WorldWideScience

Sample records for attrition resistant iron-based

  1. DEVELOPMENT OF ATTRITION RESISTANT IRON-BASED FISCHER-TROPSCH CATALYSTS

    International Nuclear Information System (INIS)

    The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H2) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRs) can largely solve this problem. The use of iron-based catalysts is attractive not only due to their low cost and ready availability, but also due to their high water-gas shift activity which makes it possible to use these catalysts with low H2/CO ratios. However, a serious problem with use of Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, makes the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. Recently, fundamental understanding of physical attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried Fe-based catalyst having aps of 70 mm with high attrition resistance. This Fe-based attrition resistant, active and selective catalyst gave 95% CO conversion through 125 hours of testing in a fixed-bed at 270 C, 1.48 MPa, H2/CO=0.67 and 2.0 NL/g-cat/h with C5+ selectivity of >78% and methane selectivity of <5%. However, further development of the catalyst is needed to address the chemical attrition due to phase changes that any Fe-catalyst goes through potentially causing internal stresses within the particle and resulting in weakening, spalling or cracking. The objective of this research is to develop robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry bubble column reactor. Specifically we aim to develop to: (i) improve the performance and preparation procedure of the high activity, high attrition resistant, high alpha iron-based catalysts

  2. Novel Attrition-Resistant Fischer Tropsch Catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Weast, Logan, E.; Staats, William, R.

    2009-05-01

    There is a strong national interest in the Fischer-Tropsch synthesis process because it offers the possibility of making liquid hydrocarbon fuels from reformed natural gas or coal and biomass gasification products. This project explored a new approach that had been developed to produce active, attrition-resistant Fischer-Tropsch catalysts that are based on glass-ceramic materials and technology. This novel approach represented a promising solution to the problem of reducing or eliminating catalyst attrition and maximizing catalytic activity, thus reducing costs. The technical objective of the Phase I work was to demonstrate that glass-ceramic based catalytic materials for Fischer-Tropsch synthesis have resistance to catalytic deactivation and reduction of particle size superior to traditional supported Fischer-Tropsch catalyst materials. Additionally, these novel glass-ceramic-based materials were expected to exhibit catalytic activity similar to the traditional materials. If successfully developed, the attrition-resistant Fischer-Tropsch catalyst materials would be expected to result in significant technical, economic, and social benefits for both producers and public consumers of Fischer-Tropsch products such as liquid fuels from coal or biomass gasification. This program demonstrated the anticipated high attrition resistance of the glass-ceramic materials. However, the observed catalytic activity of the materials was not sufficient to justify further development at this time. Additional testing documented that a lack of pore volume in the glass-ceramic materials limited the amount of surface area available for catalysis and consequently limited catalytic activity. However, previous work on glass-ceramic catalysts to promote other reactions demonstrated that commercial levels of activity can be achieved, at least for those reactions. Therefore, we recommend that glass-ceramic materials be considered again as potential Fischer-Tropsch catalysts if it can be

  3. Enhanced Corrosion Resistance of Iron-Based Amorphous Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rebak, R B; Day, S D; Lian, T; Aprigliano, L F; Hailey, P D; Farmer, J C

    2007-02-18

    Iron-based amorphous alloys possess enhanced hardness and are highly resistant to corrosion, which make them desirable for wear applications in corrosive environments. It was of interest to examine the behavior of amorphous alloys during anodic polarization in concentrated salt solutions and in the salt-fog testing. Results from the testing of one amorphous material (SAM2X5) both in ribbon form and as an applied coating are reported here. Cyclic polarization tests were performed on SAM2X5 ribbon as well as on other nuclear engineering materials. SAM2X5 showed the highest resistance to localized corrosion in 5 M CaCl{sub 2} solution at 105 C. Salt fog tests of 316L SS and Alloy 22 coupons coated with amorphous SAM2X5 powder showed resistance to rusting. Partial devitrification may be responsible for isolated pinpoint rust spots in some coatings.

  4. Effect of High Temperature Aging on the Corrosion Resistance of Iron Based Amorphous Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Day, S D; Haslam, J J; Farmer, J C; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys can be more resistant to corrosion than polycrystalline materials of similar compositions. However, when the amorphous alloys are exposed to high temperatures they may recrystallize (or devitrify) thus losing their resistance to corrosion. Four different types of amorphous alloys melt spun ribbon specimens were exposed to several temperatures for short periods of time. The resulting corrosion resistance was evaluated in seawater at 90 C and compared with the as-prepared ribbons. Results show that the amorphous alloys can be exposed to 600 C for 1-hr. without losing the corrosion resistance; however, when the ribbons were exposed at 800 C for 1-hr. their localized corrosion resistance decreased significantly.

  5. Determination of the attrition resistance of granular charcoals

    International Nuclear Information System (INIS)

    A laboratory procedure has been developed to evaluate the attrition of granular adsorbent charcoals on passing an air flow through the bed. Two factors observed in plant operations were selected as relevant: (1) the characteristic structural vibrations in plant scale equipment (motors, fans, etc.) that are transmitted to charcoal particles and cause the particles to move and rub each other, and (2) the rapid air flow that results in the movement of the attrited dust. In the test a container for charcoal [50 mm diameter and 50 mm high] was vibrated at a frequency of 60 Hz and at a constant energy input manually controlled using a vibration meter in the acceleration mode. Simultaneously, air was applied and exited through glass fiber filter paper. The quantity of dust trapped on the exit filter was then determined, either optically or gravimetrically. The dust formed per minute (attrition coefficient) was found to approach a constant value. The plateau-values from sequential determinations varied with the source of the charcoal; a 5-fold difference was found among a large variety of commercial products. The first testing of a sample released the excess dust accumulated in previous handling of the charcoal. The plateau values were then attained in the succeeding tests and these were characteristic of the material. The results were compared with those obtained for the same charcoals using older test methods such as the Ball and Pan Hardness Test described in RDTM16-1T

  6. Attrition resistant bulk iron catalysts and processes for preparing and using same

    Science.gov (United States)

    Jothimurugesan, Kandaswamy; Goodwin, Jr., James G.; Gangwal, Santosh K.

    2007-08-21

    An attrition resistant precipitated bulk iron catalyst is prepared from iron oxide precursor and a binder by spray drying. The catalysts are preferably used in carbon monoxide hydrogenation processes such as Fischer-Tropsch synthesis. These catalysts are suitable for use in fluidized-bed reactors, transport reactors and, especially, slurry bubble column reactors.

  7. Iron-Based Amorphous Metals:The High Performance Corrosion Resistant Materials(HPCRM) Program

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J

    2007-07-09

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional

  8. Iron-Based Amorphous-Metals: High-Performance Corrosion-Resistant Material (HPCRM) Development

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Choi, J S; Saw, C; Haslam, J; Day, D; Hailey, P; Lian, T; Rebak, R; Perepezko, J; Payer, J; Branagan, D; Beardsley, B; D' Amato, A; Aprigliano, L

    2008-01-09

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional

  9. Iron-Based Amorphous Metals:The High Performance Corrosion Resistant Materials(HPCRM) Program

    International Nuclear Information System (INIS)

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and nickel-based materials, and are proving to have excellent wear

  10. Iron-Based Amorphous Metals: High-Performance Corrosion-Resistant Material Development

    Science.gov (United States)

    Farmer, Joseph; Choi, Jor-Shan; Saw, Cheng; Haslam, Jeffrey; Day, Dan; Hailey, Phillip; Lian, Tiangan; Rebak, Raul; Perepezko, John; Payer, Joe; Branagan, Daniel; Beardsley, Brad; D'Amato, Andy; Aprigliano, Lou

    2009-06-01

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was cosponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the U.S. Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition, materials synthesis, thermal stability, corrosion resistance, environmental cracking, mechanical properties, damage tolerance, radiation effects, and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as meltspun ribbons (MSRs), dropcast ingots, and thermal-spray coatings. Chromium (Cr), molybdenum (Mo), and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of MSRs and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently, thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests; good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while the open-circuit corrosion potentials (OCPs) were simultaneously monitored; reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber and suitable for criticality-control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and Ni-based materials, and are proving to have excellent wear

  11. Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

    Institute of Scientific and Technical Information of China (English)

    Li-hua TENG

    2008-01-01

    Fluidized-bed reactor is a candidate for dimethyi ether(DME)synthesis from syngas because of its excellent heat removal capability.In Order to improve the attrition resistance of catalyst,an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5,which was prepared by coprecipitation and shaped by spray drying to get spherical particles.The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor.Based on the experiment results,silica sol in the range of 0~20wt% had small effect on the catalytie activity.Generally,the CO conversion and DME yield decreased with the increase in concen.tration of silica sol,while the attrition resistance of catalysts increased with increasing silica sol,indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst.In addition,the characterizations of catalysts were carried out using Brunauer-Emmett-Teller(BET),X-ray powder diffraction(XRD)and temperature programmed reduction (TPR).

  12. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gangwal, S.; Jothimurugesan, K.

    1999-07-27

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption process, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gases from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or passivating the heavy metals on the spent FCC catalyst as an intermediate step.

  13. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gangwal, Santosh (Cary, NC); Jothimurugesan, Kandaswamy (Hampton, VA)

    1999-01-01

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption processes, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gasses from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or "passivating" the heavy metals on the spent FCC catalyst as an intermediate step.

  14. Advanced oxidation-resistant iron-based alloys for LWR fuel cladding

    Science.gov (United States)

    Terrani, K. A.; Zinkle, S. J.; Snead, L. L.

    2014-05-01

    Application of advanced oxidation-resistant iron alloys as light water reactor fuel cladding is proposed. The motivations are based on specific limitations associated with zirconium alloys, currently used as fuel cladding, under design-basis and beyond-design-basis accident scenarios. Using a simplified methodology, gains in safety margins under severe accidents upon transition to advanced oxidation-resistant iron alloys as fuel cladding are showcased. Oxidation behavior, mechanical properties, and irradiation effects of advanced iron alloys are briefly reviewed and compared to zirconium alloys as well as historic austenitic stainless steel cladding materials. Neutronic characteristics of iron-alloy-clad fuel bundles are determined and fed into a simple economic model to estimate the impact on nuclear electricity production cost. Prior experience with steel cladding is combined with the current understanding of the mechanical properties and irradiation behavior of advanced iron alloys to identify a combination of cladding thickness reduction and fuel enrichment increase (∼0.5%) as an efficient route to offset any penalties in cycle length, due to higher neutron absorption in the iron alloy cladding, with modest impact on the economics.

  15. Iron-Based Amorphous-Metals: High-Performance Corrosion-Resistant Materials (HPCRM) Development Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Choi, J; Saw, C; Haslem, J; Day, D; Hailey, P; Lian, T; Rebak, R; Perepezko, J; Payer, J; Branagan, D; Beardsley, B; D' Amato, A; Aprigliano, L

    2009-03-16

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal make this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of these iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional

  16. Iron-Based Amorphous-Metals: High-Performance Corrosion-Resistant Materials (HPCRM) Development Final Report

    International Nuclear Information System (INIS)

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal make this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of these iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and nickel-based materials, and are proving to have excellent wear

  17. FY05 HPCRM Annual Report: High-Performance Corrosion-Resistant Iron-Based Amorphous Metal Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J; Choi, J; Haslam, J; Day, S; Yang, N; Headley, T; Lucadamo, G; Yio, J; Chames, J; Gardea, A; Clift, M; Blue, G; Peters, W; Rivard, J; Harper, D; Swank, D; Bayles, R; Lemieux, E; Brown, R; Wolejsza, T; Aprigliano, L; Branagan, D; Marshall, M; Meacham, B; Aprigliano, L; Branagan, D; Marshall, M; Meacham, B; Lavernia, E; Schoenung, J; Ajdelsztajn, L; Dannenberg, J; Graeve, O; Lewandowski, J; Perepezko, J; Hildal, K; Kaufman, L; Boudreau, J

    2007-09-20

    New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative corrosion resistance. Many of these materials can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in some very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Two Fe-based amorphous metal formulations have been found that appear to have corrosion resistance comparable to, or better than that of Ni-based Alloy C-22, based on breakdown potential and corrosion rate. Both Cr and Mo provide corrosion resistance, B enables glass formation, and Y lowers critical cooling rate (CCR). SAM1651 has yttrium added, and has a nominal critical cooling rate of only 80 Kelvin per second, while SAM2X7 (similar to SAM2X5) has no yttrium, and a relatively high critical cooling rate of 610 Kelvin per second. Both amorphous metal formulations have strengths and weaknesses. SAM1651 (yttrium added) has a low critical cooling rate (CCR), which enables it to be rendered as a completely amorphous thermal spray coating. Unfortunately, it is relatively difficult to atomize, with powders being irregular in shape. This causes the powder to be difficult to pneumatically convey during thermal spray deposition. Gas atomized SAM1651 powder has required cryogenic milling to eliminate irregularities that make flow difficult. SAM2X5 (no yttrium) has a high critical cooling rate, which has caused problems associated with devitrification. SAM2X5 can be gas atomized to produce spherical powders of SAM2X5, which enable more facile thermal spray deposition. The reference material, nickel-based Alloy C-22, is an outstanding corrosion-resistant engineering material. Even so, crevice corrosion has been observed with C-22 in hot sodium chloride environments without buffer

  18. Experimental investigation of attrition resistance of zeolite catalysts in two particle gas-solid-solid fluidization system

    International Nuclear Information System (INIS)

    In the study of mechanical degradation of 34 ZSM-5 and SAPO catalysts, using the gas jet attrition - ASTM standard fluidized bed test (D-5757), the effect of particle size and its quantitative analysis in co-fluidization environment was investigated on the air jet index (AJI) basis. In gas-solid-solid fluidized bed reactors (GSS-FBR), two different sized particles were fluidized under isothermal conditions. In case of ZSM-5 and SAPO-34, significant attrition resistance was observed, which was attributed to small pore size and specific structural strength of the mobile framework image (MFI) and chabasite (CHA) structures, respectively. The optimum AJI for SAPO-34 and ZSM-5 (of particle size 0.2 mm) in GSS-fluidization system was observed to be 0.0118 and 0.0062, respectively. In co-fluidization, deviations from Gwyn relationship were observed due to change in impact of collision. Therefore, zeolites are recommended as suitable catalysts or catalytic supports (for doping of expensive metals) and for commercial use in GSS-FBR. (author)

  19. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    Science.gov (United States)

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  20. Co-Production of Electricity and Hydrogen Using a Novel Iron-based Catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Hilaly, Ahmad; Georgas, Adam; Leboreiro, Jose; Arora, Salil; Head, Megann; Trembly, Jason; Turk, Brian; Gupta, Raghubir

    2011-09-30

    The primary objective of this project was to develop a hydrogen production technology for gasification applications based on a circulating fluid-bed reactor and an attrition resistant iron catalyst. The work towards achieving this objective consisted of three key activities: • Development of an iron-based catalyst suitable for a circulating fluid-bed reactor • Design, construction, and operation of a bench-scale circulating fluid-bed reactor system for hydrogen production • Techno-economic analysis of the steam-iron and the pressure swing adsorption hydrogen production processes. This report describes the work completed in each of these activities during this project. The catalyst development and testing program prepared and iron-based catalysts using different support and promoters to identify catalysts that had sufficient activity for cyclic reduction with syngas and steam oxidation and attrition resistance to enable use in a circulating fluid-bed reactor system. The best performing catalyst from this catalyst development program was produced by a commercial catalyst toll manufacturer to support the bench-scale testing activities. The reactor testing systems used during material development evaluated catalysts in a single fluid-bed reactor by cycling between reduction with syngas and oxidation with steam. The prototype SIP reactor system (PSRS) consisted of two circulating fluid-bed reactors with the iron catalyst being transferred between the two reactors. This design enabled demonstration of the technical feasibility of the combination of the circulating fluid-bed reactor system and the iron-based catalyst for commercial hydrogen production. The specific activities associated with this bench-scale circulating fluid-bed reactor systems that were completed in this project included design, construction, commissioning, and operation. The experimental portion of this project focused on technical demonstration of the performance of an iron-based catalyst and a

  1. Iron-based superconductivity

    CERN Document Server

    Johnson, Peter D; Yin, Wei-Guo

    2015-01-01

    This volume presents an in-depth review of experimental and theoretical studies on the newly discovered Fe-based superconductors.  Following the Introduction, which places iron-based superconductors in the context of other unconventional superconductors, the book is divided into three sections covering sample growth, experimental characterization, and theoretical understanding.  To understand the complex structure-property relationships of these materials, results from a wide range of experimental techniques and theoretical approaches are described that probe the electronic and magnetic prope

  2. High-Performance Corrosion-Resistant Materials: Iron-Based Amorphous-Metal Thermal-Spray Coatings: SAM HPCRM Program ? FY04 Annual Report ? Rev. 0 - DARPA DSO and DOE OCRWM Co-Sponsored Advanced Materials Program

    International Nuclear Information System (INIS)

    The multi-institutional High Performance Corrosion Resistant Materials (HPCRM) Team is cosponsored by the Defense Advanced Projects Agency (DARPA) Defense Science Office (DSO) and the Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM), and has developed new corrosion-resistant, iron-based amorphous metals that can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The Fe-based corrosion-resistant, amorphous-metal coatings under development may prove of importance for applications on ships. Such coatings could be used as an 'integral drip shield' on spent fuel containers, as well as protective coatings that could be applied over welds, thereby preventing exposure to environments that might cause stress corrosion cracking. In the future, such new high-performance iron-based materials could be substituted for more-expensive nickel-based alloys, thereby enabling a reduction in the $58-billion life cycle cost for the long-term storage of the Nation's spent nuclear fuel by tens of percent

  3. High-Performance Corrosion-Resistant Materials: Iron-Based Amorphous-Metal Thermal-Spray Coatings: SAM HPCRM Program ? FY04 Annual Report ? Rev. 0 - DARPA DSO & DOE OCRWM Co-Sponsored Advanced Materials Program

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J; Haslam, J; Wong, F; Ji, S; Day, S; Branagan, D; Marshall, M; Meacham, B; Buffa, E; Blue, C; Rivard, J; Beardsley, M; Buffa, E; Blue, C; Rivard, J; Beardsley, M; Weaver, D; Aprigliano, L; Kohler, L; Bayles, R; Lemieux, E; Wolejsza, T; Martin, F; Yang, N; Lucadamo, G; Perepezko, J; Hildal, K; Kaufman, L; Heuer, A; Ernst, F; Michal, G; Kahn, H; Lavernia, E

    2007-09-19

    The multi-institutional High Performance Corrosion Resistant Materials (HPCRM) Team is cosponsored by the Defense Advanced Projects Agency (DARPA) Defense Science Office (DSO) and the Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM), and has developed new corrosion-resistant, iron-based amorphous metals that can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The Fe-based corrosion-resistant, amorphous-metal coatings under development may prove of importance for applications on ships. Such coatings could be used as an 'integral drip shield' on spent fuel containers, as well as protective coatings that could be applied over welds, thereby preventing exposure to environments that might cause stress corrosion cracking. In the future, such new high-performance iron-based materials could be substituted for more-expensive nickel-based alloys, thereby enabling a reduction in the $58-billion life cycle cost for the long-term storage of the Nation's spent nuclear fuel by tens of percent.

  4. Bilingualism and attrition

    OpenAIRE

    Schmid, Monika; Köpke, Barbara

    2007-01-01

    This collection of articles provides theoretical foundations and perspectives for language attrition research. Its purpose is to enable investigations of L1 attrition to avail themselves more fully and more fundamentally of the theoretical frameworkes that have been formulated with respect to SLA and bilingualism.

  5. Attrition Cost Model Instruction Manual

    Science.gov (United States)

    Yanagiura, Takeshi

    2012-01-01

    This instruction manual explains in detail how to use the Attrition Cost Model program, which estimates the cost of student attrition for a state's higher education system. Programmed with SAS, this model allows users to instantly calculate the cost of attrition and the cumulative attrition rate that is based on the most recent retention and…

  6. FY05 HPCRM Annual Report: High-Performance Corrosion-Resistant Iron-Based Amorphous Metal Coatings Evaluation of Corrosion Resistance FY05 HPCRM Annual Report No. Rev. 1DOE-DARPA Co-Sponsored Advanced Materials Program

    International Nuclear Information System (INIS)

    New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative corrosion resistance. Many of these materials can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in some very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Two Fe-based amorphous metal formulations have been found that appear to have corrosion resistance comparable to, or better than that of Ni-based Alloy C-22, based on breakdown potential and corrosion rate. Both Cr and Mo provide corrosion resistance, B enables glass formation, and Y lowers critical cooling rate (CCR). SAM1651 has yttrium added, and has a nominal critical cooling rate of only 80 Kelvin per second, while SAM2X7 (similar to SAM2X5) has no yttrium, and a relatively high critical cooling rate of 610 Kelvin per second. Both amorphous metal formulations have strengths and weaknesses. SAM1651 (yttrium added) has a low critical cooling rate (CCR), which enables it to be rendered as a completely amorphous thermal spray coating. Unfortunately, it is relatively difficult to atomize, with powders being irregular in shape. This causes the powder to be difficult to pneumatically convey during thermal spray deposition. Gas atomized SAM1651 powder has required cryogenic milling to eliminate irregularities that make flow difficult. SAM2X5 (no yttrium) has a high critical cooling rate, which has caused problems associated with devitrification. SAM2X5 can be gas atomized to produce spherical powders of SAM2X5, which enable more facile thermal spray deposition. The reference material, nickel-based Alloy C-22, is an outstanding corrosion-resistant engineering material. Even so, crevice corrosion has been observed with C-22 in hot sodium chloride environments without buffer

  7. First Language Attrition

    Science.gov (United States)

    Schmid, Monika S.

    2016-01-01

    Language attrition research has developed in several clearly delimited phases spanning, roughly, each of the three decades between 1982 and 2012 (see Kopke & Schmid 2004 for a more detailed overview and analysis). The first phase was an era of stocktaking, with a number of symposia, collected volumes and special issues of journals. All of…

  8. Thermal sprayed iron base alloys coatings

    International Nuclear Information System (INIS)

    Particularities of thermal spraying of iron-based alloys coatings are associated with sufficiently great values of parameter of melting difficulty (for Fe D = 2.08 I-10/sup 10/ kJ.kg/sup -1/.m/sup -3/), and relatively low values of coefficients-of heat accumulation (for Fe b=C.raw.Lambda /sub 0.5/=108 W.m/sup -2/.K.sec/sup-0.5/). These materials are less inclined to form quality coating under the influence of the thermal activation and therefore it is reasonable to use in addition the mechanical activation of substrate surface. The powder of iron-base alloy FeSi/sub 7/AI/sub 3.5/C/sub 2/ was obtained by melt-atomization with water hardening of droplets. The main phase components of powder are alpha and gamma -solid solution on base of Fe (austenite), cementite (Fe/sub 3/C), metastable rhombic lattice x-phase, and possibly metastable carbide Fe/sub 2/C. When the powder particles shape is oval which axis dimensions about 80 and 300 micro meter, the main phase components of detonation sprayed coatings in case of oxy-acetylene gas mixture are alpha and gamma -phases, in case of oxy-propane-butane mixture the coating phase component the same as initial powder. When the powder particles size is 63-100 micro meter, the coatings phase components are alpha and gamma - solid solutions, Fe/sub 3/C, x-phase, Fe/sub 2/C, Fe/sub 3/0/sub 4/ and FeO. The main phase components of FeSi/sub 7/B/sub 12,6/ powder are alpha-solid solution, borides Fe/sub 2/B and FeB, X- phase. The sprayed coatings have the same phase composition. These types of Fe-base alloys powders have relatively low cost, easy available and can used for deposition of wear resistant coatings. (author)

  9. Cyclic and Linear Polarization of Yttrium-Containing Iron-Based Amorphous Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Day, S D; Lian, T; Farmer, J C; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys are produced by rapid solidification from the melt. These alloys may possess unique mechanical and corrosion resistant properties. The chemical composition of the alloy may influence the cooling rate that is necessary for the alloys to be completely vitreous. At the same time, the corrosion resistance of the amorphous alloys may also depend on their chemical composition. This paper examines the anodic behavior of iron-based amorphous alloys containing three different concentrations (1, 3 and 5 atomic %) of yttrium (Y) in several electrolyte solutions. Results from polarization resistance potentiodynamic polarization show that when the alloy contains 5% atomic Y, the corrosion resistance decreases.

  10. Teachers' Language: L1 Attrition in Russian-English Bilinguals

    Science.gov (United States)

    Isurin, Ludmila

    2007-01-01

    The present study reports on the evidence of first language (L1) attrition in a population that may appear to be the most resistant to L1 changes. Russian monolinguals (n=3) and Russian-English bilinguals (n=10) participated in the study. The bilinguals were graduate students teaching Russian as a foreign language at a U.S. university. The data…

  11. The influence of Chinese context on attrition of English tense

    Directory of Open Access Journals (Sweden)

    Deng Huan

    2016-01-01

    Full Text Available From psycholinguistic aspect, language learning not only requires acquisition and progression, but it also exists in attrition and regression. Within Chinese as a native language, the learning and living environment would directly affect the language input and contact for English as a foreign language (EFL learner. English tense is totally different from that of Chinese in terms of concept. Based on Inverse Hypothesis, the present thesis aims to take English tense as a breakthrough point in this diachronic research, as well as to reveal and analyze the variability of mastering tenses for EFL learners. Meanwhile, it also strives to validate the feasibility of slowing down the speed of language attrition by increasing the English input and contact. In Chinese context, how to resist attrition effectively and retain their acquired language abilities will yield a lot of benefits to language teaching and learning both for teachers and EFL learners.

  12. Optical conductivity of iron-based superconductors

    International Nuclear Information System (INIS)

    The new family of unconventional iron-based superconductors discovered in 2006 immediately relieved their copper-based high-temperature predecessors as the most actively studied superconducting compounds in the world. The experimental and theoretical effort made in order to unravel the mechanism of superconductivity in these materials has been overwhelming. Although our understanding of their microscopic properties has been improving steadily, the pairing mechanism giving rise to superconducting transition temperatures up to 55 K remains elusive. And yet the hope is strong that these materials, which possess a drastically different electronic structure but similarly high transition temperatures compared to the copper-based compounds, will shed essential new light onto the several-decade-old problem of unconventional superconductivity. In this work we review the current understanding of the itinerant-charge-carrier dynamics in the iron-based superconductors and parent compounds largely based on the optical-conductivity data the community has gleaned over the past seven years using such experimental techniques as reflectivity, ellipsometry, and terahertz transmission measurements and analyze the implications of these studies for the microscopic properties of the iron-based materials as well as the mechanism of superconductivity therein. (topical review)

  13. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ (T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ (T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ (T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s± scenario for the whole doping range. Knowing that the s± gap symmetry exists across the superconducting dome for the electron doped systems, we next looked at λ (T), in optimally - doped, SrFe2(As1-xPx)2, x =0.35. Both, as-grown (Tc ~ 25 K) and annealed (Tc ~ 35 K) single crystals of SrFe2(As1-xPx)2 were measured. Annealing decreases the absolute value of the London penetration depth from λ(0) = 300 ± 10 nm in as-grown samples to λ (0) = 275±10 nm. At low temperatures, λ (T) ~ T indicates a superconducting gap with line nodes. Analysis of the full-temperature range superfluid density is consistent with the line nodes, but differs from the simple single-gap d-wave. The observed behavior is very similar to that of BaFe2(As1-xPx)2, showing that isovalently substituted pnictides are inherently different from

  14. Quantification of corrosion resistance of a new-class of criticality control materials: thermal-spray coatings of high-boron iron-based amorphous metals - Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Choi, J S; Shaw, C K; Rebak, R; Day, S D; Lian, T; Hailey, P; Payer, J H; Branagan, D J; Aprigliano, L F

    2007-03-28

    An iron-based amorphous metal, Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} (SAM2X5), with very good corrosion resistance was developed. This material was produced as a melt-spun ribbon, as well as gas atomized powder and a thermal-spray coating. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber, and suitable for criticality control applications. Earlier studies have shown that ingots and melt-spun ribbons of these materials have good passive film stability in these environments. Thermal spray coatings of these materials have now been produced, and have undergone a variety of corrosion testing, including both atmospheric and long-term immersion testing. The modes and rates of corrosion have been determined in the various environments, and are reported here.

  15. Minimizing Attrition in Online Degree Courses

    Science.gov (United States)

    Boton, Eliani Colferai; Gregory, Sue

    2015-01-01

    The number of online programs in the higher education sector has increased dramatically in the last decade, and with it, an increase in attrition has become a recurring problem worldwide. Literature suggests that elements of culture, motivation, learning management systems and online pedagogy play a major role in attrition rates in the higher…

  16. Progress in wire fabrication of iron-based superconductors

    OpenAIRE

    Yanwei MA

    2012-01-01

    Iron-based superconductors, with Tc values up to 55 K, are of great interest for applications, due to their lower anisotropies and ultrahigh upper critical fields. In the past 4 years, great progress has been made in the fabrication of iron-based superconducting wires and tapes using the powder-in-tube (PIT) processing method, including main three types of 122, 11, and 1111 iron-based parent compounds. In this article, an overview of the current state of development of iron-based superconduct...

  17. Sand attrition in conical spouted beds

    Institute of Scientific and Technical Information of China (English)

    Aranzazu R. Fernández-Akarregui; Jon Makibar; Isabel Alava; Luis Diaz; Fernando Cueva; Roberto Aguado; Gartzen Lopez; Martin Olazar

    2012-01-01

    A study was carried out on the attrition in conical spouted beds using two sands with different properties for several bed heights and gas flow rates.Furthermore,the influence of a draft tube was studied at ambient and high temperatures.The main objective was to acquire knowledge on the attrition of sand beds for biomass pyrolysis in a pilot plant provided with a conical spouted bed reactor.A first-order kinetic equation is proposed for sand attrition in a conical spouted bed at room temperature.The predicted attrition rate constant depends exponentially on excess air velocity over that for minimum spouting.Both the draft tube and temperature increase contribute to reduction of attrition.

  18. Corrosion properties of high silicon iron-based alloys in nitric acid

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The effect of copper and rare-earth elements on corrosion behavior of ~iigh silicon iron-based alloys in nitric acid was studied by means of static and loading current corrosion experiments. The anodic polarization curve was also made to discuss the corrosion mechanism. The examination on alloy microstructure and SEM corrosion pattern showed that when silicon content reached 14.5%, the Fe3Si phase appeared and the primary structure of the iron-base alloy was ferrite. When adding 4.57% copper in the iron alloy, its corrosion resistance in static diluted sulfuric acid was improved while its corrosion resistance and electrochemical corrosion properties in the nitric acid were decreased. In contrast, the addition of rare earth elements could improve the corrosion properties in all above conditions including in static diluted sulfuric acid and in nitric acid.

  19. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason A. [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ(T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ(T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ(T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s ± scenario for the whole doping range.

  20. Analysing Attrition in Outsourced Software Project

    Directory of Open Access Journals (Sweden)

    Umesh Rao Hodeghatta

    2015-01-01

    Full Text Available Information systems (IS outsourcing has grown as a major business phenomenon, and widely accepted as a business tool. Software outsourcing c ompanies provide expertise, knowledge and capabilities to their clients by taking up the proj ects both onsite and offsite. These companies face numerous challenges including attrition of pro ject members. Attrition is a major challenge experienced by the outsourcing companies as it has severe impact on business, revenues and profitability. In this paper, attrition data of a m ajor software outsourcing company was analysed and an attempt to find the reason for attr ition is also made. The data analysis was based on the data collected by an outsourcing compa ny over a period of two years for a major client. The results show that the client initiated attrition can have an impact on project and the members quit the outsourcing company due to client initiated ramp down without revealing the reason.

  1. Reducing Attrition via Improved Strategies for Pre-clinical Drug Discovery : SPR-biosensor Aided Interaction Studies

    OpenAIRE

    Winquist, Johan

    2012-01-01

    The efficacy of a drug is tightly intertwined with its interaction mechanism with the drug target. The mechanism is dependent on the physicochemical and structural characteristics of both target and drug molecule. Drug discovery is plagued by a high attrition rate, whereas in the clinic, a major issue is drug resistance. To improve the quality of the lead compounds in the pre-clinical phase of drug discovery, and thereby reducing the attrition, a deeper understanding of interaction mechanisms...

  2. Crystal chemistry and structural design of iron-based superconductors

    Institute of Scientific and Technical Information of China (English)

    Jiang Hao; Sun Yun-Lei; Xu Zhu-An; Cao Guang-Han

    2013-01-01

    The second class of high-temperature superconductors (HTSCs),iron-based pnictides and chalcogenides,necessarily contain Fe2X2 (“X” refers to a pnictogen or a chalcogen element) layers,just like the first class of HTSCs which possess the essential CuO2 sheets.So far,dozens of iron-based HTSCs,classified into nine groups,have been discovered.In this article,the crystal-chemistry aspects of the known iron-based superconductors are reviewed and summarized by employing “hard and soft acids and bases (HSAB)” concept.Based on these understandings,we propose an alternative route to exploring new iron-based superconductors via rational structural design.

  3. An experimental study on the primary fragmentation and attrition of limestones in a fluidized bed

    International Nuclear Information System (INIS)

    In this paper, an experimental study on the primary fragmentation and attrition of 5 limestones in a fluidized bed was conducted. The intensity of fragmentation and attrition were measured in the same apparatus but at different fluidizing velocities. It was found that the averaged size of the particles decreased by about 10-20% during the fragmentation process. The important factors for particle comminution include limestone types, heating rate, calcination condition and ambient CO2 concentration. Fragmentation mainly occurred in the first a few minutes in the fluidized bed and it was more intense than that in the muffle furnace at the same temperature. The original size effect was ambiguous, depending on the limestone type. The comminution caused by attrition mainly occurred during calcination process rather than sulphation process. The sulphation process was fragmentation and attrition resisted. The attrition rate of sulphate was similar to that of lime in trend, decaying exponentially with time, but was one-magnitude-order smaller than that of lime. Present experimental results indicate that fragmentation mechanism of the limestone is dominated by CO2 release instead of thermal stress. (author)

  4. Towards a Model of Language Attrition: Neurobiological and Psychological Contributions

    OpenAIRE

    YOSHITOMI, Asako

    1992-01-01

    Research in L2 attrition is a relatively new enterprise which is in need of a comprehensive theory/model. This paper presents a tentative cognitive-psychological model of language attrition, which draws on information from studies in L2 attrition, neurobiology, and psychology. This is to demonstrate that a model based on consideration of the brain has the potential of providing a plausible account of the process of language attrition, as well as the process of language acquisition.

  5. Dropout, Nonusage Attrition, and Pretreatment Predictors of Nonusage Attrition in a Commercial Web-Based Weight Loss Program

    OpenAIRE

    Neve, Melinda J; Clare E. Collins; Morgan, Philip J

    2010-01-01

    Background An understanding of the factors that predict retention and website use are critical to the development of effective Web-based weight loss interventions. However, poor retention (dropout attrition) and website utilization (nonusage attrition) are major inhibitors to the effectiveness of Web-based programs. Objective The study aimed to (1) describe the prevalence of dropout and nonusage attrition and (2) examine pretreatment predictors of nonusage attrition in a cohort of commercial ...

  6. Spin, charge, and orbital orderings in iron-based superconductors

    Institute of Scientific and Technical Information of China (English)

    Jiang Qing; Kang Yao-Tai; Yao Dao-Xin

    2013-01-01

    In this article,we briefly review spin,charge,and orbital orderings in iron-based superconductors,as well as the multi-orbital models.The interplay of spin,charge,and orbital orderings is a key to understand the high temperature superconductivity.As an illustration,we use the two-orbital model to show the spin and charge orderings in iron-based superconductors based on the mean-field approximation in real space.The typical spin and charge orderings are shown by choosing appropriate parameters,which are in good agreement with experiments.We also show the effect of Fe vacancies,which can introduce the nematic phase and interesting magnetic ground states.The orbital ordering is also discussed in iron-based superconductors.It is found that disorder may play a role to produce the superconductivity.

  7. Predicting Student Attrition with Data Mining Methods

    Science.gov (United States)

    Delen, Dursun

    2012-01-01

    Affecting university rankings, school reputation, and financial well-being, student retention has become one of the most important measures of success for higher education institutions. From the institutional perspective, improving student retention starts with a thorough understanding of the causes behind the attrition. Such an understanding is…

  8. Reducing Attrition Rates for Maori Students

    Science.gov (United States)

    McKenzie, D. F.

    2005-01-01

    Attrition statistics for first-year students in many tertiary environments suggest that students face a wide variety of obstacles. Students in developmental education programmes usually have one additional obstacle: They have a history of failure in academic settings. Therefore there are emotional and psychological barriers in addition to academic…

  9. Satisfaction and attrition in paediatric weight management.

    Science.gov (United States)

    Skelton, J A; Martin, S; Irby, M B

    2016-04-01

    Paediatric obesity treatment experiences unacceptably high rates of attrition. Few studies have explored parent and child perspectives on dropout. This study sought to capture child and parent experience in treatment and expressed contributors to attrition. Children and parents enrolled in a single family-based weight management programme participated in semi-structured interviews, conducted either upon completion of the first intensive phase of treatment or program dropout. Interviews were recorded, transcribed and coded using a multistage inductive approach. Interviews were obtained from 57 parents and 30 children, nearly equal between 'completers' or 'dropouts'. Five themes emerged: overall positive experience with programme; logistical challenges of participation; improved health; discrepancies between child and parent experience and perception, and importance of structure and expectations of weight loss. Primary reasons given for dropout were time commitment; distance from clinic; missed school and work; lack of dedicated adolescent programme; clinic hours; and stress. Few parents or children expressed dissatisfaction. Children reportedly enjoyed 'having someone to talk to' about weight, and spending increased time with family. Children and parents overall reported positive experiences in this weight management programme. Attrition appears more related to logistical issues than low satisfaction. Innovative approaches to help overcome logistical challenges and preserve positive aspects may help in decreasing programme attrition. PMID:27008068

  10. Potentials of iron-based superconductors for practical future materials

    International Nuclear Information System (INIS)

    Since the discovery of high-Tc superconductivity in the REFeAs(O, F) system in 2008, studies on the development of superconducting materials using iron-based superconductors has been undertaken because of their high Hc2 and relatively high Tc. Although the cuprate superconductors exhibit much higher Tc and similar high Hc2, the small degree of electromagnetic anisotropy between the c-axis and ab-plane directions confirmed in 11, 122 and 1111 systems encouraged us to develop more versatile conductors. Single crystals and thin films deposited on single-crystalline and metal substrates have proved that the potentials of the iron-based superconductors are high enough for designing superconducting materials for high field generation. In addition, critical current properties of powder-in-tube processed tapes have been greatly improved in the past two years and are reaching the application level at 4.2 K in high magnetic field. However, the pinning mechanism and determining factors of the critical current properties of the iron-based superconductors have not been well understood. Characteristics and potentials of iron-based superconductors are discussed from various viewpoints in this paper in an effort to understand the current status and future prospects. (paper)

  11. EDITORIAL: Focus on Iron-Based Superconductors FOCUS ON IRON-BASED SUPERCONDUCTORS

    Science.gov (United States)

    Hosono, Hideo; Ren, Zhi-An

    2009-02-01

    pace of research within the last year, iron-based superconductors have revealed several unique properties such as a high upper critical field and a robustness to impurities. Participation of five 3d-orbitals in the Fermi levels also means that the electronic structure is complex compared with the cuprates. So, we now have a new family of superconductors and it is worth stressing that we have only just begun looking at the many varieties of candidate materials containing an iron square lattice. At this time we do not know whether a material with a critical temperature greater than 100 K exists, or if completely new properties are to be found. However, as a research community we should go ahead with hope and 'strike while the iron is hot'—this saying is always true! This focus issue of New Journal of Physics was put together to provide a broad-based, free-to-read snapshot of the current state of research in this rapidly emerging field. The papers included cover many aspects related to material exploration, physical analysis, and the theory of these materials, and, as editors, we thank the authors for their fine contributions, and the many referees for their considerable efforts that have ensured fast publication. As an aside, the first special issue on this SUBject was published in November 2008 in the Journal of the Physical Society of Japan (vol 77, supplement c) as the proceedings of the International Symposium on Iron-Pnictide Superconductors held in Tokyo on 29-30 June 2008. We would like to encourage the community to read both issues. On a final note we would like to acknowledge the staff of New Journal of Physics for all of their efficient work in bringing this collection to fruition. Focus on Iron-Based Superconductors Contents Microwave response of superconducting pnictides: extended s+/- scenario O V Dolgov, A A Golubov and D Parker Orbital and spin effects for the upper critical field in As-deficient disordered Fe pnictide superconductors G Fuchs, S

  12. Attrition in Knowledge Industry- Issues and Challenges

    Directory of Open Access Journals (Sweden)

    Harish Mittal

    2012-02-01

    Full Text Available Attrition is a phenomenon affecting any business organization in the industry. Over the past few years, organizations have taken an increased interest in aligning their HR practices to their business goals. What was originally seen as the time-keeping, records-maintaining department of the past has today metamorphosed into the equivalent of a dynamic business consultant, providing strategic support. Deficiencies like inability to influence employee perception of growth; not aligning employees to roles based on their individual talent, inflexibility in leadership styles, are causing conflicts at a very intrinsic level, resulting in knowledge employees choosing the proverbial “easy way out.” Employees thus attempt to change the manager or the work environment, resulting in employee attrition.

  13. Two Effects of Firepower: Attrition and Suppression

    OpenAIRE

    Hughes, Wayne P.

    1995-01-01

    A new basis for the quantitative study of ground combat is introduced that argues the inadequacy of attrition models and the need to incorporate the effects of suppression of the enemy with firepower. A quantitative approach to suppression of enemy fire is offered. Then an analysis shows that the effect of own fire in suppressing enemy fire will, in suitable, frequent circumstances, reverse the conclusions derived from the Lanchester square law, so that the sq...

  14. EDITORIAL: Focus on Iron-Based Superconductors FOCUS ON IRON-BASED SUPERCONDUCTORS

    Science.gov (United States)

    Hosono, Hideo; Ren, Zhi-An

    2009-02-01

    pace of research within the last year, iron-based superconductors have revealed several unique properties such as a high upper critical field and a robustness to impurities. Participation of five 3d-orbitals in the Fermi levels also means that the electronic structure is complex compared with the cuprates. So, we now have a new family of superconductors and it is worth stressing that we have only just begun looking at the many varieties of candidate materials containing an iron square lattice. At this time we do not know whether a material with a critical temperature greater than 100 K exists, or if completely new properties are to be found. However, as a research community we should go ahead with hope and 'strike while the iron is hot'—this saying is always true! This focus issue of New Journal of Physics was put together to provide a broad-based, free-to-read snapshot of the current state of research in this rapidly emerging field. The papers included cover many aspects related to material exploration, physical analysis, and the theory of these materials, and, as editors, we thank the authors for their fine contributions, and the many referees for their considerable efforts that have ensured fast publication. As an aside, the first special issue on this SUBject was published in November 2008 in the Journal of the Physical Society of Japan (vol 77, supplement c) as the proceedings of the International Symposium on Iron-Pnictide Superconductors held in Tokyo on 29-30 June 2008. We would like to encourage the community to read both issues. On a final note we would like to acknowledge the staff of New Journal of Physics for all of their efficient work in bringing this collection to fruition. Focus on Iron-Based Superconductors Contents Microwave response of superconducting pnictides: extended s+/- scenario O V Dolgov, A A Golubov and D Parker Orbital and spin effects for the upper critical field in As-deficient disordered Fe pnictide superconductors G Fuchs, S

  15. Iron based Li-ion insertion materials for battery applications

    OpenAIRE

    Blidberg, Andreas

    2016-01-01

    Li-ion batteries are currently the most efficient technology available for electrochemical energy storage. The technology has revolutionized the portable electronics market and is becoming a corner stone for large scale applications, such as electric vehicles. It is therefore important to develop materials in which the energy storage relies on abundant redox active species, such as iron. In this thesis, new iron based electrode materials for positive electrodes in Li-ion batteries were invest...

  16. Experimental Signatures of Orbital Fluctuations in Iron Based Superconductors

    Science.gov (United States)

    Lee, Wei-Cheng

    2015-03-01

    Understanding the high temperature superconductivity has been one of main subjects in the condensed matter physics. The discovery of new classes of high-temperature superconductors, iron pnictides in 2008, launched an international wave of research in the past few years. While the magnetic interactions are certainly important in these materials, there have been significant evidences suggesting that the orbital degrees of freedom could play an important role as well. In this talk, I will demonstrate that the orbital degrees of freedom do play a significant role in physical properties of iron-based superconductors. At the level of single particle properties, while the orbital order in the quasi-1D dxz and dyz bands has been proposed to be a possible driving mechanism for the structural phase transition, our study shows that the fluctuations associated with the orbital order could further drive a non-Fermi liquid behavior in the critical region of the orbital ordering phase transition. I will show that this non-Fermi liquid behavior could induce a zero-bias anomaly in the point contact spectroscopy, which has been observed in a variety of iron based superconductors. As for the magnetic properties, we also find that the orbital order and fluctuations can qualitatively change the nature of the spin excitation spectrum, giving rise to the novel incommensurate-to-commensurate transformation observed in a recent neutron scattering measurement. In the superconducting state, we predict that a new collective excitation, termed as orbital resonance mode, could exist generally in the iron-based superconductors, which in principle can be measured by Raman spectroscopy. Our findings offer a new perspective on the pairing mechanism of iron based superconductors, and suggest that orbital degrees of freedom could provide a new route to high temperature superconductivity.

  17. Iron-based bulk metallic glasses - Optimization of casting

    Czech Academy of Sciences Publication Activity Database

    Stloukal, Ivo; Král, Lubomír; Čermák, Jiří

    Ostrava: Tanger s. r. o, 2009, s. 481-487. ISBN 978-80-87294-04-8. [METAL 2009. Mezinárodní konference metalurgie a materiálů /18./. Hradec nad Moravicí (CZ), 19.05.2009-21.05.2009] R&D Projects: GA ČR GA106/08/1241 Institutional research plan: CEZ:AV0Z20410507 Keywords : bulk metallic glasses * iron-based alloy * casting optimization Subject RIV: BJ - Thermodynamics

  18. High Temperature Internal Oxidation Behavior of Iron Based Alloys

    International Nuclear Information System (INIS)

    A study of growth kinetics and microstructure of internal oxides in the iron-base alloys was carried out by an optical microscope and a scanning electron microscope, so that the growth mechanisms of the oxide precipitates in the internal oxidation zone could be understood in detail. Iron-based alloys, Fe-1%Al, Fe-1%Al-1%Hf, Fe-1%Cr, Fe-1%Cr-1%Hf and Fe-2%Hf, were oxidized in a sealed quartz tube containing Fe/FeO powder mixtures which maintained the oxygen partial pressure at the FeO decomposition pressure at 800 .deg. C for the various time periods to 121 hours. Results show that the growth rate of the oxide precipitates in the internal oxidation zone is controlled by the diffusion of oxygen. The variation of the solute element and the addition of Hf in the iron-base alloys led to a change in the depth of internal oxidation zone and in the oxide morphology. The internal precipitate adopted the form of continuous needles or feathers for the Fe-Al system, whereas that in the Fe-Cr and Fe-2%Hf systems adapted the form of discontinuous crystallites, that is, spheres or polyhedral crystallites. The mechanism of this morphological evolution was explained in detail

  19. Warm compacted NbC particulate reinforced iron-base composite(Ⅱ)--Microstructure and properties

    Institute of Scientific and Technical Information of China (English)

    李元元; 肖志瑜; 倪东惠; 夏伟; 陈维平

    2002-01-01

    Effects of different sintering temperature and sintering time on the relative density of the sintered compacts were studied to obtain the optimal sintering parameters for the fabrication of NbC particulate reinforced iron-b ase composite. With optimal sintering temperature of 1 280 ℃ and sintering time of 80 min, wear-resisting, high density NbC particulate reinforced iron-base composites can be obtained using warm compaction powder metallurgy. The microstructure , relative density, mechanical properties and tribological behaviors of the sintered composites were studied. The results indicate that the mechanical properties of the sintered compacts were closely related to the sintered density. The iron -base composite materials with different combinations of mechanical properties and tribological behaviors were developed for different applications. One of the developed composite, which contains 10%NbC, possesses a high strength of 815 Mpa with a remarkable friction and wear behaviors. The other developed composite, which contains 15%NbC, possesses a lesser strength of 515 Mpa but with excellent friction and wear behaviors.

  20. Survey on workforce retention and attrition

    Science.gov (United States)

    Showstack, Randy

    2013-03-01

    The Society of Petroleum Engineers (SPE) is conducting a survey to gather information on why technical professionals change jobs or quit working. The survey, prompted by concern about the retention of skilled workers, aims to provide information to employers that can assist them in addressing practices that can lead to significant workforce attrition. To participate in the survey, which is open to everyone (including those who are not SPE members), go to http://research.spe.org/se.ashx?s=705E3F1335720258 through 15 May 2013. For more information, contact speresearch@spe.org.

  1. Personality Has Minor Effects on Panel Attrition

    OpenAIRE

    Richter, David; Körtner, John L.; Saßenroth, Denise

    2014-01-01

    Abstract In light of the recent interest in using longitudinal panel data to study personality development, it is important to know if personality traits are related to panel attrition. We analyse the effects of personality on panel drop-out separately for an ‘older’ subsample (started in 1984), a relatively ‘young’ subsample (started in 2000), and a ‘new’ subsample (started in 2009) of the German Socio-Economic Panel (SOEP) study. We found that openness slightly decreases the probability of ...

  2. Demographic and Organizational Variables as Predictors of Teacher Attrition

    Science.gov (United States)

    Watkins, Leah Rice

    2013-01-01

    The purpose of this study was to examine the predictive capacity of specific demographic and organizational variables upon teacher attrition from the profession. The study examined the possibility of predicting attrition of teachers based upon these variables. Furthermore, the study attempted to create a profile of the most likely teachers to…

  3. The Impact of Attrition on Vocabulary Knowledge among Saudi Teachers

    Science.gov (United States)

    Alharthi, Thamer

    2014-01-01

    This two-year longitudinal study tracks the extent of vocabulary attrition among Arabic-speaking English graduate teachers. Data were collected through pre-post tests of receptive and productive vocabulary knowledge. The results showed drastic attrition in vocabulary knowledge soon after the end of formal instruction followed by slight gain,…

  4. Toward a More Nuanced Understanding of New Teacher Attrition

    Science.gov (United States)

    DeAngelis, Karen J.; Presley, Jennifer B.

    2011-01-01

    Teacher attrition, especially among new teachers, has been an issue of major concern for policy makers and administrators for many years. Prior research has provided valuable information regarding the teacher and organizational factors associated with attrition from the profession and teacher mobility across schools. Less attention, however, has…

  5. Incorporating direct marketing activity into latent attrition models

    NARCIS (Netherlands)

    Schweidel, David A.; Knox, George

    2013-01-01

    When defection is unobserved, latent attrition models provide useful insights about customer behavior and accurate forecasts of customer value. Yet extant models ignore direct marketing efforts. Response models incorporate the effects of direct marketing, but because they ignore latent attrition, th

  6. A Qualitative Study on the Effects of Teacher Attrition

    Directory of Open Access Journals (Sweden)

    Aminu Aliyu Wushishi

    2014-01-01

    Full Text Available In this study the researchers explored the effects of teacher attrition in Niger state, Nigeria. The study examined how attrition is affecting the educational development of the state from the teachers’ perspective. A qualitative method was used with the aim of extracting the inner feelings of the participants regarding the effects of attrition. Five serving teachers were purposively selected. An in-depth interview, non-participatory observation and document analysis were used as means for data collection. The findings discovered; cost implication, increased in workload, poor students’ performance and burden on school administration, as the major effects of teacher attrition. The paper therefore recommends that, the state government needs to improve the condition of service of teachers with the aim of reducing the rate of attrition so as to improve the educational standard of the state.

  7. Limestone fragmentation and attrition during fluidized bed oxyfiring

    Energy Technology Data Exchange (ETDEWEB)

    Fabrizio Scala; Piero Salatino [Istituto di Ricerche sulla Combustione - CNR, Napoli (Italy)

    2010-04-15

    Attrition/fragmentation of limestone under simulated fluidized bed oxyfiring conditions was investigated by means of an experimental protocol that had been previously developed for characterization of attrition/fragmentation of sorbents in air-blown atmospheric fluidized bed combustors. The protocol was based on the use of different and mutually complementary techniques. The extent and pattern of attrition by surface wear in the dense phase of a fluidized bed were assessed in experiments carried out with a bench scale fluidized bed combustor under simulated oxyfiring conditions. Sorbent samples generated during simulated oxyfiring tests were further characterized from the standpoint of fragmentation upon high velocity impact by means of a purposely designed particle impactor. Results showed that under calcination-hindered conditions attrition and fragmentation patterns are much different from those occurring under air-blown atmospheric combustion conditions. Noteworthy, attrition/fragmentation enhanced particle sulfation by continuously regenerating the exposed particle surface. 13 refs., 8 figs.

  8. Hybrid Crystals of Cuprates and Iron-Based Superconductors

    OpenAIRE

    Dai, Xia; Le, Congcong; Wu, Xianxin; Hu, Jiangping

    2016-01-01

    We propose two possible new compounds, Ba$_2$CuO$_2$Fe$_2$As$_2$ and K$_2$CuO$_2$Fe$_2$Se$_2$, which hybridize the building blocks of two high temperature superconductors, cuprates and iron-based superconductors. These compounds consist of square CuO$_2$ layers and antifluorite-type Fe$_2$X$_2$ (X=As,Se) layers separated by Ba/K. The calculations of binding energies and phonon spectrums indicate that they are dynamically stable, which ensures that they may be experimentally synthesized. The F...

  9. Synthesis and transformation of iron-based layered double hydroxides

    OpenAIRE

    Ruby, Christian; Usman, Muhammad; Naille, Sebastien; Hanna, Khalil; Carteret, Cédric; Mullet, Martine; François, Michel; Abdelmoula, Mustapha

    2009-01-01

    International audience Iron-based layered double hydroxides (LDHs) have the general formula [MII(1-x)MIIIx(OH)2]x+. [(x/n) An-, m H2O]x- and contain a molar fraction of iron, i.e. FeII or FeIII situated in the cationic layers, higher than 50 %. LDHs containing FeII species are interesting materials for several applications such as the reduction of anionic pollutants or the degradation of organic pollutants. They are mostly prepared either by coprecipitation of dissolved species or by oxida...

  10. Nodal spin density wave in iron-based superconductors

    International Nuclear Information System (INIS)

    We analyze the competition of SDW and SC orders in the iron-based superconductors, taking into account the orbital matrix elements. We find that the SDW order necessarily possesses the nodal structure as a result of angular dependence of the Fermi-liquid interactions. To obtain the phase diagram we solve the system of coupled mean-field gap equations, which describes the competition between SDW and s++ or s+- superconductivity. We revisit the result, obtained previously, for the constant SDW gap. We further discuss the role played by the spin-orbit coupling.

  11. Effect of mechanical attrition on microstructure and properties of electro-deposition coatings on NdFeB

    Institute of Scientific and Technical Information of China (English)

    董雪亮; 王德仁; 曾阳庆

    2014-01-01

    Surface mechanical attrition treatment (SMAT) was developed to synthesize nanostructure coatings on alloy surface. The SMAT action was applied in the process of Ni and Cu electroplating coatings on NdFeB substrates in this paper. The role of me-chanical attrition during barrel plating on the microstructure, mechanical and corrosion resistant properties of the coatings was exam-ined. The scanning electron microscopy (SEM) observation showed that the mechanical attrition could refine grain size, markedly smooth the coating surface and obviously decrease the number of pore in the coatings. The continuous collisions of glass balls onto the NdFeB samples could induce more beneficial nucleation defects on the coating, which was helpful for increasing nucleation sites and the nucleation rate. The mechanical attrition could also restrain the heterogeneous growth of the coating grain tips due to the abra-sive action of stainless steel balls. The Tafel polarization curve experimental results indicated that SMAT process could enhance the corrosion resistance of coatings on NdFeB. The scratching test revealed that the binding force between coating and NdFeB substrate could be improved dramatically with SMAT process.

  12. Thermoelectric properties of iron-based superconductors and parent compounds

    Science.gov (United States)

    Pallecchi, Ilaria; Caglieris, Federico; Putti, Marina

    2016-07-01

    Herewith, we review the available experimental data of thermoelectric transport properties of iron-based superconductors and parent compounds. We discuss possible physical mechanisms into play in determining the Seebeck effect, from whence one can extract information about Fermi surface reconstruction and Lifshitz transitions, multiband character, coupling of charge carriers with spin excitations and its relevance in the unconventional superconducting pairing mechanism, nematicity, quantum critical fluctuations close to the optimal doping for superconductivity, correlation. Additional information is obtained from the analysis of the Nernst effect, whose enhancement in parent compounds must be related partially to multiband transport and low Fermi level, but mainly to the presence of Dirac cone bands at the Fermi level. In the superconducting compounds, large Nernst effect in the normal state is explained in terms of fluctuating precursors of the spin density wave state, while in the superconducting state it mirrors the usual vortex liquid dissipative regime. A comparison between the phenomenology of thermoelectric behavior of different families of iron-based superconductors and parent compounds allows to evidence the key differences and analogies, thus providing clues on the rich and complex physics of these fascinating unconventional superconductors.

  13. Abnormal Nitride Morphologies upon Nitriding Iron-Based Substrates

    Science.gov (United States)

    Meka, Sai Ramudu; Mittemeijer, Eric Jan

    2013-06-01

    Nitriding of iron-based components is a very well-known surface engineering method for bringing about great improvement of the mechanical and chemical properties. An overview is presented of the strikingly different nitride morphologies developing upon nitriding iron-based alloy substrates. Observed abnormal morphologies are the result of intricate interplay of the thermodynamic and kinetic constraints for the nucleation and growth of both alloying element nitride particles in the matrix and iron nitrides at the surface of the substrate. Alloying elements having strong Me-N interaction, such as Cr, V, and Ti, precipitate instantaneously as internal Me-nitrides, thus allowing the subsequent nucleation and growth of "normal" layer-type iron nitride. Alloying elements having weak Me-N interaction, such as Al, Si, and Mo, and simultaneously having low solubility in iron nitride, obstruct/delay the nucleation and growth of iron nitrides at the surface, thus leading to very high nitrogen supersaturation over an extended depth range from the surface. Eventually, the nucleation and growth of "abnormal" plate-type iron nitride occurs across the depth range of high nitrogen supersaturation. On this basis, strategies can be devised for tuned development of specific nitride morphologies at the surface of nitrided components.

  14. Defect Interaction in Iron and Iron-based Alloys

    Science.gov (United States)

    Xu, Haixuan; Stocks, G. Malcolm; Stoller, Roger

    2014-03-01

    Magnetism has a profound influence on the defect properties in iron and iron-based alloys. For instance, it has been shown from first principles calculations that the helium interstitial occupies the tetrahedral site instead of octahedral site in contrast to all previous work that neglected the magnetic effects. In this study, we explore the effects of magnetism on the defect interaction, primarily interstitial-type defects, in bcc iron and Fe-Cr systems. The magnetic moment change during the interaction of two 1/2 interstitial loops in bcc iron was calculated using the ab initio locally self-consistent multiple-scattering (LSMS) method and a significant fluctuation was observed. Adding Cr significantly modifies the magnetic structure of the defects and defect interactions. In addition, the effects of magnetism on the defect energetics are evaluated. This study provides useful insights on whether magnetism can be used as a effective means to manipulate the defect evolution in iron-based structural alloys. This material is based upon work supported as part of the Center for Defect Physics, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  15. Examining Minority Attrition Among Women in Longitudinal Trauma Research.

