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Sample records for accelerated degradation studies

  1. Nylon 6.6 accelerated aging studies : thermal-oxidative degradation and its interaction with hydrolysis.

    SciTech Connect

    Bernstein, Robert; Derzon, Dora Kay; Gillen, Kenneth T.

    2004-06-01

    Accelerated aging of Nylon 6.6 fibers used in parachutes has been conducted by following the tensile strength loss under both thermal-oxidative and 100% relative humidity conditions. Thermal-oxidative studies (air circulating ovens) were performed for time periods of weeks to years at temperatures ranging from 37 C to 138 C. Accelerated aging humidity experiments (100% RH) were performed under both an argon atmosphere to examine the 'pure' hydrolysis pathway, and under an oxygen atmosphere (oxygen partial pressure close to that occurring in air) to mimic true aging conditions. As expected the results indicated that degradation caused by humidity is much more important than thermal-oxidative degradation. Surprisingly when both oxygen and humidity were present the rate of degradation was dramatically enhanced relative to humidity aging in the absence of oxygen. This significant and previously unknown phenomena underscores the importance of careful accelerated aging that truly mimics real world storage conditions.

  2. Membrane Degradation Accelerated Stress Test

    SciTech Connect

    Mukundan, Rangachary; Borup, Rodney L.

    2015-01-21

    These are a set of slides that deal with membrane degradation accelerated stress test. Specifically, the following topics are covered: membrane degradation FCTT drive cycle; membrane ASTs; current membrane ASTs damage mechanisms; proposed membrane AST, RH cycling in H2/Air; current proposed AST; 2min/2min AST damage mechanism; 30sec/45sec RH cycling at OCV.

  3. Accelerated aging studies of UHMWPE. II. Virgin UHMWPE is not immune to oxidative degradation.

    PubMed

    Edidin, A A; Villarraga, M L; Herr, M P; Muth, J; Yau, S S; Kurtz, S M

    2002-08-01

    In Part I of this series, we showed that aging at elevated oxygen pressure is more successful at increasing the depth to which degradation occurs although it, too, generally causes greater degradation at the surface than at the subsurface. Therefore we hypothesized that thermal degradation alone, in the absence of free radicals, could be sufficient to artificially age UHMWPE in a manner analogous to natural aging. In the present study, virgin and air-irradiated UHMWPE (extruded GUR 1050 and compression-molded 1900) were aged up to 4 weeks at elevated oxygen pressure, and the mechanical behavior at the surface and subsurface was examined. All the materials were substantially degraded following 4 weeks of aging, but the spatial variations in the nonirradiated materials more closely mimicked the previously observed subsurface peak of degradation seen in naturally aged UHMWPE following irradiation in air. This aged material could provide a more realistic model for subsurface mechanical degradation, making it suitable for further mechanical testing in venues such as wear simulation.

  4. Accelerated aging studies of UHMWPE. I. Effect of resin, processing, and radiation environment on resistance to mechanical degradation.

    PubMed

    Edidin, A A; Herr, M P; Villarraga, M L; Muth, J; Yau, S S; Kurtz, S M

    2002-08-01

    The resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of ultra-high molecular weight polyethylene (UHMWPE) orthopedic components. Researchers have reported that components fabricated from 1900 resin may oxidize to a lesser extent than components fabricated from GUR resin during shelf aging after gamma sterilization in air. Conflicting reports on the oxidation resistance for 1900 raise the question of whether resin or manufacturing method, or an interaction between resin and manufacturing method, influences the mechanical behavior of UHMWPE. We conducted a series of accelerated aging studies (no aging, aging in oxygen or in nitrogen) to systematically examine the influence of resin (GUR or 1900), manufacturing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE. The small punch testing technique was used to evaluate the mechanical behavior of the materials, and Fourier transform infrared spectroscopy was used to characterize the oxidation in selected samples. Our study showed that the sterilization environment, aging condition, and specimen location (surface or subsurface) significantly affected the mechanical behavior of UHMWPE. Each of the three polyethylenes evaluated seem to degrade according to a similar pathway after artificial aging in oxygen and gamma irradiation in air. The initial ability of the materials to exhibit post-yield strain hardening was significantly compromised by degradation. In general, there were only minor differences in the aging behavior of molded and extruded GUR 1050, whereas the molded 1900 material seemed to degrade slightly faster than either of the 1050 materials.

  5. Degradation mechanisms and accelerated aging test design

    SciTech Connect

    Clough, R L; Gillen, K T

    1985-01-01

    The fundamental mechanisms underlying the chemical degradation of polymers can change as a function of environmental stress level. When this occurs, it greatly complicates any attempt to use accelerated tests for predicting long-term material degradation behaviors. Understanding how degradation mechanisms can change at different stress levels facilitates both the design and the interpretation of aging tests. Oxidative degradation is a predominant mechanism for many polymers exposed to a variety of different environments in the presence of air, and there are two mechanistic considerations which are widely applicable to material oxidation. One involves a physical process, oxygen diffusion, as a rate-limiting step. This mechanism can predominate at high stress levels. The second is a chemical process, the time-dependent decomposition of peroxide species. This leads to chain branching and can become a rate-controlling factor at lower stress levels involving time-scales applicable to use environments. The authors describe methods for identifying the operation of these mechanisms and illustrate the dramatic influence they can have on the degradation behaviors of a number of polymer types. Several commonly used approaches to accelerated aging tests are discussed in light of the behaviors which result from changes in degradation mechanisms. 9 references, 4 figures.

  6. HPLC and HPLC/MS/MS Studies on Stress, Accelerated and Intermediate Degradation Tests of Antivirally Active Tricyclic Analog of Acyclovir.

    PubMed

    Lesniewska, Monika A; Dereziński, Paweł; Klupczyńska, Agnieszka; Kokot, Zenon J; Ostrowski, Tomasz; Zeidler, Joanna; Muszalska, Izabela

    2015-01-01

    The degradation behavior of a tricyclic analog of acyclovir [6-(4-MeOPh)-TACV] was determined in accordance with International Conference on Harmonization guidelines for good clinical practice under different stress conditions (neutral hydrolysis, strong acid/base degradation, oxidative decomposition, photodegradation, and thermal degradation). Accelerated [40±2°C/75%±5% relative humidity (RH)] and intermediate (30±2°C/65%±5% RH) stability tests were also performed. For observation of the degradation of the tested compound the RP-HPLC was used, whereas for the analysis of its degradation products HPLC/MS/MS was used. Degradation of the tested substance allowed its classification as unstable in neutral environment, acidic/alkaline medium, and in the presence of oxidizing agent. The tested compound was also light sensitive and was classified as photolabile both in solution and in the solid phase. However, the observed photodegradation in the solid phase was at a much lower level than in the case of photodegradation in solution. The study showed that both air temperature and RH had no significant effect on the stability of the tested substance during storage for 1 month at 100°C (dry heat) as well as during accelerated and intermediate tests. Based on the HPLC/MS/MS analysis, it can be concluded that acyclovir was formed as a degradation product of 6-(4-MeOPh)-TACV.

  7. Performance degradation studies on an poly 2,5-benzimidazole high-temperature proton exchange membrane fuel cell using an accelerated degradation technique

    NASA Astrophysics Data System (ADS)

    Jung, Guo-Bin; Chen, Hsin-Hung; Yan, Wei-Mon

    2014-02-01

    In this work, the performance degradation of a poly 2,5-benzimidazole (ABPBI) based high-temperature proton exchange membrane fuel cell (HT-PEMFC) was examined using an accelerated degradation technique (ADT). Experiments using an ADT with 30 min intervals were performed by applying 1.5 V to a membrane electrode assembly (MEA) with hydrogen and nitrogen feeding to the anode and cathode, respectively, to simulate the high voltage generated during fuel cell shutdown and restart. The characterization of the MEAs was performed using in-situ and ex-situ electrochemical methods, such as polarization curves, AC impedance, and cyclic voltammetry (CV), and TEM imaging before and after the ADT experiments. The measured results demonstrated that the ADT testing could be used to dramatically reduce the duration of the degradation. The current output at 0.4 V decreased by 48% after performing ADT testing for 30 min. From the AC impedance, CV and RTGA measurements, the decline in cell performance was found to be primarily due to corrosion and thinning of the catalyst layer (or carbon support) during the first 30 min, leading to the dissolution and agglomeration of the platinum catalyst.

  8. Acceleration of purine degradation by periodontal diseases.

    PubMed

    Barnes, V M; Teles, R; Trivedi, H M; Devizio, W; Xu, T; Mitchell, M W; Milburn, M V; Guo, L

    2009-09-01

    Periodontal diseases, such as gingivitis and periodontitis, are characterized by bacterial plaque accumulation around the gingival crevice and the subsequent inflammation and destruction of host tissues. To test the hypothesis that cellular metabolism is altered as a result of host-bacteria interaction, we performed an unbiased metabolomic profiling of gingival crevicular fluid (GCF) collected from healthy, gingivitis, and periodontitis sites in humans, by liquid and gas chromatography mass spectrometry. The purine degradation pathway, a major biochemical source for reactive oxygen species (ROS) production, was significantly accelerated at the disease sites. This suggests that periodontal-disease-induced oxidative stress and inflammation are mediated through this pathway. The complex host-bacterial interaction was further highlighted by depletion of anti-oxidants, degradation of host cellular components, and accumulation of bacterial products in GCF. These findings provide new mechanistic insights and a panel of comprehensive biomarkers for periodontal disease progression. PMID:19767584

  9. Acceleration of purine degradation by periodontal diseases.

    PubMed

    Barnes, V M; Teles, R; Trivedi, H M; Devizio, W; Xu, T; Mitchell, M W; Milburn, M V; Guo, L

    2009-09-01

    Periodontal diseases, such as gingivitis and periodontitis, are characterized by bacterial plaque accumulation around the gingival crevice and the subsequent inflammation and destruction of host tissues. To test the hypothesis that cellular metabolism is altered as a result of host-bacteria interaction, we performed an unbiased metabolomic profiling of gingival crevicular fluid (GCF) collected from healthy, gingivitis, and periodontitis sites in humans, by liquid and gas chromatography mass spectrometry. The purine degradation pathway, a major biochemical source for reactive oxygen species (ROS) production, was significantly accelerated at the disease sites. This suggests that periodontal-disease-induced oxidative stress and inflammation are mediated through this pathway. The complex host-bacterial interaction was further highlighted by depletion of anti-oxidants, degradation of host cellular components, and accumulation of bacterial products in GCF. These findings provide new mechanistic insights and a panel of comprehensive biomarkers for periodontal disease progression.

  10. Environmental aging in polycrystalline-Si photovoltaic modules: comparison of chamber-based accelerated degradation studies with field-test data

    NASA Astrophysics Data System (ADS)

    Lai, T.; Biggie, R.; Brooks, A.; Potter, B. G.; Simmons-Potter, K.

    2015-09-01

    Lifecycle degradation testing of photovoltaic (PV) modules in accelerated-degradation chambers can enable the prediction both of PV performance lifetimes and of return-on-investment for installations of PV systems. With degradation results strongly dependent on chamber test parameters, the validity of such studies relative to fielded, installed PV systems must be determined. In the present work, accelerated aging of a 250 W polycrystalline silicon module is compared to real-time performance degradation in a similar polycrystalline-silicon, fielded, PV technology that has been operating since October 2013. Investigation of environmental aging effects are performed in a full-scale, industrial-standard environmental chamber equipped with single-sun irradiance capability providing illumination uniformity of 98% over a 2 x 1.6 m area. Time-dependent, photovoltaic performance (J-V) is evaluated over a recurring, compressed night-day cycle providing representative local daily solar insolation for the southwestern United States, followed by dark (night) cycling. This cycle is synchronized with thermal and humidity environmental variations that are designed to mimic, as closely as possible, test-yard conditions specific to a 12 month weather profile for a fielded system in Tucson, AZ. Results confirm the impact of environmental conditions on the module long-term performance. While the effects of temperature de-rating can be clearly seen in the data, removal of these effects enables the clear interpretation of module efficiency degradation with time and environmental exposure. With the temperature-dependent effect removed, the normalized efficiency is computed and compared to performance results from another panel of similar technology that has previously experienced identical climate changes in the test yard. Analysis of relative PV module efficiency degradation for the chamber-tested system shows good comparison to the field-tested system with ~2.5% degradation following

  11. Involvement of microorganisms in accelerated degradation of EPTC in soil

    SciTech Connect

    Tal, A.; Rubin, B.; Katan, J. ); Aharonson, N. )

    1990-04-01

    Accelerated EPTC (S-ethyl dipropylcarbamothioate) degradation was confirmed in a mixed culture of microorganisms derived from a soil with enhanced degradation (history soil) by using {sup 14}C-labeled EPTC. The antibacterial agent chloramphenicol (D-({minus})-threo-2,2-dichloro-N-({beta}-hydroxy-{alpha}-(hydroxymethyl)-p-nitrophenethyl)acetamide) markedly suppressed {sup 14}CO{sub 2} evolution while the antifungal agent cycloheximide (4-((2R)-2((1S,3S,5S)-3,5-dimethyl-2-oxocyclohexyl)-2-hydroxyethyl)glutarimide) did not, suggesting that soil bacteria play a significant role in enhanced EPTC degradation. A fast EPTC bacterial degrader (FD1) strain and a slower one (SD1), which were isolated by a soil enrichment technique from a history soil, were capable of utilizing EPTC as a sole carbon source. Vernolate (S-propyl dipropylcarbamothioate), butylate (S-ethyl bis(2-methylpropyl)carbamothioate), or cycloate (S-ethyl cyclohexylethylcarbamothioate) were also degraded by these bacteria in a pattern similar to that in a soil with enhanced degradation. Inoculation of nonhistory soil with FD1 strain induced accelerated degradation of the herbicide in the soil at rates similar to those in field soils exhibiting EPTC accelerated degradation.

  12. High Modulus Biodegradable Polyurethanes for Vascular Stents: Evaluation of Accelerated in vitro Degradation and Cell Viability of Degradation Products

    PubMed Central

    Sgarioto, Melissa; Adhikari, Raju; Gunatillake, Pathiraja A.; Moore, Tim; Patterson, John; Nagel, Marie-Danielle; Malherbe, François

    2015-01-01

    We have recently reported the mechanical properties and hydrolytic degradation behavior of a series of NovoSorb™ biodegradable polyurethanes (PUs) prepared by varying the hard segment (HS) weight percentage from 60 to 100. In this study, the in vitro degradation behavior of these PUs with and without extracellular matrix (ECM) coating was investigated under accelerated hydrolytic degradation (phosphate buffer saline; PBS/70°C) conditions. The mass loss at different time intervals and the effect of aqueous degradation products on the viability and growth of human umbilical vein endothelial cells (HUVEC) were examined. The results showed that PUs with HS 80% and below completely disintegrated leaving no visual polymer residue at 18 weeks and the degradation medium turned acidic due to the accumulation of products from the soft segment (SS) degradation. As expected the PU with the lowest HS was the fastest to degrade. The accumulated degradation products, when tested undiluted, showed viability of about 40% for HUVEC cells. However, the viability was over 80% when the solution was diluted to 50% and below. The growth of HUVEC cells is similar to but not identical to that observed with tissue culture polystyrene standard (TCPS). The results from this in vitro study suggested that the PUs in the series degraded primarily due to the SS degradation and the cell viability of the accumulated acidic degradation products showed poor viability to HUVEC cells when tested undiluted, however particles released to the degradation medium showed cell viability over 80%. PMID:26000274

  13. Accelerating degradation rate of pure iron by zinc ion implantation.

    PubMed

    Huang, Tao; Zheng, Yufeng; Han, Yong

    2016-12-01

    Pure iron has been considered as a promising candidate for biodegradable implant applications. However, a faster degradation rate of pure iron is needed to meet the clinical requirement. In this work, metal vapor vacuum arc technology was adopted to implant zinc ions into the surface of pure iron. Results showed that the implantation depth of zinc ions was about 60 nm. The degradation rate of pure iron was found to be accelerated after zinc ion implantation. The cytotoxicity tests revealed that the implanted zinc ions brought a slight increase on cytotoxicity of the tested cells. In terms of hemocompatibility, the hemolysis of zinc ion implanted pure iron was lower than 2%. However, zinc ions might induce more adhered and activated platelets on the surface of pure iron. Overall, zinc ion implantation can be a feasible way to accelerate the degradation rate of pure iron for biodegradable applications. PMID:27482462

  14. Statistical Modeling of Photovoltaic Reliability Using Accelerated Degradation Techniques (Poster)

    SciTech Connect

    Lee, J.; Elmore, R.; Jones, W.

    2011-02-01

    We introduce a cutting-edge life-testing technique, accelerated degradation testing (ADT), for PV reliability testing. The ADT technique is a cost-effective and flexible reliability testing method with multiple (MADT) and Step-Stress (SSADT) variants. In an environment with limited resources, including equipment (chambers), test units, and testing time, these techniques can provide statistically rigorous prediction of lifetime and other interesting parameters, such as failure rate, warranty time, mean time to failure, degradation rate, activation energy, acceleration factor, and upper limit level of stress. J-V characterization can be used for degradation data and the generalized Eyring model can be used for the thermal-humidity stress condition. The SSADT model can be constructed based on the cumulative damage model (CEM), which assumes that the remaining test united are failed according to cumulative density function of current stress level regardless of the history on previous stress levels.

  15. Accelerating degradation rate of pure iron by zinc ion implantation

    PubMed Central

    Huang, Tao; Zheng, Yufeng; Han, Yong

    2016-01-01

    Pure iron has been considered as a promising candidate for biodegradable implant applications. However, a faster degradation rate of pure iron is needed to meet the clinical requirement. In this work, metal vapor vacuum arc technology was adopted to implant zinc ions into the surface of pure iron. Results showed that the implantation depth of zinc ions was about 60 nm. The degradation rate of pure iron was found to be accelerated after zinc ion implantation. The cytotoxicity tests revealed that the implanted zinc ions brought a slight increase on cytotoxicity of the tested cells. In terms of hemocompatibility, the hemolysis of zinc ion implanted pure iron was lower than 2%. However, zinc ions might induce more adhered and activated platelets on the surface of pure iron. Overall, zinc ion implantation can be a feasible way to accelerate the degradation rate of pure iron for biodegradable applications. PMID:27482462

  16. Step-Stress Accelerated Degradation Testing for Solar Reflectors: Preprint

    SciTech Connect

    Jones, W.; Elmore, R.; Lee, J.; Kennedy, C.

    2011-09-01

    To meet the challenge to reduce the cost of electricity generated with concentrating solar power (CSP) new low-cost reflector materials are being developed including metalized polymer reflectors and must be tested and validated against appropriate failure mechanisms. We explore the application of testing methods and statistical inference techniques for quantifying estimates and improving lifetimes of concentrating solar power (CSP) reflectors associated with failure mechanisms initiated by exposure to the ultraviolet (UV) part of the solar spectrum. In general, a suite of durability and reliability tests are available for testing a variety of failure mechanisms where the results of a set are required to understand overall lifetime of a CSP reflector. We will focus on the use of the Ultra-Accelerated Weathering System (UAWS) as a testing device for assessing various degradation patterns attributable to accelerated UV exposure. Depending on number of samples, test conditions, degradation and failure patterns, test results may be used to derive insight into failure mechanisms, associated physical parameters, lifetimes and uncertainties. In the most complicated case warranting advanced planning and statistical inference, step-stress accelerated degradation (SSADT) methods may be applied.

  17. Accelerator research studies

    SciTech Connect

    Not Available

    1992-01-01

    The Accelerator Research Studies program at the University of Maryland, sponsored by the Department of Energy under grant number DE-FG05-91ER40642, is currently in the first year of a three-year funding cycle. The program consists of the following three tasks: TASK A, Study of Transport and Longitudinal Compression of Intense, High-Brightness Beams, TASK B, Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams; TASK C, Study of a Gyroklystron High-power Microwave Source for Linear Colliders. In this report we document the progress that has been made during the past year for each of the three tasks.

  18. Detecting and Confirming Accelerated Atrazine Degradation in Illinois Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Technical abstract: Enhanced degradation of atrazine has been documented in many parts of the world where the herbicide has been extensively used. Atrazine is widely used in corn in Illinois, but enhanced degradation in the field has not been documented. In this study, the dissipation of atrazine...

  19. Degradation of entanglement between two accelerated parties: Bell states under the Unruh effect

    NASA Astrophysics Data System (ADS)

    Richter, Benedikt; Omar, Yasser

    2015-08-01

    We study the entanglement of families of Unruh modes in the Bell states | Φ±>=1 / √{2 }(|00 > ±|11 >) and | Ψ±>=1 / √{2 }(|01 > ±|10 >) shared by two accelerated observers and find fundamental differences in the robustness of entanglement against acceleration for these states. States Ψ± are entangled for all finite accelerations, whereas, due to the Unruh effect, states Φ± lose their entanglement for finite accelerations. This is true for Bell states of two bosonic modes, as well as for Bell states of a bosonic and a fermionic mode. Furthermore, there are also differences in the degradation of entanglement for Bell states of fermionic modes. We reveal the origin of these distinct characteristics of entanglement degradation and discuss the role that is played by particle statistics. Our studies suggest that the behavior of entanglement in accelerated frames strongly depends on the occupation patterns of the constituent states, whose superposition constitutes the entangled state, where especially states Φ± and Ψ± exhibit distinct characteristics regarding entanglement degradation. Finally, we point out possible implications of hovering over a black hole for these states.

  20. Degradation mechanisms and accelerated testing in PEM fuel cells

    SciTech Connect

    Borup, Rodney L; Mukundan, Rangachary

    2010-01-01

    The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. Although there has been recent progress in improving durability, further improvements are needed to meet the commercialization targets. Past improvements have largely been made possible because of the fundamental understanding of the underlying degradation mechanisms. By investigating component and cell degradation modes; defining the fundamental degradation mechanisms of components and component interactions new materials can be designed to improve durability. Various factors have been shown to affect the useful life of PEM fuel cells. Other issues arise from component optimization. Operational conditions (such as impurities in either the fuel and oxidant stream), cell environment, temperature (including subfreezing exposure), pressure, current, voltage, etc.; or transient versus continuous operation, including start-up and shutdown procedures, represent other factors that can affect cell performance and durability. The need for Accelerated Stress Tests (ASTs) can be quickly understood given the target lives for fuel cell systems: 5000 hours ({approx} 7 months) for automotive, and 40,000 hrs ({approx} 4.6 years) for stationary systems. Thus testing methods that enable more rapid screening of individual components to determine their durability characteristics, such as off-line environmental testing, are needed for evaluating new component durability in a reasonable turn-around time. This allows proposed improvements in a component to be evaluated rapidly and independently, subsequently allowing rapid advancement in PEM fuel cell durability. These tests are also crucial to developers in order to make sure that they do not sacrifice durability while making improvements in costs (e.g. lower platinum group metal [PGM] loading) and performance (e.g. thinner membrane or a GDL with better water management properties). To

  1. Accelerated Testing of UH-60 Viscous Bearings for Degraded Grease Fault

    NASA Technical Reports Server (NTRS)

    Dykas, Brian; Hood, Adrian; Krantz, Timothy; Klemmer, Marko

    2015-01-01

    An accelerated aging investigation of critical aviation bearings lubricated with MIL-PRF- 81322 grease was conducted to derive an understanding of the mechanisms of grease degradation and loss of lubrication over time. The current study focuses on UH-60 Black Hawk viscous damper bearings supporting the tail rotor driveshaft, which were subjected to more than 5800 hours of testing in a heated environment to accelerate the deterioration of the grease. The mechanism of grease degradation is a reduction in the oil/thickener ratio rather than the expected chemical degradation of grease constituents. Over the course of testing, vibration and temperature monitoring of bearings was conducted and trends for failing bearings are presented.

  2. Step-Stress Accelerated Degradation Testing (SSADT) for Photovoltaic (PV) Devices and Cells (Presentation)

    SciTech Connect

    Lee, J.; Elmore, R.; Suh, C.; Jones, W.

    2010-10-01

    Presentation on step-stress accelerated degradation testing (SSADT) for photovoltaics (PV). Developed are a step-stress degradation test (SSADT) for PV reliability tests and a lifetime prediction model for PV products.

  3. Stochastic Modeling and Analysis of Multiple Nonlinear Accelerated Degradation Processes through Information Fusion.

    PubMed

    Sun, Fuqiang; Liu, Le; Li, Xiaoyang; Liao, Haitao

    2016-01-01

    Accelerated degradation testing (ADT) is an efficient technique for evaluating the lifetime of a highly reliable product whose underlying failure process may be traced by the degradation of the product's performance parameters with time. However, most research on ADT mainly focuses on a single performance parameter. In reality, the performance of a modern product is usually characterized by multiple parameters, and the degradation paths are usually nonlinear. To address such problems, this paper develops a new s-dependent nonlinear ADT model for products with multiple performance parameters using a general Wiener process and copulas. The general Wiener process models the nonlinear ADT data, and the dependency among different degradation measures is analyzed using the copula method. An engineering case study on a tuner's ADT data is conducted to demonstrate the effectiveness of the proposed method. The results illustrate that the proposed method is quite effective in estimating the lifetime of a product with s-dependent performance parameters. PMID:27509499

  4. Acceleration of potential-induced degradation by salt-mist preconditioning in crystalline silicon photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Suzuki, Soh; Nishiyama, Naoki; Yoshino, Seiji; Ujiro, Takumi; Watanabe, Shin; Doi, Takuya; Masuda, Atsushi; Tanahashi, Tadanori

    2015-08-01

    We examined the sequential effects of salt-mist stress followed by high-system-voltage stress on the power loss of crystalline silicon photovoltaic (PV) modules to determine whether a crucial failure as potential-induced degradation (PID) is accelerated by material-property changes caused by the long-term effects of a less harmful stress such as salt-mist spraying. Degradation profiles confirmed in this study show that PID is accelerated by certain types of salt-mist preconditioning. For the acceleration of PID, the contribution of sodium ions liberated from the front glass of the PV module seems to be excluded. Therefore, we consider that the sodium ions penetrating into the PV modules from the ambient environment may also cause degradation according to the proposed mechanisms of PID, as the sodium ions existing in the front glass cause PID. Furthermore, this type of degradation may indicate the wear-out phenomenon after a long-term exposure in the field (especially near the coast).

  5. Hycrest crested wheatgrass accelerates the degradation of pentachlorophenol in soil

    NASA Technical Reports Server (NTRS)

    Ferro, A. M.; Sims, R. C.; Bugbee, B.

    1994-01-01

    We investigated the effects of vegetation on the fate of pentachlorophenol (PCP) in soil using a novel high-flow sealed test system. Pentachlorophenol has been widely used as a wood preservative, and this highly toxic biocide contaminates soil and ground water at many sites. Although plants are known to accelerate the rates of degradation of certain soil contaminants, this approach has not been thoroughly investigated for PCP. The fate of [14C]PCP, added to soil at a concentration of 100 mg/kg, was compared in three unplanted and three planted systems. The plant used was Hycrest, a perennial, drought-tolerant cultivar of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes]. The flow-through test system allowed us to maintain a budget for 14C-label as well as monitor mineralization (breakdown to 14CO2) and volatilization of the test compound in a 155-d trial. In the unplanted systems, an average of 88% of the total radiolabel remained in the soil and leachate and only 6% was mineralized. In the planted system, 33% of the radiolabel remained in the soil plus leachate, 22% was mineralized, and 36% was associated with plant tissue (21% with the root fraction and 15% with shoots). Mineralization rates were 23.1 mg PCP mineralized kg-1 soil in 20 wk in the planted system, and for the unplanted system 6.6 mg PCP kg-1 soil for the same time period. Similar amounts of volatile organic material were generated in the two systems (1.5%). Results indicated that establishing crested wheatgrass on PCP-contaminated surface soils may accelerate the removal of the contaminant.

  6. Limitations of predicting in vivo biostability of multiphase polyurethane elastomers using temperature-accelerated degradation testing.

    PubMed

    Padsalgikar, Ajay; Cosgriff-Hernandez, Elizabeth; Gallagher, Genevieve; Touchet, Tyler; Iacob, Ciprian; Mellin, Lisa; Norlin-Weissenrieder, Anna; Runt, James

    2015-01-01

    Polyurethane biostability has been the subject of intense research since the failure of polyether polyurethane pacemaker leads in the 1980s. Accelerated in vitro testing has been used to isolate degradation mechanisms and predict clinical performance of biomaterials. However, validation that in vitro methods reproduce in vivo degradation is critical to the selection of appropriate tests. High temperature has been proposed as a method to accelerate degradation. However, correlation of such data to in vivo performance is poor for polyurethanes due to the impact of temperature on microstructure. In this study, we characterize the lack of correlation between hydrolytic degradation predicted using a high temperature aging model of a polydimethylsiloxane-based polyurethane and its in vivo performance. Most notably, the predicted molecular weight and tensile property changes from the accelerated aging study did not correlate with clinical explants subjected to human biological stresses in real time through 5 years. Further, DMTA, ATR-FTIR, and SAXS experiments on samples aged for 2 weeks in PBS indicated greater phase separation in samples aged at 85°C compared to those aged at 37°C and unaged controls. These results confirm that microstructural changes occur at high temperatures that do not occur at in vivo temperatures. In addition, water absorption studies demonstrated that water saturation levels increased significantly with temperature. This study highlights that the multiphase morphology of polyurethane precludes the use of temperature accelerated biodegradation for the prediction of clinical performance and provides critical information in designing appropriate in vitro tests for this class of materials.

  7. Encapsulation of fibroblasts causes accelerated alginate hydrogel degradation.

    PubMed

    Hunt, N C; Smith, A M; Gbureck, U; Shelton, R M; Grover, L M

    2010-09-01

    Calcium-alginate hydrogel has been widely studied as a material for cell encapsulation for tissue engineering. At present, the effect that cells have on the degradation of alginate hydrogel is largely unknown. We have shown that fibroblasts encapsulated at a density of 7.5 x 10(5) cells ml(-1) in both 2% and 5% w/v alginate remain viable for at least 60 days. Rheological analysis was used to study how the mechanical properties exhibited by alginate hydrogel changed during 28 days in vitro culture. Alginate degradation was shown to occur throughout the study but was greatest within the first 7 days of culture for all samples, which correlated with a sharp release of calcium ions from the construct. Fibroblasts were shown to increase the rate of degradation during the first 7 days when compared with acellular samples in both 2% and 5% w/v gels, but after 28 days both acellular and cell-encapsulating samples retained disc-shaped morphologies and gel-like spectra. The results demonstrate that although at an early stage cells influence the mechanical properties of encapsulating alginate, over a longer period of culture, the hydrogels retain sufficient mechanical integrity to exhibit gel-like properties. This allows sustained immobilization of the cells at the desired location in vivo where they can produce extracellular matrix and growth factors to expedite the healing process.

  8. Experimental design and analysis for accelerated degradation tests with Li-ion cells.

    SciTech Connect

    Doughty, Daniel Harvey; Thomas, Edward Victor; Jungst, Rudolph George; Roth, Emanuel Peter

    2003-08-01

    This document describes a general protocol (involving both experimental and data analytic aspects) that is designed to be a roadmap for rapidly obtaining a useful assessment of the average lifetime (at some specified use conditions) that might be expected from cells of a particular design. The proposed experimental protocol involves a series of accelerated degradation experiments. Through the acquisition of degradation data over time specified by the experimental protocol, an unambiguous assessment of the effects of accelerating factors (e.g., temperature and state of charge) on various measures of the health of a cell (e.g., power fade and capacity fade) will result. In order to assess cell lifetime, it is necessary to develop a model that accurately predicts degradation over a range of the experimental factors. In general, it is difficult to specify an appropriate model form without some preliminary analysis of the data. Nevertheless, assuming that the aging phenomenon relates to a chemical reaction with simple first-order rate kinetics, a data analysis protocol is also provided to construct a useful model that relates performance degradation to the levels of the accelerating factors. This model can then be used to make an accurate assessment of the average cell lifetime. The proposed experimental and data analysis protocols are illustrated with a case study involving the effects of accelerated aging on the power output from Gen-2 cells. For this case study, inadequacies of the simple first-order kinetics model were observed. However, a more complex model allowing for the effects of two concurrent mechanisms provided an accurate representation of the experimental data.

  9. Acceleration of the herbicide isoproturon degradation in wheat by glycosyltransferases and salicylic acid.

    PubMed

    Lu, Yi Chen; Zhang, Shuang; Yang, Hong

    2015-01-01

    Isoproturon (IPU) is a herbicide widely used to prevent weeds in cereal production. Due to its extensive use in agriculture, residues of IPU are often detected in soils and crops. Overload of IPU to crops is associated with human health risks. Hence, there is an urgent need to develop an approach to mitigate its accumulation in crops. In this study, the IPU residues and its degradation products in wheat were characterized using ultra performance liquid chromatography-time of fight tandem-mass spectrometer/mass spectrometer (UPLC-TOF-MS/MS). Most detected IPU-derivatives were sugar-conjugated. Degradation and glycosylation of IPU-derivatives could be enhanced by applying salicylic acid (SA). While more sugar-conjugated IPU-derivatives were identified in wheat with SA application, lower levels of IPU were detected, indicating that SA is able to accelerate intracellular IPU catabolism. All structures of IPU-derivatives and sugar-conjugated products were characterized. Comparative data were provided with specific activities and gene expression of certain glucosyltransferases. A pathway with IPU degradation and glucosylation was discussed. Our work indicates that SA-accelerated degradation is practically useful for wheat crops growing in IPU-contaminated soils because such crops with SA application can potentially lower or minimize IPU accumulation in levels below the threshold for adverse effects.

  10. Degradation of mechanical behavior in UHMWPE after natural and accelerated aging.

    PubMed

    Edidin, A A; Jewett, C W; Kalinowski, A; Kwarteng, K; Kurtz, S M

    2000-07-01

    Ultra-high molecular weight polyethylene (UHMWPE) is known to degrade during natural (shelf) aging following gamma irradiation in air, but the mechanical signature of degradation remains poorly understood. Accelerated aging methods have been developed to reproduce the natural aging process as well as to precondition total joint replacement components prior to joint simulator wear testing. In this study, we compared the mechanical behavior of naturally (shelf) aged and accelerated aged tibial inserts using a previously validated miniature specimen testing technique known as the small punch test. Tibial inserts made-of GUR 1120 and sterilized with 25 to 40 kGy of gamma radiation (in air) in 1988, 1993, and 1997 were obtained; a subset of the 1997 implants were subjected to 4 weeks of accelerated aging in air at 80 degrees C. To determine the spatial variation of mechanical properties within each insert, miniature disk shaped specimens were machined from the surface and subsurface regions of the inserts. Analysis of variance of the test data showed that aging significantly affected the small punch test measures of elastic modulus, initial load, ultimate load, ultimate displacement, and work to failure. The accelerated aging protocol was unable to reproduce the spatial mechanical profile seen in shelf aged components, but it did mechanically degrade the surface of GUR 1120 tibial components to an extent comparable to that seen after 10 years of natural aging. Test specimens showed a fracture morphology consistent with the decreased ductility and toughness which was corroborated by the small punch test metrics of this study. Our data support the hypothesis that UHMWPE undergoes a spatially nonuniform change towards a less ductile (more brittle) mechanical behavior after gamma irradiation in air and shelf aging.

  11. Performance Degradation of Encapsulated Monocrystalline-Si Solar Cells upon Accelerated Weathering Exposures: Preprint

    SciTech Connect

    Glick, S. H.; Pern, F. J.; Watson, G. L.; Tomek, D.; Raaff, J.

    2001-10-01

    Presented at 2001 NCPV Program Review Meeting: Performed accelerated exposures to study performance reliability/materials degradation of encapsulated c-Si cells using weathering protocols in 2 weatherometers. We have performed accelerated exposures to study performance reliability and materials degradation of a total of forty-one 3-cm x 3-cm monocrystalline-Si (c-Si) solar cells that were variously encapsulated using accelerated weathering protocols in two weatherometers (WOMs), with and without front specimen water sprays. Laminated cells (EVA/c-Si/EVA, ethylene vinyl acetate) with one of five superstrate/substrate variations and other features including with and without: (i) load resistance, (ii) Al foil light masks, and (iii) epoxy edge-sealing were studied. Three additional samples, omitting EVA, were exposed under a full-spectrum solar simulator, or heated in an oven, for comparison. After exposures, cell performance decreased irregularly, but to a relatively greater extent for samples exposed in WOM where light, heat, and humidity cycles were present (solar simulator or oven lacked such cycles). EVA laminates in the samples masked with aluminum (Al) foils were observed to retain moisture in WOM with water spray. Moisture effects caused substantial efficiency losses probably related in part to increasing series resistance.

  12. Accelerated calcium phosphate cement degradation due to incorporation of glucono-delta-lactone microparticles.

    PubMed

    Félix Lanao, Rosa P; Sariibrahimoglu, Kemal; Wang, Huanan; Wolke, Joop G C; Jansen, John A; Leeuwenburgh, Sander C G

    2014-01-01

    Injectable calcium phosphate cements (CPC) are frequently used for filling of bone defects due to their excellent osteocompatibility. Their poor degradability, however, limits complete regeneration of bone defects. Organic additives that produce acid by-products are particularly attractive to create macroporosity in situ since CPC degrade by acid dissolution. The aim of the current study was to investigate whether glucono-delta-lactone (GDL) can be used as acid-producing microparticles for incorporation into CPC without compromising its osteocompatibility. Characterization studies confirmed that CPCs containing either low or high amounts of GDL were injectable and self-setting, while a considerable amount of porosity was formed already within 1 day of incubation in phosphate buffered saline due to dissolution of GDL. Histomorphometrical evaluation after 2 weeks of implantation revealed that CPC containing 10% of GDL degraded faster and was replaced by more bone tissue than CPCs containing either Poly (lactic-co-glycolic acid) (PLGA) or gelatin microspheres. Summarizing, the current study showed that CPCs containing appropriate amounts of GDL display accelerated degradation and new bone formation compared with CPCs containing microparticles made of conventional polymers such as PLGA or gelatin. PMID:24041246

  13. The cell-in-series method: A technique for accelerated electrode degradation in redox flow batteries

    DOE PAGES

    Pezeshki, Alan M.; Sacci, Robert L.; Veith, Gabriel M.; Zawodzinski, Thomas A.; Mench, Matthew M.

    2015-11-21

    Here, we demonstrate a novel method to accelerate electrode degradation in redox flow batteries and apply this method to the all-vanadium chemistry. Electrode performance degradation occurred seven times faster than in a typical cycling experiment, enabling rapid evaluation of materials. This method also enables the steady-state study of electrodes. In this manner, it is possible to delineate whether specific operating conditions induce performance degradation; we found that both aggressively charging and discharging result in performance loss. Post-mortem x-ray photoelectron spectroscopy of the degraded electrodes was used to resolve the effects of state of charge (SoC) and current on the electrodemore » surface chemistry. For the electrode material tested in this work, we found evidence that a loss of oxygen content on the negative electrode cannot explain decreased cell performance. Furthermore, the effects of decreased electrode and membrane performance on capacity fade in a typical cycling battery were decoupled from crossover; electrode and membrane performance decay were responsible for a 22% fade in capacity, while crossover caused a 12% fade.« less

  14. The cell-in-series method: A technique for accelerated electrode degradation in redox flow batteries

    SciTech Connect

    Pezeshki, Alan M.; Sacci, Robert L.; Veith, Gabriel M.; Zawodzinski, Thomas A.; Mench, Matthew M.

    2015-11-21

    Here, we demonstrate a novel method to accelerate electrode degradation in redox flow batteries and apply this method to the all-vanadium chemistry. Electrode performance degradation occurred seven times faster than in a typical cycling experiment, enabling rapid evaluation of materials. This method also enables the steady-state study of electrodes. In this manner, it is possible to delineate whether specific operating conditions induce performance degradation; we found that both aggressively charging and discharging result in performance loss. Post-mortem x-ray photoelectron spectroscopy of the degraded electrodes was used to resolve the effects of state of charge (SoC) and current on the electrode surface chemistry. For the electrode material tested in this work, we found evidence that a loss of oxygen content on the negative electrode cannot explain decreased cell performance. Furthermore, the effects of decreased electrode and membrane performance on capacity fade in a typical cycling battery were decoupled from crossover; electrode and membrane performance decay were responsible for a 22% fade in capacity, while crossover caused a 12% fade.

  15. Stochastic Modeling and Analysis of Multiple Nonlinear Accelerated Degradation Processes through Information Fusion

    PubMed Central

    Sun, Fuqiang; Liu, Le; Li, Xiaoyang; Liao, Haitao

    2016-01-01

    Accelerated degradation testing (ADT) is an efficient technique for evaluating the lifetime of a highly reliable product whose underlying failure process may be traced by the degradation of the product’s performance parameters with time. However, most research on ADT mainly focuses on a single performance parameter. In reality, the performance of a modern product is usually characterized by multiple parameters, and the degradation paths are usually nonlinear. To address such problems, this paper develops a new s-dependent nonlinear ADT model for products with multiple performance parameters using a general Wiener process and copulas. The general Wiener process models the nonlinear ADT data, and the dependency among different degradation measures is analyzed using the copula method. An engineering case study on a tuner’s ADT data is conducted to demonstrate the effectiveness of the proposed method. The results illustrate that the proposed method is quite effective in estimating the lifetime of a product with s-dependent performance parameters. PMID:27509499

  16. Degradation Mechanisms and Accelerated Testing in PEM Fuel Cells

    SciTech Connect

    Borup, Rodney L.

    2011-01-01

    The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. Although there has been recent progress in improving durability, further improvements are needed to meet the commercialization targets. Past improvements have largely been made possible because of the fundamental understanding of the underlying degradation mechanisms. By investigating component and cell degradation modes; defining the fundamental degradation mechanisms of components and component interactions new materials can be designed to improve durability. Various factors have been shown to affect the useful life of PEM fuel cells. Other issues arise from component optimization. Operational conditions (such as impurities in either the fuel or oxidant stream), cell environment, temperature (including subfreezing exposure), pressure, current, voltage, etc.; or transient versus continuous operation, including start-up and shutdown procedures, represent other factors that can affect cell performance and durability.

  17. Error-Induced Beam Degradation in Fermilab's Accelerators

    SciTech Connect

    Yoon, Sung-Young Phil

    2008-01-01

    In Part I, three independent models of Fermilab's Booster synchrotron are presented. All three models are constructed to investigate and explore the effects of unavoidable machine errors on a proton beam under the influence of space-charge effects. The first is a stochastic noise model. Electric current fluctuations arising from power supplies are ubiquitous and unavoidable and are a source of instabilities in accelerators of all types. A new noise module for generating the Ornstein-Uhlenbeck (O-U) stochastic noise is first created and incorporated into the existing Object-oriented Ring Beam Injection and Tracking (ORBIT-FNAL) package. After being convinced with a preliminary model that the noise, particularly non-white noise, does matter to beam quality, we proceeded to measure directly current ripples and common-mode voltages from all four Gradient Magnet Power Supplies (GMPS). Then, the current signals are Fourier-analyzed. Based upon the power spectra of current signals, we tune up the Ornstein-Uhlnbeck noise model. As a result, we are able to closely match the frequency spectra between current measurements and the modeled O-U stochastic noise. The stochastic noise modeled upon measurements is applied to the Booster beam in the presence of the full space-charge effects. This noise model, accompanied by a suite of beam diagnostic calculations, manifests that the stochastic noise, impinging upon the beam and coupled to the space-charge effects, can substantially enhance the beam degradation process throughout the injection period. The second model is a magnet misalignment model. It is the first time to utilize the latest beamline survey data for building a magnet-by-magnet misalignment model. Given as-found survey fiducial coordinates, we calculate all types of magnet alignment errors (station error, pitch, yaw, roll, twists, etc.) are implemented in the model. We then follow up with statistical analysis to understand how each type of alignment errors are

  18. Observation of radiation degradation of electrical insulators in the CERN particle accelerators

    NASA Astrophysics Data System (ADS)

    Chevalier, Ch.; Coste, V.; Fontaine, A.; Tavlet, M.

    1999-05-01

    For the selection of polymer-based materials to be used in radiation environments, radiation tests have been performed at the European Organization for Particle Physics Research (CERN) for several decades. According to the recommendations of the IEC Standard 544, mechanical tests are carried out, and the radiation degradation is measured after accelerated irradiations. It is well known that during long-term exposures, oxygen and moisture are allowed to diffuse in the materials and hence to induce more severe degradation; this phenomenon is known as the `dose-rate effect'. During machine shut-downs, samples of rigid and flexible polymeric insulators (magnet-coil resins and cable insulations) have been taken out and tested after several years of exposure in the Super Proton Synchrotron (SPS) and in the Large Electron-Position Collider (LEP). The mechanical test results are compared to the ones after the accelerated qualification tests, and to the ones of a study conducted in 1991 to estimate the lifetime of cables in the radiation environment of LEP 200. They confirm that thermoplastics are more sensitive to long-term irradiations than the thermosetting resins and the composites, but that the dose-rate effect cannot be neglected in the latter.

  19. Amps particle accelerator definition study

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.

    1975-01-01

    The Particle Accelerator System of the AMPS (Atmospheric, Magnetospheric, and Plasmas in Space) payload is a series of charged particle accelerators to be flown with the Space Transportation System Shuttle on Spacelab missions. In the configuration presented, the total particle accelerator system consists of an energetic electron beam, an energetic ion accelerator, and both low voltage and high voltage plasma acceleration devices. The Orbiter is illustrated with such a particle accelerator system.

  20. Report on accelerated corrosion studies.

    SciTech Connect

    Mowry, Curtis Dale; Glass, Sarah Jill; Sorensen, Neil Robert

    2011-03-01

    Sandia National Laboratories (SNL) conducted accelerated atmospheric corrosion testing for the U.S. Consumer Product Safety Commission (CPSC) to help further the understanding of the development of corrosion products on conductor materials in household electrical components exposed to environmental conditions representative of homes constructed with problem drywall. The conditions of the accelerated testing were chosen to produce corrosion product growth that would be consistent with long-term exposure to environments containing humidity and parts per billion (ppb) levels of hydrogen sulfide (H{sub 2}S) that are thought to have been the source of corrosion in electrical components from affected homes. This report documents the test set-up, monitoring of electrical performance of powered electrical components during the exposure, and the materials characterization conducted on wires, screws, and contact plates from selected electrical components. No degradation in electrical performance (measured via voltage drop) was measured during the course of the 8-week exposure, which was approximately equivalent to 40 years of exposure in a light industrial environment. Analyses show that corrosion products consisting of various phases of copper sulfide, copper sulfate, and copper oxide are found on exposed surfaces of the conductor materials including wires, screws, and contact plates. The morphology and the thickness of the corrosion products showed a range of character. In some of the copper wires that were observed, corrosion product had flaked or spalled off the surface, exposing fresh metal to the reaction with the contaminant gasses; however, there was no significant change in the wire cross-sectional area.

  1. In situ accelerated degradation of polyoxyethylene/poly(epsilon-caprolactone) multiblock copolymer by moderate thermal treatment.

    PubMed

    Kim, Jong-Ho; Park, Sang K; Bae, You Han

    2003-01-01

    Alternating amphiphilic multiblock copolymers, consisting of polyoxyethylene (POE) and poly(epsilon-caprolactone) (PCL) of various lengths, were synthesized by a polycondensation reaction between dicarboxylated PEG and dihydroxyl PCL. The polymer formed a physical hydrogel by PCL crystallization. For in vitro hydrolysis in phosphate-buffered saline solution, the change of molecular weight depended on the composing block length of POE. The polymer with longer POE showed a faster decline in molecular weight. The mass remaining at the end of two weeks at 25 degrees C was more than 95 w%. However, when the swollen hydrogels were exposed to temperatures slightly above PCL melting point for 30 min, the degradation rate was accelerated and the mass remaining dropped to less than 10 wt% in one week. In vivo degradation after hydrogel implantation, the polymer degraded as under in vitro. However, the implant irradiated with infrared (IR) accelerated its degradation similar to a treatment with elevated temperature. PMID:14661869

  2. Results of metallographical diagnostic examination of Navy half-watt thermoelectric converters degraded by accelerated tests

    NASA Technical Reports Server (NTRS)

    Rosell, F. E., Jr.; Rouklove, P. G.

    1977-01-01

    To verify the 15-year reliability of the Navy half-watt radioisotope thermoelectric generator (RTG), bismuth-telluride thermoelectric converters were submitted to testing at high temperatures which accelerated the degradation and caused failure of the converters. Metallographic diagnostic examination of failed units verified failure mechanisms. Results of diagnostic examinations are presented.

  3. Uniform and accelerated degradation of pure iron patterned by Pt disc arrays

    PubMed Central

    Huang, Tao; Zheng, Yufeng

    2016-01-01

    Pure iron has been confirmed as a promising biodegradable metal. However, the degradation rate of pure iron should be accelerated to meet the clinical requirements. In this work, two different designs of platinum disc arrays, including sizes of Φ20 μm × S5 μm and Φ4 μm × S4 μm, have been coated on the surface of pure iron. Corrosion tests showed the platinum discs formed plenty of galvanic cells with the iron matrix which significantly accelerated the degradation of pure iron. Simultaneously, due to the designability of the shape, size as well as distribution of Pt discs, the degradation rate as well as degradation uniformity of pure iron can be effectively controlled by coating with platinum discs. The cytotoxicity test results unveiled that Pt discs patterned pure iron exhibited almost no toxicity to human umbilical vein endothelial cells, but a significant inhibition on proliferation of vascular smooth muscle cells. In addition, the hemolysis rate of Pt discs patterned pure iron was lower than 1%. Moreover, Pt discs also effectively reduced the number of adhered platelets. All these results indicated that Pt discs patterning is an effective way to accelerate degradation and improve biocompatibility of pure iron. PMID:27033380

  4. Uniform and accelerated degradation of pure iron patterned by Pt disc arrays.

    PubMed

    Huang, Tao; Zheng, Yufeng

    2016-04-01

    Pure iron has been confirmed as a promising biodegradable metal. However, the degradation rate of pure iron should be accelerated to meet the clinical requirements. In this work, two different designs of platinum disc arrays, including sizes of Φ20 μm × S5 μm and Φ4 μm × S4 μm, have been coated on the surface of pure iron. Corrosion tests showed the platinum discs formed plenty of galvanic cells with the iron matrix which significantly accelerated the degradation of pure iron. Simultaneously, due to the designability of the shape, size as well as distribution of Pt discs, the degradation rate as well as degradation uniformity of pure iron can be effectively controlled by coating with platinum discs. The cytotoxicity test results unveiled that Pt discs patterned pure iron exhibited almost no toxicity to human umbilical vein endothelial cells, but a significant inhibition on proliferation of vascular smooth muscle cells. In addition, the hemolysis rate of Pt discs patterned pure iron was lower than 1%. Moreover, Pt discs also effectively reduced the number of adhered platelets. All these results indicated that Pt discs patterning is an effective way to accelerate degradation and improve biocompatibility of pure iron.

  5. Uniform and accelerated degradation of pure iron patterned by Pt disc arrays

    NASA Astrophysics Data System (ADS)

    Huang, Tao; Zheng, Yufeng

    2016-04-01

    Pure iron has been confirmed as a promising biodegradable metal. However, the degradation rate of pure iron should be accelerated to meet the clinical requirements. In this work, two different designs of platinum disc arrays, including sizes of Φ20 μm × S5 μm and Φ4 μm × S4 μm, have been coated on the surface of pure iron. Corrosion tests showed the platinum discs formed plenty of galvanic cells with the iron matrix which significantly accelerated the degradation of pure iron. Simultaneously, due to the designability of the shape, size as well as distribution of Pt discs, the degradation rate as well as degradation uniformity of pure iron can be effectively controlled by coating with platinum discs. The cytotoxicity test results unveiled that Pt discs patterned pure iron exhibited almost no toxicity to human umbilical vein endothelial cells, but a significant inhibition on proliferation of vascular smooth muscle cells. In addition, the hemolysis rate of Pt discs patterned pure iron was lower than 1%. Moreover, Pt discs also effectively reduced the number of adhered platelets. All these results indicated that Pt discs patterning is an effective way to accelerate degradation and improve biocompatibility of pure iron.

  6. Relatively uniform and accelerated degradation of pure iron coated with micro-patterned Au disc arrays.

    PubMed

    Cheng, J; Huang, T; Zheng, Y F

    2015-03-01

    Pure iron has been proven to be a potential biodegradable metal, but its degradation rate was too slow. To accelerate its biodegradation, micro-patterned Au disc films were deposited on the surface of pure iron by vacuum sputtering. The influence of Au disc films on the degradation of pure iron matrix in vitro was investigated in the present study. Electrochemical measurement results indicated that the corrosion current density of pure iron coated with micro-patterned Au disc films in Hank's solution was 4 times larger than that of the uncoated one, while the difference between the influences of micro-patterned Au discs with different diameters on the corrosion rate of pure iron was insignificant. Immersion test indicated that the corrosion depth for pure iron coated with Au disc films was about three times as that of bare pure iron. Both electrochemical test and immersion test revealed that the corrosion of pure iron matrix coated with Au disc array became more uniform.

  7. Contribution of Accelerated Degradation to Feedback Regulation of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase and Cholesterol Metabolism in the Liver.

    PubMed

    Hwang, Seonghwan; Hartman, Isamu Z; Calhoun, Leona N; Garland, Kristina; Young, Gennipher A; Mitsche, Matthew A; McDonald, Jeffrey; Xu, Fang; Engelking, Luke; DeBose-Boyd, Russell A

    2016-06-24

    Accumulation of sterols in endoplasmic reticulum membranes stimulates the ubiquitination of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), which catalyzes a rate-limiting step in synthesis of cholesterol. This ubiquitination marks HMGCR for proteasome-mediated degradation and constitutes one of several mechanisms for feedback control of cholesterol synthesis. Mechanisms for sterol-accelerated ubiquitination and degradation of HMGCR have been elucidated through the study of cultured mammalian cells. However, the extent to which these reactions modulate HMGCR and contribute to control of cholesterol metabolism in whole animals is unknown. Here, we examine transgenic mice expressing in the liver the membrane domain of HMGCR (HMGCR (TM1-8)), a region necessary and sufficient for sterol-accelerated degradation, and knock-in mice in which endogenous HMGCR harbors mutations that prevent sterol-induced ubiquitination. Characterization of transgenic mice revealed that HMGCR (TM1-8) is appropriately regulated in the liver of mice fed a high cholesterol diet or chow diet supplemented with the HMGCR inhibitor lovastatin. Ubiquitination-resistant HMGCR protein accumulates in the liver and other tissues disproportionately to its mRNA, indicating that sterol-accelerated degradation significantly contributes to feedback regulation of HMGCR in vivo Results of these studies demonstrate that HMGCR is subjected to sterol-accelerated degradation in the liver through mechanisms similar to those established in cultured cells. Moreover, these studies designate sterol-accelerated degradation of HMGCR as a potential therapeutic target for prevention of atherosclerosis and associated cardiovascular disease. PMID:27129778

  8. Inoculation of Pichia kudriavzevii RB1 degrades the organic acids present in raw compost material and accelerates composting.

    PubMed

    Nakasaki, Kiyohiko; Araya, Shogo; Mimoto, Hiroshi

    2013-09-01

    In this study, the yeast strain Pichia kudriavzevii RB1 was used as an inoculum to accelerate organic matter degradation of rabbit food with added organic acids, which was used as a model food waste for composting. The RB1 strain rapidly degraded the organic acids present in the raw compost material, leading to an increase in pH beyond the neutral level, within 2 days. Both mesophilic and thermophilic bacteria proliferated faster in the compost with RB1 inoculation than in that without inoculation. Although the yeast died with the increase in compost temperature, it affected the early stages of composting prior to the thermophilic stage and accelerated the composting process by 2 days by eliminating the initial lag phase seen in the growth of other microorganisms. Moreover, populations of Bacillus thermoamylovorans, Bacillus foraminis, and Bacillus coagulans became dominant during the thermophilic stages of both composting with and without RB1 inoculation. PMID:23886646

  9. Lifetime Prediction for Degradation of Solar Mirrors using Step-Stress Accelerated Testing (Presentation)

    SciTech Connect

    Lee, J.; Elmore, R.; Kennedy, C.; Gray, M.; Jones, W.

    2011-09-01

    This research is to illustrate the use of statistical inference techniques in order to quantify the uncertainty surrounding reliability estimates in a step-stress accelerated degradation testing (SSADT) scenario. SSADT can be used when a researcher is faced with a resource-constrained environment, e.g., limits on chamber time or on the number of units to test. We apply the SSADT methodology to a degradation experiment involving concentrated solar power (CSP) mirrors and compare the results to a more traditional multiple accelerated testing paradigm. Specifically, our work includes: (1) designing a durability testing plan for solar mirrors (3M's new improved silvered acrylic "Solar Reflector Film (SFM) 1100") through the ultra-accelerated weathering system (UAWS), (2) defining degradation paths of optical performance based on the SSADT model which is accelerated by high UV-radiant exposure, and (3) developing service lifetime prediction models for solar mirrors using advanced statistical inference. We use the method of least squares to estimate the model parameters and this serves as the basis for the statistical inference in SSADT. Several quantities of interest can be estimated from this procedure, e.g., mean-time-to-failure (MTTF) and warranty time. The methods allow for the estimation of quantities that may be of interest to the domain scientists.

  10. Accelerated degradation of metam-sodium in soil and consequences for root-disease management.

    PubMed

    Triky-Dotan, Shachaf; Austerweil, Miriam; Steiner, Bracha; Peretz-Alon, Yitzhak; Katan, Jaacov; Gamliel, Abraham

    2009-04-01

    We studied the development of accelerated degradation (AD) of methyl isothiocyanate (MITC) following repeated applications of its parent compound, metam-sodium (MS). Laboratory studies and four sets of field experiments were conducted during 2002-04 in three commercial fields in Israel. Repeated applications of MS to the three soils in the laboratory under controlled conditions demonstrated AD of MITC in some soils. In a peanut field, MS significantly reduced the incidence of Pythium pod rot and improved pod quality after a single application but its effectiveness was greatly reduced after two applications. In a second experiment, MS was significantly effective after a single application in controlling Verticillium wilt in potato but its efficacy diminished after three consecutive applications. In an additional experiment, fumigation with MS following single or double applications was more effective in reducing Verticillium wilt severity of potato compared with triple applications. Soils which did not develop AD of MITC were also recorded. Preplant MS fumigation of melon fields was effective at reducing sudden wilt following a single and two consecutive applications. Our study shows that development of AD of MITC might occur following repeated applications of MS in commercial fields. The data on MITC dissipation in soil following repeated MS applications under controlled conditions indicate the chemical's potential loss of activity under regular agricultural practices and the need for a management strategy to prevent such a development.

  11. Accelerated metolachlor degradation in soil by zerovalent iron and compost amendments.

    PubMed

    Kim, Sung-Chul; Yang, Jae E; Ok, Yong Sik; Skousen, Jeff; Kim, Dong-Guk; Joo, Jin-Ho

    2010-04-01

    Soil incubation and germination tests were conducted to assess zerovalent iron (ZVI), organic compost, moisture and their combinations on metolachlor degradation in soil. The ZVI alone degraded 91% of metolachlor in soil within 40 days following bi-phasic kinetics. Organic amendment alone facilitated metolachlor degradation in soil up to 60% after 40 days depending on the amendment rate. However, the combination of ZVI with compost amendment at 30 ton ha(-1) and 30% moisture content accelerated metolachlor degradation to 90% after 3 days and 98% after 40 days. The half life (t (1/2)) of metolachlor degradation with ZVI, compost at 30 ton ha(-1), and 30% moisture was about 1 day, which was faster than ZVI treatment alone and 98% faster than controls. Germination and growth of lettuce (Lactuca sativa) and crabgrass (Digitaria sanguinalis L. Scop.) were severely inhibited in unamended metolachlor-contaminated soils but when these soils were amended with ZVI, germination and growth was comparable to controls (metolachlor free soil). Metolachlor degradation was greatest when ZVI, compost and moisture were used together, suggesting that these treatments will maximize in situ remediation of metolachlor-contaminated soils in the field.

  12. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1983-01-01

    Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

  13. Kinetic study and mechanism of Niclosamide degradation.

    PubMed

    Zaazaa, Hala E; Abdelrahman, Maha M; Ali, Nouruddin W; Magdy, Maimana A; Abdelkawy, M

    2014-11-11

    A spectrophotometric kinetic study of Niclosamide alkaline degradation as a function of drug concentration, alkaline concentration and temperature has been established utilizing double divisor-ratio spectra spectrophotometric method. The developed method allowed determination of Niclosamide in presence of its alkaline degradation products; namely; 2-chloro-4-nitro aniline (DEG I) and 5-chloro salicylic acid (DEG II) with characterization of its degradation mechanism. It was found that degradation kinetic of Niclosamide followed pseudo-first order under the established experimental conditions with a degradation rate constant (k) of 0.0829 mol/h and half life (t1/2) of 8.35 h. The overall degradation rate constant as a function of the temperature under the given conditions obeyed Arrhenius equation where the activation energy was calculated to be 3.41 kcal/mol. PMID:24892546

  14. Kinetic study and mechanism of Niclosamide degradation

    NASA Astrophysics Data System (ADS)

    Zaazaa, Hala E.; Abdelrahman, Maha M.; Ali, Nouruddin W.; Magdy, Maimana A.; Abdelkawy, M.

    2014-11-01

    A spectrophotometric kinetic study of Niclosamide alkaline degradation as a function of drug concentration, alkaline concentration and temperature has been established utilizing double divisor-ratio spectra spectrophotometric method. The developed method allowed determination of Niclosamide in presence of its alkaline degradation products; namely; 2-chloro-4-nitro aniline (DEG I) and 5-chloro salicylic acid (DEG II) with characterization of its degradation mechanism. It was found that degradation kinetic of Niclosamide followed pseudo-first order under the established experimental conditions with a degradation rate constant (k) of 0.0829 mol/h and half life (t1/2) of 8.35 h. The overall degradation rate constant as a function of the temperature under the given conditions obeyed Arrhenius equation where the activation energy was calculated to be 3.41 kcal/mol.

  15. Analysis of junction temperature and modification of luminous flux degradation for white LEDs in a thermal accelerated reliability test.

    PubMed

    Ke, Hong-Liang; Jing, Lei; Hao, Jian; Gao, Qun; Wang, Yao; Wang, Xiao-Xun; Sun, Qiang; Xu, Zhi-Jun

    2016-08-01

    An accelerated aging test is the main method in evaluation of the reliability of light-emitting diodes (LEDs), and the first goal of this study is to investigate how the junction temperature (Tj) of the LED varies during accelerated aging. The Tj measured by the forward voltage method shows an upward trend over the aging time, which gives a variation about 6°C-8°C after 3,000 h of aging under an ambient temperature of 80°C. The second goal is to investigate how the variation of Tj affects the lifetime estimation. It is verified that at a certain aging stage, as Tj increases, the normalized luminous flux linearly decreases with variation rate of microns (μ) (1/°C). Then, we propose a method to modify the luminous flux degradation with the Tj and μ to meet the requirements of a constant degradation rate in the data fitting. The experimental results show that with the proposed method, the accelerated lifetimes of samples are bigger than that of the current method with increment values from 8.8% to 21.4% in this research. PMID:27505370

  16. Acceleration of degradation by highly accelerated stress test and air-included highly accelerated stress test in crystalline silicon photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Suzuki, Soh; Tanahashi, Tadanori; Doi, Takuya; Masuda, Atsushi

    2016-02-01

    We examined the effects of hyper-hygrothermal stresses with or without air on the degradation of crystalline silicon (c-Si) photovoltaic (PV) modules, to shorten the required duration of a conventional hygrothermal-stress test [i.e., the “damp heat (DH) stress test”, which is conducted at 85 °C/85% relative humidity for 1,000 h]. Interestingly, the encapsulant within a PV module becomes discolored under the air-included hygrothermal conditions achieved using DH stress test equipment and an air-included highly accelerated stress test (air-HAST) apparatus, but not under the air-excluded hygrothermal conditions realized using a highly accelerated stress test (HAST) machine. In contrast, the reduction in the output power of the PV module is accelerated irrespective of air inclusion in hyper-hygrothermal test atmosphere. From these findings, we conclude that the required duration of the DH stress test will at least be significantly shortened using air-HAST, but not HAST.

  17. Effects of UV on power degradation of photovoltaic modules in combined acceleration tests

    NASA Astrophysics Data System (ADS)

    Ngo, Trang; Heta, Yushi; Doi, Takuya; Masuda, Atsushi

    2016-05-01

    UV exposure and other factors such as high/low temperature, humidity and mechanical stress have been reported to degrade photovoltaic (PV) module materials. By focusing on the combined effects of UV stress and moisture on PV modules, two new acceleration tests of light irradiation and damp heat (DH) were designed and conducted. The effects of UV exposure were validated through a change in irradiation time (UV dosage) and a change of the light irradiation side (glass side vs backsheet side) in the UV-preconditioned DH and cyclic sequential tests, respectively. The chemical corrosion of finger electrodes in the presence of acetic acid generated from ethylene vinyl acetate used as an encapsulant was considered to be the main origin of degradation. The module performance characterized by electroluminescence images was confirmed to correlate with the measured acetic acid concentration and Ag finger electrode resistance.

  18. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1984-01-01

    Research on the reliability of terrestrial solar cells was performed to identify failure/degradation modes affecting solar cells and to relate these to basic physical, chemical, and metallurgical phenomena. Particular concerns addressed were the reliability attributes of individual single crystalline, polycrystalline, and amorphous thin film silicon cells. Results of subjecting different types of crystalline cells to the Clemson accelerated test schedule are given. Preliminary step stress results on one type of thin film amorphous silicon (a:Si) cell indicated that extraneous degradation modes were introduced above 140 C. Also described is development of measurement procedures which are applicable to the reliability testing of a:Si solar cells as well as an approach to achieving the necessary repeatability of fabricating a simulated a:Si reference cell from crystalline silicon photodiodes.

  19. Fructose Accelerates UV-C Induced Photochemical Degradation of Pentachlorophenol in Low and High Salinity Water.

    PubMed

    Nayak, Shaila; O'Donnell, Sean-Erik; Sales, Christopher M; Tikekar, Rohan V

    2016-06-01

    A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutant, in low and high salinity (0-10 g/L salt) solutions is presented. The first order rate constants in the presence of 0, 300, and 500 mM fructose were 0.23 ± 0.04, 0.54 ± 0.01, and 1.18 ± 0.03 min(-1), respectively. Experimental evidence has shown generation of hydrogen peroxide and singlet oxygen from the UV-C exposure of fructose, which may have accelerated PCP degradation. Although salts (sodium, potassium, and calcium chloride, 1101:6.4:1) are expected to enhance the degradation rate due to generation of reactive halide species (RHS) from exposure to UV-C light, 10 g/L salt decreased the degradation rates in both the absence and presence of fructose. An LC-ESI-MS spectrum of the reaction mixture revealed a high relative abundance at m/z of 215 that corresponds to a fructose-chlorine adduct, indicating that fructose may have scavenged these RHS and prevented their reaction with PCP.

  20. Fructose Accelerates UV-C Induced Photochemical Degradation of Pentachlorophenol in Low and High Salinity Water.

    PubMed

    Nayak, Shaila; O'Donnell, Sean-Erik; Sales, Christopher M; Tikekar, Rohan V

    2016-06-01

    A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutant, in low and high salinity (0-10 g/L salt) solutions is presented. The first order rate constants in the presence of 0, 300, and 500 mM fructose were 0.23 ± 0.04, 0.54 ± 0.01, and 1.18 ± 0.03 min(-1), respectively. Experimental evidence has shown generation of hydrogen peroxide and singlet oxygen from the UV-C exposure of fructose, which may have accelerated PCP degradation. Although salts (sodium, potassium, and calcium chloride, 1101:6.4:1) are expected to enhance the degradation rate due to generation of reactive halide species (RHS) from exposure to UV-C light, 10 g/L salt decreased the degradation rates in both the absence and presence of fructose. An LC-ESI-MS spectrum of the reaction mixture revealed a high relative abundance at m/z of 215 that corresponds to a fructose-chlorine adduct, indicating that fructose may have scavenged these RHS and prevented their reaction with PCP. PMID:27160945

  1. In silico prediction of pharmaceutical degradation pathways: a benchmarking study.

    PubMed

    Kleinman, Mark H; Baertschi, Steven W; Alsante, Karen M; Reid, Darren L; Mowery, Mark D; Shimanovich, Roman; Foti, Chris; Smith, William K; Reynolds, Dan W; Nefliu, Marcela; Ott, Martin A

    2014-11-01

    Zeneth is a new software application capable of predicting degradation products derived from small molecule active pharmaceutical ingredients. This study was aimed at understanding the current status of Zeneth's predictive capabilities and assessing gaps in predictivity. Using data from 27 small molecule drug substances from five pharmaceutical companies, the evolution of Zeneth predictions through knowledge base development since 2009 was evaluated. The experimentally observed degradation products from forced degradation, accelerated, and long-term stability studies were compared to Zeneth predictions. Steady progress in predictive performance was observed as the knowledge bases grew and were refined. Over the course of the development covered within this evaluation, the ability of Zeneth to predict experimentally observed degradants increased from 31% to 54%. In particular, gaps in predictivity were noted in the areas of epimerizations, N-dealkylation of N-alkylheteroaromatic compounds, photochemical decarboxylations, and electrocyclic reactions. The results of this study show that knowledge base development efforts have increased the ability of Zeneth to predict relevant degradation products and aid pharmaceutical research. This study has also provided valuable information to help guide further improvements to Zeneth and its knowledge base.

  2. A novel ER J-protein DNAJB12 accelerates ER-associated degradation of membrane proteins including CFTR.

    PubMed

    Yamamoto, Yo-hei; Kimura, Taiji; Momohara, Shuku; Takeuchi, Masato; Tani, Tokio; Kimata, Yukio; Kadokura, Hiroshi; Kohno, Kenji

    2010-01-01

    Cytosolic Hsc70/Hsp70 are known to contribute to the endoplasmic reticulum (ER)-associated degradation of membrane proteins. However, at least in mammalian cells, its partner ER-localized J-protein for this cellular event has not been identified. Here we propose that this missing protein is DNAJB12. Protease protection assay and immunofluorescence study revealed that DNAJB12 is an ER-localized single membrane-spanning protein carrying a J-domain facing the cytosol. Using co-immunoprecipitation assay, we found that DNAJB12 is able to bind Hsc70 and thus can recruit Hsc70 to the ER membrane. Remarkably, cellular overexpression of DNAJB12 accelerated the degradation of misfolded membrane proteins including cystic fibrosis transmembrane conductance regulator (CFTR), but not a misfolded luminal protein. The DNAJB12-dependent degradation of CFTR was compromised by a proteasome inhibitor, lactacystin, suggesting that this process requires the ubiquitin-proteasome system. Conversely, knockdown of DNAJB12 expression attenuated the degradation of CFTR. Thus, DNAJB12 is a novel mammalian ER-localized J-protein that plays a vital role in the quality control of membrane proteins.

