Science.gov

Sample records for accelerated degradation studies

  1. Flow accelerated organic coating degradation

    NASA Astrophysics Data System (ADS)

    Zhou, Qixin

    Applying organic coatings is a common and the most cost effective way to protect metallic objects and structures from corrosion. Water entry into coating-metal interface is usually the main cause for the deterioration of organic coatings, which leads to coating delamination and underfilm corrosion. Recently, flowing fluids over sample surface have received attention due to their capability to accelerate material degradation. A plethora of works has focused on the flow induced metal corrosion, while few studies have investigated the flow accelerated organic coating degradation. Flowing fluids above coating surface affect corrosion by enhancing the water transport and abrading the surface due to fluid shear. Hence, it is of great importance to understand the influence of flowing fluids on the degradation of corrosion protective organic coatings. In this study, a pigmented marine coating and several clear coatings were exposed to the laminar flow and stationary immersion. The laminar flow was pressure driven and confined in a flow channel. A 3.5 wt% sodium chloride solution and pure water was employed as the working fluid with a variety of flow rates. The corrosion protective properties of organic coatings were monitored inline by Electrochemical Impedance Spectroscopy (EIS) measurement. Equivalent circuit models were employed to interpret the EIS spectra. The time evolution of coating resistance and capacitance obtained from the model was studied to demonstrate the coating degradation. Thickness, gloss, and other topography characterizations were conducted to facilitate the assessment of the corrosion. The working fluids were characterized by Fourier Transform Infrared Spectrometer (FTIR) and conductivity measurement. The influence of flow rate, fluid shear, fluid composition, and other effects in the coating degradation were investigated. We conclude that flowing fluid on the coating surface accelerates the transport of water, oxygen, and ions into the coating, as

  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 Testing Of Photothermal Degradation Of Polymers

    NASA Technical Reports Server (NTRS)

    Kim, Soon Sam; Liang, Ranty Hing; Tsay, Fun-Dow

    1989-01-01

    Electron-spin-resonance (ESR) spectroscopy and Arrhenius plots used to determine maximum safe temperature for accelerated testing of photothermal degradation of polymers. Aging accelerated by increasing illumination, temperature, or both. Results of aging tests at temperatures higher than those encountered in normal use valid as long as mechanism of degradation same throughout range of temperatures. Transition between different mechanisms at some temperature identified via transition between activation energies, manifesting itself as change in slope of Arrhenius plot at that temperature.

  4. Study of the degradation mechanisms of carbon-supported platinum fuel cells catalyst via different accelerated stress test

    NASA Astrophysics Data System (ADS)

    Zhang, Yuanliang; Chen, Siguo; Wang, Yao; Ding, Wei; Wu, Rui; Li, Li; Qi, Xueqiang; Wei, Zidong

    2015-01-01

    A combination method based on three different accelerated stress test (AST) protocols along with the monitoring of electrochemical surface area (ECSA), oxygen reduction reaction (ORR) activities, X-Ray photoelectron spectrometer (XPS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) response is introduced to investigate the degradation mechanisms of carbon-supported platinum (Pt/C) catalyst. By comparing the ECSA and ORR activity loss under different AST protocols, we revealed that the activity loss in AST can be divided into recoverable activity loss and unrecoverable activity loss. The recoverable activity loss is attributed to the reduction of Pt oxide or partially due to the removal of CO formed during carbon corrosion. The unrecoverable activity loss is ascribed to the Pt dissolution/re-deposition, agglomeration, detachment and carbon corrosion. XPS results show that the Pt dissolution/re-deposition in AST can be detected by using a more negative potential window. TEM images and analysis confirmed that the Pt growth mode in this study is mainly due to the Pt agglomeration rather than dissolution/re-deposition. EIS analysis reveals that the alternative decomposition/formation of oxygen containing groups over time is the main corrosion pathway of carbon support. These findings are very important for understanding Pt/C catalyst degradation and are also useful for developing fast test protocol for screening new durable catalyst materials.

  5. Accelerated weathering-induced degradation of poly(lactic acid) fiber studied by near-infrared (NIR) hyperspectral imaging.

    PubMed

    Shinzawa, Hideyuki; Nishida, Masakazu; Tanaka, Toshiyuki; Kanematsu, Wataru

    2012-04-01

    Hydrolysis degradation of a set of drawn poly(lactic acid) (PLA) fibers was induced by an accelerated weathering test, radiating ultraviolet (UV) light under a certain temperature and humidity. The fine features of the transient behavior of the PLA fibers were captured by near-infrared (NIR) hyperspectral imaging. The PLA fibers showed a gradual decrease in mechanical property (e.g., tensile strength), indicating hydrolysis degradation. Thus, the detailed analysis of the spectral variation, in turn, offers useful information on the molecular-level degradation behavior of the drawn PLA fibers. The variation of the spectral intensity as well as band position shift of the crystalline band of PLA was analyzed. The spectral intensity of the crystalline band of PLA showed gradual decrease, suggesting the decrease in molecular weight induced by the hydrolysis degradation. In addition, the crystalline band also exhibited a coinciding shift to the lower wavenumber direction with the weathering test, revealing cleavage-induced crystallization of the PLA samples. Consequently, the hydrolysis degradation induced by the weathering test substantially accelerates predominant degradation of the amorphous structure of the PLA and such variation of the molecular structure, in turn, brings less ductility to the PLA fiber.

  6. Accelerated degradation of methyl iodide by agrochemicals.

    PubMed

    Zheng, Wei; Papiernik, Sharon K; Guo, Mingxin; Yates, Scott R

    2003-01-29

    The fumigant methyl iodide (MeI, iodomethane) is considered a promising alternative to methyl bromide (MeBr) for soil-borne pest control in high-cash-value crops. However, the high vapor pressure of MeI results in emissions of a significant proportion of the applied mass into the ambient air, and this may lead to pollution of the environment. Integrating the application of certain agrochemicals with soil fumigation provides a novel approach to reduce excessive fumigant emissions. This study investigated the potential for several agrochemicals that are commonly used in farming operations, including fertilizers and nitrification inhibitors, to transform MeI in aqueous solution. The pseudo-first-order hydrolysis half-life (t(1/2)) of MeI was approximately 108 d, while the transformation of MeI in aqueous solutions containing selected agrochemicals was more rapid, with t(1/2) < 100 d (t(1/2) < 0.5 d in some solutions containing nitrification inhibitors). The influence of these agrochemicals on the rate of MeI degradation in soil was also determined. Adsorption to soil apparently reduced the availability of some nitrification inhibitors in the soil aqueous phase and lowered the degradation rate in soil. In contrast, addition of the nitrification inhibitors thiourea and allylthiourea to soil significantly accelerated the degradation of MeI, possibly due to soil surface catalysis. The t(1/2) of MeI was <20 h in thiourea- and allylthiourea-amended soil, considerably less than that in unamended soil (t(1/2) > 300 h).

  7. Acceleration Studies

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.

    1993-01-01

    Work to support the NASA MSFC Acceleration Characterization and Analysis Project (ACAP) was performed. Four tasks (analysis development, analysis research, analysis documentation, and acceleration analysis) were addressed by parallel projects. Work concentrated on preparation for and implementation of near real-time SAMS data analysis during the USMP-1 mission. User support documents and case specific software documentation and tutorials were developed. Information and results were presented to microgravity users. ACAP computer facilities need to be fully implemented and networked, data resources must be cataloged and accessible, future microgravity missions must be coordinated, and continued Orbiter characterization is necessary.

  8. 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.

  9. 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.

  10. Photothermal degradation studies

    NASA Technical Reports Server (NTRS)

    Liang, R. H.

    1985-01-01

    Key reaction intermediates of photooxidation identified and characterized by laser flash Electron Spin Resonance (ESR) spectroscopy were discussed. Effects of temperature and ultraviolet intensity were studied in order to develop meaningful accelerated testing procedures for encapsulant evaluation. In a program to study the failure of Tedlar/ethylene vinyl acetate (EVA)/stainless steel modules, failure modes similar to those observed outdoors in real-time conditions were simulated in accelerated testing. An experimental technique was developed to quantitatively assess the extent of degradation.

  11. Accelerated degradation of silicon metallization systems

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1983-01-01

    Clemson University has been engaged for the past five years in a program to determine the reliability attributes of solar cells by means of accelerated test procedures. The cells are electrically measured and visually inspected and then subjected for a period of time to stress in excess of that normally encountered in use, and then they are reinspected. Changes are noted and the process repeated. This testing has thus far involved 23 different unencapsulated cell types from 12 different manufacturers, and 10 different encapsulated cell types from 9 different manufacturers. Reliability attributes of metallization systems can be classified as major or minor, depending on the severity of the effects observed. As a result of the accelerated testing conducted under the Clemson program, major effects have been observed related to contact resistance and to mechanical adherence and solderability. This paper does not attempt a generalized survey of accelerated test results, but rather concentrates on one particular attribute of metallization that has been observed to cause electrical degradation - increased contact resistance due to Schottky barrier formation. In this example basic semiconductor theory was able to provide an understanding of the electrical effects observed during accelerated stress testing.

  12. 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.

  13. 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

  14. Diagnosis of MEA degradation under accelerated relative humidity cycling

    NASA Astrophysics Data System (ADS)

    Vengatesan, S.; Fowler, Michael W.; Yuan, Xiao-Zi; Wang, Haijiang

    The objective of this work is to identify the failure mode diagnosis protocols for polymer electrolyte membrane (PEM) fuel cells with the use of accelerated testing conditions. The single cells used in this work were constructed using commercial Ion Power ® membrane electrode assemblies (MEAs) and the performance degradation was studied under accelerated dynamic reactant relative humidity (RH) conditions. The influence of RH on cell performance was investigated, and a strong dependence of degradation with respect to relative humidity was found. RH cycling was seen to not only cause the gradual decrease in performance at the beginning of cell operation, but it was also related to the rapid decline in performance observed after 330 h operation. This change in degradation rate is seen a change in the material degradation failure mechanism at this point in the operational history of the cell. The increase in cell resistance, membrane crossover, fluoride release rate and decrease in electrochemical surface area (ESA) were also observed with time, and these results were correlated to change in degradation rate. Infra-Red (IR) imaging of an aged MEA was utilized to show varying temperature profiles and outline the possibility of cracks, tears or pinholes in the membrane.

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

    PubMed

    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%.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Correlation between mechanical and chemical degradation after outdoor and accelerated laboratory aging for multilayer photovoltaic backsheets

    NASA Astrophysics Data System (ADS)

    Lin, Chiao-Chi; Lyu, Yadong; Yu, Li-Chieh; Gu, Xiaohong

    2016-09-01

    Channel cracking fragmentation testing and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were utilized to study mechanical and chemical degradation of a multilayered backsheet after outdoor and accelerated laboratory aging. A model sample of commercial PPE backsheet, namely polyethylene terephthalate/polyethylene terephthalate/ethylene vinyl acetate (PET/PET/EVA) was investigated. Outdoor aging was performed in Gaithersburg, Maryland, USA for up to 510 days, and complementary accelerated laboratory aging was conducted on the NIST (National Institute of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure). Fracture energy, mode I stress intensity factor and film strength were analyzed using an analytical model based on channel cracking fragmentation testing results. The correlation between mechanical and chemical degradation was discussed for both outdoor and accelerated laboratory aging. The results of this work provide preliminary understanding on failure mechanism of backsheets after weathering, laying the groundwork for linking outdoor and indoor accelerated laboratory testing for multilayer photovoltaic backsheets.

  2. 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...

  3. Mechanical loading of bovine pericardium accelerates enzymatic degradation.

    PubMed

    Ellsmere, J C; Khanna, R A; Lee, J M

    1999-06-01

    Bioprosthetic heart valves fail as the result of two simultaneous processes: structural deterioration and calcification. Leaflet deterioration and perforation have been correlated with regions of highest stress in the tissue. The failures have long been assumed to be due to simple mechanical fatigue of the collagen fibre architecture; however, we have hypothesized that local stresses-and particularly dynamic stresses-accelerate local proteolysis, leading to tissue failure. This study addresses that hypothesis. Using a novel, custom-built microtensile culture system, strips of bovine pericardium were subjected to static and dynamic loads while being exposed to solutions of microbial collagenase or trypsin (a non-specific proteolytic enzyme). The time to extend to 30% strain (defined here as time to failure) was recorded. After failure, the percentage of collagen solubilized was calculated based on the amount of hydroxyproline present in solution. All data were analyzed by analysis of variance (ANOVA). In collagenase, exposure to static load significantly decreased the time to failure (P < 0.002) due to increased mean rate of collagen solubilization. Importantly, specimens exposed to collagenase and dynamic load failed faster than those exposed to collagenase under the same average static load (P = 0.02). In trypsin, by contrast, static load never led to failure and produced only minimal degradation. Under dynamic load, however, specimens exposed to collagenase, trypsin, and even Tris/CaCl2 buffer solution, all failed. Only samples exposed to Hanks' physiological solution did not fail. Failure of the specimens exposed to trypsin and Tris/CaCl2 suggests that the non-collagenous components and the calcium-dependent proteolytic enzymes present in pericardial tissue may play roles in the pathogenesis of bioprosthetic heart valve degeneration.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Bioelectrochemical system accelerates microbial growth and degradation of filter paper.

    PubMed

    Sasaki, Kengo; Hirano, Shin-Ichi; Morita, Masahiko; Sasaki, Daisuke; Matsumoto, Norio; Ohmura, Naoya; Igarashi, Yasuo

    2011-01-01

    Bioelectrochemical reactors (BERs) with a cathodic working potential of -0.6 or -0.8 V more efficiently degraded cellulosic material, i.e., filter paper (57.4-74.1% in 3 days and 95.9-96.3% in 7 days) than did control reactors without giving exogenous potential (15.4% in 3 days and 64.2% in 7 days). At the same time, resultant conversions to methane and carbon dioxide in cathodic working chamber of BERs by application of electrochemical reduction in 3 days of operation were larger than control reactors. However, cumulative methane production in cathodic BERs was similar to those in control reactors after 7 days of operation. Microscopic observation and 16S rRNA gene analysis showed that microbial growth in the entire consortium was higher after 2 days of operation of cathodic BERs as compared with the control reactors. In addition, the number of methanogenic 16S rRNA gene copies in cathodic BERs was higher than in control reactors. Moreover, archaeal community structures constructed in cathodic BERs consisted of hydrogenotrophic methanogen-related organisms and differed from those in control reactors after 2 days of operation. Specifically, the amount of Methanothermobacter species in cathodic BERs was higher within archaeal communities than in those control reactors after 2 days of operation. Electrochemical reduction may be effective for accelerating microbial growth in the start-up period and thereby increasing microbial treatment of cellulosic waste and methane production.

  10. 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.

  11. Degradation and acute toxicity studies of degradable implant materials

    NASA Astrophysics Data System (ADS)

    Taylor, Michelle Suzette

    The present study investigated the acute toxicities of the degradation product components of six degradable polymers, the acute toxicities of nine metallic ions and accelerated degradation of one degradable polymer. Prior to these studies, the effect of the anticipated test conditions on the Microtox acute toxicity assay was determined. It was shown that the Microtox is unaffected by pH of water within the range of 5 to 10 and that the test is unaffected by tris buffer at physiologic pH and concentration. The toxicity and rates of degradation of poly(glycolic acid), PGA; two samples of poly(L-lactic acid), PLLA; samples of different molecular weights, poly(caprolactone), PCL; poly(ortho ester), POE; and poly(hydroxybutyrate-cohydroxyvalerate), PHBV, were compared, along with the toxicity of their degradation product components. The toxic concentrations ranged from 100 muM (lactic acid) to 125,000 muM (pentaerythritol). The degradation product components in order of most toxic to least toxic are lactic acid, caproic acid, glycolic acid, cyclohexanedimethanol, propionic acid, hydroxybutyric acid, 1,6-hexanediol, pentaerythritol dipropionate, pentaerythritol and hydroxyvaleric acid. Acute toxicity was determined for metallic ions in water and buffer. The toxic concentrations ranged from 33 muM (Tisp{4+} in water) to 3,580 muM (Wsp{6+} in buffer). The four most toxic ions in water (Tisp{4+}, Mosp{5+}, Fesp{3+}, Crsp{3+}) caused solution pH to decrease markedly. The six other ions (Vasp{3+}, Cosp{3+}, Alsp{3+,} Tisp{4+} adjusted to pH 6.1, Nisp{2+} and Wsp{6+}) markedly. The six other ions (Vasp{3+}, Cosp{3+}, Alsp{3+}, Tisp{4+} adjusted to pH 6.1, Nisp{2+} and Wsp{6+}) did not appreciably affect pH. In buffer, Alsp{3+}, Nisp{2+}, Wsp{6+} and Vsp{3+} became much less toxic, suggesting formation of complexes. In general the least toxic ions do not create an acid environment and/or do form protective complexes. PHBV has good mechanical properties and, compared with the

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Lathrop, J. W.

    1986-09-01

    This is the final report of a reliability research program to study the response of amorphous silicon colar cells to accelerated temperature testing. The goal of the research was to utilize accelerated testing to identify failure/degradation modes and to relate them to basic physical, chemical, and metallurgical phenomena. Four types of single junction commercial modules were subjected to 140 C testing, both in the dark and under illuminated conditions. The before and after electrical characteristics of individual cells were measured and compared and correlated with physical evidence. A fifth module type could not be tested because of poor adherence of the films to the glass superstrate. A short term effect of stressing was noted which dramatically improved cells with low Voc on one type of construction. All cells eventually showed long term irreversible degradation, but the time to 50% Pm reduction varied by as much as two orders of magnitude depending on construction. No basic difference could be detected between degradation under illuminated or non-illuminated conditions, when cells were either open or short circuited. Comparison with one type of tendem cell and with published results of Japanese cell testing indicated the marked superiority of the tandem cell to all other types. Cells were examined physically by optical, IR, and scanning electron microscopy and by Auger spectroscopy, spectroscopy, secondary ion mass spectroscopy, and energy dispersive x-ray analysis. The long term degradation was felt to be due to localized penetration of aluminum through the amorphous film.

  14. Tamoxifen inhibits ER-negative breast cancer cell invasion and metastasis by accelerating Twist1 degradation.

    PubMed

    Ma, Gang; He, Jianjun; Yu, Yang; Xu, Yixiang; Yu, Xiaobin; Martinez, Jarrod; Lonard, David M; Xu, Jianming

    2015-01-01

    Twist1 is a transcription factor driving epithelial-mesenchymal transition, invasion and metastasis of breast cancer cells. Mice with germ-line Twist1 knockout are embryonic lethal, while adult mice with inducible Twist1 knockout have no obvious health problems, suggesting that Twist1 is a viable therapeutic target for the inhibition of invasion and metastasis of breast cancer in adult patients. In this study, we expressed a luciferase protein or a Twist1-luciferase fusion protein in HeLa cells as part of a high throughput system to screen 1280 compounds in the Library of Pharmacologically Active Compounds (LOPAC) from Sigma-Aldrich for their effects on Twist1 protein expression. One of the most interesting compounds identified is tamoxifen, a selective estrogen receptor (ER) modulator used to treat ER-positive breast cancer. Tamoxifen treatment significantly accelerated Twist1 degradation in multiple cell lines including HEK293 human kidney cells, 4T1 and 168FARN mouse mammary tumor cells with either ectopically or endogenously expressed Twist1. Tamoxifen-induced Twist1 degradation could be blocked by the MG132 proteasome inhibitor, suggesting that tamoxifen induces Twist1 degradation through the ubiquitination-proteasome pathway. However, tamoxifen-induced Twist1 degradation was independent of Twist1 mRNA expression, estrogen signaling and MAPK-mediated Twist1 phosphorylation in these cells. Importantly, tamoxifen also significantly inhibited invasive behavior in Matrigel and lung metastasis in SCID-bg mice of ER-negative 4T1 mammary tumor cells, which depend on endogenous Twist1 to invade and metastasize. These results indicate that tamoxifen can significantly accelerate Twist1 degradation to suppress cancer cell invasion and metastasis, suggesting that tamoxifen can be used not only to treat ER-positive breast cancers but also to reduce Twist1-mediated invasion and metastasis in ER-negative breast cancers.

  15. Accelerated performance degradation of CIGS solar cell determined by in-situ monitoring

    NASA Astrophysics Data System (ADS)

    Theelen, Mirjam; Barreau, Nicolas; Daume, Felix; Steijvers, Henk; Hans, Vincent; Liakopoulou, Aikaterini; Vroon, Zeger; Zeman, Miro

    2014-10-01

    An `hybrid' degradation setup, in which humidity, temperature and illumination are used in order to accelerate degradation of CIGS, has been developed. This setup consists of a climate chamber, which can vary the temperature and humidity. Furthermore, an area of 80x80 cm2 is illuminated, which allows both the study of light induced behvaior and the in-situ measurement of the IV curve of the cell during the test, so the degradation behavior can be observed in time. The IV output is automatically logged and characteristic parameters like efficiency, currents, voltages, ideality factor and resistance can be extracted. The 40x40 cm2 in the center of the illuminated area was calibrated BAA according to IEC norm 60904-9. Twelve cells or minimodules can be degraded and measured in-situ at the same time. The continuous in-situ IV measurements allowed us to do various studies, including the determination of the temperature dependency and of the impact of light and dark exposure on the performance of CIGS solar cells. Furthermore, the impact of different Na and K concentrations in the CIGS absorber layer on the ininial as well as long term performance of CIGS solar cells was studied.

  16. 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

  17. 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.

  18. 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.; ...

    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

  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. 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.

  2. Error-induced beam degradation in Fermilab's accelerators

    NASA Astrophysics Data System (ADS)

    Yong, Sung-Yong Phil

    In Part I, three independent models of Fermilab's Booster synchrotron are presented. All three models are constructed to investigate and to 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 that the noise does matter to a beam with a preliminary model, we proceed 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 currently distributed around the Booster

  3. 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

  4. Photothermal degradation studies of encapsulants

    NASA Technical Reports Server (NTRS)

    Liang, R. H.

    1984-01-01

    The reliability physics program at JPL is outlined. The overall objectives and approaches are given in the program. The objectives, approaches and conclusions are given for two specific parts of the programs. These two parts are mechanistic studies of photothermal degradation and performance characteristics of materials with respect to photothermal stresses.

  5. Degradation of diclofenac by UV-activated persulfate process: Kinetic studies, degradation pathways and toxicity assessments.

    PubMed

    Lu, Xian; Shao, Yisheng; Gao, Naiyun; Chen, Juxiang; Zhang, Yansen; Xiang, Huiming; Guo, Youluo

    2017-03-21

    Diclofenac (DCF) is the frequently detected non-steroidal pharmaceuticals in the aquatic environment. In this study, the degradation of DCF was evaluated by UV-254nm activated persulfate (UV/PS). The degradation of DCF followed the pseudo first-order kinetics pattern. The degradation rate constant (kobs) was accelerated by UV/PS compared to UV alone and PS alone. Increasing the initial PS dosage or solution pH significantly enhanced the degradation efficiency. Presence of various natural water constituents had different effects on DCF degradation, with an enhancement or inhibition in the presence of inorganic anions (HCO3(-) or Cl(-)) and a significant inhibition in the presence of NOM. In addition, preliminary degradation mechanisms and major products were elucidated using LC-MS/MS. Hydroxylation, decarbonylation, ring-opening and cyclation reaction involving the attack of SO4(•)(-) or other substances, were the main degradation mechanism. TOC analyzer and Microtox bioassay were employed to evaluate the mineralization and cytotoxicity of solutions treated by UV/PS at different times, respectively. Limited elimination of TOC (32%) was observed during the mineralization of DCF. More toxic degradation products and their related intermediate species were formed, and the UV/PS process was suitable for removing the toxicity. Of note, longer degradation time may be considered for the final toxicity removal.

  6. Mechanisms of accelerated degradation in the front cells of PEMFC stacks and some mitigation strategies

    NASA Astrophysics Data System (ADS)

    Li, Pengcheng; Pei, Pucheng; He, Yongling; Yuan, Xing; Chao, Pengxiang; Wang, Xizhong

    2013-11-01

    The accelerated degradation in the front cells of a polymer electrolyte membrane fuel cell(PEMFC) stack seriously reduces the reliability and durability of the whole stack. Most researches only focus on the size and configuration of the gas intake manifold, which may lead to the maldistribution of flow and pressure. In order to find out the mechanisms of the accelerated degradation in the front cells, an extensive program of experimental and simulation work is initiated and the results are reported. It is found that after long-term lifetime tests the accelerated degradation in the front cells occurs in all three fuel cell stacks with different flow-fields under the U-type feed configuration. Compared with the rear cells of the stack, the voltage of the front cells is much lower at the same current densities and the membrane electrode assembly(MEA) has smaller active area, more catalyst particle agglomeration and higher ohmic impedance. For further investigation, a series of three dimensional isothermal numerical models are built to investigate the degradation mechanisms based on the experimental data. The simulation results reveal that the dry working condition of the membrane and the effect of high-speed gas scouring the MEA are the main causes of the accelerated degradation in the front cells of a PEM fuel cell stack under the U-type feed configuration. Several mitigation strategies that would mitigate these phenomena are presented: removing cells that have failed and replacing them with those of the same aging condition as the average of the stack; choosing a Z-type feed pattern instead of a U-type one; putting several air flow-field plates without MEA in the front of the stack; or exchanging the gas inlet and outlet alternately at a certain interval. This paper specifies the causes of the accelerated degradation in the front cells and provides the mitigation strategies.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Accelerated Degradation Due to Weakened Adhesion from Li-TFSI Additives in Perovskite Solar Cells.

    PubMed

    Lee, Inhwa; Yun, Jae Hoon; Son, Hae Jung; Kim, Taek-Soo

    2017-03-01

    Reliable integration of organometallic halide perovskite in photovoltaic devices is critically limited by its low stability in humid environments. Furthermore, additives to increase the mobility in the hole transport material (HTM) have deliquescence and hygroscopic properties, which attract water molecules and result in accelerated degradation of the perovskite devices. In this study, a double cantilever beam (DCB) test is used to investigate the effects of additives in the HTM layer on the perovskite layer through neatly delaminating the interface between the perovskite and HTM layers. Using the DCB test, the bottom surface of the HTM layers is directly observed, and it is found that the additives are accumulated at the bottom along the thickness (i.e., through-plane direction) of the films. It is also found that the additives significantly decrease the adhesion at the interface between the perovskite and HTM layers by more than 60% through hardening the HTM films. Finally, the adhesion-based degradation mechanism of perovskite devices according to the existence of additives is proposed for humid environments.

  12. 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.

  13. 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.

  14. 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.

  15. L-Lysine suppresses myofibrillar protein degradation and autophagy in skeletal muscles of senescence-accelerated mouse prone 8.

    PubMed

    Sato, Tomonori; Ito, Yoshiaki; Nagasawa, Takashi

    2017-02-01

    Sarcopenia is a condition of the loss of muscle mass that is associated with aging and that increases the risk for bedridden state, thereby warranting studies of interventions that attenuate sarcopenia. Here the effects of 2-month dietary L-lysine (Lys) supplementation (1.5-3.0 %) on myofibrillar protein degradation and major proteolytic systems were investigated in senescence-accelerated mouse prone 8 (SAMP8). At 36 weeks of age, skeletal muscle and lean body mass was reduced in SAMP8 when compared with control senescence-accelerated mouse resistant 1 (SAMR1). The myofibrillar protein degradation, which was evaluated by the release of 3-methylhistidine, was stimulated in SAMP8, and the autophagy activity, which was evaluated by light chain 3-II, was stimulated in the skeletal muscle of SAMP8. The activation of ubiquitin-proteasome system was not observed in the muscles of SAMP8. However, myofibrillar protein degradation and autophagic activity in skeletal muscles of SAMP8 were suppressed by dietary intake of 3.0 % Lys. The present data indicate that myofibrillar protein degradation by bulk autophagy is stimulated in the skeletal muscles of SAMP8 and that dietary Lys supplementation attenuates sarcopenia in SAMP8 by suppressing autophagic proteolysis.

  16. Electromagnetic acceleration studies with augmented rails

    SciTech Connect

    Maruo, T.; Fujioka, K.; Nagaoka, K.; Okamoto, A.; Ikuta, K.; Nemoto, K. )

    1991-01-01

    A comparative study of electromagnetic acceleration in the rail-type accelerators with two kinds of rail geometry was carried out experimentally. The accelerators were energized by 200kJ capacitor bank and the weight of loaded projectiles was about 1.3 grams with 10mm {times} 10mm square bore. The attained velocity was 4.3km/s in the augmented accelerator, while it was 3.8km/s in the classical device. In this paper these differences in attained velocity are briefly discussed. A theoretical understanding of the rail erosion is also described.

  17. 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.

  18. 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.

  19. Pyrene degradation accelerated by constructed consortium of bacterium and microalga: effects of degradation products on the microalgal growth.

    PubMed

    Luo, Shusheng; Chen, Baowei; Lin, Li; Wang, Xiaowei; Tam, Nora Fung-Yee; Luan, Tiangang

    2014-12-02

    Abundant microbes including bacteria, fungi, or algae are capable of biodegrading polycyclic hydrocarbons (PAHs). However, pure cultures never occur in the contaminated environments. This study aimed to understand the general potential mechanisms of interactions between microbes under pollution stress by constructing a consortium of PAH-degrading microalga (Selenastrum capricornutum) and bacterium (Mycobacterium sp. strain A1-PYR). Bacteria alone could grow on the pyrene, whereas the growth of algae alone was substantially inhibited by the pyrene of 10 mg L(-1). In the mixing culture of algae and bacteria, the growth rate of algae was significantly increased from day 4 onward. Rapid bacterial degradation of pyrene might mitigate the toxicity of pyrene to algae. Phenolic acids, the bacterial degradation products of pyrene, could serve as the phytohormone for promoting algal growth in the coculture of algae and bacteria. In turn, bacterial growth was also enhanced by the algae presented in the mixing culture. Consequently, the fastest degradation of pyrene among all biodegradation systems was achieved by the consortium of algae and bacteria probably due to such interactions between the two species by virtue of degradation products. This study reveals that the consortium containing multiple microbial species is high potential for microbial remediation of pyrene-contaminated environments, and provides a new strategy to degrade the recalcitrant PAHs.

  20. Membrane degradation during combined chemical and mechanical accelerated stress testing of polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Lim, C.; Ghassemzadeh, L.; Van Hove, F.; Lauritzen, M.; Kolodziej, J.; Wang, G. G.; Holdcroft, S.; Kjeang, E.

    2014-07-01

    A cyclic open circuit voltage (COCV) accelerated stress test (AST) is designed to screen the simultaneous effect of chemical and mechanical membrane degradation in polymer electrolyte fuel cells. The AST consists of a steady state OCV phase to accelerate chemical degradation and periodic wet/dry cycles to provide mechanical degradation. The membrane degradation process induced by COCV AST operation is analyzed using a standard MEA with PFSA ionomer membrane. The OCV shows an initially mild decay rate followed by a higher decay rate in the later stages of the experiment. Membrane failure, defined by a threshold convective hydrogen leak rate, is obtained after 160 h of operation. Uniform membrane thinning is observed with pinhole formation being the primary cause of failure. Mechanical tensile tests reveal that the membrane becomes stiffer and more brittle during AST operation, which contributes to mechanical failure upon cyclic humidity induced stress. Solid state 19F NMR spectroscopy and fluoride emission measurements demonstrate fluorine loss from both side chain and main chain upon membrane exposure to high temperature and low humidity OCV condition.

  1. Cross-correlation of backsheet degradation between real-world exposed modules and accelerated exposures of backsheet materials (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Bruckman, Laura S.; French, Roger H.; Wang, Yu; Kempe, Michael D.; Lefebvre, Amy A.; Gu, Xiaohong; Ji, Liang; Wan, Kai-Tak; Flueckiger, Christopher

    2016-09-01

    heets are a key polymeric component of a PV module and understanding its degradation is necessary to be able to predict the lifetime of PV modules. We are developing a backsheet predictive tests and a model based on point- in-time data from analytical techniques and datastreams that are applicable to both outdoor and indoor PV module backsheet studies and are supplemented with meteorology data, climatic and brand/model, and other accessible information. The predictive tests and models will specify indoor and outdoor exposure and evaluation data acquisition criteria, variable selection, and temporal duration and variation so as to be able to predict backsheet performance in various climatic zones. This backsheet performance prediction is based on defined backsheet failures in the field, and is quantified by tracking backsheet degradation in the field so as to determine degradation rates. The backsheet lifetime performance predictive tests and models, will be developed using a Stressor / Mechanism / Response framework in which all data are categorized as stressor, mechanism and performance (response) variables and are represented as discrete points-in-time datasets. We will develop and validate these accelerated indoor exposures and evaluations and models and cross-correlate the outdoor and accelerated indoor exposures and evaluations. The evaluation techniques include nondestructive spectroscopy and microscopy techniques and destructive techniques and will provide data in predefined variables, which are used in the predictive modeling.

