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Sample records for solvent attrition mechanism

  1. 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.

  2. Nanocrystalline and ultrafine grain copper obtained by mechanical attrition

    Directory of Open Access Journals (Sweden)

    Rodolfo Rodríguez Baracaldo

    2010-01-01

    Full Text Available This article presents a method for the sample preparation and characterisation of bulk copper having grain size lower than 1 μm (ultra-fine grain and lower than 100 nm grain size (nanocrystalline. Copper is initially manufactured by a milling/alloying me- chanical method thereby obtaining a powder having a nanocrystalline structure which is then consolidated through a process of warm compaction at high pressure. Microstructural characterisation of bulk copper samples showed the evolution of grain size during all stages involved in obtaining it. The results led to determining the necessary conditions for achieving a wide range of grain sizes. Mechanical characterisation indicated an increase in microhardness to values of around 3.40 GPa for unconsolida- ted nanocrystalline powder. Compressivee strength was increased by reducing the grain size, thereby obtaining an elastic limit of 650 MPa for consolidated copper having a ~ 62 nm grain size.

  3. Nanocrystalline-grained tungsten prepared by surface mechanical attrition treatment: Microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Guo, Hong-Yan; Xia, Min; Wu, Zheng-Tao; Chan, Lap-Chung; Dai, Yong; Wang, Kun; Yan, Qing-Zhi; He, Man-Chao; Ge, Chang-Chun; Lu, Jian

    2016-01-01

    A nanostructured surface layer was fabricated on commercial pure tungsten using the method of surface mechanical attrition treatment (SMAT). The microstructure evolution of the surface layer was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and its formation mechanism was discussed as well. Both refinement and elongation of the brittle W grains were confirmed. The elongated SMATed W was heavily strained, the maximum value of the strain at the grain boundaries reaches as high as 3–5%. Dislocation density in the SMATed W nanograins was found to be 5 × 10 12  cm −2 . The formation of the nanograins in the top surface layer of the W was ascribed to the extremely high strain and strain rate, as well as the multidirectional repetitive loading. Bending strength of commercial W could be improved from 825 MPa to 1850 MPa by SMAT process. Microhardness results indicated the strain range in SMATed W can reach up to 220 μm beneath the top surface. The notched Charpy testing results demonstrated that SMATed W possess higher ductility than that of commercial W. The top surface of the W plates with and without SMATe processing possesses residual compressive stress of about −881 MPa and −234 MPa in y direction, and −872 MPa and −879 MPa in x direction respectively. The improvement of toughness (DBTT shift) of SMATed W may be the synergistic effect of residual compressive stress, dislocation density improvement and microstructure refinement induced by SMAT processing. SMAT processing could be a complementary method to further decrease the DBTT value of tungsten based materials.

  4. Nanocrystalline-grained tungsten prepared by surface mechanical attrition treatment: Microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hong-Yan [State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tae Chee Avenue Kowloon, Hong Kong 999077 (China); Xia, Min, E-mail: xmdsg@ustb.edu.cn [Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); Wu, Zheng-Tao [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Chan, Lap-Chung [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tae Chee Avenue Kowloon, Hong Kong 999077 (China); Dai, Yong; Wang, Kun [Laboratory for Nuclear Materials, Paul Scherrer Institut, 5323 Villigen PSI (Switzerland); Yan, Qing-Zhi [Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); He, Man-Chao [State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); Ge, Chang-Chun, E-mail: ccge@mater.ustb.edu.cn [Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); Lu, Jian, E-mail: jianlu@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tae Chee Avenue Kowloon, Hong Kong 999077 (China)

    2016-11-15

    A nanostructured surface layer was fabricated on commercial pure tungsten using the method of surface mechanical attrition treatment (SMAT). The microstructure evolution of the surface layer was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and its formation mechanism was discussed as well. Both refinement and elongation of the brittle W grains were confirmed. The elongated SMATed W was heavily strained, the maximum value of the strain at the grain boundaries reaches as high as 3–5%. Dislocation density in the SMATed W nanograins was found to be 5 × 10{sup 12} cm{sup −2}. The formation of the nanograins in the top surface layer of the W was ascribed to the extremely high strain and strain rate, as well as the multidirectional repetitive loading. Bending strength of commercial W could be improved from 825 MPa to 1850 MPa by SMAT process. Microhardness results indicated the strain range in SMATed W can reach up to 220 μm beneath the top surface. The notched Charpy testing results demonstrated that SMATed W possess higher ductility than that of commercial W. The top surface of the W plates with and without SMATe processing possesses residual compressive stress of about −881 MPa and −234 MPa in y direction, and −872 MPa and −879 MPa in x direction respectively. The improvement of toughness (DBTT shift) of SMATed W may be the synergistic effect of residual compressive stress, dislocation density improvement and microstructure refinement induced by SMAT processing. SMAT processing could be a complementary method to further decrease the DBTT value of tungsten based materials.

  5. Surface mechanical attrition treatment induced phase transformation behavior in NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Hu, T.; Wen, C.S.; Lu, J.; Wu, S.L.; Xin, Y.C.; Zhang, W.J.; Chu, C.L.; Chung, J.C.Y.; Yeung, K.W.K.; Kwok, D.T.K.; Chu, Paul K.

    2009-01-01

    The phase constituents and transformation behavior of the martensite B19' NiTi shape memory alloy after undergoing surface mechanical attrition treatment (SMAT) are investigated. SMAT is found to induce the formation of a parent B2 phase from the martensite B19' in the top surface layer. By removing the surface layer-by-layer, X-ray diffraction reveals that the amount of the B2 phase decreases with depth. Differential scanning calorimetry (DSC) further indicates that the deformed martensite in the sub-surface layer up to 300 μm deep exhibits the martensite stabilization effect. The graded phase structure and transformation behavior in the SMATed NiTi specimen can be attributed to the gradient change in strain with depth.

  6. Martensitic phase transformations in the nanostructured surface layers induced by mechanical attrition treatment

    International Nuclear Information System (INIS)

    Ni Zhichun; Wang Xiaowei; Wu Erdong; Liu Gang

    2005-01-01

    Conversion electron Moessbauer spectroscopy (CEMS) and x-ray diffraction (XRD) analysis have been used to investigate the relationship between characteristics of phase transformation and the treatment time in surface nanocrystallized 316L stainless steel induced by surface mechanical attrition treatment (SMAT). A similar trend of development of the martensitic phase upon the treatment time has been observed from both CEMS and XRD measurements. However, in the CEMS measurement, two types of martensite phase with different magnetic hyperfine fields are revealed. Based on a random distribution of the non-iron coordinating atoms, a three-element theoretical model is developed to illustrate the difference of two types of martensite phase. The calculated results indicate the segregation of the non-iron atoms associated with SMAT treatment

  7. Prevention of weld-decay in austenitic stainless steel by using surface mechanical attrition treatment

    Science.gov (United States)

    Laleh, Majid; Kargar, Farzad; Rouhaghdam, Alireza Sabour

    2012-11-01

    Surface mechanical attrition treatment (SMAT) was applied to the samples of a type AISI 304 stainless steel in order to induce grain refinement as well as formation of twins. Transmission electron microscopy and X-ray diffraction analysis results showed that the average grain size at the surface of the SMATed sample was about 10 nm. The untreated and SMATed samples were then welded using a one-pass gas tungsten arc procedure. The heat-affected zone (HAZ) of the samples was examined by optical microscopy and corrosion tests. Results of the double loop electrochemical potentiokinetic reactivation tests showed that the degree of sensitization in the HAZ for the SMATed sample was very low as compared to that of the untreated one. The pre-SMATed sample was resistant to intergranular corrosion. This is mainly due to the formation of high density of twins which are not prone to carbide precipitation because of their regular and coherent atomic structure and extreme low grain boundary energy as compared with those of other grain boundaries.

  8. Plastic deformation to enhance plasma-assisted nitriding: On surface contamination induced by Surface Mechanical Attrition Treatment

    International Nuclear Information System (INIS)

    Samih, Youssef; Novelli, Marc; Bolle, Bernard; Allain, Nathalie; Fundenberger, Jean-Jacques; Marcos, Grégory; Czerwiec, Thierry; Grosdidier, Thierry; Thiriet, Tony

    2014-01-01

    The Surface Mechanical Attrition Treatment is a recent technique leading to the formation of nanostructured layers by the repeated action of impacting balls. While several communications have revealed possible contamination of the SMATed surfaces, the nature of this surface contamination was analyzed in the present contribution for the treatment of an AISI 316L stainless steel. It is shown, by a combination of Transmission Electron Microscopy and Glow Discharge – Optical Emission Spectrometry, that the surface was alloyed with Ti, Al and V coming from the sonotrode that is used to move the balls as well as Zr coming from the zirshot® balls themselves

  9. Plastic deformation to enhance plasma-assisted nitriding: On surface contamination induced by Surface Mechanical Attrition Treatment

    Science.gov (United States)

    Samih, Youssef; Novelli, Marc; Thiriet, Tony; Bolle, Bernard; Allain, Nathalie; Fundenberger, Jean-Jacques; Marcos, Grégory; Czerwiec, Thierry; Grosdidier, Thierry

    2014-08-01

    The Surface Mechanical Attrition Treatment is a recent technique leading to the formation of nanostructured layers by the repeated action of impacting balls. While several communications have revealed possible contamination of the SMATed surfaces, the nature of this surface contamination was analyzed in the present contribution for the treatment of an AISI 316L stainless steel. It is shown, by a combination of Transmission Electron Microscopy and Glow Discharge - Optical Emission Spectrometry, that the surface was alloyed with Ti, Al and V coming from the sonotrode that is used to move the balls as well as Zr coming from the zirshot® balls themselves.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-11-01

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

  11. Localized solid-state amorphization at grain boundaries in a nanocrystalline Al solid solution subjected to surface mechanical attrition

    Energy Technology Data Exchange (ETDEWEB)

    Wu, X [State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China); Tao, N [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Hong, Y [State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China); Lu, J [LASMIS, University of Technology of Troyes, 10000, Troyes (France); Lu, K [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2005-11-21

    Using high-resolution electron microscopy, localized solid-state amorphization (SSA) was observed in a nanocrystalline (NC) Al solid solution (weight per cent 4.2 Cu, 0.3 Mn, the rest being Al) subjected to a surface mechanical attrition treatment. It was found that the deformation-induced SSA may occur at the grain boundary (GB) where either the high density dislocations or dislocation complexes are present. It is suggested that lattice instability due to elastic distortion within the dislocation core region plays a significant role in the initiation of the localized SSA at defective sites. Meanwhile, the GB of severely deformed NC grains exhibits a continuously varying atomic structure in such a way that while most of the GB is ordered but reveals corrugated configurations, localized amorphization may occur along the same GB.

  12. Experimental study of microstructure changes due to low cycle fatigue of a steel nanocrystallised by Surface Mechanical Attrition Treatment (SMAT)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Z. [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); Retraint, D., E-mail: delphine.retraint@utt.fr [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); Baudin, T.; Helbert, A.L.; Brisset, F. [ICMMO, Univ Paris-Sud, Université Paris-Saclay, UMR CNRS 8182, 91405 Orsay Cedex (France); Chemkhi, M.; Zhou, J. [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); Kanouté, P. [ICD, P2MN, LASMIS, University of Technology of Troyes, UMR 6281, CNRS, Troyes (France); ONERA, The French Aerospace Lab, 29 avenue de la Division Leclerc, 92322 Chatillon Cedex (France)

    2017-02-15

    Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. - Highlights: •LCF tests are carried out on specimens processed by SMAT. •EBSD is used to investigate microstructural changes induced by LCF. •A grain size gradient is generated by SMAT from surface to the bulk of the fatigue samples. •New slip systems are activated by LCF and GOS is increased in plastically deformed region. •However, these phenomena are not observed in the top surface ultra-fine grain area.

  13. Experimental study of microstructure changes due to low cycle fatigue of a steel nanocrystallised by Surface Mechanical Attrition Treatment (SMAT)

    International Nuclear Information System (INIS)

    Sun, Z.; Retraint, D.; Baudin, T.; Helbert, A.L.; Brisset, F.; Chemkhi, M.; Zhou, J.; Kanouté, P.

    2017-01-01

    Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. - Highlights: •LCF tests are carried out on specimens processed by SMAT. •EBSD is used to investigate microstructural changes induced by LCF. •A grain size gradient is generated by SMAT from surface to the bulk of the fatigue samples. •New slip systems are activated by LCF and GOS is increased in plastically deformed region. •However, these phenomena are not observed in the top surface ultra-fine grain area.

  14. Synthesis of nanoparticles from malleable and ductile metals using powder-free, reactant-assisted mechanical attrition.

    Science.gov (United States)

    McMahon, Brandon W; Perez, Jesus Paulo L; Yu, Jiang; Boatz, Jerry A; Anderson, Scott L

    2014-11-26

    A reactant-assisted mechanochemical method was used to produce copious nanoparticles from malleable/ductile metals, demonstrated here for aluminum, iron, and copper. The milling media is intentionally degraded via a reactant-accelerated wear process, where the reactant aids particle production by binding to the metal surfaces, enhancing particle production, and reducing the tendency toward mechanochemical (cold) welding. The mechanism is explored by comparing the effects of different types of solvents and solvent mixtures on the amount and type of particles produced. Particles were functionalized with oleic acid to aid in particle size separation, enhance dispersion in hydrocarbon solvents, and protect the particles from oxidation. For aluminum and iron, the result is air-stable particles, but for copper, the suspended particles are found to dissolve when exposed to air. Characterization was performed using electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Density functional theory was used to examine the nature of carboxylic acid binding to the aluminum surface, confirming the dominance of bridging bidentate binding.

  15. Comparative exergy analyses of Jatropha curcas oil extraction methods: Solvent and mechanical extraction processes

    International Nuclear Information System (INIS)

    Ofori-Boateng, Cynthia; Keat Teong, Lee; JitKang, Lim

    2012-01-01

    Highlights: ► Exergy analysis detects locations of resource degradation within a process. ► Solvent extraction is six times exergetically destructive than mechanical extraction. ► Mechanical extraction of jatropha oil is 95.93% exergetically efficient. ► Solvent extraction of jatropha oil is 79.35% exergetically efficient. ► Exergy analysis of oil extraction processes allow room for improvements. - Abstract: Vegetable oil extraction processes are found to be energy intensive. Thermodynamically, any energy intensive process is considered to degrade the most useful part of energy that is available to produce work. This study uses literature values to compare the efficiencies and degradation of the useful energy within Jatropha curcas oil during oil extraction taking into account solvent and mechanical extraction methods. According to this study, J. curcas seeds on processing into J. curcas oil is upgraded with mechanical extraction but degraded with solvent extraction processes. For mechanical extraction, the total internal exergy destroyed is 3006 MJ which is about six times less than that for solvent extraction (18,072 MJ) for 1 ton J. curcas oil produced. The pretreatment processes of the J. curcas seeds recorded a total internal exergy destructions of 5768 MJ accounting for 24% of the total internal exergy destroyed for solvent extraction processes and 66% for mechanical extraction. The exergetic efficiencies recorded are 79.35% and 95.93% for solvent and mechanical extraction processes of J. curcas oil respectively. Hence, mechanical oil extraction processes are exergetically efficient than solvent extraction processes. Possible improvement methods are also elaborated in this study.

  16. Local thermal property analysis by scanning thermal microscopy of an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment

    Energy Technology Data Exchange (ETDEWEB)

    Guo, F.A. [Suzhou Institute for Nonferrous Metals Processing Technology, No. 200 Shenxu Road, Suzhou Industrial Park, Suzhou 215021 (China) and Unite de Thermique et d' Analyse Physique, Laboratoire d' Energetique et d' Optique, Universite de Reims, BP 1039, 51687 Reims Cedex 2 (France)]. E-mail: guofuan@yahoo.com; JI, Y.L. [Suzhou Institute for Nonferrous Metals Processing Technology, No. 200 Shenxu Road, Suzhou Industrial Park, Suzhou 215021 (China); Trannoy, N. [Unite de Thermique et d' Analyse Physique, Laboratoire d' Energetique et d' Optique, Universite de Reims, BP 1039, 51687 Reims Cedex 2 (France); Lu, J. [LASMIS, Universite de Technologie de Troyes, 12 Rue Marie Curie, Troyes 10010 (France)

    2006-06-15

    Scanning thermal microscopy (SThM) was used to map thermal conductivity images in an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment (SMAT). It is found that the deformed surface layer shows different thermal conductivities that strongly depend on the grain size of the microstructure: the thermal conductivity of the nanostructured surface layer decreases obviously when compared with that of the coarse-grained matrix of the sample. The role of the grain boundaries in thermal conduction is analyzed in correlation with the heat conduction mechanism in pure metal. A theoretical approach, based on this investigation, was used to calculate the heat flow from the probe tip to the sample and then estimate the thermal conductivities at different scanning positions. Experimental results and theoretical calculation demonstrate that SThM can be used as a tool for the thermal property and microstructural analysis of ultrafine-grained microstructures.

  17. Physical organogels: mechanism and kinetics of evaporation of the solvents entrapped within network scaffolding

    International Nuclear Information System (INIS)

    Markovic, Nov; Dutta, Naba K.

    2005-01-01

    A series of hydrocarbon gels (based on leaded petrol and decalin) using physically crosslinked networks have been prepared using Al-salt of fatty acid as the physical gelling agent. The effects of gel network scaffolding on the mechanism and kinetics of evaporation of the solvents from the gels were investigated using conventional, isothermal and modulated thermogravimetric analysis. It has been clearly observed that the evaporation of solvent from gels followed a complex evaporation pattern compared to the pure solvent. It appears that with increase in network scaffolding the maximum rate of evaporation of the solvent decreases and its distribution become broader. The activation energy of evaporation for these solvents was found not to be dramatically dependent on the concentration of the gelator and tightness of the network scaffolding. Amongst different methods employed, isothermal measurements provided reliable information about the mechanism of evaporation. Modulated thermogravimetric analysis proved to be an efficient method to achieve kinetic parameters of evaporation from a single dynamic experiment. Scanning electron microscopy was used to probe for both dry gelator and gel network after evaporation of the solvents for evaluation of their surface morphology

  18. 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…

  19. A review of potential neurotoxic mechanisms among three chlorinated organic solvents

    International Nuclear Information System (INIS)

    Bale, Ambuja S.; Barone, Stan; Scott, Cheryl Siegel; Cooper, Glinda S.

    2011-01-01

    The potential for central nervous system depressant effects from three widely used chlorinated solvents, trichloroethylene (TCE), perchloroethylene (PERC), and dichloromethane (DCM), has been shown in human and animal studies. Commonalities of neurobehavioral and neurophysiological changes for the chlorinated solvents in in vivo studies suggest that there is a common mechanism(s) of action in producing resultant neurotoxicological consequences. The purpose of this review is to examine the mechanistic studies conducted with these chlorinated solvents and to propose potential mechanisms of action for the different neurological effects observed. Mechanistic studies indicate that this solvent class has several molecular targets in the brain. Additionally, there are several pieces of evidence from animal studies indicating this solvent class alters neurochemical functions in the brain. Although earlier evidence indicated that these three chlorinated solvents perturb the lipid bilayer, more recent data suggest an interaction between several specific neuronal receptors produces the resultant neurobehavioral effects. Collectively, TCE, PERC, and DCM have been reported to interact directly with several different classes of neuronal receptors by generally inhibiting excitatory receptors/channels and potentiating the function of inhibitory receptors/channels. Given this mechanistic information and available studies for TCE, DCM, and PERC, we provide hypotheses on primary targets (e.g. ion channel targets) that appear to be most influential in producing the resultant neurological effects. - Research highlights: → Comparison of neurological effects among TCE, PERC, and DCM. → Correlation of mechanistic findings to neurological effects. → Data support that TCE, PERC, and DCM interact with several ion channels to produce neurological changes.

  20. Ester-free Thiol-X Resins: New Materials with Enhanced Mechanical Behavior and Solvent Resistance

    OpenAIRE

    Podgórski, Maciej; Becka, Eftalda; Chatani, Shunsuke; Claudino, Mauro; Bowman, Christopher N.

    2015-01-01

    A series of thiol-Michael and radical thiol-ene network polymers were successfully prepared from ester-free as well as ester-containing monomer formulations. Polymerization reaction rates, dynamic mechanical analysis, and solvent resistance experiments were performed and compared between compositions with varied ester loading. The incorporation of ester-free alkyl thiol, vinyl sulfone and allylic monomers significantly improved the mechanical properties when compared with commercial, mercapto...

  1. Changing the Mechanism for CO 2 Hydrogenation Using Solvent-Dependent Thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, Samantha A. [Catalysis Science Group, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Appel, Aaron M. [Catalysis Science Group, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Linehan, John C. [Catalysis Science Group, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Wiedner, Eric S. [Catalysis Science Group, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA

    2017-10-23

    A critical scientific challenge for utilization of CO2 is the development of catalyst systems that do not depend upon expensive or environmentally unfriendly reagents, such as precious metals, strong organic bases, and organic solvents. We have used thermodynamic insights to predict and demonstrate that the HCoI(dmpe)2 catalyst system, previously described for use in organic solvents, can hydrogenate CO2 to formate in water with bicarbonate as the only added reagent. Replacing tetrahydrofuran as the solvent with water changes the mechanism for catalysis by altering the thermodynamics for hydride transfer to CO2 from a key dihydride intermediate. The need for a strong organic base was eliminated by performing catalysis in water due to the change in mechanism. These studies demonstrate that the solvent plays a pivotal role in determining the reaction thermodynamics and thereby catalytic mechanism and activity. The research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  2. Effect of solvent on the charging mechanisms of poly(ethylene glycol) in droplets

    Science.gov (United States)

    Soltani, Sepideh; Oh, Myong In; Consta, Styliani

    2015-03-01

    We examine the effect of solvent on the charging mechanisms of a macromolecule in a droplet by using molecular dynamics simulations. The droplet contains excess charge that is carried by sodium ions. To investigate the principles of the charging mechanisms of a macromolecule in a droplet, we simulate aqueous and methanol droplets that contain a poly(ethylene glycol) (PEG) molecule. We find that the solvent plays a critical role in the charging mechanism and in the manner that the sodiated PEG emerges from a droplet. In the aqueous droplets, the sodiated PEG is released from the droplet while it is being charged at a droplet charge state below the Rayleigh limit. The charging of PEG occurs on the surface of the droplet. In contrast to the aqueous droplets, in the methanol droplet, the sodiated PEG resides in the interior of the droplet and it may become charged at any location in the droplet, interior or surface. The sodiated PEG emerges from the droplet by drying-out of the solvent. Even though these two mechanisms appear to be phenomenologically similar to the widely accepted ion-evaporation and charge-residue mechanisms, they have fundamental differences from those. An integral part of the mechanism that the macromolecular ions emerge from droplets is the droplet morphology. Droplet morphologies give rise to different solvation interactions between the solvent and the macromolecule. In the water-sodiated PEG system, we find the extrusion of the PEG morphology, while in methanol-sodiated droplet, we find the "pearl-on-the-necklace" morphology and the extrusion of the sodiated PEG in the last stage of the desolvation process. These findings provide insight into the mechanisms that macromolecules acquire their charge in droplets produced in electrospray ionization experiments.

  3. Carbon Nanotube Dispersion in Solvents and Polymer Solutions: Mechanisms, Assembly, and Preferences.

    Science.gov (United States)

    Pramanik, Chandrani; Gissinger, Jacob R; Kumar, Satish; Heinz, Hendrik

    2017-12-26

    Debundling and dispersion of carbon nanotubes (CNTs) in polymer solutions play a major role in the preparation of carbon nanofibers due to early effects on interfacial ordering and mechanical properties. A roadblock toward ultrastrong fibers is the difficulty to achieve homogeneous dispersions of CNTs in polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) precursor solutions in solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF). In this contribution, molecular dynamics simulations with accurate interatomic potentials for graphitic materials that include virtual π electrons are reported to analyze the interaction of pristine single wall CNTs with the solvents and polymer solutions at 25 °C. The results explain the barriers toward dispersion of SWCNTs and quantify CNT-solvent, polymer-solvent, as well as CNT-polymer interactions in atomic detail. Debundling of CNTs is overall endothermic and unfavorable with dispersion energies of +20 to +30 mJ/m 2 in the pure solvents, + 20 to +40 mJ/m 2 in PAN solutions, and +20 to +60 mJ/m 2 in PMMA solutions. Differences arise due to molecular geometry, polar, van der Waals, and CH-π interactions. Among the pure solvents, DMF restricts CNT dispersion less due to the planar geometry and stronger van der Waals interactions. PAN and PMMA interact favorably with the pure solvents with dissolution energies of -0.7 to -1.1 kcal per mole monomer and -1.5 to -2.2 kcal per mole monomer, respectively. Adsorption of PMMA onto CNTs is stronger than that of PAN in all solvents as the molecular geometry enables more van der Waals contacts between alkyl groups and the CNT surface. Polar side groups in both polymers prefer interactions with the polar solvents. Higher polymer concentrations in solution lead to polymer aggregation via alkyl groups and reduce adsorption onto CNTs. PAN and PMMA solutions in DMSO and dilute solutions in DMF support CNT dispersion more than other

  4. Surface nanocrystallization by surface mechanical attrition treatment and its effect on structure and properties of plasma nitrided AISI 321 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lin Yimin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Middle Tianshui Road, Lanzhou 730000 (China) and Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China)]. E-mail: linyimin_2001@yahoo.com.cn; Lu Jian [LASMIS, University of Technology of Troyes, 10000 Troyes (France); Wang Liping [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Middle Tianshui Road, Lanzhou 730000 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Xu Tao [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Middle Tianshui Road, Lanzhou 730000 (China); Xue Qunji [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Middle Tianshui Road, Lanzhou 730000 (China)]. E-mail: qjxue@ns.lzb.ac.cn

    2006-12-15

    A plastic deformation surface layer with nanocrystalline grains was produced on AISI 321 austenitic stainless steel by means of surface mechanical attrition treatment (SMAT). Low-temperature nitriding of SMAT and un-SMAT AISI 321 stainless steel was carried out in pulsed-DC glow discharge. The effect of SMAT pretreatment on the microstructure and properties of the stainless steel were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Vickers hardness tester and UMT-2MT tribometer. The results show that the plasma nitriding of AISI 321 steel can be enhanced considerably by means of SMAT process before nitriding, and a much thicker nitrogen diffusion layer with higher hardness was obtained for the SMAT samples when compared with un-SMAT samples. In addition, the wear resistance and load capacity of the nitrided layers on the SMAT samples was much higher than that of the un-SMAT samples due to the thicker S phase case and the gradient nitrogen diffusion layer.

  5. Ester-free Thiol-X Resins: New Materials with Enhanced Mechanical Behavior and Solvent Resistance.

    Science.gov (United States)

    Podgórski, Maciej; Becka, Eftalda; Chatani, Shunsuke; Claudino, Mauro; Bowman, Christopher N

    A series of thiol-Michael and radical thiol-ene network polymers were successfully prepared from ester-free as well as ester-containing monomer formulations. Polymerization reaction rates, dynamic mechanical analysis, and solvent resistance experiments were performed and compared between compositions with varied ester loading. The incorporation of ester-free alkyl thiol, vinyl sulfone and allylic monomers significantly improved the mechanical properties when compared with commercial, mercaptopropionate-based thiol-ene or thiol-Michael networks. For polymers with no hydrolytically degradable esters, glass transition temperatures (T g 's) as high as 100 °C were achieved. Importantly, solvent resistance tests demonstrated enhanced stability of ester-free formulations over PETMP-based polymers, especially in concentrated basic solutions. Kinetic analysis showed that glassy step-growth polymers are readily formed at ambient conditions with conversions reaching 80% and higher.

  6. Reaction mechanism of hydroxymaleimide induced by γ-irradiation in alcohol solvents

    International Nuclear Information System (INIS)

    Nakagawa, Seiko

    2010-01-01

    Methanol and 2-propanol solutions of hydroxymaleimide were irradiated with γ-ray and mechanism of its γ-irradiation-induced reactions was investigated through final-product analyses using high performance liquid chromatography (HPLC) coupled with mass spectroscopy. An addition reaction of a solvent radical toward hydroxymaleimide was dominant among its oxygen-free γ-irradiation-induced reactions in its alcohol solutions while it is known that electron attachment toward hydroxyphthalimide or hydroxysuccinimide is dominant among their γ-irradiation-induced reactions. The radical adduct abstracts hydrogen from solvent molecule to re-produce a solvent radical. Therefore, the degradation efficiency of hydroxymaleimide was more than ten times larger than that of hydroxyphthalimide and hydroxysuccinimide. Dimer was also produced through electron attachment process in the solutions of hydroxymaleimide. In addition, it was found that the degradation efficiency increased with decrease in dose rate. An additional reaction of a solvent radical toward hydroxymaleimide competes with a radical-radical recombination. The latter was reduced, with the former leading to efficient degradation of hydroxymaleimide increased by irradiation at lower dose rate. On the contrary, the production yield of the adduct radical as well as the degradation efficiency of hydroxymaleimide was inhibited in the presence of oxygen.

  7. Reaction mechanism of hydroxymaleimide induced by γ-irradiation in alcohol solvents

    International Nuclear Information System (INIS)

    Nakagawa, Seiko

    2010-01-01

    Methanol and 2-propanol solutions of hydroxymaleimide were irradiated with γ-ray and mechanism of its γ-irradiation-induced reactions was investigated through final-product analyses using high performance liquid chromatography (HPLC) coupled with mass spectroscopy. An addition reaction of a solvent radical toward hydroxymaleimide was dominant among its oxygen-free γ-irradiation-induced reactions in its alcohol solutions while it is known that electron attachment toward hydroxyphthalimide or hydroxysuccinimide is dominant among their γ-irradiation-induced reactions. The radical adduct abstracts hydrogen from solvent molecule to re-produce a solvent radical. Therefore, the degradation efficiency of hydroxymaleimide was more than 10 times larger than that of hydroxyphthalimide and hydroxysuccinimide. Dimer was also produced through electron attachment process in the solutions of hydroxymaleimide. In addition, it was found that the degradation efficiency increased with decreasing the dose rate. An addition reaction of a solvent radical toward hydroxymaleimide competes with a radical-radical recombination. The latter was reduced and the former leading to efficient degradation of hydroxymaleimide increased by irradiation at lower dose rate. On the contrary, the production yield of the adduct radical as well as the degradation efficiency of hydroxymaleimide was inhibited in the presence of oxygen.

  8. Analysis of potassium nitrate purification with recovery of solvent through single effect mechanical vapor compression

    Directory of Open Access Journals (Sweden)

    Kiprotich E. Kosgey

    2017-12-01

    Full Text Available Analysis of purification of potassium nitrate with incorporation of single effect mechanical vapor compressor for solvent recovery was done. Analysis focused on the effect of concentration and temperature of mother liquor on the energy efficiency of the process and the amount of recovered solvent. Performance coefficient of mechanical vapor compressor ranged between 1.5 and 7.5 depending primarily on the temperature of mother liquor. It was found that with increase in temperature of mother liquor through pre-heating, the power of the compressor, compression ratio and amount of heat supplied to the evaporator decrease. For a 40% concentrated feed solution and mother liquor temperature above 80 °C, performance coefficient is higher than 4. It is therefore concluded that preheating mother liquor and reduction of the effect of concentration of both mother liquor and concentrated waste stream through other methods reduces the power consumption of purification process. Keywords: Performance coefficient, Mother liquor, Concentrated solution, Recovered solvent, Boiling point elevation, Mechanical vapor compressor

  9. Characteristics and mechanism of explosive reactions of Purex solvents with Nitric Acid at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Miyata, Teijiro [Radiation Application Development Association, Tokai, Ibaraki (Japan); Takada, Junichi; Koike, Tadao; Tsukamoto, Michio; Watanabe, Koji [Department of Fuel Cycle Safety Research, Nuclear Safety Research Center, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Ida, Masaaki [JGC PLANTECH CO., LTD (Japan); Nakagiri, Naotaka [JGC Corp., Tokyo (Japan); Nishio, Gunji [Research Organization for Information Science and Technology, Tokai, Ibaraki (Japan)

    2000-03-01

    This investigation was undertaken to make clear the energetic properties and mechanism of explosive decomposition of Purex solvent systems (TBP/n-Dodecane/HNO{sub 3}) by Nitric Acid at elevated temperatures using a calorimetric technique (DSC, ARC) and a chromatographic technique (GC, GC/MS). The measurement of exothermic events of solvent-HNO{sub 3} reactions using DSC with a stainless steel sealed cell showed distinct two peaks with maxima at around 170 and 320degC, respectively. The peak at around 170degC was mainly attributed to the reactions of dealkylation products (n-butyl nitrate) of TBP and the solvent with nitric acid, and the peak at around 320degC was attributed to the exothermic decomposition of nitrated dodecanes formed in the foregoing exothermic reaction of dodecane with nitric acid. By using the data obtained in ARC experiments, activation energies of 123.2 and 152.5 kJ/mol were determined for the exothermic reaction of TBP with nitric acid and for the exothermic pyrolysis of n-butyl nitrate, respectively. Some possible pathways were considered for the explosive decomposition of TBP by nitric acid at elevated temperatures. (author)

  10. Role of solvent environments in single molecule conductance used insulator-modified mechanically controlled break junctions

    Science.gov (United States)

    Muthusubramanian, Nandini; Maity, Chandan; Galan Garcia, Elena; Eelkema, Rienk; Grozema, Ferdinand; van der Zant, Herre; Kavli Institute of Nanoscience Collaboration; Department of Chemical Engineering Collaboration

    We present a method for studying the effects of polar solvents on charge transport through organic/biological single molecules by developing solvent-compatible mechanically controlled break junctions of gold coated with a thin layer of aluminium oxide using plasma enhanced atomic layer deposition (ALD). The optimal oxide thickness was experimentally determined to be 15 nm deposited at ALD operating temperature of 300°C which yielded atomically sharp electrodes and reproducible single-barrier tunnelling behaviour across a wide conductance range between 1 G0 and 10-7 G0. The insulator protected MCBJ devices were found to be effective in various solvents such as deionized water, phosphate buffered saline, methanol, acetonitrile and dichlorobenzene. The yield of molecular junctions using such insulated electrodes was tested by developing a chemical protocol for synthesizing an amphipathic form of oligo-phenylene ethynylene (OPE3-PEO) with thioacetate anchoring groups. This work has further applications in studying effects of solvation, dipole orientation and other thermodynamic interactions on charge transport. Eu Marie Curie Initial Training Network (ITN). MOLECULAR-SCALE ELECTRONICS: ``MOLESCO'' Project Number 606728.

  11. Heterocyclic Schiff bases as non toxic antioxidants: Solvent effect, structure activity relationship and mechanism of action

    Science.gov (United States)

    Shanty, Angamaly Antony; Mohanan, Puzhavoorparambil Velayudhan

    2018-03-01

    Phenolic heterocyclic imine based Schiff bases from Thiophene-2-carboxaldehyde and Pyrrole-2-carboxaldehyde were synthesized and characterized as novel antioxidants. The solvent effects of these Schiff bases were determined and compared with standard antioxidants, BHA employing DPPH assay and ABTS assay. Fixed reaction time and Steady state measurement were used for study. IC50 and EC50 were calculated. Structure-activity relationship revealed that the electron donating group in the phenolic ring increases the activity where as the electron withdrawing moiety decreases the activity. The Schiff base derivatives showed antioxidant property by two different pathways namely SPLET and HAT mechanisms in DPPH assay. While in ABTS method, the reaction between ABTS radical and Schiff bases involves electron transfer followed by proton transfer (ET-PT) mechanism. The cytotoxicity of these compounds has been evaluated by MTT assay. The results showed that all these compounds are non toxic in nature.

  12. Conversion of glucose into 5-hydroxymethylfurfural in different solvents and catalysts: Reaction kinetics and mechanism

    Directory of Open Access Journals (Sweden)

    Cunshan Zhou

    2017-06-01

    Full Text Available Synthesis of 5-hydroxymethylfurfural (HMF from glucose was done in H2O, dimethylsulfoxide (DMSO and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl catalyzed by metal (III chloride (FeCl3·6H2O, CrCl3·6H2O and AlCl3. The effects of solvent/catalyst system and temperature/time on the performance of the reaction are studied. HMF yield in the different solvents follows a decreasing order as DMSO > [Bmim]Cl > H2O. The highest HMF yield is achieved by CrCl3·6H2O, followed by AlCl3 and then FeCl3·6H2O. An optimal temperature/time is found at 393 K or 403 K and a time between 30 min and 480 min. Under the optimal reaction conditions, HMF yields of 54.43% and 52.86% are obtained in DMSO with CrCl3·6H2O at 403 K and 480 min and AlCl3 at 393 K and 240 min, respectively. The mechanism of the halide chlorides catalyzed glucose conversion reaction is proposed. The kinetic model is established to describe the HMF formation and the experimental data conform to the model.

  13. Language Attrition: The Fate of the Start.

    Science.gov (United States)

    Hansen, Lynne

    2001-01-01

    Reviews the literature on psycholinguistic aspects of language attrition over the past half decade. Discusses evidence from studies on hesitation phenomena in attriter speech, variables affecting language attrition, and relearning. (Author/VWL)

  14. An adaptive quantum mechanics/molecular mechanics method for the infrared spectrum of water: incorporation of the quantum effect between solute and solvent.

    Science.gov (United States)

    Watanabe, Hiroshi C; Banno, Misa; Sakurai, Minoru

    2016-03-14

    Quantum effects in solute-solvent interactions, such as the many-body effect and the dipole-induced dipole, are known to be critical factors influencing the infrared spectra of species in the liquid phase. For accurate spectrum evaluation, the surrounding solvent molecules, in addition to the solute of interest, should be treated using a quantum mechanical method. However, conventional quantum mechanics/molecular mechanics (QM/MM) methods cannot handle free QM solvent molecules during molecular dynamics (MD) simulation because of the diffusion problem. To deal with this problem, we have previously proposed an adaptive QM/MM "size-consistent multipartitioning (SCMP) method". In the present study, as the first application of the SCMP method, we demonstrate the reproduction of the infrared spectrum of liquid-phase water, and evaluate the quantum effect in comparison with conventional QM/MM simulations.

  15. Workshop on Language Student Attrition

    National Research Council Canada - National Science Library

    Whelan, Bree

    2001-01-01

    Seventy individuals from Government agencies (military and civilian), academia, and contractor organizations attended all or parts of a Workshop on student Attrition held at the Defense Language Institute Foreign Language Center (DLIFLC...

  16. Sorption mechanism of solvent vapors to coals; Sekitan eno yobai joki no shuchaku kiko no kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, K.; Takanohashi, T.; Iino, M. [Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science

    1996-10-28

    With an objective to clarify the interactions between micropore structure of coal and solvent reagents, a sorption experiment was carried out under solvent saturated vapor pressure. Low-volatile bituminous coal, Pocahontas No. 3 coal, has the aromatic ring structure developed, and makes solvent more difficult to diffuse into coal, hence sorption amount is small. Methanol has permeated since its polarity is high. High-volatile bituminous coal, Illinois No. 6 coal, makes solvent penetrate easily, and the sorption amount was large with both of aromatic and polar solvents. Since brown coal, Beulah Zap coal, contains a large amount of oxygen, and hydrogen bonding is predominant, sorption amount of cyclohexane and benzene having no polarity is small. Methanol diffuses while releasing hydrogen bond due to its polarity, and its sorption amount is large. A double sorption model is available, which expresses the whole sorption amount as a sum of physical sorption amount and amount of permeation into coal. This model was applied when it explained successfully the sorption behavior of the solvents relative to coals, excepting some of the systems. However, also observed were such abnormal behavior as sorption impediment due to interactions between coal surface and solvents, and permeation impediment due to hydroxyl groups inside the coals. 1 ref., 10 figs., 2 tabs.

  17. Thermo-mechanical characterization of epoxy nanocomposites with different carbon nanotube distributions obtained by solvent aided and direct mixing.

    Directory of Open Access Journals (Sweden)

    M. Zarrelli

    2012-07-01

    Full Text Available Two different routes, namely solvent aided dispersion and direct mixing, were employed to disperse Multi-Walled Carbon Nanotubes (MWNTs into a mono-component epoxy system used as matrix for advanced composites. In the first route, MWCNTs were diluted in three different solvents (acetone, sodium dodecyl sulfate and ethanol and then mixed with the matrix by tip sonication. In the second case, carbonaceous nanoparticles were added directly into the hosting system and dispersion was carried out by using three different techniques (mechanical stirring, magnetic agitation and tip sonication. The effects of the solvents and agitation energy were investigated by optical microscopy at micron level, in order assess the more efficient dispersion procedure for the considered epoxy system. It was demonstrated that parameters associated with direct mixing rather than solvent solubility govern MWCNT dispersion. Optical analysis of the nanocomposite morphology evidenced a very low density of MWCNTs micron sized aggregates in the case of direct mixed tip sonicated samples if compared to those obtained by solution aided dispersion. In addition, nanocomposites obtained by sonication showed the lowest density of MWCNTs micron sized aggregates, also when compared with mechanically and magnetically stirred system. Dynamic Mechanical Analysis (DMA and Thermo-Mechanical Analysis (TMA results confirm the final result that among the considered direct mixing techniques, the direct tip sonication represents the most efficient route for MWCNT dispersion. Moreover, the mixing temperature of the hosting matrix system represents a fundamental feature in enhancing the MWCNT de-bundling and dispersion. Small X-ray Scattering analysis revealed that a nanosized structure of nanotubes is formed in the case of the tip sonicated samples that is heuristically correlated with both the maximum enhancement of mechanical modulus and the maximum reduction of thermal expansion coefficients.

  18. Solvent Vapour Detection with Cholesteric Liquid Crystals—Optical and Mass-Sensitive Evaluation of the Sensor Mechanism

    Directory of Open Access Journals (Sweden)

    Adnan Mujahid

    2010-05-01

    Full Text Available Cholesteric liquid crystals (CLCs are used as sensitive coatings for the detection of organic solvent vapours for both polar and non-polar substances. The incorporation of different analyte vapours in the CLC layers disturbs the pitch length which changes the optical properties, i.e., shifting the absorption band. The engulfing of CLCs around non-polar solvent vapours such as tetrahedrofuran (THF, chloroform and tetrachloroethylene is favoured in comparison to polar ones, i.e., methanol and ethanol. Increasing solvent vapour concentrations shift the absorbance maximumto smaller wavelengths, e.g., as observed for THF. Additionally, CLCs have been coated on acoustic devices such as the quartz crystal microbalance (QCM to measure the frequency shift of analyte samples at similar concentration levels. The mass effect for tetrachloroethylene was about six times higher than chloroform. Thus, optical response can be correlated with intercalation in accordance to mass detection. The mechanical stability was gained by combining CLCs with imprinted polymers. Therefore, pre-concentration of solvent vapours was performed leading to an additional selectivity.

  19. Response Mechanisms in Serratia marcescens IBBPo15 During Organic Solvents Exposure.

    Science.gov (United States)

    Stancu, Mihaela Marilena

    2016-12-01

    Serratia marcescens strain IBB Po15 (KT315653) which possesses serratiopeptidase (ser) gene (KT894207) exhibited good solvent tolerance. During the exposure of S. marcescens IBB Po15 cells to 5 % organic solvents, n-decane was less toxic for this bacterium, compared with n-hexane, cyclohexane, ethylbenzene, toluene, and styrene. The exposure of the S. marcescens IBB Po15 cells to n-hexane, cyclohexane, ethylbenzene, toluene, and styrene induced the formation of large clusters, while in control and n-decane-exposed cells, only organization into small clusters was observed. The data obtained suggested that S. marcescens IBB Po15 cells produced some secondary metabolites (i.e., surfactant serrawettin, red pigment prodigiosin) which are well known as valuable molecules due to their large applications. The exposure of the bacterial cells to organic solvents induced secondary metabolites profile modifications. However, S. marcescens IBB Po15 possesses only alkB1, todM, rhlAB, pswP, mpr, and ser genes, the unspecific amplification of other fragments being acquired also when the primers for alkM1, xylM, ndoM, and C23DO genes were used. Modifications of DNA patterns were not depicted in S. marcescens IBB Po15 cells exposed to organic solvents.

  20. Solvent effects on the excited-state double proton transfer mechanism in the 7-azaindole dimer: a TDDFT study with the polarizable continuum model.

    Science.gov (United States)

    Yu, Xue-Fang; Yamazaki, Shohei; Taketsugu, Tetsuya

    2017-08-30

    Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method. Excited-state potential energy profiles along the reaction paths in a locally excited (LE) state and a charge transfer (CT) state were calculated using the polarizable continuum model (PCM) to include the solvent effect. A series of non-polar and polar solvents with different dielectric constants were used to examine the polarity effect on the ESDPT mechanism. The present results suggest that in a non-polar solvent and a polar solvent with a small dielectric constant, ESDPT follows a concerted mechanism, similar to the case in the gas phase. In a polar solvent with a relatively large dielectric constant, however, ESDPT is likely to follow a stepwise mechanism via a stable zwitterionic intermediate in the LE state on the adiabatic potential energy surface, although inclusion of zero-point vibrational energy (ZPE) corrections again suggests the concerted mechanism. In the meantime, the stepwise reaction path involving the CT state with neutral intermediates is also examined, and is found to be less competitive than the concerted or stepwise path in the LE state in both non-polar and polar solvents. The present study provides a new insight into the experimental controversy of the ESDPT mechanism of the 7AI dimer in a solution.

  1. Australian aboriginal tooth succession, interproximal attrition, and Begg's theory.

    Science.gov (United States)

    Corruccini, R S

    1990-04-01

    In 1954, P.R. Begg analyzed interproximal attrition as a prehistorically universal mechanism to reduce tooth size. With modern processed diets and the virtual disappearance of constant interproximal attrition, Begg asserted, teeth remain too large for the arches and become crowded. Later investigators have questioned Begg's estimate of attritional tooth-size reduction, as well as aspects of his theory relating the succession sequence of permanent teeth to different malocclusions. The present paper examines the theory using longitudinal casts and records of modern Australian aborigines who are among the first generation lacking notable interproximal attrition thanks to a "modernized" diet. Deciduous and permanent tooth size, arch size, and occlusal relational variables were analyzed with respect to the expected occlusal outcomes in the absence of attritional tooth reduction. Permanent incisor overjet correlated with crowding status, as predicted by Begg. On the other hand, longer teeth did not relate to crowding in general nor to crowding in relevant local areas or during developmental stages. Unfavorable leeway space did not relate clearly to crowding or other malocclusions. Lowered correlations among structures and narrowness of the maxilla related more significantly to malocclusion. These results are in keeping with recent thinking that small jaws rather than large teeth underlie tooth/arch discrepancy.

  2. Solvent dielectric effect and side chain mutation on the structural stability of Burkholderia cepacia lipase active site: a quantum mechanical/molecular mechanics study.