  3. Accelerating the degradation of green plant waste with chemical decomposition agents.

    PubMed

    Kejun, Sun; Juntao, Zhang; Ying, Chen; Zongwen, Liao; Lin, Ruan; Cong, Liu

    2011-10-01

    Degradation of green plant waste is often difficult, and excess maturity times are typically required. In this study, we used lignin, cellulose and hemicellulose assays; scanning electron microscopy; infrared spectrum analysis and X-ray diffraction analysis to investigate the effects of chemical decomposition agents on the lignocellulose content of green plant waste, its structure and major functional groups and the mechanism of accelerated degradation. Our results showed that adding chemical decomposition agents to Ficus microcarpa var. pusillifolia sawdust reduced the contents of lignin by 0.53%-11.48% and the contents of cellulose by 2.86%-7.71%, and increased the contents of hemicellulose by 2.92%-33.63% after 24 h. With increasing quantities of alkaline residue and sodium lignosulphonate, the lignin content decreased. Scanning electron microscopy showed that, after F. microcarpa var. pusillifolia sawdust was treated with chemical decomposition agents, lignocellulose tube wall thickness increased significantlyIncreases of 29.41%, 3.53% and 34.71% were observed after treatment with NaOH, alkaline residue and sodium lignosulphonate, respectively. Infrared spectroscopy showed that CO and aromatic skeleton stretching absorption peaks were weakened and the C-H vibrational absorption peak from out-of-plane in positions 2 and 6 (S units) (890-900 cm(-1)) was strengthened after F. microcarpa var. pusillifolia sawdust was treated with chemical decomposition agents, indicating a reduction in lignin content. Several absorption peaks [i.e., C-H deformations (asymmetry in methyl groups, -CH(3)- and -CH(2)-) (1450-1460 cm(-1)); Aliphatic C-H stretching in methyl and phenol OH (1370-1380 cm(-1)); CO stretching (cellulose and hemicellulose) (1040-1060 cm(-1))] that indicate the presence of a chemical bond between lignin and cellulose was reduced, indicating that the chemical bond between lignin and cellulose had been partially broken. X-ray diffraction analysis showed that Na

  4. Accelerated degradation of 14C-atrazine in an atrazine adapted field soil from Belgium

    NASA Astrophysics Data System (ADS)

    Hamacher, Georg; Jablonowski, Nicolai David; Martinazzo, Rosane; Accinelli, Cesare; Köppchen, Stephan; Langen, Ulrike; Linden, Andreas; Krause, Martina; Burauel, Peter

    2010-05-01

    Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] is one of the most widely used herbicides in the world. Atrazine is considered to be mobile in soil and has often been characterized as a rather recalcitrant compound in the environment. In the present study the accelerated atrazine degradation in an agriculturally used soil was examined. Soil samples were collected from a Belgian field which was used for corn-plantations and was regularly treated with atrazine during the last 30 years. The experiment was conducted under controlled laboratory conditions (GLP) using 14C-labelled and unlabelled atrazine in accordance to the reported field application dose of 1 mg kg-1. Triplicates of treated subsamples were incubated at 50% WHCmax and under slurry conditions (1:4 soil:solution ratio, using distilled water) in the dark at 20° C. Control samples were collected at an adjacent pear orchard where no atrazine or other triazine pesticides application was reported. After 92 days of incubation, the mineralized amount of atrazine reached 83% of the initially applied 14C-activity in the atrazine treated soil for the slurry setup. A maximum of atrazine mineralization was observed in the treated field soil between 6 and 7 days of incubation for both, 50% WHCmax and slurry setups. The total 14C-atrazine mineralization was equally high for 50% WHCmax in the atrazine treated soil. After an extended lag-phase in comparison to the treated soil the overall mineralization of 14C-atrazine of 81% was observed in the atrazine untreated soil under slurry conditions. This observation might be due to a possible cross adaption of the microflora. These results could be attributed to an atrazine drift during application since the control samples were taken in an adjacent pear orchard with no atrazine application history. These results demonstrate an adaption of the microflora to mineralize atrazine rapidly. The formation of desorbable metabolites as well as the formation of

  5. Independent Study Unit on Accelerated Reference Frames

    ERIC Educational Resources Information Center

    Poultney, S. K.

    1973-01-01

    Presents a list of topics, research areas, references, and laboratory equipment which is prepared to facilitate general-science students' understanding of physics aspects in accelerated reference frames after their study of circular motion and Galilean relativity in mechanics. (CC)

  6. The IDS-NF Accelerator Study

    SciTech Connect

    Prior, Christopher R.

    2008-02-21

    The paper outlines the plans of the accelerator group under the International Design Study for a Neutrino Factory. The International Scoping Study, completed in 2006, identified a self-consistent accelerator scenario, which will be used as a baseline design for future work. Essential R and D was also listed, suggesting a programme of development leading into the Conceptual Design Report, to be completed by 2012.

  7. Irradiation imposed degradation of the mechanical and electrical properties of electrical insulation for future accelerator magnets

    SciTech Connect

    Polinski, J.; Chorowski, M.; Bogdan, P.; Strychalski, M.; Rijk, G. de

    2014-01-27

    Future accelerators will make extensive use of superconductors made of Nb{sub 3}Sn, which allows higher magnetic fields than NbTi. However, the wind-and-react technology of Nb{sub 3}Sn superconducting magnet production makes polyimide Kapton® non applicable for the coils' electrical insulation. A Nb{sub 3}Sn technology compatible insulation material should be characterized by high radiation resistivity, good thermal conductivity, and excellent mechanical properties. Candidate materials for the electrical insulation of future accelerator's magnet coils have to be radiation certified with respect to potential degradation of their electrical, thermal, and mechanical properties. This contribution presents procedures and results of tests of the electrical and mechanical properties of DGEBA epoxy + D400 hardener, which is one of the candidates for the electrical insulation of future magnets. Two test sample types have been used to determine the material degradation due to irradiation: a untreated one (unirradiated) and irradiated at 77 K with 11 kGy/min intense, 4MeV energy electrons beam to a total dose of 50 MGy.

  8. Accelerated degradation of caspase-8 protein correlates with TRAIL resistance in a DLD1 human colon cancer cell line.

    PubMed

    Zhang, Lidong; Zhu, Hongbo; Teraishi, Fuminori; Davis, John J; Guo, Wei; Fan, Zhen; Fang, Bingliang

    2005-06-01

    The tumor-selective cytotoxic effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) makes TRAIL an attractive candidate as an anticancer agent. However, resistance to TRAIL poses a challenge in anticancer therapy with TRAIL. Therefore, characterizing the mechanisms of resistance and developing strategies to overcome the resistance are important steps toward successful TRAIL-mediated cancer therapy. In this study, we investigated mechanisms of acquired TRAIL resistance in a colon cancer DLD1 cell line. Compared with the TRAIL-susceptible DLD1 cell line, TRAIL-resistant DLD1/TRAIL-R cells have a low level of caspase-8 protein, but not its mRNA. Suppression of caspase-8 expression by siRNA in parental DLD1 cells led to TRAIL resistance. Restoration of caspase-8 protein expression by stable transfection rendered the DLD1/TRAIL-R cell line fully sensitive to TRAIL protein, suggesting that the low level of caspase-8 protein expression might be the culprit in TRAIL resistance in DLD1/TRAIL-R cells. Sequencing analysis of the caspase-8 coding region revealed a missense mutation that is present in both TRAIL-sensitive and TRAIL-resistant DLD1 cells. Subsequent study showed that the degradation of caspase-8 protein was accelerated in DLD1/TRAIL-R cells compared to parental DLD1 cells. Thus, accelerated degradation of caspase-8 protein is one of the mechanisms that lead to TRAIL resistance. PMID:16036110

  9. Kinetic and multidimensional profiling of accelerated degradation of oil sludge by biostimulation.

    PubMed

    Dong, Yijie; Lang, Zhe; Kong, Xian; Lu, Diannan; Liu, Zheng

    2015-04-01

    Biostimulation, which employs nutrients to enhance the proliferation of indigenous microorganisms and therefore the degradation of contaminants, is an effective tool for treatment of oil-contaminated soil. However, the evolution of microbial ecology, which responds directly to stimulation procedures and intrinsically determines the degradation of oil contaminants, has rarely been explored, particularly in the context of biostimulation. In this study, the effects of biostimulation procedures including the regulation of the C : N : P ratio, as well as application of surfactants and electron acceptors in the degradation of crude oil contaminants and the evolution of the microbial community were examined simultaneously to provide ecological insights into the biostimulation. The real-time PCR showed that biostimulation promoted the proliferation of bacteria, with Gammaproteobacteria showing the greatest increase. However, the proliferation of fungi was inhibited by the accumulation of the degradation products. The degradation of polar compounds of crude oil contaminants was characterized by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (negative-ion ESI FT-ICR MS), showing a biased increase in the relative abundance of naphthenic acids. Principal component analysis (PCA) showed that different species in oil sludge have different degradation rates during biostimulation. The addition of fertilizers with surfactants and electron acceptors profoundly stimulated the indigenous microorganisms with N1, O1 and O2 species as substrates while those with O3 and O4 species were little affected. An enriched abundance of alkB genes was observed during the degradation of saturated hydrocarbons. Monitoring the kinetics of the microbial community, functional genes and degradation offers a comprehensive view for the understanding and optimization of the biostimulation process.

  10. The methodology study of time accelerated irradiation of elastomers

    NASA Astrophysics Data System (ADS)

    Ito, Masayuki

    2005-07-01

    The article studied the methods how to shorten the irradiation time by increasing dose rate without changing the relationship between dose versus properties of degraded samples. The samples used were nine kinds of EPDM which have different compounding formula. The different dose of Co-γ ray was exposed to the samples. The maximum dose was 2 MGy. The reference condition to be compared with two short time test conditions is irradiation of 0.33 kGy/h at room temperature. Two methods shown below were studied as the time-accelerate irradiation conditions.

  11. Accelerating Vaccine Formulation Development Using Design of Experiment Stability Studies.

    PubMed

    Ahl, Patrick L; Mensch, Christopher; Hu, Binghua; Pixley, Heidi; Zhang, Lan; Dieter, Lance; Russell, Ryann; Smith, William J; Przysiecki, Craig; Kosinski, Mike; Blue, Jeffrey T

    2016-10-01

    Vaccine drug product thermal stability often depends on formulation input factors and how they interact. Scientific understanding and professional experience typically allows vaccine formulators to accurately predict the thermal stability output based on formulation input factors such as pH, ionic strength, and excipients. Thermal stability predictions, however, are not enough for regulators. Stability claims must be supported by experimental data. The Quality by Design approach of Design of Experiment (DoE) is well suited to describe formulation outputs such as thermal stability in terms of formulation input factors. A DoE approach particularly at elevated temperatures that induce accelerated degradation can provide empirical understanding of how vaccine formulation input factors and interactions affect vaccine stability output performance. This is possible even when clear scientific understanding of particular formulation stability mechanisms are lacking. A DoE approach was used in an accelerated 37(°)C stability study of an aluminum adjuvant Neisseria meningitidis serogroup B vaccine. Formulation stability differences were identified after only 15 days into the study. We believe this study demonstrates the power of combining DoE methodology with accelerated stress stability studies to accelerate and improve vaccine formulation development programs particularly during the preformulation stage. PMID:27522919

  12. Adhesin degradation accelerates delivery of heat-labile toxin by enterotoxigenic Escherichia coli.

    PubMed

    Roy, Koushik; Kansal, Rita; Bartels, Scott R; Hamilton, David J; Shaaban, Salwa; Fleckenstein, James M

    2011-08-26

    Many enteric pathogens, including enterotoxigenic Escherichia coli (ETEC), produce one or more serine proteases that are secreted via the autotransporter (or type V) bacterial secretion pathway. These molecules have collectively been referred to as SPATE proteins (serine protease autotransporter of the Enterobacteriaceae). EatA, an autotransporter previously identified in ETEC, possesses a functional serine protease motif within its secreted amino-terminal passenger domain. Although this protein is expressed by many ETEC strains and is highly immunogenic, its precise function is unknown. Here, we demonstrate that EatA degrades a recently characterized adhesin, EtpA, resulting in modulation of bacterial adhesion and accelerated delivery of the heat-labile toxin, a principal ETEC virulence determinant. Antibodies raised against the passenger domain of EatA impair ETEC delivery of labile toxin to epithelial cells suggesting that EatA may be an effective target for vaccine development. PMID:21757737

  13. Polycrystalline Thin Film Device Degradation Studies

    SciTech Connect

    Albin, D. S.; McMahon, T. J.; Pankow, J. W.; Noufi, R.; Demtsu, S. H.; Davies, A.

    2005-11-01

    Oxygen during vapor CdCl2 (VCC) treatments significantly reduced resistive shunts observed in CdS/CdTe polycrystalline devices using thinner CdS layers during 100 deg C, open-circuit, 1-sun accelerated stress testing. Cu oxidation resulting from the reduction of various trace oxides present in as-grown and VCC treated films is the proposed mechanism by which Cu diffusion, and subsequent shunts are controlled. Graphite paste layers between metallization and CdTe behave like diffusion barriers and similarly benefit device stability. Ni-based contacts form a protective Ni2Te3 intermetallic layer that reduces metal diffusion but degrades performance through increased series resistance.

  14. Internal loop photo-biodegradation reactor used for accelerated quinoline degradation and mineralization.

    PubMed

    Chang, Ling; Zhang, Yongming; Gan, Lu; Xu, Hua; Yan, Ning; Liu, Rui; Rittmann, Bruce E

    2014-07-01

    Biofilm biodegradation was coupled with ultra-violet photolysis using the internal loop photobiodegradation reactor for degradation of quinoline. Three protocols-photolysis alone (P), biodegradation alone (B), and intimately coupled photolysis and biodegradation (P&B)-were used for degradation of quinoline in batch and continuous-flow experiments. For a 1,000 mg/L initial quinoline concentration, the volumetric removal rate for quinoline was 38 % higher with P&B than with B in batch experiments, and the P&B kinetics were the sum of kinetics from the P and B experiments. Continuous-flow experiments with an influent quinoline concentration of 1,000 mg/L also gave significantly greater quinoline removal in P&B, and the quinoline-removal kinetics for P&B were approximately equal to the sum of the removal kinetics for P and B. P&B similarly increased the rate and extent of quinoline mineralization, for which the kinetics for P&B were nearly equal to the sum of kinetics for P and B. These findings support that the rate-limiting step for mineralization was transformation of quinoline, which was accelerated by the simultaneous action of photolysis and biodegradation. PMID:24488551

  15. Sulforaphane promotes murine hair growth by accelerating the degradation of dihydrotestosterone.

    PubMed

    Sasaki, Mari; Shinozaki, Shohei; Shimokado, Kentaro

    2016-03-25

    Dihydrotestosterone (DHT) causes the regression of human hair follicles in the parietal scalp, leading to androgenic alopecia (AGA). Sulforaphane (SFN) increases the expression of DHT degrading enzymes, such as 3α-hydroxysteroid dehydrogenases (3α-HSDs), and, therefore, SFN treatment may improve AGA. To determine the effects of SFN on hair growth, we administered SFN (10 mg/kg BW, IP) or vehicle (DMSO) to ob/ob mice for six weeks and examined hair regeneration and the plasma levels of testosterone and DHT. We also tested the effects of SFN on the expression of two forms of 3α-HSD, aldo-keto reductase 1c21 and dehydrogenase/reductase (SDR family) member 9, both in vitro and in vivo. SNF significantly enhanced hair regeneration in ob/ob mice. The mice treated with SFN showed lower plasma levels of testosterone and DHT than those treated with vehicle. SFN increased the mRNA and protein levels of the two forms of 3α-HSD in the liver of the mice and in cultured murine hepatocyte Hepa1c1c7 cells. These results suggest that SFN treatment increases the amount of 3α-HSDs in the liver, accelerates the degradation of blood DHT, and subsequently blocks the suppression of hair growth by DHT. PMID:26923074

  16. Integrated photocatalytic-biological reactor for accelerated 2,4,6-trichlorophenol degradation and mineralization.

    PubMed

    Zhang, Yongming; Sun, Xia; Chen, Lujun; Rittmann, Bruce E

    2012-02-01

    An integrated photocatalytic-biological reactor (IPBR) was used for accelerated degradation and mineralization of 2,4,6-trichlorophenol (TCP) through simultaneous, intimate coupling of photocatalysis and biodegradation in one reactor. Intimate coupling was realized by circulating the IPBR's liquid contents between a TiO(2) film on mat glass illuminated by UV light and honeycomb ceramics as biofilm carriers. Three protocols-photocatalysis alone (P), biodegradation alone (B), and integrated photocatalysis and biodegradation (photobiodegradation, P&B)-were used for degradation of different initial TCP concentrations. Intimately coupled P&B also was compared with sequential P and B. TCP removal by intimately coupled P&B was faster than that by P and B alone or sequentially coupled P and B. Because photocatalysis relieved TCP inhibition to biodegradation by decreasing its concentration, TCP biodegradation could become more important over the full batch P&B experiments. When phenol, an easy biodegradable compounds, was added to TCP in order to promote TCP mineralization by means of secondary utilization, P&B was superior to P and B in terms of mineralization of TCP, giving 95% removal of chemical oxygen demand. Cl(-) was only partially released during P experiments (24%), and this corresponded to its poor mineralization in P experiments (32%). Thus, intimately coupled P&B in the IPBR made it possible obtain the best features of each: rapid photocatalytic transformation in parallel with mineralization of photocatalytic products.

  17. Internal loop photo-biodegradation reactor used for accelerated quinoline degradation and mineralization.

    PubMed

    Chang, Ling; Zhang, Yongming; Gan, Lu; Xu, Hua; Yan, Ning; Liu, Rui; Rittmann, Bruce E

    2014-07-01

    Biofilm biodegradation was coupled with ultra-violet photolysis using the internal loop photobiodegradation reactor for degradation of quinoline. Three protocols-photolysis alone (P), biodegradation alone (B), and intimately coupled photolysis and biodegradation (P&B)-were used for degradation of quinoline in batch and continuous-flow experiments. For a 1,000 mg/L initial quinoline concentration, the volumetric removal rate for quinoline was 38 % higher with P&B than with B in batch experiments, and the P&B kinetics were the sum of kinetics from the P and B experiments. Continuous-flow experiments with an influent quinoline concentration of 1,000 mg/L also gave significantly greater quinoline removal in P&B, and the quinoline-removal kinetics for P&B were approximately equal to the sum of the removal kinetics for P and B. P&B similarly increased the rate and extent of quinoline mineralization, for which the kinetics for P&B were nearly equal to the sum of kinetics for P and B. These findings support that the rate-limiting step for mineralization was transformation of quinoline, which was accelerated by the simultaneous action of photolysis and biodegradation.

  18. Sulforaphane promotes murine hair growth by accelerating the degradation of dihydrotestosterone.

    PubMed

    Sasaki, Mari; Shinozaki, Shohei; Shimokado, Kentaro

    2016-03-25

    Dihydrotestosterone (DHT) causes the regression of human hair follicles in the parietal scalp, leading to androgenic alopecia (AGA). Sulforaphane (SFN) increases the expression of DHT degrading enzymes, such as 3α-hydroxysteroid dehydrogenases (3α-HSDs), and, therefore, SFN treatment may improve AGA. To determine the effects of SFN on hair growth, we administered SFN (10 mg/kg BW, IP) or vehicle (DMSO) to ob/ob mice for six weeks and examined hair regeneration and the plasma levels of testosterone and DHT. We also tested the effects of SFN on the expression of two forms of 3α-HSD, aldo-keto reductase 1c21 and dehydrogenase/reductase (SDR family) member 9, both in vitro and in vivo. SNF significantly enhanced hair regeneration in ob/ob mice. The mice treated with SFN showed lower plasma levels of testosterone and DHT than those treated with vehicle. SFN increased the mRNA and protein levels of the two forms of 3α-HSD in the liver of the mice and in cultured murine hepatocyte Hepa1c1c7 cells. These results suggest that SFN treatment increases the amount of 3α-HSDs in the liver, accelerates the degradation of blood DHT, and subsequently blocks the suppression of hair growth by DHT.

  19. Conductive iron oxide minerals accelerate syntrophic cooperation in methanogenic benzoate degradation.

    PubMed

    Zhuang, Li; Tang, Jia; Wang, Yueqiang; Hu, Min; Zhou, Shungui

    2015-08-15

    Recent studies have suggested that conductive iron oxide minerals can facilitate syntrophic metabolism of the methanogenic degradation of organic matter, such as ethanol, propionate and butyrate, in natural and engineered microbial ecosystems. This enhanced syntrophy involves direct interspecies electron transfer (DIET) powered by microorganisms exchanging metabolic electrons through electrically conductive minerals. Here, we evaluated the possibility that conductive iron oxides (hematite and magnetite) can stimulate the methanogenic degradation of benzoate, which is a common intermediate in the anaerobic metabolism of aromatic compounds. The results showed that 89-94% of the electrons released from benzoate oxidation were recovered in CH4 production, and acetate was identified as the only carbon-bearing intermediate during benzoate degradation. Compared with the iron-free controls, the rates of methanogenic benzoate degradation were enhanced by 25% and 53% in the presence of hematite and magnetite, respectively. This stimulatory effect probably resulted from DIET-mediated methanogenesis in which electrons transfer between syntrophic partners via conductive iron minerals. Phylogenetic analyses revealed that Bacillaceae, Peptococcaceae, and Methanobacterium are potentially involved in the functioning of syntrophic DIET. Considering the ubiquitous presence of iron minerals within soils and sediments, the findings of this study will increase the current understanding of the natural biological attenuation of aromatic hydrocarbons in anaerobic environments.

  20. Flame acceleration studies in the MINIFLAME facility

    SciTech Connect

    Tieszen, S.R.; Sherman, M.P.; Benedick, W.B.

    1989-07-01

    Flame acceleration and deflagration-to-detonation transition (DDT) studies have been conducted in a 19.4-cm high, 14.5-cm wide, and 2. 242-m long channel (MINIFLAME) that is a 1:12.6 scale model of the 136-m{sup 3} FLAME facility. Tests were conducted with two levels of hydrogen concentration -- 20% and 30%, with and without obstacles in the channel, and with three levels of transverse top venting -- 0%, 13%, and 50%. The flame acceleration results in MINIFLAME are qualitatively similar to those in FLAME; however, the small-scale results are more benign quantitatively. The results show that insufficient venting, 13% venting in this case, can promote flame acceleration due to turbulence produced by the flow through the vents in smooth channels. However, with obstacle-generated turbulence in the channel, 13% top venting was found to be beneficial. Flame acceleration resulting in DDT was shown to occur in as little as 35 liters of mixture. Comparison of the DDT data with obstacles in MINIFLAME and FLAME supports d/{lambda} scaling of DDT, where {lambda} is the detonation cell width of the mixture and d is the characteristic open diameter of the channel. In the MINIFLAME and FLAME tests, DDT occurred for d/{lambda} greater than approximately three. Comparison with other experiments shows that the value of d/{lambda} for DDT is not constant but depends on the obstacle type, spacing, and channel geometry. The comparison of MINIFLAME and FLAME experiments extends the use of d/{lambda} scaling to different geometries and larger scales than previous studies. Small-scale-model testing of flame acceleration and DDT with the same combustible mixture as the full-scale prototype underpredicts flame speeds, overpressures, and the possibility of DDT. 18 refs., 16 figs.

  1. Using co-metabolism to accelerate synthetic starch wastewater degradation and nutrient recovery in photosynthetic bacterial wastewater treatment technology.

    PubMed

    Lu, Haifeng; Zhang, Guangming; Lu, Yufeng; Zhang, Yuanhui; Li, Baoming; Cao, Wei

    2016-01-01

    Starch wastewater is a type of nutrient-rich wastewater that contains numerous macromolecular polysaccharides. Using photosynthetic bacteria (PSB) to treat starch wastewater can reduce pollutants and enhance useful biomass production. However, PSB cannot directly degrade macromolecular polysaccharides, which weakens the starch degradation effect. Therefore, co-metabolism with primary substances was employed in PSB wastewater treatment to promote starch degradation. The results indicated that co-metabolism is a highly effective method in synthetic starch degradation by PSB. When malic acid was used as the optimal primary substrate, the chemical oxygen demand, total sugar, macromolecules removal and biomass yield were considerably higher than when primary substances were not used, respectively. Malic acid was the primary substrate that played a highly important role in starch degradation. It promoted the alpha-amylase activity to 46.8 U and the PSB activity, which induced the degradation of macromolecules. The products in the wastewater were ethanol, acetic acid and propionic acid. Ethanol was the primary product throughout the degradation process. The introduction of co-metabolism with malic acid to treat wastewater can accelerate macromolecules degradation and bioresource production and weaken the acidification effect. This method provides another pathway for bioresource recovery from wastewater. This approach is a sustainable and environmentally friendly wastewater treatment technology.

  2. Accelerated stability studies of Sufoofe Sailan: A Unani formulation

    PubMed Central

    Rani, Seema; Rahman, Khaleequr; Younis, Peerzada Mohammad

    2015-01-01

    Introduction: Sufoofe Sailan (SS) is a polyherbal powder preparation used in Unani medicine to treat gynecological diseases. It is observed that SS degrade early as it is in the form of powder; however, the stability study of SS was not carried out till date. Aim: To evaluate the accelerated stability of SS. Materials and Methods: Finished formulation of SS was packed in three airtight transparent polyethylene terephthalate containers. One pack was analyzed just after manufacturing and remaining two packs were kept in stability chamber at 40°C ± 2°C/75% ± 5% RH, of which one pack was analyzed after the completion of three and another after 6 months. Organoleptic, physico-chemical, microbiological parameters along with high-performance thin layer chromatography (HPTLC) fingerprinting were carried out. Results: Organoleptic characters showed no significant change in accelerated stability condition. All physico-chemical parameters showed changes <5%, HPTLC fingerprinting showed minimum changes and microbial studies were in confirmation to the World Health Organization guidelines. Conclusion: SS confirmed to the International Conference on Harmonization Guideline for accelerated testing of the pharmaceutical product on said parameters and as per the Grimm's statement the shelf life of SS may last 20 months. PMID:26730145

  3. Acceleration of nonylphenol and 4-tert-octylphenol degradation in sediment by Phragmites australis and associated rhizosphere bacteria.

    PubMed

    Toyama, Tadashi; Murashita, Manabu; Kobayashi, Kazutaka; Kikuchi, Shintaro; Sei, Kazunari; Tanaka, Yasuhiro; Ike, Michihiko; Mori, Kazuhiro

    2011-08-01

    We investigated biodegradation of technical nonylphenol (tNP) in Phragmites australis rhizosphere sediment by conducting degradation experiments using sediments spiked with tNP. Accelerated tNP removal was observed in P. australis rhizosphere sediment, whereas tNP persisted in unvegetated sediment without plants and in autoclaved sediment with sterile plants, suggesting that the accelerated tNP removal resulted largely from tNP biodegradation by rhizosphere bacteria. Three bacterial strains, Stenotrophomonas sp. strain IT-1 and Sphingobium spp. strains IT-4 and IT-5, isolated from the rhizosphere were capable of utilizing tNP and 4-tert-octylphenol as a sole carbon source via type II ipso-substitution. Oxygen from P. australis roots, by creating highly oxygenated conditions in the sediment, stimulated cell growth and the tNP-degrading activity of the three strains. Moreover, organic compounds from P. australis roots functioned as carbon and energy sources for two strains, IT-4 and IT-5, supporting cell growth and tNP-degrading activity. Thus, P. australis roots elevated the cell growth and tNP-degrading activity of the three bacterial strains, leading to accelerated tNP removal. These results demonstrate that rhizoremediation of tNP-contaminated sediments using P. australis can be an effective strategy.

  4. Proceedings of the SMRM Degradation Study Workshop

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The proceedings of the Solar Maximum Repair Mission Degradation Study Workshop, held at the Goddard Space Flight Center in Greenbelt, Maryland on May 9 to 10, 1985 are contained. The results of tests and studies of the returned Solar Maximum Mission hardware and materials are reported. Specifically, the workshop was concerned with the effects of four years' exposure to a low-Earth orbit environment. To provide a background for the reported findings, the summary includes a short description of the Solar Maximum Mission and the Solar Maximum Repair Mission.

  5. [Effects of Oil Pollutants on the Performance of Marine Benthonic Microbial Fuel Cells and Its Acceleration of Degradation].

    PubMed

    Meng, Yao; Fu, Yu-bin; Liang, Sheng-kang; Chen, Wei; Liu, Zhao-hui

    2015-08-01

    Degradation of oil pollutants under the sea is slow for its oxygen-free environment which has caused long-term harm to ocean environment. This paper attempts to accelerate the degradation of the sea oil pollutants through electro catalysis by using the principle of marine benthonic microbial fuel cells (BMFCs). The influence of oil pollutants on the battery performance is innovatively explored by comparing the marine benthonic microbial fuel cells ( BMFCs-A) containing oil and oil-free microbial fuel cells (BMFCs-B). The acceleration effect of BMFCs is investigated by the comparison between the oil-degrading rate and the number of heterotrophic bacteria of the BMFCs-A and BMFCs-B on their anodes. The results show that the exchange current densities in the anode of the BMFCs-A and BMFCs-B are 1. 37 x 10(-2) A x m(-2) and 1.50 x 10(-3) A x m(-2) respectively and the maximum output power densities are 105.79 mW x m(-2) and 83.60 mW x m(-2) respectively. The exchange current densities have increased 9 times and the maximum output power density increased 1. 27 times. The anti-polarization ability of BMFCs-A is improved. The heterotrophic bacteria numbers of BMFCs-A and BMFCs-C on their anodes are (66 +/- 3.61) x 10(7) CFU x g(-1) and (7.3 +/- 2.08) x 10(7) CFU x g(-1) respectively and the former total number has increased 8 times, which accelerates the oil-degrading rate. The degrading rate of the oil in the BMFCs-A is 18.7 times higher than that in its natural conditions. The BMFCs can improve its electrochemical performance, meanwhile, the degradation of oil pollutants can also be accelerated. A new model of the marine benthonic microbial fuel cells on its acceleration of oil degradation is proposed in this article.

  6. [Study on hydrophilicity and degradability of polyvinyl alcohol/polylactic acid blend film].

    PubMed

    Wang, Hualin; Sheng, Mingang; Zhai, Linfeng; Li, Yanhong

    2008-02-01

    Based on casting and solvent evaporation method, the degradable PLA/PVA blend film was prepared with polylactic acid (PLA) and polyvinyl alcohol (PVA) as raw material. The moisture absorbability, water absorbability and degradability of the polylactic acid/polyvinyl alcohol (PLA/PVA) blend film were studied; also the degradation mechanism of blend film was investigated. The results showed that the moisture absorption and water absorption of blend film decreased as the concentration of PLA increased. The degradation process of blend film in the normal saline is conducted by stepwise. At the forepart, the degradation of PLA played an important role, while PVA was the main degradation substance later. The solvent acidity could catalyze the degradation of PLA, and degradation of PLA was always turning from noncrystalline region to crystalline region. PVA had abilities to accelerate the degradation of PLA by increasing the hydrophilicity of the blend film and by breaking the crystallinity of PLA. Therefore, the hydrophilicity and degradability of PLA/PVA blend film can be controlled in a certain range by adjusting the proportion of PLA and PVA. PMID:18435276

  7. In-situ diagnostics and degradation mapping of a mixed-mode accelerated stress test for proton exchange membranes

    NASA Astrophysics Data System (ADS)

    Lai, Yeh-Hung; Fly, Gerald W.

    2015-01-01

    With increasing availability of more durable membrane materials for proton exchange membrane fuel cells, there is a need for a more stressful test that combines chemical and mechanical stressors to enable accelerated screening of promising membrane candidates. Equally important is the need for in-situ diagnostic methods with sufficient spatial resolution that can provide insights into how membranes degrade to facilitate the development of durable fuel cell systems. In this article, we report an accelerated membrane stress test and a degradation diagnostic method that satisfy both needs. By applying high-amplitude cycles of electrical load to a fuel cell fed with low-RH reactant gases, a wide range of mechanical and chemical stressful conditions can be created within the cell which leads to rapid degradation of a mechanically robust Ion Power™ N111-IP membrane. Using an in-situ shorting/crossover diagnostic method on a segmented fuel cell fixture that provides 100 local current measurements, we are able to monitor the progression and map the degradation modes of shorting, thinning, and crossover leak over the entire membrane. Results from this test method have been validated by conventional metrics of fluoride release rates, physical crossover leak rates, pinhole mapping, and cross-sectional measurements.

  8. Advanced Cell Development and Degradation Studies

    SciTech Connect

    J. E. O'Brien; C. M. Stoots; J. S. Herring; R. C. O'Brien; K. G. Condie; M. Sohal; G. K. Housley; J. J. Hartvigsen; D. Larsen; G. Tao; B. Yildiz; V. Sharma; P. Singh; N. Petigny; T. L. Cable

    2010-09-01

    The Idaho National Laboratory (INL) has been researching the application of solid-oxide electrolysis cells for large-scale hydrogen production from steam over a temperature range of 800 to 900ºC. From 2003 – 2009, this work was sponsored by the DOE Nuclear Hydrogen Initiative (NHI). Starting in 2010, the HTE research program has been sponsored by the Next Generation Nuclear Plant (NGNP) program. HTSE research priorities in FY10 are centered on understanding and reducing cell and stack performance degradation to an acceptable level to advance the technology readiness level of HTSE and to justify further large-scale demonstration activities. This report provides a summary of our FY10 experimental program, which has been focused on advanced cell and stack development and degradation studies. Advanced cell and stack development activities are under way at five technology partners: MSRI, Versa Power, Ceramatec, NASA Glenn, and St. Gobain. Performance evaluation of the advanced technology cells and stacks has been performed by the technology partners, by MIT and the University of Connecticut and at the INL HTE Laboratory. Summaries of these development activities and test results are presented.

  9. Accelerated optical polymer aging studies for LED luminaire applications

    NASA Astrophysics Data System (ADS)

    Estupiñán, Edgar; Wendling, Peter; Kostrun, Marijan; Garner, Richard

    2013-09-01

    There is a need in the lighting industry to design and implement accelerated aging methods that accurately simulate the aging process of LED luminaire components. In response to this need, we have built a flexible and reliable system to study the aging characteristics of optical polymer materials, and we have employed it to study a commercially available LED luminaire diffuser made of PMMA. The experimental system consists of a "Blue LED Emitter" and a working surface. Both the temperatures of the samples and the optical powers of the LEDs are appropriately characterized in the system. Several accelerated aging experiments are carried out at different temperatures and optical powers over a 90 hour period and the measured transmission values are used as inputs to a degradation model derived using plausibility arguments. This model seems capable of predicting the behavior of the material as a function of time, temperature and optical power. The model satisfactorily predicts the measured transmission values of diffusers aged in luminaires at two different times and thus can be used to make application recommendations for this material. Specifically, at 35000 hours (the manufacturer's stated life of the luminaire) and at the typical operational temperature of the diffuser, the model predicts a transmission loss of only a few percent over the original transmission of the material at 450 nm, which renders this material suitable for this application.

  10. Durability Improvements Through Degradation Mechanism Studies

    SciTech Connect

    Borup, Rodney L.; Mukundan, Rangachary; Spernjak, Dusan; Baker, Andrew M.; Lujan, Roger W.; Langlois, David Alan; Ahluwalia, Rajesh; Papadia, D. D.; Weber, Adam Z.; Kusoglu, Ahmet; Shi, Shouwnen; More, K. L.; Grot, Steve

    2015-08-03

    The durability of polymer electrolyte membrane (PEM) fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. By investigating cell component degradation modes and defining the fundamental degradation mechanisms of components and component interactions, new materials can be designed to improve durability. To achieve a deeper understanding of PEM fuel cell durability and component degradation mechanisms, we utilize a multi-institutional and multi-disciplinary team with significant experience investigating these phenomena.

  11. UCLA Neptune Facility for Advanced Accelerator Studies

    SciTech Connect

    Tochitsky, Sergei Ya.; Clayton, Christopher E.; Marsh, Kenneth A.; Joshi, Chandrashekhar; Rosenzweig, James B.; Pellegrini, Claudio

    2004-12-07

    The Neptune Laboratory at UCLA is being used for exploring concepts useful for advanced accelerators. This facility hosts a TW-class CO2 laser system and a high-brightness photoinjector producing a 14 MeV electron beam. The goal for the laboratory is to carry out experiments on high-gradient acceleration of externally injected electrons in both laser-driven relativistic plasma waves and EM laser field in vacuum. Experiments on plasma beat-wave acceleration using a prebunched electron beam, a high-energy gain 10-{mu}m inverse free electron laser accelerator, longitudinal electron beam shaping and laser based light-sources are planned.

  12. Comparison of environmental degradation in Hanwha 295 W and SunPower 320 W photovoltaic modules via accelerated lifecycle testing

    NASA Astrophysics Data System (ADS)

    Biggie, R.; Lai, T.; Huang, W.-J.; Potter, B. G.; Simmons-Potter, K.

    2014-10-01

    Lifecycle testing of full-scale photovoltaic (PV) modules was conducted in a large-sized, accelerated-degradation chamber in our labs that enables full-solar-spectrum irradiance, temperature, and humidity control. In-situ measurement of both polycrystalline and monocrystalline silicon PV module energy conversion characteristics were examined under environmental lifecycle conditions representative of Tucson, AZ. Specifically, the performance degradation of a Hanwha 295 W polycrystalline PV module and of a SunPower 320 W monocrystalline PV module were evaluated and compared. Results indicate that the initial efficiency of the polycrystalline module and the subsequent annual degradation occurred within expected ranges for that system. In contrast, the single-crystal module exhibited both a significant decrease in PV module efficiency during the test cycle, and early evidence of environmentally-induced materials degradation across the module. The temperature and time-dependence of PV module behavior were extracted to provide insight into early-stage performance degradation under conditions approximating field-relevant environments.

  13. Accelerated Testing and Modeling of Potential-Induced Degradation as a Function of Temperature and Relative Humidity

    SciTech Connect

    Hacke, Peter; Spataru, Sergiu; Terwilliger, Kent; Perrin, Greg; Glick, Stephen; Kurtz, Sarah; Wohlgemuth, John

    2015-06-14

    An acceleration model based on the Peck equation was applied to power performance of crystalline silicon cell modules as a function of time and of temperature and humidity, the two main environmental stress factors that promote potential-induced degradation. This model was derived from module power degradation data obtained semi-continuously and statistically by in-situ dark current-voltage measurements in an environmental chamber. The modeling enables prediction of degradation rates and times as functions of temperature and humidity. Power degradation could be modeled linearly as a function of time to the second power; additionally, we found that coulombs transferred from the active cell circuit to ground during the stress test is approximately linear with time. Therefore, the power loss could be linearized as a function of coulombs squared. With this result, we observed that when the module face was completely grounded with a condensed phase conductor, leakage current exceeded the anticipated corresponding degradation rate relative to the other tests performed in damp heat.

  14. Beam-commissioning study of high-intensity accelerators using virtual accelerator model

    NASA Astrophysics Data System (ADS)

    Harada, H.; Shigaki, K.; Irie, Y.; Noda, F.; Hotchi, H.; Saha, P. K.; Shobuda, Y.; Sako, H.; Furukawa, K.; Machida, S.

    2009-04-01

    In order to control large-scale accelerators efficiently, a control system with a virtual accelerator model was constructed. The virtual accelerator (VA) is an on-line beam simulator provided with a beam monitor scheme. The VA is based upon the Experimental Physics and Industrial Control System (EPICS) and is configured under the EPICS input/output controller (IOC) in parallel with a real accelerator (RA). Thus, the machine operator can access the parameters of the RA through the channel access client and then feed them to the VA, and vice versa. Such a control scheme facilitates developments of the commissioning tools, feasibility study of the proposed accelerator parameters and examination of the measured accelerator data. This paper describes the beam commissioning results and activities by using the VA at the J-PARC 3-GeV rapid-cycling synchrotron (RCS).

  15. Data for accelerated degradation of calcium phosphate surface-coated polycaprolactone and polycaprolactone/bioactive glass composite scaffolds.

    PubMed

    Poh, Patrina S P; Hutmacher, Dietmar W; Holzapfel, Boris M; Solanki, Anu K; Woodruff, Maria A

    2016-06-01

    Polycaprolactone (PCL)-based composite scaffolds containing 50 wt% of 45S5 bioactive glass (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated into scaffolds using melt-extrusion based additive manufacturing technique. Additionally, the PCL scaffolds were surface coated with a layer of calcium phosphate (CaP). For a comparison of the scaffold degradation, the scaffolds were then subjected to in vitro accelerated degradation by immersion in 5 M sodium hydroxide (NaOH) solution for up to 7 days. The scaffold׳s morphology was observed by means of SEM imaging and scaffold mass loss was recorded over the experimental period. PMID:27081669

  16. Data for accelerated degradation of calcium phosphate surface-coated polycaprolactone and polycaprolactone/bioactive glass composite scaffolds.

    PubMed

    Poh, Patrina S P; Hutmacher, Dietmar W; Holzapfel, Boris M; Solanki, Anu K; Woodruff, Maria A

    2016-06-01

    Polycaprolactone (PCL)-based composite scaffolds containing 50 wt% of 45S5 bioactive glass (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated into scaffolds using melt-extrusion based additive manufacturing technique. Additionally, the PCL scaffolds were surface coated with a layer of calcium phosphate (CaP). For a comparison of the scaffold degradation, the scaffolds were then subjected to in vitro accelerated degradation by immersion in 5 M sodium hydroxide (NaOH) solution for up to 7 days. The scaffold׳s morphology was observed by means of SEM imaging and scaffold mass loss was recorded over the experimental period.

  17. Data for accelerated degradation of calcium phosphate surface-coated polycaprolactone and polycaprolactone/bioactive glass composite scaffolds

    PubMed Central

    Poh, Patrina S.P.; Hutmacher, Dietmar W.; Holzapfel, Boris M.; Solanki, Anu K.; Woodruff, Maria A.

    2016-01-01

    Polycaprolactone (PCL)-based composite scaffolds containing 50 wt% of 45S5 bioactive glass (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated into scaffolds using melt-extrusion based additive manufacturing technique. Additionally, the PCL scaffolds were surface coated with a layer of calcium phosphate (CaP). For a comparison of the scaffold degradation, the scaffolds were then subjected to in vitro accelerated degradation by immersion in 5 M sodium hydroxide (NaOH) solution for up to 7 days. The scaffold׳s morphology was observed by means of SEM imaging and scaffold mass loss was recorded over the experimental period. PMID:27081669

  18. Forced Degradation Studies of Aloe Emodin and Emodin by HPTLC.

    PubMed

    Narayanan, Sindhu; Jadhav, Aruna P; Kadam, V J

    2015-01-01

    Anthraquinones are natural phenolic compounds, which are reported to act as anti-aging, anti-inflammatory, antioxidant, anti-cancer, laxative and antitumor agents. They are abudant in plants like candle bush, aloes, cascara bark and rhubarb. The present work was to observe the effect of different forced degradation conditions by high-performance thin layer chromatography on potential markers i.e. aloe emodin and emodin. Both aloe emodin and emodin were subjected to various forced degradation studies such as oxidation, acid and alkaline hydrolysis, photolysis, hydrolytic and thermal degradation. Aloe emodin, was more susceptible to acid hydrolysis and degradation was found to a lesser extent under thermal degradation whereas significant degradation was observed under acid hydrolysis, lesser extent was observed under alkali hydrolysis for emodin. Forced degradation studies on aloe emodin and emodin gives information about its storage and intrinsic stability conditions considering the advanced pharmaceutical aspects of formulation. PMID:26997712

  19. Forced Degradation Studies of Aloe Emodin and Emodin by HPTLC

    PubMed Central

    Narayanan, Sindhu; Jadhav, Aruna P.; Kadam, V. J.

    2015-01-01

    Anthraquinones are natural phenolic compounds, which are reported to act as anti-aging, anti-inflammatory, antioxidant, anti-cancer, laxative and antitumor agents. They are abudant in plants like candle bush, aloes, cascara bark and rhubarb. The present work was to observe the effect of different forced degradation conditions by high-performance thin layer chromatography on potential markers i.e. aloe emodin and emodin. Both aloe emodin and emodin were subjected to various forced degradation studies such as oxidation, acid and alkaline hydrolysis, photolysis, hydrolytic and thermal degradation. Aloe emodin, was more susceptible to acid hydrolysis and degradation was found to a lesser extent under thermal degradation whereas significant degradation was observed under acid hydrolysis, lesser extent was observed under alkali hydrolysis for emodin. Forced degradation studies on aloe emodin and emodin gives information about its storage and intrinsic stability conditions considering the advanced pharmaceutical aspects of formulation. PMID:26997712

  20. A library of L-tyrosine-derived biodegradable polyarylates for potential biomaterial applications, part I: synthesis, characterization and accelerated hydrolytic degradation.

    PubMed

    Huang, Xia; Shen, Chang-Yu; Chen, Jia-Chang; Li, Qian

    2009-01-01

    A combinatorial library of biodegradable polyarylates derived from L-tyrosine was synthesized and characterized. These polyarylates are A-B-type co-polymers consisting of a cyclic dipeptide and a diacid. General structure-property correlations were established by comparing aryl diacid co-polymers and aliphatic diacid co-polymers. The synthesized polymers were characterized by FT-IR, (1)H-NMR, (13)C-NMR for their chemical structure, by DSC and TGA for their thermal characteristics and by GPC for their molecular weight distribution. The T(g) of polymers decreased and water absorption increased with increasing number of methylene groups in the polymer backbone. Using a cyclic peptide derived from L-tyrosine as co-monomer we obtained optimum bioactivity and biocompatibility. Combinatorial approaches of designing material increased effectively the number of available degradable polymers which can be used in different biomaterials applications. General structure-property correlation makes polymers' properties varied in a predictable and systematic fashion. Accelerated hydrolytic degradation studies of polyarylates were performed at 70 degrees C in acid and alkali medium. The degradation rates of polymers were in accordance with their water absorption. The degradation rates of samples in acid medium were lower than those in alkali medium. PMID:19454161

  1. Modified betatron accelerator studies. Final report

    SciTech Connect

    Hughes, T.P.; Godfrey, B.B.

    1984-12-01

    This final report describes work carried out on the equilibrium and stability properties of circular accelerators. A rigid-disk beam model in which the fields are treated exactly is used to study linear instabilities. This approach has uncovered an important inductive effect which at high toroidal mode numbers leads to either stability or to a hybrid instability. A corresponding effect has been found in electron-layer geometry. The new theory also shows that moving the equilibrium position toward the inner wall can stabilize low mode numbers. With the aid of IVORY code simulation results it is shown that the transverse motion of beam partilces is a key factor in determining beam stability. The upper bound on particle circulation frequency spread is shown to be a function only of the beam major and minor radii. This leads to upper bounds on stable currents in the modified betatron. Numerical results on stability in the stellatron and reversing-solenoidal-lens betatrons are presented. In addition, the sensitivity of equilibrium particle orbits in the stellatron to initial conditions is calculated.

  2. Computational studies and optimization of wakefield accelerators

    SciTech Connect

    Tsung, Frank S.; Bruhwiler, David L.; Cary, John R.; Esarey, Eric H.; Mori, Warren B.; Vay, Jean-Luc; Martins, Samuel F.; Katsouleas, Tom; Cormier-Michel, Estelle; Fawley, William M.; Huang, Chengkun; Wang, Xiadong; Cowan, Ben; Decyk, Victor K.; Fonseca, Ricardo A.; Lu, Wei; Messmer, Peter; Mullowney, Paul; Nakamura, Kei; Paul, Kevin; Plateau, Guillaume R.; Schroeder, Carl B.; Silva, Luis O.; Toth, Csaba; Geddes, C.G.R.; Tzoufras, Michael; Antonsen, Tom; Vieira, Jorge; Leemans, Wim P.

    2008-06-16

    Laser- and particle beam-driven plasma wakefield accelerators produce accelerating fields thousands of times higher than radio-frequency accelerators, offering compactness and ultrafast bunches to extend the frontiers of high energy physics and to enable laboratory-scale radiation sources. Large-scale kinetic simulations provide essential understanding of accelerator physics to advance beam performance and stability and show and predict the physics behind recent demonstration of narrow energy spread bunches. Benchmarking between codes is establishing validity of the models used and, by testing new reduced models, is extending the reach of simulations to cover upcoming meter-scale multi-GeV experiments. This includes new models that exploit Lorentz boosted simulation frames to speed calculations. Simulations of experiments showed that recently demonstrated plasma gradient injection of electrons can be used as an injector to increase beam quality by orders of magnitude. Simulations are now also modeling accelerator stages of tens of GeV, staging of modules, and new positron sources to design next-generation experiments and to use in applications in high energy physics and light sources.

  3. Reactive oxygen species accelerate degradation of anion exchange membranes based on polyphenylene oxide in alkaline environments.

    PubMed

    Parrondo, Javier; Wang, Zhongyang; Jung, Min-Suk J; Ramani, Vijay

    2016-07-20

    Anion exchange membranes (AEM) based on polyphenylene oxide (PPO) suffered quaternary-ammonium-cation-site degradation in alkaline environments. Surprisingly, the degradation rate was considerably faster in the presence of molecular oxygen. We postulated that the AEM cation-site catalyzes the reduction of dioxygen by hydroxide ions to yield the superoxide anion radical and the highly reactive hydroxyl free radical. We substantiated our hypothesis by using a phosphorous-containing spin trap (5-diisopropoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide) to detect the adducts for both free radicals in situ using (31)P-NMR spectroscopy. PMID:27381009

  4. Centrifuge Study of Pilot Tolerance to Acceleration and the Effects of Acceleration on Pilot Performance

    NASA Technical Reports Server (NTRS)

    Creer, Brent Y.; Smedal, Harald A.; Wingrove, Rodney C.

    1960-01-01

    A research program the general objective of which was to measure the effects of various sustained accelerations on the control performance of pilots, was carried out on the Aviation Medical Acceleration Laboratory centrifuge, U.S. Naval Air Development Center, Johnsville, PA. The experimental setup consisted of a flight simulator with the centrifuge in the control loop. The pilot performed his control tasks while being subjected to acceleration fields such as might be encountered by a forward-facing pilot flying an atmosphere entry vehicle. The study was divided into three phases. In one phase of the program, the pilots were subjected to a variety of sustained linear acceleration forces while controlling vehicles with several different sets of longitudinal dynamics. Here, a randomly moving target was displayed to the pilot on a cathode-ray tube. For each combination of acceleration field and vehicle dynamics, pilot tracking accuracy was measured and pilot opinion of the stability and control characteristics was recorded. Thus, information was obtained on the combined effects of complexity of control task and magnitude and direction of acceleration forces on pilot performance. These tests showed that the pilot's tracking performance deteriorated markedly at accelerations greater than about 4g when controlling a lightly damped vehicle. The tentative conclusion was also reached that regardless of the airframe dynamics involved, the pilot feels that in order to have the same level of control over the vehicle, an increase in the vehicle dynamic stability was required with increases in the magnitudes of the acceleration impressed upon the pilot. In another phase, boundaries of human tolerance of acceleration were established for acceleration fields such as might be encountered by a pilot flying an orbital vehicle. A special pilot restraint system was developed to increase human tolerance to longitudinal decelerations. The results of the tests showed that human tolerance

  5. Computing requirements for S. S. C. accelerator design and studies

    SciTech Connect

    Dragt, A.; Talman, R.; Siemann, R.; Dell, G.F.; Leemann, B.; Leemann, C.; Nauenberg, U.; Peggs, S.; Douglas, D.

    1984-01-01

    We estimate the computational hardware resources that will be required for accelerator physics studies during the design of the Superconducting SuperCollider. It is found that both Class IV and Class VI facilities (1) will be necessary. We describe a user environment for these facilities that is desirable within the context of accelerator studies. An acquisition scenario for these facilities is presented.

  6. Structural basis of Ornithine Decarboxylase inactivation and accelerated degradation by polyamine sensor Antizyme1

    PubMed Central

    Wu, Donghui; Kaan, Hung Yi Kristal; Zheng, Xiaoxia; Tang, Xuhua; He, Yang; Vanessa Tan, Qianmin; Zhang, Neng; Song, Haiwei

    2015-01-01

    Ornithine decarboxylase (ODC) catalyzes the first and rate-limiting step of polyamine biosynthesis in humans. Polyamines are essential for cell proliferation and are implicated in cellular processes, ranging from DNA replication to apoptosis. Excessive accumulation of polyamines has a cytotoxic effect on cells and elevated level of ODC activity is associated with cancer development. To maintain normal cellular proliferation, regulation of polyamine synthesis is imposed by Antizyme1 (AZ1). The expression of AZ1 is induced by a ribosomal frameshifting mechanism in response to increased intracellular polyamines. AZ1 regulates polyamine homeostasis by inactivating ODC activity and enhancing its degradation. Here, we report the structure of human ODC in complex with N-terminally truncated AZ1 (cAZ1). The structure shows cAZ1 binding to ODC, which occludes the binding of a second molecule of ODC to form the active homodimer. Consequently, the substrate binding site is disrupted and ODC is inactivated. Structural comparison shows that the binding of cAZ1 to ODC causes a global conformational change of ODC and renders its C-terminal region flexible, therefore exposing this region for degradation by the 26S proteasome. Our structure provides the molecular basis for the inactivation of ODC by AZ1 and sheds light on how AZ1 promotes its degradation. PMID:26443277

  7. Coupler Studies for PBG Fiber Accelerators

    SciTech Connect

    England, J.; Ng, C.; Noble, R.; Spencer, J.; Wu, Z.; Xu, D.; /SLAC

    2011-08-17

    Photonic band gap (PBG) fiber with hollow core defects are being designed and fabricated for use as laser driven accelerators because they can provide gradients of several GeV/m for picosecond pulse lengths. We expect to produce fiber down to {lambda} = 1.5-2.0 {micro}m wavelengths but still lack a viable means for efficient coupling of laser power into such structures due to the very different character of the TM-like modes from those used in the telecom field and the fact that the defect must function as both a longitudinal waveguide for the accelerating field and a transport channel for the particles. We discuss the status of our work in pursuing both end and side coupling. For both options, the symmetry of these crystals leads to significant differences with the telecom field. Side coupling provides more options and appears to be preferred. Our goals are to test gradients, mode content and coupling efficiencies on the NLCTA at SLAC. While there are many potential types of fiber based on very different fabrication methods and materials we will concentrate on 2D axisymmetric glass with hexagonal symmetry but will discuss several different geometries including 2D and 3D planar structures. Since all of these can be fabricated using modern techniques with a variety of dielectric materials they are expected to have desirable optical and radiation hardness properties. Thus, we expect a new generation of very high gradient accelerators that extends the Livingston-Panofsky chart of exponential growth in energy vs. time at greatly reduced costs. For illustration, Fig.1 shows a simulation of our first engineered fiber with an accelerating mode expected near 7.3 {micro}m that is now ready to test on the NLCTA. In this example, one sees the uniform longitudinal accelerating field in the central defect as first shown by Lin3 together with a hexagonal array of surrounding hot spots. Contrary to what one expects from the telecom field, Ng et al. have shown4 that the ideal end

  8. Mechanistic study of a diazo dye degradation by Soybean Peroxidase

    PubMed Central

    2013-01-01

    Background Enzyme based remediation of wastewater is emerging as a novel, efficient and environmentally-friendlier approach. However, studies showing detailed mechanisms of enzyme mediated degradation of organic pollutants are not widely published. Results The present report describes a detailed study on the use of Soybean Peroxidase to efficiently degrade Trypan Blue, a diazo dye. In addition to examining various parameters that can affect the dye degradation ability of the enzyme, such as enzyme and H2O2 concentration, reaction pH and temperature, we carried out a detailed mechanistic study of Trypan Blue degradation. HPLC-DAD and LC-MS/MS studies were carried out to confirm dye degradation and analyze the intermediate metabolites and develop a detailed mechanistic dye degradation pathway. Conclusion We report that Soybean peroxidase causes Trypan Blue degradation via symmetrical azo bond cleavage and subsequent radical-initiated ring opening of the metabolites. Interestingly, our results also show that no high molecular weight polymers were produced during the peroxidase-H2O2 mediated degradation of the phenolic Trypan Blue. PMID:23711110

  9. Forced degradation studies of biopharmaceuticals: Selection of stress conditions.

    PubMed

    Tamizi, Elnaz; Jouyban, Abolghasem

    2016-01-01

    Stability studies under stress conditions or forced degradation studies play an important role in different phases of development and production of biopharmaceuticals and biological products. These studies are mostly applicable to selection of suitable candidates and formulation developments, comparability studies, elucidation of possible degradation pathways and identification of degradation products, as well as, development of stability indicating methods. Despite the integral part of these studies in biopharmaceutical industry, there is no well-established protocol for the selection of stress conditions, timing of stress testing and required extent of degradation. Therefore, due to the present gap in the stability studies guidelines, it is the responsibility of researchers working in academia and biopharmaceutical industry to set up forced degradation experiments that could fulfill all the expectations from the stability studies of biopharmaceuticals under stress conditions. Concerning the importance of the function of desired stress conditions in forced degradation studies, the present review aims to provide a practical summary of the applicable stress conditions in forced degradation studies of biopharmaceuticals according to the papers published in a time period of 1992-2015 giving detailed information about the experimental conditions utilized to induce required stresses.

  10. Strontium exerts dual effects on calcium phosphate cement: Accelerating the degradation and enhancing the osteoconductivity both in vitro and in vivo.

    PubMed

    Kuang, Guan-Ming; Yau, W P; Wu, Jun; Yeung, Kelvin W K; Pan, Haobo; Lam, W M; Lu, W W; Chiu, K Y

    2015-05-01

    Calcium phosphate cements (CPCs) have long been used as osteoconductive bone substitutes in the treatment of bone defects. However, the degradation rate of CPC is typically too slow to match the new bone growth rate. It is known that strontium increases the solubility of hydroxyapatite as well as exerts both anabolic and anticatabolic effects on bone. Therefore, we hypothesized that the incorporation of strontium would accelerate the degradation rate and enhance the osteoconductivity of CPC. In this study, Three groups, CPC (0% Sr-CPC), 5% Sr-CPC, and 10% Sr-CPC, were prepared, with the total molar ratio for Sr/(Sr+Ca) in the cement powder phase being 0, 5, and 10%, respectively. In the immersion test, less residual weight was observed in both 5% Sr-CPC and 10% Sr-CPC groups than CPC group. In addition, a higher osteoblastic cell proliferation rate and alkaline phosphatase activity were obtained in the strontium groups. In a rat femur bone defect model comparing CPC with 10% Sr-CPC, at 2 weeks postoperation, early endochondral ossification was found in the 10% Sr-CPC group, whereas only fibrous tissue was observed in control group; at 4-16 weeks postoperation, progressive osteoconduction toward the cement was observed in both groups. At 32 weeks, a higher peri-cement bone area and reduced cement area were noted in the 10% Sr-CPC group. In conclusion, in the 10% Sr-CPC group, strontium exerts dual effects on CPC: accelerating degradation rate and enhancing osteoconductivity, as shown here both in vitro and in vivo.

  11. Strontium exerts dual effects on calcium phosphate cement: Accelerating the degradation and enhancing the osteoconductivity both in vitro and in vivo.

    PubMed

    Kuang, Guan-Ming; Yau, W P; Wu, Jun; Yeung, Kelvin W K; Pan, Haobo; Lam, W M; Lu, W W; Chiu, K Y

    2015-05-01

    Calcium phosphate cements (CPCs) have long been used as osteoconductive bone substitutes in the treatment of bone defects. However, the degradation rate of CPC is typically too slow to match the new bone growth rate. It is known that strontium increases the solubility of hydroxyapatite as well as exerts both anabolic and anticatabolic effects on bone. Therefore, we hypothesized that the incorporation of strontium would accelerate the degradation rate and enhance the osteoconductivity of CPC. In this study, Three groups, CPC (0% Sr-CPC), 5% Sr-CPC, and 10% Sr-CPC, were prepared, with the total molar ratio for Sr/(Sr+Ca) in the cement powder phase being 0, 5, and 10%, respectively. In the immersion test, less residual weight was observed in both 5% Sr-CPC and 10% Sr-CPC groups than CPC group. In addition, a higher osteoblastic cell proliferation rate and alkaline phosphatase activity were obtained in the strontium groups. In a rat femur bone defect model comparing CPC with 10% Sr-CPC, at 2 weeks postoperation, early endochondral ossification was found in the 10% Sr-CPC group, whereas only fibrous tissue was observed in control group; at 4-16 weeks postoperation, progressive osteoconduction toward the cement was observed in both groups. At 32 weeks, a higher peri-cement bone area and reduced cement area were noted in the 10% Sr-CPC group. In conclusion, in the 10% Sr-CPC group, strontium exerts dual effects on CPC: accelerating degradation rate and enhancing osteoconductivity, as shown here both in vitro and in vivo. PMID:25087971

  12. Stability of CIGS solar cells and component materials evaluated by a step-stress accelerated degradation test method

    NASA Astrophysics Data System (ADS)

    Pern, F. J.; Noufi, R.

    2012-10-01

    A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15°C and then a 15% relative humidity (RH) increment step, beginning from 40°C/40%RH (T/RH = 40/40) to 85°C/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 μm to 0.50 μm on the cells. No clear "stepwise" feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH >= 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and "capacitor quality" factor (CPE-P), which were related to the cells' p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH >= 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS

  13. Stability of CIGS Solar Cells and Component Materials Evaluated by a Step-Stress Accelerated Degradation Test Method: Preprint

    SciTech Connect

    Pern, F. J.; Noufi, R.

    2012-10-01

    A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 μm to 0.50 μm on the cells. No clear 'stepwise' feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH ≥ 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and 'capacitor quality' factor (CPE-P), which were related to the cells? p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH ≥ 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS

  14. Ethylene propylene cable degradation during LOCA research tests: tensile properties at the completion of accelerated aging

    SciTech Connect

    Bustard, L.D.

    1982-05-01

    Six ethylene-propylene rubber (EPR) insulation materials were aged at elevated temperature and radiation stress exposures common in cable LOCA qualification tests. Material samples were subjected to various simultaneous and sequential aging simulations in preparation for accident environmental exposures. Tensile properties subsequent to the aging exposure sequences are reported. The tensile properties of some, but not all, specimens were sensitive to the order of radiation and elevated temperature stress exposure. Other specimens showed more severe degradation when simultaneously exposed to radiation and elevated temperature as opposed to the sequential exposure to the same stresses. Results illustrate the difficulty in defining a single test procedure for nuclear safety-related qualification of EPR elastomers. A common worst-case sequential aging sequence could not be identified.

  15. Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress

    NASA Technical Reports Server (NTRS)

    Kulkarni, Chetan S.; Celaya, Jose R.; Goebel, Kai; Biswas, Gautam

    2012-01-01

    Electrolytic capacitors are used in several applications ranging from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. This makes them good candidates for prognostics and health management research. Prognostics provides a way to assess remaining useful life of components or systems based on their current state of health and their anticipated future use and operational conditions. Past experiences show that capacitors tend to degrade and fail faster under high electrical and thermal stress conditions that they are often subjected to during operations. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters.

  16. Effect of TiO2-Crystal Forms on the Photo-Degradation of EVA/PLA Blend Under Accelerated Weather Testing

    NASA Astrophysics Data System (ADS)

    Van Cong, Do; Trang, Nguyen Thi Thu; Giang, Nguyen Vu; Lam, Tran Dai; Hoang, Thai

    2016-05-01

    Photo-degradation of poly (ethylene-co-vinyl acetate) (EVA)/poly (lactic acid) (PLA) blend and EVA/PLA/TiO2 nanocomposites was carried out under accelerated weather testing conditions by alternating cycles of ultraviolet (UV) light and moisture at controlled and elevated temperatures. The characters, properties, and morphology of these materials before and after accelerated weather testing were determined by Fourier transform infrared spectroscopy, colour changes, viscosity, tensile test, thermogravimetric analysis, and field emission scanning electron microscopy. The increases in the content of oxygen-containing groups, colour changes; the decreases in viscosity, tensile properties, and thermal stability of these materials after accelerated weather testing are the evidence for the photo-degradation of the blend and nanocomposites. After accelerated weather testing, the appearance of many micro-holes and micro-pores on the surface of the collected samples was observed. The photo-degradation degree of the nanocomposites depended on the TiO2-crystal form. Rutile TiO2 do not enhance the degradation, but anatase and mixed crystals TiO2 nanoparticles promoted the degradation of the nanocomposites. Particularly, the mixed crystals TiO2 nanoparticles showed the highest photo-catalytic activity of the nanocomposites.

  17. Analysis of degradation in UHMWPE a comparative study among the various commercial and laboratory grades UHMWPE

    NASA Astrophysics Data System (ADS)

    Azam, A. M.; Ali, A.; Khan, H.; Yasin, T.; Mehmood, M. S.

    2016-08-01

    Oxidative degradation of the ultra-high molecular weight polyethylene (UHMWPE) limits the life of implants. This degradation can be monitored to estimate the service life of UHMWPE following the standard protocols as defined by American Standards for Testing Materials (ASTM). In this work, a comparative study has been carried on two commercially available UHMWPE grades i.e. GUR 1020 and GUR 1050 and one laboratory grade UHMWPE which was purchased from Sigma Aldrich. These powder samples were pressed while using hot press with controlled heating and cooling setup in open air under 200 bar of external pressure. These sheets were then subjected to accelerated aging in an oven at 80 °C for three weeks. The degradation of the UHMWPE was monitored by ATR-FTIR techniquefor three weeks. The oxidation index (OI) measurement showed that the commercial grade UHMWPE i.e. GUR-1020 and GUR-1050 degrade more as compared to laboratory grade UHMWPE. The values of OI after three weeks of accelerating aging were found 0.18, 0.14, and 0.09 for GUR-1020, GUR-1050, and Sigma Aldrich, respectively. In addition to this, it was found that commercial grades of UHMWPE suffer more structural alterations as compared to laboratory grade one. We hope that these results will be of particular and fundamental importance for the researchers and orthopaedic industry.

  18. COMBINED STEREO/RHESSI STUDY OF CORONAL MASS EJECTION ACCELERATION AND PARTICLE ACCELERATION IN SOLAR FLARES

    SciTech Connect

    Temmer, M.; Veronig, A. M.; Krucker, S.; Vrsnak, B. E-mail: asv@igam.uni-graz.a E-mail: krucker@ssl.berkeley.ed

    2010-04-01

    Using the potential of two unprecedented missions, Solar Terrestrial Relations Observatory (STEREO) and Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), we study three well-observed fast coronal mass ejections (CMEs) that occurred close to the limb together with their associated high-energy flare emissions in terms of RHESSI hard X-ray (HXR) spectra and flux evolution. From STEREO/EUVI and STEREO/COR1 data, the full CME kinematics of the impulsive acceleration phase up to {approx}4 R{sub sun} is measured with a high time cadence of <=2.5 minutes. For deriving CME velocity and acceleration, we apply and test a new algorithm based on regularization methods. The CME maximum acceleration is achieved at heights h <= 0.4 R{sub sun}, and the peak velocity at h <= 2.1 R{sub sun} (in one case, as small as 0.5 R{sub sun}). We find that the CME acceleration profile and the flare energy release as evidenced in the RHESSI HXR flux evolve in a synchronized manner. These results support the 'standard' flare/CME model which is characterized by a feedback relationship between the large-scale CME acceleration process and the energy release in the associated flare.

  19. Accelerated light-induced degradation for detecting copper contamination in p-type silicon

    SciTech Connect

    Inglese, Alessandro Savin, Hele; Lindroos, Jeanette

    2015-08-03

    Copper is a harmful metal impurity that significantly impacts the performance of silicon-based devices if present in active regions. In this contribution, we propose a fast method consisting of simultaneous illumination and annealing for the detection of copper contamination in p-type silicon. Our results show that, within minutes, such method is capable of producing a significant reduction of the minority carrier lifetime. A spatial distribution map of copper contamination can then be obtained through the lifetime values measured before and after degradation. In order to separate the effect of the light-activated copper defects from the other metastable complexes in low resistivity Cz-silicon, we carried out a dark anneal at 200 °C, which is known to fully recover the boron-oxygen defect. Similar to the boron-oxygen behavior, we show that the dark anneal also recovers the copper defects. However, the recovery is only partial and it can be used to identify the possible presence of copper contamination.

  20. Accelerated light-induced degradation for detecting copper contamination in p-type silicon

    NASA Astrophysics Data System (ADS)

    Inglese, Alessandro; Lindroos, Jeanette; Savin, Hele

    2015-08-01

    Copper is a harmful metal impurity that significantly impacts the performance of silicon-based devices if present in active regions. In this contribution, we propose a fast method consisting of simultaneous illumination and annealing for the detection of copper contamination in p-type silicon. Our results show that, within minutes, such method is capable of producing a significant reduction of the minority carrier lifetime. A spatial distribution map of copper contamination can then be obtained through the lifetime values measured before and after degradation. In order to separate the effect of the light-activated copper defects from the other metastable complexes in low resistivity Cz-silicon, we carried out a dark anneal at 200 °C, which is known to fully recover the boron-oxygen defect. Similar to the boron-oxygen behavior, we show that the dark anneal also recovers the copper defects. However, the recovery is only partial and it can be used to identify the possible presence of copper contamination.

  1. Degradation mechanism of LiCoO2/mesocarbon microbeads battery based on accelerated aging tests

    NASA Astrophysics Data System (ADS)

    Guan, Ting; Zuo, Pengjian; Sun, Shun; Du, Chunyu; Zhang, Lingling; Cui, Yingzhi; Yang, Lijie; Gao, Yunzhi; Yin, Geping; Wang, Fuping

    2014-12-01

    A series of LiCoO2/mesocarbon microbeads (MCMB) commercial cells cycled at different rates (0.6C, 1.2C, 1.5C, 1.8C, 2.4C and 3.0C) are disassembled and the capacity fade mechanism is proposed by analyzing the structure, morphology and electrochemical performance evolution at the capacity retention of 95%, 90%, 85%, 80%. The capacity deterioration of the commercial cell is mainly caused by the decay of the reversible capacity of LiCoO2 cathode, the irreversible loss of active lithium and the lithium remaining in anode. The proportions of effects by the above three factors are calculated accurately. The consumption of the active lithium leads to a cell imbalance between the anode and the cathode. The electrochemical test results indicate that the capacity fade of the active materials at the low rate is more obvious than that at the high rate. The influence of the active lithium is gradually increscent with the increasing rate. The rate of 1.5C is the optimal value to accelerate the aging of the full cell by comparing the testing results at different capacity retentions in the specific condition of low charge/discharge rate and shallow depth of discharge.

  2. A Doping Lattice of Aluminum and Copper with Accelerated Electron Transfer Process and Enhanced Reductive Degradation Performance.

    PubMed

    Zhang, Lin; Gao, Xue; Zhang, Zhixuan; Zhang, Mingbo; Cheng, Yiqian; Su, Jixin

    2016-01-01

    Treatment of azo dye effluents has received increasing concerns over the years due to their potential harms to natural environment and human health. The present study described the degrading ability of the as-synthesized crystalline Al-Cu alloys for removal of high-concentration Acid Scarlet 3R in alkaline aqueous solutions and its degradation mechanism. Al-Cu alloy particles with Al/Cu ratios 19:1 were successfully synthesized by high-energy mechanical milling. Characterization results showed that 10 h mechanical alloying process could lead to the formation of crystalline Al(Cu) solid solution. Batch experiment results confirmed the excellent ability of Al-Cu alloy particles for the degradation of 3R in aqueous solution. Under a certain condition ([Al-Cu]0 = 2 g/L, [3R]0 = 200 mg/L, [NaCl]0 = 25 g/L, initial pH = 10.9), the 3R could be completely degraded within only 3 min. It was also found that the degradation reaction followed zero-order kinetics model with respect to the initial dye concentration. The intermediate compounds were identified by UV-vis, FT-IR and HPLC-MS, and a pathway was proposed. Additionally, post-treatment Al-Cu alloy particles were characterized by SEM and TEM, and the results showed that the degradation might be attributed to the corrosion effect of Al-Cu alloys. PMID:27535800

  3. A Doping Lattice of Aluminum and Copper with Accelerated Electron Transfer Process and Enhanced Reductive Degradation Performance

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Gao, Xue; Zhang, Zhixuan; Zhang, Mingbo; Cheng, Yiqian; Su, Jixin

    2016-08-01

    Treatment of azo dye effluents has received increasing concerns over the years due to their potential harms to natural environment and human health. The present study described the degrading ability of the as-synthesized crystalline Al-Cu alloys for removal of high-concentration Acid Scarlet 3R in alkaline aqueous solutions and its degradation mechanism. Al-Cu alloy particles with Al/Cu ratios 19:1 were successfully synthesized by high-energy mechanical milling. Characterization results showed that 10 h mechanical alloying process could lead to the formation of crystalline Al(Cu) solid solution. Batch experiment results confirmed the excellent ability of Al-Cu alloy particles for the degradation of 3R in aqueous solution. Under a certain condition ([Al-Cu]0 = 2 g/L, [3R]0 = 200 mg/L, [NaCl]0 = 25 g/L, initial pH = 10.9), the 3R could be completely degraded within only 3 min. It was also found that the degradation reaction followed zero-order kinetics model with respect to the initial dye concentration. The intermediate compounds were identified by UV-vis, FT-IR and HPLC-MS, and a pathway was proposed. Additionally, post-treatment Al-Cu alloy particles were characterized by SEM and TEM, and the results showed that the degradation might be attributed to the corrosion effect of Al-Cu alloys.

