Sample records for electron diffraction ged

  1. Molecular structures and intramolecular dynamics of pentahalides

    NASA Astrophysics Data System (ADS)

    Ischenko, A. A.

    2017-03-01

    This paper reviews advances of modern gas electron diffraction (GED) method combined with high-resolution spectroscopy and quantum chemical calculations in studies of the impact of intramolecular dynamics in free molecules of pentahalides. Some recently developed approaches to the electron diffraction data interpretation, based on direct incorporation of the adiabatic potential energy surface parameters to the diffraction intensity are described. In this way, complementary data of different experimental and computational methods can be directly combined for solving problems of the molecular structure and its dynamics. The possibility to evaluate some important parameters of the adiabatic potential energy surface - barriers to pseudorotation and saddle point of intermediate configuration from diffraction intensities in solving the inverse GED problem is demonstrated on several examples. With increasing accuracy of the electron diffraction intensities and the development of the theoretical background of electron scattering and data interpretation, it has become possible to investigate complex nuclear dynamics in fluxional systems by the GED method. Results of other research groups are also included in the discussion.

  2. The molecular structure of 4-methylpyridine-N-oxide: Gas-phase electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Belova, Natalya V.; Girichev, Georgiy V.; Kotova, Vitaliya E.; Korolkova, Kseniya A.; Trang, Nguyen Hoang

    2018-03-01

    The molecular structure of 4-methylpiridine-N-oxide, 4-MePyO, has been studied by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and quantum chemical (DFT) calculations. Both, quantum chemistry and GED analyses resulted in CS molecular symmetry with the planar pyridine ring. Obtained molecular parameters confirm the hyperconjugation in the pyridine ring and the sp2 hybridization concept of the nitrogen and carbon atoms in the ring. The experimental geometric parameters are in a good agreement with the parameters for non-substituted N-oxide and reproduced very closely by DFT calculations. The presence of the electron-donating CH3 substituent in 4-MePyO leads to a decrease of the ipso-angle and to an increase of r(N→O) in comparison with the non-substituted PyO. Electron density distribution analysis has been performed in terms of natural bond orbitals (NBO) scheme. The nature of the semipolar N→O bond is discussed.

  3. Thiobenzamide: Structure of a free molecule as studied by gas electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Kolesnikova, Inna N.; Putkov, Andrei E.; Rykov, Anatolii N.; Shishkov, Igor F.

    2018-06-01

    The equilibrium (re) molecular structure of thiobenzamide along with rh1 structure has been determined in gas phase using gas electron-diffraction (GED) at about 127 °C and quantum-chemical calculations (QC). Rovibrational distance corrections to the thermal averaged GED structure have been computed with anharmonic force constants obtained at the MP2/cc-pVTZ level of theory. According to the results of GED and QC thiobenzamide exists as mixture of two non-planar enantiomers of C1 symmetry. The selected equilibrium geometrical parameters of thiobenzamide (re, Å and ∠e, deg) are the following: (Cdbnd S) = 1.641(4), (Csbnd N) = 1.352(2), (Csbnd C) = 1.478(9), (Cdbnd C)av = 1.395(2), CCN = 114.7(5), CCS = 123.4(5), C2C1C7S = 31(4), C6C1C7N = 29(4). The structure of thiobenzamide in the gas phase is markedly different to that in the literature for the single crystal. The differences between the gas and the solid structures are ascribed to the presence of intermolecular hydrogen bonding in the solid phase.

  4. Molecular structures of Se(SCH3)2 and Te(SCH3)2 using gas-phase electron diffraction and ab initio and DFT geometry optimisations.

    PubMed

    Fleischer, Holger; Wann, Derek A; Hinchley, Sarah L; Borisenko, Konstantin B; Lewis, James R; Mawhorter, Richard J; Robertson, Heather E; Rankin, David W H

    2005-10-07

    The molecular structures of Se(SCH(3))(2) and Te(SCH(3))(2) were investigated using gas-phase electron diffraction (GED) and ab initio and DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters (r(h1)) are: rSe-S 219.1(1), rS-C 183.2(1), rC-H 109.6(4) pm; angleS-Se-S 102.9(3), angleSe-S-C 100.6(2), angleS-C-H (mean) 107.4(5), phiS-Se-S-C 87.9(20), phiSe-S-C-H 178.8(19) degrees for Se(SCH(3))(2), and rTe-S 238.1(2), rS-C 184.1(3), rC-H 110.0(6) pm; angleS-Te-S 98.9(6), angleTe-S-C 99.7(4), angleS-C-H (mean) 109.2(9), phiS-Te-S-C 73.0(48), phiTe-S-C-H 180.1(19) degrees for Te(SCH(3))(2). Ab initio and DFT calculations were performed at the HF, MP2 and B3LYP levels, employing either full-electron basis sets [3-21G(d) or 6-31G(d)] or an effective core potential with a valence basis set [LanL2DZ(d)]. The best fit to the GED structures was achieved at the MP2 level. Differences between GED and MP2 results for rS-C and angleS-Te-S were explained by the thermal population of excited vibrational states under the experimental conditions. All theoretical models agreed that each compound exists as two stable conformers, one in which the methyl groups are on the same side (g(+)g(-) conformer) and one in which they are on different sides (g(+)g(+) conformer) of the S-Y-S plane (Y = Se, Te). The conformational composition under the experimental conditions could not be resolved from the GED data. Despite GED R-factors and ab initio and DFT energies favouring the g(+)g(+) conformer, it is likely that both conformers are present, for Se(SCH(3))(2) as well as for Te(SCH(3))(2).

  5. 1-Methoxy-1-silacyclohexane: Synthesis, molecular structure and conformational behavior by gas electron diffraction, Raman spectroscopy and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Shlykov, Sergey A.; Puchkov, Boris V.; Arnason, Ingvar; Wallevik, Sunna Ó.; Giricheva, Nina I.; Girichev, Georgiy V.; Zhabanov, Yuriy A.

    2018-02-01

    The synthesis and results of gas electron diffraction (GED), temperature-dependent Raman spectroscopy, along with detailed quantum chemical (QC) study of 1-methoxy-1-silacyclohexane 1 are reported. Within the series of the QC results, DFT(B3LYP, PBE0, M06, M062X), and MP2, the conformational preference predictions are rather contradictive. From the both GED and Raman experimental methods applied, the vapour and liquid phases of 1 were found to exist as a mixture of two conformers, gauche-axial and gauche-equatorial, with almost equal contributions, while the trans-forms are much less stable. In addition, theoretical calculations on the cyclohexane analog, methoxycyclohexane 2, are performed in order to compare with the conformational properties of 1. The latter is predicted not to diminish the axial/equatorial ratio, as contrasted to the expectations at switching the point of the substituent attachment from Si to C.

  6. Determination of molecular structure of succinic acid in a very complex conformational landscape: Gas-phase electron diffraction (GED) and ab initio studies

    NASA Astrophysics Data System (ADS)

    Vogt, Natalja; Abaev, Maxim A.; Rykov, Anatolii N.; Shishkov, Igor F.

    2011-06-01

    The molecular structure of succinic acid has been investigated by the gas-phase electron diffraction (GED) method for the first time. According to predictions of MP2/cc-pVTZ calculations, the molecule has 18 stable conformers with the C sbnd C sbnd C sbnd C chain in the gauche ( G) or anti ( A) configuration, and four of them, I ( G), II ( A), III ( G) and IV ( A) belonging to the C 2, C 2h, C 1 and C 1 point groups, respectively, with relative energies ΔE ZPE within 2.2 kcal/mol can be present at the experimental temperature of 445 K in noticeable amounts. The ratio of the conformers I:II:III:IV = 45(15):20(15):10(assumed):25(15) (in %) has been determined in the GED analysis guided by theoretical predictions. To take into account vibrational effects, the corrections Δ( r e - r a) to the experimental r a bond lengths were calculated from the MP2/cc-pVTZ quadratic and cubic force constants. The obtained equilibrium structural parameters of the dominant conformer I are the following (bond lengths in Å, angles in degrees): r e(C sp3sbnd C sp3) = 1.508(3), r e(C sp3sbnd C sp2) = 1.499(2), r e(C sbnd O) = 1.343(2), r e(C dbnd O) = 1.202(1), e(C sbnd C sbnd C) = 111.8(4), e(C sbnd C sbnd O) = 112.0(4), e(O sbnd C dbnd O) = 123.0(1), τ(C sbnd C sbnd C sbnd C) = 69.9(11). Yielding the best agreement with the GED structure, the MP2/cc-pVQZ approximation overestimates the C sbnd O and C dbnd O bond lengths by ca. 0.005(2) Å.

  7. Molecular structure and conformational composition of 1,3-dihydroxyacetone studied by combined analysis of gas-phase electron diffraction data, rotational constants, and results of theoretical calculations. Ideal gas thermodynamic properties of 1,3-dihydroxyacetone.

    PubMed

    Dorofeeva, Olga V; Vogt, Natalja; Vogt, Jürgen; Popik, Mikhail V; Rykov, Anatolii N; Vilkov, Lev V

    2007-07-19

    The molecular structure of 1,3-dihydroxyacetone (DHA) has been studied by gas-phase electron diffraction (GED), combined analysis of GED and microwave (MW) data, ab initio, and density functional theory calculations. The equilibrium re structure of DHA was determined by a joint analysis of the GED data and rotational constants taken from the literature. The anharmonic vibrational corrections to the internuclear distances (re-ra) and to the rotational constants (B(i)e-B(i)0) needed for the estimation of the re structure were calculated from the B3LYP/cc-pVTZ cubic force field. It was found that the experimental data are well reproduced by assuming that DHA consists of a mixture of three conformers. The most stable conformer of C2v symmetry has two hydrogen bonds, whereas the next two lowest energy conformers (Cs and C1 symmetry) have one hydrogen bond and their abundance is about 30% in total. A combined analysis of GED and MW data led to the following equilibrium structural parameters (re) of the most abundant conformer of DHA (the uncertainties in parentheses are 3 times the standard deviations): r(C=O)=1.215(2) A, r(C-C)=1.516(2) A, r(C-O)=1.393(2) A, r(C-H)=1.096(4) A, r(O-H)=0.967(4) A, angleC-C=O=119.9(2) degrees, angleC-C-O=111.0(2) degrees, angleC-C-H=108.2(7) degrees, angleC-O-H=106.5(7) degrees. These structural parameters reproduce the experimental B(i)0 values within 0.05 MHz. The experimental structural parameters are in good agreement with those obtained from theoretical calculations. Ideal gas thermodynamic functions (S degrees (T), C degrees p(T), and H degrees (T)-H degrees (0)) of DHA were calculated on the basis of experimental and theoretical molecular parameters obtained in this work. The enthalpy of formation of DHA, -523+/-4 kJ/mol, was calculated by the atomization procedure using the G3X method.

  8. Molecular structure and conformational preferences of gaseous 1-iodo-1-silacyclohexane

    NASA Astrophysics Data System (ADS)

    Belyakov, A. V.; Baskakov, A. A.; Berger, R. J. F.; Mitzel, N. W.; Oberhammer, H.; Arnason, I.; Wallevik, S. Ò.

    2012-03-01

    The molecular structure of the axial and equatorial conformers of 1-iodo-1-silacyclohexane, CH2(CH2CH2)2SiH-I, as well as thermodynamic equilibrium between these species were investigated by means of gas-phase electron diffraction (GED) and quantum chemical calculations up to MP2(full)/SDB-AUG-CC-pVTZ level of theory (MP2). According to electron diffraction data, the vapor of this compound comprises a mixture of conformers with chair conformation and Cs symmetry differing in the axial and equatorial position of the Si-I bond (axial = 73(7) mol%/equatorial = 27(7) mol%) at T = 352 K. This corresponds to a free energy difference of A = -0.59(22) kcal mol-1. The observed gas-phase electron diffraction parameters are in good agreement with those obtained from theory. NBO analysis revealed that axial conformer of 1-iodo-1-silacyclohexane is an example for electrostatic stabilization of a conformer which is unfavorable in terms of steric and conjugation interaction.

  9. Molecular structure of the trans and cis isomers of metal-free phthalocyanine studied by gas-phase electron diffraction and high-level quantum chemical calculations: NH tautomerization and calculated vibrational frequencies.

    PubMed

    Strenalyuk, Tatyana; Samdal, Svein; Volden, Hans Vidar

    2008-05-29

    The molecular structure of the trans isomer of metal-free phthalocyanine (H2Pc) is determined using the gas electron diffraction (GED) method and high-level quantum chemical calculations. B3LYP calculations employing the basis sets 6-31G**, 6-311++G**, and cc-pVTZ give two tautomeric isomers for the inner H atoms, a trans isomer having D2h symmetry and a cis isomer having C2v symmetry. The trans isomer is calculated to be 41.6 (B3LYP/6-311++G**, zero-point corrected) and 37.3 kJ/mol (B3LYP/cc-pVTZ, not zero-point corrected) more stable than the cis isomer. However, Hartree-Fock (HF) calculations using different basis sets predict that cis is preferred and that trans does not exist as a stable form of the molecule. The equilibrium composition in the gas phase at 471 degrees C (the temperature of the GED experiment) calculated at the B3LYP/6-311++G** level is 99.8% trans and 0.2% cis. This is in very good agreement with the GED data, which indicate that the mole fraction of the cis isomer is close to zero. The transition states for two mechanisms of the NH tautomerization have been characterized. A concerted mechanism where the two H atoms move simultaneously yields a transition state of D2h symmetry and an energy barrier of 95.8 kJ/mol. A two-step mechanism where a trans isomer is converted to a cis isomer, which is converted into another trans isomer, proceeds via two transition states of C(s) symmetry and an energy barrier of 64.2 kJ/mol according to the B3LYP/6-311++G** calculation. The molecular geometry determined from GED is in very good agreement with the geometry obtained from the quantum chemical calculations. Vibrational frequencies, IR, and Raman intensities have been calculated using B3LYP/6-311++G**. These calculations indicate that the molecule is rather flexible with six vibrational frequencies in the range of 20-84 cm(-1) for the trans isomer. The cis isomer might be detected by infrared matrix spectroscopy since the N-H stretching frequencies are very different for the two isomers.

  10. Molecular structure and conformations of para-methylbenzene sulfonamide and ortho-methylbenzene sulfonamide: gas electron diffraction and quantum chemical calculations study.

    PubMed

    Petrov, Vjacheslav M; Girichev, Georgiy V; Oberhammer, Heinz; Petrova, Valentina N; Giricheva, Nina I; Bardina, Anna V; Ivanov, Sergey N

    2008-04-03

    The molecular structure and conformational properties of para-methylbenzene sulfonamide (4-MBSA) and ortho-methylbenzene sulfonamide (2-MBSA) have been studied by gas electron diffraction (GED) and quantum chemical methods (B3LYP/6-311+G** and MP2/6-31G**). Quantum chemical calculations predict the existence of two conformers for 4-MBSA with the S-N bond perpendicular to the benzene plane and the NH2 group either eclipsing or staggering the S-O bonds of the SO2 group. Both conformers possess CS symmetry. The eclipsed form is predicted to be favored by DeltaE = 0.63 kcal/mol (B3LYP) or 1.00 kcal/mol (MP2). According to the calculations, the S-N bond in 2-MBSA can possess planar direction opposite the methyl group (phi(C2C1SN) = 180 degrees ) or nonplanar direction (phi(C2C1SN) approximately 60 degrees ). In both cases, the NH2 group can adopt eclipsed or staggered orientation, resulting in a total of four stable conformers. The nonplanar eclipsed conformer (C1 symmetry) and the planar eclipsed form (CS symmetry) are predicted to be favored. According to the GED analysis, the saturated vapor over solid 4-MBSA at T = 151(3) degrees C consists as mixture of the eclipsed (78(19) %) and staggered (22(19) %) forms. The saturated vapor over solid 2-MBSA at T = 157(3) degrees C consists as a mixture of the nonplanar eclipsed (69(11) %) and planar eclipsed (31(11) %) forms.

  11. N-Sulfinylimine compounds, R-NSO: a chemistry family with strong temperament

    NASA Astrophysics Data System (ADS)

    Romano, R. M.; Della Védova, C. O.

    2000-04-01

    In this review, an update on the structural properties and theoretical studies of N-sulfinylimine compounds (R-NSO) is reported. They were deduced using several experimental techniques: gas-electron diffraction (GED), X-ray diffraction, 17O NMR, ultraviolet-visible absorption spectroscopy (UV-Vis), FTIR (including matrix studies of molecular randomisation) and Raman (including pre-resonant Raman spectra). Data are compared with those obtained by theoretical calculations. With these tools, excited state geometry using the time-dependent theory was calculated for these kinds of compounds. The existence of pre-resonant Raman effect was reported recently for R-NSO compounds. The configuration of R-NSO compounds was checked for this series confirming the existence of only one syn configuration. This finding is corroborated by theoretical calculations. The method of preparation is also summarised.

  12. Pseudo-conformer models for linear molecules: Joint treatment of spectroscopic, electron diffraction and ab initio data for the C3O2 molecule

    NASA Astrophysics Data System (ADS)

    Tarasov, Yury I.; Kochikov, Igor V.

    2018-06-01

    Dynamic analysis of the molecules with large-amplitude motions (LAM) based on the pseudo-conformer approach has been successfully applied to various molecules. Floppy linear molecules present a special class of molecular structures that possess a pair of conjugate LAM coordinates but allow one-dimensional treatment. In this paper, previously developed treatment for the semirigid molecules is applied to the carbon suboxide molecule. This molecule characterized by the extremely large CCC bending has been thoroughly investigated by spectroscopic and ab initio methods. However, the earlier electron diffraction investigations were performed within a static approach, obtaining thermally averaged parameters. In this paper we apply a procedure aimed at obtaining the short list of self-consistent reference geometry parameters of a molecule, while all thermally averaged parameters are calculated based on reference geometry, relaxation dependencies and quadratic and cubic force constants. We show that such a model satisfactorily describes available electron diffraction evidence with various QC bending potential energy functions when r.m.s. CCC angle is in the interval 151 ± 2°. This leads to a self-consistent molecular model satisfying spectroscopic and GED data. The parameters for linear reference geometry have been defined as re(CO) = 1.161(2) Å and re(CC) = 1.273(2) Å.

  13. Nitroxoline Molecule: Planar or Not? A Story of Battle between π-π Conjugation and Interatomic Repulsion.

    PubMed

    Tikhonov, Denis S; Sharapa, Dmitry I; Otlyotov, Arseniy A; Solyankin, Peter M; Rykov, Anatolii N; Shkurinov, Alexander P; Grikina, Olga E; Khaikin, Leonid S

    2018-02-15

    The conformational properties of the nitro group in nitroxoline (8-hydroxy-5-nitroquinoline, NXN) were investigated in the gas phase by means of gas electron diffraction (GED) and quantum chemical calculations, and also with solid-state analysis performed using terahertz time-domain spectroscopy (THz-TDS). The results of the GED refinement show that in the equilibrium structure the NO 2 group is twisted by angle ϕ = 8 ± 3° with respect to the 8-hydroxyoquinoline plane. This is the result of interatomic repulsion of oxygen in the NO 2 group from the closest hydrogen, which overcomes the energy gain from the π-π conjugation of the nitro group and aromatic system of 8-hydroxyoquinoline. The computation of equilibrium geometry using MP2/cc-pVXZ (X = T, Q) shows a large overestimation of the ϕ value, while DFT with the cc-pVTZ basis set performs reasonably well. On the other hand, DFT computations with double-ζ basis sets yield a planar structure of NXN. The refined potential energy surface of the torsion vibration the of nitro group in the condensed phase derived from the THz-TDS data indicates the NXN molecule to be planar. This result stays in good agreement with the previous X-ray structure determination. The strength of the π-system conjugation for the NO 2 group and 8-hydroxyoquinoline is discussed using NBO analysis, being further supported by comparison of the refined semiexperimental gas-phase structure of NXN from GED with other nitrocompounds.

  14. Molecular structure and conformational composition of methyl chloroacetate: An electron-diffraction and ab initio molecular orbital investigation

    NASA Astrophysics Data System (ADS)

    Aarset, Kirsten; Boldermo, Kjell Gunnar; Hagen, Kolbjørn

    2010-08-01

    The molecular structure and conformational composition of methyl chloroacetate, H 2ClC sbnd C( dbnd O) sbnd O sbnd CH 3, have been determined by gas-phase electron-diffraction (GED), using results from ab initio molecular orbital calculations (HF, MP2 and MP3/6-311+G(d,p)) to obtain constraints on some of the structural parameters. The molecules exist in the gas-phase at 25 °C as a mixture of two stable conformers: syn with C sbnd Cl eclipsing C dbnd O and gauche with C sbnd H approximately eclipsing C dbnd O. In both of these conformers O sbnd CH 3 is also eclipsing C dbnd O. The experimentally observed conformational composition at 25 °C was 36(8)% syn and 64(8)% gauche (parenthesised values are 2 σ), corresponding to a free energy difference between conformers of ΔGexp° = 1.4(9) kJ/mol. The corresponding theoretical values obtained for Δ G° are 1.1 kJ/mol (HF), 2.3 kJ/mol (MP2), and 2.4 kJ/mol (MP3). The results for the principal distances ( rh1) and angles ( ∠h1) for the major gauche conformer obtained from the combined GED/ ab initio study (2 σ uncertainties) are r(CO sbnd CCl) = 1.502(9) Å, r(C sbnd H) = 1.084(6) Å (average value), r(C sbnd Cl) = 1.782(4) Å, r(C dbnd O) = 1.213(4) Å, r(CO sbnd O) = 1.346(4) Å, r(CH 3sbnd O) = 1.468(10) Å, ∠C sbnd C sbnd Cl = 110.0(6)°, ∠C sbnd C dbnd O = 124.7(6)°, ∠C sbnd C sbnd O = 108.3(10)°, ∠C sbnd O sbnd C = 115.9(8)°, ϕ(Cl sbnd C sbnd C dbnd O) = 111(2)°, ϕ(C sbnd O sbnd C dbnd O) = 3(3)°.

  15. GED Items. Volume 5, Numbers 1-6.

    ERIC Educational Resources Information Center

    GED Items, 1988

    1988-01-01

    The first of six issues of the GED Items Newsletter publishied in 1988 contains articles on General Educational Development (GED) mathematics instruction, suggestions for teaching writing, and public relations and marketing. Issue 2 has articles on GED science instruction, GED for Marines, holistic scoring, and a review of the new GED tests.…

  16. Transitioning the GED[R] Mathematics Test to Computer with and without Accommodations: A Pilot Project

    ERIC Educational Resources Information Center

    Patterson, Margaret Becker; Higgins, Jennifer; Bozman, Martha; Katz, Michael

    2011-01-01

    We conducted a pilot study to see how the GED Mathematics Test could be administered on computer with embedded accessibility tools. We examined test scores and test-taker experience. Nineteen GED test centers across five states and 216 randomly assigned GED Tests candidates participated in the project. GED candidates completed two GED mathematics…

  17. Taking the Easy Way Out: How the GED Testing Program Induces Students to Drop Out.

    PubMed

    Heckman, James J; Humphries, John Eric; Lafontaine, Paul A; Rodríguez, Pedro L

    2012-07-01

    The option to obtain a General Education Development (GED) certificate changes the incentives facing high school students. This paper evaluates the effect of three different GED policy innovations on high school graduation rates. A six point decrease in the GED pass rate due to an increase in passing standards produced a 1.3 point decline in overall dropout rates. The introduction of a GED certification program in high schools in Oregon produced a four percent decrease in graduation rates. Introduction of GED certificates in California increased dropout rates by 3 points. The GED program induces high school students to drop out.

  18. Taking the Easy Way Out: How the GED Testing Program Induces Students to Drop Out

    PubMed Central

    Heckman, James J.; Humphries, John Eric; LaFontaine, Paul A.; Rodríguez, Pedro L.

    2011-01-01

    The option to obtain a General Education Development (GED) certificate changes the incentives facing high school students. This paper evaluates the effect of three different GED policy innovations on high school graduation rates. A six point decrease in the GED pass rate due to an increase in passing standards produced a 1.3 point decline in overall dropout rates. The introduction of a GED certification program in high schools in Oregon produced a four percent decrease in graduation rates. Introduction of GED certificates in California increased dropout rates by 3 points. The GED program induces high school students to drop out. PMID:24634564

  19. Repeat GED[R] Tests Examinees: Who Persists and Who Passes? GED Testing Service [R]Research Studies, 2010-2

    ERIC Educational Resources Information Center

    Zhang, Jizhi; Patterson, Margaret Becker

    2010-01-01

    Like most high-stakes testing programs, the GED[R] testing program allows examinees who do not pass on the first attempt to retake the GED Tests. Studies and reports have described GED Tests candidates' characteristics and testing performance, but no study has targeted repeat examinees. A series of questions related to repeat examinees remains…

  20. Women's and Community Issues Magazine. Final Report.

    ERIC Educational Resources Information Center

    Lutheran Social Mission Society, Philadelphia, PA. Lutheran Settlement House.

    General Educational Development (GED), pre-GED, and adult basic education students and teachers in Lutheran Settlement House Women's Program GED classes participated in the production of two magazines focusing on women's and community issues. The process included the following: surveying GED classes to determine which current issues were of…

  1. GED Items. Volume 4, Numbers 1-6.

    ERIC Educational Resources Information Center

    GED Items, 1987

    1987-01-01

    The first of six issues of the GED Items newsletter published in 1987 contains articles on one company's approach to literacy in the workplace, General Educational Development (GED) teacher training videotapes, and a process model for improving thinking skills. Articles in issue 2 address military recruiting, synthesis thinking skills, and GED in…

  2. 2009 GED Testing Program Statistical Report

    ERIC Educational Resources Information Center

    GED Testing Service, 2010

    2010-01-01

    The "2009 GED[R] Testing Program Statistical Report" is the 52nd annual report in the program's 68-year history of providing a second opportunity for adults without a high school credential to earn their jurisdiction's GED credential. The report provides candidate demographic and GED Test performance statistics as well as historical…

  3. GED Items. The Newsletter of the GED Testing Service, 1998.

    ERIC Educational Resources Information Center

    American Council on Education, Washington, DC. General Educational Development Testing Service.

    This document consists of the five issues of the newsletter of the General Educational Development (GED) Testing Service: January/February, March/April, May/June, September/October, and November/December. Each issue contains information of interest to users of the GED examinations. The feature article for the January/February issue is "Next…

  4. Mathematics: Algebra and Geometry. GED Scoreboost.

    ERIC Educational Resources Information Center

    Hoyt, Cathy

    GED "Scoreboost" materials target exactly the skills one needs to pass the General Educational Development (GED) tests. This book focuses on the GED Mathematics test. To prepare for the test, the test taker needs to learn skills in number and operation sense, data and statistics, geometry and measurement, and algebra. To pass the test,…

  5. As a Path to a Degree, the GED Is Rerouted with Students' Needs in Mind

    ERIC Educational Resources Information Center

    Sieben, Lauren

    2011-01-01

    Many community colleges, along with some public-school districts and family-literacy programs, are overhauling their GED curricula and support services. Nearly 40 million American adults do not have high-school or GED diplomas, according to 2009 data from the American Council on Education, which developed the GED test. Another of the council's…

  6. Schooling, Study, and Academic Goals: The Education of GED Candidates. GED Profiles: Adults in Transition, No. 2.

    ERIC Educational Resources Information Center

    Baldwin, Janet

    1991-01-01

    A fall 1989 nationwide survey of General Educational Development (GED) Tests candidates examined schooling experiences, study patterns, and educational plans. Findings indicated the GED Tests attracted more young adults than older adults, more older women than older men, and equal numbers of young adult men and women. Seven percent of candidates,…

  7. A Report on the Findings of an Adult Education Client Impact Study: A Five Year Follow Up.

    ERIC Educational Resources Information Center

    Moore, Lawrence H.

    A 1980 survey of General Educational Development (GED) equivalency certificate recipients who completed the GED test in 1975 measured influence and impact of successful GED completion on the individual. The sample consisted of 101 former adult students whose records came from the Murray and Paducah, Kentucky, GED testing centers. The survey…

  8. Policies of Test Centers and Jurisdictions and GED[R] Candidate Test Performance. GED Testing Service[R] Research Study, 2009-6. Executive Summary

    ERIC Educational Resources Information Center

    Medhanie, Amanuel; Patterson, Margaret Becker

    2009-01-01

    The economic and employment outlook for individuals without a high school diploma is bleak. For many of these individuals, passing the General Educational Development (GED) Test is the first step in competing in the increasingly demanding job market. GED test-taking policies vary across test centers and jurisdictions, and have the potential to…

  9. GED Test Changes and Attainment: Overview of 2014 GED Test Changes and Attainment in Washington State

    ERIC Educational Resources Information Center

    Larson, Kara; Gaeta, Cristina; Sager, Lou

    2016-01-01

    In January 2014, the GED Testing Service significantly redesigned the GED test to incorporate the Common Core State Standards and the College and Career Readiness Standards for Adult Education. The purpose of this study was to examine the significant changes made to the test in 2014, examine the impact of the changes on Washingtonians, and make…

  10. Science in the General Educational Development (GED) curriculum: Analyzing the science portion of GED programs and exploring adult students' attitudes toward science

    NASA Astrophysics Data System (ADS)

    Hariharan, Joya Reena

    The General Educational Development (GED) tests enable people to earn a high school equivalency diploma and help them to qualify for more jobs and opportunities. Apart from this main goal, GED courses aim at enabling adults to improve the condition of their lives and to cope with a changing society. In today's world, science and technology play an exceedingly important role in helping people better their lives and in promoting the national goals of informed citizenship. Despite the current efforts in the field of secondary science education directed towards scientific literacy and the concept of "Science for all Americans", the literature does not reflect any corresponding efforts in the field of adult education. Science education research appears to have neglected a population that could possibly benefit from it. The purpose of this study is to explore: the science component of GED programs, significant features of the science portion of GED curricula and GED science materials, and adult learners' attitudes toward various aspects of science. Data collection methods included interviews with GED students and instructors, content analysis of relevant materials, and classroom observations. Data indicate that the students in general feel that the science they learn should be relevant to their lives and have direct applications in everyday life. Student understanding of science and interest in it appears to be contingent to their perceiving it as relevant to their lives and to society. Findings indicate that the instructional approaches used in GED programs influence students' perceptions about the relevance of science. Students in sites that use strategies such as group discussions and field trips appear to be more aware of science in the world around them and more enthusiastic about increasing this awareness. However, the dominant strategy in most GED programs is individual reading. The educational strategies used in GED programs generally focus on developing reading skills rather than the internalization of knowledge or influencing attitudes. An interesting finding is that GED science materials do attend to the relevance of science in everyday life but students' appreciation of this depends on the strategies employed.

  11. The Canadianization of the GED. The History and Development of the General Educational Development Testing Program in Canada. Occasional Paper, Number 1.

    ERIC Educational Resources Information Center

    Quigley, Benjamin Allan

    Eight provinces and two territories have built a Canadian General Educational Development (GED) testing program. The Canadian GED program has a number of major Canadian characteristics that have evolved due to a certain inner logic set in motion as the provinces and territories joined the GED program. In order, these provinces and territories have…

  12. Taking the Easy Way Out: How the GED Testing Program Induces Students to Drop Out. NBER Working Paper No. 14044

    ERIC Educational Resources Information Center

    Heckman, James J.; LaFontaine, Paul A.; Rodriguez, Pedro L.

    2008-01-01

    We exploit an exogenous increase in General Educational Development (GED) testing requirements to determine whether raising the difficulty of the test causes students to finish high school rather than drop out and GED certify. We find that a six point decrease in GED pass rates induces a 1.3 point decline in overall dropout rates. The effect size…

  13. Role of glycogen synthase kinase-3β and PPAR-γ on epithelial-to-mesenchymal transition in DSS-induced colorectal fibrosis.

    PubMed

    Di Gregorio, Jacopo; Sferra, Roberta; Speca, Silvia; Vetuschi, Antonella; Dubuquoy, Caroline; Desreumaux, Pierre; Pompili, Simona; Cristiano, Loredana; Gaudio, Eugenio; Flati, Vincenzo; Latella, Giovanni

    2017-01-01

    Intestinal fibrosis is characterized by abnormal production and deposition of extracellular matrix (ECM) proteins by activated myofibroblasts. The main progenitor cells of activated myofibroblasts are the fibroblasts and the epithelial cells, the latter through the epithelial-mesenchymal transition (EMT). To evaluate the action of the new PPAR-γ modulator, GED-0507-34 Levo (GED) on the expression of EMT associated and regulatory proteins such as TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, and GSK-3β, in a mouse model of DSS-induced intestinal fibrosis. Chronic colitis and fibrosis were induced by oral administration of 2.5% DSS (w/v) for 6 weeks. GW9662 (GW), a selective PPAR-γ inhibitor, was also administered by intraperitoneal injection at the dose of 1 mg/kg/day combined with GED treatment. All drugs were administered at the beginning of the second cycle of DSS (day 12). 65 mice were randomly divided into five groups (H2O as controls n = 10, H2O+GED n = 10, DSS n = 15, DSS+GED n = 15, DSS+GED+GW n = 15). The colon was excised for macroscopic examination and histological and morphometric analyses. The level of expression of molecules involved in EMT and fibrosis, like TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, GSK-3β and PPAR-γ, was assessed by immunohistochemistry, immunofluorescence, western blot and Real Time PCR. GED improved the DSS-induced chronic colitis and fibrosis. GED was able to reduce the expression of the main fibrosis markers (α-SMA, collagen I-III and fibronectin) as well as the pivotal pro-fibrotic molecules IL-13, TGF-β and Smad3, while it increased the anti-fibrotic PPAR-γ. All these GED effects were nullified by co-administration of GW with GED. Furthermore, GED was able to normalize the expression levels of E-cadherin and β-catenin and upregulated GSK-3β, that are all known to be involved both in EMT and fibrosis. The DSS-induced intestinal fibrosis was improved by the new PPAR-γ modulator GED-0507-34 Levo through the modulation of EMT mediators and pro-fibrotic molecules and through GSK-3β induction.

  14. Development of NASA's Sample Cartridge Assembly: Summary of GEDS Design, Development Testing, and Thermal Analyses

    NASA Technical Reports Server (NTRS)

    O'Connor, Brian; Hernandez, Deborah; Hornsby, Linda; Brown, Maria; Horton-Mullins, Kathryn

    2017-01-01

    Outline: Background of ISS (International Space Station) Material Science Research Rack; NASA SCA (Sample Cartridge Assembly) Design; GEDS (Gravitational Effects in Distortion in Sintering) Experiment Ampoule Design; Development Testing Summary; Thermal Modeling and Analysis. Summary: GEDS design development challenging (GEDS Ampoule design developed through MUGS (Microgravity) testing; Short duration transient sample processing; Unable to measure sample temperatures); MUGS Development testing used to gather data (Actual LGF (Low Gradient Furnace)-like furnace response; Provided sample for sintering evaluation); Transient thermal model integral to successful GEDS experiment (Development testing provided furnace response; PI (Performance Indicator) evaluation of sintering anchored model evaluation of processing durations; Thermal transient model used to determine flight SCA sample processing profiles).