    Science.gov (United States)

    Boykin, Derrecka M; London, Melissa J; Orcutt, Holly K

    2016-02-01

    Research suggests that racial and ethnic minorities are more likely to attrit from longitudinal trauma studies than non-Hispanic Whites. Yet, little is known about how the loss of minority participants influences longitudinal findings as well as internal and external validity of study findings. Thus, the present study examined the effects of race/ethnicity on attrition in a longitudinal trauma study of women (minority = 223, non-Hispanic White or majority = 459) exposed to a campus shooting. Survival analyses were used to compare the attrition rates of minority participants to majority participants and assess the extent to which race/ethnicity, among other variables, predicted attrition. Minority participants were more likely to attrit than majority participants, hazard ratio (HR) = 0.69, 95% CI [0.48, 0.99], even after adjusting for study variables. A main effect was also found for age, HR = 1.06, 95% CI [1.01, 1.12]. Race/ethnicity did not interact with other study variables to influence attrition. The findings underscored the importance of assessing the effects of attrition on longitudinal findings and external validity. PMID:26764179

  16. Two- and Four-Year College Student Attrition Research to the 1980's: A Review.

    Science.gov (United States)

    Smith, Alan D.

    Basic background information on college student attrition research studies is provided. This paper is divided into nine components that were prominent in the existing literature: (1) higher education and the concern for attrition; (2) factors involved in college student attrition; (3) demographic factors involved in college student attrition; (4)…

  17. Waiting Time Increases Risk of Attrition in Gambling Disorder Treatment

    DEFF Research Database (Denmark)

    Linnet, Jakob; Pedersen, Anders Sune

    2014-01-01

    completion in gambling disorder. We compared 48 gambling disorder sufferers with a 56% completion rate (21 non-completers and 27 completers). Binomial logistic regression analysis showed that waiting time from initial contact to the first session with a therapist was a significant predictor of risk of...... attrition: longer waiting times were associated with increased risk of attrition. Age, gender, or comorbidity was not associated with an increased risk of attrition. These data suggest that gambling disorder sufferers benefit from fast access to treatment, and that longer waiting time increases the risk of...

  18. Corrosion of iron-base alloys by lithium

    International Nuclear Information System (INIS)

    A review of corrosion mechanisms operating in lithium-iron-base alloy systems is presented along with data obtained with thermal-convection loops of niobium-stabilized 2 1/4 percent Cr-1 percent Mo steel and types 304L and 321 stainless steels. A corrosion rate of 2.3 μm/year (0.09 mil/year) was obtained on the 2 1/4 percent Cr-1 percent Mo steel at 6000C. Considerably more mass transport of alloying constituents and a maximum corrosion rate of about 14 μm/year (0.55 mil/year) was obtained with the austenitic stainless steels. Results of metallography, x-ray fluorescence analysis, scanning electron microscopy, and weight-change data are presented and discussed

  19. Anisotropic Upper Critical Field of Iron-Based Superconductors

    Science.gov (United States)

    Huang, Ruiqi; She, Weilong

    2016-09-01

    The upper critical field and its anisotropy are the easiest properties to examine in the research of iron-based superconductors. Based on warped cylindrical Fermi surface models, we investigate the temperature and angle dependence of the upper critical field in detail by employing the quasi-classical formalism of the Werthamer-Helfand-Hohenberg (WHH) theory. Our numerical results reveal the anisotropy of the upper critical field, which may be caused by an anisotropic gap function (e.g., d-wave pairing) or an anisotropic Fermi surface, respectively. Further, according to our analysis, this anisotropy can be modulated by the deformation of the Fermi surface and will be strongly suppressed by the Pauli paramagnetic effect.

  20. One-Sign Order Parameter in Iron Based Superconductor

    Directory of Open Access Journals (Sweden)

    Bernd Büchner

    2012-03-01

    Full Text Available The onset of superconductivity at the transition temperature is marked by the onset of order, which is characterized by an energy gap. Most models of the iron-based superconductors find a sign-changing (s± order parameter [1–6], with the physical implication that pairing is driven by spin fluctuations. Recent work, however, has indicated that LiFeAs has a simple isotropic order parameter [7–9] and spin fluctuations are not necessary [7,10], contrary to the models [1–6]. The strength of the spin fluctuations has been controversial [11,12], meaning that the mechanism of superconductivity cannot as yet be determined. We report the momentum dependence of the superconducting energy gap, where we find an anisotropy that rules out coupling through spin fluctuations and the sign change. The results instead suggest that orbital fluctuations assisted by phonons [13,14] are the best explanation for superconductivity.

  1. An Analysis of Sample Attrition in the PSES Panel Data

    OpenAIRE

    G. M. Arif; Faiz Bilquees

    2006-01-01

    Panel household surveys study the dynamics for individual households, including their well-being, child schooling, and labour market dynamics, and they can also be used to observe who benefits or loses from general economic development. The MIMAP panel survey, covering 300 households in 60 districts, is the largest panel survey carried out in Pakistan. This paper addresses two very legitimate concerns regarding the panel data? the extent of attrition and the degree to which attrition is non-r...

  2. Attrition in surgical residency programmes: Causes and effects

    OpenAIRE

    Nadeem, Mehwash; Effendi, M. Shahrukh; M. Hammad Ather

    2013-01-01

    Objective To determine the rate and trend of attrition from a surgical residency programme and to identify the reasons for attrition. Methods A questionnaire-based survey was conducted at a university hospital. Separate questionnaires were designed for residents and programme directors (PDs). The residents who left the training voluntarily from one of the five surgical residency programmes (i.e., general surgery, orthopaedics, neurosurgery, otorhinolaryngology and urology) during the academic...

  3. Language attrition at the crossroads of brain, mind, and society

    OpenAIRE

    Köpke, Barbara

    2007-01-01

    This chapter is an attempt to survey the predictions of some of the most important factors involved in attrition and to discuss them with respect to empirical data from L1 attrition. The factors discussed include biological aspects (plasticity, activation thresholds, inhibition and emotional implication), cognitive aspects (memory, aptitude, literacy and task dependency) and external factors (the role of language use, the cultural context and attitudes). The discussion shows that (a) many of ...

  4. Theoretical study of impurity effects in iron-based superconductors

    Science.gov (United States)

    Navarro Gastiasoro, Maria; Hirschfeld, Peter; Andersen, Brian

    2013-03-01

    Several open questions remain unanswered for the iron-based superconductors (FeSC), including the importance of electronic correlations and the symmetry of the superconducting order parameter. Motivated by recent STM experiments which show a fascinating variety of resonant defect states in FeSC, we adopt a realistic five-band model including electronic Coulomb correlations to study local effects of disorder in the FeSC. In order to minimize the number of free parameters, we use the pairing interactions obtained from spin-fluctuation exchange to determine the homogeneous superconducting state. The ability of local impurity potentials to induce resonant states depends on their scattering strength Vimp; in addition, for appropriate Vimp, such states are associated with local orbital- and magnetic order. We investigate the density of states near such impurities and show how tunneling experiments may be used to probe local induced order. In the SDW phase, we show how C2 symmetry-breaking dimers are naturally formed around impurities which also form cigar-like (pi,pi) structures embedded in the (pi,0) magnetic bulk phase. Such electronic dimers have been shown to be candidates for explaining the so-called nematogens observed previously by QPI in Co-doped CaFe2As2.

  5. Superconductivity at 55 K in Iron-Based F-Doped Layered Quaternary Compound Sm[O1-xFx]FeAs

    Institute of Scientific and Technical Information of China (English)

    REN Zhi-An; ZHOU Fang; ZHAO Zhong-Xian; LU Wei; YANG Jie; YI Wei; SHEN Xiao-Li; LI Zheng-Cai; CHE Guang-Can; DONG Xiao-Li; SUN Li-Ling

    2008-01-01

    We report the superconductivity in iron-based oxyarsenide Sm[O1-xFx]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now.

  6. Attrition of sorbents during fluidized bed calcination and sulphation

    Energy Technology Data Exchange (ETDEWEB)

    Scala, F.; Salatino, P. [Naples Univ. (Italy). Dipartimento di Ingegneria Chimica; Boerefijn, R.; Ghadiri, M. [Surrey Univ., Guildford (United Kingdom). Dept. of Chemical and Process Engineering

    2000-01-24

    The attrition behavior of two different limestones during calcination and sulphation in fluidized beds as been investigated by a combination of experimental techniques. The aim of the study is to shed light on the interactions between sorbent attrition and the change of particle mechanical and morphological properties associated with the progress of chemical reactions. A number of different experimental techniques have been used to characterize breakage mechanisms relevant to particle attrition in different sections of industrial fluidized bed reactors operated at atmospheric pressure. Primary fragmentation and abrasive attrition were characterized in situ by means of experiments carried out in a bench-scale fluidized bed reactor operated batchwise. Fragmentation under high velocity impact conditions was studied ex situ by means of single particle impact tests on pre-conditioned samples at room temperature. Scanning electron and optical microscopy analyses of the particles and EDX mapping of polished particle cross-sections were used to relate topography and internal composition of sorbent particles to the attrition mechanism. (orig.)

  7. Nanocrystalline iron based powder cores for high frequency applications

    Directory of Open Access Journals (Sweden)

    P. Gramatyka

    2006-08-01

    Full Text Available Purpose: The aim of this paper was to develop a various nanocrystalline powder cores with different polymersas a binder and investigate their magnetic properties (especially permeability and power losses at highfrequency range.Design/methodology/approach: Numerous experimental techniques were used to characterize startingpowders: laser particles analysis, scanning electron microscopy (SEM, transmission electron microscopy(TEM, X-ray diffraction (XRD and Mössbauer spectrometry (MS. The dynamic magnetic properties at thefrequency range from 50 Hz up to 100 kHz of nanocrystalline iron based powder cores were measured usingcomputerized hysteresis loop tracer Remacomp C-100 and Ferrometr device.Findings: It was found from the experimental studies, that nanocrystalline powder cores proved to be suitablefor high frequency applications. Their frequency dependences are comparable to that of permalloy or carbonyliron powder cores but shows smaller power losses.Research limitations/implications: Further studies should be undertaken in order to produce high densitycomposites with good soft magnetic properties and to find a good compromise between mechanical andmagnetic properties for power electronics applications.Practical implications: Developed nanocrystalline powder cores with permeability’s below 100 are potentialcandidates for a variety of industrial applications, such as electromagnetic interference filters, radio frequencycoupling devices, filter inductors and radio frequency tuning cores.Originality/value: Soft magnetic materials have recently regained interest as inductive component whichis a result of better raw materials, more developed technologies and a need for the materials from electricalmicromotors and low power motors for automation, robotics and other equipments. The present studycomplements and extends earlier investigations of polymer bonded powders.

  8. Confirming the Lanchestrian linear-logarithmic model of attrition

    Energy Technology Data Exchange (ETDEWEB)

    Hartley, D.S. III.

    1990-12-01

    This paper is the fourth in a series of reports on the breakthrough research in historical validation of attrition in conflict. Significant defense policy decisions, including weapons acquisition and arms reduction, are based in part on models of conflict. Most of these models are driven by their attrition algorithms, usually forms of the Lanchester square and linear laws. None of these algorithms have been validated. The results of this paper confirm the results of earlier papers, using a large database of historical results. The homogeneous linear-logarithmic Lanchestrian attrition model is validated to the extent possible with current initial and final force size data and is consistent with the Iwo Jima data. A particular differential linear-logarithmic model is described that fits the data very well. A version of Helmbold's victory predicting parameter is also confirmed, with an associated probability function. 37 refs., 73 figs., 68 tabs.

  9. Iron-based superconductors: Current status of materials and pairing mechanism

    International Nuclear Information System (INIS)

    Highlight: • An up-to-date review by the discoverer and a theoretical pioneer of iron-based superconductor. - Abstract: Since the discovery of high Tc iron-based superconductors in early 2008, more than 15,000 papers have been published as a result of intensive research. This paper describes the current status of iron-based superconductors (IBSC) covering most up-to-date research progress along with the some background research, focusing on materials (bulk and thin film) and pairing mechanism

  10. The Influence of Second Language Attrition on Foreign Language Teaching

    Institute of Scientific and Technical Information of China (English)

    李臻

    2012-01-01

    Besides the sessions of teaching and learning in language learning activities,language attrition,as the concomitant product of language acquisition,exerts significant impact on language teaching,especially on foreign language teaching.By exploring this phenomenon,some effective ways against language attrition can be found in order to maximize foreign language teaching.This paper is about to illustrate the relevant theories from scholars at home and abroad,and providing some ways to help foreign language learners maintain the language proficiency.

  11. Syntax and Morphology in Language Attrition: A Study of Five Bilingual Expatriate Swedes.

    Science.gov (United States)

    Hakansson, Gisela

    1995-01-01

    Explores the attrition of different aspects of Swedish grammar. Empirical data from bilingual expatriate students are compared to data from monolingual Swedish aphasic patients. The students' noun phrase morphology had undergone attrition, but not their word order. For the aphasics, word order attrition was combined with unaffected noun phrase…

  12. Nanosynthesis of Iron Based Material for Green Energy

    Science.gov (United States)

    Kirkeminde, Alec W.

    In this work, nanosynthesis of multiple iron-based materials are explored to further their use in green renewable-energy applications. First, the nanosynthesis of the abundant, non-toxic semi-conductor Iron Disulfide (Iron Pyrite, Fool's Gold, FeS2) is investigated. Within these studies, it became possible to tune the shape of the FeS2 nanoparticles easily by modifying injection temperatures and iron precursors. From here, the growth mechanisms of the different shapes were elucidated by examining different time points within the synthesis. It was discovered that the FeS2 did not grow by Ostwald Ripening, but instead by Oriented Attachment. Knowing this, it was possible to not only further the shapes of FeS2 nanoparticles, but also manipulate the size and crystallinity. Focus was then shifted to creating larger micron sized FeS2 crystals. Larger crystals where achieved by a unique FeS nanowire precursor followed by sulfurization. The dominant crystal surface of these crystals could be regulated simply by the time and temperature of the sulfurization. Second, synthetic control of magnetic nanoparticles was examined. A novel synthesis of Iron Palladium (FePd) made possible by interdiffusion of iron into palladium nanocores was identified. Furthermore, a shell of Iron oxide (Fe2O3) could facilely be grown on the FePd nanoparticles, generating a FePd/Fe2O3 core/shell nanoparticle. These FePd/Fe2O3 core/shell particles provided an excellent foundation to create an L10- FePd/α-Fe exchange-coupled nanocomposite that exhibited improved magnetic properties compared to its single phase FePd counterpart. However, the stabilizing ligand used within this FePd synthesis doped into the final nanoparticles, degraded the magnetic properties. iii To overcome the dopant ligand problem, a novel nanoalloy synthetic strategy of Metal Redox was developed. The Metal Redox strategy utilized the inherent reducing power of zero-valent metal sources to create a vast sampling of metal

  13. Microbial synthesis of iron-based nanomaterials—A review

    Indian Academy of Sciences (India)

    Abhilash; K Revati; B D Pandey

    2011-04-01

    Nanoparticles are the materials having dimensions of the order of 100 nm or less. They exhibit a high surface/volume ratio leading to different properties far different from those of the bulk materials. The development of uniform nanoparticles has been intensively pursued because of their technological and fundamental scientific importance. A number of chemical methods are available and are extensively used, but these are often energy intensive and employ toxic chemicals. An alternative approach for the synthesis of uniform nanoparticles is the biological route that occurs at ambient temperature, pressure and at neutral pH. The main aim of this review is to enlist and compare various methods of synthesis of iron-based nanoparticles with emphasis on the biological method. Biologically induced and controlled mineralization mechanisms are the two modes through which the micro-organisms synthesize iron oxide nanoparticles. In biologically induced mineralization (BIM) mode, the environmental factors like pH, pO2, pCO2, redox potential, temperature etc govern the synthesis of iron oxide nanoparticles. In contrast, biologically controlled mineralization (BCM) process initiates the micro-organism itself to control the synthesis. BIM can be observed in the Fe(III) reducing bacterial species of Shewanella, Geobacter, Thermoanaerobacter, and sulphate reducing bacterial species of Archaeoglobus fulgidus, Desulfuromonas acetoxidans, whereas BCM mode can be observed in the magnetotactic bacteria (MTB) like Magnetospirillum magnetotacticum, M. gryphiswaldense and sulphate-reducing magnetic bacteria (Desulfovibrio magneticus). Magnetite crystals formed by Fe(III)-reducing bacteria are epicellular, poorly crystalline, irregular in shapes, having a size range of 10–50 nm super-paramagnetic particles, with a saturation magnetization value ranging from 75–77 emu/g and are not aligned in chains. Magnetite crystals produced by MTB have uniform species-specific morphologies and sizes

  14. Interplay between superconductivity and magnetism in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chubukov, Andrey V [University of Wisconsin

    2015-06-10

    This proposal is for theoretical work on strongly correlated electron systems, which are at the center of experimental and theoretical activities in condensed-matter physics. The interest to this field is driven fascinating variety of observed effects, universality of underlying theoretical ideas, and practical applications. I propose to do research on Iron-based superconductors (FeSCs), which currently attract high attention in the physics community. My goal is to understand superconductivity and magnetism in these materials at various dopings, the interplay between the two, and the physics in the phase in which magnetism and superconductivity co-exist. A related goal is to understand the origin of the observed pseudogap-like behavior in the normal state. My research explores the idea that superconductivity is of electronic origin and is caused by the exchange of spin-fluctuations, enhanced due to close proximity to antiferromagnetism. The multi-orbital/multi-band nature of FeSCs opens routes for qualitatively new superconducting states, particularly the ones which break time-reversal symmetry. By all accounts, the coupling in pnictdes is below the threshold for Mott physics and I intend to analyze these systems within the itinerant approach. My plan is to do research in two stages. I first plan to address several problems within weak-coupling approach. Among them: (i) what sets stripe magnetic order at small doping, (ii) is there a preemptive instability into a spin-nematic state, and how stripe order affects fermions; (iii) is there a co-existence between magnetism and superconductivity and what are the system properties in the co-existence state; (iv) how superconductivity emerges despite strong Coulomb repulsion and can the gap be s-wave but with nodes along electron FSs, (v) are there complex superconducting states, like s+id, which break time reversal symmetry. My second goal is to go beyond weak coupling and derive spin-mediated, dynamic interaction between

  15. A Neurobiological Basis for SLA and First Language Attrition.

    Science.gov (United States)

    de Bode, Stella

    The two-part paper examines the neurobiological processes of synapse overproduction, synapse elimination, and issues of language acquisition and attrition. The first part consists of diagrams and notes explaining some basic terms and concepts of neurobiology: cortex; white matter; neuron; synapse; synaptogenesis; and development and organization…

  16. The Effects of Turnover: What We Know about Teacher Attrition

    Science.gov (United States)

    DeAngelis, Karen

    2012-01-01

    School business officials are likely to know better than anyone else about the financial costs to districts and schools associated with teacher attrition. Perhaps less well-known, though, is what else has been learned about this issue in recent years--information that may affect how one thinks about teacher turnover. Here is some of that research:…

  17. Evolutionary dynamics of a smoothed war of attrition game.

    Science.gov (United States)

    Iyer, Swami; Killingback, Timothy

    2016-05-01

    In evolutionary game theory the War of Attrition game is intended to model animal contests which are decided by non-aggressive behavior, such as the length of time that a participant will persist in the contest. The classical War of Attrition game assumes that no errors are made in the implementation of an animal׳s strategy. However, it is inevitable in reality that such errors must sometimes occur. Here we introduce an extension of the classical War of Attrition game which includes the effect of errors in the implementation of an individual׳s strategy. This extension of the classical game has the important feature that the payoff is continuous, and as a consequence admits evolutionary behavior that is fundamentally different from that possible in the original game. We study the evolutionary dynamics of this new game in well-mixed populations both analytically using adaptive dynamics and through individual-based simulations, and show that there are a variety of possible outcomes, including simple monomorphic or dimorphic configurations which are evolutionarily stable and cannot occur in the classical War of Attrition game. In addition, we study the evolutionary dynamics of this extended game in a variety of spatially and socially structured populations, as represented by different complex network topologies, and show that similar outcomes can also occur in these situations. PMID:26903203

  18. Attrition of Women Business Majors in an Urban Community College.

    Science.gov (United States)

    Karlen, Janice M.

    2004-01-01

    Identified intervention protocols that could help reduce the attrition of women business majors at an urban community college. Review of academic progress data and data from student surveys which examined students' reasons for leaving the institution indicated that there was a need for support mechanisms throughout the freshman year and extending…

  19. Teacher Retention and Attrition: Views of Early Career Teachers

    Science.gov (United States)

    Buchanan, John; Prescott, Anne; Schuck, Sandra; Aubusson, Peter; Burke, Paul; Louviere, Jordan

    2013-01-01

    The provision and maintenance of quality teachers is a matter of priority for the profession. Moreover, teacher attrition is costly to the profession, to the community and to those teachers who leave feeling disillusioned. There is a need to investigate the experiences of early career teachers to consider how these issues contribute to decisions…

  20. Toward a Grounded Theory of Nursing Student Attrition

    Science.gov (United States)

    Cook, Lenora

    2010-01-01

    Attrition of students from a nursing program is a significant concern. It is even more critical now because there are not enough nurses to fill all open positions in the healthcare industry. It is predicted the shortage will worsen in the next decade as an aging society increases the number of people requiring nursing care. While increasing the…

  1. Historical Perspectives of Student Attrition at a Major University.

    Science.gov (United States)

    Smith, Alan D.

    1982-01-01

    The University of Akron, a major urban university, has experienced unusually high attrition rates for students enrolled in the two largest colleges. The university has attempted to meet this problem by committee recommendations and questionnaire/demographic data gathering and analysis, which has resulted in some success. (Author/RC)

  2. Examining Study Attrition: Implications for Experimental Research on Professional Development

    Science.gov (United States)

    Kubitskey, Beth W.; Vath, Richard J.; Johnson, Heather J.; Fishman, Barry J.; Konstantopoulos, Spyros; Park, Gina J.

    2012-01-01

    As teacher professional development research includes more experimental designs, new challenges arise. We examine the threat of participant attrition as an example of the types of problems researchers face. Counter-intuitively, higher levels of recruitment effort were related to higher dropout rates among teachers. We also found that teachers left…

  3. Trends in attrition among medical teaching staff at universities in Myanmar 2009-2013.

    Science.gov (United States)

    Nang Mie Mie Htun; Reyer, Joshua A; Yamamoto, Eiko; Yoshida, Yoshitoku; Hamajima, Nobuyuki

    2016-02-01

    Although lack of human resources for health is becoming a global problem, there are few studies on human resources in Myanmar. This study was conducted to investigate the attrition rates of teaching staff from universities for medical professions in Myanmar from 2009 to 2013. The data were collected from administrative records from Department of Medical Sciences, Ministry of Health, Myanmar. Numbers of staff and those who permanently left work (attrition) from 2009 to 2013 were counted. The reasons were classified into two categories; involuntary attrition (death or retirement) and voluntary attrition (resignation or absenteeism). Official records of the attrited staff were reviewed for identifying demographic characteristics. The annual attrition rate for all kinds of health workers was about 4%. Among 494 attrited staff from 2009 to 2013, 357 staff (72.3%) left their work by involuntary attrition, while 137 staff (27.7%) left voluntarily. Doctors left their work with the highest annual rate (6.7%), while the rate for nurses was the lowest (1.1%). Male staff attrited with a higher rate (4.6%) than female staff (2.7%). Staff aged 46-60 years had the highest attrition rate. PhD degree holders had the highest rate (5.9%), while basic degree holders had the second highest rate (3.5%). Associate professors and above showed the highest attrition rate (8.1%). Teaching staff from non-clinical subjects had the higher rates (8.2%). Among 494 attrited staff, significant differences between involuntary attrition and voluntary attrition were observed in age, marital status, education, overseas degree, position, field of teaching, duration of services and duration of non-residential service. These findings indicated the need to develop appropriate policies such as educational reforms, local recruitment plans, transparent regulatory and administrative measures, and professional incentives to retain the job. PMID:27019526

  4. Barrier function of a corroding iron based container

    International Nuclear Information System (INIS)

    Thick-walled cast-iron containers encapsulate highly radioactive waste in a deep geological repository and provide mechanical stabilization against lithostatic pressure and shear forces. Intrusion of water and corrosion, however, limits container integrity to a certain time period of several hundreds (BMU, 2010) to several thousands of years (NAGRA, 2002). Repository concepts in crystalline rock therefore include an additional copper coating, providing chemical resistance against water corrosion.

  5. Mechanical and Wear Properties of Nanostructured Surface Layer in Iron Induced by Surface Mechanical Attrition Treatment

    Institute of Scientific and Technical Information of China (English)

    Nairong TAO; Weiping TONG; Zhenbo WANG; Wei WANG; Manling SUI; Jian LU; Ke LU

    2003-01-01

    A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic noduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.

  6. Grammatical Gender in American Norwegian Heritage Language: Stability or Attrition?

    Science.gov (United States)

    Lohndal, Terje; Westergaard, Marit

    2016-01-01

    This paper investigates possible attrition/change in the gender system of Norwegian heritage language spoken in America. Based on data from 50 speakers in the Corpus of American Norwegian Speech (CANS), we show that the three-gender system is to some extent retained, although considerable overgeneralization of the masculine (the most frequent gender) is attested. This affects both feminine and neuter gender forms, while declension class markers such as the definite suffix remain unaffected. We argue that the gender category is vulnerable due to the lack of transparency of gender assignment in Norwegian. Furthermore, unlike incomplete acquisition, which may result in a somewhat different or reduced gender system, attrition is more likely to lead to general erosion, eventually leading to complete loss of gender. PMID:27014151

  7. Attrition and adherence in the online treatment of chronic insomnia.

    Science.gov (United States)

    Hebert, Elizabeth A; Vincent, Norah; Lewycky, Samantha; Walsh, Kaitlyn

    2010-01-01

    This study examined the ability of the Theory of Planned Behavior (TPB; Ajzen, 1985) and the Transtheoretical Model of Behavior Change (TTM; Prochaska & DiClemente, 1983) to explain adherence and attrition in an online treatment program for chronic insomnia. Responses to questionnaire measures of the TPB and TTM were used to predict adherence and dropout over the subsequent 5 weeks of treatment. Results showed that there was a 17% dropout rate and that perceived behavioral control, social support, and intention to complete the program were significantly associated with adherence to sleep hygiene homework. Attrition was predicted only by symptom severity and psychiatric comorbidity. Implications are that these models should be considered to maximize adherence. PMID:20582757

  8. Relationship between Academic Performance, Spatial Competence, Learning Styles and Attrition

    Directory of Open Access Journals (Sweden)

    Marianela Noriega Biggio

    2013-04-01

    Full Text Available This paper discusses the results of research on factors affecting academic performance and attrition in a sample of 1,500 freshman students majoring in architecture, design and urbanism at the Universidad de Buenos Aires, Argentina [University of Buenos Aires, Argentina] who were enrolled in a drafting course. The hypotheses we tested concern the mediating role of learning styles on the relationship between spatial competence and academic performance, learning-style differences by gender and cohort, and the relationship between attrition, spatial competence level and learning style. Statistical analysis of the data was performed and spatial competence enhanced by motivational profile was found to predict final achievement. Educational implications are identified, highlighting the need to promote in students those academic behaviors that characterize a self-regulated learning style and encourage the use of specific intellectual abilities.

  9. Spin fluctuations and unconventional superconducting pairing in iron-based superconductors

    Institute of Scientific and Technical Information of China (English)

    Yu Shun-Li; Li Jian-Xin

    2013-01-01

    In this article,we review the recent theoretical works on the spin fluctuations and superconductivity in iron-based superconductors.Using the fluctuation exchange approximation and multi-orbital tight-binding models,we study the characteristics of the spin fluctuations and the symmetries of the superconducting gaps for different iron-based superconductors.We explore the systems with both electron-like and hole-like Fermi surfaces (FS) and the systems with only the electronlike FS.We argue that the spin-fluctuation theories are successful in explaining at least the essential part of the problems,indicating that the spin fluctuation is the common origin of superconductivity in iron-based superconductors.

  10. Creep rupture behavior of Stirling engine materials. [Iron-base NASAUT 4G-Al

    Energy Technology Data Exchange (ETDEWEB)

    Titran, R.H.; Scheuerman, C.M.; Stephens, J.R.

    1985-01-01

    The automotive Stirling engine, being investigated jointly by the Department of Energy and NASA Lewis as an alternate to the internal combustion engine, uses high-pressure as the working fluid. The long-term effects of hydrogen on the high temperature strenth properties of materials are relatively unknown. This is especially true for the newly developed low-cost iron base alloy NASAUT 4G-Al. This iron-base alloy when tested in air has creep-rupture strengths in the directionally solidified condition comparable to the cobalt base alloy HS-31. The equiaxed (investment cast) NASAUT 4G-Al has superior creep-rupture to the equiaxed iron-base alloy XF-818 both in air and 15 MPa hydrogen.

  11. Effects of van der Waals interaction for first-principles calculations on iron-based superconductors

    International Nuclear Information System (INIS)

    Highlights: •van der Waals density functional calculations for iron-based superconductors. •Optimized structures are evaluated. •van der Waals density functional reproduce lattice constants of FeSe. •Except for FeSe, van der Waals interaction hardly affects crystal structures. -- Abstract: We investigate effects of van der Waals (vdW) interaction on various iron-based superconductors by first-principles calculations based on the van der Waals density functional (vdW-DF) taking account of non-local and long range interaction. vdW-DF reproduces well the lattice constants of FeSe, while the crystal structure of other iron-based superconductors are not so sensitive to vdW interaction. These results suggest that the effects of vdW interaction on layered superconductors are often essential although they depend on the characters of the interlayer couplings

  12. Pack cementation diffusion coatings for iron-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1995-02-01

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels. The Cr-Si ferrite layers have proven to be very resistant to high temperature cyclic oxidation and to pitting in aqueous solutions. The process has been patented, and is being transferred for industrial application, e.g. for water walls of utility boilers, etc. In the proposed extension of this project, the use of mixed pure metal powders in the pack will be extended to achieve similar ferrite Fe-Cr-Al coatings with excellent oxidation resistance, with the eventual transfer of the technology to industry. In other recent studies, Ni-base alloy rods were aluminized by the halide-activated pack cementation process to bring their average composition to that for the ORNL-developed Ni{sub 3}Al, for use as a welding rod. A similar effort to develop a welding rod for the ORNL Fe{sub 3}Al alloy did not yield reproducible coating compositions or growth kinetics. The continued effort to produce Duriron-type (Fe-18Si-5Cr) coatings on steels was not successful. Literature for the intrinsic diffusion coefficients suggests that this task cannot be achieved.

  13. COMPENSATORY STRATEGIES OF FIRST-LANGUAGE-ATTRITED CHILDREN

    Directory of Open Access Journals (Sweden)

    Syahdan Syahdan

    2012-01-01

    Full Text Available This article explores the compensatory strategies used by two Indonesian children who experienced first language attrition when acquiring English in the English-speaking environment. They use compensatory strategies to compensate for their lack of competence in first language. They employ both interlingual strategies and discourse strategies when they have difficulties in communication. Interlingual strategies used are codeswitching and lexical borrowings and the discourse strategies are overt comments, appeal for assistance, and avoidance.

  14. Non-parallel processing: Gendered attrition in academic computer science

    Science.gov (United States)

    Cohoon, Joanne Louise Mcgrath

    2000-10-01

    This dissertation addresses the issue of disproportionate female attrition from computer science as an instance of gender segregation in higher education. By adopting a theoretical framework from organizational sociology, it demonstrates that the characteristics and processes of computer science departments strongly influence female retention. The empirical data identifies conditions under which women are retained in the computer science major at comparable rates to men. The research for this dissertation began with interviews of students, faculty, and chairpersons from five computer science departments. These exploratory interviews led to a survey of faculty and chairpersons at computer science and biology departments in Virginia. The data from these surveys are used in comparisons of the computer science and biology disciplines, and for statistical analyses that identify which departmental characteristics promote equal attrition for male and female undergraduates in computer science. This three-pronged methodological approach of interviews, discipline comparisons, and statistical analyses shows that departmental variation in gendered attrition rates can be explained largely by access to opportunity, relative numbers, and other characteristics of the learning environment. Using these concepts, this research identifies nine factors that affect the differential attrition of women from CS departments. These factors are: (1) The gender composition of enrolled students and faculty; (2) Faculty turnover; (3) Institutional support for the department; (4) Preferential attitudes toward female students; (5) Mentoring and supervising by faculty; (6) The local job market, starting salaries, and competitiveness of graduates; (7) Emphasis on teaching; and (8) Joint efforts for student success. This work contributes to our understanding of the gender segregation process in higher education. In addition, it contributes information that can lead to effective solutions for an

  15. Relationship between Academic Performance, Spatial Competence, Learning Styles and Attrition

    OpenAIRE

    Marianela Noriega Biggio; Stella Maris García

    2013-01-01

    This paper discusses the results of research on factors affecting academic performance and attrition in a sample of 1,500 freshman students majoring in architecture, design and urbanism at the Universidad de Buenos Aires, Argentina [University of Buenos Aires, Argentina] who were enrolled in a drafting course. The hypotheses we tested concern the mediating role of learning styles on the relationship between spatial competence and academic performance, learning-style differences by gende...

  16. Effectiveness of student admission essays in identifying attrition.

    Science.gov (United States)

    Sadler, Judith

    2003-11-01

    Nursing school admission selection processes exist to select the "best and brightest" applicants assuming that those selected will be successful. However, attrition occurs. Effectiveness of grade point averages (GPAs) and test scores have been reported, while the effectiveness of essays in predicting attrition in undergraduate nursing education has not been reported in the literature. For the purposes of this study, attrition was defined as students enrolled in courses following acceptance into the program who did not complete the program. Data from a retrospective longitudinal sample including 236 students from one baccalaureate nursing program were analyzed for differences between students who completed the program ("completers", n=193) and those who dropped out ("non-completers", n=43). t-tests between the group mean essay scores revealed a statistical difference (t=2.092, p=0.043), while there was no statistical difference (t=0.22, p=ns) between the mean admission GPAs of the groups. Content analysis revealed thematic differences in the essays. Non-completers tended to write about nursing as external to themselves, in contrast to the completers who described an internalization of the role. Answers to questions of motivation for entering nursing and personal experience with a nurse may provide helpful information in selecting those students most likely to complete the program. PMID:14554116

  17. Properties and Application of Iron-based Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Li Jian-chen; Jiang Qing; Dai Jun

    2005-01-01

    The properties of FeMnSiCrNi shape memory alloy were investigated. The results show that the best shape memory effect of Fel4Mn6Si9Cr5Ni alloy is 85%. The transformation amount of the ε→γ transformation is not complete after heating the alloy to 1000 K, As and Af points drop with increased transformation enthalpy ( △Hγ→ε) by thermal cycling and increased prestrain. The alloy shows also good creep and stress relaxation resistance. In addition, the alloy having a tensile force of 20 kN and a sealing pressure of 6 MPa can satisfy requirements for possible industrial application on pipe joints.

  18. Fabrication and properties of iron-based soft magnetic composites coated with parylene via chemical vapor deposition polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Shen [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Mechanical and Electrical Engineering Institute, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Sun, Aizhi, E-mail: sunaizhi@126.com [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Lu, Zhenwen; Cheng, Chuan [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-03-01

    This paper focuses on novel iron-based soft magnetic composites synthesis utilizing low friction factor parylene C films to coat iron powder via chemical vapor deposition polymerization. The morphology, magnetic properties, density, and chemical stability of parylene insulated iron particles were investigated. The coated parylene insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The thickness of parylene C film is averagely 300 nm according to the results of transmission electron microscopy. Parylene C film uniformly coated the powder surface resulting in reducing the permeability imaginary part, increasing electrical resistivity and increasing the operating frequency of the synthesized magnets. It was shown that the parylene C coated compacts exhibited noticeably higher density compared to the epoxy resin coated compacts at the same pressure, suppress at 800 MPa increased the density by 17.02%. The result of Tafel curves indicated that the resistance of the iron particles to corrosion by NaCl solution is obviously improved after being insulated with parylene C film. - Highlights: • Parylene C uniformly coated the powder, increased the operating frequency of SMCs. • Compared with epoxy coated, the density of SMCs increased by 17.02% at 800 MPa. • The resistance of the iron particles is obviously improved with parylene film insulated.

  19. Fabrication and properties of iron-based soft magnetic composites coated with parylene via chemical vapor deposition polymerization

    International Nuclear Information System (INIS)

    This paper focuses on novel iron-based soft magnetic composites synthesis utilizing low friction factor parylene C films to coat iron powder via chemical vapor deposition polymerization. The morphology, magnetic properties, density, and chemical stability of parylene insulated iron particles were investigated. The coated parylene insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The thickness of parylene C film is averagely 300 nm according to the results of transmission electron microscopy. Parylene C film uniformly coated the powder surface resulting in reducing the permeability imaginary part, increasing electrical resistivity and increasing the operating frequency of the synthesized magnets. It was shown that the parylene C coated compacts exhibited noticeably higher density compared to the epoxy resin coated compacts at the same pressure, suppress at 800 MPa increased the density by 17.02%. The result of Tafel curves indicated that the resistance of the iron particles to corrosion by NaCl solution is obviously improved after being insulated with parylene C film. - Highlights: • Parylene C uniformly coated the powder, increased the operating frequency of SMCs. • Compared with epoxy coated, the density of SMCs increased by 17.02% at 800 MPa. • The resistance of the iron particles is obviously improved with parylene film insulated

  20. Influence of atomic and mechanical attrition on low temperature plasma nitriding of ferrous alloys

    International Nuclear Information System (INIS)

    AISI 316 austenitic stainless steel samples were plasma nitrided in variable process times at low temperature (300 deg. C). Two different pretreatments were performed where ball milling (mechanical attrition) and argon plasma (atomic attrition) were used in order to study their posterior effects on plasma nitriding. X-ray diffraction, scanning electron microscopy and nano-indentation experiments were performed for characterization before and after plasma nitriding. Mechanical attrition produces a phase transformation of the original crystalline structure while atomic attrition creates preferential planes in the same crystalline structure. After plasma nitriding and although both pretreatments increase the hardness, the atomic attrition shows the highest hardness values. The mechanical attrition decreases the nitrided layer thickness due to surface oxidation that creates a potential barrier for nitrogen incorporation.

  1. Weak-link behaviour observed in iron-based superconductors with thick perovskite-type blocking layers

    International Nuclear Information System (INIS)

    The synthesis of iron-based superconductors with thick perovskite-type blocking layers, (Fe2As2)(Ca4(Mg0.25,Ti0.75)3O8) (22438) and (Fe2As2)(Ca5(Sc0.5Ti0.5)4O11) (225411), has been carried out and their transport properties discussed in comparison with those of fluorine-doped SmFeAsO0.8F0.2 (Sm1111) superconductors. Microstructural observation revealed that superconducting grains have a platelet shape and are strongly coupled with each other, particularly in 22438. The onset transition temperature (Tc) of 22438 reached up to 47.5 K and its very high upper critical field at low temperatures was suggested by a steep slope (dHc2/dT) near Tc as large as −19.8 T K−1. The resistance curves under various magnetic fields showed a basically two-step-like character of the superconducting transitions, where the effect of magnetic field is weaker at the onset part near the normal state in comparison to the tail part. The broadening of the tail part suggests a weak-link connection between superconducting grains. Two distinct scales of current flow corresponding to inter- and intragranular currents were confirmed by the remanent magnetization measurement of bulk samples, and their calculated intergranular current densities are relatively low. The analysis of their superconducting properties suggests evidence of the weak-link intergrain nature and high electromagnetic anisotropy of these iron-based superconductors with thick oxide blocking layers. (paper)

  2. Understanding attrition from international internet health interventions: a step towards global eHealth

    OpenAIRE

    Geraghty, Adam W A; Torres, Leandro D.; Leykin, Yan; Pérez-Stable, Eliseo J.; Muñoz, Ricardo F.

    2012-01-01

    Worldwide automated Internet health interventions have the potential to greatly reduce health disparities. High attrition from automated Internet interventions is ubiquitous, and presents a challenge in the evaluation of their effectiveness. Our objective was to evaluate variables hypothesized to be related to attrition, by modeling predictors of attrition in a secondary data analysis of two cohorts of an international, dual language (English and Spanish) Internet smoking cessation interventi...

  3. Identification of Average Treatment Effects in Social Experiments Under Alternative Forms of Attrition

    OpenAIRE

    Huber, Martin

    2012-01-01

    As any empirical method used for causal analysis, social experiments are prone to attrition which may flaw the validity of the results. This paper considers the problem of partially missing outcomes in experiments. Firstly, it systematically reveals under which forms of attrition - in terms of its relation to observable and/or unobservable factors - experiments do (not) yield causal parameters. Secondly, it shows how the various forms of attrition can be controlled for by different methods of...

  4. Identification of average treatment effects in social experiments under different forms of attrition

    OpenAIRE

    Martin Huber

    2010-01-01

    As any empirical method used for causal analysis, social experiments are prone to attrition which may flaw the validity of the results. This paper considers the problem of partially missing outcomes in experiments. Firstly, it systematically reveals under which forms of attrition - in terms of its relation to observable and/or unobservable factors - experiments do (not) yield causal parameters. Secondly, it shows how the various forms of attrition can be controlled for by different methods of...

  5. Gilbert damping and anisotropic magnetoresistance in iron-based alloys

    Science.gov (United States)

    Berger, L.

    2016-07-01

    We use the two-current model of Campbell and Fert to understand the compositional dependence of the Gilbert damping parameter in certain iron alloys. In that model, spin-up and spin-down carriers have different resistivities ρ↑ and ρ↓. We emphasize the part of the Gilbert parameter, called Gsf, generated by spin-flip interband processes. Both Gsf and the anisotropic magnetoresistance Δρ are proportional to the square of the spin-orbit parameter, and also proportional to ρ↑. In bcc alloys of iron with V, Cr, Mo, etc. solutes on the left of iron in the periodic table, ρ↑ is increased by a scattering resonance (Gomes and Campbell, 1966, 1968). Then ρ↑, Δρ, and Gsf all exhibit a peak at the same moderate concentration of the solute. We find the best fit between this theory and existing experimental data of Gilbert damping for Fe-V epitaxial films at room temperature (Cheng, 2006; Scheck et al., 2007). At room temperature, the predicted Gsf peak is masked by a background arising from non-flip intraband processes. At elevated temperatures, the peak is expected to become more prominent, and less hidden in the background.

  6. Organo-sulfur molecules enable iron-based battery electrodes to meet the challenges of large-scale electrical energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Yang, B; Malkhandi, S; Manohar, AK; Prakash, GKS; Narayanan, SR

    2014-07-03

    Rechargeable iron-air and nickel-iron batteries are attractive as sustainable and inexpensive solutions for large-scale electrical energy storage because of the global abundance and eco-friendliness of iron, and the robustness of iron-based batteries to extended cycling. Despite these advantages, the commercial use of iron-based batteries has been limited by their low charging efficiency. This limitation arises from the iron electrodes evolving hydrogen extensively during charging. The total suppression of hydrogen evolution has been a significant challenge. We have found that organo-sulfur compounds with various structural motifs (linear and cyclic thiols, dithiols, thioethers and aromatic thiols) when added in milli-molar concentration to the aqueous alkaline electrolyte, reduce the hydrogen evolution rate by 90%. These organo-sulfur compounds form strongly adsorbed layers on the iron electrode and block the electrochemical process of hydrogen evolution. The charge-transfer resistance and double-layer capacitance of the iron/electrolyte interface confirm that the extent of suppression of hydrogen evolution depends on the degree of surface coverage and the molecular structure of the organo-sulfur compound. An unanticipated electrochemical effect of the adsorption of organo-sulfur molecules is "de-passivation" that allows the iron electrode to be discharged at high current values. The strongly adsorbed organo-sulfur compounds were also found to resist electro-oxidation even at the positive electrode potentials at which oxygen evolution can occur. Through testing on practical rechargeable battery electrodes we have verified the substantial improvements to the efficiency during charging and the increased capability to discharge at high rates. We expect these performance advances to enable the design of efficient, inexpensive and eco-friendly iron-based batteries for large-scale electrical energy storage.

  7. Attrition in the Trades. Research Overview. Monograph Series 07/2011

    Science.gov (United States)

    Wilson, Sara

    2011-01-01

    "Attrition in the trades," by Tom Karmel, Patrick Lim and Josie Misko, analyses whether attrition--the gradual reduction or weakening of a workforce--occurs more amongst tradespeople than professionals, and if this is to the detriment of the supply of tradespeople. The authors use data from the Australian Labour Mobility Survey in 2008 and 1994.…

  8. Dropouts and Turnover: The Synthesis and Test of a Causal Model of Student Attrition.

    Science.gov (United States)

    Bean, John P.

    1980-01-01

    The determinants of student attrition in higher education institutions are investigated using a causal model which synthesized research findings on job turnover and on student attrition. Many male/female differences were found but three surrogate measures for pay were found for both sexes to be related to intent to leave. (Author/LC)

  9. Identification of Average Treatment Effects in Social Experiments under Alternative Forms of Attrition

    Science.gov (United States)

    Huber, Martin

    2012-01-01

    As any empirical method used for causal analysis, social experiments are prone to attrition which may flaw the validity of the results. This article considers the problem of partially missing outcomes in experiments. First, it systematically reveals under which forms of attrition--in terms of its relation to observable and/or unobservable…

  10. Mode-switch protocols: How a seemingly small design difference can affect attrition rates and attrition bias

    OpenAIRE

    Peter Lynn

    2012-01-01

    We consider the effect of a wave of mixed-mode data collection (telephone and face-to-face), in an otherwise face-to-face survey, on panel attrition and the extent to which this effect is dependent on the nature of the mode-switch protocol. Findings are reported from an experiment on a survey in which the objective is to interview each adult member of the household. One protocol involves making extended efforts to interview each household member by telephone before switching to face-to-face, ...

  11. The network of corporate clients: customer attrition at commercial banks

    Science.gov (United States)

    Lublóy, Á.; Szenes, M.

    2008-12-01

    Commercial banks might profit from the adoption of methods widely used in network theory. A decision making process might become biased if one disregards network effects within the corporate client portfolio. This paper models the phenomenon of customer attrition by generating a weighted and directed network of corporate clients linked by financial transactions. During the numerical study of the agent-based toy model we demonstrate that multiple steady states may exist. The statistical properties of the distinct steady states show similarities. We show that most companies of the same community choose the same bank in the steady state. In contrast to the case for the steady state of the Barabási-Albert network, market shares in this model equalize by network size. When modeling customer attrition in the network of 3 × 105 corporate clients, none of the companies followed the behavior of the initial switcher in three quarters of the simulations. The number of switchers exceeded 20 in 1% of the cases. In the worst-case scenario a total of 688 companies chose a competitor bank. Significant network effects have been discovered; high correlation prevailed between the degree of the initial switcher and the severity of the avalanche effect. This suggests that the position of the corporate client in the network might be much more important than the underlying properties (industry, size, profitability, etc) of the company.

  12. Conventional empirical law reverses in the phase transitions of 122-type iron-based superconductors

    International Nuclear Information System (INIS)

    Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram of the iron-based superconductor AFe2As2 (A = Ca, Sr, Eu, and Ba). As a result, the cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure

  13. Direct observation of spin-orbit coupling in iron-based superconductors

    Science.gov (United States)

    Borisenko, S. V.; Evtushinsky, D. V.; Liu, Z.-H.; Morozov, I.; Kappenberger, R.; Wurmehl, S.; Büchner, B.; Yaresko, A. N.; Kim, T. K.; Hoesch, M.; Wolf, T.; Zhigadlo, N. D.

    2016-04-01

    Spin-orbit coupling is a fundamental interaction in solids that can induce a broad range of unusual physical properties, from topologically non-trivial insulating states to unconventional pairing in superconductors. In iron-based superconductors its role has, so far, not been considered of primary importance, with models based on spin- or orbital fluctuations pairing being used most widely. Using angle-resolved photoemission spectroscopy, we directly observe a sizeable spin-orbit splitting in all the main members of the iron-based superconductors. We demonstrate that its impact on the low-energy electronic structure and details of the Fermi surface topology is stronger than that of possible nematic ordering. The largest pairing gap is supported exactly by spin-orbit-coupling-induced Fermi surfaces, implying a direct relation between this interaction and the mechanism of high-temperature superconductivity.

  14. Low stacking fault energy steels in the context of manganese-rich iron-based alloys

    International Nuclear Information System (INIS)

    The role of stacking fault energy on defining the work-hardening behavior of manganese-rich iron-based alloys was highlighted by the tensile deformation of four high-manganese steels designed using thermodynamic mechanism maps. The flow behavior and work-hardening rate diagrams, together with the activity of different deformation mechanisms (deformation-induced martensitic transformations and deformation twinning), were evaluated in conjunction with the microstructural investigations using electron backscattering diffraction.

  15. Particle-Hole Transformation in Iron-Based High-Temperature Superconductors

    OpenAIRE

    Rodriguez, J. P.

    2016-01-01

    An exact particle-hole transformation is discovered in a local-moment description of monolayer iron-based superconductors at strong iron-site Coulomb repulsion. Application of the transformation to a surface layer of FeSe predicts a surface-layer high-temperature superconductor at strong hole doping. Comparison with existing low-Tc iron superconductors suggests that the critical temperature at heavy hole doping can be increased by increasing direct ferromagnetic exchange in between nearest ne...

  16. First-principles Studies for the Hydrogen Doping Effects on Iron-based Superconductors

    OpenAIRE

    Nakamura, Hiroki; Machida, Masahiko

    2011-01-01

    We study hydrogen doping effects in an iron-based superconductor LaFeAsO_(1-y) by using the first-principles calculation and explore the reason why the superconducting transition temperature is remarkably enhanced by the hydrogen doping. The present calculations reveal that a hydrogen cation stably locating close to an iron atom attracts a negatively-charged FeAs layer and results in structural distortion favorable for further high temperature transition. In fact, the lattice constant a avera...

  17. Corrosion and environmental-mechanical characterization of iron-base nuclear waste package structural barrier materials. Annual report, FY 1984

    International Nuclear Information System (INIS)

    Disposal of high-level nuclear waste in deep underground repositories may require the development of waste packages that will keep the radioisotopes contained for up to 1000 y. A number of iron-base materials are being considered for the structural barrier members of waste packages. Their uniform and nonuniform (pitting and intergranular) corrosion behavior and their resistance to stress-corrosion cracking in aqueous environments relevant to salt media are under study at Pacific Northwest Laboratory. The purpose of the work is to provide data for a materials degradation model that can ultimately be used to predict the effective lifetime of a waste package overpack in the actual repository environment. The corrosion behavior of the candidate materials was investigated in simulated intrusion brine (essentially NaCl) in flowing autoclave tests at 1500C, and in combinations of intrusion/inclusion (high-Mg) brine environments in moist salt tests, also at 1500C. Studies utilizing a 60Co irradiation facility were performed to determine the corrosion resistance of the candidate materials to products of brine radiolysis at dose rates of 2 x 103 and 1 x 105 rad/h and a temperature of 1500C. These irradiation-corrosion tests were ''overtests,'' as the irradiation intensities employed were 10 to 1000 times as high as those expected at the surface of a thick-walled waste package. With the exception of the high general corrosion rates found in the tests using moist salt containing high-Mg brines, the ferrous materials exhibited a degree of corrosion resistance that indicates a potentially satisfactory application to waste package structural barrier members in a salt repository environment

  18. Health workforce attrition in the public sector in Kenya: a look at the reasons

    Directory of Open Access Journals (Sweden)

    Muchiri Stephen

    2009-07-01

    Full Text Available Abstract Background Kenya, like many other countries in sub-Saharan Africa, has been affected by shortages of health workers in the public sector. Data on the rates and leading reasons for health workers attrition in the public sector are key in developing effective, evidence-based planning and policy on human resources for health. Methods This study analysed data from a human resources health facility survey conducted in 2005 in 52 health centres and 22 public hospitals (including all provincial hospitals across all eight provinces in Kenya. The study looked into the status of attrition rates and the proportion of attrition due to retirement, resignation or death among doctors, clinical officers, nurses and laboratory and pharmacy specialists in surveyed facilities. Results Overall health workers attrition rates from 2004 to 2005 were similar across type of health facility: provincial hospitals lost on average 4% of their health workers, compared to 3% for district hospitals and 5% for health centres. However, there are differences in the patterns of attrition rates by cadre. Attrition among doctors and registered nurses was much higher at the provincial hospitals than at district hospitals or health centres, whereas the opposite pattern was observed for laboratory and pharmacy staff (lost at a higher rate in lower-level facilities. In provincial hospitals, doctors had higher attrition rates than clinical officers, and registered nurses had higher attrition rates than enrolled nurses. In contrast, attrition of enrolled and registered nurses in district hospitals and health centres was similar. The main reason for health worker attrition (all cadres combined at each level of facility was retirement, followed by resignation and death. However, resignation drives attrition among doctors and clinical officers; retirement accounts for the main share of attrition among nurses and pharmacy staff; and death is the primary reason for attrition among

  19. Development of high-performance iron-based superconducting wires and tapes

    International Nuclear Information System (INIS)

    Highlights: • We review key properties and technical progress in high Jc pnictide wires during the last few years. • Providing a snapshot of these recent developments and a sense of their significance for applications. • Using the scalable rolling process, the 11 m long 122/Ag tapes with high Jc were produced for the first time. - Abstract: Conventional powder-in-tube (PIT) method has been the most effective technique for fabricating iron-based superconducting wires and tapes. Tremendous advances have been made during the last few years, especially for 122 family pnictide tapes. Here we review some of the most recent and significant developments in making high-performance iron-based tapes by the ex-situ PIT process, paying particular attention to several fabrication techniques to realize high-field Jc performance in terms of increase of core density and improvement of texture. At 4.2 K, the practical level transport Jc up to 0.12 MA/cm2 in 10 T and 0.1 MA/cm2 in 14 T have been achieved in the K-doped 122/Ag tapes. As for multifilamentary 122 iron-based wires and tapes, the highest Jc values reached so far are 61 kA/cm2 and 35 kA/cm2 at 4.2 K and 10 T, respectively for 7- and 19-core Sr-122 tapes. Recently, high Jc Cu-cladded and stainless steel/Ag double-sheathed 122 tapes have also been produced in order to improve either mechanical properties or thermal stability. More importantly, the scalable rolling process has been used for the first time to demonstrate high Jc values in 122 conductor tapes of 11 m in length

  20. Disorder-promoted C4-symmetric magnetic order in iron-based superconductors

    Science.gov (United States)

    Hoyer, Mareike; Fernandes, Rafael M.; Levchenko, Alex; Schmalian, Jörg

    2016-04-01

    In most iron-based superconductors, the transition to the magnetically ordered state is closely linked to a lowering of structural symmetry from tetragonal (C4) to orthorhombic (C2). However, recently, a regime of C4-symmetric magnetic order has been reported in certain hole-doped iron-based superconductors. This novel magnetic ground state can be understood as a double-Q spin density wave characterized by two order parameters M1 and M2 related to each of the two Q vectors. Depending on the relative orientations of the order parameters, either a noncollinear spin-vortex crystal or a nonuniform charge-spin density wave could form. Experimentally, Mössbauer spectroscopy, neutron scattering, and muon spin rotation established the latter as the magnetic configuration of some of these optimally hole-doped iron-based superconductors. Theoretically, low-energy itinerant models do support a transition from single-Q to double-Q magnetic order, but with nearly degenerate spin-vortex crystal and charge-spin density wave states. In fact, extensions of these low-energy models including additional electronic interactions tip the balance in favor of the spin-vortex crystal, in apparent contradiction with the recent experimental findings. In this paper we revisit the phase diagram of magnetic ground states of low-energy multiband models in the presence of weak disorder. We show that impurity scattering not only promotes the transition from C2 to C4-magnetic order, but it also favors the charge-spin density wave over the spin-vortex crystal phase. Additionally, in the single-Q phase, our analysis of the nematic coupling constant in the presence of disorder supports the experimental finding that the splitting between the structural and stripe-magnetic transition is enhanced by disorder.

  1. About calculation of crystal lattice parameters of iron base solid solutions

    International Nuclear Information System (INIS)

    Lattice parameters of iron base solid solutions (Fe-Be, Fe-Cr, Fe-Co, Fe-Mo, Fe-Nb, Fe-Ni, Fe-Ru, Fe-Ti, Fe-V) are calculated on the basis of previously proposed model with the use of the correction taking into account the chemical interaction between element atoms. calculation results allow the conclusion that the sue of the correction reduced the discrepancy between experimental and calculated data on lattice parameters down tp values comparable with an error of the experiment

  2. The super-super exchange mechanism in iron-based antiperovskite chalco-halides

    OpenAIRE

    Liu, Kai; LU, Zhong-Yi

    2016-01-01

    By using the first-principles electronic structure calculations, we have systematically studied the magnetism in three recently synthesized iron-based antiperovskite chalco-halides: Ba$_3$(FeS$_4$)Cl, Ba$_3$(FeS$_4$)Br, and Ba$_3$(FeSe$_4$)Br. These compounds consist of edge-sharing Ba$Q_6$ ($Q$=Cl or Br) octahedra intercalated with isolated Fe$X_4$ ($X$=S or Se) tetrahedra. We find that even though the shortest distances between the nearest-neighboring Fe atoms in these three compounds alrea...

  3. Interstitial-phase precipitation in iron-base alloys: a comparative study

    International Nuclear Information System (INIS)

    Recent developments have elucidated the atomistic mechanisms of precipitation of interstitial elements in simple alloy systems. However, in the more technologically important iron base alloys, interstitial phase precipitation is generally not well understood. The present experimental study was therefore designed to test the applicability of these concepts to more complex ferrous alloys. Hence, a comparative study was made of interstitial phase precipitation in ferritic Fe-Si-C and in austenitic phosphorus-containing Fe-Cr-Ni steels. These systems were subjected to a variety of quench-age thermal treatments, and the microstructural development was subsequently characterized by transmission electron microscopy

  4. Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kuroki, Kazuhiko; Usui, Hidetomo [Department of Applied Physics and Chemistry, The University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Onari, Seiichiro; Tanaka, Yukio [Department of Applied Physics, Nagoya University, Nagoya 464-8603 (Japan); Arita, Ryotaro [Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656 (Japan); Kontani, Hiroshi [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Aoki, Hideo [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan)], E-mail: kuroki@vivace.e-one.uec.ac.jp

    2009-02-15

    For an iron-based high T{sub c} superconductor LaFeAsO{sub 1-x}F{sub x}, we construct a minimal model where all of the five Fe d bands turn out to be involved. We then investigate the origin of superconductivity with a five-band random-phase approximation by solving the Eliashberg equation. We conclude that the spin fluctuation modes arising from the nesting between the disconnected Fermi pockets realize basically an extended s-wave pairing, where the gap changes sign across the nesting vector.

  5. Hydrothermal grown nanoporous iron based titanate, Fe₂TiO₅ for light driven water splitting.

    Science.gov (United States)

    Bassi, Prince Saurabh; Chiam, Sing Yang; Gurudayal; Barber, James; Wong, Lydia Helena

    2014-12-24

    We report the synthesis of iron based titanate (Fe2TiO5) thin films using a simple low cost hydrothermal technique. We show that this Fe2TiO5 works well as a photoanode for the photoelectrochemical splitting of water due to favorable band energetic. Further characterization of thin films including band positions with respect to water redox levels has been investigated. We conclude that Fe2TiO5 is a promising material comparable to hematite for constructing PEC cells. PMID:25474220

  6. One way of surface alloying treatment on iron surface based on surface mechanical attrition treatment and heat treatment

    International Nuclear Information System (INIS)

    A method of surface alloying treatment has been developed: Ni powders were welded into the surface of iron plates by Surface Mechanical Attrition Treatment (SMAT), followed by annealing at certain temperature for 30 min. A Ni-Fe alloy layer with thickness about 100 μm in the sample surface was fabricated on pure iron plate. Scanning electron microscope (SEM), glow discharge spectrum (GDS), and X-ray diffraction (XRD) methods were used to analyze the microstructure, the composition and the phases of the alloy layer. Studies on the interface microstructure indicated that there was significant atomic diffusion and formation of multilayer of intermetallic compound and solid solution in SMAT process. Subsequent annealing accelerates the alloying process. The corrosion test shows the sample by SMAT treated with Ni powders exhibit the best corrosion resistance.