  2. 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.

  3. 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.

  4. A Complex of Htm1 and the Oxidoreductase Pdi1 Accelerates Degradation of Misfolded Glycoproteins.

    PubMed

    Pfeiffer, Anett; Stephanowitz, Heike; Krause, Eberhard; Volkwein, Corinna; Hirsch, Christian; Jarosch, Ernst; Sommer, Thomas

    2016-06-03

    A quality control system in the endoplasmic reticulum (ER) efficiently discriminates polypeptides that are in the process of productive folding from conformers that are trapped in an aberrant state. Only the latter are transported into the cytoplasm and degraded in a process termed ER-associated protein degradation (ERAD). In the ER, an enzymatic cascade generates a specific N-glycan structure of seven mannosyl and two N-acetylglucosamine residues (Man7GlcNAc2) on misfolded glycoproteins to facilitate their disposal. We show that a complex encompassing the yeast lectin-like protein Htm1 and the oxidoreductase Pdi1 converts Man8GlcNAc2 on glycoproteins into the Man7GlcNAc2 signal. In vitro the Htm1-Pdi1 complex processes both unfolded and native proteins albeit with a preference for the former. In vivo, elevated expression of HTM1 causes glycan trimming on misfolded and folded proteins, but only degradation of the non-native species is accelerated. Thus, modification with a Man7GlcNAc2 structure does not inevitably commit a protein for ER-associated protein degradation. The function of Htm1 in ERAD relies on its association with Pdi1, which appears to regulate the access to substrates. Our data support a model in which the balanced activities of Pdi1 and Htm1 are crucial determinants for the efficient removal of misfolded secretory glycoproteins.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. Sorafenib suppresses growth and survival of hepatoma cells by accelerating degradation of enhancer of zeste homolog 2.

    PubMed

    Wang, Shanshan; Zhu, Yu; He, Hongyong; Liu, Jing; Xu, Le; Zhang, Heng; Liu, Haiou; Liu, Weisi; Liu, Yidong; Pan, Deng; Chen, Lin; Wu, Qian; Xu, Jiejie; Gu, Jianxin

    2013-06-01

    Enhancer of zeste homolog 2 (EZH2) is a mammalian histone methyltransferase that contributes to the epigenetic silencing of target genes that regulate cancer cell growth and survival. It is overexpressed in hepatocellular carcinoma (HCC) with a clinical significance that remains obscure. Sorafenib, a multikinase inhibitor, has been used as a first-line therapeutic drug and shown clinical efficiency for advanced-stage HCC patients. In the present study, we found that sorafenib lowered the protein level of EZH2 through accelerating proteasome-mediated EZH2 degradation in hepatoma cells. Overexpression of EZH2 reversed sorafenib-induced cell growth arrest, cell cycle arrest, and cell apoptosis dependent on histone methyltransferase activity in hepatoma cells. More importantly, shRNA-mediated EZH2 knockdown or EZH2 inhibition with 3-deazaneplanocin A treatment promoted sorafenib-induced hepatoma cell growth arrest and apoptosis. Sorafenib altered the hepatoma epigenome by reducing EZH2 and H3K27 trimethylation. These results revealed a novel therapeutic mechanism underlying sorafenib treatment in suppressing hepatoma growth and survival by accelerating EZH2 degradation. Genetic deletion or pharmacological ablation of EZH2 made hepatoma cells more sensitive to sorafenib, which helps provide a strong framework for exploring innovative combined therapies for advanced-stage HCC patients.

  12. 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

    2014-11-03

    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.

  13. 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.

  14. Visualization of TlBr ionic transport mechanism by the Accelerated Device Degradation technique

    NASA Astrophysics Data System (ADS)

    Datta, Amlan; Becla, Piotr; Motakef, Shariar

    2015-06-01

    Thallium Bromide (TlBr) is a promising gamma radiation semiconductor detector material. However, it is an ionic semiconductor and suffers from polarization. As a result, TlBr devices degrade rapidly at room temperature. Polarization is associated with the flow of ionic current in the crystal under electrical bias, leading to the accumulation of charged ions at the device's electrical contacts. We report a fast and reliable direct characterization technique to identify the effects of various growth and post-growth process modifications on the polarization process. The Accelerated Device Degradation (ADD) characterization technique allows direct observation of nucleation and propagation of ionic transport channels within the TlBr crystals under applied bias. These channels are observed to be initiated both directly under the electrode as well as away from it. The propagation direction is always towards the anode indicating that Br- is the mobile diffusing species within the defect channels. The effective migration energy of the Br- ions was calculated to be 0.33±0.03 eV, which is consistent with other theoretical and experimental results.

  15. Accelerated stress testing and diagnostic analysis of degradation in CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Albin, David S.

    2008-08-01

    Solar cell module reliability is inextricably linked to cell-level reliability. This is particularly so with thin-film technologies. In CdTe, reliability issues historically associate with back contact stability and the use of Cu as an extrinsic dopant. Using a simple approach by which identical cells are heated under open-circuit bias and 1-sun illumination, degradation activation energies of 0.63 and 2.94 eV in laboratory-scale CdS/CdTe devices were identified in the accelerated stress temperature range of 60 to 120 °C. At lower stress temperatures, cell performance changes were linearly correlated with changes in both fill factor (FF) and short-circuit current (Jsc). At higher stress temperatures, changes in efficiency were correlated with changes in FF and open-circuit voltage (Voc). The measured activation energy of 0.63 is associated with Cu-diffusion. During the early stage of stress testing, which may provide additional back contact annealing, improvements in FF were due to Cu-diffusion. Decreased performance observed at longer stress times (decreased FF and Voc), according to a two-diode Pspice model, were due to both increased space-charge recombination (near the junction) and decreased recombination in the bulk. Kirkendall void formation (S-outdiffusion) at the CdS/CdTe interface is given as responsible for the 2.9 eV degradation mechanism.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Characterization, Modeling, and Accelerating Emulation of Aircraft Coating Exposure and Degradation

    DTIC Science & Technology

    2009-09-30

    Maocheng Yan Stuart Croll Jun Nie Jinhai Wang Dennis Tallman Quan Su Yechung Wang Kerry Allahar Andrew Huovinen Duhua Wang Brian Hinderliter...than may natural weathering. Thus coating failure due to adhesion loss or hydrolysis can be very different between accelerated testing protocols... Kerry Allahar and Brian Hinderliter. Some of the results are discussed above. The results of these studies are also discussed in detail in the

  1. Thermal degradation of polyketones. Vibrational spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Conti, G.; Sommazzi, A.

    1993-03-01

    Thermal degradation studies of regular alternating polymers of carbon monoxide and olefin have been followed by FT-IR spectroscopy. The I.R spectra of solid samples, performed in inert atmosphere and in high vacuum, were recorded as a function of time at different temperatures. From the I.R. data it is possible to conclude that the reaction process, near the melting point of the polymers, could consist of intra or intermolecular hydrogen transfer yielding an enol and a small quantity of insaturations. The thermal degradation process, at temperatures higher than melting point, involves the scission of the polymer chain and produces fragments with a large number of insaturations.

  2. Thermally Accelerated Oxidative Degradation of Quercetin Using Continuous Flow Kinetic Electrospray-Ion Trap-Time of Flight Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Barnes, Jeremy S.; Foss, Frank W.; Schug, Kevin A.

    2013-10-01

    Thermally accelerated oxidative degradation of aqueous quercetin at pH 5.9 and 7.4 was kinetically measured using an in-house built online continuous flow device made of concentric capillary tubes, modified to fit to the inlet of an electrospray ionization-ion trap-time-of-flight-mass spectrometer (ESI-IT-TOF-MS). Time-resolved mass spectral measurements ranging from 2 to 21 min were performed in the negative mode to track intermediate degradation products and to evaluate the degradation rate of the deprotonated quercetin ion, [Q-H]-. Upon heating solutions in the presence of dissolved oxygen, degradation of [Q-H]- was observed and was accelerated by an increase in pH and temperature. Regardless of the condition, the same degradation pathways were observed. Degradation mechanisms and structures were determined using higher order tandem mass spectrometry (up to MS3) and high mass accuracy. The observed degradation mechanisms included oxidation, hydroxylation, and ring-cleavage by nucleophilic attack. A chalcan-trione structure formed by C-ring opening after hydroxylation at C2 was believed to be a precursor for other degradation products, formed by hydroxylation at the C2, C3, and C4 carbons from attack by nucleophilic species. This resulted in A-type and B-type ions after cross-ring cleavage of the C-ring. Based on time of appearance and signal intensity, nucleophilic attack at C3 was the preferred degradation pathway, which generated 2,4,6-trihydroxymandelate and 2,4,6-trihydroxyphenylglyoxylate ions. Overall, 23 quercetin-related ions were observed.

  3. 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.

  4. 4-Hydroxynonenal differentially regulates adiponectin gene expression and secretion via activating PPARγ and accelerating ubiquitin–proteasome degradation

    PubMed Central

    Wanga, Zhigang; Dou, Xiaobing; Gu, Dongfang; Shen, Chen; Yao, Tong; Nguyen, Van; Braunschweig, Carol; Song, Zhenyuan

    2011-01-01

    Although well-established, the underlying mechanisms involved in obesity-related plasma adiponectin decline remain elusive. Oxidative stress is associated with obesity and insulin resistance and considered to contribute to the progression toward obesity-related metabolic disorders. In this study, we investigated the effects of 4-hydroxynonenal (4-HNE), the most abundant lipid peroxidation end product, on adiponectin production and its potential implication in obesity-related adiponectin decrease. Long-term high-fat diet feeding led to obesity in mouse, accompanied by decreased plasma adiponectin and increased adipose tissue 4-HNE content. Exposure of adipocytes to exogenous 4-HNE resulted in decreased adiponectin secretion in a dose-dependent manner, which was consistent with significantly decreased intracellular adiponectin protein abundance. In contrast, adiponectin gene expression was significantly elevated by 4-HNE treatment, which was concomitant with increased peroxisome proliferator-activated receptor gamma (PPAR-γ) gene expression and transactivity. The effect was abolished by T0070907, a PPAR-γ antagonist, suggesting that PPAR-γ activation plays a critical role in this process. To gain insight into mechanisms involved in adiponectin protein decrease, we examined the effects of 4-HNE on adiponectin protein degradation. Cycloheximide (CHX)-chase assay revealed that 4-HNE exposure accelerated adiponectin protein degradation, which was prevented by MG132, a potent proteasome inhibitor. Immunoprecipitation assay showed that 4-HNE exposure increased ubiquitinated adiponectin protein levels. These data altogether indicated that 4-HNE enhanced adiponectin protein degradation via ubiquitin–proteasome system. Finally, we demonstrated that supplementation of HF diet with betaine, an antioxidant and methyl donor, alleviated high-fat-induced adipose tissue 4-HNE increase and attenuated plasma adiponectin decline. Taken together, our findings suggest that the lipid

  5. Accelerated degradation of methylammonium lead iodide perovskites induced by exposure to iodine vapour

    NASA Astrophysics Data System (ADS)

    Wang, Shenghao; Jiang, Yan; Juarez-Perez, Emilio J.; Ono, Luis K.; Qi, Yabing

    2017-01-01

    Efficiencies of organic-inorganic lead halide perovskite solar cells (PSCs) have significantly increased in recent years, but instability issues impede their further development and application. Previous studies reported that volatile species (for example, iodine, I2) were generated when perovskites were subjected to moisture, oxygen, light illumination, applied electric field, and thermal stress (all of which are relevant to the operation of PSCs in practical applications). Here we show that I2 vapour causes severe degradation of MAPbI3 (MA: CH3NH3+) perovskite, due to chemical chain reactions. Furthermore, I2 vapour could also induce degradation of other iodide-based perovskites, such as FAPbI3 (FA: HC(NH2)2+) and FA0.8Cs0.2PbI3. The results reveal a universal degradation factor for iodide-based perovskite by I2. As the release of I2 is nearly inevitable during practical applications, this work suggests that MAPbI3 may not be suitable for long-term stable solar cells and it is imperative to develop other types of perovskite material to achieve stable PSCs.

  6. [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.

  7. Forced degradation study of thiocolchicoside: characterization of its degradation products.

    PubMed

    Erika, Del Grosso; Silvio, Aprile; Giorgio, Grosa

    2012-03-05

    Thiocolchicoside (TCC, N-[1,2-dimethoxy-10-methylsulphanyl-9-oxo-3-(3,4,5-trihydroxy-6-hydroxymethyl-tetrahydropyran-2-yloxy)-5,6,7,9-tetrahydro-benzo[a]heptalen-7-yl]-acetamide) was subjected to hydrolytic, oxidative, and photolytic stresses. TCC underwent degradation in acidic, basic, and oxidative conditions, while it was stable toward other stress conditions. The degradation products (DPs) were detected and their separation was achieved on a SGE Wakosil C18RS 5μm (250*4.6 mm; SGE) column employing a gradient LC-MS method for a total time of analysis of 18 min. The mass fragmentation pathways of both thiocolchicoside and its degradation products were established using LC-MS experiments assigning the structures to the DPs. In particular, five DPs were identified as: D1SO (N-[1,2-dimethoxy-10-methylsulphoxide-9-oxo-3-(3,4,5-trihydroxy-6-hydroxymethyl-tetrahydropyran-2-yloxy)-5,6,7,9-tetrahydro-benzo[a]heptalen-7-yl]-acetamide), D1SO(2) (N-[1,2-dimethoxy-10-methylsulphone-9-oxo-3-(3,4,5-trihydroxy-6-hydroxymethyl-tetrahydropyran-2-yloxy)-5,6,7,9-tetrahydro-benzo[a]heptalen-7-yl]-acetamide), D2 ([1,2-dimethoxy-10-methylsulphanyl-9-oxo-3-(3,4,5-trihydroxy-6-hydroxymethyl-tetrahydropyran-2-yloxy)-5,6,7,9-tetrahydro-benzo[a]heptalen-7-yl]-amine), D3 (N-[1,2-dimethoxy-3-hydroxy-10-methylsulphanyl-9-oxo-5,6,7,9-tetrahydro-benzo[a]heptalen-7-yl]-acetamide or 3-O-demethylthiocolchicine), D4 ([1,2-dimethoxy-3-hydroxy-10-methylsulphanyl-9-oxo-5,6,7,9-tetrahydro-benzo[a]heptalen-7-yl]-amine or N-deacetyl-3-O-demethylthiocochicine). Moreover, the structures of DPs were confirmed by synthesis of the reference standards which were fully characterized by MS, NMR, IR analyses. Finally a comprehensive degradation scheme of TCC was proposed allowing to outline D1SO and D3 as the indicators of its stability for oxidative and hydrolytic stress conditions.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Serological studies on chloridazon-degrading bacteria.

    PubMed

    Layh, G; Böhm, R; Eberspächer, J; Lingens, F

    1983-01-01

    Agglutination tests and immunofluorescence tests with antisera against four strains of chloridazon-degrading bacteria revealed the serological uniformity of a group of 22 chloridazon-degrading bacterial strains. No serological relationship could be found between chloridazon-degrading bacteria and representatives of other Gram-negative bacteria. This was demonstrated by agglutination tests, including testing of the antiserum against Acinetobacter calcoaceticus, and by immunofluorescence tests, including testing of the sera against Pseudomonas and Acinetobacter strains. The tests were performed with 31 representatives of different Gram-negative bacteria, and with 22 strains of chloridazon-degrading bacteria as antigens. Differences in the extent of agglutination reactions and antibody titres among chloridazon-degrading bacterial strains together with cross-adsorption xperiments, suggest a rough classification of chloridazon-degrading bacteria into two subgroups. On the basis of immunofluorescence data, a linkage-map was worked out to represent serological relationships in the group of chloridazon-degrading strains.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Accelerated azo dye degradation and concurrent hydrogen production in the single-chamber photocatalytic microbial electrolysis cell.

    PubMed

    Hou, Yanping; Zhang, Renduo; Yu, Zebin; Huang, Lirong; Liu, Yuxin; Zhou, Zili

    2017-01-01

    The single-chamber microbial electrolysis cell constructed with a TiO2-coated photocathode, termed photocatalytic microbial electrolysis cell (PMEC), was developed to accelerate methyl orange (MO) degradation and concurrent hydrogen (H2) recovery under UV irradiation. Results showed that faster MO decolorization rates were achieved from the PMEC compared with those without UV irradiation or with open circuit. With increase of MO concentrations (acetate as co-substrate) from 50 to 300mg/L at an applied voltage of 0.8V, decolorization efficiencies decreased from 98% to 76% within 12h, and cyclic H2 production declined from 113 to 68mL. As the possible mechanism of MO degradation, bioelectrochemical reduction, co-metabolism reduction, and photocatalysis were involved; and degradation intermediates (mainly sulfanilic acid and N,N-dimethylaniline) were further degraded by OH generated from photocatalysis. This makes MO mineralization be possible in the single-chamber PMEC. Hence, the PMEC is a promising system for dyeing wastewater treatment and simultaneous H2 production.

  18. Ion source studies for particle beam accelerators

    SciTech Connect

    Bieg, K.W.; Burns, E.J.T.; Olsen, J.N.; Dorrell, L.R.

    1985-05-01

    High power particle beam accelerators are being developed for use in inertial confinement fusion applications. These pulsed power accelerators require sources of low atomic number ions (e.g., protons, deuterons, carbon, or lithium). The sources must be of high purity for efficient accelerator operation and proper target coupling, must have a rapid ''turn-on,'' and must be compatible with ion diode configurations under development. A particular type of source presently being investigated is the flashover ion source which generates ions by means of the vacuum flashover of an insulating anode material when the high voltage pulse arrives at the diode. We have developed an applied-magnetic-field, extraction ion diode for the 0.03 TW Nereus accelerator specifically to investigate these sources. Extracted ion species are measured by means of a Thomson-parabola ion analyzer, dB/dt current monitors, and Faraday cups. Experiments have been performed to investigate the surface flashover mechanism and the effects of various dielectric source materials, anode preparation methods (including rf glow discharge cleaning), and vacuum conditions on ion species and diode operation.

  19. Systemic response to thermal injury in rats. Accelerated protein degradation and altered glucose utilization in muscle.

    PubMed Central

    Clark, A S; Kelly, R A; Mitch, W E

    1984-01-01

    Negative nitrogen balance and increased oxygen consumption after thermal injury in humans and experimental animals is related to the extent of the burn. To determine whether defective muscle metabolism is restricted to the region of injury, we studied protein and glucose metabolism in forelimb muscles of rats 48 h after a scalding injury of their hindquarters. This injury increased muscle protein degradation (PD) from 140 +/- 5 to 225 +/- 5 nmol tyrosine/g per h, but did not alter protein synthesis. Muscle lactate release was increased greater than 70%, even though plasma catecholamines and muscle cyclic AMP were not increased. Insulin dose-response studies revealed that the burn decreased the responsiveness of muscle glycogen synthesis to insulin but did not alter its sensitivity to insulin. Rates of net glycolysis and glucose oxidation were increased and substrate cycling of fructose-6-phosphate was decreased at all levels of insulin. The burn-induced increase in protein and glucose catabolism was not mediated by adrenal hormones, since they persisted despite adrenalectomy. Muscle PGE2 production was not increased by the burn and inhibition of prostaglandin synthesis by indomethacin did not inhibit proteolysis. The increase in PD required lysosomal proteolysis, since inhibition of cathepsin B with EP475 reduced PD. Insulin reduced PD 20% and the effects of EP475 and insulin were additive, reducing PD 41%. An inhibitor of muscle PD, alpha-ketoisocaproate, reduced burn-induced proteolysis 28% and lactate release 56%. The rate of PD in muscle of burned and unburned rats was correlated with the percentage of glucose uptake that was directed into lactate production (r = +0.82, P less than 0.01). Thus, a major thermal injury causes hypercatabolism of protein and glucose in muscle that is distant from the injury, and these responses may be linked to a single metabolic defect. PMID:6470144

  20. 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.

  1. 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

  2. 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.

  3. Detector design studies for Turkish Accelerator Center

    NASA Astrophysics Data System (ADS)

    Aksu, Burçin; Piliçer, Ercan

    2017-02-01

    The proposed Particle Factory detector at Turkish Accelerator Center (TAC-PF) aims to search for charm physics, CP violation and mixing of D0 mesons as well as new physics effects by investigating head-on collisions of 1 GeV electron from Energy Recovery Linac (ERL) with 3.56 GeV positrons from synchrotron storage ring. In this work, we constructed the TAC-PF detector design by using a recently developed framework namely Detector Description for High Energy Physics (DD4hep). The baseline TAC-PF detector design and its qualifications were summarized, followed by a general description.

  4. 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.

  5. 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.

  6. Study on the degradation of chitosan slurries

    NASA Astrophysics Data System (ADS)

    Martini, Benjamin; Dimida, Simona; De Benedetto, Egidio; Madaghiele, Marta; Demitri, Christian

    In the present work, we measured the degradation rate of different chitosan slurries. Several parameters were monitored such as temperature (25 °C, 37 °C, 50 °C); chitosan concentration (1% and 2% (w/V)); and polymer molecular weight. The samples were tested in dynamic sweep test mode. This test is able to provide a reliable estimation of viscosity variations of the slurries; in turn, these variations could be related to degradation rate of the system in the considered conditions. The resulting information is particularly important especially in applications in which there is a close relationship between physical properties and molecular structure.

  7. 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

  8. 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.

  9. 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.

  10. Degradation of ciprofloxacin in water by advanced oxidation process: kinetics study, influencing parameters and degradation pathways.

    PubMed

    Sayed, Murtaza; Ismail, M; Khan, Sanaullah; Tabassum, Safia; Khan, Hasan M

    2016-01-01

    Gamma-radiation-induced degradation of ciprofloxacin (CIP) in aqueous solution and the factors affecting the degradation process have been investigated. The results showed that CIP (4.6 mg/L) was almost completely degraded at an absorbed dose of 870 Gy. The kinetic studies of aqueous solutions containing 4.6, 10, 15 and 17.9 mg/L indicated that the decomposition of CIP by gamma irradiation followed pseudo-first-order kinetics and the decay constant (k) decreased from 5.9  ×  10(-3) to 1.6  ×  10(-3) Gy(-1) with an increase in CIP initial concentration from 4.6 to 17.9 mg/L. The effect of saturation of CIP solution with N2, N2O or air on radiation-induced degradation of CIP was also investigated. The effects of radical scavengers, such as t-BuOH and i-PrOH, showed the role of reactive radicals towards degradation of CIP in the order of OH > e(aq)- . H. The apparent second-order rate constant of [Formula: see text] with CIP was calculated to be 2.64 × 10(9) M(-1) s(-1). The effects of solution pH as well as natural water contaminants, such as [HCO3-, CO3(2-), and NO2-, on CIP degradation by gamma-irradiation were also investigated. Major degradation products, including organic acids, were identified using UPLC-MS/MS and IC, and degradation pathways have been proposed.

  11. 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.

  12. 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.

  13. 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%.

  14. 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.

  15. 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

  16. 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

    2016-08-18

    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.

  17. 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.

  18. 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.

  19. Experimental study of a Hall current plasma accelerator

    NASA Astrophysics Data System (ADS)

    Li, Zhongmin

    Electromagnetic propulsion holds the promise of potential prime space propulsion by combining high exhaust velocities with high mass flow rates compared to other electric propulsion devices. The primary objective of this study is to experimentally investigate the plasma acceleration due to Hall effect in the presence of applied magnetic and electric fields. This is the first attempt to integrate a non-equilibrium microwave plasma with a Hall current plasma accelerator. A linear Hall current plasma accelerator segmented with 5 pairs of electrodes was developed and tested. A non-equilibrium microwave plasma generated by a 6 kW microwave generator was used to feed the accelerator. The discharge voltage, current, and the Hall current through each pair of the electrodes were measured. Velocity measurement techniques including the MHD open-circuit, the combined emissive probe and MHD open-circuit, and the time-of-flight electrostatic probe were developed and implemented. The near field plasma properties were also measured by multiple Langmuir probes. Theoretical analyses were conducted using both electromagnetic and electrostatic models. Both models predicted that large axial electric field and ionization fraction are critical to obtaining high specific impulse and efficient acceleration. The role of the magnetic field is to trap the electrons, and thus distribute the electric field across the whole plasma for acceleration of ions. The experimental results show that axial discharge voltages increased with increasing magnetic field. A strong plasma acceleration zone was noted at the region closest to the cathode. Within this zone, the Hall current and Hall parameter are much larger than elsewhere along the flow path. So is the axial electric field. This suggested a very strong Hall effect in the accelerator. The mean Hall parameters varied from less than one to the order of 10 in the high power tests. Significant acceleration of the plasma by the linear Hall current

  20. 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.

  1. Numerical Studies of Ablative Mass Loss from Wind Accelerated Clouds.

    NASA Astrophysics Data System (ADS)

    Knerr, Jeffrey Matthew

    1993-01-01

    We have used numerical hydrodynamics to study the acceleration of dense gas clouds via wind ram pressure. Our goal has been to examine a model for the explanation of broad absorption lines (BALs) seen in the spectra of a certain fraction of observed QSOs. This model postulates cool dense clouds moving at very high speeds as the source of the BALs. Furthermore, it invokes simple wind ram pressure as the acceleration mechanism for the clouds. A crucial question is whether the clouds can survive potentially disruptive fluid instabilities, allowing time for acceleration to speeds comparable to the wind velocity. Linear stability arguments imply Rayleigh-Taylor (RT) instability growth occurs on time scales much shorter than the acceleration time scale. These arguments conclude acceleration via ram pressure cannot produce bulk cloud velocities in excess of the cloud's internal sound speed. Our simulations show this is simply not true. We present two-dimensional slab-symmetric simulations where clouds are accelerated to speeds close to an order of magnitude greater than their internal sound speed. Ablative mass loss by the flow of shocked wind gas around the periphery of the clouds acts to limit the growth of potentially disruptive instabilities. Simulations run at different computational grid resolutions clearly show the stabilizing effect ablation has on the evolution of the clouds. Simplified models for line profiles have been developed using mass-velocity histograms generated from the numerical simulations. There is good qualitative agreement between the simulated line profiles and observed BAL profiles.

  2. Stable Isotope Probing Approaches to Study Anaerobic Hydrocarbon Degradation and Degraders.

    PubMed

    Vogt, Carsten; Lueders, Tillmann; Richnow, Hans H; Krüger, Martin; von Bergen, Martin; Seifert, Jana

    2016-01-01

    Stable isotope probing (SIP) techniques have become state-of-the-art in microbial ecology over the last 10 years, allowing for the targeted detection and identification of organisms, metabolic pathways and elemental fluxes active in specific processes within complex microbial communities. For studying anaerobic hydrocarbon-degrading microbial communities, four stable isotope techniques have been used so far: DNA/RNA-SIP, PLFA (phospholipid-derived fatty acids)-SIP, protein-SIP, and single-cell-SIP by nanoSIMS (nanoscale secondary ion mass spectrometry) or confocal Raman microscopy. DNA/RNA-SIP techniques are most frequently applied due to their most meaningful phylogenetic resolution. Especially using 13C-labeled benzene and toluene as model substrates, many new hydrocarbon degraders have been identified by SIP under various electron acceptor conditions. This has extended the current perspective of the true diversity of anaerobic hydrocarbon degraders relevant in the environment. Syntrophic hydrocarbon degradation was found to be a common mechanism for various electron acceptors. Fundamental concepts and recent advances in SIP are reflected here. A discussion is presented concerning how these techniques generate direct insights into intrinsic hydrocarbon degrader populations in environmental systems and how useful they are for more integrated approaches in the monitoring of contaminated sites and for bioremediation.

  3. 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

  4. Organic chemical degradation by remote study of the redox conditions

    NASA Astrophysics Data System (ADS)

    Fernandez, P. M.; Revil, A.; Binley, A. M.; Bloem, E.; French, H. K.

    2014-12-01

    Monitoring the natural (and enhanced) degradation of organic contaminants is essential for managing groundwater quality in many parts of the world. Contaminated sites often have limited access, hence non-intrusive methods for studying redox processes, which drive the degradation of organic compounds, are required. One example is the degradation of de-icing chemicals (glycols and organic salts) released to the soil near airport runways during winter. This issue has been broadly studied at Oslo airport, Gardermoen, Norway using intrusive and non-intrusive methods. Here, we report on laboratory experiments that aim to study the potential of using a self-potential, DCresistivity, and time-domain induced polarization for geochemical characterization of the degradation of Propylene Glycol (PG). PG is completely miscible in water, does not adsorb to soil particles and does not contribute to the electrical conductivity of the soil water. When the contaminant is in the unsaturated zone near the water table, the oxygen is quickly consumed and the gas exchange with the surface is insufficient to ensure aerobic degradation, which is faster than anaerobic degradation. Since biodegradation of PG is highly oxygen demanding, anaerobic pockets can exist causing iron and manganese reduction. It is hypothesised that nitrate would boost the degradation rate under such conditions. In our experiment, we study PG degradation in a sand tank. We provide the system with an electron highway to bridge zones with different redox potential. This geo-battery system is characterized by self-potential, resistivity and induced polarization anomalies. An example of preliminary results with self-potential at two different times of the experiment can be seen in the illustration. These will be supplemented with more direct information on the redox chemistry: in-situ water sampling, pH, redox potential and electrical conductivity measurements. In parallel, a series of batch experiments have been

  5. 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...

  6. The World of Wonder Accelerated Learning Community: A Case Study.

    ERIC Educational Resources Information Center

    Biddle, Julie K.

    This report presents a case study of the World of Wonders Accelerated Learning Community School (WOW). A community school in Ohio is a new kind of public school-an independent public school that is nonsectarian and nondiscriminatory. The report presents three contexts for the study--historical, local and methodological--and highlights some of the…

  7. Field quality study in Nb(3)Sn accelerator magnets

    SciTech Connect

    Kashikhin, V.V.; Ambrosio, G.; Andreev, N.; Barzi, E.; Bossert, R.; DiMarco, J.; Kashikhin, V.S.; Lamm, M.; Novitski, I.; Schlabach, P.; Velev, G.; Yamada, R.; Zlobin, A.V.; /Fermilab

    2005-05-01

    Four nearly identical Nb{sub 3}Sn dipole models of the same design were built and tested at Fermilab. It provided a unique opportunity of systematic study the field quality effects in Nb{sub 3}Sn accelerator magnets. The results of these studies are reported in the paper.

  8. 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.

  9. A study of ablation effects for an axisymmetric electromagnetic accelerator

    SciTech Connect

    Ikuta, K. . Inst. of Plasma Physics)

    1989-01-01

    In order to give the additional forward thrust to the projectile other than the electromagnetic force, the axial symmetric launcher called ablation mass driver (AMD) has been proposed using sequential z pinches in a cylindrical electrode array. The additional driving force originates from the reaction of ablating hot gas from the ablator on the rear of the projectile, since the Joule heating by the high electric current for electromagnetic acceleration is not negligiblly small. The ablated gas becomes plasma which propagates along the field-null line of z pinch, giving the forward thrust to the projectile. A proto type AMD has been built at Texas Tech University in order to see the capabilities of AMD as a launcher, although a study on the effect of ablation will remain as a future work. This paper describes a device of accelerating water blob for the study of ablation effect during acceleration together with the experimental results.

  10. 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.

  11. Diagnostics for studies of novel laser ion acceleration mechanisms

    NASA Astrophysics Data System (ADS)

    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.

  12. 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.

  13. Studies of polarized beam acceleration and Siberian Snakes

    SciTech Connect

    Lee, S.Y.

    1992-12-31

    We studied depolarization mechanisms of polarized proton acceleration in high energy accelerators with snakes and found that the perturbed spin tune due to the imperfection resonance plays an important role in beam depolarization at snake resonances. We also found that even order snake resonances exist in the overlapping intrinsic and imperfection resonances. Due to the perturbed spin tune of imperfection resonances, each snake resonance splits into two. Thus the available betatron tune space becomes smaller. Some constraints on polarized beam colliders were also examined.

  14. A Study of Polarized Proton Acceleration in J-PARC

    SciTech Connect

    Luccio, A. U.; Bai, M.; Roser, T.; Molodojentsev, A.; Ohmori, C.; Sato, H.; Hatanaka, K.

    2007-06-13

    We have studied the feasibility of polarized proton acceleration in rhe J-PARC accelerator facility, consisting of a 400 MeV linac, a 3 GeV rapid cycling synchrotron (RCS) and a 50 GeV synchrotron (MR). We show how the polarization of the beam can be preserved using an rf dipole in the RCS and two superconductve partial helical Siberian snakes in the MR. The lattice of the MR will be modified with the addition of quadrupoles to compensate for the focusing properties of the snakes.

  15. A STUDY OF POLARIZED PROTON ACCELERATION IN J-PARC.

    SciTech Connect

    LUCCIO, A.U.; BAI, M.; ROSER, T.