    Science.gov (United States)

    Tahan, A; Monajjemi, M

    2011-12-01

    Quantum mechanical and molecular dynamics methods were used to analyze the structure and stability of neutral and zwitterionic configurations of the extracted active site sequence from a Burkholderia cepacia lipase, histidyl-seryl-glutamin (His86-Ser87-Gln88) and its mutated form, histidyl-cysteyl-glutamin (His86-Cys87-Gln88) in vacuum and different solvents. The effects of solvent dielectric constant, explicit and implicit water molecules and side chain mutation on the structure and stability of this sequence in both neutral and zwitterionic forms are represented. The quantum mechanics computations represent that the relative stability of zwitterionic and neutral configurations depends on the solvent structure and its dielectric constant. Therefore, in vacuum and the considered non-polar solvents, the neutral form of the interested sequences is more stable than the zwitterionic form, while their zwitterionic form is more stable than the neutral form in the aqueous solution and the investigated polar solvents in most cases. However, on the potential energy surfaces calculated, there is a barrier to proton transfer from the positively charged ammonium group to the negatively charged carboxylat group or from the ammonium group to the adjacent carbonyl oxygen and or from side chain oxygen and sulfur to negatively charged carboxylat group. Molecular dynamics simulations (MD) were also performed by using periodic boundary conditions for the zwitterionic configuration of the hydrated molecules in a box of water molecules. The obtained results demonstrated that the presence of explicit water molecules provides the more compact structures of the studied molecules. These simulations also indicated that side chain mutation and replacement of sulfur with oxygen leads to reduction of molecular flexibility and packing.

  3. Mechanically-induced solvent-less synthesis of cobalt and nickel complexes of cimetidine

    Directory of Open Access Journals (Sweden)

    Adedibu Clement Tella

    2011-09-01

    Full Text Available Solvent-less synthesis of [Co(CIM2](SO4 and [Ni(CIM2](OAC2 by grinding of CoSO4 and Ni(CH3COO2.4H2O with cimetidine without any solvent is described. The complexes have been characterized by elemental analysis, melting point, AAS, conductivity measurements, TLC, infrared and UV-Vis spectroscopies as well as X-ray powder diffraction. Cimetidine was found to be bidentate or tridentate ligand. Cobalt ion coordinate with cimetidine through the sulphur atom in the thiol group, nitrogen atom of imidazole ring and the nitrogen atom of the secondary amine to give an octahedral geometry with ligand acting as tridentate whereas nickel ion coordinates through the sulphur atom in the thiol group, nitrogen atom of imidazole ring to give tetrahedral structure with ligand acting as bidentate. X-Ray diffraction patterns of the complex were different from that of the ligand suggesting formation of coordination compounds. The method is quick and gives a quantatively yield, without the need for solvents or external heating. Clearly, it can present higher efficiency in terms of materials, energy and time compared to classical solution phase synthesis.

  4. Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl- attack on CH3Cl.

    Science.gov (United States)

    Kuechler, Erich R; York, Darrin M

    2014-02-07

    The nucleophilic attack of a chloride ion on methyl chloride is an important prototype SN2 reaction in organic chemistry that is known to be sensitive to the effects of the surrounding solvent. Herein, we develop a highly accurate Specific Reaction Parameter (SRP) model based on the Austin Model 1 Hamiltonian for chlorine to study the effects of solvation into an aqueous environment on the reaction mechanism. To accomplish this task, we apply high-level quantum mechanical calculations to study the reaction in the gas phase and combined quantum mechanical/molecular mechanical simulations with TIP3P and TIP4P-ew water models and the resulting free energy profiles are compared with those determined from simulations using other fast semi-empirical quantum models. Both gas phase and solution results with the SRP model agree very well with experiment and provide insight into the specific role of solvent on the reaction coordinate. Overall, the newly parameterized SRP Hamiltonian is able to reproduce both the gas phase and solution phase barriers, suggesting it is an accurate and robust model for simulations in the aqueous phase at greatly reduced computational cost relative to comparably accurate ab initio and density functional models.

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

    Science.gov (United States)

    Karlen, Janice M.

    2004-01-01

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

  6. Navy Recruit Attrition Prediction Modeling

    Science.gov (United States)

    2014-09-01

    have high correlation with attrition, such as age, job characteristics, command climate, marital status, behavior issues prior to recruitment, and the...the additive model. glm(formula = Outcome ~ Age + Gender + Marital + AFQTCat + Pay + Ed + Dep, family = binomial, data = ltraining) Deviance ...0.1 ‘ ‘ 1 (Dispersion parameter for binomial family taken to be 1) Null deviance : 105441 on 85221 degrees of freedom Residual deviance

  7. Mechanical properties of wood from Pinus sylvestris L. treated with Light Organic Solvent Preservative and with waterborne Copper Azole

    Directory of Open Access Journals (Sweden)

    A.M. Villasante

    2013-12-01

    Full Text Available Aim of study: To determine the effect on wood from Pinus sylvestris of treatment with preservatives on mechanical properties and to establish the relation between the penetration and compression strength.Area of study: SpainMaterial and Methods: 40 samples of defect-free wood from Pinus sylvestris L. were treated with Light Organic Solvent Preservative (Vacsol Azure WR 2601 and 50 with waterborne Copper Azole (Tanalith E 3492. 40 control samples were not treated (water or preservative. Mechanical resistance to static bending, modulus of elasticity and compression strength parallel to the grain were compared with untreated wood. Regression analysis between the penetration and compression strength parallel was done with the samples treated with waterborne preservative.Main results: The results indicate that the treated wood (with either product presents a statistically significant increase in mechanical resistance in all three mechanical characteristics. The results obtained differ from earlier studies carried out by other authors.There was no correlation between parallel compression strength and the degree of impregnation of the wood with waterborne Copper Azole . The most probable explanation for these results concerns changes in pressure during treatment.The use of untreated control samples instead of samples treated only with water is more likely to produce significant results in the mechanical resistance studies.Research highlights: Treated wood presents a statistically significant increase in MOE, modulus of rupture to static bending  and parallel compression strength.There was no correlation between parallel compression strength and the degree of impregnation with waterborne preservative.Keywords: Light Organic Solvent Preservative; MOE; parallel compression; static bending; waterborne Copper Azole; wood technology.

  8. Obtaining bixin from semi-defatted annatto seeds by a mechanical method and solvent extraction: Process integration and economic evaluation.

    Science.gov (United States)

    Alcázar-Alay, Sylvia C; Osorio-Tobón, J Felipe; Forster-Carneiro, Tânia; Meireles, M Angela A

    2017-09-01

    This work involves the application of physical separation methods to concentrate the pigment of semi-defatted annatto seeds, a noble vegetal biomass rich in bixin pigments. Semi-defatted annatto seeds are the residue produced after the extraction of the lipid fraction from annatto seeds using supercritical fluid extraction (SFE). Semi-defatted annatto seeds are use in this work due to three important reasons: i) previous lipid extraction is necessary to recovery the tocotrienol-rich oil present in the annatto seeds, ii) an initial removal of the oil via SFE process favors bixin separation and iii) the cost of raw material is null. Physical methods including i) the mechanical fractionation method and ii) an integrated process of mechanical fractionation method and low-pressure solvent extraction (LPSE) were studied. The integrated process was proposed for processing two different semi-defatted annatto materials denoted Batches 1 and 2. The cost of manufacture (COM) was calculated for two different production scales (5 and 50L) considering the integrated process vs. only the mechanical fractionation method. The integrated process showed a significantly higher COM than mechanical fractionation method. This work suggests that mechanical fractionation method is an adequate and low-cost process to obtain a rich-pigment product from semi-defatted annatto seeds. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Mechanical properties of wood from Pinus sylvestris L. treated with Light Organic Solvent Preservative and with waterborne Copper Azole

    Energy Technology Data Exchange (ETDEWEB)

    Villasante, A.; Laina, R.; Rojas, J. A. M.; Rojas, I. M.; Vignote, S.

    2013-07-01

    Aim of study: To determine the effect on wood from Pinus sylvestris of treatment with preservatives on mechanical properties and to establish the relation between the penetration and compression strenght. Area of study: Spain. Material and methods: 40 samples of defect-free wood from Pinus sylvestris L. were treated with Light Organic Solvent Preservative (Vacsol Azure WR 2601) and 50 with waterborne Copper Azole (Tanalith E 3492). 40 control samples were not treated (water or preservative). Mechanical resistance to static bending, modulus of elasticity and compression strength parallel to the grain were compared with untreated wood. Regression analysis between the penetration and compression strength parallel was done with the samples treated with waterborne preservative. Main results: The results indicate that the treated wood (with either product) presents a statistically significant increase in mechanical resistance in all three mechanical characteristics. The results obtained differ from earlier studies carried out by other authors. There was no correlation between parallel compression strength and the degree of impregnation of the wood with waterborne Copper Azole. The most probable explanation for these results concerns changes in pressure during treatment. The use of untreated control samples instead of samples treated only with water is more likely to produce significant results in the mechanical resistance studies. Research highlights: Treated wood presents a statistically significant increase in MOE, modulus of rupture to static bending and parallel compression strength. There was no correlation between parallel compression strength and the degree of impregnation with waterborne preservative. (Author)

  10. Structural evidence for solvent-stabilisation by aspartic acid as a mechanism for halophilic protein stability in high salt concentrations.

    Science.gov (United States)

    Lenton, Samuel; Walsh, Danielle L; Rhys, Natasha H; Soper, Alan K; Dougan, Lorna

    2016-07-21

    Halophilic organisms have adapted to survive in high salt environments, where mesophilic organisms would perish. One of the biggest challenges faced by halophilic proteins is the ability to maintain both the structure and function at molar concentrations of salt. A distinct adaptation of halophilic proteins, compared to mesophilic homologues, is the abundance of aspartic acid on the protein surface. Mutagenesis and crystallographic studies of halophilic proteins suggest an important role for solvent interactions with the surface aspartic acid residues. This interaction, between the regions of the acidic protein surface and the solvent, is thought to maintain a hydration layer around the protein at molar salt concentrations thereby allowing halophilic proteins to retain their functional state. Here we present neutron diffraction data of the monomeric zwitterionic form of aspartic acid solutions at physiological pH in 0.25 M and 2.5 M concentration of potassium chloride, to mimic mesophilic and halophilic-like environmental conditions. We have used isotopic substitution in combination with empirical potential structure refinement to extract atomic-scale information from the data. Our study provides structural insights that support the hypothesis that carboxyl groups on acidic residues bind water more tightly under high salt conditions, in support of the residue-ion interaction model of halophilic protein stabilisation. Furthermore our data show that in the presence of high salt the self-association between the zwitterionic form of aspartic acid molecules is reduced, suggesting a possible mechanism through which protein aggregation is prevented.

  11. Cooperative effects in the structuring of fluoride water clusters: Ab initio hybrid quantum mechanical/molecular mechanical model incorporating polarizable fluctuating charge solvent

    Science.gov (United States)

    Bryce, Richard A.; Vincent, Mark A.; Malcolm, Nathaniel O. J.; Hillier, Ian H.; Burton, Neil A.

    1998-08-01

    A new hybrid quantum mechanical/molecular mechanical model of solvation is developed and used to describe the structure and dynamics of small fluoride/water clusters, using an ab initio wave function to model the ion and a fluctuating charge potential to model the waters. Appropriate parameters for the water-water and fluoride-water interactions are derived, with the fluoride anion being described by density functional theory and a large Gaussian basis. The role of solvent polarization in determining the structure and energetics of F(H2O)4- clusters is investigated, predicting a slightly greater stability of the interior compared to the surface structure, in agreement with ab initio studies. An extended Lagrangian treatment of the polarizable water, in which the water atomic charges fluctuate dynamically, is used to study the dynamics of F(H2O)4- cluster. A simulation using a fixed solvent charge distribution indicates principally interior, solvated states for the cluster. However, a preponderance of trisolvated configurations is observed using the polarizable model at 300 K, which involves only three direct fluoride-water hydrogen bonds. Ab initio calculations confirm this trisolvated species as a thermally accessible state at room temperature, in addition to the tetrasolvated interior and surface structures. Extension of this polarizable water model to fluoride clusters with five and six waters gave less satisfactory agreement with experimental energies and with ab initio geometries. However, our results do suggest that a quantitative model of solvent polarization is fundamental for an accurate understanding of the properties of anionic water clusters.

  12. Mechanical and barrier properties of starch-based films plasticized with two- or three component deep eutectic solvents.

    Science.gov (United States)

    Zdanowicz, Magdalena; Johansson, Caisa

    2016-10-20

    The aim of this work was to prepare two- and three-components deep eutectic solvents (DES) and investigate their potential as starch plasticizers. Starch/DES films were prepared via casting method. Mechanical properties, water vapor- and oxygen transmission rates were measured; additionally contact angle and moisture sorption were determined and FTIR analysis was applied on the films. Native potato starch and hydroxypropylated and oxidized starch (HOPS) with common plasticizers (e.g. polyols, urea) and DES were studied. Moreover, influence of three methods of DES introduction and concentration of plasticizer on the films properties were compared. HOPS films were prepared by two methods: as non-cured and cured samples. Some of DESs containing citrate anion exhibited crosslinking ability of polysaccharide matrix. Non-cured HOPS/DES films exhibited more favourable mechanical and barrier properties than cured analogue films. Samples prepared with unmodified potato starch had higher mechanical and barrier properties than films made with HOPS. Starch-based films plasticized with novel DESs with parallel crosslinking activity exhibited satisfactory mechanical and barrier properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Development of an attrition risk prediction tool.

    Science.gov (United States)

    Fowler, John; Norrie, Peter

    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. 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 financial and human implications of this are significant and worthy of investigation. A study was carried out in one medium-sized UK school of nursing and midwifery, aimed at identifying perceived factors associated with attrition and retention. Thirty-five lecturers were interviewed individually; 605 students completed a questionnaire, and of these, 10 were individually interviewed. Attrition data kept by the student service department were reviewed. Data were collected over an 18-month period in 2007-2008. Regression analysis of the student data identified eight significant predictors. Four of these were 'positive' factors in that they aided student retention and four were 'negative' in that they were associated with students' thoughts of resigning. Student attrition and retention is multifactorial, and, as such, needs to be managed holistically. One aspect of this management could be an attrition risk prediction tool.

  14. Mechanical and hydrodynamic behavior of new improved centrifugal extractor for solvent extraction process

    International Nuclear Information System (INIS)

    Retegan, Teodora; Gheorghe, Ionita; Mirica, Dumitru; Croitoru, Cornelia; Stefanescu, Ioan; Kitamoto, Asashi

    2004-01-01

    Total actinide recovery, lanthanide/actinide separation and the selective partitioning of actinides from high level waste (HLW) are nowadays of a major interest. Actinide partitioning with a view to safe disposing of HLW or utilisation in many various applications of recovered elements involves an extraction process usually by means of mixer-settler, pulse column or centrifugal contactor. This one, presents some doubtless advantages and responds to the above mentioned goals. A new type of counter-current multistage centrifugal extractor has been designed and put in operation. A similar apparatus was not found from in other published papers as yet. The counter-current multi-stage centrifugal extractor was a cylinder made of stainless steel with an effective length of 346 mm, the effective diameter of 100 mm and a volume of 1.5 liters, working in a horizontal position. The new internal structure and geometry of the new advanced centrifugal extractor consisting of nine cells (units), five rotation units, two mixing units, two propelling units and two final plates, ensures the counter-current running of the two phases.The central shaft having the rotation cells fixed on it is coupled by an intermediary connection to a electric motor of high rotation speed. Conceptual layout of the advanced counter-current multi-stage centrifugal extractor is presented. The newly designed extractor has been tested at 500-2800 rot/min for a ratio of the aqueous/organic phase =1 to examine the mechanical behavior and the hydrodynamics of the two phases in countercurrent. The results showed that the performances have been generally good and the design requirements were fulfilled. The newly designed counter-current multistage centrifugal extractor appears to be a promising way to increase extraction rate of radionuclides and metals from liquid effluents. (authors)

  15. 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...

  16. Solvent extraction

    Energy Technology Data Exchange (ETDEWEB)

    Coombs, D.M.; Latimer, E.G.

    1988-01-05

    It is an object of this invention to provide for the demetallization and general upgrading of heavy oil via a solvent extracton process, and to improve the efficiency of solvent extraction operations. The yield and demetallization of product oil form heavy high-metal content oil is maximized by solvent extractions which employ either or all of the following techniques: premixing of a minor amount of the solvent with feed and using countercurrent flow for the remaining solvent; use of certain solvent/free ratios; use of segmental baffle tray extraction column internals and the proper extraction column residence time. The solvent premix/countercurrent flow feature of the invention substantially improves extractions where temperatures and pressures above the critical point of the solvent are used. By using this technique, a greater yield of extract oil can be obtained at the same metals content or a lower metals-containing extract oil product can be obtained at the same yield. Furthermore, the premixing of part of the solvent with the feed before countercurrent extraction gives high extract oil yields and high quality demetallization. The solvent/feed ratio features of the invention substanially lower the captial and operating costs for such processes while not suffering a loss in selectivity for metals rejection. The column internals and rsidence time features of the invention further improve the extractor metals rejection at a constant yield or allow for an increase in extract oil yield at a constant extract oil metals content. 13 figs., 3 tabs.

  17. Mechanism of inactivation of human leukocyte elastase by a chloromethyl ketone: kinetic and solvent isotope effect studies

    International Nuclear Information System (INIS)

    Stein, R.L.; Trainor, D.A.

    1986-01-01

    The mechanism of inactivation of human leukocyte elastase (HLE) by the chloromethyl ketone MeOSuc-Ala-Ala-Pro-Val-CH 2 Cl was investigated. The dependence of the first-order rate constant for inactivation on concentration of chloromethyl ketone is hyperbolic and suggests formation of a reversible Michaelis complex prior to covalent interaction between the enzyme and inhibitor. However, the observed Ki value is 10 microM, at least 10-fold lower than dissociation constants for complexes formed from interaction of HLE with structurally related substrates or reversible inhibitors, and suggests that Ki is a complex kinetic constant, reflecting the formation and accumulation of both the Michaelis complex and a second complex. It is proposed that this second complex is a hemiketal formed from attack of the active site serine on the carbonyl carbon of the inhibitor. The accumulation of this intermediate may be a general feature of reactions of serine proteases and chloromethyl ketones derived from specific peptides and accounts for the very low Ki values observed for these reactions. The solvent deuterium isotope effect (SIE) on the inactivation step (ki) is 1.58 +/- 0.07 and is consistent with rate-limiting, general-catalyzed attack of the active site His on the methylene carbon of the inhibitor with displacement of chloride anion. The general catalyst is thought to be the active site Asp. In contrast, the SIE on the second-order rate constant for HLE inactivation, ki/Ki, is inverse and equals 0.64 +/- 0.05

  18. Deasphalting solvents

    International Nuclear Information System (INIS)

    Carrillo, J. A; Caceres, J; Vela, G; Bueno, H

    1996-01-01

    This paper describes how the deasphalted oil (DMO) or demetalized oil (DMO) quality (CCR, Ni, V end asphaltenes contents) changes with: DAO or DMO yield, solvent/feed ratio, type of vacuum reside (from paraffinic to blends with vis breaking bottoms), extraction temperature and extraction solvent (propane, propylene, n-butane and I butane)

  19. Solvent-free, catalyst-free aza-Michael addition of cyclohexylamine to diethyl maleate: reaction mechanism and kinetics

    Czech Academy of Sciences Publication Activity Database

    Bláha, Michal; Trhlíková, Olga; Podešva, Jiří; Abbrent, Sabina; Steinhart, Miloš; Dybal, Jiří; Dušková-Smrčková, Miroslava

    2018-01-01

    Roč. 74, č. 1 (2018), s. 58-67 ISSN 0040-4020 Institutional support: RVO:61389013 Keywords : Aza-Michael addition * solvent-free * catalyst-free Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 2.651, year: 2016

  20. Solvent substitution

    International Nuclear Information System (INIS)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general ''Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated

  1. Solvent substitution

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated.

  2. 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,

  3. 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…

  4. Exploring Beginning Teachers' Attrition in the Netherlands

    Science.gov (United States)

    den Brok, Perry; Wubbels, Theo; van Tartwijk, Jan

    2017-01-01

    Based on a review of recent studies and reports, this research investigates attrition among beginning teachers in the Netherlands as well as reasons for teacher attrition, and compares the finding with studies on this topic conducted elsewhere in the world. The findings suggest that attrition among beginning teachers in the Netherlands with a…

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

    International Nuclear Information System (INIS)

    Yao, Xuan; Zhang, Hai; Yang, Hairui; Liu, Qing; Wang, Jinwei; Yue, Guangxi

    2010-01-01

    In this paper, an experimental study on the primary fragmentation and attrition of 5 limestones in a fluidized bed was conducted. The intensity of fragmentation and attrition were measured in the same apparatus but at different fluidizing velocities. It was found that the averaged size of the particles decreased by about 10-20% during the fragmentation process. The important factors for particle comminution include limestone types, heating rate, calcination condition and ambient CO 2 concentration. Fragmentation mainly occurred in the first a few minutes in the fluidized bed and it was more intense than that in the muffle furnace at the same temperature. The original size effect was ambiguous, depending on the limestone type. The comminution caused by attrition mainly occurred during calcination process rather than sulphation process. The sulphation process was fragmentation and attrition resisted. The attrition rate of sulphate was similar to that of lime in trend, decaying exponentially with time, but was one-magnitude-order smaller than that of lime. Present experimental results indicate that fragmentation mechanism of the limestone is dominated by CO 2 release instead of thermal stress. (author)

  6. 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.

  7. Predicting Student Attrition with Data Mining Methods

    Science.gov (United States)

    Delen, Dursun

    2012-01-01

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

  8. Factors Associated with Veterinary Clinical Faculty Attrition.

    Science.gov (United States)

    Furr, Martin

    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.

  9. 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

  10. β-Secondary and solvent deuterium kinetic isotope effects and the mechanisms of base- and acid-catalyzed hydrolysis of penicillanic acid

    International Nuclear Information System (INIS)

    Deraniyagala, S.A.; Adediran, S.A.; Pratt, R.F.

    1995-01-01

    β-Secondary and solvent deuterium kinetic isotope effects have been determined at 25 degrees C for the alkaline and acid-catalyzed hydrolysis of penicillanic acid. In order to determine the former isotope effect, [6,6- 2 H 2 ]dideuteriopenicillanic acid has been synthesized. In alkaline solution, the former isotope effect was found to be 0.95 ± 0.01. These values support the B AC 2 mechanism of hydrolysis with rate-determining formation of the tetrahedral intermediate that has been proposed for other β-lactams. The measured β-secondary kinetic isotope for the acid-catalyzed reaction was 1.00 ± 0.01. The data indicates that a likely pathway of acid-catalyzed hydrolysis would be that of an A AC 1 mechanism with an intermediate acylium ion. If this were so, the calculated β-secondary isotope effect per hydrogen coplanar with the breaking C-N bond and corrected for the inductive effect of deuterium would be 1.06 ± 0.01. This suggests an early A AC 1 transition state, which would be reasonable in this case because of destabilization of the N-protonated amide with respect to the acylium ion because of ring strain. The absence of specific participation by solvent in the transition state, as would be expected of an A AC 1 but not an associative mechanism, is supported by the strongly inverse solvent deuterium kinetic isotope effect of 0.25 ± 0.00 in 1 M HCl and 0.22 ± 0.01 in 33.3 wt % H 2 SO 4 . 1 fig., 3 tabs

  11. Solvent substitutes

    International Nuclear Information System (INIS)

    Evanoff, S.P.

    1995-01-01

    The environmental and industrial hygiene regulations promulgated since 1980, most notably the Superfund Amendments and Reauthorization Act (SARA), the Hazardous and Solid Waste Amendments to the Resources Conservation and Recovery Act (RCRA), and the Clean Air Act Amendments of 1990, have brought about an increased emphasis on user exposure, hazardous waste generation, and air emissions. As a result, industry is performing a fundamental reassessment of cleaning solvents, processes, and procedures. The more progressive organizations have made their goal the elimination of solvents that may pose significant potential human health and environmental hazards. This chapter discusses solvent cleaning in metal-finishing, metal-manufacturing, and industrial maintenance applications; precision cleaning; and electronics manufacturing. Nonmetallic cleaning, adhesives, coatings, inks, and aerosols also will be addressed, but in a more cursory manner

  12. How do evaporating thin films evolve? Unravelling phase-separation mechanisms during solvent-based fabrication of polymer blends

    KAUST Repository

    Wodo, Olga

    2014-10-13

    © 2014 AIP Publishing LLC. Solvent-based fabrication is a flexible and affordable approach to manufacture polymer thin films. The properties of products made from such films can be tailored by the internal organization (morphology) of the films. However, a precise knowledge of morphology evolution leading to the final film structure remains elusive, thus limiting morphology control to a trial and error approach. In particular, understanding when and where phases are formed, and how they evolve would provide rational guidelines for more rigorous control. Here, we identify four modes of phase formation and subsequent propagation within the thinning film during solvent-based fabrication. We unravel the origin and propagation characteristics of each of these modes. Finally, we construct a mode diagram that maps processing conditions with individual modes. The idea introduced here enables choosing processing conditions to tailor film morphology characteristics and paves the ground for a deeper understanding of morphology control with the ultimate goal of precise, yet affordable, morphology manipulation for a large spectrum of applications.

  13. How do evaporating thin films evolve? Unravelling phase-separation mechanisms during solvent-based fabrication of polymer blends

    KAUST Repository

    Wodo, Olga; Ganapathysubramanian, Baskar

    2014-01-01

    © 2014 AIP Publishing LLC. Solvent-based fabrication is a flexible and affordable approach to manufacture polymer thin films. The properties of products made from such films can be tailored by the internal organization (morphology) of the films. However, a precise knowledge of morphology evolution leading to the final film structure remains elusive, thus limiting morphology control to a trial and error approach. In particular, understanding when and where phases are formed, and how they evolve would provide rational guidelines for more rigorous control. Here, we identify four modes of phase formation and subsequent propagation within the thinning film during solvent-based fabrication. We unravel the origin and propagation characteristics of each of these modes. Finally, we construct a mode diagram that maps processing conditions with individual modes. The idea introduced here enables choosing processing conditions to tailor film morphology characteristics and paves the ground for a deeper understanding of morphology control with the ultimate goal of precise, yet affordable, morphology manipulation for a large spectrum of applications.

  14. Reliability and Cost Impacts for Attritable Systems

    Science.gov (United States)

    2017-03-23

    on reliability and cost: a probabilistic model. Electric Power Systems Research, 72(3), 213-224. Kalbfleisch, J.D. & Prentice, R.L. (1980). The...copyright protection in the United States. AFIT-ENV-MS-17-M-172 RELIABILITY AND COST IMPACTS FOR ATTRITABLE SYSTEMS THESIS Presented to... power of discrete time Markov chains, whether homogeneous or non-homogeneous, to model the reliability and dependability of repairable systems should

  15. Expectations and voluntary attrition in nursing students.

    Science.gov (United States)

    O'Donnell, Hugh

    2011-01-01

    This paper presents a series of findings generated during a larger study which aimed to develop a theoretical understanding of the reasons why nursing students voluntarily leave pre-registration nursing programmes. In this study, significant incongruence was found to exist between student expectations of pre-registration nursing programmes and the reality of these programmes following entry. The resulting dissonance was identified as an important factor in student decisions to voluntarily withdraw. A single case study design was selected to explore the causes of voluntary attrition in nursing students within a School of Nursing and Midwifery. The study population was obtained through purposeful sampling and consisted of 15 students who had previously voluntarily withdrawn from pre-registration nursing programmes. A semi-structured interview method was used to collect data from study participants. The interview schedule developed for use in the study reflected the key components of the conceptual model of higher education (HE) student attrition (Tinto, 1975, 1987, 1993). All interviews were tape recorded to facilitate later transcription. The Cyclical or Interactive Model of Qualitative Research (Miles and Huberman, 1994) was used to analyse data collected from study participants. This paper describes the unrealistic range of expectations which nursing students have of nursing, the information sources and experiences which inform student expectations and how ambiguous expectations contributed to voluntarily attrition. Copyright © 2010 Elsevier Ltd. All rights reserved.

  16. Explicit treatment of active-site waters enhances quantum mechanical/implicit solvent scoring: Inhibition of CDK2 by new pyrazolo[1,5-a]pyrimidines.

    Science.gov (United States)

    Hylsová, Michaela; Carbain, Benoit; Fanfrlík, Jindřich; Musilová, Lenka; Haldar, Susanta; Köprülüoğlu, Cemal; Ajani, Haresh; Brahmkshatriya, Pathik S; Jorda, Radek; Kryštof, Vladimír; Hobza, Pavel; Echalier, Aude; Paruch, Kamil; Lepšík, Martin

    2017-01-27

    We present comprehensive testing of solvent representation in quantum mechanics (QM)-based scoring of protein-ligand affinities. To this aim, we prepared 21 new inhibitors of cyclin-dependent kinase 2 (CDK2) with the pyrazolo[1,5-a]pyrimidine core, whose activities spanned three orders of magnitude. The crystal structure of a potent inhibitor bound to the active CDK2/cyclin A complex revealed that the biphenyl substituent at position 5 of the pyrazolo[1,5-a]pyrimidine scaffold was located in a previously unexplored pocket and that six water molecules resided in the active site. Using molecular dynamics, protein-ligand interactions and active-site water H-bond networks as well as thermodynamics were probed. Thereafter, all the inhibitors were scored by the QM approach utilizing the COSMO implicit solvent model. Such a standard treatment failed to produce a correlation with the experiment (R 2  = 0.49). However, the addition of the active-site waters resulted in significant improvement (R 2  = 0.68). The activities of the compounds could thus be interpreted by taking into account their specific noncovalent interactions with CDK2 and the active-site waters. In summary, using a combination of several experimental and theoretical approaches we demonstrate that the inclusion of explicit solvent effects enhance QM/COSMO scoring to produce a reliable structure-activity relationship with physical insights. More generally, this approach is envisioned to contribute to increased accuracy of the computational design of novel inhibitors. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

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

    OpenAIRE

    Eha Djulaeha; Sukaedi Sukaedi

    2009-01-01

    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 ma...

  18. Survey on workforce retention and attrition

    Science.gov (United States)

    Showstack, Randy

    2013-03-01

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

  19. 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...

  20. 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.

  1. Early Career Teacher Attrition: Intentions of Teachers Beginning

    Science.gov (United States)

    Clandinin, D. Jean; Long, Julie; Schaefer, Lee; Downey, C. Aiden; Steeves, Pam; Pinnegar, Eliza; McKenzie Robblee, Sue; Wnuk, Sheri

    2015-01-01

    Early career teacher attrition has most often been conceptualized as either a problem associated with individual factors (e.g. burnout) or a problem associated with contextual factors (e.g. support and salary). This study considered early career teacher attrition as an identity making process that involves a complex negotiation between individual…

  2. 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…

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

    DEFF Research Database (Denmark)

    Linnet, Jakob; Pedersen, Anders Sune

    2014-01-01

    Attrition is a well known problem in psychotherapeutic treatment. Patients with addiction have high attrition rates, and it is therefore important to identify factors that can improve completion rates in addiction. Here, we investigated the influence of waiting time as a predictor of treatment...

  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. 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.

  6. Insight into resistance mechanism of anaplastic lymphoma kinase to alectinib and JH-VIII-157-02 caused by G1202R solvent front mutation

    Directory of Open Access Journals (Sweden)

    Wang H

    2018-05-01

    resistance, not JH-VIII-157-02. In addition, US simulations prove JH-VIII-157-02 has similar dissociative processes from both ALKWT and ALKG1202R, while alectinib is more easily dissociated from ALKG1202R than from ALKWT, thus indicating lesser residence time. Conclusion: Both the binding affinity and the drug residence time should be emphasized in rational drug design to overcome the G1202R solvent front mutation in ALK resistance. Keywords: ALK, G1202R, alectinib, JH-VIII-157-02, theoretical study, resistance mechanisms

  7. Limestone fragmentation and attrition during fluidized bed oxyfiring

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-04-15

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

  8. Limestone attrition under simulated oxyfiring Fluidized-Bed combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Scala, F. [Istituto di Ricerche sulla Combustione - CNR, Napoli (Italy); Salatino, P. [Dipartimento di Ingegneria Chimica - Universita degli Studi di Napoli Federico II, Napoli (Italy)

    2009-03-15

    Limestone attrition by surface wear was studied during the flue gas desulfurization under simulated fluidized-bed (FB) oxyfiring conditions and hindered calcination. Bench-scale experimental tests were carried out using well-established techniques previously developed for the characterization of sulfation and attrition of sorbents in air-blown atmospheric FB combustors. The experimental limestone conversion and attrition results were compared with those previously obtained with the same limestone under simulated air-blown combustion conditions. The differences in the conversion and attrition extents and patterns associated with oxyfiring as compared to air-blown atmospheric combustion were highlighted and related to the different particle morphologies and thicknesses of the sulfate layer. It was noted that attrition could play an important role in practical circulating FB combustor operation, by effectively enhancing particle sulfation under both oxyfiring and air-blown combustion conditions. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  9. Hydrolysis of N-succinyl-L,L-diaminopimelic acid by the Haemophilus influenzae dapE-encoded desuccinylase: metal activation, solvent isotope effects, and kinetic mechanism.

    Science.gov (United States)

    Born, T L; Zheng, R; Blanchard, J S

    1998-07-21

    Hydrolysis of N-succinyl-L,L-diaminopimelic acid by the dapE-encoded desuccinylase is required for the bacterial synthesis of lysine and meso-diaminopimelic acid. We have investigated the catalytic mechanism of the recombinant enzyme from Haemophilus influenzae. The desuccinylase was overexpressed in Escherichia coli and purified to homogeneity. Steady-state kinetic experiments verified that the enzyme is metal-dependent, with a Km for N-succinyl-L,L-diaminopimelic acid of 1.3 mM and a turnover number of 200 s-1 in the presence of zinc. The maximal velocity was independent of pH above 7 but decreased with a slope of 1 below pH 7. The pH dependence of V/K was bell-shaped with apparent pKs of 6.5 and 8.3. Both L,L- and D,L-diaminopimelic acid were competitive inhibitors of the substrate, but d,d-diaminopimelic acid was not. Solvent kinetic isotope effect studies yielded inverse isotope effects, with values for D2OV/K of 0.62 and D2OV of 0.78. Determination of metal stoichiometry by ICP-AES indicated one tightly bound metal ion, while sequence homologies suggest the presence of two metal binding sites. On the basis of these observations, we propose a chemical mechanism for this metalloenzyme, which has a number of important structurally defined homologues.

  10. Electroreduction mechanism of N-phenylhydroxylamines in aprotic solvents: N-(2-nitrophenyl)- and N-(3-nitrophenyl)hydroxylamines

    International Nuclear Information System (INIS)

    Mendkovich, Andrey S.; Syroeshkin, Mikhail A.; Nasybullina, Darya V.; Mikhailov, Mikhail N.; Gultyai, Vadim P.; Rusakov, Alexander I.

    2017-01-01

    In continuation of our previous studies on N-(4-nitrophenyl)hydroxylamine (1), we investigated the electroreduction of N-(2- (2) and N-(3-nitrophenyl)hydroxylamines (3) in N,N-dimethylformamide/Bu_4NClO_4, using chronoamperometry, cyclic voltammetry, digital simulation and quantum chemical calculations. It was shown that anion radical 3 is rather stable and does not eliminate a hydroxide anion, unlike 2 whose electroreduction mechanism is similar to that previously observed for 1. At the same time, the elimination reaction is observed for dianion of 3 formed at potentials of the first electron transfer by disproportionation of anion radicals. Results of quantum-chemical calculations show that the high stability of anion radical 3 results from the absence of unpaired electron density on its hydroxylamine group.

  11. Influence of attrition variables on iron ore flotation

    Directory of Open Access Journals (Sweden)

    Fabiana Fonseca Fortes

    Full Text Available Abstract The presence of slimes is harmful to the flotation process: the performance and consumption of reagents are negatively affected. Traditionally, the desliming stage has been responsible for removing slimes. However, depending on the porosity of the mineral particles, desliming may not be sufficient to maximize the concentration results. An attrition process before the desliming operation can improve the removal of slime, especially when slimes cover the surface and/or are confined to the cavities/pores of the mineral particles. Attrition is present in the flowcharts of the beneficiation process of phosphate and industrial sand (silica sand. Research has been undertaken for its application to produce pre-concentrates of zircon and iron ore. However, there is still little knowledge of the influence of the attrition variables on the beneficiation process of iron ore. This study presents a factorial design and analysis of the effects of these variables on the reverse flotation of iron ore. The standard of the experimental procedures for all tests included the attrition of pulp, under the conditions of dispersion, desliming and flotation. The parameter analysed (variable response was the metallurgical recovery in reverse flotation tests. The planning and analysis of the full factorial experiment indicated that with 95% reliability, the rotation speed of the attrition cell impeller was the main variable in the attrition process of the iron ore. The percentage of solid variables in the pulp and the time of the attrition, as well as their interactions, were not indicated to be significant.

  12. Active Mechanism of the Interphase Film-Forming Process for an Electrolyte Based on a Sulfolane Solvent and a Chelato-Borate Complexe.

    Science.gov (United States)

    Li, Chunlei; Wang, Peng; Li, Shiyou; Zhao, Dongni; Zhao, Qiuping; Liu, Haining; Cui, Xiao-Ling

    2018-06-14

    Electrolytes based on sulfolane (SL) solvents and lithium bis(oxalato)borate (LiBOB) chelato-borate complexes have been reported many times for use in advanced lithium-ion batteries due to their many advantages. This study aims to clarify the active mechanism of the interphase film-forming process to optimize the properties of these batteries by experimental analysis and theoretical calculations. The results indicate that the self-repairing film-forming process during the first cycle is divided into three stages: the initial film formation with an electric field force of ~1.80 V, the further growth of the preformation solid electrolyte interface (SEI) film at ~1.73 V, and the final formation of a complete SEI film at a potential below 0.7 V. Additionally, we can deduce that the decomposition of LiBOB and SL occurs throughout nearly the entire process of the formation of the SEI film. The decomposition product of BOB- anions tends to form films with an irregular structure, while the decomposition product of SL is in favor of the formation of a uniform SEI film.

  13. Microstructure and mechanical properties of biodegradable poly (D/L) lactic acid/polycaprolactone blends processed from the solvent-evaporation technique.

    Science.gov (United States)

    Esmaeilzadeh, Javad; Hesaraki, Saeed; Hadavi, Seyed Mohammad-Mehdi; Esfandeh, Masoud; Ebrahimzadeh, Mohammad Hosein

    2017-02-01

    In this study, polymer blends comprising poly(D/L) lactic acid (PDLLA) and 0-30wt% polycaprolactone (PCL) was prepared by a solvent-evaporation technique. The effect of PCL content on the dynamic-mechanical properties and tensile and flexural characteristics of the blends was evaluated. The creep and stress relaxation behaviors were also determined and using various known models such as power law, Burgers model and Weibull distribution equation. The results showed that by increasing the PCL content from 10 to 30wt%, the yield stress and flexural strength decreased from 47MPa to 26MPa and 72MPa to 29MPa respectively. In addition to tensile and flexural strength, the elastic modulus of neat PDLLA declined with increasing the PCL content, whereas the elongation or the strain percentage at the break point increased considerably. Biphasic regions were observed in the microstructures of the blends, indicating the immiscibility of PCL in PDLLA matrix. However, the PCL spherulites with an average particle diameter of 100nm to 5μm were homogeneously dispersed in PDLLA phase even at high PCL concentrations. Moreover, the microstructures of the fractured surfaces of the polymers confirmed that PDLLA with a brittle fracture behavior tends toward a soft fracture behavior when it is blended with PCL. The dynamic-mechanical tests indicated that the damping energy and dissipative ability of PDLLA improve by adding PCL. Moreover, T g of neat PDLLA by adding of 10, 20 and 30wt% decreases from 67.3 to 66.2, 65.1 and 63.5°C respectively. Increasing in the recovered viscoelastic strain due to the addition of PCL was also experienced which can be attributed to the presence of large volumetric backbone of PCL chains as well as easy movement of them in the matrix. The results of modeling studies showed a good correlation between the experimentally obtained data. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Thermal and Mechanical Properties of Novolac-Silica Hybrid Aerogels Prepared by Sol-Gel Polymerization in Solvent-Saturated Vapor Atmosphere

    Directory of Open Access Journals (Sweden)

    Mohamad Mehdi Seraji1, Seraji

    2015-05-01

    Full Text Available Nowadays organic–inorganic hybrid aerogel materials have attracted increasing interests due to improved thermal and mechanical properties. In the present research, initially, novolac type phenolic resin-silica hybrid gels with different solid concentrations were synthesized using sol-gel polymerization in solvent-saturatedvapor atmosphere. The hybrid gels were dried at air atmosphere through ambient drying process. This method removed the need for costly and risky supercritical drying process. The yields of the obtained hybrid aerogels increased with less shrinkage in comparison with conventional sol-gel process. The precursor of silica phase in this study was tetraethoxysilane and inexpensive novolac resin was used as a reinforcing phase. The results of FTIR analysis confirmed the simultaneous formation of silica and novolac gels in the hybrid systems. The resultant hybrid aerogels showed a nanostructure hybrid network with high porosity (above 80% and low density (below 0.25 g/cm3. Nonetheless, higher content of silica resulted in more shrinkage in the hybrid aerogel structure due to the tendency of the silica network to shrink more during gelation and drying process. The SEM images of samples exhibited a continuous network of interconnected colloidal particles formed during sol-gel polymerization with mean particle size of less than 100 nanometers. Si mapping analysis showed good distribution of silica phase throughout the hybrid structure. The results demonstrated improvements in insulation properties and thermal stability of novolac-silica aerogel with increasing the silica content. The results of compressive strength showed that the mechanical properties of samples declined with increasing the silica content.

  15. 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.

  16. Could Realistic Job Previews Reduce First-Term Attrition

    National Research Council Canada - National Science Library

    Brose, Gary

    1999-01-01

    .... The military's use of educational screens, trends and costs of first-term attrition, and labor market theories of turnover are discussed to provide a common frame of reference within which to view...

  17. Averting the Train Wreck of Captain Attrition - A Leadership Solution

    National Research Council Canada - National Science Library

    Weafer, Thomas

    2001-01-01

    .... This paper looks at officer attrition in the context of a leadership challenge - it examines current perceived problems in leadership culture and command climate and recommends several changes focused on improving morale and retention of young officers.

  18. Predictors of early faculty attrition at one Academic Medical Center.

    Science.gov (United States)

    Bucklin, Brenda A; Valley, Morgan; Welch, Cheryl; Tran, Zung Vu; Lowenstein, Steven R

    2014-02-10

    Faculty turnover threatens the research, teaching and clinical missions of medical schools. We measured early attrition among newly-hired medical school faculty and identified personal and institutional factors associated with early attrition. This retrospective cohort study identified faculty hired during the 2005-2006 academic year at one school. Three-year attrition rates were measured. A 40-question electronic survey measured demographics, career satisfaction, faculty responsibilities, institutional/departmental support, and reasons for resignation. Odds ratios (ORs) and 95 percent confidence intervals (95% CI) identified variables associated with early attrition. Of 139 faculty, 34% (95% CI = 26-42%) resigned within three years of hire. Attrition was associated with: perceived failure of the Department Chair to foster a climate of teaching, research, and service (OR = 6.03; 95% CI: 1.84, 19.69), inclusiveness, respect, and open communication (OR = 3.21; 95% CI: 1.04, 9.98). Lack of professional development of the faculty member (OR = 3.84; 95% CI: 1.25, 11.81); institutional recognition and support for excellence in teaching (OR = 2.96; 95% CI: 0.78, 11.19) and clinical care (OR = 3.87; 95% CI: 1.04, 14.41); and >50% of professional time devoted to patient care (OR = 3.93; 95% CI: 1.29, 11.93) predicted attrition. Gender, race, ethnicity, academic degree, department type and tenure status did not predict early attrition. Of still-active faculty, an additional 27 (48.2%, 95% CI: 35.8, 61.0) reported considering resignation within the 5 years. In this pilot study, one-third of new faculty resigned within 3 years of hire. Greater awareness of predictors of early attrition may help schools identify threats to faculty career satisfaction and retention.

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

    OpenAIRE

    Gafson, I.; Currie, J.; O Dwyer, S.; Woolf, K.; Griffin, A.

    2017-01-01

    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...

  20. 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...are specific types ot codes used, to icdentity categories of reenlistments, extensions, and losses. These SPD codes will be clustered in various ways...two enlistment terms in the Navy. The Navy’s 110 ratings were grouped into 24 occupational tields which represented clusters of similar skills, similar

  1. Solvent effects in chemistry

    CERN Document Server

    Buncel, Erwin

    2015-01-01

    This book introduces the concepts, theory and experimental knowledge concerning solvent effects on the rate and equilibrium of chemical reactions of all kinds.  It begins with basic thermodynamics and kinetics, building on this foundation to demonstrate how a more detailed understanding of these effects may be used to aid in determination of reaction mechanisms, and to aid in planning syntheses. Consideration is given to theoretical calculations (quantum chemistry, molecular dynamics, etc.), to statistical methods (chemometrics), and to modern day concerns such as ""green"" chemistry, where ut

  2. 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

  3. ART Attrition across Health Facilities Implementing Option B+ in Haiti.

    Science.gov (United States)

    Myrtil, Martine Pamphile; Puttkammer, Nancy; Gloyd, Stephen; Robinson, Julia; Yuhas, Krista; Domercant, Jean Wysler; Honoré, Jean Guy; Francois, Kesner

    2018-01-01

    Describing factors related to high attrition is important in order to improve the implementation of the Option B+ strategy in Haiti. We conducted a retrospective cohort study to describe the variability of antiretroviral therapy (ART) retention across health facilities among pregnant and lactating women and assess for differences in ART retention between Option B+ clients and other ART patients. There were 1989 Option B+ clients who initiated ART in 45 health facilities. The percentage of attrition varied from 9% to 81% across the facilities. The largest health facilities had 38% higher risk of attrition (relative risk [RR]: 1.38, 95% confidence interval [CI]: 1.08-1.77, P = .009). Private institutions had 18% less risk of attrition (RR: 0.82, 95% CI: 0.70-0.96, P = .020). Health facilities located in the West department and the South region had lower risk of attrition. Being on treatment in a large or public health facility or a facility located in the North region was a significant risk factor associated with high attrition among Option B+ clients. The implementation of the Option B+ strategy must be reevaluated in order to effectively eliminate mother-to-child HIV transmission.

  4. Mechanism of Flavoprotein l-6-Hydroxynicotine Oxidase: pH and Solvent Isotope Effects and Identification of Key Active Site Residues.

