTA–(gly)S4] was used to demonstrate that its CEST characteristics are preserved, while its BIRDS properties are also detectable. The in vitro temperature sensitivity of EuDOTA–(gly)S4 was used to show that qualitative MR contrast with CEST can be calibrated using quantitative MR mapping with BIRDS, thereby enabling quantitative molecular imaging at high spatial resolution.

  5. Gradient ascent pulse engineering for rapid exchange saturation transfer

    Science.gov (United States)

    Rancan, G.; Nguyen, T. T.; Glaser, S. J.

    2015-03-01

    Efforts in the clinical translation of the paraCEST contrast agent Yb-HPDO3A have prompted an investigation into saturation pulse optimality under energy constraints. The GRAPE algorithm has been adapted and implemented for saturation pulse optimization with chemical exchange. The flexibility of the methodology, both in extracting the microscopical parameter ensemble for the algorithm as well as in determining the characteristics of this new class of rising amplitude waveforms allows rapid testing and implementation. Optimal pulses achieve higher saturation efficiencies than the continuous wave gold standard for rapid and especially for variable exchange rates, as brought about by pH-catalysis. Gains of at least 5-15% without any tradeoff have been confirmed both on a spectrometer and on a clinical imager. Pool specific solutions, with pulses optimized for a specific exchange rate value, additionally increase the flexibility of the CEST ratiometric analysis. A simple experimental approach to determine close to optimal triangular pulses is presented.

  6. Long repetition time experiments for measurement of concentrations in systems with chemical exchange and undergoing temporal variation-comparison of methods with and without correction for saturation

    Science.gov (United States)

    Galbán, Craig J.; Spencer, Richard G. S.

    2003-02-01

    The purpose of this paper is to compare two methods for quantifying metabolite concentrations using the one-pulse experiment for a sample undergoing chemical exchange and subject to an intervention or other temporal variation. The methods, LATR-C (Long Acquisition TR (interpulse delay); Corrected for partial saturation) and LATR-NC (Long Acquisition TR; Not Corrected), are compared in terms of signal-to-noise ratio, SNR, per unit time and quantitation errors. Parameters relevant to the isolated perfused rat heart are used as a specific application, although the results are general. We assume throughout that spin-lattice relaxation times, T1, do not change. For a given flip angle, θ, TR's are calculated which result in maximal SNR per unit time under 10%, 5%, and 1% constraints on quantitation errors. Additional simulations were performed to demonstrate explicitly the dependence of the quantitation errors on TR for a fixed θ. We find (i) if the allowed error is large, and when both metabolite concentrations and rate constants vary, LATR-C permits use of shorter TR, and hence yields greater SNR per unit time, than LATR-NC; (ii) for small allowed error, the two methods give similar TR's and SNR per unit time, so that the simpler LATR-NC experiment may be preferred; (iii) large values of θ result in similar constrained TR's and hence SNR per unit time for the two methods; (iv) the ratio of concentrations of metabolites with similar T1 exhibit similar errors for the two methods.

  7. Chemical-exchange-saturation-transfer magnetic resonance imaging to map gamma-aminobutyric acid, glutamate, myoinositol, glycine, and asparagine: Phantom experiments

    Science.gov (United States)

    Oh, Jang-Hoon; Kim, Hyug-Gi; Woo, Dong-Cheol; Jeong, Ha-Kyu; Lee, Soo Yeol; Jahng, Geon-Ho

    2017-03-01

    The physical and technical development of chemical-exchange-saturation-transfer (CEST) magnetic resonance imaging (MRI) using clinical 3 T MRI was explored with the goal of mapping asparagine (Asn), gamma-aminobutyric acid (GABA), glutamate (Glu), glycine (Gly), and myoinositol (MI), which exist in the brain. Phantoms with nine different conditions at concentrations of 10, 30, and 50 mM and pH values of 5.6, 6.2, and 7.4 were prepared for the five target molecules to evaluate the dependence of the CEST effect in the concentration, the pH, and the amplitude of the applied radiofrequency field B1. CEST images in the offset frequency range of ±6 parts per million (ppm) were acquired using a pulsed radio-frequency saturation scheme with a clinical 3 T MRI system. A voxel-based main magnetic field B0 inhomogeneity correction, where B0 is the center frequency offset at zero ppm, was performed by using the spline interpolation method to fit the full Z-spectrum to estimate the center frequency. A voxel-based CEST asymmetry map was calculated to evaluate amide (-NH), amine (-NH2), and hydroxyl (-OH) groups for the five target molecules. The CEST effect for Glu, GABA, and Gly clearly increased with increasing concentrations. The CEST effect for MI was minimal, with no noticeable differences at different concentrations. The CEST effect for Glu and Gly increased with increasing acidity. The highest CEST asymmetry for GABA was observed at pH 6.2. The CEST effect for Glu, GABA, and Gly increased with increasing B1 amplitude. For all target molecules, the CEST effect for the human 3 T MRI system increased with increasing concentration and B1 amplitude, but varied with pH, depending on the characteristics of the molecules. The CEST effect for MI may be not suitable with clinical MRI systems. These results show that CEST imaging in the brain with the amine protons by using 3 T MRI is possible for several neuronal diseases.

  8. Chemical exchange saturation transfer MR imaging of articular cartilage glycosaminoglycans at 3 T: Accuracy of B0 Field Inhomogeneity corrections with gradient echo method.

    Science.gov (United States)

    Wei, Wenbo; Jia, Guang; Flanigan, David; Zhou, Jinyuan; Knopp, Michael V

    2014-01-01

    Glycosaminoglycan Chemical Exchange Saturation Transfer (gagCEST) is an important molecular MRI methodology developed to assess changes in cartilage GAG concentrations. The correction for B0 field inhomogeneity is technically crucial in gagCEST imaging. This study evaluates the accuracy of the B0 estimation determined by the dual gradient echo method and the effect on gagCEST measurements. The results were compared with those from the commonly used z-spectrum method. Eleven knee patients and three healthy volunteers were scanned. Dual gradient echo B0 maps with different ∆TE values (1, 2, 4, 8, and 10 ms) were acquired. The asymmetry of the magnetization transfer ratio at 1 ppm offset referred to the bulk water frequency, MTRasym(1 ppm), was used to quantify cartilage GAG levels. The B0 shifts for all knee patients using the z-spectrum and dual gradient echo methods are strongly correlated for all ∆TE values used (r = 0.997 to 0.786, corresponding to ∆TE = 10 to 1 ms). The corrected MTRasym(1 ppm) values using the z-spectrum method (1.34% ± 0.74%) highly agree only with those using the dual gradient echo methods with ∆TE = 10 ms (1.72% ± 0.80%; r = 0.924) and 8 ms (1.50% ± 0.82%; r = 0.712). The dual gradient echo method with longer ∆TE values (more than 8 ms) has an excellent correlation with the z-spectrum method for gagCEST imaging at 3T.

  9. Chemical Exchange Saturation Transfer MR Imaging Is Superior to Diffusion Tensor Imaging in the Diagnosis and Severity Evaluation of Parkinson's Disease: a Study on Substantia Nigra and Striatum

    Directory of Open Access Journals (Sweden)

    Chunmei eLi

    2015-10-01

    Full Text Available Parkinson’s disease (PD is a neurodegenerative disorder characterized by nigrostriatal cell loss. To date the diagnosis of PD is still based primarily on the clinical manifestations which may be typical and obvious only in advanced-stage PD. Thus, it is crucial to find a reliable marker for the diagnosis of PD. We conducted this study to assess the diagnostic efficiency of chemical-exchange-saturation-transfer (CEST imaging and diffusion-tensor imaging (DTI in PD at 3 Tesla by evaluating changes on substantia nigra and striatum. Twenty-three PD patients and twenty-three age-matched normal controls were recruited. All patients and controls were imaged on a 3 Tesla MR system, using an 8-channel head coil. CEST imaging was acquired in two transverse slices of the head, including substantia nigra and striatum. The magnetization-transfer-ratio asymmetry at 3.5 ppm, MTRasym(3.5ppm, and the total CEST signal intensity between 0 and 4 ppm were calculated. Multi-slice DTI was acquired for all the patients and normal controls. Quantitative analysis was performed on the substantia nigra, globus pallidus, putamen and caudate. The MTRasym(3.5ppm value, the total CEST signal intensity and fractional anisotropy (FA value of the substantia nigra were all significantly lower in PD patients than in normal controls (P = 0.003, P = 0.004 and P < 0.001, respectively. The MTRasym(3.5ppm values of the putamen and the caudate were significantly higher in PD patients than in normal controls (P = 0.010 and P = 0.009, respectively. There were no significant differences for the mean diffusivity (MD in these four regions between PD patients and normal controls. In conclusion, CEST MR imaging provided multiple CEST image contrasts in the substantia nigra and the striatum in PD and may be superior to DTI in the diagnosis of PD.

  10. Salicylic acid analogues as chemical exchange saturation transfer MRI contrast agents for the assessment of brain perfusion territory and blood-brain barrier opening after intra-arterial infusion.

    Science.gov (United States)

    Song, Xiaolei; Walczak, Piotr; He, Xiaowei; Yang, Xing; Pearl, Monica; Bulte, Jeff Wm; Pomper, Martin G; McMahon, Michael T; Janowski, Mirosław

    2016-07-01

    The blood-brain barrier (BBB) is a major obstacle for drug delivery to the brain. Predicted, focal opening of the BBB through intra-arterial infusion of hyperosmolar mannitol is feasible, but there is a need to facilitate imaging techniques (e.g. MRI) to guide interventional procedures and assess the outcomes. Here, we show that salicylic acid analogues (SAA) can depict the brain territory supplied by the catheter and detect the BBB opening, through chemical exchange saturation transfer (CEST) MRI. Hyperosmolar SAA solutions themselves are also capable of opening the BBB, and, when multiple SAA agents were co-injected, their locoregional perfusion could be differentiated.

  11. Lanthanide ion (III) complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate for dual biosensing of pH with chemical exchange saturation transfer (CEST) and biosensor imaging of redundant deviation in shifts (BIRDS).

    Science.gov (United States)

    Huang, Yuegao; Coman, Daniel; Ali, Meser M; Hyder, Fahmeed

    2015-01-01

    Relaxivity-based magnetic resonance of phosphonated ligands chelated with gadolinium (Gd(3+)) shows promise for pH imaging. However instead of monitoring the paramagnetic effect of lanthanide complexes on the relaxivity of water protons, biosensor (or molecular) imaging with magnetic resonance is also possible by detecting either the nonexchangeable or the exchangeable protons on the lanthanide complexes themselves. The nonexchangeable protons (e.g. -CHx, where 3 ≥ x ≥ 1) are detected using a three-dimensional chemical shift imaging method called biosensor imaging of redundant deviation in shifts (BIRDS), whereas the exchangeable protons (e.g. -OH or -NHy , where 2 ≥ y ≥ 1) are measured with chemical exchange saturation transfer (CEST) contrast. Here we tested the feasibility of BIRDS and CEST for pH imaging of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP(8-)) chelated with thulium (Tm(3+) ) and ytterbium (Yb(3+)). BIRDS and CEST experiments show that both complexes are responsive to pH and temperature changes. Higher pH and temperature sensitivities are obtained with BIRDS for either complex when using the chemical shift difference between two proton resonances vs using the chemical shift of a single proton resonance, thereby eliminating the need to use water resonance as reference. While CEST contrast for both agents is linearly dependent on pH within a relatively large range (i.e. 6.3-7.9), much stronger CEST contrast is obtained with YbDOTA-4AmP(5-) than with TmDOTA-4AmP(5-). In addition, we demonstrate the prospect of using BIRDS to calibrate CEST as new platform for quantitative pH imaging.

  12. The system applying and analyzing of Z spectrum in chemical exchange saturation transfer%化学交换饱和转移的Z谱分析展示系统

    Institute of Scientific and Technical Information of China (English)

    白帅; 侯榆青; 贺小伟; 薛心雨

    2016-01-01

    Objective:To create a simple and friendly software toolkit to display and analyze Z spectrum of Chemical Exchange Saturation Transfer (CEST), which is convenient for clinicians and researchers to apply and research. Materials and Methods: The data is collected by conventional CEST imaging method, and the system is made by MATLAB GUI. Fitting the Z spectrum of different region of interest (ROI) which are selected by taking the mouse, and also carrying on its analysis and comparison. Results:The different positions and different pixel values of image’s ROI, the Z spectrum are different, which reflect different biological information. Conclusion:Z spectrum directly determines the final CEST signal analysis and relates biomedical information extraction. The functions of this system mainly include CEST image denoising, the formation of asymmetric magnetization transfer rate (MTRasym) mapping, selecting ROI and fitting the Z spectrum. To fit the Z spectra of ROI which are selected by taking the mouse.%目的:建立一个简单友好,显示和分析化学交换饱和转移(chemical exchange saturation transfer, CEST)Z谱的软件工具包,方便临床医生和研究者进行应用研究。材料与方法使用传统CEST成像方法采集数据,通过MATLAB GUI制作系统,并通过两种方法实现定制选取以鼠标指定点为中心的任意大小的多个感兴趣区域(region of interest, ROI),展示其Z谱,并对其进行分析比较。结果图像不同位置ROI、不同像素大小ROI得到的Z谱不同,反映出不同的生物学信息。结论 Z谱决定最终CEST信号分析与相关生物医学信息提取。系统主要功能包括CEST图像归一化去噪,不对称磁化传递速率(magnetization transfer ratio, MTRasym)映射的形成,ROI选取及Z谱拟合。

  13. Observing and preventing rubidium runaway in a direct-infusion xenon-spin hyperpolarizer optimized for high-resolution hyper-CEST (chemical exchange saturation transfer using hyperpolarized nuclei) NMR

    Science.gov (United States)

    Witte, C.; Kunth, M.; Rossella, F.; Schröder, L.

    2014-02-01

    Xenon is well known to undergo host-guest interactions with proteins and synthetic molecules. As xenon can also be hyperpolarized by spin exchange optical pumping, allowing the investigation of highly dilute systems, it makes an ideal nuclear magnetic resonance probe for such host molecules. The utility of xenon as a probe can be further improved using Chemical Exchange Saturation Transfer using hyperpolarized nuclei (Hyper-CEST), but for highly accurate experiments requires a polarizer and xenon infusion system optimized for such measurements. We present the design of a hyperpolarizer and xenon infusion system specifically designed to meet the requirements of Hyper-CEST measurements. One key element of this design is preventing rubidium runaway, a chain reaction induced by laser heating that prevents efficient utilization of high photon densities. Using thermocouples positioned along the pumping cell we identify the sources of heating and conditions for rubidium runaway to occur. We then demonstrate the effectiveness of actively cooling the optical cell to prevent rubidium runaway in a compact setup. This results in a 2-3-fold higher polarization than without cooling, allowing us to achieve a polarization of 25% at continuous flow rates of 9 ml/min of 129Xe. The simplicity of this design also allows it to be retrofitted to many existing polarizers. Combined with a direction infusion system that reduces shot-to-shot noise down to 0.56% we have captured Hyper-CEST spectra in unprecedented detail, allowing us to completely resolve peaks separated by just 1.62 ppm. Due to its high polarization and excellent stability, our design allows the comparison of underlying theories of host-guest systems with experiment at low concentrations, something extremely difficult with previous polarizers.

  14. Chemical Exchange Saturation Transfer MR Imaging is Superior to Diffusion-Tensor Imaging in the Diagnosis and Severity Evaluation of Parkinson's Disease: A Study on Substantia Nigra and Striatum.

    Science.gov (United States)

    Li, Chunmei; Wang, Rui; Chen, Haibo; Su, Wen; Li, Shuhua; Zhao, Xuna; Zhou, Jinyuan; Qiao, Jian; Lou, Baohui; Song, Guodong; Chen, Min

    2015-01-01

    Parkinson's disease (PD) is a neurodegenerative disorder characterized by nigrostriatal cell loss. To date, the diagnosis of PD is still based primarily on the clinical manifestations, which may be typical and obvious only in advanced-stage PD. Thus, it is crucial to find a reliable marker for the diagnosis of PD. We conducted this study to assess the diagnostic efficiency of chemical exchange saturation transfer (CEST) imaging and diffusion-tensor imaging (DTI) in PD at 3 T by evaluating changes on substantia nigra and striatum. Twenty-three PD patients and twenty-three age-matched normal controls were recruited. All patients and controls were imaged on a 3-T MR system, using an eight-channel head coil. CEST imaging was acquired in two transverse slices of the head, including substantia nigra and striatum. The magnetization transfer ratio asymmetry at 3.5 ppm, MTRasym(3.5 ppm), and the total CEST signal intensity between 0 and 4 ppm were calculated. Multi-slice DTI was acquired for all the patients and normal controls. Quantitative analysis was performed on the substantia nigra, globus pallidus, putamen, and caudate. The MTRasym(3.5 ppm) value, the total CEST signal intensity, and fractional anisotropy value of the substantia nigra were all significantly lower in PD patients than in normal controls (P = 0.003, P = 0.004, and P diffusivity in these four regions between PD patients and normal controls. In conclusion, CEST MR imaging provided multiple CEST image contrasts in the substantia nigra and the striatum in PD and may be superior to DTI in the diagnosis of PD.

  15. Elimination of spin diffusion effects in saturation transfer experiments: application to hydrogen exchange in proteins.

    Science.gov (United States)

    Jensen, Malene Ringkjøbing; Kristensen, Søren M; Led, Jens J

    2007-03-01

    The NMR saturation transfer experiment is widely used to characterize exchange processes in proteins that take place on the ms-s timescale. However, spin diffusion effects are inherently associated with the saturation transfer experiment and may overshadow the effect of the exchange processes of interest. As shown here, the effects from spin diffusion and exchange processes can be separated by varying the field strength of the saturation pulse, thereby allowing correct exchange rates to be obtained. The method is demonstrated using the hydrogen exchange process in the protein Escherichia coli thioredoxin as an example.

  16. Speeding-up exchange-mediated saturation transfer experiments by Fourier transform

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Marta G.; Reddy, Jithender G.; Griesinger, Christian; Lee, Donghan, E-mail: dole@nmr.mpibpc.mpg.de [Max-Planck Institute for Biophysical chemistry, Department of NMR-based Structural Biology (Germany)

    2015-11-15

    Protein motions over various time scales are crucial for protein function. NMR relaxation dispersion experiments play a key role in explaining these motions. However, the study of slow conformational changes with lowly populated states remained elusive. The recently developed exchange-mediated saturation transfer experiments allow the detection and characterization of such motions, but require extensive measurement time. Here we show that, by making use of Fourier transform, the total acquisition time required to measure an exchange-mediated saturation transfer profile can be reduced by twofold in case that one applies linear prediction. In addition, we demonstrate that the analytical solution for R{sub 1}ρ experiments can be used for fitting the exchange-mediated saturation transfer profile. Furthermore, we show that simultaneous analysis of exchange-mediated saturation transfer profiles with two different radio-frequency field strengths is required for accurate and precise characterization of the exchange process and the exchanging states.

  17. Heat Exchanger Lab for Chemical Engineering Undergraduates

    Science.gov (United States)

    Rajala, Jonathan W.; Evans, Edward A.; Chase, George G.

    2015-01-01

    Third year chemical engineering undergraduate students at The University of Akron designed and fabricated a heat exchanger for a stirred tank as part of a Chemical Engineering Laboratory course. The heat exchanger portion of this course was three weeks of the fifteen week long semester. Students applied concepts of scale-up and dimensional…

  18. Numerical Study of Condensation Heat Exchanger Design in a Saturated Pool: Correlation Investigation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hee Joon [Kookmin University, Seoul (Korea, Republic of); Lee, Tae Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-10-15

    Generally the condensation heat exchanger has higher heat transfer coefficient compared to the single phase heat exchanger, so has been widely applied to the cooling systems of fissile power plant. Recently vertical or horizontal type condensation heat exchangers are being studied for the application to secondary passive cooling system of nuclear plants. To design vertical condensation heat exchanger in a saturated water pool, a thermal sizing program of condensation heat exchanger, TSCON(Thermal Sizing of CONdenser) was developed. In this study, condensing heat transfer correlation of TSCON is evaluated with the existing experimental data set to design condensation heat exchanger without noncondensable gas effect (pure steam condensation)

  19. Saturation-recovery metabolic-exchange rate imaging with hyperpolarized [1-13C] pyruvate using spectral-spatial excitation.

    Science.gov (United States)

    Schulte, Rolf F; Sperl, Jonathan I; Weidl, Eliane; Menzel, Marion I; Janich, Martin A; Khegai, Oleksandr; Durst, Markus; Ardenkjaer-Larsen, Jan Henrik; Glaser, Steffen J; Haase, Axel; Schwaiger, Markus; Wiesinger, Florian

    2013-05-01

    Within the last decade hyperpolarized [1-13C] pyruvate chemical-shift imaging has demonstrated impressive potential for metabolic MR imaging for a wide range of applications in oncology, cardiology, and neurology. In this work, a highly efficient pulse sequence is described for time-resolved, multislice chemical shift imaging of the injected substrate and obtained downstream metabolites. Using spectral-spatial excitation in combination with single-shot spiral data acquisition, the overall encoding is evenly distributed between excitation and signal reception, allowing the encoding of one full two-dimensional metabolite image per excitation. The signal-to-noise ratio can be flexibly adjusted and optimized using lower flip angles for the pyruvate substrate and larger ones for the downstream metabolites. Selectively adjusting the excitation of the down-stream metabolites to 90° leads to a so-called "saturation-recovery" scheme with the detected signal content being determined by forward conversion of the available pyruvate. In case of repetitive excitations, the polarization is preserved using smaller flip angles for pyruvate. Metabolic exchange rates are determined spatially resolved from the metabolite images using a simplified two-site exchange model. This novel contrast is an important step toward more quantitative metabolic imaging. Goal of this work was to derive, analyze, and implement this "saturation-recovery metabolic exchange rate imaging" and demonstrate its capabilities in four rats bearing subcutaneous tumors.

  20. Physico-chemical and Bio-chemical Controls on Soil C Saturation Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Six, Johan [Univ. of California, Davis, CA (United States); Plante, Alain F. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2011-05-31

    In this project, we tested through a multitude of lab and field experiments the concept of soil C stabilization and determined metrics for the level of C saturation across soils and soil organic matter fractions. The basic premise of the soil C saturation concept is that there is a maximum amount of C that can be stabilized within a soil, even when C input is further increased. In a first analysis, our results showed that linear regression models do not adequately predict maximal organic C stabilization by fine soil particles. Soil physical and chemical properties associated with soil clay mineralogy, such as specific surface area and organic C loading, should be incorporated into models for predicting maximal organic C stabilization. In a second analysis, we found significantly greater maximal C stabilization in the microaggregate-protected versus the non-microaggregate protected mineral fractions, which provides independent validation that microaggregation plays an important role in increasing the protection and stabilization of soil C leading to greater total soil C accumulation in these pools. In a third study, our results question the role of biochemical preference in mineral C stabilization and of the chemical recalcitrance of specific plant-derived compounds in non-protected soil C accumulation. Because C biochemical composition of slowly turning over mineral protected C pools does not change with C saturation, input C composition is unlikely to affect long-term C stabilization. Rather, C saturation and stabilization in soil is controlled only by the quantity of C input to the soil and the physical and chemical protection mechanisms at play in long-term C stabilization. In conclusion, we have further corroborated the concept of soil C saturation and elucidated several mechanisms underlying this soil C saturation.

  1. Multi-region Transport and Competitive Ion Exchange in Partially Saturated Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Yabusaki, Steven B.(BATTELLE (PACIFIC NW LAB)); Gamerdinger, Amy P.(WASHINGTON STATE UNIV TC); S.M. Hassanizadeh, R.J. Schotting, et al.

    2002-01-01

    In most natural subsurface settings cesium sorbs very strongly to sediments, effectively limiting its transport. At the Hanford Site in Washington State (USA), vadose zone migration of 137Cs from subsurface high-level radioactive waste tanks has been detected over 40 meters below the ground surface. Batch and saturated laboratory column studies provided the basis for a quantitative multisite, multicomponent ion exchange model of Cs+ competition with Na+, K+, Ca++, and Mg++ in a composite Hanford soil. The validity of this model under unsaturated conditions was examined in a series of reactive transport column experiments performed in an ultracentrifuge at different liquid saturations. For each experiment, a constant, uniform saturation was maintained using a steady influx of a 5 M sodium nitrate solution with 5.4E-5 M cesium iodide. Of interest was the potential for enhanced cesium transport due to the presence of immobile liquid and/or bypassed regions. Mobile and immobile fluid fractions, dispersion, and the rate of mass transfer between mobile and immobile regions were determined from the tracer breakthrough. At higher saturations ({approx} 65%), the tracer and cesium behavior could be predicted to a large degree using a single mobile region with the previously developed multicomponent ion exchange model. At lower saturations ({approx} 23%), however, the tracer breakthrough indicated a relatively large immobile fluid fraction, which could be described with a multi-region approach. In this experiment, cesium broke through earlier and at higher concentrations than predicted by multi-region theory combined with the existing cesium ion exchange model. This behavior is consistent with a higher density of exchange sites in the immobile fluid region.

  2. Solubility and cation exchange in phosphate rock and saturated clinoptilolite mixtures

    Science.gov (United States)

    Allen, E. R.; Hossner, L. R.; Ming, D. W.; Henninger, D. L.

    1993-01-01

    Mixtures of zeolite and phosphate rock (PR) have the potential to provide slow-release fertilization of plants in synthetic soils by dissolution and ion-exchange reactions. This study was conducted to examine solubility and cation-exchange relationships in mixtures of PR and NH4- and K-saturated clinoptilolite (Cp). Batch-equilibration experiments were designed to investigate the effect of PR source, the proportion of exchangeable K and NH4, and the Cp to PR ratio on solution N, P, K, and Ca concentrations. The dissolution and cation-exchange reactions that occurred after mixing NH4- and K-saturated Cp with PR increased the solubility of the PR and simultaneously released NH4 and K into solution. The more reactive North Carolina (NC) PR rendered higher solution concentrations of NH4 and K when mixed with Cp than did Tennessee (TN) PR. Solution P concentrations for the Cp-NC PR mixture and the Cp-TN PR mixture were similar. Solution concentrations of N, P, K, and Ca and the ratios of these nutrients in solution varied predictably with the type of PR, the Cp/PR ratio, and the proportions of exchangeable K and NH4 on the Cp. Our research indicated that slow-release fertilization using Cp/PR media may provide adequate levels of N, P, and K to support plant growth. Solution Ca concentrations were lower than optimum for plant growth.

  3. Ultrafast two dimensional infrared chemical exchange spectroscopy

    Science.gov (United States)

    Fayer, Michael

    2011-03-01

    The method of ultrafast two dimensional infrared (2D IR) vibrational echo spectroscopy is described. Three ultrashort IR pulses tuned to the frequencies of the vibrational transitions of interest are directed into the sample. The interaction of these pulses with the molecular vibrational oscillators produces a polarization that gives rise to a fourth pulse, the vibrational echo. The vibrational echo pulse is combined with another pulse, the local oscillator, for heterodyne detection of the signal. For fixed time between the second and third pulses, the waiting time, the first pulse is scanned. Two Fourier transforms of the data yield a 2D IR spectrum. The waiting time is increased, and another spectrum is obtained. The change in the 2D IR spectra with increased waiting time provides information on the time evolution of the structure of the molecular system under observation. In a 2D IR chemical exchange experiment, two species A and B, are undergoing chemical exchange. A's are turning into B's, and B's are turning into A's, but the overall concentrations of the species are not changing. The kinetics of the chemical exchange on the ground electronic state under thermal equilibrium conditions can be obtained 2D IR spectroscopy. A vibration that has a different frequency for the two species is monitored. At very short time, there will be two peaks on the diagonal of the 2D IR spectrum, one for A and one for B. As the waiting time is increased, chemical exchange causes off-diagonal peaks to grow in. The time dependence of the growth of these off-diagonal peaks gives the chemical exchange rate. The method is applied to organic solute-solvent complex formation, orientational isomerization about a carbon-carbon single bond, migration of a hydrogen bond from one position on a molecule to another, protein structural substate interconversion, and water hydrogen bond switching between ions and water molecules. This work was supported by the Air Force Office of Scientific

  4. High-power 1H composite pulse decoupling provides artifact free exchange-mediated saturation transfer (EST) experiments

    Science.gov (United States)

    Chakrabarti, Kalyan S.; Ban, David; Pratihar, Supriya; Reddy, Jithender G.; Becker, Stefan; Griesinger, Christian; Lee, Donghan

    2016-08-01

    Exchange-mediated saturation transfer (EST) provides critical information regarding dynamics of molecules. In typical applications EST is studied by either scanning a wide range of 15N chemical shift offsets where the applied 15N irradiation field strength is on the order of hundreds of Hertz or, scanning a narrow range of 15N chemical shift offsets where the applied 15N irradiation field-strength is on the order of tens of Hertz during the EST period. The 1H decoupling during the EST delay is critical as incomplete decoupling causes broadening of the EST profile, which could possibly result in inaccuracies of the extracted kinetic parameters and transverse relaxation rates. Currently two different 1H decoupling schemes have been employed, intermittently applied 180° pulses and composite-pulse-decoupling (CPD), for situations where a wide range, or narrow range of 15N chemical shift offsets are scanned, respectively. We show that high-power CPD provides artifact free EST experiments, which can be universally implemented regardless of the offset range or irradiation field-strengths.

  5. Oxidative regeneration of toluene-saturated natural zeolite by gaseous ozone: the influence of zeolite chemical surface characteristics.

    Science.gov (United States)

    Alejandro, Serguei; Valdés, Héctor; Manéro, Marie-Hélène; Zaror, Claudio A

    2014-06-15

    In this study, the effect of zeolite chemical surface characteristics on the oxidative regeneration of toluene saturated-zeolite samples is investigated. A Chilean natural zeolite (53% clinoptilolite, 40% mordenite and 7% quartz) was chemically modified by acid treatment with hydrochloric acid and by ion-exchange with ammonium sulphate. Thermal pre-treatments at 623 and 823K were applied and six zeolite samples with different chemical surface characteristics were generated. Chemical modification of natural zeolite followed by thermal out-gassing allows distinguishing the role of acidic surface sites on the regeneration of exhausted zeolites. An increase in Brønsted acid sites on zeolite surface is observed as a result of ammonium-exchange treatment followed by thermal treatment at 623K, thus increasing the adsorption capacity toward toluene. High ozone consumption could be associated to a high content of Lewis acid sites, since these could decompose ozone into atomic active oxygen species. Then, surface oxidation reactions could take part among adsorbed toluene at Brønsted acid sites and surface atomic oxygen species, reducing the amount of adsorbed toluene after the regenerative oxidation with ozone. Experimental results show that the presence of adsorbed oxidation by-products has a negative impact on the recovery of zeolite adsorption capacity.

  6. Oxidative regeneration of toluene-saturated natural zeolite by gaseous ozone: The influence of zeolite chemical surface characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Alejandro, Serguei [Laboratorio de Tecnologías Limpias (F. Ingeniería), Universidad Católica de la Santísima Concepción, Alonso de Ribera 2850, Concepción (Chile); Núcleo de Energías Renovables (F. Ingeniería), Universidad Católica de Temuco, Rudecindo Ortega 02950, Temuco (Chile); Valdés, Héctor, E-mail: hvaldes@ucsc.cl [Laboratorio de Tecnologías Limpias (F. Ingeniería), Universidad Católica de la Santísima Concepción, Alonso de Ribera 2850, Concepción (Chile); Manéro, Marie-Hélène [Université de Toulouse (France); INPT, UPS (France); Laboratoire de Génie Chimique, 4, Allée Emile Monso, F–31030 Toulouse (France); CNRS (France); Laboratoire de Génie Chimique, F–31030 Toulouse (France); Zaror, Claudio A. [Departamento de Ingeniería Química (F. Ingeniería), Universidad de Concepción, Concepción, Correo 3, Casilla 160–C (Chile)

    2014-06-01

    Highlights: • Surface acidity of modified natural zeolite is related to its chemical reactivity. • Brønsted acid sites are associated to toluene adsorption. • Lewis acid sites could decompose ozone generating surface active oxygen species. • Infrared spectra evidence active atomic oxygen and oxidation by-product formation. • 2NH4Z1 sample shows the highest reactivity toward adsorbed toluene. - Abstract: In this study, the effect of zeolite chemical surface characteristics on the oxidative regeneration of toluene saturated-zeolite samples is investigated. A Chilean natural zeolite (53% clinoptilolite, 40% mordenite and 7% quartz) was chemically modified by acid treatment with hydrochloric acid and by ion-exchange with ammonium sulphate. Thermal pre-treatments at 623 and 823 K were applied and six zeolite samples with different chemical surface characteristics were generated. Chemical modification of natural zeolite followed by thermal out-gassing allows distinguishing the role of acidic surface sites on the regeneration of exhausted zeolites. An increase in Brønsted acid sites on zeolite surface is observed as a result of ammonium-exchange treatment followed by thermal treatment at 623 K, thus increasing the adsorption capacity toward toluene. High ozone consumption could be associated to a high content of Lewis acid sites, since these could decompose ozone into atomic active oxygen species. Then, surface oxidation reactions could take part among adsorbed toluene at Brønsted acid sites and surface atomic oxygen species, reducing the amount of adsorbed toluene after the regenerative oxidation with ozone. Experimental results show that the presence of adsorbed oxidation by-products has a negative impact on the recovery of zeolite adsorption capacity.

  7. Radial variations in cation exchange capacity and base saturation rate in the wood of pedunculate oak and European beech

    Energy Technology Data Exchange (ETDEWEB)

    Herbauts, J.; Penninckx, V.; Gruber, W.; Meerts, P. [Universite Libre de Bruxelles, Laboratoire de genetique et d' ecologie vegetales, Brussels (Belgium)

    2002-10-01

    Visual observation of pedunculate oak trees and European beech trees in a mixed forest stand in the Belgian Ardennes revealed decreasing cation concentration profiles in wood. In order to determine whether these profiles are attributable to endogenous factors or to decreased availability of cations in the soil, radial profiles of water-soluble, exchangeable and total cations were investigated. Cation exchange capacity of wood was also determined. Results showed wood cation exchange capacity to decrease from pith to bark in European beech and from pith to outer heartwood in pedunculate oak. Decreasing profiles of exchangeable calcium and magnesium in peduncular oak and exchangeable calcium in European beech were found to be strongly constrained by cation exchange capacity, and thus not related to environmental change. Base cation saturation rate showed no consistent radial change in either species. It was concluded that the results did not provide convincing evidence to attribute the decrease in divalent cation concentration in pedunculate oak and European beech in this location to be due to atmospheric pollution. 42 refs., 1 tab., 4 figs.

  8. Stochastic Simulation of Chemical Exchange in Two Dimensional Infrared Spectroscopy

    CERN Document Server

    Sanda, F; Sanda, Frantisek; Mukamel, Shaul

    2006-01-01

    The stochastic Liouville equations are employed to investigate the combined signatures of chemical exchange (two-state-jump) and spectral diffusion (coupling to an overdamped Brownian oscillator) in the coherent response of an anharmonic vibration to three femtosecond infrared pulses. Simulations reproduce the main features recently observed in the OD stretch of phenol in benzene.

  9. Separation of the isotopes of boron by chemical exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    McCandless, F.P.; Herbst, R.S.

    1995-05-30

    The isotopes of boron, {sup 10}B and {sup 11}B, are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF{sub 3} and a liquid BF{sub 3} donor molecular addition complex formed between BF{sub 3} gas and a donor chosen from the group consisting of: nitromethane, acetone, methyl isobutyl ketone, or diisobutyl ketone. 1 Fig.

  10. Glucans monomer-exchange dynamics as an open chemical network

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Riccardo, E-mail: riccardo.rao@uni.lu; Esposito, Massimiliano, E-mail: massimiliano.esposito@uni.lu [Complex Systems and Statistical Mechanics, Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg (Luxembourg); Lacoste, David [Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI - 10 rue Vauquelin, F-75231 Paris (France)

    2015-12-28

    We describe the oligosaccharides-exchange dynamics performed by the so-called D-enzymes on polysaccharides. To mimic physiological conditions, we treat this process as an open chemical network by assuming some of the polymer concentrations fixed (chemostatting). We show that three different long-time behaviors may ensue: equilibrium states, nonequilibrium steady states, and continuous growth states. We dynamically and thermodynamically characterize these states and emphasize the crucial role of conservation laws in identifying the chemostatting conditions inducing them.

  11. Glucans monomer-exchange dynamics as an open chemical network

    CERN Document Server

    Rao, Riccardo; Esposito, Massimiliano

    2015-01-01

    We describe the oligosaccharides-exchange dynamics performed by so-called D-enzymes on polysaccharides. To mimic physiological conditions, we treat this process as an open chemical network by assuming some of the polymer concentrations fixed (chemostatting). We show that three different long-time behaviors may ensue: equilibrium states, nonequilibrium steady states, and continuous growth states. We dynamically and thermodynamically characterize these states and emphasize the crucial role of conservation laws in identifying the chemostatting conditions inducing them.

  12. Ozonation of benzothiazole saturated-activated carbons: Influence of carbon chemical surface properties

    Energy Technology Data Exchange (ETDEWEB)

    Valdes, H. [Facultad de Ingenieria, Universidad Catolica de la Santisima Concepcion, Caupolican 491, Concepcion (Chile)]. E-mail: hvaldes@ucsc.cl; Zaror, C.A. [Departamento de Ingenieria Quimica (F. Ingenieria), Universidad de Concepcion, Correo 3, Casilla 160-C, Concepcion (Chile)

    2006-09-21

    The combined or sequential use of ozone and activated carbon to treat toxic effluents has increased in recent years. However, little is known about the influence of carbon surface active sites on ozonation of organic adsorbed pollutants. This paper presents experimental results on the effect of metal oxides and oxygenated surface groups on gaseous ozonation of spent activated carbons. Benzothiazole (BT) was selected as a target organic compound in this study due to its environmental concern. Activated carbons with different chemical surface composition were prepared from a Filtrasorb-400 activated carbon. Pre-treatment included: ozonation, demineralisation, and deoxygenation of activated carbon. Ozonation experiments of BT saturated-activated carbons were conducted in a fixed bed reactor loaded with 2 g of carbon samples. The reactor was fed with an O{sub 2}/O{sub 3} gas mixture (2 dm{sup 3}/min, 5 g O{sub 3}/h), for a given exposure time, in the range 10-120 min, at 298 K and 1 atm. Results show that extended gaseous ozonation of activated carbon saturated with BT led to the effective destruction of the adsorbate by oxidation reactions. Oxidation of BT adsorbed on activated carbon seemed to occur via both direct reaction with ozone molecules, and by oxygen radical species generated by catalytic ozone decomposition on metallic surface sites.

  13. Transverse relaxation in the rotating frame induced by chemical exchange

    Science.gov (United States)

    Michaeli, Shalom; Sorce, Dennis J.; Idiyatullin, Djaudat; Ugurbil, Kamil; Garwood, Michael

    2004-08-01

    In the presence of radiofrequency irradiation, relaxation of magnetization aligned with the effective magnetic field is characterized by the time constant T1 ρ. On the other hand, the time constant T2 ρ characterizes the relaxation of magnetization that is perpendicular to the effective field. Here, it is shown that T2 ρ can be measured directly with Carr-Purcell sequences composed of a train of adiabatic full-passage (AFP) pulses. During adiabatic rotation, T2 ρ characterizes the relaxation of the magnetization, which under adiabatic conditions remains approximately perpendicular to the time-dependent effective field. Theory is derived to describe the influence of chemical exchange on T2 ρ relaxation in the fast-exchange regime, with time constant defined as T2 ρ,ex . The derived theory predicts the rate constant R 2ρ, ex (=1/T 2ρ, ex) to be dependent on the choice of amplitude- and frequency-modulation functions used in the AFP pulses. Measurements of R2 ρ,ex of the water/ethanol exchanging system confirm the predicted dependence on modulation functions. The described theoretical framework and adiabatic methods represent new tools to probe exchanging systems.

  14. Charge Exchange and Chemical Reactions with Trapped Th$^{3+}$

    CERN Document Server

    Churchill, L R; Chapman, M S

    2010-01-01

    We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th$^{3+}$ make them more prone to loss. Our results show that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide. Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the internal electronic configuration of the Th$^{3+}$.

  15. Advances in boron-10 isotope separation by chemical exchange distillation

    Energy Technology Data Exchange (ETDEWEB)

    Song Shuang, E-mail: chengruoyu2@sina.co [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Mu Yujun; Li Xiaofeng; Bai Peng [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2010-01-15

    Advances in boron-10 isotope separation by chemical exchange distillation are reviewed in this article. With a brief introduction of the principle of the separation, the progress on the research of this method and the problems relating to the separation coefficient are discussed. Several new donors, including nitromethane, acetone, methyl isobutyl ketone (MIBK) and diisobutyl ketone (DIBK), which have large separation factors are introduced. The complexes of these new donors and boron trifluoride (BF{sub 3}) are more stable than those of using the donors examined before. Among these new donors nitromethane could be a promising substitute for donors in present use to develop new technology of separating boron-10.

  16. Balanced Steady-State Free Precession (bSSFP) from an effective field perspective: Application to the detection of chemical exchange (bSSFPX)

    Science.gov (United States)

    Zhang, Shu; Liu, Zheng; Grant, Aaron; Keupp, Jochen; Lenkinski, Robert E.; Vinogradov, Elena

    2017-02-01

    Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence. The bSSFP in itself is sensitive to the exchange processes; hence, no additional saturation or preparation is needed for CEST-like data acquisition. The bSSFP experiment can be regarded as observation during saturation, without separate saturation and acquisition modules as used in standard CEST and similar experiments. One of the differences from standard CEST methods is that the bSSFP spectrum is an XY-spectrum not a Z-spectrum. As the first proof-of-principle step, we have implemented the steady-state bSSFP sequence for chemical exchange detection (bSSFPX) and verified its feasibility in phantom studies. These studies have shown that bSSFPX can achieve exchange-mediated contrast comparable to the standard CEST experiment. Therefore, the bSSFPX method has a potential for fast and quantitative CEST data acquisition.

  17. Oxidative weathering chemical migration under variably saturated conditions and supergene copper enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Pruess, K.; Brimhall, G.

    1999-04-01

    Transport of oxygen gas from the land surface through an unsaturated zone has a strong influence on oxidative weathering processes. Oxidation of sulfide minerals such as pyrite (FeS{sub 2}), one of the most common naturally occurring minerals, is the primary source of acid drainage from mines and waste rock piles. Here we present a detailed numerical model of supergene copper enrichment that involves the oxidative weathering of pyrite (FeS{sub 2}) and chalcopyrite (CuFeS{sub 2}), and acidification that causes mobilization of metals in the unsaturated zone, with subsequent formation of enriched ore deposits of chalcocite (CuS) and covellite (Cu{sub 2}S) in the reducing conditions below the water table. We examine and identify some significant conceptual and computational issues regarding the oxidative weathering processes through the modeling tool. The dissolution of gaseous oxygen induced by the oxidation reduces oxygen partial pressure, as well as the total pressure of the gas phase. As a result, the gas flow is modified, then the liquid phase flow. Results indicate that this reaction effect on the fluid flow may not be important under ambient conditions, and gas diffusion can be a more important mechanism for oxygen supply than gas or liquid advection. Acidification, mobilization of metals, and alteration of primary minerals mostly take place in unsaturated zone (oxidizing), while precipitation of secondary minerals mainly occurs in saturated zone (reducing). The water table may be considered as an interface between oxidizing and reducing zones. Moving water table due to change of infiltration results in moving oxidizing zone and redistributing aqueous chemical constitutes and secondary mineral deposits. The oxidative weathering processes are difficult to model numerically, because concentrations of redox sensitive chemical species such as O{sub 2}(aq), SO{sub 4}{sup 2-} and HS{sup -} may change over tens of orders of magnitude between oxidizing and reducing

  18. Pore-scale modeling of vapor transport in partially saturated capillary tube with variable area using chemical potential

    DEFF Research Database (Denmark)

    Addassi, Mouadh; Schreyer, Lynn; Johannesson, Björn

    2016-01-01

    Here we illustrate the usefulness of using the chemical potential as the primary unknown by modeling isothermal vapor transport through a partially saturated cylindrically symmetric capillary tube of variable cross-sectional area using a single equation. There are no fitting parameters...... of the Fick-Jacobs equation. We thus conclude that for a single, axisymmetric pore, the enhancement factor depends upon relative humidity boundary conditions at the liquid bridge interfaces, distance between liquid bridges, and bridge lengths....

  19. Tailoring exchange bias through chemical order in epitaxial FePt3 films

    Science.gov (United States)

    Saerbeck, T.; Zhu, H.; Lott, D.; Lee, H.; LeClair, P. R.; Mankey, G. J.; Stampfl, A. P. J.; Klose, F.

    2013-07-01

    Intentional introduction of chemical disorder into mono-stoichiometric epitaxial FePt3 films allows to create a ferro-/antiferromagnetic two-phase system, which shows a pronounced and controllable exchange bias effect. In contrast to conventional exchange bias systems, granular magnetic interfaces are created within the same crystallographic structure by local variation of chemical order. The amount of the exchange bias can be controlled by the relative amount and size of ferromagnetic and antiferromagnetic volume fractions and the interface between them. The tailoring of the magnetic composition alone, without affecting the chemical and structural compositions, opens the way to study granular magnetic exchange bias concepts separated from structural artifacts.

  20. In vivo chemical exchange saturation transfer imaging allows early detection of a therapeutic response in glioblastoma.

    Science.gov (United States)

    Sagiyama, Koji; Mashimo, Tomoyuki; Togao, Osamu; Vemireddy, Vamsidhara; Hatanpaa, Kimmo J; Maher, Elizabeth A; Mickey, Bruce E; Pan, Edward; Sherry, A Dean; Bachoo, Robert M; Takahashi, Masaya

    2014-03-25

    Glioblastoma multiforme (GBM), which account for more than 50% of all gliomas, is among the deadliest of all human cancers. Given the dismal prognosis of GBM, it would be advantageous to identify early biomarkers of a response to therapy to avoid continuing ineffective treatments and to initiate other therapeutic strategies. The present in vivo longitudinal study in an orthotopic mouse model demonstrates quantitative assessment of early treatment response during short-term chemotherapy with temozolomide (TMZ) by amide proton transfer (APT) imaging. In a GBM line, only one course of TMZ (3 d exposure and 4 d rest) at a dose of 80 mg/kg resulted in substantial reduction in APT signal compared with untreated control animals, in which the APT signal continued to increase. Although there were no detectable differences in tumor volume, cell density, or apoptosis rate between groups, levels of Ki67 (index of cell proliferation) were substantially reduced in treated tumors. In another TMZ-resistant GBM line, the APT signal and levels of Ki67 increased despite the same course of TMZ treatment. As metabolite changes are known to occur early in the time course of chemotherapy and precede morphologic changes, these results suggest that the APT signal in glioma may be a useful functional biomarker of treatment response or degree of tumor progression. Thus, APT imaging may serve as a sensitive biomarker of early treatment response and could potentially replace invasive biopsies to provide a definitive diagnosis. This would have a major impact on the clinical management of patients with glioma.

  1. The serum LDL/HDL cholesterol ratio is influenced more favorably by exchanging saturated with unsaturated fat than by reducing saturated fat in the diet of women.

    Science.gov (United States)

    Müller, Hanne; Lindman, Anja S; Brantsaeter, Anne Lise; Pedersen, Jan I

    2003-01-01

    We compared the effects of a high fat diet [38.4% of energy (E%) from fat; HSAFA diet, polyunsaturated/saturated fatty acid (P/S) ratio = 0.14], a low fat diet (19.7 E% from fat; LSAFA diet, P/S = 0.17), both based on coconut oil, and a diet with a high content of mono- and polyunsaturated fatty acids (PUFA; 38.2 E% from fat; HUFA diet, P/S = 1.9) on serum lipoproteins. The 25 women studied consumed each diet for 3-wk periods in a crossover design. The two high fat diets were identical except for the quality of the test fat. The LSAFA diet was identical to the HSAFA diet except that half the fat was replaced by carbohydrates. Serum total cholesterol, LDL cholesterol and apoB concentrations did not differ between the HSAFA and the LSAFA diet periods. Total cholesterol, LDL cholesterol and apoB were lower when women consumed the HUFA diet than when they consumed the other two diets. HDL cholesterol and apoA-I were 15 and 11%, respectively, higher when women consumed the HSAFA diet than when they consumed the LSAFA diet; HDL cholesterol and apoA-I were lower when women consumed the HUFA diet than when they consumed the HSAFA diet, but not the LSAFA diet. The LDL cholesterol/HDL cholesterol and apoB/apoA-I ratios were higher when women consumed the LSAFA diet than when they consumed the HSAFA diet. The LDL/HDL cholesterol ratio was higher when women consumed either the LSAFA or the HSAFA diet than when they consumed the HUFA diet, whereas apoB/apoA-I was higher when women consumed the LSAFA diet than when they consumed the HUFA diet. Triacylglycerol and VLDL cholesterol were higher when women consumed the LSAFA diet than when they consumed either the HSAFA or the HUFA diet. We conclude that, to influence the LDL/HDL cholesterol ratio, changing the proportions of dietary fatty acids may be more important than restricting the percentage of total or saturated fat energy, at least when derived mainly from lauric and myristic acids, both of which increase HDL cholesterol.

  2. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Science.gov (United States)

    2010-01-01

    ... purification and electrolytic cells for reducing the uranium U+6 or U+4 to U+3. These systems produce uranium... designed or prepared electrochemical reduction cells to reduce uranium from one valence state to another for uranium enrichment using the chemical exchange process. The cell materials in contact with...

  3. Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin

    Science.gov (United States)

    Ramana Murthy, K. V.; Ranganayakulu, C.; Ashok Babu, T. P.

    2017-01-01

    This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops.

  4. Chemical characteristics and enzymatic saccharification of lignocellulosic biomass treated using high-temperature saturated steam: comparison of softwood and hardwood.

    Science.gov (United States)

    Asada, Chikako; Sasaki, Chizuru; Hirano, Takeshi; Nakamura, Yoshitoshi

    2015-04-01

    This study investigated the effect of high-temperature saturated steam treatments on the chemical characteristics and enzymatic saccharification of softwood and hardwood. The weight loss and chemical modification of cedar and beech wood pieces treated at 25, 35, and 45 atm for 5 min were determined. Fourier transform infrared and X-ray diffraction analyses indicated that solubilization and removal of hemicellulose and lignin occurred by the steam treatment. The milling treatment of steam-treated wood enhanced its enzymatic saccharification. Maximum enzymatic saccharification (i.e., 94% saccharification rate of cellulose) was obtained using steam-treated beech at 35 atm for 5 min followed by milling treatment for 1 min. However, the necessity of the milling treatment for efficient enzymatic saccharification is dependent on the wood species.

  5. The Prediction of the Saturated Activity of 26Al in Non-Antarctic Stony Meteorites from their Chemical Compositions

    Science.gov (United States)

    Keith, J. E.; Heydegger, H. R.

    1992-07-01

    We have assembled from the literature a database of over 300 non-Antarctic stony meteorites, containing information about their chemical composition, date of fall, total mass, and gas exposure age, etc. We have developed an iterative algorithm using weighted linear multivariate regression, which surveys all the independent variables in the database, recommends the best 26 models (combinations of variables) for the prediction of Al activity, and using those models, performs weighted linear multivariate regressions. By requiring that the residuals be normally distributed, under- and super-saturated meteorites are discovered and eliminated. This process is iterated until a stable solution is obtained. As a result, we obtained a set of 128 saturated, 50 unsaturated, and 10 supersaturated meteorites. We find that the expression: ^26Al = (5.28+-0.81) . Al + (2.59+- 0.06) . Si + (1.57+-0.39) . S + (1.52+-0.59) . Ca, Chi^2(sub)nu = 2.59, where the elemental concentration is given in weight 26%, is the best predictor of the saturated ^26Al content of a stony meteorite. We find no evidence of bias or crippling multicollinearity in this expression. About one half of the remaining variability cannot be attributed to uncertainties in the determination of the ^26Al content and thus must be attributed to variations in orbit, shielding, etc. We compare our results (see figure) with those of other workers (1,2,3,4), and examine the probable causes of the disagreements displayed there. We show that saturated ^26Al is distributed among all classes of meteorites in about the same way, with the exception of the carbonaceous chondrites and the eucrites, which both have about the same excess proportion of unsaturation. We examine the question of the convergence of expressions derived from regressions on chemical composition to the predictive expressions derived from integrals of particle fluxes and nuclear reaction cross sections and show that they need not converge. We examine the

  6. Staff exchange with Chemical Waste Management. Final project report

    Energy Technology Data Exchange (ETDEWEB)

    Harrer, B.J.; Barak, D.W.

    1993-12-01

    Original objective was transfer of PNL technology and expertise in computational chemistry and waste flow/treatment modeling to CWM. Identification and characterization of a broader portfolio of PNL`s environmental remediation technologies with high potential for rapid application became the focus of the exchange, which included E-mail exchanges. Of the 14 technologies discussed, the following were identified as being of high interest to CWM: six phase soil heating (in-situ heating), high energy electrical corona, RAAS/ReOpt{trademark} (remedial, expert system), TEES{trademark} (catalytic production of methane from biological wastes), PST (process for treating petroleum sludge). CWM`s reorganization and downsizing reduced the potential benefits to industry, but a proposal for transfer and application of PST to Wheelabrator was made.

  7. Calculation of two-dimensional infrared spectra of ultrafast chemical exchange with numerical Langevin simulations

    NARCIS (Netherlands)

    Jansen, Thomas la Cour; Knoester, Jasper

    2007-01-01

    We combine numerical Langevin simulations with numerical integration of the Schrodinger equation to calculate two-dimensional infrared spectra of ultrafast chemical exchange. This provides a tool to model and interpret such spectra of molecules undergoing chemical processes, such as isomerization an

  8. Aquatic toxicity testing of liquid hydrophobic chemicals – Passive dosing exactly at the saturation limit

    DEFF Research Database (Denmark)

    Stibany, Felix; Nørgaard Schmidt, Stine; Schäffer, Andreas;

    2017-01-01

    inhibition tests with green algae Raphidocelis subcapitata. Growth rate inhibition at DDB solubility was 13 ± 5% (95% CI) in a first and 8 ± 3% (95% CI) in a repeated test, which demonstrated that improved exposure control can lead to good precision and repeatability of toxicity tests. This moderate toxicity......The aims of the present study were (1) to develop a passive dosing approach for aquatic toxicity testing of liquid substances with very high Kow values and (2) to apply this approach to the model substance dodecylbenzene (DDB, Log Kow = 8.65). The first step was to design a new passive dosing...... at chemical activity of unity was higher than expected relative to a reported hydrophobicity cut-off in toxicity, but lower than expected relative to a reported chemical activity range for baseline toxicity. The present study introduces a new effective approach for toxicity testing of an important group...

  9. Preliminary Assessment of Mercury Atmosphere-Surface Exchange Parameterizations for Incorporation into Chemical Transport Models

    Science.gov (United States)

    Khan, T.; Agnan, Y.; Obrist, D.; Selin, N. E.; Urban, N. R.; Wu, S.; Perlinger, J. A.

    2015-12-01

    Inadequate representation of process-based mechanisms of exchange behavior of elemental mercury (Hg0) and decoupled treatment of deposition and emission are two major limitations of parameterizations of atmosphere-surface exchange flux commonly incorporated into chemical transport models (CTMs). Of nineteen CTMs for Hg0 exchange we reviewed (ten global, nine regional), eight global and seven regional models have decoupled treatment of Hg0 deposition and emission, two global models include no parameterization to account for emission, and the remaining two regional models include coupled deposition and emission parameterizations (i.e., net atmosphere-surface exchange). The performance of atmosphere-surface exchange parameterizations in CTMs depends on parameterization uncertainty (in terms of both accuracy and precision) and feasibility of implementation. We provide a comparison of the performance of three available parameterizations of net atmosphere-surface exchange. To evaluate parameterization accuracy, we compare predicted exchange fluxes to field measurements conducted over a variety of surfaces compiled in a recently developed global database of terrestrial Hg0 surface-atmosphere exchange flux measurements. To assess precision, we estimate the sensitivity of predicted fluxes to the imprecision in parameter input values, and compare this sensitivity to that derived from analysis of the global Hg0 flux database. Feasibility of implementation is evaluated according to the availability of input parameters, computational requirements, and the adequacy of uncertainty representation. Based on this assessment, we provide suggestions for improved treatment of Hg0 net exchange processes in CTMs.

  10. Effects of mechanical dispersion on the morphological evolution of a chemical dissolution front in a fluid-saturated porous medium

    Science.gov (United States)

    Chen, Jui-Sheng; Liu, Chen-Wuing; Lai, Geng-Xin; Ni, Chuen-Fa

    2009-06-01

    SummaryThe dissolution-induced finger or wormhole patterns in porous medium or fracture rock play a crucial role in a variety of scientific, industrial, and engineering practices. Although previous studies have extensively presented a number of numerical models which couples a system of nonlinear governing equations of porosity change due to mineral dissolution, the conservations of groundwater flow and transport of chemical species to investigate the morphological pattern of a chemical dissolution front within a fluid-saturated porous medium, whereas the mechanical dispersion effect has generally been neglected in the model development. This study addresses the effects of mechanical dispersion on the morphological evolution of a chemical dissolution front for a variety of cases. Mechanical dispersion processes is incorporated with the coupled nonlinear governing equation system so as to rebuild a newly numerical model. The results of numerical simulations demonstrate that mechanical dispersion has pronounced impacts on the morphological pattern of the chemical dissolution front. For single local non-uniformity case, mechanical dispersion reduces the finger length of an unstable single-fingering front or retains the shape of a stable planar front while speeding up the front advancement. In the case of two local non-uniformities, adding mechanical dispersion with different flow conditions can yield one of the following results: (1) the shape of the stable planar front is maintained but its advancement is accelerated; (2) the shape of the unstable single-fingering front is maintained but its length is reduced; (3) the unstable double-fingering front is merged into an unstable single-fingering front; and (4) the shape of the unstable double-fingering front is preserved but its fingering length is reduced. A comparison between the behavior diagrams of dissolution front morphology (with and without considering mechanical dispersion) shows that the double-fingering front

  11. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    Science.gov (United States)

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-10-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X-100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

  12. Saturation-recovery metabolic‐exchange rate imaging with hyperpolarized [1‐13C] pyruvate using spectral‐spatial excitation

    DEFF Research Database (Denmark)

    Schulte, Rolf F.; Sperl, Jonathan I.; Weidl, Eliane

    2013-01-01

    Within the last decade hyperpolarized [1‐13C] pyruvate chemical‐shift imaging has demonstrated impressive potential for metabolic MR imaging for a wide range of applications in oncology, cardiology, and neurology. In this work, a highly efficient pulse sequence is described for time......‐recovery” scheme with the detected signal content being determined by forward conversion of the available pyruvate. In case of repetitive excitations, the polarization is preserved using smaller flip angles for pyruvate. Metabolic exchange rates are determined spatially resolved from the metabolite images using...

