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Sample records for attrition resistant iron-based

  1. ATTRITION RESISTANT IRON-BASED FISCHER-TROPSCH CATALYSTS

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-10-01

    Fischer-Tropsch (FT) synthesis to convert syngas (CO + H{sub 2}) derived from natural gas or coal to liquid fuels and wax is a well-established technology. For low H{sub 2} to CO ratio syngas produced from CO{sub 2} reforming of natural gas or from gasification of coal, the use of Fe catalysts is attractive because of their high water gas shift activity in addition to their high FT activity. Fe catalysts are also attractive due to their low cost and low methane selectivity. Because of the highly exothermic nature of the FT reaction, there has been a recent move away from fixed-bed reactors toward the development of slurry bubble column reactors (SBCRs) that employ 30 to 90 {micro}m catalyst particles suspended in a waxy liquid for efficient heat removal. However, the use of FeFT catalysts in an SBCR has been problematic due to severe catalyst attrition resulting in fines that plug the filter employed to separate the catalyst from the waxy product. Fe catalysts can undergo attrition in SBCRs not only due to vigorous movement and collisions but also due to phase changes that occur during activation and reaction.

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

    Energy Technology Data Exchange (ETDEWEB)

    Adeyinka A. Adeyiga

    2003-12-01

    Fischer-Tropsch (FT) synthesis to convert syngas (CO + H{sub 2}) derived from natural gas or coal to liquid fuels and wax is a well-established technology. For low H{sub 2} to CO ratio syngas produced from CO{sub 2} reforming of natural gas or from gasification of coal, the use of Fe catalysts is attractive because of their high water gas shift activity in addition to their high FT activity. Fe catalysts are also attractive due to their low cost and low methane selectivity. Because of the highly exothermic nature of the FT reaction, there has been a recent move away from fixed-bed reactors toward the development of slurry bubble column reactors (SBCRs) that employ 30 to 90 {micro}m catalyst particles suspended in a waxy liquid for efficient heat removal. However, the use of Fe FT catalysts in an SBCR has been problematic due to severe catalyst attrition resulting in fines that plug the filter employed to separate the catalyst from the waxy product. Fe catalysts can undergo attrition in SBCRs not only due to vigorous movement and collisions but also due to phase changes that occur during activation and reaction. The objectives of this research were to develop a better understanding of the parameters affecting attrition of Fe F-T catalysts suitable for use in SBCRs and to incorporate this understanding into the design of novel Fe catalysts having superior attrition resistance. The catalysts were prepared by co-precipitation, followed by binder addition and spray drying at 250 C in a 1 m diameter, 2 m tall spray dryer. The binder silica content was varied from 0 to 20 wt %. The results show that use of small amounts of precipitated SiO{sub 2} alone in spray-dried Fe catalysts can result in good attrition resistance. All catalysts investigated with SiO{sub 2} wt% {le} 12 produced fines less than 10 wt% during the jet cup attrition test, making them suitable for long-term use in a slurry bubble column reactor. Thus, concentration rather than type of SiO{sub 2

  3. Attrition Resistant Iron-Based Catalysts For F-T SBCRs

    Energy Technology Data Exchange (ETDEWEB)

    Adeyinka A. Adeyiga

    2006-01-31

    The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+ H{sub 2}) 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-(FE) 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 H{sub 2}/CO ratios. However, a serious problem with the 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. Under a previous Department of Energy (DOE)/University Research Grant (UCR) grant, Hampton University reported, for the first time, the development of demonstrably attrition-resistant Fe F-T synthesis catalysts having good activity, selectivity, and attrition resistance. These catalysts were prepared by spray drying Fe catalysts with potassium (K), copper (Cu), and silica (SiO{sub 2}) as promoters. SiO{sub 2} was also used as a binder for spray drying. These catalysts were tested for activity and selectivity in a laboratory-scale fixed-bed reactor. Fundamental understanding of attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried HPR-43 catalyst having average particle size (aps) of 70 {micro}m with high attrition resistance. This HPR-43 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, H{sub 2}/CO=0.67 and 2.0 NL/g-cat/h with C{sub 5+} selectivity of >78% and methane selectivity of less than 5% at an

  4. Attrition resistant fluidizable reforming catalyst

    Science.gov (United States)

    Parent, Yves O [Golden, CO; Magrini, Kim [Golden, CO; Landin, Steven M [Conifer, CO; Ritland, Marcus A [Palm Beach Shores, FL

    2011-03-29

    A method of preparing a steam reforming catalyst characterized by improved resistance to attrition loss when used for cracking, reforming, water gas shift and gasification reactions on feedstock in a fluidized bed reactor, comprising: fabricating the ceramic support particle, coating a ceramic support by adding an aqueous solution of a precursor salt of a metal selected from the group consisting of Ni, Pt, Pd, Ru, Rh, Cr, Co, Mn, Mg, K, La and Fe and mixtures thereof to the ceramic support and calcining the coated ceramic in air to convert the metal salts to metal oxides.

  5. Attrition resistant gamma-alumina catalyst support

    Science.gov (United States)

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  6. 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

  7. Attrition resistant Fischer-Tropsch catalyst and support

    Science.gov (United States)

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2004-05-25

    A catalyst support having improved attrition resistance and a catalyst produced therefrom. The catalyst support is produced by a method comprising the step of treating calcined .gamma.-alumina having no catalytic material added thereto with an acidic aqueous solution having an acidity level effective for increasing the attrition resistance of the calcined .gamma.-alumina.

  8. Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

    Energy Technology Data Exchange (ETDEWEB)

    Adeyiga, Adeyinka

    2010-02-05

    Commercial spent fluid catalytic cracking (FCC) catalysts provided by Engelhard and Albemarle were used as supports for Fe-based catalysts with the goal of improving the attrition resistance of typical F-T catalysts. Catalysts with the Ruhrchemie composition (100 Fe/5 Cu/4.2 K/25 spent FCC on mass basis) were prepared by wet impregnation. XRD and XANES analysis showed the presence of Fe{sub 2}O{sub 3} in calcined catalysts. FeC{sub x} and Fe{sub 3}O{sub 4} were present in the activated catalysts. The metal composition of the catalysts was analyzed by ICP-MS. F-T activity of the catalysts activated in situ in CO at the same conditions as used prior to the attrition tests was measured using a fixed bed reactor at T = 573 K, P = 1.38 MPa and H{sub 2}:CO ratio of 0.67. Cu and K promoted Fe supported over Engelhard provided spent FCC catalyst shows relatively good attrition resistance (8.2 wt% fines lost), high CO conversion (81%) and C{sub 5}+ hydrocarbons selectivity (18.3%).

  9. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, Krishnamurti (Naperville, IL)

    1992-01-01

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9-30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000.degree.-1100.degree. C.

  10. 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

  11. 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.

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

    Science.gov (United States)

    Gangwal, Santosh; Jothimurugesan, Kandaswamy

    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.

  13. Fluidizable zinc titanate materials with high chemical reactivity and attrition resistance

    Science.gov (United States)

    Gupta, Raghubir P.; Gangwal, Santosh K.; Jain, Suresh C.

    1993-01-01

    Highly durable and chemically reactive zinc titanate materials are prepared in a particle size range of 50 to 400 .mu.m suitable for a fluidized-bed reactor for removing reduced sulfur species in a gaseous form by granulating a mixture of fine zinc oxide and titanium oxide with inorganic and organic binders and by optional additions of small amounts of activators such as CoO and MoO.sub.3 ; and then indurating it at 800.degree. to 900.degree. C. for a time sufficient to produce attrition-resistant granules.

  14. 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

  15. 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

  16. Panel Attrition : Separating Stayers, Fast Attriters, Gradual Attriters, and Lurkers

    NARCIS (Netherlands)

    Lugtig, Peter|info:eu-repo/dai/nl/304824658

    2014-01-01

    Attrition is the process of dropout from a panel study. Earlier studies into the determinants of attrition study respondents still in the survey and those who attrited at any given wave of data collection. In many panel surveys, the process of attrition is more subtle than being either in or out of

  17. 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 proper

  18. 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

  19. 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.

  20. First language attrition

    NARCIS (Netherlands)

    Schmid, Monika S.

    2013-01-01

    Speakers who live in an L2 environment for an extended period of time often experience change in the way in which they use their L1, a process referred to as L1 attrition. This article provides an overview of language attrition phenomena at various linguistic levels. However, attrition cannot be

  1. 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…

  2. The law of attrition

    National Research Council Canada - National Science Library

    Eysenbach, Gunther

    2005-01-01

    In an ongoing effort of this Journal to develop and further the theories, models, and best practices around eHealth research, this paper argues for the need for a "science of attrition", that is, a...

  3. Attrition reactor system

    Science.gov (United States)

    Scott, Charles D.; Davison, Brian H.

    1993-01-01

    A reactor vessel for reacting a solid particulate with a liquid reactant has a centrifugal pump in circulatory flow communication with the reactor vessel for providing particulate attrition, resulting in additional fresh surface where the reaction can occur.

  4. FY05 HPCRM Annual Report: High-Performance Corrosion-Resistant Iron-Based Amorphous Metal Coatings Evaluation of Corrosion Reistance FY05 HPCRM Annual Report # Rev. 1DOE-DARPA Co-Sponsored Advanced Materials Program

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Haslam, J J; Day, S D

    2007-09-19

    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

  5. 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…

  6. Radiation effects on iron-based superconductors

    Science.gov (United States)

    Eisterer, M.

    2018-01-01

    This article reviews the results of irradiation experiments on iron-based superconductors, with particular emphasis on neutron irradiation. These experiments were either done to foster the theoretical understanding of superconductivity in these compounds by investigating the influence of impurity scattering on the fundamental superconducting properties or to investigate vortex physics and to benchmark flux pinning in view of applications. Results on the most explored iron-based compounds are summarized and compared with data on metallic superconductors, cuprates, and MgB2. Similarities and differences are discussed as well as the influence of the type and energy of the particles used for the experiments.

  7. Electrotransport in binary iron-based metal melts

    Science.gov (United States)

    Tekuchev, V. V.; Kalinkin, D. P.; Ivanova, I. V.

    2016-12-01

    The mobility of ions in binary iron-based liquid metal systems is calculated for the first time, based on studies on the specific resistance and self-diffusion coefficient in a wide range of concentrations. It is established that iron ions move toward the anode in Fe-V and Fe-Mo systems, and toward the cathode in Fe-W and Fe-Pt systems; i.e., there is inversion of electrotransport for iron ions. When the concentration of a component is reduced, the mobility of its ions grows in modulus.

  8. Theoretical analyses of superconductivity in iron based ...

    African Journals Online (AJOL)

    This paper focuses on the theoretical analysis of superconductivity in iron based superconductor Ba1−xKxFe2As2. After reviewing the current findings on this system, we suggest that phononexciton combined mechanism gives a right order of superconducting transition temperature (TC) for Ba1−xKxFe2As2 . By developing ...

  9. Cast iron-base alloy for cylinder/regenerator housing

    Science.gov (United States)

    Witter, Stewart L.; Simmons, Harold E.; Woulds, Michael J.

    1985-01-01

    NASACC-1 is a castable iron-base alloy designed to replace the costly and strategic cobalt-base X-40 alloy used in the automotive Stirling engine cylinder/generator housing. Over 40 alloy compositions were evaluated using investment cast test bars for stress-rupture testing. Also, hydrogen compatibility and oxygen corrosion resistance tests were used to determine the optimal alloy. NASACC-1 alloy was characterized using elevated and room temperature tensile, creep-rupture, low cycle fatigue, heat capacity, specific heat, and thermal expansion testing. Furthermore, phase analysis was performed on samples with several heat treated conditions. The properties are very encouraging. NASACC-1 alloy shows stress-rupture and low cycle fatigue properties equivalent to X-40. The oxidation resistance surpassed the program goal while maintaining acceptable resistance to hydrogen exposure. The welding, brazing, and casting characteristics are excellent. Finally, the cost of NASACC-1 is significantly lower than that of X-40.

  10. Early Attrition among Suicidal Clients

    Science.gov (United States)

    Surgenor, P. W. G.; Meehan, V.; Moore, A.

    2016-01-01

    The study aimed to identify the level of suicidal ideation in early attrition clients and their reasons for the early termination of their therapy. The cross-sectional design involved early attrition clients (C[subscript A]) who withdrew from therapy before their second session (n = 61), and continuing clients who (C[subscript C]) progressed…

  11. 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

  12. Reducing fischer-tropsch catalyst attrition losses in high agitation reaction systems

    Science.gov (United States)

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2001-01-01

    A method for reducing catalyst attrition losses in hydrocarbon synthesis processes conducted in high agitation reaction systems; a method of producing an attrition-resistant catalyst; a catalyst produced by such method; a method of producing an attrition-resistant catalyst support; and a catalyst support produced by such method. The inventive method of reducing catalyst attrition losses comprises the step of reacting a synthesis gas in a high agitation reaction system in the presence of a catalyst. In one aspect, the catalyst preferably comprises a .gamma.-alumina support including an amount of titanium effective for increasing the attrition resistance of the catalyst. In another aspect, the catalyst preferably comprises a .gamma.-alumina support which has been treated, after calcination, with an acidic, aqueous solution. The acidic aqueous solution preferably has a pH of not more than about 5. In another aspect, the catalyst preferably comprises cobalt on a .gamma.-alumina support wherein the cobalt has been applied to the .gamma.-alumina support by totally aqueous, incipient wetness-type impregnation. In another aspect, the catalyst preferably comprises cobalt on a .gamma.-alumina support with an amount of a lanthana promoter effective for increasing the attrition resistance of the catalyst. In another aspect, the catalyst preferably comprises a .gamma.-alumina support produced from boehmite having a crystallite size, in the 021 plane, in the range of from about 30 to about 55 .ANG.ngstrons. In another aspect, the inventive method of producing an attrition-resistant catalyst comprises the step of treating a .gamma.-alumina support, after calcination of and before adding catalytic material to the support, with an acidic solution effective for increasing the attrition resistance of the catalyst. In another aspect, the inventive method of producing an attrition-resistant catalyst support comprises the step of treating calcined .gamma.-alumina with an acidic, aqueous

  13. Telomere attrition due to infection

    National Research Council Canada - National Science Library

    Ilmonen, Petteri; Kotrschal, Alexander; Penn, Dustin J

    2008-01-01

    Telomeres--the terminal caps of chromosomes--become shorter as individuals age, and there is much interest in determining what causes telomere attrition since this process may play a role in biological aging...

  14. Attrition Rate of Oxygen Carriers in Chemical Looping Combustion Systems

    Science.gov (United States)

    Feilen, Harry Martin

    This project developed an evaluation methodology for determining, accurately and rapidly, the attrition resistance of oxygen carrier materials used in chemical looping technologies. Existing test protocols, to evaluate attrition resistance of granular materials, are conducted under non-reactive and ambient temperature conditions. They do not accurately reflect the actual behavior under the unique process conditions of chemical looping, including high temperatures and cyclic operation between oxidizing and reducing atmospheres. This project developed a test method and equipment that represented a significant improvement over existing protocols. Experimental results obtained from this project have shown that hematite exhibits different modes of attrition, including both due to mechanical stresses and due to structural changes in the particles due to chemical reaction at high temperature. The test methodology has also proven effective in providing reactivity changes of the material with continued use, a property, which in addition to attrition, determines material life. Consumption/replacement cost due to attrition or loss of reactivity is a critical factor in the economic application of the chemical looping technology. This test method will allow rapid evaluation of a wide range of materials that are best suited for this technology. The most important anticipated public benefit of this project is the acceleration of the development of chemical looping technology for lowering greenhouse gas emissions from fossil fuel combustion.

  15. 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.

  16. The nodal crisis in Iron based superconductivity

    Science.gov (United States)

    Coleman, Piers; Tzen Ong, T.

    2013-03-01

    The recent observation of fully gapped high temperature superconductivity in an iron chalcogenide without a hole Fermi surface, combined with the observations that rule out a node-less d-wave state constitute a ``nodal crisis'' in iron based superconductivity, for we do not understand how the underlying singlet state avoids the strong Coulomb interactions on the iron site without some kind of node within the superconducting condensate. In this work, we re-analyze the allowed symmetries of the superconducting condensate in the iron superconductors, taking into account both orbital symmetries between the zx and zy orbitals and the presence of two equivalent Fe sites per unit cell. We argue that the additional orbital degrees of freedom provide for a much richer class of pairing symmetries than normally considered. A particularly interesting possibility, is a p-wave, spin singlet, orbital triplet state that is a fully gapped iron analog of the B-phase of superfluid He-3. We will discuss this interesting possibility. Research supported by Division of Materials Research contract number DE-FG02-99ER45790.

  17. 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.

  18. Environmental transformations and ecological effects of iron-based nanoparticles.

    Science.gov (United States)

    Lei, Cheng; Sun, Yuqing; Tsang, Daniel C W; Lin, Daohui

    2018-01-01

    The increasing application of iron-based nanoparticles (NPs), especially high concentrations of zero-valent iron nanoparticles (nZVI), has raised concerns regarding their environmental behavior and potential ecological effects. In the environment, iron-based NPs undergo physical, chemical, and/or biological transformations as influenced by environmental factors such as pH, ions, dissolved oxygen, natural organic matter (NOM), and biotas. This review presents recent research advances on environmental transformations of iron-based NPs, and articulates their relationships with the observed toxicities. The type and extent of physical, chemical, and biological transformations, including aggregation, oxidation, and bio-reduction, depend on the properties of NPs and the receiving environment. Toxicities of iron-based NPs to bacteria, algae, fish, and plants are increasingly observed, which are evaluated with a particular focus on the underlying mechanisms. The toxicity of iron-based NPs is a function of their properties, tolerance of test organisms, and environmental conditions. Oxidative stress induced by reactive oxygen species is considered as the primary toxic mechanism of iron-based NPs. Factors influencing the toxicity of iron-based NPs are addressed and environmental transformations play a significant role, for example, surface oxidation or coating by NOM generally lowers the toxicity of nZVI. Research gaps and future directions are suggested with an aim to boost concerted research efforts on environmental transformations and toxicity of iron-based NPs, e.g., toxicity studies of transformed NPs in field, expansion of toxicity endpoints, and roles of laden contaminants and surface coating. This review will enhance our understanding of potential risks of iron-based NPs and proper uses of environmentally benign NPs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Method of coating an iron-based article

    Science.gov (United States)

    Magdefrau, Neal; Beals, James T.; Sun, Ellen Y.; Yamanis, Jean

    2016-11-29

    A method of coating an iron-based article includes a first heating step of heating a substrate that includes an iron-based material in the presence of an aluminum source material and halide diffusion activator. The heating is conducted in a substantially non-oxidizing environment, to cause the formation of an aluminum-rich layer in the iron-based material. In a second heating step, the substrate that has the aluminum-rich layer is heated in an oxidizing environment to oxidize the aluminum in the aluminum-rich layer.

  20. [Case of occlusal reconstruction for severe attrition].

    Science.gov (United States)

    Ueda, Takayuki

    2006-01-01

    A 57-year-old female complained of aesthetic disturbance, dysmasesis and phonation disorder by attrition. She had severe attrition of almost teeth. To avoid metal color exposure and attrition of opposing teeth, hybrid ceramics were used for veneered crowns and fixed partial denture. Since the prosthetic treatment, the patient wears a night guard to prevent attrition of her teeth and prosthesis. There has been no specific trouble during the 4-year follow-up. It is considered that using hybrid ceramics for veneering crowns and fixed partial denture and night guard help to prevent the attrition of opposing teeth and abrasion of prosthesis.

  1. High-Performance Corrosion-Resistant Iron-Based Amorphous Metals - The Effects of Composition, Structure and Environment: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J; Haslam, J; Day, S; Lian, T; Saw, C; Hailey, P; Choi, J; Yang, N; Bayles, R; Aprigliano, L; Payer, J; Perepezko, J; Hildal, K; Lavernia, E; Ajdelsztajn, L; Branagan, D J; Beardsely, M B

    2006-10-20

    Several Fe-based amorphous metal formulations have been identified that appear to have corrosion resistance comparable to (or better than) that of Ni-based Alloy C-22 (UNS No. N06022), based on measurements of breakdown potential and corrosion rate in seawater. Both chromium (Cr) and molybdenum (Mo) provide corrosion resistance, boron (B) enables glass formation, and rare earths such as yttrium (Y) lower critical cooling rate (CCR). 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}) has no yttrium, and is characterized by relatively high critical cooling rates of approximately 600 Kelvin per second. Data for the SAM2X5 formulation is reported here. In contrast to yttrium-containing iron-based amorphous metals, SAM2X5 can be readily gas atomized to produce spherical powders 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 or inhibitor. SAM2X5 also experiences crevice corrosion under sufficiently harsh conditions. Both Alloy C-22 and Type 316L stainless lose their resistance to corrosion during thermal spraying, due to the formation of deleterious intermetallic phases which depletes the matrix of key alloy elements, whereas SAM2X5 can be applied as coatings with the same corrosion resistance as a fully-dense completely amorphous melt-spun ribbon, provided that its amorphous nature is preserved during thermal spraying. The hardness of Type 316L Stainless Steel is approximately 150 VHN, that of Alloy C-22 is approximately 250 VHN, and that of HVOF SAM2X5 ranges from 1100-1300 VHN [MRS12-13]. Such hardness makes these materials particularly attractive for applications where corrosion-erosion and wear are also issues. Since SAM2X5 has high boron content, it can absorb neutrons efficiently, and may therefore find

  2. High temperature hardness of steels and iron-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Torres, H., E-mail: torres@ac2t.at; Varga, M.; Ripoll, M. Rodríguez

    2016-08-01

    Hot hardness, related to the mechanical strength and wear resistance of materials at high temperatures, has been measured from room temperature up to 800 °C for a comprehensive set of iron-based alloys having different microstructures and chemical compositions. The results obtained suggest the existence of several softening regimes with increasing temperatures, also with a massive hardness drop observed to begin at temperatures close to 0.5 times the melting temperature for most of the chosen alloys. Austenitic steel grades were also observed to show a significant softening behaviour at moderate temperatures compared to ferritic and martensitic alloys, attributed to the dislocation dynamics of face cubic centred alloys. The exact nature of the temperature dependence shown by hardness has been proposed to adopt the form of an exponential Arrhenius equation. Another model suggested in the available literature is also discussed within this context. Additionally, the role of alloying elements has been correlated to the softening behaviour. Molybdenum or boron were found to slow down the softening behaviour, while carbide-forming elements such as vanadium and tungsten were found to be beneficial for room temperature hardness.

  3. Active versus Passive Sample Attrition: The Health and Retirement Study

    OpenAIRE

    Honggao Cao; Daniel H. Hill

    2005-01-01

    This paper investigates sample attrition in the Health and Retirement Study (HRS). We compare attrition behavior in two of the HRS cohorts: original HRS cohort and AHEAD cohort. We distinguish attrition due to death (passive attrition) from attrition due to other causes (active attrition), examining potential effects of different attrition modes on the representativeness of the remaining samples. This distinction is justified based on a specification test on a multinomial logistic regression ...

  4. Navy Recruit Attrition Prediction Modeling

    Science.gov (United States)

    2014-09-01

    or had a Marriage Annulment ) had a lower probability of success. Recruits who were married at the time of accession had a higher probability of...marriage annulled ; (2) were divorced; (3) were legally separated; or (4) were widowed. The number of recruits who fall into the “Other” category is...legally separated, widowed or had their marriage annulled . Within the training data, those considered to be “Other” had the highest attrition rate of

  5. Tantalum modified ferritic iron base alloys

    Science.gov (United States)

    Oldrieve, R. E.; Blankenship, C. P. (Inventor)

    1977-01-01

    Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

  6. Theoretical Analyses of Superconductivity in Iron Based ...

    African Journals Online (AJOL)

    fire7-

    2Department of Physics, College of Science, Bahir Dar University, Bahir Dar, Ethiopia. 3Department of Physics, Addis Ababa University, Addis Ababa, ... Superconductivity is a remarkable macroscopic quantum phenomenon, which was discovered by. Onnes (1911) while investigating the electrical resistivity of mercury at ...

  7. Development of an attrition risk prediction tool.

    OpenAIRE

    Norrie, Peter; Fowler, John

    2009-01-01

    Aim: To review lecturers’ and students’ perceptions of the factors that may lead to attrition from pre-registration nursing and midwifery programmes and to identify ways to reduce the impact of such factors on the student’s experience. Background: Comparable attrition rates for nursing and midwifery students across various universities are difficult to monitor accurately; however, estimates that there is approximately a 25% national attrition rate are not uncommon. The fi...

  8. Low pre-diagnosis attrition but high pre-treatment attrition among patients with MDR-TB: An operational research from Chennai, India.

    Science.gov (United States)

    Shewade, Hemant Deepak; Nair, Dina; Klinton, Joel S; Parmar, Malik; Lavanya, J; Murali, Lakshmi; Gupta, Vivek; Tripathy, Jaya Prasad; Swaminathan, Soumya; Kumar, Ajay M V

    2017-12-01

    Worldwide, there's concern over high pre-diagnosis and pre-treatment attritions or delays in Multidrug resistant tuberculosis (MDR-TB) diagnosis and treatment pathway (DTP). We conducted this operational research among patients with presumptive MDR-TB in north and central Chennai, India to determine attrition and turnaround times (TAT) at various steps of DTP and factors associated with attrition. Study was conducted in Revised National Tuberculosis Control Programme setting. It was a retrospective cohort study involving record review of all patients with presumptive MDR-TB (eligible for DST) in 2014. Of 628 eligible for DST, 557 (88%) underwent DST and 74 (13%) patients were diagnosed as having MDR-TB. Pre-diagnosis and pre-treatment attrition was 11% (71/628) and 38% (28/74) respectively. TAT [median (IQR)] to test from eligibility for DST and initiate DR-TB treatment from diagnosis were 14 (9,27) and 18 (13,36) days respectively. Patients with smear negative TB and detected in first quarter of 2014 were less likely to undergo DST. Patients in first quarter of 2014 had significantly lower risk of pre-treatment attrition. There was high uptake of DST. However, urgent attention is required to reduce pre-treatment attrition, improve TAT to test from eligibility for DST and improve DST among patients with smear-negative TB. Copyright © 2017 Ministry of Health, Saudi Arabia. Published by Elsevier Ltd. All rights reserved.

  9. 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…

  10. Maturational Constraints and First Language Attrition

    Science.gov (United States)

    Bylund, Emanuel

    2009-01-01

    The aim of the article is to examine how first language attrition research on maturational constraints interprets and links its findings to current views on maturation in the field of second language acquisition. It is argued that attrition research exhibits certain inconsistencies in the interpretation of the structural characteristics of the…

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

    Indian Academy of Sciences (India)

    Microbial synthesis of iron-based nanomaterials—A review. ABHILASH. ∗. , K REVATI and B D PANDEY. National Metallurgical Laboratory (CSIR-NML), Jamshedpur 831 007, India. MS received 26 June 2010; revised 5 October 2010. Abstract. Nanoparticles are the materials having dimensions of the order of 100 nm or ...

  12. 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

  13. The 3-Dimensional Fermi Liquid Description for the Iron-Based Superconductors

    Science.gov (United States)

    Misawa, Setsuo

    2018-01-01

    The quasiparticles in the normal state of iron-based superconductors have been shown to behave universally as a 3-dimensional Fermi liquid. Because of interactions and the presence of sharp Fermi surfaces, the quasiparticle energy contains, as a function of the momentum \\varvec{p}, a term of the form ( p - p_0)^3 ln {( |p-p_0|/p_0)} , where p = | \\varvec{p} | and p_0 is the Fermi momentum. The electronic specific heat coefficient, magnetic susceptibility (Knight shift), electrical resistivity, Hall coefficient and thermoelectric power divided by temperature follow, as functions of temperature T, the logarithmic formula a-b T^2 ln {(T/T^*)}, a, b and T^* being constant; these formulae have been shown to explain the observed data for all iron-based superconductors. It is shown that the concept of non-Fermi liquids or anomalous metals which appears in the literature is not needed for descriptions of the present systems. When the superconducting transition temperature TC and the b / a value for the resistivity are plotted as functions of the doping content x, there appear various characteristic diagrams in which regions of positive correlation and those of negative correlation between TC and b / a are interconnected; from these diagrams, we may make speculations about the types of superconductivity and the crossover between them.

  14. The Canadian Forces Recruitment/Attrition Model

    National Research Council Canada - National Science Library

    Wait, Tracey

    1998-01-01

    ...), as part of its mandate to provide analysis of potential impacts of trends and change on defense and defense related issues, has designed a prototype model of recruitment and attrition of the Canadian Forces (C F...

  15. Elimination of Iron Based Particles in Al-Si Alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2015-03-01

    Full Text Available This paper deals with influence on segregation of iron based phases on the secondary alloy AlSi7Mg0.3 microstructure by chrome. Iron is the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In generally, iron is associated with the formation of Fe-rich phases. It is impossible to remove iron from melt by standard operations, but it is possible to eliminate its negative influence by addition some other elements that affect the segregation of intermetallics in less harmful type. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with higher iron content and influence of chrome as iron corrector of iron based phases. By experimental work were used three different amounts of AlCr20 master alloy a three different temperature of chill mold. Our experimental work confirmed that chrome can be used as an iron corrector in Al-Si alloy, due to the change of intermetallic phases and shortening their length.

  16. Rate and pattern of interproximal dental attrition.

    Science.gov (United States)

    Sarig, Rachel; Hershkovitz, Israel; Shpack, Nir; May, Hila; Vardimon, Alexander D

    2015-08-01

    Although occlusal and interproximal attrition occur because of diverse etiology and present dissimilar features, both progress with age. The objectives of this study were to reveal the rate and pattern of development of interproximal attrition facets (PAF) with age and to compare those with occlusal attrition (OA) changes. Five-hundred and ninety-four teeth were collected from 198 skulls (of adults, 20-71 yr of age). Three mandibular teeth [first premolar (P1), second premolar (P2), and first molar (M1)] were examined for PAF size and OA rate. Interproximal attrition and OA followed similar patterns of development until subjects reached 40-45 yr of age, after which they took different paths: PAF did not increase in size and were not as large as in younger groups, regardless of facet location, whereas OA continued to progress. The PAF changes with age differed between premolars and molars, unlike OA, which presented a similar rate for all teeth studied. Although OA scores presented significantly moderate correlations with age, PAF area size demonstrated low correlations with age. Low, but significant, correlations were found between the rate of OA and that of PAF. However, PAF and OA exhibited different patterns of development with age. Premolars and molars presented dissimilar development of PAF, which is probably caused by a unique attrition pattern in the molar teeth, different morphology, and force vectors. © 2015 Eur J Oral Sci.

  17. 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,

  18. Obstacles to success – Doctoral student attrition in South Africa ...

    African Journals Online (AJOL)

    Obstacles to success – Doctoral student attrition in South Africa. C Herman. Abstract. The article explores doctoral attrition in South Africa, investigating and comparing the attributions of attrition of doctoral students and PhD programme leaders. The article is based on secondary data analysis of two large studies on doctoral ...

  19. Reducing Nursing Student Attrition: The Search for Effective Strategies

    Science.gov (United States)

    Kubec, Cathy

    2017-01-01

    This review of the literature summarizes recent exploration of nursing student attrition. Attrition places financial burdens on students who leave a program, results in lost revenue for the college, and compounds the existing nursing shortage. Some research investigated the student selection process, which seeks to decrease attrition by admitting…

  20. A Qualitative Study on the Effects of Teacher Attrition

    Science.gov (United States)

    Wushishi, Aminu Aliyu; Fooi, Foo Say; Basri, Ramli; Baki, Roslen

    2014-01-01

    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.…

  1. Benchmarking Attrition: What Can We Learn From Other Industries?

    Science.gov (United States)

    Delta Cost Project at American Institutes for Research, 2012

    2012-01-01

    This brief summarizes Internet-based research into other industries that may offer useful analogies for thinking about student attrition in higher education, in particular for setting realistic benchmarks for reductions in attrition. Reducing attrition to zero or close to zero is not a realistic possibility in higher education. Students are…

  2. 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…

  3. Factors Associated with Veterinary Clinical Faculty Attrition.

    Science.gov (United States)

    Furr, Martin

    2017-06-28

    Faculty attrition and recruitment for veterinary clinical faculty positions have been reported as significant problems in veterinary medical education. To investigate the factors that may be important in veterinary clinical faculty retention, the perceptions and views of veterinary clinical academic faculty were determined using a web-distributed electronic survey. Responses were dichotomized by whether the respondent had or had not left an academic position and were analyzed for their association with faculty attrition. A total of 1,226 responses were recorded and results demonstrated that factors other than compensation were associated with veterinary clinical faculty attrition, including departmental culture, work-life balance, and recognition and support of clinical medicine by the administration. Forty-four percent of respondents who had held a faculty appointment reported leaving academia either voluntarily or for non-voluntary reasons such as failure to achieve tenure, retirement, or having their position closed. Attention to correcting deficiencies in workplace culture and professional rewards could be a beneficial means by which to decrease the faculty attrition rates currently observed in clinical academic veterinary medicine.

  4. 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.

  5. Nematic fluctuations and resonance in iron-based superconductors

    Science.gov (United States)

    Gallais, Yann

    The spontaneous appearance of nematicity, a state of matter that breaks rotation but not translation symmetry, is ubiquitous in many iron based superconductors (Fe SC), and has relevance for the cuprates as well. Here I will review recent electronic Raman scattering experiments which report the presence of critical nematic fluctuations in the charge channel in the tetragonal phase of several Fe SC systems. In electron doped Co-BaFe2As2 (Co-Ba122), these fluctuations extend over most of the superconducting dome. Their associated nematic susceptibility shows Curie-Weiss behavior, and its doping dependence suggests the presence of a nematic quantum critical point near optimal TC Similar nematic fluctuations are also observed in FeSe despite the absence of magnetic order, raising the question of the link between nematicity and magnetism in Fe SC. In FeSe I will further contrast the evolution of nematic fluctuations under isoelectronic S substitution and hydrostatic pressures up to 8 GPa, with only the former showing evidence for a nematic quantum critical point. In the superconducting state of Co-Ba122, I will show that a resonance emerges in the Raman spectra near the nematic quantum critical point. This nematic resonance is a clear fingerprint of the coupling between nematic fluctuations and Bogoliubov quasiparticles, and can be thought as the nematic counterpart of the spin resonance observed in neutron scattering experiments. Support from Agence Nationale de la Recherche via ANR Grant ''Pnictides'' is acknowledged.

  6. Student and Instructor Perceptions of Attrition in Community College Online Beginning Spanish Classes

    Science.gov (United States)

    McDonnell, Thomas

    2012-01-01

    This qualitative multiple comparative case study investigated attrition in online Spanish language courses, from both instructor and student perspectives. Attrition rates in online courses have been found to be up to 50% higher than attrition rates in face to face courses, when studying the phenomenon of attrition in higher education. Attrition is…

  7. The Erosion of the Enlisted Force: A Study of Attrition

    Science.gov (United States)

    1999-04-01

    with a high school diploma (32.5 percent). Homeschooling data indicates an attrition rate of 38.5 percent, or 7 percent less than those with a GED...high risk factor for attrition. A 1984 RAND study illustrated the effect of employment on Air Force attrition (Figure 8, Appendix A).16 A follow up...allow the recruiter to manage time most effectively and time spent “cold calling” and canvassing for interest. Recruiters have little incentive to

  8. Comparative Review on Thin Film Growth of Iron-Based Superconductors

    Directory of Open Access Journals (Sweden)

    Yoshinori Imai

    2017-07-01

    Full Text Available Since the discovery of the novel iron-based superconductors, both theoretical and experimental studies have been performed intensively. Because iron-based superconductors have a smaller anisotropy than high-Tc cuprates and a high superconducting transition temperature, there have been a lot of researchers working on the film fabrication of iron-based superconductors and their application. Accordingly, many novel features have been reported in the films of iron-based superconductors, for example, the fabrication of the epitaxial film with a higher Tc than bulk samples, the extraction of the metastable phase which cannot be obtained by the conventional solid state reaction, and so on. In this paper, we review the progress of research on thin film fabrications of iron-based superconductors, especially the four categories: LnFeAs(O,F (Ln = Lanthanide, AEFe2As2 (AE = Alkaline-earth metal, FeCh (Ch = Chalcogen, and FeSe monolayer. Furthermore, we focus on two important topics in thin films of iron-based superconductors; one is the substrate material for thin film growth on the iron-based superconductors, and the other is the whole phase diagram in FeSe1-xTex which can be obtained only by using film-fabrication technique.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hosono, Hideo, E-mail: hosono@msl.titech.ac.jp [Materials and Structures Laboratory & Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Kuroki, Kazuhiko [Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2015-07-15

    Highlight: • An up-to-date review by the discoverer and a theoretical pioneer of iron-based superconductor. - Abstract: Since the discovery of high T{sub c} 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. Principals' Perceptions of Teacher Attrition in Indiana Catholic Schools, Checking for Agreement with Ingersoll's Theoretical Framework on Teacher Attrition in Private Schools

    Science.gov (United States)

    Brettnacher, Joseph A.

    2012-01-01

    Problem. Some Catholic schools report high teacher attrition rates. Understanding reasons for teacher attrition and responding to those issues is one of the many responsibilities of principals. However, it is unclear what Catholic principals understand about teacher attrition. Ingersoll's extensive research on teacher attrition has provided a…

  11. Cleansing of sandy soils using attrition; Depollution de sols sablonneux par attrition

    Energy Technology Data Exchange (ETDEWEB)

    Schriker, H. Tiefel [A.K.W. Apparate und Verfahren, Hirschau (Germany); Neesse, T. [Universite d' Erlangen-Nuremberg (Germany)

    2001-03-01

    The attrition process used in soil cleansing has been improved thanks to a combination with classification, dosimetry and integrated measurement processes in order to ensure a constant concentration of solids. Tests have been successfully performed on quartz sands contaminated with mineral oil. Abstract only. (J.S.)

  12. The Rapier or the Club: The Relationship between Attrition and Maneuver Warfare

    National Research Council Canada - National Science Library

    Springman, Jeffrey A

    2006-01-01

    ...? This project compares the relationship between attrition and maneuver warfare. The study considers whether there are times when wars of attrition should be fought, and whether there are conditions that force wars of attrition...

  13. Descriptive Models of Monthly Officer Attrition

    Science.gov (United States)

    1994-02-01

    his zone, MOS and grade. Let us first take a brief look at the consistency issue, i.e. the comparison of annual rates produced earlier, call them Q...another time. 18 FIGURE 3 Cumulative Attrition Rates 0.16 . 0.14 - I --- modelo " 0.12 ...---- max. Ŕ.[ --- av1..... 0.1 - - ~ - --- -- 0.08- 0.06. 0...Rockville, MC 20854 8. Management Applications, Inc ...................................................................... 1 Dr. R. Butterworth 1530 N. Key Blvd., Suite 531 Arlington, VA 22209 34

  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. Crystal growth iron based pnictide compounds; Kristallzuechtung eisenbasierter Pniktidverbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Nacke, Claudia

    2012-11-15

    The present work is concerned with selected crystal growth method for producing iron-based superconductors. The first part of this work introduces significant results of the crystal growth of BaFe{sub 2}As{sub 2} and the cobalt-substituted compound Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} with x{sub Nom} = 0.025, 0.05, 0.07, 0.10 and 0.20. For this purpose a test procedure for the vertical Bridgman method was developed. The second part of this work contains substantial results for growing a crystal of LiFeAs and the nickel-substituted compound Li{sub 1-δ}Fe{sub 1-x}Ni{sub x}As with x{sub Nom} = 0.015, 0.025, 0.05, 0.06, 0.075 and 0.10. For this purpose a test procedure for the melt flow process has been developed successfully. [German] Die vorliegende Arbeit befasst sich mit ausgewaehlten Kristallzuechtungsverfahren zur Herstellung eisenbasierter Supraleiter. Der erste Teil dieser Arbeit fuehrt wesentliche Ergebnisse der Kristallzuechtung von BaFe{sub 2}As{sub 2} sowie der Cobalt-substituierten Verbindung Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} mit x{sub Nom} =0.025, 0.05, 0.07, 0.10 und 0.20 auf. Hierzu wurde eine Versuchsdurchfuehrung fuer das vertikale Bridgman-Verfahren konzipiert, mit welcher erfolgreich Kristalle dieser Zusammensetzungen gezuechtet wurden. Der zweite Teil dieser Arbeit enthaelt wesentliche Ergebnisse zur Kristallzuechtung von LiFeAs sowie der Nickel-substituierten Verbindung Li{sub 1-δ}Fe{sub 1-x}Ni{sub x}As mit x{sub Nom} = 0.015, 0.025, 0.05, 0.06, 0.075 und 0.10. Hierfuer wurde erfolgreich eine Versuchsdurchfuehrung fuer das Schmelzfluss-Verfahren entwickelt.

  16. 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

  17. Strong anisotropy effect in an iron-based superconductor CaFe0.882Co0.118AsF

    Science.gov (United States)

    Ma, Yonghui; Ji, Qiucheng; Hu, Kangkang; Gao, Bo; Li, Wei; Mu, Gang; Xie, Xiaoming

    2017-07-01

    The anisotropy of iron-based superconductors is much smaller than that of the cuprates and that predicted by theoretical calculations. A credible understanding for this experimental fact is still lacking up to now. Here we experimentally study the magnetic-field-angle dependence of electronic resistivity in the superconducting phase of an iron-based superconductor CaFe{}0.882Co{}0.118AsF, and find the strongest anisotropy effect of the upper critical field among the iron-based superconductors based on the framework of Ginzburg-Landau theory. The evidence of the energy band structure and charge density distribution from electronic structure calculations demonstrates that the observed strong anisotropic effect mainly comes from the strong ionic bonding in between the ions of Ca2+ and F-, which weakens the interlayer coupling between the layers of FeAs and CaF. This finding provides a significant insight into the nature of the experimentally-observed strong anisotropic effect of electronic resistivity, and also paves the way for designing exotic two-dimensional artificial unconventional superconductors in the future.

  18. The renaissance of iron-based Fischer-Tropsch synthesis: on the multifaceted catalyst deactivation behaviour.

    Science.gov (United States)

    de Smit, Emiel; Weckhuysen, Bert M

    2008-12-01

    Iron-based Fischer-Tropsch catalysts, which are applied in the conversion of CO and H2 into longer hydrocarbon chains, are historically amongst the most intensively studied systems in heterogeneous catalysis. Despite this, fundamental understanding of the complex and dynamic chemistry of the iron-carbon-oxygen system and its implications for the rapid deactivation of the iron-based catalysts is still a developing field. Fischer-Tropsch catalysis is characterized by its multidisciplinary nature and therefore deals with a wide variety of fundamental chemical and physical problems. This critical review will summarize the current state of knowledge of the underlying mechanisms for the activation and eventual deactivation of iron-based Fischer-Tropsch catalysts and suggest systematic approaches for relating chemical identity to performance in next generation iron-based catalyst systems (210 references).

  19. Investigating Attrition Trends in Order to Improve Student Retention

    Science.gov (United States)

    Grebennikov, Leonid; Shah, Mahsood

    2012-01-01

    Purpose: This paper aims to focus on the experience of monitoring of first year student attrition in a large metropolitan multi-campus university during 2004-2010. The paper seeks to discuss the trends in student attrition which have been found and identify key issues which have been and need to be addressed by the university in order to increase…

  20. Questioning the Research on Early Career Teacher Attrition and Retention

    Science.gov (United States)

    Schaefer, Lee; Long, Julie S.; Clandinin, D. Jean

    2012-01-01

    In this paper, we consider scholarly work on early career teacher attrition, and retention, from 1999 to 2010. Much of the literature has framed attrition as either a problem associated with individual factors (e.g., burnout), or a problem associated with contextual factors (e.g., support and salary). Some recent conceptualizations consider early…

  1. Texas Public School Attrition Study, 2011-12. IDRA Report

    Science.gov (United States)

    Johnson, Roy L.; Montes, Felix

    2012-01-01

    This document contains 3 statistical reports. The first report, "Attrition Rate Decline Seems Promising--Though High Schools are Still Losing One in Four Students" (by Roy L. Johnson), presents results of long-term trend assessments of attrition data in Texas public high schools. The second report, "Slow Declining Pace Keeps Zero…

  2. The Importance of Sample Attrition in Life Cycle Labor Supply

    NARCIS (Netherlands)

    Ziliak, J.P.; Kniesner, T.J.

    1996-01-01

    We examine the importance of possible non-random attrition to an econometric model of life cycle labor supply including joint nonlinear taxation of wage and interest incomes and latent heterogeneity.We use a Wald test comparing attriters to nonattriters and variable addition testing based on formal

  3. 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…

  4. Obstacles to Success--Doctoral Student Attrition in South Africa

    Science.gov (United States)

    Herman, Chaya

    2011-01-01

    The article explores doctoral attrition in South Africa, investigating and comparing the attributions of attrition of doctoral students and PhD programme leaders. The article is based on secondary data analysis of two large studies on doctoral education in South Africa. The main point of the article is that the different understandings of the…

  5. 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,…

  6. Student Attrition in Higher Education: Development of an Instrument to Assess Attrition Factors in Distance Learning Only Educational Environments

    Science.gov (United States)

    York, Jessica Ann

    2014-01-01

    The purpose of this mixed methods study was to discover the factors and experiences that impact attrition in DLOEEs and to develop an instrument to assess them. Student attrition, those who do not persist voluntarily or involuntarily, occurs in all facets of higher education. In the last five years, the most growth in enrollments has occurred in…

  7. Attrition of PMU Personnel Compared to Attrition from the U.S. Navy Male Enlisted Population.

    Science.gov (United States)

    1980-09-01

    of recruits to PMU who did not require that form of action causes demotivation, pipeline delays and possibly increased recruit attrition.) c. When a...DURING 2. HOMESICK /FAMILY DRILLS? PROBLEMS? CLEAN IN PERSONAL 3. TROUBLE MAKER? HABITS? 4. FOLLOWER? GOOD MIXER? 5. WISEGUY? OBEYS WITHOUT 6. IMMATURE...SUPERVISION? 7. BELLIGERENT? MAKES GOOD USE OF 8. DEPRESSED /SAD? SPARE TIME? MENTALLY CAPABLE? PHYSICALLY CAPABLE? PROGRESS GOOD? IMPROVING? RECOMMEND

  8. Mechanical properties of the iron-based superconductor SmFeAsO1-xFx

    Science.gov (United States)

    Malaeb, W.; Kazah, I.; Awad, R.; Fujioka, M.

