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Sample records for replaceable immunoaffinity disk

  1. Why Lumbar Artificial Disk Replacements (LADRs) Fail.

    Science.gov (United States)

    Pettine, Kenneth; Ryu, Robert; Techy, Fernando

    2017-07-01

    A retrospective review of prospectively collected data. To determine why artificial disk replacements (ADRs) fail by examining results of 91 patients in FDA studies performed at a single investigational device exemption (IDE) site with minimum 2-year follow-up. Patients following lumbar ADR generally achieve their 24-month follow-up results at 3 months postoperatively. Every patient undergoing ADR at 1 IDE site by 2 surgeons was evaluated for clinical success. Failure was defined as Maverick, 25 patients; Charité, 31 patients; and Kineflex, 35 patients. All procedures were 1-level operations performed at L4-L5 or L5-S1. Demographics and inclusion/exclusion criteria were similar and will be discussed. Overall clinical failure occurred in 26% (24 of 91 patients) at 2-year follow-up. Clinical failure occurred in: 28% (Maverick) (7 of 25 patients), 39% (Charité) (12 of 31 patients), and 14% (Kineflex) (5 of 35 patients). Causes of failure included facet pathology, 50% of failure patients (12 of 24). Implant complications occurred in 5% of total patients and 21% of failure patients (5 of 24). Only 5 patients went from a success to failure after 3 months. Only 1 patient went from a failure to success after a facet rhizotomy 1 year after ADR. Seventy-four percent of patients after ADR met strict clinical success after 2-year follow-up. The clinical success versus failure rate did not change from their 3-month follow-up in 85 of the 91 patients (93%). Overall clinical success may be improved most by patient selection and implant type.

  2. Calcium-sensitive immunoaffinity chromatography

    DEFF Research Database (Denmark)

    Henriksen, Maiken L; Lindhardt Madsen, Kirstine; Skjoedt, Karsten

    2014-01-01

    Immunoaffinity chromatography is a powerful fractionation technique that has become indispensable for protein purification and characterization. However, it is difficult to retrieve bound proteins without using harsh or denaturing elution conditions, and the purification of scarce antigens...... to homogeneity may be impossible due to contamination with abundant antigens. In this study, we purified the scarce, complement-associated plasma protein complex, collectin LK (CL-LK, complex of collectin liver 1 and kidney 1), by immunoaffinity chromatography using a calcium-sensitive anti-collectin-kidney-1 m...... chromatography was superior to the traditional immunoaffinity chromatographies and resulted in a nine-fold improvement of the purification factor. The technique is applicable for the purification of proteins in complex mixtures by single-step fractionation without the denaturation of eluted antigens...

  3. Adverse Event Recording and Reporting in Clinical Trials Comparing Lumbar Disk Replacement with Lumbar Fusion: A Systematic Review

    OpenAIRE

    HIRATZKA, JAYME; Rastegar, Farbod; Contag, Alec G.; Norvell, Daniel C.; Anderson, Paul A.; Hart, Robert A

    2015-01-01

    Study Design Systematic review. Objectives (1) To compare the quality of adverse event (AE) methodology and reporting among randomized trials comparing lumbar fusion with lumbar total disk replacement (TDR) using established AE reporting systems; (2) to compare the AEs and reoperations of lumbar spinal fusion with those from lumbar TDR; (3) to make recommendations on how to report AEs in randomized controlled trials (RCTs) so that surgeons and patients have more-detailed and comprehensive inf...

  4. [Dislocation of the closing element of the disk mechanical graft at aortic valve replacement].

    Science.gov (United States)

    Korostelev, A N; Kuntsevich, G I; Zotikov, A E; Chernyak, B B; Il'ina, M V; Ter-Khachaturova, I E; Solopova, G V

    2003-01-01

    Presented herein is the first case of dislocation of the closing element of the artificial low-profile aortic valve to the abdominal aorta, which happened during replacement. Toward completion of extracorporeal circulation a 37-year-old man showed the signs of aortic insufficiency because of dislocation of the closing element. After resumption of extracorporeal circulation repeated replacement was accomplished. To detect the site of graft cusp embolism, transesophageal echocardiography and duplex scanning of the abdominal aorta were employed. On the 18th day following the first intervention the patient developed thromboembolism to the distal arterial bed. Emergency thrombectomy from the arteries of the right lower extremity was performed and a foreign body was removed from the abdominal aorta, using left-sided thoracophrenolumbotomy. The patient was discharged from the clinic in a satisfactory condition.

  5. Replacement

    Directory of Open Access Journals (Sweden)

    S. Radhakrishnan

    2014-03-01

    Full Text Available The fishmeal replaced with Spirulina platensis, Chlorella vulgaris and Azolla pinnata and the formulated diet fed to Macrobrachium rosenbergii postlarvae to assess the enhancement ability of non-enzymatic antioxidants (vitamin C and E, enzymatic antioxidants (superoxide dismutase (SOD and catalase (CAT and lipid peroxidation (LPx were analysed. In the present study, the S. platensis, C. vulgaris and A. pinnata inclusion diet fed groups had significant (P < 0.05 improvement in the levels of vitamins C and E in the hepatopancreas and muscle tissue. Among all the diets, the replacement materials in 50% incorporated feed fed groups showed better performance when compared with the control group in non-enzymatic antioxidant activity. The 50% fishmeal replacement (best performance diet fed groups taken for enzymatic antioxidant study, in SOD, CAT and LPx showed no significant increases when compared with the control group. Hence, the present results revealed that the formulated feed enhanced the vitamins C and E, the result of decreased level of enzymatic antioxidants (SOD, CAT and LPx revealed that these feeds are non-toxic and do not produce any stress to postlarvae. These ingredients can be used as an alternative protein source for sustainable Macrobrachium culture.

  6. Aflatoxin determination using in-line immunoaffinity chromatopgraphy in foods

    NARCIS (Netherlands)

    Jinap, S.; Rijk, de T.C.; Arzandeh, S.; Kleijnen, H.C.H.; Zomer, P.; Weg, van der G.; Mol, J.G.J.

    2012-01-01

    Short throughput times with high precision and sensitivity are of interest of any laboratory. An in-line immunoaffinity chromatographic cleanup procedure coupled to High Performance Liquid Chromatography (HPLC) and fluorescence detection was developed for the purpose of quantification of the

  7. Aflatoxin determination using in-line immunoaffinity chromatopgraphy in foods

    NARCIS (Netherlands)

    Jinap, S.; Rijk, de T.C.; Arzandeh, S.; Kleijnen, H.C.H.; Zomer, P.; Weg, van der G.; Mol, J.G.J.

    2012-01-01

    Short throughput times with high precision and sensitivity are of interest of any laboratory. An in-line immunoaffinity chromatographic cleanup procedure coupled to High Performance Liquid Chromatography (HPLC) and fluorescence detection was developed for the purpose of quantification of the aflatox

  8. Polyglycidyl methacrylate based immunoaffinity cryogels for insulin adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Memmedova, Türkan; Armutcu, Canan; Uzun, Lokman, E-mail: lokman@hacettepe.edu.tr; Denizli, Adil

    2015-07-01

    Immunoaffinity chromatography (IAC) is a kind of bioaffinity chromatography which used antibodies or antibody-related molecules as the stationary phase. IAC is used by many applications for analytical, clinical and diagnostic purposes, particularly preferring in analytical purposes on one-step separation and purification of target compounds. Moreover, immunoaffinity chromatography is used in antibody enrichment and separation of cells. IAC columns are usually applied in the antibody experiments due to powerful and selective binding of antibodies and/or their target antigens. Antigen or antibody molecules could be immobilized to the solid support. Therefore, target antibody or cell is purified. Specific bioligands can be immobilized directly on glycidyl based polymeric material with simple acid–base catalyst. In this study, polyglycidyl methacrylate based therefore cryogels were prepared and anti-insulin antibodies were immobilized on porous surface of cryogels. Swelling test, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM) were conducted to characterize cryogels developed. To optimize separation conditions, effects of pH, initial insulin concentration, flow rate, salt concentration, contact time and temperature on insulin adsorption capacity were examined. The results indicated that the immunoaffinity cryogel developed here could be classified as good alternative with prominent properties such as high reusability and cost-friendly adsorbent and would be one of the primary reports for immunoaffinity purification of insulin molecules in not only lab-scale but also for industrial purposes. - Highlights: • Polyglycidyl methacrylate based cryogels developed as stationary phase • Immunoaffinity cryogels for reusable and cost-friendly insulin adsorption • Increase in worldwide prevalence of diabetes, type 1 or 2 • An exponential increase in the demand on insulin market • Guiding researchers for not

  9. Immunoaffinity chromatography: an introduction to applications and recent developments

    Science.gov (United States)

    Moser, Annette C

    2010-01-01

    Immunoaffinity chromatography (IAC) combines the use of LC with the specific binding of antibodies or related agents. The resulting method can be used in assays for a particular target or for purification and concentration of analytes prior to further examination by another technique. This review discusses the history and principles of IAC and the various formats that can be used with this method. An overview is given of the general properties of antibodies and of antibody-production methods. The supports and immobilization methods used with antibodies in IAC and the selection of application and elution conditions for IAC are also discussed. Several applications of IAC are considered, including its use in purification, immunodepletion, direct sample analysis, chromatographic immunoassays and combined analysis methods. Recent developments include the use of IAC with CE or MS, ultrafast immunoextraction methods and the use of immunoaffinity columns in microanalytical systems. PMID:20640220

  10. Identification of proteins interacting with ammodytoxins in Vipera ammodytes ammodytes venom by immuno-affinity chromatography.

    Science.gov (United States)

    Brgles, Marija; Kurtović, Tihana; Kovačič, Lidija; Križaj, Igor; Barut, Miloš; Lang Balija, Maja; Allmaier, Günter; Marchetti-Deschmann, Martina; Halassy, Beata

    2014-01-01

    In order to perform their function, proteins frequently interact with other proteins. Various methods are used to reveal protein interacting partners, and affinity chromatography is one of them. Snake venom is composed mostly of proteins, and various protein complexes in the venom have been found to exhibit higher toxicity levels than respective components separately. Complexes can modulate envenomation activity of a venom and/or potentiate its effect. Our previous data indicate that the most toxic components of the Vipera ammodytes ammodytes (Vaa) venom isolated so far-ammodytoxins (Atxs)-are contributing to the venom's toxicity only moderately; therefore, we aimed to explore whether they have some interacting partner(s) potentiating toxicity. For screening of possible interactions, immuno-affinity chromatography combined with identification by mass spectrometry was used. Various chemistries (epoxy, carbonyldiimidazole, ethylenediamine) as well as protein G functionality were used to immobilize antibodies on monolith support, a Convective Interaction Media disk. Monoliths have been demonstrated to better suit the separation of large biomolecules. Using such approach, several proteins were indicated as potential Atx-binding proteins. Among these, the interaction of Atxs with a Kunitz-type inhibitor was confirmed by far-Western dot-blot and surface plasmon resonance measurement. It can be concluded that affinity chromatography on monolithic columns combined with mass spectrometry identification is a successful approach for screening of protein interactions and it resulted with detection of the interaction of Atx with Kunitz-type inhibitor in Vaa venom for the first time.

  11. Verbatim Floppy Disk

    CERN Multimedia

    1976-01-01

    Introduced under the name "Verbatim", Latin for "literally", these disks that sized more than 5¼ inches have become almost universal on dedicated word processing systems and personal computers. This format was replaced more slowly by the 3½-inch format, introduced for the first time in 1982. Compared to today, these large format disks stored very little data. In reality, they could only contain a few pages of text.

  12. Optimal selection of epitopes for TXP-immunoaffinity mass spectrometry

    Directory of Open Access Journals (Sweden)

    Joos Thomas

    2010-06-01

    Full Text Available Abstract Background Mass spectrometry (MS based protein profiling has become one of the key technologies in biomedical research and biomarker discovery. One bottleneck in MS-based protein analysis is sample preparation and an efficient fractionation step to reduce the complexity of the biological samples, which are too complex to be analyzed directly with MS. Sample preparation strategies that reduce the complexity of tryptic digests by using immunoaffinity based methods have shown to lead to a substantial increase in throughput and sensitivity in the proteomic mass spectrometry approach. The limitation of using such immunoaffinity-based approaches is the availability of the appropriate peptide specific capture antibodies. Recent developments in these approaches, where subsets of peptides with short identical terminal sequences can be enriched using antibodies directed against short terminal epitopes, promise a significant gain in efficiency. Results We show that the minimal set of terminal epitopes for the coverage of a target protein list can be found by the formulation as a set cover problem, preceded by a filtering pipeline for the exclusion of peptides and target epitopes with undesirable properties. Conclusions For small datasets (a few hundred proteins it is possible to solve the problem to optimality with moderate computational effort using commercial or free solvers. Larger datasets, like full proteomes require the use of heuristics.

  13. Nonspecific native elution of proteins and mumps virus in immunoaffinity chromatography.

    Science.gov (United States)

    Brgles, Marija; Sviben, Dora; Forčić, Dubravko; Halassy, Beata

    2016-05-20

    Immunoaffinity chromatography, based on the antigen-antibody recognition, enables specific purification of any antigen (protein, virus) by its antibody. The problem with immunoaffinity chromatography is the harsh elution conditions required for disrupting strong antigen-antibody interactions, such as low pH buffers, which are often deleterious for the immobilized protein and the protein to be isolated since they can also disrupt the intramolecular forces. Therefore, immunoaffinity chromatography can only be partially used for protein and virus purification. Here we report on a nonspecific elution in immunoaffinity chromatography using native conditions by elution with amino acid solution at physiological pH for which we suppose possible competing mechanism of action. Elution potential of various amino acid solutions was tested using immunoaffinity columns specific for ovalbumin and mumps virus, and protein G affinity column. Results have shown that the most successful elution solutions were those containing imidazole and arginine of high molarity. Imidazole represents aromatic residues readily found at the antigen-antibody interaction surface and arginine is most frequently found on protein surface in general. Therefore, results on their eluting power in immunoaffinity chromatography, which increases with increasing molarity, are in line with the competing mechanism of action. Virus immunoaffinity chromatography resulted in removal on nonviable virus particles, which is important for research and biotechnology purposes. In addition, amino acids are proven stabilizers for proteins and viruses making approach presented in this work a very convenient purification method.

  14. Contributions of immunoaffinity chromatography to deep proteome profiling of human biofluids

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chaochao; Duan, Jicheng; Liu, Tao; Smith, Richard D.; Qian, Wei-Jun

    2016-05-01

    Human biofluids, especially blood plasma or serum, hold great potential as the sources of potential biomarkers for various diseases; however, the enormous dynamic range of protein concentrations in biofluids represents a significant analytical challenge to detect promising low-abundance protein biomarkers. Over the last decade, various immunoaffinity chromatographic methods have been developed and routinely applied for separating low-abundance proteins from the high and moderate-abundance proteins, thus enabling more effective detection of low-abundance proteins. Herein, we review the advances of immunoaffinity separation methods and their contributions to the proteomics applications of different human biofluids. The limitations and future perspective of immunoaffinity separation methods are also discussed.

  15. [Sample preprocessing method for residual quinolones in honey using immunoaffinity resin].

    Science.gov (United States)

    Ihara, Yoshiharu; Kato, Mihoko; Kodaira, Tsukasa; Itoh, Shinji; Terakawa, Mika; Horie, Masakazu; Saito, Koichi; Nakazawa, Hiroyuki

    2009-06-01

    A sample preparation method was developed for determination of quinolones in honey using immunoaffinity resin. For this purpose, an immunoaffinity resin for quinolones was prepared by coupling a quinolone-specific monoclonal antibody to agarose resin. Honey samples diluted with phosphate buffer were reacted with immunoaffinity resin. After the resin was washed, quinolones were eluted with glycine-HCl. Quinolones in the eluate were determined by HPLC with fluorescence detection. No interfering peak was found on the chromatograms of honey samples. The recoveries of quinolones from samples were over 70% at fortification levels of 20 ng/g (for norfloxacin, ciprofloxacin and enrofloxacin) and 10 ng/g (for danofloxacin). The quantification limits of quinolones were 2 ng/g. This sample preprocessing method using immunoaffinity resin was found to be effective and suitable for determining residual quinolones in honey.

  16. Bryan 人工颈椎间盘置换术后 X 线评估%Role of X-ray in the assessment of Bryan cervical disk replacement

    Institute of Scientific and Technical Information of China (English)

    李娜; 杨菲菲; 韩骁; 程晓光

    2016-01-01

    Objective To evaluate the value of X-ray plain film in the follow-up of Bryan cervical disk replacement.Methods A retrospective analysis was made in 33 cases accepting Bryan cervical disk replacement from December 2003 to May 2005, and all were followed up from January to October 2008 in Beijing Jishuitan Hospital. X-ray Images before and after operations were compared and evaluated. There were 25 males and 8 females ( aged 25 - 70 years, mean age 47.2 years ). Single segment replacement: 23 cases; double segment replacement: 10 cases;a total of 43 surgical segments. Cervical anteroposterior, lateral, hyperlfexion and hyperextension X-ray iflms were analyzed in the preoperative and postoperative follow-up.Results Follow-up lasted for 36 - 52 months ( mean: 42.97 months ). In this group of 43 Bryan cervical disk replacement segments, the sagittal diameter of the Bryan cervical disc was less than the vertebra: 14 segments ( 32.6% ). Displacement of Bryan cervical disc was seen in 3 segments ( 7.0% ); osteophytes and degeneration were seen in 16 segments ( 37.2% ). Cervical lordosis, segmental lordosis, disk motion, and the degeneration of adjacent discs were assessed with no statistical signiifcance before and after the operation (P > 0.05 ).Conclusions Bryan cervical disk replacement can maintain the lordosis and disk motion of the cervical spine, and can prevent the adjacent disc degeneration. There are displacement and ossiifcation in some cases, but can be avoided by proper patients’ selection and standardized operation. Long-term effects remain to be studied by large sample data.%目的:评估 X 线片在人工颈椎间盘置换术后随访中的价值。方法回顾性分析2003年12月至2005年5月,北京积水潭医院脊柱外科行 Bryan 人工颈椎间盘置换术并于2008年1~10月接受随访的病例33例。其中男25例,女8例;年龄25~70岁,平均47.2岁。单节段人工颈椎间盘置换23例,双节段人工颈椎间盘置换10

  17. Galaxy Disks

    NARCIS (Netherlands)

    van der Kruit, P. C.; Freeman, K. C.

    The disks of disk galaxies contain a substantial fraction of their baryonic matter and angular momentum, and much of the evolutionary activity in these galaxies, such as the formation of stars, spiral arms, bars and rings, and the various forms of secular evolution, takes place in their disks. The

  18. Development of immunoaffinity chromatographic method for Ara h 2 isolation.

    Science.gov (United States)

    Wu, Zhihua; Zhang, Ying; Zhan, Shaode; Lian, Jun; Zhao, Ruifang; Li, Kun; Tong, Ping; Li, Xin; Yang, Anshu; Chen, Hongbing

    2017-03-01

    Ara h 2 is considered a major allergen in peanut. Due to the difficulty of separation, Ara h 2 had not been fully studied. Immunoaffinity chromatography (IAC) column can separate target protein with high selectivity, which made it possible to purify Ara h 2 from different samples. In this study, IAC method was developed to purify Ara h 2 and its effect was evaluated. By coupling polyclonal antibody (pAb) on CNBr-activated Sepharose 4B, the column for specific extraction was constructed. The coupling efficiency of the IAC column was higher than 90%, which made the capacity of column reached 0.56 mg per 0.15 g medium (dry weight). The recovery of Ara h 2 ranged from 93% to 100% for different concentrations of pure Ara h 2 solutions in 15 min. After using a column 10 times, about 88% of the column capacity remained. When applied to extract Ara h 2 from raw peanut protein extract and boiled peanut protein extract, the IAC column could recovery 94% and 88% target protein from the mixture. SDS-PAGE and Western blotting analysis confirmed the purified protein was Ara h 2, its purity reached about 90%. Significantly, the IAC column could capture dimer of Ara h 2, which made it feasible to prepared derivative of protein after processing. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. ELISA AND SOL-GEL BASED IMMUNOAFFINITY PURIFICATION OF THE PYRETHROID BIOALLETHRIN IN FOOD AND ENVIRONMENTAL SAMPLES

    Science.gov (United States)

    The peer-reviewed article describes the development of a new sol-gel based immunoaffinity purification procedure and an immunoassay for the pyrethroid bioallethrin. The immunoaffinity chromatography procedure was applied to food samples providing an efficient cleanup prior to im...

  20. Galaxy Disks

    CERN Document Server

    van der Kruit, P C

    2011-01-01

    The formation and evolution of galactic disks is particularly important for understanding how galaxies form and evolve, and the cause of the variety in which they appear to us. Ongoing large surveys, made possible by new instrumentation at wavelengths from the ultraviolet (GALEX), via optical (HST and large groundbased telescopes) and infrared (Spitzer) to the radio are providing much new information about disk galaxies over a wide range of redshift. Although progress has been made, the dynamics and structure of stellar disks, including their truncations, are still not well understood. We do now have plausible estimates of disk mass-to-light ratios, and estimates of Toomre's $Q$ parameter show that they are just locally stable. Disks are mostly very flat and sometimes very thin, and have a range in surface brightness from canonical disks with a central surface brightness of about 21.5 $B$-mag arcsec$^{-2}$ down to very low surface brightnesses. It appears that galaxy disks are not maximal, except possibly in ...

  1. IMMUNOAFFINITY PURIFICATION AND RECONSTITUTION OF THE HUMAN BILIRUBIN PHENOL UDP-GLUCURONOSYLTRANSFERASE FAMILY

    NARCIS (Netherlands)

    SEPPEN, J; JANSEN, PLM; ELFERINK, RPJO

    1995-01-01

    When membrane proteins are solubilized and subjected to purification procedures, the loss of lipids surrounding the protein often results in irreversible inactivation. We describe a procedure for the immunoaffinity purification of the membrane protein UDP-glucuronosyltransferase from human liver. Th

  2. Rapid, sensitive separation of the three main isoflavones in soybean using immunoaffinity chromatography.

    Science.gov (United States)

    Qu, Huihua; Qu, Baoping; Wang, Xueqian; Zhang, Yue; Cheng, Jinjun; Zeng, Wenhao; Liu, Shuchen; Wang, Qingguo; Zhao, Yan

    2016-03-01

    Daidzin, genistin, and glycitein are major isoflavone compounds in soybean that are indispensable nutrients in traditional Chinese foods. Generally, strategies for detecting and separating soy isoflavones have been based on HPLC and chromatographic techniques, which are tedious and time-consuming procedures. In the present study, we developed an ELISA-based approach for daidzin detection using a broad-specificity monoclonal antibody (clone number: AA9) with an effective detection range of 10-10 000 ng/mL. Subsequently, we prepared an immunoaffinity column by coupling the monoclonal antibody AA9 to CNBr-activated Sepharose 4B. Our results demonstrate that the immunoaffinity column can efficiently and specifically extract daidzin, glycitein, and genistin from numerous structurally similar soy isoflavones in leguminous plants, thereby providing a new method for the extraction of target components from similar compounds in natural products.

  3. Thin-layer immunoaffinity chromatography with bar code quantitation of C-reactive protein.

    Science.gov (United States)

    Nilsson, S; Lager, C; Laurell, T; Birnbaum, S

    1995-09-01

    A rapid thin-layer immunoaffinity chromatographic method for quantitation in serum of an acute phase reactant, C-reactive protein (CRP), which can differentiate between viral and bacteria] infections, is described, where material and reagent costs are minimal. The analysis is based on the "sandwich" assay format using monoclonal antibodies directed against two sites of CRP. One of the antibodies is covalently bound to defined zones on a thin-layer immunoaffinity chromatography membrane, while the other antibody is covalently bound to deeply dyed blue latex particles. After incubation (CRP sample and latex particles), the CRP-latex immunocomplex is allowed to migrate along the immunoaffinity chromatography membrane. In the presence of antigen, a sandwich is formed between the CRP-latex immunocomplex and membrane-bound antibodies, which results in the appearance of blue lines on the membrane. Antibody immobilization on the TLC membrane is made with a redesigned piezoelectric-driven ink-jet printer. The time required for the analysis is less than 10 min. Quantitation is achieved either by counting the lines visually, with scanning reflectometry, or with a modified bar code reader. The limit of detection was estimated in the low femtomolar range using the naked eye as detector.

  4. Automated Aflatoxin Analysis Using Inline Reusable Immunoaffinity Column Cleanup and LC-Fluorescence Detection.

    Science.gov (United States)

    Rhemrev, Ria; Pazdanska, Monika; Marley, Elaine; Biselli, Scarlett; Staiger, Simone

    2015-01-01

    A novel reusable immunoaffinity cartridge containing monoclonal antibodies to aflatoxins coupled to a pressure resistant polymer has been developed. The cartridge is used in conjunction with a handling system inline to LC with fluorescence detection to provide fully automated aflatoxin analysis for routine monitoring of a variety of food matrixes. The handling system selects an immunoaffinity cartridge from a tray and automatically applies the sample extract. The cartridge is washed, then aflatoxins B1, B2, G1, and G2 are eluted and transferred inline to the LC system for quantitative analysis using fluorescence detection with postcolumn derivatization using a KOBRA® cell. Each immunoaffinity cartridge can be used up to 15 times without loss in performance, offering increased sample throughput and reduced costs compared to conventional manual sample preparation and cleanup. The system was validated in two independent laboratories using samples of peanuts and maize spiked at 2, 8, and 40 μg/kg total aflatoxins, and paprika, nutmeg, and dried figs spiked at 5, 20, and 100 μg/kg total aflatoxins. Recoveries exceeded 80% for both aflatoxin B1 and total aflatoxins. The between-day repeatability ranged from 2.1 to 9.6% for aflatoxin B1 for the six levels and five matrixes. Satisfactory Z-scores were obtained with this automated system when used for participation in proficiency testing (FAPAS®) for samples of chilli powder and hazelnut paste containing aflatoxins.

  5. Sol-gel immunoaffinity chromatography for the clean up of ochratoxin A contaminated grains.

    Science.gov (United States)

    Reiter, Elisabeth Viktoria; Cichna-Markl, Margit; Tansakul, Natthasit; Shim, Won-Bo; Chung, Duck-Hwa; Zentek, Jürgen; Razzazi-Fazeli, Ebrahim

    2011-10-21

    This paper describes the application of sol-gel immunoaffinity columns for clean up of ochratoxin A contaminated cereal crops. Monoclonal antibodies selective for OTA have been entrapped into the pores of a sol-gel matrix in order to prepare immunoaffinity columns. Different parameters such as amount of entrapped antibodies and loading conditions were optimized to obtain highest possible recoveries of OTA. The method has been found to be a suitable tool in sample preparation prior to HPLC-FLD determination and as selective as conventional commercially available immunoaffinity columns. In the clean up of different cereals mean recoveries of 82±5%, 90±6% and 91±3%, were obtained for wheat, barley and rye, respectively, with sol-gel columns containing 1mg of anti-OTA antibodies. The detection limit (signal-to-noise ratio, 3) was 0.5 μg/kg and the limit of quantification (signal-to-noise ratio, 10) determined to be 1 μg/kg. Sol-gel columns can be reused 7 times without significant loss of recovery. After 10 applications the recovery decreased to approx. 50%.

  6. Preparation and characterization of chitosan microparticles for immunoaffinity extraction and determination of enrofloxacin.

    Science.gov (United States)

    Yang, Yamei; Wang, Yadan; Niu, Rui; Lu, Jiandong; Zhu, Xinsheng; Wang, Yun

    2016-12-01

    The use of chitosan microparticles as chromatographic support has received much attention. In this study, the effects of process parameters, namely, chitosan molecular weight, chitosan concentration, molar ratio of amino group to aldehyde group, volume ratio of water to oil phase and stirring speed on the size and size distribution of chitosan microparticles and their application for immunoaffinity extraction were extensively investigated. Size distribution analysis indicated that the average diameter of the microparticles was 124μm with Span value of 1.1. The obtained microparticles exhibited low non-specific adsorption and kept stable in the pH range 4.0-10.0. Immunoaffinity chromatography (IAC) column was prepared by coupling antibody against enrofloxacin (ENR) with chitosan microparticles. Further characterization indicated that the binding capacity of the column was 4392ng ENR/mL gel and the variation of ENR extraction efficiency among columns was less than 5.2%. When challenged with ENR-fortified bovine milk samples, recoveries of ENR by immunoaffinity extraction were found to be in the range of 85.9% to 101.9%, demonstrated the feasibility of the prepared IAC columns for sample clean-up in ENR residue determination. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Identification of phosphorylated butyrylcholinesterase in human plasma using immunoaffinity purification and mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Aryal, Uma K.; Lin, Chiann Tso; Kim, Jong Seo; Heibeck, Tyler H.; Wang, Jun; Qian, Weijun; Lin, Yuehe

    2012-04-20

    Paraoxon (diethyl 4-nitrophenyl phosphate) is an active metabolite of the common insecticide parathion and is acutely toxic due to the inhibition of cholinesterase (ChE) activity in the nervous systems. The Inhibition of butyrylcholinesterase (BChE) activity by paraoxon is due to the formation of phosphorylated BChE adduct, and the detection of the phosphorylated BChE adduct in human plasma can serve as an exposure biomarker of organophosphate pesticides and nerve agents. In this study, we performed immunoaffinity purification and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis for identifying phosphorylated BChE in human plasma treated by paraoxon. BChE was captured by biotinylated anti-BChE polyclonal antibodies conjugated to streptavidin magnetic beads. Western blot analysis showed that the antibody was effective to recognize both native and modified BChE with high specificity. The exact phosphorylation site of BChE was confirmed on Serine 198 by MS/MS with a 108 Da modification mass and accurately measured parent ion masses. The phosphorylated BChE peptide was also successfully detected in the immunoaffinity purified sample from paraoxon treated human plasma. Thus, immunoaffinity purification combined with mass spectrometry represents a viable approach for the detection of paraoxon-modified BChE and other forms of modified BChE as exposure biomarkers of organophosphates and nerve agents.

  8. Secure Disk Mixed System

    Directory of Open Access Journals (Sweden)

    Myongchol Ri

    2013-01-01

    Full Text Available We propose a disk encryption method, called Secure Disk Mixed System (SDMS in this paper, for data protection of disk storages such as USB flash memory, USB hard disk and CD/DVD. It is aimed to solve temporal and spatial limitations of existing disk encryption methods and to control security performance flexibly according to the security requirement of system.

  9. Ankle replacement

    Science.gov (United States)

    Ankle arthroplasty - total; Total ankle arthroplasty; Endoprosthetic ankle replacement; Ankle surgery ... You may not be able to have a total ankle replacement if you have had ankle joint infections in ...

  10. Knee Replacement

    Science.gov (United States)

    Knee replacement is surgery for people with severe knee damage. Knee replacement can relieve pain and allow you to ... Your doctor may recommend it if you have knee pain and medicine and other treatments are not ...

  11. Rapid determination of total aflatoxins and ochratoxins A in meat products by immuno-affinity fluorimetry.

    Science.gov (United States)

    Abd-Elghany, Samir Mohammed; Sallam, Khalid Ibrahim

    2015-07-15

    Total aflatoxins (AFT) and ochratoxin A (OTA) levels were estimated using the VICAM AflaTest and OchraTest immunoaffinity fluorometric method in a total of 50 meat products (25 each of beef luncheon and beef burger) purchased from different supermarkets in Mansoura city, Egypt. All the meat samples analyzed were contaminated with both AFT and OTA with mean values of 1.1 μg/kg and 5.23 μg/kg, respectively, for beef luncheon and mean values of 3.22 μg/kg and 4.55 μg/kg, respectively, for beef burger. None of the beef luncheon and burger samples analyzed exceeded the permissible limits set by FDA for AFT, but 40% of beef burgers exceeded the FAO AFT permissible limit. Similarly, 52% and 36% of beef luncheon and beef burger samples exceeded the FAO OTA permissible limit. Application of the immunoaffinity fluorometric method is an accurate, safe and rapid method for mycotoxins determination in meat products to ensure their safety for human consumption.

  12. Galaxy Disks are Submaximal

    NARCIS (Netherlands)

    Bershady, Matthew A.; Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Andersen, David R.; Swaters, Rob A.

    2011-01-01

    We measure the contribution of galaxy disks to the overall gravitational potential of 30 nearly face-on intermediate-to-late-type spirals from the DiskMass Survey. The central vertical velocity dispersion of the disk stars (sigma(disk)(z,R=0)) is related to the maximum rotation speed (V-max) as sigm

  13. DVD - digital versatile disks

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, R.

    1997-05-01

    An international standard has emerged for the first true multimedia format. Digital Versatile Disk (by its official name), you may know it as Digital Video Disks. DVD has applications in movies, music, games, information CD-ROMS, and many other areas where massive amounts of digital information is needed. Did I say massive amounts of data? Would you believe over 17 gigabytes on a single piece of plastic the size of an audio-CD? That`s the promise, at least, by the group of nine electronics manufacturers who have agreed to the format specification, and who hope to make this goal a reality by 1998. In this major agreement, which didn`t come easily, the manufacturers will combine Sony and Phillip`s one side double-layer NMCD format with Toshiba and Matsushita`s double sided Super-Density disk. By Spring of this year, they plan to market the first 4.7 gigabyte units. The question is: Will DVD take off? Some believe that read-only disks recorded with movies will be about as popular as video laser disks. They say that until the eraseable/writable DVD arrives, the consumer will most likely not buy it. Also, DVD has a good market for replacement of CD- Roms. Back in the early 80`s, the international committee deciding the format of the audio compact disk decided its length would be 73 minutes. This, they declared, would allow Beethoven`s 9th Symphony to be contained entirely on a single CD. Similarly, today it was agreed that playback length of a single sided, single layer DVD would be 133 minutes, long enough to hold 94% of all feature-length movies. Further, audio can be in Dolby`s AC-3 stereo or 5.1 tracks of surround sound, better than CD-quality audio (16-bits at 48kHz). In addition, there are three to five language tracks, copy protection and parental ``locks`` for R rated movies. DVD will be backwards compatible with current CD-ROM and audio CD formats. Added versatility comes by way of multiple aspect rations: 4:3 pan-scan, 4:3 letterbox, and 16:9 widescreen. MPEG

  14. Directed Replacement

    CERN Document Server

    Karttunen, L

    1996-01-01

    This paper introduces to the finite-state calculus a family of directed replace operators. In contrast to the simple replace expression, UPPER -> LOWER, defined in Karttunen (ACL-95), the new directed version, UPPER @-> LOWER, yields an unambiguous transducer if the lower language consists of a single string. It transduces the input string from left to right, making only the longest possible replacement at each point. A new type of replacement expression, UPPER @-> PREFIX ... SUFFIX, yields a transducer that inserts text around strings that are instances of UPPER. The symbol ... denotes the matching part of the input which itself remains unchanged. PREFIX and SUFFIX are regular expressions describing the insertions. Expressions of the type UPPER @-> PREFIX ... SUFFIX may be used to compose a deterministic parser for a ``local grammar'' in the sense of Gross (1989). Other useful applications of directed replacement include tokenization and filtering of text streams.

  15. Oscillations of disks

    CERN Document Server

    Kato, Shoji

    2016-01-01

    This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...

  16. Results of investigations into coal cutting by asymmetric disks

    Energy Technology Data Exchange (ETDEWEB)

    Krauze, K.

    1985-02-01

    Effects are analyzed of design and specifications of asymmetric disk cutters on coal cutting by a shearer loader with disk cutters on helical cutting drums. Effects of disk diameter, wedge angle, cutting depth and chip thickness on cutting resistance were analyzed under operational conditions (a coal seam was cut by asymmetric disk cutters). On the basis of analysis of coal resistance to cutting by asymmetric cutting disks, regression equations were derived which describe coal cutting. Effects of disk parameters and cutting conditions on cutting resistance were determined. Analyses show that replacing radial cutting tools with asymmetric disk cutters would cause an increase in energy consumption of cutting and increase coal resistance to cutting. 1 reference.

  17. Knee Replacement

    Science.gov (United States)

    ... need knee replacement surgery usually have problems walking, climbing stairs, and getting in and out of chairs. Some ... a total living space on one floor since climbing stairs can be difficult. Install safety bars or a ...

  18. Isolation of novel indole-3-acetic acid conjugates by immunoaffinity extraction.

    Science.gov (United States)

    Pencík, Ales; Rolcík, Jakub; Novák, Ondrej; Magnus, Volker; Barták, Petr; Buchtík, Roman; Salopek-Sondi, Branka; Strnad, Miroslav

    2009-12-15

    An analytical protocol for the isolation and quantification of indole-3-acetic acid (IAA) and its amino acid conjugates was developed. IAA is an important phytohormone and formation of its conjugates plays a crucial role in regulating IAA levels in plants. The developed protocol combines a highly specific immunoaffinity extraction with a sensitive and selective LC-MS/MS analysis. By using internal standards for each of the studied compounds, IAA and seven amino acid conjugates were analyzed in quantities of fresh plant material as low as 30 mg. In seeds of Helleborus niger, physiological levels of these compounds were found to range from 7.5 nmol g(-1) fresh weight (IAA) to 0.44 pmol g(-1) fresh weight (conjugate with Ala). To our knowledge, the identification of IAA conjugates with Gly, Phe and Val from higher plants is reported here for the first time.

  19. Replacing penalties

    Directory of Open Access Journals (Sweden)

    Vitaly Stepashin

    2017-01-01

    Full Text Available УДК 343.24The subject. The article deals with the problem of the use of "substitute" penalties.The purpose of the article is to identify criminal and legal criteria for: selecting the replacement punishment; proportionality replacement leave punishment to others (the formalization of replacement; actually increasing the punishment (worsening of legal situation of the convicted.Methodology.The author uses the method of analysis and synthesis, formal legal method.Results. Replacing the punishment more severe as a result of malicious evasion from serving accused designated penalty requires the optimization of the following areas: 1 the selection of a substitute punishment; 2 replacement of proportionality is serving a sentence other (formalization of replacement; 3 ensuring the actual toughening penalties (deterioration of the legal status of the convict. It is important that the first two requirements pro-vide savings of repression in the implementation of the replacement of one form of punishment to others.Replacement of punishment on their own do not have any specifics. However, it is necessary to compare them with the contents of the punishment, which the convict from serving maliciously evaded. First, substitute the punishment should assume a more significant range of restrictions and deprivation of certain rights of the convict. Second, the perfor-mance characteristics of order substitute the punishment should assume guarantee imple-mentation of the new measures.With regard to replacing all forms of punishment are set significant limitations in the application that, in some cases, eliminates the possibility of replacement of the sentence, from serving where there has been willful evasion, a stricter measure of state coercion. It is important in the context of the topic and the possibility of a sentence of imprisonment as a substitute punishment in cases where the original purpose of the strict measures excluded. It is noteworthy that the

  20. Disk Storage Server

    CERN Multimedia

    This model was a disk storage server used in the Data Centre up until 2012. Each tray contains a hard disk drive (see the 5TB hard disk drive on the main disk display section - this actually fits into one of the trays). There are 16 trays in all per server. There are hundreds of these servers mounted on racks in the Data Centre, as can be seen.

  1. Galactic Disk Warps

    NARCIS (Netherlands)

    Kuijken, K.; García, I.

    2000-01-01

    Abstract: This review addresses recent developments in the field of disk galaxy warps. Both results from a new HI survey of edgeon disk galaxies, and of simulations of the interaction between a disk+halo and an orbiting satelite, will be discussed.

  2. Galactic Disk Warps

    CERN Document Server

    Kuijken, K; Kuijken, Konrad; Garcia, Inigo

    2000-01-01

    This review addresses recent developments in the field of disk galaxy warps. Both results from a new HI survey of edgeon disk galaxies, and of simulations of the interaction between a disk+halo and an orbiting satelite, will be discussed.

  3. Chemistry in Protoplanetary Disks

    CERN Document Server

    Henning, Thomas

    2013-01-01

    This comprehensive review summarizes our current understanding of the evolution of gas, solids and molecular ices in protoplanetary disks. Key findings related to disk physics and chemistry, both observationally and theoretically, are highlighted. We discuss which molecular probes are used to derive gas temperature, density, ionization state, kinematics, deuterium fractionation, and study organic matter in protoplanetary disks.

  4. Optical Disk Technology.

    Science.gov (United States)

    Abbott, George L.; And Others

    1987-01-01

    This special feature focuses on recent developments in optical disk technology. Nine articles discuss current trends, large scale image processing, data structures for optical disks, the use of computer simulators to create optical disks, videodisk use in training, interactive audio video systems, impacts on federal information policy, and…

  5. Esophageal replacement.

    Science.gov (United States)

    Kunisaki, Shaun M; Coran, Arnold G

    2017-04-01

    This article focuses on esophageal replacement as a surgical option for pediatric patients with end-stage esophageal disease. While it is obvious that the patient׳s own esophagus is the best esophagus, persisting with attempts to retain a native esophagus with no function and at all costs are futile and usually detrimental to the overall well-being of the child. In such cases, the esophagus should be abandoned, and the appropriate esophageal replacement is chosen for definitive reconstruction. We review the various types of conduits used for esophageal replacement and discuss the unique advantages and disadvantages that are relevant for clinical decision-making. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Cross-reactivity of some commercially available DON and ZEN immunoaffinity columns to DON and ZEN conjugated forms and metabolites

    OpenAIRE

    Versilovskis, Aleksandrs; Huybrecht, Bart; Tangni, Emmanuel K; Luc, Pussemier; De Saeger, Sarah; Callebaut, Alfons

    2011-01-01

    Abstract Abstract Seven commercially available deoxynivalenol (DON) and zearalenone (ZEN) immunoaffinity columns (IACs) were tested for cross-reactivity to conjugated forms (3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, DON-3-glucoside, DON-3-glucuronide, ZEN-glucosides, ZEN-glucuronide) and metabolites (de-epoxydeoxynivalenol, ?-zearalenol, ?-zearalenol) and nivalenol (NIV), using a semi-quantitative multi-mycotoxin ultra performance liquid chromatography ? tandem ...

  7. REMARKS ON JOHN DISKS

    Institute of Scientific and Technical Information of China (English)

    Chu Yuming; Cheng Jinfa; Wang Gendi

    2009-01-01

    Let D R2 be a Jordan domain, D* = -R2 \\ -D, the exterior of D. In this article, the authors obtained the following results: (1) If D is a John disk, then D is an outer linearly locally connected domain; (2) If D* is a John disk, then D is an inner linearly locally connected domain; (3) A homeomorphism f: R2→R2 is a quasiconformal mapping if and only if f(D) is a John disk for any John disk D(∈)R2; and (4) If D is a bounded quasidisk, then D is a John disk, and there exists an unbounded quasidisk which is not a John disk.

  8. Exploring Disks Around Planets

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    Giant planets are thought to form in circumstellar disks surrounding young stars, but material may also accrete into a smaller disk around the planet. Weve never detected one of these circumplanetary disks before but thanks to new simulations, we now have a better idea of what to look for.Image from previous work simulating a Jupiter-mass planet forming inside a circumstellar disk. The planet has its own circumplanetary disk of accreted material. [Frdric Masset]Elusive DisksIn the formation of giant planets, we think the final phase consists of accretion onto the planet from a disk that surrounds it. This circumplanetary disk is important to understand, since it both regulates the late gas accretion and forms the birthplace of future satellites of the planet.Weve yet to detect a circumplanetary disk thus far, because the resolution needed to spot one has been out of reach. Now, however, were entering an era where the disk and its kinematics may be observable with high-powered telescopes (like the Atacama Large Millimeter Array).To prepare for such observations, we need models that predict the basic characteristics of these disks like the mass, temperature, and kinematic properties. Now a researcher at the ETH Zrich Institute for Astronomy in Switzerland, Judit Szulgyi, has worked toward this goal.Simulating CoolingSzulgyi performs a series of 3D global radiative hydrodynamic simulations of 1, 3, 5, and 10 Jupiter-mass (MJ) giant planets and their surrounding circumplanetary disks, embedded within the larger circumstellar disk around the central star.Density (left column), temperature (center), and normalized angular momentum (right) for a 1 MJ planet over temperatures cooling from 10,000 K (top) to 1,000 K (bottom). At high temperatures, a spherical circumplanetary envelope surrounds the planet, but as the planet cools, the envelope transitions around 64,000 K to a flattened disk. [Szulgyi 2017]This work explores the effects of different planet temperatures and

  9. Survey of Mycotoxins in Wheat from Iran by HPLC Using Immunoaffinity Column Cleanup

    Directory of Open Access Journals (Sweden)

    Javad Feizy

    2014-05-01

    Full Text Available Mycotoxins are small, toxic chemical products produced as secondary metabolites by a few fungal spices that readily colonise crops and contaminate them with toxins in the field or after harvest. In this study a liquid chromatographic method was developed for the simultaneous determination of aflatoxins (AFs (B1, B2, G1, and G2, ochratoxin A (OTA and zearalenone(ZEA toxins in wheat. For this purpose, a total of 231 wheat samples were analyzed. Mycotoxins were extracted and purified from the samples using immunoaffinity (IAC columns. 2.67% and 2.21% of examined wheat samples contained AFB1and OTA. The method was based on the extraction of AFs, OTA and ZEA finely ground wheat sample with 80% methanol and 60% acetonitrile solution, respectively. 2.60% and 2.16% of examined wheat samples contained AFB1 and OTA. LOD was 0.27, 0.04, 0.23, 0.04, 1.18 and 21.56 for AFB1, AFB2, AFG1, AFG2, OTA and ZEA, respectively.Considering these results, these special products should not be a health concern for these collectives; however, special attention needs on foods distribution in retail shops.

  10. Advantages and drawbacks of immunoaffinity columns in analysis of mycotoxins in food.

    Science.gov (United States)

    Castegnaro, Marcel; Tozlovanu, Marianna; Wild, Christopher; Molinié, Anne; Sylla, Abdoulay; Pfohl-Leszkowicz, Annie

    2006-05-01

    A number of countries are setting legislations on mycotoxins. In order to reduce dispute between importing and exporting countries, the analytical data should be as comparable as possible, especially when levels are close to the regulatory limits. The present trend in the analysis of mycotoxins is to use immunoaffinity column (IAC) as a clean-up and enrichment technique, and Association of Official Analytical Chemists and European Union have validated methods which address a few food commodities. This study describes our experience using both conventional and IAC approaches in the analysis of three mycotoxins. Aflatoxins (AFs): Aflatoxin G1 has been detected by liquid-liquid partitioning methods with HPLC detection as false-positive in some maize. On IACs, this compound behaves as an AF, lowering the amount of the AFs trapped. The problem was solved using either TLC or HPLC with detection in the Kobra cell. Depending on the additives to food during the processing and cooking, the AFs might appear as an opened ring not recognised by the antibody. Fumonisins (FB): Compounds interfering with the FB's antibodies were also observed while analysing breakfast cereals leading to underestimation of FB. Ochratoxin A (OTA): Depending on the food composition and extraction techniques, OTA is underestimated with IAC in some breakfast cereals and coffee. These data strengthen the necessity to validate methods using IAC for each complex matrix.

  11. New lysine-acetylated proteins screened by immunoaffinity and liquid chromatography-mass spectrometry

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The lack of selective extraction specific for lysine-acetylated proteins has been a major problem in the field of acetylation biology,though acetylation plays a key role in many biological processes.In this paper,we report for the first time the proteomic screening of lysine-acetylated proteins from a mouse liver tissue,by a new approach of immunoaffinity purification of lysine-acetylated peptides combined with nano-HPLC/MS/MS analysis.We have found 20 lysine-acetylated proteins with 21 lysine-acetylated sites,among which 12 lysine-acetylated proteins and 16 lysine-acetylated sites have never been reported before.Notably,three acetyltransferases harboring in mitochondrion are newly discovered acetyltransferases responsible for the acetylation of nonhistone proteins.We have explored the significant patterns of residue preference by the hierarchical clustering analysis of amino acid residues surrounding acetylation sites,which could be helpful to the prediction of new sites of lysine acetylation.Our findings provide more candidates for studying the important roles played by acetylation in diverse cellular pathways and related human diseases.

  12. Immunoaffinity Ultrafiltration with Ion Spray HPLC/MS for Screening Small-Molecule Libraries.

    Science.gov (United States)

    Wieboldt, R; Zweigenbaum, J; Henion, J

    1997-05-01

    A solution-phase screening method for libraries of pharmaceutically relevant molecules is presented. The technique is applicable to screening combinatorial libraries of 20-30 closely related molecules. In this report, individual benzodiazepines are selected from a multicomponent library mixture by formation in solution of noncovalent immunoaffinity complexes with antibodies raised to therapeutically proven drugs such as nitrazepam, temazepam, or oxazepam. Captured compounds are separated from nonspecifically bound library components by centrifugal ultrafiltration. The specifically selected molecules retained on the filter are subsequently liberated from the antibodies by acidification and analyzed by HPLC coupled with pneumatically assisted electrospray (ion spray) ionization mass spectrometric detection. Competition by the benzodiazepines for limited antibody binding sites is controlled by varying the stoichiometry of the complexation mixture. This procedure selects library components with the greatest affinity for a particular antibody. Specific capture of benzodiazepines is demonstrated by screening both a pool of structurally similar benzodiazepines and a more complex mixture of benzodiazepines with an additional set of unrelated compounds. Affinity ultrafiltration and electrospray mass spectrometry complement each other to enhance screening and identification of pooled drug candidates and potentially can be extended to other small-molecule combinatorial libraries and macromolecular receptor preparations.

  13. Immunoaffinity purification and characterization of glyceraldehyde-3-phosphate dehydrogenase from human erythrocytes

    Institute of Scientific and Technical Information of China (English)

    Driss Mountassif; Tarik Baibai; Latifa Fourrat; Adnane Moutaouakkil; Abdelghani Iddar; M'Hammed Sa(i)d El Kebbaj; Abdelaziz Soukri

    2009-01-01

    A new procedure utilizing immunoaffinity column chromatography has been used for the purification of glyceraldehyde-3-phosphate dehydrogenase(GAPDH,EC 1.2.1.12)from human erythrocytes.The comparison between this rapid method(one step)and the traditional procedure including ammonium sulfate fractionation followed by Blue Sepharose CL-6B chromatography shows that the new method gives a highest specific activity with a highest yield in a short time.The characterization of the purified GAPDH reveals that the native enzyme is a homotetramer of ~150 kDa with an absolute specificity for the oxidized form of nicotinamide adenine dinucleotide(NAD+).Western blot analysis using purified monospecific poly clonal antibodies raised against the purified GAPDH showed a singie 36 kDa band corresponding to the enzyme subunit.Studies on the effect of temperature and pH on enzyme activity revealed optimal values of about 43℃ and 8.5, respectively.The kinetic par ameters were also calculated:the Vmax was 4.3 U/mg and the Km values against G3P and NAD+ were 20.7and 17.8μM,respectively.The new protocol described represents a simple,economic,and reproducible tool for the purification Of GAPDH and can be used for other proteins.

  14. Purification of human seminal plasma no. 7 antigen by immunoaffinity chromatography on bound monoclonal antibody.

    Science.gov (United States)

    Isojima, S; Koyama, K; Fujiwara, N

    1982-01-01

    Human seminal plasma (HSP) No. 7 antigen was purified by immunoaffinity chromatography on bound 1C4 monoclonal antibody (Moab) (Shigeta et al., 1980b). The pooled HSP protein was applied to a CNBr-activated Sepharose 4B column of bound 1C4 Moab gamma globulin and the antibody bound fraction (fr) eluted was further purified by rechromatography in the same way. The purified antigen in the antibody bound fr obtained by rechromatography gave a single band on SDS-PAGE in a position corresponding to a molecular weight of 15,000 daltons. This preparation was 196.2 times more effective than the original HSP protein in neutralizing the sperm immobilizing activity of 1C4 Moab. The purified HSP No. 7 antigen contained iron, but was different from lactoferrin and transferrin. It did not show any enzymatic activities, such as those of acid phosphatase, LDH or trypsin inhibitor, and shared antigenicity with human milk protein. It was present in seminal plasma as a molecule with a higher molecular weight but seemed to be cleaved to a monomer of 15,000 daltons during purification procedures. This antigen is present on spermatozoa as sperm-coating antigen and the corresponding antibody can immobilize spermatozoa with complement. Images Fig. 3 PMID:7127911

  15. Immunoaffinity purification of peptide hormones prior to liquid chromatography-mass spectrometry in doping controls.

    Science.gov (United States)

    Thomas, Andreas; Schänzer, Wilhelm; Delahaut, Philippe; Thevis, Mario

    2012-02-01

    For most peptide hormones prohibited in elite sports the concentrations in plasma or urine are very low (pg/mL). Accordingly, hyphenated purification and enrichment steps prior to mass spectrometric detection are required to obtain sufficient doping control assays. Immunoaffinity purification in combination with nano-scale liquid chromatography coupled to high resolution/high accuracy mass spectrometry was found to have the potential of providing the necessary sensitivity and unambiguous specificity to produce reliable results. With the presented methodology 12 prohibited peptides (porcine insulin, Novolog, Apidra, Lantus DesB30-32 metabolite, Humalog and human insulin, Synacthen (synthetic ACTH analogue), luteinizing hormone-releasing hormone (LH-RH), growth hormone releasing hormone (GH-RH(1-29)) and CJC-1295 (GH-RH analogue), LongR(3)-IGF-1 and IFG-1) were simultaneously purified from plasma/serum or urine. With limits of detection for each target compound ranging in the low pg/mL level (urine), the method enables the determination of urinary peptides at physiologically relevant concentrations. For each class of peptides an appropriate antibody and a respective internal standard was implemented ensuring robust analysis conditions. Due to the fast and simple sample preparation procedure (∼25 samples per day) and the fact that all materials are commercial available, the implementation of the methodology to laboratories from other analytical fields (forensics, pharmacokinetic sciences, etc.) is enabled.

  16. Chromatographic Monoliths for High-Throughput Immunoaffinity Isolation of Transferrin from Human Plasma

    Directory of Open Access Journals (Sweden)

    Irena Trbojević-Akmačić

    2016-06-01

    Full Text Available Changes in protein glycosylation are related to different diseases and have a potential as diagnostic and prognostic disease biomarkers. Transferrin (Tf glycosylation changes are common marker for congenital disorders of glycosylation. However, biological interindividual variability of Tf N-glycosylation and genes involved in glycosylation regulation are not known. Therefore, high-throughput Tf isolation method and large scale glycosylation studies are needed in order to address these questions. Due to their unique chromatographic properties, the use of chromatographic monoliths enables very fast analysis cycle, thus significantly increasing sample preparation throughput. Here, we are describing characterization of novel immunoaffinity-based monolithic columns in a 96-well plate format for specific high-throughput purification of human Tf from blood plasma. We optimized the isolation and glycan preparation procedure for subsequent ultra performance liquid chromatography (UPLC analysis of Tf N-glycosylation and managed to increase the sensitivity for approximately three times compared to initial experimental conditions, with very good reproducibility. This work is licensed under a Creative Commons Attribution 4.0 International License.

  17. Isolated unilateral disk edema

    OpenAIRE

    Varner P

    2011-01-01

    Paul VarnerJohn J Pershing VAMC, Poplar Bluff, MO, USAAbstract: Isolated unilateral disk edema is a familiar clinical presentation with myriad associations. Related, non-consensus terminology is a barrier to understanding a common pathogenesis. Mechanisms for the development of disk edema are reviewed, and a new framework for clinical differentiation of medical associations is presented.Keywords: disk edema, axoplasmic flow, clinical multiplier, optic neuritis, ischemic optic neuropathy, papi...

  18. Isolated unilateral disk edema

    Directory of Open Access Journals (Sweden)

    Varner P

    2011-07-01

    Full Text Available Paul VarnerJohn J Pershing VAMC, Poplar Bluff, MO, USAAbstract: Isolated unilateral disk edema is a familiar clinical presentation with myriad associations. Related, non-consensus terminology is a barrier to understanding a common pathogenesis. Mechanisms for the development of disk edema are reviewed, and a new framework for clinical differentiation of medical associations is presented.Keywords: disk edema, axoplasmic flow, clinical multiplier, optic neuritis, ischemic optic neuropathy, papilledema

  19. A valve disk

    Energy Technology Data Exchange (ETDEWEB)

    Khayrullin, N.A.; Isayev, B.N.; Kruglov, S.A.; Molokanov, Yu.K.; Shchelkunov, V.A.; Shegay, V.R.; Vizhgorodskiy, B.N.

    1982-01-01

    A valve disk is proposed which includes a horizontal bed, on which there are laminar valves arranged in staggered order. To ensure the stable and effective operation of the disk in a broad range of loads by compensating for the direct flow and the partial sectioning of the disk bed, it is equipped with compensating elements installed in openings in the bed and hinged with it. They are made in the form of straight, triangular prisms with ports in the bases. The prisms are installed with the capability of movement relative to the disk bed. The valves are positioned on the upper lateral facets of the compensating elements.

  20. Planetesimals in Debris Disks

    CERN Document Server

    Youdin, Andrew N

    2015-01-01

    Planetesimals form in gas-rich protoplanetary disks around young stars. However, protoplanetary disks fade in about 10 Myr. The planetesimals (and also many of the planets) left behind are too dim to study directly. Fortunately, collisions between planetesimals produce dusty debris disks. These debris disks trace the processes of terrestrial planet formation for 100 Myr and of exoplanetary system evolution out to 10 Gyr. This chapter begins with a summary of planetesimal formation as a prelude to the epoch of planetesimal destruction. Our review of debris disks covers the key issues, including dust production and dynamics, needed to understand the observations. Our discussion of extrasolar debris keeps an eye on similarities to and differences from Solar System dust.

  1. Human Plasma N-Glycoproteome Analysis by Immunoaffinity Subtraction, Hydrazide Chemistry, and Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tao; Qian, Weijun; Gritsenko, Marina A.; Camp, David G.; Monroe, Matthew E.; Moore, Ronald J.; Smith, Richard D.