  13. Solidification of ion exchange resins saturated with Na+ ions: Comparison of matrices based on Portland and blast furnace slag cement

    Science.gov (United States)

    Lafond, E.; Cau dit Coumes, C.; Gauffinet, S.; Chartier, D.; Stefan, L.; Le Bescop, P.

    2017-01-01

    This work is devoted to the conditioning of ion exchange resins used to decontaminate radioactive effluents. Calcium silicate cements may have a good potential to encapsulate spent resins. However, certain combinations of cement and resins produce a strong expansion of the final product, possibly leading to its full disintegration. The focus is placed on the understanding of the behaviour of cationic resins in the Na+ form in Portland or blast furnace slag (CEM III/C) cement pastes. During hydration of the Portland cement paste, the pore solution exhibits a decrease in its osmotic pressure, which causes a transient expansion of small magnitude of the resins. At 20 °C, this expansion takes place just after setting in a poorly consolidated material and is sufficient to induce cracks. In the CEM III/C paste, swelling of the resins also occurs, but before the end of setting, and induces limited stress in the matrix which is still plastic.

  14. Dual temperature dual pressure water-hydrogen chemical exchange for water detritiation

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Takahiko, E-mail: t-sugiyama@nucl.nagoya-u.ac.jp [Faculty of Engineering, Nagoya University, Fro-cho 1, Chikusa-ku, Nagoya 464-8603 (Japan); Takada, Akito; Morita, Youhei [Faculty of Engineering, Nagoya University, Fro-cho 1, Chikusa-ku, Nagoya 464-8603 (Japan); Kotoh, Kenji [Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395 (Japan); Munakata, Kenzo [Faculty of Engineering and Resource Science, Akita University, Tegata-gakuen-machi 1-1, Akita 010-8502 (Japan); Taguchi, Akira [Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555 (Japan); Kawano, Takao; Tanaka, Masahiro; Akata, Naofumi [National Institute for Fusion Science, Oroshi-cho 322-6, Toki, Gifu 509-5292 (Japan)

    2015-10-15

    Experimental and analytical studies on hydrogen-tritium isotope separation by a dual temperature dual pressure catalytic exchange (DTDP-CE) with liquid phase chemical exchange columns were carried out in order to apply it to a part of the water detritiation system for DEMO fuel cycle. A prototype DTDP-CE apparatus was successfully operated and it was confirmed that tritium was separated by the apparatus as significantly distinguishable. A calculation code was developed based on the channeling stage model. The values of separation factors and the effects of some operating parameters were well predicted by the separative analyses with the code.

  15. EXCHANGE

    Energy Technology Data Exchange (ETDEWEB)

    Boltz, J.C. (ed.)

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  16. Development of a food-exchange model to replace saturated fat with MUFAs and n-6 PUFAs in adults at moderate cardiovascular risk.

    Science.gov (United States)

    Weech, Michelle; Vafeiadou, Katerina; Hasaj, Marinela; Todd, Susan; Yaqoob, Parveen; Jackson, Kim G; Lovegrove, Julie A

    2014-06-01

    The recommendation to reduce saturated fatty acid (SFA) consumption to ≤10% of total energy (%TE) is a key public health target aimed at lowering cardiovascular disease (CVD) risk. Replacement of SFA with unsaturated fats may provide greater benefit than replacement with carbohydrates, yet the optimal type of fat is unclear. The aim of the DIVAS (Dietary Intervention and Vascular Function) study was to develop a flexible food-exchange model to investigate the effects of substituting SFAs with monounsaturated fatty acids (MUFAs) or n-6 (ω-6) polyunsaturated fatty acids (PUFAs) on CVD risk factors. In this parallel study, UK adults aged 21-60 y with moderate CVD risk (50% greater than the population mean) were identified using a risk assessment tool (n = 195; 56% females). Three 16-wk isoenergetic diets of specific fatty acid (FA) composition (%TE SFA:%TE MUFA:%TE n-6 PUFA) were designed using spreads, oils, dairy products, and snacks as follows: 1) SFA-rich diet (17:11:4; n = 65); 2) MUFA-rich diet (9:19:4; n = 64); and 3) n-6 PUFA-rich diet (9:13:10; n = 66). Each diet provided 36%TE total fat. Dietary targets were broadly met for all intervention groups, reaching 17.6 ± 0.4%TE SFA, 18.5 ± 0.3%TE MUFA, and 10.4 ± 0.3%TE n-6 PUFA in the respective diets, with significant overall diet effects for the changes in SFAs, MUFAs, and n-6 PUFAs between groups (P < 0.001). There were no differences in the changes of total fat, protein, carbohydrate, and alcohol intake or anthropometric measures between groups. Plasma phospholipid FA composition showed changes from baseline in the proportions of total SFAs, MUFAs, and n-6 PUFAs for each diet group, with the changes in SFAs and MUFAs differing between the groups (P < 0.001). In conclusion, successful implementation of the food-exchange model broadly achieved the dietary target intakes for the exchange of SFAs with MUFAs or n-6 PUFAs with minimal disruption to the overall diet in a free-living population. This trial was

  17. A Passively Mode-Locked Diode-End-Pumped Nd:YAG Laser with a Semiconductor Saturable Absorber Mirror Grown by Metal Organic Chemical Vapour Deposition

    Institute of Scientific and Technical Information of China (English)

    王勇刚; 马骁宇; 李春勇; 张治国; 张丙元; 张志刚

    2003-01-01

    We report the experimental results of a mode-locked diode-end-pumped Nd:YAG laser with a semiconductor saturable absorber mirror(SESAM)from which we achieved a 10ps pulse duration at 150MHz repetition rate.The SESAM was grown by metal organic chemical vapour deposition at low temperature.The recovery time was measured to be 0.5 ps,indicating the potential pulse compression to sub-picoseconds.

  18. Assessing Soil Available Potassium by Cation Exchange Membrane and COnventional Chemical Extractions

    Institute of Scientific and Technical Information of China (English)

    LIUZHAOHUI; J.SCHOENAU; 等

    1999-01-01

    Four testing methods using cation exchange membrane (CEM),ammonium acetate,ASI(0.25mol L-1 NaHCO3+0.01mol L-1 EDTA +0.01 molL-1 NH4F) and 1.0molL-1 boiling nitric acid,respectively,were used to evaluate soil available K.The soil K tested by CEM was significantly correlated with that by the other (conventional)methods(r2=0.43**-0.95***).The soil K tested by CEM saturated with NH4HCO3(15min extraction)was most closely correlated with that by the other methods(r2=0.60**-0.95***),Potassium availability,as predicted by soil test,was comparable to actual K uptake by canola and wheat grown on the soils in growth chamber.Regression analyses showed that plant K uptake was more closely correlated wiht K extracted by CEM(r2=0.56**-0.81***)than that by the conventional methods(r2=0.46***-0.81***),most colsely correlated with that by NH4HCO3-saturated CEM for 15 min (r2=0.81***).and worst correlated with that by HNO3(r2=0.45**-0.72***)

  19. Impact of sediment-seawater cation exchange on Himalayan chemical weathering fluxes

    Science.gov (United States)

    Lupker, Maarten; France-Lanord, Christian; Lartiges, Bruno

    2016-08-01

    Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga-Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga-Brahmaputra is estimated ca. 6.5 meq 100 g-1. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28 × 109 mol yr-1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga-Brahmaputra is responsible for an additional Ca2+ flux of 23 × 109 mol yr-1, while ca. 27 × 109 mol yr-1 of Na+, 8 × 109 mol yr-1 of Mg2+ and 4 × 109 mol yr-1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na+ flux, 8 % of the dissolved K+ flux and 4 % of the Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment-seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and

  20. SirX: a selective inversion recovery experiment on X-nuclei for the determination of the exchange rate of slow chemical exchanges between two sites.

    Science.gov (United States)

    Xie, Xiulan; Bönisch, Friedrich

    2015-10-01

    Nuclear magnetic resonance spectroscopy has proven to be powerful for the study of dynamic processes. A new pulse sequence, SirX, is designed to provide boundary conditions that simplify the McConnell equations. Both an initial rate approximation and a whole curve fitting to the time course of magnetization can be used to calculate the exchange rate. These methods were used to study the exchange kinetics of N,N-dimethylacetamide. As compared with the well-established exchange spectroscopy suitable to studies of slow exchange, SirX has the advantage of being less time consuming and capable of providing more reliable kinetic data. Furthermore, by setting the observation on X-nuclei with larger chemical shift dispersion as compared with an observation on (1)H resonance, SirX extends the upper limit of a reliable determination of exchange rates.

  1. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

    Science.gov (United States)

    Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2016-08-01

    The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

  2. Ceramic Heat Exchangers and Chemical Reactors with Micro-Scale Features for In-Situ Resource Processing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — It is proposed to develop compact and lightweight ceramic heat exchangers and chemical reactors suitable for high temperature processes. These devices will have...

  3. Non-invasive imaging of infection after treatment with tumor-homing bacteria using chemical exchange saturation transfer (CEST) MRI

    Science.gov (United States)

    Liu, Guanshu; Bettegowda, Chetan; Qiao, Yuan; Staedtke, Verena; Chan, Kannie W.Y.; Bai, Renyuan; Li, Yuguo; Riggins, Gregory J.; Kinzler, Kenneth W.; Bulte, Jeff W.M.; McMahon, Michael T.; Gilad, Assaf A.; Vogelstein, Bert; Zhou, Shibin; van Zijl, Peter C.M.

    2013-01-01

    Purpose To develop a non-invasive MRI method for determining the germination and infection of tumor-homing bacteria in bacteriolytic cancer therapy using endogenous CEST contrast. Methods The CEST parameters of the anaerobic gram-positive bacterium Clostridium novyi-NT (C. novyi-NT) were first characterized in vitro, then used to detect C. novyi-NT germination and infection in subcutaneous CT26 colorectal tumor-bearing mice (n=6) after injection of 300 million bacterial spores. Lipopolysacharide (LPS) injected mice were used to exclude that the changes of CEST MRI were due to inflammation. Results CEST contrast was observed over a broad frequency range for bacterial suspensions in vitro, with the maximum contrast around 2.6 ppm from the water resonance. No signal could be detected for bacterial spores, demonstrating the specificity for germination. In vivo, a significant elevation of CEST contrast was identified in C. novyi-NT infected tumors as compared to those before bacterial germination and infection (p 0.05, n=4). Conclusions Endogenous bacterial CEST contrast (bacCEST) can be used to monitor the germination and proliferation of the therapeutic bacterium C. novyi-NT without a need for exogenous cell labeling probes. PMID:24123389

  4. Chemical vapor transport and solid-state exchange synthesis of new copper selenite bromides

    Science.gov (United States)

    Charkin, Dmitri O.; Kayukov, Roman A.; Zagidullin, Karim A.; Siidra, Oleg I.

    2017-02-01

    A new dimorphic copper selenite bromide, Cu5(SeO3)4Br2 was obtained via chemical transport reactions. α-Cu5(SeO3)4Br2, monoclinic (1m) and β-Cu5(SeO3)4Br2, triclinic (1a) polymorphs were produced simultaneously upon reaction of amorphous, partially dehydrated copper selenite and copper bromide. 1m is similar to Cu5(SeO3)4Cl2, whereas 1a is distantly related to Ni5(SeO3)4Br2 and Co5(SeO3)4Br2. Attempts to reproduce synthesis of 1a via exchange reaction between Na2SeO3 and CuBr2 resulted in a new Na2[Cu7O2](SeO3)4Br4 (2). Current study demonstrates for the first time, that both chemical vapor and exchange reactions can be employed in preparation of new selenite halides.

  5. Effect of chemical exchange on radiation damping in aqueous solutions of the osmolyte glycine.

    Science.gov (United States)

    Rodríguez, Juan Carlos; Jennings, Patricia A; Melacini, Giuseppe

    2002-06-05

    Radiation damping is of central relevance in NMR spectroscopy especially with the advent of ultrahigh-field magnets and of supersensitive probes. Furthermore, the recent realization that the combined effect of the distant dipole field and of radiation damping causes the resurrection of undesired crushed water magnetization emphasizes the need for a thorough understanding of all the factors affecting radiation damping. While the effects of pulsed-field gradients and of active feedback have been extensively investigated, the consequences on radiation damping of chemical exchange between water and co-solutes is not as well understood. Here it is demonstrated that the rate of water radiation damping is significantly affected by free glycine (Gly), a representative of an important class of biocompatible osmolytes often used at molar concentrations as protein stabilizers. The pH and temperature dependencies of this effect were investigated and rationalized in terms of radiation damping attenuation caused by incoherent dephasing occurring in the intermediate exchange regime. For instance, at pH 6.0 and at a temperature of 313 K the Gly NH3+/water exchange has the same dramatic effect on radiation damping as a series of repeated weak PFGs, increasing the water inversion-recovery zero-crossing delay from approximately 30 ms to approximately 2.3 s. In addition, under these conditions, the Gly NH3+/water exchange suppresses the resurrection of unwanted crushed water magnetization. When used in combination with PFGs and water flip-back schemes, glycine is therefore expected to tame chaotic dynamics and improve the reproducibility of the NMR experiments affected by it.

  6. Chemical and Isotopic Variations with Depth: a Detailed Saturated Zone Profile of a 140m Thick Coastal Aquifer

    Science.gov (United States)

    Raanan, H.; Ronen, D.; Weisbrod, N.; Dahan, O.; Seiler, K.; Vengosh, A.

    2005-12-01

    A percussion borehole was constructed through the saturated zone of the Mediterranean coastal aquifer in Tel Aviv, Israel, penetrating its three subaquifers and the upper part of the underlying Saqiye aquitard. The research site was previously subjected to direct industrial contamination and is currently exposed to the industrial contaminants in the outskirts of the densely populated Tel Aviv metropolis. Here we report the results of a large variety of analysis conducted on the 140m saturated profile that included field measurements (e.g. dissolved oxygen, pH, temperature, conductivity), major elements (e.g. Cl-, SO42-, HCO3-, NO3-, Ca2+, K+, Na+), trace elements (e.g. Pb, Fe, Cu) and radium isotopic measurements (223Ra, 224Ra, 226Ra). A clear distinction between the units becomes evident along the vertical profile; the upper phreatic unit (A) appears to be more saline relative to the central unit (B) (TDS of 734 and 670 mg/L, respectively). The deep unit (C) is significantly more saline in its lower part (up to 860 mg/L). We observed two nitrate peaks in the central zones of subaquifers B and C. The high nitrate peaks are associated with low Na/Cl and high Ca/Cl ratios. The 224Ra/223Ra ratio also changes with depth; in the upper and the lower subaquifers the relatively low 224Ra/223Ra ratios (50) indicates a larger fraction of a uranium source whereas in the central zone of the aquifer high 224Ra/223Ra ratios reflect rather a predominant thorium source for the dissolved radium. The data obtained through this borehole allows a rare investigation of the heterogeneity of water quality and composition in a coastal aquifer. The data provides characterization of different end-members along the saturated zone and also indicates the different proportions of lateral versus vertical flows of groundwater in a porous media.

  7. Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

    Indian Academy of Sciences (India)

    Samanwita Pal

    2010-07-01

    Chemical exchange in solution state has been investigated traditionally by both 1D and 2D NMR, permitting the extraction of kinetic parameters (e.g. the spin-lattice relaxation time 1, the exchange rate constant and the activation parameters). This work demonstrates a simple 1D NMR approach employing multiply selective excitation to study multi-site exchange processes in solution, applying it to systems that exhibit three-site exchange. This approach involves simultaneous excitation of all - or a chosen subset of - the exchanging sites by using an appropriately modulated shaped radiofrequency pulse. The pulse sequence, as well as analysis is summarized. Significant features of the experiment, which relies on sign labelling of the exchanging sites, include considerably shorter experiment time compared to standard 2D exchange work, clear definition of the exchange time window and uniform pulse non-ideality effects for all the exchanging sites. Complete kinetic information is reported in the study of dynamic processes in superacid solutions of two weak bases, studied by 1H NMR. An analytical solution, leading to the determination of four rate parameters, is presented for proton exchange studies on these systems, which involve a mixture of two weak bases in arbitrary concentration ratio, and stoichiometric excess of the superacid.

  8. Microbial, Physical and Chemical Drivers of COS and 18O-CO2 Exchange in Soils

    Science.gov (United States)

    Meredith, L. K.; Boye, K.; Whelan, M.; Pang, E.; von Sperber, C.; Brueggemann, N.; Berry, J. A.; Welander, P. V.

    2015-12-01

    Carbonyl sulfide (COS) and the oxygen isotope composition (δ18O) of CO2 are potential tools for differentiating the contributions of photosynthesis and respiration to the balance of global carbon cycling. These processes are coupled at the leaf level via the enzyme carbonic anhydrase (CA), which hydrolyzes CO2 in the first biochemical step of the photosynthetic pathway (CO2 + H2O ⇌ HCO3- + H+) and correspondingly structural analogue COS (COS + H2O → CO2 + H2S). CA also accelerates the exchange of oxygen isotopes between CO2 and H2O leading to a distinct isotopic imprint [1]. The biogeochemical cycles of these tracers include significant, yet poorly characterized soil processes that challenge their utility for probing the carbon cycle. In soils, microbial CA also hydrolyze COS and accelerate O isotope exchange between CO2 and soil water. Soils have been observed to emit COS by undetermined processes. To account for these soil processes, measurements are needed to identify the key microbial, chemical, and physical factors. In this study, we survey COS and δ18O exchange in twenty different soils spanning a variety of biomes and soil properties. By comparing COS fluxes and δ18O-CO2 values emitted from moist soils we investigate whether the same types of CA catalyze these two processes. Additionally, we seek to identify the potential chemical drivers of COS emissions by measuring COS fluxes in dry soils. These data are compared with soil physical (bulk density, volumetric water content, texture), chemical (pH, elemental analysis, sulfate, sulfur K-edge XANES), and microbial measurements (biomass and phylogeny). Furthermore, we determine the abundance and diversity of CA-encoding genes to directly link CA with measured soil function. This work will define the best predictors for COS fluxes and δ18O-CO2 values from our suite of biogeochemical measurements. The suitability of identified predictor variables can be tested in follow-up studies and applied for modeling

  9. An assessment of the relationship between potential chemical indices of nitrogen saturation and nitrogen deposition in hardwood forests in southern Ontario.

    Science.gov (United States)

    Watmough, Shaun A

    2010-05-01

    Southern Ontario receives the highest levels of atmospheric nitrogen (N) deposition in Canada and there are concerns that forests in the region may be approaching a state of 'N saturation'. In order to evaluate whether potential chemical indices provide evidence of N saturation, 23 hardwood plots were sampled along a modeled N-deposition gradient ranging from 9.3 to 12.8 kg/ha/year. All plots were dominated by sugar maple (Acer saccharum Marsh.) and foliar N and foliar delta(15)N were positively correlated with modeled N deposition. However, forest floor N content and the C:N ratio were unrelated to N deposition, but were instead related to soil pH and annual temperature; lower C:N ratios and higher N content in the forest floor were found at the most acidic sites in the cooler, northern part of the study region despite lower N deposition. Likewise, delta(15)N values in surface mineral soil and the (15)N enrichment factor of foliage (delta(15)N foliage - delta(15)N soil) are correlated to soil pH and temperature and not N deposition. Further, potential N mineralization, ammonification, and nitrification in Ontario maple stands were highest in the northern part of the region with the lowest modeled N deposition. Nitrogen cycling in soil appears to be primarily influenced by the N status of the forest floor and other soil properties rather than N deposition, indicating that chemical indices in soil in these hardwood plots may not provide an early indicator of N saturation.

  10. Dual Exchange in PCN-333: A Facile Strategy to Chemically Robust Mesoporous Chromium Metal-Organic Framework with Functional Groups.

    Science.gov (United States)

    Park, Jihye; Feng, Dawei; Zhou, Hong-Cai

    2015-09-16

    A facile preparation of a mesoporous Cr-MOF, PCN-333(Cr) with functional group, has been demonstrated through a dual exchange strategy, involving a sequential ligand exchange and metal metathesis process. After optimization of the exchange system, the functionalized PCN-333(Cr), N3-PCN-333(Cr) shows well maintained crystallinity, porosity, as well as much improved chemical stability. Because of the exceptionally large pores (∼5.5 nm) in PCN-333(Cr), a secondary functional moiety, Zn-TEPP with a size of 18 Å × 18 Å, has been successfully clicked into the framework. In this article, we have also analyzed kinetics and thermodynamics during dual exchange process, showing our attempts to interpret the exchange event in the PCN-333. Our findings not only provide a highly stable mesoporous Cr-MOF platform for expanding MOF-based applications, but also suggest a route to functionalized Cr-MOF which may have not been achievable through conventional approaches.

  11. Ion Exchange Equilibrium and Kinetic Properties of Polyacrylate Films and Applications to Chemical Analysis and Environmental Decontamination

    Science.gov (United States)

    Tanner, Stephen P.

    1997-01-01

    One of the goals of the original proposal was to study how cross-linking affects the properties of an ion exchange material(IEM) developed at Lewis Research Center. However, prior to the start of this work, other workers at LERC investigated the effect of cross-linking on the properties of this material. Other than variation in the ion exchange capacity, the chemical characteristics were shown to be independent of the cross-linking agent, and the degree of cross-linking. New physical forms of the film were developed (film, supported film, various sizes of beads, and powder). All showed similar properties with respect to ion exchange equilibria but the kinetics of ion exchange depended on the surface area per unit mass; the powder form of the IEM exchanging much more rapidly than the other forms. The research performed under this grant was directed towards the application of the IEM to the analysis of metal ions at environmental concentrations.

  12. Separation of selected stable isotopes by liquid-phase thermal diffusion and by chemical exchange

    Science.gov (United States)

    Rutherford, W. M.; Jepson, B. E.; Michaels, E. D.

    Useful applications of enriched stable nuclides are unduly restricted by high cost and limited availability. Recent research on liquid phase thermal diffusion (LTD) has resulted in practical processes for separating S34, CL35, and CL37 in significant quantities (100 to 500 g/yr) at costs much lower than those associated with the electromagnetic (Calutron) process. The separation of the isotopes of bromine by LTD is now in progress and BR79 is being produced in relatively simple equivalent at a rate on the order of 0.5 g/day. The results of recent measurements show that the isotopes of Zn can be separated by LTD of zinc alkyls. The isotopes of calcium can be separated by LTD and by chemical exchange. The LTD process is based on the use of aqueous Ca(NO3)2 as a working fluid.

  13. Ultrasensitive anion detection by NMR spectroscopy: a supramolecular strategy based on modulation of chemical exchange rate.

    Science.gov (United States)

    Perruchoud, Loïse H; Hadzovic, Alen; Zhang, Xiao-An

    2015-06-08

    NMR spectroscopy is a powerful tool for monitoring molecular interactions and is widely used to characterize supramolecular systems at the atomic level. NMR is limited for sensing purposes, however, due to low sensitivity. Dynamic processes such as conformational changes or binding events can induce drastic effects on NMR spectra in response to variations in chemical exchange (CE) rate, which can lead to new strategies in the design of supramolecular sensors through the control and monitoring of CE rate. Here, we present an indirect NMR anion sensing technique in which increased CE rate, due to anion-induced conformational flexibility of a relatively rigid structure of a novel sensor, allows ultrasensitive anion detection as low as 120 nM.

  14. Kinetic bottlenecks to chemical exchange rates for deep-sea animals – Part 1: Oxygen

    Directory of Open Access Journals (Sweden)

    E. T. Peltzer

    2012-10-01

    Full Text Available Ocean warming will reduce dissolved oxygen concentrations which can pose challenges to marine life. Oxygen limits are traditionally reported simply as a static concentration thresholds with no temperature, pressure or flow rate dependency. Here we treat the oceanic oxygen supply potential for heterotrophic consumption as a dynamic molecular exchange problem analogous to familiar gas exchange processes at the sea surface. A combination of the purely physico-chemical oceanic properties temperature, hydrostatic pressure, and oxygen concentration defines the ability of the ocean to supply oxygen to any given animal. This general oceanic oxygen supply potential is modulated by animal specific properties such as the diffusive boundary layer thickness to define and limit maximal oxygen supply rates. Here we combine all these properties into formal, mechanistic equations defining novel oceanic properties that subsume various relevant classical oceanographic parameters to better visualize, map, comprehend, and predict the impact of ocean deoxygenation on aerobic life. By explicitly including temperature and hydrostatic pressure into our quantities, various ocean regions ranging from the cold deep-sea to warm, coastal seas can be compared. We define purely physico-chemical quantities to describe the oceanic oxygen supply potential, but also quantities that contain organism-specific properties which in a most generalized way describe general concepts and dependencies. We apply these novel quantities to example oceanic profiles around the world and find that temperature and pressure dependencies of diffusion and partial pressure create zones of greatest physical constriction on oxygen supply typically at around 1000 m depth, which coincides with oxygen concentration minimum zones. In these zones, which comprise the bulk of the world ocean, ocean warming and deoxygenation have a clear negative effect for aerobic life. In some shallow and warm waters the

  15. Cation exchange on the nanoscale: an emerging technique for new material synthesis, device fabrication, and chemical sensing.

    Science.gov (United States)

    Rivest, Jessy B; Jain, Prashant K

    2013-01-01

    Cation exchange is an age-old technique for the chemical conversion of liquids or extended solids by place-exchanging the cations in an ionic material with a different set of cations. The technique is undergoing a major revival with the advent of high-quality nanocrystals: researchers are now able to overcome the limitations in bulk systems and fully exploit cation exchange for materials synthesis and discovery via rapid, low-temperature transformations in the solid state. In this tutorial review, we discuss cation exchange as a promising materials synthesis and discovery tool. Exchange on the nanoscale exhibits some unique attributes: rapid kinetics at room temperature (orders of magnitude faster than in the bulk) and the tuning of reactivity via control of nanocrystal size, shape, and surface faceting. These features make cation exchange a convenient tool for accessing nanocrystal compositions and morphologies for which conventional synthesis may not be established. A simple exchange reaction allows extension of nanochemistry to a larger part of the periodic table, beyond the typical gamut of II-VI, IV-VI, and III-V materials. Cation exchange transformations in nanocrystals can be topotactic and size- and shape-conserving, allowing nanocrystals synthesized by conventional methods to be used as templates for production of compositionally novel, multicomponent, or doped nanocrystals. Since phases and compositions resulting from an exchange reaction can be kinetically controlled, rather than governed by the phase diagram, nanocrystals of metastable and hitherto inaccessible compositions are attainable. Outside of materials synthesis, applications for cation exchange exist in water purification, chemical staining, and sensing. Since nanoscale cation exchange occurs rapidly at room temperature, it can be integrated with sensitive environments such as those in biological systems. Cation exchange is already allowing access to a variety of new materials and processes

  16. Heat and Mass Transfer by Unsteady Natural Convection over a Moving Vertical Plate Embedded in a Saturated Porous Medium with Chemical Reaction, Soret and Dufour Effects

    Directory of Open Access Journals (Sweden)

    A.M. Rashad

    2015-01-01

    Full Text Available The thermal-diffusion and diffusion-thermo effects on heat and mass transfer by transient free convection flow of over an impulsively started isothermal vertical plate embedded in a saturated porous medium were numerically investigated, considering a homogeneous chemical reaction of first order. The transient, nonlinear and coupled governing equations are solved using an implicit finite-difference scheme. The effects of various parameters on the transient velocity, temperature, and concentration profiles as well as heat and mass transfer rates are analyzed. Numerical results for the unsteady-state velocity, temperature and concentration profiles as well as the axial distributions and the time histories of the skin-friction coefficient, Nusselt number and the Sherwood number are presented graphically and discussed.

  17. Single domain SmCo5@Co exchange-coupled magnets prepared from core/shell Sm[Co(CN)6]·4H2O@GO particles: a novel chemical approach.

    Science.gov (United States)

    Yang, Ce; Jia, Lihui; Wang, Shouguo; Gao, Chen; Shi, Dawei; Hou, Yanglong; Gao, Song

    2013-12-20

    SmCo5 based magnets with smaller size and larger maximum energy product have been long desired in various fields such as renewable energy technology, electronic industry and aerospace science. However, conventional relatively rough synthetic strategies will lead to either diminished magnetic properties or irregular morphology, which hindered their wide applications. In this article, we present a facile chemical approach to prepare 200 nm single domain SmCo5@Co core/shell magnets with coercivity of 20.7 kOe and saturation magnetization of 82 emu/g. We found that the incorporation of GO sheets is responsible for the generation of the unique structure. The single domain SmCo5 core contributes to the large coercivity of the magnets and the exchange-coupled Co shell enhances the magnetization. This method can be further utilized in the synthesis other Sm-Co based exchange-coupled magnets.

  18. Novel Chemically Stable Er3+-Yb3+ Codopded Phosphate Glass for Ion-Exchanged Active Waveguide Devices

    Institute of Scientific and Technical Information of China (English)

    陈宝玉; 赵士龙; 胡丽丽

    2003-01-01

    A novel Er3+-Yb3+ codoped phosphate glass,which combines good chemical durability with good spectroscopic properties,is developed for the ion-exchange process.The relevant properties of this glass are presented for reference in the design and modelling of ion-exchanged active waveguide devices.The weight-loss rate of this glass is 1.45 × 10-5 g.cm-2.h-1 in boiling water,which is comparable to that of Kigre's Q-246 silicate glass.The emission cross section of Er3+ in this glass is calculated to be 0.72 × 10-20 cm2 using the McCumber theory.It is found that a planar waveguide with three modes at 632.8 nm is readily realized in this glass from our primary ion-exchange experiments.

  19. Ion Exchange Processed CdS Nanorods in Powder Form Using Cadmium Hydroxide Nanowires By Wet Chemical Route

    Directory of Open Access Journals (Sweden)

    Savita L. Patil

    2010-06-01

    Full Text Available Simple, inexpensive and soft chemical route (wet chemical method was employed for the synthesis of bulk forms of cadmium hydroxide [Cd(OH2] nanowires bundles and their conversion to cadmium sulphide [CdS] nanorods at room temperature by simple anion exchange route. Due to difference in solubility product and diffusion rates of the Cd(OH2 and CdS, the anion exchange reaction was taken place and CdS nanorods were formed. CdS nanorods were characterized by X-ray diffraction (XRD, and scanning electron microscopy (SEM, energy-dispersive X-ray (EDX analysis. Since CdS is semi-conducting material, it has variety of potential applications, this work demonstrates a cost effective method for the synthesis of CdS nanorods in bulk form like CNT.

  20. Chemical assessment of ballast water exchange compliance: Implementation in North America and New Zealand

    Directory of Open Access Journals (Sweden)

    Monaca eNoble

    2016-05-01

    Full Text Available Fluorescence by naturally occurring dissolved organic matter (FDOM is a sensitive indicator of ballast water source, with high FDOM in coastal ballast water decreasing typically dramatically when replaced by oceanic seawater during ballast water exchange. In this study, FDOM was measured in 92 ships arriving at Pacific ports on the US west coast and in New Zealand, and used to assess their compliance with ballast water regulations that required 95% replacement of port water to minimize invasive species risks. Fluorescence in many ships that reported ballast water exchange was significantly higher than is usual for oceanic seawater, and in several cases, significantly higher than in other ships with similar provenance and ballast water management. Pre-exchange source port conditions represented the largest source of uncertainty in the analysis, because residual coastal FDOM when highly fluorescent can significantly influence the fluorescence signature of exchanged ballast water. A meta-analysis comparing the intensities of FDOM in un-exchanged ballast tanks with calculated pre-exchange intensities assuming that ships all correctly implemented and reported ballast water exchange revealed notable discrepancies. Thus, the incidence of high-FDOM port waters was seven times lower in reality than would be expected on the basis of these calculations. The results suggest that a significant rate of reporting errors occur due to a combination of factors that may include inadequate ballast water exchange and unintentional or deliberate misreporting of ballast water management.

  1. Auto-FACE: an NMR based binding site mapping program for fast chemical exchange protein-ligand systems.

    Directory of Open Access Journals (Sweden)

    Janarthanan Krishnamoorthy

    Full Text Available BACKGROUND: Nuclear Magnetic Resonance (NMR spectroscopy offers a variety of experiments to study protein-ligand interactions at atomic resolution. Among these experiments, 15N Heteronuclear Single Quantum Correlation (HSQCexperiment is simple, less time consuming and highly informative in mapping the binding site of the ligand. The interpretation of 15N HSQC becomes ambiguous when the chemical shift perturbations are caused by non-specific interactions like allosteric changes and local structural rearrangement. Under such cases, detailed chemical exchange analysis based on chemical shift perturbation will assist in locating the binding site accurately. METHODOLOGY/PRINCIPAL FINDINGS: We have automated the mapping of binding sites for fast chemical exchange systems using information obtained from 15N HSQC spectra of protein serially titrated with ligand of increasing concentrations. The automated program Auto-FACE (Auto-FAst Chemical Exchange analyzer determines the parameters, e.g. rate of change of perturbation, binding equilibrium constant and magnitude of chemical shift perturbation to map the binding site residues.Interestingly, the rate of change of perturbation at lower ligand concentration is highly sensitive in differentiating the binding site residues from the non-binding site residues. To validate this program, the interaction between the protein hBcl(XL and the ligand BH3I-1 was studied. Residues in the hydrophobic BH3 binding groove of hBcl(XL were easily identified to be crucial for interaction with BH3I-1 from other residues that also exhibited perturbation. The geometrically averaged equilibrium constant (3.0 x 10(4 calculated for the residues present at the identified binding site is consistent with the values obtained by other techniques like isothermal calorimetry and fluorescence polarization assays (12.8 x 10(4. Adjacent to the primary site, an additional binding site was identified which had an affinity of 3.8 times weaker

  2. Wet chemical preparation and isotope exchange process of H/D-terminated Si(111) and Si(110) studied by adsorbate vibrational analysis

    Science.gov (United States)

    Kawamoto, Erina; Kang, Jungmin; Matsuda, Takuya; Yamada, Taro; Suto, Shozo

    2017-02-01

    A convenient procedure for preparing D-terminated Si(111)-(1×1) and Si(110)-(1×1) by wet chemical etching was developed and applied to the vibrational analysis of these surfaces by high-resolution electron-energy loss spectroscopy (HREELS). Fully H-terminated Si(111)/(110) was first prepared in regular 40% NH4F/H2O solution, followed by immersion in saturated KF/D2O solution. HREELS revealed partially D-terminated H:Si(111)/(110) with the amount of deuterium termination depending on the immersion time. A series of various immersion times revealed the H/D exchange reaction kinetics, which are associated with the Si substrate etching processes on Si(111) (step-flow etching) and Si(110) (zipper reaction). The H-Si and D-Si stretching vibration frequencies as functions of the surface D fraction did not appear to change on Si(111), but on Si(110) the H-Si signal red shifted at a high D fraction. This is due to the adsorbate-adsorbate interaction, which is more intense on Si(110) because of the short nearest-neighbor distance of the adsorbates.

  3. Investigation of the swelling behavior of cationic exchange resins saturated with Na{sup +} ions in a C{sub 3}S paste

    Energy Technology Data Exchange (ETDEWEB)

    Lafond, E. [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze cedex (France); Cau Dit Coumes, C., E-mail: celine.cau-dit-coumes@cea.fr [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze cedex (France); Gauffinet, S. [UMR5209 Institut Carnot de Bourgogne, Université de Bourgogne Dijon, Faculté des Sciences Mirande, 9 Avenue Alain Savary, BP 47870, 21078 Dijon cedex (France); Chartier, D. [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze cedex (France); Le Bescop, P. [CEA, DEN, DPC, SECR, F-91192 Gif-sur-Yvette (France); Stefan, L. [AREVA, Back End Business Group, Dismantling & Services, 1 place Jean Millier, 92084 Paris La Défense (France); Nonat, A. [UMR5209 Institut Carnot de Bourgogne, Université de Bourgogne Dijon, Faculté des Sciences Mirande, 9 Avenue Alain Savary, BP 47870, 21078 Dijon cedex (France)

    2015-03-15

    Ion exchange resins (IERs) are widely used by the nuclear industry to decontaminate radioactive effluents. Spent products are usually encapsulated in cementitious materials. However, the solidified waste form can exhibit strong expansion, possibly leading to cracking, if the appropriate binder is not used. In this work, the interactions between cationic resins in the Na{sup +} form and tricalcium silicate are investigated during the early stages of hydration in order to gain a better understanding of the expansion process. It is shown that the IERs exhibit a transient swelling of small magnitude due to the decrease in the osmotic pressure of the external solution. This expansion, which occurs just after setting, is sufficient to damage the material which is poorly consolidated for several reasons: low degree of hydration, precipitation of poorly cohesive sodium-bearing C–S–H, and very heterogeneous microstructure with zones of high porosity.

  4. Assessment of chemical exchange in tryptophan–albumin solution through {sup 19}F multicomponent transverse relaxation dispersion analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Ping-Chang, E-mail: pingchang.lin@howard.edu [Howard University, Department of Radiology, College of Medicine (United States)

    2015-06-15

    A number of NMR methods possess the capability of probing chemical exchange dynamics in solution. However, certain drawbacks limit the applications of these NMR approaches, particularly, to a complex system. Here, we propose a procedure that integrates the regularized nonnegative least squares (NNLS) analysis of multiexponential T{sub 2} relaxation into Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion experiments to probe chemical exchange in a multicompartmental system. The proposed procedure was validated through analysis of {sup 19}F T{sub 2} relaxation data of 6-fluoro-DL-tryptophan in a two-compartment solution with and without bovine serum albumin. Given the regularized NNLS analysis of a T{sub 2} relaxation curve acquired, for example, at the CPMG frequency υ{sub CPMG} = 125, the nature of two distinct peaks in the associated T{sub 2} distribution spectrum indicated 6-fluoro-DL-tryptophan either retaining the free state, with geometric mean */multiplicative standard deviation (MSD) = 1851.2 ms */1.51, or undergoing free/albumin-bound interconversion, with geometric mean */MSD = 236.8 ms */1.54, in the two-compartment system. Quantities of the individual tryptophan species were accurately reflected by the associated T{sub 2} peak areas, with an interconversion state-to-free state ratio of 0.45 ± 0.11. Furthermore, the CPMG relaxation dispersion analysis estimated the exchange rate between the free and albumin-bound states in this fluorinated tryptophan analog and the corresponding dissociation constant of the fluorinated tryptophan–albumin complex in the chemical-exchanging, two-compartment system.

  5. A Novel Ion Exchange System to Purify Mixed ISS Waste Water Brines for Chemical Production and Enhanced Water Recovery

    Science.gov (United States)

    Lunn, Griffin; Spencer, LaShelle; Ruby, Anna-Maria; McCaskill, Andrew

    2014-01-01

    Current International Space Station water recovery regimes produce a sizable portion of waste water brine. This brine is highly toxic and water recovery is poor: a highly wasteful proposition. With new biological techniques that do not require waste water chemical pretreatment, the resulting brine would be chromium-free and nitrate rich which can allow possible fertilizer recovery for future plant systems. Using a system of ion exchange resins we can remove hardness, sulfate, phosphate and nitrate from these brines to leave only sodium and potassium chloride. At this point modern chlor-alkali cells can be utilized to produce a low salt stream as well as an acid and base stream. The first stream can be used to gain higher water recovery through recycle to the water separation stage while the last two streams can be used to regenerate the ion exchange beds used here, as well as other ion exchange beds in the ISS. Conveniently these waste products from ion exchange regeneration would be suitable as plant fertilizer. In this report we go over the performance of state of the art resins designed for high selectivity of target ions under brine conditions. Using ersatz ISS waste water we can evaluate the performance of specific resins and calculate mass balances to determine resin effectiveness and process viability. If this system is feasible then we will be one step closer to closed loop environmental control and life support systems (ECLSS) for current or future applications.

  6. Ab initio study of the chemical states of water on Cr 2O 3(0 0 0 1): From the isolated molecule to saturation coverage

    Science.gov (United States)

    Costa, Dominique; Sharkas, Kamal; Islam, Mazharul M.; Marcus, Philippe

    2009-08-01

    The reactivity of the (0 0 0 1)-Cr-Cr 2O 3 surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H 2O/nm 2 to 14.1H 2O/nm 2, corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr 2O 3 surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H 2O/nm 2), 5 (9.4H 2O/nm 2) and 6 (14.1H 2O/nm 2). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H 2O/nm 2, the Cr-O s (surface oxygen) acid-base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H 2O/nm 2, molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H 2O/nm 2, 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are -Cr(OH) 2 and -Cr(OH) 3- like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr ( t2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the -Cr(OH) 3-like, -Cr(OH) 2 and anhydrous surfaces may be stabilized depending on ( T, P) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation.

  7. Mixed IR/Vis two-dimensional spectroscopy: chemical exchange beyond the vibrational lifetime and sub-ensemble selective photochemistry.

    Science.gov (United States)

    van Wilderen, Luuk J G W; Messmer, Andreas T; Bredenbeck, Jens

    2014-03-03

    Two-dimensional exchange spectroscopy (2D EXSY) is a powerful method to study the interconversion (chemical exchange) of molecular species in equilibrium. This method has recently been realized in femtosecond 2D-IR spectroscopy, dramatically increasing the time resolution. However, current implementations allow the EXSY signal (and therefore the chemical process of interest) only to be tracked during the lifetime (T1 ) of the observed spectroscopic transition. This is a severe limitation, as typical vibrational T1 are only a few ps. An IR/Vis pulse sequence is presented that overcomes this limit and makes the EXSY signal independent of T1 . The same pulse sequence allows to collect time-resolved IR spectra after electronic excitation of a particular chemical species in a mixture of species with strongly overlapping UV/Vis spectra. Different photoreaction pathways and dynamics of coexisting isomers or of species involved in different intermolecular interactions can thus be revealed, even if the species cannot be isolated because they are in rapid equilibrium.

  8. Magnetic isotope effect and theory of atomic orbital hybridization to predict a mechanism of chemical exchange reactions.

    Science.gov (United States)

    Epov, Vladimir N

    2011-08-07

    A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl(2) species and with several Ru(III) chloro-species, and highly positive for reactions of this ether with TeCl(6)(2-), and with several Cd(II) and Pd(II) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d(n)5s(m) electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions.

  9. General expressions for R1ρ relaxation for N-site chemical exchange and the special case of linear chains

    Science.gov (United States)

    Koss, Hans; Rance, Mark; Palmer, Arthur G.

    2017-01-01

    Exploration of dynamic processes in proteins and nucleic acids by spin-locking NMR experiments has been facilitated by the development of theoretical expressions for the R1ρ relaxation rate constant covering a variety of kinetic situations. Herein, we present a generalized approximation to the chemical exchange, Rex, component of R1ρ for arbitrary kinetic schemes, assuming the presence of a dominant major site population, derived from the negative reciprocal trace of the inverse Bloch-McConnell evolution matrix. This approximation is equivalent to first-order truncation of the characteristic polynomial derived from the Bloch-McConnell evolution matrix. For three- and four-site chemical exchange, the first-order approximations are sufficient to distinguish different kinetic schemes. We also introduce an approach to calculate R1ρ for linear N-site schemes, using the matrix determinant lemma to reduce the corresponding 3N × 3N Bloch-McConnell evolution matrix to a 3 × 3 matrix. The first- and second order-expansions of the determinant of this 3 × 3 matrix are closely related to previously derived equations for two-site exchange. The second-order approximations for linear N-site schemes can be used to obtain more accurate approximations for non-linear N-site schemes, such as triangular three-site or star four-site topologies. The expressions presented herein provide powerful means for the estimation of Rex contributions for both low (CEST-limit) and high (R1ρ-limit) radiofrequency field strengths, provided that the population of one state is dominant. The general nature of the new expressions allows for consideration of complex kinetic situations in the analysis of NMR spin relaxation data.

  10. Saturated fat (image)

    Science.gov (United States)

    Saturated fat can raise blood cholesterol and can put you at risk for heart disease and stroke. You ... or limit any foods that are high in saturated fat. Sources of saturated fat include whole-milk dairy ...

  11. Evidence of chemical exchange in recombinant Major Urinary Protein and quenching thereof upon pheromone binding

    Energy Technology Data Exchange (ETDEWEB)

    Perazzolo, Chiara, E-mail: Chiara.Perazzolo@epfl.ch; Verde, Mariachiara [Ecole Polytechnique Federale de Lausanne, Institut des Sciences et Ingenierie Chimiques (Switzerland); Homans, Steve W. [University of Leeds, Institute of Molecular and Cellular Biology (United Kingdom); Bodenhausen, Geoffrey [Ecole Polytechnique Federale de Lausanne, Institut des Sciences et Ingenierie Chimiques (Switzerland)

    2007-05-15

    The internal dynamics of recombinant Major Urinary Protein (rMUP) have been investigated by monitoring transverse nitrogen-15 relaxation using multiple-echo Carr-Purcell-Meiboom-Gill (CPMG) experiments. While the ligand-free protein (APO-rMUP) features extensive evidence of motions on the milliseconds time scale, the complex with 2-methoxy-3-isobutylpyrazine (HOLO-rMUP) appears to be much less mobile on this time scale. At 308 K, exchange rates k{sub ex} = 500-2000 s{sup -1} were typically observed in APO-rMUP for residues located adjacent to a {beta}-turn comprising residues 83-87. These residues occlude an entry to the binding pocket and have been proposed to be a portal for ligand entry in other members of the lipocalin family, such as the retinol binding protein and the human fatty-acid binding protein. Exchange rates and populations are largely uncorrelated, suggesting local 'breathing' motions rather than a concerted global conformational change.

  12. Advanced Technologies for Monitoring CO2 Saturation and Pore Pressure in Geologic Formations: Linking the Chemical and Physical Effects to Elastic and Transport Properties

    Energy Technology Data Exchange (ETDEWEB)

    Mavko, G.; Vanorio, T.; Vialle, S.; Saxena, N.

    2014-03-31

    Ultrasonic P- and S-wave velocities were measured over a range of confining pressures while injecting CO2 and brine into the samples. Pore fluid pressure was also varied and monitored together with porosity during injection. Effective medium models were developed to understand the mechanisms and impact of observed changes and to provide the means for implementation of the interpretation methodologies in the field. Ultrasonic P- and S-wave velocities in carbonate rocks show as much as 20-50% decrease after injection of the reactive CO2-brine mixture; the changes were caused by permanent changes to the rock elastic frame associated with dissolution of mineral. Velocity decreases were observed under both dry and fluid-saturated conditions, and the amount of change was correlated with the initial pore fabrics. Scanning Electron Microscope images of carbonate rock microstructures were taken before and after injection of CO2-rich water. The images reveal enlargement of the pores, dissolution of micrite (micron-scale calcite crystals), and pitting of grain surfaces caused by the fluid- solid chemical reactivity. The magnitude of the changes correlates with the rock microtexture – tight, high surface area samples showed the largest changes in permeability and smallest changes in porosity and elastic stiffness compared to those in rocks with looser texture and larger intergranular pore space. Changes to the pore space also occurred from flow of fine particles with the injected fluid. Carbonates with grain-coating materials, such as residual oil, experienced very little permanent change during injection. In the tight micrite/spar cement component, dissolution is controlled by diffusion: the mass transfer of products and reactants is thus slow and the fluid is expected to be close to thermodynamical equilibrium with the calcite, leading to very little dissolution, or even precipitation. In the microporous rounded micrite and macropores, dissolution is controlled by

  13. New avenues to efficient chemical synthesis of exchange coupled hard/soft nanocomposite magnet.

    Science.gov (United States)

    Lee, Don Keun; Cha, Hyun Gil; Kim, Young Hwan; Kim, Chang Woo; Ji, Eun Sun; Kang, Young Soo

    2009-07-01

    Nd-Fe-B ultrafine amorphous alloy particles were prepared by reaction of metal ions with borohydride in aqueous solution. Monodispersed Fe nanoparticles were synthesized under an argon atmosphere via thermal decomposition of Fe(2+)-oleate2. Exchange coupled Nd2Fe14B/Fe nanocomposite magnets have been prepared by self-assembly using surfactant. The crystal structure of the synthesized nanoparticles was identified by using X-ray powder diffraction (XRD). The size and shape of nanoparticles were obtained by transmission electron microscope (TEM). Thermogravimetry using a microbalance with magnetic field gradient positioned below the sample was used for the measurement of a thermomagnetic analysis (TMA) curve showing the downward magnetic force versus temperature.

  14. Electrical resistivity of substitutionally disordered hcp Fe-Si and Fe-Ni alloys: Chemically-induced resistivity saturation in the Earth's core

    Science.gov (United States)

    Gomi, Hitoshi; Hirose, Kei; Akai, Hisazumi; Fei, Yingwei

    2016-10-01

    The thermal conductivity of the Earth's core can be estimated from its electrical resistivity via the Wiedemann-Franz law. However, previously reported resistivity values are rather scattered, mainly due to the lack of knowledge with regard to resistivity saturation (violations of the Bloch-Grüneisen law and the Matthiessen's rule). Here we conducted high-pressure experiments and first-principles calculations in order to clarify the relationship between the resistivity saturation and the impurity resistivity of substitutional silicon in hexagonal-close-packed (hcp) iron. We measured the electrical resistivity of Fe-Si alloys (iron with 1, 2, 4, 6.5, and 9 wt.% silicon) using four-terminal method in a diamond-anvil cell up to 90 GPa at 300 K. We also computed the electronic band structure of substitutionally disordered hcp Fe-Si and Fe-Ni alloy systems by means of Korringa-Kohn-Rostoker method with coherent potential approximation (KKR-CPA). The electrical resistivity was then calculated from the Kubo-Greenwood formula. These experimental and theoretical results show excellent agreement with each other, and the first principles results show the saturation behavior at high silicon concentration. We further calculated the resistivity of Fe-Ni-Si ternary alloys and found the violation of the Matthiessen's rule as a consequence of the resistivity saturation. Such resistivity saturation has important implications for core dynamics. The saturation effect places the upper limit of the resistivity, resulting in that the total resistivity value has almost no temperature dependence. As a consequence, the core thermal conductivity has a lower bound and exhibits a linear temperature dependence. We predict the electrical resistivity at the top of the Earth's core to be 1.12 ×10-6 Ωm, which corresponds to the thermal conductivity of 87.1 W/m/K. Such high thermal conductivity suggests high isentropic heat flow, leading to young inner core age (<0.85 Gyr old) and high initial

  15. The radiolytic and chemical degradation of organic ion exchange resins under alkaline conditions: effect on radionuclide speciation

    Energy Technology Data Exchange (ETDEWEB)

    Loon, L. van; Hummel, W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1995-10-01

    The formation of water soluble organic ligands by the radiolytic and chemical degradation of several ion exchange resins was investigated under conditions close to those of the near field of a cementitious repository. The most important degradation products were characterised and their role on radionuclide speciation evaluated thoroughly. Irradiation of strong acidic cation exchange resins (Powdex PCH and Lewatite S-100) resulted in the formation of mainly sulphate and dissolved organic carbon. A small part of the carbon (10-20%) could be identified as oxalate. The identity of the remainder is unknown. Complexation studies with Cu{sup 2+} and Ni{sup 2+} showed the presence of two ligands: oxalate and ligand X. Although ligand X could not be identified, it could be characterised by its concentration, a deprotonation constant and a complexation constant for the NiX complex. The influence of oxalate and ligand X on the speciation of radionuclides is examined in detail. For oxalate no significant influence on the speciation of radionuclides is expected. The stronger complexing ligand X may exert some influence depending on its concentration and the values of other parameters. These critical parameters are discussed and limiting values are evaluated. In absence of irradiation, no evidence for the formation of ligands was found. Irradiation of strong basic anion exchange resins (Powdex PAO and Lewatite M-500) resulted in the formation of mainly ammonia, amines and dissolved organic carbon. Up to 50% of the carbon could be identified as methyl-, dimethyl- and trimethylamine. Complexation studies with Eu{sup 3+} showed that the complexing capacity under near field conditions was negligible. The speciation of cations such as Ag, Ni, Cu and Pd can be influenced by the presence of amins. The strongest amine-complexes are formed with Pd and therefore, as an example, the aqueous Pd-ammonia system is examined in great detail. (author) 30 figs., 10 tabs., refs.

  16. Modelling static and dynamic behaviour of proton exchange membrane fuel cells on the basis of electro-chemical description

    Science.gov (United States)

    Ceraolo, M.; Miulli, C.; Pozio, A.

    A simplified dynamical model of a fuel cell of the proton exchange membrane (PEM) type, based on physical-chemical knowledge of the phenomena occurring inside the cell has been developed by the authors. The model has been implemented in the MATLAB/SIMULINK environment. Lab tests have been carried out at ENEA's laboratories; and a good agreement has been found between tests and simulations, both in static and dynamic conditions. In a previous study [M. Ceraolo, R. Giglioli, C. Miulli, A. Pozio, in: Proceedings of the 18th International Electric Fuel Cell and Hybrid Vehicle Symposium (EVS18), Berlin, 20-24 October 2001, p. 306] the basic ideas of the model, as well as its experimental validation have been published. In the present paper, the full implementation of the model is reported in detail. Moreover, a procedure for evaluating all the needed numerical parameters is presented.

  17. Chemical fractionation and speciation modelling for optimization of ion-exchange processes to recover palladium from industrial wastewater.

    Science.gov (United States)

    Folens, K; Van Hulle, S; Vanhaecke, F; Du Laing, G

    2016-01-01

    Palladium is used in several industrial applications and, given its high intrinsic value, intense efforts are made to recover the element. In this hydrometallurgic perspective, ion-exchange (IEX) technologies are principal means. Yet, without incorporating the chemical and physical properties of the Pd present in real, plant-specific conditions, the recovery cannot reach its technical nor economic optimum. This study characterized a relevant Pd-containing waste stream of a mirror manufacturer to provide input for a speciation model, predicting the Pd speciation as a function of pH and chloride concentration. Besides the administered neutral PdCl2 form, both positively and negatively charged [PdCln](2-n) species occur depending on the chloride concentration in solution. Purolite C100 and Relite 2AS IEX resins were selected and applied in combination with other treatment steps to optimize the Pd recovery. A combination of the cation and anion exchange resins was found successful to quantitatively recover Pd. Given the fact that Pd was also primarily associated with particles, laboratory-scale experiments focused on physical removal of the Pd-containing flow were conducted, which showed that particle-bound Pd can already be removed by physical pre-treatment prior to IEX, while the ionic fraction remains fully susceptible to the IEX mechanism.

  18. Kinetic bottlenecks to chemical exchange rates for deep-sea animals II: Carbon dioxide

    Science.gov (United States)

    Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

    2012-11-01

    Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑CO2] etc.) as the critical variable and with a major focus on carbonate shell dissolution. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyze the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T) and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas since, as with gas exchange of CO2 at the air-sea interface, the influence of the ensemble of reactions within the CO2-HCO3--CO32- acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and flow rate under typical oceanic concentrations.The effect of these reactions can be described by an enhancement factor. For organisms, this means mechanically increasing flow over their surface to thin the boundary layer as is required to alleviate O2 stress seems not necessary to facilitate CO2 efflux. Nevertheless the elevated pCO2 cost most likely is non-zero. Regionally as with O2 the combination of T, P, and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth. But the net result is that, for the problem of gas exchange with the bulk ocean, the combination of an increasing T combined with declining O2 poses a greater challenge to marine life than does increasing CO2. The relationships developed here allow a more accurate prediction of the impacts on marine life

  19. Kinetic bottlenecks to chemical exchange rates for deep-sea animals II: Carbon dioxide

    Directory of Open Access Journals (Sweden)

    A. F. Hofmann

    2012-11-01

    Full Text Available Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑CO2] etc. as the critical variable and with a major focus on carbonate shell dissolution. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyze the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas since, as with gas exchange of CO2 at the air-sea interface, the influence of the ensemble of reactions within the CO2-HCO3-CO32– acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and flow rate under typical oceanic concentrations.The effect of these reactions can be described by an enhancement factor. For organisms, this means mechanically increasing flow over their surface to thin the boundary layer as is required to alleviate O2 stress seems not necessary to facilitate CO2 efflux. Nevertheless the elevated pCO2 cost most likely is non-zero. Regionally as with O2 the combination of T, P, and pH/pCO2 creates a zone of maximum CO2 stress at around

  20. 7T Magnetization Transfer and Chemical Exchange Saturation Transfer MRI of Cortical Gray Matter: Can We Detect Neurochemical and Macromolecular Abnormalities

    Science.gov (United States)

    2015-10-01

    healthy volunteers (blue) and MS patients (red) with the solid line indicating the median of GM GluCEST values and the shaded region the standard...developed and deployed a quantitative MRI set of MRI scans at 7T in healthy volunteers and patients with MS, developed an analysis pipeline and QA...acquisitions have been evaluated for reproducibility. Behavioral testing shows significant differences between MS and healthy volunteers , along

  1. 7T Magnetization Transfer and Chemical Exchange Saturation Transfer MRI of Cortical Gray Matter: Can We Detect Neurochemical and Macromolecular Abnormalities?

    Science.gov (United States)

    2014-10-21

    no Images M, no, no, no Autoview image M Calculated images no, no, no, no Reference tissue Grey matter Preset window...no MIP/MPR no Images M, no, no, no Autoview image M Calculated images no, no, no, no Reference tissue Grey matter Preset...no MIP/MPR no Images M, no, no, no Autoview image M Calculated images no, no, no, no Reference tissue Grey matter EPI

  2. Chemical-Specific Representation of Air-Soil Exchange and Soil Penetration in Regional Multimedia Models

    Energy Technology Data Exchange (ETDEWEB)

    McKone, T.E.; Bennett, D.H.

    2002-08-01

    In multimedia mass-balance models, the soil compartment is an important sink as well as a conduit for transfers to vegetation and shallow groundwater. Here a novel approach for constructing soil transport algorithms for multimedia fate models is developed and evaluated. The resulting algorithms account for diffusion in gas and liquid components; advection in gas, liquid, or solid phases; and multiple transformation processes. They also provide an explicit quantification of the characteristic soil penetration depth. We construct a compartment model using three and four soil layers to replicate with high reliability the flux and mass distribution obtained from the exact analytical solution describing the transient dispersion, advection, and transformation of chemicals in soil with fixed properties and boundary conditions. Unlike the analytical solution, which requires fixed boundary conditions, the soil compartment algorithms can be dynamically linked to other compartments (air, vegetation, ground water, surface water) in multimedia fate models. We demonstrate and evaluate the performance of the algorithms in a model with applications to benzene, benzo(a)pyrene, MTBE, TCDD, and tritium.