    2017-07-01

    We have investigated the mechanical properties of the iron-based superconductor (FeSC) SmFeAsO1-xFx (Sm1111) with a wide doping range 0.09 ≤ x ≤ 0.3 by performing the Vickers microhardness test. The estimated Vickers microhardness number (Hv ) was analysed using Meyer’s law, Hays-Kendall approach, elastic/plastic deformation (EPD) model and proportional specimen resistance (PSR) model, where the PSR model showed the best match with our experimental data. Hv values showed an increase as x increases, indicating that fluorine doping results in an improvement in the mechanical properties of the Sm1111 compound and makes it more convenient for applications.

  9. Performance test of single step continuous dry attrition mill

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young Woo; Joung, C. Y.; Lee, Y. W.; Na, S. H.; Kim, H. S.; Kim, S

    2001-02-01

    This report describes the improvement of the two-step attrition mill to solve problems associated with its complexity and those of batch type attrition mill as well as the results of the performance test in view of the comparison. In the performance test of the improved single step continuous attrition mill, powder milling and discharge time per pass was systematically measured, and UO{sup 2}-5wt%CeO{sub 2} powder mixture, UO{sup 2}-5wt%CeO{sub 2} powder mixture with poreformer, M{sub 3}O{sub 8} powder and/or MO2 scrap were milled to compare the performance of the milling operations between the 2-step attrition mill and improved single-step attrition mill. The results of the performance test shows, in addition to its improved milling operation, an improved function in less contamination with impurities, simpler handling with easier operation and maintenance and hence, less contamination of operational location, especially when used for the operation in a confinement system, for the improved single step attrition mill compared with a batch type or continuous 2-step attrition mill.

  10. 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...

  11. Spin dynamics in 122-type iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jitae

    2012-07-16

    In this thesis, we present the experimental data on four different iron-based SC materials. It is mainly about the magnetic-dynamics study in the FeSC that is assumed to be among the most crucial ingredients for superconductivity in this system. Thus, the main goal of this thesis is to figure out the exact relationship between spin dynamics and superconductivity, and then further to realize what is the contribution of magnetic fluctuations for superconductivity by providing experimental data for modeling a microscopic mechanism of electron pairing in the FeSC system. In Chap. 2, we first discuss basic characteristics of FeSC, such as crystal structure and electron band-structure by briefly reviewing the relevant literature. Then, an introduction about magnetic and SC phases will follow based on the generic phase diagram. Details about current understanding of magnetic ground state in the parent compounds will be discussed in terms of spin-wave excitations which would be important when we are considering the spin dynamics in doped materials. To study magnetic dynamics in FeSC, we employed the inelastic-neutron-scattering (INS) method which can uniquely probe the underlying spin dynamics in the four dimensional energy and momentum space in a wide range. By taking advantage of the well developed theory for the magnetic neutron-scattering process, one can quantify the imaginary part of spin susceptibility that is an essential physical quantity the description of elementary magnetic excitations and can be compared with theoretical calculations directly. Moreover, the technique's energy-resolving scale spans over the most relevant energy range of magnetic fluctuations (from 0 to 100 meV). For these reasons, neutron scattering is a very powerful technique for magnetism study, and we introduce how neutron-scattering experiment works theoretically and practically in Chap. 3. For a slightly underdoped Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} compound, we report the phase

  12. First Language Attrition: An Investigation of Taiwanese Tones and Tone Sandhi

    Science.gov (United States)

    Chang, Yufen

    2012-01-01

    First language (L1) attrition research focuses on syntactic and morphological deterioration in environments where L1 "attriters" rarely have contact with their L1, such as immigrants. There is no study that investigates L1 attrition in tones and in contexts where L1 can still be often heard. This study examines this attrition type in…

  13. The Role of Personality Type on Minority Attrition at the US Naval Academy

    Science.gov (United States)

    2002-06-01

    MBTI ISTP ISTJ ISFP ISFJ INTP INTJ INFP INFJ ESTP ESTJ ESFP ESFJ ENTP ENTJ ENFP ENFJ C ou nt 400 300 200 100 0 33 Table 12: Minority Attrition...16 personality types, were predictive of attrition/persistence (see Table 13). Two personality types ENFP and INFP, were significantly more likely to...attrite. Specifically, ENFP had an attrition rate of 31.7%, in comparison with all those of other types (18.1%). Similarly, INFP had an attrition

  14. Attitudes towards attrition among UK trainees in obstetrics and gynaecology.

    Science.gov (United States)

    Gafson, Irene; Currie, Jane; O'Dwyer, Sabrina; Woolf, Katherine; Griffin, Ann

    2017-06-02

    Physician dissatisfaction in the workplace has consequences for patient safety. Currently in the UK, 1 in 5 doctors who enter specialist training in obstetrics and gynaecology leave the programme before completion. Trainee attrition has implications for workforce planning, organization of health-care services and patient care. The authors conducted a survey of current trainees' and former trainees' views concerning attrition and 'peri-attrition' - a term coined to describe the trainee who has seriously considered leaving the specialty. The authors identified six key themes which describe trainees' feelings about attrition in obstetrics and gynaecology: morale and undermining; training processes and paperwork; support and supervision; work-life balance and realities of life; NHS environment; and job satisfaction. This article discusses themes of an under-resourced health service, bullying, lack of work-life balance and poor personal support.

  15. Factors Affecting the Attrition Strength of Alumina Products

    Science.gov (United States)

    Sang, J. V.

    The attrition strength of alumina is a matter of increasing interest. The aim of the present paper is to show how the strength of alumina is related to the precipitation parameters and to the morphology of the precursor hydrate particles.

  16. Job turnover and regional attrition among physiotherapists in northern Ontario.

    Science.gov (United States)

    Noh, S; Beggs, C E

    1993-01-01

    Results of an initial study indicated that the most significant factor affecting retention for Physiotherapists in Northern Ontario was perceived opportunity for career development. A follow-up study was completed two years later to determine: 1) actual job turnover and regional attrition among physiotherapists in Northern Ontario; and 2) the predictive validity of variables identified in the first study regarding job turnover and regional attrition. Job turnover occurred in 29.5% of those sampled and the regional attrition rate was 12%. Discriminant function analysis revealed factors affecting job turnover and regional attrition including professional experience, practice location, opportunity for career development and size of community of residence. Based on previous intention, indicated by participants, follow-up revealed that the initial study correctly predicted 77.5% of those who changed their jobs and 74.1% of those who left Northern Ontario. Identified factors provide direction for the development of strategies for recruitment and retention of physiotherapists.

  17. An Epidemiological Approach to Addressing Student Attrition in Nursing Programs.

    Science.gov (United States)

    Wells, Marcia I.

    2003-01-01

    In place of Tinto's model of student retention, an epidemiological approach is recommended for nursing education. It includes primary, secondary, and tertiary interventions for preventing student attrition. (Contains 37 references.) (SK)

  18. Military Personnel Attrition and Retention: Research in Progress

    Science.gov (United States)

    1981-10-01

    NATIONAL ANALYSES OF ATTRITION 13 H. Wallace Sinaiko and Kenneth C. Scheflen AIR FORCE ATTRITION RESEARCH: ANALISIS OF PRE- AND POST- 15 ENLISTMENT FACTORS...expected satisfaction, lower attraction to the military role, lower percep- tions of work group attraction and expected leader structure ,.lower internal...extensive costs-benefit analyses. It is hrped that’ this research outline will aid in the structuring of retention research efforts. Wtis important to

  19. Attrition resistant, zinc titanate-containing, reduced sulfur sorbents

    Science.gov (United States)

    Vierheilig, Albert A.; Gupta, Raghubir P.; Turk, Brian S.

    2004-11-02

    The disclosure is directed to sorbent compositions for removing reduced sulfur species (e.g., H.sub.2 S, COS and CS.sub.2) a feed stream. The sorbent is formed from a multi-phase composition including a zinc titanate phase and a zinc oxide-aluminate phase. The sorbent composition is substantially free of unreacted alumina.

  20. Characteristics and Corrosion Behavior of Pure Titanium Subjected to Surface Mechanical Attrition

    Science.gov (United States)

    Fu, Tianlin; Wang, Xiao; Liu, Jianxiong; Li, Li; Yu, Xiaohua; Zhan, Zhaolin

    2017-10-01

    A stable passive film exhibiting good corrosion resistance in a 3.5 wt.% NaCl solution was formed on the surface of pure titanium (Ti) subjected to a surface mechanical attrition treatment (SMAT). The corrosion potential (-0.21 V) of the film was significantly higher than that (-0.92 V) of the untreated sample. Moreover, the corrosion current density was an order of magnitude lower than that of the untreated sample. SMAT resulted in a decrease in the vacancy condensation in the TiO2 film, thereby inhibiting the invasion and diffusion of Cl- in the film.

  1. Posttreatment attrition and its predictors, attrition bias, and treatment efficacy of the anxiety online programs.

    Science.gov (United States)

    Al-Asadi, Ali M; Klein, Britt; Meyer, Denny

    2014-10-14

    Although relatively new, the field of e-mental health is becoming more popular with more attention given to researching its various aspects. However, there are many areas that still need further research, especially identifying attrition predictors at various phases of assessment and treatment delivery. The present study identified the predictors of posttreatment assessment completers based on 24 pre- and posttreatment demographic and personal variables and 1 treatment variable, their impact on attrition bias, and the efficacy of the 5 fully automated self-help anxiety treatment programs for generalized anxiety disorder (GAD), social anxiety disorder (SAD), panic disorder with or without agoraphobia (PD/A), obsessive-compulsive disorder (OCD), and posttraumatic stress disorder (PTSD). A complex algorithm was used to diagnose participants' mental disorders based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision; DSM-IV-TR). Those who received a primary or secondary diagnosis of 1 of 5 anxiety disorders were offered an online 12-week disorder-specific treatment program. A total of 3199 individuals did not formally drop out of the 12-week treatment cycle, whereas 142 individuals formally dropped out. However, only 347 participants who completed their treatment cycle also completed the posttreatment assessment measures. Based on these measures, predictors of attrition were identified and attrition bias was examined. The efficacy of the 5 treatment programs was assessed based on anxiety-specific severity scores and 5 additional treatment outcome measures. On average, completers of posttreatment assessment measures were more likely to be seeking self-help online programs; have heard about the program from traditional media or from family and friends; were receiving mental health assistance; were more likely to learn best by reading, hearing and doing; had a lower pretreatment Kessler-6 total score; and were older

  2. High efficiency iron electrode and additives for use in rechargeable iron-based batteries

    Science.gov (United States)

    Narayan, Sri R.; Prakash, G. K. Surya; Aniszfeld, Robert; Manohar, Aswin; Malkhandi, Souradip; Yang, Bo

    2017-02-21

    An iron electrode and a method of manufacturing an iron electrode for use in an iron-based rechargeable battery are disclosed. In one embodiment, the iron electrode includes carbonyl iron powder and one of a metal sulfide additive or metal oxide additive selected from the group of metals consisting of bismuth, lead, mercury, indium, gallium, and tin for suppressing hydrogen evolution at the iron electrode during charging of the iron-based rechargeable battery. An iron-air rechargeable battery including an iron electrode comprising carbonyl iron is also disclosed, as is an iron-air battery wherein at least one of the iron electrode and the electrolyte includes an organosulfur additive.

  3. Attrition and erosion: restorative planning and performance.

    Science.gov (United States)

    Burrow, Michael F

    2012-04-01

    The number of patients presenting with severe attrition and associated erosion is increasing in frequency. Treatment of this patient group is very challenging as it is simply not just a case of replacing lost tooth tissue, but also trying to identify and then eliminate the aetiological factors responsible for the loss of tooth structure. In most cases restorative treatment involves extensive rehabilitation of the dentition to restore the aesthetics and function and also to prevent further tooth loss. Such treatment often involves a multidisciplinary approach to eliminate and/or reduce causative factors prior to definitive restoration of teeth. Treatment needs to focus on quick intervention when the problem has been identified and diagnosed. Restorative treatment involves careful if not complex planning culminating in the establishment of a well defined and ongoing maintenance plan. Long-term success of treatment is centred on the maintenance phase. Current restorative options include the use of extensive resin composite build-ups. This is often the best initial starting point as it allows for adjustments, as well as being a reversible and more conservative procedure. The use of indirect restorations is likely to provide a longer lasting outcome after initial stabilization, whether it is metal- or ceramic-based or a combination.

  4. The management of over closured anterior teeth due to attrition

    Directory of Open Access Journals (Sweden)

    Eha Djulaeha

    2009-12-01

    Full Text Available Background: Tooth is the hardest tissue in human body, that can be injured because of attrition process. For old people, denture attrition process is caused by psysiological process relating with the mastication function which also supported by some bad habits such an bruxism, premature contact, and consuming habit of abrasive food. Attrition or abrasion can also be happened with patien’t dentition who does not have teeth subtutition for long time due the lost of their maxillary as well as mandibulary. The pasient will loose their vertical dimension of occlusion, injure, and the lower jaw becomes over closed which is called over closure. Purpose: This article reported the management of over closured anterior teeth due to attrition. Case: a seventy six year old woman patient came to Prosthodontic Clinic in Faculty of Dentistry, Airlangga University, to rehabilitate her upper and lower severe attrited anterior teeth and her posterior teeth. The patient has experienced of wearing acrylic removable mandibular partial denture ten years ago. Unfortunaly, the denture was uncomfortable, and she did not wear it anymore since five years ago. Case management: The severe attrition of anterior teeth with the lost of occlusal vertical dimension can be treated by improving the occlusal vertical dimension gradually. The treatment is then followed by the increasing of the height of the anterior teeth by lengthening the crown teeth of upper jaw with 12 units of span bridge and the acrylic removable partial denture of lower jaw. Conclusion: The severe attrition of anterior teeth with the lost of occlusal vertical dimension can be treated by improving the occlusal vertical dimension gradually, using long span bridge and acrylic removable partial denture.

  5. Attrition, occlusion, (dys)function, and intervention: a systematic review.

    Science.gov (United States)

    van 't Spijker, Arie; Kreulen, Cees M; Creugers, Nico H J

    2007-06-01

    Attrition and occlusal factors and masticatory function or dysfunction are thought to be related. This study aims to systematically review the literature on this topic with the emphasis to find evidence for occlusion-based treatment protocols for attrition. Literature was searched using PubMed (1980 to 2/2006) and the Cochrane Library of Clinical Trials with the keywords 'tooth' and 'wear'. Five steps were followed. Exclusion was based on the following: (1) reviews, case-reports, studies on non-human tooth material, and studies not published in English and (2) historical or forensic studies. Included were (3) in vivo studies. Next, studies on (4) occlusal factors, function or dysfunction [temporomandibular disorders (TMD), bruxism], or intervention, and (5) attrition were included. Two investigators independently assessed the abstracts; measure of agreement was calculated using Cohen's kappa; disagreement was resolved by discussion. Full-text articles were obtained and correlation between outcomes on occlusal factors, (dys)function, treatment, and attrition were retrieved. References in the papers included in the final analysis were cross-matched with the original list of references to add references that met the inclusion criteria. The search procedure revealed 1289 references on tooth wear. The numbers of included studies after each step were (1) 345 (kappa=0.8), (2) 287 (kappa=0.87), (3) 174 (kappa=0.99), (4) 81 (kappa=0.71), and (5) 27 (kappa=0.68). Hand searches through the reference lists revealed six additional papers to be included. Analysis of the 33 included papers failed to find sound evidence for recommending a certain occlusion-based treatment protocol above another in the management of attrition. Some studies reported correlations between attrition and anterior spatial relationships. No studies were found suggesting that absent posterior support necessarily leads to increased attrition, though one study found that fewer number of teeth resulted in

  6. Pressure-induced superconductivity in the iron-based ladder material BaFe2S3

    Science.gov (United States)

    Takahashi, Hiroki; Sugimoto, Akira; Nambu, Yusuke; Yamauchi, Touru; Hirata, Yasuyuki; Kawakami, Takateru; Avdeev, Maxim; Matsubayashi, Kazuyuki; Du, Fei; Kawashima, Chizuru; Soeda, Hideto; Nakano, Satoshi; Uwatoko, Yoshiya; Ueda, Yutaka; Sato, Taku J.; Ohgushi, Kenya

    2015-10-01

    All the iron-based superconductors identified so far share a square lattice composed of Fe atoms as a common feature, despite having different crystal structures. In copper-based materials, the superconducting phase emerges not only in square-lattice structures but also in ladder structures. Yet iron-based superconductors without a square-lattice motif have not been found, despite being actively sought out. Here, we report the discovery of pressure-induced superconductivity in the iron-based spin-ladder material BaFe2S3, a Mott insulator with striped-type magnetic ordering below ~120 K. On the application of pressure this compound exhibits a metal-insulator transition at about 11 GPa, followed by the appearance of superconductivity below Tc = 14 K, right after the onset of the metallic phase. Our findings indicate that iron-based ladder compounds represent promising material platforms, in particular for studying the fundamentals of iron-based superconductivity.

  7. Attrition of undergraduate nursing students at selected South African universities

    Directory of Open Access Journals (Sweden)

    Erna Roos

    2016-02-01

    Full Text Available Background: The nursing profession forms the backbone of many healthcare systems. It therefore needs a consistent supply of registered nurses to deliver continuous and safe quality healthcare, and to replace the nurses leaving or retiring from the profession. Attrition actively occurs among nursing students in South Africa and threatens the future supply of registered nurses. Aim: The aim of the study was to describe the attrition rate at selected South African universities and the factors influencing undergraduate nursing students to discontinue their nursing studies at these universities. Method: A quantitative descriptive design was followed. Heads of the nursing departments at the selected universities captured data with a specifically designed questionnaire. Thereafter their former nursing students provided information via a structured telephonic interview on the reasons why they discontinued the nursing programme. Results: The study revealed that attrition of undergraduate nursing students for three intake years (2007, 2008 and 2009 at the participating universities was between 39.3% and 58.7%. Academic and financial reasons as well as poor wellness and health were the main causes for attrition. Another factor was failure to cope with the demands of the clinical environment. Conclusion: Attrition might not occur immediately when a nursing student is challenged, as the student might exploit the various types of support offered. Although some nursing students do benefit from the offered support, a large number of nursing students still discontinue the undergraduate nursing programme.

  8. Surface-Sensitive Microwear Texture Analysis of Attrition and Erosion.

    Science.gov (United States)

    Ranjitkar, S; Turan, A; Mann, C; Gully, G A; Marsman, M; Edwards, S; Kaidonis, J A; Hall, C; Lekkas, D; Wetselaar, P; Brook, A H; Lobbezoo, F; Townsend, G C

    2017-03-01

    Scale-sensitive fractal analysis of high-resolution 3-dimensional surface reconstructions of wear patterns has advanced our knowledge in evolutionary biology, and has opened up opportunities for translatory applications in clinical practice. To elucidate the microwear characteristics of attrition and erosion in worn natural teeth, we scanned 50 extracted human teeth using a confocal profiler at a high optical resolution (X-Y, 0.17 µm; Z attrition. The teeth were divided into 4 groups, including 2 wear types (attrition and erosion) and 2 locations (anterior and posterior teeth; n = 12 for each anterior group, n = 13 for each posterior group) for 2 tissue types (enamel and dentine). The raw 3-dimensional data cloud was subjected to a newly developed rigorous standardization technique to reduce interscanner variability as well as to filter anomalous scanning data. Linear mixed effects (regression) analyses conducted separately for the dependent variables, complexity and anisotropy, showed the following effects of the independent variables: significant interactions between wear type and tissue type ( P = 0.0157 and P = 0.0003, respectively) and significant effects of location ( P attrition confirm our hypothesis. The greatest geometric means were noted in dentine erosion for complexity and dentine attrition for anisotropy. Dentine also exhibited microwear characteristics that were more consistent with wear types than enamel. Overall, our findings could complement macrowear assessment in dental clinical practice and research and could assist in the early detection and management of pathologic tooth wear.

  9. Dental cervical lesions associated with occlusal erosion and attrition.

    Science.gov (United States)

    Khan, F; Young, W G; Shahabi, S; Daley, T J

    1999-09-01

    Acid demineralization of teeth causes occlusal erosion and attrition, and shallow and wedge-shaped cervical lesions putatively involving abfraction. From 250 patients with tooth wear, 122 with cervical lesions were identified. From epoxy resin replicas of their dentitions, associations of occlusal attrition or erosion or no wear with cervical lesions were recorded at 24 tooth sites (total 2928 sites). Criteria used to discriminate occlusal attrition from erosion, and shallow from grooved, wedge-shaped or restored cervical lesions were delineated by scanning electron microscopy. A 96 per cent association was found between occlusal and cervical pathology. Shallow cervical lesions were more commonly found in association with occlusal erosion. Wedge-shaped lesions were found equally commonly in association with occlusal erosion, as with attrition. Grooved and restored cervical lesions were uncommon. Differences were appreciated in the associations within incisor, canine, premolar and molar tooth sites which related more to the site-specificity of dental erosion than to attrition from occlusal forces. Non-carious lesions on teeth then have multifactorial aetiology and pathogenesis in which erosion and salivary protection play central roles. Dentists should primarily consider erosion in the diagnosis, prevention and treatment of tooth wear.

  10. Proximal attrition facets: morphometric, demographic, and aging characteristics.

    Science.gov (United States)

    Sarig, Rachel; Hershkovitz, Israel; Shvalb, Nir; Sella-Tunis, Tatiana; May, Hila; Vardimon, Alexander D

    2014-08-01

    Although interproximal attrition is considered to be limited in modern populations, it has important clinical implications. However, in contrast to occlusal attrition, proximal attrition receives limited scientific attention. The main purpose of the current study was to fill this void. Seven-hundred and sixty-five teeth were collected from 255 skulls of subjects 18-75 yr of age. For each individual, three mandibular teeth (the first and second premolars and the first molar) were examined for proximal attrition facets (PAFs). The results provide detailed information on the size, shape, and location of the facets according to age cohort, gender, and ethnicity. The validity of the method used to measure the facets was also examined. The major findings were as follows: PAFs are usually located on the upper half of the crown proximal aspect; in each tooth, the mesial facet is more lingually positioned and the distal facet is more buccally positioned; the majority of the facets are subrectangular in shape; the size of the facets tends to increase in an anteroposterior direction (from premolars to molars); and facet size and location are age- and sex-dependent and ethnicity-independent. It is our recommendation that dentists bear in mind that interproximal attrition is a dynamic, long-term process and needs to be considered in many clinical scenarios. © 2014 Eur J Oral Sci.

  11. Attrition during graduate medical education: medical school perspective.

    Science.gov (United States)

    Andriole, Dorothy A; Jeffe, Donna B; Hageman, Heather L; Klingensmith, Mary E; McAlister, Rebecca P; Whelan, Alison J

    2008-12-01

    To identify predictors of attrition during graduate medical education (GME) in a single medical school cohort of contemporary US medical school graduates. Retrospective cohort study. Single medical institution. Recent US allopathic medical school graduates. Attrition from initial GME program. Forty-seven of 795 graduates (6%) did not complete the GME in their initial specialty of choice. At bivariate analysis, attrition was associated with election to the Alpha Omega Alpha Honor Medical Society, being an MD-PhD degree holder, and specialty choice (all P sex (P = .67), or age (P = .12). In a multivariate logistic regression model, MD-PhD degree holder (odds ratio, 3.43; 95% confidence interval, 1.27-9.26; P = .02), election to Alpha Omega Alpha (2.19; 1.04-4.66; P = .04), choice of general surgery for GME (5.32; 1.98-14.27; P < .001), and choice of 5-year surgical specialty including those surgical specialties with a GME training requirement of 5 years or longer (2.74; 1.16-6.44; P = .02) each independently predicted greater likelihood of attrition. Academically highly qualified graduates and graduates who chose training in general surgery or in a 5-year surgical specialty were at increased risk of attrition during GME.

  12. High resistivity iron-based, thermally stable magnetic material for on-chip integrated inductors

    Science.gov (United States)

    Deligianni, Hariklia; Gallagher, William J.; Mason, Maurice; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang

    2017-03-07

    An on-chip magnetic structure includes a palladium activated seed layer and a substantially amorphous magnetic material disposed onto the palladium activated seed layer. The substantially amorphous magnetic material includes nickel in a range from about 50 to about 80 atomic % (at. %) based on the total number of atoms of the magnetic material, iron in a range from about 10 to about 50 at. % based on the total number of atoms of the magnetic material, and phosphorous in a range from about 0.1 to about 30 at. % based on the total number of atoms of the magnetic material. The magnetic material can include boron in a range from about 0.1 to about 5 at. % based on the total number of atoms of the magnetic material.

  13. High resistivity iron-based, thermally stable magnetic material for on-chip integrated inductors

    Energy Technology Data Exchange (ETDEWEB)

    Deligianni, Hariklia; Gallagher, William J.; Mason, Maurice; O' Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang

    2017-10-17

    An on-chip magnetic structure includes a palladium activated seed layer and a substantially amorphous magnetic material disposed onto the palladium activated seed layer. The substantially amorphous magnetic material includes nickel in a range from about 50 to about 80 atomic % (at. %) based on the total number of atoms of the magnetic material, iron in a range from about 10 to about 50 at. % based on the total number of atoms of the magnetic material, and phosphorous in a range from about 0.1 to about 30 at. % based on the total number of atoms of the magnetic material. The magnetic material can include boron in a range from about 0.1 to about 5 at. % based on the total number of atoms of the magnetic material.

  14. Reasons for African American student attrition from school psychology programs.

    Science.gov (United States)

    Proctor, Sherrie L; Truscott, Stephen D

    2012-10-01

    This phenomenological study used a series of three in-depth interviews with seven African American participants, for a total of 21 interviews, to explore their experiences in the specialist and doctoral level school psychology programs they left prior to obtaining a professional entry-level degree. The study's purpose was to investigate what factors contributed to participants' attrition. Findings indicate that misalignment between participants' career aims and the practice of school psychology (as presented in the programs they left) contributed to attrition. Poor relationships with school psychology faculty and program cohort peers also played a role in participants' decisions to leave school psychology programs. Results offer a unique lens into racial issues in school psychology. Recommendations for faculty and others interested in preventing African Americans' attrition from school psychology graduate education are discussed. Copyright © 2012 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.

  15. 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.

  16. SRM attrition rate study of the aft motor case segments due to water impact cavity collapse loading

    Science.gov (United States)

    Crockett, C. D.

    1976-01-01

    The attrition assessment of the aft segments of Solid Rocket Motor due to water impact requires the establishment of a correlation between loading occurrences and structural capability. Each discrete load case, as identified by the water impact velocities and angle, varies longitudinally and radially in magnitude and distribution of the external pressure. The distributions are further required to be shifted forward or aft one-fourth the vehicle diameter to assure minimization of the effect of test instrumentation location for the load determinations. The asymmetrical load distributions result in large geometric nonlinearities in structural response. The critical structural response is progressive buckling of the case. Discrete stiffeners have been added to these aft segments to aid in gaining maximum structural capability for minimum weight addition for resisting these loads. This report presents the development of the attrition assessment of the aft segments and includes the rationale for eliminating all assessable conservatisms from this assessment.

  17. Methods for Evaluating Respondent Attrition in Web-Based Surveys.

    Science.gov (United States)

    Hochheimer, Camille J; Sabo, Roy T; Krist, Alex H; Day, Teresa; Cyrus, John; Woolf, Steven H

    2016-11-22

    Electronic surveys are convenient, cost effective, and increasingly popular tools for collecting information. While the online platform allows researchers to recruit and enroll more participants, there is an increased risk of participant dropout in Web-based research. Often, these dropout trends are simply reported, adjusted for, or ignored altogether. To propose a conceptual framework that analyzes respondent attrition and demonstrates the utility of these methods with existing survey data. First, we suggest visualization of attrition trends using bar charts and survival curves. Next, we propose a generalized linear mixed model (GLMM) to detect or confirm significant attrition points. Finally, we suggest applications of existing statistical methods to investigate the effect of internal survey characteristics and patient characteristics on dropout. In order to apply this framework, we conducted a case study; a seventeen-item Informed Decision-Making (IDM) module addressing how and why patients make decisions about cancer screening. Using the framework, we were able to find significant attrition points at Questions 4, 6, 7, and 9, and were also able to identify participant responses and characteristics associated with dropout at these points and overall. When these methods were applied to survey data, significant attrition trends were revealed, both visually and empirically, that can inspire researchers to investigate the factors associated with survey dropout, address whether survey completion is associated with health outcomes, and compare attrition patterns between groups. The framework can be used to extract information beyond simple responses, can be useful during survey development, and can help determine the external validity of survey results.

  18. Study of Navy Enlisted Attrition: Race, Ethnicity, and Type of Occupation

    National Research Council Canada - National Science Library

    Carroll, James M

    2008-01-01

    The primary objective of this study is to gain a better understanding of Navy first-term enlisted attrition among racial/ethnic minorities by comparing attrition rates in technical and nontechnical occupations...

  19. Sensitivity of gap symmetry to an incipient band: Application to iron based superconductors

    Science.gov (United States)

    Mishra, Vivek; Scalapino, Douglas; Maier, Thomas

    Observation of high temperature superconductivity in iron-based superconductors with a submerged hole band has attracted wide interest. A spin fluctuation mediated pairing mechanism has been proposed as a possible explanation for the high transition temperatures observed in these systems. Here we discuss the importance of the submerged band in the context of the gap symmetry. We show that the incipient band can lead to an attractive pairing interaction and thus have significant effects on the pairing symmetry. We propose a framework to include the effect of the incipient band in the standard multi-orbital spin-fluctuation theories which are widely used for studying various iron-based superconductors. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

  20. Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor.

    Science.gov (United States)

    Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

    2017-12-01

    We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C_{4} (2×2) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C_{4} state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

  1. Dental attrition and associated factors in adolescents 14 to 19 years of age: a pilot study.

    Science.gov (United States)

    Casanova-Rosado, Juan F; Medina-Solís, Carlo E; Vallejos-Sánchez, Ana A; Casanova-Rosado, Alejandro J; Maupomé, Gerardo; Avila-Burgos, Leticia

    2005-01-01

    This cross-sectional study evaluated the relationship between attrition and diverse variables in 390 Mexican adolescents aged 14 to 19 years. An ordinal scoring system was used to describe the severity of attrition. Attrition prevalence was 33.3% and was associated with older age, presence of defective restorations, Class II malocclusion, and perception of stress level. Our results suggest that attrition is present in 1 of every 3 adolescents.

  2. Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free Process Control Agent

    Science.gov (United States)

    2015-02-01

    routes, but one of the more promising ways is through cryogenic attrition. One form of cryogenic attrition is low-energy grinding of conventional...Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free Process Control Agent by Frank Kellogg, Clara Hofmeister...Ground, MD 21005-5069 ARL-TR-7208 February 2015 Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free

  3. Sociodemographic and psychiatric determinants of attrition in the Netherlands Study of Depression and Anxiety (NESDA)

    NARCIS (Netherlands)

    Lamers, Femke; Hoogendoorn, Adriaan W.; Smit, Johannes H.; van Dyck, Richard; Zitman, Frans G.; Nolen, Willem A.; Penninx, Brenda

    Background: Although attrition is inevitable in longitudinal epidemiological studies, psychiatric studies are thought to be especially sensitive to attrition. This study aimed to evaluate the sociodemographic and psychiatric determinants of attrition at 2-year follow-up in the Netherlands Study of

  4. Enhancement of the Logistics Battle Command Model: Architecture Upgrades and Attrition Module Development

    Science.gov (United States)

    2017-01-05

    Battle Command Model Architecture Upgrades and Attrition Module Development U.S. Army TRADOC Analysis Center-Monterey 700 Dyer...17-010 January 2017 Enhancement of the Logistics Battle Command Model Architecture Upgrades and Attrition Module Development Nathan Parker...Logistics Battle Command Model Architecture Upgrades and Attrition Module Development 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  5. Blue-Collar Scholars?: Mediators and Moderators of University Attrition in First-Generation College Students

    Science.gov (United States)

    Martinez, Julia A.; Sher, Kenneth J.; Krull, Jennifer L.; Wood, Phillip K.

    2009-01-01

    Many college entrants' parents do not have college degrees. These entrants are at high risk for attrition, suggesting it is critical to understand mechanisms of attrition relative to parental education. Moderators and mediators of the effect of parental education on attrition were investigated in 3,290 students over 4 years. Low parental education…

  6. Team-Based Learning Reduces Attrition in a First-Semester General Chemistry Course

    Science.gov (United States)

    Comeford, Lorrie

    2016-01-01

    Team-based learning (TBL) is an instructional method that has been shown to reduce attrition and increase student learning in a number of disciplines. TBL was implemented in a first-semester general chemistry course, and its effect on attrition was assessed. Attrition from sections before implementing TBL (fall 2008 to fall 2009) was compared with…

  7. Reducing Bias Due to Systematic Attrition in Longitudinal Studies: The Benefits of Multiple Imputation

    Science.gov (United States)

    Asendorpf, Jens B.; van de Schoot, Rens; Denissen, Jaap J. A.; Hutteman, Roos

    2014-01-01

    Most longitudinal studies are plagued by drop-out related to variables at earlier assessments (systematic attrition). Although systematic attrition is often analysed in longitudinal studies, surprisingly few researchers attempt to reduce biases due to systematic attrition, even though this is possible and nowadays technically easy. This is…

  8. Literature Review on Induction and Mentoring Related to Early Career Teacher Attrition and Retention

    Science.gov (United States)

    Long, Julie S.; McKenzie-Robblee, Sue; Schaefer, Lee; Steeves, Pam; Wnuk, Sheri; Pinnegar, Eliza; Clandinin, D. Jean

    2012-01-01

    Early career teacher attrition is a matter of economic, social, and educational concern in many countries. Usually induction programs, including mentoring, are seen to alleviate the problem of early career teacher attrition. Mentoring/induction programs as a solution to what is defined as the problem of early career teacher attrition and retention…

  9. Reducing bias due to systematic attrition in longitudinal studies : The benefits of multiple imputation

    NARCIS (Netherlands)

    Asendorpf, Jens B.; van de Schoot, Rens; Denissen, Jaap J. A.; Hutteman, Roos

    Most longitudinal studies are plagued by drop-out related to variables at earlier assessments (systematic attrition). Although systematic attrition is often analysed in longitudinal studies, surprisingly few researchers attempt to reduce biases due to systematic attrition, even though this is

  10. Reevaluating the Effect of Non-Teaching Wages on Teacher Attrition

    Science.gov (United States)

    Gilpin, Gregory A.

    2011-01-01

    Most empirical teacher attrition research focuses on estimating the effect of either the alternate occupation opportunities or the teacher work environment on teacher attrition. In this paper, we use non-teaching wages of former teachers to estimate the determinants of teacher attrition, including the wage differential between teaching and…

  11. A successful approach to minimizing attrition in racial/ethnic minority, low-income populations

    Directory of Open Access Journals (Sweden)

    Glenn Flores

    2017-03-01

    Conclusions: A retention strategic framework was successful in minimizing attrition in minority, low-income children. Participants missing first assessment appointments were at highest risk of subsequent attrition. These findings suggest that deploying this framework may help RCT retention of low-income minority children, particularly those at the highest risk of subsequent attrition.

  12. Attrition among Iranian nursing students: A qualitative study.

    Science.gov (United States)

    Ashghali Farahani, Mansoureh; Ghaffari, Fatemeh; Oskouie, Fatemeh; Zagheri Tafreshi, Mansoureh

    2017-01-01

    Attrition is a major challenge facing nursing students that results in substantial costs on the education, health, and treatment systems across countries and can have an unwanted effect on the quality and quantity of health services provided as well as on the health of citizens. This descriptive study investigated nursing students' perceptions toward factors influencing attrition. We conducted a qualitative study using a content analysis approach. Nineteen students enrolled in nursing bachelor program were recruited using purposive and snowball sampling. Data were collected using face-to-face interviews, focus group interviews, and participant observation, and analysed using conventional content analysis approach. Attrition factors were categorized into two themes: 'before admission' and 'after admission'. The most important factors were obligation to choose nursing in the National Entrance Exam, poor management in workforce provision and improper supervision, discrepancy between expectations and experiences, and being work abused in clinical training. Authorities in education and practice sectors can use these findings to improve the quality of clinical and theoretical education and to avoid nursing student attrition. This can be achieved through an increase in community awareness of the identity of nursing, efficient management of workforce provision and clear and concise supervision of activities in both theoretical and clinical fields. Copyright © 2017. Published by Elsevier Ltd.

  13. 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…

  14. Evaluation of the Dehulling Efficiency of Soybean Using Attrition and ...

    African Journals Online (AJOL)

    The soaked seeds attained a moisture content of 17 – 24%, so as to facilitate dissolution of the gum layer, which bound the seed coats to the endosperm. Conditioned seeds were dehulled in the huller section of commercial rice milling machine and attrition milling machine. A dehulling efficiency (e) value of 55%, which ...

  15. Who Stays, Who Leaves? Attrition among First-Term Enlistees

    Science.gov (United States)

    1989-05-01

    helped them select the occupation of their choice and a convenient entry data. Because so many enlistees enter through DEP- virtually all seniors-it is...perhaps not surprising that DEP participation alone has no significant correlation with attrition. Still, Baldwin and I) aula found that DEP participation

  16. Examining Factors That Decrease Attrition among Special Educators

    Science.gov (United States)

    Hampton, Jessica Daneen

    2013-01-01

    Recruiting and retaining special educators has been a major concern for the department of education, school administration, and parents across the United States. Attrition, defined as the exit of teachers from their positions, has been a contributing factor to the shortage of teachers. The theoretical foundation for this study was based on the…

  17. Factors That Influence Student Attrition in Online Courses

    Science.gov (United States)

    Shaw, Melanie; Burrus, Scott; Ferguson, Karen

    2016-01-01

    Research was conducted to explore predictors for online higher education student attrition. This research was conducted using results from the SmarterMeasure Learning Readiness Indicator to track students in their degree programs. In addition, student outreach was conducted with an experimental group of at-risk students to determine if additional…

  18. Insights into Attrition from University-Based Enabling Programs

    Science.gov (United States)

    Bookallil, Cheryl; Harreveld, Bobby

    2017-01-01

    High attrition rates from university-based enabling programs continue to be the subject of much research and administrative effort. Understanding the factors behind decisions to withdraw from such programs is difficult since those who do not successfully complete an enabling program may not readily agree to participate in research into their…

  19. Texas Public School Attrition Study, 2013-14. IDRA Report

    Science.gov (United States)

    Johnson, Roy L.; Montes, Felix

    2014-01-01

    Since 1986, Intercultural Development Research Association (IDRA) has conducted an annual attrition study to track the number and percent of students in Texas who are lost from public secondary school enrollment prior to graduation. The study builds on the series of studies that began when IDRA conducted the first comprehensive study of school…

  20. Teacher Attrition Variables That Influence Retention and Job Satisfaction

    Science.gov (United States)

    Butler, Leslie Garmon

    2014-01-01

    Teacher attrition is a major problem. According to researchers at North Carolina State University, more teachers are leaving the profession than staying or entering. Accordingly, school systems in the United States find themselves in the predicament where they must hire teachers who have little teaching experience or who have not been adequately…

  1. Student Selection, Attrition, and Replacement in KIPP Middle Schools

    Science.gov (United States)

    Nichols-Barrer, Ira; Gleason, Philip; Gill, Brian; Tuttle, Christina Clark

    2016-01-01

    Skeptics of the KIPP (Knowledge Is Power Program) charter school network argue that these schools rely on selective admission, attrition, and replacement of students to produce positive achievement results. We investigate this using data covering 19 KIPP middle schools. On average, KIPP schools admit students disadvantaged in ways similar to other…

  2. 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:…

  3. Factors Influencing Students' Attrition at Sultan Qaboos University (SQU)

    Science.gov (United States)

    Al Ghanboosi, Salim Saleen

    2013-01-01

    The students' attrition rates among students enrolled at SQU ranged between 6.8% (1998), 7.8% (1999), and 7.9% (2000). However, the drop-out rate at the Sultan Qaboos University is increasing gradually, and this increase represents a problem for the university that provides free education and financial aid for all male students coming from areas…

  4. Predictors of Attrition and Achievement in a Tertiary Bridging Program

    Science.gov (United States)

    Whannell, Robert

    2013-01-01

    This study examines the attrition and achievement of a sample of 295 students in an on-campus tertiary bridging program at a regional university. A logistic regression analysis using enrolment status, age and the number of absences from scheduled classes at week three of the semester as predictor variables correctly predicted 92.8 percent of…

  5. The Institutional Costs of Student Attrition. Research Paper

    Science.gov (United States)

    Johnson, Nate

    2012-01-01

    Previous research on attrition has focused on the economic consequences of low graduation rates in terms of costs to students and families (from tuition and fees that do not culminate in a credential), lost time, and income and tax losses from low educational attainment in the workforce. However, no systematic attention has been given to another…

  6. Compensatory Strategies of First-Language-Attrited Children

    Science.gov (United States)

    Syahdan

    2012-01-01

    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…

  7. Investor Attrition and Fund Flows in Mutual Funds

    DEFF Research Database (Denmark)

    Christoffersen, Susan E. K.; Xu, Haoyu

    2017-01-01

    We explore the properties of equity mutual funds that experience a loss of assets after poor performance. We document that both inflows and outflows are less sensitive to performance, because performance-sensitive investors leave or decide not to invest after bad performance. Consistent......–performance sensitivity when attrition arises after good performance or investors invest for nonperformance reasons....

  8. Attrition and Retention of Employees in BPO Sector

    OpenAIRE

    Hradesh Kumar; Ankita Srivastava; Yogesh Tiwari

    2011-01-01

    The broad objective of this research is to identify the root causes of attrition and retention in BPOs, analyzing the level of employee motivation, satisfaction and involvement, generate a model for maximizing sustenance of employees in the organization and come up with concrete recommendations, which will eventually be valuable to the organizations to retain their employees for a long term

  9. Selected Factors of Language Learning and Language Attrition.

    Science.gov (United States)

    Papalia, Anthony

    This study began with a survey of twenty-eight school districts of Erie County, New York, and its aims were to determine and compare attrition in foreign languages in those districts. The data, obtained through discussion with teachers, interviews with students, questionnaires, and Flander's Interaction Analysis, assisted in the formulation of the…

  10. The suppression of immune system disorders by passive attrition.

    Directory of Open Access Journals (Sweden)

    Sean P Stromberg

    Full Text Available Exposure to infectious diseases has an unexpected benefit of inhibiting autoimmune diseases and allergies. This is one of many fundamental fitness tradeoffs associated with immune system architecture. The immune system attacks pathogens, but also may (inappropriately attack the host. Exposure to pathogens can suppress the deleterious response, at the price of illness and the decay of immunity to previous diseases. This "hygiene hypothesis" has been associated with several possible underlying biological mechanisms. This study focuses on physiological constraints that lead to competition for survival between immune system cell types. Competition maintains a relatively constant total number of cells within each niche. The constraint implies that adding cells conferring new immunity requires loss (passive attrition of some cells conferring previous immunities. We consider passive attrition as a mechanism to prevent the initial proliferation of autoreactive cells, thus preventing autoimmune disease. We see that this protection is a general property of homeostatic regulation and we look specifically at both the IL-15 and IL-7 regulated niches to make quantitative predictions using a mathematical model. This mathematical model yields insight into the dynamics of the "Hygiene Hypothesis," and makes quantitative predictions for experiments testing the ability of passive attrition to suppress immune system disorders. The model also makes a prediction of an anti-correlation between prevalence of immune system disorders and passive attrition rates.

  11. Language attrition and code-switching among US Americans in ...

    African Journals Online (AJOL)

    hand, it shows how intercultural identities are constructed through the employment of code- switching (qualitative ... switching and language attrition in intercultural identity research. 1.1. Social identity related .... The overall participant group has a high level of education: 30% have an MA or PhD, 50% have a BA degree and ...

  12. Health workforce deployment, attrition and density in East Wollega ...

    African Journals Online (AJOL)

    ... were budget related constraints, lack of continuing education opportunity and poor career development. Conclusions: The number of health personnel in East Wollega was low both by international standards and rela-tive to the national density. Moreover, attrition was higher for the time after decentralization process.

  13. Fabrication and Properties of Iron-based Soft Magnetic Composites Coated with NiZnFe2O4

    Directory of Open Access Journals (Sweden)

    WU Shen

    2017-07-01

    Full Text Available This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing the sol-gel method prepared Ni-Zn ferrite particles as insulating compound to coat iron powder, and the influence of NiZnFe2O4 content and molding pressure on the magnetic properties was studied. The morphology, magnetic properties and density of Ni-Zn ferrite insulated compacts were investigated. Scanning electron microscope,line-scan EDX analysis and distribution maps show that the iron particle surface is covered with a thin layer of uniform Ni-Zn ferrites. The existing of the insulating layer can effectively improve the electrical resistivity of soft magnetic composites. Magnetic measurements show that the real part of permeability decreases with the increase of the Ni-Zn ferrite content, and the sample with 3%(mass fraction, the same below Ni-Zn ferrite has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Results show that the addition of NiZnFe2O4 can dramatically decrease the internal magnetic loss, the magnetic loss of coated samples decreases by 83.8% as compared with that of uncoated samples at 100kHz. The density of the Fe-3%NiZnFe2O4 compacts reaches 7.14g/cm3 and the saturation magnetization is 1.47T when the molding pressure is 1000MPa.