  7. Surface mechanical attrition treatment of tungsten and its behavior under low energy deuterium plasma implantation relevant to ITER divertor conditions

    International Nuclear Information System (INIS)

    In the light of a foreseen application for tungsten (W) as an ITER divertor material samples have been plastically deformed by a surface mechanical attrition treatment (SMAT) and by cold rolling. The resistance to blister formation by low energy deuterium implantation in these samples has been examined, with the result that the structure is significantly improved as the structural scale is reduced to the nanometer range in the SMAT sample. The distribution of blisters in this sample is however bimodal, due to the formation of several very large blisters, which are heterogeneously distributed. The observations suggest that process optimization must be a next step in the development with a view to the application of plastically deformed W in a fusion reactor. (Author)

  8. Surface mechanical attrition treatment of tungsten and its behavior under low energy deuterium plasma implantation relevant to ITER divertor conditions

    Energy Technology Data Exchange (ETDEWEB)

    Xu, H.Y.; Yuan, Y.; Fu, B.Q.; Godfrey, A.; Liu, W. [Tsinghua Univ.. Lab. of Advanced Materials, Beijing (China); Zhang, Y.B. [Technical Univ. og Denmark. DTU Risoe Campus, Roskilde (Denmark); Tao, N.R. [Chinese Academy of Sciences, Shenyang (China)

    2012-11-01

    In the light of a foreseen application for tungsten (W) as an ITER divertor material samples have been plastically deformed by a surface mechanical attrition treatment (SMAT) and by cold rolling. The resistance to blister formation by low energy deuterium implantation in these samples has been examined, with the result that the structure is significantly improved as the structural scale is reduced to the nanometer range in the SMAT sample. The distribution of blisters in this sample is however bimodal, due to the formation of several very large blisters, which are heterogeneously distributed. The observations suggest that process optimization must be a next step in the development with a view to the application of plastically deformed W in a fusion reactor. (Author)

  9. A first-term attrition severity index for U.S. Navy ratings.

    OpenAIRE

    Griffin, Patricia

    1981-01-01

    Approved for public release; distribution in unlimited. The purpose of this thesis was the development of a first-term attrition severity index for 85 United States Navy enlisted ratings. The multiattribute model utilized in the development of the index was constructed using five rating-specific factors: 1) attrition, 2) replacement cost, 3) size (number of personnel in the rating), 4) shortage or excess of billet requirements, and 5) priority. The model provided first-te...

  10. Trends in attrition among medical teaching staff at universities in Myanmar 2009–2013

    OpenAIRE

    Nang Mie Mie Htun,; REYER, JOSHUA A; Yamamoto, Eiko; Yoshida, Yoshitoku; Hamajima, Nobuyuki

    2016-01-01

    ABSTRACT Although lack of human resources for health is becoming a global problem, there are few studies on human resources in Myanmar. This study was conducted to investigate the attrition rates of teaching staff from universities for medical professions in Myanmar from 2009 to 2013. The data were collected from administrative records from Department of Medical Sciences, Ministry of Health, Myanmar. Numbers of staff and those who permanently left work (attrition) from 2009 to 2013 were count...

  11. Attrition in rape cases: Developing a profile and identifying relevant factors

    OpenAIRE

    Lea, Susan J.; Lanvers, Ursula; Shaw, Steve

    2003-01-01

    This study sought to develop a profile of rape cases within a Constabulary in the South West of England, and identity factors associated with attrition. All cases of rape or attempted rape of a female or male over the age of 16 from 1996 to 2000 were identified. Quantitative and qualitative data on 379 cases was collected using the CIS and questionnaires sent to the relevant Chief Investigating Officer. The profile of attrition differed in several respects from previous research. Analysis of ...

  12. Bounding the Effects of Social Experiments: Accounting for Attrition in Administrative Data

    OpenAIRE

    Jeffrey Grogger

    2013-01-01

    Social experiments frequently exploit data from administrative records. However, most administrative data systems are state-specific, designed to track earnings or benefit payments among residents within a single state. Once an experimental participant moves out of state, his earnings and benefits in his state of origin consist entirely of zeros, giving rise to a form of attrition. In the presence of such attrition, the average treatment effect of the experiment is no longer point-identified,...

  13. A Study of the Causes of Attrition Among Adult on a Fully Online Training Course

    OpenAIRE

    Michael McMahon

    2013-01-01

    An online course was piloted in an Institute of Technology in Ireland for the purpose of providing training in best practice in presenting to people with dyslexia. The course was delivered fully online with no required attendances and with no interaction between participants. None of the participants in the pilot of the course completed the course. This study applies a model developed by Chyung to focus on the possible causes of the attrition and examine means by which attrition can be amelio...

  14. Study on mechanical properties of warm compacted iron-base materials

    Institute of Scientific and Technical Information of China (English)

    李元元; 倪东惠; 肖志瑜; 张大童; 陈维平

    2002-01-01

    Mechanical properties of the warm compacted iron-base powder metallurgy materials were compared with those of conventional cold compacted materials. Factors such as compaction temperature, lubricant concentration and lubricant′s property were studied. A lubricant for warm compaction powder metallurgy was developed. An iron-based powder metallurgy material with a green density of 7.31 g/cm3 (a relative density of 92.5%) can be obtained by pressing the powder at 700 MPa and 175 ℃. The sintered materials have a density of 7.2 g/cm3, an elongation of 2.1% and a tensile strength of 751 MPa compared to 546 MPa using conventional cold compaction with the same lubricant and 655 MPa using warm compaction with other lubricant. Compact density and mechanical properties were influenced strongly by the compacting temperature. Although the best quality compacts can be obtained at 175 ℃, warm compaction within 165 to 185 ℃ can give high density compacts. Evidence shows that compact density depends on the friction coefficient of the lubricant.

  15. Recycling of a spent iron based catalyst for the complete oxidation of toluene: effect of palladium.

    Science.gov (United States)

    Kim, Sang Chai; Nah, Jae Woon

    2015-01-01

    Complete oxidation of volatile organic compound (toluene) was carried out to assess the property and activity of the palladium-spent iron based catalyst. The properties of the prepared catalysts were characterized by using the Brunauer-Emmett-Teller method and by conducting temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy and field emission transmission electron microscopy. The addition of palladium to the spent iron based catalyst pretreated with oxalic acid shifted the conversion curve for the total oxidation of toluene to lower temperature. An increase in the toluene conversion due to palladium was highly related to the easier lattice oxygen mobility of the catalysts. Instrumental analysis suggested the presence of a strong interaction between palladium and iron oxide species. Moreover, in the case of reducing the Pd/Fe catalyst with hydrogen, palladium accelerated the reducing iron oxides, subsequently decreasing the toluene conversion. As a result, the oxidation states of palladium and iron had an important effect on the catalytic activity. PMID:25413115

  16. On the internal d-wave structure of s+/- pairs in Iron-based Superconductors

    Science.gov (United States)

    Ong, Tze Tzen; Coleman, Piers

    2014-03-01

    A key issue in understanding the high temperature iron-based superconductors concerns the mechanism by which the paired electrons minimize their strong mutual Coulomb repulsion. Whereas electronically paired superconductors generally avoid the Coulomb interaction through the formation of higher angular momentum pairs, iron based superconductors involve s-wave (s+/-) pairs with zero angular momentum. By taking account of the orbital degrees of freedom of the iron atoms, here we show that the s+/- pairs in these materials possess hidden d-wave symmetry, forming orbital triplets in which the the d-wave angular momentum of the pairs is compensated by the internal angular momentum of the orbitals. The recent observation of a gap with octahedral structure in KFe2As2 materials can be understood as a transition to a ``high spin'' configuration of the d-wave orbital triplets, through the alignment of the two angular momentum components of the pair. We acknowledge funding from DOE grant DE-FG02-99ER45790.

  17. Iron-based soft magnetic composites with Mn–Zn ferrite nanoparticles coating obtained by sol–gel method

    International Nuclear Information System (INIS)

    This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn–Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20 nm, were obtained via the sol–gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn–Zn ferrites. Mn–Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn–Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10 kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn–Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400 °C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability. - Highlights: ► Uniformly coated Mn–Zn ferrite powder increased the operating frequency of SMCs. ► Compared with epoxy coated, the permeability of SMCs increased by 33.5% at 10 kHz. ► 400 °C is the optimum annealing temperature to attain the desired permeability.

  18. Rethinking race and attrition in nursing programs: a hermeneutic inquiry.

    Science.gov (United States)

    Jordan, J D

    1996-01-01

    This hermeneutic study examined the lived experience of four self-identified African-American students enrolled in predominantly white baccalaureate nursing programs. An understanding of the following concerns was sought: (1) Does being black matter in an educational program that is predominantly white? (2) Does being black in a predominantly white nursing program hinder a student's ability or desire to continue toward his or her educational goal? These concerns were guided by the major research question: What is the meaning of being black in a predominantly white nursing program? Critical hermeneutic inquiry, as explicated by Jurgen Habermas, was used as the philosophical framework. Audiotaped interviews were transcribed and subsequently analyzed by a team of researchers. Three constitutive patterns emerged from the analysis of the texts: Being Different/Being the Same, Student As Teacher: Toward a Surrogate Pedagogy, and Resoluteness: I'll See You at Graduation. Findings suggest that empirical research concerning the attrition of blacks from predominantly white nursing programs must include a description of what it means to be black or different in these settings. PMID:8979642

  19. Determinants of Attrition to Follow-Up in a Multicentre Cohort Study in Children-Results from the IDEFICS Study

    OpenAIRE

    Sabrina Hense; Hermann Pohlabeln; Nathalie Michels; Staffan Mårild; Lauren Lissner; Eva Kovacs; Luis A. Moreno; Charalampos Hadjigeorgiou; Toomas Veidebaum; Licia Iacovello; Yannis Pitsiladis; Lucia Reisch; Alfonso Siani; Wolfgang Ahrens

    2013-01-01

    Cohort participant retention is a crucial element and may depend on several factors. Based on data from a multicentre cohort of European children, the effect of baseline participation on attrition and the association with and the impact of single determinants in relation to the extent of attrition were investigated. Data was available for 16,225 children from the IDEFICS baseline survey (2007/2008). Attrition was defined as nonparticipation in the first follow-up examination (2009/2010). Dete...

  20. Where Have All the Rodents Gone? The Effects of Attrition in Experimental Research on Cancer and Stroke.

    Directory of Open Access Journals (Sweden)

    Constance Holman

    2016-01-01

    Full Text Available Given small sample sizes, loss of animals in preclinical experiments can dramatically alter results. However, effects of attrition on distortion of results are unknown. We used a simulation study to analyze the effects of random and biased attrition. As expected, random loss of samples decreased statistical power, but biased removal, including that of outliers, dramatically increased probability of false positive results. Next, we performed a meta-analysis of animal reporting and attrition in stroke and cancer. Most papers did not adequately report attrition, and extrapolating from the results of the simulation data, we suggest that their effect sizes were likely overestimated.

  1. The Analysis of the Impact of Panel Attrition on Estimation of Regular-Irregular Worker Wage Gap in the KLIPS

    OpenAIRE

    Daehyun Kim

    2010-01-01

    The aim of this paper is analyzing the effect of panel attrition on estimation of regular-irregular worker wage gap using KLIPS (Korean Labor and Income Panel Study). Using two wave sub-panels of KLIPS, we first analyze the characteristics of attritions. We find that the nonrandom attrition has occurred and it causes the underestimation of regular-irregular worker wage gap. Second, we decompose the attrition bias into ‘ability bias’ and ‘distortion bias’. And third we develop the estimation s...

  2. Study of structural physics on new ordered phase found in the hydrogen-substituted iron-based superconductor

    International Nuclear Information System (INIS)

    Iron-based superconductors discovered in 2008 are new family of superconducting following copper oxide. Recently, a new ordered phase has revealed in the first reported iron-based super-conducting material LaFeAsO. In this paper, we show the electronic and magnetic phase diagram that has been significantly updated with the progress of the crystal synthesis. We also introduce the average and the local structure of the new ordered phase measured by x-ray diffractions and absorption spectra using synchrotron radiation. We consider that the advanced ordered phase has the potential to be a key for develop of the superconducting transition temperature in the iron-based superconductors. (author)

  3. Role of samarium additions on the shape memory behavior of iron based alloys

    International Nuclear Information System (INIS)

    Research highlights: → The effect of samarium contents on shape memory behavior has been studied. → Addition of samarium increases the strength, c/a ratio and ε (hcp martensite). → Addition of samarium retards the nucleation of α (bcc martensite). → Improvement in shape memory effect with the increase in samarium contents. - Abstract: The effect of samarium contents on shape memory behavior of iron based shape memory alloys has been studied. It is found that the strength of the alloys increases with the increase in samarium contents. This effect can be attributed to the solid solution strengthening of austenite by samarium addition. It is also noticed that the shape memory effect increases with the increase in samarium contents. This improvement in shape memory effect presumably can be regarded as the effect of improvement in strength, increase in c/a ratio and obstruction of nucleation of α in the microstructure.

  4. Glass forming ability of iron based amorphous alloys depending on Mo, Cr and Co content

    International Nuclear Information System (INIS)

    The Fe41Co7Cr15Mo14C15B6Y2 multicomponent Fe-based alloy is known to be one of the best glass formers in iron-based systems and shows a critical casting thickness of 16 mm. The elements constituting the alloy have different influences on the glass forming ability. Therefore, the content of Mo, Cr and Co was systematically changed in the master alloy Fe77-x(Co,Cr,Mo)xC15B6Y2 to investigate how these three elements support the glassy microstructure. It was found that a certain content of Mo, Cr, and Co leads to a microstructure of amorphous matrix and α-Fe precipitates without any carbides.

  5. Embrittlement of nickel-, cobalt-, and iron-base superalloys by exposure to hydrogen

    Science.gov (United States)

    Gray, H. R.

    1975-01-01

    Five nickel-base alloys (Inconel 718, Udimet 700, Rene 41, Hastelloy X, and TD-NiCr), one cobalt-base alloy (L-605), and an iron-base alloy (A-286) were exposed in hydrogen at 0.1 MN/sq m (15 psi) at several temperatures in the range from 430 to 980 C for as long as 1000 hours. These alloys were embrittled to varying degrees by such exposures in hydrogen. Embrittlement was found to be: (1) sensitive to strain rate, (2) reversible, (3) caused by large concentrations of absorbed hydrogen, and (4) not associated with any detectable microstructural changes in the alloys. These observations are consistent with a mechanism of internal reversible hydrogen embrittlement.

  6. Effect of sintering parameters on warm compacted iron-based material

    Institute of Scientific and Technical Information of China (English)

    李元元; 肖志瑜; 倪东惠; 夏伟; 陈维平

    2003-01-01

    Iron-based powder metallurgy material was prepared by warm compaction at 125℃ using a compacting pressure of 700 Mpa.Sintering temperature ranging from 1100℃ to 1300℃ and sintering time ranging from 40min to 80 min were used to study the effects of sintering parameters on the compacts.Die wall lubrication polytetrafluoroethylene(PTFE)emulsion was also applied in combination with warm compaction in hope to increase the compact density and the mechanical properties of the sintered material.Green and sintered density,spring back effect and sinter shrinkage were measured.Mechanical properties of both as-sinter and heat treated samples were also measured.Results show that mechanical properties of the sintered compacts increase with the increase of sintering temperature and sintering time.Sample prepared by die wall lubricated warm compaction always shows higher density and mechanical properties.

  7. Mechanical Testing of Iron based Bulk Metallic Glasses and Their Suitability for Force Sensors

    Directory of Open Access Journals (Sweden)

    Erenc-Sędziak T.

    2013-01-01

    Full Text Available Thermal, mechanical and magnetic properties of (Fe-Co-(Zr/Si-Nb-B alloys in the form of rapidly quenched rods of 1.2 mm in diameter were studied. The as-cast alloys with Zr were crystalline, and the alloys with Si were amorphous. Microhardness measured at 50 g load is from 500 to 2000 HV (the less cobalt, the higher, and the compressive strength reaches nearly 4000 MPa for Si doped alloys and 2000 MPa for Zr doped ones. This substantial difference may be attributed to partial crystallinity of the latter alloys. The magnetic hysteresis loops of fully amorphous rods measured under compression, exhibited a clear dependence of permeability vs. stress, proving that iron-based bulk metallic glasses may be promising materials for magnetoelastic force sensors.

  8. Stabilized nanocrystalline iron-based alloys: Guiding efforts in alloy selection

    International Nuclear Information System (INIS)

    Highlights: → A regular solution model for solute segregation is capable of estimating the effect of solutes on the stability of nanocrystalline Fe. → Stability increases for solutes having larger heats of segregation. → Zr and Ta had an effect on stabilizing the nanocrystalline microstructure of Fe, while Cr and Ni did not. - Abstract: Using a modified regular solution model for grain boundary solute segregation, the relative thermal stability of a number of Fe-based nanocrystalline binary alloys was predicted with considerable accuracy. It was found that nanocrystalline iron was strongly stabilized by zirconium, moderately stabilized by tantalum, and not significantly stabilized by nickel or chromium. These findings are fully in line with the aforementioned predictions. This success with iron based alloys highlights the utility of this practical approach to selecting stabilizing solutes for nanocrystalline alloys.

  9. Development of iron-based nanoparticles for Cr(VI removal from drinking water

    Directory of Open Access Journals (Sweden)

    Vourlias G.

    2013-01-01

    Full Text Available A great deal of research over recent decades has been motivated by the requirement to lower the concentration of chromium in drinking water. This study has been conducted to determine the feasibility of iron-based nanoparticles for chromium removal from contaminated water. Single Fe, Fe3O4 and binary Fe/Fe3O4 nanoparticles were grown at the 45-80 nm size range using the solar physical vapor deposition technique and tested as potential hexavalent chromium removing agents from aqueous solutions. Due to their higher electron donation ability compared to the Fe3O4 ones, single Fe nanoparticles exhibited the highest Cr(VI removal capacity of more than 3 µg/mg while maintaining a residual concentration 50 µg/L, equal to the regulation limit for drinking water. In combination to their facile and fast magnetic separation, the applicability of the studied particles in water treatment facilities should be considered.

  10. Thermodynamic Feasibility of Hydrogen-Rich Gas Production Supported by Iron Based Chemical Looping Process

    Directory of Open Access Journals (Sweden)

    Grzegorz Słowiński

    2016-01-01

    Full Text Available The continuously increasing oil prices as well as stronger environmental regulations regarding greenhouse emissions made the greatest economic powers search a new, price competitive, and environment friendly energy carrier, such as hydrogen. The world research activities in these terms focus on the development of integrated hydrogen and power generating technologies, particularly technologies of hydrogen production from various carbonaceous resources, like methane, coal, biomass, or waste, often combined with carbon dioxide capture. In the paper the thermodynamic analysis of the enhancement of hydrogen production in iron based chemical looping process is presented. In this method, iron oxide is first reduced to iron with a reducing agent, such as carbon oxide, hydrogen, or mixture of both gases (synthesis gas, and then, in the inverse reaction with steam, it is regenerated to iron oxide, and pure stream of hydrogen is produced.

  11. Thermomechanical treatment and deformation behavior of iron based shape memory alloys

    International Nuclear Information System (INIS)

    The thermomechanical treatment (training) and deformation behavior of iron based shape memory alloys have been studied. The thermomechanical treatment results in improvement of shape memory effect. This improvement in shape memory effect can be attributed to the formation of lamellar structure of (lambda)/(epsilon) and to an increase in the volume fraction of epsilon martensite (epsilon). It is also found that excessive training may result in the nucleation of bcc martensite (alpha) along with epsilon martensite (epsilon) which degrades the shape memory effect. Also the shape memory effect decreases with the increase in amount of strain, which presumably can be regarded as the effect of increasing tendency of deformation to occur through slip and formation of (alpha) which reduces the reversibility of (epsilon) into (lambda). (author)

  12. Synthesis of iron-based nanoparticles using oolong tea extract for the degradation of malachite green

    Science.gov (United States)

    Huang, Lanlan; Weng, Xiulan; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2014-01-01

    Iron-based nanoparticles (OT-FeNP) were synthesized using oolong tea extracts. Their morphology, structure and size were confirmed by scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV-visible (UV-vis) and Fourier Transform Infrared spectroscopy (FTIR). Formation of FeNP results in mostly spherical particles with diameters ranging from 40 to 50 nm. Degradation of malachite green (MG) using OT-FeNP demonstrated that kinetics fitted well to the pseudo first-order reaction by removing 75.5% of MG (50 mg/L). This indicated that OT-FeNP has the potential to serve as a green nanomaterial for environmental remediation.

  13. Influence of physicochemical treatments on iron-based spent catalyst for catalytic oxidation of toluene.

    Science.gov (United States)

    Kim, Sang Chai; Shim, Wang Geun

    2008-06-15

    The catalytic oxidation of toluene was studied over an iron-based spent and regenerated catalysts. Air, hydrogen, or four different acid solutions (oxalic acid (C2H2O4), citric acid (C6H8O7), acetic acid (CH3COOH), and nitric acid (HNO3)) were employed to regenerate the spent catalyst. The properties of pretreated spent catalyst were characterized by the Brunauer Emmett Teller (BET), inductively coupled plasma (ICP), temperature programmed reduction (TPR), and X-ray diffraction (XRD) analyses. The air pretreatment significantly enhanced the catalytic activity of the spent catalyst in the pretreatment temperature range of 200-400 degrees C, but its catalytic activity diminished at the pretreatment temperature of 600 degrees C. The catalytic activity sequence with respect to the air pretreatment temperatures was 400 degrees C>200 degrees C>parent>600 degrees C. The TPR results indicated that the catalytic activity was correlated with both the oxygen mobility and the amount of available oxygen on the catalyst. In contrast, the hydrogen pretreatment had a negative effect on the catalytic activity, and toluene conversion decreased with increasing pretreatment temperatures (200-600 degrees C). The XRD and TPR results confirmed the formation of metallic iron which had a negative effect on the catalytic activity with increasing pretreatment temperature. The acid pretreatment improved the catalytic activity of the spent catalyst. The catalytic activity sequence with respect to different acids pretreatment was found to be oxalic acid>citric acid>acetic acid>or=nitric acid>parent. The TPR results of acid pretreated samples showed an increased amount of available oxygen which gave a positive effect on the catalytic activity. Accordingly, air or acid pretreatments were more promising methods of regenerating the iron-based spent catalyst. In particular, the oxalic acid pretreatment was found to be most effective in the formation of FeC2O4 species which contributed highly to the

  14. Influence of physicochemical treatments on iron-based spent catalyst for catalytic oxidation of toluene

    International Nuclear Information System (INIS)

    The catalytic oxidation of toluene was studied over an iron-based spent and regenerated catalysts. Air, hydrogen, or four different acid solutions (oxalic acid (C2H2O4), citric acid (C6H8O7), acetic acid (CH3COOH), and nitric acid (HNO3)) were employed to regenerate the spent catalyst. The properties of pretreated spent catalyst were characterized by the Brunauer Emmett Teller (BET), inductively coupled plasma (ICP), temperature programmed reduction (TPR), and X-ray diffraction (XRD) analyses. The air pretreatment significantly enhanced the catalytic activity of the spent catalyst in the pretreatment temperature range of 200-400 deg. C, but its catalytic activity diminished at the pretreatment temperature of 600 deg. C. The catalytic activity sequence with respect to the air pretreatment temperatures was 400 deg. C > 200 deg. C > parent > 600 deg. C. The TPR results indicated that the catalytic activity was correlated with both the oxygen mobility and the amount of available oxygen on the catalyst. In contrast, the hydrogen pretreatment had a negative effect on the catalytic activity, and toluene conversion decreased with increasing pretreatment temperatures (200-600 deg. C). The XRD and TPR results confirmed the formation of metallic iron which had a negative effect on the catalytic activity with increasing pretreatment temperature. The acid pretreatment improved the catalytic activity of the spent catalyst. The catalytic activity sequence with respect to different acids pretreatment was found to be oxalic acid > citric acid > acetic acid ≥ nitric acid > parent. The TPR results of acid pretreated samples showed an increased amount of available oxygen which gave a positive effect on the catalytic activity. Accordingly, air or acid pretreatments were more promising methods of regenerating the iron-based spent catalyst. In particular, the oxalic acid pretreatment was found to be most effective in the formation of FeC2O4 species which contributed highly to the

  15. Hydrolysis behavior of zirconium diboride during attrition milling

    International Nuclear Information System (INIS)

    Highlights: ► The surface was mainly covered of Zr–O, B–O and B–OH bonds after hydrolysis. ► ZrB2 powder tended to behave like a B2O3-modified surface by milling treatment. ► The surface B/Zr atomic ratio decreased from water to ethanol medium. ► The nano-sized oxide layer (∼5 nm) was observed and helped to improve the dispersion of ZrB2 particles in dilute aqueous media. - Abstract: The hydrolysis behavior of ZrB2 powder during attrition milling was studied in de-ionized water and ethanol. Surface characterization, thermal analysis, chemical analysis and electron microscopy were utilized to analyze the surface properties of as-milled powders. The results proved that the surface of ZrB2 powder was mainly composed of Zr–O, B–O and B–OH bonds as hydrolysis proceeded, and the amount of surface B–O bond was found to increase rapidly in water, suggesting a more B2O3-like surface behavior were developed. Results also showed when milled at 300 rpm for 4 h in water, 64.45 at% of B was in the form of B2O3 at a thickness of ∼3 nm from the surface. The nano-sized surface Zr–B–O oxide layer (∼5 nm in thickness) could help to improve the dispersion of powder in aqueous media.

  16. Magnetic order close to superconductivity in the iron-based layered LaO1-xFxFeAs systems.

    Science.gov (United States)

    de la Cruz, Clarina; Huang, Q; Lynn, J W; Li, Jiying; Ratcliff, W; Zarestky, J L; Mook, H A; Chen, G F; Luo, J L; Wang, N L; Dai, Pengcheng

    2008-06-12

    Following the discovery of long-range antiferromagnetic order in the parent compounds of high-transition-temperature (high-T(c)) copper oxides, there have been efforts to understand the role of magnetism in the superconductivity that occurs when mobile 'electrons' or 'holes' are doped into the antiferromagnetic parent compounds. Superconductivity in the newly discovered rare-earth iron-based oxide systems ROFeAs (R, rare-earth metal) also arises from either electron or hole doping of their non-superconducting parent compounds. The parent material LaOFeAs is metallic but shows anomalies near 150 K in both resistivity and d.c. magnetic susceptibility. Although optical conductivity and theoretical calculations suggest that LaOFeAs exhibits a spin-density-wave (SDW) instability that is suppressed by doping with electrons to induce superconductivity, there has been no direct evidence of SDW order. Here we report neutron-scattering experiments that demonstrate that LaOFeAs undergoes an abrupt structural distortion below 155 K, changing the symmetry from tetragonal (space group P4/nmm) to monoclinic (space group P112/n) at low temperatures, and then, at approximately 137 K, develops long-range SDW-type antiferromagnetic order with a small moment but simple magnetic structure. Doping the system with fluorine suppresses both the magnetic order and the structural distortion in favour of superconductivity. Therefore, like high-T(c) copper oxides, the superconducting regime in these iron-based materials occurs in close proximity to a long-range-ordered antiferromagnetic ground state. PMID:18509333

  17. Enhanced boronizing kinetics of alloy steel assisted by surface mechanical attrition treatment

    International Nuclear Information System (INIS)

    Highlights: • Nanostructured surface layer is fabricated on H13 steel assisted by SMAT. • The boronizing kinetics of SMAT sample can be enhanced remarkably. • Borided layer can delay fatigue cracks initiation and impede their propagation. -- Abstract: A nanostructured surface layer was fabricated on AISI H13 steel by means of surface mechanical attrition treatment (SMAT). Boronizing behaviors of the SMAT samples were systematically investigated in comparison with their coarse-grained counterparts. The boron diffusion depth of the SMAT sample with pack boriding treatment at 600 °C for 2 h was about 8 μm, which was much deeper than that of the coarse-grained sample. A much thicker borided layer on the SMAT sample can be synthesized by a duplex boronizing treatment at 600 °C followed by at a higher temperature. The borided layer was composed with monophase of Fe2B and the growth of it exhibited a (0 0 2) preferred orientation. Moreover, the activation energy of boron diffusion for the SMAT sample is 140.3 kJ/mol, which is much lower than 209.4 kJ/mol for the coarse-grained counterpart. The results indicate that the boronizing kinetics can be significantly enhanced in the SMAT sample with a duplex boronizing treatment. Furthermore, the thermal fatigue tests show that the borided layer with excellent oxidation resistance and mechanical strength at elevated temperatures could effectively delay the thermal fatigue cracks initiation and impede their propagation. Therefore, the thermal fatigue property of H13 steel with a duplex boronizing treatment can be improved remarkably

  18. PREFACE: Celebrating 100 years of superconductivity: special issue on the iron-based superconductors Celebrating 100 years of superconductivity: special issue on the iron-based superconductors

    Science.gov (United States)

    Crabtree, George; Greene, Laura; Johnson, Peter

    2011-12-01

    In honor of this year's 100th anniversary of the discovery of superconductivity, this special issue of Reports on Progress in Physics is a dedicated issue to the 'iron-based superconductors'—a new class of high-temperature superconductors that were discovered in 2008. This is the first time the journal has generated a 'theme issue', and we provide this to the community to provide a 'snapshot' of the present status, both for researchers working in this fast-paced field, and for the general physics community. Reports on Progress in Physics publishes three classes of articles—comprehensive full Review Articles, Key Issues Reviews and, most recently, Reports on Progress articles that recount the current status of a rapidly evolving field, befitting of the articles in this special issue. It has been an exciting year for superconductivity—there have been numerous celebrations for this centenary recounting the fascinating history of this field, from seven Nobel prizes to life-saving discoveries that brought us medically useful magnetic resonance imaging. The discovery of a completely new class of high-temperature superconductors, whose mechanism remains as elusive as the cuprates discovered in 1986, has injected a new vitality into this field, and this year those new to the field were provided with the opportunity of interacting with those who have enjoyed a long history in superconductivity. Furthermore, as high-density current carriers with little or no power loss, high-temperature superconductors offer unique solutions to fundamental grid challenges of the 21st century and hold great promise in addressing our global energy challenges. The complexity and promise of these materials has caused our community to more freely share our ideas and results than ever before, and it is gratifying to see how we have grown into an enthusiastic global network to advance the field. This invited collection is true to this agenda and we are delighted to have received contributions

  19. A Comparative Study of Administrator and Special Education Teacher Perceptions of Special Education Teacher Attrition and Retention

    Science.gov (United States)

    Sheldrake, Danielle Angelina

    2013-01-01

    This mixed methods study identifies perceived causes of and solutions to the attrition of special education teachers. Researchers have documented that special education teaching positions encounter higher attrition rates than their general education peers (Katsiyannis, Zhang, & Conroy in Olivarez & Arnold, 2006; Mitchell & Arnold,…

  20. Derivation and Evaluation of a Risk-Scoring Tool to Predict Participant Attrition in a Lifestyle Intervention Project.

    Science.gov (United States)

    Jiang, Luohua; Yang, Jing; Huang, Haixiao; Johnson, Ann; Dill, Edward J; Beals, Janette; Manson, Spero M; Roubideaux, Yvette

    2016-05-01

    Participant attrition in clinical trials and community-based interventions is a serious, common, and costly problem. In order to develop a simple predictive scoring system that can quantify the risk of participant attrition in a lifestyle intervention project, we analyzed data from the Special Diabetes Program for Indians Diabetes Prevention Program (SDPI-DP), an evidence-based lifestyle intervention to prevent diabetes in 36 American Indian and Alaska Native communities. SDPI-DP participants were randomly divided into a derivation cohort (n = 1600) and a validation cohort (n = 801). Logistic regressions were used to develop a scoring system from the derivation cohort. The discriminatory power and calibration properties of the system were assessed using the validation cohort. Seven independent factors predicted program attrition: gender, age, household income, comorbidity, chronic pain, site's user population size, and average age of site staff. Six factors predicted long-term attrition: gender, age, marital status, chronic pain, site's user population size, and average age of site staff. Each model exhibited moderate to fair discriminatory power (C statistic in the validation set: 0.70 for program attrition, and 0.66 for long-term attrition) and excellent calibration. The resulting scoring system offers a low-technology approach to identify participants at elevated risk for attrition in future similar behavioral modification intervention projects, which may inform appropriate allocation of retention resources. This approach also serves as a model for other efforts to prevent participant attrition. PMID:26768431

  1. Attrition Rates and the Reasons for Leaving of Special Education Personnel in Kansas: 1991-92 to 1992-93.

    Science.gov (United States)

    McKnab, Paul

    This report addresses attrition of special education personnel in Kansas for those employed in the 1991-92 year who did not return for the 1992-93 year and compares these data with that of previous years. Definitions of "leavers,""movers," and "stayers" are provided. The first part of the report presents tables showing the attrition data for…

  2. Biases in Estimating Treatment Effects Due to Attrition in Randomized Controlled Trials and Cluster Randomized Controlled Trials: A Simulation Study

    Science.gov (United States)

    Dong, Nianbo; Lipsey, Mark W.

    2011-01-01

    Attrition occurs when study participants who were assigned to the treatment and control conditions do not provide outcome data and thus do not contribute to the estimation of the treatment effects. It is very common in experimental studies in education as illustrated, for instance, in a meta-analysis studying "the effects of attrition on baseline…

  3. Predictors of Attrition and Academic Success of Medical Students: A 30-Year Retrospective Study

    OpenAIRE

    Maslov Kruzicevic, Silvija; Barisic, Katarina Josipa; Banozic, Adriana; Esteban, Carlos David; Sapunar, Damir; Puljak, Livia

    2012-01-01

    Aim To determine attrition and predictors of academic success among medical students at University of Split, Croatia. Methods We analysed academic records of 2054 students enrolled during 1979–2008 period. Results We found that 26% (533/2054) of enrolled students did not graduate. The most common reasons for attrition were ‘personal’ (36.4%), transfer to another medical school (35.6%), and dismissal due to unsatisfactory academic record (21.2%). Grade point average (GPA) and study duration of...

  4. Where Are They Now? A Case Study of Health-related Web Site Attrition

    OpenAIRE

    Veronin, Michael A

    2002-01-01

    Background. When considering health-related Web sites, issues of quality generally focus on Web content. Little concern has been given to attrition of Web sites or the "fleeting" nature of health information on the World Wide Web. Since Web sites may be available for an uncertain period of time, a Web page may not be a sound reference. Objective. To address the issue of attrition, a defined set of health-related Web sites was examined at two separate time intervals. Methods. To determine the ...

  5. Adherence and Attrition in a Web-Based Lifestyle Intervention for People with Metabolic Syndrome.

    Directory of Open Access Journals (Sweden)

    Leila Jahangiry

    2014-09-01

    Full Text Available The aim of this study was to determine adherence and attrition rates in a lifestyle intervention for people with metabolic syndrome.Adherence and attrition data from a randomized controlled trial were collected. Participants were classified as adherence group if they completed assessments at 3 and 6 months follow-up and as attrition group if they did not. Physical activity and quality of life was measured using the International Physical Activity Questionnaire (IPAQ and the Short Form Health Survey (SF-36. Generalized Estimating Equations (GEE was used to explore predictors of attrition.The mean age of participants (n=160 was 44.1 years. Attrition rate in the intervention and control groups at first follow-up were the same (20%. However, the control group had significantly higher attrition rate (%33.7 compared to the intervention group (%20 at 6 months follow up. Results showed that low educated participants were more likely to not stay in the study than better educated participants (OR=2.95,CI:1.39-6.33,P=0.05. According with length of the study, attrition was decreased at six month (OR=0.66,CI:0.52-0.83,P<0.001. Also, some aspects of health-related quality of life contributed to the attrition rate. Those who had higher scores on general health (OR=0.66,CI:0.54-0.97,P=0.023, social functioning (OR=0.44,CI:0.40-0.76,P=0.032, role emotional (OR=0.74,CI:0.54-0.98,P=0.18, vitality (OR=0.55,CI:0.38-0.90,P=0.015 and mental health (OR=0.63,CI:0.45-0.85,P=0.033 were more likely to stay in the study.It remains a concern that Web-based lifestyle programs may fail to reach those who need it most. Participant in the study generally had better quality of life than those who were lost to follow up.

  6. The kinetics of phase transformations of undercooled austenite of the Mn-Ni iron based model alloy

    Directory of Open Access Journals (Sweden)

    E. Rożniata

    2011-12-01

    Full Text Available Purpose: Present work corresponds to the research on the kinetics of phase transformations of undercooled austenite of Mn-Ni iron based model alloy. The kinetics of phase transformations of undercooled austenite of investigated alloy was presented on CCT diagram (continuous cooling transformation. Also the methodology of a dilatometric samples preparation and the method of the critical points determination were described.Design/methodology/approach: The austenitising temperature was defined in a standard way i.e. 30-50°C higher than Ac3 temperature for model alloy. A technique of full annealing was proposed for the model alloy. The CCT diagrams were made on the basis of dilatograms recorded for samples cooled at various rates. The microstructure of each dilatometric sample was photographed after its cooling to the room temperature and the hardness of the samples was measured.Findings: The test material was a Mn-Ni hypoeutectoid iron based alloy. The microstructure of test Mn-Ni alloy on CCT diagram changes depending on the cooling rate. At the cooling rates of 10°C/s and 5°C/s there is ferrite in Widmannstätten structure present in the structure of tested alloy.Research limitations/implications: The new Mn-Ni iron based model alloy and a new CCT diagram.Practical implications: The paper contains a description of one from a group of iron based model alloys with 0.35-0.40% carbon content. According to PN-EN 10027 standard this steel should have a symbol 38MnNi6-4.Originality/value: The new Mn-Ni iron based model alloy.

  7. Attrition in the Austrian Generations and Gender Survey: Is there a bias by fertility-relevant aspects?

    Directory of Open Access Journals (Sweden)

    Isabella Buber-Ennser

    2014-08-01

    Full Text Available Background: In longitudinal research the loss of sample members between waves is a possible source of bias. It is therefore crucial to analyse attrition. Objective: This paper analyses attrition in a longitudinal study on family and fertility, by distinguishing between attrition due to non-contact and attrition due to non-cooperation. Methods: Based on the first two waves of the Austrian Generations and Gender Survey, the two components of attrition are studied separately by using bivariate as well as multivariate methods. Moreover, overall dropout - the combination of both components - isanalysed. Apart from various socio-economic characteristics and data collection information, the study focuses on fertility-relevant variables such as fecundity, fertility intentions, sexual orientation, and traditional attitudes. Results: Fecundity, fertility intentions, and homosexual relationships are associated with higher attrition due to non-cooperation in bivariate analyses, but have no explanatory power inthe multivariate model. Pregnancy and traditional attitudes towards marriage are associated with significantly lower attrition due to non-cooperation in the multivariate context. Overall dropout is significantly lower only among persons with traditionalattitudes towards marriage, although small in size and statistical significance. Moreover, various individual and regional characteristics are significantly associated with dropout, with differences between attrition due to non-contact and attrition due to non-cooperation. Conclusions: Detailed insights into attrition are not only important when using longitudinal data and interpreting results, but also for the design of future data collections. The Austrian GGS panel has a relatively low dropout (22Š and is affected by a small bias towards familyoriented persons as well as less-educated respondents and persons with migrationbackgrounds, but the data can be used without concern about selectivity.

  8. High temperature corrosion of iron-base and nickel-base alloys for hydrogen production apparatus by thermochemical method in H2O+SO3 atmosphere

    International Nuclear Information System (INIS)

    Corrosion tests for ten iron-base and nickel-base alloys at 850degC for 1000h in H2O + SO3 atmosphere were carried out to obtain data for selection of candidate container materials in the thermochemical process which produces hydrogen from water by use of iodine and sulfur as circulating materials. The following results were obtained: (1) Oxidation, spallation of corrosion film, uniform corrosion and grain boundary penetration composed of internal oxidation and sulfuration occur in this atmosphere and the corrosion proceeds by grain boundary penetration. (2) SUS304, SUS316 and Hastelloy C276 are inferior in corrosion resistance and SUS329J4L is superior among ten alloys used in this experiment. Alloys such as Alloy 800H and Hastelloy XR show intermediate corrosion resistance. (3) Oxide films of alloys containing iron and chromium are mostly composed of outer iron-oxide and inner chromium-oxide. Sulfur concentrates at scale/metal interfaces and grain boundary penetration portions, and sulfides form. (4) Corrosion in this atmosphere could be expressed using the parabolic law between the grain boundary penetration depth and time. It is considered that causes of the apparently observed parabolic law were a high concentration of SO3 and change of the gas composition caused by catalytic action of the corrosion film formed with the progress of corrosion. (author)

  9. Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors

    Science.gov (United States)

    Leong, Zhidong; Phillips, Philip

    2016-04-01

    Recent angle-resolved photoemission spectroscopy measurements of Co-doped LiFeAs report a large and robust superconducting gap on the Γ -centered hole band that lies 8 meV below the Fermi level. We show that, unlike a conventional superconductor described by BCS theory, a multiband system with strong interband Coulomb interactions can explain these observations. We model LiFeAs with a five-band model in which the shallow hole band is coupled with the other bands by only Coulomb interactions. Using Eliashberg theory, we find reasonable interaction parameters that reproduce the Tc and all five gaps of LiFeAs. The energy independence of the Coulomb interactions then ensures the robustness of the gap induced on the shallow band. Furthermore, due to the repulsive nature of the Coulomb interactions, the gap changes sign between the shallow band and the other hole pockets, corresponding to an unconventional s± gap symmetry. Unlike other families of iron-based superconductors, the gap symmetry of LiFeAs has not been ascertained experimentally. The experimental implications of this sign-changing state are discussed.

  10. Reductive reactivity of borohydride- and dithionite-synthesized iron-based nanoparticles: A comparative study.

    Science.gov (United States)

    Ma, Xiaoming; He, Di; Jones, Adele M; Collins, Richard N; Waite, T David

    2016-02-13

    In this study sodium dithionite (NaS2O4) and sodium borohydride (NaBH4) were employed as reducing agents for the synthesis of nanosized iron-based particles. The particles formed using NaBH4 (denoted nFe(BH4)) principally contained (as expected) Fe(0) according to XAS and XRD analyses while the particles synthesized using NaS2O4, (denoted nFe(S2O4)) were dominated by the mixed Fe(II)/Fe(III) mineral magnetite (Fe3O4) though with possible presence of Fe(0). The ability of both particles to reduce trichloroethylene (TCE) under analogous conditions demonstrated remarkable differences with nFe(BH4) resulting in complete reduction of 1.5mM of TCE in 2h while nFe(S2O4) were unable to effect complete reduction of TCE in 120 h. Moreover, acetylene was the major reaction product formed in the presence of nFe(S2O4) while the major reaction product formed following reaction with nFe(BH4) was ethylene, which was further reduced to ethane as the reaction proceeded. Considering that effective Pd reduction to Pd(0) requires the presence of Fe(0), this is consistent with our finding that Fe(0) is not the dominant phase formed when employing dithionite as a reducing agent under the conditions employed in this study. PMID:26513569

  11. Unconventional superconductivity originating from disconnected Fermi surfaces in the iron-based compound

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Hideo, E-mail: aoki@phys.s.u-tokyo.ac.j [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan)

    2009-04-15

    The iron-based LaFeAsO{sub 1-x}F{sub x} recently discovered by Hosono's group is a fresh theoretical challenge as a new class of high-temperature superconductors. Here we describe the electronic structure of the material and the mechanism of superconductivity. We start with constructing a tight-binding model in terms of the maximally localised Wannier orbitals from a first-principles electronic structure calculation, which has turned out to involve all the five Fe 3d bands. This is used to calculate the spin and charge susceptibilities with the random phase approximation. The spin susceptibility has peaks around k=(pi,0),(0,pi) arising from a nesting across disconnected Fermi surface pockets. We have then plugged the susceptibilities into the linearised Eliashberg equation. For the doping concentration x=0.1, we obtain an unconventional s-wave pairing, which is roughly an extended s in that the gap changes sign between the Fermi pockets, but the gap function is actually a 5x5 matrix. Its experimental implications are also discussed.

  12. Model construction and pairing symmetry for the iron-based oxypnictides

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Hideo, E-mail: aoki@phys.s.u-tokyo.ac.j [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan)

    2009-10-15

    PC-19-INV: In order to clarify the mechanism of superconductivity in the iron-based compound recently discovered by Hosono's group, we have first constructed a tight-binding model in terms of the maximally localized Wannier orbitals from a first-principles electronic structure calculation. The model has turned out to involve all the five Fe 3d bands. This is used to calculate the spin and charge susceptibilities with the five-band random-phase approximation, which are then plugged into the linearised Eliashberg equation. For a doped system we obtain an unconventional s-wave pairing with sign-reversing gap functions. To be more precise, the gap function is a 5x5 matrix, for which the diagonal elements mainly comprise d{sub x}{sup 2}{sub -y}{sup 2} and d{sub yz},d{sub xz} orbital components. The strong dependence of the gap between different orbitals may be observed experimentally.

  13. Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions

    International Nuclear Information System (INIS)

    The results of this thesis can be divided into three major topics, which can also be seen as different approaches of solid state chemistry to reveal interesting features of known and unknown compounds and to develop alternative synthesis routes. Firstly, known compounds with related structural motifs to the superconducting iron-arsenides were investigated regarding their structural and physical properties. In case of La3Pd4Ge4 the influence of Fe doping on the properties was studied, whereas in the series ZrMAs (M=Ti,V) the physical properties have not yet been reported at all and were investigated for the first time. Secondly, an alternative synthesis route has been developed for the synthesis of superconducting LaFeAsO1-xFx. This solid state metathesis reaction distinctly increased the quality of the samples compared to conventionally prepared products. Furthermore, the reaction pathway was investigated and clarified, which helps to understand the processes during high temperature solid state metathesis reactions in general. Thirdly, this alternative synthesis route was expanded to other systems and new compounds like co-substituted LaFe1-xMnxAsO1-yFy were prepared and thoroughly investigated. This led to a complex study of the interplay of magnetism, electronic and structural conditions and the occurrence of superconducting properties. The investigation and understanding of such complex coherences will probably be decisive for the further understanding of the superconducting mechanism in iron based superconductors.

  14. Study of the new diluted magnetic semiconductors based on the doping of iron-based superconductors

    Science.gov (United States)

    Zhang, Li; Feng, Shan; Li, Linxian; Wang, Shaolei; Li, Yuke

    Diluted magnetic semiconductors(DMSs) have attracted increasing attention because of their potential applications in spintronics. Recently, a series of new bulk DMS materialswere synthesized by doping in the 122 and 1111 phases of iron-based superconductors(Fe-SC), which sheds light on the DMS research[3]. In this report, we have synthesized two systems of 1111 phases of DMSs based on Fe-SC materials (La1-xSrx) (Ag0.925 Mn0.075) SO(x =0, 0.025, 0.05, 0.075 and 0.1) and (Y1-xSrx) (Cu0.925 Mn0.075) SO (x =0, 0.025, 0.05,0.075 and 0.1) by solid state method. The structure and electrical, magnetic and optical properties have been investigated by means of XRD, 4KCCS, MPMS, PL, UV-Vis and Raman technique, respectively. Some interesting phenomena are found (Such as the Curie temperature Tc and band-gap energy Eg change regularly with the dopants additon). The results are helpful to clarify the intrinsic mechanism of the DMSs, and will provide new insights on the fabrication and application of devices based on these materials. This work was supported by the National Science Foundation of China (Grant No 61376094). Li Zhang would like to acknowledge a scholarship Granted by China Scholarship Council (CSC-201408330028)

  15. Temperature induced transformation of metastable austenite in a hypereutectic iron-based rapidly solidified powder

    Energy Technology Data Exchange (ETDEWEB)

    Grgac, Peter [Department of Materials Engineering, Slovak University of Technology in Bratislava, Bottova 24, 917 24 Trnava (Slovakia)], E-Mail: peter.grgac@stuba.sk; Kusy, Martin [Department of Materials Engineering, Slovak University of Technology in Bratislava, Bottova 24, 917 24 Trnava (Slovakia); Caplovic, Lubomir [Department of Materials Engineering, Slovak University of Technology in Bratislava, Bottova 24, 917 24 Trnava (Slovakia); Miglierini, Marcel [Department of Nuclear Physics and Technology, Slovak University of Technology in Bratislava, Ilkovicova 3, 812 19 Bratislava (Slovakia); Kanuch, Tomas [Department of Nuclear Physics and Technology, Slovak University of Technology in Bratislava, Ilkovicova 3, 812 19 Bratislava (Slovakia); Vitazek, Klement [Department of Nuclear Physics and Technology, Slovak University of Technology in Bratislava, Ilkovicova 3, 812 19 Bratislava (Slovakia)

    2007-03-25

    Rapidly solidified powder of a hypereutectic iron-based alloy with the chemical composition of 3% C-3% Cr-12% V (wt.%) was prepared by nitrogen gas atomization. Phase identification of the rapidly solidified particles in the as-atomized state was performed by X-ray analysis and Moessbauer spectrometry. The main phase constituents present in the rapidly solidified particles were found to be metastable austenite and vanadium rich carbide phases of M{sub 4}C{sub 3} type. Magnetic {alpha}-phase was identified as a minor constituent. Thermal stability of metastable austenite in the RS particles was analyzed during differential thermal analysis continuous heating experiment and by Moessbauer spectrometry and X-ray diffraction analysis after isothermal exposition at room temperature. The beginning of a fcc (austenite) {sup {yields}} bcc (ferrite) + carbide transformation was detected during continuous heating experiment at 612 deg. C as exothermic reaction. No appreciable changes in the spectral lines after isothermal treatment were observed up to 500 deg. C. A fcc-to-bcc transformation started after tempering at 500 deg. C and was completed after tempering at 560 deg. C.

  16. Modeling of the Temperature Effect on Oxygen Absorption by Iron-Based Oxygen Scavengers.

    Science.gov (United States)

    Polyakov, Vladimir A; Miltz, Joseph

    2016-01-01

    A new engineering-oriented model for prediction of the effect of temperature on the kinetics of oxygen absorption by iron-based oxygen scavengers (IOSs) was developed. The model is based on the physicochemical mechanism of the O2 scavenging process by the active component of the IOS (iron powder). The conclusions of this study are: (1) the iron deposits formed on the iron particles are composed of 2 different layers: an inner layer of Fe3 O4 and an outer layer of FeOOH that vanishes with the depletion of oxygen. (2) The model considers the chemical processes in the heterogeneous closed system "Fe-H2 O-NaCl-O2 " and describes the kinetics of oxygen absorption by the powder, depending on the characteristics of the system. (3) The nonlinear ordinary differential equation (ODE) of the O2 absorption kinetics was derived and a simple approximate solution to this ODE was obtained theoretically that is similar to the empirical exponential formula published in the relevant literature. (4) The temperature dependence of the oxygen absorption rate is more complicated than that described by the Arrhenius equation. PMID:26650762

  17. High School Attrition Rates across Texas Education Service Center Regions: 2009-10. IDRA Report

    Science.gov (United States)

    Johnson, Roy L.

    2011-01-01

    Attrition rates are an indicator of a school's holding power, or ability to keep students enrolled in school and learning until they graduate. This study examines regional trends in Texas for the number and percent of students lost from public high school enrollment prior to graduation. A comparative analysis of 1985-86, 2005-06, 2006-07,…

  18. Special Education Teacher Attrition: Development of a Resource Manual for Understanding the Individualized Educational Plan Process

    Science.gov (United States)

    Quezada, Karina

    2013-01-01

    Beginning special education teachers have been shown to experience attrition at an increasing rate. The literature has identified many factors contributing to special education teachers leaving the profession. Some of those factors include lack of knowledge regarding special education laws, the special education referral process, individualized…

  19. AN EMPIRICAL INVESTIGATION ON FACTORS THAT INFLUENCE THE EMPLOYEE ATTRITION OF IT SMES IN MADURAI

    Directory of Open Access Journals (Sweden)

    P. Anbuoli

    2014-04-01

    Full Text Available The purpose of this research paper is to initially investigate the intrinsic factors that affect the employee attrition of SMEs of IT companies in Madurai. The in-depth interview and deeper discussion with the employees of this region and opinion from expects were asked for basic problem face by employee attrition in their companies. The primary data were collected to probe the generic tendency of how they rate their problems. The mean score of the opinion on their rating of the problem and the ANOVA indicates that the problem related to factor affect the employee attrition (or turnover represents significant costs to most organizations. It is odd, therefore, that many organizations neither measure such costs nor have targets or plans to reduce them. In this paper, we have made an endeavor to highlight attrition issue faced by IT industry. We try to find out the various reasons for this problem, and have proposed some ways in which this issue can be addressed.

  20. Interpreting trial results following use of different intention-to-treat approaches for preventing attrition bias

    DEFF Research Database (Denmark)

    Dossing, Anna; Tarp, Simon; Furst, Daniel E;

    2014-01-01

    INTRODUCTION: When participants drop out of randomised clinical trials, as frequently happens, the intention-to-treat (ITT) principle does not apply, potentially leading to attrition bias. Data lost from patient dropout/lack of follow-up are statistically addressed by imputing, a procedure prone to...

  1. Attrition, Burnout, and Job Satisfactions of Teachers of the Emotionally Disabled.

    Science.gov (United States)

    Lawrenson, Gary; McKinnon, Archie J.

    The study surveyed 33 teachers of the emotionally disabled to obtain information to help in teacher recruitment and to learn about teacher attrition and burnout. Demographic data identified teacher characteristics. Data gathered included job satisfactions, dissatisfactions, and reasons for leaving the job. A followup structured telephone interview…

  2. Rate-of-Return Attrition and Inflation-Induced Penalties in Public Utility Common Stocks

    OpenAIRE

    Wallace N. Davidson, III; John L. Glascock

    1984-01-01

    While the rate of inflation seems to be easing, the interest in its impact on corporate security prices (Feldstein, 1980) and on corporate investment policy (Caks, 1981; Higgins, 1977) has continued. Unlike nonregulated firms, utilities face the added difficulties of regulation-induced inflation penalties and return on equity (ROE) attrition.

  3. Identifying Personal and Contextual Factors that Contribute to Attrition Rates for Texas Public School Teachers

    Science.gov (United States)

    Sass, Daniel A.; Flores, Belinda Bustos; Claeys, Lorena; Perez, Bertha

    2012-01-01

    Teacher attrition is a significant problem facing schools, with a large percentage of teachers leaving the profession within their first few years. Given the need to retain high-quality teachers, research is needed to identify those teachers with higher retention rates. Using survival analyses and a large state dataset, researchers examined…

  4. Demographic and psychological predictors of panel attrition: evidence from the New Zealand attitudes and values study.

    Directory of Open Access Journals (Sweden)

    Nicole Satherley

    Full Text Available This study examines attrition rates over the first four years of the New Zealand Attitudes and Values Study, a longitudinal national panel sample of New Zealand adults. We report the base rate and covariates for the following four distinct classes of respondents: explicit withdrawals, lost respondents, intermittent respondents and constant respondents. A multinomial logistic regression examined an extensive range of demographic and socio-psychological covariates (among them the Big-Six personality traits associated with membership in these classes (N = 5,814. Results indicated that men, Māori and Asian peoples were less likely to be constant respondents. Conscientiousness and Honesty-Humility were also positively associated with membership in the constant respondent class. Notably, the effect sizes for the socio-psychological covariates of panel attrition tended to match or exceed those of standard demographic covariates. This investigation broadens the focus of research on panel attrition beyond demographics by including a comprehensive set of socio-psychological covariates. Our findings show that core psychological covariates convey important information about panel attrition, and are practically important to the management of longitudinal panel samples like the New Zealand Attitudes and Values Study.

  5. Coal-sand attrition system and its importance in fine coal cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, R.K.

    1991-12-02

    The primary objective of this project is geared toward the substitution of steel media by fracturing silica sand as a grinding media for ultrafine coal grinding. The experimental silica is as follows: (1) design and fabrication of attrition cell; (2) sample procurement, preparation, and characterization; (3) batch grinding tests; (4) continuous grinding test; and (5) fracture mechanics.

  6. The influence of temperature on limestone sulfation and attrition under fluidized bed combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Montagnaro, Fabio [Dipartimento di Chimica - Universita degli Studi di Napoli Federico II, Complesso Universitario del Monte di Sant' Angelo, 80126 Napoli (Italy); Salatino, Piero [Istituto di Ricerche sulla Combustione - CNR, Piazzale Vincenzo Tecchio 80, 80125 Napoli (Italy); Dipartimento di Ingegneria Chimica - Universita degli Studi di Napoli Federico II, Piazzale Vincenzo Tecchio 80, 80125 Napoli (Italy); Scala, Fabrizio [Istituto di Ricerche sulla Combustione - CNR, Piazzale Vincenzo Tecchio 80, 80125 Napoli (Italy)

    2010-04-15

    The influence of temperature on attrition of two limestones during desulfurization in a fluidized bed reactor was investigated. Differences in the microstructure of the two limestones were reflected by a different thickness of the sulfate shell formed upon sulfation and by a different value of the ultimate calcium conversion degree. Particle attrition and fragmentation were fairly small under moderately bubbling fluidization conditions for both limestones. An increase of temperature from 850 C to 900 C led to an increase of the attrition rate, most likely because of a particle weakening effect caused by a faster CO{sub 2} evolution during calcination. This weakening effect, however, was not sufficiently strong to enhance particle fragmentation in the bed. The progress of sulfation, associated to the build-up of a hard sulfate shell around the particles, led in any case to a decrease of the extent of attrition. Sulfation at 900 C was less effective than at 850 C, and this was shown to be related to the porosimetric features of the different samples. (author)

  7. Gender Disparity in STEM Disciplines: A Study of Faculty Attrition and Turnover Intentions

    Science.gov (United States)

    Xu, Yonghong Jade

    2008-01-01

    This study examines the underrepresentation of women faculty in science, technology, engineering, and mathematics (STEM) by comparing the intentions of attrition and turnover between genders in Research and Doctoral universities. It is found that the two genders did not differ in their intentions to depart from academia, but women faculty had a…

  8. Cross Validation and Discriminative Analysis Techniques in a College Student Attrition Application.

    Science.gov (United States)

    Smith, Alan D.

    1982-01-01

    Used a current attrition study to show the usefulness of discriminative analysis and a cross validation technique applied to student nonpersister questionnaire respondents and nonrespondents. Results of the techniques allowed delineation of several areas of sample under-representation and established the instability of the regression weights…

  9. Patterns of Student Enrolment and Attrition in Australian Open Access Online Education: A Preliminary Case Study

    Science.gov (United States)

    Greenland, Steven J.; Moore, Catherine

    2014-01-01

    Swinburne University of Technology has experienced tremendous growth in open access online learning and as such is typical of the many Australian institutions that have ventured into online tertiary education. While research in online education continues to expand, comparatively little investigates students' enrolment and attrition. This research…

  10. Stressful life events and leukocyte telomere attrition in adulthood : a prospective population-based cohort study

    NARCIS (Netherlands)

    van Ockenburg, S. L.; Bos, E. H.; de Jonge, P.; van der Harst, P.; Gans, R. O. B.; Rosmalen, J. G. M.

    2015-01-01

    Background. Telomere attrition might be one of the mechanisms through which psychosocial stress leads to somatic disease. To date it is unknown if exposure to adverse life events in adulthood is associated with telomere shortening prospectively. In the current study we investigated whether life even

  11. Massive Open Online Course Completion Rates Revisited: Assessment, Length and Attrition

    Science.gov (United States)

    Jordan, Katy

    2015-01-01

    This analysis is based upon enrolment and completion data collected for a total of 221 Massive Open Online Courses (MOOCs). It extends previously reported work (Jordan, 2014) with an expanded dataset; the original work is extended to include a multiple regression analysis of factors that affect completion rates and analysis of attrition rates…

  12. Disappearing Act: Persistence and Attrition of Uniform Resource Locators (URLs) in an Open Access Medical Journal

    Science.gov (United States)

    Nagaraja, Aragudige; Joseph, Shine A.; Polen, Hyla H.; Clauson, Kevin A.