  3. Saturated Switching Systems

    CERN Document Server

    Benzaouia, Abdellah

    2012-01-01

    Saturated Switching Systems treats the problem of actuator saturation, inherent in all dynamical systems by using two approaches: positive invariance in which the controller is designed to work within a region of non-saturating linear behaviour; and saturation technique which allows saturation but guarantees asymptotic stability. The results obtained are extended from the linear systems in which they were first developed to switching systems with uncertainties, 2D switching systems, switching systems with Markovian jumping and switching systems of the Takagi-Sugeno type. The text represents a thoroughly referenced distillation of results obtained in this field during the last decade. The selected tool for analysis and design of stabilizing controllers is based on multiple Lyapunov functions and linear matrix inequalities. All the results are illustrated with numerical examples and figures many of them being modelled using MATLAB®. Saturated Switching Systems will be of interest to academic researchers in con...

  4. Effects of chemical reaction in thermal and mass diffusion of micropolar fluid saturated in porous regime with radiation and ohmic heating

    Directory of Open Access Journals (Sweden)

    Kumar Hitesh

    2016-01-01

    Full Text Available The present paper analyzes the chemically reacting free convection MHD micropolar flow, heat and mass transfer in porous medium past an infinite vertical plate with radiation and viscous dissipation. The non-linear coupled partial differential equations are solved numerically using an implicit finite difference scheme known as Keller-box method. The results for concentration, transverse velocity, angular velocity and temperature are obtained and effects of various parameters on these functions are presented graphically. The numerical discussion with physical interpretations for the influence of various parameters also presented.

  5. Electrical conductivity and oxygen exchange kinetics of La2NiO4+delta thin films grown by chemical vapor deposition

    DEFF Research Database (Denmark)

    Garcia, G.; Burriel, M.; Bonanos, Nikolaos

    2008-01-01

    Epitaxial c-axis oriented La2NiO4+delta films were deposited onto SrTiO3 and NdGaO3 substrates by the pulsed injection metal organic chemical vapor deposition technique. Experimental conditions were optimized in order to accurately control the composition, thickness, and texture of the layers. X...... by the electrical conductivity relaxation technique, from which the surface exchange coefficient was determined. (C) 2008 The Electrochemical Society....

  6. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

  7. Saturating Sperner families

    CERN Document Server

    Gerbner, Dániel; Lemons, Nathan; Pálvölgyi, Dömötör; Palmer, Cory; Patkós, Balázs

    2011-01-01

    A family $\\cF \\subseteq 2^{[n]}$ saturates the monotone decreasing property $\\cP$ if $\\cF$ satisfies $\\cP$ and one cannot add any set to $\\cF$ such that property $\\cP$ is still satisfied by the resulting family. We address the problem of finding the minimum size of a family saturating the $k$-Sperner property and the minimum size of a family that saturates the Sperner property and that consists only of $l$-sets and $(l+1)$-sets.

  8. Saturated Domino Coverings

    CERN Document Server

    Buchanan, Andrew; Ryba, Alex

    2011-01-01

    A domino covering of a board is saturated if no domino is redundant. We introduce the concept of a fragment tiling and show that a minimal fragment tiling always corresponds to a maximal saturated domino covering. The size of a minimal fragment tiling is the domination number of the board. We define a class of regular boards and show that for these boards the domination number gives the size of a minimal X-pentomino covering. Natural sequences that count maximal saturated domino coverings of square and rectangular boards are obtained. These include the new sequences A193764, A193765, A193766, A193767, and A193768 of OEIS.

  9. Saturation and geometrical scaling

    CERN Document Server

    Praszalowicz, Michal

    2016-01-01

    We discuss emergence of geometrical scaling as a consequence of the nonlinear evolution equations of QCD, which generate a new dynamical scale, known as the saturation momentum: Qs. In the kinematical region where no other energy scales exist, particle spectra exhibit geometrical scaling (GS), i.e. they depend on the ratio pT=Qs, and the energy dependence enters solely through the energy dependence of the saturation momentum. We confront the hypothesis of GS in different systems with experimental data.

  10. Holographic Pomeron: Saturation and DIS

    CERN Document Server

    Stoffers, Alexander

    2012-01-01

    We briefly review the approach to dipole-dipole scattering in holographic QCD developed in ARXIV:1202.0831. The Pomeron is modeled by exchanging closed strings between the dipoles and yields Regge behavior for the elastic amplitude. We calculate curvature corrections to this amplitude in both a conformal and confining background, identifying the holographic direction with the virtuality of the dipoles. The it wee-dipole density is related to the string tachyon diffusion in both virtuality and the transverse directions. We give an explicit derivation of the dipole saturation momentum both in the conformal and confining metric. Our holographic result for the dipole-dipole cross section and the it wee-dipole density in the conformal limit are shown to be identical in form to the BFKL pomeron result when the non-critical string transverse dimension is $D_\\perp=3$. The total dipole-dipole cross section is compared to DIS data from HERA.

  11. Screening of Newborn Saturation

    Directory of Open Access Journals (Sweden)

    Senem Ozgur

    2014-08-01

    Full Text Available In terms of the incidence, congenital heart diseases ranks first among congenital problems in the neonatal period. Although some of those diseases are with significant clinical findings, they might be insignificant in most cases. Standardization methods have been studied in variety of points, and oxygen saturation by pulse oximetry is thougt to be a good alternative to physical examination. In several studies, it is mentioned that some of congenital heart diseases are diagnosed by saturation screening. However, the benefits of this method are marred with the false negative and false positive rates. Therefore, in 2011 American Academy of Pediatrics has revised its saturation algorithm for scanning. It was aimed to have a standardization in saturation detecting time and evaluation of achieved saturation in newborns. Despite all efforts, some newborns with congenital heart disease are not diagnosed before discharging. We beleive that the details of saturation measurements are needed to be carefully evaluated because although these measurements are widely used their details are not well known. [Archives Medical Review Journal 2014; 23(4.000: 587-604

  12. Optimization and application of atmospheric pressure chemical and photoionization hydrogen-deuterium exchange mass spectrometry for speciation of oxygen-containing compounds.

    Science.gov (United States)

    Acter, Thamina; Kim, Donghwi; Ahmed, Arif; Jin, Jang Mi; Yim, Un Hyuk; Shim, Won Joon; Kim, Young Hwan; Kim, Sunghwan

    2016-05-01

    This paper presents a detailed investigation of the feasibility of optimized positive and negative atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and atmospheric pressure photoionization (APPI) MS coupled to hydrogen-deuterium exchange (HDX) for structural assignment of diverse oxygen-containing compounds. The important parameters for optimization of HDX MS were characterized. The optimized techniques employed in the positive and negative modes showed satisfactory HDX product ions for the model compounds when dichloromethane and toluene were employed as a co-solvent in APCI- and APPI-HDX, respectively. The evaluation of the mass spectra obtained from 38 oxygen-containing compounds demonstrated that the extent of the HDX of the ions was structure-dependent. The combination of information provided by different ionization techniques could be used for better speciation of oxygen-containing compounds. For example, (+) APPI-HDX is sensitive to compounds with alcohol, ketone, or aldehyde substituents, while (-) APPI-HDX is sensitive to compounds with carboxylic functional groups. In addition, the compounds with alcohol can be distinguished from other compounds by the presence of exchanged peaks. The combined information was applied to study chemical compositions of degraded oils. The HDX pattern, double bond equivalent (DBE) distribution, and previously reported oxidation products were combined to predict structures of the compounds produced from oxidation of oil. Overall, this study shows that APCI- and APPI-HDX MS are useful experimental techniques that can be applied for the structural analysis of oxygen-containing compounds.

  13. Effect of resin charged functional group, porosity, and chemical matrix on the long-term pharmaceutical removal mechanism by conventional ion exchange resins.

    Science.gov (United States)

    Wang, Wei; Li, Xiaofeng; Yuan, Shengliu; Sun, Jian; Zheng, Shaokui

    2016-10-01

    This study attempted to clarify the long-term pharmaceutical removal mechanism from sewage treatment plant effluent during the cyclical adsorption-regeneration operation of 5 commercial resin-based fixed-bed reactors with the simultaneous occurrence of electrostatic interactions and complex non-electrostatic interactions. It examined 12 pharmaceuticals belonging to 10 therapeutic classes with different predominant existing forms and hydrophobicities. Furthermore, the effect of the resin charged functional group (strong-base vs. strong-acid vs. non-ionic), porosity (macroporous vs. gel), and chemical matrix (polystyrenic vs. polyacrylic) on the mechanism was investigated to optimize resin properties and achieve higher pharmaceutical removal. The results reported herein indicate the importance of non-electrostatic interactions between pharmaceuticals and the resin backbone during short-term cyclical operation (i.e., the 1st adsorption-regeneration cycle). With the development of cyclical operation, however, non-electrostatic interaction-induced pharmaceutical removal generally decreased and even disappeared when equilibrium was achieved between the influent and the resin. Despite pharmaceutical therapeutic class or hydrophilicity, anion (or cation) exchange resin preferentially removed those pharmaceuticals that were predominantly present as organic anions (or cations) by ion exchange process during long-term cyclical operation (i.e., ≥6 adsorption-regeneration cycles). Besides pharmaceuticals predominantly present as undissociated molecules, some amphoteric pharmaceuticals containing large amounts of zwitterions were also difficult to remove by ion exchange resin. Additionally, neither resin porosity nor chemical matrix had any significant effect on the long-term pharmaceutical removal mechanism.

  14. 1H and 15N NMR Analyses on Heparin, Heparan Sulfates and Related Monosaccharides Concerning the Chemical Exchange Regime of the N-Sulfo-Glucosamine Sulfamate Proton

    Directory of Open Access Journals (Sweden)

    Vitor H. Pomin

    2016-09-01

    Full Text Available Heparin and heparan sulfate are structurally related glycosaminoglycans (GAGs. Both GAGs present, although in different concentrations, N-sulfo-glucosamine (GlcNS as one of their various composing units. The conditional fast exchange property of the GlcNS sulfamate proton in these GAGs has been pointed as the main barrier to its signal detection via NMR experiments, especially 1H-15N HSQC. Here, a series of NMR spectra is collected on heparin, heparan sulfate and related monosaccharides. The N-acetyl glucosamine-linked uronic acid types of these GAGs were properly assigned in the 1H-15N HSQC spectra. Dynamic nuclear polarization (DNP was employed in order to facilitate 1D spectral acquisition of the sulfamate 15N signal of free GlcNS. Analyses on the multiplet pattern of scalar couplings of GlcNS 15N has helped to understand the chemical properties of the sulfamate proton in solution. The singlet peak observed for GlcNS happens due to fast chemical exchange of the GlcNS sulfamate proton in solution. Analyses on kinetics of alpha-beta anomeric mutarotation via 1H NMR spectra have been performed in GlcNS as well as other glucose-based monosaccharides. 1D 1H and 2D 1H-15N HSQC spectra recorded at low temperature for free GlcNS dissolved in a proton-rich solution showed signals from all exchangeable protons, including those belonging to the sulfamate group. This work suits well to the current grand celebration of one-century-anniversary of the discovery of heparin.

  15. Cleaning chemical and mechanical of heat exchangers in french nuclear plants; Limpieza mecanica y quimica de intercambiadores de calor en centrales nucleares francesas

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, J. t.; Guerra, P.; Carreres, C.

    2013-03-01

    This project was carried out under the frame of the approval of LAINSA as a supplier of EDF in France. The inspection performed on systems called the moisture separator reheaters (GSS) of CPO series reactor of EDF nuclear power plants has shown evidence of significant clogging due to deposits of magnetite inside the tubes of tube bundle. The pressure drop between inlet and outlet of the heating was close to maximum design criterion. This effect could result in equipment damage and loss of plant productivity. The aim of the work was the design, development, approval and implementation of a procedure for un blocking the tubes of the GSS respecting the integrity of materials and ensuring the harmlessness of cleaning procedures. The procedure used was to completely remove magnetite deposits in order to recover a passage diameter and a surface finish equivalent to the origin, thus avoiding the replacement of the GSS and obtaining a considerable reduction of costs. The achieve these objectives we have developed a procedure that is basically a mechanical pre-cleaning of all tubes of the GSS in order to unblock tem, followed by a chemical cleaning where magnetite is dissolved and crawled out of the tube bundle. The main results were: -Corrosion less than 10 microns. 100-110 Kg of magnetite removed by heat exchanger. -Final pressure drop similar to that of new equipment. -Waste water: 70 m{sup 3} per exchanger, which were managed by an authorized waste management company. This procedure has been applied successfully in 14 GSS type heat exchangers in Fessenheim and Bugey nuclear power plants in France between 2009 and 2011. This project demonstrates that the long experience of LAINSA in the Spanish nuclear industry along with the knowledge and experience in chemical cleaning of SOLARCA, have served to successfully work demanding and mature markets such as the French nuclear market, solving the problem of deposits of magnetite with an effective and safe method for the treated

  16. ¹H and (15)N NMR Analyses on Heparin, Heparan Sulfates and Related Monosaccharides Concerning the Chemical Exchange Regime of the N-Sulfo-Glucosamine Sulfamate Proton.

    Science.gov (United States)

    Pomin, Vitor H

    2016-09-07

    Heparin and heparan sulfate are structurally related glycosaminoglycans (GAGs). Both GAGs present, although in different concentrations, N-sulfo-glucosamine (GlcNS) as one of their various composing units. The conditional fast exchange property of the GlcNS sulfamate proton in these GAGs has been pointed as the main barrier to its signal detection via NMR experiments, especially ¹H-(15)N HSQC. Here, a series of NMR spectra is collected on heparin, heparan sulfate and related monosaccharides. The N-acetyl glucosamine-linked uronic acid types of these GAGs were properly assigned in the ¹H-(15)N HSQC spectra. Dynamic nuclear polarization (DNP) was employed in order to facilitate 1D spectral acquisition of the sulfamate (15)N signal of free GlcNS. Analyses on the multiplet pattern of scalar couplings of GlcNS (15)N has helped to understand the chemical properties of the sulfamate proton in solution. The singlet peak observed for GlcNS happens due to fast chemical exchange of the GlcNS sulfamate proton in solution. Analyses on kinetics of alpha-beta anomeric mutarotation via ¹H NMR spectra have been performed in GlcNS as well as other glucose-based monosaccharides. 1D ¹H and 2D ¹H-(15)N HSQC spectra recorded at low temperature for free GlcNS dissolved in a proton-rich solution showed signals from all exchangeable protons, including those belonging to the sulfamate group. This work suits well to the current grand celebration of one-century-anniversary of the discovery of heparin.

  17. Pump for Saturated Liquids

    Science.gov (United States)

    Elliott, D. G.

    1986-01-01

    Boiling liquids pumped by device based on proven components. Expanding saturated liquid in nozzle and diverting its phases along separate paths in liquid/vapor separator raises pressure of liquid. Liquid cooled in process. Pump makes it unnecessary to pressurize cryogenic liquids in order to pump them. Problems of introducing noncondensable pressurizing gas avoided.

  18. Characterization of mu s-ms dynamics of proteins using a combined analysis of N-15 NMR relaxation and chemical shift: Conformational exchange in plastocyanin induced by histidine protonations

    DEFF Research Database (Denmark)

    Hass, M. A. S.; Thuesen, Marianne Hallberg; Christensen, Hans Erik Mølager

    2004-01-01

    An approach is presented that allows a detailed, quantitative characterization of conformational exchange processes in proteins on the mus-ms time scale. The approach relies on a combined analysis of NMR relaxation rates and chemical shift changes and requires that the chemical shift...... variabilis (A.v. PCu) (Ma, L.; Hass, M. A. S.; Vierick, N.; Kristensen, S. M.; Ulstrup, J.; Led, J. J. Biochemistry 2003, 42, 320-330). The R-1 and R-2 relaxation rates of the backbone N-15 nuclei were measured at a series of pH and temperatures on an 15N labeled sample of A.v. PCu, and the 15 N chemical...... quantitatively by the correlation between the R-ex terms and the corresponding chemical shift differences of the exchanging species. By this approach, the R-ex terms of N-15 nuclei belonging to contiguous regions in the protein could be assigned to the same exchange process. Furthermore, the analysis...

  19. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  20. Intracellular water exchange for measuring the dry mass, water mass and changes in chemical composition of living cells.

    Directory of Open Access Journals (Sweden)

    Francisco Feijó Delgado

    Full Text Available We present a method for direct non-optical quantification of dry mass, dry density and water mass of single living cells in suspension. Dry mass and dry density are obtained simultaneously by measuring a cell's buoyant mass sequentially in an H2O-based fluid and a D2O-based fluid. Rapid exchange of intracellular H2O for D2O renders the cell's water content neutrally buoyant in both measurements, and thus the paired measurements yield the mass and density of the cell's dry material alone. Utilizing this same property of rapid water exchange, we also demonstrate the quantification of intracellular water mass. In a population of E. coli, we paired these measurements to estimate the percent dry weight by mass and volume. We then focused on cellular dry density - the average density of all cellular biomolecules, weighted by their relative abundances. Given that densities vary across biomolecule types (RNA, DNA, protein, we investigated whether we could detect changes in biomolecular composition in bacteria, fungi, and mammalian cells. In E. coli, and S. cerevisiae, dry density increases from stationary to exponential phase, consistent with previously known increases in the RNA/protein ratio from up-regulated ribosome production. For mammalian cells, changes in growth conditions cause substantial shifts in dry density, suggesting concurrent changes in the protein, nucleic acid and lipid content of the cell.

  1. Chemical Equilibrium and Mineral Saturation in Waters from Oil Wells of the Activo Luna Field, Tabasco, Mexico; Equilibrio quimico y grado de saturacion de minerales en aguas de pozos petroleros de Activo Luna, Tabasco, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Barragan R, Rosa Maria; Arellano G, Victor M.; Portugal M, Enrique; Torres R, Vicente [Instituto de Investigaciones Electricas (Mexico); Torres Alvarado, Ignacio [Universidad Nacional Autonoma de Mexico (Mexico); Ascencio C, Fernando; Martinez A; Ana E [Petroleos Mexicanos (Mexico)

    2001-09-01

    Chemical equilibrium of formation waters from seven oil wells of the Activo Luna field (Tabasco, Mexico) was modelled. Saturation indices of characteristic hydrothermal minerals were calculated at ambient and reservoir conditions in order to predict scaling potential of deep and surface installations. The salinity of waters was found to be in the range from 43,000 (well Escuintle 2) to 250,000 (well Lune 3B) mg/kg as total dissolved solids. The water samples were classified as sodium-chioride type. Ionic strength for the solutions was found to be between 0.75 and 6.5. Activity coefficients were estimated by virial (Pitzer equations) methods using the GEOCHEMIST WORKENCH (GWB) software. Minerals such as anhydrite, halite, alunite, fluorite and barite were found to be supersaturated at reservoir conditions. A solid scale sample obtained from well Luna-3B was analysed. Analysis indicate the presence of calcite, anhydrite, fluorite and sphalerite which suggest the occurrence of temperatures of at least 180 Celcius degrees with acidic conditions and high chemical corrosion potential. [Spanish] Se modelo el equilibrio quimico de aguas de formacion producidas por siete pozos petroleros pertenecientes al Activo Luna, en el estado de Tabasco, Mexico, se calcularon los indices de saturacion de minerales caracteristicos tanto en las condiciones ambiente como en las de yacimiento, con el proposito de apoyar el control de incrustaciones en las instalaciones superficiales y profundas. La salinidad de las salmueras se encontro en el rango de 43,000 (pozos Escuintle 2) a 250,000 (pozos Luna 3B) mg/kg de solidos disueltos totales y las muestras se clasificaron como del tipo clorurado-sodico. La fuerza ionica de las soluciones varia entre 0.75 y 6.5 molar, por lo que los coeficientes de actividad de la modelacion de equilibrio quimico se estimaron por metodos viriales empleando las ecuaciones de Pitzer mediante el programa GEOCHEMIST WORKBENCH (GWB). Minerales como anhidrita, halita

  2. Scientific Opinion on the safety and efficacy of aliphatic, alicyclic and aromatic saturated and unsaturated tertiary alcohols and esters with esters containing tertiary alcohols ethers (chemical group 6 when used as flavourings for all animal species

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP

    2012-11-01

    Full Text Available Chemical group 6 consists of aliphatic, alicyclic and aromatic saturated and unsaturated tertiary alcohols and esters with esters containing tertiary alcohols ethers, of which 13 are currently authorised for use as flavours in food. The high use level proposed by the applicant for linalool (25 mg/kg complete feed is safe for salmonids, veal calves, cattle for fattening and pets (excluding cats without a margin of safety with the exception of dogs (SF = 1.4. The safe use level for pigs and dairy cows is 20, for piglets 12 and for poultry 10 mg/kg complete feed. The high use level of 5 mg/kg complete feed for linalyl acetate, linalyl butyrate, linalyl formate, linalyl propionate, linalyl isobutyrate, terpineol, α-terpineol and terpineol acetate and 4-terpinenol is safe for all species with a margin of safety of 1.2 to 12. For nerolidol, 2-methyl-1-phenylpropan-2-ol and 2-(4-methylphenylpropan-2-ol, the maximum safe concentration is 1 mg/kg complete feed for pigs and poultry and 1.5 mg/kg complete feed for all other species. The absence of a margin of safety would not allow the simultaneous administration in feed and water for drinking of the following compounds: linalool, nerolidol, 2-methyl-1-phenylpropan-2-ol and 2-(4methylphenylpropan-2-ol. No safety concern would arise for the consumer from the use of compounds belonging to CG 6 up to the highest safe level in feedingstuffs for all animal species. All compounds should be considered as irritants to skin, eyes and respiratory tract, and as skin sensitisers. All compounds of CG 6 are predicted to be safe to the soil compartment when used at levels safe to the target species. Using predictions based on chemical structure, 2-methyl-1-phenylpropan-2-ol and 2-(4-methylphenylpropan-2-ol were estimated to be safe to aquatic compartments. In the absence of experimental data, safety to aquatic compartments could not be established for linalyl butyrate, linalyl isobutyrate, terpineol acetate, 4

  3. Conformal invariant saturation

    CERN Document Server

    Navelet, H

    2002-01-01

    We show that, in onium-onium scattering at (very) high energy, a transition to saturation happens due to quantum fluctuations of QCD dipoles. This transition starts when the order alpha^2 correction of the dipole loop is compensated by its faster energy evolution, leading to a negative interference with the tree level amplitude. After a derivation of the the one-loop dipole contribution using conformal invariance of the elastic 4-gluon amplitude in high energy QCD, we obtain an exact expression of the saturation line in the plane (Y,L) where Y is the total rapidity and L, the logarithm of the onium scale ratio. It shows universal features implying the Balitskyi - Fadin - Kuraev - Lipatov (BFKL) evolution kernel and the square of the QCD triple Pomeron vertex. For large L, only the higher BFKL Eigenvalue contributes, leading to a saturation depending on leading log perturbative QCD characteristics. For initial onium scales of same order, however, it involves an unlimited summation over all conformal BFKL Eigen...

  4. DETERGENCY OF THE 12 TO 18 CARBON SATURATED FATTY ACIDS

    Science.gov (United States)

    saturated fatty acids ) were explored to determine the relationship of the detergencies of such systems to the physico-chemical nature (HLB, hydrophile...suggested that in such systems the chief action is van der Waals adsorption between hydr oxide mole ratio adducts of tridecyl alcohol are poor detergents of the saturated fatty acids .

  5. Experimental results of acetone hydrogenation on a heat exchanger type reactor for solar chemical heat pump; Solar chemical heat pump ni okeru acetone suisoka hanno netsu kaishu jikken

    Energy Technology Data Exchange (ETDEWEB)

    Takashima, T.; Doi, T.; Tanaka, T.; Ando, Y. [Electrotechnical Laboratory, Tsukuba (Japan); Miyahara, R.; Kamoshida, J. [Shibaura Institute of Technology, Tokyo (Japan)

    1996-10-27

    With the purpose of converting solar heat energy to industrial heat energy, an experiment of acetone hydrogenation was carried out using a heat exchanger type reactor that recovers heat generated by acetone hydrogenation, an exothermic reaction, and supplies it to an outside load. In the experiment, a pellet-like activated carbon-supported ruthenium catalyst was used for the acetone hydrogenation with hydrogen and acetone supplied to the catalyst layer at a space velocity of 400-1,200 or so. In the external pipe of the double-pipe type reactor, a heating medium oil was circulated in parallel with the flow of the reactant, with the heat of reaction recovered that was generated from the acetone hydrogenation. In this experiment, an 1wt%Ru/C catalyst and a 5wt%Ru/C catalyst were used so as to examine the effects of variation in the space velocity. As a result, from the viewpoint of recovering the heat of reaction, it was found desirable to increase the reaction speed by raising catalytic density and also to supply the reactant downstream inside the reaction pipe by increasing the space velocity. 1 ref., 6 figs., 1 tab.

  6. Chemical and radiation stability of a proprietary cesium ion exchange material manufactured from WWL membrane and SuperLig{reg_sign} 644

    Energy Technology Data Exchange (ETDEWEB)

    Brown, G.N.; Carson, K.J.; DesChane, J.R.; Elovich, R.J.; Berry, P.K.

    1996-09-01

    Pretreatment of nuclear process wastes for ion exchange removal of Cs and other radionuclides is one way to minimize amount of high-level radioactive waste at Hanford. This study evaluated Cs-selective SuperLig{reg_sign}644 (IBC Advanced Technologies, American Fork UT) entrapped in a proprietary WWL web membrane (3M) for chemical/radiation stability in simulated caustic neutralized current acid waste (NCAW), 0.5M HNO{sub 3}, water, and air. After exposure up to 2.0E+09 rad, the material was evaluated for Cs uptake in 5M sodium NCAW simulants with varying Cs contents. Radiolytic stability appears to be sufficient for ion exchange pretreatment of radioactive Cs: essentially no decrease in Cs selectivity or loading (Kd) was observed during {sup 60}Cs gamma irradiation in water or 0.5M HNO{sub 3} up to 1.0E+09 rad. Cs Kd decreased by a factor of 2 after 2.0E+09 rad exposure. Cs Kd did not change during irradiation in 5M NCAW or ambient air up to 1.0E+08 rad, but decreased by more than an order of magnitude between 1.0E+08 and 2.0E+09 rad (not typical of process conditions). Chemical stability under caustic conditions is lower than in air or under neutral/acidic conditions. Results indicate that this material is less stable in caustic solution irrespective of radiation exposure. Samples of the membrane retained their physical form throughout the entire experiment and were only slightly brittle after exposure to 2.0E+09 rad. (The material evaluated was a finely ground (400 mesh) particulate engineered to form a polymeric fiber (WWL), not the macroscopic form of SuperLig{reg_sign} 644 resin (20 to 50 mesh).)

  7. Modelling of the interaction between chemical and mechanical behaviour of ion exchange resins incorporated into a cement-based matrix

    Directory of Open Access Journals (Sweden)

    Le Bescop P.

    2013-07-01

    Full Text Available In this paper, we present a predictive model, based on experimental data, to determine the macroscopic mechanical behavior of a material made up of ion exchange resins solidified into a CEM III cement paste. Some observations have shown that in some cases, a significant macroscopic expansion of this composite material may be expected, due to internal pressures generated in the resin. To build the model, we made the choice to break down the problem in two scale’s studies. The first deals with the mechanical behavior of the different heterogeneities of the composite, i.e. the resin and the cement paste. The second upscales the information from the heterogeneities to the Representative Elementary Volume (REV of the composite. The heterogeneities effects are taken into account in the REV by applying a homogenization method derived from the Eshelby theory combined with an interaction coefficient drawn from the poroelasticity theory. At the first scale, from the second thermodynamic law, a formulation is developed to estimate the resin microscopic swelling. The model response is illustrated on a simple example showing the impact of the calculated internal pressure, on the macroscopic strain.

  8. Physico-chemical study of the degradation of membrane-electrode assemblies in a proton exchange membrane fuel cell stack

    Science.gov (United States)

    Ferreira-Aparicio, P.; Gallardo-López, B.; Chaparro, A. M.; Daza, L.

    A proton exchange membrane fuel cell stack integrated by 8-elements has been evaluated in an accelerated stress test. The application of techniques such as TEM analyses of ultramicrotome-sliced sections of some samples and XRD, XPS and TGA of spent electrodes reveal the effects of several degradation processes contributing to reduce the cells performance. The reduction of the Pt surface area at the cathode is favored by the oxidation of carbon black agglomerates in the catalytic layer, the agglomeration of Pt particles and by the partial dissolution of Pt, which migrates towards the anode and precipitates within the membrane. In the light of the TEM, EDAX and XPS results, two combined effects are probably responsible of the increase of the internal resistance of the stack cells: (i) a lower proton conductivity of the membranes due to the high affinity of the sulfonic acid groups for ions originated from Pt crystallites and other peripherical elements such as the silicone elastomeric gaskets and (ii) the increment of electrically isolated islands in the cathode gas diffusion electrodes resulting from carbon corrosion and the degradation of the perfluorinated polymers. Water accumulation and inhomogeneous gas distribution throughout the stack cells originate different degradation rates in them.

  9. A theoretical analysis of the extraction of heterocyclic organic compounds from an organic phase using chemically mediated electrochemically modulated complexation in ion exchange polymer beads

    Energy Technology Data Exchange (ETDEWEB)

    Ozekin, K.; Noble, R.D.; Koval, C.A.

    1991-01-01

    A cyclical electrochemical process for the removal of heterocyclic organic compounds (pollutants) from an organic solvent using an ion-exchange polymer is analyzed. In this analysis, there are three main steps: In the first step, the polymer beads containing the active form of the complexing agent are contacted with the contaminated (feed) hydrocarbon phase. The pollutant diffuses into the beads and binds with the complexing agent which is in the reduced state. It is a fast reversible reaction. For the second step, the beads which contain a pollutant are contacted with a waste (receiving) phase and a chemical mediator is then used to oxidize the complexing agent and to reduce its affinity towards the pollutant so that it can be released. The oxidation of the complexing agent is an irreversible reaction. This is a moving boundary problem with countercurrent diffusion. For each mole of mediator that goes into the bead, one mole of pollutant exits since each complexing agent binds one pollutant. In the third step, the waste hydrocarbon phase is removed and a second chemical mediator is then used to reduce the complexing agent. The reduction of the complexing agent is also an irreversible reaction. Partial differential equations are used to analyze this process. 26 refs., 9 figs.

  10. A review on saturated boiling of liquids on tube bundles

    Science.gov (United States)

    Swain, Abhilas; Das, Mihir Kumar

    2014-05-01

    A review of recent investigation on boiling of saturated liquids over plain and enhanced tube bundles has been carried out taking the earlier review works as reference point. The experimental observations of various geometry and performance parameters studied by researchers are analyzed keeping current demand of industries in design and development of compact, efficient heat exchanging devices. The study shows that tube spacing plays an important role in determination of compactness of the heat exchanger.

  11. Mixed ion-exchanger chemically modified carbon paste ion-selective electrodes for determination of triprolidine hydrochloride

    Directory of Open Access Journals (Sweden)

    Yousry M. Issa

    2010-01-01

    Full Text Available Triprolidine hydrochloride (TpCl ion-selective carbon paste electrodes were constructed using Tp-TPB/Tp-CoN and Tp-TPB/Tp-PTA as ion-exchangers. The two electrodes revealed Nernstian responses with slopes of 58.4 and 58.1 mV decade−1 at 25 °C in the ranges 6 × 10−6–1 × 10−2 and 2 × 10−5–1 × 10−2 M for Tp-TPB/Tp-CoN and Tp-TPB/Tp-PTA, respectively. The potentials of these electrodes were independent of pH in the ranges of 2.5–7.0 and 4.5–7.0, and detection limits were 6 × 10−6 and 1 × 10−5 M for Tp-TPB/Tp-CoN and Tp-TPB/Tp-PTA, respectively. The electrodes showed a very good selectivity for TpCl with respect to a large number of inorganic cations and compounds. The standard addition, potentiometric titration methods and FIA were applied to the determination of TpCl in pure solutions and pharmaceutical preparations. The results obtained were in close agreement with those found by the official method. The mean recovery values were 100.91% and 97.92% with low coefficient of variation values of 0.94%, and 0.56% in pure solutions, 99.82% and 98.53% with coefficient of variation values of 2.20%, and 0.73% for Actifed tablet and Actifed syrup, respectively, using the Tp-TPB/Tp-CoN electrode, and 98.85%, and 99.18% with coefficient of variation values of 0.48% and 0.85% for Actifed tablet and Actifed syrup, respectively, using the Tp-TPB/Tp-PTA electrode.

  12. Targeting of chemical mutagens to differentiating B-lymphocytes in vivo: detection by direct DNA labeling and sister chromatid exchange induction

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, S.E.; Nanna, U.C.; Dietert, R.R.

    1987-01-01

    In vivo systems for analyzing mutagen interactions with a specific differentiating cell population are rare. Taking advantage of the unique anatomical features of the bursa of Fabricius in the chicken, the authors explored the possibility of targeting chemical mutagens to a defined differentiating cell population in the animal, namely, the B-lymphocytes series. Such cells are known to be the targets for the oncogene-activating avian leukosis virus. Targeting of chemicals to cells of the bursa was demonstrated by application of the DNA-specific fluorochrome 4'-6-diamidino-2-phenylindole (DAPI) to the anal lips of neonatal chicks. Bright nuclear fluorescence of cells in the bursa demonstrated to occur within minutes after the application of 500..mu..l of DAPI. DAPI labeling of nuclei was detected up to several days after a single application. No nuclear labeling was exhibited in cells of neighboring tissues. Methyl methanesulfonate (MMS)(10..mu..l) was applied to the anal lips of day-old chicks to study dose-response kinetics for mutagen targeting to DNA of dividing B-lymphocytes in the bursa. Since the mitotic index was found to be quite high (25-30%) in the bursa, chromosome analysis was used to assay for genome damage. Sister chromatid exchange frequencies of 3.9, 7.3, and 9.0 (baseline 2.5) per cell were obtained at MMS dosages per animal of 50 ..mu..g, 100..mu..g, and 200..mu..g, respectively. These results indicate the rapid and quantitative localization of DNA-binding chemicals to cells of the bursa, particularly the resident B-lymphocytes. The bursa should be a useful system for studying mutagen-DNA interactions in the differentiating B-lymphocyte and subsequent influences on the development of immunity and lymphoproliferative disease.

  13. From QCD to nuclear matter saturation

    Energy Technology Data Exchange (ETDEWEB)

    Ericson, Magda [Universite de Lyon, Univ. Lyon 1, CNRS/IN2P3, IPN Lyon, F-69622 Villeurbanne Cedex (France)]|[Theory division, CERN, CH-12111 Geneva (Switzerland); Chanfray, Guy [Universite de Lyon, Univ. Lyon 1, CNRS/IN2P3, IPN Lyon, F-69622 Villeurbanne Cedex (France)

    2007-03-15

    We discuss a relativistic chiral theory of nuclear matter with {sigma} and {omega} exchange using a formulation of the {sigma} model in which all the chiral constraints are automatically fulfilled. We establish a relation between the nuclear response to the scalar field and the QCD one which includes the nucleonic parts. It allows a comparison between nuclear and QCD information. Going beyond the mean field approach we introduce the effects of the pion loops supplemented by the short-range interaction. The corresponding Landau-Migdal parameters are taken from spin-isospin physics results. The parameters linked to the scalar meson exchange are extracted from lattice QCD results. These inputs lead to a reasonable description of the saturation properties, illustrating the link between QCD and nuclear physics. We also derive from the corresponding equation of state the density dependence of the quark condensate and of the QCD susceptibilities. (authors)

  14. Investigation into the Cause of Spontaneous Emulsification of a Free Steel Droplet; Validation of the Chemical Exchange Pathway

    Science.gov (United States)

    Spooner, Stephen; Assis, Andre N.; Warnett, Jason; Fruehan, Richard; Williams, Mark A.; Sridhar, Seetharaman

    2016-08-01

    Small Fe-based droplets have been heated to a molten phase suspended within a slag medium to replicate a partial environment within the basic oxygen furnace (BOF). The confocal scanning laser microscope (CSLM) has been used as a heating platform to interrogate the effect of impurities and their transfer across the metal/slag interface, on the emulsification of the droplet into the slag medium. The samples were then examined through X-ray computer tomography (XCT) giving the mapping of emulsion dispersion in 3D space, calculating the changing of interfacial area between the two materials, and changes of material volume due to material transfer between metal and slag. Null experiments to rule out thermal gradients being the cause of emulsification have been conducted as well as replication of the previously reported study by Assis et al.[1] which has given insights into the mechanism of emulsification. Finally chemical analysis was conducted to discover the transfer of oxygen to be the cause of emulsification, leading to a new study of a system with undergoing oxygen equilibration.

  15. Theoretical investigation of the magnetic exchange interactions in copper(II) oxides under chemical and physical pressures.

    Science.gov (United States)

    Rocquefelte, Xavier; Schwarz, Karlheinz; Blaha, Peter

    2012-01-01

    It remains a challenge to understand the unconventional mechanisms that cause high-T(C) superconductivity in cuprate superconductors, high-T(C) multiferroicity in CuO, or low-dimensional magnetism in the spin-Peierls transition compounds such as CuGeO(3). A common feature of all these copper oxide compounds (containing Cu(2+) ions) is the presence of large magnetic superexchange interactions J. It is a general strategy to apply chemical and/or physical pressure in order to tune these exotic properties. Here we show theoretically, for the first time, the impact of physical pressure on J on CuO, for which we predict a strong enhancement of the low-dimensionality of the magnetic interactions and the spin-frustration at high-pressures. Such modifications are expected to strongly influence the multiferroic properties of CuO. We finally demonstrate that PBE0 hybrid DFT calculations provide reliable J values for a wide range of copper(II) oxides compounds, i.e. CuGeO(3), BaCu(2)Si(2)O(7), BaCu(2)Ge(2)O(7), and La(2)CuO(4).

  16. Saturated fats: what dietary intake?

    Science.gov (United States)

    German, J Bruce; Dillard, Cora J

    2004-09-01

    Public health recommendations for the US population in 1977 were to reduce fat intake to as low as 30% of calories to lower the incidence of coronary artery disease. These recommendations resulted in a compositional shift in food materials throughout the agricultural industry, and the fractional content of fats was replaced principally with carbohydrates. Subsequently, high-carbohydrate diets were recognized as contributing to the lipoprotein pattern that characterizes atherogenic dyslipidemia and hypertriacylglycerolemia. The rising incidences of metabolic syndrome and obesity are becoming common themes in the literature. Current recommendations are to keep saturated fatty acid, trans fatty acid, and cholesterol intakes as low as possible while consuming a nutritionally adequate diet. In the face of such recommendations, the agricultural industry is shifting food composition toward lower proportions of all saturated fatty acids. To date, no lower safe limit of specific saturated fatty acid intakes has been identified. This review summarizes research findings and observations on the disparate functions of saturated fatty acids and seeks to bring a more quantitative balance to the debate on dietary saturated fat. Whether a finite quantity of specific dietary saturated fatty acids actually benefits health is not yet known. Because agricultural practices to reduce saturated fat will require a prolonged and concerted effort, and because the world is moving toward more individualized dietary recommendations, should the steps to decrease saturated fatty acids to as low as agriculturally possible not wait until evidence clearly indicates which amounts and types of saturated fatty acids are optimal?

  17. Testing Saturation at Hadron Colliders

    CERN Document Server

    Marquet, C

    2003-01-01

    We extend the saturation models a la Golec-Biernat and Wusthoff to cross-sections of hard processes initiated by virtual-gluon probes separated by large rapidity intervals at hadron colliders. We derive their analytic expressions and apply them to physical examples, such as saturation effects for Mueller-Navelet jets. By comparison to gamma*-gamma* cross-sections we find a more abrupt transition to saturation. We propose to study observables with a potentially clear saturation signal and to use heavy vector and flavored mesons as alternative virtual-gluon probes.

  18. Vertical exchange and chemical conversion of trace elements over topographically complex terrain; Vertikaler Austausch und chemische Umwandlung von Spurenstoffen ueber topographisch gegliedertem Gelaende

    Energy Technology Data Exchange (ETDEWEB)

    Kuntze, K.

    2001-10-01

    The influence of topography on the vertical exchange of trace elements was investigated with the aid of a numeric simulation model. It is a couopled 3D model consisting of the mesoscale model KAMM and the dispersion model DRAIS, extended by the gaseous phase mechanism of the RADM model. This way, both meteorological and chemical processes can be analyzed in a preselected time and spatial resolution. The simulations were validated by a comparison with measurements made during the TRACT campaign. Satisfactory agreement between the two was established. [German] In der vorliegenden Arbeit wurde der Einfluss der Topographie auf den vertikalen Austausch von Spurenstoffen mit Hilfe eines numerischen Simulationsmodells untersucht. Bei dem Simulationsmodell handelt es sich um ein dreidimensionales gekoppeltes Modell, welches aus dem mesoskaligen Modell KAMM und dem um den Gasphasenmechanismus des RADM-Modells erweiterten Ausbreitungsmodell DRAIS besteht. Mit diesem Modellsystem war es moeglich, sowohl meterologische als auch chemische Prozesse in einer vorher gewaehlten zeitlichen und raeumlichen Aufloesung zu betrachten. Um die Qualitaet der Simulation und damit deren Verwendbarkeit fuer die Untersuchungen festzustellen, wurde ein Vergleich mit Messungen durchgefuehrt. Dazu wurden berechnete meterologische und chemische Groessen mit den waehrend der Feldmesskampagne TRACT gemessenen Groessen verglichen. Der Vergleich der simulierten Groessen sowohl mit Radiosondenaufstiegen als auch mit Zeitreihen und Flugzeugmessungen lieferte eine gute Uebereinstimmung. (orig.)

  19. Saturation of Zonal Flows

    Science.gov (United States)

    Kim, Eun-Jin

    2002-11-01

    Zonal flows (ZF) are generated by drift wave (DW) turbulence and then regulate it near marginality by shear suppression. Since collisions damp ZF while ZF suppress DW, the amplitude of DW turbulence (i.e. turbulent transport) is, in turn, proportional to collisionality. A key question is then what happens away from marginality, namely what is the saturation mechanism of ZF in that regime? This raises the interesting physical question of how ZF interact with mne 0, poloidally non-axisymmetric modes [1], both linearly and non linearly. We investigate this issue by exploring the nonlinear excitation of GKH modes by modulational instability in the background of finite amplitude of DW turbulence, as well as the linear inflection-type instability of ZF. In a simple model with cold ions, we show that ZF can grow faster than the linear GKH for γ/ωGKH modes can be comparable to their linear generation. Here, γ and ω are the growth rate and frequency of DW, and p and k are the characteristic wavenumbers of ZF and DW. These findings imply that the linear analysis of GKH may not always be valid and also that there may be no clear distinction between secondary (ZF) and tertiary mode (GKH). The effect of finite ion temperature fluctuations is incorporated in a simple toroidal ion temperature gradient model, within which both zonal flow and temperature are generated by modulational instability. The phase between the two is calculated self-consistently and shown to be positive. Furthermore, the correction to nonlinear generation of GKH modes appears to be small. [1] We refer to these low mne 0 modes as Generalized Kelvin-Helmholtz (GKH) modes, since they will appear as mne 0 distortions of a shear layer.

  20. [Raman spectrometry of several saturated fatty acids and their salts].

    Science.gov (United States)

    Luo, Man; Guan, Ping; Liu, Wen-hui; Liu, Yan

    2006-11-01

    Saturated fatty acids and their salts widely exist in the nature, and they are well known as important chemical materials. Their infrared spectra have been studied in detail. Nevertheless, few works on the Raman spectra characteristics of saturated fatty acids and their salts have been published before. Man-made crystals of acetic acid, stearic acid, calcium acetate, magnesium acetate, calcium stearate and magnesium stearate were investigated by means of Fourier transform Raman spectrometry for purpose of realizing their Raman spectra. Positive ions can cause the distinctions between the spectra of saturated fatty acids and their salts. The differences in mass and configuration between Ca2+ and Mg2+ result in the Raman spectra's diversity between calcium and magnesium salts of saturated fatty acids. Meanwhile, it is considered that the long carbon chain weakened the influence of different positive ions on the salts of saturated fatty acids.

  1. Brief Review of Saturation Physics

    CERN Document Server

    Kovchegov, Yuri V

    2014-01-01

    We present a short overview of saturation physics followed by a summary of the recent progress in our understanding of nonlinear small-$x$ evolution. Topics include McLerran-Venugopalan model, Glauber-Mueller approximation, nonlinear BK/JIMWLK evolution equations, along with the running-coupling and NLO corrections to these equations. We conclude with selected topics in saturation phenomenology.

  2. Brine Distribution after Vacuum Saturation

    DEFF Research Database (Denmark)

    Hedegaard, Kathrine; Andersen, Bertel Lohmann

    1999-01-01

    Experiments with the vacuum saturation method for brine in plugs of chalk showed that a homogeneous distribution of brine cannot be ensured at saturations below 20% volume. Instead of a homogeneous volume distribution the brine becomes concentrated close to the surfaces of the plugs...

  3. Microfluidic chemical reaction circuits

    Science.gov (United States)

    Lee, Chung-cheng; Sui, Guodong; Elizarov, Arkadij; Kolb, Hartmuth C.; Huang, Jiang; Heath, James R.; Phelps, Michael E.; Quake, Stephen R.; Tseng, Hsian-rong; Wyatt, Paul; Daridon, Antoine

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  4. Peristaltic flow of a reactive viscous fluid through a porous saturated channel and convective cooling conditions

    Science.gov (United States)

    Asghar, S.; Hussain, Q.; Hayat, T.; Alsaedi, A.

    2015-07-01

    This article addresses the heat transfer in a peristaltic flow of a reactive combustible viscous fluid through a porous saturated medium. The flow here is induced because of travelling waves along the channel walls. It is assumed that exothermic chemical reactions take place within the channel under the Arrhenius kinetics and the convective heat exchange with the ambient medium at the surfaces of the channel walls follows Newton's law of cooling. The analysis is carried out in the presence of viscous dissipation and without consumption of the material. The governing equations are formulated by employing the long-wavelength approximation. Closed-form solutions for the stream function, axial velocity, and axial pressure gradient are obtained. It is found that the temperature decreases at high Biot numbers, and the Nusselt number increases with increasing reaction parameter. The Biot number and reaction parameter produce the opposite effects on the Nusselt number.

  5. Amide cis-trans isomerization in aqueous solutions of methyl N-formyl-D-glucosaminides and methyl N-acetyl-D-glucosaminides: chemical equilibria and exchange kinetics.

    Science.gov (United States)

    Hu, Xiaosong; Zhang, Wenhui; Carmichael, Ian; Serianni, Anthony S

    2010-04-07

    Amide cis-trans isomerization (CTI) in methyl 2-deoxy-2-acylamido-d-glucopyranosides was investigated by (1)H and (13)C NMR spectroscopy. Singly (13)C-labeled methyl 2-deoxy-2-formamido-d-glucopyranoside (MeGlcNFm) anomers provided standard (1)H and (13)C chemical shifts and (1)H-(1)H and (13)C-(13)C spin-coupling constants for cis and trans amides that are detected readily in aqueous solution. Equipped with this information, doubly (13)C-labeled methyl 2-deoxy-2-acetamido-d-glucopyranoside (MeGlcNAc) anomers were investigated, leading to the detection and quantification of cis and trans amides in this biologically important aminosugar. In comparison to MeGlcNFm anomers, the percentage of cis amide in aqueous solutions of MeGlcNAc anomers is small ( approximately 23% for MeGlcNFm versus approximately 1.8% for MeGlcNAc at 42 degrees C) but nevertheless observable with assistance from (13)C-labeling. Temperature studies gave thermodynamic parameters DeltaG degrees , DeltaH degrees , and DeltaS degrees for cis-trans interconversion in MeGlcNFm and MeGlcNAc anomers. Cis/trans equilibria depended on anomeric configuration, with solutions of alpha-anomers containing less cis amide than those of beta-anomers. Confirmation of the presence of cis amide in MeGlcNAc solutions derived from quantitative (13)C saturation transfer measurements of CTI rate constants as a function of solution temperature, yielding activation parameters E(act), DeltaG degrees (), DeltaH degrees (), and DeltaS degrees () for saccharide CTI. Rate constants for the conversion of trans to cis amide in MeGlcNFm and MeGlcNAc anomers ranged from 0.02 to 3.59 s(-1) over 31-85 degrees C, compared to 0.24-80 s(-1) for the conversion of cis to trans amide over the same temperature range. Energies of activation ranged from 16-19 and 19-20 kcal/mol for the cis --> trans and trans --> cis processes, respectively. Complementary DFT calculations on MeGlcNFm and MeGlcNAc model structures were conducted to evaluate

  6. Broadband fast semiconductor saturable absorber.

    Science.gov (United States)

    Jacobovitz-Veselka, G R; Kellerm, U; Asom, T

    1992-12-15

    Kerr lens mode-locked (KLM) solid-state lasers are typically not self-starting. We address this problem by introducing a broadband semiconductor saturable absorber that could be used as a tunable, all-solid-state, passive starting mechanism. We extend the wavelength tunability of a semiconductor saturable absorber to more than 100 nm using a band-gap-engineered low-temperature molecular-beam-epitaxy (MBE)-grown bulk AlGaAs semiconductor saturable absorber in which the absorption edge of the saturable absorber has been artificially broadened by continuously reducing the Al concentration during the MBE growth. We demonstrate its tunability and its feasibility as a starting mechanism for KLM with a picosecond resonant passive mode-locked Ti:sapphire laser. The extension to femtosecond KLM lasers has been discussed previously.

  7. Simultaneous experimental determination of labile proton fraction ratio and exchange rate with irradiation radio frequency power-dependent quantitative CEST MRI analysis.

    Science.gov (United States)

    Sun, Phillip Zhe; Wang, Yu; Xiao, Gang; Wu, Renhua

    2013-01-01

    Chemical exchange saturation transfer (CEST) imaging is sensitive to dilute proteins/peptides and microenvironmental properties, and has been increasingly evaluated for molecular imaging and in vivo applications. However, the experimentally measured CEST effect depends on the CEST agent concentration, exchange rate and relaxation time. In addition, there may be non-negligible direct radio-frequency (RF) saturation effects, particularly severe for diamagnetic CEST (DIACEST) agents owing to their relatively small chemical shift difference from that of the bulk water resonance. As such, the commonly used asymmetry analysis only provides CEST-weighted information. Recently, it has been shown with numerical simulation that both labile proton concentration and exchange rate can be determined by evaluating the RF power dependence of DIACEST effect. To validate the simulation results, we prepared and imaged two CEST phantoms: a pH phantom of serially titrated pH at a fixed creatine concentration and a concentration phantom of serially varied creatine concentration titrated to the same pH, and solved the labile proton fraction ratio and exchange rate per-pixel. For the concentration phantom, we showed that the labile proton fraction ratio is proportional to the CEST agent concentration with negligible change in the exchange rate. Additionally, we found the exchange rate of the pH phantom is dominantly base-catalyzed with little difference in the labile proton fraction ratio. In summary, our study demonstrated quantitative DIACEST MRI, which remains promising to augment the conventional CEST-weighted MRI analysis.

  8. Teaching of Chemical Engineering Thermodynamics Based on Aspen-Plus ( Ⅱ )Saturated Property Calculation of Pure Substance%基于Aspen-Plus的化工热力学教学(Ⅱ)纯物质饱和性质计算

    Institute of Scientific and Technical Information of China (English)

    陈新志; 赵倩; 钱超

    2011-01-01

    化工热力学作为化学工程的基础学科,是化学工程与工艺专业的一门核心课程,在化学工程的教学过程中占有极其重要的地位。我们借助专业化工模拟软件Aspen-Plus完成化工热力学教学中的纯物质饱和性质计算,得到了较为理想的结果,为用Aspen-Plus辅助化工热力学教学提高教学效率,加强应用能力培养夯实了基础。%As the basic subject, chemical engineering thermodynamics is a main course for process of chemical engineering. Aspen-Plus software which is widely used in chemical engineering and industry has been adopted to calculate the saturated thermodynamic properties of pure substance, and satisfactory re- suits are given. It has provided better basis for teaching of chemical engineering thermodynamics and training of its application ability with the help of Aspen-Plus.

  9. Theory of graphene saturable absorption

    CERN Document Server

    Marini, A; de Abajo, F J Garcia

    2016-01-01

    Saturable absorption is a non-perturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses. Here we show that this effect emerges in graphene at unprecedentedly low light intensities, thus opening avenues to new nonlinear physics and applications in optical technology. Specifically, we theoretically investigate saturable absorption in extended graphene by developing a non-perturbative single-particle approach, describing conduction-electron dynamics in the atomically-thin material using the two-dimensional Dirac equation for massless Dirac fermions, which is recast in the form of generalized Bloch equations. By solving the electron dynamics non-perturbatively, we account for both interband and intraband contributions to the intensity-dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material. The results are in excellent agreement with atomistic quantum-mechanical simulations including high...

  10. Thermodynamically coupled mass transport processes in a saturated clay

    Energy Technology Data Exchange (ETDEWEB)

    Carnahan, C.L.

    1984-11-01

    Gradients of temperature, pressure, and fluid composition in saturated clays give rise to coupled transport processes (thermal and chemical osmosis, thermal diffusion, ultrafiltration) in addition to the direct processes (advection and diffusion). One-dimensional transport of water and a solute in a saturated clay subjected to mild gradients of temperature and pressure was simulated numerically. When full coupling was accounted for, volume flux (specific discharge) was controlled by thermal osmosis and chemical osmosis. The two coupled fluxes were oppositely directed, producing a point of stagnation within the clay column. Solute flows were dominated by diffusion, chemical osmosis, and thermal osmosis. Chemical osmosis produced a significant flux of solute directed against the gradient of solute concentration; this effect reduced solute concentrations relative to the case without coupling. Predictions of mass transport in clays at nuclear waste repositories could be significantly in error if coupled transport processes are not accounted for. 14 references, 8 figures, 1 table.

  11. Thermal Propulsion Capture System Heat Exchanger Design

    Science.gov (United States)

    Richard, Evan M.

    2016-01-01

    One of the biggest challenges of manned spaceflight beyond low earth orbit and the moon is harmful radiation that astronauts would be exposed to on their long journey to Mars and further destinations. Using nuclear energy has the potential to be a more effective means of propulsion compared to traditional chemical engines (higher specific impulse). An upper stage nuclear engine would allow astronauts to reach their destination faster and more fuel efficiently. Testing these engines poses engineering challenges due to the need to totally capture the engine exhaust. The Thermal Propulsion Capture System is a concept for cost effectively and safely testing Nuclear Thermal Engines. Nominally, hydrogen exhausted from the engine is not radioactive, but is treated as such in case of fuel element failure. The Thermal Propulsion Capture System involves injecting liquid oxygen to convert the hydrogen exhaust into steam. The steam is then cooled and condensed into liquid water to allow for storage. The Thermal Propulsion Capture System concept for ground testing of a nuclear powered engine involves capturing the engine exhaust to be cooled and condensed before being stored. The hydrogen exhaust is injected with liquid oxygen and burned to form steam. That steam must be cooled to saturation temperatures before being condensed into liquid water. A crossflow heat exchanger using water as a working fluid will be designed to accomplish this goal. Design a cross flow heat exchanger for the Thermal Propulsion Capture System testing which: Eliminates the need for water injection cooling, Cools steam from 5800 F to saturation temperature, and Is efficient and minimizes water requirement.

  12. Lipid exchange by ultracentrifugation

    DEFF Research Database (Denmark)

    Drachmann, Nikolaj Düring; Olesen, Claus

    2014-01-01

    Lipids play an important role in maintaining P-type ATPase structure and function, and often they are crucial for ATPase activity. When the P-type ATPases are in the membrane, they are surrounded by a mix of different lipids species with varying aliphatic chain lengths and saturation......, and the complex interplay between the lipids and the P-type ATPases are still not well understood. We here describe a robust method to exchange the majority of the lipids surrounding the ATPase after solubilisation and/or purification with a target lipid of interest. The method is based on an ultracentrifugation...... step, where the protein sample is spun through a dense buffer containing large excess of the target lipid, which results in an approximately 80-85 % lipid exchange. The method is a very gently technique that maintains protein folding during the process, hence allowing further characterization...

  13. Active microchannel heat exchanger

    Science.gov (United States)

    Tonkovich, Anna Lee Y [Pasco, WA; Roberts, Gary L [West Richland, WA; Call, Charles J [Pasco, WA; Wegeng, Robert S [Richland, WA; Wang, Yong [Richland, WA

    2001-01-01

    The present invention is an active microchannel heat exchanger with an active heat source and with microchannel architecture. The microchannel heat exchanger has (a) an exothermic reaction chamber; (b) an exhaust chamber; and (c) a heat exchanger chamber in thermal contact with the exhaust chamber, wherein (d) heat from the exothermic reaction chamber is convected by an exothermic reaction exhaust through the exhaust chamber and by conduction through a containment wall to the working fluid in the heat exchanger chamber thereby raising a temperature of the working fluid. The invention is particularly useful as a liquid fuel vaporizer and/or a steam generator for fuel cell power systems, and as a heat source for sustaining endothermic chemical reactions and initiating exothermic reactions.

  14. Saturation and High Density QCD

    OpenAIRE

    Mueller, A. H.

    2005-01-01

    Recent progress in understanding general properties of high energy scattering near the unitarity limit, where high density gluon components of the wavefunction are dominant, is reviewed. The similarity of the QCD problem and that of reaction-diffusion processes in statistical physics is emphasized. The energy dependence of the saturation momentum and the status of geometric scaling are discussed.

  15. EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF); Scientific Opinion on Flavouring Group Evaluation 12, Revision 2 (FGE.12Rev2): Primary saturated or unsaturated alicyclic alcohol, aldehyde, acid, and esters from chemical group 7

    DEFF Research Database (Denmark)

    Larsen, John Christian; Nørby, Karin Kristiane; Beltoft, Vibe Meister

    The European Food Safety Authority (EFSA) asked the Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (the Panel) to provide scientific advice to the Commission on the implications for human health of chemically defined flavouring substances used in or on foodstuffs...... of the flavouring substances in Europe. However, when the Panel examined the information provided by the European Flavouring Industry on the use levels in various foods, it appeared obvious that the MSDI approach in a number of cases would grossly underestimate the intake by regular consumers of products flavoured...... at the use level reported by the Industry, especially in those cases where the annual production values were reported to be small. In consequence, the Panel had reservations about the data on use and use levels provided and the intake estimates obtained by the MSDI approach. In the absence of more precise...

  16. 基于技术系统进化理论的换热器化学除垢方法的研究%Research on Chemical Anti- fouling Methods of Heat Exchanger Based on Technical System Evolution Theory

    Institute of Scientific and Technical Information of China (English)

    李耀中; 李英利; 胡建超

    2011-01-01

    基于技术系统进化理论预测换热器化学除垢方法的研究方向,寻找一种能够代替或改善现有的除垢方法,从而解决现有化学法存在的污染环境、损伤设备、成本较高等缺点。%Based on technical system evolution theory to predict future research direction for chemical anti - fouling methods of heat exchanger and finding a method to replace or improve the present anti - fouling one. Furthmore, could overcome the shortcoming of the present chemical method such as polluting the environment, damaging equipment,and higher cost etc.