    Science.gov (United States)

    Fitzpatrick, Paul F; Chadegani, Fatemeh; Zhang, Shengnan; Dougherty, Vi

    2017-02-14

    The flavoenzyme l-6-hydroxynicotine oxidase is a member of the monoamine oxidase family that catalyzes the oxidation of (S)-6-hydroxynicotine to 6-hydroxypseudooxynicotine during microbial catabolism of nicotine. While the enzyme has long been understood to catalyze oxidation of the carbon-carbon bond, it has recently been shown to catalyze oxidation of a carbon-nitrogen bond [Fitzpatrick, P. F., et al. (2016) Biochemistry 55, 697-703]. The effects of pH and mutagenesis of active site residues have now been utilized to study the mechanism and roles of active site residues. Asn166 and Tyr311 bind the substrate, while Lys287 forms a water-mediated hydrogen bond with flavin N5. The N166A and Y311F mutations result in ∼30- and ∼4-fold decreases in k cat /K m and k red for (S)-6-hydroxynicotine, respectively, with larger effects on the k cat /K m value for (S)-6-hydroxynornicotine. The K287M mutation results in ∼10-fold decreases in these parameters and a 6000-fold decrease in the k cat /K m value for oxygen. The shapes of the pH profiles are not altered by the N166A and Y311F mutations. There is no solvent isotope effect on the k cat /K m value for amines. The results are consistent with a model in which both the charged and neutral forms of the amine can bind, with the former rapidly losing a proton to a hydrogen bond network of water and amino acids in the active site prior to the transfer of hydride to the flavin.

  5. A Novel Mechanism for Chemical Sensing Based on Solvent-Fluorophore-Substrate Interaction: Highly Selective Alcohol and Water Sensor with Large Fluorescence Signal Contrast.

    Science.gov (United States)

    Chung, Kyeongwoon; Yang, Da Seul; Jung, Jaehun; Seo, Deokwon; Kwon, Min Sang; Kim, Jinsang

    2016-10-06

    Differentiation of solvents having similar physicochemical properties, such as ethanol and methanol, is an important issue of interest. However, without performing chemical analyses, discrimination between methanol and ethanol is highly challenging due to their similarity in chemical structure as well as properties. Here, we present a novel type of alcohol and water sensor based on the subtle differences in interaction among solvent analytes, fluorescent organic molecules, and a mesoporous silica gel substrate. A gradual change in the chemical structure of the fluorescent diketopyrrolopyrrole (DPP) derivatives alters their interaction with the substrate and solvent analyte, which creates a distinct intermolecular aggregation of the DPP derivatives on the silica gel substrate depending on the solvent environment and produces a change in the fluorescence color and intensity as a sensory signal. The devised sensor device, which is fabricated with simple drop-casting of the DPP derivative solutions onto a silica gel substrate, exhibited a completely reversible fluorescence signal change with large fluorescence signal contrast, which allows selective solvent detection by simple optical observation with the naked eye under UV light. Superior selectivity of the alcohol and water sensor system, which can clearly distinguish among ethanol, methanol, ethylene glycol, and water, is demonstrated.

  6. 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.

  7. Method for Predicting Solubilities of Solids in Mixed Solvents

    DEFF Research Database (Denmark)

    Ellegaard, Martin Dela; Abildskov, Jens; O'Connell, J. P.

    2009-01-01

    A method is presented for predicting solubilities of solid solutes in mixed solvents, based on excess Henry's law constants. The basis is statistical mechanical fluctuation solution theory for composition derivatives of solute/solvent infinite dilution activity coefficients. Suitable approximatio...

  8. Solvents and solvent effects in organic chemistry

    National Research Council Canada - National Science Library

    Reichardt, C; Welton, T

    2011-01-01

    .../guest complexation equilibria and reactions in biphasic solvent systems and neoteric solvents, respectively. More than 900 new references have been added, giving preference to review articles, and many older ones have been deleted. New references either replace older ones or are added to the end of the respective reference list of each chapter. Th...

  9. 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

  10. 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.

  11. Molecular Thermodynamic Modeling of Mixed Solvent Solubility

    DEFF Research Database (Denmark)

    Ellegaard, Martin Dela; Abildskov, Jens; O’Connell, John P.

    2010-01-01

    A method based on statistical mechanical fluctuation solution theory for composition derivatives of activity coefficients is employed for estimating dilute solubilities of 11 solid pharmaceutical solutes in nearly 70 mixed aqueous and nonaqueous solvent systems. The solvent mixtures range from...... nearly ideal to strongly nonideal. The database covers a temperature range from 293 to 323 K. Comparisons with available data and other existing solubility methods show that the method successfully describes a variety of observed mixed solvent solubility behaviors using solute−solvent parameters from...

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

    Directory of Open Access Journals (Sweden)

    Erna Roos

    2016-08-01

    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.

  13. 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 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.

  14. Relative risk of home hemodialysis attrition in patients using a telehealth platform.

    Science.gov (United States)

    Weinhandl, Eric D; Collins, Allan J

    2017-12-06

    Home hemodialysis (HHD) facilitates increased treatment frequency, which may improve patient outcomes. However, attrition due to technique failure limits the clinical effectiveness of the modality. Nx2me Connected Health is a telehealth platform that enables ongoing assessment of HHD patients using NxStage equipment, and that may reduce patient burden. We aimed to assess whether use of Nx2me was associated with risk of HHD attrition. We compared risks of all-cause attrition, dialysis cessation (i.e., death or transplant), and technique failure in Nx2me users and matched control patients, using a retrospective cohort study. We also compared the likelihood of HHD training graduation in patients who initiated use of Nx2me during training with the likelihood in matched control patients. Matching factors included date of HHD initiation, NxStage treatment duration at initiation of follow-up, and prescribed treatment frequency. We used stratified Fine-Gray and Cox regression to compare risks, with adjustment for demographic factors and vascular access modality, and stratification by matched cluster. We identified 606 Nx2me users; 49.5% initiated use of Nx2me in NxStage equipment. Adjusted hazard ratios (AHRs) of all-cause attrition, dialysis cessation, and technique failure were 0.80 (95% confidence interval, 0.68-0.95), 1.10 (0.86-1.41), and 0.71 (0.57-0.87), respectively, for Nx2me users vs. matched controls. AHRs were similar in patients who initiated use of Nx2me in <3 months after initiation of HHD. The AHR of HHD training graduation was 1.61 (1.10-2.36) in patients who initiated use of Nx2me within 2 weeks of training initiation vs. matched controls. Use of Nx2me was associated with lower risk of all-cause attrition, lower risk of technique failure, and higher likelihood of HHD training graduation. Further studies are needed to identify the mechanisms by which use of a telehealth platform may improve clinical outcomes and reduce patient burden. © 2017 The Authors

  15. Organic Solvent Tropical Report

    International Nuclear Information System (INIS)

    COWLEY, W.L.

    2000-01-01

    This report provides the basis for closing the organic solvent safety issue. Sufficient information is presented to conclude that risk posed by an unmitigated organic solvent fire is within risk evaluation guidelines

  16. Canyon solvent cleaning

    International Nuclear Information System (INIS)

    Reif, D.J.

    1986-01-01

    The HM Process at the Savannah River Plant (SRP) uses 7.5% tributylphosphate in n-paraffin as an extraction solvent. During use, the solvent is altered due to hydrolysis and radiolysis, forming materials that influence product losses, produce decontamination, and separation efficiencies. Laboratory studies to improve online solvent cleaning have shown the carbonate washing, although removing residual solvent activity does not remove binding ligands that hold fission products in the solvent. Treatment of solvent by an alumina adsorption process removes binding ligands and significantly improves recycle solvent performance. Both laboratory work defining a full-scale alumina adsorption process and the use of the process to clean HM Process first cycle solvent are presented

  17. Solvent wash solution

    International Nuclear Information System (INIS)

    Neace, J.C.

    1986-01-01

    This patent describes a process for removing diluent degradation products from a solvent extraction solution comprising an admixture of an organic extractant for uranium and plutonium and a non-polar organic liquid diluent, which has been used to recover uranium and plutonium from spent nuclear fuel. Comprising combining a wash solution consisting of: (a) water; and (b) a positive amount up to about, an including, 50 volume percent of at least one highly-polar water-miscible organic solvent, based on the total volume of the water and the highly-polar organic solvent, with the solvent extraction solution after uranium and plutonium values have been stripped from the solvent extraction solution, the diluent degradation products dissolving in the highly-polar organic solvent and the extractant and diluent of the extraction solution not dissolving in the highly-polar organic solvent, and separating the highly-polar organic solvent and the extraction solution to obtain a purified extraction solution

  18. Study of Attrition Documentation at the U.S. Navy Recruit Training Command

    National Research Council Canada - National Science Library

    Condon, Nancy K; Eckenrode, John E

    2006-01-01

    .... Navy's Recruit Training Command (RTC). A random sample of 754 "retained files" from Customer Service Desk RTC was examined for attrition documentation and the information obtained was compared with attrition documentation contained...

  19. 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

    ... the service, completed training segments, conducted duty assignments, and left the service. These models explored reasons for attrition and reenlistment intentions, and suggested management strategies that might be employed to reduce attrition...

  20. 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...

  1. Blood Telomere Length Attrition and Cancer Development in the Normative Aging Study Cohort

    Directory of Open Access Journals (Sweden)

    Lifang Hou

    2015-06-01

    Interpretation: Age-related BTL attrition was faster in cancer cases but their age-adjusted BTL attrition began decelerating as diagnosis approached. This may explain prior inconsistencies and help develop BTL as a cancer detection biomarker.

  2. 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…

  3. A Conceptual Framework for Evaluating Attrition in Online Courses

    Science.gov (United States)

    Laing, C. Linda; Laing, Gregory K.

    2015-01-01

    The purpose of this paper is to develop a conceptual framework that considers the role that the sense of isolation and alienation play in contributing to attrition in online courses in the higher education sector. The approach adopted in this paper is a theoretical study aimed at synthesizing existing theories. The ultimate contribution of this…

  4. Attrition, burnout, job dissatisfaction and occupational therapy managers.

    Science.gov (United States)

    Kraeger, M M; Walker, K F

    1992-01-01

    At a time when there is growing concern about the person-power shortages in occupational therapy, there is a need to address reasons why therapists leave the job market. Two job-related reasons for attrition are burnout and job dissatisfaction. The burnout phenomenon occurs as a result of personnel shortages, high-stress demands on therapists, the severity and complexity of client's problems, and the therapist's own ''worker personality.'' Bureaucratic constraints, limited advancement, issues related to a profession which is made up predominantly of women, lack of autonomy, and type of management and supervision are factors that contribute to job dissatisfaction. Occupational therapy managers can consider the causes of burnout and job dissatisfaction and initiate resources to retain therapists. Managers can increase the job benefits, such as flexible working hours, take steps to reduce stress in the workplace, offer career laddering opportunities, and promote staff development. By identifying the causes for attrition and by addressing those causes, the threat of losing therapists from the work force may be averted. Respondents (n = 106) to a survey of occupational therapy managers indicated that job dissatisfaction, burnout, and attrition of registered occupational therapists were not major problems in their settings. They reported a variety of strategies to reduce job dissatisfaction, burnout, and attrition. When these problems were present, managers cited bureaucratic red tape, lack of opportunity for advancement, and increasing role demands as contributing factors.

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

    African Journals Online (AJOL)

    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 corresponded to an extraction yield (E) of 44% was achieved using the huller section of a commercial rice milling machine, while 90% dehulling efficiency (e), ...

  6. 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…

  7. 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…

  8. Texas Public School Attrition Study, 2016-17. IDRA Report

    Science.gov (United States)

    Johnson, Roy L.; Montes, Felix

    2017-01-01

    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…

  9. Texas Public School Attrition Study, 2014-15. IDRA Report

    Science.gov (United States)

    Johnson, Roy L.; Montes, Felix

    2015-01-01

    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…

  10. Texas Public School Attrition Study, 2015-16. IDRA Report

    Science.gov (United States)

    Johnson, Roy L.; Montes, Felix; Hinojosa, David

    2016-01-01

    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…

  11. 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:…

  12. 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…

  13. The Career Officer Attrition Dilemma: An Underlying Cause

    Science.gov (United States)

    2002-04-09

    BOOMER, XER, & MILLENIAL TRAITS COMPARISON ..................................... 23 vii viii THE CAREER OFFICER ATTRITION DILEMMA: AN UNDERLYING...provide a sustainable solution. Multiple generations in the military will always be present. What will change, however, is which generation will be in the... MILLENIAL TRAITS COMPARISON cause serious frustration both for the senior leadership and their subordinates. Even as the Xers begin to take over from

  14. Personal, Situational, and Organizational Determinants of Navy Enlisted Attrition

    Science.gov (United States)

    1980-06-01

    of regular high school instruction. The GED test battery contains five testsz writing skills, social studies, science, reading skills, and mathematics ...expanded apprentice train- ing program for airmen and seamen might, ceteris paribus, bring the GENDET attrition rate closer to acceptable lvels . 13 ] KN

  15. Attrition of Tyee Formation Sandstone in a Natural Fluvial System

    Science.gov (United States)

    brandes, J. B.; Sanfilippo, J. D.; Lancaster, S. T.

    2013-12-01

    The data from this study will provide a rate of attrition with respect to change in volume, time and distance in a natural stream setting. Sandstone gravel attrition has been observed in previous studies with the use of rock tumblers, but measurements in natural systems are rare or absent. This study will use rocks with implanted passive integrated transponders (PIT) tags to track sediment movement. The study area is a natural mountain stream of approximately 4m width and 1m depth. This study is part of larger study of sediment transport. The rock volumes will be recorded prior to placement in an active channel using water displacement, the specific location along the channel will be recorded, and each tracer rock will be tracked using its individual radio frequency identification (RFID) number. Tracer rock deployment will occur before the annual high-water season. After one rainy season, the rocks will be located and removed from the stream using a radio frequency mobile radio frequency tracker. Their travel distances will be recorded and final volumes determined. Differences between initial and final volumes and travel distances will yield a distribution of attrition rates and, therefore, a mean gravel attrition rate.

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

    Science.gov (United States)

    Iyer, Swami; Killingback, Timothy

    2016-05-07

    In evolutionary game theory the War of Attrition game is intended to model animal contests which are decided by non-aggressive behavior, such as the length of time that a participant will persist in the contest. The classical War of Attrition game assumes that no errors are made in the implementation of an animal׳s strategy. However, it is inevitable in reality that such errors must sometimes occur. Here we introduce an extension of the classical War of Attrition game which includes the effect of errors in the implementation of an individual׳s strategy. This extension of the classical game has the important feature that the payoff is continuous, and as a consequence admits evolutionary behavior that is fundamentally different from that possible in the original game. We study the evolutionary dynamics of this new game in well-mixed populations both analytically using adaptive dynamics and through individual-based simulations, and show that there are a variety of possible outcomes, including simple monomorphic or dimorphic configurations which are evolutionarily stable and cannot occur in the classical War of Attrition game. In addition, we study the evolutionary dynamics of this extended game in a variety of spatially and socially structured populations, as represented by different complex network topologies, and show that similar outcomes can also occur in these situations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Influence of Solvent-Solvent and Solute-Solvent Interaction Properties on Solvent-Mediated Potential

    International Nuclear Information System (INIS)

    Zhou Shiqi

    2005-01-01

    A recently proposed universal calculational recipe for solvent-mediated potential is applied to calculate excess potential of mean force between two large Lennard-Jones (LJ) or hard core attractive Yukawa particles immersed in small LJ solvent bath at supercritical state. Comparison between the present prediction with a hypernetted chain approximation adopted for solute-solute correlation at infinitely dilute limit and existing simulation data shows high accuracy for the region with large separation, and qualitative reliability for the solute particle contact region. The calculational simplicity of the present recipe allows for a detailed investigation on the effect of the solute-solvent and solvent-solvent interaction details on the excess potential of mean force. The resultant conclusion is that gathering of solvent particles near a solute particle leads to repulsive excess PMF, while depletion of solvent particles away from the solute particle leads to attractive excess PMF, and minor change of the solvent-solvent interaction range has large influence on the excess PMF.

  18. “Bligh and Dyer” and Folch Methods for Solid–Liquid–Liquid Extraction of Lipids from Microorganisms. Comprehension of Solvatation Mechanisms and towards Substitution with Alternative Solvents

    Directory of Open Access Journals (Sweden)

    Cassandra Breil

    2017-03-01

    Full Text Available Bligh and Dyer (B & D or Folch procedures for the extraction and separation of lipids from microorganisms and biological tissues using chloroform/methanol/water have been used tens of thousands of times and are “gold standards” for the analysis of extracted lipids. Based on the Conductor-like Screening MOdel for realistic Solvatation (COSMO-RS, we select ethanol and ethyl acetate as being potentially suitable for the substitution of methanol and chloroform. We confirm this by performing solid–liquid extraction of yeast (Yarrowia lipolytica IFP29 and subsequent liquid–liquid partition—the two steps of routine extraction. For this purpose, we consider similar points in the ternary phase diagrams of water/methanol/chloroform and water/ethanol/ethyl acetate, both in the monophasic mixtures and in the liquid–liquid miscibility gap. Based on high performance thin-layer chromatography (HPTLC to obtain the distribution of lipids classes, and gas chromatography coupled with a flame ionisation detector (GC/FID to obtain fatty acid profiles, this greener solvents pair is found to be almost as effective as the classic methanol–chloroform couple in terms of efficiency and selectivity of lipids and non-lipid material. Moreover, using these bio-sourced solvents as an alternative system is shown to be as effective as the classical system in terms of the yield of lipids extracted from microorganism tissues, independently of their apparent hydrophilicity.

  19. Hazardous solvent substitution

    International Nuclear Information System (INIS)

    Twitchell, K.E.

    1995-01-01

    This article is an overview of efforts at INEL to reduce the generation of hazardous wastes through the elimination of hazardous solvents. To aid in their efforts, a number of databases have been developed and will become a part of an Integrated Solvent Substitution Data System. This latter data system will be accessible through Internet

  20. Study of the mechanical behavior of thermo reversible gels of PS-b-poly(ethylene/butylene)-b-PS triblock copolymers in a selective solvent for the middle block of the copolymer

    International Nuclear Information System (INIS)

    Hernaez, E.; Inchausti, I.; Quintana, J. R.; Katime, I.

    2001-01-01

    The thermo reversible gelation of three triblock copolymers polystyrene-b-poly(ethylene/butylene)-b-polystyrene, with different molar mass and a similar chemical composition, in n-octane was studied. The solvent is selective for the middle poly(ethylene/butylene) block of the copolymers. the influence of the molar mass of the three copolymers on the gelation and on the mechanical properties of the gels was analysed. The sol-gel transition temperatures. T g el have been determined and they increase with the copolymer concentration and the copolymer molar mass. On the other land, the mechanical properties of the different gels were examined through oscillatory shear and compressive stress relaxation measurements. The concentration dependence of the elastic storage modules, G' for the three copolymer studied fit a sole straight line in a double-logarithmic scale and its slope (2.22) is close to that expected for systems in good solvents (2.25). As the temperature is near to the sol-gel transition temperate, the elastic modulus are smaller and the relaxation rates are higher. (Author) 12 refs

  1. Kinetics and mechanism of aquation and formation reactions of carbonato complexes. XII. Deuterium solvent isotope effect on the rate of acid-catalyzed decarboxylation of the carbonatobis (ethylenediamine) cobalt(III) complex ion. A mechanistic reappraisal

    International Nuclear Information System (INIS)

    Harris, G.M.; Hyde, K.E.

    1978-01-01

    A recent study of the acid-catalyzed decarboxylation of the carbonatotetrakis(pyridine)cobalt(III) complex ion showed there to be rate acceleration in D 2 O solvent, consistent with a proton-preequilibration mechanism. This observation directly contradicts the results of a similar study made some years ago of the analogous ion, carbonatobis(ethylenediamine)cobalt(III), for which there appeared to be deceleration in D 2 O solvent. A reinvestigation of the latter reaction over a much wider acidity range has now shown the earlier work to be in error. The previously proposed generalized mechanism for aquation of chelated carbonato complex ions of the form CoN 4 CO 3 + (N 4 identical with various tetramine ligand groupings of uni-, bi-, or quadridentate type) has thus been revised to include a proton equilibration step. An unexpected complication arises in the interpretation of the data for the bis(ethylenediamine) complex ion in the acidity range 0.1 + ] + ] term, overtakes and exceeds the true first-order rate constant for CO 2 release. The interesting implications of this unusual first-order successive reaction system are fully explored in the context of the present study

  2. Stereochemistry of Complex Marine Natural Products by Quantum Mechanical Calculations of NMR Chemical Shifts: Solvent and Conformational Effects on Okadaic Acid

    Directory of Open Access Journals (Sweden)

    Humberto J. Domínguez

    2014-01-01

    Full Text Available Marine organisms are an increasingly important source of novel metabolites, some of which have already inspired or become new drugs. In addition, many of these molecules show a high degree of novelty from a structural and/or pharmacological point of view. Structure determination is generally achieved by the use of a variety of spectroscopic methods, among which NMR (nuclear magnetic resonance plays a major role and determination of the stereochemical relationships within every new molecule is generally the most challenging part in structural determination. In this communication, we have chosen okadaic acid as a model compound to perform a computational chemistry study to predict 1H and 13C NMR chemical shifts. The effect of two different solvents and conformation on the ability of DFT (density functional theory calculations to predict the correct stereoisomer has been studied.

  3. 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.

  4. How can attrition rates be reduced in cancer drug discovery?

    Science.gov (United States)

    Moreno, Lucas; Pearson, Andrew D J

    2013-04-01

    Attrition is a major issue in anticancer drug development with up to 95% of drugs tested in Phase I trials not reaching a marketing authorisation making the drug development process enormously costly and inefficient. It is essential that this problem is addressed throughout the whole drug development process to improve efficiency which will ultimately result in increased patient benefit with more profitable drugs. The approach to reduce cancer drug attrition rates must be based on three pillars. The first of these is that there is a need for new pre-clinical models which can act as better predictors of success in clinical trials. Furthermore, clinical trials driven by tumour biology with the incorporation of predictive and pharmacodynamic biomarkers would be beneficial in drug development. Finally, there is a need for increased collaboration to combine the unique strengths between industry, academia and regulators to ensure that the needs of all stakeholders are met.

  5. 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.

  6. 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.

  7. The Impact of Fund Attrition on Superannuation Returns

    OpenAIRE

    Drew, Michael E.; Stanford, Jon D.

    2001-01-01

    This paper investigates the impact of fund attrition on returns from a sample of superannuation fund managers (specialising in the management of domestic stock portfolios) for the period 1991 through 1999, using a four-factor asset pricing model. Survivorship bias is estimated at 23 basis points per annum. The evidence presented in this study is consistent with recent international evidence that suggests that a sampling technique that excludes terminated funds would result in an overestimatio...

  8. Lanchester's attrition models and fights among social animals

    OpenAIRE

    Eldridge S. Adams; Michael Mesterton-Gibbons

    2003-01-01

    Lanchester's models of attrition during warfare have served as the basis for several predictions about conflicts between groups of animals. These models and their extensions describe rates of mortality during battles as functions of the number and fighting abilities of individuals in each group, allowing analysis of the determinants of group strength and of the cumulative numbers of casualties. We propose modifications to Lanchester's models to improve their applicability to social animals. I...

  9. Germanic heritage languages in North America: Acquisition, attrition and change

    OpenAIRE

    Johannessen, Janne Bondi; Salmons, Joseph C.; Westergaard, Marit; Anderssen, Merete; Arnbjörnsdóttir, Birna; Allen, Brent; Pierce, Marc; Boas, Hans C.; Roesch, Karen; Brown, Joshua R.; Putnam, Michael; Åfarli, Tor A.; Newman, Zelda Kahan; Annear, Lucas; Speth, Kristin

    2015-01-01

    This book presents new empirical findings about Germanic heritage varieties spoken in North America: Dutch, German, Pennsylvania Dutch, Icelandic, Norwegian, Swedish, West Frisian and Yiddish, and varieties of English spoken both by heritage speakers and in communities after language shift. The volume focuses on three critical issues underlying the notion of ‘heritage language’: acquisition, attrition and change. The book offers theoretically-informed discussions of heritage language processe...

  10. Predictors of Attrition in the Finnish Conscript Service

    Science.gov (United States)

    2006-11-01

    Dawson et al., 1994; Kassel, Jackson, & Unrod, 2000; Lazarus & Folkman , 1984; Pierce & Lydon, 1998; Thompson & Gignac, 2001). These expectations toward...organizational socialization. USAWC Strategy Research Project Carlisle Barracks, PA: U.S. Army War College. Hicks, J. M., & Nogami, G. Y . (1984...of Navy attrition. II. A demonstration of potential usefulness for screening. (Report No. 01-06). Military Medicine, 167, 770-776. Lazarus , R. S

  11. Military Enlistment and Attrition. An Analysis of Decision Reversal

    Science.gov (United States)

    1987-06-01

    instability, defined as being unemployed at the time of enlistment or having had a spell of jobless- ness within the past 12 months. For graduates, attrition...opportunities. The level of education an individual obtains is related to the value of higher education to the individual (both monetary and psychic ...value, does suggest that unemployed graduates are more likely to enlist, all other things equal, the higher their previous wage rate. The previous

  12. Limestone particle attrition and size distribution in a small circulating fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Zhongxiang Chen; John R. Grace; C. Jim Lim [University of British Columbia, Vancouver, BC (Canada). Department of Chemical and Biological Engineering

    2008-06-15

    Limestone particle attrition was investigated in a small circulating fluidized bed reactor at temperatures from 25 to 850{sup o}C, 1 atm pressure and superficial gas velocities from 4.8 to 6.2 m/s. The effects of operating time, superficial gas velocity and temperature were studied with fresh limestone. No calcination or sulfation occurred at temperatures {le} 580{sup o}C, whereas calcination and sulfation affected attrition at 850{sup o}C. Increasing the temperature (while maintaining the same superficial gas velocity) reduced attrition if there was negligible calcination. Attrition was high initially, but after about 24 h, the rate of mass change became constant. The ratio of initial mean particle diameter to that at later times increased linearly with time and with (U{sub g} - U{sub mf}){sup 2}, while decreasing exponentially with temperature, with an activation energy for fresh limestone of -4.3 kJ/mol. The attrition followed Rittinger's surface theory. The change of surface area of limestone particles was proportional to the total excess kinetic energy consumed and to the total attrition time, whereas the change of surface area decreased exponentially with increasing temperature. At 850{sup o}C, the attrition rate of calcined lime was highest, whereas the attrition rate was lowest for sulfated particles. When online impact attrition was introduced, the attrition rate was about an order of magnitude higher than without impacts. 25 refs., 14 figs., 4 tabs.

  13. Determination of the attrition resistance of granular charcoals

    International Nuclear Information System (INIS)

    Dietz, V.R.

    1979-01-01

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

  14. 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%).

  15. Solvent - solute interaction

    International Nuclear Information System (INIS)

    Urbanczyk, A.; Kalinowski, M.K.

    1983-01-01

    The electronic absorption spectrum of vanadyl acetylacetonate has been studied in 15 organic solvents. It has been found that wavenumbers and molar absorptivities of the long-wavelength bands (d-d transitions) can be well described by a complementary Lewis acid-base model including Gutmann's donor number [Gutmann V., Wychera E., Inorg. Nucl. Chem. Letters 2, 257 (1966)] and acceptor number [Mayer U., Gutmann V., Gerger W., Monatsh. Chem. 106, 1235 (1975)] of a solvent. This model describes also the solvent effect of the hyperfine splitting constant, Asub(iso)( 51 V), from e.s.r. spectra of VOacac 2 . These observations are discussed in terms of the donor-acceptor concept for solvent-solute interactions. (Author)

  16. The nature and causes of attrition in the British Household Panel Study

    OpenAIRE

    Uhrig, S.C. Noah

    2008-01-01

    Panel attrition is a process producing data absent from panel records due to survey non-participation or other data unavailability. I examine the nature and causes of attrition resulting from non-contact and survey refusal in the British Household Panel Study. Focusing on non-response transitions amongst Wave 1 respondents using discrete time transition models, I locate attrition at first non-response over the first 14 waves. Physical impediments to contact, less time spent at home and high l...

  17. 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

  18. Initial Entry Training: Reducing First Term Attrition Through Effective Organizational Socialization

    National Research Council Canada - National Science Library

    Hayden, Thomas

    2000-01-01

    .... Behavioral scientist claim that attrition in organizations can be attributed to many factors such as lack of commitment to the organization, poor skill development, mismatch in employee expectations...

  19. Solvent/non-solvent sintering: a novel route to create porous microsphere scaffolds for tissue regeneration.

    Science.gov (United States)

    Brown, Justin L; Nair, Lakshmi S; Laurencin, Cato T

    2008-08-01

    Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter, and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from -8 to 41 degrees C and poly (lactide-co-glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1 mum, respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3 MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. (c) 2007 Wiley Periodicals, Inc.

  20. Production of fines during co-combustion of coal with biomass fuels by fragmentation and attrition

    Energy Technology Data Exchange (ETDEWEB)

    I. Gulyurtlu; D. Boavida; H. Lopes (and others) [DEECA-INETI, Lisbon (Portugal)

    2005-07-01

    Results are reported from a project funded by the RFCS Programme of the European Union. The aim is to investigate, experimentally and by modeling, the production of fine char and ash particles during co-combustion of coal with wastes and biofuels in circulating fluidized bed. Work was undertaken at installations of different scales. Polish and Colombian coals were base fuels. The additional fuels were two sewage sludges. Bed temperature, feeding system, sand particle size, devolatilisation behaviour and char burn-out were studied to verify their influence on the fine particle production. Modeling was also carried out to understand the mechanisms of fragmentation and attrition. Samples from bed and cyclone were collected to determine particle size distributions. 11 refs.

  1. Purex process solvent: literature review

    Energy Technology Data Exchange (ETDEWEB)

    Geier, R.G.

    1979-10-01

    This document summarizes the data on Purex process solvent presently published in a variety of sources. Extracts from these various sources are presented herein and contain the work done, the salient results obtained, and the original, unaltered conclusions of the author of each paper. Three major areas are addressed: solvent stability, solvent quality testing, and solvent treatment processes. 34 references, 44 tables.

  2. Purex process solvent: literature review

    International Nuclear Information System (INIS)

    Geier, R.G.

    1979-10-01

    This document summarizes the data on Purex process solvent presently published in a variety of sources. Extracts from these various sources are presented herein and contain the work done, the salient results obtained, and the original, unaltered conclusions of the author of each paper. Three major areas are addressed: solvent stability, solvent quality testing, and solvent treatment processes. 34 references, 44 tables

  3. Attrition of limestone by impact loading in fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Fabrizio Scala; Fabio Montagnaro; Piero Salatino [Consiglio Nazionale delle Ricerche, Napoli (Italy). Istituto di Ricerche sulla Combustione

    2007-09-15

    The present study addresses limestone attrition and fragmentation associated with impact loading, a process which may occur extensively in various regions of fluidized bed (FB) combustors/gasifiers, primarily the jetting region of the bottom bed, the exit region of the riser, and the cyclone. An experimental protocol for the characterization of the propensity of limestone to undergo attrition/fragmentation by impact loading is reported. The application of the protocol is demonstrated with reference to an Italian limestone whose primary fragmentation and attrition by surface wear have already been characterized in previous studies. The experimental procedure is based on the characterization of the amount and particle size distribution of the debris generated upon the impact of samples of sorbent particles against a target. Experiments were carried out at a range of particle impact velocities between 10 and 45 m/s, consistent with jet velocities corresponding to typical pressure drops across FB gas distributors. The protocol has been applied to either raw or preprocessed limestone samples. In particular, the effect of calcination, sulfation, and calcination/recarbonation cycles on the impact damage suffered by sorbent particles has been assessed. The measurement of particle voidage and pore size distribution by mercury intrusion was also accomplished to correlate fragmentation with the structural properties of the sorbent samples. Fragmentation by impact loading of the limestone is significant. Lime displays the largest propensity to undergo impact damage, followed by the sorbent sulfated to exhaustion, the recarbonated sorbent, and the raw limestone. Fragmentation of the raw limestone and of the sulfated lime follows a pattern typical of the failure of brittle materials. The fragmentation behavior of lime and recarbonated lime better conforms to a disintegration failure mode, with an extensive generation of very fine fragments. 27 refs., 9 figs. 1 tab.

  4. Early nurse attrition in New Zealand and associated policy implications.

    Science.gov (United States)

    Walker, L; Clendon, J

    2018-03-01

    To examine the factors contributing to nurses choosing to exit the nursing profession before retirement age. Population growth, ageing and growing demand for health services mean increased demand for nurses. Better retention could help meet this demand, yet little work has been done in New Zealand to understand early attrition. An online survey of registered and enrolled nurses and nurse practitioners who had left nursing was used. This study reports analysis of responses from 285 ex-nurses aged under 55. The primary reasons nurses left the profession were as follows: workplace concerns; personal challenges; career factors; family reasons; lack of confidence; leaving for overseas; unwillingness to complete educational requirements; poor work-life balance; and inability to find suitable nursing work. Most nurses discussed their intentions to leave with a family member or manager and most reported gaining transferrable skills through nursing. Nurses leave for many reasons. Implementing positive practice environments and individualized approaches to retaining staff may help reduce this attrition. Generational changes in the nature of work and careers mean that nurses may continue to leave the profession sooner than anticipated by policymakers. If the nursing workforce is to be able to meet projected need, education, recruitment and retention policies must urgently address issues leading to early attrition. In particular, policies improving the wider environmental context of nursing practice and ensuring that working environments are safe and nurses are well supported must be developed and implemented. Equally, national nursing workforce planning must take into account that nursing is no longer viewed as a career for life. © 2017 International Council of Nurses.

  5. (Spectro) Electrochemical investigation of reduction mechanism of a new energetic molecule 2,2-dinitroethene-1,1-diamine (FOX-7) in aprotic solvents

    Czech Academy of Sciences Publication Activity Database

    Šimková, Ludmila; Dmitrieva, E.; Klíma, Jiří; Dunsch, L.; Ludvík, Jiří

    2015-01-01

    Roč. 19, č. 1 (2015), s. 103-112 ISSN 1432-8488 R&D Projects: GA ČR GA13-21704S Institutional support: RVO:61388955 Keywords : FOX -7 * electrochemical reduction * Autoprotonation mechanism Subject RIV: CG - Electrochemistry Impact factor: 2.327, year: 2015

  6. Separation by solvent extraction

    International Nuclear Information System (INIS)

    Holt, C.H. Jr.

    1976-01-01

    In a process for separating fission product values from U and Pu values contained in an aqueous solution, an oxidizing agent is added to the solution to secure U and Pu in their hexavalent state. The aqueous solution is contacted with a substantially water-immiscible organic solvent with agitation while the temperature is maintained at from -1 to -2 0 C until the major part of the water present is frozen. The solid ice phase is continuously separated as it is formed and a remaining aqueous liquid phase containing fission product values and a solvent phase containing Pu and U values are separated from each other. The last obtained part of the ice phase is melted and added to the separated liquid phase. The resulting liquid is treated with a new supply of solvent whereby it is practically depleted of U and Pu

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

    International Nuclear Information System (INIS)

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

    1984-01-01

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

  8. The Surgical Personality: Does Surgery Resident Motivation Predict Attrition?

    Science.gov (United States)

    Symer, Matthew M; Abelson, Jonathan S; Yeo, Heather L; Sosa, Julie A; Rosenthal, M Zachary

    2018-05-01

    There is limited understanding of the wide variation in attrition rates among general surgery residencies. We used the validated Behavior Inhibitory System/Behavior Approach System (BIS/BAS) instrument to compare motivational traits among residents who did and not complete surgical training. All US general surgery categorical interns in the class of 2007-2008 were surveyed with a validated motivational trait assessment tool. American Board of Surgery records from 2008-2016 were used to determine who completed training. Motivation, an aspect of personality, was assessed with the BIS/BAS, which correlates with an individual's tendency to approach pleasant stimuli (BAS) or avoid negative stimuli (BIS). Subscale mean scores were compared with regard to the primary end point, attrition. Eight hundred and one (76.5%) interns completed the survey and had matching records. Six hundred and forty-five (80.5%) completed training. Men had lower scores than women in the BAS Drive subscale (12.0 vs 12.5; p scale (19.3 vs 20.9; p academic 17.3 vs community 17.6 vs military 16.6; p motivational personality traits. Copyright © 2018 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

  9. 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.

  10. From emigrant to expat : Changed perspectives on first language attrition in a digital era

    NARCIS (Netherlands)

    Keijzer, Merel

    2015-01-01

    L1 attrition is the (partial) language loss that is found in healthy individuals who stop routinely using their L1 after moving to an L2 environment. Over the years, the phenomenon has attracted much interest, from the general public who have (directly and indirectly) experienced attrition, but also

  11. Causes of Teacher Attrition of First, Second, and Third Year Teachers in Rural Middle Schools

    Science.gov (United States)

    Thompson, Arkeco Lashay Lewis

    2012-01-01

    Early attrition from teaching bears enormous costs. High attrition means that schools must take funds urgently needed for school improvements and spend them instead in a manner that produces little long-term payoff for student learning (Kain & Singleton, 1996). Keeping highly qualified teachers should always be at the top of the priority list…

  12. Understanding attrition from international Internet health interventions: a step towards global eHealth.

    Science.gov (United States)

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

    2013-09-01

    Worldwide automated Internet health interventions have the potential to greatly reduce health disparities. High attrition from automated Internet interventions is ubiquitous, and presents a challenge in the evaluation of their effectiveness. Our objective was to evaluate variables hypothesized to be related to attrition, by modeling predictors of attrition in a secondary data analysis of two cohorts of an international, dual language (English and Spanish) Internet smoking cessation intervention. The two cohorts were identical except for the approach to follow-up (FU): one cohort employed only fully automated FU (n = 16 430), while the other cohort also used 'live' contact conditional upon initial non-response (n = 1000). Attrition rates were 48.1 and 10.8% for the automated FU and live FU cohorts, respectively. Significant attrition predictors in the automated FU cohort included higher levels of nicotine dependency, lower education, lower quitting confidence and receiving more contact emails. Participants' younger age was the sole predictor of attrition in the live FU cohort. While research on large-scale deployment of Internet interventions is at an early stage, this study demonstrates that differences in attrition from trials on this scale are (i) systematic and predictable and (ii) can largely be eliminated by live FU efforts. In fully automated trials, targeting the predictors we identify may reduce attrition, a necessary precursor to effective behavioral Internet interventions that can be accessed globally.

  13. "Should I Stay or Should I Go?": Unpacking Teacher Attrition/Retention as an Educational Issue

    Science.gov (United States)

    Kelchtermans, Geert

    2017-01-01

    The paper starts from the observation that teacher attrition/retention seems to be a wicked issue: it seems to have strong face validity and a commonsense meaning, but the literature doesn't provide a clear and distinctive definition. In the first section, the author analyzes the different ways in which the issue of teacher attrition and retention…

  14. The Case for Increasing Workplace Decision-Making: Proposing a Model for Special Educator Attrition Research

    Science.gov (United States)

    Tyler, Teresa A.; Brunner, C. Cryss

    2014-01-01

    The chronically high rate of special educator attrition across U.S. schools creates a dilemma for educational leaders because special educators provide direct services to students with special needs. Attrition exacerbates already high special educator shortages reported in most districts, and nearly one million schoolchildren with disabilities…

  15. 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.

  16. Explicit treatment of active-site waters enhances quantum mechanical/implicit solvent scoring: Inhibition of CDK2 by new pyrazolo[1,5-a]pyrimidines

    Czech Academy of Sciences Publication Activity Database

    Hylsová, M.; Carbain, B.; Fanfrlík, Jindřich; Musilová, L.; Haldar, Susanta; Köprülüoglu, Cemal; Ajani, Haresh; Brahmkshatriya, Pathik; Jorda, Radek; Kryštof, Vladimír; Hobza, Pavel; Echalier, A.; Paruch, K.; Lepšík, Martin

    2017-01-01

    Roč. 126, Jan 27 (2017), s. 1118-1128 ISSN 0223-5234 R&D Projects: GA ČR(CZ) GA15-15264S; GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:61388963 ; RVO:61389030 Keywords : cyclin-dependent kinase 2 * ATP-competitive type I inhibitors * pyrazolo[1,5-a]pyrimidine * quantum mechanical scoring * protein-ligand binding * molecular dynamics Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 4.519, year: 2016

  17. Ions, solutes and solvents, oh my!

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Daniel David [Iowa State Univ., Ames, IA (United States)

    2009-08-01

    Modern methods in ab initio quantum mechanics have become efficient and accurate enough to study many gas-phase systems. However, chemists often work in the solution phase. The presence of solvent molecules has been shown to affect reaction mechanisms1, lower reaction energy barriers2, participate in energy transfer with the solute3 and change the physical properties of the solute4. These effects would be overlooked in simple gas phase calculations. Careful study of specific solvents and solutes must be done in order to fully understand the chemistry of the solution phase. Water is a key solvent in chemical and biological applications. The properties of an individual water molecule (a monomer) and the behavior of thousands of molecules (bulk solution) are well known for many solvents. Much is also understood about aqueous microsolvation (small clusters containing ten water molecules or fewer) and the solvation characteristics when bulk water is chosen to solvate a solute. However, much less is known about how these properties behave as the cluster size transitions from the microsolvated cluster size to the bulk. This thesis will focus on species solvated with water clusters that are large enough to exhibit the properties of the bulk but small enough to consist of fewer than one hundred solvent molecules. New methods to study such systems will also be presented.

  18. Organic solvent topical report

    Energy Technology Data Exchange (ETDEWEB)

    COWLEY, W.L.

    1999-05-13

    This report provides the basis for closing the organic solvent safety issue. Sufficient information is presented to conclude that risk posed by an organic solvent fire is within risk evaluation guidelines. This report updates information contained in Analysis of Consequences of Postulated Solvent Fires in Hanford Site Waste Tanks. WHC-SD-WM-CN-032. Rev. 0A (Cowley et al. 1996). However, this document will not replace Cowley et al (1996) as the primary reference for the Basis for Interim Operation (BIO) until the recently submitted BIO amendment (Hanson 1999) is approved by the US Department of Energy. This conclusion depends on the use of controls for preventing vehicle fuel fires and for limiting the use of flame cutting in areas where hot metal can fall on the waste surface.The required controls are given in the Tank Waste Remediation System Technical Safety Requirements (Noorani 1997b). This is a significant change from the conclusions presented in Revision 0 of this report. Revision 0 of this calcnote concluded that some organic solvent fire scenarios exceeded risk evaluation guidelines, even with controls imposed.

  19. Organic solvent topical report

    Energy Technology Data Exchange (ETDEWEB)

    Cowley, W.L.

    1998-04-30

    This report is the technical basis for the accident and consequence analyses used in the Hanford Tank Farms Basis for Interim Operation. The report also contains the scientific and engineering information and reference material needed to understand the organic solvent safety issue. This report includes comments received from the Chemical Reactions Subcommittee of the Tank Advisory Panel.

  20. Organic solvent topical report

    International Nuclear Information System (INIS)

    COWLEY, W.L.

    1999-01-01

    This report provides the basis for closing the organic solvent safety issue. Sufficient information is presented to conclude that risk posed by an organic solvent fire is within risk evaluation guidelines. This report updates information contained in Analysis of Consequences of Postulated Solvent Fires in Hanford Site Waste Tanks. WHC-SD-WM-CN-032. Rev. 0A (Cowley et al. 1996). However, this document will not replace Cowley et al (1996) as the primary reference for the Basis for Interim Operation (BIO) until the recently submitted BIO amendment (Hanson 1999) is approved by the US Department of Energy. This conclusion depends on the use of controls for preventing vehicle fuel fires and for limiting the use of flame cutting in areas where hot metal can fall on the waste surface.The required controls are given in the Tank Waste Remediation System Technical Safety Requirements (Noorani 1997b). This is a significant change from the conclusions presented in Revision 0 of this report. Revision 0 of this calcnote concluded that some organic solvent fire scenarios exceeded risk evaluation guidelines, even with controls imposed

  1. Organic solvent topical report

    International Nuclear Information System (INIS)

    Cowley, W.L.

    1998-01-01

    This report is the technical basis for the accident and consequence analyses used in the Hanford Tank Farms Basis for Interim Operation. The report also contains the scientific and engineering information and reference material needed to understand the organic solvent safety issue. This report includes comments received from the Chemical Reactions Subcommittee of the Tank Advisory Panel

  2. DESIGNING GREENER SOLVENTS

    Science.gov (United States)

    Computer-aided design of chemicals and chemical mixtures provides a powerful tool to help engineers identify cleaner process designs and more-benign alternatives to toxic industrial solvents. Three software programs are discussed: (1) PARIS II (Program for Assisting the Replaceme...

  3. Enzymatic synthesis of farnesyl laurate in organic solvent: initial water activity, kinetics mechanism, optimization of continuous operation using packed bed reactor and mass transfer studies.

    Science.gov (United States)

    Rahman, N K; Kamaruddin, A H; Uzir, M H

    2011-08-01

    The influence of water activity and water content was investigated with farnesyl laurate synthesis catalyzed by Lipozyme RM IM. Lipozyme RM IM activity depended strongly on initial water activity value. The best results were achieved for a reaction medium with an initial water activity of 0.11 since it gives the best conversion value of 96.80%. The rate constants obtained in the kinetics study using Ping-Pong-Bi-Bi and Ordered-Bi-Bi mechanisms with dead-end complex inhibition of lauric acid were compared. The corresponding parameters were found to obey the Ordered-Bi-Bi mechanism with dead-end complex inhibition of lauric acid. Kinetic parameters were calculated based on this model as follows: V (max) = 5.80 mmol l(-1) min(-1) g enzyme(-1), K (m,A) = 0.70 mmol l(-1) g enzyme(-1), K (m,B) = 115.48 mmol l(-1) g enzyme(-1), K (i) = 11.25 mmol l(-1) g enzyme(-1). The optimum conditions for the esterification of farnesol with lauric acid in a continuous packed bed reactor were found as the following: 18.18 cm packed bed height and 0.9 ml/min substrate flow rate. The optimum molar conversion of lauric acid to farnesyl laurate was 98.07 ± 0.82%. The effect of mass transfer in the packed bed reactor has also been studied using two models for cases of reaction limited and mass transfer limited. A very good agreement between the mass transfer limited model and the experimental data obtained indicating that the esterification in a packed bed reactor was mass transfer limited.

  4. Quantification of simultaneous solvent evaporation and chemical curing in thermoset coatings

    DEFF Research Database (Denmark)

    Kiil, Søren

    2010-01-01

    The mechanisms of simultaneous solvent evaporation and film formation in high-solids thermoset coatings are considered. The relevant phenomena, chemical reactions, solvent diffusion and evaporation, gelation, vitrification, network mobility restrictions, and crosslinking, are quantified and a mat...

  5. Theoretical and experimental study of mixed solvent electrolytes

    International Nuclear Information System (INIS)

    Cummings, P.T.; O'Connell, J.P.

    1990-01-01

    In the original proposal to study mixed solvent electrolyte solutions, four major goals were formulated: fundamental modeling of mixed solvent electrolytes using numerically solved integral equation approximation theories; evaluation of intermolecular pair potential models by computer simulation of selected systems for comparison with experiment and the numerical integral equation studies; development of fundamentally based correlations for the thermodynamic properties of mixed solvent electrolyte solutions using analytically solvable statistical mechanical models; and extension of experimental database on mixed solvent electrolytes by performing vapor-liquid equilibrium measurements on selected systems. This paper discusses the progress on these goals

  6. The influence of granulating solvents on drug release from tablets ...

    African Journals Online (AJOL)

    ... significantly lower than the other wet granulated tablets, but higher than the matrix tablets. The granulating solvent influenced the release of drug which increased with increase in the water content. Key Words: Grewia gum: Granulating solvents; Release mechanisms. Journal of Pharmacy and Bioresources Vol.1(1) 2004: ...