    2011-01-01

    Purpose: The aim of this paper is to assess and catalogue the magnitude of URL attrition in a high-impact, open access (OA) general medical journal. Design/methodology/approach: All "Public Library of Science Medicine (PLoS Medicine)" articles for 2005-2007 were evaluated and the following items were assessed: number of entries per issue; type of…

  13. Ab initio downfolding study of the iron-based ladder superconductor BaFe2S3

    Science.gov (United States)

    Arita, Ryotaro; Ikeda, Hiroaki; Sakai, Shiro; Suzuki, Michi-To

    2015-08-01

    Motivated by the recent discovery of superconductivity in the iron-based ladder compound BaFe2S3 under high pressure, we derive low-energy effective Hamiltonians from first principles. We show that the complex band structure around the Fermi level is represented only by the Fe 3 dx z (mixed with 3 dx y ) and 3 dx2-y2 orbitals. The characteristic band degeneracy allows us to construct a four-band model with the band unfolding approach. We also estimate the interaction parameters and show that the system is more correlated than the 1111 family of iron-based superconductors. Provided the superconductivity is mediated by spin fluctuations, the 3 dx z -like band plays an essential role, and the gap function changes its sign between the Fermi surface around the Γ point and that around the Brillouin-zone boundary.

  14. SCIENTIFIC BASIS FOR THE PREPARATION AND CHARACTERIZATION OF IRON BASED TRADITIONAL DRUG ANNABHEDI SINDOORAM: A MATERIALISTIC APPROACH

    Directory of Open Access Journals (Sweden)

    Keerthy Unni

    2013-04-01

    Full Text Available Iron based traditional Ayurvedic drug Annabhedi Sindooram is used therapeutically for the treatment of diseases like Anaemia, Leucoderma, Prolapse of rectum and uterus, Spleenic disorders. The preparation method of iron based Indian traditional drug Annabhedi Sindooram involves conversion of a pure metal into its mixed oxide by drying and incineration. Commercially available ferrous sulphate is used as the source of iron for the preparation of Annabhedi. The structural and textural properties of the starting materials and the prepared drug were characterized systematically by different characterization techniques like PXRD, Zeta Potential Analysis, particle analysis, FTIR, ICP –AES, SEM and BET surface area analysis. The results obtained by characterization of the samples clearly explain the formation of Fe2O3, reduction in particle size, modification of surface energy and formation of metal complex with organic moieties. The strict post and pre preparation conditions followed play an important role in the morphology and medicinal activity of the drug Annabhedi Sindooram.

  15. The evaluation of iron-base hardfacing alloys on gate valves after cycling under simulated PWR conditions for one year

    International Nuclear Information System (INIS)

    Gate valves hardfaced with iron-base alloys were exposed for about one year to simulated PWR conditions. The hardfacing alloys tested were EB 5183, EVERIT 50, NOREM 01 and NOREM 04. A gate valve with Satellite 6 was included in the test program as a control standard. During the test period the valves were opened and closed 2000 times. The performance of the valves was assessed by periodic leak tests and visual and profilometric characterisation of sealing surfaces. At the end of the test program, the seats and discs were destructively examined. The various examinations indicated all the iron-base alloys were superior to Satellite 6. Based on the results of hot leakage tests, one valve with EB 5183 and the valve with NOREM 04 were the best performers

  16. EFFECTIVENESS OF USING DILUTE OXALIC ACID TO DISSOLVEHIGH LEVEL WASTE IRON BASED SLUDGE SIMULANT

    Energy Technology Data Exchange (ETDEWEB)

    Ketusky, E

    2008-07-11

    At the Savannah River Site (SRS), near Aiken South Carolina, there is a crucial need to remove residual quantities of highly radioactive iron-based sludge from large select underground storage tanks (e.g., 19,000 liters of sludge per tank), in order to support tank closure. The use of oxalic acid is planned to dissolve the residual sludge, hence, helping in the removal. Based on rigorous testing, primarily using 4 and 8 wt% oxalic acid solutions, it was concluded that the more concentrated the acid, the greater the amount of residual sludge that would be dissolved; hence, a baseline technology on using 8 wt% oxalic acid was developed. In stark contrast to the baseline technology, reports from other industries suggest that the dissolution will most effectively occur at 1 wt% oxalic acid (i.e., maintaining the pH near 2). The driver for using less oxalic acid is that less (i.e., moles) would decrease the severity of the downstream impacts (i.e., required oxalate solids removal efforts). To determine the initial feasibility of using 1 wt% acid to dissolve > 90% of the sludge solids, about 19,000 liters of representative sludge was modeled using about 530,000 liters of 0 to 8 wt% oxalic acid solutions. With the chemical thermodynamic equilibrium based software results showing that 1 wt% oxalic acid could theoretically work, simulant dissolution testing was initiated. For the dissolution testing, existing simulant was obtained, and an approximate 20 liter test rig was built. Multiple batch dissolutions of both wet and air-dried simulant were performed. Overall, the testing showed that dilute oxalic acid dissolved a greater fraction of the stimulant and resulted in a significantly larger acid effectiveness (i.e., grams of sludge dissolved/mole of acid) than the baseline technology. With the potential effectiveness confirmed via simulant testing, additional testing, including radioactive sludge testing, is planned.

  17. Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions

    Energy Technology Data Exchange (ETDEWEB)

    Frankovsky, Rainer

    2013-06-03

    The results of this thesis can be divided into three major topics, which can also be seen as different approaches of solid state chemistry to reveal interesting features of known and unknown compounds and to develop alternative synthesis routes. Firstly, known compounds with related structural motifs to the superconducting iron-arsenides were investigated regarding their structural and physical properties. In case of La{sub 3}Pd{sub 4}Ge{sub 4} the influence of Fe doping on the properties was studied, whereas in the series ZrMAs (M=Ti,V) the physical properties have not yet been reported at all and were investigated for the first time. Secondly, an alternative synthesis route has been developed for the synthesis of superconducting LaFeAsO{sub 1-x}F{sub x}. This solid state metathesis reaction distinctly increased the quality of the samples compared to conventionally prepared products. Furthermore, the reaction pathway was investigated and clarified, which helps to understand the processes during high temperature solid state metathesis reactions in general. Thirdly, this alternative synthesis route was expanded to other systems and new compounds like co-substituted LaFe{sub 1-x}Mn{sub x}AsO{sub 1-y}F{sub y} were prepared and thoroughly investigated. This led to a complex study of the interplay of magnetism, electronic and structural conditions and the occurrence of superconducting properties. The investigation and understanding of such complex coherences will probably be decisive for the further understanding of the superconducting mechanism in iron based superconductors.

  18. Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites.

    Science.gov (United States)

    Khanolkar, Gauri R; Rauls, Michael B; Kelly, James P; Graeve, Olivia A; Hodge, Andrea M; Eliasson, Veronica

    2016-01-01

    The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding. PMID:26932846

  19. Microstructural development and mechanical properties of iron based cermets processed by pressureless and spark plasma sintering

    International Nuclear Information System (INIS)

    Highlights: ► Processing of Fe-based cermets by pressureless sintering and spark plasma sintering. ► Influence of carbon content on the sintering mechanism and hardness. ► The cermet phase diagram was calculated and permits to explain the microstructure. ► SPS provides ferritic matrix and different carbide distribution than CPS samples. ► Pressureless sintered samples contain retained austenite at room temperature. - Abstract: Iron-based cermets are an interesting class of metal-ceramic composites in which properties and the factors influencing them are to be explored. In this work the metal matrix contains Cr, W, Mo and V as alloying elements, and the hard phase is constituted by 50 vol% of titanium carbonitride (TiCN) particles. The work studies the influence of the C content and the processing method on the sinterability, microstructure and hardness of the developed cermet materials. For that purpose, cermet samples with different C content in the matrix (0 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%) were prepared by conventional pressureless sintering (CPS) and, in order to achieve finer microstructures and to reduce the sintering time, by spark plasma sintering (SPS). The density and hardness (HV30) of the processed materials was evaluated, while their phase composition and microstructure was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The equilibrium phase diagram of the composite material was calculated by ThermoCalc software in order to elucidate the influence of the carbon content on the obtained phases and developed microstructures.

  20. Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites

    Science.gov (United States)

    Khanolkar, Gauri R.; Rauls, Michael B.; Kelly, James P.; Graeve, Olivia A.; Hodge, Andrea M.; Eliasson, Veronica

    2016-01-01

    The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding. PMID:26932846

  1. Unconventional effects in the magnetization and magnetoconductivity of iron based superconductors near Tc as probed by thermal fluctuation spectroscopy

    OpenAIRE

    Ramos Álvarez, Alberto

    2016-01-01

    The main objective of this thesis was to study unconventional effects on the magnetization and Magnetoconductivity of iron-based superconductors, FeSCs, mainly family '122'. This was done through the so-called superconducting fluctuation spectroscopy above the superconducting critical temperature, Tc. This technique has been used in a considerable number of work to characterize the properties of superconductors (see for example). Moreover, the nature of the thermal fluctuations is determined,...

  2. Strain heterogeneity and the production of coarse grains in mechanically alloyed iron-based PM2000 alloy

    OpenAIRE

    Capdevila, Carlos; Miller, U; Jelenak, H; Bhadeshia, H. K. D. H.

    2001-01-01

    Mechanically alloyed iron-based ODS alloys have the potential for application in heat exchangers for biomass processing, with gas operating temperatures and pressures of approximately 1100°C and 15–30 bar. The yttria dispersion in such alloys improves the high-temperature creep and stress rupture life. The elevated temperature strength is enhanced by the development of a coarse-grained microstructure during recrystallisation. Factors controlling the evolution of this desirable micros...

  3. Polarized Neutron Scatteringas a probe of spin nematicity in the iron-based superconductor BaFe2-xNixAs2

    International Nuclear Information System (INIS)

    Understanding the electronic anisotropic state associated with the nematic phase is one of the most important unresolved problems in electron correlated systems. Particularly in iron-based superconductors, an in-plane electric anisotropy has been suggested as a signature of the electron nematic phase that breaks the in-plane four-fold rotational symmetry of the underlying tetragonal lattice, and a spin nematicity also is proved by Neutron Scatteringexperiments, where its physical origin remains controversial among charge, orbital, spin or local impurity scattering. Here, we use polarized Neutron Scatteringto demonstrate that in-plane spin excitations in electron doped superconductor BaFe1.904Ni0.096As2 change from isotropic to anisotropic in the tetragonal phase well above the antiferromagnetic ordering and tetragonal-toorthorhombic lattice distortion temperatures without an uniaxial pressure. Comparing with the polarized neutron results on the detwinned samples with uniaxial pressure, we argue that the anisotropic low-energy spin excitations from single ion effects are intimately connected with the spin nematic phase in iron pnictides, and consistent with in-plane resistivity anisotropy. These results indicate that the polarized Neutron Scatteringis a good probe of the spin nematicity in iron pnictides.

  4. The impact of motor axon misdirection and attrition on behavioral deficit following experimental nerve injuries.

    Directory of Open Access Journals (Sweden)

    Jacob Daniel de Villiers Alant

    Full Text Available Peripheral nerve transection and neuroma-in-continuity injuries are associated with permanent functional deficits, often despite successful end-organ reinnervation. Axonal misdirection with non-specific reinnervation, frustrated regeneration and axonal attrition are believed to be among the anatomical substrates that underlie the poor functional recovery associated with these devastating injuries. Yet, functional deficits associated with axonal misdirection in experimental neuroma-in-continuity injuries have not yet been studied. We hypothesized that experimental neuroma-in-continuity injuries would result in motor axon misdirection and attrition with proportional persistent functional deficits. The femoral nerve misdirection model was exploited to assess major motor pathway misdirection and axonal attrition over a spectrum of experimental nerve injuries, with neuroma-in-continuity injuries simulated by the combination of compression and traction forces in 42 male rats. Sciatic nerve injuries were employed in an additional 42 rats, to evaluate the contribution of axonal misdirection to locomotor deficits by a ladder rung task up to 12 weeks. Retrograde motor neuron labeling techniques were utilized to determine the degree of axonal misdirection and attrition. Characteristic histological neuroma-in-continuity features were demonstrated in the neuroma-in-continuity groups and poor functional recovery was seen despite successful nerve regeneration and muscle reinnervation. Good positive and negative correlations were observed respectively between axonal misdirection (p<.0001, r(2=.67, motor neuron counts (attrition (p<.0001, r(2=.69 and final functional deficits. We demonstrate prominent motor axon misdirection and attrition in neuroma-in-continuity and transection injuries of mixed motor nerves that contribute to the long-term functional deficits. Although widely accepted in theory, to our knowledge, this is the first experimental evidence to

  5. Electron Backscatter Diffraction and Transmission Kikuchi Diffraction Analysis of an Austenitic Stainless Steel Subjected to Surface Mechanical Attrition Treatment and Plasma Nitriding.

    Science.gov (United States)

    Proust, Gwénaëlle; Retraint, Delphine; Chemkhi, Mahdi; Roos, Arjen; Demangel, Clemence

    2015-08-01

    Austenitic 316L stainless steel can be used for orthopedic implants due to its biocompatibility and high corrosion resistance. Its range of applications in this field could be broadened by improving its wear and friction properties. Surface properties can be modified through surface hardening treatments. The effects of such treatments on the microstructure of the alloy were investigated here. Surface Mechanical Attrition Treatment (SMAT) is a surface treatment that enhances mechanical properties of the material surface by creating a thin nanocrystalline layer. After SMAT, some specimens underwent a plasma nitriding process to further enhance their surface properties. Using electron backscatter diffraction, transmission Kikuchi diffraction, energy dispersive spectroscopy, and transmission electron microscopy, the microstructural evolution of the stainless steel after these different surface treatments was characterized. Microstructural features investigated include thickness of the nanocrystalline layer, size of the grains within the nanocrystalline layer, and depth of diffusion of nitrogen atoms within the material. PMID:26139391

  6. Pre-treatment predictors of attrition in a randomised controlled trial of psychological therapy for severe and enduring anorexia nervosa

    OpenAIRE

    Abd Elbaky, Ghada B; Hay, Phillipa J; Le Grange, Daniel; Lacey, Hubert; Crosby, Ross D.; Touyz, Stephen

    2014-01-01

    Background Attrition is common in the treatment of anorexia nervosa and its causes are complex and incompletely understood. In particular, its relationship with adaptive function and motivational stage of change has been little studied. This study aimed to (1) investigate and (2) compare the strength of associations between adaptive function, stage of change and other previously found factors such as illness sub-type and treatment attrition in women with severe and enduring anorexia nervosa (...

  7. Attrition of Knowledge Workforce in Healthcare in Northern parts of India – Health Information Technology as a Plausible Retention Strategy

    OpenAIRE

    Indrajit Bhattacharya; Anandhi Ramachandran; Suri, R K; Gupta, S. L.

    2012-01-01

    Faced with a global shortage of skilled health workers due to attrition, countries are struggling to build and maintain optimum knowledge workforce in healthcare for delivering quality healthcare services. Forces that affect healthcare professionals’ turnover needs to be addressed before a competent uniformly adoptable strategy could be proposed for mitigating the problem. In this study we investigate the effects of the socio–demographic characteristics on attrition of healthcare knowledge wo...

  8. HIGHWAY INFRASTRUCTURE FOCUS AREA NEXT-GENERATION INFRASTRUCTURE MATERIALS VOLUME I - TECHNICAL PROPOSAL & MANAGEMENTENHANCEMENT OF TRANSPORTATION INFRASTRUCTURE WITH IRON-BASED AMORPHOUS-METAL AND CERAMIC COATINGS

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C

    2007-12-04

    The infrastructure for transportation in the United States allows for a high level of mobility and freight activity for the current population of 300 million residents, and several million business establishments. According to a Department of Transportation study, more than 230 million motor vehicles, ships, airplanes, and railroads cars were used on 6.4 million kilometers (4 million miles) of highways, railroads, airports, and waterways in 1998. Pipelines and storage tanks were considered to be part of this deteriorating infrastructure. The annual direct cost of corrosion in the infrastructure category was estimated to be approximately $22.6 billion in 1998. There were 583,000 bridges in the United States in 1998. Of this total, 200,000 bridges were steel, 235,000 were conventional reinforced concrete, 108,000 bridges were constructed using pre-stressed concrete, and the balance was made using other materials of construction. Approximately 15 percent of the bridges accounted for at this point in time were structurally deficient, primarily due to corrosion of steel and steel reinforcement. Iron-based amorphous metals, including SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been developed, and have very good corrosion resistance. These materials have been prepared as a melt-spun ribbons, as well as gas atomized powders and thermal-spray coatings. During electrochemical testing in several environments, including seawater at 90 C, the passive film stabilities of these materials were found to be comparable to that of more expensive high-performance alloys, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. These materials also performed very well in standard salt fog tests. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation

  9. Change of the sign of superconducting intraband order parameters induced by interband pair hopping interaction in iron-based high-temperature superconductors

    International Nuclear Information System (INIS)

    Iron based superconductors are characterized by the s± gap symmetry, where the gap changes its sign between pockets of the Fermi surface. We discuss another sign change mechanism of the superconducting order parameter (OP)—the interband Cooper pairs hopping interaction. In the minimal two-orbital model of iron based superconductors we show that this interaction can lead to a change of the sign of the intraband superconducting OP regardless of its symmetry. (paper)

  10. A Study of the Causes of Attrition Among Adult on a Fully Online Training Course

    Directory of Open Access Journals (Sweden)

    Michael McMahon

    2013-05-01

    Full Text Available An online course was piloted in an Institute of Technology in Ireland for the purpose of providing training in best practice in presenting to people with dyslexia. The course was delivered fully online with no required attendances and with no interaction between participants. None of the participants in the pilot of the course completed the course. This study applies a model developed by Chyung to focus on the possible causes of the attrition and examine means by which attrition can be ameliorated. The findings show that the sense of isolation attached to learning alone is a very significant factor which often has a negative effect on the persistence of the learner to complete the course of study. Strategies to reduce this isolation are suggested.

  11. Attrition of schistosomes in an irradiation-attenuated cercarial immunization model of Schistosoma mansoni

    International Nuclear Information System (INIS)

    The attrition of Schistosoma mansoni challenge worms was studied in irradiation-attenuated cercaria-immunized mice as a function of site and time. The peak recovery of schistosomula from the lungs of immunized mice was delayed 2 days in comparison with non-immunized controls. The difference between the peak recoveries of control and immunized mice accounted for about half of the final attrition observed at the 7-week adult worm stge. Hepatic-mesenteric vein worm recoveries obtained 10 to 42 days after challenge were reduced in most cases at least as much as the 49-day counts. Somewhat higher reductions were observed at 14 to 28 days than at 49 days, confirming the evidence of delayed migration obtained at the lung phase. These findings, coupled with histologic observations, indicate that at least half of the worm elimination attributable to immunization occurs 8 or more days after the challenge infection

  12. A Selective Mutism Arising from First Language Attrition, Successfully Treated with Paroxetine-CBT Combination Treatment.

    Science.gov (United States)

    Serra, Agostino; Di Mauro, Paola; Andaloro, Claudio; Maiolino, Luigi; Pavone, Piero; Cocuzza, Salvatore

    2015-10-01

    After immersion in a foreign language, speakers often have difficulty retrieving native-language words and may experience a decrease in its proficiency, this phenomenon, in the non-pathological form, is known as first language attrition. Self-perception of this low native-language proficiency and apprehension occurring when speaking is expected and, may sometimes lead these people to a state of social anxiety and, in extreme forms, can involve the withholding of speech as a primitive tool for self-protection, linking them to selective mutism. We report an unusual case of selective mutism arising from first language attrition in an Italian girl after attending a two-year "German language school", who successfully responded to a paroxetine-cognitive behavioral treatment (CBT) combination treatment. PMID:26508972

  13. Identity theory as a theoretical framework to understand attrition for university students in transition

    Directory of Open Access Journals (Sweden)

    Robert Whannell

    2015-08-01

    Full Text Available There has been extensive research done with a view to explaining the processes of transition into tertiary study and the factors that may be associated with student attrition.  This paper consolidates the authors’ research in relation to the transition of students into adult and tertiary bridging programs and undergraduate university study and presents an alternative approach to the use of objective conditions such as financial challenges and first-in-family status in explaining the attrition phenomenon.  Identity theory is used as the basis to develop a theoretical framework that will assist educators working in these areas to engage more fully with and assist students to develop the academic and scholarly identity necessary to sustain appropriate and effective academic behaviours during the transition into tertiary education.

  14. Flue gas desulfurization under simulated oxyfiring fluidized bed combustion conditions: The influence of limestone attrition and fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Scala, F.; Salatino, P. [CNR, Naples (Italy)

    2010-01-01

    Flue gas desulfurization by means of limestone injection under simulated fluidized bed oxyfiring conditions was investigated, with a particular focus on particle attrition and fragmentation phenomena. An experimental protocol was applied, based on the use of complementary techniques that had been previously developed for the characterization of attrition of sorbents in air-blown atmospheric fluidized bed combustors. The extent and pattern of limestone attrition by surface wear in the dense phase of a fluidized bed were assessed in bench scale fluidized bed experiments under simulated oxyfiring conditions. Sorbent samples generated during the oxyfiring tests were further characterized from the standpoint of fragmentation upon high velocity impact by means of a particle impactor. The experimental results were compared with those previously obtained with the same limestone under air-blown atmospheric fluidized bed combustion conditions. The profound differences in the attrition and fragmentation extents and patterns associated with oxyfiring as compared to air-blown atmospheric combustion and the role played by the different attrition/fragmentation paths were highlighted. In particular, it was noted that attrition could effectively enhance particle sulfation under oxyfiring conditions by continuously disclosing unconverted calcium to the sulfur-bearing atmosphere.

  15. Structural and magnetic properties of polymer coated iron based nanoparticles for biomedical applications

    Science.gov (United States)

    Balakrishnan, Srinivasan

    reduction of the metal salt solution. Since our intention is to synthesize iron based nanoparticles we used iron salts such as FeCl3. A polymer such as polyethylene glycol is coated onto the oxide shell to make it biocompatible. Parameters such as length of the tube, diameter of the Y-tube junction and concentration of the reactants were varied to study the effect on particle size, structure and morphology of the magnetic nanoparticles. X-ray diffraction measurements revealed that the particles typically contain three iron based phases such as a crystalline (alpha-Fe), nanocrystalline/amorphous (a-FeB/n-Fe) and Fe-oxide. By controlling the synthesis parameters such as length of the reaction tube, inner diameter of the Y-tube and concentration of the reagents the volume percentage of the three phases of the nanoparticles, viz. crystalline phase, amorphous phase and Fe-Oxide phases can be controlled effectively. The Fe-Oxide phase could not be determined whether is magnetite and maghemite phase because of the very broad nature of the peak. Transmission electron microscopy was used to study the particle size and the microstructural property of the samples. Samples with particle size in the range of 3 nm to 30 nm were fabricated. The magnetic properties of the nanoparticles studied were measured with a vibrating sample magnetometer with a maximum field of 1 Tesla. The particles magnetic properties such as magnetization and coercivity were typical of a soft ferromagnetic material with a high magnetization (in emu/g) and the coercivity was in range of 50 to 450 Oe. The nanoparticles synthesized were used to study their performance in magnetic fluid hyperthermia and magnetic resonance imaging applications. In the hyperthermia, the power loss due to an alternating magnetic field had a direct correlation with the magnetization and the particle size of the nanoparticle. The power loss in magnetic fluid hyperthermia is an outcome from four loss mechanism, they are Brownian rotational

  16. Attrition and Adherence of Young Women to Aerobic Exercise: Lessons from the WISER study

    OpenAIRE

    Arikawa, Andrea Y.; O’Dougherty, Maureen; Kaufman, Beth C.; Schmitz, Kathryn H.; Kurzer, Mindy S.

    2011-01-01

    The purpose of this report is to identify factors associated with attrition and adherence of young women to a 16-week randomized aerobic exercise intervention on biomarkers associated with breast cancer risk. The exercise group was prescribed a progressive weight-bearing aerobic exercise program consisting of 30 minute workouts, 5 times/wk for 16 weeks. Adherence was calculated as the average minutes of exercise per week during participation in the study. Of the total of 212 women randomized ...

  17. Vocation, Friendship and Resilience: A Study Exploring Nursing Student and Staff Views on Retention and Attrition

    OpenAIRE

    Williamson, Graham R; Health, Val; Proctor-Childs, Tracey

    2013-01-01

    Introduction: There is international concern about retention of student nurses on undergraduate programmes. United Kingdom Higher Education Institutions are monitored on their attrition statistics and can be penalised financially, so they have an incentive to help students remain on their programmes beyond their moral duty to ensure students receive the best possible educational experience. Aims: to understand students’ and staff concerns about programmes and placements as part of developing ...

  18. Earnings Assimilation of Immigrants in Germany: The Importance of Heterogeneity and Attrition Bias

    OpenAIRE

    Michael Fertig; Stefanie Schurer

    2007-01-01

    Heterogeneity in the ethnic composition of Germany's immigrant population renders general conclusions on the degree of economic integration difficult. Using a rich longitudinal data-set, this paper tests for differences in economic assimilation profiles of four entry cohorts of foreign-born immigrants and ethnic Germans. The importance of time-invariant individual unobserved heterogeneity and panel attrition in determining the speed of assimilation is analysed. We find evidence for heterogene...

  19. Nitriding of nanocrystalline pure Fe induced by surface mechanical attrition treatment

    OpenAIRE

    Fu Yuzhu; Tong Weiping; Gong Mengying; Li Haizhi; Chen Liqing

    2015-01-01

    Properties of nanocrystalline (nc) materials are different from, and often superior to those of conventional coarse-grained counterparts. Unfortunately, it is still difficult to obtain “ideal” (e.g. full-density, residual stress-free, flaw-free, porosity-free and contamination-free) nc bulk sample by using the present preparation methods. Recently, a new technique named surface mechanical attrition treatment (SMAT) was developed. SMAT enables the fabrication of an nc surface layer on various ...

  20. A Study on Reasons of Attrition and Strategies for Employee Retention

    OpenAIRE

    N.Silpa

    2015-01-01

    The success of any manufacturing organization depends largely on the workers are considered as the backbone of any company. The study was mainly undertaken to identify the level of employee’s attitude, the dissatisfaction factors they face in the organization and for what reason they prefer to change their job. Once the levels of employee’s attitude are identified, it would be possible for the management to take necessary action to reduce attrition level. Since they are considered...

  1. Attrition in paediatric weight management: a review of the literature and new directions

    OpenAIRE

    Skelton, J. A.; Beech, B. M.

    2010-01-01

    Paediatric obesity continues to be one of the most important health issues facing children and families today, and there remains a need for effective treatment options. There are a few reports in the literature demonstrating high rates of attrition from paediatric weight management programmes, ranging from 27% to 73%. While some studies show that racial/ethnic minorities, the economically disadvantaged and those with higher levels of obesity are at risk, other studies do not. There is some co...

  2. General English Attrition and Its Significance for Business English Teaching/Learning of Prospective Economists

    OpenAIRE

    Slavica Čepon; Mihaela Zavašnik

    2007-01-01

    This article summarizes some of the findings of a large-scale study of the foreign language needs of economics students (Čepon 2007). It focuses on the rationale behind the lengthy period of disuse of general English (GE) during economics students’ first year of undergraduate study. The article presents evidence for processes of GE attrition that slowly set in and are deemed to be particularly detrimental to economics. It is also important to determine exactly which language needs are essenti...

  3. Initial research on an inventory control process for low attrition repairable items.

    OpenAIRE

    Dexter, Mark D.

    1989-01-01

    Approved for Public release; distribution is unlimited This thesis presents the initial research findings for a proposed wholesale level inventor\\" control process for low attrition Depot Level Repairables (DLRs) and is the start of a continuing research effort directed by Professor Thomas P. Moore of the Naval Postgraduate School. The main objectives of this study were to determine if the data required for the proposed model were available in the existing data bases at the Nav...

  4. Medical School Attrition-Beyond the Statistics A Ten Year Retrospective Study

    Directory of Open Access Journals (Sweden)

    Maher Bridget M

    2013-01-01

    Full Text Available Abstract Background Medical school attrition is important - securing a place in medical school is difficult and a high attrition rate can affect the academic reputation of a medical school and staff morale. More important, however, are the personal consequences of dropout for the student. The aims of our study were to examine factors associated with attrition over a ten-year period (2001–2011 and to study the personal effects of dropout on individual students. Methods The study included quantitative analysis of completed cohorts and qualitative analysis of ten-year data. Data were collected from individual student files, examination and admission records, exit interviews and staff interviews. Statistical analysis was carried out on five successive completed cohorts. Qualitative data from student files was transcribed and independently analysed by three authors. Data was coded and categorized and key themes were identified. Results Overall attrition rate was 5.7% (45/779 in 6 completed cohorts when students who transferred to other medical courses were excluded. Students from Kuwait and United Arab Emirates had the highest dropout rate (RR = 5.70, 95% Confidence Intervals 2.65 to 12.27;p  Absenteeism was documented in 30% of students, academic difficulty in 55.7%, social isolation in 20%, and psychological morbidity in 40% (higher than other studies. Qualitative analysis revealed recurrent themes of isolation, failure, and despair. Student Welfare services were only accessed by one-third of dropout students. Conclusions While dropout is often multifactorial, certain red flag signals may alert us to risk of dropout including non-EU origin, academic struggling, absenteeism, social isolation, depression and leave of absence. Psychological morbidity amongst dropout students is high and Student Welfare services should be actively promoted. Absenteeism should prompt early intervention. Behind every dropout statistic lies a personal story. All

  5. Labour Market Outcomes of Immigrants in Germany – The Importance of Heterogeneity and Attrition Bias

    OpenAIRE

    Fertig, Michael; Schurer, Stefanie

    2007-01-01

    Heterogeneity in the ethnic composition of Germanys immigrant population renders general conclusions on the degree of economic integration difficult. Using a rich longitudinal dataset, this paper tests for differences in economic assimilation profiles of four groups of foreign-born immigrants and ethnic Germans. The importance of time-invariant individual unobserved heterogeneity and panel attrition in determining the speed of assimilation is analysed. We find evidence for heterogeneity in th...

  6. Labour market outcomes of immigrants in Germany: the importance of heterogeneity and attrition bias

    OpenAIRE

    Fertig, Michael; Schurer, Stefanie

    2007-01-01

    Heterogeneity in the ethnic composition of Germany’s immigrant population renders general conclusions on the degree of economic integration difficult. Using a rich longitudinal data-set, this paper tests for differences in economic assimilation profiles of four groups of foreign-born immigrants and ethnic Germans. The importance of time-invariant individual unobserved heterogeneity and panel attrition in determining the speed of assimilation is analysed. We find evidence for heterogeneity in ...

  7. Massive Open Online Course Completion Rates Revisited: Assessment, Length and Attrition

    OpenAIRE

    Katy Jordan

    2015-01-01

    This analysis is based upon enrolment and completion data collected for a total of 221 Massive Open Online Courses (MOOCs). It extends previously reported work (Jordan, 2014) with an expanded dataset; the original work is extended to include a multiple regression analysis of factors that affect completion rates and analysis of attrition rates during courses. Completion rates (defined as the percentage of enrolled students who completed the course) vary from 0.7% to 52.1%, with a median value ...

  8. Inter-disciplinary management of a patient with severely attrited teeth

    OpenAIRE

    Padmanabhan Shyam; Reddy Venkateswara

    2010-01-01

    With increased awareness about dental esthetics, multidisciplinary periodontal therapy has begun to gain momentum. Management of severely attrited teeth is a challenging situation and is dealt with a multidisciplinary approach. In cases of severe tooth wear, the crown height is drastically reduced, in some cases up to the gingival level. This might require a contribution from the disciplines of endodontics, periodontics, orthodontics and prosthodontics for predictable results. Herein we descr...

  9. Inter-disciplinary management of a patient with severely attrited teeth

    Directory of Open Access Journals (Sweden)

    Padmanabhan Shyam

    2010-01-01

    Full Text Available With increased awareness about dental esthetics, multidisciplinary periodontal therapy has begun to gain momentum. Management of severely attrited teeth is a challenging situation and is dealt with a multidisciplinary approach. In cases of severe tooth wear, the crown height is drastically reduced, in some cases up to the gingival level. This might require a contribution from the disciplines of endodontics, periodontics, orthodontics and prosthodontics for predictable results. Herein we describe the management of one such case.

  10. Language, Teaching and Attrition: A Study on Selected Teachers Who Left the Profession

    OpenAIRE

    Aminu Aliyu Wushishi; Muhammed Baba

    2016-01-01

    Nigeria is a country with over 520 different languages, the multitude nature of languages is making instructions so difficult in Schools, particularly in North-Central Nigeria where they have students with different language background attending the same school. The difficulty of smooth teaching in this kind of situation is leading to attrition among teachers. This study examines the situation of selected teachers in Niger State, Nigeria, who left the teaching profession as a result of diffic...

  11. STEM attrition among high-performing college students in the United States: scope and potential causes

    OpenAIRE

    Xianglei Chen

    2015-01-01

    Postsecondary education plays a critical role in building a strong workforce in science, technology, engineering, and mathematics (STEM) fields. The U.S. postsecondary education system, however, frequently loses many potential STEM graduates through attrition. An increasing portion of STEM leavers are top performers who might have made valuable additions to the STEM workforce had they stayed in STEM fields. Using data from the 2004/09 Beginning Postsecondary Students Longitudinal Study (BPS:0...

  12. Attrition of Dolomitic Lime in a Fluidized-Bed at High Temperature

    Czech Academy of Sciences Publication Activity Database

    Hartman, Miloslav; Svoboda, Karel; Pohořelý, Michael; Šyc, Michal; Jeremiáš, Michal

    2013-01-01

    Roč. 67, č. 2 (2013), s. 164-172. ISSN 0366-6352 R&D Projects: GA AV ČR IAA400720701; GA MŠk(CZ) 7C11009 Grant ostatní: RFCS(XE) RFCR-CT-2010-00009 Institutional support: RVO:67985858 Keywords : attrition * catalytic gasification * dolomitic lime Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.193, year: 2013

  13. Influence of attrition scrubbing, ultrasonic treatment, and oxidant additions on uranium removal from contaminated soils

    International Nuclear Information System (INIS)

    As part of the Uranium in Soils Integrated Demonstration Project being conducted by the US Department of Energy, bench-scale investigations of selective leaching of uranium from soils at the Fernald Environmental Management Project site in Ohio were conducted at Oak Ridge National Laboratory. Two soils (storage pad soil and incinerator soil), representing the major contaminant sources at the site, were extracted using carbonate- and citric acid-based lixiviants. Physical and chemical processes were used in combination with the two extractants to increase the rate of uranium release from these soils. Attrition scrubbing and ultrasonic dispersion were the two physical processes utilized. Potassium permanganate was used as an oxidizing agent to transform tetravalent uranium to the hexavalent state. Hexavalent uranium is easily complexed in solution by the carbonate radical. Attrition scrubbing increased the rate of uranium release from both soils when compared with rotary shaking. At equivalent extraction times and solids loadings, however, attrition scrubbing proved effective only on the incinerator soil. Ultrasonic treatments on the incinerator soil removed 71% of the uranium contamination in a single extraction. Multiple extractions of the same sample removed up to 90% of the uranium. Additions of potassium permanganate to the carbonate extractant resulted in significant changes in the extractability of uranium from the incinerator soil but had no effect on the storage pad soil

  14. Language, Teaching and Attrition: A Study on Selected Teachers Who Left the Profession

    Directory of Open Access Journals (Sweden)

    Aminu Aliyu Wushishi

    2016-02-01

    Full Text Available Nigeria is a country with over 520 different languages, the multitude nature of languages is making instructions so difficult in Schools, particularly in North-Central Nigeria where they have students with different language background attending the same school. The difficulty of smooth teaching in this kind of situation is leading to attrition among teachers. This study examines the situation of selected teachers in Niger State, Nigeria, who left the teaching profession as a result of difficulty in teaching their students, whom they said cannot efficiently understand the official language of instruction (English. The teachers highlighted their main reason of leaving the profession which is mainly associated with language problem among students, they added that, the massive failure of students in the final examination has a link with the student’s inability to understand what the teachers are teaching because of their poor background in English language. The paper recommends the use of one major local language (Hausa in teaching the students, this will make learning easy and students will efficiently comprehend instructions from their teachers, which may go a long way in reducing attrition.Keywords: Language, Teaching, Attrition

  15. Schistosoma mansoni: migration and attrition of irradiated and challenge schistosomula in the mouse

    Energy Technology Data Exchange (ETDEWEB)

    Mastin, A.J.; Wilson, R.A. (York Univ. (UK)); Bickle, Q.D. (Winches Farm Field Station, St. Albans (UK))

    1983-08-01

    The fate of irradiated, immunizing cercariae and challenge schistosomula was investigated in mice using a quantitative, histological technique which would appear to be more efficient in estimating parasite numbers in skin and lungs than does the tissue mincing and incubation recovery technique used previously by other workers. There was evidence for slight retardation of irradiated parasite migration in skin, but death of schistosomula in the skin appeared negligible. The majority of irradiated parasites remained in the lungs until at least day 21 after infection, and that most schistosomula observed at this time were dead. In mice immunized with irradiated cercariae there was no evidence of attrition of the challenge infection in the skin. The migration profile of challenge parasites in the lungs of immunized animals was not significantly different from that of normal parasites in the lungs of naive animals. Dead challenge parasites were observed in the lungs but their numbers were not considered great enough to account for the final attrition measured by perfusion. It is suggested that the remainder of the attrition of challenge schistosomula may occur in the systemic and/or hepatic portal circulation.

  16. Schistosoma mansoni: migration and attrition of irradiated and challenge schistosomula in the mouse

    International Nuclear Information System (INIS)

    The fate of irradiated, immunizing cercariae and challenge schistosomula was investigated in mice using a quantitative, histological technique which would appear to be more efficient in estimating parasite numbers in skin and lungs than does the tissue mincing and incubation recovery technique used previously by other workers. There was evidence for slight retardation of irradiated parasite migration in skin, but death of schistosomula in the skin appeared negligible. The majority of irradiated parasites remained in the lungs until at least day 21 after infection, and that most schistosomula observed at this time were dead. In mice immunized with irradiated cercariae there was no evidence of attrition of the challenge infection in the skin. The migration profile of challenge parasites in the lungs of immunized animals was not significantly different from that of normal parasites in the lungs of naive animals. Dead challenge parasites were observed in the lungs but their numbers were not considered great enough to account for the final attrition measured by perfusion. It is suggested that the remainder of the attrition of challenge schistosomula may occur in the systemic and/or hepatic portal circulation. (author)

  17. The influence of attrition and cyclone performance on the particle size distribution in a CFB system

    Energy Technology Data Exchange (ETDEWEB)

    Cornelis Klett; Ernst-Ulrich Hartge; Joachim Werther [Technical University Hamburg-Harburg, Hamburg (Germany)

    2005-07-01

    Based on previous investigations in the authors' group on attrition mechanisms in fluidized bed systems a model has been developed which allows the simulation of the influences of particle attrition and cyclone performance on the time-dependent development of the particle size distribution in a circulating fluidized bed system consisting of a riser, a cyclone and a solids return leg. In an extension of previous work it was now possible to include the effect of the residence time of the particles in the system. The model takes account of the fact that fresh particles have a higher attrition rate than particles which have stayed for some time already in the system. The model is able to describe the dynamic adjustment of the particle size distribution in a given system. The model was validated with coal combustion experiments in a pilot-scale CFB combustion unit. Ash samples were taken from the bottom part of the riser and compared with the theoretical predictions. The model was used in simulation runs to study the effects of changes in the operating conditions on the steady-state solids particle size distribution and solids mass fluxes. 9 refs., 9 figs., 2 tabs.

  18. First principle study of iron based layered compounds of LaOFeX (X=P, As)

    International Nuclear Information System (INIS)

    We study the ground state crystal structure, electronic structure and magnetic properties of superconducting iron based layered compounds of LaOFeX (X= P,As) using first principle calculations. We find the electronic structures and magnetic properties of this family of superconducting compounds. In order to systematically investigate the properties of the magnetic order and electronic structure in the LaOFeX (X=P, As) system, three kinds of magnetic states were calculated, which includes the non-magnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) state

  19. Possible unconventional superconductivity in iron-based layered compound LaFePO: Study of heat capacity

    OpenAIRE

    Kohama, Yoshimitsu; Kamihara, Yoichi; Kawaji, Hitoshi; Atake, Tooru; Hirano, Masahiro; Hosono, Hideo

    2008-01-01

    Heat capacity measurements were performed on recently discovered iron based layered superconductors, non doped LaFePO and fluorine doped LaFePO. A relatively large electronic heat capacity coefficient and a small normalized heat capacity jump at Tc = 3.3 K were observed in LaFePO. LaFePO0.94F0.06 had a smaller electronic heat capacity coefficient and a larger normalized heat capacity jump at Tc = 5.8 K. These values indicate that these compounds have strong electron electron correlation and m...

  20. Attrition of Knowledge Workforce in Healthcare in Northern parts of India – Health Information Technology as a Plausible Retention Strategy

    Directory of Open Access Journals (Sweden)

    Indrajit Bhattacharya

    2012-06-01

    Full Text Available Faced with a global shortage of skilled health workers due to attrition, countries are struggling to build and maintain optimum knowledge workforce in healthcare for delivering quality healthcare services. Forces that affect healthcare professionals’ turnover needs to be addressed before a competent uniformly adoptable strategy could be proposed for mitigating the problem. In this study we investigate the effects of the socio–demographic characteristics on attrition of healthcare knowledge workforce in northern parts of India that have a wide gradient of rural and urban belt, taking into account both public and private healthcare organizations. For this purpose healthcare professional attrition tracking survey (HATS was designed. The data has been collected from a random sample of 807 respondents consisting of doctors, nurses, paramedics and administrators to explore the relationships between various factors acting as antecedents in affecting the job satisfaction, commitment and intention of a healthcare professional to stay in the job. Structured questionnaires were utilized as the data collection tools. Descriptive statistics, factor analysis and path analysis were carried out using multiple regression and correlation to propose a model that best explains the theoretical assumption of factors leading to attrition. Six factors of attrition namely compensation and perks, work life balance, sense of accomplishment, work load, need for automation and technology improvement, substandard nature of work have been identified as the main factors with a data reliability of 0.809%. It has also been identified that the intention to shift is a major decision maker that affects attrition and in turn affected by job satisfaction dimensions. Based on the survey response and analysis, a highly possible strategy of utilizing information technology implementation for increasing worker motivation, job satisfaction and commitment to reduce attrition has been

  1. Determinants of Attrition to Follow-Up in a Multicentre Cohort Study in Children-Results from the IDEFICS Study

    Directory of Open Access Journals (Sweden)

    Sabrina Hense

    2013-01-01

    Full Text Available Cohort participant retention is a crucial element and may depend on several factors. Based on data from a multicentre cohort of European children, the effect of baseline participation on attrition and the association with and the impact of single determinants in relation to the extent of attrition were investigated. Data was available for 16,225 children from the IDEFICS baseline survey (2007/2008. Attrition was defined as nonparticipation in the first follow-up examination (2009/2010. Determinants of attrition were analysed by logistic regression. The statistical significance level was set at α=0.01 to account for the large sample size. The strongest associations were seen for baseline item non-response, especially when information on migration background (odds ratio (OR = 1.55; 99% confidence interval (CI: 1.04, 2.31, single parenthood (OR = 1.37; 99% CI: 1.12, 1.67, or well-being (OR = 1.46; 99% CI: 1.19, 1.79 was lacking. Drop-out proportion rose with the number of missing items. Overweight, low education, single parenthood and low well-being scores were independent determinants of attrition. Baseline participation, and the individual determinant effects seemed unrelated to the variation of the extent of attrition between study centres. A high level of item nonresponse as well as overweight and disadvantageous sociodemographic conditions were identified as main attrition determinants, suggesting the consideration of these aspects in conduct and analysis of cohort studies in childhood obesity research.

  2. Effect of single interstitial impurity in iron-based superconductors with sign-changed s-wave pairing symmetry

    Science.gov (United States)

    Yu, Xiang-Long; Liu, Da-Yong; Quan, Ya-Min; Zheng, Xiao-Jun; Zou, Liang-Jian

    2015-12-01

    We employ the self-consistent Bogoliubov-de Gennes (BdG) formulation to investigate the effect of single interstitial nonmagnetic/magnetic impurity in iron-based superconductors with s ± -wave pairing symmetry. We find that both the nonmagnetic and magnetic impurities can induce bound states within the superconducting (SC) gap and a π phase shift of SC order parameter at the impurity site. However, different from the interstitial-nonmagnetic-impurity case characterized by two symmetric peaks with respect to zero energy, the interstitial magnetic one only induces single bound-state peak. In the strong scattering regime this peak can appear at the Fermi level, which has been observed in the recent scanning tunneling microscope (STM) experiment of Fe(Te,Se) superconductor with interstitial Fe impurities (Yin et al. 2015 [44]). This novel single in-gap peak feature also distinguishes the interstitial case from the substitutional one with two peaks. These results provide important information for comparing the different impurity effects in the iron-based superconductors.

  3. Nitriding of iron-based ternary Fe–V–Si alloy: The precipitation process of separate nitrides

    International Nuclear Information System (INIS)

    Iron-based ternary Fe–V–Si and binary Fe–Si alloy specimens were nitrided in a NH3/H2 gas mixture at 580 °C (853 K) with a nitriding potential of rN = 0.1 atm−1/2 until nitrogen saturation in the specimens was achieved. In contrast to previously investigated iron-based ternary Fe–Al–Cr and Fe–Ti–Cr alloys, no so-called “mixed” nitrides developed in the Fe–V–Si alloy. Instead, in the first stage, all vanadium precipitated as crystalline VN and, subsequently, all silicon precipitated as amorphous Si3N4. Moreover, the precipitation rate of Si3N4 in the nitrided ternary Fe–V–Si alloy was much lower than in the binary Fe–Si alloy nitrided under identical conditions. This much lower Si3N4-precipitation rate is attributed to the presence of first precipitated VN: coherency strains caused by the (semi-) coherent VN precipitates interact with the strain fields surrounding the Si3N4 precipitates and are obstacles to the movement of dislocations necessarily introduced in the ferrite matrix by growing Si3N4 precipitates. This interpretation is supported by additional experiments, in which the first precipitated VN platelets were coarsened by annealing before subsequent nitriding led to, now much faster, Si3N4 precipitation

  4. Elevated temperature corrosion behavior of iron-base ternary alloys that develop Cr/sub 2/O/sub 3/ and/or Al/sub 2/O/sub 3/ barrier scales

    Energy Technology Data Exchange (ETDEWEB)

    Nagarajan, V.; Levy, A.V.

    1978-05-01

    The elevated temperature corrosion behavior of iron-base ternary alloys that develop Cr/sub 2/O/sub 3/ and/or Al/sub 2/O/sub 3/ barrier scales was investigated by exposing them to a mixed gas environment at 982/sup 0/C whose PO/sub 2/ was approximately 10/sup -18/ atm and whose PS/sub 2/ was approximately 10/sup -6/ atm. The alloys containing 18% Cr and 2.5 to 5% Al had the best corrosion resistance of the alloys tested. They developed a duplex Cr/sub 2/O/sub 3//Al/sub 2/O/sub 3/ scale through which sulfur did not readily diffuse. The 18% Cr alloy containing only 1% Al formed a Cr/sub 2/O/sub 3/ scale and had poor corrosion resistance because of rapid sulfur diffusion through the scale. Alloys that contained 10% Al and 0 to 15% Cr did not have good corrosion resistance because of sulfur diffusion through the single Al/sub 2/O/sub 3/ scale which formed. Alloys with 18% Cr that contained Si as a ternary addition did not develop continuous SiO/sub 2/ layers beneath the Cr/sub 2/O/sub 3/ outer scale and exhibited poor corrosion resistance.

  5. Iron-based alloy and nitridation treatment for PEM fuel cell bipolar plates

    Science.gov (United States)

    Brady, Michael P. [Oak Ridge, TN; Yang, Bing [Oak Ridge, TN; Maziasz, Philip J. [Oak Ridge, TN

    2010-11-09

    A corrosion resistant electrically conductive component that can be used as a bipolar plate in a PEM fuel cell application is composed of an alloy substrate which has 10-30 wt. % Cr, 0.5 to 7 wt. % V, and base metal being Fe, and a continuous surface layer of chromium nitride and vanadium nitride essentially free of base metal. A oxide layer of chromium vanadium oxide can be disposed between the alloy substrate and the continuous surface nitride layer. A method to prepare the corrosion resistant electrically conductive component involves a two-step nitridization sequence by exposing the alloy to a oxygen containing gas at an elevated temperature, and subsequently exposing the alloy to an oxygen free nitrogen containing gas at an elevated temperature to yield a component where a continuous chromium nitride layer free of iron has formed at the surface.

  6. Modelling low pay transition probabilities, accounting for panel attrition, non-response, and initial conditions

    OpenAIRE

    Cappellari, Lorenzo; Jenkins, Stephen P.

    2004-01-01

    We model annual low pay transition probabilities taking account of three potentially endogenous selections: two sample drop-out mechanisms (panel attrition, non-employment) and ‘initial conditions’ (base-year low pay status). This model, and variants that ignore one or more of these selection mechanisms, are fitted to data for men from the British Household Panel Survey. Tests of the ignorability of the endogenous selection mechanisms suggest that ‘economic’ selection mechanisms such ...

  7. Understanding the attrition of cases of child sexual abuse and neglect in the criminal justice system

    OpenAIRE

    Gallagher, Bernard

    1999-01-01

    Research on the processing of child abuse cases has been dominated by a focus on the preparation of cases for criminal trial. However, police statistics indicate that the large majority of cases (as many as 85 per cent) are terminated, either by the police or the Crown Prosecution Service, before this stage. The police may decide not to charge, and the CPS may decline advise cases or decide not to prosecute. General child sexual abuse studies show that the termination or attrition of cases ma...

  8. Microstructure and Mechanical Property of Ni Metal Treated by Surface Mechanical Attrition

    Institute of Scientific and Technical Information of China (English)

    Wen Chun-sheng; Rong Yong-hua; T.Y. Hsu (Xu Zu-yao)

    2004-01-01

    A nanostructured surface layer can be formed in Ni metal treated by surface mechanical attrition (SMA). The microstructure was investigated by using optical microscope, X-ray diffractometer and transmission electron microscope,respectively. Mechanical property measurements indicate that the yield strength of the surface layer raises significantly while the tensile strength somewhat changes and the elongation percentage reduces severely compared with that of the inside layer. Meanwhile, yield-drop-like phenomenon occurs in the surface layer after SMA treatment. In order to compare the mechanical behavior of nanostructured materials with two phases, Fe-30Ni nanostructured alloy was also investigated.

  9. Ni-P-SiC composite coatings electroplated on carbon steel assisted by mechanical attrition

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Ni-P-SiC composite coatings were electroplated on carbon steel substrate assisted by mechanical attrition(MA).The MA action was conducted by dispersing glass balls on the cathodic surface,vibrating in the horizontal direction.The experimental results show that,under the assistant of MA action,the adhesion of Ni-P-SiC coating on the steel substrate can be improved effectively,and the Ni-P-SiC coatings exhibit a crystallized structure and Ni-P matrix can combine tightly with SiC particles,and the hardness and...

  10. Improved Fatigue Behavior of Pipeline Steel Welded Joint by Surface Mechanical Attrition Treatment (SMAT)

    Institute of Scientific and Technical Information of China (English)

    Yu Wang; Min Huang; Lei Zhou; Zhixin Cong; Huilin Gao

    2009-01-01

    A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment (SMAT). After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample, and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints. In the low and the high amplitude stress regimes, both fatigue strength and fatigue life were enhanced. Formation of the nanostructured surface layer played more important role in the enhanced fatigue behavior than that of residual stress induced by the SMAT.

  11. Attrition of Dolomitic Lime in a Fluidized-Bed at High Temperature

    OpenAIRE

    Hartman, M; Svoboda, K.; Pohořelý, M. (Michael); Šyc, M. (Michal); Jeremiáš, M. (Michal)

    2013-01-01

    The results of an experimental study on the rate of attrition of quicklime catalyst/sorbent in a high-temperature, spouted fluidized bed with quartz sand are presented. Batchwise measurements were conducted at 850oC in an electrically heated gasification reactor of an inner diameter of 5.1 cm with two sizes (605 and 980 µm) of high-grade, dolomitic limestone calcine (quicklime, lime). In addition to the influence of the particle size, the effect of operating (elapsed) time was investigated at...

  12. DECARBONATION AND ATTRITION OF CALCITE IN A PLASMA SPOUTED BED REACTOR

    OpenAIRE

    G. Flamant; Chraibi, M. (Mohamede); Vallbona, G.; Bertrand, C

    1990-01-01

    The mechanical power and the thermal energy for the processing of calcite are the main part of the energy consumption in cement industry. Experimental results about particle size reduction and calcination of CaCO3 in a plasma spouted bed reactor are presented in this paper. The main parameter seems to be the specific enthalpy of the plasma jet, it ranges between 3 kWh.m-3 20 kWh.m-3. The variations of the attrition rate, decomposition rate and particle size distribution are discussed.

  13. Attitudes of non-practicing chiropractors: a pilot survey concerning factors related to attrition

    Directory of Open Access Journals (Sweden)

    Wyatt Lawrence H

    2010-11-01

    Full Text Available Abstract Background Research into attitudes about chiropractors who are no longer engaged in active clinical practice is non-existent. Yet non-practicing chiropractors (NPCs represent a valid sub-group worthy of study. Aim The purpose of this research was to assess attrition attitudes of NPCs about the chiropractic profession and develop a scale to assess such attitudes. Methods A 48 item survey was developed using the PsychData software. This survey included 35 Likert-style items assessing various aspects of the profession namely financial, educational, psychosocial and political. An internet discussion site where NPCs may be members was accessed for recruitment purposes. Results A total of 70 valid responses were received for analysis. A majority of respondents were male with 66% being in non-practice status for 3 to 5 years and less with 43% indicating that they had graduated since the year 2000. Most respondents were employed either in other healthcare professions and non-chiropractic education. A majority of NPCs believed that business ethics in chiropractic were questionable and that overhead expense and student loans were factors in practice success. A majority of NPCs were in associate practice at one time with many believing that associates were encouraged to prolong the care of patients and that associate salaries were not fair. Most NPCs surveyed believed that chiropractic was not a good career choice and would not recommend someone to become a chiropractor. From this survey, a 12 item scale was developed called the "chiropractor attrition attitude scale" for future research. Reliability analysis of this novel scale demonstrated a coefficient alpha of 0.90. Conclusion The low response rate indicates that findings cannot be generalized to the NPC population. This study nonetheless demonstrates that NPCs attrition attitudes can be assessed. The lack of a central database of NPCs is a challenge to future research. Appropriate

  14. ADVANCED NICKEL-BASED AND NICKEL-IRON-BASED SUPERALLOYS FOR CIVIL ENGINEERING APPLICATIONS

    Institute of Scientific and Technical Information of China (English)

    U. Brill

    2005-01-01

    The use of high-temperature materials is especially important in power station construction,heating systems engineering, furnace industry, chemical and petrochemical industry, waste incineration plants, coal gasification plants and for flying gas turbines in civil and military aircrafts and helicopters. Particularly in recent years, the development of new processes and the drive to improve the economics of existing processes have increased the requirements significantly so that it is necessary to change from well-proven materials to new alloys. Hitherto, heat resistant ferritic steels sufficed in conventional power station constructions for temperatures up to 550℃ newly developed ferritic/martensitic steels provide sufficient strength up to about 600-620℃. In new processes, e.g. fiuidized-bed combustion of coal, process temperatures up to 900℃ occur. However, this is not the upper limit, since in combustion engines, e.g. gas turbines. Material temperatures up to 1100℃ are reached locally. Similar development trends can also be identified in the petrochemical industry and in the heat treatment and furnace engineering. The advance to ever higher material temperatures now not only has the consequence of having to use materials with enhanced high-strength properties, considerable attention now also has to be given to their chemical stability in corrosive media. Therefore not only examples of the use of high-temperature alloys for practical applications will be given but also be contributed to some general rules for material selection with regard to their high-temperature strength and corrosion resistance.

  15. Analysis of the attrition of a calcining limestone in a carbonation/calcination pilot plant to capture CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    B. Gonzalez; M. Alonso; I. Rodrguez; G. Grasa; J.C. Abanades [CSIC-INCAR Spanish Research Council, Oviedo (Spain)

    2009-07-01

    There is an increasing interest in CO{sub 2} looping cycles that involve the repeatedly calcination and carbonation of the sorbent as a way to capture CO{sub 2} from flue gases during the carbonation step, and the generation of a pure stream of CO{sub 2} in the oxyfired calcination. Attrition of the material in these interconnected fluidized bed reactors is one of the issues of concern. Attrition of limestone derived materials has been studied in fluidized-bed systems by many authors. Many CFB combustors in the world can cope with attrition problems of this material during repeated circulation in their life time in the boiler. In this work we have investigated the phenomenon of the attrition suffered by the limestone used in a system of two interconnected circulating fluidized bed reactors operating in continuous mode as carbonation and calciner reactors. We have found a rapid initial attrition of the limestone during the calcination step followed by a very stable period (during 140 h of added circulation) where particle size changes are negligible. This is consistent with previous observations of attrition in other systems making use of these materials. However, the comparison of attrition constants reveals that our limestone was particularly fragile during the initial calcination and the first few hours of circulation, and a careful choice of limestone according to their attrition properties will be of importance for future carbonate looping systems. 24 refs., 8 figs., 1 tab.

  16. Identification of cognitive and non-cognitive predictive variables related to attrition in baccalaureate nursing education programs in Mississippi

    Science.gov (United States)

    Hayes, Catherine

    2005-07-01

    This study sought to identify a variable or variables predictive of attrition among baccalaureate nursing students. The study was quantitative in design and multivariate correlational statistics and discriminant statistical analysis were used to identify a model for prediction of attrition. The analysis then weighted variables according to their predictive value to determine the most parsimonious model with the greatest predictive value. Three public university nursing education programs in Mississippi offering a Bachelors Degree in Nursing were selected for the study. The population consisted of students accepted and enrolled in these three programs for the years 2001 and 2002 and graduating in the years 2003 and 2004 (N = 195). The categorical dependent variable was attrition (includes academic failure or withdrawal) from the program of nursing education. The ten independent variables selected for the study and considered to have possible predictive value were: Grade Point Average for Pre-requisite Course Work; ACT Composite Score, ACT Reading Subscore, and ACT Mathematics Subscore; Letter Grades in the Courses: Anatomy & Physiology and Lab I, Algebra I, English I (101), Chemistry & Lab I, and Microbiology & Lab I; and Number of Institutions Attended (Universities, Colleges, Junior Colleges or Community Colleges). Descriptive analysis was performed and the means of each of the ten independent variables was compared for students who attrited and those who were retained in the population. The discriminant statistical analysis performed created a matrix using the ten variable model that was able to correctly predicted attrition in the study's population in 77.6% of the cases. Variables were then combined and recombined to produce the most efficient and parsimonious model for prediction. A six variable model resulted which weighted each variable according to predictive value: GPA for Prerequisite Coursework, ACT Composite, English I, Chemistry & Lab I, Microbiology

  17. Spin and quadrupolar orders in the spin-1 bilinear-biquadratic model for iron-based superconductors

    Science.gov (United States)

    Luo, Cheng; Datta, Trinanjan; Yao, Dao-Xin

    2016-06-01

    Motivated by the recent experimental and theoretical progress of the magnetic properties in iron-based superconductors, we provide a comprehensive analysis of the extended spin-1 bilinear-biquadratic (BBQ) model on the square lattice. Using a variational approach at the mean-field level, we identify the existence of various magnetic phases, including conventional spin dipolar orders (ferro- and antiferromagnet), novel quadrupolar orders (spin nematic), and mixed dipolar-quadrupolar orders. In contrast to the regular Heisenberg model, the elementary excitations of the spin-1 BBQ model are described by the SU(3) flavor-wave theory. By fitting the experimental spin-wave dispersion, we determine the refined exchange couplings corresponding to the collinear antiferromagnetic iron pnictides. We also present the dynamic structure factors of both spin dipolar and quadrupolar components with connections to the future experiments.

  18. Decreasing operating potential for water electrolysis to hydrogen via local confinement of iron-based soft coordination suprapolymers.