  4. A Doping Lattice of Aluminum and Copper with Accelerated Electron Transfer Process and Enhanced Reductive Degradation Performance

    PubMed Central

    Zhang, Lin; Gao, Xue; Zhang, Zhixuan; Zhang, Mingbo; Cheng, Yiqian; Su, Jixin

    2016-01-01

    Treatment of azo dye effluents has received increasing concerns over the years due to their potential harms to natural environment and human health. The present study described the degrading ability of the as-synthesized crystalline Al-Cu alloys for removal of high-concentration Acid Scarlet 3R in alkaline aqueous solutions and its degradation mechanism. Al-Cu alloy particles with Al/Cu ratios 19:1 were successfully synthesized by high-energy mechanical milling. Characterization results showed that 10 h mechanical alloying process could lead to the formation of crystalline Al(Cu) solid solution. Batch experiment results confirmed the excellent ability of Al-Cu alloy particles for the degradation of 3R in aqueous solution. Under a certain condition ([Al-Cu]0 = 2 g/L, [3R]0 = 200 mg/L, [NaCl]0 = 25 g/L, initial pH = 10.9), the 3R could be completely degraded within only 3 min. It was also found that the degradation reaction followed zero-order kinetics model with respect to the initial dye concentration. The intermediate compounds were identified by UV-vis, FT-IR and HPLC-MS, and a pathway was proposed. Additionally, post-treatment Al-Cu alloy particles were characterized by SEM and TEM, and the results showed that the degradation might be attributed to the corrosion effect of Al-Cu alloys. PMID:27535800

  5. Acceleration of Fast CME: A Parametric Study

    NASA Astrophysics Data System (ADS)

    Wu, S. T.; Zhang, T. X.; Tan, A.

    2003-12-01

    The analysis of LASCO/SOHO, Skylab and Solar Maximum Mission (SMM) observations show that there are many CMEs initiated with streamer and flux-rope magnetic topology (Dere et al. 1999; St. Cyr et al., 1999; Plunkett et al., 2000). Two types of CMEs have been distinguished with different kinematic characteristics (MacQueen and Fisher, 1983; Andrews and Howard, 2001). These are fast CMEs with high initial speeds (i.e. constant speed) and slow CMEs with low initial speeds but gradual acceleration (i.e. accelerated CMEs). Efforts have been made to probe the underlying physics responsible for these dual characteristics. Low and Zhang (2002) proposed that fast and slow CMEs result from initial topology of the magnetic field characterized by normal and inverse quiescent prominences, respectively. Liu et al. have successfully performed a numerical MHD simulation for this scenario. In this presentation, we explore other possible processes using a 2.5D, time-dependent streamer and flux-rope MHD model (Wu and Guo, 1997) to investigate the dual kinematic properties of the CMEs by specifying the different initiation processes with a particular magnetic topology (i.e. inverse quiescent prominence magnetic topology). Two typical initiation processes are tested; (1) injection of the magnetic flux into the flux-rope causes additional Lorentz force to destabilize the streamer launching a CME (Wu et al., 1997) resulting in a category slow CME and (2) draining the plasma from the flux-rope together with flux injection leads to a balloon instability due to the magnetic buoyancy force which results in a impulsive eruption and launches a fast CME. References Andrews, M.D. and Howard, R.A., Space Sci. Rev., 95, 147, 2001 Dere, K.P. et al., Ap. J., 529, 575, 1999 Lin, et al., Proceedings of ICSC 2003: Solar Variability as an Input to the Earth's Environemnt, ESA-SP-535, 2003 (in press). Low, B.C. and Zhang, M., Ap. J., 564, L53, 2002. MacQueen, R.M. and Fisher, R.R., Solar Phys. 89, 89

  6. Biochar accelerates organic matter degradation and enhances N mineralisation during composting of poultry manure without a relevant impact on gas emissions.

    PubMed

    Sánchez-García, M; Alburquerque, J A; Sánchez-Monedero, M A; Roig, A; Cayuela, M L

    2015-09-01

    A composting study was performed to assess the impact of biochar addition to a mixture of poultry manure and barley straw. Two treatments: control (78% poultry manure + 22% barley straw, dry weight) and the same mixture amended with biochar (3% dry weight), were composted in duplicated windrows during 19 weeks. Typical monitoring parameters and gaseous emissions (CO2, CO, CH4, N2O and H2S) were evaluated during the process as well as the agronomical quality of the end-products. Biochar accelerated organic matter degradation and ammonium formation during the thermophilic phase and enhanced nitrification during the maturation phase. Our results suggest that biochar, as composting additive, improved the physical properties of the mixture by preventing the formation of clumps larger than 70 mm. It favoured microbiological activity without a relevant impact on N losses and gaseous emissions. It was estimated that biochar addition at 3% could reduce the composting time by 20%.

  7. Biochar accelerates organic matter degradation and enhances N mineralisation during composting of poultry manure without a relevant impact on gas emissions.

    PubMed

    Sánchez-García, M; Alburquerque, J A; Sánchez-Monedero, M A; Roig, A; Cayuela, M L

    2015-09-01

    A composting study was performed to assess the impact of biochar addition to a mixture of poultry manure and barley straw. Two treatments: control (78% poultry manure + 22% barley straw, dry weight) and the same mixture amended with biochar (3% dry weight), were composted in duplicated windrows during 19 weeks. Typical monitoring parameters and gaseous emissions (CO2, CO, CH4, N2O and H2S) were evaluated during the process as well as the agronomical quality of the end-products. Biochar accelerated organic matter degradation and ammonium formation during the thermophilic phase and enhanced nitrification during the maturation phase. Our results suggest that biochar, as composting additive, improved the physical properties of the mixture by preventing the formation of clumps larger than 70 mm. It favoured microbiological activity without a relevant impact on N losses and gaseous emissions. It was estimated that biochar addition at 3% could reduce the composting time by 20%. PMID:26038333

  8. Internal loop photobiodegradation reactor (ILPBR) for accelerated degradation of sulfamethoxazole (SMX).

    PubMed

    Yan, Ning; Xia, Siqing; Xu, Linke; Zhu, Jun; Zhang, Yongming; Rittmann, Bruce E

    2012-04-01

    The internal loop photobiodegradation reactor (ILPBR) was evaluated for the degradation of the pharmaceutical sulfamethoxazole (SMX) using batch experiments following three protocols: photolysis alone (P), biodegradation alone (B), and intimately coupled photolysis and biodegradation (P&B). SMX was removed more rapidly by P&B than by either P or B alone, and the corresponding dissolved organic carbon (DOC) removals by P&B also were higher. The faster SMX removal probably was due to a synergy between photolysis and the rapid biodegradation of SMX by the biofilm. The greater DOC removal was brought about by the presence of biofilm bacteria able to biodegrade photolysis products. Ammonium N released during photolysis of SMX gave more evidence for the formation of intermediates and was enough in P&B experiments to support bioactivity when no other N was supplied. Clone libraries performed on the biofilms before and after the P&B experiments showed profound changes in the microbial community. Whereas Rhodopirellula baltica and Methylibium petroleiphilum PM1 dominated the biofilm after the B experiments, they were replaced by Micrococcus luteus, Delftia acidovorans, and Oligotropha carboxidovorans after the P&B experiments. The changes in microbial community structure mirrored the change in function in the P&B experiments: SMX biodegradation (presumably the roles of R. baltica and M. petroleiphilum) was out-competed by SMX photolysis, but biodegradation of photolysis products (most likely by M. luteus and D. acidovorans) became important. The higher removal rates of SMX and DOC, as well as the changes in microbial community structure, confirm the value of intimately coupling photolysis with biodegradation in the ILPBR. PMID:22215070

  9. Compatibility and accelerated aging study for Li(Si)/FeS/sub 2 thermally activated batteries

    NASA Astrophysics Data System (ADS)

    Mead, J. W.; Searcy, J. Q.; Neiswander, P. N.; Poole, R. L.

    1983-12-01

    Thermally activated batteries using the lithium (silicon) iron disulfide (Li(Si)/FeS2) electrochemical system are used in weapons having a required storage life of 25 years and high reliability. A review of known data revealed no information on the compatibility of Li(Si)/FeS2 with the organic materials used in the system. The compatibility question is studied. Accelerated-aging data on pairs of materials were produced. In addition, a group of production batteries was aged and tested. Three aging temperatures were used during the one-year study. Gas analyses, electrical tests and mechanical tests were compared for control and aged samples. Two results, the depletion of oxygen and an increase in hydrogen in the compatibility and accelerated-aging samples, stimulated additional studies. No unexpected or significant changes were observed in the electrical or mechanical properties of the organic materials. Calorific output and chloride ion content of heat pellets indicated no degradation with aging. Ignition sensitivity and burn rate measurements suggested no heat pellet degradation. Oxygen content in aged lithium (silicon) anodes remained within acceptable limits. Single-cell tests and battery test results showed no degradation with aging.

  10. Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and Its Effect on Hybrid Photovoltaic Devices.

    PubMed

    Kumar, S; Dhar, A

    2016-07-20

    Organometal halide perovskite materials are presently some of the pacesetters for light harvesting in hybrid photovoltaic devices because of their excellent inherent electrical and optical properties. However, long-term durability of such perovskite materials remains a major bottleneck for their commercialization especially in countries with hot and humid climatic conditions, thus violating the international standards for photovoltaic technology. Albeit, TiO2 as an electron-transport layer has been well investigated for perovskite solar cells; the high-temperature processing makes it unsuitable for low-cost and large-scale roll-to-roll production of flexible photovoltaic devices. Herein, we have chosen low-temperature (<150 °C)-processable nanostructured ZnO as the electron-selective layer and used a two-step method for sensitizing ZnO nanorods with methylammonium lead iodide (MAPbI3) perovskite, which is viable for flexible photovoltaic devices. We have also elaborately addressed the effect of the annealing duration on the conversion of a precursor solution into the required perovskite phase on ZnO nanostructures. The investigations show that the presence of ZnO nanostructures accelerates the rate of degradation of MAPbI3 films under ambient annealing and thus requires proper optimization. The role of ZnO in enhancing the degradation kinetics of the perovskite layer has been investigated by X-ray photoelectron spectroscopy and a buffer layer passivation technique. The effect of the annealing duration of the MAPbI3 perovskite on the optical, morphological, and compositional behavior has been closely studied and correlated with the photovoltaic efficiency. The study captures the degradation behavior of the commercially interesting MAPbI3 perovskite on a ZnO electron-transport layer and thus can provide insight for developing alternative families of perovskite material with better thermal and environmental stability for application in low-cost flexible photovoltaic

  11. Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and Its Effect on Hybrid Photovoltaic Devices.

    PubMed

    Kumar, S; Dhar, A

    2016-07-20

    Organometal halide perovskite materials are presently some of the pacesetters for light harvesting in hybrid photovoltaic devices because of their excellent inherent electrical and optical properties. However, long-term durability of such perovskite materials remains a major bottleneck for their commercialization especially in countries with hot and humid climatic conditions, thus violating the international standards for photovoltaic technology. Albeit, TiO2 as an electron-transport layer has been well investigated for perovskite solar cells; the high-temperature processing makes it unsuitable for low-cost and large-scale roll-to-roll production of flexible photovoltaic devices. Herein, we have chosen low-temperature (<150 °C)-processable nanostructured ZnO as the electron-selective layer and used a two-step method for sensitizing ZnO nanorods with methylammonium lead iodide (MAPbI3) perovskite, which is viable for flexible photovoltaic devices. We have also elaborately addressed the effect of the annealing duration on the conversion of a precursor solution into the required perovskite phase on ZnO nanostructures. The investigations show that the presence of ZnO nanostructures accelerates the rate of degradation of MAPbI3 films under ambient annealing and thus requires proper optimization. The role of ZnO in enhancing the degradation kinetics of the perovskite layer has been investigated by X-ray photoelectron spectroscopy and a buffer layer passivation technique. The effect of the annealing duration of the MAPbI3 perovskite on the optical, morphological, and compositional behavior has been closely studied and correlated with the photovoltaic efficiency. The study captures the degradation behavior of the commercially interesting MAPbI3 perovskite on a ZnO electron-transport layer and thus can provide insight for developing alternative families of perovskite material with better thermal and environmental stability for application in low-cost flexible photovoltaic

  12. BLISTERING AND DEGRADATION OF POLYURETHANE COATINGS UNDER DIFFERENT ACCELERATED WEATHERING TESTS. (R828081E01)

    EPA Science Inventory

    An epoxy primer with a high gloss polyurethane topcoat coating system was exposed either only in a QUV chamber or exposed in a QUV chamber and a Prohesion chamber, alternatively, in this study. AFM studies found that micro blisters formed on the coating surface after both expo...

  13. Returned Solar Max hardware degradation study results

    NASA Technical Reports Server (NTRS)

    Triolo, Jack J.; Ousley, Gilbert W.

    1989-01-01

    The Solar Maximum Repair Mission returned with the replaced hardware that had been in low Earth orbit for over four years. The materials of this returned hardware gave the aerospace community an opportunity to study the realtime effects of atomic oxygen, solar radiation, impact particles, charged particle radiation, and molecular contamination. The results of these studies are summarized.

  14. Mechanism of Heparin Acceleration of Tissue Inhibitor of Metalloproteases-1 (TIMP-1) Degradation by the Human Neutrophil Elastase

    PubMed Central

    Nunes, Gabriel L. C.; Simões, Alyne; Dyszy, Fábio H.; Shida, Claudio S.; Juliano, Maria A.; Juliano, Luiz; Gesteira, Tarsis F.; Nader, Helena B.; Murphy, Gillian; Chaffotte, Alain F.; Goldberg, Michel E.; Tersariol, Ivarne L. S.; Almeida, Paulo C.

    2011-01-01

    Heparin has been shown to regulate human neutrophil elastase (HNE) activity. We have assessed the regulatory effect of heparin on Tissue Inhibitor of Metalloproteases-1 [TIMP-1] hydrolysis by HNE employing the recombinant form of TIMP-1 and correlated FRET-peptides comprising the TIMP-1 cleavage site. Heparin accelerates 2.5-fold TIMP-1 hydrolysis by HNE. The kinetic parameters of this reaction were monitored with the aid of a FRET-peptide substrate that mimics the TIMP-1 cleavage site in pre-steady-state conditionsby using a stopped-flow fluorescence system. The hydrolysis of the FRET-peptide substrate by HNE exhibits a pre-steady-state burst phase followed by a linear, steady-state pseudo-first-order reaction. The HNE acylation step (k2 = 21±1 s−1) was much higher than the HNE deacylation step (k3 = 0.57±0.05 s−1). The presence of heparin induces a dramatic effect in the pre-steady-state behavior of HNE. Heparin induces transient lag phase kinetics in HNE cleavage of the FRET-peptide substrate. The pre-steady-state analysis revealed that heparin affects all steps of the reaction through enhancing the ES complex concentration, increasing k1 2.4-fold and reducing k−1 3.1-fold. Heparin also promotes a 7.8-fold decrease in the k2 value, whereas the k3 value in the presence of heparin was increased 58-fold. These results clearly show that heparin binding accelerates deacylation and slows down acylation. Heparin shifts the HNE pH activity profile to the right, allowing HNE to be active at alkaline pH. Molecular docking and kinetic analysis suggest that heparin induces conformational changes in HNE structure. Here, we are showing for the first time that heparin is able to accelerate the hydrolysis of TIMP-1 by HNE. The degradation of TIMP-1is associated to important physiopathological states involving excessive activation of MMPs. PMID:21731773

  15. Accelerated Stress Testing and Diagnostic Analysis of Degradation in CdTe Solar Cells

    SciTech Connect

    Albin, D. S.

    2008-11-01

    The primary goal of this study was to ascertain the presence and types of mechanisms affecting CdS/CdTe device stability in the temperature range of 60 to 120 ..deg..C. It should be noted that the results presented were specific to cells made using the specific growth conditions described.

  16. International scoping study: accelerator working group report

    SciTech Connect

    Zisman, Michael; Zisman, M.S.

    2006-09-30

    During the past several years, an International Scoping Study (ISS) of a Neutrino Factory was carried out, with the aim of developing an internationally accepted baseline facility design. Progress toward that goal will be described. Many of the key technical aspects of a Neutrino Factory facility design are presently being investigated experimentally, and the status of these investigations will be mentioned. Plans for the recently launched International Design Study (IDS), which serves as a follow-on to the ISS, will be briefly described.

  17. Translucency and low-temperature degradation of silica-doped zirconia: A pilot study.

    PubMed

    Nakamura, Takashi; Nakano, Yoshiro; Usami, Hirofumi; Wakabayashi, Kazumichi; Ohnishi, Hiroshi; Sekino, Tohru; Yatani, Hirofumi

    2016-01-01

    The purpose of this study was to examine the translucency and low-temperature degradation of silica-doped experimental Y-TZP (Yttria-stabilized tetragonal zirconia polycrystal) containing almost no alumina. The experimental Y-TZP samples were sintered at either 1,450 or 1,500°C. The samples of commercially available translucent Y-TZP and conventional Y-TZP were used as controls. The contrast ratio (CR) and translucency parameter (TP) were obtained to compare the translucencies. In addition, the specimens were also subjected to an accelerated aging test. The results showed that the experimental Y-TZP sintered at 1,500°C and translucent Y-TZP exhibited almost the same level of translucency. During the accelerated aging test, the translucent Y-TZP underwent a substantial increase in monoclinic content, an index of degradation after the aging test. However, neither the experimental Y-TZP nor the conventional Y-TZP exhibited any appreciable change. It was concluded that the silica-doped Y-TZP will develop translucency and resistance to degradation when sintered at 1,500°C. PMID:27477222

  18. NMR Studies of Cartilage Dynamics, Diffusion, Degradation

    NASA Astrophysics Data System (ADS)

    Huster, Daniel; Schiller, Jurgen; Naji, Lama; Kaufmann Jorn; Arnold, Klaus

    An increasing number of people is suffering from rheumatic diseases, and, therefore, methods of early diagnosis of joint degeneration are urgently required. For their establishment, however, an improved knowledge about the molecular organisation of cartilage would be helpful. Cartilage consists of three main components: Water, collagen and chondroitin sulfate (CS) that is (together with further polysaccharides and proteins) a major constituent of the proteoglycans of cartilage. 1H and 13C MAS (magic-angle spinning) NMR (nuclear magnetic resonance) opened new perspectives for the study of the macromolecular components in cartilage. We have primarily studied the mobilities of CS and collagen in bovine nasal and pig articular cartilage (that differ significantly in their collagen/polysaccharide content) by measuring 13C NMR relaxation times as well as the corresponding 13C CP (cross polarisation) MAS NMR spectra. These data clearly indicate that the mobility of cartilage macromolecules is broadly distributed from almost completely rigid (collagen) to highly mobile (polysaccharides), which lends cartilage its mechanical strength and shock-absorbing properties.

  19. Accelerated degradation of PAHs using edaphic biostimulants obtained from sewage sludge and chicken feathers.

    PubMed

    Rodríguez-Morgado, Bruno; Gómez, Isidoro; Parrado, Juan; García, Carlos; Hernández, Teresa; Tejada, Manuel

    2015-12-30

    We studied in the laboratory the bioremediation effects over a 100-day period of three edaphic biostimulants (BS) obtained from sewage sludge (SS) and from two different types of chicken feathers (CF1 and CF2), in a soil polluted with three polycyclic aromatic hydrocarbons (PAH) (phenanthrene, Phe; pyrene, Py; and benzo(a)pyrene, BaP), at a concentration of 100 mg kg(-1) soil. We determined their effects on enzymatic activities and on soil microbial community. Those BS with larger amounts of proteins and a higher proportion of peptides (<300 daltons), exerted a greater stimulation on the soil biochemical properties and microbial community, possibly because low molecular weight proteins can be easily assimilated by soil microorganisms. The soil dehydrogenase, urease, β-glucosidase and phosphatase activities and microbial community decreased in PAH-polluted soil. This decrease was more pronounced in soils contaminated with BaP than with Py and Phe. The application of the BS to PAH-polluted soils decreased the inhibition of the soil biological properties, principally at 7 days into the experiment. This decrease was more pronounced in soils contaminated with BaP than with Py and Phe and was higher in polluted soils amended with CF2, followed by SS and CF1, respectively.

  20. Accelerated degradation of PAHs using edaphic biostimulants obtained from sewage sludge and chicken feathers.

    PubMed

    Rodríguez-Morgado, Bruno; Gómez, Isidoro; Parrado, Juan; García, Carlos; Hernández, Teresa; Tejada, Manuel

    2015-12-30

    We studied in the laboratory the bioremediation effects over a 100-day period of three edaphic biostimulants (BS) obtained from sewage sludge (SS) and from two different types of chicken feathers (CF1 and CF2), in a soil polluted with three polycyclic aromatic hydrocarbons (PAH) (phenanthrene, Phe; pyrene, Py; and benzo(a)pyrene, BaP), at a concentration of 100 mg kg(-1) soil. We determined their effects on enzymatic activities and on soil microbial community. Those BS with larger amounts of proteins and a higher proportion of peptides (<300 daltons), exerted a greater stimulation on the soil biochemical properties and microbial community, possibly because low molecular weight proteins can be easily assimilated by soil microorganisms. The soil dehydrogenase, urease, β-glucosidase and phosphatase activities and microbial community decreased in PAH-polluted soil. This decrease was more pronounced in soils contaminated with BaP than with Py and Phe. The application of the BS to PAH-polluted soils decreased the inhibition of the soil biological properties, principally at 7 days into the experiment. This decrease was more pronounced in soils contaminated with BaP than with Py and Phe and was higher in polluted soils amended with CF2, followed by SS and CF1, respectively. PMID:26188866

  1. Fibroblast Activation Protein (FAP) Accelerates Collagen Degradation and Clearance from Lungs in Mice.

    PubMed

    Fan, Ming-Hui; Zhu, Qiang; Li, Hui-Hua; Ra, Hyun-Jeong; Majumdar, Sonali; Gulick, Dexter L; Jerome, Jacob A; Madsen, Daniel H; Christofidou-Solomidou, Melpo; Speicher, David W; Bachovchin, William W; Feghali-Bostwick, Carol; Puré, Ellen

    2016-04-01

    Idiopathic pulmonary fibrosis is a disease characterized by progressive, unrelenting lung scarring, with death from respiratory failure within 2-4 years unless lung transplantation is performed. New effective therapies are clearly needed. Fibroblast activation protein (FAP) is a cell surface-associated serine protease up-regulated in the lungs of patients with idiopathic pulmonary fibrosis as well as in wound healing and cancer. We postulate that FAP is not only a marker of disease but influences the development of pulmonary fibrosis after lung injury. In two different models of pulmonary fibrosis, intratracheal bleomycin instillation and thoracic irradiation, we find increased mortality and increased lung fibrosis in FAP-deficient mice compared with wild-type mice. Lung extracellular matrix analysis reveals accumulation of intermediate-sized collagen fragments in FAP-deficient mouse lungs, consistent within vitrostudies showing that FAP mediates ordered proteolytic processing of matrix metalloproteinase (MMP)-derived collagen cleavage products. FAP-mediated collagen processing leads to increased collagen internalization without altering expression of the endocytic collagen receptor, Endo180. Pharmacologic FAP inhibition decreases collagen internalization as expected. Conversely, restoration of FAP expression in the lungs of FAP-deficient mice decreases lung hydroxyproline content after intratracheal bleomycin to levels comparable with that of wild-type controls. Our findings indicate that FAP participates directly, in concert with MMPs, in collagen catabolism and clearance and is an important factor in resolving scar after injury and restoring lung homeostasis. Our study identifies FAP as a novel endogenous regulator of fibrosis and is the first to show FAP's protective effects in the lung.

  2. NMR Studies on the Aqueous Phase Photochemical Degradation of TNT

    SciTech Connect

    Thorn, Kevin A.; Cox, Larry G.

    2008-04-06

    Aqueous phase photochemical degradation of 2,4,6-trinitrotoluene (TNT) is an important pathway in several environments, including washout lagoon soils, impact craters from partially detonated munitions that fill with rain or groundwater, and shallow marine environments containing unexploded munitions that have corroded. Knowledge of the degradation products is necessary for compliance issues on military firing ranges and formerly used defense sites. Previous laboratory studies have indicated that UV irradiation of aqueous TNT solutions results in a multicomponent product mixture, including polymerization compounds, that has been only partially resolved by mass spectrometric analyses. This study illustrates how a combination of solid and liquid state 1H, 13C, and 15N NMR spectroscopy, including two dimensional analyses, provides complementary information on the total product mixture from aqueous photolysis of TNT, and the effect of reaction conditions. Among the degradation products detected were amine, amide, azoxy, azo, and carboxylic acid compounds.

  3. Computational Study of Flow Establishment in a Ram Accelerator

    NASA Technical Reports Server (NTRS)

    Yungster, S.; Radhakrishnan, K.; Rabinowitz, M. J.

    1995-01-01

    The temporal evolution of the combustion process established during projectile transition from the launch tube into the ram accelerator section containing an explosive hydrogen-oxygen-argon gas mixture is studied. The Navier-Stokes equations for chemically reacting flow are solved in a fully coupled manner, using an implicit, time accurate algorithm. The solution procedure is based on a spatially second order total variation diminishing scheme and a temporally second order, variable-step, backward differentiation formula method. The hydrogen-oxygen chemistry is modeled with a 9-species, 19-step mechanism. The accuracy of the solution method is first demonstrated by several benchmark calculations. Numerical simulations of two ram accelerator configurations are then presented. In particular, the temporal developments of shock-induced combustion and thrust forces are followed. Positive thrust is established in both cases; however, in one of the ram accelerator configurations studied, combustion in the boundary layer enhances its separation, ultimately resulting in unstart.

  4. Hydroxide Degradation Pathways for Imidazolium Cations. A DFT Study

    SciTech Connect

    Long, H.; Pivovar, B.

    2014-05-15

    Imidazolium cations are promising candidates as covalently tetherable cations for application in anion exchange membranes. They have generated specific interest in alkaline membrane fuel cell applications where ammonium-based cations have been the most commonly applied but have been found to be susceptible to hydroxide attack. In the search for high stability cations, a detailed understanding of the degradation pathways and reaction barriers is required. In this work, we investigate imidazolium and benzimidazolium cations in the presence of hydroxide using density functional theory calculations for their potential in alkaline membrane fuel cells. Moreover, the dominant degradation pathway for these cations is predicted to be the nucleophilic addition–elimination pathway at the C-2 atom position on the imidazolium ring. Steric interferences, introduced by substitutions at the C-2, C-4, and C-5 atom positions, were investigated and found to have a significant, positive impact on calculated degradation energy barriers. Benzimidazolium cations, with their larger conjugated systems, are predicted to degrade much faster than their imidazolium counterparts. Our results provide important insight into designing stable cations for anion exchange membranes. Some of the molecules studied have significantly increased degradation energy barriers suggesting that they could possess significantly improved (several orders of magnitude) durability compared to traditional cations and potentially enable new applications.

  5. Aspartame degradation study using electrospray ionization mass spectrometry.

    PubMed

    Pattanaargson, S; Sanchavanakit, C

    2000-01-01

    Electrospray mass spectrometry was used to simultaneously determine aspartame (APM) and five of its degradation products; aspartic acid, aspartylphenylalanine, 5-benzyl-3,6-dioxo-2-piperazieacetic acid (diketopiperazine), phenylalanine, and phenylalanine methyl ester. Under the ionization conditions used, there was no interfering fragmentation for any of the six compounds, i.e., no fragmentation of the compound being tested into other species also being monitored. A study of APM degradation in solution at various pH's and at various temperatures using this method was performed.

  6. [Study of the hydrolytic degradation of a biodegradable copolymer].

    PubMed

    Sabino, Marco A; Morales, Dayanara; Ronca, Gladys; Feijoo, José Luis

    2003-01-01

    The hydrolytic degradation of bioabsorbable Poliglactin 910 was studied in a phosphate buffer solution, pH = 7.4, at 37 degrees C. The degradation was evaluated by analyzing the changes in weight loss, pH, DSC, mechanical properties and morphological changes. After 10 weeks, the weight loss and pH changes suggested diffusion of low molecular weight chain segments into the reaction medium as a consequence of the breaking of ester bonds in the material. Breaking stress and Young Modulus decrease, indicating that chain scission proceeded in two steps: the first occurring in the amorphous regions within the intermicrofibrillar space; the second in the crystalline regions. Surface morphological changes suggest a heterogeneous degradation mechanism by layers.

  7. Chemical Degradation Studies on a Series of Dithiophosphinic Acids

    SciTech Connect

    Freiderich, Melissa E; Delmau, Laetitia Helene; Peterman, D. R.; Marc, Philippe L; Klaehn, John D.

    2014-01-01

    In this study a significant increase in the stability of a series of dithiophosphinic acids (DPAHs) under oxidizing acidic conditions was achieved. The degradation behavior of a series of DPAHs, designed for lanthanide/actinide separation, was examined. The stability of the DPAHs, when contacted with varying nitric acid concentrations, was tested and monitored using 31P {1H} NMR. Changes in the functional groups of the DPAHs resulted in substantial increases in the stability. However, all the DPAHs eventually showed signs of degradation when placed in contact with 2 M HNO3. The addition of a radical scavenger, hydrazine, inhibited the degradation of the DPAHs. With small amounts of hydrazine, five of the DPAHs remained stable for over a month in direct contact with 2 M HNO3.

  8. Synergistic acceleration of thyroid hormone degradation by phenobarbital and the PPAR{alpha} agonist WY14643 in rat hepatocytes

    SciTech Connect

    Wieneke, N.; Neuschaefer-Rube, F.; Bode, L.M.; Kuna, M.; Andres, J.; Carnevali, L.C.; Hirsch-Ernst, K.I.; Pueschel, G.P.

    2009-10-01

    Energy balance is maintained by controlling both energy intake and energy expenditure. Thyroid hormones play a crucial role in regulating energy expenditure. Their levels are adjusted by a tight feedback-controlled regulation of thyroid hormone production/incretion and by their hepatic metabolism. Thyroid hormone degradation has previously been shown to be enhanced by treatment with phenobarbital or other antiepileptic drugs due to a CAR-dependent induction of phase II enzymes of xenobiotic metabolism. We have recently shown, that PPAR{alpha} agonists synergize with phenobarbital to induce another prototypical CAR target gene, CYP2B1. Therefore, it was tested whether a PPAR{alpha} agonist could enhance the phenobarbital-dependent acceleration of thyroid hormone elimination. In primary cultures of rat hepatocytes the apparent half-life of T3 was reduced after induction with a combination of phenobarbital and the PPAR{alpha} agonist WY14643 to a larger extent than after induction with either compound alone. The synergistic reduction of the half-life could be attributed to a synergistic induction of CAR and the CAR target genes that code for enzymes and transporters involved in the hepatic elimination of T3, such as OATP1A1, OATP1A3, UGT1A3 and UGT1A10. The PPAR{alpha}-dependent CAR induction and the subsequent induction of T3-eliminating enzymes might be of physiological significance for the fasting-induced reduction in energy expenditure by fatty acids as natural PPAR{alpha} ligands. The synergism of the PPAR{alpha} agonist WY14643 and phenobarbital in inducing thyroid hormone breakdown might serve as a paradigm for the synergistic disruption of endocrine control by other combinations of xenobiotics.

  9. Comparative Study of Degradation Behavior of Bioresorbable Cardiovascular Scaffolds.

    PubMed

    Luo, Qiyi; Huang, Chubo; Wang, Shuai; Meng, Juan; Li, Zhonghua; Chang, Zhaohua; Zhu, Yufang; Hua, Zezhao

    2015-03-01

    This comparative study investigated the biodegradation behavior and mechanism of bioresorbable cardiovascular scaffolds using bench testing under physiological conditions and in vivo experiment. The results show that the molecular weight of the scaffold decreased with respect to time after implantation in both in vivo and in vitro tests. It was found that the molecular weights of the implanted scaffolds in the in vivo and in vitro models decreased to 61.8 and 68.5% respectively 6 months after implantation, but the thermodynamic properties of the scaffold material were not significantly affected by the 6-month degradation. Moreover, the study indicated that in spite of the 6-month degradation, the scaffold maintained sufficient radial strength and mechanical integrity. Furthermore, it was noted that the changes in the trends of the mechanical properties and degradation behavior of the scaffolds in the in vitro model were coherent with the results of the in vivo study, which means the in vitro study of the degradation behavior of polylactic acid (PLA) scaffold could offer clinical relevant data and physical insights to predict the in vivo performance.

  10. A study on task difficulty and acceleration stress

    NASA Technical Reports Server (NTRS)

    Repperger, D. W.; Rogers, D. B.

    1981-01-01

    The results of two experiments which relate to task difficulty and the effects of environmental stress on tracking performance are discussed and compared to subjective evaluations. The first experiment involved five different sum of sine tracking tasks which humans tracked both in a static condition and under a 5 Gz acceleration stress condition. The second experiment involved similar environmental stress conditions but in this case the tasks were constructed from deterministic functions with specially designed velocity and acceleration profiles. Phase Plane performance analysis was conducted to study potential measures of workload or tracking difficulty.

  11. Diagnostics for studies of novel laser ion acceleration mechanisms

    SciTech Connect

    Senje, Lovisa; Aurand, Bastian; Wahlström, Claes-Göran; Yeung, Mark; Kuschel, Stephan; Rödel, Christian; Wagner, Florian; Roth, Markus; Li, Kun; Neumayer, Paul; Dromey, Brendan; Jung, Daniel; Bagnoud, Vincent; Zepf, Matthew; Kuehl, Thomas

    2014-11-15

    Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.

  12. Study of accelerator neutrino detection at a spallation source

    NASA Astrophysics Data System (ADS)

    Huang, Ming-Yang

    2016-06-01

    We study the detection of accelerator neutrinos produced at the China Spallation Neutron Source (CSNS). Using the code FLUKA, we have simulated the production of neutrinos in a proton beam on a tungsten target and obtained the yield efficiency, numerical flux, and average energy of different flavors of neutrinos. Furthermore, detection of these accelerator neutrinos is investigated in two reaction channels: neutrino-electron reactions and neutrino-carbon reactions. The expected numbers of different flavors of neutrinos have also been calculated. Supported by National Natural Science Foundation of China (11205185, 11175020)

  13. Diagnostics for studies of novel laser ion acceleration mechanisms.

    PubMed

    Senje, Lovisa; Yeung, Mark; Aurand, Bastian; Kuschel, Stephan; Rödel, Christian; Wagner, Florian; Li, Kun; Dromey, Brendan; Bagnoud, Vincent; Neumayer, Paul; Roth, Markus; Wahlström, Claes-Göran; Zepf, Matthew; Kuehl, Thomas; Jung, Daniel

    2014-11-01

    Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.

  14. An Experimental Study of Laminarization Induced by Acceleration and Curvature

    NASA Astrophysics Data System (ADS)

    Jackson, R. Brian

    The Generation IV Very High Temperature Reactor (VHTR) design is being actively studied in various countries for application due to its inherent passive safe design, higher thermal efficiencies, and proposed capability of providing high temperature process heat. The pebble bed core is one of two core designs used in gas reactors. In the pebble bed core there are mechanisms present which can cause the flow to laminarize, thus reducing its heat transfer effectiveness. Wind tunnel experiments were conducted using Particle Image Velocimetry (PIV) to investigate boundary layer laminarization due to flow acceleration and convex curvature effects. The flow was subject to acceleration and curvature both separately and together and the flow behavior characterized with velocity flow profiles, mean boundary layer parameters, and turbulence quantities. Laminarization was identified and the influence of acceleration and curvature was characterized.

  15. Target Material Irradiation Studies for High-Intensity Accelerator Beams

    SciTech Connect

    Simos, N.; Kirk, H.; Ludewig, H.; Thieberger, P.; Weng, W.T.; McDonald, K.; Sheppard, J.; Evangelakis, G.; Yoshimura, K.; /KEK, Tsukuba

    2005-08-16

    This paper presents results of recent experimental studies focusing on the behavior of special materials and composites under irradiation conditions and their potential use as accelerator targets. The paper also discusses the approach and goals of on-going investigations on an expanded material matrix geared toward the neutrino superbeam and muon collider initiatives.

  16. Observational Study on Initiation and Acceleration of Coronal Mass Ejections

    NASA Technical Reports Server (NTRS)

    Zhang, Jie

    2005-01-01

    During the performance period, we have successfully carried out all the tasks and fulfilled all the scientific objectives outlined in the proposal, which are about building a C1 Ch4E catalog and studying CME accelerations in both inner and outer corona.

  17. Vacuum Insulator Studies for the Dielectric Wall Accelerator

    SciTech Connect

    Harris, J R; Chen, Y J; Blackfield, D; Sanders, D M; Caporaso, G J; Krogh, M

    2007-06-11

    As part of our ongoing development of the Dielectric Wall Accelerator, we are studying the performance of multilayer high-gradient insulators. These vacuum insulating structures are composed of thin, alternating layers of metal and dielectric, and have been shown to withstand higher gradients than conventional vacuum insulator materials. This paper describes these structures and presents some of our recent results.

  18. Optical characterization of voltage-accelerated degradation in CH3NH3PbI3 perovskite solar cells.

    PubMed

    Handa, Taketo; Tex, David M; Shimazaki, Ai; Aharen, Tomoko; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2016-05-16

    We investigate the performance degradation mechanism of CH3NH3PbI3 perovskite solar cells under bias voltage in air and nitrogen atmospheres using photoluminescence and electroluminescence techniques. When applying forward bias, the power conversion efficiency of the solar cells decreased significantly in air, but showed no degradation in nitrogen atmosphere. Time-resolved photoluminescence measurements on these devices revealed that the application of forward bias in air accelerates the generation of non-radiative recombination centers in the perovskite layer buried in the device. We found a negative correlation between the electroluminescence intensity and the injected current intensity in air. The irreversible change of the perovskite grain surface in air initiates the degradation of the perovskite solar cells. PMID:27409964

  19. The spinning disc: studying radial acceleration and its damping process with smartphone acceleration sensors

    NASA Astrophysics Data System (ADS)

    Hochberg, K.; Gröber, S.; Kuhn, J.; Müller, A.

    2014-03-01

    Here, we show the possibility of analysing circular motion and acceleration using the acceleration sensors of smartphones. For instance, the known linear dependence of the radial acceleration on the distance to the centre (a constant angular frequency) can be shown using multiple smartphones attached to a revolving disc. As a second example, the decrease of the radial acceleration and the rotation frequency due to friction can be measured and fitted with a quadratic function, in accordance with theory. Finally, because the disc is not set up exactly horizontal, each smartphone measures a component of the gravitational acceleration that adds to the radial acceleration during one half of the period and subtracts from the radial acceleration during the other half. Hence, every graph shows a small modulation, which can be used to determine the rotation frequency, thus converting a ‘nuisance effect’ into a source of useful information, making additional measurements with stopwatches or the like unnecessary.

  20. Surface degradation of CeO2 stabilized acrylic polyurethane coated thermally treated jack pine during accelerated weathering

    NASA Astrophysics Data System (ADS)

    Saha, Sudeshna; Kocaefe, Duygu; Boluk, Yaman; Pichette, Andre

    2013-07-01

    The thermally treated wood is a new value-added product and is very important for the diversification of forestry products. It drew the attention of consumers due to its attractive dark brown color. However, it loses its color when exposed to outside environment. Therefore, development of a protective coating for this value added product is necessary. In the present study, the efficiency of CeO2 nano particles alone or in combination with lignin stabilizer and/or bark extracts in acrylic polyurethane polymer was investigated by performing an accelerated weathering test. The color measurement results after accelerated weathering demonstrated that the coating containing CeO2 nano particles was the most effective whereas visual assessment suggested the coating containing CeO2 nano particles and lignin stabilizer as the most effective coating. The surface polarity changed for all the coatings during weathering and increase in contact angle after weathering suggested cross linking and reorientation of the polymer chain during weathering. The surface chemistry altered during weathering was evaluated by ATR-FTIR analysis. It suggested formation of different carbonyl byproducts during weathering. The chain scission reactions of the urethane linkages were not found to be significant during weathering.

  1. [Study on electrochemical degradation of ceftazidime by carbon nanotubes electrode].

    PubMed

    Zhu, Hong; Hu, Xiang; Li, Jun-Feng

    2013-08-01

    A self-made multi-walled carbon nanotubes electrode was characterized by SEM, FITR, CV and Tafel, and applied to study the electrochemical reduction degradation of refractory organics, using ceftazidime as model pollutant, and the mass concentration after the reduction was measured by the HPLC. The results indicate that the electrode has perfect stability, good resistance to corrosion, and perfect performance. According to the CV, a larger oxidation peak was obtained at about 800 mV, with a peak value of -0.2 mA, and the degradation of ceftazidime on the electrode was irreversible. The optimum conditions of the the electrochemical reduction degradation of ceftazidime on carbon nanotubes electrode were: electrode spacing of 1 cm, a voltage of 15 V, an initial concentration of 1 mg x L(-1), ionic strength of 1 g x L(-1), and a pH value of 6.0. Under such conditions, the removal efficiency of ceftazidime reached up to 90% when the reaction time was 60 min, and the degradation process conforms to the second-order kinetics.

  2. Crystalline Silicon Short-Circuit Current Degradation Study: Initial Results

    SciTech Connect

    Osterwald, C. R.; Pruett, J.; Moriarty, T.

    2005-02-01

    Following our observation of slow degradation of short-circuit current (Isc) in crystalline silicon (x-Si) modules that was correlated with ultraviolet (UV) exposure dose, we initiated a new study of individual x-Si cells designed to determine the degradation cause. In this paper, we report the initial results of this study, which has accumulated 1056 MJ/m2 of UV dose from 1-sun metal-halide irradiance, equivalent to 3.8 years at our test site. At this time, the control samples are unchanged, the unencapsulated samples have lost about 2% of Isc, and the samples encapsulated in module-style packages have declined from 1% to 3%, depending on the cell technology.

  3. Catalase protects HepG2 cells from apoptosis induced by DNA-damaging agents by accelerating the degradation of p53.

    PubMed

    Bai, Jingxiang; Cederbaum, Arthur I

    2003-02-14

    Oxidants such as H(2)O(2) play a role in the toxicity of certain DNA-damaging agents, a process that often involves the tumor suppressor p53. H(2)O(2) is rapidly degraded by catalase, which protects cells against oxidant injury. To study the effect of catalase on apoptosis induced by DNA-damaging agents, HepG2 cells were infected with adenovirus containing the cDNA of catalase (Ad-Cat). Forty-eight hours after infection, catalase protein and activity was increased 7-10-fold compared with control cells infected with Ad-LacZ. After treatment with Vp16 or mitomycin C, control cells underwent apoptosis in a p53-dependent manner; however, overexpression of catalase inhibited this apoptosis. Basal levels as well as Vp16- or mitomycin C-stimulated levels of p53 and p21 protein were decreased in the catalase-overexpressing cells as compared with control cells; however, p53 mRNA levels were not decreased by catalase. There was no difference in p53 protein synthesis between catalase-overexpressing cells and control cells. However, pulse-chase experiments indicated that p53 protein degradation was enhanced in the catalase-overexpressing cells. Proteasome inhibitors but not calpeptin prevented the catalase-mediated decrease of p53 content. Whereas Vp16 increased, catalase overexpression decreased the phosphorylation of p53. The protein phosphatase inhibitor okadaic acid did not prevent the catalase-mediated down-regulation of p53 or phosphorylated p53. These results demonstrate that catalase protects HepG2 cells from apoptosis induced by DNA-damaging agents in association with decreasing p53 phosphorylation; the latter may lead to an acceleration in the degradation of p53 protein by the proteasome complex. This suggests that the level of catalase may play a critical role in cell-induced resistance to the effects of anti-cancer drugs which up-regulate p53. PMID:12468545

  4. Novel durable bio-photocatalyst purifiers, a non-heterogeneous mechanism: accelerated entrapped dye degradation into structural polysiloxane-shield nano-reactors.

    PubMed

    Dastjerdi, Roya; Montazer, Majid; Shahsavan, Shadi; Böttcher, Horst; Moghadam, M B; Sarsour, Jamal

    2013-01-01

    This research has designed innovative Ag/TiO(2) polysiloxane-shield nano-reactors on the PET fabric to develop novel durable bio-photocatalyst purifiers. To create these very fine nano-reactors, oppositely surface charged multiple size nanoparticles have been applied accompanied with a crosslinkable amino-functionalized polysiloxane (XPs) emulsion. Investigation of photocatalytic dye decolorization efficiency revealed a non-heterogeneous mechanism including an accelerated degradation of entrapped dye molecules into the structural polysiloxane-shield nano-reactors. In fact, dye molecules can be adsorbed by both Ag and XPs due to their electrostatic interactions and/or even via forming a complex with them especially with silver NPs. The absorbed dye and active oxygen species generated by TiO(2) were entrapped by polysiloxane shelter and the presence of silver nanoparticles further attract the negative oxygen species closer to the adsorbed dye molecules. In this way, the dye molecules are in close contact with concentrated active oxygen species into the created nano-reactors. This provides an accelerated degradation of dye molecules. This non-heterogeneous mechanism has been detected on the sample containing all of the three components. Increasing the concentration of Ag and XPs accelerated the second step beginning with an enhanced rate. Further, the treated samples also showed an excellent antibacterial activity.

  5. Microbial adaption to a pesticide in agricultural soils: Accelerated degradation of 14C-atrazine in field soils from Brazil and Belgium

    NASA Astrophysics Data System (ADS)

    Jablonowski, Nicolai David; Martinazzo, Rosane; Hamacher, Georg; Accinelli, Cesare; Köppchen, Stephan; Langen, Ulrike; Linden, Andreas; Krause, Martina; Burauel, Peter

    2010-05-01

    An increasing demand for food, feed and bioenergy, and simultaneously a decline of arable land will require an intensive agricultural production including the use of pesticides. With an increasing use of pesticides the occurrence of an accelerated degradation potential has to be assessed. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] is one of the most widely used herbicides in the world. Even though its use was banned in several countries it is still widely used throughout America and the Asia-Pacific region. Atrazine is the most widely used herbicide in maize plantations in Brazil and the US. The use of atrazine in Belgium and all EU member states was banned in September 2004, with the permission to consume existing stocks until October 2005. Atrazine and its residues are still regularly detected in soil, ground and surface waters even years after its prohibition. Its persistence in soil and in association with organic particles might become crucial in terms of erosion due to climate and environmental changes. Due to its potential microbiological accessibility, the microbial mineralization of atrazine competes with chemical/physical interaction such as sorption and binding processes of the chemical molecule in the soil matrix. Binding or intrusion of the chemical on soil components results in a decrease of its accessibility for soil microbes, which does not necessarily exclude the molecule from environmental interactions. In the present study the accelerated atrazine degradation in agriculturally used soils was examined. Soil samples were collected from a Rhodic Ferralsol, Campinas do Sul, South Brazil, and Geric Ferralsol, Correntina, Northeastern Brazil. The sampling site of the Rhodic Ferralsol soil has been under crop rotation (soybean/wheat/maize/oat) since 1990. The Geric Ferralsol site has alternately been cultivated with maize and soybean since 2000. Both areas have been treated biennially with atrazine at recommended doses of 1.5 - 3

  6. Synthesis of new poly(ether-urethane-urea)s based on amino acid cyclopeptide and PEG: study of their environmental degradation.

    PubMed

    Rafiemanzelat, Fatemeh; Fathollahi Zonouz, Abolfazl; Emtiazi, Giti

    2013-02-01

    Conventional polyurethanes (PUs) are among biomaterials not intended to degrade but are susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. Biodegradable PUs are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. In this work we have developed a degradable monomer based on α-amino acid to accelerate hard segment degradation. Thus a new class of degradable poly(ether-urethane-urea)s (PEUUs) was synthesized via direct reaction of 4,4'-methylene-bis(4-phenylisocyanate) (MDI), L-leucine anhydride (LA) and polyethylene glycol with molecular weight of 1,000 (PEG-1000) as polyether soft segment. The resulting polymers are environmentally biodegradable and thermally stable. Decomposition temperatures for 5 % weight loss occurred above 300 °C by TGA in nitrogen atmospheres. Some structural characterization and physical properties of these polymers before and after degradation in soil, river water and sludge are reported. The environmental degradation of the polymer films was investigated by SEM, FTIR, TGA, DSC, GPC and XRD techniques. A significant rate of degradation occurred in PEUU samples under river water and sludge condition. The polymeric films were not toxic to E. coli (Gram negative), Staphylococcus aureus and Micrococcus (Gram positive) bacteria and showed good biofilm formation on polymer surface. Our results show that hard segment degraded selectively as much as soft segment and these polymers are susceptible to degradation in soil and water. Thus our study shows that new environment-friendly polyurethane, which can degrade in soil, river water and sludge, is synthesized.

  7. Regional Satellite Observations for Dryland Degradation Studies (Invited)

    NASA Astrophysics Data System (ADS)

    Prince, S. D.

    2009-12-01

    The lack of global scale maps of degraded drylands remains a significant obstacle to identification, prevention and mitigation of desertification. To fill this gap, maps are needed that have some or all of the following characteristics. i Use quantitative variables that have defined biogeophysical meaning. ii Identify areas that are currently in a state of desertification as well as showing areas having higher risk of degradation. iii Provide a synopsis of the condition of land over a number of years, not only a single point in time. iv Repeatable, using consistent observations and an explicit methodology, with a clear link to methods for monitoring and change detection. v Flexible enough to allow adaptation to regional needs while not compromising the ability to compare regions on the basis of consistent criteria. vi At a scale adequate to identify the normal spatial scales of desertification - sub-national, but greater than individual land holdings. vii Down-scalable to allow the specific factors and processes responsible for degradation in a specific location to be identified. viii Can be used as state variables in household-scale studies. ix Up-scalable to allow impacts on processes such as climate change that are relevant at a coarse spatial resolution. x Presented in a data base with appropriate additional maps, such as topography, land use, soil properties, and rainfall, to allow interpretation. xi Can be validated and have information on potential error. xii Not reliant on a single data source nor on a single institution.

  8. Corrosion and degradation studies utilizing X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Hixson, Holly Gwyndolen

    1997-08-01

    This dissertation involves studies of corrosion behavior at the surface of various metal samples, as well as the degradation of wool fibers obtained from the Star-Spangled Banner. Molybdenum metal and iron-zinc alloys were examined under corrosive conditions, and the degradation of the wool fibers was studied. The behavior of a polished molybdenum metal surface upon exposure to both aerated and deaerated water and 1.0 M NaCl solution was studied by X-ray Photoelectron Spectroscopy (XPS). Exposure to deaerated water and NaCl failed to produce oxidation of the metal surfaces, but exposing the polished metal surface to aerated water produced significant oxidation. Metal surfaces cleaned by argon-ion etching were found to be inert to oxidation by aerated water. The etching process also appears to passivate the metal surface. The behavior of molybdenum metal in 0.5 M Hsb2SOsb4 treated at various potentials has been studied using core and valence band XPS. The study indicates that Mosp{IV} and Mosp{VI} (including possibly Mosp{V} in some cases) were formed as the potential of the system was increased within the active range of molybdenum. The corrosive behavior of iron-zinc alloys that have been electroplated on plain steel in both aerated and deaerated quadruply-distilled water has been studied using XPS. Several different iron-zinc alloys were electroplated for comparative purposes: an iron-rich alloy, a zinc-rich alloy, and an alloy of similar iron and zinc composition. Treatment in aerated water produces oxidation for the iron-rich and similar composition alloys, but the oxide is reduced for the zinc-rich alloy. Degradation of the fibers in the original Star-Spangled Banner has been monitored using XPS and Scanning Electron Microscopy (SEM). Comparison of white and red wool fibers and linen fibers from the flag with new, mechanically-abraded, and chemically-treated white, red, and linen fibers, respectively, was performed in an attempt to determine the fibers' levels

  9. Numerical studies of multipactor in dielectric-loaded accelerator structures

    NASA Astrophysics Data System (ADS)

    Sinitsyn, Oleksandr; Nusinovich, Gregory; Antonsen, Thomas

    2009-11-01

    Multipactor (MP) is known as the avalanche growth of the number of secondary electrons emitted from a solid surface exposed to an rf electric field under vacuum conditions. MP may occur in various microwave and rf systems such as microwave tubes, rf windows and launchers, accelerating structures, and rf satellite payloads. In this work we present results of MP analysis in dielectric-loaded accelerator (DLA) structures. The starting point of our work was experimental and theoretical studies of DLA structures jointly done by Argonne National Laboratory and Naval Research Laboratory (J. G. Power et al., Phys. Rev. Lett. 92, 164801 (2004); J. G. Power et al., AIP Conf. Proc. 877, 362 (2006)). In the theoretical model developed during those studies the space-charge field due to the total number of particles is taken into account as a parameter. We perform our studies using a self-consistent approach with the help of time-dependent two-dimensional code developed at the University of Maryland (O. V. Sinitsyn et al., Phys. Plasmas 16, 073102 (2009)). Results include analysis of MP evolution at an early stage, detailed studies of individual electron trajectories, analysis of MP onset time under various conditions and comparison of some results with the experimental data.

  10. Tryptophan degradation in women with breast cancer: a pilot study

    PubMed Central

    2011-01-01

    Background Altered tryptophan metabolism and indoleamine 2,3-dioxygenase activity are linked to cancer development and progression. In addition, these biological factors have been associated with the development and severity of neuropsychiatric syndromes, including major depressive disorder. However, this biological mechanism associated with both poor disease outcomes and adverse neuropsychiatric symptoms has received little attention in women with breast cancer. Therefore, a pilot study was undertaken to compare levels of tryptophan and other proteins involved in tryptophan degradation in women with breast cancer to women without cancer, and secondarily, to examine levels in women with breast caner over the course of chemotherapy. Findings Blood samples were collected from women with a recent diagnosis of breast cancer (n = 33) before their first cycle of chemotherapy and after their last cycle of chemotherapy. The comparison group (n = 24) provided a blood sample prior to breast biopsy. Plasma concentrations of tryptophan, kynurenine, and tyrosine were determined. The kynurenine to tryptophan ratio (KYN/TRP) was used to estimate indoleamine 2,3-dioxygenase activity. On average, the women with breast cancer had lower levels of tryptophan, elevated levels of kynurenine and tyrosine and an increased KYN/TRP ratio compared to women without breast cancer. There was a statistically significant difference between the two groups in the KYN/TRP ratio (p = 0.036), which remained elevated in women with breast cancer throughout the treatment trajectory. Conclusions The findings of this pilot study suggest that increased tryptophan degradation may occur in women with early-stage breast cancer. Given the multifactorial consequences of increased tryptophan degradation in cancer outcomes and neuropsychiatric symptom manifestation, this biological mechanism deserves broader attention in women with breast cancer. PMID:21615916

  11. Analysis of a Proposed Student Laboratory to Study Nonuniform Acceleration.

    ERIC Educational Resources Information Center

    Mowat, J. Richard

    1991-01-01

    Considered is an experiment used to investigate one-dimensional, nonuniform acceleration. Presented is the correct expression for the acceleration, generalized to include friction and describe simulations supporting student data. The feasibility of the experiment is questioned. (CW)

  12. Stability study for matching in laser driven plasma acceleration

    NASA Astrophysics Data System (ADS)

    Rossi, A. R.; Anania, M. P.; Bacci, A.; Belleveglia, M.; Bisesto, F. G.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Gallo, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Marocchino, A.; Massimo, F.; Mostacci, A.; Petrarca, M.; Pompili, R.; Serafini, L.; Tomassini, P.; Vaccarezza, C.; Villa, F.

    2016-09-01

    In a recent paper [14], a scheme for inserting and extracting high brightness electron beams to/from a plasma based acceleration stage was presented and proved to be effective with an ideal bi-Gaussian beam, as could be delivered by a conventional photo-injector. In this paper, we extend that study, assessing the method stability against some jitters in the properties of the injected beam. We find that the effects of jitters in Twiss parameters are not symmetric in results; we find a promising configuration that yields better performances than the setting proposed in [14]. Moreover we show and interpret what happens when the beam charge profiles are modified.

  13. Study of a multi-beam accelerator driven thorium reactor

    SciTech Connect

    Ludewig, H.; Aronson, A.

    2011-03-01

    The primary advantages that accelerator driven systems have over critical reactors are: (1) Greater flexibility regarding the composition and placement of fissile, fertile, or fission product waste within the blanket surrounding the target, and (2) Potentially enhanced safety brought about by operating at a sufficiently low value of the multiplication factor to preclude reactivity induced events. The control of the power production can be achieved by vary the accelerator beam current. Furthermore, once the beam is shut off the system shuts down. The primary difference between the operation of an accelerator driven system and a critical system is the issue of beam interruptions of the accelerator. These beam interruptions impose thermo-mechanical loads on the fuel and mechanical components not found in critical systems. Studies have been performed to estimate an acceptable number of trips, and the value is significantly less stringent than had been previously estimated. The number of acceptable beam interruptions is a function of the length of the interruption and the mission of the system. Thus, for demonstration type systems and interruption durations of 1sec < t < 5mins, and t > 5mins 2500/yr and 50/yr are deemed acceptable. However, for industrial scale power generation without energy storage type systems and interruption durations of t < 1sec., 1sec < t < 10secs., 10secs < t < 5mins, and t > 5mins, the acceptable number of interruptions are 25000, 2500, 250, and 3 respectively. However, it has also been concluded that further development is required to reduce the number of trips. It is with this in mind that the following study was undertaken. The primary focus of this study will be the merit of a multi-beam target system, which allows for multiple spallation sources within the target/blanket assembly. In this manner it is possible to ameliorate the effects of sudden accelerator beam interruption on the surrounding reactor, since the remaining beams will still

  14. Chemiluminescence Study on Thermal Degradation of Aircraft Tire Elastomers

    NASA Technical Reports Server (NTRS)

    Mendenhall, G. D.; Stanford, T. B.; Nathan, R. A.

    1976-01-01

    Since the autoxidative process accounts in part for the degradation of rubber, including aircraft tires, it was felt that a study of the chemiluminescence from unsaturated elastomers could contribute significantly to an understanding of the degradation mechanism. The study revealed similarities in chemiluminescence behavior between four elastomers which were investigated, and it shows that similar oxidation mechanisms occur. Oxidative chemiluminescence was observed from purified samples of cis-1,4-polybutadiene, cis-1,4-polyisoprene, trans-polypentenamer, and 1,2-polybutadiene in an oxygen atmosphere at 25-150 C. The elastomer samples were placed in a 600 watt oven which is equipped with gas inlets for introducing any desired atmosphere. Chemiluminescence emission from the samples was focused with a two inch quartz lens onto the detector of a 12" photomultiplier which is connected to a photon counter. A strip-chart recorder, connected to the counter, permitted automatic data collection. Diagrams of the apparatus are included. The chemical reactions which occurred from the thermal decomposition of the polymer samples are described, and results (and tabulated data) are discussed.

  15. Overexpression of 14-3-3z promotes tau phosphorylation at Ser262 and accelerates proteosomal degradation of synaptophysin in rat primary hippocampal neurons.

    PubMed

    Qureshi, Hamid Y; Han, Dong; MacDonald, Ryen; Paudel, Hemant K

    2013-01-01

    b-Amyloid peptide accumulation, tau hyperphosphorylation, and synapse loss are characteristic neuropathological symptoms of Alzheimer's disease (AD). Tau hyperphosphorylation is suggested to inhibit the association of tau with microtubules, making microtubules unstable and causing neurodegeneration. The mechanism of tau phosphorylation in AD brain, therefore, is of considerable significance. Although PHF-tau is phosphorylated at over 40 Ser/Thr sites, Ser(262) phosphorylation was shown to mediate b-amyloid neurotoxicity and formation of toxic tau lesions in the brain. In vitro, PKA is one of the kinases that phosphorylates tau at Ser(262), but the mechanism by which it phosphorylates tau in AD brain is not very clear. 14-3-3z is associated with neurofibrillary tangles and is upregulated in AD brain. In this study, we show that 14-3-3z promotes tau phosphorylation at Ser(262) by PKA in differentiating neurons. When overexpressed in rat hippocampal primary neurons, 14-3-3z causes an increase in Ser(262) phosphorylation, a decrease in the amount of microtubule-bound tau, a reduction in the amount of polymerized microtubules, as well as microtubule instability. More importantly, the level of pre-synaptic protein synaptophysin was significantly reduced. Downregulation of synaptophysin in 14-3-3z overexpressing neurons was mitigated by inhibiting the proteosome, indicating that 14-3-3z promotes proteosomal degradation of synaptophysin. When 14-3-3z overexpressing neurons were treated with the microtubule stabilizing drug taxol, tau Ser(262) phosphorylation decreased and synaptophysin level was restored. Our data demonstrate that overexpression of 14-3-3z accelerates proteosomal turnover of synaptophysin by promoting the destabilization of microtubules. Synaptophysin is involved in synapse formation and neurotransmitter release. Our results suggest that 14-3-3z may cause synaptic pathology by reducing synaptophysin levels in the brains of patients suffering from AD. PMID

  16. Cases Studies of Irrigated Soil Degradation and Progradation

    NASA Astrophysics Data System (ADS)

    Zeyliger, Anatoly; Kust, German; Rozov, Sergey; Stoma, Galina

    2013-04-01

    Waterlogging and salination, along with interaction with other degradation processes, have not only caused the collapse of irrigation-based societies in the past, but are indeed threatening the viability of irrigation at present. The problem is global in scope. Decimation of natural ecosystems, deterioration of soil productivity depletion and pollution of water resources, and conflicts over dwindling supplies have become international problems closely linked with extension of irrigation development to large scale and associated impact to soil fertility and surrounding environment. Practical experience and scientific research done in the frame of FP6 DESIRE project provided an affirmative answer to the question - can irrigated agriculture be sustained for long time. In present contribution two case studies will be discussed and analysed in scope to compare different irrigation practises used for about 35 years and their impact to soil fertility. Investigated areas of both case studies are situated in the same Saratov Region of Russia at the left bank of middle part of Volga River with distance between about 100 km. First case study was developed during 2009-2010 by field trials at irrigated and surrounded areas of agricultural farms situated at Privolghskaya Irrigation System (Marksovsky District). Second case study was developed during summer of 2011 by field trial at experimental farm of research institute called VolgNIIGiM (Enghelsky District). During fields trail soil maps of both case studies were developed and compared with soil maps of the same areas done at 1970th before irrigation projects at both areas were started. Results of soil map comparison are showing that in the territory of first case study considerable soil degradation is taken place, but in the territory of the second case study a substantial soil progradation is taken place. Thus is supported by the time series of ground water monitoring at both irrigated areas. Obtained results will be

  17. Studies of dished accelerator grids for 30-cm ion thrusters

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.

    1973-01-01

    Eighteen geometrically different sets of dished accelerator grids were tested on five 30-cm thrusters. The geometric variation of the grids included the grid-to-grid spacing, the screen and accelerator hole diameters and thicknesses, the screen and accelerator open area fractions, ratio of dish depth to dish diameter, compensation, and aperture shape. In general, the data taken over a range of beam currents for each grid set included the minimum total accelerating voltage required to extract a given beam current and the minimum accelerator grid voltage required to prevent electron backstreaming.

  18. Studies of dished accelerator grids for 30-cm ion thrusters

    NASA Technical Reports Server (NTRS)

    Rawlin, V. K.

    1973-01-01

    Geometrically different sets of dished accelerator grids were tested on five 30-cm thrusters. The geometric variation of the grids included the grid-to-grid spacing, the screen and accelerator hole diameters and thicknesses, the screen and accelerator open area fractions, ratio of dish depth to the dish diameter, compensation, and aperture shape. In general, the data taken over a range of beam currents for each grid set included the minimum total accelerating voltage required to extract a given beam current and the minimum accelerator grid voltage required to prevent electron backstreaming.

  19. Pressurized-water reactor internals aging degradation study. Phase 1

    SciTech Connect

    Luk, K.H.

    1993-09-01

    This report documents the results of a Phase I study on the effects of aging degradations on pr internals. Primary stressers for internals an generated by the primary coolant flow in the they include unsteady hydrodynamic forces and pump-generated pressure pulsations. Other stressors are applied loads, manufacturing processes, impurities in the coolant and exposures to fast neutron fluxes. A survey of reported aging-related failure information indicates that fatigue, stress corrosion cracking (SCC) and mechanical wear are the three major aging-related degradation mechanisms for PWR internals. Significant reported failures include thermal shield flow-induced vibration problems, SCC in guide tube support pins and core support structure bolts, fatigue-induced core baffle water-jet impingement problems and excess wear in flux thimbles. Many of the reported problems have been resolved by accepted engineering practices. Uncertainties remain in the assessment of long-term neutron irradiation effects and environmental factors in high-cycle fatigue failures. Reactor internals are examined by visual inspections and the technique is access limited. Improved inspection methods, especially one with an early failure detection capability, can enhance the safety and efficiency of reactor operations.

  20. Hydrolytic degradation and morphologic study of poly-p-dioxanone.

    PubMed

    Lin, H L; Chu, C C; Grubb, D

    1993-02-01

    The in vitro hydrolytic degradation of 2-0 size PDS monofilament suture was studied for the purpose of revealing its morphologic structure and degradation mechanism. The sutures were immersed in phosphate buffer of pH 7.44 for up to 120 days at 37 degrees C. These hydrolyzed sutures were examined by the changes in tensile properties, weight, thermal properties, x-ray diffraction structure, surface morphology, and dye diffusion phenomena. It was found that hydrolysis had significant effects on the change of PDS fiber morphology and properties. Hydrolysis, however, had no significant effect on overall molecular orientation of the fiber until the very late stage. PDS suture fibers retained their skeleton throughout the earlier periods of hydrolysis concurrent with mass and tensile strength losses. PDS sutures exhibited an absorption delay of 120 days. Both heat of fusion and melting point exhibited a maximum function of hydrolysis time. Hydrolysis of PDS suture fibers proceeded through two stages: random scission of chain segments located in the amorphous regions of microfibrils and intermicrofibrillar space, followed by stepwise scission of chain segments located in the crystalline regions of microfibrils. Dye diffusion data showed that the passage along the longitudinal direction of the fiber was relatively easier than the lateral direction as evident in the diffusion coefficient, activation energy, and flexibility of chain segments. Swiss-cheese model of fiber structure appears to describe the observed dye diffusion phenomena and their dependence on hydrolysis time and dying temperature. PMID:8436572

  1. Inhomogeneous radiation degradation in polymers studied with a density gradient column

    NASA Astrophysics Data System (ADS)

    Gillen, K. T.; Clough, R. L.

    these metals diffused into the insulation during the high-temperature processing conditions necessary for extruding the cable and/or during storage at room temperature. The discovery of evidence for important copper-catalyzed oxidation occurring under room-temperature, radiation-aging conditions points out the potential dangers inherent in material degradation studies on compression molded sheets of material, since such studies may overlook important interactions between materials. The results of this study also show the potential of the density gradient technique for elucidating mechanisms of radiation degradation in polymers and for assessing the validity of accelerated-aging exposures by comparing density profiles of accelerated-aged samples with real-time aged samples.

  2. A Test House Study of Pesticides and PesticideDegradation Products Following an Indoor Application

    EPA Science Inventory

    Preexisting pesticide degradates are a concern for pesticide biomonitoring studies as exposure to them may result in overestimation of pesticide exposure. The purpose of this research was to determine whether there was significant formation and movement, of pesticide degradates o...

  3. Characterization and degradation studies on synthetic polymers for aerospace application

    NASA Technical Reports Server (NTRS)

    Hsu, M. T. S.

    1982-01-01

    The anti-misting additive for jet fuels known as FM-9 (proprietary polymer) was characterized by elemental analysis, solubility studies and molecular weight determination. Physical properties of surface tension, viscosity, specific gravity and other physical parameters were determined. These results are compared with properties of polyisobutylene and fuels modified with the same; the misting characteristics of polyisobutylene and FM-9 in Jet A fuel are included. Characterization and degradation of phthalocyanine and its derivatives were accomplished by use of a mass spectrometer and a pyroprobe solid pyrolyzer. Metal phthalocyanine tetracarboxylic acids and phthalocyanine-tetraamine cured epoxies were studied. Epoxy/graphite composite panels were exposed to a NASA-Ames radiant panel fire simulator in the flaming and non-flaming modes; toxic gases of HCN and HZS were measured along with oxygen, Co2, Co, and organic gases.

  4. An Experimental Study of a Pulsed Electromagnetic Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Eskridge, Richard; Lee, Mike; Smith, James; Martin, Adam; Markusic, Tom E.; Cassibry, Jason T.; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    Experiments are being performed on the NASA Marshall Space Flight Center (MSFC) pulsed electromagnetic plasma accelerator (PEPA-0). Data produced from the experiments provide an opportunity to further understand the plasma dynamics in these thrusters via detailed computational modeling. The detailed and accurate understanding of the plasma dynamics in these devices holds the key towards extending their capabilities in a number of applications, including their applications as high power (greater than 1 MW) thrusters, and their use for producing high-velocity, uniform plasma jets for experimental purposes. For this study, the 2-D MHD modeling code, MACH2, is used to provide detailed interpretation of the experimental data. At the same time, a 0-D physics model of the plasma initial phase is developed to guide our 2-D modeling studies.

  5. Solvent degradation and cleanup: a survey and recent ORNL studies

    SciTech Connect

    Mailen, J.C.; Tallent, O.K.

    1984-01-01

    This paper surveys the mechanisms for degradation of the tributyl phosphate and diluent components of Purex solvent by acid and radiation, reviews the problems encountered in plant operations resulting from the presence of these degradation products, and discusses methods for minimizing the formation of degradation products and accomplishing their removal. Scrubbing solutions containing sodium carbonate or hydroxylamine salts and secondary cleanup of solvents using solid sorbents are evaluated. Finally, recommendations for improved solvent cleanup are presented. 50 references, 4 figures, 3 tables.

  6. Vibrational spectroscopy to study degradation of natural dyes. Assessment of oxygen-free cassette for safe exposition of artefacts.

    PubMed

    Koperska, Monika; Łojewski, Tomasz; Łojewska, Joanna

    2011-03-01

    An important issue connected with conservation chemistry is how to improve the storage and exposure conditions in order to suppress the fading and degradation of dyes and other components of paintings. Although the oxygen-free exposure cassettes are commonly known in museums, there is still lack of information in the literature about the effect of anoxic conditions on the degradation of dyes. This study is an attempt to start a database formation on the dyes degradation. Five commercial dyes (indigo, dragon's blood, curcumin, madder, carminic acid) were submitted to accelerated ageing by exposure to intensive light in the visible range in both oxygen-free (anoxia) and -rich conditions. Degradation of the samples was investigated by several analytical techniques (attenuated total reflectance infrared spectroscopy, Raman spectroscopy, reflectance UV-Vis spectroscopy, X-ray fluorescence spectroscopy and optical microscopy). The conclusions are based on the estimators (derived from the determination of colour differences from Vis spectra and from the changes in FTIR and Raman vibrational bands intensity). According to them, only indigo, dragon's blood and curcumin show greater stability in anoxic conditions in comparison with oxygen-rich ones while madder, carminic acid undergo greater degradation. PMID:21165610

  7. AC impedance study of degradation of porous nickel battery electrodes

    NASA Technical Reports Server (NTRS)

    Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.

    1987-01-01

    AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.

  8. Studies of the thermal degradation of waste rubber.

    PubMed

    Chen, Fengzhen; Qian, Jialin

    2003-01-01

    One kind of Chinese waste tire's sample was pyrolyzed under an inert atmosphere by using thermo-gravimetric apparatus (TGA) and differential thermal analysis (DTA). Different pyrolysis temperature ranges were determined according to the reaction transition temperature obtained by TGA and DTA. Then, at each temperature range, the pyrolysis gaseous products were analyzed by gas chromatography (GC). The influence of the temperature range on the relative yields of the major decomposition products is studied, and a mechanism for the formation of the main components was also investigated. The results indicate that pyrolysis of waste rubber follows the radical mechanism, and the major products are not seriously affected by increasing the temperature from room temperature to 420 degrees C and from 421 to 600 degrees C, but the degradation of blend rubber is different for each of the compositional elastomer.