  7. Effects of solvent and structure on the reactivity of 6-substituted nicotinic acids with diazodiphenylmethane in aprotic solvents

    Directory of Open Access Journals (Sweden)

    BRATISLAV Ž. JOVANOVIĆ

    2009-12-01

    Full Text Available The rate constants for the reactions of diazodiphenylmethane (DDM with 6-substituted nicotinic acids in aprotic solvents at 30 °C were determined. The obtained second order rate constants in aprotic solvents, together with literature data for benzoic and nicotinic acids in protic solvents, were used for the calculation of solvent effects, employing the Kamlet-Taft solvatochromic equation (linear solvation energy relationship – LSER in the form: log k = log k0 + s* + a + b. The correlations of the kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The sign of the equation coefficients (s, a and b were in agreement with the postulated reaction mechanism, and the mode of the solvent influences on the reaction rate is discussed based on the correlation results. A similar contribution of the non-specific solvent effect and electrophilic solvation was observed for all acids, while the highest contribution of nucleophilic solvation was influenced by their high acidity. Correlation analysis of the rate data with substituent p parameters in an appropriate solvent using the Hammett equation was also performed. The substituent effect on the acid reactivity was higher in aprotic solvents of higher dipolarity/polarizability. The mode of the transmission of the substituent effect is discussed in light of the contribution of solute–solvent interaction on the acid reactivity.

  8. Attrition from surgical residency training: perspectives from those who left.

    Science.gov (United States)

    Bongiovanni, Tasce; Yeo, Heather; Sosa, Julie A; Yoo, Peter S; Long, Theodore; Rosenthal, Marjorie; Berg, David; Curry, Leslie; Nunez-Smith, Marcella

    2015-10-01

    High rates of attrition from general surgery residency may threaten the surgical workforce. We sought to gain further insight regarding resident motivations for leaving general surgery residency. We conducted in-depth interviews to generate rich narrative data that explored individual experiences. An interdisciplinary team used the constant comparative method to analyze the data. Four themes characterized experiences of our 19 interviewees who left their residency program. Participants (1) felt an informal contract was breached when clinical duties were prioritized over education, (2) characterized a culture in which there was no safe space to share personal and programmatic concerns, (3) expressed a scarcity of role models who demonstrated better work-life balance, and (4) reported negative interactions with authority resulting in a profound loss of commitment. As general surgery graduate education continues to evolve, our findings may inform interventions and policies regarding programmatic changes to boost retention in surgical residency. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Solvent selection methodology for pharmaceutical processes: Solvent swap

    DEFF Research Database (Denmark)

    Papadakis, Emmanouil; Kumar Tula, Anjan; Gani, Rafiqul

    2016-01-01

    A method for the selection of appropriate solvents for the solvent swap task in pharmaceutical processes has been developed. This solvent swap method is based on the solvent selection method of Gani et al. (2006) and considers additional selection criteria such as boiling point difference...... in pharmaceutical processes as well as new solvent swap alternatives. The method takes into account process considerations such as batch distillation and crystallization to achieve the swap task. Rigorous model based simulations of the swap operation are performed to evaluate and compare the performance...

  10. Improvements in solvent extraction columns

    International Nuclear Information System (INIS)

    Aughwane, K.R.

    1987-01-01

    Solvent extraction columns are used in the reprocessing of irradiated nuclear fuel. For an effective reprocessing operation a solvent extraction column is required which is capable of distributing the feed over most of the column. The patent describes improvements in solvent extractions columns which allows the feed to be distributed over an increased length of column than was previously possible. (U.K.)

  11. 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

  12. Solvent extraction columns

    International Nuclear Information System (INIS)

    Middleton, P.; Smith, J.R.

    1979-01-01

    In pulsed columns for use in solvent extraction processes, e.g. the reprocessing of nuclear fuel, the horizontal perforated plates inside the column are separated by interplate spacers manufactured from metallic neutron absorbing material. The spacer may be in the form of a spiral or concentric circles separated by radial limbs, or may be of egg-box construction. Suitable neutron absorbing materials include stainless steel containing boron or gadolinium, hafnium metal or alloys of hafnium. (UK)

  13. 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.

  14. Hazardous solvent substitution

    International Nuclear Information System (INIS)

    Twitchell, K.E.

    1995-01-01

    Eliminating hazardous solvents is good for the environment, worker safety, and the bottom line. However, even though we are motivated to find replacements, the big question is 'What can we use as replacements for hazardous solvents?'You, too, can find replacements for your hazardous solvents. All you have to do is search for them. Search through the vendor literature of hundreds of companies with thousands of products. Ponder the associated material safety data sheets, assuming of course that you can obtain them and, having obtained them, that you can read them. You will want to search the trade magazines and other sources for product reviews. You will want to talk to users about how well the product actually works. You may also want to check US Environmental Protection Agency (EPA) and other government reports for toxicity and other safety information. And, of course, you will want to compare the product's constituent chemicals with the many hazardous constituency lists to ensure the safe and legal use of the product in your workplace

  15. SOLVENT FIRE BY-PRODUCTS

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D; Samuel Fink, S

    2006-05-22

    Southwest Research Institute (SwRI) conducted a burn test of the Caustic-Side Solvent Extraction (CSSX) solvent to determine the combustion products. The testing showed hydrogen fluoride gas is not a combustion product from a solvent fire when up to 70% of the solvent is consumed. The absence of HF in the combustion gases may reflect concentration of the modifier containing the fluoride groups in the unburned portion. SwRI reported results for other gases (CO, HCN, NOx, formaldehyde, and hydrocarbons). The results, with other supporting information, can be used for evaluating the consequences of a facility fire involving the CSSX solvent inventory.

  16. Health worker attrition at a rural district hospital in Rwanda: a need ...

    African Journals Online (AJOL)

    Health worker attrition at a rural district hospital in Rwanda: a need for improved placement and retention strategies. Jackline Odhiambo, Felix Cyamatare Rwabukwisi, Christian Rusangwa, Vincent Rusanganwa, Lisa Ruth Hirschhorn, Evrard Nahimana, Patient Ngamije, Bethany Lynn Hedt-Gauthier ...

  17. Initial Entry Training: Reducing First Term Attrition Through Effective Organizational Socialization

    National Research Council Canada - National Science Library

    Hayden, Thomas

    2000-01-01

    This paper examines Initial Entry Training (IET) from an organizational behavior perspective to identify if the Army's socialization experience can be enhanced to have a positive impact on first term attrition within the Army...

  18. The relationship between beginning teachers' stress causes, stress responses, teaching behaviour and attrition

    NARCIS (Netherlands)

    Harmsen, Ruth; Lorenz, Michelle; Maulana, Ridwan; van Veen, Klaas

    2018-01-01

    In this study, the relationships between beginning teachers’ perceived stress causes, stress responses, observed teaching behaviour and attrition is investigated employing structural equation modelling (SEM). A total of 143 BTs were surveyed using the Questionnaire on the Experience and Evaluation

  19. 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...... 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...... to findings of temporal stability in overall risk aversion. However, that stability is around different levels of risk aversion than one might naively infer without the controls for sample selection and attrition we are able to implement. This evidence of “randomization bias” from sample selection...

  20. 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...

  1. 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...

  2. Research on mechanism of and catalysts for extraction liquefaction of coal using coal-based solvents; Sekitankei yozai ni yoru sekitan no chushutsu ekika kiko to shokubai no kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1981-07-01

    Papers of Professor Yoshio Kamiya of Tokyo University are compiled into this report. The list of the papers includes (1) Synthesis of heavy fuel oils from coal; (2) Research and development of coal liquefaction; (3) Dissolution reaction of coal by hydrogen-donating aromatic solvents (I); (4) Effect of hydrogen-donor solvent on the liquefaction of coal; (5) Recent studies on the chemical structure of solvent refined coal; (6) Dissolution reaction of coal by hydrogen-donating aromatic solvents (II); (7) Future of coal as energy material; (8), (9), (10) same as (6) in the subject discussed; (11) Recent studies on coal liquefaction catalysts; (12) Environmental problems and drain treatment to accompany processes of converting fossil resources into fuels; (13) Chemistry of coal oxidation; (14) Fractionation and analysis of solvent refined coal by gel permeation chromatography; (15) Current state of research and development of coal liquefaction; (16) Properties and components of coal oils from coal liquefaction processes under development; (17) Solvent effect of coal derived aromatic compounds on the liquefaction of Akabira coal; (18) Chemistry of coal liquefaction; (19) Research and development of coal liquefaction in the U.S.; (20) Thermal treatment of coal-related aromatic ethers in tetralin solution; (21) Recent technology of utilizing heavy carbon resources; (22) Chemical properties and reactivity of coal; (23) Current state and future of development of coal liquefaction processes; and (24) Development of overseas coal liquefaction projects. (NEDO)

  3. A Qualitative Evaluation of Engagement and Attrition in a Nurse Home Visiting Program: From the Participant and Provider Perspective.

    Science.gov (United States)

    Beasley, Lana O; Ridings, Leigh E; Smith, Tyler J; Shields, Jennifer D; Silovsky, Jane F; Beasley, William; Bard, David

    2018-05-01

    Beginning parenting programs in the prenatal and early postnatal periods have a large potential for impact on later child and maternal outcomes. Home-based parenting programs, such as the Nurse Family Partnership (NFP), have been established to help address this need. Program reach and impact is dependent on successful engagement of expecting mothers with significant risks; however, NFP attrition rates remain high. The current study qualitatively examined engagement and attrition from the perspectives of NFP nurses and mothers in order to identify mechanisms that enhance service engagement. Semi-structured interviews were conducted in focus groups composed of either engaged (27 total mothers) or unengaged (15 total mothers) mothers from the NFP program. NFP nurses (25 total nurses) were recruited for individual semi-structured interviews. Results suggest that understanding engagement in the NFP program requires addressing both initial and sustained engagement. Themes associated with enhanced initial engagement include nurse characteristics (e.g., flexible, supportive, caring) and establishment of a solid nurse-family relationship founded on these characteristics. Factors impacting sustained engagement include nurse characteristics, provision of educational materials on child development, individualized services for families, and available family support. Identified barriers to completing services include competing demands and lack of support. Findings of this study have direct relevance for workforce planning, including hiring and training through integrating results regarding effective nurse characteristics. Additional program supports to enhance parent engagement may be implemented across home-based parenting programs in light of the current study's findings.

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

    International Nuclear Information System (INIS)

    Nawaz, Z.; Ziaoping, T.; Shu, Q.; Wei, F.; Naveed, S.

    2010-01-01

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

  5. Solvent effects in the synergistic solvent extraction of Co2+

    International Nuclear Information System (INIS)

    Kandil, A.T.; Ramadan, A.

    1979-01-01

    The extraction of Co 2+ from a 0.1M ionic strength aqueous phase (Na + , CH 3 COOH) of pH = 5.1 was studied using thenoyltrifluoroacetone, HTTA, in eight different solvents and HTTA + trioctylphosphine oxide, TOPO, in the same solvents. A comparison of the effect of solvent dielectric constant on the equilibrium constant shows a synergism as a result of the increased hydrophobic character imparted to the metal complex due to the formation of the TOPO adduct. (author)

  6. Attrition and success rates of accelerated students in nursing courses: a systematic review

    OpenAIRE

    Doggrell, Sheila Anne; Schaffer, Sally

    2016-01-01

    Background There is a comprehensive literature on the academic outcomes (attrition and success) of students in traditional/baccalaureate nursing programs, but much less is known about the academic outcomes of students in accelerated nursing programs. The aim of this systematic review is to report on the attrition and success rates (either internal examination or NCLEX-RN) of accelerated students, compared to traditional students. Methods For the systematic review, the databases (Pubmed, Cinah...

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

    Science.gov (United States)

    2002-06-01

    Provost as more likely to attrite were ISTP, ESTP, ISFP, and ENFJ . “These students tend to be less organized, more passive in their relationship to...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...reason to believe that all who are admitted have the potential to graduate. B. PURPOSE OF STUDY This thesis examines the relationship

  8. The impact of attrition on the representativeness of cohort studies of older people

    Directory of Open Access Journals (Sweden)

    Brilleman Samuel L

    2010-08-01

    Full Text Available Abstract Background There are well-established risk factors, such as lower education, for attrition of study participants. Consequently, the representativeness of the cohort in a longitudinal study may deteriorate over time. Death is a common form of attrition in cohort studies of older people. The aim of this paper is to examine the effects of death and other forms of attrition on risk factor prevalence in the study cohort and the target population over time. Methods Differential associations between a risk factor and death and non-death attrition are considered under various hypothetical conditions. Empirical data from the Australian Longitudinal Study on Women's Health (ALSWH for participants born in 1921-26 are used to identify associations which occur in practice, and national cross-sectional data from Australian Censuses and National Health Surveys are used to illustrate the evolution of bias over approximately ten years. Results The hypothetical situations illustrate how death and other attrition can theoretically affect changes in bias over time. Between 1996 and 2008, 28.4% of ALSWH participants died, 16.5% withdrew and 10.4% were lost to follow up. There were differential associations with various risk factors, for example, non-English speaking country of birth was associated with non-death attrition but not death whereas being underweight (body mass index Conclusions Deaths occur in both the target population and study cohort, while other forms of attrition occur only in the study cohort. Therefore non-death attrition may cause greater bias than death in longitudinal studies. However although more than a quarter of the oldest participants in the ALSWH died in the 12 years following recruitment, differences from the national population changed only slightly.

  9. Solvent extraction of zirconium

    International Nuclear Information System (INIS)

    Kim, S.S.; Yoon, J.H.

    1981-01-01

    The extraction of zirconium(VI) from an aqueous solution of constant ionic strength with versatic acid-10 dissolved in benzen was studied as a function of pH and the concentration of zirconium(VI) and organic acid. The effects of sulphate and chlorine ions on the extraction of the zirconium(VI) were briefly examined. It was revealed that (ZrOR 2 .2RH) is the predominant species of extracted zirconium(VI) in the versatic acid-10. The chemical equation and the apparent equilibrium constants thereof have been determined as follows. (ZrOsup(2+))aq+ 2(R 2 H 2 )sub(org) = (ZrOR 2 .2RH)sub(org)+2(H + )aq Ksub(Zr) = (ZrOR 2 .2RH)sub(org)(H + ) 2 /(ZrOsup(2+))sub(aq)(R 2 H 2 )sup(2)sub(org) = 3.3 x 10 -7 . The synergistic effects of TBP and D2EHPA were also studied. In the mixed solvent with 0.1M TBP, the synergistic effect was observed, while the mixed solvent with D2EHPA showed the antisynergistic effect. (Author)

  10. Flotability Improvement of Ilmenite Using Attrition-Scrubbing as a Pretreatment Method

    Directory of Open Access Journals (Sweden)

    Jihua Zhai

    2017-01-01

    Full Text Available Flotation technology of the recovery and utilization of ilmenite from tailings of iron beneficiated in Panzhihua was investigated based on mineralogical study. The results of mineralogical study show that the main occurrence of the valuable mineral are liberated grains of ilmenite. Experimental results of flotation conditions show that attrition-scrubbing raw ores exhibit good flotability with higher recoveries and a slight decrease in grade compared to ores without attrition-scrubbing. Further, open-circuit experiments also prove the superiority of attrition-scrubbing raw ores. The results of closed-circuit experiments show that qualified ilmenite concentrate can be obtained and the yield, grade, and recovery are 22.26%, 47.06%, and 60.73%, respectively. Theoretical study and analysis show that there are two contributions to superior flotability for attrition-scrubbing samples. The first is that the attrition-scrubbing samples can uncover more ferrous ions on the newly-produced fresh ilmenite surface, resulting in the increase in active sites. The other is that in the process of attrition-scrubbing, the transformation of ferrous ions to ferric ions can be promoted.

  11. Selective attrition and intraindividual variability in response time moderate cognitive change.

    Science.gov (United States)

    Yao, Christie; Stawski, Robert S; Hultsch, David F; MacDonald, Stuart W S

    2016-01-01

    Selection of a developmental time metric is useful for understanding causal processes that underlie aging-related cognitive change and for the identification of potential moderators of cognitive decline. Building on research suggesting that time to attrition is a metric sensitive to non-normative influences of aging (e.g., subclinical health conditions), we examined reason for attrition and intraindividual variability (IIV) in reaction time as predictors of cognitive performance. Three hundred and four community dwelling older adults (64-92 years) completed annual assessments in a longitudinal study. IIV was calculated from baseline performance on reaction time tasks. Multilevel models were fit to examine patterns and predictors of cognitive change. We show that time to attrition was associated with cognitive decline. Greater IIV was associated with declines on executive functioning and episodic memory measures. Attrition due to personal health reasons was also associated with decreased executive functioning compared to that of individuals who remained in the study. These findings suggest that time to attrition is a useful metric for representing cognitive change, and reason for attrition and IIV are predictive of non-normative influences that may underlie instances of cognitive loss in older adults.

  12. 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.

  13. 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.

  14. Tone Attrition in Mandarin Speakers of Varying English Proficiency

    Science.gov (United States)

    Creel, Sarah C.

    2017-01-01

    Purpose The purpose of this study was to determine whether the degree of dominance of Mandarin–English bilinguals' languages affects phonetic processing of tone content in their native language, Mandarin. Method We tested 72 Mandarin–English bilingual college students with a range of language-dominance profiles in the 2 languages and ages of acquisition of English. Participants viewed 2 photographs at a time while hearing a familiar Mandarin word referring to 1 photograph. The names of the 2 photographs diverged in tone, vowels, or both. Word recognition was evaluated using clicking accuracy, reaction times, and an online recognition measure (gaze) and was compared in the 3 conditions. Results Relative proficiency in English was correlated with reduced word recognition success in tone-disambiguated trials, but not in vowel-disambiguated trials, across all 3 dependent measures. This selective attrition for tone content emerged even though all bilinguals had learned Mandarin from birth. Lengthy experience with English thus weakened tone use. Conclusions This finding has implications for the question of the extent to which bilinguals' 2 phonetic systems interact. It suggests that bilinguals may not process pitch information language-specifically and that processing strategies from the dominant language may affect phonetic processing in the nondominant language—even when the latter was learned natively. PMID:28124064

  15. Attrition and success rates of accelerated students in nursing courses: a systematic review.

    Science.gov (United States)

    Doggrell, Sheila Anne; Schaffer, Sally

    2016-01-01

    There is a comprehensive literature on the academic outcomes (attrition and success) of students in traditional/baccalaureate nursing programs, but much less is known about the academic outcomes of students in accelerated nursing programs. The aim of this systematic review is to report on the attrition and success rates (either internal examination or NCLEX-RN) of accelerated students, compared to traditional students. For the systematic review, the databases (Pubmed, Cinahl and PsychINFO) and Google Scholar were searched using the search terms 'accelerated' or 'accreditation for prior learning', 'fast-track' or 'top up' and 'nursing' with 'attrition' or 'retention' or 'withdrawal' or 'success' from 1994 to January 2016. All relevant articles were included, regardless of quality. The findings of 19 studies of attrition rates and/or success rates for accelerated students are reported. For international accelerated students, there were only three studies, which are heterogeneous, and have major limitations. One of three studies has lower attrition rates, and one has shown higher success rates, than traditional students. In contrast, another study has shown high attrition and low success for international accelerated students. For graduate accelerated students, most of the studies are high quality, and showed that they have rates similar or better than traditional students. Thus, five of six studies have shown similar or lower attrition rates. Four of these studies with graduate accelerated students and an additional seven studies of success rates only, have shown similar or better success rates, than traditional students. There are only three studies of non-university graduate accelerated students, and these had weaknesses, but were consistent in reporting higher attrition rates than traditional students. The paucity and weakness of information available makes it unclear as to the attrition and/or success of international accelerated students in nursing programs. The

  16. A validation of the fibre orientation and fibre length attrition prediction for long fibre-reinforced thermoplastics

    Science.gov (United States)

    Hopmann, Ch.; Weber, M.; van Haag, J.; Schöngart, M.

    2015-05-01

    To improve the mechanical performance of polymeric parts, fibre reinforcement has established in industrial applications during the last decades. Next to the widely used Short Fibre-reinforced Thermoplastics (SFT) the use of Long Fibre-reinforced Thermoplastics (LFT) is increasingly growing. Especially for non-polar polymeric matrices like polypropylene (PP), longer fibres can significantly improve the mechanical performance. As with every kind of discontinuous fibre reinforcement the fibre orientations (FO) show a high impact on the mechanical properties. On the contrary to SFT where the local fibre length distribution (FLD) can be often neglected, for LFT the FLD show a high impact on the material's properties and has to be taken into account in equal measure to the FOD. Recently numerical models are available in commercial filling simulation software and allow predicting both the local FOD and FLD in LFT parts. The aim of this paper is to compare i.) the FOD results and ii) the FLD results from available orientation- and fibre length attrition-models to those obtained from experimental data. The investigations are conducted by the use of different injection moulded specimens made from long glass fibre reinforced PP. In order to determine the FOD, selected part sections are examined by means of Computed Tomographic (CT) analyses. The fully three dimensional measurement of the FOD is then performed by digital image processing using grey scale correlation. The FLD results are also obtained by using digital image processing after a thermal pyrolytic separation of the polymeric matrix from the fibres. Further the FOD and the FLD are predicted by using a reduced strain closure (RSC) as well as an anisotropic rotary diffusion - reduced strain closure model (ARD-RSC) and Phelps-Tucker fibre length attrition model implemented in the commercial filling software Moldflow, Autodesk Inc., San Rafael, CA, USA.

  17. A validation of the fibre orientation and fibre length attrition prediction for long fibre-reinforced thermoplastics

    International Nuclear Information System (INIS)

    Hopmann, Ch.; Weber, M.; Haag, J. van; Schöngart, M.

    2015-01-01

    To improve the mechanical performance of polymeric parts, fibre reinforcement has established in industrial applications during the last decades. Next to the widely used Short Fibre-reinforced Thermoplastics (SFT) the use of Long Fibre-reinforced Thermoplastics (LFT) is increasingly growing. Especially for non-polar polymeric matrices like polypropylene (PP), longer fibres can significantly improve the mechanical performance. As with every kind of discontinuous fibre reinforcement the fibre orientations (FO) show a high impact on the mechanical properties. On the contrary to SFT where the local fibre length distribution (FLD) can be often neglected, for LFT the FLD show a high impact on the material’s properties and has to be taken into account in equal measure to the FOD. Recently numerical models are available in commercial filling simulation software and allow predicting both the local FOD and FLD in LFT parts. The aim of this paper is to compare i.) the FOD results and ii) the FLD results from available orientation- and fibre length attrition-models to those obtained from experimental data. The investigations are conducted by the use of different injection moulded specimens made from long glass fibre reinforced PP. In order to determine the FOD, selected part sections are examined by means of Computed Tomographic (CT) analyses. The fully three dimensional measurement of the FOD is then performed by digital image processing using grey scale correlation. The FLD results are also obtained by using digital image processing after a thermal pyrolytic separation of the polymeric matrix from the fibres. Further the FOD and the FLD are predicted by using a reduced strain closure (RSC) as well as an anisotropic rotary diffusion - reduced strain closure model (ARD-RSC) and Phelps-Tucker fibre length attrition model implemented in the commercial filling software Moldflow, Autodesk Inc., San Rafael, CA, USA

  18. A validation of the fibre orientation and fibre length attrition prediction for long fibre-reinforced thermoplastics

    Energy Technology Data Exchange (ETDEWEB)

    Hopmann, Ch.; Weber, M.; Haag, J. van; Schöngart, M. [Institute of Plastics Processing (IKV) at RWTH Aachen University, Pontstr. 49, 52062 Aachen (Germany)

    2015-05-22

    To improve the mechanical performance of polymeric parts, fibre reinforcement has established in industrial applications during the last decades. Next to the widely used Short Fibre-reinforced Thermoplastics (SFT) the use of Long Fibre-reinforced Thermoplastics (LFT) is increasingly growing. Especially for non-polar polymeric matrices like polypropylene (PP), longer fibres can significantly improve the mechanical performance. As with every kind of discontinuous fibre reinforcement the fibre orientations (FO) show a high impact on the mechanical properties. On the contrary to SFT where the local fibre length distribution (FLD) can be often neglected, for LFT the FLD show a high impact on the material’s properties and has to be taken into account in equal measure to the FOD. Recently numerical models are available in commercial filling simulation software and allow predicting both the local FOD and FLD in LFT parts. The aim of this paper is to compare i.) the FOD results and ii) the FLD results from available orientation- and fibre length attrition-models to those obtained from experimental data. The investigations are conducted by the use of different injection moulded specimens made from long glass fibre reinforced PP. In order to determine the FOD, selected part sections are examined by means of Computed Tomographic (CT) analyses. The fully three dimensional measurement of the FOD is then performed by digital image processing using grey scale correlation. The FLD results are also obtained by using digital image processing after a thermal pyrolytic separation of the polymeric matrix from the fibres. Further the FOD and the FLD are predicted by using a reduced strain closure (RSC) as well as an anisotropic rotary diffusion - reduced strain closure model (ARD-RSC) and Phelps-Tucker fibre length attrition model implemented in the commercial filling software Moldflow, Autodesk Inc., San Rafael, CA, USA.

  19. Selective solvent extraction of oils

    Energy Technology Data Exchange (ETDEWEB)

    1938-04-09

    In the selective solvent extraction of naphthenic base oils, the solvent used consists of the extract obtained by treating a paraffinic base oil with a selective solvent. The extract, or partially spent solvent is less selective than the solvent itself. Selective solvents specified for the extraction of the paraffinic base oil are phenol, sulphur dioxide, cresylic acid, nitrobenzene, B:B/sup 1/-dichlorethyl ether, furfural, nitroaniline and benzaldehyde. Oils treated are Coastal lubricating oils, or naphthenic oils from the cracking, or destructive hydrogenation of coal, tar, lignite, peat, shale, bitumen, or petroleum. The extraction may be effected by a batch or counter-current method, and in the presence of (1) liquefied propane, or butane, or naphtha, or (2) agents which modify the solvent power such as, water, ammonia, acetonitrile, glycerine, glycol, caustic soda or potash. Treatment (2) may form a post-treatment effected on the extract phase. In counter-current treatment in a tower some pure selective solvent may be introduced near the raffinate outlet to wash out any extract therefrom.

  20. Selection and design of solvents

    DEFF Research Database (Denmark)

    Gani, Rafiqul

    and design of solvents will be presented together with application examples. The selection problem is defined as finding known chemicals that match the desired functions of a solvent for a specified set of applications. The design problem is defined as finding the molecular structure (or mixture of molecules....... With increasing interest on issues such as waste, sustainability, environmental impact and green chemistry, the selection and design of solvents have become important problems that need to be addressed during chemical product-process design and development. Systematic methods and tools suitable for selection......) that match the desired functions of a solvent for a specified set of applications. Use of organic chemicals and ionic liquids as solvents will be covered....

  1. 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.

  2. Predicting Attrition, Performance, Reenlistment, and Hospitalizations from the Smoking History of Women Prior to Entering the Navy

    National Research Council Canada - National Science Library

    Conway, Terry L

    2006-01-01

    This study of women sailors examined whether tobacco use prior to entering the Navy predicted subsequent career outcomes related to length of service, early attrition, misconduct, and hospitalizations...

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

    International Nuclear Information System (INIS)

    Adeyinka A. Adeyiga

    2001-01-01

    The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H 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-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 2 /CO ratios. However, a serious problem with use of Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, makes the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. Recently, fundamental understanding of physical attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried Fe-based catalyst having aps of 70 mm with high attrition resistance. This Fe-based attrition resistant, active and selective catalyst gave 95% CO conversion through 125 hours of testing in a fixed-bed at 270 C, 1.48 MPa, H 2 /CO=0.67 and 2.0 NL/g-cat/h with C 5 + selectivity of >78% and methane selectivity of <5%. However, further development of the catalyst is needed to address the chemical attrition due to phase changes that any Fe-catalyst goes through potentially causing internal stresses within the particle and resulting in weakening, spalling or cracking. The objective of this research is to develop robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry bubble column reactor. Specifically we aim to develop to: (i) improve the performance and preparation procedure of the high activity, high attrition resistant, high alpha iron

  4. Solvent extraction of Zn and metals in Zn ores by nonphosphorous solvents

    International Nuclear Information System (INIS)

    Auchapt, J.M.; Tostain, Jacqueline.

    1975-07-01

    This bibliography follows a first work on Zn solvent extraction by organo-phosphorous compounds. The other solvents used in Zn extraction, are studied: oxygenated nonphosphorous solvents (ketones, alcohols, carboxylic acids, sulfonates), nitrogenous solvents and hydrocarbons [fr

  5. Cesium Concentration in MCU Solvent

    International Nuclear Information System (INIS)

    Walker, D

    2006-01-01

    During Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) operations, Cs-137 concentrations in product streams will vary depending on the location in the process and on the recent process conditions. Calculations of cesium concentrations under a variety of operating conditions reveal the following: (1) Under nominal operations with salt solution feed containing 1.1 Ci Cs-137 per gallon, the maximum Cs-137 concentration in the process will occur in the strip effluent (SE) and equal 15-16.5 Ci/gal. (2) Under these conditions, the majority of the solvent will contain 0.005 to 0.01 Ci/gal, with a limited portion of the solvent in the contactor stages containing ∼4 Ci/gal. (3) When operating conditions yield product near 0.1 Ci Cs-137/gal in the decontaminated salt solution (DSS), the SE cesium concentration will be the same or lower than in nominal operations, but majority of the stripped solvent will increase to ∼2-3 Ci/gal. (4) Deviations in strip and waste stream flow rates cause the largest variations in cesium content: (a) If strip flow rates deviate by -30% of nominal, the SE will contain ∼23 Ci/gal, although the cesium content of the solvent will increase to only 0.03 Ci/gal; (b) If strip flow rate deviates by -77% (i.e., 23% of nominal), the SE will contain 54 Ci/gal and solvent will contain 1.65 Ci/gal. At this point, the product DSS will just reach the limit of 0.1 Ci/gal, causing the DSS gamma monitors to alarm; and (c) Moderate (+10 to +30%) deviations in waste flow rate cause approximately proportional increases in the SE and solvent cesium concentrations. Recovery from a process failure due to poor cesium stripping can achieve any low cesium concentration required. Passing the solvent back through the contactors while recycling DSS product will produce a ∼70% reduction during one pass through the contactors (assuming the stripping D value is no worse than 0.36). If the solvent is returned to the solvent hold tank (containing additional

  6. Bounding the effects of social experiments: accounting for attrition in administrative data.

    Science.gov (United States)

    Grogger, Jeffrey

    2012-12-01

    Social experiments frequently exploit data from administrative records. However, most administrative data systems are designed to track earnings or benefit payments among residents within a single state. When an experimental participant moves across state lines, his entries in the data system of his state of origin consist entirely of zeros. Such attrition may bias the estimated effect of the experiment. To estimate the attrition arising from interstate mobility and provide bounds on the effect of the experiment. Attrition is estimated from runs of zeros at the end of the sample period. Bounds are constructed from these estimates. These estimates can be refined by imposing a stationarity assumption. The width of the estimated bounds depends importantly on the nature of the data being analyzed. Negatively correlated outcomes provide tighter bounds than positively correlated outcomes. Attrition can introduce considerable ambiguity into the estimated effects of experimental programs. To reduce ambiguity, one should collect as much data as possible. Even data on outcomes of no direct interest to the objectives of the experiment may be valuable for reducing the ambiguity that arises due to attrition.

  7. Self-esteem and self-efficacy as predictors of attrition in associate degree nursing students.

    Science.gov (United States)

    Peterson-Graziose, Virginia; Bryer, Jennifer; Nikolaidou, Maria

    2013-06-01

    There is a serious and growing shortage of nurses in the United States, and the high rate of student attrition from nursing programs has further added to this problem. The challenge for schools of nursing is to recruit increased numbers of qualified candidates into their programs and to determine ways to decrease the rate of student attrition. The purpose of this study was to determine whether self-esteem, self-efficacy, and life stressors were significantly related to student attrition in first-semester associate degree nursing students. A descriptive correlational design and nonprobability convenience sample of first-semester associate degree nursing students was used. Data were gathered using the Rosenberg Self-Esteem Scale, the General Self-Efficacy Scale, and the Holmes and Rahe Social Readjustment Rating Scale. Findings indicated that self-esteem was significantly associated with student attrition. Results from this study provide the basis for targeted interventions designed to decrease student attrition rates in associate degree nursing programs. Copyright 2013, SLACK Incorporated.

  8. Processing of polymers using reactive solvents

    NARCIS (Netherlands)

    Lemstra, P.J.; Kurja, J.; Meijer, H.E.H.; Meijer, H.E.H.

    1997-01-01

    A review with many refs. on processing of polymers using reactive solvents including classification of synthetic polymers, guidelines for the selection of reactive solvents, basic aspects of processing, examples of intractable and tractable polymer/reactive solvent system

  9. 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

  10. Handbook of organic solvent properties

    CERN Document Server

    Smallwood, Ian

    2012-01-01

    The properties of 72 of the most commonly used solvents are given, tabulated in the most convenient way, making this book a joy for industrial chemists to use as a desk reference. The properties covered are those which answer the basic questions of: Will it do the job? Will it harm the user? Will it pollute the air? Is it easy to handle? Will it pollute the water? Can it be recovered or incinerated? These are all factors that need to be considered at the early stages of choosing a solvent for a new product or process.A collection of the physical properties of most commonly used solvents, their

  11. Acetone-based cellulose solvent.

    Science.gov (United States)

    Kostag, Marc; Liebert, Tim; Heinze, Thomas

    2014-08-01

    Acetone containing tetraalkylammonium chloride is found to be an efficient solvent for cellulose. The addition of an amount of 10 mol% (based on acetone) of well-soluble salt triethyloctylammonium chloride (Et3 OctN Cl) adjusts the solvent's properties (increases the polarity) to promote cellulose dissolution. Cellulose solutions in acetone/Et3 OctN Cl have the lowest viscosity reported for comparable aprotic solutions making it a promising system for shaping processes and homogeneous chemical modification of the biopolymer. Recovery of the polymer and recycling of the solvent components can be easily achieved. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Particle Separation of Non-Decontamination Soil using Attrition and Washing

    International Nuclear Information System (INIS)

    Koo, Daeseo; Sung, Hyun-Hee; Kim, Seung-Soo; Hong, Sang Bum; Seo, Bum Kyoung; Choi, Jong-Won

    2017-01-01

    In this study, to improve the decontamination efficiency of uranium soil, a preliminary experiment on the particle separation of non-decontamination soil was carried out using attrition and washing. The characteristics of the attrition and washing system are investigated. A conditional experiment on particle separation of non-decontamination soil will be performed. A preliminary experiment on the particle separation of non-decontamination soil was carried out to improve the decontamination efficiency of uranium soil. This experiment was performed with the ratio of soil to water (1:4) for the particle separation of non-decontamination soil. The operations of all equipment such as attrition scrubber, ultrasonic reaction, vibrating screen, and hydro-cyclone were conducted and confirmed. In the future, the additional experiments will be conducted for optimal experimental condition.

  13. The implications of selective attrition for estimates of intergenerational elasticity of family income.

    Science.gov (United States)

    Schoeni, Robert F; Wiemers, Emily E

    2015-09-01

    Numerous studies have estimated a high intergenerational correlation in economic status. Such studies do not typically attend to potential biases that may arise due to survey attrition. Using the Panel Study of Income Dynamics - the data source most commonly used in prior studies - we demonstrate that attrition is particularly high for low-income adult children with low-income parents and particularly low for high-income adult children with high-income parents. Because of this pattern of attrition, intergenerational upward mobility has been overstated for low-income families and downward mobility has been understated for high-income families. The bias among low-income families is greater than the bias among high-income families implying that intergenerational elasticity in family income is higher than previous estimates with the Panel Study of Income Dynamics would suggest.

  14. 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; Wysler Domerçant, Jean; Labbé Coq, Nancy Rachel; Atwood Raphael, Nernst; Sherr, Kenneth; Tegger, Mary; Yuhas, Krista; Barnhart, Scott

    2014-10-01

    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. 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. 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 Hospital site, earlier year of ART start, spending less time enrolled in HIV care prior to ART initiation, receiving a non-standard ART regimen, lacking counseling prior to ART initiation, and having a higher body mass index were also associated with attrition risk. The findings suggest quality improvement interventions at the two hospitals, including: enhanced retention support and transportation subsidies for patients accessing care from remote areas; counseling for all patients prior to ART initiation; timely outreach to patients who miss ART pick-ups; "bridging services" for patients transferring care to alternative facilities; routine screening for anticipated interruptions in future ART pick-ups; and medical case review for patients placed on non-standard ART regimens. The findings are also relevant for policymaking on decentralization of ART services in Haiti.

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

    Directory of Open Access Journals (Sweden)

    Nancy H. Puttkammer

    2014-10-01

    Full Text Available 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 < 0.001. Hospital site, earlier year of ART start, spending less time enrolled in HIV care prior to ART initiation, receiving a non-standard ART regimen, lacking counseling prior to ART initiation, and having a higher body mass index were also associated with attrition risk. CONCLUSIONS: The findings suggest quality improvement interventions at the two hospitals, including: enhanced retention support and transportation subsidies for patients accessing care from remote areas; counseling for all patients prior to ART initiation; timely outreach to patients who miss ART pick-ups; "bridging services" for patients transferring care to alternative facilities; routine screening for anticipated interruptions in future ART pick-ups; and medical case review for patients placed on non-standard ART regimens. The findings are also relevant for policymaking on decentralization of ART services in Haiti.

  16. A qualitative and quantitative study of the reasons of attrition in an Indian hospital

    Directory of Open Access Journals (Sweden)

    Kasturi Shukla

    2017-01-01

    Full Text Available Background: The study attempts to evaluate the reasons of attrition in the organization from the perspective of the existing as well as the leaving employees; compare and identify the gaps, if any between the perspectives of these two employees groups. The study also aims to critically analyze the utility of ′exit interviews′ for analyzing the reasons of attrition. Methods: This cross-sectional study was conducted in a 150-bedded hospital in Ahmedabad, India, during May-July 2015. Exit interview data of forty leaving employees were collected and reviewed. One hundred existing employees were interviewed through quantitative and qualitative methods to understand their perceptions about attrition in the organization. Results: Attrition rate of 26% was observed in the study and 57% leaving employees were nurses. 70% leaving employees cite "blanket reasons" such as better opportunity and personal reasons during exit interviews. 72.5% leaving employees believed that exit interview is largely for record purpose and 11% were unsure of its utility. However, when existing employees were probed qualitatively, a variety of responses were received. 65% existing employees quoted salary issues, partiality/poor recognition, improper assignment of tasks, and monotonous work as reasons for attrition in the organization. Conclusion: Exit interviews somewhere fail to probe into the real reasons of attrition. To improve retention, organizations must monitor their existing employee′s intention to continue working in the organization and any sign indicating a poor intention to continue must be addressed immediately to avoid ripple effects. Moreover, to use exit interview as a tool to improve employee retention, leaving employees must be interviewed in-depth to uncover the actual reasons for quitting the job.

  17. Examining the Relationship Between Mental, Physical, and Organizational Factors Associated With Attrition During Maritime Forces Training.

    Science.gov (United States)

    Binsch, Olaf; Banko, Katherine M; Veenstra, Bertil J; Valk, Pierre J L

    2015-11-01

    For infantry units of the Dutch Ministry of Defence, high attrition rates (varying from 42 to 68%) during initial training are a persisting problem. The reasons for this attrition are diverse. Having better insight into the causes of attrition is a prerequisite for implementing preventive measures. To achieve this, a monitoring assessment system was developed that integrated the effects of physical, mental, and organizational determinants on operational readiness. The aim of this study was to implement the monitoring tools and to establish the set of determinants that best predicted attrition during infantry training of new recruits. Eighty-five recruits were monitored over a 24-week infantry training course. Before the training, recruits were screened for medical, psychological, and physical wellness. During the monitoring phase, mental, physiological, and organizational indicants were obtained using an array of tools such as questionnaires, chest belt monitors (for heart rate, acceleration, and skin temperature measurements), and computerized tests (e.g., vigilance, long-term memory). Survival analyses were used to tease out the determinants of individual and grouped predictors of attrition. Nearly half the recruits (47%) failed the training. Attrition was predicted by both physiological and mental determinants. However, the organizational determinant "trainers' judgment" on the "recruits' military quality" dominated the physiological and mental determinants. It was concluded that the monitoring system was successfully implemented during infantry training, and that the survival analysis method emphasized on single effects and interactions between the different determinants. Based on the current findings, we recommend several steps to successfully implement a monitoring method in settings with high demands.

  18. Mirror-symmetry-breaking in poly[(9,9-di-n-octylfluorenyl- 2,7-diyl)-alt-biphenyl] (PF8P2) is susceptible to terpene chirality, achiral solvents, and mechanical stirring.

    Science.gov (United States)

    Fujiki, Michiya; Kawagoe, Yoshifumi; Nakano, Yoko; Nakao, Ayako

    2013-06-17

    Solvent chirality transfer of (S)-/(R)-limonenes allows the instant generation of optically active PF8P2 aggregates with distinct circular dichroism (CD)/circularly polarized luminescence (CPL) amplitudes with a high quantum yield of 16-20%. The present paper also reports subtle mirror-symmetry-breaking effects in CD-/CPL-amplitude and sign, CD/UV-vis spectral wavelengths, and photodynamics of the aggregates, though the reasons for the anomaly are unsolved. However, these photophysical properties depend on (i) the chemical natures of chiral and achiral molecules when used in solvent quantity, (ii) clockwise and counterclockwise stirring operations, and (iii) the order of addition of limonene and methanol to the chloroform solution.

  19. Mirror-Symmetry-Breaking in Poly[(9,9-di-n-octylfluorenyl-2,7-diyl-alt-biphenyl] (PF8P2 is Susceptible to Terpene Chirality, Achiral Solvents, and Mechanical Stirring

    Directory of Open Access Journals (Sweden)

    Ayako Nakao

    2013-06-01

    Full Text Available Solvent chirality transfer of (S-/(R-limonenes allows the instant generation of optically active PF8P2 aggregates with distinct circular dichroism (CD/circularly polarized luminescence (CPL amplitudes with a high quantum yield of 16–20%. The present paper also reports subtle mirror-symmetry-breaking effects in CD-/CPL-amplitude and sign, CD/UV-vis spectral wavelengths, and photodynamics of the aggregates, though the reasons for the anomaly are unsolved. However, these photophysical properties depend on (i the chemical natures of chiral and achiral molecules when used in solvent quantity, (ii clockwise and counterclockwise stirring operations, and (iii the order of addition of limonene and methanol to the chloroform solution.

  20. Lead optimization attrition analysis (LOAA): a novel and general methodology for medicinal chemistry.

    Science.gov (United States)

    Munson, Mark; Lieberman, Harvey; Tserlin, Elina; Rocnik, Jennifer; Ge, Jie; Fitzgerald, Maria; Patel, Vinod; Garcia-Echeverria, Carlos

    2015-08-01

    Herein, we report a novel and general method, lead optimization attrition analysis (LOAA), to benchmark two distinct small-molecule lead series using a relatively unbiased, simple technique and commercially available software. We illustrate this approach with data collected during lead optimization of two independent oncology programs as a case study. Easily generated graphics and attrition curves enabled us to calibrate progress and support go/no go decisions on each program. We believe that this data-driven technique could be used broadly by medicinal chemists and management to guide strategic decisions during drug discovery. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. 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,…

  2. Uranium refining by solvent extraction

    International Nuclear Information System (INIS)

    Kraikaew, J.

    1996-01-01

    The yellow cake refining was studied in both laboratory and semi-pilot scales. The process units mainly consist of dissolution and filtration, solvent extraction, and precipitation and filtration. Effect of flow ratio (organic flow rate/ aqueous flow rate) on working efficiencies of solvent extraction process was studied. Detailed studies were carried out on extraction, scrubbing and stripping processes. Purity of yellow cake product obtained is high as 90.32% U 3 O 8

  3. 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.

  4. Glutathione reductase: solvent equilibrium and kinetic isotope effects

    International Nuclear Information System (INIS)

    Wong, K.K.; Vanoni, M.A.; Blanchard, J.S.

    1988-01-01

    Glutathione reductase catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). The kinetic mechanism is ping-pong, and we have investigated the rate-limiting nature of proton-transfer steps in the reactions catalyzed by the spinach, yeast, and human erythrocyte glutathione reductases using a combination of alternate substrate and solvent kinetic isotope effects. With NADPH or GSSG as the variable substrate, at a fixed, saturating concentration of the other substrate, solvent kinetic isotope effects were observed on V but not V/K. Plots of Vm vs mole fraction of D 2 O (proton inventories) were linear in both cases for the yeast, spinach, and human erythrocyte enzymes. When solvent kinetic isotope effect studies were performed with DTNB instead of GSSG as an alternate substrate, a solvent kinetic isotope effect of 1.0 was observed. Solvent kinetic isotope effect measurements were also performed on the asymmetric disulfides GSSNB and GSSNP by using human erythrocyte glutathione reductase. The Km values for GSSNB and GSSNP were 70 microM and 13 microM, respectively, and V values were 62 and 57% of the one calculated for GSSG, respectively. Both of these substrates yield solvent kinetic isotope effects greater than 1.0 on both V and V/K and linear proton inventories, indicating that a single proton-transfer step is still rate limiting. These data are discussed in relationship to the chemical mechanism of GSSG reduction and the identity of the proton-transfer step whose rate is sensitive to solvent isotopic composition. Finally, the solvent equilibrium isotope effect measured with yeast glutathione reductase is 4.98, which allows us to calculate a fractionation factor for the thiol moiety of GSH of 0.456

  5. 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.

  6. Solvent/Non-Solvent Sintering To Make Microsphere Scaffolds

    Science.gov (United States)

    Laurencin, Cato T.; Brown, Justin L.; Nair, Lakshmi

    2011-01-01

    A solvent/non-solvent sintering technique has been devised for joining polymeric microspheres to make porous matrices for use as drug-delivery devices or scaffolds that could be seeded with cells for growing tissues. Unlike traditional sintering at elevated temperature and pressure, this technique is practiced at room temperature and pressure and, therefore, does not cause thermal degradation of any drug, protein, or other biochemical with which the microspheres might be loaded to impart properties desired in a specific application. Also, properties of scaffolds made by this technique are more reproducible than are properties of comparable scaffolds made by traditional sintering. The technique involves the use of two miscible organic liquids: one that is and one that is not a solvent for the affected polymer. The polymeric microspheres are placed in a mold having the size and shape of the desired scaffold, then the solvent/non-solvent mixture is poured into the mold to fill the void volume between the microspheres, then the liquid mixture is allowed to evaporate. Some of the properties of the resulting scaffold can be tailored through choice of the proportions of the liquids and the diameter of the microspheres.