  17. Saturation of the turbulent dynamo.

    Science.gov (United States)

    Schober, J; Schleicher, D R G; Federrath, C; Bovino, S; Klessen, R S

    2015-08-01

    The origin of strong magnetic fields in the Universe can be explained by amplifying weak seed fields via turbulent motions on small spatial scales and subsequently transporting the magnetic energy to larger scales. This process is known as the turbulent dynamo and depends on the properties of turbulence, i.e., on the hydrodynamical Reynolds number and the compressibility of the gas, and on the magnetic diffusivity. While we know the growth rate of the magnetic energy in the linear regime, the saturation level, i.e., the ratio of magnetic energy to turbulent kinetic energy that can be reached, is not known from analytical calculations. In this paper we present a scale-dependent saturation model based on an effective turbulent resistivity which is determined by the turnover time scale of turbulent eddies and the magnetic energy density. The magnetic resistivity increases compared to the Spitzer value and the effective scale on which the magnetic energy spectrum is at its maximum moves to larger spatial scales. This process ends when the peak reaches a characteristic wave number k☆ which is determined by the critical magnetic Reynolds number. The saturation level of the dynamo also depends on the type of turbulence and differs for the limits of large and small magnetic Prandtl numbers Pm. With our model we find saturation levels between 43.8% and 1.3% for Pm≫1 and between 2.43% and 0.135% for Pm≪1, where the higher values refer to incompressible turbulence and the lower ones to highly compressible turbulence.

  18. SATURATED PICRIC ACID PREVENTS AUTOPHAGIA

    Directory of Open Access Journals (Sweden)

    V Rahimi-Movaghar

    2008-08-01

    Full Text Available "nThe dysesthesia and paresthesia that occurs in laboratory rats after spinal cord injury (SCI results in autophagia. This self-destructive behavior interferes with functional assessments in designed studies and jeopardizes the health of the injured rat. In this study, we evaluated role of saturated picric acid in the prevention of autophagia and self-mutilation. All rats were anesthetized with an intraperitoneal injection of a mixture of ketamine (100 mg/kg and xylazine (10 mg/kg for the SCI procedures. In the first 39 rats, no solution applied to the hind limbs, but in the next 26 cases, we smeared the saturated picric acid on the tail, lower extremities, pelvic, and abdomen of the rats immediately after SCI. In the rats without picric acid, 23 rats died following autophagia, but in the 26 rats with picric acid, there was no autophagia (P < 0.001. Picric acid side effects in skin and gastrointestinal signs such as irritation, redness and diarrhea were not seen in any rat. Saturated picric acid is a topical solution that if used appropriately and carefully, might be safe and effectively prevents autophagia and self-mutilation. When the solution is applied to the lower abdomen and limbs, we presume that its bitterness effectively prevents the rat from licking and biting the limb.

  19. FCC/BCC competition and enhancement of saturation magnetization in nanocrystalline Co-Ni-Fe films

    NARCIS (Netherlands)

    Chechenin, N. G.; Khomenko, E. V.; de Hosson, J. Th. M.

    2007-01-01

    The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B-s = 21 kG was attained. An enhancement of the saturation magnetization compared to t

  20. Pharmaceutical Applications of Ion-Exchange Resins

    Science.gov (United States)

    Elder, David

    2005-01-01

    The historical uses of ion-exchanged resins and a summary of the basic chemical principles involved in the ion-exchanged process are discussed. Specific applications of ion-exchange are provided that include drug stabilization, pharmaceutical excipients, taste-masking agents, oral sustained-release products, topical products for local application…

  1. Heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Craig, L.B.; Farma, A.J.

    1987-01-06

    This invention concerns a heat exchanger as used in a space heater, of the type in which hot exhaust gases transfer heat to water or the like flowing through a helical heat exchange coil. A significant improvement to the efficiency of the heat exchange occurring between the air and water is achieved by using a conduit for the water having external helical fluting such that the hot gases circulate along two paths, rather than only one. A preferred embodiment of such a heat exchanger includes a porous combustion element for producing radiant heat from a combustible gas, surrounded by a helical coil for effectively transferring the heat in the exhaust gas, flowing radially from the combustion element, to the water flowing through the coil. 4 figs.

  2. Ion-exchange chromatographic protein refolding.

    Science.gov (United States)

    Freydell, Esteban J; van der Wielen, Luuk; Eppink, Michel; Ottens, Marcel

    2010-11-12

    The application of ion-exchange (IEX) chromatography to protein refolding (IExR) has been successfully proven, as supported by various studies using different model proteins, ion-exchange media and flow configurations. Ion-exchange refolding offers a relatively high degree of process intensification, represented by the possibility of performing protein refolding, product purification and product concentration, in one unit operation. Besides its high degree of process intensification, IExR offers an additional set of key advantages including: spatial isolation of the bound protein molecules and the controllable change in chemical composition using gradients. Despite of the acknowledgement of the former advantages, the lack of mechanistic understanding on how they influence the process performance of the ion-exchange refolding reactor, limits the ability to exploit them in order to optimize the performance of the unit. This paper presents a quantitative analysis that assesses the effect that the spatial isolation and the urea gradient, have on the IExR performance, judged on the basis of the refolding yield (Y(N)) and the fractional mass recovery (f(Prot,Rec)). Additionally, this work discusses the effect of the protein load, the protein loading state (i.e., native, denatured, denatured and reduced (D&R)) and the adsorbent type on f(Prot,Rec). The presented work shows: (1) that the protein load has a direct effect on f(Prot,Rec), and the magnitude of this effect depends on the loading state of the protein solution and the adsorbent type; (2) that irrespectively of the type of adsorbent used, the saturation capacity of a denatured protein is less than the native protein and that this difference can be linked to differences in accessible binding surface area; (3) that there is a clear correlation between fractional surface coverage (θ) and f(Prot,Rec), indicating that the former could serve as a good descriptor to assess spatial isolation, and (4) that the urea

  3. CATION EXCHANGE CAPACITY OF DOMINANT SOIL TYPES IN THE REPUBLIC OF CROATIA

    Directory of Open Access Journals (Sweden)

    Marija Tomasic

    2013-09-01

    Full Text Available The study was conducted on 18 locations and 11 dominant soil types in the Republic of Croatia including their evolution-genetic horizons. In total, 51 soil samples were examined. Analysis of soil was done by saturating patterns using barium chloride solution in three replications. Descriptive statistics of the analyzed data was conducted. Basic statistical parameters were calculated, and functional dependence between the base saturation (V% of analyzed soil samples and their pH was observed. The correlation coefficient (r between base saturation (V% and pH for all examined soils was r=0.79 (n=51; very strong correlation. For acid soils it was r=0.82 (n=17; very strong correlation, for neutral soils r=0.75 (n=8; very strong correlation, and finally for alkaline soils r=0.15 (n=26; very weak correlation. Cation exchange capacity values ranged from 2.39 cmol+*kg-1 to 33.8 cmol+*kg-1 depending on soil type, pH, organic content and other soil parameters. The content of exchangeable cations in the sum of basic cations ranged from: Ca2+ (16% - 94%, Mg2+ (2% - 41%, K+ (1% - 68% and Na+ (<0.01% also depending on soil type, depth, location and other physical and chemical soil parameters.

  4. Promoter analysis by saturation mutagenesis

    Directory of Open Access Journals (Sweden)

    Baliga Nitin

    2001-01-01

    Full Text Available Gene expression and regulation are mediated by DNA sequences, in most instances, directly upstream to the coding sequences by recruiting transcription factors, regulators, and a RNA polymerase in a spatially defined fashion. Few nucleotides within a promoter make contact with the bound proteins. The minimal set of nucleotides that can recruit a protein factor is called a cis-acting element. This article addresses a powerful mutagenesis strategy that can be employed to define cis-acting elements at a molecular level. Technical details including primer design, saturation mutagenesis, construction of promoter libraries, phenotypic analysis, data analysis, and interpretation are discussed.

  5. Saturated versus non-saturated two-scales permeability

    Science.gov (United States)

    Lopez, Elena; Ammar, Amine; Abisset-Chavanne, Emmanuelle; Binetruy, Christophe; Chinesta, Francisco

    2016-10-01

    A crucial step in many composites manufacturing processes is the impregnation of fibrous medium with the resin. The fundamental property needed to quantify the flow is the permeability of the fibrous medium. Process models require the permeability as input data to predict flow patterns and pressure fields. Efficient numerical techniques are needed to solve homogenization problems with geometrical data coming from high-resolution images, involving two-scales and linear fluids. Within this frame-work, this work addresses the question of how to compute the macroscopic permeability from a microscopic description consisting of a viscous fluid flow model defined in a two-scale porous medium, considering the saturated and unsaturated cases.

  6. NMR studies of proton exchange kinetics in aqueous formaldehyde solutions

    Science.gov (United States)

    Rivlin, Michal; Eliav, Uzi; Navon, Gil

    2014-05-01

    Aqueous solutions of formaldehyde, formalin, are commonly used for tissue fixation and preservation. Treatment with formalin is known to shorten the tissue transverse relaxation time T2. Part of this shortening is due to the effect of formalin on the water T2. In the present work we show that the shortening of water T2 is a result of proton exchange between water and the major constituent of aqueous solutions of formaldehyde, methylene glycol. We report the observation of the signal of the hydroxyl protons of methylene glycol at 2 ppm to high frequency of the water signal that can be seen at low temperatures and at pH range of 6.0 ± 1.5 and, at conditions where it cannot be observed by the single pulse experiment, it can be detected indirectly through the water signal by the chemical exchange saturation transfer (CEST) experiment. The above finding made it possible to obtain the exchange rate between the hydroxyl protons of the methylene glycol and water in aqueous formaldehyde solutions, either using the dispersion of the spin-lattice relaxation rate in the rotating frame (1/T1ρ) or, at the slow exchange regime, from the line width hydroxyl protons of methylene glycol. The exchange rate was ∼104 s-1 at pH 7.4 and 37 °C, the activation energy, 50.2 kJ/mol and its pH dependence at 1.1 °C was fitted to: k (s-1) = 520 + 6.5 × 107[H+] + 3.0 × 109[OH-].

  7. The use of saturation in qualitative research.

    Science.gov (United States)

    Walker, Janiece L

    2012-01-01

    Understanding qualitative research is an important component of cardiovascular nurses' practice and allows them to understand the experiences, stories, and perceptions of patients with cardiovascular conditions. In understanding qualitative research methods, it is essential that the cardiovascular nurse understands the process of saturation within qualitative methods. Saturation is a tool used for ensuring that adequate and quality data are collected to support the study. Saturation is frequently reported in qualitative research and may be the gold standard. However, the use of saturation within methods has varied. Hence, the purpose of this column is to provide insight for the cardiovascular nurse regarding the use of saturation by reviewing the recommendations for which qualitative research methods it is appropriate to use and how to know when saturation is achieved. In understanding saturation, the cardiovascular nurse can be a better consumer of qualitative research.

  8. Using X-ray computed tomography to evaluate the initial saturation resulting from different saturation procedures

    DEFF Research Database (Denmark)

    Christensen, Britt Stenhøj Baun; Wildenschild, D; Jensen, K.H.

    2006-01-01

    saturation. In this study three techniques often applied in the laboratory have been evaluated for a fine sand sample: (1) venting of the sample with carbon dioxide prior to saturation, (2) applying vacuum to the sample in the beginning of the saturation procedure, and finally (3) the use of degassed water...... with pressurized nitrogen between each saturation and allowed to saturate for the same length of time for all the different procedures. Both gravimetric measurements and CT attenuation levels showed that venting the sample with carbon dioxide prior to saturation clearly improved initial saturation whereas the use...

  9. Relation between electric properties and water saturation for hematitic sandstone with frequency

    Directory of Open Access Journals (Sweden)

    M. M. Gomaa

    2008-06-01

    Full Text Available This paper focuses on the effect of water saturation on A. C. electrical conductivity and dielectric constant of fully and partially saturated hematitic sandstone sample (Aswan area, Egypt. The saturation of the sample was changed from partial to full saturation. Complex resistivity measurements at room temperature (~16°C, were performed in the frequency range from 0.1 Hz to 100 KHz. Experimental electrical spectra indicate, generally, that the electrical conductivity and dielectric constant vary strongly with water saturations and frequency. The low frequency electrical conductivity and dielectric constant are mainly controlled by surface conduction and polarization of the electrical double layer. The behaviour of the electrical conductivity and dielectric constant, with increasing water content, were argued to the orientational polarization of bound water for very low saturations, displacement of the excess surface charges for relatively low saturations, and free exchange of excess ions in double layer with the bulk electrolyte and generation of transient diffusion potentials which lag behind the applied field for high saturations.

  10. Next Generation Microchannel Heat Exchangers

    CERN Document Server

    Ohadi, Michael; Dessiatoun, Serguei; Cetegen, Edvin

    2013-01-01

    In Next Generation Microchannel Heat Exchangers, the authors’ focus on the new generation highly efficient heat exchangers and presentation of novel data and technical expertise not available in the open literature.  Next generation micro channels offer record high heat transfer coefficients with pressure drops much less than conventional micro channel heat exchangers. These inherent features promise fast penetration into many mew markets, including high heat flux cooling of electronics, waste heat recovery and energy efficiency enhancement applications, alternative energy systems, as well as applications in mass exchangers and chemical reactor systems. The combination of up to the minute research findings and technical know-how make this book very timely as the search for high performance heat and mass exchangers that can cut costs in materials consumption intensifies.

  11. International Exchanges

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    <正>On April 1st,2014,CPAPD Deputy Secretary General Ms.Chen Huaifan met with Mr.Djudjuk Juyoto Suntani,President of the World Peace Committee,Indonesia,who headed the delegation,in the CPAPD office.The two sides exchanged views on issues of common concern including cooperation between the two organizations and the inheritance of Chinese culture.

  12. Exchange Options

    NARCIS (Netherlands)

    Jamshidian, Farshid

    2007-01-01

    The contract is described and market examples given. Essential theoretical developments are introduced and cited chronologically. The principles and techniques of hedging and unique pricing are illustrated for the two simplest nontrivial examples: the classical Black-Scholes/Merton/Margrabe exchange

  13. Evidence from sup 18 O exchange measurements for steps involving a weak acid and a slow chemical transformation in the mechanism of phosphorylation of the gastric H sup + ,K sup + -ATPase by inorganic phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Faller, L.D.; Diaz, R.A. (Univ. of California School of Medicine and Veterans Administration Hospital Center, Los Angeles (USA))

    1989-08-22

    Phosphorylation of the gastric H,K-ATPase by P{sub i} has been studied by measuring the P{sup 18}O{sub j}{sup 16}O{sub 4-j} distribution as a function of time at different H{sup +}, K{sup +}, and ({sup 18}O)P{sub i} concentrations. The advantage of isotope exchange measurements is that the P{sup 18}O{sub j}{sup 16}O{sub 4-j} distribution depends on the relative rates of HOH loss to form the phosphoenzyme intermediate and P{sub i} dissociation from the enzyme. Therefore, {sup 18}O exchange is a sensitive probe of mechanism. K{sup +} increases the exchange rate ({nu}{sub ex}) but does not affect the partition coefficient (P{sub c}) that determines the P{sup 18}O{sub j}{sup 16}O{sub 4-j} distribution. Conversely, H{sup +} inhibits exchange. A single P{sub c} describes the data at every pH, but the value increases from 0.04 to pH 8 to 0.64 at pH 5.5. {nu}{sub ex} depends hyperbolically on (P{sub i}){sub 0}. K{sub m} for P{sub i} does not depend on pH, and P{sub c} does not depend on (P{sub i}){sub 0}. Individual rate constants in the phosphorylation mechanism are estimated. Formation of the E{center dot}P{sub i} complex that looses HOH is 1-2 orders of magnitude slower at pH 5.5 than at pH 8 and is not diffusion controlled. The observed change in P{sub c} with pH is compatible with catalysis occurring by a different mechanism when a group with pK{sub a} = 7.2 is protonated. Slower than diffusion-controlled formation of the E{center dot}P{sub i} complex that splits out HOH is evidence for a relatively slow, unimolecular chemical transformation involving an additional intermediate in the phosphorylation mechanism, such as a protein conformational change.

  14. Impact of the electrochemical porosity and chemical composition on the lithium ion exchange behavior of polypyrroles (ClO4-, TOS-, TFSI-) prepared electrochemically in propylene carbonate. comparative EQCM, EIS and CV studies.

    Science.gov (United States)

    Dziewoński, Paweł Marek; Grzeszczuk, Maria

    2010-06-03

    Conditions of electrodeposition, i.e. a potential window of the process, addition of water, the current density, and morphology of substrate electrodes (Pt, Pt/TiO(2), Au), were shown to influence strongly ion-exchange properties of polypyrrole (PPy) synthesized in propylene carbonate (PC), doped with ClO(4)(-) or p-toluenesulfonate (TOS(-)). "Electrochemical porosity" and redox activity of PPy films were compared to the characteristics of poly(3,4-ethylenedioxythiophene) (PEDOT). A molecular indicator of the PPy film structure packing was bis(trifluoromethylsulfonyl)imide anion (TFSI(-)). Ion-exchange properties of PPy were found to be almost independent of chemical composition of the polymer, described in the literature as PPy(I), PPy(II), PPy(III). Instead, micro- and nanoscopic morphology of the polymer film and a molecular level packing of the polymer chains as well as the counterion nature are of the foremost importance. The polymer film structure/properties are shown to change upon prolonged redox/ionic stimulations. Lithium exchange between PPy films and contacting phases (PC electrolyte, TiO(2)) proceeds in addition to the anion exchange, the latter being a dominant process under conditions of the reversible electrochemical p-doping of PPy, although diffusion coefficients of PC solvated lithium ions in PPy are higher than diffusion coefficients of perchlorate, p-toluenesulfonate or bis(trifluoromethylsulfonyl)imide anions. The highest flux of Li(+) ions into/out of the PPy phase takes place about -1.0 V vs Ag/Ag(+) which is clearly evidenced by the cathodic/anodic CV peaks. Cation transport phenomena can be analyzed independently from anion transport when observed at a longer time scale (low values of potential scan rate) as each prevails at different redox states of the polymer. However, in a shorter time scale (v > or = 10 mV s(-1)), the opposite fluxes of cations and anions were observed to interfere. Furthermore, a net uptake of propylene carbonate by

  15. Power flow control using distributed saturable reactors

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrovski, Aleksandar D.

    2016-02-13

    A magnetic amplifier includes a saturable core having a plurality of legs. Control windings wound around separate legs are spaced apart from each other and connected in series in an anti-symmetric relation. The control windings are configured in such a way that a biasing magnetic flux arising from a control current flowing through one of the plurality of control windings is substantially equal to the biasing magnetic flux flowing into a second of the plurality of control windings. The flow of the control current through each of the plurality of control windings changes the reactance of the saturable core reactor by driving those portions of the saturable core that convey the biasing magnetic flux in the saturable core into saturation. The phasing of the control winding limits a voltage induced in the plurality of control windings caused by a magnetic flux passing around a portion of the saturable core.

  16. Casimir experiments showing saturation effects

    CERN Document Server

    Sernelius, Bo E

    2009-01-01

    We address several different Casimir experiments where theory and experiment disagree. First out is the classical Casimir force measurement between two metal half spaces; here both in the form of the torsion pendulum experiment by Lamoreaux and in the form of the Casimir pressure measurement between a gold sphere and a gold plate as performed by Decca et al.; theory predicts a large negative thermal correction, absent in the high precision experiments. The third experiment is the measurement of the Casimir force between a metal plate and a laser irradiated semiconductor membrane as performed by Chen et al.; the change in force with laser intensity is larger than predicted by theory. The fourth experiment is the measurement of the Casimir force between an atom and a wall in the form of the measurement by Obrecht et al. of the change in oscillation frequency of a 87 Rb Bose-Einstein condensate trapped to a fused silica wall; the change is smaller than predicted by theory. We show that saturation effects can exp...

  17. VERTICAL VIBRATION ANALYSIS OF AXISYMMETRIC SATURATED SOIL

    Institute of Scientific and Technical Information of China (English)

    CAI Yuan-qiang; XU Chang-jie; ZHENG Zao-feng; WU Da-zhi

    2006-01-01

    Based on Biot's dynamic consolidation equations, by means of Laplace-Hankel transform technology, the integral solutions of stress and displacement in saturated soil with subjacent rock-stratum under axisymmetric arbitrary excitations were derived. Influence of the reflected wave generated by the boundary was revealed. Numerical results indicate that the vibration frequency has some effect on the vertical displacement of saturated soil. The vertical displacement at the surface of saturated soil lags in phase with the load. Furthermore, the dynamic permeability coefficient of saturated soil has significant effect on the vertical displacement at the initial stage of load applied, but when the load becomes stable, the effect is inapparent.

  18. Ion exchange equilibrium constants

    CERN Document Server

    Marcus, Y

    2013-01-01

    Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and

  19. EP-toxicity test of saturated GT-73 resin and resin in grout

    Energy Technology Data Exchange (ETDEWEB)

    Bibler, J.P.

    1985-04-24

    The results of EP-toxicity tests on mercury saturated Duolite{reg_sign} GT-73 cation exchange resin clarify options for the ultimate disposal of spent resin. Samples of GT-73 saturated with mercury passed the EP-toxicity test, indicating that fully spent resin may be classifed as ``solid``-not``hazardous``-waste and stored or disposed-of as such. Samples of GT-73 resin saturated with mercury and then incorporated into Portland Type 1 cement did not pass the EP-toxicity test and fall into the ``hazardous waste`` category. Samples of GT-73 resin less-than-saturated with mercury which were in corporated in Portland Type 1 cement passed the EP-toxicity test and may be classified as ``solid waste.`` Other commercially available materials are being investigated for incorporating fully spent GT-73 resin in a solid waste form.

  20. Violation of homeostasis of the main types of exchange and immune resistance status in children with subclinical hypovitaminosis in conditions of exposure to chemical environmental factors

    Directory of Open Access Journals (Sweden)

    A.M. Yambulatov

    2016-03-01

    Full Text Available The study of the chemical substances’ content of anthropogenic origin in children with subclinical polyhypovitaminosis was conducted. It was found that a deficiency of vitamins A, C, E, B6 and B12 increases the risk of developing of elevated concentrations of organic substances of technogenic origin in blood in 1.4–6.9 times. In children with subclinical polyhypovitaminosis and high blood phenol, formaldehyde, aromatic hydrocarbons, and organ chlorine compounds increases the tension of erythropoiesis, decreases the activity of proliferating processes of lympfomonocytic germ cell factors of nonspecific resistance. Even subclinical forms of polyhypovitaminosis on the background of high content of organic compounds in the blood of children are accompanied by a slowdown of protein and carbohydrate metabolism, depletion of antioxidant defense system of reserves and shortage of energy metabolism. Developing disorders of fat metabolism in children with subclinical polyhypovitaminosis occur against a background of strained reactions of hormonal regulation that, in case of the progressive course may pose a threat to the early development of cardiovascular disease in older age groups.

  1. Development of carbon nanotubes based gas diffusion layers by in situ chemical vapor deposition process for proton exchange membrane fuel cells

    Science.gov (United States)

    Kannan, A. M.; Kanagala, P.; Veedu, V.

    A proprietary in situ chemical vapor deposition (CVD) process was developed for gas diffusion layer (GDL) by growing a micro-porous layer on the macro-porous, non-woven fibrous carbon paper. The characteristics of the GDL samples such as, surface morphology, wetting characteristics, and cross-section were characterized using electron microscopes, goniometer and focused ion beam, respectively. Fuel cell performance of the GDLs was evaluated using single cell with hydrogen/oxygen as well as hydrogen/air at ambient pressure, at elevated temperature and various RH conditions using Nafion-212 as an electrolyte. The GDLs with in situ growth of micro-porous layers containing carbon nanotubes (CNTs) without any hydrophobic agent showed significant improvement in mechanical robustness as well as fuel cell performance at elevated temperature at lower RH conditions. The micro-porous layer of the GDLs as seen under scanning electron microscope showed excellent surface morphology with surface homogeneity through reinforcement by the multi-walled CNTs.

  2. Interpreting HSE Contents of Planetary Basalts: The Importance of Sulfide Saturation and Under-Saturation

    Science.gov (United States)

    Righter, K.

    2000-01-01

    Highly siderophile elements provide important constraints on planetary differentiation due to their siderophile behavior. Their interpretation in terms of planetary differentiation models has so far overlooked the importance of sulfide saturation and under-saturation.

  3. Saturated fat, carbohydrate, and cardiovascular disease.

    Science.gov (United States)

    Siri-Tarino, Patty W; Sun, Qi; Hu, Frank B; Krauss, Ronald M

    2010-03-01

    A focus of dietary recommendations for cardiovascular disease (CVD) prevention and treatment has been a reduction in saturated fat intake, primarily as a means of lowering LDL-cholesterol concentrations. However, the evidence that supports a reduction in saturated fat intake must be evaluated in the context of replacement by other macronutrients. Clinical trials that replaced saturated fat with polyunsaturated fat have generally shown a reduction in CVD events, although several studies showed no effects. An independent association of saturated fat intake with CVD risk has not been consistently shown in prospective epidemiologic studies, although some have provided evidence of an increased risk in young individuals and in women. Replacement of saturated fat by polyunsaturated or monounsaturated fat lowers both LDL and HDL cholesterol. However, replacement with a higher carbohydrate intake, particularly refined carbohydrate, can exacerbate the atherogenic dyslipidemia associated with insulin resistance and obesity that includes increased triglycerides, small LDL particles, and reduced HDL cholesterol. In summary, although substitution of dietary polyunsaturated fat for saturated fat has been shown to lower CVD risk, there are few epidemiologic or clinical trial data to support a benefit of replacing saturated fat with carbohydrate. Furthermore, particularly given the differential effects of dietary saturated fats and carbohydrates on concentrations of larger and smaller LDL particles, respectively, dietary efforts to improve the increasing burden of CVD risk associated with atherogenic dyslipidemia should primarily emphasize the limitation of refined carbohydrate intakes and a reduction in excess adiposity.

  4. Seismic determination of saturation in fractured reservoirs

    Science.gov (United States)

    Brown, R.L.; Wiggins, M.L.; Gupta, A.

    2002-01-01

    Detecting the saturation of a fractured reservoir using shear waves is possible when the fractures have a geometry that induces a component of movement perpendicular to the fractures. When such geometry is present, vertically traveling shear waves can be used to examine the saturation of the fractured reservoir. Tilted, corrugated, and saw-tooth fracture models are potential examples.

  5. Saturation and geometrical scaling in small systems

    CERN Document Server

    Praszalowicz, Michal

    2016-01-01

    Saturation and geometrical scaling (GS) of gluon distributions are a consequence of the non-linear evolution equations of QCD. We argue that in pp GS holds for the inelastic cross-section rather than for the multiplicity distributions. We also discuss possible fluctuations of the proton saturation scale in pA collisions at the LHC.

  6. Semiconductor saturable absorbers for ultrafast terahertz signals

    DEFF Research Database (Denmark)

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductors GaAs, GaP, and Ge in the terahertz THz frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum...

  7. Ultrafast THz Saturable Absorption in Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hoffmann, Matthias C.

    2011-01-01

    We demonstrate THz saturable absorption in n-doped semiconductors GaAs, GaP, and Ge in a nonlinear THz time-domain spectroscopy experiment. Saturable absorption is caused by sample conductivity modulation due to electron heating and satellite valley scattering in the field of a strong THz pulse....

  8. Determination of saturation functions and wettability for chalk based on measured fluid saturations

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, D.; Bech, N.; Moeller Nielsen, C.

    1998-08-01

    The end effect of displacement experiments on low permeable porous media is used for determination of relative permeability functions and capillary pressure functions. Saturation functions for a drainage process are determined from a primary drainage experiment. A reversal of the flooding direction creates an intrinsic imbibition process in the sample, which enables determination if imbibition saturation functions. The saturation functions are determined by a parameter estimation technique. Scanning effects are modelled by the method of Killough. Saturation profiles are determined by NMR. (au)

  9. Characterization of creatine guanidinium proton exchange by water-exchange (WEX) spectroscopy for absolute-pH CEST imaging in vitro.

    Science.gov (United States)

    Goerke, Steffen; Zaiss, Moritz; Bachert, Peter

    2014-05-01

    Chemical exchange saturation transfer (CEST) enables indirect detection of small metabolites in tissue by MR imaging. To optimize and interpret creatine-CEST imaging we characterized the dependence of the exchange-rate constant k(sw) of creatine guanidinium protons in aqueous creatine solutions as a function of pH and temperature T in vitro. Model solutions in the low pH range (pH = 5-6.4) were measured by means of water-exchange (WEX)-filtered ¹H NMR spectroscopy on a 3 T whole-body MR tomograph. An extension of the Arrhenius equation with effective base-catalyzed Arrhenius parameters yielded a general expression for k(sw) (pH, T). The defining parameters were identified as the effective base-catalyzed rate constant k(b,eff) (298.15 K) = (3.009 ± 0.16) × 10⁹  Hz l/mol and the effective activation energy E(A,b,eff)  = (32.27 ± 7.43) kJ/mol at a buffer concentration of c(buffer)  = (1/15) M. As expected, a strong dependence of k(sw) on temperature was observed. The extrapolation of the exchange-rate constant to in vivo conditions (pH = 7.1, T = 37 °C) led to the value of the exchange-rate constant k(sw)  = 1499 Hz. With the explicit function k(sw) (pH, T) available, absolute-pH CEST imaging could be realized and experimentally verified in vitro. By means of our calibration method it is possible to adjust the guanidinium proton exchange-rate constant k(sw) to any desired value by preparing creatine model solutions with a specific pH and temperature.

  10. Saturation process of nonlinear standing waves

    Institute of Scientific and Technical Information of China (English)

    马大猷; 刘克

    1996-01-01

    The sound pressure of the nonlinear standing waves is distorted as expected, but also tends to saturate as being found in standing-wave tube experiments with increasing sinusoidal excitation. Saturation conditions were not actually reached, owing to limited excitation power, but the evidence of tendency to saturation is without question. It is the purpose of this investigation to find the law of saturation from the existing experimental data. The results of curve fitting indicate that negative feedback limits the growth of sound pressure with increasing excitation, the growth of the fundamental and the second harmonic by the negative feedback of their sound pressures, and the growth of the third and higher harmonics, however, by their energies (sound pressures squared). The growth functions of all the harmonics are derived, which are confirmed by the experiments. The saturation pressures and their properties are found.

  11. Saturated pattern-illuminated Fourier ptychography microscopy

    Science.gov (United States)

    Fang, Yue; Chen, Youhua; Kuang, Cuifang; Xiu, Peng; Liu, Qiulan; Ge, Baoliang; Liu, Xu

    2017-01-01

    We report a series of simulation studies which extends pattern-illuminated Fourier ptychography microscopy by integrating with the nonlinearity arising from saturation of the fluorophore excited state for super-resolution fluorescence imaging. This extended technique, termed Saturated pattern-illuminated Fourier ptychography (SpiFP) microscopy, could achieve a resolution four times that of wide field when the illuminating light intensity approaches the saturation threshold in simulations. Increasing light intensity leads to further resolution enhancement. In order to demonstrate the performance of SpiFP, we make a comparison between SpiFP and saturated structure illumination microscopy in simulations, and prove that the SpiFP exhibits superior robustness to noise, aberration correcting ability, and pattern’s flexibility. Introducing the saturation of the fluorescent emission brings in notable improvements in imaging performance, implying its potential in nanoscale-sized biological observations by wide-field microscopy.

  12. Fault-Tolerant Heat Exchanger

    Science.gov (United States)

    Izenson, Michael G.; Crowley, Christopher J.

    2005-01-01

    A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing. The reason this heat exchanger can tolerate a single-point leak is that the heat-transfer fluids are everywhere separated by a vented volume and at least two seals. The combination of fault tolerance, compactness, and light weight is implemented in a unique heat-exchanger core configuration: Each fluid passage is entirely surrounded by a vented region bridged by solid structures through which heat is conducted between the fluids. Precise, proprietary fabrication techniques make it possible to manufacture the vented regions and heat-conducting structures with very small dimensions to obtain a very large coefficient of heat transfer between the two fluids. A large heat-transfer coefficient favors compact design by making it possible to use a relatively small core for a given heat-transfer rate. Calculations and experiments have shown that in most respects, the fault-tolerant heat exchanger can be expected to equal or exceed the performance of the non-fault-tolerant heat exchanger that it is intended to supplant (see table). The only significant disadvantages are a slight weight penalty and a small decrease in the mass-specific heat transfer.

  13. International Exchanges

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    On October 12,2015,Mr.Zhu Rui,CPAPD Secretary General,chaired informal discussions with U.S.young experts and scholars on arms control and non-proliferation.The two sides exchanged views on international arms control,disarmament,non-proliferation and nuclear security,etc.During October 12 to 16,2015,at the invitation of the CPAPD,a four-member delegation from the Vietnam Peace Committee headed by its Vice-President Ms.Nguyen Thi Hoang Van

  14. Scraped surface heat exchangers.

    Science.gov (United States)

    Rao, Chetan S; Hartel, Richard W

    2006-01-01

    Scraped surface heat exchangers (SSHEs) are commonly used in the food, chemical, and pharmaceutical industries for heat transfer, crystallization, and other continuous processes. They are ideally suited for products that are viscous, sticky, that contain particulate matter, or that need some degree of crystallization. Since these characteristics describe a vast majority of processed foods, SSHEs are especially suited for pumpable food products. During operation, the product is brought in contact with a heat transfer surface that is rapidly and continuously scraped, thereby exposing the surface to the passage of untreated product. In addition to maintaining high and uniform heat exchange, the scraper blades also provide simultaneous mixing and agitation. Heat exchange for sticky and viscous foods such as heavy salad dressings, margarine, chocolate, peanut butter, fondant, ice cream, and shortenings is possible only by using SSHEs. High heat transfer coefficients are achieved because the boundary layer is continuously replaced by fresh material. Moreover, the product is in contact with the heating surface for only a few seconds and high temperature gradients can be used without the danger of causing undesirable reactions. SSHEs are versatile in the use of heat transfer medium and the various unit operations that can be carried out simultaneously. This article critically reviews the current understanding of the operations and applications of SSHEs.

  15. Saturation Physics on the Energy Frontier

    CERN Document Server

    Zaslavsky, David

    2015-01-01

    Saturation physics is expected to be relevant at sufficiently small parton momentum fractions $x$ in high-energy proton- (or deuteron-)ion collisions at RHIC and the LHC. Accordingly, these collisions provide the best available testing ground for the saturation model. However, producing precise numerical predictions from the model is a complicated task; the state of the art in this area involves next-to-leading order QCD calculations, which are difficult to do numerically. Here I'll review recent progress in extracting numerical predictions from saturation models and matching them to experimental results.

  16. SATURATION BIOPSY OF THE PROSTATE (REVIEW

    Directory of Open Access Journals (Sweden)

    A. V. Sadchenko

    2014-07-01

    Full Text Available Prostate biopsy is the principal method of diagnois of prostate cancer, allowing to start the adequate treatment. The tactics of the patients, which have negative initial biopsy, is a subject of discussion. Saturation biopsy is a “gold standard„ of diagnostics of PCA with repeat biopsy. Saturation biopsy of the prostate is not a primary procedure, usually apply in patients with negative biopsies in anamnesis, patients with multifocal PIN and ASAP. Saturation biopsy allows to more precisely predict the volume and degree of malignancy of PCA, that can be used for planning tactics of active surveillance and focal therapy.

  17. Electric conductivity for laboratory and field monitoring of induced partial saturation (IPS) in sands

    Science.gov (United States)

    Kazemiroodsari, Hadi

    Liquefaction is loss of shear strength in fully saturated loose sands caused by build-up of excess pore water pressure, during moderate to large earthquakes, leading to catastrophic failures of structures. Currently used liquefaction mitigation measures are often costly and cannot be applied at sites with existing structures. An innovative, practical, and cost effective liquefaction mitigation technique titled "Induced Partial Saturation" (IPS) was developed by researchers at Northeastern University. The IPS technique is based on injection of sodium percarbonate solution into fully saturated liquefaction susceptible sand. Sodium percarbonate dissolves in water and breaks down into sodium and carbonate ions and hydrogen peroxide which generates oxygen gas bubbles. Oxygen gas bubbles become trapped in sand pores and therefore decrease the degree of saturation of the sand, increase the compressibility of the soil, thus reduce its potential for liquefaction. The implementation of IPS required the development and validation of a monitoring and evaluation technique that would help ensure that the sands are indeed partially saturated. This dissertation focuses on this aspect of the IPS research. The monitoring system developed was based on using electric conductivity fundamentals and probes to detect the transport of chemical solution, calculate degree of saturation of sand, and determine the final zone of partial saturation created by IPS. To understand the fundamentals of electric conductivity, laboratory bench-top tests were conducted using electric conductivity probes and small specimens of Ottawa sand. Bench-top tests were used to study rate of generation of gas bubbles due to reaction of sodium percarbonate solution in sand, and to confirm a theory based on which degree of saturation were calculated. In addition to bench-top tests, electric conductivity probes were used in a relatively large sand specimen prepared in a specially manufactured glass tank. IPS was

  18. Segmented heat exchanger

    Science.gov (United States)

    Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann

    2010-12-14

    A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.

  19. Combinatorics of saturated secondary structures of RNA.

    Science.gov (United States)

    Clote, P

    2006-11-01

    Following Zuker (1986), a saturated secondary structure for a given RNA sequence is a secondary structure such that no base pair can be added without violating the definition of secondary structure, e.g., without introducing a pseudoknot. In the Nussinov-Jacobson energy model (Nussinov and Jacobson, 1980), where the energy of a secondary structure is -1 times the number of base pairs, saturated secondary structures are local minima in the energy landscape, hence form kinetic traps during the folding process. Here we present recurrence relations and closed form asymptotic limits for combinatorial problems related to the number of saturated secondary structures. In addition, Python source code to compute the number of saturated secondary structures having k base pairs can be found at the web servers link of bioinformatics.bc.edu/clotelab/.

  20. Saturated thickness, High Plains aquifer, 2009

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This raster data set represents the saturated thickness of the High Plains aquifer of the United States, 2009, in feet. The High Plains aquifer underlies...

  1. Semiconductor saturable absorbers for ultrafast THz signals

    DEFF Research Database (Denmark)

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths.......We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths....

  2. Ultrafast THz Saturable Absorption in Doped Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hoffmann, Matthias C.

    2011-01-01

    We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields.......We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields....

  3. No saturation in the accumulation of alien species worldwide.

    Science.gov (United States)

    Seebens, Hanno; Blackburn, Tim M; Dyer, Ellie E; Genovesi, Piero; Hulme, Philip E; Jeschke, Jonathan M; Pagad, Shyama; Pyšek, Petr; Winter, Marten; Arianoutsou, Margarita; Bacher, Sven; Blasius, Bernd; Brundu, Giuseppe; Capinha, César; Celesti-Grapow, Laura; Dawson, Wayne; Dullinger, Stefan; Fuentes, Nicol; Jäger, Heinke; Kartesz, John; Kenis, Marc; Kreft, Holger; Kühn, Ingolf; Lenzner, Bernd; Liebhold, Andrew; Mosena, Alexander; Moser, Dietmar; Nishino, Misako; Pearman, David; Pergl, Jan; Rabitsch, Wolfgang; Rojas-Sandoval, Julissa; Roques, Alain; Rorke, Stephanie; Rossinelli, Silvia; Roy, Helen E; Scalera, Riccardo; Schindler, Stefan; Štajerová, Kateřina; Tokarska-Guzik, Barbara; van Kleunen, Mark; Walker, Kevin; Weigelt, Patrick; Yamanaka, Takehiko; Essl, Franz

    2017-02-15

    Although research on human-mediated exchanges of species has substantially intensified during the last centuries, we know surprisingly little about temporal dynamics of alien species accumulations across regions and taxa. Using a novel database of 45,813 first records of 16,926 established alien species, we show that the annual rate of first records worldwide has increased during the last 200 years, with 37% of all first records reported most recently (1970-2014). Inter-continental and inter-taxonomic variation can be largely attributed to the diaspora of European settlers in the nineteenth century and to the acceleration in trade in the twentieth century. For all taxonomic groups, the increase in numbers of alien species does not show any sign of saturation and most taxa even show increases in the rate of first records over time. This highlights that past efforts to mitigate invasions have not been effective enough to keep up with increasing globalization.

  4. No saturation in the accumulation of alien species worldwide

    Science.gov (United States)

    Seebens, Hanno; Blackburn, Tim M.; Dyer, Ellie E.; Genovesi, Piero; Hulme, Philip E.; Jeschke, Jonathan M.; Pagad, Shyama; Pyšek, Petr; Winter, Marten; Arianoutsou, Margarita; Bacher, Sven; Blasius, Bernd; Brundu, Giuseppe; Capinha, César; Celesti-Grapow, Laura; Dawson, Wayne; Dullinger, Stefan; Fuentes, Nicol; Jäger, Heinke; Kartesz, John; Kenis, Marc; Kreft, Holger; Kühn, Ingolf; Lenzner, Bernd; Liebhold, Andrew; Mosena, Alexander; Moser, Dietmar; Nishino, Misako; Pearman, David; Pergl, Jan; Rabitsch, Wolfgang; Rojas-Sandoval, Julissa; Roques, Alain; Rorke, Stephanie; Rossinelli, Silvia; Roy, Helen E.; Scalera, Riccardo; Schindler, Stefan; Štajerová, Kateřina; Tokarska-Guzik, Barbara; van Kleunen, Mark; Walker, Kevin; Weigelt, Patrick; Yamanaka, Takehiko; Essl, Franz

    2017-01-01

    Although research on human-mediated exchanges of species has substantially intensified during the last centuries, we know surprisingly little about temporal dynamics of alien species accumulations across regions and taxa. Using a novel database of 45,813 first records of 16,926 established alien species, we show that the annual rate of first records worldwide has increased during the last 200 years, with 37% of all first records reported most recently (1970–2014). Inter-continental and inter-taxonomic variation can be largely attributed to the diaspora of European settlers in the nineteenth century and to the acceleration in trade in the twentieth century. For all taxonomic groups, the increase in numbers of alien species does not show any sign of saturation and most taxa even show increases in the rate of first records over time. This highlights that past efforts to mitigate invasions have not been effective enough to keep up with increasing globalization. PMID:28198420

  5. Scientific Opinion on the safety and efficacy of primary aliphatic saturated or unsaturated alcohols/aldehydes/acids/acetals/esters with a second primary, secondary or tertiary oxygenated functional group including aliphatic lactones (chemical group 9 when used as flavourings for all animal species

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP

    2012-10-01

    Full Text Available

    Chemical group 9 consists of primary aliphatic saturated or unsaturated alcohols/aldehydes/acids/acetals/esters with a second primary, secondary or tertiary oxygenated functional group including aliphatic lactones, of which 30 are currently authorised for use as flavours in food. The FEEDAP Panel was unable to perform an assessment of 2-oxopropanal because of issues related to the purity of the compound. The FEEDAP Panel concludes that lactic acid, succinic acid, fumaric acid, 4-oxovaleric acid, ethyl lactate, butyl lactate, butyl-O-butyryllactate, hex-3-enyl lactate, hexyl lactate, ethyl acetoacetate, ethyl 4-oxovalerate, diethylsuccinate and diethyl malonate are considered to be safe for all animal species at the use levels proposed when used as feed flavourings; octano-1,4-lactone, nonano-1,4-lactone, decano-1,4-lactone and undecano-1,4-lactone are safe at 20 mg/kg complete feed; butyro-1,4-lactone, pentano-1,4-lactone, hexano-1,4-lactone, heptano-1,4-lactone, octano-1,5-lactone, nonano-1,5-lactone, decano-1,5-lactone and undecano-1,5-lactone at 5 mg/kg complete feed; dodecano-1,4-lactone, dodecano-1,5-lactone, tetradecano-1,5-lactone, and pentadecano-1,15-lactone at a maximum of 1.5 mg/kg complete feed for cattle, salmonids and non food producing animals and of 1 mg/kg complete feed for pigs and poultry. No safety concern was identified for the consumer from the use of compounds belonging to CG 9 up to the highest safe level in feedingstuffs for all animal species. All compounds should be considered as irritants to skin, eyes and respiratory tract, and as skin sensitizers. The compounds do not pose a risk to the environment when used at concentrations considered safe for the target species. Since all compounds are used in food as flavourings, no further demonstration of efficacy is necessary.

  6. Phase field modeling of partially saturated deformable porous media

    Science.gov (United States)

    Sciarra, Giulio

    2016-09-01

    A poromechanical model of partially saturated deformable porous media is proposed based on a phase field approach at modeling the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the porous skeleton, depending on the porous texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field model based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field model. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged model with that one endowed with the concept of average interfacial area. The considered poromechanical model is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).

  7. τ-MnAl with high coercivity and saturation magnetization

    Directory of Open Access Journals (Sweden)

    J. Z. Wei

    2014-12-01

    Full Text Available In this paper, high purity τ-Mn54Al46 and Mn54−xAl46Cxalloys were successfully prepared using conventional arc-melting, melt-spinning, and heat treatment process. The magnetic and the structural properties were examined using x-ray diffraction (XRD, powder neutron diffraction and magnetic measurements. A room temperature saturation magnetization of 650.5 kAm-1, coercivity of 0.5 T, and a maximum energy product of (BHmax = 24.7 kJm-3 were achieved for the pure Mn54Al46 powders without carbon doping. The carbon substituted Mn54−xAl46Cx, however, reveals a lower Curie temperature but similar saturation magnetization as compared to the carbon-free sample. The electronic structure of MnAl shows that the Mn atom possesses a magnetic moment of 2.454 μB which results from strong hybridization between Mn-Al and Mn-Mn. We also investigated the volume and c/a ratio dependence of the magnetic moments of Mn and Al. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion, leads to a large magnetic moment for the Mn atom. The Mn magnetic moment can reach a value of 2.9 μB at a volume expansion rate of ΔV/V ≈ 20%.

  8. SATURATED ZONE IN-SITU TESTING

    Energy Technology Data Exchange (ETDEWEB)

    P.W. REIMUS

    2004-11-08

    The purpose of this scientific analysis is to document the results and interpretations of field experiments that test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain, Nevada. The test interpretations provide estimates of flow and transport parameters used in the development of parameter distributions for total system performance assessment (TSPA) calculations. These parameter distributions are documented in ''Site-Scale Saturated Zone Flow Model (BSC 2004 [DIRS 170037]), Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]), Saturated Zone Colloid Transport (BSC 2004 [DIRS 170006]), and ''Saturated Zone Flow and Transport Model Abstraction'' (BSC 2004 [DIRS 170042]). Specifically, this scientific analysis contributes the following to the assessment of the capability of the SZ to serve as part of a natural barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvial Testing Complex (ATC) located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass

  9. [The identification of several saturated fatty acids and their salts by means of infrared spectrometry].

    Science.gov (United States)

    Luo, Man; Guan, Ping; Liu, Wen-hui

    2007-02-01

    It is considered that saturated fatty acids and their salts may be potential hydrocarbon-generation matters in carbonate rocks. However, there is no effective method to distinguish them from natural sediments, making recognizing their distribution in sediments a challenge. Formic acid, acetic acid, stearic acid, calcium formate, calcium acetate, magnesium acetate, calcium stearate, and magnesium stearate from some chemical plants were investigated by means of Fourier transform infrared spectroscopy. Their infrared spectra were obtained and the distinctions of the infrared spectra between saturated fatty acids and their salts were studied in detail. The differences in the group's electron-releasing ability, molecular reduced mass, ion configuration and the length of carbon chain can cause wavelength shifts of infrared absorption peaks of the saturated fatty acids and their salts. The research provides a method for the identification of saturated fatty acids and their salts in samples from nature.

  10. A model for strong interactions at high energy based on the CGC/saturation approach

    Energy Technology Data Exchange (ETDEWEB)

    Gotsman, E.; Maor, U. [Tel Aviv University, Department of Particle Physics, School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Science, Tel Aviv (Israel); Levin, E. [Tel Aviv University, Department of Particle Physics, School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Science, Tel Aviv (Israel); Universidad Tecnica Federico Santa Maria and Centro Cientifico-Tecnologico de Valparaiso, Departamento de Fisica, Valparaiso (Chile)

    2015-01-01

    We present our first attempt to develop a model for soft interactions at high energy, based on the BFKL Pomeron and the CGC/saturation approach. We construct an eikonal-type model, whose opacity is determined by the exchange of the dressed BFKL Pomeron. The Green function of the Pomeron is calculated in the framework of the CGC/saturation approach. Using five parameters we achieve a reasonable description of the experimental data at high energies (W ≥ 0.546TeV) with overall χ{sup 2}/d.o.f. ∼ 2. The model results in different behavior for the single- and double-diffraction cross sections at high energies.The singlediffraction cross section reaches a saturated value (about 10mb) at high energies, while the double-diffraction cross section continues growing slowly. (orig.)

  11. A model for strong interactions at high energy based on the CGC/saturation approach

    CERN Document Server

    Gotsman, E; Maor, U

    2014-01-01

    We present our first attempt to develop a model for soft interactions at high energy, based on the BFKL Pomeron and the CGC/saturation approach. We construct an eikonal-type model, whose opacity is determined by the exchange of the dressed BFKL Pomeron. The Green's function of the Pomeron is calculated in the framework of the CGC/saturation approach. Using five parameters we achieve a good description of the experimental data at high energies ( $W\\,\\geq\\,0.546\\,TeV$). The model results in different behaviour for the single and double diffraction cross sections at high energies. The single diffraction cross section reaches a saturated value (about 10 mb) at high energies, while the double diffraction cross section continues growing slowly

  12. Local translational diffusion rates of membranous Na+,K(+)-ATPase measured by saturation transfer ESR spectroscopy.

    OpenAIRE

    Esmann, M.; Marsh, D.

    1992-01-01

    Diffusion-controlled Heisenberg spin exchange between spin-labeled Na+,K(+)-ATPase [ATP phosphohydrolase (Na+/K(+)-transporting), EC 3.6.1.37] proteins has been studied by saturation transfer ESR spectroscopy in reconstituted membranes. Na+,K(+)-ATPase from the salt gland of Squalus acanthias was solubilized in a polyoxyethylene ether detergent, octa(ethylene glycol) dodecyl monoether. Part of the solubilized enzyme was covalently spin-labeled with a nitroxide derivative of indanedione and re...

  13. Saturable inductor and transformer structures for magnetic pulse compression

    Science.gov (United States)

    Birx, Daniel L.; Reginato, Louis L.

    1990-01-01

    Saturable inductor and transformer for magnetic compression of an electronic pulse, using a continuous electrical conductor looped several times around a tightly packed core of saturable inductor material.

  14. Totalization Data Exchange (TDEX)

    Data.gov (United States)

    Social Security Administration — The Totalization Data Exchange (TDEX) process is an exchange between SSA and its foreign country partners to identify deaths of beneficiaries residing abroad. The...

  15. Separation of Primary Alcohols and Saturated Alkanes from Fisher-Tropsch Synthesis Products

    Institute of Scientific and Technical Information of China (English)

    Suqiao Li; Zhongli Tang⁎; Fujun Zhou; Wenbin Li; Xigang Yuan

    2014-01-01

    abstract A method for separating primary alcohols and saturated alkanes from the products of Fisher-Tropsch synthesis is developed. The separation scheme consists of three steps:(1) the raw material is pre-separated by fractional distillation into four fractions according to normal boiling points;(2) appropriate extractants are selected to sep-arate the primary alcohols from the saturated alkanes in each fraction;(3) the extractants are recovered by azeotropic distillation and the primary alcohols in the extract phase are purified. Based on the proposed method, the total recovery rates of the primary alcohols and the saturated alkanes are 86.23%and 84.62%respectively. © 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.

  16. Soil Structure and Saturated Hydraulic Conductivity

    Science.gov (United States)

    Houskova, B.; Nagy, V.

    The role of soil structure on saturated hydraulic conductivity changes is studied in plough layers of texturally different soils. Three localities in western part of Slovakia in Zitny ostrov (Corn Island) were under investigation: locality Kalinkovo with light Calcaric Fluvisol (FAO 1970), Macov with medium heavy Calcari-mollic Fluvisol and Jurova with heavy Calcari-mollic Fluvisol. Soil structure was determined in dry as well as wet state and in size of macro and micro aggregates. Saturated hydraulic conductivity was measured by the help of double ring method. During the period of ring filling the soil surface was protected against aggregates damage by falling water drops. Spatial and temporal variability of studied parameters was evaluated. Cultivated crops were ensilage maize at medium heavy and heavy soil and colza at light soil. Textural composition of soil and actual water content at the beginning of measurement are one of major factor affecting aggregate stability and consequently also saturated hydraulic conductivity.

  17. The Danish tax on saturated fat

    DEFF Research Database (Denmark)

    Vallgårda, Signild; Holm, Lotte; Jensen, Jørgen Dejgård

    2015-01-01

    BACKGROUND/OBJECTIVES: Health promoters have repeatedly proposed using economic policy tools, taxes and subsidies, as a means of changing consumer behaviour. As the first country in the world, Denmark introduced a tax on saturated fat in 2011. It was repealed in 2012. In this paper, we present...... on saturated fat had been suggested by two expert committees and was introduced with a majority in parliament, as a part of a larger economic reform package. Many actors, including representatives from the food industry and nutrition researchers, opposed the tax both before and after its introduction, claiming......, research was published showing that consumption of saturated fat had declined in Denmark. CONCLUSIONS: The analysis indicates that the Danish tax on fat was introduced mainly to increase public revenue. As the tax had no strong proponents and many influential adversaries, it was repealed. New research...

  18. Dilatant hardening of fluid-saturated sandstone

    Science.gov (United States)

    Makhnenko, Roman Y.; Labuz, Joseph F.

    2015-02-01

    The presence of pore fluid in rock affects both the elastic and inelastic deformation processes, yet laboratory testing is typically performed on dry material even though in situ the rock is often saturated. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained, undrained, and unjacketed response. Confined compression experiments, both conventional triaxial and plane strain, were performed on water-saturated Berea sandstone to investigate poroelastic and inelastic behavior. Measured drained response was used to calibrate an elasto-plastic constitutive model that predicts undrained inelastic deformation. The experimental data show good agreement with the model: dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed.

  19. Exchange frequency in replica exchange molecular dynamics

    Science.gov (United States)

    Sindhikara, Daniel; Meng, Yilin; Roitberg, Adrian E.

    2008-01-01

    The effect of the exchange-attempt frequency on sampling efficiency is studied in replica exchange molecular dynamics (REMD). We show that sampling efficiency increases with increasing exchange-attempt frequency. This conclusion is contrary to a commonly expressed view in REMD. Five peptides (1-21 residues long) are studied with a spectrum of exchange-attempt rates. Convergence rates are gauged by comparing ensemble properties between fixed length test REMD simulations and longer reference simulations. To show the fundamental correlation between exchange frequency and convergence time, a simple model is designed and studied, displaying the same basic behavior of much more complex systems.

  20. Femoral venous oxygen saturation is no surrogate for central venous oxygen saturation

    NARCIS (Netherlands)

    van Beest, Paul A.; van der Schors, Alice; Liefers, Henriette; Coenen, Ludo G. J.; Braam, Richard L.; Habib, Najib; Braber, Annemarije; Scheeren, Thomas W. L.; Kuiper, Michael A.; Spronk, Peter E.

    2012-01-01

    Objective:  The purpose of our study was to determine if central venous oxygen saturation and femoral venous oxygen saturation can be used interchangeably during surgery and in critically ill patients. Design:  Prospective observational controlled study. Setting:  Nonacademic university-affiliated t

  1. Formation mechanism of cracks in saturated sand

    Institute of Scientific and Technical Information of China (English)

    Xiaobing Lu; Zhemin Zheng; Yongren Wu

    2006-01-01

    The formation mechanism of "water film" (or crack) in saturated sand is analyzed theoretically and numerically.The theoretical analysis shows that there will be no stable "water film" in the saturated sand if the strength of the skeleton is zero and no positions are choked.It is shown by numerical simulation that stable water films initiate and grow if the choking state keeps unchanged once the fluid velocities decrease to zero in the liquefied sand column.The developments of "water film" based on the model presented in this paper are compared with experimental results.

  2. Site-Scale Saturated Zone Flow Model

    Energy Technology Data Exchange (ETDEWEB)

    G. Zyvoloski

    2003-12-17

    The purpose of this model report is to document the components of the site-scale saturated-zone flow model at Yucca Mountain, Nevada, in accordance with administrative procedure (AP)-SIII.lOQ, ''Models''. This report provides validation and confidence in the flow model that was developed for site recommendation (SR) and will be used to provide flow fields in support of the Total Systems Performance Assessment (TSPA) for the License Application. The output from this report provides the flow model used in the ''Site-Scale Saturated Zone Transport'', MDL-NBS-HS-000010 Rev 01 (BSC 2003 [162419]). The Site-Scale Saturated Zone Transport model then provides output to the SZ Transport Abstraction Model (BSC 2003 [164870]). In particular, the output from the SZ site-scale flow model is used to simulate the groundwater flow pathways and radionuclide transport to the accessible environment for use in the TSPA calculations. Since the development and calibration of the saturated-zone flow model, more data have been gathered for use in model validation and confidence building, including new water-level data from Nye County wells, single- and multiple-well hydraulic testing data, and new hydrochemistry data. In addition, a new hydrogeologic framework model (HFM), which incorporates Nye County wells lithology, also provides geologic data for corroboration and confidence in the flow model. The intended use of this work is to provide a flow model that generates flow fields to simulate radionuclide transport in saturated porous rock and alluvium under natural or forced gradient flow conditions. The flow model simulations are completed using the three-dimensional (3-D), finite-element, flow, heat, and transport computer code, FEHM Version (V) 2.20 (software tracking number (STN): 10086-2.20-00; LANL 2003 [161725]). Concurrently, process-level transport model and methodology for calculating radionuclide transport in the saturated zone at Yucca

  3. On the saturation of astrophysical dynamos

    DEFF Research Database (Denmark)

    Dorch, Bertil; Archontis, Vasilis

    2004-01-01

    In the context of astrophysical dynamos we illustrate that the no-cosines flow, with zero mean helicity, can drive fast dynamo action and we study the dynamo's mode of operation during both the linear and non-linear saturation regimes. It turns out that in addition to a high growth rate in the li......In the context of astrophysical dynamos we illustrate that the no-cosines flow, with zero mean helicity, can drive fast dynamo action and we study the dynamo's mode of operation during both the linear and non-linear saturation regimes. It turns out that in addition to a high growth rate...