    2005-12-01

    The enormous complexity, wide dynamic range of relative protein abundance of interest (over 10 orders of magnitude), and tremendous heterogeneity (due to post-translational modifications, such as glycosylation) of the human blood plasma proteome severely challenges the capabilities of existing analytical methodologies. We describe here the comprehensive analysis of human plasma N-glycoproteins using the combination of immunoaffinity subtraction and glycoprotein capture to reduce both the protein concentration range and the overall sample complexity. Six high-abundance plasma proteins were simultaneously removed using a pre-packed, immobilized antibody column. N-linked glycoproteins were then captured from the depleted plasma using hydrazide resin, enzymatically digested, and the bound, N-linked glycopeptides were released using peptide-N-glycosidase F. Following strong cation exchange (SCX) fractionation, the deglycosylated peptides were analyzed by reversed-phase capillary liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). A total of 2140 different N-glycopeptides were confidently identified using stringent criteria, covering 371 non-redundant N-glycoproteins with the majority of them being extracellular or membrane proteins. The strategy significantly improved the detection, enabling the identification of a number of low-abundance proteins, exemplified by interleukin-1 receptor antagonist protein ({approx}200 pg/mL), cathepsin L ({approx}1 ng/mL), and transforming growth factor beta 1 ({approx}2 ng/mL). A total of 712 N-glycosylation sites were identified and the confidence of these site identifications was further validated by accurate mass measurements using high resolution liquid chromatography coupled to Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR). This study provides the basis for future high-throughput measurements using the accurate mass and time tag approach.

  2. Antigen-binding properties of monoclonal antibodies reactive with EBNA1 and use in immunoaffinity chromatography.

    Directory of Open Access Journals (Sweden)

    Sarah J Duellman

    Full Text Available Epstein-Barr virus (EBV nuclear antigen 1 (EBNA1 was overexpressed and purified from Escherichia coli. Mouse monoclonal antibodies (mAbs were prepared that react with EBNA1. Eleven high affinity mAbs were recovered. Nine mAbs are isotype IgG (all subisotype IgG(1 and two mAbs are isotype IgM. All mAbs react strongly with EBNA1 in an ELISA assay while only one mAb (designated 1EB6 fails to react in a Western blot assay. The epitopes for these mAbs were mapped to seven different regions, providing good coverage of the entire EBNA1 protein. The mAbs had differing affinity for an EBNA1/DNA complex with four mAbs able to supershift the complex completely. All mAbs can immunoprecipitate EBNA1 from E. coli overexpressing EBNA1. A modified ELISA assay, termed ELISA-elution assay, was used to screen for mAbs that release EBNA1 in the presence of a low molecular weight polyhydroxylated compound (polyol and a nonchaotropic salt. MAbs with this property, termed polyol-responsive (PR-mAbs, allow gentle elution of labile proteins and protein complexes. Four mAbs are polyol-responsive with two showing usefulness in gentle immunoaffinity chromatography. Purification with these PR-mAbs may be useful in purifying EBNA1 complexes and elucidating EBNA1-associated proteins. This panel of anti-EBNA1 mAbs will advance the study of EBV by providing new tools to detect and purify EBNA1.

  3. Method for determination of aflatoxin M₁ in cheese and butter by HPLC using an immunoaffinity column.

    Science.gov (United States)

    Sakuma, Hisako; Kamata, Yoichi; Sugita-Konishi, Yoshiko; Kawakami, Hiroshi

    2011-01-01

    A rapid, sensitive convenient method for determination of aflatoxin M₁ (AFM₁) in cheese and butter by HPLC was developed and validated. The method employs a safe extraction solution (mixture of acetonitrile, methanol and water) and an immunoaffinity column (IAC) for clean-up. Compared with the widely used method employing chloroform and a Florisil column, the IAC method has a short analytical time and there are no interference peaks. The limits of quantification (LOQ) of the IAC method were 0.12 and 0.14 µg/kg, while those of the Florisil column method were 0.47 and 0.23 µg/kg in cheese and buffer, respectively. The recovery and relative standard deviation (RSD) for cheese (spiked at 0.5 µg/kg) in the IAC method were 92% and 7%, respectively, while for the Florisil column method the corresponding values were 76% and 10%. The recovery and RSD for butter (spiked at 0.5 µg/kg) in the IAC method were 97% and 9%, and those in the Florisil method were 74% and 9%, respectively. In the IAC method, the values of in-house precision (n=2, day=5) of cheese and butter (spiked at 0.5 µg/kg) were 9% and 13%, respectively. The IAC method is superior to the Florisil column method in terms of safety, ease of handling, sensitivity and reliability. A survey of AFM₁ contamination in imported cheese and butter in Japan was conducted by the IAC method. AFM₁ was not detected in 60 samples of cheese and 30 samples of butter.

  4. Quantitation of Insulin Analogues in Serum Using Immunoaffinity Extraction, Liquid Chromatography, and Tandem Mass Spectrometry.

    Science.gov (United States)

    Van Der Gugten, J Grace; Wong, Sophia; Holmes, Daniel T

    2016-01-01

    Insulin analysis is used in combination with glucose, C-peptide, beta-hydroxybutyrate, and proinsulin determination for the investigation of adult hypoglycemia. The most common cause is the administration of too much insulin or insulin secretagogue to a diabetic patient or inadequate caloric intake after administration of either. Occasionally there is a question as to whether hypoglycemia has been caused by an exogenous insulin-whether by accident, intent, or even malicious intent. While traditionally this was confirmed by a low or undetectable C-peptide in a hypoglycemic specimen, this finding is not entirely specific and would also be expected in the context of impaired counter-regulatory response, fatty acid oxidation defects, and liver failure-though beta-hydroxybutyrate levels can lend diagnostic clarity. For this reason, insulin is often requested. However, popular automated chemiluminescent immunoassays for insulin have distinctly heterogeneous performance in detecting analogue synthetic insulins with cross-reactivities ranging from near 0 % to greater than 100 %. The ability to detect synthetic insulins is vendor-specific and varies between insulin products. Liquid Chromatography and Tandem Mass Spectrometry (LC-MS/MS) offers a means to circumvent these analytical issues and both quantify synthetic insulins and identify the specific type. We present an immunoaffinity extraction and LC-MS/MS method capable of independent identification and quantitation of native sequence insulins (endogenous, Insulin Regular, Insulin NPH), and analogues Glargine, Lispro, Detemir, and Aspart with an analytical sensitivity for endogenous insulin of between 1 and 2 μU/mL in patient serum samples.

  5. Biochips that Sequentially Capture and Focus Antigens for Immunoaffinity MALDI-TOF MS: A New Tool for Biomarker Verification

    Science.gov (United States)

    Brauer, Heather Ann; Lampe, Paul D.; Yasui, Yutaka Y.; Hamajima, Nobuyuki; Stolowitz, Mark L.

    2011-01-01

    A novel approach to immunoaffinity MS is described wherein antibodies are appended to a patterned gold Biochip surface. The Biochip surface is patterned with an array of concentric immunocapture zones comprised of highly hydrophilic central zones surrounded by moderately hydrophilic zones that reside on a non-wetting background, with protein attachment via electrochemically cleavable linkers. After linker cleavage, matrix application forms a discrete spot suitable for MALDI-TOF-MS. Use of the Biochip to purify Transthyretin from human serum allowed distinct resolution of four disulfide conjugates and one truncated form isoforms with good mass resolution and sensitivity. PMID:20957758

  6. Preparation and Application of an Immunoaffinity Column for Direct Extraction of Morphine and its Analogs from Opium

    Institute of Scientific and Technical Information of China (English)

    Xiao Hua QI; Jian Qiu MI; Xin Xiang ZHANG; Wen Bao CHANG

    2004-01-01

    A rapid, simple and accurate method using an immunoaffinity column (IAC) and capillary electrophoresis (CE) for the analysis of the major alkaloids in opium is developed. The IAC was synthesized by coupling specific morphine polyclonal antibodies to CNBr-actived Sepharose 4B. The IAC showed high selectivity and obvious enrichment to morphine, codeine, dionin and thebaine. The extraction solution was analyzed by CE with β-cyclodextrin as an additive. Recoveries of the four alkaloids from PBS were between 93%-105% with RSD value less than 5.0%. The result showed that this method was practical for the determination of morphine analogs in opium.

  7. Use of Differential Scanning Calorimetry and Immunoaffinity Chromatography to Identify Disease Induced Changes in Human Blood Plasma Proteome.

    Science.gov (United States)

    Brudar, Sandi; Černigoj, Urh; Podgornik, Helena; Kržan, Mojca; Prislan, Iztok

    2017-09-01

    Differential scanning calorimetry provides unique signatures of blood plasma samples. Plasma samples from diseased individuals yield specific thermograms, which differ from each other and from plasma samples of healthy individuals. Thermograms from individuals suffering from chronic lymphocytic leukemia, multiple myeloma and acute myeloid leukemia were measured with DSC. To obtain additional information about thermal behaviour of plasma proteins immunoaffinity chromatography was introduced. An immunoextraction of HSA using a chromatographic column with immobilized anti-HSA was carried out in order to enrich less abundant plasma proteins, which could provide a further insight into disease development. Efficiency of HSA depletion and protein composition of fractionated plasma was validated by SDS-PAGE.

  8. [Estrogen replacement].

    Science.gov (United States)

    Søgaard, A J; Berntsen, G K; Magnus, J H; Tollan, A

    1998-02-10

    Recent research on long-term postmenopausal hormone replacement therapy (HRT) indicates a positive effect on both total mortality and morbidity. This has raised the question of widespread preventive long-term use of HRT. Possible side-effects and ideological issues related to preventive HRT have led to debate and uncertainty among health professionals, in the media, and in the population at large. In order to evaluate the level of knowledge about and attitudes towards HRT, a randomly selected group of 737 Norwegian women aged 16-79 was interviewed by the Central Bureau of Statistics. One in three women had received information about HRT in the last two years, mainly through weekly magazines and physicians. The proportion who answered the questions on knowledge correctly varied from 36% to 47%. Those who had been given information by a physician possessed accurate knowledge, had more positive attitudes towards HRT and were more willing to use HRT than women who had reviewed information through other channels. Women with a higher level of education were better informed and more knowledgeable than others, but were nevertheless more reluctant to use HRT than those who were less educated. The limited number of women who actually receive information on HRT, the low level of knowledge and the ambivalent attitudes toward HRT are a major challenge to the public health service.

  9. Disk Defect Data

    Data.gov (United States)

    National Aeronautics and Space Administration — How Data Was Acquired: The data presented is from a physical simulator that simulated engine disks. Sample Rates and Parameter Description: All parameters are...

  10. Antigen digestion on the target plate of MALDI-TOF MS after isolation using an immunoaffinity membrane.

    Science.gov (United States)

    Shimazaki, Youji; Nishimura, Yuri; Saito, Masaki

    2013-09-01

    A combination of methods is required to achieve separation of intact proteins and subsequently perform structure analysis to examine their unstable or external structures. The aim of this study was to develop a method of structure analysis in intact proteins after purification. Transferrin from human plasma was trapped by membrane-immobilized anti-transferrin antibody, which was produced by non-denaturing two-dimensional electrophoresis (2-DE), and transferred to a polyvinylidene fluoride (PVDF) membrane and stained with Ponceau S. The antigen transferrin was eluted by rinsing the membrane with trifluoroacetic acid (TFA) or aspartic acid. In addition, a method was established by which the purified human transferrin was enzymatically digested on a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) target plate. Thus, after purification of the human transferrin antigen from tens of microlitres of human plasma using an immunoaffinity membrane, transferrin polypeptide fragments were obtained on the plate following digestion with pepsin in the presence of 0.1% TFA or endoproteinase Lys-C or Lys-C/trypsin with 0.001% sodium dodecyl sulphate (SDS). The results indicated that the combined methods of isolation using an immunoaffinity membrane and enzymatic digestion on a MALDI-TOF MS plate could be applied to the purification and microanalysis of antigens. This approach would be particularly applicable to the analysis of the primary structure and the less stable and highly accessible regions of antigens from limited sample volumes.

  11. Determination of 11 quinolones in bovine milk using immunoaffinity stir bar sorptive microextraction and liquid chromatography with fluorescence detection.

    Science.gov (United States)

    Yao, Kai; Zhang, Wei; Yang, Linyan; Gong, Jianfang; Li, Liuan; Jin, Tianming; Li, Cun

    2015-10-15

    A sensitive, selective and reproducible immunoaffinity stir bar sorptive microextraction (SBSME) coupled with liquid chromatography-fluorescence method for determination of 11 quinolones (QNs) in bovine milk was developed and validated. It is first report of a broad-specificity monoclonal antibody to QNs that has been immobilized to glass bar for preparation of a re-usable immunoaffinity stir bar. Analytes were extracted by placing stir bar in milk and shaking on a rotary shaker for 30min at 30rpm, followed by liquid chromatography and fluorescence detection. The newly developed method has limits of detection for each QN from 0.05 to 0.1ng/g with intra-day and inter-day precision ranging from 3.2 to 11.9% and from 5.2 to 12.5%, respectively. This allowed us to quantitatively analyze drugs in bovine milk with the advantage of significantly simplified sample preparation. The proposed method was successfully applied to the bovine milk samples analyses with QNs, demonstrating its rare application in animal food safety analysis.

  12. 2TB hard disk drive

    CERN Multimedia

    This particular object was used up until 2012 in the Data Centre. It slots into one of the Disk Server trays. Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes (link is external). They were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). They later became known as "hard disks" to distinguish them from "floppy disks (link is external)." Hard disks have a hard platter that holds the magnetic medium, as opposed to the flexible plastic film found in tapes and floppies.

  13. Immunoaffinity chromatography for the sample pretreatment of Taxus plant and cell extracts prior to analysis of taxanes by high-performance liquid chromatography

    NARCIS (Netherlands)

    Theodoridis, G; Haasnoot, W; Schilt, R; Jaziri, M; Diallo, B; Papadoyannis, IN; de Jong, GJ; Cazemier, G.

    2002-01-01

    The application of immunoaffinity chromatography for the purification of Taxus plant and cell extracts prior to the HPLC analysis is described. Polyclonal antibodies raised against 10-deacetylbaccatin III (10-DAB III), paclitaxel's main precursor in plant, were characterised by enzymed-linked immuno

  14. DETERMINATION OF CARBENDAZIM IN WATER BY HIGH-PERFORMANCE IMMUNOAFFINITY CHROMATOGRAPHY ON-LINE WITH HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH DIODE-ARRAY OR MASS SPECTROMETRIC DETECTION

    Science.gov (United States)

    An automated method for the determination of carbendazim in water that combines high-performance immunoaffinity chromatography (HPIAC), high-performance liquid chromatography (HPLC) in the reversed-phase mode, and detection by either UV-Vis diode array detector (DAD) spectroscopy...

  15. DEVELOPMENT AND APPLICATION OF IMMUNOAFFINITY COLUMN CHROMATOGRAPHY AS A CLEANUP METHOD FOR THE DETERMINATION OF ATRAZINE IN COMPLEX ENVIRONMENTAL SAMPLE MEDIA

    Science.gov (United States)

    A rabbit antibody immunoaffinity (IA) column procedure was evaluated as a cleanup method for the determination of atrazine in soil, sediment, and food. Four IA columns were prepared by immobilizing a polyclonal rabbit anti-atrazine antibody solution to HiTrap Sepharose columns. A...

  16. Development of an immunoaffinity column method using broad-specificity monoclonal antibodies for simultaneous extraction and cleanup of quinolone and sulfonamide antibiotics in animal muscle tissues

    Science.gov (United States)

    This paper describes a novel mixed-bed immunoaffinity column (IAC) method. The IAC was produced by coupling anti-fluoroquinolone and anti-sulfonamide broad-specificity monoclonal antibodies (Mabs) to Sepharose 4B for simultaneously isolating 13 fluoroquinolones (FQs) and 6 sulfonamides (SAs) from s...

  17. Dispersion in unit disks

    CERN Document Server

    Dumitrescu, Adrian

    2009-01-01

    We present two new approximation algorithms with (improved) constant ratios for selecting $n$ points in $n$ unit disks such that the minimum pairwise distance among the points is maximized. (I) A very simple $O(n \\log{n})$-time algorithm with ratio 0.5110 for disjoint unit disks. In combination with an algorithm of Cabello \\cite{Ca07}, it yields a $O(n^2)$-time algorithm with ratio of 0.4487 for dispersion in $n$ not necessarily disjoint unit disks. (II) A more sophisticated LP-based algorithm with ratio 0.6495 for disjoint unit disks that uses a linear number of variables and constraints, and runs in polynomial time. The algorithm introduces a novel technique which combines linear programming and projections for approximating distances. The previous best approximation ratio for disjoint unit disks was 1/2. Our results give a partial answer to an open question raised by Cabello \\cite{Ca07}, who asked whether 1/2 could be improved.

  18. Silica in Protoplanetary Disks

    CERN Document Server

    Sargent, B A; Tayrien, C; McClure, M K; Li, A; Basu, A R; Manoj, P; Watson, D M; Bohac, C J; Furlan, E; Kim, K H; Green, J D; Sloan, G C

    2008-01-01

    Mid-infrared spectra of a few T Tauri stars (TTS) taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope show prominent narrow emission features indicating silica (crystalline silicon dioxide). Silica is not a major constituent of the interstellar medium; therefore, any silica present in the circumstellar protoplanetary disks of TTS must be largely the result of processing of primitive dust material in the disks surrouding these stars. We model the silica emission features in our spectra using the opacities of various polymorphs of silica and their amorphous versions computed from earth-based laboratory measurements. This modeling indicates that the two polymorphs of silica, tridymite and cristobalite, which form at successively higher temperatures and low pressures, are the dominant forms of silica in the TTS of our sample. These high temperature, low pressure polymorphs of silica present in protoplanetary disks are consistent with a grain composed mostly of tridymite named Ada found...

  19. Chemistry in Protoplanetary Disks

    CERN Document Server

    Semenov, Dmitry

    2010-01-01

    Protoplanetary disks (PPDs) surrounding young stars are short-lived (~0.3-10 Myr), compact (~10-1000 AU) rotating reservoirs of gas and dust. PPDs are believed to be birthplaces of planetary systems, where tiny grains are assembled into pebbles, then rocks, planetesimals, and eventually planets, asteroids, and comets. Strong variations of physical conditions (temperature, density, ionization rate, UV/X-rays intensities) make a variety of chemical processes active in disks, producing simple molecules in the gas phase and complex polyatomic (organic) species on the surfaces of dust particles. In this entry, we summarize the major modern observational methods and theoretical paradigms used to investigate disk chemical composition and evolution, and present the most important results. Future research directions that will become possible with the advent of the Atacama Large Millimeter Array (ALMA) and other forthcoming observational facilities are also discussed.

  20. The black disk to be observed in the Orear region

    CERN Document Server

    Dremin, I M

    2012-01-01

    It is argued that the very first signatures of the approach to the black disk asymptotical limit in hadron collisions may be observed in the differential cross section of elastic scattering. The exponentially decreasing with the angle (or $\\sqrt {|t|}$) regime beyond the diffraction peak will become replaced by an oscillatory behavior. Some estimates of energies where this can happen are presented.

  1. From Disks to Planets

    Science.gov (United States)

    Youdin, Andrew N.; Kenyon, Scott J.

    This pedagogical chapter covers the theory of planet formation, with an emphasis on the physical processes relevant to current research. After summarizing empirical constraints from astronomical and geophysical data, we describe the structure and evolution of protoplanetary disks. We consider the growth of planetesimals and of larger solid protoplanets, followed by the accretion of planetary atmospheres, including the core accretion instability. We also examine the possibility that gas disks fragment directly into giant planets and/or brown dwarfs. We defer a detailed description of planet migration and dynamical evolution to other work, such as the complementary chapter in this series by Morbidelli.

  2. Lupus Alma Disk Survey

    Science.gov (United States)

    Ansdell, Megan

    2016-07-01

    We present the first unbiased ALMA survey of both dust and gas in a large sample of protoplanetary disks. We surveyed 100 sources in the nearby (150-200 pc), young (1-2 Myr) Lupus region to constrain M_dust to 2 M_Mars and M_gas to 1 M_Jup. Most disks have masses < MMSN and gas-to-dust ratios < ISM. Such rapid gas depletion may explain the prevalence of super-Earths in the exoplanet population.

  3. Immunoaffinity sample purification and MALDI-TOF MS analysis of alpha-Solanine and alpha-chaconine in serum.

    Science.gov (United States)

    Driedger, D R; Sporns, P

    2001-02-01

    A sample purification technique was developed for the detection of potato glycoalkaloids (GAs) in blood serum by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). GAs were extracted from spiked serum (5 mL) using a C(18) solid-phase extraction cartridge. The GAs were then selectively captured on antibody-coated agarose beads. The agarose beads were washed with water and the GAs eluted with 25 microL of methanol. MALDI-TOF MS was used to detect the GAs in the methanol eluent. Immunoaffinity sample purification of the GAs effectively reduced the signal suppression observed during the analysis of unpurified samples. alpha-Chaconine and alpha-solanine were detected in serum spiked with 1 ng/mL of each GA.

  4. Multiplexed Quantification of Proglucagon-Derived Peptides by Immunoaffinity Enrichment and Tandem Mass Spectrometry after a Meal Tolerance Test

    DEFF Research Database (Denmark)

    Lee, Anita Y H; Chappell, Derek L; Bak, Monika J;

    2016-01-01

    BACKGROUND: Proglucagon-derived peptides (PGDPs), which include glucagon-like peptide (GLP)-1, glucagon, and oxyntomodulin, are key regulators of glucose homeostasis and satiety. These peptide hormones are typically measured with immuno-based assays (e.g., ELISA, RIA), which often suffer from...... issues of selectivity. METHODS: We developed a multiplexed assay for measuring PGDPs including GLP-1 (7-36) amide, GLP-1 (9-36) amide, glucagon, and oxyntomodulin by mass spectrometry and used this assay to examine the effect of a meal tolerance test on circulating concentrations of these hormones....... Participants fasted overnight and were either given a meal (n = 8) or continued to fast (n = 4), with multiple blood collections over the course of 3 h. Plasma samples were analyzed by microflow immunoaffinity (IA)-LC-MS/MS with an isotope dilution strategy. RESULTS: Assay performance characteristics were...

  5. On the Gravitational Stability of the Maclaurin Disk

    Science.gov (United States)

    Roshan, Mahmood; Abbassi, Shahram; Khosroshahi, Habib G.

    2016-12-01

    We study the global gravitational stability of a gaseous self-gravitating Maclaurin disk in the absence of a halo. Further, we replace Newtonian gravity with the specific modified gravity theory known as MOG in the relevant literature. MOG is an alternative theory for addressing the dark matter problem without invoking exotic dark matter particles, and it possesses two free parameters α and μ 0 in the weak field limit. We derive the equilibrium gravitational potential of the Maclaurin disk in MOG and develop a semianalytic method for studying the response of the disk to linear nonaxisymmetric perturbations. The eigenvalue spectrum of the normal modes of the disk is obtained, and its physical meaning has been explored. We show that Maclaurin disks are less stable in MOG than in Newtonian gravity. In fact, both parameters (α, μ 0) have destabilizing effects on the disk. Interestingly, μ 0 excites only the bar mode m = 2, while α affects all of the modes. More specifically, when α > 1, the bar mode is strongly unstable and unlike in Newtonian gravity cannot be avoided, at least in the weak field limit, with increasing the pressure support of the disk.

  6. The effect of radial migration on galactic disks

    Energy Technology Data Exchange (ETDEWEB)

    Vera-Ciro, Carlos; D' Onghia, Elena [Department of Astronomy, University of Wisconsin, 2535 Sterling Hall, 475 North Charter Street, Madison, WI 53076 (United States); Navarro, Julio [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2 (Canada); Abadi, Mario, E-mail: ciro@astro.wisc.edu [Observatorio Astronómico, Universidad Nacional de Córdoba, Córdoba X5000BGR (Argentina)

    2014-10-20

    We study the radial migration of stars driven by recurring multi-arm spiral features in an exponential disk embedded in a dark matter halo. The spiral perturbations redistribute angular momentum within the disk and lead to substantial radial displacements of individual stars, in a manner that largely preserves the circularity of their orbits and that results, after 5 Gyr (∼40 full rotations at the disk scale length), in little radial heating and no appreciable changes to the vertical or radial structure of the disk. Our results clarify a number of issues related to the spatial distribution and kinematics of migrators. In particular, we find that migrators are a heavily biased subset of stars with preferentially low vertical velocity dispersions. This 'provenance bias' for migrators is not surprising in hindsight, for stars with small vertical excursions spend more time near the disk plane, and thus respond more readily to non-axisymmetric perturbations. We also find that the vertical velocity dispersion of outward migrators always decreases, whereas the opposite holds for inward migrators. To first order, newly arrived migrators simply replace stars that have migrated off to other radii, thus inheriting the vertical bias of the latter. Extreme migrators might therefore be recognized, if present, by the unexpectedly small amplitude of their vertical excursions. Our results show that migration, understood as changes in angular momentum that preserve circularity, can strongly affect the thin disk, but cast doubts on models that envision the Galactic thick disk as a relic of radial migration.

  7. Determination of diniconazole in agricultural samples by sol-gel immunoaffinity extraction procedure coupled with HPLC and ELISA.

    Directory of Open Access Journals (Sweden)

    Zhenjiang Liu

    Full Text Available BACKGROUND: In the European Union (EU, the use of diniconazole-M is no longer authorized. However, residues of diniconazole-M occur in various plant commodities. METHODOLOGY/PRINCIPAL FINDINGS: A selective and simple analytical method for the trace level determination of diniconazole in soil, fruit, vegetables and water samples was developed based on immunoaffinity extraction followed by Enzyme-linked immunosorbent assay (ELISA and the high-performance liquid chromatography (HPLC analysis. The ELISA was based on monoclonal antibodies highly specific to diniconazole and was a fast, cost-effective, and selective screening method for the detection of diniconazole. The results of the ELISA correlated well with gas chromatography (GC results, with the correlation coefficient of 0.9879 (n = 19. A simple gel permeation chromato- graphy clean-up method was developed to purify extracts from matrices containing high amounts of fat and natural pigments, without the need for a large dilution of the sample. The immunoaffinity column (IAC capacity was 0.180 mg g(-1. The columns could be re-used approximately 20 times with no significant alteration in capacity. The recoveries from complex samples were in the range of 89.2% to 96.1% with a relative standard deviation (RSD of 0.770%-6.11% by ELISA. The results were in good agreement with those obtained by HPLC method. CONCLUSION/SIGNIFICANCE: The IAC extraction procedure coupled with HPLC and ELISA analysis could be also used as alternative effective analytical methods for the determination of diniconazole concentrations in complex samples.

  8. Determination for multiple mycotoxins in agricultural products using HPLC-MS/MS via a multiple antibody immunoaffinity column.

    Science.gov (United States)

    Zhang, Zhaowei; Hu, Xiaofeng; Zhang, Qi; Li, Peiwu

    2016-05-15

    Mycotoxins usually found in agricultural products such as peanut, corn, and wheat, are a serious threat to human health and their detection requires multiplexed and sensitive analysis methods. Herein, a simultaneous determination for aflatoxin B1, B2, G1, G2, ochratoxin A, zearalanone and T-2 toxin was investigated using high performance liquid chromatography coupled with tandem mass spectrometry in a single run via a home-made multiple immunoaffinity column. Four monoclonal antibodies were produced in our lab against aflatoxins, ochratoxin A, zearalanone and T-2 toxin, respectively, then combined as a pool and bound to Sepharose-4B for affinity chromatography. Seven mycotoxins were effectively extracted from the agricultural product samples by using acetonitrile/water/acetic acid (80:19:1, v/v/v) Then, the extraction was cleanup by multiple immunoaffinity column. This method demonstrated a considerable linear range of 0.30-25, 0.12-20, 0.30-20, 0.12-20, 0.60-30, 0.30-25, and 1.2-40μgkg(-1)and lower limits of detection at 0.1, 0.04, 0.1, 0.04, 0.2, 0.1 and 0.4μgkg(-1) for AFB1, AFB2, AFG1, AFG2, OTA, ZEN and T-2, respectively, in comparison with previously reported methods, as well as excellent recoveries. The mIAC capacity for AFB1, AFB2, AFG1, AFG2, OTA, ZEN, and T-2 were 187, 181, 153, 151, 105, 130, 88ng, respectively. It was found that all of the 7 mycotoxins were present in 90 agricultural product samples. The proposed method meets the requirements for rapid sample preparation and highly sensitive identification of multiple mycotoxins in agricultural product and food safety. This method provides a promising alternative with high throughput and high sensitivity for rapid analysis of seven mycotoxins in the monitoring of food safety.

  9. A protocol for exosome isolation and characterization: evaluation of ultracentrifugation, density-gradient separation, and immunoaffinity capture methods.

    Science.gov (United States)

    Greening, David W; Xu, Rong; Ji, Hong; Tauro, Bow J; Simpson, Richard J

    2015-01-01

    Exosomes are 40-150 nm extracellular vesicles that are released from a multitude of cell types, and perform diverse cellular functions including intercellular communication, antigen presentation, and transfer of tumorigenic proteins, mRNA and miRNA. Exosomes are important regulators of the cellular niche, and their altered characteristics in many diseases, such as cancer, suggest their importance for diagnostic and therapeutic applications, and as drug delivery vehicles. Exosomes have been purified from biological fluids and in vitro cell cultures using a variety of strategies and techniques. In this chapter, we reveal the protocol and key insights into the isolation, purification and characterization of exosomes, distinct from shed microvesicles and apoptotic blebs. Using the colorectal cancer cell line LIM1863 as a cell model, a comprehensive evaluation of exosome isolation methods including ultracentrifugation (UC-Exos), OptiPrep™ density-based separation (DG-Exos), and immunoaffinity capture using anti-EpCAM-coated magnetic beads (IAC-Exos) were examined. All exosome isolation methodologies contained 40-150 nm vesicles based on electron microscopy, and positive for exosome markers (Alix, TSG101, HSP70) based on immunoblotting. This protocol employed a proteomic profiling approach to characterize the protein composition of exosomes, and label-free spectral counting to evaluate the effectiveness of each method in exosome isolation. Based on the number of MS/MS spectra identified for exosome markers and proteins associated with their biogenesis, trafficking, and release, IAC-Exos was shown to be the most effective method to isolate exosomes. However, the use of density-based separation (DG-Exos) provides significant advantages for exosome isolation when the use of immunoaffinity capture is limited (due to antibody availability and suitability of exosome markers).

  10. Polarimetric microlensing of circumstellar disks

    CERN Document Server

    Sajadian, Sedighe

    2015-01-01

    We study the benefits of polarimetry observations of microlensing events to detect and characterize circumstellar disks around the microlensed stars located at the Galactic bulge. These disks which are unresolvable from their host stars make a net polarization effect due to their projected elliptical shapes. Gravitational microlensing can magnify these signals and make them be resolved. The main aim of this work is to determine what extra information about these disks can be extracted from polarimetry observations of microlensing events in addition to those given by photometry ones. Hot disks which are closer to their host stars are more likely to be detected by microlensing, owing to more contributions in the total flux. By considering this kind of disks, we show that although the polarimetric efficiency for detecting disks is similar to the photometric observation, but polarimetry observations can help to constraint the disk geometrical parameters e.g. the disk inner radius and the lens trajectory with resp...

  11. Warm gas in protoplanetary disks

    Science.gov (United States)

    van der Plas, Gerrit

    2010-12-01

    This thesis presents a study of warm CO, [OI] and H2 gas coming from the disks around Herbig Ae/Be stars. These various gas tracers are each a proxy for a different radial and vertical region of the PP disk surface. Our sample consists of disks whose shape (based on modeling of the the disk dust emission) can be divided into flaring and self-shadowed (flat). We find [1] evidence for the vertical decoupling of gas and dust in one disks (Chapter 2); [2] That disk geometry has a large influence on the spatial distribution and excitation mechanism of the CO emission (chapters 3,4); [3] Near-IR H 2 emission around 2 (out of 14) HAEBE stars, probably originating from large (±50AU) radii of the disk (chapter 5). In chapter 6 we investigate the trends between CO emission and disk geometry as noted in Chapter 3 and 4.

  12. Galactic Thin Disk

    NARCIS (Netherlands)

    van der Kruit, P.; Murdin, P.; Murdin, Paul

    2000-01-01

    Of the components of our MILKY WAY GALAXY, the thin disk is the most prominent part to our eyes. It manifests itself as the band of faint light that we see encircling the whole sky. Except for the bulge in the direction of the center of our Galaxy, the stars that make up the Milky Way as we see it

  13. More approximation on disks

    NARCIS (Netherlands)

    de Paepe, P.J.I.M.; Wiegerinck, J.J.O.O.

    2007-01-01

    Abstract: In this article we study the function algebra generated by z2 and g2 on a small closed disk centred at the origin of the complex plane. We prove, using a biholomorphic change of coordinates and already developed techniques in this area, that for a large class of functions g this algebra co

  14. Herniated disk repair (image)

    Science.gov (United States)

    ... is one of the most common causes of lower back pain. The mainstay of treatment for herniated disks is an initial period of rest with pain and anti-inflammatory medications followed by physical therapy. If pain and symptoms persist, surgery to remove ...

  15. The Tilt between Acretion Disk and Stellar Disk

    Indian Academy of Sciences (India)

    Shiyin Shen; Zhengyi Shao; Minfeng Gu

    2011-03-01

    The orientations of the accretion disk of active galactic nuclei (AGN) and the stellar disk of its host galaxy are both determined by the angular momentum of their forming gas, but on very different physical environments and spatial scales. Here we show the evidence that the orientation of the stellar disk is correlated with the accretion disk by comparing the inclinations of the stellar disks of a large sample of Type 2 AGNs selected from Sloan Digital Sky Survey (SDSS, York et al. 2000) to a control galaxy sample. Given that the Type 2 AGN fraction is in the range of 70–90 percent for low luminosity AGNs as a priori, we find that the mean tilt between the accretion disk and stellar disk is ∼ 30 degrees (Shen et al. 2010).

  16. Vibration of imperfect rotating disk

    Directory of Open Access Journals (Sweden)

    Půst L.

    2011-12-01

    Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.

  17. Volatiles in protoplanetary disks

    CERN Document Server

    Pontoppidan, Klaus M; Bergin, Edwin A; Brittain, Sean; Marty, Bernard; Mousis, Olvier; Oberg, Karin L

    2014-01-01

    Volatiles are compounds with low sublimation temperatures, and they make up most of the condensible mass in typical planet-forming environments. They consist of relatively small, often hydrogenated, molecules based on the abundant elements carbon, nitrogen and oxygen. Volatiles are central to the process of planet formation, forming the backbone of a rich chemistry that sets the initial conditions for the formation of planetary atmospheres, and act as a solid mass reservoir catalyzing the formation of planets and planetesimals. This growth has been driven by rapid advances in observations and models of protoplanetary disks, and by a deepening understanding of the cosmochemistry of the solar system. Indeed, it is only in the past few years that representative samples of molecules have been discovered in great abundance throughout protoplanetary disks - enough to begin building a complete budget for the most abundant elements after hydrogen and helium. The spatial distributions of key volatiles are being mapped...

  18. The Evolution of Inner Disk Gas in Transition Disks

    CERN Document Server

    Hoadley, Keri; Alexander, Richard D; McJunkin, Matthew; Schneider, Christian

    2015-01-01

    Investigating the molecular gas in the inner regions of protoplanetary disks provides insight into how the molecular disk environment changes during the transition from primordial to debris disk systems. We conduct a small survey of molecular hydrogen (H$_2$) fluorescent emission, using 14 well-studied Classical T Tauri stars at two distinct dust disk evolutionary stages, to explore how the structure of the inner molecular disk changes as the optically thick warm dust dissipates. We simulate the observed HI-Lyman $\\alpha$-pumped H$_2$ disk fluorescence by creating a 2D radiative transfer model that describes the radial distributions of H$_{2}$ emission in the disk atmosphere and compare these to observations from the Hubble Space Telescope. We find the radial distributions that best describe the observed H$_2$ FUV emission arising in primordial disk targets (full dust disk) are demonstrably different than those of transition disks (little-to-no warm dust observed). For each best-fit model, we estimate inner a...

  19. Calcium-sensitive immunoaffinity chromatography: Gentle and highly specific retrieval of a scarce plasma antigen, collectin-LK (CL-LK).

    Science.gov (United States)

    Henriksen, Maiken L; Madsen, Kirstine L; Skjoedt, Karsten; Hansen, Soren

    2014-11-01

    Immunoaffinity chromatography is a powerful fractionation technique that has become indispensable for protein purification and characterization. However, it is difficult to retrieve bound proteins without using harsh or denaturing elution conditions, and the purification of scarce antigens to homogeneity may be impossible due to contamination with abundant antigens. In this study, we purified the scarce, complement-associated plasma protein complex, collectin LK (CL-LK, complex of collectin liver 1 and kidney 1), by immunoaffinity chromatography using a calcium-sensitive anti-collectin-kidney-1 mAb. This antibody was characterized by binding to CL-LK at hypo- and physiological calcium concentrations and dissociated from CK-LK at hyperphysiological concentrations of calcium. We purified CL-LK from plasma to a purity of 41% and a yield of 38%, resulting in a purification factor of more than 88,000 in a single step. To evaluate the efficiency of this new purification scheme, we purified CL-LK using the same calcium-sensitive mAb in combination with acidic elution buffer and by using calcium-dependent anti-CL-K1 mAbs in combination with EDTA elution buffer. We found that calcium-sensitive immunoaffinity chromatography was superior to the traditional immunoaffinity chromatographies and resulted in a nine-fold improvement of the purification factor. The technique is applicable for the purification of proteins in complex mixtures by single-step fractionation without the denaturation of eluted antigens, and it allows for the purification of scarce proteins that would have otherwise been impossible to purify and, hence, to characterize. This technique may also potentially be applied for the purification of proteins that only interact with calcium ions at hyperphysiological concentrations.

  20. On the gravitational stability of the Maclaurin disk

    CERN Document Server

    Roshan, Mahmood; Khosroshahi, Habib G

    2016-01-01

    We study the global gravitational stability of a gaseous self-gravitating Maclaurin disk in the absence of a halo. Further, we replace Newtonian gravity with the specific Modified gravity theory known as MOG in the relevant literature. MOG is an alternative theory for addressing the dark matter problem without invoking exotic dark matter particles, and possesses two free parameters $\\alpha$ and $\\mu_0$ in the weak field limit. We derive the equilibrium gravitational potential of the Maclaurin disk in MOG and develop a semi-analytic method for studying the response of the disk to linear non-axysymmetric perturbations. The eigenvalue spectrum of the normal modes of the disk is obtained and its physical meaning has been explored. We show that Maclaurin disks are less stable in MOG than in Newtonian gravity. In fact both parameters $(\\alpha,\\mu_0)$ have destabilizing effects on the disk. Interestingly $\\mu_0$ excites only the bar mode $m=2$ while $\\alpha$ affects all the modes. More specifically, when $\\alpha>1$,...

  1. Shoulder Joint Replacement

    Science.gov (United States)

    ... Shoulder Replacement Options Shoulder replacement surgery is highly technical. It should be performed by a surgical team ... area and will meet a doctor from the anesthesia department. You, your anesthesiologist, and your surgeon will ...

  2. Partial knee replacement - slideshow

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/presentations/100225.htm Partial knee replacement - series—Normal anatomy To use the sharing ... A.M. Editorial team. Related MedlinePlus Health Topics Knee Replacement A.D.A.M., Inc. is accredited ...

  3. Audit: Automated Disk Investigation Toolkit

    Directory of Open Access Journals (Sweden)

    Umit Karabiyik

    2014-09-01

    Full Text Available Software tools designed for disk analysis play a critical role today in forensics investigations. However, these digital forensics tools are often difficult to use, usually task specific, and generally require professionally trained users with IT backgrounds. The relevant tools are also often open source requiring additional technical knowledge and proper configuration. This makes it difficult for investigators without some computer science background to easily conduct the needed disk analysis. In this paper, we present AUDIT, a novel automated disk investigation toolkit that supports investigations conducted by non-expert (in IT and disk technology and expert investigators. Our proof of concept design and implementation of AUDIT intelligently integrates open source tools and guides non-IT professionals while requiring minimal technical knowledge about the disk structures and file systems of the target disk image.

  4. Ringed accretion disks: equilibrium configurations

    CERN Document Server

    Pugliese, D

    2015-01-01

    We investigate a model of ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the General Relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can be then determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We pr...

  5. IBM 3390 Hard Disk Platter

    CERN Multimedia

    1991-01-01

    The 3390 disks rotated faster than those in the previous model 3380. Faster disk rotation reduced rotational delay (ie. the time required for the correct area of the disk surface to move to the point where data could be read or written). In the 3390's initial models, the average rotational delay was reduced to 7.1 milliseconds from 8.3 milliseconds for the 3380 family.

  6. Disks and Outflows

    Science.gov (United States)

    Rodriguez, L. F.

    2002-05-01

    The presence of disks and outflows characterizes the earliest stages of stellar evolution. I will review recent results that exemplify how the radio observations have become powerful tools in the study of these extremely young objects. Binarity and multiplicity seem to be factors that we are only starting to understand. Outflows are now seen as laboratories for the chemistry of shocked regions. Finally, the efforts to extend the paradigm for low-mass stellar formation to more massive protostars can be tested critically in the radio wavelengths. I acknowledge the support from CONACyT, Mexico.

  7. The Formation of Galactic Disks

    CERN Document Server

    Mo, H J; White, S D M; Mao, Shude; White, Simon D.M.

    1997-01-01

    We study the population of galactic disks expected in current hierarchical clustering models for structure formation. A rotationally supported disk with exponential surface density profile is assumed to form with a mass and angular momentum which are fixed fractions of those of its surrounding dark halo. We assume that haloes respond adiabatically to disk formation, and that only stable disks can correspond to real systems. With these assumptions the predicted population can match both present-day disks and the damped Lyman alpha absorbers in QSO spectra. Good agreement is found provided: (i) the masses of disks are a few percent of those of their haloes; (ii) the specific angular momenta of disks are similar to those of their haloes; (iii) present-day disks were assembled recently (at z3kpc/h and about 10% at r>10kpc/h. The cross-section for absorption is strongly weighted towards disks with large angular momentum and so large size for their mass. The galaxy population associated with damped absorbers should...

  8. Studies in the Use of Magnetic Microspheres for Immunoaffinity Extraction of Paralytic Shellfish Poisoning Toxins from Shellfish

    Directory of Open Access Journals (Sweden)

    Christopher Elliott

    2011-01-01

    Full Text Available Paralytic shellfish poisoning (PSP is a potentially fatal human health condition caused by the consumption of shellfish containing high levels of PSP toxins. Toxin extraction from shellfish and from algal cultures for use as standards and analysis by alternative analytical monitoring methods to the mouse bioassay is extensive and laborious. This study investigated whether a selected MAb antibody could be coupled to a novel form of magnetic microsphere (hollow glass magnetic microspheres, brand name Ferrospheres-N and whether these coated microspheres could be utilized in the extraction of low concentrations of the PSP toxin, STX, from potential extraction buffers and spiked mussel extracts. The feasibility of utilizing a mass of 25 mg of Ferrospheres-N, as a simple extraction procedure for STX from spiked sodium acetate buffer, spiked PBS buffer and spiked mussel extracts was determined. The effects of a range of toxin concentrations (20–300 ng/mL, incubation times and temperature on the capability of the immuno-capture of the STX from the spiked mussel extracts were investigated. Finally, the coated microspheres were tested to determine their efficiency at extracting PSP toxins from naturally contaminated mussel samples. Toxin recovery after each experiment was determined by HPLC analysis. This study on using a highly novel immunoaffinity based extraction procedure, using STX as a model, has indicated that it could be a convenient alternative to conventional extraction procedures used in toxin purification prior to sample analysis.

  9. Simultaneous determination of capsaicin and dihydrocapsaicin for vegetable oil adulteration by immunoaffinity chromatography cleanup coupled with LC-MS/MS.

    Science.gov (United States)

    Ma, Fei; Yang, Qingqing; Matthäus, Bertrand; Li, Peiwu; Zhang, Qi; Zhang, Liangxiao

    2016-05-15

    Capsaicin and dihydrocapsaicin were selected as adulteration markers to authenticate vegetable oils. In this study, a method of immunoaffinity chromatography (IAC) combined with liquid chromatography-tandem mass spectrometry was established for the determination of capsaicin and dihydrocapsaicin in vegetable oils. In this method, immunosorbents were obtained by covalently coupling highly specific capsaicinoid polyclonal antibodieswith CNBr-activated Sepharose 4B, and then packed into a polyethylene column. In this paper, the major parameters affecting IAC extraction efficiency, including loading, washing and eluting conditions, were also investigated. The IAC column displayed high selectivity for capsaicin and dihydrocapsaicin with the maximum capacity of 240ng. The limit of detection (LOD) and limit of quantification (LOQ) for capsaicin were calculated as 0.02 and 0.08μgkg(-1), and for dihydrocapsaicin were 0.03 and 0.10μgkg(-1). The recoveries of capsaicin and dihydrocapsaicin in oil samples were in the range of 87.3-95.2% with the relative standard deviation (RSD) of less than 6.1%. The results indicated that capsaicinoid compounds could not be found in edible vegetable oils. Therefore, the proposed method is simple, reliable and adequate for routine monitoring of capsaicinoid compounds in vegetable oils and has an excellent potential for detection of adulteration with inedible waste oil.

  10. Retaining activity of enzymes after capture and extraction within a single-drop of biological fluid using immunoaffinity membranes.

    Science.gov (United States)

    Shimazaki, Youji; Sato, Yuki

    2016-05-15

    The purpose of this study was the measurement of enzyme activity within a single-drop of biological fluid after micropurification. Esterase and lactate dehydrogenase (LDH) retained their enzymatic activities after being captured by membrane-immobilized antibodies, which were prepared by non-denaturing two-dimensional electrophoresis, transferred to polyvinylidene difluoride and then stained by Ponceau S. The activities of both enzymes were also measured after being captured by antibodies and biotinylated antibodies bound to membrane-immobilized protein A or avidin, respectively. After esterase and LDH were captured from biological samples by membrane-immobilized protein A or avidin, their activities were semi-quantitatively measured on the surface of the membrane using fluorescence determination. More than 51% of enzyme activities were retained even after the enzymes were captured by biotinylated antibody bound to membrane-immobilized avidin and eluted by rinsing with 5μL of 1% Triton X-100, compared with the activities of the enzyme on the immunoaffinity membrane.

  11. Application of single immunoaffinity clean-up for simultaneous determination of regulated mycotoxins in cereals and nuts.

    Science.gov (United States)

    Vaclavikova, Marta; MacMahon, Shaun; Zhang, Kai; Begley, Timothy H

    2013-12-15

    A rapid and sensitive analytical strategy for the simultaneous determination of twelve mycotoxins (aflatoxins, fumonisins, zearalenon, deoxynivalenol, ochratoxin A, T-2 and HT-2 toxins) using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. The method was validated for peanuts, barley and maize-breakfast cereals; selected as they represent the matrices most often contaminated by mycotoxins. The method is designed for fast and reliable analyses of mycotoxins in regulatory, industrial and private laboratories. Multi-target immunoaffinity columns containing antibodies for all mycotoxins studied herein were used for sample clean-up. Method optimization was predominantly focused on the simplification of extraction and clean-up procedure recommended by column producers. This newly developed and simplified procedure decreased both the sample preparation time and the solvent volumes used for their processing. The analysis of all regulated mycotoxins was conducted by a newly developed UHPLC-MS/MS method with a sample run time of only ten minutes. The method trueness was tested with analytical spikes and certified reference materials, with recoveries ranging from 71% to 112% for all of the examined mycotoxins.

  12. [Determination of 14 mycotoxins in Chinese herbs by liquid chromatography-tandem mass spectrometry with immunoaffinity purification].

    Science.gov (United States)

    Ge, Baokun; Zhao, Kongxiang; Wang, Wei; Mi, Jiebo

    2011-06-01

    A method was developed for the determination of 14 mycotoxins, aflatoxins, T-2, HT-2, fumonisins, ochratoxin A, zearalenone, etc. in Chinese herbs by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). The sample was extracted with phosphate buffer solution (PBS) and methanol in turn, and then purified by a high selective multi-functional immunoaffinity column. The column was washed by PBS (containing 0.1% Twain) and water, and then eluted by methanol. The eluate was dried under nitrogen, dissolved in methanol-10 mmol/L NH4Ac (40 : 60, v/v) solution. The mycotoxins were separated on a Waters Xterra C18 MS column (100 mm x 2.1 mm, 3.5 microm) and detected by MS/MS. The limits of quantification (LOQs) of the 14 mycotoxins were from 1.0 to 5.0 microg/kg. The average recoveries of the 14 mycotoxins spiked in Chinese herbs (Ginseng, Campanulaceae, Radix and Ophiopogonis) ranged from 71.9% to 99.7% at the three spiked levels of 1.0, 5.0, 10.0 microg/kg, and the relative standard deviations (RSDs, n = 6) were between 4.8% and 15.8%. The method is rapid, sensitive and accurate, and suitable for the determination of the 14 mycotoxins in Chinese medicines. The quantification limits of aflatoxins can meet the domestic and foreign requirements.

  13. Disk storage at CERN

    CERN Document Server

    Mascetti, L; Chan, B; Espinal, X; Fiorot, A; Labrador, H Gonz; Iven, J; Lamanna, M; Presti, G Lo; Mościcki, JT; Peters, AJ; Ponce, S; Rousseau, H; van der Ster, D

    2015-01-01

    CERN IT DSS operates the main storage resources for data taking and physics analysis mainly via three system: AFS, CASTOR and EOS. The total usable space available on disk for users is about 100 PB (with relative ratios 1:20:120). EOS actively uses the two CERN Tier0 centres (Meyrin and Wigner) with 50:50 ratio. IT DSS also provide sizeable on-demand resources for IT services most notably OpenStack and NFS-based clients: this is provided by a Ceph infrastructure (3 PB) and few proprietary servers (NetApp). We will describe our operational experience and recent changes to these systems with special emphasis to the present usages for LHC data taking, the convergence to commodity hardware (nodes with 200-TB each with optional SSD) shared across all services. We also describe our experience in coupling commodity and home-grown solution (e.g. CERNBox integration in EOS, Ceph disk pools for AFS, CASTOR and NFS) and finally the future evolution of these systems for WLCG and beyond.

  14. Disk storage at CERN

    Science.gov (United States)

    Mascetti, L.; Cano, E.; Chan, B.; Espinal, X.; Fiorot, A.; González Labrador, H.; Iven, J.; Lamanna, M.; Lo Presti, G.; Mościcki, JT; Peters, AJ; Ponce, S.; Rousseau, H.; van der Ster, D.

    2015-12-01

    CERN IT DSS operates the main storage resources for data taking and physics analysis mainly via three system: AFS, CASTOR and EOS. The total usable space available on disk for users is about 100 PB (with relative ratios 1:20:120). EOS actively uses the two CERN Tier0 centres (Meyrin and Wigner) with 50:50 ratio. IT DSS also provide sizeable on-demand resources for IT services most notably OpenStack and NFS-based clients: this is provided by a Ceph infrastructure (3 PB) and few proprietary servers (NetApp). We will describe our operational experience and recent changes to these systems with special emphasis to the present usages for LHC data taking, the convergence to commodity hardware (nodes with 200-TB each with optional SSD) shared across all services. We also describe our experience in coupling commodity and home-grown solution (e.g. CERNBox integration in EOS, Ceph disk pools for AFS, CASTOR and NFS) and finally the future evolution of these systems for WLCG and beyond.

  15. Expression and purification of a human, soluble Arylsulfatase A for Metachromatic Leukodystrophy enzyme replacement therapy.

    Science.gov (United States)

    Martino, Sabata; Consiglio, Antonella; Cavalieri, Cristina; Tiribuzi, Roberto; Costanzi, Egidia; Severini, Giovanni Maria; Emiliani, Carla; Bordignon, Claudio; Orlacchio, Aldo

    2005-05-25

    The production of active Arylsulfatase A is a key step in the development of enzyme replacement therapy for Metachromatic Leukodystrophy. To obtain large amounts of purified Arylsulfatase A for therapeutic use, we combined a retroviral expression system with a versatile and rapid purification protocol that can easily and reliably be adapted to high-throughput applications. The purification method consists of an initial ion-exchange DEAE-cellulose chromatography step followed by immuno-affinity purification using a polyclonal antibody against a 29-mer peptide of the Arylsulfatase A sequence. Immuno-adsorbed protein was eluted with a combination of acidic pH and an optimal concentration of the 29-mer peptide. This protocol reproducibly yielded approximately 100 microg of >99% pure human Arylsulfatase A, corresponding to 152 mU of enzyme activity, per liter of culture medium with properties similar to those of human non-recombinant protein.

  16. The black disk to be observed in the Orear region

    Science.gov (United States)

    Dremin, I. M.

    2012-08-01

    It is argued that the very first signatures of the approach to the black disk asymptotical limit in hadron collisions may be observed in the differential cross section of elastic scattering. The exponentially decreasing with the angle (or √{|t|} ) regime beyond the diffraction peak will become replaced by an oscillatory behavior or by the power-like falloff. Some estimates of energies where this can happen are presented.

  17. The black disk to be observed in the Orear region

    Energy Technology Data Exchange (ETDEWEB)

    Dremin, I.M., E-mail: dremin@td.lpi.ru [Lebedev Physical Institute, Moscow 119991 (Russian Federation)

    2012-08-15

    It is argued that the very first signatures of the approach to the black disk asymptotical limit in hadron collisions may be observed in the differential cross section of elastic scattering. The exponentially decreasing with the angle (or {radical}(|t|) ) regime beyond the diffraction peak will become replaced by an oscillatory behavior or by the power-like falloff. Some estimates of energies where this can happen are presented.

  18. Chemistry in evolving protoplanetary disks

    NARCIS (Netherlands)

    Jonkheid, Bastiaan Johan

    2006-01-01

    Planets form in disks of gas and dust around young stars. Since the gas makes up 99 % of the disk mass, it is critical for our understanding of planet formation to gain direct information from the gas, independently of what can be learned from dust emission. In this thesis, calculations are presente

  19. RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

    2015-12-15

    We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

  20. Friction characteristics of floppy disks

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This note presents the principle and structure of a tribological measure for floppy disks.The precision of the force measuring system is 1 mN in loading and 3×10-6 N in friction.The resolution of the film thickness between head and floppy disk is 0.5 nm in the vertical and 1.5 nm in the horizontal direction.In order to investigate the tribological characteristics of floppy disks,six types of floppy disks have been tested and the floating properties of these disks are also studied with film measuring system.The experimental results of the surface morphology and friction coefficient of these floppy disks using the atomic force microscope/friction force mcroscope (AFM/FFM) are in accordance with the conclusion made by our own measuring system.The experimental results show that the air film thickness between head and disk is of the same order as the surface roughness of floppy disks.

  1. Melting of polydisperse hard disks

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.

    2004-01-01

    The melting of a polydisperse hard-disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation-unbinding mechanism, as an extension of the two-dimensional hard-disk melting problem. We find

  2. Melting of polydisperse hard disks

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.

    2004-01-01

    The melting of a polydisperse hard-disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation-unbinding mechanism, as an extension of the two-dimensional hard-disk melting problem. We find th

  3. Physical processes in protoplanetary disks

    CERN Document Server

    Armitage, Philip J

    2015-01-01

    This review introduces physical processes in protoplanetary disks relevant to accretion and the initial stages of planet formation. After reprising the elementary theory of disk structure and evolution, I discuss the gas-phase physics of angular momentum transport through turbulence and disk winds, and how this may be related to episodic accretion observed in Young Stellar Objects. Turning to solids, I review the evolution of single particles under aerodynamic forces, and describe the conditions necessary for the development of collective gas-particle instabilities. Observations show that disks are not always radially smooth axisymmetric structures, and I discuss how gas and particle processes can interact to form observable large-scale structure (at ice lines, vortices and in zonal flows). I conclude with disk dispersal.

  4. Detection of precessing circumpulsar disks

    CERN Document Server

    Grimani, C

    2014-01-01

    Experimental evidences indicate that formations of disks and planetary systems around pulsars are allowed. Unfortunately, direct detections through electromagnetic observations appear to be quite rare. In the case of PSR 1931+24, the hypothesis of a rigid precessing disk penetrating the pulsar light cylinder is found consistent with radio transient observations from this star. Disk self-occultation and precession may limit electromagnetic observations. Conversely, we show here that gravitational waves generated by disk precessing near the light cylinder of young and middle aged pulsars would be detected by future space interferometers with sensitivities like those expected for DECIGO (DECI-hertz Interferometer Gravitational Wave Observatory) and BBO (Big Bang Observer). The characteristics of circumpulsar detectable precessing disks are estimated as a function of distance from the Solar System. Speculations on upper limits to detection rates are presented.

  5. A Disk Scheduling Algorithm: SPFF

    Institute of Scientific and Technical Information of China (English)

    HU Ming

    2005-01-01

    We put forward an optimal disk schedule with n disk requests and prove its optimality mathematically. Generalizing the idea of an optimal disk schedule, we remove the limit of n requests and, at the same time, consider the dynamically arrival model of disk requests to obtain an algorithm, shortest path first-fit first (SPFF). This algorithm is based on the shortest path of disk head motion constructed by all the pendent requests. From view of the head-moving distance, it has the stronger globality than SSTF. From view of the head-moving direction, it has the better flexibility than SCAN. Therefore, SPFF keeps the advantage of SCAN and, at the same time, absorbs the strength of SSTF. The algorithm SPFF not only shows the more superiority than other scheduling polices, but also have higher adjustability to meet the computer system's different demands.

  6. Numerical Investigation of Circumplanetary Disks

    Science.gov (United States)

    Mitchell, Tyler R.; Stewart, G. R.

    2012-10-01

    The regular satellites of Jupiter and Saturn are believed to have formed in circumplanetary disks that were present during the late stages of giant planet formation. At present, there is a large amount of uncertainly in both the structure of these disks and the nature of angular momentum transport within them. In circumstellar disks, magnetorotational rotational instability (MRI) is generally invoked as a mechanism to transfer angular momentum and drive accretion. It is unclear whether circumplanetary disks are sufficiently ionized for the MRI to be active. In an effort to better understand the physical nature of circumplanetary disks, we present 1+1D numerical models of Jovian and Saturnian circumplanetary disks. Our models include viscous diffusion, infall from the solar nebula and external photoevaporation. The combination of these three processes allow for steady-state, truncated disks roughly consistent with the present state of the regular satellite systems of Jupiter and Saturn (Mitchell & Stewart, 2011). Unlike recent models of tidal truncation (Martin & Lubow, 2010), our initial models showed that photoevaporation is able to truncate circumplanetary disks to a small fraction of the Hill radius. One goal of this work is to verify our previous results and confirm that truncated disks can be formed using models with more realistic viscous processes. In order to simplify the problem, our initial models employed a viscosity that was linearly dependent on radius. Our current disk models use a viscosity that is calculated locally based on the midplane temperature that is determined from detailed vertical structure calculations. These models are used to conduct an initial investigation of the viability of an active MRI as well as baroclinic instability and other instabilities that may exist.