    2006-10-02

    We have studied the feasibility of polarized proton acceleration in rhe J-PARC accelerator facility, consisting of a 400 MeV linac, a 3 GeV rapid cycling synchrotron (RCS) and a 50 GeV synchrotron (MR). We show how the polarization of the beam can be preserved using an rf dipole in the RCS and two superconductive partial helical Siberian snakes in the MR. The lattice of the MR will be modified with the addition of quadrupoles to compensate for the focusing properties of the snakes.

  16. Studying astrophysical particle acceleration with laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Fiuza, Frederico

    2016-10-01

    The acceleration of non-thermal particles in plasmas is critical for our understanding of explosive astrophysical phenomena, from solar flares to gamma ray bursts. Particle acceleration is thought to be mediated by collisionless shocks and magnetic reconnection. The microphysics underlying these processes and their ability to efficiently convert flow and magnetic energy into non-thermal particles, however, is not yet fully understood. By performing for the first time ab initio 3D particle-in-cell simulations of the interaction of both magnetized and unmagnetized laser-driven plasmas, it is now possible to identify the optimal parameters for the study of particle acceleration in the laboratory relevant to astrophysical scenarios. It is predicted for the Omega and NIF laser conditions that significant non-thermal acceleration can occur during magnetic reconnection of laser-driven magnetized plasmas. Electrons are accelerated by the electric field near the X-points and trapped in contracting magnetic islands. This leads to a power-law tail extending to nearly a hundred times the thermal energy of the plasma and that contains a large fraction of the magnetic energy. The study of unmagnetized interpenetrating plasmas also reveals the possibility of forming collisionless shocks mediated by the Weibel instability on NIF. Under such conditions, both electrons and ions can be energized by scattering out of the Weibel-mediated turbulence. This also leads to power-law spectra that can be detected experimentally. The resulting experimental requirements to probe the microphysics of plasma particle acceleration will be discussed, paving the way for the first experiments of these important processes in the laboratory. As a result of these simulations and theoretical analysis, there are new experiments being planned on the Omega, NIF, and LCLS laser facilities to test these theoretical predictions. This work was supported by the SLAC LDRD program and DOE Office of Science, Fusion

  17. Studies on the sonic degradation of deoxyribonucleic acid.

    PubMed

    FREIFELDER, D; DAVISON, P F

    1962-05-01

    T7 DNA was partially degraded by x-rays, DNAase, and sonic irradiation. The molecular weight distributions were calculated from sedimentation velocity studies on the resulting preparations. Comparison with the theoretical curve derived by Montroll and Simha showed that the first two degradative methods act grossly at random, whereas sonication is a non-random process resulting in the preferential halving of the DNA molecules in solution.

  18. Studies on the Sonic Degradation of Deoxyribonucleic Acid

    PubMed Central

    Freifelder, David; Davison, Peter F.

    1962-01-01

    T7 DNA was partially degraded by x-rays, DNAase, and sonic irradiation. The molecular weight distributions were calculated from sedimentation velocity studies on the resulting preparations. Comparison with the theoretical curve derived by Montroll and Simha showed that the first two degradative methods act grossly at random, whereas sonication is a non-random process resulting in the preferential halving of the DNA molecules in solution. PMID:13894963

  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. 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.

  1. 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.

  2. 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.

  3. 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

    2016-04-08

    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.

  4. Degradation studies of nitride-based low-e films

    NASA Astrophysics Data System (ADS)

    Andersson, Kent E.; Wahlstrom, M. K.; Roos, Arne; Ribbing, Carl-Gustaf

    1992-11-01

    Triple layer structures of TiO2/TiN/TiO2 and quadruple layer structures of TiO2/Al/TiN/TiO2 have been sputtered on glass substrates at temperatures ranging from room temperature to 300 degree(s)C. The reflectance and transmittance were measured in the visible and the near infrared wavelength regions. Accelerated degradation tests with respect to high temperature and acid exposure have been performed with these laboratory samples of low-e coatings and the degradation has been compared with that of commercial silver based window coatings. As expected the durability of the nitride based coatings is far superior to the stability of those based on noble metals. Furthermore, the nitride coatings with an aluminum sacrificial layer have been found to resist aging at elevated temperatures (as high as 350 - 400 degree(s)C) far better than similar coatings without the aluminum. It has also been shown that the aluminum layer protects the nitride film during deposition of the top oxide layer. The effects of high temperature annealing have been modeled with optical multilayer calculations. Comparison of two degradation mechanisms demonstrates that the silver layers fail by agglomeration while the nitride suffers successive oxidation. This explains the effectiveness of the aluminum layer which forms a dense oxide during the initial stages of TiO2- deposition.

  5. Cluster Multi-Point Studies of the Auroral Acceleration Region

    NASA Astrophysics Data System (ADS)

    Marklund, G. T.

    2014-12-01

    Multi-point studies of the auroral acceleration region (AAR) by the Cluster spacecraft has enabled a number of open issues on the auroral acceleration to be addressed and revealed. Data from AAR crossings of Inverted-V aurora, by the C1 and C3 spacecraft at different altitudes, enabled a detailed reconstruction of the acceleration potential and a verification of its stability on a five min time scale. The relative role of quasi-static and Alfvénic acceleration behind aurora are addressed in two event studies. In one of these, the two processes are shown to operate jointly on the plasma population within the polar cap boundary. In the other, the electron energy flux producing multiple arcs within a surge is found to be generally dominated by the quasi-static contribution. Acceleration features and the FAC closure associated with surge-horn aurora crossed by the Cluster fleet were derived in another event study. A study of the density distribution within the auroral cavity, showed for all included events, exponential density decreases, relative to the ambient densities, from the mid to top of the AAR. In another study, cavities were found to extend well beyond the top of the AAR. Finally, statistical high-latitude electric field and plasma density distributions are presented based on 10 years of Cluster data collected between 2 and 4 RE altitudes. Intense electric fields appear in two altitude regimes on the nightside, separated by a gap at 2.8 RE. The upper altitude fields were interpreted to be Alfvénic and the lower altitude fields quasi-static, related to the AAR. The gap in the electric field intensity indicates a partial closure of the potentials in the lower region, with similarities to model results of reflected Alfvén waves and earlier reported observations

  6. 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.

  7. 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.

  8. Study of Cu ions acceleration via UV laser ablation

    NASA Astrophysics Data System (ADS)

    Belloni, F.; Doria, D.; Lorusso, A.; Nassisi, Vincenzo; Torrisi, Lorenzo

    2005-03-01

    In this work an ion acceleration system based on a laser ion source was studied. It was able to generate ion beams utilizing as a source a laser plasma produced by a XeCl laser from a copper target. The focused laser beam provided a power density on the target surface of about 3.5x108 W/cm2. Laser wavelength and pulse duration were 308 nm and 20 ns, respectively. The experimental apparatus consisted substantially of a plasma generation chamber, a drift tube and an expansion chamber mounted on the target stem inside the generation chamber. The expansion chamber end formed the acceleration gap together with a grounded bored electrode, placed in front of it at a distance of 1.3 cm. A Faraday cup placed at the end of the drift tube was used to reveal the ion intensity. Many attempts were done in order to accelerate plasma ions without the expansion chamber, but arcs were present. The maximum accelerating voltage applied to the extraction gap was 18 kV, resulting in an ion bunch of about 4.2 nC and a peak current of 220 μA.

  9. Degradation study on optical materials for concentrator photovoltaics

    NASA Astrophysics Data System (ADS)

    Eltermann, Fabian; Roeder, Kerstin; Wiesenfarth, Maike; Wilde, Juergen; Bett, Andreas W.

    2012-10-01

    In this work the impact of accelerated aging on the spectral transmission and the mechanical robustness of silicone elastomers for concentrator photovoltaic applications was investigated. Therefore, specific test samples were manufactured. The samples were annealed at 150 °C to assure a complete cross-linking. These samples were exposed to humidity freeze, to a pressure cooker test, and to UV light. To investigate optical materials under UVA intensity up to 10 W/cm2 a test setup was developed. Thus, a UV dosage of 10000 kWh/m2 was applied to the silicone samples after thermal treatment. The mean transmission was used as a measure to identify changes in the spectral behavior and was, therefore, compared after the stress tests with the initial value. No total failures but rather degradation was observed, mainly in the range of ultraviolet and visible light. In addition, the shear strengths for the silicone elastomers were compared before and after stress.

  10. Degradation studies of Martian impact craters

    NASA Technical Reports Server (NTRS)

    Barlow, N. G.

    1991-01-01

    The amount of obliteration suffered by Martian impact craters is quantified by comparing measurable attributes of the current crater shape to those values expected for a fresh crater of identical size. Crater diameters are measured from profiles obtained using photoclinometry across the structure. The relationship between the diameter of a fresh crater and a crater depth, floor width, rim height, central peak height, etc. was determined by empirical studies performed on fresh Martian impact craters. We utilized the changes in crater depth and rim height to judge the degree of obliteration suffered by Martian impact craters.

  11. 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.

  12. Establishment of an equivalence acceptance criterion for accelerated stability studies.

    PubMed

    Burdick, Richard K; Sidor, Leslie

    2013-01-01

    In this article, the use of statistical equivalence testing for providing evidence of process comparability in an accelerated stability study is advocated over the use of a test of differences. The objective of such a study is to demonstrate comparability by showing that the stability profiles under nonrecommended storage conditions of two processes are equivalent. Because it is difficult at accelerated conditions to find a direct link to product specifications, and hence product safety and efficacy, an equivalence acceptance criterion is proposed that is based on the statistical concept of effect size. As with all statistical tests of equivalence, it is important to collect input from appropriate subject-matter experts when defining the acceptance criterion.

  13. 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.

  14. 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.

  15. Mechanical Stability Study for Integrable Optics Test Accelerator at Fermilab

    SciTech Connect

    McGee, Mike; Andrews, Richard; Carlson, Kermit; Leibfritz, Jerry; Nobrega, Lucy; Valishev, Alexander

    2016-07-01

    The Integrable Optics Test Accelerator (IOTA) is proposed for operation at Fermilab. The goal of IOTA is to create practical nonlinear accelerator focusing systems with a large frequency spread and stable particle motion. The IOTA is a 40 m circumference, 150 MeV (e-), 2.5 MeV (p⁺) diagnostic test ring. A heavy low frequency steel floor girder is proposed as the primary tier for IOTA device component support. Two design lengths; (8) 4 m and (2) 2.8 m long girders with identical cross section completely encompass the ring. This study focuses on the 4 m length girder and the development of a working prototype. Hydrostatic Level Sensor (HLS), temperature, metrology and fast motion measurements characterize the anticipated mechanical stability of the IOTA ring.

  16. 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.

  17. Degradation of diclofenac by advanced oxidation and reduction processes: kinetic studies, degradation pathways and toxicity assessments.

    PubMed

    Yu, Hui; Nie, Er; Xu, Jun; Yan, Shuwen; Cooper, William J; Song, Weihua

    2013-04-01

    Many pharmaceutical compounds and metabolites are found in surface and ground waters suggesting their ineffective removal by conventional wastewater treatment technologies. Advanced oxidation/reduction processes (AO/RPs), which utilize free radical reactions to directly degrade chemical contaminants, are alternatives to traditional water treatment. This study reports the absolute rate constants for reaction of diclofenac sodium and model compound (2, 6-dichloraniline) with the two major AO/RP radicals: the hydroxyl radical (•OH) and hydrated electron (e(aq)(-)). The bimolecular reaction rate constants (M(-1) s(-1)) for diclofenac for •OH was (9.29 ± 0.11) × 10(9), and for e(-)(aq) was (1.53 ± 0.03) ×10(9). To provide a better understanding of the decomposition of the intermediate radicals produced by hydroxyl radical reactions, transient absorption spectra are observed from 1 - 250 μs. In addition, preliminary degradation mechanisms and major products were elucidated using (60)Co γ-irradiation and LC-MS. The toxicity of products was evaluated using luminescent bacteria. These data are required for both evaluating the potential use of AO/RPs for the destruction of these compounds and for studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime.

  18. 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.

  19. Functional and RNA-Sequencing Analysis Revealed Expression of a Novel Stay-Green Gene from Zoysia japonica (ZjSGR) Caused Chlorophyll Degradation and Accelerated Senescence in Arabidopsis

    PubMed Central

    Teng, Ke; Chang, Zhihui; Li, Xiao; Sun, Xinbo; Liang, Xiaohong; Xu, Lixin; Chao, Yuehui; Han, Liebao

    2016-01-01

    Senescence is not only an important developmental process, but also a responsive regulation to abiotic and biotic stress for plants. Stay-green protein plays crucial roles in plant senescence and chlorophyll degradation. However, the underlying mechanisms were not well-studied, particularly in non-model plants. In this study, a novel stay-green gene, ZjSGR, was isolated from Zoysia japonica. Subcellular localization result demonstrated that ZjSGR was localized in the chloroplasts. Quantitative real-time PCR results together with promoter activity determination using transgenic Arabidopsis confirmed that ZjSGR could be induced by darkness, ABA and MeJA. Its expression levels could also be up-regulated by natural senescence, but suppressed by SA treatments. Overexpression of ZjSGR in Arabidopsis resulted in a rapid yellowing phenotype; complementary experiments proved that ZjSGR was a functional homolog of AtNYE1 from Arabidopsis thaliana. Over expression of ZjSGR accelerated chlorophyll degradation and impaired photosynthesis in Arabidopsis. Transmission electron microscopy observation revealed that overexpression of ZjSGR decomposed the chloroplasts structure. RNA sequencing analysis showed that ZjSGR could play multiple roles in senescence and chlorophyll degradation by regulating hormone signal transduction and the expression of a large number of senescence and environmental stress related genes. Our study provides a better understanding of the roles of SGRs, and new insight into the senescence and chlorophyll degradation mechanisms in plants. PMID:28018416

  20. 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

  1. Methanogenic Hydrocarbon Degradation: Evidence from Field and Laboratory Studies.

    PubMed

    Jiménez, Núria; Richnow, Hans H; Vogt, Carsten; Treude, Tina; Krüger, Martin

    2016-01-01

    Microbial transformation of hydrocarbons to methane is an environmentally relevant process taking place in a wide variety of electron acceptor-depleted habitats, from oil reservoirs and coal deposits to contaminated groundwater and deep sediments. Methanogenic hydrocarbon degradation is considered to be a major process in reservoir degradation and one of the main processes responsible for the formation of heavy oil deposits and oil sands. In the absence of external electron acceptors such as oxygen, nitrate, sulfate or Fe(III), fermentation and methanogenesis become the dominant microbial metabolisms. The major end product under these conditions is methane, and the only electron acceptor necessary to sustain the intermediate steps in this process is CO2, which is itself a net product of the overall reaction. We are summarizing the state of the art and recent advances in methanogenic hydrocarbon degradation research. Both the key microbial groups involved as well as metabolic pathways are described, and we discuss the novel insights into methanogenic hydrocarbon-degrading populations studied in laboratory as well as environmental systems enabled by novel cultivation-based and molecular approaches. Their possible implications on energy resources, bioremediation of contaminated sites, deep-biosphere research, and consequences for atmospheric composition and ultimately climate change are also addressed.

  2. Free-radical-induced oxidative and reductive degradation of fibrate pharmaceuticals: kinetic studies and degradation mechanisms.

    PubMed

    Razavi, Behnaz; Song, Weihua; Cooper, William J; Greaves, John; Jeong, Joonseon

    2009-02-19

    The presence of pharmaceutically active compounds (PhACs) in aquatic systems is an emerging environmental issue and poses a potential threat to ecosystems and human health. Unfortunately, current water treatment techniques do not efficiently remove all of the PhACs, which results in the occurrence of such compounds in surface and ground waters. Advanced oxidation/reduction processes (AO/RPs) which utilize free radical reactions to directly degrade chemical contaminants are alternatives to traditional water treatment methods. This study reports the absolute bimolecular reaction rate constants for three pharmaceutical compounds (fibrates), clofibric acid, bezafibrate, and gemfibrozil, with the hydroxyl radical (*OH) and hydrated electron (e(-)(aq)). The bimolecular reaction rate constants for *OH were (6.98 +/- 0.12) x 10(9), (8.00 +/- 0.22) x 10(9), and (10.0 +/- 0.6) x 10(9), and for e(-)(aq) were (6.59 +/- 0.43) x 10(8), (112 +/- 3) x 10(8), and (6.26 +/- 0.58) x 10(8), for clofibric acid, bezafibrate, and gemfibrozil, respectively. Transient spectra were obtained for the intermediate radicals produced by the hydroxyl radical reactions. In addition, preliminary degradation mechanisms and major products were elucidated using (137)Cs gamma-irradiation and LC-MS. These data are required for evaluating the potential use of AO/RPs for the destruction of these compounds in treating water for various purposes.

  3. Detector-accelerator interface studies at the Tevatron

    SciTech Connect

    Drozhdin, A.I.; Mokhov, N.V.

    1998-04-10

    A summary of studies is presented towards minimization of beam loss in the critical locations at the Fermilab Tevatron to reduce background rates in the collider detectors and to protect machine components. Based on detailed Monte-Carlo simulations, measures have been proposed and incorporated in the machine to reduce accelerator-related instantaneous and residual background levels in the D0 and CDF detectors. Measurements performed are in good agreement with the predictions. Most recent results on acceptance and background rates in the D0 and CDF forward detectors are presented and discussed in detail.

  4. Monte Carlo study of neutrino acceleration in supernova shocks

    NASA Technical Reports Server (NTRS)

    Kazanas, D.; Ellison, D. C.

    1981-01-01

    The first order Fermi acceleration mechanism of cosmic rays in shocks may be at work for neutrinos in supernova shocks when the latter are at densities greater than 10 to the 13th g/cu cm, at which the core material is opaque to neutrinos. A Monte Carlo approach to study this effect is employed, and the emerging neutrino power law spectra are presented. The increased energy acquired by the neutrinos may facilitate their detection in supernova explosions and provide information about the physics of collapse.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Electromagnetic induction of nanoscale zerovalent iron particles accelerates the degradation of chlorinated dense non-aqueous phase liquid: Proof of concept.

    PubMed

    Phenrat, Tanapon; Kumloet, Itsaraphong

    2016-12-15

    In this study, a novel electromagnetically enhanced treatment concept is proposed for in situ remediation of a source zone of chlorinated dense non-aqueous phase liquid (DNAPL) that is slowly dissolved, causing contaminated groundwater for centuries. Here, we used polystyrene sulfonate (PSS)-modified nanoscale zerovalent iron (NZVI) particles (ferromagnetic) in combination with a low frequency (LF) (150 kHz) AC electromagnetic field (EMF) to accelerate the degradation of the DNAPLs via enhanced dissolution and reductive dechlorination. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were used in a bench-scaled evaluation. The PSS-modified NZVI successfully targeted the DNAPL/water interface, as evidenced by the Pickering emulsion formation. Dechlorination of TCE- and PCE-DNAPL was measured by quantifying the by-product formation (acetylene, ethene, and ethane). Without magnetic induction heating (MIH) by LF EMF, PSS-modified NZVI transformed TCE- and PCE-DNAPL to ethene and ethane at the rate constants of 12.19 × 10(-3) and 1.00 × 10(-3) μmol/h/m(2), respectively, following pseudo zero-order reactions. However, four MIH cycles of PSS-NZVI increased the temperature up to 87 °C and increased the rate constants of TCE-DNAPL and PCE-DNAPL up to 14.58 and 58.01 times, respectively, in comparison to the dechlorination rate without MIH. Theoretical analysis suggested that the MIH of the PSS-modified NZVI enhanced the dechlorination of TCE- and PCE-DNAPL via the combination of the enhanced thermal dissolution of DNAPL, the effect of increasing the temperature on the rate constant (the Arrhenius equation), and the accelerated NZVI corrosion. Nevertheless, the effect of the Arrhenius equation was dominant. For the first time, this proof-of-concept study reveals the potential for using polyelectrolyte-modified NZVI coupled with LF EMF as a combined remediation technique for increasing the rate and completeness of in situ chlorinated DNAPL source remediation.

  10. 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.

  11. Studying Radiation Damage in Structural Materials by Using Ion Accelerators

    NASA Astrophysics Data System (ADS)

    Hosemann, Peter

    2011-02-01

    Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.

  12. Thermal degradation of aqueous 2-aminoethylethanolamine in CO2 capture; identification of degradation products, reaction mechanisms and computational studies.

    PubMed

    Saeed, Idris Mohamed; Lee, Vannajan Sanghiran; Mazari, Shaukat Ali; Si Ali, B; Basirun, Wan Jeffrey; Asghar, Anam; Ghalib, Lubna; Jan, Badrul Mohamed

    2017-01-01

    Amine degradation is the main significant problems in amine-based post-combustion CO2 capture, causes foaming, increase in viscosity, corrosion, fouling as well as environmental issues. Therefore it is very important to develop the most efficient solvent with high thermal and chemical stability. This study investigated thermal degradation of aqueous 30% 2-aminoethylethanolamine (AEEA) using 316 stainless steel cylinders in the presence and absence of CO2 for 4 weeks. The degradation products were identified by gas chromatography mass spectrometry (GC/MS) and liquid chromatography-time-of-flight-mass spectrometry (LC-QTOF/MS). The results showed AEEA is stable in the absence of CO2, while in the presence of CO2 AEEA showed to be very unstable and numbers of degradation products were identified. 1-(2-Hydroxyethyl)-2-imidazolidinone (HEIA) was the most abundance degradation product. A possible mechanism for the thermal degradation of AEEA has been developed to explain the formation of degradation products. In addition, the reaction energy of formation of the most abundance degradation product HEIA was calculated using quantum mechanical calculation.

  13. Degradation Characterization of Aliphatic POLYESTERS—IN Vitro Study

    NASA Astrophysics Data System (ADS)

    Vieira, A. C.; Vieira, J. C.; Guedes, R. M.; Marques, A. T.

    2008-08-01

    The most popular and important biodegradable polymers are aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydoxyalkanoates (PHA's) and polyethylene oxide (PEO). However, each of these has some shortcomings which restrict its applications. Blending techniques are an extremely promising approach which can improve or tune the original properties of the polymers[1]. Aliphatic polyesters are a central class of biodegradable polymers, because hydrolytic and/or enzymatic chain cleavage of these materials leads to α-hydroxyacids, which in most cases are ultimately metabolized in human body. This is particularly useful for controlled release devices and for other biomedical applications like suture fibers and ligaments. For aliphatic polyesters, hydrolysis rates are affected by the temperature, molecular structure, and ester group density as well as by the species of enzyme used. The degree of crystallinity may be a crucial factor, since enzymes attack mainly the amorphous domains of a polymer. Four different aliphatic polyesters were characterized in terms of degradation. Sutures fibers of PGA-PCL, PGA, PLA-PCL and PDO were used in this study. Weight loss, pH, molecular weight, crystallinity and strength were measured after six stages of incubation in distilled water, physiological saline and phosphate buffer solution (PBS). Degradation rate was determined, using a first order kinetic equation for all materials in the three incubation media. A relatively wide range of mechanical properties and degradation rates were observed among the materials studied. PBS was the most aggressive environment for the majority of cases.

  14. 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.

  15. Inhibition of methyltransferases accelerates degradation of cFLIP and sensitizes B-cell lymphoma cells to TRAIL-induced apoptosis.

    PubMed

    Braun, Frank K; Mathur, Rohit; Sehgal, Lalit; Wilkie-Grantham, Rachel; Chandra, Joya; Berkova, Zuzana; Samaniego, Felipe

    2015-01-01

    Non-Hodgkin lymphomas (NHLs) are characterized by specific abnormalities that alter cell cycle regulation, DNA damage response, and apoptotic signaling. It is believed that cancer cells are particularly sensitive to cell death induced by tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL). However, many cancer cells show blocked TRAIL signaling due to up-regulated expression of anti-apoptotic factors, such as cFLIP. This hurdle to TRAIL's tumor cytotoxicity might be overcome by combining TRAIL-based therapy with drugs that reverse blockages of its apoptotic signaling. In this study, we investigated the impact of a pan-methyltransferase inhibitor (3-deazaneplanocin A, or DZNep) on TRAIL-induced apoptosis in aggressive B-cell NHLs: mantle cell, Burkitt, and diffuse large B-cell lymphomas. We characterized TRAIL apoptosis regulation and caspase activation in several NHL-derived cell lines pre-treated with DZNep. We found that DZNep increased cancer cell sensitivity to TRAIL signaling by promoting caspase-8 processing through accelerated cFLIP degradation. No change in cFLIP mRNA level indicated independence of promoter methylation alterations in methyltransferase activity induced by DZNep profoundly affected cFLIP mRNA stability and protein stability. This appears to be in part through increased levels of cFLIP-targeting microRNAs (miR-512-3p and miR-346). However, additional microRNAs and cFLIP-regulating mechanisms appear to be involved in DZNep-mediated enhanced response to extrinsic apoptotic stimuli. The capacity of DZNep to target cFLIP expression on multiple levels underscores DZNep's potential in TRAIL-based therapies for B-cell NHLs.

  16. Ballistocardiogaphic studies with acceleration and electromechanical film sensors.

    PubMed

    Alametsä, J; Värri, A; Viik, J; Hyttinen, J; Palomäki, A

    2009-11-01

    The purpose of this research is to demonstrate and compare the utilization of electromechanical film (EMFi) and two acceleration sensors, ADXL202 and MXA2500U, for ballistocardiographic (BCG) and pulse transit time (PTT) studies. We have constructed a mobile physiological measurement station including amplifiers and a data collection system to record the previously mentioned signals and an electrocardiogram signal. Various versions of the measuring systems used in BCG studies in the past are also presented and evaluated. We have showed the ability of the EMFi sensor to define the elastic properties of the cardiovascular system and to ensure the functionality of the proposed instrumentation in different physiological loading conditions, before and after exercise and sauna bath. The EMFi sensor provided a BCG signal of good quality in the study of the human heart and function of the cardiovascular system with different measurement configurations. EMFi BCG measurements provided accurate and repeatable results for the different components of the heart cycle. In multiple-channel EMFi measurements, the carotid and limb pulse signals acquired were detailed and distinctive, allowing accurate PTT measurements. Changes in blood pressure were clearly observed and easily determined with EMFi sensor strips in pulse wave velocity (PWV) measurements. In conclusion, the configuration of the constructed device provided reliable measurements of the electrocardiogram, BCG, heart sound, and carotid and ankle pulse wave signals. Attached EMFi sensor strips on the neck and limbs yield completely new applications of the EMFi sensors aside from the conventional seat and supine recordings. Higher sensitivity, ease of utilization, and minimum discomfort of the EMFi sensor compared with acceleration sensors strengthen the status of the EMFi sensor for accurate and reliable BCG and PWV measurements, providing novel evaluation of the elastic properties of the cardiovascular system.

  17. Study of Kapton Degradation under Simulated Shuttle Environment

    NASA Technical Reports Server (NTRS)

    Eck, T. G.; Hoffman, R. W.

    1985-01-01

    Weight loss and severe degradation of the surface of Kapton that occurs in low Earth orbit is studied. Atomic oxygen, the major ambient species at low Earth altitude and incident with approximately 5 eV energy in ram conditions, is the primary suspect, but a thorough study of oxygen-Kapton interactions has not yet been carried out. A low-energy ion source is used to simulate the shuttle low Earth orbit environment. This source, together with diagnostic tools including surface analysis and mass spectroscopic capability, is being used to carry out experiments from which quantum yields may be obtained.

  18. Comparative degradation study of carbon supported proton exchange membrane fuel cell electrocatalysts - The influence of the platinum to carbon ratio on the degradation rate

    NASA Astrophysics Data System (ADS)

    Speder, Jozsef; Zana, Alessandro; Spanos, Ioannis; Kirkensgaard, Jacob J. K.; Mortensen, Kell; Hanzlik, Marianne; Arenz, Matthias

    2014-09-01

    A colloidal synthesis approach is used to prepare supported proton exchange membrane fuel cell (PEMFC) catalysts with various Pt loadings - from low to extremely high ones. The catalyst samples are used to continue our investigation of the role of the Pt:C ratio in the degradation processes. The influence of the platinum loading on the electrochemical surface area (ECSA) loss is evaluated in a systematic electrochemical study by using two commercially available carbon blacks, namely Vulcan XC72R and Ketjenblack EC-300J. Accelerated degradation tests simulating load cycle and start-up/shutdown conditions are carried out in accordance with the Fuel Cell Commercialization Conference of Japan (FCCJ) recommendations. Under conditions simulating the load cycle of PEM fuel cells no unambiguous correlation between the ECSA loss and the Pt:C ratio is found. By contrast, under conditions simulating the repetitive start-up/shutdown processes of PEMFCs the ECSA loss first increases with increasing Pt loading. However, it decreases again for very high loadings. Furthermore, the Vulcan samples exhibited higher ECSA losses than the Ketjenblack samples, indicating the important role of the physical and chemical properties of pristine carbon supports in the carbon degradation mechanism.

  19. Note: Matching index technique for avoiding higher order mode resonance in accelerators: INDUS-2 accelerator as a case study

    SciTech Connect

    Jain, V.; Joshi, S. C.; Bhandarkar, U. V.; Krishnagopal, S.

    2013-08-15

    Resonance between circulating beam frequencies and RF cavity Higher Order Modes (HOMs) of accelerators can lead to coupled-bunch instabilities. Shifting these HOMs to avoid the resonance is a topic of active interest. A study has been carried out for the accelerating cavities of the INDUS-2. For quantitative measure of deciding which modes have to be moved and by how much, we introduce a new index called the matching index (I{sub M}), as a measure of how close a HOM is to the nearest beam mode. Depending on the value of I{sub M}, the operating scenarios are classified as safe and unsafe.

  20. 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

  1. Degradation studies of hydrophilic, partially degradable and bioactive cements (HDBCs) incorporating chemically modified starch.

    PubMed

    Mendes, Ana C; Boesel, Luciano F; Reis, Rui L

    2012-03-01

    The degradation rate in Hydrophilic, Degradable and Bioactive Cements (HDBCs) containing starch/cellulose acetate blends (SCA) is still low. In order to increase degradation, higher amounts of starch are required to exceed the percolation threshold. In this work, gelatinization, acetylation and methacrylation of corn starch were performed and assessed as candidates to replace SCA in HDBCs. Formulations containing methacrylated starch were prepared with different molar ratios of 2-hydroxyethyl methacrylate and methyl methacrylate in the liquid component and the amount of residual monomer released into water was evaluated. The concentration of reducing sugars, percentage of weight loss and morphologic analyses after degradation all confirmed increased degradation of HDBC with α-amylase, with the appearance of pores and voids from enzymatic action. Methacrylated starch therefore is a better alternative to be used as the solid component of HDBC then SCA, since it leads to the formation of cements with a lower release of toxic monomers and more prone to hydrolytic degradation while keeping the other advantages of HDBCs.

  2. 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

  3. Parameterizations for shielding electron accelerators based on Monte Carlo studies

    SciTech Connect

    P. Degtyarenko; G. Stapleton

    1996-10-01

    Numerous recipes for designing lateral slab neutron shielding for electron accelerators are available and each generally produces rather similar results for shield thicknesses of about 2 m of concrete and for electron beams with energy in the 1 to 10 GeV region. For thinner or much thicker shielding the results tend to diverge and the standard recipes require modification. Likewise for geometries other than lateral to the beam direction further corrections are required so that calculated results are less reliable and hence additional and costly conservatism is needed. With the adoption of Monte Carlo (MC) methods of transporting particles a much more powerful way of calculating radiation dose rates outside shielding becomes available. This method is not constrained by geometry, although deep penetration problems need special statistical treatment, and is an excellent approach to solving any radiation transport problem providing the method has been properly checked against measurements and is free from the well known errors common to such computer methods. This present paper utilizes the results of MC calculations based on a nuclear fragmentation model named DINREG using the MC transport code GEANT and models them with the normal two parameter shielding expressions. Because the parameters can change with electron beam energy, angle to the electron beam direction and target material, the parameters are expressed as functions of some of these variables to provide a universal equations for shielding electron beams which can used rather simply for deep penetration problems in simple geometry without the time consuming computations needed in the original MC programs. A particular problem with using simple parameterizations based on the uncollided flux is that approximations based on spherical geometry might not apply to the more common cylindrical cases used for accelerator shielding. This source of error has been discussed at length by Stevenson and others. To study

  4. Module Degradation Mechanisms Studied by a Multi-Scale Approach

    SciTech Connect

    Johnston, Steve; Al-Jassim, Mowafak; Hacke, Peter; Harvey, Steven P.; Jiang, Chun-Sheng; Gerber, Andreas; Guthrey, Harvey; Moutinho, Helio; Albin, David; To, Bobby; Tynan, Jerry; Moseley, John; Aguiar, Jeffery; Xiao, Chuanxiao; Waddle, John; Nardone, Marco

    2016-11-21

    A key pathway to meeting the Department of Energy SunShot 2020 goals is to reduce financing costs by improving investor confidence through improved photovoltaic (PV) module reliability. A comprehensive approach to further understand and improve PV reliability includes characterization techniques and modeling from module to atomic scale. Imaging techniques, which include photoluminescence, electroluminescence, and lock-in thermography, are used to locate localized defects responsible for module degradation. Small area samples containing such defects are prepared using coring techniques and are then suitable and available for microscopic study and specific defect modeling and analysis.