  14. Attrition in a clinical laboratory technician associate degree program.

    Science.gov (United States)

    Blume, W M; Krefetz, R G

    1997-01-01

    To determine the reasons for attrition in a clinical laboratory technician-associate degree program, a retrospective study was done on classes entering from 1987 to 1992. Suggestions are made to increase retention. The medical laboratory department at the Community College of Philadelphia in Pennsylvania. There were 43,987 students enrolled for the 1993 to 1994 academic year; 17,846 full time equivalents at the college. Clinical laboratory technician students averaged 26.2 years and were 26% male and 74% female, which closely paralleled the college. The ethnic make-up of the clinical laboratory technician classes was 54% White, 32% African American, 11% Asian, and 3% Latin American, compared to 48% African American, 36% White, 10% Asian, and 6% Latin American students in the college. A retrospective study was performed to evaluate attrition rates for the classes entering the clinical laboratory technician program at the Community College of Philadelphia from 1987 to 1992. Reasons for this attrition were tabulated and evaluated. One hundred twenty-nine students entered the program and 75 graduated, producing an attrition rate of 42%. There were 6 categories of reasons given for not completing the program: academic difficulties, dislike of the laboratory science field, family problems, financial problems, substance abuse, and other problems not specified. Because 80% of the attrition was due to poor academic performance and a dislike of the field, several changes are being made in the Community College of Philadelphia's retention program. An enhanced orientation will be given to all students, and students will be required to visit a hospital laboratory. Early faculty intervention and peer counseling for students with poor academic performance will be instituted.

  15. Income and attrition in the treatment of depression: a STAR*D report.

    Science.gov (United States)

    Warden, Diane; Rush, A John; Wisniewski, Stephen R; Lesser, Ira M; Thase, Michael E; Balasubramani, G K; Shores-Wilson, Kathy; Nierenberg, Andrew A; Trivedi, Madhukar H

    2009-01-01

    Attrition, or dropping out of treatment, remains a major issue in the care of depressed outpatients. Whether different factors are associated with attrition for different socioeconomic groups is not known. This report assessed whether attrition rates and predictors of attrition differed among depressed outpatients with different income levels. Outpatients with nonpsychotic major depressive disorder treated for up to 14 weeks with citalopram in the first step of the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study were divided by household incomes of or=$40,000. Attrition rates and sociodemographic and clinical correlates of attrition were identified for each group. Regardless of income level, remission rates were lower for participants who dropped out of treatment. Attrition rates increased as income decreased. For all income levels, younger age was independently associated with attrition. For the lowest income level, less education, better mental health functioning, being on public insurance, and having more concurrent Axis I conditions were associated with a greater likelihood of attrition. For the middle income group, less education, better mental health functioning, being Black or of another non-White race, and treatment in a psychiatric versus primary-care setting predicted greater attrition. For the highest income group, being Hispanic, having a family history of drug abuse, and melancholic features predicted attrition. Atypical symptom features (middle income group) and recurrent depression (highest income group) were associated with retention. Efforts to retain patients in antidepressant treatment should focus especially on less educated patients with lower household incomes and younger patients.

  16. The Effect of State Unemployment Rate on Attrition for First-Term U.S. Navy Enlisted Personnel

    Science.gov (United States)

    2011-03-01

    through homeschooling attrited at a rate of 8.0 percent. Recruits who reported to have not graduated from high school attrited at a rate of 11.6 percent... college degree were less likely to attrite. The more education an individual has upon entry into the Navy, the less likely he or she is to attrite

  17. Regeneration of iron-based adsorptive media used for removing arsenic from groundwater.

    Science.gov (United States)

    Chen, Abraham S C; Sorg, Thomas J; Wang, Lili

    2015-06-15

    Adsorptive media technology is regarded as a simple, low cost method of removing arsenic from drinking water particularly for small systems. Currently, when the effluent of a treatment system reaches the USEPA maximum contaminant level (MCL) of 10 ug/L, the exhausted media is removed and replaced by new virgin media. Although the commonly used iron-based media products are reasonable in price, the replacement cost accounts for around 80% of the systems total operational costs. One option to media replacement is on-site regeneration and reuse of the exhausted media. To determine whether an iron based media can be successfully regenerated and reused, laboratory batch and column regeneration tests were conducted on six exhausted iron-based media products obtained from six full scale arsenic removal treatment systems. Batch tests conducted on three of the media products to evaluate the effectiveness of 1-6% caustic regenerant solutions found that arsenic desorption increased until around 4%. Using 4% caustic solutions, the columns tests on the six exhausted media products showed arsenic removals ranged from 25 to 90% with the best results obtained with the Severn Trent E33 media. Exposing the media to caustic (pH ≥ 13) and acid (pH ≤ 2) solutions found minimal media loss with the caustic solution, but significant media dissolution with a pH 2 acid solution. A six column pilot plant test at an Ohio test site with the lab regenerated media products found that the regenerated media could achieve arsenic removals somewhat similar to virgin media. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. A study of lattice dynamics in iron-based superconductors by inelastic light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Um, Youngje

    2013-12-13

    After the discovery of high temperature (high T{sub c}) superconductivity in copper oxide-based materials (cuprates) in 1986, this phenomenon was a unique property of the cuprates for more than 20 years. The origin of high T{sub c} superconductivity is still under debate. In 2008, high T{sub c} superconductivity was discovered in iron-based compounds. This discovery presents new opportunities for the development of a fundamental understanding of high T{sub c} superconductivity. Density functional calculations indicate a weak electron-phonon coupling strength in iron-based superconductors and these suggest that superconductivity is not mediated by phonons. However, experimental report of a large isotope effect of the iron atoms on the superconductivity T{sub c} suggests that phonons play an important role in iron-based superconductors. Motivated by these findings, this thesis presents a Raman scattering study of the lattice dynamics of the iron-based superconductors Fe{sub 1+y}Te{sub 1-x}Se{sub x}, LiFeAs and NaFe{sub 1-x}Co{sub x}As as a function of chemical composition and temperature. In Fe{sub 1+y}Te{sub 1-x}Se{sub x}, an unconventional linewidth broadening of the c-axis polarized Fe phonon of B{sub 1g} symmetry is found with decreasing temperature, which indicates an unusual coupling between the phonon and iron excessinduced magnetic fluctuations in this compound. In LiFeAs, the Raman scattering data provide evidence for a weak electron-phonon coupling, which is consistent with non-phonon mediated Cooper pairing in this compound. In NaFe{sub 1-x}Co{sub x}As, upon cooling two features are observed: (i) an unconventional linewidth broadening of several phonons, which is indicative of spin fluctuation-phonon coupling, and (ii) a superconductivity-induced phonon lineshape renormalization, which can not be explained by standard model calculations.

  19. Spin wave mediated interaction as a mechanism of pairs formation in iron-based superconductors

    Science.gov (United States)

    Lima, Leonardo S.

    2018-03-01

    The spin wave mediated interaction between electrons has been proposed as mechanism to formation of electron pairs in iron-based superconductors. We employe the diagrammatic expansion to calculate the binding energy of electrons pairs mediated by spin wave. Therefore, we propose the coupling of electrons in high-temperature superconductors mediated by spin waves, since that is well known that this class of superconductors materials if relates with spin-1/2 two-dimensional antiferromagnets, where it is well known there be an interplay between antiferromagnetism 2D and high-temperature superconductivity.

  20. Wavelength-Dependence on the Initiation of Iron-Based Photoactive Explosives

    Science.gov (United States)

    Brown, Kathryn; Myers, Thomas; Clarke, Steven

    2017-06-01

    Photoactive explosives show promise to be relatively insensitive to impact and friction compared to PETN and other detonator materials, but can be more easily initiated with laser light. Metal-ligand charge transfer (MLCT) complexes have been shown to have tunable explosive properties and absorption profiles, making them strong candidates for laser detonator material. Here, we discuss the synthesis and characterization of several iron-based MLCT complexes, as well as results from recent experiments on their sensitivity to initiation from different wavelengths of laser light.

  1. Pairing susceptibility of iron-based superconductors within a two-layer Hubbard model

    Science.gov (United States)

    Wei, Dan; Wang, Jingyao; Wu, Yang; Liang, Ying; Ma, Tianxing

    2017-12-01

    By using the determinant quantum Monte Carlo method, we studied the dominant pairing susceptibility of iron-based superconductors within an extended Hubbard model, which describes the underlying electronic structure of both iron pnictides and iron chalcogenides. The extended Hubbard model is constructed by two iron layers, each of which forms two sublattices on a square structure. Although the coupling between the two layers has different effects on the behavior of pairings in iron pnictides and iron chalcogenides, our non-biased numerical simulations reveal that the pairing with Sxy symmetry dominates over the studied parameter for both materials.

  2. Graphitic Layer Encapsulated Iron Based Non‐precious Catalysts for the Oxygen Reduction Reaction

    DEFF Research Database (Denmark)

    Zhong, Lijie

    evidences are found from the catalyst synthesized from nitrogen free precursors. This catalyst, consisting of only carbon encapsulated iron-based nanoparticles, shows some, though low, ORR activity, which is enhanced by the post heat treatment in an ammonia atmosphere, indicating the contribution...... are made to develop non-precious metal catalysts (NPMCs) as a replacement to the Pt/C electrocatalysts. In this thesis, a new type of NPMCs is synthesized by means of a dry autoclave with volatile ferrocene and cyanamide as precursors. The catalysts are morphologically featured by porous microspheres...

  3. Ash production by attrition in volcanic conduits and plumes.

    Science.gov (United States)

    Jones, T J; Russell, J K

    2017-07-17

    Tephra deposits result from explosive volcanic eruption and serve as indirect probes into fragmentation processes operating in subsurface volcanic conduits. Primary magmatic fragmentation creates a population of pyroclasts through volatile-driven decompression during conduit ascent. In this study, we explore the role that secondary fragmentation, specifically attrition, has in transforming primary pyroclasts upon transport in volcanic conduits and plumes. We utilize total grain size distributions from a suite of natural and experimentally produced tephra to show that attrition is likely to occur in all explosive volcanic eruptions. Our experimental results indicate that fine ash production and surface area generation is fast (eruption column stability, tephra dispersal, aggregation, volcanic lightening generation, and has concomitant effects on aviation safety and Earth's climate.

  4. Delay between recruitment and participation impacts on preinclusion attrition.

    Science.gov (United States)

    Walsh, Erin I; Brinker, Jay K

    2015-01-01

    Despite being a common aspect of psychological research, the impact of delay between recruitment and active participation on dropout rates has received little research attention. This is probably due to the intuitive sense that longer delays will increase the dropout rate. Preinclusion attrition diminishes sample sizes and may threaten data representativeness. One hundred and two university undergraduates were recruited to participate in a short, one-off study via Short Message Service (SMS). Upon receipt of an SMS indicating consent to participate, the researchers delayed sending the study questions for one day, one week, one month, or two months. Delay was significantly associated with response rate with an 80% response rate in the one-day delay condition, 56% at one week, and 42% at one month. No responses were received in the two-month delay condition. This research confirms that the delay between recruitment and active participation impacts on preinclusion attrition when conducting research via SMS.

  5. 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.

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

    Directory of Open Access Journals (Sweden)

    Terje eLohndal

    2016-03-01

    Full Text Available 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.

  7. 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

  8. Quels changements linguistiques dans l'attrition de la L1 chez le bilingue tardif (What Linguistic Changes in the Attrition of the L1 in Late Bilinguals)?

    Science.gov (United States)

    Kopke, Barbara

    2001-01-01

    This article reports on a psycholinguistic study of first language attrition in German first generation immigrants. On the basis of the individual variation in performance evidenced by the data, the study claims that first language (L1) attrition in late bilinguals is not only the consequence of a lack of use. A comparison of the performance of…

  9. Contribution to the Study of the Relation between Microstructure and Electrochemical Behavior of Iron-Based FeCoC Ternary Alloys

    Directory of Open Access Journals (Sweden)

    Farida Benhalla-Haddad

    2012-01-01

    Full Text Available This work deals with the relation between microstructure and electrochemical behavior of four iron-based FeCoC ternary alloys. First, the arc-melted studied alloys were characterized using differential thermal analyses and scanning electron microscopy. The established solidification sequences of these alloys show the presence of two primary crystallization phases (δ(Fe and graphite as well as two univariante lines : peritectic L+(Fe↔(Fe and eutectic L↔(Fe+Cgraphite. The ternary alloys were thereafter studied in nondeaerated solution of 10−3 M NaHCO3 + 10−3 M Na2SO4, at 25°C, by means of the potentiodynamic technique. The results indicate that the corrosion resistance of the FeCoC alloys depends on the carbon amount and the morphology of the phases present in the studied alloys.

  10. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    Science.gov (United States)

    Holanda, R.

    1984-01-01

    The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

  11. Contribution to the Study of the Relation between Microstructure and Electrochemical Behavior of Iron-Based FeCoC Ternary Alloys

    Science.gov (United States)

    Benhalla-Haddad, Farida; Amara, Sif Eddine; Benchettara, Abdelkader; Taibi, Kamel; Kesri, Rafika

    2012-01-01

    This work deals with the relation between microstructure and electrochemical behavior of four iron-based FeCoC ternary alloys. First, the arc-melted studied alloys were characterized using differential thermal analyses and scanning electron microscopy. The established solidification sequences of these alloys show the presence of two primary crystallization phases (δ(Fe) and graphite) as well as two univariante lines : peritectic L + δ(Fe)↔γ(Fe) and eutectic L↔γ(Fe) + Cgraphite. The ternary alloys were thereafter studied in nondeaerated solution of 10−3 M NaHCO3 + 10−3 M Na2SO4, at 25°C, by means of the potentiodynamic technique. The results indicate that the corrosion resistance of the FeCoC alloys depends on the carbon amount and the morphology of the phases present in the studied alloys. PMID:22448342

  12. Mandibular movement during sleep bruxism associated with current tooth attrition.

    Science.gov (United States)

    Okura, Kazuo; Shigemoto, Shuji; Suzuki, Yoshitaka; Noguchi, Naoto; Omoto, Katsuhiro; Abe, Susumu; Matsuka, Yoshizo

    2017-01-01

    Observation of attrition patterns suggests that mandibular movement in sleep bruxism (SB) may be associated with current tooth attrition. The aim of this study was to confirm this phenomenon by investigating mandibular movement and masseter muscle activity. The subject was a healthy 21-year-old Japanese male. We recorded biological signals including mandibular movement and masseter electromyograms (EMGs) with a polysomnograph. Based on the EMG using Okura's criteria, SB events were classified into clenching, grinding and mixed types according to mandibular movement criteria. The close-open mandibular movement cycles (CO-cycles) during grinding and mixed type events were selected based on mandibular movement trajectories. Fifty-eight CO-cycles were selected in seven grinding and three mixed types. We found that SB mandibular movements associated with current tooth attrition. Excessive lateral movements (ELM) beyond the canine edge-to-edge position were observed in the closing (10.3%) and opening (13.8%) phases of the CO-cycle. Total masseter muscle activity was significantly higher during voluntary grinding (VGR) than during CO-cycle including ELM (working side: P=0.036, balancing side: P=0.025). However, in the middle and late parts of the opening phase, working side masseter muscle activity was significantly higher during CO-cycle including ELM than during VGR (P=0.012). In the early part of the closing phase, balancing side masseter muscle activity was significantly higher during CO-cycle including ELM than during VGR (P=0.017). These findings suggest that excessive forceful grinding during ongoing SB events may have caused canine attrition in this patient. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  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. Attrition of Canadian Internet pharmacy websites: what are the implications?

    Directory of Open Access Journals (Sweden)

    Veronin MA

    2013-08-01

    Full Text Available Michael A Veronin,1 Kristen M Clancy2 1Rangel College of Pharmacy, Texas A&M Health Science Center, Texas, USA; 2Christus Dubuis Health System, Texas, USA Background: The unavailability of Internet pharmacy websites may impact a consumer's drug purchases and health care. Objective: To address the issue of attrition, a defined set of Canadian Internet pharmacy websites was examined at three separate time intervals. Methods: In February to March 2006, 117 distinct, fully functional "Canadian Internet pharmacy" websites were located using the advanced search options of Google and the uniform resource locator (URL for each website was recorded. To determine website attrition, each of the 117 websites obtained and recorded from the previous study was revisited at two later periods of time within a 4-year period. Results: After approximately 4 years and 5 months, only 59 (50.4% sites were found in the original state. Thirty-four sites (29.1% had moved to a new URL address and were not functioning as the original Internet pharmacy. For 24 sites (20.5% the viewer was redirected to another Canadian Internet pharmacy site. Conclusion: Of concern for patients if Internet pharmacy sites were suddenly inaccessible would be the disruption of continuity of care. Keywords: Canadian Internet pharmacy, online pharmacy, website attrition, continuity of care

  16. Irradiation creep analysis base on rate theory in iron based cladding materials

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sang Il; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of); Lee, Gyeong-Geun; Kwon, Jun Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Irradiation degradation mechanism of zirconium are well developed including growth, hardening, and creep. However, in the same times, irradiation behaviour of iron based materials was not systemically organised and mechanism is not well established when it is compared with zirconium based alloy. Therefore in this paper, our research goal is development the prediction model of irradiation behaviour of iron based cladding materials in SFR condition. In order to calculate irradiation creep, point defect, cluster number density, and radius was calculated. From point defect concentration, it could be recognized that steady state behavior of defect flux. However irradiation creep behavior show exponent tendency because cluster number density is not saturated. The radius of each type of sink was calculated using defect concentration and cluster number density. In the engineering point of view, radius is most important parameter because it can be compared with experimental result. In order to confirm mobile cluster effect on dislocation loop number density, cluster behavior will be more specifically demonstrated by grouping method in next research step.

  17. Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors

    Science.gov (United States)

    Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J.; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F.; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V.

    2015-01-01

    The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm2 cross-section. The impurities suppress superconductivity in a three-dimensional ‘Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities. PMID:26139568

  18. 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.

  19. Reduction kinetics of iron-based oxygen carriers using methane for chemical-looping combustion

    Science.gov (United States)

    Luo, Ming; Wang, Shuzhong; Wang, Longfei; Lv, Mingming

    2014-12-01

    The performance of three iron-based oxygen carriers (pure Fe2O3, synthetic Fe2O3/MgAl2O4 and iron ore) in reduction process using methane as fuel is investigated in thermo-gravimetric analyzer (TGA). The reaction rate and mechanism between three oxygen carriers and methane are investigated. On the basis of reactivity in reduction process, it may be concluded that Fe2O3/MgAl2O4 has the best reactivity with methane. The reaction rate constant is found to be in the following order: Fe2O3/MgAl2O4 > pure Fe2O3 > iron ore and the activation energy varies between 49 and 184 kJ mol-1. Reduction reactions for the pure Fe2O3 and synthetic Fe2O3/MgAl2O4 are well represented by the reaction controlling mechanism, and for the iron ore the phase-boundary controlled (contracting cylinder) model dominates. The particles of iron ore and synthetic Fe2O3/MgAl2O4 have better stability than that of pure Fe2O3 when the reaction temperature is limited to lower than 1223 K. These preliminary results suggest that iron-based mixed oxygen carrier particles are potential to be used in methane chemical looping process, but the reactivity of the iron ore needs to be increased.

  20. Competing orders in strongly correlated systems. Dirac materials and iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Classen, Laura

    2016-11-04

    In this work we address the collective phenomena appearing in interacting fermion systems due to the competition of distinct orders at the example of Dirac materials and iron-based superconductors. On the one hand we determine leading ordering tendencies in an unbiased way, when Fermi liquid instabilities are expected simultaneously in the particle-particle and particle-hole channel. In this context we analyze the impact of electron-phonon interactions on the many-body instabilities of electrons on the honeycomb lattice. Furthermore we investigate the interplay between superconductivity, magnetism and orbital order in five-pocket iron-based superconductors including the full orbital composition of low-energy excitations. On the other hand we study how the close proximity of different phases affects the structure of the phase diagram and the nature of transitions, as well as the corresponding quantum multicritical behavior. To this end we consider the semimetal-insulator transitions to an antiferromagnetic and a staggered-density state of low-energy Dirac fermions. To account for the decisive role of interactions and the various degrees of freedom in these models, modern renormalization group techniques are applied.

  1. Measuring and reporting attrition from obesity treatment programs: A call to action!

    Science.gov (United States)

    Miller, Beth M L; Brennan, Leah

    2015-01-01

    The high attrition rates in obesity interventions are associated with poorer weight loss and maintenance for the individual and poorer overall treatment effectiveness and cost-effectiveness for the treatment provider. Increased knowledge about factors associated with attrition can facilitate the identification of individuals at risk of drop-out and inform treatment program improvements with the aim of maximising treatment retention. To date, a relatively small body of literature has explored attrition from weight-loss interventions using two methods of attrition assessment: identification of pre-treatment predictors of attrition and eliciting post-treatment reasons for attrition. A range of attrition rates have been reported and no reliable or consistent predictors of attrition have been found. It is unknown whether the lack of consistent findings reflects population or treatment differences, or if the discrepant findings simply reflect differences in definition and measurement of attrition. Further research is required to address these limitations. There is a need for a recognised definition of obesity treatment attrition, the consideration of predictors that are theoretically and empirically associated with attrition, the development of a well-validated and standardised measure of barriers to attendance, and assessment of both treatment completers and drop-outs. Understanding the factors that influence attrition can be used to inform the modification of treatment programs and to target those most at risk of drop-out so as to maximise the success of obesity interventions. Copyright © 2014 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.

  2. An Analysis of Recruit Training Attrition in the U.S. Marine Corps

    Science.gov (United States)

    1978-02-01

    Administration NR 170-819 I I. CONTROLLING OFFICE NAME AND ADDRESS It. ROILPORT CATS Organizational Effectiveness Research Programs February 1978 / Office of...for over 60% of the administrativo reasons for attrition. This finding underscores the importance of behavioral approaches to understanding and... controlled attrition may serve to confound individual level analyses of attrition. Although the R2 in this study is .10, this is not trivial. This

  3. Encapsulated iron-based oxygen reduction electrocatalysts by high pressure pyrolysis

    DEFF Research Database (Denmark)

    Zhong, Lijie; Hu, Yang; Cleemann, Lars Nilausen

    2017-01-01

    the nitrogen containing precursors and can be improved by post treatment in ammonia. These results indicate the contribution to the catalysis from surface nitrogen functionalities and encapsulated metal-containing nanoparticles. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights......Non-precious metal catalysts (NPMCs) are candidate materials to replace platinum for proton exchange membrane fuel cells (PEMFCs). Herein we reported a type of iron-based NPMCs prepared by high pressure pyrolysis for the oxygen reduction reaction (ORR) in acidic media. The catalysts are in form...... of carbon microspheres in a sub-microscale consisting of iron-containing nanoparticles encapsulated by graphitic layers. By tailoring temperatures and duration of pyrolysis, the best ORR catalyst was achieved at 700 degrees C and 75 min, which exhibits an onset potential of 0.85 V at 0.1 mA cm(-2...

  4. Processing of New Materials by Additive Manufacturing: Iron-Based Alloys Containing Silver for Biomedical Applications

    Science.gov (United States)

    Niendorf, Thomas; Brenne, Florian; Hoyer, Peter; Schwarze, Dieter; Schaper, Mirko; Grothe, Richard; Wiesener, Markus; Grundmeier, Guido; Maier, Hans Jürgen

    2015-07-01

    In the biomedical sector, production of bioresorbable implants remains challenging due to improper dissolution rates or deficient strength of many candidate alloys. Promising materials for overcoming the prevalent drawbacks are iron-based alloys containing silver. However, due to immiscibility of iron and silver these alloys cannot be manufactured based on conventional processing routes. In this study, iron-manganese-silver alloys were for the first time synthesized by means of additive manufacturing. Based on combined mechanical, microscopic, and electrochemical studies, it is shown that silver particles well distributed in the matrix can be obtained, leading to cathodic sites in the composite material. Eventually, this results in an increased dissolution rate of the alloy. Stress-strain curves showed that the incorporation of silver barely affects the mechanical properties.

  5. Nematic fluctuations, fermiology and the pairing potential in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kretzschmar, Florian

    2015-08-18

    The thesis comprises a systematic study on the doping, temperature and momentum dependent electron dynamics in iron-based superconductors using inelastic light scattering. The observation of Bardasis-Schrieffer modes in the excitation spectrum of superconducting Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} is reported and the energy and symmetry dependence of the modes are analyzed. The analysis yields the identification of a strong subdominant component of the interaction potential V(k,k{sup '}). Strong nematic fluctuations are investigated in Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2}. The nature of the fluctuations and the origin of nematicity in Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} are identified.

  6. Tribo-evaluation of iron based metal matrix nanocomposites for heavy duty applications

    Science.gov (United States)

    Gupta, Pallav; Kumar, Devendra; Parkash, Om; Jha, A. K.

    2017-09-01

    The present paper reports dry sliding wear behavior of Iron based Metal Matrix Nanocomposites (MMNCs). Specimens were synthesized by ball milling followed by compaction and sintering in an argon atmosphere. Dry sliding wear behavior of undoped and doped Fe-Al2O3 metal matrix nanocomposite system was evaluated respectively. It was found that due to the reactive sintering between iron and alumina particles a nano iron aluminate phase (FeAl2O4) forms as a result of which the various structural and mechanical properties were found to improve. The results so obtained are critically analyzed and discussed to illustrate the interaction of various process parameters involved. It is expected that the results of the present work will be beneficial in developing quality MMNC products for heavy duty applications.

  7. 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.

  8. Vacuum thermal-mechanical fatigue behavior of two iron-base alloys

    Science.gov (United States)

    Sheffler, K. D.

    1976-01-01

    The present study extends the concept of in-phase grain boundary ratcheting to two iron-base alloys (Type 304 stainless steel and A286 alloy) and provides a clearer interpretation of out-of-phase grain boundary ratcheting effects observed in the A286 alloy which does not exhibit geometric instability. Elevated-temperature low-cycle thermal-mechanical fatigue tests in an ion-pumped ultrahigh vacuum chamber revealed significant effects of frequency and combined temperature-strain cycling on fatigue life. In-phase thermal cycling (tension at high temperature and compression at low temperature) caused large life reductions in both materials due to grain boundary cavitation caused by unreversed grain boundary sliding (grain boundary ratcheting). Out-of-phase thermal cycling (tension at low temperature and compression at high temperature) also caused large cyclic life reductions in both materials. In the A286 alloy, out-of-phase life reductions are attributed to compressive ratcheting.

  9. High-temperature oxidation/corrosion of iron-based superalloys

    Science.gov (United States)

    Lemkey, F. D.; Smeggil, J. G.; Bailey, R. S.; Schuster, J. C.; Nowotny, H.

    1987-01-01

    The oxidation and sulfidation of several novel iron-base superalloys were evaluated in high-temperature cyclic tests. The experimental austenitic alloys examined were modifications of NASAUT-4GA which were developed for Stirling-engine application. The weight gains and resulting surface scales were measured and analyzed. Mixed oxide scales were found to form on all specimens exposed above 871 C. The build-up of these scales led to a depletion of Mn and Cr in a zone adjacent to the oxides. In addition, the initial oxidation of the Fe-rich alloy was inhibited by a thin but tenacious Si layer which formed at the interface between oxides and the parent layer. Sulfidation tests using Na2SO4 coatings resulted in the formation of a protective spinel and alpha-Fe2O3 phases. Preferential attack of the carbide phase by hydrogen was not observed after 350 h at 871 C.

  10. 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.

  11. Nanophase iron-based liquefaction catalysts: synthesis, characterization and model compound reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Matson, D.W.; Lineham, J.C.; Darab, J.G.; Buehler, M.F. (Pacific Northwest Laboratory, Richland, WA (United States))

    Ultrafine nanometer-scale iron-based catalyst precursor powders were generated using two novel technologies, the rapid thermal decomposition of precursors in solution (RTDS) and the modified reverse micelle (MRM) processes. The powders were characterized according to their phase and crystallite size and were evaluated for activity toward C-C bond scission using the model compound, naphthylbibenzylmethane, in the presence of elemental sulfur and 9,10-dihydrophenanthrene. The catalytic activities of the powders were found to be strongly dependent on their crystallographic phase. RTDS magnetite, six-line ferrihydrite, and ferric oxyhydroxysulfate were found to have very high activity toward conversion of the model compound whereas two-line ferrihydrite and hematite were determined to be poor or mediocre catalyst precursors. MRM magnetite/maghemite was also found to be a relatively good catalyst precursor but exhibited reduced activity when compared to the RTDS magnetite. 20 refs., 6 figs., 4 tabs.

  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

    2014-01-03

    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. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Imaging the real space structure of the spin fluctuations in an iron-based superconductor.

    Science.gov (United States)

    Chi, Shun; Aluru, Ramakrishna; Grothe, Stephanie; Kreisel, A; Singh, Udai Raj; Andersen, Brian M; Hardy, W N; Liang, Ruixing; Bonn, D A; Burke, S A; Wahl, Peter

    2017-06-29

    Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonance comes almost exclusively from neutron scattering. Here we demonstrate that by using low-temperature scanning tunnelling microscopy and spectroscopy we can characterize the spin resonance in real space. We show that inelastic tunnelling leads to the characteristic dip-hump feature seen in tunnelling spectra in high temperature superconductors and that this feature arises from excitations of the spin fluctuations. Spatial mapping of this feature near defects allows us to probe non-local properties of the spin susceptibility and to image its real space structure.

  14. Exploring iron-based multifunctional catalysts for Fischer-Tropsch synthesis: a review.

    Science.gov (United States)

    Abelló, Sònia; Montané, Daniel

    2011-11-18

    The continuous increase in oil prices together with an increase in carbon dioxide concentration in the atmosphere has prompted an increased interest in the production of liquid fuels from non-petroleum sources to ensure the continuation of our worldwide demands while maximizing CO(2) utilization. In this sense, the Fischer-Tropsch (FT) technology provides a feasible option to render high value-added hydrocarbons. Alternative sources, such as biomass or coal, offer a real possibility to realize these purposes by making use of H(2)-deficient or CO(2)-rich syngas feeds. The management of such feeds ideally relies on the use of iron catalysts, which exhibit the unique ability to adjust the H(2)/CO molar ratio to an optimum value for hydrocarbon synthesis through the water-gas-shift reaction. Taking advantage of the emerging attention to hybrid FT-synthesis catalysts based on cobalt and their associated benefits, an overview of the current state of literature in the field of iron-based multifunctional catalysts is presented. Of particular interest is the use of zeolites in combination with a FT catalyst in a one-stage operation, herein named multifunctional, which offer key opportunities in the modification of desired product distributions and selectivity, to eventually overcome the quality limitations of the fuels prepared under intrinsic FT conditions. This review focuses on promising research activities addressing the conversion of syngas to liquid fuels mediated by iron-based multifunctional materials, highlights their preparation and properties, and discusses their implication and challenges in the area of carbon utilization through H(2)/CO(+CO(2)) mixtures. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. 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

  16. Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

    Directory of Open Access Journals (Sweden)

    Andrey V. Chubukov

    2016-12-01

    Full Text Available Magnetism and nematic order are the two nonsuperconducting orders observed in iron-based superconductors. To elucidate the interplay between them and ultimately unveil the pairing mechanism, several models have been investigated. In models with quenched orbital degrees of freedom, magnetic fluctuations promote stripe magnetism, which induces orbital order. In models with quenched spin degrees of freedom, charge fluctuations promote spontaneous orbital order, which induces stripe magnetism. Here, we develop an unbiased approach, in which we treat magnetic and orbital fluctuations on equal footing. Key to our approach is the inclusion of the orbital character of the low-energy electronic states into renormalization group (RG analysis. We analyze the RG flow of the couplings and argue that the same magnetic fluctuations, which are known to promote s^{+-} superconductivity, also promote an attraction in the orbital channel, even if the bare orbital interaction is repulsive. We next analyze the RG flow of the susceptibilities and show that, if all Fermi pockets are small, the system first develops a spontaneous orbital order, then s^{+-} superconductivity, and magnetic order does not develop down to T=0. We argue that this scenario applies to FeSe. In systems with larger pockets, such as BaFe_{2}As_{2} and LaFeAsO, we find that the leading instability is either towards a spin-density wave or superconductivity. We argue that in this situation nematic order is caused by composite spin fluctuations and is vestigial to stripe magnetism. Our results provide a unifying description of different iron-based materials.

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

    NARCIS (Netherlands)

    Xie, Jingxiu; Torres Galvis, Hirsa|info:eu-repo/dai/nl/314116249; Koeken, Ard C J|info:eu-repo/dai/nl/322131278; Kirilin, Alexey; Dugulan, A Iulian; Ruitenbeek, Matthijs; de Jong, Krijn P|info:eu-repo/dai/nl/06885580X

    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

  18. Attrition analysed in five waves of a longitudinal yearly survey of smokers: Findings from the ITC Netherlands Survey

    NARCIS (Netherlands)

    Zethof, D.; Nagelhout, G.E.; de Rooij, M.; Driezen, P.; Fong, G.T.; van den Putte, B.; Hummel, K.; de Vries, H.; Thompson, M.E.; Willemsen, M.C.

    Background: Attrition bias can affect the external validity of findings. This article analyses attrition bias and assesses the effectiveness of replenishment samples on demographic and smoking-related characteristics for the International Tobacco Control Netherlands Survey, a longitudinal survey

  19. The Problem of Student Attrition in Higher Education: An Alternative Perspective

    Science.gov (United States)

    Beer, Colin; Lawson, Celeste

    2017-01-01

    Student attrition continues to be a significant and costly challenge for higher education institutions across the globe. In Australia, universities cite the importance of addressing student attrition through strategic statements and policy documents, and expend time and resources on the problem. Despite vast expenditures, they have made little…

  20. Plenary address: Aging attriters : How methodological challenges can help construct bilingual theories

    NARCIS (Netherlands)

    Keijzer, Merel

    (First) language attrition has long established itself as a subfield of the broader realm of bilingualism studies. As such, it can feed off well-researched bilingualism constructs such as transfer, and (bi)directional language interference. But attrition can itself also feed back into bilingual

  1. The Marine Corps Basic Training Experience: Psychosocial Predictors of Performance, Health, and Attrition

    Science.gov (United States)

    1983-01-01

    these variables affect the probability of attrition in some other way. Stress theories do not predict that these variables will influence either how...stresses in BT. Analyses relatingi recruit psychosocial characteristics to BT attrition identified three variables which, on the basis of stress ... theories , may uetermine -20- whether a recruit responds strongly to BT stresses. These variables included emotional control factors (specifically

  2. Who Will Stay and Who Will Leave? Predicting Secondary English Teacher Attrition Risk

    Science.gov (United States)

    Hancock, Carl B.; Scherff, Lisa

    2010-01-01

    Although there are considerable large-scale data on teacher attrition, few researchers have culled information specifically related to English teachers' risk for attrition. This study examines the effects of teacher characteristics, teaching conditions, student variables, self-efficacy, external support, and salary on secondary English language…

  3. Analysis of Students Attrition in the Sciences Subjects Areas in Ambrose Alli University, Ekpoma

    Science.gov (United States)

    Olusi, F. I.; Akahomen, D. O.; Otete, C. O.

    2013-01-01

    The study, analysis of student's attrition in Ambrose Alli University (AAU) Ekpoma Nigeria was carried out to determine the exact number of students who attrite from selected faculties of the university. The study employed the descriptive survey design. Three hypotheses were stated and tested. On the hypothesis which tested the general attrition…

  4. Retention and Attrition in a Home Visiting Programme: Looking Back and Moving Forward

    Science.gov (United States)

    Fifolt, Matthew; Lanzi, Robin G.; Johns, Elisabeth; Strichik, Tracye; Preskitt, Julie

    2017-01-01

    Objective: The purpose of this study was to investigate retention and attrition in First Teacher, Alabama's Maternal, Infant, and Early Childhood Home Visiting (MIECHV) programme. Methods: Secondary data analysis was used to identify families that were most likely to leave through attrition; focus groups were conducted to discuss potential reasons…

  5. Analyzing the Findings of the Saudi Research on Student Attrition in Higher Education

    Science.gov (United States)

    Aljohani, Othman

    2016-01-01

    This paper presents a comprehensive review of the available literature on student attrition in Saudi higher education context. Despite the reported low student retention rates in Saudi tertiary institutions, student attrition remains an under-researched phenomenon. Thus, this paper aims to trace and collect all the available studies that addressed…

  6. Completion and Attrition Rates for Apprentices and Trainees 2014. Australian Vocational Education and Training Statistics

    Science.gov (United States)

    National Centre for Vocational Education Research (NCVER), 2015

    2015-01-01

    This publication presents completion and attrition rates for apprentices and trainees using three different methodologies: (1) contract completion and attrition rates: based on the outcomes of contracts of training; (2) individual completion rates: based on contract completion rates and adjusted for factors representing average recommencements by…

  7. Measuring (and Managing) the Invisible Costs of Postsecondary Attrition. Policy Brief

    Science.gov (United States)

    Wellman, Jane; Johnson, Nate; Steele, Patricia

    2012-01-01

    The collision between funding realities and the paramount goal of increasing educational attainment has brought new attention to ways to reduce postsecondary attrition and get more students who enroll in college to complete a degree or credential. Reductions in attrition are both educationally effective and cost effective. Students reach…

  8. Theoretical and Empirical Underpinnings of the What Works Clearinghouse Attrition Standard for Randomized Controlled Trials

    Science.gov (United States)

    Deke, John; Chiang, Hanley

    2014-01-01

    Meeting the What Works Clearinghouse (WWC) attrition standard (or one of the attrition standards based on the WWC standard) is now an important consideration for researchers conducting studies that could potentially be reviewed by the WWC (or other evidence reviews). Understanding the basis of this standard is valuable for anyone seeking to meet…

  9. The Cost of College Attrition at Four-Year Colleges & Universities. Policy Perspectives

    Science.gov (United States)

    Raisman, Neal

    2013-01-01

    This report, an analysis of 1669 U.S. institutions, is a first-time study of the relationship of attrition to revenues lost in four-year public, private, and for-profit colleges and universities on an annual basis. The report is the result of a study investigating the financial impact of attrition on four-year colleges and universities. Other…

  10. Australian Vocational Education and Training Statistics: Completion and Attrition Rates for Apprentices and Trainees, 2010

    Science.gov (United States)

    National Centre for Vocational Education Research (NCVER), 2011

    2011-01-01

    By tracking the outcome of a contract of training over time, individuals can measure contract completion and attrition rates. This method requires enough time to pass to accurately report on outcomes for the majority of contracts. This publication presents completion and attrition rates for apprentices and trainees using three different…

  11. 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…

  12. Spiritual Practices as a Means of Coping with and Ameliorating Stress to Reduce Teacher Attrition

    Science.gov (United States)

    Hartwick, James M. M.; Kang, Shin Ji

    2013-01-01

    Teacher attrition has been a serious problem in maintaining quality education in the United States. Although the research produced extensive documentation on teachers' stress and attrition, little attention has been paid to their spiritual stress coping strategies. This article documents various spiritual practices as a means of coping with…

  13. Language Aptitude in First Language Attrition: A Study on Late Spanish-Swedish Bilinguals

    Science.gov (United States)

    Bylund, Emanuel; Ramírez-Galan, Pedro

    2016-01-01

    Language aptitude remains one of the most understudied predictor variables in L1 attrition research. The current study seeks to address this gap by investigating the effects of language aptitude on L1 retention in late attriters. Forty L1 Spanish-L2 Swedish bilinguals living in Sweden participated in the study, along with 20 functionally…

  14. Stemming the Revolving Door: Teacher Retention and Attrition in Arctic Alaska Schools

    Science.gov (United States)

    Kaden, Ute; Patterson, Philip P.; Healy, Joanne; Adams, Barbara L.

    2016-01-01

    Limited research is available concerning teacher retention and teacher attrition in Arctic Alaska. This paper reports survey research findings, which identify factors related to teacher retention and attrition in Alaskan Arctic Native communities. Teacher retention rates (2009-2013) vary widely over time showing no significant trends. Results…

  15. Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

    Science.gov (United States)

    2014-11-01

    in which the aluminum alloy powder size refinement occurs at cryogenic temperatures. Milling is a process of grinding solid matter under exposure...Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and

  16. Second/Foreign Language Teacher Efficacy and Its Relationship to Professional Attrition

    Science.gov (United States)

    Swanson, Peter

    2012-01-01

    There is a shortage of second/foreign language (S/FL) teachers in many parts of the world and the attrition rates are startling. The present study, grounded in social cognitive theory, investigates Canadian and US teachers' (N = 1065) sense of efficacy in teaching languages as it relates to teacher attrition. Findings indicate that S/FL teachers…

  17. Differential Effects of Language Attrition in the Domains of Verb Placement and Object Expression

    Science.gov (United States)

    Flores, Cristina

    2012-01-01

    This study investigates the differential effects of language attrition in two diverse linguistic domains: verb placement and object expression. Linguistic phenomena at the syntax--discourse interface, such as object expression, have been shown to be more vulnerable to attrition than narrow syntax properties, such as verb placement. This study aims…

  18. Academic Momentum and Undergraduate Student Attrition: Comparative Analysis in US and Russian Universities

    Science.gov (United States)

    Kondratjeva, Olga; Gorbunova, Elena V.; Hawley, Joshua D.

    2017-01-01

    Student attrition in postsecondary education is a significant public policy problem. Nations invest substantial resources in college systems, and when students leave, this investment is lost. To understand the factors that influence student attrition in US and Russian public universities, we use the perspective of academic momentum, defined…

  19. Attrition in Developmental Psychology: A Review of Modern Missing Data Reporting and Practices

    Science.gov (United States)

    Nicholson, Jody S.; Deboeck, Pascal R.; Howard, Waylon

    2017-01-01

    Inherent in applied developmental sciences is the threat to validity and generalizability due to missing data as a result of participant drop-out. The current paper provides an overview of how attrition should be reported, which tests can examine the potential of bias due to attrition (e.g., t-tests, logistic regression, Little's MCAR test,…

  20. Travel time and attrition from VHA care among women veterans: how far is too far?

    Science.gov (United States)

    Friedman, Sarah A; Frayne, Susan M; Berg, Eric; Hamilton, Alison B; Washington, Donna L; Saechao, Fay; Maisel, Natalya C; Lin, Julia Y; Hoggatt, Katherine J; Phibbs, Ciaran S

    2015-04-01

    Travel time, an access barrier, may contribute to attrition of women veterans from Veterans Health Administration (VHA) care. We examined whether travel time influences attrition: (a) among women veterans overall, (b) among new versus established patients, and (c) among rural versus urban patients. This retrospective cohort study used logistic regression to estimate the association between drive time and attrition, overall and for new/established and rural/urban patients. In total, 266,301 women veteran VHA outpatients in the Fiscal year 2009. An "attriter" did not return for VHA care during the second through third years after her first 2009 visit (T0). Drive time (log minutes) was between the patient's residence and her regular source of VHA care. "New" patients had no VHA visits within 3 years before T0. Models included age, service-connected disability, health status, and utilization as covariates. Overall, longer drive times were associated with higher odds of attrition: drive time adjusted odds ratio=1.11 (99% confidence interval, 1.09-1.14). The relationship between drive time and attrition was stronger among new patients but was not modified by rurality. Attrition among women veterans is sensitive to longer drive time. Linking new patients to VHA services designed to reduce distance barriers (telemedicine, community-based clinics, mobile clinics) may reduce attrition among women new to VHA.

  1. Mining Rare Events Data for Assessing Customer Attrition Risk

    Science.gov (United States)

    Au, Tom; Chin, Meei-Ling Ivy; Ma, Guangqin

    Customer attrition refers to the phenomenon whereby a customer leaves a service provider. As competition intensifies, preventing customers from leaving is a major challenge to many businesses such as telecom service providers. Research has shown that retaining existing customers is more profitable than acquiring new customers due primarily to savings on acquisition costs, the higher volume of service consumption, and customer referrals. For a large enterprise, its customer base consists of tens of millions service subscribers, more often the events, such as switching to competitors or canceling services are large in absolute number, but rare in percentage, far less than 5%. Based on a simple random sample, popular statistical procedures, such as logistic regression, tree-based method and neural network, can sharply underestimate the probability of rare events, and often result a null model (no significant predictors). To improve efficiency and accuracy for event probability estimation, a case-based data collection technique is then considered. A case-based sample is formed by taking all available events and a small, but representative fraction of nonevents from a dataset of interest. In this article we showed a consistent prior correction method for events probability estimation and demonstrated the performance of the above data collection techniques in predicting customer attrition with actual telecommunications data.

  2. Analytical modelling for ultrasonic surface mechanical attrition treatment

    Directory of Open Access Journals (Sweden)

    Guan-Rong Huang

    2015-07-01

    Full Text Available The grain refinement, gradient structure, fatigue limit, hardness, and tensile strength of metallic materials can be effectively enhanced by ultrasonic surface mechanical attrition treatment (SMAT, however, never before has SMAT been treated with rigorous analytical modelling such as the connection among the input energy and power and resultant temperature of metallic materials subjected to SMAT. Therefore, a systematic SMAT model is actually needed. In this article, we have calculated the averaged speed, duration time of a cycle, kinetic energy and kinetic energy loss of flying balls in SMAT for structural metallic materials. The connection among the quantities such as the frequency and amplitude of attrition ultrasonic vibration motor, the diameter, mass and density of balls, the sample mass, and the height of chamber have been considered and modelled in details. And we have introduced the one-dimensional heat equation with heat source within uniform-distributed depth in estimating the temperature distribution and heat energy of sample. In this approach, there exists a condition for the frequency of flying balls reaching a steady speed. With these known quantities, we can estimate the strain rate, hardness, and grain size of sample.