  15. Perceptions of Program Impact: ABE/GED in Maryland.

    ERIC Educational Resources Information Center

    Walker, Sharon M.; And Others

    A study was conducted among adults enrolled in adult basic education (ABE) General Educational Development (GED) courses to determine their perceptions of the impact of the ABE/GED programs on their employment/economic position, skill and knowledge acquisition, community involvement, attitudinal changes, personal relationships, and continuing…

  16. Technical Manual: 2002 Series GED Tests

    ERIC Educational Resources Information Center

    Ezzelle, Carol; Setzer, J. Carl

    2009-01-01

    This manual was written to provide technical information regarding the 2002 Series GED (General Educational Development) Tests. Throughout this manual, documentation is provided regarding the development of the GED Tests, data collection activities, as well as reliability and validity evidence. The purpose of this manual is to provide evidence…

  17. The Allochthon of Misfit Toys

    ERIC Educational Resources Information Center

    Feig, Anthony D.

    2013-01-01

    This study provides a narrative analysis of the challenges and opportunities faced by scholars in the field of geoscience education (GED). A set of interviews was conducted with five GED professionals in 2010. Participants discussed challenges and opportunities in GED both for individual practitioners and as a discipline. Select participants were…

  18. GED Revision Opens Path to Higher Ed.

    ERIC Educational Resources Information Center

    Gewertz, Catherine

    2011-01-01

    The General Educational Development program, or GED, is undergoing the biggest revamping in its 69-year history, driven by mounting recognition that young adults' future success depends on getting more than a high-school-level education. Potent forces have converged to stoke the GED's redesign. A labor market that increasingly seeks some…

  19. Educational and Labor Market Performance of GED Recipients. Research Synthesis.

    ERIC Educational Resources Information Center

    Boesel, David; Alsalam, Nabeel; Smith, Thomas M.

    In 1995, nearly three-quarters of a million high school dropouts, age 16 and above, took the General Educational Development (GED) tests in pursuit of alternative secondary certification. The GED performs the following functions: stimulate human capital investment; measure and assess cognitive skills; certify dropouts with specified skill and…

  20. Three Studies of General Educational Development (GED) Students--1971-1981.

    ERIC Educational Resources Information Center

    Swarm, Christine C.

    Three studies examined General Educational Development (GED) students in postsecondary institutions and determined their ability to achieve in college without a traditional high school education. A literature review focused on admittance of GED students to institutions of higher learning and students' characteristics. Tests that predict GED…

  1. Interrelation of nonequivalent Csbnd C bonds of naphthalene frame and spatial orientation of substituents: Beta-naphthalene sulfonyl fluoride and beta-naphthalene sulfonyl chloride

    NASA Astrophysics Data System (ADS)

    Giricheva, Nina I.; Petrov, Vjacheslav M.; Oberhammer, Heinz; Petrova, Valentina N.; Dakkouri, Marwan; Ivanov, Sergey N.; Girichev, Georgiy V.

    2013-06-01

    β-naphthalene sulfonyl fluoride, β-NaphSF, and β-naphthalene sulfonyl chloride, β-NaphSCl, were studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 in combination with cc-pVDZ, aug-cc-pVDZ and cc-pVTZ basis sets). For each compound the calculations predicted the existence of two conformers which are enantiomers. On the basis of the experimental data it was found that the gas phase over β-NaphSF and NaphSCl at 357(5) K and 395(5) K, respectively, consists of molecular species of C1 symmetry in which the Cβsbnd Ssbnd Hal plane deviates from the perpendicular orientation relative to the naphthalene skeleton plane. The following geometrical parameters (Å and degrees) were obtained from the experiment (uncertainties are in parentheses): rh1(Csbnd H)aver. = 1.097(7), rh1(Csbnd C)aver. = 1.410(3), rh1(Csbnd S) = 1.753(6), rh1(Ssbnd O)aver. = 1.414(4), rh1(Ssbnd F) = 1.559(5), ∠Csbnd Cβsbnd C = 122.8(3), ∠Cβsbnd Ssbnd F = 103.3(30); Φ(Cαsbnd Cβsbnd Ssbnd F) = 104(6) for β-NaphSF, and rh1(Csbnd H)aver. = 1.089(4), rh1(Csbnd C)aver. = 1.411(3), rh1(Csbnd S) = 1.757(5), rh1(Ssbnd O)aver. = 1.419(3), rh1(Ssbnd Сl) = 2.053(4), ∠Csbnd Cβsbnd C = 122.8(1), ∠Cβsbnd Ssbnd Cl = 102.2(7), Φ(Cαsbnd Cβsbnd Ssbnd Cl) = 108(3) for β-NaphSCl. The calculated barriers to internal rotation of the sulfonyl halide groups exceed considerably the thermal energy values corresponding to the temperatures of the GED experiments. Natural bond orbital (NBO) analyses of the electron density distribution were applied to explain the peculiarities of the molecular structure of the studied compounds and the deviation from the structures of their benzene analogs.

  2. Unifying distance-based goodness-of-fit indicators for hydrologic model assessment

    NASA Astrophysics Data System (ADS)

    Cheng, Qinbo; Reinhardt-Imjela, Christian; Chen, Xi; Schulte, Achim

    2014-05-01

    The goodness-of-fit indicator, i.e. efficiency criterion, is very important for model calibration. However, recently the knowledge about the goodness-of-fit indicators is all empirical and lacks a theoretical support. Based on the likelihood theory, a unified distance-based goodness-of-fit indicator termed BC-GED model is proposed, which uses the Box-Cox (BC) transformation to remove the heteroscedasticity of model errors and the generalized error distribution (GED) with zero-mean to fit the distribution of model errors after BC. The BC-GED model can unify all recent distance-based goodness-of-fit indicators, and reveals the mean square error (MSE) and the mean absolute error (MAE) that are widely used goodness-of-fit indicators imply statistic assumptions that the model errors follow the Gaussian distribution and the Laplace distribution with zero-mean, respectively. The empirical knowledge about goodness-of-fit indicators can be also easily interpreted by BC-GED model, e.g. the sensitivity to high flow of the goodness-of-fit indicators with large power of model errors results from the low probability of large model error in the assumed distribution of these indicators. In order to assess the effect of the parameters (i.e. the BC transformation parameter λ and the GED kurtosis coefficient β also termed the power of model errors) of BC-GED model on hydrologic model calibration, six cases of BC-GED model were applied in Baocun watershed (East China) with SWAT-WB-VSA model. Comparison of the inferred model parameters and model simulation results among the six indicators demonstrates these indicators can be clearly separated two classes by the GED kurtosis β: β >1 and β ≤ 1. SWAT-WB-VSA calibrated by the class β >1 of distance-based goodness-of-fit indicators captures high flow very well and mimics the baseflow very badly, but it calibrated by the class β ≤ 1 mimics the baseflow very well, because first the larger value of β, the greater emphasis is put on high flow and second the derivative of GED probability density function at zero is zero as β >1, but discontinuous as β ≤ 1, and even infinity as β < 1 with which the maximum likelihood estimation can guarantee the model errors approach zero as well as possible. The BC-GED that estimates the parameters (i.e. λ and β) of BC-GED model as well as hydrologic model parameters is the best distance-based goodness-of-fit indicator because not only the model validation using groundwater levels is very good, but also the model errors fulfill the statistic assumption best. However, in some cases of model calibration with a few observations e.g. calibration of single-event model, for avoiding estimation of the parameters of BC-GED model the MAE i.e. the boundary indicator (β = 1) of the two classes, can replace the BC-GED, because the model validation of MAE is best.

  3. GED Preparation through Distance Learning in Rural Pennsylvania

    ERIC Educational Resources Information Center

    Prins, Esther; Drayton, Brendaly; Gungor, Ramazan; Kassab, Cathy

    2011-01-01

    This study investigated the types, use, and effectiveness of distance learning (DL) for General Education Development (GED) candidates in rural Pennsylvania. The research goal was to provide information for enhancing DL GED study options. Specifically, the study, which was conducted in 2009-2010, sought to: identify the types and use of GED…

  4. The Adolescentizing of the GED

    ERIC Educational Resources Information Center

    Rachal, John R.; Bingham, Millard J.

    2004-01-01

    The changing demographic population of GED test-takers from the period of returning World War II veterans to today's younger, recent high school dropouts invites debate as to whether GED instruction should utilize methods of adult education. The growth trends in the U. S. from 1989 to 2001 indicate increasing numbers of 16- and 17-year-olds…

  5. Reliability Analysis for the Internationally Administered 2002 Series GED Tests. GED Testing Service[R] Research Studies, 2009-3

    ERIC Educational Resources Information Center

    Setzer, J. Carl; He, Yi

    2009-01-01

    Reliability Analysis for the Internationally Administered 2002 Series GED (General Educational Development) Tests Reliability refers to the consistency, or stability, of test scores when the authors administer the measurement procedure repeatedly to groups of examinees (American Educational Research Association [AERA], American Psychological…

  6. An Analysis of Rural and Urban Pennsylvania Adults Taking, Completing and Passing the GED

    ERIC Educational Resources Information Center

    Van Horn, Barbara L.; Kassab, Cathy

    2011-01-01

    Dropping out of high school seriously impacts an individual's job opportunities, income potential and employment stability. To minimize those risks, individuals can earn a General Educational Development (GED) credential. Researchers have studied the impact of obtaining a GED on candidates' lives and found that the credential affects their…

  7. Perceptions of College Readiness and Social Capital of GED Completers in Entry-Level College Courses

    ERIC Educational Resources Information Center

    Lott, Donalyn Leufroy

    2012-01-01

    Examining the efficacy of literacy improvement, general education development (GED) completion, and GED completers' perceptions of college readiness and social capital was the purpose of this study. The participant sample (n = 321), derived from the target population (N = 1050), consisted of former participants of Adult Literacy Education…

  8. Examining the Feasibility and Effect of Transitioning GED Tests to Computer

    ERIC Educational Resources Information Center

    Higgins, Jennifer; Patterson, Margaret Becker; Bozman, Martha; Katz, Michael

    2010-01-01

    This study examined the feasibility of administering GED Tests using a computer based testing system with embedded accessibility tools and the impact on test scores and test-taker experience when GED Tests are transitioned from paper to computer. Nineteen test centers across five states successfully installed the computer based testing program,…

  9. Emotional Maturity of Adolescents and Adults in GED Programs

    ERIC Educational Resources Information Center

    Riffle, Billy Joe

    2010-01-01

    When discussing issues relating to students in General Educational Development (GED) Option and pre-GED programs with educators, the contention exists that it is possible to make reasonably accurate predictions on the success or failure of a student by observing a number of items. Looking at their cumulative records shows their academic and…

  10. Crossing the Bridge: GED Credentials and Postsecondary Educational Outcomes. Year One Report

    ERIC Educational Resources Information Center

    Patterson, Margaret Becker; Zhang, Jizhi; Song, Wei; Guison-Dowdy, Anne

    2010-01-01

    For most high school non-completers, the GED[R] credential provides a bridge to postsecondary education, but little is known about how successfully GED (General Educational Development) Test candidates make that transition and whether enrollment rates change with time. The American Council on Education (ACE) has begun a three-year longitudinal…

  11. Factors Influencing the Successful Completion of the General Educational Development (GED) Preparation Program as Perceived by the Students

    ERIC Educational Resources Information Center

    Styles, Theresa

    2011-01-01

    This replicated study (A. Tucho, 2000, "Factors Influencing the General Educational Development [GED] Program at Community College of Philadelphia as Perceived by the GED Students") determined which of the 3 types of educational barriers (institutional, situational, and dispositional) represented the major difficulty preventing adult…

  12. Academic Achievement of GED Graduates of the Community College of Allegheny County.

    ERIC Educational Resources Information Center

    Clark, Renee Smith

    The tests of General Education Development (GED) provide adults with opportunities to attend and graduate from postsecondary institutions. A study investigated the academic achievement of GED recipients compared to that of high school diploma (HSD) students graduating from the Community College of Allegheny County (Pennsylvania) between June 1985…

  13. GED Recipients in Postsecondary Education: A Rural-Urban Analysis of Pennsylvania FAFSA Applicants' Educational, Demographic, and Financial Characteristics

    ERIC Educational Resources Information Center

    Prins, Esther; Kassab, Cathy

    2015-01-01

    Transitions to postsecondary education for GED graduates are a growing concern for educators and policy makers. This article analyzes the educational, demographic, and financial characteristics of Pennsylvania postsecondary students with a GED credential compared with traditional high school graduates, and identifies rural-urban differences within…

  14. GED Items. The Newsletter of the GED Testing Service, 1997.

    ERIC Educational Resources Information Center

    Hone, Lisa Richards, Ed.

    1997-01-01

    This document consists of the six issues of the newsletter of the General Educational Development Testing (GED) Service published during 1997. The lead articles of the six issues are, respectively: (1) "Task Force Considers Improvements to Test Center Security Rules," by Cathy Allin discusses the implementation of a monitoring team and…

  15. GED, HiSET and TASC: A Comparison of High School Equivalency Assessments. ECS Education Trends

    ERIC Educational Resources Information Center

    Zinth, Jennifer

    2015-01-01

    Until January 2014, the General Educational Development (GED) was the only option for youth and adults lacking a high school diploma, but needing a high school credential to pursue employment opportunities or postsecondary education. However, in January 2014, some states began administering one or both alternatives to the GED--the Educational…

  16. Educational and Labor Market Performance of GED Recipients. Research Synthesis. Executive Summary.

    ERIC Educational Resources Information Center

    Boesel, David; Alsalam, Nabeel; Smith, Thomas M.

    In 1995, nearly three-quarters of a million high school dropouts took the General Educational Development (GED) tests. The half million individuals who passed the test accounted for approximately one-sixth of all high school diplomas issued that year. On average, GED recipients perform as well as graduating high school seniors on the five tests…

  17. START! The Successful Transitions and Retention Track Program: A Comprehensive Approach to Supporting GED Holders Entering College

    ERIC Educational Resources Information Center

    Nix, J. Vincent; Michalak, Megan B.

    2012-01-01

    Students entering college face many obstacles to success. Students who received a General Education Development (GED) face additional barriers that must be addressed in order for success in higher education. The Successful Transitions and Retention Track Program employs a holistic approach to addressing the needs of GED holders entering college.

  18. Study of the CASAS Relationship to GED 2002. Research Brief

    ERIC Educational Resources Information Center

    CASAS - Comprehensive Adult Student Assessment Systems (NJ1), 2003

    2003-01-01

    CASAS, in cooperation with the CASAS National Consortium Policy Council, conducted a study to provide guidance to program and instructional staff regarding student readiness to take the GED Tests. The study looked at the relationship of CASAS reading and math scores to official 2002 GED test results from five states--California, Hawaii, Iowa,…

  19. Evaluation of Struggling Readers' Ability to Pass the General Equivalency Diploma

    ERIC Educational Resources Information Center

    Colon, Esteban

    2017-01-01

    There is a lack of standardized instruction among the different General Educational Development (GED) preparatory programs in the country as a result of different state requirements for taking the GED exams. As such, the purpose of this quantitative non-experimental correlational study is to examine if scores of students on GED Ready Opt and the…

  20. The Effect of GED Candidate Race and Motivation Factors on Exam Outcomes

    ERIC Educational Resources Information Center

    Middleton, Kathi Linn

    2017-01-01

    Earning a General Educational Development (GED) credential can have positive results in a student's life including higher wages and better job opportunities. The 2014 version of the GED exam changed the format from a paper-based test to a computer-based test. This change coincided with a 35% decline in the pass rate indicating not all students are…

  1. Academic Rigor and Economic Value: GED[R] and High School Students' Perceptions and Misperceptions of the GED[R] vs. the High School Diploma

    ERIC Educational Resources Information Center

    Horne, Lela M.; Rachal, John R.; Shelley, Kyna

    2012-01-01

    A mixed methods framework utilized quantitative and qualitative data to determine whether statistically significant differences existed between high school and GED[R] student perceptions of credential value. An exploratory factor analysis (n=326) extracted four factors and then a MANOVA procedure was performed with a stratified quota sample…

  2. Is the GED an Effective Route to Postsecondary Education for School Dropouts? NBER Working Paper No. 13816

    ERIC Educational Resources Information Center

    Tyler, John H.; Lofstrom, Magnus

    2008-01-01

    We use data from the Texas Schools Microdata Panel (TSMP) to examine the extent to which dropouts use the GED as a route to post-secondary education. The paper develops a model pointing out the potential biases in estimating the effects of taking the "GED path" to postsecondary education. Lacking suitable instruments that would allow us…

  3. From GED to College Degree: Creating Pathways to Postsecondary Success for High School Dropouts

    ERIC Educational Resources Information Center

    Garvey, John

    2011-01-01

    For many years, the General Educational Development (GED) credential has been viewed as the high school dropout's safety net. Though not as well regarded as the high school diploma, the GED has opened up educational and economic opportunity for millions of young people and adults who did not finish high school. Nearly 680,000 people take the full…

  4. Factors Influencing the Completion of the GED in a Federal Correctional Setting a Multiple Regression Correlation-Predictive Study

    ERIC Educational Resources Information Center

    Akers, Kimberly

    2013-01-01

    Correctional education's primary goal is to reduce recidivism and increase employment among ex-offenders. The Bureau of Prison's practical goal in its mandatory GED program is to maximize the number of inmates obtaining the GED in a given time period. The purpose of this research is to model the number of instructional hours an inmate requires to…

  5. GED Candidates and Their Postsecondary Educational Outcomes: A Pilot Study. GED Testing Service[R] Research Studies, 2009-5. Executive Summary

    ERIC Educational Resources Information Center

    Patterson, Margaret Becker; Song, Wei; Zhang, Jizhi

    2009-01-01

    For most high school non-completers, the GED[R] (General Educational Development) credential is the bridge to postsecondary education, but little is known about how successfully they could make that transition and whether their participation shifts across time. The American Council on Education (ACE) has begun a three-year longitudinal study to…

  6. GED Candidates and Their Postsecondary Educational Outcomes: A Pilot Study. GED Testing Service[R] Research Studies, 2009-5

    ERIC Educational Resources Information Center

    Patterson, Margaret Becker; Song, Wei; Zhang, Jizhi

    2009-01-01

    For most high school non-completers, the GED[R] credential is the bridge to postsecondary education, but little is known about how successfully they could make that transition and whether their participation shifts across time. The American Council on Education (ACE) has begun a three-year longitudinal study to understand the effect of the GED…

  7. What Has Happened to Iowa's GED Graduates? A Two-, Five-, and Ten-Year Follow-Up Study. Final Report.

    ERIC Educational Resources Information Center

    Iowa State Dept. of Education, Des Moines. Div. of Community Colleges.

    A longitudinal study was conducted to determine the short-term (2-year), intermediate (5-year), and long-term (10-year) impact of earning a high school equivalency diploma by taking the General Educational Development (GED) Tests in Iowa. The random sample of 2,500 GED graduates was drawn from each time cohort (individuals who had passed the GED…

  8. The long-term effects of school dropout and GED attainment on substance use disorders.

    PubMed

    Reingle Gonzalez, Jennifer M; Salas-Wright, Christopher P; Connell, Nadine M; Jetelina, Katelyn K; Clipper, Stephen J; Businelle, Michael S

    2016-01-01

    Epidemiologic research suggests that 14% of the population do not complete high school, and dropout has been linked to mental health conditions, substance use, chronic health problems, and criminal behavior. Few studies have assessed whether attainment of the general education development (GED) credential is protective from substance use. To assess the long-term outcomes of school dropout and GED attainment on past year substance use disorders, age of onset, and current smoking status. Longitudinal data were included for lifetime substance users who participated in the National Epidemiological Survey on Alcohol and Related Conditions (Waves I and II). Eligible participants (N=30,608) were classified as having completed high school, dropped out of high school and did not complete a GED, or completed GED at Wave I. Survey logistic regression analyses were used to determine whether high school graduation status was associated with substance use disorders and smoking at Wave II. Multivariate results suggest that participants who dropped out of high school (OR=1.53; p<.01) or attained a GED were more likely to have a past year marijuana use disorder (OR=1.62 p<.01) compared to high school graduates. High school dropouts were also more likely to be current smokers (OR=1.88; p<.05) than graduates. High school dropouts have higher long-term rates of marijuana use disorder and smoking in adulthood than graduates. Attainment of a GED does not appear to be protective from marijuana use disorders in adulthood. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  9. The Influence of Self-Efficacy on Reading Achievement of General Educational Development (GED) and High School Graduates Enrolled in Developmental Reading Skills Courses in an Urban Community College System

    ERIC Educational Resources Information Center

    Barnes, Martha J.

    2010-01-01

    This study was undertaken to investigate the effects of self-efficacy on the performance of General Educational Development (GED) and high school graduates enrolled in developmental reading skills courses. The sample for the study consisted of 100 high school and 31 GED graduates enrolled in developmental reading courses in a midwestern community…

  10. Journeys through College: Postsecondary Transitions and Outcomes of GED[R] Test Passers. Follow-Up Report, Crossing the Bridge, Year Two

    ERIC Educational Resources Information Center

    Guison-Dowdy, Anne; Patterson, Margaret Becker

    2011-01-01

    Since the 1990s, a wealth of literature has compared the benefits of having a GED[R] test credential versus a traditional high school diploma or no high school credential, with an early emphasis on economic impact. One advantage of passing the GED test lies in its ability to open doors to the postsecondary system. Nearly two-thirds of U.S.…

  11. The GED4GEM project: development of a Global Exposure Database for the Global Earthquake Model initiative

    USGS Publications Warehouse

    Gamba, P.; Cavalca, D.; Jaiswal, K.S.; Huyck, C.; Crowley, H.

    2012-01-01

    In order to quantify earthquake risk of any selected region or a country of the world within the Global Earthquake Model (GEM) framework (www.globalquakemodel.org/), a systematic compilation of building inventory and population exposure is indispensable. Through the consortium of leading institutions and by engaging the domain-experts from multiple countries, the GED4GEM project has been working towards the development of a first comprehensive publicly available Global Exposure Database (GED). This geospatial exposure database will eventually facilitate global earthquake risk and loss estimation through GEM’s OpenQuake platform. This paper provides an overview of the GED concepts, aims, datasets, and inference methodology, as well as the current implementation scheme, status and way forward.

  12. Multivariate cross-frequency coupling via generalized eigendecomposition

    PubMed Central

    Cohen, Michael X

    2017-01-01

    This paper presents a new framework for analyzing cross-frequency coupling in multichannel electrophysiological recordings. The generalized eigendecomposition-based cross-frequency coupling framework (gedCFC) is inspired by source-separation algorithms combined with dynamics of mesoscopic neurophysiological processes. It is unaffected by factors that confound traditional CFC methods—such as non-stationarities, non-sinusoidality, and non-uniform phase angle distributions—attractive properties considering that brain activity is neither stationary nor perfectly sinusoidal. The gedCFC framework opens new opportunities for conceptualizing CFC as network interactions with diverse spatial/topographical distributions. Five specific methods within the gedCFC framework are detailed, these are validated in simulated data and applied in several empirical datasets. gedCFC accurately recovers physiologically plausible CFC patterns embedded in noise that causes traditional CFC methods to perform poorly. The paper also demonstrates that spike-field coherence in multichannel local field potential data can be analyzed using the gedCFC framework, which provides significant advantages over traditional spike-field coherence analyses. Null-hypothesis testing is also discussed. DOI: http://dx.doi.org/10.7554/eLife.21792.001 PMID:28117662

  13. Estimation of Value-at-Risk for Energy Commodities via CAViaR Model

    NASA Astrophysics Data System (ADS)

    Xiliang, Zhao; Xi, Zhu

    This paper uses the Conditional Autoregressive Value at Risk model (CAViaR) proposed by Engle and Manganelli (2004) to evaluate the value-at-risk for daily spot prices of Brent crude oil and West Texas Intermediate crude oil covering the period May 21th, 1987 to Novermber 18th, 2008. Then the accuracy of the estimates of CAViaR model, Normal-GARCH, and GED-GARCH was compared. The results show that all the methods do good job for the low confidence level (95%), and GED-GARCH is the best for spot WTI price, Normal-GARCH and Adaptive-CAViaR are the best for spot Brent price. However, for the high confidence level (99%), Normal-GARCH do a good job for spot WTI, GED-GARCH and four kind of CAViaR specifications do well for spot Brent price. Normal-GARCH does badly for spot Brent price. The result seems suggest that CAViaR do well as well as GED-GARCH since CAViaR directly model the quantile autoregression, but it does not outperform GED-GARCH although it does outperform Normal-GARCH.

  14. 28 CFR 544.73 - Program participation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) shall be deemed to be making satisfactory progress toward earning a GED credential or high school... program until the inmate earns a GED credential or high school diploma. At these meetings, the inmate may...

  15. 28 CFR 544.73 - Program participation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) shall be deemed to be making satisfactory progress toward earning a GED credential or high school... program until the inmate earns a GED credential or high school diploma. At these meetings, the inmate may...

  16. 28 CFR 544.73 - Program participation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) shall be deemed to be making satisfactory progress toward earning a GED credential or high school... program until the inmate earns a GED credential or high school diploma. At these meetings, the inmate may...

  17. 28 CFR 544.73 - Program participation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) shall be deemed to be making satisfactory progress toward earning a GED credential or high school... program until the inmate earns a GED credential or high school diploma. At these meetings, the inmate may...

  18. Emergency Department Management of Bronchiolitis in the United States.

    PubMed

    Gong, Constance; Byczkowski, Terri; McAneney, Constance; Goyal, Monika K; Florin, Todd A

    2017-04-24

    The aim of this study was to examine differences between general and pediatric emergency departments (PEDs) in adherence to the American Academy of Pediatrics bronchiolitis management guidelines. We conducted a nationally representative study of ED visits by infants younger than 24 months with bronchiolitis from 2002 to 2011 using the National Hospital Ambulatory Medical Care Survey. Diagnostic testing (complete blood counts, radiographs) and medication use (albuterol, corticosteroids, antibiotics and intravenous fluids) in general emergency departments (GEDs) were compared with those in PEDs before and after 2006 American Academy of Pediatrics guideline publication. Weighted percentages were compared, and logistic regression evaluated the association between ED type and resource use. Of more than 2.5 million ED visits for bronchiolitis from 2002 to 2011, 77.3% occurred in GEDs. General emergency departments were more likely to use radiography (62.7% vs 42.1%; adjusted odds ratio [aOR], 2.4; 95% confidence interval [CI], 1.4-4.1), antibiotics (41.3% vs 18.8%; aOR, 2.8; 95% CI, 1.5-5.2), and corticosteroids (24.3% vs 12.5%; aOR, 2.1; 95% CI, 1.0-4.5) compared with PEDs. Compared with preguideline, after guideline publication PEDs had a greater decrease in radiography use (-19.7%; 95% CI, -39.3% to -0.03%) compared with GEDs (-12.2%; 95% CI, -22.3% to -2.1%), and PEDs showed a significant decline in corticosteroid use (-12.4%; 95% CI, -22.1% to -2.8%), whereas GEDs showed no significant decline (-4.6%; 95% CI, -13.5% to 4.3%). The majority of ED visits for bronchiolitis in the United States occurred in GEDs, yet GEDs had increased use of radiography, corticosteroids, and antibiotics and did not show substantial declines with national guideline publication. Given that national guidelines discourage the use of such tests and treatments in the management of bronchiolitis, efforts are required to decrease ED use of these resources in infants with bronchiolitis, particularly in GEDs.

  19. 28 CFR 544.74 - Work assignment limitations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... program. (2) An inmate ordinarily must show prior attainment of a GED credential or high school diploma in... attainment of a GED credential or high school diploma to be promoted above the minimum pay level or grade in...

  20. 28 CFR 544.74 - Work assignment limitations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... program. (2) An inmate ordinarily must show prior attainment of a GED credential or high school diploma in... attainment of a GED credential or high school diploma to be promoted above the minimum pay level or grade in...

  1. 28 CFR 544.74 - Work assignment limitations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... program. (2) An inmate ordinarily must show prior attainment of a GED credential or high school diploma in... attainment of a GED credential or high school diploma to be promoted above the minimum pay level or grade in...

  2. 28 CFR 544.74 - Work assignment limitations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... program. (2) An inmate ordinarily must show prior attainment of a GED credential or high school diploma in... attainment of a GED credential or high school diploma to be promoted above the minimum pay level or grade in...

  3. 28 CFR 523.20 - Good conduct time.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Judicial Administration BUREAU OF PRISONS, DEPARTMENT OF JUSTICE INMATE ADMISSION, CLASSIFICATION, AND... Educational Development (GED) credential. (c) For inmates serving a sentence for an offense committed on or... satisfactory progress toward earning a General Educational Development (GED) credential, to be eligible for a...

  4. The molecular structure of 5-X-isatines where (X = F, Cl, and Br) determined by gas-phase electron diffraction with theoretical calculations

    NASA Astrophysics Data System (ADS)

    Belyakov, Alexander V.; Nikolaenko, Kirill O.; Davidovich, Pavel B.; Ivanov, Anatolii D.; Ponyaev, Alexander I.; Rykov, Anatolii N.; Shishkov, Igor F.

    2018-01-01

    The molecular structures of 5-X-isatines where X = F (1), Cl (2), and Br (3) were studied by gas-phase electron diffraction (GED) and theoretical calculations at M062X/aug-cc-pVTZ and MP2/aug-cc-pVTZ levels. The best fit of the experimental scattering intensities was obtained for a molecular model of Cs symmetry. The small differences between similar geometric parameters were constrained at the values calculated at the M062X level. The bond distances in the benzene ring are in agreement with their standard values. The (Odbnd)Csbnd C(dbnd O) carbon-carbon bonds of the pyrrole moiety in title compounds (1.581(11), 1.578(8), 1.574(12) Å, respectively) are remarkably lengthened in comparison with standard C(sp2)-C(sp2) value, 1.425(11) Å for N-methylpyrrole. According to NBO analysis this lengthening cannot be attributed to the electrostatic repulsion of oxygen lone pairs alone and is, mainly, due to the hyperconjugation, that is delocalization of oxygen lone pairs of π-type into the corresponding carbon-carbon antibonding orbital, nπ(O)→σ*(Csbnd C). Deletion of σ*(Csbnd C) orbital followed by subsequent geometry optimization led to shortening of the corresponding Csbnd C bond by 0.05-0.06 Å. Electronegative halogen atoms led to increase of Csbnd CXsbnd C endocyclic bond angles at ipso carbon atom as compared with the value of 120° in regular hexagon. According to different aromaticity descriptors, aromaticity of benzene moiety of title compounds is smaller in comparison with benzene molecule. External magnetic field induces diatropic ring current in benzene moiety. Local reactivity descriptors that indicate sites in a molecule that are susceptible to nucleophilic, electrophilic and radical attack are calculated.

  5. Geography matters: the prevalence of diabetes in the Auckland Region by age, gender and ethnicity.

    PubMed

    Warin, Briar; Exeter, Daniel J; Zhao, Jinfeng; Kenealy, Timothy; Wells, Susan

    2016-06-10

    To determine whether the prevalence of diagnosed diabetes in the greater Auckland Region varies by General Electoral District (GED). Using encrypted National Health Identifiers and record linkage of routine health datasets, we identified a regional cohort of people with diagnosed diabetes in 2011 from inpatient records and medication dispensing. The geographical unit of a person's residence (meshblock) was used to determine the GED of residence. We calculated prevalence estimates and 95% confidence intervals and used binary logistic regression to map geographical variations in diabetes. An estimated 63,014 people had diagnosed diabetes in Auckland in 2011, a prevalence of 8.5% of the adult population ≥30 years of age. We found significant variation in diabetes prevalence by age, gender, ethnicity and GED. There was a more than five-fold difference in the unadjusted prevalence of diabetes by GED, ranging from 3.2% (3.1 to 3.4%) in the North Shore to 17.3% (16.8 to 17.7%) in Mangere. Such variations remained after binary logistic regression adjusting for socio-demographic variables. Compared to New Zealand Europeans, Indian people had the highest odds of having diabetes at 3.85 (3.73 to 3.97), while the odds of people living in the most deprived areas having diabetes was nearly twice that of those living in least deprived areas (OR 1.93, [1.87 to 1.99]). Geographic variations in diabetes remained after adjusting for socio-demographic circumstances: people living in GEDs in south-west Auckland were at least 60% more likely than people living in the North Shore GED to have diabetes. There is significant variation in the prevalence of diabetes by GED in Auckland that persists across strata of age group, gender and ethnicity, and persists after controlling for these same variables. These inequities should prompt action by politicians, policymakers, funders, health providers and communities for interventions aimed at reducing such inequities. Geography and its implications on access to and availability of health resources appears to be a key driver of inequity in diabetes rates, supporting an argument for interventions based on geography, especially a public health rather than an individual risk approach.

  6. In Defense of the GED.

    ERIC Educational Resources Information Center

    Hawking, James

    1995-01-01

    Rebuts Cameron and Heckman's conclusion that the General Educational Development (GED) Test is too easy and irrelevant to employers by arguing that their sample was unrepresentative, credible evidence of ease is lacking, and there is no evidence that traditional high school curricula meet employers' needs. Also presents noneconomic and other…

  7. Genomic, Proteomic, and Metabolite Characterization of Gemfibrozil-Degrading Organism Bacillus sp. GeD10.

    PubMed

    Kjeldal, Henrik; Zhou, Nicolette A; Wissenbach, Dirk K; von Bergen, Martin; Gough, Heidi L; Nielsen, Jeppe L

    2016-01-19

    Gemfibrozil is a widely used hypolipidemic and triglyceride lowering drug. Excess of the drug is excreted and discharged into the environment primarily via wastewater treatment plant effluents. Bacillus sp. GeD10, a gemfibrozil-degrader, was previously isolated from activated sludge. It is the first identified bacterium capable of degrading gemfibrozil. Gemfibrozil degradation by Bacillus sp. GeD10 was here studied through genome sequencing, quantitative proteomics and metabolite analysis. From the bacterial proteome of Bacillus sp. GeD10 1974 proteins were quantified, of which 284 proteins were found to be overabundant by more than 2-fold (FDR corrected p-value ≤0.032, fold change (log2) ≥ 1) in response to gemfibrozil exposure. Metabolomic analysis identified two hydroxylated intermediates as well as a glucuronidated hydroxyl-metabolite of gemfibrozil. Overall, gemfibrozil exposure in Bacillus sp. GeD10 increased the abundance of several enzymes potentially involved in gemfibrozil degradation as well as resulted in the production of several gemfibrozil metabolites. The potential catabolic pathway/modification included ring-hydroxylation preparing the substrate for subsequent ring cleavage by a meta-cleaving enzyme. The identified genes may allow for monitoring of potential gemfibrozil-degrading organisms in situ and increase the understanding of microbial processing of trace level contaminants. This study represents the first omics study on a gemfibrozil-degrading bacterium.