  7. Evolution of magnetized protoplanetary disks

    Science.gov (United States)

    Reyes-Ruiz, Mauricio; Stepinski, Tomasz F.

    1995-01-01

    We investigate the global evolution of a turbulent protoplanetary disk in its viscous stage, incorporating the effects of Maxwell stress due to a large-scale magnetic field permeating disk. We assume that the viscous stress is given by an alpha model. A magnetic field is produced contemporaneously by an alpha omega dynamo mechanism and the resultant Maxwell stress assists the viscous stress in providing the means for disk evolution. The aim of this work is to compare the evolution of magnetized and nonmagnetized disks driven by turbulent viscosity of the same magnitude and thus assess the effects of a self-generated magnetic field on the structure and dynamical evolution of protoplanetary disks. Two illustrative examples corresponding to two different initial conditions are considered: a high-mass case that starts with a disk of 0.245 solar mass and angular momentum of 5.6 x 10(exp 52)g sq cm/s, and a low-mass that case starts with a disk of 0.11 solar mass and angular momentum of 1.8 x 10(exp 52)g sq cm/s. For each of these two cases the radial development of a disk is calculated numerically assuming a fiducial value of the dimensionless viscosity parameter alpha(sub ss) = 0.01, as well as alpha(sub ss) = 2 x 10(exp -3). In all cases the central star has a mass equal to 1 solar mass. The most striking feature of magnetized disk evolution is the presence of the surface density bulge located in the region of the disk where the dynamo mechanism cannot support a magnetic field. The bulge persists for a time of the order of 10(exp 5)-10(exp 6) yr. The presence and persistence of the surface density bulge may have important implications for the process of planet formation and the overall characteristics of resultant planetary systems.

  8. Stochastic disks that roll

    Science.gov (United States)

    Holmes-Cerfon, Miranda

    2016-11-01

    We study a model of rolling particles subject to stochastic fluctuations, which may be relevant in systems of nano- or microscale particles where rolling is an approximation for strong static friction. We consider the simplest possible nontrivial system: a linear polymer of three disks constrained to remain in contact and immersed in an equilibrium heat bath so the internal angle of the polymer changes due to stochastic fluctuations. We compare two cases: one where the disks can slide relative to each other and the other where they are constrained to roll, like gears. Starting from the Langevin equations with arbitrary linear velocity constraints, we use formal homogenization theory to derive the overdamped equations that describe the process in configuration space only. The resulting dynamics have the formal structure of a Brownian motion on a Riemannian or sub-Riemannian manifold, depending on if the velocity constraints are holonomic or nonholonomic. We use this to compute the trimer's equilibrium distribution with and without the rolling constraints. Surprisingly, the two distributions are different. We suggest two possible interpretations of this result: either (i) dry friction (or other dissipative, nonequilibrium forces) changes basic thermodynamic quantities like the free energy of a system, a statement that could be tested experimentally, or (ii) as a lesson in modeling rolling or friction more generally as a velocity constraint when stochastic fluctuations are present. In the latter case, we speculate there could be a "roughness" entropy whose inclusion as an effective force could compensate the constraint and preserve classical Boltzmann statistics. Regardless of the interpretation, our calculation shows the word "rolling" must be used with care when stochastic fluctuations are present.

  9. TRANSITIONAL DISKS AROUND YOUNG LOW MASS STARS

    Directory of Open Access Journals (Sweden)

    P. D'Alessio

    2009-01-01

    have been interpreted as produced by disks with inner holes, which have been classi ed as \\Transitional Disks". These disks are considered the evolutionary link between the full disks typically found around the young T Tauri and Herbig Ae stars, and the debris disks, found around some main sequence stars. In this contribution we summarize the observed/inferred characteristics of these transitional disks and also some of the models proposed to explain their peculiar geometry.

  10. Accretion of solid materials onto circumplanetary disks from protoplanetary disks

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, Takayuki [Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819 (Japan); Maruta, Akito; Machida, Masahiro N., E-mail: tanigawa@pop.lowtem.hokudai.ac.jp [Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581 (Japan)

    2014-04-01

    We investigate the accretion of solid materials onto circumplanetary disks from heliocentric orbits rotating in protoplanetary disks, which is a key process for the formation of regular satellite systems. In the late stage of the gas-capturing phase of giant planet formation, the accreting gas from protoplanetary disks forms circumplanetary disks. Since the accretion flow toward the circumplanetary disks affects the particle motion through gas drag force, we use hydrodynamic simulation data for the gas drag term to calculate the motion of solid materials. We consider a wide range of size for the solid particles (10{sup –2}-10{sup 6} m), and find that the accretion efficiency of the solid particles peaks around 10 m sized particles because energy dissipation of drag with circum-planetary disk gas in this size regime is most effective. The efficiency for particles larger than 10 m becomes lower because gas drag becomes less effective. For particles smaller than 10 m, the efficiency is lower because the particles are strongly coupled with the background gas flow, which prevents particles from accretion. We also find that the distance from the planet where the particles are captured by the circumplanetary disks is in a narrow range and well described as a function of the particle size.

  11. The Gas Disk: Evolution and Chemistry

    Science.gov (United States)

    Rab, Christian; Baldovin-Saavedra, Carla; Dionatos, Odysseas; Vorobyov, Eduard; Güdel, Manuel

    2016-12-01

    Protoplanetary disks are the birthplaces of planetary systems. The evolution of the star-disk system and the disk chemical composition determines the initial conditions for planet formation. Therefore a comprehensive understanding of the main physical and chemical processes in disks is crucial for our understanding of planet formation. We give an overview of the early evolution of disks, discuss the importance of the stellar high-energy radiation for disk evolution and describe the general thermal and chemical structure of disks. Finally we provide an overview of observational tracers of the gas component and disk winds.

  12. The gas disk: Evolution and chemistry

    CERN Document Server

    Rab, Ch; Dionatos, O; Vorobyov, E; Güdel, Manuel

    2016-01-01

    Protoplanetary disks are the birthplaces of planetary systems. The evolution of the star-disk system and the disk chemical composition determines the initial conditions for planet formation. Therefore a comprehensive understanding of the main physical and chemical processes in disks is crucial for our understanding of planet formation. We give an overview of the early evolution of disks, discuss the importance of the stellar high-energy radiation for disk evolution and describe the general thermal and chemical structure of disks. Finally we provide an overview of observational tracers of the gas component and disk winds.

  13. Protecting geothermal operations with rupture disks

    Energy Technology Data Exchange (ETDEWEB)

    Porter, D.W.

    1983-02-01

    Potential rupture disk applications in geothermal operations are reviewed. Several wells manifolded together, to form the geothermal feed, cause erratic pressure. Rupture disks are used for relief. Flash tanks are equipped with rupture disks. Brine separators, heat exchanger shells, and turbine casings are protected by rupture disks. An analysis of geothermal steam will determine the rupture disk metal. Reverse Buckling disks are recommended over tension loaded disks for dealing with geothermal pressure cycling. Erratic temperature suggests that metals which retain tensile strength with temperature be used (Inconel is mentioned). In summary, geothermal projects represent an excellent rupture disk market.

  14. Instabilities at planetary gap edges in 3D self-gravitating disks

    Directory of Open Access Journals (Sweden)

    Lin Min-Kai

    2013-04-01

    Full Text Available Numerical simulations are presented to study the stability of gaps opened by giant planets in 3D self-gravitating disks. In weakly self-gravitating disks, a few vortices develop at the gap edge and merge on orbital time-scales. The result is one large but weak vortex with Rossby number -0.01. In moderately self-gravitating disks, more vortices develop and their merging is resisted on dynamical time-scales. Self-gravity can sustain multi-vortex configurations, with Rossby number -0.2 to -0.1, over a time-scale of order 100 orbits. Self-gravity also enhances the vortex vertical density stratification, even in disks with initial Toomre parameter of order 10. However, vortex formation is suppressed in strongly self-gravitating disks and replaced by a global spiral instability associated with the gap edge which develops during gap formation.

  15. Instabilities at planetary gap edges in 3D self-gravitating disks

    CERN Document Server

    Lin, Min-Kai

    2013-01-01

    Numerical simulations are presented to study the stability of gaps opened by giant planets in 3D self-gravitating disks. In weakly self-gravitating disks, a few vortices develop at the gap edge and merge on orbital time-scales. The result is one large but weak vortex with Rossby number -0.01. In moderately self-gravitating disks, more vortices develop and their merging is resisted on dynamical time-scales. Self-gravity can sustain multi-vortex configurations, with Rossby number -0.2 to -0.1, over a time-scale of order 100 orbits. Self-gravity also enhances the vortex vertical density stratification, even in disks with initial Toomre parameter of order 10. However, vortex formation is suppressed in strongly self-gravitating disks and replaced by a global spiral instability associated with the gap edge which develops during gap formation.

  16. Aeronautical Information System Replacement -

    Data.gov (United States)

    Department of Transportation — Aeronautical Information System Replacement is a web-enabled, automation means for the collection and distribution of Service B messages, weather information, flight...

  17. Study of clean up procedures using Charcoal-Alumina-Celite column, immunoaffinity column and strata x column to determine deoxynivalenol by high performance liquid chromatography in wheat

    Directory of Open Access Journals (Sweden)

    Jacqueline Cea

    2011-04-01

    Full Text Available Fusarium graminearum is the most common toxic fungal species affecting grains in Uruguay. Since 1977, due to favorable climate conditions, there have been harvests with prominent Fusarium Head Blight in wheat. This were in 1984, 1990, 1993, 1996 and 2001.Natural Toxin Department of Technological Laboratory of Uruguay as National Reference Laboratory, is continuously improving the analytical methods in order to have a good response to the industry requirements and to the monitoring programs for import and exports commodities. The objective of this work was to compare different clean up methods in order to select the best one for routine determination of deoxynivalenol (DON in wheat (grain and flour.  Charcoal-alumina-celite (7+5+3,  immunoaffinity columns DONPREP R-Biopharm Rhone and Strata X 33 m polymeric sorbent  Phenomenex columns were used to perform the study. Considering as reference analytical method the internal protocol  PEC.TOX.063 accredited by United Kingdom Accreditation Service (UKAS  following the ISO 17025 requirements, and  based on AOAC method 986.17( chapter 49, 2002 for extraction and clean-up  and on J.AOAC 70(3, 1987:479-483 for the high performance liquid chromatography (HPLC detection, two more clean up methods were evaluated. In all of them PEC.TOX.063 detection procedure was carried out. PEC.TOX.063 used for the clean up an in house column chromatography prepared with charcoal-alumina-celite (7+5+3 . Extraction was performed using acetonitrile- water (84+16 and an aliquot of the extract was passed through the column. Extract was dryed under vacuum and DON detected by HPLC using photodiode array detector. For the method that used immunoaffinity columns, water was the extraction solvent, and manufacture protocol was followed up. An aliquot of the extract was passed through the column. Column was washed using water and DON eluated using methanol 100%. For the method that used Strata X column for the clean up, the

  18. Enantiomeric quantification of (S)-(+)-methamphetamine in urine by an immunoaffinity column and liquid chromatography-electrospray-mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Lua, Ahai C. [Department of Laboratory Medicine and Biotechnology and Graduate Institute of Medical Biotechnology, Tzu Chi University, 701, Chung Yang Road Section 3, Hualien, 970, Taiwan (China); Sutono, Yenny [Department of Laboratory Medicine and Biotechnology and Graduate Institute of Medical Biotechnology, Tzu Chi University, 701, Chung Yang Road Section 3, Hualien, 970, Taiwan (China); Chou, T.-Y. [Department of Laboratory Medicine and Biotechnology and Graduate Institute of Medical Biotechnology, Tzu Chi University, 701, Chung Yang Road Section 3, Hualien, 970, Taiwan (China)]. E-mail: cty@mail.tcu.edu.tw

    2006-08-18

    A method using an immunoaffinity column (IAC) and liquid chromatography-electrospray ionization mass spectrometry (LC/MS) for on-line detecting the presence of MA in the effluent was developed for the quantitative and enantiomeric determination of (S)-(+)-methamphetamine (D-MA) in urine. The IAC was made in our laboratory and utilized in the LC/MS to simultaneously extract and separate enantiomers of MA from urine samples. An aqueous ammonium acetate buffer was used as the mobile phase. Urine samples were spiked with racemic deuterated methamphetamine (MA-d{sub 14}) as internal standard (IS), filtered through a membrane, and injected into the LC/MS without any further pre-treatment. Protonated molecular ion of MA and MA-d{sub 14} (m/z 150 and 164) were isolated and further fragmented, the respective product ions, m/z 119 and 130, were collected for quantitative determination. This is an improvement of our previous method (A.C. Lua, Tsong-Yung Chou, J. Chromatogr. A 967 (2002) 191). In the previous method, MA was separated with HPLC, the efflux was fractionated and each fraction was either determined with an immunoassay or GC/MS. Monitoring of MA in the efflux is tedious and time consuming. Urine samples spiked with different concentrations of D-MA were measured by this method. A linear relationship exists in the 150-1050 ng/mL range, and the detection limit (defined as signal-to-noise ratio 3) of D-MA was determined to be 18 ng/mL. The linearity of the method for D-MA can be described by the equation (Y = 1.415 x 10{sup -3} X + 0.034, correlation coefficient: r {sup 2} = 0.999). Within run, accuracy and precision (n = 6, relative error: -7.2 to +4.0% and relative standard deviation: 3.8-9.3%) of the method are fairly good.

  19. Usefulness of gold nanoparticles as labels for the determination of gliadins by immunoaffinity chromatography with light scattering detection.

    Science.gov (United States)

    Molina-Delgado, M A; Aguilar-Caballos, M P; Gómez-Hens, A

    2011-10-15

    A simple and fast immunoaffinity method is proposed for the determination of gliadins for the first time using gold nanoparticles (AuNPs) as labels. The tracer used consists in a gliadin-AuNP conjugate prepared by the adsorption of gliadins onto the nanoparticle surface. Two AuNP sizes with diameters of 10nm and 20 nm were assayed to compare the behaviour of the corresponding tracer in the assay. The method relies on the injection in a commercial Protein G column of a preincubated mixture containing gliadins, polyclonal anti-gliadin antibodies, and the gliadin-AuNP tracer. This approach allows the separation of free and bound tracer fractions without any additional elution step, and the direct measurement of the resonance light scattering intensity of the free tracer through the peak height of the immunochromatogram, which is proportional to the analyte concentration. The immunocolumn can be used up to 25 times without eluting and it can be regenerated for at least 20 times. The dynamic ranges of the calibration graphs and the detection limits are 0.5-15.0 and 1.5-15.0 μg mL(-1) gliadins, and 0.2 μg mL(-1) and 0.8 μg mL(-1) gliadins, using 20-nm and 10-nm Au-NPs as labels, respectively. The precision, expressed as relative standard deviation, ranges between 2.7% and 2.9% using 20-nm AuNPs and 4% and 6.1% for 10-nm AuNPs. The method has been applied to the determination of the prolamin fraction in beer samples, obtaining recovery values in the range 71.2% and 101.7%.

  20. CD45 immunoaffinity depletion of vesicles from Jurkat T cells demonstrates that exosomes contain CD45: no evidence for a distinct exosome/HIV-1 budding pathway

    Directory of Open Access Journals (Sweden)

    Ott David E

    2008-07-01

    Full Text Available Abstract The presence of relatively high levels of cellular protein contamination in density-purified virion preparations is a confounding factor in biochemical analyses of HIV and SIV produced from hematopoietic cells. A major source of this contamination is from vesicles, either microvesicles or exosomes, that have similar physical properties as virions. Thus, these particles can not be removed by size or density fractionation. Although virions and vesicles have similar cellular protein compositions, CD45 is excluded from HIV-1 yet is present in vesicles produced from hematopoietic cells. By exploiting this finding, we have developed a CD45 immunoaffinity depletion procedure that removes vesicles from HIV-1 preparations. While this approach has been successfully applied to virion preparations from several different cell types, some groups have concluded that "exosomes" from certain T cell lines, specifically Jurkat, do not contain CD45. If this interpretation is correct, then these vesicles could not be removed by CD45 immunoaffinity depletion. Here we show that dense vesicles produced by Jurkat and SupT1/CCR5 cells contain CD45 and are efficiently removed from preparations by CD45-immunoaffinity depletion. Also, contaminating cellular proteins were removed from virion preparations produced by these lines. Previously, the absence of CD45 from both "exosomes" and virions has been used to support the so called Trojan exosome hypothesis, namely that HIV-1 is simply an exosome containing viral material. The presence of CD45 on vesicles, including exosomes, and its absence on virions argues against a specialized budding pathway that is shared by both exosomes and HIV-1.

  1. In-depth Qualitative and Quantitative Profiling of Tyrosine Phosphorylation Using a Combination of Phosphopeptide Immunoaffinity Purification and Stable Isotope Dimethyl Labeling*

    Science.gov (United States)

    Boersema, Paul J.; Foong, Leong Yan; Ding, Vanessa M. Y.; Lemeer, Simone; van Breukelen, Bas; Philp, Robin; Boekhorst, Jos; Snel, Berend; den Hertog, Jeroen; Choo, Andre B. H.; Heck, Albert J. R.

    2010-01-01

    Several mass spectrometry-based assays have emerged for the quantitative profiling of cellular tyrosine phosphorylation. Ideally, these methods should reveal the exact sites of tyrosine phosphorylation, be quantitative, and not be cost-prohibitive. The latter is often an issue as typically several milligrams of (stable isotope-labeled) starting protein material are required to enable the detection of low abundance phosphotyrosine peptides. Here, we adopted and refined a peptidecentric immunoaffinity purification approach for the quantitative analysis of tyrosine phosphorylation by combining it with a cost-effective stable isotope dimethyl labeling method. We were able to identify by mass spectrometry, using just two LC-MS/MS runs, more than 1100 unique non-redundant phosphopeptides in HeLa cells from about 4 mg of starting material without requiring any further affinity enrichment as close to 80% of the identified peptides were tyrosine phosphorylated peptides. Stable isotope dimethyl labeling could be incorporated prior to the immunoaffinity purification, even for the large quantities (mg) of peptide material used, enabling the quantification of differences in tyrosine phosphorylation upon pervanadate treatment or epidermal growth factor stimulation. Analysis of the epidermal growth factor-stimulated HeLa cells, a frequently used model system for tyrosine phosphorylation, resulted in the quantification of 73 regulated unique phosphotyrosine peptides. The quantitative data were found to be exceptionally consistent with the literature, evidencing that such a targeted quantitative phosphoproteomics approach can provide reproducible results. In general, the combination of immunoaffinity purification of tyrosine phosphorylated peptides with large scale stable isotope dimethyl labeling provides a cost-effective approach that can alleviate variation in sample preparation and analysis as samples can be combined early on. Using this approach, a rather complete qualitative

  2. Immunoaffinity purification of factor IX (Christmas factor) by using conformation-specific antibodies directed against the factor IX-metal complex.

    OpenAIRE

    1985-01-01

    Factor IX is a vitamin K-dependent blood clotting zymogen that is functionally defective or absent in patients with hemophilia B. A method of immunoaffinity chromatography has been developed for a one-step high yield purification of factor IX directly from plasma. The technique utilizes conformation-specific antibodies that bind solely to the metal-stabilized factor IX conformer, but not to the conformer of factor IX found in the absence of metal ions. Anti-factor IX-Ca(II) antibodies were im...

  3. 8-inch IBM floppy disk

    CERN Multimedia

    1971-01-01

    The 8-inch floppy disk was a magnetic storage disk for the data introduced commercially by IBM in 1971. It was designed by an IBM team as an inexpensive way to load data into the IBM System / 370. Plus it was a read-only bare disk containing 80 KB of data. The first read-write version was introduced in 1972 by Memorex and could contain 175 KB on 50 tracks (with 8 sectors per track). Other improvements have led to various coatings and increased capacities. Finally, it was surpassed by the mini diskette of 5.25 inches introduced in 1976.

  4. Radiation Source Replacement Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, Jeffrey W.; Moran, Traci L.; Bond, Leonard J.

    2010-12-01

    This report summarizes a Radiation Source Replacement Workshop in Houston Texas on October 27-28, 2010, which provided a forum for industry and researchers to exchange information and to discuss the issues relating to replacement of AmBe, and potentially other isotope sources used in well logging.

  5. Magneto-thermal Disk Wind from Protoplanetary Disks

    CERN Document Server

    Bai, Xue-Ning; Goodman, Jeremy; Yuan, Feng

    2015-01-01

    Global evolution and dispersal of protoplanetary disks (PPDs) is governed by disk angular momentum transport and mass-loss processes. Recent numerical studies suggest that angular momentum transport in the inner region of PPDs is largely driven by magnetized disk wind, yet the wind mass-loss rate remains unconstrained. On the other hand, disk mass loss has conventionally been attributed to photoevaporation, where external heating on the disk surface drives a thermal wind. We unify the two scenarios by developing a 1D model of magnetized disk winds with a simple treatment of thermodynamics as a proxy for external heating. The wind properties largely depend on 1) the magnetic field strength at the wind base, characterized by the poloidal Alfv\\'en speed $v_{Ap}$, 2) the sound speed $c_s$ near the wind base, and 3) how rapidly poloidal field lines diverge (achieve $R^{-2}$ scaling). When $v_{Ap}\\gg c_s$, corotation is enforced near the wind base, resulting in centrifugal acceleration. Otherwise, the wind is accel...

  6. Chondrule Transport in Protoplanetary Disks

    CERN Document Server

    Goldberg, Aaron Z; Jacquet, Emmanuel

    2015-01-01

    Chondrule formation remains one of the most elusive early Solar System events. Here, we take the novel approach of employing numerical simulations to investigate chondrule origin beyond purely cosmochemical methods. We model the transport of generically-produced chondrules and dust in a 1D viscous protoplanetary disk model, in order to constrain the chondrule formation events. For a single formation event we are able to match analytical predictions of the memory chondrule and dust populations retain of each other (complementarity), finding that a large mass accretion rate ($\\gtrsim 10^{-7}$~M$_\\odot$~yr$^{-1}$) allows for delays on the order of the disk's viscous timescale between chondrule formation and chondrite accretion. Further, we find older disks to be severely diminished of chondrules, with accretion rates $\\lesssim 10^{-9}$~M$_\\odot$~yr$^{-1}$ for nominal parameters. We then characterize the distribution of chondrule origins in both space and time, as functions of disk parameters and chondrule format...

  7. Poynting Jets from Accretion Disks

    CERN Document Server

    Lovelace, R V E; Ustyugova, G V; Romanova, M M; Colgate, S A

    2002-01-01

    The powerful narrow jets observed to emanate from many compact accreting objects may arise from the twisting of a magnetic field threading a differentially rotating accretion disk which acts to magnetically extract angular momentum and energy from the disk. Two main regimes have been discussed, {\\it hydromagnetic outflows}, which have a significant mass flux and have energy and angular momentum carried by both the matter and the electromagnetic field and, Poynting outflows, where the mass flux is negligible and energy and angular momentum are carried predominantly by the electromagnetic field. Here we consider a Keplerian disk initially threaded by a dipole-like magnetic field and we present solutions of the force-free Grad-Shafranov equation for the coronal plasma. We find solutions with Poynting jets where there is a continuous outflow of energy and toroidal magnetic flux from the disk into the external space. This behavior contradicts the commonly accepted ``theorem'' of Solar plasma physics that the motio...

  8. Secular Evolution in Disk Galaxies

    CERN Document Server

    Kormendy, John

    2013-01-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via available evolution processes. The inner parts shrink and the outer parts expand, provided that some physical process transports energy or angular momentum outward. The evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks, and galaxy disks are all fundamentally similar. These processes for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. Part 1 discusses formation, growth, and death of bars. Part 2 details the slow ("secular") rearrangement of angular momentum that results from interactions between stars or gas and nonaxisymmetries such as bars. We have a heuristic understanding of how this forms outer rings, inner rings, and stuff dumped into the center. Observations show that barred galaxies have central concentrations of gas and star formation. Timescales imply that they grow central "pseudobulges" that get mistaken for ellip...

  9. Gravitational Instabilities in Circumstellar Disks

    CERN Document Server

    Kratter, Kaitlin M

    2016-01-01

    [Abridged] Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability, and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability, supplemented with a survey of numerical simulations that aim to capture the non-linear evolution. We emphasize the role of thermodynamics and large scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analyt...

  10. Collisional Grooming of Debris Disks

    CERN Document Server

    Kuchner, Marc J

    2009-01-01

    Debris disk images show clumps, rings, warps, and other structures, many of which have been interpreted as perturbations from hidden planets. But so far, no models of these structures have properly accounted for collisions between dust grains. We have developed new steady-state 3D models of debris disks that self-consistently incorporate grain-grain collisions. We summarize our algorithm and use it to illustrate how collisions interact with resonant trapping in the presence of a planet.

  11. Heating of protostellar accretion disks

    Science.gov (United States)

    de Campos, R. R.; Jatenco-Pereira, V.

    2017-07-01

    The magneto-rotational instability (MRI) is believed to be the mechanism responsible for a magneto-hydrodynamic turbulence that could lead to the accretion observed in protoplanetary disks. The need of a minimum amount of ionization in protostellar accretion disks is necessary for the MRI to take place. There are in the literature several studies that include the damping of Alfvén waves as an additional heating source besides the viscous heating mechanism in a geometrically thin and optically thick disk. The damping of the waves transfers energy to the disk increasing the temperature and consequently its ionization fraction, making possible the presence of the MRI in a large part of the disk. We analyzed the contribution of non-ideal effects such as Ohmic and ambipolar diffusion for the disk heating and compare these heating rates with those obtained by damping of Alfvén waves. In order to study these non-ideal effects, we have estimated the radiation emission of each effect through the energy conservation equation, and associated each emission with a black body radiation, which enabled us to assign a temperature contribution of each effect. Using the ATHENA code we were able to simulate the disk at different radial distances, and estimate the electric current density needed to calculate the radiation emission associated with each effect. Once we have those data, we were able to compare the results with other heating sources, like viscosity and Alfvén waves damping, and we concluded that the Ohmic and ambipolar diffusions do not heat the disk in any significant way.

  12. Gravitational Instabilities in Circumstellar Disks

    Science.gov (United States)

    Kratter, Kaitlin; Lodato, Giuseppe

    2016-09-01

    Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review, we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. We emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. In the next part of our review, we focus on the astrophysical consequences of the instability. We show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, Md/M*≥0.1. They will develop quasi-stable spiral arms that process infall from the background cloud. Although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. In this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. In some cases the instability may lead to fragmentation into bound companions. These companions are more likely to be brown dwarfs or stars than planetary mass objects. Finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular

  13. Resolved observations of transition disks

    CERN Document Server

    Casassus, Simon

    2016-01-01

    Resolved observations are bringing new constraints on the origin of radial gaps in protoplanetary disks. The kinematics, sampled in detail in one case-study, are indicative of non-Keplerian flows, corresponding to warped structures and accretion which may both play a role in the development of cavities. Disk asymmetries seen in the radio continuum are being interpreted in the context of dust segregation via aerodynamic trapping. We summarise recent observational progress, and also describe prospects for improvements in the near term.

  14. Two-dimensional vortices and accretion disks

    NARCIS (Netherlands)

    Nauta, Michiel Doede

    2001-01-01

    Observations show that there are disks around certain stars that slowly rain down on the central (compact) object: accretion disks. The rate of depletion of the disk might be slow but is still larger than was expected on theoretical grounds. That is why it has been suggested that the disks are tu

  15. Herschel evidence for disk flattening or gas depletion in transitional disks

    CERN Document Server

    Keane, J T; Espaillat, C; Woitke, P; Andrews, S; Kamp, I; Thi, W -F; Meeus, G; Dent, W R F

    2014-01-01

    Transitional disks are protoplanetary disks characterized by reduced near- and mid-infrared emission with respect to full disks. This characteristic spectral energy distribution indicates the presence of an optically thin inner cavity within the dust disk believed to mark the disappearance of the primordial massive disk. We present new Herschel Space Observatory PACS spectra of [OI] 63 micron for 21 transitional disks. Our survey complements the larger Herschel GASPS program "Gas in Protoplanetary Systems" (Dent et al. 2013) by quadrupling the number of transitional disks observed with PACS at this wavelength. [OI] 63 micron traces material in the outer regions of the disk, beyond the inner cavity of most transitional disks. We find that transitional disks have [OI] 63 micron line luminosities two times fainter than their full disk counterparts. We self consistently determine various stellar properties (e.g. bolometric luminosity, FUV excess, etc.) and disk properties (e.g. disk dust mass, etc.) that could in...

  16. Disks around young stellar objects

    Indian Academy of Sciences (India)

    H C Bhatt

    2011-07-01

    By 1939, when Chandrasekhar’s classic monograph on the theory of Stellar Structure was published, although the need for recent star formation was fully acknowledged, no one had yet recognized an object that could be called a star in the process of being born. Young stellar objects (YSOs), as pre-main-sequence stars, were discovered in the 1940s and 1950s. Infrared excess emission and intrinsic polarization observed in these objects in the 1960s and 1970s indicated that they are surrounded by flattened disks. The YSO disks were seen in direct imaging only in the 1980s. Since then, high-resolution optical imaging with HST, near-infrared adaptive optics on large groundbased telescopes, mm and radiowave interferometry have been used to image disks around a large number of YSOs revealing disk structure with ever-increasing detail and variety. The disks around YSOs are believed to be the sites of planet formation and a few such associations have now been confirmed. The observed properties of the disk structure and their evolution, that have very important consequences for the theory of star and planet formation, are discussed.

  17. Global Models for Embedded, Accreting Protostellar Disks

    CERN Document Server

    Kratter, Kaitlin M; Krumholz, Mark R

    2007-01-01

    Most analytic work to date on protostellar disks has focused on disks in isolation from their environments. However, observations are now beginning to probe the earliest, most embedded phases of star formation, during which disks are rapidly accreting from their parent cores and cannot be modeled in isolation. We present a simple, one-zone model of protostellar accretion disks with high mass infall rates. Our model combines a self-consistent calculation of disk temperatures with an approximate treatment of angular momentum transport via several mechanisms. We use this model to survey the properties of protostellar disks across a wide range of stellar masses and evolutionary times, and make predictions for disks' masses, sizes, spiral structure, and fragmentation that will be directly testable by future large-scale surveys of deeply embedded disks. We define a dimensionless accretion-rotation parameter which, in conjunction with the disk's temperature, controls the disk evolution. We track the dominant mode of...

  18. Fragmentation of Kozai–Lidov Disks

    Science.gov (United States)

    Fu, Wen; Lubow, Stephen H.; Martin, Rebecca G.

    2017-02-01

    We analyze the gravitational instability (GI) of a locally isothermal inclined disk around one component of a binary system. Such a disk can undergo global Kozai–Lidov (KL) cycles if the initial disk tilt is above the critical KL angle (of about 40◦). During these cycles, an initially circular disk exchanges its inclination for eccentricity, and vice versa. Self-gravity may suppress the cycles under some circumstances. However, with hydrodynamic simulations that include self-gravity, we show that for a sufficiently high initial disk tilts and for certain disk masses, disks can undergo KL oscillations and fragment due to GI, even when the Toomre Q value for an equivalent undisturbed disk is well within the stable regime (Q> 2). We suggest that KL triggered disk fragmentation provides a mechanism for the efficient formation of giant planets in binary systems and may enhance the fragmentation of disks in massive black hole binaries.

  19. Magneto-thermal Disk Winds from Protoplanetary Disks

    Science.gov (United States)

    Bai, Xue-Ning; Ye, Jiani; Goodman, Jeremy; Yuan, Feng

    2016-02-01

    The global evolution and dispersal of protoplanetary disks (PPDs) are governed by disk angular-momentum transport and mass-loss processes. Recent numerical studies suggest that angular-momentum transport in the inner region of PPDs is largely driven by magnetized disk wind, yet the wind mass-loss rate remains unconstrained. On the other hand, disk mass loss has conventionally been attributed to photoevaporation, where external heating on the disk surface drives a thermal wind. We unify the two scenarios by developing a one-dimensional model of magnetized disk winds with a simple treatment of thermodynamics as a proxy for external heating. The wind properties largely depend on (1) the magnetic field strength at the wind base, characterized by the poloidal Alfvén speed vAp, (2) the sound speed cs near the wind base, and (3) how rapidly poloidal field lines diverge (achieve {R}-2 scaling). When {v}{Ap}\\gg {c}{{s}}, corotation is enforced near the wind base, resulting in centrifugal acceleration. Otherwise, the wind is accelerated mainly by the pressure of the toroidal magnetic field. In both cases, the dominant role played by magnetic forces likely yields wind outflow rates that exceed purely hydrodynamical mechanisms. For typical PPD accretion-rate and wind-launching conditions, we expect vAp to be comparable to cs at the wind base. The resulting wind is heavily loaded, with a total wind mass-loss rate likely reaching a considerable fraction of the wind-driven accretion rate. Implications for modeling global disk evolution and planet formation are also discussed.

  20. Bioanalysis of bevacizumab and infliximab by high-temperature reversed-phase liquid chromatography with fluorescence detection after immunoaffinity magnetic purification.

    Science.gov (United States)

    Todoroki, Kenichiro; Nakano, Tatsuki; Eda, Yasuhiro; Ohyama, Kaname; Hayashi, Hideki; Tsuji, Daiki; Min, Jun Zhe; Inoue, Koichi; Iwamoto, Naoki; Kawakami, Atsushi; Ueki, Yukitaka; Itoh, Kunihiko; Toyo'oka, Toshimasa

    2016-04-15

    This study presents two simple and rapid methods for the quantification of therapeutic mAbs based on LC. Two mAbs (bevacizumab and infliximab) in plasma samples were purified using magnetic beads immobilized with a commercially-available idiotype antibody for each mAb. Purified mAbs were separated with HT-RPLC and detected with their native fluorescence. Using immunoaffinity beads, each mAb was selectively purified and detected as a single peak in the chromatogram. The HT-RPLC achieved good separation for the mAbs with sharp peaks within 20 min. The calibration curves of the two mAbs ranged from 1 to 20 μg mL(-1) (bevacizumab) and 1-10 μg mL(-1) (infliximab), and they had strong correlation coefficients (r(2) > 0.998). The LOD of bevacizumab and infliximab was 0.07 and 0.15 μg mL(-1), and the LLOQ of bevacizumab and infliximab was 0.12 and 0.25 μg mL(-1), respectively. Thus, the sensitivities were sufficient for clinical analysis. Immunoaffinity purification with HT-RPLC produced a selective and accurate bioanalysis without an LC-MS/MS instrument. Both methods could become general-purpose analytical methods and complement the results obtained with conventional LBA.

  1. [Simultaneous determination of zeranols and chloramphenicol in foodstuffs of animal origin by combination immunoaffinity column clean-up and liquid chromatography-tandem mass spectrometry].

    Science.gov (United States)

    Wang, Qing; Wang, Guomin; Xi, Cunxian; Li, Xianliang; Chen, Dongdong; Tang, Bobin; Zhang, Lei; Zhao, Hua

    2014-06-01

    A combination immunoaffinity column (IAC-CZ) clean-up and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical method was successfully developed for zearalenol, beta-zearalenol and zearalenone) and chloramphenicol (CAP) in foodstuffs of animal origin. The samples (fish, liver, milk and honey) were enzymatically digested by beta-glucuronidase/sulfatase for about 16 h and then extracted with ether. The extracts were evaporated to dryness and then the residues were dissolved by 1.0 mL of 50% acetonitrile solution. After filtered and diluted with PBS buffer, the reconstituted solution were cleaned-up with a IAC-CZ and then analyzed by LC-MS/MS in multiple reaction monitoring (MRM) mode. The chromatographic separation was performed on a Shimadzu Shim-pack VP-ODS column with gradient elution by acetonitrile and 2 mmol/L ammonium acetate solution. The detection was carried out by electrospray negative ionization mass spectrometry in MRM mode. The proposed method was validated by the limit of detection (0.04-0.10 microg/kg), linearity (R2 > or = 0.999 0), average recoveries (70.9%-95.6%) and precisions (2.0% - 11.8%). The developed method is reliable, sensitive and has good applicability. The combination immunoaffinity column was proved to be an effective pretreatment technique to decrease the matrix effect, and it met the requirements of residue analysis of co-occurring zeranols and chloramphenicol.

  2. Covering and piercing disks with two centers

    KAUST Repository

    Ahn, Heekap

    2013-04-01

    We give exact and approximation algorithms for two-center problems when the input is a set D of disks in the plane. We first study the problem of finding two smallest congruent disks such that each disk in D intersects one of these two disks. Then we study the problem of covering the set D by two smallest congruent disks. © 2012 Elsevier B.V.

  3. Covering and piercing disks with two centers

    KAUST Repository

    Ahn, Heekap

    2011-01-01

    We consider new versions of the two-center problem where the input consists of a set D of disks in the plane. We first study the problem of finding two smallest congruent disks such that each disk in intersects one of these two disks. Then we study the problem of covering the set D by two smallest congruent disks. We give exact and approximation algorithms for these versions. © 2011 Springer-Verlag.

  4. Timescales of Disk Evolution and Planet Formation

    CERN Document Server

    Jayawarhana, R

    2000-01-01

    It has been suggested that circumstellar disks evolve from dense, actively accreting structures to low-mass, replenished remnants. During this transition, grains may assemble into planetesimals, or the disk may be cleared by newborn planets. Recently identified nearby groups of young stars provide valuable laboratories for probing disk evolution. I discuss the properties of dust disks in the TW Hydrae Association and the MBM 12 cloud, and compare the results to other studies of disk evolution and planet formation timescales.

  5. Replacing a Missing Tooth

    Science.gov (United States)

    ... vessels in the tooth pulps are rather large. Drilling down these teeth for crowns may expose the ... porcelain replacement tooth is held in place by metal extensions cemented to the backs of the adjacent ...

  6. Hormone Replacement Therapy

    Science.gov (United States)

    ... before and during menopause, the levels of female hormones can go up and down. This can cause ... hot flashes and vaginal dryness. Some women take hormone replacement therapy (HRT), also called menopausal hormone therapy, ...

  7. Knee joint replacement

    Science.gov (United States)

    ... of your kneecap. Your kneecap is called the patella. The replacement part is usually made from a ... long. Then your surgeon will: Move your kneecap (patella) out of the way, then cut the ends ...

  8. Knee joint replacement - slideshow

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/presentations/100088.htm Knee joint replacement - series—Normal anatomy To use the ... to slide 4 out of 4 Overview The knee is a complex joint. It contains the distal ...

  9. Product Platform Replacements

    DEFF Research Database (Denmark)

    Sköld, Martin; Karlsson, Christer

    2012-01-01

    Purpose – It is argued in this article that too little is known about product platforms and how to deal with them from a manager's point of view. Specifically, little information exists regarding when old established platforms are replaced by new generations in R&D and production environments...... originality and value is achieved by focusing on product platform replacements believed to represent a growing management challenge....

  10. Ultrafast disk lasers and amplifiers

    Science.gov (United States)

    Sutter, Dirk H.; Kleinbauer, Jochen; Bauer, Dominik; Wolf, Martin; Tan, Chuong; Gebs, Raphael; Budnicki, Aleksander; Wagenblast, Philipp; Weiler, Sascha

    2012-03-01

    Disk lasers with multi-kW continuous wave (CW) output power are widely used in manufacturing, primarily for cutting and welding applications, notably in the automotive industry. The ytterbium disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency, and high reliability with low investment and operating costs. Fundamental mode picosecond disk lasers are well established in micro machining at high throughput and perfect precision. Following the world's first market introduction of industrial grade 50 W picosecond lasers (TruMicro 5050) at the Photonics West 2008, the second generation of the TruMicro series 5000 now provides twice the average power (100 W at 1030 nm, or 60 W frequency doubled, green output) at a significantly reduced footprint. Mode-locked disk oscillators achieve by far the highest average power of any unamplified lasers, significantly exceeding the 100 W level in laboratory set-ups. With robust long resonators their multi-microjoule pulse energies begin to compete with typical ultrafast amplifiers. In addition, significant interest in disk technology has recently come from the extreme light laser community, aiming for ultra-high peak powers of petawatts and beyond.

  11. Disk Instabilities and Cooling Fronts

    CERN Document Server

    Vishniac, E T

    1998-01-01

    Accretion disk outbursts, and their subsequent decline, offer a unique opportunity to constrain the physics of angular momentum transport in hot accretion disks. Recent work has centered on the claim by Cannizzo et al. that the exponential decay of luminosity following an outburst in black hole accretion disk systems is only consistent with a particular form for the dimensionless viscosity, $\\alpha=35(c_s/r\\Omega)^{3/2}$. This result can be understood in terms of a simple model of the evolution of cooling fronts in accretion disks. In particular, the cooling front speed during decline is $\\sim cooling front, and the exact value of $n$ depends on the hot state opacity, (although generally $n\\approx 1/2$). Setting this speed proportional to $r$ constrains the functional form of $\\alpha$ in the hot phase of the disk, which sets it apart from previous arguments based on the relative durations of outburst and quiescence. However, it remains uncertain how well we know the exponent $n$. In addition, more work is nee...

  12. Simultaneity on the Rotating Disk

    Science.gov (United States)

    Koks, Don

    2017-04-01

    The disk that rotates in an inertial frame in special relativity has long been analysed by assuming a Lorentz contraction of its peripheral elements in that frame, which has produced widely varying views in the literature. We show that this assumption is unnecessary for a disk that corresponds to the simplest form of rotation in special relativity. After constructing such a disk and showing that observers at rest on it do not constitute a true rotating frame, we choose a "master" observer and calculate a set of disk coordinates and spacetime metric pertinent to that observer. We use this formalism to resolve the "circular twin paradox", then calculate the speed of light sent around the periphery as measured by the master observer, to show that this speed is a function of sent-direction and disk angle traversed. This result is consistent with the Sagnac Effect, but constitutes a finer analysis of that effect, which is normally expressed using an average speed for a full trip of the periphery. We also use the formalism to give a resolution of "Selleri's paradox".

  13. Simulations of magnetic fields in isolated disk galaxies

    CERN Document Server

    Pakmor, R

    2012-01-01

    Magnetic fields are known to be dynamically important in the interstellar medium of our own Galaxy, and they are ubiquitously observed in diffuse gas in the halos of galaxies and galaxy clusters. Yet, magnetic fields have typically been neglected in studies of the formation of galaxies, leaving their global influence on galaxy formation largely unclear. We extend our MHD implementation in the moving-mesh code Arepo to cosmological problems which include radiative cooling and the formation of stars. In particular, we replace our previously employed divergence cleaning approach with a Powell 8-wave scheme, which turns out to be significantly more stable, even in very dynamic environments. We verify the improved accuracy through simulations of the MRI in accretion disks, that reproduce its correct linear growth rate. Using this new MHD code, we simulate the formation of isolated disk galaxies similar to the Milky Way using idealized initial conditions with and without magnetic fields. We find that the magnetic f...

  14. The Milky Way's Stellar Disk

    CERN Document Server

    Rix, Hans-Walter

    2013-01-01

    A suite of vast stellar surveys mapping the Milky Way, culminating in the Gaia mission, is revolutionizing the empirical information about the distribution and properties of stars in the Galactic stellar disk. We review and lay out what analysis and modeling machinery needs to be in place to test mechanisms of disk galaxy evolution and to stringently constrain the Galactic gravitational potential, using such Galactic star-by-star measurements. We stress the crucial role of stellar survey selection functions in any such modeling; and we advocate the utility of viewing the Galactic stellar disk as made up from `mono-abundance populations' (MAPs), both for dynamical modeling and for constraining the Milky Way's evolutionary processes. We review recent work on the spatial and kinematical distribution of MAPs, and lay out how further study of MAPs in the Gaia era should lead to a decisively clearer picture of the Milky Way's dark matter distribution and formation history.

  15. Dust Evolution in Protoplanetary Disks

    Science.gov (United States)

    Testi, L.; Birnstiel, T.; Ricci, L.; Andrews, S.; Blum, J.; Carpenter, J.; Dominik, C.; Isella, A.; Natta, A.; Williams, J. P.; Wilner, D. J.

    In the core-accretion scenario for the formation of planetary rocky cores, the first step toward planet formation is the growth of dust grains into larger and larger aggregates and eventually planetesimals. Although dust grains are thought to grow up to micrometer-sized particles in the dense regions of molecular clouds, the growth to pebbles and kilometer-sized bodies must occur at the high densities within protoplanetary disks. This critical step is the last stage of solids evolution that can be observed directly in extrasolar systems before the appearance of large planetary-sized bodies. In this chapter we review the constraints on the physics of grain-grain collisions as they have emerged from laboratory experiments and numerical computations. We then review the current theoretical understanding of the global processes governing the evolution of solids in protoplanetary disks, including dust settling, growth, and radial transport. The predicted observational signatures of these processes are summarized. We briefly discuss grain growth in molecular cloud cores and in collapsing envelopes of protostars, as these likely provide the initial conditions for the dust in protoplanetary disks. We then review the observational constraints on grain growth in disks from millimeter surveys, as well as the very recent evidence for radial variations of the dust properties in disks. We also include a brief discussion on the small end of the grain size distribution and dust settling as derived from optical, near-, and mid-infrared observations. Results are discussed in the context of global dust-evolution models; in particular, we focus on the emerging evidence for a very efficient early growth of grains and the radial distribution of maximum grain sizes as the result of growth barriers. We also highlight the limits of the current models of dust evolution in disks, including the need to slow the radial drift of grains to overcome the migration/fragmentation barrier.

  16. Dust in protoplanetary disks: observations*

    Directory of Open Access Journals (Sweden)

    Waters L.B.F.M.

    2015-01-01

    Full Text Available Solid particles, usually referred to as dust, are a crucial component of interstellar matter and of planet forming disks surrounding young stars. Despite the relatively small mass fraction of ≈1% (in the solar neighborhood of our galaxy; this number may differ substantially in other galaxies that interstellar grains represent of the total mass budget of interstellar matter, dust grains play an important role in the physics and chemistry of interstellar matter. This is because of the opacity dust grains at short (optical, UV wavelengths, and the surface they provide for chemical reactions. In addition, dust grains play a pivotal role in the planet formation process: in the core accretion model of planet formation, the growth of dust grains from the microscopic size range to large, cm-sized or larger grains is the first step in planet formation. Not only the grain size distribution is affected by planet formation. Chemical and physical processes alter the structure and chemical composition of dust grains as they enter the protoplanetary disk and move closer to the forming star. Therefore, a lot can be learned about the way stars and planets are formed by observations of dust in protoplanetary disks. Ideally, one would like to measure the dust mass, the grain size distribution, grain structure (porosity, fluffiness, the chemical composition, and all of these as a function of position in the disk. Fortunately, several observational diagnostics are available to derive constrains on these quantities. In combination with rapidly increasing quality of the data (spatial and spectral resolution, a lot of progress has been made in our understanding of dust evolution in protoplanetary disks. An excellent review of dust evolution in protoplanetary disks can be found in Testi et al. (2014.

  17. Preparation of Immunoaffinity Column for Anti-AFM1%抗黄曲霉毒素M1免疫亲和柱的制备

    Institute of Scientific and Technical Information of China (English)

    孙兴荣; 裴世春; 柳家鹏; 王莹

    2011-01-01

    制备黄曲霉毒素M1污染样品的净化前处理免疫亲和柱.利用无血清培养基制备的高纯度抗黄曲霉毒素M1单克隆抗体和溴化氰活化的Sepharose 4B进行偶联、装柱后通过IC-ELSIA对免疫亲和柱的性能评价确立了最佳反应条件.免疫亲和柱的有效柱容量为500ng,经添加回收试验测定的平均回收率为92.46%0,变异系数2.3%-7.2%.利用高纯度抗黄曲霉毒素M1单克隆抗体和溴化氰活化的Sepharose 4B制备的免疫亲和柱可应用于乳制品等食品中黄曲霉毒素M1污染度测定的样品快速前处理.%Preparation of aflatoxin Ml immunoaffinity column for clean-up contaminated samples. The high-purity anti-aflatoxin M1 monoclonal antibody with serum-free medium was prepared and coupled with CNBr activated Sepharose 4B, and then packed in a column.Then the column was evaluated through IC-ELISA and established the optimum reaction conditions. The capacity of immunoaffinity column was 500 ng, the average recovery of aflatoxin M1 was 92.46%; and the variation coefficients were 2.3%~7.2%. The immunoaffinity columns was prepared by coupling high-purity anti-aflatoxin M1 monoclonal antibody with CNBr Activated Sepharose 4B can be applied to detect contamination samples fast, such as aflatoxin M1 in dairy products.

  18. Nonaxisymmetric evolution in protostellar disks

    Science.gov (United States)

    Laughlin, Gregory; Bodenheimer, Peter

    1994-01-01

    We present a two-dimensional, multigridded hydrodynamical simulation of the collapse of an axisymmetric, rotating, 1 solar mass protostellar cloud, which forms a resolved, hydrotastic disk. The code includes the effects of physical viscosity, radiative transfer and radiative acceleration but not magnetic fields. We examine how the disk is affected by the inclusion of turbulent viscosity by comparing a viscous simulation with an inviscid model evolved from the same initial conditions, and we derive a disk evolutionary timescale on the order of 300,000 years if alpha = 0.01. Effects arising from non-axisymmetric gravitational instabilities in the protostellar disk are followed with a three-dimensional SPH code, starting from the two-dimensional structure. We find that the disk is prone to a series of spiral instabilities with primary azimulthal mode number m = 1 and m = 2. The torques induced by these nonaxisymmetric structures elicit material transport of angular momentum and mass through the disk, readjusting the surface density profile toward more stable configurations. We present a series of analyses which characterize both the development and the likely source of the instabilities. We speculate that an evolving disk which maintains a minimum Toomre Q-value approximately 1.4 will have a total evolutionary span of several times 10(exp 5) years, comparable to, but somewhat shorter than the evolutionary timescale resulting from viscous turbulence alone. We compare the evolution resulting from nonaxisymmetric instabilities with solutions of a one-dimensional viscous diffusion equation applied to the initial surface density and temperature profile. We find that an effective alpha-value of 0.03 is a good fit to the results of the simulation. However, the effective alpha will depend on the minimum Q in the disk at the time the instability is activated. We argue that the major fraction of the transport characterized by the value of alpha is due to the action of

  19. The Herschel Cold Debris Disks

    CERN Document Server

    Gaspar, Andras

    2013-01-01

    The Herschel "DUst around NEarby Stars (DUNES)" survey has found a number of debris disk candidates that are apparently very cold, with temperatures near 22K. It has proven difficult to fit their spectral energy distributions with conventional models for debris disks. Given this issue we carefully examine the alternative explanation, that the detections arise from confusion with IR cirrus and/or background galaxies that are not physically associated with the foreground star. We find that such an explanation is consistent with all of these detections.

  20. Robotic mitral valve replacement.

    Science.gov (United States)

    Senay, Sahin; Gullu, Ahmet Umit; Kocyigit, Muharrem; Degirmencioglu, Aleks; Karabulut, Hasan; Alhan, Cem

    2014-01-01

    Robotic surgical techniques allow surgeons to perform mitral valve surgery. This procedure has gained acceptance, particularly for mitral valve repair in degenerative mitral disease. However, mitral repair may not always be possible, especially in severely calcified mitral valve of rheumatic origin. This study demonstrates the basic concepts and technique of robotic mitral valve replacement for valve pathologies that are not suitable for repair.

  1. Replacing America's Job Bank

    Science.gov (United States)

    Vollman, Jim

    2009-01-01

    The Job Central National Labor Exchange (www.jobcentral.com) has become the effective replacement for America's Job Bank with state workforce agencies and, increasingly, with community colleges throughout the country. The American Association of Community Colleges (AACC) has formed a partnership with Job Central to promote its use throughout the…

  2. Replacing America's Job Bank

    Science.gov (United States)

    Vollman, Jim

    2009-01-01

    The Job Central National Labor Exchange (www.jobcentral.com) has become the effective replacement for America's Job Bank with state workforce agencies and, increasingly, with community colleges throughout the country. The American Association of Community Colleges (AACC) has formed a partnership with Job Central to promote its use throughout the…

  3. Production and characterization of murine monoclonal anti-human DNase II antibodies, and their use for immunoaffinity purification of DNase II from human liver and urine.

    Science.gov (United States)

    Nakajima, Tamiko; Yasuda, Toshihiro; Takeshita, Haruo; Mori, Shinjiro; Mogi, Kouichi; Kaneko, Yasushi; Nakazato, Emiko; Kishi, Koichiro

    2002-04-15

    Four murine monoclonal anti-human deoxyribonuclease II (DNase II) antibodies were obtained from BALB/c mice immunized with human DNase II purified from human liver. Both single radial enzyme diffusion (SRED) and DNA-cast polyacrylamide gel electrophoresis (DNA-cast PAGE) were very useful for obtaining the DNase II-specific antibodies. All of the antibodies showed specific inhibition of human DNase II enzyme activity and specific immunostaining of the 32-kDa enzyme band, which is one of the three non-identical subunits of human DNase II molecule separated by sodium dodecyl sulfate (SDS)-PAGE followed by blotting on a transfer membrane. A formyl-cellulofine resin conjugated with each antibody specifically adsorbed and efficiently desorbed the active DNase II enzyme. Insertion of the immunoaffinity step in our purification procedure made the purification of human DNase II easier, faster and more effective than the conventional procedure.

  4. IgY14 and SuperMix immunoaffinity separations coupled with liquid chromatography-mass spectrometry for human plasma proteomic biomarker discovery

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Tujin; Zhou, Jianying; Gritsenko, Marina A.; Hossain, Mahmud; Camp, David G.; Smith, Richard D.; Qian, Weijun

    2012-02-01

    Interest in the application of advanced proteomics technologies to human blood plasma- or serum-based clinical samples for the purpose of discovering disease biomarkers continues to grow; however, the enormous dynamic range of protein concentrations in these types of samples (often >10 orders of magnitude) represents a significant analytical challenge, particularly for detecting low-abundance candidate biomarkers. In response, immunoaffinity separation methods for depleting multiple high- and moderate-abundance proteins have become key tools for enriching low-abundance proteins and enhancing detection of these proteins in plasma proteomics. Herein, we describe IgY14 and tandem IgY14-Supermix separation methods for removing 14 high-abundance and up to 60 moderate-abundance proteins, respectively, from human blood plasma and highlight their utility when combined with liquid chromatography-tandem mass spectrometry for interrogating the human plasma proteome.

  5. IgY14 and SuperMix immunoaffinity separations coupled with liquid chromatography-mass spectrometry for human plasma proteomics biomarker discovery.

    Science.gov (United States)

    Shi, Tujin; Zhou, Jian-Ying; Gritsenko, Marina A; Hossain, Mahmud; Camp, David G; Smith, Richard D; Qian, Wei-Jun

    2012-02-01

    Interest in the application of advanced proteomics technologies to human blood plasma- or serum-based clinical samples for the purpose of discovering disease biomarkers continues to grow; however, the enormous dynamic range of protein concentrations in these types of samples (often >10 orders of magnitude) represents a significant analytical challenge, particularly for detecting low-abundance candidate biomarkers. In response, immunoaffinity separation methods for depleting multiple high- and moderate-abundance proteins have become key tools for enriching low-abundance proteins and enhancing detection of these proteins in plasma proteomics. Herein, we describe IgY14 and tandem IgY14-Supermix separation methods for removing 14 high-abundance and up to 60 moderate-abundance proteins, respectively, from human blood plasma and highlight their utility when combined with liquid chromatography-tandem mass spectrometry for interrogating the human plasma proteome.

  6. Herniated Disk in the Lower Back

    Science.gov (United States)

    ... two components: Healthy intervertebral disk (cross- section view). • Annulus fibrosus. This is the tough, flexible outer ring ... the Lower Back cont. Surgical Treatment Only a small percentage of patients with lumbar disk herniations require ...

  7. Vortex migration in protoplanetary disks

    CERN Document Server

    Paardekooper, S -J; Papaloizou, J C B

    2010-01-01

    We consider the radial migration of vortices in two-dimensional isothermal gaseous disks. We find that a vortex core, orbiting at the local gas velocity, induces velocity perturbations that propagate away from the vortex as density waves. The resulting spiral wave pattern is reminiscent of an embedded planet. There are two main causes for asymmetries in these wakes: geometrical effects tend to favor the outer wave, while a radial vortensity gradient leads to an asymmetric vortex core, which favors the wave at the side that has the lowest density. In the case of asymmetric waves, which we always find except for a disk of constant pressure, there is a net exchange of angular momentum between the vortex and the surrounding disk, which leads to orbital migration of the vortex. Numerical hydrodynamical simulations show that this migration can be very rapid, on a time scale of a few thousand orbits, for vortices with a size comparable to the scale height of the disk. We discuss the possible effects of vortex migrat...

  8. Determination of vitamin B12 in infant formula and adult nutritionals by liquid chromatography/UV detection with immunoaffinity extraction: First Action 2011.08.

    Science.gov (United States)

    Campos-Giménez, Esther; Fontannaz, Patric; Trisconi, Marie-José; Kilinc, Tamara; Gimenez, Catherine; Andrieux, Pierre; Nelson, Maria

    2012-01-01

    At the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting," on June 29, 2011, an Expert Review Panel agreed that the method "Determination of Vitamin B12 in Infant Formulas and Adult Nutritionals by Liquid Chromatography/UV Detection with Immunoaffinity Extraction" be adopted AOAC Official First Action status. The method is applicable for the determination of vitamin B12, which includes added cyanocobalamin and natural forms, making it applicable to both fortified and nonfortified products. Vitamin B12 is extracted from the sample in sodium acetate buffer in the presence of sodium cyanide (100 degrees C, 30 min). After purification and concentration with an immunoaffinity column, vitamin B12 is determined by LC with UV detection (361 nm). A single-laboratory validation study was conducted on a range of products, including milk- and soy-based infant formulas, cereals, cocoa beverages, health care products, and polyvitamin premixes. The method demonstrated linear response over a large range of concentrations, recovery rates of 100.8 +/- 7.5% (average +/- SD), repeatability RSD (RSDr) of 2.1%, and intermediate reproducibility (RSD(iR)) of 4.3%. LOD and LOQ values were 0.10 and 0.30 microg/100 g, respectively, and correlation with the reference microbiological assay was good (R2 = 0.9442). The results of the study were published in J. AOAC Int. 91, 786-793 (2008). The performance characteristics of the method met the standard method performance requirements set forth by the Stakeholder Panel on Infant Formula and Adult Nutritionals; thus, the method was determined to be appropriate for First Action status.