  9. Degradation in PV Encapsulation Transmittance: An Interlaboratory Study Toward a Climate-Specific Test

    SciTech Connect

    Miller, David C.; Hacke, Peter L.; Kempe, Michael D.; Wohlgemuth, John H.; Annigoni, Eleonora; Sculati-Meillaud, Fanny; Ballion, Amal; Kohl, Michael; Bokria, Jayesh G.; Bruckman, Laura S.; French, Roger H.; Burns, David; Phillips, Nancy H.; Feng; Jiangtao; Elliott, Lamont; Scott, Kurt P.; Fowler, Sean; Gu, Xiaohong; Honeker, Christian C.; Khonkar, Hussam; Perret-Aebi, Laure-Emmanuelle; Shioda, Tsy

    2015-06-14

    Reduced optical transmittance of encapsulation resulting from ultraviolet (UV) degradation has frequently been identified as a cause of decreased PV module performance through the life of installations in the field. The present module safety and qualification standards, however, apply short UV doses only capable of examining design robustness or 'infant mortality' failures. Essential information that might be used to screen encapsulation through product lifetime remains unknown. For example, the relative efficacy of xenon-arc and UVA-340 fluorescent sources or the typical range of activation energy for degradation is not quantified. We have conducted an interlaboratory experiment to provide the understanding that will be used towards developing a climate- and configuration-specific (UV) weathering test. Five representative, known formulations of EVA were studied in addition to one TPU material. Replicate laminated silica/polymer/silica specimens are being examined at 14 institutions using a variety of indoor chambers (including Xe, UVA-340, and metal-halide light sources) or field aging. The solar-weighted transmittance, yellowness index, and the UV cut-off wavelength, determined from the measured hemispherical transmittance, are examined to provide understanding and guidance for the UV light source (lamp type) and temperature used in accelerated UV aging tests. Index Terms -- reliability, durability, thermal activation.

  10. Degradation in PV Encapsulation Transmittance: An Interlaboratory Study Towards a Climate-Specific Test

    SciTech Connect

    Miller, David C.; Annigoni, Eleonora; Ballion, Amal; Bokria, Jayesh G.; Bruckman, Laura S.; Burns, David M.; Chen, Xinxin; Elliott, L.; Feng, J.; French, Roger H.; Fowler, S.; Gu, X.; Hacke, Peter L.; Honeker, C. C.; Kempe, Michael D.; Khonkar, H.; Kohl, M.; Perret-Aebi, Laure-Emmanuelle; Phillips, N. H.; Scott, K. P.; Sculati-Meillaud, F.; Shioda, T.; Suga, S.; Watanabe, S.; Wohlgemuth, John H.

    2015-06-14

    Reduced optical transmittance of encapsulants resulting from ultraviolet (UV) degradation has frequently been identified as a cause of decreased PV module performance through the life of service in the field. The present module safety and qualification standards, however, apply short UV doses only capable of examining design robustness or 'infant mortality' failures. Essential information that might be used to screen encapsulation through product lifetime remains unknown. For example, the relative efficacy of xenon-arc and UVA-340 fluorescent sources or the typical range of activation energy for degradation is not quantified. We have conducted an interlaboratory experiment to provide the understanding that will be used towards developing a climate- and configuration-specific (UV) weathering test. Five representative, known formulations of EVA were studied in addition to one TPU material. Replicate laminated silica/polymer/silica specimens are being examined at 14 institutions using a variety of indoor chambers (including Xenon, UVA-340, and metal-halide light sources) or field aging. The solar-weighted transmittance, yellowness index, and the UV cut-off wavelength, determined from the measured hemispherical transmittance, are examined to provide understanding and guidance for the UV light source (lamp type) and temperature used in accelerated UV aging tests.

  11. Degradation in PV Encapsulation Transmittance: An Interlaboratory Study Towards a Climate-Specific Test: Preprint

    SciTech Connect

    Miller, David C.; Annigoni, Eleonora; Ballion, Amal; Bokria, Jayesh G.; Bruckman, Laura S.; Burns, David M.; Chen, Xinxin; Elliott, Lamont; Feng, Jiangtao; French, Roger H.; Fowler, Sean; Gu, Xiaohong; Hacke, Peter L.; Honeker, Christian C.; Kempe, Michael D.; Khonkar, Hussam; Kohl, Michael; Perret-Aebi, Laure-Emmanuelle; Phillips, Nancy H.; Scott, Kurt P.; Sculati-Meillaud, Fanny; Shioda, Tsuyos

    2015-08-12

    Reduced optical transmittance of encapsulants resulting from ultraviolet (UV) degradation has frequently been identified as a cause of decreased PV module performance through the life of service in the field. The present module safety and qualification standards, however, apply short UV doses only capable of examining design robustness or 'infant mortality' failures. Essential information that might be used to screen encapsulation through product lifetime remains unknown. For example, the relative efficacy of xenon-arc and UVA-340 fluorescent sources or the typical range of activation energy for degradation is not quantified. We have conducted an interlaboratory experiment to provide the understanding that will be used towards developing a climate- and configuration-specific (UV) weathering test. Five representative, known formulations of EVA were studied in addition to one TPU material. Replicate laminated silica/polymer/silica specimens are being examined at 14 institutions using a variety of indoor chambers (including Xenon, UVA-340, and metal-halide light sources) or field aging. The solar-weighted transmittance, yellowness index, and the UV cut-off wavelength, determined from the measured hemispherical transmittance, are examined to provide understanding and guidance for the UV light source (lamp type) and temperature used in accelerated UV aging tests.

  12. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    SciTech Connect

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  13. Multiwavelength studies of Galactic TeV particle accelerators

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2016-07-01

    Our Milky Way galaxy is host to a variety of astrophysical objects capable of accelerating particles to TeV energies, including supernova remnants and pulsar wind nebulae. I will review recent multiwavelength results on Galactic TeV sources and discuss the implications for particle acceleration and diffusion in these systems.

  14. Experimental study of ion heating and acceleration during magnetic reconnection

    SciTech Connect

    Hsu, S.C.

    2000-01-28

    This dissertation reports an experimental study of ion heating and acceleration during magnetic reconnection, which is the annihilation and topological rearrangement of magnetic flux in a conductive plasma. Reconnection is invoked often to explain particle heating and acceleration in both laboratory and naturally occurring plasmas. However, a simultaneous account of reconnection and its associated energy conversion has been elusive due to the extreme inaccessibility of reconnection events, e.g. in the solar corona, the Earth's magnetosphere, or in fusion research plasmas. Experiments for this work were conducted on MRX (Magnetic Reconnection Experiment), which creates a plasma environment allowing the reconnection process to be isolated, reproduced, and diagnosed in detail. Key findings of this work are the identification of local ion heating during magnetic reconnection and the determination that non-classical effects must provide the heating mechanism. Measured ion flows are sub-Alfvenic and can provide only slight viscous heating, and classical ion-electron interactions can be neglected due to the very long energy equipartition time. The plasma resistivity in the reconnection layer is seen to be enhanced over the classical value, and the ion heating is observed to scale with the enhancement factor, suggesting a relationship between the magnetic energy dissipation mechanism and the ion heating mechanism. The observation of non-classical ion heating during reconnection has significant implications for understanding the role played by non-classical dissipation mechanisms in generating fast reconnection. The findings are relevant for many areas of space and laboratory plasma research, a prime example being the currently unsolved problem of solar coronal heating. In the process of performing this work, local measurements of ion temperature and flows in a well-characterized reconnection layer were obtained for the first time in either laboratory or observational

  15. Accelerating Monte Carlo power studies through parametric power estimation.

    PubMed

    Ueckert, Sebastian; Karlsson, Mats O; Hooker, Andrew C

    2016-04-01

    Estimating the power for a non-linear mixed-effects model-based analysis is challenging due to the lack of a closed form analytic expression. Often, computationally intensive Monte Carlo studies need to be employed to evaluate the power of a planned experiment. This is especially time consuming if full power versus sample size curves are to be obtained. A novel parametric power estimation (PPE) algorithm utilizing the theoretical distribution of the alternative hypothesis is presented in this work. The PPE algorithm estimates the unknown non-centrality parameter in the theoretical distribution from a limited number of Monte Carlo simulation and estimations. The estimated parameter linearly scales with study size allowing a quick generation of the full power versus study size curve. A comparison of the PPE with the classical, purely Monte Carlo-based power estimation (MCPE) algorithm for five diverse pharmacometric models showed an excellent agreement between both algorithms, with a low bias of less than 1.2 % and higher precision for the PPE. The power extrapolated from a specific study size was in a very good agreement with power curves obtained with the MCPE algorithm. PPE represents a promising approach to accelerate the power calculation for non-linear mixed effect models.

  16. Thermal Degradation Studies of Polyurethane/POSS Nanohybrid Elastomers

    SciTech Connect

    Lewicki, J P; Pielichowski, K; TremblotDeLaCroix, P; Janowski, B; Todd, D; Liggat, J J

    2010-03-05

    Reported here is the synthesis of a series of Polyurethane/POSS nanohybrid elastomers, the characterization of their thermal stability and degradation behavior at elevated temperatures using a combination of Thermal Gravimetric Analysis (TGA) and Thermal Volatilization Analysis (TVA). A series of PU elastomers systems have been formulated incorporating varying levels of 1,2-propanediol-heptaisobutyl-POSS (PHIPOSS) as a chain extender unit, replacing butane diol. The bulk thermal stability of the nanohybrid systems has been characterized using TGA. Results indicate that covalent incorporation of POSS into the PU elastomer network increase the non-oxidative thermal stability of the systems. TVA analysis of the thermal degradation of the POSS/PU hybrid elastomers have demonstrated that the hybrid systems are indeed more thermally stable when compared to the unmodified PU matrix; evolving significantly reduced levels of volatile degradation products and exhibiting a {approx}30 C increase in onset degradation temperature. Furthermore, characterization of the distribution of degradation products from both unmodified and hybrid systems indicate that the inclusion of POSS in the PU network is directly influencing the degradation pathways of both the soft and hard block components of the elastomers: The POSS/PU hybrid systems show reduced levels of CO, CO2, water and increased levels of THF as products of thermal degradation.

  17. Accelerated degradation of exogenous indole by Burkholderia unamae strain CK43B exposed to pyrogallol-type polyphenols.

    PubMed

    Kim, Dongyeop; Rahman, Atiqur; Sitepu, Irnayuli R; Hashidoko, Yasuyuki

    2013-01-01

    In modified Winogradsky's (MW) medium supplemented with excessive indole (1), Burkholderia unamae strain CK43B isolated from polyphenol-rich Shorea rhizosphere showed almost no cell growth, but it showed drastic cell growth given further supplementation of gallic acid, a simple plant polyphenol. This active cell growth of B. unamae CK43B was due to the stimulating effect of gallic acid on 1-degradation of bacterial cells, which acquired a nitrogen source in 1. Under aerobic culture conditions with appropriate concentrations (0.5-2.0 mM) of gallic acid, B. unamae CK43B started to decompose exogenous 1 in a dose-dependent manner, and finally accumulated catechol (5) via anthranilic acid (4). Pyrogallol also showed a cometabolic effect on decarboxylation-coupled oxidative deamination of B. unamae CK43B, producing 5 from 4, as gallic acid did. These results suggest that pyrogallol-type plant polyphenols act as stimulators on B. unamae CK43B, causing it to degrade an N-heterocyclic aromatic compound (NHAC) including nitrogen-containing humic substances.

  18. Hydroxide Degradation Pathways for Substituted Benzyltrimethyl Ammonium: A DFT Study

    SciTech Connect

    Long, Hai; Pivovar, Bryan S.

    2014-11-01

    The stability of cations used in the alkaline exchange membranes has been a major challenge. In this paper, degradation energy barriers were investigated by density functional theory for substituted benzyltrimethyl ammonium (BTMA+) cations. Findings show that electron-donating substituent groups at meta-position(s) of the benzyl ring could result in increased degradation barriers. However, after investigating more than thirty substituted BTMA+ cations, the largest improvement in degradation barrier found was only 6.7 kJ/mol. This suggests a modest (8×) improvement in stability for this type of approach may be possible, but for anything greater other approaches will need to be pursued.

  19. Electrochemical degradation, kinetics & performance studies of solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Das, Debanjan

    Linear and Non-linear electrochemical characterization techniques and equivalent circuit modelling were carried out on miniature and sub-commercial Solid Oxide Fuel Cell (SOFC) stacks as an in-situ diagnostic approach to evaluate and analyze their performance under the presence of simulated alternative fuel conditions. The main focus of the study was to track the change in cell behavior and response live, as the cell was generating power. Electrochemical Impedance Spectroscopy (EIS) was the most important linear AC technique used for the study. The distinct effects of inorganic components usually present in hydrocarbon fuel reformates on SOFC behavior have been determined, allowing identification of possible "fingerprint" impedance behavior corresponding to specific fuel conditions and reaction mechanisms. Critical electrochemical processes and degradation mechanisms which might affect cell performance were identified and quantified. Sulfur and siloxane cause the most prominent degradation and the associated electrochemical cell parameters such as Gerisher and Warburg elements are applied respectively for better understanding of the degradation processes. Electrochemical Frequency Modulation (EFM) was applied for kinetic studies in SOFCs for the very first time for estimating the exchange current density and transfer coefficients. EFM is a non-linear in-situ electrochemical technique conceptually different from EIS and is used extensively in corrosion work, but rarely used on fuel cells till now. EFM is based on exploring information obtained from non-linear higher harmonic contributions from potential perturbations of electrochemical systems, otherwise not obtained by EIS. The baseline fuel used was 3 % humidified hydrogen with a 5-cell SOFC sub-commercial planar stack to perform the analysis. Traditional methods such as EIS and Tafel analysis were carried out at similar operating conditions to verify and correlate with the EFM data and ensure the validity of the

  20. High transformer ratio drive beams for wakefield accelerator studies

    SciTech Connect

    England, R. J.; Ng, C.-K.; Frederico, J.; Hogan, M. J.; Litos, M.; Muggli, P.; Joshi, C.; An, W.; Andonian, G.; Mori, W.; Lu, W.

    2012-12-21

    For wakefield based acceleration schemes, use of an asymmetric (or linearly ramped) drive bunch current profile has been predicted to enhance the transformer ratio and generate large accelerating wakes. We discuss plans and initial results for producing such bunches using the 20 to 23 GeV electron beam at the FACET facility at SLAC National Accelerator Laboratory and sending them through plasmas and dielectric tubes to generate transformer ratios greater than 2 (the limit for symmetric bunches). The scheme proposed utilizes the final FACET chicane compressor and transverse collimation to shape the longitudinal phase space of the beam.

  1. Free-radical-induced oxidative and reductive degradation of fluoroquinolone pharmaceuticals: kinetic studies and degradation mechanism.

    PubMed

    Santoke, Hanoz; Song, Weihua; Cooper, William J; Greaves, John; Miller, George E

    2009-07-01

    Fluoroquinolones, as a class of broad-spectrum antibiotics, have been detected in both surface and ground waters, and advanced oxidation/reduction processes (AO/RPs) are currently in development to remove these and other pharmaceuticals from wastewater because currently utilized treatment methods have proven to be ineffective. This article reports the reaction kinetics of six common fluoroquinolones with hydroxyl radicals and hydrated electrons, which are the major reactive species involved in AO/RPs. The bimolecular reaction rate constants (M(-1) s(-1)) for orbifloxacin, flumequine, marbofloxacin, danofloxacin, enrofloxacin, and the model compound, 6-fluoro-4-oxo-1,4-dihydro-3-quinoline carboxylic acid, with *OH are (6.94 +/- 0.08) x 10(9), (8.26 +/- 0.28) x 10(9), (9.03 +/- 0.39) x 10(9), (6.15 +/- 0.11) x 10(9), (7.95 +/- 0.23) x 10(9), (7.65 +/- 0.20) x 10(9), and with e(aq)(-), (2.25 +/- 0.02) x 10(10), (1.83 +/- 0.01) x 10(10), (2.41 +/- 0.02) x 10(10), (1.68 +/- 0.02) x 10(10), (1.89 +/- 0.02) x 10(10), and (1.49 +/- 0.01) x 10(10). These rate constants are related to the functional groups attached to the quinolone core, particularly the steric hindrance of the piperazine ring, making it possible to obtain a preliminary estimate of the *OH rate constant of an arbitrary fluoroquinolone by observing the ring constituents. In addition, the products of gamma-irradiation degradation of fluoroquinolones were analyzed by LC-MS to elucidate the probable pathways of AO/RPs degradation. Results indicate that preliminary degradation pathways include hydroxyl radical attack on the aromatic ring with subsequent hydroxylation, the substitution of a fluorine atom with a hydroxyl group, and the removal of the piperazine-derived side chain.

  2. The tissue plasminogen activator-plasminogen proteolytic cascade accelerates amyloid-beta (Abeta) degradation and inhibits Abeta-induced neurodegeneration.

    PubMed

    Melchor, Jerry P; Pawlak, Robert; Strickland, Sidney

    2003-10-01

    Accumulation of the amyloid-beta (Abeta) peptide depends on both its generation and clearance. To better define clearance pathways, we have evaluated the role of the tissue plasminogen activator (tPA)-plasmin system in Abeta degradation in vivo. In two different mouse models of Alzheimer's disease, chronically elevated Abeta peptide in the brain correlates with the upregulation of plasminogen activator inhibitor-1 (PAI-1) and inhibition of the tPA-plasmin system. In addition, Abeta injected into the hippocampus of mice lacking either tPA or plasminogen persists, inducing PAI-1 expression and causing activation of microglial cells and neuronal damage. Conversely, Abeta injected into wild-type mice is rapidly cleared and does not cause neuronal degeneration. Thus, the tPA-plasmin proteolytic cascade aids in the clearance of Abeta, and reduced activity of this system may contribute to the progression of Alzheimer's disease.

  3. Study on degradation process of polymer electrolyte by solution analysis

    NASA Astrophysics Data System (ADS)

    Akiyama, Yoko; Sodaye, Hemant; Shibahara, Yuji; Honda, Yoshihide; Tagawa, Seiichi; Nishijima, Shigehiro

    Degradation process of Nafion which is one of the polymer electrolyte generally used for polymer electrolyte membrane fuel cell was investigated by solution analysis and structural analysis of eluted species. Nafion degraded by gamma-ray irradiation and heat treatment was immersed in distilled water and the solutions were analyzed using ion chromatograph, total organic carbon (TOC) analyzer, and inductively coupled plasma atomic emission spectrometer (ICP-AES). The solutions after the Fenton reaction were also analyzed with the same methods. Proton, sulfide ion, fluorine ion and organic carbon were eliminated into the solution, and their ratio was changed depending on the degradation method. To determine the eliminated species to the solution, structural analysis of concentrated dissolved species was performed using FT-IR. As the results, the initial process of degradation was detected sensitively in solution analysis compared with membrane analysis, and difference of the degradation process under different conditions was clearly observed. It was also found that new functional group COOH was formed in the eliminated species. These results showed that solution analysis are very simple yet powerful methods to elucidate the degradation process, which can also be applied to actual fuel cell operation to track minute changes in the polymer electrolyte.

  4. Proposed Dark Current Studies at the Argonne Wakefield Accelerator Facility

    SciTech Connect

    Antipov, S.P.; Conde, Manoel Eduardo; Gai, Wei; Power, John Gorham; Yusof, Z.M.; Spentzouris, L.K.; Dolgashev, V.A.; /SLAC

    2008-01-18

    A study of dark currents has been initiated at the Argonne Wakefield Accelerator Facility (AWA). Emission of dark current is closely related to a breakdown. Breakdown may include several factors such as local field enhancement, explosive electron emission, Ohmic heating, tensile stress produced by electric field, and others. The AWA is building a dedicated facility to test various models for breakdown mechanisms and to determine the roles of different factors in the breakdown. An imaging system is being put together to identify single emitters on the cathode surface. This will allow us to study dark current properties in the gun. We also plan to trigger breakdown events with a high-powered laser at various wavelengths (IR to UV). Another experimental idea follows from the recent work on a Schottky-enabled photoemission in an RF photoinjector that allows us to determine in situ the field enhancement factor on a cathode surface. Monitoring the field enhancement factor before and after can shed some light on a modification of metal surface after the breakdown.

  5. Accelerating S3D: A GPGPU case study

    SciTech Connect

    Spafford, Kyle L; Meredith, Jeremy S; Vetter, Jeffrey S; Chen, Jackie; Grout, Ray W; Sankaran, Ramanan

    2009-01-01

    The graphics processor (GPU) has evolved into an appealing choice for high performance computing due to its superior memory bandwidth, raw processing power, and flexible programmability. As such, GPUs represent an excellent platform for accelerating scientific applications. This paper explores a methodology for identifying applications which present significant potential for acceleration. In particular, this work focuses on experiences from accelerating S3D, a high-fidelity turbulent reacting flow solver. The acceleration process is examined from a holistic viewpoint, and includes details that arise from different phases of the conversion. This paper also addresses the issue of floating point accuracy and precision on the GPU, a topic of immense importance to scientific computing. Several performance experiments are conducted, and results are presented from the NVIDIA Tesla C1060 GPU. We generalize from our experiences to provide a roadmap for deploying existing scientific applications on heterogeneous GPU platforms.

  6. Introduction of atrazine degrader to enhance rhizodegradation of atrazine

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introducing atrazine (ATR) degraders into riparian vegetative buffer strips (VBS) can be a promising bioremediation approach to accelerate the degradation of ATR and its degradation products deposited into VBS by surface runoff. A growth chamber study was conducted to investigated the synergistic ef...

  7. Aqueous photodegradation of antibiotic florfenicol: kinetics and degradation pathway studies.

    PubMed

    Zhang, Ya; Li, Jianhua; Zhou, Lei; Wang, Guoqing; Feng, Yanhong; Wang, Zunyao; Yang, Xi

    2016-04-01

    The occurrence of antibacterial agents in natural environment was of scientific concern in recent years. As endocrine disrupting chemicals, they had potential risk on ecology system and human beings. In the present study, the photodegradation kinetics and pathways of florfenicol were investigated under solar and xenon lamp irradiation in aquatic systems. Direct photolysis half-lives of florfenicol were determined as 187.29 h under solar irradiation and 22.43 h under xenon lamp irradiation, respectively. Reactive oxygen species (ROS), such as hydroxyl radical (·OH) and singlet oxygen ((1)O2) were found to play an important role in indirect photolysis process. The presence of nitrate and dissolved organic matters (DOMs) could affect photolysis of florfenicol in solutions through light screening effect, quenching effect, and photoinduced oxidization process. Photoproducts of florfenicol in DOMs solutions were identified by solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) analysis techniques, and degradation pathways were proposed, including photoinduced hydrolysis, oxidation by (1)O2 and ·OH, dechlorination, and cleavage of the side chain. PMID:26705756

  8. Boiling-Water Reactor internals aging degradation study. Phase 1

    SciTech Connect

    Luk, K.H.

    1993-09-01

    This report documents the results of an aging assessment study for boiling water reactor (BWR) internals. Major stressors for BWR internals are related to unsteady hydrodynamic forces generated by the primary coolant flow in the reactor vessel. Welding and cold-working, dissolved oxygen and impurities in the coolant, applied loads and exposures to fast neutron fluxes are other important stressors. Based on results of a component failure information survey, stress corrosion cracking (SCC) and fatigue are identified as the two major aging-related degradation mechanisms for BWR internals. Significant reported failures include SCC in jet-pump holddown beams, in-core neutron flux monitor dry tubes and core spray spargers. Fatigue failures were detected in feedwater spargers. The implementation of a plant Hydrogen Water Chemistry (HWC) program is considered as a promising method for controlling SCC problems in BWR. More operating data are needed to evaluate its effectiveness for internal components. Long-term fast neutron irradiation effects and high-cycle fatigue in a corrosive environment are uncertainty factors in the aging assessment process. BWR internals are examined by visual inspections and the method is access limited. The presence of a large water gap and an absence of ex-core neutron flux monitors may handicap the use of advanced inspection methods, such as neutron noise vibration measurements, for BWR.

  9. Studies of beam dynamics in relativistic klystron two- beam accelerators

    NASA Astrophysics Data System (ADS)

    Lidia, Steven Michael

    Two-beam accelerators (TBAs) based upon free-electron lasers (FELs) or relativistic klystrons (RK-TBAs) have been proposed as efficient power sources for next generation high-energy linear colliders. Studies have demonstrated the possibility of building TBAs from X-band (~8-12 GHz) through Ka-band (~30-35 GHz) frequency regions. A new method of simulating the beam dynamics in accelerators of this type has been developed in this dissertation. There are three main components to this simulation. The first is a tracking algorithm to generate nonlinear transfer maps for pushing noninteracting particles through the external fields. A mapping algorithm is used so that tens or hundreds of thousands of macroparticles can be pushed from the solution of a few hundreds of differential equations. This is a great cost-savings device from the standpoint of CPU cycles. It can increase by several orders of magnitude the number of macroparticles that take place in the simulation, enabling more accurate modeling of the evolution of the beam distribution and enhanced sensitivity to effects due to the beam's halo. The second component is a 3D Particle-In-Cell (PIC) algorithm that solves a set of Helmholtz equations for the self-fields, including the conducting boundary condition, and generates impulses that are interleaved with the nonlinear maps by means of a split- operator algorithm. The Helmholtz equations are solved by a multi-grid algorithm. The third component is an equivalent circuit equation solver that advances the modal rf cavity fields in time due to excitation by the modulated beam. The beam-cavity interaction is analyzed and divided naturally into two distinct times scales. The RTA project is described, and the simulation code is used to design the latter portions of the experiment. Detailed calculations of the beam dynamics and of the rf cavity output are presented and discussed. A beamline design is presented that will generate nearly 1.2 TW of power from 40 input, gain

  10. The SuperB Accelerator: Overview and Lattice Studies

    SciTech Connect

    Biagini, M.E.; Boni, R.; Boscolo, M.; Drago, A.; Guiducci, S.; Preger, M.; Raimondi, P.; Tomassini, S.; Vaccarezza, C.; Zobov, M.; Cai, Y.; Fisher, A.; Heifets, S.; Novokhatski, A.; Pivi, M.T.; Seeman, J.; Sullivan, M.; Wienands, U.; Paoloni, E.; Marchiori, G.; Koop, I.; /Novosibirsk, IYF /Daresbury /LBL, Berkeley /CERN /Orsay, LAL /KEK, Tsukuba

    2011-11-22

    SuperB aims at the construction of a very high luminosity (10{sup 36} cm{sup -2} s{sup -1}) asymmetric e{sup +}e{sup -} Flavour Factory, with possible location at the campus of the University of Rome Tor Vergata, near the INFN Frascati National Laboratory. In this paper the basic principles of the design and details on the lattice are given. SuperB is a new machine that can exploit novel very promising design approaches: (1) large Piwinski angle scheme will allow for peak luminosity of the order of 10{sup 36} cm{sup -2} s{sup -1}, well beyond the current state-of-the-art, without a significant increase in beam currents or shorter bunch lengths; (2) 'crab waist' sextupoles will be used for suppression of dangerous resonances; (3) the low beam currents design presents reduced detector and background problems, and affordable operating costs; (4) a polarized electron beam can produce polarized {tau} leptons, opening an entirely new realm of exploration in lepton flavor physics. SuperB studies are already proving useful to the accelerator and particle physics communities. The principle of operation is being tested at DAFNE. The baseline lattice, based on the reuse of all PEP-II hardware, fits in the Tor Vergata University campus site, near Frascati. A CDR is being reviewed by an International Review Committee, chaired by J. Dainton (UK). A Technical Design Report will be prepared to be ready by beginning of 2010.

  11. Model for initiation of quality factor degradation at high accelerating fields in superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Dzyuba, A.; Romanenko, A.; Cooley, L. D.

    2010-12-01

    A model for the onset of the reduction in superconducting radio-frequency (SRF) cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration Hpen. Such defects were argued to be the worst case by Buzdin and Daumens (1998 Physica C 294 257), whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter κ. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of Hpen when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower Hpen was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of κ. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by ~ 20%, and that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model was

  12. Model for Initiation of Quality Factor Degradation at High Accelerating Fields in Superconducting Radio-Frequency Cavaties

    SciTech Connect

    Dzyuba, A.; Romanenko, A.; Cooley, L.D.; /Fermilab

    2010-07-13

    A model for the onset of the reduction in SRF cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration H{sub pen}. Such defects were argued to be the worst case by Buzdin and Daumens, [1998 Physica C 294 257], whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter {kappa}. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of H{sub pen} when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower H{sub pen} was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice-versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of {kappa}. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by {approx}20%, and that that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model

  13. Acceleration of cerebral ventricular expansion in the Cardiovascular Health Study.

    PubMed

    Carmichael, Owen T; Kuller, L H; Lopez, O L; Thompson, P M; Dutton, R A; Lu, A; Lee, S E; Lee, J Y; Aizenstein, H J; Meltzer, C C; Liu, Y; Toga, A W; Becker, J T

    2007-09-01

    Interactions between prevalent late-life medical conditions and expansion of the cerebral ventricles are not well understood. Thirty elderly subjects received three magnetic resonance (MR) scans each, in 1997-1999, 2002-2004, and 2003-2005. A linear expansion model of MR-measured lateral ventricle volume was estimated for each subject by fitting a line to a plot of their 1997-1999 and 2002-2004 volumes as a function of time. Acceleration in ventricular expansion was defined as the deviation between the 2003-2005 volumes measured from MR and the 2003-2005 volumes predicted by the linear expansion model. Ventricular acceleration was analyzed in a multivariate model with age, race, history of heart disease, diabetes, and hypertension as fixed effects. Ventricular acceleration was significantly higher in non-whites, diabetics, and those without heart disease (p<0.05). Ventricular acceleration was higher in subjects with a history of hypertension, but the difference was not statistically significant (p=0.08). Acceleration of ventricular expansion in the elderly may be related to demographic and cardiovascular factors.

  14. A study of tannic acid degradation by soil bacteria.

    PubMed

    Ilori, Matthew O; Adebusoye, Sunday A; Amund, Olukayode O; Oyetoran, Bodunde O

    2007-09-15

    A tannin-degrading strain of Bacillus sp. AB1 was isolated from a garden soil by enrichment. This organism was able to utilize 1% (w/v) tannic acid-a gallotannin at 30 degrees C and pH below 4.5 in a defined mineral medium where the acid was the sole source of carbon and energy under 96 h. Growth resulted in increase in OD concomitant with gradual decrease in pH of the culture medium. Analysis of the culture fluid by paper chromatography revealed glucose and gallic acid as major metabolites of tannic acid degradative pathway. Mineralization of tannic acid was informed when none of the metabolites was recovered after 96 h of incubation. The degradation potential of this isolate could be exploited for the production of tannase, improvement of livestock production and also detoxification of tannery effluents at extreme acidic conditions.

  15. Chemical Degradation Studies on a Series of Dithiophosphinic Acids

    SciTech Connect

    Melissa E. Freiderich; Dean R. Peterman; John R. Klaehn; Philippe Marc; Laetitia H. Delmau

    2014-04-01

    A significant increase in the stability of a series of dithiophosphinic acids (DPAHs) under oxidizing acidic conditions was achieved. The degradation behavior of a series of DPAHs, designed for lanthanide/actinide separation, was examined. The stability of the DPAHs, when contacted with varying nitric acid concentrations, was tested and monitored using 31P {1H} NMR. Changes in the functional groups of the DPAHs resulted in substantial increases in the stability. However, when placed in contact with 2 M HNO3 all the DPAHs eventually showed signs of degradation. The addition of a radical scavenger, hydrazine, inhibited the degradation of the DPAHs. In the presence of a small concentration of hydrazine, five of the DPAHs remained stable for over a month in direct contact with 2 M HNO3.

  16. Study on photocatalytic degradation of several volatile organic compounds.

    PubMed

    Zuo, Guo-Min; Cheng, Zhen-Xing; Chen, Hong; Li, Guo-Wen; Miao, Ting

    2006-02-01

    The gas-phase photolytic and photocatalytic reactions of several aromatics and chlorohydrocarbons were investigated. The experimental results revealed that chlorohydrocarbons like trichloroethylene, dichloromethane and chloroform could be degraded through either photolysis or photocatalysis under irradiation of germicidal lamp, and the elimination rate of chlorohydrocarbons through photolysis was quicker than that through photocatalysis. UV light from a germicidal lamp could directly lead to degradation of toluene but could hardly act on benzene. The photodegradation rate for these volatile organic compounds (VOCs) through photolysis followed an order: trichloroethylene>chloroform>dichloromethane>toluene>benzene>carbon tetrachloride, and through photocatalysis followed: trichloroethylene>chloroform>toluene>dichloromethane>benzene>carbon tetrachloride. Besides, a series of modified TiO2 photocatalysts were prepared by depositing noble metal, doping with transition metal ion, recombining with metal oxides and modifying with super strong acid. Activity of these catalysts was examined upon photocatalytic degradation of benzene as a typical compound that was hard to be degraded. It indicated that these modification methods could promote the activity of TiO2 catalyst to different extent. The apparent zero-order reaction rate constant for degrading benzene over SnO2/TiO2 catalyst had the highest value, which was nearly three times as that over P25 TiO2. But it simultaneously had the lowest rate for mineralizing the objective compound. In spite that Fe3+/TiO2 catalyst behaved slightly less active than SnO2/TiO2 for degradation of benzene, the mineralization rate over Fe3+/TiO2 was the highest one among the prepared catalysts.

  17. Multiprogramming performance degradation - Case study on a shared memory multiprocessor

    NASA Technical Reports Server (NTRS)

    Dimpsey, R. T.; Iyer, R. K.

    1989-01-01

    The performance degradation due to multiprogramming overhead is quantified for a parallel-processing machine. Measurements of real workloads were taken, and it was found that there is a moderate correlation between the completion time of a program and the amount of system overhead measured during program execution. Experiments in controlled environments were then conducted to calculate a lower bound on the performance degradation of parallel jobs caused by multiprogramming overhead. The results show that the multiprogramming overhead of parallel jobs consumes at least 4 percent of the processor time. When two or more serial jobs are introduced into the system, this amount increases to 5.3 percent

  18. Surface wave accelerator based on silicon carbide: theoretical study

    SciTech Connect

    Kalmykov, S.; Korobkin, D.; Neuner, B.; Shvets, G.

    2009-01-22

    Compact near-field solid-state accelerating structure powered by a carbon dioxide (CO{sub 2}) laser is considered. The accelerating luminous transverse magnetic mode is excited in a few-micron wide evacuated planar channel between two silicon carbide (SiC) films grown on silicon (Si) wafers. Laser coupling to this mode is accomplished through the properly designed Si gratings. Operating wavelength is dictated by the frequency-dependent dielectric permittivity of SiC and the channel width. The geometric loss factor {kappa} of the accelerating mode is computed. It is found that the unwanted excitation of the guided modes in Si wafers reduces the laser coupling efficiency and increases the fields inside the Si wafer.

  19. Enzymatic degradation studies of pectin and cellulose from red beets.

    PubMed

    Dongowski, G

    2001-10-01

    The influence of structural features of the cell wall polysaccharides pectin and cellulose on the enzymatic degradation of red beet was evaluated. Alcohol-insoluble substances and acetone-insoluble residues were prepared from red beets and characterized with respect to the content of dietary fibre, pectin fractions, neutral saccharide composition and water absorption. The high-methylated and high-acetylated pectin component was partly soluble in water and in EDTA. Pectin was hardly extractable from alcohol-insoluble substances as well as from red beets. Isolated pectin could not be completely degraded by pectolytic enzymes. After de-acetylation, the pectic acid from red beets was degradable in a similar rate like citrus pectic acid. From alcohol-insoluble substances, several cellulose and lignin fractions were prepared and analysed. A cellulose preparation from red beets was intensely degraded by cellulases with high activities as shown by the release of reducing end-groups, viscosity and scanning electron microscopy. Cell wall preparations from red beets were able to bind high amounts of water. A decrease in water absorption during enzymatic action or changes in viscosity and flow behaviour are sensitive markers for decomposition or depolymerization processes. Furthermore, an inhibitor of microbial enzymes was isolated from red beets and acetone-insoluble residues. The main reason for the poor enzymatic liquefaction or maceration of red beets by pectolytic and cellulolytic enzymes is the high degree of acetylation of the pectin component.

  20. Inclined Planes and Motion Detectors: A Study of Acceleration.

    ERIC Educational Resources Information Center

    Tracy, Dyanne M.

    2001-01-01

    Presents an activity in which students work in cooperative groups and roll balls down inclined planes, collect data with the help of an electronic motion detector, and represent data with a graphing calculator to explore concepts such as mass, gravity, velocity, and acceleration. (Contains 12 references.) (Author/ASK)

  1. Oxidative degradation studies of an oxazolidinone-derived antibacterial agent, RWJ416457, in aqueous solutions.

    PubMed

    Dong, Jinquan; Karki, Shyam B; Parikh, Mansi; Riggs, Jason C; Huang, Lian

    2012-11-01

    The rates of oxidative degradation of a new antibacterial drug, RWJ416457, in aqueous solutions were investigated over the pH-range of 2 to 10. Two oxidative degradates were identified and the influences of pH, buffer concentration, metal ions, metal chelating agents, and temperatures were studied. The pH, metal chelating agents, and metal ions significantly changed the product distribution in addition to the degradation rate. Oxidative degradation is believed to follow a hydrogen abstraction (HAT) pathway. One degradate was the major product under acidic conditions and its predominance is attributed to a resonance-stabilized intermediate. The importance of the resonance structure was diminished under neutral and basic conditions. The product distribution changed and two degradates were formed in equal amounts. The study results guided the formulation development to minimize oxidation.

  2. Study of acaricide stability in honey. Characterization of amitraz degradation products in honey and beeswax.

    PubMed

    Korta, E; Bakkali, A; Berrueta, L A; Gallo, B; Vicente, F; Kilchenmann, V; Bogdanov, S

    2001-12-01

    A study on the possible degradation of amitraz, bromopropylate, coumaphos, chlordimeform, cymiazole, flumethrin, and tau-fluvalinate during the storage of honey was carried out by HPLC. Except amitraz, the other acaricides are stable in this medium for at least 9 months. Degradation studies of amitraz in honey and beeswax were carried out; the degradation products detected in both matrices were 2,4-dimethylphenylformamide (DMF) and N-(2,4-dimethylphenyl)-N'-methylformamidine (DPMF). The reaction rate constants and the half-lives of the amitraz degradation in honey and wax were calculated. Amitraz was nearly completely degraded within 1 day in beeswax and within 10 days in honey. When amitraz-spiked combs are recycled into new beeswax, DMF was found to be the principal degradation product left in pure wax. PMID:11743771

  3. Spectroscopic evaluation of a freeze-dried vaccine during an accelerated stability study.

    PubMed

    Hansen, Laurent; Van Renterghem, Jeroen; Daoussi, Rim; Vervaet, Chris; Remon, Jean Paul; De Beer, Thomas

    2016-07-01

    This research evaluates a freeze-dried live, attenuated virus vaccine during an accelerated stability study using Near Infrared (NIR) and Fourier Transform Infrared (FTIR) spectroscopy in addition to the traditional quality tests (i.e., potency assay and residual moisture analysis) and Modulated Differential Scanning Calorimetry (MDSC). Therefore, freeze-dried live, attenuated virus vaccines were stored during four weeks at 4°C (i.e., recommended storage condition) and at 37°C (i.e., accelerated storage condition) and weekly analyzed using these techniques. The potency assay showed that the virus titer decreased in two phases when the samples were stored at 37°C. The highest titer loss occurred during the first week storage at 37°C after which the degradation rate decreased. Both the residual moisture content and the relaxation enthalpy also increased according to this two-phase pattern during storage at 37°C. In order to evaluate the virus and its interaction with the amorphous stabilizer in the formulation (trehalose), the NIR spectra were analyzed via principal component analysis (PCA) using the amide A/II band (5029-4690cm(-1)). The FTIR spectra were also analyzed via PCA using the amide III spectral range (1350-1200cm(-1)). Analysis of the amide A/II band in the NIR spectra revealed that the titer decrease during storage was probably linked to a change of the hydrogen bonds (i.e., interaction) between the virus proteins and the amorphous trehalose. Analyzing the amide III band (FTIR spectra) showed that the virus destabilization was coupled to a decrease of the coated proteins β turn and an increase of α helix. During storage at 4°C, the titer remained constant, no enthalpic relaxation was observed and neither the Amide A/II band (NIR spectra) nor the Amide III band (FTIR spectra) varied. PMID:27102305

  4. Degradation studies on biodegradable nanocomposite based on polycaprolactone/polycarbonate (80:20%) polyhedral oligomeric silsesquioxane.

    PubMed

    Raghunath, Joanne; Georgiou, George; Armitage, David; Nazhat, Showan N; Sales, Kevin M; Butler, Peter E; Seifalian, Alexander M

    2009-12-01

    The development of biocompatible polymers has greatly advanced the field of tissue engineering. Some tissues can be propagated on a nondegradable scaffold. Tissue such as cartilage, however, is a complex tissue in which the chondrocytes require their own synthesized extracellular matrix (ECM) to function. Suitable scaffolds for tissue engineering cartilage should provide mechanical strength and degrade at a similar rate to that of cell growth and ECM production. We have developed a biodegradable nanocomposite based on polycaprolactone and polycarbonate polyurethane (PCU) with an incorporated polyhedral oligomeric silsesquioxane (POSS) (POSS modified Poly(caprolactone/carbonate) urethane/urea). Previous work on POSS incorporated into PCU (POSS-PCU) has been shown to possess good mechanical strength, elasticity and resistance to degradation. This series of experiments involved exposing this polymer to a selection of accelerated degradative solutions for up to 8 weeks. The samples were analyzed by infra-red spectroscopy, scanning electron microscopy, X-ray microanalysis, contact angle analysis, and stress-strain mechanical analysis. Degradation of hard and soft segments of the nanocomposite was evident by infra-red spectroscopy in all conditioned samples. POSS nanocage degradation was evident in some oxidative/peroxidative systems accompanied by gross changes in surface topography and significant changes in mechanical properties. The hydrophobic polymer became more hydrophilic in all conditions. This biodegradable nanocomposite demonstrated steady degradation with protection of mechanical properties when exposed to hydrolytic enzymes and plasma protein fractions and exhibited more dramatic degradation by oxidation.This pattern may be potentially employed in tissue engineering scaffolds where controlled degradation and retained structural stability of the scaffold is required.

  5. Exploring the microbiota dynamics related to vegetable biomasses degradation and study of lignocellulose-degrading bacteria for industrial biotechnological application

    NASA Astrophysics Data System (ADS)

    Ventorino, Valeria; Aliberti, Alberto; Faraco, Vincenza; Robertiello, Alessandro; Giacobbe, Simona; Ercolini, Danilo; Amore, Antonella; Fagnano, Massimo; Pepe, Olimpia

    2015-02-01

    The aims of this study were to evaluate the microbial diversity of different lignocellulosic biomasses during degradation under natural conditions and to isolate, select, characterise new well-adapted bacterial strains to detect potentially improved enzyme-producing bacteria. The microbiota of biomass piles of Arundo donax, Eucalyptus camaldulensis and Populus nigra were evaluated by high-throughput sequencing. A highly complex bacterial community was found, composed of ubiquitous bacteria, with the highest representation by the Actinobacteria, Proteobacteria, Bacteroidetes and Firmicutes phyla. The abundances of the major and minor taxa retrieved during the process were determined by the selective pressure produced by the lignocellulosic plant species and degradation conditions. Moreover, cellulolytic bacteria were isolated using differential substrates and screened for cellulase, cellobiase, xylanase, pectinase and ligninase activities. Forty strains that showed multienzymatic activity were selected and identified. The highest endo-cellulase activity was seen in Promicromonospora sukumoe CE86 and Isoptericola variabilis CA84, which were able to degrade cellulose, cellobiose and xylan. Sixty-two percent of bacterial strains tested exhibited high extracellular endo-1,4-ß-glucanase activity in liquid media. These approaches show that the microbiota of lignocellulosic biomasses can be considered an important source of bacterial strains to upgrade the feasibility of lignocellulose conversion for the `greener' technology of second-generation biofuels.

  6. Exploring the microbiota dynamics related to vegetable biomasses degradation and study of lignocellulose-degrading bacteria for industrial biotechnological application

    PubMed Central

    Ventorino, Valeria; Aliberti, Alberto; Faraco, Vincenza; Robertiello, Alessandro; Giacobbe, Simona; Ercolini, Danilo; Amore, Antonella; Fagnano, Massimo; Pepe, Olimpia

    2015-01-01

    The aims of this study were to evaluate the microbial diversity of different lignocellulosic biomasses during degradation under natural conditions and to isolate, select, characterise new well-adapted bacterial strains to detect potentially improved enzyme-producing bacteria. The microbiota of biomass piles of Arundo donax, Eucalyptus camaldulensis and Populus nigra were evaluated by high-throughput sequencing. A highly complex bacterial community was found, composed of ubiquitous bacteria, with the highest representation by the Actinobacteria, Proteobacteria, Bacteroidetes and Firmicutes phyla. The abundances of the major and minor taxa retrieved during the process were determined by the selective pressure produced by the lignocellulosic plant species and degradation conditions. Moreover, cellulolytic bacteria were isolated using differential substrates and screened for cellulase, cellobiase, xylanase, pectinase and ligninase activities. Forty strains that showed multienzymatic activity were selected and identified. The highest endo-cellulase activity was seen in Promicromonospora sukumoe CE86 and Isoptericola variabilis CA84, which were able to degrade cellulose, cellobiose and xylan. Sixty-two percent of bacterial strains tested exhibited high extracellular endo-1,4-ß-glucanase activity in liquid media. These approaches show that the microbiota of lignocellulosic biomasses can be considered an important source of bacterial strains to upgrade the feasibility of lignocellulose conversion for the ‘greener' technology of second-generation biofuels. PMID:25641069

  7. Design study of double-layer beam trajectory accelerator based on the Rhodotron structure

    NASA Astrophysics Data System (ADS)

    Jabbari, Iraj; Poursaleh, Ali Mohammad; Khalafi, Hossein

    2016-08-01

    In this paper, the conceptual design of a new structure of industrial electron accelerator based on the Rhodotron accelerator is presented and its properties are compared with those of Rhodotron-TT200 accelerator. The main goal of this study was to reduce the power of RF system of accelerator at the same output electron beam energy. The main difference between the new accelerator structure with the Rhodotron accelerator is the length of the coaxial cavity that is equal to the wavelength at the resonant frequency. Also two sets of bending magnets were used around the acceleration cavity in two layers. In the new structure, the beam crosses several times in the coaxial cavity by the bending magnets around the cavity at the first layer and then is transferred to the second layer using the central bending magnet. The acceleration process in the second layer is similar to the first layer. Hence, the energy of the electron beam will be doubled. The electrical power consumption of the RF system and magnet system were calculated and simulated for the new accelerator structure and TT200. Comparing the calculated and simulated results of the TT200 with those of experimental results revealed good agreement. The results showed that the overall electrical power consumption of the new accelerator structure was less than that of the TT200 at the same energy and power of the electron beam. As such, the electrical efficiency of the new structure was improved.

  8. Radioactive microsphere study of cerebral blood flow under acceleration. Technical report

    SciTech Connect

    Greenlees, K.J.; Yoder, J.E.; Toth, D.M.; Oloff, C.M.; Karl, A.

    1980-11-01

    A study using radioactive microspheres for the investigation of cerebral blood flow during acceleration is described. Details of a technique for the blunt dissection of cerebral tissues are included. Results of flow studies at 3 and 5 G sub z acceleration stress indicate there is no selective regional preservation of cerebral tissue. (Author)

  9. Materials Degradation Studies for High Temperature Steam Electrolysis Systems

    SciTech Connect

    Paul Demkowicz; Pavel Medvedev; Kevin DeWall; Paul Lessing

    2007-06-01

    Experiments are currently in progress to assess the high temperature degradation behavior of materials in solid oxide electrolysis systems. This research includes the investigation of various electrolysis cell components and balance of plant materials under both anodic and cathodic gas atmospheres at temperatures up to 850°C. Current results include corrosion data for a high temperature nickel alloy used for the air-side flow field in electrolysis cells and a commercial ferritic stainless steel used as the metallic interconnect. Three different corrosion inhibiting coatings were also tested on the steel material. The samples were tested at 850ºC for 500 h in both air and H2O/H2 atmospheres. The results of this research will be used to identify degradation mechanisms and demonstrate the suitability of candidate materials for long-term operation in electrolysis cells.

  10. Sonochemical degradation of ethylbenzene in aqueous solution: a product study.

    PubMed

    De Visscher, A; Van Langenhove, H; Van Eenoo, P

    1997-04-01

    The degradation of ethylbenzene in aqueous solution by 520 kHz ultrasound was investigated. The products formed were analysed using solid phase microextraction (SPME), a sampling technique that allows convenient GC-MS and GC-FID analysis in the micromolar range. A broad range of monosubstituted monocyclic and dicyclic aromatic hydrocarbons was found as well as some oxygenated products. The results clearly indicate that pyrolysis is an important pathway of ethylbenzene degradation. The side chain is dehydrogenated, forming styrene, or cleaved. The radicals formed upon cleavage are subsequently added to the double bond of the styrene side chain or recombined. This mechanism explains the formation of most of the products. Formation and breakdown of the reaction products follow first-order kinetics in spite of the fact that the selectivity of the reactions depends on the initial ethylbenzene concentration considerably. Changes in the temperature and the pressure of cavitation are expected to cause this dependence. PMID:11237033

  11. [Study of degradation of flavonols in the mutants of poppy (Papaver somniferum L.)].

    PubMed

    Rat'kin, A V; Evdokimova, L I; Zhanaeva, T A

    2003-01-01

    We studied flavonol-degrading activity of cell-free extracts from petals of the flower color and structure mutants. The relationship between degradation of flavonols (kaempferol, quercetin, and myricetin) and biosynthesis of anthocyanins has been revealed. The highest flavonol-degrading activity has been revealed in white flower mutants towards all substrates, particularly, quercetin. The mutations inhibiting synthesis of an anthocyanin pelargonidin provide for synthesis of various quantities of cyanidin in the petals. The flavonol-degrading activity considerably increases with the content of cyanidin. A similar relationship has been revealed in the mutants synthesizing both cyanidin and pelargonidin. The plants accumulating considerable quantities of pelargonidin in their petals have accordingly higher flavonol-degrading activity and predominantly hydrolyze kaempferol. The plants forming additional pods in their flower (pistillody) have higher flavonol-degrading activity as compared to the anther-in-petal and doubleness mutants.

  12. Microcalorimetric study of cellulose degradation by Cellulomonas uda ATCC 21399

    SciTech Connect

    Dermoun, Z.; Belaich, J.P.

    1985-07-01

    A newly designed batch calorimeter was used to investigate the degradability of some celluloses having varying degrees of crystallinity. The PTC of an aerobic culture of Cellulomonas uda ATCC 21399 obtained revealed a diauxic growth which is attributed to the presence of hemicellulose contaminating Avicel and MN300 cellulose. The microcrystalline celluloses used were not completely utilized, whereas amorphous cellulose was easily metabolized, indicating that under the growth conditions used here, the physical structure of cellulose strongly influenced its microbial degradability. An equivalent growth yield of ca. 0.44 g/g was found with all the substrates used. The heat evolved by metabolism of one g cellulose was - 5.86 kJ/g, a value similar to that obtained with glucose culture. The growth rate was the only variable parameter. The data obtained showed as expected that the hydrolysis product of cellulose was consumed in the same way as that of glucose and that the only limiting factor to the biodegradability of cellulose was the breakdown of the polymeric substrate. It is concluded that data obtained with glucose metabolism can be used to evaluate the extent of cellulose degradation.

  13. Hydroxide Degradation Pathways for Substituted Trimethylammonium Cations: A DFT Study

    SciTech Connect

    Long, H.; Kim, K.; Pivovar, B. S.

    2012-05-03

    Substituted trimethylammonium cations serve as small molecule analogues for tetherable cations in anion exchange membranes. In turn, these membranes serve as the basis for alkaline membrane fuel cells by allowing facile conduction of hydroxide. As these cations are susceptible to hydroxide attack, they degrade over time and greatly limit the lifetime of the fuel cell. In this research, we performed density functional theory calculations to investigate the degradation pathways of substituted trimethylammonium cations to probe the relative durability of cation tethering strategies in alkyl and aromatic tethers. Our results show that significant changes in calculated energy barriers occur when substitution groups change. Specifically, we have found that, when available, the Hofmann elimination pathway is the most vulnerable pathway for degradation; however, this barrier is also found to depend on the carbon chain length and number of hydrogens susceptible to Hofmann elimination. S{sub N}2 barriers were also investigated for both methyl groups and substitution groups. The reported findings give important insight into potential tethering strategies for trimethylammonium cations in anion exchange membranes.

  14. Accelerated acquisition of tagged MRI for cardiac motion correction in simultaneous PET-MR: Phantom and patient studies

    SciTech Connect

    Huang, Chuan; Petibon, Yoann; Ouyang, Jinsong; El Fakhri, Georges; Reese, Timothy G.; Ahlman, Mark A.; Bluemke, David A.

    2015-02-15

    Purpose: Degradation of image quality caused by cardiac and respiratory motions hampers the diagnostic quality of cardiac PET. It has been shown that improved diagnostic accuracy of myocardial defect can be achieved by tagged MR (tMR) based PET motion correction using simultaneous PET-MR. However, one major hurdle for the adoption of tMR-based PET motion correction in the PET-MR routine is the long acquisition time needed for the collection of fully sampled tMR data. In this work, the authors propose an accelerated tMR acquisition strategy using parallel imaging and/or compressed sensing and assess the impact on the tMR-based motion corrected PET using phantom and patient data. Methods: Fully sampled tMR data were acquired simultaneously with PET list-mode data on two simultaneous PET-MR scanners for a cardiac phantom and a patient. Parallel imaging and compressed sensing were retrospectively performed by GRAPPA and kt-FOCUSS algorithms with various acceleration factors. Motion fields were estimated using nonrigid B-spline image registration from both the accelerated and fully sampled tMR images. The motion fields were incorporated into a motion corrected ordered subset expectation maximization reconstruction algorithm with motion-dependent attenuation correction. Results: Although tMR acceleration introduced image artifacts into the tMR images for both phantom and patient data, motion corrected PET images yielded similar image quality as those obtained using the fully sampled tMR images for low to moderate acceleration factors (<4). Quantitative analysis of myocardial defect contrast over ten independent noise realizations showed similar results. It was further observed that although the image quality of the motion corrected PET images deteriorates for high acceleration factors, the images were still superior to the images reconstructed without motion correction. Conclusions: Accelerated tMR images obtained with more than 4 times acceleration can still provide

  15. Accelerated acquisition of tagged MRI for cardiac motion correction in simultaneous PET-MR: Phantom and patient studies

    PubMed Central

    Huang, Chuan; Petibon, Yoann; Ouyang, Jinsong; Reese, Timothy G.; Ahlman, Mark A.; Bluemke, David A.; El Fakhri, Georges

    2015-01-01

    Purpose: Degradation of image quality caused by cardiac and respiratory motions hampers the diagnostic quality of cardiac PET. It has been shown that improved diagnostic accuracy of myocardial defect can be achieved by tagged MR (tMR) based PET motion correction using simultaneous PET-MR. However, one major hurdle for the adoption of tMR-based PET motion correction in the PET-MR routine is the long acquisition time needed for the collection of fully sampled tMR data. In this work, the authors propose an accelerated tMR acquisition strategy using parallel imaging and/or compressed sensing and assess the impact on the tMR-based motion corrected PET using phantom and patient data. Methods: Fully sampled tMR data were acquired simultaneously with PET list-mode data on two simultaneous PET-MR scanners for a cardiac phantom and a patient. Parallel imaging and compressed sensing were retrospectively performed by GRAPPA and kt-FOCUSS algorithms with various acceleration factors. Motion fields were estimated using nonrigid B-spline image registration from both the accelerated and fully sampled tMR images. The motion fields were incorporated into a motion corrected ordered subset expectation maximization reconstruction algorithm with motion-dependent attenuation correction. Results: Although tMR acceleration introduced image artifacts into the tMR images for both phantom and patient data, motion corrected PET images yielded similar image quality as those obtained using the fully sampled tMR images for low to moderate acceleration factors (<4). Quantitative analysis of myocardial defect contrast over ten independent noise realizations showed similar results. It was further observed that although the image quality of the motion corrected PET images deteriorates for high acceleration factors, the images were still superior to the images reconstructed without motion correction. Conclusions: Accelerated tMR images obtained with more than 4 times acceleration can still provide

  16. Physiological Effects of Acceleration Observed During a Centrifuge Study of Pilot Performance

    NASA Technical Reports Server (NTRS)

    Smedal, Harald A.; Creer, Brent Y.; Wingrove, Rodney C.

    1960-01-01

    An investigation was conducted by the National Aeronautics and Space Administration, Ames Research Center, and the Naval Air Development Center, Aviation Medical Acceleration Laboratory, to study the effects of acceleration on pilot performance and to obtain some meaningful data for use in establishing tolerance to acceleration levels. The flight simulator used in the study was the Johnsville centrifuge operated as a closed loop system. The pilot was required to perform a control task in various sustained acceleration fields typical of those that Might be encountered by a pilot flying an entry vehicle in which he is seated in a forward-facing position. A special restraint system was developed and designed to increase the pilot's tolerance to these accelerations. The results of this study demonstrated that a well-trained subject, such as a test pilot, can adequately carry out a control task during moderately high accelerations for prolonged periods of time. The maximum levels of acceleration tolerated were approximately 6 times that of gravity for approximately 6 minutes, and varied slightly with the acceleration direction. The tolerance runs were in each case terminated by the subject. In all but two instances, the cause was extreme fatigue. On two occasions the subject terminated the run when he "grayed out." Although there were subjective and objective findings involving the visual and cardiovascular systems, the respiratory system yielded the more critical limiting factors. It would appear that these limiting factors were less severe during the "eyeballs-out" accelerations when compared with the "eyeballs-in" accelerations. These findings are explained on the basis of the influence that the inertial forces of acceleration have on the mechanics of respiration. A condensed version of this report was presented at the Annual Meeting of the Aerospace Medical Association, Miami Beach, May 5-11, 1960, in a paper entitled "Ability of Pilots to Perform a Control Task in

  17. A tracking code for injection and acceleration studies in synchrotrons

    SciTech Connect

    Lessner, E.; Symon, K. |

    1996-11-01

    CAPTURE-SPC is a Monte-Carlo-based tracking program that simulates the injection and acceleration processes in proton synchrotrons. The time evolution of a distribution of charged particles is implemented by a symplectic, second-order-accurate integration algorithm. The recurrence relations follow a time-stepping leap--frog method. The time-step can be varied optionally to reduce computer time. Space-charge forces are calculated by binning the phase-projected particle distribution. The statistical fluctuations introduced by the binning process are reduced by presmoothing the data by the cloud-in-cell method and by filtering. Both the bin size and amount of filtering can be varied during the acceleration cycle so that the bunch fine structure is retained while the short wavelength noise is attenuated. The initial coordinates of each macro particle together with its time of injection are retained throughout the calculations. This information is useful in determining low-loss injection schemes.

  18. Transverse effects in plasma wakefield acceleration at FACET - Simulation studies

    SciTech Connect

    Adli, E.; Hogan, M.; Frederico, J.; Litos, M. D.; An, W.; Mori, W.

    2012-12-21

    We investigate transverse effects in the plasma-wakefield acceleration experiments planned and ongoing at FACET. We use PIC simulation tools, mainly QuickPIC, to simulate the interaction of the drive electron beam and the plasma. In FACET a number of beam dynamics knobs, including dispersion and bunch length knobs, can be used to vary the beam transverse characteristics in the plasma. We present simulation results and the status of the FACET experimental searches.

  19. In Situ Fourier transform infrared spectroscopic study of the thermal degradation of isotactic poly(propylene).

    PubMed

    He, Peng; Xiao, Yan; Zhang, Puming; Zhu, Na; Zhu, Xinyuan; Yan, Deyue

    2005-01-01

    The conformational change of isotactic poly(propylene) (iPP) during the thermal degradation process has been carefully studied by in situ Fourier transform infrared (FT-IR) spectroscopy. This new method of studying thermal degradation of iPP not only shows the conventional kinetic parameter information of thermal degradation such as the degradation activation energy DeltaE and the degradation factor n, which are in accord with the results of traditional thermogravimetry experiments, but also indicates that many significant molecular structure changes occur during the thermal degradation process that come from some characteristic absorption band changes of in situ FT-IR. A multivariate approach, principal components analysis (PCA), is applied to the analysis of infrared (IR) data, and the results further confirm the multi-step processes of the thermal degradation of iPP. Above all, this is a new application to polymer thermal degradation by in situ FT-IR that connects the intermediate conformational change with final results during thermal degradation.

  20. Analytical and Experimental Studies of the Degradation in Hydrogenated Amorphous Silicon Solar Cells and Materials.

    NASA Astrophysics Data System (ADS)

    Yeung, Ping Fai

    1995-01-01

    An improved understanding of a-Si:H pin solar cells stability was obtained by studying light induced degradation in a-Si:H films and in devices. The current -voltage characteristics and the quantum efficiencies of a-Si:H pin solar cells were measured as a function of intrinsic layer thickness, bias light intensity and degradation condition. Photoconductivity measurements on device quality intrinsic a-Si:H thin film materials showed that the majority carrier (electron) mutau product degraded from 3times 10^{-7}rm cm ^2/V to 2times 10^{ -7}rm cm^2/V after 6 minutes of 50-Suns light illumination. Using a dual beam technique with steady white light and modulated monochromatic light, a degradation profile was detected in the degraded materials. These results suggest that inhomogeneous degradation may be important to understanding the stability of a-Si:H pin solar cells. An analytical model was developed for degradation in a-Si:H pin solar cells based on inhomogeneous degradation, which was used to explain the 'blue-dip' effect observed in the quantum efficiencies of degraded cells. A new method was developed to investigate the minority carrier (hole) diffusion length in device quality a-Si:H films as a function of degradation. This method uses the Schottky barrier structure to establish a depletion region, which can be controlled by the applied voltage and the bias light intensity. Modulated blue light is used to generate electron hole pairs near the ohmic contacts, and the holes diffuse across the neutral region to be collected. The modulated current is related to the diffusion length of the holes due to this current limiting hole transport. Comparing the results of this new technique to that of the Photocarrier Grating method, the electron drift mobility was found to degrade from rm 2.5cm^2/Vs to rm 0.15cm^2/Vs after 6 minutes of 50-Suns degradation.

  1. Study on enhanced degradation of atrazine by ozonation in the presence of hydroxylamine.

    PubMed

    Yang, Jingxin; Li, Ji; Dong, Wenyi; Ma, Jun; Cao, Jie; Li, Tingting; Li, Jiayin; Gu, Jia; Liu, Pingxin

    2016-10-01

    Degradation of atrazine (ATZ) by ozonation in the presence of hydroxylamine (HA) was experimentally investigated in this study. The results showed approximately 80% of ATZ was degraded by ozonation in the presence of HA, while only 20% was degraded by ozonation alone. The obvious inhibition of the ATZ degradation by tert-butanol suggested the enhanced ATZ degradation by ozone/HA was primarily attributed to OH. The OH yield was determined to be 25.8%. Additionally, the optimum HA dosage for the ATZ degradation was 4μM, when the ozone dosage was 20μM. The effects of pH, bicarbonate and temperature on ATZ degradation by ozone/HA were investigated in details. Most importantly, the enhanced ATZ degradation by ozonation in the presence of HA was still observed in real water especially at acidic pHs. Furthermore, the potential mechanism of OH formation during the reaction of ozone with HA was proposed herein. Nine products were identified by UPLC/Q-TOF-MS system. The ATZ degradation involved dealkylation, dechlorination-hydroxylation and olefination. The evolutions of the concentrations of three available transformation products including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine in ozone/HA were evaluated and compared with that in ozonation alone.

  2. Study on enhanced degradation of atrazine by ozonation in the presence of hydroxylamine.

    PubMed

    Yang, Jingxin; Li, Ji; Dong, Wenyi; Ma, Jun; Cao, Jie; Li, Tingting; Li, Jiayin; Gu, Jia; Liu, Pingxin

    2016-10-01

    Degradation of atrazine (ATZ) by ozonation in the presence of hydroxylamine (HA) was experimentally investigated in this study. The results showed approximately 80% of ATZ was degraded by ozonation in the presence of HA, while only 20% was degraded by ozonation alone. The obvious inhibition of the ATZ degradation by tert-butanol suggested the enhanced ATZ degradation by ozone/HA was primarily attributed to OH. The OH yield was determined to be 25.8%. Additionally, the optimum HA dosage for the ATZ degradation was 4μM, when the ozone dosage was 20μM. The effects of pH, bicarbonate and temperature on ATZ degradation by ozone/HA were investigated in details. Most importantly, the enhanced ATZ degradation by ozonation in the presence of HA was still observed in real water especially at acidic pHs. Furthermore, the potential mechanism of OH formation during the reaction of ozone with HA was proposed herein. Nine products were identified by UPLC/Q-TOF-MS system. The ATZ degradation involved dealkylation, dechlorination-hydroxylation and olefination. The evolutions of the concentrations of three available transformation products including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine in ozone/HA were evaluated and compared with that in ozonation alone. PMID:27232722

  3. Relationship between acceleration of hydroxyl radical initiation and increase of multiple-ultrasonic field amount in the process of ultrasound catalytic ozonation for degradation of nitrobenzene in aqueous solution.

    PubMed

    Zhao, Lei; Ma, Weichao; Ma, Jun; Wen, Gang; Liu, Qianliang

    2015-01-01

    The synergetic effect between ozone and ultrasound can enhance the degradation of nitrobenzene and removal efficiency of TOC in aqueous solution, and the degradation of nitrobenzene follows the mechanism of hydroxyl radical (OH) oxidation. Under the same total ultrasonic power input condition, the degradation rate of nitrobenzene (kNB), the volumetric mass transfer coefficient of ozone (kLa), and the initiation rate of OH (kOH) increases with introduction of additional ultrasonic field (1-4) in the process of ozone/ultrasound. The increasing amount of ultrasonic fields accelerates the decomposition of ozone, leading to the rapid appearance of the maximum equilibrium value and the decrease in the accumulation concentration of ozone in aqueous solution with the increasing reaction time. The increase in mass transfer of gaseous ozone dissolved into aqueous solution and the acceleration in the decomposition of ozone in aqueous solution synchronously contribute to the increase of kLa. The investigation of mechanism confirms that the increasing amount of ultrasonic fields yields the increase in cavitation activity that improves the mass transfer and decomposition of ozone, resulting in acceleration of OH initiation, which determines the degradation of nitrobenzene in aqueous solution.

  4. Novel oxygen atom source for material degradation studies

    NASA Technical Reports Server (NTRS)

    Krech, R. H.; Caledonia, G. E.

    1988-01-01

    Physical Sciences Inc. (PSI) has developed a high flux pulsed source of energetic (8 km/s) atomic oxygen to bombard specimens in experiments on the aging and degradation of materials in a low earth orbit environment. The proof-of-concept of the PSI approach was demonstrated in a Phase 1 effort. In Phase 2 a large O-atom testing device (FAST-2) has been developed and characterized. Quantitative erosion testing of materials, components, and even small assemblies (such as solar cell arrays) can be performed with this source to determine which materials and/or components are most vulnerable to atomic oxygen degradation. The source is conservatively rated to irradiate a 100 sq cm area sample at greater than 10(exp 17) atoms/s, at a 10 Hz pulse rate. Samples can be exposed to an atomic oxygen fluence equivalent to the on-orbit ram direction exposure levels incident on Shuttle surfaces at 250 km during a week-long mission in a few hours.

  5. A study of light ion accelerators for cancer treatment

    SciTech Connect

    Prelec, K.

    1997-07-01

    This review addresses several issues, such as possible advantages of light ion therapy compared to protons and conventional radiation, the complexity of such a system and its possible adaptation to a hospital environment, and the question of cost-effectiveness compared to other modalities for cancer treatment or to other life saving procedures. Characteristics and effects of different types of radiation on cells and organisms will be briefly described; this will include conventional radiation, protons and light ions. The status of proton and light ion cancer therapy will then be described, with more emphasis on the latter; on the basis of existing experience the criteria for the use of light ions will be listed and areas of possible medical applications suggested. Requirements and parameters of ion beams for cancer treatment will then be defined, including ion species, energy and intensity, as well as parameters of the beam when delivered to the target (scanning, time structure, energy spread). Possible accelerator designs for light ions will be considered, including linear accelerators, cyclotrons and synchrotrons and their basic features given; this will be followed by a review of existing and planned facilities for light ions. On the basis of these considerations a tentative design for a dedicated light ion facility will be suggested, a facility that would be hospital based, satisfying the clinical requirements, simple to operate and reliable, concluding with its cost-effectiveness in comparison with other modalities for treatment of cancer.

  6. Thermal Degradation Studies of A Polyurethane Propellant Binder

    SciTech Connect

    Assink, R.A.; Celina, M.; Gillen, K.T.; Graham, A.C.; Minier, L.M.

    1999-06-12

    The thermal oxidative aging of a crosslinked hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) based polyurethane rubber, used as a polymeric binder in solid propellant grain, was investigated at temperatures from 25 C to 125 C. The changes in tensile elongation, polymer network properties and chain dynamics, mechanical hardening and density were determined with a range of techniques including modulus profiling, solvent swelling, NMR relaxation and O{sub 2} permeability measurements. We critically evaluated the Arrhenius methodology that is commonly used with a linear extrapolation of high temperature aging data using extensive data superposition and highly sensitive oxygen consumption experiments. The effects of other constituents in the propellant formulation on aging were also investigated. We conclude that crosslinking is the dominant process at higher temperatures and that the degradation involves only limited hardening in the bulk of the material. Significant curvature in the Arrhenius diagram of the oxidation rates was observed. This is similar to results for other rubber materials.

  7. FTIR study of degradation products of aliphatic polyesters carbon fibres composites

    NASA Astrophysics Data System (ADS)

    Pamuła, Elżbieta; Błażewicz, Marta; Paluszkiewicz, Czesława; Dobrzyński, Piotr

    2001-09-01

    Biodegradable polymer composites based on polylactides and polyglycolides constitute a group of materials characterised by good biocompatibility. They are considered in tissue engineering as scaffolds for cells proliferation and controlled tissue regeneration. Two types of biodegradable polymers possessing different chemical structure, molecular weights and crystallinity degrees and two composite materials made up of them and carbon fibres were analysed in this study. The samples were incubated in aqueous media for 8 weeks and analysed by means of Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR). Infrared spectroscopy enabled identification of degradation products and estimation of the influence of carbon fibres on hydrolytic degradation of analysed polymers. Analysis of the infrared spectra showed that hydrolytic degradation process depends on chemical structure, molecular weight and crystallinity of polymers. Catalytic effect of carbon fibres at the initial stage of polymer degradation was observed. Further degradation is dependent on the properties of polymer.

  8. Dating Studies of Elephant Tusks Using Accelerator Mass Spectrometry

    SciTech Connect

    Sideras-Haddad, E; Brown, T A

    2002-10-03

    A new method for determining the year of birth, the year of death, and hence, the age at death, of post-bomb and recently deceased elephants has been developed. The technique is based on Accelerator Mass Spectrometry radiocarbon analyses of small-sized samples extracted from along the length of a ge-line of an elephant tusk. The measured radiocarbon concentrations in the samples from a tusk can be compared to the {sup 14}C atmospheric bomb-pulse curve to derive the growth years of the initial and final samples from the tusk. Initial data from the application of this method to two tusks will be presented. Potentially, the method may play a significant role in wildlife management practices of African national parks. Additionally, the method may contribute to the underpinnings of efforts to define new international trade regulations, which could, in effect, decrease poaching and the killing of very young animals.

  9. Experimental study of a shock accelerated thin gas layer

    SciTech Connect

    Jacobs, J.W.; Jenkins, D.G.; Klein, D.L.; Benjamin, R.F.