  8. GED Test Preparation: Practical Reading. Nutrition, Health, Recipes.

    ERIC Educational Resources Information Center

    Goodman, Deborah

    These instructional materials provide reading materials, recipes, and exercises to help students prepare for the practical reading section of the General Educational Development (GED) Tests. The passages can also help students learn and practice some important life skills in the areas of nutrition and food safety. Basic skill improvement is in…

  9. The Waikiki Lifelong Learning Center. Final Report.

    ERIC Educational Resources Information Center

    Ching, Noelani; Mahuka, Ruth

    The Waikiki Lifelong Learning Center (WLLC) project was undertaken to establish a literacy consortium of visitor industry businesses and the University of Hawaii at Manoa and to develop/implement an instructional program that included bilingual/English-as-a-second language (ESL) and General Educational Development (GED)/pre-GED components. After…

  10. Iowa's Community College Adult Literacy Annual Report. Program Year 2007, July 1, 2006-June 30, 2007

    ERIC Educational Resources Information Center

    Division of Community Colleges and Workforce Preparation, Iowa Department of Education, 2007

    2007-01-01

    This comprehensive document replaces the previously published Benchmark Report, Benchmark Report Executive Summary, Iowa's Community College Basic Literacy Skills Credential Report, Iowa GED Statistical Report, GED Annual Performance Report and Iowa's Adult Literacy Program National Reporting System Annual Performance Report (Graphic…

  11. Post-GED-Credential Employment Experiences of Adults with Special Needs

    ERIC Educational Resources Information Center

    Patterson, Margaret Becker

    2013-01-01

    When transitioning to employment, students with disabilities who do not complete high school face multiple challenges; even beyond the challenges of students who complete a GED® credential later, especially in times of economic downturn and job instability. They cope with sometimes overwhelming struggles from disabling conditions. Thus GED passers…

  12. The Learner Persistence Project at Quinsigamond Community College

    ERIC Educational Resources Information Center

    Kefallinou, Maria

    2009-01-01

    Quinsigamond Community College's (QCC's) Adult Community Learning Center is located in Worcester, Massachusetts, and offers ESOL and ABE/GED classes to students who reside in Worcester and the surrounding towns (urban area). Its ABE/GED program has historically had low retention and persistence. Students often left before the end of the year or…

  13. Disparate Reading Identities of Adult Students in One GED Program

    ERIC Educational Resources Information Center

    Compton-Lilly, Catherine

    2009-01-01

    Identities are constructed throughout people's lives. In this paper, I explored the emerging reading identities of 10 adults who were pursuing GED (General Educational Development) credentials. While part of a much larger study that included many data sources, this paper draws on interview data to examine how one group of adults positioned…

  14. Personological Differences Between Enrolling GED Students Who Drop Out and Who Retain.

    ERIC Educational Resources Information Center

    Wilson, Russell C.

    The Adjective Check List (ACL) was administered to 142 enrolling GED students to investigate the relationship between students' self-descriptions on the instrument and their persuant persistence behavior in the program. It was hypothesized that there would be no significant ACL scale score differences between those students who discontinued their…

  15. The GED. NBER Working Paper No. 16064

    ERIC Educational Resources Information Center

    Heckman, James J.; Humphries, John Eric; Mader, Nicholas S.

    2010-01-01

    The General Educational Development (GED) credential is issued on the basis of an eight hour subject-based test. The test claims to establish equivalence between dropouts and traditional high school graduates, opening the door to college and positions in the labor market. In 2008 alone, almost 500,000 dropouts passed the test, amounting to 12% of…

  16. The Effect of Adaptive Confidence Strategies in Computer-Assisted Instruction on Learning and Learner Confidence

    ERIC Educational Resources Information Center

    Warren, Richard Daniel

    2012-01-01

    The purpose of this research was to investigate the effects of including adaptive confidence strategies in instructionally sound computer-assisted instruction (CAI) on learning and learner confidence. Seventy-one general educational development (GED) learners recruited from various GED learning centers at community colleges in the southeast United…

  17. A source-specific model for lossless compression of global Earth data

    NASA Astrophysics Data System (ADS)

    Kess, Barbara Lynne

    A Source Specific Model for Global Earth Data (SSM-GED) is a lossless compression method for large images that captures global redundancy in the data and achieves a significant improvement over CALIC and DCXT-BT/CARP, two leading lossless compression schemes. The Global Land 1-Km Advanced Very High Resolution Radiometer (AVHRR) data, which contains 662 Megabytes (MB) per band, is an example of a large data set that requires decompression of regions of the data. For this reason, SSM-GED compresses the AVHRR data as a collection of subwindows. This approach defines the statistical parameters for the model prior to compression. Unlike universal models that assume no a priori knowledge of the data, SSM-GED captures global redundancy that exists among all of the subwindows of data. The overlap in parameters among subwindows of data enables SSM-GED to improve the compression rate by increasing the number of parameters and maintaining a small model cost for each subwindow of data. This lossless compression method is applicable to other large volumes of image data such as video.

  18. Classrooms of Spatial Justice: Counter-Spaces and Young Men of Color in a GED Program

    ERIC Educational Resources Information Center

    Schwartz, Joni

    2014-01-01

    This article, based on an ethnographic study of an urban General Education Development (GED) program, suggests that for some marginalized young men of color, Adult education programs are counter-spaces of spatial justice in opposition to previous negative school spaces. Framed by critical race theory (CRT) and drawing on critical geography and…

  19. Implementing the General Education Development (GED) Program in First Nations Communities: Struggles for Power

    ERIC Educational Resources Information Center

    Shields, Tracy Jill; Melville, Wayne

    2015-01-01

    This paper describes an ethnographic case study of eleven First Nations adult learners in a Northern Ontario community attempting to earn secondary school equivalency through the General Education Development (GED) program. The paper maintains a focus on the power differentials at work in both the learners' prior educational endeavours and their…

  20. GED 21st Century Learning Pathways Pilots. Final Report

    ERIC Educational Resources Information Center

    Rutschow, Elizabeth Zachry; Grossman, Amanda; Cullinan, Dan

    2014-01-01

    For the nearly 39 million U.S. adults who do not have a high school diploma, the General Educational Development (GED) programs and exam have served as the main avenue for improving individuals' skills and helping them earn a high school credential. However, few students who start these programs ever get this credential, and even fewer advance to…

  1. Post-GED-Credential College Prospects for Adults with Special Needs

    ERIC Educational Resources Information Center

    Patterson, Margaret Becker

    2014-01-01

    Many adults with special needs, who did not finish high school, complete a GED® credential to go to college. As they prepare to transition, they may encounter barriers and likely require supports to succeed in college. The purpose of this qualitative research paper is to describe the college prospects of transitioning adults with a GED credential…

  2. Examining the Validity of GED[R] Tests Scores with Scheduling and Setting Accommodations. GED Testing Service Research Studies, 2004-1

    ERIC Educational Resources Information Center

    George-Ezzelle, Carol E.; Skaggs, Gary

    2004-01-01

    Current testing standards call for test developers to provide evidence that testing procedures and test scores, and the inferences made based on the test scores, show evidence of validity and are comparable across subpopulations (American Educational Research Association [AERA], American Psychological Association [APA], & National Council on…

  3. General Education Development (GED) Recipients' Life Course Experiences: Humanizing the Findings

    ERIC Educational Resources Information Center

    Hartigan, Lacey A.

    2017-01-01

    This study examines a range of GED recipients' life course contexts and experiences and their relationship with long-term outcomes. Using descriptive comparisons, bivariate tests, and propensity-score matched regression models to analyze data from rounds 1-15 of the National Longitudinal Survey of Youth, 1997, analyses aim to examine: (1)…

  4. G. ED. Paper-Book 1974-1984. The Process of Growth of an Innovation.

    ERIC Educational Resources Information Center

    Verduin-Muller, Henriette, Ed.

    Fifteen papers presented at conferences throughout Europe and in the USSR, Nigeria, Japan, Jamaica, and Tunesia provide an introduction to the research work being done by the graduate level Department of Geography for Education (G.ED.) at the University of Utrecht in the Netherlands. An introductory chapter describes the three G.ED. modules, which…

  5. Promoting Health Literacy through GED Testing

    ERIC Educational Resources Information Center

    Golbeck, Amanda L.; LaBonty, Jan; Paschal, Angelia M.; Harris, Margaret; Ryan, Kerry E.; Molgaard, Craig A.

    2010-01-01

    Using the World Health Organization definition of health for reference and a diverse group of raters, we sought to determine the following about the 931 questions that comprise the seven English pencil-and-paper versions of U.S. GED Official Practice Tests: (a) the prevalence of health-related questions and (b) representation of the eight U.S.…

  6. An Evaluation of the General Educational Development Program at Seminole Community College, Sanford, Florida.

    ERIC Educational Resources Information Center

    Mize, Joanne Page

    In order to gather current data about the General Educational Development (GED) program at Seminole Community College (SCC), Florida, a random sample of 1982 GED examinees were surveyed to determine the examinees' assessment of the quality of instruction, course materials, and learning laboratories at SCC; the center(s) used most often and for…

  7. Constitution of the State of Illinois and United States: Study Guide.

    ERIC Educational Resources Information Center

    Illinois State Office of Education, Springfield.

    The study guide, intended for adults wishing to obtain a General Educational Development (GED) certificate in Illinois, discusses the U.S. Constitution, the Illinois Constitution, the Declaration of Independence, and rules for displaying the U.S. flag. The objective is to aid adults in passing the constitution component of the GED examination.…

  8. The Effects of Self-Regulated Strategy Development on the Writing of Expository Essays for Adults with Written Expression Difficulties: Preparing for the GED

    ERIC Educational Resources Information Center

    Berry, Ann Bassett; Mason, Linda H.

    2012-01-01

    A multiple-probe, multiple-baseline, across-subjects design was used to examine the writing performance of four low-achieving adult students with and without disabilities enrolled in general equivalency diploma (GED) preparatory classes. Students' writing was evaluated before instruction and after self-regulated strategy development (SRSD)…

  9. Second Chances. The Value of Adult Education and the GED

    ERIC Educational Resources Information Center

    Rose, Mike

    2013-01-01

    This is an excerpt from "Back to School: Why Everyone Deserves a Second Chance at Education" (The New Press, 2012). It concludes that GED programs need more resources, not less. The programs tend to be populated by low-to-modest income people who failed school the first time around and now are considered less worthy of investment. GED…

  10. Type of High-School Credentials and Older Age ADL and IADL Limitations: Is the GED Credential Equivalent to a Diploma?

    ERIC Educational Resources Information Center

    Liu, Sze Yan; Chavan, Niraj R.; Glymour, M. Maria

    2013-01-01

    Purpose: Educational attainment is a robust predictor of disability in elderly Americans: older adults with high-school (HS) diplomas have substantially lower disability than individuals who did not complete HS. General Educational Development (GED) diplomas now comprise almost 20% of new HS credentials issued annually in the United States but it…

  11. The Writing Skills Workbook--In Preparation for the GED Test. Test I: The Writing Skills Test. Revised Edition.

    ERIC Educational Resources Information Center

    Carter, Marilyn; And Others

    Intended for students preparing for the General Educational Development (GED) test, this workbook enables them to complete lessons in writing and spelling skills and to take the simulated writing skills tests. The first section contains worksheets on basic writing skills, such as sentence structure, capitalization, and punctuation and the use of…

  12. GED® Collapse: Ohio Needs Launch Pads, Not Barricades. Executive Summary

    ERIC Educational Resources Information Center

    Halbert, Hannah

    2016-01-01

    The number of people attempting and passing the GED has plummeted. The Ohio economy is tough on low-wage workers with limited formal education. Without a high school diploma, it is virtually impossible to get a family-supporting job. But the GED has become a barricade, blocking Ohio workers from career goals, instead of a launching pad. Employers…

  13. GED® Collapse in Ohio: State Needs Launch Pads, Not Barricades. Workforce Development

    ERIC Educational Resources Information Center

    Halbert, Hannah

    2016-01-01

    The number of people attempting and passing the GED has plummeted. The Ohio economy is tough on low-wage workers with limited formal education. Without a high school diploma, it is virtually impossible to get a family-supporting job. But the GED has become a barricade, blocking Ohio workers from career goals, instead of a launching pad. Employers…

  14. The Lived Experiences of GED (RTM) Students: What Do Their Experiences Tell Us?

    ERIC Educational Resources Information Center

    Snider, Susan Lynn

    2010-01-01

    The General Educational Development (GED[R]) Tests, established in 1945, helped determine soldiers' high school qualifications for the workforce, as they returned home from WWII. Because many soldiers dropped out of school to join the military, achieving a certain score on the test was a way for them to demonstrate that they had attained high…

  15. An Exploratory Study of the Educational Support Systems of Female G.E.D. Students.

    ERIC Educational Resources Information Center

    Champagne, Delight E.

    Structured interviews and case analyses were used to assess the support systems of 20 women enrolled in General Educational Development (GED) preparation classes in Connecticut. None was found to have a complete system of support--that is, one lacking in neither sources nor types of support as defined by the researchers--for their educational…

  16. GED Holders in Prison Read Better than Those in the Household Population: Why?

    ERIC Educational Resources Information Center

    Harlow, Caroline Wolf; Jenkins, H. David; Steurer, Stephen

    2010-01-01

    The National Adult Literacy Survey, conducted by the U.S. Department of Education in 1992 and 2003, included federal and state prisoners. One finding of the 2003 survey was that prisoners with a GED scored higher in reading skills than persons in the general population with the equivalent education. In an attempt to explain that unexpected…

  17. High School Equivalency Testing in Arizona. Forum: Responding to Changes in High School Equivalency Testing

    ERIC Educational Resources Information Center

    Hart, Sheryl

    2015-01-01

    For decades, the state of Arizona has used the General Educational Development (GED) Test to award the Arizona High School Equivalency (HSE) Diploma, as the GED Test was the only test available, recognized and accepted in the United States as the measure by which adults could demonstrate the educational attainment equivalent to high school…

  18. Challenges and Solutions to Assisting Older Adults in Completing the GED: A Study of What the Experts Say

    ERIC Educational Resources Information Center

    Brinkley-Etzkorn, Karen E.

    2016-01-01

    The purpose of this study was to investigate the challenges and solutions encountered by Adult Basic Education (ABE) programs currently serving older adults seeking a GED credential in states where this is the only high school equivalency option available. The following questions guided this research: (1) what are the perceived characteristics and…

  19. Development of NASA's Sample Cartridge Assembly: Summary of GEDS Design, Development Testing, and Thermal Analyses

    NASA Technical Reports Server (NTRS)

    O'Connor, Brian; Hernandez, Deborah; Hornsby, Linda; Brown, Maria; Horton-Mullins, Kathryn

    2017-01-01

    NASA's Sample Cartridge Assembly (SCA) project is responsible for designing and validating a payload that contains materials research samples in a sealed environment. The SCA will be heated in the European Space Agency's (ESA) Low Gradient Furnace (LGF) that is housed inside the Material Science Research Rack (MSRR) located on the International Space Station (ISS). The first Principle Investigator (PI) to utilize the SCA will focus on Gravitational Effects on Distortion in Sintering (GEDS) research. This paper will give a summary of the design and development test effort for the GEDS SCA and will discuss the role of thermal analysis in developing test profiles to meet the science and engineering requirements. Lessons learned will be reviewed and salient design features that may differ for each PI will be discussed.

  20. The Devil Is in the Details: Evidence from the GED on the Role of Examination System Details in Determining Who Passes. NCSALL Reports #16.

    ERIC Educational Resources Information Center

    Tyler, John H.; Murnane, Richard J.; Willett, John B.

    A study used data from a long-standing examination system, the General Educational Development (GED) certificate, to illustrate that the details of examination systems have marked impacts on the number of test takers who obtain the desired credential and on the racial/ethnic composition of passers. Data provided by the Florida Department of…

  1. The Health Literacy of U.S. Adults across GED Credential Recipients, High School Graduates, and Non-High School Graduates. GED Testing Service[TM] Research Studies, 2008-1

    ERIC Educational Resources Information Center

    Hsu, Yung-chen

    2008-01-01

    Health literacy is important for all adults. Because lower health literacy is associated with lower educational attainment, many adult basic and literacy education programs increasingly provide health education to low-literate adults to improve their health literacy. Using data from the 2003 National Assessment of Adult Literacy (NAAL), this study…

  2. The Health Literacy of U.S. Adults across GED[R] Credential Recipients, High School Graduates, and Non-High School Graduates. GED Testing Service[R] Research Study, 2008-1. Executive Summary

    ERIC Educational Resources Information Center

    Hsu, Yung-chen

    2008-01-01

    Health literacy is important for all adults. Because lower health literacy is associated with lower educational attainment, many adult basic and literacy education programs increasingly provide health education to low-literate adults to improve their health literacy. Using data from the 2003 National Assessment of Adult Literacy (NAAL), this study…

  3. Comparison of College Performance of General Educational Development (GED) and High School Diploma Students in Nova Scotia and PEI. Now and Tomorrow Excellence in Everything We Do. SP-978-01-11E

    ERIC Educational Resources Information Center

    Penner, Audrey J.

    2011-01-01

    The purpose of this study was to identify differences in performance if any, between learners with a high school diploma, and those with a GED credential, at two postsecondary institutions, Holland College on Prince Edward Island (PEI) and Nova Scotia Community College in Nova Scotia (NS). Of interest is how these adults perform in a postsecondary…

  4. Technology and Application of Indium Phosphide and Related Semiconductors

    DTIC Science & Technology

    1989-03-01

    Application and Insertion, GED-L 80/84-9, Oct 1984 1.2: M. Y. Yen , B. F. Levine, C. G. Bethea, K. K. Choi, and A. Y. Cho, Appl. Phys. Lett. 50 (1987) 927...Schlachetzki, Solid-State Electron. 28 (1985) 299 40 IV,A,5: F. B. Fank, J. D. Crowley, and J. J. Berenz, Microwave Journal, June 1979, p. 86 IV,A.6...Ser. 79 (1986) 703 IV,CIb.6: N. K. Dutta, S. G. Napholtz, R. Yen , R. L. Brown, T. M. Shen, N. A. Olsson, and D. C. Craft, Appl. Phys. Lett. 46 (1985

  5. Time-frequency representations of the sternocleidomastoid muscle electromyographic signal recorded with concentric ring electrodes.

    PubMed

    Estrada, Luis; Torres, Abel; Garcia-Casado, Javier; Sarlabous, Leonardo; Prats-Boluda, Gema; Jane, Raimon

    2016-08-01

    The use of non-invasive methods for the study of respiratory muscle signals can provide clinical information for the evaluation of the respiratory muscle function. The aim of this study was to evaluate time-frequency characteristics of the electrical activity of the sternocleidomastoid muscle recorded superficially by means of concentric ring electrodes (CREs) in a bipolar configuration. The CREs enhance the spatial resolution, attenuate interferences, as the cardiac activity, and also simplify the orientation problem associated to the electrode location. Five healthy subjects underwent a respiratory load test in which an inspiratory load was imposed during the inspiratory phase. During the test, the electromyographic signal of the sternocleidomastoid muscle (EMGsc) and the inspiratory mouth pressure (Pmouth) were acquired. Time-frequency characteristics of the EMGsc signal were analyzed by means of eight time-frequency representations (TFRs): the spectrogram (SPEC), the Morlet scalogram (SCAL), the Wigner-Ville distribution (WVD), the Choi-Williams distribution (CHWD), two generalized exponential distributions (GED1 and GED2), the Born-Jordan distribution (BJD) and the Cone-Kernel distribution (CKD). The instantaneous central frequency of the EMGsc showed an increasing behavior during the inspiratory cycle and with the increase of the inspiratory load. The bilinear TFRs (WVD, CHWD, GEDs and BJD) were less sensitive to cardiac activity interference than classical TFRs (SPEC and SCAL). The GED2 was the TFR that shown the best results for the characterization of the instantaneous central frequency of the EMGsc.

  6. Application of classical simulations for the computation of vibrational properties of free molecules.

    PubMed

    Tikhonov, Denis S; Sharapa, Dmitry I; Schwabedissen, Jan; Rybkin, Vladimir V

    2016-10-12

    In this study, we investigate the ability of classical molecular dynamics (MD) and Monte-Carlo (MC) simulations for modeling the intramolecular vibrational motion. These simulations were used to compute thermally-averaged geometrical structures and infrared vibrational intensities for a benchmark set previously studied by gas electron diffraction (GED): CS 2 , benzene, chloromethylthiocyanate, pyrazinamide and 9,12-I 2 -1,2-closo-C 2 B 10 H 10 . The MD sampling of NVT ensembles was performed using chains of Nose-Hoover thermostats (NH) as well as the generalized Langevin equation thermostat (GLE). The performance of the theoretical models based on the classical MD and MC simulations was compared with the experimental data and also with the alternative computational techniques: a conventional approach based on the Taylor expansion of potential energy surface, path-integral MD and MD with quantum-thermal bath (QTB) based on the generalized Langevin equation (GLE). A straightforward application of the classical simulations resulted, as expected, in poor accuracy of the calculated observables due to the complete neglect of quantum effects. However, the introduction of a posteriori quantum corrections significantly improved the situation. The application of these corrections for MD simulations of the systems with large-amplitude motions was demonstrated for chloromethylthiocyanate. The comparison of the theoretical vibrational spectra has revealed that the GLE thermostat used in this work is not applicable for this purpose. On the other hand, the NH chains yielded reasonably good results.

  7. The structure and conformations of piracetam (2-oxo-1-pyrrolidineacetamide): Gas-phase electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Ksenafontov, Denis N.; Moiseeva, Natalia F.; Khristenko, Lyudmila V.; Karasev, Nikolai M.; Shishkov, Igor F.; Vilkov, Lev V.

    2010-12-01

    The geometric structure of piracetam was studied by quantum chemical calculations (DFT and ab initio), gas electron diffraction (GED), and FTIR spectroscopy. Two stable mirror symmetric isomers of piracetam were found. The conformation of pyrrolidine ring is an envelope in which the C4 atom deviates from the ring plane, the angle between the planes (C3 sbnd C4 sbnd C5) and (C2 sbnd C3 sbnd C5) is 154.1°. The direction of the deviation is the same as that of the side acetamide group. The piracetam molecule is stabilized in the gas phase by an intramolecular hydrogen bond between the N9H 2 group and the oxygen O6, bonded to C2. The principal structural parameters ( re, Å and ∠e, degrees; uncertainties are 3 σLS values) were found to be: r(С3 sbnd С4) = 1.533(1), r(C4 sbnd C5) = 1.540(1), r(N1 sbnd C5) = 1.456(1), r(C2 sbnd C3) = 1.520(1), r(N1 sbnd C7) = 1.452(1), r(C7 sbnd C8) = 1.537(1), r(N1 sbnd C2) = 1.365(2), r(C8 sbnd N9) = 1.360(2), r(C2 dbnd O6) = 1.229(1), r(C8 dbnd O10) = 1.221(1), ∠C2 sbnd N1 sbnd C5 = 113.4(6), ∠N1 sbnd C2 sbnd C3 = 106.9(6), ∠N1 sbnd C7 sbnd C8 = 111.9(6), ∠C7 sbnd C8 sbnd N9 = 112.5(6), ∠N1 sbnd C2 sbnd O6 = 123.0(4), ∠C3 sbnd N1 sbnd C7 = 120.4(4), ∠C7 sbnd C8 sbnd O10 = 120.2(4), ∠C5 sbnd N1 sbnd C2 sbnd O6 = 170(6), ∠C3 sbnd C2 sbnd N1 sbnd C7 = 178(6), ∠C2 sbnd N1 sbnd C7 sbnd C8 = 84.2, ∠N1 sbnd C7 sbnd C8 sbnd O10 = 111.9.

  8. Comparison of ASTER Global Emissivity Database (ASTER-GED) With In-Situ Measurement In Italian Vulcanic Areas

    NASA Astrophysics Data System (ADS)

    Silvestri, M.; Musacchio, M.; Buongiorno, M. F.; Amici, S.; Piscini, A.

    2015-12-01

    LP DAAC released the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Emissivity Database (GED) datasets on April 2, 2014. The database was developed by the National Aeronautics and Space Administration's (NASA) Jet Propulsion Laboratory (JPL), California Institute of Technology. The database includes land surface emissivities derived from ASTER data acquired over the contiguous United States, Africa, Arabian Peninsula, Australia, Europe, and China. In this work we compare ground measurements of emissivity acquired by means of Micro-FTIR (Fourier Thermal Infrared spectrometer) instrument with the ASTER emissivity map extract from ASTER-GED and the emissivity obtained by using single ASTER data. Through this analysis we want to investigate differences existing between the ASTER-GED dataset (average from 2000 to 2008 seasoning independent) and fall in-situ emissivity measurement. Moreover the role of different spatial resolution characterizing ASTER and MODIS, 90mt and 1km respectively, by comparing them with in situ measurements. Possible differences can be due also to the different algorithms used for the emissivity estimation, Temperature and Emissivity Separation algorithm for ASTER TIR band( Gillespie et al, 1998) and the classification-based emissivity method (Snyder and al, 1998) for MODIS. In-situ emissivity measurements have been collected during dedicated fields campaign on Mt. Etna vulcano and Solfatara of Pozzuoli. Gillespie, A. R., Matsunaga, T., Rokugawa, S., & Hook, S. J. (1998). Temperature and emissivity separation from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. IEEE Transactions on Geoscience and Remote Sensing, 36, 1113-1125. Snyder, W.C., Wan, Z., Zhang, Y., & Feng, Y.-Z. (1998). Classification-based emissivity for land surface temperature measurement from space. International Journal of Remote Sensing, 19, 2753-2574.

  9. Nanometres-resolution Kikuchi patterns from materials science specimens with transmission electron forward scatter diffraction in the scanning electron microscope.

    PubMed

    Brodusch, N; Demers, H; Gauvin, R

    2013-04-01

    A charge-coupled device camera of an electron backscattered diffraction system in a scanning electron microscope was positioned below a thin specimen and transmission Kikuchi patterns were collected. Contrary to electron backscattered diffraction, transmission electron forward scatter diffraction provides phase identification and orientation mapping at the nanoscale. The minimum Pd particle size for which a Kikuchi diffraction pattern was detected and indexed reliably was 5.6 nm. An orientation mapping resolution of 5 nm was measured at 30 kV. The resolution obtained with transmission electron forward scatter diffraction was of the same order of magnitude than that reported in electron nanodiffraction in the transmission electron microscope. An energy dispersive spectrometer X-ray map and a transmission electron forward scatter diffraction orientation map were acquired simultaneously. The high-resolution chemical, phase and orientation maps provided at once information on the chemical form, orientation and coherency of precipitates in an aluminium-lithium 2099 alloy. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

  10. Electron Diffraction Using Transmission Electron Microscopy

    PubMed Central

    Bendersky, Leonid A.; Gayle, Frank W.

    2001-01-01

    Electron diffraction via the transmission electron microscope is a powerful method for characterizing the structure of materials, including perfect crystals and defect structures. The advantages of electron diffraction over other methods, e.g., x-ray or neutron, arise from the extremely short wavelength (≈2 pm), the strong atomic scattering, and the ability to examine tiny volumes of matter (≈10 nm3). The NIST Materials Science and Engineering Laboratory has a history of discovery and characterization of new structures through electron diffraction, alone or in combination with other diffraction methods. This paper provides a survey of some of this work enabled through electron microscopy. PMID:27500060

  11. Evaluation of the performance of accelerometer-based gait event detection algorithms in different real-world scenarios using the MAREA gait database.

    PubMed

    Khandelwal, Siddhartha; Wickström, Nicholas

    2017-01-01

    Numerous gait event detection (GED) algorithms have been developed using accelerometers as they allow the possibility of long-term gait analysis in everyday life. However, almost all such existing algorithms have been developed and assessed using data collected in controlled indoor experiments with pre-defined paths and walking speeds. On the contrary, human gait is quite dynamic in the real-world, often involving varying gait speeds, changing surfaces and varying surface inclinations. Though portable wearable systems can be used to conduct experiments directly in the real-world, there is a lack of publicly available gait datasets or studies evaluating the performance of existing GED algorithms in various real-world settings. This paper presents a new gait database called MAREA (n=20 healthy subjects) that consists of walking and running in indoor and outdoor environments with accelerometers positioned on waist, wrist and both ankles. The study also evaluates the performance of six state-of-the-art accelerometer-based GED algorithms in different real-world scenarios, using the MAREA gait database. The results reveal that the performance of these algorithms is inconsistent and varies with changing environments and gait speeds. All algorithms demonstrated good performance for the scenario of steady walking in a controlled indoor environment with a combined median F1score of 0.98 for Heel-Strikes and 0.94 for Toe-Offs. However, they exhibited significantly decreased performance when evaluated in other lesser controlled scenarios such as walking and running in an outdoor street, with a combined median F1score of 0.82 for Heel-Strikes and 0.53 for Toe-Offs. Moreover, all GED algorithms displayed better performance for detecting Heel-Strikes as compared to Toe-Offs, when evaluated in different scenarios. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Energy-resolved coherent diffraction from laser-driven electronic motion in atoms

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony F.

    2017-10-01

    We investigate theoretically the use of energy-resolved ultrafast electron diffraction to image laser-driven electronic motion in atoms. A chirped laser pulse is used to transfer the valence electron of the lithium atom from the ground state to the first excited state. During this process, the electronic motion is imaged by 100-fs and 1-fs electron pulses in energy-resolved diffraction measurements. Simulations show that the angle-resolved spectra reveal the time evolution of the energy content and symmetry of the electronic state. The time-dependent diffraction patterns are further interpreted in terms of the momentum transfer. For the case of incident 1-fs electron pulses, the rapid 2 s -2 p quantum beat motion of the target electron is imaged as a time-dependent asymmetric oscillation of the diffraction pattern.

  13. Ultrafast electron diffraction with megahertz MeV electron pulses from a superconducting radio-frequency photoinjector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Feng, L. W.; Lin, L.; Huang, S. L.

    We report ultrafast relativistic electron diffraction operating at the megahertz repetition rate where the electron beam is produced in a superconducting radio-frequency (rf) photoinjector. We show that the beam quality is sufficiently high to provide clear diffraction patterns from gold and aluminium samples. With the number of electrons, several orders of magnitude higher than that from a normal conducting photocathode rf gun, such high repetition rate ultrafast MeV electron diffraction may open up many new opportunities in ultrafast science.

  14. A measurement of electron-wall interactions using transmission diffraction from nanofabricated gratings

    NASA Astrophysics Data System (ADS)

    Barwick, Brett; Gronniger, Glen; Yuan, Lu; Liou, Sy-Hwang; Batelaan, Herman

    2006-10-01

    Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement of the image charge potential between the electron and the grating bars. Image charge potentials that were about 15% of the value for that of a pure electron-metal wall interaction were found. We varied the electron energy from 50to900eV. The interaction time is of the order of typical metal image charge response times and in principle allows the investigation of image charge formation. In addition to the image charge interaction there is a dephasing process reducing the transverse coherence length of the electron wave. The dephasing process causes broadening of the diffraction peaks and is consistent with a model that ascribes the dephasing process to microscopic contact potentials. Surface structures with length scales of about 200nm observed with a scanning tunneling microscope, and dephasing interaction strength typical of contact potentials of 0.35eV support this claim. Such a dephasing model motivated the investigation of different metallic coatings, in particular Ni, Ti, Al, and different thickness Au-Pd coatings. Improved quality of diffraction patterns was found for Ni. This coating made electron diffraction possible at energies as low as 50eV. This energy was limited by our electron gun design. These results are particularly relevant for the use of these gratings as coherent beam splitters in low energy electron interferometry.

  15. Digital electron diffraction – seeing the whole picture

    PubMed Central

    Beanland, Richard; Thomas, Paul J.; Woodward, David I.; Thomas, Pamela A.; Roemer, Rudolf A.

    2013-01-01

    The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters. PMID:23778099

  16. X-Ray Sum Frequency Diffraction for Direct Imaging of Ultrafast Electron Dynamics

    NASA Astrophysics Data System (ADS)

    Rouxel, Jérémy R.; Kowalewski, Markus; Bennett, Kochise; Mukamel, Shaul

    2018-06-01

    X-ray diffraction from molecules in the ground state produces an image of their charge density, and time-resolved x-ray diffraction can thus monitor the motion of the nuclei. However, the density change of excited valence electrons upon optical excitation can barely be monitored with regular diffraction techniques due to the overwhelming background contribution of the core electrons. We present a nonlinear x-ray technique made possible by novel free electron laser sources, which provides a spatial electron density image of valence electron excitations. The technique, sum frequency generation carried out with a visible pump and a broadband x-ray diffraction pulse, yields snapshots of the transition charge densities, which represent the electron density variations upon optical excitation. The technique is illustrated by ab initio simulations of transition charge density imaging for the optically induced electronic dynamics in a donor or acceptor substituted stilbene.

  17. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory.

    PubMed

    Musumeci, P; Moody, J T; Scoby, C M

    2008-10-01

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10(7)-10(8) electrons packed in bunches of approximately 100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics.

  18. Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

    NASA Astrophysics Data System (ADS)

    Nanni, E. A.; Graves, W. S.; Moncton, D. E.

    2018-01-01

    We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately ten meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.

  19. Energy-weighted dynamical scattering simulations of electron diffraction modalities in the scanning electron microscope.

    PubMed

    Pascal, Elena; Singh, Saransh; Callahan, Patrick G; Hourahine, Ben; Trager-Cowan, Carol; Graef, Marc De

    2018-04-01

    Transmission Kikuchi diffraction (TKD) has been gaining momentum as a high resolution alternative to electron back-scattered diffraction (EBSD), adding to the existing electron diffraction modalities in the scanning electron microscope (SEM). The image simulation of any of these measurement techniques requires an energy dependent diffraction model for which, in turn, knowledge of electron energies and diffraction distances distributions is required. We identify the sample-detector geometry and the effect of inelastic events on the diffracting electron beam as the important factors to be considered when predicting these distributions. However, tractable models taking into account inelastic scattering explicitly are lacking. In this study, we expand the Monte Carlo (MC) energy-weighting dynamical simulations models used for EBSD [1] and ECP [2] to the TKD case. We show that the foil thickness in TKD can be used as a means of energy filtering and compare band sharpness in the different modalities. The current model is shown to correctly predict TKD patterns and, through the dictionary indexing approach, to produce higher quality indexed TKD maps than conventional Hough transform approach, especially close to grain boundaries. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  20. Femtosecond time-resolved MeV electron diffraction

    DOE PAGES

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; ...