  5. Development of Cu(In,Ga)Se2 Test Coupons for Potential Induced Degradation Studies

    SciTech Connect

    Contreras, Miguel A.; Hacke, Peter; Repins, Ingrid

    2016-11-21

    We report on the design, fabrication and accelerated testing of fully encapsulated small area coupons (approximately 7.5cm x 7.5 cm) for the purpose of researching potential induced degradation in Cu(In, Ga)Se2 based PV modules. The fabrication of these coupons enables the study of the solar cells and the materials used in PV module manufacturing such as top and bottom glass covers of different composition (soda-lime glass, high temperature glass, alkaline-free glass, etc), plastic-based top covers, ethylene vinyl acetate and edge seal encapsulation materials. The coupons can also be used to emulate framed and frameless modules that utilize either monolithically interconnected modules or singular cell type of modules. The design of the coupons, their fabrication, the materials used and their testing for 1000 hours under 85 degrees C and 85% RH conditions are presented.

  6. 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.

  7. Study of the effect of temperature on Pt dissolution in polymer electrolyte membrane fuel cells via accelerated stress tests

    NASA Astrophysics Data System (ADS)

    Dhanushkodi, S. R.; Kundu, S.; Fowler, M. W.; Pritzker, M. D.

    2014-01-01

    Operation of polymer electrolyte membrane fuel cells (PEMFC) at higher cell temperatures accelerates Pt dissolution in the catalyst layer. In this study, a Pt dissolution accelerated stress testing protocol involving the application of a potentiostatic square-wave with 3 s at 0.6 V followed by 3 s at 1.0 V was developed to test fuel cell membrane electrode assemblies (MEAs). The use of this Pt dissolution protocol at three different temperatures (40 °C, 60 °C and 80 °C) was investigated for the same membrane electrode assembly composition. Impedance analysis of the membrane electrode assemblies showed an increase in polarization resistance during the course of the accelerated stress testing. Polarization analysis and electrochemical active surface area (ECSA) loss measurements revealed evidence of increased cathode catalyst layer (CCL) degradation due to Pt dissolution and deposition in the membrane as the cell temperature was raised. Scanning electron microscope (SEM) images confirmed the formation of Pt bands in the membrane. A diagnostic expression was developed to estimate kinetic losses due to oxygen reduction using the effective platinum surface area (EPSA) estimated from cyclic voltammograms. The results indicated that performance degradation occurred mainly due to Pt loss.

  8. 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.

  9. Mechanistic insights into lithium ion battery electrolyte degradation - a quantitative NMR study.

    PubMed

    Wiemers-Meyer, S; Winter, M; Nowak, S

    2016-09-29

    The changes in electrolyte composition on the molecular level and the reaction mechanisms of electrolyte degradation upon thermal aging are monitored by quantitative NMR spectroscopy, revealing similar rates of degradation for pristine and already aged electrolytes. The data analysis is not in favor of an autocatalytic reaction mechanism based on OPF3 but rather indicates that the degradation of LiPF6 in carbonate based solvents proceeds via a complex sequence of "linear" reactions rather than a cyclic reaction pattern which is determined by the amount of water present in the samples. All investigated electrolytes are reasonably stable at temperatures of up to 60 °C in the presence of minor amounts or absence of water hence indicating that chemical instability of electrolyte components against water is decisive for degradation and an increase in temperature ("thermal aging") just accelerates the degradation impact of water.

  10. A study of the UV and VUV degradation of FEP

    NASA Technical Reports Server (NTRS)

    George, Graeme A.; Hill, David J. T.; Odonnell, James H.; Pomery, Peter J.; Rasoul, Firas A.

    1993-01-01

    UV and VUV degradation of fluorinated ethylene propylene (FEP) copolymer was studied using electron spin resonance (ESR) spectroscopy, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The ESR study revealed the formation of a terminal polymer radical. The stability of this radical was investigated under different environments. An XPS study of FEP film exposed to VUV and atomic oxygen showed that oxidation takes place on the polymer surface. The study revealed also that the percentage of CF2 in the polymer surface decreased with exposure time and the percentage of CF, CF3, and carbon attached to oxygen increased. SEM micrographs of FEP film exposed to VUV and atomic oxygen identified a rough surface with undulations similar to sand dunes.

  11. 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.

  12. 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

  13. Study of the degradation of gelatin in paper upon aging using aqueous size-exclusion chromatography.

    PubMed

    Dupont, Anne-Laurence

    2002-03-15

    We studied the aging behaviour of gelatin used to size paper. Thus far, research on the aging of paper has largely ignored the sizing agent. Degradation of the protein was characterised and the impact of paper components, such as cellulose, and aluminium potassium sulphate was evaluated. Whatman No. 1 filter papers sized with two types of gelatins (A and B) were prepared as model samples. Commercially sized modern papers (Arches) were also studied in order to compare laboratory samples with real artist papers. Both types of papers were artificially aged (80 degrees C, 50% relative humidity for 35 and 94 days). Historic papers were included in the study in order to compare artificially aged with naturally aged gelatin. The aqueous extracts from the papers were characterised by aqueous size-exclusion chromatography (SEC) using four PL-Aquagel-OH columns and UV photodiode array detection at 220, 254 and 280 nm. Results showed that gelatin undergoes hydrolysis upon aging, type A gelatin showing a faster degradation rate than type B. The result was an increase in the lower-molar-mass fractions, under 50,000 g mol(-1), and especially in a characteristic fraction with a peak molecular mass (MP) of 14,000 g mol(-1). A significant decrease in the extraction yields of alpha-, beta- and gamma-chains occurred after aging. This was attributed to crosslinking, leading to the formation of less-soluble polypeptides with very high molar mass (>800,000 g mol(-1)) Less than 10% alum had no impact on the degradation rate; higher alum contents accelerated hydrolysis reactions.

  14. Study of spin resonances in the accelerators with snakes

    SciTech Connect

    Lee, S.Y.

    1988-01-01

    Spin resonances in the circular accelerators with snakes are studied to understand the nature of snake resonances. We analyze the effect of snake configuration, and the snake superperiod on the resonance. Defining the critical resonance strength epsilon/sub c/ as the maximum tolerable resonance strength without losing the beam polarization after passing through the resonance, we found that epsilon/sub c/ is a sensitive function of the snake configuration, the snake superperiod at the first order snake resonance, the higher order snake resonance conditions and the spin matching condition. Under properly designed snake configuration, the critical resonance strength epsilon/sub c/ is found to vary linearly with N/sub S/ as = (1/..pi..)sin/sup /minus/1/(/vert bar/cos ..pi nu../sub z//vert bar//sup /1/2//)N/sub S/, where ..nu../sub z/ and N/sub S/ are the betatron tune and the number of snakes respectively. We also study the effect of overlapping intrinsic and imperfection resonances. The imperfection resonance should be corrected to a magnitude of insignificance (e.g., epsilonless than or equal to0.1 for two snakes case) to maintain proper polarization. 23 refs., 25 figs.

  15. 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.

  16. 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.

  17. 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...

  18. 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.

  19. Radio Studies of Electron Acceleration and Transport During Solar Flares

    NASA Astrophysics Data System (ADS)

    Lee, J.

    2002-05-01

    At centimeter wavelengths solar flare radiation is dominated by incoherent gyrosynchrotron emissions from 10 keV to several MeV electrons. Due to unique sensitivity of the gyrosynchrotron radiation to electron momentum distribution and ambient magnetic field, the radio observations at these wavelengths can provide important clues to the evolution of high-energy electrons residing in the flaring loops. In this talk I review some of recent progress made primarily using the Owens Valley Solar Array (OVSA) to understand acceleration, trapping, and precipitation of electrons during solar flares. These works are extensions of the traditional, correlative studies of temporal and spatial morphologies of radio bursts versus those of other flare radiations (X-rays, UV/EUV, and Hα ) to exploit the multi-frequencies of the OVSA. The results demonstrate additional advantages of radio observations as a flare diagnostic tool when both spatial and spectral resolutions are available, and provide a major initiative in building the Frequency-Agile Radio Telescope (FASR). This work has been supported by NASA grant NAG5-10891. The OVSA is supported by NSF grant AST-9987366 to New Jersey Institute of Technology.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    Compact near-field solid-state accelerating structure powered by a carbon dioxide (CO2) 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 κ 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.

  7. 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.

  8. Experimental study on effect of anion surfactant on degradation rate of aldicarb in soil.

    PubMed

    Liu, Guangliang; Dai, Shugui; Qian, Yun; Gan, Quan

    2003-07-01

    Degradation kinetics of aldicarb [2-methyl-2-(methylthio) propionaldehyde O-(methyl carbamoyl) oxime] in surface and subsurface soil containing different levels of sodium dodecylbenzenesulfonate (SDBS) were determined to understand complex effect of SDBS on aldicarb degradation process. The results showed that degradation curves of aldicarb in soil can be described with first order kinetics formula and the degradation rate constant. k (d(-1)), in surface soil was larger than that in subsurface soil. SDBS can accelerate the degradation of aldicarb in soil and there was a good linear relationship between degradation rate constant and the logarithm of SDBS concentration. The possible reasons were that SDBS could change pH value of soil, have solubilization effect on aldicarb, and be used as carbon source of microorganisms. But SDBS had a larger promotion to the degradation of aldicarb in surface than in subsurface soil. When SDBS concentration was 1000 mg/kg of dried soil the first order degradation rate constant of aldicarb could be increased by 56.6 percent in surface soil and by 27.6 percent in subsurface soil, respectively.

  9. 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.

  10. 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.

  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. 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)

  14. 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).

  15. Micromechanical Modeling Study of Mechanical Inhibition of Enzymatic Degradation of Collagen Tissues

    PubMed Central

    Tonge, Theresa K.; Ruberti, Jeffrey W.; Nguyen, Thao D.

    2015-01-01

    This study investigates how the collagen fiber structure influences the enzymatic degradation of collagen tissues. We developed a micromechanical model of a fibrous collagen tissue undergoing enzymatic degradation based on two central hypotheses. The collagen fibers are crimped in the undeformed configuration. Enzymatic degradation is an energy activated process and the activation energy is increased by the axial strain energy density of the fiber. We determined the intrinsic degradation rate and characteristic energy for mechanical inhibition from fibril-level degradation experiments and applied the parameters to predict the effect of the crimped fiber structure and fiber properties on the degradation of bovine cornea and pericardium tissues under controlled tension. We then applied the model to examine the effect of the tissue stress state on the rate of tissue degradation and the anisotropic fiber structures that developed from enzymatic degradation. PMID:26682825

  16. 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...

  17. 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.

  18. 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.

  19. 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)

  20. Fundamental study of mechanical and chemical degradation mechanisms of PEM fuel cell membranes

    NASA Astrophysics Data System (ADS)

    Yoon, Wonseok

    One of the important factors determining the lifetime of polymer electrolyte membrane fuel cells (PEMFCs) is membrane degradation and failure. The lack of effective mitigation methods is largely due to the currently very limited understanding of the underlying mechanisms for mechanical and chemical degradations of fuel cell membranes. In order to understand degradation of membranes in fuel cells, two different experimental approaches were developed; one is fuel cell testing under open circuit voltage (OCV) with bi-layer configuration of the membrane electrode assemblies (MEAs) and the other is a modified gas phase Fenton's test. Accelerated degradation tests for polymer electrolyte membrane (PEM) fuel cells are frequently conducted under open circuit voltage (OCV) conditions at low relative humidity (RH) and high temperature. With the bi-layer MEA technique, it was found that membrane degradation is highly localized across thickness direction of the membrane and qualitatively correlated with location of platinum (Pt) band through mechanical testing, Infrared (IR) spectroscopy, fluoride emission, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) measurement. One of the critical experimental observations is that mechanical behavior of membranes subjected to degradation via Fenton's reaction exhibit completely different behavior with that of membranes from the OCV testing. This result led us to believe that other critical factors such as mechanical stress may affect on membrane degradation and therefore, a modified gas phase Fenton's test setup was developed to test the hypothesis. Interestingly, the results showed that mechanical stress directly accelerates the degradation rate of ionomer membranes, implying that the rate constant for the degradation reaction is a function of mechanical stress in addition to commonly known factors such as temperature and humidity. Membrane degradation induced by

  1. Environmental degradation study of multilevel biocomposites based on polyolefins

    NASA Astrophysics Data System (ADS)

    Mastalygina, E. E.; Kolesnikova, N. N.; Popov, A. A.; Olkhov, A. A.

    2015-10-01

    The properties and dynamics of degradation of composite materials based on isotactic polypropylene/low density polyethylene blends and cellulose filler have been investigated. The composite materials with a high PP content (as PP is a continuous phase) more sensitive to oxidative destruction have higher values of weight loss at the initial period of environmental degradation. However, the materials with the low PP content characterized by a lower degree of crystallinity and density of amorphous regions show a higher capacity for biofouling by microorganisms that may has a significant effect on the period of ultimate degradation.

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

    DOE PAGES

    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.

  3. 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

  4. 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

  5. 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

  6. Study of Magnetogasdynamic Flow Acceleration in a Scramjet Nozzle

    DTIC Science & Technology

    2005-06-01

    direction along the electrodes to be parallel with the flow. At the end of the electrodes, the vectors push the flow toward the wall. The x-y midplane...accelerated case features long regions of slower Mach number along the walls. This is probably due to a combination of the Lorentz forces pushing ...Institute of Tecnology , WPAFB, OH, March 2004. 8. Einstein, A. Relativity, The Special and General Theory . Three Rivers Press, 1961. 9. “Ramjet, Scramjet

  7. New pseudopeptidic cross-linker containing urea bonds: study of its degradation routes in aqueous media using capillary electrophoresis-mass spectrometry.

    PubMed

    Pérez, Paloma; Simó, Carolina; Neusüss, Christian; Pelzing, Matthias; San Roman, Julio; Cifuentes, Alejandro; Gallardo, Alberto

    2006-03-01

    An accelerated degradation study has been performed on TLT, a pseudopeptide that includes esterified tyrosine and lysine linked by urea bonds, as well as on their derivatives, i.e., a dimethacrylic cross-linker (DMTLT) and a poly(dimethylacrylamide) cross-linked with DMTLT. The monitoring and analytical characterization has been carried out by capillary electrophoresis-mass spectrometry (CE-MS), using ion trap and time-of-flight MS analyzers. Several degradative species have been identified, and a kinetic analysis of the variation of their concentration with time has been obtained. During the initial stages of degradation, there is a competition between hydrolysis of the ester groups and cyclization by nucleophilic attack of the NHs of the urea groups to the carbonyl ester group. At higher degradation time (weeks or months), evidences of backbone breakdown, including urea hydrolysis, have been found.

  8. Degradation in photoelectrochemical devices: review with an illustrative case study

    NASA Astrophysics Data System (ADS)

    Nandjou, Fredy; Haussener, Sophia

    2017-03-01

    The durability, reliability, and robustness of photoelectrochemical (PEC) devices are key factors for advancing the practical large-scale implementation of cost-competitive solar fuel production. We review the known degradation mechanisms occurring in water-splitting photoelectrochemical devices. The degradation of single components is discussed in detail, and the parameters and conditions which influence it are presented. Device short-term durability depends on the semiconductor material and its interface with the electrolyte. Catalyst and electrolyte degradations are considerable challenges for long-term durability. We highlight how PEC device design choices can affect the salience of alternative degradation mechanisms. The PEC device architecture and the initial operating design point are crucial for observed device performance loss. Device degradation behavior is further impacted by irradiation intensity and concentration, and by current density and concentration. Enhancing a physical understanding of degradation phenomena and investigating their effect on component properties is of utmost importance for predicting performance loss and tackling the durability challenge of PEC devices.

  9. A long-term in vitro biocompatibility study of a biodegradable polyurethane and its degradation products.

    PubMed

    van Minnen, B; Stegenga, B; van Leeuwen, M B M; van Kooten, T G; Bos, R R M

    2006-02-01

    The biological safety of degradation products from degradable biomaterials is very important. In this study a new method is proposed to test the cytotoxicity of these degradation products with the aim to save time, laboratory animals, and research funds. A biodegradable polyurethane (PU) foam was subjected to this test method. The PU had soft segments of DL-lactide/epsilon-caprolactone and hard segments synthesized from butanediol and 1,4-butanediiosocyanate. Copolymer foams without urethane segments, consisting of DL-lactide/epsilon-caprolactone, were tested as well. Accumulated degradation products were collected by degrading the foams in distilled water at 60 degrees C up to 52 weeks. Cell-culture medium was prepared from powder medium with this water. In different tests the cytotoxicity of this medium was established. The first signs of cytotoxicity were observed after 3-5 weeks of degradation. This accounts for both materials and reestablishes the good short-term biocompatibility of these materials. The PU showed more toxicity toward the end stages of degradation in comparison with the copolymer. This is probably related to the accumulation of degradation products of the urethane segments. In the in vivo situation the degradation of the PU and the metabolism and excretion of degradation products may differ. Therefore, long-term in vivo studies will have to establish whether these in vitro results are representative for the in vivo behavior of the degrading PU.

  10. 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.

  11. Surface catalytic degradation study of two linear perfluoropolyalkylethers at 345 C

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1987-01-01

    Thin-liquid-film degradation studies of two commercially available perfluoropolyalkylether fluids (PFAE) were performed at 345 C, in nitrogen and air atmospheres, on iron and 440 C stainless steel surfaces. It was found that one fluid degraded on both iron and 440 C stainless steel surfaces in an air atmosphere, whereas the other fluid did not degrade. Chemical analysis revealed that the test fluid degraded to lower molecular weight products and that the degradation was accompanied by the formation of a brownish deposit on both the iron and 440 C stainless steel surfaces. Surface analysis of the deposit revealed a susbstantial amount of iron oxide (Fe2O3). It was hypothesized that the fluid which degraded did so because of its acetal structure. The other fluid, lacking the acetal structure, did not degrade.

  12. Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo

    PubMed Central

    Ågren, Magnus S.; Schnabel, Reinhild; Christensen, Lise H.; Mirastschijski, Ursula

    2015-01-01

    Tumor necrosis factor (TNF)-α induces matrix metalloproteinases (MMPs) that may disrupt skin integrity. We have investigated the effects and mechanisms of exogenous TNF-α on collagen degradation by incubating human skin explants in defined serum-free media with or without TNF-α (10 ng/ml) in the absence or presence of the nonselective MMP inhibitor GM6001 for 8 days. The basal culture conditions promoted type I collagen catabolism that was accelerated by TNF-α (p < 0.005) and accomplished by MMPs (p < 0.005). Levels of the collagenases MMP-8 and MMP-13 were insignificant and neither MMP-2 nor MMP-14 were associated with increased collagen degradation. TNF-α increased secretion of MMP-1 (p < 0.01) but had no impact on MMP-1 quantities in the tissue. Immunohistochemical analysis confirmed similar tissue MMP-1 expression with or without TNF-α with epidermis being the major source of MMP-1. Increased tissue-derived collagenolytic activity with TNF-α exposure was blocked by neutralizing MMP-1 monoclonal antibody and was not due to down-regulation of tissue inhibitor of metalloproteinase-1. TNF-α increased production (p < 0.01), tissue levels (p < 0.005) and catalytic activity of the endogenous MMP-1 activator MMP-3. Type I collagen degradation correlated with MMP-3 tissue levels (rs = 0.68, p < 0.05) and was attenuated with selective MMP-3 inhibitor. Type I collagen formation was down-regulated in cultured compared with native skin explants but was not reduced further by TNF-α. TNF-α had no significant effect on epidermal apoptosis. Our data indicate that TNF-α augments collagenolytic activity of MMP-1, possibly through up-regulation of MMP-3 leading to gradual loss of type I collagen in human skin. PMID:25457675

  13. 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.

  14. 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.

  15. Inhibition of Hepatitis B Virus Replication by MyD88 Involves Accelerated Degradation of Pregenomic RNA and Nuclear Retention of Pre-S/S RNAs▿

    PubMed Central

    Li, Jianhua; Lin, Shanshan; Chen, Qiying; Peng, Lu; Zhai, Jianwei; Liu, Yinghui; Yuan, Zhenghong

    2010-01-01

    Myeloid differentiation primary response protein 88 (MyD88), which can be induced by alpha interferon (IFN-α), has an antiviral activity against the hepatitis B virus (HBV). The mechanism of this antiviral activity remains poorly understood. Here, we report that MyD88 inhibited HBV replication in HepG2.2.15 cells and in a mouse model. The knockdown of MyD88 expression weakened the IFN-α-induced inhibition of HBV replication. Furthermore, MyD88 posttranscriptionally reduced the levels of viral RNA. Remarkably, MyD88 accelerated the decay of viral pregenomic RNA in the cytoplasm. Mapping analysis showed that the RNA sequence located in the 5′-proximal region of the pregenomic RNA was critical for the decay. In addition, MyD88 inhibited the nuclear export of pre-S/S RNAs via the posttranscriptional regulatory element (PRE). The retained pre-S/S RNAs were shown to degrade in the nucleus. Finally, we found that MyD88 inhibited the expression of polypyrimidine tract-binding protein (PTB), a key nuclear export factor for PRE-containing RNA. Taken together, our results define a novel antiviral mechanism against HBV mediated by MyD88. PMID:20410269

  16. Accumulation of a Threonine Biosynthetic Intermediate Attenuates General Amino Acid Control by Accelerating Degradation of Gcn4 via Pho85 and Cdk8

    PubMed Central

    Rawal, Yashpal; Qiu, Hongfang; Hinnebusch, Alan G.

    2014-01-01

    Gcn4 is a master transcriptional regulator of amino acid and vitamin biosynthetic enzymes subject to the general amino acid control (GAAC), whose expression is upregulated in response to amino acid starvation in Saccharomyces cerevisiae. We found that accumulation of the threonine pathway intermediate β-aspartate semialdehyde (ASA), substrate of homoserine dehydrogenase (Hom6), attenuates the GAAC transcriptional response by accelerating degradation of Gcn4, already an exceedingly unstable protein, in cells starved for isoleucine and valine. The reduction in Gcn4 abundance on ASA accumulation requires Cdk8/Srb10 and Pho85, cyclin-dependent kinases (CDKs) known to mediate rapid turnover of Gcn4 by the proteasome via phosphorylation of the Gcn4 activation domain under nonstarvation conditions. Interestingly, rescue of Gcn4 abundance in hom6 cells by elimination of SRB10 is not accompanied by recovery of transcriptional activation, while equivalent rescue of UAS-bound Gcn4 in hom6 pho85 cells restores greater than wild-type activation of Gcn4 target genes. These and other findings suggest that the two CDKs target different populations of Gcn4 on ASA accumulation, with Srb10 clearing mostly inactive Gcn4 molecules at the promoter that are enriched for sumoylation of the activation domain, and Pho85 clearing molecules unbound to the UAS that include both fully functional and inactive Gcn4 species. PMID:25079372

  17. A study of degradation of historic parchment using small-angle X-ray scattering, synchrotron-IR and multivariate data analysis.

    PubMed

    Možir, Alenka; Gonzalez, Lee; Kralj Cigić, Irena; Wess, Tim J; Rabin, Ira; Hahn, Oliver; Strlič, Matija

    2012-02-01

    Parchment has been in use for thousands of years and has been used as the writing or drawing support for many important historic works. A variety of analytical techniques is currently used for routine assessment of the degree of denaturation of historic parchment; however, because parchment has a heterogeneous nature, analytical methods with high spatial resolution are desirable. In this work, the use of small-angle X-ray scattering (SAXS) and synchrotron-IR (SR-IR) was examined in conjunction with multivariate data analysis to study degradation of an extended set of historic parchment samples, and particularly to investigate the effect of lipids and the presence of iron gall ink on the degradation processes. In the data analysis, shrinkage temperature, lipid content, sample age, presence of ink and accelerated degradation were included. The analysis of loading factors in partial least-squares regression and principal component analyses based on SAXS, SR-IR and other analytical and descriptive data reveals the effect of lipid removal on diffraction patterns, and lipids are found to cause the degradation process in parchment to accelerate. The effect of iron gall ink is also evident, although the mechanism of ageing is different to that of natural ageing in the absence of ink. In addition, a historic parchment score from ca. 1750 is examined, demonstrating the significant effect of iron gall ink, and lipids and inorganic soiling on its increased degradation.

  18. Studies of acceleration processes in the corona using ion measurements on the solar probe mission

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1978-01-01

    The energy spectra and composition of particles escaping from the Sun provide essential information on mechanisms responsible for their acceleration, and may also be used to characterize the regions where they are accelerated and confined and through which they propagate. The suprathermal energy range, which extends from solar wind energies (approximately 1 KeV) to about 1 MeV/nucleon, is of special interest to studies of nonthermal acceleration processes because a large fraction of particles is likely to be accelerated into this energy range. Data obtained from near earth observations of particles in the suprathermal energy range are reviewed. The necessary capabilities of an a ion composition experiment in the solar probe mission and the required ion measurements are discussed. A possible configuration of an instrument consisting of an electrostatic deflection system, modest post acceleration, and a time of flight versus energy system is described as well as its possible location on the spacecraft.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Environmental degradation: Implications for national security. Study report

    SciTech Connect

    Schlegel, J.D.

    1990-03-30

    As the United States prepares to move into the 21st century, the threat of armed conflict between the United States and the Soviet Union appears to have receded into the realm of the improbable. At the same time, however, a new and perhaps more ominous threat is emerging to challenge the security of nations: environmental degradation. Burgeoning world populations and the quest for industrial/economic development have begun seriously to erode the capability of the earth's environment to sustain itself. The phenomena of global warming, ozone depletion, deforestation, desertification and many forms of pollution are destroying the delicate life support systems upon which humanity depends for its very survival. National security, therefore, must be redefined and in this instance must be viewed in a context outside the traditional concept of military capability. This paper examines economic, social, political and military implications of environmental degradation as threats to the security of the United States and to world security. The paper concludes that a new level of international cooperation and technological innovation are required to reduce the negative impact of environmental degradation. An appendix provides additional data on specific forms of environmental degradation.

  4. Study of Biochemical Pathways and Enzymes Involved in Pyrene Degradation by Mycobacterium sp. Strain KMS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pyrene degradation is known in bacteria. In this study, Mycobacterium sp. Strain KMS was used to study the metabolites produced during, and enzymes involved in, pyrene degradation. Several key metabolites, including pyrene-4,5-dione, cis-4,5-pyrene-dihydrodiol, phenanthrene-4,5-dicarboxylic acid, ...

  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. 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

  8. 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.

  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. In vitro quantitative study of the degradation of endomorphins.

    PubMed

    Tömböly, Csaba; Péter, Antal; Tóth, Géza

    2002-09-01

    The catabolism of the endomorphins was investigated in detail. The endomorphins were degraded relatively slowly in the rat brain homogenate (t1/2(endomorphin-1)=4.94 min; t1/2(endomorphin-2)=3.81 min). The inhibition of metalloproteases and aminopeptidases stabilised the endomorphins to the greatest extent. The digestion of endomorphins tritiated specifically on Tyr(1), Pro(2) or Phe(3) established also that only the aminopeptidase pathways were essential for inactivation of the endomorphins, and that the tetrapeptides were degraded by cleavage of the Pro(2)-Trp(3) or Pro(2)-Phe(3) bond. The end-products of the catabolism were amino acids; the fragments Tyr-Pro-OH and Pro-Trp-Phe-NH2 were present as intermediates. Metabolites produced by brain carboxypeptidases were not detected.

  11. Numerical studies of diffusive shock acceleration at spherical shocks

    NASA Astrophysics Data System (ADS)

    Kang, Hyesung; Jones, T. W.

    2006-05-01

    We have developed a cosmic ray (CR) shock code in one-dimensional spherical geometry with which the particle distribution, the gas flow and their nonlinear interaction can be followed numerically in a frame comoving with an expanding shock. In order to accommodate a very wide dynamic range of diffusion length scales in the CR shock problem, we have incorporated subzone shock tracking and adaptive mesh refinement techniques. We find the spatial grid resolution required for numerical convergence is less stringent in this code compared to typical, fixed-grid Eulerian codes. The improved convergence behavior derives from maintaining the shock discontinuity inside the same grid zone in the comoving code. That feature improves numerical estimates of the compression rate experienced by CRs crossing the subshock compared to codes that allow the subshock to drift on the grid. Using this code with a Bohm-like diffusion model we have calculated the CR acceleration and the nonlinear feedback at supernova remnant shocks during the Sedov-Taylor stage. Similarly to plane-parallel shocks, with an adopted thermal leakage injection model, about 10 -3 of the particles that pass through the shock and up to 60% of the explosion energy are transferred to the CR component. These results are in good agreement with previous nonlinear spherical CR shock calculations of Berezhko and collaborators.

  12. 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.

  13. 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.

  14. Nano-Mechanical Studies on Polyglactin Sutures Subjected to In Vitro Hydrolytic and Enzymatic Degradation.

    PubMed

    Sun, Leming; Wanasekara, Nandula; Chalivendra, Vijaya; Calvert, Paul

    2015-01-01

    An experimental investigation on the effects of in vitro hydrolytic and enzymatic degradation on mechanical properties of polyglactin 910 monofilament sutures was performed by conducting nanoindentation studies using an atomic force microscope (AFM). For hydrolytic degradation, the sutures were incubated in phosphate buffered saline (PBS) solution at three different pH conditions, 5, 7.4, and 10. For enzymatic degradation, esterase was employed at pH condition of 7.4. The property of the sutures changed with time at different conditions were investigated by nanoindentation, tensile test experiments, image analysis using both of scanning electron microscopy (SEM) and AFM, and also Fourier transform infrared spectroscopy (FTIR). The effects of degradation on gradation of Young's modulus values across the cross section of the sutures were studied by doing progressive nanoindentation from center to surface. FTIR studies revealed the formation of new hydroxyl bonds due to both hydrolytic and enzymatic degradations. Nanoindentation results indicated that the degradation does not cause a gradient of Young's modulus of the polyglactin 910 monofilament sutures across the cross section from center to surface at different degradation times for both hydrolytic and enzymatic degradations. However, in general, the Young's modulus of all samples was decreased over 4 weeks of degradation. The microscopic evaluation of the samples also showed both qualitative changes in surface morphology and quantitative changes in surface roughness on the surface of degraded sutures. This study provided a deep understanding of the polyglactin sutures subjected to in vitro hydrolytic and enzymatic degradation, and also opened a new avenue to study the biomaterials at nano-scale.

  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.

  16. 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.

  17. 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

  18. Compatibility study of a parenteral microdose polyethylene glycol formulation in medical devices and identification of degradation impurity by 2D-LC/MS.

    PubMed

    Dai, Lulu; Yeh, Geoffrey K; Ran, Yingqing; Yehl, Peter; Zhang, Kelly

    2017-04-15

    Polyethylene glycol (PEG) based formulation and polyvinylchloride (PVC) tubing are frequently used for drug delivery and administration. The compatibility of a parenteral drug microdose formulation in intravenous infusion (IV) devices was studied to support the clinical determination of absolute bioavailability by the microdosing method. The investigational microdose formulation containing PEG was found prone to significant loss of potency within hours of storage in the PVC IV tubing due to degradation. Degradation occurred only when both PEG and PVC tubing were present. The degradation product could not be detected by LC/MS due to the significant interference from the high concentration of PEG (4%) matrix and the extremely low level of drug (0.6ppm). To obtain structural information of the degradation impurity and understand the cause of the degradation, a simple heart-cutting 2D-LC/MS approach was utilized to effectively separate the impurity from the complex PEG oligomers and overcome the matrix interference, enabling mass spectrometric analysis of the impurity. An oxidation- dominated mechanism was proposed in which the combination of PEG auto-oxidation and dehydrochlorination of the PVC tubing yielded an oxidative environment that enhanced radical propagation and accelerated degradation of the investigational parent drug.

  19. 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.

  20. 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.

  1. Oxidative degradation of alternative gasoline oxygenates in aqueous solution by ultrasonic irradiation: mechanistic study.