  7. Recent Advances in Anhydrous Solvents for CO{sub 2} Capture: Ionic Liquids, Switchable Solvents, and Nanoparticle Organic Hybrid Materials

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngjune [School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju (Korea, Republic of); Lin, Kun-Yi Andrew [Department of Environmental Engineering, National Chung Hsing University, Taichung City (China); Park, Ah-Hyung Alissa, E-mail: ap2622@columbia.edu [Department of Earth and Environmental Engineering, Lenfest Center for Sustainable Energy, Columbia University, New York, NY (United States); Department of Chemical Engineering, Lenfest Center for Sustainable Energy, Columbia University, New York, NY (United States); Petit, Camille, E-mail: ap2622@columbia.edu [Department of Chemical Engineering, Imperial College London, London (United Kingdom)

    2015-10-01

    CO{sub 2} capture by amine scrubbing, which has a high CO{sub 2} capture capacity and a rapid reaction rate, is the most employed and investigated approach to date. There are a number of recent large-scale demonstrations including the Boundary Dam Carbon Capture Project by SaskPower in Canada that have reported successful implementations of aqueous amine solvent in CO{sub 2} capture from flue gases. The findings from these demonstrations will significantly advance the field of CO{sub 2} capture in the coming years. While the latest efforts in aqueous amine solvents are exciting and promising, there are still several drawbacks to amine-based CO{sub 2} capture solvents including high volatility and corrosiveness of the amine solutions as well as the high parasitic energy penalty during the solvent regeneration step. Thus, in a parallel effort, alternative CO{sub 2} capture solvents, which are often anhydrous, have been developed as the third-generation CO{sub 2} capture solvents. These novel classes of liquid materials include ionic liquids, CO{sub 2}-triggered switchable solvents (i.e., CO{sub 2}-binding organic liquids, reversible ionic liquids), and nanoparticle organic hybrid materials. This paper provides a review of these various anhydrous solvents and their potential for CO{sub 2} capture. Particular attention is given to the mechanisms of CO{sub 2} absorption in these solvents, their regeneration and their processability – especially taking into account their viscosity. While not intended to provide a complete coverage of the existing literature, this review aims at pointing the major findings reported for these new classes of CO{sub 2} capture media.

  8. Recent Advances in Anhydrous Solvents for CO2 Capture: Ionic Liquids, Switchable Solvents, and Nanoparticle Organic Hybrid Materials

    Directory of Open Access Journals (Sweden)

    YOUNGJUNE ePARK

    2015-10-01

    Full Text Available CO2 capture by amine scrubbing, which has a high CO2 capture capacity and a rapid reaction rate, is the most employed and investigated approach to date. There are a number of recent large-scale demonstrations including the Boundary Dam Carbon Capture Project by SaskPower in Canada that have reported successful implementations of aqueous amine solvent in CO2 capture from flue gases. The findings from these demonstrations will significantly advance the field of CO2 capture in the coming years. While the latest efforts in aqueous amine solvents are exciting and promising, there are still several drawbacks to amine-based CO2 capture solvents including high volatility and corrosiveness of the amine solutions, as well as the high parasitic energy penalty during the solvent regeneration step. Thus, in a parallel effort, alternative CO2 capture solvents, which are often anhydrous, have been developed as the third-generation CO2 capture solvents. These novel classes of liquid materials include: Ionic Liquids (ILs, CO2-triggered switchable solvents (i.e., CO2 Binding Organic Liquids (CO2BOLs, Reversible Ionic Liquids (RevILs, and Nanoparticle Organic Hybrid Materials (NOHMs. This paper provides a review of these various anhydrous solvents and their potential for CO2 capture. Particular attention is given to the mechanisms of CO2 absorption in these solvents, their regeneration and their processability – especially taking into account their viscosity. While not intended to provide a complete coverage of the existing literature, this review aims at pointing the major findings reported for these new classes of CO2 capture media.

  9. Recent Advances in Anhydrous Solvents for CO2 Capture: Ionic Liquids, Switchable Solvents, and Nanoparticle Organic Hybrid Materials

    International Nuclear Information System (INIS)

    Park, Youngjune; Lin, Kun-Yi Andrew; Park, Ah-Hyung Alissa; Petit, Camille

    2015-01-01

    CO 2 capture by amine scrubbing, which has a high CO 2 capture capacity and a rapid reaction rate, is the most employed and investigated approach to date. There are a number of recent large-scale demonstrations including the Boundary Dam Carbon Capture Project by SaskPower in Canada that have reported successful implementations of aqueous amine solvent in CO 2 capture from flue gases. The findings from these demonstrations will significantly advance the field of CO 2 capture in the coming years. While the latest efforts in aqueous amine solvents are exciting and promising, there are still several drawbacks to amine-based CO 2 capture solvents including high volatility and corrosiveness of the amine solutions as well as the high parasitic energy penalty during the solvent regeneration step. Thus, in a parallel effort, alternative CO 2 capture solvents, which are often anhydrous, have been developed as the third-generation CO 2 capture solvents. These novel classes of liquid materials include ionic liquids, CO 2 -triggered switchable solvents (i.e., CO 2 -binding organic liquids, reversible ionic liquids), and nanoparticle organic hybrid materials. This paper provides a review of these various anhydrous solvents and their potential for CO 2 capture. Particular attention is given to the mechanisms of CO 2 absorption in these solvents, their regeneration and their processability – especially taking into account their viscosity. While not intended to provide a complete coverage of the existing literature, this review aims at pointing the major findings reported for these new classes of CO 2 capture media.

  10. Career Stories of Israeli Teachers Who Left Teaching: A Salutogenic View of Teacher Attrition

    Science.gov (United States)

    Yinon, Hayuta; Orland-Barak, Lily

    2017-01-01

    Many countries experience a high percentage of teachers who leave the profession before retirement. Most of the explanations, such as teacher burnout, adopt a pathogenic point of view which perceives attrition as a negative work outcome. In contrast, the qualitative project that this article is based on, which characterizes the career…

  11. Teacher Attrition in the USA: The Relational Elements in a Utah Case Study

    Science.gov (United States)

    Newberry, Melissa; Allsop, Yvonne

    2017-01-01

    Previous work on teacher attrition in the US has indicated that those who stay in the profession and those who leave are not separate homogenous groups. In this study, the lived experience of former teachers is examined to determine the issues that distinguish leavers from stayers. The sample is from the state of Utah, a state with one of the…

  12. Pilot Testing for Feasibility in a Study of Student Retention and Attrition in Online Undergraduate Programs

    Science.gov (United States)

    Fraser, Joy; Fahlman, Dorothy; Arscott, Jane; Guillot, Isabelle

    2018-01-01

    Prior to undertaking a descriptive study on attrition and retention of students in two online undergraduate health administration and human service programs, a pilot test was conducted to assess the procedures for participant recruitment, usability of the survey questionnaire, and data collection processes. A retention model provided the…

  13. 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…

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-04-15

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

  15. In Their Own Words: A Text Analytics Investigation of College Course Attrition

    Science.gov (United States)

    Michalski, Greg V.

    2014-01-01

    Excessive course attrition is costly to both the student and the institution. While most institutions have systems to quantify and report the numbers, far less attention is typically paid to each student's reason(s) for withdrawal. In this case study, text analytics was used to analyze a large set of open-ended written comments in which students…

  16. 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.

  17. 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…

  18. Unemployment, the Great Recession, and Apprenticeship Attrition in the U.S.

    Science.gov (United States)

    Bilginsoy, Cihan

    2018-01-01

    The author estimates the impacts of the local rate of unemployment and the Great Recession on the quit and graduation rates of the U.S. construction trade apprentices over the 2001-2014 period. Trade union participation in training sponsorship had a strong influence on attrition rates. The impacts of the business cycle and the Great Recession on…

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

    Directory of Open Access Journals (Sweden)

    Nicole Satherley

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

  20. 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...

  1. Predicting the Risk of Attrition for Undergraduate Students with Time Based Modelling

    Science.gov (United States)

    Chai, Kevin E. K.; Gibson, David

    2015-01-01

    Improving student retention is an important and challenging problem for universities. This paper reports on the development of a student attrition model for predicting which first year students are most at-risk of leaving at various points in time during their first semester of study. The objective of developing such a model is to assist…

  2. 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…

  3. A Strategy of Attrition through Enforcement: The Unmaking of Irregular Migration in Malaysia

    OpenAIRE

    Choo Chin Low

    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 ...

  4. The Effect of Household and Community on School Attrition: An Analysis of Thai Youth

    Science.gov (United States)

    Korinek, Kim; Punpuing, Sureeporn

    2012-01-01

    We analyze school attrition among youth in Kanchanaburi province, Thailand. We find that family investments in schooling are shaped by both household and local community contexts. There is an enrollment advantage for girls across different households and communities. We find that youth whose mothers have migrated and youth in immigrant households…

  5. 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…

  6. The Role of Social Support in First-Term Sailors’ Attrition from Recruit Training

    Science.gov (United States)

    2008-04-01

    absenteeism , and job turnover during the first year of employment. Academy of Management Journal, 28, 88-109. Shils, E. A. & Janowitz, M. (1948). Cohesion and...British Army. Journal of Organizational Behavior, 19, 745-767. Tinto, V. (1993). Leaving college: Rethinking the causes and cures of student attrition

  7. 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...

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

    Science.gov (United States)

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

    2011-01-01

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

  9. Special Education Teacher Perception of Administrative Supports That Encourage, Decrease Burnout, and Reduce Attrition

    Science.gov (United States)

    Beebe, Jay

    2017-01-01

    The field of special education is facing a shortage of teachers. A shortage of special education teachers is an example of a pressing issue within education. The problem is that teacher attrition rates are among the highest within special education. Many special education teachers are leaving the profession after a few years of teaching for varied…

  10. 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.

  11. 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…

  12. Minimising Attrition: Strategies for Assisting Students Who Are at Risk of Withdrawal

    Science.gov (United States)

    Park, Caroline L.; Perry, Beth; Edwards, Margaret

    2011-01-01

    This paper explores strategies aimed at minimising attrition by encouraging persistence among online graduate students who are considering withdrawal. It builds upon earlier studies conducted by a team of researchers who teach online graduate students in health care at Athabasca University. First, in 2008-2009, Park, Boman, Care, Edwards, and…

  13. 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…

  14. Journey to Becoming a Thai English Teacher: New Perspective on Investigating Teacher Attrition

    Science.gov (United States)

    Prabjandee, Denchai

    2014-01-01

    In this study, the author provides a unique perspective on teacher shortage by focusing on teacher retention, in terms of why teachers stay in the teaching profession, rather than focusing on teacher attrition, or why teachers leave the teaching profession. The change in perspective created an opportunity to study the journey of how teachers chose…

  15. Solvents interactions with thermochromic print

    Directory of Open Access Journals (Sweden)

    Mirela Rožić

    2017-12-01

    Full Text Available In this study, the interactions between different solvents (benzene, acetone, cyclohexanone, various alcohols and water and thermochromic printing ink were investigated. Thermochromic printing ink was printed on metal surface. Components of thermochromic printing inks are polymeric microcapsules and classic yellow offset printing ink. Below its activation temperature, dye and developer within the microcapsules form a blue coloured complex. Therefore, thermochromic print is green. By heating above the activation temperature, blue colour of the complex turns into the leuco dye colourless state and the green colour of the prints turns into the yellow colour of the classic offset pigment. The results of the interaction with various solvents show that the thermochromic print is stable in all tested solvents except in ethanol, acetone and cyclohexanone. In ethanol, the green colour of the print becomes yellow. SEM analysis shows that microcapsules are dissolved. In acetone and cyclohexanone, the green colour of the print turns into blue, and the microcapsules become significantly more visible. Thus, the yellow pigment interacts with examined ketones. Based on the obtained interactions it can be concluded that the microcapsules have more polar nature than the classical pigment particles. Solvent-thermocromic print interactions were analysed using Hansen solubility parameters that rank the solvents based on their estimated interaction capabilities.

  16. The pattern of attrition from an antiretroviral treatment program in Nigeria.

    Directory of Open Access Journals (Sweden)

    Solomon Odafe

    Full Text Available To evaluate the rate and factors associated with attrition of patients receiving ART in tertiary and secondary hospitals in Nigeria.We reviewed patient level data collected between 2007 and 2010 from 11 hospitals across Nigeria. Kaplan-Meier product-limit and Cox regression were used to determine probability of retention in care and risk factors for attrition respectively. Of 6,408 patients in the cohort, 3,839 (59.9% were females, median age of study population was 33years (IQR: 27-40 and 4,415 (69% were from secondary health facilities. The NRTI backbone was Stavudine (D4T in 3708 (57.9% and Zidovudine (ZDV in 2613 (40.8% of patients. Patients lost to follow up accounted for 62.7% of all attrition followed by treatment stops (25.3% and deaths (12.0%. Attrition was 14.1 (N = 624 and 15.1% (N = 300 in secondary and tertiary hospitals respectively (p = 0.169 in the first 12 months on follow up. During the 13 to 24 months follow up period, attrition was 10.7% (N = 407 and 19.6% (N = 332 in secondary and tertiary facilities respectively (p<0.001. Median time to lost to follow up was 11.1 (IQR: 6.1 to 18.5 months in secondary compared with 13.6 (IQR: 9.9 to 17.0 months in tertiary sites (p = 0.002. At 24 months follow up, male gender [AHR 1.18, 95% CI: 1.01-1.37, P = 0.038]; WHO clinical stage III [AHR 1.30, 95%CI: 1.03-1.66, P = 0.03] and clinical stage IV [AHR 1.90, 95%CI: 1.20-3.02, p = 0.007] and care in a tertiary hospital [AHR 2.21, 95% CI: 1.83-2.67, p<0.001], were associated with attrition.Attrition could potentially be reduced by decentralizing patients on ART after the first 12 months on therapy to lower level facilities, earlier initiation on treatment and strengthening adherence counseling amongst males.

  17. Industrial rag cleaning process for the environmentally safe removal of petroleum-based solvents

    International Nuclear Information System (INIS)

    Fierro, J.V.

    1993-01-01

    A process for the cleaning of industrial rags contaminated with environmentally unsafe petroleum-based solvent is described, comprising the step of: (a) placing a load of the industrial rags in a mechanically driven rotary drum; (b) revolving the drum at a high speed sufficient to physically extract liquid petroleum-based solvent contaminate from the industrial rags; (c) routing the extracted petroleum-based solvent contaminate from the rotary drum to a waste solvent collection line for environmentally safe disposal; (d) revolving the rotary drum to cause a tumbling of the industrial rags while maintaining the temperature within the drum at below the flash point of the petroleum-based solvent; (e) intermittently forcing cold air and hot air through the rotary drum to vaporize solvent from the industrial rags; (f) routing the vaporized petroleum-based solvent contaminant from the rotary drum to a condenser wherein the petroleum-based solvent contaminate is condensed and thereafter further routing said condensed solvent to a waste collection line for environmentally safe disposal; and (g) cleaning the industrial rags in the presence of a dry cleaning solvent to remove residual petroleum-based solvents and soil

  18. Solvent jet desorption capillary photoionization-mass spectrometry.

    Science.gov (United States)

    Haapala, Markus; Teppo, Jaakko; Ollikainen, Elisa; Kiiski, Iiro; Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2015-03-17

    A new ambient mass spectrometry method, solvent jet desorption capillary photoionization (DCPI), is described. The method uses a solvent jet generated by a coaxial nebulizer operated at ambient conditions with nitrogen as nebulizer gas. The solvent jet is directed onto a sample surface, from which analytes are extracted into the solvent and ejected from the surface in secondary droplets formed in collisions between the jet and the sample surface. The secondary droplets are directed into the heated capillary photoionization (CPI) device, where the droplets are vaporized and the gaseous analytes are ionized by 10 eV photons generated by a vacuum ultraviolet (VUV) krypton discharge lamp. As the CPI device is directly connected to the extended capillary inlet of the MS, high ion transfer efficiency to the vacuum of MS is achieved. The solvent jet DCPI provides several advantages: high sensitivity for nonpolar and polar compounds with limit of detection down to low fmol levels, capability of analyzing small and large molecules, and good spatial resolution (250 μm). Two ionization mechanisms are involved in DCPI: atmospheric pressure photoionization, capable of ionizing polar and nonpolar compounds, and solvent assisted inlet ionization capable of ionizing larger molecules like peptides. The feasibility of DCPI was successfully tested in the analysis of polar and nonpolar compounds in sage leaves and chili pepper.

  19. The impact of oil dispersant solvent on performance

    International Nuclear Information System (INIS)

    Fiocco, R.J.; Lessard, R.R.; Canevari, G.P.; Becker, K.W.; Daling, P.S.

    1995-01-01

    Modern oil spill dispersant formulations are concentrated blends of surface active agents (surfactants) in a solvent carrier system. The surfactants are effective for lowering the interfacial tension of the oil slick and promoting and stabilizing oil-in-water dispersions. The solvent system has 2 key functions: (1) reduce viscosity of the surfactant blend to allow efficient dispersant application, and (2) promote mixing and diffusion of the surfactant blend into the oil film. A more detailed description than previously given in the literature is proposed to explain the mechanism of chemical dispersion and illustrate how the surfactant is delivered by the solvent to the oil-water interface. Laboratory data are presented which demonstrate the variability in dispersing effectiveness due to different solvent composition, particularly for viscous and emulsified test oils with viscosities up to 20,500 mPa·s. Other advantages of improved solvent components can include reduced evaporative losses during spraying, lower marine toxicity and reduced protective equipment requirements. Through this improved understanding of the role of the solvent, dispersants which are more effective over a wider range of oil types are being developed

  20. 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

  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

    2012-09-01

    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. 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. 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. 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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. [Attrition and poor performance in general practice training: age, competence and knowledge play a role].

    Science.gov (United States)

    Vermeulen, Margit I; Kuyvenhoven, Marijke M; Zuithoff, N P A Peter; van der Graaf, Yolanda; Pieters, H M Ron

    2011-01-01

    To investigate which determinants are related to poor performance and forced attrition in the first year residency in general practice (GP). Observational retrospective cohort study. We collected data relating to personal characteristics such as age, sex and clinical experience from residents who started the GP training in Utrecht, the Netherlands, in the period March 2005-August 2007. We also collected competence scores from the domains 'medical expertise', 'doctor-patient communication' and 'professionalism', as well as scores on a national GP knowledge test. The outcome measures were 'poor performance' and 'forced attrition'. Multivariate logistic regression was used to analyse correlations between personal characteristics, competence scores on the 3 domains and knowledge scores in the first trimester on the one hand and poor performance or forced attrition on the other. 215 residents started the GP training. In the first trimester a quarter of the residents had an insufficient score in 1 or more of the domains. Competence scores were mutually correlated, but did not correlate with the knowledge score. 18 residents showed poor performance and 3 were forced to stop their training. Poor performance and forced attrition were correlated with age (adjusted odds ratio (OR): 1.1; 95% CI: 1.0-1.3), insufficient knowledge (adjusted OR: 8.9; 3.0-26.3) and medical expertise (adjusted OR: 2.1; 1.1-4.0) at the beginning of the training. Age, insufficient knowledge of general practice, and insufficient competence in the domain of 'medical expertise' at the beginning of the training are risk factors for poor performance by residents and attrition from their GP training.

  3. Factors affecting attrition from associate degree nursing programs in North Carolina.

    Science.gov (United States)

    Fraher, Erin; Belsky, Daniel W; Gaul, Katie; Carpenter, Jessica

    2010-01-01

    Projected nursing shortfalls have spurred the state of North Carolina to initiate a series of strategies to increase the number of graduates from pre-licensure Registered Nurse (RN) programs. These efforts have been largely successful, but attrition rates from Associate Degree Nursing (ADN) programs remain high. Only 58% of students entering ADN programs complete the degree. While policy makers are keenly aware that attrition from ADN programs is problematic, there is a lack of empirical evidence to identify the specific factors contributing to student attrition. In late 2007, the North Carolina Community College System (NCCCS) asked the Cecil G. Sheps Center for Health Services Research to conduct a study of Associate Degree Nursing program attrition and its causes. This paper summarizes the findings from that study and identifies the student- and program-level characteristics associated with more and less successful ADN programs. While this study was conducted in a single state in the US, the substantive findings--as well as the methodological approach--may be useful to other states and other countries. The study revealed that socioeconomically disadvantaged students (those with GEDs and those who received Pell Grants), non-white students, and younger and older students were less likely to graduate on-time. When programs were grouped into high and low performance categories on the basis of risk adjusted graduation rates, high performing programs were distinguished by more stringent admissions policies and better educated faculties. Nursing shortages have garnered significant attention and resources from state and national workforce planners in recent years. But to date, investments in expanding program capacity have not been matched by attention to program completion rates, with the result that we have enlarged the pipeline without fixing the leaks. Faculty shortages and recession-induced resource constraints limit further program expansion. Addressing attrition

  4. Multiple sclerosis and organic solvents

    DEFF Research Database (Denmark)

    Mortensen, J T; Brønnum-Hansen, Henrik; Rasmussen, K

    1998-01-01

    We investigated a possible causal relation between exposure to organic solvents in Danish workers (housepainters, typographers/printers, carpenters/cabinetmakers) and onset of multiple sclerosis. Data on men included in the Danish Multiple Sclerosis Register (3,241 men) were linked with data from......, and butchers. Over a follow-up period of 20 years, we observed no increase in the incidence of multiple sclerosis among men presumed to be exposed to organic solvents. It was not possible to obtain data on potential confounders, and the study design has some potential for selection bias. Nevertheless......, the study does not support existing hypotheses regarding an association between occupational exposure to organic solvents and multiple sclerosis....

  5. Indium recovery by solvent extraction

    International Nuclear Information System (INIS)

    Fortes, Marilia Camargos Botelho

    1999-04-01

    Indium has been recovered as a byproduct from residues generated from the sulfuric acid leaching circuits in mineral plants for zinc recovery. Once its recovery comes from the slags of other metals recovery, it is necessary to separate it from the other elements which usually are present in high concentrations. Many works have been approaching this separation and indicate the solvent extraction process as the main technique used. In Brazilian case, indium recovery depends on the knowledge of this technique and its development. This paper describes the solvent extraction knowledge for the indium recovery from aqueous solutions generated in mineral plants. The results for determination of the best experimental conditions to obtain a high indium concentration solution and minimum iron poisoning by solvent extraction with di (2-ethylhexyl)-phosphoric acid (D2EHPA) solubilized in isoparafin and exxsol has been presented. (author)

  6. High throughput research and evaporation rate modeling for solvent screening for ethylcellulose barrier membranes in pharmaceutical applications.

    Science.gov (United States)

    Schoener, Cody A; Curtis-Fisk, Jaime L; Rogers, True L; Tate, Michael P

    2016-10-01

    Ethylcellulose is commonly dissolved in a solvent or formed into an aqueous dispersion and sprayed onto various dosage forms to form a barrier membrane to provide controlled release in pharmaceutical formulations. Due to the variety of solvents utilized in the pharmaceutical industry and the importance solvent can play on film formation and film strength it is critical to understand how solvent can influence these parameters. To systematically study a variety of solvent blends and how these solvent blends influence ethylcellulose film formation, physical and mechanical film properties and solution properties such as clarity and viscosity. Using high throughput capabilities and evaporation rate modeling, thirty-one different solvent blends composed of ethanol, isopropanol, acetone, methanol, and/or water were formulated, analyzed for viscosity and clarity, and narrowed down to four solvent blends. Brookfield viscosity, film casting, mechanical film testing and water permeation were also completed. High throughput analysis identified isopropanol/water, ethanol, ethanol/water and methanol/acetone/water as solvent blends with unique clarity and viscosity values. Evaporation rate modeling further rank ordered these candidates from excellent to poor interaction with ethylcellulose. Isopropanol/water was identified as the most suitable solvent blend for ethylcellulose due to azeotrope formation during evaporation, which resulted in a solvent-rich phase allowing the ethylcellulose polymer chains to remain maximally extended during film formation. Consequently, the highest clarity and most ductile films were formed. Employing high throughput capabilities paired with evaporation rate modeling allowed strong predictions between solvent interaction with ethylcellulose and mechanical film properties.

  7. Tri-n-butyl phosphate - the universal solvent for the nuclear fuel cycle

    International Nuclear Information System (INIS)

    Naylor, A.; Eccles, H.

    1988-01-01

    Tri-n-butyl phosphates (TBP) is now Widely used in the processes of solvent extraction, especially in those, used in nuclear fuel cycle. Problems, related with actinide separation and purification, can be solved easily by accurate sampling of diluent, concentration and purification degree of a solvent, aqueous phase acidity and temperature. Physical and chemical properties of TBP, mechanism of actinide solvent extraction, TBP hydrolysis and radiolysis are considered

  8. No differential attrition was found in randomized controlled trials published in general medical journals: a meta-analysis.

    Science.gov (United States)

    Crutzen, Rik; Viechtbauer, Wolfgang; Kotz, Daniel; Spigt, Mark

    2013-09-01

    Differential attrition is regarded as a major threat to the internal validity of a randomized controlled trial (RCT). This study identifies the degree of differential attrition in RCTs covering a broad spectrum of clinical areas and factors that are related to this. A PubMed search was conducted to obtain a random sample of 100 RCTs published between 2008 and 2010 in journals from the ISI Web of Knowledge(SM) category of medicine, general and internal. Eligibility criteria for selecting studies were primary publications of two-arm parallel randomized clinical trials, containing human participants and one or multiple follow-up measurements whose availability depended on the patients' willingness to participate. A significant amount of differential attrition was observed in 8% of the trials. The average differential attrition rate was 0.99 (95% confidence interval: 0.97-1.01), indicating no general difference in attrition rates between intervention and control groups. Moreover, no indication of heterogeneity was found, suggesting that the occurrence of differential attrition in the published literature is mostly a chance finding, unrelated to any particular design factors. Differential attrition did not generally occur in RCTs covering a broad spectrum of clinical areas within general and internal medicine. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Solvent sorting in (mixed solvent electrolyte) systems: Time-resolved ...

    Indian Academy of Sciences (India)

    lar solvents as an effective single component dipo- lar liquid that is characterized ... and time (t) dependent solvation energy of mobile dipo- lar solute with density ..... Even though this way for modification of C is purely ad- hoc, the observation ...

  10. Solvent extraction of thorium(IV) with dibutyldithiophosphoric acid in various organic solvents

    International Nuclear Information System (INIS)

    Curtui, M.; Haiduc, I.

    1994-01-01

    The extraction of thorium(IV) from perchlorate solutions with di-n-butyldithiophosphoric acid (HBudtp) in various organic solvents occurs through an ion exchange mechanism. The extracted species in the organic phase is an eight-coordinate complex Th(Budtp) 4 . The higher values of the distribution ratio obtained in HBudtp-benzene-water system than in HBudtp-n-butanol-water system are explained by higher solubility of the complex species in nonpolar solvents. The position of the extraction curves in the pH-range lower than 0.7 reduces the complexation of thorium(IV) with Budtp - in the aqueous phase and also the hydrolysis process. (author) 8 refs.; 4 figs.; 1 tab

  11. Retention and Attrition Among African Americans in the STAR*D Study: What Causes Research Volunteers to Stay or Stray?

    Science.gov (United States)

    Murphy, Eleanor J; Kassem, Layla; Chemerinski, Anat; Rush, A. John; Laje, Gonzalo; McMahon, Francis J.

    2013-01-01

    Background High attrition rates among African-Americans (AA) volunteers are a persistent problem that makes clinical trials less representative and complicates estimation of treatment outcomes. Many studies contrast AA with other ethnic/racial groups, but few compare the AA volunteers who remain in treatment with those who leave. Here, in addition to comparing patterns of attrition between African Americans and whites, we identify predictors of overall and early attrition among African Americans. Method Sample comprised non-Hispanic African-American (n=673) and white (n=2,549) participants in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Chi-square tests were used to examine racial group differences in reasons for exit. Multivariate logistic regression was used to examine predictors of overall attrition, early attrition (by Level 2) and top reasons cited for attrition among African Americans. Results For both African-American and white dropouts, non-compliance reasons for attrition were most commonly cited during the earlier phases of the study while reasons related to efficacy and medication side effects were cited later in the study. Satisfaction with treatment strongly predicted overall attrition among African Americans independent of socioeconomic, clinical, medical or psychosocial factors. Early attrition among African American dropouts was associated with less psychiatric comorbidity, and higher perceived physical functioning but greater severity of clinician-rated depression. Conclusions The decision to drop out is a dynamic process that changes over the course of a clinical trial. Strategies aimed at retaining African Americans in such trials should emphasize engagement with treatment and patient satisfaction immediately following enrollment and after treatment initiation. PMID:23723044

  12. Benchmarking Continuum Solvent Models for Keto-Enol Tautomerizations.

    Science.gov (United States)

    McCann, Billy W; McFarland, Stuart; Acevedo, Orlando

    2015-08-13

    Experimental free energies of tautomerization, ΔGT, were used to benchmark the gas-phase predictions of 17 different quantum mechanical methods and eight basis sets for seven keto-enol tautomer pairs dominated by their enolic form. The G4 method and M06/6-31+G(d,p) yielded the most accurate results, with mean absolute errors (MAE's) of 0.95 and 0.71 kcal/mol, respectively. Using these two theory levels, the solution-phase ΔGT values for 23 unique tautomer pairs composed of aliphatic ketones, β-dicarbonyls, and heterocycles were computed in multiple protic and aprotic solvents. The continuum solvation models, namely, polarizable continuum model (PCM), polarizable conductor calculation model (CPCM), and universal solvation model (SMD), gave relatively similar MAE's of ∼1.6-1.7 kcal/mol for G4 and ∼1.9-2.0 kcal/mol with M06/6-31+G(d,p). Partitioning the tautomer pairs into their respective molecular types, that is, aliphatic ketones, β-dicarbonyls, and heterocycles, and separating out the aqueous versus nonaqueous results finds G4/PCM utilizing the UA0 cavity to be the overall most accurate combination. Free energies of activation, ΔG(‡), for the base-catalyzed keto-enol interconversion of 2-nitrocyclohexanone were also computed using six bases and five solvents. The M06/6-31+G(d,p) reproduced the ΔG(‡) with MAE's of 1.5 and 1.8 kcal/mol using CPCM and SMD, respectively, for all combinations of base and solvent. That specific enolization was previously proposed to proceed via a concerted mechanism in less polar solvents but shift to a stepwise mechanism in more polar solvents. However, the current calculations suggest that the stepwise mechanism operates in all solvents.

  13. Dissolution of covalent adaptable network polymers in organic solvent

    Science.gov (United States)

    Yu, Kai; Yang, Hua; Dao, Binh H.; Shi, Qian; Yakacki, Christopher M.

    2017-12-01

    It was recently reported that thermosetting polymers can be fully dissolved in a proper organic solvent utilizing a bond-exchange reaction (BER), where small molecules diffuse into the polymer, break the long polymer chains into short segments, and eventually dissolve the network when sufficient solvent is provided. The solvent-assisted dissolution approach was applied to fully recycle thermosets and their fiber composites. This paper presents the first multi-scale modeling framework to predict the dissolution kinetics and mechanics of thermosets in organic solvent. The model connects the micro-scale network dynamics with macro-scale material properties: in the micro-scale, a model is developed based on the kinetics of BERs to describe the cleavage rate of polymer chains and evolution of chain segment length during the dissolution. The micro-scale model is then fed into a continuum-level model with considerations of the transportation of solvent molecules and chain segments in the system. The model shows good prediction on conversion rate of functional groups, degradation of network mechanical properties, and dissolution rate of thermosets during the dissolution. It identifies the underlying kinetic factors governing the dissolution process, and reveals the influence of different material and processing variables on the dissolution process, such as time, temperature, catalyst concentration, and chain length between cross-links.

  14. Mechanics

    CERN Document Server

    Hartog, J P Den

    1961-01-01

    First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e

  15. Improved Purex solvent scrubbing methods

    International Nuclear Information System (INIS)

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

    1984-01-01

    Studies of hydrazine and hydroxylamine salts as solvent scrubbing agents that can be decomposed into gases are summarized. Results from testing of countercurrent scrubbers and solid sorber columns that produce lesser amounts of permanent salts are reported. The status of studies of the acid-degradation of paraffin diluent and the options for removal of long-chain organic acids is given

  16. Risk assessment for halogenated solvents

    International Nuclear Information System (INIS)

    Travis, C.C.

    1988-01-01

    A recent development in the cancer risk area is the advent of biologically based pharmacokinetic and pharmacodynamic models. These models allow for the incorporation of biological and mechanistic data into the risk assessment process. These advances will not only improve the risk assessment process for halogenated solvents but will stimulate and guide basic research in the biological area

  17. Deep eutectic solvents as performance additives in biphasic reactions

    NARCIS (Netherlands)

    Lan, Dongming; Wang, Xuping; Zhou, Pengfei; Hollmann, F.; Wang, Yonghua

    2017-01-01

    Deep eutectic solvents act as surfactants in biphasic (hydrophobic/aqueous) reaction mixtures enabling higher interfacial surface areas at lower mechanical stress as compared to simple emulsions. Exploiting this effect the rate of a chemoenzymatic epoxidation reaction was increased more than

  18. Solvent isotope effect on the fluorescence of azoalkanes

    International Nuclear Information System (INIS)

    Mirbach, M.J.; Mirbach, M.F.; Cherry, W.R.; Turro, N.J.; Engel, P.

    1977-01-01

    A study of fluorescence quantum yields and fluorescence lifetimes of two cyclic azoalkanes reveal a striking dependence of phisub(F) and tausub(F) on solvent and on isotopic substitution (OH → OD). A mechanism involving specific deactivation of the fluorescent state from a hydrogen bonded complex is proposed to rationalize the data. (orig./HK) [de

  19. 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

  20. The effects of three different food acids on the attrition-corrosion wear of human dental enamel

    Science.gov (United States)

    Zhang, Yichi; Arsecularatne, Joseph A.; Hoffman, Mark

    2015-07-01

    With increased consumption of acidic drinks and foods, the wear of human teeth due to attrition in acidic environments is an increasingly important issue. Accordingly, the present paper investigates in vitro the wear of human enamel in three different acidic environments. Reciprocating wear tests in which an enamel cusp slides on an enamel flat surface were carried out using acetic, citric and lactic acid lubricants (at pH 3-3.5). Distilled water was also included as a lubricant for comparison. Focused ion beam milling and scanning electron microscopy imaging were then used to investigate the enamel subsurfaces following wear tests. Nanoindentation was used to ascertain the changes in enamel mechanical properties. The study reveals crack generation along the rod boundaries due to the exposure of enamel to the acidic environments. The wear mechanism changes from brittle fracture in distilled water to ploughing or shaving of the softened layer in acidic environments, generating a smooth surface with the progression of wear. Moreover, nanoindentation results of enamel samples which were exposed to the above acids up to a duration of the wear tests show decreasing hardness and Young’s modulus with exposure time.

  1. Investigations of the reactivity of pyridine carboxylic acids with diazodiphenylmethane in protic and aprotic solvents.

    Directory of Open Access Journals (Sweden)

    ALEKSANDAR D. MARINKOVIC

    2005-04-01

    Full Text Available Rate constants for the reaction of diazodiphenylmethane with isomeric pyridine carboxylic acids were determined in chosen protic and aprotic solvents at 30 °C, using the well known UV spectrophotometric method. The values of the rate constants of the investigated acids in protic solvents were higher than those in aprotic solvents. The second order rate constants were correlated with solvent parameters using the Kamlet-Taft solvatochromic equation in the form: log k = log k0 + sp* + aa + bb . The correlation of the obtained kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The signs of the equation coefficients were in agreement with the postulated reaction mechanism. The mode of the influence of the solvent on the reaction rate in all the investigated acids are discussed on the basis of the correlation results.

  2. Behaviour of solvent extraction of niobium in nitric acid

    International Nuclear Information System (INIS)

    Lin Cansheng; Huang Meixin; Zhang Xianzi; Zhang Chonghai

    1988-01-01

    The behaviour of solvent extraction of niobium is discussed. The expractants, includding TBP, HDBP, H 2 MBP, TBP irradiated, HDEHP, TTA and Aliquat-7402, are used. The special influence of molybdenum and zirconium on solvent extraction of niobium and the extraction behaviur of niobium with TBP irradiated are described. The effect of fluorine and uranium in aqueous phase on extraction of niobium is mentioned. It is observed that the interfacial crud has not relevance to D Nb , but niobium-95 can be absorbed on it. The species of extractable niobium, extraction mechanism, and the reason brought niobum into organic phase are discussed. Finally, the idea of increasing decontamination factor for niobium is suggested

  3. Uranium reextraction from D2EHPA-TOPO solvent

    International Nuclear Information System (INIS)

    Duarte Neto, J.

    1985-01-01

    A comparative study for recovering uranium from the solvent D 2 EHPA-TOPO (di-2-ethyl hexyl phosphoric acid - tri-n-octyl phosphine oxide) with ammonium carbonate and sodium carbonate solutions has been made. The paper discusses the precipitation of iron during stripping and the extracctant solubilization in the aqueous phases. Continuous tests showed that uranium is efficiently stripped from the solvent by using both solutions and that the choice of a specific system is dependent on the uranium precipitation mechanism to be employed. (Author) [pt

  4. Separation of rare earth metal using micro solvent extraction system

    International Nuclear Information System (INIS)

    Nishihama, S.; Tajiri, Y.; Yoshizuka, K.

    2005-01-01

    A micro solvent extraction system for the separation of rare earth metals has been investigated. The micro flow channel was fabricated on a PMMA plate. Extraction equilibrium was quickly achieved, without any mechanical mixing. The solvent extraction results obtained for the Pr/Sm binary solutions revealed that both rare earth metals are firstly extracted together. Following, the Pr is extracted in the organic solution and Sm remains in the aqueous phase. The phase separation can be successively achieved by contriving the cross section of the flow channel

  5. Positron lifetime studies of the hcp to fcc transformation induced by mechanical attrition of elemental titanium

    International Nuclear Information System (INIS)

    Manna, I.; Chattopadhyay, P.P.; Nandi, P.; Nambissan, P.M.G.

    2004-01-01

    Nanocrystallisation by planetary ball-milling of high purity elemental titanium (Ti) revealed a polymorphic transformation from its normal hexagonal close packed (hcp) structure to a face-centered cubic (fcc) phase. Positron lifetime measurements were carried out on samples collected after different hours of milling to characterize the defect structures at grain surfaces. With increasing hours of milling, the nanocrystalline grain size decreased and the positron lifetimes--one related to the annihilation at the grain surfaces and the other to that at the intergranular open volume domains--increased significantly due to the increased free volume at the trapping vacancy sites. However, between 5 to 10 hours of milling, the two lifetimes decreased before resuming increasing once again. This marked deviation from an otherwise expected continuous increase of positron lifetime coincided with structural rearrangement within the system bringing in an enhancement in the density of electrons. The repacking of atoms along the [0001] crystallographic direction could be a possibility for this observation. Positron radiation effects on the migration and agglomeration of nanoparticles are also discussed

  6. Iodine removing method in organic solvent

    International Nuclear Information System (INIS)

    Suzuki, Takeo; Sakurai, Manabu

    1988-01-01

    Purpose: To effectively remove iodine in an organic solvent to thereby remove iodine in the solvent that can be re-used or put to purning treatment. Method: Organic solvent formed from wastes of nuclear facilities is mixed with basic lead acetate, or silica gel or activated carbon incorporated with such a compound to adsorb iodine in the organic solvent to the basic lead acetate. Then, iodine in the organic solvent is removed by separating to eliminate the basic lead acetate adsorbing iodine from the organic solvent or by passing the organic solvent through a tower or column charged or pre-coated with silica gel or activated carbon incorporated with lead acetate. By using basic lead acetate as the adsorbents, iodine can effective by adsorbed and eliminated. Thus, the possibility of circumstantial release of iodine can be reduced upon reusing or burning treatment of the organic solvent. (Kamimura, M.)

  7. Computer Aided Solvent Selection and Design Framework

    DEFF Research Database (Denmark)

    Mitrofanov, Igor; Conte, Elisa; Abildskov, Jens

    and computer-aided tools and methods for property prediction and computer-aided molecular design (CAMD) principles. This framework is applicable for solvent selection and design in product design as well as process design. The first module of the framework is dedicated to the solvent selection and design...... in terms of: physical and chemical properties (solvent-pure properties); Environment, Health and Safety (EHS) characteristic (solvent-EHS properties); operational properties (solvent–solute properties). 3. Performing the search. The search step consists of two stages. The first is a generation and property...... identification of solvent candidates using special software ProCAMD and ProPred, which are the implementations of computer-aided molecular techniques. The second consists of assigning the RS-indices following the reaction–solvent and then consulting the known solvent database and identifying the set of solvents...

  8. Canyon solvent cleaning with solid adsorbents

    International Nuclear Information System (INIS)

    Reif, D.J.

    1987-01-01

    The HM Process at the Savannah River Plant (SRP) uses 7.5% tributyl phosphate in n-paraffin as an extraction solvent. During use, the solvent is altered due to hydrolysis and radiolysis, forming materials that influence product losses, product decontamination, and separation efficiencies. Laboratory studies to improve online solvent cleaning have shown that carbonate washing, although removing residual solvent activity, does not remove binding ligands that hold fission products in the solvent. Treatment of solvent with a solid adsorbent removes binding ligands and significantly improves recycle solvent performance. Both laboratory work defining a full-scale adsorption process and the use of the process to clean HM Process first cycle solvent are presented

  9. 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.

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

    International Nuclear Information System (INIS)

    Stek, M. Jr.; Dean, D.A.; Clark, S.S.

    1981-01-01

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

  11. Recent solvent extraction experience at Savannah River

    International Nuclear Information System (INIS)

    Gray, L.W.; Burney, G.A.; Gray, J.H.; Hodges, M.E.; Holt, D.L.; Macafee, I.M.; Reif, D.J.; Shook, H.E.

    1986-01-01

    Tributyl phosphate-based solvent extraction processes have been used at Savannah River for more than 30 years to separate and purify thorium, uranium, neptunium, plutonium, americium, and curium isotopes. This report summarizes the advancement of solvent extraction technology at Savannah River during the 1980's. Topics that are discussed include equipment improvements, solvent treatment, waste reduction, and an improved understanding of the various chemistries in the process streams entering, within, and leaving the solvent extraction processes

  12. Solvent extraction studies of RERTR silicide fuels

    International Nuclear Information System (INIS)

    Gouge, Anthony P.

    1983-01-01

    Uranium silicide fuels, which are candidate RERTR fuel compositions, may require special considerations in solvent extraction reprocessing. Since Savannah River Plant may be reprocessing RERTR fuels as early as 1985, studies have been conducted at Savannah River Laboratory to demonstrate the solvent extraction behavior of this fuel. Results of solvent extraction studies with both unirradiated and irradiated fuel are presented along with the preliminary RERTR solvent extraction reprocessing flow sheet for Savannah River Plant. (author)

  13. 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.

  14. Medical school attrition-beyond the statistics a ten year retrospective study.

    Science.gov (United States)

    Maher, Bridget M; Hynes, Helen; Sweeney, Catherine; Khashan, Ali S; O'Rourke, Margaret; Doran, Kieran; Harris, Anne; Flynn, Siun O'

    2013-01-31

    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. 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. 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 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. 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 medical schools have a duty of care to support students who leave the medical programme.

  15. 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.

  16. 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

  17. 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

  18. Attrition, elutriation, and growth of particles produced in fluidized-bed waste calciners

    International Nuclear Information System (INIS)

    McDonald, F.N.

    1982-09-01

    The Idaho Chemical Processing Plant reduces the volume of high-level liquid radioactive wastes in a fluidized bed to produce a granular calcine product. In the past, difficulties have been experienced in controlling the product's particle size when processing certain blends of sodium-bearing waste. Therefore, experiments in attrition, elutriation, and particle growth were done to characterize how best to control these three parameters. 15 figures, 16 tables

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

    Science.gov (United States)

    2015-02-01

    Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free Process Control Agent by Frank Kellogg , Clara Hofmeister...Process Control Agent Frank Kellogg Bowhead Science and Technology Clara Hofmeister Advanced Materials Processing and Analysis Center...NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Frank Kellogg , Clara Hofmeister, Anit Giri, and Kyu Cho 5d. PROJECT NUMBER 5e

  20. Non-Rated Air Force Line Officer Attrition Rates Using Survival Analysis

    Science.gov (United States)

    2015-03-26

    Further complicating human resourcing, all Air Force members–enlisted and officer–start at entry-level. Personnel entering the Air Force inventory are...the system [8]. Chi-squared automatic interaction detection (CHAID) is an algorithm “to predict the response behaviour [sic] of individuals as...branches with the highest probability may require incentives to increase attrition. The branches could be defined by gender, career field, religion

  1. Predicting Active Duty Air Force Pilot Attrition Given an Anticipated Increase in Major Airline Pilot Hiring

    Science.gov (United States)

    2015-01-01

    the Air Force in addressing some quality-of-life issues, such as updating 3,800 family housing units, 21 dormitories, and building three child ...of pilots into the airlines (Air Force Personnel Center, FY 07). By allowing this crop of pilots to leave on the Air Force’s terms, the service felt...attrition rates compared with pilots with more general skills (flying mobility aircraft) (Stephen P. Barrows, 1993). This may be due to the phenomenon in

  2. Carbothermic reduction of uranium oxides into solvent metallic baths

    International Nuclear Information System (INIS)

    Guisard Restivo, Thomaz A.; Capocchi, Jose D.T.

    2004-01-01

    The carbothermic reduction of UO 2 and U 3 O 8 is studied employing tin and silicon solvent metallic baths in thermal analysis equipment, under Ar inert and N 2 reactive atmospheres. The metallic solvents are expected to lower the U activity by several orders of magnitude owing to strong interactions among the metals. The reduction products are composed of the solvent metal matrix and intermetallic U compounds. Silicon is more effective in driving the reduction since there is no residual UO 2 after the reaction. The gaseous product detected by mass spectrometer (MS) during the reduction is CO. A kinetic study for the Si case was accomplished by the stepwise isothermal analysis (SAI) method, leading to the identification of the controlling mechanisms as chemical reaction at the surface and nucleation, for UO 2 and U 3 O 8 charges, respectively. One example for another system containing Al 2 O 3 is also shown

  3. Separation of lanthanides using micro solvent extraction system

    International Nuclear Information System (INIS)

    Nishihama, S.; Tajiri, Y.; Yoshizuka, K.

    2006-01-01

    A micro solvent extraction system for the separation of lanthanides has been investigated. The micro flow channel is fabricated on a poly(methyl methacrylate) (PMMA) plate, and solvent extraction progresses by feeding aqueous and organic solutions into the channel simultaneously. The extraction equilibrium is quickly achieved, without any mechanical mixing, when a narrow channel (100 μm width and 100 μm depth) is used. The results of solvent extraction from the Pr/Nd and Pr/Sm binary solutions revealed that both lanthanides are firstly extracted together, and then, the lighter lanthanide extracted in the organic solution alternatively exchanges to the heavier one in the aqueous solution to achieve the extraction equilibrium. The phase separation of the aqueous and organic phases after extraction can also be successively achieved by contriving the cross section of the flow channel, and the extractive separation of Pr/Sm is demonstrated. (authors)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-01-01

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

  5. 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.