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS 2 are obtained utilizing a 5 fC (~3 × 10 4 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated bymore » observing the evolution of Bragg and superlattice peaks of 1T-TaS 2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.« less

  1. Electron diffraction covering a wide angular range from Bragg diffraction to small-angle diffraction.

    PubMed

    Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Mori, Shigeo

    2018-04-09

    We construct an electron optical system to investigate Bragg diffraction (the crystal lattice plane, 10-2 to 10-3 rad) with the objective lens turned off by adjusting the current in the intermediate lenses. A crossover was located on the selected-area aperture plane. Thus, the dark-field imaging can be performed by using a selected-area aperture to select Bragg diffraction spots. The camera length can be controlled in the range of 0.8-4 m without exciting the objective lens. Furthermore, we can observe the magnetic-field dependence of electron diffraction using the objective lens under weak excitation conditions. The diffraction mode for Bragg diffraction can be easily switched to a small-angle electron diffraction mode having a camera length of more than 100 m. We propose this experimental method to acquire electron diffraction patterns that depict an extensive angular range from 10-2 to 10-7 rad. This method is applied to analyze the magnetic microstructures in three distinct magnetic materials, i.e. a uniaxial magnetic structure of BaFe10.35Sc1.6Mg0.05O19, a martensite of a Ni-Mn-Ga alloy, and a helical magnetic structure of Ba0.5Sr1.5Zn2Fe12O22.

  2. Hybrid Modes in Long Wavelength Free Electron Lasers

    DTIC Science & Technology

    2010-12-01

    response, including the time for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and...diffraction along one axis, allowing free space diffraction along the other axis. We continue the analysis of the relativistic electron beam, co-propagating...control diffraction along one axis, allowing free space diffraction along the other axis. We continue the analysis of the relativistic electron beam, co

  3. Structure analysis of the single-domain Si(111)4 × 1-In surface by μ-probe Auger electron diffraction and μ-probe reflection high energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Nakamura, N.; Anno, K.; Kono, S.

    1991-10-01

    A single-domain Si(111)4 × 1-In surface has been studied by μ-probe reflection high-energy electron diffraction (RHEED) to elucidate the symmetry of the 4 × 1 surface. Azimuthal diffraction patterns of In MNN Auger electron have been obtained by a μ-probe Auger electron diffraction (AED) apparatus from the single-domain Si(111)4 × 1-In surface. On the basis of information from scanning tunneling microscopy [J. Microsc. 152 (1988) 727] and under the assumption that the 4 × 1 surface is composed of In-overlayers, the μ-probe AED patterns were kinematically analyzed to reach a concrete model of indium arrangement.

  4. Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

    DOE PAGES

    Nanni, E. A.; Graves, W. S.; Moncton, D. E.

    2018-01-19

    We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately tenmore » meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.« less

  5. Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nanni, E. A.; Graves, W. S.; Moncton, D. E.

    We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately tenmore » meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.« less

  6. 24 CFR 585.3 - Program components.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... have dropped out of high school for educational and employment opportunities by employing them as... to the attainment of a high school diploma or its equivalency (GED), or counseling and assistance in...

  7. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao, Haishuang; Krysiak, Yaşar; Hoffmann, Kristin

    The crystal structure and disorder phenomena of Al{sub 4}B{sub 2}O{sub 9}, an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al{sub 4}B{sub 2}O{sub 9}, prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab initio structure determination based on three-dimensional electron diffraction data from single ordered crystals reveals that edge-connected AlO{sub 6} octahedra expanding along the b axis constitute the backbone. The ordered structure (A) was confirmed by TEM and HAADF-STEM images. Furthermore, disordered crystals with diffuse scattering along themore » b axis are observed. Analysis of the modulation pattern implies a mean superstructure (AAB) with a threefold b axis, where B corresponds to an A layer shifted by ½a and ½c. Diffraction patterns simulated for the AAB sequence including additional stacking disorder are in good agreement with experimental electron diffraction patterns. - Graphical abstract: Crystal structure and disorder phenomena of B-rich Al{sub 4}B{sub 2}O{sub 9} studied by automated electron diffraction tomography (ADT) and described by diffraction simulation using DISCUS. - Highlights: • Ab-initio structure solution by electron diffraction from single nanocrystals. • Detected modulation corresponding mainly to three-fold superstructure. • Diffuse diffraction streaks caused by stacking faults in disordered crystals. • Observed streaks explained by simulated electron diffraction patterns.« less

  8. Observations on the Role of Hydrogen in Facet Formation in Near-alpha Titanium (Preprint)

    DTIC Science & Technology

    2011-05-01

    using quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning...quantitative tilt fractography and electron backscatter diffraction while facet topography was examined using ultra high resolution scanning electron...tilt fractography / electron backscatter diffraction (EBSD) technique in which both the crystallographic orientation of the fractured grain and the

  9. 28 CFR 544.70 - Purpose and scope.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... federal institution who does not have a verified General Educational Development (GED) credential or high school diploma is required to attend an adult literacy program for a minimum of 240 instructional hours...

  10. 28 CFR 544.70 - Purpose and scope.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... federal institution who does not have a verified General Educational Development (GED) credential or high school diploma is required to attend an adult literacy program for a minimum of 240 instructional hours...

  11. 28 CFR 544.70 - Purpose and scope.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... federal institution who does not have a verified General Educational Development (GED) credential or high school diploma is required to attend an adult literacy program for a minimum of 240 instructional hours...

  12. 28 CFR 544.70 - Purpose and scope.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... federal institution who does not have a verified General Educational Development (GED) credential or high school diploma is required to attend an adult literacy program for a minimum of 240 instructional hours...

  13. Total-scattering pair-distribution function of organic material from powder electron diffraction data.

    PubMed

    Gorelik, Tatiana E; Schmidt, Martin U; Kolb, Ute; Billinge, Simon J L

    2015-04-01

    This paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam damage of the sample are possible to resolve.

  14. rf streak camera based ultrafast relativistic electron diffraction.

    PubMed

    Musumeci, P; Moody, J T; Scoby, C M; Gutierrez, M S; Tran, T

    2009-01-01

    We theoretically and experimentally investigate the possibility of using a rf streak camera to time resolve in a single shot structural changes at the sub-100 fs time scale via relativistic electron diffraction. We experimentally tested this novel concept at the UCLA Pegasus rf photoinjector. Time-resolved diffraction patterns from thin Al foil are recorded. Averaging over 50 shots is required in order to get statistics sufficient to uncover a variation in time of the diffraction patterns. In the absence of an external pump laser, this is explained as due to the energy chirp on the beam out of the electron gun. With further improvements to the electron source, rf streak camera based ultrafast electron diffraction has the potential to yield truly single shot measurements of ultrafast processes.

  15. 20 CFR 638.502 - Job Corps basic education program.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... education program. The Job Corps Director shall prescribe or provide for basic education curricula to be... Educational Development (GED); (d) World of work; (e) Health education; (f) Driver education; and (g) English...

  16. 77 FR 33201 - Proposed Collection; Comment Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-05

    ... jointly by states and the state National Guard units, targets at-risk male and female youth ages 16-18... cadets attain a GED (General Education Development) credential. The program also focuses on noncognitive...

  17. Beta-carotene-rich carotenoid-protein preparation and exopolysaccharide production by Rhodotorula rubra GED8 grown with a yogurt starter culture.

    PubMed

    Frengova, Ginka I; Simova, Emilina D; Beshkova, Dora M

    2006-01-01

    The underlying method for obtaining a beta-carotene-rich carotenoid-protein preparation and exopolysaccharides is the associated cultivation of the carotenoid-synthesizing lactose-negative yeast strain Rhodotorula rubra GED8 with the yogurt starter culture (Lactobacillus bulgaricus 2-11 + Streptococcus thermophilus 15HA) in whey ultrafiltrate (45 g lactose/l) with a maximum carotenoid yield of 13.37 mg/l culture fluid on the 4.5th day. The chemical composition of the carotenoid-protein preparation has been identified. The respective carotenoid and protein content is 497.4 microg/g dry cells and 50.3% per dry weight, respectively. An important characteristic of the carotenoid composition is the high percentage (51.1%) of beta-carotene (a carotenoid pigment with the highest provitamin A activity) as compared to 12.9% and 33.7%, respectively, for the other two individual pigments--torulene and torularhodin. Exopolysaccharides (12.8 g/l) synthesized by the yeast and lactic acid cultures, identified as acid biopolymers containing 7.2% glucuronic acid, were isolated in the cell-free supernatant. Mannose, produced exclusively by the yeast, predominated in the neutral carbohydrate biopolymer component (76%). The mixed cultivation of R. rubra GED8 with the yogurt starter (L. bulgaricus 2-11 + S. thermophilus 15HA) in ultrafiltrate under conditions of intracellular production of maximum amount of carotenoids and exopolysaccharides synthesis enables combined utilization of the culture fluid from the fermentation process.

  18. The Heisenberg Uncertainty Principle Demonstrated with An Electron Diffraction Experiment

    ERIC Educational Resources Information Center

    Matteucci, Giorgio; Ferrari, Loris; Migliori, Andrea

    2010-01-01

    An experiment analogous to the classical diffraction of light from a circular aperture has been realized with electrons. The results are used to introduce undergraduate students to the wave behaviour of electrons. The diffraction fringes produced by the circular aperture are compared to those predicted by quantum mechanics and are exploited to…

  19. High quality single shot ultrafast MeV electron diffraction from a photocathode radio-frequency gun

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fu, Feichao; Liu, Shengguang; Zhu, Pengfei

    2014-08-15

    A compact ultrafast electron diffractometer, consisting of an s-band 1.6 cell photocathode radio-frequency gun, a multi-function changeable sample chamber, and a sensitive relativistic electron detector, was built at Shanghai Jiao Tong University. High-quality single-shot transmission electron diffraction patterns have been recorded by scattering 2.5 MeV electrons off single crystalline gold and polycrystalline aluminum samples. The high quality diffraction pattern indicates an excellent spatial resolution, with the ratio of the diffraction ring radius over the ring rms width beyond 10. The electron pulse width is estimated to be about 300 fs. The high temporal and spatial resolution may open new opportunities inmore » various areas of sciences.« less

  20. High quality single shot ultrafast MeV electron diffraction from a photocathode radio-frequency gun.

    PubMed

    Fu, Feichao; Liu, Shengguang; Zhu, Pengfei; Xiang, Dao; Zhang, Jie; Cao, Jianming

    2014-08-01

    A compact ultrafast electron diffractometer, consisting of an s-band 1.6 cell photocathode radio-frequency gun, a multi-function changeable sample chamber, and a sensitive relativistic electron detector, was built at Shanghai Jiao Tong University. High-quality single-shot transmission electron diffraction patterns have been recorded by scattering 2.5 MeV electrons off single crystalline gold and polycrystalline aluminum samples. The high quality diffraction pattern indicates an excellent spatial resolution, with the ratio of the diffraction ring radius over the ring rms width beyond 10. The electron pulse width is estimated to be about 300 fs. The high temporal and spatial resolution may open new opportunities in various areas of sciences.

  1. Total-scattering pair-distribution function of organic material from powder electron diffraction data

    DOE PAGES

    Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; ...

    2015-04-01

    This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering datamore » and avoiding beam-damage of the sample are possible to resolve.« less

  2. Ultrafast electron diffraction optimized for studying structural dynamics in thin films and monolayers

    PubMed Central

    Badali, D. S.; Gengler, R. Y. N.; Miller, R. J. D.

    2016-01-01

    A compact electron source specifically designed for time-resolved diffraction studies of free-standing thin films and monolayers is presented here. The sensitivity to thin samples is achieved by extending the established technique of ultrafast electron diffraction to the “medium” energy regime (1–10 kV). An extremely compact design, in combination with low bunch charges, allows for high quality diffraction in a lensless geometry. The measured and simulated characteristics of the experimental system reveal sub-picosecond temporal resolution, while demonstrating the ability to produce high quality diffraction patterns from atomically thin samples. PMID:27226978

  3. Dark-field imaging based on post-processed electron backscatter diffraction patterns of bulk crystalline materials in a scanning electron microscope.

    PubMed

    Brodusch, Nicolas; Demers, Hendrix; Gauvin, Raynald

    2015-01-01

    Dark-field (DF) images were acquired in the scanning electron microscope with an offline procedure based on electron backscatter diffraction (EBSD) patterns (EBSPs). These EBSD-DF images were generated by selecting a particular reflection on the electron backscatter diffraction pattern and by reporting the intensity of one or several pixels around this point at each pixel of the EBSD-DF image. Unlike previous studies, the diffraction information of the sample is the basis of the final image contrast with a pixel scale resolution at the EBSP providing DF imaging in the scanning electron microscope. The offline facility of this technique permits the selection of any diffraction condition available in the diffraction pattern and displaying the corresponding image. The high number of diffraction-based images available allows a better monitoring of deformation structures compared to electron channeling contrast imaging (ECCI) which is generally limited to a few images of the same area. This technique was applied to steel and iron specimens and showed its high capability in describing more rigorously the deformation structures around micro-hardness indents. Due to the offline relation between the reference EBSP and the EBSD-DF images, this new technique will undoubtedly greatly improve our knowledge of deformation mechanism and help to improve our understanding of the ECCI contrast mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Femtosecond gas phase electron diffraction with MeV electrons.

    PubMed

    Yang, Jie; Guehr, Markus; Vecchione, Theodore; Robinson, Matthew S; Li, Renkai; Hartmann, Nick; Shen, Xiaozhe; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Gaffney, Kelly; Gorkhover, Tais; Hast, Carsten; Jobe, Keith; Makasyuk, Igor; Reid, Alexander; Robinson, Joseph; Vetter, Sharon; Wang, Fenglin; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin

    2016-12-16

    We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect of velocity mismatch between pump laser pulses and the probe electron pulses, and maintaining a low timing jitter. At electron kinetic energies above 3 MeV, the velocity mismatch between laser and electron pulses becomes negligible. The relativistic electrons are also less susceptible to temporal broadening due to the Coulomb force. One of the challenges of diffraction with relativistic electrons is that the small de Broglie wavelength results in very small diffraction angles. In this paper we describe the new setup and its characterization, including capturing static diffraction patterns of molecules in the gas phase, finding time-zero with sub-picosecond accuracy and first time-resolved diffraction experiments. The new device can achieve a temporal resolution of 100 fs root-mean-square, and sub-angstrom spatial resolution. The collimation of the beam is sufficient to measure the diffraction pattern, and the transverse coherence is on the order of 2 nm. Currently, the temporal resolution is limited both by the pulse duration of the electron pulse on target and by the timing jitter, while the spatial resolution is limited by the average electron beam current and the signal-to-noise ratio of the detection system. We also discuss plans for improving both the temporal resolution and the spatial resolution.

  5. A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

    PubMed Central

    Nederlof, Igor; van Genderen, Eric; Li, Yao-Wang; Abrahams, Jan Pieter

    2013-01-01

    When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e− Å−2), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins. PMID:23793148

  6. Three-dimensional electron diffraction of plant light-harvesting complex

    PubMed Central

    Wang, Da Neng; Kühlbrandt, Werner

    1992-01-01

    Electron diffraction patterns of two-dimensional crystals of light-harvesting chlorophyll a/b-protein complex (LHC-II) from photosynthetic membranes of pea chloroplasts, tilted at different angles up to 60°, were collected to 3.2 Å resolution at -125°C. The reflection intensities were merged into a three-dimensional data set. The Friedel R-factor and the merging R-factor were 21.8 and 27.6%, respectively. Specimen flatness and crystal size were critical for recording electron diffraction patterns from crystals at high tilts. The principal sources of experimental error were attributed to limitations of the number of unit cells contributing to an electron diffraction pattern, and to the critical electron dose. The distribution of strong diffraction spots indicated that the three-dimensional structure of LHC-II is less regular than that of other known membrane proteins and is not dominated by a particular feature of secondary structure. ImagesFIGURE 1FIGURE 2 PMID:19431817

  7. Imaging electronic motions by ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony F.

    2017-08-01

    Recently ultrafast electron diffraction and microscopy have reached unprecedented temporal resolution, and transient structures with atomic precision have been observed in various reactions. It is anticipated that these extraordinary advances will soon allow direct observation of electronic motions during chemical reactions. We therefore performed a series of theoretical investigations and simulations to investigate the imaging of electronic motions in atoms and molecules by ultrafast electron diffraction. Three prototypical electronic motions were considered for hydrogen atoms. For the case of a breathing mode, the electron density expands and contracts periodically, and we show that the time-resolved scattering intensities reflect such changes of the charge radius. For the case of a wiggling mode, the electron oscillates from one side of the nucleus to the other, and we show that the diffraction images exhibit asymmetric angular distributions. The last case is a hybrid mode that involves both breathing and wiggling motions. Owing to the demonstrated ability of ultrafast electrons to image these motions, we have proposed to image a coherent population transfer in lithium atoms using currently available femtosecond electron pulses. A frequency-swept laser pulse adiabatically drives the valence electron of a lithium atom from the 2s to 2p orbitals, and a time-delayed electron pulse maps such motion. Our simulations show that the diffraction images reflect this motion both in the scattering intensities and the angular distributions.

  8. Incident-beam effects in electron-stimulated Auger-electron diffraction

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Cao, Jianming

    1991-04-01

    We have examined incident-beam effects in electron-stimulated Auger-electron diffraction (AED) on a cleaved GaAs(110) surface. The results indicate that incident-beam diffraction is significant in an AED experiment, and that the dissipative nature of the incident beam in contributing to the Auger process must be accounted for. We have developed a qualitative model that describes the trend of the polar-angle dependence of the Auger intensity for both the incident and exit beams. In calculating the diffraction features, we used a zeroth-order approximation to simulate the dissipation of the incident beam, which is found to adequately describe the experimental data.

  9. Exploring coherent electron excitation and migration dynamics by electron diffraction with ultrashort X-ray pulses.

    PubMed

    Yuan, Kai-Jun; Bandrauk, André D

    2017-10-04

    Exploring ultrafast charge migration is of great importance in biological and chemical reactions. We present a scheme to monitor attosecond charge migration in molecules by electron diffraction with spatial and temporal resolutions from ab initio numerical simulations. An ultraviolet pulse creates a coherent superposition of electronic states, after which a time-delayed attosecond X-ray pulse is used to ionize the molecule. It is found that diffraction patterns in the X-ray photoelectron spectra show an asymmetric structure, which is dependent on the time delay between the pump-probe pulses, encoding the information of molecular orbital symmetry and chemical bonding. We describe these phenomena by developing an electronic time-dependent ultrafast molecular photoionization model of a coherent superposition state. The periodical distortion of electron diffraction patterns illustrates the evolution of the electronic coherence, providing a tool for attosecond imaging of ultrafast molecular reaction processes.

  10. School connectedness and high school graduation among maltreated youth.

    PubMed

    Lemkin, Allison; Kistin, Caroline J; Cabral, Howard J; Aschengrau, Ann; Bair-Merritt, Megan

    2018-01-01

    Maltreated youth have higher rates of school dropout than their non-maltreated peers. School connectedness is a modifiable predictor of school success. We hypothesized maltreated youth's school connectedness (supportive relationships with adults at school and participation in school clubs) would be positively associated with high school graduation. We included youth with at least one Child Protective Services (CPS) report by age twelve from Longitudinal Studies of Child Abuse and Neglect, a prospective cohort study. Participation in extracurricular activities and adult relationships reported at age 16, high school graduation/General Education Development (GED) status reported at age 18, and demographics were provided by youth and caregivers. Maltreatment data were coded from CPS records. The outcome was graduation/receipt of GED. Multivariable logistic regressions examined the association between school connectedness and graduation/receipt of GED, controlling for confounders. In our sample of 318 maltreated youth, 73.3% graduated. School club was the only activity with a statistically significant association with graduation in bivariate analysis. Having supportive relationships with an adult at school was not significantly associated with graduation, though only 10.7% of youth reported this relationship. Maltreated youth who participated in school clubs had 2.54 times the odds of graduating, adjusted for study site, gender, poverty status, caregiver high school graduation status, and age at first CPS report (95% CI: [1.02, 6.33]). Few maltreated youth reported relationships with adults at school, and additional efforts may be needed to support these vulnerable youth. School club participation may represent an opportunity to modify maltreated youth's risk for school dropout. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Improvement and comparison of likelihood functions for model calibration and parameter uncertainty analysis within a Markov chain Monte Carlo scheme

    NASA Astrophysics Data System (ADS)

    Cheng, Qin-Bo; Chen, Xi; Xu, Chong-Yu; Reinhardt-Imjela, Christian; Schulte, Achim

    2014-11-01

    In this study, the likelihood functions for uncertainty analysis of hydrological models are compared and improved through the following steps: (1) the equivalent relationship between the Nash-Sutcliffe Efficiency coefficient (NSE) and the likelihood function with Gaussian independent and identically distributed residuals is proved; (2) a new estimation method of the Box-Cox transformation (BC) parameter is developed to improve the effective elimination of the heteroscedasticity of model residuals; and (3) three likelihood functions-NSE, Generalized Error Distribution with BC (BC-GED) and Skew Generalized Error Distribution with BC (BC-SGED)-are applied for SWAT-WB-VSA (Soil and Water Assessment Tool - Water Balance - Variable Source Area) model calibration in the Baocun watershed, Eastern China. Performances of calibrated models are compared using the observed river discharges and groundwater levels. The result shows that the minimum variance constraint can effectively estimate the BC parameter. The form of the likelihood function significantly impacts on the calibrated parameters and the simulated results of high and low flow components. SWAT-WB-VSA with the NSE approach simulates flood well, but baseflow badly owing to the assumption of Gaussian error distribution, where the probability of the large error is low, but the small error around zero approximates equiprobability. By contrast, SWAT-WB-VSA with the BC-GED or BC-SGED approach mimics baseflow well, which is proved in the groundwater level simulation. The assumption of skewness of the error distribution may be unnecessary, because all the results of the BC-SGED approach are nearly the same as those of the BC-GED approach.

  12. Electron coherent diffraction tomography of a nanocrystal

    NASA Astrophysics Data System (ADS)

    Dronyak, Roman; Liang, Keng S.; Tsai, Jin-Sheng; Stetsko, Yuri P.; Lee, Ting-Kuo; Chen, Fu-Rong

    2010-05-01

    Coherent diffractive imaging (CDI) with electron or x-ray sources is a promising technique for investigating the structure of nanoparticles down to the atomic scale. In electron CDI, a two-dimensional reconstruction is demonstrated using highly coherent illumination from a field-emission gun as a source of electrons. In a three-dimensional (3D) electron CDI, we experimentally determine the morphology of a single MgO nanocrystal using the Bragg diffraction geometry. An iterative algorithm is applied to invert the 3D diffraction pattern about a (200) reflection of the nanoparticle measured at an angular range of 1.8°. The results reveal a 3D image of the sample at ˜8 nm resolution, and agree with a simulation. Our work demonstrates an alternative approach to obtain the 3D structure of nanocrystals with an electron microscope.

  13. Suppressing Ghost Diffraction in E-Beam-Written Gratings

    NASA Technical Reports Server (NTRS)

    Wilson, Daniel; Backlund, Johan

    2009-01-01

    A modified scheme for electron-beam (E-beam) writing used in the fabrication of convex or concave diffraction gratings makes it possible to suppress the ghost diffraction heretofore exhibited by such gratings. Ghost diffraction is a spurious component of diffraction caused by a spurious component of grating periodicity as described below. The ghost diffraction orders appear between the main diffraction orders and are typically more intense than is the diffuse scattering from the grating. At such high intensity, ghost diffraction is the dominant source of degradation of grating performance. The pattern of a convex or concave grating is established by electron-beam writing in a resist material coating a substrate that has the desired convex or concave shape. Unfortunately, as a result of the characteristics of electrostatic deflectors used to control the electron beam, it is possible to expose only a small field - typically between 0.5 and 1.0 mm wide - at a given fixed position of the electron gun relative to the substrate. To make a grating larger than the field size, it is necessary to move the substrate to make it possible to write fields centered at different positions, so that the larger area is synthesized by "stitching" the exposed fields.

  14. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hayashida, Misa; Malac, Marek; Egerton, Ray F.

    Electron tomography is a method whereby a three-dimensional reconstruction of a nanoscale object is obtained from a series of projected images measured in a transmission electron microscope. We developed an electron-diffraction method to measure the tilt and azimuth angles, with Kikuchi lines used to align a series of diffraction patterns obtained with each image of the tilt series. Since it is based on electron diffraction, the method is not affected by sample drift and is not sensitive to sample thickness, whereas tilt angle measurement and alignment using fiducial-marker methods are affected by both sample drift and thickness. The accuracy ofmore » the diffraction method benefits reconstructions with a large number of voxels, where both high spatial resolution and a large field of view are desired. The diffraction method allows both the tilt and azimuth angle to be measured, while fiducial marker methods typically treat the tilt and azimuth angle as an unknown parameter. The diffraction method can be also used to estimate the accuracy of the fiducial marker method, and the sample-stage accuracy. A nano-dot fiducial marker measurement differs from a diffraction measurement by no more than ±1°.« less

  15. The prototype nuclear Compton telescope: Observations of the Galactic Anticenter region

    NASA Astrophysics Data System (ADS)

    Bowen, Jason Dione

    Observations of the Galactic Anticenter region and atmospheric 511 keV positron annihilation emission have been performed with a prototype of the Nuclear Compton Telescope (NCT) during a high altitude balloon flight on June 1, 2005 from Ft. Sumner, NM. NCT is a balloon-borne soft gamma-ray (0.2 MeV to 10 MeV) germanium Compton telescope (GCT) designed to study astrophysical sources of nuclear line emission and polarization through spectroscopy and imaging. A prototype instrument was successfully launched from Ft. Sumner, NM on June 1, 2005. The NCT prototype consists of two 3D position-sensitive high purity germanium strip detectors (GeDs). The compact design and new technologies allow NCT to achieve high efficiencies with excellent spectral resolution and background reduction. The GeDs are custom 15 mm thick cross-strip detectors each with an active area of 54 cm 2 and are enclosed in an aluminum cryostat capable of supporting up to 12 detectors. Here is presented a detailed study of approximately 8 hours of background measurements made from 890 g/cm 2 (1265 m ) to an average float altitude of 3.0 g/cm 2 (40 km ), with particular emphasis on float observations. A total of 6 hr 9 min of observation time was acquired at float, while the duration of the ascent portion of the flight included in this study was 2 hr. The expected contributions to the background are discussed, especially in light of detailed Monte Carlo simulations modeling the entire flight and incorporating complete depth dependent environmental inputs, including 4 cosmic components (protons, photons, electrons, and positrons) and 8 atmospheric components (photons, atmospheric 511 keV emission, neutrons, protons, electrons, positrons, and muons). The results of these investigations include the component makeup of the total background as a function of atmospheric depth, and the contribution of delayed emission due to neutron and proton activation of passive materials. At 1 MeV photons emitted following delayed neutron induced reactions comprise ~ 15% of the total background at small depths. The observed background due to this component is a result of Compton scattering of 1.779 MeV ( 29 Al, t 1/2 = 2.24 min ) photons out of the instrument following neutron capture by 28 Al nuclei. The sources of these photons are the substantial amount of aluminum materials surrounding the instrument. Studies of nuclear line emission require accurate energy calibrations. The NCT prototype consists of two 3D position-sensitive GeDs with 2 × 37 × 37 orthogonal strips for energy measurements. Each strip requires a unique energy calibration. For the electrodes under high voltage (-800 V ) the collected charge is dependent on interaction depth, with charge losses in transit presumably due to trapping and/or recombination. The measured electron trapping lengths for the two GeDs are 1264 cm and 930.3 cm , and the measured hole trapping lengths are 1149.2 cm and 847.3 cm , respectively. The total energy loss at 662 keV approaches 0.1%. Additional losses of up to 0.4% occur at the detector surfaces containing the low voltage electrodes. The positron annihilation line has been observed as a function of atmospheric depth. Simulations suggest contributions to this line from b + -decay and pair production in passive materials are negligible at all depths, and that the line fraction due to positron annihilation in passive materials varies approximately linearly with depth: at large depths (> 700 g cm -2 ) the fraction is > 50% and for depths < 5 g cm -2 the contribution is less than 0.3%. A major result of these studies is that essentially all of the 511 keV line measurements at float are due to atmospheric emissions. At an average float altitude of 2.9 g cm - 2 the vertical atmospheric annihilation line flux measured by the prototype Nuclear Compton Telescope is 3.5 × 10^-2 ( cm 2 s sr keV ) -1 . Images of 511 keV emission at float altitudes are presented. The Galactic Anticenter Region was observed in nine continuum energy bands from 100 keV to 1.5 MeV. Received fluxes from the Crab Nebula are at the sensitivity threshold of the NCT prototype for this flight. 3 s upper limits for the 100- 200, 150-450, 200-600, 250-750, 300-900, 350-1050, 400-1200, 450-1350, and 500- 1500 keV bands are 8.9, 4.9, 3.2, 5.3, 3.1, 4.0, 3.8, 4.7, and 4.7 × 10^-2 cm - 2 s -1 , respectively.

  16. Dynamic diffraction effects and coherent breathing oscillations in ultrafast electron diffraction in layered 1T-TaSeTe

    PubMed Central

    Wei, Linlin; Sun, Shuaishuai; Guo, Cong; Li, Zhongwen; Sun, Kai; Liu, Yu; Lu, Wenjian; Sun, Yuping; Tian, Huanfang; Yang, Huaixin; Li, Jianqi

    2017-01-01

    Anisotropic lattice movements due to the difference between intralayer and interlayer bonding are observed in the layered transition-metal dichalcogenide 1T-TaSeTe following femtosecond laser pulse excitation. Our ultrafast electron diffraction investigations using 4D-transmission electron microscopy (4D-TEM) clearly reveal that the intensity of Bragg reflection spots often changes remarkably due to the dynamic diffraction effects and anisotropic lattice movement. Importantly, the temporal diffracted intensity from a specific crystallographic plane depends on the deviation parameter s, which is commonly used in the theoretical study of diffraction intensity. Herein, we report on lattice thermalization and structural oscillations in layered 1T-TaSeTe, analyzed by dynamic diffraction theory. Ultrafast alterations of satellite spots arising from the charge density wave in the present system are also briefly discussed. PMID:28470025

  17. Coherent diffraction imaging analysis of shape-controlled nanoparticles with focused hard X-ray free-electron laser pulses.

    PubMed

    Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi

    2013-01-01

    We report the first demonstration of the coherent diffraction imaging analysis of nanoparticles using focused hard X-ray free-electron laser pulses, allowing us to analyze the size distribution of particles as well as the electron density projection of individual particles. We measured 1000 single-shot coherent X-ray diffraction patterns of shape-controlled Ag nanocubes and Au/Ag nanoboxes and estimated the edge length from the speckle size of the coherent diffraction patterns. We then reconstructed the two-dimensional electron density projection with sub-10 nm resolution from selected coherent diffraction patterns. This method enables the simultaneous analysis of the size distribution of synthesized nanoparticles and the structures of particles at nanoscale resolution to address correlations between individual structures of components and the statistical properties in heterogeneous systems such as nanoparticles and cells.

  18. Time-resolved measurements with streaked diffraction patterns from electrons generated in laser plasma wakefield

    NASA Astrophysics Data System (ADS)

    He, Zhaohan; Nees, John; Hou, Bixue; Krushelnick, Karl; Thomas, Alec; Beaurepaire, Benoît; Malka, Victor; Faure, Jérôme

    2013-10-01

    Femtosecond bunches of electrons with relativistic to ultra-relativistic energies can be robustly produced in laser plasma wakefield accelerators (LWFA). Scaling the electron energy down to sub-relativistic and MeV level using a millijoule laser system will make such electron source a promising candidate for ultrafast electron diffraction (UED) applications due to the intrinsic short bunch duration and perfect synchronization with the optical pump. Recent results of electron diffraction from a single crystal gold foil, using LWFA electrons driven by 8-mJ, 35-fs laser pulses at 500 Hz, will be presented. The accelerated electrons were collimated with a solenoid magnetic lens. By applying a small-angle tilt to the magnetic lens, the diffraction pattern can be streaked such that the temporal evolution is separated spatially on the detector screen after propagation. The observable time window and achievable temporal resolution are studied in pump-probe measurements of photo-induced heating on the gold foil.

  19. High quality single shot diffraction patterns using ultrashort megaelectron volt electron beams from a radio frequency photoinjector.

    PubMed

    Musumeci, P; Moody, J T; Scoby, C M; Gutierrez, M S; Bender, H A; Wilcox, N S

    2010-01-01

    Single shot diffraction patterns using a 250-fs-long electron beam have been obtained at the UCLA Pegasus laboratory. High quality images with spatial resolution sufficient to distinguish closely spaced peaks in the Debye-Scherrer ring pattern have been recorded by scattering the 1.6 pC 3.5 MeV electron beam generated in the rf photoinjector off a 100-nm-thick Au foil. Dark current and high emittance particles are removed from the beam before sending it onto the diffraction target using a 1 mm diameter collimating hole. These results open the door to the study of irreversible phase transformations by single shot MeV electron diffraction.

  20. High-resolution scanning precession electron diffraction: Alignment and spatial resolution.

    PubMed

    Barnard, Jonathan S; Johnstone, Duncan N; Midgley, Paul A

    2017-03-01

    Methods are presented for aligning the pivot point of a precessing electron probe in the scanning transmission electron microscope (STEM) and for assessing the spatial resolution in scanning precession electron diffraction (SPED) experiments. The alignment procedure is performed entirely in diffraction mode, minimising probe wander within the bright-field (BF) convergent beam electron diffraction (CBED) disk and is used to obtain high spatial resolution SPED maps. Through analysis of the power spectra of virtual bright-field images extracted from the SPED data, the precession-induced blur was measured as a function of precession angle. At low precession angles, SPED spatial resolution was limited by electronic noise in the scan coils; whereas at high precession angles SPED spatial resolution was limited by tilt-induced two-fold astigmatism caused by the positive spherical aberration of the probe-forming lens. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Evidence for the suppression of incident beam effects in Auger electron diffraction

    NASA Astrophysics Data System (ADS)

    Davoli, I.; Gunnella, R.; Bernardini, R.; De Crescenzi, M.