  9. Determination of vitamin B12 in infant formula and adult nutritionals using HPLC after purification on an immunoaffinity column: first action 2011.09.

    Science.gov (United States)

    Kirchner, Ursula; Degenhardt, Katharina; Raffler, Guenther; Nelson, Maria

    2012-01-01

    During the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting," on June 29, 2011, the method "Determination of vitamin B12 in infant formula and adult nutritionals using HPLC after purification on an immunoaffinity column" was recommended by an Expert Review Panel and adopted as AOAC Official First Action status. The method is applicable for the determination of vitamin B12 in milk-based infant formula. Vitamin B12 is extracted from the sample in sodium acetate buffer in the presence of potassium cyanide. After purification and concentration with an immunoaffinity column (IAC), vitamin B12 is determined by LC with UV detection (361 nm). Data supplied by CLF demonstrated linear response over a wide range of concentrations (1.4-39 microg/100 mL). The analytical range is 0.2-10 microg/100 g, depending on the capacity of the IACs (0.01-0.5 microg), the input weight, and dilutions. Recovery rates were assessed using National Institute of Standards and Technology SRM 1849, and determined to be 95.1%, with SD of 0.34 and CV of 9.0. Measurement uncertainty (UE) was 0.8 microg/100 g, which was calculated from the validation data. It is an expanded measurement uncertainty and was obtained through multiplication with a coverage factor k. LOQ values were reported as 0.10 microg/100 g. The performance characteristics of the method met the standard method performance requirements set forth by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals; thus, the method was determined to be appropriate for First Action status.

  10. [Determination of five aflatoxins in Chinese patent medicines and medicinal herbs by immunoaffinity extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry].

    Science.gov (United States)

    Han, Shen; Liu, Ying; Lu, Meiling; Li, Jianzhong; Wang, Jinhua

    2011-07-01

    A method for the determination of five aflatoxins (B1 , B2, G1 , G2, M1 ) in Chinese patent medicines and medicinal herbs by immunoaffinity extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed. The samples were extracted with 80% (v/v) methanol-water solution, followed by stepwise purification using an immunoaffinity column. The target compounds were then eluted with methanol. The extract was filtered then analyzed. With the gradient elution using a binary mobile phase containing of 0.1% formic acid-5 mmol/L ammonium acetate solution and methanol, the five aflatoxins were separated on an UHPLC BEH C18 column, followed by positive electrospray ionization and multi-reaction monitoring (MRM) provided by a triple-quadrupole tandem mass spectrometer. The limits of detection for the standard solution of aflatoxins ranged from 0.05-0.3 microg/L. The linear response was observed in the spiked concentration range of 0.5-100 microg/L with the correlation coefficients higher than 0.99. The spiked recoveries were within 62.3%-82.4% at the spiked levels of 1.0 microg/kg and 5.0 microg/kg for all the five aflatoxins with the relative standard deviations (RSDs) below 10% (n = 6). The developed method is sensitive, accurate, and reproducible with the reasonable recoveries, and can be applied to the determination of the 5 aflatoxins in the Chinese traditional patent medicines, medicinal herbs as well as other similar complex matrices.

  11. Simultaneous determination of four aflatoxins and ochratoxin A in ginger and related products by HPLC with fluorescence detection after immunoaffinity column clean-up and postcolumn photochemical derivatization.

    Science.gov (United States)

    Wen, Jing; Kong, Weijun; Wang, Jian; Yang, Meihua

    2013-12-01

    Ginger, a widely used spice and traditional Chinese medicine, is prone to be contaminated by mycotoxins. A simple, sensitive, and reproducible method based on immunoaffinity column clean-up coupled with HPLC and on-line postcolumn photochemical derivatization with fluorescence detection was developed for the simultaneous determination of aflatoxins (AFs) B1 , B2 , G1 , G2 , and ochratoxin A (OTA) in 25 batches of gingers and related products marketed in China for the first time. The samples were first extracted by ultrasonication with methanol/water (80:20, v/v) and then cleaned up with immunoaffinity columns for analysis. Under the optimized conditions, the LODs and LOQs for the five mycotoxins were 0.03-0.3 and 0.1-0.9 μg/kg, respectively. The average recoveries ranged from 81.3-100.8% for AFs and from 88.6-99.5% for OTA at three spiking levels. Good linearity was observed for the analytes with correlation coefficients all >0.9995. All moldy gingers were contaminated with at least one kind of the five investigated mycotoxins, while none of them were found in normal gingers. Ginger powder samples were contaminated slightly with the contamination levels below the LOQs, while ginger tea bags were mainly contaminated by OTA at 1.05-1.19 μg/kg and ginger black tea bags were mainly contaminated by AFs at 3.37-5.76 μg/kg. All the contamination levels were below the legally allowable limits.

  12. The Structure of Brown Dwarf Circumstellar Disks

    OpenAIRE

    Walker, Christina; Wood, Kenneth; Lada, C. J.; Robitaille, Thomas; Bjorkman, J. E.; Whitney, Barbara

    2004-01-01

    We present synthetic spectra for circumstellar disks that are heated by radiation from a central brown dwarf. Under the assumption of vertical hydrostatic equilibrium, our models yield scaleheights for brown dwarf disks in excess of three times those derived for classical T Tauri (CTTS) disks. If the near-IR excess emission observed from brown dwarfs is indeed due to circumstellar disks, then the large scaleheights we find could have a significant impact on the optical and near-IR detectabili...

  13. Optimization of the Processing of Mo Disks

    Energy Technology Data Exchange (ETDEWEB)

    Tkac, Peter [Argonne National Lab. (ANL), Argonne, IL (United States); Rotsch, David A. [Argonne National Lab. (ANL), Argonne, IL (United States); Stepinski, Dominique [Argonne National Lab. (ANL), Argonne, IL (United States); Makarashvili, Vakhtang [Argonne National Lab. (ANL), Argonne, IL (United States); Harvey, James [NorthStar Medical Technologies, LLC, Madison, WI (United States); Vandegrift, George F. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-01

    The objective of this work is to decrease the processing time for irradiated disks of enriched Mo for the production of 99Mo. Results are given for the dissolution of nonirradiated Mo disks, optimization of the process for large-scale dissolution of sintered disks, optimization of the removal of the main side products (Zr and Nb) from dissolved targets, and dissolution of irradiated Mo disks.

  14. Fabrication of Large YBCO Superconducting Disks

    Science.gov (United States)

    Koczor, Ronald J.; Noever, David A.; Robertson, Glen A.

    1999-01-01

    We have undertaken fabrication of large bulk items to develop a repeatable process and to provide test articles in laboratory experiments investigating reported coupling of electromagnetic fields with the local gravity field in the presence of rotating superconducting disks. A successful process was developed which resulted in fabrication of 30 cm diameter annular disks. The disks were fabricated of the superconductor YBa2Cu3O(7-x). Various material parameters of the disks were measured.

  15. PSOCT studies of intervertebral disk

    Science.gov (United States)

    Matcher, Stephen J.; Winlove, Peter C.; Gangnus, Sergey V.

    2004-07-01

    Polarization-sensitive optical coherence tomography (PSOCT) is an emerging optical imaging technique that is sensitive to the birefringence properties of tissues. It thus has applications in studying the large-scale ordering of collagen fibers within connective tissues. This ordering not only provides useful insights into the relationship between structure and function for various anatomical structures but also is an indicator of pathology. Intervertebral disk is an elastic tissue of the spine and possesses a 3-D collagen structure well suited to study using PSOCT. Since the outer layer of the disk has a lamellar structure with collagen fibers oriented in a trellis-like arrangement between lamellae, the birefringence fast-axis shows pronounced variations with depth, on a spatial scale of about 100 μm. The lamellar thickness varies with age and possibly with disease. We have used a polarisation-sensitive optical coherence tomography system to measure the birefringence properties of freshly excised, hydrated bovine caudal intervertebral disk and compared this with equine flexor tendon. Our results clearly demonstrate the ability of PSOCT to detect the outer three lamellae, down to a depth of at least 700 μm, via discontinuities in the depth-resolved retardance. We have applied a simple semi-empirical model based on Jones calculus to quantify the variation in the fast-axis orientation with depth. Our data and modeling is in broad agreement with previous studies using x-ray diffraction and polarization microscopy applied to histological sections of dehydrated disk. Our results imply that PSOCT may prove a useful tool to study collagen organisation within intervertebral disk in vitro and possibly in vivo and its variation with age and disease.

  16. The Evolutionary State of Anemic Circumstellar Disks and the Primordial-to-Debris Disk Transition

    CERN Document Server

    Currie, Thayne

    2008-01-01

    We investigate the evolution of $\\sim$ 3 Myr-old MIPS-detected circumstellar disks in IC 348 that may be in an intermediate stage between primordial, optically-thick disks of gas/dust and debris disks characteristic of the final stages of planet formation. We demonstrate that these \\textit{anemic} disks are not a homogenous class of objects corresponding to a unique evolutionary state. Rather, such disks around early (B/A) spectral type stars are most likely warm, terrestrial zone debris disks; MIPS-detected anemic disks around later (M) stars are likely \\textit{evolved primordial disks} such as transition disks in their mid-IR colors, accretion signatures, and disk luminosities. Anemic disks surrounding G and K stars contain both populations. The difference in evolutionary states between anemic disks surrounding early type vs. late-type stars is consistent with a mass-dependent evolution of circumstellar disks from the primordial disk phase through the debris disk phase. Specifically, disks characteristicall...

  17. NASA Lunar and Meteorite Sample Disk Program

    Science.gov (United States)

    Foxworth, Suzanne

    2017-01-01

    The Lunar and Meteorite Sample Disk Program is designed for K-12 classroom educators who work in K-12 schools, museums, libraries, or planetariums. Educators have to be certified to borrow the Lunar and Meteorite Sample Disks by attending a NASA Certification Workshop provided by a NASA Authorized Sample Disk Certifier.

  18. Air-lubrication of magnetic disk sliders

    Science.gov (United States)

    Dreßler, B.; Graichen, K.; Bärwolff, G.; Jehring, L.; Seifert, G.

    1993-03-01

    Steady-state and dynamic flying of a self-acting magnetic disk slider over a hard disk are considered. Some tasks for computations are formulated and the possibilities of developed numerical codes are illustrated. Numerical results of dynamic flying over a disk surface with an obstacle are in agreement with experimental data.

  19. Growing and moving planets in disks

    NARCIS (Netherlands)

    Paardekooper, Sijme-Jan

    2006-01-01

    Planets form in disks that are commonly found around young stars. The intimate relationship that exists between planet and disk can account for a lot of the exotic extrasolar planetary systems known today. In this thesis we explore disk-planet interaction using numerical hydrodynamical simulations.

  20. Circumplanetary disks around young giant planets: a comparison between core-accretion and disk instability

    CERN Document Server

    Szulágyi, J; Quinn, T

    2016-01-01

    Circumplanetary disks can be found around forming giant planets, regardless of whether core accretion or gravitational instability built the planet. We carried out state-of-the-art hydrodynamical simulations of the circumplanetary disks for both formation scenarios, using as similar initial conditions as possible to unveil possible intrinsic differences in the circumplanetary disk mass and temperature between the two formation mechanisms. We found that the circumplanetary disks mass linearly scales with the circumstellar disk mass. Therefore, in an equally massive protoplanetary disk, the circumplanetary disks formed in the disk instability model can be only a factor of eight more massive than their core-accretion counterparts. On the other hand, the bulk circumplanetary disk temperature differs by more than an order of magnitude between the two cases. The subdisks around planets formed by gravitational instability have a characteristic temperature below 100 K, while the core accretion circumplanetary disks a...

  1. Ulnar head replacement.

    Science.gov (United States)

    Herbert, Timothy J; van Schoonhoven, Joerg

    2007-03-01

    Recent years have seen an increasing awareness of the anatomical and biomechanical significance of the distal radioulnar joint (DRUJ). With this has come a more critical approach to surgical management of DRUJ disorders and a realization that all forms of "excision arthroplasty" can only restore forearm rotation at the expense of forearm stability. This, in turn, has led to renewed interest in prosthetic replacement of the ulnar head, a procedure that had previously fallen into disrepute because of material failures with early implants, in particular, the Swanson silicone ulnar head replacement. In response to these early failures, a new prosthesis was developed in the early 1990s, using materials designed to withstand the loads across the DRUJ associated with normal functional use of the upper limb. Released onto the market in 1995 (Herbert ulnar head prosthesis), clinical experience during the last 10 years has shown that this prosthesis is able to restore forearm function after ulnar head excision and that the materials (ceramic head and noncemented titanium stem), even with normal use of the limb, are showing no signs of failure in the medium to long term. As experience with the use of an ulnar head prosthesis grows, so does its acceptance as a viable and attractive alternative to more traditional operations, such as the Darrach and Sauve-Kapandji procedures. This article discusses the current indications and contraindications for ulnar head replacement and details the surgical procedure, rehabilitation, and likely outcomes.

  2. Kinematic Dynamo In Turbulent Circumstellar Disks

    Science.gov (United States)

    Stepinski, T.

    1993-01-01

    Many circumstellar disks associated with objects ranging from protoplanetary nebulae, to accretion disks around compact stars allow for the generation of magnetic fields by an (alpha)omega dynamo. We have applied kinematic dynamo formalism to geometrically thin accretion disks. We calculate, in the framework of an adiabatic approximation, the normal mode solutions for dynamos operating in disks around compact stars. We then describe the criteria for a viable dynamo in protoplanetary nebulae, and discuss the particular features that make accretion disk dynamos different from planetary, stellar, and galactic dynamos.

  3. Accretion disks in Algols: progenitors and evolution

    CERN Document Server

    Van Rensbergen, W

    2016-01-01

    There are only a few Algols with measured accretion disk parameters. These measurements provide additional constraints for tracing the origin of individual systems, narrowing down the initial parameter space. We investigate the origin and evolution of 6 Algol systems with accretion disks to find the initial parameters and evolutionary constraints for them. With a modified binary evolution code, series of close binary evolution are calculated to obtain the best match for observed individual systems. Initial parameters for 6 Algol systems with accretion disks were determined matching both the present system parameters and the observed disk characteristics. When RLOF starts during core hydrogen burning of the donor, the disk lifetime was found to be short. The disk luminosity is comparable to the luminosity of the gainer during a large fraction of the disk lifetime.

  4. The Evolving Structure of Galactic Disks

    CERN Document Server

    Martel, H; McGee, S; Gibson, B; Kawata, D; Martel, Hugo; Brook, Chris; Gee, Sean Mc; Gibson, Brad

    2005-01-01

    Observations suggest that the structural parameters of disk galaxies have not changed greatly since redshift 1. We examine whether these observations are consistent with a cosmology in which structures form hierarchically. We use SPH/N-body galaxy-scale simulations to simulate the formation and evolution of Milky-Way-like disk galaxies by fragmentation, followed by hierarchical merging. The simulated galaxies have a thick disk, that forms in a period of chaotic merging at high redshift, during which a large amount of alpha-elements are produced, and a thin disk, that forms later and has a higher metallicity. Our simulated disks settle down quickly and do not evolve much since redshift z~1, mostly because no major mergers take place between z=1 and z=0. During this period, the disk radius increases (inside-out growth) while its thickness remains constant. These results are consistent with observations of disk galaxies at low and high redshift.

  5. Why are some galaxy disks extremely thin?

    CERN Document Server

    Banerjee, Arunima

    2012-01-01

    Some low surface brightness galaxies are known to have extremely thin stellar disks with the vertical to planar axes ratio 0.1 or less, often referred to as superthin disks. Although their existence is known for over three decades, the physical origin for the thin distribution is not understood. We model the stellar thickness for a two-component (gravitationally coupled stars and gas) disk embedded in a dark matter halo, for a superthin galaxy UGC 7321 which has a dense, compact halo, and compare with a typical dwarf galaxy HoII which has a non-compact halo. We show that while the presence of gas does constrain the disk thickness, it is the compact dark matter halo which plays the decisive role in determining the superthin disk distribution in low-mass disks. Thus the compact dark matter halo significantly affects the disk structure and this could be important for the early evolution of galaxies.

  6. Magnetic interchange instability of accretion disks

    Science.gov (United States)

    Kaisig, M.; Tajima, T.; Lovelace, R. V. E.

    1992-01-01

    The nonlinear evolution of the magnetic interchange or buoyancy instability of a differentially rotating disk threaded by an ordered vertical magnetic field is investigated. A 2D ideal fluid in the equatorial plane of a central mass in the corotating frame of reference is considered as a model for the disk. If the rotation rate of the disk is Keplerian, the disk is found to be stable. If the vertical magnetic field is sufficiently strong, and the field strength decreases with distance from the central object, and thus the rotation of the disk deviates from Keplerian, if is found that an instability develops. The magnetic flux and disk matter expand outward in certain ranges of azimuth, while disk matter with less magnetic flux moves inward over the remaining range of azimuth, showing a characteristic development of an interchange instability.

  7. Dust Evolution in Protoplanetary Disks

    CERN Document Server

    Testi, Leonardo; Ricci, Luca; Andrews, Sean; Blum, Juergen; Carpenter, John; Dominik, Carsten; Isella, Andrea; Natta, Antonella; Williams, Jonathan; Wilner, David

    2014-01-01

    (abridged) In the core accretion scenario for the formation of planetary rocky cores, the first step toward planet formation is the growth of dust grains into larger and larger aggregates and eventually planetesimals. Although dust grains are thought to grow from the submicron sizes typical of interstellar dust to micron size particles in the dense regions of molecular clouds and cores, the growth from micron size particles to pebbles and kilometre size bodies must occur in protoplanetary disks. This step in the formation of planetary systems is the last stage of solids evolution that can be observed directly in young extrasolar systems. In this chapter we review the constraints on the physics of grain-grain collisions as they have emerged from laboratory experiments and numerical computations. We then review the current theoretical understanding of the global processes governing the evolution of solids in protoplanetary disks, including dust settling, growth, and radial transport. The predicted observational...

  8. Secular evolution of disk galaxies

    CERN Document Server

    Combes, F

    2008-01-01

    Galaxy disks evolve through angular momentum transfers between sub-components, like gas, stars, or dark matter halos, through non axi-symmetric instabilities. The speed of this evolution is boosted in presence of a large fraction of cold and dissipative gas component. When the visible matter dominates over the whole disk, angular momentum is exchanged between gas and stars only. The gas is driven towards the center by bars, stalled transiently in resonance rings, and driven further by embedded bars, which it contributes to destroy. From a small-scale molecular torus, the gas can then inflow from viscous torques, dynamical friction, or m=1 perturbations. In the weakened bar phases, multiple-speed spiral patterns can develop and help the galaxy to accrete external gas flowing from cosmic filaments. The various phases of secular evolution are illustrated by numerical simulations.

  9. Mechanics of Forming Ring Disks

    Directory of Open Access Journals (Sweden)

    Avakyan R.M.

    2010-12-01

    Full Text Available The analysis of forming ring disk of constant thickness in conditions of large plastic deformations taking into account the interconnected change of effective strain and deformation hardening is carried out. The analytical dependences characterizing the relative size of plastic area are obtained. The interrelation between the initial and final form of a product is established at maximum possible size of internal pressure.

  10. Parallel Readout of Optical Disks

    Science.gov (United States)

    1992-08-01

    27, 2987-2992 (1988). 11. T. Yatagai, J. G. Camacho-Basilio, and H. Onda , "Recording of Computer-Generated Holograms on an Optical Disk Master...Multivariate Observations," Proceedings of the Fifth Berkeley Symposium on Math. Stat. and Prob I., L. M. LeCam and J. Neyman, eds. (University of...California Press, Berkeley and Los Angeles California, 1967), pp. 281-297. [9] R. Duda and P Hart, "Pattern Classification and Scene Analysis," (John

  11. A Supersymmetric Dark Disk Universe

    CERN Document Server

    Fischler, Willy; Tangarife, Walter

    2014-01-01

    We present a model of partially interacting dark matter (PIDM) within the framework of supersymmetry with gauge mediated symmetry breaking. Dark sector atoms are produced through Affleck-Dine baryogenesis in the dark sector while avoiding the production of Q-ball relics. We discuss the astrophysical constraints relevant for this model and the possibility of dark galactic disk formation. In addition, jet emission from rotating black holes is discussed in the context of this class of models.

  12. A Pulsar and a Disk

    Science.gov (United States)

    Kohler, Susanna

    2016-07-01

    Recent, unusual X-ray observations from our galactic neighbor, the Small Magellanic Cloud, have led to an interesting model for SXP 214, a pulsar in a binary star system.Artists illustration of the magnetic field lines of a pulsar, a highly magnetized, rotating neutron star. [NASA]An Intriguing BinaryAn X-ray pulsar is a magnetized, rotating neutron star in a binary system with a stellar companion. Material is fed from the companion onto the neutron star, channeled by the objects magnetic fields onto a hotspot thats millions of degrees. This hotspot rotating past our line of sight is what produces the pulsations that we observe from X-ray pulsars.Located in the Small Magellanic Cloud, SXP 214 is a transient X-ray pulsar in a binary with a Be-type star. This star is spinning so quickly that material is thrown off of it to form a circumstellar disk.Recently, a team of authors led by JaeSub Hong (Harvard-Smithsonian Center for Astrophysics) have presented new Chandra X-ray observations of SXP 214, tracking it for 50 ks (~14 hours) in January 2013. These observations reveal some very unexpected behavior for this pulsar.X-ray PuzzleThe energy distribution of the X-ray emission from SXP 214 over time. Dark shades or blue colors indicate high counts, and light shades or yellow colors indicate low counts. Lower-energy X-ray emission appeared only later, after about 20 ks. [Hong et al. 2016]Three interesting pieces of information came from the Chandra observations:SXP 214s rotation period was measured to be 211.5 s an increase in the spin rate since the discovery measurement of a 214-second period. Pulsars usually spin down as they lose angular momentum over time so what caused this one to spin up?Its overall X-ray luminosity steadily increased over the 50 ks of observations.Its spectrum became gradually softer (lower energy) over time; in the first 20 ks, the spectrum only consisted of hard X-ray photons above 3 keV, but after 20 ks, softer X-ray photons below 2 ke

  13. Regression of lumbar disk herniation

    Directory of Open Access Journals (Sweden)

    G. Yu Evzikov

    2015-01-01

    Full Text Available Compression of the spinal nerve root, giving rise to pain and sensory and motor disorders in the area of its innervation is the most vivid manifestation of herniated intervertebral disk. Different treatment modalities, including neurosurgery, for evolving these conditions are discussed. There has been recent evidence that spontaneous regression of disk herniation can regress. The paper describes a female patient with large lateralized disc extrusion that has caused compression of the nerve root S1, leading to obvious myotonic and radicular syndrome. Magnetic resonance imaging has shown that the clinical manifestations of discogenic radiculopathy, as well myotonic syndrome and morphological changes completely regressed 8 months later. The likely mechanism is inflammation-induced resorption of a large herniated disk fragment, which agrees with the data available in the literature. A decision to perform neurosurgery for which the patient had indications was made during her first consultation. After regression of discogenic radiculopathy, there was only moderate pain caused by musculoskeletal diseases (facet syndrome, piriformis syndrome that were successfully eliminated by minimally invasive techniques. 

  14. Heating and Cooling Protostellar Disks

    CERN Document Server

    Hirose, S

    2011-01-01

    We examine heating and cooling in protostellar disks using 3-D radiation-MHD calculations of a patch of the Solar nebula at 1 AU, employing the shearing-box and flux-limited radiation diffusion approximations. The disk atmosphere is ionized by stellar X-rays, well-coupled to magnetic fields, and sustains a turbulent accretion flow driven by magneto-rotational instability, while the interior is resistive and magnetically dead. The turbulent layers heat by absorbing the light from the central star and by dissipating the magnetic fields. They are optically-thin to their own radiation and cool inefficiently. The optically-thick interior in contrast is heated only weakly, by re-emission from the atmosphere. The interior is colder than a classical viscous model, and isothermal. The magnetic fields support an extended atmosphere that absorbs the starlight 1.5 times higher than the hydrostatic viscous model. The disk thickness thus measures not the internal temperature, but the magnetic field strength. Fluctuations i...

  15. Disk Detective Follow-Up Program

    Science.gov (United States)

    Kuchner, Marc

    As new data on exoplanets and young stellar associations arrive, we will want to know: which of these planetary systems and young stars have circumstellar disks? The vast allsky database of 747 million infrared sources from NASA's Wide-field Infrared Survey Explorer (WISE) mission can supply answers. WISE is a discovery tool intended to find targets for JWST, sensitive enough to detect circumstellar disks as far away as 3000 light years. The vast WISE archive already serves us as a roadmap to guide exoplanet searches, provide information on disk properties as new planets are discovered, and teach us about the many hotly debated connections between disks and exoplanets. However, because of the challenges of utilizing the WISE data, this resource remains underutilized as a tool for disk and planet hunters. Attempts to use WISE to find disks around Kepler planet hosts were nearly scuttled by confusion noise. Moreover, since most of the stars with WISE infrared excesses were too red for Hipparcos photometry, most of the disks sensed by WISE remain obscure, orbiting stars unlisted in the usual star databases. To remedy the confusion noise problem, we have begun a massive project to scour the WISE data archive for new circumstellar disks. The Disk Detective project (Kuchner et al. 2016) engages layperson volunteers to examine images from WISE, NASA's Two Micron All-Sky Survey (2MASS) and optical surveys to search for new circumstellar disk candidates via the citizen science website DiskDetective.org. Fueled by the efforts of > 28,000 citizen scientists, Disk Detective is the largest survey for debris disks with WISE. It has already uncovered 4000 disk candidates worthy of follow-up. However, most host stars of the new Disk Detective disk candidates have no known spectral type or distance, especially those with red colors: K and M stars and Young Stellar Objects. Others require further observations to check for false positives. The Disk Detective project is supported by

  16. Connecting the shadows: probing inner disk geometries using shadows in transitional disks

    Science.gov (United States)

    Min, M.; Stolker, T.; Dominik, C.; Benisty, M.

    2017-08-01

    Aims: Shadows in transitional disks are generally interpreted as signs of a misaligned inner disk. This disk is usually beyond the reach of current day high contrast imaging facilities. However, the location and morphology of the shadow features allow us to reconstruct the inner disk geometry. Methods: We derive analytic equations of the locations of the shadow features as a function of the orientation of the inner and outer disk and the height of the outer disk wall. In contrast to previous claims in the literature, we show that the position angle of the line connecting the shadows cannot be directly related to the position angle of the inner disk. Results: We show how the analytic framework derived here can be applied to transitional disks with shadow features. We use estimates of the outer disk height to put constraints on the inner disk orientation. In contrast with the results from Long et al. (2017, ApJ, 838, 62), we derive that for the disk surrounding HD 100453 the analytic estimates and interferometric observations result in a consistent picture of the orientation of the inner disk. Conclusions: The elegant consistency in our analytic framework between observation and theory strongly support both the interpretation of the shadow features as coming from a misaligned inner disk as well as the diagnostic value of near infrared interferometry for inner disk geometry.

  17. Aortic valve replacement

    DEFF Research Database (Denmark)

    Kapetanakis, Emmanouil I; Athanasiou, Thanos; Mestres, Carlos A

    2008-01-01

    BACKGROUND AND AIMS OF THE STUDY: Prompted by anecdotal evidence and observations by surgeons, an investigation was undertaken into the potential differences in implanted aortic valve prosthesis sizes, during aortic valve replacement (AVR) procedures, between northern and southern European...... countries. METHODS: A multi-institutional, non-randomized, retrospective analysis was conducted among 2,932 patients who underwent AVR surgery at seven tertiary cardiac surgery centers throughout Europe. Demographic and perioperative variables including valve size and type, body surface area (BSA) and early...

  18. Total ankle joint replacement.

    Science.gov (United States)

    2016-02-01

    Ankle arthritis results in a stiff and painful ankle and can be a major cause of disability. For people with end-stage ankle arthritis, arthrodesis (ankle fusion) is effective at reducing pain in the shorter term, but results in a fixed joint, and over time the loss of mobility places stress on other joints in the foot that may lead to arthritis, pain and dysfunction. Another option is to perform a total ankle joint replacement, with the aim of giving the patient a mobile and pain-free ankle. In this article we review the efficacy of this procedure, including how it compares to ankle arthrodesis, and consider the indications and complications.

  19. The Optimum Replacement of Weapon

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao; ZHANG Jin-chun

    2002-01-01

    The theory of LCC (Life Cycle Cost) is applied in this paper. The relation between the economic life of weapon and the optimum replacement is analyzed. The method to define the optimum replacement time of weapon is discussed.

  20. Determination of oxytocin in biological samples by isocratic high-performance liquid chromatography with coulometric detection using C18 solid-phase extraction and polyclonal antibody-based immunoaffinity column purification.

    Science.gov (United States)

    Kukucka, M A; Misra, H P

    1994-03-04

    A specific high-performance liquid chromatographic (HPLC) method is described for the reliable quantitation of oxytocin using culture media supernatants. The procedure employs solid-phase extraction, antibody-based immunoaffinity purification and isocratic HPLC with dual channel coulometric detection (ED). The lower limit of detection for this cyclic nonapeptide was 40 pg (40 fmol). Due to its relative simplicity, specificity and precision, the HPLC-ED of oxytocin is an accurate and attractive alternative to many existing quantitative methods.

  1. Foundations of Black Hole Accretion Disk Theory.

    Science.gov (United States)

    Abramowicz, Marek A; Fragile, P Chris

    2013-01-01

    This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin) disks, slim disks, and advection-dominated accretion flows (ADAFs). After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of black hole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of black hole mass and spin, black hole vs. neutron star accretion disks, black hole accretion disk spectral states, and quasi-periodic oscillations (QPOs).

  2. Ring shaped dust accumulation in transition disks

    CERN Document Server

    Pinilla, P; Birnstiel, T

    2012-01-01

    Context.Transition disks are believed to be the final stages of protoplanetary disks, during which a forming planetary system or photoevaporation processes open a gap in the inner disk, drastically changing the disk structure. From theoretical arguments it is expected that dust growth, fragmentation and radial drift are strongly influenced by gas disk structure, and pressure bumps in disks have been suggested as key features that may allow grains to converge and grow efficiently. Aims. We want to study how the presence of a large planet in a disk influences the growth and radial distribution of dust grains, and how observable properties are linked to the mass of the planet. Methods. We combine two-dimensional hydrodynamical disk simulations of disk-planet interactions with state-of-the-art coagulation/fragmentation models to simulate the evolution of dust in a disk which has a gap created by a massive planet. We compute images at different wavelengths and illustrate our results using the example of the transi...

  3. Thin disk lasers: history and prospects

    Science.gov (United States)

    Speiser, Jochen

    2016-04-01

    During the early 1990s, collaboration between the German Aerospace Center and the University of Stuttgart started to work on the Thin Disk concept. The core idea behind the thin disk design is the use of a thin, disk-shaped active medium that is cooled through one of the flat faces of the disk. This ensures a large surface-to-volume ratio and therefore provides very efficient thermal management. Today, the thin disk concept is used in various commercial lasers - ranging from compact, efficient low power systems to multi-kW lasers, including cw lasers and also pulsed (femtosecond to nanosecond) oscillators and amplifiers. The whole development of the Thin Disk laser was and will be accompanied by numerical modeling and optimization of the thermal and thermo-mechanic behavior of the disk and also the heat sink structure, mostly based on finite element models. For further increasing the energy and efficiency of pulsed Thin Disk lasers, the effects of amplified spontaneous emission (ASE) are a core issue. Actual efforts are oriented towards short pulse and ultra-short pulse amplifiers with (multi-)kW average power or Joule-class Thin Disk amplifiers, but also on new designs for cw thin disk MOPA designs.

  4. Power Plant Replacement Study

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Gary

    2010-09-30

    This report represents the final report for the Eastern Illinois University power plant replacement study. It contains all related documentation from consideration of possible solutions to the final recommended option. Included are the economic justifications associated with the chosen solution along with application for environmental permitting for the selected project for construction. This final report will summarize the results of execution of an EPC (energy performance contract) investment grade audit (IGA) which lead to an energy services agreement (ESA). The project includes scope of work to design and install energy conservation measures which are guaranteed by the contractor to be self‐funding over its twenty year contract duration. The cost recovery is derived from systems performance improvements leading to energy savings. The prime focus of this EPC effort is to provide a replacement solution for Eastern Illinois University’s aging and failing circa 1925 central steam production plant. Twenty‐three ECMs were considered viable whose net impact will provide sufficient savings to successfully support the overall project objectives.

  5. Total disc replacement.

    Science.gov (United States)

    Vital, J-M; Boissière, L

    2014-02-01

    Total disc replacement (TDR) (partial disc replacement will not be described) has been used in the lumbar spine since the 1980s, and more recently in the cervical spine. Although the biomechanical concepts are the same and both are inserted through an anterior approach, lumbar TDR is conventionally indicated for chronic low back pain, whereas cervical TDR is used for soft discal hernia resulting in cervicobrachial neuralgia. The insertion technique must be rigorous, with precise centering in the disc space, taking account of vascular anatomy, which is more complex in the lumbar region, particularly proximally to L5-S1. All of the numerous studies, including prospective randomized comparative trials, have demonstrated non-inferiority to fusion, or even short-term superiority regarding speed of improvement. The main implant-related complication is bridging heterotopic ossification with resulting loss of range of motion and increased rates of adjacent segment degeneration, although with an incidence lower than after arthrodesis. A sufficiently long follow-up, which has not yet been reached, will be necessary to establish definitively an advantage for TDR, particularly in the cervical spine. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  6. REPLACEMENT OF FRENCH CARDS

    CERN Multimedia

    HR/SOC

    2001-01-01

    The French Ministry of Foreign Affairs has informed the Organization that it is shortly to replace all diplomatic cards, special cards and employment permits ('attestations de fonctions') now held by members of the personnel and their families. Between 2 July and 31 December 2001, these cards are to be replaced by secure, computerized equivalents. The old cards may continue to be used until 31 December 2001. For the purposes of the handover, members of the personnel must go personally to the cards office (33/1-015), in order to fill in a 'fiche individuelle' form, taking the following documents for themselves and members of their families already in possession of a French card : A recent identity photograph in 4.5 cm x 3.5 cm format. The French card in their possession. An A4 photocopy of the same French card, certified by the cards office as being a true copy. Those members of the personnel whose cards (and/or cards belonging to members of their families) are shortly due to expire, or have recently done...

  7. REPLACEMENT OF FRENCH CARDS

    CERN Multimedia

    Human Resources Division; Cards.Service@cern.ch

    2001-01-01

    The French Ministry of Foreign Affairs is currently replacing all diplomatic cards, special cards and employment permits («attestations de fonctions») held by members of the personnel and their families. These cards are replaced by secure, computerized equivalents. The old cards may no longer be used after 31 December 2001. For the purposes of the handover, members of the personnel must go personally to the cards office (33/1-015) between 8h30 and 12h30, in order to fill in a «fiche individuelle» form, taking the following documents for themselves and members of their families already in possession of a French card : A recent identity photograph in 4.5 cm x 3.5 cm format, the French card in their possession, an A4 photocopy of the same French card, certified by the cards office as being a true copy. Those members of the personnel whose cards (and/or cards belonging to members of their families) are shortly due to expire, or have recently done so, are also requested...

  8. REPLACEMENT OF FRENCH CARDS

    CERN Multimedia

    Human Resources Division

    2001-01-01

    The French Ministry of Foreign Affairs has informed the Organization that it is shortly to replace all diplomatic cards, special cards and employment permits ('attestations de fonctions') now held by members of the personnel and their families. Between 2 July and 31 December 2001, these cards are to be replaced by secure, computerized equivalents. The old cards may continue to be used until 31 December 2001. For the purposes of the handover, members of the personnel are asked to go to the cards office (33/1-015), taking the following documents for themselves and members of their families already in possession of a French card : A recent identity photograph in 4.5 cm x 3.5 cm format, The French card in their possession, an A4 photocopy of the same French card, certified by the cards office as being a true copy. Those members of the personnel whose cards (and/or cards belonging to members of their families) are shortly due to expire, or have recently done so, are also requested to take these items to the c...

  9. REPLACEMENT OF FRENCH CARDS

    CERN Multimedia

    Human Resources Division

    2001-01-01

    The French Ministry of Foreign Affairs has informed the Organization that it is shortly to replace all diplomatic cards, special cards and employment permits ('attestations de fonctions') now held by members of the personnel and their families. Between 2 July and 31 December 2001, these cards are to be replaced by secure, computerized equivalents. A 'personnel office' stamped photocopy of the old cards may continue to be used until 31 December 2001. For the purposes of the handover, members of the personnel must go personally to the cards office (33/1-015), between 8:30 and 12:30, in order to fill a 'fiche individuelle' form (in black ink only), which has to be personally signed by themselves and another separately signed by members of their family, taking the following documents for themselves and members of their families already in possession of a French card : A recent identity photograph in 4.5 cm x 3.5 cm format (signed on the back) The French card in their possession an A4 photocopy of the same Fre...

  10. Power Plant Replacement Study

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Gary

    2010-09-30

    This report represents the final report for the Eastern Illinois University power plant replacement study. It contains all related documentation from consideration of possible solutions to the final recommended option. Included are the economic justifications associated with the chosen solution along with application for environmental permitting for the selected project for construction. This final report will summarize the results of execution of an EPC (energy performance contract) investment grade audit (IGA) which lead to an energy services agreement (ESA). The project includes scope of work to design and install energy conservation measures which are guaranteed by the contractor to be self-funding over its twenty year contract duration. The cost recovery is derived from systems performance improvements leading to energy savings. The prime focus of this EPC effort is to provide a replacement solution for Eastern Illinois University's aging and failing circa 1925 central steam production plant. Twenty-three ECMs were considered viable whose net impact will provide sufficient savings to successfully support the overall project objectives.

  11. Faster Replacement Paths

    CERN Document Server

    Williams, Virginia Vassilevska

    2010-01-01

    The replacement paths problem for directed graphs is to find for given nodes s and t and every edge e on the shortest path between them, the shortest path between s and t which avoids e. For unweighted directed graphs on n vertices, the best known algorithm runtime was \\tilde{O}(n^{2.5}) by Roditty and Zwick. For graphs with integer weights in {-M,...,M}, Weimann and Yuster recently showed that one can use fast matrix multiplication and solve the problem in O(Mn^{2.584}) time, a runtime which would be O(Mn^{2.33}) if the exponent \\omega of matrix multiplication is 2. We improve both of these algorithms. Our new algorithm also relies on fast matrix multiplication and runs in O(M n^{\\omega} polylog(n)) time if \\omega>2 and O(n^{2+\\eps}) for any \\eps>0 if \\omega=2. Our result shows that, at least for small integer weights, the replacement paths problem in directed graphs may be easier than the related all pairs shortest paths problem in directed graphs, as the current best runtime for the latter is \\Omega(n^{2.5...

  12. Power Plant Replacement Study

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Gary

    2010-09-30

    This report represents the final report for the Eastern Illinois University power plant replacement study. It contains all related documentation from consideration of possible solutions to the final recommended option. Included are the economic justifications associated with the chosen solution along with application for environmental permitting for the selected project for construction. This final report will summarize the results of execution of an EPC (energy performance contract) investment grade audit (IGA) which lead to an energy services agreement (ESA). The project includes scope of work to design and install energy conservation measures which are guaranteed by the contractor to be self-funding over its twenty year contract duration. The cost recovery is derived from systems performance improvements leading to energy savings. The prime focus of this EPC effort is to provide a replacement solution for Eastern Illinois University’s aging and failing circa 1925 central steam production plant. Twenty-three ECMs were considered viable whose net impact will provide sufficient savings to successfully support the overall project objectives.

  13. The early evolution of protostellar disks

    Science.gov (United States)

    Stahler, Steven W.; Korycansky, D. G.; Brothers, Maxwell J.; Touma, Jihad

    1994-01-01

    We consider the origin and intital growth of the disks that form around protostars during the collapse of rotating molecular cloud cores. These disks are assumed to be inviscid and pressure free, and to have masses small compared to those of their central stars. We find that there exist three distinct components-an outer disk, in which shocked gas moves with comparable azimuthal and radical velocities; and inner disk, where material follows nearly circular orbits, but spirals slowly toward the star because of the drag exerted by adjacent onfalling matter, and a turbulent ring adjoining the first two regions. Early in the evolution, i.e., soon after infalling matter begins to miss the star, only the outer disk is present, and the total mass acceration rate onto the protostar is undiminished. Once the outer disk boundary grows to more than 2.9 times the stellar radius, first the ring, and then the inner disk appear. Thereafter, the radii of all three components expand as t(exp 3). The mass of the ring increase with time and is always 13% of the total mass that has fallen from the cloud. Concurrently with the buildup of the inner disk and ring, the accretion rate onto the star falls off. However, the protostellar mass continue to rise, asymptotically as t(exp 1/4). We calculated the radiated flux from the inner and outer disk components due to the release of gravitational potential energy. The flux from the inner disk is dominant and rises steeply toward the stellar surface. We also determine the surface temperature of the inner disk as a function of radius. The total disk luminosity decreases slowly with time, while the contributions from the ring and inner disk both fall as t(exp -2).

  14. Generalized Similarity for Accretion/Decretion Disks

    Science.gov (United States)

    Rafikov, Roman R.

    2016-10-01

    Decretion (or external) disks are gas disks freely expanding to large radii due to their internal stresses. They are expected to naturally arise in tidal disruption events, around Be stars, in mass-losing post-main-sequence binaries, as a result of supernova fallback, etc. Their evolution is theoretically understood in two regimes: when the central object does not exert torque on the disk (a standard assumption for conventional accretion disks) or when no mass inflow (or outflow) occurs at the disk center. However, many astrophysical objects—circumbinary disks, Be stars, neutron stars accreting in a propeller regime, etc.—feature non-zero torque simultaneously with the non-zero accretion (or ejection of mass) at the disk center. We provide a general description for the evolution of such disks (both linear and nonlinear) in the self-similar regime, to which the disk should asymptotically converge with time. We identify a similarity parameter λ, which is uniquely related to the degree, to which the central mass accretion is suppressed by the non-zero central torque. The known decretion disk solutions correspond to the two discrete values of λ, while our new solutions cover a continuum of its physically allowed values, corresponding to either accretion or mass ejection by the central object. A direct relationship between λ and central \\dot{M} and torque is also established. We describe the time evolution of the various disk characteristics for different λ, and show that the observable properties (spectrum and luminosity evolution) of the decretion disks, in general, are different from the standard accretion disks with no central torque.

  15. Secular Evolution in Disk Galaxies

    Science.gov (United States)

    Kormendy, John

    2013-10-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -- the inner parts shrink while the outer parts expand -- provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. I begin with a review of the formation, growth and death of bars. Then I review the slow (`secular') rearrangement of energy, angular momentum, and mass that results from interactions between stars or gas clouds and collective phenomena such as bars, oval disks, spiral structure and triaxial dark haloes. The `existence-proof' phase of this work is largely over: we have a good heuristic understanding of how nonaxisymmetric structures rearrange disk gas into outer rings, inner rings and stuff dumped onto the centre. The results of simulations correspond closely to the morphology of barred and oval galaxies. Gas that is transported to small radii reaches high densities. Observations confirm that many barred and oval galaxies have dense central concentrations of gas and star formation. The result is to grow, on timescales of a few Gyr, dense central components that are frequently mistaken for classical (elliptical-galaxy-like) bulges but that were grown slowly out of the disk (not made rapidly by major mergers). The resulting picture of secular galaxy evolution accounts for the richness observed in galaxy structure. We can distinguish between classical and pseudo

  16. Site-directed immobilization of a genetically engineered anti-methotrexate antibody via an enzymatically introduced biotin label significantly increases the binding capacity of immunoaffinity columns.

    Science.gov (United States)

    Davenport, Kaitlynn R; Smith, Christopher A; Hofstetter, Heike; Horn, James R; Hofstetter, Oliver

    2016-05-15

    In this study, the effect of random vs. site-directed immobilization techniques on the performance of antibody-based HPLC columns was investigated using a single-domain camelid antibody (VHH) directed against methotrexate (MTX) as a model system. First, the high flow-through support material POROS-OH was activated with disuccinimidyl carbonate (DSC), and the VHH was bound in a random manner via amines located on the protein's surface. The resulting column was characterized by Frontal Affinity Chromatography (FAC). Then, two site-directed techniques were explored to increase column efficiency by immobilizing the antibody via its C-terminus, i.e., away from the antigen-binding site. In one approach, a tetra-lysine tail was added, and the antibody was immobilized onto DSC-activated POROS. In the second site-directed approach, the VHH was modified with the AviTag peptide, and a biotin-residue was enzymatically incorporated at the C-terminus using the biotin ligase BirA. The biotinylated antibody was subsequently immobilized onto NeutrAvidin-derivatized POROS. A comparison of the FAC analyses, which for all three columns showed excellent linearity (R(2)>0.999), revealed that both site-directed approaches yield better results than the random immobilization; the by far highest efficiency, however, was determined for the immunoaffinity column based on AviTag-biotinylated antibody. As proof of concept, all three columns were evaluated for quantification of MTX dissolved in phosphate buffered saline (PBS). Validation using UV-detection showed excellent linearity in the range of 0.04-12μM (R(2)>0.993). The lower limit of detection (LOD) and lower limit of quantification (LLOQ) were found to be independent of the immobilization strategy and were 40nM and 132nM, respectively. The intra- and inter-day precision was below 11.6%, and accuracy was between 90.7% and 112%. To the best of our knowledge, this is the first report of the AviTag-system in chromatography, and the first

  17. Astrophysical disks Collective and Stochastic Phenomena

    CERN Document Server

    Fridman, Alexei M; Kovalenko, Ilya G

    2006-01-01

    The book deals with collective and stochastic processes in astrophysical discs involving theory, observations, and the results of modelling. Among others, it examines the spiral-vortex structure in galactic and accretion disks , stochastic and ordered structures in the developed turbulence. It also describes sources of turbulence in the accretion disks, internal structure of disk in the vicinity of a black hole, numerical modelling of Be envelopes in binaries, gaseous disks in spiral galaxies with shock waves formation, observation of accretion disks in a binary system and mass distribution of luminous matter in disk galaxies. The editors adaptly brought together collective and stochastic phenomena in the modern field of astrophysical discs, their formation, structure, and evolution involving the methodology to deal with, the results of observation and modelling, thereby advancing the study in this important branch of astrophysics and benefiting Professional Researchers, Lecturers, and Graduate Students.

  18. Counterrotating Stars in Simulated Galaxy Disks

    CERN Document Server

    Algorry, David G; Abadi, Mario G; Sales, Laura V; Steinmetz, Matthias; Piontek, Franziska

    2013-01-01

    Counterrotating stars in disk galaxies are a puzzling dynamical feature whose origin has been ascribed to either satellite accretion events or to disk instabilities triggered by deviations from axisymmetry. We use a cosmological simulation of the formation of a disk galaxy to show that counterrotating stellar disk components may arise naturally in hierarchically-clustering scenarios even in the absence of merging. The simulated disk galaxy consists of two coplanar, overlapping stellar components with opposite spins: an inner counterrotating bar-like structure made up mostly of old stars surrounded by an extended, rotationally-supported disk of younger stars. The opposite-spin components originate from material accreted from two distinct filamentary structures which at turn around, when their net spin is acquired, intersect delineating a "V"-like structure. Each filament torques the other in opposite directions; the filament that first drains into the galaxy forms the inner counterrotating bar, while material ...

  19. Molecular Gas in Young Debris Disks

    Science.gov (United States)

    Moór, Attila; Kóspál, Ágnes; Ábrahám, Péter; Juhász, Attila; Apai, Dániel; Csengeri, Timea; Grady, Carol; Henning, Thomas; Kiss, Csaba; Pascucci, Ilaria

    2013-07-01

    Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. So far only a very few debris disks with measurable gas component have been known. We carried out a survey with the APEX radio telescope to detect molecular gas at millimeter wavelengths in 28 infrared-luminous young debris disks, and discovered two new systems with substantial amount of CO. Motivated to understand the origin, physics, and evolutionary status of the gas in these systems we observed one of them, HD 21997, with ALMA and Herschel. Our results suggest that HD 21997 may be a hybrid system where secondary debris dust and residual primordial gas coexist. This poses a serious question to the current paradigm, since the age of the system (30 Myr) significantly exceeds model predictions for disk clearing and the ages of the oldest transitional disks.

  20. Erasing Data and Recycling of Optical Disks

    Directory of Open Access Journals (Sweden)

    T Fujita

    2007-03-01

    Full Text Available Optical disks, DVDs and CDs, are convenient recording media on which to safely store data for a long period of time. However, the complete data erasure from recorded media is also important for the security of the data. After erasure of data from optical disks, recycling the material is needed in order to recover the valuable components of the optical disks. Here, data erasure methods for optical disks are discussed in the view of material recycling. The main finding of the study is that the explosion of optical disks in water is a very suitable method for complete erasure of data on the disks as well as recycling of their materials.

  1. Non-isothermal effects on Be disks

    CERN Document Server

    Vieira, Rodrigo G; Bjorkman, Jon E

    2016-01-01

    In the last decade, the viscous decretion disk model has emerged as the new paradigm for Be star disks. In this contribution, we propose a simple analytical model to estimate the continuum infrared excess arising from these circumstellar disks, in the light of the currently accepted scenario. We demonstrate that the disk can be satisfactorily described by a two component system: an inner optically thick region, which we call the pseudo-photosphere, and a diffuse outer part. In particular, a direct connexion between the disk brightness profile and the thermal structure is derived, and then confronted to realistic numerical simulations. This result quantifies how the non-isothermality of the disk ultimately affects both infrared measured fluxes and visibilities.

  2. Dusty Disks around White Dwarfs I: Origin of Debris Disks

    CERN Document Server

    Dong, Ruobing; Lin, D N C; Liu, X -W

    2010-01-01

    A significant fraction of the mature FGK stars have cool dusty disks at least an orders of magnitudes brighter than the solar system's outer zodiacal light. Since such dusts must be continually replenished, they are generally assumed to be the collisional fragments of residual planetesimals analogous to the Kuiper Belt objects. At least 10% of solar type stars also bear gas giant planets. The fraction of stars with known gas giants or detectable debris disks (or both) appears to increase with the stellar mass. Here, we examine the dynamical evolution of systems of long-period gas giant planets and residual planetesimals as their host stars evolve off the main sequence, lose mass, and form planetary nebula around remnant white dwarf cores. The orbits of distant gas giant planets and super-km-size planetesimals expand adiabatically. During the most intense AGB mass loss phase, sub-meter-size particles migrate toward their host stars due to the strong hydrodynamical drag by the intense stellar wind. Along their ...

  3. Toleration, Synthesis or Replacement?

    DEFF Research Database (Denmark)

    Holtermann, Jakob v. H.; Madsen, Mikael Rask

    2016-01-01

    to have considerable problems keeping a clear focus on the key question: What are the implications of this empirical turn in terms of philosophy of legal science, of the social understanding of IL, and, not least, of the place of doctrinal scholarship after the alleged Wende? What is needed, we argue......, in order to answer is not yet another partisan suggestion, but rather an attempt at making intelligible both the oppositions and the possibilities of synthesis between normative and empirical approaches to law. Based on our assessment and rational reconstruction of current arguments and positions, we...... therefore outline a taxonomy consisting of the following three basic, ideal-types in terms of the epistemological understanding of the interface of law and empirical studies: toleration, synthesis and replacement. This tripartite model proves useful with a view to teasing out and better articulating...

  4. Early dust evolution in protostellar accretion disks

    OpenAIRE

    2000-01-01

    We investigate dust dynamics and evolution during the formation of a protostellar accretion disk around intermediate mass stars via 2D numerical simulations. Using three different detailed dust models, compact spherical particles, fractal BPCA grains, and BCCA grains, we find that even during the early collapse and the first 10,000 yr of dynamical disk evolution, the initial dust size distribution is strongly modified. Close to the disk's midplane coagulation produces dust particles of sizes ...

  5. ON THE FORMATION OF GALACTIC THICK DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Minchev, I.; Streich, D.; Scannapieco, C.; De Jong, R. S.; Steinmetz, M. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Martig, M. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2015-05-01

    Recent spectroscopic observations in the Milky Way suggest that the chemically defined thick disk (stars that have high [α/Fe] ratios and are thus old) has a significantly smaller scale-length than the thin disk. This is in apparent contradiction with observations of external edge-on galaxies, where the thin and thick components have comparable scale-lengths. Moreover, while observed disks do not flare (scale-height does not increase with radius), numerical simulations suggest that disk flaring is unavoidable, resulting from both environmental effects and secular evolution. Here we address these problems by studying two different suites of simulated galactic disks formed in the cosmological context. We show that the scale-heights of coeval populations always increase with radius. However, the total population can be decomposed morphologically into thin and thick disks, which do not flare. We relate this to the disk inside-out formation, where younger populations have increasingly larger scale-lengths and flare at progressively larger radii. In this new picture, thick disks are composed of the imbedded flares of mono-age stellar populations. Assuming that disks form inside out, we predict that morphologically defined thick disks must show a decrease in age (or [α/Fe] ratios) with radius and that coeval populations should always flare. This also explains the observed inversion in the metallicity and [α/Fe] gradients for stars away from the disk midplane in the Milky Way. The results of this work are directly linked to, and can be seen as evidence of, inside-out disk growth.

  6. Theory of Disk Accretion onto Magnetic Stars

    Directory of Open Access Journals (Sweden)

    Lai Dong

    2014-01-01

    Full Text Available Disk accretion onto magnetic stars occurs in a variety of systems, including accreting neutron stars (with both high and low magnetic fields, white dwarfs, and protostars. We review some of the key physical processes in magnetosphere-disk interaction, highlighting the theoretical uncertainties. We also discuss some applications to the observations of accreting neutron star and protostellar systems, as well as possible connections to protoplanetary disks and exoplanets.

  7. Theory of Disk Accretion onto Magnetic Stars

    CERN Document Server

    Lai, Dong

    2014-01-01

    Disk accretion onto magnetic stars occurs in a variety of systems, including accreting neutron stars (with both high and low magnetic fields), white dwarfs, and protostars. We review some of the key physical processes in magnetosphere-disk interaction, highlighting the theoretical uncertainties. We also discuss some applications to the observations of accreting neutron stars and protostellar systems, as well as possible connections to protoplanetary disks and exoplanets.

  8. Protoplanetary Disks in Multiple Star Systems

    Science.gov (United States)

    Harris, Robert J.

    Most stars are born in multiple systems, so the presence of a stellar companion may commonly influence planet formation. Theory indicates that companions may inhibit planet formation in two ways. First, dynamical interactions can tidally truncate circumstellar disks. Truncation reduces disk lifetimes and masses, leaving less time and material for planet formation. Second, these interactions might reduce grain-coagulation efficiency, slowing planet formation in its earliest stages. I present three observational studies investigating these issues. First is a spatially resolved Submillimeter Array (SMA) census of disks in young multiple systems in the Taurus-Auriga star-forming region to study their bulk properties. With this survey, I confirmed that disk lifetimes are preferentially decreased in multiples: single stars have detectable millimeter-wave continuum emission twice as often as components of multiples. I also verified that millimeter luminosity (proportional to disk mass) declines with decreasing stellar separation. Furthermore, by measuring resolved-disk radii, I quantitatively tested tidal-truncation theories: results were mixed, with a few disks much larger than expected. I then switch focus to the grain-growth properties of disks in multiple star systems. By combining SMA, Combined Array for Research in Millimeter Astronomy (CARMA), and Jansky Very Large Array (VLA) observations of the circumbinary disk in the UZ Tau quadruple system, I detected radial variations in the grain-size distribution: large particles preferentially inhabit the inner disk. Detections of these theoretically predicted variations have been rare. I related this to models of grain coagulation in gas disks and find that our results are consistent with growth limited by radial drift. I then present a study of grain growth in the disks of the AS 205 and UX Tau multiple systems. By combining SMA, Atacama Large Millimeter/submillimeter Array (ALMA), and VLA observations, I detected radial

  9. Structure, mass and stability of galactic disks

    CERN Document Server

    van der Kruit, P C

    2010-01-01

    In this review I concentrate on three areas related to structure of disks in spiral galaxies. First I will review the work on structure, kinematics and dynamics of stellar disks. Next I will review the progress in the area of flaring of HI layers. These subjects are relevant for the presence of dark matter and lead to the conclusion that disk are in general not `maximal', have lower M/L ratios than previously suspected and are locally stable w.r.t. Toomre's Q criterion for local stability. I will end with a few words on `truncations' in stellar disks.

  10. Evaluation of powder metallurgy superalloy disk materials

    Science.gov (United States)

    Evans, D. J.

    1975-01-01

    A program was conducted to develop nickel-base superalloy disk material using prealloyed powder metallurgy techniques. The program included fabrication of test specimens and subscale turbine disks from four different prealloyed powders (NASA-TRW-VIA, AF2-1DA, Mar-M-432 and MERL 80). Based on evaluation of these specimens and disks, two alloys (AF2-1DA and Mar-M-432) were selected for scale-up evaluation. Using fabricating experience gained in the subscale turbine disk effort, test specimens and full scale turbine disks were formed from the selected alloys. These specimens and disks were then subjected to a rigorous test program to evaluate their physical properties and determine their suitability for use in advanced performance turbine engines. A major objective of the program was to develop processes which would yield alloy properties that would be repeatable in producing jet engine disks from the same powder metallurgy alloys. The feasibility of manufacturing full scale gas turbine engine disks by thermomechanical processing of pre-alloyed metal powders was demonstrated. AF2-1DA was shown to possess tensile and creep-rupture properties in excess of those of Astroloy, one of the highest temperature capability disk alloys now in production. It was determined that metallographic evaluation after post-HIP elevated temperature exposure should be used to verify the effectiveness of consolidation of hot isostatically pressed billets.