    1993-08-01

    Planar laser-induced fluorescence imaging is utilized in shock-tube experiments to visualize the development of a shock-accelerated thin gas layer. The Richtmyer-Meshkov instability of both sides of the heavy gas layer causes perturbations initially imposed on the two interfaces to develop into one of three distinct flow patterns. Two of the patterns exhibit vortex pairs which travel either upstream or downstream in the shock tube, while the third is a sinuous pattern that shows no vortex development until late in its evolution. The development of the observed patterns as well as the growth in the layer thickness is modeled by considering the dynamics of vorticity deposited in the layer by the shock interaction process. This model yields an expression for the layer growth which is in good agreement with measurements.

  10. Forced Degradation Studies of Ivabradine and In Silico Toxicology Predictions for Its New Designated Impurities.

    PubMed

    Pikul, Piotr; Jamrógiewicz, Marzena; Nowakowska, Joanna; Hewelt-Belka, Weronika; Ciura, Krzesimir

    2016-01-01

    All activities should aim to eliminate genotoxic impurities and/or protect the API against degradation. There is a necessity to monitor impurities from all classification groups, hence ivabradine forced degradation studies were performed. Ivabradine was proved to be quite durable active substance, but still new and with insufficient stability data. Increased temperature, acid, base, oxidation reagents and light were found to cause its degradation. Degradation products were determined with the usage of HPLC equipped with Q-TOF-MS detector. Calculations of pharmacological and toxicological properties were performed for six identified degradation products. Target prediction algorithm was applied on the basis of Hyperpolarization-activated cyclic nucleotide-gated cation channels, as well as more general parameters like logP and aqueous solubility. Ames test and five cytochromes activities were calculated for toxicity assessment for selected degradation products. Pharmacological activity of photodegradation product (UV4), which is known as active metabolite, was qualified and identified. Two other degradation compounds (Ox1 and N1), which were formed during degradation process, were found to be pharmacologically active. PMID:27199759

  11. Forced Degradation Studies of Ivabradine and In Silico Toxicology Predictions for Its New Designated Impurities

    PubMed Central

    Pikul, Piotr; Jamrógiewicz, Marzena; Nowakowska, Joanna; Hewelt-Belka, Weronika; Ciura, Krzesimir

    2016-01-01

    All activities should aim to eliminate genotoxic impurities and/or protect the API against degradation. There is a necessity to monitor impurities from all classification groups, hence ivabradine forced degradation studies were performed. Ivabradine was proved to be quite durable active substance, but still new and with insufficient stability data. Increased temperature, acid, base, oxidation reagents and light were found to cause its degradation. Degradation products were determined with the usage of HPLC equipped with Q-TOF-MS detector. Calculations of pharmacological and toxicological properties were performed for six identified degradation products. Target prediction algorithm was applied on the basis of Hyperpolarization-activated cyclic nucleotide-gated cation channels, as well as more general parameters like logP and aqueous solubility. Ames test and five cytochromes activities were calculated for toxicity assessment for selected degradation products. Pharmacological activity of photodegradation product (UV4), which is known as active metabolite, was qualified and identified. Two other degradation compounds (Ox1 and N1), which were formed during degradation process, were found to be pharmacologically active. PMID:27199759

  12. Anaerobic degradation of naphthalene in a fluvial aquifer: a radiotracer study.

    PubMed

    Bianchin, Mario; Smith, Leslie; Barker, James F; Beckie, Roger

    2006-03-20

    A radiotracer study was conducted in a creosote-contaminated aquifer beneath the Fraser River, British Columbia Canada to investigate the in situ degradation of naphthalene. The groundwater is anaerobic, with abundant methane, ferrous iron and carbon dioxide. This study followed earlier work at the site where the contaminant distribution could only be explained by invoking a mass loss through degradation, even though extensive field and laboratory microcosm studies closer to the source zone onshore could not confirm degradation. Accordingly, 14C-naphthalene was injected into the aquifer offshore, further from the source zone where modeling suggested degradation was occurring. During the 230-day monitoring period, 14CO2 was detected, confirming the degradation of the radio-labeled naphthalene tracer. A zero-order degradation rate of naphthalene of 5 microg/L-day was estimated based on the decrease in 14C-naphthalene concentration with time. While the degradation pathway could not be determined from the radiotracer study alone, the geochemistry of the site suggests that either iron reduction or methanogenesis is the terminal electron accepting processes responsible for naphthalene oxidation. PMID:16487624

  13. [Study on natural photo-oxidation degradation of polypropylene nanocomposites by infrared microscopy].

    PubMed

    Li, Ji-fang; Yang, Rui; Yu, Jian

    2008-08-01

    Polymer nanocomposites have attracted great attention because of the demand for polymer materials with high performance and high functionality at the same time. Nano CaCO3 and SiO2 can be used to improve the rigidity of polypropylene (PP), which is quite importance for biaxial orientation PP film. However, the effect of these nano fillers on natural photo-oxidation degradation of PP has not been studied. In the present paper, the natural photo-oxidation profiles along the depth of PP and PP nanocomposites bars were studied with infrared microscope (IM) as well as polarizing lighu microscope (PLM) and scanning electron microscope (SEM). The results indicated that nano CaCO3 and SiO2, especially the latter, accelerated the oxidation rate of PP significantly, with more and deeper surface cracks. Larger amount of nano filler gave rise to greater oxidation degradation. The existence of nano CaCO3 and SiO2 helped to diminish the spherulite and broaden the transition region from amorphous to crystal The oxidation development along the depth in PP nanocomposites depended on the diffusion rate of oxygen and underwent two stages. In the first stage, the oxidation degree increased with time because of the low density in the transition region. In the layer under this region, the oxidation is difficult to occur owing to the high density of crystals and oxygen starvation. Therefore, the oxidation depth profiles decreased to near zero at nearly the same depth--about 200 microm from the exposed surface, corresponding to the transition region in PLM observation, namely surface oxidation layer. The high degree of oxidation in the surface layer gave rise to crack formation, and these surface cracks helped further oxidation in PP nanocomposites. In the second stage, the interconnection of surface cracks resulted in the fracture of the seriously oxidized surface oxidation layer. Consequently, the oxidation of the subsurface layer began and the depth profile developed to deeper place

  14. Studying astrophysical particle acceleration mechanisms with colliding magnetized laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Fox, W.; Deng, W.; Bhattacharjee, A.; Fiksel, G.; Nilson, P.; Haberberger, D.; Chang, P.-Y.; Barnak, D.

    2015-11-01

    Significant particle energization is observed to occur in many astrophysical environments, and in the standard models this acceleration occurs as a part of the energy conversion processes associated with collisionless shocks or magnetic reconnection. A recent generation of laboratory experiments conducted using magnetized laser-produced plasmas has opened opportunities to study these particle acceleration processes in the laboratory. Ablated plasma plumes are externally magnetized using an externally-applied magnetic field in combination with a low-density background plasma. Colliding unmagnetized plasmas demonstrated ion-driven Weibel instability while colliding magnetized plasmas drive magnetic reconnection. Both magnetized and unmagnetized colliding plasma are modeled with electromagnetic particle-in-cell simulations which provide an end-to-end model of the experiments. Using particle-in-cell simulations, we provide predictions of particle acceleration driven by reconnection, resulting from both direct x-line acceleration and Fermi-like acceleration at contracting magnetic fields lines near magnetic islands.

  15. Accelerated Biodegradation of Veterinary Antibiotics in Agricultural Soil following Long-Term Exposure, and Isolation of a Sulfamethazine-degrading sp.

    PubMed

    Topp, Edward; Chapman, Ralph; Devers-Lamrani, Marion; Hartmann, Alain; Marti, Romain; Martin-Laurent, Fabrice; Sabourin, Lyne; Scott, Andrew; Sumarah, Mark

    2013-01-01

    The World Health Organization has identified antibiotic resistance as one of the top three threats to global health. There is concern that the use of antibiotics as growth promoting agents in livestock production contributes to the increasingly problematic development of antibiotic resistance. Many antibiotics are excreted at high rates, and the land application of animal manures represents a significant source of environmental exposure to these agents. To evaluate the long-term effects of antibiotic exposure on soil microbial populations, a series of field plots were established in 1999 that have since received annual applications of a mixture of sulfamethazine (SMZ), tylosin (TYL), and chlortetracycline (CTC). During the first 6 yr (1999-2004) soils were treated at concentrations of 0, 0.01 0.1, and 1.0 mg kg soil, in subsequent years at concentrations of 0, 0.1, 1.0, and 10 mg kg soil. The lower end of this concentration range is within that which would result from an annual application of manure from medicated swine. Following ten annual applications, the fate of the drugs in the soil was evaluated. Residues of SMZ and TYL, but not CTC were removed much more rapidly in soil with a history of exposure to 10 mg/kg drugs than in untreated control soil. Residues of C-SMZ were rapidly and thoroughly mineralized to CO in the historically treated soils, but not in the untreated soil. A SMZ-degrading sp. was isolated from the treated soil. Overall, these results indicate that soil bacteria adapt to long-term exposure to some veterinary antibiotics resulting in sharply reduced persistence. Accelerated biodegradation of antibiotics in matrices exposed to agricultural, wastewater, or pharmaceutical manufacturing effluents would attenuate environmental exposure to antibiotics, and merits investigation in the context of assessing potential risks of antibiotic resistance development in environmental matrices. PMID:23673752

  16. Soybean peroxidase-mediated degradation of an azo dye– a detailed mechanistic study

    PubMed Central

    2013-01-01

    Background Peroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published. Results In the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process. Conclusions Detailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids. PMID:24308857

  17. Supernova Acceleration Probe: Studying Dark Energy with Type Ia Supernovae

    SciTech Connect

    Albert, J.; Aldering, G.; Allam, S.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Aumeunier, M.; Bailey, S.; Baltay, C.; Barrelet, E.; Basa, S.; Bebek, C.; Bergstom, L.; Bernstein, G.; Bester, M.; Besuner, B.; Bigelow, B.; Blandford, R.; Bohlin, R.; Bonissent, A.; /Caltech /LBL, Berkeley /Fermilab /SLAC /Stockholm U. /Paris, IN2P3 /Marseille, CPPM /Marseille, Lab. Astrophys. /Yale U. /Pennsylvania U. /UC, Berkeley /Michigan U. /Baltimore, Space Telescope Sci. /Indiana U. /Caltech, JPL /Australian Natl. U., Canberra /American Astron. Society /Chicago U. /Cambridge U. /Saclay /Lyon, IPN

    2005-08-08

    The Supernova Acceleration Probe (SNAP) will use Type Ia supernovae (SNe Ia) as distance indicators to measure the effect of dark energy on the expansion history of the Universe. (SNAP's weak-lensing program is described in a separate White Paper.) The experiment exploits supernova distance measurements up to their fundamental systematic limit; strict requirements on the monitoring of each supernova's properties leads to the need for a space-based mission. Results from pre-SNAP experiments, which characterize fundamental SN Ia properties, will be used to optimize the SNAP observing strategy to yield data, which minimize both systematic and statistical uncertainties. With early R&D funding, we have achieved technological readiness and the collaboration is poised to begin construction. Pre-JDEM AO R&D support will further reduce technical and cost risk. Specific details on the SNAP mission can be found in Aldering et al. (2004, 2005). The primary goal of the SNAP supernova program is to provide a dataset which gives tight constraints on parameters which characterize the dark-energy, e.g. w{sub 0} and w{sub a} where w(a) = w{sub 0} + w{sub a}(1-a). SNAP data can also be used to directly test and discriminate among specific dark energy models. We will do so by building the Hubble diagram of high-redshift supernovae, the same methodology used in the original discovery of the acceleration of the expansion of the Universe that established the existence of dark energy (Perlmutter et al. 1998; Garnavich et al. 1998; Riess et al. 1998; Perlmutter et al. 1999). The SNAP SN Ia program focuses on minimizing the systematic floor of the supernova method through the use of characterized supernovae that can be sorted into subsets based on subtle signatures of heterogeneity. Subsets may be defined based on host-galaxy morphology, spectral-feature strength and velocity, early-time behavior, inter alia. Independent cosmological analysis of each subset of ''like'' supernovae can be

  18. Thermal degradation reaction mechanism of xylose: A DFT study

    NASA Astrophysics Data System (ADS)

    Huang, Jinbao; He, Chao; Wu, Longqin; Tong, Hong

    2016-08-01

    The thermal degradation reaction mechanism of xylose as hemicellulose model compound was investigated by using density functional theory methods M062X with the 6-31++G(d,p) basis set. Eight possible pyrolytic reaction pathways were proposed and the standard kinetic and thermodynamic parameters in all reaction pathways were calculated at different temperatures. In reaction pathway (1), xylose is first transformed into acyclic containing-carbonyl isomer, and then the isomer further decomposes through four possible pyrolysis pathways (1-1)-(1-4). Pathways (2) and (3) depict an immediate ring-opening process through the simultaneous breaking of C-O and C-C bonds. Pathways (4)-(7) describe the pyrolysis processes of various anhydro-xyloses through a direct ring-opening process. Pathway (8) gives the evolutionary process of pyranones. The calculation results show that reaction pathways (1), (2) and (5) are the major reaction channels and reaction pathways (3), (4), and (6)-(8) are the competitive reaction channels in pyrolysis of xylose. The major products of xylose pyrolysis are low molecular products such as 2-furaldehyde, glycolaldehyde, acetaldehyde, methylglyoxal and acetone, and the main competitive products are formaldehyde, formic acid, acetic acid, CO2, CH4, acetol, pyranone, and so on.

  19. Studies on nitrile rubber degradation in zinc bromide completion fluid and its prevention by surface fluorination

    NASA Astrophysics Data System (ADS)

    Vega-Cantu, Yadira Itzel

    Poly(acrylonitrile-co-butadiene) or nitrile-butadiene rubber (NBR) is frequently used as an O-ring material in the oil extraction industry due to its excellent chemical properties and resistance to oil. However, degradation of NBR gaskets is known to occur during the well completion and oil extraction process where packers are exposed to completion fluids such as ZnBr2 brine. Under these conditions NBR exhibits accelerated chemical degradation resulting in embrittlement and cracking. Samples of NBR, poly(acrylonitrile) (PAN) and poly(butadiene) (PB) have been exposed to ZnBr2 based completion fluid, and analyzed by ATR and diffuse reflectance IR. Analysis shows the ZnBr2 based completion fluid promotes hydrolysis of the nitrile group to form amides and carboxylic groups. Analysis also shows that carbon-carbon double bonds in NBR are unaffected after short exposure to zinc bromide based completion fluid, but are quickly hydrolyzed in acidic bromide mixtures. Although fluoropolymers have excellent chemical resistance, their strength is less than nitrile rubber and replacing the usual gasket materials with fluoroelastomers is expensive. However, a fluoropolymer surface on a nitrile elastomer can provide the needed chemical resistance while retaining their strength. In this study, we have shown that this can be achieved by direct fluorination, a rather easy and inexpensive process. Samples of NBR O-rings have been fluorinated by exposure to F2 and F2/HF mixtures at various temperatures. Fluorination with F 2 produces the desired fluoropolymer layer; however, fluorination by F2/HF mixtures gave a smoother fluorinated layer at lower temperatures and shorter times. Fluorinated samples were exposed to ZnBr2 drilling fluid and solvents. Elemental analysis shows that the fluorinated layer eliminates ZnBr2 diffusion into the NBR polymeric matrix. It was also found that surface fluorination significantly retards the loss of mechanical properties such as elasticity, tensile

  20. Study of adsorption and degradation of dimethylphthalate on TiO2-based photocatalysts

    NASA Astrophysics Data System (ADS)

    Pulido Melián, E.; Henríquez-Cárdenes, E.; González Díaz, O.; Doña Rodríguez, J. M.

    2016-08-01

    This work studied the degradation and adsorption of dimethylphthalate (DMP) using various TiO2-based photocatalysts: TiO2 Aeroxide P25, Kronos vlp7000, Hombikat UV-100, Kemira 650 and a synthesized photocatalyst named SG750. As the photocatalysts with mixed anatase and rutile phases, P25 and SG750, showed greater activity than those of pure phase, an in-depth study was undertaken of these two catalysts in the adsorption and degradation of DMP. The degradation results were fitted with a high degree of correlation to the Langmuir-Hinshelwood model and those for adsorption to the Freundlich model. The Freundlich constants showed good correlation with FTIR observations of the DMP-P25 and DMP-SG750 interactions. These two photocatalysts were additionally modified by photodeposition with Pt and Au (0.5-1.5 wt%) to study the effect of these metals on degradation and mineralization kinetics.

  1. The study of two-dimensional oscillations using a smartphone acceleration sensor: example of Lissajous curves

    NASA Astrophysics Data System (ADS)

    Tuset-Sanchis, Luis; Castro-Palacio, Juan C.; Gómez-Tejedor, José A.; Manjón, Francisco J.; Monsoriu, Juan A.

    2015-08-01

    A smartphone acceleration sensor is used to study two-dimensional harmonic oscillations. The data recorded by the free android application, Accelerometer Toy, is used to determine the periods of oscillation by graphical analysis. Different patterns of the Lissajous curves resulting from the superposition of harmonic motions are illustrated for three experiments. This work introduces an example of how two-dimensional oscillations can be easily studied with a smartphone acceleration sensor.

  2. Accelerated Molecular Dynamics studies of He Bubble Growth in Tungsten

    NASA Astrophysics Data System (ADS)

    Uberuaga, Blas; Sandoval, Luis; Perez, Danny; Voter, Arthur

    2015-11-01

    Understanding how materials respond to extreme environments is critical for predicting and improving performance. In materials such as tungsten exposed to plasmas for nuclear fusion applications, novel nanoscale fuzzes, comprised of tendrils of tungsten, form as a consequence of the implantation of He into the near surface. However, the detailed mechanisms that link He bubble formation to the ultimate development of fuzz are unclear. Molecular dynamics simulations provide insight into the He implantation process, but are necessarily performed at implantation rates that are orders of magnitudes faster than experiment. Here, using accelerated molecular dynamics methods, we examine the role of He implantation rates on the physical evolution of He bubbles in tungsten. We find that, as the He rate is reduced, new types of events involving the response of the tungsten matrix to the pressure in the bubble become competitive and change the overall evolution of the bubble as well as the subsequent morphology of the tungsten surface. We have also examined how bubble growth differs at various microstructural features. These results highlight the importance of performing simulations at experimentally relevant conditions in order to correctly capture the contributions of the various significant kinetic processes and predict the overall response of the material.

  3. Target studies for accelerator-based boron neutron capture therapy

    SciTech Connect

    Powell, J.R.; Ludewig, H.; Todosow, M.; Reich, M.

    1996-03-01

    Two new concepts, NIFTI and DISCOS, are described. These concepts enable the efficient production of epithermal neutrons for BNCT (Boron Neutron Capture Therapy) medical treatment, utilizing a low current, low energy proton beam impacting on a lithium target. The NIFTI concept uses an iron layer that strongly impedes the transmission of neutrons with energies above 24 KeV. Lower energy neutrons readily pass through this iron ``filter``, which has a deep ``window`` in its scattering cross section at 24 KeV. The DISCOS concept uses a rapidly rotating, high g disc to create a series of thin ({approximately} 1 micron thickness) liquid lithium targets in the form of continuous films through which the proton beam passes. The average energy lost by a proton as it passes through a single target is small, approximately 10 KeV. Between the targets, the proton beam is reaccelerated by an applied DC electric field. The DISCOS approach enables the accelerator -- target facility to operate with a beam energy only slightly above the threshold value for neutron production -- resulting in an output beam of low-energy epithermal neutrons -- while achieving a high yield of neutrons per milliamp of proton beam current.

  4. Study of kinetics of degradation of cyclohexane carboxylic acid by acclimated activated sludge.

    PubMed

    Wang, Chunhua; Shi, Shuian; Chen, Hongyan

    2016-01-01

    Activated sludge contains complex microorganisms, which are highly effective biodegrading agents. In this study, the kinetics of biodegradation of cyclohexane carboxylic acid (CHCA) by an acclimated aerobic activated sludge were investigated. The results showed that after 180 days of acclimation, the activated sludge could steadily degrade >90% of the CHCA in 120 h. The degradation of CHCA by the acclimated activated sludge could be modeled using a first-order kinetics equation. The equations for the degradation kinetics for different initial CHCA concentrations were also obtained. The kinetics constant, kd, decreased with an increase in the CHCA concentration, indicating that, at high concentrations, CHCA had an inhibiting effect on the microorganisms in the activated sludge. The effects of pH on the degradation kinetics of CHCA were also investigated. The results showed that a pH of 10 afforded the highest degradation rate, indicating that basic conditions significantly promoted the degradation of CHCA. Moreover, it was found that the degradation efficiency for CHCA increased with an increase in temperature and concentration of dissolved oxygen under the experimental conditions.

  5. Oxidative degradation of hydrocortisone in presence of attapulgite.

    PubMed

    Cornejo, J; Hermosin, M C; White, J L; Peck, G E; Hem, S L

    1980-08-01

    Degradation of hydrocortisone in attapulgite suspensions was monitored by high-pressure liquid chromatography and UV spectrophotometry. The rate of oxidative degration of hydrocortisone was accelerated significantly in the presence of attapulgite. In addition, degradation appeared to be composed of two apparent first-order reactions rather than the single apparent first-order degradation reaction observed for hydrocortisone solutions. However, the same degradation products were obtained in both hydrocortisone solutions and attapulgite suspensions, indicating that interaction with attapulgite did not alter the degradation pathway. Kinetic and adsorption studies suggested that hydrocortisone is adsorbed weakly by attapulgite and undergoes oxidative degradation, which is catalyzed by adsorbed iron oxides or hydroxides as well as by structural ferric iron at the clay surface. Since clay minerals generally contain surface ferric iron, the potentiala for accelerating the oxidative degradation of drugs should be considered whenever clays and drugs are combined.

  6. Accelerated aging studies and environmental stability of prototype tamper tapes

    SciTech Connect

    Wright, B.W.; Wright, C.W.; Bunk, A.R.

    1995-05-01

    This report describes the results of accelerated aging experiments (weathering) conducted on prototype tamper tapes bonded to a variety of surface materials. The prototype tamper tapes were based on the patented Confirm{reg_sign} tamper-indicating technology developed and produced by 3M Company. Tamper tapes bonded to surfaces using pressure sensitive adhesive (PSA) and four rapid-set adhesives were evaluated. The configurations of the PSA-bonded tamper tapes were 1.27-cm-wide Confirm{reg_sign} 1700 windows with vinyl underlay and 2.54-cm-wide Confirm{reg_sign} 1700 windows with vinyl and polyester underlays. The configurations of the rapid-set adhesive-bonded tamper tapes were 2.54-cm-wide Confirm{reg_sign} (1700, 1500 with and without primer, and 1300) windows with vinyl underlay. Surfaces used for bonding included aluminum, steel, stainless steel, Kevlar{reg_sign}, brass, copper, fiberglass/resin with and without gel coat, polyurethane-painted steel, acrylonitrile:butadiene:styrene plastic, polyester fiberglass board, Lexan polycarbonate, and cedar wood. Weathering conditions included a QUV cabinet (ultraviolet light at 60{degrees}C, condensing humidity at 40{degrees}C), a thermal cycling cabinet (-18{degrees}C to 46{degrees}C), a Weather-O-Meter (Xenon lamp), and exposure outdoors in Daytona Beach, Florida. Environmental aging exposures lasted from 7 weeks to 5 months. After exposure, the tamper tapes were visually examined and tested for transfer resistance. Tamper tapes were also exposed to a variety of chemical liquids (including organic solvents, acids, bases, and oxidizing liquids) to determine chemical resistance and to sand to determine abrasion resistance.

  7. Analyzing insulin samples by size-exclusion chromatography: a column degradation study.

    PubMed

    Teska, Brandon M; Kumar, Amit; Carpenter, John F; Wempe, Michael F

    2015-04-01

    Investigating insulin analogs and probing their intrinsic stability at physiological temperature, we observed significant degradation in the size-exclusion chromatography (SEC) signal over a moderate number of insulin sample injections, which generated concerns about the quality of the separations. Therefore, our research goal was to identify the cause(s) for the observed signal degradation and attempt to mitigate the degradation in order to extend SEC column lifespan. In these studies, we used multiangle light scattering, nuclear magnetic resonance, and gas chromatography-mass spectrometry methods to evaluate column degradation. The results from these studies illustrate: (1) that zinc ions introduced by the insulin product produced the observed column performance issues; and (2) that including ethylenediaminetetraacetic acid, a zinc chelator, in the mobile phase helped to maintain column performance.

  8. Studies on degradation of glyphosate by several oxidative chemical processes: ozonation, photolysis and heterogeneous photocatalysis.

    PubMed

    Assalin, Marcia R; De Moraes, Sandra G; Queiroz, Sonia C N; Ferracini, Vera L; Duran, Nelson

    2010-01-01

    Several different Advanced Oxidation Processes (AOPs) including ozonation at pH 6.5 and 10, photolysis and heterogeneous photocatalysis using TiO(2) as semiconductor and dissolved oxygen as electron acceptor were applied to study the degradation of glyphosate (N-phosphonomethyl glycine) in water. The degree of glyphosate degradation, the reactions kinetic and the formation of the major metabolite, aminomethyl phosphonic acid (AMPA), were evaluated. Ozonation at pH 10 resulted in the maximum mineralization of glyphosate. It was observed that under the experimental conditions used in this study the degradation of glyphosate followed the first-order kinetics. The half-life obtained for glyphosate degradation in the O(3)/pH 10 process was 1.8 minutes.

  9. Design study of electron cyclotron resonance-ion plasma accelerator for heavy ion cancer therapy.

    PubMed

    Inoue, T; Hattori, T; Sugimoto, S; Sasai, K

    2014-02-01

    Electron Cyclotron Resonance-Ion Plasma Accelerator (ECR-IPAC) device, which theoretically can accelerate multiple charged ions to several hundred MeV with short acceleration length, has been proposed. The acceleration mechanism is based on the combination of two physical principles, plasma electron ion adiabatic ejection (PLEIADE) and Gyromagnetic Autoresonance (GYRAC). In this study, we have designed the proof of principle machine ECR-IPAC device and simulated the electromagnetic field distribution generating in the resonance cavity. ECR-IPAC device consisted of three parts, ECR ion source section, GYRAC section, and PLEIADE section. ECR ion source section and PLEIADE section were designed using several multi-turn solenoid coils and sextupole magnets, and GYRAC section was designed using 10 turns coil. The structure of ECR-IPAC device was the cylindrical shape, and the total length was 1024 mm and the maximum diameter was 580 mm. The magnetic field distribution, which maintains the stable acceleration of plasma, was generated on the acceleration center axis throughout three sections. In addition, the electric field for efficient acceleration of electrons was generated in the resonance cavity by supplying microwave of 2.45 GHz. PMID:24593537

  10. Design study of electron cyclotron resonance-ion plasma accelerator for heavy ion cancer therapy

    SciTech Connect

    Inoue, T. Sugimoto, S.; Sasai, K.; Hattori, T.

    2014-02-15

    Electron Cyclotron Resonance-Ion Plasma Accelerator (ECR-IPAC) device, which theoretically can accelerate multiple charged ions to several hundred MeV with short acceleration length, has been proposed. The acceleration mechanism is based on the combination of two physical principles, plasma electron ion adiabatic ejection (PLEIADE) and Gyromagnetic Autoresonance (GYRAC). In this study, we have designed the proof of principle machine ECR-IPAC device and simulated the electromagnetic field distribution generating in the resonance cavity. ECR-IPAC device consisted of three parts, ECR ion source section, GYRAC section, and PLEIADE section. ECR ion source section and PLEIADE section were designed using several multi-turn solenoid coils and sextupole magnets, and GYRAC section was designed using 10 turns coil. The structure of ECR-IPAC device was the cylindrical shape, and the total length was 1024 mm and the maximum diameter was 580 mm. The magnetic field distribution, which maintains the stable acceleration of plasma, was generated on the acceleration center axis throughout three sections. In addition, the electric field for efficient acceleration of electrons was generated in the resonance cavity by supplying microwave of 2.45 GHz.

  11. Microbial degradation of Paclitaxel using Citrobacter amalonaticus Rashtia isolated from pharmaceutical wastewater: kinetic and thermodynamic study.

    PubMed

    Zamani, Hojjatolah; Grakoee, Seyed Reza; Rakhshaee, Roohan

    2016-08-01

    Paclitaxel is a highly toxic anticancer agent which is used in a wide range against ovarian, breast, lung, and prostate cancers. Paclitaxel is manufactured recently in the north of Iran which may lead to the introduction of the drug into the environment via pharmaceutical wastewater. To our knowledge, Paclitaxel degradation is currently performed using physicochemical methods and biological degradation of Paclitaxel has not been reported. In this study, a Paclitaxel degrading bacterium was isolated from pharmaceutical wastewater for the first time. The bacterium was identified using biochemical and molecular assays and its Paclitaxel degradation potential was evaluated using High Performance Liquid Chromatography (HPLC). In addition, kinetic and thermodynamic study of Paclitaxel degradation at different experimental conditions was performed. A Citrobacter species named as C. amalonaticus Rashtia able to degrade and utilize Paclitaxel as the sole carbon source was isolated. The isolated strain tolerated high level concentration of Paclitaxel (0.4 mg/mL) in liquid culture media and was able to degrade spillage-level concentrations of the drug (0.01-0.1 mg/mL) with 87-93 % efficacy under aerobic condition. Kinetic and thermodynamic study at different pHs (4.0, 7.0 and 10.0) and temperatures (285, 295 and 310 K) revealed that Paclitaxel degradation is a non-spontaneous process and the highest rate constant was observed in the basic condition and at the highest temperature. The ΔG values at 285, 295 and 310 K were determined 103.3, 105.9 and 109.9 kJ/mol, respectively. In addition, The ΔH and activation energy (Ea) of the process were determined +28.7 kJ/mol and +30.87 kJ/mol, respectively. PMID:27339310

  12. Microbial degradation of Paclitaxel using Citrobacter amalonaticus Rashtia isolated from pharmaceutical wastewater: kinetic and thermodynamic study.

    PubMed

    Zamani, Hojjatolah; Grakoee, Seyed Reza; Rakhshaee, Roohan

    2016-08-01

    Paclitaxel is a highly toxic anticancer agent which is used in a wide range against ovarian, breast, lung, and prostate cancers. Paclitaxel is manufactured recently in the north of Iran which may lead to the introduction of the drug into the environment via pharmaceutical wastewater. To our knowledge, Paclitaxel degradation is currently performed using physicochemical methods and biological degradation of Paclitaxel has not been reported. In this study, a Paclitaxel degrading bacterium was isolated from pharmaceutical wastewater for the first time. The bacterium was identified using biochemical and molecular assays and its Paclitaxel degradation potential was evaluated using High Performance Liquid Chromatography (HPLC). In addition, kinetic and thermodynamic study of Paclitaxel degradation at different experimental conditions was performed. A Citrobacter species named as C. amalonaticus Rashtia able to degrade and utilize Paclitaxel as the sole carbon source was isolated. The isolated strain tolerated high level concentration of Paclitaxel (0.4 mg/mL) in liquid culture media and was able to degrade spillage-level concentrations of the drug (0.01-0.1 mg/mL) with 87-93 % efficacy under aerobic condition. Kinetic and thermodynamic study at different pHs (4.0, 7.0 and 10.0) and temperatures (285, 295 and 310 K) revealed that Paclitaxel degradation is a non-spontaneous process and the highest rate constant was observed in the basic condition and at the highest temperature. The ΔG values at 285, 295 and 310 K were determined 103.3, 105.9 and 109.9 kJ/mol, respectively. In addition, The ΔH and activation energy (Ea) of the process were determined +28.7 kJ/mol and +30.87 kJ/mol, respectively.

  13. Study on degradation kinetics of 2-(2-hydroxypropanamido) benzoic acid in aqueous solutions and identification of its major degradation product by UHPLC/TOF-MS/MS.

    PubMed

    Zhang, Qili; Guan, Jiao; Rong, Rong; Zhao, Yunli; Yu, Zhiguo

    2015-08-10

    A RP-HPLC method was developed and validated for the degradation kinetic study of 2-(2-hydroxypropanamido) benzoic acid (HPABA), a promising anti-inflammatory drug, which would provide a basis for further studies on HPABA. The effects of pH, temperature, buffer concentration and ionic strength on the degradation kinetics of HPABA were discussed. Experimental parameters such as degradation rate constants (k), activation energy (Ea), acid and alkali catalytic constants (k(ac), k(al)), shelf life (t1/2) and temperature coefficient (Q10) were calculated. The results indicated that degradation kinetics of HPABA followed zero-order reaction kinetics; degradation rate constants (k) of HPABA at different pH values demonstrated that HPABA was more stable in neutral and near-neutral conditions; the function of temperature on k obeyed the Arrhenius equation (r = 0.9933) and HPABA was more stable at lower temperature; with the increase of ionic strength and buffer concentration, the stability of HPABA was decreased. The major unknown degradation product of HPABA was identified by UHPLC/TOF-MS/MS with positive electrospray ionization. Results demonstrated that the hydrolysis product was the primary degradation product of HPABA and it was deduced as anthranilic acid.

  14. Laser ion acceleration toward future ion beam cancer therapy - Numerical simulation study -

    PubMed Central

    Kawata, Shigeo; Izumiyama, Takeshi; Nagashima, Toshihiro; Takano, Masahiro; Barada, Daisuke; Kong, Qing; Gu, Yan Jun; Wang, Ping Xiao; Ma, Yan Yun; Wang, Wei Min

    2013-01-01

    Background: Ion beam has been used in cancer treatment, and has a unique preferable feature to deposit its main energy inside a human body so that cancer cell could be killed by the ion beam. However, conventional ion accelerator tends to be huge in its size and its cost. In this paper a future intense-laser ion accelerator is proposed to make the ion accelerator compact. Subjects and methods: An intense femtosecond pulsed laser was employed to accelerate ions. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum control, the ion beam bunching and the ion particle energy control. In the study particle computer simulations were performed to solve the issues, and each component was designed to control the ion beam quality. Results: When an intense laser illuminates a target, electrons in the target are accelerated and leave from the target; temporarily a strong electric field is formed between the high-energy electrons and the target ions, and the target ions are accelerated. The energy efficiency from the laser to ions was improved by using a solid target with a fine sub-wavelength structure or by a near-critical density gas plasma. The ion beam collimation was realized by holes behind the solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching were successfully realized by a multi-stage laser-target interaction. Conclusions: The present study proposed a novel concept for a future compact laser ion accelerator, based on each component study required to control the ion beam quality and parameters. PMID:24155555

  15. Motion sickness and otolith sensitivity - A pilot study of habituation to linear acceleration

    NASA Technical Reports Server (NTRS)

    Potvin, A. R.; Sadoff, M.; Billingham, J.

    1977-01-01

    Astronauts, particularly in Skylab flights, experienced varying degrees of motion sickness lasting 3-5 days. One possible mechanism for this motion sickness adaptation is believed to be a reduction in otolith sensitivity with an attendant reduction in sensory conflict. In an attempt to determine if this hypothesis is valid, a ground-based pilot study was conducted on a vertical linear accelerator. The extent of habituation to accelerations which initially produced motion sickness was evaluated, along with the possible value of habituation training to minimize the space motion sickness problem. Results showed that habituation occurred for 6 of the 8 subjects tested. However, in tests designed to measure dynamic and static otolith function, no significant differences between pre- and post-habituation tests were observed. Cross habituation effects to a standard Coriolis acceleration test were not significant. It is unlikely that ground-based pre-habituation to linear accelerations of the type examined would alter susceptibility to space motion sickness.

  16. A Non-scaling Fixed Field Alternating Gradient Accelerator for the Final Acceleration Stage of the International Design Study of the Neutrino Factory.

    SciTech Connect

    Berg, J.S.; Aslaninejad, M.; Pasternak, J.; Witte, H.; Bliss, N. Cordwell M.; Jones, T.; Muir, A., Kelliher, D.; Machida, S.

    2011-09-04

    The International Design Study of the Neutrino Factory (IDS-NF) has recently completed its Interim Design Report (IDR), which presents our current baseline design of the neutrino factory. To increase the efficiency and reduce the cost of acceleration, the IDR design uses a linear non-scaling fixed field alternating gradient accelerator (FFAG) for its final acceleration stage. We present the current lattice design of that FFAG, including the main ring plus its injection and extraction systems. We describe parameters for the main ring magnets, kickers, and septa, as well as the power supplies for the kickers. We present a first pass at an engineering layout for the ring and its subsystems.

  17. Light-dependent degradation of the D1 protein in photosystem II is accelerated after inhibition of the water splitting reaction

    SciTech Connect

    Jegerschoeld, C.V.; Virgin, I.; Styring, S. )

    1990-07-03

    Strong illumination of oxygen-evolving organisms inhibits the electron transport through photosystem II (photoinhibition). In addition the illumination leads to a rapid turnover of the D1 protein in the reaction center of photosystem II. In this study the light-dependent degradation of the D1 reaction center protein and the light-dependent inhibition of electron-transport reactions have been studied in thylakoid membranes in which the oxygen evolution has been reversibly inhibited by Cl- depletion. The results show that Cl(-)-depleted thylakoid membranes are very vulnerable to damage induced by illumination. Both the D1 protein and the inhibition of the oxygen evolution are 15-20 times more sensitive to illumination than in control thylakoid membranes. The presence, during the illumination, of the herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) prevented both the light-dependent degradation of the D1 protein and the inhibition of the electron transport. The protection exerted by DCMU is seen only in Cl(-)-depleted thylakoid membranes. These observations lead to the proposal that continuous illumination of Cl(-)-depleted thylakoid membranes generates anomalously long-lived, highly oxidizing radicals on the oxidizing side of photosystem II, which are responsible for the light-induced protein damage and inhibition. The presence of DCMU during the illumination prevents the formation of these radicals, which explains the protective effects of the herbicide. It is also observed that in Cl(-)-depleted thylakoid membranes, oxygen evolution (measured after the readdition of Cl-) is inhibited before electron transfer from diphenylcarbazide to dichlorophenolindophenol.

  18. Study of in-situ degradation of thermal control surfaces

    NASA Technical Reports Server (NTRS)

    Gilligan, J. E.; Zerlaut, G. A.

    1972-01-01

    Experimental technique used in study of damage mechanism to semiconductor pigments exposed to ultraviolet radiation can be adapted for investigations of surface chemistry and may be used analytically to determine contamination.

  19. Object-based cropland degradation identification: a case study in Uzbekistan

    NASA Astrophysics Data System (ADS)

    Dubovyk, Olena; Menz, Gunter; Conrad, Christopher; Khamzina, Asia

    2012-10-01

    Sustainability of irrigated agriculture-based economies, such as in Central Asia, is threatened by cropland degradation. The field-based identification of the degraded agricultural areas can aid in developing appropriate land rehabilitation and monitoring programs. This paper combined the object-based change detection and spectral mixture analysis to develop an approach for identifying parcels of irrigated degraded cropland in Northern Uzbekistan, Central Asia. A linear spectral unmixing, followed by the object-based change vector analysis, was applied to the multiple Landsat TM images, acquired in 1987 and 2009. Considering a spectral dimensionality of Landsat TM, a multiple 4-endmember model (green vegetation, water, dark soil, and bright soil) was set up for the analysis. The spectral unmixing results were valid, as indicated by the overall root mean square errors of <2.5% reflectance for all images. The results of change detection revealed that about 33% (84,540 ha) of cropland in the study area were affected by the degradation processes to varying degrees. Spatial distribution of degraded fields was mainly associated with the abandoned fields and lands with inherently low fertile soils. The proposed approach could be elaborated for a field-based monitoring of cropland degradation in similar landscapes of Central Asia and elsewhere.

  20. New, More Authentic Model for AIDS Will Accelerate Studies | Poster

    Cancer.gov

    By Frank Blanchard, Staff Writer, and Jeff Lifson, Guest Writer Researchers are working to develop a more authentic animal model of human immunodeficiency virus (HIV) infection and AIDS that is expected to speed up studies of experimental treatments and vaccines.

  1. Experimental studies of W-band accelerator structures at high field

    NASA Astrophysics Data System (ADS)

    Hill, Marc Edward

    2001-06-01

    A high-gradient electron accelerator is desired for high- energy physics research, where frequency scalings of breakdown and trapping of itinerant beamline particles dictates operation of the accelerator at short wavelengths. The first results of design and test of a high-gradient mm-wave linac with an operating frequency at 91.392 GHz (W-band) are presented. A novel approach to particle acceleration is presented employing a planar, dielectric lined waveguide used for particle acceleration. The traveling wave fields in the planar dielectric accelerator (PDA) are analyzed for an idealized structure, along with a circuit equivalent model used for understanding the structure as a microwave circuit. Along with the W-band accelerator structures, other components designed and tested are high power rf windows, high power attenuators, and a high power squeeze-type phase shifter. The design of the accelerator and its components where eased with the aide of numerical simulations using a finite-difference electromagnetic field solver. Manufacturing considerations of the small, delicate mm-wave components and the steps taken to reach a robust fabrication process are detailed. These devices were characterized under low power using a two-port vector network analyzer to verify tune and match, including measurements of the structures' fields using a bead-pull. The measurements are compared with theory throughout. Addition studies of the W-band structures were performed under high power utilizing a 11.424 GHz electron linac as a current source. Test results include W-band power levels of 200 kW, corresponding to fields in the PDA of over 20 MV/m, higher than any collider. Also presented are the first measurements of the quadrapole component of the monopole accelerating field.

  2. Plasma wakefield acceleration studies using the quasi-static code WAKE

    SciTech Connect

    Jain, Neeraj; Palastro, John; Antonsen, T. M.; Mori, Warren B.; An, Weiming

    2015-02-15

    The quasi-static code WAKE [P. Mora and T. Antonsen, Phys. Plasmas 4, 217 (1997)] is upgraded to model the propagation of an ultra-relativistic charged particle beam through a warm background plasma in plasma wakefield acceleration. The upgraded code is benchmarked against the full particle-in-cell code OSIRIS [Hemker et al., Phys. Rev. Spec. Top. Accel. Beams 3, 061301 (2000)] and the quasi-static code QuickPIC [Huang et al., J. Comput. Phys. 217, 658 (2006)]. The effect of non-zero plasma temperature on the peak accelerating electric field is studied for a two bunch electron beam driver with parameters corresponding to the plasma wakefield acceleration experiments at Facilities for Accelerator Science and Experimental Test Beams. It is shown that plasma temperature does not affect the energy gain and spread of the accelerated particles despite suppressing the peak accelerating electric field. The role of plasma temperature in improving the numerical convergence of the electric field with the grid resolution is discussed.

  3. Experimental, Theoretical and Computational Studies of Plasma-Based Concepts for Future High Energy Accelerators

    SciTech Connect

    Joshi, Chan; Mori, W.

    2013-10-21

    This is the final report on the DOE grant number DE-FG02-92ER40727 titled, “Experimental, Theoretical and Computational Studies of Plasma-Based Concepts for Future High Energy Accelerators.” During this grant period the UCLA program on Advanced Plasma Based Accelerators, headed by Professor C. Joshi has made many key scientific advances and trained a generation of students, many of whom have stayed in this research field and even started research programs of their own. In this final report however, we will focus on the last three years of the grant and report on the scientific progress made in each of the four tasks listed under this grant. Four tasks are focused on: Plasma Wakefield Accelerator Research at FACET, SLAC National Accelerator Laboratory, In House Research at UCLA’s Neptune and 20 TW Laser Laboratories, Laser-Wakefield Acceleration (LWFA) in Self Guided Regime: Experiments at the Callisto Laser at LLNL, and Theory and Simulations. Major scientific results have been obtained in each of the four tasks described in this report. These have led to publications in the prestigious scientific journals, graduation and continued training of high quality Ph.D. level students and have kept the U.S. at the forefront of plasma-based accelerators research field.

  4. Studies of a hybrid Trojan Horse wakefield accelerator with high transformer ratio

    NASA Astrophysics Data System (ADS)

    Cook, Nathan; Bruhwiler, David; Hidding, Bernhard; Vay, Jean-Luc; Webb, Stephen

    2015-11-01

    Plasma wakefield acceleration uses relativistic high-charge electron bunches to generate a plasma blowout supporting intense electric fields for trapping and acceleration. Dramatic improvements in emittance, peak current and brightness are achievable through laser-controlled ionization in the plasma blowout, which is the premise of the Trojan Horse approach. The hybrid Trojan Horse concept extends this approach to use the output beam from a laser plasma accelerator to drive a Trojan Horse, resulting in a compact system that can produce higher brightness bunches with order-of-magnitude lower energy spread. We are exploring the use of multiple, shaped laser pulses to resonantly inject a shaped electron drive bunch. The resulting output bunch could generate wakes in PWFA or beam-driven dielectric structures with transformer ratios of 5 to 10 or larger. Hence, a hybrid Trojan Horse accelerator with bunch shaping may provide a compact source of nC bunches that can drive a variety of systems for studying high-gradient wakefields and lepton acceleration. Initial work will use previously simulated electron bunches from a laser plasma accelerator to drive the plasma wakefield stage. We present preliminary results from simulations using the parallel, particle-in-cell framework Warp. Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Award Number DE-SC0013855.

  5. School Restructuring: A Study of the Role of Parents in Selected Accelerated Schools.

    ERIC Educational Resources Information Center

    Davidson, Betty M.

    This paper presents findings of a study that examined the change process involved when four elementary schools implemented the accelerated schools model. Specifically, the study focused on transitions in parental roles that occurred when the schools changed from a conventional mode of organization to a participatory mode. The case study data were…

  6. Accelerator research studies. Final report, June 1, 1990--November 30, 1991

    SciTech Connect

    Not Available

    1991-12-31

    The program consisted of the following three tasks: TASK A, ``Study of Transport and Longitudinal Compression of Intense, High-Brightness Beams,`` TASK B, ``Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams,`` and TASK C, ``Study of a Gyroklystron High-Power Microwave Source for Linear Colliders.``

  7. Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction

    NASA Astrophysics Data System (ADS)

    Scisciò, M.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Papaphilippou, Y.; Antici, P.

    2016-03-01

    In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.

  8. Long-term degradation study of hyaluronic acid in aqueous solutions without protection against microorganisms.

    PubMed

    Simulescu, Vasile; Kalina, Michal; Mondek, Jakub; Pekař, Miloslav

    2016-02-10

    The degradation of hyaluronan (HA) of different molecular weights (Mw 14.3, 267.2 and 1160.6 kDa, measured for fresh solutions, before degradation) was studied in aqueous solutions by SEC-MALLS determination of molecular mass, polydispersity and conformation parameters. The solutions were stored either at laboratory or refrigerator temperatures for two months. After this period the weight average molecular weight decreased by 90% for 14.3 kDa, 95% for 267.2 kDa and 71% for 1160.6 kDa hyaluronan (room temperature) or 5.6% for 14.3 kDa, 6.2% for 267.2 kDa and 7.7% for 1160.6 kDa hyaluronan (refrigerator temperature). The hyaluronan aqueous solutions studied did not contain sodium azide or other protectants against microorganisms, because the aim of our study was to assess the degradation in solutions to be used in medicine or cosmetics (without any compounds that are poisonous or toxic for the human body). The solvent used to prepare the samples was pure water. The polydispersity of all the samples remained unaltered during the entire degradation at both temperatures. This indicates a non-random mechanism of degradation. PMID:26686177

  9. Forced degradation, LC-UV, MS(n) and LC-MS-TOF studies on azilsartan: Identification of a known and three new degradation impurities.

    PubMed

    Kaushik, Dhiraj; Kaur, Jasmeen; Paul Kaur, Vaneet; Saini, Balraj; Bansal, Yogita; Bansal, Gulshan

    2016-02-20

    In the present study, Azilsartan (AZL) was subjected to ICH recommended forced degradation conditions of hydrolysis, oxidation, dry heat and photolysis. The drug degraded to four degradation products (I-IV) under acidic, alkaline and water hydrolysis and photolysis. All the four degradation products were resolved in a single run on a C-18 column (250mm×4.6mm; 5μ) with isocratic elution using mobile phase composed of ammonium formate (20mM, pH 3.0), methanol and acetonitrile (40:5:40% v/v), at a flow rate of 0.8mlmin(-1) at ambient temperature. The products were characterized through +ESI-MS(n) spectra of AZL and LC-MS-TOF studies as 2-ethoxy-3H-benzo-imidazole-4-carboxylic acid (I), 2-hydroxy-3-[2'-(5-oxo-4,5-dihydro-[1,2,4]oxadiazol-4-ylmethyl]-3H-benzoimidazole-4-carboxylic acid (II, deethylated AZL), 3-[2'-(1H-diazirin-3-yl)-biphenyl]-4-ylmethyl]-2-ethoxy-3H-benzoimidazole-4-carboxylic acid (III), and 3-[4'-(2-ethoxy-benzo-imidazol-1-ylmethyl)-biphenyl-2-yl]-4H-[1,2,4]oxadiazol-5-one (IV, decarboxylated AZL). Product I was found to be a known process related impurity whereas the products II-IV were identified as new degradation impurities. The most probable mechanisms for formation of these degradation products were proposed. PMID:26752083

  10. Structural and degradation studies of a biocompatible Zn-L-tartrate metal–organic framework

    SciTech Connect

    Palǒić, Ana; Puškarić, Andreas; Mazaj, Matjaž; Žunkoviǒ, Emanuela; Logar, Nataša Zabukovec; Bronić, Josip

    2015-05-15

    New anhydrous Zn-L-tratrate was synthesized under hydrothermal conditions. Crystal structure which was solved by powder X-ray diffraction data from monoclinic unit cell (I{sub 2}, a=11.7557(1), b=9.0319(1), c=5.0750(1), β=91.920(1)) consists of the three-dimensional framework where each Zn atom coordinates four tartrate ligands in distorted octahedral geometry. Due to its biocompatible components, the degradation of material was studied in aqueous media under different pH values (pH=1–7) and in the simulated body fluid (pH=7.4) performed by the measurement of the released Zn{sup 2+} concentrations at thermostatic conditions (37 °C). The results showed that under acidic conditions approximately 60% of Zn{sup 2+} is released from the investigated material after 6 h of degradation process. With the increase of the solution’s pH, the rate of degradation gradually decreases. XRD and SEM analyses indicate that in aqueous media the compound slowly disintegrates and does not undergo hydrolysis process regardless of pH. Biocompatibility of the compound and its controllable rate of degradation even in acid conditions open its potential use in the fields of bio-applications. - Graphical abstract: The degradation kinetics of Zn-L-tar MOF material in aqueous media at different pH conditions. - Highlights: • Anhydrous chiral Zn-L-tratrate was synthesized under hydrothermal conditions. • 3-D framework consists of Zn atoms, each chelating four tartrate ligands. • Degradation of material was studied in aqueous media at different pH values. • The compound disintegrates in controllable manner in aqueous solutions. • The rate compound degradation is increasing with increased acidity of solution.

  11. Infrared laser heating for studies of cellulose degradation

    SciTech Connect

    Jackson, J.P.; Arthurs, E.; Schwalbe, L.A.; Sega, R.M.; Windish, D.; Long, W.H.; Stappaerts, E.A.

    1988-09-15

    We describe a new technique for studying thermally induced chemical transformations in cellulose. The apparatus consists of a carbon dioxide laser for heating, an IR thermometer, and an optical reflectance spectrometer for tracking the progressive discoloration of the sample. To illustrate the technique, we present measurements from a single piece of sample linen along five isotherms in the 200--290/sup 0/C range. We derive an algebraic expression for the reflectivity of the sample as a function of the areal concentrations of the chromophoric states produced at temperature. The results are then explained in terms of first-order chemical rate theory and a four-step model. From the measurements we derive the activation energies, Arrhenius constants, and reflectivities of the chromophoric states.

  12. Onjisaponin B Derived from Radix Polygalae Enhances Autophagy and Accelerates the Degradation of Mutant α-Synuclein and Huntingtin in PC-12 Cells

    PubMed Central

    Wu, An-Guo; Wong, Vincent Kam-Wai; Xu, Su-Wei; Chan, Wai-Kit; Ng, Choi-In; Liu, Liang; Law, Betty Yuen-Kwan

    2013-01-01

    Emerging evidence indicates important protective roles being played by autophagy in neurodegenerative disorders through clearance of aggregate-prone or mutant proteins. In the current study, we aimed to identify autophagy inducers from Chinese medicinal herbs as a potential neuroprotective agent that enhances the clearance of mutant huntingtin and α-synuclein in PC-12 cells. Through intensive screening using the green fluorescent protein-light chain 3 (GFP-LC3) autophagy detection platform, we found that the ethanol extracts of Radix Polygalae (Yuan Zhi) were capable of inducing autophagy. Further investigation showed that among three single components derived from Radix Polygalae—i.e., polygalacic acid, senegenin and onjisaponin B—onjisaponin B was able to induce autophagy and accelerate both the removal of mutant huntingtin and A53T α-synuclein, which are highly associated with Huntington disease and Parkinson disease, respectively. Our study further demonstrated that onjisaponin B induces autophagy via the AMPK-mTOR signaling pathway. Therefore, findings in the current study provide detailed insights into the protective mechanism of a novel autophagy inducer, which is valuable for further investigation as a new candidate agent for modulating neurodegenerative disorders through the reduction of toxicity and clearance of mutant proteins in the cellular level. PMID:24248062

  13. Accelerated heat-aging studies on fluororubber in various media

    NASA Technical Reports Server (NTRS)

    Kalfayan, S. H.; Silver, R. H.; Liu, S. S.

    1976-01-01

    Heat-aging studies were conducted on fluororubber (copolymers of vinylidene fluoride and perfluoropropylene) using N,N-dicinnamylidene-1,6-hexanediamine, a Schiff's base of 1,6-hexanediamine, and MgO as acid acceptor. The principal technique employed was chemical stress relaxation for determining network changes brought about in the heat-aged fluororubber. This technique was backed up by swelling measurements, gel permeation chromatography, and IR spectroscopy. Stress relaxation curves are plotted for a wide range of variation in parameters (time, crosslinking density, state of curing, temperature, intermittent and continuous relaxation).

  14. FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

    2002-01-01

    The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identity the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral SnapshoT (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data was used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and a long-system particle-in-cell simulation to model the magnetically connected region between the two satellites.

  15. Study of cement-epoxy interfaces, accelerated testing, and surface modification

    NASA Astrophysics Data System (ADS)

    Stewart, Andrew

    Adhesion between concrete and fiber reinforced polymer (FRP) repair materials is of great importance for increasing the longevity of damaged surfaces in civil infrastructure in the US. This adhesion is dominated by a relatively weak interfacial bond that is attacked by environmental agents including water and UV radiation. Therefore, a strong bond between the two materials is essential in making a successful, long lasting repair. In this study, the fundamental question of the epoxy-concrete interface is investigated in terms of how it exists, how it is attacked by the environment, and how it may be improved to resist the elements. In this study, interactions between epoxy analogs and cement paste were investigated to get a fundamental understanding of the elusive interfacial bond. Various FTIR and NMR techniques were utilized to demonstrate the nature of this interaction. Only one of the small molecules (Bisphenol A), suggested a small interaction, however, based on the results it appeared that hydrogen bonding did not take place. The second part of this work focused on accelerated aging two epoxy systems, including a model DGEBA-POPDA system, and a commercial system. Mechanical testing was performed along with IR spectroscopy and diffusion modeling to determine the change in properties and mechanisms of degradation. The absorption of water up to 90°C resulted in a decrease in modulus and stress, along with an increase in strain. IR data confirmed the absorption of water within the epoxy network. With UV exposure, oxidation was demonstrated by the appearance of carbonyl peaks in the FTIR spectra. UV and water exposure gave evidence of hydrolysis through a decrease in ether groups and an increase in hydroxyl groups. While samples exposed to UV showed less of a loss in modulus as compared to those only exposed to water at the same temperature, the peak stress of samples exposed to UV was lower than those exposed to water. However, the data from the mechanical

  16. Mechanistic Study of the Acid Degradation of Lignin Model Compounds

    SciTech Connect

    Sturgeon, M.; Kim, S.; Chmely, S. C.; Foust, T. D.; Beckham, G. T.

    2012-01-01

    Lignin is a major constituent of biomass, which remains underutilized in selective biomass conversion strategies to renewable fuels and chemicals. Here we are interested in understanding the mechanisms related to the acid deconstruction of lignin with a combined theoretical and experimental approach. Two model dimers with a b-O-4 aryl ether linkage (2-phenoxy-1-phenethanol and 2-phenoxy-1-phenyl-1,3 propanediol) and model dimmers with an a-O-4 aryl ether linkage were synthesized and deconstructed in H2SO4. The major products of the acidolysis of the b-O-4 compounds consisted of phenol and two aldehydes, phenylacetaldehyde and benzaldehyde. Quantum mechanical calculations were employed to elucidate possible deconstruction mechanisms with transition state theory. To confirm proposed mechanisms several possible intermediates were studied under similar acidolysis conditions. Although the resonance time for cleavage was on the order several hours, we have shown that the cleavage of the aryl ether linkage affords phenol and aldehydes. We would next like to utilize our mechanism of aryl ether cleavage in actual lignin.

  17. A thin film degradation study of a fluorinated polyether liquid lubricant using an HPLC method

    NASA Technical Reports Server (NTRS)

    Morales, W.

    1986-01-01

    A High Pressure Liquid Chromatography (HPLC) separation method was developed to study and analyze a fluorinated polyether fluid which is promising liquid lubricant for future applications. This HPLC separation method was used in a preliminary study investigating the catalytic effect of various metal, metal alloy, and ceramic engineering materials on the degradation of this fluid in a dry air atmosphere at 345 C. Using a 440 C stainless steel as a reference catalytic material it was found that a titanium alloy and a chromium plated material degraded the fluorinated polyether fluid substantially more than the reference material.

  18. Degradation behavior and biosafety studies of the mPEG-PLGA-PLL copolymer.

    PubMed

    He, Zelai; Sun, Ying; Cao, Jun; Duan, Yourong

    2016-04-28

    In a previous study, a novel biodegradable multiblock copolymer, monomethoxy(poly-ethylene glycol)-poly(d,l-lactide-co-glycolide)-poly(l-lysine) (PEAL), was developed as a new drug carrier material. It is imperative to study the biocompatibility and degradation behavior of PEAL to pave the way for clinical applications. Here, we systematically demonstrated that the PEAL copolymer has the appropriate hydrophilicity and biosafety. The degradation rate of the PEAL films was obtained by observing changes in mass, molecular weight (Mw), Mw distribution and degradation products. The degradation rate was observed to have a highly positive correlation with the pH of the medium and negative correlation with the ratio of lactic acid to glycolic acid (LA/GA). Cytotoxicity tests indicated that the degradation products of the copolymer were non-toxic to cells. In zebrafish embryos, the PEAL nanoparticles had no obvious impact on heart rate, production of reactive oxygen species, mortality, or cell apoptosis, and they were observed to have a long circulation time. Therefore, the PEAL copolymer has great potential for use as a drug carrier material.

  19. The impact of charcoal production on forest degradation: a case study in Tete, Mozambique

    NASA Astrophysics Data System (ADS)

    Sedano, F.; Silva, J. A.; Machoco, R.; Meque, C. H.; Sitoe, A.; Ribeiro, N.; Anderson, K.; Ombe, Z. A.; Baule, S. H.; Tucker, C. J.

    2016-09-01

    Charcoal production for urban energy consumption is a main driver of forest degradation in sub Saharan Africa. Urban growth projections for the continent suggest that the relevance of this process will increase in the coming decades. Forest degradation associated to charcoal production is difficult to monitor and commonly overlooked and underrepresented in forest cover change and carbon emission estimates. We use a multitemporal dataset of very high-resolution remote sensing images to map kiln locations in a representative study area of tropical woodlands in central Mozambique. The resulting maps provided a characterization of the spatial extent and temporal dynamics of charcoal production. Using an indirect approach we combine kiln maps and field information on charcoal making to describe the magnitude and intensity of forest degradation linked to charcoal production, including aboveground biomass and carbon emissions. Our findings reveal that forest degradation associated to charcoal production in the study area is largely independent from deforestation driven by agricultural expansion and that its impact on forest cover change is in the same order of magnitude as deforestation. Our work illustrates the feasibility of using estimates of urban charcoal consumption to establish a link between urban energy demands and forest degradation. This kind of approach has potential to reduce uncertainties in forest cover change and carbon emission assessments in sub-Saharan Africa.

  20. Study of the influential factors in the simultaneous photocatalytic degradation process of three textile dyes.

    PubMed

    Fernández, Cristina; Larrechi, M Soledad; Callao, M Pilar

    2009-10-15

    The influence of several factors in the simultaneous photocatalytic degradation of three textile dyes - Acid Red 97, Acid Orange 61 and Acid Brown 425 - has been studied using a fractional factorial design 2(5-1). The considered factors were: the initial concentration of each dye, the catalyst concentration (TiO(2)) and pH. First, we developed a rapid analytical methodology based on recording UV-visible spectra during the degradation process and a data treatment using multivariate curve resolution with alternating least squares (MCR-ALS), which enabled the three dyes to be quantified simultaneously despite the overlap of their spectra. The kinetic constant of degradation for each dye in all the experiments was evaluated. In all cases the degradation followed a first order kinetics. For a significance level of 5%, the most important factor in the photodegradation of each dye is the concentration of Acid Red 97, the degradation is more effective at higher pHs and, in the studied range, the concentration of the catalyst is not important.

  1. Structural elucidation of degradation products of a benzopyridooxathiazepine under stress conditions using electrospray orbitrap mass spectrometry - study of degradation kinetic.

    PubMed

    Lecoeur, Marie; Vérones, Valérie; Vaccher, Claude; Bonte, Jean-Paul; Lebegue, Nicolas; Goossens, Jean-François

    2012-04-11

    1-(4-Methoxyphenylethyl)-11H-benzo[f]-1,2-dihydro-pyrido[3,2,c][1,2,5]oxathiazepine 5,5 dioxide (BZN) is a cytotoxic derivative with very promising in vitro activity. Regulatory authority for registration of pharmaceuticals for human use requires to evaluate the stability of active compound under various stress conditions. Forced degradation of BZN was investigated under hydrolytic (0.1M NaOH, 0.1M HCl, neutral), oxidative (3.3% H(2)O(2)), photolytic (visible light) and thermal (25 °C, 70 °C) settings. Relevant degradation took place under thermal acidic (0.1M HCl, 70 °C) and oxidative (3.3% H(2)O(2)) conditions. Liquid chromatography-mass spectrometry (LC-MS) analyses revealed the presence of ten degradation products whose structures were characterized by electrospray ionization-orbitrap mass spectrometry. The full scan accurate mass analysis of degradation products was confirmed or refuted using three tools furnished by the MS software: (1) predictive chemical formula and corresponding mass error; (2) double bond equivalent (DBE) calculation; and (3) accurate mass product ion spectra of degradation products. The structural elucidation showed that the tricycle moiety was unstable under thermal acidic and oxidative conditions since four degradation products possess an opened oxathiazepine ring. Then, a simple and fast HPLC-UV method was developed and validated for the determination of the degradation kinetic of BZN under acidic and oxidative conditions. The method was linear in the 5-100 μg mL(-1) concentration range with a good precision (RSD=2.2% and 2.7% for the repeatability and the intermediate precision, respectively) and a bias which never exceeded 1.6%, whatever the quality control level. With regards to the BZN concentration, a first-order degradation process was determined, with t(1/2)=703 h and 1140 h, under oxidative and acidic conditions, respectively.

  2. Thermal degradation events as health hazards - Particle vs gas phase effects, mechanistic studies with particles

    NASA Technical Reports Server (NTRS)

    Oberdoerster, G.; Ferin, J.; Finkelstein, J.; Soderholm, S.

    1992-01-01

    Experiments on animal subjects are performed to demonstrate that significant lung injury can result from the inhalation of ultrafine TiO2 or Al2O3 particles. The methods include intratracheal instillation of particles, long-term inhalation of particles, and in vitro studies of alveolar macrophages (AMs) to study the production of fibroplast growth factors. The ultrafine TiO2 particles are shown to induce more acute inflammatory reactions than larger particles and lead to persistent chronic effects in the AM-mediated clearance function of particles. The ultrafine particles also induce cytokines more readily, and the data generally suggests that the occurrence of such particles in thermal degradation events makes the fumes highly toxic. The exposure to thermal degradation products is therefore a critical concern for manned space missions with potentially degradable plastic products.

  3. Comparison study of different coatings on degradation performance and cell response of Mg-Sr alloy.

    PubMed

    Shangguan, Yongming; Sun, Lina; Wan, Peng; Tan, Lili; Wang, Chengyue; Fan, Xinmin; Qin, Ling; Yang, Ke

    2016-12-01

    To solve the problem of rapid degradation for magnesium-based implants, surface modification especially coating method is widely studied and showed the great potential for clinical application. However, as concerned to the further application and medical translation for biodegradable magnesium alloys, there are still lack of data and comparisons among different coatings on their degradation and biological properties. This work studied three commonly used coatings on Mg-Sr alloy, including micro-arc oxidation coating, electrodeposition coating and chemical conversion coating, and compared these coatings for requirements of favorable degradation and biological performances, how each of these coating systems has performed. Finally the mechanism for the discrepancy between these coatings is proposed. The results indicate that the micro-arc oxidation coating on Mg-Sr alloy exhibited the best corrosion resistance and cell response among these coatings, and is proved to be more suitable for the orthopedic application. PMID:27612693

  4. Accelerator Research Studies. Annual report for June 1, 2003 - May 31, 2004

    SciTech Connect

    O'Shea, P. G.; Reiser, M.; Granatstein, V. L.; Lawson, W.; Haber, I.; Kishek, R.

    2004-01-23

    The report provides a summary progress on three tasks: Task A: Study of the Physics of Space-Charge Dominated Beams for Advanced Accelerator Applications; Task B: Studies of High-Power Gyroklystrons and Application to Linear Colliders; and, Task C: Theory and Simulation of the Physics Space-Charge Dominated Beams

  5. Promoting Acceleration of Comprehension and Content through Text in High School Social Studies Classes

    ERIC Educational Resources Information Center

    Wanzek, Jeanne; Swanson, Elizabeth A.; Roberts, Greg; Vaughn, Sharon; Kent, Shawn C.

    2015-01-01

    The purpose of this study was to evaluate the efficacy of Promoting Acceleration of Comprehension and Content Through Text intervention implemented with 11th-grade students enrolled in U.S. History classes. Using a within-teacher randomized design, the study was conducted in 41 classes (23 treatment classes) with 14 teachers providing the…

  6. Study of Spray Disintegration in Accelerating Flow Fields

    NASA Technical Reports Server (NTRS)

    Nurick, W. H.

    1972-01-01

    An analytical and experimental investigation was conducted to perform "proof of principlem experiments to establish the effects of propellant combustion gas velocity on propella'nt atomization characteristics. The propellants were gaseous oxygen (GOX) and Shell Wax 270. The fuel was thus the same fluid used in earlier primary cold-flow atomization studies using the frozen wax method. Experiments were conducted over a range in L* (30 to 160 inches) at two contraction ratios (2 and 6). Characteristic exhaust velocity (c*) efficiencies varied from SO to 90 percent. The hot fire experimental performance characteristics at a contraction ratio of 6.0 in conjunction with analytical predictions from the drovlet heat-up version of the Distributed Energy Release (DER) combustion computer proDam showed that the apparent initial dropsize compared well with cold-flow predictions (if adjusted for the gas velocity effects). The results also compared very well with the trend in perfomnce as predicted with the model. significant propellant wall impingement at the contraction ratio of 2.0 precluded complete evaluation of the effect of gross changes in combustion gas velocity on spray dropsize.

  7. Recent studies in microbial degradation of petroleum hydrocarbons in hypersaline environments

    PubMed Central

    Fathepure, Babu Z.

    2014-01-01

    Many hypersaline environments are often contaminated with petroleum compounds. Among these, oil and natural gas production sites all over the world and hundreds of kilometers of coastlines in the more arid regions of Gulf countries are of major concern due to the extent and magnitude of contamination. Because conventional microbiological processes do not function well at elevated salinities, bioremediation of hypersaline environments can only be accomplished using high salt-tolerant microorganisms capable of degrading petroleum compounds. In the last two decades, there have been many reports on the biodegradation of hydrocarbons in moderate to high salinity environments. Numerous microorganisms belonging to the domain Bacteria and Archaea have been isolated and their phylogeny and metabolic capacity to degrade a variety of aliphatic and aromatic hydrocarbons in varying salinities have been demonstrated. This article focuses on our growing understanding of bacteria and archaea responsible for the degradation of hydrocarbons under aerobic conditions in moderate to high salinity conditions. Even though organisms belonging to various genera have been shown to degrade hydrocarbons, members of the genera Halomonas Alcanivorax, Marinobacter, Haloferax, Haloarcula, and Halobacterium dominate the published literature. Despite rapid advances in understanding microbial taxa that degrade hydrocarbons under aerobic conditions, not much is known about organisms that carry out similar processes in anaerobic conditions. Also, information on molecular mechanisms and pathways of hydrocarbon degradation in high salinity is scarce and only recently there have been a few reports describing genes, enzymes and breakdown steps for some hydrocarbons. These limited studies have clearly revealed that degradation of oxygenated and non-oxygenated hydrocarbons by halophilic and halotolerant microorganisms occur by pathways similar to those found in non-halophiles. PMID:24795705

  8. Studies of Multipactor in Dielectric-Loaded Accelerator Structures: Comparison of Simulation Results with Experimental Data

    SciTech Connect

    Sinitsyn, Oleksandr; Nusinovich, Gregory; Antonsen, Thomas Jr.

    2010-11-04

    In this paper new results of numerical studies of multipactor in dielectric-loaded accelerator structures are presented. The results are compared with experimental data obtained during recent studies of such structures performed by Argonne National Laboratory, the Naval Research Laboratory, SLAC National Accelerator Laboratory and Euclid TechLabs, LLC. Good agreement between the theory and experiment was observed for the structures with larger inner diameter, however the structures with smaller inner diameter demonstrated a discrepancy between the two. Possible reasons for such discrepancy are discussed.

  9. Tripartite entanglement of fermionic system in accelerated frames

    SciTech Connect

    Khan, Salman

    2014-09-15

    The dynamics of tripartite entanglement of fermionic system in noninertial frames through linear contraction criterion when one or two observers are accelerated is investigated. In one observer accelerated case the entanglement measurement is not invariant with respect to the partial realignment of different subsystems and for two observers accelerated case it is invariant. It is shown that the acceleration of the frame does not generate entanglement in any bipartite subsystems. Unlike the bipartite states, the genuine tripartite entanglement does not completely vanish in both one observer accelerated and two observers accelerated cases even in the limit of infinite acceleration. The degradation of tripartite entanglement is fast when two observers are accelerated than when one observer is accelerated. It is shown that tripartite entanglement is a better resource for quantum information processing than the bipartite entanglement in noninertial frames. - Highlights: • Tripartite entanglement of fermionic system in noninertial frames is studied. • Linear contraction criterion for quantifying tripartite entanglement is used. • Acceleration does not produce any bipartite entanglement. • The invariance of entanglement quantifier depends on accelerated observers. • The tripartite entanglement degrades against the acceleration, it never vanishes.

  10. A study on degradation kinetics of ascorbic acid in amla (Phyllanthus emblica L.) during cooking.

    PubMed

    Nisha, P; Singhal, Rekha S; Pandit, Aniruddha B

    2004-08-01

    The kinetics of ascorbic acid degradation in amla (Phyllanthus emblica L.) as well as in pure ascorbic acid solutions at initial concentrations present in amla over a temperature range of 50-120 degrees C (steady-state temperature) has been studied. The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by the Arrhenius equation. The activation energies were found to be 4.09 kcal/mole for amla and 4.49 kcal/mole for pure vitamin solution. The degradation kinetics of ascorbic acid was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient EcoCooker (unsteady state heating process). A mathematical model was developed using the steady-state kinetic parameters obtained to predict the losses of ascorbic acid from the time-temperature data of the unsteady state heating processing method. The results obtained indicate the ascorbic acid degradation is of a similar order of magnitude in all the methods of cooking.