  4. Chemical and mineralogical characterization of the bentonite buffer for the acceptance control procedure in a KBS-3 repository

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, Ola (Clay Technology AB, Lund (Sweden))

    2010-09-15

    The present report concerns the chemical and mineralogical characterization of potential buffer materials. A short mineralogical description of bentonite and montmorillonite is given. The report defines, and exemplifies analyses and tests planned for the acceptance control of the bulk material concerning chemical composition, mineralogical composition, original exchangeable cations, cation exchange capacity (CEC), grain density, specific surface area, granule size, water content. In addition, analyses of the clay fraction, i.e. material with a grain size smaller than 2 mum, are described with respect to chemical composition including layer charge, layer charge distribution and cation exchange capacity (CEC). Results from the report by /Karnland et al. 2006/ concerning the two reference bentonites MX-80 and IBECO RWC are used to illustrate the accuracy and precision of the analyses. For each type of analyses the purpose, technique and, in relevant cases, also limits are discussed briefly. An empirical model for determining swelling pressure is presented and used for the quantification of the expected sealing properties given the limits concerning buffer density and montmorillonite content. For the reference bentonites MX-80, the stipulated montmorillonite content interval from 0.75 to 0.9 gives a pressure interval from 8 to 11 MPa at the nominal saturated density 2,000 kg/m3. The stipulated saturated density interval from 1,950 to 2,050 kg/m3 gives a pressure range from 6 to 15 MPa at the measured montmorillonite content of 83% by weight. The combined effects of the stipulated montmorillonite content interval and saturated density interval lead to a pressure range from 5 to 17 MPa. If the increasing effect of accessory minerals, which is proposed by the model, is not taken into account then the combined pressure range is 3 to 14 MPa

  5. Temperature buffer test. Hydro-mechanical and chemical/ mineralogical characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias; Olsson, Siv; Dueck, Ann; Nilsson, Ulf; Karnland, Ola [Clay Technology AB, Lund (Sweden); Kiviranta, Leena; Kumpulainen, Sirpa [BandTech Oy, Helsinki (Finland); Linden, Johan [Aabo Akademi, Aabo (Finland)

    2012-01-15

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modeling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aspo HRL. It was installed during the spring of 2003. Two steel heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by rings of compacted Wyoming bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the hydro-mechanical and chemical/mineralogical characterization program which was launched subsequent to the dismantling operation. The main goal has been to investigate if any significant differences could be observed between material from the field experiment and the reference material. The field samples were mainly taken from Ring 4 (located at the mid-section around the lower heater), in which the temperature in the innermost part reached 155 deg C. The following hydro-mechanical properties have been determined for the material (test technique within brackets): hydraulic conductivity (swelling pressure device), swelling pressure (swelling pressure device), unconfined compression strength (mechanical press), shear strength (triaxial cell) and retention properties (jar method). The following chemical/mineralogical properties (methods within brackets) were determined: anion analysis of water leachates (IC), chemical composition (ICP/AES+MS, EGA), cation exchange capacity (CEC, Cu-trien method) and exchangeable cations (exchange with NH4, ICPAES), mineralogical composition (XRD and FTIR), element distribution and microstructure (SEM and

  6. 煤化工大型缠绕管式换热器的设计与制造%Design and Manufacturing of Large-scale Spiral Wound Heat Exchanger in Coal-chemical Industry

    Institute of Scientific and Technical Information of China (English)

    陈永东; 张贤安

    2015-01-01

    Due to its excellent heat transfer property,the adaptability to variable loads of unit and the op-eration reliability,large-scale spiral wound heat exchanger (SWHE)has a bright application prospect in such fields as the coal deep processing,refinery and natural gas of China.With respect to the multi-stream SWHE for large-scale coal-chemical plant,the design and manufacturing technology difficulties are ana-lyzed for large-scale SWHE.As to the multi-stream SWHE,such contents as the different structure styles of tube-sheet,particularity of tube-sheet design calculation,compatibility of each tube side in the same shell and the large-scale combined raw gas cooler are discussed.Additionally,the outlet structure between tube bundle and tube -sheet is also discussed .Combined with the analysis results of strain aging for austenitic stainless steel,the normal deformation rate range is obtained for the heat exchanger tube during wrapping. Radiographic testing (RT)is carried out for the weldment between tubes and tube-sheet of large-scale SWHE,and the RT operation rule is presented for reference.In China,the large-scale SWHE with area larger than 10000 m2 can be produced now,and abundant experience has been accumulated in the design and manufacturing technology.However,there is still a certain gap between our country and the advanced countries in Europe and America in such aspects as the material variety of SWHE,the process design of large-scale main cryogenic heat exchanger,the application of numerical simulation technology in design and the quantified technology of quality inspection for the weldment between heat exchanger tube and tube-sheet etc.%大型缠绕管式换热器不仅具有较好的传热性能,还同时具有对装置变负荷的适应性和运行可靠的操作特性,在我国煤炭深加工、炼油、天然气等领域的应用呈现出良好的发展前景。从煤化工大型多股流缠绕管式换热器出发,对缠绕管式换热器设计和制

  7. Performance of multiple mini-tube heat exchangers as an internal heat exchanger of a vapor-injection cycle heat pump

    Science.gov (United States)

    Jang, Jin Yong; Jeong, Ji Hwan

    2016-04-01

    A multiple mini-tube (MMT) heat exchanger was considered as an internal heat exchanger of vapor-injection cycle heat pump. Heat transfer and pressure drop in multiple mini-tube heat exchangers were numerically and experimentally investigated. Results show that the best performance of the MMT heat exchanger can be obtained when the intermediate-pressure two-phase refrigerant is supplied to the shell-side and this refrigerant reaches a saturated vapor state at the exit of the heat exchanger.

  8. Radiation Chemistry of Organic Liquids: Saturated Hydrocarbons

    CERN Document Server

    Shkrob, Ilya A; Trifunac, A D

    2004-01-01

    In this review (124 refs), several problems in radiolysis of saturated hydrocarbons are examined. Special attention is paid to the chemistry of radical cations, high-mobility holes, excited state and spur dynamics, magnetic field and spin effects, and optically detected magnetic resonance spectroscopy.

  9. Nasal pulse oximetry overestimates oxygen saturation

    DEFF Research Database (Denmark)

    Rosenberg, J; Pedersen, M H

    1990-01-01

    Ten surgical patients were monitored with nasal and finger pulse oximetry (Nellcor N-200) for five study periods with alternating mouth and nasal breathing and switching of cables and sensors. Nasal pulse oximetry was found to overestimate arterial oxygen saturation by 4.7 (SD 1.4%) (bias...

  10. Two-beam interaction in saturable media

    DEFF Research Database (Denmark)

    Schjødt-Eriksen, Jens; Schmidt, Michel R.; Juul Rasmussen, Jens

    1998-01-01

    The dynamics of two coupled soliton solutions of the nonlinear Schrodinger equation with a saturable nonlinearity is investigated It is shown by means of a variational method and by direct numerical calculations that two well-separated solitons can orbit around each other, if their initial velocity...

  11. Modeling of Current Transformers Under Saturation Conditions

    Directory of Open Access Journals (Sweden)

    Martin Prochazka

    2006-01-01

    Full Text Available During a short circuit the input signal of the relay can be distort by the magnetic core saturation of the current transformer. It is useful to verify the behavior of CT by a mathematical model. The paper describes one phase and three phase models and it presents some methods of how to analyze and classify a deformed secondary current

  12. Saturation at low x and nonlinear evolution

    OpenAIRE

    Stasto, A. M.

    2002-01-01

    In this talk the results of the analytical and numerical analysis of the nonlinear Balitsky-Kovchegov equation are presented. The characteristic BFKL diffusion into infrared regime is suppressed by the generation of the saturation scale. We identify the scaling and linear regimes for the solution. We also study the impact of subleading corrections onto the nonlinear evolution.

  13. Consistent effects of canopy vs. understory nitrogen addition on the soil exchangeable cations and microbial community in two contrasting forests.

    Science.gov (United States)

    Shi, Leilei; Zhang, Hongzhi; Liu, Tao; Zhang, Weixin; Shao, Yuanhu; Ha, Denglong; Li, Yuanqiu; Zhang, Chuangmao; Cai, Xi-an; Rao, Xingquan; Lin, Yongbiao; Zhou, Lixia; Zhao, Ping; Ye, Qing; Zou, Xiaoming; Fu, Shenglei

    2016-05-15

    Anthropogenic N deposition has been well documented to cause substantial impacts on the chemical and biological properties of forest soils. In most studies, however, atmospheric N deposition has been simulated by directly adding N to the forest floor. Such studies thus ignored the potentially significant effect of some key processes occurring in forest canopy (i.e., nitrogen retention) and may therefore have incorrectly assessed the effects of N deposition on soils. Here, we conducted an experiment that included both understory addition of N (UAN) and canopy addition of N (CAN) in two contrasting forests (temperate deciduous forest vs. subtropical evergreen forest). The goal was to determine whether the effects on soil exchangeable cations and microbial biomass differed between CAN and UAN. We found that N addition reduced pH, BS (base saturation) and exchangeable Ca and increased exchangeable Al significantly only at the temperate JGS site, and reduced the biomass of most soil microbial groups only at the subtropical SMT site. Except for soil exchangeable Mn, however, effects on soil chemical properties and soil microbial community did not significantly differ between CAN and UAN. Although biotic and abiotic soil characteristics differ significantly and the responses of both soil exchangeable cations and microbial biomass were different between the two study sites, we found no significant interactive effects between study site and N treatment approach on almost all soil properties involved in this study. In addition, N addition rate (25 vs. 50 kg N ha(-1) yr(-1)) did not show different effects on soil properties under both N addition approaches. These findings did not support previous prediction which expected that, by bypassing canopy effects (i.e., canopy retention and foliage fertilization), understory addition of N would overestimate the effects of N deposition on forest soil properties, at least for short time scale.

  14. Effects of Navier slip on unsteady flow of a reactive variable viscosity non- Newtonian fluid through a porous saturated medium with asymmetric convecti- ve boundary conditions

    Institute of Scientific and Technical Information of China (English)

    RUNDORA Lazarus; MAKINDE Oluwole Daniel

    2015-01-01

    A study on the effects of Navier slip, in conjunction with other flow parameters, on unsteady flow of reactive variable viscosity third-grade fluid through a porous saturated medium with asymmetric convective boundary conditions is presented. The channel walls are assumed to be subjected to asymmetric convective heat exchange with the ambient, and exothermic chemical reactions take place within the flow system. The heat exchange with the ambient obeys Newton’s law of cooling. The coupled equations, arising from the law of conservation of momentum and the first law of thermodynamics, then the derived system are non- dimensionalised and solved using a semi-implicit finite difference scheme. The lower wall slip parameter is observed to increase the fluid velocity profiles, whereas the upper wall slip parameter retards them because of backflow at the upper channel wall. Heat pro- duction in the fluid is seen to increase with the slip parameters. The wall shear stress increases with the slip parameters while the wall heat transfer rate is largely unaltered by the lower wall slip parameter but marginally increased by the upper wall slip parameter.

  15. Soil aquifer treatment of artificial wastewater under saturated conditions

    KAUST Repository

    Essandoh, H. M K

    2011-05-01

    A 2000 mm long saturated laboratory soil column was used to simulate soil aquifer treatment under saturated conditions to assess the removal of chemical and biochemical oxygen demand (COD and BOD), dissolved organic carbon (DOC), nitrogen and phosphate, using high strength artificial wastewater. The removal rates were determined under a combination of constant hydraulic loading rates (HLR) and variable COD concentrations as well as variable HLR under a constant COD. Within the range of COD concentrations considered (42 mg L-1-135 mg L-1) it was found that at fixed hydraulic loading rate, a decrease in the influent concentrations of dissolved organic carbon (DOC), biochemical oxygen demand (BOD), total nitrogen and phosphate improved their removal efficiencies. At the high COD concentrations applied residence times influenced the redox conditions in the soil column. Long residence times were detrimental to the removal process for COD, BOD and DOC as anoxic processes and sulphate reduction played an important role as electron acceptors. It was found that total COD mass loading within the range of 911 mg d-1-1780 mg d-1 applied as low COD wastewater infiltrated coupled with short residence times would provide better effluent quality than the same mass applied as a COD with higher concentration at long residence times. The opposite was true for organic nitrogen where relatively high concentrations coupled with long residence time gave better removal efficiency. © 2011.

  16. Saturated Zone In-Situ Testing

    Energy Technology Data Exchange (ETDEWEB)

    P. W. Reimus; M. J. Umari

    2003-12-23

    The purpose of this scientific analysis is to document the results and interpretations of field experiments that have been conducted to test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain. The test interpretations provide estimates of flow and transport parameters that are used in the development of parameter distributions for Total System Performance Assessment (TSPA) calculations. These parameter distributions are documented in the revisions to the SZ flow model report (BSC 2003 [ 162649]), the SZ transport model report (BSC 2003 [ 162419]), the SZ colloid transport report (BSC 2003 [162729]), and the SZ transport model abstraction report (BSC 2003 [1648701]). Specifically, this scientific analysis report provides the following information that contributes to the assessment of the capability of the SZ to serve as a barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvium Testing Complex (ATC), which is located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, and

  17. Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil

    Institute of Scientific and Technical Information of China (English)

    李保忠; 蔡袁强

    2003-01-01

    Biot's two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasi-transverse wave (QSV) and the anti-plane transverse wave (SH). Numerical results are given to illustrate the influence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering.

  18. High resolution NMR theory and chemical applications

    CERN Document Server

    Becker, Edwin D

    1969-01-01

    High Resolution NMR: Theory and Chemical Applications focuses on the applications of nuclear magnetic resonance (NMR), as well as chemical shifts, lattices, and couplings. The book first offers information on the theory of NMR, including nuclear spin and magnetic moment, spin lattice relaxation, line widths, saturation, quantum mechanical description of NMR, and ringing. The text then ponders on instrumentation and techniques and chemical shifts. Discussions focus on the origin of chemical shifts, reference compounds, empirical correlations of chemical shifts, modulation and phase detection,

  19. Advanced Takagi‒Sugeno fuzzy systems delay and saturation

    CERN Document Server

    Benzaouia, Abdellah

    2014-01-01

    This monograph puts the reader in touch with a decade’s worth of new developments in the field of fuzzy control specifically those of the popular Takagi-Sugeno (T-S) type. New techniques for stabilizing control analysis and design based on multiple Lyapunov functions and linear matrix inequalities (LMIs), are proposed. All the results are illustrated with numerical examples and figures and a rich bibliography is provided for further investigation. Control saturations are taken into account within the fuzzy model. The concept of positive invariance is used to obtain sufficient asymptotic stability conditions for the fuzzy system with constrained control inside a subset of the state space. The authors also consider the non-negativity of the states. This is of practical importance in many chemical, physical and biological processes that involve quantities that have intrinsically constant and non-negative sign: concentration of substances, level of liquids, etc. Results for linear systems are then extended to l...

  20. Mineralogical, chemical and physical study of potential buffer and backfill materials from ABM. Test Package 1

    Energy Technology Data Exchange (ETDEWEB)

    Kumpulainen, S.; Kiviranta, L. (B and Tech Oy, Helsinki (Finland))

    2011-07-15

    In the ABM experiment, three test packages with centre steel heaters surrounded by stacks of compacted bentonite rings of various clay materials were placed in boreholes in Aespoe tunnel. The first parcel was saturated with Aespoe groundwater and the heater was turned on simultaneously with the start of saturation. This parcel was excavated 30 months after its installation. Chemical, mineralogical and physical properties of the MX-80, Dep-CaN, Asha and Friedland clay samples from the ABM parcel 1 were analysed and compared to reference samples. Chemical analyses (ICP-AES, C, CO{sub 3}, S, water soluble SO{sub 4}, Fe2+/Fe3+), exchangeable cation analyses, mineralogical analyses (XRD, FTIR) and selective extractions were used to determine changes in the chemistry and mineralogy of ABM materials. Swelling pressure and hydraulic conductivity measurements were performed both for extracted samples and for ground and recompacted samples. Major changes in exchangeable cation composition were observed in all samples originating from equilibration with Aespoe groundwater and interactions with equilibrated waters from neighbouring block materials. Some minor changes in chemical composition were observed as well. Increases in soluble sulphate content in the vicinity of the heater were thought to result from precipitation of sulphate salts. Decreases in sodium content and increases in calcium content were ascribed to changes in exchangeable cations. Interaction with iron was observed to occur only in the close vicinity (first few mm) of the heater. No significantly measureable change in mineralogical composition was seen in any of the studied materials. Extracted Dep-CaN samples showed a slight decrease in swelling pressure. However, when the material was ground, compacted and measured again the swelling pressure was fully recovered. No related change in hydraulic conductivities was observed. (orig.)

  1. The use of synthetic colloids in tracer transport experiments in saturated rock fractures

    Energy Technology Data Exchange (ETDEWEB)

    Reimus, Paul William [Univ. of California, Berkeley, CA (United States)

    1995-08-01

    Studies of groundwater flow and contaminant transport in saturated, fractured geologic media are of great interest to researchers studying the potential long-term storage of hazardous wastes in or near such media. A popular technique for conducting such studies is to introduce tracers having different chemical and physical properties into a system and then observe the tracers at one or more downstream locations, inferring flow and transport mechanisms from the breakthrough characteristics of the different tracers. Many tracer studies have been conducted in saturated, fractured media to help develop and/or refine models capable of predicting contaminant transport over large scales in such media.

  2. Controls on Highly Siderophile Element Concentrations in Martian Basalt: Sulfide Saturation and Under-Saturation

    Science.gov (United States)

    Righter, Kevin

    2009-01-01

    Highly siderophile elements (HSE; Re, Au and the platinum group elements) in shergottites exhibit a wide range from very high, similar to the terrestrial mantle, to very low, similar to sulfide saturated mid ocean ridge basalt (e.g., [1]). This large range has been difficult to explain without good constraints on sulfide saturation or under-saturation [2]. A new model for prediction of sulfide saturation places new constraints on this problem [3]. Shergottite data: For primitive shergottites, pressure and temperature estimates are between 1.2-1.5 GPa, and 1350-1470 C [4]. The range of oxygen fugacities is from FMQ-2 to IW, where the amount of Fe2O3 is low and thus does not have a significant effect on the S saturation values. Finally, the bulk compositions of shergottites have been reported in many recent studies (e.g., [5]). All of this information will be used to test whether shergottites are sulfide saturated [3]. Modeling values and results: The database for HSE partition coefficients has been growing with many new data for silicates and oxides [6-8] to complement a large sulfide database [9- 11]. Combining these data with simple batch melting models allows HSE contents of mantle melts to be estimated for sulfide-bearing vs. sulfide-free mantle. Combining such models with fractional crystallization modeling (e.g., [12]) allows HSE contents of more evolved liquids to be modeled. Most primitive shergottites have high HSE contents (and low S contents) that can be explained by sulfide under-saturated melting of the mantle. An exception is Dhofar 019 which has high S contents and very low HSE contents suggesting sulfide saturation. Most evolved basaltic shergottites have lower S contents than saturation, and intermediate HSE contents that can be explained by olivine, pyroxene, and chromite fractionation. An exception is EET A79001 lithology B, which has very low HSE contents and S contents higher than sulfide saturation values . evidence for sulfide saturation

  3. Saturation dynamics and working limits of saturated absorption cavity ringdown spectroscopy.

    Science.gov (United States)

    Sadiek, Ibrahim; Friedrichs, Gernot

    2016-08-17

    Cavity ringdown spectroscopy (CRDS) in the linear absorption regime is a well-established method for sensitive trace gas detection, but only a few studies have addressed quantitative measurements in the presence of a saturated sample. In fact, saturation is usually avoided in order to escape from the required complex modeling of the saturation process that depends on the characteristics of the absorbing species, its interaction with the surrounding gas as well as on the temporal and spectral characteristics of the cavity excitation. Conversely, the novel saturated-absorption cavity ringdown spectroscopy approach (SCAR/Sat-CRDS) takes advantage of sample saturation in order to allow one to extract both the gas absorption and the empty cavity loss rates from a single ringdown event. Using a new continuous-wave infrared CRD spectrometer equipped with a tunable narrow-bandwidth high-power OPO laser system and a 18 bit digitizer, the transient dynamics of absorption saturation and the working limits of the Sat-CRDS approach in terms of its ability to extract reliable trace gas concentrations have been experimentally studied in this work. Using a strong methane transition as a test case, the excitation power P0 and saturation power PS have been systematically varied to explore a wide range of saturation regimes. At pressures 5 μbar γc, a pronounced coupling between the two parameters has been observed. Finally, a standard error analysis was performed revealing that the Sat-CRDS approach holds its advantages over conventional CRDS implementations in particular when the attainable ultimate detection sensitivity is limited by uncertainties in the empty cavity ringdown constant.

  4. Space Charge Saturated Sheath Regime and Electron Temperature Saturation in Hall Thrusters

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses; D. Staack; A. Smirnov; N.J. Fisch

    2005-03-16

    Secondary electron emission in Hall thrusters is predicted to lead to space charge saturated wall sheaths resulting in enhanced power losses in the thruster channel. Analysis of experimentally obtained electron-wall collision frequency suggests that the electron temperature saturation, which occurs at high discharge voltages, appears to be caused by a decrease of the Joule heating rather than by the enhancement of the electron energy loss at the walls due to a strong secondary electron emission.

  5. Comparison of pulseoximetry oxygen saturation and arterial oxygen saturation in open heart intensive care unit

    Directory of Open Access Journals (Sweden)

    Alireza Mahoori

    2013-08-01

    Full Text Available Background: Pulseoximetry is widely used in the critical care setting, currently used to guide therapeutic interventions. Few studies have evaluated the accuracy of SPO2 (puls-eoximetry oxygen saturation in intensive care unit after cardiac surgery. Our objective was to compare pulseoximetry with arterial oxygen saturation (SaO2 during clinical routine in such patients, and to examine the effect of mild acidosis on this relationship.Methods: In an observational prospective study 80 patients were evaluated in intensive care unit after cardiac surgery. SPO2 was recorded and compared with SaO2 obtained by blood gas analysis. One or serial arterial blood gas analyses (ABGs were performed via a radial artery line while a reliable pulseoximeter signal was present. One hundred thirty seven samples were collected and for each blood gas analyses, SaO2 and SPO2 we recorded.Results: O2 saturation as a marker of peripheral perfusion was measured by Pulseoxim-etry (SPO2. The mean difference between arterial oxygen saturation and pulseoximetry oxygen saturation was 0.12%±1.6%. A total of 137 paired readings demonstrated good correlation (r=0.754; P<0.0001 between changes in SPO2 and those in SaO2 in samples with normal hemoglobin. Also in forty seven samples with mild acidosis, paired readings demonstrated good correlation (r=0.799; P<0.0001 and the mean difference between SaO2 and SPO2 was 0.05%±1.5%.Conclusion: Data showed that in patients with stable hemodynamic and good signal quality, changes in pulseoximetry oxygen saturation reliably predict equivalent changes in arterial oxygen saturation. Mild acidosis doesn’t alter the relation between SPO2 and SaO2 to any clinically important extent. In conclusion, the pulse oximeter is useful to monitor oxygen saturation in patients with stable hemodynamic.

  6. Flux saturation length of sediment transport.

    Science.gov (United States)

    Pähtz, Thomas; Kok, Jasper F; Parteli, Eric J R; Herrmann, Hans J

    2013-11-22

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars.

  7. The Danish tax on saturated fat

    DEFF Research Database (Denmark)

    Jensen, Jørgen Dejgård; Smed, Sinne

    2013-01-01

    Denmark introduced a new tax on saturated fat in food products with effect from October 2011. The objective of this paper is to make an effect assessment of this tax for some of the product categories most significantly affected by the new tax, namely fats such as butter, butter-blends, margarine...... and oils. This assessment is done by conducting an econometric analysis on weekly food purchase data from a large household panel dataset (GfK Consumer Tracking Scandinavia), spanning the period from January 2008 until July 2012.The econometric analysis suggest that the introduction of the tax on saturated...... fat in food products has had some effects on the market for the considered products, in that the level of consumption of fats dropped by 10 – 20%. Furthermore, the analysis points at shifts in demand from high-price supermarkets towards low-price discount stores – at least for some types of oils...

  8. The danish tax on saturated fat

    DEFF Research Database (Denmark)

    Jensen, Jørgen Dejgård; Smed, Sinne

    Denmark introduced a new tax on saturated fat in food products with effect from October 2011. The objective of this paper is to make an effect assessment of this tax for some of the product categories most significantly affected by the new tax, namely fats such as butter, butter-blends, margarine...... on saturated fat in food products has had some effects on the market for the considered products, in that the level of consumption of fats dropped by 10 – 20%. Furthermore, the analysis points at shifts in demand from high-price supermarkets towards low-price discount stores – a shift that seems to have been...... – and broaden – the analysis at a later stage, when data are available for a longer period after the introduction of the fat tax....

  9. Cause of winter gravity wave spectrum saturation

    Institute of Scientific and Technical Information of China (English)

    WU; Yongfu; XU; Jiyao

    2005-01-01

    This paper utilizes horizontal velocity measurements observed from 19 chaff rockets and nearly simultaneous temperature measurements collected from 19 falling sphere rockets to study the cause of winter gravity wave spectrum saturation. Results suggest that strong horizontal velocity shears larger than 0.04 s-1 are observed to be present at various heights near the winter mesopause. On one single chaff rocket flight, an extremely strong horizontal velocity shear as high as 0.33 s-1 is observed at 87.4 km and is believed to be the strongest value ever measured in the mesosphere. These strong horizontal velocity shears, together with Brunt-V(a)is(a)l(a) frequency squared obtained from the temperature profile, act collectively to yield two dynamical instability regions of Richardson number smaller than 1/4, suggesting that the saturated gravity wave spectrum observed by the chaff rockets in winter is a result of dynamical instability.

  10. Wave propagation in thermoelastic saturated porous medium

    Indian Academy of Sciences (India)

    M D Sharma

    2008-12-01

    Biot ’s theory for wave propagation in saturated porous solid is modified to study the propagation of thermoelastic waves in poroelastic medium. Propagation of plane harmonic waves is considered in isotropic poroelastic medium. Relations are derived among the wave-induced temperature in the medium and the displacements of fluid and solid particles. Christoffel equations obtained are modified with the thermal as well as thermoelastic coupling parameters. These equations explain the existence and propagation of four waves in the medium. Three of the waves are attenuating longitudinal waves and one is a non-attenuating transverse wave. Thermal properties of the medium have no effect on the transverse wave. The velocities and attenuation of the longitudinal waves are computed for a numerical model of liquid-saturated sandstone. Their variations with thermal as well as poroelastic parameters are exhibited through numerical examples.

  11. Stabilization of Neutral Systems with Saturating Actuators

    Directory of Open Access Journals (Sweden)

    F. El Haoussi

    2012-01-01

    to determine stabilizing state-feedback controllers with large domain of attraction, expressed as linear matrix inequalities, readily implementable using available numerical tools and with tuning parameters that make possible to select the most adequate solution. These conditions are derived by using a Lyapunov-Krasovskii functional on the vertices of the polytopic description of the actuator saturations. Numerical examples demonstrate the effectiveness of the proposed technique.

  12. 2D Saturable Absorbers for Fibre Lasers

    Directory of Open Access Journals (Sweden)

    Robert I. Woodward

    2015-11-01

    Full Text Available Two-dimensional (2D nanomaterials are an emergent and promising platform for future photonic and optoelectronic applications. Here, we review recent progress demonstrating the application of 2D nanomaterials as versatile, wideband saturable absorbers for Q-switching and mode-locking fibre lasers. We focus specifically on the family of few-layer transition metal dichalcogenides, including MoS2, MoSe2 and WS2.

  13. Gluon saturation beyond (naive) leading logs

    Energy Technology Data Exchange (ETDEWEB)

    Beuf, Guillaume

    2014-12-15

    An improved version of the Balitsky–Kovchegov equation is presented, with a consistent treatment of kinematics. That improvement allows to resum the most severe of the large higher order corrections which plague the conventional versions of high-energy evolution equations, with approximate kinematics. This result represents a further step towards having high-energy QCD scattering processes under control beyond strict Leading Logarithmic accuracy and with gluon saturation effects.

  14. Chemical changes in an oxisol treated with pyroligneous acid

    Directory of Open Access Journals (Sweden)

    Aluísio Hideki Togoro

    2014-04-01

    Full Text Available The use of pyroligneous acid (PA, a by-product of charcoal production, is an ancient practice applied in agriculture to control soil and plant pests and diseases. However, little is known about the chemical alterations that this product may cause on treated soil. Thus, the present work aimed to evaluate the effect of PA concentrations on soil ions movement and to verify possible soil chemical properties changes. Detachable columns were filled with Oxisol, submitted to application of 5 PA concentrations (0, 1, 2, 4, 8% v/v, followed by water infiltration in an amount corresponding to 1.5 times the soil total pore volume, and evaluated the soil of four depths (0-10, 10-20, 20-30, 30-40cm and the leachate. The use of pyroligneous acid in concentrations up to 2 % (v/v induces only slight decrease of k, Mg, basis saturation and total cation exchange capacity, in the 0-20 cm soil layer. The application of 4 % (v/v and 8 % (v/v pyroligneous acid induces severe increase on the potential acidity, and the decrease on the pH, basis saturation, total cation exchange capacity, and Ca concentration, in the layer of 0-20 cm soil. The P and K concentration reduces in the 0-20 cm soil layer by increasing from 1% to 8% the concentration of pyroligneous acid solution applied on soil surface. By increasing the PA concentration applied on the soil, there is increase of acidity, organic matter, P, K, Ca, and Mg, and decrease of sulfate in the leachate.

  15. Optimal oxygen saturation in premature infants

    Directory of Open Access Journals (Sweden)

    Meayoung Chang

    2011-09-01

    Full Text Available There is a delicate balance between too little and too much supplemental oxygen exposure in premature infants. Since underuse and overuse of supplemental oxygen can harm premature infants, oxygen saturation levels must be monitored and kept at less than 95% to prevent reactive oxygen species-related diseases, such as retinopathy of prematurity and bronchopulmonary dysplasia. At the same time, desaturation below 80 to 85% must be avoided to prevent adverse consequences, such as cerebral palsy. It is still unclear what range of oxygen saturation is appropriate for premature infants; however, until the results of further studies are available, a reasonable target for pulse oxygen saturation (SpO2 is 90 to 93% with an intermittent review of the correlation between SpO2 and the partial pressure of arterial oxygen tension (PaO2. Because optimal oxygenation depends on individuals at the bedside making ongoing adjustments, each unit must define an optimal target range and set alarm limits according to their own equipment or conditions. All staff must be aware of these values and adjust the concentration of supplemental oxygen frequently.

  16. Resonance trapping and saturation of decay widths

    CERN Document Server

    Persson, E; Rotter, I

    1998-01-01

    Resonance trapping appears in open many-particle quantum systems at high level density when the coupling to the continuum of decay channels reaches a critical strength. Here a reorganization of the system takes place and a separation of different time scales appears. We investigate it under the influence of additional weakly coupled channels as well as by taking into account the real part of the coupling term between system and continuum. We observe a saturation of the mean width of the trapped states. Also the decay rates saturate as a function of the coupling strength. The mechanism of the saturation is studied in detail. In any case, the critical region of reorganization is enlarged. When the transmission coefficients for the different channels are different, the width distribution is broadened as compared to a chi_K^2 distribution where K is the number of channels. Resonance trapping takes place before the broad state overlaps regions beyond the extension of the spectrum of the closed system.

  17. Modeling of synchronous machines with magnetic saturation

    Energy Technology Data Exchange (ETDEWEB)

    Rehaoulia, H. [Universite de Tunis-Ecole Superieure des Sciences et Techniques de Tunis (Unite de Recherche CSSS), 5 Avenue Taha Hussein Tunis 10008 (Tunisia); Henao, H.; Capolino, G.A. [Universite de Picardie Jules Vernes-Centre de Robotique, d' Electrotechnique et d' Automatique (UPRES-EA3299), 33 Rue Saint Leu, 80039 Amiens Cedex 1 (France)

    2007-04-15

    This paper deals with a method to derive multiple models of saturated round rotor synchronous machines, based on different selections of state-space variables. By considering the machine currents and fluxes as space vectors, possible d-q models are discussed and adequately numbered. As a result several novel models are found and presented. It is shown that the total number of d-q models for a synchronous machine, with basic dampers, is 64 and therefore much higher than known. Found models are classified into three families: current, flux and mixed models. These latter, the mixed ones, constitute the major part (52) and hence offer a large choice. Regarding magnetic saturation, the paper also presents a method to account for whatever the choice of state-space variables. The approach consists of just elaborating the saturation model with winding currents as main variables and deriving all the other models from it, by ordinary mathematical manipulations. The paper emphasizes the ability of the proposed approach to develop any existing model without exception. An application to prove the validity of the method and the equivalence between all developed models is reported. (author)

  18. Indiana Health Information Exchange

    Science.gov (United States)

    The Indiana Health Information Exchange is comprised of various Indiana health care institutions, established to help improve patient safety and is recognized as a best practice for health information exchange.

  19. Cooperativity and saturation in biochemical networks: a saturable formalism using Taylor series approximations.

    Science.gov (United States)

    Sorribas, Albert; Hernández-Bermejo, Benito; Vilaprinyo, Ester; Alves, Rui

    2007-08-01

    Cooperative and saturable systems are common in molecular biology. Nevertheless, common canonical formalisms for kinetic modeling that are theoretically well justified do not have a saturable form. Modeling and fitting data from saturable systems are widely done using Hill-like equations. In practice, there is no theoretical justification for the generalized use of these equations, other than their ability to fit experimental data. Thus it is important to find a canonical formalism that is (a) theoretically well supported, (b) has a saturable functional form, and (c) can be justifiably applicable to any biochemical network. Here we derive such a formalism using Taylor approximations in a special transformation space defined by power-inverses and logarithms of power-inverses. This formalism is generalized for processes with n-variables, leading to a useful mathematical representation for molecular biology: the Saturable and Cooperative Formalism (SC formalism). This formalism provides an appropriate representation that can be used for modeling processes with cooperativity and saturation. We also show that the Hill equation can be seen as a special case within this formalism. Parameter estimation for the SC formalism requires information that is also necessary to build Power-Law models, Metabolic Control Analysis descriptions or (log)linear and Lin-log models. In addition, the saturation fraction of the relevant processes at the operating point needs to be considered. The practical use of the SC formalism for modeling is illustrated with a few examples. Similar models are built using different formalisms and compared to emphasize advantages and limitations of the different approaches.

  20. Mineral saturation states in natural waters and their sensitivity to thermodynamic and analytic errors

    Science.gov (United States)

    Nordstrom, D.K.; Ball, J.W.

    1989-01-01

    Saturation indices computed with WATEQ4F for chemical analyses from a groundwater in crystalline bedrock and a surface water receiving acid mine drainage are frequently at or above saturation with respect to calcite, fluorite, barite, gibbsite and ferrihydrite. A sensitivity analysis has been performed by varying the analytic and thermodynamic parameters for which the saturation indices are most sensitive. For calcite, fluorite and barite, the supersaturation effect appears to be real because it is only slightly decreased by sources of uncertainty. Apparent supersaturation for gibbsite is most likely caused by the degree of crystallinity on solubility behavior. Apparent supersaturation for ferric hydroxide is likely caused by small colloidal particles (<0.1 ??m) in the water sample that cannot be removed by standard field filtration, although several other possible explanations cannot be easily excluded. -from Authors

  1. Gas diffusion-derived tortuosity governs saturated hydraulic conductivity in sandy soils

    DEFF Research Database (Denmark)

    Masis Melendez, Federico; Deepagoda Thuduwe Kankanamge Kelum, Chamindu; de Jonge, Lis Wollesen

    2014-01-01

    Accurate prediction of saturated hydraulic conductivity (Ksat) is essential for the development of better distributed hydrological models and area-differentiated risk assessment of chemical leaching. The saturated hydraulic conductivity is often estimated from basic soil properties such as particle...... size distribution or, more recently, soil-air permeability. However, similar links to soil gas diffusivity (Dp/Do) have not been fully explored even though gas diffusivity is a direct measure of connectivity and tortuosity of the soil pore network. Based on measurements for a coarse sandy soil....../Do model to measured data, and subsequently linked to the cementation exponent of the wellestablished Revil and Cathles predictive model for saturated hydraulic conductivity. Furthermore, a two-parameter model, analogue to the Kozeny-Carman equation, was developed for the Ksat - Dp/Do relationships. All 44...

  2. Synthesis of LiAlTiO4 and its selectivity to Li+ exchange

    Institute of Scientific and Technical Information of China (English)

    Dong Dianquan; Zhang Fengbao; Zhang Guoliang; Liu Yifan

    2006-01-01

    The ion-exchanger LiAlTiO4 of spinel type was prepared by the common precipitation/hydrothermal crystallization method,and was acid-modified.Its ion-exchange properties for alkali ions such as saturation capacity of exchange,distribution coefficient and pH titration curve were determined.LiAlTiO4 was characterized by the X-ray diffraction method.The acid treatment of LiAlTiO4 caused Li+ extraction ratio to change from 28% to 72%,while the dissolution of Al is less than 6.8%.This inorganic ion-exchanger (LiAlTiO4-700) has a higher saturation capacity of exchange for Li than for other alkali ions,the saturation capacity of exchange for Li+ reaches 4.29 mmol/g (30.03 mg/g); LiAlTiO4-700(H) has a higher selectivity of ion exchange for Li+ than for other alkali ions.These results show LiAlTiO4-700(H) has better memory and selectivity of ion exchange,and higher capacity of ion exchange for Li+.It is a kind of prospective ionic sieve for Li+.

  3. Density of Saturated Nuclear Matter at Large $N_{c}$ and Heavy Quark Mass Limits

    CERN Document Server

    Adhikari, Prabal; Datta, Ishaun

    2013-01-01

    We exhibit the existence of stable, saturated nuclear matter in the large $N_{c}$ and heavy quark mass limits of QCD. In this limit, baryons (with the same spin flavor structure) interact at leading order in $N_{c}$ via a repulsive interaction due to the Pauli exclusion principle and at subleading order in $1/N_c$ via the exchange of glueballs. Assuming that the lightest glueball is a scalar, which implies that the subleading baryon interaction is attractive, we find that nuclear matter saturates since the subleading attractive interaction is longer ranged than the leading order repulsive one. We find that the saturated matter is in the form of a crystal with either a face-centered cubic or a hexagonal-close-packed symmetry with baryon densities of $\\mathcal{O}((\\, \\tilde{\\alpha}_{s} m_q (\\ln (N_{c}m_{q}\\Lambda_{\\textrm{QCD}}^{-1}))^{-1})^3 )$. Remarkably, the leading order expression for the density of saturated nuclear matter is independent of the lighest glueball mass and scalar-glueball-baryon coupling in...

  4. PLD-grown thin film saturable absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Tellkamp, Friedjof

    2012-11-01

    The subject of this thesis is the preparation and characterization of thin films made of oxidic dielectrics which may find their application as saturable absorber in passively Q-switched lasers. The solely process applied for fabrication of the thin films was the pulsed laser deposition (PLD) which stands out against other processes by its flexibility considering the composition of the systems to be investigated. Within the scope of this thesis the applied saturable absorbers can be divided into two fundamentally different kinds of functional principles: On the one hand, saturable absorption can be achieved by ions embedded in a host medium. Most commonly applied bulk crystals are certain garnets like YAG (Y{sub 3}Al{sub 5}O{sub 12}) or the spinel forsterite (Mg{sub 2}SiO{sub 4}), in each case with chromium as dopant. Either of these media was investigated in terms of their behavior as PLD-grown saturable absorber. Moreover, experiments with Mg{sub 2}GeO{sub 4}, Ca{sub 2}GeO{sub 4}, Sc{sub 2}O{sub 3}, and further garnets like YSAG or GSGG took place. The absorption coefficients of the grown films of Cr{sup 4+}:YAG were determined by spectroscopic investigations to be one to two orders of magnitude higher compared to commercially available saturable absorbers. For the first time, passive Q-switching of a Nd:YAG laser at 1064 nm with Cr{sup 4+}:YAG thin films could be realized as well as with Cr:Sc{sub 2}O{sub 3} thin films. On the other hand, the desirable effect of saturable absorption can also be generated by quantum well structures. For this purpose, several layer system like YAG/LuAG, Cu{sub 2}O/MgO, and ZnO/corumdum were investigated. It turned out that layer systems with indium oxide (In{sub 2}O{sub 3}) did not only grew in an excellent way but also showed up a behavior regarding their photo luminescence which cannot be explained by classical considerations. The observed luminescence at roughly 3 eV (410 nm) was assumed to be of excitonic nature and its

  5. Trans Fat Now Listed With Saturated Fat and Cholesterol

    Science.gov (United States)

    ... Trans Fat Now Listed With Saturated Fat and Cholesterol Share Tweet Linkedin Pin it More sharing options ... I Do About Saturated Fat, Trans Fat, and Cholesterol? When comparing foods, look at the Nutrition Facts ...

  6. Crystallization of accessory phases in magmas by local saturation adjacent to phenocrysts

    Science.gov (United States)

    Bacon, C.R.

    1989-01-01

    Accessory minerals commonly occur attached to or included in the major crystalline phases of felsic and some intermediate igneous rocks. Apatite is particularly common as inclusions, but Fe-Ti oxides, pyrrhotite, zircon, monazite, chevkinite and xenotime are also known from silicic rocks. Accessories may nucleate near the host crystal/ liquid interface as a result of local saturation owing to formation of a differentiated chemical boundary layer in which accessory mineral solubility would be lower than in the surrounding liquid. Differentiation of this boundary layer would be greatest adjacent to ferromagnesian phenocrysts, especially Fe-Ti oxides; it is with oxides that accessories are most commonly associated in rocks. A boundary layer may develop if the crystal grows more rapidly than diffusion can transport incorporated and rejected elements to and from the phenocryst. Diffusion must dominate over convection as a mode of mass transfer near the advancing crystal/liquid interface in order for a boundary layer to exist. Accumulation of essential structural constituent elements of accessory minerals owing to their slow diffusion in evolved silicate melt also may force local saturation, but this is not a process that applies to all cases. Local saturation is an attractive mechanism for enhancing fractionation during crystallization differentiation. If accessory minerals attached to or included in phenocrysts formed because of local saturation, their host phenocrysts must have grown rapidly when accessories nucleated in comparison to lifetimes of magma reservoirs. Some inconsistencies remain in a local saturation origin for accessory phases that cannot be evaluated without additional information. ?? 1989.

  7. Modeling of Water Movement Near Saturation

    Science.gov (United States)

    Ippisch, O.; Graf, H.; Bastian, P.; Roth, K.

    Water transport in unsaturated porous media is often described using Richards' equa- tion. However Richards' equation is based on the assumption that the gas phase is mobile enough to be always (nearly) at atmospheric pressure. This assumption is not valid if the porous medium is nearly saturated with water. The difference between model calculations using Richards' equation and a multiphase formulation is analyzed and compared to results from multistep outflow experiments with columns of sintered glass. The chosen parameterization for the hydraulic param- eters (van Genuchten/Brooks-Corey) proves to expecially important.

  8. Elevated transferrin saturation and risk of diabetes

    DEFF Research Database (Denmark)

    Ellervik, Christina; Mandrup-Poulsen, Thomas; Andersen, Henrik Ullits;

    2011-01-01

    OBJECTIVE We tested the hypothesis that elevated transferrin saturation is associated with an increased risk of any form of diabetes, as well as type 1 or type 2 diabetes separately. RESEARCH DESIGN AND METHODS We used two general population studies, The Copenhagen City Heart Study (CCHS, N = 9......,121) and The Copenhagen General Population Study (CGPS, N = 24,195), as well as a 1:1 age- and sex-matched population-based case-control study with 6,129 patients with diabetes from the Steno Diabetes Centre and 6,129 control subjects, totaling 8,535 patients with diabetes and 37,039 control subjects. RESULTS...

  9. Evolutions of Compaction Bands of Saturated Soils

    Institute of Scientific and Technical Information of China (English)

    鲁晓兵; 王义华; 崔鹏

    2004-01-01

    The development of compaction bands in saturated soils, which is coupling-rate, inertial and pore-pressure-dependent, under axisymmetric loading was discussed, using a simple model and a matching technique at the moving boundary of a band. It is shown that the development of compaction bands is dominated by the coupling-rate and pore-pressure effects of material. The soil strength makes the band shrinking, whilst pore pressure diffusion makes the band expand. Numerical simulations were carried out in this paper.

  10. Chloride diffusion in partially saturated cementitious material

    DEFF Research Database (Denmark)

    Nielsen, Erik Pram; Geiker, Mette Rica

    2003-01-01

    The paper proposes a combined application of composite theory and Powers' model for microstructural development for the estimation of the diffusion coefficient as a function of the moisture content of a defect-free cementitious material. Measurements of chloride diffusion in mortar samples (440 kg....../m(3) rapid-hardening Portland cement, w/c = 0.5, maturity minimum 6 months) stored at 65% and 85% RH, as well as in vacuum-saturated mortar samples, illustrate the applicability of the method. (C) 2003 Elsevier Science Ltd. All rights reserved....

  11. Saturation of the f-mode instability in neutron stars: I. Theoretical framework

    CERN Document Server

    Pnigouras, Pantelis

    2015-01-01

    The basic formulation describing quadratic mode coupling in rotating Newtonian stars is presented, focusing on polar modes. Due to the Chandrasekhar-Friedman-Schutz mechanism, the f-mode (fundamental oscillation) is driven unstable by the emission of gravitational waves. If the star falls inside the so-called instability window, the mode's amplitude grows exponentially, until it is halted by non-linear effects. Quadratic perturbations form three-mode networks inside the star, which evolve as coupled oscillators, exchanging energy. Coupling of the unstable f-mode to other (stable) modes can lead to a parametric resonance and the subsequent saturation of its amplitude, thus suppressing the instability. The saturation point determines the amplitude of the gravitational-wave signal obtained from an individual source, as well as the evolutionary path of the latter inside the instability window.

  12. Saturation of the f -mode instability in neutron stars: Theoretical framework

    Science.gov (United States)

    Pnigouras, Pantelis; Kokkotas, Kostas D.

    2015-10-01

    The basic formulation describing quadratic mode coupling in rotating Newtonian stars is presented, focusing on polar modes. Due to the Chandrasekhar-Friedman-Schutz mechanism, the f -mode (fundamental oscillation) is driven unstable by the emission of gravitational waves. If the star falls inside the so-called instability window, the mode's amplitude grows exponentially, until it is halted by nonlinear effects. Quadratic perturbations form three-mode networks inside the star, which evolve as coupled oscillators, exchanging energy. Coupling of the unstable f -mode to other (stable) modes can lead to a parametric resonance and the subsequent saturation of its amplitude, thus suppressing the instability. The saturation point determines the amplitude of the gravitational-wave signal obtained from an individual source, as well as the evolutionary path of the latter inside the instability window.

  13. Penetrative Brinkman convection in an anisotropic porous layer saturated by a nanofluid

    Directory of Open Access Journals (Sweden)

    I.S. Shivakumara

    2015-06-01

    Full Text Available The onset of penetrative Brinkman convection in a nanofluid saturated anisotropic porous layer is investigated via uniform internal heating for rigid-rigid, free-free, and lower-rigid and upper-free boundaries. The flux of volume fraction of nanoparticles is taken to be zero on the isothermal boundaries and the eigenvalue problem is solved using the Galerkin method. The numerical computations carried out indicated the validity of principle of exchange of stability for all types of velocity boundary conditions. The effect of heat source strength, mechanical anisotropy parameter, modified diffusivity ratio, nanoparticle concentration Darcy-Rayleigh number and Lewis number is to hasten, while the Darcy number and thermal anisotropy parameter are to delay the onset of convection. In contrast to the regular fluid saturating a Darcy porous medium, the onset of convection for nanofluids is found to be influenced even when the ratio of mechanical anisotropy parameter to thermal anisotropy parameter is unity.

  14. Space charge saturated sheath regime and electron temperature saturation in Hall thrusters

    Science.gov (United States)

    Raitses, Y.; Staack, D.; Smirnov, A.; Fisch, N. J.

    2005-07-01

    Existing electron-wall interaction models predict that secondary electron emission in Hall thrusters is significant and that the near-wall sheaths are space charge saturated. The experimental electron-wall collision frequency is computed using plasma parameters measured in a laboratory Hall thruster. In spite of qualitative similarities between the measured and predicted dependencies of the maximum electron temperature on the discharge voltage, the deduced electron-wall collision frequency for high discharge voltages is much lower than the theoretical value obtained for space charge saturated sheath regime, but larger than the wall recombination frequency. The observed electron temperature saturation appears to be directly associated with a decrease of the Joule heating rather than with the enhancement of the electron energy loss at the walls due to a strong secondary electron emission. Another interesting experimental result is related to the near-field plasma plume, where electron energy balance appears to be independent on the magnetic field.

  15. Extended Reconstruction Approaches for Saturation Measurements Using Reserved Quantization Indices

    DEFF Research Database (Denmark)

    Li, Peng; Arildsen, Thomas; Larsen, Torben

    2012-01-01

    This paper proposes a reserved quantization indices method for saturated measurements in compressed sensing. The existing approaches tailored for saturation effect do not provide a way to identify saturated measurements, which is mandatory in practical implementations.We introduce a method using...

  16. Test of Scintillometer Saturation Correction Methods Using Field Experimental Data

    NARCIS (Netherlands)

    Kleissl, J.; Hartogensis, O.K.; Gomez, J.D.

    2010-01-01

    Saturation of large aperture scintillometer (LAS) signals can result in sensible heat flux measurements that are biased low. A field study with LASs of different aperture sizes and path lengths was performed to investigate the onset of, and corrections for, signal saturation. Saturation already occu

  17. Synthesis, characterization and ion exchange properties of zirconium(IV) tungstoiodophosphate, a new cation exchanger

    Indian Academy of Sciences (India)

    Weqar Ahmad Siddiqui; Shakeel Ahmad Khan

    2007-02-01

    Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0.5 mol L-1 sodium tungstate, potassium iodate and 1 mol L-1 orthophosphoric acid to aqueous solution of 0.1 mol L-1 zirconium(IV) oxychloride. Its ion exchange capacity for Na+ and K+ was found to be 2.20 and 2.35 meq g-1 dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has been studied. The analytical importance of the material has been established by quantitative separation of Pb2+ from other metal ions.

  18. The saturable absorption and reverse saturable absorption properties of Cu doped zinc oxide thin films

    Science.gov (United States)

    Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin

    2017-03-01

    We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.

  19. Users` manual for LEHGC: A Lagrangian-Eulerian Finite-Element Model of Hydrogeochemical Transport Through Saturated-Unsaturated Media. Version 1.1

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Gour-Tsyh [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil and Environmental Engineering; Carpenter, S.L. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences; Hopkins, P.L.; Siegel, M.D. [Sandia National Labs., Albuquerque, NM (United States)

    1995-11-01

    The computer program LEHGC is a Hybrid Lagrangian-Eulerian Finite-Element Model of HydroGeo-Chemical (LEHGC) Transport Through Saturated-Unsaturated Media. LEHGC iteratively solves two-dimensional transport and geochemical equilibrium equations and is a descendant of HYDROGEOCHEM, a strictly Eulerian finite-element reactive transport code. The hybrid Lagrangian-Eulerian scheme improves on the Eulerian scheme by allowing larger time steps to be used in the advection-dominant transport calculations. This causes less numerical dispersion and alleviates the problem of calculated negative concentrations at sharp concentration fronts. The code also is more computationally efficient than the strictly Eulerian version. LEHGC is designed for generic application to reactive transport problems associated with contaminant transport in subsurface media. Input to the program includes the geometry of the system, the spatial distribution of finite elements and nodes, the properties of the media, the potential chemical reactions, and the initial and boundary conditions. Output includes the spatial distribution of chemical element concentrations as a function of time and space and the chemical speciation at user-specified nodes. LEHGC Version 1.1 is a modification of LEHGC Version 1.0. The modification includes: (1) devising a tracking algorithm with the computational effort proportional to N where N is the number of computational grid nodes rather than N{sup 2} as in LEHGC Version 1.0, (2) including multiple adsorbing sites and multiple ion-exchange sites, (3) using four preconditioned conjugate gradient methods for the solution of matrix equations, and (4) providing a model for some features of solute transport by colloids.

  20. HFO1234ze(Z) saturated vapour condensation inside a brazed plate heat exchanger

    OpenAIRE

    Longo, Giovanni A.; Zilio, Claudio; Righetti, Giulia; Brown, J. Steven

    2014-01-01

    All commonly used Hydro-Fluoro-Carbon (HFC) refrigerants have a high Global Warming Potential (GWP), higher than 1000, and some countries have already enacted legislative measures towards a limitation in the use or a gradual phase-out of HFCs. HFO1234ze(Z) was identified as a new low GWP refrigerant, which has the potential to be a global sustainable solution particularly for heat pump application. HFO1234ze(Z) is a pure compound which exhibits low pressure and is classified by ANSI / ASHRAE ...

  1. Nuclear Magnetic Resonance Measurements of Original Water Saturation and Mobile Water Saturation in Low Permeability Sandstone Gas

    Institute of Scientific and Technical Information of China (English)

    GAO Shu-Sheng; YE Li-You; XIONG Wei; GUO He-Kun; HU Zhi-Ming

    2010-01-01

    @@ We use nuclear magnetic resonance(NMR)and centrifugation to measure the original water saturation and mobile water saturation of cores from the Xujiahe low permeability sandstone gas reservoir,and compare the NMR results with the corresponding field data.It is shown that the NMR water saturation after 300 psi centrifugation effectively represents the original water saturation measured by weighing fresh cores.There is a good correlation between mobile water saturation and the water production performance of the corresponding gas wells.The critical mobile water saturation whether reservoir produces water of the Xujiahe low permeability sandstone gas is 6%.The higher the mobile water saturation,the greater the water production rate of gas well.This indicates that well's water production performance can be forecasted by mobile water saturation of cores.

  2. Facilitated transport near the carrier saturation limit

    Directory of Open Access Journals (Sweden)

    Anawat Sungpet

    2002-11-01

    Full Text Available Permeation of ethylbenzene, styrene and 1-hexene through perfluorosulfonate ionomer membranes was carried out with the feed concentrations ranging from 1 M to pure. On comparison, fluxes of ethylbenzene through the Ag+-form membrane were the lowest. Only a small increase in ethylbenzene flux was observed after the feed concentration exceeded 3 M, indicating the existence of carrier saturation. The increase in styrene flux was suppressed to some degree at high concentration driving forces. In contrast, 1-hexene flux was the highest and continued to increase even at very high feed concentrations. After the experiments with pure feeds, extraction of the solutes from the membranes revealed that 62.5% of Ag+ ions reacted with 1-hexene as against 40.6% for styrene and 28.9% for ethylbenzene. Equilibrium constants, determined by distribution method, of 1-hexene, styrene and ethylbenzene were 129, 2.2 and 0.7 M-1 respectively, which suggested that stability of the complex was a key factor in the carrier saturation phenomenon.

  3. Pressure drop in saturated flow boiling

    Energy Technology Data Exchange (ETDEWEB)

    Collado, Francisco J. [Universidad de Zaragoza, Zaragoza (Spain)

    2003-07-01

    A new mass balance for flow boiling have been recently suggested by the author following a quite simple idea: if the phases have different velocities, they can not cover the same distance -the control volume length for a 1-d system- in the same time. Thus, the time scales of the phases have to be different, and we should scale the time dependent magnitudes of one phase to the other one before combining them. Furthermore, it is reasonable to think that conservation equations should have to include in some manner this evident physical fact. In complete coherence with the former mass balance, a new energy balance, which does include the slip ratio has been also stated. This work, whilst reviews these new fundamentals for saturated flow boiling, stresses those aspects related with the prediction of the pressure drop in saturated flow boiling. The new correlations found for the data carefully measured by Thom during the Cambridge project would confirm the new two-phase flowapproach.

  4. Failure of geomaterials in variably saturated soils

    Science.gov (United States)

    Song, X.; Borja, R. I.

    2013-12-01

    The first law of thermodynamics suggests an energy-conjugate relationship among degree of saturation, suction stress, and density of an unsaturated porous material. Experimental evidence affirms that this constitutive relationship exists, and that the water retention curves are dependent on the specific volume or density of the material. This constitutive feature must be incorporated into the mathematical formulation of boundary-value problems involving finite deformation. We present a fully coupled hydromechanical formulation in the finite deformation range that incorporates the variation of degree of saturation with the Kirchhoff suction stress and the Jacobian determinant of the solid-phase motion. A numerical simulation of solid deformation-fluid flow in unsaturated soil with a random microstructure demonstrates an intricate but well-established coupling of the hydromechanical processes. As deformation localizes into a persistent shear band, we show that bifurcation of the hydromechanical response manifests itself not only in the form of a softening behavior but also through bifurcation of the state paths on the water-retention surface.

  5. VARUN: discovering extensible motifs under saturation constraints.

    Science.gov (United States)

    Apostolico, Alberto; Comin, Matteo; Parida, Laxmi

    2010-01-01

    The discovery of motifs in biosequences is frequently torn between the rigidity of the model on one hand and the abundance of candidates on the other hand. In particular, motifs that include wild cards or "don't cares" escalate exponentially with their number, and this gets only worse if a don't care is allowed to stretch up to some prescribed maximum length. In this paper, a notion of extensible motif in a sequence is introduced and studied, which tightly combines the structure of the motif pattern, as described by its syntactic specification, with the statistical measure of its occurrence count. It is shown that a combination of appropriate saturation conditions and the monotonicity of probabilistic scores over regions of constant frequency afford us significant parsimony in the generation and testing of candidate overrepresented motifs. A suite of software programs called Varun is described, implementing the discovery of extensible motifs of the type considered. The merits of the method are then documented by results obtained in a variety of experiments primarily targeting protein sequence families. Of equal importance seems the fact that the sets of all surprising motifs returned in each experiment are extracted faster and come in much more manageable sizes than would be obtained in the absence of saturation constraints.

  6. Saturable absoprtion of graphene (Conference Presentation)

    Science.gov (United States)

    Marini, Andrea; Cox, Joel D.; Garcia de Abajo, Javier F.

    2016-09-01

    Saturable absorption (SA) is an inherent property of photonic materials that manifests itself as an absorption quenching at high light intensities and is a key element for passive mode-locking (PML) in laser cavities, where continuous waves break into a train of ultrashort optical pulses. Currently, state-of-the-art semiconductor-based SA mirrors are routinely employed for PML lasers. However, these mirrors operate in a narrow spectral range, are poorly tunable, and require advanced fabrication techniques. Graphene overcomes this limitation thanks to its peculiar conical band structure, providing a universally-resonant wavelength-independent SA at low light intensity that can be further electrically tuned be means of an externally applied gate voltage. Here, we calculate intraband and interband contributions to SA of extended graphene by solving non-perturbatively the single-particle Dirac equation for massless Dirac fermions in the presence of an external electromagnetic field and comparing results with atomistic calculations in the framework of tight-binding and random-phase approximation. Further, we investigate the optical properties of randomly-oriented undoped graphene flakes embedded in externally pumped amplifying media. We demonstrate a novel mechanism leading to stable and tunable single-mode cavity-free lasing characterized by a well-determined and highly coherent spatial pattern. This cavity-free lasing mechanism profoundly relies on graphene highly-saturated absorption at rather modest light intensities, a remarkable property which enables self-organization of light into a well determined spatial mode profile.