    1998-01-01

    Auger electron diffraction (AED) of the Cu(100) surface has been studied through the anisotropy of the elastic backdiffused beam electrons, the L 2,3M 4,5M 4,5 (LVV) and the M 2,3M 4,5M 4,5 (MVV) transitions in polar scan along the two main directions [001], [011] and in azimuth scan at normal emission. The intensity anisotropies of the low and high kinetic energy Auger lines are in antiphase to each other as in experiments in which these transitions are excited by X-ray photons. This behaviour has been exploited to single out the origin of the physical mechanisms accompanying the diffraction of the emitted electrons. Incident beam effects appear to be sizeable only when the collection of the AED spectra are made with an angle integrating electron analyser (cylindrical mirror analyser or low electron energy diffraction apparatus), but they appear negligible when electron collection is performed through a small solid-angle detector. The conclusions reached by our measurements are supported by good agreement with experimental and theoretical X-ray photoelectron diffraction data and demonstrate that, when the incident beam energy is sufficiently higher than the kinetic energy of the Auger electron detected, the influence of the incident beam on AED is negligible.

  2. Structure of a Bacterial Dynamin-like Protein Lipid Tube Provides a Mechanism For Assembly and Membrane Curving

    PubMed Central

    Low, Harry H.; Sachse, Carsten; Amos, Linda A.; Löwe, Jan

    2009-01-01

    Summary Proteins of the dynamin superfamily mediate membrane fission, fusion, and restructuring events by polymerizing upon lipid bilayers and forcing regions of high curvature. In this work, we show the electron cryomicroscopy reconstruction of a bacterial dynamin-like protein (BDLP) helical filament decorating a lipid tube at ∼11 Å resolution. We fitted the BDLP crystal structure and produced a molecular model for the entire filament. The BDLP GTPase domain dimerizes and forms the tube surface, the GTPase effector domain (GED) mediates self-assembly, and the paddle region contacts the lipids and promotes curvature. Association of BDLP with GMPPNP and lipid induces radical, large-scale conformational changes affecting polymerization. Nucleotide hydrolysis seems therefore to be coupled to polymer disassembly and dissociation from lipid, rather than membrane restructuring. Observed structural similarities with rat dynamin 1 suggest that our results have broad implication for other dynamin family members. PMID:20064379

  3. Crystallography and Morphology of Niobium Carbide in As-Cast HP-Niobium Reformer Tubes

    NASA Astrophysics Data System (ADS)

    Buchanan, Karl G.; Kral, Milo V.

    2012-06-01

    The microstructures of two as-cast heats of niobium-modified HP stainless steels were characterized. Particular attention was paid to the interdendritic niobium-rich carbides formed during solidification of these alloys. At low magnifications, these precipitates are grouped in colonies of similar lamellae. Higher magnifications revealed that the lamellae actually obtain two distinct morphologies. The type I morphology exhibits broad planar interfaces with a smooth platelike shape. Type II lamellae have undulating interfaces and an overall reticulated shape. To provide further insight into the origin of these two different morphologies, the microstructure and crystallography of each have been studied in detail using high resolution scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (electron backscatter diffraction (EBSD), selected area diffraction (SAD), and convergent beam electron diffraction (CBED)), and energy dispersive X-ray spectroscopy.

  4. Excitation of phonons in medium-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Alvarez, M. A. Vicente; Ascolani, H.; Zampieri, G.

    1996-03-01

    The ``elastic'' backscattering of electrons from crystalline surfaces presents two regimes: a low-energy regime, in which the characteristic low-energy electron diffraction (LEED) pattern is observed, and a medium-energy regime, in which the diffraction pattern is similar to those observed in x-ray photoemission diffraction (XPD) and Auger electron diffraction (AED) experiments. We present a model for the electron scattering which, including the vibrational degrees of freedom of the crystal, contains both regimes and explains the passage from one regime to the other. Our model is based on a separation of the electron and atomic motions (adiabatic approximation) and on a cluster-type formulation of the multiple scattering of the electron. The inelastic scattering events (excitation and/or absorption of phonons) are treated as coherent processes and no break of the phase relation between the incident and the exit paths of the electron is assumed. The LEED and the medium-energy electron diffraction regimes appear naturally in this model as the limit cases of completely elastic scattering and of inelastic scattering with excitation and/or absorption of multiple phonons. Intensity patterns calculated with this model are in very good agreement with recent experiments of electron scattering on Cu(001) at low and medium energies. We show that there is a correspondence between the type of intensity pattern and the mean number of phonons excited and/or absorbed during the scattering: a LEED-like pattern is observed when this mean number is less than 2, LEED-like and XPD/AED-like features coexist when this number is 3-4, and a XPD/AED-like pattern is observed when this number is greater than 5-6.

  5. Diffraction effects and inelastic electron transport in angle-resolved microscopic imaging applications.

    PubMed

    Winkelmann, A; Nolze, G; Vespucci, S; Naresh-Kumar, G; Trager-Cowan, C; Vilalta-Clemente, A; Wilkinson, A J; Vos, M

    2017-09-01

    We analyse the signal formation process for scanning electron microscopic imaging applications on crystalline specimens. In accordance with previous investigations, we find nontrivial effects of incident beam diffraction on the backscattered electron distribution in energy and momentum. Specifically, incident beam diffraction causes angular changes of the backscattered electron distribution which we identify as the dominant mechanism underlying pseudocolour orientation imaging using multiple, angle-resolving detectors. Consequently, diffraction effects of the incident beam and their impact on the subsequent coherent and incoherent electron transport need to be taken into account for an in-depth theoretical modelling of the energy- and momentum distribution of electrons backscattered from crystalline sample regions. Our findings have implications for the level of theoretical detail that can be necessary for the interpretation of complex imaging modalities such as electron channelling contrast imaging (ECCI) of defects in crystals. If the solid angle of detection is limited to specific regions of the backscattered electron momentum distribution, the image contrast that is observed in ECCI and similar applications can be strongly affected by incident beam diffraction and topographic effects from the sample surface. As an application, we demonstrate characteristic changes in the resulting images if different properties of the backscattered electron distribution are used for the analysis of a GaN thin film sample containing dislocations. © 2017 The Authors. Journal of Microscopy published by JohnWiley & Sons Ltd on behalf of Royal Microscopical Society.

  6. Data processing software suite SITENNO for coherent X-ray diffraction imaging using the X-ray free-electron laser SACLA.

    PubMed

    Sekiguchi, Yuki; Oroguchi, Tomotaka; Takayama, Yuki; Nakasako, Masayoshi

    2014-05-01

    Coherent X-ray diffraction imaging is a promising technique for visualizing the structures of non-crystalline particles with dimensions of micrometers to sub-micrometers. Recently, X-ray free-electron laser sources have enabled efficient experiments in the `diffraction before destruction' scheme. Diffraction experiments have been conducted at SPring-8 Angstrom Compact free-electron LAser (SACLA) using the custom-made diffraction apparatus KOTOBUKI-1 and two multiport CCD detectors. In the experiments, ten thousands of single-shot diffraction patterns can be collected within several hours. Then, diffraction patterns with significant levels of intensity suitable for structural analysis must be found, direct-beam positions in diffraction patterns determined, diffraction patterns from the two CCD detectors merged, and phase-retrieval calculations for structural analyses performed. A software suite named SITENNO has been developed to semi-automatically apply the four-step processing to a huge number of diffraction data. Here, details of the algorithm used in the suite are described and the performance for approximately 9000 diffraction patterns collected from cuboid-shaped copper oxide particles reported. Using the SITENNO suite, it is possible to conduct experiments with data processing immediately after the data collection, and to characterize the size distribution and internal structures of the non-crystalline particles.

  7. Data processing software suite SITENNO for coherent X-ray diffraction imaging using the X-ray free-electron laser SACLA

    PubMed Central

    Sekiguchi, Yuki; Oroguchi, Tomotaka; Takayama, Yuki; Nakasako, Masayoshi

    2014-01-01

    Coherent X-ray diffraction imaging is a promising technique for visualizing the structures of non-crystalline particles with dimensions of micrometers to sub-micrometers. Recently, X-ray free-electron laser sources have enabled efficient experiments in the ‘diffraction before destruction’ scheme. Diffraction experiments have been conducted at SPring-8 Angstrom Compact free-electron LAser (SACLA) using the custom-made diffraction apparatus KOTOBUKI-1 and two multiport CCD detectors. In the experiments, ten thousands of single-shot diffraction patterns can be collected within several hours. Then, diffraction patterns with significant levels of intensity suitable for structural analysis must be found, direct-beam positions in diffraction patterns determined, diffraction patterns from the two CCD detectors merged, and phase-retrieval calculations for structural analyses performed. A software suite named SITENNO has been developed to semi-automatically apply the four-step processing to a huge number of diffraction data. Here, details of the algorithm used in the suite are described and the performance for approximately 9000 diffraction patterns collected from cuboid-shaped copper oxide particles reported. Using the SITENNO suite, it is possible to conduct experiments with data processing immediately after the data collection, and to characterize the size distribution and internal structures of the non-crystalline particles. PMID:24763651

  8. A compact electron gun for time-resolved electron diffraction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Robinson, Matthew S.; Lane, Paul D.; Wann, Derek A., E-mail: derek.wann@york.ac.uk

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolutionmore » of the diffraction pattern.« less

  9. Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

    NASA Astrophysics Data System (ADS)

    He, Z.-H.; Thomas, A. G. R.; Beaurepaire, B.; Nees, J. A.; Hou, B.; Malka, V.; Krushelnick, K.; Faure, J.

    2013-02-01

    We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

  10. 28 CFR 544.81 - Program goals.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Program goals. 544.81 Section 544.81 Judicial Administration BUREAU OF PRISONS, DEPARTMENT OF JUSTICE INSTITUTIONAL MANAGEMENT EDUCATION... an Adult Literacy program leading to a General Educational Development (GED) certificate and/or high...

  11. 78 FR 49548 - Comment Request for Information Collection for Job Corps Application Data (Job Corps Enrollee...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-14

    ... the nation's largest residential educational and career technical training program for young Americans... Educational Development (GED), and career technical training credentials, including industry-recognized... DEPARTMENT OF LABOR Employment and Training Administration Comment Request for Information...

  12. Innovations and Planning.

    ERIC Educational Resources Information Center

    Schwartz, Beverly, Ed.

    The proceedings deal with a wide range of topics in Adult Basic Education. Workshop proceedings are included covering: resources and dissemination; administrators; curriculum and instructional personnel in both General Educational Development (GED) and English as a Second Language programs; use and dissemination of new programing practices;…

  13. Diffraction and microscopy with attosecond electron pulse trains

    NASA Astrophysics Data System (ADS)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Attosecond spectroscopy1-7 can resolve electronic processes directly in time, but a movie-like space-time recording is impeded by the too long wavelength ( 100 times larger than atomic distances) or the source-sample entanglement in re-collision techniques8-11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons1-7 or re-colliding wavepackets8-11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a < 10-as delay of Bragg emission and demonstrates the possibility of analytic attosecond-ångström diffraction. Real-space electron microscopy visualizes with sub-light-cycle resolution how an optical wave propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space-time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

  14. Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Genderen, E. van; Clabbers, M. T. B.; Center for Cellular Imaging and NanoAnalytics

    A specialized quantum area detector for electron diffraction studies makes it possible to solve the structure of small organic compound nanocrystals in non-cryo conditions by direct methods. Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e{sup −} Å{sup −2} s{sup −1}) were collected at roommore » temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014)« less

  15. Two-dimensional mapping of polarizations of rhombohedral nanostructures in the orthorhombic phase of KNbO3 by the combined use of scanning transmission electron microscopy and convergent-beam electron diffraction

    NASA Astrophysics Data System (ADS)

    Tsuda, Kenji; Tanaka, Michiyoshi

    2015-08-01

    Rhombohedral nanostructures previously found in the orthorhombic phase of KNbO3, by convergent-beam electron diffraction [Tsuda et al., Appl. Phys. Lett. 102, 051913 (2013)], have been investigated by the combined use of scanning transmission electron microscopy and convergent-beam electron diffraction. Two-dimensional distributions of the rhombohedral nanostructures, or nanometer-scale spatial fluctuations of polarization clusters, have been successfully visualized. The correlation length of the observed spatial fluctuations of local polarizations is related to the cpc/apc ratio and the transition entropy.

  16. Oxygen isotope geochemistry of the amphiboles: isotope effects of cation substitutions in minerals

    NASA Astrophysics Data System (ADS)

    Kohn, Matthew J.; Valley, John W.

    1998-06-01

    The occurrence of coexisting amphiboles in rocks and the likelihood of concurrent isotope closure allows equilibrium oxygen isotope fractionations among the amphiboles to be recovered from natural samples. Oxygen isotope analyses of mineral separates using laser fluorination show that coexisting amphiboles increasingly partition 18O in the order: hornblende ≪ gedrite < cummingtonite ≤ anthophyllite. The observed fractionations at ˜575°C are: Δ(Ged-Hbl) = 0.8‰, Δ(Cum-Hbl) = 0.9, Δ(Cum-Ged) = 0.2, Δ(Ath-Ged) = 0.3, and Δ(Ath-Hbl) > 0.9. Previously published data for hornblende, actinolite, glaucophane, and garnet show that Δ(Act-Hbl) ˜ 0.2, Δ(Gln-Grt) ≫ 1, and Δ(Hbl-Grt) ˜ 0. Thus, glaucophane strongly partitions 18O relative to the calcic amphiboles. The fractionation between two amphiboles of arbitrary composition can be predicted from the known fractionations for mica endmembers, pyroxene endmembers, and exchange components such as CaAl(NaSi) -1, NaAl(CaMg) -1, CaMg -1, MgFe -1, FeMn -1, KNa -1, KAl( Si) -1, and Fe 3+Al -1. Applications of the exchange component method reproduce measured amphibole fractionations to within ±0.1 to ±0.2‰, whereas other predictive methods cause misfit for typical metamorphic hornblende of ≥0.5‰ at 575°C. Although the isotope effects of cation exchanges may be small at high-T, they magnify dramatically for minerals formed in surficial, diagenetic, and low-T metamorphic environments. Different composition clays are predicted to have equilibrium δ 18O differences of 2-9‰. If the isotope fractionation can be determined for one mineral endmember, then calibrated exchanges allow accurate prediction of the isotope fractionations for intermediate compositions of most ortho-, ring-, chain-, and sheet-silicates.

  17. Comparison of in-situ measurements and satellite-derived surface emissivity over Italian volcanic areas

    NASA Astrophysics Data System (ADS)

    Silvestri, Malvina; Musacchio, Massimo; Cammarano, Diego; Fabrizia Buongiorno, Maria; Amici, Stefania; Piscini, Alessandro

    2016-04-01

    In this work we compare ground measurements of emissivity collected during dedicated fields campaign on Mt. Etna and Solfatara of Pozzuoli volcanoes and acquired by means of Micro-FTIR (Fourier Thermal Infrared spectrometer) instrument with the emissivity obtained by using single ASTER data (Advanced Spaceborne Thermal Emission and Reflection Radiometer, ASTER 05) and the ASTER emissivity map extract from ASTER Global Emissivity Database (GED), released by LP DAAC on April 2, 2014. The database was developed by the National Aeronautics and Space Administration's (NASA) Jet Propulsion Laboratory (JPL), California Institute of Technology. The database includes land surface emissivity derived from ASTER data acquired over the contiguous United States, Africa, Arabian Peninsula, Australia, Europe, and China. Through this analysis we want to investigate the differences existing between the ASTER-GED dataset (average from 2000 to 2008 seasoning independent) and fall in-situ emissivity measurement. Moreover the role of different spatial resolution characterizing ASTER and MODIS, 90mt and 1km respectively, by comparing them with in situ measurements, is analyzed. Possible differences can be due also to the different algorithms used for the emissivity estimation, Temperature and Emissivity Separation algorithm for ASTER TIR band( Gillespie et al, 1998) and the classification-based emissivity method (Snyder and al, 1998) for MODIS. Finally land surface temperature products generated using ASTER-GED and ASTER 05 emissivity are also analyzed. Gillespie, A. R., Matsunaga, T., Rokugawa, S., & Hook, S. J. (1998). Temperature and emissivity separation from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. IEEE Transactions on Geoscience and Remote Sensing, 36, 1113-1125. Snyder, W.C., Wan, Z., Zhang, Y., & Feng, Y.-Z. (1998). Classification-based emissivity for land surface temperature measurement from space. International Journal of Remote Sensing, 19, 2753-2574.

  18. Teaching Diffraction of Light and Electrons: Classroom Analogies to Classic Experiments

    ERIC Educational Resources Information Center

    Velentzas, Athanasios

    2014-01-01

    Diffraction and interference are phenomena that demonstrate the wave nature of light and of particles. Experiments relating to the diffraction/interference of light can easily be carried out in an educational lab, but it may be impossible to perform experiments involving electrons because of the lack of specialized equipment needed for such…

  19. Exploring transmission Kikuchi diffraction using a Timepix detector

    NASA Astrophysics Data System (ADS)

    Vespucci, S.; Winkelmann, A.; Mingard, K.; Maneuski, D.; O'Shea, V.; Trager-Cowan, C.

    2017-02-01

    Electron backscatter diffraction (EBSD) is a well-established scanning electron microscope (SEM)-based technique [1]. It allows the non-destructive mapping of the crystal structure, texture, crystal phase and strain with a spatial resolution of tens of nanometers. Conventionally this is performed by placing an electron sensitive screen, typically consisting of a phosphor screen combined with a charge coupled device (CCD) camera, in front of a specimen, usually tilted 70° to the normal of the exciting electron beam. Recently, a number of authors have shown that a significant increase in spatial resolution is achievable when Kikuchi diffraction patterns are acquired in transmission geometry; that is when diffraction patterns are generated by electrons transmitted through an electron-transparent, usually thinned, specimen. The resolution of this technique, called transmission Kikuchi diffraction (TKD), has been demonstrated to be better than 10 nm [2,3]. We have recently demonstrated the advantages of a direct electron detector, Timepix [4,5], for the acquisition of standard EBSD patterns [5]. In this article we will discuss the advantages of Timepix to perform TKD and for acquiring spot diffraction patterns and more generally for acquiring scanning transmission electron microscopy micrographs in the SEM. Particularly relevant for TKD, is its very compact size, which allows much more flexibility in the positioning of the detector in the SEM chamber. We will furthermore show recent results using Timepix as a virtual forward scatter detector, and will illustrate the information derivable on producing images through processing of data acquired from different areas of the detector. We will show results from samples ranging from gold nanoparticles to nitride semiconductor nanorods.

  20. Transmission Kikuchi diffraction and transmission electron forescatter imaging of electropolished and FIB manufactured TEM specimens

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zieliński, W., E-mail: wiziel@inmat.pw.edu.pl; Płociński, T.; Kurzydłowski, K.J.

    2015-06-15

    We present a study of the efficiency of the utility of scanning electron microscope (SEM)-based transmission methods for characterizing grain structure in thinned bulk metals. Foils of type 316 stainless steel were prepared by two methods commonly used for transmission electron microscopy — double-jet electropolishing and focused ion beam milling. A customized holder allowed positioning of the foils in a configuration appropriate for both transmission electron forward scatter diffraction, and for transmission imaging by the use of a forescatter detector with two diodes. We found that both crystallographic orientation maps and dark-field transmitted images could be obtained for specimens preparedmore » by either method. However, for both methods, preparation-induced artifacts may affect the quality or accuracy of transmission SEM data, especially those acquired by the use of transmission Kikuchi diffraction. Generally, the quality of orientation data was better for specimens prepared by electropolishing, due to the absence of ion-induced damage. - Highlights: • The transmission imaging and diffraction techniques are emerging in scanning electron microscopy (SEM) as promising new field of materials characterization. • The manuscript titled: “Transmission Kikuchi Diffraction and Transmission Electron Forescatter Imaging of Electropolished and FIB Manufactured TEM Specimens” documents how different specimen thinning procedures can effect efficiency of transmission Kikuchi diffraction and transmission electron forescatter imaging. • The abilities to make precision crystallographic orientation maps and dark-field images in transmission was studied on electropolished versus focus ion beam manufactured TEM specimens. • Depending on the need, electropolished and focused ion beam technique may produce suitable specimens for transmission imaging and diffraction in SEM.« less

  1. Atomic-scale diffractive imaging of sub-cycle electron dynamics in condensed matter

    PubMed Central

    Yakovlev, Vladislav S.; Stockman, Mark I.; Krausz, Ferenc; Baum, Peter

    2015-01-01

    For interaction of light with condensed-matter systems, we show with simulations that ultrafast electron and X-ray diffraction can provide a time-dependent record of charge-density maps with sub-cycle and atomic-scale resolutions. Using graphene as an example material, we predict that diffraction can reveal localised atomic-scale origins of optical and electronic phenomena. In particular, we point out nontrivial relations between microscopic electric current and density in undoped graphene. PMID:26412407

  2. Atomic-scale diffractive imaging of sub-cycle electron dynamics in condensed matter

    DOE PAGES

    Yakovlev, Vladislav S.; Stockman, Mark I.; Krausz, Ferenc; ...

    2015-09-28

    For interaction of light with condensed-matter systems, we show with simulations that ultrafast electron and X-ray diffraction can provide a time-dependent record of charge-density maps with sub-cycle and atomic-scale resolutions. Using graphene as an example material, we predict that diffraction can reveal localised atomic-scale origins of optical and electronic phenomena. Here, we point out nontrivial relations between microscopic electric current and density in undoped graphene.

  3. Low-kilovolt coherent electron diffractive imaging instrument based on a single-atom electron source

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, Chun-Yueh; Chang, Wei-Tse; Chen, Yi-Sheng

    2016-03-15

    In this work, a transmission-type, low-kilovolt coherent electron diffractive imaging instrument was constructed. It comprised a single-atom field emitter, a triple-element electrostatic lens, a sample holder, and a retractable delay line detector to record the diffraction patterns at different positions behind the sample. It was designed to image materials thinner than 3 nm. The authors analyzed the asymmetric triple-element electrostatic lens for focusing the electron beams and achieved a focused beam spot of 87 nm on the sample plane at the electron energy of 2 kV. High-angle coherent diffraction patterns of a suspended graphene sample corresponding to (0.62 Å){sup −1} were recorded. This workmore » demonstrated the potential of coherent diffractive imaging of thin two-dimensional materials, biological molecules, and nano-objects at a voltage between 1 and 10 kV. The ultimate goal of this instrument is to achieve atomic resolution of these materials with high contrast and little radiation damage.« less

  4. Capturing Structural Dynamics in Crystalline Silicon Using Chirped Electrons from a Laser Wakefield Accelerator

    PubMed Central

    He, Z.-H.; Beaurepaire, B.; Nees, J. A.; Gallé, G.; Scott, S. A.; Pérez, J. R. Sánchez; Lagally, M. G.; Krushelnick, K.; Thomas, A. G. R.; Faure, J.

    2016-01-01

    Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have enormous benefits for ultrafast science. These novel sources promise to become indispensable tools for the investigation of structural dynamics on the femtosecond time scale, with spatial resolution on the atomic scale. Here, we demonstrate the use of laser-wakefield-accelerated electron bunches for time-resolved electron diffraction measurements of the structural dynamics of single-crystal silicon nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept study, we resolve the silicon lattice dynamics on a picosecond time scale by deflecting the momentum-time correlated electrons in the diffraction peaks with a static magnetic field to obtain the time-dependent diffraction efficiency. Further improvements may lead to femtosecond temporal resolution, with negligible pump-probe jitter being possible with future laser-wakefield-accelerator ultrafast-electron-diffraction schemes. PMID:27824086

  5. Capturing Structural Dynamics in Crystalline Silicon Using Chirped Electrons from a Laser Wakefield Accelerator

    DOE PAGES

    He, Z. -H.; Beaurepaire, B.; Nees, J. A.; ...

    2016-11-08

    Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have enormous benefits for ultrafast science. These novel sources promise to become indispensable tools for the investigation of structural dynamics on the femtosecond time scale, with spatial resolution on the atomic scale. Here in this paper, we demonstrate the use of laser-wakefield-accelerated electron bunches for time-resolved electron diffraction measurements of the structural dynamics of single-crystal silicon nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept study, we resolve the silicon lattice dynamics on a picosecond time scalemore » by deflecting the momentum-time correlated electrons in the diffraction peaks with a static magnetic field to obtain the time-dependent diffraction efficiency. Further improvements may lead to femtosecond temporal resolution, with negligible pump-probe jitter being possible with future laser-wakefield-accelerator ultrafast-electron-diffraction schemes.« less

  6. The significance of Bragg's law in electron diffraction and microscopy, and Bragg's second law.

    PubMed

    Humphreys, C J

    2013-01-01

    Bragg's second law, which deserves to be more widely known, is recounted. The significance of Bragg's law in electron diffraction and microscopy is then discussed, with particular emphasis on differences between X-ray and electron diffraction. As an example of such differences, the critical voltage effect in electron diffraction is described. It is then shown that the lattice imaging of crystals in high-resolution electron microscopy directly reveals the Bragg planes used for the imaging process, exactly as visualized by Bragg in his real-space law. Finally, it is shown how in 2012, for the first time, on the centennial anniversary of Bragg's law, single atoms have been identified in an electron microscope using X-rays emitted from the specimen. Hence atomic resolution X-ray maps of a crystal in real space can be formed which give the positions and identities of the different atoms in the crystal, or of a single impurity atom in the crystal.

  7. Focus on Basics, 1999.

    ERIC Educational Resources Information Center

    Focus on Basics, 1999

    1999-01-01

    This volume consists of four issues that present best practices, current research on adult learning and literacy, and how research is used. Issue 1(A) on adult multiple intelligences has seven articles: "MI (Multiple Intelligences), the GED (General Educational Development), and Me (Martha Jean); "Understanding Multiple Intelligences: The Theory…

  8. 28 CFR 544.70 - Purpose and scope.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Purpose and scope. 544.70 Section 544.70 Judicial Administration BUREAU OF PRISONS, DEPARTMENT OF JUSTICE INSTITUTIONAL MANAGEMENT EDUCATION... federal institution who does not have a verified General Educational Development (GED) credential or high...

  9. 78 FR 2284 - Methodology for Selecting Job Corps Centers for Closure; Comments Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-10

    ... (GED), and career technical training credentials, including industry-recognized credentials, state... align existing career technical training programs to technical standards established by industries or... technical training. Both PIPs and CAPs are used for continued monitoring and implemented for USDA and...

  10. 78 FR 42803 - Comment Request for Information Collection for Job Corps Health Questionnaire (OMB Control No...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-17

    ... Job Corps is the nation's largest residential, educational, and career technical training program for... Educational Development (GED), and career technical training credentials, including industry-recognized... DEPARTMENT OF LABOR Employment and Training Administration Comment Request for Information...

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

    DTIC Science & Technology

    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

  12. JOBSTART. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2008

    2008-01-01

    "JOBSTART" is an alternative education and training program designed to improve the economic prospects of young, disadvantaged high school dropouts by increasing educational attainment and developing occupational skills. The program has four main components: (1) basic academic skills instruction with a focus on GED (General Educational…

  13. Minnesota Youthbuild Program Overview, 1999.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Economic Security, St. Paul.

    Minnesota's Youthbuild program helps at-risk youths gain useful job skills while building safe, affordable housing in their neighborhoods and working toward their high school diploma or General Educational Development (GED) certificate. In 1999, the Minnesota Legislature appropriated 751,000 dollars per year in Youthbuild funds. The program…

  14. Forecasting Tehran stock exchange volatility; Markov switching GARCH approach

    NASA Astrophysics Data System (ADS)

    Abounoori, Esmaiel; Elmi, Zahra (Mila); Nademi, Younes

    2016-03-01

    This paper evaluates several GARCH models regarding their ability to forecast volatility in Tehran Stock Exchange (TSE). These include GARCH models with both Gaussian and fat-tailed residual conditional distribution, concerning their ability to describe and forecast volatility from 1-day to 22-day horizon. Results indicate that AR(2)-MRSGARCH-GED model outperforms other models at one-day horizon. Also, the AR(2)-MRSGARCH-GED as well as AR(2)-MRSGARCH-t models outperform other models at 5-day horizon. In 10 day horizon, three models of AR(2)-MRSGARCH outperform other models. Concerning 22 day forecast horizon, results indicate no differences between MRSGARCH models with that of standard GARCH models. Regarding Risk management out-of-sample evaluation (95% VaR), a few models seem to provide reasonable and accurate VaR estimates at 1-day horizon, with a coverage rate close to the nominal level. According to the risk management loss functions, there is not a uniformly most accurate model.

  15. Quasi-parallel precession diffraction: Alignment method for scanning transmission electron microscopes.

    PubMed

    Plana-Ruiz, S; Portillo, J; Estradé, S; Peiró, F; Kolb, Ute; Nicolopoulos, S

    2018-06-06

    A general method to set illuminating conditions for selectable beam convergence and probe size is presented in this work for Transmission Electron Microscopes (TEM) fitted with µs/pixel fast beam scanning control, (S)TEM, and an annular dark field detector. The case of interest of beam convergence and probe size, which enables diffraction pattern indexation, is then used as a starting point in this work to add 100 Hz precession to the beam while imaging the specimen at a fast rate and keeping the projector system in diffraction mode. The described systematic alignment method for the adjustment of beam precession on the specimen plane while scanning at fast rates is mainly based on the sharpness of the precessed STEM image. The complete alignment method for parallel condition and precession, Quasi-Parallel PED-STEM, is presented in block diagram scheme, as it has been tested on a variety of instruments. The immediate application of this methodology is that it renders the TEM column ready for the acquisition of Precessed Electron Diffraction Tomographies (EDT) as well as for the acquisition of slow Precessed Scanning Nanometer Electron Diffraction (SNED). Examples of the quality of the Precessed Electron Diffraction (PED) patterns and PED-STEM alignment images are presented with corresponding probe sizes and convergence angles. Copyright © 2018. Published by Elsevier B.V.

  16. Comments on the paper "Bragg's law diffraction simulations for electron backscatter diffraction analysis" by Josh Kacher, Colin Landon, Brent L. Adams & David Fullwood.

    PubMed

    Maurice, Claire; Fortunier, Roland; Driver, Julian; Day, Austin; Mingard, Ken; Meaden, Graham

    2010-06-01

    This comment on the paper "Bragg's Law diffraction simulations for electron backscatter diffraction analysis" by Kacher et al. explains the limitations in determining elastic strains using synthetic EBSD patterns. Of particular importance are those due to the accuracy of determination of the EBSD geometry projection parameters. Additional references and supporting information are provided. Copyright 2010 Elsevier B.V. All rights reserved.

  17. Anomalous Diffraction in Crystallographic Phase Evaluation

    PubMed Central

    Hendrickson, Wayne A.

    2014-01-01

    X-ray diffraction patterns from crystals of biological macromolecules contain sufficient information to define atomic structures, but atomic positions are inextricable without having electron-density images. Diffraction measurements provide amplitudes, but the computation of electron density also requires phases for the diffracted waves. The resonance phenomenon known as anomalous scattering offers a powerful solution to this phase problem. Exploiting scattering resonances from diverse elements, the methods of multiwavelength anomalous diffraction (MAD) and single-wavelength anomalous diffraction (SAD) now predominate for de novo determinations of atomic-level biological structures. This review describes the physical underpinnings of anomalous diffraction methods, the evolution of these methods to their current maturity, the elements, procedures and instrumentation used for effective implementation, and the realm of applications. PMID:24726017

  18. Structures of Astromaterials Revealed by EBSD

    NASA Technical Reports Server (NTRS)

    Zolensky, M.

    2018-01-01

    Groups at the Johnson Space Center and the University of Tokyo have been using electron back-scattered diffraction (EBSD) to reveal the crystal structures of extraterrestrial minerals for many years. Even though we also routinely use transmission electron microscopy, synchrotron X-ray diffraction (SXRD), and conventional electron diffraction, we find that EBSD is the most powerful technique for crystal structure elucidation in many instances. In this talk I describe a few of the cases where we have found EBSD to provide crucial, unique information. See attachment.

  19. Serial single molecule electron diffraction imaging: diffraction background of superfluid helium droplets

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; He, Yunteng; Lei, Lei; Alghamdi, Maha; Oswalt, Andrew; Kong, Wei

    2017-08-01

    In an effort to solve the crystallization problem in crystallography, we have been engaged in developing a method termed "serial single molecule electron diffraction imaging" (SS-EDI). The unique features of SS-EDI are superfluid helium droplet cooling and field-induced orientation: together the two features constitute a molecular goniometer. Unfortunately, the helium atoms surrounding the sample molecule also contribute to a diffraction background. In this report, we analyze the properties of a superfluid helium droplet beam and its doping statistics, and demonstrate the feasibility of overcoming the background issue by using the velocity slip phenomenon of a pulsed droplet beam. Electron diffraction profiles and pair correlation functions of ferrocene-monomer-doped droplets and iodine-nanocluster-doped droplets are presented. The timing of the pulsed electron gun and the effective doping efficiency under different dopant pressures can both be controlled for size selection. This work clears any doubt of the effectiveness of superfluid helium droplets in SS-EDI, thereby advancing the effort in demonstrating the "proof-of-concept" one step further.

  20. Native American Adult Reader III.

    ERIC Educational Resources Information Center

    King, Lovern Root, Ed.

    This reader, one of three designed to provide adults in basic education/GED programs with meaningful material based on Native American cultures, includes selections appropriate for advanced reading ability (grade 7 and above). The twelve readings focus on culture, history, and contemporary concerns of Native Americans. Each selection includes a…

  1. RESPONSE OF GULF COAST ESTUARIES TO NUTRIENT LOAD: DISSOLVED OXYGEN DEPLETION

    EPA Science Inventory

    GED has developed a process-based approach to hypoxia research on Pensacola Bay as a model Gulf of Mexico estuary. We selected Pensacola Bay because, like many Gulf coast estuaries, it is shallow, microtidal, and experiences seasonal hypoxia. We also have an historical database ...

  2. Collaborative Partnerships in Maryland To Reduce Adult Illiteracy.

    ERIC Educational Resources Information Center

    National Inst. for Work and Learning, Washington, DC.

    A study examined existing collaborative activities between private or public employers and adult basic education (ABE), general educational development (GED), and English as a second language (ESL) programs in Maryland's 24 local education agencies. Information was gathered directly from 16 ABE administrators (including 4 community college…

  3. 28 CFR 544.75 - Disciplinary action.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Disciplinary action. 544.75 Section 544... EDUCATION Literacy Program § 544.75 Disciplinary action. As with other mandatory programs, such as work assignments, staff may take disciplinary action against an inmate lacking a GED credential or high school...