  3. Analytical modelling for ultrasonic surface mechanical attrition treatment

    Science.gov (United States)

    Huang, Guan-Rong; Tsai, W. Y.; Huang, J. C.; Hu, Chin-Kun

    2015-07-01

    The grain refinement, gradient structure, fatigue limit, hardness, and tensile strength of metallic materials can be effectively enhanced by ultrasonic surface mechanical attrition treatment (SMAT), however, never before has SMAT been treated with rigorous analytical modelling such as the connection among the input energy and power and resultant temperature of metallic materials subjected to SMAT. Therefore, a systematic SMAT model is actually needed. In this article, we have calculated the averaged speed, duration time of a cycle, kinetic energy and kinetic energy loss of flying balls in SMAT for structural metallic materials. The connection among the quantities such as the frequency and amplitude of attrition ultrasonic vibration motor, the diameter, mass and density of balls, the sample mass, and the height of chamber have been considered and modelled in details. And we have introduced the one-dimensional heat equation with heat source within uniform-distributed depth in estimating the temperature distribution and heat energy of sample. In this approach, there exists a condition for the frequency of flying balls reaching a steady speed. With these known quantities, we can estimate the strain rate, hardness, and grain size of sample.

  4. 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.

  5. Beyond demographics: Predicting student attrition within the Bachelor of Arts degree

    Directory of Open Access Journals (Sweden)

    Andrew Harvey

    2014-03-01

    Full Text Available This paper examines factors linked to first year attrition within the Bachelor of Arts (BA degree at an Australian university. Drawing on a broad range of institutional data, the authors considered correlations between attrition and several variables. Our research revealed the need to move beyond analysis of geo-demographic factors towards indicators of student choice and educational achievement. While few demographic factors were found to be strong indicators of attrition, two other factors were clearly correlated. These factors – course preference, and first year educational performance – were significant predictors of attrition. Because subject failure is the single strongest predictor of attrition, and because the BA offers a wide range of subjects, developing strategies to ensure consistency and quality across those subjects is imperative.

  6. Patient attrition from the HIV antiretroviral therapy program at two hospitals in Haiti

    Science.gov (United States)

    Puttkammer, Nancy H.; Zeliadt, Steven B.; Baseman, Janet G.; Destiné, Rodney; Domerçant, Jean Wysler; Coq, Nancy Rachel Labbé; Raphael, Nernst Atwood; Sherr, Kenneth; Tegger, Mary; Yuhas, Krista; Barnhart, Scott

    2016-01-01

    Objective To identify factors associated with antiretroviral therapy (ART) attrition among patients initiating therapy in 2005–2011 at two large, public-sector department-level hospitals, and to inform interventions to improve ART retention. Methods This retrospective cohort study used data from the iSanté electronic medical record (EMR) system. The study characterized ART attrition levels and explored the patient demographic, clinical, temporal, and service utilization factors associated with ART attrition, using time-to-event analysis methods. Results Among the 2 023 patients in the study, ART attrition on average was 17.0 per 100 person-years (95% confidence interval (CI): 15.8–18.3). In adjusted analyses, risk of ART attrition was up to 89% higher for patients living in distant communes compared to patients living in the same commune as the hospital (hazard ratio: 1.89, 95%CI: 1.54–2.33; P Haiti. PMID:25563149

  7. Multifunctional iron-based metal oxide nanostructured materials: Synthesis, characterization, and properties

    Science.gov (United States)

    Park, Tae-Jin

    Iron-based metal oxides, such as iron oxides, iron-containing perovskites, and iron-containing perovskite composites or solid solutions, are promising materials for the design and synthesis of technologically important multifunctional materials. They are noteworthy for their unique and diverse properties including electronic, magnetic, and elastic ones. Stimulated by interest in the bulk properties of these materials as well as scientific potential and applications at the nanoscale, iron-based metal oxide nanostructured (FeMONS) materials are being considered as an interesting model system to investigate fundamental properties and for a host of potential applications as diverse as additives, catalysts, electronic devices, magnetic recording media, information storage, spintronics, and sensors. Recent research on a multiferroic system, such as BiFeO3, reveals that there are unique couplings among the independent physical properties including ferroelectricity, ferromagnetism, and ferroelasticity. Developing approaches to designing as well as investigating properties of new synthetic formulations of these transition metal oxide nanomaterials has been the recent focus of much of our efforts in this group. Multiferroic bismuth ferrite (BiFeO 3) nanoparticles have been synthesized employing a facile sol-gel method and their size-dependent magnetic properties have been studied and correlated with: (i) increased suppression of the known spiral spin structure (period length of ˜62 nm) with decreasing nanoparticle size and (ii) uncompensated spins and strain anisotropies at the surface. Moreover, BiFeO 3 nanotubes have been generated using a modified template methodology and extensively characterized. Furthermore, solid solutions of BiFeO 3 and typical perovskites, such as BaTiO3 and SrTiO 3, have been prepared employing a molten salt method and the study has been extended to properties associated with their inherent compositions. Single-crystalline Bi2Fe4O9 nanocubes have

  8. [Sucroferric oxyhydroxide, a novel iron-based phosphate binder. Which current use in dialysis patients?

    Science.gov (United States)

    Bataille, Pierre; Delattre, Vincent; Daroux, Maité

    2017-04-01

    International guidelines suggest lowering elevated phosphorus level to the normal range in patients on dialysis. Among the phosphate-lowering strategies, phosphate binder is frequently used in addition to dietary phosphate restriction and an adequate dialysis strategy. However, serum phosphate concentration higher than 1.78mmol/L is observed in more than 40% of patients justifying the quest for new drugs. Sucroferric oxyhydroxide is one of the new iron-based agents and is available in France since May 2016. A recent international multicentre study showed this new drug to be as efficacious and non-inferior to sevelamer carbonate in magnitude of serum phosphate control. The serum phosphorus-lowering effect was maintained over 1year. When compared to carbonate sevelamer, the pill-burden was half with sucroferric oxyhydroxide because of its high phosphate binding capacity. As previously shown by experimental studies, no risk of iron accumulation was observed since iron absorption is negligible. Discolored feces and diarrhea were fairly frequent side effects. When diarrhea subsides, the tolerability of this new phosphate binder is excellent on a long-term basis. Copyright © 2017 Association Société de néphrologie. Published by Elsevier Masson SAS. All rights reserved.

  9. Coupling Inward Diffusion and Precipitation Kinetics; the Case of Nitriding Iron-Based Alloys

    Science.gov (United States)

    Jung, Minsu; Meka, Sai Ramudu; Rheingans, Bastian; Mittemeijer, Eric Jan

    2016-03-01

    A model that describes the inward diffusion of an element I into a solid substrate and the simultaneous precipitation of a compound M y I z , with M as the alloying element initially dissolved in the substrate matrix, is presented for the case of nitriding iron-based alloys. The model was developed by coupling the diffusion kinetics and the precipitation (nucleation and growth) kinetics. Additionally, the role of excess nitrogen and the kinetics of ammonia dissociation at the iron surface were incorporated into this coupled model. The model was successfully applied to the case of nitriding an Fe-2.23 at. pct V alloy; the simulation results are in good agreement with the measured data and allow for detailed understanding of the evolution of the nitride precipitates (volume fraction, number density, and size distribution) as a function of both nitriding time and depth in the specimen. The present model exposed the pronounced effects of the precipitation kinetics, of excess nitrogen, and of the surface-reaction kinetics on the overall nitriding kinetics and demonstrated a striking, nonmonotonous change with time of precipitate particle size at a distinct depth in the specimen.

  10. Atomistic simulations of deuterium irradiation on iron-based alloys in future fusion reactors

    Directory of Open Access Journals (Sweden)

    E. Safi

    2016-12-01

    Full Text Available Iron-based alloys are now being considered as plasma-facing materials for the first wall of future fusion reactors. Therefore, the iron (Fe and carbon (C erosion will play a key role in predicting the life-time and viability of reactors with steel walls. In this work, the surface erosion and morphology changes due to deuterium (D irradiation in pure Fe, Fe with 1% C impurity and the cementite, are studied using molecular dynamics (MD simulations, varying surface temperature and impact energy. The sputtering yields for both Fe and C were found to increase with incoming energy. In iron carbide, C sputtering was preferential to Fe and the deuterium was mainly trapped as D2 in bubbles, while mostly atomic D was present in Fe and Fe–1%C. The sputtering yields obtained from MD were compared to SDTrimSP yields. At lower impact energies, the sputtering mechanism was of both physical and chemical origin, while at higher energies (>100eV the physical sputtering dominated.

  11. Coexistence of ferromagnetism and superconductivity in iron based pnictides: a time resolved magnetooptical study.

    Science.gov (United States)

    Pogrebna, A; Mertelj, T; Vujičić, N; Cao, G; Xu, Z A; Mihailovic, D

    2015-01-13

    Ferromagnetism and superconductivity are antagonistic phenomena. Their coexistence implies either a modulated ferromagnetic order parameter on a lengthscale shorter than the superconducting coherence length or a weak exchange coupling between the itinerant superconducting electrons and the localized ordered spins. In some iron based pnictide superconductors the coexistence of ferromagnetism and superconductivity has been clearly demonstrated. The nature of the coexistence, however, remains elusive since no clear understanding of the spin structure in the superconducting state has been reached and the reports on the coupling strength are controversial. We show, by a direct optical pump-probe experiment, that the coupling is weak, since the transfer of the excess energy from the itinerant electrons to ordered localized spins is much slower than the electron-phonon relaxation, implying the coexistence without the short-lengthscale ferromagnetic order parameter modulation. Remarkably, the polarization analysis of the coherently excited spin wave response points towards a simple ferromagnetic ordering of spins with two distinct types of ferromagnetic domains.

  12. Fermi surface deformation in a simple iron-based superconductor, FeSe

    Science.gov (United States)

    Coldea, Amalia; Watson, Matthew; Kim, Timur; Haghighirad, Amir; McCollam, Alix; Hoesch, Moritz; Schofield, Andrew

    2015-03-01

    One of the outstanding problems in the field superconductivity is the identification of the normal state out of which superconductivity emerges. FeSe is one of the simplest and most intriguing iron-based superconductors, since in its bulk form it undergoes a structural transition before it becomes superconducting, whereas its single-layer form is believed to be a high-temperature superconductor. The nature of the structural transition, occurring in the absence of static magnetism, is rather unusual and how the electronic structure is stabilized by breaking of the rotational symmetry is the key to understand the superconductivity in bulk FeSe. Here we report angle-resolved photoemission spectroscopy measurements on FeSe that gives direct access to the band structure and orbital-dependent effects. We complement our studies on bulk FeSe with low-temperature angular-dependent quantum oscillation measurements using applied magnetic fields that are sufficiently strong to suppress superconductivity and reach the normal state. These studies reveal a strong deformation of Fermi surface through the structural transition driven by electronic correlations and orbital-dependent effects. . This work was supported by EPSRC, UK (EP/I004475/1), Diamond Light Source, UK and HFML, Nijmegen.

  13. Correlation-driven metal-insulator transition in proximity to an iron-based superconductor

    Science.gov (United States)

    Charnukha, A.; Yin, Z. P.; Song, Y.; Cao, C. D.; Dai, Pengcheng; Haule, K.; Kotliar, G.; Basov, D. N.

    2017-11-01

    We report the direct spectroscopic observation of a metal to correlated-insulator transition in the family of iron-based superconducting materials. By means of optical spectroscopy we demonstrate that the excitation spectrum of NaFe1 -xCuxAs develops a large gap with increasing copper substitution. Dynamical mean-field theory calculations show a good agreement with the experimental data and suggest that the formation of the charge gap requires an intimate interplay of strong on-site electronic correlations and spin-exchange coupling, revealing the correlated Slater-insulator nature of the antiferromagnetic ground state. Our calculations further predict the high-temperature paramagnetic state of the same compound to be a highly incoherent correlated metal. We verify this prediction experimentally by showing that the doping-induced weakening of antiferromagnetic correlations enables a thermal crossover from an insulating to an incoherent metallic state. Redistribution of the optical spectral weight in this crossover uncovers the characteristic energy of Hund's-coupling and Mott-Hubbard electronic correlations essential for the electronic localization. Our results demonstrate that NaFe1 -xCuxAs continuously transitions from the typical itinerant phases of iron pnictides to a highly incoherent metal and ultimately a correlated insulator. Such an electronic state is expected to favor high-temperature superconductivity.

  14. Common ground: Addressing attrition across diverse institutions in higher education

    Directory of Open Access Journals (Sweden)

    Rebecca L. Jobe

    2014-06-01

    Full Text Available Student attrition is an ongoing concern in American higher education, where institutions are being increasingly held accountable for the success of the students they admit. While differences across diverse institutions exist, research suggests that there are many similarities regarding issues related to student persistence and success. In fact, this common ground presents an opportunity for common solutions. The variety of higher education institutions utilizing knowledge gained through institutional initiatives continues to identify new, better ways of serving students. This article sheds light on the known differences between institution types while recognizing the common goals of improving student persistence. The article further supports the need for additional research in this area to fully understand how the higher education community can best prepare and support students of all types, from all institutions, to reach their educational goals. DOI: 10.18870/hlrc.v4i2.209

  15. The interactions between attrition, abrasion and erosion in tooth wear.

    Science.gov (United States)

    Shellis, R Peter; Addy, Martin

    2014-01-01

    Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Knowledge of these tooth wear processes and their interactions is reviewed. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence is insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear, especially through formation of pellicle, but cannot prevent it. © 2014 S. Karger AG, Basel.

  16. Association of General Surgery Resident Remediation and Program Director Attitudes With Resident Attrition.

    Science.gov (United States)

    Schwed, Alexander C; Lee, Steven L; Salcedo, Edgardo S; Reeves, Mark E; Inaba, Kenji; Sidwell, Richard A; Amersi, Farin; Are, Chandrakanth; Arnell, Tracey D; Damewood, Richard B; Dent, Daniel L; Donahue, Timothy; Gauvin, Jeffrey; Hartranft, Thomas; Jacobsen, Garth R; Jarman, Benjamin T; Melcher, Marc L; Mellinger, John D; Morris, Jon B; Nehler, Mark; Smith, Brian R; Wolfe, Mary; Kaji, Amy H; de Virgilio, Christian

    2017-12-01

    Previous studies of resident attrition have variably included preliminary residents and likely overestimated categorical resident attrition. Whether program director attitudes affect attrition has been unclear. To determine whether program director attitudes are associated with resident attrition and to measure the categorical resident attrition rate. This multicenter study surveyed 21 US program directors in general surgery about their opinions regarding resident education and attrition. Data on total resident complement, demographic information, and annual attrition were collected from the program directors for the study period of July 1, 2010, to June 30, 2015. The general surgery programs were chosen on the basis of their geographic location, previous collaboration with some coauthors, prior work in surgical education and research, or a program director willing to participate. Only categorical surgical residents were included in the study; thus, program directors were specifically instructed to exclude any preliminary residents in their responses. Five-year attrition rates (2010-2011 to 2014-2015 academic years) as well as first-time pass rates on the General Surgery Qualifying Examination and General Surgery Certifying Examination of the American Board of Surgery (ABS) were collected. High- and low-attrition programs were compared. The 21 programs represented different geographic locations and 12 university-based, 3 university-affiliated, and 6 independent program types. Programs had a median (interquartile range [IQR]) number of 30 (20-48) categorical residents, and few of those residents were women (median [IQR], 12 [5-17]). Overall, 85 of 966 residents (8.8%) left training during the study period: 15 (17.6%) left after postgraduate year 1, 34 (40.0%) after postgraduate year 2, and 36 (42.4%) after postgraduate year 3 or later. Forty-four residents (51.8%) left general surgery for another surgical discipline, 21 (24.7%) transferred to a different surgery

  17. Are Final Comments in Web Survey Panels Associated with Next-Wave Attrition?

    Directory of Open Access Journals (Sweden)

    Cynthia McLauchlan

    2016-12-01

    Full Text Available Near the end of a web survey respondents are often asked whether they have further comments. Such final comments are usually ignored, in part because open-ended questions are challenging to analyse. We explored whether final comments are associated with next-wave attrition in survey panels. We categorized a random sample of final comments in the Longitudinal Studies for the Social Sciences (LISS panel and Dutch Immigrant panel into one of eight categories (neutral, positive, six subcategories of negative and regressed the indicator of next-wave attrition on comment length, comment category and socio-demographic variables. In the Immigrant panel we found shorter final comments (55 words with decreased next-wave attrition relative to making no comment. Comments about unclear survey questions quadruple the odds of attrition and “other” (uncategorized negative comments almost double the odds of attrition. In the LISS panel, making a comment (vs. not and comment length are not associated with attrition. However, when specifying individual comment categories, neutral comments are associated with half the odds of attrition relative to not making a comment.

  18. [Study of dental attrition in a medieval adult population from Southwest France].

    Science.gov (United States)

    Esclassan, R; Boimond, L; Sevin, A; Donat, R; Lucas, S; Grimoud, A M

    2009-02-01

    The aim of the authors was to study dental attrition in a medieval sample of paired mandibles and maxillas from the Southwest France (IX to XV century). We selected 58 adult individuals with maxillas and mandibles in good state of conservation, 29 women and 29 men from the medieval collection of Vilarnau-d'Amont (Western Pyrenees, France). Attrition was graded according to the Brabant index. We found a high prevalence of attrition in this sample. The first molars (M1) were the maxillary and mandibular teeth most concerned by attrition. The most frequent attrition level was level 2, with dentin exposure. We did not find any significant difference of tooth wear between maxillary and mandibular teeth, even if maxillary teeth seemed to be more worn. There was symmetry of attrition between the left and right side. There was no significant difference between men and women. Working on paired mandibles and maxillas showed that attrition in the middle age was a global phenomenon, intermaxillary and symmetric. It was much more severe than today, rapidly evolving and generalized because of the abrasive quality of food, cooking, chewing habits, and intensity of chewing pressure.

  19. CFD-DEM Analysis of Particle Attrition in a Jet in a Fluidised Bed

    Science.gov (United States)

    Fulchini, F.; Nan, W.; Ghadiri, M.; Yazdan Panah, M.; Bertholin, S.; Amblard, B.; Cloupet, A.; Gauthier, T.

    2017-06-01

    In fluidised bed processes, the solids are in vigorous motion and thus inevitably subjected to mechanical stresses due to inter-particle and particle-wall impacts. These stresses lead to a gradual degradation of the particles by surface wear, abrasion and body fragmentation commonly termed attrition. One significant contribution of attrition comes from the air jets of the fluidised bed distributor. Particles are entrained into the air jet, where they get accelerated and impacted onto the fluidised bed particles. The jet induced attrition only affects the part of the bed which is limited by the jet length, where the mode of attrition is largely collisional. The overall jet attrition rate is therefore the result of the combination of the single particle damage and the flux of particles entering into that region. The attrition behaviour of particles in the jet region is analysed by evaluating their propensity of breakage experimentally and by simulating an air-jet in a bed of particles by CFD-DEM. The frequency of collisions and impact velocities are estimated from which the attrition due to a single air-jet is predicted.

  20. Dental attrition models predicting temporomandibular joint disease or masticatory muscle pain versus asymptomatic controls.

    Science.gov (United States)

    Seligman, D A; Pullinger, A G

    2006-11-01

    To determine whether patients with temporomandibular joint disease or masticatory muscle pain can be usefully differentiated from asymptomatic controls using multifactorial classification tree models of attrition severity and/or rates. Measures of attrition severity and rates in patients diagnosed with disc displacement (n = 52), osteoarthrosis (n = 74), or masticatory muscle pain only (n = 43) were compared against those in asymptomatic controls (n = 132). Cross-validated classification tree models were tested for fit with sensitivity, specificity, accuracy and log likelihood accountability. The model for identifying asymptomatic controls only required the three measures of attrition severity (anterior, mediotrusive and laterotrusive posterior) to be differentiated from the patients with a 74.2 +/- 3.8% cross-validation accuracy. This compared with cross-validation accuracies of 69.7 +/- 3.7% for differentiating disc displacement using anterior and laterotrusive attrition severity, 68.7 +/- 3.9% for differentiating disc displacement using anterior and laterotrusive attrition rates, 70.9 +/- 3.3% for differentiating osteoarthrosis using anterior attrition severity and rates, 94.6 +/- 2.1% for differentiating myofascial pain using mediotrusive and laterotrusive attrition severity, and 92.0 +/- 2.1% for differentiating myofascial pain using mediotrusive and anterior attrition rates. The myofascial pain models exceeded the > or =75% sensitivity and > or =90% specificity thresholds recommended for diagnostic tests, and the asymptomatic control model approached these thresholds. Multifactorial models using attrition severity and rates may differentiate masticatory muscle pain patients from asymptomatic controls, and have some predictive value for differentiating intracapsular temporomandibular disorder patients as well.

  1. Socio-demographic, anthropometric, and psychosocial predictors of attrition across behavioral weight-loss trials.

    Science.gov (United States)

    Goode, Rachel W; Ye, Lei; Sereika, Susan M; Zheng, Yaguang; Mattos, Meghan; Acharya, Sushama D; Ewing, Linda J; Danford, Cynthia; Hu, Lu; Imes, Christopher C; Chasens, Eileen; Osier, Nicole; Mancino, Juliet; Burke, Lora E

    2016-01-01

    Preventing attrition is a major concern in behavioral weight loss intervention studies. The purpose of this analysis was to identify baseline and six-month predictors associated with participant attrition across three independent clinical trials of behavioral weight loss interventions (PREFER, SELF, and SMART) that were conducted over 10 years. Baseline measures included body mass index, Barriers to Healthy Eating, Beck Depression Inventory-II (BDI), Hunger Satiety Scale (HSS), Binge Eating Scale (BES), Medical Outcome Study Short Form (MOS SF-36 v2) and Weight Efficacy Lifestyle Questionnaire (WEL). We also examined early weight loss and attendance at group sessions during the first 6 months. Attrition was recorded at the end of the trials. Participants included 504 overweight and obese adults seeking weight loss treatment. The sample was 84.92% female and 73.61% white, with a mean (± SD) age of 47.35 ± 9.75 years. After controlling for the specific trial, for every one unit increase in BMI, the odds of attrition increased by 11%. For every year increase in education, the odds of attrition decreased by 10%. Additional predictors of attrition included previous attempts to lose 50-79 lbs, age, not possessing health insurance, and BES, BDI, and HSS scores. At 6 months, the odds of attrition increased by 10% with reduced group session attendance. There was also an interaction between percent weight change and trial (pthree trials showed education, age, BMI, and BES scores were independently associated with attrition (ps ≤ .01). These findings may inform the development of more robust strategies for reducing attrition. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. The Vanishing Pronoun: A Case Study of Language Attrition in Russian

    Directory of Open Access Journals (Sweden)

    Dmitri Priven

    2002-06-01

    Full Text Available Abstract This study presents a shifting pattern in the use of second person singular pronouns of address in Russian by adult Russian immigrants in Toronto. The newly developing pattern is treated as a case of L1 attrition. The observed changes to the pronominal system of Russian are discussed in the framework typically employed in language attrition literature, with reference to various linguistic phenomena such as lexical transfer, simplification of morphosyntax, markedness theory and competence vs. performance attrition. Reference is also made to sociolinguistic phenomena such as L1/L2 use in sociolinguistic domains, ethnolinguisitic vitality and shift in cultural identity.

  3. Effect of surface mechanical attrition treatment on biodegradable Mg-1Ca alloy.

    Science.gov (United States)

    Li, N; Li, Y D; Li, Y X; Wu, Y H; Zheng, Y F; Han, Y

    2014-02-01

    Surface mechanical attrition treatment (SMAT) is considered to be an effective approach to obtain a nanostructured layer in the treated surface of metals. In this study, we evaluated the effect of SMAT on the microstructure, mechanical properties and corrosion properties of biodegradable Mg-1Ca alloy, with pure Mg as control. Grain refinement layers with grain size at the nanometer scale in the topmost surface were successfully prepared on Mg-1Ca alloy using SMAT technique, similar to pure Mg. The SMAT not only refined the surface layer of Mg-1Ca alloy, but also promoted the re-dissolution of the Mg2Ca phase into the matrix. As a result, the microhardness of the SMATed samples in the near-surface region was considerably enhanced, and the surface roughness and wettability of the SMATed samples were increased. However, the SMAT led to high density of crystalline defects such as grain boundaries (subgrain boundaries) and dislocations, which severely weakened the corrosion resistance of Mg-1Ca alloy, same as pure Mg. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Study on side effects of iron-based amendments on soil structure

    Science.gov (United States)

    Gargiulo, Laura; Mele, Giacomo; Di Matteo, Bruno; Terribile, Fabio

    2013-04-01

    Recent trends in green and sustainable remediation require an increased attention on the environmental side effects. Among them the physical consequences of soil remediation practices on soil structure are very rarely investigated, although such physical property largely influences the soil quality. The use of in situ elemental immobilization by means iron-based technologies is rapidly developing in contaminated land and groundwater remediation. Iron-rich soil amendments may be applied as part of "assisted natural remediation" schemes at metal/metalloid contaminated sites to immobilize contaminants and then improve vegetation growth and microbial diversity, and reduce offsite metal transport. The current approach is to evaluate the mobility of heavy metals in soil and their translocation to plants rather than to verify also the extent of modifications occurred to some key characteristics of soil structure after the remediation practices. The aim of this work was to focus on the direct quantification of the effects of iron-rich soil amendments on soil pore system and on the understanding of the underlying physical mechanisms. A laboratory experiment was carried out by adding iron grit to three different soils subjected to several wetting-drying cycles. The physical effects of the treatment on soil pore system were identified and quantified combining soil micromorphology and pore image analysis. The impact of iron grit on soil structure resulted strongly influenced by some soil physical properties. In high shrinkage-swelling soils was observed a porosity increase, more evident in the less plastic soil, while in the very low shrinking-swelling soil the porosity decreased. The obtained results showed overall the high potential of soil micromorphology and pore image analysis in order to evaluate the environmental impact of soil remediation practices.

  5. Versatile and Biomass Synthesis of Iron-based Nanoparticles Supported on Carbon Matrix with High Iron Content and Tunable Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dongmao [ORNL; Shi, Sheldon Q [ORNL; Jiang, Dongping [Mississippi State University (MSU); Che, Wen [Mississippi State University (MSU); Gai, Zheng [ORNL; Howe, Jane Y [ORNL; More, Karren Leslie [ORNL; Arockiasamy, Antonyraj [Mississippi State University (MSU)

    2012-01-01

    Iron-based nanoparticles supported on carbon (FeNPs{at}C) have enormous potential for environmental applications. Reported is a biomass-based method for FeNP{at}C synthesis that involves pyrolysis of bleached wood fiber pre-mixed with Fe{sub 3}O{sub 4} nanoparticles. This method allows synthesis of iron-based nanoparticles with tunable chemical reactivity by changing the pyrolysis temperature. The FeNP{at}C synthesized at a pyrolysis temperature of 500 C (FeNP{at}C-500) reacts violently (pyrophoric) when exposed to air, while FeNP{at}C prepared at 800 C (FeNP{at}C-800) remains stable in ambient condition for at least 3 months. The FeNPs in FeNP{at}C-800 are mostly below 50 nm in diameter and are surrounded by carbon. The immediate carbon layer (within 5-15 nm radius) on the FeNPs is graphitized. Proof-of-concept environmental applications of FeNPs{at}C-800 were demonstrated by Rhodamine 6G and arsenate (V) removal from water. This biomass-based method provides an effective way for iron-based nanoparticle fabrication and biomass utilization.

  6. Versatile and biomass synthesis of iron-based nanoparticles supported on carbon matrix with high iron content and tunable reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Dongmao, E-mail: DZ33@msstate.edu [Mississippi State University, Department of Chemistry (United States); Shi, Sheldon Q. [University of North Texas, Mechanical and Energy Engineering (United States); Pittman, Charles U.; Jiang Dongping [Mississippi State University, Department of Chemistry (United States); Che Wen [University of North Texas, Mechanical and Energy Engineering (United States); Gai Zheng; Howe, Jane Y.; More, Karren L. [Oak Ridge National Laboratory, Center for Nanophase Materials Sciences (United States); Antonyraj, Arockiasamy [Mississippi State University, Center for Advanced Vehicular Systems (United States)

    2012-08-15

    Iron-based nanoparticles supported on carbon (FeNPs-C) have enormous potential for environmental applications. Reported is a biomass-based method for FeNP-C synthesis that involves pyrolysis of bleached wood fiber pre-mixed with Fe{sub 3}O{sub 4} nanoparticles. This method allows synthesis of iron-based nanoparticles with tunable chemical reactivity by changing the pyrolysis temperature. The FeNP-C synthesized at a pyrolysis temperature of 500 Degree-Sign C (FeNP-C-500) reacts violently (pyrophoric) when exposed to air, while FeNP-C prepared at 800 Degree-Sign C (FeNP-C-800) remains stable in ambient condition for at least 3 months. The FeNPs in FeNP-C-800 are mostly below 50 nm in diameter and are surrounded by carbon. The immediate carbon layer (within 5-15 nm radius) on the FeNPs is graphitized. Proof-of-concept environmental applications of FeNPs-C-800 were demonstrated by Rhodamine 6G and arsenate (V) removal from water. This biomass-based method provides an effective way for iron-based nanoparticle fabrication and biomass utilization.

  7. Relations between Select21 Predictor Measures and First-Term Attrition

    National Research Council Canada - National Science Library

    Putka, Dan J; Bradley, Kevin M

    2008-01-01

    ...) validate the experimental predictor measures against valued criteria. This report summarizes attrition-related findings for Soldiers who participated in three Select21 reception battalion data collections: the pilot test...

  8. The Role of Personality Type on Minority Attrition at the US Naval Academy

    National Research Council Canada - National Science Library

    Burkins, Carl

    2002-01-01

    ...: gender, academic measures, and MBTI personality type. Specifically, the study focuses on the theories of college student attrition based on data from Historically Black Colleges and Universities, as well as traditional civilian universities...

  9. Global Warming, Elevational Range Shifts, and Lowland Biotic Attrition in the Wet Tropics

    National Research Council Canada - National Science Library

    Robert K. Colwell; Gunnar Brehm; Catherine L. Cardelús; Alex C. Gilman; John T. Longino

    2008-01-01

    .... Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected warming...

  10. A Longitudinal Examination of First Term Attrition and Reenlistment among FY1999 Enlisted Accessions

    National Research Council Canada - National Science Library

    Strickland, William J

    2005-01-01

    .... This effort allowed the evaluation of models of attrition and reenlistment intentions based on information contained in personnel records and collected from Soldiers who were surveyed as they entered...

  11. Risk Attitudes, Sample Selection and Attrition in a Longitudinal Field Experiment

    DEFF Research Database (Denmark)

    Harrison, Glenn W.; Lau, Morten Igel

    with respect to risk attitudes. Our design builds in explicit randomization on the incentives for participation. We show that there are significant sample selection effects on inferences about the extent of risk aversion, but that the effects of subsequent sample attrition are minimal. Ignoring sample...... temporal stability. We evaluate the hypothesis that risk preferences are stable over time using a remarkable data set combining administrative information from the Danish registry with longitudinal experimental data we designed to allow better identification of joint selection and attrition effects...... selection leads to inferences that subjects in the population are more risk averse than they actually are. Correcting for sample selection and attrition affects utility curvature, but does not affect inferences about probability weighting. Properly accounting for sample selection and attrition effects leads...

  12. Analysis of Recruit Attrition from the Navy's Delayed Entry Program and Recruit Training Command

    National Research Council Canada - National Science Library

    Neuhalfen, Jon K

    2007-01-01

    .... The analysis uses the PRIDE database, provided by Commander, Navy Recruiting Command. Trend analyses are used to identify significant changes in enlistment and attrition behavior for recruits who joined from fiscal years 1998 through 2005...

  13. Evaluating the Tailored Adaptive Personality Assessment System on Delayed Entry Program Attrition

    Science.gov (United States)

    2014-03-01

    and considers whether or not the recruit took a trigonometry and/or geometry class, along with AFQT as measures of cognitive ability. Use of a...includes whether or not the recruit took any trigonometry or geometry classes. This appears to be an early effort to investigate whether AFQT...attrition, but it also investigated if taking mathematics classes such as trigonometry and geometry had any relation with Army DEP attrition. While the

  14. Personnel Attrition Rates in Historical Land Combat Operations: An Annotated Bibliography

    Science.gov (United States)

    1993-06-01

    Issus, Arbela, Jaxartes, and Hydaspes . 10. Summary of Findings Regarding Battle Casualties. States that "The wounded are mostly estimated at the usual...ersonnel, combat, attrition, battle , casualties, losses, bibliography. 472 16. PRICE CODE 17. SECURITY CLASSIFICATION IR. SECURITY CLASSIFICATION 19...20814-2797 CAA-RP-93-2 PREFACE The Personnel Attrition Rates (PAR) Study is limited to studying personnel strengths and battle casualties in historical

  15. SRB attrition rate study of the aft skirt due to water impact cavity collapse loading

    Science.gov (United States)

    Crockett, C. D.

    1976-01-01

    A methodology was presented so that realistic attrition prediction could aid in selecting an optimum design option for minimizing the effects of updated loads on the Space Shuttle Solid Rocket Booster (SRB) aft skirt. The updated loads resulted in water impact attrition rates greater than 10 percent for the aft skirt structure. Adding weight to reinforce the aft skirt was undesirable. The refined method treats the occurrences of the load distribution probabilistically, radially and longitudinally, with respect to the critical structural response.

  16. Retention and attrition in bariatric surgery research: an integrative review of the literature.

    Science.gov (United States)

    Gourash, William F; Lockhart, Joan Such; Kalarchian, Melissa A; Courcoulas, Anita P; Nolfi, David

    2016-01-01

    Bariatric surgery research, often longitudinal, bears the challenge of maintaining retention and decreasing attrition of participants to avoid bias. To explore factors influencing the retention and attrition for bariatric surgical research participants. Databases searched included: PubMed, CINAHL, Scopus, and others. As a secondary aim, studies reporting on retention/attrition factors in clinical follow-up visits were included. Of the 1145 articles retrieved, 44 met inclusion criteria, and underwent qualitative analysis. Four descriptive articles focused on longitudinal research participation and 40 on clinical follow-up visits. Willingness to participate in research was high (92%) and decreased with more invasive procedures or extra visits. A large observational longitudinal study presented 24-month retention/attrition data (92% for some data and 66% visit completion) and the retention strategies employed. One study indicated that research follow-up possibly increased clinical follow-up and another demonstrated a higher retention by increasing compensation. No consistent, modifiable demographic or psychosocial variables associated or predictive of retention or attrition in clinical follow-up were identified. Research on factors related to participant retention and attrition is sparse. It is essential for studies to document retention/attrition data. Existing research has demonstrated a patient willingness to participate in research and that retention strategies have been successful in the short term. Further research should explore the motivations, perspectives and attitudes of bariatric surgical research participants regarding participation and explore predictors to develop evidence-based retention strategies. Research has yet to identify consistent and modifiable demographic or psychosocial variables predictive of clinical follow-up, possibly due to the heterogeneity of follow-up across studies. Further investigation into follow-up definition, content

  17. The Phenomenon of Staff Attrition in Sri Lanka’s Hospitality Industry

    OpenAIRE

    Galagoda, Emadhrie Arundanie

    2016-01-01

    Sri Lankan Hospitality Industry has just commenced to emerge as a mainstream socio-economic sector, with acknowledgement of its job-creating significance. Undeniably, in recent times the Sri Lanka hotel industry is challenged with a comparatively high attrition rate fueled by a dearth of hospitality manpower in the imminent future. This study aims to fulfill an unidentified study on the phenomena of staff attrition, the dominant antecedents underlying an employee’s intention to exit the indus...

  18. Weight Loss Expectations and Attrition in Treatment-Seeking Obese Women

    OpenAIRE

    Dalle Grave, Riccardo; Calugi, Simona; Compare, Angelo; El Ghoch, Marwan; Petroni, Maria Letizia; Tomasi, Franco; Mazzali, Gloria; Marchesini, Giulio

    2015-01-01

    Objective The analysis of the relation between weight loss goals and attrition in the treatment of obesity has produced conflicting results. The aim of the present study was to investigate the role of weight loss goals on attrition in a cohort of obese women seeking treatment at 8 Italian medical centres. Methods 634 women with obesity, consecutively enrolled in weight loss programmes, were included in the study. Weight loss goals were evaluated with the Goals and Relative Weights Questionnai...

  19. Weight loss expectations and attrition in treatment-seeking obese women

    OpenAIRE

    Riccardo Dalle Grave; Simona Calugi; Angelo Compare; Marwan El Ghoch; Maria Letizia Petroni; Franco Tomasi; Gloria Mazzali; Giulio Marchesini

    2015-01-01

    Objective: The analysis of the relation between weight loss goals and attrition in the treatment of obesity has produced conflicting results. The aim of the present study was to investigate the role of weight loss goals on attrition in a cohort of obese women seeking treatment at 8 Italian medical centres. Methods: 634 women with obesity, consecutively enrolled in weight loss programmes, were included in the study. Weight loss goals were evaluated with the Goals and Relative Weights Questionn...

  20. Weight Loss Expectations and Attrition in Treatment-Seeking Obese Women

    Science.gov (United States)

    Dalle Grave, Riccardo; Calugi, Simona; Compare, Angelo; El Ghoch, Marwan; Petroni, Maria Letizia; Tomasi, Franco; Mazzali, Gloria; Marchesini, Giulio

    2015-01-01

    Objective The analysis of the relation between weight loss goals and attrition in the treatment of obesity has produced conflicting results. The aim of the present study was to investigate the role of weight loss goals on attrition in a cohort of obese women seeking treatment at 8 Italian medical centres. Methods 634 women with obesity, consecutively enrolled in weight loss programmes, were included in the study. Weight loss goals were evaluated with the Goals and Relative Weights Questionnaire (GRWQ), reporting a sequence of unrealistic (‘dream’ and ‘happy’) and more realistic (‘acceptable’ and ‘disappointing’) weight loss goals. Attrition was assessed at 12 months on the basis of patients' medical records. Results At 12 months, 205/634 patients (32.3%) had interrupted their programme and were lost to follow-up. After adjustment for age, baseline weight, education and employment status, attrition was significantly associated with higher percent acceptable and disappointing weight loss targets, not with dream and happy weight loss. Conclusion In ‘real world’ clinical settings, only realistic expectations might favour attrition whenever too challenging, whereas unrealistic weight loss goals have no effect. Future studies should assess the effect of interventions aimed at coping with too challenging weight goals on attrition. PMID:26444382

  1. Weight Loss Expectations and Attrition in Treatment-Seeking Obese Women

    Directory of Open Access Journals (Sweden)

    Riccardo Dalle Grave

    2015-10-01

    Full Text Available Objective: The analysis of the relation between weight loss goals and attrition in the treatment of obesity has produced conflicting results. The aim of the present study was to investigate the role of weight loss goals on attrition in a cohort of obese women seeking treatment at 8 Italian medical centres. Methods: 634 women with obesity, consecutively enrolled in weight loss programmes, were included in the study. Weight loss goals were evaluated with the Goals and Relative Weights Questionnaire (GRWQ, reporting a sequence of unrealistic (‘dream' and ‘happy' and more realistic (‘acceptable' and ‘disappointing' weight loss goals. Attrition was assessed at 12 months on the basis of patients' medical records. Results: At 12 months, 205/634 patients (32.3% had interrupted their programme and were lost to follow-up. After adjustment for age, baseline weight, education and employment status, attrition was significantly associated with higher percent acceptable and disappointing weight loss targets, not with dream and happy weight loss. Conclusion: In ‘real world' clinical settings, only realistic expectations might favour attrition whenever too challenging, whereas unrealistic weight loss goals have no effect. Future studies should assess the effect of interventions aimed at coping with too challenging weight goals on attrition.

  2. Caregiver Report of Child Symptoms Predicts Attrition in Abuse-Specific Cognitive Behavioral Therapies.

    Science.gov (United States)

    Tebbett, Alison A; Brown, Elissa J; Chaplin, William F

    2017-01-01

    A common critique of empirically supported treatments for abuse-related psychopathology is attrition during critical phases of therapy (i.e., exposure). The goal of this study was to examine whether child and caregiver symptoms were predictive of attrition among families in abuse-specific cognitive-behavioral therapies (CBTs). Children ( N = 104) and their caregivers completed baseline assessments of internalizing symptoms, externalizing problems, and post-traumatic stress disorder (PTSD) and were enrolled in abuse-specific CBTs. Logistic regressions were conducted with baseline symptoms as predictor variables and treatment status (attrition vs. completion) as the criterion variable. Caregiver report of child internalizing symptoms showed the predicted quadratic relation to attrition. Caregiver report of child externalizing symptoms at moderate and high (vs. low) levels was associated with attrition. Child self-report and caregiver self-report of symptoms were not associated with the dyad's attrition. These results underscore the importance of attending to caregivers' initial perceptions of children's symptoms in abuse-specific therapy.

  3. Weight Loss Expectations and Attrition in Treatment-Seeking Obese Women.

    Science.gov (United States)

    Dalle Grave, Riccardo; Calugi, Simona; Compare, Angelo; El Ghoch, Marwan; Petroni, Maria Letizia; Tomasi, Franco; Mazzali, Gloria; Marchesini, Giulio

    2015-01-01

    The analysis of the relation between weight loss goals and attrition in the treatment of obesity has produced conflicting results. The aim of the present study was to investigate the role of weight loss goals on attrition in a cohort of obese women seeking treatment at 8 Italian medical centres. 634 women with obesity, consecutively enrolled in weight loss programmes, were included in the study. Weight loss goals were evaluated with the Goals and Relative Weights Questionnaire (GRWQ), reporting a sequence of unrealistic ('dream' and 'happy') and more realistic ('acceptable' and 'disappointing') weight loss goals. Attrition was assessed at 12 months on the basis of patients' medical records. At 12 months, 205/634 patients (32.3%) had interrupted their programme and were lost to follow-up. After adjustment for age, baseline weight, education and employment status, attrition was significantly associated with higher percent acceptable and disappointing weight loss targets, not with dream and happy weight loss. In 'real world' clinical settings, only realistic expectations might favour attrition whenever too challenging, whereas unrealistic weight loss goals have no effect. Future studies should assess the effect of interventions aimed at coping with too challenging weight goals on attrition. © 2015 S. Karger GmbH, Freiburg.

  4. The susceptibility of adult schistosomes to immune attrition

    Directory of Open Access Journals (Sweden)

    A. M. Agnew

    1992-01-01

    Full Text Available Mouse infection models are described that demonstrate reduction of egg production in Schistosoma haematobium infections and both worm loss and reduced fecundity in S. bovis infections. Neither phenomenum could be shown in S. mansoni infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by the serum transfer of the ability to reduce a S. bovis worm burden into immunocompromised hosts. Vaccination with irradiation attenuated parasites was also shown to have consequences for the adults of a challenge infections of S. haematobium and S. bovis specifically. Prior vaccination resulted in an abrogation of the anti-fecundity and adult worm elimination that occurred in non-vaccinated similary infected mice. hese models are being used to define the targets and mechanisms involved in anti-adult attrition. A serological assay, quantitation of a circulating antigen (CAA has been assessed for its ability to measure worm burdens of different species of schistosome in mice. This assay will be used to question whether anti-adult immunity contributes to the pattern of infection with S. mansoni and S. haematobium in man.

  5. Computational toxicology: Its essential role in reducing drug attrition.

    Science.gov (United States)

    Naven, R T; Louise-May, S

    2015-12-01

    Predictive toxicology plays a critical role in reducing the failure rate of new drugs in pharmaceutical research and development. Despite recent gains in our understanding of drug-induced toxicity, however, it is urgent that the utility and limitations of our current predictive tools be determined in order to identify gaps in our understanding of mechanistic and chemical toxicology. Using recently published computational regression analyses of in vitro and in vivo toxicology data, it will be demonstrated that significant gaps remain in early safety screening paradigms. More strategic analyses of these data sets will allow for a better understanding of their domain of applicability and help identify those compounds that cause significant in vivo toxicity but which are currently mis-predicted by in silico and in vitro models. These 'outliers' and falsely predicted compounds are metaphorical lighthouses that shine light on existing toxicological knowledge gaps, and it is essential that these compounds are investigated if attrition is to be reduced significantly in the future. As such, the modern computational toxicologist is more productively engaged in understanding these gaps and driving investigative toxicology towards addressing them. © The Author(s) 2015.

  6. 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

  7. Reflections on High School and Doctoral Student Attrition Experiences in Argentina. Closing Modes, and Individual and Institutional Constraints

    OpenAIRE

    Bartolini, Ana María; Universidad Autónoma de Entre Ríos (UADER) Universidad Nacionalde Entre Ríos (UNER); Gerlo, Graciela; Universidad Autónoma de Entre Ríos (UADER) Universidad Católica Argentina Santa María de los Buenos Aires (UCA)

    2016-01-01

    The article reflects critically on school attrition, comparing high school and doctoral dropout rates in Argentina. The theoretical perspective integrates the categories of voluntary attrition and academic exclusion of Tinto (1989) with the concepts of habitus and symbolic violence of Bourdieu (Bourdieu and Passeron, 1981). The reflections arise from the interpretative analysis of attrition experiences in high schools and doctoral programs. This was done by rereading, and making a new coding ...

  8. Toxicity of iron-based nanoparticles to green algae: Effects of particle size, crystal phase, oxidation state and environmental aging.