  11. Circumstellar Debris Disks: Diagnosing the Unseen Perturber

    CERN Document Server

    Nesvold, Erika R; Vican, Laura; Farr, Will M

    2016-01-01

    The first indication of the presence of a circumstellar debris disk is usually the detection of excess infrared emission from the population of small dust grains orbiting the star. This dust is short-lived, requiring continual replenishment, and indicating that the disk must be excited by an unseen perturber. Previous theoretical studies have demonstrated that an eccentric planet orbiting interior to the disk will stir the larger bodies in the belt and produce dust via interparticle collisions. However, motivated by recent observations, we explore another possible mechanism for heating a debris disk: a stellar-mass perturber orbiting exterior to and inclined to the disk and exciting the disk particles' eccentricities and inclinations via the Kozai-Lidov mechanism. We explore the consequences of an exterior perturber on the evolution of a debris disk using secular analysis and collisional N-body simulations. We demonstrate that a Kozai-Lidov excited disk can generate a dust disk via collisions and we compare t...

  12. Modeling the Circumstellar Disk of $\\zeta$ Tauri

    OpenAIRE

    Carciofi, A. C.; Bjorkman, J. E.

    2004-01-01

    We present a model for the disk of the classical Be star $\\zeta$ Tauri. The model consists of a Keplerian rotating disk with a power-law surface density and a vertical density distribution that follows from the balance between the thermal gas pressure and the z-component of the stellar gravitation. The opening angle of such a disk is not a fixed value but increases with the distance to the star (flared disk). We use a Monte Carlo code that solves simultaneously the thermal equilibrium, the st...

  13. Strength of Cracked Reinforced Concrete Disks

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1999-01-01

    The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...... for the shear strength of disks with initial cracks and disks suffering from isotropic cracking are presented. Furthermore, in the case of isotropicly cracked disks subjected to arbitrary in-plane loading, a general yield condition is derived....

  14. Generalized Similarity for Accretion/Decretion Disks

    CERN Document Server

    Rafikov, Roman R

    2016-01-01

    Decretion (or external) disks are gas disks freely expanding to large radii due to their internal stresses. They are expected to naturally arise in tidal disruption events, around Be stars, in mass-losing post main sequence binaries, as a result of supernova fallback, etc. Their evolution is theoretically understood in two regimes: when the central object does not exert torque on the disk (a standard assumption for conventional accretion disks) or when no mass inflow (or outflow) occurs at the disk center. However, many astrophysical objects - circumbinary disks, Be stars, neutron stars accreting in a propeller regime, etc. - feature non-zero torque simultaneously with the non-zero accretion (or ejection of mass) at the disk center. We provide a general description for the evolution of such disks (both linear and non-linear) in the self-similar regime, to which the disk should asymptotically converge with time. We identify a similarity parameter $\\lambda$, which is uniquely related to the degree, to which the...

  15. Sub-Keplerian accretion onto circumstellar disks

    CERN Document Server

    Visser, R

    2010-01-01

    Models of the formation, evolution and photoevaporation of circumstellar disks are an essential ingredient in many theories of the formation of planetary systems. The ratio of disk mass over stellar mass in the circumstellar phase of a disk is largely determined by the angular momentum of the original cloud core from which the system was formed. While full 3D or 2D axisymmetric hydrodynamical models of accretion onto the disk automatically treat all aspects of angular momentum, this is not so trivial for 1D and semi-2D viscous disk models. Since 1D and semi-2D disk models are still very useful for long-term evolutionary modelling of disks with relatively little numerical effort, we investigate how the 2D nature of accretion affects the formation and evolution of the disk in such models. A proper treatment of this problem requires a correction for the sub-Keplerian velocity at which accretion takes place. We develop an update of our semi-2D time-dependent disk evolution model to properly treat the effects of s...

  16. Dust amorphization in protoplanetary disks

    CERN Document Server

    Glauser, Adrian M; Watson, Dan M; Henning, Thomas; Schegerer, Alexander A; Wolf, Sebastian; Audard, Marc; Baldovin-Saavedra, Carla

    2009-01-01

    High-energy irradiation of the circumstellar material might impact the structure and the composition of a protoplanetary disk and hence the process of planet formation. In this paper, we present a study on the possible influence of the stellar irradiation, indicated by X-ray emission, on the crystalline structure of the circumstellar dust. The dust crystallinity is measured for 42 class II T Tauri stars in the Taurus star-forming region using a decomposition fit of the 10 micron silicate feature, measured with the Spitzer IRS instrument. Since the sample includes objects with disks of various evolutionary stages, we further confine the target selection, using the age of the objects as a selection parameter. We correlate the X-ray luminosity and the X-ray hardness of the central object with the crystalline mass fraction of the circumstellar dust and find a significant anti-correlation for 20 objects within an age range of approx. 1 to 4.5 Myr. We postulate that X-rays represent the stellar activity and consequ...

  17. Hard disks with SCSI interface

    CERN Document Server

    Denisov, O Yu

    1999-01-01

    The testing of 20 models of hard SCSI-disks is carried out: the Fujitsu MAE3091LP; the IBM DDRS-39130, DGHS-318220, DNES-318350, DRHS-36V and DRVS-18V; the Quantum Atlas VI 18.2; the Viking 11 9.1; the Seagate ST118202LW, ST118273LW, ST118273W, ST318203LW, ST318275LW, ST34520W, ST39140LW and ST39173W; and the Western Digital WDE9100-0007, WDE9100-AV0016, WDE9100-AV0030 and WDE9180-0048. All tests ran under the Windows NT 4.0 workstation operating system with Service Pack 4, under video mode with 1024*768 pixel resolution, 32- bit colour depth and V-frequency equal to 85 Hz. The detailed description and characteristics of SCSI stores are presented. Test results (ZD Winstone 99 and ZD WinBench 99 tests) are given in both table and diagram (disk transfer rate) forms. (0 refs).

  18. Turbulent dynamo in a disk

    Energy Technology Data Exchange (ETDEWEB)

    Ruzmaikin, A.A.; Sokolov, D.D.; Turchaninov, V.I.

    1980-03-01

    The large-scale magnetic field in a rotating, turbulent gaseous disk will be generated by a dynamo process (the ..cap alpha omega..-dynamo) determined by the differential rotation ..omega..(r) and the spirality function ..cap alpha..(z). The generation is best described by a difference approximation to the dynamo equations, using a step greater than the turbulence correlation length and a smooth function ..cap alpha..(z). The critical dynamo-number for exciting the lowest even quadrupole mode is D/sub q/ = -8. The odd dipole mode will be excited only for large dynamo-numberabsolute value (D/sub d/) > or approx. = 500. When absolute value (D) > or approx. = 20, all modes other than the lowest quadrupole mode (for which the threshold Dapprox. =-500) are oscillatory. The results are applied to the Galaxy (D approx. = -10; characteristic growth time, 3 x 10/sup 8/ yr) and to accretion disks in binary systems containing a black hole, where several oscillatory modes can be excited.

  19. Circumplanetary disk or circumplanetary envelope?

    CERN Document Server

    Szulágyi, J; Lega, E; Crida, A; Morbidelli, A; Guillot, T

    2016-01-01

    We present three-dimensional simulations with nested meshes of the dynamics of the gas around a Jupiter mass planet with the JUPITER and FARGOCA codes. We implemented a radiative transfer module into the JUPITER code to account for realistic heating and cooling of the gas. We focus on the circumplanetary gas flow, determining its characteristics at very high resolution ($80\\%$ of Jupiter's diameter). In our nominal simulation where the temperature evolves freely by the radiative module and reaches 13000 K at the planet, a circumplanetary envelope was formed filling the entire Roche-lobe. Because of our equation of state is simplified and probably overestimates the temperature, we also performed simulations with limited maximal temperatures in the planet region (1000 K, 1500 K, and 2000 K). In these fixed temperature cases circumplanetary disks (CPDs) were formed. This suggests that the capability to form a circumplanetary disk is not simply linked to the mass of the planet and its ability to open a gap. Inste...

  20. Thick-disk Evolution Induced by the Growth of an Embedded Thin Disk

    NARCIS (Netherlands)

    Villalobos, Álvaro; Kazantzidis, Stelios; Helmi, Amina

    2010-01-01

    We perform collisionless N-body simulations to investigate the evolution of the structural and kinematical properties of simulated thick disks induced by the growth of an embedded thin disk. The thick disks used in the present study originate from cosmologically common 5:1 encounters between initial

  1. The physical and chemical evolution of protostellar disks. The growth of protostellar disks: Progress to date

    Science.gov (United States)

    Stahler, Steven W.

    1993-01-01

    This study constitutes one part of our multi-disciplinary approach to the evolution of planet-forming disks. The goal is to establish the disks' thermal and mechanical properties as they grow by the infall of their parent interstellar clouds. Thus far, significant advances toward establishing the evolving surface density of such disks was made.

  2. Aflatoxin M1 determination in yoghurt produced in Guilan province of Iran using immunoaffinity column and high-performance liquid chromatography.

    Science.gov (United States)

    Tabari, Mahsa; Tabari, Khashayar; Tabari, Orod

    2013-02-01

    The present study was aimed to determine the presence and levels of aflatoxin M(1) (AFM(1)) in 120 natural yoghurt samples consisting of 80 samples of commercial and 40 samples of traditional yoghurt in Guilan province in the north of Iran. The occurrence and concentration range of AFM(1) in samples were determined by immunoaffinity column extraction and high-performance liquid chromatography. Analysis of yoghurts showed that all the samples were contaminated with AFM(1) in concentration levels ranging from 4.2 to 78.9 ng/kg. In general, 16 samples (13.33%) had higher AFM(1) level than the maximum tolerance limit (50 ng/kg) accepted by European Union, but the contamination level was lower than 500 ng/kg in all the samples, which is accepted by Codex Alimentarius and National Standard. The concentration of AFM(1) in 26 samples (21.66) was lower than 10 ng/kg. The range of contamination of AFM(1) was comparatively higher in traditional yoghurt (average concentration of 32.9 ng/kg) than that in commercial yoghurt (average concentration of 21.6 ng/kg; p yoghurt is the most popular dairy product consumed in Iran, the AFM(1) contamination is a serious problem for public health. This study reports the data of a first survey on the presence of AFM1 in yoghurt in Guilan, Iran.

  3. Confirmatory method for the determination of resorcylic acid lactones in urine sample using immunoaffinity cleanup and liquid chromatography-tandem mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Dusi, Guglielmo [Istituto Zooprofilattico Sperimentale della Lombardia e dell' Emilia Romagna, ' B. Ubertini' , Via Bianchi 7, 25124 Brescia (Italy)], E-mail: guglielmo.dusi@bs.izs.it; Bozzoni, Eros; Assini, Walter; Tognoli, Nadia; Gasparini, Mara; Ferretti, Enrica [Istituto Zooprofilattico Sperimentale della Lombardia e dell' Emilia Romagna, ' B. Ubertini' , Via Bianchi 7, 25124 Brescia (Italy)

    2009-04-01

    The presence of zeranol ({alpha}-zearalanol) in urine samples due to natural contamination or illegal treatment is under debate within the European Union. The simultaneous determination of zeranol, its epimer taleranol ({beta}-zearalanol), zearalanone and the structurally related mycotoxin zearalenone with the corresponding {alpha}- and {beta}-zearalenol metabolites appears to be critical in deciding whether an illegal use has occurred. The aim of this study is to develop and validate a simple analytical procedure applicable to bovine and swine urine samples for the determination of all six resorcylic acid lactones. After an enzymatic deconjugation, the urine was subjected to a one-step cleanup on a commercially available immunoaffinity chromatography cartridge. The analytes were detected by liquid chromatography-negative-ion electrospray tandem mass spectrometry using deuterium-labelled internal standards. The method was validated as a quantitative confirmatory method according to European Commission Decision 2002/657/EC. The evaluated parameters were: linearity, specificity, precision (repeatability and intra-laboratory reproducibility), recovery, decision limit, detection capability and ruggedness. The decision limits (CC{alpha}) obtained, were between 0.56 and 0.68 {mu}g L{sup -1}; recovery above 66% for all the analytes. Repeatability was between 1.4 and 5.3% and within-laboratory reproducibility between 1.9 and 16.1% for the six resorcylic acid lactones.

  4. Determination of vitamin B12 in food products by liquid chromatography/UV detection with immunoaffinity extraction: single-laboratory validation.

    Science.gov (United States)

    Campos-Giménez, Esther; Fontannaz, Patric; Trisconi, Marie-Jose; Kilinc, Tamara; Gimenez, Catherine; Andrieux, Pierre

    2008-01-01

    A fast and simple method to determine vitamin B12 in foods is presented. The method allows, in addition to the determination of added cyanocobalamin, the determination of natural vitamin B12 forms, making it also applicable to nonfortified products, especially those that are milk-based. Vitamin B12 is extracted in sodium acetate buffer in the presence of sodium cyanide (100 degrees C, 30 min). After purification and concentration with an immunoaffinity column, vitamin B12 is determined by liquid chromatography with UV detection (361 nm). The method has been validated in analyses of a large range of products: milk- and soy-based infant formulas, cereals, cocoa beverages, health care products, and polyvitamin premixes. The method showed appropriate performance characteristics: linear response over a large range of concentrations, recovery rates of 100.8 +/- 7.5% (average +/- standard deviation), relative standard deviation of repeatability, RSDr, of 2.1%, and intermediate reproducibility, RSDiR, of 4.3%. Limits of detection and quantitation were 0.10 and 0.30 microg/100 g, respectively, and correlation with the reference microbiological assay was good (R2 = 0.9442). The proposed method is suitable for the routine determination of vitamin B12 in fortified foods, as well as in nonfortified dairy products. It can be used as a faster, more selective, and more precise alternative to the classical microbiological determination.

  5. Determination of carbofuran in surface water and biological tissue by sol-gel immunoaffinity extraction and on-line preconcentration/HPLC/UV analysis.

    Science.gov (United States)

    Vera-Avila, Luz E; Márquez-Lira, Bani P; Villanueva, Marcos; Covarrubias, Rosario; Zelada, Gustavo; Thibert, Valérie

    2012-01-15

    A selective and simple analytical method for the trace level determination of carbofuran in complex environmental and biological samples was developed based on immunoaffinity extraction (IAE) followed by on-line preconcentration and HPLC/UV analysis of the purified extract. The immunosorbent for IAE was prepared by sol-gel encapsulation of monoclonal anti-carbofuran antibodies, and was fully characterized for capacity, repeatability, binding strength, binding kinetics and cross-reactivity. Method performance was evaluated with two different types of difficult samples: dam water and methanolic extracts of epithelial cervical-uterine tissue. Linear behavior and quantitative recoveries were obtained from the analysis of samples spiked with carbofuran at 0.2-4 ng/mL (dam water, 50 mL samples) and 10-40 ng/mL (biological tissue extract, 2 mL samples). RSD (n=7) and detection limits were, respectively, 10.1% (spike 0.40 ng/mL) and 0.13 ng/mL for dam water; 8.5% (spike 20 ng/mL) and 5 ng/mL for the biological tissue extract. The excellent sample purification achieved with the IAE column allows precise and accurate determination of carbofuran in complex matrices, even when using non-selective UV detection in the chromatographic analysis.

  6. On-line immunoaffinity solid-phase extraction capillary electrophoresis mass spectrometry for the analysis of large biomolecules: a preliminary report.

    Science.gov (United States)

    Medina-Casanellas, Silvia; Benavente, Fernando; Giménez, Estela; Barbosa, José; Sanz-Nebot, Victoria

    2014-08-01

    The analysis of large biomolecules by on-line immunoaffinity solid-phase extraction capillary electrophoresis mass spectrometry (IA-SPE-CE-MS) remains unexplored because of the complex issues that need to be addressed. In this preliminary study, we used the human glycoprotein transferrin (Tf) as a model of a large biomolecule. First, we established by CE-UV a novel method compatible with IA-SPE-CE-MS, based on the use of a fused silica capillary coated with an anionic derivative of polyacrylamide (UltraTrol(TM) Dynamic Pre-Coat High Normal, HN) to prevent protein adsorption. The methodology allowed the detection of the most abundant Tf sialoforms. Repeatability studies demonstrated high stability of the coated capillaries, which was required for on-line immunoextraction and MS detection. IA-SPE-CE-UV and IA-SPE-CE-MS methods were optimized for the analysis of Tf standards and human serum samples using a laboratory-made IA sorbent. Three peaks corresponding to Tf were detected with UV detection when on-line immunoextraction was applied to the standards. The use of MS detection, however, reduced the resolution of the electrophoretic separation. Finally, we demonstrated that it was possible to detect Tf in human serum samples, after off-line serum sample de-salting by centrifugal filtration.

  7. Analysis of sterigmatocystin in cereals, animal feed, seeds, beer and cheese by immunoaffinity column clean-up and HPLC and LC-MS/MS quantification.

    Science.gov (United States)

    Marley, Elaine; Brown, Phyllis; Mackie, Jennifer; Donnelly, Carol; Wilcox, Joyce; Pietri, Amedeo; Macdonald, Susan

    2015-01-01

    A method is reported for the analysis of sterigmatocystin in various food and feed matrices using a commercial sterigmatocystin immunoaffinity column (IAC) for sample clean-up prior to HPLC analysis by UV with mass spectrometric detection (LC-MS/MS). Cereals (wheat, oats, rye, maize and rice), sunflower seeds and animal feed were spiked with sterigmatocystin at levels from 0.75 to 50 µg kg(-1) to establish method performance. Using acetonitrile/water extraction followed by IAC clean-up, and analysis by HPLC with detection at 325 nm, recoveries ranged from 68% to 106%, with repeatability from 4.2% to 17.5%. The limit of quantification with UV detection in these matrices was 1.5 µg kg(-1). For the analysis of beer and cheese the sample preparation prior to IAC clean-up was changed to accommodate the different properties of the matrix, prior to analysis by LC-MS/MS. For beer and cheese spiked at 5.0 µg kg(-1) the recoveries were 94% and 104%, and precision (RSDs) were 1.9% and 2.9% respectively. The limits of quantification by LC-MS/MS in beer and cheese were 0.02 and 0.6 µg kg(-1) respectively. The sterigmatocystin IAC was demonstrated to provide an efficient clean-up of various matrices to enable this mycotoxin to be determined by either HPLC with UV detection or LC-MS/MS.

  8. Qualitative identification of growth hormone-releasing hormones in human plasma by means of immunoaffinity purification and LC-HRMS/MS.

    Science.gov (United States)

    Knoop, Andre; Thomas, Andreas; Fichant, Eric; Delahaut, Philippe; Schänzer, Wilhelm; Thevis, Mario

    2016-05-01

    The use of growth hormone-releasing hormones (GHRHs) is prohibited in sports according to the regulations of the World Anti-Doping Agency (WADA). The aim of the present study was to develop a method for the simultaneous detection of four different GHRHs and respective metabolites from human plasma by means of immunoaffinity purification and subsequent nano-ultrahigh performance liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry. The target analytes included Geref (Sermorelin), CJC-1293, CJC-1295, and Egrifta (Tesamorelin) as well as two metabolites of Geref and CJC-1293, which were captured from plasma samples using a polyclonal GHRH antibody in concert with protein A/G monolithic MSIA™ D.A.R.T.'S® (Disposable Automation Research Tips) prior to separation and detection. The method was fully validated and found to be fit for purpose considering the parameters specificity, linearity, recovery (19-37%), lower limit of detection (sports drug testing samples. Further studies are however required and warranted to account for potential species-related differences in metabolism and elimination of the target analytes.

  9. Simultaneous determination and validated quantification of human insulin and its synthetic analogues in human blood serum by immunoaffinity purification and liquid chromatography-mass spectrometry.

    Science.gov (United States)

    Hess, Cornelius; Thomas, Andreas; Thevis, Mario; Stratmann, Bernd; Quester, Wulf; Tschoepe, Diethelm; Madea, Burkhard; Musshoff, Frank

    2012-10-01

    Possible fatal complications of human insulin and its synthetic analogues like hypoglycemia require precise classification and quantitative determination of these drugs both for clinical purposes as well as for forensic toxicologists. A procedure was developed for the identification and quantification of human insulin and different long-acting as well as short-acting synthetic insulins in human blood serum specimens. After an immunoaffinity purification step and separation by liquid chromatography, the insulins were characterized by their five- or sixfold protonated molecule ions and diagnostic product ions. Clinical samples of 207 diabetic and 50 non-diabetic patients after the administration of human insulin or oral antidiabetics and forensic samples were analyzed for human/synthetic insulin concentrations. The method was validated according to international guidelines. Limits of detection of the insulins ranged between 1.3 and 2.8 μU/ml. Recoveries ranged between 33.2 % and 51.7 %. Precision data was in accordance with international guidelines. Clinical samples showed concentrations of human insulin lower than 301 μU/ml. Our liquid chromatography tandem mass spectrometry procedure allows unambiguous identification and quantification of the intact human insulin and its intact synthetic analogues Humalog®, Novolog®, Apidra®, Lantus®, and Levemir® in human blood serum in clinical and overdose cases. The assay could be successfully tested in patients with diabetes mellitus on therapy with insulins or oral antidiabetics.

  10. Improving the thin-disk models of circumstellar disk evolution. The 2+1-dimensional model

    Science.gov (United States)

    Vorobyov, Eduard I.; Pavlyuchenkov, Yaroslav N.

    2017-09-01

    Context. Circumstellar disks of gas and dust are naturally formed from contracting pre-stellar molecular cores during the star formation process. To study various dynamical and chemical processes that take place in circumstellar disks prior to their dissipation and transition to debris disks, the appropriate numerical models capable of studying the long-term disk chemodynamical evolution are required. Aims: We improve the frequently used 2D hydrodynamical model for disk evolution in the thin-disk limit by employing a better calculation of the disk thermal balance and adding a reconstruction of the disk vertical structure. Together with the hydrodynamical processes, the thermal evolution is of great importance since it influences the strength of gravitational instability and the chemical evolution of the disk. Methods: We present a new 2+1-dimensional numerical hydrodynamics model of circumstellar disk evolution, where the thin-disk model is complemented with the procedure for calculating the vertical distributions of gas volume density and temperature in the disk. The reconstruction of the disk vertical structure is performed at every time step via the solution of the time-dependent radiative transfer equations coupled to the equation of the vertical hydrostatic equilibrium. Results: We perform a detailed comparison between circumstellar disks produced with our previous 2D model and with the improved 2+1D approach. The structure and evolution of resulting disks, including the differences in temperatures, densities, disk masses, and protostellar accretion rates, are discussed in detail. Conclusions: The new 2+1D model yields systematically colder disks, while the in-falling parental clouds are warmer. Both effects act to increase the strength of disk gravitational instability and, as a result, the number of gravitationally bound fragments that form in the disk via gravitational fragmentation as compared to the purely 2D thin-disk simulations with a simplified

  11. Sustaining star formation rates in spiral galaxies - Supernova-driven turbulent accretion disk models applied to THINGS galaxies

    CERN Document Server

    Vollmer, B

    2010-01-01

    Gas disks of spiral galaxies can be described as clumpy accretion disks without a coupling of viscosity to the actual thermal state of the gas. The model description of a turbulent disk consisting of emerging and spreading clumps (Vollmer & Beckert 2003) contains free parameters, which can be constrained by observations of molecular gas, atomic gas and the star formation rate for individual galaxies. Radial profiles of 18 nearby spiral galaxies from THINGS, HERACLES, SINGS, and GALEX data are used to compare the observed star formation efficiency, molecular fraction, and velocity dispersion to the model. The observed radially decreasing velocity dispersion can be reproduced by the model. In the framework of this model the decrease in the inner disk is due to the stellar mass distribution which dominates the gravitational potential. Introducing a radial break in the star formation efficiency into the model improves the fits significantly. This change in star formation regime is realized by replacing the fr...

  12. Iron replacement therapy

    DEFF Research Database (Denmark)

    Nielsen, Ole Haagen; Coskun, Mehmet; Weiss, Günter

    2016-01-01

    PURPOSE OF REVIEW: Approximately, one-third of the world's population suffers from anemia, and at least half of these cases are because of iron deficiency. With the introduction of new intravenous iron preparations over the last decade, uncertainty has arisen when these compounds should be admini...... treatment, when to follow-up for relapse, which dosage and type of therapy should be recommended or not recommended, and if some patients should not be treated....... be administered and under which circumstances oral therapy is still an appropriate and effective treatment. RECENT FINDINGS: Numerous guidelines are available, but none go into detail about therapeutic start and end points or how iron-deficiency anemia should be best treated depending on the underlying cause...... of iron deficiency or in regard to concomitant underlying or additional diseases. SUMMARY: The study points to major issues to be considered in revisions of future guidelines for the true optimal iron replacement therapy, including how to assess the need for treatment, when to start and when to stop...

  13. Development of Powered Disk Type Sugar Cane Stubble Saver

    Directory of Open Access Journals (Sweden)

    Radite P.A.S.

    2009-04-01

    Full Text Available The objective of this research was to design, fabricate and test a prototype of sugar cane stubble saver based on powered disk mechanism. In this research, a heavy duty disk plow or disk harrow was used as a rotating knife to cut the sugarcane stubble. The parabolic disk was chosen because it is proven reliable as soil working tools and it is available in the market as spare part of disk plow or disk harrow unit. The prototype was mounted on the four wheel tractor’s three point hitch, and powered by PTO of the tractor. Two kinds of disks were used in these experiments, those were disk with regular edge or plain disk and disk with scalloped edge or scalloped disk. Both disks had diameter of 28 inch. Results of field test showed that powered disk mechanism could satisfy cut sugar cane’s stubble. However, scalloped disk type gave smoother stubble cuts compared to that of plain disk. Plain disk type gave broken stubble cut. Higher rotation (1000 rpm resulted better cuts as compared to lower rotation (500 rpm both either on plain disk and scalloped disk. The developed prototype could work below the soil surface at depth of 5 to 10 cm. With tilt angle setting 20O and disk angle 45O the width of cut was about 25 cm.

  14. Computer modeling of the stress-strain state of a linear friction welded disk

    Directory of Open Access Journals (Sweden)

    V. Bychkov

    2015-09-01

    Full Text Available The paper is dedicated to design issues of tooling for linear friction welding (LFW machine. Computer model of a LFW machine was built. As a result of computer simulation, the stress-strain state of the machine and disk module for linear friction welding of aluminum alloy blisks also was obtained. On the basis of the results of computer simulation a module with a replaceable unit and a new variant fixing of disc in the module were designed.

  15. Performance Considerations for Gigabyte per Second Transcontinental Disk-to-Disk File Transfers

    CERN Document Server

    Kukol, P; Kukol, Peter; Gray, Jim

    2005-01-01

    Moving data from CERN to Pasadena at a gigabyte per second using the next generation Internet requires good networking and good disk IO. Ten Gbps Ethernet and OC192 links are in place, so now it is simply a matter of programming. This report describes our preliminary work and measurements in configuring the disk subsystem for this effort. Using 24 SATA disks at each endpoint we are able to locally read and write an NTFS volume is striped across 24 disks at 1.2 GBps. A 32-disk stripe delivers 1.7 GBps. Experiments on higher performance and higher-capacity systems deliver up to 3.5 GBps.

  16. Scaling Ratios and Triangles in Siegel Disks

    DEFF Research Database (Denmark)

    Buff, Xavier; Henriksen, Christian

    1999-01-01

    Let f(z)=e^{2i\\pi \\theta} + z^2, where \\theta is a quadratic irrational. McMullen proved that the Siegel disk for f is self-similar about the critical point, and we show that if \\theta = (\\sqrt{5}-1)/2 is the golden mean, then there exists a triangle contained in the Siegel disk, and with one...

  17. Simulating planet migration in globally evolving disks

    CERN Document Server

    Crida, A; Masset, F

    2006-01-01

    Numerical simulations of planet-disk interactions are usually performed with hydro-codes that -- because they consider only an annulus of the disk, over a 2D grid -- can not take into account the global evolution of the disk. However, the latter governs planetary migration of type II, so that the accuracy of the planetary evolution can be questioned. To develop an algorithm that models the local planet-disk interactions together with the global viscous evolution of the disk, we surround the usual 2D grid with a 1D grid ranging over the real extension of the disk. The 1D and 2D grids are coupled at their common boundaries via ghost rings, paying particular attention to the fluxes at the interface, especially the flux of angular momentum carried by waves. The computation is done in the frame centered on the center of mass to ensure angular momentum conservation. The global evolution of the disk and the local planet-disk interactions are both well described and the feedback of one on the other can be studied wit...

  18. A Primer on Unifying Debris Disk Morphologies

    Science.gov (United States)

    Lee, Eve J.; Chiang, Eugene

    2016-08-01

    A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, disk inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.

  19. Capillary condensation between disks in two dimensions

    DEFF Research Database (Denmark)

    Gil, Tamir; Ipsen, John Hjorth

    1997-01-01

    Capillary condensation between two two-dimensional wetted circular substrates (disks) is studied by an effective free energy description of the wetting interface. The interfacial free-energy potential is developed on the basis of the theory for the wetting of a single disk, where interfacial capi....... The theory can be applied to the description of flocculations in two-dimensional systems of colloids....

  20. Protoplanetary disks and exoplanets in scattered light

    NARCIS (Netherlands)

    Stolker, T.

    2017-01-01

    High-contrast imaging facilitates the direct detection of protoplanetary disks in scattered light and self-luminous exoplanets on long-period orbits. The combined power of extreme adaptive optics and differential imaging techniques delivers high spatial resolution images of disk morphologies down to

  1. 10 MB disk platter from CDC 7638

    CERN Multimedia

    1974-01-01

    This magnetic disk was one of three which interfaced with various Control Data machines. This single platter came from a Control Data 7638 Disk Storage Subsystem and could contain up to 10MB - about the size of a few MP4's on your iPod.

  2. The Transitional Disks Associated With Herbig Stars

    Science.gov (United States)

    Grady, C.; Fukagawa, M.; Maruta, Y.; Ohta, Y.; Wisniewski, J.; Lomax, J.; Hashimoto, J.; Currie, T.; Okamoto, Y.; Momose, M.; McElwain, M.

    2015-01-01

    As part of the Strategic Exploration of Exoplanets and Disks with Subaru YSO survey, we have surveyed a number of Herbig B-F stars mainly at H-band using Polarimetric Differential Imaging + Angular differential imaging. Historically, Herbig stars have been sorted by the shape of the IR SEDs into those which can be fit by power laws over 1-200 micrometers (Meeus et al. 2001, group II), and those which can be interpreted as a power law + a blackbody component (Meeus group I) or as transitional or pre-transitional disks (Maaskant et al. 2013). Meeus group II disks, when imaged with HiCIAO show featureless disks with depolarization along the projection of the disk semi-minor axis (Kusakabe et al. 2012). This is what we had expected to see for the Meeus group I disks, except for the addition of wide gaps or central cavities. Instead we find wild diversity, suggesting that transitional disks are highly perturbed compared to Meeus group II disks. To date, similar structure continues to be observed as higher Strehl ratio imagery becomes available.

  3. Chemical history of molecules in circumstellar disks

    CERN Document Server

    Visser, Ruud; Doty, Steven D

    2011-01-01

    The chemical composition of a protoplanetary disk is determined not only by in situ chemical processes during the disk phase, but also by the history of the gas and dust before it accreted from the natal envelope. In order to understand the disk's chemical composition at the time of planet formation, especially in the midplane, one has to go back in time and retrace the chemistry to the molecular cloud that collapsed to form the disk and the central star. Here we present a new astrochemical model that aims to do just that. The model follows the core collapse and disk formation in two dimensions, which turns out to be a critical upgrade over older collapse models. We predict chemical stratification in the disk due to different physical conditions encountered along different streamlines. We argue that the disk-envelope accretion shock does not play a significant role for the material in the disk at the end of the collapse phase. Finally, our model suggests that complex organic species are formed on the grain su...

  4. Early Phases of Protoplanetary Disk Evolution

    NARCIS (Netherlands)

    Kamp, Inga; Macchetto, FD

    2010-01-01

    It is widely accepted that planetary systems form from protoplanetary disks, and observations of the dust reveal significant grain growth over timescales of a few million years. However, we know little about the gas processing in the first 10-20 Myr of disk evolution. This is the phase where protopl

  5. Circular plate capacitor with different disks

    CERN Document Server

    Paffuti, Giampiero; Di Lieto, Alberto; Maccarrone, Francesco

    2016-01-01

    In this paper we write a system of integral equations for a capacitor composed by two disks of different radii, generalizing Love's equation for equal disks. We compute the complete asymptotic form of the capacitance matrix both for large and small distances obtaining a generalization of Kirchhoff's formula for the latter case.

  6. Molecular gas in young debris disks

    CERN Document Server

    Moór, A; Juhász, A; Kiss, Cs; Pascucci, I; Kóspál, Á; Apai, D; Henning, Th; Csengeri, T; Grady, C

    2011-01-01

    Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. Interestingly, the debris disk around the young main-sequence star 49 Ceti possesses a substantial amount of molecular gas, and possibly represents the missing link between the two phases. Motivated to understand the evolution of the gas component in circumstellar disks via finding more 49 Ceti-like systems, we carried out a CO J=3-2 survey with Atacama Pathfinder EXperiment, targeting 20 infrared-luminous debris disks. These systems fill the gap between primordial and old tenuous debris disks in terms of fractional luminosity. Here we report on the discovery of a second 49 Ceti-like disk around the 30 Myr old A3-type star HD21997, a member of the Columba Association. This system was also detected in the CO(2-1) transition, and the reliable age determination makes it an even clearer example of an old gas-bearing disk than 49 Ceti. While the fractional luminosities...

  7. Ancient bronze disks, decorations and calendars

    CERN Document Server

    Sparavigna, Amelia Carolina

    2012-01-01

    Recently, it was published that some ancient bronze disks could had been calendars, that is, that their decorations had this function. Here I am discussing an example, the disk of the Trundholm Sun Chariot, proposing a new interpretation of it, giving a calendar of 360 days. Some geometric diagrams concerning the decoration layout are also proposed.

  8. Snow Line Localization in Classical Protoplanetary Disks

    Science.gov (United States)

    Blevins, S.

    2014-04-01

    Protoplanetary disks are volatile-rich environments capable of producing the essential conditions that make planet formation viable. Establishing a molecular inventory of dominant volatile species, such as water, in the planet-forming zones surrounding young, solar-type stars elevates our understanding of the chemistry involved with planet formation, composition and disk evolution. For this study we measure the water vapor content and determine the location of the condensation front, or snow line, for four classical disks selected for the strong water emission present in their mid-infrared spectra. To accomplish this we combine deep Herschel PACS observations with high resolution Spitzer IRS spectra to create molecular maps comprised of water lines with excitation temperatures that trace the disks' surfaces from 1-100 AU. We use two-dimensional, axisymmetric radiative transfer modeling to retrieve the disks' dust structures and the RADLite raytracer to render model spectra for each disk. A simple step function is used to define the abundance structure and the model spectra are fit to the observed water lines. Preliminary results will be discussed, including the inner disk chemical content, snow line radius and fractional water vapor abundances for the classical disk RNO 90.

  9. MHD Turbulence in Accretion Disk Boundary Layers

    CERN Document Server

    Chan, Chi-kwan

    2012-01-01

    The physical modeling of the accretion disk boundary layer, the region where the disk meets the surface of the accreting star, usually relies on the assumption that angular momentum transport is opposite to the radial angular frequency gradient of the disk. The standard model for turbulent shear viscosity, widely adopted in astrophysics, satisfies this assumption by construction. However, this behavior is not supported by numerical simulations of turbulent magnetohydrodynamic (MHD) accretion disks, which show that angular momentum transport driven by the magnetorotational instability is inefficient in this inner disk region. I will discuss the results of a recent study on the generation of hydromagnetic stresses and energy density in the boundary layer around a weakly magnetized star. Our findings suggest that although magnetic energy density can be significantly amplified in this region, angular momentum transport is rather inefficient. This seems consistent with the results obtained in numerical simulations...

  10. Magnetic fields in early protostellar disk formation

    CERN Document Server

    González-Casanova, Diego F; Lazarian, Alexander

    2016-01-01

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac (1999) model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called "magnetic braking catastrophe". In particular, we provide a detailed study of the dynamics of a 0.5 M$_\\odot$ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, "reconnection diffusion", removes the magnetic flux from the disk, the other involves the change of the magnetic field's topology, but does not change the a...

  11. From disks to planets: observational insights

    Science.gov (United States)

    Isella, Andrea

    The unprecedented sensitivity and imaging capabilities offered by the Atacama Large Millimeter Array (ALMA) are transforming our understanding of protoplanetary disks and, hence, of planet formation. In this brief chapter, I first discuss the main results and caveats related to the measurement of the mass of solids in protoplanetary disks based on millimeter-wave observations. I then present a recent analysis of the ALMA observations of the HL Tau disk, which suggests that the observed circular rings might be due to the tidal interaction between Saturn mass planets and the circumstellar material. In the conclusion, I argue that the existing observations of protoplanetary disks suggest that planets might form very early on, perhaps at the same time as the formation of the disk itself.

  12. Gravitational Instabilities in Disks with Radiative Cooling

    CERN Document Server

    Mejia, A C; Pickett, M K; Mej\\'ia, Annie C.; Durisen, Richard H.; Pickett, Megan K.

    2003-01-01

    Previous simulations of self-gravitating protostellar disks have shown that, once developed, gravitational instabilities are enhanced by cooling the disk constantly during its evolution (Pickett et al. 2002). These earlier calculations included a very simple form of volumetric cooling, with a constant cooling time throughout the disk, which acted against the stabilizing effects of shock heating. The present work incorporates more realistic treatments of energy transport. The initial disk model extends from 2.3 to 40 AU, has a mass of 0.07 Msun and orbits a 0.5 Msun star. The models evolve for a period of over 2500 years, during which extensive spiral arms form. The disks structure is profoundly altered, transient clumps form in one case, but no permanent bound companion objects develop.

  13. Structures of magnetized thin accretion disks

    Institute of Scientific and Technical Information of China (English)

    LI; xiaoqing(李晓卿); JI; Haisheng(季海生)

    2002-01-01

    We investigate the magnetohydrodynamic (MHD) process in thin accretion disks. Therelevant momentum as well as magnetic reduction equations in the thin disk approximation areincluded. On the basis of these equations, we examine numerically the stationary structures, includingdistributions of the surface mass density, temperature and flow velocities of a disk around a youngstellar object (YSO). The numerical results are as follows: (i) There should be an upper limit to themagnitude of magnetic field, such an upper limit corresponds to the equipartition field. For relevantmagnitude of magnetic field of the disk's interior the disk remains approximately Keplerian. (ii) Thedistribution of effective temperature T(r) is a smoothly decreasing function of radius with power 1 corresponding to the observed radiation flux density, provided that the magnetic fieldindex γ= -1/2,is suitably chosen.

  14. Reverberation Mapping of AGN Accretion Disks

    Science.gov (United States)

    Fausnaugh, Michael; AGN STORM Collaboration

    2017-01-01

    I will discuss new reverberation mapping results that allow us to investigate the temperature structure of AGN accretion disks. By measuring time-delays between broad-band continuum light curves, we can determine the size of the disk as a function of wavelength. I will discuss the detection of continuum lags in NGC 5548 reported by the AGN STORM project and implications for the accretion disk. I will also present evidence for continuum lags in two other AGN for which we recently measured black hole masses from continuum-Hbeta reverberations. The mass measurements allow us to compare the continuum lags to predictions from standard thin disk theory, and our results indicate that the accretion disks are larger than the simplest expectations.

  15. The WEAVE disk dynamics survey

    Science.gov (United States)

    Famaey, B.; Antoja, T.; Romero-Gomez, M.; Siebert, A.; Babusiaux, C.; Di Matteo, P.; Figueras, F.; Fragkoudi, F.; Garzon-Lopez, F.; Gonzalez-Fernandez, C.; Martinez-Valpuesta, I.; Monari, G.; Mor-Crespo, R.; Hill, V.

    2016-12-01

    WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope. It consists of a multi-object fibre spectrograph with a 2°-diameter field of view that can obtain ˜ 1000 spectra simultaneously. The "WEAVE Galactic Archaeology survey" is the survey focused on the Milky Way, as a complement to the Gaia space mission, and will start operating in early 2018. This survey is subdivided in four sub-surveys, among which the "WEAVE disk dynamics survey". This survey plans to measure the radial velocities (and abundances as far as possible) of ˜ 10^6 stars with magnitude 15speed? -, as well as (iii) about their influence on secular processes such as stellar radial migration are essential elements for a better understanding of the chemo-dynamical evolution of our Galaxy, and of galaxies in general. This survey is designed to answer these questions.

  16. Streaming Instabilities in Protoplanetary Disks

    CERN Document Server

    Youdin, A N; Youdin, Andrew N.; Goodman, Jeremy

    2004-01-01

    Interpenetrating streams of solids and gas in a Keplerian disk produce a local, linear instability. The two components mutually interact via aerodynamic drag, which generates radial drift and triggers unstable modes. The secular instability does not require self-gravity, yet it generates growing particle density perturbations that could seed planetesimal formation. Growth rates are slower than dynamical, but faster than radial drift, timescales. Growth rates, like streaming velocities, are maximized for marginal coupling (stopping times comparable dynamical times). Fastest growth occurs when the solid to gas density ratio is order unity and feedback is strongest. Curiously, growth is strongly suppressed when the densities are too nearly equal. The relation between background drift and wave properties is explained by analogy with Howard's semicircle theorem. The three-dimensional, two-fluid equations describe a sixth order (in the complex frequency) dispersion relation. A terminal velocity approximation allows...

  17. Experiments with the Secchi disk

    Science.gov (United States)

    Aas, E.; Høkedal, J.; Sørensen, K.

    2013-10-01

    The Secchi depth and its relationships to other properties of the sea water in the Oslofjord-Skagerrak area have been investigated. White and black disks of different sizes have been applied, and the Secchi depth has been observed with the naked eye, through colour filters and with a water telescope. Spectral luminances and illuminances have been calculated from recordings of radiance and irradiance. A theoretical expression for the Secchi depth has been tested against field observations, and statistical relationships between Secchi depths and attenuation coefficients have been determined. Effects of size, colour filters, sun glitter and ship shadow have been quantified. The possibility to estimate quanta irradiance, chlorophyll a and total suspended material has also been studied.

  18. Using your shoulder after replacement surgery

    Science.gov (United States)

    Joint replacement surgery - using your shoulder; Shoulder replacement surgery - after ... You have had shoulder replacement surgery to replace the bones of your shoulder joint with artificial parts. The parts include a stem made of metal and a ...

  19. Disk-loss and Disk-renewal Phases in Classical Be Stars. II. Contrasting with Stable and Variable Disks

    Science.gov (United States)

    Draper, Zachary H.; Wisniewski, John P.; Bjorkman, Karen S.; Meade, Marilyn R.; Haubois, Xavier; Mota, Bruno C.; Carciofi, Alex C.; Bjorkman, Jon E.

    2014-05-01

    Recent observational and theoretical studies of classical Be stars have established the utility of polarization color diagrams (PCDs) in helping to constrain the time-dependent mass decretion rates of these systems. We expand on our pilot observational study of this phenomenon, and report the detailed analysis of a long-term (1989-2004) spectropolarimetric survey of nine additional classical Be stars, including systems exhibiting evidence of partial disk-loss/disk-growth episodes as well as systems exhibiting long-term stable disks. After carefully characterizing and removing the interstellar polarization along the line of sight to each of these targets, we analyze their intrinsic polarization behavior. We find that many steady-state Be disks pause at the top of the PCD, as predicted by theory. We also observe sharp declines in the Balmer jump polarization for later spectral type, near edge-on steady-state disks, again as recently predicted by theory, likely caused when the base density of the disk is very high, and the outer region of the edge-on disk starts to self absorb a significant number of Balmer jump photons. The intrinsic V-band polarization and polarization position angle of γ Cas exhibits variations that seem to phase with the orbital period of a known one-armed density structure in this disk, similar to the theoretical predictions of Halonen & Jones. We also observe stochastic jumps in the intrinsic polarization across the Balmer jump of several known Be+sdO systems, and speculate that the thermal inflation of part of the outer region of these disks could be responsible for producing this observational phenomenon. Finally, we estimate the base densities of this sample of stars to be between ≈8 × 10-11 and ≈4 × 10-12 g cm-3 during quasi steady state periods given there maximum observed polarization.

  20. Disk-loss and disk-renewal phases in classical Be stars. II. Contrasting with stable and variable disks

    Energy Technology Data Exchange (ETDEWEB)

    Draper, Zachary H. [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Rd, Victoria, BC V8P 5C2 (Canada); Wisniewski, John P. [HL Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St, Norman, OK 73019 (United States); Bjorkman, Karen S.; Bjorkman, Jon E. [Ritter Observatory, Department of Physics and Astronomy, Mail Stop 113, University of Toledo, Toledo, OH 43606 (United States); Meade, Marilyn R. [Space Astronomy Lab, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706 (United States); Haubois, Xavier; Mota, Bruno C.; Carciofi, Alex C., E-mail: wisniewski@ou.edu, E-mail: karen.bjorkman@utoledo.edu, E-mail: jon@physics.utoledo.edu, E-mail: meade@astro.wisc.edu, E-mail: xhaubois@astro.iag.usp.br, E-mail: carciofi@usp.br [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universitária de São Paulo, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, SP (Brazil)

    2014-05-10

    Recent observational and theoretical studies of classical Be stars have established the utility of polarization color diagrams (PCDs) in helping to constrain the time-dependent mass decretion rates of these systems. We expand on our pilot observational study of this phenomenon, and report the detailed analysis of a long-term (1989-2004) spectropolarimetric survey of nine additional classical Be stars, including systems exhibiting evidence of partial disk-loss/disk-growth episodes as well as systems exhibiting long-term stable disks. After carefully characterizing and removing the interstellar polarization along the line of sight to each of these targets, we analyze their intrinsic polarization behavior. We find that many steady-state Be disks pause at the top of the PCD, as predicted by theory. We also observe sharp declines in the Balmer jump polarization for later spectral type, near edge-on steady-state disks, again as recently predicted by theory, likely caused when the base density of the disk is very high, and the outer region of the edge-on disk starts to self absorb a significant number of Balmer jump photons. The intrinsic V-band polarization and polarization position angle of γ Cas exhibits variations that seem to phase with the orbital period of a known one-armed density structure in this disk, similar to the theoretical predictions of Halonen and Jones. We also observe stochastic jumps in the intrinsic polarization across the Balmer jump of several known Be+sdO systems, and speculate that the thermal inflation of part of the outer region of these disks could be responsible for producing this observational phenomenon. Finally, we estimate the base densities of this sample of stars to be between ≈8 × 10{sup –11} and ≈4 × 10{sup –12} g cm{sup –3} during quasi steady state periods given there maximum observed polarization.

  1. Educating My Replacement

    Science.gov (United States)

    Tarter, Jill

    , in partnership with the dedicated teachers out there, I think I can help promote the critical thinking skills and scientific literacy of the next generation of voters. Hopefully, I can also help train my replacement to be a better scientist, capable of seizing all the opportunities generated by advances in technology and our improved understanding of the universe to craft search strategies with greater probability of success than those I have initiated.

  2. Are all flaring Herbig disks transitional?

    Science.gov (United States)

    Maaskant, K. M.; Honda, M.; Waters, L. B. F. M.; Tielens, A. G. G. M.; Dominik, Carsten; Min, M.; Verhoeff, A.; Meeus, G.; Ancker, M. E.

    2013-07-01

    Context: The evolution of young massive protoplanetary disks toward planetary systems is expected to correspond to structural changes in observational appearance, which includes the formation of gaps and the depletion of dust and gas. Aims. A special group of disks around Herbig Ae/Be stars do not show prominent silicate emission features, although they still bear signs of flaring disks, the presence of gas, and small grains. We focus our attention on four key Herbig Ae/Be stars to understand the structural properties responsible for the absence of silicate feature emission. Methods: We investigate Q- and N-band images taken with Subaru/COMICS, Gemini South/T-ReCS, and VLT/VISIR. We perform radiative transfer modeling to examine the radial distribution of dust and polycyclic aromatic hydrocarbons (PAHs). Our solutions require a separation of inner- and outer- disks by a large gap. From this, we characterize the radial density structure of dust and PAHs in the disk. Results: The inner edge of the outer disk has a high surface brightness and a typical temperature between ˜100-150 K and therefore, dominates the emission in the Q-band. All four disks are characterized by large gaps. We derive radii of the inner edge of the outer disk of 34+4 , 23+3 , 30+5 and 63+4 AU for HD 97048, HD 169142, HD 135344 B, and Oph IRS 48, respectively. For HD 97048 this is the first -4 -5 -3 -4 detection of a disk gap. The large gaps deplete the entire population of silicate particles with temperatures suitable for prominent mid- infrared feature emission, while small carbonaceous grains and PAHs can still show prominent emission at mid-infrared wavelengths. The continuum emission in the N-band is not due to emission in the wings of PAHs. This continuum emission can be due to very small grains or to thermal emission from the inner disk. We find that PAH emission is not always dominated by PAHs on the surface of the outer disk. Conclusions: The absence of silicate emission features is

  3. [Ascending aorta replacement late after aortic valve replacement].

    Science.gov (United States)

    Hayashi, Yasunari; Ito, Toshiaki; Maekawa, Atsuo; Sawaki, Sadanari; Fujii, Genyo; Hoshino, Satoshi; Tokoro, Masayoshi; Yanagisawa, Junji

    2013-07-01

    Replacement of the asceding aorta is indicated in patients undergoing aortic valve replacement( AVR), if the diameter of the ascending aorta is greater than 5.0 cm. If the diameter of the asceding aorta is from 4.0 to 5.0 cm, it was arguable whether replacement of the ascending aorta should be performed. Nine patients who underwent reoperative ascending aorta replacement after AVR were reviewed retrospectively. Reoperation on the asending aorta replacement was performed 11.8±7.2 years (range 1y5m~23y3m) after AVR. Mean patient age was 69.9±6.3 (range 60~81). In 2 cases, reoperations were performed early year after AVR. Although ascending aorta was dilated at the 1st operation, replacement wasn't performed for the age and minimally invasive cardiac surgery (MICS). In 3 cases, reoperations were performed more than 10 years later. On these cases, ascending aorta aneurysm and dissection occurred with no pain and were pointed out by computed tomography(CT) or ultrasonic cardiogram(UCG). We think that patients with dilatation of the ascending aorta should undergo AVR and aorta replacement at the 1st operation regardness of age. It is important that patients who underwent AVR should undergo a regular checkup on the ascending aorta.

  4. [Appendicular ureteroplasty to repair a ureteric lesion during disk surgery].

    Science.gov (United States)

    Joual, Abdenbi; Taha, Abdellatif; Querfani, Badereddine; Sahnoun, Abderrazak; Hamid, Fekak; El Mrini, Mohamed

    2005-09-01

    Extensive ureteric lesions raise difficult problems of surgical repair. This is also the case for upper ureteric lesions that often require replacement of the damaged segment or even autologous transplantation. The authors report a case of iatrogenic ureteric lesion resulting in a large defect in a patient operated 6 months previously for an L4-L5 disk hernia, which was treated successfully by interposition of an appendicular graft between the two ureteric stumps. In the light of this case, the authors discuss the various appearances of iatrogenic ureteric lesions with particular emphasis on the value of appendicular ureteroplasty due to its simplicity and low morbidity, while waiting for progress in the field of biocompatible substitutes.

  5. Spectral Feature Analysis of Semiconductor Thin Disk Laser

    Institute of Scientific and Technical Information of China (English)

    HE Chun-feng; QIN Li; LI Jun; CHENG Li-wen; LIANG Xue-mei; NING Yong-qiang; WANG Li-jun

    2007-01-01

    The semiconductor thin disk laser is a new type of semiconductor laser. This work gives the basic operation function of the semiconductor disk laser, and analyses the heat effect by the experimentally measured photoluminescence spectrum of the laser chip at different pump power and different temperatures. We can see that: with increasing pump power, the thermal effect of the gain material becomes seriously and causes the saturation of carrier lifetime, so the electron-hole pair created in the absorbtion layer has no enough time to rate to one of the wells, and the non-radiative recombination happens in the barrier. When the thermal effect becomes stronger, the chip will be not lasing. This phenomenon is from the smaller energy offset between barrier and quantum well. We optimize the original structure design and experimental technology. A non-absorbing AlGaAs layer which is transparent to the pumping and laser wavelength is added to confine the carriers in the quantum wells. At the same time a DBR with double reflecting band is induced to improve the absorbing efficiency of the pumping light. The single QW is replaced by the three narrow QWs. This three QWs structure can add the quantum state of QW, increase the recombination probability of carriers in the QWs and reduce the heat effect. The chemical etching equipment is also improved to control the surface unevenness to be within 50 nm.

  6. Warped Circumbinary Disks in Active Galactic Nuclei

    CERN Document Server

    Hayasaki, Kimitake; Okazaki, Atsuo T; Jung, Taehyun; Zhao, Guangyao; Naito, Tsuguya

    2014-01-01

    We study a warping instability of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on a circular orbit. Such a circumbinary disk is subject to not only tidal torques due to the binary gravitational potential but also radiative torques due to radiation emitted from an accretion disk around each black hole. We find that a circumbinary disk initially aligned with the binary orbital plane is unstable to radiation-driven warping beyond the marginally stable warping radius, which is sensitive to both the ratio of vertical to horizontal shear viscosities and the mass-to-energy conversion efficiency. As expected, the tidal torques give no contribution to the growth of warping modes but tend to align the circumbinary disk with the orbital plane. Since the tidal torques can suppress the warping modes in the inner part of circumbinary disk, the circumbinary disk starts to be warped at radii larger than the marginally stable warping radius. If the warping radius is of the order ...

  7. Disk Accretion Onto High-Mass Planets

    CERN Document Server

    Lubow, S H; Artymowicz, P

    1999-01-01

    We analyze the nonlinear, two-dimensional response of a gaseous, viscous protoplanetary disk to the presence of a planet of one Jupiter mass (1 M_J) and greater that orbits a 1 solar mass star by using the ZEUS hydrodynamics code with high resolution near the planet's Roche lobe. The planet is assumed to be in a circular orbit about the central star and is not allowed to migrate. A gap is formed about the orbit of the planet, but there is a nonaxisymmetric flow through the gap and onto the planet. The gap partitions the disk into an inner (outer) disk that extends inside (outside) the planet's orbit. For a 1 M_J planet and typical disk parameters, the accretion through the gap onto the planet is highly efficient. For typical disk parameters, the mass doubling time scale is less than 10^5 years, considerably shorter than the disk lifetime. Following shocks near the L1 and L2 Lagrange points, disk material enters the Roche lobe in the form of two gas streams. Shocks occur within the Roche lobe as the gas stream...

  8. Numerical simulations of dissipationless disk accretion

    Science.gov (United States)

    Bogovalov, S. V.; Tronin, I. V.

    2017-09-01

    Our goal is to study the regime of disk accretion in which almost all of the angular momentum and energy is carried away by the wind outflowing from the disk in numerical experiments. For this type of accretion the kinetic energy flux in the outflowing wind can exceed considerably the bolometric luminosity of the accretion disk, what is observed in the plasma flow from galactic nuclei in a number of cases. In this paper we consider the nonrelativistic case of an outflow from a cold Keplerian disk. All of the conclusions derived previously for such a system in the self-similar approximation are shown to be correct. The numerical results agree well with the analytical predictions. The inclination angle of the magnetic field lines in the disk is less than 60°, which ensures a free wind outflow from the disk, while the energy flux per wind particle is greater than the particle rotation energy in its Keplerian orbit by several orders of magnitude, provided that the ratio r A/ r ≫ 1, where r A is the Alfvénic radius and r is the radius of the Keplerian orbit. In this case, the particle kinetic energy reaches half the maximum possible energy in the simulation region. The magnetic field collimates the outflowing wind near the rotation axis and decollimates appreciably the wind outflowing from the outer disk periphery.

  9. Dynamics of acoustically levitated disk samples.

    Science.gov (United States)

    Xie, W J; Wei, B

    2004-10-01

    The acoustic levitation force on disk samples and the dynamics of large water drops in a planar standing wave are studied by solving the acoustic scattering problem through incorporating the boundary element method. The dependence of levitation force amplitude on the equivalent radius R of disks deviates seriously from the R3 law predicted by King's theory, and a larger force can be obtained for thin disks. When the disk aspect ratio gamma is larger than a critical value gamma(*) ( approximately 1.9 ) and the disk radius a is smaller than the critical value a(*) (gamma) , the levitation force per unit volume of the sample will increase with the enlargement of the disk. The acoustic levitation force on thin-disk samples ( gammafield for stable levitation of a large water drop is to adjust the reflector-emitter interval H slightly above the resonant interval H(n) . The simulation shows that the drop is flattened and the central parts of its top and bottom surface become concave with the increase of sound pressure level, which agrees with the experimental observation. The main frequencies of the shape oscillation under different sound pressures are slightly larger than the Rayleigh frequency because of the large shape deformation. The simulated translational frequencies of the vertical vibration under normal gravity condition agree with the theoretical analysis.

  10. Lunar and Meteorite Sample Disk for Educators

    Science.gov (United States)

    Foxworth, Suzanne; Luckey, M.; McInturff, B.; Allen, J.; Kascak, A.

    2015-01-01

    NASA Johnson Space Center (JSC) has the unique responsibility to curate NASA's extraterrestrial samples from past and future missions. Curation includes documentation, preservation, preparation and distribution of samples for research, education and public outreach. Between 1969 and 1972 six Apollo missions brought back 382 kilograms of lunar rocks, core and regolith samples, from the lunar surface. JSC also curates meteorites collected from a US cooperative effort among NASA, the National Science Foundation (NSF) and the Smithsonian Institution that funds expeditions to Antarctica. The meteorites that are collected include rocks from Moon, Mars, and many asteroids including Vesta. The sample disks for educational use include these different samples. Active relevant learning has always been important to teachers and the Lunar and Meteorite Sample Disk Program provides this active style of learning for students and the general public. The Lunar and Meteorite Sample Disks permit students to conduct investigations comparable to actual scientists. The Lunar Sample Disk contains 6 samples; Basalt, Breccia, Highland Regolith, Anorthosite, Mare Regolith and Orange Soil. The Meteorite Sample Disk contains 6 samples; Chondrite L3, Chondrite H5, Carbonaceous Chondrite, Basaltic Achondrite, Iron and Stony-Iron. Teachers are given different activities that adhere to their standards with the disks. During a Sample Disk Certification Workshop, teachers participate in the activities as students gain insight into the history, formation and geologic processes of the moon, asteroids and meteorites.