    PubMed

    Kim, Duk Kyung; O'Shea, Kevin E; Cooper, William J

    2012-07-15

    Widespread pollution has been associated with gasoline oxygenates of branched ethers methyl tert-butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), and tert-amyl ether (TAME) which enter groundwater. The contaminated plume develops rapidly and treatment for the removal/destruction of these ethers is difficult when using conventional methods. Degradation of MTBE, with biological methods and advanced oxidation processes, are rather well known; however, fewer studies have been reported for degradation of alternative oxygenates. Degradation of alternative gasoline oxygenates (DIPE, ETBE, and TAME) by ultrasonic irradiation in aqueous oxygen saturation was investigated to elucidate degradation pathways. Detailed degradation mechanisms are proposed for each gasoline oxygenate. The common major degradation pathways are proposed to involve abstraction of α-hydrogen atoms by hydroxyl radicals generated during ultrasound cavitation and low temperature pyrolytic degradation of ETBE and TAME. Even some of the products from β-H abstraction overlap with those from high temperature pyrolysis, the effect of β-H abstraction was not shown clearly from product study because of possible 1,5 H-transfer inside cavitating bubbles. Formation of hydrogen peroxide and organic peroxides was also determined during sonolysis. These data provide a better understanding of the degradation pathways of gasoline oxygenates by sonolysis in aqueous solutions. The approach may also serve as a model for others interested in the details of sonolysis.

  2. Effects of Frequency and Acceleration Amplitude on Osteoblast Mechanical Vibration Responses: A Finite Element Study

    PubMed Central

    Hsu, Hung-Yao

    2016-01-01

    Bone cells are deformed according to mechanical stimulation they receive and their mechanical characteristics. However, how osteoblasts are affected by mechanical vibration frequency and acceleration amplitude remains unclear. By developing 3D osteoblast finite element (FE) models, this study investigated the effect of cell shapes on vibration characteristics and effect of acceleration (vibration intensity) on vibrational responses of cultured osteoblasts. Firstly, the developed FE models predicted natural frequencies of osteoblasts within 6.85–48.69 Hz. Then, three different levels of acceleration of base excitation were selected (0.5, 1, and 2 g) to simulate vibrational responses, and acceleration of base excitation was found to have no influence on natural frequencies of osteoblasts. However, vibration response values of displacement, stress, and strain increased with the increase of acceleration. Finally, stress and stress distributions of osteoblast models under 0.5 g acceleration in Z-direction were investigated further. It was revealed that resonance frequencies can be a monotonic function of cell height or bottom area when cell volumes and material properties were assumed as constants. These findings will be useful in understanding how forces are transferred and influence osteoblast mechanical responses during vibrations and in providing guidance for cell culture and external vibration loading in experimental and clinical osteogenesis studies. PMID:28074178

  3. Design of an electromagnetic accelerator for turbulent hydrodynamic mix studies. Revision 1

    SciTech Connect

    Susoeff, A.R.; Hawke, R.S.; Morrison, J.J.; Dimonte, G.; Remington, B.A.

    1994-03-01

    An electromagnetic accelerator in the form of a linear electric motor (LEM) has been designed to achieve controlled acceleration profiles of a carriage containing hydrodynamically unstable fluids for the investigation of the development of turbulent mix. Key features of the design include: (1) independent control of acceleration, deceleration and augmentation currents to provide a variety of acceleration-time profiles, (2) a robust support structure to minimized deflection and dampen vibration which could create artifacts in the data interfering with the intended study and (3) a compliant, non-arcing solid armature allowing optimum electrical contact. Electromagnetic modeling codes were used to optimize the rail and augmentation coil positions within the support structure framework. Design of the driving armature and the dynamic electromagnetic braking system is based on results of contemporary studies for non-arcing sliding contact of solid armatures. A 0.6MJ electrolytic capacitor bank is used for energy storage to drive the LEM. This report will discuss a LEM and armature design which will accelerate masses of up to 3kg to a maximum of about 3000g{sub o}, where g{sub o} is acceleration due to gravity.

  4. Kinetic study of olive oil degradation monitored by fourier transform infrared spectrometry. Application to oil characterization.

    PubMed

    Román Falcó, Iván P; Grané Teruel, Nuria; Prats Moya, Soledad; Martín Carratalá, M Luisa

    2012-11-28

    A new approach for the determination of kinetic parameters of the cis/trans isomerization during the oxidation process of 24 virgin olive oils belonging to 8 different varieties is presented. The accelerated process of degradation at 100 °C was monitored by recording the Fourier transform infrared spectra. The parameters obtained confirm pseudo-first-order kinetics for the degradation of cis and the appearance of trans double bonds. The kinetic approach affords the induction time and the rate coefficient; these parameters are related to the fatty acid profile of the fresh olive oils. The data obtained were used to compare the oil stability of the samples with the help of multivariate statistical techniques. Fatty acid allowed a classification of the samples in five groups, one of them constituted by the cultivars with higher stability. Meanwhile, the kinetic parameters showed greater ability for the characterization of olive oils, allowing the classification in seven groups.

  5. 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.

  6. Psychopharmacological studies on (--)-nuciferine and its Hofmann degradation product atherosperminine.

    PubMed

    Bhattacharya, S K; Bose, R; Ghosh, P; Tripathi, V J; Ray, A B; Dasgupta, B

    1978-09-15

    (--)-Nuciferine and its Hofmann degradation product atherosperminine showed divergent psychopharmacological effects. Because nuciferine has been reported to be a neuroleptic and atherosperminine has some chemical resemblance to dopamine, they were investigated for their dopamine-receptor activities. Nuciferine had a pharmacologic profile of action associated with dopamine-receptor blockade; i.e., it induced catalepsy, inhibited spontaneous motor activity, conditioned avoidance response, amphetamine toxicity and stereotypy. On the other hand, atherosperminine produced effects associated with dopamine receptor stimulation, i.e., stereotypy, increase in spontaneous motor activity and amphetamine toxicity, reversal of haloperidol-induced catalepsy and inhibition of conditioned avoidance response, inhibition of morphine analgesia, and potentiation of the anticonvulsant action of diphenylhydantoin. The results are discussed on the basis of the chemical configuration of the two compounds.

  7. A study on the degradation of direct pink by the low-frequency ultrasonic irradiation.

    PubMed

    Zheng, Huaili; Zhu, Guocheng; He, Qiang; Hu, Peng; Jiao, Shijun; Tshukudu, Tiroyaone; Zhang, Peng

    2010-01-01

    The ultrasonic degradation of direct pink was investigated in this study. Parameters affecting ultrasonic degradation degree such as ultrasonic power, pH, bubbling gas and the presence of inorganic salts, were examined. The results showed that the addition of inorganic salts (NaCl, CuSO₄) facilitated the degradation of direct pink while the addition of K₂CO₃ inhibited it. The degradation degree was enhanced significantly in the presence of saturated gases as listed here in decreasing order of effectiveness: argon > air > oxygen > nitrogen. The degradation degree of direct pink was largely influenced by pH value and boosted by acidic condition. The optimum degree could be achieved when pH value was 3.0 or when the sound power was 150 W. However, the degradability decreased notably in alkaline condition. Also, ultrasound/H₂O₂ technology was used, and the results showed that ultrasound/H₂O₂ has a better effect on the degradation than ultrasound alone or with H₂O₂ oxidation. After 120 minutes, the degradation degree could reach 78.0% under the optimum conditions, when the ultrasonic power was 150 W, 50 μL H₂O₂, CuSO₄ and argon atmosphere being added and the initial pH value of the model dye was 3.0.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. Parameter study of a laser-driven dielectric accelerator for radiobiology research

    NASA Astrophysics Data System (ADS)

    Koyama, Kazuyoshi; Otsuki, Shohei; Uesaka, Mitsuru; Yoshida, Mitsuhiro; Aimidula, Aimiding

    2014-12-01

    A parameter study for a transmission grating type laser-driven dielectric accelerator (TG-LDA) was performed. The optimum pulse laser width was concluded to be 2 ps from the restrictions on the optical damage threshold intensity and the nonlinear optical effects such as the self-phase modulation and self-focus. An irradiation intensity of 5× {{10}11} W c{{m}-2} (2 GV m-1) was suitable for a silica TG-LDA with a pulse width range from 1 ps to 10 ps. The higher order harmonics of the axial electric field distribution was capable of accelerating electrons provided that the electron speed approximately satisfies the conditions of v/c=1/2,1/3, or 1/4. The electrons at the initial energy of 20 kV are accelerated by an acceleration field strength of 20 MV m-1, and the electrons were accelerated by higher fields as the speed increased. For relativistic energy electrons,the acceleration gradient was 600 MV {{m}-1}.

  13. 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.

  14. Accelerated Storage Stability and Corrosion Characteristics Study Protocol

    EPA Pesticide Factsheets

    EPA has determined that studies using this protocol will, in certain circumstances, provide the Agency with all the information it needs to make a determination on the storage stability of pesticides.

  15. 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.

  16. 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.``

  17. 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.

  18. Application and Rheoencephalography to Study Physiological Responses Under Acceleration Stress.

    DTIC Science & Technology

    1991-09-01

    unavailable to neural tissues. Therefore, this rate is not inconsistent with neck occlusion studies reported by Rossen et al (43) in which blood flow to...Automatically Resetting Electrical Impedance Plethysmograph." IEEE 1980 Frontiers of Enaineerina in Health Care, p.346-349, 1980. 43. Rossen , R., Kabat, H

  19. 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.

  20. 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.

  1. Desiccant degradation in desiccant cooling systems: An experimental study

    SciTech Connect

    Pesaran, A.A.

    1993-11-01

    The authors conducted experiments to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. The source of contamination was cigarette smoke, which is considered one of the worst pollutants in building cooling applications. The authors exposed five different solid desiccants to ``ambient`` and ``contaminated`` humid air: silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. They obtained the moisture capacity of samples as a function of exposure time. Compared to virgin desiccant samples, the capacity loss caused by thermal cycling with humid ambient air was 10 percent to 30 percent for all desiccants. The capacity loss because of combined effect of thermal cycling with ``smoke-filled`` humid air was between 30 percent to 70 percent. The higher losses occurred after four months of experiment time, which is equivalent to four to eight years of field operation. Using a system model and smoke degradation data on silica gel, the authors predicted that, for low-temperature regeneration, the loss in performance of a ventilation-cycle desiccant cooling system would be between 10 percent to 35 percent, in about eight years, with higher value under worst conditions.

  2. Accelerator transmutation studies at Los Alamos with LAHET, MCNP, and CINDER`90

    SciTech Connect

    Wilson, W.B.; England, T.R.; Arthur, E.D.

    1993-09-01

    Versions of the CINDER code have been used over three decades for determination of reactor fuel inventories and aggregate neutron absorption and radioactive decay properties. The CINDER`90 code, an evolving version which requires no predetermined nuclide chain structure, is suitable for a wider range of transmutation problems including those treated with older versions. In recent accelerator transmutation studies, the CINDER`90 code has been linked with the LAHET Code System (LCS) and, for high-energy calculations, with SUPERHET. A description of the nature of these linked calculational tools is given; data requirements for the transmutation studies are described; and, examples of linked calculations are described for some interesting accelerator applications.

  3. 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.

  4. 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…

  5. 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

  6. Laser-wakefield accelerators for medical phase contrast imaging: Monte Carlo simulations and experimental studies

    NASA Astrophysics Data System (ADS)

    Cipiccia, S.; Reboredo, D.; Vittoria, Fabio A.; Welsh, G. H.; Grant, P.; Grant, D. W.; Brunetti, E.; Wiggins, S. M.; Olivo, A.; Jaroszynski, D. A.

    2015-05-01

    X-ray phase contrast imaging (X-PCi) is a very promising method of dramatically enhancing the contrast of X-ray images of microscopic weakly absorbing objects and soft tissue, which may lead to significant advancement in medical imaging with high-resolution and low-dose. The interest in X-PCi is giving rise to a demand for effective simulation methods. Monte Carlo codes have been proved a valuable tool for studying X-PCi including coherent effects. The laser-plasma wakefield accelerators (LWFA) is a very compact particle accelerator that uses plasma as an accelerating medium. Accelerating gradient in excess of 1 GV/cm can be obtained, which makes them over a thousand times more compact than conventional accelerators. LWFA are also sources of brilliant betatron radiation, which are promising for applications including medical imaging. We present a study that explores the potential of LWFA-based betatron sources for medical X-PCi and investigate its resolution limit using numerical simulations based on the FLUKA Monte Carlo code, and present preliminary experimental results.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Pentabromophenol suppresses TGF-β signaling by accelerating degradation of type II TGF-β receptors via caveolae-mediated endocytosis

    PubMed Central

    Chen, Chun-Lin; Yang, Pei-Hua; Kao, Yu-Chen; Chen, Pei-Yu; Chung, Chih-Ling; Wang, Shih-Wei

    2017-01-01

    Pentabromophenol (PBP), a brominated flame retardant (BFR), is widely used in various consumer products. BFRs exert adverse health effects such as neurotoxic and endocrine-disrupting effects. In this study, we found that PBP suppressed TGF-β response by accelerating the turnover rate of TGF-β receptors. PBP suppressed TGF-β-mediated cell migration, PAI-1 promoter-driven reporter gene activation, and Smad2/3 phosphorylation in various cell types. Furthermore, PBP abolished TGF-β-mediated repression of E-cadherin expression, in addition to the induction of vimentin expression and N-cadherin and fibronectin upregulation, thus blocking TGF-β-induced epithelial–mesenchymal transition in A549 and NMuMG cells. However, this inhibition was not observed with other congeners such as tribromophenol and triiodophenol. TGF-β superfamily members play key roles in regulating various biological processes including cell proliferation and migration as well as cancer development and progression. The results of this in vitro study provide a basis for studies on the detailed relationship between PBP and modulation of TGF-β signalling. Because PBP is similar to other BFRs such as polybrominated diphenyl ethers (PBDEs), additional laboratory and mechanistic studies should be performed to examine BFRs as potential risk factors for tumorigenesis and other TGF-β-related diseases. PMID:28230093

  12. 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.

  13. Degradation of electron-irradiated polyethylene studied by positron annihilation lifetime spectroscopy

    NASA Astrophysics Data System (ADS)

    Onodera, K.; Oka, T.; Kino, Y.; Sekine, T.

    2017-01-01

    Degradation of electron beam irradiated high-density polyethylene was studied by positron annihilation lifetime spectroscopy (PALS), micro-FT-IR, and gel fraction measurements. The obtained results indicated that ortho-positronium intensity is influenced not only by the irradiation but also the post oxidation, which illustrates that PALS may be a promising tool to monitor/evaluate the degradation of polyethylene induced by irradiation and long-term storage.

  14. YOUNG SUPERNOVAE AS EXPERIMENTAL SITES FOR STUDYING THE ELECTRON ACCELERATION MECHANISM

    SciTech Connect

    Maeda, Keiichi

    2013-01-10

    Radio emissions from young supernovae ({approx}<1 year after the explosion) show a peculiar feature in the relativistic electron population at a shock wave, where their energy distribution is steeper than typically found in supernova remnants and than that predicted from the standard diffusive shock acceleration (DSA) mechanism. This has been especially established for the case for a class of stripped envelope supernovae (SNe IIb/Ib/Ic), where a combination of high shock velocity and low circumstellar material density makes it easier to derive the intrinsic energy distribution than in other classes of SNe. We suggest that this apparent discrepancy reflects a situation where the low energy electrons, before being accelerated by the DSA-like mechanism, are responsible for the radio synchrotron emission from young SNe, and that studying young SNe sheds light on the still-unresolved electron injection problem in the acceleration theory of cosmic rays. We suggest that the electron's energy distribution could be flattened toward high energy, most likely around 100 MeV, which marks a transition from inefficient to efficient acceleration. Identifying this feature will be a major advance in understanding the electron acceleration mechanism. We suggest two further probes: (1) millimeter/submillimeter observations in the first year after the explosion and (2) X-ray observations at about one year and thereafter. We show that these are reachable by ALMA and Chandra for nearby SNe.

  15. Efficiency of particle acceleration at interplanetary shocks: Statistical study of STEREO observations

    NASA Astrophysics Data System (ADS)

    Dresing, N.; Theesen, S.; Klassen, A.; Heber, B.

    2016-04-01

    Context. Among others, shocks are known to be accelerators of energetic charged particles. However, many questions regarding the acceleration efficiency and the required conditions are not fully understood. In particular, the acceleration of electrons by shocks is often questioned. Aims: In this study we determine the efficiency of interplanetary shocks for <100 keV electrons, and for ions at ~0.1 and ~2 MeV energies, as measured by the Solar Electron and Proton Telescope (SEPT) instruments aboard the twin Solar Terrestrial Relations Observatory (STEREO) spacecraft. Methods: We employ an online STEREO in situ shock catalog that lists all shocks observed between 2007 and mid 2014 (observed by STEREO A) and until end of 2013 (observed by STEREO B). In total 475 shocks are listed. To determine the particle acceleration efficiency of these shocks, we analyze the associated intensity increases (shock spikes) during the shock crossings. For the near-relativistic electrons, we take into account the issue of possible ion contamination in the SEPT instrument. Results: The highest acceleration efficiency is found for low energy ions (0.1 MeV), which show a shock-associated increase at 27% of all shocks. The 2 MeV ions show an associated increase only during 5% of the shock crossings. In the case of the electrons, the shocks are nearly ineffective. Only five shock-associated electron increases were found, which correspond to only 1% of all shock crossings.

  16. Monte Carlo study of backscatter in a flattening filter free clinical accelerator.

    PubMed

    Titt, U; Vassiliev, O N; Pönisch, F; Kry, S F; Mohan, R

    2006-09-01

    In conventional linear accelerators, the flattening filter provides a uniform lateral dose profile. In intensity modulated radiation therapy applications, however, the flatness of the photon field and hence the presence of a flattening filter, is not necessary. Removing the filter may provide some advantages, such as faster treatments and smaller out-of-field doses to the patients. In clinical accelerators the backscattered radiation dose from the collimators must be taken into account when the dose to the target volume in the patient is being determined. In the case of a conventional machine, this backscatter is known to great precision. In a flattening filter free accelerator, however, the amount of backscatter may be different. In this study we determined the backscatter contribution to the monitor chamber signal in a flattening filter free clinical accelerator (Varian Clinac 21EX) with Monte Carlo simulations. We found that with the exception of very small fields in the 18-MV photon mode, the contribution of backscattered radiation to the monitor signal did not differ from that of conventional machines with a flattening filter. Hence, a flattening filter free clinical accelerator would not necessitate a different backscatter correction.

  17. FT-IR and FT-Raman study of hydrothermally degraded groundwood containing paper

    NASA Astrophysics Data System (ADS)

    Proniewicz, Leonard M.; Paluszkiewicz, Czesława; Wesełucha-Birczyńska, Aleksandra; Barański, Andrzej; Dutka, Dorota

    2002-09-01

    Accelerated aging test of paper is used to understand mechanisms of acidic hydrolysis and oxidative degradation of cellulose, hemicellulose and lignin. In recent years FT-IR and FT-Raman spectroscopy have been used together with mass spectrometry and nuclear magnetic resonance as well as chemometrics methods to characterize degradation products of paper. In this work we present FT-IR and FT-Raman spectra of hydrothermally treated sample of acid paper (Paper 3—bleached sulfite softwood pulp) in extreme humid conditions (100% humidity and 100 °C). Degradation reaction is monitored mainly based on CO stretching vibrations formed during the process of carbonyl compounds, however, some changes in CC stretching vibrations are also noticed. We showed that in these conditions paper undergoes oxidation process in which at least three new carbonyl species that can be characterized by their CO stretches are formed. Additionally, during this process, one can observe disappearance of the CC stretching that can be associated with changes that involve, for example, coniferyl alcohol. We also show that water molecules play very important role in this process. Thus, we report here, changes caused by hydrothermal treatment of groundwood containing paper mainly associated with the appearance of new carbonyl species, besides others, as well as rearrangement of existing hydrogen bond network.

  18. 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

  19. Accelerated hydrolysis of substituted cellulose for potential biofuel production: kinetic study and modeling.

    PubMed

    Mu, Bingnan; Xu, Helan; Yang, Yiqi

    2015-11-01

    In this work, kinetics of substitution accelerated cellulose hydrolysis with multiple reaction stages was investigated to lay foundation for mechanism study and molecular design of substituting compounds. High-efficiency hydrolysis of cellulose is critical for cellulose-based bioethanol production. It is known that, substitution could substantially decrease activation energy and increase reaction rate of acidic hydrolysis of glycosidic bonds in cellulose. However, reaction kinetics and mechanism of the accelerated hydrolysis were not fully revealed. In this research, it was proved that substitution therefore accelerated hydrolysis only occurred in amorphous regions of cellulose fibers, and was a process with multiple reaction stages. With molar ratio of substitution less than 1%, the overall hydrolysis rate could be increased for around 10 times. We also quantified the relationship between the hydrolysis rate of individual reaction stage and its major influences, including molar ratio of substitution, activation energy of acidic hydrolysis, pH and temperature.

  20. The CASPAR underground accelerator facility for the study of low energy nuclear astrophysics

    NASA Astrophysics Data System (ADS)

    Robertson, Daniel; Couder, Manoel; Greife, Uwe; Strieder, Frank; Wiescher, Michael

    2016-09-01

    The drive of nuclear astrophysics is to push the limits of reaction measurements into the burning regime of astrophysical interest. As current laboratory experiments approach the stellar burning window, the rapid drop off of cross-sections is a significant barrier and drives the need for higher intensity accelerators, more robust and isotopically enriched target material and lower background interference. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to the lower energies needed. The CASPAR facility is the first and only underground accelerator facility in the US, focused on the study of low energy reactions of nuclear astrophysical interest. Support provided by NSF Grant No. PHY 1419765, JINA-CEE Grant No. PHY 1430152 and the South Dakota Science and Technology Authority.

  1. [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.

  2. 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.

    2003-01-01

    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 identi@ 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 were 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/or a long-system particle in cell simulation to model the magnetically connected region between the two satellites. Results from the study indicate that there are three main drivers of auroral acceleration: (1) field-aligned currents that lead to quasistatic parallel potential drops (parallel electric fields), (2) earthward flow of high-energy plasma beams from the magnetotail into the auroral zone that lead to quasistatic parallel potential drops, and (3) large-amplitude Alfven waves that propagate into the auroral region from the magnetotail. The events examined thus far confm the previously established invariant latitudinal dependence of the drivers and show a strong dependence on magnetic activity. Alfven waves tend to occur primarily at the poleward edge of the auroral region during more magnetically active times and are correlated with intense electron precipitation. At lower latitudes away

  3. 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.

  4. 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.

  5. A Numerical and Experimental Study of a Shock-Accelerated Heavy Gas Cylinder

    SciTech Connect

    Zoldi, Cindy Anne

    2002-01-01

    In this thesis we study the evolution of an SF6 gas cylinder surrounded by air when accelerated by a planar Mach 1.2 shock wave. Vorticity generated by the interaction of the shock wave's pressure gradient with the density gradient at the air/SF6 interface drives the evolution of the cylinder into a vortex pair

  6. 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…

  7. 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…

  8. 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.

  9. 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…

  10. [Study on the selective removal of plasma low-density lipoprotein and fibrinogen by degraded carrageenan].

    PubMed

    Cong, Haixia; Yin, Liang; Fang, Bo; Du, Longbing; Zhao, Hui; Chen, Jingling; You, Chao

    2010-08-01

    The selective removal of low density lipoprotein (LDL) and fibrinogen (Fib) by degraded carrageenan was studied by the present authors. Degraded carrageenan was prepared by acid with carrageenan as the main material. The effects of acid conditions on the molecular weight were investigated, and the proper reaction conditions were ascertained. The results of infrared spectrometry indicated that the degraded carrageenan is a heparin-like polysaccharide. Then the selective removal of LDL/Fibrinogen by degraded carrageenan was studied. When molecular weight was about 10,000, pH was 5.10 and the concentration of degraded carrageenan was 800 mg/L, the average reduction percentages were 60.0% for total cholesterol(TC), 79.4% for LDL and very low-density lipoprotein (VLDL), and 93.8% for fibrinogen. There were no significant changes with relation to the level of high-density lipoprotein (HDL) and total protein (TP). So, degraded carrageenan was shown to be of good selectivity on plasma LDL/Fibrinogen apheresis.

  11. 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.

  12. Ultra-performance liquid chromatography quadrupole time-of-flight MS for identification of electron beam from accelerator degradation products of aflatoxin B1.

    PubMed

    Wang, Ruiqi; Liu, Ruijie; Chang, Ming; Jin, Qingzhe; Huang, Jianhua; Liu, Yuanfa; Wang, Xingguo

    2015-02-01

    Electron beam irradiation was proven to be a successful method in aflatoxin degradation in earlier researches. However, the exact nature of the result radiation products generated by the aflatoxins remains unknown. Based on ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF MS) analysis, the solution of aflatoxin B1 (AFB1) in acetonitrile irradiated by electron beam degraded to two kinds of major products. The doses employed were in the range of 0 (control) to 8.60 kGy. The absorbed doses were monitored with FWT-60-00 radio-chromic dosimeters. By using UPLC-Q-TOF MS, accurate masses and proposed molecular formula for the degradation products, 261.1233 m/z (C14H13O5) and 299.1104 m/z (C17H15O5), were obtained from low mass error and high matching properties. Structural formula for the radio-degradation products and the degradation pathways leading to the compounds were proposed, based on the molecular formula and MS-MS spectra. The results showed that electron beam (EB) irradiation is an effective method for degrading AFB1.

  13. Study on degrading graphene oxide in wastewater under different conditions for developing an efficient and economical degradation method.

    PubMed

    Li, Ting; Zhang, Chao-Zhi; Gu, Chengyue

    2017-02-13

    With popular application of graphene and graphene oxide (GO), they have been discharged into water. Graphene and GO harm organisms. However, an efficient and economical method for removing graphene and GO in wastewater has seldom been reported. Graphene can be oxidized by hydrogen peroxide to give GO; therefore, degradation of graphene oxide is an important step in the procedure of removal of graphene from water. In this paper, GO degradation via photo-Fenton reaction under different conditions was carried out. Experimental results suggested that GO in wastewater can be efficiently and economically degraded into carbon dioxide and H2O when pH value is 3, concentration of H2O2 and FeCl3 are 35 mM and 5 ppm, respectively. Degradation mechanism of GO was suggested based on UV-vis absorption spectra, scanning electron microscopy, X-ray diffraction and liquid chromatography-mass spectra data of degradation intermediates. This paper suggests an efficient and economical degradation way of GO in wastewater.

  14. Fe-Mn alloys for metallic biodegradable stents: degradation and cell viability studies.

    PubMed

    Hermawan, Hendra; Purnama, Agung; Dube, Dominique; Couet, Jacques; Mantovani, Diego

    2010-05-01

    Biodegradable stents have shown their potential to be a valid alternative for the treatment of coronary artery occlusion. This new class of stents requires materials having excellent mechanical properties and controllable degradation behaviour without inducing toxicological problems. The properties of the currently considered gold standard material for stents, stainless steel 316L, were approached by new Fe-Mn alloys. The degradation characteristics of these Fe-Mn alloys were investigated including in vitro cell viability. A specific test bench was used to investigate the degradation in flow conditions simulating those of coronary artery. A water-soluble tetrazolium test method was used to study the effect of the alloy's degradation product to the viability of fibroblast cells. These tests have revealed the corrosion mechanism of the alloys. The degradation products consist of metal hydroxides and calcium/phosphorus layers. The alloys have shown low inhibition to fibroblast cells' metabolic activities. It is concluded that they demonstrate their potential to be developed as degradable metallic biomaterials.

  15. Study of photocatalytic degradation of tributyltin, dibutylin and monobutyltin in water and marine sediments.

    PubMed

    Brosillon, Stephan; Bancon-Montigny, Chrystelle; Mendret, Julie

    2014-08-01

    This study reports on the first assessment of the treatment of sediments contaminated by organotin compounds using heterogeneous photocatalysis. Photocatalysis of organotins in water was carried out under realistic concentration conditions (μgL(-1)). Degradation compounds were analyzed by GC-ICP-MS; a quasi-complete degradation of tributyltin (TBT) in water (99.8%) was achieved after 30min of photocatalytic treatment. The degradation by photolysis was about (10%) in the same conditions. For the first time decontamination of highly polluted marine sediments (certified reference material and harbor sediments) by photocatalysis proves that the use of UV and the production of hydroxyl radicals are an efficient way to treat organotins adsorbed onto marine sediment despite the complexity of the matrix. In sediment, TBT degradation yield ranged from 32% to 37% after only 2h of irradiation (TiO2-UV) and the by-products: dibutyltin (DBT) and monobutyltin (MBT) were degraded very rapidly in comparison with TBT. It was shown that during photocatalysis of organotins in sediments, the hydroxyl radical attack and photolysis are the two ways for the degradation of adsorbed TBT.

  16. Activity and adaptation of nitrilotriacetate (NTA)-degrading bacteria: field and laboratory studies

    NASA Technical Reports Server (NTRS)

    McFeters, G. A.; Egli, T.; Wilberg, E.; Alder, A.; Schneider, R.; Suozzi, M.; Giger, W.

    1990-01-01

    Adaptation of bacterial activity for the degradation of nitrilotriacetate (NTA) was studied using natural sediment samples and an NTA-degrading bacterium (strain ATCC 29600). Sediment samples from a river with persistent levels of NTA had much higher NTA-degradative activity than comparable samples from a less contaminated control site. When sediment from the control site was exposed to high levels of NTA a 5 day lag preceded an abrupt increase in NTA degradation while strain 29600 colonized on sand and grown in the absence of NTA became induced within eight hours. The induction of strain 29600 was compared between bacteria in suspension and cells attached to sand. The sand-associated bacteria became induced 4 to 5 h before the planktonic suspension and displayed over threefold greater specific activity. Suspensions of strain 29600 became adapted within 8 h when placed in membrane diffusion chambers that were immersed within a municipal wastewater reactor containing NTA. These findings support the concept that induction is a part of the process of bacterial adaptation to degrade NTA and sand-associated bacteria can adapt more quickly to and have a greater degradative activity for NTA than planktonic cells.

  17. Degradation of polysorbates 20 and 80: studies on thermal autoxidation and hydrolysis.

    PubMed

    Kishore, Ravuri S K; Pappenberger, Astrid; Dauphin, Isabelle Bauer; Ross, Alfred; Buergi, Beatrice; Staempfli, Andreas; Mahler, Hanns-Christian

    2011-02-01

    The purpose of this work was to study the mechanistic pathways of degradation of polysorbates (PS) 20 and PS80 in parenteral formulations. The fate of PS in typical protein formulations was monitored and analyzed by a variety of methods, including (1)H NMR, high-performance liquid chromatography/evaporative light scattering detection, and ultraviolet-visible spectroscopy. Oxidative degradation of PS in neat raw material was studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and headspace gas chromatography-mass spectrometry. TGA-DSC studies revealed that autoxidation via a radical mechanism is dominated by statistical random scission in PS20 and PS80. Thermal initiation of radical formation occurs at the polyoxyethylene (POE) as well as the olefin sites. In PS80, radical initiation at the olefinic site precedes initiation at the POE site, leading to modified degradation profile. Corresponding to these results, in aqueous formulations, a surge peroxide content was detected in PS20-containing samples and in higher concentrations in those containing PS80. Hydrolysis in aqueous formulations, as followed by (1)H NMR, was found to have a half-life of 5 months at 40°C. On the basis of the obtained results, PSs degrade mainly via autoxidation and also via hydrolysis at higher temperatures. Further studies are required to investigate on potential effects of degradation on surface activity and protein stability in PS-containing formulations.

  18. Studies of Ion Acceleration from Thin Solid-Density Targets on High-Intensity Lasers

    NASA Astrophysics Data System (ADS)

    Willis, Christopher R.

    Over the past two decades, a number of experiments have been performed demonstrating the acceleration of ions from the interaction of an intense laser pulse with a thin, solid density target. These ions are accelerated by quasi-static electric fields generated by energetic electrons produced at the front of the target, resulting in ion energies up to tens of MeV. These ions have been widely studied for a variety of potential applications ranging from treatment of cancer to the production of neutrons for advanced radiography techniques. However, realization of these applications will require further optimization of the maximum energy, spectrum, or species of the accelerated ions, which has been a primary focus of research to date. This thesis presents two experiments designed to optimize several characteristics of the accelerated ion beam. The first of these experiments took place on the GHOST laser system at the University of Texas at Austin, and was designed to demonstrate reliable acceleration of deuterium ions, as needed for the most efficient methods of neutron generation from accelerated ions. This experiment leveraged cryogenically cooled targets coated in D2 O ice to suppress the protons which typically dominate the accelerated ions, producing as many as 2 x 1010 deuterium ions per 1 J laser shot, exceeding the proton yield by an average ratio of 5:1. The second major experiment in this work was performed on the Scarlet laser system at The Ohio State University, and studied the accelerated ion energy, yield, and spatial distribution as a function of the target thickness. In principle, the peak energy increases with decreasing target thickness, with the thinnest targets accessing additional acceleration mechanisms which provide favorable scaling with the laser intensity. However, laser prepulse characteristics provide a lower bound for the target thickness, yielding an optimum target thickness for ion acceleration which is dependent on the laser system. This

  19. A Kinetic Degradation Study of Curcumin in Its Free Form and Loaded in Polymeric Micelles.

    PubMed

    Naksuriya, Ornchuma; van Steenbergen, Mies J; Torano, Javier S; Okonogi, Siriporn; Hennink, Wim E

    2016-05-01

    Curcumin, a phenolic compound, possesses many pharmacological activities and is under clinical evaluation to treat different diseases. However, conflicting data about its stability have been reported. In this study, the kinetic degradation of curcumin from a natural curcuminoid mixture under various conditions (pH, temperature, and dielectric constant of the medium) was investigated. Moreover, the degradation of pure curcumin at some selected conditions was also determined. To fully solubilize curcumin and to prevent precipitation of curcumin that occurs when low concentrations of co-solvent are present, a 50:50 (v/v) aqueous buffer/methanol mixture was used as standard medium to study its degradation kinetics. The results showed that degradation of curcumin both as pure compound and present in the curcuminoid mixture followed first order kinetic reaction. It was further shown that an increasing pH, temperature, and dielectric constant of the medium resulted in an increase in the degradation rate. Curcumin showed rapid degradation due to autoxidation in aqueous buffer pH = 8.0 with a rate constant of 280 × 10(-3) h(-1), corresponding with a half-life (t1/2) of 2.5 h. Dioxygenated bicyclopentadione was identified as the final degradation product. Importantly, curcumin loaded as curcuminoid mixture in ω-methoxy poly (ethylene glycol)-b-(N-(2-benzoyloxypropyl) methacrylamide) (mPEG-HPMA-Bz) polymeric micelles and in Triton X-100 micelles was about 300-500 times more stable than in aqueous buffer. Therefore, loading of curcumin into polymeric micelles is a promising approach to stabilize this compound and develop formulations suitable for further pharmaceutical and clinical studies.