  4. GED Math for Workplace Students.

    ERIC Educational Resources Information Center

    Goschen, Claire

    This curriculum module contains lesson plans and application activities that were developed to help adult students master the mathematics skills needed to earn a general high school equivalency diploma. Included in the module are materials designed to help students improve their understanding of mathematics and achieve the following objectives:…

  5. USEPA – Gulf Ecology Division is “Adapting to Change”

    EPA Science Inventory

    CERF 2011’s theme reflects a growing realization that human societies are an integral component of ecosystems and the dynamics of these societies and ecosystems are interactive - their futures are interdependent. The USEPA Gulf Ecology Division’s (USEPA-GED) mission is to conduc...

  6. Device and method for creating Gaussian aberration-corrected electron beams

    DOEpatents

    McMorran, Benjamin; Linck, Martin

    2016-01-19

    Electron beam phase gratings have phase profiles that produce a diffracted beam having a Gaussian or other selected intensity profile. Phase profiles can also be selected to correct or compensate electron lens aberrations. Typically, a low diffraction order produces a suitable phase profile, and other orders are discarded.

  7. Breaking resolution limits in ultrafast electron diffraction and microscopy.

    PubMed

    Baum, Peter; Zewail, Ahmed H

    2006-10-31

    Ultrafast electron microscopy and diffraction are powerful techniques for the study of the time-resolved structures of molecules, materials, and biological systems. Central to these approaches is the use of ultrafast coherent electron packets. The electron pulses typically have an energy of 30 keV for diffraction and 100-200 keV for microscopy, corresponding to speeds of 33-70% of the speed of light. Although the spatial resolution can reach the atomic scale, the temporal resolution is limited by the pulse width and by the difference in group velocities of electrons and the light used to initiate the dynamical change. In this contribution, we introduce the concept of tilted optical pulses into diffraction and imaging techniques and demonstrate the methodology experimentally. These advances allow us to reach limits of time resolution down to regimes of a few femtoseconds and, possibly, attoseconds. With tilted pulses, every part of the sample is excited at precisely the same time as when the electrons arrive at the specimen. Here, this approach is demonstrated for the most unfavorable case of ultrafast crystallography. We also present a method for measuring the duration of electron packets by autocorrelating electron pulses in free space and without streaking, and we discuss the potential of tilting the electron pulses themselves for applications in domains involving nuclear and electron motions.

  8. Enhancement of diffraction efficiency and storage life of poly(vinyl chloride)-based optical recording medium with incorporation of an electron donor

    NASA Astrophysics Data System (ADS)

    John, Beena Mary; Ushamani, M.; Sreekumar, K.; Joseph, Rani; Sudha Kartha, C.

    2007-01-01

    The diffraction efficiency, sensitivity, and storage life of methylene blue-sensitized poly(vinyl chloride) film was improved by the addition of an electron donor in the matrix. The addition of pyridine enhanced the diffraction efficiency by two times, and storage life of the gratings was increased to 2-3 days.

  9. Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector.

    PubMed

    van Genderen, E; Clabbers, M T B; Das, P P; Stewart, A; Nederlof, I; Barentsen, K C; Portillo, Q; Pannu, N S; Nicolopoulos, S; Gruene, T; Abrahams, J P

    2016-03-01

    Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼ 0.013 e(-) Å(-2) s(-1)) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014).

  10. Single-shot coherent diffraction imaging of microbunched relativistic electron beams for free-electron laser applications.

    PubMed

    Marinelli, A; Dunning, M; Weathersby, S; Hemsing, E; Xiang, D; Andonian, G; O'Shea, F; Miao, Jianwei; Hast, C; Rosenzweig, J B

    2013-03-01

    With the advent of coherent x rays provided by the x-ray free-electron laser (FEL), strong interest has been kindled in sophisticated diffraction imaging techniques. In this Letter, we exploit such techniques for the diagnosis of the density distribution of the intense electron beams typically utilized in an x-ray FEL itself. We have implemented this method by analyzing the far-field coherent transition radiation emitted by an inverse-FEL microbunched electron beam. This analysis utilizes an oversampling phase retrieval method on the transition radiation angular spectrum to reconstruct the transverse spatial distribution of the electron beam. This application of diffraction imaging represents a significant advance in electron beam physics, having critical applications to the diagnosis of high-brightness beams, as well as the collective microbunching instabilities afflicting these systems.

  11. Solving the jitter problem in microwave compressed ultrafast electron diffraction instruments: Robust sub-50 fs cavity-laser phase stabilization

    PubMed Central

    Otto, M. R.; René de Cotret, L. P.; Stern, M. J.; Siwick, B. J.

    2017-01-01

    We demonstrate the compression of electron pulses in a high-brightness ultrafast electron diffraction instrument using phase-locked microwave signals directly generated from a mode-locked femtosecond oscillator. Additionally, a continuous-wave phase stabilization system that accurately corrects for phase fluctuations arising in the compression cavity from both power amplification and thermal drift induced detuning was designed and implemented. An improvement in the microwave timing stability from 100 fs to 5 fs RMS is measured electronically, and the long-term arrival time stability (>10 h) of the electron pulses improves to below our measurement resolution of 50 fs. These results demonstrate sub-relativistic ultrafast electron diffraction with compressed pulses that is no longer limited by laser-microwave synchronization. PMID:28852686

  12. Quantum diffraction and shielding effects on the low-energy electron-ion bremsstrahlung in two-component semiclassical plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590

    2015-10-15

    The quantum diffraction and shielding effects on the low-energy bremsstrahlung process are investigated in two-component semiclassical plasmas. The impact-parameter analysis with the micropotential taking into account the quantum diffraction and shielding effects is employed to obtain the electron-ion bremsstrahlung radiation cross section as a function of the de Broglie wavelength, density parameter, impact parameter, photon energy, and projectile energy. The result shows that the influence of quantum diffraction and shielding strongly suppresses the bremsstrahlung radiation spectrum in semiclassical plasmas. It is found that the quantum diffraction and shielding effects have broaden the photon emission domain. It is also found thatmore » the photon emission domain is almost independent of the radiation photon energy. In addition, it is found that the influence of quantum diffraction and shielding on the bremsstrahlung spectrum decreases with an increase of the projectile energy. The density effect on the electron-ion bremsstrahlung cross section is also discussed.« less

  13. Holographic Reconstruction of Photoelectron Diffraction and Its Circular Dichroism for Local Structure Probing

    NASA Astrophysics Data System (ADS)

    Matsui, Fumihiko; Matsushita, Tomohiro; Daimon, Hiroshi

    2018-06-01

    The local atomic structure around a specific element atom can be recorded as a photoelectron diffraction pattern. Forward focusing peaks and diffraction rings around them indicate the directions and distances from the photoelectron emitting atom to the surrounding atoms. The state-of-the-art holography reconstruction algorithm enables us to image the local atomic arrangement around the excited atom in a real space. By using circularly polarized light as an excitation source, the angular momentum transfer from the light to the photoelectron induces parallax shifts in these diffraction patterns. As a result, stereographic images of atomic arrangements are obtained. These diffraction patterns can be used as atomic-site-resolved probes for local electronic structure investigation in combination with spectroscopy techniques. Direct three-dimensional atomic structure visualization and site-specific electronic property analysis methods are reviewed. Furthermore, circular dichroism was also found in valence photoelectron and Auger electron diffraction patterns. The investigation of these new phenomena provides hints for the development of new techniques for local structure probing.

  14. Radiation damage free ghost diffraction with atomic resolution

    DOE PAGES

    Li, Zheng; Medvedev, Nikita; Chapman, Henry N.; ...

    2017-12-21

    The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here in this paper, we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghostmore » diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several Ångstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.« less

  15. Radiation damage free ghost diffraction with atomic resolution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Zheng; Medvedev, Nikita; Chapman, Henry N.

    The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here in this paper, we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghostmore » diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several Ångstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.« less

  16. The use of analytical surface tools in the fundamental study of wear. [atomic nature of wear

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1977-01-01

    Various techniques and surface tools available for the study of the atomic nature of the wear of materials are reviewed These include chemical etching, x-ray diffraction, electron diffraction, scanning electron microscopy, low-energy electron diffraction, Auger emission spectroscopy analysis, electron spectroscopy for chemical analysis, field ion microscopy, and the atom probe. Properties of the surface and wear surface regions which affect wear, such as surface energy, crystal structure, crystallographic orientation, mode of dislocation behavior, and cohesive binding, are discussed. A number of mechanisms involved in the generation of wear particles are identified with the aid of the aforementioned tools.

  17. Local nanoscale strain mapping of a metallic glass during in situ testing

    NASA Astrophysics Data System (ADS)

    Gammer, Christoph; Ophus, Colin; Pekin, Thomas C.; Eckert, Jürgen; Minor, Andrew M.

    2018-04-01

    The local elastic strains during tensile deformation in a CuZrAlAg metallic glass are obtained by fitting an elliptic shape function to the characteristic amorphous ring in electron diffraction patterns. Scanning nanobeam electron diffraction enables strain mapping with a resolution of a few nanometers. Here, a fast direct electron detector is used to acquire the diffraction patterns at a sufficient speed to map the local transient strain during continuous tensile loading in situ in the transmission electron microscope. The elastic strain in tensile direction was found to increase during loading. After catastrophic fracture, a residual elastic strain that relaxes over time was observed.

  18. Low-energy transmission electron diffraction and imaging of large-area graphene

    PubMed Central

    Zhao, Wei; Xia, Bingyu; Lin, Li; Xiao, Xiaoyang; Liu, Peng; Lin, Xiaoyang; Peng, Hailin; Zhu, Yuanmin; Yu, Rong; Lei, Peng; Wang, Jiangtao; Zhang, Lina; Xu, Yong; Zhao, Mingwen; Peng, Lianmao; Li, Qunqing; Duan, Wenhui; Liu, Zhongfan; Fan, Shoushan; Jiang, Kaili

    2017-01-01

    Two-dimensional (2D) materials have attracted interest because of their excellent properties and potential applications. A key step in realizing industrial applications is to synthesize wafer-scale single-crystal samples. Until now, single-crystal samples, such as graphene domains up to the centimeter scale, have been synthesized. However, a new challenge is to efficiently characterize large-area samples. Currently, the crystalline characterization of these samples still relies on selected-area electron diffraction (SAED) or low-energy electron diffraction (LEED), which is more suitable for characterizing very small local regions. This paper presents a highly efficient characterization technique that adopts a low-energy electrostatically focused electron gun and a super-aligned carbon nanotube (SACNT) film sample support. It allows rapid crystalline characterization of large-area graphene through a single photograph of a transmission-diffracted image at a large beam size. Additionally, the low-energy electron beam enables the observation of a unique diffraction pattern of adsorbates on the suspended graphene at room temperature. This work presents a simple and convenient method for characterizing the macroscopic structures of 2D materials, and the instrument we constructed allows the study of the weak interaction with 2D materials. PMID:28879233

  19. Low-energy transmission electron diffraction and imaging of large-area graphene.

    PubMed

    Zhao, Wei; Xia, Bingyu; Lin, Li; Xiao, Xiaoyang; Liu, Peng; Lin, Xiaoyang; Peng, Hailin; Zhu, Yuanmin; Yu, Rong; Lei, Peng; Wang, Jiangtao; Zhang, Lina; Xu, Yong; Zhao, Mingwen; Peng, Lianmao; Li, Qunqing; Duan, Wenhui; Liu, Zhongfan; Fan, Shoushan; Jiang, Kaili

    2017-09-01

    Two-dimensional (2D) materials have attracted interest because of their excellent properties and potential applications. A key step in realizing industrial applications is to synthesize wafer-scale single-crystal samples. Until now, single-crystal samples, such as graphene domains up to the centimeter scale, have been synthesized. However, a new challenge is to efficiently characterize large-area samples. Currently, the crystalline characterization of these samples still relies on selected-area electron diffraction (SAED) or low-energy electron diffraction (LEED), which is more suitable for characterizing very small local regions. This paper presents a highly efficient characterization technique that adopts a low-energy electrostatically focused electron gun and a super-aligned carbon nanotube (SACNT) film sample support. It allows rapid crystalline characterization of large-area graphene through a single photograph of a transmission-diffracted image at a large beam size. Additionally, the low-energy electron beam enables the observation of a unique diffraction pattern of adsorbates on the suspended graphene at room temperature. This work presents a simple and convenient method for characterizing the macroscopic structures of 2D materials, and the instrument we constructed allows the study of the weak interaction with 2D materials.

  20. Protein structure determination by electron diffraction using a single three-dimensional nanocrystal.

    PubMed

    Clabbers, M T B; van Genderen, E; Wan, W; Wiegers, E L; Gruene, T; Abrahams, J P

    2017-09-01

    Three-dimensional nanometre-sized crystals of macromolecules currently resist structure elucidation by single-crystal X-ray crystallography. Here, a single nanocrystal with a diffracting volume of only 0.14 µm 3 , i.e. no more than 6 × 10 5 unit cells, provided sufficient information to determine the structure of a rare dimeric polymorph of hen egg-white lysozyme by electron crystallography. This is at least an order of magnitude smaller than was previously possible. The molecular-replacement solution, based on a monomeric polyalanine model, provided sufficient phasing power to show side-chain density, and automated model building was used to reconstruct the side chains. Diffraction data were acquired using the rotation method with parallel beam diffraction on a Titan Krios transmission electron microscope equipped with a novel in-house-designed 1024 × 1024 pixel Timepix hybrid pixel detector for low-dose diffraction data collection. Favourable detector characteristics include the ability to accurately discriminate single high-energy electrons from X-rays and count them, fast readout to finely sample reciprocal space and a high dynamic range. This work, together with other recent milestones, suggests that electron crystallography can provide an attractive alternative in determining biological structures.

  1. Protein structure determination by electron diffraction using a single three-dimensional nanocrystal

    PubMed Central

    Clabbers, M. T. B.; van Genderen, E.; Wiegers, E. L.; Gruene, T.; Abrahams, J. P.

    2017-01-01

    Three-dimensional nanometre-sized crystals of macromolecules currently resist structure elucidation by single-crystal X-ray crystallography. Here, a single nanocrystal with a diffracting volume of only 0.14 µm3, i.e. no more than 6 × 105 unit cells, provided sufficient information to determine the structure of a rare dimeric polymorph of hen egg-white lysozyme by electron crystallography. This is at least an order of magnitude smaller than was previously possible. The molecular-replacement solution, based on a monomeric polyalanine model, provided sufficient phasing power to show side-chain density, and automated model building was used to reconstruct the side chains. Diffraction data were acquired using the rotation method with parallel beam diffraction on a Titan Krios transmission electron microscope equipped with a novel in-house-designed 1024 × 1024 pixel Timepix hybrid pixel detector for low-dose diffraction data collection. Favourable detector characteristics include the ability to accurately discriminate single high-energy electrons from X-rays and count them, fast readout to finely sample reciprocal space and a high dynamic range. This work, together with other recent milestones, suggests that electron crystallography can provide an attractive alternative in determining biological structures. PMID:28876237

  2. Single-electron pulses for ultrafast diffraction

    PubMed Central

    Aidelsburger, M.; Kirchner, F. O.; Krausz, F.; Baum, P.

    2010-01-01

    Visualization of atomic-scale structural motion by ultrafast electron diffraction and microscopy requires electron packets of shortest duration and highest coherence. We report on the generation and application of single-electron pulses for this purpose. Photoelectric emission from metal surfaces is studied with tunable ultraviolet pulses in the femtosecond regime. The bandwidth, efficiency, coherence, and electron pulse duration are investigated in dependence on excitation wavelength, intensity, and laser bandwidth. At photon energies close to the cathode’s work function, the electron pulse duration shortens significantly and approaches a threshold that is determined by interplay of the optical pulse width and the acceleration field. An optimized choice of laser wavelength and bandwidth results in sub-100-fs electron pulses. We demonstrate single-electron diffraction from polycrystalline diamond films and reveal the favorable influences of matched photon energies on the coherence volume of single-electron wave packets. We discuss the consequences of our findings for the physics of the photoelectric effect and for applications of single-electron pulses in ultrafast 4D imaging of structural dynamics. PMID:21041681

  3. Adult Tech Prep.

    ERIC Educational Resources Information Center

    Schaad, Donna

    For over 2 years, Blak Hawk College (Illinois) has provided high school equivalency (GED) candidates and recipients, older returning students, and underprepared high school graduates with a Tech Prep curriculum to give them the skills to make the transition from adult basic education to college or work. The Adult Tech Prep (ATP) core curriculum…

  4. New Chance. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2008

    2008-01-01

    "New Chance," a program for young welfare mothers who have dropped out of school, aims to improve both their employment potential and their parenting skills. Participants take GED (General Educational Development) preparation classes and complete a parenting and life skills curriculum. Once they complete this first phase of the program,…

  5. 310 Individualized Teacher Practicum. Final Report, 1979-80.

    ERIC Educational Resources Information Center

    Barabe, Rosemeri, Comp.; And Others

    Objectives and program descriptions are presented for the Scottsdale Adult Learning Center (Arizona) which in 1979-80 conducted a number of practicums for adult educators on individualized techniques, Adult Basic Education (ABE), High School Equivalency (GED), and English as a Second Language (ESL). First described is a paid internship program for…

  6. Strategy Instruction in Writing for Adult Literacy Learners

    ERIC Educational Resources Information Center

    MacArthur, Charles A.; Lembo, Leah

    2009-01-01

    This study investigated the effectiveness of cognitive strategy instruction in writing with adult literacy learners. Three middle-aged African-American adults participating in adult education with the goal of passing the GED received tutoring in a strategy for planning, writing, and revising persuasive essays along with self-regulation strategies.…

  7. Test Anxiety Reduction. Student Workbook.

    ERIC Educational Resources Information Center

    Silverman, Eda; Hanna, Joyce

    This student workbook is intended for use in helping teenage and adult basic education (ABE) students reduce their anxiety over tests in general and over the General Educational Development (GED) test in particular. Exercises are provided to help students analyze and understand their feelings about and while taking tests, recall the childhood…

  8. State Strategies to Facilitate Adult Learners' Transitions to Postsecondary Opportunities. REL 2017-223

    ERIC Educational Resources Information Center

    Hector-Mason, Anestine; Narlock, Jason; Muhisani, Helen; Bhatt, Monica P.

    2017-01-01

    Prior research has classified strategies to facilitate adult learners' transitions to postsecondary opportunities into five broad categories: advising, General Educational Development-plus (GED-plus), English as a second language, career pathways, and college preparatory (Zafft, Kallenbach, & Spohn, 2006). This two-part study relied on…

  9. Creating Opportunities: Tennessee's Southeast Regional Skills Center.

    ERIC Educational Resources Information Center

    Baldwin, Fred D.

    2002-01-01

    Rural Marion County (Tennessee), the town of Kimball, the Appalachian Regional Commission, and a local community college founded a regional skills center. The center offers a 2-year associate of science degree and classes in GED preparation, parenting, drug abuse prevention, cosmetology, and air conditioning and refrigeration. It has expanded…

  10. Formation of Educational Expectations of Lower Socioeconomic Status Children

    ERIC Educational Resources Information Center

    Kim, Kyung-Nyun

    2014-01-01

    The purpose of this study was to investigate the mediation effects of children's cognitive and noncognitive traits on the relationship between dropout mothers' traits and their children's educational expectations and to examine the interaction effects of dropout mothers' General Education Development (GED) on children's traits and educational…

  11. Massachusetts One-Stop Career Centers: Job Placement for Disadvantaged Students

    ERIC Educational Resources Information Center

    Matrundola, Lisa A.

    2010-01-01

    This study investigated the services provided to students' participating in career preparation programs (e.g., career counseling, mentoring, apprenticeships, work-based learning, or GED programs) provided by the Massachusetts One-Stop Career Centers. A study conducted by the President's Task Force for Disadvantaged Students (2003) found that…

  12. 34 CFR 654.5 - What definitions apply?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... that student's program. HEA means the Higher Education Act of 1965, as amended. High school graduate means an individual who has— (i) A high school diploma; (ii) A General Education Development (GED) Certificate; or (iii) Any other evidence recognized by the State as the equivalent of a high school diploma...

  13. 34 CFR 654.5 - What definitions apply?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... that student's program. HEA means the Higher Education Act of 1965, as amended. High school graduate means an individual who has— (i) A high school diploma; (ii) A General Education Development (GED) Certificate; or (iii) Any other evidence recognized by the State as the equivalent of a high school diploma...

  14. 34 CFR 654.5 - What definitions apply?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... that student's program. HEA means the Higher Education Act of 1965, as amended. High school graduate means an individual who has— (i) A high school diploma; (ii) A General Education Development (GED) Certificate; or (iii) Any other evidence recognized by the State as the equivalent of a high school diploma...

  15. 34 CFR 654.5 - What definitions apply?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... that student's program. HEA means the Higher Education Act of 1965, as amended. High school graduate means an individual who has— (i) A high school diploma; (ii) A General Education Development (GED) Certificate; or (iii) Any other evidence recognized by the State as the equivalent of a high school diploma...

  16. 34 CFR 654.5 - What definitions apply?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... that student's program. HEA means the Higher Education Act of 1965, as amended. High school graduate means an individual who has— (i) A high school diploma; (ii) A General Education Development (GED) Certificate; or (iii) Any other evidence recognized by the State as the equivalent of a high school diploma...

  17. Publications - GMC 58 | Alaska Division of Geological & Geophysical Surveys

    Science.gov Websites

    DGGS GMC 58 Publication Details Title: X-ray diffraction and scanning electron microscopy mineral , Michael, and Core Laboratories, 1985, X-ray diffraction and scanning electron microscopy mineral analyses

  18. Non-spectroscopic composition measurements of SrTiO 3-La 0.7Sr 0.3MnO 3 multilayers using scanning convergent beam electron diffraction

    DOE PAGES

    Ophus, Colin; Ercius, Peter; Huijben, Mark; ...

    2017-02-08

    The local atomic structure of a crystalline sample aligned along a zone axis can be probed with a focused electron probe, which produces a convergent beam electron diffraction pattern. The introduction of high speed direct electron detectors has allowed for experiments that can record a full diffraction pattern image at thousands of probe positions on a sample. By incoherently summing these patterns over crystalline unit cells, we demonstrate in this paper that in addition to crystal structure and thickness, we can also estimate the local composition of a perovskite superlattice sample. This is achieved by matching the summed patterns tomore » a library of simulated diffraction patterns. Finally, this technique allows for atomic-scale chemical measurements without requiring a spectrometer or hardware aberration correction.« less

  19. Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

    PubMed Central

    van Genderen, E.; Clabbers, M. T. B.; Das, P. P.; Stewart, A.; Nederlof, I.; Barentsen, K. C.; Portillo, Q.; Pannu, N. S.; Nicolopoulos, S.; Gruene, T.; Abrahams, J. P.

    2016-01-01

    Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e− Å−2 s−1) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014). PMID:26919375

  20. Structure resolution by electron diffraction tomography of the complex layered iron-rich Fe-2234-type Sr{sub 5}Fe{sub 6}O{sub 15.4}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lepoittevin, Christophe, E-mail: christophe.lepoittevin@neel.cnrs.fr

    2016-10-15

    The crystal structure of the strontium ferrite Sr{sub 5}Fe{sub 6}O{sub 15.4}, was solved by direct methods on electron diffraction tomography data acquired on a transmission electron microscope. The refined cell parameters are a=27.4047(3) Å, b=5.48590(7) Å and c=42.7442(4) Å in Fm2m symmetry. Its structure is built up from the intergrowth sequence between a quadruple perovskite-type layer with a complex rock-salt (RS)-type block. In the latter iron atoms are found in two different environments : tetragonal pyramid and tetrahedron. The structural model was refined by Rietveld method based on the powder X-ray diffraction pattern. - Highlights: • Complex structure of Sr{submore » 5}Fe{sub 6}O{sub 15.4} solved by electron diffraction tomography. • Observed Fourier maps allow determining missing oxygen atoms in the structure. • Structural model refined from powder X-ray diffraction data. • Intergrowth between quadruple perovskite layer with double rock-salt-type layer.« less

  1. Electron and lattice dynamics of transition metal thin films observed by ultrafast electron diffraction and transient optical measurements.

    PubMed

    Nakamura, A; Shimojima, T; Nakano, M; Iwasa, Y; Ishizaka, K

    2016-11-01

    We report the ultrafast dynamics of electrons and lattice in transition metal thin films (Au, Cu, and Mo) investigated by a combination of ultrafast electron diffraction (UED) and pump-probe optical methods. For a single-crystalline Au thin film, we observe the suppression of the diffraction intensity occuring in 10 ps, which direcly reflects the lattice thermalization via the electron-phonon interaction. By using the two-temperature model, the electron-phonon coupling constant ( g ) and the electron and lattice temperatures ( T e , T l ) are evaluated from UED, with which we simulate the transient optical transmittance. The simulation well agrees with the experimentally obtained transmittance data, except for the slight deviations at the initial photoexcitation and the relaxed quasi-equilibrium state. We also present the results similarly obtained for polycrystalline Au, Cu, and Mo thin films and demonstrate the electron and lattice dynamics occurring in metals with different electron-phonon coupling strengths.

  2. Breaking resolution limits in ultrafast electron diffraction and microscopy

    PubMed Central

    Baum, Peter; Zewail, Ahmed H.

    2006-01-01

    Ultrafast electron microscopy and diffraction are powerful techniques for the study of the time-resolved structures of molecules, materials, and biological systems. Central to these approaches is the use of ultrafast coherent electron packets. The electron pulses typically have an energy of 30 keV for diffraction and 100–200 keV for microscopy, corresponding to speeds of 33–70% of the speed of light. Although the spatial resolution can reach the atomic scale, the temporal resolution is limited by the pulse width and by the difference in group velocities of electrons and the light used to initiate the dynamical change. In this contribution, we introduce the concept of tilted optical pulses into diffraction and imaging techniques and demonstrate the methodology experimentally. These advances allow us to reach limits of time resolution down to regimes of a few femtoseconds and, possibly, attoseconds. With tilted pulses, every part of the sample is excited at precisely the same time as when the electrons arrive at the specimen. Here, this approach is demonstrated for the most unfavorable case of ultrafast crystallography. We also present a method for measuring the duration of electron packets by autocorrelating electron pulses in free space and without streaking, and we discuss the potential of tilting the electron pulses themselves for applications in domains involving nuclear and electron motions. PMID:17056711

  3. Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

    2009-11-01

    In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

  4. Low-energy electron point projection microscopy/diffraction study of suspended graphene

    NASA Astrophysics Data System (ADS)

    Hsu, Wei-Hao; Chang, Wei-Tse; Lin, Chun-Yueh; Chang, Mu-Tung; Hsieh, Chia-Tso; Wang, Chang-Ran; Lee, Wei-Li; Hwang, Ing-Shouh

    2017-11-01

    In this work, we present our study of suspended graphene with low-energy electrons based on a point projection microscopic/diffractive imaging technique. Both exfoliated and chemical vapor deposition (CVD) graphene samples were studied in an ultra-high vacuum chamber. This method allows imaging of individual adsorbates at the nanometer scale and characterizing graphene layers, graphene lattice orientations, ripples on graphene membranes, etc. We found that long-duration exposure to low-energy electron beams induced aggregation of adsorbates on graphene when the electron dose rate was above a certain level. We also discuss the potential of this technique to conduct coherent diffractive imaging for determining the atomic structures of biological molecules adsorbed on suspended graphene.

  5. Feynman Path Integral Approach to Electron Diffraction for One and Two Slits: Analytical Results

    ERIC Educational Resources Information Center

    Beau, Mathieu

    2012-01-01

    In this paper we present an analytic solution of the famous problem of diffraction and interference of electrons through one and two slits (for simplicity, only the one-dimensional case is considered). In addition to exact formulae, various approximations of the electron distribution are shown which facilitate the interpretation of the results.…

  6. Dark-field phase retrieval under the constraint of the Friedel symmetry in coherent X-ray diffraction imaging.

    PubMed

    Kobayashi, Amane; Sekiguchi, Yuki; Takayama, Yuki; Oroguchi, Tomotaka; Nakasako, Masayoshi

    2014-11-17

    Coherent X-ray diffraction imaging (CXDI) is a lensless imaging technique that is suitable for visualizing the structures of non-crystalline particles with micrometer to sub-micrometer dimensions from material science and biology. One of the difficulties inherent to CXDI structural analyses is the reconstruction of electron density maps of specimen particles from diffraction patterns because saturated detector pixels and a beam stopper result in missing data in small-angle regions. To overcome this difficulty, the dark-field phase-retrieval (DFPR) method has been proposed. The DFPR method reconstructs electron density maps from diffraction data, which are modified by multiplying Gaussian masks with an observed diffraction pattern in the high-angle regions. In this paper, we incorporated Friedel centrosymmetry for diffraction patterns into the DFPR method to provide a constraint for the phase-retrieval calculation. A set of model simulations demonstrated that this constraint dramatically improved the probability of reconstructing correct electron density maps from diffraction patterns that were missing data in the small-angle region. In addition, the DFPR method with the constraint was applied successfully to experimentally obtained diffraction patterns with significant quantities of missing data. We also discuss this method's limitations with respect to the level of Poisson noise in X-ray detection.

  7. Fine Structure of Diffuse Scattering Rings in Al-Li-Cu Quasicrystal: A Comparative X-ray and Electron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Donnadieu, P.; Dénoyer, F.

    1996-11-01

    A comparative X-ray and electron diffraction study has been performed on Al-Li-Cu icosahedral quasicrystal in order to investigate the diffuse scattering rings revealed by a previous work. Electron diffraction confirms the existence of rings but shows that the rings have a fine structure. The diffuse aspect on the X-ray diffraction patterns is then due to an averaging effect. Recent simulations based on the model of canonical cells related to the icosahedral packing give diffractions patterns in agreement with this fine structure effect. Nous comparons les diagrammes de diffraction des rayon-X et des électrons obtenus sur les mêmes échantillons du quasicristal icosaèdrique Al-Li-Cu. Notre but est d'étudier les anneaux de diffusion diffuse mis en évidence par un travail précédent. Les diagrammes de diffraction électronique confirment la présence des anneaux mais ils montrent aussi que ces anneaux possèdent une structure fine. L'aspect diffus des anneaux révélés par la diffraction des rayons X est dû à un effet de moyenne. Des simulations récentes basées sur la décomposition en cellules canoniques de l'empilement icosaédrique produisent des diagrammes de diffraction en accord avec ces effects de structure fine.

  8. Application of δ recycling to electron automated diffraction tomography data from inorganic crystalline nanovolumes.

    PubMed

    Rius, Jordi; Mugnaioli, Enrico; Vallcorba, Oriol; Kolb, Ute

    2013-07-01

    δ Recycling is a simple procedure for directly extracting phase information from Patterson-type functions [Rius (2012). Acta Cryst. A68, 399-400]. This new phasing method has a clear theoretical basis and was developed with ideal single-crystal X-ray diffraction data. On the other hand, introduction of the automated diffraction tomography (ADT) technique has represented a significant advance in electron diffraction data collection [Kolb et al. (2007). Ultramicroscopy, 107, 507-513]. When combined with precession electron diffraction, it delivers quasi-kinematical intensity data even for complex inorganic compounds, so that single-crystal diffraction data of nanometric volumes are now available for structure determination by direct methods. To check the tolerance of δ recycling to missing data-collection corrections and to deviations from kinematical behaviour of ADT intensities, δ recycling has been applied to differently shaped nanocrystals of various inorganic materials. The results confirm that it can phase ADT data very efficiently. In some cases even more complete structure models than those derived from conventional direct methods and least-squares refinement have been found. During this study it has been demonstrated that the Wilson-plot scaling procedure is largely insensitive to sample thickness variations and missing absorption corrections affecting electron ADT intensities.

  9. Structural and electron diffraction scaling of twisted graphene bilayers

    NASA Astrophysics Data System (ADS)

    Zhang, Kuan; Tadmor, Ellad B.

    2018-03-01

    Multiscale simulations are used to study the structural relaxation in twisted graphene bilayers and the associated electron diffraction patterns. The initial twist forms an incommensurate moiré pattern that relaxes to a commensurate microstructure comprised of a repeating pattern of alternating low-energy AB and BA domains surrounding a high-energy AA domain. The simulations show that the relaxation mechanism involves a localized rotation and shrinking of the AA domains that scales in two regimes with the imposed twist. For small twisting angles, the localized rotation tends to a constant; for large twist, the rotation scales linearly with it. This behavior is tied to the inverse scaling of the moiré pattern size with twist angle and is explained theoretically using a linear elasticity model. The results are validated experimentally through a simulated electron diffraction analysis of the relaxed structures. A complex electron diffraction pattern involving the appearance of weak satellite peaks is predicted for the small twist regime. This new diffraction pattern is explained using an analytical model in which the relaxation kinematics are described as an exponentially-decaying (Gaussian) rotation field centered on the AA domains. Both the angle-dependent scaling and diffraction patterns are in quantitative agreement with experimental observations. A Matlab program for extracting the Gaussian model parameters accompanies this paper.

  10. Specimen preparation for cryogenic coherent X-ray diffraction imaging of biological cells and cellular organelles by using the X-ray free-electron laser at SACLA

    PubMed Central

    Kobayashi, Amane; Sekiguchi, Yuki; Oroguchi, Tomotaka; Okajima, Koji; Fukuda, Asahi; Oide, Mao; Yamamoto, Masaki; Nakasako, Masayoshi

    2016-01-01

    Coherent X-ray diffraction imaging (CXDI) allows internal structures of biological cells and cellular organelles to be analyzed. CXDI experiments have been conducted at 66 K for frozen-hydrated biological specimens at the SPring-8 Angstrom Compact Free-Electron Laser facility (SACLA). In these cryogenic CXDI experiments using X-ray free-electron laser (XFEL) pulses, specimen particles dispersed on thin membranes of specimen disks are transferred into the vacuum chamber of a diffraction apparatus. Because focused single XFEL pulses destroy specimen particles at the atomic level, diffraction patterns are collected through raster scanning the specimen disks to provide fresh specimen particles in the irradiation area. The efficiency of diffraction data collection in cryogenic experiments depends on the quality of the prepared specimens. Here, detailed procedures for preparing frozen-hydrated biological specimens, particularly thin membranes and devices developed in our laboratory, are reported. In addition, the quality of the frozen-hydrated specimens are evaluated by analyzing the characteristics of the collected diffraction patterns. Based on the experimental results, the internal structures of the frozen-hydrated specimens and the future development for efficient diffraction data collection are discussed. PMID:27359147

  11. Specimen preparation for cryogenic coherent X-ray diffraction imaging of biological cells and cellular organelles by using the X-ray free-electron laser at SACLA.