    Science.gov (United States)

    Liang, Yawei; Xu, Limin; Zhou, Yinglin; Zhang, Xinxiang; Huang, Jianbin; Yan, Yun

    2013-10-14

    Currently there is intense interest in decreasing the operating potential for hydrogen evolution in water electrolysis to considerably decrease the energy cost. In this work we report a significant decrease of the operating potential for hydrogen evolution from neutral water mediated by an iron based soft coordination polymer (Fe(III)-SCSP). The creation of a local acidic environment with a thickness in the range of ~40 nm on the surface of a glassy carbon electrode allows enrichment of H(+) on the GCE, so that the operating potentials were effectively decreased. This strategy thus generates a new paradigm for lowering the operating potential of hydrogen generation from neutral water without the use of additional acids and organic cosolvents. PMID:23949627

  19. Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion

    Institute of Scientific and Technical Information of China (English)

    CHEN Qing-Jun; SHEN Jun; FAN Hong-Bo; SUN Jian-Fei; HUANG Yong-Jiang; MCCARTNEY D. G.

    2005-01-01

    @@ A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.

  20. Anisotropic energy-gaps of iron-based superconductivity from intra-band quasiparticle interference in LiFeAs

    International Nuclear Information System (INIS)

    Cooper pairing in the Fe-based superconductors is thought to occur due to the projection of the antiferromagnetic interactions between iron atoms onto the complex momentum-space electronic structure. A key consequence is that distinct anisotropic energy gaps Δi(k) with specific relative orientations should occur on the different electronic bands i. To determine this previously unresolved gap structure high-precision spectroscopy is required. Here we introduce the STM technique of intra-band Bogolyubov quasiparticle scattering interference (QPI) to iron-based superconductor studies, focusing on LiFeAs. We identify the QPI signatures of three hole-like dispersions and, by introducing a new QPI technique, determine the magnitude and relative orientations of corresponding anisotropic Δi(k). Intra-band Bogolyubov QPI therefore yields the spectroscopic information required to identify the mechanism of superconductivity in Fe-based superconductors.

  1. Effect of Addition Sequence during Neutralization and Precipitation on Iron-based Catalysts for High Temperature Shift Reaction

    Institute of Scientific and Technical Information of China (English)

    Li Wei; Zhu Jianhua; Mou Zhanjun

    2007-01-01

    The preparation of the iron-based catalysts promoted by cobalt with a small amount of copper and aluminum for the high temperature shift reaction (HTS) with different sequences of adding catalyst raw materials during neutralization and precipitation was investigated. XRD,BET and particle size distribution (PSD) were used to characterize the prepared catalysts. It was found that the catalyst crystals were all γ-Fe2O3,and the intermediate of the catalyst after aging was Fe3O4. The crystallographic form of the catalyst and its intermediate was not affected by the addition sequence in the neutralization and precipitation process. The results showed that the specific surface area and the particle size of the catalysts depended on the addition sequence to the mother liquor. Cobalt with a small amount of copper and aluminum could increase the specific surface area and decrease the particle size of catalysts.

  2. Removal of As, Cd, Cr, Cu, Ni and Zn from polluted water using an iron based sorbent

    DEFF Research Database (Denmark)

    Genc-Fuhrman, Hülya; Wu, P.; Zhou, Y.;

    2008-01-01

    In this study fixed-bed sorption filters are filled with an iron based sorbent (ferrosorp plus, FP) and used to remove a range of heavy metals (i.e. As, Cd, Cr, Cu, Ni, and Zn) from polluted water. It is found that FP is very effective at simultaneous removal of the heavy metals, and the magnitude...... average inflow pH of 6.8 and heavy metal concentration of ≈2.8 μM. It is concluded that FP has high affinity to heavy metals and it can be used (e.g. as a filter medium) to treat waters containing a wide range of heavy metals, e.g. stormwater, industrial wastewater....

  3. Continuous production of iron-based nanocrystals by laser pyrolysis. Effect of operating variables on size, composition and magnetic response

    Science.gov (United States)

    Malumbres, A.; Martínez, G.; Mallada, R.; Hueso, J. L.; Bomatí-Miguel, O.; Santamaría, J.

    2013-08-01

    Well dispersed iron-based magnetic nanoparticles have been prepared by gas phase laser-driven decomposition of iron pentacarbonyl. Agglomeration of the newly synthesized nanoparticles could be avoided by using a liquid collection system in which the exit stream from the laser reactor was bubbled through triethylene glycol (TREG). The effect of different experimental parameters (precursor concentration, laser power, working pressure, residence time) was studied and, by selecting the appropriate conditions, the size of the resulting magnetic nanocrystals could be tuned from ultrasmall (ca. 2.5 nm) to around 12 nm. For nanoparticle sizes around 10 nm and larger a metallic iron core could be preserved. These iron/iron oxide core-shell compositions exhibit very high values of magnetization, 127 emu g-1.

  4. Sleep bruxism in individuals with and without attrition-type tooth wear: An exploratory matched case-control electromyographic study

    OpenAIRE

    Jonsgar, Christine; Hordvik, Paul-Arne; Berge, Morten Eirik; Johansson, Ann-Katrin Gerd; Svensson, Peter; Johansson, Anders

    2015-01-01

    OBJECTIVES: To examine if there is a difference in possible sleep bruxism activity (SB) in subjects with or without attrition-type tooth wear. METHODS: Sixteen individuals with pronounced attritional-type tooth wear were compared with sex and aged matched controls without tooth wear by means of measurement of electromyographic (EMG) activity during a minimum of four consecutive nights of sleep. Mean age and range for the study- and control- group was 23.7 years (range 19.9-28.5) and 23.6 y...

  5. Effect of mass transfer limitations on catalyst performance during reduction and carburization of iron based Fischer-Tropsch synthesis catalysts

    Institute of Scientific and Technical Information of China (English)

    Akbar; Zamaniyan; Yadollah; Mortazavi; Abbas; Ali; Khodadadi; Ali; Nakhaei; Pour

    2013-01-01

    Existence of intraparticle mass transfer limitations under typical Fischer-Tropsch synthesis has been reported previously,but there is no suitable study on the existence of intraparticle diffusion limitations under pretreatment steps (reduction and activation) and their effect on catalytic performance for iron based catalysts.In this study,Fe-Cu-La-SiO2 catalysts were prepared by co-precipitation method.To investigate the intraparticle mass transfer limitation under reduction,activation and reaction steps,and its effect on catalytic performance,catalyst pellets with different sizes of 6,3,1 and 0.5 mm have been prepared.All catalysts were calcined,pretreated and tested under similar conditions.The catalysts were activated in hydrogen (5%H2in N2) at 450℃ for 3 h and exposed to syngas (H2/CO=1) at 270℃ and atmospheric pressure for 40 h.Afterwards,FTS reaction tests were performed for approximately 120 h to reach steady state conditions at 290℃,17 bar and a feed flow (syngas H2/CO=1) rate of 3 L/h (STP).Using small pellets resulted in higher CO conversion,FT reaction rate and C5+ productivity as compared with larger pellets.The small pellets reached steady state conditions just 20 h after starting the reaction.Whereas for larger pellets,CO conversion,FT reaction rate and C5+ productivity increased gradually,and reached steady state and maximum values after 120 h of operation.The results illustrate that mass transfer limitations exist not only for FTS reaction but also for the reduction and carburization steps which lead to various phase formation through catalyst activation.Also the results indicate that some effects of mass transfer limitations in activation step,can be compensated in the reaction step.The results can be used for better design of iron based catalyst to improve the process economy.

  6. Corrosion of iron-base waste package container materials in salt environments

    International Nuclear Information System (INIS)

    Low-carbon ferrous materials are being considered for waste package container materials in high-level nuclear waste salt repositories. The short-term corrosion rates of ASTM Type A216 Grade WCA steel have been determined under both brine-only and moist-salt conditions at 1500C for time ranging from 1 to 12 months. Tests run in moist salt with low Mg content brine yielded relatively low corrosion rates, below an adjusted value of 0.032 mm (1.3 mils) per year at 1500C. Corrosion rates in brine-only and moist-salt environments containing high concentrations of Mg were found to be a factor of 20 to 50 higher over the same experimental test times, depending on the steel's heat treatment and the specific test conditions. Austenitizing treatment reduced the corrosion resistance of the material. In the case of the as-cast steel, the measured average corrosion rates decreased with time by more than a factor of two during the 12-month testing program. Post-test examinations have shown that the corrosion product is a complex Fe-Mg hydroxide of amakinite structure, as opposed to the Fe3O4 observed in the low-Mg brines. The Mg content of the environment is believed to be a major factor leading to the higher corrosion rates and studies to understand the operative corrosion mechanisms are in progress. 1 ref., 4 figs., 2 tabs

  7. Facile fabrication of iron-based superhydrophobic surfaces via electric corrosion without bath

    Science.gov (United States)

    Sun, Qinghe; Liu, Hongtao; Chen, Tianchi; Wei, Yan; Wei, Zhu

    2016-04-01

    Superhydrophobic surface is of wide application in the field of catalysis, lubrication, waterproof, biomedical materials, etc. The superhydrophobic surface based on hard metal is worth further study due to its advantages of high strength and wear resistance. This paper investigates the fabrication techniques towards superhydrophobic surface on carbon steel substrate via electric corrosion and studies the properties of as-prepared superhydrophobic surface. The hydrophobic properties were characterized by a water sliding angle (SA) and a water contact angle (CA) measured by the Surface tension instrument. A Scanning electron microscope was used to analyze the structure of the corrosion surface. The surface compositions were characterized by an Energy Dispersive Spectrum. The Electrochemical workstation was used to measure its anti-corrosion property. The anti-icing performance was characterized by a steam-freezing test in Environmental testing chamber. The SiC sandpaper and 500 g weight were used to test the friction property. The research result shows that the superhydrophobic surface can be successfully fabricated by electrocorrosion on carbon steel substrate under appropriate process; the contact angle of the as-prepared superhydrophobic surface can be up to 152 ± 0.5°, and the sliding angle is 1-2°; its anti-corrosion property, anti-icing performance and the friction property all show an excellent level. This method provides the possibility of industrialization of superhydrophobic surface based on iron substrate as it can prepare massive superhydrophobic surface quickly.

  8. Effects of sample attrition in a longitudinal study of the association between alcohol intake and all-cause mortality

    DEFF Research Database (Denmark)

    Thygesen, Lau C; Johansen, Christoffer; Keiding, Niels;

    2008-01-01

    BACKGROUND AND AIMS: Longitudinal studies show higher mortality among abstainers and heavy drinkers than among light and moderate alcohol consumers. The influence on this association of missing information on alcohol intake due to attrition (dropout) has not been examined previously. The aims of...

  9. Determinants of Attrition to Follow-Up in a Multicentre Cohort Study in Children-Results from the IDEFICS Study

    DEFF Research Database (Denmark)

    Hense, Sabrina; Pohlabeln, Hermann; Michels, Nathalie;

    2013-01-01

    -being (OR = 1.46; 99% CI: 1.19, 1.79) was lacking. Drop-out proportion rose with the number of missing items. Overweight, low education, single parenthood and low well-being scores were independent determinants of attrition. Baseline participation, and the individual determinant effects seemed unrelated to...

  10. STEM Attrition: College Students' Paths into and out of STEM Fields. Statistical Analysis Report. NCES 2014-001

    Science.gov (United States)

    Chen, Xianglei

    2013-01-01

    Producing sufficient numbers of graduates who are prepared for science, technology, engineering, and mathematics (STEM) occupations has become a national priority in the United States. To attain this goal, some policymakers have targeted reducing STEM attrition in college, arguing that retaining more students in STEM fields in college is a…

  11. The Effect of an Intrusive Advisement Program on First-term Freshmen Attrition. AIR Forum 1981 Paper.

    Science.gov (United States)

    Tata, Chet, Jr.

    The effect of an intrusive advisement program implemented at the University of Texas at Arlington to reduce first-term freshmen attrition was studied. A randomly selected sample of 1,100 entering fall 1980 freshmen (51 percent) was assessed in terms of student characteristics, based on questionnaire responses. The questionnaire also determined…

  12. Evaluating motivational interviewing to promote breastfeeding by rural Mexican-American mothers: the challenge of attrition.

    Science.gov (United States)

    Wilhelm, Susan L; Aguirre, Trina M; Koehler, Ann E; Rodehorst, T Kim

    2015-03-01

    Although most Hispanic/Latino-American mothers initiate breastfeeding, duration and exclusivity of breastfeeding remain low. We explored whether a motivational interviewing (MI) intervention could help rural Mexican-American mothers continue breastfeeding. We used a two-group (MI intervention n = 26, attention control [AC] n = 27) repeated measures experimental design. Assessments and interventions occurred at 3 days, 2 weeks, and 6 weeks postpartum (time points when mothers are particularly vulnerable to discontinuing breastfeeding), with a final phone assessment at 6 months postpartum. We collected demographic data and measured intent to breastfeed for 6 months (intent question), self-efficacy (Breastfeeding Self-Efficacy Scale-Short Form), and collected breastfeeding information (breastfeeding assessment questionnaire). Independent t-tests and Mann Whitney U non-parametric tests were used to evaluate group differences (α = 0.05). High levels of attrition by week 6 impaired our ability to evaluate the potential of our MI intervention. No significant differences were found between groups for any of the outcome variables (intent to breastfeed for 6 months, breastfeeding self-efficacy, and duration of breastfeeding). Though the mothers intended to breastfeed for 6 months and were confident in their ability to do so, most did not breastfeed for 6 months. At 6 months, mothers receiving the MI intervention had breastfed an average of 90 days compared to 82 days for those receiving the AC sessions and 22% of the mothers in each group were still breastfeeding at some level. Because of the impact of attrition during this study, we discuss factors that contributed to attrition and approaches to lessen this problem in future studies. Such efforts may require a greater investment of time and resources and should be budgeted accordingly. Culturally appropriate interventions are needed to help rural Mexican-American mothers meet their breastfeeding goals, thus

  13. Factors associated with long-term antiretroviral therapy attrition among adolescents in rural Uganda: a retrospective study

    Directory of Open Access Journals (Sweden)

    Stephen Okoboi

    2016-07-01

    Full Text Available Introduction: As access to antiretroviral therapy (ART increases, the success of treatment programmes depends on ensuring high patient retention in HIV care. We examined retention and attrition among adolescents in ART programmes across clinics operated by The AIDS Support Organization (TASO in Uganda, which has operated both facility- and community-based distribution models of ART delivery since 2004. Methods: Using a retrospective cohort analysis of patient-level clinical data, we examined attrition and retention in HIV care and factors associated with attrition among HIV-positive adolescents aged 10–19 years who initiated ART at 10 TASO clinics between January 2006 and December 2011. Retention in care was defined as the proportion of adolescents who had had at least one facility visit within the six months prior to 1 June 2013, and attrition was defined as the proportion of adolescents who died, were lost to follow-up, or stopped treatment. Descriptive statistics and Cox proportional hazards regression models were used to determine the levels of retention in HIV care and the factors associated with attrition following ART initiation. Results: A total of 1228 adolescents began ART between 2006 and 2011, of whom 57% were female. The median duration in HIV care was four years (IQR=3–6 years. A total of 792 (65% adolescents were retained in care over the five-year period; 36 (3% had died or transferred out and 400 (32% were classified as loss to follow-up. Factors associated with attrition included being older (adjusted hazard ratio (AHR=1.38, 95% confidence interval (CI 1.02–1.86, having a higher CD4 count (250+ cells/mm3 at treatment initiation (AHR=0.49, 95% CI 0.34–0.69 and HIV care site with a higher risk of attrition among adolescents in Gulu (AHR=2.26; 95% CI 1.27–4.02 and Masindi (AHR=3.30, 95% CI 1.87–5.84 and a lower risk of attrition in Jinja (AHR=0.24, 95% CI 0.08–0.70. Having an advanced WHO clinical stage at initiation

  14. First-principle electronic structure calculations for magnetic moment in iron-based superconductors: An LSDA + negative U study

    Science.gov (United States)

    Nakamura, H.; Hayashi, N.; Nakai, N.; Okumura, M.; Machida, M.

    2009-10-01

    In order to resolve a discrepancy of the magnetic moment on Fe between the experimental and calculation results, we perform first-principle electronic structure calculations for iron-based superconductors LaFeAsO1-x and LiFeAs also show similar SDW. So far, the first-principle calculations on LaFeAsO actually predicted the SDW state as a ground state. However, the predicted magnetic moment (∼2 μB) per an Fe atom is much larger than the observed one (∼0.35 μB) in experiments [2,4]. The authors suggested that the discrepancy can be resolved by expanding U into a negative U range within LSDA + U framework. In this paper, we revisit the discrepancy and clarify why the negative correction is essential in these compounds. See Ref. [5] for the details of calculation data by LSDA + negative U. In the first-principle calculation on compounds including transition metals, the total energy is frequently corrected by “LSDA + U” approach. The parameter U is theoretically re-expressed as U(≡U-J), where U is the on-site Coulomb repulsion (Hubbard U) and J is the atomic-orbital intra-exchange energy (Hund’s coupling parameter) [6]. The parameter U employed in the electronic structure calculations is usually positive. The positivity promotes the localized character of d-electrons and enhances the magnetic moment in the cases of magnetically ordered compounds. Normally, this positive correction successfully works. In choosing the parameter, one can principally extend the parameter U range to a negative region. The negative case [7] is not popular, but it can occur in the following two cases [8]: (i) the Hubbard U becomes negative and (ii) the intra-exchange J is effectively larger than the Hubbard U. The case (i) has been suggested by many authors based on various theoretical considerations. Here, we note that U should be estimated once screening effects on the long-range Coulomb interaction are taken into account. In fact, small U has been reported [9]. Thus, when the

  15. Research Progress on Iron-based Biodegradable Coronary Stents%可降解铁基心血管支架材料的研究进展

    Institute of Scientific and Technical Information of China (English)

    徐文利; 吴竞尧; 谭丽丽; 杨柯

    2012-01-01

    The history and current status of studies on iron-based coronary stents are summarized, and the advantage of iron-based biodegradable stents and preliminary results of animal tests are presented. The results show that iron-based alloy is a suitable biodegradable coronary stent material, but the low degradation rate is its existing problem. On the basis of the analysis of the novel research progress investigation of biodegradable iron-based alloy, it is presented that though many useful attempts have been made to improve the degradation rate, no instructive result has been achieved. It is suggested that the biodegradation mechanism of iron-based alloy in human body be studied to develop novel methods to improve its degradation rate.%概述了可降解铁基心血管支架材料的研究历史及现状,介绍了可降解铁基心血管支架的优势及其早期动物实验结果.结果表明,铁基合金是一种非常适宜制作可降解心血管支架的材料,但其存在降解速度过慢的问题.在分析可降解铁基合金的最新研究进展基础上,认为在提高铁基合金的降解速度方面虽然目前已经进行了很多有益的尝试,但是尚无极具意义的结果.同时提出,应在对人体环境下铁基合金的降解行为研究基础上发展新的提高铁基合金降解速度的方法.

  16. Five-year survey of medical student attrition in a medical school in Nigeria: a pilot study

    Directory of Open Access Journals (Sweden)

    Ogugua A Egwu

    2010-10-01

    Full Text Available Ogugua A Egwu1, Godson E Anyanwu21Department of Anatomy, Faculty of Basic Medical Sciences, Ebonyi State University, Ebonyi State; 2Department of Anatomy, College of Medicine, Faculty of Medical Sciences, University of Nigeria, Enugu State, NigeriaBackground: Student attrition represents a waste of career opportunity and, at times, results in a holistic loss of sense of self-worth for the students involved. The aim of this study was to evaluate the nature, causes, and impact of medical student attrition in Nigeria.Method: A pilot analysis was undertaken using the records of students who failed at medical school as a result of inability to pass the second MBBS examination at Ebonyi State University, Abakaliki, Nigeria, between 2002 and 2007. Some of these students were interviewed using a structured questionnaire.Results: Data analysis showed that 58 (7.8% of the students admitted into preclinical class withdrew from their study. Thirty-six (62.1% were males and the rest were females. Thirteen of those withdrawn were interviewed, and 53.8% of them believed they had poor academic ability, while 15.4% attributed their withdrawal to family pressure. No record of guidance or counseling session programs was noted for these students either at the point of withdrawal from the faculty and on the choice of a new career path.Conclusion: As a result of the high attrition rate due to low academic ability, efforts should be made to check students for evidence of this at the point of admission to medicine training. Also, more accommodating teaching programs should be encouraged in faculties to accommodate students with such challenges. Good guidance and counseling programs should be encouraged to handle these inevitable cases of attrition when they occur, to avoid the demoralizing low self-esteem that plagues these individuals for the rest of their lives.Keywords: medical students, attrition, medical education, Nigeria

  17. Attrition of Knowledge Workforce in Healthcare in Northern parts of India – Health Information Technology as a Plausible Retention Strategy

    Directory of Open Access Journals (Sweden)

    R. K. Suri

    2012-01-01

    Full Text Available Faced with a global shortage of skilled health workers due to attrition, countries are struggling to build and maintain an optimum knowledge workforce in healthcare for delivering quality healthcare services. Forces that affect healthcare professional turnover needs to be addressed before a competent uniformly adoptable strategy could be proposed for mitigating the problem. In this study we investigate the effect of the socio –demographic characteristics on attrition of healthcare knowledge workforce in northern parts of India that have a wide gradient of rural and urban belt, taking into account both public and private healthcare organizations. For this purpose healthcare professional attrition tracking survey (HATS was designed. The data has been collected from a random sample of 807 respondents consisting of doctors, nurses, paramedics and administrators to explore the relationships between various factors acting as antecedents in affecting the job satisfaction, commitment and intention of a healthcare professional to stay in the job. Structured questionnaires were utilized as the data collection tools. Both public and private healthcare organizations in urban and rural areas were covered for the survey. Descriptive statistics and factor analyses using analysis on Rotated Factor Matrix using Principal Components Analysis (PCA in SPSS 16.0 package were carried out. Six factors of attrition namely Compensation and perks, Work Life Balance, Sense of Accomplishment, Work load leading to exhaustion, Need for automation and technology improvement, Break Monotony of Work have been identified as the main factors with a data reliability of 0.809%. Based on the survey response and analysis, a highly possible strategy of utilizing information technology implementation for increasing worker motivation, job satisfaction and commitment to reduce attrition has been proposed.

  18. Increased attrition of leukocyte telomere length in young adults is associated with poorer cognitive function in midlife.

    Science.gov (United States)

    Cohen-Manheim, Irit; Doniger, Glen Michael; Sinnreich, Ronit; Simon, Ely Samuel; Pinchas, Ronit; Aviv, Abraham; Kark, Jeremy David

    2016-02-01

    Evidence for an association of leukocyte telomere length (LTL) with cognitive function, predominantly in older adults, is inconsistent. No report has examined the association of LTL dynamics (age-specific LTL and its attrition rate) with cognitive function. We aimed to examine the association of LTL dynamics over 13 years in young adulthood with cognitive function in midlife. 497 individuals who had LTL measured at ages 28-32 and 41-46 years were assessed at ages 48-52 for global cognitive function and its five specific component domains with a NeuroTrax computerized test battery. Multivariable regression and logistic models were applied for cognition treated as a continuous and categorical variable, respectively. We found that LTL attrition (adjusted for sex, baseline LTL and potential confounders including socioeconomic variables) was inversely associated with global cognition (standardized β = -.119, p = .004) and its component domains: information processing speed (β = -.102, p = .024), visual-spatial function (β = -.102, p = .017) and memory (β = -.093, p = .045), but less so for the attention and executive domains. The multivariable-adjusted odds ratio for low global cognition comparing the upper versus lower thirds of LTL attrition was 2.12 (95 % CI 1.11-4.08, p for trend = .023). There was no association of baseline or follow-up LTL with cognition. No effect modification was evident for sex, smoking or inflammatory markers. In conclusion, faster LTL attrition in young adulthood was associated with poorer global and domain-specific cognitive function in midlife, suggesting that more rapid LTL attrition may be predictive of cognitive aging in healthy young adults. PMID:26076919

  19. Retention and risk factors for attrition in a large public health ART program in Myanmar: a retrospective cohort analysis.

    Directory of Open Access Journals (Sweden)

    Aye Thida

    Full Text Available BACKGROUND: The outcomes from an antiretroviral treatment (ART program within the public sector in Myanmar have not been reported. This study documents retention and the risk factors for attrition in a large ART public health program in Myanmar. METHODS: A retrospective analysis of a cohort of adult patients enrolled in the Integrated HIV Care (IHC Program between June 2005 and October 2011 and followed up until April 2012 is presented. The primary outcome was attrition (death or loss-follow up; a total of 10,223 patients were included in the 5-year cumulative survival analysis. Overall 5,718 patients were analyzed for the risk factors for attrition using both logistic regression and flexible parametric survival models. RESULT: The mean age was 36 years, 61% of patients were male, and the median follow up was 13.7 months. Overall 8,564 (84% patients were retained in ART program: 750 (7% were lost to follow-up and 909 (9% died. During the 3 years follow-up, 1,542 attritions occurred over 17,524 person years at risk, giving an incidence density of 8.8% per year. The retention rates of participants at 12, 24, 36, 48 and 60 months were 86, 82, 80, 77 and 74% respectively. In multivariate analysis, being male, having high WHO staging, a low CD4 count, being anaemic or having low BMI at baseline were independent risk factors for attrition; tuberculosis (TB treatment at ART initiation, a prior ART course before program enrollment and literacy were predictors for retention in the program. CONCLUSION: High retention rate of IHC program was documented within the public sector in Myanmar. Early diagnosis of HIV, nutritional support, proper investigation and treatment for patients with low CD4 counts and for those presenting with anaemia are crucial issues towards improvement of HIV program outcomes in resource-limited settings.

  20. Efficient and stable iron based perovskite La0.9Ca0.1Fe0.9Nb0.1O3-δ anode material for solid oxide fuel cells

    Science.gov (United States)

    Kong, Xiaowei; Zhou, Xiaoliang; Tian, Yu; Wu, Xiaoyan; Zhang, Jun; Zuo, Wei; Gong, Xiaobo; Guo, Zhanhu

    2016-06-01

    A novel La0.9Ca0.1Fe0.9Nb0.1O3-δ (LCFNb) perovskite for solid oxide fuel cells (SOFCs) anode is prepared by means of the citrate-nitrate route and composited with Ce0.8Sm0.2O1.9 (SDC) by impregnation method to form nano-scaled LCFNb/SDC anode catalytic layers. The single cells with LCFNb and LCFNb/SDC impregnated anodes both achieve relatively high power output with maximum power densities (MPDs) reaching up to 610, 823 mW·cm-2 in H2 at 800 °C, respectively, presenting a high potential of LCFNb for use as SOFCs anode. The power outputs of the single cells with LCFNb/SDC composite anode in CO and syngas (COsbnd H2 mixture) are almost identical to that in H2 at each testing temperature. This composite anode also presents excellent durability in both H2 and CO for as long as 50 h, showing desirable anti-reduction and carbon deposition resistance abilities. Besides, the cell output is stable in 100 ppm H2Ssbnd H2 atmospheres for 20 h at a current density of 600 mA·cm-2 with negligible sulfur accumulation on the anode surface. Hence, a novel iron based perovskite LCFNb anode with remarkable cell performance, carbon deposition resistance and sulfur poisoning tolerance for SOFCs is successfully obtained.

  1. High temperature corrosion of iron-base and nickel-base alloys for hydrogen production apparatus by thermochemical method in H{sub 2}O+SO{sub 3} atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Kurata, Yuji; Suzuki, Tomio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Shimizu, Saburo [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment

    2000-03-01

    Corrosion tests for ten iron-base and nickel-base alloys at 850degC for 1000h in H{sub 2}O + SO{sub 3} atmosphere were carried out to obtain data for selection of candidate container materials in the thermochemical process which produces hydrogen from water by use of iodine and sulfur as circulating materials. The following results were obtained: (1) Oxidation, spallation of corrosion film, uniform corrosion and grain boundary penetration composed of internal oxidation and sulfuration occur in this atmosphere and the corrosion proceeds by grain boundary penetration. (2) SUS304, SUS316 and Hastelloy C276 are inferior in corrosion resistance and SUS329J4L is superior among ten alloys used in this experiment. Alloys such as Alloy 800H and Hastelloy XR show intermediate corrosion resistance. (3) Oxide films of alloys containing iron and chromium are mostly composed of outer iron-oxide and inner chromium-oxide. Sulfur concentrates at scale/metal interfaces and grain boundary penetration portions, and sulfides form. (4) Corrosion in this atmosphere could be expressed using the parabolic law between the grain boundary penetration depth and time. It is considered that causes of the apparently observed parabolic law were a high concentration of SO{sub 3} and change of the gas composition caused by catalytic action of the corrosion film formed with the progress of corrosion. (author)

  2. Predictors of Study Attrition in a Randomized Controlled Trial Evaluating a Perinatal Home-Visiting Program with Mothers with Psychosocial Vulnerabilities.

    Directory of Open Access Journals (Sweden)

    Stéphanie Foulon

    Full Text Available Randomised controlled trials evaluating perinatal home-visiting programs are frequently confronted with the problem of high attrition rates. The aim of the present study is to identify predictors of study attrition in a trial evaluating a perinatal home-visiting program in France.CAPEDP is a French randomized trial comparing a perinatal home-visiting program using psychologists versus usual care (N = 440. The first assessment was at inclusion into the trial at the 27th week of pregnancy and the final assessment when the child reached the age of two. Attrition rates were calculated at 3 and 24 months postpartum. Stepwise logistic regression was used to identify predictors of early (between inclusion and 3 months postpartum and later (between 3 and 24 months postpartum attrition among social, psychological and parenting factors.Attrition rates were 17% and 63% at 3 and 24 months respectively. At 24 months, there was significantly more attrition in the control arm (70.6% compared to the intervention arm (55.2%. Five independent predictors of early attrition were identified: having already had an abortion; having greater attachment insecurity as measured with the Vulnerable Attachment Style Questionnaire (VASQ; having lower global severity of psychiatric symptoms as assessed with the Symptom Check-List (SCL-90 at inclusion, being neither currently employed nor studying; and declaring no tobacco consumption during pregnancy. Being randomized into the control arm, having undergone early parental loss before age 11 and having lower global severity of psychiatric symptoms (SCL-90 at 3 months postpartum were the only variables associated with later attrition.This study provides key information for identifying mothers who may require specific support to avoid study attrition in trials evaluating a home-visiting program.

  3. The measurement of change in functional ability: dealing with attrition and the floor/ceiling effect

    DEFF Research Database (Denmark)

    Holstein, Bjørn E; Avlund, Kirsten; Due, Pernille; Martinussen, Torben; Keiding, Niels

    2006-01-01

    The purpose was to describe four-year change in functional ability among older persons and the relationship to sex, age, and other background factors. The baseline study, performed in 1986, is based on a random sample of older persons (n=1261). Follow-up data were collected four-years later (n=912......). The analyses of change in functional ability were based on the assumption that the categories reflected an underlying latent continuous dimension. The change in functional ability, DeltaFA, was calculated by a logistic model for paired observations and applied in parallel analyses with and without...... inclusion of the dead to deal with the attrition problem. Fifty percent had no change in functional ability, 37% had declined and 13% improved. Models including the dead showed more functional decline with increasing age but this was not the case when the dead were excluded. Functional change was not...

  4. Superconducting properties of MgB2 prepared from attrition ball-milled boron powder

    International Nuclear Information System (INIS)

    We report superconducting properties of the MgB2 pellets prepared from the attrition ball-milled boron, in order to control the grain size of the MgB2 that is formed from it. We observed that the semi-crystalline peaks in the ball-milled boron became broader when the ball-milling time was further increased, indicating that the boron powders had lost their crystalline. In addition, the B2O3 peak was appeared in the ball-milled powders, resulting in an increase in the amount of MgO. However, the sample prepared from boron that was ball milled for 5 h showed an improvement of critical current density (Jc), even with increased MgO phase, under an external magnetic field at 5 K and 20 K.

  5. Application of a Duration Model in Programs for Prevention of University Attrition

    Directory of Open Access Journals (Sweden)

    Verónica Herrero

    2013-12-01

    Full Text Available Institutional practices related to the prevention of desertion of university students increasingly require validated instruments in order to anticipate such behavior. In this regard, different statistical models generated from information related to the students themselves, their homes, their academic performance, among other determinants have demonstrated to be of crucial value. This study aims to demonstrate the importance of a series of determinants explored in other studies. The main objective is to apply a dropout rate predictive model with at risk university students in order to generate early and progressively more effective results. The research demonstrates the usefulness of the duration models in a sample of classroom students and the capacity to anticipate behavior of permanence/attrition across time. This was done with risk estimates using the Cox model.

  6. A Study on Reasons of Attrition and Strategies for Employee Retention

    Directory of Open Access Journals (Sweden)

    N.Silpa

    2015-12-01

    Full Text Available The success of any manufacturing organization depends largely on the workers are considered as the backbone of any company. The study was mainly undertaken to identify the level of employee’s attitude, the dissatisfaction factors they face in the organization and for what reason they prefer to change their job. Once the levels of employee’s attitude are identified, it would be possible for the management to take necessary action to reduce attrition level. Since they are considered as backbone of the company, their progression will lead to the success of the company for the long run. This study can be helpful in knowing, why the employees prefer to change their job and which factors make employee dissatisfy. Since the study is critical issue, it is needed by the originations in order to assess the overall interest and the feelings of the employees towards their Retention.

  7. Reinforcement of laser-welded stainless steels by surface mechanical attrition treatment

    International Nuclear Information System (INIS)

    The laser-welded stainless steel was treated by surface mechanical attrition treatment (SMAT) in order to improve its mechanical properties. The microstructure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties were measured by means of microhardness and tensile tests. Results show that the microstructure of weldment after SMAT is composed of ultra-fine grains, multiscale twins, and residual dendrites. The mechanical properties of laser-welded stainless steels after SMAT are significantly improved. The strengthening of weldment can be attributed to the refinement of dendrites and formation of multiscale twins during SMAT. The influence of dendrites on the formation of twins is discussed

  8. Accounting for expected attrition in the planning of community intervention trials.

    Science.gov (United States)

    Taljaard, Monica; Donner, Allan; Klar, Neil

    2007-06-15

    Trials in which intact communities are the units of randomization are increasingly being used to evaluate interventions which are more naturally administered at the community level, or when there is a substantial risk of treatment contamination. In this article we focus on the planning of community intervention trials in which k communities (for example, medical practices, worksites, or villages) are to be randomly allocated to each of an intervention and a control group, and fixed cohorts of m individuals enrolled in each community prior to randomization. Formulas to determine k or m may be obtained by adjusting standard sample size formulas to account for the intracluster correlation coefficient rho. In the presence of individual-level attrition however, observed cohort sizes are likely to vary. We show that conventional approaches of accounting for potential attrition, such as dividing standard sample size formulas by the anticipated follow-up rate pi or using the average anticipated cohort size m pi, may, respectively, overestimate or underestimate the required sample size when cluster follow-up rates are highly variable, and m or rho are large. We present new sample size estimation formulas for the comparison of two means or two proportions, which appropriately account for variation among cluster follow-up rates. These formulas are derived by specifying a model for the binary missingness indicators under the population-averaged approach, assuming an exchangeable intracluster correlation coefficient, denoted by tau. To aid in the planning of future trials, we recommend that estimates for tau be reported in published community intervention trials. PMID:17068842

  9. CU-STARs: Promoting STEM Diversity by Addressing First-year Attrition of Underrepresented Minorities

    Science.gov (United States)

    Battersby, Cara; Silvia, Devin W.; Ellingson, Erica; Sturner, Andrew P.; Peck, Courtney

    2015-01-01

    Upon first entering university, the fraction of students interested in pursuing a STEM major are distributed according to societal demographics (with 25% being underrepresented minorities), but by graduation, the fraction of students receiving STEM degrees is unbalanced, with underrepresented minorities receiving only 15% of STEM bachelor's degrees. The CU-STARs (CU Science, Technology, and Astronomy Recruits) program at the University of Colorado, Boulder is targeted to address the main triggers of early career attrition for underrepresented minorities in STEM disciplines. A select group of students are given financial support through work-study at the Fiske planetarium on campus, while resources to address other triggers of attrition are available to the entire cohort of interested students (typically ~5-10 per year). These resources are designed to promote social engagement and mentorship, while also providing a support network and resources to combat inadequate high school preparation for STEM courses. We achieve these goals through activities that include social events, mentor meetings, free tutoring, and special events to meet and talk with scientists. The culmination of the program for the recruits are a series of high school outreach events in underserved areas (inner city and rural alike), in which they become the expert. The STARs are paid for their time and take the lead in planning, teaching, and facilitating programs for the high school students, including classroom presentations, interactive lab activities, solar observing, and star parties. The high school outreach events provide role models and STEM exposure for the underserved high school community while simultaneously cementing the personal achievements and successes for the STARs. CU-STARs is now in its 4th year and is still growing. We are beginning the process of formal assessments of the program's success. We present details of the program implementation, a discussion of potential obstacles

  10. The Role of Attrition and Solids Recovery in a Chemical Looping Combustion Process

    International Nuclear Information System (INIS)

    In the present work, the steady-state behavior of a Chemical Looping Combustion process of interconnected fluidized bed reactors is simulated. The simulations have been carried out in two different scales, 50 kWth and 100 MWth. Attrition model derived from small scale laboratory experiments has been employed for the prediction of the process behavior in terms of attrition and Oxygen Carrier loss. Information on Oxygen Carrier characteristics and reaction kinetics were taken from literature. Realistic circulation mass flows of Oxygen Carrier particles are obtained and Oxygen Carrier losses are quantified. The large scale process looses significantly more Oxygen Carrier than the small scale process based on the same amount of thermal energy produced. Incomplete conversion in the air reactor could be identified as a critical point. Another issue is the fuel gas bypassing the Oxygen Carrier particles through bubbles in the large scale process which leads to lowered fuel conversions. The simulations indicate that a similar performance of a pilot scale and a large scale process is not guaranteed due to the scale-up effect on fluid dynamics. Furthermore, the simulations allow an assessment of the influence of the quality of the solids recovery system on the Oxygen Carrier loss. The distribution of the losses between possible origins is investigated and different changes in the solids recovery system are discussed regarding their potential to decrease the Oxygen Carrier loss. For example, the addition of a second-stage cyclone after the air reactor of the large scale process reduces the Oxygen Carrier loss significantly. (authors)

  11. Direct decomposition of nitric oxide in low temperature over iron-based perovskite-type catalyst modified by Ru

    Institute of Scientific and Technical Information of China (English)

    LI Li; ZHANG Mi-lin; YUAN Fu-long; SHI Ke-ying; ZHANG Guo; ZHANG Dan

    2006-01-01

    Iron-based perovskite-type compounds modified by Ru were prepared through sol-gel process to study its catalytic activity of NOx direct decomposition at low temperature and evaluate the conversion of NO under the experimental conditions. The catalytic activity of La0.9Ce0.1Fe0.8-nCo0.2RunO3 ( n = 0.01,0.03,0.05,0.07,0.09)series for the NO, NO-CO two components, CO-HC-NO three components were also analyzed. The catalytic investigation evidenced that the presence of Ru is necessary for making highly activity in decomposition of nitric oxide even at low temperature (400 ℃ ) and La0.9Ce0.9Fe0.75Co0.2Ru0.05O3( n = 0. 05 ) has better activity in all the samples, the conversion of it is 58.5%. With the reducing gas (CO, C3 H6 )added into the gas, the catalyst displayed very high activity in decomposition of NO and the conversion of it is 80% and 92. 5% separately.

  12. Magnetic properties of iron-based soft magnetic composites with SiO2 coating obtained by reverse microemulsion method

    Science.gov (United States)

    Wu, Shen; Sun, Aizhi; Lu, Zhenwen; Cheng, Chuan; Gao, Xuexu

    2015-05-01

    In this work, iron-based soft magnetic composites coated with the amorphous SiO2 layer have been fabricated by utilizing tetraethoxysilane in the reverse microemulsion method, and then the effects of addition amount of SiO2 and annealing temperature on the magnetic properties were investigated. The results show that the surface of iron powders contains a thin amorphous SiO2 insulation layer, which effectively decreases the magnetic loss of synthesized magnets. The magnetic loss of coated samples decreased by 87.8% as compared with that of uncoated samples at 150 kHz. Magnetic measurements show that the sample with 1.25 wt% SiO2 has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Also, the annealing treatment increased the initial permeability, the maximum permeability and the magnetic induction and decreased the coercivity with increasing temperature in the range 300-600 °C. The results of the loss separation imply that the annealed SMCs have a higher hysteresis loss coefficient (k2) and lower eddy current loss coefficient (k3) as compared with the pure iron compacts after the same heat treatment due to the preservation of the SiO2 layer.

  13. Progress in development of coated indexable cemented carbide inserts for machining of iron based work piece materials

    Science.gov (United States)

    Czettl, C.; Pohler, M.

    2016-03-01

    Increasing demands on material properties of iron based work piece materials, e.g. for the turbine industry, complicate the machining process and reduce the lifetime of the cutting tools. Therefore, improved tool solutions, adapted to the requirements of the desired application have to be developed. Especially, the interplay of macro- and micro geometry, substrate material, coating and post treatment processes is crucial for the durability of modern high performance tool solutions. Improved and novel analytical methods allow a detailed understanding of material properties responsible for the wear behaviour of the tools. Those support the knowledge based development of tailored cutting materials for selected applications. One important factor for such a solution is the proper choice of coating material, which can be synthesized by physical or chemical vapor deposition techniques. Within this work an overview of state-of-the-art coated carbide grades is presented and application examples are shown to demonstrate their high efficiency. Machining processes for a material range from cast iron, low carbon steels to high alloyed steels are covered.

  14. Assessment Of The Production Of Antiquity Pigments Through Experimental Treatment Of Ochres And Other Iron Based Precursors.

    Science.gov (United States)

    Matrotheodoros, G.; Beltsios, K. G.; Zacharias., N.

    In this work we explore the effects of various grinding and thermal-oxidative treatments applied to natural and artificial iron-based materials available (or related to those available) during GraecoRoman antiquity. The raw materials examined are: (a) commercial natural iron pigments (ochres, natrojarosite, caput mortum), (b) artificial melanterite (FeSO4.7H2O), (c) mineral pyrite (FeS2) and mineral metallic hematite. Additionally explored are: (a) the non-attested in surviving sources, yet highly probable during antiquity, route of pigment preparation from iron (or steel) plates exposed to vinegar vapors, (b) a Vitruvius recipe for purplish pigment via vinegar quenching of hot ochre. We obtain oxide pigments with colors ranging from yellowish and red to brownish and purplish. The puzzling variation of colors obtained by subjecting iron-oxide containing materials to identical oxidative heat treatments is found to be explainable on the basis of starting grain size and possible size modifications. We also show, by using highly purity starting materials, that purplish colors obtainable in certain cases by heat treatment do not necessitate, as often claimed, the presence of impurities such as manganese etc. A framework of antiquity color possibilities for iron-oxide based pigments obtainable under the conditions explored is included. All samples prepared are examined via scanning electron microscopy for micromorphology coupled with EDAX for composition, and X-Rays Diffraction for mineralogy.

  15. Crystal growth of iron-based superconductor FeSe0.94 by KCl flux method

    International Nuclear Information System (INIS)

    Highlights: • SC crystals of FeSe0.94 bigger than previous reports are grown by KCl flux method. • The crystal sizes are 6 × 3 × 0.1–0.2 mm3 or 5 × 5 × 0.1–0.2 mm3; the TC is around 10 K. • Relatively big crystal size is realized by optimizing crystal growth conditions. • Optimized are the dissolution and convection, temperature gradient and flux content. - Abstract: Single crystals of iron-based superconductor FeSe0.94, the 11 phase, have been grown using KCl as flux. The size of as-grown crystals is up to 6 × 3 mm2 or 5 × 5 mm2. The relatively big crystal size is achieved by optimizing the experimental scheme. The main phase of the crystal samples is identified to be tetragonal β-FeSe by X-ray diffraction analysis. The superconducting transition temperature is determined to be around 10 K by both electron transport and diamagnetism measurements

  16. Photovoltaic effect in iron-based SmO0.7F0.3FeAs superconductors

    International Nuclear Information System (INIS)

    A remarkable photovoltaic effect in an iron-based SmO0.7F0.3FeAs–Ag system has been observed in the temperature range from 50 to 300 K. An interface potential exists directly from the superconductor to the metal electrode, which provides the separation force for the photo-induced electron–hole pairs. The mechanism of this interface potential is completely different below and above the superconducting transition temperature and has been discussed in terms of the proximity effect and Schottky barrier, respectively. In contrast to that found in the YBCO-Ag system, a photovoltaic effect of opposite polarity is obtained in a SmO0.7F0.3FeAs–Ag system at a normal state, consistent with the different type of charge carriers in these two superconductors. A very fast laser response (7.5 ms) may open a door to new device applications such as optical sensors. (paper)

  17. Crystal growth of iron-based superconductor FeSe{sub 0.94} by KCl flux method

    Energy Technology Data Exchange (ETDEWEB)

    Ma, M.W.; Yuan, D.N.; Wu, Y.; Dong, X.L.; Zhou, F., E-mail: fzhou@aphy.iphy.ac.cn

    2014-11-15

    Highlights: • SC crystals of FeSe{sub 0.94} bigger than previous reports are grown by KCl flux method. • The crystal sizes are 6 × 3 × 0.1–0.2 mm{sup 3} or 5 × 5 × 0.1–0.2 mm{sup 3}; the T{sub C} is around 10 K. • Relatively big crystal size is realized by optimizing crystal growth conditions. • Optimized are the dissolution and convection, temperature gradient and flux content. - Abstract: Single crystals of iron-based superconductor FeSe{sub 0.94}, the 11 phase, have been grown using KCl as flux. The size of as-grown crystals is up to 6 × 3 mm{sup 2} or 5 × 5 mm{sup 2}. The relatively big crystal size is achieved by optimizing the experimental scheme. The main phase of the crystal samples is identified to be tetragonal β-FeSe by X-ray diffraction analysis. The superconducting transition temperature is determined to be around 10 K by both electron transport and diamagnetism measurements.

  18. Methyl red removal from water by iron based metal-organic frameworks loaded onto iron oxide nanoparticle adsorbent

    Energy Technology Data Exchange (ETDEWEB)

    Dadfarnia, S., E-mail: sdadfarnia@yazd.ac.ir [Department of Chemistry, Faculty of Science, Yazd University, Yazd 89195-741 (Iran, Islamic Republic of); Haji Shabani, A.M.; Moradi, S.E. [Department of Chemistry, Faculty of Science, Yazd University, Yazd 89195-741 (Iran, Islamic Republic of); Emami, S. [Department of Medicinal Chemistry and Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari (Iran, Islamic Republic of)

    2015-03-01

    Highlights: • Synthesis and characterization of (Fe{sub 3}O{sub 4}@MIL-100(Fe)). • Studying the capability of (Fe{sub 3}O{sub 4}@MIL-100(Fe)) for the removal of methyl red. • Studying the adsorption kinetic of MR on (Fe{sub 3}O{sub 4}@MIL-100(Fe)). • Studying the adsorption thermodynamic of MR on (Fe{sub 3}O{sub 4}@MIL-100(Fe)). • Introduction of a sorbent with high capacity for MR removal. - Abstract: The objective followed by this research is the synthesis of iron based metal organic framework loaded on iron oxide nanoparticles (Fe{sub 3}O{sub 4}@MIL-100(Fe)) and the study of its capability for the removal of methyl red. Effective parameters in the selection of a new adsorbent, i.e. adsorption capacity, thermodynamics, and kinetics were investigated. All the studies were carried out in batch experiments. Removal of methyl red from aqueous solutions varied with the amount of adsorbent, methyl red contact time, initial concentration of dye, adsorbent dosage, and solution pH. The capability of the synthesized adsorbent in the removal of methyl red was compared with the metal organic framework (MIL-100(Fe)) and iron oxide nanoparticles. The results show that Fe{sub 3}O{sub 4}@MIL-100(Fe) nanocomposite exhibits an enhanced adsorption capacity.

  19. Methyl red removal from water by iron based metal-organic frameworks loaded onto iron oxide nanoparticle adsorbent

    International Nuclear Information System (INIS)

    Highlights: • Synthesis and characterization of (Fe3O4@MIL-100(Fe)). • Studying the capability of (Fe3O4@MIL-100(Fe)) for the removal of methyl red. • Studying the adsorption kinetic of MR on (Fe3O4@MIL-100(Fe)). • Studying the adsorption thermodynamic of MR on (Fe3O4@MIL-100(Fe)). • Introduction of a sorbent with high capacity for MR removal. - Abstract: The objective followed by this research is the synthesis of iron based metal organic framework loaded on iron oxide nanoparticles (Fe3O4@MIL-100(Fe)) and the study of its capability for the removal of methyl red. Effective parameters in the selection of a new adsorbent, i.e. adsorption capacity, thermodynamics, and kinetics were investigated. All the studies were carried out in batch experiments. Removal of methyl red from aqueous solutions varied with the amount of adsorbent, methyl red contact time, initial concentration of dye, adsorbent dosage, and solution pH. The capability of the synthesized adsorbent in the removal of methyl red was compared with the metal organic framework (MIL-100(Fe)) and iron oxide nanoparticles. The results show that Fe3O4@MIL-100(Fe) nanocomposite exhibits an enhanced adsorption capacity

  20. Synthesis of iron-based chemical looping sorbents integrated with pH swing carbon mineral sequestration.

    Science.gov (United States)

    Kim, Hyung Ray; Lee, Dong Hyun; Fan, Liang-Shih; Park, Ah-Hyung Alissa

    2009-12-01

    The previously developed pH swing carbon mineral sequestration immobilizes the gaseous CO2 into a thermodynamically stable solid, MgCO3, using Mg-bearing minerals such as serpentine. This mineral carbonation technology is particularly promising since it generates value-added solid products: high surface area silica, iron oxide, and magnesium carbonate, while providing a safe and permanent storage option for CO2. By carefully controlling the pH of the system, these solids products can be produced with high purity. This study focuses on the synthesis of iron oxide particles as a chemical looping sorbent in order to achieve the integration between carbon capture and storage technologies. Since the solubility of Fe in aqueous phase is relatively low at neutral pH, the effect of the weak acid and chelating agents on the extraction of Fe from serpentine was investigated. The synthesized iron-based chemical looping sorbent was found to be as effective as commercially available iron oxide nanoparticles at converting syngas into high purity H2, while producing a sequestration-ready CO2 stream. PMID:19908801

  1. The growth of 122 and 11 iron-based superconductor single crystals and the influence of doping

    International Nuclear Information System (INIS)

    This review focuses on the various single crystal growth techniques applied to the new class of high temperature superconductors—iron-based layered pnictides, such as the parent compounds AFe2As2 (A = Ba, Sr, Ca) (122), hole-doped A1 − xK xFe2As2, electron/hole-doped AFe2 − xM xAs2 (M = Co, Ni, Mn, Cr), isovalently doped AFe2As2 − xP x, the chalcogenides A xFe2 − ySe2(A = K, Rb, Cs) (122), and Fe1 − δTe1 − xSe x (11). Detailed single crystal growth methods (fluxes, Bridgman, floating zone(FZ)), the associated procedures, and their impact on crystal size and quality are presented. We also discuss the influence of doping on the structure, and the electric, magnetic, and superconducting properties of these compounds by a comparative study of different growth methods. (topical review)

  2. High-strength alloy with resistance to hydrogen-environment embrittlement

    Science.gov (United States)

    Mcnamara, T. G.

    1975-01-01

    Alloy is precipitation-hardened, high-strength, and low-thermal-expansion materials. It is iron-based and contains nickel and chromium at lower levels than high-strength alloys. It is readily welded and brazed and has good oxidation resistance. Tests indicated there was no reduction of notched or smooth strength.

  3. Predictors of Study Attrition in a Randomized Controlled Trial Evaluating a Perinatal Home-Visiting Program with Mothers with Psychosocial Vulnerabilities

    OpenAIRE

    Foulon, Stéphanie; Greacen, Tim; Pasquet, Blandine; Dugravier, Romain; Saïas, Thomas; Guedeney, Nicole; Guedeney, Antoine; Tubach, Florence; ,

    2015-01-01

    Objective Randomised controlled trials evaluating perinatal home-visiting programs are frequently confronted with the problem of high attrition rates. The aim of the present study is to identify predictors of study attrition in a trial evaluating a perinatal home-visiting program in France. Materials and Methods CAPEDP is a French randomized trial comparing a perinatal home-visiting program using psychologists versus usual care (N = 440). The first assessment was at inclusion into the trial a...

  4. Size and Promoter Effects on Stability of Carbon-Nanofiber-Supported Iron-Based Fischer–Tropsch Catalysts

    Science.gov (United States)

    2016-01-01

    The Fischer–Tropsch Synthesis converts synthesis gas from alternative carbon resources, including natural gas, coal, and biomass, to hydrocarbons used as fuels or chemicals. In particular, iron-based catalysts at elevated temperatures favor the selective production of C2–C4 olefins, which are important building blocks for the chemical industry. Bulk iron catalysts (with promoters) were conventionally used, but these deactivate due to either phase transformation or carbon deposition resulting in disintegration of the catalyst particles. For supported iron catalysts, iron particle growth may result in loss of catalytic activity over time. In this work, the effects of promoters and particle size on the stability of supported iron nanoparticles (initial sizes of 3–9 nm) were investigated at industrially relevant conditions (340 °C, 20 bar, H2/CO = 1). Upon addition of sodium and sulfur promoters to iron nanoparticles supported on carbon nanofibers, initial catalytic activities were high, but substantial deactivation was observed over a period of 100 h. In situ Mössbauer spectroscopy revealed that after 20 h time-on-stream, promoted catalysts attained 100% carbidization, whereas for unpromoted catalysts, this was around 25%. In situ carbon deposition studies were carried out using a tapered element oscillating microbalance (TEOM). No carbon laydown was detected for the unpromoted catalysts, whereas for promoted catalysts, carbon deposition occurred mainly over the first 4 h and thus did not play a pivotal role in deactivation over 100 h. Instead, the loss of catalytic activity coincided with the increase in Fe particle size to 20–50 nm, thereby supporting the proposal that the loss of active Fe surface area was the main cause of deactivation. PMID:27330847

  5. Recent progress in the synthesis of magnetic titania/iron-based, composite nanoparticles manufactured by laser pyrolysis

    Science.gov (United States)

    Fleaca, C. T.; Scarisoreanu, M.; Morjan, I.; Alexandrescu, R.; Dumitrache, F.; Luculescu, C.; Morjan, I. P.; Birjega, R.; Niculescu, A.-M.; Filoti, G.; Kuncser, V.; Vasile, E.; Danciu, V.; Popa, M.

    2014-05-01

    We report the continuous, single step synthesis of titania/iron-based magnetic nanocomposites in a single step using gas-phase laser pyrolysis technique by separately and simultaneously introducing the precursors (together with C2H4 sensitizer) in the reaction zone: Fe(CO)5 on the central flow and, using air as carrier, TiCl4 on the annular coflow. The laser power and, for the last experiment, the injection geometry were modified in order to change the Fe/Ti ratio in the resulted nanopowders. Due to the specific geometry, the reaction zone (visible as a flame) have a reductive inner central zone surrounded by and oxidative environment, allowing the formation of the metallic-carbidic iron and/or iron-doped titania and iron oxide nanophases. The raw Fe-containing nanopowders have a ferromagnetic behavior, those synthesized at higher laser power and gas velocities show significant saturation magnetization Ms values (10-12 emu/g), whereas those obtained (with higher yield and carbon content) at lower laser power and gas velocities (using wider central nozzle cross-section) have a very weak magnetization (Ms ∼ 0.05 emu/g) in spite of the higher ethylene carried Fe(CO)5 flow. The powders were annealed in air at 400 °C show lower carbon content and, for those highly Fe-doped, the hematite phase formation. Preliminary tests using UV light confirm the photocatalytic action of the annealed nanopowders in salicylic acid degradation process in solution.

  6. Pairing symmetries of several iron-based superconductor families and some similarities with cuprates and heavy-fermions

    Directory of Open Access Journals (Sweden)

    Das Tanmoy

    2012-03-01

    Full Text Available We show that, by using the unit-cell transformation between 1 Fe per unit cell to 2 Fe per unit cell, one can qualitatively understand the pairing symmetry of several families of iron-based superconductors. In iron-pnictides and iron-chalcogenides, the nodeless s±-pairing and the resulting magnetic resonance mode transform nicely between the two unit cells, while retaining all physical properties unchanged. However, when the electron-pocket disappears from the Fermi surface with complete doping in KFe2As2, we find that the unit-cell invariant requirement prohibits the occurrence of s±-pairing symmetry (caused by inter-hole-pocket nesting. However, the intra-pocket nesting is compatible here, which leads to a nodal d-wave pairing. The corresponding Fermi surface topology and the pairing symmetry are similar to Ce-based heavy-fermion superconductors. Furthermore, when the Fermi surface hosts only electron-pockets in KyFe2-xSe2, the inter-electron-pocket nesting induces a nodeless and isotropic d-wave pairing. This situation is analogous to the electron-doped cuprates, where the strong antiferromagnetic order creates similar disconnected electron-pocket Fermi surface, and hence nodeless d-wave pairing appears. The unit-cell transformation in KyFe2-xSe2 exhibits that the d-wave pairing breaks the translational symmetry of the 2 Fe unit cell, and thus cannot be realized unless a vacancy ordering forms to compensate for it. These results are consistent with the coexistence picture of a competing order and nodeless d-wave superconductivity in both cuprates and KyFe1.6Se2.

  7. Magnetic properties of iron-based soft magnetic composites with SiO2 coating obtained by reverse microemulsion method

    International Nuclear Information System (INIS)

    In this work, iron-based soft magnetic composites coated with the amorphous SiO2 layer have been fabricated by utilizing tetraethoxysilane in the reverse microemulsion method, and then the effects of addition amount of SiO2 and annealing temperature on the magnetic properties were investigated. The results show that the surface of iron powders contains a thin amorphous SiO2 insulation layer, which effectively decreases the magnetic loss of synthesized magnets. The magnetic loss of coated samples decreased by 87.8% as compared with that of uncoated samples at 150 kHz. Magnetic measurements show that the sample with 1.25 wt% SiO2 has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Also, the annealing treatment increased the initial permeability, the maximum permeability and the magnetic induction and decreased the coercivity with increasing temperature in the range 300–600 °C. The results of the loss separation imply that the annealed SMCs have a higher hysteresis loss coefficient (k2) and lower eddy current loss coefficient (k3) as compared with the pure iron compacts after the same heat treatment due to the preservation of the SiO2 layer. - Highlights: • SiO2 coated the iron powder by reverse microemulsion method, decreased the magnetic loss of SMCs. • 25 wt% is the optimum coating amount to attain the desired permeability. • The influence of annealing temperature on the magnetic performance of the core was discussed. • Compare with the pure iron compacts, the annealed SMCs have lower value of eddy current coefficient

  8. Ferric Citrate, an Iron-Based Phosphate Binder, Reduces Health Care Costs in Patients on Dialysis Based on Randomized Clinical Trial Data

    OpenAIRE

    Rodby, Roger A.; Umanath, Kausik; Niecestro, Robert; Christopher Bond, T.; Sika, Mohammed; Lewis, Julia; Dwyer, Jamie P.; . .

    2015-01-01

    Background Patients with end-stage renal disease (ESRD) require phosphate binders for hyperphosphatemia and erythropoiesis-stimulating agents (ESAs) and intravenous (IV) iron for anemia. Ferric citrate (FC) is a novel, iron-based phosphate binder that increases iron stores and decreases IV iron and ESA usage while maintaining hemoglobin levels, and may decrease the cost of ESRD care. The study objectives were to (1) quantify differences in ESA and IV iron usage among ESRD patients receiving F...

  9. Factors influencing medical student attrition and their implications in a large multi-center randomized education trial.