  7. SITE-SCALE SATURATED ZONE TRANSPORT

    Energy Technology Data Exchange (ETDEWEB)

    S. KELLER

    2004-11-03

    This work provides a site-scale transport model for calculating radionuclide transport in the saturated zone (SZ) at Yucca Mountain, for use in the abstractions model in support of ''Total System Performance Assessment for License Application'' (TSPA-LA). The purpose of this model report is to provide documentation for the components of the site-scale SZ transport model in accordance with administrative procedure AP-SIII.10Q, Models. The initial documentation of this model report was conducted under the ''Technical Work Plan For: Saturated Zone Flow and Transport Modeling and Testing'' (BSC 2003 [DIRS 163965]). The model report has been revised in accordance with the ''Technical Work Plan For: Natural System--Saturated Zone Analysis and Model Report Integration'', Section 2.1.1.4 (BSC 2004 [DIRS 171421]) to incorporate Regulatory Integration Team comments. All activities listed in the technical work plan that are appropriate to the transport model are documented in this report and are described in Section 2.1.1.4 (BSC 2004 [DIRS 171421]). This report documents: (1) the advection-dispersion transport model including matrix diffusion (Sections 6.3 and 6.4); (2) a description and validation of the transport model (Sections 6.3 and 7); (3) the numerical methods for simulating radionuclide transport (Section 6.4); (4) the parameters (sorption coefficient, Kd ) and their uncertainty distributions used for modeling radionuclide sorption (Appendices A and C); (5) the parameters used for modeling colloid-facilitated radionuclide transport (Table 4-1, Section 6.4.2.6, and Appendix B); and (6) alternative conceptual models and their dispositions (Section 6.6). The intended use of this model is to simulate transport in saturated fractured porous rock (double porosity) and alluvium. The particle-tracking method of simulating radionuclide transport is incorporated in the finite-volume heat and mass transfer numerical

  8. User`s guide for UTCHEM-5.32m a three dimensional chemical flood simulator. Final report, September 30, 1992--December 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-07-01

    UTCHEM is a three-dimensional chemical flooding simulator. The solution scheme is analogous to IMPES, where pressure is solved for implicitly, but concentrations rather than saturations are then solved for explicitly. Phase saturations and concentrations are then solved in a flash routine. An energy balance equation is solved explicitly for reservoir temperature. The energy balance equation includes heat flow between the reservoir and the over-and under-burden rocks. The major physical phenomena modeled in the simulator are: dispersion; dilution effects; adsorption; interfacial tension; relative permeability; capillary trapping; cation exchange; phase density; compositional phase viscosity; phase behavior (pseudoquaternary); aqueous reactions; partitioning of chemical species between oil and water; dissolution/precipitation; cation exchange reactions involving more than two cations; in-situ generation of surfactant from acidic crude oil; pH dependent adsorption; polymer properties: shear thinning viscosity; inaccessible pore volume; permeability reduction; adsorption; gel properties: viscosity; permeability reduction; adsorption; tracer properties: partitioning; adsorption; radioactive decay; reaction (ester hydrolization); temperature dependent properties: viscosity; tracer reaction; gel reactions The following options are available with UTCHEM: isothermal or non-isothermal conditions, a constant or variable time-step, constant pressure or constant rate well conditions, horizontal and vertical wells, and a radial or Cartesian geometry. Please refer to the dissertation {open_quotes}Field Scale Simulation of Chemical Flooding{close_quotes} by Naji Saad, August, 1989, for a more detailed discussion of the UTCHEM simulator and its formulation.

  9. Modeling of Crystalline Silicotitanate Ion Exchange Columns

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.D.

    1999-03-09

    Non-elutable ion exchange is being considered as a potential replacement for the In-Tank Precipitation process for removing cesium from Savannah River Site (SRS) radioactive waste. Crystalline silicotitanate (CST) particles are the reference ion exchange medium for the process. A major factor in the construction cost of this process is the size of the ion exchange column required to meet product specifications for decontaminated waste. To validate SRS column sizing calculations, SRS subcontracted two reknowned experts in this field to perform similar calculations: Professor R. G. Anthony, Department of Chemical Engineering, Texas A&038;M University, and Professor S. W. Wang, Department of Chemical Engineering, Purdue University. The appendices of this document contain reports from the two subcontractors. Definition of the design problem came through several meetings and conference calls between the participants and SRS personnel over the past few months. This document summarizes the problem definition and results from the two reports.

  10. Modern Chemical Technology, Volume 9.

    Science.gov (United States)

    Pecsok, Robert L.; Chapman, Kenneth

    This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: ion exchange, electrphoresis, dialysis, electrochemistry, corrosion, electrolytic cells, coulometry,…

  11. The Expected Order of Saturated RNA Secondary Structures

    CERN Document Server

    Jin, Emma Yu

    2011-01-01

    We show the expected order of RNA saturated secondary structures of size $n$ is $\\log_4n(1+O(\\frac{\\log_2n}{n}))$, if we select the saturated secondary structure uniformly at random. Furthermore, the order of saturated secondary structures is sharply concentrated around its mean. As a consequence saturated structures and structures in the traditional model behave the same with respect to the expected order. Thus we may conclude that the traditional model has already drawn the right picture and conclusions inferred from it with respect to the order (the overall shape) of a structure remain valid even if enforcing saturation (at least in expectation).

  12. {sup 13}CHD{sub 2}–CEST NMR spectroscopy provides an avenue for studies of conformational exchange in high molecular weight proteins

    Energy Technology Data Exchange (ETDEWEB)

    Rennella, Enrico; Huang, Rui; Velyvis, Algirdas; Kay, Lewis E., E-mail: kay@pound.med.utoronto.ca [The University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada)

    2015-10-15

    An NMR experiment for quantifying slow (millisecond) time-scale exchange processes involving the interconversion between visible ground state and invisible, conformationally excited state conformers is presented. The approach exploits chemical exchange saturation transfer (CEST) and makes use of {sup 13}CHD{sub 2} methyl group probes that can be readily incorporated into otherwise highly deuterated proteins. The methodology is validated with an application to a G48A Fyn SH3 domain that exchanges between a folded conformation and a sparsely populated and transiently formed unfolded ensemble. Experiments on a number of different protein systems, including a 360 kDa half-proteasome, establish that the sensitivity of this {sup 13}CHD{sub 2}{sup 13}C–CEST technique can be upwards of a factor of 5 times higher than for a previously published {sup 13}CH{sub 3}{sup 13}C–CEST approach (Bouvignies and Kay in J Biomol NMR 53:303–310, 2012), suggesting that the methodology will be powerful for studies of conformational exchange in high molecular weight proteins.

  13. Energy dependent saturable and reverse saturable absorption in cube-like polyaniline/polymethyl methacrylate film

    Energy Technology Data Exchange (ETDEWEB)

    Thekkayil, Remyamol [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, C.V. Raman Avenue, Bangalore 560 080 (India); Gopinath, Pramod [Department of Physics, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547 (India); John, Honey, E-mail: honey@iist.ac.in [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547 (India)

    2014-08-01

    Solid films of cube-like polyaniline synthesized by inverse microemulsion polymerization method have been fabricated in a transparent PMMA host by an in situ free radical polymerization technique, and are characterized by spectroscopic and microscopic techniques. The nonlinear optical properties are studied by open aperture Z-scan technique employing 5 ns (532 nm) and 100 fs (800 nm) laser pulses. At the relatively lower laser pulse energy of 5 μJ, the film shows saturable absorption both in the nanosecond and femtosecond excitation domains. An interesting switchover from saturable absorption to reverse saturable absorption is observed at 532 nm when the energy of the nanosecond laser pulses is increased. The nonlinear absorption coefficient increases with increase in polyaniline concentration, with low optical limiting threshold, as required for a good optical limiter. - Highlights: • Synthesized cube-like polyaniline nanostructures. • Fabricated polyaniline/PMMA nanocomposite films. • At 5 μJ energy, saturable absorption is observed both at ns and fs regime. • Switchover from SA to RSA is observed as energy of laser beam increases. • Film (0.1 wt % polyaniline) shows high β{sub eff} (230 cm GW{sup −1}) and low limiting threshold at 150 μJ.

  14. Nonlinear optical properties of laser synthesized Pt nanoparticles: saturable and reverse saturable absorption

    Science.gov (United States)

    Chehrghani, A.; Torkamany, M. J.

    2014-01-01

    In this paper, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are presented. The Pt NPs were prepared by laser ablation of a Pt metallic target in distilled water using a 1064 nm high frequency Nd:YAG laser. The intensity-dependent nonlinear optical absorption and nonlinear refraction behaviors of the sample exposed to the 532 nm nanosecond laser pulses were investigated by applying the Z-scan technique. The saturated nonlinear absorption coefficient 5.4 × 10-7 cm W-1 was obtained in a saturation intensity of 1.8 × 107 W cm-2. The saturable absorption response of the Pt NPs was switched to the reverse saturable absorption in the higher laser intensities. The nonlinear refractive index that has a negative value was increased from -3.5 × 10-13 cm2 W-1 up to -15 × 10-13 cm2 W-1 by increasing the laser intensity.

  15. Effect of solution saturation state and temperature on diopside dissolution

    Directory of Open Access Journals (Sweden)

    Carroll Susan A

    2007-03-01

    Full Text Available Abstract Steady-state dissolution rates of diopside are measured as a function of solution saturation state using a titanium flow-through reactor at pH 7.5 and temperature ranging from 125 to 175°C. Diopside dissolved stoichiometrically under all experimental conditions and rates were not dependent on sample history. At each temperature, rates continuously decreased by two orders of magnitude as equilibrium was approached and did not exhibit a dissolution plateau of constant rates at high degrees of undersaturation. The variation of diopside dissolution rates with solution saturation can be described equally well with a ion exchange model based on transition state theory or pit nucleation model based on crystal growth/dissolution theory from 125 to 175°C. At 175°C, both models over predict dissolution rates by two orders of magnitude indicating that a secondary phase precipitated in the experiments. The ion exchange model assumes the formation of a Si-rich, Mg-deficient precursor complex. Lack of dependence of rates on steady-state aqueous calcium concentration supports the formation of such a complex, which is formed by exchange of protons for magnesium ions at the surface. Fit to the experimental data yields Rate (moldiopsidecm−2s−1=k×10−Ea/2.303RT(aH+2aMg2+n MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaaieaacqWFsbGucqWFHbqycqWF0baDcqWFLbqzcqqGGaaicqGGOaakcqWFTbqBcqWFVbWBcqWFSbaBcqWFGaaicqWFKbazcqWFPbqAcqWFVbWBcqWFWbaCcqWFZbWCcqWFPbqAcqWFKbazcqWFLbqzcqWFGaaicqWFJbWycqWFTbqBdaahaaWcbeqaaiabgkHiTiabikdaYaaakiab=bcaGiab=nhaZnaaCaaaleqabaGaeyOeI0IaeGymaedaaOGaeiykaKIaeyypa0Jaem4AaSMaey41aqRaeeymaeJaeeimaaZaaWbaaSqabeaacqGHsislcqWGfbqrdaWgaaadbaGaemyyaegabeaaliabc+caViabikdaYiabc6caUiabioda

  16. Torque Characteristics of Saturated Permanent-Magnet Synchronous Motors

    Science.gov (United States)

    Takahashi, Akeshi; Kikuchi, Satoshi; Wakui, Shinichi; Mikami, Hiroyuki; Ide, Kazumasa; Shima, Kazuo

    The evaluation of torque characteristics in a saturated magnetic field for permanent-magnet (PM) synchronous motors is presented. The torque saturation characteristics of non-salient and salient pole machines are investigated by finite element analysis and measurement. Thus, it is found that the torque saturation originates in the magnetic saturation in both the stator teeth, which are located on the leading position toward the direct axis, and in the stator back yoke, which is located on the lagging position toward the direct axis. This mechanism can also explain the reason for the significant torque saturation in the salient-pole machine; the higher inductance of the quadrature axis of the salient-pole machine causes a significant magnetic saturation in the stator back yoke. Therefore, less saliency or a wider back yoke can improve the torque saturation.

  17. Predicting saturated hydraulic conductivity using soil morphological properties

    Directory of Open Access Journals (Sweden)

    Gülay Karahan

    2016-01-01

    Full Text Available Many studies have been conducted to predict soil saturated hydraulic conductivity (Ks by parametric soil properties such as bulk density and particle-size distribution. Although soil morphological properties have a strong effect on Ks, studies predicting Ks by soil morphological properties such as type, size, and strength of soil structure; type, orientation and quantity of soil pores and roots and consistency are rare. This study aimed at evaluating soil morphological properties to predict Ks. Undisturbed soil samples (15 cm length and 8.0 cm id. were collected from topsoil (0-15 cm and subsoil (15-30 cm (120 samples with a tractor operated soil sampler at sixty randomly selected sampling sites on a paddy field and an adjecent grassland in Central Anatolia (Cankırı, Turkey. Synchronized disturbed soil samples were taken from the same sampling sites and sampling depths for basic soil analyses. Saturated hydraulic conductivity was measured on the soil columns using a constant-head permeameter. Following the Ks measurements, the upper part of soil columns were covered to prevent evaporation and colums were left to drain in the laboratory. When the water flow through the column was stopped, a subsample were taken for bulk density and then soil columns were disturbed for describing the soil morphological properties. In addition, soil texture, bulk density, pH, field capacity, wilting point, cation exchange capacity, specific surface area, aggregate stability, organic matter, and calcium carbonate were measured on the synchronized disturbed soil samples. The data were divided into training (80 data values and validation (40 data values sets. Measured values of Ks ranged from 0.0036 to 2.14 cmh-1 with a mean of 0.86 cmh-1. The Ks was predicted from the soil morphological and parametric properties by stepwise multiple linear regression analysis. Soil structure class, stickiness, pore-size, root-size, and pore-quantity contributed to the Ks prediction

  18. Novel microwave assisted chemical synthesis of Nd₂Fe₁₄B hard magnetic nanoparticles.

    Science.gov (United States)

    Swaminathan, Viswanathan; Deheri, Pratap Kumar; Bhame, Shekhar Dnyaneswar; Ramanujan, Raju Vijayaraghavan

    2013-04-07

    The high coercivity and excellent energy product of Nd2Fe14B hard magnets have led to a large number of high value added industrial applications. Chemical synthesis of Nd2Fe14B nanoparticles is challenging due to the large reduction potential of Nd(3+) and the high tendency for Nd2Fe14B oxidation. We report the novel synthesis of Nd2Fe14B nanoparticles by a microwave assisted combustion process. The process consisted of Nd-Fe-B mixed oxide preparation by microwave assisted combustion, followed by the reduction of the mixed oxide by CaH2. This combustion process is fast, energy efficient and offers facile elemental substitution. The coercivity of the resulting powders was ∼8.0 kOe and the saturation magnetization was ∼40 emu g(-1). After removal of CaO by washing, saturation magnetization increased and an energy product of 3.57 MGOe was obtained. A range of magnetic properties was obtained by varying the microwave power, reduction temperature and Nd to Fe ratio. A transition from soft to exchange coupled to hard magnetic properties was obtained by varying the composition of NdxFe1-xB8 (x varies from 7% to 40%). This synthesis procedure offers an inexpensive and facile platform to produce exchange coupled hard magnets.

  19. Adaptively Compressed Exchange Operator

    CERN Document Server

    Lin, Lin

    2016-01-01

    The Fock exchange operator plays a central role in modern quantum chemistry. The large computational cost associated with the Fock exchange operator hinders Hartree-Fock calculations and Kohn-Sham density functional theory calculations with hybrid exchange-correlation functionals, even for systems consisting of hundreds of atoms. We develop the adaptively compressed exchange operator (ACE) formulation, which greatly reduces the computational cost associated with the Fock exchange operator without loss of accuracy. The ACE formulation does not depend on the size of the band gap, and thus can be applied to insulating, semiconducting as well as metallic systems. In an iterative framework for solving Hartree-Fock-like systems, the ACE formulation only requires moderate modification of the code, and can be potentially beneficial for all electronic structure software packages involving exchange calculations. Numerical results indicate that the ACE formulation can become advantageous even for small systems with tens...

  20. Terahertz Saturable Absorption in Superconducting Metamaterials

    CERN Document Server

    Keiser, George R; Zhao, Xiaoguang; Zhang, Xin; Averitt, Richard D

    2016-01-01

    We present a superconducting metamaterial saturable absorber at terahertz frequencies. The absorber consists of an array of split ring resonators (SRRs) etched from a 100nm YBaCu3O7 (YBCO) film. A polyimide spacer layer and gold ground plane are deposited above the SRRs, creating a reflecting perfect absorber. Increasing either the temperature or incident electric field (E) decreases the superconducting condensate density and corresponding kinetic inductance of the SRRs. This alters the impedance matching in the metamaterial, reducing the peak absorption. At low electric fields, the absorption was optimized near 80% at T=10K and decreased to 20% at T=70K. For E=40kV/cm and T=10K, the peak absorption was 70% decreasing to 40% at 200kV/cm, corresponding to a modulation of 43%.

  1. Convection of Moist Saturated Air: Analytical Study

    Directory of Open Access Journals (Sweden)

    Robert Zakinyan

    2016-01-01

    Full Text Available In the present work, the steady-state stationary thermal convection of moist saturated air in a lower atmosphere has been studied theoretically. Thermal convection was considered without accounting for the Coriolis force, and with only the vertical temperature gradient. The analytical solution of geophysical fluid dynamics equations, which generalizes the formulation of the moist convection problem, is obtained in the two-dimensional case. The stream function is derived in the Boussinesq approximation with velocity divergence taken as zero. It has been shown that the stream function is asymmetrical in vertical direction contrary to the dry and moist unsaturated air convection. It has been demonstrated that the convection in moist atmosphere strongly depends on the vapor mass fraction gradient.

  2. Saturation and time dependence of geodynamo models

    CERN Document Server

    Schrinner, M; Cameron, R; Hoyng, P

    2009-01-01

    In this study we address the question under which conditions a saturated velocity field stemming from geodynamo simulations leads to an exponential growth of the magnetic field in a corresponding kinematic calculation. We perform global self-consistent geodynamo simulations and calculate the evolution of a kinematically advanced tracer field. The self-consistent velocity field enters the induction equation in each time step, but the tracer field does not contribute to the Lorentz force. This experiment has been performed by Cattaneo & Tobias (2009) and is closely related to the test field method by Schrinner et al. (2005, 2007). We find two dynamo regimes in which the tracer field either grows exponentially or approaches a state aligned with the actual self-consistent magnetic field after an initial transition period. Both regimes can be distinguished by the Rossby number and coincide with the dipolar and multipolar dynamo regimes identified by Christensen & Aubert (2006). Dipolar dynamos with low Ros...

  3. Saturated Reconstruction of a Volume of Neocortex.

    Science.gov (United States)

    Kasthuri, Narayanan; Hayworth, Kenneth Jeffrey; Berger, Daniel Raimund; Schalek, Richard Lee; Conchello, José Angel; Knowles-Barley, Seymour; Lee, Dongil; Vázquez-Reina, Amelio; Kaynig, Verena; Jones, Thouis Raymond; Roberts, Mike; Morgan, Josh Lyskowski; Tapia, Juan Carlos; Seung, H Sebastian; Roncal, William Gray; Vogelstein, Joshua Tzvi; Burns, Randal; Sussman, Daniel Lewis; Priebe, Carey Eldin; Pfister, Hanspeter; Lichtman, Jeff William

    2015-07-30

    We describe automated technologies to probe the structure of neural tissue at nanometer resolution and use them to generate a saturated reconstruction of a sub-volume of mouse neocortex in which all cellular objects (axons, dendrites, and glia) and many sub-cellular components (synapses, synaptic vesicles, spines, spine apparati, postsynaptic densities, and mitochondria) are rendered and itemized in a database. We explore these data to study physical properties of brain tissue. For example, by tracing the trajectories of all excitatory axons and noting their juxtapositions, both synaptic and non-synaptic, with every dendritic spine we refute the idea that physical proximity is sufficient to predict synaptic connectivity (the so-called Peters' rule). This online minable database provides general access to the intrinsic complexity of the neocortex and enables further data-driven inquiries.

  4. Microsoft Exchange 2013 cookbook

    CERN Document Server

    Van Horenbeeck, Michael

    2013-01-01

    This book is a practical, hands-on guide that provides the reader with a number of clear, step-by-step exercises.""Microsoft Exchange 2013 Cookbook"" is targeted at network administrators who deal with the Exchange server in their day-to-day jobs. It assumes you have some practical experience with previous versions of Exchange (although this is not a requirement), without being a subject matter expert.

  5. Exchange rate regime choice

    Directory of Open Access Journals (Sweden)

    Beker Emilija

    2006-01-01

    Full Text Available The choice of an adequate exchange rate regime proves to be a highly sensitive field within which the economic authorities present and confirm themselves. The advantages and disadvantages of fixed and flexible exchange rate regimes, which have been quite relativized from the conventional point of view, together with simultaneous, but not synchronized effects of structural and external factors, remain permanently questioned throughout a complex process of exchange rate regime decision making. The paper reflects the attempt of critical identification of the key exchange rate performances with emphasis on continuous non-uniformity and (uncertainty of shelf life of a relevant choice.

  6. Usable optimistic fair exchange

    OpenAIRE

    Küpçü, Alptekin; Lysyanskaya, A.

    2012-01-01

    Fairly exchanging digital content is an everyday problem. It has been shown that fair exchange cannot be achieved without a trusted third party (called the Arbiter). Yet, even with a trusted party, it is still non-trivial to come up with an efficient solution, especially one that can be used in a p2p file sharing system with a high volume of data exchanged. We provide an efficient optimistic fair exchange mechanism for bartering digital files, where receiving a payment in return for a file (b...

  7. Modeling variably saturated multispecies reactive groundwater solute transport with MODFLOW-UZF and RT3D

    Science.gov (United States)

    Bailey, Ryan T.; Morway, Eric D.; Niswonger, Richard G.; Gates, Timothy K.

    2013-01-01

    A numerical model was developed that is capable of simulating multispecies reactive solute transport in variably saturated porous media. This model consists of a modified version of the reactive transport model RT3D (Reactive Transport in 3 Dimensions) that is linked to the Unsaturated-Zone Flow (UZF1) package and MODFLOW. Referred to as UZF-RT3D, the model is tested against published analytical benchmarks as well as other published contaminant transport models, including HYDRUS-1D, VS2DT, and SUTRA, and the coupled flow and transport modeling system of CATHY and TRAN3D. Comparisons in one-dimensional, two-dimensional, and three-dimensional variably saturated systems are explored. While several test cases are included to verify the correct implementation of variably saturated transport in UZF-RT3D, other cases are included to demonstrate the usefulness of the code in terms of model run-time and handling the reaction kinetics of multiple interacting species in variably saturated subsurface systems. As UZF1 relies on a kinematic-wave approximation for unsaturated flow that neglects the diffusive terms in Richards equation, UZF-RT3D can be used for large-scale aquifer systems for which the UZF1 formulation is reasonable, that is, capillary-pressure gradients can be neglected and soil parameters can be treated as homogeneous. Decreased model run-time and the ability to include site-specific chemical species and chemical reactions make UZF-RT3D an attractive model for efficient simulation of multispecies reactive transport in variably saturated large-scale subsurface systems.

  8. Anion exchange polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

    2013-07-23

    Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

  9. Climatological distribution of aragonite saturation state in the global oceans

    Science.gov (United States)

    Jiang, Li-Qing; Feely, Richard A.; Carter, Brendan R.; Greeley, Dana J.; Gledhill, Dwight K.; Arzayus, Krisa M.

    2015-10-01

    Aragonite saturation state (Ωarag) in surface and subsurface waters of the global oceans was calculated from up-to-date (through the year of 2012) ocean station dissolved inorganic carbon (DIC) and total alkalinity (TA) data. Surface Ωarag in the open ocean was always supersaturated (Ω > 1), ranging between 1.1 and 4.2. It was above 2.0 (2.0-4.2) between 40°N and 40°S but decreased toward higher latitude to below 1.5 in polar areas. The influences of water temperature on the TA/DIC ratio, combined with the temperature effects on inorganic carbon equilibrium and apparent solubility product (K'sp), explain the latitudinal differences in surface Ωarag. Vertically, Ωarag was highest in the surface mixed layer. Higher hydrostatic pressure, lower water temperature, and more CO2 buildup from biological activity in the absence of air-sea gas exchange helped maintain lower Ωarag in the deep ocean. Below the thermocline, aerobic decomposition of organic matter along the pathway of global thermohaline circulation played an important role in controlling Ωarag distributions. Seasonally, surface Ωarag above 30° latitudes was about 0.06 to 0.55 higher during warmer months than during colder months in the open-ocean waters of both hemispheres. Decadal changes of Ωarag in the Atlantic and Pacific Oceans showed that Ωarag in waters shallower than 100 m depth decreased by 0.10 ± 0.09 (-0.40 ± 0.37% yr-1) on average from the decade spanning 1989-1998 to the decade spanning 1998-2010.

  10. Tracking Controller for Intrinsic Output Saturated Systems in Presence of Amplitude and Rate Input Saturations

    DEFF Research Database (Denmark)

    Chater, E.; Giri, F.; Guerrero, Josep M.;

    2014-01-01

    We consider the problem of controlling plants that are subject to multiple saturation constraints. Especially, we are interested in linear systems whose input is subject to amplitude and rate constraints of saturation type. Furthermore, the considered systems output is also subject to an intrinsic......-loop control system is analyzed using input-output stability tools. Thus, conditions guaranteeing l2-tracking performances are formally defined. Interestingly, the proposed controller is shown to ensure perfect output-reference tracking in presence of varying with l2-vanishing rate inputs. On the other hand......, in the case of arbitrary inputs, the proposed controller guarantees that the less changing the inputs are the better the output-reference tracking....

  11. Assessment of calculation methods for calcium carbonate saturation in drinking water for DIN 38404-10 compliance

    NARCIS (Netherlands)

    De Moel, P.J.; Van der Helm, A.W.C.; Van Rijn, M.; Van Dijk, J.C.; Van der Meer, W.G.J.

    2013-01-01

    The new German standard on the calculation of calcite saturation in drinking water, DIN 38404-10, 2012 (DIN), marks a change in drinking water standardization from using simplified equations applicable for nomographs and simple calculators to using extensive chemical modeling requiring computer prog

  12. Hydronium-dominated ion transport in carbon-dioxide-saturated electrolytes at low salt concentrations in nanochannels

    DEFF Research Database (Denmark)

    Pennathur, Sumita; Kristensen, Jesper; Crumrine, Andrew

    2011-01-01

    conductance for low salt concentrations, we identify a minimum conductance value before saturation at a value independent of salt concentration in the dilute limit. Our model self-consistently couples chemical equilibrium models of the silica wall and the electrolyte bulk, and is parameterized by only...

  13. Hydronium-dominated ion transport in carbon-dioxide-saturated electrolytes at low salt concentrations in nanochannels

    DEFF Research Database (Denmark)

    Lund Jensen, Kristian; Kristensen, Jesper Toft; Crumrine, Andrew Michael

    2011-01-01

    the nanochannel conductance at low salt concentrations and identify a conductance minimum before saturation at a value independent of salt concentration in the dilute limit. Via the Poisson-Boltzmann equation, our model self-consistently couples chemical-equilibrium dissociation models of the silica wall...

  14. Building Relationships through Exchange

    Science.gov (United States)

    Primavera, Angi; Hall, Ellen

    2011-01-01

    From the moment of birth, children form and develop relationships with others in their world based on exchange. Children recognize that engaging in such encounters offers them the opportunity to enter into a relationship with another individual and to nurture that relationship through the exchange of messages and gifts, items and ideas. At Boulder…

  15. Optimization of Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Ivan Catton

    2010-10-01

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.

  16. Shell-and-double concentric-tube heat exchangers

    Science.gov (United States)

    Bougriou, Chérif; Baadache, Khireddine

    2010-03-01

    This study concerns a new type of heat exchangers, which is that of shell-and-double concentric-tube heat exchangers. These heat exchangers can be used in many specific applications such as air conditioning, waste heat recovery, chemical processing, pharmaceutical industries, power production, transport, distillation, food processing, cryogenics, etc. The case studies include both design calculations and performance calculations. It is demonstrated that the relative diameter sizes of the two tubes with respect to each other are the most important parameters that influence the heat exchanger size.

  17. Nitrogen Saturation in Highly Retentive Watersheds?

    Science.gov (United States)

    Daley, M. L.; McDowell, W. H.

    2009-12-01

    Watershed managers are often concerned with minimizing the amount of N delivered to N-limited estuaries and coastal zones. A major concern is that watersheds might reach N saturation, in which N delivered to coastal zones increases due to declines in the efficiency of N retention despite constant or even reduced N inputs. We have quantified long-term changes in N inputs (atmospheric deposition, imported food and agricultural fertilizers), outputs (N concentration and export) and retention in the urbanizing Lamprey River watershed in coastal NH. Overall, the Lamprey watershed is 70% forested, receives about 13.5 kg N/ha/yr and has a high rate of annual N retention (85%). Atmospheric deposition (8.7 kg/ha/yr) is the largest N input to the watershed. Of the 2.2 kg N/ha/yr exported in the Lamprey River, dissolved organic N (DON) is the dominant form (50% of total) and it varies spatially throughout the watershed with wetland cover. Nitrate accounts for 30% of the N exported, shows a statistically significant increase from 1999 to 2009, and its spatial variability in both concentration and export is related to human population density. In sub-basins throughout the Lamprey, inorganic N retention is high (85-99%), but the efficiency of N retention declines sharply with increased human population density and associated anthropogenic N inputs. N assimilation in the vegetation, denitrification to the atmosphere and storage in the groundwater pool could all be important contributors to the current high rates of N retention. The temporal and spatial patterns that we have observed in nitrate concentration and export are driven by increases in N inputs and impervious surfaces over time, but the declining efficiency of N retention suggests that the watershed may also be reaching N saturation. The downstream receiving estuary, Great Bay, already suffers from low dissolved oxygen levels and eelgrass loss in part due to N loading from the Lamprey watershed. Targeting and reducing

  18. In-situ Spectroscopic Characterization of a Solution-Phase X-Type Ligand Exchange at Colloidal Lead Sulphide Quantum Dot Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kroupa, Daniel M.; Anderson, Nicholas C.; Castaneda, Chloe V.; Nozik, Arthur J.; Beard, Matt C.

    2016-12-14

    We employed quantitative NMR spectroscopy and spectrophotometric absorbance titration to study a quantum dot X-type ligand exchange reaction. We find that the exchange is highly cooperative, where at low extents of exchange the change in free energy of the reaction, ..delta..GXC, is ~11 kJ mol-1 while at higher extents of exchange ..delta..GXC saturates to ~-4 kJ mol-1. A modified Fowler binding isotherm is developed to describe the reaction.

  19. Saturation model for squirrel-cage induction motors

    Energy Technology Data Exchange (ETDEWEB)

    Pedra, J. [Department of Electrical Engineering, ETSEIB-UPC, Av. Diagonal 647, 08028 Barcelona (Spain); Candela, I. [Department of Electrical Engineering, ETSEIT-UPC, Colom 1, 08222 Terrassa (Spain); Barrera, A. [Asea Brown Boveri, S.A. Fabrica de Motores, Poligono Industrial S.O., 08192 Sant Quirze del Valles, Barcelona (Spain)

    2009-07-15

    An induction motor model which includes stator leakage reactance saturation, rotor leakage reactance saturation and magnetizing reactance saturation is presented. This improved model is based on experimental data from 96 motors. The power range of the motors is between 11 and 90 kW. The effects on the torque-speed and current-speed curves of each kind of saturation have been studied. In addition, the parameters of magnetizing reactance saturation and stator leakage reactance saturation have been studied for each motor, and an average value and its dispersion for each parameter are given. This model is considerably more accurate than other models. In particular, it explains the significant differences between theoretical and experimental torque-speed curves in the braking regime (s > 1). (author)

  20. Brain oxygen saturation assessment in neonates using T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy.

    Science.gov (United States)

    Alderliesten, Thomas; De Vis, Jill B; Lemmers, Petra Ma; Hendrikse, Jeroen; Groenendaal, Floris; van Bel, Frank; Benders, Manon Jnl; Petersen, Esben T

    2017-03-01

    Although near-infrared spectroscopy is increasingly being used to monitor cerebral oxygenation in neonates, it has a limited penetration depth. The T2-prepared Blood Imaging of Oxygen Saturation (T2-BIOS) magnetic resonance sequence provides an oxygen saturation estimate on a voxel-by-voxel basis, without needing a respiratory calibration experiment. In 15 neonates, oxygen saturation measured by T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy were compared. In addition, these measures were compared to cerebral blood flow and venous oxygen saturation in the sagittal sinus. A strong linear relation was found between the oxygen saturation measured by magnetic resonance imaging and the oxygen saturation measured by near-infrared spectroscopy ( R(2 )= 0.64, p infrared spectroscopy oxygen saturation, and magnetic resonance imaging measures of frontal cerebral blood flow, whole brain cerebral blood flow and venous oxygen saturation in the sagittal sinus ( R(2 )= 0.71, 0.50, 0.65; p infrared spectroscopy and T2-prepared blood imaging of oxygen saturation, confirming the validity of using of these techniques for determining cerebral oxygenation.

  1. Effect of pH on saturated hydraulic conductivity and soil dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, D.L.; Roades, J.D.; Lavado, R.; Grieve, C.M.

    The adverse effects of exchangeable sodium on soil hydraulic conductivity (K) are well known, but at present only sodicity and total electrolyte concentration are used in evaluating irrigation water suitability. In arid areas, high sodicity is often associatd with high dissolved carbonate and thus high pH, but in humid areas high sodicity may be associated with low pH. To evaluate the effect of pH (as an independent variable) on K, solutions with the same SAR and electrolyte level were prepared at pH 6, 7, 8, and 9. Saturated K values were determined at constant flux in columns packed at a bulk density of 1.5 Mg m/sup -3/. At pH 9, saturated K values were lower than at pH 6 for a montmorillonitic and kaolinitic soil. For a vermiculitic soil with lower organic carbon and higher silt content, pH changes did not cause large K differences. Decreases in K were not reversible on application of waters with higher electrolyte levels. The results from the K experiments were generally consistent with optical transmission measurements of dispersion. Although anion adsorption was at or below detection limits and cation exchange capacity (CEC) was only slightly dependent on pH, differences in pH effects on K among soils are likely due to differences in quantities of variable-charge minerals and organic matter.

  2. Aberration Corrected Emittance Exchange

    CERN Document Server

    Nanni, Emilio A

    2015-01-01

    Full exploitation of emittance exchange (EEX) requires aberration-free performance of a complex imaging system including active radio-frequency (RF) elements which can add temporal distortions. We investigate the performance of an EEX line where the exchange occurs between two dimensions with normalized emittances which differ by orders of magnitude. The transverse emittance is exchanged into the longitudinal dimension using a double dog-leg emittance exchange setup with a 5 cell RF deflector cavity. Aberration correction is performed on the four most dominant aberrations. These include temporal aberrations that are corrected with higher order magnetic optical elements located where longitudinal and transverse emittance are coupled. We demonstrate aberration-free performance of emittances differing by 4 orders of magnitude, i.e. an initial transverse emittance of $\\epsilon_x=1$ pm-rad is exchanged with a longitudinal emittance of $\\epsilon_z=10$ nm-rad.

  3. Ion exchange tempering of glass ophthalmic lenses.

    Science.gov (United States)

    Keeney, A H; Duerson, H L

    1975-08-01

    We performed low velocity drop-ball tests using 5/8-, 7/8-, and 1-inch diameter steel balls on ophthalmic crown glass lenses chemically tempered by the ion exchange process. Four representative dioptric strengths (+ 2.50 spherical, - 2.50 spherical, -2.50 cylindrical, and plano) were studied with the isolated lenses mounted, convex side up, on the American National Standards Institute Z80 test block. New ion exchange lenses exhibited a 100 to 350% greater capacity for attenuation of energy from low velocity, large size missiles than matched lenses of similar strength prepared by the conventional heat-treating and air-quenching process.

  4. CONSTRUCTION OF EXPERIMENTAL INSTALLATION FOR RESEARCHING OF DENSITY AND SATURATED VAPOR PRESSURE (SVP OF PETROLEUM PRODUCTS

    Directory of Open Access Journals (Sweden)

    Kharchenko P. M.

    2015-03-01

    Full Text Available The most important physical properties that characterize the substance are density and saturated vapor pressure (SVP. These parameters are required for the development of new technical processes in the petroleum and chemical industries, design of pipelines, pumping and fuel equipment, etc. Existing methods for calculating of density near and on the saturation lines are imperfect, and finding of the analytic dependence of SVP of petroleum products from all defining parameters associated with great difficulties. The purpose of present work is an experimental research and development of methods for calculating the density (specific volume near and on saturation lines, and saturated vapor pressure of gasoline straight-run fraction derived from petroleums from three fields: Mangyshlaksky, Trinity-Anastasevsky and West Siberian. The choice of objects for research is due to the necessity of creating methods for calculating of density and SVP of oils obtained from various hydrocarbon group composition petroleums. Area of state parameters in the present work by temperature (20 ÷ 320°C and pressure (0,03 ÷ 30 MPa provides the ability to research gasoline fractions to supercritical regions. Measurement of density and SVP of petroleum fractions performed with help of a specially created for this purpose experimental installation

  5. Visualization and modeling of the colonization dynamics of a bioluminscent bacterium in variably saturated, translucent quartz sand.

    Energy Technology Data Exchange (ETDEWEB)

    Rockhold, M. L.; Yarwood, R. R.; Niemet, M. R.; Bottomley, Peter J.; Brockman, Fred J.; Selker, John S.

    2007-06-01

    An experimental and numerical investigation was conducted to study the colonization dynamics of a bioluminescent bacterium, Pseudomonas fluorescens HK44, during growth in a porous medium under steady, variably saturated flow conditions. Experiments were conducted in a thin-slab light transmission chamber filled with uniform, translucent quartz sand. Steady, variably saturated flow conditions were established using drip emitters mounted on the top of the chamber, with glucose applied through a central dripper located directly above an inoculated region of the chamber. Periodic pulses of salicylate and a dye tracer were applied to induce bioluminescence of the bacterium to monitor colony expansion and to track changes in the hydraulic and transport properties of the sand. Changes in the apparent water saturation of the sand were quantified by monitoring light transmission through the chamber with a CCD camera. The colonized region expanded laterally by about 15 cm, and upward against the flow by 7-8 cm during the 6-day experiment while apparent saturations in the colonized region decreased by 7-9% and the capillary fringe dropped by ~5 cm. The observed data were reproduced approximately using a numerical model that accounted for the processes of water flow, solute and bacterial transport, cell growth and accumulation, glucose and oxygen consumption, and gas diffusion and exchange. The results of this study illustrate some of the complexities associated with coupled flow, reactive transport, and biological processes in variably saturated porous media, which are not readily observable using other experimental techniques.

  6. Magnetic Field Saturation in the Riga Dynamo Experiment

    CERN Document Server

    Gailitis, A; Platacis, E; Dementev, S; Cifersons, A; Gerbeth, G; Gundrum, T; Stefani, F; Christen, M; Will, G; Gailitis, Agris; Lielausis, Olgerts; Platacis, Ernests; Dement'ev, Sergej; Cifersons, Arnis; Gerbeth, Gunter; Gundrum, Thomas; Stefani, Frank; Christen, Michael; Will, Gotthard

    2001-01-01

    After the dynamo experiment in November 1999 had shown magnetic field self-excitation in a spiraling liquid metal flow, in a second series of experiments emphasis was placed on the magnetic field saturation regime as the next principal step in the dynamo process. The dependence of the strength of the magnetic field on the rotation rate is studied. Various features of the saturated magnetic field are outlined and possible saturation mechanisms are discussed.

  7. Cyclic Shearing Deformation Behavior of Saturated Clays

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform stress-controlled cyclic single-direction torsional shear tests and two-direction coupled shear tests under unconsolidated-undrained conditions. Through a series of tests on saturated clay, the effects of initial shear stress and stress reversal on the clay's strain-stress behavior are examined, and the behavior of pore water pressure is studied. The experimental results indicate that the patterns of stress-strain relations are distinctly influenced by the initial shear stress in the cyclic single-direction shear tests. When the initial shear stress is large and no stress reversal occurs, the predominant deformation behavior is characterized by an accumulative effect. When the initial shear stress is zero and symmetrical cyclic stress occurs, the predominant deformation behavior is characterized by a cyclic effect. The pore water pressure fluctuates around the confining pressure with the increase of cycle number. It seems that the fluctuating amplitude increases with the increase of the cyclic stress. But a buildup of pore water pressure does not occur. The deformations of clay samples under the complex initial and the cyclic coupled stress conditions include the normal deviatoric deformation and horizontal shear deformation, the average deformation and cyclic deformation. A general strain failure criterion taking into account these deformations is recommended and is proved more stable and suitable compared to the strain failure criteria currently used.

  8. DYNAMIC EFFECTIVE SHEAR STRENGTH OF SATURATED SAND

    Institute of Scientific and Technical Information of China (English)

    邵生俊; 谢定义

    2002-01-01

    The dynamic effective shear strength of saturated sand under cyclic loading is discussed in this paper. The discussion includes the transient time dependency behaviors based on the analysis of the results obtained in conventional cyclic triaxial tests and cyclic torsional shear triaxial tests. It has been found that the dynamic effective shear strength is composed of effective frictional resistance and viscous resistance, which are characterized by the strain rate dependent feature of strength magnitude, the coupling of consolidation stress with cyclic stress and the dependency of time needed to make the soil strength suffciently mobilized, and can also be expressed by the extended Mohr-Coulomb's law. The two strength parameters of the dynamic effective internal frictional angle φd and the dynamic viscosity coefficient η are determined. The former is unvaried for different number of cyclic loading, dynamic stress form and consolidation stress ratio. And the later is unvaried for the different dynamic shear strain rate γt developed during the sand liquefaction, but increases with the increase of initial density of sand. The generalization of dynamic effective stress strength criterion in the 3-dimensional effective stress space is studied in detail for the purpose of its practical use.

  9. Partly saturated polyacene structures: a theoretical study.

    Science.gov (United States)

    El Khatib, Muammar; Evangelisti, Stefano; Leininger, Thierry; Bendazzoli, Gian Luigi

    2014-07-01

    Planar molecular edifices obtained by joining polyacene fragments (polyacene stripes) are investigated at tight-binding (i.e., with a Hückel Hamiltonian) and ab initio level. For this kind of system, it is known that the presence of 60-degree angles between two stripes of the polyacene molecular skeleton induces the formation of singly occupied molecular orbitals, whose combination gives rise to quasi-degenerate electronic states. In particular, two types of convex polygons having a unique side length (rhombuses and triangles) are considered in this work. It is shown that the saturation via hydrogen atoms of the apical carbons located on outer borders of the 60-degree angles increases the number of quasi-degenerate orbitals, and hence the maximal multiplicity of the low-lying states of the system. Our tight-binding and ab initio (CAS-CI, NEVPT2) calculations indicate that the spin multiplicity of these molecular structures is in systematical accord with the Ovchinnikov rule.

  10. SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION

    Energy Technology Data Exchange (ETDEWEB)

    B.W. ARNOLD

    2004-10-27

    The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ.

  11. Saturated fat, carbohydrates and cardiovascular disease.

    Science.gov (United States)

    Kuipers, R S; de Graaf, D J; Luxwolda, M F; Muskiet, M H A; Dijck-Brouwer, D A J; Muskiet, F A J

    2011-09-01

    The dietary intake of saturated fatty acids (SAFA) is associated with a modest increase in serum total cholesterol, but not with cardiovascular disease (CVD). Replacing dietary SAFA with carbohydrates (CHO), notably those with a high glycaemic index, is associated with an increase in CVD risk in observational cohorts, while replacing SAFA with polyunsaturated fatty acids (PUFA) is associated with reduced CVD risk. However, replacing a combination of SAFA and trans-fatty acids with n-6 PUFA (notably linoleic acid) in controlled trials showed no indication of benefit and a signal toward increased coronary heart disease risk, suggesting that n-3 PUFA may be responsible for the protective association between total PUFA and CVD. High CHO intakes stimulate hepatic SAFA synthesis and conservation of dietary SAFA . Hepatic de novo lipogenesis from CHO is also stimulated during eucaloric dietary substitution of SAFA by CHO with high glycaemic index in normo-insulinaemic subjects and during hypocaloric high-CHO/low-fat diets in subjects with the metabolic syndrome. The accumulation of SAFA stimulates chronic systemic low-grade inflammation through its mimicking of bacterial lipopolysaccharides and÷or the induction of other pro-inflammatory stimuli. The resulting systemic low-grade inflammation promotes insulin resistance, reallocation of energy-rich substrates and atherogenic dyslipidaemia that concertedly give rise to increased CVD risk. We conclude that avoidance of SAFA accumulation by reducing the intake of CHO with high glycaemic index is more effective in the prevention of CVD than reducing SAFA intake per se.

  12. Heat Saturation Time of Solid Spherical Regenerator of HTAC

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In order to control the heat saturation time, the temperature field of the regenerators of high temperature air combustion (HTAC) technology after reheating furnace was studied. A one-dimensional unsteady mathematical model was established and discretized through finite difference method. The relationship between the heat saturation time and some factors was determined through the calculation of a program developed by language C. The heat saturation time decreases with the increase of heat convection coefficient, however, the increase of heat capacity,density and radius of regenerator all increase the heat saturation time approximately linearly.

  13. Chemical Emergencies

    Science.gov (United States)

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  14. A Laboratory Exercise Using a Physical Model for Demonstrating Countercurrent Heat Exchange

    Science.gov (United States)

    Loudon, Catherine; Davis-Berg, Elizabeth C.; Botz, Jason T.

    2012-01-01

    A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of…

  15. Observation of Multibubble Sonoluminescence from Water Saturated with Various Gases during Ultrasonic Atomization

    Science.gov (United States)

    Harada, Hisashi; Iwata, Naohiro; Shiratori, Keisuke

    2009-07-01

    Multibubble sonoluminescence (MBSL) from water saturated with various atmospheric gases was observed using an ultrasonic atomizer (2.4 MHz). The majority of sonoluminescence (SL) in the system did not originate from capillary waves but from acoustic cavitation. The dependence of MBSL intensity on the type of dissolved gas was confirmed. Atomization occurred similarly in all cases. The intensities for the dissolved gases were in the following order: Ar > Air > O2 > N2 ≫He, H2, CO2. The intensity for water saturated with air is higher than those for the O2- and N2-saturated solutions. To examine the effect of gas mixing, MBSL was measured for various ratios of O2 to N2. The maximum intensity was obtained at 40% O2/60% N2. In the regions above and below this ratio, the intensity decreased gradually. To explain this result, the possibilities of Ar rectification and chemical reactions between O2 and N2 gases were also discussed. After examination, it could not be confirmed that Ar rectification occurred. Chemical reactions of O2 with N2 proceed inside the cavitation bubble.

  16. Roles of Na+/H+ exchange in regulation of p38 mitogen-activated protein kinase activity and cell death after chemical anoxia in NIH3T3 fibroblasts

    DEFF Research Database (Denmark)

    Rentsch, Maria L; Ossum, Carlo G; Hoffmann, Else K;

    2007-01-01

    , p38 mitogen-activated protein kinase (MAPK), ERK1/2, p53, and Akt activity, and cell death, after chemical anoxia in NIH3T3 fibroblasts. The NHE1 inhibitor 5'-(N-ethyl-N-isopropyl) amiloride (EIPA) (5 muM), as well as removal of extracellular Na(+) [replaced by N-methyl-D: -glucamine (NMDG......) and extracellular signal-regulated kinase (ERK) (PD98059). In contrast, chemical anoxia activated p38 MAPK in an NHE-dependent manner, while ERK1/2 activity was unaffected. Anoxia-induced cell death was caspase-3-independent, mildly attenuated by EIPA, potently exacerbated by SB203580, and unaffected by PD98059...

  17. Anion exchange membrane

    Science.gov (United States)

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  18. Heat exchanger design handbook

    CERN Document Server

    Thulukkanam, Kuppan

    2013-01-01

    Completely revised and updated to reflect current advances in heat exchanger technology, Heat Exchanger Design Handbook, Second Edition includes enhanced figures and thermal effectiveness charts, tables, new chapter, and additional topics--all while keeping the qualities that made the first edition a centerpiece of information for practicing engineers, research, engineers, academicians, designers, and manufacturers involved in heat exchange between two or more fluids.See What's New in the Second Edition: Updated information on pressure vessel codes, manufacturer's association standards A new c

  19. Exchange Rate in Focus

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    China announced the reform of its decade-old RMB exchange rate regime last July, linking the RMB to a basket of currencies rather than the U.S. dollar alone, and allowing the RMB to appreciate 2 percent against the U.S. currency. Since then, different viewpoints on the new regime have been voiced. The People's Bank of China, the central bank, said in a statement in late March that it would further improve the system, broadening the foreign exchange market, increasing the flexibility of the RMB exchange r...

  20. Void fraction prediction in saturated flow boiling

    Energy Technology Data Exchange (ETDEWEB)

    Francisco J Collado [Dpto de Ingenieria Mecanica-Motores Termicos, CPS-B, Universidad de Zaragoza, Maria de Luna 50018-Zaragoza (Spain)

    2005-07-01

    Full text of publication follows: An essential element in thermal-hydraulics is the accurate prediction of the vapor void fraction, or fraction of the flow cross-sectional area occupied by steam. Recently, the author has suggested to calculate void fraction working exclusively with thermodynamic properties. It is well known that the usual 'flow' quality, merely a mass flow rate ratio, is not at all a thermodynamic property because its expression in function of thermodynamic properties includes the slip ratio, which is a parameter of the process not a function of state. By the other hand, in the classic and well known expression of the void fraction - in function of the true mass fraction of vapor (also called 'static' quality), and the vapor and liquid densities - does not appear the slip ratio. Of course, this would suggest a direct procedure for calculating the void fraction, provided we had an accurate value of the true mass fraction of vapor, clearly from the heat balance. However the classic heat balance is usually stated in function of the 'flow' quality, what sounds really contradictory because this parameter, as we have noted above, is not at all a thermodynamic property. Then we should check against real data the actual relationship between the thermodynamic properties and the applied heat. For saturated flow boiling just from the inlet of the heated tube, and not having into account the kinetic and potential terms, the uniform applied heat per unit mass of inlet water and per unit length (in short, specific linear heat) should be closely related to a (constant) slope of the mixture enthalpy. In this work, we have checked the relation between the specific linear heat and the thermodynamic enthalpy of the liquid-vapor mixture using the actual mass fraction. This true mass fraction is calculated using the accurate measurements of the outlet void fraction taken during the Cambridge project by Knights and Thom in the sixties for

  1. Modifications of Oxygen Saturation During Transesophageal Echocardiography.

    Science.gov (United States)

    Macor, Franco; Zottarel, Gabriella; Antonini-Canterin, Francesco; Mimo, Renata; Pavan, Daniela; Cervesato, Eugenio; Nicolosi, Gianluigi; Zanuttini, Domenico

    1997-05-01

    The present study was designed: (1) to establish the effects of transesophageal echocardiography (TEE) on arterial oxygen saturation (SAO(2)%); (2) to verify the possible clinical consequences of this phenomenon; and (3) to study the possibility of predicting modifications of SAO(2)% by clinical or hemodynamic variables or by specific factors related to the TEE procedure. We prospectively studied 116 unselected patients, aged 61 +/- 12 years, who underwent diagnostic TEE for various clinical indications. Thirty-seven patients had mitral valve disease, 19 aortic valve disease, 14 combined mitroaortic disease, 8 congenital heart disease, and 38 other cardiovascular diseases. Eight patients were affected by chronic obstructive pulmonary disease. Ninety-seven patients were sedated by 4 +/- 2 mg of diazepam IV SAO(2)% (5-min average) (Ohmeda Biox 3700 pulse oxymeter finger probe), heart rate (HR), and blood pressure (BP) were considered during baseline transthoracic examination, after pharmacological sedation but before the introduction of the probe, and finally during TEE. Neither clinical complications nor major arrhythmias were observed. Baseline SAO(2)%, HR and BP were, respectively, 93.6 +/- 3.3%, 76 +/- 14 beats/min, and 129 +/- 20/75 +/- 10 mmHg. Pharmacological sedation did not modify SAO(2)%, HR, and BP (P > 0.1). During TEE a small but significant reduction in SAO(2)% by an average of 1.2 +/- 3.2% was observed (P 0.1 for both systolic and diastolic). The changes of SAO(2)% and HR were not interrelated and were not related to the duration of the procedure and to any of the clinical and hemodynamic variables taken into consideration. TEE can induce a small but significant drop in SAO(2)% and a small increase in HR even without any clinical relevance. No clinical or hemodynamic variable or specific factors related to the TEE procedure were related to these changes.

  2. Saturation-state sensitivity of marine bivalve larvae to ocean acidification

    Science.gov (United States)

    Waldbusser, George G.; Hales, Burke; Langdon, Chris J.; Haley, Brian A.; Schrader, Paul; Brunner, Elizabeth L.; Gray, Matthew W.; Miller, Cale A.; Gimenez, Iria

    2015-03-01

    Ocean acidification results in co-varying inorganic carbon system variables. Of these, an explicit focus on pH and organismal acid-base regulation has failed to distinguish the mechanism of failure in highly sensitive bivalve larvae. With unique chemical manipulations of seawater we show definitively that larval shell development and growth are dependent on seawater saturation state, and not on carbon dioxide partial pressure or pH. Although other physiological processes are affected by pH, mineral saturation state thresholds will be crossed decades to centuries ahead of pH thresholds owing to nonlinear changes in the carbonate system variables as carbon dioxide is added. Our findings were repeatable for two species of bivalve larvae could resolve discrepancies in experimental results, are consistent with a previous model of ocean acidification impacts due to rapid calcification in bivalve larvae, and suggest a fundamental ocean acidification bottleneck at early life-history for some marine keystone species.

  3. Calculation Method to Determine the Group Composition of Vacuum Distillate with High Content of Saturated Hydrocarbons

    Directory of Open Access Journals (Sweden)

    Nazarova Galina

    2016-01-01

    Full Text Available Calculation method to determine the group composition of the heavy fraction of vacuum distillate with high content of saturated hydrocarbons, obtained by vacuum distillation of the residue from the West Siberian oil with subsequent hydrotreating, are given in this research. The method is built on the basis of calculation the physico-chemical characteristics and the group composition of vacuum distillate according to the fractional composition and density considering with high content of saturated hydrocarbons in the fraction. Calculation method allows to determine the content of paraffinic, naphthenic, aromatic hydrocarbons and the resins in vacuum distillate with high accuracy and can be used in refineries for rapid determination of the group composition of vacuum distillate.

  4. Understanding the structure and electronic properties of N-doped graphene nanoribbons upon hydrogen saturation

    Indian Academy of Sciences (India)

    Michael Mananghaya

    2014-11-01

    Structures and electronic properties of zigzag graphene nanoribbon (ZGNR) with pyridine (3NVZGNR) functionalized by Scandium (Sc) at the edge were studied through quantum chemical calculations in the formalism of density-functional theory (DFT). Pyridine-like nitrogen defects is very crucial for enhancing the Sc atom binding to the defects and is thermodynamically favoured. During Sc decoration of ZGNR there is a shift from 0.35 eV small gap semiconductor regime to that of a metal which can be used for band gap tuning by controlled saturation of Sc. ZGNR decorated with Sc can attract H2. Upon saturation of multiple H2 in quasi-molecular fashion, the metallic character is converted to semiconductors of small gap of 0.10 eV, which are predicted to be interesting materials not only for hydrogen storage but also for their band gap engineered properties.

  5. Exchange between a river and groundwater, assessed with hydrochemical data

    Directory of Open Access Journals (Sweden)

    E. Hoehn

    2011-03-01

    Full Text Available We describe the chemical composition of groundwater from an alluvial granular aquifer in a valley fill flood plain (River Thur Valley. The river flows along this valley and is mostly downwelling on its way, indirectly through an unsaturated zone in the upstream part, and directly through the water-saturated bed in the downstream part. River Thur has been channelized with barriers for more than a century. In 1992, the authorities started to restore a section of River Thur with riverbed enlargements. The land use in the flood plain and the seasonal and climatic conditions (e.g., hot dry summer 2003 result in alterations of the natural geochemical composition of the river water. This groundwater is partly to mainly recharged by bank filtration. Several wells exist near the river that draw groundwater for drinking. In some of these wells, the groundwater has a very short residence time in the subsurface of days to weeks. Bed enlargements and other operations for an enhancement of the exchange of water between the river and groundwater increase the contamination risk of the nearby wells. During bank filtration, the groundwater changes gradually its composition, with increasing distance from the river and with depth in the aquifer. From today's changes of the water quality during riverbank filtration, we tried to extrapolate to the groundwater quality that may arise from future river restorations. Today the groundwater body consists of a mixture of groundwater from the seepage of precipitation and from riverbank filtration. The main difference between river water and groundwater results from the microbial activity in riverbed and bank materials. This activity leads to a consumption of O2 and to a higher partial pressure of CO2 in the groundwater. Criteria for the distinction of different groundwater compositions are the distance of a well from the river and the subsurface residence time of the groundwater to reach this well.

  6. Data Exchange Inventory System (DEXI)

    Data.gov (United States)

    Social Security Administration — Enterprise tool used to identify data exchanges occurring between SSA and our trading partners. DEXI contains information on both incoming and outgoing exchanges and...

  7. Gain characteristics of a saturated fiber optic parametric amplifier

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Lorenzen, Michael Rodas; Noordegraaf, Danny

    2008-01-01

    In this work we discuss saturation performance of a fiber optic parametric amplifier. A simple numerical model is described and applied to specific cases. A system experiment using a saturated amplifier illustrates a 4 dB improvement in required signal to noise ratio for a fixed bit error ratio....

  8. Renal vein oxygen saturation in renal artery stenosis

    DEFF Research Database (Denmark)

    Nielsen, K; Rehling, M; Henriksen, Jens Henrik Sahl

    1992-01-01

    Renal vein oxygen-saturation was measured in 56 patients with arterial hypertension and unilateral stenosis or occlusion of the renal artery. Oxygen-saturation in blood from the ischaemic kidney (84.4%, range 73-93%) was significantly higher than that from the 'normal' contralateral kidney (81...