  11. Statistical Study on Main and Residual Accelerations of Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Zhang, J.

    2006-05-01

    We present the results of a statistical study on the main and residual accelerations of coronal mass ejections (CMEs). This work is based on a laborious but careful visual search of about 100000 images taken by LASCO (Large Angle Spectrometric Coronagraph) C1 from 1996 Jan. to 1998 Jun. Among a large number of active phenomena seen in the inner corona from 1.1 to 3.0 Rs by C1, we have identified 74 CMEs, which all have counterparts seen by LASCO C2 and C3 from 2 to 30 Rs. Out of these 74 C1 CMEs, 50 CMEs are found to be suitable for a quantitative study on their main acceleration in the inner corona and their residual acceleration in the outer corona. We find that, for the 50 events, the magnitude of the main acceleration ranges from 2.8 m/s2 to 4464.0 m/s2 with a median (average) value of 170.1 (330.9 m/s2 ) and a standard deviation of 644.8 m/s2, whereas the magnitude of the residual acceleration ranges only from -131.0 m/s2 to 52.0 m/s2 with a median (average) value of 3.1 (0.9 m/s2) and a standard deviation of 25.3 m/s2, The distribution of the duration of the main acceleration is from 6 min to 1200 min, with a median (average) value of 54 (180 min) and a standard deviation of 286 min. Apparently, the main acceleration has a wide distribution over almost three orders of magnitude in terms of both magnitude and duration, representing a continuous spectrum of events from extremely gradual ones all the way to extremely impulsive ones. We also find an interesting scaling law between acceleration magnitude (A) and acceleration duration (T) over the entire parameter range, that is A (m/s2) = 10000 T-1 (min); in the logarithmic scale, there is a strong inverse linear correlation between the two parameters, with a correlation coefficient of 0.95.

  12. An in vitro Study of Diffusibility and Degradation of Three Calcium Hydroxide Pastes

    PubMed Central

    2011-01-01

    ABSTRACT Aims and objectives : The aim of this in vitro study is to assess the diffusibility and degradation of three calcium hydroxide pastes. Materials and methods : Three pastes were prepared by mixing calcium hydroxide powder with three different vehicles namely water, propylene glycol and CMCP for the investigation. The three pastes were sealed in porcelain caps and immersed in distilled water for the diffusion study. The change in the pH of the surrounding water indicated the rate and degree of diffusion in the degradation study (1 to 7 days, 14th day, 21st day and 30th day). The pastes were exposed to an atmosphere of carbon dioxide in the degradation study to assess the degree to which they can undergo degradation by carbonation. Mordant Black or Solochrome Black indicator was used for the estimation. Results and conclusion : Calcium hydroxide readily diffuses from all the three pastes. Calcium hydroxide diffuses marginally less from a paste made with propylene glycol as compared to CMCP paste. The comparative stability of Ca(OH)2 was studied and the results showed that consistently significant protection is imparted to Ca(OH)2 by CMCP over widely ranging periods. PMID:27616853

  13. A kinetic study of textile dyeing wastewater degradation by Penicillium chrysogenum.

    PubMed

    Durruty, Ignacio; Fasce, Diana; González, Jorge Froilán; Wolski, Erika Alejandra

    2015-06-01

    The potential of Penicillium chrysogenum to decolorize azo dyes and a real industrial textile wastewater was studied. P. chrysogenum was able to decolorize and degrade three azo dyes (200 mg L(-1)), either independently or in a mixture of them, using glucose as a carbon source. A kinetic model for degradation was developed and it allowed predicting the degradation kinetics of the mixture of the three azo dyes. In addition, P. chrysogenum was able to decolorize real industrial wastewater. The kinetic model proposed was also able to predict the decolorization of the real wastewater. The calibration of the proposed model makes it a useful tool for future wastewater facilities' design and for practical applications.

  14. An efficient TiO2 coated immobilized system for the degradation studies of herbicide isoproturon: durability studies.

    PubMed

    Verma, A; Prakash, N T; Toor, A P

    2014-08-01

    The investigation presents the observations on the use of cement beads for the immobilization of TiO2 for the degradation of herbicide isoproturon. The immobilized system was effective in degrading and mineralizing the herbicide for continuous thirty cycles without losing its durability. Catalyst was characterized by SEM-EDAX for checking the durability of the catalyst. The degradation rate followed first order kinetics as measured by change in absorption intensity in UV range as well as HPLC analysis. Two rounds of TiO2 coating on inert cement beads with average diameter 1.5cm at UV Intensity 25Wm(-2) calcined at 400°C were the optimized conditions for the degradation of herbicide isoproturon. More than 90% TOC and COD reduction along with ammonium ions generation (80%) confirmed the mineralization of isoproturon. Fixed bed baffled reactor studies under solar irradiations using the TiO2 immobilized beads confirmed 85% degradation after 6h. LC-MS studies confirmed the intermediates formation and their subsequent degradation using immobilized system.

  15. A comparative study of microbial communities in four soil slurries capable of RDX degradation using illumina sequencing.

    PubMed

    Jayamani, Indumathy; Cupples, Alison M

    2015-06-01

    The nitramine explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has contaminated many military sites. Recently, attempts to remediate these sites have focused on biostimulation to promote RDX biodegradation. Although many RDX degrading isolates have been obtained in the laboratory, little is known about the potential of microorganisms to degrade this chemical while existing in a soil community. The current study examined and compared the RDX degrading communities in four soil slurries to elucidate the potential of natural systems to degrade this chemical. These soils were selected as they had no previous exposure to RDX, therefore their microbial communities offered an excellent baseline to determine changes following RDX degradation. High throughput sequencing was used to determine which phylotypes experienced an increase in relative abundance following RDX degradation. For this, total genomic DNA was sequenced from (1) the initial soil, (2) soil slurry microcosms following RDX degradation and (3) control soil slurry microcosms without RDX addition. The sequencing data provided valuable information on which phylotypes increased in abundance following RDX degradation compared to control microcosms. The most notable trend was the increase in abundance of Brevundimonas and/or unclassified Bacillaceae 1 in the four soils studied. Although isolates of the family Bacillaceae 1 have previously been linked to RDX degradation, isolates of the genus Brevundimonas have not been previously associated with RDX degradation. Overall, the data suggest these two phylotypes have key roles in RDX degradation in soil communities.

  16. Design of a grating for studying Smith-Purcell radiation and electron acceleration

    SciTech Connect

    Fernow, R.C.

    1989-01-01

    We describe work on the design of a diffraction grating which we intend to use for studying the production of Smith-Purcell radiation and the acceleration of electrons. We have developed computer codes based on the solution of the appropriate Maxwell's equations. A specific grating profile is given which is feasible to construct and which supports enhanced surface accelerating modes. We examine the possibility of using the Smith-Purcell effect to make a beam position monitor. 13 refs., 10 figs., 2 tabs.

  17. [A study of mandibular movement velocity and acceleration in young adults with normal people].

    PubMed

    Lu, P J

    1993-09-01

    The velocity and acceleration of mandibular movements including the border movement, habitual movement and functional movement were studied in 25 young adults by using D-SGG measuring instrument. The results showed that the conception of functional velocity and the maximum velocity of mandibular movement were developed. The physiological and clinical significance of the value of mandibular movement acceleration can be explained by Newton's Second law, F = ma. The author pointed out that in order to keep the necessary masticatory efficiency, the masticatory velocity enjoy the priority in matching with the masticatory force in mastication.

  18. A study on factors affecting the degradation of magnesium and a magnesium-yttrium alloy for biomedical applications.

    PubMed

    Johnson, Ian; Liu, Huinan

    2013-01-01

    Controlling degradation of magnesium or its alloys in physiological saline solutions is essential for their potential applications in clinically viable implants. Rapid degradation of magnesium-based materials reduces the mechanical properties of implants prematurely and severely increases alkalinity of the local environment. Therefore, the objective of this study is to investigate the effects of three interactive factors on magnesium degradation, specifically, the addition of yttrium to form a magnesium-yttrium alloy versus pure magnesium, the metallic versus oxide surfaces, and the presence versus absence of physiological salt ions in the immersion solution. In the immersion solution of phosphate buffered saline (PBS), the magnesium-yttrium alloy with metallic surface degraded the slowest, followed by pure magnesium with metallic or oxide surfaces, and the magnesium-yttrium alloy with oxide surface degraded the fastest. However, in deionized (DI) water, the degradation rate showed a different trend. Specifically, pure magnesium with metallic or oxide surfaces degraded the slowest, followed by the magnesium-yttrium alloy with oxide surface, and the magnesium-yttrium alloy with metallic surface degraded the fastest. Interestingly, only magnesium-yttrium alloy with metallic surface degraded slower in PBS than in DI water, while all the other samples degraded faster in PBS than in DI water. Clearly, the results showed that the alloy composition, presence or absence of surface oxide layer, and presence or absence of physiological salt ions in the immersion solution all influenced the degradation rate and mode. Moreover, these three factors showed statistically significant interactions. This study revealed the complex interrelationships among these factors and their respective contributions to degradation for the first time. The results of this study not only improved our understanding of magnesium degradation in physiological environment, but also presented the key

  19. Accelerating rate calorimetry: A new technique for safety studies in lithium systems

    NASA Technical Reports Server (NTRS)

    Ebner, W. B.

    1982-01-01

    The role of exothermic reactions in battery test modes is discussed. The exothermic reactions are characterized with respect to their time-temperature and time-pressure behavior. Reactions occuring for any major exotherm were examined. The accelerating rate calorimetry methods was developed to study lithium cells susceptibility to thermal runaway reactions following certain abuse modes such as forced discharge into reversal and charging.

  20. An Experiment in ''Less Time, More Options": A Study of Accelerated University Students.

    ERIC Educational Resources Information Center

    Litwin, James L.; And Others

    This study investigated the characteristics and experiences of 59 college students accelerated from their freshman to their junior year. The students showed high academic performance and few social problems, but questions of personal identity remained problematic; the best single predictor of academic success was found to be freshman grade-point…

  1. From Eighth Grade to Selective College in One Jump: Case Studies in Radical Acceleration.

    ERIC Educational Resources Information Center

    Keating, Daniel P.; Stanley, Julian C.

    The paper examines the problem of highly gifted junior high school students who are intellectually ready for college-level study before beginning high school. The term radical accelerates is used to describe gifted students who jump from junior high to college education, bypassing the high school years. Briefly described are two widely known and…

  2. The Study of Two-Dimensional Oscillations Using a Smartphone Acceleration Sensor: Example of Lissajous Curves

    ERIC Educational Resources Information Center

    Tuset-Sanchis, Luis; Castro-Palacio, Juan C.; Gómez-Tejedor, José A.; Manjón, Francisco J.; Monsoriu, Juan A.

    2015-01-01

    A smartphone acceleration sensor is used to study two-dimensional harmonic oscillations. The data recorded by the free android application, Accelerometer Toy, is used to determine the periods of oscillation by graphical analysis. Different patterns of the Lissajous curves resulting from the superposition of harmonic motions are illustrated for…

  3. The Gift of Time: Today's Academic Acceleration Case Study Voices of Experience

    ERIC Educational Resources Information Center

    Scheibel, Susan Riley

    2010-01-01

    The purpose of this qualitative case study was to examine today's academic acceleration from the lived experience and perspectives of two young adults whose education was shortened, thereby allowing them the gift of time. Through personal interviews, parent interviews, and physical artifacts, the researcher gained a complex, holistic understanding…

  4. Aerobic degradation study of three fluoroanilines and microbial community analysis: the effects of increased fluorine substitution.

    PubMed

    Zhao, Zhi-Qing; Tian, Bao-Hu; Zhang, Xuan; Ghulam, Abbas; Zheng, Tu-Cai; Shen, Dong-Sheng

    2015-02-01

    The fate of fluorinated compounds in the environment, especially polyfluorinated aromatics, is a matter of great concern. In this work, 4-Fluoroaniline (4-FA), 2,4-Difluoroanilines (2,4-DFA), and 2,3,4-Trifluoroanilines (2,3,4-TFA), were chosen as the target pollutants to study their biodegradability under aerobic conditions. The required enriched time of the mixed bacterial culture for degrading 4-FA, 2,4-DFA, and 2,3,4-TFA was 26, 51, and 165 days, respectively, which suggested that the longer enrichment time was required with the increase of fluorine substitution. At the initial concentrations of 100-200 mg L(-1), the 4-FA, 2,4-DFA, and 2,3,4-TFA could be degraded completely by the mixed bacterial culture. The maximum specific degradation rates of 4-FA, 2,4-DFA, and 2,3,4-TFA were 22.48 ± 0.55, 15.27 ± 2.04, and 8.84 ± 0.93 mg FA (g VSS h)(-1), respectively. Also, the three FAs enriched cultures showed certain potential of degrading other two FAs. The results from enzyme assay suggested the expression of meta-cleavage pathways during three FAs degradation. The denaturing gradient gel electrophoresis analysis revealed that unique bacterial communities were formed after FAs enrichment and these were principally composed of β-Proteobacteria, Oscillatoriophycideae, δ-Proteobacteria, α-Proteobacteria, Thermales, Xanthomonadales, Deinococci, Flavobacteriia, and Actinobacteridae. The Shannon-Wiener indexes in three FAs enriched culture decreased with the increase of fluorine substitution, indicating the significant effect of fluorine substitution on the microbial diversity. These findings supply important information on the fate of three FAs under aerobic environment, and the bacterial communities in their degradation systems.

  5. A facility for studying irradiation accelerated corrosion in high temperature water

    NASA Astrophysics Data System (ADS)

    Raiman, Stephen S.; Flick, Alexander; Toader, Ovidiu; Wang, Peng; Samad, Nassim A.; Jiao, Zhijie; Was, Gary S.

    2014-08-01

    A facility for the study of irradiation accelerated corrosion in high temperature water using in situ proton irradiation has been developed and validated. A specially designed beamline and flowing-water corrosion cell added to the 1.7 MV tandem accelerator at the Michigan Ion Beam Laboratory provide the capability to study the simultaneous effects of displacement damage and radiolysis on corrosion. A thin sample serves as both a “window” into the corrosion cell through which the proton beam passes completely, and the sample for assessing irradiation accelerated corrosion. The facility was tested by irradiating stainless steel samples at beam current densities between 0.5 and 10 μA/cm2 in 130 °C and 320 °C deaerated water, and 320 °C water with 3 wppm H2. Increases in the conductivity and dissolved oxygen content of the water varied with the proton beam current, suggesting that proton irradiation was accelerating the corrosion of the sample. Conductivity increases were greatest at 320 °C, while DO increases were highest at 130 °C. The addition of 3 wppm H2 suppressed DO below detectable levels. The facility will enable future studies into the effect of irradiation on corrosion in high temperature water with in situ proton irradiation.

  6. Thermal Degradation studies of nitroplasticized estane 5703 utilizing [sup 13] C enriched model polymers.

    SciTech Connect

    Wrobleski, Debra A.; Langlois, D. A.; Orler, E. B.; Schoonover, J. R.; Osborn, J. C.; Small, J. H.

    2002-01-01

    have been foi-mulated into a polymer-rich binder without stabilizer, thennally aged under different enviroimients, and examined using NMR and FTIR spectroscopy to identify degradation products and possible degradation pathways. Results of these preliminary aging studies on unstabilized polymer rich binder are presented herein.

  7. Degradation of colour in beetroot (Beta vulgaris L.): a kinetics study.

    PubMed

    Chandran, Janu; Nisha, P; Singhal, Rekha S; Pandit, Anirudha B

    2014-10-01

    The kinetics of colour (measured as Hunter 'a/b' value) degradation in beetroot puree (Beta vulgaris L.) was studied over a temperature range of 50-120 °C (isothermal process), and also during normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient 'EcoCooker' (non-isothermal heating process). The degradation of visual colour as measured as Hunter 'a/b' value was found to follow a first order kinetics, where the rate constant increased with an increase in the temperature. The temperature dependence of degradation was adequately modeled by Arrhenius equation. A mathematical model has been developed using the kinetic parameters obtained from the isothermal experiments to predict the losses of color in the non-isothermal heating/processing method based on the time-temperature data for each of the methods. The results obtained indicate a colour degradation of similar magnitude in all the three modes of cooking used in the study.

  8. PLK1 and HOTAIR accelerate proteasomal degradation of SUZ12 and ZNF198 during hepatitis B virus-induced liver carcinogenesis

    PubMed Central

    Zhang, Hao; Diab, Ahmed; Fan, Huitao; Mani, Saravana Kumar Kailasam; Hullinger, Ronald; Merle, Philippe; Andrisani, Ourania

    2015-01-01

    Elucidating mechanisms of hepatitis B virus (HBV)-mediated hepatocarcinogenesis is needed to gain insights into the etiology and treatment of liver cancer. Cells where HBV is replicating exhibit increased expression of Plk1 kinase and reduced levels of two transcription repression factors, SUZ12 and ZNF198. SUZ12 is an essential subunit of the transcription repressive complex PRC2. ZNF198 stabilizes the transcription repressive complex composed of LSD1, Co-REST and HDAC1. These two transcription repressive complexes are held together by binding the long noncoding RNA HOTAIR. In this study we linked these regulatory events mechanistically, by showing that Plk1 induces proteasomal degradation of SUZ12 and ZNF198 by site-specific phosphorylation. Plk1-dependent ubiquitination of SUZ12 and ZNF198 was enhanced by expression of HOTAIR, significantly reducing SUZ12 and ZNF198 stability. In cells expressing the HBV X protein (HBx) downregulation of SUZ12 and ZNF198 mediated global changes in histone modifications. In turn, HBx-expressing cells propagated an altered chromatin landscape after cell division, as exemplified by changes in histone modifications of the EpCAM promoter, a target of PRC2 and LSD1/Co-REST/HDAC1 complexes. Notably, liver tumors from X/cmyc bitransgenic mice exhibited downregulation of SUZ12 and ZNF198 along with elevated expression of Plk1, HOTAIR, and EpCAM. Clinically, similar effects were documented in a set of HBV-related liver tumors consistent with the likelihood that downregulation of SUZ12 and ZNF198 leads to epigenetic reprogramming of infected hepatocytes. Since both Plk1 and HOTAIR are elevated in many human cancers, we propose that their combined effects are involved in epigenetic reprogramming associated broadly with oncogenic transformation. PMID:25855382

  9. In vitro study of the proteolytic degradation of Antheraea pernyi silk fibroin.

    PubMed

    Taddei, Paola; Arai, Takayuki; Boschi, Alessandra; Monti, Patrizia; Tsukada, Masuhiro; Freddi, Giuliano

    2006-01-01

    In this study, Antheraea pernyi silk fibroin (Ap-SF) films were incubated with Protease Type XXI from Streptomyces griseus, at 37 degrees C, to investigate the degradation behavior in an in vitro model system. The enzyme-resistant fractions of Ap-SF films and the soluble peptides formed by proteolytic degradation were collected at specified times, from 1 to 17 days, and analyzed by high performance liquid chromatography, differential scanning calorimetry, FT-Raman, and FT-IR spectroscopy. Proteolysis resulted in extensive weight loss and progressive fragmentation of films, especially at long degradation times. A range of soluble peptides was formed by proteolysis. By high performance-size exclusion chromatography it was found that their average molecular weight changed with the time of incubation. The chemical analysis of the enzyme-resistant fraction of Ap-SF films at different times of degradation indicated that the proteolytic attack preferentially occurred in the less ordered Gly rich sequences and that the contribution of the Ala rich crystalline regions to the composition of biodegraded films became progressively larger. Accordingly, DSC and spectroscopic results showed an enhancement of the crystalline character of the biodegraded films. From the behavior of the most important thermal transitions, it was deduced that the alpha-helix domains probably represent the most enzyme-resistant fraction. The in vitro approach used in the present study seems to be a valid tool for studying the rate and mechanism of degradation of Ap-SF films and of other biopolymers of potential biomedical utility.

  10. Experimental study of X-band dielectric-loaded accelerating structures

    NASA Astrophysics Data System (ADS)

    Jing, Chunguang

    A joint Argonne National Laboratory (ANL)/Naval Research Laboratory (NRL) program is under way to investigate X-band dielectric-loaded accelerating (DLA) structures, using high-power 11.424GHz radiation from the NRL Magnicon facility. As an advanced accelerator concepts, the dielectric-loaded accelerator offers the potential for a simple, inexpensive alternative to high-gradient RF linear accelerators. In this thesis, a comprehensive account of X-band DLA structure design, including theoretical calculation, numerical simulation, fabrication and testing, is presented in detail. Two types of loading dielectrics, alumina and MgxCa1-xTiO 3 (MCT), are investigated. For alumina (with dielectric constant 9.4), no RF breakdown has been observed up to 5 MW of drive power (equivalent to 8MV/m accelerating gradient) in the high power RF testing at NRL, but multipactor was observed to absorb a large fraction of the incident microwave power. Experimental results on suppression of multipactor using TiN coating on the inner surface of the dielectric are also reported. For MCT (with dielectric constant 20), although we did not observe dielectric breakdown in the structures, breakdown did occur at the ceramic joint, where the electric field is greatly enhanced (estimated to be around 100MV/m) due to the micro-scale vacuum gap. In addition, the MCT structure showed significantly less multipactor for the same level of RF field. The thesis also introduced a new design, a multilayered dielectric-loaded accelerating structure, to improve the performance over the conventional one layer DLA structure. Results of analysis for the case of a four layered DLA structure indicate a large reduction of RF power attenuation and an increase of shunt impedance for the structure. Beyond the main contents, the appendices of the thesis present two individual projects prompted by the experimental study of the dielectric-loaded accelerating structure. Appendix A shows a resonant loop technique that can

  11. High-resolution photoelectron spectroscopy study of degradation of rubber-to-brass adhesion by thermal aging

    NASA Astrophysics Data System (ADS)

    Ozawa, Kenichi; Kakubo, Takashi; Shimizu, Katsunori; Amino, Naoya; Mase, Kazuhiko; Izumi, Yudai; Muro, Takayuki; Komatsu, Takayuki

    2013-03-01

    High resolution photoelectron spectroscopy is utilized to investigate degradation of rubber-to-brass adhesion by thermal aging. Special attention is given to the role of water in the environment surrounding brass-embedded rubber so that three aging processes are employed; hydrothermal aging, moist-heat aging and dry-heat aging. All aging processes lead to the decrease in the amount of S at the rubber/brass interface. This desulfurization accompanies the decrease in the ratio of CuxS (x ≃ 2) to CuS, i.e., CuxS/CuS, and the increase in the amount of ZnO, Zn(OH)2 and ZnS, all of which are key factors for degradation of adhesion. The changes in the chemical composition are enhanced by water in the surrounding environment during the aging treatments, indicating that the water molecules accelerate degradation of rubber-to-brass adhesion.

  12. 3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies

    SciTech Connect

    Shu, Anthony; Horanyi, Mihaly; Kempf, Sascha; Thomas, Evan; Collette, Andrew; Drake, Keith; Northway, Paige; Gruen, Eberhard; Mocker, Anna; Munsat, Tobin; Srama, Ralf; and others

    2012-07-15

    A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Instituet fuer Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10{sup -7} torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10{sup -10} torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

  13. 3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies

    NASA Astrophysics Data System (ADS)

    Shu, Anthony; Collette, Andrew; Drake, Keith; Grün, Eberhard; Horányi, Mihály; Kempf, Sascha; Mocker, Anna; Munsat, Tobin; Northway, Paige; Srama, Ralf; Sternovsky, Zoltán; Thomas, Evan

    2012-07-01

    A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10-7 torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10-10 torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

  14. 3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies.

    PubMed

    Shu, Anthony; Collette, Andrew; Drake, Keith; Grün, Eberhard; Horányi, Mihály; Kempf, Sascha; Mocker, Anna; Munsat, Tobin; Northway, Paige; Srama, Ralf; Sternovsky, Zoltán; Thomas, Evan

    2012-07-01

    A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10(-7) torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10(-10) torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

  15. Oxidative degradation of triazine- and sulfonylurea-based herbicides using Fe(VI): The case study of atrazine and iodosulfuron with kinetics and degradation products

    EPA Science Inventory

    The occurrence of common herbicides (Atrazine, ATZ and Iodosufuron, IDS), in waters presents potential risk to human and ecological health. The oxidative degradation of ATZ and IDS by ferrate(VI) (FeVIO42-, Fe(VI)) is studied at different pH levels where kinetically observed se...

  16. Accelerator research studies. Technical progress report, June 1, 1991--May 31, 1992

    SciTech Connect

    Not Available

    1992-02-01

    The Accelerator Research Studies program at the University of Maryland, sponsored by the Department of Energy under grant number DE-FG05-91ER40642, is currently in the first year of a three-year funding cycle. The program consists of the following three tasks: TASK A, Study of Transport and Longitudinal Compression of Intense, High-Brightness Beams, TASK B, Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams; TASK C, Study of a Gyroklystron High-power Microwave Source for Linear Colliders. In this report we document the progress that has been made during the past year for each of the three tasks.

  17. Preparation and degradation study of photocurable oligolactide-HA composite: a potential resin for stereolithography application.

    PubMed

    Tanodekaew, Siriporn; Channasanon, Somruethai; Uppanan, Paweena

    2014-04-01

    The merging of stereolithography (SLA) technology to the medical field certainly benefits the manufacturing of parts, especially those patient-specific for the clinical use. This technique, however, has hardly been exploited medically due to a limited number of biodegradable resins for SLA processing. To extend application of SLA in the biomedical field, photocurable oligolactide resins were developed and examined for biodegradation and biocompatibility. The degradation was studied by monitoring the changes in weight loss, and thermal and mechanical properties of the photocured specimens in phosphate buffered saline (PBS) at 37°C. The results demonstrated that a resin composition played an important role in degradation, and the retarded degradation rate was observed for the highly crosslinked resin containing hydroxyapatite (HA). The less cytotoxic sample was also obtained from the resin with higher content of HA. These findings suggest the possible use of the developed photocurable oligolactide resins in SLA manufacturing of biodegradable implants, where their degradation behaviors can be designed by varying the resin composition.

  18. Space Station water degradation study covering the first 24 months of exposure

    NASA Technical Reports Server (NTRS)

    Mcright, P. S.; Roman, M. C.

    1995-01-01

    This report describes the MSFC space station water degradation study (WDS) and presents interim results from the first 24 months of testing. The WDS simulates the stagnant storage of water in distribution lines before the activation of the space station's water processor by storing processed water at ambient temperature in valved sections of 1-in stainless steel and titanium tube. The WDS seeks to determine whether the water quality will degrade unacceptably and whether microbial growth will proceed to an unmanageable extent during extended stagnation. During the first 24 months, significant changes have occurred. Although iodine, which is used as a biocide, was nearly depleted within the first 6 months of testing, microbial growth has been minimal. This report describes the decrease in iodine concentration and the results of microbial and biofilm analyses. Increases in total organic carbon, iodide, chloride, nickel, iron, and chromium concentrations are presented and discussed. The observed increase in conductivity and the decreases in pH and turbidity are also presented. The authors conclude that, with proper preparation, potable water can be stored under stagnant conditions without unmanageable degradation in water quality; a flushing operation and subsequent processing of the degraded water should render the water system ready for use.

  19. Influence of different beverages on the force degradation of intermaxillary elastics: an in vitro study

    PubMed Central

    LEÃO FILHO, Jorge César Borges; GALLO, Daphine Beatriz; SANTANA, Regis Meller; GUARIZA-FILHO, Odilon; CAMARGO, Elisa Souza; TANAKA, Orlando Motohiro

    2013-01-01

    Objective: The aim of this study was to evaluate in vitro the effects of frequently ingested beverages on force degradation of intermaxillary elastics. Material and Methods: One hundred and eighty 1/4-inch intermaxillary elastics (TP Orthodontics) were immersed into six different beverages: (1) Coca-Cola®; (2) Beer; (3) Orange juice; (4) Red wine; (5) Coffee and (6) artificial saliva (control). The period of immersion was 15 min for the first and second cycles and 30 min for the third to fifth cycles. Tensile forces were read in a tensile testing machine before and after the five immersion cycles. One-way repeated measures ANOVA was used to identify significant differences. Results: Force degradation was seen in all evaluated groups and at all observation periods (p<0.05). A greater degree of degradation was present at the initial periods, decreasing gradually over time. However, no statistically significant differences were seen among groups at the same periods, showing that different groups behaved similarly. Conclusion: The chemical nature of the evaluated beverages was not able to influence the degree of force degradation at all observation periods. PMID:23739862

  20. FT-Raman spectroscopy study of organic matrix degradation in nanofilled resin composite.

    PubMed

    Soares, Luís Eduardo Silva; Nahórny, Sídnei; Martin, Airton Abrahão

    2013-04-01

    This in vitro study evaluated the effect of light curing unit (LCU) type, mouthwashes, and soft drink on chemical degradation of a nanofilled resin composite. Samples (80) were divided into eight groups: halogen LCU, HS--saliva (control); HPT--Pepsi Twist®; HLC--Listerine®; HCP--Colgate Plax®; LED LCU, LS--saliva (control); LPT--Pepsi Twist®; LLC--Listerine®; LCP--Colgate Plax®. The degree of conversion analysis and the measure of the peak area at 2,930 cm-1 (organic matrix) of resin composite were done by Fourier-transform Raman spectroscopy (baseline, after 7 and 14 days). The data were subjected to multifactor analysis of variance (ANOVA) at a 95% confidence followed by Tukey's HSD post-hoc test. The DC ranged from 58.0% (Halogen) to 59.3% (LED) without significance. Differences in the peak area between LCUs were found after 7 days of storage in S and PT. A marked increase in the peak intensity of HLC and LLC groups was found. The soft-start light-activation may influence the chemical degradation of organic matrix in resin composite. Ethanol contained in Listerine® Cool Mint mouthwash had the most significant degradation effect. Raman spectroscopy is shown to be a useful tool to investigate resin composite degradation. PMID:23388411

  1. Integrative computational approach for genome-based study of microbial lipid-degrading enzymes.

    PubMed

    Vorapreeda, Tayvich; Thammarongtham, Chinae; Laoteng, Kobkul

    2016-07-01

    Lipid-degrading or lipolytic enzymes have gained enormous attention in academic and industrial sectors. Several efforts are underway to discover new lipase enzymes from a variety of microorganisms with particular catalytic properties to be used for extensive applications. In addition, various tools and strategies have been implemented to unravel the functional relevance of the versatile lipid-degrading enzymes for special purposes. This review highlights the study of microbial lipid-degrading enzymes through an integrative computational approach. The identification of putative lipase genes from microbial genomes and metagenomic libraries using homology-based mining is discussed, with an emphasis on sequence analysis of conserved motifs and enzyme topology. Molecular modelling of three-dimensional structure on the basis of sequence similarity is shown to be a potential approach for exploring the structural and functional relationships of candidate lipase enzymes. The perspectives on a discriminative framework of cutting-edge tools and technologies, including bioinformatics, computational biology, functional genomics and functional proteomics, intended to facilitate rapid progress in understanding lipolysis mechanism and to discover novel lipid-degrading enzymes of microorganisms are discussed. PMID:27263017

  2. Structural and degradation studies of a biocompatible Zn-L-tartrate metal-organic framework

    NASA Astrophysics Data System (ADS)

    Palǒić, Ana; Puškarić, Andreas; Mazaj, Matjaž; Žunkoviǒ, Emanuela; Logar, Nataša Zabukovec; Bronić, Josip

    2015-05-01

    New anhydrous Zn-L-tratrate was synthesized under hydrothermal conditions. Crystal structure which was solved by powder X-ray diffraction data from monoclinic unit cell (I2, a=11.7557(1), b=9.0319(1), c=5.0750(1), β=91.920(1)) consists of the three-dimensional framework where each Zn atom coordinates four tartrate ligands in distorted octahedral geometry. Due to its biocompatible components, the degradation of material was studied in aqueous media under different pH values (pH=1-7) and in the simulated body fluid (pH=7.4) performed by the measurement of the released Zn2+ concentrations at thermostatic conditions (37 °C). The results showed that under acidic conditions approximately 60% of Zn2+ is released from the investigated material after 6 h of degradation process. With the increase of the solution's pH, the rate of degradation gradually decreases. XRD and SEM analyses indicate that in aqueous media the compound slowly disintegrates and does not undergo hydrolysis process regardless of pH. Biocompatibility of the compound and its controllable rate of degradation even in acid conditions open its potential use in the fields of bio-applications.

  3. FT-Raman spectroscopy study of organic matrix degradation in nanofilled resin composite.

    PubMed

    Soares, Luís Eduardo Silva; Nahórny, Sídnei; Martin, Airton Abrahão

    2013-04-01

    This in vitro study evaluated the effect of light curing unit (LCU) type, mouthwashes, and soft drink on chemical degradation of a nanofilled resin composite. Samples (80) were divided into eight groups: halogen LCU, HS--saliva (control); HPT--Pepsi Twist®; HLC--Listerine®; HCP--Colgate Plax®; LED LCU, LS--saliva (control); LPT--Pepsi Twist®; LLC--Listerine®; LCP--Colgate Plax®. The degree of conversion analysis and the measure of the peak area at 2,930 cm-1 (organic matrix) of resin composite were done by Fourier-transform Raman spectroscopy (baseline, after 7 and 14 days). The data were subjected to multifactor analysis of variance (ANOVA) at a 95% confidence followed by Tukey's HSD post-hoc test. The DC ranged from 58.0% (Halogen) to 59.3% (LED) without significance. Differences in the peak area between LCUs were found after 7 days of storage in S and PT. A marked increase in the peak intensity of HLC and LLC groups was found. The soft-start light-activation may influence the chemical degradation of organic matrix in resin composite. Ethanol contained in Listerine® Cool Mint mouthwash had the most significant degradation effect. Raman spectroscopy is shown to be a useful tool to investigate resin composite degradation.

  4. Micro- and nano-scale characterization to study the thermal degradation of cement-based materials

    SciTech Connect

    Lim, Seungmin Mondal, Paramita

    2014-06-01

    The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis. Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste. - Highlights: • The thermal degradation of hydration products of cement is characterized at micro- and nano-scale using scanning electron microscopy (SEM) and atomic force microscopy (AFM). • The interface between unhydrated cement particles and the paste matrix is considered the origin of micro-cracks. • When cement paste is exposed to temperatures above 300 ºC, the nano-structure of C-S-H becomes a more loosely packed globular structure, which could be indicative of C-S-H shrinkage.

  5. Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies.

    PubMed

    Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus; Hansen, Steen Honoré

    2015-05-15

    Microwave ovens have been used extensively in organic synthesis in order to accelerate reaction rates. Here, a set up comprising a microwave oven combined with silicon carbide (SiC) plates for the controlled microwave heating of model formulations has been applied in order to investigate, if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. In the accelerated stability studies, a design of experiments (DoE) approach was applied in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating leading to temperatures between 150°C and 180°C as compared to accelerated stability studies performed at 40°C and 80°C using a conventional oven. Ranking of the reactivity of the excipients could be made in the DoE studies performed at 150-180°C, which was representative for the ranking obtained after storage at 40°C and 80°C. It was possible to reduce the time needed for drug-excipient compatibility testing of the three model formulations from weeks to less than an hour in the three case studies. The microwave oven is therefore considered to be an interesting alternative to conventional thermal techniques for the investigation of drug-excipient interactions during preformulation.

  6. Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies.

    PubMed

    Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus; Hansen, Steen Honoré

    2015-05-15

    Microwave ovens have been used extensively in organic synthesis in order to accelerate reaction rates. Here, a set up comprising a microwave oven combined with silicon carbide (SiC) plates for the controlled microwave heating of model formulations has been applied in order to investigate, if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. In the accelerated stability studies, a design of experiments (DoE) approach was applied in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating leading to temperatures between 150°C and 180°C as compared to accelerated stability studies performed at 40°C and 80°C using a conventional oven. Ranking of the reactivity of the excipients could be made in the DoE studies performed at 150-180°C, which was representative for the ranking obtained after storage at 40°C and 80°C. It was possible to reduce the time needed for drug-excipient compatibility testing of the three model formulations from weeks to less than an hour in the three case studies. The microwave oven is therefore considered to be an interesting alternative to conventional thermal techniques for the investigation of drug-excipient interactions during preformulation. PMID:25746946

  7. Study of beamlet deflection and its compensations in a MeV accelerator

    SciTech Connect

    Kashiwagi, Mieko; Inoue, Takashi; Taniguchi, Masaki; Umeda, Naotaka; Dairaku, Masayuki; Takemoto, Jumpei; Tobari, Hiroyuki; Tsuchida, Kazuki; Watanabe, Kazuhiro; Yamanaka, Haruhiko; Sakamoto, Keishi; Grisham, Larry R.

    2011-09-26

    In a five stage multi-aperture and multi-grid (MAMuG) accelerator in JAEA, beam acceleration tests are in progress toward 1 MeV, 200 A/m{sup 2} H{sup -} ion beams for ITER. The 1 MV voltage holding has been successfully demonstrated for 4,000 s with the accelerator of expanded gap length that lowered local electric field concentrations. This led to increase of the beam energy up to 900 keV-level. However, it was found that beamlets were deflected more in long gaps and direct interceptions of the deflected beamlet caused breakdowns. The beamlet deflection and its compensation methods were studied utilizing a three-dimensional multi beamlet analysis. The analysis showed that the 1 MeV beam can be compensated by a combination of the aperture offset of 0.8 mm applied in the electron suppression (ESG) and the metal bar called a field shaping plate with a thickness of 1 mm attached beneath the ESG. The paper reports these compensation methods and analytical predictions, with experimental results of the MAMuG accelerator in which those compensation techniques have been applied.

  8. Simulation studies of acceleration of heavy ions and their elemental compositions; IFSR--755

    SciTech Connect

    Toida, Mieko; Ohsawa, Yukiharu

    1996-07-01

    By using a one-dimensional, electromagnetic particle simulation code with full ion and electron dynamics, we have studied the acceleration of heavy ions by a nonlinear magnetosonic wave in a multi-ion-species plasma. First, we describe the mechanism of heavy ion acceleration by magnetosonic waves. We then investigate this by particle simulations. The simulation plasma contains four ion species: H, He, O, and Fe. The number density of He is taken to be 10% of that of H, and those of O and Fe are much lower. Simulations confirm that, as in a single-ion-species plasma, some of the hydrogens can be accelerated by the longitudinal electric field formed in the wave. Furthermore, they show that magnetosonic waves can accelerate all the particles of all the heavy species (He, O, and Fe) by a different mechanism, i.e., by the transverse electric field. The maximum speeds of the heavy species are about the same, of the order of the wave propagation speed. These are in good agreement with theoretical prediction. These results indicate that, if high-energy ions are produced in the solar corona through these mechanisms, the elemental compositions of these heavy ions can be similar to that of the background plasma, i.e., the corona.

  9. VERITAS observations of supernova remnants for studies of cosmic ray acceleration

    NASA Astrophysics Data System (ADS)

    Park, Nahee

    Supernova remnants (SNRs) have been suggested as the main sites for acceleration of cosmic rays (CRs) with energies up to the knee region ( 10(15) eV). Gamma-ray emission from SNRs can provide a unique window to observe the cosmic ray acceleration and to test existing acceleration models in these objects. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an array of atmospheric Cherenkov telescopes that measures gamma rays with energies higher than 100 GeV. Located in Arizona, USA, VERITAS has observed several SNRs in the northern hemisphere since the beginning of operations in 2007. These include two young SNRs of different types (Cassiopeia A and Tycho), as well as middle- to old-aged remnants with nearby target material such as molecular clouds. Gamma-ray data from different types of SNRs in different evolutionary stages are important to study SNRs as CR accelerators. Here we present a summary of VERITAS results on Galactic SNRs including Tycho, and discuss what these observations have taught us.

  10. Fluorescence intensity of resin composites and dental tissues before and after accelerated aging: a comparative study.

    PubMed

    Takahashi, Marcos Kenzo; Vieira, Sergio; Rached, Rodrigo Nunes; de Almeida, Janaina Bertoncelo; Aguiar, Marcelo; de Souza, Evelise Machado

    2008-01-01

    This study quantitatively evaluated the fluorescence intensity of resin composites with different opacities and translucencies and determined changes in fluorescence after accelerated aging, using human enamel and dentin as controls. Six microhybrid and nanofilled composites, each in three different shades, were tested. Ten sound human incisors were used to obtain enamel and dentin specimens separately. Fluorescence measurements were obtained with a fluorescence spectrophotometer before (baseline) and after accelerated aging at 150 kJ energy for 120 hours. One-way analysis of variance (ANOVA) and Games-Howell multiple comparison tests were performed at a significance level of 0.05. Student's t-test was also used for comparison before and after aging. At baseline, there was no statistically significant difference (p>0.05) between the fluorescence intensity of dentin and any of the shades of Charisma or Opallis, Esthet-X dentin shade or Vit-l-escence enamel, or the translucent shades. After accelerated aging, all shades of the 4 Seasons, enamel and the translucent shades of Esthet-X had fluorescence intensities statistically similar to that of aged dentin (p>0.05). A significant reduction in fluorescence after aging (p<0.05) was observed for all the materials, except for human enamel and translucent Filtek Supreme XT. Accelerated aging reduced fluorescence in most of the composites evaluated.

  11. Alternative methods for degradation studies by alpha radiolysis: tributyl phosphate and CMPO

    SciTech Connect

    Pearson, J.; Nilsson, M.; Miller, G.E.

    2013-07-01

    Solvent extraction separation processes used in the recycling of used nuclear fuel are susceptible to radiolytic damage from radioactive isotopes present in used fuel. Studying the respective effects on matter of both low linear energy transfer (LET) radiation such as gamma radiation and high LET such as alpha radiation will allow for accurate prediction and modeling of process performance losses with respect to dose. The effects of gamma radiation on solvent extraction ligands have been more extensively studied than the effects of alpha radiation due to the inherent difficulty in producing a sufficient and confluent dose of alpha particles within a sample without leaving the sample contaminated with long lived radioactive isotopes. We have developed a method for studying the effects of high LET radiation in situ via {sup 10}B activation and the high LET particles that result from the {sup 10}B(n,a){sup 7}Li reaction which follows. In this study we applied this method to organic solutions of tributyl phosphate (TBP) and CMPO (compound octylphenyl-N, N-diisobutyl-carbamoyl methyl phosphine oxide) representing the PUREX and TRUEX processes respectively. Rates of degradation of TBP and CMPO and their respective degradation products in the presence of both high and low LET radiation are presented and compared to values reported in the literature. Preliminary data appears to show decreased degradation of CMPO in the presence of an aqueous acidic phase, which agrees with other studies performed on TBP solutions. (authors)

  12. Accelerating the life of transistors

    NASA Astrophysics Data System (ADS)

    Haochun, Qi; Changzhi, Lü; Xiaoling, Zhang; Xuesong, Xie

    2013-06-01

    Choosing small and medium power switching transistors of the NPN type in a 3DK set as the study object, the test of accelerating life is conducted in constant temperature and humidity, and then the data are statistically analyzed with software developed by ourselves. According to degradations of such sensitive parameters as the reverse leakage current of transistors, the lifetime order of transistors is about more than 104 at 100 °C and 100% relative humidity (RH) conditions. By corrosion fracture of transistor outer leads and other failure modes, with the failure truncated testing, the average lifetime rank of transistors in different distributions is extrapolated about 103. Failure mechanism analyses of degradation of electrical parameters, outer lead fracture and other reasons that affect transistor lifetime are conducted. The findings show that the impact of external stress of outer leads on transistor reliability is more serious than that of parameter degradation.

  13. Magneto-hydrodynamics simulation study of deflagration mode in co-axial plasma accelerators

    SciTech Connect

    Sitaraman, Hariswaran; Raja, Laxminarayan L.

    2014-01-15

    Experimental studies by Poehlmann et al. [Phys. Plasmas 17(12), 123508 (2010)] on a coaxial electrode magnetohydrodynamic (MHD) plasma accelerator have revealed two modes of operation. A deflagration or stationary mode is observed for lower power settings, while higher input power leads to a detonation or snowplow mode. A numerical modeling study of a coaxial plasma accelerator using the non-ideal MHD equations is presented. The effect of plasma conductivity on the axial distribution of radial current is studied and found to agree well with experiments. Lower conductivities lead to the formation of a high current density, stationary region close to the inlet/breech, which is a characteristic of the deflagration mode, while a propagating current sheet like feature is observed at higher conductivities, similar to the detonation mode. Results confirm that plasma resistivity, which determines magnetic field diffusion effects, is fundamentally responsible for the two modes.

  14. Laser Wakefield Acceleration: Structural and Dynamic Studies. Final Technical Report ER40954

    SciTech Connect

    Downer, Michael C.

    2014-04-30

    Particle accelerators enable scientists to study the fundamental structure of the universe, but have become the largest and most expensive of scientific instruments. In this project, we advanced the science and technology of laser-plasma accelerators, which are thousands of times smaller and less expensive than their conventional counterparts. In a laser-plasma accelerator, a powerful laser pulse exerts light pressure on an ionized gas, or plasma, thereby driving an electron density wave, which resembles the wake behind a boat. Electrostatic fields within this plasma wake reach tens of billions of volts per meter, fields far stronger than ordinary non-plasma matter (such as the matter that a conventional accelerator is made of) can withstand. Under the right conditions, stray electrons from the surrounding plasma become trapped within these “wake-fields”, surf them, and acquire energy much faster than is possible in a conventional accelerator. Laser-plasma accelerators thus might herald a new generation of compact, low-cost accelerators for future particle physics, x-ray and medical research. In this project, we made two major advances in the science of laser-plasma accelerators. The first of these was to accelerate electrons beyond 1 gigaelectronvolt (1 GeV) for the first time. In experimental results reported in Nature Communications in 2013, about 1 billion electrons were captured from a tenuous plasma (about 1/100 of atmosphere density) and accelerated to 2 GeV within about one inch, while maintaining less than 5% energy spread, and spreading out less than ½ milliradian (i.e. ½ millimeter per meter of travel). Low energy spread and high beam collimation are important for applications of accelerators as coherent x-ray sources or particle colliders. This advance was made possible by exploiting unique properties of the Texas Petawatt Laser, a powerful laser at the University of Texas at Austin that produces pulses of 150 femtoseconds (1 femtosecond is 10

  15. [Study on apparent kinetics of photocatalytic oxidation degradation Rhodamine B by photo-Fenton reaction].

    PubMed

    Li, Hong; Zheng, Huai-Li; Li, Xiao-Hong; Xie, Li-Guo; Tang, Xue

    2008-11-01

    The Fenton process, mixed by hydrogen peroxide and iron salts with highly oxidative effect, is recognized as one of powerful advanced oxidation technologies available and can be used to destroy a variety of persistent organic pollutants. The oxidation power of Fenton reagent is due to the generation of hydroxyl radical (* OH) during the iron catalysed decomposition of hydrogen peroxide in acid medium. The hydroxyl radical with a high oxidation potential (2.8 eV) attacks and completely destroys the pollutants in Fenton process. The degradation of pollutants can be considerably improved by using sunlight radiation, which is due to the generation of additional hydroxyl radicals. This photo-Fenton process had been effectively used to degrade the pollutants. In this paper, the definite quantity of Fenton reagent was added in the definite concentration of Rhodamine B solution. The degradation reaction was carried out at pH 3.5 under natural sunlight. The factors influencing on photocatalytic oxidation degradation rate of Rhodamine B were studied following: the initial concentration of Rhodamine B, initial concentrateions of Fe2+ and H2O2. The orders of degradation reaction were obtained by solving exponential kinetics equations of curve fitting, thereby gaining the kinetic parameters and reaction dynamics equation of the reaction system. The research contents included mainly: the UV-Vis spectra of Rhodamine B solution, the concentration-absorbency work curve of Rhodamine B solution, the analysis of the reaction system at various initial Rhodamine B concentrations, the analysis of the reaction system at various initial Fe2+ concentrateions, the analysis of the reaction system at various initial H2O2 concentrations, and the calculation of the apparent kinetics parameters in reaction dynamics equation. The reaction dynamics equation from experiments was constructed: V = 5 x 10(-9) P1.28 F0.366 E0.920, and overall reaction order was 2.57.

  16. Photosensitized degradation of Irgarol 1051 in water.

    PubMed

    Okamura, Hideo; Sugiyama, Yuko

    2004-11-01

    Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine) is a herbicide analogue that is added to antifouling agents used on ships. Our former study on its degradation in sunlight suggested that unknown photosensitizers in natural waters accelerated the photodegradation to the degradation product, M1. In this study, the photodegradation of Irgarol in water was investigated in the presence of some photosensitizers. Test water containing Irgarol or M1, with or without photosensitizers, was irradiated with light from a UV-A fluorescent lamp for 48h. The concentrations of Irgarol and M1 in the test water were determined by HPLC after solid-phase extraction. M1 was more stable than Irgarol when irradiated in the presence of photosensitizers such as acetone, benzophenone, tryptophan, and rose bengal. Hydrogen peroxide (HP) accelerated the photodegradation of Irgarol, and the product M1 was degraded in the presence of more than 100mgl(-1) HP after 10h. Natural humic substances (NHS) also accelerated the photodegradation of Irgarol, but in this case, the product M1 persisted even when Irgarol was completely degraded. Photosensitized degradation of Irgarol by NHS may result in the accumulation of M1 in aquatic environments.

  17. Quantitative analysis of driving factors of grassland degradation: a case study in Xilin River Basin, Inner Mongolia.

    PubMed

    Xie, Yichun; Sha, Zongyao

    2012-01-01

    Current literature suggests that grassland degradation occurs in areas with poor soil conditions or noticeable environmental changes and is often a result of overgrazing or human disturbances. However, these views are questioned in our analyses. Based on the analysis of satellite vegetation maps from 1984, 1998, and 2004 for the Xilin River Basin, Inner Mongolia, China, and binary logistic regression (BLR) analysis, we observe the following: (1) grassland degradation is positively correlated with the growth density of climax communities; (2) our findings do not support a common notion that a decrease of biological productivity is a direct indicator of grassland degradation; (3) a causal relationship between grazing intensity and grassland degradation was not found; (4) degradation severity increased steadily towards roads but showed different trends near human settlements. This study found complex relationships between vegetation degradation and various microhabitat conditions, for example, elevation, slope, aspect, and proximity to water. PMID:22619613

  18. Quantitative analysis of driving factors of grassland degradation: a case study in Xilin River Basin, Inner Mongolia.

    PubMed

    Xie, Yichun; Sha, Zongyao

    2012-01-01

    Current literature suggests that grassland degradation occurs in areas with poor soil conditions or noticeable environmental changes and is often a result of overgrazing or human disturbances. However, these views are questioned in our analyses. Based on the analysis of satellite vegetation maps from 1984, 1998, and 2004 for the Xilin River Basin, Inner Mongolia, China, and binary logistic regression (BLR) analysis, we observe the following: (1) grassland degradation is positively correlated with the growth density of climax communities; (2) our findings do not support a common notion that a decrease of biological productivity is a direct indicator of grassland degradation; (3) a causal relationship between grazing intensity and grassland degradation was not found; (4) degradation severity increased steadily towards roads but showed different trends near human settlements. This study found complex relationships between vegetation degradation and various microhabitat conditions, for example, elevation, slope, aspect, and proximity to water.

  19. Quantitative Analysis of Driving Factors of Grassland Degradation: A Case Study in Xilin River Basin, Inner Mongolia

    PubMed Central

    Xie, Yichun; Sha, Zongyao

    2012-01-01

    Current literature suggests that grassland degradation occurs in areas with poor soil conditions or noticeable environmental changes and is often a result of overgrazing or human disturbances. However, these views are questioned in our analyses. Based on the analysis of satellite vegetation maps from 1984, 1998, and 2004 for the Xilin River Basin, Inner Mongolia, China, and binary logistic regression (BLR) analysis, we observe the following: (1) grassland degradation is positively correlated with the growth density of climax communities; (2) our findings do not support a common notion that a decrease of biological productivity is a direct indicator of grassland degradation; (3) a causal relationship between grazing intensity and grassland degradation was not found; (4) degradation severity increased steadily towards roads but showed different trends near human settlements. This study found complex relationships between vegetation degradation and various microhabitat conditions, for example, elevation, slope, aspect, and proximity to water. PMID:22619613

  20. Rheological and kinetic study of the ultrasonic degradation of locust bean gum in aqueous saline and salt-free solutions.

    PubMed

    Li, Ruoshi; Feke, Donald L

    2015-11-01

    The ultrasonic degradation of locust bean gum (LBG) in aqueous solutions has been studied at 25°C for ultrasonication times up to 120 min. Although LBG is not a polyelectrolyte, the degradation extent and kinetics were found to be somewhat sensitive to the ionic conditions in solution, and this is attributed to changes in molecular conformation that can occur in different salt environments. Ultrasonic degradation was tracked by rheological measurements that lead to the determination of intrinsic viscosity for the LBG molecules. A kinetic model was also developed and successfully applied to characterize and predict the degradation results.

  1. Rheological and kinetic study of the ultrasonic degradation of locust bean gum in aqueous saline and salt-free solutions.

    PubMed

    Li, Ruoshi; Feke, Donald L

    2015-11-01

    The ultrasonic degradation of locust bean gum (LBG) in aqueous solutions has been studied at 25°C for ultrasonication times up to 120 min. Although LBG is not a polyelectrolyte, the degradation extent and kinetics were found to be somewhat sensitive to the ionic conditions in solution, and this is attributed to changes in molecular conformation that can occur in different salt environments. Ultrasonic degradation was tracked by rheological measurements that lead to the determination of intrinsic viscosity for the LBG molecules. A kinetic model was also developed and successfully applied to characterize and predict the degradation results. PMID:26186852

  2. The influence of combined alignments on lateral acceleration on mountainous freeways: a driving simulator study.

    PubMed

    Wang, Xuesong; Wang, Ting; Tarko, Andrew; Tremont, Paul J

    2015-03-01

    Combined horizontal and vertical alignments are frequently used in mountainous freeways in China; however, design guidelines that consider the safety impact of combined alignments are not currently available. Past field studies have provided some data on the relationship between road alignment and safety, but the effects of differing combined alignments on either lateral acceleration or safety have not systematically examined. The primary reason for this void in past research is that most of the prior studies used observational methods that did not permit control of the key variables. A controlled parametric study is needed that examines lateral acceleration as drivers adjust their speeds across a range of combined horizontal and vertical alignments. Such a study was conducted in Tongji University's eight-degree-of-freedom driving simulator by replicating the full range of combined alignments used on a mountainous freeway in China. Multiple linear regression models were developed to estimate the effects of the combined alignments on lateral acceleration. Based on these models, domains were calculated to illustrate the results and to assist engineers to design safer mountainous freeways.

  3. Design studies and commissioning plans for plasma acceleration research station experimental program

    SciTech Connect

    Mete, O.; Xia, G.; Hanahoe, K.; Dover, M.; Wigram, M.; Wright, J.; Zhang, J.; Smith, J.

    2015-10-15

    Plasma acceleration research station is an electron beam driven plasma wakefield acceleration test stand proposed for CLARA facility in Daresbury Laboratory. In this paper, the interaction between the electron beam and the plasma is numerically characterised via 2D numerical studies by using VSIM code. The wakefields induced by a single bunch travelling through the plasma were found to vary from 200 MV/m to 3 GV/m for a range of bunch length, bunch radius, and plasma densities. Energy gain for the particles populating the bunch tail through the wakefields driven by the head of the bunch was demonstrated. After determining the achievable field for various beams and plasma configurations, a reference setting was determined for further studies. Considering this reference setting, the beam quality studies were performed for a two-bunch acceleration case. The maximum energy gain as well as the energy spread mitigation by benefiting from the beam loading was investigated by positioning the witness and driver bunches with respect to each other. Emittance growth mechanisms were studied considering the beam-plasma and beam-wakefield interactions. Eventually, regarding the findings, the initial commissioning plans and the aims for the later stages were summarised.

  4. STUDIES OF A FREE ELECTRON LASER DRIVEN BY A LASER-PLASMA ACCELERATOR

    SciTech Connect

    Montgomery, A.; Schroeder, C.; Fawley, W.

    2008-01-01

    A free electron laser (FEL) uses an undulator, a set of alternating magnets producing a periodic magnetic fi eld, to stimulate emission of coherent radiation from a relativistic electron beam. The Lasers, Optical Accelerator Systems Integrated Studies (LOASIS) group at Lawrence Berkeley National Laboratory (LBNL) will use an innovative laserplasma wakefi eld accelerator to produce an electron beam to drive a proposed FEL. In order to optimize the FEL performance, the dependence on electron beam and undulator parameters must be understood. Numerical modeling of the FEL using the simulation code GINGER predicts the experimental results for given input parameters. Among the parameters studied were electron beam energy spread, emittance, and mismatch with the undulator focusing. Vacuum-chamber wakefi elds were also simulated to study their effect on FEL performance. Energy spread was found to be the most infl uential factor, with output FEL radiation power sharply decreasing for relative energy spreads greater than 0.33%. Vacuum chamber wakefi elds and beam mismatch had little effect on the simulated LOASIS FEL at the currents considered. This study concludes that continued improvement of the laser-plasma wakefi eld accelerator electron beam will allow the LOASIS FEL to operate in an optimal regime, producing high-quality XUV and x-ray pulses.

  5. Accelerator mass spectrometry-enabled studies: current status and future prospects.

    PubMed

    Arjomand, Ali

    2010-03-01

    Accelerator mass spectrometry is a detection platform with exceptional sensitivity compared with other bioanalytical platforms. Accelerator mass spectrometry (AMS) is widely used in archeology for radiocarbon dating applications. Early exploration of the biological and pharmaceutical applications of AMS began in the early 1990s. AMS has since demonstrated unique problem-solving ability in nutrition science, toxicology and pharmacology. AMS has also enabled the development of new applications, such as Phase 0 microdosing. Recent development of AMS-enabled applications has transformed this novelty research instrument to a valuable tool within the pharmaceutical industry. Although there is now greater awareness of AMS technology, recognition and appreciation of the range of AMS-enabled applications is still lacking, including study-design strategies. This review aims to provide further insight into the wide range of AMS-enabled applications. Examples of studies conducted over the past two decades will be presented, as well as prospects for the future of AMS.

  6. A computer study of radionuclide production in high power accelerators for medical and industrial applications

    NASA Astrophysics Data System (ADS)

    Van Riper, K. A.; Mashnik, S. G.; Wilson, W. B.

    2001-05-01

    Methods for radionuclide production calculation in a high power proton accelerator have been developed and applied to study production of 22 isotopes by high-energy protons and neutrons. These methods are readily applicable to accelerator, and reactor, environments other than the particular model we considered and to the production of other radioactive and stable isotopes. We have also developed methods for evaluating cross sections from a wide variety of sources into a single cross section set and have produced an evaluated library covering about a third of all natural elements. These methods also are applicable to an expanded set of reactions. A 684 page detailed report on this study, with 37 tables and 264 color figures is available on the Web at http://t2.lanl.gov/publications/publications.html, or, if not accessible, in hard copy from the authors.

  7. Accelerated simulation study of space charge effects in quadrupole ion traps using GPU techniques.

    PubMed

    Xiong, Xingchuang; Xu, Wei; Fang, Xiang; Deng, Yulin; Ouyang, Zheng

    2012-10-01

    Space charge effects play important roles in the performance of various types of mass analyzers. Simulation of space charge effects is often limited by the computation capability. In this study, we evaluate the method of using graphics processing unit (GPU) to accelerate ion trajectory simulation. Simulation using GPU has been compared with multi-core central processing unit (CPU), and an acceleration of about 390 times have been obtained using a single computer for simulation of up to 10(5) ions in quadrupole ion traps. Characteristics of trapped ions can be investigated at detailed levels within a reasonable simulation time. Space charge effects on the trapping capacities of linear and 3D ion traps, ion cloud shapes, ion motion frequency shift, mass spectrum peak coalescence effects between two ion clouds of close m/z are studied with the ion trajectory simulation using GPU.

  8. Beam dynamics studies for the relativistic klystron two-beam accelerator experiment

    NASA Astrophysics Data System (ADS)

    Lidia, Steven M.

    2001-04-01

    Two-beam accelerators (TBAs) have been proposed as efficient power sources for next generation high-energy linear colliders. Studies have demonstrated the possibility of building TBAs from X-band \\(~8-12 GHz\\) through Ka-band \\(~30-35 GHz\\) frequency regions. The relativistic klystron two-beam accelerator project, whose aim is to study TBAs based upon extended relativistic klystrons, is described, and a new simulation code is used to design the latter portions of the experiment. Detailed, self-consistent calculations of the beam dynamics and of the rf cavity output are presented and discussed together with a beam line design that will generate nearly 1.2 GW of power from 40 rf cavities over a 10 m distance. The simulations show that beam current losses are acceptable and that longitudinal and transverse focusing techniques are sufficiently capable of maintaining a high degree of beam quality along the entire beam line.

  9. Early Acceleration of Mathematics Students and its Effect on Growth in Self-esteem: A Longitudinal Study

    NASA Astrophysics Data System (ADS)

    Ma, Xin

    2002-11-01

    The Longitudinal Study of American Youth (LSAY) database was employed to examine the educational practice of early acceleration of students of mathematics on the development of their self-esteem across the entire secondary grade levels. Students were classified into three different academic categories (gifted, honors, and regular). Results indicated that, in terms of the development of their self-esteem, gifted students benefited from early acceleration, honors students neither benefited nor were harmed by early acceleration, and regular students were harmed by early acceleration. Early acceleration in mathematics promoted significant growth in self-esteem among gifted male students and among gifted, honors, and regular minority students. When students were accelerated, schools showed similar average growth in self-esteem among gifted students and regular students and a large effect of general support for mathematics on the average growth in self-esteem among honors students.

  10. Stress degradation study on sulfadimethoxine and development of a validated stability-indicating HPLC assay.

    PubMed

    Louati, K; Mistiri, F; Kallel, M; Safta, F

    2011-03-01

    Sulfadimethoxine was subjected to different International Conference on Harmonisation prescribed stress conditions (hydrolysis, oxidation and photolysis). A stability-indicating high-performance liquid chromatography method was developed for analysis of the drug in the presence of its major degradation products. It involved a Knauer Eurospher C18 thermostated column at 25°C, and 9.57 mM phosphate buffer (pH adjusted to 2.0 with orthophosphoric acid)-acetonitrile (70:30 v/v) as mobile phase. The mobile phase flow rate and sample volume injected were 1.2 mL/min and 20 μL respectively. The selected wavelength for the determination was 248 nm. The method was validated for its linearity, precision, accuracy, specificity and selectivity, and then applied to the assay of sulfadimethoxine in pharmaceutical formulations. The results of the study show that sulfadimethoxine is highly sensitive to basic hydrolysis and oxidation. The mechanisms and schemas of hydrolytic, oxidative and photolytic degradation are also studied. The method developed, which separates all of the most degradation products, is simple, accurate, precise and specific. Thus, it can be applied to study the stability of veterinary preparations containing sulfadimethoxine. PMID:21440101

  11. Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.

    PubMed

    Sarkar, Santanu; Bhattacharjee, Chiranjib; Curcio, Stefano

    2015-11-01

    The photocatalytic degradation of chlorhexidine digluconate (CHD), a disinfectant and topical antiseptic and adsorption of CHD catalyst surface in dark condition has been studied. Moreover, the value of kinetic parameters has been measured and the effect of adsorption on photocatalysis has been investigated here. Substantial removal was observed during the photocatalysis process, whereas 40% removal was possible through the adsorption route on TiO2 surface. The parametric variation has shown that alkaline pH, ambient temperature, low initial substrate concentration, high TiO2 loading were favourable, though at a certain concentration of TiO2 loading, photocatalytic degradation efficiency was found to be maximum. The adsorption study has shown good confirmation with Langmuir isotherm and during the reaction at initial stage, it followed pseudo-first-order reaction, after that Langmuir Hinshelwood model was found to be appropriate in describing the system. The present study also confirmed that there is a significant effect of adsorption on photocatalytic degradation. The possible mechanism for adsorption and photocatalysis has been shown here and process controlling step has been identified. The influences of pH and temperature have been explained with the help of surface charge distribution of reacting particles and thermodynamic point of view respectively.

  12. The effect of simulated low earth orbit radiation on polyimides (UV degradation study)

    NASA Technical Reports Server (NTRS)

    Forsythe, John S.; George, Graeme A.; Hill, David J. T.; Odonnell, James H.; Pomery, Peter J.; Rasoul, Firas A.

    1995-01-01

    UV degradation of polyimide films in air and vacuum were studied using UV-visible, ESR, FTIR, and XPS spectroscopies. The UV-visible spectra of polyimide films showed a blue shift in the absorption compared to Kapton. This behavior was attributed to the presence of bulky groups and kinks along the polymer chains which disrupt the formation of a charge transfer complex. The UV-visible spectra showed also that UV irradiation of polyimides result extensively in surface degradation, leaving the bulk of the polymer intact. ESR spectra of polyimides irradiated in vacuum revealed the formation of stable carbon-centered radicals which give a singlet ESR spectrum, while polyimides irradiated in air produced an asymmetric signal shifted to a lower magnetic field, with a higher g value and line width. This signal was attributed to oxygen-cenetered radicals of peroxy and/or alkoxy type. The rate of radical formation in air was two fold higher than for vacuum irradiation, and reached a plateau after a short time. This suggests a continuous depletion of radicals on the surface via an ablative degradation process. FTIR, XPS, and weight loss studies supported this postulate. An XPS study of the surface indicated a substantial increase in the surface oxidation after irradiation in air. The sharp increase in the C-O binding energy peak relative to the C-C peak was believed to be associated with an aromatic ring opening reaction.

  13. Hamiltonian methods for the study of polarized proton beam dynamics in accelerators and storage rings

    SciTech Connect

    Balandin, Vladimir; Golubeva, Nina

    1997-02-01

    The equations of classical spin-orbit motion can be extended to a Hamiltonian system in 9-dimensional phase space by introducing a coupled spin-orbit Poisson bracket and Hamiltonian function. After this extension it becomes possible to apply the methods of the theory of Hamiltonian systems to the study of polarized particles beam dynamics in circular accelerators and storage rings. Some of those methods have been implemented in the computer code FORGET-ME-NOT.

  14. Alkaline degradation studies of anion exchange polymers to enable new membrane designs

    NASA Astrophysics Data System (ADS)

    Nunez, Sean Andrew

    Current performance targets for anion-exchange membrane (AEM) fuel cells call for greater than 95% alkaline stability for 5000 hours at temperatures up to 120 °C. Using this target temperature of 120 °C, an incisive 1H NMR-based alkaline degradation method to identify the degradation products of n-alkyl spacer tetraalkylammonium cations in various AEM polymers and small molecule analogs. Herein, the degradation mechanisms and rates of benzyltrimethylammonium-, n-alkyl interstitial spacer- and n-alkyl terminal pendant-cations are studied on several architectures. These findings demonstrate that benzyltrimethylammonium- and n-alkyl terminal pendant cations are more labile than an n-alkyl interstitial spacer cation and conclude that Hofmann elimination is not the predominant mechanism of alkaline degradation. Additionally, the alkaline stability of an n-alkyl interstitial spacer cation is enhanced when combined with an n-alkyl terminal pendant. Interestingly, at 120 °C, an inverse trend was found in the overall alkaline stability of AEM poly(styrene) and AEM poly(phenylene oxide) samples than was previously shown at 80 °C. Successive small molecule studies suggest that at 120 °C, an anion-induced 1,4-elimination degradation mechanism may be activated on styrenic AEM polymers bearing an acidic alpha-hydrogen. In addition, an ATR-FTIR based method was developed to assess the alkaline stability of solid membranes and any added resistance to degradation that may be due to differential solubilities and phase separation. To increase the stability of anion exchange membranes, Oshima magnesate--halogen exchange was demonstrated as a method for the synthesis of new anion exchange membranes that typically fail in the presence of organolithium or Grignard reagents alone. This new chemistry, applied to non-resinous polymers for the first time, proved effective for the n-akyl interstitial spacer functionalization of poly(phenylene oxide) and poly(styrene- co

  15. Assessment of land degradation susceptibility by scenario analysis. A case study in Southern Tuscany, Italy

    NASA Astrophysics Data System (ADS)

    Maerker, Michael; Angeli, Luca; Bottai, Lorenzo; Innocenti, Lucia; Sicilliano, Giuseppina

    2010-05-01

    In the Mediterranean area land degradation phenomena are becoming more and more important due to future climate change and increasing climate variability as highlighted in recent global assessment projects such as the "Millennium Ecosystem Assessment" or "The Dialogue on water and Climate". Thus, there are consistent evidences that extreme events such as droughts and floods are more frequent than before. On the other hand the Mediterranean area is strongly influenced by human activities such as cultivations over hundreds of years. However, in the last decades the cultivation methods and techniques are subject to profound changes such as mechanization, use of fertilizer and pesticides, remodellation of entire hillslopes etc.. This particular situation leads to, and aggravates the existing stress on land resources. As a result, land degradation and soil erosion phenomena are leading to decreasing soil productivity or the loss of fertile top soil and related water quality and quantity issues. The aim of this paper is to assess land degradation sensitivity by scenario analysis. As a proxi for land degradation surface wash erosion processes such as rill-interill erosion processes are chosen. This present day processes are identified by aerial photo interpretation and subsequently modelled with a simple RUSLE approach on a monthly basis. In this study boundary conditions such as future precipitation were taken form the A2 future climate scenario published by the International Panel on Climate Change (IPCC) - Special Report on Emission Scenarios (SRES). Moreover, current landuse was identified from aerial photographs and future land use scenarios were developed considering ecological and socio-economical issues for present day conditions of the test area. Subsequently, the different climate and landuse scenarios were analysed to study soil erosion susceptibility on the landscape scale. The study shows that even with a decline in precipitation volume till 2070, in some

  16. Accelerator-based conversion (ABC) of weapons plutonium: Plant layout study and related design issues

    SciTech Connect

    Cowell, B.S.; Fontana, M.H.; Krakowski, R.A.; Beard, C.A.; Buksa, J.J.; Davidson, J.W.; Sailor, W.C.; Williamson, M.A.

    1995-04-01

    In preparation for and in support of a detailed R and D Plan for the Accelerator-Based Conversion (ABC) of weapons plutonium, an ABC Plant Layout Study was conducted at the level of a pre-conceptual engineering design. The plant layout is based on an adaptation of the Molten-Salt Breeder Reactor (MSBR) detailed conceptual design that was completed in the early 1070s. Although the ABC Plant Layout Study included the Accelerator Equipment as an essential element, the engineering assessment focused primarily on the Target; Primary System (blanket and all systems containing plutonium-bearing fuel salt); the Heat-Removal System (secondary-coolant-salt and supercritical-steam systems); Chemical Processing; Operation and Maintenance; Containment and Safety; and Instrumentation and Control systems. Although constrained primarily to a reflection of an accelerator-driven (subcritical) variant of MSBR system, unique features and added flexibilities of the ABC suggest improved or alternative approaches to each of the above-listed subsystems; these, along with the key technical issues in need of resolution through a detailed R&D plan for ABC are described on the bases of the ``strawman`` or ``point-of-departure`` plant layout that resulted from this study.

  17. Feasibility study of a nonequilibrium MHD accelerator concept for hypersonic propulsion ground testing

    SciTech Connect

    Lee, Ying-Ming; Simmons, G.A.; Nelson, G.L.

    1995-12-31

    A National Aeronautics and Space Administration (NASA) funded research study to evaluate the feasibility of using magnetohydrodynamic (MHD) body force accelerators to produce true air simulation for hypersonic propulsion ground testing is discussed in this paper. Testing over the airbreathing portion of a transatmospheric vehicle (TAV) hypersonic flight regime will require high quality air simulation for actual flight conditions behind a bow shock wave (forebody, pre-inlet region) for flight velocities up to Mach 16 and perhaps beyond. Material limits and chemical dissociation at high temperature limit the simulated flight Mach numbers in conventional facilities to less than Mach 12 for continuous and semi-continuous testing and less than Mach 7 for applications requiring true air chemistry. By adding kinetic energy directly to the flow, MHD accelerators avoid the high temperatures and pressures required in the reservoir region of conventional expansion facilities, allowing MHD to produce true flight conditions in flight regimes impossible with conventional facilities. The present study is intended to resolve some of the critical technical issues related to the operation of MHD at high pressure. Funding has been provided only for the first phase of a three to four year feasibility study that would culminate in the demonstration of MHD acceleration under conditions required to produce true flight conditions behind a bow shock wave to flight Mach numbers of 16 or greater. MHD critical issues and a program plan to resolve these are discussed.