  20. Sediment and nutrient loading from non-degraded and degraded watershed area in to a tropical water body: a case study using remote sensing

    NASA Astrophysics Data System (ADS)

    Gupta, Mool Chandra

    2006-12-01

    The present study deals with the works relating to integrated watershed management on sustainable basis for evolving tractable operational package so that nutrient, sediment and runoff losses from catchment could be minimized. Study area lies between latitudes 22°5' and 22°12' and longitudes 77°17' and 77°23' covering an area of 6357.5 hectares. Physically it is divided into two different parts, hills and plains. The height of elevation of study area is in between 518 to 630 meters above m.s.l. The thematic maps were generated using satellite data. The present tropical catchment possessing diverse forest ecosystem and agriculture land characterized by weathered black cotton soil derived from basalt with the slope ranging from nearly level to moderately steep to steep sloping and receiving average annual rainfall 1150 mm. The annual return of carbon and nutrient (N, P, K, Ca, Na and Mg) in non degraded and degraded forest and nutrient concentrations in runoff flow and sediment output (sediment loss) during monsoon period from non-degraded forest, degraded forest and agriculture lands were worked out. The sediment and nutrient losses from the catchment to the tropical water body are alarming particularly from agricultural land. The nutrient losses in both the forms (runoff water plus sediment movement) are in the order of agriculture > degraded forest > non-degraded forest. The loss of soil in the form of sediment loss follows the same pattern. The results were alarming when the value of sediment loss of forest was compared to the agriculture land of the catchment. The soil loss as sediment is 33.5 times greater in agriculture land compared to non-degraded forest and 10.2 times greater in agriculture land compared to degraded forest.

  1. 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.

  2. 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.

  3. 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.

  4. Quantification of omeprazole degradation by enteric coating polymers: an UV-VIS spectroscopy study.

    PubMed

    Riedel, A; Leopold, C S

    2005-02-01

    The aim of this study was to investigate the degradation of the acid-labile proton-pump-inhibitor omeprazole in organic polymer solutions and aqueous dispersions of enteric coating polymers by UV spectroscopy. Furthermore, data were compared with those obtained in a previous HPLC study. For comparative purposes the cationic Eudragit RS 100 and the monomeric acid acetic acid were included in this study. The discolorations of degraded omeprazole solutions were analysed by VIS spectroscopy. UV-VIS spectra were recorded after preparation of the solutions and after 180 min of storage. The change of absorption was calculated as the difference of the absorption values at 305 nm. Degradation of omeprazole depends on the amount of acidic groups in the polymer structure. This decomposition manifests itself in a shifting of the absorption maximum to lower wavelengths and a decrease of absorption intensity. UV-VIS spectroscopy was used to determine the extent of degradation induced by enteric polymers. A good correlation of these results with previous HPLC data was found when excluding UV absorbing polymers. Nevertheless, values obtained by UV-VIS spectroscopy were always lower than those obtained by HPLC. For evaluation of the discoloration of degraded omeprazole solutions, VIS spectroscopy is a simple and fast method.

  5. 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.

  6. 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.

  7. 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.

  8. Degradation and rejuvenation studies of AC electroluminescent ZnS:Cu,Cl phosphors

    NASA Astrophysics Data System (ADS)

    Stanley, Jacob; Jiang, Yu; Bridges, Frank; Carter, Sue A.; Ruhlen, Laurel

    2010-02-01

    We report detailed degradation and rejuvenation studies of AC electroluminescence (EL) of the phosphor ZnS:Cu,Cl, aiming to better understand the physical mechanisms that control EL emission. We find that the AC EL emission spectra vary considerably with the AC driving frequency but all spectra can be fit to a sum of four Gaussians. During degradation, although there is a large overall decrease in amplitude, the shape of the emission spectra measured at a given AC frequency does not change. Annealing the samples after they are significantly degraded can rejuvenate the phosphors with a maximum rejuvenation occurring (for fixed annealing times) near 180 °C. Further, these test cells can be degraded and rejuvenated multiple times. However studies at slightly higher annealing temperatures (240 °C) show significant thermal degradation and, perhaps more importantly, a change in the spectral shape; this likely indicates that two distinct mechanisms are then operative. In extended x-ray absorption fine structure (EXAFS) experiments we find that the CuS nanoprecipitates in the ZnS host (~75% of the Cu is in the CuS precipitates) do not change significantly after the 240 °C anneal; these experiments also provide a more detailed comparison of the local structure about Cu in pure CuS, and in ZnS:Cu,Cl. In addition, the EXAFS experiments also place an upper limit on the fraction of possible interstitial Cu sites, proposed as a blue emission center, at less than 10%. The combined experiments place strong constraints on the mechanisms for degradation and rejuvenation and suggest that EL degradation is most likely caused by either Cu or Cl diffusion under high E-fields, while thermal diffusion at slightly elevated temperatures without E-fields present, re-randomizes the (isolated) dopant distributions. Higher T anneals appear to damage the sharp tips on the precipitates.

  9. 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.

  10. The Dust Accelerator Facility of the Colorado Center for Lunar Dust and Atmospheric Studies

    SciTech Connect

    Horanyi, M.; Colette, A.; Drake, K.; Gruen, E.; Kempf, S.; Munsat, T.; Robertson, S.; Shu, A.; Sternovsky, Z.; Wang, X.

    2011-11-29

    The NASA Lunar Institute's Colorado Center for Lunar Dust and Atmospheric Studies has recently completed the construction of a new experimental facility to study hypervelocity dust impacts. The installation includes a 3 MV Pelletron, accelerating small particles in the size range of 0.1 to few microns to velocities in the range of 1 to 100 km/s. Here we report the capabilities of our facility, and the results of our first experiments.

  11. Design Study of Linear Accelerator-Based Positron Re-Emission Microscopy

    NASA Astrophysics Data System (ADS)

    Ogawa, Hiroshi; Kinomura, Atsushi; Oshima, Nagayasu; Suzuki, Ryoichi; O'Rourke, Brian E.

    In order to shorten the acquisition time of positron re-emission microscopy (PRM), a linear accelerator (LINAC)-based PRM system has been studied. The beam focusing system was designed to obtain a high brightness positron beam on the PRM sample. The beam size at the sample was calculated to be 0.8mm (FWHM), and the positron intensity within the field of view of the PRM was more than one order of magnitude higher in comparison with the previous studies.

  12. Effect of floating toes on knee and trunk acceleration during walking: a preliminary study

    PubMed Central

    Uritani, Daisuke; Sakamoto, Chinatsu; Fukumoto, Takahiko

    2017-01-01

    [Purpose] This study investigated the effect of floating toes on knee and trunk acceleration during walking in experimental setting. [Subjects and Methods] Twelve healthy volunteers walked barefoot at a preferred speed along a linear pathway under 2 conditions: normal gait (control) condition and floating toes (FT) condition. In the latter, weight bearing by the toes was avoided using kinesiology tape applied along the toe extensors. Accelerations of the knee (Kn) and lumbar spine (Lx) were assessed using triaxial accelerometers mounted on the right fibular head and the spinous process of L3. Acceleration vectors were oriented such that the anterior, right, and cranial deviations were positive along the anteroposterior, lateral, and vertical axes, respectively. The root mean squares (RMSs; anteroposterior, RMSap; lateral, RMSl; vertical, RMSv) were calculated, and the mean values of 3 trials in each condition were determined. Differences between the conditions were assessed using the Wilcoxon signed-rank test. [Results] LxRMSap and LxRMSv were larger in the FT condition than in the control condition. KnRMSv tended to be higher in the FT condition than in the control condition. [Conclusion] Floating toes increase acceleration and might create mechanical stress on the lower back and knee during walking. PMID:28265174

  13. 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

  14. Infrared spectrometric study of acid-degradable glasses.

    PubMed

    De Maeyer, E A P; Verbeeck, R M H; Vercruysse, C W J

    2002-08-01

    The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass.

  15. 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.

  16. 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.

  17. Magneto-hydrodynamics simulation study of deflagration mode in co-axial plasma accelerators

    NASA Astrophysics Data System (ADS)

    Sitaraman, Hariswaran; Raja, Laxminarayan L.

    2014-01-01

    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.

  18. 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.

  19. 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.

  20. 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.

  1. A Critical Appraisal of Quantitative Studies of Protein Degradation in the Framework of Cellular Proteostasis

    PubMed Central

    Alvarez-Castelao, Beatriz; Ruiz-Rivas, Carmen; Castaño, José G.

    2012-01-01

    Protein homeostasis, proteostasis, is essential to understand cell function. Protein degradation is a crucial component of the proteostatic mechanisms of the cell. Experiments on protein degradation are nowadays present in many investigations in the field of molecular and cell biology. In the present paper, we focus on the different experimental approaches to study protein degradation and present a critical appraisal of the results derived from steady-state and kinetic experiments using detection of unlabelled and labelled protein methodologies with a proteostatic perspective. This perspective allows pinpointing the limitations in interpretation of results and the need of further experiments and/or controls to establish “definitive evidence” for the role of protein degradation in the proteostasis of a given protein or the entire proteome. We also provide a spreadsheet for simple calculations of mRNA and protein decays for mimicking different experimental conditions and a checklist for the analysis of experiments dealing with protein degradation studies that may be useful for researchers interested in the area of protein turnover. PMID:23119163

  2. Chlorpyrifos and Endosulfan degradation studies in an annular slurry photo reactor.

    PubMed

    Sivagami, K; Vikraman, B; Krishna, R Ravi; Swaminathan, T

    2016-12-01

    TiO2 is one of those compounds which are highly used in photocatalytic degradation of substrates using UV radiation. The substrates are degraded oxidatively and hence finds an important position in advanced oxidation for water/wastewater treatment processes. The thrust of this research was to evaluate the effectiveness of Heterogeneous Photocatalysis (HP) technique, for the removal of pesticides from water/wastewater. The photo-catalytic degradation of two pesticides, widely used in India, viz., Endosulfan (ES) and Chlorpyriphos (CPS) was studied in an annular slurry photo reactor under UVillumination at 254nm. Results revealed that the degradation rate is significantly affected by the initial pesticide concentration, pH of the solution and catalyst concentration. Batch degradation studies on Endosulphan and Chlorpyrifos were conducted in the concentration range from 5 to 25mg/L at a pH ranging from 3.5 to 10.5 and at a catalyst loading of 0.5-2g/L. Endosulphan removal efficiency was about 80-99% and chlorpyrifos removal efficiency was about 84-94%. L-H rate constants were determined using L-H kinetics. High removal efficiencies obtained (80-99%) indicate the effectiveness of this process and its potential for practical application.

  3. 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.

  4. Benzene degradation coupled with chlorate reduction in a soil column study.

    PubMed

    Tan, N C G; van Doesburg, W; Langenhoff, A A M; Stams, A J M

    2006-03-01

    Perchlorate and chlorate are electron acceptors that during reduction result in the formation of molecular oxygen. The produced oxygen can be used for activation of anaerobic persistent pollutants, like benzene. In this study chlorate was tested as potential electron acceptor to stimulate benzene degradation in anoxic polluted soil column. A chlorate amended benzene polluted soil column was operated over a period of 500 days. Benzene was immediately degraded in the column after start up, and benzene removal recovered completely after omission of chlorate or a too high influent chlorate concentration (22 mM). Mass balance calculations showed that per mole of benzene five mole of chlorate were reduced. At the end of the experiment higher loading rates were applied to measure the maximal benzene degradation rate in this system; a breakthrough of benzene was not observed. The average benzene degradation rate over this period was 31 micromol l(-1) h(-1) with a maximal of 78 micromol l(-1) h(-1). The high degradation rate and the necessity of chlorate indicate that oxygen produced during chlorate reduction indeed is used for the activation of benzene. This is the first column study where benzene biodegradation at a high rate coupled with anaerobic chlorate reduction is observed.

  5. 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.

  6. 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.

  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. Glyphosate degradation by immobilized bacteria: laboratory studies showing feasibility for glyphosate removal from waste water.

    PubMed

    Heitkamp, M A; Adams, W J; Hallas, L E

    1992-09-01

    To evaluate immobilized bacteria technology for the removal of low levels of glyphosate (N-phosphonomethylglycine) from aqueous industrial effluents, microorganisms with glyphosate-degrading activity obtained from a fill and draw enrichment reactor inoculated with activated sludge were first exposed to glyphosate production wastes containing 500-2000 mg glyphosate/L. The microorganisms were then immobilized by adsorption onto a diatomaceous earth biocarrier contained in upflow Plexiglas columns. The columns were aerated, maintained at pH 7.0-8.0, incubated at 25 degrees C, supplemented with NH4NO3 (50 mg/L), and exposed to glyphosate process wastes pumped upflow through the biocarrier. Glyphosate degradation to aminomethylphosphonic acid was initially > 96% for 21 days of operation at flows yielding hydraulic residence times (HRTs) as short as 42 min. Higher flow rate studies showed > 98% removal of 50 mg glyphosate/L from the waste stream could be achieved at a HRT of 23 min. Glyphosate removal of > 99% at a 37-min HRT was achieved under similar conditions with a column inoculated with a pure culture of Pseudomonas sp. strain LBr, a bacterium known to have high glyphosate-degrading activity. After acid shocking (pH 2.8 for 18 h) of a column of immobilized bacteria, glyphosate-degrading activity was regained within 4 days without reinoculation. Although microbial growth and glyphosate degradation were not maintained under low organic nutrient conditions in the laboratory, the low levels of degradable carbon (45-94 mg/L) in the industrial effluent were sufficient to support prolonged glyphosate-degrading activity. The results demonstrated that immobilized bacteria technology is effective in removing low levels of glyphosate in high-volume liquid waste streams.

  9. Internalization and degradation of human chorionic gonadotropin in ovine luteal cells: Kinetic studies

    SciTech Connect

    Ahmed, C.E.; Sawyer, H.R.; Niswender, G.D.

    1981-11-01

    Ovine luteal cells grown in suspensions and/or monolayer culture were used to study the rates of internalization and degradation of (/sup 125/I)hCG. At specified times after a 5- to 7-min exposure to (/sup 125/I)hCG, cells were treated with acidic buffer (pH 3.9) to elute membrane-bound hormone, which left the internalized radioactivity associated with the cell pellet. Radioactivity released into the medium during the incubation periods was subjected to 20% trichloroacetic acid and/or thin layer chromatography to monitor the extent of degradation of the radioactive hormone. Secretion of progesterone into the medium and exclusion of trypan blue were used to monitor the viability of the cells in each experiment. Radioactivity was lost from the plasma membrane with a tsub1/2 of 9.6 h, with approximately 85% of the radioactivity being lost within 24 h. Cell-associated radioactivity increased linearly with time to a plateau at 4 h, remained stable until 12 h, and then decreased between 12-24 h. The plateau between 4-12 h reflected an equilibrium between the (/sup 125/I)hCG which was internalized and degraded and the (/sup 125/I)hCG which was released into the medium. The degraded (/sup 125/I)hCG increased essentially linearly up to 24 h. These data suggest that the majority of (/sup 125/I)hCG bound to receptors in luteal cells is internalized and degraded. Less than 20% of the radioactivity bound initially to cells dissociated into the incubation medium and was trichloroacetic acid precipitable within 24 h. The internalization and degradation of (/sup 125/I)hCG was temperature dependent, with essentially no hCG internalized and/or degraded at 4C.

  10. 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

  11. The Small C-terminal Domain Phosphatase 1 Inhibits Cancer Cell Migration and Invasion by Dephosphorylating Ser(P)68-Twist1 to Accelerate Twist1 Protein Degradation.

    PubMed

    Sun, Tong; Fu, Junjiang; Shen, Tao; Lin, Xia; Liao, Lan; Feng, Xin-Hua; Xu, Jianming

    2016-05-27

    Twist1 is a basic helix-loop-helix transcription factor that strongly promotes epithelial-to-mesenchymal transition, migration, invasion, and metastasis of cancer cells. The MAPK-phosphorylated Twist1 on its serine 68 (Ser(P)(68)-Twist1) has a significantly enhanced stability and function to drive cancer cell invasion and metastasis. However, the phosphatase that dephosphorylates Ser(P)(68)-Twist1 and destabilizes Twist1 has not been identified and characterized. In this study, we screened a serine/threonine phosphatase cDNA expression library in HEK293T cells with ectopically coexpressed Twist1. We found that the small C-terminal domain phosphatase 1 (SCP1) specifically dephosphorylates Ser(P)(68)-Twist1 in both cell-free reactions and living cells. SCP1 uses its amino acid residues 43-63 to interact with the N terminus of Twist1. Increased SCP1 expression in cells decreased Ser(P)(68)-Twist1 and total Twist1 proteins, whereas knockdown of SCP1 increased Ser(P)(68)-Twist1 and total Twist1 proteins. Furthermore, the levels of SCP1 are negatively correlated with Twist1 protein levels in several cancer cell lines. SCP1-dephosphorylated Twist1 undergoes fast degradation via the ubiquitin-proteasome pathway. Importantly, an increase in SCP1 expression in breast cancer cells with either endogenous or ectopically expressed Twist1 largely inhibits the Twist1-induced epithelial-to-mesenchymal transition phenotype and the migration and invasion capabilities of these cells. These results indicate that SCP1 is the phosphatase that counterregulates the MAPK-mediated phosphorylation of Ser(68)-Twist1. Thus, an increase in SCP1 expression and activity may be a useful strategy for eliminating the detrimental roles of Twist1 in cancer cells.

  12. PLK1 and HOTAIR Accelerate Proteasomal Degradation of SUZ12 and ZNF198 during Hepatitis B Virus-Induced Liver Carcinogenesis.

    PubMed

    Zhang, Hao; Diab, Ahmed; Fan, Huitao; Mani, Saravana Kumar Kailasam; Hullinger, Ronald; Merle, Philippe; Andrisani, Ourania

    2015-06-01

    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/c-myc 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. Because 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.

  13. The Role of the Interface in Thin Film and Droplet Accelerated Reactions Studied by Competitive Substituent Effects.

    PubMed

    Li, Yafeng; Yan, Xin; Cooks, R Graham

    2016-03-01

    Based on a study of competitive substituent effects in a Claisen-Schmidt reaction, interfacial effects have been shown to play an important role in accelerated reactions that occur in thin films and droplets. A role for the interface in an accelerated C-C bond-formation reaction between 6hydroxy-1-indanone and aromatic aldehydes is indicated by cooperative interactions between p-methylbenzaldehyde and p-nitrobenzaldehyde. Additional acceleration over that occurring in bulk reactions is seen for p-methylbenzaldehyde, but only in the presence of p-nitrobenzaldehyde. A decrease in the degree of acceleration is detected when the reaction is forced electrostatically to occur inside the thin film, and the interface is shown to participate in the accelerated reactions. This experimental evidence for interfacial thin film and droplet acceleration supports a recent model and builds on earlier work which locates molecules within evaporating droplets in electrosprays.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Accelerator mass spectrometry-enabled studies: current status and future prospects

    PubMed Central

    Arjomand, Ali

    2010-01-01

    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. PMID:20440378

  19. 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.

  20. Study on degradation of dimethoate solution in ultrasonic airlift loop reactor.

    PubMed

    Liu, Yue-Nan; Jin, Dong; Lu, Xiao-Ping; Han, Ping-Fang

    2008-07-01

    In this work, the degradation of dimethoate solution in ultrasonic airlift loop reactor (UALR) assisted with advanced oxidation processes was studied. The effects of O3 flow rate, ultrasonic intensity, pH value and reaction temperature on the degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O3 transfer rate. Under the optimal operation conditions: ultrasonic irradiation time was 4h, O3 flow rate was 0.41 m3h(-1), ultrasonic intensity was 4.64 W cm(-2), pH value was 10.0, reaction temperature was 25 degrees C, and initial concentration of dimethoate was 20 mg L(-1), degradation rate of dimethoate increased to 90.8%. The experimental results indicated that the method of UALR degradation of organic pollutants in the presence of gas could reduce reaction time and improve degradation rate. UALR was an advisable choice for treating organic waste waters and this device could be easily scale up. Thus this process has wide application prospect in industry.

  1. [Studies on photo-electron-chemical catalytic degradation of the malachite green].

    PubMed

    Li, Ming-yu; Diao, Zeng-hui; Song, Lin; Wang, Xin-le; Zhang, Yuan-ming

    2010-07-01

    A novel two-compartment photo-electro-chemical catalytic reactor was designed. The TiO2/Ti thin film electrode thermally formed was used as photo-anode, and graphite as cathode and a saturated calomel electrode (SCE) as the reference electrode in the reactor. The anode compartment and cathode compartment were connected with the ionic exchange membrane in this reactor. Effects of initial pH, initial concentration of malachite green and connective modes between the anode compartment and cathode compartment on the decolorization efficiency of malachite green were investigated. The degradation dynamics of malachite green was studied. Based on the change of UV-visible light spectrum, the degradation process of malachite green was discussed. The experimental results showed that, during the time of 120 min, the decolouring ratio of the malachite green was 97.7% when initial concentration of malachite green is 30 mg x L(-1) and initial pH is 3.0. The catalytic degradation of malachite green was a pseudo-first order reaction. In the degradation process of malachite green the azo bond cleavage and the conjugated system of malachite green were attacked by hydroxyl radical. Simultaneity, the aromatic ring was oxidized. Finally, malachite green was degraded into other small molecular compounds.

  2. 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.

  3. Abiotic degradation of plastic films

    NASA Astrophysics Data System (ADS)

    Ángeles-López, Y. G.; Gutiérrez-Mayen, A. M.; Velasco-Pérez, M.; Beltrán-Villavicencio, M.; Vázquez-Morillas, A.; Cano-Blanco, M.

    2017-01-01

    Degradable plastics have been promoted as an option to mitigate the environmental impacts of plastic waste. However, there is no certainty about its degradability under different environmental conditions. The effect of accelerated weathering (AW), natural weathering (NW) and thermal oxidation (TO) on different plastics (high density polyethylene, HDPE; oxodegradable high density polyethylene, HDPE-oxo; compostable plastic, Ecovio ® metalized polypropylene, PP; and oxodegradable metalized polypropylene, PP-oxo) was studied. Plastics films were exposed to AW per 110 hours; to NW per 90 days; and to TO per 30 days. Plastic films exposed to AW and NW showed a general loss on mechanical properties. The highest reduction in elongation at break on AW occurred to HDPE-oxo (from 400.4% to 20.9%) and was higher than 90% for HDPE, HDPE-oxo, Ecovio ® and PP-oxo in NW. No substantial evidence of degradation was found on plastics exposed to TO. Oxo-plastics showed higher degradation rates than their conventional counterparts, and the compostable plastic was resistant to degradation in the studied abiotic conditions. This study shows that degradation of plastics in real life conditions will vary depending in both, their composition and the environment.

  4. Aperture studies of the BNL colliding beam accelerator with reduced superperiodicity

    SciTech Connect

    Dell, G.F.

    1983-01-01

    Chromatic properties of the Brookhaven CBA (Colliding Beam Accelerator) with one low ..beta.. insertion in each of the three superperiods have been studied using the PATRICIA particle tracking program. Systematic multipoles of order 5 < n less than or equal to 10 as well as random multipoles of order 1 less than or equal to n less than or equal to 10 are, along with random closed orbit errors and sagitta effects, included when determining the aperture of the lattice. 3 references, 6 figures.

  5. LANL sunnyside experiment: Study of neutron production in accelerator-driven targets

    NASA Astrophysics Data System (ADS)

    Morgan, G.; Butler, G.; Cappiello, M.; Carius, S.; Daemen, L.; DeVolder, B.; Frehaut, J.; Goulding, C.; Grace, R.; Green, R.; Lisowski, P.; Littleton, P.; King, J.; King, N.; Prael, R.; Stratton, T.; Turner, S.; Ullmann, J.; Venneri, F.; Yates, M.

    1995-09-01

    Measurements have been made of the neutron production in prototypic targets for accelerator driven systems. Studies were conducted on four target assemblies containing lead, lithium, tungsten, and a thorium-salt mixture. Integral data on total neutron production were obtained as well as more differential data on neutron leakage and neutron flux profiles in the blanket/moderator region. Data analysis on total neutron production is complete and shows excellent agreement with calculations using the LAHET/MCNP code system.

  6. Central California studies on the degradation and movement of aldicarb residues

    NASA Astrophysics Data System (ADS)

    Jones, Russell L.

    1987-03-01

    Studies to measure the degradation and movement of aldicarb residues in the unsaturated and saturated zone were conducted during 1984 at three central California locations. These test sites, which consist of a tomato field near Manteca and vineyards near Livingston and Fresno are representative of conditions in central California under which aldicarb residues are most likely to reach drinking-water supplies. Results indicate that aldicarb residues degrade in the unsaturated zone with a half-life of 1.5-2.0 months. In areas with shallow water tables (less than three meters deep), traces of aldicarb residues may occasionally enter the upper one to five meters of the saturated zone where they degrade before reaching deeper, potable water supplies.

  7. 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.

  8. Identification of four new degradation products of epirubicin through forced degradation, LC-UV, MSn and LC-MS-TOF studies.

    PubMed

    Kaushik, Dheeraj; Saini, Balraj; Bansal, Gulshan

    2015-01-01

    Epirubicin (EPI) was subjected to International Conference on Harmonization recommended forced degradation under the conditions of hydrolysis, oxidation, dry heat and photolysis to characterize its possible impurities and/or degradation products. The drug was found highly unstable to alkaline hydrolysis even at room temperature, unstable to acid hydrolysis at 80°C and to oxidation at room temperature. The hydrolytic and oxidative degradation products were resolved on an Agilent RP8 (150 mm × 4.6 mm; 5 µm) column with isocratic elution using mobile phase composed of ammonium formate (10 mM, pH 3.0), acetonitrile and methanol. The drug degraded to four oxidative products (O-I, O-II, O-III and O-IV) and to one acid hydrolyzed product (A-I). Purity of each peak in liquid chromatography-ultraviolet (LC-UV) chromatogram was ascertained through photodiode array (LC-PDA) analysis. The products were characterized through electrospray ionization-mass spectrometry (+ESI-MS(n)) studies on EPI and liquid chromatography-time of flight mass spectrometry (LC-MS-TOF) studies on degraded drug solutions. The products, O-I-O-IV, were characterized as 2-hydroxy-8-desacetylepirubicin-8-hydroperoxide, 4-hydroxy-8-desacetylepirubicin-8-hydroperoxide, 8-desacetylepirubicin-8-hydroperoxide and 8-desacetylepirubicin, respectively, and product A-I was characterized as deglucosaminylepirubicin. While A-I was found to be a pharmacopoeial impurity, all oxidative products were found to be new degradation impurities. The mechanisms and pathways of degradation of EPI were discussed and outlined.

  9. Functional Studies of β-Glucosidases of Cytophaga hutchinsonii and Their Effects on Cellulose Degradation

    PubMed Central

    Bai, Xinfeng; Wang, Xifeng; Wang, Sen; Ji, Xiaofei; Guan, Zhiwei; Zhang, Weican; Lu, Xuemei

    2017-01-01

    Cytophaga hutchinsonii can rapidly digest crystalline cellulose without free cellulases or cellulosomes. Its cell-contact cellulose degradation mechanism is unknown. In this study, the four β-glucosidase (bgl) genes in C. hutchinsonii were singly and multiply deleted, and the functions of these β-glucosidases in cellobiose and cellulose degradation were investigated. We found that the constitutively expressed BglB played a key role in cellobiose utilization, while BglA which was induced by cellobiose could partially make up for the deletion of bglB. The double deletion mutant ΔbglA/bglB lost the ability to digest cellobiose and could not thrive in cellulose medium, indicating that β-glucosidases were important for cellulose degradation. When cultured in cellulose medium, a small amount of glucose accumulated in the medium in the initial stage of growth for the wild type, while almost no glucose accumulated for ΔbglA/bglB. When supplemented with a small amount of glucose, ΔbglA/bglB started to degrade cellulose and grew in cellulose medium. We inferred that glucose might be essential for initiating cellulose degradation, and with additional glucose, C. hutchinsonii could partially utilize cellulose without β-glucosidases. We also found that there were both cellulose binding cells and free cells when cultured in cellulose. Since direct contact between C. hutchinsonii cells and cellulose is necessary for cellulose degradation, we deduced that the free cells which were convenient to explore new territory in the environment might be fed by the adherent cells which could produce cello-oligosaccharide and glucose into the environment. This study enriched our knowledge of the cellulolytic pathway of C. hutchinsonii. PMID:28210251

  10. Functional Studies of β-Glucosidases of Cytophaga hutchinsonii and Their Effects on Cellulose Degradation.

    PubMed

    Bai, Xinfeng; Wang, Xifeng; Wang, Sen; Ji, Xiaofei; Guan, Zhiwei; Zhang, Weican; Lu, Xuemei

    2017-01-01

    Cytophaga hutchinsonii can rapidly digest crystalline cellulose without free cellulases or cellulosomes. Its cell-contact cellulose degradation mechanism is unknown. In this study, the four β-glucosidase (bgl) genes in C. hutchinsonii were singly and multiply deleted, and the functions of these β-glucosidases in cellobiose and cellulose degradation were investigated. We found that the constitutively expressed BglB played a key role in cellobiose utilization, while BglA which was induced by cellobiose could partially make up for the deletion of bglB. The double deletion mutant ΔbglA/bglB lost the ability to digest cellobiose and could not thrive in cellulose medium, indicating that β-glucosidases were important for cellulose degradation. When cultured in cellulose medium, a small amount of glucose accumulated in the medium in the initial stage of growth for the wild type, while almost no glucose accumulated for ΔbglA/bglB. When supplemented with a small amount of glucose, ΔbglA/bglB started to degrade cellulose and grew in cellulose medium. We inferred that glucose might be essential for initiating cellulose degradation, and with additional glucose, C. hutchinsonii could partially utilize cellulose without β-glucosidases. We also found that there were both cellulose binding cells and free cells when cultured in cellulose. Since direct contact between C. hutchinsonii cells and cellulose is necessary for cellulose degradation, we deduced that the free cells which were convenient to explore new territory in the environment might be fed by the adherent cells which could produce cello-oligosaccharide and glucose into the environment. This study enriched our knowledge of the cellulolytic pathway of C. hutchinsonii.

  11. A Study on Factors Affecting the Degradation of Magnesium and a Magnesium-Yttrium Alloy for Biomedical Applications

    PubMed Central

    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

  12. 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

  13. 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.

  14. openSE: a Systems Engineering Framework Particularly Suited to Particle Accelerator Studies and Development Projects

    SciTech Connect

    Bonnal, P.; Féral, B.; Kershaw, K.; Nicquevert, B.; Baudin, M.; Lari, L.; Le Cardinal, J.

    2016-07-15

    Particle accelerator projects share many characteristics with industrial projects. However, experience has shown that best practice of industrial project management is not always well suited to particle accelerator projects. Major differences include the number and complexity of technologies involved, the importance of collaborative work, development phases that can last more than a decade, and the importance of telerobotics and remote handling to address future preventive and corrective maintenance requirements due to induced radioactivity, to cite just a few. The openSE framework it is a systems engineering and project management framework specifically designed for scientific facilities’ systems and equipment studies and development projects. Best practices in project management, in systems and requirements engineering, in telerobotics and remote handling and in radiation safety management were used as sources of inspiration, together with analysis of current practices surveyed at CERN, GSI and ESS.

  15. 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.