  6. Contribution to the study of the degradation of the solvent used in a nuclear fuel reprocessing plant

    International Nuclear Information System (INIS)

    Goasmat, F.

    1984-01-01

    The degradation of a mixed solvent (tributylphosphate - hydrocarbons) in a fuel reprocessing plant (UP 2 at La Hague, France) is studied in this thesis. Laboratory studies on degradation mechanisms, decomposition products and regeneration processes are reviewed in a bibliographic synthesis. Solvent degradation is investigated on a real solvent from a reprocessing plant. Influence of degradation on solvent performance is shown and regeneration processes should be improved. Many regeneration processes are tested on solvent from the plant and results are discussed. Separation and analysis of degradation products show the polyfunctional structure of compounds formed [fr

  7. Restoring solvent for nuclear separation processes

    International Nuclear Information System (INIS)

    Reif, D.J.

    1987-01-01

    Solvent extraction separation processes are used to recover usable nuclear materials from spent fuels. These processes involve the use of an extractant/diluent (solvent) for separation of the reusable actinides from unwanted fission products. The most widely used processes employ tributyl phosphate as an extractant diluted with a normal-paraffin hydrocarbon. During use, the solvent is altered due to hydrolysis and radiolysis, forming materials that influence product losses, product decontamination, and separation efficiencies. In most processes, the solvent is recycled after cleaning. Solvent cleaning generally involves scrubbing with a sodium carbonate solution. Studies at the Savannah River Laboratory have shown that carbonate washing, although removing residual solvent activity, does not remove more solvent-soluble binding ligands (formed by solvent degradation), which hold fission products in the solvent. Treatment of the solvent with a solid adsorbent after carbonate washing removes binding ligands and significantly improves recycled solvent performance. Laboratory work to establish the advantage of adsorbent cleaning and the development of a full-scale adsorption process is described. The application of this process for cleaning the first cycle solvent of a Savannah River Plant production process is discussed

  8. Solvent Extraction of Furfural From Biomass

    Science.gov (United States)

    Humphrey, M. F.

    1984-01-01

    Solvent-extraction method reduces energy required to remove furfural produced during acid hydrolysis of biomass. Acid hydrolysis performed in vessel containing both solvents and reacting ingredients. With intimate contact between solvents and aqueous hydrolyis liqour, furfural removed form liquor almost as fast as it forms.

  9. Adaptive Resolution Simulation of MARTINI Solvents

    NARCIS (Netherlands)

    Zavadlav, Julija; Melo, Manuel N.; Cunha, Ana V.; de Vries, Alex H.; Marrink, Siewert J.; Praprotnik, Matej

    We present adaptive resolution dynamics simulations of aqueous and apolar solvents coarse-grained molecular models that are compatible with the MARTINI force field. As representatives of both classes solvents we have chosen liquid water and butane, respectively, at ambient temperature. The solvent

  10. 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.

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

    International Nuclear Information System (INIS)

    Timpson, M.E.; Elless, M.P.; Francis, C.W.

    1994-01-01

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

  12. 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 Medline, 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. © 2013 National Association for Healthcare Quality.

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

    International Nuclear Information System (INIS)

    Mastin, A.J.; Wilson, R.A.; Bickle, Q.D.

    1983-01-01

    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. (author)

  14. Factors affecting employee attrition among engineers and non-engineers in manufacturing industry

    Directory of Open Access Journals (Sweden)

    Bhardwaj, Shikha

    2017-12-01

    Full Text Available Almost every industry nowadays is badly affected by attrition. Retention of talented employees is the biggest problem faced by India Incorporation. In order to gather more insights on the talent crunch, the undertaken study was conducted on technical and non-technical jobs in manufacturing sector in Delhi NCR. Research has identified three major factors – Salary, Boss and Stress in the jobs after conducted interviews with around 50 technical and non-technical respondents. A set of questions were prepared and send to 120 employee but only 75 responded. The study shows a strong relationship between type of job and factors of attrition. Chi-square test clearly states strong relationship among two. Thus, any change in one will affect the other also. At the same time other important outcomes were that for technical jobs salary is the most important factor whereas non-technical Boss is the factor. Out 75, 63 were engineer and rest were non-engineer. The research can be further done to understand factors of attrition with other demographic variable.

  15. The Solvent Selection framework: solvents for organic synthesis, separation processes and ionic-organic synthesis

    DEFF Research Database (Denmark)

    Mitrofanov, Igor; Sansonetti, Sascha; Abildskov, Jens

    2012-01-01

    This paper presents a systematic integrated framework for solvent selection and solvent design. The framework is divided into several modules, which can tackle specific problems in various solvent-based applications. In particular, three modules corresponding to the following solvent selection pr...

  16. Solvent cleaning system and method for removing contaminants from solvent used in resin recycling

    Science.gov (United States)

    Bohnert, George W [Harrisonville, MO; Hand, Thomas E [Lee's Summit, MO; DeLaurentiis, Gary M [Jamestown, CA

    2009-01-06

    A two step solvent and carbon dioxide based system that produces essentially contaminant-free synthetic resin material and which further includes a solvent cleaning system for periodically removing the contaminants from the solvent so that the solvent can be reused and the contaminants can be collected and safely discarded in an environmentally safe manner.

  17. Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation

    Directory of Open Access Journals (Sweden)

    Matthews Fiona E

    2004-04-01

    Full Text Available Abstract Background Any hypothesis in longitudinal studies may be affected by attrition and poor response rates. The MRC Cognitive Function and Ageing study (MRC CFAS is a population based longitudinal study in five centres with identical methodology in England and Wales each recruiting approximately 2,500 individuals. This paper aims to identify potential biases in the two-year follow-up interviews. Methods Initial non-response: Those not in the baseline interviews were compared in terms of mortality to those who were in the baseline interviews at the time of the second wave interviews (1993–1996. Longitudinal attrition: Logistic regression analysis was used to examine baseline differences between individuals who took part in the two-year longitudinal wave compared with those who did not. Results Initial non-response: Individuals who moved away after sampling but before baseline interview were 1.8 times more likely to die by two years (95% Confidence interval(CI 1.3–2.4 compared to respondents, after adjusting for age. The refusers had a slightly higher, but similar mortality pattern to responders (Odds ratio 1.2, 95%CI 1.1–1.4. Longitudinal attrition: Predictors for drop out due to death were being older, male, having impaired activities of daily living, poor self-perceived health, poor cognitive ability and smoking. Similarly individuals who refused were more likely to have poor cognitive ability, but had less years of full-time education and were more often living in their own home though less likely to be living alone. There was a higher refusal rate in the rural centres. Individuals who moved away or were uncontactable were more likely to be single, smokers, demented or depressed and were less likely to have moved if in warden-controlled accommodation at baseline. Conclusions Longitudinal estimation of factors mentioned above could be biased, particularly cognitive ability and estimates of movements from own home to residential homes

  18. 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 (χ 2 2 =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 (F 2,262 =1.534, P=.21, partial η 2 =0.012). Our findings raise doubts about the ability of gamification to reduce attrition from longitudinal cognitive testing studies

  19. Insecticide solvents: interference with insecticidal action.

    Science.gov (United States)

    Brattsten, L B; Wilkinson, C F

    1977-06-10

    Several commercial solvent mixtures commonly used as insecticide carriers in spray formulations increase by more than threefold the microsomal N-demethylation of p-chloro N-methylaniline in midgut preparations of southern army-worm (Spodoptera eridania) larvae exposed orally to the test solvents. Under laboratory conditions, the same solvent mixtures exhibit a protective action against the in vivo toxicity of the insecticide carbaryl to the larvae. The data are discussed with respect to possible solvent-insecticide interactions occurring under field conditions and, more broadly, to potential toxicological hazards of these solvents to humans.

  20. Organic solvents in electromembrane extraction: recent insights

    DEFF Research Database (Denmark)

    Huang, Chuixiu; Gjelstad, Astrid; Pedersen-Bjergaard, Stig

    2016-01-01

    the introduction. Under the influence of an electrical field, EME is based on electrokinetic migration of the analytes through a supported liquid membrane (SLM), which is an organic solvent immobilized in the pores of the polymeric membrane, and into the acceptor solution. Up to date, close to 150 research...... articles with focus on EME have been published. The current review summarizes the performance of EME with different organic solvents and discusses several criteria for efficient solvents in EME. In addition, the authors highlight their personal perspective about the most promising organic solvents for EME...... and have indicated that more fundamental work is required to investigate and discover new organic solvents for EME....

  1. Alternative solvents for natural products extraction

    CERN Document Server

    Chemat, Farid

    2014-01-01

    This book presents a complete picture of the current state-of-the-art in alternative and green solvents used for laboratory and industrial natural product extraction in terms of the latest innovations, original methods and safe products. It provides the necessary theoretical background and details on extraction, techniques, mechanisms, protocols, industrial applications, safety precautions and environmental impacts. This book is aimed at professionals from industry, academicians engaged in extraction engineering or natural product chemistry research, and graduate level students. The individual chapters complement one another, were written by respected international researchers and recognized professionals from the industry, and address the latest efforts in the field. It is also the first sourcebook to focus on the rapid developments in this field.

  2. Solvent extraction studies on cadmium. Pt. 2

    International Nuclear Information System (INIS)

    Alian, A.; Badran, A.; El-Bassiouny, M.S.

    1975-01-01

    An extraction study was performed on tracer concentrations of cadmium, zinc and silver halides in absence and presence of phosphoric acid. A long chain amine (Amberlite LA-2) and an organophosphorus solvent (TBP) have been investigated. Since orthophosphoric acid was found to have a similar role as sulphuric acid, it was interesting to carry out a systematic investigation on the extraction behaviour of the halides of the three elements Cs, Zn and Ag in orthophosphoric acid medium. The separation of Cd from Zn or Ag is frequently encountered in chemical as well as radiochemical analysis. The results presented here give many possibilities for such separation. Amberlite LA-2 was always used as 5 vol% and TBP as 50 vol% in benzene. The presence of phosphoric acid was found to enhance considerably the extraction of most halides. The mechanism of extraction has been discussed in light of the obtained results. (T.G.)

  3. Mechanics

    CERN Document Server

    Chester, W

    1979-01-01

    When I began to write this book, I originally had in mind the needs of university students in their first year. May aim was to keep the mathematics simple. No advanced techniques are used and there are no complicated applications. The emphasis is on an understanding of the basic ideas and problems which require expertise but do not contribute to this understanding are not discussed. How­ ever, the presentation is more sophisticated than might be considered appropri­ ate for someone with no previous knowledge of the subject so that, although it is developed from the beginning, some previous acquaintance with the elements of the subject would be an advantage. In addition, some familiarity with element­ ary calculus is assumed but not with the elementary theory of differential equations, although knowledge of the latter would again be an advantage. It is my opinion that mechanics is best introduced through the motion of a particle, with rigid body problems left until the subject is more fully developed. Howev...

  4. Efforts Aimed To Reduce Attrition in Antimalarial Drug Discovery: A Systematic Evaluation of the Current Antimalarial Targets Portfolio.

    Science.gov (United States)

    Chaparro, María Jesús; Calderón, Félix; Castañeda, Pablo; Fernández-Alvaro, Elena; Gabarró, Raquel; Gamo, Francisco Javier; Gómez-Lorenzo, María G; Martín, Julio; Fernández, Esther

    2018-04-13

    Malaria remains a major global health problem. In 2015 alone, more than 200 million cases of malaria were reported, and more than 400,000 deaths occurred. Since 2010, emerging resistance to current front-line ACTs (artemisinin combination therapies) has been detected in endemic countries. Therefore, there is an urgency for new therapies based on novel modes of action, able to relieve symptoms as fast as the artemisinins and/or block malaria transmission. During the past few years, the antimalarial community has focused their efforts on phenotypic screening as a pragmatic approach to identify new hits. Optimization efforts on several chemical series have been successful, and clinical candidates have been identified. In addition, recent advances in genetics and proteomics have led to the target deconvolution of phenotypic clinical candidates. New mechanisms of action will also be critical to overcome resistance and reduce attrition. Therefore, a complementary strategy focused on identifying well-validated targets to start hit identification programs is essential to reinforce the clinical pipeline. Leveraging published data, we have assessed the status quo of the current antimalarial target portfolio with a focus on the blood stage clinical disease. From an extensive list of reported Plasmodium targets, we have defined triage criteria. These criteria consider genetic, pharmacological, and chemical validation, as well as tractability/doability, and safety implications. These criteria have provided a quantitative score that has led us to prioritize those targets with the highest probability to deliver successful and differentiated new drugs.

  5. Investigation of factors influencing the attrition breakage of coal

    Energy Technology Data Exchange (ETDEWEB)

    Oberholzer, V.; van der Walt, J. [North West University, Mmabatho (South Africa). School of Chemical & Minerals Engineering

    2009-04-15

    The presence of fines (particles smaller than 6 mm in diameter) causes hydrodynamic problems in gasifiers and therefore it is of great importance to minimize the amount of fine coal in the feed. This serves as motivation for understanding coal's breakage mechanisms, which could lead to the ability to predict the generation of fines. The aim of this project was to simulate the pulsating effect of the conveyor belt in order to investigate factors influencing the breakage. Results indicated that an increased initial particle size had an increasing effect in the amount of fines generated. Weathering had an insignificant effect on the breakage of coal. To conclude, a breakage model was developed to describe the rate of breakage out of the top size when a combination of two breakage modes is present.

  6. Effect of water-methanol mixed solvents on the ultrasonic relaxation of cadmium acetate

    International Nuclear Information System (INIS)

    Sree Rama Murthy, J.; Ramachandra Rao, B.

    1976-01-01

    Measurements of ultrasonic absorption have been made by pulse technique in 1 M solutions of cadmium acetate with water-methanol mixed solvents. Results are analysed by assuming a single relaxation mechanism. The characteristic frequency of relaxation is found to decrease with increasing composition of methanol in the solvent. It is proposed that the mechanism of relaxation may be perturbation of chemical equilibrium between complex CdAc + ions and Cd ++ , Ac - species by soundwaves. (author)

  7. Are pilot trials useful for predicting randomisation and attrition rates in definitive studies: A review of publicly funded trials

    Science.gov (United States)

    Whitehead, Amy; Pottrill, Edward; Julious, Steven A; Walters, Stephen J

    2018-01-01

    Background/aims: External pilot trials are recommended for testing the feasibility of main or confirmatory trials. However, there is little evidence that progress in external pilot trials actually predicts randomisation and attrition rates in the main trial. To assess the use of external pilot trials in trial design, we compared randomisation and attrition rates in publicly funded randomised controlled trials with rates in their pilots. Methods: Randomised controlled trials for which there was an external pilot trial were identified from reports published between 2004 and 2013 in the Health Technology Assessment Journal. Data were extracted from published papers, protocols and reports. Bland–Altman plots and descriptive statistics were used to investigate the agreement of randomisation and attrition rates between the full and external pilot trials. Results: Of 561 reports, 41 were randomised controlled trials with pilot trials and 16 met criteria for a pilot trial with sufficient data. Mean attrition and randomisation rates were 21.1% and 50.4%, respectively, in the pilot trials and 16.8% and 65.2% in the main. There was minimal bias in the pilot trial when predicting the main trial attrition and randomisation rate. However, the variation was large: the mean difference in the attrition rate between the pilot and main trial was −4.4% with limits of agreement of −37.1% to 28.2%. Limits of agreement for randomisation rates were −47.8% to 77.5%. Conclusion: Results from external pilot trials to estimate randomisation and attrition rates should be used with caution as comparison of the difference in the rates between pilots and their associated full trial demonstrates high variability. We suggest using internal pilot trials wherever appropriate. PMID:29361833

  8. 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

  9. Advanced integrated solvent extraction systems

    Energy Technology Data Exchange (ETDEWEB)

    Horwitz, E.P.; Dietz, M.L.; Leonard, R.A. [Argonne National Lab., IL (United States)

    1997-10-01

    Advanced integrated solvent extraction systems are a series of novel solvent extraction (SX) processes that will remove and recover all of the major radioisotopes from acidic-dissolved sludge or other acidic high-level wastes. The major focus of this effort during the last 2 years has been the development of a combined cesium-strontium extraction/recovery process, the Combined CSEX-SREX Process. The Combined CSEX-SREX Process relies on a mixture of a strontium-selective macrocyclic polyether and a novel cesium-selective extractant based on dibenzo 18-crown-6. The process offers several potential advantages over possible alternatives in a chemical processing scheme for high-level waste treatment. First, if the process is applied as the first step in chemical pretreatment, the radiation level for all subsequent processing steps (e.g., transuranic extraction/recovery, or TRUEX) will be significantly reduced. Thus, less costly shielding would be required. The second advantage of the Combined CSEX-SREX Process is that the recovered Cs-Sr fraction is non-transuranic, and therefore will decay to low-level waste after only a few hundred years. Finally, combining individual processes into a single process will reduce the amount of equipment required to pretreat the waste and therefore reduce the size and cost of the waste processing facility. In an ongoing collaboration with Lockheed Martin Idaho Technology Company (LMITCO), the authors have successfully tested various segments of the Advanced Integrated Solvent Extraction Systems. Eichrom Industries, Inc. (Darien, IL) synthesizes and markets the Sr extractant and can supply the Cs extractant on a limited basis. Plans are under way to perform a test of the Combined CSEX-SREX Process with real waste at LMITCO in the near future.

  10. Anti-solvent co-crystallization of carbamazepine and saccharin.

    Science.gov (United States)

    Wang, In-Chun; Lee, Min-Jeong; Sim, Sang-Jun; Kim, Woo-Sik; Chun, Nan-Hee; Choi, Guang J

    2013-06-25

    The co-crystal approach has been investigated extensively over the past decade as one of the most promising methods to enhance the dissolution properties of insoluble drug substances. Co-crystal powders are typically produced by mechanical grinding (neat or wet) or a solution method (evaporation or cooling). In this study, high-purity carbamazepine-saccharin (CBZ-SAC) co-crystals were manufactured by a novel method, anti-solvent addition. Among various solvents, methanol was found to perform well with water as the anti-solvent for the co-crystallization of CBZ and SAC. When water was added to the methanol solution of CBZ and SAC at room temperature under agitation, nucleation of CBZ-SAC co-crystals occurred within 2-3 min. Co-crystallization was complete after 30 min, giving a solid yield as high as 84.5% on a CBZ basis. The effects of initial concentrations, focusing on the SAC/CBZ ratio, were examined to establish optimal conditions. The whole anti-solvent co-crystallization process was monitored at-line via ATR-FTIR analysis of regularly sampled solutions. The nucleation and crystal growth of CBZ-SAC co-crystals were detected by a significant increase in absorption in the range of 2400-2260 cm(-1), associated with the formation of hydrogen bonds between the carbonyl group in CBZ and the N-H of SAC. When CBZ hydrates were formed as impurities during anti-solvent co-crystallization, the hydrogen bonding between methanol and water was reduced greatly, primarily due to the incorporation of water molecules into the CBZ crystal lattice. In conclusion, an anti-solvent approach can be used to produce highly pure CBZ-SAC co-crystal powders with a high solid yield. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Theory of polyelectrolytes in solvents.

    Science.gov (United States)

    Chitanvis, Shirish M

    2003-12-01

    Using a continuum description, we account for fluctuations in the ionic solvent surrounding a Gaussian, charged chain and derive an effective short-ranged potential between the charges on the chain. This potential is repulsive at short separations and attractive at longer distances. The chemical potential can be derived from this potential. When the chemical potential is positive, it leads to a meltlike state. For a vanishingly low concentration of segments, this state exhibits scaling behavior for long chains. The Flory exponent characterizing the radius of gyration for long chains is calculated to be approximately 0.63, close to the classical value obtained for second order phase transitions. For short chains, the radius of gyration varies linearly with N, the chain length, and is sensitive to the parameters in the interaction potential. The linear dependence on the chain length N indicates a stiff behavior. The chemical potential associated with this interaction changes sign, when the screening length in the ionic solvent exceeds a critical value. This leads to condensation when the chemical potential is negative. In this state, it is shown using the mean-field approximation that spherical and toroidal condensed shapes can be obtained. The thickness of the toroidal polyelectrolyte is studied as a function of the parameters of the model, such as the ionic screening length. The predictions of this theory should be amenable to experimental verification.

  12. Attrition Bias in Panel Data: A Sheep in Wolf's Clothing? A Case Study Based on the Mabel Survey.

    Science.gov (United States)

    Cheng, Terence C; Trivedi, Pravin K

    2015-09-01

    This paper investigates the nature and consequences of sample attrition in a unique longitudinal survey of medical doctors. We describe the patterns of non-response and examine if attrition affects the econometric analysis of medical labour market outcomes using the estimation of physician earnings equations as a case study. We compare the econometric gestimates obtained from a number of different modelling strategies, which are as follows: balanced versus unbalanced samples; an attrition model for panel data based on the classic sample selection model; and a recently developed copula-based selection model. Descriptive evidence shows that doctors who work longer hours, have lower years of experience, are overseas trained and have changed their work location are more likely to drop out. Our analysis suggests that the impact of attrition on inference about the earnings of general practitioners is small. For specialists, there appears to be some evidence for an economically significant bias. Finally, we discuss how the top-up samples in the Medicine in Australia: Balancing Employment and Life survey can be used to address the problem of panel attrition. Copyright © 2015 John Wiley & Sons, Ltd.

  13. Attrition of memory CD8 T cells during sepsis requires LFA-1.

    Science.gov (United States)

    Serbanescu, Mara A; Ramonell, Kimberly M; Hadley, Annette; Margoles, Lindsay M; Mittal, Rohit; Lyons, John D; Liang, Zhe; Coopersmith, Craig M; Ford, Mandy L; McConnell, Kevin W

    2016-11-01

    CD8 T cell loss and dysfunction have been implicated in the increased susceptibility to opportunistic infections during the later immunosuppressive phase of sepsis, but CD8 T cell activation and attrition in early sepsis remain incompletely understood. With the use of a CLP model, we assessed CD8 T cell activation at 5 consecutive time points and found that activation after sepsis results in a distinct phenotype (CD69 + CD25 int CD62L HI ) independent of cognate antigen recognition and TCR engagement and likely through bystander-mediated cytokine effects. Additionally, we observed that sepsis concurrently results in the preferential depletion of a subset of memory-phenotype CD8 T cells that remain "unactivated" (i.e., fail to up-regulate activation markers) by apoptosis. Unactivated CD44 HI OT-I cells were spared from sepsis-induced attrition, as were memory-phenotype CD8 T cells of mice treated with anti-LFA-1 mAb, 1 h after CLP. Perhaps most importantly, we demonstrate that attrition of memory phenotype cells may have a pathologic significance, as elevated IL-6 levels were associated with decreased numbers of memory-phenotype CD8 T cells in septic mice, and preservation of this subset after administration of anti-LFA-1 mAb conferred improved survival at 7 d. Taken together, these data identify potentially modifiable responses of memory-phenotype CD8 T cells in early sepsis and may be particularly important in the application of immunomodulatory therapies in sepsis. © Society for Leukocyte Biology.

  14. Biodegradation of Chlorinated Solvents: Reactions near DNAPL and Enzyme Function

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, P. L.; Spormann, Alfred M.; Criddle, Craig, S.

    2003-12-11

    Chlorinated solvents are among the most widespread groundwater contaminants in the country, contamination which is also among the most difficult and expensive for remediation. These solvents are biodegradable in the absence of oxygen, but this biodegradation requires both a food source for the organisms (electron donor) and the presence of chlorinated solvent biodegrading organisms. These two requirements are present naturally at some contamination sites, leading to natural attenuation of the solvents. If one or both requirements are absent, then engineered bioremediation either through addition of an external electron donor or through bioaugmentation with appropriate microorganisms, or both, may be used for site remediation. The most difficult case for cleanup is when a large residual of undissolved chlorinated solvents are present, residing as dense -non-aqueous-phase- liquid ( DNAPL). A major focus of this study was on the potential for biodegradation of the solvents when pre sent as DNAPL where concentrations are very high and potential for toxicity to microorganisms exist. Another focus was on a better understanding of the biological mechanisms involved in chlorinated solvent biodegradation . These studies were directed towards the chlorinated solvents, trichloroethene (TCE), tetrachloroethene or perchloroethene (PCE), and carbon tetrachloride (CT). The potential for biodegradation of TCE and PCE DNAPL was clearly demonstrated in this research. From column soil studies and batch studies we found there to be a clear advantage in focusing efforts at bioremediation near the DNAPL. Here, chlorinated solvent concentrations are the highest, both because of more favorable reaction kinetics and because such high solvent concentrations are toxic to microorganisms, such as methanogens, which compete with dehalogenators for the electron donor. Additionally, biodegradation near a PCE DNAPL results in an enhanced dissolution rate for the chlorinated solvent, by factors of

  15. Biodegradation of Chlorinated Solvents: Reactions near DNAPL and Enzyme Function

    International Nuclear Information System (INIS)

    McCarty, P. L.; Spormann, Alfred M.; Criddle, Craig S.

    2003-01-01

    Chlorinated solvents are among the most widespread groundwater contaminants in the country, contamination which is also among the most difficult and expensive for remediation. These solvents are biodegradable in the absence of oxygen, but this biodegradation requires both a food source for the organisms (electron donor) and the presence of chlorinated solvent biodegrading organisms. These two requirements are present naturally at some contamination sites, leading to natural attenuation of the solvents. If one or both requirements are absent, then engineered bioremediation either through addition of an external electron donor or through bioaugmentation with appropriate microorganisms, or both, may be used for site remediation. The most difficult case for cleanup is when a large residual of undissolved chlorinated solvents are present, residing as dense -non-aqueous-phase- liquid ( DNAPL). A major focus of this study was on the potential for biodegradation of the solvents when pre sent as DNAPL where concentrations are very high and potential for toxicity to microorganisms exist. Another focus was on a better understanding of the biological mechanisms involved in chlorinated solvent biodegradation . These studies were directed towards the chlorinated solvents, trichloroethene (TCE), tetrachloroethene or perchloroethene (PCE), and carbon tetrachloride (CT). The potential for biodegradation of TCE and PCE DNAPL was clearly demonstrated in this research. From column soil studies and batch studies we found there to be a clear advantage in focusing efforts at bioremediation near the DNAPL. Here, chlorinated solvent concentrations are the highest, both because of more favorable reaction kinetics and because such high solvent concentrations are toxic to microorganisms, such as methanogens, which compete with dehalogenators for the electron donor. Additionally, biodegradation near a PCE DNAPL results in an enhanced dissolution rate for the chlorinated solvent, by factors of

  16. 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

  17. 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.

  18. Attrition in longitudinal randomized controlled trials: home visits make a difference

    Directory of Open Access Journals (Sweden)

    Peterson Janey C

    2012-11-01

    Full Text Available Abstract Background Participant attrition in longitudinal studies can introduce systematic bias, favoring participants who return for follow-up, and increase the likelihood that those with complications will be underestimated. Our aim was to examine the effectiveness of home follow-up (Home F/U to complete the final study evaluation on potentially “lost” participants by: 1 evaluating the impact of including and excluding potentially “lost” participants (e.g., those who required Home F/U to complete the final evaluation on the rates of study complications; 2 examining the relationship between timing and number of complications on the requirement for subsequent Home F/U; and 3 determining predictors of those who required Home F/U. Methods We used data from a randomized controlled trial (RCT conducted from 1991–1994 among coronary artery bypass graft surgery patients that investigated the effect of High mean arterial pressure (MAP (intervention vs. Low MAP (control during cardiopulmonary bypass on 5 complications: cardiac morbidity/mortality, neurologic morbidity/mortality, all-cause mortality, neurocognitive dysfunction and functional decline. We enhanced completion of the final 6-month evaluation using Home F/U. Results Among 248 participants, 61 (25% required Home F/U and the remaining 187 (75% received Routine F/U. By employing Home F/U, we detected 11 additional complications at 6 months: 1 major neurologic complication, 6 cases of neurocognitive dysfunction and 4 cases of functional decline. Follow-up of 61 additional Home F/U participants enabled us to reach statistical significance on our main trial outcome. Specifically, the High MAP group had a significantly lower rate of the Combined Trial Outcome compared to the Low MAP group, 16.1% vs. 27.4% (p=0.032. In multivariate analysis, participants who were ≥ 75 years (OR=3.23, 95% CI 1.52-6.88, p=0.002 or on baseline diuretic therapy (OR=2.44, 95% CI 1.14-5.21, p=0.02 were more

  19. Sustainable development of gree solvent separation process

    OpenAIRE

    Lisickov, Kiril; Fidancevska, Emilija; Grujic, Radoslav; Srebrenkoska, Vineta; Kuvendziev, Stefan

    2011-01-01

    Solvents defi ne a major part of the environmental performance of processes in the chemical industry and impact on cost, safety and health issues. The idea of green solvents expresses the goal to minimize the environmental impact resulting from the use of solvents in chemical production. In spite of conventional separation methods, precise process green technologies are based on the application of modern processes and process equipment as well as control and management...

  20. Supercritical solvent extraction of oil sand bitumen

    Science.gov (United States)

    Imanbayev, Ye. I.; Ongarbayev, Ye. K.; Tileuberdi, Ye.; Mansurov, Z. A.; Golovko, A. K.; Rudyk, S.

    2017-08-01

    The supercritical solvent extraction of bitumen from oil sand studied with organic solvents. The experiments were performed in autoclave reactor at temperature above 255 °C and pressure 29 atm with stirring for 6 h. The reaction resulted in the formation of coke products with mineral part of oil sands. The remaining products separated into SARA fractions. The properties of the obtained products were studied. The supercritical solvent extraction significantly upgraded extracted natural bitumen.

  1. Canyon solvent cleaning with activated alumina

    International Nuclear Information System (INIS)

    Reif, D.J.

    1987-01-01

    This paper presents recent work at SRL concerning the cleaning of solvent extraction solvent used at SRP. The paper explains why we undertook the work, and some laboratory studies on two approaches to solvent cleaning, namely extended carbonate washing and use of solid adsorbents. The paper then discusses scale-up of the preferred method and the results of the full-scale cleaning. 19 figs

  2. Process for hydrogenating coal and coal solvents

    Energy Technology Data Exchange (ETDEWEB)

    Shridharani, K.G.; Tarrer, A.R.

    1983-02-15

    A novel process is described for the hydrogenation of coal by the hydrogenation of a solvent for the coal in which the hydrogenation of the coal solvent is conducted in the presence of a solvent hydrogenation catalyst of increased activity, wherein the hydrogenation catalyst is produced by reacting ferric oxide with hydrogen sulfide at a temperature range of 260/sup 0/ C to 315/sup 0/ C in an inert atmosphere to produce an iron sulfide hydrogenation catalyst for the solvent. Optimally, the reaction temperature is 275/sup 0/ C. Alternately, the reaction can be conducted in a hydrogen atmosphere at 350/sup 0/ C.

  3. Process for hydrogenating coal and coal solvents

    Science.gov (United States)

    Tarrer, Arthur R.; Shridharani, Ketan G.

    1983-01-01

    A novel process is described for the hydrogenation of coal by the hydrogenation of a solvent for the coal in which the hydrogenation of the coal solvent is conducted in the presence of a solvent hydrogenation catalyst of increased activity, wherein the hydrogenation catalyst is produced by reacting ferric oxide with hydrogen sulfide at a temperature range of 260.degree. C. to 315.degree. C. in an inert atmosphere to produce an iron sulfide hydrogenation catalyst for the solvent. Optimally, the reaction temperature is 275.degree. C. Alternately, the reaction can be conducted in a hydrogen atmosphere at 350.degree. C.

  4. Aminosilicone solvent recovery methods and systems

    Science.gov (United States)

    Spiry, Irina Pavlovna; Perry, Robert James; Wood, Benjamin Rue; Singh, Surinder Prabhjot; Farnum, Rachel Lizabeth; Genovese, Sarah Elizabeth

    2018-02-13

    The present invention is directed to aminosilicone solvent recovery methods and systems. The methods and systems disclosed herein may be used to recover aminosilicone solvent from a carbon dioxide containing vapor stream, for example, a vapor stream that leaves an aminosilicone solvent desorber apparatus. The methods and systems of the invention utilize a first condensation process at a temperature from about 80.degree. C. to about 150.degree. C. and a second condensation process at a temperature from about 5.degree. C. to about 75.degree. C. The first condensation process yields recovered aminosilicone solvent. The second condensation process yields water.

  5. Solvents and Parkinson disease: A systematic review of toxicological and epidemiological evidence

    International Nuclear Information System (INIS)

    Lock, Edward A.; Zhang, Jing; Checkoway, Harvey

    2013-01-01

    Parkinson disease (PD) is a debilitating neurodegenerative motor disorder, with its motor symptoms largely attributable to loss of dopaminergic neurons in the substantia nigra. The causes of PD remain poorly understood, although environmental toxicants may play etiologic roles. Solvents are widespread neurotoxicants present in the workplace and ambient environment. Case reports of parkinsonism, including PD, have been associated with exposures to various solvents, most notably trichloroethylene (TCE). Animal toxicology studies have been conducted on various organic solvents, with some, including TCE, demonstrating potential for inducing nigral system damage. However, a confirmed animal model of solvent-induced PD has not been developed. Numerous epidemiologic studies have investigated potential links between solvents and PD, yielding mostly null or weak associations. An exception is a recent study of twins indicating possible etiologic relations with TCE and other chlorinated solvents, although findings were based on small numbers, and dose–response gradients were not observed. At present, there is no consistent evidence from either the toxicological or epidemiologic perspective that any specific solvent or class of solvents is a cause of PD. Future toxicological research that addresses mechanisms of nigral damage from TCE and its metabolites, with exposure routes and doses relevant to human exposures, is recommended. Improvements in epidemiologic research, especially with regard to quantitative characterization of long-term exposures to specific solvents, are needed to advance scientific knowledge on this topic. -- Highlights: ► The potential for organic solvents to cause Parkinson's disease has been reviewed. ► Twins study suggests etiologic relations with chlorinated solvents and Parkinson's. ► Animal studies with TCE showed potential to cause damage to dopaminergic neurons. ► Need to determine if effects in animals are relevant to human exposure

  6. Solvents and Parkinson disease: A systematic review of toxicological and epidemiological evidence

    Energy Technology Data Exchange (ETDEWEB)

    Lock, Edward A., E-mail: e.lock@ljmu.ac.uk [Liverpool John Moores University, School of Pharmacy and Biomolecular Sciences, Byrom Street, Liverpool (United Kingdom); Zhang, Jing [University of Washington, Department of Pathology, School of Medicine, Seattle, WA (United States); Checkoway, Harvey [University of Washington, Department of Environmental and Occupational Health Sciences, Seattle, WA (United States)

    2013-02-01

    Parkinson disease (PD) is a debilitating neurodegenerative motor disorder, with its motor symptoms largely attributable to loss of dopaminergic neurons in the substantia nigra. The causes of PD remain poorly understood, although environmental toxicants may play etiologic roles. Solvents are widespread neurotoxicants present in the workplace and ambient environment. Case reports of parkinsonism, including PD, have been associated with exposures to various solvents, most notably trichloroethylene (TCE). Animal toxicology studies have been conducted on various organic solvents, with some, including TCE, demonstrating potential for inducing nigral system damage. However, a confirmed animal model of solvent-induced PD has not been developed. Numerous epidemiologic studies have investigated potential links between solvents and PD, yielding mostly null or weak associations. An exception is a recent study of twins indicating possible etiologic relations with TCE and other chlorinated solvents, although findings were based on small numbers, and dose–response gradients were not observed. At present, there is no consistent evidence from either the toxicological or epidemiologic perspective that any specific solvent or class of solvents is a cause of PD. Future toxicological research that addresses mechanisms of nigral damage from TCE and its metabolites, with exposure routes and doses relevant to human exposures, is recommended. Improvements in epidemiologic research, especially with regard to quantitative characterization of long-term exposures to specific solvents, are needed to advance scientific knowledge on this topic. -- Highlights: ► The potential for organic solvents to cause Parkinson's disease has been reviewed. ► Twins study suggests etiologic relations with chlorinated solvents and Parkinson's. ► Animal studies with TCE showed potential to cause damage to dopaminergic neurons. ► Need to determine if effects in animals are relevant to human

  7. Solvent cleanup using base-treated silica gel solid adsorbent

    International Nuclear Information System (INIS)

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

    1984-06-01

    A solvent cleanup method using silica gel columns treated with either sodium hydroxide (NaOH) or lithium hydroxide (LiOH) has been investigated. Its effectiveness compares favorably with that of traditional wash methods. After treatment with NaOH solution, the gels adsorb HNO 3 , dibutyl phosphate (DBP), UO 2 2+ , Pu 4+ , various metal-ion fission products, and other species from the solvent. Adsorption mechanisms include neutralization, hydrolysis, polymerization, and precipitation, depending on the species adsorbed. Sodium dibutyl phosphate, which partially distributes to the solvent from the gels, can be stripped with water; the stripping coefficient ranges from 280 to 540. Adsorption rates are diffusion controlled such that temperature effects are relatively small. Recycle of the gels is achieved either by an aqueous elution and recycle sequence or by a thermal treatment method, which may be preferable. Potential advantages of this solvent cleanup method are that (1) some operational problems are avoided and (2) the amount of NaNO 3 waste generated per metric ton of nuclear fuel reprocessed would be reduced significantly. 19 references, 6 figures, 12 tables

  8. A Green Solvent Induced DNA Package

    Science.gov (United States)

    Satpathi, Sagar; Sengupta, Abhigyan; Hridya, V. M.; Gavvala, Krishna; Koninti, Raj Kumar; Roy, Bibhisan; Hazra, Partha

    2015-03-01

    Mechanistic details of DNA compaction is essential blue print for gene regulation in living organisms. Many in vitro studies have been implemented using several compaction agents. However, these compacting agents may have some kinds of cytotoxic effects to the cells. To minimize this aspect, several research works had been performed, but people have never focused green solvent, i.e. room temperature ionic liquid as DNA compaction agent. To the best of our knowledge, this is the first ever report where we have shown that guanidinium tris(pentafluoroethyl)trifluorophosphate (Gua-IL) acts as a DNA compacting agent. The compaction ability of Gua-IL has been verified by different spectroscopic techniques, like steady state emission, circular dichroism, dynamic light scattering and UV melting. Notably, we have extensively probed this compaction by Gua-IL through field emission scanning electron microscopy (FE-SEM) and fluorescence microscopy images. We also have discussed the plausible compaction mechanism process of DNA by Gua-IL. Our results suggest that Gua-IL forms a micellar kind of self aggregation above a certain concentration (>=1 mM), which instigates this compaction process. This study divulges the specific details of DNA compaction mechanism by a new class of compaction agent, which is highly biodegradable and eco friendly in nature.

  9. Solvent anode for plutonium purification

    International Nuclear Information System (INIS)

    Bowersox, D.F.; Fife, K.W.; Christensen, D.C.

    1986-01-01

    The purpose of this study is to develop a technique to allow complete oxidation of plutonium from the anode during plutonium electrorefining. This will eliminate the generation of a ''spent'' anode heel which requires further treatment for recovery. Our approach is to employ a solvent metal in the anode to provide a liquid anode pool throughout electrorefining. We use molten salts and metals in ceramic crucibles at 700 0 C. Our goal is to produce plutonium metal at 99.9% purity with oxidation and transfer of more than 98% of the impure plutonium feed metal from the anode into the salt and product phases. We have met these criteria in experiments on the 100 to 1000 g scale. We plan to scale our operations to 4 kg of feed plutonium and to optimize the process parameters

  10. Quantitation of buried contamination by use of solvents. [degradation of silicone polymers by amine solvents

    Science.gov (United States)

    Pappas, S. P.; Hsiao, Y. C.; Hill, L. W.

    1973-01-01

    Spore recovery form cured silicone potting compounds using amine solvents to degrade the cured polymers was investigated. A complete list of solvents and a description of the effect of each on two different silicone polymers is provided.

  11. Cleanup of 7.5% tributyl phosphate/n-paraffin solvent-extraction solvent

    International Nuclear Information System (INIS)

    Reif, D.J.

    1987-02-01

    The HM process at the Savannah River Plant uses 7.5% tributyl phosphate in n-paraffin as an extraction solvent. During use, the solvent is altered due to hydrolysis and radiolysis, forming materials which influence product losses, product decontamination, and separation efficiencies. Laboratory studies to improve online solvent cleaning have shown that carbonate washing, although removing residual solvent activity, does not remove binding ligands which hold fission products in the solvent. Treatment of solvent by an alumina adsorption process removes binding ligands and significantly improves recycle solvent performance. Both laboratory work defining a full-scale alumina adsorption process and the use of the process to clean HM process first cycle solvent is discussed

  12. Implicit solvent simulations of DNA and DNA-protein complexes: Agreement with explicit solvent vs experiment

    Czech Academy of Sciences Publication Activity Database

    Chocholoušová, Jana; Feig, M.

    2006-01-01

    Roč. 110, č. 34 (2006), s. 17240-17251 ISSN 1520-6106 Keywords : implicit solvent * explicit solvent * protein DNA complex Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.115, year: 2006

  13. 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

  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

    clinical centres in 7 European countries, who underwent a 10-week dietary intervention study comparing two hypo-energetic (-600 kcal/day) diets varying in fat content. Results: The multiple regression model showed that weight loss at week 10 was predicted by: 6.55 + 1.27 × early weight loss (kg) at week 1...... kg weight loss at week 5 emerged as an optimal predictor for reaching at least 10% weight loss at week 10. Greater attrition likelihood was predicted by high-fat diet, decreased early and half-way weight losses. Conclusion: Early and half-way weight losses are associated with and could contribute......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. 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.

  16. 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.

  17. 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

    2014-12-01

    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 setting. We used data from the Our Pathways to Health program, implemented in Humboldt County, California, from 2008 to 2011. Our conceptual framework is based on Bandura's self-efficacy theory, and we used logistic regression to investigate whether baseline self-efficacy and other members' efficacy are associated with participants dropping out of the CDSMP. Twenty-three percent of the participants did not complete the program similar to previous studies. Lower baseline self-efficacy increased the odds of dropout, but other members' efficacy was not associated with differential odds of dropout. Age, educational difference between the individual and the group, weekday sessions, and social/role activity limitations are also found to be associated with program attrition. Our results suggest that participants with low starting self-efficacy may need extra help to complete the program. Further research is needed to understand how to effectively provide additional support to this group. © 2014 Society for Public Health Education.

  18. Explaining attrition and decreased effectiveness of experienced teachers: A research synthesis.

    Science.gov (United States)

    Torenbeek, Marjolein; Peters, Velibor

    2017-01-01

    Teacher retention and development of the full potential of teachers is important at a national level in order to be able to belong to the top world economies. A number of studies suggests that part of the group of experienced teachers with more than 20 years of experience perform didactically at a lower level than would be expected and are at a greater risk for attrition. The aim of the present study is to find explanations for this by making use of the Job Demands Resources Model. Specific demands of the teaching profession, interpersonal demands related to the developmental stage of experienced teachers, job resources and personal resources in relation to health and motivation are explored by reviewing a vast amount of literature. The proposed conceptual model is an extension of the Job Demands Resources Model with the inclusion of personal demands related to adulthood and personal resources. The resulting model provides us with clues on how attrition and decreased performance could be counteracted.

  19. Faculty Promotion and Attrition: The Importance of Coauthor Network Reach at an Academic Medical Center.

    Science.gov (United States)

    Warner, Erica T; Carapinha, René; Weber, Griffin M; Hill, Emorcia V; Reede, Joan Y

    2016-01-01

    Business literature has demonstrated the importance of networking and connections in career advancement. This is a little-studied area in academic medicine. To examine predictors of intra-organizational connections, as measured by network reach (the number of first- and second-degree coauthors), and their association with probability of promotion and attrition. Prospective cohort study between 2008 and 2012. Academic medical center. A total of 5787 Harvard Medical School (HMS) faculty with a rank of assistant professor or full-time instructor as of January 1, 2008. Using negative binomial models, multivariable-adjusted predictors of continuous network reach were assessed according to rank. Poisson regression was used to compute relative risk (RR) and 95 % confidence intervals (CI) for the association between network reach (in four categories) and two outcomes: promotion or attrition. Models were adjusted for demographic, professional and productivity metrics. Network reach was positively associated with number of first-, last- and middle-author publications and h-index. Among assistant professors, men and whites had greater network reach than women and underrepresented minorities (p advancement and retention in academic medicine. They can and should be investigated at other institutions.

  20. 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.

  1. 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,…

  2. The Dissertation Story: What Is the Relationship between the Officer Candidate School Attrition Rate and Officer Training Command, Naval Service Training Command and Navy Recruiting Command Leadership Intervention?

    Science.gov (United States)

    2013-03-01

    attrition (Goodstadt, 1981). Kubisiak, et al. contend that leaders should consider attrition a negative occurrence and that each leader should develop...related to the information, and the consequences associated with the options. The ability to ruminate before acting when presented with new information or

  3. 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, M.G.E.; Oort, F.J.; van der Linden, Y.M.; Sprangers, M.A.G.

    2015-01-01

    Purpose: 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

  4. 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

  5. Revisiting the effects of organic solvents on the thermal reduction of graphite oxide

    International Nuclear Information System (INIS)

    Barroso-Bujans, Fabienne; Fierro, José Luis G.; Alegría, Angel; Colmenero, Juan

    2011-01-01

    Highlights: ► Retention of organic solvent on graphite oxide interlayer space. ► Decreasing exfoliation temperature. ► Close link between structure and thermal behavior of solvent treated graphite oxide. ► Restacking inhibition of thermally reduced graphite oxide sheets. ► Changes in kinetic mechanisms of thermal reduction. - Abstract: Treatment of graphite oxide (GO) with organic solvents via sorption from either liquid or gas phase, and subsequent desorption, induces profound changes in the layered GO structure: loss of stacking order, retention of trace amounts of solvents and decreasing decomposition temperature. This study presents new evidences of the effect of organic solvents on the thermal reduction of GO by means of thermogravimetric analysis, X-ray diffraction and X-ray photoelectron spectroscopy. The results reveal a relative higher decrease of the oxygen amounts in solvent-treated GO as compared to untreated GO and the restacking inhibition of the thermally reduced GO sheets upon slow heating. The kinetic experiments evidence changes occurring in the reduction mechanisms of the solvent-treated GO, which support the close link between GO structure and thermal properties.

  6. Solvent-vapor-assisted imprint lithography

    NARCIS (Netherlands)

    Voicu, Nicoleta E.; Ludwigs, Sabine; Crossland, Edward J. W.; Andrew, Piers; Steiner, Ullrich

    2007-01-01

    Sub-micrometer features are replicated into high-molecular-weight polymer resists by using solvent-assisted nanoimprint lithography (see figure). By swelling the polymer in a controlled solvent-vapor atmosphere, millibar pressures and ambient temperatures are sufficient to achieve high-fidelity

  7. Into the depths of deep eutectic solvents

    NARCIS (Netherlands)

    Rodriguez, N.; Alves da Rocha, M.A.; Kroon, M.C.