  9. Serum albumin--a non-saturable carrier

    DEFF Research Database (Denmark)

    Brodersen, R; Honoré, B; Larsen, F G

    1984-01-01

    The shape of binding isotherms for sixteen ligands to human serum albumin showed no signs of approaching saturation at high ligand concentrations. It is suggested that ligand binding to serum albumin is essentially different from saturable binding of substrates to enzymes, of oxygen to haemoglobi...

  10. Polar spots and stellar spindown: Is dynamo saturation needed?

    NARCIS (Netherlands)

    Solanki, S. K.; Motamen, S.; Keppens, R.

    1997-01-01

    Dynamo saturation is often invoked when calculating the rotational evolution of cool stars. At rapid rotation rates a saturated dynamo reduces the angular momentum carried away by the stellar wind. This, in turn, may explain the high rotation rates present in the distribution of rotation periods in

  11. Polar spots and stellar spindown: is dynamo saturation needed?

    NARCIS (Netherlands)

    Solanki, S. K.; Motamen, S.; Keppens, R.

    1997-01-01

    Dynamo saturation is often invoked when calculating the rotational evolution of cool stars. At rapid rotation rates a saturated dynamo reduces the angular momentum carried away by the stellar wind. This, in turn, may explain the high rotation rates present in the distribution of rotation periods in

  12. Stability and stabilization of linear systems with saturating actuators

    CERN Document Server

    Tarbouriech, Sophie; Gomes da Silva Jr, João Manoel; Queinnec, Isabelle

    2011-01-01

    Gives the reader an in-depth understanding of the phenomena caused by the more-or-less ubiquitous problem of actuator saturation. Proposes methods and algorithms designed to avoid, manage or overcome the effects of actuator saturation. Uses a state-space approach to ensure local and global stability of the systems considered. Compilation of fifteen years' worth of research results.

  13. Quantitative 1D saturation profiles on chalk by NMR

    DEFF Research Database (Denmark)

    Olsen, Dan; Topp, Simon; Stensgaard, Anders;

    1996-01-01

    Quantitative one-dimensional saturation profiles showing the distribution of water and oil in chalk core samples are calculated from NMR measurements utilizing a 1D CSI spectroscopy pulse sequence. Saturation profiles may be acquired under conditions of fluid flow through the sample. Results reveal...

  14. Saturation effects in QCD from linear transport equation

    OpenAIRE

    Kutak, Krzysztof

    2010-01-01

    We show that the GBW saturation model provides an exact solution to the one-dimensional linear transport equation. We also show that it is motivated by the BK equation considered in the saturated regime when the diffusion and the splitting term in the diffusive approximation are balanced by the nonlinear term.

  15. Emittance exchange results

    Energy Technology Data Exchange (ETDEWEB)

    Fliller, R.P., III; /Brookhaven; Koeth, T.; /Rutgers U., Piscataway

    2009-09-01

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  16. Emittance Exchange Results

    Energy Technology Data Exchange (ETDEWEB)

    Fliller III,R.; Koeth, T.

    2009-05-04

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  17. Exchange Risk Management Policy

    CERN Document Server

    2005-01-01

    At the Finance Committee of March 2005, following a comment by the CERN Audit Committee, the Chairman invited the Management to prepare a document on exchange risk management policy. The Finance Committee is invited to take note of this document.

  18. NASA Earth Exchange (NEX)

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA Earth Exchange (NEX) represents a new platform for the Earth science community that provides a mechanism for scientific collaboration and knowledge sharing....

  19. HUD Exchange Grantee Database

    Data.gov (United States)

    Department of Housing and Urban Development — The About Grantees section of the HUD Exchange brings up contact information, reports, award, jurisdiction, and location data for organizations that receive HUD...

  20. Microplate Heat Exchanger Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a microplate heat exchanger for cryogenic cooling systems used for continuous flow distributed cooling systems, large focal plane arrays, multiple cooling...

  1. Surface exchange kinetics and chemical diffusivities of BaZr{sub 0.2}Ce{sub 0.65}Y{sub 0.15}O{sub 3−δ} by electrical conductivity relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dae-Kwang; Jeon, Sang-Yun; Singh, Bhupendra [Ionics Lab, School of Materials Science and Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwang-Ju 500-757 (Korea, Republic of); Park, Jun-Young [Department of Advanced Materials Engineering, Sejong University, Seoul 143-747 (Korea, Republic of); Song, Sun-Ju, E-mail: song@chonnam.ac.kr [Ionics Lab, School of Materials Science and Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwang-Ju 500-757 (Korea, Republic of)

    2014-10-15

    Highlights: • Electrical conductivity relaxation in BaCe{sub 0.65}Zr{sub 0.2}Y{sub 0.15}O{sub 3−δ} was monitored. • Monotonic relaxation behavior was observed during oxidation/reduction. • Nonmonotonic twofold relaxation behavior was observed during hydration/dehydration. • Surface exchange coefficients and diffusivities of O and H were calculated. - Abstract: Perovskite-type oxide BaCe{sub 0.65}Zr{sub 0.2}Y{sub 0.15}O{sub 3−δ} (BCZY2015) was synthesized by a solid state reaction method. BCZY2015 samples were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The time dependent variation in electrical conductivity of BCZY2015 was monitored during the oxidation/reduction in oxygen partial pressure (pO{sub 2}) range of −2.28 ⩽ log (pO{sub 2}/atm) ⩽ −0.68 at a fixed water vapor pressure (pH{sub 2}O), and during the hydration/dehydration in −3.15 ⩽ log (pH{sub 2}O/atm) ⩽ −2.35 range in air. The electrical conductivity showed a monotonic relaxation behavior by the ambipolar diffusion of V{sub o}{sup ··} and OH{sub o}{sup ·} during the oxidation/reduction and the relaxation process was governed by the diffusivity of oxygen (D-tilde{sub vO}). On the other hand, during the hydration/dehydration process, a non-monotonic twofold relaxation behavior was observed due to the decoupled diffusion of H and O components with the mediation of holes, and the conductivity relaxation process was governed by the diffusivities of both H (D-tilde{sub iH}) and O (D-tlde{sub vH}). The values of surface exchange coefficients and diffusivities of oxygen and hydrogen were calculated from Fick’s second law by the nonlinear least squares fitting of the conductivity data, as proposed by Yoo et al. (2008)

  2. Compact, super heat exchanger

    Science.gov (United States)

    Fortini, A.; Kazaroff, J. M.

    1980-01-01

    Heat exchanger uses porous media to enhance heat transfer through walls of cooling channels, thereby lowering wall temperature. Porous media within cooling channel increases internal surface area from which heat can be transferred to coolant. Comparison data shows wall has lower temperature and coolant has higher temperature when porous medium is used within heat exchanger. Media can be sintered powedered metal, metal fibers, woven wire layers, or any porous metal having desired permeability and porosity.

  3. Physico-chemical characterization of bentonite and its application for Mn2+ removal from water

    Directory of Open Access Journals (Sweden)

    Ranđelović Marjan S.

    2011-01-01

    Full Text Available Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface.

  4. Input saturation in nonlinear multivariable processes resolved by nonlinear decoupling

    Directory of Open Access Journals (Sweden)

    Jens G. Balchen

    1995-04-01

    Full Text Available A new method is presented for the resolution of the problem of input saturation in nonlinear multivariable process control by means of elementary nonlinear decoupling (END. Input saturation can have serious consequences particularly in multivariable control because it may lead to very undesirable system behaviour and quite often system instability. Many authors have searched for systematic techniques for designing multivariable control systems in which saturation may occur in any of the control variables (inputs, manipulated variables. No generally accepted method seems to have been presented so far which gives a solution in closed form. The method of elementary nonlinear decoupling (END can be applied directly to the case of saturation control variables by deriving as many control strategies as there are combinations of saturating control variables. The method is demonstrated by the multivariable control of a simulated Fluidized Catalytic Cracker (FCC with very convincing results.

  5. Segmentation and intensity estimation for microarray images with saturated pixels

    Directory of Open Access Journals (Sweden)

    Yang Yan

    2011-11-01

    Full Text Available Abstract Background Microarray image analysis processes scanned digital images of hybridized arrays to produce the input spot-level data for downstream analysis, so it can have a potentially large impact on those and subsequent analysis. Signal saturation is an optical effect that occurs when some pixel values for highly expressed genes or peptides exceed the upper detection threshold of the scanner software (216 - 1 = 65, 535 for 16-bit images. In practice, spots with a sizable number of saturated pixels are often flagged and discarded. Alternatively, the saturated values are used without adjustments for estimating spot intensities. The resulting expression data tend to be biased downwards and can distort high-level analysis that relies on these data. Hence, it is crucial to effectively correct for signal saturation. Results We developed a flexible mixture model-based segmentation and spot intensity estimation procedure that accounts for saturated pixels by incorporating a censored component in the mixture model. As demonstrated with biological data and simulation, our method extends the dynamic range of expression data beyond the saturation threshold and is effective in correcting saturation-induced bias when the lost information is not tremendous. We further illustrate the impact of image processing on downstream classification, showing that the proposed method can increase diagnostic accuracy using data from a lymphoma cancer diagnosis study. Conclusions The presented method adjusts for signal saturation at the segmentation stage that identifies a pixel as part of the foreground, background or other. The cluster membership of a pixel can be altered versus treating saturated values as truly observed. Thus, the resulting spot intensity estimates may be more accurate than those obtained from existing methods that correct for saturation based on already segmented data. As a model-based segmentation method, our procedure is able to identify inner

  6. Exact exchange with non-orthogonal generalized Wannier functions

    Science.gov (United States)

    Mountjoy, Jeff; Todd, Michelle; Mosey, Nicholas J.

    2017-03-01

    The evaluation of exact exchange (EXX) is an important component of quantum chemical calculations performed with ab initio and hybrid density functional methods. While evaluating exact exchange is routine in molecular quantum chemical calculations performed with localized basis sets, the non-local nature of the exchange operator presents a major impediment to the efficient use of exact exchange in calculations that employ planewave basis sets. Non-orthogonal generalized Wannier functions (NGWFs) corresponding to planewave expansions of localized basis functions are an alternative form of basis set that can be used in quantum chemical calculations. The periodic nature of these functions renders them suitable for calculations of periodic systems, while the contraction of sets of planewaves into individual basis functions reduces the number of variational parameters, permitting the construction and direct diagonalization of the Fock matrix. The present study examines how NGWFs corresponding to Fourier series representations of conventional atom-centered basis sets can be used to evaluate exact exchange in periodic systems. Specifically, an approach for constructing the exchange operator with NGWFs is presented and used to perform Hartree-Fock calculations with a series of molecules in periodically repeated simulation cells. The results demonstrate that the NGWF approach is significantly faster than the EXX method, which is a standard approach for evaluating exact exchange in periodic systems.

  7. Temperature buffer test. Hydro-mechanical and chemical/ mineralogical characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias; Olsson, Siv; Dueck, Ann; Nilsson, Ulf; Karnland, Ola [Clay Technology AB, Lund (Sweden); Kiviranta, Leena; Kumpulainen, Sirpa [BandTech Oy, Helsinki (Finland); Linden, Johan [Aabo Akademi, Aabo (Finland)

    2012-01-15

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modeling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aspo HRL. It was installed during the spring of 2003. Two steel heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by rings of compacted Wyoming bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the hydro-mechanical and chemical/mineralogical characterization program which was launched subsequent to the dismantling operation. The main goal has been to investigate if any significant differences could be observed between material from the field experiment and the reference material. The field samples were mainly taken from Ring 4 (located at the mid-section around the lower heater), in which the temperature in the innermost part reached 155 deg C. The following hydro-mechanical properties have been determined for the material (test technique within brackets): hydraulic conductivity (swelling pressure device), swelling pressure (swelling pressure device), unconfined compression strength (mechanical press), shear strength (triaxial cell) and retention properties (jar method). The following chemical/mineralogical properties (methods within brackets) were determined: anion analysis of water leachates (IC), chemical composition (ICP/AES+MS, EGA), cation exchange capacity (CEC, Cu-trien method) and exchangeable cations (exchange with NH4, ICPAES), mineralogical composition (XRD and FTIR), element distribution and microstructure (SEM and

  8. Elastoplastic model for unsaturated, quasi-saturated and fully saturated fine soils

    Directory of Open Access Journals (Sweden)

    Lai Ba Tien

    2016-01-01

    Full Text Available In unsaturated soils, the gaseous phase is commonly assumed to be continuous. This assumption is no more valid at high saturation ratio. In that case, air bubbles and pockets can be trapped in the porous network by the liquid phase and the gas phase becomes discontinuous. This trapped air reduces the apparent compressibility of the pore fluid and affect the mechanical behavior of the soil. Although it is trapped in the pores, its dissolution can take place. Dissolved air can migrate through the pore space, either by following the flow of the fluid or by diffusion. In this context, this paper present a hydro mechanical model that separately considers the kinematics and the mechanical behavior of each fluid species (eg liquid water, dissolved air, gaseous air and the solid matrix. This new model was implemented in a C++ code. Some numerical simulations are performed to demonstrate the ability of this model to reproduce a continuous transition of unsaturated to saturated states.

  9. Simulation of Partially Saturated - Saturated Flow in the Caspar Creek E-Road Groundwater System

    Science.gov (United States)

    Fisher, J.; Fisher, J.

    2001-12-01

    Over the past decade, the U.S. Forest Service has monitored the subsurface hillslope flow of the E-Road swale. The swale is located in the Caspar Creek watershed near Fort Bragg, California. In hydrologic year 1990 a logging road was built across the middle section of the hillslope followed by a total clearcut of the area during the following year. Development of the logging road has resulted in a large build up of subsurface waters upslope of the road. The increase in pore pressures behind the road is of major concern for slope stability and road failure. A conceptual model is developed to describe the movement of water within the E-Road groundwater system. The two-dimensional SUTRA model is used to describe both saturated and partially saturated flow within the system. SUTRA utilizes a finite element and integrated finite difference method to approximate the governing equation for flow. The model appears to reproduce the uniquely different frequency responses within the E-Road groundwater system. A comparison of simulated and historical piezometric responses demonstrates the model's inability to reproduce historical drainage rates. The low rates of simulated drainage are attributed to the absence of pipeflow within the model. Finally, road consolidation is associated with increased water pressures beneath the road bed.

  10. Radiochemical separation of gold by amalgam exchange

    Science.gov (United States)

    Ruch, R.R.

    1970-01-01

    A rapid and simple method for the radiochemical separation of gold after neutron activation. The technique is based on treatment with a dilute indium-gold amalgam, both chemical reduction and isotopic exchange being involved. The counting efficiency for 198Au in small volumes of the amalgam is good. Few interferences occur and the method is applicable to clays, rocks, salts and metals. The possibility of determining silver, platinum and palladium by a similar method is mentioned. ?? 1970.

  11. 换热器对化学吸附式制冷系统的影响%Study of the Effects of Heat Exchanger on the Chemical Adsorption Refrigeration System

    Institute of Scientific and Technical Information of China (English)

    彭庆龙; 齐朝晖

    2014-01-01

    The dynamic characteristics of the CaCl2-NH3 chemical adsorption refrigeration system driven by engine exhausted gas was studied. A thermal dynamic model is established to simulate the performanceofevaporation temperature, condensation temperature, evaporator and condenser outlet temperature in the running system and the article summarizes the varieties of system performance parameters in the different evaporation temperature and condensation temperature.Sothis result can provide a reference for the further research on the matching and optimization inthe chemical adsorption refrigeration system.%研究了内燃机尾气驱动的氯化钙-氨化学吸附式制冷系统的动态运行状况。通过建立热力学动态模型,仿真得到蒸发温度、冷凝温度、蒸发器与冷凝器出口温度在系统运行时的变化,并总结了在变蒸发温度或冷凝温度下系统性能参数的变化规律。结论可以为今后有关化学吸附式制冷系统各部件的匹配性和优化系统性能的进一步研究提供参考。

  12. Effect of Humic Acid on Soil Chemical and Physical Characteristics of Embankment

    Directory of Open Access Journals (Sweden)

    Ali Munawar

    2016-01-01

    Full Text Available The effectiveness of the treatment of pathogens disease in fish using chemicals is very limited because of the stress of toxic ions. A treatment of humic acid of 50-90 mg /L on a farmland has been able to reduce illness and death compared to a mixture of formaldehyde and blue-green methylene. Humic acid is suspected to be able to increase yield, through improved conditions and resistance to diseases, health, and cultural vitality, either by itself or combined with cation species toxic. Humic acid can balance the soil cation so that the soil pH reached 7-8, through a chelate of Al, Fe, Ca or exchanged with NH4, Na and K. Humic acids were extracted from compost plants with a weak base of 0.1 N NaOH and precipitated at pH 2. The concentration of AH 0- 400 ml was applied to three soil types with an area of 0.12 m2 and 15 cm thickness. The results showed that the application of 100-200 ml HA/0.12 m2 gave optimum yield in improving the physical-chemical characteristics of the soil embankment. Soil pH reached a value of 7-8, cation exchange to 60% saturated, and soil bulk density was reached in the range of 1.1- 0.97 g / cm3.This condition is suitable for fish or shrimp in the embankment.

  13. Characterization and nutrient release from silicate rocks and influence on chemical changes in soil

    Directory of Open Access Journals (Sweden)

    Douglas Ramos Guelfi Silva

    2012-06-01

    Full Text Available The expansion of Brazilian agriculture has led to a heavy dependence on imported fertilizers to ensure the supply of the growing food demand. This fact has contributed to a growing interest in alternative nutrient sources, such as ground silicate rocks. It is necessary, however, to know the potential of nutrient release and changes these materials can cause in soils. The purpose of this study was to characterize six silicate rocks and evaluate their effects on the chemical properties of treated soil, assessed by chemical extractants after greenhouse incubation. The experimental design consisted of completely randomized plots, in a 3 x 6 factorial scheme, with four replications. The factors were potassium levels (0-control: without silicate rock application; 200; 400; 600 kg ha-1 of K2O, supplied as six silicate rock types (breccia, biotite schist, ultramafic rock, phlogopite schist and two types of mining waste. The chemical, physical and mineralogical properties of the alternative rock fertilizers were characterized. Treatments were applied to a dystrophic Red-Yellow Oxisol (Ferralsol, which was incubated for 100 days, at 70 % (w/w moisture in 3.7 kg/pots. The soil was evaluated for pH; calcium and magnesium were extracted with KCl 1 mol L-1; potassium, phosphorus and sodium by Mehlich 1; nickel, copper and zinc with DTPA; and the saturation of the cation exchange capacity was calculated for aluminum, calcium, magnesium, potassium, and sodium, and overall base saturation. The alternative fertilizers affected soil chemical properties. Ultramafic rock and Chapada mining byproduct (CMB were the silicate rocks that most influenced soil pH, while the mining byproduct (MB led to high K levels. Zinc availability was highest in the treatments with mining byproduct and Cu in soil fertilized with Chapada and mining byproduct.

  14. Saturation Detection-Based Blocking Scheme for Transformer Differential Protection

    Directory of Open Access Journals (Sweden)

    Byung Eun Lee

    2014-07-01

    Full Text Available This paper describes a current differential relay for transformer protection that operates in conjunction with a core saturation detection-based blocking algorithm. The differential current for the magnetic inrush or over-excitation has a point of inflection at the start and end of each saturation period of the transformer core. At these instants, discontinuities arise in the first-difference function of the differential current. The second- and third-difference functions convert the points of inflection into pulses, the magnitudes of which are large enough to detect core saturation. The blocking signal is activated if the third-difference of the differential current is larger than the threshold and is maintained for one cycle. In addition, a method to discriminate between transformer saturation and current transformer (CT saturation is included. The performance of the proposed blocking scheme was compared with that of a conventional harmonic blocking method. The test results indicate that the proposed scheme successfully discriminates internal faults even with CT saturation from the magnetic inrush, over-excitation, and external faults with CT saturation, and can significantly reduce the operating time delay of the relay.

  15. Saturated fats: a perspective from lactation and milk composition.

    Science.gov (United States)

    German, J Bruce; Dillard, Cora J

    2010-10-01

    For recommendations of specific targets for the absolute amount of saturated fat intake, we need to know what dietary intake is most appropriate? Changing agricultural production and processing to lower the relative quantities of macronutrients requires years to accomplish. Changes can have unintended consequences on diets and the health of subsets of the population. Hence, what are the appropriate absolute amounts of saturated fat in our diets? Is the scientific evidence consistent with an optimal intake of zero? If not, is it also possible that a finite intake of saturated fats is beneficial to overall health, at least to a subset of the population? Conclusive evidence from prospective human trials is not available, hence other sources of information must be considered. One approach is to examine the evolution of lactation, and the composition of milks that developed through millennia of natural selective pressure and natural selection processes. Mammalian milks, including human milk, contain 50% of their total fatty acids as saturated fatty acids. The biochemical formation of a single double bond converting a saturated to a monounsaturated fatty acid is a pathway that exists in all eukaryotic organisms and is active within the mammary gland. In the face of selective pressure, mammary lipid synthesis in all mammals continues to release a significant content of saturated fatty acids into milk. Is it possible that evolution of the mammary gland reveals benefits to saturated fatty acids that current recommendations do not consider?

  16. On the propagation of a coupled saturation and pressure front

    Energy Technology Data Exchange (ETDEWEB)

    Vasco, D. W.

    2010-12-01

    Using an asymptotic technique, valid for a medium with smoothly varying heterogeneity, I derive an expression for the velocity of a propagating, coupled saturation and pressure front. Due to the nonlinearity of the governing equations, the velocity of the propagating front depends upon the magnitude of the saturation and pressure changes across the front in addition to the properties of the medium. Thus, the expression must be evaluated in conjunction with numerical reservoir simulation. The propagation of the two-phase front is governed by the background saturation distribution, the saturation-dependent component of the fluid mobility, the porosity, the permeability, the capillary pressure function, the medium compressibility, and the ratio of the slopes of the relative permeability curves. Numerical simulation of water injection into a porous layer saturated with a nonaqueous phase liquid indicates that two modes of propagation are important. The fastest mode of propagation is a pressure-dominated disturbance that travels through the saturated layer. This is followed, much later, by a coupled mode with a large saturation change. These two modes are also observed in a simulation using a heterogeneous porous layer. A comparison between the propagation times estimated from the results of the numerical simulation and predictions from the asymptotic expression indicates overall agreement.

  17. CO 2 adsorption in mono-, di- and trivalent cation-exchanged metal-organic frameworks: A molecular simulation study

    KAUST Repository

    Chen, Yifei

    2012-02-28

    A molecular simulation study is reported for CO 2 adsorption in rho zeolite-like metal-organic framework (rho-ZMOF) exchanged with a series of cations (Na +, K +, Rb +, Cs +, Mg 2+, Ca 2+, and Al 3+). The isosteric heat and Henry\\'s constant at infinite dilution increase monotonically with increasing charge-to-diameter ratio of cation (Cs + < Rb + < K + < Na + < Ca 2+ < Mg 2+ < Al 3+). At low pressures, cations act as preferential adsorption sites for CO 2 and the capacity follows the charge-to-diameter ratio. However, the free volume of framework becomes predominant with increasing pressure and Mg-rho-ZMOF appears to possess the highest saturation capacity. The equilibrium locations of cations are observed to shift slightly upon CO 2 adsorption. Furthermore, the adsorption selectivity of CO 2/H 2 mixture increases as Cs + < Rb + < K + < Na + < Ca 2+ < Mg 2+ ≈ Al 3+. At ambient conditions, the selectivity is in the range of 800-3000 and significantly higher than in other nanoporous materials. In the presence of 0.1% H 2O, the selectivity decreases drastically because of the competitive adsorption between H 2O and CO 2, and shows a similar value in all of the cation-exchanged rho-ZMOFs. This simulation study provides microscopic insight into the important role of cations in governing gas adsorption and separation, and suggests that the performance of ionic rho-ZMOF can be tailored by cations. © 2012 American Chemical Society.

  18. COOEE bitumen: chemical aging

    CERN Document Server

    Lemarchand, Claire A; Dyre, Jeppe C; Hansen, Jesper S

    2013-01-01

    We study chemical aging in "COOEE bitumen" using molecular dynamic simulations. The model bitumen is composed of four realistic molecule types: saturated hydrocarbon, resinous oil, resin, and asphaltene. The aging reaction is modelled by the chemical reaction: "2 resins $\\rightarrow$ 1 asphaltene". Molecular dynamic simulations of four bitumen compositions, obtained by a repeated application of the aging reaction, are performed. The stress autocorrelation function, the fluid structure, the rotational dynamics of the plane aromatic molecules, and the diffusivity of each molecule, are determined for the four different compositions. The aging reaction causes a significant dynamics slowdown, which is correlated to the aggregation of asphaltene molecules in larger and dynamically slower nanoaggregates. Finally, a detailed description of the role of each molecule types in the aggregation and aging processes is given.

  19. Exchanging Description Logic Knowledge Bases

    NARCIS (Netherlands)

    Arenas, M.; Botoeva, E.; Calvanese, D.; Ryzhikov, V.; Sherkhonov, E.

    2012-01-01

    In this paper, we study the problem of exchanging knowledge between a source and a target knowledge base (KB), connected through mappings. Differently from the traditional database exchange setting, which considers only the exchange of data, we are interested in exchanging implicit knowledge. As rep

  20. Transport and Retention of CdSe/ZnS Quantum Dots in Saturated Sand: Effects of Organic Ligands, pH and Ionic Strength

    Science.gov (United States)

    Li, Chunyan; Snee, Preston; Darnault, Christophe

    2016-04-01

    The presence of nanomaterials in soil, water, and air systems following their life cycle or accidents and their effects on the environment and public health are inevitable. Ability to forecast the public health and ecological impacts of these nanomaterials encountered in the environment is limited. Therefore, it is critical to be able to predict the fate and transport on nanomaterials in the environment, in particular the subsurface, in order to conduct risk assessments. To assess the transport and retention of nanomaterials in the subsurface environment, we selected quantum dots (QDs). QDs are metal and semiconductor based nanomaterials that are essential to nanoscience and nanotechnology. Understanding the parameters that effect the transport and retention of QDs in the soil water environment is critical. Natural organic ligands are commonly found in soils and impact the soil physico-chemical processes through multifaceted reactions with metal ions present in soil solution and ligand exchange reactions on soil surfaces. Therefore, ligands may modify the surface properties of QDs and effect their stability, transport and retention in the subsurface environment. In this research, size, surface charge, and stability of CdSe/ZnS QDs in water solutions are monitored in batch experiments. The influence of organic ligands (acetate, oxalate, and citrate) on the stability of QDs at different pHs (1.5, 3.5, 5, 7 and 9) and ionic strengths (0.05 and 0.1 M) conditions were examined. The stability and aggregation phenomena of QDs were studied using UV-vis and DLS methods. Parameters from batch studies were selected to establish chemical conditions to be used in transport experiments to produce breakthrough curves and retention profiles in order to characterize the fate and transport of QDs in saturated sand. These transport experiments are essential to understand the mobility and retention processes in porous media where QD interactions with surfaces of heterogeneous

  1. Hydrogen Isotope Exchange Properties of Porous Solids Containing Hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    HEUNG, LEUNGK.

    2004-08-18

    Porous solids such as activated alumina, silica and molecular sieves generally contain significant amounts of hydrogen atoms in the form of H2O or OH even at high temperature and low humidity environment. A significant amount of this hydrogen is available for reversible isotopic exchange. This exchange reaction is slow under normal conditions and does not render itself to practical applications. But if the exchange kinetics is improved this reaction has the potential to be used for tritium removal from gas streams or for hydrogen isotopic separation.The use of catalysts to improve the exchange kinetics between hydrogen isotope in the gas phase and that in the solid phase was investigated. Granules of alumina, silica and molecular sieve were coated with platinum or palladium as the catalyst. The granules were packed in a 2-cm diameter column for isotope exchange tests. Gas streams containing different concentrations of deuterium in nitrogen or argon were fed through the protium saturated column. Isotope concentration in column effluent was monitored to generate isotope break-through curves. The curves were analyzed to produce information on the kinetics and capacity of the material. The results showed that all materials tested provided some extent of isotope exchange but some were superior both in kinetics and capacity. This paper will present the test results.

  2. Hydrate morphology: Physical properties of sands with patchy hydrate saturation

    Science.gov (United States)

    Dai, S.; Santamarina, J.C.; Waite, William F.; Kneafsey, T.J.

    2012-01-01

    The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

  3. Retinal oxygen saturation evaluation by multi-spectral fundus imaging

    Science.gov (United States)

    Khoobehi, Bahram; Ning, Jinfeng; Puissegur, Elise; Bordeaux, Kimberly; Balasubramanian, Madhusudhanan; Beach, James

    2007-03-01

    Purpose: To develop a multi-spectral method to measure oxygen saturation of the retina in the human eye. Methods: Five Cynomolgus monkeys with normal eyes were anesthetized with intramuscular ketamine/xylazine and intravenous pentobarbital. Multi-spectral fundus imaging was performed in five monkeys with a commercial fundus camera equipped with a liquid crystal tuned filter in the illumination light path and a 16-bit digital camera. Recording parameters were controlled with software written specifically for the application. Seven images at successively longer oxygen-sensing wavelengths were recorded within 4 seconds. Individual images for each wavelength were captured in less than 100 msec of flash illumination. Slightly misaligned images of separate wavelengths due to slight eye motion were registered and corrected by translational and rotational image registration prior to analysis. Numerical values of relative oxygen saturation of retinal arteries and veins and the underlying tissue in between the artery/vein pairs were evaluated by an algorithm previously described, but which is now corrected for blood volume from averaged pixels (n > 1000). Color saturation maps were constructed by applying the algorithm at each image pixel using a Matlab script. Results: Both the numerical values of relative oxygen saturation and the saturation maps correspond to the physiological condition, that is, in a normal retina, the artery is more saturated than the tissue and the tissue is more saturated than the vein. With the multi-spectral fundus camera and proper registration of the multi-wavelength images, we were able to determine oxygen saturation in the primate retinal structures on a tolerable time scale which is applicable to human subjects. Conclusions: Seven wavelength multi-spectral imagery can be used to measure oxygen saturation in retinal artery, vein, and tissue (microcirculation). This technique is safe and can be used to monitor oxygen uptake in humans. This work

  4. Heat exchanger restart evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-02-28

    On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4kA was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summarized herein.

  5. Ion Exchange Technology Development in Support of the Urine Processor Assembly

    Science.gov (United States)

    Mitchell, Julie; Broyan, James; Pickering, Karen

    2013-01-01

    The urine processor assembly (UPA) on the International Space Station (ISS) recovers water from urine via a vacuum distillation process. The distillation occurs in a rotating distillation assembly (DA) where the urine is heated and subjected to sub-ambient pressure. As water is removed, the original organics, salts, and minerals in the urine become more concentrated and result in urine brine. Eventually, water removal will concentrate the urine brine to super saturation of individual constituents, and precipitation occurs. Under typical UPA DA operating conditions, calcium sulfate or gypsum is the first chemical to precipitate in substantial quantity. During preflight testing with ground urine, the UPA achieved 85% water recovery without precipitation. However, on ISS, it is possible that crewmember urine can be significantly more concentrated relative to urine from ground donors. As a result, gypsum precipitated in the DA when operating at water recovery rates at or near 85%, causing the failure and subsequent re14 NASA Tech Briefs, September 2013 placement of the DA. Later investigations have demonstrated that an excess of calcium and sulfate will cause precipitation at water recovery rates greater than 70%. The source of the excess calcium is likely physiological in nature, via crewmembers' bone loss, while the excess sulfate is primarily due to the sulfuric acid component of the urine pretreatment. To prevent gypsum precipitation in the UPA, the Precipitation Prevention Project (PPP) team has focused on removing the calcium ion from pretreated urine, using ion exchange resins as calcium removal agents. The selectivity and effectiveness of ion exchange resins are determined by such factors as the mobility of the liquid phase through the polymer matrix, the density of functional groups, type of functional groups bound to the matrix, and the chemical characteristics of the liquid phase (pH, oxidation potential, and ionic strength). Previous experience with ion

  6. The Reverse Saturation Absorption Property of Indanthrone and Its Derivatives

    Institute of Scientific and Technical Information of China (English)

    LIU Dajun; DUAN Qian; HE Xingquan; ZOU Ying

    2005-01-01

    The syntheses of three nonlinear reverse saturation absorption compounds-Indanthrone and its two derivatives are discussed. The properties of nonlinear reverse saturable absorption of the compounds were studied by using the Z- scanning technique, and the influences of its conjugated structure on the absorption threshold value and the absorbable light density were discussed based on the reverse saturation absorption principle. The results shows that when the structure' s conjugation property of Indanthrone and its derivatives becomes more powerful , its absorption threshold reduces, the light lowest transmittance increases.

  7. Prediction of saturated liquid enthalpy of refrigerant mixtures

    Institute of Scientific and Technical Information of China (English)

    CHEN ZeShao; CHEN JianXin; HU Peng

    2007-01-01

    New corresponding temperature and corresponding enthalpy of refrigerant mixtures were defined. The relationship between saturated liquid corresponding enthalpy and corresponding temperature of refrigerant mixtures accorded with that of pure components. The characteristic parameters of saturated liquid enthalpy difference of refrigerant mixtures were calculated by three methods according to the different application conditions. The generalized equation of saturated liquid enthalpy of refrigerant mixtures was presented. The calculated values were compared with the values in literature for five ternary and binary refrigerant mixtures, namely R404A, R407A, R407B, R32/R134a, and R410A. The overall average absolute deviation was less than 1.0%.

  8. An Elastoplastic Model for Partially Saturated Collapsible Rocks

    Science.gov (United States)

    Ma, Jianjun

    2016-02-01

    A unified elastoplastic model for describing the stress-strain behavior of partially saturated collapsible rocks is proposed. The elastic-plastic response due to loading and unloading is captured using bounding surface plasticity. The coupling effect of hydraulic and mechanical responses is addressed by applying the effective stress concept. Special attention is paid to the rock-fluid characteristic curve (RFCC), effective stress parameter, and suction hardening. A wide range of saturation degree is considered. The characteristics of mechanical behavior in partially saturated collapsible rocks are captured for all cases considered.

  9. Cross-correlations in Warsaw Stock Exchange

    CERN Document Server

    Rak, R; Drozdz, S; Oswiecimka, P

    2008-01-01

    We study the inter-stock correlations for the largest companies listed on Warsaw Stock Exchange and included in the WIG20 index. Our results from the correlation matrix analysis indicate that the Polish stock market can be well described by a one factor model. We also show that the stock-stock correlations tend to increase with the time scale of returns and they approach a saturation level for the time scales of at least 200 min, i.e. an order of magnitude longer than in the case of some developed markets. We also show that the strength of correlations among the stocks crucially depends on their capitalization. These results combined with our earlier findings together suggest that now the Polish stock market situates itself somewhere between an emerging market phase and a mature market phase.

  10. Analysis of the heavy oil production technology effectiveness using natural thermal convection with heat agent recirculation method in reservoirs with varying initial water saturation

    Science.gov (United States)

    Osnos, V. B.; Kuneevsky, V. V.; Larionov, V. M.; Saifullin, E. R.; Gainetdinov, A. V.; Vankov, Yu V.; Larionova, I. V.

    2017-01-01

    The method of natural thermal convection with heat agent recirculation (NTC HAR) in oil reservoirs is described. The analysis of the effectiveness of this method for oil reservoir heating with the values of water saturation from 0 to 0.5 units is conducted. As the test element Ashalchinskoye oil field is taken. CMG STARS software was used for calculations. Dynamics of cumulative production, recovery factor and specific energy consumption per 1 m3 of crude oil produced in the application of the heat exchanger with heat agent in cases of different initial water saturation are defined and presented as graphs.

  11. STRUCTURAL FEATURE AND EXCHANGE KINETICS OF CARBOXYLATED POLYPROPYLENE ION EXCHANGE RESIN

    Institute of Scientific and Technical Information of China (English)

    WU Chinyung; YANG Chaoshiung; YANG Chong

    1987-01-01

    The present article deals with the exchange process of bivalent metal ions, such as Zn2 +, Cd2 + and Hg2+, etc., taken up by non-crosslinked carboxylated polypropylene (CPP) resin. The control factor of the exchange rate deduced from the kinetic data is governed basically by the chemical reaction rather than the mass transfer effect particle diffusion and/or liquid film diffusion. In solution, all the graft chains in the outer shell ofa CPP resin could form a "quasi-macromolecular solution" domain. This opinion further demonstrates the structural pattern of CPP resin proposed in earlier paper[1].

  12. Polarization insensitive graphene saturable absorbers using etched fiber for highly stable ultrafast fiber lasers.

    Science.gov (United States)

    Lee, Hyub; Kwon, Won Sik; Kim, Jin Hwan; Kang, Daewon; Kim, Soohyun

    2015-08-24

    In this paper, we introduce a graphene-based saturable absorber (GSA) with high damage threshold employing symmetrical evanescent wave interaction for highly stable mode-locking of ultrafast fiber lasers. To enhance the evanescent wave interaction between the graphene layer and the propagating light, graphene flakes are mixed with polydimethylsiloxane (PDMS), and the graphene/PDMS composite is coated onto a chemically etched fiber. The GSA exhibits polarization insensitivity due to its symmetric cross-section, which enables stable operation against environmental disturbance such as stress, bending, and temperature variation. Finally, we demonstrate a fiber laser generating 216 fs pulses with an 80 dB signal-to-noise ratio.

  13. A simplified transfer function for estimating saturated hydraulic conductivity of porous drainage filters

    DEFF Research Database (Denmark)

    Canga, Eriona; Iversen, Bo Vangsø; Kjærgaard, Charlotte

    2013-01-01

    Knowledge of the saturated hydraulic conductivity (Ksat) of porous filters used in water treatment technologies is important for optimizing the retention of nutrients and pollutants. This parameter determines the hydraulic capacity, which together with the Chemical properties of the filter media......, bulk density, uniformity coefficient, particle density, and porosity of 46 porous media fractions. The fractions ranged in grain size from 0.5 to 20 mm and were obtained from seven commercial available coarse filter materials. A backward stepwise regression analysis was performed between Ksat and 10...

  14. Ion exchange phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Bourg, I.C.; Sposito, G.

    2011-05-01

    Ion exchange phenomena involve the population of readily exchangeable ions, the subset of adsorbed solutes that balance the intrinsic surface charge and can be readily replaced by major background electrolyte ions (Sposito, 2008). These phenomena have occupied a central place in soil chemistry research since Way (1850) first showed that potassium uptake by soils resulted in the release of an equal quantity of moles of charge of calcium and magnesium. Ion exchange phenomena are now routinely modeled in studies of soil formation (White et al., 2005), soil reclamation (Kopittke et al., 2006), soil fertilitization (Agbenin and Yakubu, 2006), colloidal dispersion/flocculation (Charlet and Tournassat, 2005), the mechanics of argillaceous media (Gajo and Loret, 2007), aquitard pore water chemistry (Tournassat et al., 2008), and groundwater (Timms and Hendry, 2007; McNab et al., 2009) and contaminant hydrology (Chatterjee et al., 2008; van Oploo et al., 2008; Serrano et al., 2009).

  15. Microgravity condensing heat exchanger

    Science.gov (United States)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

    2011-01-01

    A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

  16. Insertion of apoLp-III into a lipid monolayer is more favorable for saturated, more ordered, acyl-chains

    Energy Technology Data Exchange (ETDEWEB)

    Rathnayake, Sewwandi S. [Kent State Univ., Kent, OH (United States); Mirheydari, Mona [Kent State Univ., Kent, OH (United States); Schulte, Adam [Kent State Univ., Kent, OH (United States); Gillahan, James E. [Kent State Univ., Kent, OH (United States); Gentit, Taylor [Kent State Univ., Kent, OH (United States); Phillips, Ashley N. [Kent State Univ., Kent, OH (United States); Okonkwo, Rose K. [Kent State Univ., Kent, OH (United States); Burger, Koert N.J. [Utrecht Univ. (Netherlands); Mann, Elizabeth K. [Kent State Univ., Kent, OH (United States); Vaknin, David [Ames Lab., Ames, IA (United States); Bu, Wei [Ames Lab., Ames, IA (United States); Agra-Kooijman, Dena Mae [Kent State Univ., Kent, OH (United States); Kooijman, Edgar E. [Kent State Univ., Kent, OH (United States)

    2013-10-04

    Neutral lipid transport in mammals is complicated involving many types of apolipoprotein. The exchangeable apolipoproteins mediate the transfer of hydrophobic lipids between tissues and particles, and bind to cell surface receptors. Amphipathic a-helices form a common structural motif that facilitates their lipid binding and exchangeability. ApoLp-III, the only exchangeable apolipoprotein found in insects, is a model amphipathic a:helix bundle protein and its three dimensional structure and function mimics that of the mammalian proteins apoE and apoAI. Even the intracellular exchangeable lipid droplet protein TIP47/perilipin 3 contains an a-helix bundle domain with high structural similarity to that of apoE and apoLp-III. Here, we investigated the interaction of apoLp-III from Locusta migratoria with lipid monolayers. Consistent with earlier work we find that insertion of apoLp-III into fluid lipid monolayers is highest for diacylglycerol. We observe a preference for saturated and more highly ordered lipids, suggesting a new mode of interaction for amphipathic a-helix bundles. X-ray reflectivity shows that apoLp-III unfolds at a hydrophobic interface and flexible loops connecting the amphipathic cc-helices stay in solution. X-ray diffraction indicates that apoLp-III insertion into diacylglycerol monolayers induces additional ordering of saturated acyl-chains. These results thus shed important new insight into the protein-lipid interactions of a model exchangeable apolipoprotein with significant implications for its mammalian counterparts. (C) 2013 Elsevier B.V. All rights reserved.

  17. Tuning Exchange Anisotropy of Exchange-Biased System

    Institute of Scientific and Technical Information of China (English)

    XU Yan; HU Jing-Guo; R.L.Stamps

    2008-01-01

    Exchange anisotropy in FM/AFM bilayers has given a lot of static magnetization properties such as enhanced coercivity and magnetization loop shifts.These phenomena are primarily from the effective anisotropies intro-duced into a ferromagnet by exchange coupling with a strongly anisotropic antiferromagnet.These effective anisotropies can also be used to explain the dynamic consequences of exchange-biased bilayers.In this article,the dynamic con-sequences such as exchange-induced susceptibility,exchange-induced permeability,and the corresponding domain wall characteristics in the exchange-biased structures of ferromagnet/antiferromagnetl/antiferromagnet2 are studied.The results show that the second antiferromagnetic layer can largely affect the dynamic consequences of exchange-biased bilayers.Especially in the ease of critical temperature,the effects become more obvious.Practically,the exchange anisotropy of biased bilayer system can be tuned by exchange coupling with the second antiferromagnetic layer.

  18. Saturation recovery EPR and ELDOR at W-band for spin labels

    Science.gov (United States)

    Froncisz, Wojciech; Camenisch, Theodore G.; Ratke, Joseph J.; Anderson, James R.; Subczynski, Witold K.; Strangeway, Robert A.; Sidabras, Jason W.; Hyde, James S.

    2008-08-01

    A reference arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) [J.W. Sidabras, R.R. Mett, W. Froncisz, T.G. Camenisch, J.R. Anderson, J.S. Hyde, Multipurpose EPR loop-gap resonator and cylindrical TE 011 cavity for aqueous samples at 94 GHz, Rev. Sci. Instrum. 78 (2007) 034701]. The high efficiency parameter (8.2 GW -1/2 with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T1e previously reported for these molecules in the range of 2-35 GHz [J.S. Hyde, J.-J. Yin, W.K. Subczynski, T.G. Camenisch, J.J. Ratke, W. Froncisz, Spin label EPR T 1 values using saturation recovery from 2 to 35 GHz. J. Phys. Chem. B 108 (2004) 9524-9529]. The values of T1e decrease at 94 GHz relative to values at 35 GHz.

  19. 15N Hyperpolarization by Reversible Exchange Using SABRE-SHEATH

    OpenAIRE

    2015-01-01

    NMR signal amplification by reversible exchange (SABRE) is a NMR hyperpolarization technique that enables nuclear spin polarization enhancement of molecules via concurrent chemical exchange of a target substrate and parahydrogen (the source of spin order) on an iridium catalyst. Recently, we demonstrated that conducting SABRE in microtesla fields provided by a magnetic shield enables up to 10% 15N-polarization (Theis, T.; et al. J. Am. Chem. Soc. 2015, 137, 1404). Hyperpolarization on 15N (an...

  20. Global evaluation of ammonia bi-directional exchange

    OpenAIRE

    Zhu, L; D. Henze; J. Bash; G.-R. Jeong; Cady-Pereira, K.; Shephard, M; Luo, M; F. Paulot; Capps, S.

    2015-01-01

    Bi-directional air–surface exchange of ammonia (NH3) has been neglected in many air quality models. In this study, we implement the bi-directional exchange of NH3 in the GEOS-Chem global chemical transport model. We also introduce an updated diurnal variability scheme for NH3 livestock emissions and evaluate the recently developed MASAGE_NH3 bottom up inventory. While updated diurnal variability improves comparison of modeled-to-hourly in situ measurements i...

  1. Thermal performance modeling of cross-flow heat exchangers

    CERN Document Server

    Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria

    2014-01-01

    This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges

  2. Core size effect on the dry and saturated ultrasonic pulse velocity of limestone samples.

    Science.gov (United States)

    Ercikdi, Bayram; Karaman, Kadir; Cihangir, Ferdi; Yılmaz, Tekin; Aliyazıcıoğlu, Şener; Kesimal, Ayhan

    2016-12-01

    This study presents the effect of core length on the saturated (UPVsat) and dry (UPVdry) P-wave velocities of four different biomicritic limestone samples, namely light grey (BL-LG), dark grey (BL-DG), reddish (BL-R) and yellow (BL-Y), using core samples having different lengths (25-125mm) at a constant diameter (54.7mm). The saturated P-wave velocity (UPVsat) of all core samples generally decreased with increasing the sample length. However, the dry P-wave velocity (UPVdry) of samples obtained from BL-LG and BL-Y limestones increased with increasing the sample length. In contrast to the literature, the dry P-wave velocity (UPVdry) values of core samples having a length of 75, 100 and 125mm were consistently higher (2.8-46.2%) than those of saturated (UPVsat). Chemical and mineralogical analyses have shown that the P wave velocity is very sensitive to the calcite and clay minerals potentially leading to the weakening/disintegration of rock samples in the presence of water. Severe fluctuations in UPV values were observed to occur between 25 and 75mm sample lengths, thereafter, a trend of stabilization was observed. The maximum variation of UPV values between the sample length of 75mm and 125mm was only 7.3%. Therefore, the threshold core sample length was interpreted as 75mm for UPV measurement in biomicritic limestone samples used in this study.

  3. Determination of the activity of a molecular solute in saturated solution

    Energy Technology Data Exchange (ETDEWEB)

    Nordstroem, Fredrik L. [Department of Chemical Engineering and Technology, Royal Institute of Technology, 100 44 Stockholm (Sweden); Rasmuson, Ake C. [Department of Chemical Engineering and Technology, Royal Institute of Technology, 100 44 Stockholm (Sweden)], E-mail: rasmuson@ket.kth.se

    2008-12-15

    Prediction of the solubility of a solid molecular compound in a solvent, as well as, estimation of the solution activity coefficient from experimental solubility data both require estimation of the activity of the solute in the saturated solution. The activity of the solute in the saturated solution is often defined using the pure melt at the same temperature as the thermodynamic reference. In chemical engineering literature also the activity of the solid is usually defined on the same reference state. However, far below the melting temperature, the properties of this reference state cannot be determined experimentally, and different simplifications and approximations are normally adopted. In the present work, a novel method is presented to determine the activity of the solute in the saturated solution (=ideal solubility) and the heat capacity difference between the pure supercooled melt and solid. The approach is based on rigorous thermodynamics, using standard experimental thermodynamic data at the melting temperature of the pure compound and solubility measurements in different solvents at various temperatures. The method is illustrated using data for ortho-, meta-, and para-hydroxybenzoic acid, salicylamide and paracetamol. The results show that complete neglect of the heat capacity terms may lead to estimations of the activity that are incorrect by a factor of 12. Other commonly used simplifications may lead to estimations that are only one-third of the correct value.

  4. PHT3D-UZF: A reactive transport model for variably-saturated porous media

    Science.gov (United States)

    Wu, Ming Zhi; Post, Vincent E. A.; Salmon, S. Ursula; Morway, Eric; Prommer, H.

    2016-01-01

    A modified version of the MODFLOW/MT3DMS-based reactive transport model PHT3D was developed to extend current reactive transport capabilities to the variably-saturated component of the subsurface system and incorporate diffusive reactive transport of gaseous species. Referred to as PHT3D-UZF, this code incorporates flux terms calculated by MODFLOW's unsaturated-zone flow (UZF1) package. A volume-averaged approach similar to the method used in UZF-MT3DMS was adopted. The PHREEQC-based computation of chemical processes within PHT3D-UZF in combination with the analytical solution method of UZF1 allows for comprehensive reactive transport investigations (i.e., biogeochemical transformations) that jointly involve saturated and unsaturated zone processes. Intended for regional-scale applications, UZF1 simulates downward-only flux within the unsaturated zone. The model was tested by comparing simulation results with those of existing numerical models. The comparison was performed for several benchmark problems that cover a range of important hydrological and reactive transport processes. A 2D simulation scenario was defined to illustrate the geochemical evolution following dewatering in a sandy acid sulfate soil environment. Other potential applications include the simulation of biogeochemical processes in variably-saturated systems that track the transport and fate of agricultural pollutants, nutrients, natural and xenobiotic organic compounds and micropollutants such as pharmaceuticals, as well as the evolution of isotope patterns.

  5. Current saturation in submicrometer graphene transistors with thin gate dielectric: experiment, simulation, and theory.

    Science.gov (United States)

    Han, Shu-Jen; Reddy, Dharmendar; Carpenter, Gary D; Franklin, Aaron D; Jenkins, Keith A

    2012-06-26

    Recently, graphene field-effect transistors (FET) with cutoff frequencies (f(T)) between 100 and 300 GHz have been reported; however, the devices showed very weak drain current saturation, leading to an undesirably high output conductance (g(ds)= dI(ds)/dV(ds)). A crucial figure-of-merit for analog/RF transistors is the intrinsic voltage gain (g(m)/g(ds)) which requires both high g(m) (primary component of f(T)) and low g(ds). Obtaining current saturation has become one of the key challenges in graphene device design. In this work, we study theoretically the influence of the dielectric thickness on the output characteristics of graphene FETs by using a surface-potential-based device model. We also experimentally demonstrate that by employing a very thin gate dielectric (equivalent oxide thickness less than 2 nm), full drain current saturation can be obtained for large-scale chemical vapor deposition graphene FETs with short channels. In addition to showing intrinsic voltage gain (as high as 34) that is comparable to commercial semiconductor FETs with bandgaps, we also demonstrate high frequency AC voltage gain and S21 power gain from s-parameter measurements.

  6. Saturated thickness of the Minnelusa aquifer, Black Hills, South Dakota.

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set is a polygon coverage created in ARC/INFO that represents the saturated thickness of the Minnelusa aquifer, Black Hills area, South Dakota. The...

  7. Pore capillary pressure and saturation of methane hydrate bearing sediments

    Institute of Scientific and Technical Information of China (English)

    SUN Shicai; LIU Changling; YE Yuguang; LIU Yufeng

    2014-01-01

    To better understand the relationship between the pore capillary pressure and hydrate saturation in sedi-ments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capil-lary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.

  8. Saturation of Zeldovich stretch-twist-fold map dynamos

    Science.gov (United States)

    Seta, Amit; Bhat, Pallavi; Subramanian, Kandaswamy

    2015-10-01

    > value is determined by the relative importance of the increased diffusion versus the reduced stretching. These saturation properties are akin to the range of possibilities that have been discussed in the context of fluctuation dynamos.

  9. Using historical biogeography to test for community saturation.

    Science.gov (United States)

    Pinto-Sánchez, Nelsy Rocío; Crawford, Andrew J; Wiens, John J

    2014-09-01

    Saturation is the idea that a community is effectively filled with species, such that no more can be added without extinctions. This concept has important implications for many areas of ecology, such as species richness, community assembly, invasive species and climate change. Here, we illustrate how biogeography can be used to test for community saturation, when combined with data on local species richness, phylogeny and climate. We focus on a clade of frogs (Terrarana) and the impact of the Great American Biotic Interchange on patterns of local richness in Lower Middle America and adjacent regions. We analyse data on species richness at 83 sites and a time-calibrated phylogeny for 363 species. We find no evidence for saturation, and show instead that biotic interchange dramatically increased local richness in the region. We suggest that historical biogeography offers thousands of similar long-term natural experiments that can be used to test for saturation.

  10. Delayed system control in presence of actuator saturation

    Directory of Open Access Journals (Sweden)

    A. Mahjoub

    2014-09-01

    Full Text Available The paper is introducing a new design method for systems’ controllers with input delay and actuator saturations and focuses on how to force the system output to track a reference input not necessarily saturation-compatible. We propose a new norm based on the way we quantify tracking performance as a function of saturation errors found using the same norm. The newly defined norm is related to signal average power making possible to account for most common reference signals e.g. step, periodic. It is formally shown that, whatever the reference shape and amplitude, the achievable tracking quality is determined by a well defined reference tracking mismatch error. This latter depends on the reference rate and its compatibility with the actuator saturation constraint. In fact, asymptotic output-reference tracking is achieved in the presence of constraint-compatible step-like references.

  11. Saturated thickness of the Madison aquifer, Black Hills, South Dakota.

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set is a polygon coverage created in ARC/INFO that represents the saturated thickness of the Madison aquifer, which includes the entire thickness of the...

  12. Saturation of Photoassociation in Cs Magneto-optical Trap

    Institute of Scientific and Technical Information of China (English)

    MA Jie; WANG Li-Rong; JI Wei-Bang; XIAO Lian-Tuan; JIA Suo-Tang

    2007-01-01

    An ultrahigh resolution photoassociation spectrum of caesium atoms in a magneto-optical trap is presented. Hyperfine structure of the excited state molecule is obtained by using the lock-in method based on modulated cold atoms in this spectrum. Amplitude of resonant lines related to the rotational levels increases with photoassociation laser intensity, and saturation effect of photoassociation of cold atoms is observed in our experiment. The saturation intensity of photoassociation is deduced by fitting the experimental data to a saturation model based on scattering theory. Differences among saturation intensities of different rotational progressions in the v = 55vibrational state of the caesium molecular long-range O-g state have been found.

  13. Information point and saturation flow at signalized intersections

    Directory of Open Access Journals (Sweden)

    Lijun Gao

    2016-08-01

    Full Text Available This paper introduces an information point factor and attempts to identify how it affects saturation flow and their relationship at signalized intersections. An information point is defined as any object, structure, or activity located outside of a traveling vehicle that can potentially attract the visual attention of the driver. Saturation flow rates are studied at three pairs of signalized intersections in Toledo, Ohio, USA. Each pair of intersections consists of one intersection with a high number of information points and one intersection with a low number of information points. Study results reveal that, for each pair of intersections, the one with high information points has a lower saturation flow rate than the one with low information points. A statistical analysis shows that the differences are significant. Based on the saturation flow data of the paired intersections, information point effect models are developed and presented in this paper.

  14. Soil hydraulic properties near saturation, an improved conductivity model

    DEFF Research Database (Denmark)

    Børgesen, Christen Duus; Jacobsen, Ole Hørbye; Hansen, Søren;

    2006-01-01

    The hydraulic properties near saturation can change dramatically due to the presence of macropores that are usually difficult to handle in traditional pore size models. The purpose of this study is to establish a data set on hydraulic conductivity near saturation, test the predictive capability...... of commonly used hydraulic conductivity models and give suggestions for improved models. Water retention and near saturated and saturated hydraulic conductivity were measured for a variety of 81 top and subsoils. The hydraulic conductivity models by van Genuchten [van Genuchten, 1980. A closed-form equation...... for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J. 44, 892–898.] (vGM) and Brooks and Corey, modified by Jarvis [Jarvis, 1991. MACRO—A Model of Water Movement and Solute Transport in Macroporous Soils. Swedish University of Agricultural Sciences. Department of Soil Sciences...

  15. Pulse Distortion in Saturated Fiber Optical Parametric Chirped Pulse Amplification

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Da Ros, Francesco; Rottwitt, Karsten

    2012-01-01

    Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation.......Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation....

  16. Simulation of Nonlinear Gain Saturation in Active Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2012-01-01

    In this paper we present a theoretical analysis of slowlight enhanced traveling wave amplification in an active semiconductor Photonic crystal waveguides. The impact of group index on nonlinear modal gain saturation is investigated.......In this paper we present a theoretical analysis of slowlight enhanced traveling wave amplification in an active semiconductor Photonic crystal waveguides. The impact of group index on nonlinear modal gain saturation is investigated....

  17. Response of Saturated Porous Nonlinear Materials to Dynamic Loadings

    Science.gov (United States)

    1984-05-31

    the following section a bilinear hysteretic skeleton was modeled, followed by calculations on an actual sand from Enewetak Atoll . In this section...the response of saturated sand from Enewetak Atoll . The skeleton properties are taken from laboratory data reported in the second volunie of this study...with an actual saturated sand from Enewetak Atoll . In Section 2, the theoretical background and numerical code, TPDAP, used in this study are described

  18. Design of saturated controllers for linear singular systems

    Institute of Scientific and Technical Information of China (English)

    Wang Ruliang; Liu Yongqing

    2005-01-01

    A designing method is presented to find stabilizing saturated linear controllers for linear continuous time and discrete time singular systems with control constraints. The idea is as follows: The system is first stabilized by a low-gain linear state feedback control. A general Lyapunov function is found, on the basis of which another linear state feedback control is computed.The second step is very similar to a relay control design. The two controls are added and saturated.

  19. Nonlinear Gain Saturation in Active Slow Light Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2013-01-01

    We present a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguides. The impact of slow-light propagation on the nonlinear gain saturation of the device is investigated.......We present a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguides. The impact of slow-light propagation on the nonlinear gain saturation of the device is investigated....

  20. Law of nonlinear flow in saturated clays and radial consolidation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    It was derived that micro-scale amount level of average pore radius of clay changed from 0.01 to 0.1 micron by an equivalent concept of flow in porous media. There is good agreement between the derived results and test ones. Results of experiments show that flow in micro-scale pore of saturated clays follows law of nonlinear flow. Theoretical analyses demonstrate that an interaction of solid-liquid interfaces varies inversely with permeability or porous radius. The interaction is an important reason why nonlinear flow in saturated clays occurs. An exact mathematical model was presented for nonlinear flow in micro-scale pore of saturated clays. Dimension and physical meanings of parameters of it are definite. A new law of nonlinear flow in saturated clays was established. It can describe characteristics of flow curve of the whole process of the nonlinear flow from low hydraulic gradient to high one. Darcy law is a special case of the new law. A mathematical model was presented for consolidation of nonlinear flow in radius direction in saturated clays with constant rate based on the new law of nonlinear flow. Equations of average mass conservation and moving boundary, and formula of excess pore pressure distribution and average degree of consolidation for nonlinear flow in saturated clay were derived by using an idea of viscous boundary layer, a method of steady state in stead of transient state and a method of integral of an equation. Laws of excess pore pressure distribution and changes of average degree of consolidation with time were obtained. Results show that velocity of moving boundary decreases because of the nonlinear flow in saturated clay. The results can provide geology engineering and geotechnical engineering of saturated clay with new scientific bases. Calculations of average degree of consolidation of the Darcy flow are a special case of that of the nonlinear flow.