  11. The Dark Disk of the Milky Way

    CERN Document Server

    Purcell, Chris W; Kaplinghat, Manoj

    2009-01-01

    Massive satellite accretions onto early galactic disks can lead to the deposition of dark matter in disk-like configurations that co-rotate with the galaxy. This phenomenon has potentially dramatic consequences for dark matter detection experiments. We utilize focused, high-resolution simulations of accretion events onto disks designed to be Galaxy analogues, and compare the resultant disks to the morphological and kinematic properties of the Milky Way's thick disk in order to bracket the range of co-rotating accreted dark matter. We find that the Milky Way's merger history must have been unusually quiescent compared to median LCDM expectations and therefore its dark disk must be relatively small: the fraction of accreted dark disk material near the Sun is about 20% of the host halo density or smaller and the co-rotating dark matter fraction near the Sun, defined as particles moving with a rotational velocity lag less than 50 km/s, is enhanced by about 30% or less compared to a standard halo model. Such a dar...

  12. The CDF Run II Disk Inventory Manager

    Institute of Scientific and Technical Information of China (English)

    PaulHubbard; StephanLammel

    2001-01-01

    The Collider Detector at Fermilab(CDF) experiment records and analyses proton-antiprotion interactions at a center-of -mass energy of 2 TeV,Run II of the Fermilab Tevatron started in April of this year,The duration of the run is expected to be over two years.One of the main data handling strategies of CDF for RUn II is to hide all tape access from the user and to facilitate sharing of data and thus disk space,A disk inventory manager was designed and developed over the past years to keep track of the data on disk.to coordinate user access to the data,and to stage data back from tape to disk as needed.The CDF Run II disk inventory manager consists of a server process,a user and administrator command line interfaces.and a library with the routines of the client API.Data are managed in filesets which are groups of one or more files.The system keeps track of user acess to the filesets and attempts to keep frequently accessed data on disk.Data that are not on disk are automatically staged back from tape as needed.For CDF the main staging method is based on the mt-tools package as tapes are written according to the ANSI standard.

  13. SPH simulations of structures in protoplanetary disks

    Science.gov (United States)

    Demidova, T. V.; Grinin, V. P.

    2017-02-01

    Using the GADGET-2 code modified by us, we have computed hydrodynamic models of a protoplanetary disk perturbed by a low-mass companion. We have considered the cases of circular and eccentric orbits coplanar with the disk and inclined relative to its midplane. During our simulations we computed the column density of test particles on the line of sight between the central star and observer. On this basis we computed the column density of circumstellar dust by assuming the dust and gas to be well mixed with a mass ratio of 1: 100. To study the influence of the disk orientation relative to the observer on the interstellar extinction, we performed our computations for four inclinations of the line of sight to the disk plane and eight azimuthal directions. The column densities in the circumstellar disk of the central star and the circumbinary disk were computed separately. Our computations have shown that periodic column density oscillations can arise in both inner and circumbinary disks. The amplitude and shape of these oscillations depend on the system's parameters (the orbital eccentricity and inclination, the component mass ratio) and its orientation in space. The results of our simulations can be used to explain the cyclic brightness variations of young UX Ori stars.

  14. Detecting circumstellar disks around gravitational microlenses

    CERN Document Server

    Hundertmark, M; Dreizler, S

    2009-01-01

    We investigate the chance of detecting proto-planetary or debris disks in stars that induce microlensing events (lenses). The modification of the light curves shapes due to occultation and extinction by the disks as well as the additional gravitational deflection caused by the additional mass is considered. The magnification of gravitational microlensing events is calculated using the ray shooting method. The occultation is taken into account by neglecting or weighting the images on the lens plane according to a transmission map of the corresponding disk for a point source point lens (PSPL) model. The estimated frequency of events is obtained by taking the possible inclinations and optical depths of the disk into account. We conclude that gravitational microlensing can be used, in principle, as a tool for detecting debris disks beyond 1 kpc, but estimate that each year of the order of 1 debris disk is expected for lens stars of F, G, or K spectral type and of the order of 10 debris disks might have shown sign...

  15. Cold Dark Matter Substructure and Galactic Disks

    CERN Document Server

    Kazantzidis, Stelios; Bullock, James S

    2008-01-01

    We perform a set of high-resolution, dissipationless N-body simulations to investigate the influence of cold dark matter (CDM) substructure on the dynamical evolution of thin galactic disks. Our method combines cosmological simulations of galaxy-sized CDM halos to derive the properties of substructure populations and controlled numerical experiments of consecutive subhalo impacts onto initially-thin, fully-formed disk galaxies. We demonstrate that close encounters between massive subhalos and galactic disks since z~1 should be common occurrences in LCDM models. In contrast, extremely few satellites in present-day CDM halos are likely to have a significant impact on the disk structure. One typical host halo merger history is used to seed controlled N-body experiments of subhalo-disk encounters. As a result of these accretion events, the disk thickens considerably at all radii with the disk scale height increasing in excess of a factor of 2 in the solar neighborhood. We show that interactions with the subhalo p...

  16. The Hot Inner Disk of FU Ori

    CERN Document Server

    Zhu, Zhaohuan; Calvet, Nuria; Hernandez, Jesus; Muzerolle, James; Tannirkulam, Ajay-Kumar

    2007-01-01

    We have constructed a detailed radiative transfer disk model which reproduces the main features of the spectrum of the outbursting young stellar object FU Orionis from ~ 4000 angstrom, to ~ 8 micron. Using an estimated visual extinction Av~1.5, a steady disk model with a central star mass ~0.3 Msun and a mass accretion rate ~ 2e-4 Msun/yr, we can reproduce the spectral energy distribution of FU Ori quite well. With the mid-infrared spectrum obtained by the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, we estimate that the outer radius of the hot, rapidly accreting inner disk is ~ 1 AU using disk models truncated at this outer radius. Inclusion of radiation from a cooler irradiated outer disk might reduce the outer limit of the hot inner disk to ~ 0.5 AU. In either case, the radius is inconsistent with a pure thermal instability model for the outburst. Our radiative transfer model implies that the central disk temperature Tc > 1000 K out to ~ 0.5 - 1 AU, suggesting that the magnetorotationa...

  17. The effects of viscosity on circumplanetary disks

    Institute of Scientific and Technical Information of China (English)

    De-Fu Bu; Hsien Shang; Feng Yuan

    2013-01-01

    The effects of viscosity on the circumplanetary disks residing in the vicinity of protoplanets are investigated through two-dimensional hydrodynamical simulations with the shearing sheet model.We find that viscosity can considerably affect properties of the circumplanetary disk when the mass of the protoplanet Mp (<) 33 M(⊙),where M(⊙) is the Earth's mass.However,effects of viscosity on the circumplanetary disk are negligibly small when the mass of the protoplanet Mp(>) 33 M(⊙).We find that when Mp(<) 33 M(⊙),viscosity can markedly disrupt the spiral structure of the gas around the planet and smoothly distribute the gas,which weakens the torques exerted on the protoplanet.Thus,viscosity can slow the migration speed of a protoplanet.After including viscosity,the size of the circumplanetary disk can be decreased by a factor of (>) 20%.Viscosity helps to transport gas into the circumplanetary disk from the differentially rotating circumstellar disk.The mass of the circumplanetary disk can be increased by a factor of 50% after viscosity is taken into account when Mp(<) 33 M(⊙).Effects of viscosity on the formation of planets and satellites are briefly discussed.

  18. Viscous Stability of Relativistic Keplerian Accretion Disks

    CERN Document Server

    Ghosh, P

    1998-01-01

    We investigate the viscous stability of thin, Keplerian accretion disks in regions where general relativistic (GR) effects are essential. For gas pressure dominated (GPD) disks, we show that the Newtonian conclusion that such disks are viscously stable is reversed by GR modifications in the behaviors of viscous stress and surface density over a significantly large annular region not far from the innermost stable orbit at $r=\\rms$. For slowly-rotating central objects, this region spans a range of radii $14\\lo r\\lo 19$ in units of the central object's mass $M$. For radiation pressure dominated (RPD) disks, the Newtonian conclusion that they are viscously unstable remains valid after including the above GR modifications, except in a very small annulus around $r\\approx 14M$, which has a negligible influence. Inclusion of the stabilizing effect of the mass-inflow through the disk's inner edge via a GR analogue of Roche-lobe overflow adds a small, stable region around \\rms~for RPD disks, but leaves GPD disks unchan...

  19. Gravitational Stirring in Planetary Debris Disks

    CERN Document Server

    Kenyon, S J; Kenyon, Scott J.; Bromley, Benjamin C.

    2001-01-01

    We describe gravitational stirring models of planetary debris disks using a new multi-annulus planetesimal evolution code. The current code includes gravitational stirring and dynamical friction; future studies will include coagulation, fragmentation, Poynting-Robertson drag, and other physical processes. We use the results of our calculations to investigate the physical conditions required for small bodies in a planetesimal disk to reach the shattering velocity and begin a collisional cascade. Our results demonstrate that disks composed primarily of bodies with a single size will not undergo a collisional cascade which produces small dust grains at 30-150 AU on timescales of 1 Gyr or smaller. Disks with a size distribution of bodies reach conditions necessary for a collisional cascade in 10 Myr to 1 Gyr if the disk is at least as massive as a minimum mass solar nebula and if the disk contains objects with radii of 500 km or larger. The estimated 500 Myr survival time for these disks is close to the median ag...

  20. Circumstellar disks around Herbig Be stars

    CERN Document Server

    Alonso-Albi, T; Bachiller, R; Neri, R; Planesas, P; Testi, L; Berne, O; Joblin, C

    2008-01-01

    We have carried out a search for circumstellar disks around Herbig Be stars using the NRAO Very Large Array (VLA) and the IRAM Plateau de Bure (PdB) interferometers. In this Paper, we present our new VLA and PdBI data on the three objects MWC 297, Z CMa and LKHa 215. We have constructed the SED from near-IR to centimeter wavelengths by adding our millimeter and centimeter data to the available data at other wavelengths, mainly Spitzer images. The whole SED has been fitted using a disk+envelope model. In addition, we have compiled all the disk millimeter observations in the literature and made some statistics. We show that the disk mass is usually only a small percentage (less than 10%) of the mass of the whole envelope in HBe stars. Concerning the disks, there are large source to source variations. Two disks of our sample, R Mon and Z CMa, have similar sizes and masses to those found in T Tauri and Herbig Ae stars. The disks around MWC 1080 and MWC 297 are, however, smaller (rout<100 AU). We have not detec...

  1. Accretion Disks around Young Low Mass Stars

    Directory of Open Access Journals (Sweden)

    Paola D´Alessio

    2001-01-01

    Full Text Available In the past decade, it has become clear that almost half of the low mass pre-main sequence stars are surrounded by disks, which are responsible for the observed infrared and optical-UV excess emission. The characterization of the structure of circumstellar disks is a crucial step towards understanding the early stellar evolution and planet formation. The thesis summarized here presents physical models of the detailed structure of accretion disks surrounding T Tauri stars. The disks are assumed to be in steady state, in vertical hydrostatic equilibrium, and with a turbulent viscosity described by the alpha-prescription. We consider different heating mechanisms: viscous dissipation, heating by cosmic rays and radioactive decay, irradiation by the central star or irradiation by an infalling envelope. The energy is transported in the vertical direction by radiation, convection and the turbulent flux. Give n the disk structure, we calculate its emission by integrating the radiative transfer equation for an arbitrary orientation of the disk relative to the line of sight. Spectral energy distributions (SEDs and images are compared with observations, and disk properties can be inferred or constrained.

  2. The $Spitzer$ infrared spectrograph survey of protoplanetary disks in Orion A: I. disk properties

    CERN Document Server

    Kim, K H; Manoj, P; Forrest, W J; Furlan, Elise; Najita, Joan; Sargent, Benjamin; Hernández, Jesús; Calvet, Nuria; Adame, Lucía; Espaillat, Catherine; Megeath, S T; Muzerolle, James; McClure, M K

    2016-01-01

    We present our investigation of 319 Class II objects in Orion A observed by $Spitzer$/IRS. We also present the follow-up observation of 120 of these Class II objects in Orion A from IRTF/SpeX. We measure continuum spectral indices, equivalent widths, and integrated fluxes that pertain to disk structure and dust composition from IRS spectra of Class II objects in Orion A. We estimate mass accretion rates using hydrogen recombination lines in the SpeX spectra of our targets. Utilizing these properties, we compare the distributions of the disk and dust properties of Orion A disks to those of Taurus disks with respect to position within Orion A (ONC and L1641) and to the sub-groups by the inferred radial structures, such as transitional disks vs. radially continuous full disks. Our main findings are as follows. (1) Inner disks evolve faster than the outer disks. (2) Mass accretion rate of transitional disks and that of radially continuous full disks are statistically significantly displaced from each other. The m...

  3. Yb Thin-Disk Laser Results

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, L E; Beach, R A; Mitchell, S; Payne, S A

    2002-05-14

    Thin-disk laser configurations have recently been demonstrated at cw output povters exceeding 1 kW [1]. Thin-disk lasers enable the generation of high average power by minimizing the distance over which waste heat is transported. A disk-laser of transverse dimensions significantly larger than its thickness will sustain laser output with intensity proportional to the thermal flux it dissipates. The fracture strength of the laser material limits the maximum temperature difference of a credible design. Further increases in the heat dissipation capacity of a disk varies inversely with the disk thickness (t) thus, the average laser output intensity of a thin/disk laser scales as 1/t; that is, to maximize the output intensity we must use the thinnest possible disk that is consistent with the pump geometry. The main challenge for the laser designer is then to coerce a thin gain sample into absorbing pump power efficiently. For this purpose, use of a highly absorbing gain medium is desirable in combination with a pumping geometry that allows multi-passing of the pump light. An important feature of the thin-disk laser is that one-dimensional thermal gradients away from the edges are made to align with the extraction beam Thus, as long as pumping and cooling fields are uniformly distributed, the contributions to wavefront error from dn/dT and the stress optic effect integrate along a 1-dimensional thermal gradient and a constant optical path-length-difference across the extent of the beam. The thin-disk laser therefore, holds promise for high beam quality at high average power.

  4. MAGNETIC FIELDS IN EARLY PROTOSTELLAR DISK FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    González-Casanova, Diego F.; Lazarian, Alexander [Astronomy Department, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706-1582 (United States); Santos-Lima, Reinaldo, E-mail: casanova@astro.wisc.edu [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090 (Brazil)

    2016-03-10

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian and Vishniac model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called “magnetic braking catastrophe.” In particular, we provide a detailed study of the dynamics of a 0.5 M{sub ⊙} protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, “reconnection diffusion,” removes the magnetic flux from the disk; the other involves the change of the magnetic field's topology, but does not change the absolute value of the magnetic flux through the disk. We demonstrate that for the first mechanism, turbulence causes a magnetic flux transport outward from the inner disk to the ambient medium, thus decreasing the coupling of the disk to the ambient material. A similar effect is achieved through the change of the magnetic field's topology from a split monopole configuration to a dipole configuration. We explore how both mechanisms prevent the catastrophic loss of disk angular momentum and compare both above turbulent reconnection mechanisms with alternative mechanisms from the literature.

  5. Total cervical disk replacement with a prestige LP® prosthesis: clinical and functional outcomes

    Directory of Open Access Journals (Sweden)

    Rafael Osório Rocha

    2014-01-01

    Full Text Available Objective: To determine the clinical and functional results of short- and medium-term cervical arthroplasty with the Prestige LP® prosthesis for the treatment of compressive myelopathy, radiculopathy and axial pain with radiculopathty. Methods: This retrospective study, conducted from 2009 to 2012, included 18 patients. Only 16 were found for the second stage of research, conducted in 2011 and 2012. Pre- and postoperative assessments were carried out using the CSOQ (Cervical Spine Outcomes Questionnaire. Odom criteria were used only in the postoperative evaluation. Both were translated and adapted to the local culture. Results: There was no postoperative radiculopathy or other complications requiring prolonged hospitalization. In most patients, there was a significant improvement in axial pain and radiculopathy, and there was only one indication of conversion to fusion. Conclusions: In selected cases of cervical degenerative disc disease, herniated cervical disc and compressive myeolopathy, cervical arthroplasty proved to be an effective and safe treatment in the short and medium terms.

  6. Simultaneous identification and quantification of tetrodotoxin in fresh pufferfish and pufferfish-based products using immunoaffinity columns and liquid chromatography/quadrupole-linear ion trap mass spectrometry

    Science.gov (United States)

    Guo, Mengmeng; Wu, Haiyan; Jiang, Tao; Tan, Zhijun; Zhao, Chunxia; Zheng, Guanchao; Li, Zhaoxin; Zhai, Yuxiu

    2016-08-01

    In this study, we established a comprehensive method for simultaneous identification and quantification of tetrodotoxin (TTX) in fresh pufferfish tissues and pufferfish-based products using liquid chromatography/quadrupole-linear ion trap mass spectrometry (LC-QqLIT-MS). TTX was extracted by 1% acetic acid-methanol, and most of the lipids were then removed by freezing lipid precipitation, followed by purification and concentration using immunoaffinity columns (IACs). Matrix effects were substantially reduced due to the high specificity of the IACs, and thus, background interference was avoided. Quantitation analysis was therefore performed using an external calibration curve with standards prepared in mobile phase. The method was evaluated by fortifying samples at 1, 10, and 100 ng/g, respectively, and the recoveries ranged from 75.8%-107%, with a relative standard deviation of less than 15%. The TTX calibration curves were linear over the range of 1-1 000 μg/L, with a detection limit of 0.3 ng/g and a quantification limit of 1 ng/g. Using this method, samples can be further analyzed using an information-dependent acquisition (IDA) experiment, in the positive mode, from a single liquid chromatography-tandem mass spectrometry injection, which can provide an extra level of confirmation by matching the full product ion spectra acquired for a standard sample with those from an enhanced product ion (EPI) library. The scheduled multiple reaction monitoring method enabled TTX to be screened for, and TTX was positively identified using the IDA and EPI spectra. This method was successfully applied to analyze a total of 206 samples of fresh pufferfish tissues and pufferfish-based products. The results from this study show that the proposed method can be used to quantify and identify TTX in a single run with excellent sensitivity and reproducibility, and is suitable for the analysis of complex matrix pufferfish samples.

  7. Preparation of Silica Gel Immunoaffinity Column for Chloramphenicol Determination%硅胶载体氯霉素免疫亲和柱的制备

    Institute of Scientific and Technical Information of China (English)

    张灿; 周婷; 陆介宇; 段玉清; 王硕; 于娇

    2012-01-01

    以硅胶为载体,通过硅烷偶联剂3-氨基丙基三乙氧基硅烷在其表面引入氨基,采用戊二醛法与氯霉素抗体进行偶联。该方法制备的免疫亲和柱对氯霉素抗体的偶联率达到72%,对氯霉素的最大吸附容量达到80ng/mL柱体积,选择含70%甲醇的PBS为洗脱溶液。以牛奶为检测对象分别采用3种不同方法进行样品处理,利用免疫亲和柱实现对样品中痕量残留的氯霉素纯化富集并进行ELISA检测。%Silica gel was used as a carrier for preparing an immunoaffinity column (IAC) to determine chloramphenicol. Amino groups were introduced to the surface of silica gel using 3-aminopropyltriethoxysilane (APTES) as a silane coupling agent and the modified silica gel was conjugated with anti-chloramphenicol antibodies using glutaraldehyde. As a result, a conjugation ratio of 72% was obtained. The maximum adsorption capacity of the prepared IAC was 80 ng/mL. The elution solvent was PBS containing 70% methanol. After sample pretreatment by three different methods, chloramphenicol residues in milk were ourified and enriched using the IAC and determined by ELISA

  8. Simultaneous identification and quantification of tetrodotoxin in fresh pufferfish and pufferfish-based products using immunoaffinity columns and liquid chromatography/quadrupole-linear ion trap mass spectrometry

    Science.gov (United States)

    Guo, Mengmeng; Wu, Haiyan; Jiang, Tao; Tan, Zhijun; Zhao, Chunxia; Zheng, Guanchao; Li, Zhaoxin; Zhai, Yuxiu

    2017-07-01

    In this study, we established a comprehensive method for simultaneous identification and quantification of tetrodotoxin (TTX) in fresh pufferfish tissues and pufferfish-based products using liquid chromatography/quadrupole-linear ion trap mass spectrometry (LC-QqLIT-MS). TTX was extracted by 1% acetic acid-methanol, and most of the lipids were then removed by freezing lipid precipitation, followed by purification and concentration using immunoaffinity columns (IACs). Matrix effects were substantially reduced due to the high specificity of the IACs, and thus, background interference was avoided. Quantitation analysis was therefore performed using an external calibration curve with standards prepared in mobile phase. The method was evaluated by fortifying samples at 1, 10, and 100 ng/g, respectively, and the recoveries ranged from 75.8%-107%, with a relative standard deviation of less than 15%. The TTX calibration curves were linear over the range of 1-1 000 μg/L, with a detection limit of 0.3 ng/g and a quantification limit of 1 ng/g. Using this method, samples can be further analyzed using an information-dependent acquisition (IDA) experiment, in the positive mode, from a single liquid chromatography-tandem mass spectrometry injection, which can provide an extra level of confirmation by matching the full product ion spectra acquired for a standard sample with those from an enhanced product ion (EPI) library. The scheduled multiple reaction monitoring method enabled TTX to be screened for, and TTX was positively identified using the IDA and EPI spectra. This method was successfully applied to analyze a total of 206 samples of fresh pufferfish tissues and pufferfish-based products. The results from this study show that the proposed method can be used to quantify and identify TTX in a single run with excellent sensitivity and reproducibility, and is suitable for the analysis of complex matrix pufferfish samples.

  9. Characterization of anti-Salmonella enterica serotype Typhi antibody responses in bacteremic Bangladeshi patients by an immunoaffinity proteomics-based technology.

    Science.gov (United States)

    Charles, Richelle C; Sheikh, Alaullah; Krastins, Bryan; Harris, Jason B; Bhuiyan, M Saruar; LaRocque, Regina C; Logvinenko, Tanya; Sarracino, David A; Kudva, Indira T; Eisenstein, Jana; Podolsky, Michael J; Kalsy, Anuj; Brooks, W Abdullah; Ludwig, Albrecht; John, Manohar; Calderwood, Stephen B; Qadri, Firdausi; Ryan, Edward T

    2010-08-01

    Salmonella enterica serotype Typhi is the cause of typhoid fever and a human-restricted pathogen. Currently available typhoid vaccines provide 50 to 90% protection for 2 to 5 years, and available practical diagnostic assays to identify individuals with typhoid fever lack sensitivity and/or specificity. Identifying immunogenic S. Typhi antigens expressed during human infection could lead to improved diagnostic assays and vaccines. Here we describe a platform immunoaffinity proteomics-based technology (IPT) that involves the use of columns charged with IgG, IgM, or IgA antibody fractions recovered from humans bacteremic with S. Typhi to capture S. Typhi proteins that were subsequently identified by mass spectrometry. This screening tool identifies immunogenic proteins recognized by antibodies from infected hosts. Using this technology and the plasma of patients with S. Typhi bacteremia in Bangladesh, we identified 57 proteins of S. Typhi, including proteins known to be immunogenic (PagC, HlyE, OmpA, and GroEL) and a number of proteins present in the human-restricted serotypes S. Typhi and S. Paratyphi A but rarely found in broader-host-range Salmonella spp. (HlyE, CdtB, PltA, and STY1364). We categorized identified proteins into a number of major groupings, including those involved in energy metabolism, protein synthesis, iron homeostasis, and biosynthetic and metabolic functions and those predicted to localize to the outer membrane. We assessed systemic and mucosal anti-HlyE responses in S. Typhi-infected patients and detected anti-HlyE responses at the time of clinical presentation in patients but not in controls. These findings could assist in the development of improved diagnostic assays.

  10. Assessment of critical points and development of a practical strategy to extend the applicable scope of immunoaffinity column cleanup for aflatoxin detection in medicinal herbs.

    Science.gov (United States)

    Zhang, Lei; Dou, Xiaowen; Kong, Weijun; Liu, Congmin; Han, Xu; Yang, Meihua

    2017-02-03

    Although extraction methods based on immunoaffinity column (IAC) cleanup have been used to detect aflatoxins in medicinal herbs, they do not yield satisfactory results for all sample matrices. The difficulty arises from the chemical complexity of the herbs, and there is a pressing need to determine which steps in IAC cleanup limit the scope of aflatoxin detection in many different kinds of medicinal herbs. In this work, we found that there were two main factors that severely decreased antibody-antigen recognition and led to serious nonspecific adsorption: (1) high extract acidity and (2) high co-extraction of interfering compounds. We therefore carried out a systematic study to optimize extraction efficiency. We found that dilution of samples in 0.1M phosphate buffer solution (pH 7.8, 2% Tween-20) at a 1:8 dilution ratio mitigated the effect of high acidity, decreased co-precipitation of compounds and nonspecific adsorption, and ameliorated the matrix effect. To validate this finding, and test if our method is widely applicable to in different kinds of herbal materials, we analyzed several representative complex sample matrices including fructus, cortex, and radix with varying extract pH values. The recovery efficiency was generally higher than 70%. We further validated our method by testing a certified reference material, and found that our approach accurately quantified aflatoxin concentration. After validation, we successfully used this method to determine the aflatoxin concentration of real samples. The approach described here could potentially be used to extract aflatoxin from other complex matrices with varying acidity. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Determination of Aflatoxins and Ochratoxin A in Ginseng and Other Botanical Roots by Immunoaffinity Column Cleanup and Liquid Chromatography with Fluorescence Detection

    Science.gov (United States)

    Trucksess, Mary; Weaver, Carol; Oles, Carolyn; D’Ovidio, Kathleen; Rader, Jeanne

    2008-01-01

    Mycotoxins are toxic secondary metabolites produced by certain molds and are common contaminants of many important food crops, such as grains, nuts, and spices. Some mycotoxins are found in fruits, vegetables, and botanical roots. These contaminants have a broad range of toxic effects, including carcinogenicity, immunotoxicity, neurotoxicity, and reproductive and developmental toxicity. The public health concerns related to both acute and chronic effects of mycotoxins in animals have prompted more than 100 countries to establish regulatory limits for some of the well-known mycotoxins, such as the aflatoxins (AFL). Our research focused on method development for 2 of these toxins, AFL and ochratoxin A (OTA), in ginseng and other selected botanical roots. Methods using an immunoaffinity column (IAC) cleanup, liquid chromatographic separation, and fluorescence detection were modified and evaluated. Two types of IAC cleanup were evaluated: IAC for AFL, and IAC for both AFL and OTA. Three derivatization techniques to enhance the fluorescence of the AFL were compared: precolumn trifluoroacetic acid, postcolumn bromination, and postcolumn ultraviolet irradiation. No derivatization was needed for OTA. Results for AFL using the single analyte IAC cleanup and the 3 derivatization techniques were all comparable for ginseng and for other roots such as ginger, licorice, and kava-kava. Recoveries of added AFL for ginseng at levels from 2 to 16 ng/g were about 80%. Using IAC cleanup for both AFL and OTA recoveries of added AFL for ginseng at 4–16 ng/g were about 70%, and for ginger, licorice, and kava-kava were about 60%. Recoveries of added OTA for ginseng, ginger, and echinacea at 4 ng/g were about 55%. PMID:16792061

  12. Mass Extinctions and a Dark Disk

    CERN Document Server

    Kramer, Eric David

    2016-01-01

    We consider whether the observed periodicity of mass extinctions and of comet impacts on Earth is consistent with Solar oscillation about the Galactic midplane and spiral arm crossings. It is of further interest to determine whether a hypothetical thin dark disk is necessary to give the right periodicity, and whether such a dark disk is allowed given kinematic and other observational constaints on the Galaxy's gravitational potential. We show that a dark disk consistent with recent bounds, combined with data for spiral arm crossing, can lead to the required periodicity. Moreover, we find that the best fit values correctly predict the date of the Chicxulub crater dated to 66 My ago.

  13. The innermost astronomical unit of protoplanetary disks

    CERN Document Server

    Kluska, J; Benisty, M

    2016-01-01

    Circumstellar disks around young stars are the birthsites of planets. It is thus fundamental to study the disks in which they form, their structure and the physical conditions therein. The first astronomical unit is of great interest because this is where the terrestrial-planets form and the angular momentum is controled via massloss through winds/jets. With its milli-arcsecond resolution, optical interferometry is the only technic able to spatially resolve the first few astronomical units of the disk. In this review, we will present a broad overview of studies of young stellar objects with interferometry, and discuss prospects for the future.

  14. Scattered light mapping of protoplanetary disks

    Science.gov (United States)

    Stolker, T.; Dominik, C.; Min, M.; Garufi, A.; Mulders, G. D.; Avenhaus, H.

    2016-12-01

    Context. High-contrast scattered light observations have revealed the surface morphology of several dozen protoplanetary disks at optical and near-infrared wavelengths. Inclined disks offer the opportunity to measure part of the phase function of the dust grains that reside in the disk surface which is essential for our understanding of protoplanetary dust properties and the early stages of planet formation. Aims: We aim to construct a method which takes into account how the flaring shape of the scattering surface of an optically thick protoplanetary disk projects onto the image plane of the observer. This allows us to map physical quantities (e.g., scattering radius and scattering angle) onto scattered light images and retrieve stellar irradiation corrected images (r2-scaled) and dust phase functions. Methods: The scattered light mapping method projects a power law shaped disk surface onto the detector plane after which the observed scattered light image is interpolated backward onto the disk surface. We apply the method on archival polarized intensity images of the protoplanetary disk around HD 100546 that were obtained with VLT/SPHERE in the R' band and VLT/NACO in the H and Ks bands. Results: The brightest side of the r2-scaled R' band polarized intensity image of HD 100546 changes from the far to the near side of the disk when a flaring instead of a geometrically flat disk surface is used for the r2-scaling. The decrease in polarized surface brightness in the scattering angle range of 40°-70° is likely a result of the dust phase function and degree of polarization which peak in different scattering angle regimes. The derived phase functions show part of a forward scattering peak, which indicates that large, aggregate dust grains dominate the scattering opacity in the disk surface. Conclusions: Projection effects of a protoplanetary disk surface need to be taken into account to correctly interpret scattered light images. Applying the correct scaling for the

  15. Patterns In Debris Disks: No Planets Required?

    Science.gov (United States)

    Kuchner, Marc

    2012-01-01

    Debris disks like those around Fomalhaut and Beta Pictoris show striking dust patterns often attributed to hidden exoplanets. These patterns have been crucial for constraining the masses and orbits of these planets. But adding a bit of gas to our models of debris disks--too little gas to detect--seems to alter this interpretation. Small amounts of gas lead to new dynamical instabilities that may mimic the narrow eccentric rings and other structures planets would create in a gas-free disk. Can we still use dust patterns to find hidden exoplanets?

  16. Millimeter Continuum Observations Of Disk Solids

    Science.gov (United States)

    Andrews, Sean

    2016-07-01

    I will offer a condensed overview of some key issues in protoplanetary disk research that makes use interferometric measurements of the millimeter-wavelength continuum emitted by their solid particles. Several lines of evidence now qualitatively support theoretical models for the growth and migration of disk solids, but also advertise a quantitative tension with the traditional efficiency of that evolution. New observations of small-scale substructures in disks might both reconcile the conflict and shift our focus in the mechanics of planet formation.

  17. Electrocatalysts Prepared by Galvanic Replacement

    OpenAIRE

    Athanasios Papaderakis; Ioanna Mintsouli; Jenia Georgieva; Sotiris Sotiropoulos

    2017-01-01

    Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, Mnoble, when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mMnoblen+ → nMm+ + mMnoble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases) hydrogen evolution too...

  18. Disk-Loss and Disk-Renewal Phases in Classical Be Stars II. Contrasting with Stable and Variable Disks

    CERN Document Server

    Draper, Zachary H; Bjorkman, Karen S; Meade, Marilyn R; Haubois, Xavier; Mota, Bruno C; Carciofi, Alex C; Bjorkman, Jon E

    2014-01-01

    Recent observational and theoretical studies of classical Be stars have established the utility of polarization color diagrams (PCD) in helping to constrain the time-dependent mass decretion rates of these systems. We expand on our pilot observational study of this phenomenon, and report the detailed analysis of a long-term (1989-2004) spectropolarimetric survey of 9 additional classical Be stars, including systems exhibiting evidence of partial disk-loss/disk-growth episodes as well as systems exhibiting long-term stable disks. After carefully characterizing and removing the interstellar polarization along the line of sight to each of these targets, we analyze their intrinsic polarization behavior. We find that many steady-state Be disks pause at the top of the PCD, as predicted by theory. We also observe sharp declines in the Balmer jump polarization for later spectral type, near edge-on steady-state disks, again as recently predicted by theory, likely caused when the base density of the disk is very high, ...

  19. Effects of inclined star-disk encounter on protoplanetary disk size

    CERN Document Server

    Bhandare, Asmita; Pfalzner, Susanne

    2016-01-01

    Most, if not all, young stars are initially surrounded by protoplanetary disks. Owing to the preferential formation of stars in stellar clusters, the protoplanetary disks around these stars may potentially be affected by the cluster environment. Various works have investigated the influence of stellar fly-bys on disks, although many of them consider only the effects due to parabolic, coplanar encounters often for equal-mass stars, which is only a very special case. We perform numerical simulations to study the fate of protoplanetary disks after the impact of parabolic star-disk encounter for the less investigated case of inclined up to coplanar, retrograde encounters, which is a much more common case. Here, we concentrate on the disk size after such encounters because this limits the size of the potentially forming planetary systems. In addition, with the possibilities that ALMA offers, now a direct comparison to observations is possible. Covering a wide range of periastron distances and mass ratios between t...

  20. Disk-cylinder and disk-sphere nanoparticles via a block copolymer blend solution construction.

    Science.gov (United States)

    Zhu, Jiahua; Zhang, Shiyi; Zhang, Ke; Wang, Xiaojun; Mays, Jimmy W; Wooley, Karen L; Pochan, Darrin J

    2013-01-01

    Researchers strive to produce nanoparticles with complexity in composition and structure. Although traditional spherical, cylindrical and membranous, or planar, nanostructures are ubiquitous, scientists seek more complicated geometries for potential functionality. Here we report the simple solution construction of multigeometry nanoparticles, disk-sphere and disk-cylinder, through a straightforward, molecular-level, blending strategy with binary mixtures of block copolymers. The multigeometry nanoparticles contain disk geometry in the core with either spherical patches along the disk periphery in the case of disk-sphere particles or cylindrical edges and handles in the case of the disk-cylinder particles. The portions of different geometry in the same nanoparticles contain different core block chemistry, thus also defining multicompartments in the nanoparticles. Although the block copolymers chosen for the blends are important for the definition of the final hybrid particles, the control of the kinetic pathway of assembly is critical for successful multigeometry particle construction.

  1. Disk Winds Driven by Magnetorotational Instability and Dispersal of Proto-Planetary Disks

    CERN Document Server

    Suzuki, T K

    2008-01-01

    By performing local three-dimensional MHD simulations of stratified accretion disks, we investigate disk winds driven by MHD turbulence. Initially given weak vertical magnetic fields are effectively amplified by magnetorotational instability and winding due to differential rotation. Large scale channel flows develop most effectively at 1.5 - 2 times the scale heights where the magnetic pressure is comparable to but slightly smaller than the gas pressure. The breakup of these channel flows drives structured disk winds by transporting the Poynting flux to the gas. These features are universally observed in the simulations of various initial fields. This disk wind process should play an essential role in the dynamical evaporation of proto-planetary disks. The breakup of channel flows also excites the momentum fluxes associated with Alfvenic and (magneto-)sonic waves toward the mid-plane, which possibly contribute to the sedimentation of small dust grains in protoplanetary disks.

  2. New Scattered Disk Object and Centaur Colors

    Science.gov (United States)

    Brucker, Melissa; Wilcox, P.; Stansberry, J.

    2013-10-01

    We report B, V, and R magnitudes for scattered disk objects and centaurs from observations taken in December 2011 and August 2013 using the Lowell Observatory Perkins Telescope with PRISM and observations taken in March 2012 at the Vatican Advanced Technology Telescope (VATT) on Mt. Graham, Arizona. Targeted scattered disk objects include 2002 CY224, 2003 UY117, 2006 QJ181, 2008 CT190, 2009 YG19, 2010 FD49, 2010 VZ98. Targeted centaurs include 2002 QX47, 2005 UJ438, 2006 UX184, and 2007 RH283. We will determine if the resultant centaur colors follow the bimodal distribution (B-R either red or gray) previously detected. We will also compare the resultant scattered disk object colors to those published for other scattered disk objects. This work is based on observations with the Perkins Telescope at Lowell Observatory, and with the VATT: The Alice P. Lennon Telescope and the Thomas J. Bannan Astrophysics Facility.

  3. Stochastic oscillations of general relativistic disks

    CERN Document Server

    Harko, Tiberiu

    2012-01-01

    We analyze the general relativistic oscillations of thin accretion disks around compact astrophysical objects interacting with the surrounding medium through non-gravitational forces. The interaction with the external medium (a thermal bath) is modeled via a friction force, and a random force, respectively. The general equations describing the stochastically perturbed disks are derived by considering the perturbations of trajectories of the test particles in equatorial orbits, assumed to move along the geodesic lines. By taking into account the presence of a viscous dissipation and of a stochastic force we show that the dynamics of the stochastically perturbed disks can be formulated in terms of a general relativistic Langevin equation. The stochastic energy transport equation is also obtained. The vertical oscillations of the disks in the Schwarzschild and Kerr geometries are considered in detail, and they are analyzed by numerically integrating the corresponding Langevin equations. The vertical displacement...

  4. Radiation-Driven Warping. 2; Nonisothermal Disks

    Science.gov (United States)

    Maloney, Philip R.; Begelman, Mitchell C.; Nowak, Michael A.

    1998-01-01

    Recent work by Pringle and by Maloney, Begelman, & Pringle has shown that geometrically thin, optically thick, accretion disks are unstable to warping driven by radiation torque from the central source. This work was confined to isothermal (i.e., surface density Sigma varies as R(sup -3/2) disks. In this paper we generalize the study of radiation-driven warping to include general power-law surface density distributions, Sigma varies as R(sup -delta).We consider the range from Delta = 3/2 (the isothermal case) to Delta = -3/2, which corresponds to a radiation-pressure-supported disk; this spans the range of surface density distributions likely to be found in real astrophysical disks. In all cases there are an infinite number of zero-crossing solutions (i.e., solutions that cross the equator), which are the physically relevant modes if the outer boundary of the disk is required to lie in a specified plane. However, unlike the isothermal disk, which is the degenerate case, the frequency eigenvalues for Delta does not equal 3/2 are all distinct. In all cases the location of the zero moves outward from the steady state (pure precession) value with increasing growth rate; thus, there is a critical minimum size for unstable disks. Modes with zeros at smaller radii are damped. The critical radius and the steady state precession rate depend only weakly on Delta. An additional analytic solution has been found for Delta = 1. The case Delta = 1 divides the solutions into two qualitatively different regimes. For Delta greater than or equal to 1, the fastest growing modes have maximum warp amplitude, close to the disk outer edge, and the ratio of Beta(sub max) to the warp amplitude at the disk inner edge, Beta(sub o), is much greater than 1. For Delta less than 1, Beta(sub max/Beta(sub o) approximately equals 1, and the warp maximum steadily approaches the origin as Delta decreases. This implies that nonlinear effects must be important if the warp extends to the disk inner edge

  5. Accretion disks around a mass with quadrupole

    CERN Document Server

    Abishev, Medeu; Quevedo, Hernando; Toktarbay, Saken

    2015-01-01

    We consider the stability properties of test particles moving along circular orbits around a mass with quadrupole. We show that the quadrupole modifies drastically the properties of an accretion disk made of such test particles.

  6. Foundations of Black Hole Accretion Disk Theory

    National Research Council Canada - National Science Library

    Abramowicz, Marek A; Fragile, P. Chris

    2013-01-01

    This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves...

  7. Analytic Creep Durability of Rotating Uniform Disks

    Directory of Open Access Journals (Sweden)

    Yuriy Nyashin

    1998-01-01

    Full Text Available Turbine disks of aircraft engines in operation are subjected to alternating thermocyclic deformation under high temperatures. Operation gives rise to sufficiently high stresses and subsequent creep damaging effects.

  8. Magnetohydrodynamic Origin of Jets from Accretion Disks

    CERN Document Server

    Lovelace, R V E; Koldoba, A V

    1999-01-01

    A review is made of recent magnetohydrodynamic (MHD) theory and simulations of origin of jets from accretion disks. Many compact astrophysical objects emit powerful, highly-collimated, oppositely directed jets. Included are the extra galactic radio jets of active galaxies and quasars, and old compact stars in binaries, and emission line jets in young stellar objects. It is widely thought that these different jets arise from rotating, conducting accretion disks threaded by an ordered magnetic field. The twisting of the magnetic field by the rotation of the disk drives the jets by magnetically extracting matter, angular momentum, and energy from the accretion disk. Two main regimes have been discussed theoretically, hydromagnetic winds which have a significant mass flux, and Poynting flux jets where the mass flux is negligible. Over the past several years, exciting new developments on models of jets have come from progress in MHD simulations which now allow the study of the origin - the acceleration and collima...

  9. Interstellar Gas and a Dark Disk

    Science.gov (United States)

    Kramer, Eric David; Randall, Lisa

    2016-10-01

    We introduce a potentially powerful method for constraining or discovering a thin dark matter disk in the Milky Way. The method relies on the relationship between the midplane densities and scale heights of interstellar gas being determined by the gravitational potential, which is sensitive to the presence of a dark disk. We show how to use the interstellar gas parameters to set a bound on a dark disk and discuss the constraints suggested by the current data. However, current measurements for these parameters are discordant, with the uncertainty in the constraint being dominated by the molecular hydrogen midplane density measurement, as well as by the atomic hydrogen velocity dispersion measurement. Magnetic fields and cosmic ray pressure, which are expected to play a role, are uncertain as well. The current models and data are inadequate to determine the disk's existence, but taken at face value, may favor its existence depending on the gas parameters used.

  10. Observations of Solids in Protoplanetary Disks

    CERN Document Server

    Andrews, Sean M

    2015-01-01

    This review addresses the state of research that employs astronomical (remote sensing) observations of solids ("dust") in young circumstellar disks to learn about planet formation. The intention is for it to serve as an accessible, introductory, pedagogical resource for junior scientists interested in the subject. After some historical background and a basic observational primer, the focus is shifted to the three fundamental topics that broadly define the field: (1) demographics -- the relationships between disk properties and the characteristics of their environments and hosts; (2) structure -- the spatial distribution of disk material and its associated physical conditions and composition; and (3) evolution -- the signposts of key changes in disk properties, including the growth and migration of solids and the impact of dynamical interactions with young planetary systems. Based on the state of the art results in these areas, suggestions are made for potentially fruitful lines of work in the near future.

  11. Accretion disks around a mass with quadrupole

    Science.gov (United States)

    Abishev, M.; Boshkayev, K.; Quevedo, H.; Toktarbay, S.

    We consider the stability properties of circular orbits of test particles moving around a mass with quadrupole. We show that the quadrupole modifies drastically the properties of an accretion disk made of such test particles.

  12. Open clusters and the galactic disk

    CERN Document Server

    Roeser, Siegfried; Piskunov, Anatoly E; Schilbach, Elena; Scholz, Ralf-Dieter; Zinnecker, Hans

    2010-01-01

    It is textbook knowledge that open clusters are conspicuous members of the thin disk of our Galaxy, but their role as contributors to the stellar population of the disk was regarded as minor. Starting from a homogenous stellar sky survey, the ASCC-2.5, we revisited the population of open clusters in the solar neighbourhood from scratch. In the course of this enterprise we detected 130 formerly unknown open clusters, constructed volume- and magnitude-limited samples of clusters, re-determined distances, motions, sizes, ages, luminosities and masses of 650 open clusters. We derived the present-day luminosity and mass functions of open clusters (not the stellar mass function in open clusters), the cluster initial mass function CIMF and the formation rate of open clusters. We find that open clusters contributed around 40 percent to the stellar content of the disk during the history of our Galaxy. Hence, open clusters are important building blocks of the Galactic disk.

  13. Disks, accretion and outflows of brown dwarfs

    CERN Document Server

    Joergens, V; Liu, Y; Pascucci, I; Whelan, E; Alcala, J; Biazzo, K; Costigan, G; Gully-Santiago, M; Henning, Th; Natta, A; Rigliaco, E; Rodriguez-Ledesma, V; Sicilia-Aguilar, A; Tottle, J; Wolf, S

    2012-01-01

    Characterization of the properties of young brown dwarfs are important to constraining the formation of objects at the extreme low-mass end of the IMF. While young brown dwarfs share many properties with solar-mass T Tauri stars, differences may be used as tests of how the physics of accretion/outflow and disk chemistry/dissipation depend on the mass of the central object. This article summarizes the presentations and discussions during the splinter session on 'Disks, accretion and outflows of brown dwarfs' held at the CoolStars17 conference in Barcelona in June 2012. Recent results in the field of brown dwarf disks and outflows include the determination of brown dwarf disk masses and geometries based on Herschel far-IR photometry (70-160 um), accretion properties based on X-Shooter spectra, and new outflow detections in the very low-mass regime.

  14. Carbon isotope fractionation in protoplanetary disks

    CERN Document Server

    Woods, Paul M

    2008-01-01

    We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the UV radiation field. We discuss inner-disk chemistry in general, obtaining excellent agreement with recent observations which have probed the material in the inner regions of protoplanetary disks. We also apply our model to study the isotopic fractionation of carbon. Results show that the fractionation ratio, 12C/13C, of the system varies with radius and height in the disk. Different behaviour is seen in the fractionation of different species. We compare our results with 12C/13C ratios in the Solar System comets, and find a stark contrast, indicative of reprocessing.

  15. Ionization and Dust Charging in Protoplanetary Disks

    CERN Document Server

    Ivlev, A V; Caselli, P

    2016-01-01

    Ionization-recombination balance in dense interstellar and circumstellar environments is a key factor for a variety of important physical processes, such as chemical reactions, dust charging and coagulation, coupling of the gas with magnetic field and the development of magnetorotational instability in protoplanetary disks. We present a self-consistent analytical model which allows us to exactly calculate abundances of charged species in dusty gas, in the regime where the dust-phase recombination dominates over the gas-phase recombination. The model is employed to verify applicability of a conventional approximation of low dust charges in protoplanetary disks, and to discuss the implications for the dust coagulation and the development of the "dead zone" in the disk. Furthermore, the importance of mutually consistent models for the ionization and dust evolution is addressed: These processes are coupled via several mechanisms operating in the disk, and therefore their interplay can be crucial for the ultimate ...

  16. Exact Relativistic Magnetized Haloes around Rotating Disks

    Directory of Open Access Journals (Sweden)

    Antonio C. Gutiérrez-Piñeres

    2015-01-01

    Full Text Available The study of the dynamics of magnetic fields in galaxies is one of important problems in formation and evolution of galaxies. In this paper, we present the exact relativistic treatment of a rotating disk surrounded by a magnetized material halo. The features of the halo and disk are described by the distributional energy-momentum tensor of a general fluid in canonical form. All the relevant quantities and the metric and electromagnetic potentials are exactly determined by an arbitrary harmonic function only. For instance, the generalized Kuzmin-disk potential is used. The particular class of solutions obtained is asymptotically flat and satisfies all the energy conditions. Moreover, the motion of a charged particle on the halo is described. As far as we know, this is the first relativistic model describing analytically the magnetized halo of a rotating disk.

  17. Moving Mesh Cosmology: Properties of Gas Disks

    CERN Document Server

    Torrey, Paul; Sijacki, Debora; Springel, Volker; Hernquist, Lars

    2011-01-01

    We compare the structural properties of galaxies formed in cosmological simulations using the smoothed particle hydrodynamics (SPH) code GADGET with those using the moving-mesh code AREPO. Both codes employ identical gravity solvers and the same sub-resolution physics but use very different methods to track the hydrodynamic evolution of gas. This permits us to isolate the effects of the hydro solver on the formation and evolution of galactic disks. In a matching sample of GADGET and AREPO haloes we fit simulated gas disks with exponential profiles. We find that the cold gas disks formed using AREPO have systematically larger disk scale lengths and higher specific angular momenta than their GADGET counterparts. The reason for these differences is rooted in the inaccuracies of the SPH solver and calls for a reassessment of commonly adopted feedback prescriptions in cosmological simulations.

  18. Herman's condition and Siegel disks of polynomials

    CERN Document Server

    Chéritat, Arnaud

    2011-01-01

    Herman proved the presence of critical points on the boundary of Siegel disks of unicritical polynomials under some diophantine condition now called the Herman condition. We extend this result to polynomials with two critical points.

  19. Minimally invasive aortic valve replacement

    DEFF Research Database (Denmark)

    Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

    2009-01-01

    In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy....... The 30-day mortality rate for the 98 patients was zero, although 14 of the 98 mini-sternotomies had to be converted to complete sternotomies intraoperatively due to technical problems. Such conversion doubled the operative time over that of the planned full sternotomies. In the group of patients whose...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

  20. The Debris Disk Explorer: a balloon-borne coronagraph for observing debris disks

    CERN Document Server

    Roberts, Lewis C; Traub, Wesley; Unwin, Stephen; Trauger, John; Krist, John; Aldrich, Jack; Brugarolas, Paul; Stapelfeldt, Karl; Wyatt, Mark; Stuchlik, David; Lanzi, James

    2013-01-01

    The Debris Disk Explorer (DDX) is a proposed balloon-borne investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. DDX will measure the size, shape, brightness, and color of tens of disks. These measurements will enable us to place the Solar System in context. By imaging debris disks around nearby stars, DDX will reveal the presence of perturbing planets via their influence on disk structure, and explore the physics and history of debris disks by characterizing the size and composition of disk dust. The DDX instrument is a 0.75-m diameter off-axis telescope and a coronagraph carried by a stratospheric balloon. DDX will take high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Two flights are planned; an overnight test flight within the United States followed by a month-long science flight launched from New Zealand. The long flight will fully explore the set of known de...

  1. A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective

    CERN Document Server

    Silverberg, Steven M; Wisniewski, John P; Gagne, Jonathan; Bans, Alissa S; Bhattacharjee, Shambo; Currie, Thayne R; Debes, John R; Biggs, Joseph R; Bosch, Milton; Doll, Katharina; Durantini-Luca, Hugo A; Enachioaie, Alexandru; Griffith,, Philip; Hyogo, Michiharu; Piniero, Fernanda

    2016-01-01

    We used the Disk Detective citizen science project and the BANYAN II Bayesian analysis tool to identify a new candidate member of a nearby young association with infrared excess. WISE J080822.18-644357.3, an M5.5-type debris disk system with significant excess at both 12 and 22 $\\mu$m, is a likely member ($\\sim 90\\%$ BANYAN II probability) of the $\\sim 45$ Myr-old Carina association. Since this would be the oldest M dwarf debris disk detected in a moving group, this discovery could be an important constraint on our understanding of M dwarf debris disk evolution.

  2. A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective

    Science.gov (United States)

    Silverberg, Steven M.; Kuchner, Marc J.; Wisniewski, John P.; Gagne, Jonathan; Bans, Alissa S.; Bhattacharjee, Shambo; Currie, Thayne R.; Debes, John R.; Biggs, Joseph R; Bosch, Milton

    2016-01-01

    We used the Disk Detective citizen science project and the BANYAN II Bayesian analysis tool to identify a new candidate member of a nearby young association with infrared excess. WISE J080822.18-644357.3, an M5.5-type debris disk system with significant excess at both 12 and 22 microns, is a likely member (approx.90% BANYAN II probability) of the approx.45 Myr old Carina association. Since this would be the oldest M dwarf debris disk detected in a moving group, this discovery could be an important constraint on our understanding of M dwarf debris disk evolution.

  3. YottaYotta announces new world record set for TCP disk-to-disk bulk transfer

    CERN Multimedia

    2002-01-01

    The Yottabyte NetStorage(TM) Company, today announced a new world record for TCP disk-to-disk data transfer using the company's NetStorager(R) System. The record-breaking demonstration transferred 5 terabytes of data between Chicago, Il. to Vancouver, BC and Ottawa, ON, at a sustained average throughput of 11.1 gigabits per second. Peak throughput exceeded 11.6 gigabits per second, more than 15-times faster than previous records for TCP transfer from disk-to-disk (1 page).

  4. A Search for Extended Ultraviolet Disk (XUV-disk) Galaxies in the Local Universe

    CERN Document Server

    Thilker, David A; Meurer, Gerhardt; de Paz, Armando Gil; Boissier, Samuel; Madore, Barry F; Boselli, Alessandro; Ferguson, Annette M N; Muńoz-Mateos, Juan Carlos; Madsen, Greg J; Hameed, Salman; Overzier, Roderik A; Forster, Karl; Friedman, Peter G; Martin, D Christopher; Morrissey, Patrick; Neff, Susan G; Schiminovich, David; Seibert, Mark; Small, Todd; Wyder, Ted K; Donas, Jose; Heckman, Timothy M; Lee, Young-Wook; Milliard, Bruno; Rich, R Michael; Szalay, A S; Welsh, Barry Y; Yi, Sukyoung K

    2007-01-01

    We have initiated a search for extended ultraviolet disk (XUV-disk) galaxies in the local universe. Herein, we compare GALEX UV and visible--NIR images of 189 nearby (D$<$40 Mpc) S0--Sm galaxies included in the GALEX Atlas of Nearby Galaxies and present the first catalogue of XUV-disk galaxies. We find that XUV-disk galaxies are surprisingly common but have varied relative (UV/optical) extent and morphology. Type~1 objects ($\\ga$20% incidence) have structured, UV-bright/optically-faint emission features in the outer disk, beyond the traditional star formation threshold. Type~2 XUV-disk galaxies ($\\sim$10% incidence) exhibit an exceptionally large, UV-bright/optically-low-surface-brightness (LSB) zone having blue $UV-K_s$ outside the effective extent of the inner, older stellar population, but not reaching extreme galactocentric distance. If the activity occuring in XUV-disks is episodic, a higher fraction of present-day spirals could be influenced by such outer disk star formation. Type~1 disks are associa...

  5. A Note on Disk Drag Dynamics

    CERN Document Server

    Gunther, Neil J

    2012-01-01

    The electrical power consumed by typical magnetic hard disk drives (HDD) not only increases linearly with the number of spindles but, more significantly, it increases as very fast power-laws of speed (RPM) and diameter. Since the theoretical basis for this relationship is neither well-known nor readily accessible in the literature, we show how these exponents arise from aerodynamic disk drag and discuss their import for green storage capacity planning.

  6. Gas dynamics for accretion disk simulations

    Science.gov (United States)

    Whitehurst, R.

    1994-01-01

    The behavior of accretion disks can largely be understood in terms of the basic physical processes of mass, energy, and momentum conservation. Despite this, detailed modeling of these systems using modern computational techniques is challenging and controversial. Disturbing differences exist between methods used widely in astrophysics, namely Eulerian finite-difference techniques and particle codes such as SPH. Therefore neither technique is fully satisfactory for accretion disk simulations. This paper describes a new fully Lagrangian method designed to resolve these difficulties.

  7. Variational thermodynamics of relativistic thin disks

    Science.gov (United States)

    Gutiérrez-Piñeres, Antonio C.; Lopez-Monsalvo, Cesar S.; Quevedo, Hernando

    2015-12-01

    We present a relativistic model describing a thin disk system composed of two fluids. The system is surrounded by a halo in the presence of a non-trivial electromagnetic field. We show that the model is compatible with the variational multifluid thermodynamics formalism, allowing us to determine all the thermodynamic variables associated with the matter content of the disk. The asymptotic behavior of these quantities indicates that the single fluid interpretation should be abandoned in favor of a two-fluid model.

  8. Shock Waves in Dense Hard Disk Fluids

    OpenAIRE

    Sirmas, Nick; Tudorache, Marion; Barahona, Javier; Radulescu, Matei I.

    2011-01-01

    Media composed of colliding hard disks (2D) or hard spheres (3D) serve as good approximations for the collective hydrodynamic description of gases, liquids and granular media. In the present study, the compressible hydrodynamics and shock dynamics are studied for a two-dimensional hard-disk medium at both the continuum and discrete particle level descriptions. For the continuum description, closed form analytical expressions for the inviscid hydrodynamic description, shock Hugoniot, isentropi...

  9. Improved Thermal-Switch Disks Protect Batteries

    Science.gov (United States)

    Darcy, Eric; Bragg, Bobby

    1990-01-01

    Improved thermal-switch disks help protect electrical batteries against high currents like those due to short circuits or high demands for power in circuits supplied by batteries. Protects batteries against excessive temperatures. Centered by insulating fiberglass washer. Contains conductive polymer that undergoes abrupt increase in electrical resistance when excessive current raises its temperature above specific point. After cooling, polymer reverts to low resistance. Disks reusable.

  10. Circumstellar disks during various evolutionary stages

    CERN Document Server

    Oudmaijer, Rene D

    2013-01-01

    Disks are ubiquitous in stellar astronomy, and play a crucial role in the formation and evolution of stars. In this contribution we present an overview of the most recent results, with emphasis on high spatial and spectral resolution. We will start with a general discussion on direct versus indirect detection of disks, and then traverse the HR diagram starting with the pre-Main Sequence and ending with evolved stars.

  11. Multiplication operators on Sobolev disk algebra

    Institute of Scientific and Technical Information of China (English)

    WANG; Zongyao

    2005-01-01

    In this paper, we study the algebra consisting of analytic functions in the Sobolev space W2,2(D) (D is the unit disk), called the Sobolev disk algebra, explore the properties of the multiplication operators Mf on it and give the characterization of the commutant algebra A'(Mf) of Mf. We show that A'(Mf) is commutative if and only if Mf* is a Cowen-Douglas operator of index 1.