    PubMed

    Kobayashi, Amane; Sekiguchi, Yuki; Oroguchi, Tomotaka; Okajima, Koji; Fukuda, Asahi; Oide, Mao; Yamamoto, Masaki; Nakasako, Masayoshi

    2016-07-01

    Coherent X-ray diffraction imaging (CXDI) allows internal structures of biological cells and cellular organelles to be analyzed. CXDI experiments have been conducted at 66 K for frozen-hydrated biological specimens at the SPring-8 Angstrom Compact Free-Electron Laser facility (SACLA). In these cryogenic CXDI experiments using X-ray free-electron laser (XFEL) pulses, specimen particles dispersed on thin membranes of specimen disks are transferred into the vacuum chamber of a diffraction apparatus. Because focused single XFEL pulses destroy specimen particles at the atomic level, diffraction patterns are collected through raster scanning the specimen disks to provide fresh specimen particles in the irradiation area. The efficiency of diffraction data collection in cryogenic experiments depends on the quality of the prepared specimens. Here, detailed procedures for preparing frozen-hydrated biological specimens, particularly thin membranes and devices developed in our laboratory, are reported. In addition, the quality of the frozen-hydrated specimens are evaluated by analyzing the characteristics of the collected diffraction patterns. Based on the experimental results, the internal structures of the frozen-hydrated specimens and the future development for efficient diffraction data collection are discussed.

  12. Single-slit electron diffraction with Aharonov-Bohm phase: Feynman's thought experiment with quantum point contacts.

    PubMed

    Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan

    2014-01-10

    In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.

  13. Compression of subrelativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction.

    PubMed

    van Oudheusden, T; Pasmans, P L E M; van der Geer, S B; de Loos, M J; van der Wiel, M J; Luiten, O J

    2010-12-31

    We demonstrate the compression of 95 keV, space-charge-dominated electron bunches to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are of sufficient quality to capture a diffraction pattern with a single shot, which we demonstrate by a diffraction experiment on a polycrystalline gold foil. Compression is realized by means of velocity bunching by inverting the positive space-charge-induced velocity chirp. This inversion is induced by the oscillatory longitudinal electric field of a 3 GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs.

  14. Digital direct electron imaging of energy-filtered electron backscatter diffraction patterns

    NASA Astrophysics Data System (ADS)

    Vespucci, S.; Winkelmann, A.; Naresh-Kumar, G.; Mingard, K. P.; Maneuski, D.; Edwards, P. R.; Day, A. P.; O'Shea, V.; Trager-Cowan, C.

    2015-11-01

    Electron backscatter diffraction is a scanning electron microscopy technique used to obtain crystallographic information on materials. It allows the nondestructive mapping of crystal structure, texture, and strain with a lateral and depth resolution on the order of tens of nanometers. Electron backscatter diffraction patterns (EBSPs) are presently acquired using a detector comprising a scintillator coupled to a digital camera, and the crystallographic information obtainable is limited by the conversion of electrons to photons and then back to electrons again. In this article we will report the direct acquisition of energy-filtered EBSPs using a digital complementary metal-oxide-semiconductor hybrid pixel detector, Timepix. We show results from a range of samples with different mass and density, namely diamond, silicon, and GaN. Direct electron detection allows the acquisition of EBSPs at lower (≤5 keV) electron beam energies. This results in a reduction in the depth and lateral extension of the volume of the specimen contributing to the pattern and will lead to a significant improvement in lateral and depth resolution. Direct electron detection together with energy filtering (electrons having energy below a specific value are excluded) also leads to an improvement in spatial resolution but in addition provides an unprecedented increase in the detail in the acquired EBSPs. An increase in contrast and higher-order diffraction features are observed. In addition, excess-deficiency effects appear to be suppressed on energy filtering. This allows the fundamental physics of pattern formation to be interrogated and will enable a step change in the use of electron backscatter diffraction (EBSD) for crystal phase identification and the mapping of strain. The enhancement in the contrast in high-pass energy-filtered EBSD patterns is found to be stronger for lighter, less dense materials. The improved contrast for such materials will enable the application of the EBSD technique to be expanded to materials for which conventional EBSD analysis is not presently practicable.

  15. Observation of coherent optical phonons excited by femtosecond laser radiation in Sb films by ultrafast electron diffraction method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mironov, B. N.; Kompanets, V. O.; Aseev, S. A., E-mail: isanfemto@yandex.ru

    2017-03-15

    The generation of coherent optical phonons in a polycrystalline antimony film sample has been investigated using femtosecond electron diffraction method. Phonon vibrations have been induced in the Sb sample by the main harmonic of a femtosecond Ti:Sa laser (λ = 800 nm) and probed by a pulsed ultrashort photoelectron beam synchronized with the pump laser. The diffraction patterns recorded at different times relative to the pump laser pulse display oscillations of electron diffraction intensity corresponding to the frequencies of vibrations of optical phonons: totally symmetric (A{sub 1g}) and twofold degenerate (E{sub g}) phonon modes. The frequencies that correspond to combinationsmore » of these phonon modes in the Sb sample have also been experimentally observed.« less

  16. Transmission electron microscope studies of extraterrestrial materials

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.

    1995-01-01

    Transmission Electron Microscopy, X-Ray spectrometry and electron-energy-loss spectroscopy are used to analyse carbon in interplanetary dust particles. Optical micrographs are shown depicting cross sections of the dust particles embedded in sulphur. Selected-area electron diffraction patterns are shown. Transmission Electron Microscope specimens of lunar soil were prepared using two methods: ion-milling and ultramicrotomy. A combination of high resolution TEM imaging and electron diffraction is used to characterize the opaque assemblages. The opaque assemblages analyzed in this study are dominated by ilmenite with lesser rutile and spinel exsolutions, and traces of Fe metal.

  17. Proceedings of the Annual Adult Education Research Conference (30th, Madison, Wisconsin, April 27-29, 1989).

    ERIC Educational Resources Information Center

    Coggins, Chere Campbell, Ed.

    Among the 59 papers are: "Comparisons in Performance of Adults and High School Seniors on the 1988 Tests of General Educational Development (GED)" (Baldwin, Whitney); "Research Writing" (Baskett, Garrison); "Popular Education in Latin America" (Beder); "Framework for the Study of Ethical Issues in Adult…

  18. Exploring Motivational System Theory within the Context of Adult Education

    ERIC Educational Resources Information Center

    Hutto, Debra Jean

    2013-01-01

    Adult Basic Education (ABE) and the General Equivalency Diploma (GED) programs serve those students who, for whatever reason, have left the educational system without attaining a regular high school diploma. Because of the manner in which they may have left the school system, many have negative emotions and personal agency beliefs hindering their…

  19. Steps Forward and Back in Adult Numeracy Teacher Professional Development: A Reflection on a Teacher Workshop Experience

    ERIC Educational Resources Information Center

    Saliga, Linda Marie; Daviso, Al; Stuart, Denise; Pachnowski, Lynne

    2015-01-01

    In this project, a university team of teacher education and mathematics professors conducted eight professional development sessions for General Educational Development (GED) teachers in the area of mathematics teaching. Topics included concretely modeling mathematics concepts in algebra, number sense, geometry, and differentiating instruction in…

  20. Construction Cluster Volume I [Wood Structural Framing].

    ERIC Educational Resources Information Center

    Pennsylvania State Dept. of Justice, Harrisburg. Bureau of Correction.

    The document is the first of a series, to be integrated with a G.E.D. program, containing instructional materials at the basic skills level for the construction cluster. It focuses on wood structural framing and contains 20 units: (1) occupational information; (2) blueprint reading; (3) using leveling instruments and laying out building lines; (4)…

  1. Construction Cluster Volume II [Masonry Work].

    ERIC Educational Resources Information Center

    Pennsylvania State Dept. of Justice, Harrisburg. Bureau of Correction.

    The document is the second of a series, to be integrated with a G.E.D. program, containing instructional materials at the basic skills level for the construction cluster. The volume focuses on masonry and consists of 20 instructional units which require a month of study. The units include: (1) historical aspects of masonry work and occupational…

  2. The GED and the Rise of Contextless Accountability

    ERIC Educational Resources Information Center

    Hutt, Ethan

    2014-01-01

    Background/Context:Policy discussions in the U.S. and abroad have become increasingly studded with reference to the results of international tests like PISA. Unlike most assessments, PISA is not designed to measure whether students have mastered a particular school curriculum but rather provide a measure of students' ability to meet future…

  3. Adult Basic Education and the Welfare Roles: An Economic and Social Alternative.

    ERIC Educational Resources Information Center

    Pennsylvania Association for Adult Continuing Education, Harrisburg, PA.

    In Pennsylvania where 30 percent of the adult population is functionally illiterate and another 24 percent has only marginal competence, no state funds are appropriated for adult basic education and general educational development (ABE/GED) programs. All programs are supported by federal aid. Information shows that economic revitalization and a…

  4. An Unlikely Scholar

    ERIC Educational Resources Information Center

    Chew, Cassie

    2006-01-01

    Iraq War veteran and law professor Christopher Cooper's path to the academy has been anything but traditional. Having worked from the age of 13, he enlisted in the Marine Corps at 17 and earned his GED. He later earned a bachelor's degree in government and public administration, then joined the New York City Police Department. Then, he decided to…

  5. Construction Cluster Volume III [Plumbing].

    ERIC Educational Resources Information Center

    Pennsylvania State Dept. of Justice, Harrisburg. Bureau of Correction.

    The document is the third of a series, to be integrated with a G.E.D. program, containing instructional materials at the basic skills level for the construction cluster. The volume focuses on plumbing and consists of 20 instructional units which require a month of study. The units include: (1) importance of plumbing; (2) pipe and tubing…

  6. GOAL Academy: Giving Dropouts a Second Chance

    ERIC Educational Resources Information Center

    Dicksteen, Lisa Napell

    2012-01-01

    The U.S. Department of Education's (ED) National Center for Education Statistics defines dropouts as "16- through 21-year-olds who are not enrolled in school and have not earned a high school credential (either a diploma or an equivalency credential such as a General Education Development (GED) certificate)." According to the feds, the…

  7. Factors Contributing to the Attrition of Adult Basic and Secondary Education Students.

    ERIC Educational Resources Information Center

    Leonard, Rex; And Others

    Attrition among students in adult basic and secondary education programs has been a perennial problem. Conducting research on this population is also problematic once they have dropped out of a program. A study surveyed 76 dropouts and 35 General Educational Development (GED) program completers from two large, multisite programs about factors…

  8. Construction Cluster Volume 5 [Electrical].

    ERIC Educational Resources Information Center

    Pennsylvania State Dept. of Justice, Harrisburg. Bureau of Correction.

    The document is the fifth of a series, to be integrated with a G.E.D. program, containing instructional materials for the construction cluster. The volume focuses on electrical work and consists of 20 instructional units which require a month of study: (1) safety precautions and first aid for electrical workers; (2) planning a simple installation;…

  9. 4-Year Cohort Graduation Rate: FAQ

    ERIC Educational Resources Information Center

    Pennsylvania Department of Education, 2010

    2010-01-01

    This paper offers a list of questions and corresponding answers about the 4-year cohort graduation rate. Answers to the following questions are presented: (1) Why don't GED (General Educational Development) students count as graduates?; (2) How does a district code students who have moved out of state? How should a district code a student who…

  10. Relationship of Education Level to Capabilities and Attitudes of Young Enlisted Men.

    ERIC Educational Resources Information Center

    Melching, William H.; And Others

    The objective of this research was to determine the feasibility of developing a functionally oriented General Educational Development (GED) program. To obtain information about problems of adaptation common to undereducated men, and to obtain information about knowledges and skills such men may not have, an achievement test/attitude questionnaire…

  11. The Community College Transfer Problem

    ERIC Educational Resources Information Center

    Roach, Ronald

    2009-01-01

    Once a high school dropout, Hamilton Cunningham beat the odds in navigating the transition from earning a GED, serving in the U.S. Air Force, and attending community college to enrolling at Howard University in fall 2007 as a sophomore where he is now a Truman Scholar and a Jack Kent Cooke Foundation undergraduate transfer scholarship recipient.…

  12. Transitions for Success: A Phenomenological Study of Non-Traditional GED Completers into the Community College

    ERIC Educational Resources Information Center

    Dunn Carpenter, Christina Marie

    2011-01-01

    The vision statement of one large Midwestern community college is "dedicated to helping students achieve lifelong fulfillment by providing a quality, innovative and responsive learning environment. Each day, [the college] champions the aspirations of individuals, communities and the state..." Helping each individual realize a lifelong…

  13. 20 CFR 672.300 - Who is an eligible participant?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... their high school diploma, GED credential, or other State-recognized equivalent; or (2) Have been... the date of enrollment; and (2) A school dropout or an individual who has dropped out of school and reenrolled in an alternative school, if that reenrollment is part of a sequential service strategy; and (3...

  14. 20 CFR 672.300 - Who is an eligible participant?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... their high school diploma, GED credential, or other State-recognized equivalent; or (2) Have been... the date of enrollment; and (2) A school dropout or an individual who has dropped out of school and reenrolled in an alternative school, if that reenrollment is part of a sequential service strategy; and (3...

  15. 20 CFR 672.300 - Who is an eligible participant?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... their high school diploma, GED credential, or other State-recognized equivalent; or (2) Have been... the date of enrollment; and (2) A school dropout or an individual who has dropped out of school and reenrolled in an alternative school, if that reenrollment is part of a sequential service strategy; and (3...

  16. Project Re-Start. A Program for Homeless Adults.

    ERIC Educational Resources Information Center

    Pelzer, Dagmar F.; And Others

    Project Re-Start, of the Dade County Public Schools in Florida, was funded under the Adult Education Act and the Stewart B. McKinney Homeless Assistance Act. Classes in literacy skills, General Educational Development (GED) preparation, English for speakers of other languages, employability skills, and life coping skills were conducted at most of…

  17. GED Success: Case Study of an English Language Learner in Correctional Education

    ERIC Educational Resources Information Center

    Gardner, Susanne

    2017-01-01

    Understanding the elements of educational success for adult English language learners (ELLs) is an important priority for correctional educators, especially today with an increased population of non-English speaking students in correctional schools throughout the country. There is a dearth of information, however, about incarcerated adult ELLs and…

  18. Adult Education and Postsecondary Success. Policy Brief

    ERIC Educational Resources Information Center

    Reder, Stephen

    2007-01-01

    This Policy Brief takes a first look at a newly identified national population of GED holders, who are compared with their counterparts who received a high school diploma as well as with their counterparts who have no high school credential. The focus of these comparisons is on long-term postsecondary education outcomes. Because these…

  19. Low-energy Auger electron diffraction: influence of multiple scattering and angular momentum

    NASA Astrophysics Data System (ADS)

    Chassé, A.; Niebergall, L.; Kucherenko, Yu.

    2002-04-01

    The angular dependence of Auger electrons excited from single-crystal surfaces is treated theoretically within a multiple-scattering cluster model taking into account the full Auger transition matrix elements. In particular the model has been used to discuss the influence of multiple scattering and angular momentum of the Auger electron wave on Auger electron diffraction (AED) patterns in the region of low kinetic energies. Theoretical results of AED patterns are shown and discussed in detail for Cu(0 0 1) and Ni(0 0 1) surfaces, respectively. Even though Cu and Ni are very similar in their electronic and scattering properties recently strong differences have been found in AED patterns measured in the low-energy region. It is shown that the differences may be caused to superposition of different electron diffraction effects in an energy-integrated experiment. A good agreement between available experimental and theoretical results has been achieved.

  20. Symposium N: Materials and Devices for Thermal-to-Electric Energy Conversion

    DTIC Science & Technology

    2010-08-24

    X - ray diffraction, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. Thermal conductivity measurements...SEM), X - ray diffraction (XRD) measurements as well as Raman spectroscopy. The results from these techniques indicate a clear modification...was examined by using scanning electron microscope (SEM; HITACHI S-4500 model) attached with an energy dispersive x - ray spectroscopy. The electrical

  1. Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8 from electron diffraction data.

    PubMed

    Samuha, Shmuel; Mugnaioli, Enrico; Grushko, Benjamin; Kolb, Ute; Meshi, Louisa

    2014-12-01

    The crystal structure of the novel Al77Rh15Ru8 phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8 E-phase is orthorhombic [Pbma, a = 23.40 (5), b = 16.20 (4) and c = 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E-phase is described using hierarchical packing of polyhedra and a single type of tiling in the form of a parallelogram. Based on this description, the structure of the E-phase is compared with that of the ε6-phase formed in Al-Rh-Ru at close compositions.

  2. Auger electron diffraction study of Fe 1- xNi x alloys epitaxially grown on Cu(100)

    NASA Astrophysics Data System (ADS)

    Martin, M. G.; Foy, E.; Chevrier, F.; Krill, G.; Asensio, M. C.

    1999-08-01

    We have combined Auger electron diffraction (AED), low-energy electron diffraction (LEED) and high-energy electron diffraction (RHEED) to examine the structure of Fe xNi 1- x alloys when the Fe content approaches 65%. At this concentration, the 'invar effect' takes place, so the magnetization falls to zero, and the thermal expansion coefficient is very small. The Fe xNi 1- x alloys, grown as metastable thin films by molecular-beam epitaxy on Cu(100) substrates, were studied as a function of the x stoichiometry. In contrast to the related bulk alloy compounds, we observe the collapse of the fcc-to-bcc structural transition in the Fe-rich films. Furthermore, the local atomic structure around Fe and Ni in the alloy has been simultaneously determined by the angular intensity distributions of Fe L 3VV (703 eV) and Ni L 3VV (848 eV) Auger electrons measured as a function of polar and azimuthal angles. For the films deposited at room temperature, we have confirmed the pseudomorphic growth morphology and the uniformity of the alloys.

  3. ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES ON A HOMOLOGOUS SERIES OF SATURATED PHOSPHATIDYLCHOLINES.

    PubMed

    ELBERS, P F; VERVERGAERT, P H

    1965-05-01

    Three homologous saturated phosphatidylcholines were studied by electron microscopy after tricomplex fixation. The results are compared with those obtained by x-ray diffraction analysis of the same and some other homologous compounds, in the dry crystalline state and after tricomplex fixation. By electron microscopy alternating dark and light bands are observed which are likely to correspond to phosphatide double layers. X-Ray diffraction reveals the presence of lamellar structures of regular spacing. The layer spacings obtained by both methods are in good agreement. From the electron micrographs the width of the polar parts of the double layers can be derived directly. The width of the carboxylglycerylphosphorylcholine moiety of the layers is found by extrapolating the x-ray diffraction data to zero chain length of the fatty acids. When from this width the contribution of the carboxylglyceryl part of the molecules is subtracted, again we find good agreement with the electron microscope measurements. An attempt has been made to account for the different layer spacings measured in terms of orientation of the molecules within the double layers.

  4. Investigation of the effect of phase nonuniformities and the microwave field distribution on the electronic efficiency of a diffraction-radiation generator

    NASA Astrophysics Data System (ADS)

    Maksimov, P. P.; Tsvyk, A. I.; Shestopalov, V. P.

    1985-10-01

    The effect of local phase nonuniformities of the diffraction gratings and the field distribution of the open cavity on the electronic efficiency of a diffraction-radiation generator (DRG) is analyzed numerically on the basis of a self-consistent system of nonlinear stationary equations for the DRG. It is shown that the interaction power and efficiency of a DRG can be increased by the use of an open cavity with a nonuniform diffraction grating and a complex form of microwave field distribution over the interaction space.

  5. Modulated Electron Emission by Scattering-Interference of Primary Electrons

    NASA Astrophysics Data System (ADS)

    Valeri, Sergio; di Bona, Alessandro

    We review the effects of scattering-interference of the primary, exciting beam on the electron emission from ordered atomic arrays. The yield of elastically and inelastically backscattered electrons, Auger electrons and secondary electrons shows a marked dependence on the incidence angle of primary electrons. Both the similarity and the relative importance of processes experienced by incident and excident electrons are discussed. We also present recent studies of electron focusing and defocusing along atomic chains. The interplay between these two processes determines the in-depth profile of the primary electron intensity anisotropy. Finally, the potential for surface-structural studies and limits for quantitative analysis are discussed, in comparison with the Auger electron diffraction (AED) and photoelectron diffraction (PD) techniques.

  6. Imaging ultrafast dynamics of molecules with laser-induced electron diffraction.

    PubMed

    Lin, C D; Xu, Junliang

    2012-10-14

    We introduce a laser-induced electron diffraction method (LIED) for imaging ultrafast dynamics of small molecules with femtosecond mid-infrared lasers. When molecules are placed in an intense laser field, both low- and high-energy photoelectrons are generated. According to quantitative rescattering (QRS) theory, high-energy electrons are produced by a rescattering process where electrons born at the early phase of the laser pulse are driven back to rescatter with the parent ion. From the high-energy electron momentum spectra, field-free elastic electron-ion scattering differential cross sections (DCS), or diffraction images, can be extracted. With mid-infrared lasers as the driving pulses, it is further shown that the DCS can be used to extract atomic positions in a molecule with sub-angstrom spatial resolution, in close analogy to the standard electron diffraction method. Since infrared lasers with pulse duration of a few to several tens of femtoseconds are already available, LIED can be used for imaging dynamics of molecules with sub-angstrom spatial and a few-femtosecond temporal resolution. The first experiment with LIED has shown that the bond length of oxygen molecules shortens by 0.1 Å in five femtoseconds after single ionization. The principle behind LIED and its future outlook as a tool for dynamic imaging of molecules are presented.

  7. Programs to Increase High School Completion

    PubMed Central

    Hahn, Robert A.; Knopf, John A.; Wilson, Sandra Jo; Truman, Benedict I.; Milstein, Bobby; Johnson, Robert L.; Fielding, Jonathan E.; Muntaner, Carles J.M.; Jones, Camara Phyllis; Fullilove, Mindy T.; Moss, Regina Davis; Uefffng, Erin; Hunt, Pete C.

    2015-01-01

    Context High school completion (HSC) is an established predictor of long-term morbidity and mortality. U.S. rates of HSC are substantially lower among students from low-income families and most racial/ethnic minority populations than students from high-income families and the non-Hispanic white population. This systematic review assesses the effectiveness of programs to increase HSC and the potential of these programs to improve lifelong health among at-risk students. Evidence acquisition A search located a meta-analysis (search period 1985–2010/2011) on the effects of programs to increase HSC or General Educational Development (GED) diploma receipt; the meta-analysis was concordant with Community Guide definitions and methodologic standards. Programs were assessed separately for the general student population (152 studies) and students who were parents or pregnant (15 studies). A search for studies published between 2010 and August 2012 located ten more recent studies, which were assessed for consistency with the meta-analysis. Analyses were conducted in 2013. Evidence synthesis The review focused on the meta-analysis. Program effectiveness was measured as the increased rate of HSC (or GED receipt) by the intervention group compared with controls. All assessed program types were effective in increasing HSC in the general student population: vocational training, alternative schooling, social–emotional skills training, college-oriented programming, mentoring and counseling, supplemental academic services, school and class restructuring, multiservice packages, attendance monitoring and contingencies, community service, and case management. For students who had children or were pregnant, attendance monitoring and multiservice packages were effective. Ten studies published after the search period for the meta-analysis were consistent with its findings. Conclusions There is strong evidence that a variety of HSC programs can improve high school or GED completion rates. Because many programs are targeted to high-risk students and communities, they are likely to advance health equity. PMID:25818117

  8. Disparities in Adherence to Pediatric Sepsis Guidelines across a Spectrum of Emergency Departments: A Multicenter, Cross-Sectional Observational In Situ Simulation Study.

    PubMed

    Kessler, David O; Walsh, Barbara; Whitfill, Travis; Dudas, Robert A; Gangadharan, Sandeep; Gawel, Marcie; Brown, Linda; Auerbach, Marc

    2016-03-01

    Each year in the United States, 72,000 pediatric patients develop septic shock, at a cost of $4.8 billion. Adherence to practice guidelines can significantly reduce mortality; however, few methods to compare performance across a spectrum of emergency departments (EDs) have been described. We employed standardized, in situ simulations to measure and compare adherence to pediatric sepsis guidelines across a spectrum of EDs. We hypothesized that pediatric EDs (PEDs) would have greater adherence to the guidelines than general EDs (GEDs). We also explored factors associated with improved performance. This multi-center observational study examined in situ teams caring for a simulated infant in septic shock. The primary outcome was overall adherence to the pediatric sepsis guideline as measured by six subcomponent metrics. Characteristics of teams were compared using multivariable logistic regression to describe factors associated with improved performance. We enrolled 47 interprofessional teams from 24 EDs. Overall, 21/47 teams adhered to all six sepsis metrics (45%). PEDs adhered to all six metrics more than GEDs (93% vs. 22%; difference 71%, 95% confidence interval [CI] 43-84). Adherent teams had significantly higher Emergency Medical Services for Children readiness scores, MD composition of physicians to total team members, teamwork scores, provider perceptions of pediatric preparedness, and provider perceptions of sepsis preparedness. In a multivariable regression model, only greater composite team experience had greater adjusted odds of achieving an adherent sepsis score (adjusted odds ratio 1.38, 95% CI 1.01-1.88). Using standardized in situ scenarios, we revealed high variability in adherence to the pediatric sepsis guideline across a spectrum of EDs. PEDs demonstrated greater adherence to the guideline than GEDs; however, in adjusted analysis, only composite team experience level of the providers was associated with improved guideline adherence. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Influence of quantum diffraction and shielding on electron-ion collision in two-component semiclassical plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hong, Woo-Pyo; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791

    2015-01-15

    The influence of quantum diffraction and shielding on the electron-ion collision process is investigated in two-component semiclassical plasmas. The eikonal method and micropotential taking into account the quantum diffraction and shielding are used to obtain the eikonal scattering phase shift and the eikonal collision cross section as functions of the collision energy, density parameter, Debye length, electron de Broglie wavelength, and the impact parameter. The result shows that the quantum diffraction and shielding effects suppress the eikonal scattering phase shift as well as the differential eikonal collision cross section, especially, in small-impact parameter regions. It is also shown that themore » quantum shielding effect on the eikonal collision cross section is more important in low-collision energies. In addition, it is found that the eikonal collision cross section increases with an increase in the density parameter. The variations of the eikonal cross section due to the quantum diffraction and shielding effects are also discussed.« less

  10. Efficacy of a post-secondary environmental science education program on the attitude toward science of a group of Mississippi National Guard Youth ChalleNGe Program students

    NASA Astrophysics Data System (ADS)

    Smith, William Bradford, Jr.

    The National Guard Youth ChalleNGe Program (ChalleNGe) is a 17 month quasi-military training program authorized by Congress in the 1993 Defense Authorization Bill designed to improve life skills, education levels, and employment potential of 16--18 year old youth who drop out of high school. ChalleNGe is currently operational in 27 states/territories with the focus of this study on the Mississippi National Guard Program operated at Camp Shelby, Mississippi. During the five month residential portion of the program students are guided through an eight step process designed to meet the goals of improving life skills, education levels, and employment potential while ultimately leading to completion of high school equivalency credentials followed by a 12 month mentoring phase to encourage and track progress toward goals. The purpose of this study was to investigate the attitude toward science of a group of students enrolled in the ChalleNGe Program at Camp Shelby (ChalleNGe). The GED test is administered approximately two months into the residential phase of the program. While the program boasts an overall GED pass rate of nearly 80%, approximately 30--35% of students successfully complete the initial offering of the GED. As high school graduates, these students are offered college courses through William Carey College in Hattiesburg, Mississippi. Twenty four students elected to take the Introduction to Environmental Science course and formed the experimental group while 24 other students who passed the GED comprised the control group. Each group was administered the Scientific Attitude Inventory II, a 40 statement instrument with Likert Scale responses, as a pretest. Paired samples t-tests indicated no significant difference in attitude toward science between the experimental and control groups on the pretest. Following the two week Introduction to Environmental Science course for the experimental group, both groups were post tested. As predicted, the attitude toward science of the experimental group was significantly higher than that of the control group. Further investigation into correlation between the length of time students were away from the traditional school prior to starting ChalleNGe, the number of science classes previously taken, and reading scores on the Test of Adult Basic Education revealed no significant relationship. Responses provided by students to each of these three factors was significantly different between the experimental and control groups. In summary, attitude toward science can be positively impacted by short term interventions such as the environmental science course described herein. While the positive impact on attitude toward science caused by this course was the desired outcome of this project, appropriate emphasis should be placed on prevention of dropouts and the accompanying social issues.

  11. Folding and stacking defects of graphene flakes probed by electron nanobeam

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Persichetti, L.; Fanfoni, M.; Sgarlata, A.

    2011-07-25

    Combining nanoscale imaging with local electron spectroscopy and diffraction has provided direct information on folding and stacking defects of graphene flakes produced by unrolled multi-walled carbon nanotubes. Structural data obtained by nanoarea electron diffraction complemented with systematic electron energy loss spectroscopy measurements of the surface plasmon losses of single flakes show the presence of flat bilayer regions coexisting with folded areas where the topology of buckled graphene resembles that of warped carbon nanostructures.

  12. Structural changes induced by lattice-electron interactions: SiO2 stishovite and FeTiO3 ilmenite.

    PubMed

    Yamanaka, Takamitsu

    2005-09-01

    The bright source and highly collimated beam of synchrotron radiation offers many advantages for single-crystal structure analysis under non-ambient conditions. The structure changes induced by the lattice-electron interaction under high pressure have been investigated using a diamond anvil pressure cell. The pressure dependence of electron density distributions around atoms is elucidated by a single-crystal diffraction study using deformation electron density analysis and the maximum entropy method. In order to understand the bonding electrons under pressure, diffraction intensity measurements of FeTiO3 ilmenite and gamma-SiO2 stishovite single crystals at high pressures were made using synchrotron radiation. Both diffraction studies describe the electron density distribution including bonding electrons and provide the effective charge of the cations. In both cases the valence electrons are more localized around the cations with increasing pressure. This is consistent with molecular orbital calculations, proving that the bonding electron density becomes smaller with pressure. The thermal displacement parameters of both samples are reduced with increasing pressure.

  13. Femtosecond Electron Wave Packet Propagation and Diffraction: Towards Making the ``Molecular Movie"

    NASA Astrophysics Data System (ADS)

    Miller, R. J. Dwayne

    2003-03-01

    Time-resolved electron diffraction harbors great promise for achieving atomic resolution of the fastest chemical processes. The generation of sufficiently short electron pulses to achieve this real time view of a chemical reaction has been limited by problems in maintaining short electron pulses with realistic electron densities to the sample. The propagation dynamics of femtosecond electron packets in the drift region of a photoelectron gun are investigated with an N-body numerical simulation and mean-field model. This analyis shows that the redistribution of electrons inside the packet, arising from space-charge and dispersion contributions, changes the pulse envelope and leads to the development of a spatially linear axial velocity distribution. These results have been used in the design of femtosecond photoelectron guns with higher time resolution and novel electron-optical methods of pulse characterization that are approaching 100 fs timescales. Time-resolved diffraction studies with electron pulses of approximately 500 femtoseconds have focused on solid-liquid phase transitions under far from equilibrium conditions. This work gives a microscopic description of the melting process and illustrates the promise of atomically resolving transition state processes.

  14. Classification and assessment of retrieved electron density maps in coherent X-ray diffraction imaging using multivariate analysis.

    PubMed

    Sekiguchi, Yuki; Oroguchi, Tomotaka; Nakasako, Masayoshi

    2016-01-01

    Coherent X-ray diffraction imaging (CXDI) is one of the techniques used to visualize structures of non-crystalline particles of micrometer to submicrometer size from materials and biological science. In the structural analysis of CXDI, the electron density map of a sample particle can theoretically be reconstructed from a diffraction pattern by using phase-retrieval (PR) algorithms. However, in practice, the reconstruction is difficult because diffraction patterns are affected by Poisson noise and miss data in small-angle regions due to the beam stop and the saturation of detector pixels. In contrast to X-ray protein crystallography, in which the phases of diffracted waves are experimentally estimated, phase retrieval in CXDI relies entirely on the computational procedure driven by the PR algorithms. Thus, objective criteria and methods to assess the accuracy of retrieved electron density maps are necessary in addition to conventional parameters monitoring the convergence of PR calculations. Here, a data analysis scheme, named ASURA, is proposed which selects the most probable electron density maps from a set of maps retrieved from 1000 different random seeds for a diffraction pattern. Each electron density map composed of J pixels is expressed as a point in a J-dimensional space. Principal component analysis is applied to describe characteristics in the distribution of the maps in the J-dimensional space. When the distribution is characterized by a small number of principal components, the distribution is classified using the k-means clustering method. The classified maps are evaluated by several parameters to assess the quality of the maps. Using the proposed scheme, structure analysis of a diffraction pattern from a non-crystalline particle is conducted in two stages: estimation of the overall shape and determination of the fine structure inside the support shape. In each stage, the most accurate and probable density maps are objectively selected. The validity of the proposed scheme is examined by application to diffraction data that were obtained from an aggregate of metal particles and a biological specimen at the XFEL facility SACLA using custom-made diffraction apparatus.

  15. Recombinant Reflectin-Based Optical Materials

    DTIC Science & Technology

    2012-01-01

    sili- con substrates were placed in a sealed plastic box. The RH was controlled using a Dydra electronic cigar humidifier and monitored using a Fisher...diffraction gratings to generate diffraction patterns. Nano-spheres and la- mellar microstructures of refCBA samples were observed by scanning electron ...samples were observed by scanning electron microscopy and atomic force microscopy. Despite the reduced complexity of the refCBA protein compared to natural

  16. Effect of screw threading dislocations and inverse domain boundaries in GaN on the shape of reciprocal-space maps.

    PubMed

    Barchuk, Mykhailo; Motylenko, Mykhaylo; Lukin, Gleb; Pätzold, Olf; Rafaja, David

    2017-04-01

    The microstructure of polar GaN layers, grown by upgraded high-temperature vapour phase epitaxy on [001]-oriented sapphire substrates, was studied by means of high-resolution X-ray diffraction and transmission electron microscopy. Systematic differences between reciprocal-space maps measured by X-ray diffraction and those which were simulated for different densities of threading dislocations revealed that threading dislocations are not the only microstructure defect in these GaN layers. Conventional dark-field transmission electron microscopy and convergent-beam electron diffraction detected vertical inversion domains as an additional microstructure feature. On a series of polar GaN layers with different proportions of threading dislocations and inversion domain boundaries, this contribution illustrates the capability and limitations of coplanar reciprocal-space mapping by X-ray diffraction to distinguish between these microstructure features.