    Science.gov (United States)

    Lei, Cheng; Zhang, Luqing; Yang, Kun; Zhu, Lizhong; Lin, Daohui

    2016-11-01

    With the increasing environmental application and discharge of iron-based nanoparticles (NPs), a comprehensive understanding of their fate and ecotoxicological effect in the aquatic environment is very urgent. In this study, toxicities of 4 zero-valent iron NPs (nZVI) of different sizes, 2 Fe 2 O 3 NPs of different crystal phases, and 1 type of Fe 3 O 4 NPs to a green alga (Chlorella pyrenoidosa) were investigated, with a focus on the effects of particle size, crystal phase, oxidation state, and environmental aging. Results show that the algal growth inhibition of nZVI increased significantly with decreasing particle size; with similar particle sizes (20-30 nm), the algal growth inhibition decreased with oxidation of the NPs with an order of nZVI > Fe 3 O 4 NPs > Fe 2 O 3 NPs, and α-Fe 2 O 3 NPs presented significantly higher toxicity than γ-Fe 2 O 3 NPs. The NP-induced oxidative stress was the main toxic mechanism, which could explain the difference in algal toxicity of the NPs. The NP-cell heteroagglomeration and physical interactions also contributed to the nanotoxicity, whereas the effect of NP dissolution was negligible. The aging in distilled water and 3 surface water samples for 3 months increased surface oxidation of the iron-based NPs especially nZVI, which decreased the toxicity to algae. These findings will be helpful for the understanding of the fate and toxicity of iron-based NPs in the aquatic environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Forms of attrition in a longitudinal study of religion and health in older adults and implications for sample bias

    Science.gov (United States)

    Hayward, R. David; Krause, Neal

    2014-01-01

    The use of longitudinal designs in the field of religion and health makes it important to understand how attrition bias may affect findings in this area. This study examines attrition in a 4-wave, 8-year study of older adults. Attrition resulted in a sample biased towards more educated and more religiously-involved individuals. Conditional linear growth curve models found that trajectories of change for some variables differed among attrition categories. Ineligibles had worsening depression, declining control, and declining attendance. Mortality was associated with worsening religious coping styles. Refusers experienced worsening depression. Nevertheless, there was no evidence of bias in the key religion and health results. PMID:25257794

  10. Forms of Attrition in a Longitudinal Study of Religion and Health in Older Adults and Implications for Sample Bias.

    Science.gov (United States)

    Hayward, R David; Krause, Neal

    2016-02-01

    The use of longitudinal designs in the field of religion and health makes it important to understand how attrition bias may affect findings in this area. This study examines attrition in a 4-wave, 8-year study of older adults. Attrition resulted in a sample biased toward more educated and more religiously involved individuals. Conditional linear growth curve models found that trajectories of change for some variables differed among attrition categories. Ineligibles had worsening depression, declining control, and declining attendance. Mortality was associated with worsening religious coping styles. Refusers experienced worsening depression. Nevertheless, there was no evidence of bias in the key religion and health results.

  11. 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.

  12. Effect of sorbent attrition on utilization. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Keener, T.C.; Khang, S.J.; Li, G. [Cincinnati Univ., OH (United States). Dept. of Civil and Environmental Engineering

    1993-09-30

    The overall objective for 1992-1993 was to investigate ways of using chemical attrition to improve dolomitic sorbent utilization for duct injection processes. It is known that one of the primary mechanisms for poor sorbent utilization lies in the fact that the products of SO{sub 2}-sorbent reactions have such large molar volumes that they plug the pores necessary for SO{sub 2} to diffuse into the particle interior. Any method that may cause the fracture of used sorbent particles will thus expose fresh un-reacted surface of sorbent and result in available sorbent recovery. There are several mechanisms that may cause the breakage of particles. External mechanical stress may be exerted on a particle and cause particle fracture when it exceeds the cohesive forces to prevent the breakage. Heat and pressure can also induce particle fracture. In addition, chemical reaction is also a very important factor in leading to particle fracture. Among many sorbents currently used in desulfurization processes, dolomitic lime may be a good candidate for use in medium temperature duct injection. Dolomites are characterized by a large portion of magnesium (instead of high calcium) in the crystal structure of common limestones. Because of the special composition of dolomitic lime and its reactions with flue gas constituents under medium temperature duct injection conditions, a unique structure is formed for spent dolomitic particles that provides for the potential of recovering available sorbent just by hydration-induced particle fracture. By re-injecting the recovered sorbent, it is expected that a high sorbent utilization can be obtained.

  13. Expectations for Treatment in Pediatric Weight Management and Relationship to Attrition.

    Science.gov (United States)

    Rhodes, Erinn T; Boles, Richard E; Chin, Kimberly; Christison, Amy; Testa, Elizabeth Getzoff; Guion, Kimberly; Hawkins, Mary Jane; Petty, Carter R; Sallinen Gaffka, Bethany; Santos, Melissa; Shaffer, Laura; Tucker, Jared; Hampl, Sarah E

    2017-04-01

    Attrition in pediatric weight management negatively impacts treatment outcomes. A potentially modifiable contributor to attrition is unmet family expectations. This study aimed to evaluate the association between adolescent and parent/guardian treatment expectations and attrition. A prospective, nonrandomized, uncontrolled, single-arm pilot trial was conducted among 12 pediatric weight management programs in the Children's Hospital Association's FOCUS on a Fitter Future collaborative. Parents/guardians and adolescents completed an expectations/goals survey at their initial visit, with categories including healthier food/drinks, physical activity/exercise, family support/behavior, and weight management goals. Attrition was assessed at 3 months. From January to August 2013, 405 parents/guardians were recruited and reported about their children (203 adolescents, 202 children goal for both adolescents and parents. For adolescents with this goal, the median weight-loss goal was 50 pounds. Attrition was associated with adolescent weight-loss goals above the desired median (50% above the median vs. 28% below the median, p = 0.02). Assessing initial expectations may help tailor treatment to meet families' needs, especially through focus on family-based change and realistic goal setting. Clinicaltrials.gov NCT01753063.

  14. Sustaining Engagement in Longitudinal Research With Vulnerable Families: A Mixed-Methods Study of Attrition.

    Science.gov (United States)

    Ginn, Carla S; Mughal, Muhammad Kashif; Syed, Hafsa; Storteboom, Amanda Rae; Benzies, Karen M

    2017-11-01

    The aim of this mixed-methods study was to investigate attrition at the age 10-year follow-up in a study of vulnerable children and their families living with low income following a two-generation preschool program in Calgary, Alberta, Canada. Quantitative factors associated with attrition included: (a) food bank use; (b) unstable housing; (c) child welfare involvement; (d) unpartnered status; and (e) caregiver noncompletion of high school. Qualitative themes related to attrition included: (a) income and employment; (b) health; (c) unstable housing; (d) change of guardianship; (e) domestic violence; (f) work and time management challenges; and (g) negative caregiver-child relationships. Triangulation of quantitative and qualitative results occurred using Maslow's Hierarchy of Needs; families with unmet physiological, safety, belongingness and love needs, and esteem needs were more likely to attrite. Attrition in longitudinal studies with vulnerable families is complex, affected by frequently changing life circumstances, and struggles to access necessities of life. Strategies for retaining vulnerable families in longitudinal research are offered.

  15. Cumulative stress in research animals: Telomere attrition as a biomarker in a welfare context?

    Science.gov (United States)

    Bateson, Melissa

    2016-02-01

    Progress in improving animal welfare is currently limited by the lack of objective methods for assessing lifetime experience. I propose that telomere attrition, a cellular biomarker of biological age, provides a molecular measure of cumulative experience that could be used to assess the welfare impact of husbandry regimes and/or experimental procedures on non-human animals. I review evidence from humans that telomere attrition is accelerated by negative experiences in a cumulative and dose-dependent manner, but that this attrition can be mitigated or even reversed by positive life-style interventions. Evidence from non-human animals suggests that despite some specific differences in telomere biology, stress-induced telomere attrition is a robust phenomenon, occurring in a range of species including mice and chickens. I conclude that telomere attrition apparently integrates positive and negative experience in an accessible common currency that translates readily to novel species--the Holy Grail of a cumulative welfare indicator. © 2015 The Author. BioEssays published by WILEY Periodicals, Inc.

  16. Developmental telomere attrition predicts impulsive decision-making in adult starlings.

    Science.gov (United States)

    Bateson, Melissa; Brilot, Ben O; Gillespie, Robert; Monaghan, Pat; Nettle, Daniel

    2015-01-22

    Animals in a poor biological state face reduced life expectancy, and as a consequence should make decisions that prioritize immediate survival and reproduction over long-term benefits. We tested the prediction that if, as has been suggested, developmental telomere attrition is a biomarker of state and future life expectancy, then individuals who have undergone greater developmental telomere attrition should display greater choice impulsivity as adults. We measured impulsive decision-making in a cohort of European starlings (Sturnus vulgaris) in which we had previously manipulated developmental telomere attrition by cross-fostering sibling chicks into broods of different sizes. We show that as predicted by state-dependent optimality models, individuals who had sustained greater developmental telomere attrition and who had shorter current telomeres made more impulsive foraging decisions as adults, valuing smaller, sooner food rewards more highly than birds with less attrition and longer telomeres. Our findings shed light on the biological embedding of early adversity and support a functional explanation for its consequences that could be applicable to other species, including humans.

  17. The Effect of Copper Addition on the Activity and Stability of Iron-Based CO2 Hydrogenation Catalysts

    Directory of Open Access Journals (Sweden)

    Matthew J. Bradley

    2017-09-01

    Full Text Available Iron-based CO2 catalysts have shown promise as a viable route to the production of olefins from CO2 and H2 gas. However, these catalysts can suffer from low conversion and high methane selectivity, as well as being particularly vulnerable to water produced during the reaction. In an effort to improve both the activity and durability of iron-based catalysts on an alumina support, copper (10–30% has been added to the catalyst matrix. In this paper, the effects of copper addition on the catalyst activity and morphology are examined. The addition of 10% copper significantly increases the CO2 conversion, and decreases methane and carbon monoxide selectivity, without significantly altering the crystallinity and structure of the catalyst itself. The FeCu/K catalysts form an inverse spinel crystal phase that is independent of copper content and a metallic phase that increases in abundance with copper loading (>10% Cu. At higher loadings, copper separates from the iron oxide phase and produces metallic copper as shown by SEM-EDS. An addition of copper appears to increase the rate of the Fischer–Tropsch reaction step, as shown by modeling of the chemical kinetics and the inter- and intra-particle transport of mass and energy.

  18. Mössbauer studies of the peculiar magnetism in parent compounds of the iron-based superconductors

    Science.gov (United States)

    Jasek, A. K.; Komędera, K.; Błachowski, A.; Ruebenbauer, K.; Żukrowski, J.; Bukowski, Z.; Karpinski, J.

    2015-02-01

    A review of the magnetism in the parent compounds of the iron-based superconductors is given based on the transmission Mössbauer spectroscopy of 57Fe and 151Eu. It was found that the 3d magnetism is of the itinerant character with varying admixture of the spin-polarized covalent bonds. For the '122' compounds, a longitudinal spin density wave (SDW) develops. In the case of the EuFe2As2, a divalent europium arranges in an anti-ferromagnetical order at a much lower temperature as compared with the onset of SDW. These two magnetic systems remain almost uncoupled one to another. For the non-stoichiometric Fe1+xTe parent of the '11' family, one has a transversal SDW and magnetic order of the interstitial iron with relatively high and localized magnetic moments. These two systems are strongly coupled one to another. For the 'grand parent' of the iron-based superconductors FeAs, one observes two mutually orthogonal phase-related transversal SDW on the iron sites. There are two sets of such spin arrangements due to two crystallographic iron sites. The FeAs exhibits the highest covalency among the compounds studied, but it has still a metallic character. A contribution to XVI National Conference on Superconductivity, Zakopane, Poland, 7-12 October 2013.

  19. Hydrogen induced cracking tests of high strength steels and nickel-iron base alloys using the bolt-loaded specimen

    Energy Technology Data Exchange (ETDEWEB)

    Vigilante, G.N.; Underwood, J.H.; Crayon, D.; Tauscher, S.; Sage, T.; Troiano, E. [Army Armament RD and E Center, Watervliet, NY (United States). Benet Labs.

    1997-12-31

    Hydrogen induced cracking tests were conducted on high strength steels and nickel-iron base alloys using the constant displacement bolt-loaded compact specimen. The bolt-loaded specimen was subjected to both acid and electrochemical cell environments in order to produce hydrogen. The materials tested were A723, Maraging 200, PH 13-8 Mo, Alloy 718, Alloy 706, and A286, and ranged in yield strength from 760--1400 MPa. The effects of chemical composition, refinement, heat treatment, and strength on hydrogen induced crack growth rates and thresholds were examined. In general, all high strength steels tested exhibited similar crack growth rates and thresholds were examined. In general, all high strength steels tested exhibited similar crack growth rates and threshold levels. In comparison, the nickel-iron base alloys tested exhibited up to three orders of magnitude lower crack growth rates than the high strength steels tested. It is widely known that high strength steels and nickel base alloys exhibit different crack growth rates, in part, because of their different crystal cell structure. In the high strength steels tested, refinement and heat treatment had some effect on hydrogen induced cracking, though strength was the predominant factor influencing susceptibility to cracking. When the yield strength of one of the high strength steels tested was increased moderately, from 1130 MPa to 1275 MPa, the incubation times decreased by over two orders of magnitude, the crack growth rates increased by an order of magnitude, and the threshold stress intensity was slightly lower.

  20. Attrition in a 30-year follow-up of a perinatal birth risk cohort: factors change with age

    Directory of Open Access Journals (Sweden)

    Jyrki Launes

    2014-07-01

    Full Text Available Background. Attrition is a major cause of potential bias in longitudinal studies and clinical trials. Attrition rate above 20% raises concern of the reliability of the results. Few studies have looked at the factors behind attrition in follow-ups spanning decades.Methods. We analyzed attrition and associated factors of a 30-year follow-up cohort of subjects who were born with perinatal risks for neurodevelopmental disorders. Attrition rates were calculated at different stages of follow-up and differences between responders and non-responders were tested. To find combinations of variables influencing attrition and investigate their relative importance at birth, 5, 9, 16 and 30 years of follow-up we used the random forest classification.Results. Initial loss of potential participants was 13%. Attrition was 16% at five, 24% at nine, 35% at 16 and 46% at 30 years. The only group difference that emerged between responders and non-responders was in socioeconomic status (SES. The variables identified by random forest classification analysis were classified into Birth related, Development related and SES related. Variables from all these categories contributed to attrition, but SES related variables were less important than birth and development associated variables. Classification accuracy ranged between 0.74 and 0.96 depending on age.Discussion. Lower SES is linked to attrition in many studies. Our results point to the importance of the growth and development related factors in a longitudinal study. Parents’ decisions to participate depend on the characteristics of the child. The same association was also seen when the child, now grown up, decided to participate at 30 years. In addition, birth related medical variables are associated with the attrition still at the age of 30. Our results using a data mining approach suggest that attrition in longitudinal studies is influenced by complex interactions of a multitude of variables, which are not

  1. 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.

  2. Soft magnetic properties of rapidly quenched pig-iron-based alloys

    Science.gov (United States)

    Chakrabarti, P. K.; Mazaleyrat, F.; Varga, L. K.

    2003-01-01

    A family of rapidly quenched alloys based on pig iron (PI) having 6-10 at% additions (B, Ge, Ga,Al) has been found. In spite of small crystalline fraction, the best sample has the interesting values of resistivity, saturation polarization and magnetostriction of 129 μΩ cm , 1.59 T and 1.3 ppm, respectively. The AC power losses of these alloys were found comparable with those of the commercial glassy alloys.

  3. Oxidation resistant iron and nickel alloys for high temperature use

    Science.gov (United States)

    Hill, V. L.; Misra, S. K.; Wheaton, H. L.

    1970-01-01

    Iron-base and nickel-base alloys exhibit good oxidation resistance and improved ductility with addition of small amounts of yttrium, tantalum /or hafnium/, and thorium. They can be used in applications above the operating temperatures of the superalloys, if high strength materials are not required.

  4. Iron aluminide useful as electrical resistance heating elements

    Science.gov (United States)

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1997-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  5. Oxidation, carburization and/or sulfidation resistant iron aluminide alloy

    Science.gov (United States)

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2003-08-19

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or Zro.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B. .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  6. Mathematics and Science Education Attrition, Retention, and Migration: A Study of Three Urban School Districts in the State of Texas

    Science.gov (United States)

    Davis, Margaret Cheri

    2013-01-01

    Teacher attrition has far-reaching implications that contribute to the success of student performance at many different educational levels. Research indicates as many as 50% of public school teachers leave the profession within the first 5 years, and some suggest that as many as 20% to 30% leave teaching after the first year. Attrition is a…

  7. 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…

  8. A Theoretical Model and Analysis of the Effect of Self-Regulation on Attrition from Voluntary Online Training

    Science.gov (United States)

    Sitzmann, Traci

    2012-01-01

    A theoretical model is presented that examines self-regulatory processes and trainee characteristics as predictors of attrition from voluntary online training in order to determine who is at risk of dropping out and the processes that occur during training that determine when they are at risk of dropping out. Attrition increased following declines…

  9. A Comparison of Teacher Preparation Models and Implications for Teacher Attrition: Evidence from a 14-Year Longitudinal Study

    Science.gov (United States)

    Latham, Nancy; Mertens, Steven B.; Hamann, Kira

    2015-01-01

    This large-scale, longitudinal study examines teacher attrition data from over 6,500 teachers in Illinois over a 14-year period from 1997 to 2010. Attrition rates between teachers who participated in a Professional Development School (PDS) versus students prepared traditionally are compared. The effects of teacher preparation experiences on…

  10. A Correlational Study of a Reading Comprehension Program and Attrition Rates of ESL Nursing Students in Texas

    Science.gov (United States)

    Donnell, Wendy

    2013-01-01

    Decreasing the attrition rate of nursing students has become an important issue for programs in Texas as a means to alleviate the nursing shortage (THECB, 2009). Programs are admitting a more diverse group of students but attrition has historically been high among minority groups (Gilchrist & Rector, 2007). The purpose of this study was to…

  11. 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,…

  12. Quantitative evaluation of dental abfraction and attrition using a swept-source optical coherence tomography system.

    Science.gov (United States)

    Marcauteanu, Corina; Bradu, Adrian; Sinescu, Cosmin; Topala, Florin Ionel; Negrutiu, Meda Lavinia; Podoleanu, Adrian Gh

    2014-02-01

    A fast swept-source optical coherence tomography (SS-OCT) system is employed to acquire volumes of dental tissue, in order to monitor the temporal evolution of dental wear. An imaging method is developed to evaluate the volume of tissue lost in ex vivo artificially induced abfractions and attritions. The minimal volume (measured in air) that our system could measure is 2352 μm3. A volume of 25,000 A-scans is collected in 2.5 s. All these recommend the SS-OCT method as a valuable tool for dynamic evaluation of the abfraction and attrition with remarkable potential for clinical use.

  13. A Correlational Study of a Reading Comprehension Program and Attrition Rates of ESL Nursing Students in Texas.

    Science.gov (United States)

    Donnell, Wendy M

    The purpose of this study was to examine the associations between English as a second language (ESL), a reading comprehension program, and attrition rates of nursing students. Higher attrition rates of ESL nursing students are an assumption, seemingly based on anecdotal evidence. Data reflecting ESL student attrition should be measured and analyzed so that students can be identified prior to attrition. A secondary analysis of a large database of 27 initial licensure programs in Texas was completed. Data analysis identified that ESL students who used a reading comprehension program were almost twice as likely to be off track or out of the program as ESL students who did not use the program. Nurse educators need to evaluate student profile characteristics in a comprehensive way when determining risk of attrition.

  14. 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

    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......-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...

  15. High attrition before and after ART initiation among youth (15-24 years of age) enrolled in HIV care.

    Science.gov (United States)

    Lamb, Matthew R; Fayorsey, Ruby; Nuwagaba-Biribonwoha, Harriet; Viola, Violante; Mutabazi, Vincent; Alwar, Teresa; Casalini, Caterina; Elul, Batya

    2014-02-20

    To compare pre and post-ART attrition between youth (15-24 years) and other patients in HIV care, and to investigate factors associated with attrition among youth. Cohort study utilizing routinely collected patient-level data from 160 HIV clinics in Kenya, Mozambique, Tanzania, and Rwanda. Patients at least 10 years of age enrolling in HIV care between 01/05 and 09/10 were included. Attrition (loss to follow-up or death 1 year after enrollment or ART initiation) was compared between youth and other patients using multivariate competing risk (pre-ART) and traditional (post-ART) Cox proportional hazards methods accounting for within-clinic correlation. Among youth, patient-level and clinic-level factors associated with attrition were similarly assessed. A total of 312,335 patients at least 10 years of age enrolled in HIV care; 147,936 (47%) initiated ART, 17% enrolling in care and 10% initiating ART were youth. Attrition before and after ART initiation was substantially higher among youth compared with other age groups. Among youth, nonpregnant women experienced lower pre-ART attrition than men [sub-division hazard ratio = 0.90, 95% confidence interval (CI): 0.86-0.94], while both pregnant [adjusted hazard ratio (AHR) = 0.85, 95% CI: 0.74-0.97] and nonpregnant (AHR = 0.79, 95% CI: 0.73-0.86) female youth experienced lower post-ART attrition than men. Youth attending clinics providing sexual and reproductive health services including condoms (AHR = 0.47, 95% CI: 0.32-0.70) and clinics offering adolescent support groups (AHR = 0.73, 95% CI: 0.52-1.0) experienced significantly lower attrition after ART initiation. Youth experienced substantially higher attrition before and after ART initiation compared with younger adolescents and older adults. Adolescent-friendly services were associated with reduced attrition among youth, particularly after ART initiation.

  16. 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.

  17. Attrition analysed in five waves of a longitudinal yearly survey of smokers: findings from the ITC Netherlands survey.

    Science.gov (United States)

    Zethof, Dennis; Nagelhout, Gera E; de Rooij, Mark; Driezen, Pete; Fong, Geoffrey T; van den Putte, Bas; Hummel, Karin; de Vries, Hein; Thompson, Mary E; Willemsen, Marc C

    2016-08-01

    Attrition bias can affect the external validity of findings. This article analyses attrition bias and assesses the effectiveness of replenishment samples on demographic and smoking-related characteristics for the International Tobacco Control Netherlands Survey, a longitudinal survey among smokers. Attrition analyses were conducted for the first five survey waves (2008-12). We assessed, including and excluding replenishment samples, whether the demographic composition of the samples changed between the first and fifth waves. Replenishment samples were tailored to ensure the sample remained representative of the smoking population. We also constructed a multivariable survival model of attrition that included all five waves with replenishment samples. Of the original 1820 respondents recruited in 2008, 46% participated again in 2012. Demographic differences between waves due to attrition were generally small and replenishment samples tended to minimize them further. The multivariable survival analysis revealed that only two of the 10 variables analysed were significant predictors of attrition: a weak effect for gender (men dropped out more often) and weak to moderate effects for age (respondents aged 15-24 years dropped out more than aged 25-39 years, who dropped out more than those aged 40+ years). Weak to moderate attrition effects were found for men and younger age groups. This information could be used to minimize respondent attrition. Our findings suggest that sampling weights and tailored replenishment samples can effectively compensate for attrition effects. This is already being done for the International Tobacco Control Netherlands Survey, including the categories that significantly predicted attrition in this study. © The Author 2016. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.

  18. Enhanced Fischer-Tropsch synthesis performance of iron-based catalysts supported on nitric acid treated N-doped CNTs

    Science.gov (United States)

    Li, Zhenhua; Liu, Renjie; Xu, Yan; Ma, Xinbin

    2015-08-01

    Iron-based catalysts supported on N-doped CNTs (NCNTs) treated by various concentrations of nitric acid for Fischer-Tropsch synthesis (FTS) were investigated. An improved catalytic performance for the iron catalyst supported on acid treated NCNTs was obtained and the suitable nitric acid concentration was 10 M. The physiochemical properties of the NCNTs and the corresponding catalysts were characterized by BET, TEM, XRD, XPS, TGA and H2-TPR. The acid treatment removed the impurity and amorphous carbon, damaged the bamboo-like structure and increased the number of oxygen-containing functional groups and graphitization degree on the NCNTs. The more iron particles located inside the channels of NCNTs, the better catalytic FTS performance due to high dispersion and reducibility.

  19. Non-conventional superconducting fluctuations in Ba(Fe1-xRhx)2As2 iron-based superconductors.

    Science.gov (United States)

    Bossoni, L; Romanó, L; Canfield, P C; Lascialfari, A

    2014-10-08

    We measured the static uniform spin susceptibility of Ba(Fe(1-x)Rh(x))(2)As(2) 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.

  20. 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...... of heavy metal removal in a decreasing order is Cd, Ni, Cr, Zn, Cu and As. Furthermore, the effect of humic acid (HA) and light on the heavy metal removal is also tested. The data show that both the presence of 100 mg/L HA and the absence of light suppress the removal, with the suppression due to HA being...

  1. Phase diagram of the two-dimensional 16-band d-p model for iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yanagi, Y., E-mail: yanagi@phys.sc.niigata-u.ac.j [Department of Physics, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Yamakawa, Y. [Department of Physics, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Ono, Y. [Department of Physics, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Center for Transdisciplinary, Research, Niigata University, Ikarashi, Niigata 950-2181 (Japan)

    2010-12-15

    The electronic state of the Fe{sub 2}As{sub 2} plane in iron-based superconductors is investigated on the basis of the two-dimensional 16-band d-p model. Using the random phase approximation for the on-site Coulomb interaction between Fe d electrons, we obtain the phase diagram including the magnetic ordered states and the superconductivity. It is found that the s{sub {+-}-}wave superconductivity, where the gap functions have different signs between the electron pockets and the hole pockets, is realized near the incommensurate magnetic ordered phase with q{approx}({pi},{pi}). The absolute values of the gap functions on the Fermi surfaces are almost isotropic but largely depend on the energy bands.

  2. Polyvinylpyrrolidone and arsenic-induced changes in biological responses of model aquatic organisms exposed to iron-based nanoparticles

    Science.gov (United States)

    Llaneza, Verónica; Rodea-Palomares, Ismael; Zhou, Zuo; Rosal, Roberto; Fernández-Pina, Francisca; Bonzongo, Jean-Claude J.

    2016-08-01

    The efficiency of zero-valent iron particles used in the remediation of contaminated groundwater has, with the emergence of nanotechnology, stimulated interest on the use of nano-size particles to take advantage of high-specific surface area and reactivity characteristics of nanoparticles (NPs). Accordingly, engineered iron-NPs are among the most widely used nanomaterials for in situ remediation. However, while several ecotoxicity studies have been conducted to investigate the adverse impacts of these NPs on aquatic organisms, research on the implications of spent iron-based NPs is lacking. In this study, a comparative approach is used, in which the biological effects of three iron-based NPs (Fe3O4 and γ-Fe2O3 NPs with particle sizes ranging from 20 to 50 nm, and Fe0-NPs with an average particle size of 40 nm) on Raphidocelis subcapitata (formely known as Pseudokirchneriella subcapitata) and Daphnia magna were investigated using both as-prepared and pollutant-doped Fe-based NPs. For the latter, arsenic (As) was used as example sorbed pollutant. The results show that improved degree of NP dispersion by use of polyvinylpyrrolidone overlapped with both increased arsenic adsorption capacity and toxicity to the tested organisms. For R. subcapitata, Fe-oxide NPs were more toxic than Fe0-NPs, due primarily to differences in the degree of NPs aggregation and ability to produce reactive oxygen species. For the invertebrate D. magna, a similar trend of biological responses was observed, except that sorption of As to Fe0-NPs significantly increased the toxic response when compared to R. subcapitata. Overall, these findings point to the need for research on downstream implications of NP-pollutant complexes generated during water treatment by injection of NPs into aquatic systems.

  3. Polyvinylpyrrolidone and arsenic-induced changes in biological responses of model aquatic organisms exposed to iron-based nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Llaneza, Verónica [University of Florida, Engineering School of Sustainable Infrastructure and Environment, Department of Environmental Engineering Sciences (United States); Rodea-Palomares, Ismael [Univ. Autonoma de Madrid, Dept. de Biologia, Facultad de Ciencias (Spain); Zhou, Zuo [University of Florida, Engineering School of Sustainable Infrastructure and Environment, Department of Environmental Engineering Sciences (United States); Rosal, Roberto [Univ. de Alcalá, Dept. de Ingeniería Química (Spain); Fernández-Pina, Francisca [Univ. Autonoma de Madrid, Dept. de Biologia, Facultad de Ciencias (Spain); Bonzongo, Jean-Claude J., E-mail: bonzongo@ufl.edu [University of Florida, Engineering School of Sustainable Infrastructure and Environment, Department of Environmental Engineering Sciences (United States)

    2016-08-15

    The efficiency of zero-valent iron particles used in the remediation of contaminated groundwater has, with the emergence of nanotechnology, stimulated interest on the use of nano-size particles to take advantage of high-specific surface area and reactivity characteristics of nanoparticles (NPs). Accordingly, engineered iron-NPs are among the most widely used nanomaterials for in situ remediation. However, while several ecotoxicity studies have been conducted to investigate the adverse impacts of these NPs on aquatic organisms, research on the implications of spent iron-based NPs is lacking. In this study, a comparative approach is used, in which the biological effects of three iron-based NPs (Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3} NPs with particle sizes ranging from 20 to 50 nm, and Fe{sup 0}-NPs with an average particle size of 40 nm) on Raphidocelis subcapitata (formely known as Pseudokirchneriella subcapitata) and Daphnia magna were investigated using both as-prepared and pollutant-doped Fe-based NPs. For the latter, arsenic (As) was used as example sorbed pollutant. The results show that improved degree of NP dispersion by use of polyvinylpyrrolidone overlapped with both increased arsenic adsorption capacity and toxicity to the tested organisms. For R. subcapitata, Fe-oxide NPs were more toxic than Fe{sup 0}-NPs, due primarily to differences in the degree of NPs aggregation and ability to produce reactive oxygen species. For the invertebrate D. magna, a similar trend of biological responses was observed, except that sorption of As to Fe{sup 0}-NPs significantly increased the toxic response when compared to R. subcapitata. Overall, these findings point to the need for research on downstream implications of NP-pollutant complexes generated during water treatment by injection of NPs into aquatic systems.

  4. The Effect of Different Enlistment Ages on First-Term Attrition Rate

    Science.gov (United States)

    2014-03-01

    first-term attrition rate. Raw data included single, married, annulled , divorced, interlocutory, widowed, and unknown. We have regrouped the marital...otherwise. • Other_Mar_Statusit is a dummy variable equal to 1 if enlistee i is legally separated, divorced, annulled , and otherwise 0 37 • Whiteit is a

  5. A study of Enlisted Attrition in the United States Coast Guard.

    Science.gov (United States)

    1981-12-01

    Executive behavior and interaction. Industrial Relations, 1964, 3,(2), 99-108. Festinger , L. A Theory of cognitive dissonance . 1957 , Evanston, Ill.: Row...reenlist or exit. Data analyses were performed Jointly at Stanford University and Johns Hopkins Applied Physics Laboratory. Standard descriptive...leading to retention or attrition, Lieutenant Kerry Patterson of Stanford University , Commander Robert Kuhnle, and Chief Warrant Officer Stephen

  6. An Exploration of Factors Associated with Student Attrition and Success in Enabling Programs

    Science.gov (United States)

    Morison, Anthony; Cowley, Kym

    2017-01-01

    University-based enabling programs (EPs) provide a tertiary pathway for up to twenty percent of undergraduate enrolments at Australian universities. Attrition from these programs and the resulting costs to students, universities and society at large is an important issue deserving research attention. This research project aimed to investigate the…

  7. Exploratory Development Research of U.S. Navy Marine Corps Personnel, Phase 1. Factors Affecting Attrition

    Science.gov (United States)

    1977-09-30

    enough. The reasons are consistent with current recruiting advertising appeals. Although attriters and adjusted men each rank "learning a skill" as the...necessity of reproducing them in part or in full each time a factor is discussed. It also provides an over- view, or gestalt , of the relative importance

  8. Factors of Non-Persistence in Civilian Helicopter Flight Training: A Narrative Inquiry of Pilot Attrition

    Science.gov (United States)

    Wentworth, Rebecca

    2012-01-01

    Previous literature on retention of student helicopter pilots shows a gap in research of civilian schools and qualitative studies. To address this gap in the literature and to help helicopter flight schools better understand the incidents of attrition from flight training, this qualitative study investigated student and school-based factors…

  9. Factors of Attrition in Cohort Doctoral Education: A Self-Determination Theory Perspective

    Science.gov (United States)

    Garcia, Linda Ann

    2013-01-01

    Attrition rates, completion rates, and time to degree are the key areas researchers have sought to examine influencing factors and patterns of behavior that describe the departure process of students in doctoral study. Through the lens of self-determination theory (Deci & Ryan, 1985), the purpose of this phenomenological qualitative study was…

  10. Career development and professional attrition of novice ESL teachers of adults

    National Research Council Canada - National Science Library

    Valeo, Antonella; Faez, Farahnaz

    2013-01-01

    ..., we report on a study of the career development and professional attrition of novice ESL teachers as they attempt to secure and maintain teaching positions in their first years of practice. The study draws on data gathered in a broader research project investigating the self-efficacy of novice ESL teachers in the Canadian p...

  11. The Association between Testing Strategies and Performance in College Algebra, Attitude towards Mathematics, and Attrition Rate.

    Science.gov (United States)

    Johnson, Charles W.

    1989-01-01

    Compares the performance in college algebra for four testing strategy classes: a homework class; a quiz class; a test class; and the control class. Adjusted mean scores in performance and adjusted final attitude were not different among the four strategy groups. The test class had a higher attrition rate than the homework class. (YP)

  12. Predictors of attrition and academic success of medical students: a 30-year retrospective study.

    Science.gov (United States)

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

    2012-01-01

    To determine attrition and predictors of academic success among medical students at University of Split, Croatia. We analysed academic records of 2054 students enrolled during 1979-2008 period. 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 attrition students were significantly associated with parental education. There were 1126 graduates, 395 men and 731 women. Their average graduation GPA was 3.67±0.53 and study duration 7.6±2.44 years. During 5-year curriculum only 6.4% (42/654) of students graduated in time, and 55% (240/472) of students graduated in time after curriculum was extended to 6 years. Variables predicting whether a student will graduate or not were high school grades, entrance exam score and year of enrollment. Significant predictors of graduation grades were high school grades and entrance exam score. Entrance exam score predicted length of studying. Preadmission academic qualifications and year of enrollment predict academic success in medical school. More attention should be devoted to high attrition.

  13. Toothbrush abrasion, simulated tongue friction and attrition of eroded bovine enamel in vitro

    NARCIS (Netherlands)

    Vieira, A.; Overweg, E.; Ruben, J. L.; Huysmans, M. C. D. N. J. M.

    Objectives: Enamel erosion results in the formation of a softened layer that is susceptible to disruption by mechanical factors such as brushing abrasion, tongue friction and attrition. The aim of this study was to investigate the individual contribution of those mechanical insults to the enamel

  14. Teacher Attrition and Retention Research in Australia: Towards a New Theoretical Framework

    Science.gov (United States)

    Mason, Shannon; Matas, Cristina Poyatos

    2015-01-01

    During the last decades, the search to try to understand why Australian teachers prematurely leave their jobs has become an increasing focus of research interest. This article yields significant insights into the history and potential future of the teacher attrition research field. Using a thematic content analysis methodology, a study of the…

  15. Physical Education Teachers in Motion: An Account of Attrition and Area Transfer

    Science.gov (United States)

    Mäkelä, Kasper; Hirvensalo, Mirja; Laakso, Lauri; Whipp, Peter R.

    2014-01-01

    Background: Teacher turnover has been identified as a major problem that represents instability in teaching. Teacher turnover can be divided into three components: attrition means that the teacher is leaving the profession; "area transfer" means that the teacher is changing his/her subject area and "migration" means that the…

  16. An Exploration of Teacher Attrition and Mobility in High Poverty Racially Segregated Schools

    Science.gov (United States)

    Djonko-Moore, Cara M.

    2016-01-01

    The purpose of this study was to examine the mobility (movement to a new school) and attrition (quitting teaching) patterns of teachers in high poverty, racially segregated (HPRS) schools in the US. Using 2007-9 survey data from the National Center for Education Statistics, a multi-level multinomial logistic regression was performed to examine the…

  17. Retention, Attrition, and Mobility among Teachers and Administrators in West Virginia. REL 2016-161

    Science.gov (United States)

    Lochmiller, Chad R.; Adachi, Eishi; Chesnut, Colleen E.; Johnson, Jerry

    2016-01-01

    Members of the West Virginia School Leadership Research Alliance partnered with Regional Educational Laboratory Appalachia to study the average retention, attrition, and mobility rates among teachers and administrators in the West Virginia public school system. There is increasing evidence nationwide that low teacher and administrator retention…

  18. Prevalence of dental attrition in in vitro fertilization children of West Bengal.

    Science.gov (United States)

    Kar, Sudipta; Sarkar, Subrata; Mukherjee, Ananya

    2014-01-01

    Dental attrition is one of the problems affecting the tooth structure. It may affect both in vitro fertilization (IVF) and spontaneously conceived children. This study was aimed to evaluate and to compare the prevalence of dental attrition in deciduous dentition of IVF and spontaneously conceived children. In a cross-sectional case control study dental attrition status of 3-5 years old children were assessed. The case group consisted of term, singleton babies who were the outcome of IVF in the studied area in 2009. The control group consisted of term, first child, singleton and spontaneously conceived 3-5 years old children who were also resident of the studied area. A sample of 153 IVF and 153 spontaneously conceived children was examined according to Hansson and Nilner classification. Statistical analysis was carried out using Chi-square tests (χ(2) ) or Z test. No statistically significant difference found in studied (IVF children) and control group (spontaneously conceived children). IVF children are considered same as spontaneously conceived children when studied in relation to dental attrition status.

  19. 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…

  20. STEM Attrition among High-Performing College Students in the United States: Scope and Potential Causes

    Science.gov (United States)

    Chen, Xianglei

    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…

  1. A Meta-Analysis of Predictors of Offender Treatment Attrition and Its Relationship to Recidivism

    Science.gov (United States)

    Olver, Mark E.; Stockdale, Keira C.; Wormith, J. Stephen

    2011-01-01

    Objective: The failure of offenders to complete psychological treatment can pose significant concerns, including increased risk for recidivism. Although a large literature identifying predictors of offender treatment attrition has accumulated, there has yet to be a comprehensive quantitative review. Method: A meta-analysis of the offender…

  2. Predictors of attrition and academic success of medical students: a 30-year retrospective study.

    Directory of Open Access Journals (Sweden)

    Silvija Maslov Kruzicevic

    Full Text Available 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 attrition students were significantly associated with parental education. There were 1126 graduates, 395 men and 731 women. Their average graduation GPA was 3.67±0.53 and study duration 7.6±2.44 years. During 5-year curriculum only 6.4% (42/654 of students graduated in time, and 55% (240/472 of students graduated in time after curriculum was extended to 6 years. Variables predicting whether a student will graduate or not were high school grades, entrance exam score and year of enrollment. Significant predictors of graduation grades were high school grades and entrance exam score. Entrance exam score predicted length of studying. CONCLUSION: Preadmission academic qualifications and year of enrollment predict academic success in medical school. More attention should be devoted to high attrition.

  3. Vocabulary Attrition among Adult English as a Foreign Language Persian Learners

    Science.gov (United States)

    Asgari, Azadeh; Bin Mustapha, Ghazali

    2010-01-01

    This study aims to investigate the attrition rate of EFL concrete and abstract vocabulary among continuing and non-continuing Iranian female and male English language learners across different proficiency levels. They are students of a University and majored in different fields (between 20 and 25 years old). There was no treatment in this study…

  4. 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

    2006-01-01

    , functional ability at baseline, relative wealth, social network, self-rated health, and life-satisfaction. Inclusion of the dead in statistical models for the study of change in functional ability reduced the attrition problem. A logistic model for paired observations of functional ability at two points...

  5. Attrition from Student Affairs: Perspectives from Those Who Exited the Profession

    Science.gov (United States)

    Marshall, Sarah M.; Gardner, Megan Moore; Hughes, Carole; Lowery, Ute

    2016-01-01

    Attrition of student affairs professionals is an issue of concern for the profession. This mixed methods study highlights reasons why participants left their student affairs careers. Seven general themes emerged from the study, including burnout, salary issues, career alternatives, work/family conflict, limited advancement, supervisor issues and…

  6. 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…

  7. Attrition in Chronic Disease Self-Management Programs and Self-Efficacy at Enrollment

    Science.gov (United States)

    Verevkina, Nina; Shi, Yunfeng; Fuentes-Caceres, Veronica Alejandra; Scanlon, Dennis Patrick

    2014-01-01

    Among other goals, the Chronic Disease Self-Management Program (CDSMP) is designed to improve self-efficacy of the chronically ill. However, a substantial proportion of the enrollees often leave CDSMPs before completing the program curriculum. This study examines factors associated with program attrition in a CDSMP implemented in a community…

  8. Analysis of Civilian Employee Attrition at the Naval Postgraduate School and Naval Support Activity - Monterey Bay

    National Research Council Canada - National Science Library

    Valverde, Xavier

    1997-01-01

    ...) and Naval Support Activity-Monterey Bay (NSA-MB) to determine what civilian non-faculty employee jobs are likely to be left vacant in the next three years due to attrition and to identify what training and skills will be needed by personnel whose...

  9. Selectivity in L1 Attrition: Differential Object Marking in Spanish Near-Native Speakers of English

    Science.gov (United States)

    Chamorro, Gloria; Sturt, Patrick; Sorace, Antonella

    2016-01-01

    Previous research has shown L1 attrition to be restricted to structures at the interfaces between syntax and pragmatics, but not to occur with syntactic properties that do not involve such interfaces ("Interface Hypothesis", Sorace and Filiaci in "Anaphora resolution in near-native speakers of Italian." "Second Lang…

  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

  11. Attrition in a multi-component smoking cessation study for females.

    Science.gov (United States)

    Leeman, Robert F; Quiles, Zandra N; Molinelli, Laurence A; Terwal, Donna Medaglia; Nordstrom, Beth L; Garvey, Arthur J; Kinnunen, Taru

    2006-08-15

    Limiting attrition (i.e., participant dropout before the conclusion of a study) is a major challenge faced by researchers when implementing clinical trials. Data from a smoking cessation trial for females (N = 246) were analyzed in order to identify baseline smoking-related, demographic and psychological characteristics affecting likelihood of early (i.e., before the quit attempt) and late (i.e., after the quit attempt) dropout. There were a number of significant demographic predictors of attrition. Participants with at least one child living at home were at increased risk of both early and late dropout. Non-Whites were at increased risk of early dropout, while not having a college degree put one at increased risk of late dropout. Age was found to be a protective factor in that the older a participant was, the less likely she was to drop out in the early stages of the trial. With respect to psychological variables, weight concerns increased risk of attrition, as did the experience of guilt. In terms of smoking-related variables, mean cigarettes per day was not a significant predictor of attrition, although length of longest prior quit attempt was a significant predictor of early dropout when age was removed from the regression.

  12. Attrition in a Multi-Component Smoking Cessation Study for Females

    Directory of Open Access Journals (Sweden)

    Garvey Arthur J

    2006-08-01

    Full Text Available Abstract Limiting attrition (i.e., participant dropout before the conclusion of a study is a major challenge faced by researchers when implementing clinical trials. Data from a smoking cessation trial for females (N = 246 were analyzed in order to identify baseline smoking-related, demographic and psychological characteristics affecting likelihood of early (i.e., before the quit attempt and late (i.e., after the quit attempt dropout. There were a number of significant demographic predictors of attrition. Participants with at least one child living at home were at increased risk of both early and late dropout. Non-Whites were at increased risk of early dropout, while not having a college degree put one at increased risk of late dropout. Age was found to be a protective factor in that the older a participant was, the less likely she was to drop out in the early stages of the trial. With respect to psychological variables, weight concerns increased risk of attrition, as did the experience of guilt. In terms of smoking-related variables, mean cigarettes per day was not a significant predictor of attrition, although length of longest prior quit attempt was a significant predictor of early dropout when age was removed from the regression.

  13. ART attrition and risk factors among Option B+ patients in Haiti: A retrospective cohort study.

    Directory of Open Access Journals (Sweden)

    Nancy Puttkammer

    Full Text Available In October 2012, the Haitian Ministry of Health endorsed the "Option B+" strategy to eliminate mother-to-child transmission of HIV and achieve HIV epidemic control. The objective of this paper is to assess and identify risk factors for attrition from the national ART program among Option B+ patients in the 12 months after ART initiation.This retrospective cohort study included patients newly initiating ART from October 2012-August 2013 at 68 ART sites covering 45% of all newly enrolled ART patients in all regions of Haiti.With data from electronic medical records, we carried out descriptive analysis of sociodemographic, clinical, and pregnancy-related correlates of ART attrition, and used a modified Poisson regression approach to estimate relative risks in a multivariable model.There were 2,166 Option B+ patients who initiated ART, of whom 1,023 were not retained by 12 months (47.2%. One quarter (25.3% dropped out within 3 months of ART initiation. Protective factors included older age, more advanced HIV disease progression, and any adherence counseling prior to ART initiation, while risk factors included starting ART late in gestation, starting ART within 7 days of HIV testing, and using an atypical ART regimen.Our study demonstrates early ART attrition among Option B+ patients and contributes evidence on the characteristics of women who are most at risk of attrition in Haiti. Our findings highlight the importance of targeted strategies to support retention among Option B+ patients.

  14. Clinical correlates of weight loss and attrition during a 10-week dietary intervention study

    DEFF Research Database (Denmark)

    Handjieva-Darlenska, Teodora; Holst, Claus; Grau, Katrine

    2012-01-01

    Objective: The aim of this study was to identify the pre-treatment subject characteristics and weight loss changes as determinants of weight loss and attrition during a 10-week dietary intervention study. Methods: A total of 771 obese subjects (BMI 35.6 kg/m(2)) of both genders were included from 8...