    2015-01-01

    Ionic liquids (ILs) have been successfully tested in a wide range of applications; however, their high price and complicated synthesis make them infeasible for large scale implementation. A decade ago, a new generation of solvents so called deep eutectic solvents (DESs) was reported for the first

  8. Remediation of Contaminated Soils by Solvent Flushing

    NARCIS (Netherlands)

    Augustijn, Dionysius C.M.; Jessup, Ron E.; Rao, P. Suresh C.; Wood, A. Lynn

    1994-01-01

    Solvent flushing is a potential technique for remediating a waste disposal/spill site contaminated with organic chemicals. This technique involves the injection of a solvent mixture (e.g., water plus alcohols) that enhances contaminant solubility, reduces the retardation factor, and increases the

  9. Structuring of polymer solutions upon solvent evaporation

    NARCIS (Netherlands)

    Schaefer, C.; van der Schoot, P.|info:eu-repo/dai/nl/102140618; Michels, J. J.

    2015-01-01

    The morphology of solution-cast, phase-separated polymers becomes finer with increasing solvent evaporation rate. We address this observation theoretically for a model polymer where demixing is induced by steady solvent evaporation. In contrast to what is the case for a classical, thermal quench

  10. Solvent distillations studies for a reprocessing plant

    International Nuclear Information System (INIS)

    Ginisty, C.; Guillaume, B.

    1989-01-01

    The substantial amounts of solvent used in large reprocessing plants are such that considerable care must be paid to solvent management to limit the production of organic wastes. The installation of intensive treatment by chemical regeneration serves to increase the service life of the solvent. General solvent management, combined with a distillation unit under reduced pressure also helps to recycle the two components of the solvent at a low activity level. Distillation also serves to remove the heavy degradation products that are generally responsible for poor hydraulic behavior and for the holdup of radioactive products such as plutonium, zirconium and ruthenium. From the safety standpoint, the flashpoint of the distilled diluent tends to rise. It can therefore be recycled without risk

  11. Method of decomposing radioactive organic solvent wastes

    International Nuclear Information System (INIS)

    Uki, Kazuo; Ichihashi, Toshio; Hasegawa, Akira; Sato, Tatsuaki

    1986-01-01

    Purpose: To decompose radioactive organic solvent wastes or radioactive hydrocarbon solvents separated therefrom into organic materials under moderate conditions, as well as greatly decrease the amount of secondary wastes generated. Method: Radioactive organic solvent wastes comprising an organic phosphoric acid ester ingredient and a hydrocarbon ingredient as a diluent therefor, or radioactive hydrocarbon solvents separated therefrom are oxidatively decomposed by hydrogen peroxide in an aqueous phosphoric acid solution of phosphoric acid metal salts finally into organic materials to perform decomposing treatment for the radioactive organic solvent wastes. The decomposing reaction is carried out under relatively moderate conditions and cause less burden to facilities or the likes. Further, since the decomposed liquid after the treatment can be reused for the decomposing reaction as a catalyst solution secondary wastes can significantly be decreased. (Yoshihara, H.)

  12. The chemistry of nonaqueous solvents v.4 solution phenomena and aprotic solvents

    CERN Document Server

    Lagowski, J J

    1976-01-01

    The Chemistry of Nonaqueous Solvents, Volume IV: Solution Phenomena and Aprotic Solvents focuses on the chemistry of nonaqueous solvents, with emphasis on solution phenomena and aprotic solvents such as tetramethylurea, inorganic acid chlorides, cyclic carbonates, and sulfolane. This book is organized into seven chapters and begins with an overview of the theory of electrical conductivity and elementary experimental considerations, along with some of the interesting research on nonaqueous solvents. It then turns to a discussion on hydrogen bonding phenomena in nonaqueous systems as probed

  13. PARIS II: Computer Aided Solvent Design for Pollution Prevention

    Science.gov (United States)

    This product is a summary of U.S. EPA researchers' work developing the solvent substitution software tool PARIS II (Program for Assisting the Replacement of Industrial Solvents, version 2.0). PARIS II finds less toxic solvents or solvent mixtures to replace more toxic solvents co...

  14. Combining Solvent Isotope Effects with Substrate Isotope Effects in Mechanistic Studies of Alcohol and Amine Oxidation by Enzymes*

    Science.gov (United States)

    Fitzpatrick, Paul F.

    2014-01-01

    Oxidation of alcohols and amines is catalyzed by multiple families of flavin-and pyridine nucleotide-dependent enzymes. Measurement of solvent isotope effects provides a unique mechanistic probe of the timing of the cleavage of the OH and NH bonds, necessary information for a complete description of the catalytic mechanism. The inherent ambiguities in interpretation of solvent isotope effects can be significantly decreased if isotope effects arising from isotopically labeled substrates are measured in combination with solvent isotope effects. The application of combined solvent and substrate (mainly deuterium) isotope effects to multiple enzymes is described here to illustrate the range of mechanistic insights that such an approach can provide. PMID:25448013

  15. Distribution of multi-component solvents in solvent vapor extraction chamber

    Energy Technology Data Exchange (ETDEWEB)

    Das, S. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Marathon Oil Corp., Houston, TX (United States)

    2008-10-15

    Vapex process performance is sensitive to operating pressures, temperatures and the types of solvent used. The hydrocarbon solvents used in Vapex processes typically have between 5 and 10 per cent hydrocarbon impurities, and the accumulation of dense phases inside the vapor chamber reduces gravity drainage potential. This study investigated the partitioning of solvent compounds inside the vapor chamber during in situ Vapex processes.The aim of the study was to examine how the different components of the mixed solvent partitioned inside the extracted chamber during the oil and vapor phase. A 2-D homogenous reservoir model was used to simulate the Vapex process with a solvent mixture comprised of propane and methane at various percentages. The effect of injecting a hot solvent vapor was also investigated. The study showed that injected methane accumulated at both the top and the extraction interface. Accumulations near the top had a positive impact on solvent confinement in thin reservoirs. Diffusion of the solvent component was controlled by gas phase molecular diffusion, and was much faster than the diffusion of solvent molecules in the liquid phase. The use of hot solvent mixtures slowed the extraction process due to lower solvent solubility in the oil phase. It was concluded that the negative impact on viscosity reduction by dilution was not compensated by rises in temperature. 6 refs., 11 figs.

  16. Summary of ALSEP Test Loop Solvent Irradiation Testing

    Energy Technology Data Exchange (ETDEWEB)

    Peterman, Dean Richard [Idaho National Lab. (INL), Idaho Falls, ID (United States); Olson, Lonnie Gene [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-08-01

    Separating the minor actinide elements (americium and curium) from the fission product lanthanides is an important step in closing the nuclear fuel cycle. Isolating the minor actinides will allow transmuting them to short lived or stable isotopes in fast reactors, thereby reducing the long-term hazard associated with these elements. The Actinide Lanthanide Separation Process (ALSEP) is being developed by the DOE-NE Material Recovery and Waste Form Development Campaign to accomplish this separation with a single process. To develop a fundamental understanding of the solvent degradation mechanisms for the ALSEP Process, testing was performed in the INL Radiolysis/Hydrolysis Test Loop for the extraction section of the ALSEP flowsheet. This work culminated in the completion of the level two milestone (M2FT-16IN030102021) "Complete ALSEP test loop solvent irradiation test.” This report summarizes the testing performed and the impact of radiation on the ALSEP Process performance as a function of dose.

  17. Estimation of phase separation temperatures for polyethersulfone/solvent/non-solvent systems in RTIPS and membrane properties

    DEFF Research Database (Denmark)

    Liu, Min; Liu, Sheng-Hui; Skov, Anne Ladegaard

    2018-01-01

    was observed. When the membrane-forming temperature was higher than the cloud point, membranes with a bi-continuous structure were acquired and showed a higher pure water permeation flux than that of membranes prepared with the non-solvent induced phase separation (NIPS) process. The pure water permeation flux...... and the mean pore size of membranes prepared with the RTIPS process decreased in line with an increase of PES molecular weight. When the membrane formation mechanism was the RTIPS process, the mechanical properties were better than those of the corresponding membranes prepared with the NIPS process....

  18. Organic Solvent Tolerant Lipases and Applications

    Directory of Open Access Journals (Sweden)

    Shivika Sharma

    2014-01-01

    Full Text Available Lipases are a group of enzymes naturally endowed with the property of performing reactions in aqueous as well as organic solvents. The esterification reactions using lipase(s could be performed in water-restricted organic media as organic solvent(s not only improve(s the solubility of substrate and reactant in reaction mixture but also permit(s the reaction in the reverse direction, and often it is easy to recover the product in organic phase in two-phase equilibrium systems. The use of organic solvent tolerant lipase in organic media has exhibited many advantages: increased activity and stability, regiospecificity and stereoselectivity, higher solubility of substrate, ease of products recovery, and ability to shift the reaction equilibrium toward synthetic direction. Therefore the search for organic solvent tolerant enzymes has been an extensive area of research. A variety of fatty acid esters are now being produced commercially using immobilized lipase in nonaqueous solvents. This review describes the organic tolerance and industrial application of lipases. The main emphasis is to study the nature of organic solvent tolerant lipases. Also, the potential industrial applications that make lipases the biocatalysts of choice for the present and future have been presented.

  19. Increased prevalence of pregnancy and comparative risk of program attrition among individuals starting HIV treatment in East Africa.

    Directory of Open Access Journals (Sweden)

    Charles B Holmes

    Full Text Available The World Health Organization now recommends initiating all pregnant women on life-long antiretroviral therapy (ART, yet there is limited information about the characteristics and program outcomes of pregnant women already on ART in Africa. Our hypothesis was that pregnant women comprised an increasing proportion of those starting ART, and that sub-groups of these women were at higher risk for program attrition.We used the International Epidemiology Databases to Evaluate AIDS- East Africa (IeDEA-EA to conduct a retrospective cohort study including HIV care and treatment programs in Kenya, Uganda, and Tanzania. The cohort consecutively included HIV-infected individuals 13 years or older starting ART 2004-2014. We examined trends over time in the proportion pregnant, their characteristics and program attrition rates compared to others initiating and already receiving ART. 156,474 HIV-infected individuals (67.0% women started ART. The proportion of individuals starting ART who were pregnant women rose from 5.3% in 2004 to 12.2% in 2014. Mean CD4 cell counts at ART initiation, weighted for annual program size, increased from 2004 to 2014, led by non-pregnant women (annual increase 20 cells/mm3 and men (17 cells/mm3 annually, with lower rates of change in pregnant women (10 cells/mm3 per year (p<0.0001. There was no significant difference in the cumulative incidence of program attrition at 6 months among pregnant women starting ART and non-pregnant women. However, healthy pregnant women starting ART (WHO stage 1/2 had a higher rate of attrition rate (9.6%, compared with healthy non-pregnant women (6.5%; in contrast among women with WHO stage 3/4 disease, pregnant women had lower attrition (8.4% than non-pregnant women (14.4%. Among women who initiated ART when healthy and remained in care for six months, subsequent six-month attrition was slightly higher among pregnant women at ART start (3.5% compared to those who were not pregnant (2.4%, (absolute

  20. Increased prevalence of pregnancy and comparative risk of program attrition among individuals starting HIV treatment in East Africa.

    Science.gov (United States)

    Holmes, Charles B; Yiannoutsos, Constantin T; Elul, Batya; Bukusi, Elizabeth; Ssali, John; Kambugu, Andrew; Musick, Beverly S; Cohen, Craig; Williams, Carolyn; Diero, Lameck; Padian, Nancy; Wools-Kaloustian, Kara K

    2018-01-01

    The World Health Organization now recommends initiating all pregnant women on life-long antiretroviral therapy (ART), yet there is limited information about the characteristics and program outcomes of pregnant women already on ART in Africa. Our hypothesis was that pregnant women comprised an increasing proportion of those starting ART, and that sub-groups of these women were at higher risk for program attrition. We used the International Epidemiology Databases to Evaluate AIDS- East Africa (IeDEA-EA) to conduct a retrospective cohort study including HIV care and treatment programs in Kenya, Uganda, and Tanzania. The cohort consecutively included HIV-infected individuals 13 years or older starting ART 2004-2014. We examined trends over time in the proportion pregnant, their characteristics and program attrition rates compared to others initiating and already receiving ART. 156,474 HIV-infected individuals (67.0% women) started ART. The proportion of individuals starting ART who were pregnant women rose from 5.3% in 2004 to 12.2% in 2014. Mean CD4 cell counts at ART initiation, weighted for annual program size, increased from 2004 to 2014, led by non-pregnant women (annual increase 20 cells/mm3) and men (17 cells/mm3 annually), with lower rates of change in pregnant women (10 cells/mm3 per year) (p<0.0001). There was no significant difference in the cumulative incidence of program attrition at 6 months among pregnant women starting ART and non-pregnant women. However, healthy pregnant women starting ART (WHO stage 1/2) had a higher rate of attrition rate (9.6%), compared with healthy non-pregnant women (6.5%); in contrast among women with WHO stage 3/4 disease, pregnant women had lower attrition (8.4%) than non-pregnant women (14.4%). Among women who initiated ART when healthy and remained in care for six months, subsequent six-month attrition was slightly higher among pregnant women at ART start (3.5%) compared to those who were not pregnant (2.4%), (absolute

  1. Micron-sized columnar grains of CH3NH3PbI3 grown by solvent-vapor assisted low-temperature (75 °C) solid-state reaction: The role of non-coordinating solvent-vapor

    Science.gov (United States)

    Zheng, Huifeng; Liu, Yangqiao; Sun, Jing

    2018-04-01

    The preparation of hybrid perovskite films with large columnar grains via low-temperature solid-state reaction remains a big challenge. Conventional solvent annealing using DMF, DMSO and ethanol, etc. fails to work effectively at low temperature (solar cells based on benzyl-alcohol-vapor annealing (75 °C), delivered much higher photovoltaic performance, better stability and smaller hysteresis than those based on conventional thermal annealing. Additionally, a champion power conversion efficiency (PCE) of 15.1% was obtained and the average PCE reached 12.2% with a tiny deviation. Finally, the mechanism of solvent annealing with non-coordinating solvent was discussed. Moreover, we revealed that high polarity and high boiling point of the solvent used for generating vapor, was critical to grow micron-sized columnar grains at such a low temperature (75 °C). This work will contribute to understanding the mechanism of grain growth in solvent annealing and improving its facility and effectiveness.

  2. Solvent Handbook Database System user's manual

    International Nuclear Information System (INIS)

    1993-03-01

    Industrial solvents and cleaners are used in maintenance facilities to remove wax, grease, oil, carbon, machining fluids, solder fluxes, mold release, and various other contaminants from parts, and to prepare the surface of various metals. However, because of growing environmental and worker-safety concerns, government regulations have already excluded the use of some chemicals and have restricted the use of halogenated hydrocarbons because they affect the ozone layer and may cause cancer. The Solvent Handbook Database System lets you view information on solvents and cleaners, including test results on cleaning performance, air emissions, recycling and recovery, corrosion, and non-metals compatibility. Company and product safety information is also available

  3. Modeling of Salt Solubilities in Mixed Solvents

    DEFF Research Database (Denmark)

    Chiavone-Filho, O.; Rasmussen, Peter

    2000-01-01

    A method to correlate and predict salt solubilities in mixed solvents using a UNIQUAC+Debye-Huckel model is developed. The UNIQUAC equation is applied in a form with temperature-dependent parameters. The Debye-Huckel model is extended to mixed solvents by properly evaluating the dielectric...... constants and the liquid densities of the solvent media. To normalize the activity coefficients, the symmetric convention is adopted. Thermochemical properties of the salt are used to estimate the solubility product. It is shown that the proposed procedure can describe with good accuracy a series of salt...

  4. Solvent extraction in the nuclear fuel cycle

    International Nuclear Information System (INIS)

    Eccles, H.; Naylor, A.

    1987-01-01

    Solvent extraction techniques have been used in the uranium nuclear fuel cycle in three main areas; concentration of uranium from ore leach liquor, purification of ore concentrates and fuel reprocessing. Solvent extraction has been extended to the removal of transuranic elements from active waste liquor, the recovery of uranium from natural sources and the recovery of noble metals from active waste liquor. Schemes are presented for solvent extraction of uranium using the Amex or Dapex process; spent fuel reprocessing and the Purex process. Recent and future developments of the techniques are outlined. (UK)

  5. Chemical reactions in solvents and melts

    CERN Document Server

    Charlot, G

    1969-01-01

    Chemical Reactions in Solvents and Melts discusses the use of organic and inorganic compounds as well as of melts as solvents. This book examines the applications in organic and inorganic chemistry as well as in electrochemistry. Organized into two parts encompassing 15 chapters, this book begins with an overview of the general properties and the different types of reactions, including acid-base reactions, complex formation reactions, and oxidation-reduction reactions. This text then describes the properties of inert and active solvents. Other chapters consider the proton transfer reactions in

  6. Spreadsheet algorithm for stagewise solvent extraction

    International Nuclear Information System (INIS)

    Leonard, R.A.; Regalbuto, M.C.

    1994-01-01

    The material balance and equilibrium equations for solvent extraction processes have been combined with computer spreadsheets in a new way so that models for very complex multicomponent multistage operations can be setup and used easily. A part of the novelty is the way in which the problem is organized in the spreadsheet. In addition, to facilitate spreadsheet setup, a new calculational procedure has been developed. The resulting Spreadsheet Algorithm for Stagewise Solvent Extraction (SASSE) can be used with either IBM or Macintosh personal computers as a simple yet powerful tool for analyzing solvent extraction flowsheets. 22 refs., 4 figs., 2 tabs

  7. TRUEX process solvent cleanup with solid sorbents

    International Nuclear Information System (INIS)

    Tse, Pui-Kwan; Reichley-Yinger, L.; Vandegrift, G.F.

    1989-01-01

    Solid sorbents, alumina, silica gel, and Amberlyst A-26 have been tested for the cleanup of degraded TRUEX-NPH solvent. A sodium carbonate scrub alone does not completely remove acidic degradation products from highly degraded solvent and cannot restore the stripping performance of the solvent. By following the carbonate scrub with either neutral alumina or Amberlyst A-26 anion exchange resin, the performance of the TRUEX-NPH is substantially restored. The degraded TRUEX-NPH was characterized before and after treatment by supercritical fluid chromatography. Its performance was evaluated by americium distribution ratios, phase-separation times, and lauric acid distribution coefficients. 17 refs., 2 figs., 5 tabs

  8. SCENARIOS EVALUATION TOOL FOR CHLORINATED SOLVENT MNA

    Energy Technology Data Exchange (ETDEWEB)

    Vangelas, K; Brian02 Looney, B; Michael J. Truex; Charles J. Newell

    2006-08-16

    Over the past three decades, much progress has been made in the remediation of chlorinated solvents from the subsurface. Yet these pervasive contaminants continue to present a significant challenge to the U.S. Department of Energy (DOE), other federal agencies, and other public and private organizations. The physical and chemical properties of chlorinated solvents make it difficult to rapidly reach the low concentrations typically set as regulatory limits. These technical challenges often result in high costs and long remediation time frames. In 2003, the DOE through the Office of Environmental Management funded a science-based technical project that uses the U.S. Environmental Protection Agency's technical protocol (EPA, 1998) and directives (EPA, 1999) on Monitored Natural Attenuation (MNA) as the foundation on which to introduce supporting concepts and new scientific developments that will support remediation of chlorinated solvents based on natural attenuation processes. This project supports the direction in which many site owners want to move to complete the remediation of their site(s), that being to complete the active treatment portion of the remedial effort and transition into MNA. The overarching objective of the effort was to examine environmental remedies that are based on natural processes--remedies such as Monitored Natural Attenuation (MNA) or Enhanced Attenuation (EA). The research program did identify several specific opportunities for advances based on: (1) mass balance as the central framework for attenuation based remedies, (2) scientific advancements and achievements during the past ten years, (3) regulatory and policy development and real-world experience using MNA, and (4) exploration of various ideas for integrating attenuation remedies into a systematic set of ''combined remedies'' for contaminated sites. These opportunities are summarized herein and are addressed in more detail in referenced project documents and

  9. Investigation of the Use of a Bio-Derived Solvent for Non-Solvent-Induced Phase Separation (NIPS Fabrication of Polysulfone Membranes

    Directory of Open Access Journals (Sweden)

    Xiaobo Dong

    2018-05-01

    Full Text Available Organic solvents, such as N-methyl-2-pyrrolidone (NMP and dimethylacetamide (DMAc, have been traditionally used to fabricate polymeric membranes. These solvents may have a negative impact on the environment and human health; therefore, using renewable solvents derived from biomass is of great interest to make membrane fabrication sustainable. Methyl-5-(dimethylamino-2-methyl-5-oxopentanoate (Rhodiasolv PolarClean is a bio-derived, biodegradable, nonflammable and nonvolatile solvent. Polysulfone is a commonly used polymer to fabricate membranes due to its thermal stability, strong mechanical strength and good chemical resistance. From cloud point curves, PolarClean showed potential to be a solvent for polysulfone. Membranes prepared with PolarClean were investigated in terms of their morphology, porosity, water permeability and protein rejection, and were compared to membranes prepared with traditional solvents. The pores of polysulfone/PolarClean membranes were sponge-like, and the membranes displayed higher water flux values (176.0 ± 8.8 LMH along with slightly higher solute rejection (99.0 ± 0.51%. On the other hand, PSf/DMAc membrane pores were finger-like with lower water flux (63.1 ± 12.4 LMH and slightly lower solute rejection (96 ± 2.00% when compared to PSf/PolarClean membranes.

  10. Uranium refining by solvent extraction

    International Nuclear Information System (INIS)

    Kraikaew, J.; Srinuttrakul, W.

    2014-01-01

    The solvent extraction process to produce higher purity uranium from yellowcake was studied in laboratory scale. Yellowcake, which the uranium purity is around 70% and the main impurity is thorium, was obtained from monazite processing pilot plant of Rare Earth Research and Development Center in Thailand. For uranium re-extraction process, the extractant chosen was Tributylphosphate (TBP) in kerosene. It was found that the optimum concentration of TBP was 10% in kerosene and the optimum nitric acid concentration in uranyl nitrate feed solution was 4 N. An increase in concentrations of uranium and thorium in feed solution resulted in a decrease in the distribution of both components in the extractant. However, the distribution of uranium into the extractant was found to be more than that of thorium. The equilibration study of the extraction system, UO_2(NO_3)/4N HNO_3 – 10%TBP/Kerosene, was also investigated. Two extraction stages were calculated graphically from 100,000 ppm uranium concentration in feed solution input with 90% extraction efficiency and the flow ratio of aqueous phase to organic phase was adjusted to 1.0. For thorium impurity scrubbing process, 10% TBP in kerosene was loaded with uranium and minor thorium from uranyl nitrate solution prepared from yellowcake and was scrubbed with different low concentration nitric acid. The results showed that at nitric acid normality was lower than 1 N, uranium distributed well to aqueous phase. As conclusion, optimum nitric acid concentration for scrubbing process should not less than 1 N and diluted nitric acid or de-ionized water should be applied to strip uranium from organic phase in the final refining process. (author)

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

    Directory of Open Access Journals (Sweden)

    Verónica Herrero

    2013-12-01

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

  12. Properties and sinterability of wet and dry attrition-milled OREOXed powder

    International Nuclear Information System (INIS)

    Lee, J. W.; Kim, J. H.; Kim, W. K.; Park, K. I.; Lee, J. W.

    2001-01-01

    The powder properties and sinterability were investigated with the powder prepared by wet and dry attrition milling of OREOX-treated powder. The OREOX-treated powder was prepared from the simulated spent fuel. Powder having less than 1 μm of average particle size could be obtained by dry milling, but not be obtained by wet milling. Thus, specific surface area of dry milled powder was higher than that of wet milled powder. With increasing of milling time, dry milled powder formed dense agglomerate while wet milled powder showed loose agglomerate. The pellets with higher than 95% T.D. of sintered density and larger than 7 μm of grain size were made with the milled powder regardless of milling method. The milling time in wet milling has greatly improved the sinterability. The pellets produced with dry milled powder have higher sintered density and larger grain size

  13. Attrition-free pyrolysis to produce bio-oil and char.

    Science.gov (United States)

    Mauviel, Guillain; Guillain, Mauviel; Kies, Fairouz; Fairouz, Kies; René, Mar Sans; Mar, Sans Rene; Ferrer, Monique; Monique, Ferrer; Lédé, Jacques; Jacques, Lédé

    2009-12-01

    Experiments are performed on a laboratory scale setup where beech wood chips are heated by gas convection and walls radiation. This study shows that it is possible to obtain high bio-oil and char yields with relatively low external heat transfer coefficients. The main advantage of this convection/radiation heat transfer mode compared to solid-solid collisions, applied in fluidized bed or twin screw reactors, is the reduction of solid attrition (char and sand). Thus tricky gas-solid separation through hot cyclones and/or hot filters could be avoided or reduced. It should be possible to recover directly bio-oil with less char particles and char free of sand dust. These qualities would allow easier use of these bio-products in different applications.

  14. 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.

  15. Application and results of whole-body autoradiography in distribution studies of organic solvents.

    Science.gov (United States)

    Bergman, K

    1983-01-01

    With the growing concern for the health hazards of occupational exposure to toxic substances attention has been focused on the organic solvents, which are associated with both deleterious nervous system effects and specific tissue injuries. Relatively little is known about the distribution of organic solvents and their metabolites in the living organism. Knowledge of the specific tissue localizations and retention of solvents and solvent metabolites is of great value in revealing and understanding the sites and mechanisms of organic solvent toxicity. Whole-body autoradiography has been modified and applied to distribution studies of benzene, toluene, m-xylene, styrene, methylene chloride, chloroform, carbon tetrachloride, trichloroethylene and carbon disulfide. The high volatility of these substances has led to the development of cryo-techniques. Whole-body autoradiographic techniques applicable to the study of volatile substances are reviewed. The localizations of nonvolatile solvent metabolites and firmly bound metabolites have also been examined. The obtained results are discussed in relation to toxic effects and evaluated by comparison with other techniques used in distribution studies of organic solvents and their metabolites.

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

    Directory of Open Access Journals (Sweden)

    Aye Thida

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

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

    Science.gov (United States)

    Thida, Aye; Tun, Sai Thein Than; Zaw, Sai Ko Ko; Lover, Andrew A; Cavailler, Philippe; Chunn, Jennifer; Aye, Mar Mar; Par, Par; Naing, Kyaw Win; Zan, Kaung Nyunt; Shwe, Myint; Kyaw, Thar Tun; Waing, Zaw Htoon; Clevenbergh, Philippe

    2014-01-01

    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. 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. 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. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. [Chemical hazards when working with solvent glues].

    Science.gov (United States)

    Domański, Wojciech; Makles, Zbigniew

    2012-01-01

    Solvent glues are used in a wide variety of industries, e.g., textile, footwear and rubber. The problem of workers' exposure to solvent vapors is rarely tackled within the area of occupational safety and health in small and medium-sized enterprises. In order to assess exposure to solvents, organic solvents emitted by glues were identified in the samples of workplace air. The concentration of acetone, benzene, cyclohexane, ethylbenzene, n-hexane, methylcyclohexane, butyl acetate and toluene were determined. The obtained results evidenced the presence of cyclohexane, ethylbenzene, ethylcyclohexane, heptane, n-hexane, o-xylene, methylcyclohexane, methylcyclopentane, butyl acetate and toluene in workplace air. The concentration of those compounds in workplace air was low, usually below 0.15 of MAC. At some workstations the presence of benzene was also observed. Occupational risk was assessed at workstations where gluing took place. It showed that the risk at those workstations was medium or low.

  3. Organic solvents from sugar cane molasses

    Energy Technology Data Exchange (ETDEWEB)

    Oeser, H

    1970-01-01

    The production of organic solvents by fermentation of low priced cane molasses is discussed. Processes described and illustrated in detail include the production of acetone, butanol, ethanol, acetic acid, ethyl acetate and butyl acetate.

  4. Solvent induced supramolecular anisotropy in molecular gels

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Michael A., E-mail: mroger09@uoguelph.ca [Department of Food Science, University of Guelph, Guelph, Ontario, N3C3X9 (Canada); Corradini, Maria G. [Department of Food Science, University of Massachusetts Amherst, Amherst, MA, 01003 (United States); Emge, Thomas [Department of Chemistry and Biochemistry, Rutgers University, New Brunswick, NJ, 08901 (United States)

    2017-06-15

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  5. Solvent induced supramolecular anisotropy in molecular gels

    International Nuclear Information System (INIS)

    Rogers, Michael A.; Corradini, Maria G.; Emge, Thomas

    2017-01-01

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  6. Full scale solvent extraction remedial results

    International Nuclear Information System (INIS)

    Cash, A.B.

    1992-01-01

    Sevenson Extraction Technology, Inc. has completed the development of the Soil Restoration Unit (initially developed by Terra-Kleen Corporation), a mobile, totally enclosed solvent extraction treatment facility for the removal of organic contaminated media is greater by a closed loop, counter current process that recycles all solvents. The solvents used are selected for the individual site dependant upon the contaminants, such as PCB's, oil, etc. and the soil conditions. A mixture of up to fourteen non-toxic solvents can be used for complicated sites. The full scale unit has been used to treat one superfund site, the Traband Site in Tulsa, Oklahoma, and is currently treating another superfund site, the Pinette's Salvage Yard Site in Washburn, Maine. The full scale Soil Restoration Unit has also been used at a non-superfund site, as part of a TSCA Research and Development permit. The results from these sites will be discussed in brief herein, and in more detail in the full paper

  7. Enantioselective solvent-free Robinson annulation reactions

    Indian Academy of Sciences (India)

    Unknown

    solvents to effect an asymmetric synthesis is an important step forward towards ... In continuation of our preliminary communication 2, we wish to ..... formation of chiral enamine 74 from the reaction of S-proline with pro-R carbonyl group.

  8. STUDIES ON SOLVENT EXTRACTION OF FREE HYDROGEN ...

    African Journals Online (AJOL)

    synthesized through glucose degradation (glycolysis) to lactic acid. ... g sample into a well stoppered plastic bottle and mixed with 20 mL of distilled .... Recovery of used solvent is necessary because methylchloroform is toxic to the bacteria.

  9. Green and Bio-Based Solvents.

    Science.gov (United States)

    Calvo-Flores, Francisco G; Monteagudo-Arrebola, María José; Dobado, José A; Isac-García, Joaquín

    2018-04-24

    Chemical reactions and many of the procedures of separation and purification employed in industry, research or chemistry teaching utilize solvents massively. In the last decades, with the birth of Green Chemistry, concerns about the employment of solvents and the effects on human health, as well as its environmental impacts and its dependence on non-renewable raw materials for manufacturing most of them, has drawn the attention of the scientific community. In this work, we review the concept of green solvent and the properties and characteristics to be considered green. Additionally, we discuss the different possible routes to prepare many solvents from biomass, as an alternative way to those methods currently applied in the petrochemical industry.

  10. Activity coefficients of solutes in binary solvents

    International Nuclear Information System (INIS)

    Gokcen, N.A.

    1982-01-01

    The activity coefficients in dilute ternary systems are discussed in detail by using the Margules equations. Analyses of some relevant data at high temperatures show that the sparingly dissolved solutes in binary solvents follow complex behavior even when the binary solvents are very nearly ideal. It is shown that the activity data on the solute or the binary system cannot permit computation of the remaining activities except for the regular solutions. It is also shown that a fourth-order equation is usually adequate in expressing the activity coefficient of a solute in binary solvents at high temperatures. When the activity data for a binary solvent are difficult to obtain in a certain range of composition, the activity data for a sparingly dissolved solute can be used to supplement determination of the binary activities

  11. An overview of industrial solvent use or is there life after chlorinated solvents?

    International Nuclear Information System (INIS)

    Green, B.

    1991-01-01

    Everyone using industrial chemicals has been affected by the fire- storm of new regulations governing solvent use. How will companies currently using hazardous solvents prepare for the changes ahead? What will the impact be on commonly used industrial solvents? What effect are environmental pressures having on solvent use and disposal? Are the responsible individuals in your company up-to-date on phase-out schedules? This paper is written for an audience of compliance coordinators, consultants, production engineers and corporate management. In it, the either addresses the above questions and discusses the specific products affected. The author reviews currently available alternatives to chlorinated and hazardous solvents and introduces a simple system for rating alternatives. The program also includes a discussion of solvent minimization programs and worker reeducation

  12. Occupational exposure to solvents and bladder cancer

    DEFF Research Database (Denmark)

    Hadkhale, Kishor; Martinsen, Jan Ivar; Weiderpass, Elisabete

    2017-01-01

    logistic regression model was used to estimate hazard ratios (HR) and their 95% confidence intervals (95% CI). Increased risks were observed for trichloroethylene (HR 1.23, 95% 95% CI 1.12-1.40), toluene (HR 1.20, 95% CI 1.00-1.38), benzene (HR 1.16, 95% CI 1.04-1.31), aromatic hydrocarbon solvents (HR 1...... of occupational exposure to trichloroethylene, perchloroethylene, aromatic hydrocarbon solvents, benzene and toluene and the risk of bladder cancer....

  13. Computer-Aided Solvent Screening for Biocatalysis

    DEFF Research Database (Denmark)

    Abildskov, Jens; Leeuwen, M.B. van; Boeriu, C.G.

    2013-01-01

    constrained properties related to chemical reaction equilibrium, substrate and product solubility, water solubility, boiling points, toxicity and others. Two examples are provided, covering the screening of solvents for lipase-catalyzed transesterification of octanol and inulin with vinyl laurate....... Esterification of acrylic acid with octanol is also addressed. Solvents are screened and candidates identified, confirming existing experimental results. Although the examples involve lipases, the method is quite general, so there seems to be no preclusion against application to other biocatalysts....

  14. Solvent management in a reprocessing plant

    International Nuclear Information System (INIS)

    Guillaume, B.; Germain, M.; Puyou, M.; Rouyer, H.

    1987-01-01

    Solvent management in large capacity reprocessing plant is studied to limit production of organic wastes. Chemical processing increases life time of solvent. Low pressure distillation allows the recycling of TBP and diluent at a low activity level. Besides heavy degradation products are eliminated. For the safety the flash point of distillated diluent increases slightly. Tests on an industrial scale started in 1985 and since more than 500 cubic meters were treated [fr

  15. Hazardous Solvent Substitution Data System reference manual

    International Nuclear Information System (INIS)

    Branham-Haar, K.A.; Twitchell, K.E.

    1993-07-01

    Concern for the environment, in addition to Federal regulation, mandate the replacement of hazardous solvents with safer cleaning agents. Manufacturers are working to produce these replacement solvents. As these products are developed, potential users need to be informed of their availability. To promote the use of these new products instead of traditional solvents, the Idaho National Engineering Laboratory (INEL) has developed the Hazardous Solvent Substitution Data System (HSSDS). The HSSDS provides a comprehensive system of information on alternatives to hazardous solvents and related subjects, and it makes that information available to solvent users, industrial hygienists, and process engineers. The HSSDS uses TOPIC reg-sign, a text retrieval system produced by Verity, Inc., to allow a user to search for information on a particular subject. TOPIC reg-sign produces a listing of the retrieved documents and allows the use to examine the documents individually and to use the information contained in them. This reference manual does not replace the comprehensive TOPIC reg-sign user documentation (available from Verity, Inc.), or the HSSDS Tutorial (available from the INEL). The purpose of this reference manual is to provide enough instruction on TOPIC reg-sign so the user may begin accessing the data contained in the HSSDS

  16. Solvent consumption in non-catalytic alcohol solvolysis of biorefinery lignin

    DEFF Research Database (Denmark)

    Nielsen, J. B.; Jensen, A.; Schandel, Christian Bækhøj

    2017-01-01

    Lignin solvolysis in supercritical alcohols provides a method for producing a deoxygenated liquid bio-oil. Solvent consumption is however inevitable and due to the high cost of alcohols, relative to a bio-oil product, it can hinder commercial viability. In order to investigate the reactions...... of solvent consumption we studied solvolysis of biorefinery lignin in several primary alcohols. Lignin solvolysis in methanol, ethanol, 1-propanol and 1-butanol performed similarly with respect to bio-oil composition; however, methanol gave much lower bio-oil yield. Solvent consumption increases...... with reaction temperature for all alcohols and from 10 wt% at 300 °C to 35 wt% at 400 °C when using ethanol. The mechanism for solvent consumption was found mainly to take place through three different reactions: direct decomposition to gas through decarbonylation, formation of light condensation products...

  17. A multi target approach to control chemical reactions in their inhomogeneous solvent environment

    International Nuclear Information System (INIS)

    Keefer, Daniel; Thallmair, Sebastian; Zauleck, Julius P P; Vivie-Riedle, Regina de

    2015-01-01

    Shaped laser pulses offer a powerful tool to manipulate molecular quantum systems. Their application to chemical reactions in solution is a promising concept to redesign chemical synthesis. Along this road, theoretical developments to include the solvent surrounding are necessary. An appropriate theoretical treatment is helpful to understand the underlying mechanisms. In our approach we simulate the solvent by randomly selected snapshots from molecular dynamics trajectories. We use multi target optimal control theory to optimize pulses for the various arrangements of explicit solvent molecules simultaneously. This constitutes a major challenge for the control algorithm, as the solvent configurations introduce a large inhomogeneity to the potential surfaces. We investigate how the algorithm handles the new challenges and how well the controllability of the system is preserved with increasing complexity. Additionally, we introduce a way to statistically estimate the efficiency of the optimized laser pulses in the complete thermodynamical ensemble. (paper)

  18. Caustic-Side Solvent Extraction: Chemical and Physical Properties of the Optimized Solvent

    Energy Technology Data Exchange (ETDEWEB)

    Delmau, L.H.

    2002-10-08

    This work was undertaken to optimize the solvent used in the Caustic Side Solvent Extraction (CSSX) process and to measure key chemical and physical properties related to its performance in the removal of cesium from the alkaline high-level salt waste stored in tanks at the Savannah River Site. The need to adjust the solvent composition arose from the prior discovery that the previous baseline solvent was supersaturated with respect to the calixarene extractant. The following solvent-component concentrations in Isopar{reg_sign} L diluent are recommended: 0.007 M calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) extractant, 0.75 M 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (Cs-7SB) phase modifier, and 0.003 M tri-n-octylamine (TOA) stripping aid. Criteria for this selection included BOBCalixC6 solubility, batch cesium distribution ratios (D{sub Cs}), calculated flowsheet robustness, third-phase formation, coalescence rate (dispersion numbers), and solvent density. Although minor compromises within acceptable limits were made in flowsheet robustness and solvent density, significant benefits were gained in lower risk of third-phase formation and lower solvent cost. Data are also reported for the optimized solvent regarding the temperature dependence of D{sub Cs} in extraction, scrubbing, and stripping (ESS); ESS performance on recycle; partitioning of BOBCalixC6, Cs-7SB, and TOA to aqueous process solutions; partitioning of organic anions; distribution of metals; solvent phase separation at low temperatures; solvent stability to elevated temperatures; and solvent density and viscosity. Overall, the technical risk of the CSSX process has been reduced by resolving previously identified issues and raising no new issues.

  19. 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.

  20. Assessing the toxicity and biodegradability of deep eutectic solvents.

    Science.gov (United States)

    Wen, Qing; Chen, Jing-Xin; Tang, Yu-Lin; Wang, Juan; Yang, Zhen

    2015-08-01

    Deep eutectic solvents (DESs) have emerged as a new type of promising ionic solvents with a broad range of potential applications. Although their ecotoxicological profile is still poorly known, DESs are generally regarded as "green" because they are composed of ammonium salts and H-bond donors (HBDs) which are considered to be eco-friendly. In this work, cholinium-based DESs comprised of choline chloride (ChCl) and choline acetate (ChAc) as the salt and urea (U), acetamide (A), glycerol (G) and ethylene glycol (EG) as the HBD were evaluated for their toxic effects on different living organisms such as Escherichia coli (a bacterium), Allium sativum (garlic, a plant) and hydra (an invertebrate), and their biodegradabilities were assessed by means of closed bottle tests. These DESs possessed an anti-bacterial property and exhibited inhibitory effects on the test organisms adopted, depending on the composition and concentration of the DES. The mechanism for the impact of DESs and their components on different living organisms can be associated to their interactions with the cellular membranes. Not all DESs can be considered readily biodegradable. By extending the limited knowledge about the toxicity and biodegradation of this particular solvent family, this investigation on DESs provides insight into our structure-based understanding of their ecotoxicological behavior. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Solvent-dependent transformation of aflatoxin B1 in soil.

    Science.gov (United States)

    Starr, James M; Rushing, Blake R; Selim, Mustafa I

    2017-08-01

    To date, all studies of aflatoxin B 1 (AFB 1 ) transformation in soil or in purified mineral systems have identified aflatoxins B 2 (AFB 2 ) and G 2 (AFG 2 ) as the primary transformation products. However, identification in these studies was made using thin layer chromatography which has relatively low resolution, and these studies did not identify a viable mechanism by which such transformations would occur. Further, the use of methanol as the solvent delivery vehicle in these studies may have contributed to formation of artifactual transformation products. In this study, we investigated the role of the solvent vehicle in the transformation of AFB 1 in soil. To do this, we spiked soils with AFB 1 dissolved in water (93:7, water/methanol) or methanol and used HPLC-UV and HPLC-MS to identify the transformation products. Contrasting previous published reports, we did not detect AFB 2 or AFG 2 . In an aqueous-soil environment, we identified aflatoxin B 2a (AFB 2a ) as the single major transformation product. We propose that AFB 2a is formed from hydrolysis of AFB 1 with the soil acting as an acid catalyst. Alternatively, when methanol was used, we identified methoxy aflatoxin species likely formed via acid-catalyzed addition of methanol to AFB 1 . These results suggest that where soil moisture is adequate, AFB 1 is hydrolyzed to AFB 2a and that reactive organic solvents should be avoided when replicating natural conditions to study the fate of AFB 1 in soil.

  2. Solvent Effects in the Hydrogenation of 2-Butanone

    Energy Technology Data Exchange (ETDEWEB)

    Akpa, B. S.; DAgostino, C.; Gladden, L. F.; Hindle, K.; Manyar, H.; McGregor, J.; Li, Ruoyu; Neurock, Matthew; Sinha, N.; Stitt, E. H.; Weber, D.; Zeitler, J. A.; Rooney, D. W.

    2012-03-27

    In liquid-phase reaction systems, the role of the solvent is often limited to the simple requirement of dissolving and/or diluting substrates. However, the correct choice, either pure or mixed, can significantly influence both reaction rate and selectivity. For multi-phase heterogeneously catalysed reactions observed variations may be due to changes in mass transfer rates, reaction mechanism, reaction kinetics, adsorption properties and combinations thereof. The liquid-phase hydrogenation of 2-butanone to 2- butanol over a Ru/SiO2 catalyst, for example, shows such complex rate behaviour when varying water/isopropyl alcohol (IPA) solvent ratios. In this paper, we outline a strategy which combines measured rate data with physical property measurements and molecular simulation in order to gain a more fundamental understanding of mixed solvent effects for this heterogeneously catalysed reaction. By combining these techniques, the observed complex behaviour of rate against water fraction is shown to be a combination of both mass transfer and chemical effects.

  3. Environment effects on the optical properties of some fluorinated poly(oxadiazole ether)s in binary solvent mixtures

    International Nuclear Information System (INIS)

    Homocianu, Mihaela; Ipate, Alina Mirela; Hamciuc, Corneliu; Airinei, Anton

    2015-01-01

    The solvatochromic behavior of some fluorinated poly(oxadiazole ether)s was studied using UV–vis absorption and fluorescence spectroscopy in neat solvents and in their solvent mixtures at several ratios of cosolvents. Quantitative investigations of the spectral changes caused by solvent polarity were discussed using the Lippert‐Mataga, Bakhshiev and Kawski–Chamma–Viallet polarity functions. Repartitioning of cosolvent between local (solvation shell) and bulk phase was investigated by means of a solvatochromic shift method in chloroform–N,N-dimethylformamide (CHCl 3 /DMF) and chloroform–dimethyl sulfoxide (CHCl 3 /DMSO) solvent mixtures. Solvatochromic properties in the binary solvent environments were predominantly influenced by the acidity and basicity of the solvent systems. The fluorescence quenching process by nitrobenzene was characterized by Stern–Volmer plots which display a positive deviation from linearity. This was explained by static and dynamic quenching mechanisms. - Highlights: • Solvatochromic behavior in solvent mixtures was studied. • Stokes shift and local environments in binary mixed solvent were discussed. • Repartitioning of cosolvent between local and bulk phase in solvent mixture has been investigated. • Fluorescence intensity was quenched in presence of nitrobenzene

  4. Analysis of solvent extracts from coal liquefaction in a flowing solvent reactor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wen-Ying; Feng, Jie; Xie, Ke-Chang [Key Laboratory of Coal Science and Technology, Taiyuan University of Technology, Ministry of Education and Shanxi Province, No. 79 Yingze West Street, Taiyuan 030024 (China); Kandiyoti, R. [Department of Chemical Engineering and Chemical Technology, Imperial College, University of London, London SW7 2BY (United Kingdom)

    2004-10-15

    Point of Ayr coal has been extracted using three solvents, tetralin, quinoline and 1-methyl-2-pyrrolidinone (NMP) at two temperatures 350 and 450 C, corresponding approximately to before and after the onset of massive covalent bond scission by pyrolysis. The three solvents differ in solvent power and the ability to donate hydrogen atoms to stabilise free radicals produced by pyrolysis of the coal. The extracts were prepared in a flowing solvent reactor to minimise secondary thermal degradation of the primary extracts. Analysis of the pentane-insoluble fractions of the extracts was achieved by size exclusion chromatography, UV-fluorescence spectroscopy in NMP solvent and probe mass. With increasing extraction temperature, the ratio of the amount having big molecular weight to that having small molecular weight in tetralin extracts was increased; the tetralin extract yield increased from 12.8% to 75.9%; in quinoline, increasing extraction temperature did not have an effect on the molecular weight of products but there was a big increase in extract yield. The extracts in NMP showed the enhanced solvent extraction power at both temperatures, with a shift in the ratio of larger molecules to smaller molecules with increasing extraction temperature and with the highest conversion of Point of Ayr coal among these three solvents at both temperatures. Solvent adducts were detected in the tetralin and quinoline extracts by probe mass spectrometry; solvent products were formed from NMP at both temperatures.

  5. A New Class of Solvents for TRU Dissolution and Separation: Ionic Liquids. Project No. 81891

    International Nuclear Information System (INIS)

    Rogers, Robin D.

    2004-01-01

    Through the current EMSP funding, solvent extraction technologies based on liquid-liquid partitioning of TRU to an Ionic Liquid phase containing conventional complexants has been shown to be viable. The growing understanding of the role that the different components of an ionic liquid can have on the partitioning mechanism, and on the nature of the subsequent dissolved species indicates strongly that ionic liquids are not necessarily direct replacements for volatile or otherwise hazardous organic solvents. Separations and partitioning can be exceptionally complex with competing solvent extraction, cation, anion and sacrificial ion exchange mechanisms are all important, depending on the selection of components for formation of the ionic liquid phase, and that control of these competing mechanisms can be utilized to provide new, alternative separations schemes

  6. 29 CFR 1915.32 - Toxic cleaning solvents.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Toxic cleaning solvents. 1915.32 Section 1915.32 Labor... Preservation § 1915.32 Toxic cleaning solvents. (a) When toxic solvents are used, the employer shall employ one or more of the following measures to safeguard the health of employees exposed to these solvents. (1...