    Science.gov (United States)

    Kalet, A; Ellaway, R H; Song, H S; Nick, M; Sarpel, U; Hopkins, M A; Hill, J; Plass, J L; Pusic, M V

    2013-08-01

    Participant attrition may be a significant threat to the generalizability of the results of educational research studies if participants who do not persist in a study differ from those who do in ways that can affect the experimental outcomes. A multi-center trial of the efficacy of different computer-based instructional strategies gave us the opportunity to observe institutional and student factors linked to attrition from a study and the ways in which they altered the participation profile. The data is from a randomized controlled trial conducted at seven US medical schools investigating the educational impact of different instructional designs for computer-based learning modules for surgical clerks. All students undertaking their surgical clerkships at the participating schools were invited participate and those that consented were asked to complete five study measures during their surgery clerkship. Variations in study attrition rates were explored by institution and by participants' self-regulation, self-efficacy, perception of task value, and mastery goal orientation measured on entry to the study. Of the 1,363 invited participants 995 (73 %) consented to participate and provided baseline data. There was a significant drop in the rate of participation at each of the five study milestones with 902 (94 %) completing at least one of two module post-test, 799 (61 %) both module post-tests, 539 (36 %) the mid-rotation evaluation and 252 (25 %) the final evaluation. Attrition varied between institutions on survival analysis (p self-regulated, self-efficacious and higher achievers than their peers who drop out and as such do not represent the class as a whole. PMID:22869047

  10. The effect of surface mechanical attrition treatment on low temperature plasma nitriding of an austenitic stainless steel

    OpenAIRE

    Chemkhi, Mahdi; Retraint, Delphine; Roos, Arjen; Garnier, Claude; Waltz, Laurent; Demangel, Clémence; Proust, Gwénaëlle

    2013-01-01

    The combined effect of superficial nanocrystallisation by SMAT (Surface Mechanical Attrition Treatment) followed by plasma nitriding on the mechanical properties of a medical grade austenitic stainless steel was studied. SMAT conditions were optimised to enhance nitrogen diffusion. Experimental observations (energy dispersive X-ray spectroscopy profiles, cross-sectional optical micrographs, phase analysis by X-ray diffraction and micro-hardness profiles) show that polishing away a very thin l...

  11. Complaints of rape and the criminal justice system: Fresh evidence on the attrition problem in England and Wales

    OpenAIRE

    Hohl, K; Stanko, E.

    2015-01-01

    The UK has one of the lowest conviction rates for rape in Europe. This article presents unique evidence on the factors that influence the attrition of rape allegations in the English criminal justice system. The study is based on a large, representative sample of rape allegations reported to the London Metropolitan Police, the UK’s biggest police force. The dataset contains unprecedented detail on the incident, victim, suspect and police investigation. The results lend support to the influenc...

  12. Reasons for Student Attrition in Posgraduate Virtual Programs: Case Revision and Considerations from Educational and Relational Marketing for Retention Programs

    OpenAIRE

    Murcia Agudelo, Nubia Esther; Ramírez Angulo, Pedro Julián

    2015-01-01

    The Colombian government has focused on the education of its citizens. In line with this initiative, this paper aims at making a contribution from educational relationship marketing, to strengthen virtual methodology in the post- graduate level. A qualitative study with in- depth interviews until saturation level is used to ascertain the reasons that affect attrition and retention in the academic program. The factors with greater impact found were first, those programs related to academic ser...

  13. Attritional rupture of extensor pollicis longus: a rare complication following elastic stable intramedullary nailing of a paediatric radial fracture.

    LENUS (Irish Health Repository)

    Sproule, James A

    2011-01-01

    Elastic stable intramedullary nail fixation has become established as an acceptable method of treatment for diaphyseal fractures of both forearm bones in the paediatric population. It is considered safe, minimally invasive and does not compromise physeal growth. We report a case of delayed rupture of extensor pollicis longus due to attrition over the sharp edges of a protruding nail end after elastic stable intramedullary nailing of a paediatric radial diaphyseal fracture.

  14. Engagement and Nonusage Attrition With a Free Physical Activity Promotion Program: The Case of 10,000 Steps Australia

    OpenAIRE

    Guertler, Diana; Vandelanotte, Corneel; Kirwan, Morwenna; Duncan, Mitch J.

    2015-01-01

    Background Data from controlled trials indicate that Web-based interventions generally suffer from low engagement and high attrition. This is important because the level of exposure to intervention content is linked to intervention effectiveness. However, data from real-life Web-based behavior change interventions are scarce, especially when looking at physical activity promotion. Objective The aims of this study were to (1) examine the engagement with the freely available physical activity p...

  15. Five-year survey of medical student attrition in a medical school in Nigeria: a pilot study

    OpenAIRE

    Egwu, Ogugua A; Anyanwu, Godson E

    2010-01-01

    Ogugua A Egwu1, Godson E Anyanwu21Department of Anatomy, Faculty of Basic Medical Sciences, Ebonyi State University, Ebonyi State; 2Department of Anatomy, College of Medicine, Faculty of Medical Sciences, University of Nigeria, Enugu State, NigeriaBackground: Student attrition represents a waste of career opportunity and, at times, results in a holistic loss of sense of self-worth for the students involved. The aim of this study was to evaluate the nature, causes, and impact of medical studen...

  16. Enrolment, Attrition and Graduation of the Girl Child in Public Junior Secondary Schools in South West Nigeria, 1996-2006

    OpenAIRE

    Ayodeji Olasunkanmi Abari; Grace Okaima Oshun

    2010-01-01

    The study examined the enrolment, attrition and graduation of the girl child in Junior Secondary Schools in South West Nigeria from 1999 to 2006 during which five cohorts were produced. This is against the backdrop of the launching of the Universal Basic Education (UBE) Programme of the Federal Government of Nigeria in 1999, a programme that is designed not only to ensure that the child acquires basic skills in life but also to redress the gender imbalance in the Nigerian educational landscap...

  17. Cross Cultural Adaptation, Validity, and Reliability of the Farsi Breastfeeding Attrition Prediction Tools in Iranian Pregnant Women

    OpenAIRE

    Mortazavi, Forough; MOUSAVI, Seyed Abbas; Chaman, Reza; Khosravi, Ahmad; Janke, Jill R.

    2015-01-01

    Background: The rate of exclusive breastfeeding in Iran is decreasing. The breastfeeding attrition prediction tools (BAPT) have been validated and used in predicting premature weaning. Objectives: We aimed to translate the BAPT into Farsi, assess its content validity, and examine its reliability and validity to identify exclusive breastfeeding discontinuation in Iran. Materials and Methods: The BAPT was translated into Farsi and the content validity of the Farsi version of the BAPT was assess...

  18. Demonstration of a silicon nitride attrition mill for production of fine pure Si and Si3N4 powders

    Science.gov (United States)

    Herbell, T. P.; Glasgow, T. K.; Orth, N. W.

    1984-01-01

    To avoid metallic impurities normally introduced by milling ceramic powders in conventional steel hardware, an attrition mill (high-energy stirred ball mill) was constructed with the wearing parts (mill body, stirring arms, and media) made from silicon nitride. Commercial silicon and Si3N4 powders were milled to fine uniform particles with only minimal contamination - primarily from wear of the sintered Si3N4 media.

  19. Attrition and Rape Case Characteristics: A Profile and Comparison of Female Sex Workers and Non-Sex Workers.

    Science.gov (United States)

    Lea, Susan J; Callaghan, Lynne; Grafton, Iain; Falcone, M Aurora; Shaw, Steve

    2016-07-01

    The attrition of rape cases from the criminal justice system (CJS) remains high and there is a paucity of research in relation to marginalized groups. Sex workers (SWs) are vulnerable to sexual violence due to the nature of their work. They are also unlikely to report such violence to police for a range of reasons. Two stages of research sought to describe the victim, perpetrator, and offense characteristics of SW rape and to examine the attrition of these cases. All rapes and attempted rapes (N = 1,146) reported to police in a large city in the South West of England over a 21-year period were examined; 67 cases involved SWs. Data were extracted from police files in line with the variables of interest. Secondary analysis of the total number of SW rapes (n = 67) resulted in a profile of these cases. A matched pairs study revealed significant differences in victim, perpetrator, and assault characteristics between SW (n = 62) and non-sex-worker (NSW) samples (n = 62). Although no significant difference was found in terms of attrition from the CJS, SW cases were observed to secure more convictions for rape than NSW cases. The implications of the findings for practice and future research are discussed. PMID:25724877

  20. Elements related to attrition of women faculty at the University of Pittsburgh, School of Medicine: A case study

    Science.gov (United States)

    Gandhi, Pooja

    Recent studies have shown that the number of women faculty in academic medicine is much lesser than the number of women that are graduating from medical schools. Many academic institutes face the challenge of retaining talented faculty and this attrition from academic medicine prevents career advancement of women faculty. This case study attempts to identify some of the reasons for dissatisfaction that may be related to the attrition of women medical faculty at the University of Pittsburgh, School of Medicine. Data was collected using a job satisfaction survey, which consisted of various constructs that are part of a faculty's job and proxy measures to gather the faculty's intent to leave their current position at the University of Pittsburgh or academic medicine in general. The survey results showed that although women faculty were satisfied with their job at the University of Pittsburgh, there are some important factors that influenced their decision of potentially dropping out. The main reasons cited by the women faculty were related to funding pressures, work-life balance, mentoring of junior faculty and the amount of time spent on clinical responsibilities. The analysis of proxy measures showed that if women faculty decided to leave University of Pittsburgh, it would most probably be due to better opportunity elsewhere followed by pressure to get funding. The results of this study aim to provide the School of Medicine at the University of Pittsburgh with information related to attrition of its women faculty and provide suggestions for implications for policy to retain their women faculty.

  1. In Situ Synthesis of Nanocrystalline Intermetallic Compound Layer during Surface Mechanical Attrition Treatment of Zirconium

    Institute of Scientific and Technical Information of China (English)

    SUNCai-yun; XIEJi-jia; WUXiao-lei; HONGYou-shi; LIUGang; LUJian; LUKe

    2004-01-01

    The surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanocrystalline (NC) layer on the surface of metallic materials for upgrading their overall properties and performance. In this paper, by means of SMAT to a pure zirconium plate at the room temperature, repetitive multidirectional peening of steel shots (composition (wt%): 1C, 1.5Cr, base Fe) severely deformed the surface layer. A NC surface layer consisting of the intermetallic compound FeCr was fabricated on the surface of the zirconium. The microstructure characterization of the surface layer was performed by using X-ray diffraction analysis, optical microscopy, scanning and transmission electron microscopy observations. The NC surface layer was about 25μm thick and consisted of the intermetallic compound FeCr with an average grain size of 25+10 nm. The deformation-induced fast diffusion of Fe and Cr from the steel shots into Zr occurred during SMAT, leading to the formation of intermetallic compound. In addition, the NC surface layer exhibited an ultrahigh nanohardness of 10.2 GPa.

  2. In Situ Synthesis of Nanocrystalline Intermetallic Compound Layer during Surface Mechanical Attrition Treatment of Zirconium

    Institute of Scientific and Technical Information of China (English)

    SUN Cai-yun; XIE Ji-jia; WU Xiao-lei; HONG You-shi; LIU Gang; LU Jian; LU Ke

    2004-01-01

    The surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanocrystalline (NC)layer on the surface of metallic materials for upgrading their overall properties and performance. In this paper, by means of SMAT to a pure zirconium plate at the room temperature, repetitive multidirectional peening of steel shots (composition (wt%): 1C, 1.5Cr, base Fe) severely deformed the surface layer. A NC surface layer consisting of the intermetallic compound FeCr was fabricated on the surface of the zirconium. The microstructure characterization of the surface layer was performed by using X-ray diffraction analysis, optical microscopy, scanning and transmission electron microscopy observations. The NC surface layer was about 25 μm thick and consisted of the intermetallic compound FeCr with an average grain size of 25+10 nm. The deformation-induced fast diffusion of Fe and Cr from the steel shots into Zr occurred during SMAT, leading to the formation of intermetallic compound. In addition, the NC surface layer exhibited an ultrahigh nanohardness of 10.2 GPa.

  3. A research on the microstructure evolution of austenite stainless steel by surface mechanical attrition treatment

    International Nuclear Information System (INIS)

    Severe plastic deformation (SPD) was performed on AISI304 stainless steel by surface mechanical attrition treatment (SMAT). The microstructure evolution of the specimens along the depth direction were examined by transmission electron microscope (TEM) and electron backscattered diffraction (EBSD) associated with field emission scanning electron microscope (FESEM). The results show that the specimens by SMAT can be divided into three regions. Region I is the untreated one, where a large number of annealing twins exist. Region II is the small plastic-deformed one, where the grains are deformed by dislocation slipping. Region III is the severe plastic-deformed one, where the grains are deformed by mechanical twinning. The hardness of the untreated and the treated specimens were determined, which shows that the hardness of the untreated specimen (including region I) is about 250HV, while the hardness is uniformly increased from region II to region III, and the largest value appears on the surface. The untreated and the 600 N-treated specimens were determined and observed by X-ray diffractometer (XRD) and confocal laser scanning microscope (CLSM), which shows that the SMAT treated specimen exhibits a layer of ultra-fined γ-Fe grains on the treated surface

  4. A research on the microstructure evolution of austenite stainless steel by surface mechanical attrition treatment

    Energy Technology Data Exchange (ETDEWEB)

    Liu, S. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Gao, S.Y. [College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Zhou, Y.F. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Xing, X.L.; Hou, X.R. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Yang, Y.L. [College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Yang, Q.X., E-mail: qxyang@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2014-11-03

    Severe plastic deformation (SPD) was performed on AISI304 stainless steel by surface mechanical attrition treatment (SMAT). The microstructure evolution of the specimens along the depth direction were examined by transmission electron microscope (TEM) and electron backscattered diffraction (EBSD) associated with field emission scanning electron microscope (FESEM). The results show that the specimens by SMAT can be divided into three regions. Region I is the untreated one, where a large number of annealing twins exist. Region II is the small plastic-deformed one, where the grains are deformed by dislocation slipping. Region III is the severe plastic-deformed one, where the grains are deformed by mechanical twinning. The hardness of the untreated and the treated specimens were determined, which shows that the hardness of the untreated specimen (including region I) is about 250HV, while the hardness is uniformly increased from region II to region III, and the largest value appears on the surface. The untreated and the 600 N-treated specimens were determined and observed by X-ray diffractometer (XRD) and confocal laser scanning microscope (CLSM), which shows that the SMAT treated specimen exhibits a layer of ultra-fined γ-Fe grains on the treated surface.

  5. Mechanical properties and thermal stability of nanocrystallized pure aluminum produced by surface mechanical attrition treatment

    International Nuclear Information System (INIS)

    By means of surface mechanical attrition treatment (SMAT), nanocrystalline surface layers were generated in pure aluminum (Al) sheet. The microstructure of the nanocrystalline surface layer was systematically characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that dislocation slip is the main mechanism for grain refinement of Al with SMAT. The mechanical properties were tested by uniaxial tensile and micro-hardness tests. After SMAT, the yield strength of the nanostructured Al was about two times higher than that of the coarse-grained counterpart, with compromise of elongation. The relationship between microstructure and mechanical properties of Al with SMAT was discussed. Moreover, the Al sample after SMAT exhibits a much faster strain hardening rate reduction and a weaker strain hardening than the one without SMAT. Furthermore, the thermal stability of the nanocrystalline surface layer was studied by isothermal and isochronal annealing treatments at the temperature range from 155 °C to 355 °C. It reveals that such nanocrystalline surface layer of Al exhibits high thermal stability, which can be retained up to 275 °C. The growth kinetics of nano-sized grain of Al subjected to SMAT was investigated

  6. Association between recruitment methods and attrition in Internet-based studies.

    Directory of Open Access Journals (Sweden)

    Paolo Bajardi

    Full Text Available Internet-based systems for epidemiological studies have advantages over traditional approaches as they can potentially recruit and monitor a wider range of individuals in a relatively inexpensive fashion. We studied the association between communication strategies used for recruitment (offline, online, face-to-face and follow-up participation in nine Internet-based cohorts: the Influenzanet network of platforms for influenza surveillance which includes seven cohorts in seven different European countries, the Italian birth cohort Ninfea and the New Zealand birth cohort ELF. Follow-up participation varied from 43% to 89% depending on the cohort. Although there were heterogeneities among studies, participants who became aware of the study through an online communication campaign compared with those through traditional offline media seemed to have a lower follow-up participation in 8 out of 9 cohorts. There were no clear differences in participation between participants enrolled face-to-face and those enrolled through other offline strategies. An Internet-based campaign for Internet-based epidemiological studies seems to be less effective than an offline one in enrolling volunteers who keep participating in follow-up questionnaires. This suggests that even for Internet-based epidemiological studies an offline enrollment campaign would be helpful in order to achieve a higher participation proportion and limit the cohort attrition.

  7. Attrition of limestones by impact loading in fluidized beds: The influence of reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Scala, Fabrizio [Istituto di Ricerche sulla Combustione, Consiglio Nazionale delle Ricerche, Napoli (Italy); Salatino, Piero [Istituto di Ricerche sulla Combustione, Consiglio Nazionale delle Ricerche, Napoli (Italy); Dipartimento di Ingegneria Chimica, Universita degli Studi di Napoli Federico II, Napoli (Italy)

    2010-09-15

    The extent of attrition associated with impact loading was studied for five different limestones pre-processed in fluidized bed under different reaction conditions. The experimental procedure was based on the measurement of the amount and the particle size distribution of the debris generated upon impact of sorbent samples against a target at velocities between 10 and 45 m/s. The effect of calcination, sulfation and calcination/re-carbonation on impact damage was assessed. Fragmentation by impact loading of the limestones was significant and increased with the impact velocity. Lime samples displayed the largest propensity to undergo impact damage, followed by sulfated, re-carbonated and raw limestones. Fragmentation of the sulfated samples followed a pattern typical of the failure of brittle materials. On the other hand, the behaviour of lime samples better conformed to a disintegration failure mode, with extensive generation of very fine fragments. Raw limestone and re-carbonated lime samples followed either of the two patterns depending on the sorbent nature. The extent of particle fragmentation increased after multiple impacts, but the incremental amount of fragments generated upon one impact decreased with the number of successive impacts. (author)

  8. POSSIBILITY OF BENEFICIATION OF SILICA SAND FROM THE CROATIAN DEPOSITS USING ATTRITION SCRUBBING

    Directory of Open Access Journals (Sweden)

    Ivan Sobota

    2011-12-01

    Full Text Available To meet high quality requirements defined for specific industrial applications, the raw sand often has to be subjected to extensive physical and chemical processing. The possibility of achieving silica sand concentrate of required quality depends mostly on raw sand properties, primarily mineral impurity types and contents, and features of applied beneficiation methods. When the impurities occur in the form of oxide coatings on the surfaces of the single sand grains, attriton scrubbing is applied. By reducing the proportion of oxide coatings on the grains, the quality of sand can be improved. With the aim to determine the possibilities of the beneficiation of silica sand from significant Croatian deposits (“Vrtlinska”, “Štefanac” and “Španovica” and achieve concentrate grade complying with the requirements of domestic industry, laboratory tests were conducted on three raw sand samples with different SiO2 and impurity contents. Grain size distribution, chemical and mineral composition of raw sand samples, and the possibility of their quality improvement by applying the washing, classification and attrition scrubbing were defined by analysis of test results (the paper is published in Croatian.

  9. Massive Open Online Course Completion Rates Revisited: Assessment, Length and Attrition

    Directory of Open Access Journals (Sweden)

    Katy Jordan

    2015-06-01

    Full Text Available This analysis is based upon enrolment and completion data collected for a total of 221 Massive Open Online Courses (MOOCs. It extends previously reported work (Jordan, 2014 with an expanded dataset; the original work is extended to include a multiple regression analysis of factors that affect completion rates and analysis of attrition rates during courses. Completion rates (defined as the percentage of enrolled students who completed the course vary from 0.7% to 52.1%, with a median value of 12.6%. Since their inception, enrolments on MOOCs have fallen while completion rates have increased. Completion rates vary significantly according to course length (longer courses having lower completion rates, start date (more recent courses having higher percentage completion and assessment type (courses using auto grading only having higher completion rates. For a sub-sample of courses where rates of active use and assessment submission across the course are available, the first and second weeks appear to be critical in achieving student engagement, after which the proportion of active students and those submitting assessments levels out, with less than 3% difference between them.

  10. There and Back Again: Exploring Teacher Attrition and Mobility with Two Transitioning Science Teachers

    Science.gov (United States)

    Gilbert, Andrew

    2011-08-01

    This study chronicled the professional journeys of two beginning science teachers. The focus of the research effort documents what brought them to science teaching and investigated their resulting career paths. Data artifacts for this instrumental case study approach included: interviews, written survey responses, personal communications and member checks. All data was transcribed and coded into emergent categories using a constant comparative analysis approach. The findings indicated that their decisions to enter and leave teaching were a complex mélange of issues that included career disposition, notions of isolation, overarching culture of the school, and future possibilities. However, most striking was their re-entry into teaching on a temporary basis after considerable time away from the classroom, which suggests that teachers develop a sense of agency regarding their career decisions. This may require researchers to reconsider how we view teacher decision-making within the context of teacher attrition and mobility. Implications for science teacher education indicate that some teachers may enter the profession considering teaching to be a transition into a different career path. Secondary science teachers may perceive multiple career options (beyond the classroom) based on their preparation and teaching experience. Further implications and possibilities for science teacher education are discussed.

  11. When did they leave, and why? A retrospective case study of attrition on the Nottingham undergraduate medical course

    Directory of Open Access Journals (Sweden)

    Yates Janet

    2012-06-01

    Full Text Available Abstract Background As part of a wider study into students who experience difficulties, we examined the course files of those who had failed to graduate. This was an exploratory, descriptive study investigating how many students left after academic failure or non-academic problems, or simply changed their minds about reading medicine, and at what stage. The aim of the study was to increase our knowledge about the timings of, and reasons for, attrition. This understanding might help to reduce student loss in the future, by informing selection procedures and improving pastoral support at critical times. It might also assist in long-term workforce planning in the NHS. Methods Relevant data on admission and course progress were extracted manually from the archived files of students who had failed to graduate from five recent consecutive cohorts (entry in 2000–2004 inclusive, using a customised Access database. Discrete categories of information were supplemented with free text entries. Results 1188 students registered over the five-year entry period and 73 (6% failed to graduate. The highest rates of attrition (46/1188, 4% occurred during the first two years (largely preclinical studies, with 34 students leaving voluntarily, including 11 within the first semester, and 12 having their courses terminated for academic failure. Seventeen left at the end of the third year (Honours course plus early clinical practice and the remaining ten during the final two clinical years. The reasons for attrition were not always clear-cut and often involved a mixture of academic, personal, social and health factors, especially mental health problems. Conclusions The causes of attrition are complex. A small number of students with clear academic failure might require individual educational interventions for remediation. However, this could have substantial resource implications for the Faculty. Mental health problems predominate in late course attrition and may have

  12. Iron-based syngas chemical looping process and coal-direct chemical looping process development at Ohio State University

    International Nuclear Information System (INIS)

    Highlights: • Moving bed reducer maximizes solids conversion and maintains full fuel conversion. • 850+ Operating hours completed in 25-kWth sub-pilot chemical looping units. • Full solid and gaseous fuel conversion achieved in sub-pilot chemical looping units. • Fully integrated, pressurized 250-kWth pilot SCL unit construction initiated. • Extensive techno-economic analysis performed on CDCL and SCL process configurations. - Abstract: The increasing demands for energy and concern of global warming are intertwined issues of critical importance. With the pressing need for clean, efficient, and cost-effective energy conversion processes, the chemical looping strategy has evolved as a promising alternative to the traditional carbonaceous fuel conversion processes. Chemical looping processes utilize oxygen carrier particles to indirectly convert carbonaceous fuels while capturing CO2 for sequestration and/or utilization. Throughout its development, multiple oxygen carrier compositions and reactor configurations have been studied and demonstrated. The Ohio State University (OSU) chemical looping technologies have received significant attention over the recent years. OSU’s unique moving-bed chemical looping technologies coupled with iron-based oxygen carrier particles capable of sustaining hundreds of redox cycles have the advantage of converting a variety of carbonaceous fuels, such as natural gas, coal and biomass, to electricity, H2, liquid fuels, or any combination thereof with zero to negative net CO2 emissions. Specifically, two chemical looping processes are being developed and studied, the syngas chemical looping (SCL) and the coal direct chemical looping (CDCL) technologies. Over the past 14 years, these processes have developed from a novel concept to successful sub-pilot (25 kWth) demonstrations. With the support of the Advanced Research Projects Agency – Energy (ARPA-E) of the US Department of Energy (USDOE), a 250 kWth high pressure SCL pilot

  13. First-principle study of antimony doping effects on the iron-based superconductor CaFe(Sb$_{x}$As$_{1-x}$)$_{2}$

    OpenAIRE

    Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; Kuroki, Kazuhiko

    2015-01-01

    We study antimony doping effects in the iron-based superconductor CaFe(Sb$_{x}$As$_{1-x}$)$_{2}$ by using the first-principle calculation. The calculations reveal that the substitution of the doped antimony atom into As of the chainlike As layers is more stable than that in FeAs layers. This prediction can be checked by experiments. Our results suggest that doping homologous elements into the chainlike As layers existing only in novel 112 system is responsible for rising up the critical tempe...

  14. Before and after the earthquake: a case study of attrition from the HIV antiretroviral therapy program in Haiti

    Directory of Open Access Journals (Sweden)

    Nancy H. Puttkammer

    2014-08-01

    Full Text Available Background: On January 12, 2010, a devastating 7.0 magnitude earthquake struck the West Department of Haiti, killing more than 200,000 people and injuring or displacing many more. This disaster threatened continuity of HIV care and treatment services. Objectives: This case study examined the effect of the devastating 2010 earthquake in Haiti on attrition from the HIV antiretroviral therapy (ART program. Design: The study triangulated retrospective data from existing sources, including: 1 individual-level longitudinal patient data from an electronic medical record for ART patients at two large public sector departmental hospitals differently affected by the earthquake; and 2 aggregate data on the volume of HIV-related services delivered at the two hospitals before and after the earthquake. Methods: The study compared ART attrition and service delivery in Jacmel, a site in the ‘very strong’ zone of earthquake impact, and in Jérémie, a site in the ‘light’ zone of earthquake impact. The analysis used time-to-event analysis methods for the individual-level patient data, and descriptive statistical methods for the aggregate service delivery data. Results: Adjusted ART attrition risk was lower at the hospital in Jacmel after vs. before the earthquake (HR=0.51; p=0.03, and was lower in Jacmel vs. Jérémie both before (HR=0.55; p=0.01 and after the earthquake (HR=0.35; p=0.001. The number of new ART patient enrollments, new HIV patient registrations, and HIV clinical visits dropped notably in Jacmel immediately after the earthquake, but then rapidly rebounded. On average, there was no change in new ART enrollments per month after vs. before the earthquake at either site. Conclusion: These findings underscore the resilience of Haitian ART providers and patients, and contribute evidence that it is possible to maintain continuity of ART services even in the context of a complex humanitarian crisis.

  15. Evolution of texture and microstructure in pulsed electro-deposited Cu treated by Surface Mechanical Attrition Treatment (SMAT)

    International Nuclear Information System (INIS)

    This paper presents the microstructure and texture evolution in pulsed electro-deposited copper samples and the additional effect of the Surface Mechanical Attrition Treatment (SMAT), which were analyzed by means of electron backscattering and X-ray diffractions. A transition in the microstructure was observed as the thickness of the deposit increased: from randomly oriented equiaxed (3D) nanograins at the beginning of the deposition process towards elongated (2D) nanograins having a strong fibre texture. Meanwhile, the SMAT treatment is shown to randomize the strong texture of the electrodeposits.

  16. Increased attrition of leukocyte telomere length in young adults is associated with poorer cognitive function in midlife

    OpenAIRE

    Cohen-Manheim, Irit; Doniger, Glen Michael; Sinnreich, Ronit; Simon, Ely Samuel; Pinchas, Ronit; Aviv, Abraham; Kark, Jeremy David

    2015-01-01

    Evidence for an association of leukocyte telomere length (LTL) with cognitive function, predominantly in older adults, is inconsistent. No report has examined the association of LTL dynamics (age-specific LTL and its attrition rate) with cognitive function. We aimed to examine the association of LTL dynamics over 13 years in young adulthood with cognitive function in midlife. 497 individuals who had LTL measured at ages 28–32 and 41–46 years were assessed at ages 48–52 for global cognitive fu...

  17. The Effect of Implementing a Weight Loss Program on Participant Attendance, Club Usage, and Gym Membership Attrition

    OpenAIRE

    Haymond, Stephanie Bonkemeyer

    2013-01-01

    The purpose of this research study was to evaluate the effect of a weight loss program on individual participant attendance, total club usage and membership attrition. This retrospective study involved a fitness gym located in Utah County, Utah with a total membership of 1,100. The number of clients participating in the weight loss program between December 2011 and May 2012 was 36 (32 females and 4 males). A total of 11 clients were analyzed for the individual attendance data as this analysis...

  18. Mechanical Behavior of Ultrafine Gradient Grain Structures Produced via Ambient and Cryogenic Surface Mechanical Attrition Treatment in Iron

    Directory of Open Access Journals (Sweden)

    Heather A. Murdoch

    2015-06-01

    Full Text Available Ambient and cryogenic surface mechanical attrition treatments (SMAT are applied to bcc iron plate. Both processes result in significant surface grain refinement down to the ultrafine-grained regime; the cryogenic treatment results in a 45% greater grain size reduction. However, the refined region is shallower in the cryogenic SMAT process. The tensile ductility of the grain size gradient remains low (<10%, in line with the expected behavior of the refined surface grains. Good tensile ductility in a grain size gradient requires the continuation of the gradient into an undeformed region.

  19. Analytical Study of Values of Business Process Outsourcing Employees to Address Issue of Attrition and Suggestion of Work life Balance Intervention

    Directory of Open Access Journals (Sweden)

    K. Santhanalakshmi

    2014-07-01

    Full Text Available Business process outsourcing sector (BPO offered opportunities for employment to a large number of persons with diverse skill sets in India. However, the industry is plagued by attrition of employees due to technological intensity, work intensity at the intersection of globalization and liberalization made organizations to adopt high performance work practices and higher working hours. Values and changes in value priorities are considered as axial principle and are posited to impact attrition. Values priorities are measured using factor analysis and thirteen of them are identified in the context of BPO sector is identified, measured and ordered. The value priorities provided insights to design human resource interventions to discourage hedonistic practices and encourage work life balance which may help organizations to tide over the issue of attrition.

  20. 激光熔覆原位生成增强相强化铁基涂层性能研究%Performance Improvement of Iron Base Coating by Laser Cladding In-situ Generated Reinforced Phase

    Institute of Scientific and Technical Information of China (English)

    尹泉; 彭如恕; 朱红梅

    2016-01-01

    . 9wt%) composite powder were studied experimentally. The microstructure of laser cladding layers and composition of reinforced particles were analyzed using scanning electron microscope ( SEM ) and X-ray diffraction (XRD), the microhardness of the laser cladding layer was tested using optical microscopy hardness tester, and the corrosion resist-ance of the cladding layer was tested using electricity chemistry workstation. Results The results showed that the cladding layer had no obvious defects such as cracks, porosity, and was well bound with the base material. Reaction occurred in the process of laser cladding among the graphite, ilmenite and boron iron added, and rigid reinforced phases such as Cr23 C6 ,Cr3 C2 ,TiO2 ,Ti1. 8 B50 were in situ generated. With increasing mass fractions of graphite, ilmenite and boron iron, the contents of rigid reinforced phase generated in the cladding layer increased, and the microhardness value of the cladding layer was also obviously improved. The hardness of cladding layer containing 30% of the composite powder was 3. 6 fold as high as that of the base material. The corrosion resistance of the laser cladding specimens was also higher than that of the base material, and it increased with the increasing mass ratio of the composite powder. The corrosion resistance of cladding layer containing 30% of the composite powder was 1. 58 fold as high as that of the base material. Conclusion Iron base cladding layers containing reinforced phases such as carbon chromium, titanium boron compounds and titanium oxide prepared by laser cladding had significantly improved performance than the base material performance.

  1. Design, Synthesis, and Mechanistic Evaluation of Iron-Based Catalysis for Synthesis Gas Conversion to Fuels and Chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Enrique Iglesia; Akio Ishikawa; Manual Ojeda; Nan Yao

    2007-09-30

    ) structural evolution of Fe-Zn oxide promoted with K and Cu, and (ii) evaluation of hydrocarbon and CH{sub 4} formation rates during activation procedures at various temperature and H{sub 2}/CO ratios. On the basis of the obtained results, we suggest that lower reactor temperature can be sufficient to activate catalysts and lead to the high FTS performance. In this project, we have also carried out a detailed kinetic and mechanistic study of the Fischer-Tropsch Synthesis with Fe-based catalysts. We have proposed a reaction mechanism with two CO activation pathways: unassisted and H-assisted. Both routes lead to the formation of the same surface monomers (CH{sub 2}). However, the oxygen removal mechanism is different. In the H-assisted route, oxygen is removed exclusively as water, while oxygen is rejected as carbon dioxide in the unassisted CO dissociation. The validity of the mechanism here proposed has been found to be in agreement with the experimental observation and with theoretical calculations over a Fe(110) surface. Also, we have studied the validity of the mechanism that we propose by analyzing the H{sub 2}/D{sub 2} kinetic isotope effect (r{sub H}/r{sub D}) over a conventional iron-based Fischer-Tropsch catalyst Fe-Zn-K-Cu. We have observed experimentally that the use of D{sub 2} instead of H{sub 2} leads to higher hydrocarbons formation rates (inverse kinetic isotopic effect). On the contrary, primary carbon dioxide formation is not influenced. These experimental observations can be explained by two CO activation pathways. We have also explored the catalytic performance of Co-based catalysts prepared by using inverse micelles techniques. We have studied several methods in order to terminate the silanol groups on SiO{sub 2} support including impregnation, urea homogeneous deposition-precipitation, or zirconium (IV) ethoxide titration. Although hydroxyl groups on the SiO{sub 2} surface are difficult to be stoichiometrically titrated by ZrO{sub 2}, a requirement to

  2. Hydrogen environment embrittlement of astroloy and Udimet 700 (nickel-base) and V-57 (iron-base) superalloys

    Science.gov (United States)

    Gray, H. R.; Joyce, J. P.

    1975-01-01

    The sensitivity to hydrogen environment embrittlement of three superalloys was determined. Astroloy forgings were resistant to embrittlement during smooth tensile, notched tensile, and creep testing in 3.5-MN/sq m hydrogen over the range 23 to 760 C. The notched tensile strength of Udimet 700 bar stock in hydrogen at 23 C was only 50 percent of the baseline value in helium. Forgings of V-57 were not significantly embrittled by hydrogen during smooth tensile testing over the range 23 to 675 C; creep and rupture lives of V-57 were degraded by hydrogen. Postcreep tensile ductility of V-57 was reduced by 40 percent after creep exposure in hydrogen.

  3. Screening for depression and anxiety: correlates of non-response and cohort attrition in the Netherlands study of depression and anxiety (NESDA).

    Science.gov (United States)

    Van Der Veen, Willem Jan; Van Der Meer, Klaas; Penninx, Brenda W

    2009-12-01

    A major problem in the analysis of attrition of cohorts in studies on mental health problems is that data on those who do not participate at the outset of a study are largely unavailable. It is not known how underlying psychopathology affects the first stages of screening where non-response and selectivity are usually highest. This article presents results of one of the centres of the Netherlands Study of Depression and Anxiety (NESDA), a longitudinal study aimed at describing the long-term course and consequences of depression and anxiety disorders. The aim is to describe the different ways of attrition during the first NESDA-wave in a cohort of patients aged 18-65 years of the Registration Network Groningen and to analyse whether attrition is related to gender, age and psychopathology as recorded in general practice. The attrition of the study cohort (n = 8475) was highest during the first stages, eventually leading to a population of 169 patients only who participated in the full NESDA-programme. Probabilities of transition from one stage of the screening process to the next were regressed on selected background variables using binary logistic regression. Correlates of participation were being female and being older (>40). Psychopathology was an important variable in the formation of the initial sample cohort, but only had a weak influence on patient response to the screening questionnaire. Study design factors had a stronger impact on the changing composition of the cohort at each screening stage compared to patient factors. PMID:20027601

  4. Why They Leave: The Impact of Stereotype Threat on the Attrition of Women and Minorities from Science, Math and Engineering Majors

    Science.gov (United States)

    Beasley, Maya A.; Fischer, Mary J.

    2012-01-01

    This paper examines the effects of group performance anxiety on the attrition of women and minorities from science, math, and engineering majors. While past research has relied primarily on the academic deficits and lower socioeconomic status of women and minorities to explain their absence from these fields, we focus on the impact of stereotype…

  5. Relationship between Measures of Academic Quality and Undergraduate Student Attrition: The Case of Higher Education Institutions in the Colombian Caribbean Region

    Science.gov (United States)

    Martínez, Anabella; Borjas, Mónica; Herrera, Mariela; Valencia, Jorge

    2015-01-01

    Undergraduate student attrition is a major concern in higher education. It is usually explained by the impact of student attributes; however, recent developments in student success literature point to the need of exploring institutional practices that may impact a student's decision to abandon their studies. The current weight of academic quality…

  6. Concordance of Race or Ethnicity of Interventionists and Caregivers of Dementia Patients: Relationship to Attrition and Treatment Outcomes in the REACH Study

    Science.gov (United States)

    McGinnis, Kathleen A.; Schulz, Richard; Stone, Roslyn A.; Klinger, Julie; Mercurio, Rocco

    2006-01-01

    Purpose: We assess the effects of racial or ethnic concordance between caregivers and interventionists on caregiver attrition, change in depression, and change in burden in a multisite randomized clinical trial. Design and Methods: Family caregivers of patients with Alzheimer's disease were randomized to intervention or control groups at six sites…

  7. Multiple imputation for estimation of an occurrence rate in cohorts with attrition and discrete follow-up time points: a simulation study

    Science.gov (United States)

    2010-01-01

    Background In longitudinal cohort studies, subjects may be lost to follow-up at any time during the study. This leads to attrition and thus to a risk of inaccurate and biased estimations. The purpose of this paper is to show how multiple imputation can take advantage of all the information collected during follow-up in order to estimate the cumulative probability P(E) of an event E, when the first occurrence of this event is observed at t successive time points of a longitudinal study with attrition. Methods We compared the performance of multiple imputation with that of Kaplan-Meier estimation in several simulated attrition scenarios. Results In missing-completely-at-random scenarios, the multiple imputation and Kaplan-Meier methods performed well in terms of bias (less than 1%) and coverage rate (range = [94.4%; 95.8%]). In missing-at-random scenarios, the Kaplan-Meier method was associated with a bias ranging from -5.1% to 7.0% and with a very poor coverage rate (as low as 0.2%). Multiple imputation performed much better in this situation (bias 83.4%). Conclusions Multiple imputation shows promise for estimation of an occurrence rate in cohorts with attrition. This study is a first step towards defining appropriate use of multiple imputation in longitudinal studies. PMID:20815883

  8. Multiple imputation for estimation of an occurrence rate in cohorts with attrition and discrete follow-up time points: a simulation study

    Directory of Open Access Journals (Sweden)

    Soullier Noémie

    2010-09-01

    Full Text Available Abstract Background In longitudinal cohort studies, subjects may be lost to follow-up at any time during the study. This leads to attrition and thus to a risk of inaccurate and biased estimations. The purpose of this paper is to show how multiple imputation can take advantage of all the information collected during follow-up in order to estimate the cumulative probability P(E of an event E, when the first occurrence of this event is observed at t successive time points of a longitudinal study with attrition. Methods We compared the performance of multiple imputation with that of Kaplan-Meier estimation in several simulated attrition scenarios. Results In missing-completely-at-random scenarios, the multiple imputation and Kaplan-Meier methods performed well in terms of bias (less than 1% and coverage rate (range = [94.4%; 95.8%]. In missing-at-random scenarios, the Kaplan-Meier method was associated with a bias ranging from -5.1% to 7.0% and with a very poor coverage rate (as low as 0.2%. Multiple imputation performed much better in this situation (bias 83.4%. Conclusions Multiple imputation shows promise for estimation of an occurrence rate in cohorts with attrition. This study is a first step towards defining appropriate use of multiple imputation in longitudinal studies.

  9. Coal-sand attrition system and its importance in fine coal cleaning. First quarterly report, September 1, 1991--November 30, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, R.K.

    1991-12-02

    The primary objective of this project is geared toward the substitution of steel media by fracturing silica sand as a grinding media for ultrafine coal grinding. The experimental silica is as follows: (1) design and fabrication of attrition cell; (2) sample procurement, preparation, and characterization; (3) batch grinding tests; (4) continuous grinding test; and (5) fracture mechanics.

  10. Listen-Identify-Brainstorm-Reality-Test-Encourage (LIBRE) Problem-Solving Model: Addressing Special Education Teacher Attrition through a Cognitive-Behavioral Approach to Teacher Induction

    Science.gov (United States)

    Guerra, Norma S.; Hernandez, Art; Hector, Alison M.; Crosby, Shane

    2015-01-01

    Special education teacher attrition rates continue to challenge the profession. A cognitive-behavioral problem-solving approach was used to examine three alternative certification program special education teachers' professional development through a series of 41 interviews conducted over a 2-year period. Beginning when they were novice special…

  11. Should I Stay or Should I Go? Factors that Influence the Retention, Turnover, and Attrition of K-12 Music Teachers in the United States

    Science.gov (United States)

    Gardner, Robert D.

    2010-01-01

    The purpose of this study was to construct a profile of K-12 music teachers in the United States and develop a model to predict their retention, turnover, and attrition. Responses to the "Schools and Staffing Survey" from 47,857 K-12 public and private school teachers, including 1,903 music teachers, were analyzed using comparative statistics,…

  12. I Ain't Gonna Make It. Comparing Job Demands-Resources and Attrition Intention Between Senior Teachers and Senior Employees of Six Other Occupational Categories in Flanders.

    Science.gov (United States)

    Van Droogenbroeck, Filip; Spruyt, Bram

    2016-07-01

    Teachers are often thought to retire early and have more stress and burnout than other human service professionals. In this article, we investigate attrition intention amongst senior teachers and senior employees of six other blue- and white-collar occupational categories using the Job Demands-Resources (JD-R) model. We followed a two-step approach. First, analysis of variance and logistic regression analysis was used to assess differences in the level of job demands, resources, and attrition intention between occupations for male and female employees separately. Subsequently, multiple group path analysis was used to assess the invariance of the JD-R model across occupational groups and genders. We used representative data gathered in Flanders among 6,810 senior employees (45 years or older). Results indicate that there are differences in the determinants of attrition intention between men and women. The differences in attrition intention are minimal between occupations once controlled for job demands and resources. In addition, the JD-R model is largely invariant across white-collar occupations and gender. We provide support for both the energetic and motivational process of the JD-R model. PMID:27166367

  13. An Examination of Freshman Student Attrition from the Fall Semester to the Spring Semester as Related to William Glasser's Choice Theory and Basic Needs

    Science.gov (United States)

    Price, Erin S.

    2010-01-01

    Freshman student retention has become a major focus in higher education. The loss of incoming students is not only financially burdensome to the institution, but it can be academically and personally discouraging for students. Many theoretical constructs have been applied to the problem of student attrition, including the individual constructs of…

  14. Microstructure and wear resistance of spray-formed supermartensitic stainless steel

    Directory of Open Access Journals (Sweden)

    Guilherme Zepon

    2013-06-01

    Full Text Available Since the early 90's the oil industry has been encouraging the development of corrosion and wear resistant alloys for onshore and offshore pipeline applications. In this context supermartensitic stainless steel was introduced to replace the more expensive duplex stainless steel for tubing applications. Despite the outstanding corrosion resistance of stainless steels, their wear resistance is of concern. Some authors reported obtaining material processed by spray forming, such as ferritic stainless steel, superduplex stainless steel modified with boron, and iron-based amorphous alloys, which presented high wear resistance while maintaining the corrosion performance1,2. The addition of boron to iron-based alloys promotes the formation of hard boride particles (M2B type which improve their wear resistances3-9. This work aimed to study the microstructure and wear resistance of supermartensitic stainless steel modified with 0.3 wt. (% and 0.7 wt. (% processed by spray forming (SF-SMSS 0.3%B and SF-SMSS 0.7%B, respectively. These boron contents were selected in order to improve the wear resistance of supermartensitic stainless steel through the formation of uniformly distributed borides maintaining the characteristics of the corrosion resistant matrix. SF-SMSS 0.7%B presents an abrasive wear resistance considerably higher than spray-formed supermartensitic stainless steel without boron addition (SF-SMSS.

  15. Non-conventional superconducting fluctuations in Ba(Fe1−xRhx)2As2 iron-based superconductors

    International Nuclear Information System (INIS)

    We measured the static uniform spin susceptibility of Ba(Fe1−xRhx)2As2 iron-based superconductors, over a broad range of doping (0.041 ⩽ x ⩽ 0.094) and magnetic fields. At small fields (H ⩽ 1 kOe) we observed, above the transition temperature Tc, the occurrence of precursor diamagnetism, which is not ascribable to the Ginzburg–Landau theory. On the contrary, our data agree with a phase fluctuation model, which has been used to interpret a similar phenomenology occurring in the high-Tc cuprate superconductors. Additionally, in the presence of strong fields, the unconventional fluctuating diamagnetism is suppressed, whereas Ginzburg–Landau fluctuations are found, in agreement with literature. (paper)

  16. First-Principles Study of Antimony Doping Effects on the Iron-Based Superconductor CaFe(SbxAs1-x)2

    Science.gov (United States)

    Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; Kuroki, Kazuhiko

    2015-09-01

    We study antimony doping effects on the iron-based superconductor CaFe(SbxAs1-x)2 by using the first-principles calculation. The calculations reveal that the substitution of a doped antimony atom into As of the chainlike As layers is more stable than that into FeAs layers. This prediction can be checked by experiments. Our results suggest that doping homologous elements into the chainlike As layers, which only exist in the novel 112 system, is responsible for rising up the critical temperature. We discuss antimony doping effects on the electronic structure. It is found that the calculated band structures with and without the antimony doping are similar to each other within our framework.

  17. First-principles study of antimony doping effects on the iron-based superconductor CaFe(SbxAs1−x)2

    International Nuclear Information System (INIS)

    We study antimony doping effects on the iron-based superconductor CaFe(SbxAs1−x)2 by using the first-principles calculation. The calculations reveal that the substitution of a doped antimony atom into As of the chainlike As layers is more stable than that into FeAs layers. This prediction can be checked by experiments. Our results suggest that doping homologous elements into the chainlike As layers, which only exist in the novel 112 system, is responsible for rising up the critical temperature. We discuss antimony doping effects on the electronic structure. It is found that the calculated band structures with and without the antimony doping are similar to each other within our framework. (author)

  18. Rapid, sensitive, and selective fluorescent DNA detection using iron-based metal-organic framework nanorods: Synergies of the metal center and organic linker.

    Science.gov (United States)

    Tian, Jingqi; Liu, Qian; Shi, Jinle; Hu, Jianming; Asiri, Abdullah M; Sun, Xuping; He, Yuquan

    2015-09-15

    Considerable recent attention has been paid to homogeneous fluorescent DNA detection with the use of nanostructures as a universal "quencher", but it still remains a great challenge to develop such nanosensor with the benefits of low cost, high speed, sensitivity, and selectivity. In this work, we report the use of iron-based metal-organic framework nanorods as a high-efficient sensing platform for fluorescent DNA detection. It only takes about 4 min to complete the whole "mix-and-detect" process with a low detection limit of 10 pM and a strong discrimination of single point mutation. Control experiments reveal the remarkable sensing behavior is a consequence of the synergies of the metal center and organic linker. This work elucidates how composition control of nanostructures can significantly impact their sensing properties, enabling new opportunities for the rational design of functional materials for analytical applications. PMID:25879891

  19. Magnetic resonance imaging reveals detailed spatial and temporal distribution of iron-based nanoparticles transported through water-saturated porous media

    Science.gov (United States)

    Cuny, Laure; Herrling, Maria Pia; Guthausen, Gisela; Horn, Harald; Delay, Markus

    2015-11-01

    The application of engineered nanoparticles (ENP) such as iron-based ENP in environmental systems or in the human body inevitably raises the question of their mobility. This also includes aspects of product optimization and assessment of their environmental fate. Therefore, the key aim was to investigate the mobility of iron-based ENP in water-saturated porous media. Laboratory-scale transport experiments were conducted using columns packed with quartz sand as model solid phase. Different superparamagnetic iron oxide nanoparticles (SPION) were selected to study the influence of primary particle size (dP = 20 nm and 80 nm) and surface functionalization (plain, -COOH and -NH2 groups) on particle mobility. In particular, the influence of natural organic matter (NOM) on the transport and retention behaviour of SPION was investigated. In our approach, a combination of conventional breakthrough curve (BTC) analysis and magnetic resonance imaging (MRI) to non-invasively and non-destructively visualize the SPION inside the column was applied. Particle surface properties (surface functionalization and resulting zeta potential) had a major influence while their primary particle size turned out to be less relevant. In particular, the mobility of SPION was significantly increased in the presence of NOM due to the sorption of NOM onto the particle surface resulting in a more negative zeta potential. MRI provided detailed spatially resolved information complementary to the quantitative BTC results. The approach can be transferred to other porous systems and contributes to a better understanding of particle transport in environmental porous media and porous media in technical applications.

  20. Influence of the thermal history of a particle during atomization on the morphology of carbides in a hypereutectic iron based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kusy, M. [Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava, Paulinska 16, 917 24 Trnava (Slovakia); Behulova, M., E-mail: maria.behulova@stuba.sk [Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava, Paulinska 16, 917 24 Trnava (Slovakia); Grgac, P. [Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava, Paulinska 16, 917 24 Trnava (Slovakia)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Identification of solidification microstructures in RS powder from iron based alloy. Black-Right-Pointing-Pointer Microstructures affected and nonaffected during the post-recalescence period. Black-Right-Pointing-Pointer Thermokinetic newtonian model of rapid solidification of a droplet in gas atomization. Black-Right-Pointing-Pointer Droplet thermal history and conditions for the microstructure development. Black-Right-Pointing-Pointer Parameters influencing development of different solidification microstructures. - Abstract: Basic principles and consequences of the rapid solidification processing of melts have been successfully exploited in several progressive technologies of material production. In the paper, the solidification microstructures developed in the hypereutectic iron based alloy with the chemical composition of 3% C-3% Cr-12% V (wt.%) prepared by nitrogen gas atomization are presented and analysed. Several main types of solidification microstructures were identified in the rapidly solidified powder particles. According to the morphological features of carbide phases and computed thermal history of rapidly solidified particles, the microstructures were divided into two groups - microstructures morphologically non-affected during the post-recalescence period of solidification, and microstructures with morphological transitions occurring during the quasi-isothermal period of structure development. Based on the thermokinetic newtonian model of rapid solidification of a spherical droplet in the process of atomization, the thermal history of droplets with diameter from 20 {mu}m to 400 {mu}m rapidly solidified from different nucleation temperatures was studied. The thermo-physical conditions necessary for the development of variable microstructures in single rapidly solidified powder particles are predicted and discussed. The nucleation temperature, recalescence temperature and duration of quasi-isothermal plateau

  1. Magnetic properties of iron-based amorphous and nanocrystalline Fe-Zr-X-B (X: Cu, Al) alloy films

    International Nuclear Information System (INIS)

    Thermal stability and magnetic properties of thin films, of a few Fe-based amorphous and nanocrystalline alloys, have been studied. The alloys belong to the class Fe-M-B, whose representatives are Fe87Zr4CuB8, Fe87Zr7B6, and Fe87Zr7AlB5 and are of particular interest because of their wide variety of magnetic properties. The films were prepared by flash evaporation onto liquid nitrogen cooled substrates. Measurements of the Kerr effect, the Hall effect, and ferromagnetic resonance in the films were carried out as functions of the annealing temperature. It was found that the changes in the coercive field Hc, resonance linewidth ΔHpp, effective magnetization Meff, Hall parameters, and resistance were correlated with the structural changes in the studied films. (author)

  2. Al-Zn-Si coatings on iron-base alloys obtained by batch hot-dip method

    International Nuclear Information System (INIS)

    The aluminium addition in the zinc bath causes an increase in corrosion resistance of the obtained coatings. The work presents investigations results of obtained coatings by batch hot dip method in the alloy bath containing Zn + 55%Al + 1.6%Si. The surface treatment process of iron alloys before metallization is presented. Kinetics of the coating growth in the tested alloys was determined in the changeable conditions of bath temperature and dip time. The structure of coatings and their phase composition was revealed. As the result of the performed tests it has been found that an increase in total thickness of coatings in the dip time function at stable temperature has character close to parabolic, whereas an increase in the transient layer has character close to linear. (author)

  3. The Role of Attrition and Solids Recovery in a Chemical Looping Combustion Process; Effet de l'attrition et de la recuperation des particules dans le procede de combustion en boucle chimique

    Energy Technology Data Exchange (ETDEWEB)

    Kramp, M.; Thon, A.; Hartge, E.U.; Heinrich, S.; Werther, J. [Institute of Solids Process Engineering and Particle Technology, Hamburg University of Technology, 21071 Hamburg (Germany)

    2011-03-15

    In the present work, the steady-state behavior of a Chemical Looping Combustion process of interconnected fluidized bed reactors is simulated. The simulations have been carried out in two different scales, 50 kWth and 100 MWth. Attrition model derived from small scale laboratory experiments has been employed for the prediction of the process behavior in terms of attrition and Oxygen Carrier loss. Information on Oxygen Carrier characteristics and reaction kinetics were taken from literature. Realistic circulation mass flows of Oxygen Carrier particles are obtained and Oxygen Carrier losses are quantified. The large scale process looses significantly more Oxygen Carrier than the small scale process based on the same amount of thermal energy produced. Incomplete conversion in the air reactor could be identified as a critical point. Another issue is the fuel gas bypassing the Oxygen Carrier particles through bubbles in the large scale process which leads to lowered fuel conversions. The simulations indicate that a similar performance of a pilot scale and a large scale process is not guaranteed due to the scale-up effect on fluid dynamics. Furthermore, the simulations allow an assessment of the influence of the quality of the solids recovery system on the Oxygen Carrier loss. The distribution of the losses between possible origins is investigated and different changes in the solids recovery system are discussed regarding their potential to decrease the Oxygen Carrier loss. For example, the addition of a second-stage cyclone after the air reactor of the large scale process reduces the Oxygen Carrier loss significantly. (authors)

  4. The feasibility of progressive resistance training in women with polycystic ovary syndrome: a pilot randomized controlled trial

    OpenAIRE

    Vizza, Lisa; Smith, Caroline A.; Swaraj, Soji; Agho, Kingsley; Cheema, Birinder S.

    2016-01-01

    Background To evaluate the feasibility of executing a randomized controlled trial of progressive resistance training (PRT) in women with polycystic ovary syndrome (PCOS). Methods Women with PCOS were randomized to an experimental (PRT) group or a no-exercise (usual care) control group. The PRT group was prescribed two supervised and two unsupervised (home-based) training sessions per week for 12 weeks. Feasibility outcomes included recruitment and attrition, adherence, adverse events, and com...

  5. Personality Disorder in Adult Attention-Deficit/Hyperactivity Disorder: Attrition and Change During Long-term Treatment.

    Science.gov (United States)

    Gift, Thomas E; Reimherr, Frederick W; Marchant, Barrie K; Steans, Tammy A; Wender, Paul H

    2016-05-01

    Personality disorders (PDs) are commonly found in adults with attention-deficit/hyperactivity disorder (ADHD) and are associated with increased ADHD symptoms and psychosocial impairment. To assess the impact of PDs or personality traits on retention rates in ADHD trials and whether treating ADHD affects the expression of PD, data were analyzed from 2 methylphenidate trials. Assessment of PDs and personality traits included using the Wisconsin Personality Disorders Inventory IV and the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Personality Disorders. Attention-deficit/hyperactivity disorder symptoms were evaluated using the Wender-Reimherr Adult Attention Deficit Disorder Scale. Major findings were that subjects with cluster A, cluster B, passive-aggressive, or more than 1 PD showed more attrition. Subjects dropping out also had more schizoid and narcissistic traits. Attention-deficit/hyperactivity disorder symptoms (p Disorders Inventory IV items that improved most, 8 resembled ADHD or oppositional defiant disorder symptoms. PMID:27082828

  6. Effect of treatment time on characterization and properties of nanocrystalline surface layer in copper induced by surface mechanical attrition treatment

    Indian Academy of Sciences (India)

    Farzad Kargar; M Laleh; T Shahrabi; A Sabour Rouhaghdam

    2014-08-01

    Nanocrystalline surface layers were synthesized on pure copper by means of surface mechanical attrition treatment (SMAT) at various treatment times. The microstructural features of the surface layers produced by SMAT were systematically characterized by optical microscopy (OM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. Hardness and surface roughness measurements were also carried out. It is found that the thickness of the deformed layer increased from 50 to 500 m with increasing treatment time from 10 to 300 min, while the average grain size of the top surface layer decreased from 20 to 7 nm. Hardness of the all SMATed samples decreased with depth. Furthermore, the hardness of the top surface layer of the SMATed samples was at least two times higher than that of the un-treated counterpart. Surface roughness results showed different trend with treatment time. Amounts of PV and a values first sharply increased and then decreased.

  7. Impact and attrition shear breakage of enzyme granules and placebo particles-application to particle design and formulation

    DEFF Research Database (Denmark)

    Jørgensen, Kåre; Bach, Poul; Jensen, Anker

    2005-01-01

    The strength and breakage mechanisms of detergent enzyme granules and typical core materials used for enzyme granules (all of size 500-600 mum) have been investigated under impact and shear stress conditions to simulate the stresses experienced in a detergent factory. In an Impact Tester, single......-particle experiments were performed at impact velocities of 8-25 m/s. Multiple (bulk) particle experiments were performed in an Attrition Shear Cell (ASC), where the particles were exposed to shear strains of about 1250 and normal stresses of 1-30 kPa. For coated enzyme granules the results indicate that the primary...... breakage mechanism after repeated impacts at 10 m/s is chipping associated with local delamination. Damages to the coating layer may expose the underlying enzyme-containing layer or core and lead to the release of enzyme-active dust. Markedly lower enzyme dust release was obtained by incorporating...

  8. Concentration and distribution of platinum-group elements (PGE) in soils. Platinum emission by attrition of automobile exhaust catalysts

    International Nuclear Information System (INIS)

    In Germany automobile exhaust control by platinum-group element (PGE) loaded catalysts is now well established. By mechanical or chemical attrition, these catalysts could act as a potential source for a significant increase of PGE abundances in the environment. During a recent research program concentrations and distributions of PGE in different soils were measured along the highway A66 Frankfurt - Wiesbaden. 71 nearsurface soil samples were analysed by graphite furnace atomic absorption spectrometry (GFAAS). The results revealed average abundances of 10 ppb platinum and 3 ppb ruthenium. Palladium as well as rhodium were below the analytical detection limit of 2 ppb. With increasing distance from the highway edge PGE values gradually decreased. Only the upmost soil layer, down to 20 cm depth, contains measurable PGE concentrations. Results: There are irregular PGE concentrations of anthropogenic origin in different soils along the highway A66 Frankfurt -Wiesbaden possibly arising from automobile exhaust catalysts. Further monitoring could help to avoid potential environmental hazards. (orig.)

  9. Thermal stability of nanocrystalline layer prepared by surface mechanical attrition in 0Cr18Ni9Ti stainless steel

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-bin; WU Xiao-chun; XU Ling-yun

    2004-01-01

    By means of surface mechanical attrition (SMA), a nanostructured surface layer was formed on a 0Cr18Ni9Ti austenite stainless steel plate. A strain-induced martensite transformation was observed during SMA treatment, and a single magnetic martensite phase layer with thickness of about 30 μm was gotten. The grain growth and phase transformations in the nanocrystalline layer are investigated during heating. The grain growth exponent for nanocrystalline polycrystalline steel is estimated. The kinetics mechanism governing the grain growth in the nanocrystalline layer is discussed. The martensite in the surface layer is quite stable and the temperature at which the reverse transformation of martensite to austenite starts during heating is about 500 ℃.

  10. A validation of the fibre orientation and fibre length attrition prediction for long fibre-reinforced thermoplastics

    Science.gov (United States)

    Hopmann, Ch.; Weber, M.; van Haag, J.; Schöngart, M.