  16. 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…

  17. A computational study of dielectric photonic-crystal-based accelerator cavities

    NASA Astrophysics Data System (ADS)

    Bauer, C. A.

    Future particle accelerator cavities may use dielectric photonic crystals to reduce harmful wakefields and increase the accelerating electric field (or gradient). Reduced wakefields are predicted based on the bandgap property of some photonic crystals (i.e. frequency-selective reflection/transmission). Larger accelerating gradients are predicted based on certain dielectrics' strong resistance to electrical breakdown. Using computation, this thesis investigated a hybrid design of a 2D sapphire photonic crystal and traditional copper conducting cavity. The goals were to test the claim of reduced wakefields and, in general, judge the effectiveness of such structures as practical accelerating cavities. In the process, we discovered the following: (1) resonant cavities in truncated photonic crystals may confine radiation weakly compared to conducting cavities (depending on the level of truncation); however, confinement can be dramatically increased through optimizations that break lattice symmetry (but retain certain rotational symmetries); (2) photonic crystal cavities do not ideally reduce wakefields; using band structure calculations, we found that wakefields are increased by flat portions of the frequency dispersion (where the waves have vanishing group velocities). A complete comparison was drawn between the proposed photonic crystal cavities and the copper cavities for the Compact Linear Collider (CLIC); CLIC is one of the candidates for a future high-energy electron-positron collider that will study in greater detail the physics learned at the Large Hadron Collider. We found that the photonic crystal cavity, when compared to the CLIC cavity: (1) can lower maximum surface magnetic fields on conductors (growing evidence suggests this limits accelerating gradients by inducing electrical breakdown); (2) shows increased transverse dipole wakefields but decreased longitudinal monopole wakefields; and (3) exhibits lower accelerating efficiencies (unless

  18. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    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.

  19. 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.

  20. Artificially controlled degradable inorganic nanomaterial for cancer theranostics.

    PubMed

    Liu, Yuxin; Zhang, Ge; Guo, Quanwei; Ma, Liyi; Jia, Qi; Liu, Lidong; Zhou, Jing

    2017-01-01

    Multifunctional nanomaterials for cancer diagnosis and therapy have recently prompted widespread concern. To avoid nanotoxicity, the development of novel degradable functional materials must be our main focus. In this study, we firstly developed ethylenediaminetetraacetic acid calcium disodium salt (EDTA)- and bovine serum albumin (BSA)-capped Mn3O4 nanoparticles (MONPs-BSA-EDTA) as a novel inorganic nanomaterials for multifunctional imaging-guided photothermal therapy, which can be degraded in a progress-controlled way by artificially introduced ascorbic acid. The degradation products can also be captured and their excretion accelerated. Careful studies suggested that the toxicity of the MONPs-BSA-EDTA and its degradation products is low. The degradation mechanism also suggests a new method of controlled drug release. The development of artificially controlled degradable inorganic nanomaterials also provides a new way to degrade nanomaterials and minimize ion release, which may have potential applications in cancer theranostics without nanotoxicity.

  1. 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.

  2. 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.

  3. An experimental study of nonlinear waves produced by an accelerating plate

    NASA Astrophysics Data System (ADS)

    Yang, S. A.; Chwang, Allen T.

    1992-11-01

    The free-surface flow generated by an impulsively accelerating, surface-piercing, vertical plate has been studied experimentally in an open channel of constant depth. The flat vertical plate is fixed on a towing carriage that is set off by suddenly dropping a weight bucket through a connecting steel cable in a pulley system. The free-surface profile in front of the plate and the pressure distribution on the plate surface are measured for three different accelerations of the plate. A capacitance-type wave gauge is used to measure the variations of the water surface, while a variable reluctance pressure transducer is used to measure the pressure on the plate surface. The acceleration of the plate is obtained by means of an accelerometer. All response voltage outputs are recorded on an IBM PC-XT personal computer with a data-acquisition electrical board. Experimental measurements are compared with the numerical, viscous-flow results of Yang and Chwang (IIHR Report No. 332; Iowa Institute of Hydraulic Research, The University of Iowa, 1989) and the analytical, inviscid-flow solution of Chwang [Phys. Fluids 26, 383 (1983)]. The agreement of the free-surface profile and the pressure distribution between the numerical results and the present experimental measurements is fairly good. However, the inviscid-flow solution overpredicts the wave amplitude and the pressure distribution on the plate. In the physical experiments, the water surface is observed to rise in front of the vertical plate where the potential-flow theory becomes singular.

  4. 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.

  5. 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.

  6. 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.

  7. 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...

  8. A comparative kinetics study of thermal degradation of some novel ABA block copolymers

    NASA Astrophysics Data System (ADS)

    Blanco, Ignazio; Cicala, Gianluca; Mamo, Antonino; Latteri, Alberta; Recca, Antonino

    2012-07-01

    Some novel ABA block copolymers, synthesized with three different molecular weights, where the block A is a PPO while the block B is a random copoly(aryl ether sulfone), were studied by TGA and DTA techniques, in both flowing nitrogen and static air atmosphere, in order to draw useful information about their resistance to thermal degradation. The results obtained for the various compounds investigated were discussed and compared with each other and a thermal stability classifications in the studied environments were made.

  9. 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

  10. Stress degradation studies and stability-indicating TLC-densitometric method of glycyrrhetic acid

    PubMed Central

    2013-01-01

    Background Glycyrrhetic acid, a pentacyclic triterpenoid, possesses a broad range of pharmacological activities and serves as template to synthesize many bioactive drugs. This paper describes a simple, accurate, and sensitive stability-indicating TLC densitometric method for the determination of glycyrrhetic acid and its degradation product as per the ICH guidelines. Results Separation was carried out on TLC aluminium sheet pre-coated with silica gel 60F254 using chloroform, methanol and formic acid (9:0.9:0.1, v/v). Compact spot for glycyrrhetic acid was found at Rf value of 0.42 ± 0.03. Densitometric analysis was carried out in the absorbance mode at λmax 254 nm. Glycyrrhetic acid was found to be stable to the exposure of base, neutral, oxidation, dry heating treatment and wet heating treatment, but showed degradation under acidic and photochemical conditions. Moreover, fragmentation pattern of glycyrrhetic acid was developed by using a positive ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QqTOF-MS/MS) hybrid instrument. A photo-degraded product was characterized through comparison of mass spectrometric studies with glycyrrhetic acid. Conclusion The developed stability-indicating TLC-densitometric method can be applied for routine analysis of glycyrrhetic acid in the presence of its degradation products. PMID:23327365

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. [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.

  17. Photochemical Degradation of Persistent Organic Pollutants: A Study of Ice Photochemistry Mediated by Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Pierce, B.; Grannas, A. M.

    2010-12-01

    Contamination and accumulation of persistent organic pollutants (POPs) in the Arctic, an area previously considered as pristine and removed from human influence, has become a growing concern. Volatile and semi-volatile contaminants from lower latitudes are transported to the Arctic through a process known as global distillation. The polar regions are unique in that they sit in darkness during the winter until polar sunrise. These conditions allow pollutants to accumulate during winter and then undergo 24-hours of continuous irradiance in sunlit conditions. Photochemical degradation may thus be an important pathway to consider in the spring/summer Arctic season. Additionally, active photochemistry has also been observed in mid-latitude snowpacks. However, the potential photodegradation of anthropogenic contaminants in mid-latitude snow has received little attention in the literature. Aldrin, a once globally distributed pesticide, is of particular environmental concern due to its low solubility in water, known persistence in the environment, and its ability to degrade into environmentally persistent products. To investigate the potential photochemical degradation of aldrin, samples of aqueous aldrin solution (20 µg/L), in liquid and frozen phases, were irradiated under Q-Panel 340 lamps to simulate the UV radiation profile of natural sunlight. Following irradiation, samples were extracted with organic solvent containing an internal standard for GC-ECD analysis. Results indicated that frozen samples degrade more quickly than liquid samples. Photochemical half lives for frozen and liquid samples were found to be approximately 13.5 hours and 45 hours respectively. It was found that the addition of natural organic matter increased the aldrin degradation rate significantly. Ongoing studies will further evaluate the differences in liquid and frozen reactivity and the influence of different sources of natural organic matter.

  18. Degradation Study on Sulfasalazine and a Validated HPLC-UV Method for its Stability Testing.

    PubMed

    Saini, Balraj; Bansal, Gulshan

    2014-01-01

    Sulfasalazine (SSZ) was subjected to degradation under the conditions of hydrolysis (acid, alkali, and water), oxidation (30% H2O2), dry heat, and photolysis (UV-VIS light) in accordance with the ICH guidelines. An RP-HPLC method was developed to study the degradation behavior. No degradation was noted under any condition except alkaline hydrolysis where SSZ was degraded to a single minor product. SSZ was optimally resolved from this product on an XTerra(®) RP18 column with a mobile phase composed of methanol and an ammonium acetate buffer (10 mM, pH 7.0) (48:52, v/v) delivered at a rate of 0.8 mL/min in an isocratic mode. The method was validated and found to be linear (r(2)=0.99945), precise (%RSD <2), robust, and accurate (94-102%) in the concentration range of 0.5-50 μg/mL of SSZ. The PDA analysis of the degraded sample revealed the SSZ peak purity to be 998.99 and the drug peak eluted with a resolution factor of >2 from the nearest resolving peak, indicating the method to be selectively stability-indicating for the drug analysis. The method was applied successfully for the stability testing of the commercially available SSZ tablets that were under varied ICH-prescribed conditions. An explanation for the unusual stability of the drug when exposed to acidic hydrolysis, despite the presence of the sulfonamide linkage, is also discussed.

  19. 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.

  20. Compatibility and accelerated aging study for Li(Si)/FeS2 thermally activated batteries

    NASA Astrophysics Data System (ADS)

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

    Thermally activated batteries using Li(Si)/FeS2 for use in systems which require a storage life of 25 years and high reliability are examined. All of the materials in the system, both organic and inorganic are incorporated except the heat paper and electric match are studied. No compatibility or aging problems are indicated. The following results are reported: oxygen vanishes from the overgas in containers that were accelerated aged; hydrogen increases sharply in the overgas initially but generally decreases as aging progresses. No unexpected or significant changes were observed in the volume resistivity, glass transition temperature, or shear modulus or organic materials.

  1. Experimental Study on the Control of the Supersonic Axisymmetric Intake under the Acceleration/Deceleration Conditions

    NASA Astrophysics Data System (ADS)

    Kojima, Takayuki; Sato, Tetsuya; Tanatsugu, Nobuhiro; Enomoto, Yoshinari

    A control system of variable geometry mixed compression axisymmetric intake is experimentally studied at ONERA S3 supersonic wind tunnel. The acceleration/deceleration of the space plane is simulated by changing the free stream velocity. The intake is successfully controlled with 90% of the maximum total pressure recovery and mass capture ratio. In this experiment, two subjects about control of axisymmetric intake are also cleared. First, the effect of the trapping of the terminal shock by bleed holes causes the disturbances in the terminal shock control system. Second, a special compression form change operation is necessary when the intake compression form change from all external compression to mixed compression.

  2. 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.

  3. 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

  4. Hydrolytic Degradation of Poly(L-Lactide-co-Glycolide) Studied by Positron Annihilation Lifetime Spectroscopy and Other Techniques

    NASA Astrophysics Data System (ADS)

    Pamuła, E.; Dryzek, E.; Dobrzyński, P.

    2006-11-01

    Changes of the poly(L-lactide-co-glycolide) structure as a function of degradation time in phosphate-buffered saline for 7 weeks were investigated by gel permeation chromatography, differential scanning calorimetry, nuclear magnetic resonance (1H NMR), and positron annihilation lifetime spectroscopy. Surface properties as wettability by sessile drop and topography by atomic force microscopy were also characterized. Chain-scission of polyester bonds in hydrolysis reaction causes a quite uniform decrease in molecular weight, and finally results in an increase in semicrystallinity. Molecular composition of the copolymer and water contact angle do not change considerably during degradation time. Atomic force microscopy studies suggest that the copolymer degrades by "in bulk" mechanism. The average size of the molecular-level free volume holes declines considerably after one week of degradation and remains constant till the sixth week of degradation. The free volume fraction decreases as a function of degradation time.

  5. PARTICLE ACCELERATOR

    DOEpatents

    Teng, L.C.

    1960-01-19

    ABS>A combination of two accelerators, a cyclotron and a ring-shaped accelerator which has a portion disposed tangentially to the cyclotron, is described. Means are provided to transfer particles from the cyclotron to the ring accelerator including a magnetic deflector within the cyclotron, a magnetic shield between the ring accelerator and the cyclotron, and a magnetic inflector within the ring accelerator.

  6. 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.

  7. High Power Accelerator and Magnetically Insulated Ion Diode for Ion Ring Studies.

    NASA Astrophysics Data System (ADS)

    Jones, Stephen Edward

    Ion ring generation for Cornell University's Megavolt Ion Coil Experiment (MICE) requires a suitable pulsed power accelerator to drive a high-power magnetically insulated ion diode. The diode then emits an intense ion-beam which forms an ion ring by using a cusped magnetic field. The goal of this thesis is to provide the necessary beam to form the ion-ring, and the present work consists of two parts: (1) the design, construction, testing, and operation of the pulsed power accelerator; and (2) the design, construction, testing, operation, and physics studies of a magnetically insulated diode for ion ring generation. For the required pulsed-power driver, we use a modified 2-MV, 100 kJ Marx generator, connected to a new 2-Omega-200-nsec pulse-forming line. For the diode, we use a novel applied-B, extraction diode with anode-side as well as cathode-side coils. This coil arrangement forms an easily variable pseudo-separatrix within the gap allowing flexibility for diode studies and optimization. Diode investigations reveal the efficacy of such a pseudo-separatrix located in the gap near the flashboard, in terms of anode turn-on and ion beam current. Further results (1) support the hypothesis that leakage electrons to the flashboard are instrumental for anode turn-on, (2) indicate that the gap electron-population has two different electron sources, and (3) discuss the possible long development time scale for diode development. Extensive computer simulations have also been conducted on the accelerator and diode, and results are compared with experiment. A driving constraint throughout this work is affordability on a university budget; also, unfortunately, some of the experiments had to be cut short due to funding cuts.

  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. 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.

  10. 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

  11. A Monte Carlo study of a flattening filter-free linear accelerator verified with measurements

    NASA Astrophysics Data System (ADS)

    Dalaryd, Mårten; Kragl, Gabriele; Ceberg, Crister; Georg, Dietmar; McClean, Brendan; Wetterstedt, Sacha af; Wieslander, Elinore; Knöös, Tommy

    2010-12-01

    A Monte Carlo model of an Elekta Precise linear accelerator has been built and verified by measured data for a 6 and 10 MV photon beam running with and without a flattening filter in the beam line. In this study the flattening filter was replaced with a 6 mm thick copper plate, provided by the linac vendor, in order to stabilize the beam. Several studies have shown that removal of the filter improves some properties of the photon beam, which could be beneficial for radiotherapy treatments. The investigated characteristics of this new beam included output, spectra, mean energy, half value layer and the origin of scattered photons. The results showed an increased dose output per initial electron at the central axis of 1.76 and 2.66 for the 6 and 10 MV beams, respectively. The number of scattered photons from the accelerator head was reduced by (31.7 ± 0.03)% (1 SD) for the 6 MV beam and (47.6 ± 0.02)% for the 10 MV beam. The photon energy spectrum of the unflattened beam was softer compared to a conventional beam and did not vary significantly with the off-axis distance, even for the largest field size (0-20 cm off-axis).

  12. Beam quality study for a grating-based dielectric laser-driven accelerator

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Jamison, S.; Xia, G.; Hanahoe, K.; Li, Y.; Smith, J. D. A.; Welsch, C. P.

    2017-02-01

    Dielectric laser-driven accelerators (DLAs) based on grating structures are considered to be one of the most promising technologies to reduce the size and cost of future particle accelerators. They offer high accelerating gradients of up to several GV/m in combination with mature lithographic techniques for structure fabrication. This paper numerically investigates the beam quality for acceleration of electrons in a realistic dual-grating DLA. In our simulations, we use beam parameters of the future Compact Linear Accelerator for Research and Applications facility to load an electron bunch into an optimized 100-period dual-grating structure where it interacts with a realistic laser pulse. The emittance, energy spread, and loaded accelerating gradient for modulated electrons are then analyzed in detail. Results from simulations show that an accelerating gradient of up to 1.13 ± 0.15 GV/m with an extremely small emittance growth, 3.6%, can be expected.

  13. Numerical Study of a Multi-stage Dielectric Laser-driven Accelerator

    NASA Astrophysics Data System (ADS)

    Wei, Yelong; Xia, Guoxing; Smith, Jonathan. D. A.; Hanahoe, Kieran; Mete, Oznur; Jamison, Steve P.; Welsch, Carsten P.

    In order to overcome the limits of commonly used radiofrequency accelerators, it is highly desirable to reduce the unit cost and increase the maximum achievable accelerating gradient. Dielectric laser-driven accelerators (DLAs) based on grating structures have received considerable attention due to maximum acceleration gradients of several GV/m and mature lithographic techniques for structure fabrication. This paper explores different spatial harmonics excited by an incident laser pulse and their interaction with the electron beam from the non-relativistic (25 keV) to the highly relativistic regime in double-grating silica structures. The achievable acceleration gradient for different spatial harmonics and the optimal compromise between maximum acceleration gradient and simplicity of structure fabrication are discussed. Finally, the suitability of a multi-stage DLA which would enable the acceleration of electrons from 25 keV to relativistic energies is discussed.

  14. A study on degradation mechanisms and low voltage operations in MNOS-type memory devices

    NASA Astrophysics Data System (ADS)

    Suzuki, E.

    1984-05-01

    Metal-nitride-oxide semiconductor (MNOS) type nonvolatile semiconductor memory devices that use electronic traps in the gate insulator as memory sites are studied. A method for measuring the separation of electrons and holes by utilizing the structure of insulated-gate field effect transistors is examined, and mechanisms of carrier conduction in MNOS structures are clarified. Degradation mechanisms of MNOS structure are investigated to improve the devices and to develop new memory devices. It is shown that positive holes, especially those injected from the gate into the nitride, play an important role in degrading the devices. A new electrically erasable programmable read-only memory with metal oxide nitride oxide semiconductor structures is proposed, and its superior memory properties are demonstrated.

  15. Preparation and antibacterial activity studies of degraded polysaccharide selenide from Enteromorpha prolifera.

    PubMed

    Lü, Haitao; Gao, Yujie; Shan, Hu; Lin, Yingting

    2014-07-17

    Polysaccharide extracted from Enteromorpha prolifera possessed excellent biological activities, but its molecular weight was greatly high which influenced the activity. Organic Se had higher biological activities and was safer than inorganic Se species. In the present study, degraded polysaccharide selenide (Se-LEP) was synthesized from sodium selenite and degraded polysaccharide (LEP) with the catalysis of nitric acid. The preparation conditions of LEP and Se-LEP were optimized by orthogonal experiments. The selenite ester group was formed, and the selenium content was 1335.27 µg/g. The thermal stability of Se-LEP decreased. LEP had less inhibitory effects on bacteria and plant pathogenic fungi. Se-LEP had stronger inhibitory effect on Eschetichia coli, and weaker inhibitory effect on Staphylococcus aureus than polysaccharide selenide (Se-EP). Se-LEP also had better inhibitory effects on plant pathogenic fungi.

  16. [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.

  17. Stress degradation studies of nelfinavir mesylate by Fourier transform infrared spectroscopy.

    PubMed

    Singh, Parul; Mehrotra, Ranjana; Bakhshi, A K

    2010-11-02

    Nelfinavir mesylate is the first nonpeptidic protease inhibitor available in pediatric formulation. In the present paper the stability of nelfinavir mesylate under different stress conditions is evaluated using Fourier transform infrared spectroscopy. The drug is subjected to thermal degradation, photodegradation, acid hydrolysis, base hydrolysis and oxidation as per ICH guidelines. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and high performance liquid chromatography (HPLC) are carried out to support the implementation of infrared spectroscopy for the stability studies of nelfinavir mesylate. Significant changes are observed in the IR spectra collected after exposing the drug to thermal radiations, acid and base hydrolysis and oxidative degradation. No change is observed in the spectra of the drug after exposing it to sunlight indicating the good photostability of nelfinavir mesylate. The results of infrared spectroscopy agree well with that of other complementary techniques as DSC, TGA, XRD and HPLC.

  18. Human hemoglobin structural and functional alterations and heme degradation upon interaction with benzene: A spectroscopic study.

    PubMed

    Hosseinzadeh, Reza; Moosavi-Movahedi, Ali Akbar

    2016-03-15

    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.

  19. 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.

  20. 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.

  1. Thermal degradation in a trimodal poly(dimethylsiloxane) network studied by (1)H multiple quantum NMR.

    PubMed

    Giuliani, Jason R; Gjersing, Erica L; Chinn, Sarah C; Jones, Ticora V; Wilson, Thomas S; Alviso, Cynthia T; Herberg, Julie L; Pearson, Mark A; Maxwell, Robert S

    2007-11-15

    Thermal degradation of a filled, cross-linked siloxane material synthesized from poly(dimethylsiloxane) chains of three different average molecular weights and with two different cross-linking species has been studied by (1)H multiple quantum (MQ) NMR methods. Multiple domains of polymer chains were detected by MQ NMR exhibiting residual dipolar coupling () values of 200 and 600 Hz, corresponding to chains with high average molecular weight between cross-links and chains with low average molecular weight between cross-links or near the multifunctional cross-linking sites. Characterization of the values and changes in distributions present in the material were studied as a function of time at 250 degrees C and indicate significant time-dependent degradation. For the domains with low , a broadening in the distribution was observed with aging time. For the domain with high , increases in both the mean and the width in were observed with increasing aging time. Isothermal thermal gravimetric analysis reveals a 3% decrease in weight over 20 h of aging at 250 degrees C. Degraded samples also were analyzed by traditional solid-state (1)H NMR techniques, and off-gassing products were identified by solid-phase microextraction followed by gas chromatography-mass spectrometry. The results, which will be discussed here, suggest that thermal degradation proceeds by complex competition between oxidative chain scissioning and postcuring cross-linking that both contribute to embrittlement.

  2. Reproductive effort accelerates actuarial senescence in wild birds: an experimental study.

    PubMed

    Boonekamp, Jelle J; Salomons, Martijn; Bouwhuis, Sandra; Dijkstra, Cor; Verhulst, Simon

    2014-05-01

    Optimality theories of ageing predict that the balance between reproductive effort and somatic maintenance determines the rate of ageing. Laboratory studies find that increased reproductive effort shortens lifespan, but through increased short-term mortality rather than ageing. In contrast, high fecundity in early life is associated with accelerated senescence in free-living vertebrates, but these studies are non-experimental. We performed lifelong brood size manipulation in free-living jackdaws. Actuarial senescence--the increase in mortality rate with age--was threefold higher in birds rearing enlarged- compared to reduced broods, confirming a key prediction of the optimality theory of ageing. Our findings contrast with the results of single-year brood size manipulation studies carried out in many species, in which there was no overall discernible manipulation effect on mortality. We suggest that our and previous findings are in agreement with predictions based on the reliability theory of ageing and propose further tests of this proposition.

  3. 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.

  4. In Vivo Lung Morphometry with Accelerated Hyperpolarized 3He Diffusion MRI: A Preliminary Study

    PubMed Central

    Chang, Yulin V.; Quirk, James D.; Yablonskiy, Dmitriy A.

    2014-01-01

    Purpose Parallel imaging can be used to reduce imaging time and to increase the spatial coverage in hyperpolarized gas MRI of the lung. In this proof-of-concept study we investigate the effects of parallel imaging on the morphometric measurement of lung microstructure using diffusion MRI with hyperpolarized 3He. Methods Fully sampled and under-sampled multi-b diffusion data were acquired from human subjects using an 8-channel 3He receive coil. A parallel imaging reconstruction technique (GRAPPA) was used to reconstruct under-sampled k-space data. The morphometric results of the GRAPPA-reconstructed data were compared with the results of fully sampled data for three types of subjects: healthy volunteers, mild, and moderate COPD patients. Results Morphometric measurements varied only slightly at mild acceleration factors. The results were largely well preserved compared to fully sampled data for different lung conditions. Conclusion Parallel imaging, given sufficient signal-to-noise ratio, provides a reliable means to accelerate hyperpolarized-gas MRI with no significant difference in the measurement of lung morphometry from the fully sampled images. GRAPPA is a promising technique to significantly reduce imaging time and/or to improve the spatial coverage for the morphometric measurement with hyperpolarized gases. PMID:24799044

  5. 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.

  6. Preliminary Study of the Effects of Prolonged Acceleration on Spinal Dynamics of Baboons. 1. Acceleration. 2. Biomechanical Analysis

    DTIC Science & Technology

    1981-06-01

    cortical thickness, increased diameter/cortlcal thickness ratio, thinned and distorted epiphyseal plate, and thickened condylar cartilage in female rats...histomorphometric and histodynamic (tetracycline fixation) studies were conducted on calcified sections by analyzing six bone parameters (e,g,, bone volume , relative...growth cartilage alterations, a decrease in bone volume without an Increase in osteocytic activity, and (by tetracycline fluroescent analysis) a reduced

  7. 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.

  8. The degradation of 14C-labelled drilling chemicals in a simulated seabed study

    NASA Astrophysics Data System (ADS)

    Eriksen, D. Ö.; Songe, P.; Schaanning, M. T.

    2003-01-01

    In an experiment, which lasted nine months, real sea bed sections and naturally occurring sediment dwelling organisms have been used to study the decomposition of today’s “green” chemicals, i.e. drilling mud chemicals comprising α-olefins or esters made from fatty acid extracted from fish. Both types have been shown to be degraded at aerobic conditions at sea bed. However, the fate of the alcoholic part of the ester has been unknown, as was the rate of degradation of the olefin. Both olefin and alcohol were labelled with 14C at the C1 atom. The results show that the ester hydrolyses quickly and after a lag phase the alcohol is oxidised, while the olefin degrades more slowly. 133Ba-labelled baryte was used as a bioturbidity marker. The measurements, i.e. scanned sediment columns, show very little bioturbation in the boxes where oil-contaminated sediment was present whereas the control boxes showed more activity from the sediment dwelling organisms down to the depth of the contaminated layer.

  9. Study of mechanical degradation of UHMWPE acetabular components due to clinical X-ray procedures.

    PubMed

    Vasconcellos, Letícia A; Blando, Eduardo; Souto, André A; Oliveira, Marilia G; Woitchunas, Gilséia F P; Hübler, Roberto

    2007-08-01

    The use of multi-component femoral implants to replace the femur head and re-establish bone motion has been widespread since the 70s. Frequently these implants have spherical metallic heads made of, for example, 316-L stainless steel or Cr-Co alloys, which allow rotational motion towards a polymeric component (UHMWPE). One of the major causes of implant rejection is the generation of UHMWPE debris on the surface between the implant head and the polymeric component. The gamma ray sterilization of implants and the periodical X-ray medical control could contribute to premature degradation of the polymeric surface, resulting in increased wear and shortened lifetime of the implant. In this work we study the degradation degree of the polymeric UHMWPE component as function of the X-ray dose. The elasto-plastic deformation and recovery were carried out by means of a nanohardness tester equipment and the polymer degradation was measured using a fast Fourier transform infra-red (FT-IR) equipment. The results show the compromise among the irradiation doses, the surface oxidation and the mechanical properties of the samples.

  10. A degradation study of cefepime hydrochloride in solutions under various stress conditions by TLC-densitometry.

    PubMed

    Dąbrowska, Monika; Starek, Małgorzata; Krzek, Jan; Papp, Elżbieta; Król, Piotr

    2015-03-01

    A rapid, accurate and sensitive thin-layer chromatography (TLC) method with densitometric detection has been developed and validated for the determination of cefepime in pharmaceuticals. Chromatographic separation was achieved on a silica gel TLC F254 plates with a mobile phase consisting of ethanol-2-propanol-glacial acetic acid 99.5%-water (4:4:1:3, v/v). Densitometric detection was carried out at wavelength of 266 nm in reflectance/absorbance mode. The validation of the method was found to be satisfactory with high accuracy (from 99.24 to 101.37%) and precision (RSD from 0.06 to 0.36%). Additionally, the stability of cefepime in solution was investigated, including the effect of pH, temperature and incubation time. Favorable retention parameters (Rf , Rs, α) were obtained under the developed conditions, which guaranteed good separation of the studied components. The degradation process of cefepime hydrochloride was described by kinetic and thermodynamic parameters (k, t0.1 , t0.5 and Ea ). Moreover, the chemical properties of degradation products were characterized by the Rf values, absorption spectra, HPLC-MS/MS and TLC-densitometry analysis. As the method could effectively separate the active substance from its main degradation product (1-methylpyrrolidine), it can be employed as a method to indicate the stability of this drug.

  11. 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.

  12. Study of novel pure culture HBCD-1, effectively degrading Hexabromocyclododecane, isolated from an anaerobic reactor.

    PubMed

    Peng, Xingxing; Huang, Xiangyan; Jing, Fei; Zhang, Zaili; Wei, Dongyang; Jia, Xiaoshan

    2015-06-01

    In this study, two pure strains, named HBCD-1 and HBCD-2, were isolated from a continuous anaerobic reactor over 300-days acclimation, which processed high capability of biodegrading Hexabromocyclododecane. Both of the two strains degraded HBCD diastereomers in different extents, especially strain HBCD-1, which interestingly degraded α-HBCD effectively. All of the degrading results were well fitted with the first-order kinetics model. By morphological observation and 16S rRNA gene sequence analysis, the strain HBCD-1 showed highest similarity with Achromobacter sp. Under the optimal culturing conditions of 30°C, pH 7 and the initial HBCD concentration of 500μg/L, the biodegradation rate of HBCD-1 reached 90% after 8days treatment. Moreover, during the biodegradation process by HBCD-1 strain, the concentration of bromide ion was lower than the theoretical value. Finally, 4 metabolites were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as well as a biodegradation pathway was proposed.

  13. Naphthalene degradation by catalytic ozonation based on nickel oxide: study of the ethanol as cosolvent.

    PubMed

    Aguilar, C Marissa; Rodríguez, Julia L; Chairez, Isaac; Tiznado, Hugo; Poznyak, Tatyana

    2016-01-30

    Naphthalene (NA) is a polycyclic aromatic hydrocarbon with toxic properties in aquatic systems. Ozonation (O3) and catalytic ozonation (O3-cat) processes are attractive alternatives of degradation for this kind of compound. NA (20 mg L(-1)) degradation by conventional and catalytic ozonation in the presence of a cosolvent (ethanol) was the aim of this study. This solution was proposed to simulate some aspects of real wastewaters where not only water acts as solvent. Two proportions of the mixture ethanol/water were selected (30:70 and 50:50) with the purpose of studying the cosolvent effect on NA degradation system by ozonation. O3-cat process used nickel oxide as catalyst (0.1 g L(-1)). The degradation analysis of NA by O3-cat in two different proportions of cosolvent showed that in the case of 30:70 (ethanol/water), a 95 % of NA elimination in 60 min was obtained, while in the case 50:50 (ethanol/water), only 55 % was achieved. The O3 process showed similar results of degradation to the initial compound in comparison with catalytic system. According to these results, there is an inhibition effect in pollutant removal by ethanol due to the higher ethanol concentration; the lower elimination rate of NA was obtained (by 40 % during the 60 min). The by-products analysis of ozonation process detected oxalic and formic acids. Treatments with NiO presented less production of organic acids in comparison with conventional ozonation process. The high concentration of ethanol has a relevant factor in the elimination of NA and formation of organic acids; samples with 50 % of cosolvent have showed a higher concentration of organic acids. X-ray photoelectron spectroscopy (XPS) study of O3-cat of diluent (O3-NiO control) and O3-NA-NiO showed the presence of -CO3 absorbed on catalyst due to ethanol decomposition.

  14. 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...

  15. Curing study of orthophtalic polyester resin: Effect on the degradation in saline environment

    NASA Astrophysics Data System (ADS)

    Sanchez Nacher, Lourdes

    Nowadays, composite materials based on a polymeric matrix are widely used in structural applications as engineering materials which offer high performances in advanced industrial sectors such as aerospace, aeronautical, transport, construction, etc. They can provide excellent mechanical and chemical properties, good chemical and weather resistance and low cost. Unsaturated polyester is one of the most used thermoset as a matrix for glass fibre reinforcements because of its good relationship properties/cost/quality, since it allows a more competitive cost. Due to the importance that this type of materials reach in some industrial sectors, it is important the mechanical behaviour evaluation as one of the priorities in practically any of their applications; also, it is important to keep in mind that most of industrial sectors that use this resin are subjected to extreme environmental conditions that can produce degradation in the material and therefore, chemical resistance of composites becomes a critical characteristic in those applications that require a contact with environmental agents that can induce some degradation processes and, consequently, a substantial change on general performance. The present study is focussed in the analysis of the effect of curing reaction of the thermosetting matrix of unsaturated orthophtalic polyester in the long term behaviour of materials made up of this type of matrix and glass fibre reinforcement. This is to determine the optimum processing conditions and its behaviour in an aggressive environment, concretely, marine environment. Considering this, crosslinking level of the resin is a decisive parameter, since we can expect lower saline water absorption for high crosslinking levels. The optimum processing conditions are those that permit to obtain the highest crosslinking level in the unsaturated polyester internal structure. Since the degradation effect is related to the crosslinking level of the internal structure, with the

  16. 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.