  1. Stability of the barium–benzo-15-crown-5 complex in nitrobenzene saturated with water

    Directory of Open Access Journals (Sweden)

    E. MAKRLÍK

    2006-11-01

    Full Text Available From extraction experiments and g-activity measurements, the exchange extraction constant corresponding to the equilibrium Ba2+(aq + SrL22+(nb D BaL22+(nb + Sr2+(aq occurring in the two-phase water–nitrobenzene system (L =benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase was evaluated as log Kex (Ba2+, SrL22+ = 0.3 ± 0.1. Furthermore, the stability constant of the benzo-15-crown-5–barium complex in nitrobenzene saturated with water was calculated for the temperature of 25 °C: log bnb (BaL22+=13.3±0.1.

  2. The relation between oxygen saturation level and retionopathy of prematurity

    Directory of Open Access Journals (Sweden)

    Mohammad Gharavi Fard

    2016-03-01

    Full Text Available Introduction: Oxygen therapy used for preterm infant disease might be associated with oxygen toxicity or oxidative stress. The exact oxygen concentration to control and maintain the arterial oxygen saturation balance is not certainly clear. We aimed to compare the efficacy of higher or lower oxygen saturations on the development of severe retinopathy of prematurity which is a major cause of blindness in preterm neonates. Methods: PubMed was searched for obtaining the relevant articles. A total of seven articles were included after studying the titles, abstracts, and the full text of retrieved articles at initial search. Inclusion criteria were all the English language human clinical randomized controlled trials with no time limitation, which studied the efficacy of low versus high oxygen saturation measured by pulse oximetry in preterm infants.Result: It can be suggested that lower limits of oxygen saturations have higher efficacy at postmesetural age of ≤28 weeks in preterm neonates. This relation has been demonstrated in five large clinical trials including three Boost trials, COT, and Support.Discussion: Applying higher concentrations of oxygen supplementations at mesentural age ≥32 weeks reduced the development of retinopathy of prematurity. Lower concentrations of oxygen saturation decreased the incidence and the development of retinopathy of prematurity in preterm neonates while applied soon after the birth.Conclusions: Targeting levels of oxygen saturation in the low or high range should be performed cautiously with attention to the postmesentural age in preterm infants at the time of starting the procedures.

  3. Biodegradation of crude oil saturated fraction supported on clays.

    Science.gov (United States)

    Ugochukwu, Uzochukwu C; Jones, Martin D; Head, Ian M; Manning, David A C; Fialips, Claire I

    2014-02-01

    The role of clay minerals in crude oil saturated hydrocarbon removal during biodegradation was investigated in aqueous clay/saturated hydrocarbon microcosm experiments with a hydrocarbon degrading microorganism community. The clay minerals used for this study were montmorillonite, palygorskite, saponite and kaolinite. The clay mineral samples were treated with hydrochloric acid and didecyldimethylammonium bromide to produce acid activated- and organoclays respectively which were used in this study. The production of organoclay was restricted to only montmorillonite and saponite because of their relative high CEC. The study indicated that acid activated clays, organoclays and unmodified kaolinite, were inhibitory to biodegradation of the hydrocarbon saturates. Unmodified saponite was neutral to biodegradation of the hydrocarbon saturates. However, unmodified palygorskite and montmorillonite were stimulatory to biodegradation of the hydrocarbon saturated fraction and appears to do so as a result of the clays' ability to provide high surface area for the accumulation of microbes and nutrients such that the nutrients were within the 'vicinity' of the microbes. Adsorption of the saturated hydrocarbons was not significant during biodegradation.

  4. Saturation curves of parallel-plate ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Fallone, B.G.; Podgorsak, E.B.

    A new analytical expression is presented to describe the full saturation curve of parallel-plate ionization chambers. In contrast to the presently known expressions, which hold only for the near saturation region, this empirically determined expression is in excellent agreement with measurements in the whole collection efficiency range from 0 to 1 for x-ray sources with effective energies from 20 to 150 keV and cobalt-60 gamma rays. The dependence of the ion collection efficiency and the extrapolated electric field, which is a parameter in the new saturation curve expression, on electric field, dose, dose rate, beam quality, and chamber volume, is discussed. The effect of photoemission from the chamber polarizing electrode for low-energy x-ray beams on the saturation current is demonstrated. A universal ionization chamber constant is derived experimentally. It is shown that all parameters of the saturation curve equation and thus the saturation curve itself, can be calculated from one single measurement of ionization current at a given electric field and air gap thickness.

  5. Prevalence of Sensor Saturation in Wheelchair Seat Interface Pressure Mapping.

    Science.gov (United States)

    Wininger, Michael; Crane, Barbara A

    2015-01-01

    Pressure mapping is a frequently used tool with great power to provide information about the forces between a patient and a wheelchair seat. One widely recognized limitation to this paradigm is the possibility of data loss due to sensor saturation. In this study, we seek to quantify and describe the saturation observed in the measurement of interface pressures of wheelchair users. We recorded approximately two minutes of interface pressure data from 22 elderly wheelchair users (11M/11F, 80 ± 10 years) and found that 4.7% of data frames had 1 saturated sensor, and 9.0% had more than one saturated sensor, for a total of 13.7% of all frames of data. Data from three of the 22 subjects (13.6%) were substantially affected by the persistent presence of saturated sensors. We conclude that for this population of elderly wheelchair users, sensor saturation may be a concern and should be factored properly into study design a priori.

  6. Advanced ion exchange resins for PWR condensate polishing

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, B. [Rohm and Haas Co. (United States); Tsuzuki, S. [Rohm and Haas Co. (Japan)

    2002-07-01

    The severe chemical and mechanical requirements of a pressurized water reactor (PWR) condensate polishing plant (CPP) present a major challenge to the design of ion exchange resins. This paper describes the development and initial operating experience of improved cation and anion exchange resins that were specifically designed to meet PWR CPP needs. Although this paper focuses specifically on the ion exchange resins and their role in plant performance, it is also recognized and acknowledged that excellent mechanical design and operation of the CPP system are equally essential to obtaining good results. (authors)

  7. Physical and chemical degradation of grassland soils in semi-arid regions: A case from Central Anatolia, Turkey

    Science.gov (United States)

    Yaşar Korkanç, Selma; Korkanç, Mustafa

    2016-12-01

    The aim of this study is to determine some hydro-physical and chemical characteristics of soils on the grassland areas under semi-arid conditions in terms of soil degradation processes. Three sampling plots of 20 × 20 m size were selected from the Emen Plain as Locations-I, II and III basing on the area covered with vegetation and visual soil properties; and total 108 soil samples from 2 points and 3 depth levels (0-20 cm, 20-40 cm, 40-60 cm) of each sampling plot. Soils of the research area are in degradation process in terms of some physical and chemical characteristics. It was observed that soil properties (i.e. bulk density, total porosity, organic matter, pH, electrical conductivity and saturated hydraulic conductivity) in Location-II and Location-III changed negatively in comparison to Location-I almost at all depths. In the Location-III grassland, bulk density, pH, electrical conductivity and Na + values are higher than those in Location-I, whereas the organic matter, total porosity and saturated hydraulic conductivity values are low. Grassland area is vulnerable to erosion. High Exchangeable Sodium Percentage (ESP) values in Locations-II and III indicates the sodicity problem in these areas.

  8. Gas exchange measurements in natural systems

    Energy Technology Data Exchange (ETDEWEB)

    Broecker, W.S.; Peng, T.H.

    1983-01-01

    Direct knowledge of the rates of gas exchange in lakes and the ocean is based almost entirely on measurements of the isotopes /sup 14/C, /sup 222/Rn and /sup 3/He. The distribution of natural radiocarbon has yielded the average rate of CO/sub 2/ exchange for the ocean and for several closed basin lakes. That of bomb produced radiocarbon has been used in the same systems. The /sup 222/Rn to /sup 226/Ra ratio in open ocean surface water has been used to give local short term gas exchange rates. The radon method generally cannot be used in lakes, rivers, estuaries or shelf areas because of the input of radon from sediments. A few attempts have been made to use the excess /sup 3/He produced by decay of bomb produced tritium in lakes to give gas transfer rates. The uncertainty in the molecular diffusivity of helium and in the diffusivity dependence of the rate of gas transfer holds back the application of this method. A few attempts have been made to enrich the surface waters of small lakes with /sup 226/Ra and /sup 3/H in order to allow the use of the /sup 222/Rn and /sup 3/He methods. While these studies give broadly concordant results, many questions remain unanswered. The wind velocity dependence of gas exchange rate has yet to be established in field studies. The dependence of gas exchange rate on molecular diffusivity also remains in limbo. Finally, the degree of enhancement of CO/sub 2/ exchange through chemical reactions has been only partially explored. 49 references, 2 figures, 2 tables.

  9. Baltic Exchange toodi Tallinna

    Index Scriptorium Estoniae

    2007-01-01

    Viimane osa merekonteineritesse kokkupakitud Londoni laevandus- ja merebörsi Baltic Exchange'i endise peakorteri detailidest jõudis 2007. a. juunis Tallinna. Hoone detailid ostnud ärimehed Heiti Hääl ja Eerik-Niiles Kross plaanivad leida hoonele koha Tallinna kesklinnas. E.-N. Krossi kommentaar

  10. Telephone Exchange Maintenance

    CERN Multimedia

    2005-01-01

    Urgent maintenance work on CERN telephone exchanges will be performed on 24 March from 6 a.m. to 8 a.m. Telephone services may be disrupted or even interrupted during this time. For more details, please contact us by email at Standard.Telephone@cern.ch.

  11. Nature's Heat Exchangers.

    Science.gov (United States)

    Barnes, George

    1991-01-01

    Discusses the heat-transfer systems of different animals. Systems include heat conduction into the ground, heat transferred by convection, heat exchange in lizards, fish and polar animals, the carotid rete system, electromagnetic radiation from animals and people, and plant and animal fiber optics. (MDH)

  12. Exchangeable lower previsions

    CERN Document Server

    de Cooman, Gert; Miranda, Enrique; 10.3150/09-BEJ182

    2009-01-01

    We extend de Finetti's [Ann. Inst. H. Poincar\\'{e} 7 (1937) 1--68] notion of exchangeability to finite and countable sequences of variables, when a subject's beliefs about them are modelled using coherent lower previsions rather than (linear) previsions. We derive representation theorems in both the finite and countable cases, in terms of sampling without and with replacement, respectively.

  13. Microtube strip heat exchanger

    Science.gov (United States)

    Doty, F. D.

    1991-04-01

    During the last quarter, Doty Scientific, Inc. (DSI) continued to make progress on the microtube strip (MTS) heat exchangers. The team has begun a heat exchanger stress analysis; however, they have been concentrating the bulk of their analytical energies on a computational fluid dynmaics (CFD) model to determine the location and magnitude of shell-side flow maldistribution which decreases heat exchanger effectiveness. DSI received 120 fineblanked tubestrips from Southern Fineblanking (SFB) for manufacturing process development. Both SFB and NIST provided inspection reports of the tubestrips. DSI completed the tooling required to encapsulate a tube array and press tubestrips on the array. Pressing the tubestrips on tube arrays showed design deficiencies both in the tubestrip design and the tooling design. DSI has a number of revisions in process to correct these deficiencies. The research effort has identified a more economical fusible alloy for encapsulating the tube array, and determined the parameters required to successfully encapsulate the tube array with the new alloy. A more compact MTS heat exchanger bank was designed.

  14. Currency Exchange Rates.

    Science.gov (United States)

    Siler, Carl R.

    This curriculum unit of the Muncie (Indiana) Southside High School is to simulate the dynamics of foreign currency exchange rates from the perspectives of: (1) a major U.S. corporation, ABB Power T & D Company, Inc., of Muncie, Indiana, a manufacturer of large power transformers for the domestic and foreign markets; and (2) individual…

  15. Properties of meso-Erythritol; phase state, accommodation coefficient and saturation vapour pressure

    Science.gov (United States)

    Emanuelsson, Eva; Tschiskale, Morten; Bilde, Merete

    2016-04-01

    Introduction Saturation vapour pressure and the associated temperature dependence (enthalpy ΔH), are key parameters for improving predictive atmospheric models. Generally, the atmospheric aerosol community lack experimentally determined values of these properties for relevant organic aerosol compounds (Bilde et al., 2015). In this work we have studied the organic aerosol component meso-Erythritol. Methods Sub-micron airborne particles of meso-Erythritol were generated by nebulization from aqueous solution, dried, and a mono disperse fraction of the aerosol was selected using a differential mobility analyser. The particles were then allowed to evaporate in the ARAGORN (AaRhus Atmospheric Gas phase OR Nano particle) flow tube. It is a temperature controlled 3.5 m long stainless steel tube with an internal diameter of 0.026 m (Bilde et al., 2003, Zardini et al., 2010). Changes in particle size as function of evaporation time were determined using a scanning mobility particle sizer system. Physical properties like air flow, temperature, humidity and pressure were controlled and monitored on several places in the setup. The saturation vapour pressures were then inferred from the experimental results in the MATLAB® program AU_VaPCaP (Aarhus University_Vapour Pressure Calculation Program). Results Following evaporation, meso-Erythriol under some conditions showed a bimodal particle size distribution indicating the formation of particles of two different phase states. The issue of physical phase state, along with critical assumptions e.g. the accommodation coefficient in the calculations of saturation vapour pressures of atmospheric relevant compounds, will be discussed. Saturation vapour pressures from the organic compound meso-Erythritol will be presented at temperatures between 278 and 308 K, and results will be discussed in the context of atmospheric chemistry. References Bilde, M. et al., (2015), Chemical Reviews, 115 (10), 4115-4156. Bilde, M. et. al., (2003

  16. Effects of Heterogeneity on Transport of Graphene Oxide in Saturated and Unsaturated Porous Media

    Science.gov (United States)

    Dong, S.; Sun, Y.; Shi, X.; Wu, J.; Gao, B.

    2015-12-01

    Graphene oxide (GO) has received increasing attention in many fields with its wide applications and rapid growth in production. Therefore, it is expected that GO nanoparticles will inevitably be released into the subsurface and cause the environmental risk subsequently. In view of this, knowledge of the fate for GO in the vadose zone and groundwater systems is indispensable. So far most research has focused on the deposition and transport of GO nanoparticles in one-dimensional homogenous porous media; nonetheless, the complex heterogeneous system is extensively distributed in natural subsurface environment and may not be well represented by the homogeneous packed columns. However, little investigations have been directed toward understanding the transport of GO in heterogeneous porous media. The overarching objective of this study is to advance current understanding of GO transport in structured heterogeneous porous media. The saturated and unsaturated columns packed with different sand combinations and solution ionic strength, were used to examine the breakthrough behavior of GO in heterogeneous porous media. A two-domain model considering GO exchange between zones was developed to describe GO transport in structured, heterogeneous porous media. The experimental data indicate that volumetric moisture content and water flow are the critical factors that control GO transport in heterogeneous porous media. And higher ionic strength decrease the mobility of GO particles in both saturated and unsaturated heterogeneous pore media. Simulations of this two-domain nanoparticle transport model matched experimental breakthrough data well for all the experimental conditions. Experimental and model results show that under saturated conditions, both fast-flow and slow-flow domains affect colloid transport in heterogeneous media. Under unsaturated conditions, however, our results indicate that flows in the fast flow domain dominate the colloid transport and retention processes.

  17. Numerical analysis of heat exchange processes for the ground source heat pump system

    Science.gov (United States)

    Saito, H.; Muto, H.; Moritani, S.; Kohgo, Y.; Hamamoto, S.; Takemura, T.; Ohnishi, J.; Komatsu, T.

    2012-12-01

    Ground source heat pump systems (GSHP) use ground or groundwater as a heat source. They can achieve much higher coefficient of performance (COP) than conventional air source heat pump systems because the temperature of the ground is much more stable than that of the air. Heat energy in the ground is then viewed as one of the renewable energy sources. GSHP has been receiving great interests among countries in North America and Western Europe, as well as some developed countries in Asia because it can potentially reduce energy consumption and greenhouse gas emission. While GSHP can inject heat from the buildings to the ground for cooling during the summer, it can pump heat stored in the ground for heating during the winter. As some physical, chemical, and biological properties of the ground and groundwater are temperature dependent, running GSHP can eventually affect groundwater quality. The main objective of this project was to develop a model that allows predicting not only ground and groundwater temperatures but also changes in physical, chemical, and biological properties of ground and groundwater with GSHP under operations. This particular study aims at simulating heat exchange and transfer processes in the ground for a vertical-loop closed GSHP system. In the closed GSHP system, an anti-freezing solution is circulated inside the closed-loop tube, called U-tube, that is buried in the ground. Heat is then transferred to the anti-freezing solution in the U-tube by a heat exchanger. In this study we used HYDRUS to predict temperature of the anti-freezing solution, as well as that of the ground. HYDRUS allows one to simulate variably-saturated water flow and solute and heat transport in porous media numerically in two- and three-dimensional domains with great flexibility in defining boundary conditions. At first changes in anti-freezing solution temperatures measured were predicted in response to Thermal Response Test (TRT) conducted at our study site. Then, heat

  18. The Biofilm Lifestyle Involves an Increase in Bacterial Membrane Saturated Fatty Acids.

    Science.gov (United States)

    Dubois-Brissonnet, Florence; Trotier, Elsa; Briandet, Romain

    2016-01-01

    Biofilm formation on contact surfaces contributes to persistence of foodborne pathogens all along the food and feed chain. The specific physiological features of bacterial cells embedded in biofilms contribute to their high tolerance to environmental stresses, including the action of antimicrobial compounds. As membrane lipid adaptation is a vital facet of bacterial response when cells are submitted to harsh or unstable conditions, we focused here on membrane fatty acid composition of biofilm cells as compared to their free-growing counterparts. Pathogenic bacteria (Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium) were cultivated in planktonic or biofilm states and membrane fatty acid analyses were performed on whole cells in both conditions. The percentage of saturated fatty acids increases in biofilm cells in all cases, with a concomitant decrease of branched-chain fatty acids for Gram-positive bacteria, or with a decrease in the sum of other fatty acids for Gram-negative bacteria. We propose that increased membrane saturation in biofilm cells is an adaptive stress response that allows bacteria to limit exchanges, save energy, and survive. Reprogramming of membrane fluidity in biofilm cells might explain specific biofilm behavior including bacterial recalcitrance to biocide action.

  19. The U.S. Imperial Jugger-not: Saturation Points and Cultural Globalization

    Directory of Open Access Journals (Sweden)

    Meg Spohn Bertoni

    2010-03-01

    Full Text Available Globalization is not merely inevitable western cultural conquest. The assumption that the juggernaut of western hegemonic domination will continue until the world is consumed is a common one, but not an accurate one. That accuracy is compromised by a number of related misconceptions about the nature of globalization. Some of these have to do with an attachment to dichotomy in a world too complex for dualism. Some of them are related to assumptions about the nature of trade, of trends, of inevitability, and of statistical prediction that turn out not to be accurate—and by extension misconceptions about the unidirectionality of cultural exchange. Most are related to misconceptions about the nature of culture—particularly in oversimplifying, and making strange assumptions about, nonwestern cultures. Cultures change over time, with generations and historical forces—today’s cultural changes make up tomorrow’s cohesive culture. Cultures die not when they change to reflect the new attitudes and lifestyles of the peoples who live in them, but when they stagnate and become static, preserved only in museums, artifacts and books, and not in the everyday lives of the people themselves. Finally, phenomena do reach a saturation point, from biological populations to the motion of catamarans to absorption of cultural values, and these can be observed using methods of nonlinear dynamics. This project considers common misconceptions about globalization and culture, and uses concepts from nonlinear dynamics to expose the nature of the movement and saturation points of cultural globalization.

  20. Counterflow Regolith Heat Exchanger

    Science.gov (United States)

    Zubrin, Robert; Jonscher, Peter

    2013-01-01

    A problem exists in reducing the total heating power required to extract oxygen from lunar regolith. All such processes require heating a great deal of soil, and the heat energy is wasted if it cannot be recycled from processed material back into new material. The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat exchanger with internal and external augers attached to the inner rotating tube to move the regolith. Hot regolith in the outer tube is moved in one direction by a right-hand - ed auger, and the cool regolith in the inner tube is moved in the opposite direction by a left-handed auger attached to the inside of the rotating tube. In this counterflow arrangement, a large fraction of the heat from the expended regolith is transferred to the new regolith. The spent regolith leaves the heat exchanger close to the temperature of the cold new regolith, and the new regolith is pre-heated close to the initial temperature of the spent regolith. Using the CoRHE can reduce the heating requirement of a lunar ISRU system by 80%, reducing the total power consumption by a factor of two. The unique feature of this system is that it allows for counterflow heat exchange to occur between solids, instead of liquids or gases, as is commonly done. In addition, in variants of this concept, the hydrogen reduction can be made to occur within the counterflow heat exchanger itself, enabling a simplified lunar ISRU (in situ resource utilization) system with excellent energy economy and continuous nonbatch mode operation.

  1. Preparation of a Cation Exchanger from Cork Waste: Thermodynamic Study of the Ion Exchange Processes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An ion exchanger was prepared by sulfonation of cork-waste chars. The exchange properties of the resultant materialwere characterized using Na+, Ca2+ or Fe3+ aqueous solutions, The content of metal ions in the solutions weredetermined by atomic absorption spectrometry. On the basis of the results obtained, the chemical equilibrium andits thermodynamic aspects related to the ion exchange process were studied. It was found that equilibrium constantK varies by the order: Na+<Ca2+<Fe3+, its value increasing with increasing temperature, and that △H°>0 and△S°>0, with -△G° following the sequence: Ca2+>Na+>Fe3+,

  2. Analytical applications of ion exchangers

    CERN Document Server

    Inczédy, J

    1966-01-01

    Analytical Applications of Ion Exchangers presents the laboratory use of ion-exchange resins. This book discusses the development in the analytical application of ion exchangers. Organized into 10 chapters, this book begins with an overview of the history and significance of ion exchangers for technical purposes. This text then describes the properties of ion exchangers, which are large molecular water-insoluble polyelectrolytes having a cross-linked structure that contains ionic groups. Other chapters consider the theories concerning the operation of ion-exchange resins and investigate th

  3. PREDICTION OF TOTAL DISSOLVED GAS EXCHANGE AT HYDROPOWER DAMS

    Energy Technology Data Exchange (ETDEWEB)

    Hadjerioua, Boualem [ORNL; Pasha, MD Fayzul K [ORNL; Stewart, Kevin M [ORNL; Bender, Merlynn [Bureau of Reclamation; Schneider, Michael L. [U.S. Army Corps of Engineers

    2012-07-01

    Total dissolved gas (TDG) supersaturation in waters released at hydropower dams can cause gas bubble trauma in fisheries resulting in physical injuries and eyeball protrusion that can lead to mortality. Elevated TDG pressures in hydropower releases are generally caused by the entrainment of air in spillway releases and the subsequent exchange of atmospheric gasses into solution during passage through the stilling basin. The network of dams throughout the Columbia River Basin (CRB) are managed for irrigation, hydropower production, flood control, navigation, and fish passage that frequently result in both voluntary and involuntary spillway releases. These dam operations are constrained by state and federal water quality standards for TDG saturation which balance the benefits of spillway operations designed for Endangered Species Act (ESA)-listed fisheries versus the degradation to water quality as defined by TDG saturation. In the 1970s, the United States Environmental Protection Agency (USEPA), under the federal Clean Water Act (Section 303(d)), established a criterion not to exceed the TDG saturation level of 110% in order to protect freshwater and marine aquatic life. The states of Washington and Oregon have adopted special water quality standards for TDG saturation in the tailrace and forebays of hydropower facilities on the Columbia and Snake Rivers where spillway operations support fish passage objectives. The physical processes that affect TDG exchange at hydropower facilities have been studied throughout the CRB in site-specific studies and routine water quality monitoring programs. These data have been used to quantify the relationship between project operations, structural properties, and TDG exchange. These data have also been used to develop predictive models of TDG exchange to support real-time TDG management decisions. These empirically based predictive models have been developed for specific projects and account for both the fate of spillway and

  4. On the water saturation calculation in hydrocarbon sandstone reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Stalheim, Stein Ottar

    2002-07-01

    The main goal of this work was to identify the most important uncertainty sources in water saturation calculation and examine the possibility for developing new S{sub w} - equations or possibility to develop methods to remove weaknesses and uncertainties in existing S{sub w} - equations. Due to the need for industrial applicability of the equations we aimed for results with the following properties: The accuracy in S{sub w} should increase compared with existing S{sub w} - equations. The equations should be simple to use in petrophysical evaluations. The equations should be based on conventional logs and use as few as possible input parameters. The equations should be numerical stable. This thesis includes an uncertainty and sensitivity analysis of the most common S{sub w} equations. The results are addressed in chapter 3 and were intended to find the most important uncertainty sources in water saturation calculation. To increase the knowledge of the relationship between R{sub t} and S{sub w} in hydrocarbon sandstone reservoirs and to understand how the pore geometry affects the conductivity (n and m) of the rock a theoretical study was done. It was also an aim to examine the possibility for developing new S{sub w} - equations (or investigation an effective medium model) valid inhydrocarbon sandstone reservoirs. The results are presented in paper 1. A new equation for water saturation calculation in clean sandstone oil reservoirs is addressed in paper 2. A recommendation for best practice of water saturation calculation in non water wet formation is addressed in paper 3. Finally a new equation for water saturation calculation in thinly interbedded sandstone/mudstone reservoirs is presented in paper 4. The papers are titled: 1) Is the saturation exponent n a constant. 2) A New Model for Calculating Water Saturation In 3) Influence of wettability on water saturation modeling. 4) Water Saturation Calculations in Thinly Interbedded Sandstone/mudstone Reservoirs. A

  5. On the pressure drop in Plate Heat Exchangers used as desorbers in absorption chillers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Hernando, N.; de Vega, M. [Energy System Engineering (ISE), Departamento de Ingenieria Termica y de Fluidos, Universidad Carlos III de Madrid, Avda. Universidad, 30, 28911 Leganes, Madrid (Spain); Almendros-Ibanez, J.A. [Escuela de Ingenieros Industriales de Albacete, Departamento de Mecanica Aplicada e Ingenieria de Proyectos, Universidad de Castilla La Mancha, Campus Universitario s/n, 02071 Albacete (Spain); Renewable Energy Research Institute, c/de la Investigacion s/n, 02071 Albacete (Spain); Ruiz, G. [Energy Efficiency and Renewables Department, Tecnicas Reunidas S.A., C/Arapiles No. 13, 10a, 28015 Madrid (Spain)

    2011-02-15

    The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr-H{sub 2}O and NH{sub 3}-H{sub 2}O solutions is studied. For the NH{sub 3}-H{sub 2}O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr-H{sub 2}O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed. (author)

  6. Irreversible catalyst activation enables hyperpolarization and water solubility for NMR signal amplification by reversible exchange.

    Science.gov (United States)

    Truong, Milton L; Shi, Fan; He, Ping; Yuan, Bingxin; Plunkett, Kyle N; Coffey, Aaron M; Shchepin, Roman V; Barskiy, Danila A; Kovtunov, Kirill V; Koptyug, Igor V; Waddell, Kevin W; Goodson, Boyd M; Chekmenev, Eduard Y

    2014-12-04

    Activation of a catalyst [IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD = cyclooctadiene)] for signal amplification by reversible exchange (SABRE) was monitored by in situ hyperpolarized proton NMR at 9.4 T. During the catalyst-activation process, the COD moiety undergoes hydrogenation that leads to its complete removal from the Ir complex. A transient hydride intermediate of the catalyst is observed via its hyperpolarized signatures, which could not be detected using conventional nonhyperpolarized solution NMR. SABRE enhancement of the pyridine substrate can be fully rendered only after removal of the COD moiety; failure to properly activate the catalyst in the presence of sufficient substrate can lead to irreversible deactivation consistent with oligomerization of the catalyst molecules. Following catalyst activation, results from selective RF-saturation studies support the hypothesis that substrate polarization at high field arises from nuclear cross-relaxation with hyperpolarized (1)H spins of the hydride/orthohydrogen spin bath. Importantly, the chemical changes that accompanied the catalyst's full activation were also found to endow the catalyst with water solubility, here used to demonstrate SABRE hyperpolarization of nicotinamide in water without the need for any organic cosolvent--paving the way to various biomedical applications of SABRE hyperpolarization methods.

  7. Multiphase fluid flow and subsequent geochemical transport invariably saturated fractured rocks: 1. Approaches

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Pruess, Karsten

    2000-08-08

    Reactive fluid flow and geochemical transport in unsaturated fractured rocks has received increasing attention for studies of contaminant transport, groundwater quality, waste disposal, acid mine drainage remediation, mineral deposits, sedimentary diagenesis, and fluid-rock interactions in hydrothermal systems. This paper presents methods for modeling geochemical systems that emphasize: (1) involvement of the gas phase in addition to liquid and solid phases in fluid flow, mass transport and chemical reactions, (2) treatment of physically and chemically heterogeneous and fractured rocks, (3) the effect of heat on fluid flow and reaction properties and processes, and (4) the kinetics of fluid-rock interaction. The physical and chemical process model is embodied in a system of partial differential equations for flow and transport, coupled to algebraic equations and ordinary differential equations for chemical interactions. For numerical solution, the continuum equations are discretized in space and time. Space discretization is based on a flexible integral finite difference approach that can use irregular gridding to model geologic structure; time is discretized fully implicitly as a first-order finite difference. Heterogeneous and fractured media are treated with a general multiple interacting continua method that includes double-porosity, dual-permeability, and multi-region models as special cases. A sequential iteration approach is used to treat the coupling between fluid flow and mass transport on the one hand, chemical reactions on the other. Applications of the methods developed here to variably saturated geochemical systems are presented in a companion paper (part 2, this issue).

  8. Radiation effects on ion exchange materials

    Energy Technology Data Exchange (ETDEWEB)

    Gangwer, T.E.; Goldstein, M.; Pillay, K.K.S.

    1977-11-01

    An extensive literature review and data compilation has been completed on the radiation-damage of ion exchange resins. The primary goal of the study has been to review the available literature on ion exchange materials used in, as well as those with potential for use in, the nuclear fuel and waste reprocessing areas. The physical and chemical properties of ion exchangers are reviewed. Experimental parameters useful in characterizing the effects of radiation on synthetic ion exchange resins are identified or defined. In compiling the diverse types of data, an effort was made to present the experimental data or experimentally based parameters in a format that would be useful for inter-comparing radiation effects on resins. When subject to radiation there are various general trends or qualitative effects displayed by the different types of resins. These radiation-trends and effects have been formulated into qualitative statements. The present day level of understanding of the behavior of resins under ionizing radiation is too limited to justify quantitative predictive modeling. The limitations and deficiencies of the literature are discussed and the experimentation needed to achieve quantitative modeling are outlined. 14 figs., 108 references.

  9. Effects of water re-saturation conditions and associated extractives leaching on thermal softening of wet wood

    OpenAIRE

    BREMAUD, Iris; Bardet, Sandrine; Gril, Joseph; Perré, Patrick

    2014-01-01

    International audience; Thermal softening, or thermo-activated viscoelasticity, is involved in several industrial and/or traditional craftsmanship techniques processing of wood. More fundamentally, it represents a very useful probe of chemical differences and/or of physical histories of wood samples [1,2,3,4,5]. Thermal softening of wet (= water-saturated) wood occurs at much lower temperature than that of completely (anhydrous) dried wood [6,7]. Softening of oven-dry wood happens at temperat...

  10. Memory Effects on Nonlinear Temperature and Pressure Wave Propagation in the Boundary between Two Fluid-Saturated Porous Rocks

    OpenAIRE

    Garra, R.; Salusti, E.; Droghei, R.

    2015-01-01

    The evolution of strong transients of temperature and pressure in two adjacent fluid-saturated porous rocks is described by a Burgers equation in an early model of Natale and Salusti (1996). We here consider the effect of a realistic intermediate region between the two media and infer how transient processes can also happen, such as chemical reactions, diffusion of fine particles, and filter cake formations. This suggests enlarging our analysis and taking into account not only punctual quanti...

  11. Numerical modelling of multicomponent LNAPL dissolution kinetics at residual saturation in a saturated subsurface system

    Indian Academy of Sciences (India)

    M Vasudevan; G Suresh Kumar; Indumathi M Nambi

    2014-12-01

    Characterization of aquifers contaminated by petroleum hydrocarbons is limited by the use of dissolution mass transfer correlations developed for single compounds without considering the effects of the mass transfer limitations in presence of other components. A one-dimensional implicit numerical model is developed for the coupled mass transfer and transport processes and the results are analysed using existing mass transfer correlations for better understanding of the single and multicomponent dissolution processes. Themass transfer coefficient in the multicomponent system is found to be more nonlinear and extending with changing slope, unlike the exponential reduction for single compound system. During the initial phase, the dissolution rate of a soluble compound is very high due to the high concentration gradient, and as dissolution progresses, its effective solubility decreases with change in mole fraction. At higher pore volumes, the mole fractions of lower solubility fractions increase which can result in higher effective solubility. The kinetics of interphase mass transfer by dissolution and sorption is favoured by coupled biodegradation. However, mass transfer limitation for more soluble compounds under the conditions of low residual saturation and low mole fraction is observed to be due to low dissolution rate coefficient rather than decreasing concentration gradient.

  12. Elastic laboratory measurements and modeling of saturated basalts

    Science.gov (United States)

    Adam, Ludmila; Otheim, Thomas

    2013-03-01

    Understanding the elastic behavior of basalt is important to seismically monitor volcanoes, subsea basalts, and carbon sequestration in basalt. We estimate the elastic properties of basalt samples from the Snake River Plain, Idaho, at ultrasonic (0.8 MHz) and seismic (2-300 Hz) frequencies. To test the sensitivity of seismic waves to the fluid content in the pore structure, measurements are performed at three saturation conditions: saturated with liquid CO2, water, and dry. When CO2 replaces water, the P-wave velocity drops, on average, by 10%. Vesicles and cracks, observed in the rock microstructure, control the relaxation of pore-fluid pressures in the rock as a wave propagates. The bulk and shear moduli of basalts saturated with liquid CO2 are not frequency dependent, suggesting that fluid pore pressures are in equilibrium between 2 Hz and 0.8 MHz. However, when samples are water saturated, the bulk modulus of the rock is frequency dependent. Modeling with Gassmann's equations predicts the measured saturated rock bulk modulus for all fluids for frequencies below 20 Hz but underpredicts the water-saturated basalt bulk modulus for frequencies greater than 20 Hz. The most likely reason is that the pore-fluid pressures are unrelaxed. Instead, the ultrasonic frequency rock moduli are modeled with high-frequency elastic theories of squirt flow and Kuster-Toksöz (KT). Although KT's model is based on idealized pore shapes, a combination of spheres (vesicles) and penny-shaped cracks (fractures) interpreted and quantified from petrographical data predicts the ultrasonic dry and saturated rock moduli for the measured basalts.

  13. Effects of ionic speciation of lysine on its adsorption and desorption through a sulfone-type ion-exchange column.

    Science.gov (United States)

    Choi, Dong-Hyouk; Lee, Kisay

    2007-09-01

    Lysine produced during microbial fermentation is usually recovered by an ion-exchange process, in which lysine is first converted to the cationic form (by lowering the pH to less than 2.0 with sulfuric acid) and then fed to a cation-exchange column containing an exchanger that has a sulfone group with a weak counterion such as NH4+. Ammonia water with a pH above 11 is then supplied to the column to displace the purified lysine from the column and allow its recovery. To enhance the adsorption capacity and for a possible reduction in chemical consumption, monovalent lysine fed at pH 4 was investigated in comparison with conventional divalent lysine fed at pH 1.5. The adsorption capacity increased by more than 70% on a mass basis using pH 4 feeding compared with pH 1.5 feeding. Lysine adsorbed at pH 4 started to elute earlier than that adsorbed at pH 1.5 when ammonia water was used as the eluant solution, and the extent of early elution became more notable at lower concentrations of ammonia. Moreover, the elution of monovalent lysine fed at pH 4 displayed a stiffer front boundary and higher peak concentration. However, when the ammonium concentration was greater than 2.0 N, complete saturation of the bed was delayed during adsorption and the percent recovery yield from elution was lowered, both drawbacks that were considered inevitable features originating from the increased adsorption of monovalent lysine.

  14. Diurnal fluctuations of electrical conductivity in a pre-alpine river: Effects of photosynthesis and groundwater exchange

    Science.gov (United States)

    Hayashi, Masaki; Vogt, Tobias; Mächler, Lars; Schirmer, Mario

    2012-07-01

    SummaryDiurnal fluctuations of dissolved oxygen (DO) concentration and pH due to photosynthesis and respiration are commonly observed in rivers that support periphyton growth. Diurnal fluctuations of electrical conductivity (EC) in connection with photosynthesis have also been reported, but mostly in small, first-order streams or in streams fed by karst springs. The objective of this study is to examine the diurnal EC fluctuations in a large river and understand biological, chemical, and hydrological processes controlling the fluctuations, using long-term archived data, focused field monitoring, and laboratory experiments. The study was conducted in the Thur River draining a 1700 km2 catchment in northeastern Switzerland. The river showed distinct diurnal fluctuations of DO and pH caused by photosynthesis and respiration except during December and part of January. Fluctuations were frequently disrupted by spates with peak discharge exceeding 150 m3 s-1, which removed biofilm and periphyton. During a period of low flow (12 m3 s-1) and clear sky, photosynthesis released O2 and consumed CO2 in water during the daytime, thereby increasing pH and the saturation index of calcite. This caused calcite to precipitate and removed Ca and alkalinity from water, and reduced EC. Laboratory experiments showed that the increase in pH and the saturation index alone cannot cause calcite precipitation without the presence of periphyton. It is likely that the precipitation occurs in the microenvironment in the close vicinity of photosynthesizing cells, where the pH and the calcite saturation index are much higher than in the bulk river water. Calcite precipitation stopped during the nighttime despite supersaturated conditions, and EC gradually increased presumably due to the input of Ca and alkalinity by groundwater exchange. The study clearly showed that photosynthesis and calcite precipitation have a strong influence on the chemistry of the large river, and pointed out the need for

  15. Design and Study of Multifarious Plans on Superheated Steam Saturator%过热蒸汽饱和器的多种方案设计研究

    Institute of Scientific and Technical Information of China (English)

    周根明; 程颖

    2011-01-01

    本文基于传热传质基本原理,提出了一种过热蒸汽饱和器,可将换热设备中的过热蒸汽转化成饱和蒸汽.并详细介绍没计了3种供液方案--重力水箱式、文丘里管式和泵式装置,使之满足不同用户的多种需要.%Based on the principle of heat and mass exchange , a type of superheated steam saturator is designed. The superheated steam could be saturated by the saturator. Three plans of feed liquid equipments are described in detail, and the style contains gravity water tank、Venturi tube pattern and pump form. It would be satisfied by the multiple demands of many consumers.

  16. EXCHANGE RATE - REGIMES AND POLICIES

    Directory of Open Access Journals (Sweden)

    Novak Lučić

    2014-12-01

    Full Text Available Exchange rate of one currency is the price of the currency expressed in units of other currency. It is formed by the interaction of supply and demand in the foreign exchange market. Given that the exchange rate has a direct impact on the competitiveness of a country in terms of features of its exports and imports, in its balance of payments, and indirectly the overall economic and social development, in addition to acting in market principles - supply and demand in the formation of the equilibrium exchange rate, exchange rate is subject to different, stronger or weaker, more or less, forms of intervention. In the search for the optimal exchange rate policy of the national currency, the monetary authorities are positioned between the two extremes - the complete abandonment of the exchange rate to the market laws of supply and demand, or fixing the exchange rate for any of the selected anchor currency.

  17. Data Exchange Inventory (DEXI) System

    Data.gov (United States)

    Social Security Administration — DEXI is an intranet application used by SSA users to track all incoming and outgoing data exchanges between SSA and our data exchange partners. Information such as...

  18. Soil chemical atributtes on brachiaria spp in integrated crop livestock system

    Directory of Open Access Journals (Sweden)

    Valdinei Tadeu Paulino

    2013-12-01

    Full Text Available Integrated crop-livestock systems have attracted more interest in the last few years due to their capacity of improving stability and sustainability of agricultural systems when compared to more specialized production ones. The crop-livestock integration is an effective technique, but complex to maintain pasture productivity and its recovery, whose efficiency depends on soil physical management and its chemical fertility. Regarding the soil fertility, the corrective practices generally begin with the liming due to the high acidity of most Brazilian soils and low levels of Ca and Mg in the exchange complex and high Al saturation. In areas of crop-livestock systems, liming corrects the surface acidity potential. However, this practice can leave the subsoil with excess aluminum and lack of calcium, which inhibit root growth and affect the absorption of water and nutrients. The application of gypsum allows the improvement of the subsoil, reducing Al saturation and increasing levels of calcium and sulfur. The aim of this study was to investigate changes in the soil chemical properties of a Haplorthox soil in integrated crop-livestock system (ICL with Brachiaria brizantha cv. Marandu and Piatã, Brachiaria ruziziensis with gypsum and liming application. This study was conducted at the Instituto de Zootecnia, Nova Odessa/SP, a pasture established on a soil with medium texture (61.4% sand, silt 14.6% and 24.0% clay. The treatment plots consisted on integration crop-livestock (ICL cultivated - maize and B. Marandu,  ICL - maize and B. ruziziensis, ICL - maize and B. Piatã and an untreated control group (control - without liming and fertilization grazed pasture throughout the year, located immediately adjacent to the ICL evaluation, which was cultivated for 25 years with B. brizantha cv. Marandu. All pastures were desiccated in October with glyphosate-based herbicide (4 liters per hectare. Then gypsum (1.2 Mg ha-1 and liming (1.2 Mg ha-1 were applied

  19. Diffusion of inorganic chemical species in compacted clay soil

    Science.gov (United States)

    Shackelford, Charles D.; Daniel, David E.; Liljestrand, Howard M.

    1989-08-01

    This research was conducted to study the diffusion of inorganic chemicals in compacted clay soil for the design of waste containment barriers. The effective diffusion coefficients ( D ∗) of anionic (Cl -, Br -, and I -) and cationic (K +, Cd 2+, and Zn 2+) species in a synthetic leachate were measured. Two clay soils were used in the study. The soils were compacted and pre-soaked to minimize mass transport due to suction in the soil. The results of the diffusion tests were analyzed using two analytical solutions to Fick's second law and a commercially available semi-analytical solution, POLLUTE 3.3. Mass balance calculations were performed to indicate possible sinks/sources in the diffusion system. Errors in mass balance were attributed to problems with the chemical analysis (I -), the inefficiency of the extraction procedure (K +), precipitation (Cd 2+ and Zn 2+), and chemical complexation (Cl - and Br -). The D ∗ values for Cl - reported in this study are in excellent agreement with previous findings for other types of soil. The D ∗ values for the metals (K +, Cd 2+, and Zn 2+) are thought to be high (conservative) due to: (1) Ca 2+ saturation of the exchange complex of the clays; (2) precipitation of Cd 2+ and Zn 2+; and (3) nonlinear adsorption behavior. In general, high D ∗ values and conservative designs of waste containment barriers will result if the procedures described in this study are used to determine D ∗ and the adsorption behavior of the solutes is similar to that described in this study.

  20. The Exchange Rate Forecasting Puzzle

    OpenAIRE

    Francis Vitek

    2005-01-01

    We survey and update the empirical literature concerning the predictability of nominal exchange rates using structural macroeconomic models over the recent floating exchange rate period. In particular, we consider both flexible and sticky price versions of the monetary model of nominal exchange rate determination. In agreement with the existing empirical literature, we find that nominal exchange rate movements are difficult to forecast, with a random walk generally dominating the monetary mod...

  1. Geology Exchange Program

    Science.gov (United States)

    Because geology professors cannot bring ore deposits from around the globe into their classrooms, the next best thing is to take their students to the deposits, according to David Norman, an associate professor of geochemistry at New Mexico Tech and Angus Moore of the Royal School of Mines. They organized a new exchange program between the New Mexico Institute of Mining and Technology in Socorro, N.M., and the Royal School of Mines in London, England. In May, 14 students from England toured deposits in New Mexico, Arizona, Utah, and Colorado; in the photograph, Norman (on the right) describes a rock from a New Mexico ore deposit to some of the visitors from England. In early June a contingency from New Mexico Tech began studying deposits in England, Spain, and Portugal. Norman and Moore say that the exchange program may be expanded next year.

  2. Analytical model for flux saturation in sediment transport.

    Science.gov (United States)

    Pähtz, Thomas; Parteli, Eric J R; Kok, Jasper F; Herrmann, Hans J

    2014-05-01

    The transport of sediment by a fluid along the surface is responsible for dune formation, dust entrainment, and a rich diversity of patterns on the bottom of oceans, rivers, and planetary surfaces. Most previous models of sediment transport have focused on the equilibrium (or saturated) particle flux. However, the morphodynamics of sediment landscapes emerging due to surface transport of sediment is controlled by situations out of equilibrium. In particular, it is controlled by the saturation length characterizing the distance it takes for the particle flux to reach a new equilibrium after a change in flow conditions. The saturation of mass density of particles entrained into transport and the relaxation of particle and fluid velocities constitute the main relevant relaxation mechanisms leading to saturation of the sediment flux. Here we present a theoretical model for sediment transport which, for the first time, accounts for both these relaxation mechanisms and for the different types of sediment entrainment prevailing under different environmental conditions. Our analytical treatment allows us to derive a closed expression for the saturation length of sediment flux, which is general and thus can be applied under different physical conditions.

  3. Repulsion-based model for contact angle saturation in electrowetting.

    Science.gov (United States)

    Ali, Hassan Abdelmoumen Abdellah; Mohamed, Hany Ahmed; Abdelgawad, Mohamed

    2015-01-01

    We introduce a new model for contact angle saturation phenomenon in electrowetting on dielectric systems. This new model attributes contact angle saturation to repulsion between trapped charges on the cap and base surfaces of the droplet in the vicinity of the three-phase contact line, which prevents these surfaces from converging during contact angle reduction. This repulsion-based saturation is similar to repulsion between charges accumulated on the surfaces of conducting droplets which causes the well known Coulombic fission and Taylor cone formation phenomena. In our model, both the droplet and dielectric coating were treated as lossy dielectric media (i.e., having finite electrical conductivities and permittivities) contrary to the more common assumption of a perfectly conducting droplet and perfectly insulating dielectric. We used theoretical analysis and numerical simulations to find actual charge distribution on droplet surface, calculate repulsion energy, and minimize energy of the total system as a function of droplet contact angle. Resulting saturation curves were in good agreement with previously reported experimental results. We used this proposed model to predict effect of changing liquid properties, such as electrical conductivity, and system parameters, such as thickness of the dielectric layer, on the saturation angle, which also matched experimental results.

  4. Saturated and trans fats and dementia: a systematic review.

    Science.gov (United States)

    Barnard, Neal D; Bunner, Anne E; Agarwal, Ulka

    2014-09-01

    Cognitive disorders of later life are potentially devastating. To estimate the relationship between saturated and trans fat intake and risk of cognitive disorders. PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials were searched for studies reporting saturated or trans fat intake and incident dementia, Alzheimer's disease (AD), or mild cognitive impairment (MCI) or cognitive decline. Only observational studies met the inclusion criteria: 4 for AD or other dementias, 4 for MCI, and 4 for cognitive decline. Saturated fat intake was positively associated with AD risk in 3 of 4 studies, whereas the fourth suggested an inverse relationship. Saturated fat intake was also positively associated with total dementia in 1 of 2 studies, with MCI in 1 of 4 studies, and with cognitive decline in 2 of 4 studies. Relationships between trans fat intake and dementia were examined in 3 reports with mixed results. Several, although not all, prospective studies indicate relationships between saturated and trans fat intake and risk of cognitive disorders.

  5. RESEARCH METHODS OF SATURATED VAPOR PRESSURE AND EXPERIMENTAL INSTALLATIONS

    Directory of Open Access Journals (Sweden)

    Kharchenko P. M.

    2015-02-01

    Full Text Available The static method is the most common, because it is applicable for measuring SVP of substances in wide ranges of temperatures and pressures. The essence of the method consists in measuring of vapor pressure in equilibrium with its liquid at a given temperature. Dynamic method is based on measurement of the boiling point of the liquid at a certain pressure. Saturation method of moving gas used in the case when the SVP does not exceed a few mm Hg. The method consists the following: the liquid is passed through the inert gas and saturated with vapor of liquids and then it flows into a cooler where the absorbed vapors are condensed. Knowing the amount of absorbed liquid and gas, as well as their molecular weight, allow us calculate saturated vapor pressure of the liquid. Knudsen effusion method is applicable for the measurement of very low pressures (up to 100 Pa. This method consists in researching of depending between the pressure and volume of saturated steam at a constant temperature. At the point of saturation an isotherm should have a break and turn into a straight line. Chromatographic method is based on complete chromatographic analysis of liquid and calculating the sum of partial pressures of all mixture components. Also, the article has a description of existing experimental installation for these researches and their advantages and disadvantages compared with each other

  6. Seasonal variations of halite saturation in the Dead Sea

    Science.gov (United States)

    Sirota, Ido; Arnon, Ali; Lensky, Nadav G.

    2016-09-01

    Hypersaline lakes and seas were common in the past, precipitating thick evaporitic salt deposits. The only modern analogue for the paleolimnology of deep salt-saturated aquatic environments exists in the Dead Sea. In this study, we present new insights from the Dead Sea on the role of seasonal thermohaline stratification and water balance on the seasonal and depth variations of the degree of saturation of halite (salt) and the rate of halite growth along the water column. We developed methodologies to accurately determine the empirical degree of halite saturation of the lake based on high accuracy densitometry, and to quantify halite growth rate along the water column. During summer, the epilimnion is undersaturated and halite is dissolved, whereas during winter the entire water column is supersaturated and crystallizes halite. This result is not trivial because the variations in the water balance suggest the opposite; summer is associated with higher loss of water by evaporation from the lake compared to the winter. Hence, the thermal effect overcomes the hydrological balance effect and thus governs the seasonal saturation cycle. The hypolimnion is supersaturated with respect to halite and crystallizes throughout the year, with higher super saturation and higher crystallization rates during winter. During summer, simultaneous opposing environments coexist—an undersaturated epilimnion that dissolves halite and a supersaturated hypolimnion that crystallizes halite, which results in focusing of halite deposits in the deep hypolimnetic parts of the evaporitic basins and thinning the shallow epilimnetic deposits.

  7. Exchange rate rebounds after foreign exchange market interventions

    Science.gov (United States)

    Hoshikawa, Takeshi

    2017-03-01

    This study examined the rebounds in the exchange rate after foreign exchange intervention. When intervention is strongly effective, the exchange rate rebounds at next day. The effect of intervention is reduced slightly by the rebound after the intervention. The exchange rate might have been 67.12-77.47 yen to a US dollar without yen-selling/dollar-purchasing intervention of 74,691,100 million yen implemented by the Japanese government since 1991, in comparison to the actual exchange rate was 103.19 yen to the US dollar at the end of March 2014.

  8. Chemical use

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This is a summary of research and activities related to chemical use on Neal Smith National Wildlife Refuge between 1992 and 2009. The chemicals used on the Refuge...

  9. Chemical Reactors.

    Science.gov (United States)

    Kenney, C. N.

    1980-01-01

    Describes a course, including content, reading list, and presentation on chemical reactors at Cambridge University, England. A brief comparison of chemical engineering education between the United States and England is also given. (JN)

  10. Hydrogen Exchange Mass Spectrometry.

    Science.gov (United States)

    Mayne, Leland

    2016-01-01

    Hydrogen exchange (HX) methods can reveal much about the structure, energetics, and dynamics of proteins. The addition of mass spectrometry (MS) to an earlier fragmentation-separation HX analysis now extends HX studies to larger proteins at high structural resolution and can provide information not available before. This chapter discusses experimental aspects of HX labeling, especially with respect to the use of MS and the analysis of MS data.

  11. Thermoelectric heat exchange element

    Science.gov (United States)

    Callas, James J.; Taher, Mahmoud A.

    2007-08-14

    A thermoelectric heat exchange module includes a first substrate including a heat receptive side and a heat donative side and a series of undulatory pleats. The module may also include a thermoelectric material layer having a ZT value of 1.0 or more disposed on at least one of the heat receptive side and the heat donative side, and an electrical contact may be in electrical communication with the thermoelectric material layer.

  12. Exchange Rate Predictions

    OpenAIRE

    Yablonskyy, Karen

    2012-01-01

    The aim of this thesis is to analyze the foreign exchange currency forecasting techniques. Moreover the central idea behind the topic is to develop the strategy of forecasting by choosing indicators and techniques to make own forecast on currency pair EUR/USD. This thesis work is a mixture of theory and practice analyses. The goal during the work on this project was to study different types of forecasting techniques and make own forecast, practice forecasting and trading on Forex platform, ba...

  13. Heat exchange apparatus

    Science.gov (United States)

    Degtiarenko, Pavel V.

    2003-08-12

    A heat exchange apparatus comprising a coolant conduit or heat sink having attached to its surface a first radial array of spaced-apart parallel plate fins or needles and a second radial array of spaced-apart parallel plate fins or needles thermally coupled to a body to be cooled and meshed with, but not contacting the first radial array of spaced-apart parallel plate fins or needles.

  14. Integrated foreign exchange risk management

    DEFF Research Database (Denmark)

    Aabo, Tom; Høg, Esben; Kuhn, Jochen

    2010-01-01

    Empirical research has focused on export as a proxy for exchange rate exposure and the use of foreign exchange derivatives as an instrument to deal with this exposure. This empirical study applies an integrated foreign exchange risk management approach with a particular focus on the role of impor...

  15. On Exchange QB∞-Rings

    Institute of Scientific and Technical Information of China (English)

    Huanyin Chen

    2007-01-01

    In this paper, we introduce a new class of rings, the QB∞-rings. We investigate necessary and sufficient conditions under which an exchange ring is a QB∞-ring. The modules over an exchange QB∞-ring are studied. Also, we prove that every regular square matrix over an exchange QB∞-ring admits a diagonal reduction by pseudo-invertible matrices.

  16. The stability of exchange networks

    NARCIS (Netherlands)

    Doğan, G.; Assen, M. van; Rijt, A. van de; Buskens, V.W.

    2009-01-01

    Economic and sociological exchange theories predict divisions of exchange benefits given an assumed fixed network of exchange relations. Since network structure has been found to have a large impact on actors’ payoffs, actors have strong incentives for network change.Weanswer the question what happe

  17. The exchangeability of shape

    Directory of Open Access Journals (Sweden)

    Kaba Dramane

    2010-10-01

    Full Text Available Abstract Background Landmark based geometric morphometrics (GM allows the quantitative comparison of organismal shapes. When applied to systematics, it is able to score shape changes which often are undetectable by traditional morphological studies and even by classical morphometric approaches. It has thus become a fast and low cost candidate to identify cryptic species. Due to inherent mathematical properties, shape variables derived from one set of coordinates cannot be compared with shape variables derived from another set. Raw coordinates which produce these shape variables could be used for data exchange, however they contain measurement error. The latter may represent a significant obstacle when the objective is to distinguish very similar species. Results We show here that a single user derived dataset produces much less classification error than a multiple one. The question then becomes how to circumvent the lack of exchangeability of shape variables while preserving a single user dataset. A solution to this question could lead to the creation of a relatively fast and inexpensive systematic tool adapted for the recognition of cryptic species. Conclusions To preserve both exchangeability of shape and a single user derived dataset, our suggestion is to create a free access bank of reference images from which one can produce raw coordinates and use them for comparison with external specimens. Thus, we propose an alternative geometric descriptive system that separates 2-D data gathering and analyzes.

  18. Timing Foreign Exchange Markets

    Directory of Open Access Journals (Sweden)

    Samuel W. Malone

    2016-03-01

    Full Text Available To improve short-horizon exchange rate forecasts, we employ foreign exchange market risk factors as fundamentals, and Bayesian treed Gaussian process (BTGP models to handle non-linear, time-varying relationships between these fundamentals and exchange rates. Forecasts from the BTGP model conditional on the carry and dollar factors dominate random walk forecasts on accuracy and economic criteria in the Meese-Rogoff setting. Superior market timing ability for large moves, more than directional accuracy, drives the BTGP’s success. We explain how, through a model averaging Monte Carlo scheme, the BTGP is able to simultaneously exploit smoothness and rough breaks in between-variable dynamics. Either feature in isolation is unable to consistently outperform benchmarks throughout the full span of time in our forecasting exercises. Trading strategies based on ex ante BTGP forecasts deliver the highest out-of-sample risk-adjusted returns for the median currency, as well as for both predictable, traded risk factors.

  19. Experimental study on heat exchange of several types of exchangers

    Institute of Scientific and Technical Information of China (English)

    周志华; 赵振华; 于洋

    2009-01-01

    Aiming at the ground-coupled source heat pump that possesses the shortcomings of occupying larger land,this article studies the heat exchanged of heat exchanger in piling,and compares it with common heat exchangers buried directly. The result indicates that the heat exchanger makes the best use of structure of building,saves land,reduces the construction cost,and the heat exchanged is obviously more than exchangers buried directly. In winter condition,when W-shape pipe heat exchanger in pile foundation is 50 m deep and diameter is 800 mm,it transfers 1.2-1.3 times as large as the one of single U-shape buried directly at the flow rate of 0.6 m/s,whose borehole diameter is 300 mm. And in summer condition it does about 2.0-2.3 times as that of U-shape one.

  20. Determining the Porosity and Saturated Hydraulic Conductivity of Binary Mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.; Ward, Anderson L.; Keller, Jason M.

    2009-09-27

    Gravels and coarse sands make up significant portions of some environmentally important sediments, while the hydraulic properties of the sediments are typically obtained in the laboratory using only the fine fraction (e.g., <2 mm or 4.75 mm). Researchers have found that the content of gravel has significant impacts on the hydraulic properties of the bulk soils. Laboratory experiments were conducted to measure the porosity and the saturated hydraulic conductivity of binary mixtures with different fractions of coarse and fine components. We proposed a mixing-coefficient model to estimate the porosity and a power-averaging method to determine the effective particle diameter and further to predict the saturated hydraulic conductivity of binary mixtures. The proposed methods could well estimate the porosity and saturated hydraulic conductivity of the binary mixtures for the full range of gravel contents and was successfully applied to two data sets in the literature.