  18. Accelerator research studies. Final report, June 1, 1994--May 31, 1995

    SciTech Connect

    1995-08-01

    The Accelerator Research Studies program at the University of Maryland, sponsored by the Department of Energy has completed the third year of its three-year funding cycle and an additional one-year, no-cost extension. The program consisted of the following three tasks: Task A -- Study of the transport and longitudinal compression of intense, high-brightness beams; Task B -- Study of high-brightness beam generation in pseudospark devices; Task C -- Study of a gyroklystron high-power microwave source for linear colliders. The research carried out for each task and progress made is reported.

  19. Lupus-prone mice as models to study xenobiotic-induced acceleration of systemic autoimmunity.

    PubMed Central

    Pollard, K M; Pearson, D L; Hultman, P; Hildebrandt, B; Kono, D H

    1999-01-01

    The linkage between xenobiotic exposures and autoimmune diseases remains to be clearly defined. However, recent studies have raised the possibility that both genetic and environmental factors act synergistically at several stages or checkpoints to influence disease pathogenesis in susceptible populations. These observations predict that individuals susceptible to spontaneous autoimmunity should be more susceptible following xenobiotic exposure by virtue of the presence of predisposing background genes. To test this possibility, mouse strains with differing genetic susceptibility to murine lupus were examined for acceleration of autoimmune features characteristic of spontaneous systemic autoimmune disease following exposure to the immunostimulatory metals nickel and mercury. Although NiCl(2) exposure did not exacerbate autoimmunity, HgCl(2) significantly accelerated systemic disease in a strain-dependent manner. Mercury-exposed (NZB X NZW)F1 mice had accelerated lymphoid hyperplasia, hypergammaglobulinemia, autoantibodies, and immune complex deposits. Mercury also exacerbated immunopathologic manifestations in MRL+/+ and MR -lpr mice. However, there was less disease acceleration in lpr mice compared with MRL+/+ mice, likely due to the fact that environmental factors are less critical for disease induction when there is strong genetic susceptibility. Non-major histocompatibility complex genes also contributed to mercury-exacerbated disease, as the nonautoimmune AKR mice, which are H-2 identical with the MRL, showed less immunopathology than either the MRL/lpr or MRL+/+ strains. This study demonstrates that genetic susceptibility to spontaneous systemic autoimmunity can be a predisposing factor for HgCl(2)-induced exacerbation of autoimmunity. Such genetic predisposition may have to be considered when assessing the immunotoxicity of xenobiotics. Additional comparative studies using autoimmune-prone and nonautoimmune mice strains with different genetic backgrounds will

  20. [Study of petroleum-degrading activity of microflora from the shoreline region of the Caspian Sea].

    PubMed

    Shkidchenko, A N; Arinbasarov, M U

    2002-01-01

    Soil samples from the shore of Baku Bay (Caspian Sea), were studied. The content of oil products in the samples amounted to 2.7-8.0 wt%. The total counts of microorganisms were 1.8 x 10(6) cells per g soil, which is by two orders of magnitude lower compared to soils free from oil pollution. In addition, the diversity of microflora is considerably narrower. The samples were used to isolate pure cultures of microbial degraders capable of assimilating 24 to 32% of the oil introduced into liquid nutrient medium in six days. It was demonstrated that the fraction composition of residual oil changed and both light and heavy oil fractions were degraded.

  1. Microbial degradation of quinoline: Kinetic studies with Comamonas acidovorans DSM 6426

    SciTech Connect

    Miethling, R.; Hecht, V.; Deckwer, W.D. . Dept. of Biochemical Engineering)

    1993-08-20

    The microbial degradation of quinoline by Comamonas acidovorans was studied in a laboratory scale stirred tank reactor. In continuous culture experiments using quinoline as a sole source of carbon and nitrogen, it was shown by means of mass balances that quinoline was converted completely to biomass, carbon dioxide, and ammonia. Degradation rates up to 0.7 g/L h were obtained. Measured yield coefficients Y[sub x/s] for quinoline were about 0.7 g/g, which is in agreement with the theoretical value for complete mineralization. Kinetic constants based on Haldane substrate inhibition were evaluated. The values were [mu][sub max] = 0.48 h[sup [minus]1], K[sub i] = 69 mg/L, and K[sub s]<1.45 mg/L.

  2. Thermal Degradation Studies on Polyaniline-Polypyrrole Copolymers Prepared by Microemulsion Methods

    NASA Astrophysics Data System (ADS)

    Prasannan, A.; Somanathan, N.; Hong, Po-Da

    2010-05-01

    Solvent- and water-based microemulsions of aniline and pyrrole copolymers were synthesized, and the thermal degradation properties of the copolymers were studied. The morphology of the copolymers prepared using solvent-based microemulsions containing 80 % aniline in the feed showed highly oriented, crystalline, ordered long nano-fibers which were even more structured than that of pure aniline prepared by the same method. The influence of the degree of crystallinity calculated from X-ray diffraction and morphology had an overlap with thermal degradation and activation energies of different transitions. Copolymers prepared with water-based microemulsions were thermally less stable than the ones prepared using solvent-based microemulsions. The concentration of pyrrole and aniline mutually influenced the thermal properties of the copolymers.

  3. Degradation of Bilayer Organic Light-Emitting Diodes Studied by Impedance Spectroscopy.

    PubMed

    Sato, Shuri; Takata, Masashi; Takada, Makoto; Naito, Hiroyoshi

    2016-04-01

    The degradation of bilayer organic light-emitting diodes (OLEDs) with a device structure of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) (hole transport layer) and tris-(8-hydroxyquinolate)aluminum (Alq3) (emissive layer and electron transport layer) has been studied by impedance spectroscopy and device simulation. Two modulus peaks are found in the modulus spectra of the OLEDs below the electroluminescence threshold. After aging of the OLEDs, the intensity of electroluminescence is degraded and the modulus peak due to the Alq3 layer is shifted to lower frequency, indicating that the resistance of the Alq3 layer is increased. Device simulation reveals that the increase in the resistance of the Alq3 layer is due to the decrease in the electron mobility in the Alq3 layer. PMID:27451634

  4. Human hemoglobin structural and functional alterations and heme degradation upon interaction with benzene: A spectroscopic study

    NASA Astrophysics Data System (ADS)

    Hosseinzadeh, Reza; Moosavi-Movahedi, Ali Akbar

    2016-03-01

    Here, the effect of benzene on hemoglobin structure, stability and heme prosthetic group integrity was studied by different methods. These included UV-vis absorption spectrophotometry, normal and synchronous fluorescence techniques, and differential scanning calorimetry (DSC). Our results indicated that benzene has high hemolytic potential even at low concentrations. The UV-vis spectroscopic results demonstrated that benzene altered both the globin chain and the heme prosthetic group of hemoglobin increasing met- and deoxy-Hb, while decreasing oxy-Hb. However, with increasing benzene the concentration of all species decreased due to heme destruction. The spectrophotometric results show that benzene has a high potential for penetrating the hydrophobic pocket of hemoglobin. These results were consistent with the molecular docking simulation results of benzene-hHb. Aggregation and thermal denaturation studies show that the increased benzene concentration induced hemoglobin aggregation with a decrease in stability, which is consistent with the DSC results. Conventional fluorescence spectroscopy revealed that the heme degradation species were produced in the presence of benzene. The results of constant wavelength synchronous fluorescence spectroscopy (CWSFS) indicated that at least five heme-degraded species were produced. Together, our results indicated that benzene has adverse effects on hemoglobin structure and function, and heme degradation.

  5. Laboratory studies on formation of bound residues and degradation of propiconazole in soils.

    PubMed

    Kim, In Seon; Shim, Jae Han; Suh, Yong Tack

    2003-03-01

    Laboratory studies on the formation of bound residues and on the degradation of the triazole fungicide propiconazole were conducted in two different soils. Soils treated with 14C-propiconazole were incubated at 22 degrees C and extracted exhaustively with a solvent at each sampling date until no further propiconazole was extracted. The solvent-extractable residues were used to measure propiconazole remaining in the soil, and the extracted soils were used to investigate bound residues of propiconazole. Mineralization of propiconazole was investigated by measuring [14C]carbon dioxide evolved from the soil samples. Formation of bound residues of propiconazole was higher in silty clay loam soil than in sandy loam soil, giving approximately 38 and 23% of the applied 14C, respectively. In contrast, the rates of degradation and mineralization of propiconazole were lower in silty clay loam soil than in sandy loam soil. Decreased extractability of the 14C residues with incubation time was observed with increased formation of bound residues. When the propiconazole remaining in the solvent-extractable residues was quantitatively measured by high-pressure liquid chromatographic analysis, the half-life value in sandy loam soil was about 315 days, while the half-life in silty clay loam soil exceeded the duration of the 1 year experimental period. Increased formation of bound residues was observed as propiconazole degraded with incubation time, suggesting that degradation products are involved in the formation of bound residues. Our study suggests that the formation of bound residues of propiconazole contributes to the persistence of this fungicide in soil.

  6. The solution, solid state stability and kinetic investigation in degradation studies of lercanidipine: study of excipients compatibility of lercanidipine.

    PubMed

    Parmar, Nitin; Amin, Saima; Singla, Neelam; Kohli, Kanchan

    2012-01-01

    The objectives of this research were to evaluate the stability of lercanidipine in solution state and solid state and explore the compatibility of drug with oils, surfactants and cosurfactants as excipients. The effect of pH on the degradation in solution state was studied through pH-rate profile of lercanidipine in constant ionic strength buffer solutions in pH range 1-8 which gives the pH of maximum stability. Powdered lercanidipine was stored under 40°C/0%~75% relative humidities (RH) or 0% RH/5~50°C to study the influence of RH and temperature on the stability of lercanidipine in solid state. Binary mixtures of lercanidipine and different excipients were stored at 40°C/75% RH, 40°C and at room temperature for excipient compatibility evaluation. The degradation of lercanidipine at different pH appears to fit a typical first-order reaction, but in solid state, it does not fit any obvious reaction model. Moisture content and temperature both play important roles affecting the degradation rate. Lercanidipine exhibits good compatibility with surfactants, cosurfactants and oils as excipients under stressed conditions of different storage temperature in a 3-week screening study. Moreover, the proposed high-performance liquid chromatography method was utilized to investigate the kinetics of the acidic and alkaline degradation processes of lercanidipine at different temperatures.

  7. Study of a national 2-GeV continuous beam electron accelerator

    SciTech Connect

    Cho, Y.; Holt, R.J.; Jackson, H.E.; Khoe, T.K.; Mavrogenes, G.S.

    1980-08-01

    Current trends in research in medium energy physics with electromagnetic probes are reviewed briefly and design objectives are proposed for a continuous beam 2 GeV electron accelerator. Various types of accelerator systems are discussed and exploratory designs developed for two concepts, the linac-stretcher ring and a double-sided microtron system. Preliminary cost estimates indicate that a linac-ring system which meets all the design objectives with the exception of beam quality and uses state-of-the-art technology can be built for approximately $29 million. However, the double-sided microtron shows promise for development into a substantially less expensive facility meeting all design objectives. Its technical feasibility remains to be established. Specific areas requiring additional engineering studies are discussed, and current efforts at Argonne and elsewhere are identified.

  8. Charge-exchange erosion studies of accelerator grids in ion thrusters

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Ruyten, Wilhelmus M.; Keefer, Dennis

    1993-01-01

    A particle simulation model is developed to study the charge-exchange grid erosion in ion thrusters for both ground-based and space-based operations. Because the neutral gas downstream from the accelerator grid is different for space and ground operation conditions, the charge-exchange erosion processes are also different. Based on an assumption of now electric potential hill downstream from the ion thruster, the calculations show that the accelerator grid erosion rate for space-based operating conditions should be significantly less than experimentally observed erosion rates from the ground-based tests conducted at NASA Lewis Research Center (LeRC) and NASA Jet Propulsion Laboratory (JPL). To resolve this erosion issue completely, we believe that it is necessary to accurately measure the entire electric potential field downstream from the thruster.

  9. Study on radiation production in the charge stripping section of the RISP linear accelerator

    NASA Astrophysics Data System (ADS)

    Oh, Joo-Hee; Oranj, Leila Mokhtari; Lee, Hee-Seock; Ko, Seung-Kook

    2015-02-01

    The linear accelerator of the Rare Isotope Science Project (RISP) accelerates 200 MeV/nucleon 238U ions in a multi-charge states. Many kinds of radiations are generated while the primary beam is transported along the beam line. The stripping process using thin carbon foil leads to complicated radiation environments at the 90-degree bending section. The charge distribution of 238U ions after the carbon charge stripper was calculated by using the LISE++ program. The estimates of the radiation environments were carried out by using the well-proved Monte Carlo codes PHITS and FLUKA. The tracks of 238U ions in various charge states were identified using the magnetic field subroutine of the PHITS code. The dose distribution caused by U beam losses for those tracks was obtained over the accelerator tunnel. A modified calculation was applied for tracking the multi-charged U beams because the fundamental idea of PHITS and FLUKA was to transport fully-ionized ion beam. In this study, the beam loss pattern after a stripping section was observed, and the radiation production by heavy ions was studied. Finally, the performance of the PHITS and the FLUKA codes was validated for estimating the radiation production at the stripping section by applying a modified method.

  10. Moving at the Speed of Potential: A Mixed-Methods Study of Accelerating Developmental Students in a California Community College

    ERIC Educational Resources Information Center

    Parks, Paula L.

    2014-01-01

    Most developmental community college students are not completing the composition sequence successfully. This mixed-methods study examined acceleration as a way to help developmental community college students complete the composition sequence more quickly and more successfully. Acceleration is a curricular redesign that includes challenging…

  11. A Study of the Effects of the Accelerated Reader Program on Fifth Grade Students' Reading Achievement Growth

    ERIC Educational Resources Information Center

    Melton, Cindy M.; Smothers, Bobbie C.; Anderson, Eugene; Fulton, Ray; Replogle, William H.; Thomas, Lisa

    2004-01-01

    The purpose of this study was to compare the reading achievement growth of fifth grade students following a year of participation in the Accelerated Reader program with the reading achievement growth of fifth grade students who did not participate in the Accelerated Reader program. The Terra Nova standardized achievement test was used as the…

  12. Towards A Model-Based Prognostics Methodology for Electrolytic Capacitors: A Case Study Based on Electrical Overstress Accelerated Aging

    NASA Technical Reports Server (NTRS)

    Celaya, Jose R.; Kulkarni, Chetan S.; Biswas, Gautam; Goebel, Kai

    2012-01-01

    A remaining useful life prediction methodology for electrolytic capacitors is presented. This methodology is based on the Kalman filter framework and an empirical degradation model. Electrolytic capacitors are used in several applications ranging from power supplies on critical avionics equipment to power drivers for electro-mechanical actuators. These devices are known for their comparatively low reliability and given their criticality in electronics subsystems they are a good candidate for component level prognostics and health management. Prognostics provides a way to assess remaining useful life of a capacitor based on its current state of health and its anticipated future usage and operational conditions. We present here also, experimental results of an accelerated aging test under electrical stresses. The data obtained in this test form the basis for a remaining life prediction algorithm where a model of the degradation process is suggested. This preliminary remaining life prediction algorithm serves as a demonstration of how prognostics methodologies could be used for electrolytic capacitors. In addition, the use degradation progression data from accelerated aging, provides an avenue for validation of applications of the Kalman filter based prognostics methods typically used for remaining useful life predictions in other applications.

  13. Anticataractogenesis Mechanisms of Curcumin and a Comparison of Its Degradation Products: An in Vitro Study.

    PubMed

    Liao, Jiahn-Haur; Huang, Yi-Shiang; Lin, Yu-Ching; Huang, Fu-Yung; Wu, Shih-Hsiung; Wu, Tzu-Hua

    2016-03-16

    Curcumin (Cur) exhibits anticataractogenesis activity. This study aimed to compare the activities of Cur with those of its degradation products in a series of in vitro lens protein turbidity assays. The results show that Cur (200 μM) ameliorates selenite-induced crystallin aggregation, and the mean OD value was 0.10 ± 0.02 (p < 0.05), which was significantly different from controls (0.15 ± 0.01) after incubating for 3 days. However, Cur did not significantly inhibit calcium-induced proteolysis after incubating for 3 days. Such results were supported by isothermal titration calorimetry observation that Cur binds with selenite but not with calcium. Presence of Cur and the degradation products examined (ferulic acid, cinnamic acid, vanillin, and vanillic acid) indicates significantly protective activities on lens γ-crystallins after UVC exposure for 3 h. Among the compounds examined, only ferulic acid exhibited a significant inhibitory effect against UVB-induced turbidity with a mean OD of 0.32 ± 0.01 (p < 0.05), which was significantly different from controls (0.49 ± 0.02). The previously reported anticataract effects of Cur may stem not only from Cur but also from its degradation products through various cataractogenesis mechanisms in vitro. PMID:26905955

  14. Determination of latent fingerprint degradation patterns-a real fieldwork study.

    PubMed

    De Alcaraz-Fossoul, Josep; Mestres Patris, Cristina; Balaciart Muntaner, Antoni; Barrot Feixat, Carme; Gené Badia, Manel

    2013-07-01

    For over a century, law enforcement agencies, forensic laboratories, and penal courts worldwide have used fingerprint impressions as reliable and conclusive evidence to identify perpetrators of criminal activity. Although fingerprint identification has been repeatedly proven as one of the most robust and definite forensic techniques, a measure of the rate at which latent fingerprints degrade over time has not been established effectively. Ideally, criminal investigators should be able not only to place any given individual at a crime scene but also be able to date the moment any latent fingerprints were deposited at the location. The present report aims to determine particular visual patterns of degradation of latent fingerprints exposed to certain monitored laboratory conditions simulating those in the field. Factors considered include temperature, relative humidity, air currents, composition of fingerprint depositions (sebaceous and eccrine), various exposures to daylight (direct, penumbra, and darkness), and type of physical substrate (glass and plastic) over a period of 6 months. The study employs a titanium dioxide-based powder as developer. Our results indicate that, contrary to common belief, certain latent fingerprints exposed to direct sunlight indoors degrade similarly to those in the dark where environmental conditions are more constant. While all sebaceous latent fingerprints on glass are still useful for identification after 6 months, diverse results are obtained with impressions on plastic; these demonstrate a much higher and faster degree of decay, making identification difficult or impossible, especially for eccrine depositions.

  15. Glycolic acid-catalyzed deamidation of asparagine residues in degrading PLGA matrices: a computational study.

    PubMed

    Manabe, Noriyoshi; Kirikoshi, Ryota; Takahashi, Ohgi

    2015-03-31

    Poly(lactic-co-glycolic acid) (PLGA) is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn) residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA) in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3) as a model compound. The first step is cyclization (intramolecular addition) to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  16. Photochemical Degradation of Persistent Organic Pollutants: A Study of Ice Photochemistry Mediated by Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Bobby, R.; Pagano, L.; Grannas, A. M.

    2012-12-01

    It is well established that ice is a reactive medium in the environment and that active photochemistry occurs in frozen systems. Snow and ice contain a number of absorbing species including nitrate, peroxide and organic matter. Upon irradiation, they can generate a variety of reactive intermediates such as hydroxyl radical and singlet oxygen. It has been shown that dissolved organic matter is a ubiquitous component of snow and ice and plays an important role in overall light absorption properties of the sample. Additionally, the reactive intermediates produced can further react with contaminants present and alter their fate in the environment. Unfortunately, the role of dissolved organic matter in ice photochemistry has received little attention. Here we present results from laboratory-based studies aimed at elucidating the role of dissolved organic matter photochemistry on contaminant degradation in ice. Aqueous samples of our target pollutant, aldrin (20 μg/L), in liquid and frozen phases, were irradiated under Q-Panel 340 lamps to simulate the UV radiation profile of natural sunlight. Results indicated that frozen samples degraded more quickly than liquid samples and that the addition of dissolved organic matter increases the aldrin degradation rate significantly. Both terrestrial (Suwannee River, U.S.) and microbial sources (Pony Lake, Antarctica) of DOM were able to sensitize aldrin loss in ice. Scavengers of singlet oxygen, such as furfuryl alcohol and β-carotene, were also added to DOM solutions. Based on the type of organic matter present, the scavengers had different effects on the photochemical degradation of aldrin. Our results indicate that natural organic matter present in ice is an important component of ice photochemical processes.

  17. Laboratory study on OH-initiated degradation kinetics of dehydroabietic acid.

    PubMed

    Lai, Chengyue; Liu, Yongchun; Ma, Jinzhu; Ma, Qingxin; He, Hong

    2015-04-28

    Dehydroabietic acid (DHAA) is a specific organic tracer for the pyrolysis of conifer resin. To understand its atmospheric stability, the degradation behavior of particulate DHAA in the presence of hydroxyl radicals (OH) was investigated under different environmental conditions using a stainless steel reactor with volume of 30 cm(3), in the dark. At 25 °C and 40% relative humidity (RH), the second-order rate constant (k2) of pure DHAA with OH was measured to be 5.72 ± 0.87 × 10(-12) cm(3) molecule(-1) s(-1). The influence of temperature, RH and mixing state on the degradation kinetics of DHAA were also investigated. At 40% RH, k2 of pure DHAA increases with increasing temperature and follows the Arrhenius equation k2 = (8.9 ± 1.9) × 10(-10) exp[-(1508.2 ± 64.2)/T], while RH does not have significant impact on k2 at 25 °C. At 25 °C and 40% RH, compared with pure DHAA, the corresponding k2 for DHAA mixed with (NH4)2SO4 decreased to 4.58 ± 0.95 × 10(-12) cm(3) molecule(-1) s(-1), while the value was 3.30 ± 0.79 × 10(-12) cm(3) molecule(-1) s(-1) when mixed with soot. The atmospheric lifetime of DHAA varied from 2.3 ± 0.2 to 4.4 ± 0.8 days under different environmental conditions. This study indicates that degradation of DHAA by OH radicals is appreciable, and a significant error in source apportionment should be introduced if the contribution of degradation to DHAA concentration is not considered during air mass aging. PMID:25824374

  18. Laboratory degradation studies of bentazone, dichlorprop, MCPA, and propiconazole in Norwegian soils.

    PubMed

    Thorstensen, C W; Lode, O

    2001-01-01

    Laboratory degradation studies were performed in Norwegian soils using two commercial formulations (Tilt and Triagran-P) containing either propiconazole alone or a combination of bentazone, dichlorprop, and MCPA. These soils included a fine sandy loam from Hole and a loam from Kroer, both of which are representative of Norwegian agricultural soils. The third soil was a highly decomposed organic material from the Froland forest. A fourth soil from the Skuterud watershed was used only for propiconazole degradation. After 84 d, less than 0.1% of the initial MCPA concentration remained in all three selected soils. For dichlorprop, the same results were found for the fine sandy loam and the organic-rich soil, but in the loam, 26% of the initial concentration remained. After 84 d, less than 0.1% of the initial concentration of bentazone remained in the organic-rich soil, but in the loam and the fine sandy loam 52 and 69% remained, respectively. Propiconazole was shown to be different from the other pesticides by its persistence. Amounts of initial concentration remaining varied from 40, 70, and 82% in the reference soils after 84 d for the organic-rich soil, fine sandy loam, and loam, respectively. The organic-rich soil showed the highest capacity to decompose all four pesticides. The results from the agricultural soils and the Skuterud watershed showed that the persistence of propiconazole was high. Pesticide degradation was approximated to first-order kinetics. Slow rates of degradation, where more than 50% of the pesticide remained in the soil after the 84-d duration of the experiment, did not fit well with first-order kinetics.

  19. Status and Plans for the Accelerator Working Group of the International Design Study of the Neutrino Factory

    SciTech Connect

    Berg, J. Scott

    2010-03-30

    The purpose of the International Design Study of the Neutrino Factory (IDS-NF) is to produce a design report for a neutrino factory in 2013. I report the status of the accelerator design and plans for future studies.

  20. Experimental study of a shock accelerated water layer with imaging and velocity measurement

    NASA Astrophysics Data System (ADS)

    Meekunnasombat, P.; Oakley, J. G.; Anderson, M. H.; Bonazza, R.

    A shock tube investigation of a shocked water layer is undertaken to study the mitigating effects that a liquid sheet may provide for the protection of cooling tubes in an inertial fusion energy reactor chamber. The shock wave blast from the fusion microexplosion will cause the protecting liquid layer to break apart and the liquid droplets will then be suspended throughout the chamber. Some reactor designs require clearing the chamber (approximately 115 m3) between reactions, and therefore, the understanding of how a shock-accelerated liquid layer breaks up could be a critical consideration in the design. A large vertical shock tube is used to conduct shock-accelerated liquid layer experiments to model this scenario. A planar shock wave contacts, and then accelerates, a water layer down the shock tube where it is imaged in the test section using shadowgraphy and laser sheet techniques. Quantitative data of the water layer velocity inside the shock tube is measured using an array of photodiodes. It is found that the measured velocity of the leading edge of the shocked water layer is nearly constant, and this velocity is slightly less than the particle velocity behind the incident shock.

  1. [Anti-aging studies on the senescence accelerated mouse (SAM) strains].

    PubMed

    Takahashi, Ryoya

    2010-01-01

    Senescence accelerated mouse (SAM), a murine model of accelerated senescence, was established by Toshio Takeda and colleagues. SAM consists of series of SAMP (prone) and SAMR (resistant) lines. All SAMP lines (from SAMP1 to SAMP11) are characterized by accelerated accumulation of senile features, earlier onset and faster progress of age-associated pathological phenotypes, such as amyloidosis, impaired immune response, senile osteoporosis and deficits in learning and memory. These SAMP lines are useful for evaluation of putative anti-aging therapies. For example, SAMP1 line is used to study the anti-aging effect of the antioxidant containing foods and various anti-oxidants, such as coenzyme Q10, vitamin C, lycopene. SAMP8 line exhibiting an early onset of impaired learning and memory is often used for test strategies for therapeutic intervention of dementia of early onset. SAMP6 is used as an animal model for developing new strategies for the treatment of osteoporosis in humans. Various lines of SAM (P1, P6, P8, P10 and R1) are now commercially available for research. In this review, I will briefly introduce various usages of SAM in anti-aging research. PMID:20046059

  2. Study of the pd reaction in the astrophysical energy region using the Hall accelerator

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Gerasimov, V. V.; Krylov, A. R.; Parzhitskii, S. S.; Dudkin, G. N.; Kaminskii, V. L.; Nechaev, B. A.; Padalko, V. N.; Petrov, A. V.; Mesyats, G. A.; Filipowicz, M.; Wozniak, J.; Bystritskii, Vit. M.

    2008-10-01

    The pd reaction at ultra-low proton deuteron collision energies has been studied using the Hall pulsed ion accelerator and the solid target of heavy water D2O. The experiment on measurement of the astrophysical Spd factor and the pd reaction cross-section was carried out at average pd collision energies 8.28, 9.49, and 10.10 keV. The 5.5-MeV γ rays from the pd reaction were detected by detectors based on plastic scintillators and NaI(Tl) crystals. Parameters of the accelerated hydrogen ion flux were measured and monitored with diagnostic equipment consisting of an energy analyzer, plasma optical radiation detectors, the Rogovsky belt, and collimated Faraday cups. The results obtained agree within the errors with the data of the pd experiments carried out by the LUNA collaboration at the Gran Sasso Laboratory with a target filled with gaseous deuterium. The reported experiment was carried out at the Hall ion accelerator of the Research Institute of Nuclear Physics, Tomsk Polytechnic University.

  3. Adult student satisfaction in an accelerated RN-to-BSN program: a follow-up study.

    PubMed

    Boylston, Mary T; Jackson, Christina

    2008-01-01

    This mixed-method study revealed accelerated RN-to-BSN (bachelor of science in nursing) students' levels of satisfaction with a wide range of college services in a small university. Building on seminal research on the topic [Boylston, M. T., Peters, M. A., & Lacey, M. (2004). Adult student satisfaction in traditional and accelerated RN-to-BSN programs. Journal of Professional Nursing, 20, 23-32.], the Noel-Levitz Adult Student Priorities Survey (ASPS) and qualitative interview data revealed primary factors involved in nontraditional (adult) accelerated RN-to-BSN student satisfaction. The ASPS assesses both satisfaction with and importance of the following factors: academic advising effectiveness, academic services, admissions and financial aid effectiveness, campus climate, instructional effectiveness, registration effectiveness, safety and security, and service excellence. Of these factors, participants considered instructional effectiveness and academic advising effectiveness as most important and concomitantly gave high satisfaction ratings to each. In contrast, convenience of the bookstore, counseling services, vending machines, and computer laboratories were given low importance ratings. The participants cited convenience as a strong marketing factor. Loss of financial aid or family crisis was given as a reason for withdrawal and, for most students, would be the only reason for not completing the BSN program. Outcomes of this investigation may guide faculty, staff, and administrators in proactively creating an educational environment in which a nontraditional student can succeed. PMID:18804082

  4. To study the emittance dilution in Superconducting Linear Accelerator Design for International Linear Collider (ILC)

    NASA Astrophysics Data System (ADS)

    Ranjan, Kirti; Solyak, Nikolay; Tenenbaum, Peter

    2005-04-01

    Recently the particle physics community has chosen a single technology for the new accelerator, opening the way for the world community to unite and concentrate resources on the design of an International Linear collider (ILC) using superconducting technology. One of the key operational issues in the design of the ILC will be the preservation of the small beam emittances during passage through the main linear accelerator (linac). Sources of emittance dilution include incoherent misalignments of the quadrupole magnets and rf-structure misalignments. In this work, the study of emittance dilution for the 500-GeV center of mass energy main linac of the Superconducting Linear Accelerator design, based on adaptation of the TESLA TDR design is performed using LIAR simulation program. Based on the tolerances of the present design, effect of two important Beam-Based steering algorithms, Flat Steering and Dispersion Free Steering, are compared with respect to the emittance dilution in the main linac. We also investigated the effect of various misalignments on the emittance dilution for these two steering algorithms.

  5. A study of gait acceleration and synchronisation in healthy adult subjects.

    PubMed

    Yoneyama, Mitsuru

    2014-01-01

    Accelerometry-based gait analysis is widely recognised as a promising tool in healthcare and clinical settings since it is unobtrusive, inexpensive and capable of providing insightful information on human gait characteristics. In order to expand the application of this technology in daily environments, it is desirable to develop reliable gait measures and their extraction methods from the acceleration signal that can differentiate between normal and atypical gait. Important examples of such measures are gait cycle and gait-induced acceleration magnitude, which are known to be closely related to each other depending on each individual's physical condition. In this study, we derive a model equation with two parameters which captures the essential relationships between gait cycle and gait acceleration based on experiments and physical modelling. We also introduce as a new gait parameter a set of indexes to evaluate the synchronisation behaviour of gait timing. The function and utility of the proposed parameters are examined in 11 healthy subjects during walking under various selected conditions.

  6. Results from recent hydrogen pellet acceleration studies with a 2-m railgun

    SciTech Connect

    Kim, K.; Zhang, D.J.; King, T.; Haywood, R.; Manns, W.; Venneri, F.

    1989-12-01

    A new 3.2-mm-diameter, two-stage, fuseless, plasma-arc-driven electromagnetic railgun has been designed, constructed, and successfully operated to achieve a record velocity of 2.67 km/s({sup b}) for 3.2 mmD {times} 4 mmL solid hydrogen pellet. The first stage of this hydrogen pellet injector is a combination of a hydrogen pellet generator and a gas fun. The second stage is a 2-m-long railgun which serves as a booster accelerator. The gas fun accelerates a frozen hydrogen pellet to a medium velocity and injects it into the railgun through a perforated coupling piece, which also serves a pressure-relieving mechanism. An electrical breakdown of the propellant gas, which has followed the pellet from the gas fun into the railgun, forms a conducting plasma-arc armature immediately behind the pellet allowing for fuseless operation of the railgun. Study of the pressure profile and the behavior of the plasma-arc armature inside the railgun bore led to elimination of spurious arcing, which prevents operation of the railgun at high voltages (and, therefore, at high currents). A timing circuit that can automatically measure the pellet input velocity and allows for accurate control of arc initiation behind the pellet helps prevent pellet disintegration and mistriggering of the arc initiation circuit. Results from the recent cryogenic operation of the two-stage pellet acceleration system are reported. 11 refs., 2 figs., 1 tab.

  7. Relationship between bacterial diversity and function under biotic control: the soil pesticide degraders as a case study

    PubMed Central

    Monard, Cécile; Vandenkoornhuyse, Philippe; Le Bot, Barbara; Binet, Françoise

    2011-01-01

    In soil, the way biotic parameters impact the relationship between bacterial diversity and function is still unknown. To understand these interactions better, we used RNA-based stable-isotope probing to study the diversity of active atrazine-degrading bacteria in relation to atrazine degradation and to explore the impact of earthworm-soil engineering with respect to this relationship. Bulk soil, burrow linings and earthworm casts were incubated with 13C-atrazine. The pollutant degradation was quantified by liquid chromatography–mass spectrometry for 8 days, whereas active atrazine degraders were identified at 2 and 8 days by sequencing the 16S ribosomal RNA in the 13C-RNA fractions from the three soil microsites. An original diversity of atrazine degraders was found. Earthworm soil engineering greatly modified the taxonomic composition of atrazine degraders with dominance of α-, β- and γ-proteobacteria in burrow linings and of Actinobacteria in casts. Earthworm soil bioturbation increased the γ-diversity of atrazine degraders over the soil microsites generated. Atrazine degradation was enhanced in burrow linings in which primary atrazine degraders, closely related to Pelomonas aquatica, were detected only 2 days after atrazine addition. Atrazine degradation efficiency was not linearly related to the species richness of degraders but likely relied on keystone species. By enhancing soil heterogeneity, earthworms sustained high phylogenetic bacterial diversity and exerted a biotic control on the bacterial diversity–function relationships. Our findings call for future investigations to assess the ecological significance of biotic controls on the relationships between diversity and function on ecosystem properties and services (for example, soil detoxification) at larger scales. PMID:21160539

  8. Relationship between bacterial diversity and function under biotic control: the soil pesticide degraders as a case study.

    PubMed

    Monard, Cécile; Vandenkoornhuyse, Philippe; Le Bot, Barbara; Binet, Françoise

    2011-06-01

    In soil, the way biotic parameters impact the relationship between bacterial diversity and function is still unknown. To understand these interactions better, we used RNA-based stable-isotope probing to study the diversity of active atrazine-degrading bacteria in relation to atrazine degradation and to explore the impact of earthworm-soil engineering with respect to this relationship. Bulk soil, burrow linings and earthworm casts were incubated with (13)C-atrazine. The pollutant degradation was quantified by liquid chromatography-mass spectrometry for 8 days, whereas active atrazine degraders were identified at 2 and 8 days by sequencing the 16S ribosomal RNA in the (13)C-RNA fractions from the three soil microsites. An original diversity of atrazine degraders was found. Earthworm soil engineering greatly modified the taxonomic composition of atrazine degraders with dominance of α-, β- and γ-proteobacteria in burrow linings and of Actinobacteria in casts. Earthworm soil bioturbation increased the γ-diversity of atrazine degraders over the soil microsites generated. Atrazine degradation was enhanced in burrow linings in which primary atrazine degraders, closely related to Pelomonas aquatica, were detected only 2 days after atrazine addition. Atrazine degradation efficiency was not linearly related to the species richness of degraders but likely relied on keystone species. By enhancing soil heterogeneity, earthworms sustained high phylogenetic bacterial diversity and exerted a biotic control on the bacterial diversity-function relationships. Our findings call for future investigations to assess the ecological significance of biotic controls on the relationships between diversity and function on ecosystem properties and services (for example, soil detoxification) at larger scales.

  9. Treatment of industrial effluents using electron beam accelerator and adsorption with activated carbon: a comparative study

    NASA Astrophysics Data System (ADS)

    de Oliveira Sampa, Maria Helena; Rela, Paulo Roberto; Casas, Alexandre Las; Mori, Manoel Nunes; Duarte, Celina Lopes

    2004-09-01

    This paper presents preliminary results of a study that compares the use of electron beam processing and activated carbon adsorption to clean up a standardized organic aqueous solution and a real industrial effluent. The electron beam treatment was performed in a batch system using the IPEN's Electron Beam Accelerators from Radiation Dynamics Inc., Dynamitron 37.5 kW. The granular activated carbon removal treatment was performed using charcoal made from wood "pinus". If the adequate irradiation dose is delivered to the organic pollutant, it is possible to conclude for the studied compounds that the Electron Beam Process is similar to the activated carbon process in organic removal efficiency.

  10. Beam dynamics studies for the relativistic klystron two-beam accelerator experiment

    SciTech Connect

    Lidia, Steven M.

    2001-06-22

    Two-beam accelerators based upon relativistic klystron s (RK s) have been proposed as power sources for future generation linear electron-positron colliders. These drivers are known to suffer from several transverse beam break-up (BBU) instabilities. A program to study a particular technique (the betatron node scheme ) for ameliorating the high frequency BBU is under way at LBNL. Central to this study are the pillbox RF cavities and RF beam position monitors (BPM s) employed. This paper describes the design, fabrication, and testing of the RF components. Performance details during operation are also discussed.

  11. A study of elementary mechanisms of degradation of Cu2S-CdS heterojunction cells

    NASA Astrophysics Data System (ADS)

    Torchinskaia, T. V.

    Elementary mechanisms of degradation of Cu2S-CdS heterojunction cells are reviewed, and ways to develop stable solar cells based on II-VI compounds are discussed. The degradation mechanisms discussed include the oxidation of Cu2S due to interaction with air oxygen, electrochemical degradation associated with the decomposition of Cu2S, degradation associated with the ion conductivity of Cu(x)S, and a reduction in the concentration of donor-type defects. In order to stabilize the parameters of solar cells and prevent the latter type of degradation, it is recommended, among other degradation-preventing techniques, that the base material be doped with donor impurities.

  12. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  13. Assessment of land degradation susceptibility by scenario analysis: A case study in Southern Tuscany, Italy

    NASA Astrophysics Data System (ADS)

    Märker, Michael; Angeli, Luca; Bottai, Lorenzo; Costantini, Roberto; Ferrari, Raffaella; Innocenti, Lucia; Siciliano, Giuseppina

    2008-01-01

    In the Mediterranean area land degradation phenomena are becoming more and more important due to future climate change and increasing climate variability, as highlighted in recent global assessment projects such as the "Millennium Ecosystem Assessment" or "The Dialogue on Water and Climate". Thus, there is consistent evidence that extreme events such as droughts and floods are more frequent than before. On the other hand the Mediterranean area is strongly influenced by human activities such as cultivation over hundreds of years. However, in the last decades the cultivation methods and techniques are subject to profound changes such as mechanization, use of fertilizers and pesticides, remodellation of entire hillslopes etc. This particular situation leads to, and aggravates the existing stress on land resources. As a result, land degradation and soil erosion phenomena are leading to decreasing soil productivity or the loss of fertile top soil and related water quality and quantity issues. The Centre for Soil Erosion Studies (CRES) in Grosseto, Tuscany recently started a study to identify and monitor changes of land-use in southern Tuscany, Italy. The aim of this study is to assess land degradation sensitivity by scenario analysis. As a proxi for land degradation surface wash erosion processes such as rill and interill erosion processes are chosen. These present day processes are identified by aerial photo interpretation and subsequently modelled with a simple RUSLE approach on a monthly basis. In this study boundary conditions such as future precipitation were taken from the A2 future climate scenario published by the International Panel on Climate Change (IPCC)-Special Report on Emission Scenarios (SRES). Moreover, current land-use was identified from aerial photographs and future land-use scenarios were developed considering ecological and socio-economical issues for present day conditions of the test area. Subsequently, the different climate and land

  14. Forced degradation study of racecadotril: Effect of co-solvent, characterization of degradation products by UHPLC-Q-TOF-MS/MS, NMR and cytotoxicity assay.

    PubMed

    Chiguru, Vishnuvardhan; Lingesh, Allakonda; R, Srinivas; N, Satheeshkumar

    2016-09-01

    Racecadotril, an enkephalinase inhibitor, was subjected to hydrolysis (acidic and alkaline), oxidation, photolysis and thermal stress, as per ICH specified conditions. The drug showed extensive degradation under acidic, basic hydrolysis and oxidative stress conditions whereas, it was stable under other stress conditions. A total of seven degradation products (DPs) were observed. The chromatographic separation was optimized on Acquity HSS Cyano (100×2.1mm, 1.8μ) column using 0.1% formic acid and acetonitrile as mobile phase in gradient mode. Six DPs were characterised by LC-MS/MS and DP1 by GC-MS. The major DPs (DP 2 and DP 5) were isolated and characterised by NMR. This is a typical case of degradation where co solvent methanol reacts with racecadotril leading to the formation of pseudo DPs, DP 6 and DP 5. Interestingly the MS/MS spectra of protonated drug, DP 4 and DP 7 showed product ions which were formed due to intramolecular benzyl migrations. In vitro cytotoxic activity studies on isolated DP 2 and DP 5 revealed that the former has no cytotoxic nature, whereas the latter has potential pulmonary and hepatic toxicity. PMID:27209450

  15. Study on effects of temperature, moisture and pH in degradation and degradation kinetics of aldrin, endosulfan, lindane pesticides during full-scale continuous rotary drum composting.

    PubMed

    Ali, Muntjeer; Kazmi, A A; Ahmed, Naseem

    2014-05-01

    Study focused on effects of temperature, moisture and pH on degradation and degradation kinetics of aldrin, endosulfan (α), endosulfan (β) and lindane during vegetable waste composting using full-scale continuous rotary drum composter (FSCRDC). Extraction, concentration and quantification of pesticides were made from waste material at different stages by ultra-sonification, silica gel column and GC-MS analysis. Removal efficiency of aldrin, endosulfan α, endosulfan β and lindane was found 85.67%, 84.95%, 83.20% and 81.36% respectively due to optimum temperature, moisture, pH and enhanced microbial activity. Maximum temperature in inlet zone was found 60-65°C which is most suitable for complex microbial population. After feeding and turning in inlet zone, temperature reduced to 38°C from 60 to 65°C and regained it within 7-8h, and pH reduced to 5.3±0.2 from 7.5±0.3 in 4h and regained it in 10h. Heterotrophic bacteria Bacillus sp., Pseudomonas sp. and Lactobacillus sp. also decreased from 4.4×10(3) to 7.80×10(2)CFU g(-1) in 2 h due to gradual variation in temperature and pH. No significant temperature change was found in middle and outlet zones during feeding and turning. Degradation of pesticides was observed as first order kinetics and half-life of aldrin, endosulfan α, endosulfan β and lindane was reduced to 25.54, 18.43, 18.43 and 27.43 d from 1095, 60, 270 and 160 d respectively. Thus, the observations in contrast of removal and degradation kinetics of organochlorine pesticides residues in vegetable waste though full-scale rotary drum composting proved it the best suited technique.

  16. Soil quality degradation processes along a deforestation chronosequence in the Ziwuling Area, China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accelerated erosion caused by deforestation and soil degradation has become the primary factor limiting sustainable utilization of soil resources on the Loess Plateau of Northwestern China. We studied the physical, chemical, and microbiological processes of soil degradation along a chronosequence o...

  17. Numerical simulation study of positron production by intense laser-accelerated electrons

    SciTech Connect

    Yan, Yonghong; Dong, Kegong; Wu, Yuchi; Zhang, Bo; Gu, Yuqiu; Yao, Zeen

    2013-10-15

    Positron production by ultra-intense laser-accelerated electrons has been studied with two-dimensional particle-in-cell and Monte Carlo simulations. The dependence of the positron yield on plasma density, plasma length, and converter thickness was investigated in detail with fixed parameters of a typical 100 TW laser system. The results show that with the optimal plasma and converter parameters a positron beam containing up to 1.9 × 10{sup 10} positrons can be generated, which has a small divergence angle (10°), a high temperature (67.2 MeV), and a short pulse duration (1.7 ps)

  18. Application of convergence acceleration to the reactor kinetic equations: A comparative study

    SciTech Connect

    Picca, P.; Furfaro, R.; Ganapol, B. D.

    2013-07-01

    This presentation provides a comparison of two methodologies for the solution of reactor kinetic equations, namely for a standard finite difference and a semi-analytical approach. The above-mentioned methods are implemented in a convergence acceleration framework to enhance their efficiency and a comparative study is reported to verify whether it is more convenient to use a rudimentary but fast algorithm (finite difference) with respect to the more refined but computationally intense approach of the semi-analytical method. Performance on several test cases from the literature are compared. (authors)

  19. Hamiltonian methods for the study of polarized proton beam dynamics in accelerators and storage rings

    SciTech Connect

    Balandin, V. |; Golubeva, N.

    1997-02-01

    The equations of classical spin-orbit motion can be extended to a {bold Hamiltonian system} in 9-dimensional phase space by introducing a coupled spin-orbit {bold Poisson bracket} (3) and {bold Hamiltonian function} (5). After this extension it becomes possible to apply the {bold methods of the theory of Hamiltonian systems} to the study of polarized particles beam dynamics in circular accelerators and storage rings. Some of those methods have been implemented in the computer code {bold FORGET-ME-NOT} [1], [2]. {copyright} {ital 1997 American Institute of Physics.}

  20. Simulation study of accelerator based quasi-mono-energetic epithermal neutron beams for BNCT.

    PubMed

    Adib, M; Habib, N; Bashter, I I; El-Mesiry, M S; Mansy, M S

    2016-01-01

    Filtered neutron techniques were applied to produce quasi-mono-energetic neutron beams in the energy range of 1.5-7.5 keV at the accelerator port using the generated neutron spectrum from a Li (p, n) Be reaction. A simulation study was performed to characterize the filter components and transmitted beam lines. The feature of the filtered beams is detailed in terms of optimal thickness of the primary and additive components. A computer code named "QMNB-AS" was developed to carry out the required calculations. The filtered neutron beams had high purity and intensity with low contamination from the accompanying thermal, fast neutrons and γ-rays.

  1. Study of the near-electrode processes in quasi-steady plasma accelerators with impenetrable electrodes

    SciTech Connect

    Kozlov, A. N.

    2012-01-15

    Near-electrode processes in a coaxial plasma accelerator with equipotential impenetrable electrodes are simulated using a two-dimensional (generally, time-dependent) two-fluid MHD model with allowance for the Hall effect and the plasma conductivity tensor. The simulations confirm the theoretically predicted mechanism of the so-called 'crisis of current' caused by the Hall effect. The simulation results are compared with available experimental data. The influence of both the method of plasma supply to the channel and an additional longitudinal magnetic field on the development of near-electrode instabilities preceding the crisis of current is studied.

  2. Impact of permafrost degradation on debris flow initiation - a case study from the north Italian Alps

    NASA Astrophysics Data System (ADS)

    Damm, Bodo; Felderer, Astrid

    2014-05-01

    Atmospheric warming in high mountain environments causes a range of impacts, including glacier recession, reduction of permafrost extent and distribution as well as changes in thermal permafrost properties. Furthermore, it is likely that climate change affects the occurrence of natural hazards, like shallow landslides and debris flows, as their initiation is related to the degradation of the cryosphere. The present study demonstrates the importance of recent atmospheric warming for the spatial distribution of debris flow initiation in a central alpine area of the Italian Alps (Europe). It is primarily based on the modelling of the spatial distribution of permafrost using a database of geomorphologic, hydrologic, and physical permafrost indicators and the CRYOSNOW-approach. There is first evidence that it is possible to quantify the regional debris flow hazard potential based on field survey, in-situ measurements, climate data analyses, and GIS-based simulations for different climate scenarios and variable geomorphic stability. In particular, permafrost degradation due to increasing mean annual air temperature (MAAT) since the end of the Little Ice Age (LIA) caused mechanical instabilities of sediments and slopes. In the study area it can be shown that almost half of the debris flow initiation zones originate in areas with loose rock that were still stabilized by glacier ice and/or permafrost about 150 years ago. Compared to present conditions the permafrost area would decrease by approximately 72% by the middle of the 21st century with regard to an increased air temperature of +1 to +2 K. Moreover, glaciers widely disappear in this scenario. This may presumed to be a moderate increase of temperature in relation to the predicted climate development of the IPCC. Ongoing glacier recession and permafrost degradation increase the amount of instable debris as well as the potential of debris flow detachment zones in the future. References Damm, B., Felderer, A. (2013

  3. Field research studies on the movement and degradation of thiodicarb and its metabolite methomyl

    NASA Astrophysics Data System (ADS)

    Jones, Russell L.; Hunt, Timothy W.; Norris, Frank A.; Harden, Christal F.

    1989-09-01

    The movement and degradation of thiodicarb and its metabolite methomyl were measured at three locations in the United States. At a site near Clayton, North Carolina, soil samples were used to determine the degradation rate of thiodicarb in surface soils and methomyl in both surface and subsoils. At sites near Palermo, New York, and Oviedo, Florida, the shallow groundwater was monitored following multiple foliar applications of thiodicarb. These groundwater monitoring studies were conducted under conditions favorable to movement of pesticides to groundwater since surface soils were loamy sand or sand, subsoils were sand, water tables ranged between 0.1 and 1.8 m, and rainfall was supplemented by irrigation to ensure that the sum of irrigation and rainfall was at least 1.5 times the normal monthly rainfall. In these studies the half-life of thiodicarb was only a few hours in surface soils, while the half-life methomyl was about two days in surface soils and about 0.5 to 1.6 months in subsoils. Although methomyl residues were detected in shallow groundwater in the Oviedo and Palermo studies (designed to be representative of worst case situations), these residues were present in only one well cluster and one sampling interval, and at concentrations substantially below the established health advisory level.

  4. Concept study of high volume food irradiation with a pulsed power accelerator

    SciTech Connect

    Turman, B.N.; Prestwich, K.R.; Neau, E.L.; Johnson, D.L.; Kensek, R.P.

    1993-12-31

    A concept study was initiated to establish technical requirements and processing cost estimates for a high power, high volume x-radiation food processing facility using pulsed power technology. The design study was directed toward a central processing plant that would transport and process the food products in standard pallets of 1.1m {times} 1.2m {times} 1.2m dimensions. The 1.2m depth of penetration, and a dose uniformity requirement of a factor of 2 between the maximum and minimum dose, led to a decision to employ x-radiation, produced from a 5 MeV electron beam. The electron beam is produced from a large-area cathode and accelerated by a multi-module pulsed power accelerator. The beam power for this design is 500 kW. An example application is developed for illustration, based on produce disinfestation at maximum exposure level of l00 krad and minimum exposure of 50 krad. In order to achieve this ratio of maximum to minimum dose, the pallet is rotated through 3609 while being exposed. The estimated process rate is approximately 30 metric tons/hour. The accelerator design was developed by scaling from the present high average power beam experiments in the Repetitive High Energy Pulsed Power (RHEPP) program, which will deliver an output of 350 kW in a 2.5 MeV beam. The high voltage is achieved by using 250 kV pulses that are added together with inductively-isolated adder cavities. This technology will be described, and results from the RHEPP experiments will be compared with the design requirements for the high power food processor application. Processing issues, technology limits, dose calculations, and cost estimates will be discussed.

  5. Study of the Synchrotron Radiation Emission from the NRL Modified Betatron Accelerator

    NASA Astrophysics Data System (ADS)

    Smith, Tab Jay

    1990-01-01

    Incoherent synchrotron radiation from a relativistic electron beam circulating in the magnetic field configuration of the NRL modified betatron accelerator has been studied numerically and experimentally. Numerical studies show that, for relativistic electron energies up to approximately 2 MeV, the single particle spectrum of radiation is dominated by a peak in the intensity distribution at the Doppler -shifted cyclotron frequency about the toroidal field. This intensity distribution very closely approximates the distribution for a linear helical electron trajectory with relativistic velocity along the axis of the helix. The radiated electric field oscillations, however, are 'modulated' due to the curvature of the major radius. As the electrons accelerate above an energy of a few MeV, the modulation width becomes so narrow that even the fast gyro-oscillation about the toroidal field produces no significant variation in the total radiated fields. Thus, the amplitude, polarization, and frequency content in the spectrum approaches that of a purely circular orbit. Experimental studies of the radiation have been conducted by monitoring the temporal evolution of radiated power during acceleration using fixed-frequency heterodyne receivers. Radiation was measured for electron beam energies in the range of 0.5 MeV to about 10 MeV, trapped beam currents up to approximately 500 A, and for values of toroidal guide field in the range of approximately 1900 to 3500 Gauss. At electron energies less than about 2 MeV, the polarization, amplitude, scaling with trapped beam current, and the temporal evolution of measured radiation during acceleration are in very good agreement with the predicted single particle spectrum. Furthermore, there is no evidence of collective emission at least within the frequency ranges 8 to 12 GHz and 26 to 40 GHz. The only significant discrepancy between the experimental and predicted results is the apparent absence of the horizontally polarized radiation

  6. Thermal degradation events as health hazards: Particle vs gas phase effects, mechanistic studies with particles

    NASA Astrophysics Data System (ADS)

    Oberdörster, G.; Ferin, J.; Finkelstein, J.; Soderholm, S.

    Exposure to thermal degradation products arising from fire or smoke could be a major concern for manned space missions. Severe acute lung damage has been reported in people after accidental exposure to fumes from plastic materials, and animal studies revealed the extremely high toxicity of freshly generated fumes whereas a decrease in toxicity of aged fumes has been found. This and the fact that toxicity of the freshly generated fumes can be prevented with filters raises the question whether the toxicity may be due to the particulate rather than the gas phase components of the thermodegradation products. Indeed, results from recent studies implicate ultrafine particles (particle diameter in the nm range) as potential severe pulmonary toxicants. We have conducted a number of in vivo (inhalation and instillation studies in rats) and in vitro studies to test the hypothesis that ultrafine particles possess an increased potential to injure the lung compared to larger-sized particles. We used as surrogate particles ultrafine TiO 2 particles (12 and 20 nm diameter). Results in exposed rats showed that the ultrafine TiO 2 particles not only induce a greater acute inflammatory reaction in the lung than larger-sized TiO 2 particles, but can also lead to persistent chronic effects, as indicated by an adverse effect on alveolar macrophage mediated clearance function of particles. Release of mediators from alveolar macrophages during phagocytosis of the ultrafine particles and an increased access of the ultrafine particles to the pulmonary interstitium are likely factors contributing to their pulmonary toxicity. In vitro studies with lung cells (alveolar macrophages) showed, in addition, that ultrafine TiO 2 particles have a greater potential to induce cytokines than larger-sized particles. We conclude from our present studies that ultrafine particles have a significant potential to injure the lung and that their occurrence in thermal degradation events can play a major role in

  7. Thermal degradation events as health hazards: particle vs gas phase effects, mechanistic studies with particles.

    PubMed

    Oberdörster, G; Ferin, J; Finkelstein, J; Soderholm, S

    1992-01-01

    Exposure to thermal degradation products arising from fire or smoke could be a major concern for manned space missions. Severe acute lung damage has been reported in people after accidental exposure to fumes from plastic materials, and animal studies revealed the extremely high toxicity of freshly generated fumes whereas a decrease in toxicity of aged fumes has been found. This and the fact that toxicity of the freshly generated fumes can be prevented with filters raises the question whether the toxicity may be due to the particulate rather than the gas phase components of the thermodegradation products. Indeed, results from recent studies implicate ultrafine particles (particle diameter in the nm range) as potential severe pulmonary toxicants. We have conducted a number of in vivo (inhalation and instillation studies in rats) and in vitro studies to test the hypothesis that ultrafine particles possess an increased potential to injure the lung compared to larger-sized particles. We used as surrogate particles ultrafine TiO2 particles (12 and 20 nm diameter). Results in exposed rats showed that the ultrafine TiO2 particles not only induce a greater acute inflammatory reaction in the lung than larger-sized TiO2 particles, but can also lead to persistent chronic effects, as indicated by an adverse effect on alveolar macrophage mediated clearance function of particles. Release of mediators from alveolar macrophages during phagocytosis of the ultrafine particles and an increased access of the ultrafine particles to the pulmonary interstitium are likely factors contributing to their pulmonary toxicity. In vitro studies with lung cells (alveolar macrophages) showed, in addition, that ultrafine TiO2 particles have a greater potential to induce cytokines than larger-sized particles. We conclude from our present studies that ultrafine particles have a significant potential to injure the lung and that their occurrence in thermal degradation events can play a major role in the

  8. A Parametric Study of Accelerations of an Airplane Due to a Wake Vortex System

    NASA Technical Reports Server (NTRS)

    Stewart, Eric C.

    1999-01-01

    A study was conducted using strip theory to systematically investigate the effects of progressively more complete descriptions of the interaction of an airplane with a wake vortex system. The emphasis was in roll-dominant, parallel, vortex encounters. That is, the simulated airplane's longitudinal axis was nearly parallel to the rotation axis of the vortex system for most of the results presented. The study began with a drag-less rectangular wing in the flow field of a single vortex and progressed to a complete airplane with aerodynamic surfaces possessing taper, sweep, dihedral, and stalling and immersed in the flow field of a vortex pair in ground effect. The effects of the pitch, roll, and yaw attitudes of the airplane on the calculated accelerations were also investigated. The airplane had the nominal characteristics of a Boeing 757, and the vortex flow field had the nominal characteristics of the wake of a Boeing 767. The Bumham-Hallock model of a vortex flow field was used throughout the study. The data are presented mainly in terms of contours of equal acceleration in a two-dimensional area centered on the vortex pair and having dimensions of 300 feet by 300 feet.

  9. Hardware accelerated C-arm CT and fluoroscopy: a pilot study

    NASA Astrophysics Data System (ADS)

    Riabkov, Dmitri; Brown, Todd; Cheryauka, Arvi; Tokhtuev, Alexander

    2008-03-01

    Clinical demands of image-guided procedures present technical challenges in X-ray 1K×1K fluoroscopy and cone-beam CT on a mobile C-arm. Performance-per-watt and performance-per-dollar are other major considerations in a search for an optimal computational platform. Real-time constraints of processing high-resolution fluoroscopic images currently necessitate the use of highly specialized proprietary image processing hardware, which cannot be easily repurposed for acceleration of other computing tasks. In our previous studies, we were investigating heterogeneous computing architectures and suitable hardware/software components to assist in time-critical surgical applications. Through those studies, it has been shown that Graphics Processing Units (GPUs) can provide outstanding levels of computational power utilizing the Single Instruction Multiple Data (SIMD) programming model. In the present study, we expand our research in the domain of real-time processing and continue to explore the feasibility of GPU acceleration for both fluoroscopic and tomographic imaging. Current emphasis is being placed on applicability of NVIDIA's novel Tesla computing solutions and Compute Unified Device Architecture (CUDA). The results of this pilot project comprise the Cg/OpenGL and CUDA algorithm implementations, benchmark evaluations, and examples of processing image data acquired with use of anthropomorphic phantoms.

  10. COP-compost: a software to study the degradation of organic pollutants in composts.

    PubMed

    Zhang, Y; Lashermes, G; Houot, S; Zhu, Y-G; Barriuso, E; Garnier, P

    2014-02-01

    Composting has been demonstrated to be effective in degrading organic pollutants (OP) whose behaviour depends on the composting conditions, the microbial populations activated and interactions with organic matters. The fate of OP during composting involves complex mechanisms and models can be helpful tools for educational and scientific purposes, as well as for industrialists who want to optimise the composting process for OP elimination. A COP-Compost model, which couples an organic carbon (OC) module and an organic pollutant (OP) module and which simulates the changes of organic matter, organic pollutants and the microbial activities during the composting process, has been proposed and calibrated for a first set of OP in a previous study. The objectives of the present work were (1) to introduce the COP-Compost model from its convenient interface to a potential panel of users, (2) to show the variety of OP that could be simulated, including the possibility of choosing between degradation through co-metabolism or specific metabolism and (3) to show the effect of the initial characteristics of organic matter quality and its microbial biomass on the simulated results of the OP dynamic. In the model, we assumed that the pollutants can be adsorbed on organic matter according to the biochemical quality of the OC and that the microorganisms can degrade the pollutants at the same time as they degrade OC (by co-metabolism). A composting experiment describing two different (14)C-labelled organic pollutants, simazine and pyrene, were chosen from the literature because the four OP fractions simulated in the model were measured during the study (the mineralised, soluble, sorbed and non-extractable fractions). Except for the mineralised fraction of simazine, a good agreement was achieved between the simulated and experimental results describing the evolution of the different organic fractions. For simazine, a specific biomass had to be added. To assess the relative importance

  11. Application of TAM III to study sensitivity of soil organic matter degradation to temperature

    NASA Astrophysics Data System (ADS)

    Vikegard, Peter; Barros, Nieves; Piñeiro, Verónica

    2014-05-01

    Traditionally, studies of soil biodegradation are based on CO2 dissipation rates. CO2 is a product of aerobic degradation of labile organic substrates like carbohydrates. That limits the biodegradation concept to just one of the soil organic matter fractions. This feature is responsible for some problems to settle the concept of soil organic matter (SOM) recalcitrance and for controversial results defining sensitivity of SOM to temperature. SOM consists of highly complex macromolecules constituted by fractions with different chemical nature and redox state affecting the chemical nature of biodegradation processes. Biodegradation of fractions more reduced than carbohydrates take place through metabolic pathways that dissipate less CO2 than carbohydrate respiration, that may not dissipate CO2, or that even may uptake CO2. These compounds can be considered more recalcitrant and with lower turnover times than labile SOM just because they are degraded at lower CO2 rates that may be just a consequence of the metabolic path. Nevertheless, decomposition of every kind of organic substrate always releases heat. For this reason, the measurement of the heat rate by calorimetry yields a more realistic measurement of the biodegradation of the SOM continuum. TAM III is one of the most recent calorimeters designed for directly measuring in real time the heat rate associated with any degradation process. It is designed as a multichannel system allowing the concomitant measurement of to up 24 samples at isothermal conditions or through a temperature scanning mode from 18 to 100ºC, allowing the continous measure of any sample at controlled non-isothermal conditions. The temperature scanning mode was tested in several soil samples collected at different depths to study their sensitivity to temperature changes from 18 to 35 ºC calculating the Q10 and the activation energy (EA) by the Arrhenius equation. It was attempted to associate the obtained EA values with the soil thermal

  12. Deglycosylation-dependent fluorescent proteins provide unique tools for the study of ER-associated degradation

    PubMed Central

    Grotzke, Jeff E.; Lu, Qiao; Cresswell, Peter

    2013-01-01

    Endoplasmic reticulum–associated degradation (ERAD) is a constitutive process that identifies misfolded proteins in the ER and shuttles them to the cytosol, where they can be degraded by the proteasome. The accumulation of misfolded proteins can be catastrophic at both the cellular and organismal level. Although the players involved and mechanistic details of ERAD are being characterized, much remains to be learned. Because of the complexity of the pathway, experimental studies generally require labor-intensive biochemical techniques. Here, we report the development of a system to analyze ERAD based on mutants of split or intact Venus fluorescent protein for which fluorescence depends on enzymatic deglycosylation. We have generated variants that only become fluorescent when they are first glycosylated in the ER and subsequently deglycosylated after retrotranslocation into the cytosol. The E3 ubiquitin ligase HMG-coA reductase degradation 1 homolog (Hrd1) and, consistent with the demonstrated glycosylation/deglycosylation requirement, the cytosolic deglycosylating enzyme peptide:N′glycanase are both required for fluorescence. Furthermore, although these deglycosylation-dependent fluorescent proteins are themselves ERAD substrates, they can also be fused to additional ERAD substrates to interrogate substrate-specific pathways. To validate the system we performed a genomewide siRNA screen that successfully identified known ERAD factors such as Hrd1; homocysteine-inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1 (HERP); sel-1 suppressor of lin-12-like (SEL1L); and p97. These tools should greatly facilitate the identification of ERAD components and investigation of the mechanisms involved in this critical pathway. PMID:23401531

  13. Transition Metal Complexes of Naproxen: Synthesis, Characterization, Forced Degradation Studies, and Analytical Method Verification

    PubMed Central

    Hasan, Md. Sharif; Kayesh, Ruhul; Begum, Farida; Rahman, S. M. Abdur

    2016-01-01

    The aim of our current research was to synthesize some transition metal complexes of Naproxen, determine their physical properties, and examine their relative stability under various conditions. Characterizations of these complexes were done by 1H-NMR, Differential Scanning Calorimetry (DSC), FT-IR, HPLC, and scanning electron microscope (SEM). Complexes were subjected to acidic, basic, and aqueous hydrolysis as well as oxidation, reduction, and thermal degradation. Also the reversed phase high-performance liquid chromatography (RP-HPLC) method of Naproxen outlined in USP was verified for the Naproxen-metal complexes, with respect to accuracy, precision, solution stability, robustness, and system suitability. The melting points of the complexes were higher than that of the parent drug molecule suggesting their thermal stability. In forced degradation study, complexes were found more stable than the Naproxen itself in all conditions: acidic, basic, oxidation, and reduction media. All the HPLC verification parameters were found within the acceptable value. Therefore, it can be concluded from the study that the metal complexes of Naproxen can be more stable drug entity and offer better efficacy and longer shelf life than the parent Naproxen. PMID:27034891

  14. Environmental degradation and migration: the U.S.-Mexico case study.

    PubMed

    1998-01-01

    This article provides a detailed account of the conclusions and policy recommendations of a study of environmental degradation and migration between the US and Mexico. Key recommendations and findings were included in the official US Congressional Commission on Immigration Reform report (September 1997). The Congressional report urges Congress to consider environment and development root causes of migration in establishing foreign policies with Mexico and other countries. It appears that the root cause of Mexican migration is rural land degradation or desertification. The study suggests feasible solutions, and not additional border security and employment-related sanctions. The US has the technology and expertise to facilitate programs that address environmental and development issues in targeted and integrated ways. The recommendations serve as a framework for policy reform and debate on rural development and agricultural productivity. Mexican states should be targeted that are new migration-sending states with extensive poverty and soil erosion problems and well-established migration states. Environment, population, and migration are all housed in the Global Affairs Office in the US Department of State, but there is little program integration. The USAID bureaucracy separates agricultural and environmental programs. Solutions include, for example, reducing the costs of remittances from the US to Mexico, conducting research on integrated solutions, and contributing to improved land and water management practices, forest management and land tenure, and the competitiveness of smallholders.

  15. Transition Metal Complexes of Naproxen: Synthesis, Characterization, Forced Degradation Studies, and Analytical Method Verification.

    PubMed

    Hasan, Md Sharif; Kayesh, Ruhul; Begum, Farida; Rahman, S M Abdur

    2016-01-01

    The aim of our current research was to synthesize some transition metal complexes of Naproxen, determine their physical properties, and examine their relative stability under various conditions. Characterizations of these complexes were done by 1H-NMR, Differential Scanning Calorimetry (DSC), FT-IR, HPLC, and scanning electron microscope (SEM). Complexes were subjected to acidic, basic, and aqueous hydrolysis as well as oxidation, reduction, and thermal degradation. Also the reversed phase high-performance liquid chromatography (RP-HPLC) method of Naproxen outlined in USP was verified for the Naproxen-metal complexes, with respect to accuracy, precision, solution stability, robustness, and system suitability. The melting points of the complexes were higher than that of the parent drug molecule suggesting their thermal stability. In forced degradation study, complexes were found more stable than the Naproxen itself in all conditions: acidic, basic, oxidation, and reduction media. All the HPLC verification parameters were found within the acceptable value. Therefore, it can be concluded from the study that the metal complexes of Naproxen can be more stable drug entity and offer better efficacy and longer shelf life than the parent Naproxen. PMID:27034891

  16. Theoretical investigation of loratadine reactivity in order to understand its degradation properties: DFT and MD study.

    PubMed

    Armaković, Stevan; Armaković, Sanja J; Abramović, Biljana F

    2016-10-01

    Antihistamines are frequently used pharmaceuticals that treat the symptoms of allergic reactions. Loratadine (LOR) is an active component of the second generation of selective antihistaminic pharmaceutical usually known as Claritin. Frequent usage of this type of pharmaceuticals imposes the need for understanding their fundamental reactive properties. In this study we have theoretically investigated reactive properties of LOR using both density functional theory (DFT) calculations and molecular dynamics (MD) simulations. DFT study is used for collecting information related to the molecule stability, structure, frontier molecular orbitals, quantum molecular descriptors, charge distribution, molecular electrostatic potential surfaces, charge polarization, and local reactivity properties according to average local ionization energy surfaces. Based on these results, N24 atom of pyridine ring and oxygen atom O1 were identified with nucleophilic nature. In order to collect the information necessary for the proposition of degradation compounds we also calculated bond dissociation energies (BDE) for hydrogen abstraction and single acyclic bonds as well. According to BDE, the oxidation is likely to occur in the piperidine and cycloheptane rings. MD simulations were used in order to understand the interactions with water through radial distribution functions (RDF). Based on RDFs the most important interactions with solvent are determined for carbon atom C5, chlorine atom Cl15, and oxygen atom O1. Collected results based on DFT calculations and MD simulations provided information important for suggestion of possible degradation compounds. Covalent and noncovalent interactions between LOR and (•)OH have also been investigated. PMID:27640160

  17. In vitro studies of degradation and bioactivity of aliphatic polyester composites

    NASA Astrophysics Data System (ADS)

    Chouzouri, Georgia

    In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation. Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray-diffraction (XRD) and changes in ion concentration. In the case of the six neat fillers evaluated, the filler shape, form and chemical structure showed significant differences in bioactivity response. Bioglass and calcium silicate fillers showed faster nucleation and growth rates in the screening experiments. Composites at 30% by weight filler were prepared by solution and/or melt mixing. Polycaprolactone (PCL) composites containing five different fillers were evaluated. Solution processed PCL/calcium silicate (CS) samples showed faster bioactivity, as determined by apatite growth, compared to melt mixed samples. The onset time for bioactivity was different for all PCL composites. The limited bioactivity in the PCL composites over longer periods of time could be attributed to the PCL hydrophobicity leading to a slow polymer degradation rate, and also to the lack of SBF replenishment. For both polylactic acid (PLA) composites containing CS and bioglass, significant growth was observed after one week and in the case of CS was still evident after four weeks immersion. However, at prolonged time periods no further bioactivity was observed, although ion release results indicated a faster release rate that would

  18. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  19. Can Accelerators Accelerate Learning?

    SciTech Connect

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-10

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ)[1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  20. [Study on cooperating degradation of cypermethrin and 3-phenoxybenzoic acid by two bacteria strains].

    PubMed

    Xu, Yu-Xin; Sun, Ji-Quan; Li, Xiao-Hui; Li, Shun-Peng; Chen, Yi

    2007-10-01

    The microbial cooperated reaction is one of the most important forms of microbial degradation of organic pollutants. Although there were many research reports of cooperating degradation, less report on the microbial cooperated of pyrethroid degradation to be found. We have isolated one degrading-bacteria strain named CDT3 for degradation of cypermethrin, which can degraded the cypermethrin into 3-PBA and DCVA. At the same time, we also isolated another degrading-bacteria strain named as PBM11, which could get multiplication on 3-PBA as its C source and energy source. The cooperative degradation process of cypermethrin and 3-Phenoxybenzoic acid (3-PBA) using the two degrading-bacteria strain CDT3 and PBM11 was investigated. An obvious inhibition to the cypermethrin degrading-bacterium strain CDT3 (Rhodococcus sp.) by its metabolic mediate 3-PBA was found; meanwhile there is no effect on the growth of 3-PBA degrading-bacterium strain PBM11 (Pesudomonas sp.) when the concentration of cypermethrin was lower than 200 mg/L. The degradation rate of cypermethrin by both strain CDT3 and PBM11 was higher than that by CDT3 alone. The biomass of PBM11 increased along with the degradation of cypermethrin and 3-PBA, but that of CDT3 not. There was no the accumulation of 3-PBA when the simultaneous addition of strain CDT3 and PBM11, however, an obvious one within 24h if inoculation of strain PBM11 was later 24h after inoculation of strain CDT3, Subsequently the 3-PBA was degraded rapidly by strain PBM11. The strains CDT3 and PBM11 showed some characteristics of co-metabolism, however it is not actual degradation form of co-metabolism. For examples, although the degrading sub product of cypermethrin by CDT3 could be utilized, the multiplication of PBM11 could not enhance the multiplication of CDT3, implied there is no obvious relationship between the two strains. Also, to add PBM11 could eliminate the inhibition of 3-PBA to CDT3. Thus, the cooperating degradation of strains CDT3

  1. Solid state electrical conductivity and thermal degradation studies on some phenothiazine derivatives

    NASA Astrophysics Data System (ADS)

    Achar, B. N.; Ashok, M. A.