  7. COMPUTER-AIDED SOLVENT DESIGN FOR POLLUTION PREVENTION: PARIS II

    Science.gov (United States)

    Solvent substitution is an attractive way of elijminating the use of regulated solvents because it usually does not require major chanages in existing processes, equipment or operations. Successful solvent substitution is dependent on finding solvents that are as effective or be...

  8. The Impact of Junior Reserve Officer Training Corps and Other Youth Programs on Navy First-Term Attrition, Promotion, and Reenlistment

    National Research Council Canada - National Science Library

    Lamont, Roy A

    2007-01-01

    ...) and other youth programs significantly affects the performance of first-term Navy enlistees. This analysis makes use of multivariate models to estimate the causal effect of JROTC participation on first-term attrition, promotion and reenlistment...

  9. Transformation of eutectic emulsion to nanosuspension fabricating with solvent evaporation and ultrasonication technique

    Directory of Open Access Journals (Sweden)

    Phaechamud T

    2016-06-01

    Full Text Available Thawatchai Phaechamud,1 Sarun Tuntarawongsa2 1Department of Pharmaceutical Technology, 2Pharmaceutical Intelligence Unit Prachote Plengwittaya, Faculty of Pharmacy, Silpakorn University, Nakhon Pathom, Thailand Abstract: Eutectic solvent can solubilize high amount of some therapeutic compounds. Volatile eutectic solvent is interesting to be used as solvent in the preparation of nanosuspension with emulsion solvent evaporation technique. The mechanism of transformation from the eutectic emulsion to nanosuspension was investigated in this study. The 30% w/w ibuprofen eutectic solution was used as the internal phase, and the external phase is composed of Tween 80 as emulsifier. Ibuprofen nanosuspension was prepared by eutectic emulsion solvent evaporating method followed with ultrasonication. During evaporation process, the ibuprofen concentration in emulsion droplets was increased leading to a drug supersaturation but did not immediately recrystallize because of low glass transition temperature (Tg of ibuprofen. The contact angle of the internal phase on ibuprofen was apparently lower than that of the external phase at all times of evaporation, indicating that the ibuprofen crystals were preferentially wetted by the internal phase than the external phase. From calculated dewetting value ibuprofen crystallization occurred in the droplet. Crystallization of the drug was initiated with external mechanical force, and the particle size of the drug was larger due to Ostwald ripening. Cavitation force from ultrasonication minimized the ibuprofen crystals to the nanoscale. Particle size and zeta potential of formulated ibuprofen nanosuspension were 330.87±51.49 nm and -31.1±1.6 mV, respectively, and exhibited a fast dissolution. Therefore, the combination of eutectic emulsion solvent evaporation method with ultrasonication was favorable for fabricating an ibuprofen nanosuspension, and the transformation mechanism was attained successfully. Keywords

  10. Characterization and antioxidant activity of bovine serum albumin and sulforaphane complex in different solvent systems

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xueyan; Zhou, Rui; Jing, Hao, E-mail: h200521@cau.edu.cn

    2014-02-15

    Modes and influencing factors of bovine serum albumin (BSA) and sulforaphane (SFN) interaction will help us understand the interaction mechanisms and functional changes of bioactive small molecule and biomacromolecule. This study investigated interaction mechanisms of BSA and SFN and associated antioxidant activity in three solvent systems of deionized water (dH{sub 2}O), dimethyl sulfoxide (DMSO) and ethanol (EtOH), using Fourier transform infrared spectroscopy (FT-IR), fluorescence spectroscopy, synchronous fluorescence spectroscopy, DPPH and ABTS radical scavenging assays. The results revealed that SFN had ability to quench BSA's fluorescence in static modes, and to interact with BSA at both tyrosine (Tyr) and tryptophan (Trp) residues, while the Trp residues were highly sensitive, which was demonstrated by fluorescence at 340 nm. Hydrophobic forces, hydrogen bonds and van der Waals interactions were all involved in BSA and SFN interaction, which were not significantly changed by three solvents. The binding constant values and binding site numbers were in a descending order of dH{sub 2}O>DMSO>EtOH. The values of free energy change were in a descending order of dH{sub 2}O>DMSO>EtOH, which indicated that the binding forces were in a descending order of dH{sub 2}O>DMSO>EtOH. There was no significant difference in antioxidant activity between SFN and BSA–SFN. Moreover, three solvents had not significant influence on antioxidant activity of SFN and BSA–SFN. -- Highlights: • We report interaction mechanisms of BSA and sulforaphane in three solvent systems. • We report antioxidant activity of BSA–sulforaphane complex in three solvent systems. • Decreasing the solvent polarity will decrease the binding of BSA and sulforaphane. • Three solvents had not influence on antioxidant activity of BSA–sulforaphane.

  11. New Polymeric Membranes for Organic Solvent Nanofiltration

    KAUST Repository

    Aburabie, Jamaliah

    2017-05-01

    The focus of this dissertation was the development, synthesis and modification of polymers for the preparation of membranes for organic solvent nanofiltration. High chemical stability in a wide range of solvents was a key requirement. Membranes prepared from synthesized polymers as well as from commercial polymers were designed and chemically modified to reach OSN requirements. A solvent stable thin-film composite (TFC) membrane is reported, which is fabricated on crosslinked polythiosemicarbazide (PTSC) as substrate. The membranes exhibited high fluxes towards solvents like THF, DMF and DMSO ranging around 20 L/m2 h at 5 bar with a MWCO of around 1000 g/mol. Ultrafiltration PTSC membranes were prepared by non-solvent induced phase separation and crosslinked with GPTMS. The crosslinking reaction was responsible for the formation of an inorganic-type-network that tuned the membrane pore size. The crosslinked membranes acquired high solvent stability in DMSO, DMF and THF with a MWCO above 1300 g/mol. Reaction Induced Phase Separation (RIPS) was introduced as a new method for the preparation of skinned asymmetric membranes. These membranes have two distinctive layers with different morphologies both from the same polymer. The top dense layer is composed of chemically crosslinked polymer chains while the bottom layer is a porous structure formed by non-crosslinked polymer chains. Such membranes were tested for vitamin B12 in solvents after either crosslinking the support or dissolving the support and fixing the freestanding membrane on alumina. Pebax® 1657 was utilized for the preparation of composite membranes by simple coating. Porous PAN membranes were coated with Pebax® 1657 which was then crosslinked using TDI. Crosslinked Pebax® membranes show high stability towards ethanol, propanol and acetone. The membranes were also stable in DMF once crosslinked PAN supports were used. Sodium alginate polymer was investigated for the preparation of thin film composite

  12. Measurement and correlation of solubility of cefmenoxime hydrochloride in pure solvents and binary solvent mixtures

    International Nuclear Information System (INIS)

    Wang, Jinxiu; Xie, Chuang; Yin, Qiuxiang; Tao, Linggang; Lv, Jun; Wang, Yongli; He, Fang; Hao, Hongxun

    2016-01-01

    Highlights: • Solubility of cefmenoxime hydrochloride in pure and binary solvents was determined. • The experimental solubility data were correlated by thermodynamic models. • A model was employed to calculate the melting temperature of cefmenoxime hydrochloride. • Mixing thermodynamic properties of cefmenoxime hydrochloride were calculated. - Abstract: The solubility of cefmenoxime hydrochloride in pure solvents and binary solvent mixtures was measured at temperatures from (283.15 to 313.15) K by using the UV spectroscopic method. The results reveal that the solubility of cefmenoxime hydrochloride increases with increasing temperature in all solvent selected. The solubility of cefmenoxime hydrochloride reaches its maximum value when the mole fraction of isopropanol is 0.2 in the binary solvent mixtures of (isopropanol + water). The modified Apelblat equation and the NRTL model were successfully used to correlate the experimental solubility in pure solvents while the modified Apelblat equation, the CNIBS/R–K model and the Jouyban–Acree model were applied to correlate the solubility in binary solvent mixtures. In addition, the mixing thermodynamic properties of cefmenoxime hydrochloride in different solvents were also calculated based on the NRTL model and experimental solubility data.

  13. Solvent extraction studies in miniature centrifugal contactors

    International Nuclear Information System (INIS)

    Siczek, A.A.; Meisenhelder, J.H.; Bernstein, G.J.; Steindler, M.J.

    1980-01-01

    A miniature short-residence-time centrifugal solvent extraction contactor and an eight-stage laboratory minibank of centrifugal contactors were used for testing the possibility of utilizing kinetic effects for improving the separation of uranium from ruthenium and zirconium in the Purex process. Results of these tests showed that a small improvement found in ruthenium and zirconium decontamination in single-stage solvent extraction tests was lost in the multistage extraction tests- in fact, the extent of saturation of the solvent by uranium, rather than the stage residence time, controlled the extent of ruthenium and zirconium extraction. In applying the centrifugal contactor to the Purex process, the primary advantages would be less radiolytic damage to the solvent, high troughput, reduced solvent inventory, and rapid attainment of steady-state operating conditions. The multistage mini contactor was also tested to determine the suitability of short-residence-time contactors for use with the Civex and Thorex processes and was found to be compatible with the requirements of these processes. (orig.) [de

  14. High attrition among HIV-infected patients with advanced disease treated in an intermediary referral center in Maputo, Mozambique

    Directory of Open Access Journals (Sweden)

    Lucas Molfino

    2014-04-01

    Full Text Available Background: In Mozambique, antiretroviral therapy (ART scale-up has been successfully implemented. However, attrition in care remains a major programmatic challenge. In 2009, an intermediary-level HIV referral center was created in Maputo to ensure access to specialized care for HIV-infected patients with complications (advanced clinical-immunological stage, Kaposi sarcoma, or suspected ART failure. Objective: To determine the attrition from care and to identify risk factors that lead to high attrition among patients referred to an intermediary-level HIV referral center. Design: This was a retrospective cohort study from 2009 to 2011. Results: A total of 1,657 patients were enrolled, 847 (51% were men, the mean age was 36 years (standard deviation: 11, the mean CD4 count was 27 cells/µl (interquartile range: 11–44, and one-third were severely malnourished. The main reasons for referral were advanced clinical stages (WHO stages 3 and 4, and CD4 count <50 cells/µl in 70% of the cases, and 19% had Kaposi sarcoma. The overall attrition rate was 28.7 per 100 person-years (PYs – the mortality rate was 5.0 (95% confidence interval [CI]: 4.2–5.9 per 100 PYs, and the loss-to-follow-up rate was 23.7 (95% CI: 21.9–25.6 per 100 PYs. There were 793 attritions – 137 deaths and 656 lost to follow-up (LTFU; 77% of all attrition happened within the first year. The factors independently associated with attrition were male sex (adjusted hazard ratio [aHR]: 1.15, 95% CI: 1.0–1.3, low body mass index (aHR: 1.51, 95% CI: 1.2–1.8, WHO clinical stage 3 or 4 (aHR: 1.30, 95% CI: 1.0–1.6; and aHR: 1.91, 95% CI: 1.4–2.5, later year of enrollment (aHR 1.61, 95% CI 1.3–1.9, and ‘being already on ART’ at enrollment (aHR 13.71, 95% CI 11.4–16.4. Conclusions: Attrition rates among HIV-infected patients enrolled in an intermediary referral center were high, mainly related to advanced stage of clinical disease. Measures are required to address this

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

    Science.gov (United States)

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

    2015-07-15

    Data from controlled trials indicate that Web-based interventions generally suffer from low engagement and high attrition. This is important because the level of exposure to intervention content is linked to intervention effectiveness. However, data from real-life Web-based behavior change interventions are scarce, especially when looking at physical activity promotion. The aims of this study were to (1) examine the engagement with the freely available physical activity promotion program 10,000 Steps, (2) examine how the use of a smartphone app may be helpful in increasing engagement with the intervention and in decreasing nonusage attrition, and (3) identify sociodemographic- and engagement-related determinants of nonusage attrition. Users (N=16,948) were grouped based on which platform (website, app) they logged their physical activity: Web only, app only, or Web and app. Groups were compared on sociodemographics and engagement parameters (duration of usage, number of individual and workplace challenges started, and number of physical activity log days) using ANOVA and chi-square tests. For a subsample of users that had been members for at least 3 months (n=11,651), Kaplan-Meier survival curves were estimated to plot attrition over the first 3 months after registration. A Cox regression model was used to determine predictors of nonusage attrition. In the overall sample, user groups differed significantly in all sociodemographics and engagement parameters. Engagement with the program was highest for Web-and-app users. In the subsample, 50.00% (5826/11,651) of users stopped logging physical activity through the program after 30 days. Cox regression showed that user group predicted nonusage attrition: Web-and-app users (hazard ratio=0.86, 95% CI 0.81-0.93, Pworkplace challenges (hazard ratio=0.94, 95% CI 0.90-0.97, Pphysical activity logging days (hazard ratio=0.921, 95% CI 0.919-0.922, P<.001), and steps logged per day (hazard ratio=0.99999, 95% CI 0

  16. 40 CFR Table 5 to Subpart Qqqq of... - Default Organic HAP Mass Fraction for Solvents and Solvent Blends

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Default Organic HAP Mass Fraction for... HAP Mass Fraction for Solvents and Solvent Blends You may use the mass fraction values in the.... Solvent/solvent blend CAS. No. Average organic HAP mass fraction Typical organic HAP, percent by mass 1...

  17. 40 CFR Table 3 to Subpart IIIi of... - Default Organic HAP Mass Fraction for Solvents and Solvent Blends

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Default Organic HAP Mass Fraction for... Organic HAP Mass Fraction for Solvents and Solvent Blends You may use the mass fraction values in the... Solvent/solvent blend CAS. No. Averageorganic HAP mass fraction Typical organic HAP, percent by mass 1...

  18. 40 CFR Table 4 to Subpart Oooo of... - Default Organic HAP Mass Fraction for Solvents and Solvent Blends

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Default Organic HAP Mass Fraction for... 63—Default Organic HAP Mass Fraction for Solvents and Solvent Blends You may use the mass fraction... formulation data. Solvent/solvent blend CAS. No. Averageorganic HAP mass fraction Typical organic HAP, percent...

  19. Green solvents and technologies for oil extraction from oilseeds

    OpenAIRE

    Kumar, S. P. Jeevan; Prasad, S. Rajendra; Banerjee, Rintu; Agarwal, Dinesh K.; Kulkarni, Kalyani S.; Ramesh, K. V.

    2017-01-01

    Oilseeds are crucial for the nutritional security of the global population. The conventional technology used for oil extraction from oilseeds is by solvent extraction. In solvent extraction, n-hexane is used as a solvent for its attributes such as simple recovery, non-polar nature, low latent heat of vaporization (330?kJ/kg) and high selectivity to solvents. However, usage of hexane as a solvent has lead to several repercussions such as air pollution, toxicity and harmfulness that prompted to...

  20. 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.

  1. 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

  2. Volatile solvents as drugs of abuse: focus on the cortico-mesolimbic circuitry.

    Science.gov (United States)

    Beckley, Jacob T; Woodward, John J

    2013-12-01

    Volatile solvents such as those found in fuels, paints, and thinners are found throughout the world and are used in a variety of industrial applications. However, these compounds are also often intentionally inhaled at high concentrations to produce intoxication. While solvent use has been recognized as a potential drug problem for many years, research on the sites and mechanisms of action of these compounds lags behind that of other drugs of abuse. In this review, we first discuss the epidemiology of voluntary solvent use throughout the world and then consider what is known about their basic pharmacology and how this may explain their use as drugs of abuse. We next present data from preclinical and clinical studies indicating that these substances induce common addiction sequelae such as dependence, withdrawal, and cognitive impairments. We describe how toluene, the most commonly studied psychoactive volatile solvent, alters synaptic transmission in key brain circuits such as the mesolimbic dopamine system and medial prefrontal cortex (mPFC) that are thought to underlie addiction pathology. Finally, we make the case that activity in mPFC circuits is a critical regulator of the mesolimbic dopamine system's ability to respond to volatile solvents like toluene. Overall, this review provides evidence that volatile solvents have high abuse liability because of their selective effects on critical nodes of the addiction neurocircuitry, and underscores the need for more research into how these compounds induce adaptations in neural circuits that underlie addiction pathology.

  3. Strongly Iridescent Hybrid Photonic Sensors Based on Self-Assembled Nanoparticles for Hazardous Solvent Detection

    Directory of Open Access Journals (Sweden)

    Ayaka Sato

    2018-03-01

    Full Text Available Facile detection and the identification of hazardous organic solvents are essential for ensuring global safety and avoiding harm to the environment caused by industrial wastes. Here, we present a simple method for the fabrication of silver-coated monodisperse polystyrene nanoparticle photonic structures that are embedded into a polydimethylsiloxane (PDMS matrix. These hybrid materials exhibit a strong green iridescence with a reflectance peak at 550 nm that originates from the close-packed arrangement of the nanoparticles. This reflectance peak measured under Wulff-Bragg conditions displays a 20 to 50 nm red shift when the photonic sensors are exposed to five commonly employed and highly hazardous organic solvents. These red-shifts correlate well with PDMS swelling ratios using the various solvents, which suggests that the observable color variations result from an increase in the photonic crystal lattice parameter with a similar mechanism to the color modulation of the chameleon skin. Dynamic reflectance measurements enable the possibility of clearly identifying each of the tested solvents. Furthermore, as small amounts of hazardous solvents such as tetrahydrofuran can be detected even when mixed with water, the nanostructured solvent sensors we introduce here could have a major impact on global safety measures as innovative photonic technology for easily visualizing and identifying the presence of contaminants in water.

  4. Effect of pre-swelling of coal on its solvent extraction and liquefaction properties

    Energy Technology Data Exchange (ETDEWEB)

    Hengfu Shui; Zhicai Wang; Meixia Cao [Anhui University of Technology, Ma' anshan (China). School of Chemistry and Chemical Engineering

    2008-10-15

    Effects of pre-swelling of coal on solvent extraction and liquefaction properties were studied with Shenhua coal. It was found that pre-swelling treatments of the coal in three solvents, i.e., toluene (TOL), N-methyl-2-pyrrolidinone (NMP) and tetralin (THN) increased its extraction yield and liquefaction conversion, and differed the liquefied product distributions. The pre-swollen coals after removing the swelling solvents showed increased conversion in liquefaction compared with that of the swollen coals in the presence of swelling solvents. It was also found that the yields of (oil + gas) in liquefaction of the pre-swollen coals with NMP and TOL dramatically decreased in the presence of swelling solvent. TG and FTIR analyses of the raw coal, the swollen coals and the liquefied products were carried out in order to investigate the mechanism governing the effects of pre-swelling treatment on coal extraction and liquefaction. The results showed that the swelling pre-treatment could disrupt some non-covalent interactions of the coal molecules, relax its network structure and loosened the coal structure. It would thus benefit diffusion of a hydrogen donor solvent into the coal structure during liquefaction, and also enhance the hydrogen donating ability of the hydrogen-rich species derived from the coal. 21 refs., 4 figs., 3 tabs.

  5. Solvent effects on polymer sorting of carbon nanotubes with applications in printed electronics.

    Science.gov (United States)

    Wang, Huiliang; Hsieh, Bing; Jiménez-Osés, Gonzalo; Liu, Peng; Tassone, Christopher J; Diao, Ying; Lei, Ting; Houk, Kendall N; Bao, Zhenan

    2015-01-07

    Regioregular poly(3-alkylthiophene) (P3AT) polymers have been previously reported for the selective, high-yield dispersion of semiconducting single-walled carbon nanotubes (SWCNTs) in toluene. Here, five alternative solvents are investigated, namely, tetrahydrofuran, decalin, tetralin, m-xylene, and o-xylene, for the dispersion of SWCNTs by poly(3-dodecylthiophene) P3DDT. The dispersion yield could be increased to over 40% using decalin or o-xylene as the solvents while maintaining high selectivity towards semiconducting SWCNTs. Molecular dynamics (MD) simulations in explicit solvents are used to explain the improved sorting yield. In addition, a general mechanism is proposed to explain the selective dispersion of semiconducting SWCNTs by conjugated polymers. The possibility to perform selective sorting of semiconducting SWCNTs using various solvents provides a greater diversity of semiconducting SWCNT ink properties, such as boiling point, viscosity, and surface tension as well as toxicity. The efficacy of these new semiconducting SWCNT inks is demonstrated by using the high boiling point and high viscosity solvent tetralin for inkjet-printed transistors, where solvent properties are more compatible with the inkjet printing head and improved droplet formation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Sustainable and Low Viscous 1-Allyl-3-methylimidazolium Acetate + PEG Solvent for Cellulose Processing

    Directory of Open Access Journals (Sweden)

    Airong Xu

    2017-02-01

    Full Text Available Developing sustainable, low viscous and efficient solvents are always advantageous to the processing/fabricating of cellulose materials in practical applications. To this end, in this work novel solvents were developed; ([Amim][CH3COO]/PEG by dissolving polyethylene glycol 200 (PEG-200 in 1-allyl-3-methylimidazolium acetate ([Amim][CH3COO]. The solubilities of cellulose in [Amim][CH3COO]/PEG solvents were determined as a function of temperature, and the possible dissolution mechanism of cellulose in [Amim][CH3COO]/PEG solvent was investigated. The novel solvent exhibits outstanding advantages for good dissolution capacity of cellulose, such as low viscosity, negligible vapor pressure, and recycling capability. The [CH3COO]− anion and the [Amim]+ cation of [Amim][CH3COO] in [Amim][CH3COO]/PEG-10 are the driving force for cellulose dissolution verified by the 13C NMR spectra. In addition, the regenerated cellulose films from [Amim][CH3COO]/PEG solvent were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR, and thermogravimetric analysis (TGA to estimate their morphologies and structures.

  7. Rational Design of Molecular Gelator - Solvent Systems Guided by Solubility Parameters

    Science.gov (United States)

    Lan, Yaqi

    Self-assembled architectures, such as molecular gels, have attracted wide interest among chemists, physicists and engineers during the past decade. However, the mechanism behind self-assembly remains largely unknown and no capability exists to predict a priori whether a small molecule will gelate a specific solvent or not. The process of self-assembly, in molecular gels, is intricate and must balance parameters influencing solubility and those contrasting forces that govern epitaxial growth into axially symmetric elongated aggregates. Although the gelator-gelator interactions are of paramount importance in understanding gelation, the solvent-gelator specific (i.e., H-bonding) and nonspecific (dipole-dipole, dipole-induced and instantaneous dipole induced forces) intermolecular interactions are equally important. Solvent properties mediate the self-assembly of molecular gelators into their self-assembled fibrillar networks. Herein, solubility parameters of solvents, ranging from partition coefficients (logP), to Henry's law constants (HLC), to solvatochromic ET(30) parameters, to Kamlet-Taft parameters (beta, alpha and pi), to Hansen solubility parameters (deltap, deltad, deltah), etc., are correlated with the gelation ability of numerous classes of molecular gelators. Advanced solvent clustering techniques have led to the development of a priori tools that can identify the solvents that will be gelled and not gelled by molecular gelators. These tools will greatly aid in the development of novel gelators without solely relying on serendipitous discoveries.

  8. Alternative Solvents through Green Chemistry Project

    Science.gov (United States)

    Hintze, Paul E.; Quinn, Jacqueline

    2014-01-01

    Components in the aerospace industry must perform with accuracy and precision under extreme conditions, and surface contamination can be detrimental to the desired performance, especially in cases when the components come into contact with strong oxidizers such as liquid oxygen. Therefore, precision cleaning is an important part of a components preparation prior to utilization in aerospace applications. Current cleaning technologies employ a variety of cleaning agents, many of which are halogenated solvents that are either toxic or cause environmental damage. Thus, this project seeks to identify alternative precision cleaning solvents and technologies, including use of less harmful cleaning solvents, ultrasonic and megasonic agitation, low-pressure plasma cleaning techniques, and supercritical carbon dioxide extraction. Please review all data content found in the Public Data tab located at: https:techport.nasa.govview11697public

  9. Hazardous Solvent Substitution Data System tutorial

    International Nuclear Information System (INIS)

    Twitchell, K.E.; Skinner, N.L.

    1993-07-01

    This manual is the tutorial for the Hazardous Solvent Substitution Data System (HSSDS), an online, comprehensive system of information on alternatives to hazardous solvents and related subjects. The HSSDS data base contains product information, material safety data sheets, toxicity reports, usage reports, biodegradable data, product chemical element lists, and background information on solvents. HSSDS use TOPIC reg-sign to search for information based on a query defined by the user. TOPIC provides a full text retrieval of unstructured source documents. In this tutorial, a series of lessons is provided that guides the user through basic steps common to most queries performed with HSSDS. Instructions are provided for both window-based and character-based applications

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

    Science.gov (United States)

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

    2016-07-01

    The attrition of rape cases from the criminal justice system (CJS) remains high and there is a paucity of research in relation to marginalized groups. Sex workers (SWs) are vulnerable to sexual violence due to the nature of their work. They are also unlikely to report such violence to police for a range of reasons. Two stages of research sought to describe the victim, perpetrator, and offense characteristics of SW rape and to examine the attrition of these cases. All rapes and attempted rapes (N = 1,146) reported to police in a large city in the South West of England over a 21-year period were examined; 67 cases involved SWs. Data were extracted from police files in line with the variables of interest. Secondary analysis of the total number of SW rapes (n = 67) resulted in a profile of these cases. A matched pairs study revealed significant differences in victim, perpetrator, and assault characteristics between SW (n = 62) and non-sex-worker (NSW) samples (n = 62). Although no significant difference was found in terms of attrition from the CJS, SW cases were observed to secure more convictions for rape than NSW cases. The implications of the findings for practice and future research are discussed. © The Author(s) 2015.

  11. Peroneus Brevis Attrition & Longitudinal Split Tear without Subluxation and Associated Hypertrophy of Peronal Tubercle" - Treatment of an Uncommon Lesion.

    Science.gov (United States)

    Tiwari, Mukesh; Singh, Varun; Bhargava, Rakesh

    2015-01-01

    Peroneus brevis tendinitis with its attritional longitudinal split rupture without any subluxation from peroneal groove and associated enlarged peroneal tubercle is un common presentation. A 40 year old female presented with moderate swelling and tenderness over the lateral and dorso-lateral aspect of left ankle with history of old trauma to ankle with swelling, persistant pain and difficulty in walking. On physical examination during passive eversion and inversion the excursion of the peroneal tendons was painful. Most tender point was just posterior to the tip of the fibula. During surgery we found the intact superior peroneal ligament with both peroneal tendons placed at normal site without subluxation, tendon sheath was inflamed and swollen, on further dissection we could see the attrition of inner surface of the peroneus brevis and a 2 cm longitudinal split tear of the same. Although rare but peroneus brevis tendon attrition and tear can occur without subluxation from peronal groove. Refractory ankle pain on lateral aspect presenting with on and off swelling should arise suspicion of peroneal tendon tear. Correct diagnosis and proper surgical repair can produce excellent results.

  12. 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.

  13. 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

    2015-07-01

    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. 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. 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. 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.

  14. NMR spectroscopy using liquid crystal solvents

    CERN Document Server

    Emsley, JW

    2013-01-01

    NMR Spectroscopy using Liquid Crystal Solvents covers the importance of using a liquid crystal solvent in NMR to derive nuclear dipolar spin-spin coupling constants. This book is composed of ten chapters, and begins with a brief description of the features and benefits of liquid crystal in NMR spectroscopic analysis. The succeeding chapters deal with the mode of operation of nuclear spin Hamiltonian for partially oriented molecules and the analysis of NMR spectra of partially oriented molecules, as well as the determination of rigid molecule structure. These topics are followed by discussions

  15. Catalog solvent extraction: anticipate process adjustments

    International Nuclear Information System (INIS)

    Campbell, S.G.; Brass, E.A.; Brown, S.J.; Geeting, M.W.

    2008-01-01

    The Modular Caustic-Side Solvent Extraction Unit (MCU) utilizes commercially available centrifugal contactors to facilitate removal of radioactive cesium from highly alkaline salt solutions. During the fabrication of the contactor assembly, demonstrations revealed a higher propensity for foaming than was initially expected. A task team performed a series of single-phase experiments that revealed that the shape of the bottom vanes and the outer diameter of those vanes are key to the successful deployment of commercial contactors in the Caustic-Side Solvent Extraction Process. (authors)

  16. 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)

  17. 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.

  18. Retaining the mental health nursing workforce: early indicators of retention and attrition.

    Science.gov (United States)

    Robinson, Sarah; Murrells, Trevor; Smith, Elizabeth M

    2005-12-01

    In the UK, strategies to improve retention of the mental health workforce feature prominently in health policy. This paper reports on a longitudinal national study into the careers of mental health nurses in the UK. The findings reveal little attrition during the first 6 months after qualification. Investigation of career experiences showed that the main sources of job satisfaction were caregiving opportunities and supportive working relationships. The main sources of dissatisfaction were pay in relation to responsibility, paperwork, continuing education opportunities, and career guidance. Participants were asked whether they predicted being in nursing in the future. Gender and ethnicity were related to likelihood to remain in nursing in 5 years time. Age, having children, educational background, ethnic background, and time in first job were associated with likelihood of remaining in nursing at 10 years. Associations between elements of job satisfaction (quality of clinical supervision, ratio of qualified to unqualified staff, support from immediate line manager, and paperwork) and anticipated retention are complex and there are likely to be interaction effects because of the complexity of the issues. Sustaining positive experiences, remedying sources of dissatisfaction, and supporting diplomats from all backgrounds should be central to the development of retention strategies.

  19. 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.

  20. The Views of Ex-Police Officers on Child Abuse Case Attrition in the United Kingdom.

    Science.gov (United States)

    Krahenbuhl, Sarah J; Dent, Helen R

    2017-11-01

    Attrition in child abuse cases is of continuing concern. International research has produced evidence to suggest that the form and quality of the evidence available in many child abuse cases is of insufficient quality to allow progression through the judicial system. Recent revelations have led to an increase in public and professional awareness of the prevalence of child sexual abuse, and how this is managed by the legal and social care systems. The aim of this research was to explore the opinions of ex-Police Officers who had direct experience relating to the management of child abuse cases about the factors affecting case progression. Seven ex-Police Officers were interviewed and the transcribed data were thematically analyzed. The five main themes derived from the data were Global Myths, Assumptions, and Misconceptions; Suitability; Resources; Professionals' Attributes; and Working Together. These themes demonstrated that the primary issues indicated by ex-Police Officers were more about relationships between professionals, an understanding of the child's perspective, and their subsequent involvement in the legal processes than simply being related to a lack of resources.

  1. Sampling protein motion and solvent effect during ligand binding

    Science.gov (United States)

    Limongelli, Vittorio; Marinelli, Luciana; Cosconati, Sandro; La Motta, Concettina; Sartini, Stefania; Mugnaini, Laura; Da Settimo, Federico; Novellino, Ettore; Parrinello, Michele

    2012-01-01

    An exhaustive description of the molecular recognition mechanism between a ligand and its biological target is of great value because it provides the opportunity for an exogenous control of the related process. Very often this aim can be pursued using high resolution structures of the complex in combination with inexpensive computational protocols such as docking algorithms. Unfortunately, in many other cases a number of factors, like protein flexibility or solvent effects, increase the degree of complexity of ligand/protein interaction and these standard techniques are no longer sufficient to describe the binding event. We have experienced and tested these limits in the present study in which we have developed and revealed the mechanism of binding of a new series of potent inhibitors of Adenosine Deaminase. We have first performed a large number of docking calculations, which unfortunately failed to yield reliable results due to the dynamical character of the enzyme and the complex role of the solvent. Thus, we have stepped up the computational strategy using a protocol based on metadynamics. Our approach has allowed dealing with protein motion and solvation during ligand binding and finally identifying the lowest energy binding modes of the most potent compound of the series, 4-decyl-pyrazolo[1,5-a]pyrimidin-7-one. PMID:22238423

  2. Dichlorobenzene: an effective solvent for epoxy/graphene nanocomposites preparation.

    Science.gov (United States)

    Wei, Jiacheng; Saharudin, Mohd Shahneel; Vo, Thuc; Inam, Fawad

    2017-10-01

    It is generally recognized that dimethylformamide (DMF) and ethanol are good media to uniformly disperse graphene, and therefore have been used widely in the preparation of epoxy/graphene nanocomposites. However, as a solvent to disperse graphene, dichlorobenzene (DCB) has not been fully realized by the polymer community. Owing to high values of the dispersion component ( δ d ) of the Hildebrand solubility parameter, DCB is considered as a suitable solvent for homogeneous graphene dispersion. Therefore, epoxy/graphene nanocomposites have been prepared for the first time with DCB as a dispersant; DMF and ethanol have been chosen as the reference. The colloidal stability, mechanical properties, thermogravimetric analysis, dynamic mechanical analysis and scanning electron microscopic images of nanocomposites have been obtained. The results show that with the use of DCB, the tensile strength of graphene has been improved from 64.46 to 69.32 MPa, and its flexural strength has been increased from 97.17 to 104.77 MPa. DCB is found to be more effective than DMF and ethanol for making stable and homogeneous graphene dispersion and composites.

  3. Solvent vapor annealing in the molecular regime drastically improves carrier transport in small-molecule thin-film transistors

    KAUST Repository

    Khan, Hadayat Ullah

    2013-04-10

    We demonstrate a new way to investigate and control the solvent vapor annealing of solution-cast organic semiconductor thin films. Solvent vapor annealing of spin-cast films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) is investigated in situ using quartz crystal microbalance with dissipation (QCM-D) capability, allowing us to monitor both solvent mass uptake and changes in the mechanical rigidity of the film. Using time-resolved grazing incidence wide angle X-ray scattering (GIWAXS) and complementary static atomic force microscopy (AFM), we demonstrate that solvent vapor annealing in the molecular regime can cause significant performance improvements in organic thin film transistors (OTFTs), whereas allowing the solvent to percolate and form a liquid phase results in catastrophic reorganization and dewetting of the film, making the process counterproductive. Using these lessons we devise processing conditions which prevent percolation of the adsorbed solvent vapor molecules for extended periods, thus extending the benefits of solvent vapor annealing and improving carrier mobility by nearly two orders of magnitude. Ultimately, it is demonstrated that QCM-D is a very powerful sensor of the state of the adsorbed solvent as well as the thin film, thus making it suitable for process development as well as in-line process monitoring both in laboratory and in future manufacturing settings. © 2013 American Chemical Society.

  4. Solvent vapor annealing in the molecular regime drastically improves carrier transport in small-molecule thin-film transistors

    KAUST Repository

    Khan, Hadayat Ullah; Li, Ruipeng; Ren, Yi; Chen, Long; Payne, Marcia M.; Bhansali, Unnat Sampatraj; Smilgies, Detlef Matthias; Anthony, John Edward; Amassian, Aram

    2013-01-01

    We demonstrate a new way to investigate and control the solvent vapor annealing of solution-cast organic semiconductor thin films. Solvent vapor annealing of spin-cast films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) is investigated in situ using quartz crystal microbalance with dissipation (QCM-D) capability, allowing us to monitor both solvent mass uptake and changes in the mechanical rigidity of the film. Using time-resolved grazing incidence wide angle X-ray scattering (GIWAXS) and complementary static atomic force microscopy (AFM), we demonstrate that solvent vapor annealing in the molecular regime can cause significant performance improvements in organic thin film transistors (OTFTs), whereas allowing the solvent to percolate and form a liquid phase results in catastrophic reorganization and dewetting of the film, making the process counterproductive. Using these lessons we devise processing conditions which prevent percolation of the adsorbed solvent vapor molecules for extended periods, thus extending the benefits of solvent vapor annealing and improving carrier mobility by nearly two orders of magnitude. Ultimately, it is demonstrated that QCM-D is a very powerful sensor of the state of the adsorbed solvent as well as the thin film, thus making it suitable for process development as well as in-line process monitoring both in laboratory and in future manufacturing settings. © 2013 American Chemical Society.

  5. 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

  6. Next Generation Solvent Performance in the Modular Caustic Side Solvent Extraction Process - 15495

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Tara E. [Savannah River Remediation, LLC., Aiken, SC (United States); Scherman, Carl [Savannah River Remediation, LLC., Aiken, SC (United States); Martin, David [Savannah River Remediation, LLC., Aiken, SC (United States); Suggs, Patricia [Savannah River Site (SRS), Aiken, SC (United States)

    2015-01-14

    Changes to the Modular Caustic Side Solvent Extraction Unit (MCU) flow-sheet were implemented in the facility. Implementation included changing the scrub and strip chemicals and concentrations, modifying the O/A ratios for the strip, scrub, and extraction contactor banks, and blending the current BoBCalixC6 extractant-based solvent in MCU with clean MaxCalix extractant-based solvent. During the successful demonstration period, the MCU process was subject to rigorous oversight to ensure hydraulic stability and chemical/radionuclide analysis of the key process tanks (caustic wash tank, solvent hold tank, strip effluent hold tank, and decontaminated salt solution hold tank) to evaluate solvent carryover to downstream facilities and the effectiveness of cesium removal from the liquid salt waste. Results indicated the extraction of cesium was significantly more effective with an average Decontamination Factor (DF) of 1,129 (range was 107 to 1,824) and that stripping was effective. The contactor hydraulic performance was stable and satisfactory, as indicated by contactor vibration, contactor rotational speed, and flow stability; all of which remained at or near target values. Furthermore, the Solvent Hold Tank (SHT) level and specific gravity was as expected, indicating that solvent integrity and organic hydraulic stability were maintained. The coalescer performances were in the range of processing results under the BOBCalixC6 flow sheet, indicating negligible adverse impact of NGS deployment. After the Demonstration period, MCU began processing via routine operations. Results to date reiterate the enhanced cesium extraction and stripping capability of the Next Generation Solvent (NGS) flow sheet. This paper presents process performance results of the NGS Demonstration and continued operations of MCU utilizing the blended BobCalixC6-MaxCalix solvent under the NGS flowsheet.

  7. Controlling Actinide Hydration in Mixed Solvent Systems: Towards Tunable Solvent Systems to Close the Fuel Cycle

    International Nuclear Information System (INIS)

    Clark, Sue B.

    2016-01-01

    The goal of this project has been to define the extent of hydration the f-elements and other cations in mixed solvent electrolyte systems. Methanol-water and other mixed solvent systems have been studied, where the solvent dielectric constant was varied systematically. Thermodynamic and spectroscopic studies provide details concerning the energetics of complexation and other reactions of these cations. This information has also been used to advance new understanding of the behavior of these cations in a variety of systems, ranging from environmental studies, chromatographic approaches, and ionization processes for mass spectrometry.

  8. Controlling Actinide Hydration in Mixed Solvent Systems: Towards Tunable Solvent Systems to Close the Fuel Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Sue B. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry

    2016-10-31

    The goal of this project has been to define the extent of hydration the f-elements and other cations in mixed solvent electrolyte systems. Methanol-water and other mixed solvent systems have been studied, where the solvent dielectric constant was varied systematically. Thermodynamic and spectroscopic studies provide details concerning the energetics of complexation and other reactions of these cations. This information has also been used to advance new understanding of the behavior of these cations in a variety of systems, ranging from environmental studies, chromatographic approaches, and ionization processes for mass spectrometry.

  9. Solvent-tolerant bacteria in biocatalysis.

    NARCIS (Netherlands)

    Bont, de J.A.M.

    1998-01-01

    The toxicity of fine chemicals to the producer organism is a problem in several biotechnological production processes. In several instances, an organic phase can be used to extract the toxic product from the aqueous phase during a fermentation. With the discovery of solvent-tolerant bacteria, more

  10. SHORT COMMUNICATION SOLVENT FREE PREPARATION OF N ...

    African Journals Online (AJOL)

    Preferred Customer

    KEYWORDS: Solvent free, Maleanilic acids, Maleic anhydride, Aniline derivatives ... associated with the carboxylic group between 3275-2877 cm-1, the weak –NH .... Chemical shifts (σ/ppm) relative to TMS*. O-H N-H Ha. Hb. Hc. Hd. He. Hf.

  11. Simulation of solvent extraction in reprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Shekhar; Koganti, S B [Reprocessing Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    1994-06-01

    A SIMulation Program for Solvent EXtraction (SIMPSEX) has been developed for simulation of PUREX process used in nuclear fuel reprocessing. This computer program is written in double precision structured FORTRAN77 and at present it is used in DOS environment on a PC386. There is a plan to port it to ND supermini computers in future. (author). 5 refs., 3 figs.

  12. Deposition dynamics of multi-solvent bioinks

    Science.gov (United States)

    Kaneelil, Paul; Pack, Min; Cui, Chunxiao; Han, Li-Hsin; Sun, Ying

    2017-11-01

    Inkjet printing cellular scaffolds using bioinks is gaining popularity due to the advancement of printing technology as well as the growing demands of regenerative medicine. Numerous studies have been conducted on printing scaffolds of biomimetic structures that support the cell production of human tissues. However, the underlying physics of the deposition dynamics of bioinks remains elusive. Of particular interest is the unclear deposition dynamics of multi-solvent bioinks, which is often used to tune the micro-architecture formation. Here we systematically studied the effects of jetting frequency, solvent properties, substrate wettability, and temperature on the three-dimensional deposition patterns of bioinks made of Methacrylated Gelatin and Carboxylated Gelatin. The microflows inside the inkjet-printed picolitre drops were visualized using fluorescence tracer particles to decipher the complex processes of multi-solvent evaporation and solute self-assembly. The evolution of droplet shape was observed using interferometry. With the integrated techniques, the interplay of solvent evaporation, biopolymer deposition, and multi-drop interactions were directly observed for various ink and substrate properties, and printing conditions. Such knowledge enables the design and fabrication of a variety of tissue engineering scaffolds for potential use in regenerative medicine.

  13. Double Solvent for Extracting Rare Earth Concentrate

    International Nuclear Information System (INIS)

    Bintarti, AN; Bambang EHB

    2007-01-01

    An extraction process to rare earth concentrate which contain elements were yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), gadolinium (Gd) and dysprosium (Dy) which were dissolved in to nitric acid has been done. The experiment of the extraction by double solvent in batch to mix 10 ml of the feed with 10 ml solvent contained the pair of solvent was TBP and TOA, D2EHPA and TOA, TBP and D2EHPA in cyclohexane as tinner. It was selected a right pairs of solvent for doing variation such as the acidity of the feed from 2 - 6 M and the time of stirring from 5 - 25 minutes gave the good relatively extraction condition to Dy element such as using 10 % volume of TOA in D2EHPA and cyclohexane, the acidity of the feed 3 M and the time stirring 15 minutes produced coefficient distribution to dysprosium = 0.586 and separation factor Dy-Ce = ∼ (unlimited); Dy-Nd = 4.651. (author)

  14. Dynamics of solvent-free grafted nanoparticles

    KAUST Repository

    Chremos, Alexandros; Panagiotopoulos, Athanassios Z.; Koch, Donald L.

    2012-01-01

    as well as grafted nanoparticles in a melt were compared to a reference system of bare (ungrafted) particles in a melt. Whereas longer chains lead to a larger hydrodynamic radius and lower relative diffusivity for grafted particles in a melt, bulk solvent

  15. Solvent (acetone-butanol: ab) production

    Science.gov (United States)

    This article describes production of butanol [acetone-butanol-ethanol, (also called AB or ABE or solvent)] by fermentation using both traditional and current technologies. AB production from agricultural commodities, such as corn and molasses, was an important historical fermentation. Unfortunately,...

  16. Expanding solvent SAGD in heavy oil reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Govind, P.A. [Society of Petroleum Engineers, Canadian Section, Calgary, AB (Canada)]|[ConocoPhillips Canada Resources Corp., Calgary, AB (Canada); Das, S.; Wheeler, T.J. [Society of Petroleum Engineers, Richardson, TX (United States)]|[ConocoPhillips Co., Houston, TX (United States); Srinivasan, S. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Texas Univ., Austin, TX (United States)

    2008-10-15

    Steam assisted gravity drainage (SAGD) projects have proven effective for the recovery of oil and bitumen. Expanding solvent (ES) SAGD pilot projects have also demonstrated positive results of improved performance. This paper presented the results of a simulation study that investigated several important factors of the ES-SAGD process, including solvent types; concentration; operating pressure; and injection strategy. The objectives of the study were to examine the effectiveness of the ES-SAGD process in terms of production acceleration and energy requirements; to optimize solvent selection; to understand the effect of dilation in unconsolidated oil sands and the directional impact on reservoir parameters and oil production rate in ES-SAGD; and to understand the impact of operating conditions such as pressure, solvent concentration, circulation preheating period and the role of conduction heating and grid size in this process. The advantages of ES-SAGD over SAGD were also outlined. The paper presented results of sensitivity studies that were conducted on these four factors. Conclusions and recommendations for operating strategy were also offered. It was concluded that dilation is an important factor for SAGD performance at high operating pressure. 8 refs., 15 figs.

  17. Processing of thermoplastic polymers using reactive solvents

    NARCIS (Netherlands)

    Meijer, H.E.H.; Venderbosch, R.W.; Goossens, J.G.P.; Lemstra, P.J.

    1996-01-01

    The use of reactive solvents offers an interesting and flexible route to extent the processing characteristics of thermoplastic polymers beyond their existing limits. This holds for both intractable and tractable polymers. The first mainly applies for amorphous high-Tg polymers where processing may

  18. Mixed Solvent Reactive Recrystallization of Sodium Carbonate

    NARCIS (Netherlands)

    Gaertner, R.S.

    2005-01-01

    Investigation of the reactive recrystallization of trona (sodium sesquicarbonate) and sodium bicarbonate to sodium carbonate (soda) in a mixed solvent led to the design of several alternative, less energy consumptive, economically very attractive process routes for the production of soda from all

  19. Gas separation by composite solvent-swollen membranes

    Science.gov (United States)

    Matson, Stephen L.; Lee, Eric K. L.; Friesen, Dwayne T.; Kelly, Donald J.

    1989-01-01

    There is disclosed a composite immobulized liquid membrane of a solvent-swollen polymer and a microporous organic or inorganic support, the solvent being at least one highly polar solvent containing at least one nitrogen, oxygen, phosphorous or sulfur atom, and having a boiling point of at least 100.degree. C. and a specified solubility parameter. The solvent or solvent mixture is homogeneously distributed through the solvent-swollen polymer from 20% to 95% by weight. The membrane is suitable for acid gas scrubbing and oxygen/nitrogen separation.

  20. Gas separation by composite solvent-swollen membranes

    Science.gov (United States)

    Matson, S.L.; Lee, E.K.L.; Friesen, D.T.; Kelly, D.J.

    1989-04-25

    There is disclosed a composite immobilized liquid membrane of a solvent-swollen polymer and a microporous organic or inorganic support, the solvent being at least one highly polar solvent containing at least one nitrogen, oxygen, phosphorus or sulfur atom, and having a boiling point of at least 100 C and a specified solubility parameter. The solvent or solvent mixture is homogeneously distributed through the solvent-swollen polymer from 20% to 95% by weight. The membrane is suitable for acid gas scrubbing and oxygen/nitrogen separation. 3 figs.