    2015-05-01

    To improve the mechanical performance of polymeric parts, fibre reinforcement has established in industrial applications during the last decades. Next to the widely used Short Fibre-reinforced Thermoplastics (SFT) the use of Long Fibre-reinforced Thermoplastics (LFT) is increasingly growing. Especially for non-polar polymeric matrices like polypropylene (PP), longer fibres can significantly improve the mechanical performance. As with every kind of discontinuous fibre reinforcement the fibre orientations (FO) show a high impact on the mechanical properties. On the contrary to SFT where the local fibre length distribution (FLD) can be often neglected, for LFT the FLD show a high impact on the material's properties and has to be taken into account in equal measure to the FOD. Recently numerical models are available in commercial filling simulation software and allow predicting both the local FOD and FLD in LFT parts. The aim of this paper is to compare i.) the FOD results and ii) the FLD results from available orientation- and fibre length attrition-models to those obtained from experimental data. The investigations are conducted by the use of different injection moulded specimens made from long glass fibre reinforced PP. In order to determine the FOD, selected part sections are examined by means of Computed Tomographic (CT) analyses. The fully three dimensional measurement of the FOD is then performed by digital image processing using grey scale correlation. The FLD results are also obtained by using digital image processing after a thermal pyrolytic separation of the polymeric matrix from the fibres. Further the FOD and the FLD are predicted by using a reduced strain closure (RSC) as well as an anisotropic rotary diffusion - reduced strain closure model (ARD-RSC) and Phelps-Tucker fibre length attrition model implemented in the commercial filling software Moldflow, Autodesk Inc., San Rafael, CA, USA.

  11. A validation of the fibre orientation and fibre length attrition prediction for long fibre-reinforced thermoplastics

    Energy Technology Data Exchange (ETDEWEB)

    Hopmann, Ch.; Weber, M.; Haag, J. van; Schöngart, M. [Institute of Plastics Processing (IKV) at RWTH Aachen University, Pontstr. 49, 52062 Aachen (Germany)

    2015-05-22

    To improve the mechanical performance of polymeric parts, fibre reinforcement has established in industrial applications during the last decades. Next to the widely used Short Fibre-reinforced Thermoplastics (SFT) the use of Long Fibre-reinforced Thermoplastics (LFT) is increasingly growing. Especially for non-polar polymeric matrices like polypropylene (PP), longer fibres can significantly improve the mechanical performance. As with every kind of discontinuous fibre reinforcement the fibre orientations (FO) show a high impact on the mechanical properties. On the contrary to SFT where the local fibre length distribution (FLD) can be often neglected, for LFT the FLD show a high impact on the material’s properties and has to be taken into account in equal measure to the FOD. Recently numerical models are available in commercial filling simulation software and allow predicting both the local FOD and FLD in LFT parts. The aim of this paper is to compare i.) the FOD results and ii) the FLD results from available orientation- and fibre length attrition-models to those obtained from experimental data. The investigations are conducted by the use of different injection moulded specimens made from long glass fibre reinforced PP. In order to determine the FOD, selected part sections are examined by means of Computed Tomographic (CT) analyses. The fully three dimensional measurement of the FOD is then performed by digital image processing using grey scale correlation. The FLD results are also obtained by using digital image processing after a thermal pyrolytic separation of the polymeric matrix from the fibres. Further the FOD and the FLD are predicted by using a reduced strain closure (RSC) as well as an anisotropic rotary diffusion - reduced strain closure model (ARD-RSC) and Phelps-Tucker fibre length attrition model implemented in the commercial filling software Moldflow, Autodesk Inc., San Rafael, CA, USA.

  12. Differential Effects of L2 on Children's L1 Development/Attrition.

    Science.gov (United States)

    Saville-Troike, Muriel; Pan, Junlin; Dutkova, Ludmila

    1995-01-01

    Examines how second-language knowledge is integrated with the first, noting elements of native language development that are most resistant to influence from second languages and those that are most permeable. Discusses how the process of integration and influence can be universal or different depending on the language, using data from native…

  13. A short leucocyte telomere length is associated with development of insulin resistance

    DEFF Research Database (Denmark)

    Verhulst, Simon; Dalgård, Christine; Labat, Carlos;

    2016-01-01

    AIMS/HYPOTHESIS: A number of studies have shown that leucocyte telomere length (LTL) is inversely associated with insulin resistance and type 2 diabetes mellitus. The aim of the present longitudinal cohort study, utilising a twin design, was to assess whether shorter LTL predicts insulin resistance...... and insulin resistance over an average of 12 years were performed in a subset of the Registry consisting of 338 (184 monozygotic and 154 dizygotic) same-sex twin pairs. RESULTS: Age at baseline examination was 37.4 ± 9.6 (mean ± SD) years. Baseline insulin resistance was not associated with age......-dependent changes in LTL (attrition) over the follow-up period, whereas baseline LTL was associated with changes in insulin resistance during this period. The shorter the LTL at baseline, the more pronounced was the increase in insulin resistance over the follow-up period (p 

  14. Critical Evaluation of Prediction Models for Phosphorus Partition between CaO-based Slags and Iron-based Melts during Dephosphorization Processes

    Science.gov (United States)

    Yang, Xue-Min; Li, Jin-Yan; Chai, Guo-Ming; Duan, Dong-Ping; Zhang, Jian

    2016-08-01

    According to the experimental results of hot metal dephosphorization by CaO-based slags at a commercial-scale hot metal pretreatment station, the collected 16 models of equilibrium quotient k_{{P}} or phosphorus partition L_{{P}} between CaO-based slags and iron-based melts from the literature have been evaluated. The collected 16 models for predicting equilibrium quotient k_{{P}} can be transferred to predict phosphorus partition L_{{P}} . The predicted results by the collected 16 models cannot be applied to be criteria for evaluating k_{{P}} or L_{{P}} due to various forms or definitions of k_{{P}} or L_{{P}} . Thus, the measured phosphorus content [pct P] in a hot metal bath at the end point of the dephosphorization pretreatment process is applied to be the fixed criteria for evaluating the collected 16 models. The collected 16 models can be described in the form of linear functions as y = c0 + c1 x , in which independent variable x represents the chemical composition of slags, intercept c0 including the constant term depicts the temperature effect and other unmentioned or acquiescent thermodynamic factors, and slope c1 is regressed by the experimental results of k_{{P}} or L_{{P}} . Thus, a general approach to developing the thermodynamic model for predicting equilibrium quotient k_{{P}} or phosphorus partition L P or [pct P] in iron-based melts during the dephosphorization process is proposed by revising the constant term in intercept c0 for the summarized 15 models except for Suito's model (M3). The better models with an ideal revising possibility or flexibility among the collected 16 models have been selected and recommended. Compared with the predicted result by the revised 15 models and Suito's model (M3), the developed IMCT- L_{{P}} model coupled with the proposed dephosphorization mechanism by the present authors can be applied to accurately predict phosphorus partition L_{{P}} with the lowest mean deviation δ_{{L_{{P}} }} of log L_{{P}} as 2.33, as

  15. Psychological and sociodemographic predictors of premature discontinuation of a 1-year multimodal outpatient weight-reduction program: an attrition analysis

    Directory of Open Access Journals (Sweden)

    Liebl ME

    2012-03-01

    Full Text Available Anne Ahnis1, Andrea Riedl1, Andrea Figura1, Elisabeth Steinhagen-Thiessen2, Max E Liebl3, Burghard F Klapp11Internal Medicine and Dermatology, Medical Department, Division of Psychosomatic Medicine, Charité – Universitätsmedizin Berlin, Campus Mitte, 2Internal Medicine with Gastroenterology and Nephrology, Specialty network of Gastroenterology, Endocrinology and Metabolic Diseases, Division of Lipid Metabolism, Charité – Universitätsmedizin Berlin, Campus Virchow-Klinikum, 3Medical Department, Division of Rheumatology and Clinical Immunology, Department for Physical Medicine, Charité – Universitätsmedizin Berlin, Campus Mitte, Berlin, GermanyObjective: Attrition rates of up to 77% have been reported in conservative weight-reduction programs for the treatment of obesity. In view of the cost of such programs to the health system, there is a need to identify the variables that predict premature discontinuation of treatment. Previous studies have focused mainly on somatic and sociodemographic parameters. The prospective influence of psychological factors has not been systematically investigated to date.Methods: A total of 164 patients (138 of whom were women with a mean age of 45 years and a mean body mass index of 39.57 participated in a 1-year outpatient weight-reduction program at the Charité – Universitätsmedizin Berlin University Hospital. The program included movement therapy, dietary advice, psychoeducational and behavioral interventions, relaxation procedures, and consultations with a specialist in internal medicine and a psychologist. Patients also underwent regular laboratory and psychological testing. The results were evaluated using a t-test, χ2-test, and logistic regression analysis.Results: Seventy-one of the 164 patients (61 women, mean age = 43 years, mean body mass index = 39.53 withdrew before the end of the program (attrition rate = 43.3%. While there were no differences between the somatic and metabolic

  16. Atomic short-range order in mechanically synthesized iron based Fe-Zn alloys studied by 57Fe Mössbauer spectroscopy

    Directory of Open Access Journals (Sweden)

    Konieczny Robert

    2015-03-01

    Full Text Available Mechanical alloying method was applied to prepare nanocrystalline iron-based Fe1−xZnx solid solutions with x in the range 0.01 ≤ x ≤ 0.05. The structural properties of the materials were investigated with the Mössbauer spectroscopy by measuring the room temperature spectra of 57Fe for as-obtained and annealed samples. The spectra were analyzed in terms of parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of zinc atoms existing in the neighborhood of iron atoms. The obtained results gave clear evidence that after annealing process, the distribution of impurity atoms in the first coordination spheres of 57Fe nuclei is not random and it cannot be described by binomial distribution. The estimated, positive values of the short-range order parameters suggest clustering tendencies of Zn atoms in the Fe-Zn alloys with low zinc concentration. The results were compared with corresponding data derived from Calphad calculation and resulting from the cellular atomic model of alloys by Miedema.

  17. Electronic structure and phonon spectrum of binary iron-based superconductor FeSe in both nonmagnetic and striped antiferromagnetic phases

    Energy Technology Data Exchange (ETDEWEB)

    Wang Wei, E-mail: wangweiphysics@yahoo.com.cn [School of Physics and Electronic Information, Huaibei Normal University, Huaibei, Anhui 235000 (China); Sun Jiafa [Information College of Huaibei Normal University, Huaibei, Anhui 235000 (China); Li Suwen; Lu Hongyan [School of Physics and Electronic Information, Huaibei Normal University, Huaibei, Anhui 235000 (China)

    2012-01-15

    Phonon softening in orthorhombic striped antiferromagnetic phase of FeSe. A large frequency gap exists in orthorhombic striped antiferromagnetic phase of FeSe. Magnetic phonons are still not responsible for superconductivity of FeSe. Using first-principles calculations, we investigate electronic structure and phonon spectrum of binary iron-based superconductor FeSe in both tetragonal nonmagnetic (NM) phase and orthorhombic striped antiferromagnetic (SAF) phase. It is found that the softening of atomic vibration modes and main electron-phonon coupling contribution from low-frequency Eliashberg spectral function {alpha}{sup 2}F({omega}) in SAF phase of FeSe lead to the enhancement of electron-phonon coupling strength {lambda}{sub ep} and logarithmically average frequency {omega}{sub ln}. However, the obtained superconducting T{sub c} in SAF phase just increases up to 0.34 K, even though Coulomb pseudopotential {mu}{sup Asterisk-Operator} is limited to zero. As a result, our magnetic phonons calculation still rules out phonon mediated superconductivity, although the electron-phonon coupling through the spin channel play an important role in FeSe.

  18. Improvement of the electron collection efficiency in porous hematite using a thin iron oxide underlayer: towards efficient all-iron based photoelectrodes.

    Science.gov (United States)

    Dalle Carbonare, Nicola; Carli, Stefano; Argazzi, Roberto; Orlandi, Michele; Bazzanella, Nicola; Miotello, Antonio; Caramori, Stefano; Bignozzi, Carlo A

    2015-11-28

    Different approaches have been explored to increase the water oxidation activity of nanostructured hematite (α-Fe2O3) photoanodes, including doping with various elements, surface functionalization with both oxygen evolving catalysts (OEC) and functional overlayers and, more recently, the introduction of ultrathin oxide underlayers as tunneling back contacts. Inspired by this latter strategy, we present here a photoanode design with a nanometric spin-coated iron oxide underlayer coupled with a mesoporous hematite film deposited by electrophoresis. The electrodes equipped with the thin underlayer exhibit a four-fold improvement in photoactivity over the simple hematite porous film, reaching a stable photocurrent density of ca. 1 mA cm(-2) at 0.65 V versus the saturated calomel electrode (SCE) at pH 13.3 (NaOH 0.1 M) under air mass (AM) 1.5G illumination. A further improvement to 1.5 mA cm(-2) is observed after decoration of the hematite surface with a Fe(iii)-OEC. These results demonstrate that by combining different iron oxide morphologies, it is possible to improve the selectivity of the interfaces towards both electron collection at the back contact and hole transfer to the electrolyte, obtaining an efficient all-iron based photoelectrode entirely realized with simple wet solution scalable procedures. PMID:26477966

  19. Effect of nitriding/nanostructuration of few layer graphene supported iron-based particles; catalyst in graphene etching and carbon nanofilament growth.

    Science.gov (United States)

    Baaziz, Walid; Melinte, Georgian; Ersen, Ovidiu; Pham-Huu, Cuong; Janowska, Izabela

    2014-08-14

    Stable, highly faceted and dispersed iron nitride particles supported on few layer graphene are obtained by ammonia decomposition on iron-based particles at the temperature commonly used for the synthesis of N-doped CNTs and graphene etching. The TEM/EELS analysis reveals nitrogen diffusion in a bulk of the particles. The resulting facet FeNx catalyst exhibits high activity in the etching of graphene, which is assisted by catalyst reorganization. Ammonia decomposition is used for the first time for graphene etching, while the highly faceted catalyst has an impact on the etched channels structures. According to the shape of the active planes of the catalyst, the etching results in sharp "V" channel ends and often "step-like" edges. The FeNx morphology proves previously reported triangularisation of arches in highly N-doped carbon nanotubes. The conditioning of the catalyst by its shaping and nitrogen incorporation is investigated additionally in the carbon nanostructure formation, for decomposition of ethane. The herringbone CNFs, "hollow" bamboo-like CNFs/CNTs or CNTs are effectively observed. PMID:24964374

  20. Comparing the detection of iron-based pottery pigment on a carbon-coated sherd by SEM-EDS and by Micro-XRF-SEM.

    Science.gov (United States)

    Pendleton, Michael W; Washburn, Dorothy K; Ellis, E Ann; Pendleton, Bonnie B

    2014-03-01

    The same sherd was analyzed using a scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) and a micro X-ray fluorescence tube attached to a scanning electron microscope (Micro-XRF-SEM) to compare the effectiveness of elemental detection of iron-based pigment. To enhance SEM-EDS mapping, the sherd was carbon coated. The carbon coating was not required to produce Micro-XRF-SEM maps but was applied to maintain an unbiased comparison between the systems. The Micro-XRF-SEM analysis was capable of lower limits of detection than that of the SEM-EDS system, and therefore the Micro-XRF-SEM system could produce elemental maps of elements not easily detected by SEM-EDS mapping systems. Because SEM-EDS and Micro-XRF-SEM have been used for imaging and chemical analysis of biological samples, this comparison of the detection systems should be useful to biologists, especially those involved in bone or tooth (hard tissue) analysis. PMID:24600333

  1. Enhanced Coagulation-Flocculation Performance of Iron-Based Coagulants: Effects of PO4(3- and SiO3(2- Modifiers.

    Directory of Open Access Journals (Sweden)

    Wei Chen

    Full Text Available PO4(3- and SiO3(2- are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants--polyferric phosphoric sulfate (PFPS, polysilicon ferric sulfate (PFSS, and polyferric sulfate (PFS were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR spectroscopy, X-ray diffraction (XRD and Scanning electron microscope (SEM. Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO4(3- and SiO3(2-. Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond.

  2. Intrinsic Josephson junctions in the iron-based multi-band superconductor (V2Sr4O6)Fe2As2

    Science.gov (United States)

    Moll, Philip J. W.; Zhu, Xiyu; Cheng, Peng; Wen, Hai-Hu; Batlogg, Bertram

    2014-09-01

    In layered superconductors, Josephson junctions may be formed within the unit cell as a result of sufficiently low inter-layer coupling. These intrinsic Josephson junction (iJJ) systems have attracted considerable interest for their application potential in quantum computing as well as efficient sources of THz radiation, closing the famous `THz gap'. So far, iJJ have been demonstrated in single-band, copper-based high-Tc superconductors, mainly in Bi-Sr-Ca-Cu-O (refs , , ). Here we report clear experimental evidence for iJJ behaviour in the iron-based superconductor (V2Sr4O6)Fe2As2. The intrinsic junctions are identified by periodic oscillations of the flux-flow voltage on increasing a well-aligned in-plane magnetic field. The periodicity is explained by commensurability effects between the Josephson vortex lattice and the crystal structure, which is a hallmark signature of Josephson vortices confined into iJJ stacks. This finding adds the pnictide (V2Sr4O6)Fe2As2 to the copper-based iJJ materials of interest for Josephson junction applications. In particular, novel devices based on multi-band Josephson coupling may be realized.

  3. Effects of an iron-based fuel-borne catalyst and a diesel particle filter on exhaust toxicity in lung cells in vitro.

    Science.gov (United States)

    Steiner, Sandro; Czerwinski, Jan; Comte, Pierre; Heeb, Norbert V; Mayer, Andreas; Petri-Fink, Alke; Rothen-Rutishauser, Barbara

    2015-08-01

    Metal-containing fuel additives catalyzing soot combustion in diesel particle filters are used in a widespread manner, and with the growing popularity of diesel vehicles, their application is expected to increase in the near future. Detailed investigation into how such additives affect exhaust toxicity is therefore necessary and has to be performed before epidemiological evidence points towards adverse effects of their application. The present study investigates how the addition of an iron-based fuel additive (Satacen®3, 40 ppm Fe) to low-sulfur diesel affects the in vitro cytotoxic, oxidative, (pro-)inflammatory, and mutagenic activity of the exhaust of a passenger car operated under constant, low-load conditions by exposing a three-dimensional model of the human airway epithelium to complete exhaust at the air-liquid interface. We could show that the use of the iron catalyst without and with filter technology has positive as well as negative effects on exhaust toxicity compared to exhaust with no additives: it decreases the oxidative and, compared to a non-catalyzed diesel particle filter, the mutagenic potential of diesel exhaust, but increases (pro-)inflammatory effects. The presence of a diesel particle filter also influences the impact of Satacen®3 on exhaust toxicity, and the proper choice of the filter type to be used is of importance with regards to exhaust toxicity. Figure ᅟ. PMID:24880869

  4. Theoretical approach to resonant inelastic x-ray scattering in iron-based superconductors at the energy scale of the superconducting gap.

    Science.gov (United States)

    Marra, Pasquale; van den Brink, Jeroen; Sykora, Steffen

    2016-01-01

    We develop a phenomenological theory to predict the characteristic features of the momentum-dependent scattering amplitude in resonant inelastic x-ray scattering (RIXS) at the energy scale of the superconducting gap in iron-based super-conductors. Taking into account all relevant orbital states as well as their specific content along the Fermi surface we evaluate the charge and spin dynamical structure factors for the compounds LaOFeAs and LiFeAs, based on tight-binding models which are fully consistent with recent angle-resolved photoemission spectroscopy (ARPES) data. We find a characteristic intensity redistribution between charge and spin dynamical structure factors which discriminates between sign-reversing and sign-preserving quasiparticle excitations. Consequently, our results show that RIXS spectra can distinguish between s± and s++ wave gap functions in the singlet pairing case. In addition, we find that an analogous intensity redistribution at small momenta can reveal the presence of a chiral p-wave triplet pairing. PMID:27151253

  5. Raman spectra in iron-based quaternary CeO1-xFxFeAs and LaO1-xFxFeAs

    International Nuclear Information System (INIS)

    Raman spectra have been measured on iron-based quaternary CeO1-xFxFeAs and LaO1-xFxFeAs with different amounts of fluorine doping at room temperatures. A group analysis has been made to clarify the optical modes. Based on first-principle calculations, the observed phonon modes can be assigned accordingly. In LaO1-xFxFeAs, the Eg and A1g modes related to the vibrations of La are suppressed with increasing F doping. However, F doping only has a small effect on the Eg and A1g modes of Fe and As. The Raman modes of La and As are absent in rare-earth substituted CeO1-xFxFeAs, and the Eg mode of oxygen, corresponding to the in-plane vibration of oxygen, moves to around 450 cm-1 and shows a very sharp peak. The electronic scattering background is low, and electron-phonon coupling is not evident for the observed phonon modes. Three features are found above 500 cm-1, which may be associated with multi-phonon processes. Nevertheless, it is also possible that they are related to magnetic fluctuations or interband transitions of d orbitals, considering their energies.

  6. Predictors of attrition and immunological failure in HIV-1 patients on highly active antiretroviral therapy from different healthcare settings in Mozambique.

    Directory of Open Access Journals (Sweden)

    Claudia Palladino

    Full Text Available In Mozambique, the evaluation of retention in HIV care and ART programmes is limited. To assess rate and predictors of attrition (no retention in care and HAART effectiveness in HIV-1 infected patients who pay for medication and laboratory testing in Mozambique, we conducted a multicenter survey of HIV-1-infected patients who started HAART during 2002-2006. Cox proportional hazard models were used to assess risk of attrition and of therapy failure. Overall, 142 patients from 16 healthcare centers located in the capital city Maputo were followed-up for 22.2 months (12.1-46.7. The retention rate was 75%, 48% and 37% after one, two and three years, respectively. Risk of attrition was lower in patients with higher baseline CD4 count (P = 0.022 and attending healthcare center 1 (HCC1 (P = 0.013. The proportion of individuals with CD4 count ≤ 200 cells/µL was 55% (78/142 at baseline and decreased to 6% (3/52 at 36 months. Among the patients with available VL, 86% (64/74 achieved undetectable VL levels. The rate of immunologic failure was 17.2% (95% CI: 12.6-22.9 per 100 person-years. Risk of failure was associated to higher baseline CD4 count (P = 0.002, likely reflecting low adherence levels, and decreased with baseline VL ≥ 10,000 copies/mL (P = 0.033. These results suggest that HAART can be effective in HIV-1 infected patients from Mozambique that pay for their medication and laboratory testing. Further studies are required to identify the causes for low retention rates in patients with low CD4 counts and to better understand the association between healthcare setting and attrition rate.

  7. Comparison of Trial Participants and Open Access Users of a Web-Based Physical Activity Intervention Regarding Adherence, Attrition, and Repeated Participation

    OpenAIRE

    Wanner, Miriam; Martin-Diener, Eva; Bauer, Georg; Braun-Fahrländer, Charlotte; Martin, Brian W

    2010-01-01

    Background Web-based interventions are popular for promoting healthy lifestyles such as physical activity. However, little is known about user characteristics, adherence, attrition, and predictors of repeated participation on open access physical activity websites. Objective The focus of this study was Active-online, a Web-based individually tailored physical activity intervention. The aims were (1) to assess and compare user characteristics and adherence to the website (a) in the open access...

  8. Comparison of Trial Participants and Open Access Users of a Web-Based Physical Activity Intervention Regarding Adherence, Attrition, and Repeated Participation

    OpenAIRE

    Wanner, M.; Martin-Diener, E; Bauer, G; Braun-Fahrländer, C.; De Martin, B W

    2010-01-01

    Background: Web-based interventions are popular for promoting healthy lifestyles such as physical activity. However, little is known about user characteristics, adherence, attrition, and predictors of repeated participation on open access physical activity websites. Objective: The focus of this study was Active-online, a Web-based individually tailored physical activity intervention. The aims were (1) to assess and compare user characteristics and adherence to the website (a) in the open a...

  9. Influence of Lubricants and Attrition Milling Parameters on the Quality of Zirconolite Ceramics, Consolidated by Hot Isostatic Pressing, for Immobilization of Plutonium

    OpenAIRE

    Squire, J.; Maddrell, E.R; Hyatt, N. C.; Stennett, M. C.

    2014-01-01

    The effect of attrition milling on the processing of precursor oxides was investigated, with reference to the fabrication of titanate ceramics for the immobilization of plutonium and actinides, consolidated by hot isostatic pressing. Difficulties encountered during the lubricant removal step masked any correlation between the milling conditions and the final product. Four lubricants were investigated zinc stearate, Ceridust™, polyethylene glycol and oleic acid. The precursor blends were added...

  10. Gender-related differences in outcomes and attrition on antiretroviral treatment among an HIV-infected patient cohort in Zimbabwe: 2007–2010

    Directory of Open Access Journals (Sweden)

    Kudakwashe C. Takarinda

    2015-01-01

    Conclusions: Our findings show that males presented late for ART initiation compared to females. Similar to other studies, males had higher patient attrition and mortality compared to females and this may be attributed in part to late presentation for HIV treatment and care. These observations highlight the need to encourage early HIV testing and enrolment into HIV treatment and care, and eventually patient retention on ART, particularly amongst men.

  11. Individual and contextual factors influencing patient attrition from antiretroviral therapy care in an urban community of Lusaka, Zambia

    Directory of Open Access Journals (Sweden)

    Sonja Merten

    2012-06-01

    Full Text Available Background: Despite the relatively effective roll-out of free life-prolonging antiretroviral therapy (ART in public sector clinics in Zambia since 2005, and the proven efficacy of ART, some people living with HIV (PLHIV are abandoning the treatment. Drawing on a wider ethnographic study in a predominantly low-income, high-density residential area of Lusaka, this paper reports the reasons why PLHIV opted to discontinue their HIV treatment. Methods: Opened-ended, in-depth interviews were held with PLHIV who had stopped ART (n = 25, ART clinic staff (n = 5, religious leaders (n = 5, herbal medicine providers (n = 5 and lay home-based caregivers (n = 5. In addition, participant observations were conducted in the study setting for 18 months. Interview data were analysed using open coding first, and then interpreted using latent content analysis. The presentation of the results is guided by a social-ecological framework. Findings: Patient attrition from ART care is influenced by an interplay of personal, social, health system and structural-level factors. While improved corporeal health, side effects and need for normalcy diminished motivation to continue with treatment, individuals also weighed the social and economic costs of continued uptake of treatment. Long waiting times for medical care and placing “defaulters” on intensive adherence counselling in the context of insecure labour conditions and livelihood constraints not only imposed opportunity costs which patients were not willing to forego, but also forced individuals to balance physical health with social integrity, which sometimes forced them to opt for faith healing and traditional medicine. Conclusions: Complex and dynamic interplay of personal, social, health system and structural-level factors coalesces to influence patient attrition from ART care. Consequently, while patient-centred interventions are required, efforts should be made to improve ART care by

  12. Retention of HIV-Infected Children in the First 12 Months of Anti-Retroviral Therapy and Predictors of Attrition in Resource Limited Settings: A Systematic Review

    Science.gov (United States)

    Smith, Christiana; McFarland, Elizabeth J.

    2016-01-01

    Current UNAIDS goals aimed to end the AIDS epidemic set out to ensure that 90% of all people living with HIV know their status, 90% initiate and continue life-long anti-retroviral therapy (ART), and 90% achieve viral load suppression. In 2014 there were an estimated 2.6 million children under 15 years of age living with HIV, of which only one-third were receiving ART. Little literature exists describing retention of HIV-infected children in the first year on ART. We conducted a systematic search for English language publications reporting on retention of children with median age at ART initiation less than ten years in resource limited settings. The proportion of children retained in care on ART and predictors of attrition were identified. Twelve studies documented retention at one year ranging from 71–95% amongst 31877 African children. Among the 5558 children not retained, 4082 (73%) were reported as lost to follow up (LFU) and 1476 (27%) were confirmed to have died. No studies confirmed the outcomes of children LFU. Predictors of attrition included younger age, shorter duration of time on ART, and severe immunosuppression. In conclusion, significant attrition occurs in children in the first 12 months after ART initiation, the majority attributed to LFU, although true outcomes of children labeled as LFU are unknown. Focused efforts to ensure retention and minimize early mortality are needed as universal ART for children is scaled up. PMID:27280404

  13. The effects of three different food acids on the attrition-corrosion wear of human dental enamel

    Science.gov (United States)

    Zhang, Yichi; Arsecularatne, Joseph A.; Hoffman, Mark

    2015-07-01

    With increased consumption of acidic drinks and foods, the wear of human teeth due to attrition in acidic environments is an increasingly important issue. Accordingly, the present paper investigates in vitro the wear of human enamel in three different acidic environments. Reciprocating wear tests in which an enamel cusp slides on an enamel flat surface were carried out using acetic, citric and lactic acid lubricants (at pH 3-3.5). Distilled water was also included as a lubricant for comparison. Focused ion beam milling and scanning electron microscopy imaging were then used to investigate the enamel subsurfaces following wear tests. Nanoindentation was used to ascertain the changes in enamel mechanical properties. The study reveals crack generation along the rod boundaries due to the exposure of enamel to the acidic environments. The wear mechanism changes from brittle fracture in distilled water to ploughing or shaving of the softened layer in acidic environments, generating a smooth surface with the progression of wear. Moreover, nanoindentation results of enamel samples which were exposed to the above acids up to a duration of the wear tests show decreasing hardness and Young’s modulus with exposure time.

  14. Accelerated telomere attrition is associated with relative household income, diet and inflammation in the pSoBid cohort.

    Directory of Open Access Journals (Sweden)

    Paul G Shiels

    Full Text Available BACKGROUND: It has previously been hypothesized that lower socio-economic status can accelerate biological ageing, and predispose to early onset of disease. This study investigated the association of socio-economic and lifestyle factors, as well as traditional and novel risk factors, with biological-ageing, as measured by telomere length, in a Glasgow based cohort that included individuals with extreme socio-economic differences. METHODS: A total of 382 blood samples from the pSoBid study were available for telomere analysis. For each participant, data was available for socio-economic status factors, biochemical parameters and dietary intake. Statistical analyses were undertaken to investigate the association between telomere lengths and these aforementioned parameters. RESULTS: The rate of age-related telomere attrition was significantly associated with low relative income, housing tenure and poor diet. Notably, telomere length was positively associated with LDL and total cholesterol levels, but inversely correlated to circulating IL-6. CONCLUSIONS: These data suggest lower socio-economic status and poor diet are relevant to accelerated biological ageing. They also suggest potential associations between elevated circulating IL-6, a measure known to predict cardiovascular disease and diabetes with biological ageing. These observations require further study to tease out potential mechanistic links.

  15. Drug Resistance

    Science.gov (United States)

    HIV Treatment Drug Resistance (Last updated 3/1/2016; last reviewed 3/1/2016) Key Points As HIV multiplies in the ... the risk of drug resistance. What is HIV drug resistance? Once a person becomes infected with HIV, ...

  16. Friction and wear with a single-crystal abrasive grit of silicon carbide in contact with iron base binary alloys in oil: Effects of alloying element and its content

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with various iron-base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a rider of 0.025-millimeter-radius, single-crystal silicon carbide in mineral oil. Results indicate that atomic size and content of alloying element play a dominant role in controlling the abrasive-wear and -friction properties of iron-base binary alloys. The coefficient of friction and groove height (wear volume) general alloy decrease, and the contact pressure increases in solute content. There appears to be very good correlation of the solute to iron atomic radius ratio with the decreasing rate of coefficient of friction, the decreasing rate of groove height (wear volume), and the increasing rate of contact pressure with increasing solute content C. Those rates increase as the solute to iron atomic radius ratio increases from unity.

  17. The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO

    Energy Technology Data Exchange (ETDEWEB)

    Warringham, Robbie; McFarlane, Andrew R.; Lennon, David, E-mail: David.Lennon@Glasgow.ac.uk [School of Chemistry, University of Glasgow, Joseph Black Building, Glasgow, Scotland G12 8QQ (United Kingdom); MacLaren, Donald A. [School of Physics and Astronomy, University of Glasgow, The Kelvin Building, Glasgow, Scotland G12 8QQ (United Kingdom); Webb, Paul B.; Tooze, Robert P. [Sasol Technology UK Ltd., Purdie Building, North Haugh, St Andrews, Fife KY16 9ST (United Kingdom); Taylor, Jon; Ewings, Russell A.; Parker, Stewart F. [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)

    2015-11-07

    An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe{sub 2}O{sub 3}) is distinguished by a relatively intense band at 810 cm{sup −1}, which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered.

  18. The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO

    International Nuclear Information System (INIS)

    An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe2O3) is distinguished by a relatively intense band at 810 cm−1, which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered

  19. Iron-based superconductors: Foreword

    OpenAIRE

    Alloul, Henri; Cano, Andres

    2016-01-01

    We introduce the thematic (open access) issue published in Comptes Rendus Physique. This issue is focused on the so-called Fe-based superconductors that, since the discovery of superconductivity in F-doped LaFeAsO by Hosono group in 2008, have become one of the latest hot topics in the field of condensed matter. The idea is to give an up-to-date overview of the fundamental properties of this novel family of high-Tc superconductors. First we briefly recall the scientific context of superconduc...

  20. Iron - based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2010-07-01

    Full Text Available Purpose: The paper presents a structure characterization, thermal and soft magnetic properties analysis of Fe-based bulk amorphous materials in as-cast state and after crystallization process. In addition, the paper gives some brief review about achieving, formation and structure of bulk metallic glasses as a special group of amorphous materials.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4 metallic glass in form of ribbons and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples were measured using differential thermal analysis (DTA and differential scanning calorimetry (DSC. The magnetic properties contained initial and maximum magnetic permeability, coercive force and magnetic after-effects measurements were determined by the Maxwell-Wien bridge and VSM methods.Findings: The X-ray diffraction and transmission electron microscopy investigations revealed that the studied as-cast bulk metallic glasses in form of ribbons and rods were amorphous. Two stage crystallization process was observed for studied bulk amorphous alloy. The differences of crystallization temperature between ribbons and rods with chosen thickness are probably caused by different amorphous structures as a result of the different cooling rates in casting process. The SEM images showed that studied fractures could be classified as mixed fractures with indicated two zones contained “river” and “smooth” areas. The changing of chosen soft magnetic properties (μr, Bs, Hc obtained for samples with different thickness is a result of the non-homogenous amorphous structure of tested metallic glasses. The annealing process in temperature range from 373 to 773 K causes structural relaxation of tested amorphous materials, which leads to changes in their physical properties. The qualitative phase analysis from X-ray and TEM diffraction data enables the identification of a single phase of α-Fe for sample annealed at 823 K and a mixture of Fe2B, Fe3B and Fe23B6 and α-Fe phases for samples annealed at temperature of 873 and 923 K.Practical implications: The magnetic properties allow to classify the studied Fe-based glassy alloy for suitable material for electric and magnetic applications. These properties of could be improved by applying the appropriate conditions of heat treatment (crystallization process.Originality/value: The applied investigation methods are suitable to determine the changes of structure, thermal and magnetic properties in function of sample thickness or annealing conditions.

  1. Alumina forming iron base superalloy

    Science.gov (United States)

    Yamamoto, Yukinori; Muralidharan, Govindarajan; Brady, Michael P.

    2014-08-26

    An austenitic stainless steel alloy, consists essentially of, in weight percent 2.5 to 4 Al; 25 to 35 Ni; 12 to 19 Cr; at least 1, up to 4 total of at least one element selected from the group consisting of Nb and Ta; 0.5 to 3 Ti; less than 0.5 V; 0.1 to 1 of at least on element selected from the group consisting of Zr and Hf; 0.03 to 0.2 C; 0.005 to 0.1 B; and base Fe. The weight percent Fe is greater than the weight percent Ni. The alloy forms an external continuous scale including alumina, and contains coherent precipitates of .gamma.'-Ni.sub.3Al, and a stable essentially single phase FCC austenitic matrix microstructure. The austenitic matrix is essentially delta-ferrite-free and essentially BCC-phase-free.

  2. Catalyst dispersion and activity under conditions of temperature- staged liquefaction. [Catalyst precursors for molybdenum-based catalyst and iron-based catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

    1992-07-01

    Two coals, a Texas subbituminous C and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling and catalyst impregnation on liquefaction conversion behavior in temperature staged reactions for 30 minutes each at 275{degree} and 425{degree}C in H{sub 2} and 95:5 H{sub 2}:H{sub 2}S atmospheres. Methanol, pyridine, tetrahydrofuran, and tetrabutylammonium hydroxide were used as swelling agents. Molybdenum-based catalyst precursors were ammonium tetrathiomolybdate, molybdenum trisulfide, molybdenum hexacarbonyl, and bis(tricarbonylcyclopentadienyl-molybdenum). Ferrous sulfate and bis(dicarbonylcyclo-pentadienyliron) served as iron-based catalyst precursors. In addition, ion exchange was used for loading iron onto the subbituminous coal. For most experiments, liquefaction in H{sub 2}:H{sub 2}S was superior to that in H{sub 2}, regardless of the catalyst precursor. The benefit of the H{sub 2}S was greater for the subbituminous, presumably because of its higher iron content relative to the hvab coal. Tetrabutylammonium hydroxide was the only swelling agent to enhance conversion of the hvab coal significantly; it also caused a remarkable increase in conversion of the subbituminous coal. The combined application of solvent swelling and catalyst impregnation also improves liquefaction, mainly through increased oil yields from the hvab coal and increased asphaltenes from the subbituminous. A remarkable effect from use of ammonium tetrathiomolybdate as a catalyst precursor is substantial increase in pristane and phytane yields. Our findings suggest that these compounds are, at least in part, bound to the coal matrix.

  3. Iron-based microbial ecosystem on and below the seafloor: a case study of hydrothermal fields of the Southern Mariana Trough

    Directory of Open Access Journals (Sweden)

    Shingo eKato

    2012-03-01

    Full Text Available Microbial community structures in deep-sea hydrothermal vents fields are constrained by available energy yields provided by inorganic redox reactions, which are in turn controlled by chemical composition of hydrothermal fluids. In the past two decades, geochemical and microbiological studies have been conducted in deep-sea hydrothermal vents at three geographically different areas of the Southern Mariana Trough (SMT. A variety of geochemical data of hydrothermal fluids and an unparalleled microbiological dataset of various samples (i.e., sulfide structures of active vents, iron-rich mats, borehole fluids and ambient seawater are available for comparative analyses. Here, we summarize the geochemical and microbiological characteristics in the SMT and assess the relationship between the microbial community structures and the fluid geochemistry in the SMT by thermodynamic modeling. In the high-temperature vent fluids, aerobic sulfide-oxidation has the potential to yield large amounts of bioavailable energy in the vent fluids, which is consistent with the detection of species related to sulfide-oxidizing bacteria (such as Thiomicrospira in the Gammaproteobacteria and Sulfurimonas in the Epsilonproteobacteria. Conversely, the bioavailable energy yield from aerobic iron-oxidation reactions in the low-temperature fluids collected from man-made boreholes and several natural vents were comparable to or higher than those from sulfide-oxidation. This is also consistent with the detection of species related to iron-oxidizing bacteria (Mariprofundus in the Zetaproteobacteria in such low-temperature samples. The results of combination of microbiological, geochemical and thermodynamic analyses in the SMT provide novel insights into the presence and significance of iron-based microbial ecosystems in deep-sea hydrothermal fields.

  4. Fenton-like oxidation of 2,4-DCP in aqueous solution using iron-based nanoparticles as the heterogeneous catalyst.

    Science.gov (United States)

    Li, Renchao; Gao, Ying; Jin, Xiaoying; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

    2015-01-15

    In this report, various iron-based nanoparticles (nZVI, n-Ni/Fe, n-Pd/Fe) were used for both heterogeneous Fenton oxidation of 2,4-dichlorophenol (2,4-DCP) and reductive dechlorination of 2,4-DCP in order to understand their roles in the Fenton oxidation and the reductive degradation of 2,4-DCP. The dechlorination efficiency of 2,4-DCP using nZVI, n-Ni/Fe, n-Fe/Pd and Fe(2)(+) was 6.48%, 6.80%, 15.95%, 5.02%, while Fenton oxidation efficiency of 2,4-DCP was 57.87%, 34.23%, 27.94%, 19.61% after 180 min, respectively. The new findings included a higher dechlorination using n-Fe/Pd due to Pd effective catalysis and the effective heterogeneous Fenton oxidation using nZVI depending on reductive dechlorination and heterogeneous Fenton oxidation occurs simultaneously. However, nZVI as the potential catalyst for heterogeneous Fenton was observed, and SEM, EDS and XRD demonstrate that change on the nZVI surface occurred due to the Fe(2+) leaching, and Total Organic Carbon (TOC) (30.71%) shows that 2,4-DCP was degraded. Furthermore, the experiment indicates that the pH values and concentration of 2,4-DCP significantly impacted on the heterogeneous Fenton oxidation of 2,4-DCP and the data fits well with the pseudo first-order kinetic model, which was a diffusion-controlled reaction. Finally, a possible mechanism for degradation of 2,4-DCP was proposed. PMID:25454429

  5. Magnetic properties of iron-based soft magnetic composites with SiO{sub 2} coating obtained by reverse microemulsion method

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Shen [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Sun, Aizhi, E-mail: sunaizhi@126.com [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Lu, Zhenwen; Cheng, Chuan [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Gao, Xuexu [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-05-01

    In this work, iron-based soft magnetic composites coated with the amorphous SiO{sub 2} layer have been fabricated by utilizing tetraethoxysilane in the reverse microemulsion method, and then the effects of addition amount of SiO{sub 2} and annealing temperature on the magnetic properties were investigated. The results show that the surface of iron powders contains a thin amorphous SiO{sub 2} insulation layer, which effectively decreases the magnetic loss of synthesized magnets. The magnetic loss of coated samples decreased by 87.8% as compared with that of uncoated samples at 150 kHz. Magnetic measurements show that the sample with 1.25 wt% SiO{sub 2} has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Also, the annealing treatment increased the initial permeability, the maximum permeability and the magnetic induction and decreased the coercivity with increasing temperature in the range 300–600 °C. The results of the loss separation imply that the annealed SMCs have a higher hysteresis loss coefficient (k{sub 2}) and lower eddy current loss coefficient (k{sub 3}) as compared with the pure iron compacts after the same heat treatment due to the preservation of the SiO{sub 2} layer. - Highlights: • SiO{sub 2} coated the iron powder by reverse microemulsion method, decreased the magnetic loss of SMCs. • 25 wt% is the optimum coating amount to attain the desired permeability. • The influence of annealing temperature on the magnetic performance of the core was discussed. • Compare with the pure iron compacts, the annealed SMCs have lower value of eddy current coefficient.

  6. Research on Language Attrition in China--Based on Literature Review%语言磨蚀研究在中国--基于相关文献分析

    Institute of Scientific and Technical Information of China (English)

    汤朝菊; 马玉玲; 汤甜; 张丽

    2015-01-01

    Language attrition is a phenomenon of language competence decay or loss which happened in the process of language learning. Researching language attrition is instructive for both foreign and native language teaching and learning. This paper summarized the main issues of language attrition discussed in China based on the literature review (CNKI database). The findings show that language attrition research is independently becoming a sub-field of applied linguistics in China. The process of research experienced the journey of introducing the theoretical and tentative results from other countries and then applying into our situation. With more and more research scholars’ concerns, most topics related to attrition were supported by academic funds. Basically, most researches focused on foreign language attrition contrast to native language attrition. The main research aspects are concerning the empirical tests, influence factors, reason analysis. The problems reflected as follows: The various tentative researches on language attrition are seldom related to the language acquisition; the interactive effects among attrition factors were not detected. It is necessary to do cross-disciplinary analysis with other subjects such as psychology, cognitive linguistics, neuro-linguistics and social linguistics. Meanwhile, further work should be done on native language and dialects attrition. Future research will be focused on the language community attrition and follow-up research on the time-ranged attrition. Most work will be done on establishing attrition theories applicable into Chinese linguistic environment.%语言磨蚀(语蚀)是语言学习过程中语言能力减弱或损失现象,研究语言磨蚀对外语及母语教学都有指导意义。基于CNKI相关文献发现我国语蚀研究从国外引介走向本土研究,已经作为应用语言学的研究领域,相关课题大多得到基金资助;研究角度走向多元,主要从实证研究、影响

  7. Design of a rotary reactor for chemical-looping combustion. Part 2: Comparison of copper-, nickel-, and iron-based oxygen carriers

    KAUST Repository

    Zhao, Zhenlong

    2014-04-01

    Chemical-looping combustion (CLC) is a novel and promising option for several applications including carbon capture (CC), fuel reforming, H 2 generation, etc. Previous studies demonstrated the feasibility of performing CLC in a novel rotary design with micro-channel structures. Part 1 of this series studied the fundamentals of the reactor design and proposed a comprehensive design procedure, enabling a systematic methodology of designing and evaluating the rotary CLC reactor with different OCs and operating conditions. This paper presents the application of the methodology to the designs with three commonly used OCs, i.e., copper, nickel, and iron. The physical properties and the reactivities of the three OCs are compared at operating conditions suitable for the rotary CLC. Nickel has the highest reduction rate, but relatively slow oxidation reactivity while the iron reduction rate is most sensitive to the fuel concentration. The design parameters and the operating conditions for the three OCs are selected, following the strategies proposed in Part 1, and the performances are evaluated using a one-dimensional plug-flow model developed previously. The simulations show that for all OCs, complete fuel conversion and high carbon separation efficiency can be achieved at periodic stationary state with reasonable operational stabilities. The nickel-based design includes the smallest dimensions because of its fast reduction rate. The operation of nickel case is mainly limited to the slow oxidation rate, and hence a relatively large share of air sector is used. The iron-based design has the largest size, due to its slow reduction reactivity near the exit or in the fuel purge sector where the fuel concentration is low. The gas flow temperature increases monotonically for all the cases, and is mainly determined by the solid temperature. In the periodic state, the local temperature variation is within 40 K and the thermal distortion is limited. The design of the rotary CLC is

  8. Parametric and dynamic studies of an iron-based 25-kWth coal direct chemical looping unit using sub-bituminous coal

    International Nuclear Information System (INIS)

    Highlights: • Integrated, moving bed chemical looping reactor with iron-oxide based oxygen carrier. • Coal carbon conversion from 84.8% to 99.9%, thermal capacity 7.4 to 27.7 kWth, O2 demand less than 1.3%. • Dynamic temperature of moving bed reducer is established and tracked during coal injection. • CH4 and CO present at initial coal injection, eliminated after oxygen carrier activated. • Lower coal injection had higher volatiles residence time and conversion. - Abstract: The iron-based Coal-Direct Chemical Looping (CDCL) combustion process is an alternative to conventional oxy-combustion technologies, where the oxygen used for fuel conversion in the CDCL process is provided by an iron-oxide based oxygen carrier instead of an air separation unit. The iron oxide is reduced using coal in the reducer reactor, producing highly-pure CO2 in the flue gas, and the reduced iron oxide is regenerated in a separate combustor reactor using air. The CDCL process at Ohio State has been developed and demonstrated in a 25 kWth sub-pilot unit, and it is the first chemical looping demonstration unit with a circulating moving bed reactor for solid fuel conversion. To date, the CDCL sub-pilot unit at OSU has been operated for more than 680 h, with a 200-h continuous operation, providing important data on long term operability as well as parametric optimization. This paper discusses recent parametric operational experience with sub-bituminous coal as the fuel, where dynamic changes in variables were performed to observe the effects on the unit itself. Measurements included temperature, pressure, and gas concentrations from the reducer and combustor. Furthermore, effects of different variables, such as flue gas recycle ratios (enhancer gas flow rates), feed port injection, and temperature, were observed. Tests confirmed high coal conversions with high purity of CO2 achieved in the flue gas. Overall, the moving bed design of the reducer results in nearly full coal conversion

  9. Explicit Analytical Expression for a Lanchester Attrition-Rate Coefficient for Bonder and Farrell’s m-Period Target-Engagement Policy

    OpenAIRE

    Taylor, James G.; Neta, Beny

    2001-01-01

    Working Paper #5, DTRA Project, July 9, 2001 The purpose of this working paper is to give an explicit analytical expression for a Lanche s- ter-type attrition-rate coefficient for direct-fire combat in a heterogeneous-target environment with serial acquisition of targets for Bonder and Farrell’s m-period target-acquisition policy1. It develops this result (its main result) from Taylor’s [2001d] new important general result (that does not depend on the target-engagement policy of a firer ty...

  10. Multiple imputation for estimation of an occurrence rate in cohorts with attrition and discrete follow-up time points: a simulation study

    OpenAIRE

    Soullier Noémie; de La Rochebrochard Elise; Bouyer Jean

    2010-01-01

    Abstract Background In longitudinal cohort studies, subjects may be lost to follow-up at any time during the study. This leads to attrition and thus to a risk of inaccurate and biased estimations. The purpose of this paper is to show how multiple imputation can take advantage of all the information collected during follow-up in order to estimate the cumulative probability P(E) of an event E, when the first occurrence of this event is observed at t successive time points of a longitudinal stud...

  11. Patient retention, clinical outcomes and attrition-associated factors of HIV-infected patients enrolled in Zimbabwe's National Antiretroviral Therapy Programme, 2007-2010.

    Directory of Open Access Journals (Sweden)

    Tsitsi Mutasa-Apollo

    Full Text Available BACKGROUND: Since establishment of Zimbabwe's National Antiretroviral Therapy (ART Programme in 2004, ART provision has expanded from <5,000 to 369,431 adults by 2011. However, patient outcomes are unexplored. OBJECTIVE: To determine improvement in health status, retention and factors associated with attrition among HIV-infected patients on ART. METHODS: A retrospective review of abstracted patient records of adults ≥ 15 years who initiated ART from 2007 to 2009 was done. Frequencies and medians were calculated for rates of retention in care and changes in key health status outcomes at 6, 12, 24 and 36 months respectively. Cox proportional hazards models were used to determine factors associated with attrition. RESULTS: Of the 3,919 patients, 64% were female, 86% were either WHO clinical stage III or IV. Rates of patient retention at 6, 12, 24 and 36 months were 90.7%, 78.1%, 68.8% and 64.4%, respectively. After ART initiation, median weight gains at 6, 12, and 24 months were 3, 4.5, and 5.0 kgs whilst median CD4+ cell count gains at 6, 12 and 24 months were 122, 157 and 279 cells/µL respectively. Factors associated with an increased risk of attrition included male gender (AHR 1.2; 95% CI, 1.1-1.4, baseline WHO stage IV (AHR 1.7; 95% CI, 1.1-2.6, lower baseline body weight (AHR 2.0; 95% CI, 1.4-2. 8 and accessing care from higher level healthcare facilities (AHR 3.5; 95% 1.1-11.2. CONCLUSIONS: Our findings with regard to retention as well as clinical and immunological improvements following uptake of ART, are similar to what has been found in other settings. Factors influencing attrition also mirror those found in other parts of sub-Saharan Africa. These findings suggest the need to strengthen earlier diagnosis and treatment to further improve treatment outcomes. Whilst decentralisation improves ART coverage it should be coupled with strategies aimed at improving patient retention.

  12. Antibiotic Resistance

    Science.gov (United States)

    Antibiotics are medicines that fight bacterial infections. Used properly, they can save lives. But there is a growing problem of antibiotic resistance. It happens when bacteria change and become able to resist the effects of an antibiotic. Using antibiotics can lead to resistance. ...

  13. Opposite Effects of Early-Life Competition and Developmental Telomere Attrition on Cognitive Biases in Juvenile European Starlings.

    Directory of Open Access Journals (Sweden)

    Melissa Bateson

    Full Text Available Moods are enduring affective states that we hypothesise should be affected by an individual's developmental experience and its current somatic state. We tested whether early-life adversity, induced by manipulating brood size, subsequently altered juvenile European starlings' (Sturnus vulgaris decisions in a judgment bias task designed to provide a cognitive measure of mood. We predicted that starlings from larger broods, specifically those that had experienced more nest competitors larger than themselves would exhibit reduced expectation of reward, indicative of a 'pessimistic', depression-like mood. We used a go/no-go task, in which 30 starlings were trained to probe a grey card disc associated with a palatable mealworm hidden underneath and avoid a different shade of grey card disc associated with a noxious quinine-injected mealworm hidden underneath. Birds' response latencies to the trained stimuli and also to novel, ambiguous stimuli intermediate between these were subsequently tested. Birds that had experienced greater competition in the nest were faster to probe trained stimuli, and it was therefore necessary to control statistically for this difference in subsequent analyses of the birds' responses to the ambiguous stimuli. As predicted, birds with more, larger nest competitors showed relatively longer latencies to probe ambiguous stimuli, suggesting reduced expectation of reward and a 'pessimistic', depression-like mood. However, birds with greater developmental telomere attrition--a measure of cellular aging associated with increased morbidity and reduced life-expectancy that we argue could be used as a measure of somatic state--showed shorter latencies to probe ambiguous stimuli. This would usually be interpreted as evidence for a more positive or 'optimistic' affective state. Thus, increased competition in the nest and poor current somatic state appear to have opposite effects on cognitive biases. Our results lead us to question

  14. Opposite Effects of Early-Life Competition and Developmental Telomere Attrition on Cognitive Biases in Juvenile European Starlings.

    Science.gov (United States)

    Bateson, Melissa; Emmerson, Michael; Ergün, Gökçe; Monaghan, Pat; Nettle, Daniel

    2015-01-01

    Moods are enduring affective states that we hypothesise should be affected by an individual's developmental experience and its current somatic state. We tested whether early-life adversity, induced by manipulating brood size, subsequently altered juvenile European starlings' (Sturnus vulgaris) decisions in a judgment bias task designed to provide a cognitive measure of mood. We predicted that starlings from larger broods, specifically those that had experienced more nest competitors larger than themselves would exhibit reduced expectation of reward, indicative of a 'pessimistic', depression-like mood. We used a go/no-go task, in which 30 starlings were trained to probe a grey card disc associated with a palatable mealworm hidden underneath and avoid a different shade of grey card disc associated with a noxious quinine-injected mealworm hidden underneath. Birds' response latencies to the trained stimuli and also to novel, ambiguous stimuli intermediate between these were subsequently tested. Birds that had experienced greater competition in the nest were faster to probe trained stimuli, and it was therefore necessary to control statistically for this difference in subsequent analyses of the birds' responses to the ambiguous stimuli. As predicted, birds with more, larger nest competitors showed relatively longer latencies to probe ambiguous stimuli, suggesting reduced expectation of reward and a 'pessimistic', depression-like mood. However, birds with greater developmental telomere attrition--a measure of cellular aging associated with increased morbidity and reduced life-expectancy that we argue could be used as a measure of somatic state--showed shorter latencies to probe ambiguous stimuli. This would usually be interpreted as evidence for a more positive or 'optimistic' affective state. Thus, increased competition in the nest and poor current somatic state appear to have opposite effects on cognitive biases. Our results lead us to question whether increased

  15. Pathways in STEM: Factors affecting the retention and attrition of talented men and women from the STEM pipeline

    Science.gov (United States)

    Heilbronner, Nancy N.

    attrition was interest in another (non-STEM) field. Participants placed little importance on other reasons for leaving STEM that were identified in previous research, such as competition, social isolation, or financial considerations.

  16. Development on iron-based moving bed chemical looping process%铁基移动床化学链技术进展

    Institute of Scientific and Technical Information of China (English)

    许迪恺; Tong Andrew; 曾亮; 罗四维; 范良士

    2014-01-01

    在日益增长的能源需求与日益严峻的全球气候变化带来的双重压力下,清洁、高效且经济的能源利用方法显得尤为重要。将化学链概念用于传统化石能源的转化是一种前景广阔的新技术。化学链燃烧利用载氧体间接转化含碳燃料,同时实现二氧化碳的捕集。俄亥俄州立大学研发了采用铁基载氧体和移动床反应器的化学链技术,可实现天然气、煤、生物质等多种燃料向电力、氢、液体燃料等产品的零排放转化。目前,合成气化学链(syngas chemical looping, SCL)和煤直接化学链(coal direct chemical looping, CDCL)技术两套25 kWth级小试装置已成功运行总计超过850 h,一套250 kWth级的高压SCL装置即将投入示范运行。%Driven by increasing demands for energy and concerns for climate change, more attention are paid to the development of clean, efficient, and economical technologies for energy conversion, among which chemical looping is considered as a promising alternative for fossil fuel conversion. Chemical looping processes enable highly efficient in situ CO2 capture in oxidation of carbonaceous fuels by making use of solid oxygen carriers. The Ohio State University (OSU) has developed a unique chemical looping technology utilizing iron-based oxygen carrier and moving bed reactors. Thermodynamic analysis shows that counter-current moving bed reactor can maximize oxygen carrier conversion while fully converting fuels, enabling high purity H2 production by iron-steam reaction. OSU chemical looping is highly flexible for converting a variety of gaseous and solid fuels to electricity, H2, and chemicals with CO2 captured. To date, the syngas chemical looping (SCL) technology and the coal direct chemical looping technology has been successfully operated for more than 850 h in total on two 25 kWth sub-pilot units. A 250 kWth high pressure SCL pilot unit is constructed at National Carbon Capture Center

  17. Spectral radiation property investigation of iron based oxide micro-particles%铁基氧化物微颗粒的光谱辐射特性

    Institute of Scientific and Technical Information of China (English)

    黄兴; 张筱娴; 帅永; 袁远; 李炳熙

    2015-01-01

    太阳能热化学制氢过程中金属氧化物颗粒物性随反应温度、波长以及组分发生改变且其对反应过程的能量传递起着重要的作用.为了获得金属氧化物的光谱辐射特性,搭建了光谱透反射测量系统.首先,通过一系列实验测量校核了该系统测量结果的精确性以及稳定性.其次,研究了含有 NiFe2O4金属氧化物颗粒的溴化钾压片在光谱区间0.3~1.2μm的透过率.结果表明:该系统具有良好的测试精度;NiFe2O4压片的透过率随波长的增大而增大,随厚度的增大而减小;在部分光谱处均存在透过率振荡现象,意味着颗粒在该波段区间存在吸收效果.上述研究为太阳能热化学制氢过程中的反应颗粒的辐射特性的反演提供了实验基础,同时也为太阳能反应器内传热、传质模型的建立提供了理论基础.%The radiative property of metallic oxide during solar hydrogen production process varies with reaction temperature, wavelength and component and it plays a important role during energy transfer process. In order to acquire the spectral radiative property of metallic oxide during 0.3—1.2μm, an experimental system is built. Some experiments are applied to validate the measuring accuracy of this system. Then the transmittance of NiFe2O4 particles are obtained based on KBr pellet method. The experimental results show that the system has a good performance on radiative measurement. The transmittance of sample increases with increase of wavelength and decreases with increase of sample thickness. There are manylocalized fluctuations are also observed in all sample types, which suggesting possible sharp peaks in the absorption coefficient of iron based oxide at these wavelengths. The above investigation will provide a base for a detailed radiative transfer analysis to quantify the radiative properties, like extinction coefficient, scattering albedo and scattering phase function,etc., and provide the basis for

  18. "Shadows of the heart": a dramatic video for the treatment resistance of spouse abusers.

    Science.gov (United States)

    Stosny, S

    1994-11-01

    Successful intervention with spouse abusers, most of whom are ordered into treatment by the courts, must overcome formidable anger and resistance, often expressed by high attrition and scant participation in the group treatment process. The dramatic video "Shadows of the Heart" dissipates client resistance by providing internal motivation to control violent behavior. The video dramatizes spouse abuse from the viewpoint of a young boy, who as a man has become a spouse abuser. As clients experience compassion for the child witness to family violence, they learn to convert their habitual anger response into nonviolent actions. Developed to combat treatment resistance, the video presentation was tested in a randomized experiment with 106 male spouse abusers drawn from seven public and private agencies. Results indicate that the video presentation significantly increased attendance and participation in the group treatment process. PMID:7992138

  19. Novel Applications for Oxalate-Phosphate-Amine Metal-Organic-Frameworks (OPA-MOFs): Can an Iron-Based OPA-MOF Be Used as Slow-Release Fertilizer?

    OpenAIRE

    Manuela Anstoetz; Rose, Terry J.; Clark, Malcolm W.; Yee, Lachlan H.; Raymond, Carolyn A.; Tony Vancov

    2015-01-01

    A porous iron-based oxalate-phosphate-amine metal-organic framework material (OPA-MOF) was investigated as a microbially-induced slow-release nitrogen (N) and phosphorus (P) fertilizer. Seedling growth, grain yields, nutrient uptake of wheat plants, and soil dynamics in incubated soil, were investigated using OPA-MOF vs standard P (triple-superphosphate) and N (urea) fertilizers in an acidic Ferralsol at two application rates (equivalent 120 and 40 kg N ha(-1)). While urea hydrolysis in the O...