  12. HD95881 : a gas rich to gas poor transition disk?

    NARCIS (Netherlands)

    Verhoeff, A. P.; Min, M.; Acke, B.; van Boekel, R.; Pantin, E.; Waters, L. B. F. M.; Tielens, A. G. G. M.; van den Ancker, M. E.; Mulders, G. D.; de Koter, A.; Bouwman, J.

    2010-01-01

    Context. Based on the far infrared excess the Herbig class of stars is divided into a group with flaring circumstellar disks (group I) and a group with flat circumstellar disks (group II). Dust sedimentation is generally proposed as an evolution mechanism to transform flaring disks into flat disks.

  13. HD 95881: a gas rich to gas poor transition disk?

    NARCIS (Netherlands)

    Verhoeff, A.P.; Min, M.; Acke, B.; van Boekel, R.; Pantin, E.; Waters, L.B.F.M.; Tielens, A.G.G.M.; van den Ancker, M.E.; Mulders, G.D.; de Koter, A.; Bouwman, J.

    2010-01-01

    Context. Based on the far infrared excess the Herbig class of stars is divided into a group with flaring circumstellar disks (group I) and a group with flat circumstellar disks (group II). Dust sedimentation is generally proposed as an evolution mechanism to transform flaring disks into flat disks.

  14. HD95881 : a gas rich to gas poor transition disk?

    NARCIS (Netherlands)

    Verhoeff, A. P.; Min, M.; Acke, B.; van Boekel, R.; Pantin, E.; Waters, L. B. F. M.; Tielens, A. G. G. M.; van den Ancker, M. E.; Mulders, G. D.; de Koter, A.; Bouwman, J.

    2010-01-01

    Context. Based on the far infrared excess the Herbig class of stars is divided into a group with flaring circumstellar disks (group I) and a group with flat circumstellar disks (group II). Dust sedimentation is generally proposed as an evolution mechanism to transform flaring disks into flat disks.

  15. HD 95881: A gas rich to gas poor transition disk?

    NARCIS (Netherlands)

    Verhoeff, A. P.; Min, M.; Acke, B.; Van Boekel, R.; Pantin, E.; Waters, L.B.F.M.; Tielens, A. G. G. M.; Van Den Ancker, M. E.; Mulders, G. D.; de Koter, A.; Bouwman, J.

    2010-01-01

    Context. Based on the far infrared excess the Herbig class of stars is divided into a group with flaring circumstellar disks (group I) and a group with flat circumstellar disks (group II). Dust sedimentation is generally proposed as an evolution mechanism to transform flaring disks into flat disks.

  16. Tilt, Warp, and Simultaneous Precessions in Disks

    CERN Document Server

    Montgomery, M M

    2012-01-01

    Warps are suspected in disks around massive compact objects. However, the proposed warping source -- non-axisymmetric radiation pressure -- does not apply to white dwarfs. In this letter we report the first Smoothed Particle Hydrodynamic simulations of accretion disks in SU UMa-type systems that naturally tilt, warp, and simultaneously precess in the prograde and retrograde directions using white dwarf V344 Lyrae in the Kepler field as our model. After ~79 days in V344 Lyrae, the disk angular momentum L_d becomes misaligned to the orbital angular momentum L_o. As the gas stream remains normal to L_o, hydrodynamics (e.g., the lift force) is a likely source to disk tilt. In addition to tilt, the outer disk annuli cyclically change shape from circular to highly eccentric due to tidal torques by the secondary star. The effect of simultaneous prograde and retrograde precession is a warp of the colder, denser midplane as seen along the disk rim. The simulated rate of apsidal advance to nodal regression per orbit ne...

  17. Instability of counter-rotating stellar disks

    Science.gov (United States)

    Hohlfeld, R. G.; Lovelace, R. V. E.

    2015-09-01

    We use an N-body simulation, constructed using GADGET-2, to investigate an accretion flow onto an astrophysical disk that is in the opposite sense to the disk's rotation. In order to separate dynamics intrinsic to the counter-rotating flow from the impact of the flow onto the disk, we consider an initial condition in which the counter-rotating flow is in an annular region immediately exterior the main portion of the astrophysical disk. Such counter-rotating flows are seen in systems such as NGC 4826 (known as the "Evil Eye Galaxy"). Interaction between the rotating and counter-rotating components is due to two-stream instability in the boundary region. A multi-armed spiral density wave is excited in the astrophysical disk and a density distribution with high azimuthal mode number is excited in the counter-rotating flow. Density fluctuations in the counter-rotating flow aggregate into larger clumps and some of the material in the counter-rotating flow is scattered to large radii. Accretion flow processes such as this are increasingly seen to be of importance in the evolution of multi-component galactic disks.

  18. An MCMC Circumstellar Disks Modeling Tool

    Science.gov (United States)

    Wolff, Schuyler; Perrin, Marshall D.; Mazoyer, Johan; Choquet, Elodie; Soummer, Remi; Ren, Bin; Pueyo, Laurent; Debes, John H.; Duchene, Gaspard; Pinte, Christophe; Menard, Francois

    2016-01-01

    We present an enhanced software framework for the Monte Carlo Markov Chain modeling of circumstellar disk observations, including spectral energy distributions and multi wavelength images from a variety of instruments (e.g. GPI, NICI, HST, WFIRST). The goal is to self-consistently and simultaneously fit a wide variety of observables in order to place constraints on the physical properties of a given disk, while also rigorously assessing the uncertainties in the derived properties. This modular code is designed to work with a collection of existing modeling tools, ranging from simple scripts to define the geometry for optically thin debris disks, to full radiative transfer modeling of complex grain structures in protoplanetary disks (using the MCFOST radiative transfer modeling code). The MCMC chain relies on direct chi squared comparison of model images/spectra to observations. We will include a discussion of how best to weight different observations in the modeling of a single disk and how to incorporate forward modeling from PCA PSF subtraction techniques. The code is open source, python, and available from github. Results for several disks at various evolutionary stages will be discussed.

  19. A Primer on Unifying Debris Disk Morphologies

    CERN Document Server

    Lee, Eve J

    2016-01-01

    A "minimum model" for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: "rings," "needles," "ships-and-wakes," "bars," and "moths (a.k.a. fans)," depending on the viewing geometry. Moths can also sport "double wings." We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, disk inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intui...

  20. Disk generator, its status and its potential

    Energy Technology Data Exchange (ETDEWEB)

    Louis, J.F.

    1984-01-01

    The MHD disk generator has been used as an experimental tool to study plasma properties and to explore new diagnostic techniques, since it provides a near-ideal geometry for plasma studies due to its electrodeless configuration combined with near-perfect insulating walls. Both experimental and theoretical studies have also determined the conditions for favorable performance of the disk, often with inlet swirl, as a configuration for electrical power generation in both open- and closed-cycle applications. This paper describes the state-of-the-art of the disk geometry for power generation, and it also reviews recent system studies which have integrated the disk generator in electrical power plants using coal as a fuel. These studies indicate that the disk system can achieve overall efficiencies comparable to linear generator systems, but they also show that the disk configuration might provide significant reliability and require lower capital investments. These cost advantages are derived from the simplicity of the superconducting magnet and power management systems.

  1. Vertical Structure of Magnetized Accretion Disks around Young Stars

    CERN Document Server

    Lizano, S; Boehler, Y; D'Alessio, P

    2015-01-01

    We model the vertical structure of magnetized accretion disks subject to viscous and resistive heating, and irradiation by the central star. We apply our formalism to the radial structure of magnetized accretion disks threaded by a poloidal magnetic field dragged during the process of star formation developed by Shu and coworkers. We consider disks around low mass protostars, T Tauri, and FU Orionis stars. We consider two levels of disk magnetization, $\\lambda_{sys} = 4$ (strongly magnetized disks), and $\\lambda_{sys} = 12$ (weakly magnetized disks). The rotation rates of strongly magnetized disks have large deviations from Keplerian rotation. In these models, resistive heating dominates the thermal structure for the FU Ori disk. The T Tauri disk is very thin and cold because it is strongly compressed by magnetic pressure; it may be too thin compared with observations. Instead, in the weakly magnetized disks, rotation velocities are close to Keplerian, and resistive heating is always less than 7\\% of the visc...

  2. The Birth of Disks Around Protostars

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    The dusty disks around young stars make the news regularly due to their appeal as the birthplace of early exoplanets. But how do disks like these first form and evolve around their newly born protostars? New observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are helping us to better understand this process.Formation from CollapseStars are born from the gravitational collapse of a dense cloud of molecular gas. Long before they start fusing hydrogen at their centers when they are still just hot overdensities in the process of contracting we call them protostars. These low-mass cores are hidden at the hearts of the clouds of molecular gas from which they are born.Aerial image of the Atacama Large Millimeter/submillimeter Array. [EFE/Ariel Marinkovic]During this contraction phase, before a protostar transitions to a pre-main-sequence star (which it does by blowing away its outer gas envelope, halting the stars growth), much of the collapsing material will spin into a centrifugally supported Keplerian disk that surrounds the young protostar. Later, these circumstellar disks will become the birthplace for young planets something for which weve seen observational evidence in recent years.But how do these Keplerian disks which eventually have scales of hundreds of AU first form and grow around protostars? We need observations of these disks in their early stages of formation to understand their birth and evolution a challenging prospect, given the obscuring molecular gas that hides them at these stages. ALMA, however, is up to the task: it can peer through to the center of the gas clouds to see the emission from protostellar cores and their surroundings.ALMA observations of the protostar Lupus 3 MMS. The molecular outflows from the protostar are shown in panel a. Panel b shows the continuum emission, which has a compact component that likely traces a disk surrounding the protostar. [Adapted from Yen et al. 2017]New Disks Revealed?In a recent

  3. Geometrical Structures of Chemically Decomposed Thick and Thin Disk Populations

    Science.gov (United States)

    Kawata, D.; Brook, C. B.; Rahimi, A.; Gibson, B. K.

    2016-10-01

    We summarize the thick and thin disk formation commonly seen in cosmological N-body simulations. As suggested in Brook et al. (2004), a hierarchical clustering scenario causes multiple minor gas-rich mergers, and leads to the formation of a kinematically hot disk, thick disk population, at a high redshift. Once the mergers become less significant at a later epoch, the thin disk population starts building up. Because in this scenario the thick disk population forms intensively at high redshift through multiple gas-rich mergers, the thick disk population is compact and has systematically higher [α/Fe] abundance than the thin disk population. We discuss that the thick disk population would be affected by the formation of the thin disk and suffer from the radial migration, which helps the thick disk population to be observed in the solar neighborhood. In addition, we show that the current cosmological simulations also naturally predict that the thin disk population is flaring at the outer region. As shown in Rahimi et al. (2014), at high vertical height from the disk plane, the compact thick disk population (low metallicity and high [α/Fe]) is dominant in the inner region and the flaring thin disk population (high metallicity and low [α/Fe]) contributes more in the outer region. This helps to explain the positive radial metallicity gradient and negative radial [α/Fe] gradient observed at high vertical height in the Milky Way stellar disk.

  4. Thermal Test on Target with Pressed Disks

    Energy Technology Data Exchange (ETDEWEB)

    Woloshun, Keith Albert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dale, Gregory E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Olivas, Eric Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Romero, Frank Patrick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalmas, Dale Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chemerisov, Sergey [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gromov, Roman [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lowden, Rick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-27

    A thorough test of the thermal performance of a target for Mo99 production using solid Mo100 target to produce the Mo99 via a gamma-n reaction has previously been conducted at Argonne National Laboratory (ANL). The results are reported in “Zero Degree Line Mo Target Thermal Test Results and Analysis,” LANL report Number LA-UR-15-23134 dated 3/27/15. This target was comprised of 25 disks 1 mm thick and 12 mm in diameter, separated by helium coolant gaps 0.5 mm wide. The test reported in the above referenced report was conducted with natural Mo disks all cut from commercial rod. The production plant will have Mo100 disks pressed and sintered using a process being developed at Oak Ridge National Laboratory (ORNL). The structural integrity of press-and-sinter disks is of some concern. The test reported herein included 4 disks made by the ORNL process and placed in the high heat, and therefore high thermal stress, region of the target. The electron beam energy was 23 MeV for these tests. Beam spot size was 3.5 mm horizontal and 3 mm vertical, FWHM. The thermal stress test of pressed-and-sintered disks resulted in no mechanical failures. The induced thermal stresses were below yield stress for natural Mo, indicating that up to that stress state no inherent deficiencies in the mechanical properties of the fabricated disks were evident.

  5. Corrosion fatigue of bladed disk attachments of low-pressure turbine

    Energy Technology Data Exchange (ETDEWEB)

    Asai, K. [Material Research Lab., Hitachi, Ltd., Hitachi (Japan); Sakurai, S.; Nomura, K. [Thermal Power and Hydroelectric Systems Div., Hitachi, Ltd., Hitachi (Japan); Saito, E.; Namura, K. [Power and Industrial Systems R and D Lab., Hitachi, Ltd., Hitachi (Japan)

    2004-07-01

    The mechanism of a disk cracking in a low-pressure steam turbine was investigated by finite-element and fracture mechanics analysis and, based on the results of the investigation, a life assessment method was derived. The disk cracking was found to be caused by growth of corrosion pits, superposition of multiple vibration modes, and an increase in the standard deviation of the natural frequency of grouped blades after long-term operation. Taking these findings into consideration, the authors then developed a life-assessment method for disk cracking composed of evaluations (1) maximum corrosion pit size at the current situation, (2) corrosion pit growth after a certain term, and (3) failure-occurrence ratio for the estimated corrosion pit depth. Maximum corrosion-pit size is evaluated by extreme value statistical analysis using the data obtained by replica inspection. The failure-occurrence ratio is evaluated by Monte Carlo simulation considering two uncertainties, namely, the standard deviation of the natural frequency of grouped blades and the stimulus ratio. The values of both uncertainties were determined by the inverse problem analysis of the disk cracking. In light of these results, the authors found that replacing conventional tenon-shroud grouped blades with continuous-cover blades is effective from the view point of vibratory behavior. (orig.)

  6. Knee Replacement: What you can Expect

    Science.gov (United States)

    ... improves function lessen with each additional surgery. Artificial knees can wear out Another risk of knee replacement ... replacement surgery to last about two hours. After knee replacement surgery After surgery, you're wheeled to ...

  7. Disk Radii and Grain Sizes in Herschel-Resolved Debris Disks

    CERN Document Server

    Pawellek, Nicole; Marshall, Jonathan P; Montesinos, Benjamin; Ábrahám, Péter; Moór, Attila; Bryden, Geoffrey; Eiroa, Carlos

    2014-01-01

    (Abridged) The radii of debris disks and the sizes of their dust grains are tracers of the formation mechanisms and physical processes operating in these systems. We use a sample of 34 debris disks spatially resolved in various Herschel programs to constrain them. While we modeled disks with both warm and cold components, we focus our analysis only on the cold outer disks, i.e. Kuiper-belt analogs. The disk radii derived from the resolved images reveal a large dispersion, but no significant trend with the stellar luminosity, which argues against ice lines as a dominant player in setting the debris disk sizes. Fixing the disk radii to those inferred from the resolved images, we model the spectral energy distributions to determine the dust temperatures and the grain size distributions. While the dust temperature systematically increases towards earlier spectral types, its ratio to the blackbody temperature at the disk radius decreases with the stellar luminosity. This is explained by an increase of typical grai...

  8. Cold disks : Spitzer spectroscopy of disks around young stars with large gaps

    NARCIS (Netherlands)

    Blake, G. A.; Dullemond, C. P.; Merin, B.; Augereau, J. C.; Boogert, A. C. A.; Evans, N. J.; Geers, V. C.; Lahuis, F.; Kessler-Silacci, J. E.; Pontoppidan, K. M.; van Dishoeck, E. F.; Brown, J.M.

    2007-01-01

    We have identified four circumstellar disks with a deficit of dust emission from their inner 15-50 AU. All four stars have F-G spectral type and were uncovered as part of the Spitzer Space Telescope "Cores to Disks" Legacy Program Infrared Spectrograph (IRS) first-look survey of similar to 100 pre -

  9. Failure characterization at head/disk interface of hard disk drive

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The characterization of sub-micron features and particles between hard disk interface(HDI) is becoming even more important to the hard disk industry in the fields of corrosion, tribologyand the contamination. In this paper, media scratch and particles are characterized with AES,TOF-SIMS, SEM/EDX and LPC. The main causes resulted in serious media scratch have beenanalyzed and discussed.

  10. Homologous gene replacement in Physarum

    Energy Technology Data Exchange (ETDEWEB)

    Burland, T.G. [Univ. of Wisconsin, Madison, WI (United States); Pallotta, D. [Laval Univ., Quebec (Canada)

    1995-01-01

    The protist Physarum polycephalum is useful for analysis of several aspects of cellular and developmental biology. To expand the opportunities for experimental analysis of this organism, we have developed a method for gene replacement. We transformed Physarum amoebae with plasmid DNA carrying a mutant allele, ardD{Delta}1, of the ardD actin gene; ardD{Delta}1 mutates the critical carboxy-terminal region of the gene product. Because ardD is not expressed in the amoeba, replacement of ardD{sup +} with ardD{Delta}1 should not be lethal for this cell type. Transformants were obtained only when linear plasmid DNA was used. Most transformants carried one copy of ardD{Delta}1 in addition to ardD{sup +}, but in two (5%), ardD{sup +} was replaced by a single copy of ardD{Delta}1. This is the first example of homologous gene replacement in Physarum. ardD{Delta}1 was stably maintained in the genome through growth, development and meiosis. We found no effect of ardD{Delta}l on viability, growth, or development of any of the various cell types of Physarum. Thus, the carboxy-terminal region of the ardD product appears not to perform a unique essential role in growth or development. Nevertheless, this method for homologous gene replacement can be applied to analyze the function of any cloned gene. 38 refs., 6 figs., 1 tab.

  11. Development of an immunoaffinity chromatography column for selective extraction of a new agonist phenylethylamine A from feed, meat and liver samples.

    Science.gov (United States)

    Mei, Liyun; Cao, Biyun; Yang, Hong; Xie, Yun; Xu, Shouming; Deng, Anping

    2014-01-15

    Phenylethanolamine A (PA) is a new emerged β-adrenergic agonist that has been illegally used as an animal feed additive for growth promotion in China. In this study, an immunoaffinity chromatography (IAC) column for selective extraction of PA from swine feed, meat and liver samples was developed. The IAC column was constructed by covalently coupling specific polyclonal antibody (Ab) against PA to CNBr-activated Sepharose 4B and packed into a common solid phase extraction (SPE) cartridge. The extraction conditions including loading, washing and eluting solutions were carefully optimized. Under optimal conditions, the IAC column was characterized in terms of maximum capacity, selectivity, extraction recovery and stability. The maximum capacity of the ICA for PA extraction was found to be 239.4ng. For selectivity testing, 100ng of other three β-adrenergic agonists (clenbuterol, ractopamine and salbutamol) was separately loaded onto the column, and it was observed that the tested compounds could not be captured on the column, e.g. the column could only selectively recognize PA. The recovery of the IAC for PA extraction was found within 96.47-101.98% when 10, 50 and 100ng PA were separately loaded onto IAC column. The IAC column was also applied to real sample extraction. Swine feed, meat and liver samples were collected and spiked with PA in range of 1.0-20ngg(-1). The spiked and unspiked samples were extracted by IAC column and measured by high performance liquid chromatography (HPLC). It was found that there was no detectable PA in the blank samples, and the extraction recoveries of the IAC for PA from the spiked samples were within 89.48-104.89%. The stability of the column was also tested. It was showed that after 35 times repeated usage, 60% of the maximum capacity was still remained. The proposed IAC was proven to be a feasible extraction method for PA from different matrices with the properties of high maximum capacity, selectivity, extraction efficiency and

  12. Dynamics of binary-disk interaction. 1: Resonances and disk gap sizes

    Science.gov (United States)

    Artymowicz, Pawel; Lubow, Stephen H.

    1994-01-01

    We investigate the gravitational interaction of a generally eccentric binary star system with circumbinary and circumstellar gaseous disks. The disks are assumed to be coplanar with the binary, geometrically thin, and primarily governed by gas pressure and (turbulent) viscosity but not self-gravity. Both ordinary and eccentric Lindblad resonances are primarily responsible for truncating the disks in binaries with arbitrary eccentricity and nonextreme mass ratio. Starting from a smooth disk configuration, after the gravitational field of the binary truncates the disk on the dynamical timescale, a quasi-equilibrium is achieved, in which the resonant and viscous torques balance each other and any changes in the structure of the disk (e.g., due to global viscous evolution) occur slowly, preserving the average size of the gap. We analytically compute the approximate sizes of disks (or disk gaps) as a function of binary mass ratio and eccentricity in this quasi-equilibrium. Comparing the gap sizes with results of direct simulations using the smoothed particle hydrodynamics (SPH), we obtain a good agreement. As a by-product of the computations, we verify that standard SPH codes can adequately represent the dynamics of disks with moderate viscosity, Reynolds number R approximately 10(exp 3). For typical viscous disk parameters, and with a denoting the binary semimajor axis, the inner edge location of a circumbinary disk varies from 1.8a to 2.6a with binary eccentricity increasing from 0 to 0.25. For eccentricities 0 less than e less than 0.75, the minimum separation between a component star and the circumbinary disk inner edge is greater than a. Our calculations are relevant, among others, to protobinary stars and the recently discovered T Tau pre-main-sequence binaries. We briefly examine the case of a pre-main-sequence spectroscopic binary GW Ori and conclude that circumbinary disk truncation to the size required by one proposed spectroscopic model cannot be due to

  13. Disk Radii and Grain Sizes in Herschel-resolved Debris Disks

    Science.gov (United States)

    Pawellek, Nicole; Krivov, Alexander V.; Marshall, Jonathan P.; Montesinos, Benjamin; Ábrahám, Péter; Moór, Attila; Bryden, Geoffrey; Eiroa, Carlos

    2014-09-01

    The radii of debris disks and the sizes of their dust grains are important tracers of the planetesimal formation mechanisms and physical processes operating in these systems. Here we use a representative sample of 34 debris disks resolved in various Herschel Space Observatory (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) programs to constrain the disk radii and the size distribution of their dust. While we modeled disks with both warm and cold components, and identified warm inner disks around about two-thirds of the stars, we focus our analysis only on the cold outer disks, i.e., Kuiper-belt analogs. We derive the disk radii from the resolved images and find a large dispersion for host stars of any spectral class, but no significant trend with the stellar luminosity. This argues against ice lines as a dominant player in setting the debris disk sizes, since the ice line location varies with the luminosity of the central star. Fixing the disk radii to those inferred from the resolved images, we model the spectral energy distribution to determine the dust temperature and the grain size distribution for each target. While the dust temperature systematically increases toward earlier spectral types, the ratio of the dust temperature to the blackbody temperature at the disk radius decreases with the stellar luminosity. This is explained by a clear trend of typical sizes increasing toward more luminous stars. The typical grain sizes are compared to the radiation pressure blowout limit s blow that is proportional to the stellar luminosity-to-mass ratio and thus also increases toward earlier spectral classes. The grain sizes in the disks of G- to A-stars are inferred to be several times s blow at all stellar luminosities, in agreement with collisional models of debris disks. The sizes, measured in the units of s blow, appear to decrease with the luminosity

  14. Disk radii and grain sizes in Herschel-resolved debris disks

    Energy Technology Data Exchange (ETDEWEB)

    Pawellek, Nicole; Krivov, Alexander V. [Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität Jena, Schillergäßchen 2-3, 07745 Jena (Germany); Marshall, Jonathan P. [School of Physics, University of New South Wales, Sydney NSW 2052 (Australia); Montesinos, Benjamin [Departmento de Astrofísica, Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Ábrahám, Péter; Moór, Attila [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, H-1525 Budapest (Hungary); Bryden, Geoffrey [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Eiroa, Carlos [Departamento de Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain)

    2014-09-01

    The radii of debris disks and the sizes of their dust grains are important tracers of the planetesimal formation mechanisms and physical processes operating in these systems. Here we use a representative sample of 34 debris disks resolved in various Herschel Space Observatory (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) programs to constrain the disk radii and the size distribution of their dust. While we modeled disks with both warm and cold components, and identified warm inner disks around about two-thirds of the stars, we focus our analysis only on the cold outer disks, i.e., Kuiper-belt analogs. We derive the disk radii from the resolved images and find a large dispersion for host stars of any spectral class, but no significant trend with the stellar luminosity. This argues against ice lines as a dominant player in setting the debris disk sizes, since the ice line location varies with the luminosity of the central star. Fixing the disk radii to those inferred from the resolved images, we model the spectral energy distribution to determine the dust temperature and the grain size distribution for each target. While the dust temperature systematically increases toward earlier spectral types, the ratio of the dust temperature to the blackbody temperature at the disk radius decreases with the stellar luminosity. This is explained by a clear trend of typical sizes increasing toward more luminous stars. The typical grain sizes are compared to the radiation pressure blowout limit s {sub blow} that is proportional to the stellar luminosity-to-mass ratio and thus also increases toward earlier spectral classes. The grain sizes in the disks of G- to A-stars are inferred to be several times s {sub blow} at all stellar luminosities, in agreement with collisional models of debris disks. The sizes, measured in the units of s {sub blow}, appear to decrease

  15. Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry

    Directory of Open Access Journals (Sweden)

    Maxim E. Stebliy

    2015-03-01

    Full Text Available Magnetic nanostructures in the form of a sandwich consisting of two permalloy (Py disks with diameters of 600 and 200 nm separated by a nonmagnetic interlayer are studied. Magnetization reversal of the disk-on-disk nanostructures depends on the distance between centers of the small and big disks and on orientation of an external magnetic field applied during measurements. It is found that manipulation of the magnetic vortex chirality and the trajectory of the vortex core in the big disk is only possible in asymmetric nanostructures. Experimentally studied peculiarities of a motion path of the vortex core and vortex parameters by the magneto-optical Kerr effect (MOKE magnetometer are supported by the magnetic force microscopy imaging and micromagnetic simulations.

  16. Milky Way's Thick and Thin disk: Is there distinct thick disk?

    CERN Document Server

    Kawata, D

    2016-01-01

    This article is based on our discussion session on Milky Way models at the 592 WE-Heraeus Seminar, Reconstructing the Milky Way's History: Spectroscopic Surveys, Asteroseismology and Chemodynamical models. The discussion focused on the following question: "Are there distinct thick and thin disks?". The answer to this question depends on the definition one adopts for thin and thick disks. The participants of this discussion converged to the idea that there are at least two different types of disks in the Milky Way. However, there are still important open questions on how to best define these two types of disks (chemically, kinematically, geometrically or by age?). The question of what is the origin of the distinct disks remains open. The future Galactic surveys which are highlighted in this conference should help us answering these questions. The almost one-hour debate involving researchers in the field representing different modelling approaches (Galactic models such as TRILEGAL, Besancon and Galaxia, chemica...

  17. Chemical evolution of protoplanetary disks - the effects of viscous accretion, turbulent mixing and disk winds

    CERN Document Server

    Heinzeller, Dominikus; Walsh, Catherine; Millar, Tom J

    2011-01-01

    We calculate the chemical evolution of protoplanetary disks considering radial viscous accretion, vertical turbulent mixing and vertical disk winds. We study the effects on the disk chemical structure when different models for the formation of molecular hydrogen on dust grains are adopted. Our gas-phase chemistry is extracted from the UMIST Database for Astrochemistry (Rate06) to which we have added detailed gas-grain interactions. We use our chemical model results to generate synthetic near- and mid-infrared LTE line emission spectra and compare these with recent Spitzer observations. Our results show that if H2 formation on warm grains is taken into consideration, the H2O and OH abundances in the disk surface increase significantly. We find the radial accretion flow strongly influences the molecular abundances, with those in the cold midplane layers particularly affected. On the other hand, we show that diffusive turbulent mixing affects the disk chemistry in the warm molecular layers, influencing the line ...

  18. Cobra Probes Containing Replaceable Thermocouples

    Science.gov (United States)

    Jones, John; Redding, Adam

    2007-01-01

    A modification of the basic design of cobra probes provides for relatively easy replacement of broken thermocouples. Cobra probes are standard tube-type pressure probes that may also contain thermocouples and that are routinely used in wind tunnels and aeronautical hardware. They are so named because in side views, they resemble a cobra poised to attack. Heretofore, there has been no easy way to replace a broken thermocouple in a cobra probe: instead, it has been necessary to break the probe apart and then rebuild it, typically at a cost between $2,000 and $4,000 (2004 prices). The modified design makes it possible to replace the thermocouple, in minimal time and at relatively low cost, by inserting new thermocouple wire in a tube.

  19. Radially Magnetized Protoplanetary Disk: Vertical Profile

    CERN Document Server

    Russo, Matthew

    2015-01-01

    This paper studies the response of a thin accretion disk to an external radial magnetic field. Our focus is on protoplanetary disks (PPDs), which are exposed during their later evolution to an intense, magnetized wind from the central star. A radial magnetic field is mixed into a thin surface layer, is wound up by the disk shear, and is pushed downward by a combination of turbulent mixing and ambipolar and Ohmic drift. The toroidal field reaches much greater strengths than the seed vertical field that is usually invoked in PPD models, even becoming superthermal. Linear stability analysis indicates that the disk experiences the magnetorotational instability (MRI) at a higher magnetization than a vertically magnetized disk when both the effects of ambipolar and Hall drift are taken into account. Steady vertical profiles of density and magnetic field are obtained at several radii between 0.06 and 1 AU in response to a wind magnetic field $B_r \\sim (10^{-4}$-$10^{-2})(r/{\\rm AU})^{-2}$ G. Careful attention is giv...

  20. Water vapor distribution in protoplanetary disks

    CERN Document Server

    Du, Fujun

    2014-01-01

    Water vapor has been detected in protoplanetary disks. In this work we model the distribution of water vapor in protoplanetary disks with a thermo-chemical code. For a set of parameterized disk models, we calculate the distribution of dust temperature and radiation field of the disk with a Monte Carlo method, and then solve the gas temperature distribution and chemical composition. The radiative transfer includes detailed treatment of scattering by atomic hydrogen and absorption by water of Lyman alpha photons, since the Lyman alpha line dominates the UV spectrum of accreting young stars. In a fiducial model, we find that warm water vapor with temperature around 300 K is mainly distributed in a small and well-confined region in the inner disk. The inner boundary of the warm water region is where the shielding of UV field due to dust and water itself become significant. The outer boundary is where the dust temperature drops below the water condensation temperature. A more luminous central star leads to a more ...

  1. The Recent Disk Evolution of Achernar

    Science.gov (United States)

    Faes, D. M.; Carciofi, A. C.; Domiciano de Souza, A.

    2016-11-01

    Achernar is a key star to investigate the Be phemonemon. Its importance derives from the possibility of investigating in detail its photospheric and circumstellar emission due to its proximity. Since early 2013 the star entered a new outburst phase, having since then formed a large disk. Here we report our first results to model the recent disk evolution based on a recent precise photospheric characterization. The analysis combine multi-technique data, including broadband polarimetry (OPD/LNA), spectroscopy (FEROS and others) and interferometry (VLTI/AMBER and PIONIER). The radiative transfer problem is solved by the HDUST code. The preliminary results indicate that the circumstellar disk was not formed by a constant mass injection, as indicated by the large variability in small temporal scales seen in polarization. Also, the forming disk manifests noticeable azimuthal asymmetries, as seen by the V/R variations in Hα, which suggests that mass ejection from the star is also non-axisymmetric. These elements offer a rare opportunity to evaluate the evolution of a just formed Be disk in detail and derive relevant physical quantities governing the system.

  2. Planetary Torque in 3D Isentropic Disks

    CERN Document Server

    Fung, Jeffrey; Lega, Elena; Velasco, David

    2016-01-01

    Planet migration is inherently a three-dimensional (3D) problem, because Earth-size planetary cores are deeply embedded in protoplanetary disks. Simulations of these 3D disks remain challenging due to the steep requirement in resolution. Using two different hydrodynamics code, FARGO3D and PEnGUIn, we simulate disk-planet interaction for a 1 to 5 Earth-mass planet embedded in an isentropic disk. We measure the torque on the planet and ensure that the measurements are converged both in resolution and between the two codes. We find that the torque is independent of the smoothing length of the planet's potential ($r_{\\rm s}$), and that it has a weak dependence on the adiabatic index of the gaseous disk ($\\gamma$). The torque values correspond to an inward migration rate qualitatively similar to previous linear calculations. We perform additional simulations with explicit radiative transfer using FARGOCA, and again find agreement between 3D simulations and existing torque formulae. We also present the flow pattern...

  3. Scattered light mapping of protoplanetary disks

    CERN Document Server

    Stolker, T; Min, M; Garufi, A; Mulders, G D; Avenhaus, H

    2016-01-01

    High-contrast scattered light observations have revealed the surface morphology of several dozens of protoplanetary disks at optical and near-infrared wavelengths. Inclined disks offer the opportunity to measure part of the phase function of the dust grains that reside in the disk surface which is essential for our understanding of protoplanetary dust properties and the early stages of planet formation. We aim to construct a method which takes into account how the flaring shape of the scattering surface of an (optically thick) protoplanetary disk projects onto the image plane of the observer. This allows us to map physical quantities (scattering radius and scattering angle) onto scattered light images and retrieve stellar irradiation corrected (r^2-scaled) images and dust phase functions. We apply the method on archival polarized intensity images of the protoplanetary disk around HD 100546 that were obtained with VLT/SPHERE in R'-band and VLT/NACO in H- and Ks-band. The brightest side of the r^2-scaled R'-ban...

  4. Water Masers in AGN Accretion Disks

    Science.gov (United States)

    Braatz, J. A.; Reid, M. J.; Greenhill, L. J.; Kuo, C.-Y.; Condon, J. J.; Lo, K.-Y.; Henkel, C.

    2009-08-01

    Water vapor masers at 22 GHz have been detected in over 100 galaxies, most of them AGNs. High resolution VLBI observations of these masers provide the only opportunity for direct imaging of sub-parsec structure in AGN accretion disks. The key science goals associated with such observations are concentrated in two areas. First, observations of nearby, bright sources, exemplified by NGC 4258, enable unique investigations of accretion disk geometry, substructure, thickness, and rotation properties. Second, when combined with spectral line monitoring, VLBI imaging and subsequent disk modeling enables the estimation of a distance to the host galaxy independent of standard candle arguments. In this contribution we present VLBI observations of two maser disk systems in galaxies well into the Hubble flow, UGC 3789 and NGC 6323. A long term goal in these studies is to measure the Hubble constant with high precision and, as a complement to CMB observations, constrain several key cosmological parameters, including the equation of state for dark energy. Observations with VSOP-2 at 22 GHz will have the resolution critical for mapping substructure in these accretion disks and will contribute to reducing systematic errors in the measurement of distances to galaxies.

  5. Ionization and Dust Charging in Protoplanetary Disks

    Science.gov (United States)

    Ivlev, A. V.; Akimkin, V. V.; Caselli, P.

    2016-12-01

    Ionization-recombination balance in dense interstellar and circumstellar environments is a key factor for a variety of important physical processes, such as chemical reactions, dust charging and coagulation, coupling of the gas with magnetic field, and development of instabilities in protoplanetary disks. We determine a critical gas density above which the recombination of electrons and ions on the grain surface dominates over the gas-phase recombination. For this regime, we present a self-consistent analytical model, which allows us to calculate exactly the abundances of charged species in dusty gas, without making assumptions on the grain charge distribution. To demonstrate the importance of the proposed approach, we check whether the conventional approximation of low grain charges is valid for typical protoplanetary disks, and discuss the implications for dust coagulation and development of the “dead zone” in the disk. The presented model is applicable for arbitrary grain-size distributions and, for given dust properties and conditions of the disk, has only one free parameter—the effective mass of the ions, shown to have a small effect on the results. The model can be easily included in numerical simulations following the dust evolution in dense molecular clouds and protoplanetary disks.

  6. Low EUV Luminosities Impinging on Protoplanetary Disks

    CERN Document Server

    Pascucci, I; Gorti, U; Hollenbach, D; Hendler, N P; Brooks, K J; Contreras, Y

    2014-01-01

    The amount of high-energy stellar radiation reaching the surface of protoplanetary disks is essential to determine their chemistry and physical evolution. Here, we use millimetric and centimetric radio data to constrain the EUV luminosity impinging on 14 disks around young (~2-10Myr) sun-like stars. For each object we identify the long-wavelength emission in excess to the dust thermal emission, attribute that to free-free disk emission, and thereby compute an upper limit to the EUV reaching the disk. We find upper limits lower than 10$^{42}$ photons/s for all sources without jets and lower than $5 \\times 10^{40}$ photons/s for the three older sources in our sample. These latter values are low for EUV-driven photoevaporation alone to clear out protoplanetary material in the timescale inferred by observations. In addition, our EUV upper limits are too low to reproduce the [NeII] 12.81 micron luminosities from three disks with slow [NeII]-detected winds. This indicates that the [NeII] line in these sources prima...

  7. Bar instability in disk-halo systems

    CERN Document Server

    Sellwood, J A

    2016-01-01

    We show that the exponential growth rate of a bar in a stellar disk is substantially greater when the disk is embedded in a live halo than in a rigid one having the same mass distribution. We also find that the vigor of the instability in disk-halo systems varies with the shape of the halo velocity ellipsoid. Disks in rigid halos that are massive enough to be stable by the usual criteria, quickly form bars in isotropic halos and much greater halo mass is needed to avoid a strong bar; thus stability criteria derived for disks in rigid halos do not apply when the halo is responsive. The study presented here is of an idealized family of models with near uniform central rotation and that lack an extended halo; we present more realistic models with extended halos in a companion paper. The puzzle presented by the absence of strong bars in some galaxies having gently rising inner rotation curves is compounded by the results presented here.

  8. The Migrating Embryo Model for Disk Evolution

    CERN Document Server

    Basu, Shantanu

    2012-01-01

    A new view of disk evolution is emerging from self-consistent numerical simulation modeling of the formation of circumstellar disks from the direct collapse of prestellar cloud cores. This has implications for many aspects of star and planet formation, including the growth of dust and high-temperature processing of materials. A defining result is that the early evolution of a disk is crucially affected by the continuing mass loading from the core envelope, and is driven into recurrent phases of gravitational instability. Nonlinear spiral arms formed during these episodes fragment to form gaseous clumps in the disk. These clumps generally migrate inward due to gravitational torques arising from their interaction with a trailing spiral arm. Occasionally, a clump can open up a gap in the disk and settle into a stable orbit, revealing a direct pathway to the formation of companion stars, brown dwarfs, or giant planets. At other times, when multiple clumps are present, a low mass clump may even be ejected from the...

  9. Radiative Ablation of Disks Around Massive Stars

    CERN Document Server

    Kee, N D

    2015-01-01

    Hot, massive stars (spectral types O and B) have extreme luminosities ($10^4 -10^6 L_\\odot$) that drive strong stellar winds through UV line-scattering. Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating "Classical Be stars"), or accretion during the star's formation. This dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of Classical Be disks can be explained by line-driven ablation without, as previously done, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation by coupling observationally inferred non-radial pulsation modes and rapid stellar...

  10. Building massive compact planetesimal disks from the accretion of pebbles

    CERN Document Server

    Moriarty, John

    2015-01-01

    We present a model in which planetesimal disks are built from the combination of planetesimal formation and accretion of radially drifting pebbles onto existing planetesimals. In this model, the rate of accretion of pebbles onto planetesimals quickly outpaces the rate of direct planetesimal formation in the inner disk. This allows for the formation of a high mass inner disk without the need for enhanced planetesimal formation or a massive protoplanetary disk. Our proposed mechanism for planetesimal disk growth does not require any special conditions to operate. Consequently, we expect that high mass planetesimal disks form naturally in nearly all systems. The extent of this growth is controlled by the total mass in pebbles that drifts through the inner disk. Anything that reduces the rate or duration of pebble delivery will correspondingly reduce the final mass of the planetesimal disk. Therefore, we expect that low mass stars (with less massive protoplanetary disks), low metallicity stars and stars with gian...

  11. Identifying Planet-Forming Disks Around Young Stars

    Science.gov (United States)

    Espaillat, C.

    2013-04-01

    In the past few years, several disks with inner holes that are relatively empty of small dust grains have been detected and are known as transitional disks. Spitzer identified a new class of “pre-transitional disks” with gaps; these objects have an optically thick inner disk separated from an optically thick outer disk by an optically thin disk gap. Here we review spectral observations which provided the first confirmations of gaps in the pre-transitional disks of LkCa 15 and UX Tau A. We also review the results of a Spitzer IRS study of variability in transitional and pre-transitional objects. The structure and behavior of pre-transitional and transitional disks may be a sign of young planets forming in these disks and future studies of these disks will provide constraints to aid in theoretical modeling of planet formation.

  12. Three-dimensional modeling of radiative disks in binaries

    CERN Document Server

    Picogna, Giovanni

    2013-01-01

    Circumstellar disks in binaries are perturbed by the companion gravity causing significant alterations of the disk morphology. Spiral waves due to the companion tidal force also develop in the vertical direction and affect the disk temperature profile. These effects may significantly influence the process of planet formation. We perform 3D numerical simulations of disks in binaries with different initial dynamical configurations and physical parameters. Our goal is to investigate their evolution and their propensity to grow planets. We use an improved version of the SPH code VINE modified to better account for momentum and energy conservation. The energy equation includes a flux--limited radiative transfer algorithm and the disk cooling is obtained via "boundary particles". We model a system made of star/disk + star/disk where the secondary star (and relative disk) is less massive than the primary. The numerical simulations performed for different values of binary separation and disk density show that the dis...

  13. Self-consistent massive disks in triaxial dark matter halos

    CERN Document Server

    Bailin, Jeremy; Bolatto, Alberto D; Gibson, Brad K; Power, Chris

    2007-01-01

    Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to calculate the equilibrium configuration of such a disk in the combined disk-halo potential, which is based on the method of Jog (2000) but accounts for the radial variation in both the halo potential and the disk ellipticity. This crucial ingredient results in qualitatively different behavior of the disk: the disk circularizes the potential at small radii, even for a reasonably low disk mass. This effect has important implications for proposals to reconcile cuspy halo density profiles with low surface brightness galaxy rotation curves using halo triaxiality. The disk ellipticities in our models are consistent with observational estimates based on two-dimensional velocity fields and isophotal axis ratios.

  14. Renal replacement therapy in ICU

    Directory of Open Access Journals (Sweden)

    C Deepa

    2012-01-01

    Full Text Available Diagnosing and managing critically ill patients with renal dysfunction is a part of the daily routine of an intensivist. Acute kidney insufficiency substantially contributes to the morbidity and mortality of critically ill patients. Renal replacement therapy (RRT not only does play a significant role in the treatment of patients with renal failure, acute as well as chronic, but also has spread its domains to the treatment of many other disease conditions such as myaesthenia gravis, septic shock and acute on chronic liver failure. This article briefly outlines the role of renal replacement therapy in ICU.

  15. Prioritization methodology for chemical replacement

    Science.gov (United States)

    Goldberg, Ben; Cruit, Wendy; Schutzenhofer, Scott

    1995-01-01

    This methodology serves to define a system for effective prioritization of efforts required to develop replacement technologies mandated by imposed and forecast legislation. The methodology used is a semi quantitative approach derived from quality function deployment techniques (QFD Matrix). QFD is a conceptual map that provides a method of transforming customer wants and needs into quantitative engineering terms. This methodology aims to weight the full environmental, cost, safety, reliability, and programmatic implications of replacement technology development to allow appropriate identification of viable candidates and programmatic alternatives.

  16. Wafer Replacement Cluster Tool (Presentation);

    Energy Technology Data Exchange (ETDEWEB)

    Branz, H. M.

    2008-04-01

    This presentation on wafer replacement cluster tool discusses: (1) Platform for advanced R and D toward SAI 2015 cost goal--crystal silicon PV at area costs closer to amorphous Si PV, it's 15% efficiency, inexpensive substrate, and moderate temperature processing (<800 C); (2) Why silicon?--industrial and knowledge base, abundant and environmentally benign, market acceptance, and good efficiency; and (3) Why replace wafers?--expensive, high embedded energy content, and uses 50-100 times more silicon than needed.

  17. Effects of Turbulence on Cosmic Ray Propagation in Protostars and Young Star/Disk Systems

    CERN Document Server

    Fatuzzo, Marco

    2014-01-01

    The magnetic fields associated with young stellar objects are expected to have an hour-glass geometry, i.e., the magnetic field lines are pinched as they thread the equatorial plane surrounding the forming star but merge smoothly onto a background field at large distances. With this field configuration, incoming cosmic rays experience both a funneling effect that acts to enhance the flux impinging on the circumstellar disk and a magnetic mirroring effect that acts to reduce that flux. To leading order, these effects nearly cancel out for simple underlying magnetic field structures. However, the environments surrounding young stellar objects are expected to be highly turbulent. This paper shows how the presence of magnetic field fluctuations affects the process of magnetic mirroring, and thereby changes the flux of cosmic rays striking circumstellar disks. Turbulence has two principle effects: 1) The (single) location of the magnetic mirror point found in the absence of turbulence is replaced with a wide distr...

  18. Mineralogical Evolution in Extreme Debris Disks

    Science.gov (United States)

    Su, Kate

    2015-10-01

    Young (10-200 Myr), luminous (fractional luminosity on the order of 1.E-2) extreme debris disks provide a unique opportunity to explore exo-asteriod and exo-planetesimal collisions during the oligarchic and chaotic phases of terrestrial planet-building. We propose to obtain low-resolution grism spectra of four extreme debris disks to document and characterize the mineralogy changes in the mid-IR region where strong peaks originating from silica and forsterite dust can be easily identified. The proposed observations will supplement our on-going warm Spitzer monitoring program studying disk variability at 3.6 and 4.5 microns, provide immediate insights on the long-term mineralogical evolution in comparison with the existing Spitzer IRS spectra, and will bridge to similar studies that JWST will provide in the near future.

  19. From Disks To Planets: A Theoretical Perspective

    Science.gov (United States)

    Bromley, Ben

    2016-07-01

    Circumstellar disks of gas and dust naturally produce planets. Observations of young stellar systems tell us the starting conditions, while planet surveys reveal an amazing diversity of outcomes. Theory tries to connect the dots with ideas on how planets emerge from dust within an evolving gas disk. Here I give a broad-brush view of planet formation from a theoretical perspective, noting recent ideas and successes. I also consider the challenges. The conversion of primordial dust into planetesimals is uncertain. Even the mass budget in solids is a problem, since the total mass in dust observed around young stars seems insufficient to account for the census of full-fledged planets. Toward resolving these issues, the Atacama Large Millimeter Array and the Karl G. Jansky Very Large Array are playing key roles in illuminating how disks become planets.

  20. Galactic disks as reaction-diffusion systems

    CERN Document Server

    Smolin, L

    1996-01-01

    A model of a galactic disk is presented which extends the homogeneous one zone models by incorporating propagation of material and energy in the disk. For reasonable values of the parameters the homogeneous steady state is unstable to the development of inhomogeneities, leading to the development of spatial and temporal structure. At the linearized level a prediction for the length and time scales of the patterns is found. These instabilities arise for the same reason that pattern formation is seen in non-equilibrium chemical and biological systems, which is that the positive and negative feedback effects which govern the rates of the critical processes act over different distance scales, as in Turing's reaction-diffusion models. This shows that patterns would form in the disk even in the absence of gravitational effects, density waves, rotation, shear and external perturbations. These nonlinear effects may thus explain the spiral structure seen in the star forming regions of isolated flocculent galaxies.

  1. Subaru SEEDS Survey of Exoplanets and Disks

    Science.gov (United States)

    McElwain, Michael W.

    2012-01-01

    The Strategic Exploration of Exoplanets and Disks at Subaru (SEEDS) is the first strategic observing program (SSOPs) awarded by the National Astronomical Observatory of Japan (NAOJ). SEEDS targets a broad sample of stars that span a wide range of masses and ages to explore the formation and evolution of planetary systems. This survey has been awarded 120 nights over five years time to observe nearly 500 stars. Currently in the second year, SEEDS has already produced exciting new results for the protoplanetary disk AB Aur, transitional disk LkCa15, and nearby companion to GJ 758. We present the survey architecture, performance, recent results, and the projected sample. Finally, we will discuss planned upgrades to the high contrast instrumentation at the Subaru Telescope

  2. An interferometric view of hot star disks

    CERN Document Server

    Faes, Daniel Moser

    2015-01-01

    Optical long baseline interferometry was recently established as a technique capable of resolving stars and their circumstellar environments at the milliarcsecond (mas) resolution level. This high-resolution opens an entire new window to the study of astrophysical systems, providing information inaccessible by other techniques. Astrophysical disks are observed in a wide variety of systems, from galaxies up to planetary rings, commonly sharing similar physical processes. Two particular disk like systems are studied in the thesis: (i) B He-rich stars that exhibits magnetic fields in order of kG and that trap their winds in structures called magnetospheres; and (ii) Be stars, fast rotating stars that create circumstellar viscous disks. This study uses the interferometric technique to investigate both the photosphere proper and the circumstellar environment of these stars. The objective is to combine interferometry with other observational techniques (such as spectroscopy and polarimetry) to perform a complete an...

  3. Formulas for Radial Transport in Protoplanetary Disks

    Science.gov (United States)

    Desch, Steven J.; Estrada, Paul R.; Kalyaan, Anusha; Cuzzi, Jeffrey N.

    2017-05-01

    The quantification of the radial transport of gaseous species and solid particles is important to many applications in protoplanetary disk evolution. An especially important example is determining the location of the water snow lines in a disk, which requires computing the rates of outward radial diffusion of water vapor and the inward radial drift of icy particles; however, the application is generalized to evaporation fronts of all volatiles. We review the relevant formulas using a uniform formalism. This uniform treatment is necessary because the literature currently contains at least six mutually exclusive treatments of radial diffusion of gas, only one of which is correct. We derive the radial diffusion equations from first principles using Fick's law. For completeness, we also present the equations for radial transport of particles. These equations may be applied to studies of diffusion of gases and particles in protoplanetary and other accretion disks.

  4. Complex Organic Molecules in Protoplanetary Disks

    Science.gov (United States)

    Walsh, Catherine; Millar, T. J.; Nomura, H.; Herbst, E.; Widicus-Weaver, S.

    2013-06-01

    Protoplanetary disks are vital objects in star and planet formation. In addition to aiding mass accretion onto the central star and angular momentum dissipation, they also contain all material which may form an orbiting planetary system. Of great interest to the astrochemistry and astrobiology communities is the origin of prebiotic molecules, considered the "building blocks" of Life. Is it possible for complex molecules to form in protoplanetary disks and survive assimilation into planets and other planetary system objects, such as, comets? We explore the synthesis of large complex organic molecules (COMs) in protoplanetary disks which encompass young stars. We use a chemical network primarily developed for use in hot core models to calculate the abundance and distribution of gas-phase and grain-mantle (ice) COMs and discuss the potential of observing the gas-phase form of these species with new facilities, such as, ALMA.

  5. Pressure drop in CIM disk monolithic columns.

    Science.gov (United States)

    Mihelic, Igor; Nemec, Damjan; Podgornik, Ales; Koloini, Tine

    2005-02-11

    Pressure drop analysis in commercial CIM disk monolithic columns is presented. Experimental measurements of pressure drop are compared to hydrodynamic models usually employed for prediction of pressure drop in packed beds, e.g. free surface model and capillary model applying hydraulic radius concept. However, the comparison between pressure drop in monolith and adequate packed bed give unexpected results. Pressure drop in a CIM disk monolithic column is approximately 50% lower than in an adequate packed bed of spheres having the same hydraulic radius as CIM disk monolith; meaning they both have the same porosity and the same specific surface area. This phenomenon seems to be a consequence of the monolithic porous structure which is quite different in terms of the pore size distribution and parallel pore nonuniformity compared to the one in conventional packed beds. The number of self-similar levels for the CIM monoliths was estimated to be between 1.03 and 2.75.

  6. Earth, Moon, Sun, and CV Accretion Disks

    CERN Document Server

    Montgomery, M M

    2009-01-01

    Net tidal torque by the secondary on a misaligned accretion disk, like the net tidal torque by the Moon and the Sun on the equatorial bulge of the spinning and tilted Earth, is suggested by others to be a source to retrograde precession in non-magnetic, accreting Cataclysmic Variable (CV) Dwarf Novae systems that show negative superhumps in their light curves. We investigate this idea in this work. We generate a generic theoretical expression for retrograde precession in spinning disks that are misaligned with the orbital plane. Our generic theoretical expression matches that which describes the retrograde precession of Earths' equinoxes. By making appropriate assumptions, we reduce our generic theoretical expression to those generated by others, or to those used by others, to describe retrograde precession in protostellar, protoplanetary, X-ray binary, non-magnetic CV DN, quasar and black hole systems. We find that differential rotation and effects on the disk by the accretion stream must be addressed. Our a...

  7. Herschel Observations of Dusty Debris Disks

    CERN Document Server

    Vican, Laura; Bryden, Geoff; Melis, Carl; Zuckerman, B; Rhee, Joseph; Song, Inseok

    2016-01-01

    We present results from two Herschel observing programs using the Photodetector Array Camera and Spectrometer. During three separate campaigns, we obtained Herschel data for 24 stars at 70, 100, and 160 microns. We chose stars that were already known or suspected to have circumstellar dust based on excess infrared emission previously measured with IRAS or Spitzer, and used Herschel to examine long-wavelength properties of the dust. Fifteen stars were found to be uncontaminated by background sources, and possess infrared emission most likely due to a circumstellar debris disk. We analyzed the properties of these debris disks to better understand the physical mechanisms responsible for dust production and removal. Seven targets were spatially resolved in the Herschel images. Based on fits to their spectral energy distributions, nine disks appear to have two temperature components. Of these nine, in three cases, the warmer dust component is likely the result of a transient process rather than a steady state coll...

  8. Electrovacuum Static Counterrotating Relativistic Dust Disks

    CERN Document Server

    García-Reyes, Gonzalo

    2004-01-01

    A detailed study is presented of the counterrotating model (CRM) for generic electrovacuum static axially symmetric relativistic thin disks without radial pressure. We find a general constraint over the counterrotating tangential velocities needed to cast the surface energy-momentum tensor of the disk as the superposition of two counterrotating charged dust fluids. We also find explicit expressions for the energy densities, charge densities and velocities of the counterrotating fluids. We then show that this constraint can be satisfied if we take the two counterrotating streams as circulating along electro-geodesics. However, we show that, in general, it is not possible to take the two counterrotating fluids as circulating along electro-geodesics nor take the two counterrotating tangential velocities as equal and opposite. Four simple families of models of counterrotating charged disks based on Chazy-Curzon-like, Zipoy-Voorhees-like, Bonnor-Sackfield-like and Kerr-like electrovacuum solutions are considered w...

  9. High Power Disk Loaded Guide Load

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, Z.D.; /SLAC

    2006-02-22

    A method to design a matching section from a smooth guide to a disk-loaded guide, using a variation of broadband matching, [1, 2] is described. Using this method, we show how to design high power loads. The load consists of a disk-loaded coaxial guide operating in the TE{sub 01}-mode. We use this mode because it has no electric field terminating on a conductor, has no axial currents, and has no current at the cylinder-disk interface. A high power load design that has -35 dB reflection and a 200 MHz, -20 dB bandwidth, is presented. It is expected that it will carry the 600 MW output peak power of the pulse compression network. We use coaxial geometry and stainless steel material to increase the attenuation per cell.

  10. Dynamics of Disk Galaxies and Their Satellites

    Directory of Open Access Journals (Sweden)

    Héctor Velázquez

    2001-01-01

    Full Text Available We address the heating and survival of galaxy disks by infalling satellites using self-consistent N-body simulations. We consider satellites with a variety of internal structures as well several orbits with different eccentricities and orientations. Also, the role of the central region of the galaxy (through a bulge is studied. We found that the analytical results of Toth & Ostriker (1992 overestimate the heating and thickening of the disk by a factor of 2-3. In particular, we found disks are more robust to the accretion of massive satellites (MS ~ 0.2 MD that follow retrograte orbits. Finally, the importance of the responsiveness of the halo is analized.

  11. The Spin History of Protostars: Disk Locking, Revisited

    Science.gov (United States)

    Matt, S.; Pudritz, R. E.

    2004-12-01

    In this talk, we take a new look at the theory of disk locking, which assumes that an accreting protostar rids itself of accreted angular momentum through a magnetic coupling with the accretion disk. We consider that differential rotation between the star and disk twists the field lines. For large enough twist, the magnetic field lines connecting the star and disk open and disconnect. This significantly reduces the spin-down torque on the star by the disk, and so we find that disk-locking theory predicts spin periods that are much too short to account for typical observed systems.

  12. Debris Disks in Aggregate: Using Hubble Space Telescope Coronagraphic Imagery to Understand the Scattered-Light Disk Detection Rate

    Science.gov (United States)

    Grady, Carol A.

    2011-01-01

    Despite more than a decade of coronagraphic imaging of debris disk candidate stars, only 16 have been imaged in scattered light. Since imaged disks provide our best insight into processes which sculpt disks, and can provide signposts of the presence of giant planets at distances which would elude radial velocity and transit surveys, we need to understand under what conditions we detect the disks in scattered light, how these disks differ from the majority of debris disks, and how to increase the yield of disks which are imaged with 0.1" angular resolution. In this talk, I will review what we have learned from a shallow HSTINICMOS NIR survey of debris disks, and present first results from our on-going HST /STIS optical imaging of bright scattered-light disks.

  13. Simulating a Thin Accretion Disk Using PLUTO

    Science.gov (United States)

    Phillipson, Rebecca; Vogeley, Michael S.; Boyd, Patricia T.