    2007-02-01

    Electrical conductivity and thermal degradation studies of promethazine hydrochloride (PH); 2-chlorophenothiazine (CP); diethazine hydrochloride (DH) and trifluoperazine dihydrochloride (TFP) are reported. The activation energies are evaluated based on their electrical conductivity study conducted over the temperature range 30 150 °C. These energies for PH, CP, DH and TFP are found to be 0.86, 1.02, 0.68 and 1.08 eV, respectively. The materials are analyzed for the kinetic parameters like the activation energies for decomposition and the Arrhenious pre-exponential factors in their pyrolysis region using Broido's, Coats Redfern and Horowitz Metzger methods. Using these factors and the standard equations thermodynamic parameters such as enthalpy, entropy and free energies are calculated. Thermogravimetric study on these phenothiazine derivatives in air indicated that their stabilities are in the order CP>TFP>PH >DH.

  2. High intensity 5 eV O-atom exposure facility for material degradation studies

    NASA Technical Reports Server (NTRS)

    Cross, J. B.; Spangler, L. H.; Hoffbauer, M. A.; Archuleta, F. A.; Leger, Lubert; Visentine, James; Hunton, Don E.; Cross, J. B.

    1986-01-01

    An atomic oxygen exposure facility was developed for studies of material degradation. The goal of these studies is to provide design criteria and information for the manufacture of long life (20 to 30 years) construction materials for use in low Earth orbit. The studies that are being undertaken will provide: (1) absolute reaction cross sections for the engineering design problems, (2) formulations of reaction mechanisms for use in the selection of suitable existing materials and the design of new more resistant ones, and (3) the calibration of flight hardware (mass spectrometers, etc.) in order to directly relate experiments performed in low Earth orbit to ground based investigations. The facility consists of a CW laser sustained discharge source of O-atoms, an atomic beam formation and diagnostics system, a spinning rotor viscometer, and provision for using the system for calibration of actual flight instruments.

  3. [Simulated study of algal fatty acid degradation in hypoxia seawater-sediment interface along China coastal area].

    PubMed

    Sui, Wei-Wei; Ding, Hai-Bing; Yang, Gui-Peng; Lu, Xiao-Lan; Li, Wen-Juan; Sun, Li-Qun

    2013-11-01

    Series of laboratory incubation experiments were conducted to simulate degradation of organic matter in sediment-seawater interface in hypoxia enviroments along China coastal area. Under four different redox conditions (oxygen saturation: 100%, 50%, 25% and 0%), degradations of seveal biomarkers originated from Skeletonema costatum, a typical red tide alage along China coastal area were tracked. By analyzing concentrations of four fatty acid biomarkers [14:0, 16:0, 16:1(7) and 20:5] obtained at various sampling time, results showed that their concentrations decreased significantly after 2-3 weeks' incubation. Then, their concentrations changed very slowly or very little. However, degradation of the four fatty acids varied dramatically in different incubation systems. Fatty acids 14:0, 16:1(7) and 20:5 were degraded completely in all incubation systems after two-month incubation, but 25% to 35% of 16:0 was reserved in the systems. Based on multi-G model, degradations of the four fatty acids were quantively described. The results indicated that all four fatty acids had fast-degraded and slow-degraded fractions. Their degradation rate constants (k(av)) ranged from 0.079 to 0.84 d(-1). The fastest degradation of 14:0 and 16:1 (7) occurred under 25% oxygen concentrations. For these two compounds, in the fastest degradation system, their k(av), values were 2.3 folds and 1.7 folds higher than those in the slowest degradation system [50% oxygen saturation for 14:0 and 100% oxygen saturation for 16:1(7)] respectively. The 16:0 was degraded fastest under the anoxic condition and slowest under the 50% oxygen saturation. The ratio of the two k(av)s was 2.1. The k(av)s of 20:5 had a positive relationship with oxygen saturations. Results of this study suggested that besides oxgen saturations, structure and features of organic compounds, roles of microbe in the envrioments and etc. might affect degradations of fatty acids in S. costatum in hypoxia sediment-seawater interface

  4. Development and validation of a stability-indicating LC-UV method for the determination of pantethine and its degradation product based on a forced degradation study.

    PubMed

    Canavesi, Rossana; Aprile, Silvio; Varese, Elena; Grosa, Giorgio

    2014-08-01

    Pantethine (d-bis-(N-pantothenyl-β-aminoethyl)-disulfide, PAN), the stable disulfide form of pantetheine, has beneficial effects in vascular diseases being able to decrease the hyperlipidaemia, moderate the platelet function and prevent the lipid peroxidation. Furthermore, recent studies suggested that PAN may be an effective therapeutic agent for cerebral malaria and, possibly, for neurodegenerative processes. Interestingly, in the literature, there were no data dealing with the chemical stability and the analytical aspects of PAN. Hence, in the present work the chemical stability of PAN was for the first time established through a forced degradation study followed by liquid chromatography tandem mass spectrometry investigation showing the formation of three degradation products of PAN (PD1, PD2 and POx) arising from hydrolytic, thermal and oxidative stresses. Based on these data a stability-indicating LC-UV method for simultaneous estimation of PAN, and its most relevant degradation product (PD1) was developed and validated; moreover the method allowed also the separation and the quantification of the preservative system, constituted by a paraben mixture. The method showed linearity for PAN (0.4-1.2mgmL(-1)), MHB, PHB (0.4-1.2μgmL(-1)) and PD1 (2.5-100μgmL(-1)); the precision, determined in terms of intra-day and inter-day precision, expressed as RSDs, were in the ranges 0.4-1.2 and 0.7-1.4, respectively. The method demonstrated to be accurate and robust; indeed the average recoveries were 100.2, 99.9, and 100.0% for PAN, MHB and PHB, respectively, and 99.9% for PD1. By applying small variations of the mobile phase composition, counter-ion concentration and pH the separation of analytes was not affected. Finally, the applicability of this method was evaluated analyzing the available commercial forms at release as well as during stability studies. PMID:24863372

  5. Accelerated thermal and radiative ageing of hydrogenated NBR for DRC

    SciTech Connect

    Mares, G.; Notingher, P.

    1996-12-31

    The accelerated thermal and gamma radiation ageing of HNBR carbon black-T80 has been studied by measuring the residual deformation under constant deflection -- DRC, in air, using a relevant equation for the relaxation phenomena. The residual deformation under constant deflection during the process of accelerated ageing is increasing but the structure of polymer answers in the proper manner to the mechanical stress. The degradation equations were obtained, using Alfrey model for the relaxation polymer subject to compression and an Arrhenius dependence for the chemical reaction rate. The inverted relaxation time for the thermal degradation is depending on the chemical reaction rate and the dose rate of gamma radiation.

  6. The Impact of Land Use/Land Cover Changes on Land Degradation Dynamics: A Mediterranean Case Study

    NASA Astrophysics Data System (ADS)

    Bajocco, S.; De Angelis, A.; Perini, L.; Ferrara, A.; Salvati, L.

    2012-05-01

    In the last decades, due to climate changes, soil deterioration, and Land Use/Land Cover Changes (LULCCs), land degradation risk has become one of the most important ecological issues at the global level. Land degradation involves two interlocking systems: the natural ecosystem and the socio-economic system. The complexity of land degradation processes should be addressed using a multidisciplinary approach. Therefore, the aim of this work is to assess diachronically land degradation dynamics under changing land covers. This paper analyzes LULCCs and the parallel increase in the level of land sensitivity to degradation along the coastal belt of Sardinia (Italy), a typical Mediterranean region where human pressure affects the landscape characteristics through fires, intensive agricultural practices, land abandonment, urban sprawl, and tourism concentration. Results reveal that two factors mainly affect the level of land sensitivity to degradation in the study area: (i) land abandonment and (ii) unsustainable use of rural and peri-urban areas. Taken together, these factors represent the primary cause of the LULCCs observed in coastal Sardinia. By linking the structural features of the Mediterranean landscape with its functional land degradation dynamics over time, these results contribute to orienting policies for sustainable land management in Mediterranean coastal areas.

  7. The impact of land use/land cover changes on land degradation dynamics: a Mediterranean case study.

    PubMed

    Bajocco, S; De Angelis, A; Perini, L; Ferrara, A; Salvati, L

    2012-05-01

    In the last decades, due to climate changes, soil deterioration, and Land Use/Land Cover Changes (LULCCs), land degradation risk has become one of the most important ecological issues at the global level. Land degradation involves two interlocking systems: the natural ecosystem and the socio-economic system. The complexity of land degradation processes should be addressed using a multidisciplinary approach. Therefore, the aim of this work is to assess diachronically land degradation dynamics under changing land covers. This paper analyzes LULCCs and the parallel increase in the level of land sensitivity to degradation along the coastal belt of Sardinia (Italy), a typical Mediterranean region where human pressure affects the landscape characteristics through fires, intensive agricultural practices, land abandonment, urban sprawl, and tourism concentration. Results reveal that two factors mainly affect the level of land sensitivity to degradation in the study area: (i) land abandonment and (ii) unsustainable use of rural and peri-urban areas. Taken together, these factors represent the primary cause of the LULCCs observed in coastal Sardinia. By linking the structural features of the Mediterranean landscape with its functional land degradation dynamics over time, these results contribute to orienting policies for sustainable land management in Mediterranean coastal areas.

  8. Microscopic study of surface degradation of glass fiber-reinforced polymer rods embedded in concrete castings subjected to environmental conditioning

    SciTech Connect

    Bank, L.C.; Puterman, M.

    1997-12-31

    The surface degradation of glass fiber-reinforced polymer (GFRP) pultruded rods when embedded in concrete castings and subjected to environmental conditioning is discussed in this paper. Investigation of the degradation of the GFRP rods were performed using optical microscopy and scanning electron microscopy (SEM). Unidirectionally reinforced pultruded rods (6.3- and 12.7-mm diameters) containing E-glass fibers in polyester and vinylester matrices were conditioned at standard laboratory conditions (21 C, 65% relative humidity) or submerged in aqueous solutions (tap water) at 80 C for durations of 14 and 84 days. Observations of the surfaces and cross-sections of the rods by optical microscopy and SEM revealed a variety of degradation phenomena. Embedded hygrothermally conditioned rods were found to have developed surface blisters of different sizes and depths. SEM studies of the surface revealed degradation of the polymer matrix material and exposure and degradation of the fibers close to the surface of the rods. The rods with the vinylester resin matrix showed less extensive degradation than those with the polyester resin matrix; however, the degradation characteristics of the two types of rods appear to be similar.

  9. The impact of land use/land cover changes on land degradation dynamics: a Mediterranean case study.

    PubMed

    Bajocco, S; De Angelis, A; Perini, L; Ferrara, A; Salvati, L

    2012-05-01

    In the last decades, due to climate changes, soil deterioration, and Land Use/Land Cover Changes (LULCCs), land degradation risk has become one of the most important ecological issues at the global level. Land degradation involves two interlocking systems: the natural ecosystem and the socio-economic system. The complexity of land degradation processes should be addressed using a multidisciplinary approach. Therefore, the aim of this work is to assess diachronically land degradation dynamics under changing land covers. This paper analyzes LULCCs and the parallel increase in the level of land sensitivity to degradation along the coastal belt of Sardinia (Italy), a typical Mediterranean region where human pressure affects the landscape characteristics through fires, intensive agricultural practices, land abandonment, urban sprawl, and tourism concentration. Results reveal that two factors mainly affect the level of land sensitivity to degradation in the study area: (i) land abandonment and (ii) unsustainable use of rural and peri-urban areas. Taken together, these factors represent the primary cause of the LULCCs observed in coastal Sardinia. By linking the structural features of the Mediterranean landscape with its functional land degradation dynamics over time, these results contribute to orienting policies for sustainable land management in Mediterranean coastal areas. PMID:22419398

  10. Accelerated Molecular Dynamics Study of the Effects of Surface Hydrophilicity on Protein Adsorption.

    PubMed

    Mücksch, Christian; Urbassek, Herbert M

    2016-09-13

    The adsorption of streptavidin is studied on two surfaces, graphite and titanium dioxide, using accelerated molecular dynamics. Adsorption on graphite leads to strong conformational changes while the protein spreads out over the surface. Interestingly, also adsorption on the highly hydrophilic rutile surface induces considerable spreading of the protein. We pin down the cause for this unfolding to the interaction of the protein with the ordered water layers above the rutile surface. For special orientations, the protein penetrates the ordered water layers and comes into direct contact with the surface where the positively charged amino acids settle in places adjacent to the negatively charged top surface atom layer of rutile. We conclude that for both surface materials studied, streptavidin changes its conformation so strongly that it loses its potential for binding biotin. Our results are in good qualitative agreement with available experimental studies. PMID:27533302

  11. Experimental stand for studying the impact of laser-accelerated protons on biological objects

    NASA Astrophysics Data System (ADS)

    Burdonov, K. F.; Eremeev, A. A.; Ignatova, N. I.; Osmanov, R. R.; Sladkov, A. D.; Soloviev, A. A.; Starodubtsev, M. V.; Ginzburg, V. N.; Kuz'min, A. A.; Maslennikova, A. V.; Revet, G.; Sergeev, A. M.; Fuchs, J.; Khazanov, E. A.; Chen, S.; Shaykin, A. A.; Shaikin, I. A.; Yakovlev, I. V.

    2016-04-01

    An original experimental stand is presented, aimed at studying the impact of high-energy protons, produced by the laser-plasma interaction at a petawatt power level, on biological objects. In the course of pilot experiments with the energy of laser-accelerated protons up to 25 MeV, the possibility is demonstrated of transferring doses up to 10 Gy to the object of study in a single shot with the magnetic separation of protons from parasitic X-ray radiation and fast electrons. The technique of irradiating the cell culture HeLa Kyoto and measuring the fraction of survived cells is developed. The ways of optimising the parameters of proton beams and the suitable methods of their separation with respect to energy and transporting to the studied living objects are discussed. The construction of the stand is intended for the improvement of laser technologies for hadron therapy of malignant neoplasms.

  12. A Proteomic Study of Pectin Degrading Enzymes Secreted by Botrytis cinerea Grown in Liquid Culture

    PubMed Central

    Shah, Punit; Gutierrez-Sanchez, Gerardo; Orlando, Ron; Bergmann, Carl

    2009-01-01

    Botrytis cinerea is a pathogenic filamentous fungus which infects more than 200 plant species. The enzymes secreted by B. cinerea play an important role in the successful colonization of a host plant. Some of the secreted enzymes are involved in the degradation of pectin, a major component of the plant cell wall. A total of 126 proteins secreted by B. cinerea were identified by growing the fungus on highly or partially esterified pectin, or on sucrose in liquid culture. Sixty-seven common proteins were identified in each of the growth conditions, of which 50 proteins exhibited a Signal P motif. Thirteen B. cinerea proteins with functions related to pectin degradation were identified in both pectin growth conditions, while only four were identified in sucrose. Our results indicate it is unlikely that the activation of B. cinerea from the dormant state to active infection is solely dependent on changes in the degree of esterification of the pectin component of the plant cell wall. Further, these results suggest that future studies of the B. cinerea secretome in infections of ripe and unripe fruits will provide important information that will describe the mechanisms that the fungus employs to access nutrients and decompose tissues. PMID:19526562

  13. Degradation and annealing studies on gamma rays irradiated COTS PPD CISs at different dose rates

    NASA Astrophysics Data System (ADS)

    Wang, Zujun; Ma, Yingwu; Liu, Jing; Xue, Yuan; He, Baoping; Yao, Zhibin; Huang, Shaoyan; Liu, Minbo; Sheng, Jiangkun

    2016-06-01

    The degradation and annealing studies on Colbalt-60 gamma-rays irradiated commercial-off-the-shelf (COTS) pinned photodiode (PPD) CMOS image sensors (CISs) at the various dose rates are presented. The irradiation experiments of COTS PPD CISs are carried out at 0.3, 3.0 and 30.0 rad(Si)/s. The COTS PPD CISs are manufactured using a standard 0.18-μm CMOS technology with four-transistor pixel PPD architecture. The behavior of the tested CISs shows a remarkable degradation after irradiation and differs in the dose rates. The dark current, dark signal non-uniformity (DSNU), random noise, saturation output, signal to noise ratio (SNR), and dynamic range (DR) versus the total ionizing dose (TID) at the various dose rates are investigated. The tendency of dark current, DSNU, and random noise increase and saturation output, SNR, and DR to decrease at 3.0 rad(Si)/s are far greater than those at 0.3 and 30.0 rad(Si)/s. The damage mechanisms caused by TID irradiation at the various dose rates are also analyzed. The annealing tests are carried out at room temperature with unbiased conditions after irradiation.

  14. Determination of acrylamide monomer in polyacrylamide degradation studies by high-performance liquid chromatography.

    PubMed

    Ver Vers, L M

    1999-12-01

    A high-performance liquid chromatography method using C18 and ion-exchange columns in series is developed for the determination of acrylamide and acrylic acid monomers in polymeric samples. The C18 column acts as a guard column, trapping surfactants and impurities and retaining the nonionic species. The ion-exchange column then separates the monomers according to their respective ionic strengths. This method has been proven in the laboratory to work successfully for all types of acrylamide/acrylic acid polymers and matrices. Detection limits for both monomers can be achieved in the parts-per-billion range. The method is used to study the possible degradation of polyacrylamide to acrylamide monomer in the presence of glyphosate (a herbicide) and sunlight. Polyacrylamide is used as a spray drift reduction aid in combination with glyphosate. In normal applications, the polymer and herbicide are in contact with each other in the presence of sunlight. The results show that the polymer does not degrade to acrylamide in the presence of glyphosate or sunlight or any combination of the two. It is also observed that glyphosate influences the solubility of polyacrylamide, and care must be used when combining the two.

  15. Land Degradation on Barren Hills: A Case Study in Northeast Vietnam

    NASA Astrophysics Data System (ADS)

    Nikolic, Nina; Schultze-Kraft, Rainer; Nikolic, Miroslav; Böcker, Reinhard; Holz, Ingo

    2008-07-01

    The term “barren hills” has been a keyword for land degradation in the uplands of Vietnam for over a decade. Nevertheless, the “barren” land is still not adequately ecologically characterized. In this work, we analyze land use-induced changes in vegetation and soil properties along a sequence of barren hills types formed on one physiotope. The study is undertaken in the Bac Kan province, one of the poorest upland regions where livestock plays an important role. A transition from an old-growth laurel forest to a sparse manmade grassland is characterized by a total of 177 species, rapid species turnover, and discrete dominants, and an overwhelming effect of disturbance history on both soil and vegetation patterning. Land degradation is most apparent in land use-induced maintenance of arrested successions, and the regeneration course is shifted towards drier formations. We hypothesize a conceptual model as an aid to understanding the process of early fallow differentiation in response to the patterned, fine-scale disturbances. The larger-scale implications of the observed trends in regeneration potentials deviation, and, in particular, the effect of water buffaloes in halting fallow successions, are discussed.

  16. Ultrasonic degradation of polysaccharides studied by multi-angle laser light scattering

    NASA Astrophysics Data System (ADS)

    Eschette, Regina; Norwood, David

    2003-03-01

    Ultrasonic degradation of polymers is a well-studied field. It is understood that the degradation process results from shock waves generated by cavitation and collapse. That is, cavities formed when the pressure wave is at a minimum violently collapse as the pressure increases. The rapid collapse sends out shock waves into the material and the main-chain rupture is believed to stem from this rapid motion of solvents. We explore this process using the experimental technique of multi-angle light scattering (MALLS). MALLS provides the molecular weight, RMS radius and virial coefficient of polymers in dilute solution. We monitor the change in these parameters as a function of time exposed to ultrasound for three polymers: Xanthan, Hyaluronic acid (HA), and Lambda Carrageenan (LC). These polysaccharides are chosen because they have similar initial molecular weights ( 10 ^6 g/mol) but different architectures. Xanthan is a wormlike chain, HA is an expanded random coil (large persistence length) and LC is a contracted random coil (small persistence length).

  17. Degradation study of XVIII century graffiti on the walls of Chiaramonte Palace (Palermo, Italy)

    NASA Astrophysics Data System (ADS)

    Alberghina, M. F.; Barraco, R.; Brai, M.; Casaletto, M. P.; Ingo, G. M.; Marrale, M.; Policarpo, D.; Schillaci, T.; Tranchina, L.

    2010-09-01

    A systematic investigation of the original materials and the degradation phenomena induced by soluble salts on the wall matrix and on the graffiti of the Inquisition jails of Chiaramonte Palace in Palermo (Italy) was carried out. Built in the XIV century, Chiaramonte Palace was used as Inquisition court during the XV-XVI centuries. The ancient graffiti, recently discovered, represent a unique historical witness of the prisoners that lived during that terrible period. In order to study the nature, the amount and the distribution of the salts in the masonry, stone materials sampled at different depth from the wall matrix and saline efflorescences were analysed. Different physical techniques were used, such as X-ray Photoelectron Spectroscopy, X-ray Fluorescence, Laser Induced Breakdown Spectroscopy, X-ray Diffraction and Ionic Chromatography. Results of the chemical and physical characterisation showed that the main cause of the degradation of graffiti and wall paintings was the presence of soluble salts, such as nitrates, chlorides and sulphates. Traces of oxalates, coming from a previous conservation treatment, were also found. The results obtained by the stratigraphical characterisation of soluble salts in the wall matrix can be used to recommend a procedure based on air humidification at high relative humidity values in order to avoid salt crystallisation and to prevent the crumbling process of the graffiti.

  18. Photochemical degradation study of polyvinyl acetate paints used in artworks by Py–GC/MS

    PubMed Central

    Wei, Shuya; Pintus, Valentina; Schreiner, Manfred

    2012-01-01

    Photochemical degradation of commercial polyvinyl acetate (PVAc) homopolymer and PVAc paints mixed with burnt umber, cobalt blue, cadmium red dark, nickel azo yellow and titanium white commonly used for artworks were studied by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Py–GC/MS with single-shot technique was used for the characterization of the thermal degradation of PVAc at different temperatures, while the double-shot technique of Py–GC/MS was used to reveal the differences in the specimens before and after UV ageing, including the changes of detectable amounts of deacetylation product – acetic acid and plasticizers such as diethyl phthalate (DEP). Furthermore, the relative concentration of the pyrolysis products of the paint samples could be measured and compared in the second step of the double-shot Py–GC/MS, which are highly dependent on the presence of pigments and the ageing status of PVAc paints. PMID:23024446

  19. Land degradation on barren hills: a case study in northeast Vietnam.

    PubMed

    Nikolic, Nina; Schultze-Kraft, Rainer; Nikolic, Miroslav; Böcker, Reinhard; Holz, Ingo

    2008-07-01

    The term "barren hills" has been a keyword for land degradation in the uplands of Vietnam for over a decade. Nevertheless, the "barren" land is still not adequately ecologically characterized. In this work, we analyze land use-induced changes in vegetation and soil properties along a sequence of barren hills types formed on one physiotope. The study is undertaken in the Bac Kan province, one of the poorest upland regions where livestock plays an important role. A transition from an old-growth laurel forest to a sparse manmade grassland is characterized by a total of 177 species, rapid species turnover, and discrete dominants, and an overwhelming effect of disturbance history on both soil and vegetation patterning. Land degradation is most apparent in land use-induced maintenance of arrested successions, and the regeneration course is shifted towards drier formations. We hypothesize a conceptual model as an aid to understanding the process of early fallow differentiation in response to the patterned, fine-scale disturbances. The larger-scale implications of the observed trends in regeneration potentials deviation, and, in particular, the effect of water buffaloes in halting fallow successions, are discussed.

  20. Study of proton acceleration at the target front surface in laser-solid interactions by neutron spectroscopy

    SciTech Connect

    Youssef, A.; Kodama, R.; Tampo, M.

    2006-03-15

    Proton acceleration inside solid LiF and CH-LiF targets irradiated by a 450-fs, 20-J, 1053-nm laser at an intensity of 3x10{sup 18} W/cm{sup 2} has been studied via neutron spectroscopy. Neutron spectra produced through the {sup 7}Li(p,n){sup 7}Be reaction that occurs between accelerated protons, at the front surface, and background {sup 7}Li ions inside the target. From measured and calculated spectra, by three-dimensional Monte Carlo code, the maximum energy, total number, and slope temperature of the accelerated protons are investigated. The study indicates that protons originate at the front surface and are accelerated to a maximum energy that is reasonably consistent with the calculated one due to the ponderomotive force.

  1. Multi-flare Study on Acceleration Regions using Correlated X-ray and Radio Observations

    NASA Astrophysics Data System (ADS)

    Reid, H.; Vilmer, N.; Kontar, E. P.

    2012-12-01

    X-ray and radio observations are found to be both temporally and spatially correlated in a large number of solar flares. We use both wavelength ranges to estimate properties about the spatial region in solar flares which accelerate electrons. A list of events were studied using the RHESSI X-ray flare catalogue and the PHOENIX 2 type III burst catalogue. We find that some events show a very good anti-correlation between the hard X-ray spectral index and the starting frequency of type III radio bursts. Through an analytical relation we then constrain the distance an upwardly travelling electron beam can propagate before it becomes unstable to the generation of Langmuir waves. By assuming a background density model we then infer the height and vertical extent of a variety of different solar flare acceleration regions. Spatially resolved images of each flare in both X-ray and radio wavelengths via RHESSI and the Nançay Radioheliograph respectively are then used to check the validity of the predicted heights.

  2. Speeding up CRMs for cloud-climate interaction studies by acceleration of mean state tendencies

    NASA Astrophysics Data System (ADS)

    Jones, C. R.; Bretherton, C. S.

    2014-12-01

    Cloud-resolving models (CRMs) are routinely used to simulate boundary-layer and deep convective cloud processes, aid in the development of moist physical parameterization for global models, study cloud-climate feedbacks and cloud-aerosol interaction, and as the heart of superparameterized climate models. CRMs are computationally demanding, placing practical constraints on their use in these applications, especially for long, climate-relevant simulations. In many situations, the horizontal-mean atmospheric structure evolves slowly compared to the turnover time of the most energetic turbulent eddies. We use this time scale separation to accelerate the time-integration of a CRM, the System for Atmospheric Modelling. Our approach uses a large time step to evolve the horizontally averaged state variables, followed by a short time step to calculate the turbulent fluctuations about the mean state. Using this approach, we are able to accelerate the model evolution by a factor of 8 or more in idealized stratocumulus, shallow and deep cumulus convection without substantial loss of accuracy in simulating mean cloud statistics and their sensitivity to climate change perturbations. We show how to adapt the approach to challenges arising from rapidly falling precipitation and from advecting scalars with a variety of lifetimes.

  3. Emotional states of drivers and the impact on speed, acceleration and traffic violations - a simulator study.

    PubMed

    Roidl, Ernst; Frehse, Berit; Höger, Rainer

    2014-09-01

    Maladjusted driving, such as aggressive driving and delayed reactions, is seen as one cause of traffic accidents. Such behavioural patterns could be influenced by strong emotions in the driver. The causes of emotions in traffic are divided into two distinct classes: personal factors and properties of the specific driving situation. In traffic situations, various appraisal factors are responsible for the nature and intensity of experienced emotions. These include whether another driver was accountable, whether goals were blocked and whether progress and safety were affected. In a simulator study, seventy-nine participants took part in four traffic situations which each elicited a different emotion. Each situation had critical elements (e.g. slow car, obstacle on the street) based on combinations of the appraisal factors. Driving parameters such as velocity, acceleration, and speeding, together with the experienced emotions, were recorded. Results indicate that anger leads to stronger acceleration and higher speeds even for 2 km beyond the emotion-eliciting event. Anxiety and contempt yielded similar but weaker effects, yet showed the same negative and dangerous driving pattern as anger. Fright correlated with stronger braking momentum and lower speeds directly after the critical event.

  4. Radiation shielding and patient organ dose study for an accelerator- based BNCT Facility at LBNL

    SciTech Connect

    Costes, S.V.; Vujic, J.; Donahue, R.J.

    1996-10-24

    This study considers the radiation safety aspects of several designs discussed in a previous report of an accelerator-based source of neutrons, based on the [sup 7]Li(p,n) reaction, for a Boron Neutron Capture Therapy (BNCT) Facility at Lawrence Berkeley National Laboratory (LBNL). determines the optimal radiation shield thicknesses for the patient treatment room. Since this is an experimental facility no moderator or reflector is considered in the bulk wall shield design. This will allow the flexibility of using any postulated moderator/reflector design and assumes sufficient shielding even in the absence of a moderator/reflector. In addition the accelerator is assumed to be capable of producing 100 mA of 2.5 MeV proton beam current. The addition of 1% and 2% [sup 10]B (by weight) to the concrete is also investigated. The second part of this paper determines the radiation dose to the major organs of a patient during a treatment. Simulations use the MIRD 5 anthropomorphic phantom to calculate organ doses from a 20 mA proton beam assuming various envisioned moderator/reflector in place. Doses are tabulated by component and for a given uniform [sup 10]B loading in all organs. These are presented in for a BeO moderator and for an Al/AlF[sub 3] moderator. Dose estimates for different [sup 10]B loadings may be scaled.

  5. Experimental study of temperature fields and thermal fluxes in the electrode walls of an MGD accelerator

    SciTech Connect

    Alferov, V.I.; Vitkovskaya, O.N.; Panfilova, O.V.; Rudakova, A.P.; Sukhobokov, A.D.; Shcherbakov, G.I.

    1980-07-01

    Results are presented of an experimental study of the features of heat transfer from a flow of air with KNa admixture to the electrode walls of an MGD accelerator in a wide range of operating modes (B=1--2.5 T,j=4--45 A/cm/sup 2/,P/sub st/0.2=(en-dash0.5)x10/sup 5/ Pa). Data are obtained on the size and distribution of the thermal fluxes in different zones of an MGD channel and over the electrodes, taken separately. Methods are chosen for calculating the convective thermal flux on the electrode walls over the entire length of the accelerator channel, and the values of the thermal flux in the discharge zone due to processes at the electrodes are determined. A possible explanation is proposed for the difference between the values of the thermal fluxes at the electrode walls over different portions of the MGD channel, which is based on features of the behavior of microarcs on the surface of the electrodes.

  6. Laboratory studies of magnetized collisionless flows and shocks using accelerated plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, T. E.; Smith, R. J.; Hsu, S. C.

    2015-11-01

    Magnetized collisionless shocks are thought to play a dominant role in the overall partition of energy throughout the universe, but have historically proven difficult to create in the laboratory. The Magnetized Shock Experiment (MSX) at LANL creates conditions similar to those found in both space and astrophysical shocks by accelerating hot (100s of eV during translation) dense (1022 - 1023 m-3) Field Reversed Configuration (FRC) plasmoids to high velocities (100s of km/s); resulting in β ~ 1, collisionless plasma flows with sonic and Alfvén Mach numbers of ~10. The FRC subsequently impacts a static target such as a strong parallel or anti-parallel (reconnection-wise) magnetic mirror, a solid obstacle, or neutral gas cloud to create shocks with characteristic length and time scales that are both large enough to observe yet small enough to fit within the experiment. This enables study of the complex interplay of kinetic and fluid processes that mediate cosmic shocks and can generate non-thermal distributions, produce density and magnetic field enhancements much greater than predicted by fluid theory, and accelerate particles. An overview of the experimental capabilities of MSX will be presented, including diagnostics, selected recent results, and future directions. Supported by the DOE Office of Fusion Energy Sciences under contract DE-AC52-06NA25369.

  7. Plasma-Surface Interaction Research At The Cambridge Laboratory Of Accelerator Studies Of Surfaces

    NASA Astrophysics Data System (ADS)

    Wright, G. M.; Barnard, H. S.; Hartwig, Z. S.; Stahle, P. W.; Sullivan, R. M.; Woller, K. B.; Whyte, D. G.

    2011-06-01

    The material requirements for plasma-facing components in a nuclear fusion reactor are some of the strictest and most challenging facing us today. These materials are simultaneously exposed to extreme heat loads (20 MW/m2 steady-state, 1 GW/m2 in millisecond transients) and particle fluxes (>1024 m-2 s-1) while also undergoing high neutron irradiation (1018 neutrons/m2 s). At the Cambridge Laboratory of Accelerator Studies of Surfaces (CLASS), many of the most important issues in plasma-surface interaction research, such as plasma-driven material erosion and deposition, material transport and irradiation and hydrogenic retention are investigated with the use of a 1.7 MV tandem ion accelerator. Ion-Beam Analysis (IBA) is used to investigate and quantify changes in materials due to plasma exposure and ion irradiation is used as a proxy for neutron irradiation to investigate plasma-surface interactions for irradiated materials. This report will outline the capabilities and current research activities at CLASS.

  8. OpenARC: Extensible OpenACC Compiler Framework for Directive-Based Accelerator Programming Study

    SciTech Connect

    Lee, Seyong; Vetter, Jeffrey S

    2014-01-01

    Directive-based, accelerator programming models such as OpenACC have arisen as an alternative solution to program emerging Scalable Heterogeneous Computing (SHC) platforms. However, the increased complexity in the SHC systems incurs several challenges in terms of portability and productivity. This paper presents an open-sourced OpenACC compiler, called OpenARC, which serves as an extensible research framework to address those issues in the directive-based accelerator programming. This paper explains important design strategies and key compiler transformation techniques needed to implement the reference OpenACC compiler. Moreover, this paper demonstrates the efficacy of OpenARC as a research framework for directive-based programming study, by proposing and implementing OpenACC extensions in the OpenARC framework to 1) support hybrid programming of the unified memory and separate memory and 2) exploit architecture-specific features in an abstract manner. Porting thirteen standard OpenACC programs and three extended OpenACC programs to CUDA GPUs shows that OpenARC performs similarly to a commercial OpenACC compiler, while it serves as a high-level research framework.

  9. Study of banana and coconut fibers Botanical composition, thermal degradation and textural observations.

    PubMed

    Bilba, Ketty; Arsene, Marie-Ange; Ouensanga, Alex

    2007-01-01

    Four fibers from banana-trees (leaf, trunk) and coconut-tree (husk, fabric) were examined before their incorporation in cementitious matrices, in order to prepare insulating material for construction. Their botanical compositions have been determined following a method described previously. Thermal degradation of these fibers were studied between 200 and 700 degrees C under nitrogen gas flow. Temperature of pyrolysis was the experimental parameter investigated. The solid residues obtained were analyzed by classical elemental analysis, Fourier Transform Infra Red (FTIR) spectroscopy and were observed by Scanning Electron Microscopy (SEM). This study has shown (1) the relation between botanical, chemical composition with both localization of fibers in the tree and type of tree; (2) the rapid and preferential decomposition of banana fibers with increasing temperature of pyrolysis and (3) the rough samples are made of hollow fibers.

  10. Enhancing sample preparation capabilities for accelerator mass spectrometry radiocarbon and radiocalcium studies

    SciTech Connect

    Taylor, R E

    1991-08-20

    With support provided by the LLNL Accelerator Mass Spectrometry Laboratory, the UCR Radiocarbon Laboratory continued its studies involving sample pretreatment and target preparation for both AMS radiocarbon ({sup 14}C) and radiocalcium ({sup 41}Ca) involving applications to archaeologically -- and paleoanthropologically- related samples. With regard to AMS {sup 14}C-related studies, we have extended the development of a series of procedures which have, as their initial goal, the capability to combust several hundred microgram amounts of a chemically-pretreated organic sample and convert the resultant CO{sub 2} to graphitic carbon which will consistently yield relatively high {sup 13}C{sup {minus}} ion currents and blanks which will yield, on a consistent basis, {sup 14}C count rates at or below 0.20% modern, giving an 2 sigma age limit of >50,000 yr BP.

  11. A comparative study on the in vivo degradation of poly(L-lactide) based composite implants for bone fracture fixation

    PubMed Central

    Wang, Zongliang; Wang, Yu; Ito, Yoshihiro; Zhang, Peibiao; Chen, Xuesi

    2016-01-01

    Composite of nano-hydroxyapatite (n-HAP) surface grafted with poly(L-lactide) (PLLA) (g-HAP) showed improved interface compatibility and mechanical property for bone fracture fixation. In this paper, in vivo degradation of n-HAP/PLLA and g-HAP/PLLA composite implants was investigated. The mechanical properties, molecular weight, thermal properties as well as crystallinity of the implants were measured. The bending strength of the n- and g-HAP/PLLA composites showed a marked reduction from an initial value of 102 and 114 MPa to 33 and 24 MPa at 36 weeks, respectively. While the bending strength of PLLA was maintained at 80 MPa at 36 weeks compared with initial value of 107 MPa. The impact strength increased over time especially for the composites. Significant differences in the molecular weight were seen among all the materials and g-HAP/PLLA appeared the fastest rate of decrease than others. Environmental scanning electron microscope (ESEM) results demonstrated that an apparently porous morphology full of pores and hollows were formed in the composites. The results indicated that the in vivo degradation of PLLA could be accelerated by the g-HAP nanoparticles. It implied that g-HAP/PLLA composites might be a candidate for human non-load bearing bone fracture fixation which needs high initial strength and fast degradation rate. PMID:26857951

  12. A comparative study on the in vivo degradation of poly(L-lactide) based composite implants for bone fracture fixation

    NASA Astrophysics Data System (ADS)

    Wang, Zongliang; Wang, Yu; Ito, Yoshihiro; Zhang, Peibiao; Chen, Xuesi

    2016-02-01

    Composite of nano-hydroxyapatite (n-HAP) surface grafted with poly(L-lactide) (PLLA) (g-HAP) showed improved interface compatibility and mechanical property for bone fracture fixation. In this paper, in vivo degradation of n-HAP/PLLA and g-HAP/PLLA composite implants was investigated. The mechanical properties, molecular weight, thermal properties as well as crystallinity of the implants were measured. The bending strength of the n- and g-HAP/PLLA composites showed a marked reduction from an initial value of 102 and 114 MPa to 33 and 24 MPa at 36 weeks, respectively. While the bending strength of PLLA was maintained at 80 MPa at 36 weeks compared with initial value of 107 MPa. The impact strength increased over time especially for the composites. Significant differences in the molecular weight were seen among all the materials and g-HAP/PLLA appeared the fastest rate of decrease than others. Environmental scanning electron microscope (ESEM) results demonstrated that an apparently porous morphology full of pores and hollows were formed in the composites. The results indicated that the in vivo degradation of PLLA could be accelerated by the g-HAP nanoparticles. It implied that g-HAP/PLLA composites might be a candidate for human non-load bearing bone fracture fixation which needs high initial strength and fast degradation rate.

  13. Accelerated changes in white matter microstructure during aging: a longitudinal diffusion tensor imaging study.

    PubMed

    Sexton, Claire E; Walhovd, Kristine B; Storsve, Andreas B; Tamnes, Christian K; Westlye, Lars T; Johansen-Berg, Heidi; Fjell, Anders M

    2014-11-12

    It is well established that human brain white matter structure changes with aging, but the timescale and spatial distribution of this change remain uncertain. Cross-sectional diffusion tensor imaging (DTI) studies indicate that, after a period of relative stability during adulthood, there is an accelerated decline in anisotropy and increase in diffusivity values during senescence; and, spatially, results have been discussed within the context of several anatomical frameworks. However, inferring trajectories of change from cross-sectional data can be challenging; and, as yet, there have been no longitudinal reports of the timescale and spatial distribution of age-related white matter change in healthy adults across the adult lifespan. In a longitudinal DTI study of 203 adults between 20 and 84 years of age, we used tract-based spatial statistics to characterize the pattern of annual change in fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity and examined whether there was an acceleration of change with age. We found extensive and overlapping significant annual decreases in fractional anisotropy, and increases in axial diffusivity, radial diffusivity, and mean diffusivity. Spatially, results were consistent with inferior-to-superior gradients of lesser-to-greater vulnerability. Annual change increased with age, particularly within superior regions, with age-related decline estimated to begin in the fifth decade. Charting white matter microstructural changes in healthy aging provides essential context to clinical studies, and future studies should compare age trajectories between healthy participants and at-risk populations and also explore the relationship between DTI rates of change and cognitive decline.

  14. Transport and degradation of pesticides in a biopurification system under variable flux Part II: A macrocosm study.

    PubMed

    De Wilde, Tineke; Spanoghe, Pieter; Ryckeboer, Jaak; Jaeken, Peter; Springael, Dirk

    2010-10-01

    Transport of bentazone, isoproturon, linuron, metamitron and metalaxyl were studied under three different flows in macrocosms. The aim was to verify the observations from Part I of the accompanying paper, with an increase in column volume and decrease in chemical and hydraulic load. Very limited breakthrough occurred in the macrocosms for all pesticides, except bentazone, at all flows. From batch degradation experiments, it was observed that the lag time of metamitron and linuron decreased drastically in time for all flows, indicating a growth in the pesticide degrading population. This in contrast to isoproturon and metalaxyl, where an increase in lag time could be observed in time for all flows. From the batch degradation experiments, it could be concluded that the influence of flow on the lag time was minimal and that the inoculation of the pesticide-primed soil had a little surplus value on degradation. PMID:20696511

  15. Contribution To Degradation Study, Behavior Of Unsaturated Polyester Resin Under Neutron Irradiation

    NASA Astrophysics Data System (ADS)

    Abellache, D.; Lounis, A.; Taïbi, K.

    2010-01-01

    Applications of unsaturated polyester thermosetting resins are numerous in construction sector, in transport, electric spare parts manufactures, consumer goods, and anticorrosive materials. This survey reports the effect of thermosetting polymer degradation (unsaturated polyester): degradation by neutrons irradiation. In order to evaluate the deterioration of our material, some comparative characterizations have been done between standard samples and damaged ones. Scanning electron microscopy (SEM), ultrasonic scanning, hardness test (Shore D) are the techniques which have been used. The exposure to a neutrons flux is carried out in the column of the nuclear research reactor of Draria (Algiers-Algeria). The energetic profile of the incidental fluxes is constituted of fast neutrons (ΦR = 3.1012n.cm-2.s-1, E = 2 Mev) of thermal neutrons (ΦTH = 1013n.cm-2.s-1; E = 0.025 ev) and epithermal neutrons (Φepi = 7.1011 n.cm-2.s-1; E>4,9 ev). The received dose flow is 0,4 Kgy. We notice only a few scientific investigations can be found in this field. In comparison with the standard sample (no exposed) it is shown that the damage degree is an increasing process with the exposure. Concerning the description of irradiation effects on polymers, we can advance that several reactions are in competition : reticulation, chain break, and oxidation by radical mechanism. In our case the incidental particle of high energy fast neutrons whose energy is greater or equal to 2 Mev, is braked by the target with a nuclear shock during which the incidental particle transmits a part of its energy to an atom. If the energy transfer is sufficient, the nuclear shock permits to drive out an atom of its site the latter will return positioning interstitially, the energy that we used oversteps probably the energy threshold (displacement energy). This fast neutrons collision with target cores proceeds to an indirect ionization by the preliminary creation of excited secondary species that will

  16. Contribution To Degradation Study, Behavior Of Unsaturated Polyester Resin Under Neutron Irradiation

    SciTech Connect

    Abellache, D.; Lounis, A.; Taiebi, K.

    2010-01-05

    Applications of unsaturated polyester thermosetting resins are numerous in construction sector, in transport, electric spare parts manufactures, consumer goods, and anticorrosive materials. This survey reports the effect of thermosetting polymer degradation (unsaturated polyester): degradation by neutrons irradiation. In order to evaluate the deterioration of our material, some comparative characterizations have been done between standard samples and damaged ones. Scanning electron microscopy (SEM), ultrasonic scanning, hardness test (Shore D) are the techniques which have been used. The exposure to a neutrons flux is carried out in the column of the nuclear research reactor of Draria (Algiers-Algeria). The energetic profile of the incidental fluxes is constituted of fast neutrons (PHI{sub R} = 3.10{sup 12} n.cm{sup -2}.s{sup -1}, E = 2 Mev) of thermal neutrons (PHI{sub TH} = 10{sup 13} n.cm{sup -2}.s{sup -1}; E = 0.025 ev) and epithermal neutrons (PHI{sub epi} = 7.10{sup 11} n.cm{sup -2}.s{sup -1}; E>4,9 ev). The received dose flow is 0,4 Kgy. We notice only a few scientific investigations can be found in this field. In comparison with the standard sample (no exposed) it is shown that the damage degree is an increasing process with the exposure. Concerning the description of irradiation effects on polymers, we can advance that several reactions are in competition: reticulation, chain break, and oxidation by radical mechanism. In our case the incidental particle of high energy fast neutrons whose energy is greater or equal to 2 Mev, is braked by the target with a nuclear shock during which the incidental particle transmits a part of its energy to an atom. If the energy transfer is sufficient, the nuclear shock permits to drive out an atom of its site the latter will return positioning interstitially, the energy that we used oversteps probably the energy threshold (displacement energy). This fast neutrons collision with target cores proceeds to an indirect

  17. Simulation chamber studies of the atmospheric degradation of xylene oxidation products

    NASA Astrophysics Data System (ADS)

    Clifford, G.; Rea, G.; Thuener, L.; Wenger, J.

    2003-04-01

    Aromatic compounds are emitted to the atmosphere from their use in automobile fuels and solvents. In addition to being important primary pollutants, many aromatics, including the xylenes, possess high photochemical reactivity and make a major contribution to the formation of oxidants, such as ozone and nitrates, in the troposphere. The atmospheric oxidation of aromatics produces a wide variety of products and the atmospheric reactivity of many of these species is unknown. The aim of this work was to study the atmospheric degradation processes for dimethylphenols, tolualdehydes and dicarbonyl compounds which are produced from the hydroxyl radical initiated oxidation of the xylenes. Experiments on the hydroxyl (OH) and nitrate radical initiated oxidation of dimethylphenols and tolualdehydes have been performed in a large atmospheric simulation chamber in our laboratory. The chamber is made of FEP foil and has a volume of about 4750 litres. It is equipped with gas chromatography, GC-MS, and in situ FTIR spectroscopy for chemical analysis and a scanning mobility particle sizer for aerosol measurements. Rate coefficients have been determined for the reactions of hydroxyl and nitrate radicals with dimethylphenols and tolualdehydes. Gas-phase products and the yield of secondary organic aerosol have also been determined for the OH-initiated oxidation of these compounds. Mechanisms for the formation of the products are proposed. The photolysis of the unsaturated dicarbonyls, butenedial and 4-oxo-pent-2-enal, has been studied using real sunlight at the European Photoreactor (EUPHORE) in Valencia, Spain. Photolysis rates were measured and indicate that photolysis by sunlight is the major atmospheric degradation process for these compounds. Product studies show the formation of a ketene intermediate that decays to form five membered ring compounds such as furanones and maleic anhydride. Mechanisms for the formation of the products are proposed. Finally, the data obtained in

  18. A study on significant microbial interaction leading to decolorization and degradation of textile dye Rubine 3GP.

    PubMed

    Phugare, Swapnil S; Kagalkar, Anuradha N; Govindwar, Sanjay P; Jadhav, Jyoti P

    2011-10-01

    The present study evaluates an obligatory interaction between the yeast Saccharomyces cerevisiae NCIM 3312 and the bacterium Pseudomonas sp. strain BCH3 for the biodegradation of the dye Rubin 3GP (R3GP). No significant degradation of R3GP was observed either by Saccharomyces cerevisiae NCIM 3312 or by Pseudomonas sp. strain BCH3, when both the cultures were tested individually under their respective optimum medium conditions. However, when both of them were allowed to intermingle with each other, R3GP was found to be degraded within 72 h, with a steady increase in β -1,3-glucanase, chitinase and protease activity in the culture supernatant; indicating the possible role of Pseudomonas sp. strain BCH3 in cell wall lysis of S. cerevisiae NCIM 3312. The present study elucidates a rare microbial interaction where the bacterium Pseudomonas sp. strain BCH3 utilizes lysed yeast cells as the sole source of nutrients for its own growth and subsequently performs decolorization and degradation of R3GP. Enzymatic status showed involvement of various oxidoreductive enzymes like lignin peroxidase, laccase, DCIP reductase and azo reductase, indicating their role in decolorization and degradation of R3GP. Degradation was confirmed using HPLC, FTIR analysis and the biochemical pathway of degradation was elucidated by using GC-MS analysis.

  19. Studies on Muon Induction Acceleration and an Objective Lens Design for Transmission Muon Microscope

    NASA Astrophysics Data System (ADS)

    Artikova, Sayyora; Yoshida, Mitsuhiro; Naito, Fujio

    Muon acceleration will be accomplished by a set of induction cells, where each increases the energy of the muon beam by an increment of up to 30 kV. The cells are arranged in a linear way resulting in total accelerating voltage of 300 kV. Acceleration time in the linac is about hundred nanoseconds. Induction field calculation is based on an electrostatic approximation. Beam dynamics in the induction accelerator is investigated and final beam focusing on specimen is realized by designing a pole piece lens.

  20. Studies of the Mirrortron ion accelerator concept and its application to heavy-ion drivers

    SciTech Connect

    Post, R.F.; Schwager, L.A. ); Douglass, S.R.; Jones, B.R.; Lambert, M.A.; Larson, D.L. . Dept. of Applied Science)

    1990-11-30

    The Mirrortron accelerator is a plasma-based ion accelerator concept that, when implemented, should permit both higher acceleration gradients and higher peak-current capabilities than is possible with conventional induction-type accelerators. Control over the acceleration and focussing of an accelerated beam should approach that achieved in vacuum-field-based ion accelerators. In the Mirrortron a low density (10{sup 10} to 10{sup 11} cm{sup {minus}3}) hot electron'' plasma is confined by a long solenoidal magnetic field capped by mirrors.'' Acceleration of pre-bunched ions is accomplished by activating a series of fast-pulsed mirror coils spaced along the acceleration tube. The hot electrons, being repelled by mirror action, leave the plasma ions behind to create a localized region of high electrical gradient (up to of order 100 MV/m). At the laboratory an experiment and analyses to elucidate the concept and its scaling laws as applied to heavy-ion drivers are underway and will be described. 4 refs., 5 figs.

  1. Voltage holding study of 1 MeV accelerator for ITER neutral beam injector.

    PubMed

    Taniguchi, M; Kashiwagi, M; Umeda, N; Dairaku, M; Takemoto, J; Tobari, H; Tsuchida, K; Yamanaka, H; Watanabe, K; Kojima, A; Hanada, M; Sakamoto, K; Inoue, T

    2012-02-01

    Voltage holding test on MeV accelerator indicated that sustainable voltage was a half of that of ideal quasi-Rogowski electrode. It was suggested that the emission of the clumps is enhanced by a local electric field concentration, which leads to discharge initiation at lower voltage. To reduce the electric field concentration in the MeV accelerator, gaps between the grid supports were expanded and curvature radii at the support corners were increased. After the modifications, the accelerator succeeded in sustaining -1 MV in vacuum without beam acceleration. However, the beam energy was still limited at a level of 900 keV with a beam current density of 150 A∕m(2) (346 mA) where the 3 × 5 apertures were used. Measurement of the beam profile revealed that deflection of the H(-) ions was large and a part of the H(-) ions was intercepted at the acceleration grid. This causes high heat load on the grids and the breakdowns during beam acceleration. To suppress the direct interception, new grid system was designed with proper aperture displacement based on a 3D beam trajectory analysis. As the result, the beam deflection was compensated and the voltage holding during the beam acceleration was improved. Beam parameter of the MeV accelerator was increased to 980 keV, 185 A∕m(2) (427 mA), which is close to the requirement of ITER accelerator (1 MeV, 200 A∕m(2)).

  2. Study of Degradation Processes in Dielectric Materials Used in Electronic Control Equipment Operated in ``Kozloduy'' NPP

    NASA Astrophysics Data System (ADS)

    Naydenov, Nayden; Popov, Angel

    2007-04-01

    The electronic equipment for control of different systems of Units 5 and 6 is studied for presence of degradation processes occurring in result of continuous usage in conditions of controlled radiation background in compliance with ``Kozloduy'' NPP safety codes. Systems, operated in a continuous mode in the course of about 10 years were chosen - separate units containing different dielectric materials (varnish coating, circuit board bases, cable insulations, electro protective elements, etc.) were extrapolated. Series of test samples were prepared which were connected with flat or coaxial condensers and their characteristic parameters were measured: tgδ, ɛ, low voltage conductivity and leak currents at voltages that exceed the working ones several times. When comparing the obtained data with the reference ones, a conclusion is made about the effectiveness of electric ageing during operation in the course of time.

  3. Effect of hydrogen on degradation mechanism of zirconium: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Chakraborty, Poulami; Moitra, Amitava; Saha-Dasgupta, Tanusri

    2015-11-01

    Using large scale molecular dynamics simulation, we investigate the deleterious effect of hydrogen in Zr. We consider both dilute and concentrated limit of H. In the dilute and concentrated H limits, we study the effect of 1-5 atomic percentage of hydrogen, and that of ε-ZrH2 precipitate having 5-10 nm diameters, respectively. From the stress-strain curves and micro-structure analysis at different strain values, we characterize the deformation behavior and correlate our result with previously reported mechanisms. We show hydrogen atoms in dilute limit help in dislocation multiplication, following the hydrogen-enhanced localized plasticity mechanism. In the concentrated limit, on the other hand, dislocations and cracks nucleate from precipitate-matrix interface, indicating the decohesion mechanism as primary method for Zr degradation. These findings are corroborated with a nucleation and growth model as expressed in Kolmogorov-Johnson-Mehl-Avrami equation.

  4. Quantitative degradation studies of coal derived jet fuel using statistical analysis

    SciTech Connect

    Sanghani, P.C.; Boehman, A.L.

    1996-10-01

    The kinetics of coke formation from coal-derived jet fuel were studied using statistical methods. The degree of correlation between deposit (coke) growth and species concentration has been examined. Formation of deposits from the mixtures of jet fuel and tetradecane was proportional to the initial concentration of tetradecane present in the fuel. Decomposition of tetradecane was found to be first order with con-elation coefficient of 0.98. Other normal alkanes species such as dodecane, tridecane, and pentadecane which are present in very small amount also contribute significantly to deposit growth. Cycloalkanes, alkylated c1,c2,c3 benzenes, alkylated naphathalenes present in coal derived jet fuel were very stable compared to tetradecane. The statistical approach helps in identifying or arranging species in terms of their contribution to deposit formation. Grouping species on the basis of their correlation with deposit formation clarifies the required structure for a general kinetic model of the jet fuel degradation process.

  5. Use of the 3-D scanner in mapping and monitoring the dynamic degradation of soils: case study of the Cucuteni-Baiceni Gully on the Moldavian Plateau (Romania)

    NASA Astrophysics Data System (ADS)

    Romanescu, G.; Cotiuga, V.; Asandulesei, A.; Stoleriu, C.

    2012-03-01

    The 3-D scanner, a rapid and precise means of monitoring the dynamics of erosive processes, was first used nationally (Romania) as a new technique of cartography and monitoring the dynamics of soil degradation processes in the Moldavian Plateau. Three sets of measurements took place: in 2008, in 2009 and in 2010, at intervals of exactly one year for the first and six months for the second part. Qualitative and quantitative differences were highlighted. The data obtained were corroborated with precipitation in the area studied. The 3-D scanner has a measurement accuracy of 6 mm. The map highlights the dynamics of gullies developed and may form the basis for the prediction of soil degradation phenomena. The dynamics of the gully and the type of land use show that the phenomenon of erosion of the Moldova Plateau will continue to accelerate. In this case, the gully attacked and destroyed an archaeological site of national importance. The rate of advance of the Cucuteni-Baiceni gully is extremely high (10 m/1.6 years). There are no measures at all to reduce or fight the process of the gully advance. Maximum erosion occurred at the beginning of spring after a winter rich in rainfall, which made the terrain subject to the process of subsidence.

  6. Use of the 3-D scanner in mapping and monitoring the dynamic degradation of soils. Case study of the Cucuteni-Baiceni Gully on the Moldavian Plateau (Romania).

    NASA Astrophysics Data System (ADS)

    Romanescu, G.; Venedict, B.; Cotiuga, V.; Asandulesei, A.

    2011-07-01

    The 3-D Scanner, a rapid and precise means of monitoring the dynamics of erosive processes, was used, first of all nationally (Romania), as a new technique of cartography and monitoring the dynamics of soil degradation processes in the Moldavian Plateau. Three sets of measurements took place: in 2008, in 2009 and in 2010, at intervals of exactly one year for the first and six months for the second part. Qualitative and quantitative differences were highlighted. The data obtained were corroborated with precipitation in the area studied. The 3-D scanner has a measurement accuracy of 6 mm. The map highlights the dynamics of gullies developed and may form the basis for the prediction of soil degradation phenomena. The dynamics of the gully and the type of land use show that the phenomenon of erosion of the Moldova Plateau will continue to accelerate. In this case the gully attacked and destroyed an archaeological site of national importance. The rate of advance of the Cucuteni-Baiceni gully is extremely high (10 m/1.6 yr). There are no measures at all to reduce or fight the process of the gully advance. Maximum erosion occurred at the beginning of spring after a winter rich in rainfall, which made the terrain subject to the process of subsidence.

  7. Experimental studies on ion acceleration and stream line detachment in a diverging magnetic field

    PubMed Central

    Terasaka, K.; Yoshimura, S.; Ogiwara, K.; Aramaki, M.; Tanaka, M. Y.

    2010-01-01

    The flow structure of ions in a diverging magnetic field has been experimentally studied in an electron cyclotron resonance plasma. The flow velocity field of ions has been measured with directional Langmuir probes calibrated with the laser induced fluorescence spectroscopy. For low ion-temperature plasmas, it is concluded that the ion acceleration due to the axial electric field is important compared with that of gas dynamic effect. It has also been found that the detachment of ion stream line from the magnetic field line takes place when the parameter |fciLB∕Vi| becomes order unity, where fci, LB, and Vi are the ion cyclotron frequency, the characteristic scale length of magnetic field inhomogeneity, and the ion flow velocity, respectively. In the detachment region, a radial electric field is generated in the plasma and the ions move straight with the E×B rotation driven by the radial electric field. PMID:20838424

  8. Study of muon-induced neutron production using accelerator muon beam at CERN

    SciTech Connect

    Nakajima, Y.; Lin, C. J.; Ochoa-Ricoux, J. P.; Draeger, E.; White, C. G.; Luk, K. B.; Steiner, H.

    2015-08-17

    Cosmogenic muon-induced neutrons are one of the most problematic backgrounds for various underground experiments for rare event searches. In order to accurately understand such backgrounds, experimental data with high-statistics and well-controlled systematics is essential. We performed a test experiment to measure muon-induced neutron production yield and energy spectrum using a high-energy accelerator muon beam at CERN. We successfully observed neutrons from 160 GeV/c muon interaction on lead, and measured kinetic energy distributions for various production angles. Works towards evaluation of absolute neutron production yield is underway. This work also demonstrates that the setup is feasible for a future large-scale experiment for more comprehensive study of muon-induced neutron production.

  9. Modelling third harmonic ion cyclotron acceleration of deuterium beams for JET fusion product studies experiments

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Johnson, T.; Dumont, R.; Eriksson, J.; Eriksson, L.-G.; Giacomelli, L.; Girardo, J.-B.; Hellsten, T.; Khilkevitch, E.; Kiptily, V. G.; Koskela, T.; Mantsinen, M.; Nocente, M.; Salewski, M.; Sharapov, S. E.; Shevelev, A. E.; Contributors, JET

    2016-11-01

    Recent JET experiments have been dedicated to the studies of fusion reactions between deuterium (D) and Helium-3 (3He) ions using neutral beam injection (NBI) in synergy with third harmonic ion cyclotron radio-frequency heating (ICRH) of the beam. This scenario generates a fast ion deuterium tail enhancing DD and D3He fusion reactions. Modelling and measuring the fast deuterium tail accurately is essential for quantifying the fusion products. This paper presents the modelling of the D distribution function resulting from the NBI+ICRF heating scheme, reinforced by a comparison with dedicated JET fast ion diagnostics, showing an overall good agreement. Finally, a sawtooth activity for these experiments has been observed and interpreted using SPOT/RFOF simulations in the framework of Porcelli’s theoretical model, where NBI+ICRH accelerated ions are found to have a strong stabilizing effect, leading to monster sawteeth.

  10. Physics and engineering studies on the MITICA accelerator: comparison among possible design solutions

    SciTech Connect

    Agostinetti, P.; Antoni, V.; Chitarin, G.; Pilan, N.; Marcuzzi, D.; Serianni, G.; Veltri, P.; Cavenago, M.

    2011-09-26

    Consorzio RFX in Padova is currently using a comprehensive set of numerical and analytical codes, for the physics and engineering design of the SPIDER (Source for Production of Ion of Deuterium Extracted from RF plasma) and MITICA (Megavolt ITER Injector Concept Advancement) experiments, planned to be built at Consorzio RFX. This paper presents a set of studies on different possible geometries for the MITICA accelerator, with the objective to compare different design concepts and choose the most suitable one (or ones) to be further developed and possibly adopted in the experiment. Different design solutions have been discussed and compared, taking into account their advantages and drawbacks by both the physics and engineering points of view.

  11. Study of electron acceleration through the ? mode in a collisional plasma-filled cylindrical waveguide

    NASA Astrophysics Data System (ADS)

    Abdoli-Arani, A.; Moghaddasi, M.

    2016-07-01

    Acceleration of an externally injected electron inside the collisional plasma-filled cylindrical waveguide during its motion in the fields of the ? mode excited by microwave radiation is studied. The effect of the electron collision frequency with background ions on the deflection angle and energy gain of electron, when it is injected along the direction of the mode propagation is investigated. The fields for the mode, the deflection angle of electron trajectory, due to these fields, and the electron energy gradient are obtained. The results for collisionless and collisional plasma are graphically presented. The numerical results illustrate that the presence of the electron collision term in the dielectric permittivity can reduce the electron's energy gain in the configuration.

  12. Acceleration of skin wound healing with tragacanth (Astragalus) preparation: an experimental pilot study in rats.

    PubMed

    Fayazzadeh, Ehsan; Rahimpour, Sina; Ahmadi, Seyed Mohsen; Farzampour, Shahrokh; Sotoudeh Anvari, Maryam; Boroumand, Mohammad Ali; Ahmadi, Seyed Hossein

    2014-01-01

    Gum tragacanth is a natural complex mixture of polysaccharides and alkaline minerals extracted from species of Astragalus plant, which is found widely in arid regions of the Middle East. In a pilot experimental study we examined the effects of its topical application on wound healing in ten albino adult male rats. Two similar parasagittal elliptical full-thickness wounds (control vs. test samples) were created on the dorsum of each animal. Test group samples were fully covered by a thin layer of gum tragacanth daily. The extent of wound healing was evaluated by planimetric analysis on multiple occasions during the 10-day study period. On the 7th day of the study, the percent of wound closure was significantly higher in gum tragacanth-treated specimens compared to the control samples (87%±2% vs. 70%±4%, P<0.001). The majority of wounds in the test group were completely closed by the 10th day of the study. The difference in wound healing index measured by histological examination on day 10 of the study was also statistically meaningful between the two groups (0.624±0.097 vs. 0.255±0.063, P<0.05). The results of this study clearly showed the useful effects of topical application of gum tragacanth in acceleration of skin wound contraction and healing. More studies are encouraged to identify the implicating agents and precisely understand the mechanism by which they exert their wound healing effects.

  13. Storage life of power switching transistors based on performance degradation data

    NASA Astrophysics Data System (ADS)

    Haochun, Qi; Xiaoling, Zhang; Xuesong, Xie; Changzhi, Lü; Chengju, Chen; Li, Zhao

    2014-04-01

    NPN-type small and medium power switching transistors in 3DK series are used to conduct analyses and studies of accelerating degradation. Through three group studies of accelerating degradation in different temperature-humidity constant stresses, the failure sensitive parameters of transistors are identified and the lifetime of samples is extrapolated from the performance degradation data. Average lifetimes in three common distributions are given, when, combined with the Hallberg-Peck temperature-humidity model, the storage lifetime of transistor samples in the natural storage condition is extrapolated between 105-107 h. According to its definition, the accelerating factor is 1462 in 100°C/100% relative humidity (RH) stress condition, and 25°C/25% RH stress condition. Finally, the degradation causes of performance parameters of the test samples are analyzed. The findings can provide certain references for the storage reliability of domestic transistors.

  14. Maize production and land degradation: a Portuguese agriculture field case study

    NASA Astrophysics Data System (ADS)

    Ferreira, Carla S. S.; Pato, João V.; Moreira, Pedro M.; Valério, Luís M.; Guilherme, Rosa; Casau, Fernando J.; Santos, Daniela; Keizer, Jacob J.; Ferreira, António J. D.

    2016-04-01

    While food security is a main challenge faced by human kind, intensive agriculture often leads to soil degradation which then can threaten productivity. Maize is one of the most important crops across the world, with 869 million tons produced worldwide in 2012/2013 (IGC 2015), of which 929.5 thousand tons in Portugal (INE 2014). In Portugal, maize is sown in April/May and harvest occurs generally in October. Conventional maize production requires high inputs of water and fertilizers to achieve higher yields. As Portuguese farmers are typically rather old (on average, 63 years) and typically have a low education level (INE 2014), sustainability of their land management practises is often not a principal concern. This could explain why, in 2009, only 4% of the Portuguese temporary crops were under no-tillage, why only 8% of the farmers performed soil analyses in the previous three years, and why many soils have a low organic matter content (INE 2014). Nonetheless, sustainable land management practices are generally accepted to be the key to reducing agricultural soil degradation, preventing water pollution, and assuring long-term crop production objectives and food security. Sustainable land management should therefore not only be a concern for policy makers but also for farmers, since land degradation will have negative repercussions on the productivity, thus, on their economical income. This paper aims to assess the impact of maize production on soil properties. The study focusses on an 8 ha maize field located in central Portugal, with a Mediterranean climate on a gently sloping terrain (<3%) and with a soil classified as Eutric Fluvisol. On the field, several experiments were carried out with different maize varieties as well as with different fertilizers (solid, liquid and both). Centre pivot irrigation was largely used. Data is available from 2003, and concerns crop yield, fertilization and irrigation practices, as well as soil properties assessed through

  15. Biogeochemical indicators of peatland degradation - a case study of a temperate bog in northern Germany

    NASA Astrophysics Data System (ADS)

    Kruger, J. P.; Leifeld, J.; Glatzel, S.; Szidat, S.; Alewell, C.

    2015-05-01

    Organic soils in peatlands store a great proportion of the global soil carbon pool and can lose carbon via the atmosphere due to degradation. In Germany, most of the greenhouse gas (GHG) emissions from organic soils are attributed to sites managed as grassland. Here, we investigated a land use gradient from near-natural wetland (NW) to an extensively managed (GE) to an intensively managed grassland site (GI), all formed in the same bog complex in northern Germany. Vertical depth profiles of δ13C, δ15N, ash content, C / N ratio and bulk density as well as radiocarbon ages were studied to identify peat degradation and to calculate carbon loss. At all sites, including the near-natural site, δ13C depth profiles indicate aerobic decomposition in the upper horizons. Depth profiles of δ15N differed significantly between sites with increasing δ15N values in the top soil layers paralleling an increase in land use intensity owing to differences in peat decomposition and fertilizer application. At both grassland sites, the ash content peaked within the first centimetres. In the near-natural site, ash contents were highest in 10-60 cm depth. The ash profiles, not only at the managed grassland sites, but also at the near-natural site indicate that all sites were influenced by anthropogenic activities either currently or in the past, most likely due to drainage. Based on the enrichment of ash content and changes in bulk density, we calculated the total carbon loss from the sites since the peatland was influenced by anthropogenic activities. Carbon loss at the sites increased in the following order: NW < GE < GI. Radiocarbon ages of peat in the topsoil of GE and GI were hundreds of years, indicating the loss of younger peat material. In contrast, peat in the first centimetres of the NW was only a few decades old, indicating recent peat growth. It is likely that the NW site accumulates carbon today but was perturbed by anthropogenic activities in the past. Together, all

  16. An accelerator-based neutron microbeam system for studies of radiation effects

    PubMed Central

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A.; Bigelow, Alan W.; Akselrod, Mark S.; Sykora, Jeff G.; Brenner, David J.

    2011-01-01

    A novel neutron microbeam is being developed at the Radiological Research Accelerator Facility (RARAF) of Columbia University. The RARAF microbeam facility has been used for studies of radiation bystander effects in mammalian cells for many years. Now a prototype neutron microbeam is being developed that can be used for bystander effect studies. The neutron microbeam design here is based on the existing charged particle microbeam technology at the RARAF. The principle of the neutron microbeam is to use the proton beam with a micrometre-sized diameter impinging on a very thin lithium fluoride target system. From the kinematics of the 7Li(p,n)7Be reaction near the threshold of 1.881 MeV, the neutron beam is confined within a narrow, forward solid angle. Calculations show that the neutron spot using a target with a 17-µm thick gold backing foil will be <20 µm in diameter for cells attached to a 3.8-µm thick propylene-bottomed cell dish in contact with the target backing. The neutron flux will roughly be 2000 per second based on the current beam setup at the RARAF singleton accelerator. The dose rate will be about 200 mGy min−1. The principle of this neutron microbeam system has been preliminarily tested at the RARAF using a collimated proton beam. The imaging of the neutron beam was performed using novel fluorescent nuclear track detector technology based on Mg-doped luminescent aluminum oxide single crystals and confocal laser scanning fluorescent microscopy. PMID:21131327

  17. Characterization of stress degradation products of duloxetine hydrochloride employing LC-UV/PDA and LC-MS/TOF studies.

    PubMed

    Chadha, Renu; Bali, Alka; Bansal, Gulshan

    2016-03-20

    Duloxetine HCl was subjected to forced degradation under conditions of hydrolysis (neutral, acidic and alkaline), oxidation, photolysis and thermal stress, as suggested in the ICH guideline Q1A(R2). The drug showed significant degradation under acidic, alkaline and aqueous hydrolytic as well as photolytic conditions. The drug remained stable under thermal and oxidative stress conditions. In total, seventeen degradation products (I-XVII) were formed under varied conditions, which could be separated by chromatography of respective degraded solutions on C18 (250 mm×4.6 mm; 5 μ, Nulceodur) column using isocratic elution method. Detection wavelength was selected as 290 nm. MS/TOF accurate mass studies were carried out to establish the complete fragmentation pathway of the drug and degradation products, which, in turn, was utilized in characterization of the products. The degradation pathway of the drug leading to generation of fifteen products I-X, XII-XIII, XV-XVII was postulated and this has not been reported so far. PMID:26775018

  18. Kinetic study of trichloroethylene and toluene degradation by a bioluminescent reporter bacterium

    SciTech Connect

    Kelly, C.J.; Sanseverino, J.; Bienkowski, P.R.; Sayler, G.S.

    1995-12-31

    A constructed bioluminescent reporter bacterium, Pseudomonas putida B2, is very briefly described in this paper. The bacterium degrades toluene and trichloroethylene (TCE), and produces light in the presence of toluene. The light response is an indication of cellular viability and expression of the genes encoding toluene and TCE degrading enzymes.

  19. An SEC/MALS Study of Alternan Degradation During Size-exclusion Chromatographic Analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The degradation of high molar mass polymers during size-exclusion chromatography (SEC) analysis has been a topic of interest for several decades. Should a polymer degrade during analysis, the accuracy of the molar mass (M) and architectural information obtained will be compromised. To this effect,...

  20. Preliminary observations of sugarcane trash degradation for repurposing as mulch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A potential use for sugarcane trash is to convert it to mulch. This study was undertaken to evaluate whether a compost enhancer or nitrogen would accelerate degradation of leaf trash. Trash was obtained from a sugarcane grower, and was treated with water only, a commercial compost starter composed o...