  15. Factors related to attrition from trauma-focused cognitive behavioral therapy.

    Science.gov (United States)

    Wamser-Nanney, Rachel; Steinzor, Cazzie E

    2017-04-01

    Attrition from child trauma-focused treatments such as Trauma-Focused Cognitive Behavioral Therapy (TF-CBT) is common; yet, the factors of children who prematurely terminate are unknown. The aim of the current study was to identify risk factors for attrition from TF-CBT. One hundred and twenty-two children (ages 3-18; M=9.97, SD=3.56; 67.2% females; 50.8% Caucasian) who received TF-CBT were included in the study. Demographic and family variables, characteristics of the trauma, and caregiver- and child-reported pretreatment symptoms levels were assessed in relation to two operational definitions of attrition: 1) clinician-rated dropout, and 2) whether the child received an adequate dose of treatment (i.e., 12 or more sessions). Several demographic factors, number of traumatic events, and children's caregiver-rated pretreatment symptoms were related to clinician-rated dropout. Fewer factors were associated with the adequate dose definition. Child Protective Services involvement, complex trauma exposure, and child-reported pretreatment trauma symptoms were unrelated to either attrition definition. Demographics, trauma characteristics, and level of caregiver-reported symptoms may help to identify clients at risk for premature termination from TF-CBT. Clinical and research implications for different operational definitions and suggestions for future work will be presented. Published by Elsevier Ltd.

  16. A qualitative study on attrition of student nurses in Kwazulu-Natal ...

    African Journals Online (AJOL)

    The purpose of the study to explore reasons behind high students' attrition rates in the four-year comprehensive diploma course at a college of nursing in KZN Province and measures to address them.. The research design was qualitative, exploratory and contextual. A purposive sampling was used and ten (10) principals of ...

  17. ART attrition and risk factors among Option B+ patients in Haiti: A retrospective cohort study.

    Science.gov (United States)

    Puttkammer, Nancy; Domerçant, Jean Wysler; Adler, Michelle; Yuhas, Krista; Myrtil, Martine; Young, Paul; François, Kesner; Grand'Pierre, Reynold; Lowrance, David

    2017-01-01

    In October 2012, the Haitian Ministry of Health endorsed the "Option B+" strategy to eliminate mother-to-child transmission of HIV and achieve HIV epidemic control. The objective of this paper is to assess and identify risk factors for attrition from the national ART program among Option B+ patients in the 12 months after ART initiation. This retrospective cohort study included patients newly initiating ART from October 2012-August 2013 at 68 ART sites covering 45% of all newly enrolled ART patients in all regions of Haiti. With data from electronic medical records, we carried out descriptive analysis of sociodemographic, clinical, and pregnancy-related correlates of ART attrition, and used a modified Poisson regression approach to estimate relative risks in a multivariable model. There were 2,166 Option B+ patients who initiated ART, of whom 1,023 were not retained by 12 months (47.2%). One quarter (25.3%) dropped out within 3 months of ART initiation. Protective factors included older age, more advanced HIV disease progression, and any adherence counseling prior to ART initiation, while risk factors included starting ART late in gestation, starting ART within 7 days of HIV testing, and using an atypical ART regimen. Our study demonstrates early ART attrition among Option B+ patients and contributes evidence on the characteristics of women who are most at risk of attrition in Haiti. Our findings highlight the importance of targeted strategies to support retention among Option B+ patients.

  18. Attrition resistant, zinc titanate-containing, reduced sulfur sorbents and methods of use thereof

    Science.gov (United States)

    Vierheilig, Albert A.; Gupta, Raghubir P.; Turk, Brian S.

    2006-06-27

    Reduced sulfur gas species (e.g., H.sub.2S, COS and CS.sub.2) are removed from a gas stream by compositions wherein a zinc titanate ingredient is associated with a metal oxide-aluminate phase material in the same particle species. Nonlimiting examples of metal oxides comprising the compositions include magnesium oxide, zinc oxide, calcium oxide, nickel oxide, etc.

  19. Do factors other than trauma volume affect attrition of ATLS-acquired skills?

    Science.gov (United States)

    Ali, Jameel; Howard, Mary; Williams, J Ivan

    2003-05-01

    We previously demonstrated that trauma patient volume affects attrition rate of Advanced Trauma Life Support (ATLS)-acquired skills. This study assesses the possible roles of age, gender, and practice specialty on attrition of these skills over 8 years. Cognitive (assessed by the 40-item Multiple Choice Question Examination [MCQE]) and clinical (assessed by four trauma Objective Structured Clinical Examination [OSCE] stations) skills performance were compared among physicians who completed the ATLS course 0 months, 6 months, 2 years, 4 years, 6 years, and 8 years previously. The physicians were further divided into the following groups: age 32 or older (18.0 +/- 0.3 to 12.4 +/- 1.3). Decrease in Priorities and Organized Approach scores also showed no differences between the groups. Regarding gender, MCQE decreased similarly in both groups (women, 81.5 +/- 2.2% to 64.4 +/- 2.4%; men, 83.3 +/- 3.2% to 64.1 +/- 4.2%) and so did OSCE, Priorities, and Organized Approach scores. Regarding specialty, surgeons (83.0 +/- 3.1% to 66.1 +/- 4.5%), nonsurgeons (82.9 +/- 3.2% to 63.3 +/- 3.9%), and general surgeons (82.5 +/- 3.5% to 63.8 +/- 5.3%) showed similar decreases in MCQE scores. Overall OSCE scores and Priority and Approach scores decreased similarly in all specialty groups. When trauma volume was controlled, there was still no difference in attrition rate between surgeons and nonsurgeons. Trauma patient volume is the most critical determinant of attrition rate of ATLS-acquired skills. Gender, age (at time of taking the course), and practice specialty do not alter this attrition rate.

  20. Attrition from Web-Based Cognitive Testing: A Repeated Measures Comparison of Gamification Techniques.

    Science.gov (United States)

    Lumsden, Jim; Skinner, Andy; Coyle, David; Lawrence, Natalia; Munafo, Marcus

    2017-11-22

    The prospect of assessing cognition longitudinally and remotely is attractive to researchers, health practitioners, and pharmaceutical companies alike. However, such repeated testing regimes place a considerable burden on participants, and with cognitive tasks typically being regarded as effortful and unengaging, these studies may experience high levels of participant attrition. One potential solution is to gamify these tasks to make them more engaging: increasing participant willingness to take part and reducing attrition. However, such an approach must balance task validity with the introduction of entertaining gamelike elements. This study aims to investigate the effects of gamelike features on participant attrition using a between-subjects, longitudinal Web-based testing study. We used three variants of a common cognitive task, the Stop Signal Task (SST), with a single gamelike feature in each: one variant where points were rewarded for performing optimally; another where the task was given a graphical theme; and a third variant, which was a standard SST and served as a control condition. Participants completed four compulsory test sessions over 4 consecutive days before entering a 6-day voluntary testing period where they faced a daily decision to either drop out or continue taking part. Participants were paid for each session they completed. A total of 482 participants signed up to take part in the study, with 265 completing the requisite four consecutive test sessions. No evidence of an effect of gamification on attrition was observed. A log-rank test showed no evidence of a difference in dropout rates between task variants (χ22=3.0, P=.22), and a one-way analysis of variance of the mean number of sessions completed per participant in each variant also showed no evidence of a difference (F2,262=1.534, P=.21, partial η2=0.012). Our findings raise doubts about the ability of gamification to reduce attrition from longitudinal cognitive testing studies.

  1. Predictors of attrition with buprenorphine/naloxone treatment in opioid dependent youth☆

    Science.gov (United States)

    Warden, Diane; Subramaniam, Geetha A.; Carmody, Thomas; Woody, George E.; Minhajuddin, Abu; Poole, Sabrina A.; Potter, Jennifer; Fishman, Marc; Bogenschutz, Michael; Patkar, Ashwin; Trivedi, Madhukar H.

    2012-01-01

    Background In opioid dependent youth there is substantial attrition from medication-assisted treatment. If youth at risk for attrition can be identified at treatment entry or early in treatment, they can be targeted for interventions to help retain them in treatment. Methods Opioid dependent adolescents and young adults (n=152), aged 15–21, were randomized to 12 weeks (BUP, n=74) or 2 weeks of detoxification (DETOX, n=78) with buprenorphine/naloxone (Bup/Nal), both in combination with 12 weeks of psychosocial treatment. Baseline and early treatment related predictors of treatment attrition were identified in each group using bivariate and multivariate logistic regression. Results In the DETOX group 36% left between weeks 2 and 4, at the end of the dose taper, while in the BUP group only 8% left by week 4. In the BUP group, early adherence to Bup/Nal, early opioid negative urines, use of any medications in the month prior to treatment entry, and lifetime non-heroin opioid use were associated with retention while prior 30-day hallucinogen use was associated with attrition. In the DETOX group, only use of sleep medications was associated with retention although not an independent predictor. A broad range of other pre-treatment characteristics was unrelated to attrition. Conclusions Prompt attention to those with early non-adherence to medication or an early opioid positive urine, markers available in the first 2 weeks of treatment, may improve treatment retention. Extended Bup/ Nal treatment appeared effective in improving treatment retention for youth with opioid dependence across a wide range of demographics, and pre-treatment clinical characteristics. PMID:22626890

  2. Attrition among Women and Minorities in Earth and Space Science (ESS) Graduate Programs

    Science.gov (United States)

    Alexander, C. J.; Hawthorne, C.; Allen, W. R.; Alvarez, R.; Geisler, J.

    2001-05-01

    Recent data collected by the American Geological Institute (AGI) indicates that the rate of enrollment of ethnic minorities in the geosciences has steadily declined since the 1980's, and in that time the number of geoscience degrees awarded to ethnic minorities has been fairly steady at less than 1%. Data from the National Science Foundation suggests that only 43 of 186 Universities offering an ESS program have ever graduated an ethnic minority in the history of their program. Factors contributing to these abysmal figures differ for different ethnic-minority groups. We will address institutional obstacles to graduate learning which result in above-normal attrition of ethnic-minorities in ESS graduate programs. The recent studies show an attrition rate of 70% among African American males in ESS graduate programs, while among Hispanic females the attrition rate is only 3%. Studies by sociologists have recently shown that some law schools and medical schools have traits in common with these geoscience departments in the rates at which degrees are awarded to ethnic minorities. Institutional barriers encountered by ethnic minorities in graduate schools may take many forms, but can also be as simple as a lack of community support. In the 1990's the California Institute of Technology (Caltech) made a commitment to the retention of women in their graduate and undergraduate schools. Their program included mentoring, focussed tutoring, self-esteem support groups, and other retention efforts. Under this program, the attrition rate of women has dramatically slowed. In this paper, we will discuss the AGI data, the program instituted by Caltech, possible causes of attrition among populations of Hispanic, and African American males and females, as well as potential programs to address these problems. We will also present, from the nationwide study, data on geoscience departments which have been relatively successful at retaining and graduating ethnic minorities in Earth and Space

  3. Trunk muscle strength tests to predict injuries, attrition and military ability in soldiers.

    Science.gov (United States)

    Wunderlin, S; Roos, L; Roth, R; Faude, O; Frey, F; Wyss, T

    2015-05-01

    Physical fitness is related to injuries, attrition and military ability in military organisations. Therefore, all military organizations of the North Atlantic Treaty Organizations (NATO) test their employees' physical fitness at least once a year. The sit-up test is part of most of the fitness test batteries used. A possible alternative to the sit-up test is the global trunk muscle strength test (TMS). The aim of the present study was to compare the predictability of injuries, attrition and military ability between TMS and sit-up test performances. A total of 230 male recruits in a Swiss Army fusilier company completed TMS and sit-up tests in week 1 of military training school. During the following 13 weeks, injuries, attrition and military ability data were collected. Statistical analysis included backward binary regression and receiver operating characteristic (ROC) curve analysis to compare the discriminative power of TMS and the sit-up test to predict injuries, attrition and military ability. ROC analysis revealed larger areas under the curve for total injuries, attrition and military ability for the TMS (areatotal injuries=0.58; areaattrition=0.60; areamilitary ability=0.59) than for the sit-up test (areatotal injuries=0.53; areaattrition=0.50; areamilitary ability=0.56). Binary logistic regression analysis revealed low body mass index, low TMS performance and cigarette smoking to be potential risk factors for injuries; while sit-up performance was extracted from the model. The TMS seems to be a valid alternative to the sit-up test in a military setting due to its appropriate results in predicting injuries in the present study.

  4. Attrition from antiretroviral treatment services among pregnant and non-pregnant patients following adoption of Option B+ in Haiti.

    Science.gov (United States)

    Domercant, Jean Wysler; Puttkammer, Nancy; Young, Paul; Yuhas, Krista; François, Kesner; Grand'Pierre, Reynold; Lowrance, David; Adler, Michelle

    2017-01-01

    Access to antiretroviral therapy (ART) has expanded in Haiti because of the adoption of Option B+ and the revision of treatment guidelines. Retention in care and treatment varies greatly and few studies have examined retention rates, particularly among women enrolled in Option B+. To assess attrition among pregnant and non-pregnant patients initiating ART following adoption of Option B+ in Haiti. Longitudinal data of adult patients initiated on ART from October 2012 through August 2014 at 73 health facilities across Haiti were analyzed using a survival analysis framework to determine levels of attrition. The Kaplan-Meier method and Cox proportional hazards regression were used to examine risk factors associated with attrition. Among 17,059 patients who initiated ART, 7627 (44.7%) were non-pregnant women, 5899 (34.6%) were men, and 3533 (20.7%) were Option B+ clients. Attrition from the ART program was 36.7% at 12 months (95% CI: 35.9-37.5%). Option B+ patients had the highest level of attrition at 50.4% at 12 months (95% CI: 48.6-52.3%). While early HIV disease stage at ART initiation was protective among non-pregnant women and men, it was a strong risk factor among Option B+ clients. In adjusted analyses, key protective factors were older age (p B+ patients. Identifying newly initiated patients most at risk for attrition and providing appropriate interventions could help reduce ART attrition.

  5. Confusing similar words: ERP correlates of lexical-semantic processing in first language attrition and late second language acquisition.

    Science.gov (United States)

    Kasparian, Kristina; Steinhauer, Karsten

    2016-12-01

    First language (L1) attrition is a socio-linguistic circumstance where second language (L2) learning coincides with changes in exposure and use of the native-L1. Attriters often report experiencing a decline in automaticity or proficiency in their L1 after a prolonged period in the L2 environment, while their L2 proficiency continues to strengthen. Investigating the neurocognitive correlates of attrition alongside those of late L2 acquisition addresses the question of whether the brain mechanisms underlying both L1 and L2 processing are strongly determined by proficiency, irrespective of whether the language was acquired from birth or in adulthood. Using event-related-potentials (ERPs), we examined lexical-semantic processing in Italian L1 attriters, compared to adult Italian L2 learners and to Italian monolingual native speakers. We contrasted the processing of classical lexical-semantic violations (Mismatch condition) with sentences that were equally semantically implausible but arguably trickier, as the target-noun was "swapped" with an orthographic neighbor that differed only in its final vowel and gender-marking morpheme (e.g., cappello (hat) vs. cappella (chapel)). Our aim was to determine whether sentences with such "confusable nouns" (Swap condition) would be processed as semantically correct by late L2 learners and L1 attriters, especially for those individuals with lower Italian proficiency scores. We found that lower-proficiency Italian speakers did not show significant N400 effects for Swap violations relative to correct sentences, regardless of whether Italian was the L1 or the L2. Crucially, N400 response profiles followed a continuum of "nativelikeness" predicted by Italian proficiency scores - high-proficiency attriters and high-proficiency Italian learners were indistinguishable from native controls, whereas attriters and L2 learners in the lower-proficiency range showed significantly reduced N400 effects for "Swap" errors. Importantly, attriters

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

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Qinghe [College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Liu, Hongtao, E-mail: liuht100@126.com [College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Chen, Tianchi [College of Mechanical & Electrical Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Wei, Yan; Wei, Zhu [College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China)

    2016-04-30

    Graphical abstract: - Highlights: • This paper investigates the fabrication techniques towards superhydrophobic surface on carbon steel substrate via electric corrosion without a bath. • It has a vital significance to the industrialization of the fabrication of superhydrophobic surface on hard metal due to the advantages such as low cost, high efficiency, can be prepared in a large area, easy to construct in the field. • The preparation approach is so facile and time-saving that it delivers an opportunity to construct a superhydrophobic surface on carbon steel substrate and provides the feasibility for industrial application of superhydrophobic surface. • The as-prepared surface has many excellent properties, like low adhesive property, anti-corrosion ability, mechanical durability and anti-icing performance. - Abstract: 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

  7. Web-Based Alcohol Intervention: Study of Systematic Attrition of Heavy Drinkers.

    Science.gov (United States)

    Radtke, Theda; Ostergaard, Mathias; Cooke, Richard; Scholz, Urte

    2017-06-28

    Web-based alcohol interventions are a promising way to reduce alcohol consumption because of their anonymity and the possibility of reaching a high numbers of individuals including heavy drinkers. However, Web-based interventions are often characterized by high rates of attrition. To date, very few studies have investigated whether individuals with higher alcohol consumption show higher attrition rates in Web-based alcohol interventions as compared with individuals with lower alcohol consumption. The aim of this study was to examine the attrition rate and predictors of attrition in a Web-based intervention study on alcohol consumption. The analysis of the predictors of attrition rate was performed on data collected in a Web-based randomized control trial. Data collection took place at the University of Konstanz, Germany. A total of 898 people, which consisted of 46.8% males (420/898) and 53.2% females (478/898) with a mean age of 23.57 years (SD 5.19), initially volunteered to participate in a Web-based intervention study to reduce alcohol consumption. Out of the sample, 86.9% (781/898) were students. Participants were classified as non-completers (439/898, 48.9%) if they did not complete the Web-based intervention. Potential predictors of attrition were self-reported: alcohol consumption in the last seven days, per week, from Monday to Thursday, on weekends, excessive drinking behavior measured with the Alcohol Use Disorder Identification Test (AUDIT), and drinking motives measured by the Drinking Motive Questionnaire (DMQ-R SF). Significant differences between completers and non-completers emerged regarding alcohol consumption in the last seven days (B=-.02, P=.05, 95% CI [0.97-1.00]), on weekends (B=-.05, P=.003, 95% CI [0.92-0.98]), the AUDIT (B=-.06, P=.007, 95% CI [0.90-0.98], and the status as a student (B=.72, P=.001, 95% CI [1.35-3.11]). Most importantly, non-completers had a significantly higher alcohol consumption compared with completers. Hazardous

  8. Effect of pressure on normal and superconducting state properties of iron based superconductor PrFeAsO0.6Fy(y = 0.12, 0.14).

    Science.gov (United States)

    Arumugam, S; Ganguli, C; Thiyagarajan, R; Bhoi, D; Selvan, G Kalai; Manikandan, K; Pariari, A; Mandal, P; Uwatoko, Y

    2017-09-15

    The effect of high pressure (up to 8 GPa) on normal and superconducting state properties of PrFeAsO 0.6 F 0.12 , an 1111-type iron based superconductor close to optimal doped region, has been investigated by measuring the temperature dependence of resistivity. Initially, the superconducting transition temperature (T c ) is observed to increase slowly by about 1 K as pressure (P) increases from 0 to 1.3 GPa. With further increase in pressure above 1.3 GPa, T c decreases at the rate of ~1.5 K/GPa. The normal-state resistivity decreases monotonically up to 8 GPa. We have also measured the pressure dependence of magnetization (M) on the same piece of PrFeAsO 0.6 F 0.12 sample up to 1.1 GPa and observed T c as well as the size of the Meissner signal to increase with pressure in this low-pressure region. In contrast, for an over-doped PrFeAsO 0.6 F 0.14 sample, magnetization measurements up to 1.06 GPa show that both T c and the Meissner signal decrease with pressure. The present study clearly reveals two distinct regions in the dome-shaped (T c -P) phase diagram of PrFeAsO 0.6 F 0.12 .

  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

    at 훼 = 0 . 0 1 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......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...

  10. Effect of incorporation manner of Mn promoter on the performances of iron-based catalysts in Fischer-Tropsch synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Tao Zhi-chao; Yang Yong; Li Ting-zhen; Wan Hai-jun; An Xia; Xiang Hong-wei; Li Yong-wang [Chinese Academy of Sciences, Taiyuan (China). State Key Laboratory of Coal Conversion

    2008-07-01

    A series of spherical iron-based (Fe/Mn/K) catalysts were prepared by the combination of coprecipitation and spray drying method; the influences of the incorporation manner of Mn promoter on their crystallite structure, reduction and carburization behaviors and performances in Fischer-Tropsch synthesis were investigated though H{sub 2} differential thermo gravimetric analysis (H{sub 2}-DTG), CO temperature-programmed reduction (COOTPR), Moessbauer spectroscopy as well as catalytic tests. The catalysts were evaluated in a slurry reactor under the industrially relevant reaction conditions of 250{sup o}C, 1.5 MPa, H{sub 2}/CO = 0.67 and a space velocity of 2.0 L/gcat-h. The results illustrated that the addition of precipitated Mn brings on a stronger Fe-Mn interaction than other incorporation manners; this may suppress the reduction and carburization of the catalyst, decrease the catalytic activity but enhance the catalytic stability. The addition of partial precipitated and binder Mn promotes the reduction and carburization of the catalyst, improves the catalytic activity but speeds up the catalyst deactivation. Compared with the precipitated Mn-promoted catalyst, the addition of partial precipitated and binder Mn can enhance the selectivity of heavy hydrocarbons and olefins and restrain the formation of oxygenates. 26 refs., 6 figs., 5 tabs.

  11. 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.

  12. Static and dynamic cyclic oxidation of 12 nickel-, cobalt-, and iron-base high-temperature alloys

    Science.gov (United States)

    Barrett, C. A.; Johnston, J. R.; Sanders, W. A.

    1978-01-01

    Twelve typical high-temperature nickel-, cobalt-, and iron-base alloys were tested by 1 hr cyclic exposures at 1038, 1093, and 1149 C and 0.05 hr exposures at 1093 C. The alloys were tested in both a dynamic burner rig at Mach 0.3 gas flow and in static air furnace for times up to 100 hr. The alloys were evaluated in terms of specific weight loss as a function of time, and X-ray diffraction analysis and metallographic examination of the posttest specimens. A method previously developed was used to estimate specific metal weight loss from the specific weight change of the sample. The alloys were then ranked on this basis. The burner-rig test was more severe than a comparable furnace test and resulted in an increased tendency for oxide spalling due to volatility of Cr in the protective scale and the more drastic cooling due to the air-blast quench of the samples. Increased cycle frequency also increased the tendency to spall for a given test exposure. The behavior of the alloys in both types of tests was related to their composition and their tendency to form scales. The alloys with the best overall behavior formed alpha-Al2O3 aluminate spinels.

  13. Metal-Insulator Transition and Superconductivity in the Two-Orbital Hubbard-Holstein Model for Iron-Based Superconductors

    Science.gov (United States)

    Yamada, Takemi; Ishizuka, Jun; Ōno, Yoshiaki

    2014-04-01

    We investigate a two-orbital model for iron-based superconductors to elucidate the effect of interplay between electron correlation and Jahn-Teller electron-phonon coupling by using the dynamical mean-field theory combined with the exact diagonalization method. When the intra- and inter-orbital Coulomb interactions, U and U', increase with U = U', both the local spin and orbital susceptibilities, χs and χo, increase with χs = χo in the absence of the Hund's rule coupling J and the electron-phonon coupling g. In the presence of J and g, there are distinct two regimes: for J ≳ 2g2/ω 0 with the phonon frequency ω0, χs is enhanced relative to χo and shows a divergence at J = Jc above which the system becomes Mott insulator, while for J ≲ 2g2/ω 0, χo is enhanced relative to χs and shows a divergence at g = gc above which the system becomes bipolaronic insulator. In the former regime, the superconductivity is mediated by antiferromagnetic fluctuations enhanced due to Fermi-surface nesting and is found to be largely dependent on carrier doping. On the other hand, in the latter regime, the superconductivity is mediated by ferro-orbital fluctuations and is observed for wide doping region including heavily doped case without the Fermi-surface nesting.

  14. Hydrogen sulfide removal from sediment and water in box culverts/storm drains by iron-based granules.

    Science.gov (United States)

    Sun, J L; Shang, C; Kikkert, G A

    2013-01-01

    A renewable granular iron-based technology for hydrogen sulfide removal from sediment and water in box culverts and storm drains is discussed. Iron granules, including granular ferric hydroxide (GFH), granular ferric oxide (GFO) and rusted waste iron crusts (RWIC) embedded in the sediment phase removed aqueous hydrogen sulfide formed from sedimentary biological sulfate reduction. The exhausted iron granules were exposed to dissolved oxygen and this regeneration process recovered the sulfide removal capacities of the granules. The recovery is likely attributable to the oxidation of the ferrous iron precipitates film and the formation of new reactive ferric iron surface sites on the iron granules and sand particles. GFH and RWIC showed larger sulfide removal capacities in the sediment phase than GFO, likely due to the less ordered crystal structures on their surfaces. This study demonstrates that the iron granules are able to remove hydrogen sulfide from sediment and water in box culverts and storm drains and they have the potential to be regenerated and reused by contacting with dissolved oxygen.

  15. Comparisons of the reactivity, reusability and stability of four different zero-valent iron-based nanoparticles.

    Science.gov (United States)

    Xie, Yingying; Fang, Zhanqiang; Qiu, Xinhong; Tsang, Eric Pokeung; Liang, Bin

    2014-08-01

    Our previous reports showed that nano zero-valent iron (nZVI), steel pickle liquor for the synthesis of nZVI (S-nZVI), nZVI immobilised in mesoporous silica microspheres (SiO2@FeOOH@Fe) and nano Ni/Fe bimetallic particles (Ni/Fe) have been proved to show good property for elimination of polybrominated diphenyl ethers (PBDEs). However, it is necessary to compare their reactivity, reusability and stability when applied to in situ remediation. In this study, the performances of different iron-based nanoparticles were compared through reusability, sedimentation and iron dissolution experiments. The SiO2@FeOOH@Fe and Ni/Fe nanoparticles were shown to have higher reusability and stability, as they could be reused more than seven times, and that the SiO2@FeOOH@Fe can effectively avoid leaching iron ions into the solution and causing secondary pollution in the reaction. This study may serve as a reference for PBDE remediation in the future. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Enhanced Coagulation-Flocculation Performance of Iron-Based Coagulants: Effects of PO43- and SiO32- Modifiers

    Science.gov (United States)

    Teng, Houkai; Wang, Yili; Zhang, Yuxin; Zhao, Chuanliang; Liao, Yong

    2015-01-01

    PO43- and SiO32- 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 PO43- and SiO32-. 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. PMID:26339902

  17. Assessment of DNA damage as an index of genetic toxicity in welding microenvironments among iron-based industries.

    Science.gov (United States)

    Singh, Zorawar; Chadha, Pooja

    2016-10-01

    Welding is used extensively in different industries. Welders are always at a risk of exposure to a number of gases and metal-containing fumes in their respective microenvironments in which they work. Welding fumes consist of a wide range of complex metal oxide particles which can deposit in different parts of their bodies causing serious health problems. In the present study, 35 welders (age: 33.80 ± 1.04 years) from two iron-based industries have been assessed for DNA damage in peripheral blood lymphocytes using single-cell gel electrophoresis. An equal number of subjects (N = 35; age: 30.40 ± 1.51 years) matched to exposed subjects with respect to sex, age, socioeconomic status, smoking, and alcoholic habits were taken as controls. The results revealed that the damaged cell frequency (DCF) and mean comet tail length (CTL) in welders were significantly higher as compared to the controls (DCF: 69.74 ± 1.68 vs. 31.14 ± 1.67 and CTL: 29.21 ± 1.48 vs. 1.47 ± 0.08; p < 0.05). The effect of confounding factors such as age, duration of exposure, smoking, and drinking habits was also studied. Blood lead levels also showed a positive correlation with duration of exposure and CTL, and the overall results indicated an increased genetic damage as an index of genotoxicity in workers occupationally engaged in welding microenvironments. © The Author(s) 2015.

  18. Nonaqueous System of Iron-Based Ionic Liquid and DMF for the Oxidation of Hydrogen Sulfide and Regeneration by Electrolysis.

    Science.gov (United States)

    Guo, Zhihui; Zhang, Tingting; Liu, Tiantian; Du, Jun; Jia, Bing; Gao, Shujing; Yu, Jiang

    2015-05-05

    To improve the hydrogen sulfide removal efficiency with the application of an iron-based imidazolium chloride ionic liquid (Fe(III)-IL) as desulfurizer, Fe(II) and N,N-dimethylformamide (DMF) are introduced to Fe(III)-IL to construct a new nonaqueous desulfurization system (Fe(III/II)-IL/DMF). Following desulfurization, the system can be regenerated using the controlled-potential electrolysis method. The addition of Fe(II) in Fe(III)-IL is beneficial for the hydrogen sulfide removal and the electrochemical regeneration of the desulfurizer. The addition of DMF in Fe(III/II)-IL does not change the structure of Fe(III/II)-IL but clearly decreases the acidity, increases the electrolytic current, and decreases the stability of the Fe-Cl bond in Fe(III/II)-IL. Fe(III/II)-IL/DMF can remove hydrogen sulfide and can be regenerated through an electrochemical method more efficiently than can Fe(III/II)-IL. After six cycles, the desulfurization efficiency remains higher than 98%, and the average conversion rate of Fe(II) is essentially unchanged. No sulfur peroxidation occurs, and the system remains stable. Therefore, this new nonaqueous system has considerable potential for removing H2S in pollution control applications.

  19. The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro.

    Science.gov (United States)

    Austin, R S; Rodriguez, J M; Dunne, S; Moazzez, R; Bartlett, D W

    2010-10-01

    To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm x 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n=10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle=artificial saliva (2h, pH 7.0)+erosion (0.3% citric acid, pH 3.2, 5 min)+fluoride/control (5 min)+attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in mum was measured using optical profilometry. When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine. Copyright 2010 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2015-12-01

    To examine if there is a difference in possible sleep bruxism activity (SB) in subjects with or without attrition-type tooth wear. 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 years (range 20.3-27.9), respectively. There were 11 females and five males in each of the two groups. The attrition group presented incisal/occlusal attrition wear into dentin and matching wear facets between opposing anterior teeth. The controls had negligible signs of incisal/occlusal wear and a minimal number of matching wear facets. The prevalence of both self-reported and partner-reported SB was significantly more common in the attrition group compared to the controls (P=0.04 and P=0.007, respectively). Self-reported morning facial pain was similarly more common in the attrition group (P=0.014). Maximum opening capacity, number of muscles painful to palpation, salivary flow rate and buffering capacity were not significantly different between the groups. Interestingly, none of the measures of jaw muscle EMG activity during sleep, as recorded by the portable EMG equipment, differed significantly between the attrition group and the matched controls (P>0.05). The results from this exploratory study suggest that there is no difference in EMG activity between subjects with and without attrition-type tooth wear. Further research is needed in order to substantiate these preliminary findings. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  1. Risk Attitudes, Sample Selection and Attrition in a Longitudinal Field Experiment

    DEFF Research Database (Denmark)

    Harrison, Glenn W.; Lau, Morten; Yoo, Hong Il

    incentives can affect sample response rates and help one identify the effects of selection. Correcting for endogenous sample selection and panel attrition changes inferences about risk preferences in an economically and statistically significant manner. We draw mixed conclusions on temporal stability of risk......Longitudinal experiments allow one to evaluate the temporal stability of latent preferences, but raise concerns about sample selection and attrition that may confound inferences about temporal stability. We evaluate the hypothesis of temporal stability in risk preferences using a remarkable data...... set that combines socio-demographic information from the Danish Civil Registry with information on risk attitudes from a longitudinal field experiment. Our experimental design builds in explicit randomization on the incentives for participation. The results show that the use of different participation...

  2. 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.

  3. 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.

  4. Personality, attrition and weight loss in treatment seeking women with obesity.

    Science.gov (United States)

    Dalle Grave, R; Calugi, S; Compare, A; El Ghoch, M; Petroni, M L; Colombari, S; Minniti, A; Marchesini, G

    2015-10-01

    Studies on small samples or in single units applying specific treatment programmes found an association between some personality traits and attrition and weight loss in individuals treated for obesity. We aimed to investigate whether pre-treatment personality traits were associated with weight loss outcomes in the general population of women with obesity. Attrition and weight loss outcomes after 12 months were measured in 634 women with obesity (mean age, 48; body mass index (BMI), 37.8 kg m(-2)) seeking treatment at eight Italian medical centres, applying different medical/cognitive behavioural programmes. Personality traits were assessed with the Temperament and Character Inventory (TCI), eating disorder features with the Binge Eating Scale (BES) and Night Eating Questionnaire (NEQ). Within the 12-month observation period, 32.3% of cases were lost to follow-up. After adjustment for demographic confounders and the severity of eating disorders, no TCI personality traits were significantly associated with attrition, while low scores of the novelty seeking temperament scale remained significantly associated with weight loss ≥ 10% (odds ratio, 0.983; 95% confidence interval, 0.975-0.992). Additional adjustment for education and job did not change the results. We conclude that personality does not systematically influence attrition in women with obesity enrolled into weight loss programmes in the community, whereas an association is maintained between novelty seeking and weight loss outcome. Studies adapting obesity interventions on the basis of individual novelty seeking scores might be warranted to maximize the results on body weight. © 2015 World Obesity.

  5. Predictors of attrition for a sexual assault forensic examiner (SAFE) blended learning training program.

    Science.gov (United States)

    Patterson, Debra; Resko, Stella

    2015-01-01

    Participant attrition is a major concern for online continuing education health care courses. The current study sought to understand what factors predicted health care professionals completing the online component of a sexual assault forensic examiner (SAFE) blended learning training program (12-week online course and 2-day in-person clinical skills workshop). The study used a Web-based survey to examine participant characteristics, motivation, and external barriers that may influence training completion. Hierarchical logistic regression was utilized to examine the predictors of training completion, while the Cox proportional hazards (Cox PH) regression model helped determine the factors associated with the timing of participant attrition. Results show that 79.3% of the enrolled professionals completed the online component. The study also found that clinicians who work in rural communities and those who were interested in a 2-day clinical skills workshop were more likely to complete the online course. In terms of when attrition occurred, we found that participants who were motivated by the 2-day clinical workshop, those who worked in a rural community, and participants interested in the training program because of its online nature were more likely to complete more of the online course. Blending an online course with a brief in-person clinical component may serve as a motivator for completing an online course because it provides the opportunity to develop clinical skills while receiving immediate feedback. Participant attrition appears to be less of a concern for rural clinicians because this modality can reduce their barriers to accessing continuing education. © 2015 The Alliance for Continuing Education in the Health Professions, the Society for Academic Continuing Medical Education, and the Council on Continuing Medical Education, Association for Hospital Medical Education.

  6. 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 - others: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

  7. 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

  8. The Flip Side of the Attrition Coin: Faculty Perceptions of Factors Supporting Graduate Student Success

    OpenAIRE

    Gilmore, Joanna A.; Annie M Wofford; Michelle A Maher

    2016-01-01

    Doctoral attrition consistently hovers around 50% with relevant literature identifying several mediating factors, including departmental culture, student demographics, and funding. To advance this literature, we interviewed 38 graduate faculty advisors in science, engineering, or mathematics disciplines at a research-extensive university to capture their perceptions of factors supporting graduate student success. Using a constant-comparison method, we found that faculty perceptions aligned wi...

  9. Effect of acidity upon attrition-corrosion of human dental enamel.

    Science.gov (United States)

    Wu, Yun-Qi; Arsecularatne, Joseph A; Hoffman, Mark

    2015-04-01

    Attrition-corrosion is a synthesized human enamel wear process combined mechanical effects (attrition) with corrosion. With the rising consumption of acidic food and beverages, attrition-corrosion is becoming increasingly common. Yet, research is limited and the underlying mechanism remains unclear. In this study, in vitro wear loss of human enamel was investigated and the attrition-corrosion process and wear mechanism were elucidated by the analysis of the wear scar and its subsurface using focused ion beam (FIB) sectioning and scanning electron microscopy (SEM). Human enamel flat-surface samples were prepared with enamel cusps as the wear antagonists. Reciprocating wear testing was undertaken under load of 5N at the speed of 66 cycle/min for 2250 cycles with lubricants including citric acid (at pH 3.2 and 5.5), acetic acid (at pH 3.2 and 5.5) and distilled water. All lubricants were used at 37°C. Similar human enamel flat-surface samples were also exposed to the same solutions as a control group. The substance loss of enamel during wear can be linked to the corrosion potential of a lubricant used. Using a lubricant with very low corrosion potential (such as distilled water), the wear mechanism was dominated by delamination with high wear loss. Conversely, the wear mechanism changed to shaving of the softened layer with less material loss in an environment with medium corrosion potential such as citric acid at pH 3.2 and 5.5 and acetic acid at pH 5.5. However, a highly corrosive environment (e.g., acetic acid at pH 3.2) caused the greatest loss of substance during wear. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Characteristics of school-sanctioned sports: participation and attrition in Wisconsin public high schools.

    Science.gov (United States)

    Landis, Matthew J; Peppard, Paul P; Remington, Patrick L

    2007-09-01

    Successful approaches are needed to decrease the burden of obesity on America's youth. Researchers often look to the high school interscholastic sports experience as a promising area for intervention. The purpose of this paper is to examine trends in participation over the course of a 4-year educational period. Two research questions are posed in this study: (1) how does participation in interscholastic sports change over the high school interscholastic sports experience, and (2) how do gender and school size influence these patterns? To answer these questions, a panel study is used to prospectively follow 412 Wisconsin public high schools from freshman year (2000-2001) to senior year (2003-2004). Participation prevalence (percent participation) in freshman year and risk of attrition (defined as a reduction in prevalence) from freshman to senior year are reported for sport, gender, and school size characteristics. Overall sports participation is greatest in smaller schools versus larger schools for both females (36% versus 20%) and males (38% versus 25%). Most high school sports exhibit declines in participation, including those sports with the highest prevalence of freshman participation. Compared to sports participants attending large schools, participants attending small schools have a lower risk of attrition from freshman to senior year. However, female attrition is much higher than male attrition in small schools, whereas this difference is not as apparent in large schools. The results of this research suggest school size and gender play important roles in initial and sustained involvement during high school. Despite the potential immediate and long-term benefits of high school interscholastic sports participation, there is limited research that prospectively examines patterns of participation through high school. Expanding the use of this measurement approach may effectively promote physical activity as youth grow into adults.

  11. A strategy of attrition through enforcement: the unmaking of irregular migration in Malaysia

    OpenAIRE

    Low, Choo Chin

    2017-01-01

    This article reviews Malaysia’s attempt to achieve zero migration irregularity by focusing on workplace enforcement, and examines how Malaysia’s migration control has become a struggle between the state and employers. Applying the framework of “enforcement through attrition,” this research examines three newly introduced principles governing workplace enforcement: employer sanctions, the Strict Liability Principle, and the Employers’ Mandatory Commitment. The shift to employers in Malaysia’s ...

  12. Characteristics and Trends of Attrition from the United States Naval Academy

    Science.gov (United States)

    2006-06-01

    Understanding why different types of attrition occur could lead to cost saving selection solutions, counseling solutions, or other interventions to...Nearly half the students in this category report having experienced racism or sexism (Landry, 2003). Thus, personal, social, and marginalization...a system of intervention and coaching may be developed to reduce at risk students. 16 THIS PAGE INTENTIONALLY LEFT BLANK 17 III. DESCRIPTION OF

  13. Psychological and Organizational Factors Related to Attrition and Performance in Marine Corps Recruit Training

    Science.gov (United States)

    1979-11-21

    management and employee turnover (Mobley, Griffet!h, Hand, S I Meglino, 1977). More specifically, the research of these investigators has been quided...predictive value vis-a-vis , ttrition . The best single predictor of attrition =77=,.-. 3 was the recruits’ initial expectation of completion (r .22...W., Hand, H. H., & Meglino, B. M. Review and conceptual analysis of the employee turnover process (TR-4). South Carolina: University of South

  14. 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...

  15. Losing a Language in Childhood: A Longitudinal Case Study on Language Attrition

    Science.gov (United States)

    Flores, Cristina

    2015-01-01

    This paper is based upon a longitudinal study of L2 attrition in a bilingual child who grew up in an L2 migration background (Germany) and moved to the country of origin (Portugal) at the age of nine, experiencing a "dominance shift from the L2 to the L1." The study aims to analyze the effects of language loss in L2 German. Data…

  16. 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.

  17. Effects of Stress, Coping Style, and Confidence on Basic Combat Training Performance, Discipline, and Attrition

    OpenAIRE

    Davis, Thomas Wayne

    2006-01-01

    The attrition rate of enlistees in basic combat training is of particular concern to all Branches of the military due to the high cost associated with recruiting and training a new enlistee. Each year the military loses hundreds of millions of dollars invested in enlistees whom never make it to their first duty station. Investigators have extensively examined the impact of physiological injuries on the rate of enlistee discharge from basic combat training. Also, investigators have ...

  18. Effects of Moral Conduct Waivers on First-Term Attrition of U.S. Army Soldiers

    Science.gov (United States)

    2008-03-01

    diploma or obtained additional years of education (which range from some college to advanced degrees), receive a value of zero for this variable. Similar...military officer training in college . I assume these programs will have a small negative 18 effect on attrition due to the soldiers having some...this may in part be due to the proliferation of alternative certifications for high school completion. These would include GED, homeschooling , adult

  19. 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 ...

  20. A Longitudinal Examination of First Term Attrition and Reenlistment among FY1999 Enlisted Accessions

    Science.gov (United States)

    2005-11-01

    homesickness Successful implementation of attrition management strategies will necessarily involve a combination of these approaches. ix A LONGITUDINAL...being homesick ). The remaining five items did not load highly on any of these factors, and therefore were analyzed individually. However, we developed a...Soldiers whether they would leave because they could not adjust to Army life (e.g., homesickness ). The remaining eight items did not load on any of these

  1. Critical Mass: Is Female Marine Attrition Higher in Non-Traditional Military Occupational Specialties

    Science.gov (United States)

    2017-03-01

    any variety of reasons. Pregnancy or childbirth and being the surviving family member were the only two separation reasons due to family matters. The...Flatter, J. R. (1996). First-term attrition due to pregnancy in the Marine Corps: Issues, trends, and options (Master’s thesis). Retrieved from http...military testing . Retrieved from http://official-asvab.com/history_rec.htm Patten, E. &Parker, K. (2011). Women in the U.S. military: growing share

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

    Science.gov (United States)

    Padmanabhan, Shyam; Reddy, Venkateswara Allu

    2010-07-01

    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 describe the management of one such case.

  3. Determinants of First-Term Attrition for Enlisted and Officer Selected Marine Corps Reservists

    Science.gov (United States)

    2015-03-01

    through 2014. Any personal identification information was eliminated before acquisition, and unique numbers are assigned to each individual to prevent...specialties. There are numerous types of waivers such as conduct, medical, dependent, age, tattoo , or dmg. There m·e also subcategories for each of...significance of the results and predictive ability of the model. Another limitation which affects both models is the identification of the attrition variable

  4. A Study on Prevalence of Dental Attrition and its Relation to Factors of Age, Gender and to the Signs of TMJ Dysfunction.

    Science.gov (United States)

    Yadav, Sangeeta

    2011-06-01

    A study was planned to determine the severity of dental attrition in adults of both sexes in different age groups and its possible relationship to temporomandibular disorders. 500 subjects comprising of 260 females and 240 males in the age group of 18-55 years were clinically examined for bruxism, attrition, and signs of temporomandibular disorders. Tooth sensitivity, tooth or restoration fracture, scalloping of tongue, ridging of buccal mucosa, TMJ sounds, muscle tenderness, TMJ tenderness, referred pain, pain on mouth opening and limitation of mouth opening were recorded along with attrition score in a proforma. The basic data was then analysed to arrive at certain conclusions. A high prevalence of attrition (88.0%) with increase in age (P attrition with some of the signs of bruxism it was shown that tooth or restoration fracture and scalloping of tongue had no relation to the severity of attrition score. Whereas a significant relation was seen between attrition and tooth sensitivity (P attrition. Other signs of temporomandibular disorders such as joint tenderness, referred pain, joint sounds and limitation of mouth opening had no relation to attrition score. This study showed a limited association between the severity of attrition and TMJ dysfunction.

  5. The pitfall of experimenting on the web: How unattended selective attrition leads to surprising (yet false) research conclusions.

    Science.gov (United States)

    Zhou, Haotian; Fishbach, Ayelet

    2016-10-01

    The authors find that experimental studies using online samples (e.g., MTurk) often violate the assumption of random assignment, because participant attrition-quitting a study before completing it and getting paid-is not only prevalent, but also varies systemically across experimental conditions. Using standard social psychology paradigms (e.g., ego-depletion, construal level), they observed attrition rates ranging from 30% to 50% (Study 1). The authors show that failing to attend to attrition rates in online panels has grave consequences. By introducing experimental confounds, unattended attrition misled them to draw mind-boggling yet false conclusions: that recalling a few happy events is considerably more effortful than recalling many happy events, and that imagining applying eyeliner leads to weight loss (Study 2). In addition, attrition rate misled them to draw a logical yet false conclusion: that explaining one's view on gun rights decreases progun sentiment (Study 3). The authors offer a partial remedy (Study 4) and call for minimizing and reporting experimental attrition in studies conducted on the Web. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  6. Issues concerning recruitment, retention and attrition of student nurses in the 1950/60s: a comparative study.