    2017-08-01

    Accreting black hole systems such as X-ray binaries and active galactic nuclei exhibit variability in their luminosity on many timescales ranging from milliseconds to tens of days, and even hundreds of days. The mechanism(s) driving this variability and the relationship between short- and long-term variability is poorly understood. Current studies on accretion disks seek to determine how the changes in black hole mass, the rate at which mass accretes onto the central black hole, and the external environment affect the variability on scales ranging from stellar-mass black holes to supermassive black holes. Traditionally, the fluid mechanics equations governing accretion disks have been simplified by considering only the kinematics of the disk, and perhaps magnetic fields, in order for their phenomenological behavior to be predicted analytically. We seek to employ numerical techniques to study accretion disks including more complicated physics traditionally ignored in order to more accurately understand their behavior over time. We present a proof-of-concept three dimensional, global simulation using the astrophysical hydrodynamic code PLUTO of a simplified thin disk model about a central black hole which will serve as the basis for development of more complicated models including external effects such as radiation and magnetic fields. We also develop a tool to generate a synthetic light curve that displays the variability in luminosity of the simulation over time. The preliminary simulation and accompanying synthetic light curve demonstrate that PLUTO is a reliable code to perform sophisticated simulations of accretion disk systems which can then be compared to observational results.

  14. Double emulsions as fat replacers

    NARCIS (Netherlands)

    Oppermann, Anika

    2017-01-01

    The use of double (w1/o/w2) emulsions, in which part of the oil is replaced by small water droplets, is a promising strategy to reduce oil content in food products. For successful applications, (1) significant levels of fat reduction (i.e. significant amounts of water inside the oil droplets) have

  15. Replacement policies for dairy cows

    DEFF Research Database (Denmark)

    Nielsen, Lars Relund

    In a recent paper a hierarchical Markov decision processes (MDP) with finite state and action space was formulated for the dairy cow replacement problem with stage lengths of 1 d. Bayesian updating was used to predict the performance of each cow in the herd and economic decisions were based...

  16. Electrocatalysts Prepared by Galvanic Replacement

    Directory of Open Access Journals (Sweden)

    Athanasios Papaderakis

    2017-03-01

    Full Text Available Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, Mnoble, when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mMnoblen+ → nMm+ + mMnoble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases hydrogen evolution too, both oxygen levels and the pH must be optimized. The resulting bimetallic material can in principle have a Mnoble-rich shell and M-rich core (denoted as Mnoble(M leading to a possible decrease in noble metal loading and the modification of its properties by the underlying metal M. This paper reviews a number of bimetallic or ternary electrocatalytic materials prepared by galvanic replacement for fuel cell, electrolysis and electrosynthesis reactions. These include oxygen reduction, methanol, formic acid and ethanol oxidation, hydrogen evolution and oxidation, oxygen evolution, borohydride oxidation, and halide reduction. Methods for depositing the precursor metal M on the support material (electrodeposition, electroless deposition, photodeposition as well as the various options for the support are also reviewed.

  17. Lithium Niobate Disk Sensor Using Photonic Heterodyning

    Science.gov (United States)

    Sasagawa, Kiyotaka; Tsuchiya, Masahiro

    2009-08-01

    We demonstrate a highly sensitive electro-optic sensor based on a LiNbO3 disk resonator with high-Q whispering gallery modes. In this sensor, the electric field is measured by observing a frequency shift of the disk resonator via the Pockels effect. The measured electro-optic signal is downconverted to 150 kHz by a photonic heterodyne method and detected by a low cost (slow) photodiode. At multiple frequencies within the free spectral range, a sensitivity enhancement is achieved. The minimum detectable input power into a 50-Ω microstrip line used as a test device was -60.5 dBm.

  18. Pulsed pumping of semiconductor disk lasers.

    Science.gov (United States)

    Hempler, Nils; Hopkins, John-Mark; Kemp, Alan J; Schulz, Nico; Rattunde, Marcel; Wagner, Joachim; Dawson, Martin D; Burns, David

    2007-03-19

    Efficient operation of semiconductor disk lasers is demonstrated using uncooled and inexpensive 905nm high-power pulsed semiconductor pump lasers. Laser emission, with a peak power of 1.7W, is obtained from a 2.3mum semiconductor disk laser. This is seven times the power achieved under continuous pumping. Analysis of the time-dependent spectral characteristics of the laser demonstrate that significant device heating occurs over the 100-200ns duration of the pumping pulse - finite element modelling of the thermal processes is undertaken in support of these data. Spectral narrowing to below 0.8nm is obtained by using an intra-cavity birefringent filter.

  19. Extended HI disks in nearby spiral galaxies

    Science.gov (United States)

    Bosma, Albert

    2017-03-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a ``tilted ring model'' allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  20. Extended HI disks in nearby spiral galaxies

    CERN Document Server

    Bosma, A

    2016-01-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a "tilted ring model" allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  1. Scale Length of the Galactic Thin Disk

    Indian Academy of Sciences (India)

    D. Κ. Ojha

    2000-06-01

    This paper presents an analysis of the first 2MASS (The Two Micron All Sky Survey) sampler data as observed at lower Galactic latitude in our Galaxy. These new near-infrared data provide insight into the structure of the thin disk of our Galaxy, The interpretation of star counts and color distributions of stars in the near-infrared with the synthetic stellar population model, gives strong evidence that the Galactic thin disk density scale length, ℎ, is rather short (2.7 ± 0.1 kpc).

  2. Relativistic Static Thin Disks of Polarized Matter

    Science.gov (United States)

    Navarro, Anamaria; Lora-Clavijo, F. D.; González, Guillermo A.

    2017-03-01

    An infinite family of exact solutions of the electrovacuum Einstein-Maxwell equations is presented. The family is static, axially symmetric and describe thin disks composed by electrically polarized material in a conformastatic spacetime. The form of the conformastatic metric allows us to write down the metric functions and the electromagnetic potentials in terms of a solution of the Laplace equation. We find a general expression for the surface energy density of the disk, the pressure, the polarization vector, the electromagnetic fields and the velocity rotation for circular orbits. As an example, we present the first model of the family and show the behavior of the different physical variables.

  3. HTS nonlinearities in microwave disk resonators

    Science.gov (United States)

    Collado, Carlos; Mateu, Jordi; Shaw, Timothy J.; O'Callaghan, Juan M.

    2002-08-01

    This article describes a procedure for the calculation of the intermodulation behavior of the TM0 1 0 mode in high temperature superconducting (HTS) disk resonators from a description of the local HTS nonlinearities. Successful cross-checks are performed by comparing the theoretical results with experimental measurements and simulations based on the multiport harmonic balance algorithm for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated and compared to theoretical predictions.

  4. The short circuit instability in protoplanetary disks

    DEFF Research Database (Denmark)

    Hubbard, A.; McNally, C.P.; Mac Low, M.M.

    2013-01-01

    We introduce a magneto-hydrodynamic instability which occurs, among other locations, in the inner, hot regions of protoplanetary disks, and which alters the way in which resistive dissipation of magnetic energy into heat proceeds. This instability can be likened to both an electrical short circuit...... and lightning, as it concentrates the dissipation of magnetic energy by means of the enhanced release of free electrons. This instability can generate very high temperatures, making it an excellent candidate for thermally processing protoplanetary disk solids, from annealing silicates to melting chondrules...

  5. Explorations of Dusty Debris Disk Geometry

    CERN Document Server

    Dennihy, E; Clemens, J C

    2016-01-01

    As the sample of white dwarfs with signatures of planetary systems has grown, statistical studies have begun to suggest our picture of compact debris disk formation from disrupted planetary bodies is incomplete. Here we present the results of an effort to extend the preferred dust disk model introduced by \\citet{jur03} to include elliptical geometries. We apply this model the observed distribution of fractional infrared luminosities, and explore the difference in preferred parameter spaces for a circular and highly elliptical model on a well-studied dusty white dwarf.

  6. Variational thermodynamics of relativistic thin disks

    CERN Document Server

    Gutiérrez-Piñeres, A C; Quevedo, H

    2013-01-01

    We present a relativistic model describing a thin disk system composed of two fluids. The system is surrounded by a halo in the presence of a non-trivial electromagnetic field. We show that the model is compatible with the variational multi-fluid thermodynamics formalism, allowing us to determine all the thermodynamic variables associated with the matter content of the disk. The asymptotic behaviour of these quantities indicates that the single fluid interpretation should be abandoned in favour of a two-fluid model.

  7. A new concept in Bitter disk design

    Energy Technology Data Exchange (ETDEWEB)

    Gao, B.J.; Schneider-Muntau, H.J.; Eyssa, Y.M.; Bird, M.D. [National High Magnetic Field Lab., Tallahassee, FL (United States)

    1996-07-01

    A new concept in cooling hole design in Bitter disks that allows for much higher power densities and results in considerably lower hoop stresses has been developed and successfully tested at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, FL. The new cooling hole shape allows for extreme power densities (up to 12 W.mm{sup 3}) at a moderate heat flux of only 5 W/mm{sup 2}. The new concept also reduces the hoop stress by about 30--50% by making a Bitter disk compliant in the radial direction through staggering small width and closely spaced elongated cooling holes. Finally, the design is optimized for equal temperature.

  8. Kozai-Lidov Oscillations of Circumstellar Disks

    Science.gov (United States)

    Lubow, Stephen H.; Fu, Wen; Martin, Rebecca G.

    2015-01-01

    It has been known for over 50 years that the orbit of an object in a binary system can undergo strong tilt and eccentricity oscillations. This effect, known as the Kozai-Lidov effect, may explain several observed astronomical phenomena, including the high eccentricities observed for some extra-solar planets. Martin et al. 2014 recently reported simulation results showing that fluid disks can undergo Kozai-Lidov oscillations. Such oscillations can have important consequences on disk and planet evolution. We have continued investigating the conditions for which such oscillations are possible.

  9. Winds from disks in compact binaries

    Energy Technology Data Exchange (ETDEWEB)

    Mauche, C.W.

    1993-10-27

    We herein present an observational and theoretical review of the winds of compact binaries. After a brief consideration of the accretion disk coronae and winds of X-ray binaries, the review concentrates on the winds of cataclysmic variables (CVs). Specifically, we consider the related problems of the geometry and mass-loss rate of the winds of CVs, their ionization state and variability, and the results from studies of eclipsing CVs. Finally, the properties of bona fide accretion disk wind models are reviewed.

  10. INTELLIGENT INTEGRATION CONTROL OF ROTATING DISK VIBRATION

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The rotating disk is a basic machine part that is u sed widely in industry. The motion equation is transformed into the dynamic equa tion in real modal space. The personating intelligent integration is introduced to improve the existing control method. These modes that affect the transverse v ibration mainly are included to simulate the vibration of rotating disk, and two methods are applied separately on condition that the sensor and the ac tuator are collocated and non-collocated. The results obtained by all-sided si mulations show that the new method can obtain better control effect, especially when the sensor and the actuator are non-collocated.

  11. Bonding over Dentin Replacement Materials.

    Science.gov (United States)

    Meraji, Naghmeh; Camilleri, Josette

    2017-08-01

    Dentin replacement materials are necessary in large cavities to protect the pulp and reduce the bulk of filling material. These materials are layered with a composite resin restorative material. Microleakage caused by poor bonding of composite resin to underlying dentin replacement material will result in pulp damage. The aim of this study was to characterize the interface between dentin replacement materials and composite resin and to measure the shear bond strength after dynamic aging. Biodentine (Septodont, Saint Maur-des-Fosses, France), Theracal LC (Bisco, Schaumburg, IL), and Fuji IX (GC, Tokyo, Japan) were used as dentin replacement materials. They were then overlaid with a total-etch and bonding agent or a self-etch primer and composite resin or a glass ionomer cement. All combinations were thermocycled for 3000 cycles. The interface was characterized using scanning electron microscopy and elemental mapping. Furthermore, the shear bond strength was assessed. The Biodentine surface was modified by etching. The Theracal LC and Fuji IX microstructure was unchanged upon the application of acid etch. The Biodentine and glass ionomer interface showed an evident wide open space, and glass particles from the glass ionomer adhered to the Biodentine surface. Elemental migration was shown with aluminum, barium, fluorine, and ytterbium present in Biodentine from the overlying composite resin. Calcium was more stable. The bond strength between Theracal LC and composite using a total-etch technique followed by self-etch primer achieved the best bond strength values. Biodentine exhibited the weakest bond with complete failure of bonding shown after demolding and thermocycling. Dynamic aging is necessary to have clinically valid data. Bonding composite resin to water-based dentin replacement materials is still challenging, and further alternatives for restoration of teeth using such materials need to be developed. Copyright © 2017 American Association of Endodontists

  12. TOWARD A GLOBAL EVOLUTIONARY MODEL OF PROTOPLANETARY DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Xue-Ning, E-mail: xbai@cfa.harvard.edu [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-51, Cambridge, MA 02138 (United States)

    2016-04-20

    A global picture of the evolution  of protoplanetary disks (PPDs) is key to understanding almost every aspect of planet formation, where standard α-disk models have been continually employed for their simplicity. In the meantime, disk mass loss has been conventionally attributed to photoevaporation, which controls disk dispersal. However, a paradigm shift toward accretion driven by magnetized disk winds has taken place in recent years, thanks to studies of non-ideal magnetohydrodynamic effects in PPDs. I present a framework of global PPD evolution aiming to incorporate these advances, highlighting the role of wind-driven accretion and wind mass loss. Disk evolution is found to be largely dominated by wind-driven processes, and viscous spreading is suppressed. The timescale of disk evolution is controlled primarily by the amount of external magnetic flux threading the disks, and how rapidly the disk loses the flux. Rapid disk dispersal can be achieved if the disk is able to hold most of its magnetic flux during the evolution. In addition, because wind launching requires a sufficient level of ionization at the disk surface (mainly via external far-UV (FUV) radiation), wind kinematics is also affected by the FUV penetration depth and disk geometry. For a typical disk lifetime of a few million years, the disk loses approximately the same amount of mass through the wind as through accretion onto the protostar, and most of the wind mass loss proceeds from the outer disk via a slow wind. Fractional wind mass loss increases with increasing disk lifetime. Significant wind mass loss likely substantially enhances the dust-to-gas mass ratio and promotes planet formation.

  13. Evolution of Thick Accretion Disks Produced by Tidal Disruption Events

    CERN Document Server

    Ulmer, A

    1997-01-01

    Geometrically thick disks may form after tidal disruption events, and rapid accretion may lead to short flares followed by long-term, lower-level emission. Using a novel accretion disk code which relies primarily on global conservation laws and the assumption that viscosity is everywhere positive, a broad range of physically allowed evolutionary sequences of thick disks is investigated. The main result is that accretion in the thick disk phase can consume only a fraction of the initial disk material before the disk cools and becomes thin. This fraction is ~0.5-0.9 for disruptions around 10^6 to 10^7 M_ødot black holes and is sensitive to the mean angular momentum of the disk. The residual material will accrete in some form of thin disk over a longer period of time. The initial thick disk phase may reduce the dimming timescale of the disk by a factor of ~2 from estimates based on thin disks alone. Assuming an 0.5 M_ødot initial thick disk, even if the thin disks become advection dominated, the black hole mas...

  14. Conservative GRMHD simulations of moderately thin, tilted accretion disks

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, Danilo Morales [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, SP 05508-090 (Brazil); Fragile, P. Chris [Department of Physics and Astronomy, College of Charleston, Charleston, SC 29424 (United States); Zhuravlev, Viacheslav V. [Sternberg Astronomical Institute, Moscow M. V. Lomonosov State University, Universitetskij pr. 13, 119992 Moscow (Russian Federation); Ivanov, Pavel B., E-mail: danilo.morales@iag.usp.br [Astro Space Centre, P. N. Lebedev Physical Institute, 84/32 Profsoyuznaya Street, 117810 Moscow (Russian Federation)

    2014-12-01

    This paper presents our latest numerical simulations of accretion disks that are misaligned with respect to the rotation axis of a Kerr black hole. In this work, we use a new, fully conservative version of the Cosmos++ general relativistic magnetohydrodynamics (GRMHD) code, coupled with an ad hoc cooling function designed to control the thickness of the disk. Together these allow us to simulate the thinnest tilted accretion disks ever using a GRMHD code. In this way, we are able to probe the regime where the dimensionless stress and scale height of the disk become comparable. We present results for both prograde and retrograde cases. The simulated prograde tilted disk shows no sign of Bardeen-Petterson alignment even in the innermost parts of the disk. The simulated retrograde tilted disk, however, does show modest alignment. The implication of these results is that the parameter space associated with Bardeen-Petterson alignment for prograde disks may be rather small, only including very thin disks. Unlike our previous work, we find no evidence for standing shocks in our simulated tilted disks. We ascribe this to the black hole spin, tilt angle, and disk scale height all being small in these simulations. We also add to the growing body of literature pointing out that the turbulence driven by the magnetorotational instability in global simulations of accretion disks is not isotropic. Finally, we provide a comparison between our moderately thin, untilted reference simulation and other numerical simulations of thin disks in the literature.

  15. Fomalhaut's Debris Disk and Planet: Constraining the Mass of Formalhaut B from Disk Morphology

    Science.gov (United States)

    Chiang, E.; Kite, E.; Kalas, P.; Graham, J. R.; Clampin, M.

    2008-01-01

    Following the optical imaging of exoplanet candidate Fomalhaut b (Fom b), we present a numerical model of how Fomalhaut's debris disk is gravitationally shaped by a single interior planet. The model is simple, adaptable to other debris disks, and can be extended to accommodate multiple planets. If Fom b is the dominant perturber of the belt, then to produce the observed disk morphology it must have a mass M(sub pl) 101.5AU, and an orbital eccentricity e(sub pl) = 0.11 - 0.13. These conclusions are independent of Fom b's photometry. To not disrupt the disk, a greater mass for Fom b demands a smaller orbit farther removed from the disk; thus, future astrometric measurement of Fom b's orbit, combined with our model of planet-disk interaction, can be used to determine the mass more precisely. The inner edge of the debris disk at a approximately equals 133AU lies at the periphery of Fom b's chaotic zone, and the mean disk eccentricity of e approximately equals 0.11 is secularly forced by the planet, supporting predictions made prior to the discovery of Fom b. However, previous mass constraints based on disk morphology rely on several oversimplifications. We explain why our constraint is more reliable. It is based on a global model of the disk that is not restricted to the planet's chaotic zone boundary. Moreover, we screen disk parent bodies for dynamical stability over the system age of approximately 100 Myr, and model them separately from their dust grain progeny; the latter's orbits are strongly affected by radiation pressure and their lifetimes are limited to approximately 0.1 Myr by destructive grain-grain collisions. The single planet model predicts that planet and disk orbits be apsidally aligned. Fomalhaut b's nominal space velocity does not bear this out, but the astrometric uncertainties are difficult to quantify. Even if the apsidal misalignment proves real, our calculated upper mass limit of 3 M(sub J) still holds. Parent bodies are evacuated from mean

  16. The Implementation of Hard-Disk Protection Method Based on Disk Filter Driver

    OpenAIRE

    Yangwu Liu; Xisan Wei

    2013-01-01

    In this paper, it analyzes the working mechanism for the hard disk protection based on the current disk filter driver. The core ideology of the mechanism is to redirect the I/O request packet to the disk operation and to restore data automatically after restart the system in the case of transparent operating system to its upper storey. Also, it specifically analyzes the safety trouble by new virus, like the emerging virus, which can penetrate through the filter driver and results the failure ...

  17. Truncation of the Inner Accretion Disk Around a Black Hole at Low Luminosity

    Science.gov (United States)

    Tomsick, John A.; Yamoka, Kazutaka; Corbel, Stephane; Kaaret, Philip; Kalemci, Emrah; Migliari, Simone

    2011-01-01

    Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the accretion disk recedes at low accretion rate. Measurements of the location of the inner edge (R(sub in)) can be made using iron emission lines that arise due to fluorescence of iron in the disk, and these indicate that R(sub in) is very close to the black hole at high and moderate luminosities (greater than or equal to 1% of the Eddington luminosity, L(sub Edd). Here, we report on X-ray observations of the black hole GX 339-4 in the hard state by Suzaku and the Rossi X-ray Timing Explorer that extend iron line studies to 0.14% L(sub Edd) and show that R(sub in) increases by a factor of greater than 27 over the value found when GX 339-4 was bright. The exact value of R(sub in) depends on the inclination of the inner disk (i), and we derive 90% confidence limits of R(sub in) greater than 35 R(sub g) at i = 0 degrees and R(sub in) greater than 175 R(sub g) at i = 30 degrees. This provides direct evidence that the inner portion of the disk is not present at low luminosity, allowing for the possibility that the inner disk is replaced by advection- or magnetically dominated accretion flows.

  18. Stability of accretion disk around rotating black holes

    CERN Document Server

    Mukhopadhyay, B

    2004-01-01

    I discuss the stability of accretion disks when the black hole is considered to be rotating. I show, how the fluid properties get changed for different choices of angular momentum of black holes. I treat the problem in pseudo-Newtonian approach with a suitable potential from Kerr geometry. When the angular momentum of a black hole is considered to be significant, the valid disk parameter region affects and a disk may become unstable. Also the possibility of shock in an accretion disk around rotating black holes is checked. When the black hole is chosen to be rotating, the sonic locations of the accretion disk get shifted or disappear, making the disk unstable by means of loosing entropy. To bring the disk in a stable situation, the angular momentum of the accreting matter has to be reduced/enhanced (for co/counter-rotating disk) by means of some physical process.

  19. Gas and dust structures in protoplanetary disks hosting multiple planets

    CERN Document Server

    Pinilla, P; Ataiee, S; Benisty, M; Birnstiel, T; van Dishoeck, E F; Min, M

    2014-01-01

    Transition disks have dust depleted inner regions and may represent an intermediate step of an on-going disk dispersal process, where planet formation is probably in progress. Recent millimetre observations of transition disks reveal radially and azimuthally asymmetric structures, where micron- and millimetre-sized dust particles may not spatially coexist. These properties can be the result of particle trapping and grain growth in pressure bumps originating from the disk interaction with a planetary companion. The multiple features observed in some transition disks such as SR 21 suggest the presence of more than one planet. We study the gas and dust distributions of a disk hosting two massive planets as function of different disk and dust parameters. Observational signatures such as the spectral energy distribution, sub-millimetre, and polarised images are simulated for the various parameters. We confirm that planets can lead to particle trapping, although for a disk with high viscosity ($\\alpha_{\\rm{turb}}=1...

  20. failure analysis and shock protection of external hard disk drive

    African Journals Online (AJOL)

    user

    Technology for processing and storage of data in portable external storage hard disks has ... system was used to simulate the impact of stress on the structure of the hard disk before and ... highlighted [1] that mechanical vibration and shock.

  1. Viscosity prescription for gravitationally unstable accretion disks

    CERN Document Server

    Rafikov, Roman R

    2015-01-01

    Gravitationally unstable accretion disks emerge in a variety of astrophysical contexts - giant planet formation, FU Orioni outbursts, feeding of AGNs, and the origin of Pop III stars. When a gravitationally unstable disk is unable to cool rapidly it settles into a quasi-stationary, fluctuating gravitoturbulent state, in which its Toomre Q remains close to a constant value Q_0~1. Here we develop an analytical formalism describing the evolution of such a disk, which is based on the assumptions of Q=Q_0 and local thermal equilibrium. Our approach works in the presence of additional sources of angular momentum transport (e.g. MRI), as well as external irradiation. Thermal balance dictates a unique value of the gravitoturbulent stress \\alpha_{gt} driving disk evolution, which is a function of the local surface density and angular frequency. We compare this approach with other commonly used gravitoturbulent viscosity prescriptions, which specify the explicit dependence of stress \\alpha_{gt} on Toomre Q in an ad hoc...

  2. The DiskMass Survey : I. Overview

    NARCIS (Netherlands)

    Bershady, Matthew A.; Verheijen, Marc A. W.; Swaters, Rob A.; Andersen, David R.; Westfall, Kyle B.; Martinsson, Thomas

    2010-01-01

    We present a survey of the mass surface density of spiral disks, motivated by outstanding uncertainties in rotation-curve decompositions. Our method exploits integral-field spectroscopy to measure stellar and gas kinematics in nearly face-on galaxies sampled at 515, 660, and 860 nm, using the custom

  3. Evaporation of ion-irradiated disks

    CERN Document Server

    Dullemond, C P

    2005-01-01

    We calculate the evaporation of a cool accretion disk around a black hole due to the ion-bombardment by an ion supported accretion flow (here ISAF, or optically thin ADAF). As first suggested by Spruit & Deufel (2002), this evaporation takes place in two stages: ion bombardment of the cool disk (Shakura-Sunyaev disk: SSD) produces an intermediate-temperature layer on top of the disk (`warm layer') which constitutes an independent accretion flow on both sides of the SSD. As this warm material accretes inward of the inner radius of the SSD, it becomes thermally unstable by lack of cooling of photons, and evaporates into the ISAF, thereby feeding the latter. Angular momentum conservation forces a certain fraction of the ISAF material to move outward, where it can bombard the SSD with its hot ions. The flow geometry is derived by computing stationary solutions of the continuity- and angular momentum equations for the three components (ISAF, warm flow and SSD). The overall radiative output is dominated by hard...

  4. MHD of accretion-disk flows

    Science.gov (United States)

    Yankova, Krasimira

    2015-01-01

    Accretion is one of the most important problems of astrophysics concerning the transfer of matter and the transformation of energy into space. Process represents a falling of the substance on a cosmic object from the surrounding area and is a powerful gravitational mechanism for the production of radiation. Accretion disc effectively converts the mass of the substance by viscous friction and released potential energy transformed into radiation by particle collisions. Accretion onto compact object shows high energy efficiency and temporal variability in a broad class of observational data in all ranges. In the disks of these objects are developed a series instabilities and structures that govern the distribution of the energy. They are expressed in many variety non-stationary phenomena that we observe. That is why we propose generalized model of magnetized accretion disk with advection, which preserves the nonlinearity of the problem. We study interaction of the plasmas flow with the magnetic field, and how this affects the self-organizing disk. The aim of the work is to describe the accretion flow in detail, in his quality of the open astrophysical system, to investigate the evolution and to reveal the mechanisms of the structuring the disk-corona system for to interpret correctly the high energy behavior of such sources.

  5. Complex organic molecules in protoplanetary disks

    CERN Document Server

    Walsh, Catherine; Nomura, Hideko; Herbst, Eric; Weaver, Susanna L Widicus; Aikawa, Yuri; Laas, Jake C; Vasyunin, Anton I

    2014-01-01

    (Abridged) Protoplanetary disks are vital objects in star and planet formation, possessing all the material which may form a planetary system orbiting the new star. We investigate the synthesis of complex organic molecules (COMs) in disks to constrain the achievable chemical complexity and predict species and transitions which may be observable with ALMA. We have coupled a 2D model of a protoplanetary disk around a T Tauri star with a gas-grain chemical network including COMs. We compare compare synthesised line intensities and calculated column densities with observations and determine those COMs which may be observable in future. COMs are efficiently formed in the disk midplane via grain-surface chemical reactions, reaching peak grain-surface fractional abundances 1e-6 - 1e-4 that of the H nuclei number density. COMs formed on grain surfaces are returned to the gas phase via non-thermal desorption; however, gas-phase species reach lower fractional abundances than their grain-surface equivalents, 1e-12 - 1e-...

  6. Planetary Torque in 3D Isentropic Disks

    Science.gov (United States)

    Fung, Jeffrey; Masset, Frédéric; Lega, Elena; Velasco, David

    2017-03-01

    Planetary migration is inherently a three-dimensional (3D) problem, because Earth-size planetary cores are deeply embedded in protoplanetary disks. Simulations of these 3D disks remain challenging due to the steep resolution requirements. Using two different hydrodynamics codes, FARGO3D and PEnGUIn, we simulate disk–planet interaction for a one to five Earth-mass planet embedded in an isentropic disk. We measure the torque on the planet and ensure that the measurements are converged both in resolution and between the two codes. We find that the torque is independent of the smoothing length of the planet’s potential (r s), and that it has a weak dependence on the adiabatic index of the gaseous disk (γ). The torque values correspond to an inward migration rate qualitatively similar to previous linear calculations. We perform additional simulations with explicit radiative transfer using FARGOCA, and again find agreement between 3D simulations and existing torque formulae. We also present the flow pattern around the planets that show active flow is present within the planet’s Hill sphere, and meridional vortices are shed downstream. The vertical flow speed near the planet is faster for a smaller r s or γ, up to supersonic speeds for the smallest r s and γ in our study.

  7. Computing Temperatures in Optically Thick Protoplanetary Disks

    Science.gov (United States)

    Capuder, Lawrence F.. Jr.

    2011-01-01

    We worked with a Monte Carlo radiative transfer code to simulate the transfer of energy through protoplanetary disks, where planet formation occurs. The code tracks photons from the star into the disk, through scattering, absorption and re-emission, until they escape to infinity. High optical depths in the disk interior dominate the computation time because it takes the photon packet many interactions to get out of the region. High optical depths also receive few photons and therefore do not have well-estimated temperatures. We applied a modified random walk (MRW) approximation for treating high optical depths and to speed up the Monte Carlo calculations. The MRW is implemented by calculating the average number of interactions the photon packet will undergo in diffusing within a single cell of the spatial grid and then updating the packet position, packet frequencies, and local radiation absorption rate appropriately. The MRW approximation was then tested for accuracy and speed compared to the original code. We determined that MRW provides accurate answers to Monte Carlo Radiative transfer simulations. The speed gained from using MRW is shown to be proportional to the disk mass.

  8. Magnetic Field Transport in Accretion Disks

    Science.gov (United States)

    Jafari, Amir; Vishniac, Ethan

    2017-06-01

    The most plausible theories for launching astrophysical jets rely on strong magnetic fields at the inner parts of some accretion disks. An internal dynamo can in principle generate small scale magnetic fields in situ but generating a large scale field in a disk seems a difficult task in the dynamo theories. In fact, as far as numerous numerical experiments indicate, a dynamo-generated field in general would not be coherent enough over the large length scales of order the disk's radius. Instead, a large scale poloidal field dragged in from the environment, and compressed by the accretion, provides a more promising possibility. The difficulty in the latter picture, however, arises from the reconnection of the radial field component across the mid-plane which annihilates the field faster than it is dragged inward by the accretion. We suggest that a combination of different effects, including magnetic buoyancy and turbulent pumping, is responsible for the vertical transport of the field lines toward the surface of the disk. The radial component of the poloidal field vanishes at the mid-plane, which efficiently impedes reconnection, and grows exponentially toward the surface where it can become much larger than the vertical field component. This allows the poloidal field to be efficiently advected to small radii until the allowed bending angle drops to of order unity, and the field can drive a strong outflow.

  9. The Inner Rim in Protoplanetary Disks

    Science.gov (United States)

    Flock, Mario; Turner, Neal J.

    2016-10-01

    Many stars host planets orbiting within one astronomical unit (AU). These close planets origins are a mystery that motivates investigating protoplanetary disks central regions.A key factor governing the conditions near the star is the silicate sublimation front, which largely determines where the starlight is absorbed, and which is often called the inner rim. We present the first radiation hydrodynamical modeling of the sublimation front in the disks around the young intermediate-mass stars called Herbig Ae stars. The models are axisymmetric, and include starlight heating, silicate grains sublimating and condensing to equilibrium at the local, timedependent temperature and density, and accretion stresses parametrizing the results of MHD magneto-rotational turbulence models.The results show for the first time the dynamical stability of the rim. Passing the model disks into Monte Carlo radiative transfer calculations allows us to directly compare with observational constraints. The inner rim has a substantial radial extent, corresponding to several disk scale heights. A pressure maximum develops at the position of thermal ionization at temperatures about 1000 K. The pressure maximum is capable of halting solid pebbles radial drift and concentrating them in a zone where temperatures are sufficiently high for annealing to form crystalline silicates.

  10. Rossby Wave Instability of Keplerian Accretion Disks

    CERN Document Server

    Lovelace, R V E; Colgate, S A; Nelson, A F

    1999-01-01

    We find a linear instability of non-axisymmetric Rossby waves in a thin non-magnetized Keplerian disk when there is a local maximum in the radial profile of a key function ${\\cal L}(r) \\equiv {\\cal F}(r) S^{2/\\Gamma}(r)$, where ${\\cal F}^{-1} = \\hat {\\bf z}\\cdot ({\\bf \

  11. Exoplanets and debris disk imaging with JWST

    Science.gov (United States)

    Pueyo, Laurent; Soummer, Remi; Perrin, Marshall D.

    2017-06-01

    Dramatic progress in exoplanetary systems imaging has occurred since the first generation of space coronagraphs on HST (NICMOS, STIS, ACS). While HST remains at forefront of both exoplanetary and circumstellar disk science, ground-based instruments have improved by three orders of magnitudes over the past decade. JWST will extend the current state of the art with a larger set of superior coronagraphs and greater sensitivity across more than a factor of 10 in wavelength, making it extraordinarily capable for detailed imaging characterization of planets and disks. We will address specific questions about nearby exoplanetary systems, while also optimizing observing strategies across the breadth of JWST’s high-contrast imaging modes, as follows: (a) Deep, multi-wavelength observations of selected nearby stars hosting known debris disks & planets. We will use the NIRCam and MIRI coronagraphs across the full range of JWST wavelengths, and perhaps MIRI MRS spatially resolved spectroscopy. Each comprehensive dataset will support a variety of investigations addressing both disk characterization and exoplanet detection & characterization. (b) Characterization of Planetary Systems around Cool M Stars. We will observe young and dusty M dwarfs, to complement observations of the closer but older M dwarf samples under consideration by other GTO groups. JWST observations will dramatically exceed HST images in their ability to address questions about the properties of dust rings, while the more favorable contrast ratios of planets relative to M dwarf hosts will enable sensitivity to relatively low mass planetary companions.

  12. Fast Radial Flows in Transition Disk Holes

    CERN Document Server

    Rosenfeld, Katherine A; Andrews, Sean M

    2013-01-01

    Protoplanetary "transition" disks have large, mass-depleted central cavities, yet also deliver gas onto their host stars at rates comparable to disks without holes. The paradox of simultaneous transparency and accretion can be explained if gas flows inward at much higher radial speeds inside the cavity than outside the cavity, since surface density (and by extension optical depth) varies inversely with inflow velocity at fixed accretion rate. Radial speeds within the cavity might even have to approach free-fall values to explain the huge surface density contrasts inferred for transition disks. We identify observational diagnostics of fast radial inflow in channel maps made in optically thick spectral lines. Signatures include (1) twisted isophotes in maps made at low systemic velocities and (2) rotation of structures observed between maps made in high-velocity line wings. As a test case, we apply our new diagnostic tools to archival ALMA data on the transition disk HD 142527, and uncover evidence for free-fal...

  13. Tilting of a Disk of Gravitating Rings

    CERN Document Server

    Lovelace, R V E

    1997-01-01

    The present work represents an attempt to understand the `rules of behavior' of observed warps in the HI disks of spiral galaxies found by Briggs (1990). In contrast with most earlier theoretical work, the present study investigates different initial value problems of a warped disk in an oblate (or prolate) halo potential, and it represents the disk warp in terms of $N$ independently tilted, self-gravitating, concentric rings. This representation gives new insight into the disk warping. A new constant of the motion of $N$ tilted rings is identified (in addition to the energy). The phenomenon of phase-locking of the lines-of-nodes of nearby rings due to self-gravity is demonstrated. We consider the influence of dynamical friction due to ring motion through the halo matter as well as friction between gaseous rings with different vertical motions due to turbulent viscosity. We first consider the dynamics of one, two, and three tilted rings of different radii in a halo potential. We go on to develop dynamical equ...

  14. Asymmetric transition disks: Vorticity or eccentricity?

    CERN Document Server

    Zsom, A; Ghanbari, J

    2013-01-01

    Context. Transition disks typically appear in resolved millimeter observations as giant dust rings surrounding their young host stars. More accurate observations with ALMA have shown several of these rings to be in fact asymmetric: they have lopsided shapes. It has been speculated that these rings act as dust traps, which would make them important laboratories for studying planet formation. It has been shown that an elongated giant vortex produced in a disk with a strong viscosity jump strikingly resembles the observed asymmetric rings. Aims. We aim to study a similar behavior for a disk in which a giant planet is embedded. However, a giant planet can induce two kinds of asymmetries: (1) a giant vortex, and (2) an eccentric disk. We studied under which conditions each of these can appear, and how one can observationally distinguish between them. This is important because only a vortex can trap particles both radially and azimuthally, while the eccentric ring can only trap particles in radial direction. Method...

  15. Strength of Cracked Reinforced Concrete Disks

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1999-01-01

    The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...

  16. Resolving the inner disk of UX Orionis

    Science.gov (United States)

    Kreplin, A.; Madlener, D.; Chen, L.; Weigelt, G.; Kraus, S.; Grinin, V.; Tambovtseva, L.; Kishimoto, M.

    2016-05-01

    Aims: The cause of the UX Ori variability in some Herbig Ae/Be stars is still a matter of debate. Detailed studies of the circumstellar environment of UX Ori objects (UXORs) are required to test the hypothesis that the observed drop in photometry might be related to obscuration events. Methods: Using near- and mid-infrared interferometric AMBER and MIDI observations, we resolved the inner circumstellar disk region around UX Ori. Results: We fitted the K-, H-, and N-band visibilities and the spectral energy distribution (SED) of UX Ori with geometric and parametric disk models. The best-fit K-band geometric model consists of an inclined ring and a halo component. We obtained a ring-fit radius of 0.45 ± 0.07 AU (at a distance of 460 pc), an inclination of 55.6 ± 2.4°, a position angle of the system axis of 127.5 ± 24.5°, and a flux contribution of the over-resolved halo component to the total near-infrared excess of 16.8 ± 4.1%. The best-fit N-band model consists of an elongated Gaussian with a HWHM ~ 5 AU of the semi-major axis and an axis ration of a/b ~ 3.4 (corresponding to an inclination of ~72°). With a parametric disk model, we fitted all near- and mid-infrared visibilities and the SED simultaneously. The model disk starts at an inner radius of 0.46 ± 0.06 AU with an inner rim temperature of 1498 ± 70 K. The disk is seen under an nearly edge-on inclination of 70 ± 5°. This supports any theories that require high-inclination angles to explain obscuration events in the line of sight to the observer, for example, in UX Ori objects where orbiting dust clouds in the disk or disk atmosphere can obscure the central star. Based on observations made with ESO telescopes at Paranal Observatory under program IDs: 090.C-0769, 074.C-0552.

  17. THE COLLISIONAL EVOLUTION OF DEBRIS DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Gaspar, Andras; Rieke, George H. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Balog, Zoltan, E-mail: agaspar@as.arizona.edu, E-mail: grieke@as.arizona.edu, E-mail: balog@mpia.de [Max-Plank Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

    2013-05-01

    We explore the collisional decay of disk mass and infrared emission in debris disks. With models, we show that the rate of the decay varies throughout the evolution of the disks, increasing its rate up to a certain point, which is followed by a leveling off to a slower value. The total disk mass falls off {proportional_to}t {sup -0.35} at its fastest point (where t is time) for our reference model, while the dust mass and its proxy-the infrared excess emission-fades significantly faster ({proportional_to}t {sup -0.8}). These later level off to a decay rate of M{sub tot}(t){proportional_to}t {sup -0.08} and M{sub dust}(t) or L{sub ir}(t){proportional_to}t {sup -0.6}. This is slower than the {proportional_to}t {sup -1} decay given for all three system parameters by traditional analytic models. We also compile an extensive catalog of Spitzer and Herschel 24, 70, and 100 {mu}m observations. Assuming a log-normal distribution of initial disk masses, we generate model population decay curves for the fraction of stars harboring debris disks detected at 24 {mu}m. We also model the distribution of measured excesses at the far-IR wavelengths (70-100 {mu}m) at certain age regimes. We show general agreement at 24 {mu}m between the decay of our numerical collisional population synthesis model and observations up to a Gyr. We associate offsets above a Gyr to stochastic events in a few select systems. We cannot fit the decay in the far-infrared convincingly with grain strength properties appropriate for silicates, but those of water ice give fits more consistent with the observations (other relatively weak grain materials would presumably also be successful). The oldest disks have a higher incidence of large excesses than predicted by the model; again, a plausible explanation is very late phases of high dynamical activity around a small number of stars. Finally, we constrain the variables of our numerical model by comparing the evolutionary trends generated from the exploration

  18. Urbanization, Ikization, and Replacement Dynamics

    CERN Document Server

    Chen, Yanguang

    2015-01-01

    The phenomenon of Iks was first found by anthropologists and biologists, but it is actually a problem of human geography. However, it has not yet drawn extensive attention of geographers. In this paper, a hypothesis of ikization is presented that sudden and violent change of geographical environments results in dismantling of traditional culture, which then result in collective depravity of a nationality. By quantitative analysis and mathematical modeling, the causality between urbanization and ikization is discussed, and the theory of replacement dynamics is employed to interpret the process of ikization. Urbanization is in essence a nonlinear process of population replacement. Urbanization may result in ikization because that the migration of population from rural regions to urban regions always give rise to abrupt changes of geographical environments and traditional culture. It is necessary to protect the geographical environment against disruption, and to inherit and develop traditional culture in order t...

  19. [MINIMALLY INVASIVE AORTIC VALVE REPLACEMENT].

    Science.gov (United States)

    Tabata, Minoru

    2016-03-01

    Minimally invasive aortic valve replacement (MIAVR) is defined as aortic valve replacement avoiding full sternotomy. Common approaches include a partial sternotomy right thoracotomy, and a parasternal approach. MIAVR has been shown to have advantages over conventional AVR such as shorter length of stay and smaller amount of blood transfusion and better cosmesis. However, it is also known to have disadvantages such as longer cardiopulmonary bypass and aortic cross-clamp times and potential complications related to peripheral cannulation. Appropriate patient selection is very important. Since the procedure is more complex than conventional AVR, more intensive teamwork in the operating room is essential. Additionally, a team approach during postoperative management is critical to maximize the benefits of MIAVR.

  20. Radiation thermo-chemical models of protoplanetary disks I. Hydrostatic disk structure and inner rim

    NARCIS (Netherlands)

    Woitke, P.; Kamp, I.; Thi, W. -F.

    Context. Emission lines from protoplanetary disks originate mainly in the irradiated surface layers, where the gas is generally warmer than the dust. Therefore, interpreting emission lines requires detailed thermo-chemical models, which are essential to converting line observations into

  1. Planetesimal and Protoplanet Dynamics in a Turbulent Protoplanetary Disk: Ideal Stratified Disks

    CERN Document Server

    Yang, Chao-Chin; Menou, Kristen

    2011-01-01

    Due to the gravitational influence of density fluctuations driven by magneto-rotational instability in the gas disk, planetesimals and protoplanets undergo diffusive radial migration as well as changes in other orbital properties. The magnitude of the effect on particle orbits can have important consequences for planet formation scenarios. We use the local-shearing-box approximation to simulate an ideal, isothermal, magnetized gas disk with vertical density stratification and simultaneously evolve numerous massless particles moving under the gravitational field of the gas and the host star. We measure the evolution of the particle orbital properties, including mean radius, eccentricity, inclination, and velocity dispersion, and its dependence on the disk properties and the particle initial conditions. Although the results converge with resolution for fixed box dimensions, we find the response of the particles to the gravity of the turbulent gas correlates with the horizontal box size, up to 16 disk scale heig...

  2. Resonant Excitation of Disk Oscillations in Deformed Disks VII: Stability Criterion in MHD Systems

    CERN Document Server

    Kato, Shoji

    2013-01-01

    In a disk with an oscillatory deformation from an axisymmetric state with frequency $\\omega_{\\rm D}$ and azimuthal wavenumber $m_{\\rm D}$, a set of two normal mode oscillations with frequency and azimuthal wavenumber being ($\\omega_1$, $m_1$) and ($\\omega_2$, $m_2$) resonantly couple through the disk deformation, when the resonant conditions ($\\omega_1+\\omega_2+\\omega_{\\rm D}=0$ and $m_1+m_2+m_{\\rm D}=0$) are satisfied. In the case of hydrodynamical disks, the resonance amplifies the set of the oscillations if $(E_1/\\omega_1)(E_2/\\omega_2)>0$ (Kato 2013b), where $E_1$ and $E_2$ are wave energies of the two oscillations with $\\omega_1$ and $\\omega_2$, respectively. In this paper we show that this instability criterion is still valid even when the oscillations are ideal MHD ones in magnetized disks, if the displacements associated with the oscillations vanish on the boundary of the system.

  3. Modeling Dust Emission of HL Tau Disk Based on Planet-Disk Interactions

    CERN Document Server

    Jin, Sheng; Isella, Andrea; Li, Hui; Ji, Jianghui

    2016-01-01

    We use extensive global two-dimensional hydrodynamic disk gas+dust simulations with embedded planets, coupled with three dimensional radiative transfer calculations, to model the dust ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We include the self-gravity of disk gas and dust components and make reasonable choices of disk parameters, assuming an already settled dust distribution and no planet migration. We can obtain quite adequate fits to the observed dust emission using three planets with masses 0.35, 0.17, and 0.26 $M_{Jup}$ at 13.1, 33.0, and 68.6 AU, respectively. Implications for the planet formation as well as the limitations of this scenario are discussed.

  4. MODELING DUST EMISSION OF HL TAU DISK BASED ON PLANET–DISK INTERACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Sheng; Ji, Jianghui [Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Li, Shengtai; Li, Hui [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Isella, Andrea [Rice University, Houston, TX (United States)

    2016-02-10

    We use extensive global two-dimensional hydrodynamic disk gas+dust simulations with embedded planets, coupled with three-dimensional radiative transfer calculations, to model the dust ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We include the self-gravity of disk gas and dust components and make reasonable choices of disk parameters, assuming an already settled dust distribution and no planet migration. We can obtain quite adequate fits to the observed dust emission using three planets with masses of 0.35, 0.17, and 0.26 M{sub Jup} at 13.1, 33.0, and 68.6 AU, respectively. Implications for the planet formation as well as the limitations of this scenario are discussed.

  5. Mitochondrial Replacement: Ethics And Identity

    OpenAIRE

    Wrigley, Anthony; Wilkinson, Stephen; Appleby, John B

    2015-01-01

    Mitochondrial replacement techniques (MRTs) have the potential to allow prospective parents who are at risk of passing on debilitating or even life-threatening mitochondrial disorders to have healthy children to whom they are genetically related. Ethical concerns have however been raised about these techniques. This article focuses on one aspect of the ethical debate, the question of whether there is any moral difference between the two types of MRT proposed: Pronuclear Transfer (PNT) and Mat...

  6. Replacing magnets at the LHC

    CERN Multimedia

    LHC, LSI2, Point 4

    2013-01-01

    CERN engineers have been working through the night this week to move the final replacement dipole magnets into position on the Large Hadron Collider (LHC). Though there are several still to go, the teams expect to have completed the task by the end of this month. Dipole magnets bend the paths of particles as they travel around the circular accelerator. Of the LHC's 1232 dipoles – each 15 metres long and weighing 35 tonnes – 15 are being replaced as part of the long shutdown of CERN's accelerator complex. These 15 magnets suffered wear and tear during the LHC's first 4-year run. Three quadrupole-magnet assemblies – which help to focus particles into a tight beam – have also been replaced. Moving such heavy magnets requires specially adapted cranes and trailers both above and below ground. There are several access points on the LHC. Some, such as the 100-metre vertical access shaft down to the ALICE experiment, are equipped with lifts to allow technical personnel and visitors down to the caverns. Other ...

  7. Results of Austin Moore replacement.

    Directory of Open Access Journals (Sweden)

    Jadhav A

    1996-04-01

    Full Text Available Forty cases of Austin Moore Replacement done for transcervical fractures of the femur in patients were reviewed after a period of 12 to 48 months postoperatively (mean 26 mth. 30 cases (75% had mild to severe pain of non-infective origin, starting as early as 6 months postoperatively. This was irrespective of the make, size or position (varus/valgus of the prosthesis. Though the Aufranc and Sweet clinical scoring was satisfactory in 65% cases, radiological evidence of complications like sinking, protrusion, etc. were seen in majority of the cases. Calcar resorption was seen in 34 cases (85% as early as 4 months postoperatively. Results of THR and bipolar replacement done for transcervical fractures in recent literature show 85% pain-free cases at 5 years. We feel that Austin Moore Replacement should be reserved for patients more than 65 years of age and those who are less active or debilitated because of other factors, because of increased acetabular wear with time in the younger individual. This is corroborated by unsatisfactory results in patients less than 65 years of age (p < 0.05.

  8. The caudal septum replacement graft.

    Science.gov (United States)

    Foda, Hossam M T

    2008-01-01

    To describe a technique for reconstructing the lost tip support in cases involving caudal septal and premaxillary deficiencies. The study included 120 patients with aesthetic and functional nasal problems resulting from the loss of caudal septal and premaxillary support. An external rhinoplasty approach was performed to reconstruct the lost support using a cartilaginous caudal septum replacement graft and premaxillary augmentation with Mersilene mesh. The majority of cases (75%) involved revisions in patients who had previously undergone 1 or more nasal surgical procedures. A caudal septum replacement graft was combined with premaxillary augmentation in 93 patients (77.5%). The mean follow-up period was 3 years (range, 1-12 years). The technique succeeded in correcting the external nasal deformities in all patients and resulted in a significant improvement in breathing in 74 patients (86%) with preoperative nasal obstruction. There were no cases of infection, displacement, or extrusion. The caudal septum replacement graft proved to be very effective in restoring the lost tip support in patients with caudal septal deficiency. Combining the graft with premaxillary augmentation using Mersilene mesh helped increase support and stability over long-term follow-up.

  9. THE VLA VIEW OF THE HL TAU DISK: DISK MASS, GRAIN EVOLUTION, AND EARLY PLANET FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco-González, Carlos; Rodríguez, Luis F.; Galván-Madrid, Roberto [Instituto de Radioastronomía y Astrofísica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Henning, Thomas; Linz, Hendrik; Birnstiel, Til; Boekel, Roy van; Klahr, Hubert [Max-Planck-Institut für Astronomie Heidelberg, Königstuhl 17, D-69117 Heidelberg (Germany); Chandler, Claire J.; Pérez, Laura [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States); Anglada, Guillem; Macias, Enrique; Osorio, Mayra [Instituto de Astrofísica de Andalucía (CSIC), Apartado 3004, E-18080 Granada (Spain); Flock, Mario [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Menten, Karl [Jansky Fellow of the National Radio Astronomy Observatory (United States); Testi, Leonardo [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany); Torrelles, José M. [Institut de Ciències de l’Espai (CSIC-IEEC) and Institut de Ciències del Cosmos (UB-IEEC), Martí i Franquès 1, E-08028 Barcelona (Spain); Zhu, Zhaohuan, E-mail: c.carrasco@crya.unam.mx, E-mail: l.rodriguez@crya.unam.mx, E-mail: r.galvan@crya.unam.mx, E-mail: henning@mpia.de, E-mail: linz@mpia.de [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2016-04-10

    The first long-baseline ALMA campaign resolved the disk around the young star HL Tau into a number of axisymmetric bright and dark rings. Despite the very young age of HL Tau, these structures have been interpreted as signatures for the presence of (proto)planets. The ALMA images triggered numerous theoretical studies based on disk–planet interactions, magnetically driven disk structures, and grain evolution. Of special interest are the inner parts of disks, where terrestrial planets are expected to form. However, the emission from these regions in HL Tau turned out to be optically thick at all ALMA wavelengths, preventing the derivation of surface density profiles and grain-size distributions. Here, we present the most sensitive images of HL Tau obtained to date with the Karl G. Jansky Very Large Array at 7.0 mm wavelength with a spatial resolution comparable to the ALMA images. At this long wavelength, the dust emission from HL Tau is optically thin, allowing a comprehensive study of the inner disk. We obtain a total disk dust mass of (1–3) × 10{sup −3} M {sub ⊙}, depending on the assumed opacity and disk temperature. Our optically thin data also indicate fast grain growth, fragmentation, and formation of dense clumps in the inner densest parts of the disk. Our results suggest that the HL Tau disk may be actually in a very early stage of planetary formation, with planets not already formed in the gaps but in the process of future formation in the bright rings.

  10. The 2009 Analysis of Information Remaining on Disks Offered for Sale on the Second Hand Market

    Directory of Open Access Journals (Sweden)

    Andy Jones

    2010-12-01

    Full Text Available The ever increasing use and reliance upon computers in both the public and private sector has led to enormous numbers of computers being disposed of at the end of their useful life within an organisation. As the cost of computers has dropped, their use in the home has also continued to increase. In most organisations, computers have a relatively short life and are replaced on a regular basis with the result that, if not properly cleansed of data, they are released into the public domain containing data that can be relatively up to date. This problem is exacerbated by the increasing popularity and use of smart phones, which also contain significant storage capacity. From the results of the research it remains clear that the majority of organisations and private individuals that are using these computers still remain ignorant or misinformed of the potential volume and type of information that is stored on the hard disks contained within these systems. The evidence of the research is that neither organisations nor individuals have considered, or are aware of, the potential impact of the information that is contained in the disks from these systems becoming available to an unintended third party.This is the fifth study in an ongoing research programme being conducted into the levels and types of information that remain on computer hard disks that have been offered for sale on the second hand market. This ongoing research series has been undertaken to gain an understanding of the level and types of information that remains on these disks, to determine the damage that could potentially be caused if the information was misused, and to determine whether there are any developing trends. The disks used have been purchased in a number of countries.The rationale for this was to determine whether there are any national or regional differences in the way that computer disks are disposed of and to compare the results for any regional or temporal trends. The

  11. Simulations of minor mergers. I. General properties of thick disks

    NARCIS (Netherlands)

    Villalobos, Álvaro; Helmi, Amina

    2008-01-01

    We present simulations of the formation of thick disks via the accretion of twocomponent satellites onto a pre-existing thin disk. Our goal is to establish the detailed characteristics of the thick disks obtained in this way, as well as their dependence on the initial orbital and internal properties

  12. POLAR DISK GALAXY FOUND IN WALL BETWEEN VOIDS

    NARCIS (Netherlands)

    Stanonik, K.; Platen, E.; Aragon-Calvo, M. A.; van Gorkom, J. H.; van de Weygaert, R.; van der Hulst, J. M.; Peebles, P. J. E.

    2009-01-01

    We have found an isolated polar disk galaxy in what appears to be a cosmological wall situated between two voids. This void galaxy is unique as its polar disk was discovered serendipitously in an Hi survey of SDSS void galaxies, with no optical counterpart to the Hi polar disk. Yet the Hi mass in th

  13. Interactions between massive dark halos and warped disks

    NARCIS (Netherlands)

    Kuijken, K; Persic, M; Salucci, P

    1997-01-01

    The normal mode theory for warping of galaxy disks, in which disks are assumed to be tilted with respect to the equator of a massive, flattened dark halo, assumes a rigid, fixed halo. However, consideration of the back-reaction by a misaligned disk on a massive particle halo shows there to be strong

  14. Outer Spiral Disks as Clues to Galaxy Formation and Evolution

    CERN Document Server

    Vlajić, Marija

    2010-01-01

    Recent studies of outer spiral disks have given rise to an abundance of new results. We discuss the observational and theoretical advances that have spurred the interest in disk outskirts, as well as where we currently stand in terms of our understanding of outer disk structure, ages and metallicities.

  15. Hydrocarbon Emission Rings in Protoplanetary Disks Induced by Dust Evolution

    Science.gov (United States)

    Bergin, Edwin A.; Du, Fujun; Cleeves, L. Ilsedore; Blake, G. A.; Schwarz, K.; Visser, R.; Zhang, K.

    2016-11-01

    We report observations of resolved C2H emission rings within the gas-rich protoplanetary disks of TW Hya and DM Tau using the Atacama Large Millimeter Array. In each case the emission ring is found to arise at the edge of the observable disk of millimeter-sized grains (pebbles) traced by submillimeter-wave continuum emission. In addition, we detect a C3H2 emission ring with an identical spatial distribution to C2H in the TW Hya disk. This suggests that these are hydrocarbon rings (i.e., not limited to C2H). Using a detailed thermo-chemical model we show that reproducing the emission from C2H requires a strong UV field and C/O > 1 in the upper disk atmosphere and outer disk, beyond the edge of the pebble disk. This naturally arises in a disk where the ice-coated dust mass is spatially stratified due to the combined effects of coagulation, gravitational settling and drift. This stratification causes the disk surface and outer disk to have a greater permeability to UV photons. Furthermore the concentration of ices that transport key volatile carriers of oxygen and carbon in the midplane, along with photochemical erosion of CO, leads to an elemental C/O ratio that exceeds unity in the UV-dominated disk. Thus the motions of the grains, and not the gas, lead to a rich hydrocarbon chemistry in disk surface layers and in the outer disk midplane.

  16. Simulations of minor mergers. I. General properties of thick disks

    NARCIS (Netherlands)

    Villalobos, Álvaro; Helmi, Amina

    2008-01-01

    We present simulations of the formation of thick disks via the accretion of twocomponent satellites onto a pre-existing thin disk. Our goal is to establish the detailed characteristics of the thick disks obtained in this way, as well as their dependence on the initial orbital and internal properties

  17. The Design of a High-Integrity Disk Management Subsystem

    NARCIS (Netherlands)

    Oey, M.A.

    2005-01-01

    This dissertation describes and experimentally evaluates the design of the Logical Disk, a disk management subsystem that guarantees the integrity of data stored on disk even after system failures, while still providing performance competitive to other storage systems. Current storage systems that

  18. Swimming of a circular disk at low Reynolds number

    CERN Document Server

    Felderhof, B U

    2014-01-01

    The swimming of a circular disk at low Reynolds number is studied for distortion waves along its two planar surfaces with wavelength much smaller than the size of the disk. The calculation is based on an extension of Taylor's work for a planar sheet. It is shown that in general the disk performs both translational and rotational swimming, resulting in a circular orbit.

  19. POLAR DISK GALAXY FOUND IN WALL BETWEEN VOIDS

    NARCIS (Netherlands)

    Stanonik, K.; Platen, E.; Aragon-Calvo, M. A.; van Gorkom, J. H.; van de Weygaert, R.; van der Hulst, J. M.; Peebles, P. J. E.

    2009-01-01

    We have found an isolated polar disk galaxy in what appears to be a cosmological wall situated between two voids. This void galaxy is unique as its polar disk was discovered serendipitously in an Hi survey of SDSS void galaxies, with no optical counterpart to the Hi polar disk. Yet the Hi mass in th

  20. On the Solar System-Debris Disk Connecction

    OpenAIRE

    Moro-Martin, Amaya

    2007-01-01

    This paper emphasizes the connection between solar and extra-solar debris disks: how models and observations of the Solar System are helping us understand the debris disk phenomenon, and vice versa, how debris disks are helping us place our Solar System into context.