  17. 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.

  18. 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.

  19. Bilirubin degradation in methanol induced by continuous UV-B irradiation: a UHPLC--ESI-MS study.

    PubMed

    Stanojević, J S; Zvezdanović, J B; Marković, D Z

    2015-04-01

    Degradation of bilirubin in aerobic methanol solution by continuous UV-B irradiation has been investigated in this work. The purpose of this study was to shed more light on bilirubin interaction with the UV-B component of natural sunlight, since bilirubin is a very efficient UV-B absorber located in the skin epidermis. The degradation products have been detected and studied by a combined method of Ultra High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry (UHPLC-ESI-MS). Bilirubin, a toxic pigment which itself is a product of (hemoglobin) degradation in organisms, undergoes its own degradation under aerobic conditions of UV-B continuous irradiation (e.g. photooxidation) that can be partly self-sensitized. Two dipyrrolic structures have been identified as a result of the bilirubin degradation, not including the bilirubin derivative biliverdin whose increase in the irradiated system is synchronous with a time dynamics of bilirubin degradation. It appears that one of dipyrrolic products originates directly from bilirubin and biliverdin molecules, while the other one is probably connected to bilirubin self-sensitized degradation. The precursor role of biliverdin in the degradation process--related to the detected dipyrroles--has not been confirmed.

  20. A study on the effects of the proton flux on the irradiated degradation of GaAs/Ge solar cells

    NASA Astrophysics Data System (ADS)

    Jianmin, Hu; Yiyong, Wu; Dezhuang, Yang; Shiyu, He; Zhongwei, Zhang; Yong, Qian; Mengyan, Zhang

    2008-08-01

    Low-energy proton irradiation is one of the important factors which affect applications of GaAs solar cells in space. The proton flux encountered in orbit is much lower than that used during ground-base radiation experiments, thus ground-based experiments are a so-called accelerated simulating process. In this paper, effects of the proton flux on the degradation of GaAs/Ge solar cells using I- V measurements are investigated. The results indicate that low-energy irradiation seriously damages the solar cells. Regardless of the proton energy, the radiation flux shows no influence on the degradation process of the solar cell. The mechanisms for these effects are discussed in detail here.

  1. 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

  2. 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.

  3. 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.

  4. Active Vitamin D and Accelerated Progression of Aortic Stiffness in Hemodialysis Patients: A Longitudinal Observational Study

    PubMed Central

    Fortier, Catherine; Mac-Way, Fabrice; De Serres, Sacha A.; Marquis, Karine; Douville, Pierre; Desmeules, Simon; Larivière, Richard

    2014-01-01

    BACKGROUND We hypothesized that high-dose active vitamin D therapy in the form of alphacalcidol (α-calcidol), used to treat secondary hyperparathyroidism in chronic kidney disease, could lead to vascular calcification and accelerated progression of aortic stiffness. METHODS We conducted an observational study in 85 patients on chronic hemodialysis, among which 70 were taking a weekly dose of α-calcidol of <2 µg and 15 were taking a weekly dose of ≥2 µg (pharmacological dose). Parathyroid hormone, 25-hydroxyvitamin D, fibroblast growth factor 23, and α-klotho were determined. Aortic stiffness was assessed by determination of carotid–femoral pulse wave velocity (cf-PWV) at baseline and after a mean follow-up of 1.2 years. A multivariable regression model was used to evaluate the impact of pharmacological dose of α-calcidol on the progression of aortic stiffness. RESULTS At baseline, clinical, biological, and hemodynamic parameters were similar. At follow-up, cf-PWV increased more in patients with pharmacological dose of α-calcidol (0.583±2.291 m/s vs. 1.948±1.475 m/s; P = 0.04). After adjustment for changes in mean blood pressure and duration of follow-up, pharmacological dose of α-calcidol was associated with a higher rate of progression of cf-PWV (0.969 m/s; 95% confidence interval = 0.111–1.827; P = 0.03), and this association persisted after further adjustments for parameters of mineral metabolism. CONCLUSIONS In this study, pharmacological dose of α-calcidol was associated with accelerated progression of aortic stiffness. This study suggest that the vascular safety of active vitamin D posology may need to be specifically addressed in the treatment of chronic kidney disease–related bone mineral disorder. PMID:24695980

  5. 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

  6. Microdosing studies using accelerated mass spectrometry as exploratory investigational new drug trials.

    PubMed

    Bae, Soo Kyung; Shon, Ji-Hong

    2011-11-01

    Innovative attempts have been made to overcome nonproductivity and high expenditure in the clinical stages of new drug development. Microdosing studies using subpharmacological doses provide early insight into the body's disposition toward candidate compounds, and are innovative exploratory trials that can promote productivity in drug development. Highly sensitive analytical technology is crucial in microdosing studies that employ qualitative and quantitative assays of target materials in humans. Accelerator mass spectrometry (AMS) has facilitated the adoption of a human microdosing study in the early phase of clinical drug development. Results derived from AMS microdosing studies using labeled compounds can provide various types of information for candidate selection, including pharmacokinetic characteristics and metabolic profiles of candidate compounds. The applicability of microdosing studies is currently expanding into absolute bioavailability and mass balance studies. Although it remains uncertain whether microdosing adequately predicts the pharmacokinetics of therapeutic doses, further development of microdosing studies using AMS may benefit the field of new drug development and could pose a new challenge to researchers. The use of advanced technology in candidate selection will contribute to improved productivity and competitiveness in pharmaceutical research and development. The introduction of microdosing studies using AMS in Korea will present a newly applicable method for innovative clinical trials and contribute to development potential in global competition.

  7. 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.

  8. 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

  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. 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.

  11. Multi-spacecraft studies of the auroral acceleration region: From cluster to nanosatellites

    NASA Astrophysics Data System (ADS)

    Sadeghi, S.; Emami, M. R.

    2017-03-01

    This paper discusses the utilization of multiple Cubesats in various formations for studies in the auroral acceleration region. The focus is on the quasi-static properties, spatio-temporal features, electric potential structures, field-aligned currents, and their relationships, all of which are fundamentally important for an understanding of the magnetosphere-ionosphere coupling. It is argued that a multitude of nanosatellites can address some of the relevant outstanding questions in a broader range of spatial, temporal, and geometrical features, with higher redundancy and data consistency, potentially resulting in a shorter mission period and a higher chance of mission success. A number of mission concepts consisting of a cluster of 6-12 Cubesats with their specific onboard payloads are suggested for such missions over a period of as short as two months.

  12. 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.

  13. Physics and engineering studies on the MITICA accelerator: comparison among possible design solutions

    NASA Astrophysics Data System (ADS)

    Agostinetti, P.; Antoni, V.; Cavenago, M.; Chitarin, G.; Pilan, N.; Marcuzzi, D.; Serianni, G.; Veltri, P.

    2011-09-01

    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.

  14. An accelerator-based neutron microbeam system for studies of radiation effects.

    PubMed

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A; Bigelow, Alan W; Akselrod, Mark S; Sykora, Jeff G; Brenner, David J

    2011-06-01

    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.

  15. 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

  16. A mechanistic study of in vitro degradation of magnesium alloy using electrochemical techniques.

    PubMed

    Bobby Kannan, M; Singh, R K Raman

    2010-06-01

    To understand the in vitro degradation mechanism of magnesium alloy, electrochemical experiments viz., electrochemical impedance spectroscopy and potentiodynamic polarization, were carried out on AZ91 magnesium alloy under different experimental conditions. The study suggests: (i) the body temperature decreases significantly the corrosion resistance of the alloy, (ii) alkali-treatment of the alloy enhances the corrosion resistance, and (iii) although chloride in simulated body fluid minimizes the corrosion resistance, the presence of other constituents viz., phosphate, calcium, and carbonate, enhances the film forming tendency and hence increases the corrosion resistance of the alloy.

  17. NMR studies on a new method for selective degradation of lignins

    SciTech Connect

    Lu, F.; Ralph, J.

    1996-10-01

    The selectivity and cleanliness of reactions which form the basis of a proposed new alternative to the analytical thioacidolysis method have been examined by NMR using model compounds and isolated lignins The results from the model study show that all steps involved in the new selective method are almost quantitative. When applied to isolated lignins, the NMR spectra show that the main substructures of lignin a selectively and cleanly converted to desired derivatives which are further degraded by specific ether cleavage reactions resulting in high yields of analyzable monomers. The beautiful selectivity and cleanliness demonstrated here, combined with its mildness, should make this method very attractive to lignin researchers.

  18. Dosimetric study of total skin irradiation with a scanning beam electron accelerator

    SciTech Connect

    Sharma, S.C.; Wilson, D.L.

    1987-05-01

    The Therac 20 6-MeV scanned electron beam may be used for partial or total skin therapy. The maximum field size at 1 m is 30 x 30 cm defined by a set of primary photon collimators in conjunction with secondary trimmers. We have studied electron beam profiles with and without trimmers at the nominal source--skin distance of 1 m versus extended distances of 3--5 m. We find that the trimmers limit the field size and add little to the beam uniformity at extended distances. Beam energy, dose distributions, and output factors at extended distances were measured for single and multiple field arrangements with and without trimmers. Beam parameters were measured after introducing a degrader that lowered the energy to 3.7 MeV.

  19. Dosimetric study of total skin irradiation with a scanning beam electron accelerator.

    PubMed

    Sharma, S C; Wilson, D L

    1987-01-01

    The Therac 20 6-MeV scanned electron beam may be used for partial or total skin therapy. The maximum field size at 1 m is 30 X 30 cm defined by a set of primary photon collimators in conjunction with secondary trimmers. We have studied electron beam profiles with and without trimmers at the nominal source-skin distance of 1 m versus extended distances of 3-5 m. We find that the trimmers limit the field size and add little to the beam uniformity at extended distances. Beam energy, dose distributions, and output factors at extended distances were measured for single and multiple field arrangements with and without trimmers. Beam parameters were measured after introducing a degrader that lowered the energy to 3.7 MeV.

  20. Forced degradation studies, and effect of surfactants and titanium dioxide on the photostability of paliperidone by HPLC.

    PubMed

    Marothu, V K; Nellutla, A; Gorrepati, M; Majeti, S; Mamidala, S K

    2015-07-01

    Forced degradation study of paliperidone under hydrolytic, oxidative, thermal and photolytic stress conditions was conducted using HPLC. The drug was found to be labile under hydrolytic, oxidative and photolytic stress conditions; whereas, it was stable under dry heat stress conditions. Effect of anionic, cationic and non-ionic surfactants applied to the concentration exceeding critical micellar concentration on the photostability of paliperidone was also studied by exposing the samples to sunlight for 72h. Major degradation of the drug was found in presence of cationic and non-ionic surfactants. Effect of titanium dioxide on the photo-degradation of paliperidone in solution state was also studied and it was found that 53% of the drug was degraded after 72h of exposure to sunlight. A common degradation peak was observed in oxidative and TiO2 photocatalysed samples. This peak may be due to the generation of N-oxide of paliperidone. The same degradation peak was also observed in all other photostability samples. Chromatographic separation of drug and its degradation products was achieved on an Alltima C8 (250mm×4.6mm, 5μm) analytical column, using a mobile phase consisting of acetonitrile-ammonium acetate buffer with 0.2% triethylamine (pH 3.5; 20mM) (60:40, v/v) at a flow rate of 1mL/min. Quantification was performed with UV detection at 280nm. The method was validated as per ICH guidelines.

  1. Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure

    SciTech Connect

    Soong, Ken; Peralta, E.A.; Byer, R.L.; Colby, E.; /SLAC

    2011-08-12

    A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator. The concept of accelerating electrons with the tremendous electric fields found in lasers has been proposed for decades. However, until recently the realization of such an accelerator was not technologically feasible. Recent advances in the semiconductor industry, as well as advances in laser technology, have now made laser-driven dielectric accelerators imminent. The grating-based accelerator is one proposed design for a dielectric laser-driven accelerator. This design, which was introduced by Plettner, consists of a pair of opposing transparent binary gratings, illustrated in Fig. 1. The teeth of the gratings serve as a phase mask, ensuring a phase synchronicity between the electromagnetic field and the moving particles. The current grating accelerator design has the drive laser incident perpendicular to the substrate, which poses a laser-structure alignment complication. The next iteration of grating structure fabrication seeks to monolithically create an array of grating structures by etching the grating's vacuum channel into a fused silica wafer. With this method it is possible to have the drive laser confined to the plane of the wafer, thus ensuring alignment of the laser-and-structure, the two grating halves, and subsequent accelerator components. There has been previous work using 2-dimensional finite difference time domain (2D-FDTD) calculations to evaluate the performance of the grating accelerator structure. However, this work approximates the grating as an infinite structure and does not accurately model a

  2. Studies on phytoremediation potentiality of Typhonium flagelliforme for the degradation of Brilliant Blue R.

    PubMed

    Kagalkar, Anuradha N; Jagtap, Umesh B; Jadhav, Jyoti P; Govindwar, Sanjay P; Bapat, Vishwas A

    2010-06-01

    In vitro culture plants of Typhonium flagelliforme were found to decolorize a variety of dyes, including Malachite Green, Red HE 8B, Methyl Orange, Reactive Red 2, Direct Red 5B (DR5B), Red HE 7B, Golden Yellow HER, Patent Blue, and Brilliant Blue R (BBR), to varying extents within 4 days. The enzymatic analysis of plant roots of aseptically raised plantlets performed before and after degradation of the dye BBR by these plantlets showed a significant induction in the activities of peroxidase, laccase, tyrosinase, and 2,6-dichlorophenol-indophenol reductase, which indicated the involvement of these enzymes in the metabolism of the dye. Comparative study of the enzyme status of the plants Typhonium flagelliforme and Blumea malcolmii during the degradation of DR5B and BBR showed marked variations in the enzyme profile with respect to the use of different sources of the enzyme. Phytoremediation of BBR using Typhonium flagelliforme was confirmed with high performance liquid chromatography and Fourier transform infrared spectroscopy analysis performed before and after the degradation of the dye. One of the products of the metabolism of the dye was identified as 4-(4-ethylimino-cyclohexa-2,5-dienylidinemethyl)-phenylamine with the aid of gas chromatography-mass spectroscopy (GC-MS) analysis. Significant decrease in the American Dye Manufacturer's Institute, biological oxygen demand, and chemical oxygen demand values of synthetic mixture of textile dyes and industrial effluent confirmed the decolorization and detoxification. Phytotoxicity studies also revealed the nontoxic nature of the metabolites of BBR.

  3. Particle acceleration and plasma energization in substorms: MHD and test particle studies

    SciTech Connect

    Birn, Joachim

    2015-07-16

    The author organizes his slide presentation under the following topics: background, MHD simulation, orbit integration, typical orbits, spatial and temporal features, acceleration mechanisms, source locations, and source energies. Field-­aligned energetic particle fluxes are shown for 45-keV electrons and 80-keV protons. It is concluded that the onset from local thin current sheet is electron tearing. Acceleration is mainly from field collapse, governed by Ey = -vxXBz: importance of localization; betatron acceleration (similar if nonadiabatic); 1st order Fermi, type B (or A; current sheet acceleration). There are two source regions (of comparable importance in magnetotail): - flanks, inner tail - drift entry - early, higher energy - outer plasma sheet - reconnection entry - later, lower energy. Both thermal and suprathermal sources are important, with limited energy range for acceleration

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

    SciTech Connect

    Lidia, Steven M.

    1999-11-01

    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. Provided that further prototyping shows stable beam propagation with minimal current loss and production of good quality, high-power rf fields, this technology is compatible with current schemes for electron-positron colliders in the multi-TeV center-of-mass scale. 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. 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-operation 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 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 GW of power from 40 input, gain, and output rv cavities over a 10 m distance. The simulations show that beam current losses are acceptable, and that longitudinal and transverse focusing techniques are sufficient capable of maintaining a high degree of beam quality along the entire beamline. Additional experimental efforts are also

  5. Acceleration training for managing nonalcoholic fatty liver disease: a pilot study

    PubMed Central

    Oh, Sechang; Shida, Takashi; Sawai, Akemi; Maruyama, Tsuyoshi; Eguchi, Kiyoshi; Isobe, Tomonori; Okamoto, Yoshikazu; Someya, Noriko; Tanaka, Kiyoji; Arai, Emi; Tozawa, Akiko; Shoda, Junichi

    2014-01-01

    Background While aerobic training is generally recommended as therapeutic exercise in guidelines, the effectiveness of resistance training has recently been reported in the management of nonalcoholic fatty liver disease (NAFLD). Acceleration training (AT) is a new training method that provides a physical stimulation effect on skeletal muscles by increasing gravitational acceleration with vibration. AT has recently been indicated as a component of medicine. In this study, we evaluated the effectiveness of AT in the management of NAFLD in obese subjects. Methods A total of 18 obese patients with NAFLD who had no improvement in liver function test abnormalities and/or steatosis grade after 12 weeks of lifestyle counseling were enrolled in an AT program. These patients attended a 20-minute session of AT twice a week for 12 consecutive weeks. Results During the AT program, the NAFLD patients showed a modest increase in the strength (+12.6%) and cross-sectional area (+3.1%) of the quadriceps, coupled with a significant reduction in intramyocellular lipids (−26.4%). Notably, they showed a modest reduction in body weight (−1.9%), abdominal visceral fat area (−3.4%), and hepatic fat content (−8.7%), coupled with a significant reduction in levels of aminotransferase (−15.7%), γ-glutamyltransferase (−14.4%), leptin (−9.7%), interleukin-6 (−26.8%), and tumor necrosis factor-α (−17.9%), and a significant increase of adiponectin (+8.7%). On a health-related quality of life survey, the patients showed an improvement in physical functioning (+17.3%), physical role (+9.7%), general health (+22.1), and social functioning (+6.0%). Conclusion AT reduced hepatic and intramyocellular fat contents and ameliorated liver function test abnormalities in obese patients with NAFLD, which was coupled with improved physical function and body adiposity. AT is clinically beneficial for the management of NAFLD. PMID:25404857

  6. 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.

  7. Compatability and accelerated aging study for Li(Si)FeS2 thermally activated batteries

    NASA Astrophysics Data System (ADS)

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

    1982-04-01

    Thermally activated batteries using the Li(Si)/FeS2 system are being developed by Sandia National Laboratories. These components ae used in systems which require a storage life of 25 years and high reliability. A previous aging study was completed on this system, but no organic materials other than those in the electrical match and heat paper fuse strips were included. The present study incorporates all of the materials in the system, both organic and inorganic, except for the electric match and heat paper. There are two main parts in this study: (1) a compatibility study in which the four organic materials under investigation are placed in a hermetically sealed stainless steel container with battery components; (2) an aging study of pairs of material and individual materials in which one organic material is placed in a hermetically sealed stainless steel container with battery components. The compatibility study examines effects of some materials upon others (outgassing, etc.) which would cause degradation and/or functional failure.

  8. Characterization of degradation products of idarubicin through LC-UV, MS(n) and LC-MS-TOF studies.

    PubMed

    Kaushik, Dheeraj; Bansal, Gulshan

    2013-11-01

    Idarubicin was subjected to forced degradation under the ICH recommended conditions of hydrolysis, oxidation, dry heat and photolysis to characterize its possible impurities and/or degradation products. The drug was found unstable to acid hydrolysis at 85°C and to alkaline hydrolysis, and oxidation at room temperature. The hydrolytic and oxidative degradation products were resolved with gradient and isocratic elution, respectively on an Inertsil RP18 (250 mm × 4.6mm; 5 μ) column with HCOONH4 (20mM, pH 3.0) and acetonitrile. The drug degraded to two products (O-I and O-II) in oxidative condition, two products (K-I and K-II) in alkaline hydrolytic, and one product (A-I) in acidic hydrolytic conditions. The purity of each in the LC-UV chromatogram was ascertained through LC-PDA analysis. The products were characterized through +ESI-MS(n) studies on the drug and LC-MS-TOF studies on the degraded drug solutions. Based on the multistage mass fragmentation pattern of idarubicin and accurate mass analysis of the degradation products, the O-I, O-II and A-I were characterized as desacetylidarubicin hydroperoxide, desacetylidarubicin and deglucosaminylidarubicin, respectively. The products K-I and K-II were not characterized due to their low concentrations and/or extremely weak ionization. The mechanisms of degradation of idarubicin to these products were proposed and discussed.

  9. 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

  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. Measuring forgetting: a critical review of accelerated long-term forgetting studies.

    PubMed

    Elliott, Gemma; Isaac, Claire L; Muhlert, Nils

    2014-05-01

    Accelerated long-term forgetting (ALF) refers to abnormal forgetting over hours to weeks despite normal acquisition or initial consolidation. Since standardised assessments of memory typically only test at delays of up to 40-minutes, ALF may go undetected in clinical practice. The memory difficulties associated with ALF can however cause considerable distress to patients. It is important therefore that clinicians are aware that ALF may represent a distinct phenomenon that will require additional and careful assessment to aid patients' understanding of the condition and assist in developing strategies to address its effects. At the same time, ALF may also provide insight into long-term memory processes. Studies of ALF in patients with epilepsy have so far demonstrated mixed results, which may reflect differences in methodology. This review explores the methodological issues that can affect forgetting, such as the effects of age, general cognitive function, test sensitivity and initial learning. It then evaluates the extent to which existing studies have considered these key issues. We outline the points to consider when designing ALF studies that can be used to help improve their validity. These issues can also help to explain some of the mixed findings in studies of ALF and inform the design of standardised tests for assessing ALF in clinical practice.

  13. Real time and accelerated stability studies of Tetanus toxoid manufactured in public sector facilities of Pakistan.

    PubMed

    Parveen, Ghazala; Hussain, Shahzad; Malik, Farnaz; Begum, Anwar; Mahmood, Sidra; Raza, Naeem

    2013-11-01

    Tetanus is an acute illness represented by comprehensive increased inflexibility and spastic spasms of skeletal muscles. The poor quality tetanus toxoid vaccine can raise the prevalence of neonatal tetanus. WHO has taken numerous steps to assist national regulatory authorities and vaccine manufacturers to ensure its quality and efficacy. It has formulated international principles for stability evaluation of each vaccine, which are available in the form of recommendations and guidelines. The aim of present study was to ensure the stability of tetanus vaccines produced by National Institute of Health, Islamabad, Pakistan by employing standardized methods to ensure constancy of tetanus toxoid at elevated temperature, if during storage/transportation cold chain may not be maintained in hot weather. A total of three batches filled during full-scale production were tested. All Stability studies determination were performed on final products stored at 2-8°C and elevated temperatures in conformance with the ICH Guideline of Stability Testing of Biological Products. These studies gave comparison between real time shelf-life stability and accelerated stability studies. The findings indicate long﷓term thermo stability and prove that this tetanus vaccine can remain efficient under setting of routine use when suggested measures for storage and handling are followed in true spirit.

  14. Thermodynamic and kinetic study of phenol degradation by a non-catalytic wet air oxidation process.

    PubMed

    Lefèvre, Sébastien; Boutin, Olivier; Ferrasse, Jean-Henry; Malleret, Laure; Faucherand, Rémy; Viand, Alain

    2011-08-01

    This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350°C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H(2)O and CO(2). The Arrhenius law data obtained for the phenol disappearance are the following: k=1.8×10(6)±3.9×10(5)M(-1)s(-1) (pre-exponential factor) and E(a)=77±8 kJ mol(-1) (activation energy).

  15. Stress Degradation Studies of Tebipenem and a Validated Stability-Indicating LC Method.

    PubMed

    Cielecka-Piontek, Judyta; Zalewski, Przemysław; Barszcz, Bolesław; Lewandowska, Kornelia; Paczkowska, Magdalena

    2013-04-01

    A inexpensive and rapid isocratic LC method has been developed for the quantitative determination of tebipenem-a new β-lactam antibiotic. Stress degradation studies were performed on tebipenem in acidic (0.2 N hydrochloric acid) and basic (0.02 N sodium hydroxide) solutions, in a solution with oxidizing agent (3 % hydrogen peroxide), and in the solid state, during thermolysis and photolysis. For a chromatographic separation of tebipenem and its degradation products, a C-18 stationary phase and 12 mM ammonium acetate-acetonitrile (96:4 v/v) were used. A quantitative determination of tebipenem was carried out by using a PDA detector at 298 nm, with a flow rate of 1.2 mL min(-1). The linear regression analysis for the calibration plots showed a good linear relationship (r = 0.999) in the concentration range 0.041-0.240 mg mL(-1). The method demonstrated good precision (1.14-1.96 % RSD) and recovery (99.60-101.90 %). The limits of detection and quantitation were 9.69 and 29.36 μg mL(-1), respectively. The analysis of tebipenem reactivity was supported by quantum chemical calculations based on the density functional theory (DFT). The analysis of the electron density of the HOMO and LUMO of tebipenem suggested the possibility of electron transport in the molecule during the degradation of bi-cyclic 4:5 fused penem rings.

  16. Study on the aerobic biodegradability and degradation kinetics of 3-NP; 2,4-DNP and 2,6-DNP.

    PubMed

    She, Zonglian; Xie, Tian; Zhu, Yingjie; Li, Leilei; Tang, Gaifeng; Huang, Jian

    2012-11-30

    Four biodegradability tests (BOD(5)/COD ratio, production of carbon dioxide, relative oxygen uptake rate and relative enzymatic activity) were used to determine the aerobic biodegradability of 3-nitrophenol (3-NP), 2,4-dinitrophenol (2,4-DNP) and 2,6-dinitrophenol (2,6-DNP). Furthermore, biodegradation kinetics of the compounds was investigated in sequencing batch reactors both in the presence of glucose (co-substrate) and with nitrophenol as the sole carbon source. Among the three tested compounds, 3-NP showed the best biodegradability while 2,6-DNP was the most difficult to be biodegraded. The Haldane equation was applied to the kinetic test data of the nitrophenols. The kinetic constants are as follows: the maximum specific degradation rate (K(max)), the saturation constants (K(S)) and the inhibition constants (K(I)) were in the range of 0.005-2.98 mg(mgSS d)(-1), 1.5-51.9 mg L(-1) and 1.8-95.8 mg L(-1), respectively. The presence of glucose enhanced the degradation of the nitrophenols at low glucose concentrations. The degradation of 3-NP was found to be accelerated with the increasing of glucose concentrations from 0 to 660 mg L(-1). At high (1320-2000 mg L(-1)) glucose concentrations, the degradation rate of 3-NP was reduced and the K(max) of 3-NP was even lower than the value obtained in the absence of glucose, suggesting that high concentrations of co-substrate could inhibit 3-NP biodegradation. At 2,4-DNP concentration of 30 mg L(-1), the K(max) of 2,4-DNP with glucose as co-substrate was about 30 times the value with 2,4-DNP as sole substrate. 2,6-DNP preformed high toxicity in the case of sole carbon source degradation and the kinetic data was hardly obtained.

  17. 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.

  18. Sorption, degradation and transport phenomena of alcohol ethoxysulfates in agricultural soils. Laboratory studies.

    PubMed

    Fernández-Ramos, C; Rodríguez-Gómez, R; Reis, M S; Zafra-Gómez, A; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L

    2017-03-01

    In the present work, laboratory studies were conducted in order to determine and model the sorption, degradation and transport processes of alcohol ethoxysulfates (AES), one of the most important groups of anionic surfactants. Adsorption/desorption isotherms were obtained for several structurally related AES ethoxymers (homologue AES-C12En with n = 0-10 ethoxymer units and homologue AES-C14En with n = 0-7 ethoxymer units) using a batch equilibrium method. Data were fitted to a linear and a Freundlich isotherm models. Additionally, experiments in continuous-flow soil columns were also carried out and the breakthrough curves observed for each compound were studied. Breakthrough curves were used to determine the fundamental parameters of the transport model (hydrodynamic dispersion coefficient, degradation rate constant and adsorption/desorption isotherm slope), that is the main phenomena that take place simultaneously when AES move through agricultural soil. When the results obtained for the AES ethoxymers are combined, they reveal a clear and consistent trend towards a sorption increase with the number of ethoxylated units and with the length of the alkyl chain that opens the possibility to estimate the values of the transport parameters for other structurally related ethoxymers.

  19. Analytical study proving alprazolam degradation to its main impurity triazolaminoquinoleine through Maillard reaction.

    PubMed

    Huidobro, A L; Barbas, C

    2009-07-01

    Triazolaminoquinoleine is rapidly formed in formulations of alprazolam tablets in presence of excipients, and its generation is speeded up with increasing temperature and humidity. The present paper deals with detailed quantitative and qualitative studies into the nonactive constituents of the formulation in order to determine the excipient (or the mixture) responsible for the degradation. Our studies have demonstrated that reducing carbohydrate excipients play a fundamental role in the generation of triazolaminoquinoleine, with lactose as the main one responsible, through a Maillard reaction. In order to demonstrate the validity of the proposed degradation mechanism, p-nitrobenzaldehyde has been employed as a model of reaction of the nucleophylic attack of amino-opened structure of alprazolam to an aldehyde to generate the first intermediate involved in Maillard reaction, a Schiff base. This model enables the identification of all the intermediates by mass spectrometry and/or nuclear magnetic resonance techniques, with the outcome of this experiment leading to a full understanding of the generation pathway. Calcium carbonate has been proposed as a possible tablet diluent replacing lactose in the pharmaceutical formulation.

  20. 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.

  1. 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

  2. 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

  3. Study of forced degradation behavior of enalapril maleate by LC and LC-MS and development of a validated stability-indicating assay method.

    PubMed

    Bhardwaj, Sunny Piyush; Singh, Saranjit

    2008-01-07

    In the present study, comprehensive stress testing of enalapril maleate was carried out according to ICH guideline Q1A(R2). The drug was subjected to acid (0.1N HCl), neutral and alkaline (0.1N NaOH) hydrolytic conditions at 80 degrees C, as well as to oxidative decomposition at room temperature. Photolysis was carried out in 0.1N HCl, water and 0.1N NaOH at 40 degrees C. Additionally, the solid drug was subjected to 50 degrees C for 60 days in a dri-bath, and to the combined effect of temperature and humidity, with and without light, at 40 degrees C/75% RH. The products formed under different stress conditions were investigated by LC and LC-MS. The LC method that could separate all degradation products formed under various stress conditions involved a C18 column and a mobile phase comprising of ACN and phosphate buffer (pH 3). The flow rate and detection wavelength were 1 ml min(-1) and 210 nm, respectively. The developed method was found to be precise, accurate, specific and selective. It was suitably modified for LC-MS studies by replacing phosphate buffer with water, where pH was adjusted to 3.0 with formic acid. The drug showed instability in solution state (under acidic, neutral, alkaline and photolytic stress conditions), but was relatively stable in the solid-state, except formation of minor products under accelerated conditions. Primarily, maximum degradation products were formed in acid conditions, though the same were also produced variably under other stress conditions. The LC-MS m/z values and fragmentation patterns of two of the five products matched with enalaprilat and diketopiperazine derivative, previously known degradation products of enalapril. Also, m/z value of another product matched with an impurity listed in the drug monograph in European Pharmacopoeia. Rest two were hitherto unknown degradation products. The products were characterized through LC-MS fragmentation studies. Based on the results, a more complete degradation pathway for the

  4. Fiber Accelerating Structures

    SciTech Connect

    Hammond, Andrew P.; /Reed Coll. /SLAC

    2010-08-25

    One of the options for future particle accelerators are photonic band gap (PBG) fiber accelerators. PBG fibers are specially designed optical fibers that use lasers to excite an electric field that is used to accelerate electrons. To improve PBG accelerators, the basic parameters of the fiber were tested to maximize defect size and acceleration. Using the program CUDOS, several accelerating modes were found that maximized these parameters for several wavelengths. The design of multiple defects, similar to having closely bound fibers, was studied to find possible coupling or the change of modes. The amount of coupling was found to be dependent on distance separated. For certain distances accelerating coupled modes were found and examined. In addition, several non-periodic fiber structures were examined using CUDOS. The non-periodic fibers produced several interesting results and promised more modes given time to study them in more detail.

  5. 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.

  6. 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.

  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. 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.

  9. Analytical bunch compression studies for a linac-based electron accelerator

    NASA Astrophysics Data System (ADS)

    Schreck, M.; Wesolowski, P.

    2015-10-01

    The current paper deals with analytical bunch compression studies for FLUTE whose results are compared to simulations. FLUTE is a linac-based electron accelerator with a design energy of approximately 40 MeV currently being constructed at the Karlsruhe Institute of Technology. One of the goals of