    Science.gov (United States)

    Jinks, Annette M; Richardson, Kathleen; Jones, Chris; Kirton, Jennifer A

    2014-11-01

    To investigate student nurse recruitment and attrition in the 1950' and 1960s and undertake comparisons to modern day concerns. The study was set in one hospital in the U.K. In the period studied nursing was unpopular as a profession and there were difficulties surrounding recruitment. Attrition rates were high. Documentary analysis of 641 training records dating 1955 to 1968 was undertaken. Attrition rates, reasons for non-completion and employment following successful completion were determined. Most recruits were young, unmarried, females and had overseas addresses. The majority (n = 88) had prior nursing experience. Over 69% (n = 443) successfully completed their training. Attrition rates were over 30% (n = 198), the main reason being academic failure. Following completion over 40% (n = 183) undertook midwifery training (n = 183) or secured a staff nurse post (n = 153). Issues relating to recruitment, retention and attrition in the 1950s and 1960s put into context present day issues. Recent attrition rates from pre-registration nurse education have fallen, nevertheless some of the issues of yesteryear remain problematic. In the present study significant numbers of entrants left due to domestic and ill-health problems resonates with many modern day studies. Also failure to complete due to academic shortcomings continues to be a concern. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. 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.

  8. Attrition of on-line graduate nursing students before and after program structural changes.

    Science.gov (United States)

    Rice, Jan; Rojjanasrirat, Wilaiporn; Trachsel, Pat

    2013-01-01

    This study assessed attrition rates and reasons for withdrawal among on-line graduate students before and after the implementation of program structural changes in 2008. A descriptive retrospective cohort study was conducted using the academic and advising records of 853 on-line graduate nursing students enrolled between 2005 and 2010. Three student cohorts were examined: (Cohort 1) students who entered and withdrew prior to 2008, (Cohort 2) students who entered before and withdrew after 2008, and (Cohort 3) students who entered and withdrew after 2008. The proportions of student attrition from each cohort were 43% (97 out of 225 students), 19% (52 out of 277 students), and 7.4% (26 out of 351 students), respectively. Results indicated that students' attrition rates in Cohorts 2 and 3 were significantly less than Cohort 1. Supported by Alexander Astin's input-experience-output model, 2 major themes emerged as reasons for withdrawal--personal and academic. Findings from this study provided a critical view for further investigation and serve as an evaluation tool to identify trends and develop appropriate supportive interventions that facilitate positive student outcomes. Further research is warranted to investigate the effects of the program structural changes on students' attitudes and program satisfaction. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Personality and attrition from behavioral weight-loss treatment for obesity.

    Science.gov (United States)

    De Panfilis, Chiara; Torre, Mariateresa; Cero, Sara; Salvatore, Paola; Dall'Aglio, Elisabetta; Marchesi, Carlo; Cabrino, Chiara; Aprile, Sonja; Maggini, Carlo

    2008-01-01

    Some personality features, as measured by the Temperament and Character Inventory (TCI), have recently been found to be related to successful weight outcome after both behavioral and surgical therapies for obesity. However, personality features could possibly influence attendance in obesity treatments as well. Thus, the aim of this study was to explore whether personality variables assessed by the TCI predict attrition from a behavioral weight-loss program for obesity. The TCI was administered to 92 obese patients [body mass index (BMI) >30 kg/m2] applying for a 6-month behavioral weight-loss program. Logistic stepwise regression analysis was performed to evaluate whether TCI scores predicted 6-month treatment attrition, after controlling for baseline psychiatric comorbidity, current age, gender, age at onset of obesity and initial BMI. Sixty-two subjects (67.4%) completed the 6-month program, while 30 (32.6%) dropped out. Treatment attrition was predicted only by low reward dependence (P=.03) and the presence of mental disorders (P=.004). Personality features denoting difficulty relying on others' support (low reward dependence) are associated with treatment noncompletion in obese patients attending a behavioral weight-loss program. These data may possibly serve to inform clinicians how to proceed in order to reduce dropout risk.

  10. A Systematic Review of Satisfaction and Pediatric Obesity Treatment: New Avenues for Addressing Attrition

    Science.gov (United States)

    Skelton, Joseph A.; Irby, Megan Bennett; Geiger, Ann M.

    2014-01-01

    Pediatric obesity treatment programs report high attrition rates, but it is unknown if family experience and satisfaction contributes. This review surveys the literature regarding satisfaction in pediatric obesity and questions used in measurement. A systematic review of the literature was conducted using Med-line, PsychINFO, and CINAHL. Studies of satisfaction in pediatric weight management were reviewed, and related studies of obesity were included. Satisfaction survey questions were obtained from the articles or from the authors. Eighteen studies were included; 14 quantitative and 4 qualitative. Only one study linked satisfaction to attrition, and none investigated the association of satisfaction and weight outcomes. Most investigations included satisfaction as a secondary aim or used single-item questions of overall satisfaction; only one assessed satisfaction in noncompleters. Overall, participants expressed high levels of satisfaction with obesity treatment or prevention programs. Surveys focused predominantly on overall satisfaction or specific components of the program. Few in-depth studies of satisfaction with pediatric obesity treatment have been conducted. Increased focus on family satisfaction with obesity treatment may provide an avenue to lower attrition rates and improve outcomes. Enhancing measurement of satisfaction to yield actionable responses could positively influence outcomes, and a framework, via patient-centered care principles, is provided. PMID:23414547

  11. Growing up Overseas: Perceptions of Second Language Attrition and Retrieval Amongst Expatriate Children in India

    Directory of Open Access Journals (Sweden)

    Steve R. Sider

    2004-12-01

    Full Text Available Abstract This study involves expatriate children whose first language (L1 is English and who learned Hindi as their second language (L2 while their parents worked in India. The purpose of the study was to investigate the linguistic experiences of the children after they had left India, particularly experiences with L2 attrition. Through semi-structured interviews, subjects shared their stories of L2 acquisition and attrition. Common experiences which contributed to the attrition of the L2 included periods of non-use of the L2, social responses to the use of the L2, the lack of development of Hindi literacy and subjects’ attitude toward using the L2. Some of the subjects were able to retrieve the L2 on return trips to India and an examination is made of their perceptions of what supported this retrieval process. These include exposure to the “environment” of India and personal motivation. The conclusion provides questions and suggestions for further research to contribute to a better understanding of the linguistic experiences of expatriate children.

  12. Factors influencing nursing students' academic and clinical performance and attrition: an integrative literature review.

    Science.gov (United States)

    Pitt, Victoria; Powis, David; Levett-Jones, Tracy; Hunter, Sharyn

    2012-11-01

    Predicted workforce shortages have resulted in government initiatives to increase student numbers in preregistration nursing education. In tandem schools of nursing need to ensure students' progress and complete. The aim of this review was to identify factors that influence preregistration nursing students' academic performance, clinical performance and attrition. An integrative review of both quantitative and qualitative literature was conducted using validated appraisal checklists. The review included studies published from 1999 to 2011 in the databases: MEDLINE, CINAHL, Proquest nursing, Proquest Education (via Proquest 5000), ERIC, Journals@Ovid, PsychINFO and ScienceDirect. Studies were categorised according to their impact on academic progression, clinical progression and attrition. Forty four studies were found; most used quantitative methodologies. The review identified that few studies explored factors that impact on students' clinical performance. The four categories that potentially impact on nursing students' academic performance and attrition were: demographic, academic, cognitive and personality/behavioural factors. The challenge for universities committed to students' success is to develop strategies aimed at addressing these factors that are appropriate to specific contexts and student cohorts. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Steam reforming of tar derived from lignin over pompom-like potassium-promoted iron-based catalysts formed on calcined scallop shell.

    Science.gov (United States)

    Guan, Guoqing; Kaewpanha, Malinee; Hao, Xiaogang; Zhu, Ai-Min; Kasai, Yutaka; Kakuta, Seiji; Kusakabe, Katsuki; Abudula, Abuliti

    2013-07-01

    In order to understand the improvement effect of potassium (K) on the catalytic activity of iron-loaded calcined scallop shell (CS) for the steam reforming tar derived from biomass, various K precursors were applied for the catalyst preparation. It is found that pompom-like iron-based particles with a mesoporous structure were easily formed on the surface of calcined scallop shell (CS) when K2CO3 was used as K precursor while no such kind of microsphere was formed when other kinds of K precursors such as KOH and KNO3 were applied. The optimum K-loading amount for the preparation of this catalyst was investigated. Based on the experimental results obtained, a mechanism for the formation of these microspheres was proposed. This pompom-like potassium-promoted iron-based catalyst showed a better catalytic activity and reusability for the steam reforming of tar derived from lignin. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. High attrition before and after ART initiation among youth (15–24 years of age) enrolled in HIV care

    Science.gov (United States)

    Lamb, Matthew R.; Fayorsey, Ruby; Nuwagaba-Biribonwoha, Harriet; Viola, Violante; Mutabazi, Vincent; Alwar, Teresa; Casalini, Caterina; Elul, Batya

    2015-01-01

    Objectives To compare pre and post-ART attrition between youth (15–24 years) and other patients in HIV care, and to investigate factors associated with attrition among youth. Design Cohort study utilizing routinely collected patient-level data from 160 HIV clinics in Kenya, Mozambique, Tanzania, and Rwanda. Methods Patients at least 10 years of age enrolling in HIV care between 01/05 and 09/10 were included. Attrition (loss to follow-up or death 1 year after enrollment or ART initiation) was compared between youth and other patients using multivariate competing risk (pre-ART) and traditional (post-ART) Cox proportional hazards methods accounting for within-clinic correlation. Among youth, patient-level and clinic-level factors associated with attrition were similarly assessed. Results A total of 312 335 patients at least 10 years of age enrolled in HIV care; 147 936(47%) initiated ART, 17% enrolling in care and 10% initiating ART were youth. Attrition before and after ART initiation was substantially higher among youth compared with other age groups. Among youth, nonpregnant women experienced lower pre-ART attrition than men [sub-division hazard ratio=0.90, 95% confidence interval (CI): 0.86–0.94], while both pregnant [adjusted hazard ratio (AHR) = 0.85, 95% CI: 0.74–0.97] and nonpregnant (AHR = 0.79, 95% CI: 0.73–0.86) female youth experienced lower post-ART attrition than men. Youth attending clinics providing sexual and reproductive health services including condoms (AHR = 0.47, 95% CI: 0.32–0.70) and clinics offering adolescent support groups (AHR = 0.73, 95% CI: 0.52–1.0) experienced significantly lower attrition after ART initiation. Conclusion Youth experienced substantially higher attrition before and after ART initiation compared with younger adolescents and older adults. Adolescent-friendly services were associated with reduced attrition among youth, particularly after ART initiation. PMID:24076661

  15. 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.

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

    Science.gov (United States)

    Xie, Jingxiu; Torres Galvis, Hirsa M; Koeken, Ard C J; Kirilin, Alexey; Dugulan, A Iulian; Ruitenbeek, Matthijs; de Jong, Krijn P

    2016-06-03

    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.

  17. 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

  18. 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.

  19. New strategies to prolong the in vivo life span of iron-based contrast agents for MRI.

    Science.gov (United States)

    Antonelli, Antonella; Sfara, Carla; Battistelli, Serafina; Canonico, Barbara; Arcangeletti, Marcella; Manuali, Elisabetta; Salamida, Sonia; Papa, Stefano; Magnani, Mauro

    2013-01-01

    Superparamagnetic iron oxide (SPIO) and ultra small superparamagnetic iron oxide (USPIO) nanoparticles have been developed as magnetic resonance imaging (MRI) contrast agents. Iron oxide nanoparticles, that become superparamagnetic if the core particle diameter is ~ 30 nm or less, present R1 and R2 relaxivities which are much higher than those of conventional paramagnetic gadolinium chelates. Generally, these magnetic particles are coated with biocompatible polymers that prevent the agglomeration of the colloidal suspension and improve their blood distribution profile. In spite of their potential as MRI blood contrast agents, the biomedical application of iron oxide nanoparticles is still limited because of their intravascular half-life of only few hours; such nanoparticles are rapidly cleared from the bloodstream by macrophages of the reticulo-endothelial system (RES). To increase the life span of these MRI contrast agents in the bloodstream we proposed the encapsulation of SPIO nanoparticles in red blood cells (RBCs) through the transient opening of cell membrane pores. We have recently reported results obtained by applying our loading procedure to several SPIO nanoparticles with different chemical physical characteristics such as size and coating agent. In the current investigation we showed that the life span of iron-based contrast agents in the mice bloodstream was prolonged to 12 days after the intravenous injection of murine SPIO-loaded RBCs. Furthermore, we developed an animal model that implicates the pretreatment of animals with clodronate to induce a transient suppression of tissue macrophages, followed by the injection of human SPIO-loaded RBCs which make it possible to encapsulate nanoparticle concentrations (5.3-16.7 mM Fe) higher than murine SPIO-loaded RBCs (1.4-3.55 mM Fe). The data showed that, when human RBCs are used as more capable SPIO nanoparticle containers combined with a depletion of tissue macrophages, Fe concentration in animal blood is

  20. Effects of disorder on the intrinsically hole-doped iron-based superconductor KC a2F e4A s4F2 by cobalt substitution

    Science.gov (United States)

    Ishida, Junichi; Iimura, Soshi; Hosono, Hideo

    2017-11-01

    In this paper, the effects of cobalt substitution on the transport and electronic properties of the recently discovered iron-based superconductor KC a2F e4A s4F2 , with Tc=33 K , are reported. This material is an unusual superconductor showing intrinsic hole conduction (0.25 holes /F e2 + ). Upon doping of Co, the Tc of KC a2(Fe1-xC ox) 4A s4F2 gradually decreased, and bulk superconductivity disappeared when x ≥0.25 . Conversion of the primary carrier from p type to n type upon Co-doping was clearly confirmed by Hall measurements, and our results are consistent with the change in the calculated Fermi surface. Nevertheless, neither spin density wave (SDW) nor an orthorhombic phase, which are commonly observed for nondoped iron-based superconductors, was observed in the nondoped or electron-doped samples. The electron count in the 3 d orbitals and structural parameters were compared with those of other iron-based superconductors to show that the physical properties can be primarily ascribed to the effects of disorder.

  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. 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

  3. Baseline risk has greater influence over behavioral attrition on the real-world clinical effectiveness of cardiac rehabilitation.

    Science.gov (United States)

    Biswas, Aviroop; Oh, Paul I; Faulkner, Guy E; Alter, David A

    2016-11-01

    Few studies have examined the correlates of real-world cardiac rehabilitation (CR) effectiveness. The objective of this study was to determine the relationship between baseline risk, behavioral attrition, and the number needed to treat (NNT) associated with CR. A retrospective study was conducted among 16,061 CR patients between 1995 and 2011 in Canada. Multiple logistic regression models were derived from patient characteristics and measured baseline risk (individual's risk of death within 3 years) and behavioral attrition (individual's risk of premature dropout). We examined the treatment efficacy of CR among nondropouts using a 20% relative risk reduction. Further sensitivity analyses were performed to assess the robustness of our assumptions. We assumed no efficacy among dropouts. Both baseline risk and behavioral attrition were independently associated with NNT, although baseline risk had a stronger association with NNT than behavioral attrition. Increasing age, lower baseline fitness, history of diabetes, hypertension, and greater comorbidities were associated with lower NNT. Being female, living alone, living in the lowest neighborhood income quintile, and greater adiposity were associated with higher NNT. The clinical effectiveness of CR is largely driven by the baseline risk rather than the behavioral attrition of the populations they serve. These findings have implications for risk stratification among those with greatest survival yields and programmatic needs. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. New strategies to prolong the in vivo life span of iron-based contrast agents for MRI.

    Directory of Open Access Journals (Sweden)

    Antonella Antonelli

    Full Text Available Superparamagnetic iron oxide (SPIO and ultra small superparamagnetic iron oxide (USPIO nanoparticles have been developed as magnetic resonance imaging (MRI contrast agents. Iron oxide nanoparticles, that become superparamagnetic if the core particle diameter is ~ 30 nm or less, present R1 and R2 relaxivities which are much higher than those of conventional paramagnetic gadolinium chelates. Generally, these magnetic particles are coated with biocompatible polymers that prevent the agglomeration of the colloidal suspension and improve their blood distribution profile. In spite of their potential as MRI blood contrast agents, the biomedical application of iron oxide nanoparticles is still limited because of their intravascular half-life of only few hours; such nanoparticles are rapidly cleared from the bloodstream by macrophages of the reticulo-endothelial system (RES. To increase the life span of these MRI contrast agents in the bloodstream we proposed the encapsulation of SPIO nanoparticles in red blood cells (RBCs through the transient opening of cell membrane pores. We have recently reported results obtained by applying our loading procedure to several SPIO nanoparticles with different chemical physical characteristics such as size and coating agent. In the current investigation we showed that the life span of iron-based contrast agents in the mice bloodstream was prolonged to 12 days after the intravenous injection of murine SPIO-loaded RBCs. Furthermore, we developed an animal model that implicates the pretreatment of animals with clodronate to induce a transient suppression of tissue macrophages, followed by the injection of human SPIO-loaded RBCs which make it possible to encapsulate nanoparticle concentrations (5.3-16.7 mM Fe higher than murine SPIO-loaded RBCs (1.4-3.55 mM Fe. The data showed that, when human RBCs are used as more capable SPIO nanoparticle containers combined with a depletion of tissue macrophages, Fe concentration in

  5. Village Health Worker Attrition and Function Levels in the ILE-IFE Area of Nigeria.

    Science.gov (United States)

    Ewoigbokhan, S E; Ches, W R

    1993-01-01

    Volunteer village health workers (VHWs) form the backbone of primary health care (PHC) from both philosophical and logistical perspectives. They represent an underlying PHC ethic of community involvement as well as a practical means for delivering health care at the grassroots. Although VHW recruitment and training does not rival the cost of training formal medical and health workers, the investment in not insubstantial. Thus when VHW dropout rates approach 50 percent in many countries, there is cause for alarm and for investigation into the possible causes of attrition. Nigeria embarked on a national PHC program in 1986, supported by national PHC policy in 1987. Nearly 1500 VHWs have been trained in model local government areas (LGAs) during the intervening years. Although there have been anecdotal reports of VHW attrition, little study into the reasons for drop-out from this large scale and expensive operation have been undertaken. This study looked at the former Oranmiyan LGA (now divided into three) where 115 VHWs had been trained. Only 79 percent of trainees took up PHC tasks, and another 7 percent left their villages shortly thereafter due to school admission or job opportunities. Two to three years after the initial training, 58 percent of the original trainees self-reported that they were still functioning as VHWs. A PHC function test, based on VHW job descriptions, was developed and administered within a questionnaire among the VHWs still living in their villages. Three factors were associated with function score: farming as an occupation, reported recent supervision and reported attendance at a continuing education activity. The results indicate two main points of intervention for preventing VHW attrition. During recruitment, effort should be made to explain the voluntary nature of the work and to encourage villagers to select people (like farmers) who will reside permanently in the village. After training, supervision and continuing education must be

  6. 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

  7. Attrition tendinitis of long head of biceps brachii in relation to humeral head osteonecrosis: case report.

    Science.gov (United States)

    Wiesler, Ethan R; Sarlikiotis, Thomas; Mavrogenis, Andreas F; Kokkalis, Zinon T

    2013-01-01

    This case report identifies a 41-year-old male patient who developed anterior shoulder pain in the setting of humeral head osteonecrosis. As a consequence of the cartilage degeneration, multiple loose bodies formed and migrated into the bicipital tendon sheath, causing attrition tendinitis, which was a feature of the clinical presentation. The patient was treated by a combination of arthroscopic glenohumeral joint debridement and open tenodesis of the biceps using a suture anchor. Follow-up revealed asymptomatic shoulder function by 18 months. This is the first report in the literature of bicipital tendinitis in the context of avascular necrosis of the shoulder.

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

    Directory of Open Access Journals (Sweden)

    Slavica Čepon

    2007-06-01

    Full Text Available 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 essential for the future professional development of the economics graduates. It is hoped that this will spur foreign language policy renewal.

  9. Commentary: physician-scientist attrition: stemming the tide through national networks for training and development.

    Science.gov (United States)

    Schwartz, Alan L

    2011-09-01

    Future advances in medicine depend on a reliable pipeline of physician-scientists. However, the changing demographics of physician-scientists, including the advanced age of new MD investigators, and attrition along the physician-scientist developmental pathway are cause for concern. Recently developed National Institutes of Health-funded national networks for physician-scientist training and development-such as the Advanced Research Institute in Geriatric Mental Health and the Pediatric Scientist Development Program-offer valuable approaches to supporting and retaining these trainees.

  10. Attrition and retention in the nursing major: understanding persistence in beginning nursing students.

    Science.gov (United States)

    Williams, Margaret G

    2010-01-01

    To meet the challenges of the ongoing nursing shortage, it is imperative to increase the retention of students enrolled in schools of nursing. This article reports on findings from a larger research study on faculty-directed strategies to address the attrition of beginning students during the early, nonclinical phase of nursing education. Four themes that influenced students' persistence in the nursing major were uncovered during interviews: Keeping Up, Not Giving Up, Doing It, and Connecting to the use of resources. Diekelmann's concernful practices as enacted by faculty are linked to student narratives.

  11. 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

    intake and other life-style factors during 28 years of follow-up, were linked with nation-wide registers on socio-economic covariates, mortality and disease incidence. Logistic regression was used to describe life-style and socio-economic determinants of attrition, and Poisson regression was used...... to evaluate how attrition affected the association between alcohol intake and mortality. The statistical methods used for dealing with missing values were complete case analysis, carry last observation forward, simple imputations, multiple imputation and weighting. FINDINGS: Abstinence and high alcohol intake......, current smoking, physical inactivity and high body mass index increased the odds of dropping out, whereas being married, more years of education, skilled occupation, high income and large residential area decreased the odds. Attrition was associated with increased mortality and incidence rates of heart...

  12. 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

  13. Association between self-reported bruxism activity and occurrence of dental attrition, abfraction, and occlusal pits on natural teeth.

    Science.gov (United States)

    Tsiggos, Nikolaos; Tortopidis, Dimitrios; Hatzikyriakos, Andreas; Menexes, George

    2008-07-01

    It is unclear whether subjects who report tooth clenching and/or grinding have more noticeable clinical signs of dental attrition, abfractions, and occlusal pits on their natural teeth than subjects who do not report bruxism activity. The purpose of this study was to determine whether there was an association between self-reported (or not reported) bruxism activity and occurrence of dental attrition (anterior, posterior), abfractions, and occlusal pits on natural teeth. One hundred and two volunteer adult Greek subjects (mean age 44.6 +/-5.7 years) were classified into 2 groups (50 self-reported bruxers and 52 nonbruxers) according to 2 inquires regarding grinding and/or clenching of their teeth. Dental attrition (anterior, posterior) was assessed by 2 calibrated experienced examiners on diagnostic casts on a tooth-by-tooth basis, using a previously well established ordinal scale. Abfraction lesions (V-shaped, in the cervical region) and occlusal pits were recorded if these clinical signs were found on at least 2 natural teeth. Statistical comparisons between the 2 groups relative to the distribution of the occurrence of the 4 clinical signs were performed by means of the exact version of the chi-square test. The Fisher's exact test was used for the comparison of percentages. The intra- and interexaminer reliability was assessed by means of the Cohen's kappa coefficient (alpha=.05). The results demonstrated that there was a significant association between self-reported bruxism and occurrence of the 4 clinical signs. Although the 2 groups were significantly different according to the distribution of the 4 clinical signs, the greatest differences occurred for the anterior and posterior attrition signs. In this study, the occurrence of 4 clinical signs (posterior or anterior dental attrition, abfractions, and occlusal pits) was associated with self-reported bruxers. It is suggested that, primarily, signs of dental attrition may differentiate self-reported bruxers from

  14. Forest dynamics in the U.S. indicate disproportionate attrition in western forests, rural areas and public lands.

    Science.gov (United States)

    Yang, Sheng; Mountrakis, Giorgos

    2017-01-01

    Forests are experiencing significant changes; studying geographic patterns in forests is critical in understanding the impact of forest dynamics to biodiversity, soil erosion, water chemistry and climate. Few studies have examined forest geographic pattern changes other than fragmentation; however, other spatial processes of forest dynamics are of equal importance. Here, we study forest attrition, the complete removal of forest patches, that can result in complete habitat loss, severe decline of population sizes and species richness, and shifts of local and regional environmental conditions. We aim to develop a simple yet insightful proximity-based spatial indicator capturing forest attrition that is independent of spatial scale and boundaries with worldwide application potential. Using this proximity indicator, we evaluate forest attrition across ecoregions, land ownership and urbanization stratifications across continental United States of America. Nationally, the total forest cover loss was approximately 90,400 km2, roughly the size of the state of Maine, constituting a decline of 2.96%. Examining the spatial arrangement of this change the average FAD was 3674m in 1992 and increased by 514m or 14.0% in 2001. Simulations of forest cover loss indicate only a 10m FAD increase suggesting that the observed FAD increase was more than an order of magnitude higher than expected. Furthermore, forest attrition is considerably higher in the western United States, in rural areas and in public lands. Our mathematical model (R2 = 0.93) supports estimation of attrition for a given forest cover. The FAD metric quantifies forest attrition across spatial scales and geographic boundaries and assesses unambiguously changes over time. The metric is applicable to any landscape and offers a new complementary insight on forest landscape patterns from local to global scales, improving future exploration of drivers and repercussions of forest cover changes and supporting more informative

  15. A Descriptive Study of the Impact of the Highly Qualified Teacher Requirement of NCLB on the Attrition of Special Education Personnel

    Science.gov (United States)

    VanCise, Sandra A.

    2013-01-01

    According to current research, attrition of teachers in public schools throughout the United States has become increasingly worrisome, especially since the passage and inception of No Child Left Behind (2001) as well as the reauthorization of Individuals with Disabilities Act (1997). This rate of attrition remains especially problematic in the…

  16. Beyond the First-Year Experience: The Impact on Attrition of Student Experiences throughout Undergraduate Degree Studies in Six Diverse Universities

    Science.gov (United States)

    Willcoxson, Lesley; Cotter, Julie; Joy, Sally

    2011-01-01

    In the face of difficult economic circumstances, increased competition and student diversity, attrition and retention have become issues of great significance to higher education institutions seeking to survive. A large body of work has explored the relationship between attrition and the first-year experience, but there has been little focus on…

  17. Taking into account the impact of attrition on the assessment of response shift and true change: a multigroup structural equation modeling approach

    NARCIS (Netherlands)

    Verdam, Mathilde G. E.; Oort, Frans J.; van der Linden, Yvette M.; Sprangers, Mirjam A. G.

    2015-01-01

    Missing data due to attrition present a challenge for the assessment and interpretation of change and response shift in HRQL outcomes. The objective was to handle such missingness and to assess response shift and 'true change' with the use of an attrition-based multigroup structural equation

  18. First Language Attrition Induces Changes in Online Morphosyntactic Processing and Re-Analysis: An ERP Study of Number Agreement in Complex Italian Sentences

    Science.gov (United States)

    Kasparian, Kristina; Vespignani, Francesco; Steinhauer, Karsten

    2017-01-01

    First language (L1) attrition in adulthood offers new insight on neuroplasticity and the role of language experience in shaping neurocognitive responses to language. Attriters are multilinguals for whom advancing L2 proficiency comes at the cost of the L1, as they experience a shift in exposure and dominance (e.g., due to immigration). To date,…

  19. Sex offender risk assessment: the need to place recidivism research in the context of attrition in the criminal justice system.

    Science.gov (United States)

    Larcombe, Wendy

    2012-04-01

    Jurisdictions in the United States, United Kingdom, and Australia now have laws that enable preventive detention of post-sentence sex offenders based on an assessment of the offender's likely recidivism. Measures of recidivism, or risk assessments, rely on the criminal justice process to produce the "pool" of sex offenders studied. This article argues that recidivism research needs to be placed in the context of attrition studies that document the disproportionate and patterned attrition of sexual offenses and sexual offenders from the criminal justice process. Understanding the common biases that affect criminal prosecution of sex offenses would improve sexual violence prevention policies.

  20. High pre-diagnosis attrition among patients with presumptive MDR-TB: an operational research from Bhopal district, India.

    Science.gov (United States)

    Shewade, Hemant Deepak; Kokane, Arun M; Singh, Akash Ranjan; Verma, Manoj; Parmar, Malik; Chauhan, Ashish; Chahar, Sanjay Singh; Tiwari, Manoj; Khan, Sheeba Naz; Gupta, Vivek; Tripathy, Jaya Prasad; Nagar, Mukesh; Singh, Sanjai Kumar; Mehra, Pradeep Kumar; Kumar, Ajay Mv

    2017-04-04

    Pre-diagnosis attrition needs to be addressed urgently if we are to make progress in improving MDR-TB case detection and achieve universal access to MDR-TB care. We report the pre-diagnosis attrition, along with factors associated, and turnaround times related to the diagnostic pathway among patient with presumptive MDR-TB in Bhopal district, central India (2014). Study was conducted under the Revised National Tuberculosis Control Programme setting. It was a retrospective cohort study involving record review of all registered TB cases in Bhopal district that met the presumptive MDR-TB criteria (eligible for DST) in 2014. In quarter 1, Line Probe Assay (LPA) was used if sample was smear/culture positive. Quarter 2 onwards, LPA and Cartridge-based Nucleic Acid Amplification Test (CbNAAT) was used for smear positive and smear negative samples respectively. Pre-diagnosis attrition was defined as failure to undergo DST among patients with presumptive MDR-TB (as defined by the programme). Of 770 patients eligible for DST, 311 underwent DST and 20 patients were diagnosed as having MDR-TB. Pre-diagnosis attrition was 60% (459/770). Among those with pre-diagnosis attrition, 91% (417/459) were not identified as 'presumptive MDR-TB' by the programme. TAT [median (IQR)] to undergo DST after eligibility was 4 (0, 10) days. Attrition was more than 40% across all subgroups. Age more than 64 years; those from a medical college; those eligible in quarter 1; patients with presumptive criteria 'previously treated - recurrent TB', 'treatment after loss-to-follow-up' and 'previously treated-others'; and patients with extra-pulmonary TB were independent risk factors for not undergoing DST. High pre-diagnosis attrition was contributed by failure to identify and refer patients. Attrition reduced modestly with time and one factor that might have contributed to this was introduction of CbNAAT in quarter 2 of 2014. General health system strengthening which includes improvement in

  1. Analysis of civilian employee attrition at the Naval Postgraduate School and Naval Support Activity-Monterey Bay.

    OpenAIRE

    Valverde, Xavier F.

    1997-01-01

    The purpose of this thesis is to assist management at the Naval Postgraduate School (NPS) and Naval Support Activity-Monterey Bay (NSA-MB) to determine what civilian non-faculty employee jobs are likely to be left vacant in the next three years due to attrition and to identify what training and skills will be needed by personnel whose jobs may be eliminated in order to be transferred to jobs left vacant due to attrition. The research methods include forecasting and work-analysis. The data wer...

  2. When the Second Language Takes the Lead: Neurocognitive Processing Changes in the First Language of Adult Attriters.

    Science.gov (United States)

    Kasparian, Kristina; Steinhauer, Karsten

    2017-01-01

    Although research on multilingualism has revealed continued neuroplasticity for language-learning beyond what was previously expected, it remains controversial whether and to what extent a second language (L2) acquired in adulthood may induce changes in the neurocognitive processing of a first language (L1). First language (L1) attrition in adulthood offers new insight on neuroplasticity and the factors that modulate neurocognitive responses to language. To date, investigations of the neurocognitive correlates of L1 attrition and of factors influencing these mechanisms are still scarce. Moreover, most event-related-potential (ERP) studies of second language processing have focused on L1 influence on the L2, while cross-linguistic influence in the reverse direction has been underexplored. Using ERPs, we examined the real-time processing of Italian relative-clauses in 24 Italian-English adult migrants with predominant use of English since immigration and reporting attrition of their native-Italian (Attriters), compared to 30 non-attriting monolinguals in Italy (Controls). Our results showed that Attriters differed from Controls in their acceptability judgment ratings and ERP responses when relative clause constructions were ungrammatical in English, though grammatical in Italian. Controls' ERP responses to unpreferred sentence constructions were consistent with garden path effects typically observed in the literature for these complex sentences. In contrast, due to L2-English influence, Attriters were less sensitive to semantic cues than to word-order preferences, and processed permissible Italian sentences as outright morphosyntactic violations. Key factors modulating processing differences within Attriters were the degree of maintained L1 exposure, length of residence in the L2 environment and L2 proficiency - with higher levels of L2 immersion and proficiency associated with increased L2 influence on the L1. To our knowledge, this is the first demonstration that

  3. An experiment on the attrition of acid demineralized dentine in vitro.

    Science.gov (United States)

    Li, H; Liu, M C; Deng, M; Moazzez, R; Bartlett, D W

    2011-03-01

    A laboratory investigation was designed to test the hypothesis that acids increase the rate of wear caused by attrition on dentine. Dentine sections from 10 teeth were polished, cleaned in an ultrasonic bath and divided into 8 equally sized areas. The occlusal tip of a tooth, placed vertically in a wear machine and loaded at 150 N, was moved against each dentine section for 5000 return strokes with artificial saliva acting as a lubricant. Each dentine section was divided into 8 sections and half randomly immersed in a 1% citric acid solution (pH 2.3) for 20 minutes. The wear regime produced 8 wear scars in total per dentine sample. The volume of each wear scar was measured using a contacting digitizing profilometer. A total of 80 wear scars were produced with 40 treated with acid and 40 acting as controls. The mean for wear volume of the dentine scars with acid was 4.84 μm(3) (1.38) and for the non-acid surface 2.95 μm(3) (0.86). This difference was statistically significant (p attrition on dentine. © 2011 Australian Dental Association.

  4. Computer-based self-help therapy: A qualitative analysis of attrition.

    Science.gov (United States)

    Hermes, Eric DA; Merrel, Jeremy; Clayton, Ashley; Morris, Christa; Rowe, Michael

    2016-12-01

    The impact of computer-based cognitive-behavioral self-help therapy programs is limited by high attrition. This study explored reactions to computer-based cognitive-behavioral self-help therapy use among individuals not completing a full treatment course. Individuals receiving outpatient substance use disorder treatment at a Veterans Health Administration clinic who enrolled in a study implementing a computer-based cognitive-behavioral self-help therapy for insomnia, but subsequently dropped out prior to completion, were interviewed. Reactions to use and reasons for attrition were explored through thematic analysis of interviews. Among barriers to use, themes of competing demands, personal attributes, the computer-based format of computer-based cognitive-behavioral self-help therapies, and negative experiences with the specific program used were identified. Among facilitators of use, themes of personal support, the computer-based cognitive-behavioral self-help therapy format, and personal attributes were identified. Recommendations for future implementation efforts to include additional person-to-person contact during computer-based cognitive-behavioral self-help therapy participation were made. These themes may be employed to develop strategies for computer-based cognitive-behavioral self-help therapy implementation in order to maximize program engagement and completion.

  5. Subclinical Partial Attritional Rupture of the Flexor Digitorum Profundus as an Etiology of Atraumatic Trigger Finger

    Directory of Open Access Journals (Sweden)

    D. Anthony Bastian

    2017-01-01

    Full Text Available Background. Trigger finger is a relatively common clinical entity. The etiology is most often attributable to stenosing tenosynovitis though traumatic cases have been described. When trigger finger is associated with an underlying flexor tendon rupture, previous cases have reported a clear association with overt laceration or previous trauma. Methods. We present the case of a 23-year-old male active duty military service member who presented with a characteristic history and clinical exam consistent with trigger finger. The symptomatic onset was gradual, with no history of inciting trauma. Results. Given symptomatic persistent triggering following failure of conservative management to include cortisone injections, the patient was taken for open A1 pulley release. Intraoperatively, the triggering was found to be attributable to a partial attritional rupture of the small finger flexor digitorum profundus tendon. Tendon debridement, tubularization, and A1 and partial A2 pulley releases were performed with subsequent resolution of triggering. Conclusion. We present the rare case of subclinical atraumatic attritional rupture of the FDP tendon to the small finger as a cause of clinically apparent trigger finger. This is an important consideration as the hand surgeon must be prepared to address more atypical pathologies.

  6. The Flip Side of the Attrition Coin: Faculty Perceptions of Factors Supporting Graduate Student Success

    Directory of Open Access Journals (Sweden)

    Joanna A Gilmore

    2016-12-01

    Full Text Available Doctoral attrition consistently hovers around 50% with relevant literature identifying several mediating factors, including departmental culture, student demographics, and funding. To advance this literature, we interviewed 38 graduate faculty advisors in science, engineering, or mathematics disciplines at a research-extensive university to capture their perceptions of factors supporting graduate student success. Using a constant-comparison method, we found that faculty perceptions aligned within three major categories, termed: motivated student behaviors, formative student learning experiences, and essential student knowledge and skills. Student motivation was most prominently represented in findings. This aligns with prior studies showing that faculty tend to identify the cause of graduate student failure as lying within the students themselves and rarely discuss their role or the department’s contribution to attrition. Thus findings offer an opportunity to reflect and improve upon practice. The study also highlights actions graduate students can take to increase success, such as developing collegial relationships and early involvement in research and scholarly writing. We encourage graduate faculty advisors and others to identify ways to help graduate students overcome common obstacles to enduring and succeeding within graduate programs. Faculty perceptions are also examined by discipline and faculty rank, and directions for future research are offered.

  7. Vocation, friendship and resilience: a study exploring nursing student and staff views on retention and attrition.

    Science.gov (United States)

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

    2013-01-01

    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. to understand students' and staff concerns about programmes and placements as part of developing our retention strategies. This study reports qualitative data on retention and attrition collected as part of an action research study. One University School of Nursing and Midwifery in the South West of England. Staff, current third year and ex-student nurses from the adult field. Data were collected in focus groups, both face-to face and virtual, and individual telephone interviews. These were transcribed and subjected to qualitative content analysis. FOUR THEMES EMERGED: Academic support, Placements and mentors, Stresses and the reality of nursing life, and Dreams for a better programme. The themes Academic support, Placements and mentors and Stresses and the reality of nursing life, resonate with international literature. Dreams for a better programme included smaller group learning. Vocation, friendship and resilience seem instrumental in retaining students, and Higher Education Institutions should work to facilitate these. 'Vocation' has been overlooked in the retention discussions, and working more actively to foster vocation and belongingness could be important.

  8. Reconciling viability and cost-effective shape memory alloy options – A review of copper and iron based shape memory metallic systems

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2016-09-01

    Full Text Available Shape memory alloys (SMAs are group of alloys that display anthropomorphic characteristics. These alloys recover their pre-deformed morphology when heated above their transition temperatures after being deformed in their lower temperature phase (martensitic phase. This unique material behavior is explored in industrial and technological applications where capacity for strain recovery is a key design parameter. Copper and iron based SMAs are largely viewed as potential cost effective substitute to Ni–Ti SMAs judging from their promising shape memory properties, damping capacity and other functional properties. Despite their outstanding potentials, the susceptibility of copper based SMAS to phase stabilization, transition hysteresis, aging and brittleness creates doubt on the possibility of transiting from the realm of potential to functional long term use in engineering applications. On the other hand the low percentage shape recovery in the Fe based SMAs also creates a gap between the theory and potential use of these alloys. This paper takes a critical look at the science of shape memory phenomena as applicable to copper and iron based SMA systems. It also covers the limitations of these systems, the effect of processing parameters on these alloys, proposed solutions to limitations associated with this group of shape memory alloys and thoughts for future consideration.

  9. Iron-based adsorbent prepared from Litchi peel biomass via pyrolysis process for the removal of pharmaceutical pollutant from synthetic aqueous solution.

    Science.gov (United States)

    Foletto, Vitória Segabinazzi; Ferreira, Ananda Bulegon; da Cruz Severo, Eric; Collazzo, Gabriela Carvalho; Foletto, Edson Luiz; Dotto, Guilherme Luiz

    2017-04-01

    A porous iron-based adsorbent obtained from litchi peel via pyrolysis process was prepared in this work, in order to evaluate its adsorptive potential for the removal of a pharmaceutical dye (amaranth) from aqueous solution. The material was characterized by X-ray diffraction, nitrogen adsorption-desorption isotherms, and scanning electron microscopy. Several isotherm and kinetic models were tested aiming to represent the amaranth dye adsorption. The prepared sample presented magnetic property, and a mesoporous texture constituted of graphite and three iron-based phases. The adsorption kinetics of amaranth on the adsorbent followed the pseudo-second-order model, whereas the equilibrium data were in good agreement with the BET isotherm, being represented by a sigmoid-shaped adsorption isotherm. The maximum adsorption capacity for the amaranth dye was found to be 44.87 mg g(-1), demonstrating that the material prepared in this work showed to be a promising adsorbent for the removal of amaranth from aqueous solution.

  10. Relationship between Los Angeles attrition test and Nordic abrasion test of volcanic rocks

    Science.gov (United States)

    Krutilová, Kateřina; Prikryl, Richard

    2015-04-01

    Various volcanic rocks contribute significantly to the production of crushed stone in the Czech Republic. When used for road surfacing, results of Los Angeles attrition test (LA value below 25 or 30 depending on the mode of use) together with polished stone value are required. In the recent study, we have focused on the search for possible correlation between results obtained by Los Angeles attrition test and Nordic abrasion test, a test widely employed in Scandinavia. For the experimental study, a set of volcanic rocks from 36 active quarries was used. The rocks under study represent range of volcanic rocks from ultrabasic to acid members, formed form Neoproterozoic to Tertiary. The most favourable results of Los Angeles attrition test (i.e. the lowest LA values) were obtained for basalts (range of values 9.4-19.4) and spilites (range of values 8.4-14.9) which are in fact Neoproterozoic to Late Palaeozoic basalts affected by low grade metamorphism. Nordic abrasion test exhibited much broader range of values (6.4 to 36.9) with average value at 15.2 for basalts, resulting in weak coefficient of determination (0.19). . On contrary, narrow range of values from Nordic abrasion test of spilites (7.2-15.9), very similar to the range of LA values, is reflect in higher coefficient of determination (0.56). On contrary, the least favourable properties (LA values 12.3-29.2, Nordic abrasion 16.8-43.3) have been observed for a group of basic to intermediate rocks classified in older literature as melaphyres and diabases (ranging from basalts to trachyndesites and/or trachybasalts) of Palaeozoic age. However, in this specific group of volcanic rocks, the highest coefficient of determination (0.89) between both tests has been achieved. For volcanic rocks exhibiting acid composition (rhyolites and quartz porphyry), coefficient of determination between LA values (15.1-19.3) and Nordic abrasion test (7.3-21.9) is weak (0.42). The weakest relationship between LA values (14

  11. 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

  12. Perceived Foreign Accent in First Language Attrition and Second Language Acquisition: The Impact of Age of Acquisition and Bilingualism

    Science.gov (United States)

    Hopp, Holger; Schmid, Monika S.

    2013-01-01

    This study investigates constraints on ultimate attainment in second language (L2) pronunciation in a direct comparison of perceived foreign accent of 40 late L2 learners and 40 late first language (L1) attriters of German. Both groups were compared with 20 predominantly monolingual controls. Contrasting participants who acquired the target…

  13. Should all attrition households in rural panel datasets be tracked? Lessons from a panel survey in Nepal

    DEFF Research Database (Denmark)

    Walelign, Solomon Zena

    2016-01-01

    Panel surveys are always subject to attrition: the original number of respondents is reduced over time and this process potentially affects the internal and external validity of a study. This is a common challenge in rural panel surveys in developing countries, where ‘attritors’ are typically not...

  14. The Development of a Diagnostic Tool to Limit Student Attrition through Programmed Instruction in Large Accounting Classes.

    Science.gov (United States)

    Fitzgerald, Daniel F.; Francis, Robert M.

    After the determination that the Principles of Accounting course offered at Herkimer County Community College, New York, had a higher attrition rate than other introductory courses, a study was conducted to develop a computer-assisted diagnostic system which could identify the learning deficiences of accounting students and prescribe corrective…

  15. When Is Ignorance Bliss? The Effects of Inaccurate Self-Assessments of Knowledge on Learning and Attrition

    Science.gov (United States)

    Sitzmann, Traci; Johnson, Stefanie K.

    2012-01-01

    Two studies were conducted to examine the implications of inaccurate self-appraisals in online training. Self-assessment of knowledge moderated the effects of trainees' performance on subsequent performance and attrition. Performance was highest after uniformly positive ratings (i.e., high self-assessment and high performance), followed by…

  16. A Study of Attrition and the Use of Student Learning Communities in the Computer Science Introductory Programming Sequence

    Science.gov (United States)

    Howles, Trudy

    2009-01-01

    Student attrition and low graduation rates are critical problems in computer science education. Disappointing graduation rates and declining student interest have caught the attention of business leaders, researchers and universities. With weak graduation rates and little interest in scientific computing, many are concerned about the USA's ability…

  17. A Longitudinal Investigation of the Effect of Information Perception and Focus on Attrition in Online Learning Environments

    Science.gov (United States)

    Terrell, Steven R.

    2005-01-01

    To better understand causes of attrition from a limited residency doctoral program, this paper describes the results of a seven-year study wherein the author collected data reflecting a given student's preference for information perception and focus. These constructs, based on Jung's theory of psychological type, have been hypothesized to be…

  18. The influence of autonomy support on self-regulatory processes and attrition in the Royal Dutch Navy

    NARCIS (Netherlands)

    Delahaij, R.; Theunissen, N.C.M.; Six, C.

    2014-01-01

    The purpose of this study was to investigate the underlying mechanisms that explain the influence of instructor support on attrition levels within Navy basic military training. Based on self-determination theory, we hypothesized that higher autonomy support leads to lower intent to quit, mediated by

  19. From Attrition to Retention: A Narrative Inquiry of Why Beginning Teachers Leave and Then Rejoin the Profession

    Science.gov (United States)

    Harfitt, Gary James

    2015-01-01

    The issue of beginning teachers leaving the profession in the first few years of their career represents a global problem, and while discrepancies exist over precise numbers, there is consensus that the attrition rate of new teachers is high. This paper reports on a narrative inquiry into two beginning teachers who left the profession after just…

  20. Early Career Outcomes for the "Best and the Brightest": Selectivity, Satisfaction, and Attrition in the Beginning Teacher Longitudinal Survey

    Science.gov (United States)

    Kelly, Sean; Northrop, Laura

    2015-01-01

    Educational efforts aimed at attracting the "best and brightest" into the teaching profession are widespread and include national programs, such as Teach for America and the New Teacher Project Teaching Fellows, as well as regional and state-based programs, city-based programs, and university-based programs. Yet, studies of attrition in…

  1. After the Two-Year Commitment: A Quantitative and Qualitative Inquiry of Teach For America Teacher Retention and Attrition

    Science.gov (United States)

    Heineke, Amy J.; Mazza, Bonnie Streff; Tichnor-Wagner, Ariel

    2014-01-01

    Teach For America (TFA), an organization that places college graduates as teachers in low-income areas for 2 years, contributes to teacher attrition. With this mixed methods study in one urban region, we investigated teachers' professional decisions at the end of 2 years. Respondents fell into categories in relation to the organization's 2-year…

  2. 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…

  3. The Application of Margin in Life Theory in Regard to Attrition and Remediation among Emergency Medicine Residents

    Science.gov (United States)

    Kalynych, Colleen J.