  20. Resistant Hypertension.

    Science.gov (United States)

    Doroszko, Adrian; Janus, Agnieszka; Szahidewicz-Krupska, Ewa; Mazur, Grzegorz; Derkacz, Arkadiusz

    2016-01-01

    Resistant hypertension is a severe medical condition which is estimated to appear in 9-18% of hypertensive patients. Due to higher cardiovascular risk, this disorder requires special diagnosis and treatment. The heterogeneous etiology, risk factors and comorbidities of resistant hypertension stand in need of sophisticated evaluation to confirm the diagnosis and select the best therapeutic options, which should consider lifestyle modifications as well as pharmacological and interventional treatment. After having excluded pseudohypertension, inappropriate blood pressure measurement and control as well as the white coat effect, suspicion of resistant hypertension requires an analysis of drugs which the hypertensive patient is treated with. According to one definition - ineffective treatment with 3 or more antihypertensive drugs including diuretics makes it possible to diagnose resistant hypertension. A multidrug therapy including angiotensin - converting enzyme inhibitors, angiotensin II receptor blockers, beta blockers, diuretics, long-acting calcium channel blockers and mineralocorticoid receptor antagonists has been demonstrated to be effective in resistant hypertension treatment. Nevertheless, optional, innovative therapies, e.g. a renal denervation or baroreflex activation, may create a novel pathway of blood pressure lowering procedures. The right diagnosis of this disease needs to eliminate the secondary causes of resistant hypertension e.g. obstructive sleep apnea, atherosclerosis and renal or hormonal disorders. This paper briefly summarizes the identification of the causes of resistant hypertension and therapeutic strategies, which may contribute to the proper diagnosis and an improvement of the long term management of resistant hypertension. PMID:26935512

  1. Antimicrobial Resistance

    Science.gov (United States)

    ... others. For example, the emergence of Plasmodium falciparum multidrug resistance, including resistance to ACTs in the Greater Mekong subregion is an urgent public health concern that is threatening global efforts to reduce the burden of malaria. Although MDR-TB is a growing concern, it is still ...

  2. Anticoagulant Resistance

    DEFF Research Database (Denmark)

    Heiberg, Ann-Charlotte

    specific PCR to verify this genetic form of resistance, but in contrast to animals tested from various surface populations, we could not confirm the Y139C mutation in any of the sewer rats. Our findings could indicate that resistance in surface and sewer population may be caused by different mechanism or...

  3. Camptothecin resistance

    DEFF Research Database (Denmark)

    Brangi, M; Litman, Thomas; Ciotti, M; Nishiyama, K; Kohlhagen, G; Takimoto, C; Robey, R; Pommier, Y; Fojo, T; Bates, S E

    1999-01-01

    after camptothecin treatment. In addition to topotecan and SN-38, MXR-overexpressing cells are highly resistant to mitoxantrone and epirubicin. Because these compounds are susceptible to glucuronidation, we examined UDP-glucurono-syltransferase (UGT) activity in parental and resistant cells by TLC...

  4. Antibiotic Resistance

    DEFF Research Database (Denmark)

    Munck, Christian

    morbidity and mortality as well as an increase in the cost of treatment. Understanding how bacteria respond to antibiotic exposure gives the foundations for a rational approach to counteract antimicrobial resistance. In the work presented in this thesis, I explore the two fundamental sources of...... antimicrobial resistance: (1) adaptive mutations and (2) horizontal acquisition of resistance genes from antibiotic gene reservoirs. By studying the geno- and phenotypic changes of E. coli in response to single and drug-pair exposures, I uncover the evolutionary trajectories leading to adaptive resistance. I...... to rationally design drug combinations that limit the evolution of antibiotic resistance due to counteracting evolutionary trajectories. My results highlight that an in-depth knowledge about the genetic responses to the individual antimicrobial compounds enables the prediction of responses to drug...

  5. Energy saving using solar filters with iron base in windows; Ahorro de energia usando filtros solares con base en hierro en ventanas

    Energy Technology Data Exchange (ETDEWEB)

    Chavez Galan, Jesus

    2003-07-01

    For the high temperature seasons, the radiation emitted by the sun later introduced through the windows, provokes a great thermal gain in the buildings causing within them an excessive warming. For the cold seasons, the exterior is at low temperature and the window is the main element through which the building losses the heat generated in the interior. The former turns out into an elevated energy consumption (mainly electricity) to obtain the conditions of human thermal comfort; this altogether with the growing energy demand that the residential, commercial and public sector experiences in Mexico, constitutes a serious problem. As a proposal for the solution to the problem of thermal discomfort generated in the interior of the buildings because of the inadequate properties of the construction materials, in this work were developed solar filers with iron base by means of which it is obtained a selective control of the solar radiation that is transmitted through the windows. These solar filters consist in thin films of FeO deposited over subtracts of lime-soda glass (the most used in our country for buildings) of 600 x 300 x 3 mm, by means of the sputtering technique added with a radio frequency and flat magnetrons, starting from a pure iron target of 127 x 254 mm and using an argon plasma. To obtain the desired oxidation degree in the iron, small samples (45 x 22 mm) were subjected to a heating process in a reducing atmosphere constituted by 50% H{sub 2} + 50% N{sub 2} for a period of time of 10 minutes at a temperature of 400 centigrade. The solar filters with the FeO base present a transmissibility of 30.2 % for the visible interval of the electromagnetic spectrum (radiation with a wave length of 380-780 nm) and of 39.9 % for the near infrared (radiation with a wave length of 780-2500 nm); while the reflectivity is of 17.5 and 19% for the visible intervals and near infrared of electromagnetic spectrum respectively. A simulation was performed by means of the

  6. Antibiotic Resistance

    Science.gov (United States)

    ... Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco Products For Consumers Home For Consumers Consumer Information by Audience For Women Antibiotic Resistance Share Tweet Linkedin Pin it More ...

  7. Non-conventional superconducting fluctuations in Ba(Fe1-xRhx)2As2 iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bossoni, L. [Univ. of Pavia (Italy); Romano, L. [Univ. of Parma (Italy); Canfield, Paul C. [Ames Lab., Ames, IA (United States); Lascialfari, A. [Univ. degli Studi di Milano (Italy)

    2014-09-17

    We measured the static uniform spin susceptibility of Ba(Fe1-xRhx)2As2 iron-based superconductors, over a broad range of doping (0.041x0.094) and magnetic fields. At small fields (H ≤ 1 kOe) we observed, above the transition temperature Tc, the occurrence of precursor diamagnetism, which is not ascribable to the Ginzburg–Landau theory. On the contrary, our data agree with a phase fluctuation model, which has been used to interpret a similar phenomenology occurring in the high-Tc cuprate superconductors. Additionally, in the presence of strong fields, the unconventional fluctuating diamagnetism is suppressed, whereas Ginzburg–Landau fluctuations are found, in agreement with literature.

  8. Dynamics of bigeye (Thunnus obesus) and yellowfin (T. albacares) tuna in Hawaii’s pelagic fisheries: analysis of tagging data with a bulk transfer model incorporating size-specific attrition

    OpenAIRE

    Adam, M. Shiham; Sibert, John; Itano, David; Holland, Kim

    2003-01-01

    Tag release and recapture data of bigeye (Thunnus obesus) and yellowfin tuna (T. albacares) from the Hawaii Tuna Tagging Project (HTTP) were analyzed with a bulk transfer model incorporating size-specific attrition to infer population dynamics and transfer rates between various fishery components. For both species, the transfer rate estimates from the offshore handline fishery areas to the longline fishery area were higher than the estimates of transfer from those same areas into the inshore ...

  9. Roadside Accumulation of Pt, Pd, Rh and Other Trace Elements From Automobiles: Catalytic Converter Attrition and Platinum-Group Element Mobility in the Roadside Environment.

    Science.gov (United States)

    Ely, J. C.; Dahlheimer, S. R.; Neal, C. R.

    2003-12-01

    Elemental abundances of Pt, Pd and Rh have been documented across the industrialized world in roadside environments due to attrition of automotive catalytic converters (Zereini and Alt, 2000, Anthropogenic PGE Emissions, Springer, 308pp; Ely et al., 2001, EnvSci&Tech, 35:3816-3822; Whiteley and Murray, 2003, SciTotEnv, in press). In our ongoing study, the highest reported roadside Pt abundance 1.8 ppm has been found immediately adjacent to the road at a field site in South Bend, IN, USA. Furthermore, initial studies show positive correlations of Pt, Pd and Rh with some trace elements (Ni, Cu, Zn and Pb), which has been confirmed by further analysis for these and other elements (Ce, Cr). It has been demonstrated that elements such as Ce are present in catalytic converters at concentrations of 100's ppm to 3-wt.%. These elements are also being attrited with Pt, Pd and Rh and aerially transported and deposited. Our field site was established next to US-933 adjacent to the Notre Dame campus. Areas were cleared of the top 2-4 cm of soil (removing surficial Pt, Pd and Rh) at 1, 5, 10 and 50 meters from the roadside. Within 3 months the 1-meter site contained 67% of the initial Rh and Pt concentrations and 100% of the initial Pd concentration. The sites at 5, 10 and 50 meters showed similar results, in some cases exceeding the initial concentrations. After 6 months the concentrations of Pt, Pd and Rh were all within error of the initial concentrations, indicating steady state abundances had probably been reached. Grass samples from each site showed that washed vs. unwashed samples were within error of each other, and there may be a slight enrichment (approx. 1 ppb) in the grasses of Pd and Pt, but this enrichment was independent of distance from the road. The steady-state situation suggests that the PGEs are being removed from the immediate roadside environment, which requires that the metals are being oxidized and/or complexed in such a way to facilitate transport. The

  10. [Resistant fungi].

    Science.gov (United States)

    Vehreschild, M J G T; Cornely, O A

    2015-11-01

    Particularly in the area of hematology/oncology and intensive care medicine, infections due to resistant fungi are to be expected. Emergence of resistance in fungi is a less dynamic process than in bacteria; it can, however, have an equally important impact on treatment strategies. In the following article, the most important resistance patterns of yeasts and molds (Candida albicans , Aspergillus fumigatus, the order Mucorales and the genus Fusarium) will be presented and discussed. Their diagnosis mostly being based on blood cultures, resistance testing for yeasts is usually readily available. Culture-based therapeutic adjustments in mold infections are, however, only rarely possible, as most antifungal therapies for these infections are initiated on an empirical basis after identification of typical infiltrates on a CT scan. Response to therapy is then evaluated on the basis of clinical signs and symptoms in combination with follow-up CT scans. In case of therapeutic failure or appearance of suspicious infiltrates under antifungal prophylaxis, an open or CT-guided biopsy is recommended to allow efficient adaptation of antifungal treatment. In individual cases, particularly in patients diagnosed with mucormycosis, resection of the focus of infection may be necessary to achieve a satisfactory treatment response. PMID:26432089

  11. Resisting "Reason"

    DEFF Research Database (Denmark)

    Merrild, Camilla Hoffmann; Andersen, Rikke Sand; Risør, Mette Bech;

    2016-01-01

    Social differences in health and illness are well documented in Denmark. However, little is known about how health practices are manifested in the everyday lives of different social classes. We propose acts of resistance and formation of health subjectivities as helpful concepts to develop our un...

  12. 语言磨蚀的主要理论简介及其对教与学的启示%Brief Introduction to the Main Theories of Language Attrition and the Relevant Revelations to Language Learning and Teaching

    Institute of Scientific and Technical Information of China (English)

    刘晓梅

    2013-01-01

    语言磨蚀理论研究对保持外语能力,提高外语学习效率具有重要意义。同时,语言磨蚀理论对高校英语教与学有着重要的启示作用。文章通过简要分析语言磨蚀的主要理论,对教与学分别提出针对性的指导意见,以使其更具实践可操作性。%The study on the theories of language attrition is of great significance in terms of keeping language ability and improv-ing the learning efficiency. Besides, language attrition theories also inspire the way to learn and to teach foreign languages in col-leges. In accordance with the main theories of language attrition, some pertinent and practical teaching and learning suggestions are presented.

  13. The resistance of selected high strength alloys to embrittlement by a hydrogen environment

    Science.gov (United States)

    Benson, R. B., Jr.

    1974-01-01

    Selected high strength iron base and cobalt base alloys with yield strengths in the range from 1233 to 2129 MN per sq m (179 to 309 KSI) were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced epsilon prime-hcp martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level to a maximum of 2129 MN per sq m (309 KSI). High-strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

  14. Creep resistant, precipitation-dispersion-strengthened, martensitic stainless steel and method thereof

    Science.gov (United States)

    Buck, Robert F.

    1994-01-01

    An iron-based, corrosion-resistant, precipitation strengthened, martensitic steel essentially free of delta ferrite for use at high temperatures has a nominal composition of 0.05-0.1 C, 8-12 Cr, 1-5 Co, 0.5-2.0 Ni, 0.41-1.0 Mo, 0.1-0.5 Ti, and the balance iron. This steel is different from other corrosion-resistant martensitic steels because its microstructure consists of a uniform dispersion of fine particles, which are very closely spaced, and which do not coarsen at high temperatures. Thus at high temperatures this steel combines the excellent creep strength of dispersion-strengthened steels, with the ease of fabricability afforded by precipitation hardenable steels.

  15. 铁基脱硫剂超重力法脱除硫化氢%Experimental research on hydrogen sulfide removal by high gravity technology with iron-based desulfurizer

    Institute of Scientific and Technical Information of China (English)

    梁作中; 王伟; 韩翔龙; 刘杰; 陈建峰; 初广文; 邹海魁; 赵宏

    2015-01-01

    用 N2和 H2S 的混合气模拟含硫天然气,以铁基脱硫剂为脱硫液,采用超重力旋转填充床(RPB)进行脱除 H2S 的集约化实验研究,考察了原料气 H2S 质量浓度、含硫原料气流量、脱硫液流量、温度及 RPB 转子转速对 H2S 脱除率的影响。实验结果表明,铁基脱硫剂超重力法脱除 H2S 的较佳工艺条件为原料气 H2S 含量14g/m3,原料气流量0.45m3/h,脱硫液流量13.5L/h,脱硫液温度40℃,RPB 转子转速1000r/min。在此条件下,H2S 脱除率稳定在99.98%以上,脱硫后净化气 H2S 含量小于2mg/m3。另外,舍弃再生用 RPB,采用直接向脱硫富液储槽鼓空气的方法,脱硫剂氧化再生良好,脱硫效果保持不变,且可长时间稳定运行。因此,铁基脱硫剂超重力法脱硫工艺简单、效率高、设备体积小,可实现海洋油气平台天然气或石油伴生气脱硫的集约化,工业化应用前景广阔。%The intensive experimental research on the removal of H2S was conducted using a high gravity rotating packed bed(RPB)with iron-based desulfurizer and a mixture of N2 and H2S,which was used to simulate natural gas. The effects of inlet mass concentration of H2S,gas flow rate, desulfurizer flow rate and temperature and RPB rotor speed on removal rate of H2S were investigated. The optimized experimental conditions using high gravity technology with iron-based desulfurizer were as follows:mass concentration of H2S in feed 14g/m3,gas flow rate 0.45m3/h,liquid flow rate 13.5L/h,desulfurizer temperature 40℃,and rotor speed of RPB 1000 r/min. Removal rate of H2S could reach above 99.98%,and concentration of H2S after desulfurization was lower than 2mg/m3 under the present experimental condition. Oxidation of used iron-based desulfurizer was also studied by bubbling the air into a storage tank instead of another RPB. Oxidation efficiency could be maintained well and removal rate of H2S still remained very high

  16. An electromyographic study to assess the minimal time duration for using the splint to raise the vertical dimension in patients with generalized attrition of teeth

    Directory of Open Access Journals (Sweden)

    Aditi Nanda

    2011-01-01

    Full Text Available Background: To investigate the effect of restoration of lost vertical by centric stabilizing splint on electromyographic (EMG activity of masseter and anterior temporalis muscles bilaterally in patients with generalized attrition of teeth. Materials and Methods: EMG activity of anterior temporalis and masseter muscle was recorded bilaterally for 10 patients whose vertical was restored with centric stabilizing splint. The recording was done at postural rest position and in maximum voluntary clenching for each subject before the start of treatment, immediately after placement of splint and at subsequent recall visits, with splint and without the splint. Results: The EMG activity at postural rest position (PRP and maximum voluntary clench (MVC decreased till 1 month for both the muscles. In the third month, an increase in muscle activity toward normalization was noted at PRP, both with and without splint. At MVC in the third month, the muscle activity without splint decreased significantly as compared to pretreatment values for anterior temporalis and masseter, while with the splint an increase was seen beyond the pretreatment values. Conclusion: A definite response of anterior temporalis and masseter muscle was observed over a period of 3 months. This is suggestive that the reversible increase in vertical prior to irreversible intervention must be carried out for a minimum of 3 months to achieve neuromuscular deprogramming. This allows the muscle to get adapted to the new postural position and attain stability in occlusion following splint therapy.

  17. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    Science.gov (United States)

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-08-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  18. Novel Applications for Oxalate-Phosphate-Amine Metal-Organic-Frameworks (OPA-MOFs): Can an Iron-Based OPA-MOF Be Used as Slow-Release Fertilizer?

    Science.gov (United States)

    Anstoetz, Manuela; Rose, Terry J; Clark, Malcolm W; Yee, Lachlan H; Raymond, Carolyn A; Vancov, Tony

    2015-01-01

    A porous iron-based oxalate-phosphate-amine metal-organic framework material (OPA-MOF) was investigated as a microbially-induced slow-release nitrogen (N) and phosphorus (P) fertilizer. Seedling growth, grain yields, nutrient uptake of wheat plants, and soil dynamics in incubated soil, were investigated using OPA-MOF vs standard P (triple-superphosphate) and N (urea) fertilizers in an acidic Ferralsol at two application rates (equivalent 120 and 40 kg N ha(-1)). While urea hydrolysis in the OPA-MOF treatment was rapid, conversion of ammonium to nitrate was significantly inhibited compared to urea treatment. Reduced wheat growth in OPA-MOF treatments was not caused by N-deficiency, but by limited P-bioavailability. Two likely reasons were slow P-mobilisation from the OPA-MOF or rapid P-binding in the acid soil. P-uptake and yield in OPA-MOF treatments were significantly higher than in nil-P controls, but significantly lower than in conventionally-fertilised plants. OPA-MOF showed potential as enhanced efficiency N fertilizer. However, as P-bioavailability was insufficient to meet plant demands, further work should determine if P-availability may be enhanced in alkaline soils, or whether central ions other than Fe, forming the inorganic metal-P framework in the MOF, may act as a more effective P-source in acid soils. PMID:26633174

  19. Novel Applications for Oxalate-Phosphate-Amine Metal-Organic-Frameworks (OPA-MOFs: Can an Iron-Based OPA-MOF Be Used as Slow-Release Fertilizer?

    Directory of Open Access Journals (Sweden)

    Manuela Anstoetz

    Full Text Available A porous iron-based oxalate-phosphate-amine metal-organic framework material (OPA-MOF was investigated as a microbially-induced slow-release nitrogen (N and phosphorus (P fertilizer. Seedling growth, grain yields, nutrient uptake of wheat plants, and soil dynamics in incubated soil, were investigated using OPA-MOF vs standard P (triple-superphosphate and N (urea fertilizers in an acidic Ferralsol at two application rates (equivalent 120 and 40 kg N ha(-1. While urea hydrolysis in the OPA-MOF treatment was rapid, conversion of ammonium to nitrate was significantly inhibited compared to urea treatment. Reduced wheat growth in OPA-MOF treatments was not caused by N-deficiency, but by limited P-bioavailability. Two likely reasons were slow P-mobilisation from the OPA-MOF or rapid P-binding in the acid soil. P-uptake and yield in OPA-MOF treatments were significantly higher than in nil-P controls, but significantly lower than in conventionally-fertilised plants. OPA-MOF showed potential as enhanced efficiency N fertilizer. However, as P-bioavailability was insufficient to meet plant demands, further work should determine if P-availability may be enhanced in alkaline soils, or whether central ions other than Fe, forming the inorganic metal-P framework in the MOF, may act as a more effective P-source in acid soils.

  20. Novel Applications for Oxalate-Phosphate-Amine Metal-Organic-Frameworks (OPA-MOFs): Can an Iron-Based OPA-MOF Be Used as Slow-Release Fertilizer?

    Science.gov (United States)

    Anstoetz, Manuela; Rose, Terry J.; Clark, Malcolm W.; Yee, Lachlan H.; Raymond, Carolyn A.; Vancov, Tony

    2015-01-01

    A porous iron-based oxalate-phosphate-amine metal-organic framework material (OPA-MOF) was investigated as a microbially-induced slow-release nitrogen (N) and phosphorus (P) fertilizer. Seedling growth, grain yields, nutrient uptake of wheat plants, and soil dynamics in incubated soil, were investigated using OPA-MOF vs standard P (triple-superphosphate) and N (urea) fertilizers in an acidic Ferralsol at two application rates (equivalent 120 and 40 kg N ha-1). While urea hydrolysis in the OPA-MOF treatment was rapid, conversion of ammonium to nitrate was significantly inhibited compared to urea treatment. Reduced wheat growth in OPA-MOF treatments was not caused by N-deficiency, but by limited P-bioavailability. Two likely reasons were slow P-mobilisation from the OPA-MOF or rapid P-binding in the acid soil. P-uptake and yield in OPA-MOF treatments were significantly higher than in nil-P controls, but significantly lower than in conventionally-fertilised plants. OPA-MOF showed potential as enhanced efficiency N fertilizer. However, as P-bioavailability was insufficient to meet plant demands, further work should determine if P-availability may be enhanced in alkaline soils, or whether central ions other than Fe, forming the inorganic metal-P framework in the MOF, may act as a more effective P-source in acid soils. PMID:26633174

  1. Sense of coherence and attrition during four-year follow-up in cohorts of permanent and non-permanent Finnish employees

    Directory of Open Access Journals (Sweden)

    Pentti Jaana

    2008-03-01

    Full Text Available Abstract Background We studied whether health resources, measured as sense of coherence (SOC, are associated with participation in a follow-up survey among permanent and non-permanent employees who responded at baseline. Methods Of a cohort of 5,981 permanent employees, those who after four years were still in the service of the same employer were asked to participate in a follow-up survey. Another cohort consisted of 2,194 fixed-term and 682 subsidised employees; among these the follow-up survey was posted to those whose addresses were found in the population register. Non-participation was divided into loss to follow-up (i.e., failure to locate the individual, death and, among permanent employees, turnover or exit from labour market and non-response to the follow-up survey. Logistic regression analyses were used to examine whether the respondents differed from the non-respondents with respect to SOC and other characteristics at baseline. Results Among permanent employees the follow-up survey yielded 3,998 respondents, 1,051 were lost, and 932 did not reply. Among non-permanent employees the follow-up survey yielded 1,563 respondents on initially fixed-term and 467 on subsidised contracts, the corresponding figures for those lost were 145 and 38, and for the non-respondents 486 and 177. Low SOC was associated with lower response rate among fixed-term but not among permanent or subsidised employees. No association was found between SOC and loss to follow-up. Conclusion SOC is a potential source of non-random sample attrition and should be taken into account for when estimating bias due to non-participation in occupational cohorts that include fixed-term employees.

  2. Resistance welding

    DEFF Research Database (Denmark)

    Bay, Niels; Zhang, Wenqi; Rasmussen, Mogens H.;

    2003-01-01

    Resistance welding comprises not only the well known spot welding process but also more complex projection welding operations, where excessive plastic deformation of the weld point may occur. This enables the production of complex geometries and material combinations, which are often not possible...... to weld by traditional spot welding operations. Such joining processes are, however, not simple to develop due to the large number of parameters involved. Development has traditionally been carried out by large experimental investigations, but the development of a numerical programme system has...... changed this enabling prediction of the welding performance in details. The paper describes the programme in short and gives examples on industrial applications. Finally investigations of causes for failure in a complex industrial joint of two dissimilar metals are carried out combining numerical...

  3. DFT studies of iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Boeri, Lilia; Dolgov, Oleg V.; Krogh Andersen, Ole [MPI-FKF, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Golubov, Alexander A. [Faculty of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente,7500 AE Enschede (Netherlands)

    2009-07-01

    The discovery of superconductivity in iron pnicticides has generated considerable interest. So far, however, not only the pairing mechanism, but even the basic electronic structure of these materials is not well understood. We use Density Functional Theory to understand the electronic and vibrational properties of LaOFeAs, which can be considered a prototype for iron pnictides. First, we calculate the phonon dispersions and electron-phonon coupling using linear response and show that standard Migdal-Eliashberg theory cannot explain the experimental T{sub c}. Then we derive ab-initio an accurate tight-binding Hamiltonian, which allows us to elucidate the origin of the complicated band structure of iron pnicticides. As a first application of our model, we study itinerant magnetism.

  4. Iron-based superconductors via soft chemistry

    International Nuclear Information System (INIS)

    This thesis provides new soft chemistry approaches to Fe-based superconductors. Mild syntheses were demonstrated to be able to overcome difficulties, occurring in conventional synthesis and to enable the access to new metastable phases. A solvent-based metathesis reaction led to β-FeSe exclusively. Contrary to solid state syntheses, the formation of hexagonal α-FeSe could be avoided under mild conditions. The deintercalation of interstitial Fe (by formation of Fe3O4) could be proven by low temperature O2-annealing of Fe1+xTe1-ySey. By using redox (de)intercalations K1-xFe2-ySe2, metastable Na1-xFe2-yAs2 and Na1-x((Fe1-yCoy)1-zAs)2 could successfully be obtained at room temperature. The mild synthesis conditions led to compounds like FeSe and K1-xFe2-ySe2 which exhibited different physical properties than found by conventional high temperature methods. In general, the developed (de)intercalation reactions represent a new, universally applicable tool in order to manipulate the structure along with the properties of Fe-based superconductors. The basic structural features of the characteristic FeX4/4 tetrahedral layers, however, are preserved. Soft chemistry syntheses have been shown to allow the formation of a variety of phases, like Na1-xFe2-yAs2, Na1-x((Fe1-yCoy)1-zAs)2 and K1-xFe2-ySe2. Hence, especially low temperature approaches may enable the realization of complex stacking sequences, potentially leading to the fulfillment of the greatest goal in the research of superconductors - room temperature superconductivity.

  5. Iron-based superconductors via soft chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Friederichs, Gina Maya

    2015-06-30

    This thesis provides new soft chemistry approaches to Fe-based superconductors. Mild syntheses were demonstrated to be able to overcome difficulties, occurring in conventional synthesis and to enable the access to new metastable phases. A solvent-based metathesis reaction led to β-FeSe exclusively. Contrary to solid state syntheses, the formation of hexagonal α-FeSe could be avoided under mild conditions. The deintercalation of interstitial Fe (by formation of Fe{sub 3}O{sub 4}) could be proven by low temperature O{sub 2}-annealing of Fe{sub 1+x}Te{sub 1-y}Se{sub y}. By using redox (de)intercalations K{sub 1-x}Fe{sub 2-y}Se{sub 2}, metastable Na{sub 1-x}Fe{sub 2-y}As{sub 2} and Na{sub 1-x}((Fe{sub 1-y}Co{sub y}){sub 1-z}As){sub 2} could successfully be obtained at room temperature. The mild synthesis conditions led to compounds like FeSe and K{sub 1-x}Fe{sub 2-y}Se{sub 2} which exhibited different physical properties than found by conventional high temperature methods. In general, the developed (de)intercalation reactions represent a new, universally applicable tool in order to manipulate the structure along with the properties of Fe-based superconductors. The basic structural features of the characteristic FeX{sub 4/4} tetrahedral layers, however, are preserved. Soft chemistry syntheses have been shown to allow the formation of a variety of phases, like Na{sub 1-x}Fe{sub 2-y}As{sub 2}, Na{sub 1-x}((Fe{sub 1-y}Co{sub y}){sub 1-z}As){sub 2} and K{sub 1-x}Fe{sub 2-y}Se{sub 2}. Hence, especially low temperature approaches may enable the realization of complex stacking sequences, potentially leading to the fulfillment of the greatest goal in the research of superconductors - room temperature superconductivity.

  6. Iron based superconductors: Pnictides versus chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Sadovskii, M.V., E-mail: sadovski@iep.uran.ru [Institute for Electrophysics, Russian Academy of Sciences, Ural Branch, Amundsen str. 106, Ekaterinburg 620016 (Russian Federation); Institute for Metal Physics, Russian Academy of Sciences, Ural Branch, S. Kovalevskaya str. 18, Ekaterinburg 620990 (Russian Federation); Kuchinskii, E.Z.; Nekrasov, I.A. [Institute for Electrophysics, Russian Academy of Sciences, Ural Branch, Amundsen str. 106, Ekaterinburg 620016 (Russian Federation)

    2012-10-15

    We present a brief review of the present day situation with studies of high-temperature superconductivity in iron pnictides and chalcogenides. Recent discovery of superconductivity with T{sub c}>30K in A{sub x}Fe{sub 2-x/2}Se{sub 2} (A=K, Cs, Tl, etc) represents the major new step in the development of new concepts in the physics of Fe-based high-temperature superconductors. We compare LDA and ARPES data on the band structure and Fermi surfaces of novel superconductors and those of the previously studied FeAs superconductors, especially isostructural 122-superconductors like BaFe{sub 2}As{sub 2}. It appears that electronic structure of new superconductors is rather different from that of FeAs 122-systems. In particular, no nesting properties of electron and hole-like Fermi surfaces is observed, casting doubts on most popular theoretical schemes of Cooper pairing for these systems. Doping of novel materials is extremely important as a number of topological transitions of Fermi surface near the {Gamma} point in the Brillouin zone are observed for different doping levels. The discovery of Fe vacancies ordering and antiferromagnetic (AFM) ordering at pretty high temperatures (T{sub N}>500K), much exceeding superconducting T{sub c} makes these systems unique antiferromagnetic superconductors with highest T{sub N} observed up to now. This poses very difficult problems for theoretical understanding of superconductivity. We discuss the role of both vacancies and AFM ordering in transformations of band structure and Fermi surfaces, as well as their importance for superconductivity. In particular, we show that system remains metallic with unfolded Fermi surfaces quite similar to that in paramagnetic state. Superconducting transition temperature T{sub c} of new superconductors is discussed within the general picture of superconductivity in multiple band systems. It is demonstrated that both in FeAs-superconductors and in new FeSe-systems the value of T{sub c} correlates with the value of the total density of states (DOSs) at the Fermi level.

  7. Magnetorheological characterisation of carbonyl iron based suspension

    Directory of Open Access Journals (Sweden)

    M. Kciuk

    2009-04-01

    Full Text Available Purpose: The main aim of this article was to present the investigation results of magnetorheological fluids (MR composed of carbonyl iron (CI particles and analyse their flow behaviour in terms of the internal structure formation by a control of applied external magnetic field. The morphology, magnetic properties, sedimentation stability, and magnetorheological properties of the examined MR fluids were studied.Design/methodology/approach: Model MR fluid was prepared using silicone oil OKS 1050 mixed with carbonyl iron powder CI. Furthermore, to reduce sedimentation Aerosil 200 was added as stabilizers. In the purpose to determine the properties of the analyzed fluids the sedimentation and dynamic viscosity were investigated.Findings: Dynamic viscosity of investigated magnetorheological fluids rapidly and reversibly change in response to the applied external magnetic field. Moreover added particles of fumed silica inhibited sedimentation of carbonyl iron particles.Research limitations/implications: MR fluids with excellent properties can be applied in various fields of civil engineering, safety engineering, transportation and life science. They offer an outstanding capability of active control of mechanical properties. But there are no systematic published studies of factors affecting the durability of MR fluids and devices. There is very little information on the effects of exposing different MR fluids to temperature, for this reasons further efforts are needed in order to obtain even better results.Originality/value: The investigation results are reliable and could be very useful both for designers and the practitioners of many branches of industry.

  8. Iron based superconductors: Pnictides versus chalcogenides

    International Nuclear Information System (INIS)

    We present a brief review of the present day situation with studies of high-temperature superconductivity in iron pnictides and chalcogenides. Recent discovery of superconductivity with Tc>30K in AxFe2−x/2Se2 (A=K, Cs, Tl, etc) represents the major new step in the development of new concepts in the physics of Fe-based high-temperature superconductors. We compare LDA and ARPES data on the band structure and Fermi surfaces of novel superconductors and those of the previously studied FeAs superconductors, especially isostructural 122-superconductors like BaFe2As2. It appears that electronic structure of new superconductors is rather different from that of FeAs 122-systems. In particular, no nesting properties of electron and hole-like Fermi surfaces is observed, casting doubts on most popular theoretical schemes of Cooper pairing for these systems. Doping of novel materials is extremely important as a number of topological transitions of Fermi surface near the Γ point in the Brillouin zone are observed for different doping levels. The discovery of Fe vacancies ordering and antiferromagnetic (AFM) ordering at pretty high temperatures (TN>500K), much exceeding superconducting Tc makes these systems unique antiferromagnetic superconductors with highest TN observed up to now. This poses very difficult problems for theoretical understanding of superconductivity. We discuss the role of both vacancies and AFM ordering in transformations of band structure and Fermi surfaces, as well as their importance for superconductivity. In particular, we show that system remains metallic with unfolded Fermi surfaces quite similar to that in paramagnetic state. Superconducting transition temperature Tc of new superconductors is discussed within the general picture of superconductivity in multiple band systems. It is demonstrated that both in FeAs-superconductors and in new FeSe-systems the value of Tc correlates with the value of the total density of states (DOSs) at the Fermi level.

  9. 学习动机对公外学生英语水平磨蚀的影响%A Study on the Influence of Learning Motivation to the Attrition of English Proficiency for Non-English Majors

    Institute of Scientific and Technical Information of China (English)

    叶譞

    2014-01-01

    Based on the learning motivation scale designed by Wen Qiufang as questionnaire and the CET4 score, coupled with the method of interview, the influence of learning motivation to the attrition of English proficiency for non-English majors is studied. As is discovered in matched sample T-test, all participants and high-score group have significant improvement in English proficiency while low-score group have significant attrition.High-score and low score group are similar in most items of extrinsic motivation but the influences of endeavor and metacognitive strategy determine whether their English will go through attrition or not. Due to a pessimistic attitide to English learning and the belief that English learning is valueless as well as the reluctance to learn English after passing CET4 and to use English as a tool for academic study, the low-score group have a low intensity of intrinsic motivation, which results in attrition in English proficiency.%!!!!!!!!!!!!押以文秋芳制作的学习动机量表和两次四级成绩为测量工具,通过问卷调查、访谈的方式,研究了学习动机对公外学生英语水平磨蚀的影响。配对样本T检验发现:全体受试对象、高分组受试对象英语水平有显著提高,低分组有显著磨蚀。高、低分组大多数表层动机强度相似,但努力程度和元认知策略影响他们英语水平是否磨蚀。低分组学生由于对英语学习持悲观态度且认为英语学习没有价值,在通过四级后不会继续学习,加之不会将英语作为交流工具及用于学术研究而造成深层动机强度较低,从而磨蚀英语水平。

  10. The resistance to embrittlement by a hydrogen environment of selected high strength iron-manganese base alloys

    Science.gov (United States)

    Benson, R. B., Jr.; Kim, D. K.; Atteridge, D.; Gerberich, W. W.

    1974-01-01

    Fe-16Mn and Fe-25Mn base alloys, which had been cold worked to yield strength levels of 201 and 178 KSI, were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature under the loading conditions employed in this investigation. Transmission electron microscopy established that bands of epsilon phase martensite and fcc mechanical twins were formed throughout the fcc matrix when these alloys were cold worked. In the cold worked alloys a high density of crystal defects were observed associated with both types of strain induced structures, which should contribute significantly to the strengthening of these alloys. High strength iron base alloys can be produced which appear to have some resistance to degradation of mechanical properties in a hydrogen environment under certain conditions.

  11. DOE-DARPA High-Performance Corrosion-Resistant Materials (HPCRM), Annual HPCRM Team Meeting & Technical Review

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J; Brown, B; Bayles, B; Lemieux, T; Choi, J; Ajdelsztajn, L; Dannenberg, J; Lavernia, E; Schoenung, J; Branagan, D; Blue, C; Peter, B; Beardsley, B; Graeve, O; Aprigliano, L; Yang, N; Perepezko, J; Hildal, K; Kaufman, L; Lewandowski, J; Perepezko, J; Hildal, K; Kaufman, L; Lewandowski, J; Boudreau, J

    2007-09-21

    The overall goal is to develop high-performance corrosion-resistant iron-based amorphous-metal coatings for prolonged trouble-free use in very aggressive environments: seawater & hot geothermal brines. The specific technical objectives are: (1) Synthesize Fe-based amorphous-metal coating with corrosion resistance comparable/superior to Ni-based Alloy C-22; (2) Establish processing parameter windows for applying and controlling coating attributes (porosity, density, bonding); (3) Assess possible cost savings through substitution of Fe-based material for more expensive Ni-based Alloy C-22; (4) Demonstrate practical fabrication processes; (5) Produce quality materials and data with complete traceability for nuclear applications; and (6) Develop, validate and calibrate computational models to enable life prediction and process design.

  12. Animation of Antimicrobial Resistance

    Medline Plus

    Full Text Available ... use of antimicrobial drugs will result in the development of resistant strains of bacteria, complicating clinician's efforts ... More in Antimicrobial Resistance National Antimicrobial Resistance Monitoring System About NARMS Bacteria (NARMS) NARMS at Work Reports ...

  13. Animation of Antimicrobial Resistance

    Medline Plus

    Full Text Available ... 08 Animation of Antimicrobial Resistance (text version) Arabic Translation - Animation of Antimicrobial Resistance (WMV - 19.2MB) Chinese Translation - Animation of Antimicrobial Resistance (WMV - 19.2MB) French ...

  14. HIV Resistance Testing

    Science.gov (United States)

    ... 14, 2016 Select a Language: Fact Sheet 126 HIV Resistance Testing WHAT IS RESISTANCE? HOW DOES RESISTANCE ... ARVs. If you miss doses of your medications, HIV will multiply more easily. More mutations will occur. ...

  15. Animation of Antimicrobial Resistance

    Medline Plus

    Full Text Available ... Veterinary Home Animal & Veterinary Safety & Health Antimicrobial Resistance Animation of Antimicrobial Resistance Share Tweet Linkedin Pin it ... Veterinary Medicine is cited as the corporate author. Animation Animation of Antimicrobial Resistance (WMV - 19.2MB) 9: ...

  16. Animation of Antimicrobial Resistance

    Medline Plus

    Full Text Available ... More in Antimicrobial Resistance National Antimicrobial Resistance Monitoring System ... Note: If you need help accessing information in different file formats, see Instructions for Downloading ...

  17. Passive transfer of resistance and the site of immune-dependent elimination of the challenge infection in rats vaccinated with highly irradiated cercariae of Schistosoma mansoni

    Energy Technology Data Exchange (ETDEWEB)

    Ford, M.J.; Bickle, Q.D.; Taylor, M.G.; Andrews, B.J. (London School of Hygiene and Tropical Medicine (UK))

    1984-12-01

    The immune-dependent elimination of a challenge infection in rats vaccinated with highly-irradiated cercariae of Schistosoma mansoni was analysed by passive transfer of serum, recovery of the challenge from the lungs and livers and by transferring lung-stage schistosomula. Recipients of serum from rats immunized with either unirradiated, 20 or 40 krad.-irradiated cercariae, were equally resistant if the serum was injected on the day of infection or 5-7 days after infection. Vaccinated rat serum transferred to mice and vaccinated rabbit serum transferred to rats conferred comparable protection when injected on day 0 or 5 days after infection of the recipients. This apparent susceptibility of the lung schistosomula to immune attack was confirmed by challenging 20 or 40 krad.-irradiated cercariae vaccinated rats with lung-stage schistosomula derived from mice or rats. All the detectable attrition of a cercarial challenge in vaccinated rats occurred between 7 and 10 days post-challenge, before the parasites reached the liver. Since there was no evidence of damage or attrition in the skin or lungs before day 7 it was concluded that immune-dependent elimination occurred rapidly following a 'window of sensitivity' coinciding with the migration of the parasites from the lungs to the liver.

  18. Passive transfer of resistance and the site of immune-dependent elimination of the challenge infection in rats vaccinated with highly irradiated cercariae of Schistosoma mansoni

    International Nuclear Information System (INIS)

    The immune-dependent elimination of a challenge infection in rats vaccinated with highly-irradiated cercariae of Schistosoma mansoni was analysed by passive transfer of serum, recovery of the challenge from the lungs and livers and by transferring lung-stage schistosomula. Recipients of serum from rats immunized with either unirradiated, 20 or 40 krad.-irradiated cercariae, were equally resistant if the serum was injected on the day of infection or 5-7 days after infection. Vaccinated rat serum transferred to mice and vaccinated rabbit serum transferred to rats conferred comparable protection when injected on day 0 or 5 days after infection of the recipients. This apparent susceptibility of the lung schistosomula to immune attack was confirmed by challenging 20 or 40 krad.-irradiated cercariae vaccinated rats with lung-stage schistosomula derived from mice or rats. All the detectable attrition of a cercarial challenge in vaccinated rats occurred between 7 and 10 days post-challenge, before the parasites reached the liver. Since there was no evidence of damage or attrition in the skin or lungs before day 7 it was concluded that immune-dependent elimination occurred rapidly following a 'window of sensitivity' coinciding with the migration of the parasites from the lungs to the liver. (author)

  19. The Role of Attrition and Solids Recovery in a Chemical Looping Combustion Process Effet de l’attrition et de la récupération des particules dans le procédé de combustion en boucle chimique

    Directory of Open Access Journals (Sweden)

    Kramp M.

    2011-05-01

    Full Text Available In the present work, the steady-state behavior of a Chemical Looping Combustion process of interconnected fluidized bed reactors is simulated. The simulations have been carried out in two different scales, 50 kWth and 100 MWth. Attrition model derived from small scale laboratory experiments has been employed for the prediction of the process behavior in terms of attrition and Oxygen Carrier loss. Information on Oxygen Carrier characteristics and reaction kinetics were taken from literature. Realistic circulation mass flows of Oxygen Carrier particles are obtained and Oxygen Carrier losses are quantified. The large scale process looses significantly more Oxygen Carrier than the small scale process based on the same amount of thermal energy produced. Incomplete conversion in the air reactor could be identified as a critical point. Another issue is the fuel gas bypassing the Oxygen Carrier particles through bubbles in the large scale process which leads to lowered fuel conversions. The simulations indicate that a similar performance of a pilot scale and a large scale process is not guaranteed due to the scale-up effect on fluid dynamics. Furthermore, the simulations allow an assessment of the influence of the quality of the solids recovery system on the Oxygen Carrier loss. The distribution of the losses between possible origins is investigated and different changes in the solids recovery system are discussed regarding their potential to decrease the Oxygen Carrier loss. For example, the addition of a second-stage cyclone after the air reactor of the large scale process reduces the Oxygen Carrier loss significantly. Le présent travail propose un modèle de simulation en continu du procédé de combustion en boucle chimique constitué de deux lits fluidisés interconnectés. Les simulations ont été conduites à deux échelles 50 kWth correspondant à une installation pilote et 100 MWth correspondant à une installation industrielle. Un modèle d

  20. The Damping of Large Sediment Input Signals due to Attrition, Channel Morphologic Change, and Storage: the Fly River Watershed, Papua New Guinea

    Science.gov (United States)

    Dietrich, W. E.; Cui, Y.; Parker, G.; Moi, A.

    2001-12-01

    the 15 year period, 30% of the sediment was stored in the fan and gravel bedded reaches, 18% in the bed of the sand bedded channel, 17% on the adjacent floodplains, 2% was dredged from the channel and only 28% of the total load was transported to the lower end of the middle Fly. Modeling which generally predicts well the field observations, demonstrates that: 1) about 70% of the gravel input broke down to silt and clay, 2) channel widening (which is not modeled) strongly reduces aggradation thickness, 3) sand aggradation is damped by steepening slopes and increased transport, 4) rates of overbank deposition markedly increases with channel bed aggradataion, and 5) post-mining (and end of sediment input) , the aggraded gravel will eroded and disperse downstream (though trapped within the gravel reach), whereas the sand slug will move as an aggradation wave downstream for many decades. These findings demonstrate that upstream sediment pulses are strongly damped by particle attrition, channel widening and transient storage effects. Prediction of downstream fining of the sand bedded reach and channel width change in response to large fluctuations in sediment load remain significant theoretical challenges.

  1. Resistance patterns, prevalence, and predictors of fluoroquinolones resistance in multidrug resistant tuberculosis patients

    OpenAIRE

    Nafees Ahmad; Arshad Javaid; Syed Azhar Syed Sulaiman; Long Chiau Ming; Izaz Ahmad; Amer Hayat Khan

    2016-01-01

    Abstract Background Fluoroquinolones are the backbone of multidrug resistant tuberculosis treatment regimens. Despite the high burden of multidrug resistant tuberculosis in the country, little is known about drug resistance patterns, prevalence, and predictors of fluoroquinolones resistance among multidrug resistant tuberculosis patients from Pakistan. Objective To evaluate drug resistance patterns, prevalence, and predictors of fluoroquinolones resistance in multidrug resistant tuberculosi...

  2. The Differences among the Phenomenon of"Disappearance of Languages"with Language Attrition%从语言磨蚀谈“语言消失”现象的区别

    Institute of Scientific and Technical Information of China (English)

    李雪松

    2013-01-01

      Language attrition is the inverse process of language acquisition , which to some extent belongs to "disappearance of languages".In contrast, we made a study of the distinction between language attrition and the phenomenon of "disappearance of languages", which including language transfer , aphasia and senile de-mentia, language endangered, and language forgotten through the five attributes of generations relationship , occurrence mechanism, target groups, cause factors and existing forms.We found though they are in the same category of "disappearance of languages", it appears a big difference between them by their nature .Mean-while we take a contrast for differences.Therefore, dividing "language disappear"into language macroscopic disappear and language microscopic disappear on further .%  语言磨蚀是语言习得的逆过程,在某种程度上属于“语言消失”。从对比的角度出发,通过代际关系、发生机制、目标群体、造成因素以及存在形式等五个属性来考查语言磨蚀与语言迁移、失语症和老年痴呆、语言濒危以及遗忘等“语言消失”现象的区别。研究发现,它们虽同属“语言消失”,但在本质上存在着很大的差别,同时对差别项进行了对比。由此更进一步把“语言消失”分为语言宏观消失与语言微观消失。

  3. Animation of Antimicrobial Resistance

    Medline Plus

    Full Text Available ... More in Antimicrobial Resistance National Antimicrobial Resistance Monitoring System About NARMS Bacteria (NARMS) NARMS at Work Reports ... Emergency Preparedness International Programs News & Events Training & Continuing Education Inspections & Compliance Federal, State & Local Officials Consumers Health ...

  4. HIV Genotypic Resistance Testing

    Science.gov (United States)

    ... of the disease progression and to minimize viral replication and mutation. However, a person may be initially infected with a drug-resistant HIV strain or drug resistance may develop during treatment, ...

  5. Animation of Antimicrobial Resistance

    Medline Plus

    Full Text Available ... how antimicrobial resistance both emerges and proliferates among bacteria. Over time, the use of antimicrobial drugs will result in the development of resistant strains of bacteria, complicating clinician's efforts to select the appropriate antimicrobial ...

  6. Oxidation-resistant cermet

    Science.gov (United States)

    Phillips, W. M.

    1977-01-01

    Chromium metal alloys and chromium oxide ceramic are combined to produce cermets with oxidation-resistant properties. Application of cermets includes use in hot corrosive environments requiring strong resistive materials.

  7. Pneumococcal resistance to antibiotics.

    OpenAIRE

    Klugman, K P

    1990-01-01

    The geographic distribution of pneumococci resistant to one or more of the antibiotics penicillin, erythromycin, trimethoprim-sulfamethoxazole, and tetracycline appears to be expanding, and there exist foci of resistance to chloramphenicol and rifampin. Multiply resistant pneumococci are being encountered more commonly and are more often community acquired. Factors associated with infection caused by resistant pneumococci include young age, duration of hospitalization, infection with a pneumo...

  8. Resisting Mind Control.

    Science.gov (United States)

    Anderson, Susan M.; Zimbardo, Philip G.

    1980-01-01

    Provides conceptual analyses of mind control techniques along with practical advice on how to resist these techniques. The authors stress that effective mind control stems more from everyday social relations than from exotic technological gimmicks. Suggestions are given for resisting persuasion, resisting systems, and challenging the system.…

  9. Resisting Organizational Change

    Directory of Open Access Journals (Sweden)

    Gunnar Andersson

    2015-03-01

    Full Text Available We are continuously reminded of how change induces controversy and resistance, regardless of support. We repeatedly experience resistance in difficulties of implementation, little progress, and poor results, rather than increased productivity as anticipated. In a detailed account of how change plays out, a mosaic of what resistance looks like emerges. The picture is both familiar and absolutely concrete, and challenges the structural assumptions and dichotomies on support and resistance in an organization. The findings invite technologies, people, actions, practices and materiality to the discussions on support and resistance.

  10. [Rodenticide resistance and consequences].

    Science.gov (United States)

    Esther, A; Endepols, S; Freise, J; Klemann, N; Runge, M; Pelz, H-J

    2014-05-01

    Resistance to anticoagulant rodenticides, such as warfarin was first described in 1958. Polymorphisms in the vitamin K epoxide reductase complex subunit 1 (VKORC1) gene and respective substitutions of amino acids in the VKOR enzyme are the major cause for rodenticide resistance. Resistant Norway rats in Germany are characterized by the Tyr139Cys genotype, which is spread throughout the northwest of the country. Resistant house mice with the VKOR variants Tyr139Cys, Leu128Ser and Arg12Trp/Ala26Ser/Ala48Thr/Arg61Leu (spretus type) are distributed over a number of locations in Germany. Resistance can reduce management attempts with consequences for stored product protection, hygiene and animal health. Anticoagulants of the first generation (warfarin, chlorophacinone, coumatetralyl) as well as bromadiolone and difenacoum are not an option for the control of resistant Norway rats. The same applies for house mice whereby the tolerance to compounds can be different between local incidences. Due to the higher toxicity and tendency to persist, the most potent anticoagulant rodenticides brodifacoum, flocoumafen and difethialone should be applied but only where resistance is known. In other cases less toxic anticoagulants should be preferred for rodent management in order to mitigate environmental risks. Resistance effects of further VKOR polymorphisms and their combinations, the spread of resistant rats and conditions supporting and reducing resistance should be investigated in order to improve resistance management strategies. PMID:24781908

  11. Spectacles of resistance and resistance of spectacles

    OpenAIRE

    Gabriel, Yiannis

    2008-01-01

    This paper explores organizational controls in an era dominated by spectacles, images and pictures and seeks to identify some forms of resistance that subvert and undermine these controls. It develops the metaphor of today’s organizations a ‘glass cages’ in juxtaposition to the Weberian ‘iron cages’ that summed up some of the qualities of organizations of yesteryear. The paper analyses new forms of resistance, such as whistleblowing and subvertizing, that are particularly aimed at besmirching...

  12. Genetics of metabolic resistance.

    Science.gov (United States)

    Richter, Otto; Langemann, Dirk; Beffa, Roland

    2016-09-01

    Herbicide resistance has become a major issue for many weeds. Metabolic resistance refers to the biochemical processes within organisms that degrade herbicides to less toxic compounds, resulting in a shift of the dose response curve. This type of resistance involves polygenic inheritance. A model is presented linking the biochemical pathway of amino acid synthesis and the detoxifying pathway of an inhibitor of the key enzyme ALS. From this model, resistance factors for each biotype are derived, which are then applied to a polygenic population genetic model for an annual weed plant. Polygenic inheritance is described by a new approach based on tensor products of heredity matrices. Important results from the model are that low dose regimes favour fast emergence of resistant biotypes and that the emergence of resistant biotypes occurs as abrupt outbreaks. The model is used to evaluate strategies for the management of metabolic resistance. PMID:27424952

  13. 铁基催化剂对将军庙煤低压直接液化性能影响%Effect of Iron-based Catalysts on Direct Liquefaction Performance of Coal From Jiangjunmiao, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    王海龙; 廖玲

    2015-01-01

    以将军庙煤为研究对象,催化剂用量按活性金属元素计为3%(wtCoaldaf)、反应温度T=420℃、反应时间τ=75 min、溶煤比S/C=2/1和氢初压PH2=6.5 MPa条件下,首先,以油产率为目标,Fe2O3为主催化剂,S为助催化剂,通过考察S/Fe对煤样直接液化性能的影响,确定了最佳S/Fe=1/1。其次,在S/Fe为1/1和上述反应条件下,考察了一系列铁基催化剂对煤样液化性能的影响。结果表明,以油产率为目标,其活性由高到低为:Fe2O3/S>油溶性Fe3O4/S >油溶性Fe3O4(中试)/S >飞灰/S >纳米Fe3O4/S>黄铁矿/Fe2O3>油酸铁/S > FeSO4/S> Fe(NO3)3/S>β-FeOOH/S >FeCl3/S >还原铁粉/S >FeS。最后,将Fe2O3/S与MoO3/S、FeSO4/S与NiSO4/S和CoSO4/S分别进行了比较。结果表明:Fe2O3/S比MoO3/S更能促进沥青质向油的转化;FeSO4/S与NiSO4/S和CoSO4/S三者油产率相差甚小,均约67%。故此,Fe2O3/S的催化活性最好。%The research objectwasthe coal from Jiangjunmiao. First of all,takingoil yield as the target and Fe2O3as the maincatalyst and S as the sub-catalyst, the best S/Fe=1∶1wasconfirmedby investigating the effect of S/Fe on direct liquefaction performanceof coal sample under the reaction conditions of catalysts 3%( wt), 420℃,reaction time 75 min, solvent/coal=2/1 and H2initial pressure 6.5 MPa. Theneffect of a series of iron-based catalysts on liquefaction performanceof coal sample under S/Fe=1/1andotheraboveconditionswas investigated. The results showthat:the rank ordering of the activity of catalysts according to the oil yield is Fe2O3/S>oil-soluble Fe3O4/S > oil-soluble(pilot plant) Fe3O4/S >fly ash/S >nanometer Fe3O4/S>pyrite/Fe2O3>oleic acid iron/S > FeSO4/S> Fe(NO3)3/S > β-FeOOH/S>FeCl3/S >iron powder/S >FeS. At last,Fe2O3/S and MoO3/S, FeSO4/S and NiSO4/S and CoSO4/Swererespectively compared. Theresults show that:Fe2O3/S can more promote theconversionof asphaltene to oil than MoO3/S;thegap of the oil yieldsamong FeSO4/S

  14. Nonvolatile Bipolar Resistive Switching Behavior in the Perovskite-like (CH3NH3)2FeCl4.

    Science.gov (United States)

    Lv, Fengzhen; Gao, Cunxu; Zhou, Heng-An; Zhang, Peng; Mi, Kui; Liu, Xiaoxing

    2016-07-27

    The bipolar resistive switching behavior in a device based on an crystalline iron-based organic-inorganic, perovskite-like material of (CH3NH3)2FeCl4 (MAFC), was examined and studied. Both high and low resistance states appeared to have no obvious degradation during a measurement period of 600 s with 400 cycles in a Ag/MAFC/Cu device, which also exhibited good thermal stability over a wide temperature range of 290 to 340 K. The conductivity-state switching behavior was derived from the competition between the ionic current within the MAFC and the Faradaic current that originated from oxidative reactions at the Ag/MAFC/Cu interface. A model explaining the oxidative reaction process was established to describe the symmetric resistive switching behavior in the Ag/MAFC/Cu cell. With an applied bias voltage sweeping, the oxidative layers passivated and dissipated at the Ag/MAFC/Cu interface that resulted in the competition between the induced current and the ionic current, and thus caused a symmetric resistance change. On the basis of this interfacial effect, the MAFC crystals can be used as memristor elements in devices for write-read-erase-rewrite process. PMID:27414403

  15. Challenges to Resistance Welding

    DEFF Research Database (Denmark)

    Song, Quanfeng

    This report originates from the compulsory defense during my Ph.D. study at the Technical University of Denmark. Resistance welding is an old and well-proven technology. Yet the emergence of more and more new materials, new designs, invention off new joining techniques, and more stringent...... requirement in quality have imposed challenges to the resistance welding. More some research and development have to be done to adapt the old technology to the manufacturing industry of the 21st century. In the 1st part of the report, the challenging factors to the resistance welding are reviewed. Numerical...... simulation of resistance welding has been under development for many years. Yet it is no easy to make simulation results reliable and accurate because of the complexity of resistance welding process. In the 2nd part of the report numerical modeling of resistance welding is reviewed, some critical factors to...

  16. Management of resistant depression.

    OpenAIRE

    Warneke, L

    1996-01-01

    Treatment-resistant depression is a relative concept. It has been formally defined as a mood disorder that fails to respond to three adequate trials of antidepressants. However, treatment resistance is relative to the expertise and knowledge of the treating physician and the availability of resources, such as electroconvulsive therapy. Only about 7% of patients show absolute treatment resistance, and even they can be helped.

  17. The Study on the Anti-attrition Teaching Method of Writing Based on Training of Critical Thinking Skills%以培养思辨能力为导向的外语写作抗磨蚀教学方法研究

    Institute of Scientific and Technical Information of China (English)

    王青华

    2015-01-01

    Based on the reviews of the studies on the attrition of foreign language writing skills, this paper points out the significance of teaching writing with the critical-thinking-skills oriented method, so as to help with improving the learners’ writing skills and seeking effective anti-attrition method when teaching writing.%本文在介绍语言磨蚀研究领域中外语写作技能磨蚀的研究背景基础上,提出在外语教学中运用以培养思辨能力为导向的外语写作抗磨蚀教学方法,将对提高学习者的外语写作水平以及在外语教学中寻求外语写作抗磨蚀方案具有一定的实践意义。

  18. Resistance to Powdery Mildews

    DEFF Research Database (Denmark)

    Siwoszek, Agnieszka Izabela

    resistance. I attempt to determine how the basic resistance components contribute to resistance against powdery mildews. Furthermore, I propose an alternative strategy of achieving resistance to barley powdery mildew by application of peptide aptamers. Peptide aptamers are small proteins selected to...... specifically target conserved YxC motif of barley powdery mildew effectors. I present a proof-of-concept study in Arabidopsis, where overexpression of peptide aptamers significantly reduced the susceptibility to barley powdery mildew. Moreover, I set the discovery in a bigger context by summarizing genetic...

  19. Bacterial resistance to uncouplers.

    Science.gov (United States)

    Lewis, K; Naroditskaya, V; Ferrante, A; Fokina, I

    1994-12-01

    Uncoupler resistance presents a potential challenge to the conventional chemiosmotic coupling mechanism. In E. coli, an adaptive response to uncouplers was found in cell growing under conditions requiring oxidative phosphorylation. It is suggested that uncoupler-resistant mutants described in the earlier literature might represent a constitutive state of expression of this "low energy shock" adaptive response. In the environment, bacteria are confronted by nonclassical uncoupling factors such as organic solvents, heat, and extremes of pH. It is suggested that the low energy shock response will aid the cell in coping with the effects of natural uncoupling factors. The genetic analysis of uncoupler resistance has only recently began, and is yielding interesting and largely unexpected results. In Bacillus subtilis, a mutation in fatty acid desaturase causes an increased content of saturated fatty acids in the membrane and increased uncoupler resistance. The protonophoric efficiency of uncouplers remains unchanged in the mutants, inviting nonorthodox interpretations of the mechanism of resistance. In E. coli, two loci conferring resistance to CCCP and TSA were cloned and were found to encode multidrug resistance pumps. Resistance to one of the uncouplers, TTFB, remained unchanged in strains mutated for the MDRs, suggesting a resistance mechanism different from uncoupler extrusion. PMID:7721726

  20. Facts about Antibiotic Resistance

    Science.gov (United States)

    ... Recommendations Pediatric Treatment Recommendations Inpatient Healthcare Professionals Community Pharmacists Continuing Education & Curriculum Opportunities Weighing in on Antibiotic Resistance Improving Prescribing Outpatient Antibiotic Stewardship Interventions That Work Systematic Reviews ...