    2010-01-01

    Medical residency is a time of high stress, long hours, high case loads, fatigue, and lack of free time. Burnout rates among residents have been reported to be between 25-76%. Scant literature exists in regard to resident stress and its impact on learning and attrition during residency. The theory of margin posits that a healthy margin is…

  4. Validity of the Military Applicant Profile (MAP) for Predicting Early Attrition in Different Educational, Age, and Racial Groups

    Science.gov (United States)

    1982-12-01

    participation in sports , reasons for dropping out of school, personal activities and civilian job experience (Bell, Kristiansen & Seeley, 1974). At...prediction of early Arm attrition through the use of autobiographical information questionaires . Alexandria, VA: US Army Research Institute, Technical Report

  5. A crowdsourced nickel-and-dime approach to analog OBM research: A behavioral economic framework for understanding workforce attrition.

    Science.gov (United States)

    Henley, Amy J; DiGennaro Reed, Florence D; Reed, Derek D; Kaplan, Brent A

    2016-09-01

    Incentives are a popular method to achieve desired employee performance; however, research on optimal incentive magnitude is lacking. Behavioral economic demand curves model persistence of responding in the face of increasing cost and may be suitable to examine the reinforcing value of incentives on work performance. The present use-inspired basic study integrated an experiential human operant task within a crowdsourcing platform to evaluate the applicability of behavioral economics for quantifying changes in workforce attrition. Participants included 88 Amazon Mechanical Turk Workers who earned either a $0.05 or $0.10 incentive for completing a progressively increasing response requirement. Analyses revealed statistically significant differences in breakpoint between the two groups. Additionally, a novel translation of the Kaplan-Meier survival-curve analyses for use within a demand curve framework allowed for examination of elasticity of workforce attrition. Results indicate greater inelastic attrition in the $0.05 group. We discuss the benefits of a behavioral economic approach to modeling employee behavior, how the metrics obtained from the elasticity of workforce attrition analyses (e.g., P max ) may be used to set goals for employee behavior while balancing organizational costs, and how economy type may have influenced observed outcomes. © 2016 Society for the Experimental Analysis of Behavior.

  6. Research Findings on Early First Language Attrition: Implications for the Discussion on Critical Periods in Language Acquisition

    Science.gov (United States)

    Francis, Norbert

    2005-01-01

    Childhood bilingualism may develop toward a steady state of balanced competence in 2 languages or toward an imbalanced competence in which one of the child's languages begins to undergo attrition or early stabilization. In child second language learning an analogous distinction is often drawn between additive and subtractive bilingualism. This…

  7. 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...

  8. 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

    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 attritio...

  9. Perceived foreign accent in first language attrition and second language acquisition : The impact of age of acquisition and bilingualism

    NARCIS (Netherlands)

    Hopp, Holger; Schmid, Monika S.

    This study investigates constraints on ultimate attainment in second language (L2) pronunciation in a direct comparison of perceived foreign accent of 40 late L2 learners and 40 late first language (L1) attriters of German. Both groups were compared with 20 predominantly monolingual controls.

  10. Translation between L2 Acquisition and L1 Attrition: Anaphora Resolution in Italian by English-Italian Trainee Translators

    Science.gov (United States)

    Milicevic, Maja; Kraš, Tihana

    2017-01-01

    This article reports on the findings of an empirical study that relates translation studies and research on language acquisition/attrition by looking at the interpretation of overt pronominal subjects, previously found to be problematic in both domains. The focus is on the resolution of intra-sentential anaphora and cataphora in Italian by two…

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

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    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

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

    Science.gov (United States)

    Yates, Janet

    2012-06-20

    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. 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. 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. 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 been undisclosed for some time. The introduction of a structured

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

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    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.

  14. Physical Performance and Attrition Among U.S. Air Force Trainees Participating in the Basic Military Training Fueling Initiative.

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    Bartlett, Carrissa G; Stankorb, Susan

    2017-01-01

    Dietary intake of military initial entry trainees is often inadequate because of the structured food environment, lack of snacking, and limited time for meals. Inadequate intake during training increases risk for injury, poor performance, and attrition from training. A performance nutrition initiative was implemented at Joint Base San Antonio Lackland to mitigate this inadequacy in Air Force trainees and better reflect recommendations for active populations and mitigate nutritional inadequacy. Trainees (N = 867) in two squadrons either received a nutrition bar before bed (snack squadron n = 423) or did not (standard squadron n = 444). This study retrospectively compared trainees' attrition and fitness measures as recorded in the Basic Military Training (BMT) Surveillance database. Both groups had similar rates of attrition and graduation at the end of 8 weeks (p = 0.23). At the start of training, only one out of four trainees in either Squadron passed the Physical Fitness Assessment (PFA). Although both squadrons' fitness measures improved as a result of the effects of training, the snack squadron had a significantly greater percent improvement in all PFA categories (p fitness measures (p fitness improves with a modest nutritional supplement and suggests that optimizing overall nutrition benefits trainees. Attrition from BMT costs the U.S. Air Force up to $22,000 per trainee lost. In contrast, a trainee could receive one nutrition bar per day during BMT for $34. As the nutrition bar initiative improves fitness as well as costs less than recruiting and medically treating trainees whom ultimately attrite from training, the snack intervention was beneficial. Future studies of strategic nutrition interventions in military training populations can help trainees to better meet their macronutrient and micronutrient needs and further optimize training performance. Reprint & Copyright © 2017 Association of Military Surgeons of the U.S.

  15. Psychosocial Determinants of Attrition in a Longitudinal Study of Tobacco Use in Youth

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    Ann Post

    2012-01-01

    Full Text Available To gain knowledge on psychosocial characteristics that predict the propensity of participation in longitudinal studies, attrition was analysed in a cohort of 3020 adolescents participating in the baseline survey of a longitudinal study with repeated followup focusing on adolescents’ tobacco use. During the followup surveys, the proportion of responders was constantly at or above 90%. There were 941 adolescents (31.2% who failed to participate in at least one of the six followup surveys. Boys had a fifty percent increased risk of nonparticipation compared with girls. Adolescents in families with experience of divorce, unemployment, and change of residence had a higher risk of nonparticipation. An increasing number of stressful life events during the previous year, uptake of tobacco use, number of friends, perceived performance at school, truancy, and alcohol use during the last term also independently associated with nonparticipation. Diverse psychosocial characteristics are independently associated with nonparticipation of youths in longitudinal studies.

  16. Enhancing the ag precipitation by surface mechanical attrition treatment on Cu-Ag alloys

    Science.gov (United States)

    Liu, Jiabin; Zhang, Lehao; Liu, Jingjing; Huang, Liuyi; Gu, Hao; Fang, Youtong; Meng, Liang; Zhang, Jian

    2016-09-01

    The influence of surface mechanical attrition treatment (SMAT) on Ag precipitation in Cu-Ag alloys was investigated. Cu-6 wt% Ag was melt, cold rolled and solution treated to be Cu-Ag solid solution, which was either aged at 250 and 350 °C for 24 h directly or SMAT-ed before aging. Ag precipitates were hard be found in the directly aged Cu-Ag sample while they were observed clearly in the SMAT-ed counterpart at 250 °C. The Ag precipitates formed in the surface layer by SMAT are much coarser than those in the un-SMAT-ed sample. It is obvious that the precipitating behavior of Ag was promoted significantly by SMAT approach. A large number of defects were generated by SMAT and they were acting as fast atomic diffusion channels that facilitated the atomic diffusion of Ag.

  17. Exercise Intervention: Attrition, Compliance, Adherence, and Progression Following Hematopoietic Stem Cell Transplantation
.

    Science.gov (United States)

    Peters, Tara; Erdmann, Ruby; Hacker, Eileen Danaher

    2018-02-01

    Exercise is widely touted as an effective intervention to optimize health and well-being after high-dose chemotherapy and hematopoietic stem cell transplantation. 
. This article reports attrition, compliance, adherence, and progression from the strength training arm of the single-blind randomized, controlled trial Strength Training to Enhance Early Recovery (STEER). 
. 37 patients were randomized to the intervention and participated in a structured strength training program introduced during hospitalization and continued for six weeks after release. Research staff and patients maintained exercise logs to document compliance, adherence, and progression. 
. No patients left the study because of burden. Patients were compliant with completion of exercise sessions, and their adherence was high; they also progressed on their exercise prescription. Because STEER balances intervention effectiveness with patient burden, the findings support the likelihood of successful translation into clinical practice.

  18. Nursing attrition and the work environment in South African health facilities

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    E.J. Hall

    2004-09-01

    Full Text Available A number of media reports appeared on the shortages of professional health workers in the public health sector. Unsatisfactory working conditions in health facilities were mentioned as one of the key aspects responsible for the shortages. Literature indicates that stress caused by unsatisfactory work environments may play a major role in employees’ decision to resign their jobs, in spite of enjoying the nature of their work. The aim of this article is to explore the current human resource situation in nursing i.e. to determine if a shortage of nursing skills exists, to establish the challenges that nurses have to face in performing their duties and to establish the potential effect of the work environment on attrition.

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

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    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.

  20. Analysis of tagging data from North Atlantic Albacore (Thunnus Alalunga): Attrition Rate Estimates

    OpenAIRE

    Ortiz De Zarate, Victoria; Bertignac, Michel

    2001-01-01

    La présente étude tente d'estimer le taux de mortalité naturelle du germon nordatlantique. Nous appliquons un modèle d'attrition des marques agrégé dans l'espace pour analyser les résultats d'une expérience de marquage de germon menée dans le golfe de Gascogne de 1988 à 1991. Le modèle prédit la probabilité du destin éventuel du poisson marqué et de la marque dont il est porteur. Le modèle comprend plusieurs paramètres qui consistent de la capturabilité des flottes concernées par les recaptur...

  1. Dreams and disappointments regarding nursing: Student nurses' reasons for attrition and retention. A qualitative study design.

    Science.gov (United States)

    Ten Hoeve, Yvonne; Castelein, Stynke; Jansen, Gerard; Roodbol, Petrie

    2017-07-01

    In the Netherlands, hundreds of students register annually for a nursing programme, but not all of these students manage to complete their training. The main aim of this study was to examine which factors affect student nurses' decision to leave or complete their programme. The study used an exploratory descriptive design, employing a qualitative phenomenological approach. Student nurses (n=17) at the beginning of their third year of the four-year Bachelor's programme. Data were collected at four Universities of Applied Sciences in the Netherlands, from December 2013 to January 2014. Semi-structured interviews were used to collect the data, using an interview guide. The main reasons for students to become nurses were the caring aspect, personal experiences with healthcare, role models in their immediate environment, and job opportunities. They had both altruistic and professional perceptions of their profession. Reasons for attrition were strongly related to the training programme and to their clinical placements, in particular the perceived lack of support from mentors and team. Feelings of being welcomed and working in a nice team proved to be more important reasons for completing the programme than the specific clinical field. Student nurses started their studies with many dreams, such as caring for people and having the opportunity to deliver excellent nursing care. When their expectations were not met, their dreams became disappointments which caused them to consider stopping and even to leave (attrition). The role of lecturers and mentors seems invaluable in protecting and guiding students through their programme and placements. Optimal cooperation between lecturers and mentors is of paramount importance to retain student nurses in their training programmes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Articulating attrition: Graduate school experiences of female doctoral students in the sciences

    Science.gov (United States)

    Osburn, Kathryn Ann

    2005-07-01

    Despite decades of research and reform efforts designed to bolster female retention in scientific disciplines, the conundrum of women's departure from doctoral programs in the sciences remains. This qualitative case study investigated the aspects of the graduate school experience that female doctoral students described as facilitating or impeding their successful degree completion in chemistry. I analyzed the graduate school narratives of twelve female participants who represented both successful and unsuccessful doctoral recipients from four advisors at one university. Participants identified four types of experiences that facilitated their retention in the doctoral program: feeling successful and confident in meeting the program requirements, having positive research experiences, receiving support from social networks, and being dedicated to career goals. Participants cited four kinds of experiences that impeded their continued participation in the doctoral program: having negative research experiences, feeling a lack of success and confidence in meeting the program requirements, changing career goals, and receiving no support from social networks. The graduate school experiences of participants who did and did not successfully attain their degree objectives differed in terms of four dimensions: pre-program experiences, academic experiences, advisory experiences, and social experiences. Based on these findings, I have proposed a model of attrition and retention that emphasizes the role that these unique program experiences play in shaping participants' sense of professional fit within the community of doctoral chemists, consequently contributing to their differential program outcomes. This study not only offers a new perspective on the phenomenon of female doctoral attrition in the sciences but also informs the development of more gender-inclusive graduate science practices and policies that will support the retention of female doctoral students.

  3. 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

  4. Predictors of Short- and Long-Term Attrition From the Parents as Agents of Change Randomized Controlled Trial for Managing Pediatric Obesity.

    Science.gov (United States)

    Spence, Nicholas D; Newton, Amanda S; Keaschuk, Rachel A; Ambler, Kathryn A; Jetha, Mary M; Holt, Nicholas L; Rosychuk, Rhonda J; Spence, John C; Sharma, Arya M; Ball, Geoff D C

    Attrition in pediatric weight management is a substantial problem. This study examined factors associated with short- and long-term attrition from a lifestyle and behavioral intervention for parents of children with overweight or obesity. Fifty-two families with children ages 6 to 12 years old and body mass index at or above the 85th percentile participated in a randomized controlled trial focused on parents, comparing parent-based cognitive behavioral therapy with parent-based psychoeducation for pediatric weight management. We examined program attrition using two clinical phases of the intervention: short-term and long-term attrition, modeled using the general linear model. Predictors included intervention type, child/parent weight status, sociodemographic factors, and health of the family system. Higher self-assessed health of the family system was associated with lower short-term attrition; higher percentage of intervention sessions attended by parents was associated with lower long-term attrition. Different variables were significant in our short- and long-term models. Attrition might best be conceptualized based on short- and long-term phases of clinical, parent-based interventions for pediatric weight management. Copyright © 2016 National Association of Pediatric Nurse Practitioners. Published by Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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 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. Results 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. Conclusion This study provides key information for identifying mothers who may require specific support to avoid study attrition in trials evaluating a home-visiting program. PMID:26554839

  6. Sociodemographic and psychiatric predictors of attrition in a prospective psychiatric epidemiological study among the general population. Result of the Netherlands Mental Health Survey and Incidence Study-2.

    Science.gov (United States)

    de Graaf, Ron; van Dorsselaer, Saskia; Tuithof, Marlous; ten Have, Margreet

    2013-11-01

    In prospective psychiatric epidemiological studies, attrition at follow-up can be selective, and can bias the research findings. Therefore, knowledge of predictors of attrition and of its different types (noncontact, refusal, inability to participate) is of importance. By means of (multinomial) logistic regression analyses, predictors of attrition were studied in the first 3-year follow-up of the second Netherlands Mental Health Survey and Incidence Study (NEMESIS-2), a prospective psychiatric epidemiological study among 6646 subjects of the general population aged 18-64 years. Baseline sociodemographic characteristics, physical health, mental disorders and their clinical characteristics, and experience with the previous interview were studied as predictors of attrition and of its different types. The attrition rate at follow-up was 20.2%. Refusal (14.2%) was more common than noncontact (4.6%) and inability to participate (1.4%). Compared to respondents, nonrespondents were more often younger, lower educated, unemployed and born outside the Netherlands. A less positive experience with the baseline interview and shorter interview duration also predicted attrition. Any 12-month mental disorder, the categories and separate mental disorders, and their clinical characteristics, were not significantly associated with attrition, after controlling for sociodemographics. Sociodemographic predictors and experience with the baseline interview differed between the three types of attrition, but these types were also hardly or not associated with previous mental disorders. The authors conclude that bias due to selective attrition was limited to sociodemographics and experience with the baseline interview. Mental health status at baseline was not of influence, possibly due to the large time investment to persuade respondents to re-participate and to find them in case of noncontact or removal to an unknown address. During follow-up waves of future prospective studies it is

  7. 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.

  8. Factors associated with attrition, mortality, and loss to follow up after antiretroviral therapy initiation: data from an HIV cohort study in India

    Directory of Open Access Journals (Sweden)

    Gerardo Alvarez-Uria

    2013-09-01

    Full Text Available Background: Studies from sub-Saharan Africa have shown high incidence of attrition due to mortality or loss to follow-up (LTFU after initiating antiretroviral therapy (ART. India is the third largest country in the world in terms of HIV infected people, but predictors of attrition after ART initiation are not well known. Design: We describe factors associated with attrition, mortality, and LTFU in 3,159 HIV infected patients who initiated ART between 1 January 2007 and 4 November 2011 in an HIV cohort study in India. The study included 6,852 person-years with a mean follow-up of 2.17 years. Results: After 5 years of follow-up, the estimated cumulative incidence of attrition was 37.7%. There was no significant difference between attrition due to mortality and attrition due to LTFU. Having CD4 counts <100 cells/µl and being homeless [adjusted hazard ratio (aHR 3.1, 95% confidence interval (CI 2.6–3.8] were associated with a higher risk of attrition, and female gender (aHR 0.64, 95% CI 0.6–0.8 was associated with a reduced risk of attrition. Living near a town (aHR 0.82, 95% CI 0.7–0.999 was associated with a reduced risk of mortality. Being single (aHR 1.6, 95% CI 1.2–2.3, illiteracy (aHR 1.3, 95% CI 1.1–1.6, and age <25 years (aHR 1.3, 95% CI 1–1.8 were associated with an increased risk of LTFU. Although the cumulative incidence of attrition in patients diagnosed with tuberculosis after ART initiation was 47.4%, patients who started anti-tuberculous treatment before ART had similar attrition to patients without tuberculosis (36 vs. 35.2%, P=0.19 after four years of follow-up. Conclusions: In this cohort study, the attrition was similar to the one found in sub-Saharan Africa. Earlier initiation of ART, improving the diagnosis of tuberculosis before initiating ART, and giving more support to those patients at higher risk of attrition could potentially reduce the mortality and LTFU after ART initiation.

  9. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. 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.

  11. Raman spectroscopic studies on single crystals of the iron-based superconductor SmFeAsO{sub 1-x}F{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Jursic, Ivan; Schoenes, Joachim [Technische Universitaet Braunschweig, Institut fuer Physik der Kondensierten Materie, 38106 Braunschweig (Germany); Bukowski, Zbigniew; Karpinski, Janusz [ETH Zuerich, Laboratorium fuer Festkoerperphysik, 8093 Zuerich (Switzerland)

    2009-07-01

    The recent discovery of superconductivity in iron-based oxypnctides has led to a great interest in this new class of non-cuprate high-T{sub c} superconductors. Though theoretical work predicts a small electron-phonon coupling, which means that this should not be the driving mechanism for the observed T{sub c}'s in this class of material, the exact coupling mechanism is still under debate. We present Raman studies on superconducting SmFeAsO{sub 1-x}F{sub x} single crystals where the T{sub c} was determined by SQUID magnetometric measurements to be 34 K. At room temperature polarized measurements were performed to assign the phonon modes. Furthermore studies at different temperatures reaching from 5K to 300K were done to investigate the phonon behavior. The phonon frequencies shift with temperature and we investigate this shift in terms of electron-phonon coupling.

  12. A Survey on Synthesis Processes of Structured Materials for Biomedical Applications: Iron-based Magnetic Nanoparticles, Polymeric Materials and Polymerization Processes.

    Science.gov (United States)

    Neto, Weslany Silvério; Jensen, Alan Thyago; Ferreira, Gabriella Ribeiro; Valadares, Leonardo Fonseca; Gambetta, Rossano; Gonçalves, Sílvia Belém; Machado, Fabricio

    2015-01-01

    Magnetic materials based on iron oxides are extensively designed for several biomedical applications. Heterogeneous polymerization processes are powerful tools for the production of tailored micro-sized and nanosized magneto-polymeric particles. Although several polymerization processes have been adopted along the years, suspension, emulsion and miniemulsion systems deserve special attention due to its ability to produce spherical polymer particles containing magnetic nanoparticles homogeneously dispersed into the polymer thermoplastic matrices. The main objective of this paper is to review the main methods of synthesis of iron-based magnetic nanoparticles and to illustrate how typical polymerization processes in different dispersion medium can be successfully used to produce engineered magnetic core-shell structures. It is exemplified the use of suspension, emulsion and miniemulsion polymerization processes in order to support experimental methodologies required for the production of magnetic polymer particles intended for biomedical applications such as intravascular embolization treatments, drug delivery systems and hyperthermia treatment.

  13. Retention and risk factors for attrition among adults in antiretroviral treatment programmes in Tanzania, Uganda and Zambia.

    Science.gov (United States)

    Koole, Olivier; Tsui, Sharon; Wabwire-Mangen, Fred; Kwesigabo, Gideon; Menten, Joris; Mulenga, Modest; Auld, Andrew; Agolory, Simon; Mukadi, Ya Diul; Colebunders, Robert; Bangsberg, David R; van Praag, Eric; Torpey, Kwasi; Williams, Seymour; Kaplan, Jonathan; Zee, Aaron; Denison, Julie

    2014-12-01

    We assessed retention and predictors of attrition (recorded death or loss to follow-up) in antiretroviral treatment (ART) clinics in Tanzania, Uganda and Zambia. We conducted a retrospective cohort study among adults (≥18 years) starting ART during 2003-2010. We purposefully selected six health facilities per country and randomly selected 250 patients from each facility. Patients who visited clinics at least once during the 90 days before data abstraction were defined as retained. Data on individual and programme level risk factors for attrition were obtained through chart review and clinic manager interviews. Kaplan-Meier curves for retention across sites were created. Predictors of attrition were assessed using a multivariable Cox-proportional hazards model, adjusted for site-level clustering. From 17 facilities, 4147 patients were included. Retention ranged from 52.0% to 96.2% at 1 year to 25.8%-90.4% at 4 years. Multivariable analysis of ART initiation characteristics found the following independent risk factors for attrition: younger age [adjusted hazard ratio (aHR) and 95% confidence interval (95%CI) = 1.30 (1.14-1.47)], WHO stage 4 ([aHR (95% CI): 1.56 (1.29-1.88)], >10% bodyweight loss [aHR (95%CI) = 1.17 (1.00-1.38)], poor functional status [ambulatory aHR (95%CI) = 1.29 (1.09-1.54); bedridden aHR1.54 (1.15-2.07)], and increasing years of clinic operation prior to ART initiation in government facilities [aHR (95%CI) = 1.17 (1.10-1.23)]. Patients with higher CD4 cell count were less likely to experience attrition [aHR (95%CI) = 0.88 (0.78-1.00)] for every log (tenfold) increase. Sites offering community ART dispensing [aHR (95%CI) = 0.55 (0.30-1.01) for women; 0.40 (0.21-0.75) for men] had significantly less attrition. Patient retention to an individual programme worsened over time especially among males, younger persons and those with poor clinical indicators. Community ART drug dispensing programmes could improve retention. © 2014 John Wiley & Sons Ltd.

  14. 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.

  15. Methadone treatment for HIV prevention-feasibility, retention, and predictors of attrition in Dar es Salaam, Tanzania: a retrospective cohort study

    National Research Council Canada - National Science Library

    Lambdin, Barrot H; Masao, Frank; Chang, Olivia; Kaduri, Pamela; Mbwambo, Jessie; Magimba, Ayoub; Sabuni, Norman; Bruce, R Douglas

    2014-01-01

    .... Kaplan-Meier survival curves were constructed to assess retention probability. Proportional hazards regression models were used to evaluate the association of characteristics with attrition from the methadone program...

  16. High-pressure electrical resistivity studies for Ba1-xCsxFe2Se3

    Science.gov (United States)

    Kawashima, C.; Soeda, H.; Takahashi, H.; Hawai, T.; Nambu, Y.; Sato, T. J.; Hirata, Y.; Ohgushi, K.

    2017-10-01

    High-pressure electrical resistance measurements were performed for iron-based ladder material Ba1-xCsxFe2Se3 (x = 0.25 and 0.65) using a diamond anvil cell (DAC). Recent high-pressure study revealed that iron-based ladder material BaFe2S3 exhibits an insulator-metal transition and superconductivity, and this discovery would provide important insight for understanding the mechanism of iron-based superconductors. Therefore, it is intriguing to investigate the high-pressure properties for the iron-based ladder material Ba1-xCsxFe2Se3 system. The parent compounds BaFe2Se3 and CsFe2Se3 show insulating and magnetic ordering features. For Ba1-xCsxFe2Se3 system, no magnetic ordering is observed for x = 0.25 and minimum charge gap was estimated for x = 0.65. The insulator-metal transitions are observed in both materials.

  17. The Next Best Alternative to an Ideal Recruit: Attrition Characteristics of Recruits with Waivers and Low Educational Credentials in the U.S. Army

    Science.gov (United States)

    2009-03-01

    college enrollment rates among youth have increased (Asch et.al. RAND 2002). Attracting and retaining more high quality recruits is costly. As a...policies can affect attrition rates: homeschooled students from states with minimal regulation have higher attrition rates than homeschooled students from...some college to post-secondary degrees), receive a value of zero for this variable. Appendix B provides the detailed list of education levels and their

  18. Comparative analysis of sclerotic dentinal changes in attrited and carious teeth around pulp chamber for age determination.

    Science.gov (United States)

    Chatterjee, S

    2011-05-01

    The aim of this study was to estimate age by comparing sclerotic dentin thickness around coronal pulp chamber in carious and attrited teeth. Inclusion criteria for teeth selection was eruption age around six to seven years (incisors and first molars). 100 teeth (50 carious + 50 attrited) were ground up to their pulp chamber, observed and photographed under an Olympus stereomicroscope. Image J 1.38 NIH software was employed to analyze dentinal thickness. Regression formula was employed for evaluating age and compared with clinical age obtained at time of extraction. No matching values were found between calculated age and actual clinical age. Sclerotic dentin thickness values cannot be used as an indicator for the purpose of age estimation. Copyright © 2011 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

  19. Attrition of advanced trauma life support (ATLS) skills among ATLS instructors and providers in Mexico.

    Science.gov (United States)

    Azcona, Luis Am; Gutierrez, Guillermo E O; Fernandez, Cesar J P; Natera, Octavio M; Ruiz-Speare, Octavio; Ali, Jameel

    2002-09-01

    Mexico has had the Advanced Trauma Life Support (ATLS) program since 1986. We assessed the attrition of ATLS skills among ATLS providers and instructors in this country. Three groups (S, 16 students [new medical graduates enrolled for an ATLS course]; P, 33 providers; and I, 26 instructors [who had completed courses previously]) were evaluated. Group S read the manual before pretesting. Groups P and I were subdivided based on the length of time since the course had been completed: P1, less than 2 years (n = 22); P2, more than 2 years (n = 11); I1, less than 2 years (n = 16); and I2, more than 2 years (n = 10). Multiple-choice and psychomotor testing using ATLS scoring criteria were used. Affect was assessed post-ATLS for motivational factors, interactivity, and attitude toward trauma care. Multiple-choice test scores (means +/- SD) out of a maximum of 40 were as follows: S, 24.3 +/- 2.6; P1, 24.0 +/- 5.7; P2, 21.3 +/- 8.0; I1, 23.2 +/- 8.2; and I2, 24.0 +/- 7.2. Group S all passed the post-ATLS multiple-choice test (with correct answer percentages of 60.3% +/- 6.6% pre-ATLS versus 88.8% +/- 5.6% post-ATLS). An ATLS passing score of 80% correct answers was achieved in 2 of 33 for group P and 8 of 26 for group I (p ATLS group than in the P and I groups (p ATLS attitude to trauma care. Reading the manual alone yields similar cognitive but inferior psychomotor performance compared with subjects who completed the course previously. The majority of previous providers and instructors did not obtain a passing score (80%) in the multiple-choice test, but all the new providers passed the post-ATLS multiple-choice test, suggesting major attrition of cognitive skills but maintenance of psychomotor skills. Instructors had superior cognitive performance versus providers with worsening performance over time, but clinical skills performance was maintained at an equally high level by all groups. A very positive attitude toward ATLS prevailed among all participants.

  20. The Effect of Class Size on Teacher Attrition: Evidence from Class Size Reduction Policies in New York State

    OpenAIRE

    Emily Pas Isenberg

    2010-01-01

    Starting in 1999, New York State implemented class size reduction policies targeted at early elementary grades, but due to funding limitations, most schools reduced class size in some grades and not others. I use class size variation within a school induced by the policies to construct instrumental variable estimates of the effect of class size on teacher attrition. Teachers with smaller classes were not significantly less likely to leave schools in the full sample of districts but were less ...

  1. Second Language Attainment and First Language Attrition: The Case of VOT in Immersed Dutch-German Late Bilinguals

    Science.gov (United States)

    Stoehr, Antje; Benders, Titia; van Hell, Janet G.; Fikkert, Paula

    2017-01-01

    Speech of late bilinguals has frequently been described in terms of cross-linguistic influence (CLI) from the native language (L1) to the second language (L2), but CLI from the L2 to the L1 has received relatively little attention. This article addresses L2 attainment and L1 attrition in voicing systems through measures of voice onset time (VOT)…

  2. 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.

  3. Developing a national computerised absence monitoring and management system to reduce nursing student attrition: evaluation of staff and student perspectives.

    Science.gov (United States)

    Currie, Kay; McCallum, Jacqueline; Murray, John; Scott, Janine; Strachan, Evelyn; Yates, Lynda; Wright, Marty

    2014-05-01

    Reducing avoidable nursing student attrition is an international challenge. A pattern of falling attendance is recognised as a frequent precursor to withdrawal from nursing programmes. To address concerns regarding nursing student attrition, the Scottish Government implemented a pilot project for a centralised Computerised Absence Management and Monitoring System (CAMMS). The CAMMS adopted an 'assertive outreach' approach, contacting students every two weeks via colour coded letters to tell them whether their attendance was 'excellent', 'good, but potentially causing concern'; or 'warning; attendance concerns/contact academic staff for support'. This article reports key findings from an evaluation of CAMMS. To explore the perceived impact of CAMMS on student support and attrition, from the perspectives of academic and administrative staff and students. Mixed methods evaluation design. Three large geographically dispersed Schools of Nursing in Scotland. 83 students; 20 academic staff; and 3 lead administrators. On-line cohort survey of academic staff and students; structured interviews with lead administrators. Findings reflected a spectrum of negative and positive views of CAMMS. Students who are attending regularly seem pleased that their commitment is recognised. Lecturers who teach larger groups report greater difficulty getting to know students individually and acknowledge the benefit of identifying potential attendance concerns at an early stage. Conversely, some students who received a 'warning' letter were frequently annoyed or irritated, rather than feeling supported. Increased staff workload resulted in negative perceptions and a consequent reluctance to use CAMMS. However, students who were causing concern reported subsequent improvement in attendance. CAMMS has the potential to identify 'at-risk' students at an early stage; however, the system should have flexibility to tailor automatically generated letters in response to individual circumstances, to

  4. Effects of attrition, prior acid-etching, and cyclic loading on the bond strength of a self-etching adhesive system to dentin.

    Science.gov (United States)

    Shinkai, Koichi; Ebihara, Takashi; Shirono, Manabu; Seki, Hideaki; Wakaki, Suguru; Suzuki, Masaya; Suzuki, Shiro; Katoh, Yoshiroh

    2009-03-01

    The purpose of this study was to evaluate the effects of dentin attrition, phosphoric acid etching, and cyclic loading on the microtensile bond strength (microTBS) of a self-etching adhesive system to dentin. Flat dentin surfaces of human molars were assigned to eight experimental groups based on those with or without attrition, prior acid-etching, and cyclic loading. Resin composite paste was placed and polymerized after the bonding procedure according to manufacturer's instructions. The specimens were subjected to microTBS testing at a crosshead speed of 0.5 mm/min. Results showed that the minimum mean value of microTBS was 14.9 MPa in the group without attrition and acid-etching but with loading, while the maximum mean value of microTBS was 40.0 MPa in the group without attrition and loading but with acid etching. Therefore, the value of microTBS to dentin without attrition was significantly decreased by cyclic loading but that to dentin with attrition was not affected.

  5. Second language attainment and first language attrition: The case of VOT in immersed Dutch-German late bilinguals.

    Science.gov (United States)

    Stoehr, Antje; Benders, Titia; van Hell, Janet G; Fikkert, Paula

    2017-10-01

    Speech of late bilinguals has frequently been described in terms of cross-linguistic influence (CLI) from the native language (L1) to the second language (L2), but CLI from the L2 to the L1 has received relatively little attention. This article addresses L2 attainment and L1 attrition in voicing systems through measures of voice onset time (VOT) in two groups of Dutch-German late bilinguals in the Netherlands. One group comprises native speakers of Dutch and the other group comprises native speakers of German, and the two groups further differ in their degree of L2 immersion. The L1-German-L2-Dutch bilinguals ( N = 23) are exposed to their L2 at home and outside the home, and the L1-Dutch-L2-German bilinguals ( N = 18) are only exposed to their L2 at home. We tested L2 attainment by comparing the bilinguals' L2 to the other bilinguals' L1, and L1 attrition by comparing the bilinguals' L1 to Dutch monolinguals ( N = 29) and German monolinguals ( N = 27). Our findings indicate that complete L2 immersion may be advantageous in L2 acquisition, but at the same time it may cause L1 phonetic attrition. We discuss how the results match the predictions made by Flege's Speech Learning Model and explore how far bilinguals' success in acquiring L2 VOT and maintaining L1 VOT depends on the immersion context, articulatory constraints and the risk of sounding foreign accented.

  6. 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.

  7. A noncognitive temperament test to predict risk of mental disorders and attrition in U.S. Army recruits.

    Science.gov (United States)

    Gubata, Marlene E; Oetting, Alexis A; Weber, Natalya S; Feng, Xiaoshu; Cowan, David N; Niebuhr, David W

    2012-04-01

    U.S. military accession mental health screening includes cognitive testing and questions regarding the applicants' past mental health history. This process relies on applicants' knowledge of and willingness to disclose symptoms and conditions. Applicants have a strong incentive to appear qualified, which has resulted in a long history of frequent mental health conditions presenting during recruit training. To assess the predictive value of a pre-enlistment noncognitive temperament test score for risk of mental disorders and attrition in the first year of service. A retrospective cohort study was conducted on non-high school diploma U.S. Army active duty recruits who took the Assessment of Individual Motivation (AIM). Multivariate logistic regression models were used to determine associations between AIM score quintiles, mental disorders, and attrition. AIM scorers in the lowest quintile were at increased risk for a mental disorder (OR, 1.44; 95% CI, 1.35-1.53) and of discharge (OR, 1.65; 95% CI, 1.44-1.68) compared to AIM scorers in the highest quintile, with significant linear trends for decreased risk with increasing AIM score. AIM offers the potential to improve screening of military applicants and reduce mental disorders and attrition in new recruits beyond the current process.

  8. The best laid plans: examining the conditions under which a planning intervention improves learning and reduces attrition.

    Science.gov (United States)

    Sitzmann, Traci; Johnson, Stefanie K

    2012-09-01

    Planning plays an instrumental role in prominent self-regulation theories (e.g., action regulation, control, goal setting), yet as a scientific community we know little about how people carry out their learning plans. Using an experimental field study, we implemented a repeated-measures intervention requiring trainees to create a plan for when, where, and how much time they intended to devote to training before each of 4 online modules and examined the conditions under which the planning intervention improved learning and reduced attrition. Trainees benefited from the planning intervention when it was paired with another intervention-prompting self-regulation-targeting self-regulatory processes that occur subsequent to planning (e.g., monitoring, concentration, learning strategies). Trainees' learning performance was highest and attrition lowest when they received both interventions. The planning intervention was also advantageous for enhancing learning and reducing attrition when trainees followed through on the amount of time that they planned to devote to training. Finally, the relationship between planned study time, time on task, and learning performance was cyclical. Planned study time had a positive effect on time on task, which, in turn, had a positive effect on learning performance. However, trainees planned to devote less time to training following higher rather than lower learning performance. The current study contributes to our theoretical understanding of self-regulated learning by researching one of the most overlooked components of the process-planning-and examining the conditions under which establishing a learning plan enhances training outcomes.

  9. Impact of diet on incisor growth and attrition and the development of dental disease in pet rabbits.

    Science.gov (United States)

    Meredith, A L; Prebble, J L; Shaw, D J

    2015-06-01

    To assess the impact of four rabbit diets (hay only; extruded diet with hay; muesli with hay; muesli only) on length and curvature of cheek teeth and eruption and attrition rates of incisors. Thirty-two Dutch rabbits, randomly divided into four diet groups, had length and saggital plane curvature of the first cheek teeth measured radiographically at 1, 9 and 17 months. Eruption/attrition of the left upper incisor was directly measured at weeks 30, 32 and 35. Eruption rates matched attrition rates in all groups, but were higher in the hay only group than in both groups fed muesli. By month 9, a greater degree of tooth curvature was present in rabbits fed muesli only than in those fed hay only and extruded diet with hay. After 17 months, rabbits fed muesli only and muesli with hay had longer lower first cheek teeth and larger interdental spaces between the first two molars than rabbits fed extruded diet and hay and hay only. Three rabbits fed muesli only developed evidence of dental disease. Presence of increased tooth length, curvature and interdental spaces indicated early dental pathology in rabbits fed muesli. Muesli diets cannot be recommended for pet rabbits. © 2015 British Small Animal Veterinary Association.

  10. Delineating the third age: joint models of older people's quality of life and attrition in Britain 2002–2010

    Science.gov (United States)

    Tampubolon, Gindo

    2015-01-01

    Objectives: In the public mind, later life is being transformed by the emerging possibility of a flourishing third age with sustained quality of life. We draw trajectories of life quality measured using CASP-19 over eight years. We refine these trajectories by jointly modelling attrition, since older people tend to leave longitudinal studies (attrite) not at random. Methods: Growth curve models are applied to the English Longitudinal Study of Ageing waves 1 to 5. Then joint model is estimated where attrition is considered. Extensive predictors are entered including demographic attributes, social and economic status, health conditions, and behaviours. Results: Strong non-linear age trajectory of life quality is revealed by the growth curve models where the peak is achieved in the late 60s. Then the joint model uncovers the peak somewhat later in time, and also reveals secular improvement in life quality experienced by recent cohorts. Sharp estimates for many predictors of higher levels of life quality are also found. Conclusion: For the first time, the trajectories of life quality in the third age are drawn and improvement across cohorts is demonstrated. The contributions are estimated for predictors amenable to intervention such as social capital. This can help in policy discussion on improving the lives of older people in the third age. PMID:25642833

  11. The effects of attrition and ball milling on the properties of magnesium diboride

    Energy Technology Data Exchange (ETDEWEB)

    Dancer, C E J; Crossley, A; Todd, R I; Grovenor, C R M [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Prabhakaran, D, E-mail: claire.dancer@materials.ox.ac.u [Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom)

    2010-06-15

    Commercially produced magnesium diboride powder was modified by attrition milling and ball milling in propan-2-ol for various durations. These powders were characterized by means of particle size distribution measurements using laser diffraction, impurity analysis using x-ray diffraction, energy dispersive spectroscopy and x-ray photoelectron spectroscopy, and scanning electron microscopy, and were then used to produce magnesium diboride samples through pressureless heat treatment at peak temperatures up to 1100 {sup 0}C. X-ray diffraction, scanning electron microscopy, Vickers hardness measurements, and density measurements using the Archimedes method were used to characterize the properties of the samples, and a determination of their superconducting properties using the magnetization method was carried out. Magnesium diboride produced from powder milled under certain conditions had a higher J{sub c,mag} than samples produced from as-purchased powder, but the relationship between the milling duration or energy and the superconducting performance is a complex one, affected by both the particle size and the impurity content of the starting powder.

  12. 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)

  13. 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.

  14. Attrition factors in clinical trials of comorbid bipolar and substance-related disorders.

    Science.gov (United States)

    Nomamiukor, Nicole; Brown, E Sherwood

    2009-01-01

    This study analyzed and defined specific factors that account for attrition in clinical research for patients with bipolar and substance-related disorders. Data were analyzed from two completed studies: an open-label trial of lamotrigine in patients with bipolar disorder (BPD) and cocaine-related disorder, and a placebo-controlled trial of quetiapine in patients with BPD and alcohol-related disorders. Correlations and Independent sample t-tests were performed to assess the impact of baseline characteristics including on length of study participation. Significance was set at the p=0.05 level. In the lamotrigine-treated patients, the presence of an amphetamine-related disorder, in addition to cocaine-related disorders, was associated with a shorter time in the study. In the quetiapine-treated patients higher scores on the Addiction Severity Index Legal subscale were associated with shorter length in the study. The presence of panic disorder was associated with shorter time in both studies. Although the data were taken from the two largest clinical trials, to date, in patients with BPD and substance-related disorders, the sample sizes were relatively modest. In addition, the baseline assessments were somewhat different in the two studies limiting our ability to make conclusions on differences between patients with BPD and cocaine use versus alcohol use. This study adds to an emerging literature on the significance of panic disorder in patients with BPD.

  15. Microstructure and thermal stability of bulk nanocrystalline alloys produced by surface mechanical attrition treatment

    Science.gov (United States)

    Liu, Wenbo; Zhang, Chi; Yang, Zhigang; Xia, Zhixin

    2014-02-01

    Bulk nanocrystalline has been produced in the surface of a tempered reduced activation ferrite/martensite (RAFM) steel by means of surface mechanical attrition treatment (SMAT), the grain size decreases gradually from the strain-free matrix to the treated surface with the increase of deformation strains. Both XRD and SEM results indicate the dissolving or refinement of carbides during SMAT. The nanocrystalline has excellent thermal stability when annealing at 823 K; the average grain sizes calculated from statistical analysis of the TEM images after annealing for 5 min, 30 min, 120 min and 240 min are 67.6 nm, 87.1 nm, 93.8 nm and 109.6 nm, respectively. Because of the large volume fraction of grain boundaries (GBs) and enhanced diffusion rates in the nanocrystalline (NC) steels, fast grain growth and small precipitated carbides are observed after annealing for 5 min at 823 K, while the existence of numerous second-phase particles hinders grain growth after annealing for longer times.

  16. Superhydrophobic NiTi shape memory alloy surfaces fabricated by anodization and surface mechanical attrition treatment

    Science.gov (United States)

    Ou, Shih-Fu; Wang, Kuang-Kuo; Hsu, Yen-Chi

    2017-12-01

    This paper describes the fabrication of superhydrophobic NiTi shape memory alloy (SMA) surfaces using an environmentally friendly method based on an economical anodizing process. Perfluorooctyltriethoxysilane was used to reduce the surface energy of the anodized surfaces. The wettability, morphology, composition, and microstructure of the surfaces were investigated by scanning electron microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy. The surface of the treated NiTi SMA exhibited superhydrophobicity, with a water contact angle of 150.6° and sliding angle of 8°. The anodic film on the NiTi SMA comprised of TiO2 and NiO, as well as traces of TiCl3. In addition, before the NiTi SMA was anodized, it underwent a surface mechanical attrition treatment to grain-refine its surface. This method efficiently enhanced the growth rate of the anodic oxide film, and improved the hydrophobic uniformity of the anodized NiTi-SMA-surface.

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

    Science.gov (United States)

    Bajardi, Paolo; Paolotti, Daniela; Vespignani, Alessandro; Eames, Ken; Funk, Sebastian; Edmunds, W John; Turbelin, Clement; Debin, Marion; Colizza, Vittoria; Smallenburg, Ronald; Koppeschaar, Carl; Franco, Ana O; Faustino, Vitor; Carnahan, AnnaSara; Rehn, Moa; Merletti, Franco; Douwes, Jeroen; Firestone, Ridvan; Richiardi, Lorenzo

    2014-01-01

    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.

  18. 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.

  19. Implant-Supported Prosthetic Rehabilitation of a Patient with Localized Severe Attrition: A Clinical Report.

    Science.gov (United States)

    Cekic-Nagas, Isil; Ergun, Gulfem

    2015-06-01

    Patients usually adapt to their existing occlusal vertical dimension (OVD). It is essential to resolve each of the problems associated with decreased vertical dimension as a result of attrition. This report describes the multidisciplinary dental treatment of a 40-year-old male patient who had severe tooth wear, resulting in reduced vertical dimension. After clinical evaluations, extraoral examination showed a reduction of the lower facial height, drooping, and overclosed commissures. Ten dental implants were placed into the maxillary and mandibular alveolar processes. During the osseointegration period, an interim removable partial denture was made at increased OVD to use in the first stage of rehabilitation. It was used for 3 months as a guide for preparing the definitive restorations. The patient's adaptation to the increased OVD was evaluated. During this period, he was asymptomatic. Following the evaluation period, the provisional fixed restoration was used for 3 months. Then, full-mouth definitive prostheses supported by a combination of implants and teeth were fabricated to upper and lower jaws. Osseointegration of the implants, peri-implant mucosa health, prosthesis function, and esthetics were assessed after 1 week and 1, 3, and 6 months. After 3 years of follow-up, no functional or esthetic difficulties with the implants and restorations were noted. © 2014 by the American College of Prosthodontists.

  20. 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