  17. Coherent Diffractive Imaging: From Nanometric Down to Picometric Resolution

    NASA Astrophysics Data System (ADS)

    De Caro, Liberato; Carlino, Elvio; Siliqi, Dritan; Giannini, Cinzia

    Coherent diffractive imaging (CDI) is a novel technique for inspecting (crystalline and non-crystalline) matter from nanometric down to picometric resolution. It was used originally with X-rays and, more recently, with electrons (so-called electron diffractive imaging, or EDI). This chapter introduces basic concepts concerning CDI and addresses the different types of X-ray CDI experiments that have been conducted, namely plane wave CDI from isolated objects in forward scattering, focused-beam Fresnel CDI from isolated objects in forward scattering, Bragg CDI from nanocrystals, and keyhole CDI and ptychography from extended objects. A CDI experiment with a transmission electron microscope, alternatively named an EDI experiment, is also introduced.

  18. TAKASAGO-6 apparatus for cryogenic coherent X-ray diffraction imaging of biological non-crystalline particles using X-ray free electron laser at SACLA.

    PubMed

    Kobayashi, Amane; Sekiguchi, Yuki; Takayama, Yuki; Oroguchi, Tomotaka; Shirahama, Keiya; Torizuka, Yasufumi; Manoda, Masahiro; Nakasako, Masayoshi; Yamamoto, Masaki

    2016-05-01

    Coherent X-ray diffraction imaging (CXDI) is a technique for structure analyses of non-crystalline particles with dimensions ranging from micrometer to sub-micrometer. We have developed a diffraction apparatus named TAKASAGO-6 for use in single-shot CXDI experiments of frozen-hydrated non-crystalline biological particles at cryogenic temperature with X-ray free electron laser pulses provided at a repetition rate of 30 Hz from the SPring-8 Angstrom Compact free-electron LAser. Specimen particles are flash-cooled after being dispersed on thin membranes supported by specially designed disks. The apparatus is equipped with a high-speed translation stage with a cryogenic pot for raster-scanning of the disks at a speed higher than 25 μm/33 ms. In addition, we use devices assisting the easy transfer of cooled specimens from liquid-nitrogen storages to the cryogenic pot. In the current experimental procedure, more than 20 000 diffraction patterns can be collected within 1 h. Here we report the key components and performance of the diffraction apparatus. Based on the efficiency of the diffraction data collection and the structure analyses of metal particles, biological cells, and cellular organelles, we discuss the future application of this diffraction apparatus for structure analyses of biological specimens.

  19. The collection of MicroED data for macromolecular crystallography.

    PubMed

    Shi, Dan; Nannenga, Brent L; de la Cruz, M Jason; Liu, Jinyang; Sawtelle, Steven; Calero, Guillermo; Reyes, Francis E; Hattne, Johan; Gonen, Tamir

    2016-05-01

    The formation of large, well-ordered crystals for crystallographic experiments remains a crucial bottleneck to the structural understanding of many important biological systems. To help alleviate this problem in crystallography, we have developed the MicroED method for the collection of electron diffraction data from 3D microcrystals and nanocrystals of radiation-sensitive biological material. In this approach, liquid solutions containing protein microcrystals are deposited on carbon-coated electron microscopy grids and are vitrified by plunging them into liquid ethane. MicroED data are collected for each selected crystal using cryo-electron microscopy, in which the crystal is diffracted using very few electrons as the stage is continuously rotated. This protocol gives advice on how to identify microcrystals by light microscopy or by negative-stain electron microscopy in samples obtained from standard protein crystallization experiments. The protocol also includes information about custom-designed equipment for controlling crystal rotation and software for recording experimental parameters in diffraction image metadata. Identifying microcrystals, preparing samples and setting up the microscope for diffraction data collection take approximately half an hour for each step. Screening microcrystals for quality diffraction takes roughly an hour, and the collection of a single data set is ∼10 min in duration. Complete data sets and resulting high-resolution structures can be obtained from a single crystal or by merging data from multiple crystals.

  20. A pipeline for comprehensive and automated processing of electron diffraction data in IPLT.

    PubMed

    Schenk, Andreas D; Philippsen, Ansgar; Engel, Andreas; Walz, Thomas

    2013-05-01

    Electron crystallography of two-dimensional crystals allows the structural study of membrane proteins in their native environment, the lipid bilayer. Determining the structure of a membrane protein at near-atomic resolution by electron crystallography remains, however, a very labor-intense and time-consuming task. To simplify and accelerate the data processing aspect of electron crystallography, we implemented a pipeline for the processing of electron diffraction data using the Image Processing Library and Toolbox (IPLT), which provides a modular, flexible, integrated, and extendable cross-platform, open-source framework for image processing. The diffraction data processing pipeline is organized as several independent modules implemented in Python. The modules can be accessed either from a graphical user interface or through a command line interface, thus meeting the needs of both novice and expert users. The low-level image processing algorithms are implemented in C++ to achieve optimal processing performance, and their interface is exported to Python using a wrapper. For enhanced performance, the Python processing modules are complemented with a central data managing facility that provides a caching infrastructure. The validity of our data processing algorithms was verified by processing a set of aquaporin-0 diffraction patterns with the IPLT pipeline and comparing the resulting merged data set with that obtained by processing the same diffraction patterns with the classical set of MRC programs. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. A pipeline for comprehensive and automated processing of electron diffraction data in IPLT

    PubMed Central

    Schenk, Andreas D.; Philippsen, Ansgar; Engel, Andreas; Walz, Thomas

    2013-01-01

    Electron crystallography of two-dimensional crystals allows the structural study of membrane proteins in their native environment, the lipid bilayer. Determining the structure of a membrane protein at near-atomic resolution by electron crystallography remains, however, a very labor-intense and time-consuming task. To simplify and accelerate the data processing aspect of electron crystallography, we implemented a pipeline for the processing of electron diffraction data using the Image Processing Library & Toolbox (IPLT), which provides a modular, flexible, integrated, and extendable cross-platform, open-source framework for image processing. The diffraction data processing pipeline is organized as several independent modules implemented in Python. The modules can be accessed either from a graphical user interface or through a command line interface, thus meeting the needs of both novice and expert users. The low-level image processing algorithms are implemented in C++ to achieve optimal processing performance, and their interface is exported to Python using a wrapper. For enhanced performance, the Python processing modules are complemented with a central data managing facility that provides a caching infrastructure. The validity of our data processing algorithms was verified by processing a set of aquaporin-0 diffraction patterns with the IPLT pipeline and comparing the resulting merged data set with that obtained by processing the same diffraction patterns with the classical set of MRC programs. PMID:23500887

  2. A Charter School in Partnerships for At-Risk Youth.

    ERIC Educational Resources Information Center

    Czaja, Marion D.; Belcher, Sandi

    This report describes and evaluates the Raven School, a charter school established in 1998 to serve adjudicated youths ages 16 to 18. The school is administered by the Gulf Coast Trades Center, a private nonprofit organization located in the Sam Houston National Forest in rural Texas. In addition to academics and GED preparation, other program…

  3. Beyond the GED: Promising Models for Moving High School Dropouts to College

    ERIC Educational Resources Information Center

    Rutschow, Elizabeth Zachry; Crary-Ross, Shane

    2014-01-01

    As globalization and technological change remake the labor market, it has become increasingly clear that the United States must create better educational and workforce training programs if we are to remain competitive. In order to help disadvantaged and low-skilled workers advance in the new labor market, educational opportunities are needed that…

  4. Education in Rural County Jails: Need versus Opportunity

    ERIC Educational Resources Information Center

    Gee, Jeremiah

    2006-01-01

    An action research project was undertaken by a GED instructor at a rural county jail. A survey tool was developed to determine if the perceived needs of the students were being met by the educational and rehabilitative programs currently offered to them. Data from the survey were grouped into four domains: perceived inmate need, attitude toward…

  5. Ged® Completers' Perceptions of College Readiness and Social Capital: Linking Adult Literacy to a Greater Quality of Life

    ERIC Educational Resources Information Center

    Lott, Donalyn; O'Dell, Jade

    2014-01-01

    This study examined the efficacy of general education development (GED®) acquisition and GED® completers' perceptions of college readiness and social capital using a quantitative methodology. Also, the study used a descriptive, cross-sectional research design framed by the social capital theoretical perspective. The conceptual framework developed…

  6. An Urban Mid-Western Adult Education Program: Perspectives of Stakeholders

    ERIC Educational Resources Information Center

    Willis, Dedria Lynette

    2017-01-01

    The purpose of this qualitative research study is two-fold: (1) to narrate the realities and perspectives of adult students' learning experiences in a General Education Development (GED) preparation program in a Mid-western urban city; and (2) to document the thinking of the former director of adult education at the state level to understand the…

  7. Rogue Community College Student Satisfaction Survey, Winter 2000. Management Report: ABE/GED Program.

    ERIC Educational Resources Information Center

    Wild, Nancy

    The report discusses the winter 2000 student satisfaction survey at Rogue Community College (RCC) (Oregon). The annual survey is an important tool by which the college measures its achievement in the areas of services, classes, and facilities. The primary purpose of the study is to obtain feedback from attending students regarding the issues that…

  8. Dyslexia Defined. NetNews. Volume 5, Number 2

    ERIC Educational Resources Information Center

    LDA of Minnesota, 2004

    2004-01-01

    Learning Disabilities Association (LDA) of Minnesota has gotten many questions over the years about dyslexia. Examples of questions answered in this issue include: (1) When a learner reverses letters, is this dyslexia? (2) How does one teach an adult with dyslexia? (3) Can dyslexia be cured? and (4) Can GED accommodations be received for dyslexia?…

  9. Lafayette Parish Cooperative Jail Project--LPCJP. Phase III Final Report.

    ERIC Educational Resources Information Center

    Lafayette Parish School Board, LA.

    A three-phase project was conducted to further the education of inmates in the Lafayette (Louisiana) Parish Correctional Center. Phase I of the project was designed to prepare inmates to be eligible to take the General Educational Development (GED) test, and/or to teach life-coping skills so that they would better function in society upon their…

  10. MUJER: Mothers United for Jobs, Education, and Results. 1997-8 Project FORWARD Project-based Learning Project Summary.

    ERIC Educational Resources Information Center

    Green, Anson M.

    Students in the Culebra Road GED/JOBS (General Educational Development/Job Opportunities and Basic Skills) class, an adult education class for Temporary Assistance for Needy Families (TANF) students, created their own website. First, students completed a computer literacy survey to gauge their computer skills. Next, students were encouraged to…

  11. A Comparison of the Self-Descriptions of High School Completion (GED) Dropouts and Persisters.

    ERIC Educational Resources Information Center

    Rolfe, Paula G.; Wilson, Russell C.

    Differences in self-descriptive patterns of adults who dropped out of high school completion courses and those who completed their courses were examined using the Adjective Check List (ACL) to measure adult personality attributes. Subjects (N=142) were asked to endorse those adjectives which best described themselves and to skip those which did…

  12. The Effect of Prison Education Programs on Recidivism

    ERIC Educational Resources Information Center

    Esperian, John H.

    2010-01-01

    With constraints on budgets everywhere across America, many programs in U S prisons are being closely monitored to determine if costs can be cut and money saved in daily operations. A dramatic example occurred most recently at the College of Southern Nevada where, at a June graduation ceremony for inmates who earned a GED, or a high school…

  13. Alcohol Use and Antisocial Behavior in Late Adolescence: Characteristics of a Sample Attending a GED Program

    ERIC Educational Resources Information Center

    Owens, Meredith Reesman; Bergman, Andrea

    2010-01-01

    This study examined peer deviance, disinhibition, and ADHD symptoms as differential predictors of alcohol use, alcohol use disorder symptoms, and antisocial behavior. It was hypothesized that peer deviance would most strongly predict alcohol use while disinhibition and ADHD would predict alcohol use disorder symptoms and antisocial behavior.…

  14. High School Credentialing in Wisconsin. Forum: Responding to Changes in High School Equivalency Testing

    ERIC Educational Resources Information Center

    Panzer, Willa; Johnson, Mark; Lewis, Beth

    2015-01-01

    Wisconsinites interested in pursuing a high school credential rely on the unique collaboration between the State GED Administrator at the Wisconsin Department of Instruction (DPI), the State Director of Adult Basic Education (ABE) and staff of the Wisconsin Technical College System (WTCS), and the many providers of instruction throughout the…

  15. Direct Measurement of Polarization-Induced Fields in GaN/AlN by Nano-Beam Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Carvalho, Daniel; Müller-Caspary, Knut; Schowalter, Marco; Grieb, Tim; Mehrtens, Thorsten; Rosenauer, Andreas; Ben, Teresa; García, Rafael; Redondo-Cubero, Andrés; Lorenz, Katharina; Daudin, Bruno; Morales, Francisco M.

    2016-06-01

    The built-in piezoelectric fields in group III-nitrides can act as road blocks on the way to maximizing the efficiency of opto-electronic devices. In order to overcome this limitation, a proper characterization of these fields is necessary. In this work nano-beam electron diffraction in scanning transmission electron microscopy mode has been used to simultaneously measure the strain state and the induced piezoelectric fields in a GaN/AlN multiple quantum well system.

  16. Orientation and phase mapping in the transmission electron microscope using precession-assisted diffraction spot recognition: state-of-the-art results.

    PubMed

    Viladot, D; Véron, M; Gemmi, M; Peiró, F; Portillo, J; Estradé, S; Mendoza, J; Llorca-Isern, N; Nicolopoulos, S

    2013-10-01

    A recently developed technique based on the transmission electron microscope, which makes use of electron beam precession together with spot diffraction pattern recognition now offers the possibility to acquire reliable orientation/phase maps with a spatial resolution down to 2 nm on a field emission gun transmission electron microscope. The technique may be described as precession-assisted crystal orientation mapping in the transmission electron microscope, precession-assisted crystal orientation mapping technique-transmission electron microscope, also known by its product name, ASTAR, and consists in scanning the precessed electron beam in nanoprobe mode over the specimen area, thus producing a collection of precession electron diffraction spot patterns, to be thereafter indexed automatically through template matching. We present a review on several application examples relative to the characterization of microstructure/microtexture of nanocrystalline metals, ceramics, nanoparticles, minerals and organics. The strengths and limitations of the technique are also discussed using several application examples. ©2013 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

  17. Use of reciprocal lattice layer spacing in electron backscatter diffraction pattern analysis

    PubMed

    Michael; Eades

    2000-03-01

    In the scanning electron microscope using electron backscattered diffraction, it is possible to measure the spacing of the layers in the reciprocal lattice. These values are of great use in confirming the identification of phases. The technique derives the layer spacing from the higher-order Laue zone rings which appear in patterns from many materials. The method adapts results from convergent-beam electron diffraction in the transmission electron microscope. For many materials the measured layer spacing compares well with the calculated layer spacing. A noted exception is for higher atomic number materials. In these cases an extrapolation procedure is described that requires layer spacing measurements at a range of accelerating voltages. This procedure is shown to improve the accuracy of the technique significantly. The application of layer spacing measurements in EBSD is shown to be of use for the analysis of two polytypes of SiC.

  18. Characterization of calcium crystals in Abelia using x-ray diffraction and electron microscopes

    USDA-ARS?s Scientific Manuscript database

    Localization, chemical composition, and morphology of calcium crystals in leaves and stems of Abelia mosanensis and A. ×grandiflora were analyzed with a variable pressure scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, low temperature SEM (LT-SEM) and a transmission ...

  19. Development of Thin Films as Potential Structural Cathodes to Enable Multifunctional Energy-Storage Structural Composite Batteries for the U.S. Army’s Future Force

    DTIC Science & Technology

    2011-09-01

    glancing angle X - ray diffraction (GAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and electrochemical...Emission SEM FWHM full width at half maximum GAXRD glancing angle X - ray diffraction H3COCH2CH2OH 2-methoxyethanol LiMn2O4 lithium manganese oxide...were characterized by scanning electron microscopy (SEM), X - ray diffraction (XRD), and atomic force microscopy (AFM). In addition,

  20. Multiple defocused coherent diffraction imaging: method for simultaneously reconstructing objects and probe using X-ray free-electron lasers.

    PubMed

    Hirose, Makoto; Shimomura, Kei; Suzuki, Akihiro; Burdet, Nicolas; Takahashi, Yukio

    2016-05-30

    The sample size must be less than the diffraction-limited focal spot size of the incident beam in single-shot coherent X-ray diffraction imaging (CXDI) based on a diffract-before-destruction scheme using X-ray free electron lasers (XFELs). This is currently a major limitation preventing its wider applications. We here propose multiple defocused CXDI, in which isolated objects are sequentially illuminated with a divergent beam larger than the objects and the coherent diffraction pattern of each object is recorded. This method can simultaneously reconstruct both objects and a probe from the coherent X-ray diffraction patterns without any a priori knowledge. We performed a computer simulation of the prposed method and then successfully demonstrated it in a proof-of-principle experiment at SPring-8. The prposed method allows us to not only observe broad samples but also characterize focused XFEL beams.

  1. Electron-spectroscopy and -diffraction study of the conductivity of CVD diamond ( 0 0 1 )2×1 surface

    NASA Astrophysics Data System (ADS)

    Kono, S.; Takano, T.; Shimomura, M.; Goto, T.; Sato, K.; Abukawa, T.; Tachiki, M.; Kawarada, H.

    2003-04-01

    A chemical vapor deposition as-grown diamond (0 0 1) single-domain 2 × 1 surface was studied by electron-spectroscopy and electron-diffraction in ultrahigh vacuum (UHV). In order to change the surface conductivity (SC) of the diamond in UHV, three annealing stages were used; without annealing, annealing at 300 °C and annealing at 550 °C. From low energy electron diffraction and X-ray photoelectron spectroscopic (XPS) studies, an existence of SC was suggested for the first two stages of annealing and an absence of SC was suggested for the last stage of annealing. Changes in C KVV Auger electron spectroscopic spectra, C KVV Auger electron diffraction (AED) patterns and C 1s XPS peak positions were noticed between the annealing stages at 300 and 550 °C. These changes are interpreted as such that the state of hydrogen involvement in a subsurface of diamond (0 0 1)2 × 1 changes as SC changes. In particular, the presence of local disorder in diamond configuration in SC subsurface is pointed out from C KVV AED. From C 1s XPS peak shifts, a lower bound for the Fermi-level for SC layers from the valence band top is presented to be ˜0.5 eV.

  2. Two-Dimensional Light Diffraction from an EPROM Chip

    ERIC Educational Resources Information Center

    Ekkens, Tom

    2018-01-01

    In introductory physics classes, a laser pointer and a compact disc are all the items required to illustrate diffraction of light in a single dimension. If a two-dimensional diffraction pattern is desired, double axis diffraction grating material is available or a CCD sensor can be extracted from an unused electronics device. This article presents…

  3. Characterization of X80 and X100 Microalloyed Pipeline Steel Using Quantitative X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    Wiskel, J. B.; Li, X.; Ivey, D. G.; Henein, H.

    2018-06-01

    Quantitative X-ray diffraction characterization of four (4) X80 and three (3) X100 microalloyed steels was undertaken. The effect of through-thickness position, processing parameters, and composition on the measured crystallite size, microstrain, and J index (relative magnitude of crystallographic texture) was determined. Microstructure analysis using optical microscopy, scanning electron microscopy, transmission electron microscopy, and electron-backscattered diffraction was also undertaken. The measured value of microstrain increased with increasing alloy content and decreasing cooling interrupt temperature. Microstructural features corresponding to crystallite size in the X80 steels were both above and below the detection limit for quantitative X-ray diffraction. The X100 steels consistently exhibited microstructure features below the crystallite size detection limit. The yield stress of each steel increased with increasing microstrain. The increase in microstrain from X80 to X100 is also associated with a change in microstructure from predominantly polygonal ferrite to bainitic ferrite.

  4. Mapping of reciprocal space of La{sub 0.30}CoO{sub 2} in 3D: Analysis of superstructure diffractions and intergrowths with Co{sub 3}O{sub 4}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brázda, Petr, E-mail: brazda@fzu.cz; Palatinus, Lukáš; Klementová, Mariana

    2015-07-15

    We have used electron diffraction tomography and powder X-ray diffraction to elucidate the structural properties of layered cobaltate γ-La{sub 0.30}CoO{sub 2}. The structure consists of hexagonal sheets of edge-sharing CoO{sub 6} octahedra interleaved by lanthanum monolayers. The La{sup 3+} cations occupy only one third of available P2 sites, forming a 2-dimensional a√3×a√3 superstructure in a–b plane. The results show that there exists no order in the mutual relative shift between the neighbouring La interlayers within the a–b plane. This is manifested in the observed monotonous decrease of the diffracted intensity of the superstructure diffractions along c{sup ⁎} in both X-raymore » and electron diffraction data. The observed lack of stacking order differentiates the La{sub x}CoO{sub 2} from its Ca and Sr analogues where at least a partial stacking order of the cationic interlayers is manifested in experimental data published in literature. - Highlights: • We use electron diffraction tomography for reciprocal space mapping of La{sub 0.30}CoO{sub 2}. • We observed a complete disorder of the stacking of Lanthanum interlayers. • Co{sub 3}O{sub 4} intergrown with La{sub 0.30}CoO{sub 2} crystals brings about fake superstructure diffractions. • Twinning of Co{sub 3}O{sub 4} enhances the problem of fake superstructure diffractions.« less

  5. Three-dimensional rotation electron diffraction: software RED for automated data collection and data processing

    PubMed Central

    Wan, Wei; Sun, Junliang; Su, Jie; Hovmöller, Sven; Zou, Xiaodong

    2013-01-01

    Implementation of a computer program package for automated collection and processing of rotation electron diffraction (RED) data is described. The software package contains two computer programs: RED data collection and RED data processing. The RED data collection program controls the transmission electron microscope and the camera. Electron beam tilts at a fine step (0.05–0.20°) are combined with goniometer tilts at a coarse step (2.0–3.0°) around a common tilt axis, which allows a fine relative tilt to be achieved between the electron beam and the crystal in a large tilt range. An electron diffraction (ED) frame is collected at each combination of beam tilt and goniometer tilt. The RED data processing program processes three-dimensional ED data generated by the RED data collection program or by other approaches. It includes shift correction of the ED frames, peak hunting for diffraction spots in individual ED frames and identification of these diffraction spots as reflections in three dimensions. Unit-cell parameters are determined from the positions of reflections in three-dimensional reciprocal space. All reflections are indexed, and finally a list with hkl indices and intensities is output. The data processing program also includes a visualizer to view and analyse three-dimensional reciprocal lattices reconstructed from the ED frames. Details of the implementation are described. Data collection and data processing with the software RED are demonstrated using a calcined zeolite sample, silicalite-1. The structure of the calcined silicalite-1, with 72 unique atoms, could be solved from the RED data by routine direct methods. PMID:24282334

  6. Three-dimensional rotation electron diffraction: software RED for automated data collection and data processing.

    PubMed

    Wan, Wei; Sun, Junliang; Su, Jie; Hovmöller, Sven; Zou, Xiaodong

    2013-12-01

    Implementation of a computer program package for automated collection and processing of rotation electron diffraction (RED) data is described. The software package contains two computer programs: RED data collection and RED data processing. The RED data collection program controls the transmission electron microscope and the camera. Electron beam tilts at a fine step (0.05-0.20°) are combined with goniometer tilts at a coarse step (2.0-3.0°) around a common tilt axis, which allows a fine relative tilt to be achieved between the electron beam and the crystal in a large tilt range. An electron diffraction (ED) frame is collected at each combination of beam tilt and goniometer tilt. The RED data processing program processes three-dimensional ED data generated by the RED data collection program or by other approaches. It includes shift correction of the ED frames, peak hunting for diffraction spots in individual ED frames and identification of these diffraction spots as reflections in three dimensions. Unit-cell parameters are determined from the positions of reflections in three-dimensional reciprocal space. All reflections are indexed, and finally a list with hkl indices and intensities is output. The data processing program also includes a visualizer to view and analyse three-dimensional reciprocal lattices reconstructed from the ED frames. Details of the implementation are described. Data collection and data processing with the software RED are demonstrated using a calcined zeolite sample, silicalite-1. The structure of the calcined silicalite-1, with 72 unique atoms, could be solved from the RED data by routine direct methods.

  7. Study of residual stresses in CT test specimens welded by electron beam

    NASA Astrophysics Data System (ADS)

    Papushkin, I. V.; Kaisheva, D.; Bokuchava, G. D.; Angelov, V.; Petrov, P.

    2018-03-01

    The paper reports result of residual stress distribution studies in CT specimens reconstituted by electron beam welding (EBW). The main aim of the study is evaluation of the applicability of the welding technique for CT specimens’ reconstitution. Thus, the temperature distribution during electron beam welding of a CT specimen was calculated using Green’s functions and the residual stress distribution was determined experimentally using neutron diffraction. Time-of-flight neutron diffraction experiments were performed on a Fourier stress diffractometer at the IBR-2 fast pulsed reactor in FLNP JINR (Dubna, Russia). The neutron diffraction data estimates yielded a maximal stress level of ±180 MPa in the welded joint.

  8. Geometry of phase-separated domains in phospholipid bilayers by diffraction-contrast electron microscopy.

    PubMed Central

    Hui, S W

    1981-01-01

    The sizes and shapes of solidus (gel) phase domains in the hydrated molecular bilayers of dilauroylphosphatidylcholine/dipalmitoylphasphatidylcholine (DLPC/DPPC) (1:1) and phosphatidylserine (PS)/DPPC (1:2) are visualized directly by low dose diffraction-contrast electron microscopy. The temperature and humidity of the bilayers are controlled by an environmental chamber set in an electron microscope. The contrast between crystalline domains is enhanced by electron optical filtering of the diffraction patterns of the bilayers. The domains are seen as a patchwork in the plane of the bilayer, with an average width of 0.2-0.5 micrometer. The percentage of solidus area measured from diffraction-contrast micrographs at various temperatures agrees in general with those depicted by known phase diagrams. The shape and size of the domains resemble those seen by freeze-fracture in multilamellar vesicles. Temperature-related changes in domain size and in phase boundary per unit area are more pronounced in the less miscible DLPC/DPPC mixture. No significant change in these geometric parameters with temperature is found in the PS/DPPC mixture. Mapping domains by their molecular diffraction signals not only verifies the existance of areas of different molecular packing during phase separation but also provides a quantitative measurement of structural boundaries and defects in lipid bilayers. Images FIGURE 1 FIGURE 3 FIGURE 6 PMID:6894707

  9. Diffraction of real and virtual photons in a pyrolytic graphite crystal as source of intensive quasimonochromatic X-ray beam

    NASA Astrophysics Data System (ADS)

    Bogomazova, E. A.; Kalinin, B. N.; Naumenko, G. A.; Padalko, D. V.; Potylitsyn, A. P.; Sharafutdinov, A. F.; Vnukov, I. E.

    2003-01-01

    A series of experiments on the parametric X-rays radiation (PXR) generation and radiation soft component diffraction of relativistic electrons in pyrolytic graphite (PG) crystals have been carried out at the Tomsk synchrotron. It is shown that the experimental results with PG crystals are explained by the kinematic PXR theory if we take into account a contribution of the real photons diffraction (transition radiation, bremsstrahlung and PXR photons as well). The measurements of the emission spectrum of channeled electrons in the photon energy range much smaller than the characteristic energy of channeling radiation have been performed with a crystal-diffraction spectrometer. For electrons incident along the <1 1 0> axis of a silicon crystal, the radiation intensity in the energy range 30⩽ ω⩽360 keV exceeds the bremsstrahlung one almost by an order of magnitude. Different possibilities to create an effective source of the monochromatic X-ray beam based on the real and virtual photons diffraction in the PG crystals have been considered.

  10. Combining experiment and optical simulation in coherent X-ray nanobeam characterization of Si/SiGe semiconductor heterostructures

    DOE PAGES

    Tilka, J. A.; Park, J.; Ahn, Y.; ...

    2016-07-06

    Here, the highly coherent and tightly focused x-ray beams produced by hard x-ray light sources enable the nanoscale characterization of the structure of electronic materials but are accompanied by significant challenges in the interpretation of diffraction and scattering patterns. X-ray nanobeams exhibit optical coherence combined with a large angular divergence introduced by the x-ray focusing optics. The scattering of nanofocused x-ray beams from intricate semiconductor heterostructures produces a complex distribution of scattered intensity. We report here an extension of coherent xray optical simulations of convergent x-ray beam diffraction patterns to arbitrary x-ray incident angles to allow the nanobeam diffraction patternsmore » of complex heterostructures to be simulated faithfully. These methods are used to extract the misorientation of lattice planes and the strain of individual layers from synchrotron x-ray nanobeam diffraction patterns of Si/SiGe heterostructures relevant to applications in quantum electronic devices. The systematic interpretation of nanobeam diffraction patterns from semiconductor heterostructures presents a new opportunity in characterizing and ultimately designing electronic materials.« less

  11. Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source.

    PubMed

    Rupp, Daniela; Monserud, Nils; Langbehn, Bruno; Sauppe, Mario; Zimmermann, Julian; Ovcharenko, Yevheniy; Möller, Thomas; Frassetto, Fabio; Poletto, Luca; Trabattoni, Andrea; Calegari, Francesca; Nisoli, Mauro; Sander, Katharina; Peltz, Christian; J Vrakking, Marc; Fennel, Thomas; Rouzée, Arnaud

    2017-09-08

    Coherent diffractive imaging of individual free nanoparticles has opened routes for the in situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using extreme ultraviolet pulses from a femtosecond-laser-driven high harmonic source. We obtain bright wide-angle scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.Diffraction imaging studies of free individual nanoparticles have so far been restricted to XUV and X-ray free - electron laser facilities. Here the authors demonstrate the possibility of using table-top XUV laser sources to image prolate shapes of superfluid helium droplets.

  12. Dynamical electron diffraction simulation for non-orthogonal crystal system by a revised real space method.

    PubMed

    Lv, C L; Liu, Q B; Cai, C Y; Huang, J; Zhou, G W; Wang, Y G

    2015-01-01

    In the transmission electron microscopy, a revised real space (RRS) method has been confirmed to be a more accurate dynamical electron diffraction simulation method for low-energy electron diffraction than the conventional multislice method (CMS). However, the RRS method can be only used to calculate the dynamical electron diffraction of orthogonal crystal system. In this work, the expression of the RRS method for non-orthogonal crystal system is derived. By taking Na2 Ti3 O7 and Si as examples, the correctness of the derived RRS formula for non-orthogonal crystal system is confirmed by testing the coincidence of numerical results of both sides of Schrödinger equation; moreover, the difference between the RRS method and the CMS for non-orthogonal crystal system is compared at the accelerating voltage range from 40 to 10 kV. Our results show that the CMS method is almost the same as the RRS method for the accelerating voltage above 40 kV. However, when the accelerating voltage is further lowered to 20 kV or below, the CMS method introduces significant errors, not only for the higher-order Laue zone diffractions, but also for zero-order Laue zone. These indicate that the RRS method for non-orthogonal crystal system is necessary to be used for more accurate dynamical simulation when the accelerating voltage is low. Furthermore, the reason for the increase of differences between those diffraction patterns calculated by the RRS method and the CMS method with the decrease of the accelerating voltage is discussed. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  13. Attosecond electron pulses for 4D diffraction and microscopy

    PubMed Central

    Baum, Peter; Zewail, Ahmed H.

    2007-01-01

    In this contribution, we consider the advancement of ultrafast electron diffraction and microscopy to cover the attosecond time domain. The concept is centered on the compression of femtosecond electron packets to trains of 15-attosecond pulses by the use of the ponderomotive force in synthesized gratings of optical fields. Such attosecond electron pulses are significantly shorter than those achievable with extreme UV light sources near 25 nm (≈50 eV) and have the potential for applications in the visualization of ultrafast electron dynamics, especially of atomic structures, clusters of atoms, and some materials. PMID:18000040

  14. TAKASAGO-6 apparatus for cryogenic coherent X-ray diffraction imaging of biological non-crystalline particles using X-ray free electron laser at SACLA

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kobayashi, Amane; Sekiguchi, Yuki; Oroguchi, Tomotaka

    Coherent X-ray diffraction imaging (CXDI) is a technique for structure analyses of non-crystalline particles with dimensions ranging from micrometer to sub-micrometer. We have developed a diffraction apparatus named TAKASAGO-6 for use in single-shot CXDI experiments of frozen-hydrated non-crystalline biological particles at cryogenic temperature with X-ray free electron laser pulses provided at a repetition rate of 30 Hz from the SPring-8 Angstrom Compact free-electron LAser. Specimen particles are flash-cooled after being dispersed on thin membranes supported by specially designed disks. The apparatus is equipped with a high-speed translation stage with a cryogenic pot for raster-scanning of the disks at a speedmore » higher than 25 μm/33 ms. In addition, we use devices assisting the easy transfer of cooled specimens from liquid-nitrogen storages to the cryogenic pot. In the current experimental procedure, more than 20 000 diffraction patterns can be collected within 1 h. Here we report the key components and performance of the diffraction apparatus. Based on the efficiency of the diffraction data collection and the structure analyses of metal particles, biological cells, and cellular organelles, we discuss the future application of this diffraction apparatus for structure analyses of biological specimens.« less

  15. Quantum-chemical calculations and electron diffraction study of the equilibrium molecular structure of vitamin K3

    NASA Astrophysics Data System (ADS)

    Khaikin, L. S.; Tikhonov, D. S.; Grikina, O. E.; Rykov, A. N.; Stepanov, N. F.

    2014-05-01

    The equilibrium molecular structure of 2-methyl-1,4-naphthoquinone (vitamin K3) having C s symmetry is experimentally characterized for the first time by means of gas-phase electron diffraction using quantum-chemical calculations and data on the vibrational spectra of related compounds.

  16. Noble Gas Isotopic Signatures and X-Ray and Electron Diffraction Characteristics of Tagish Lake Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Nakamura, T.; Noguchi, T.; Zolensky, M. E.; Takaoka, N.

    2001-01-01

    Noble gas isotopic signatures and X-ray and electron diffraction characteristics of Tagish Lake indicate that it is a unique carbonaceous chondrite rich in saponite, Fe-Mg-Ca carbonate, primordial noble gases, and presolar grains. Additional information is contained in the original extended abstract.

  17. Electron diffraction study of the sillenites Bi{sub 12}SiO{sub 20}, Bi{sub 25}FeO{sub 39} and Bi{sub 25}InO{sub 39}: Evidence of short-range ordering of oxygen-vacancies in the trivalent sillenites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Scurti, Craig A.; Arenas, D. J.; Auvray, Nicolas

    We present an electron diffraction study of three sillenites, Bi{sub 12}SiO{sub 20}, Bi{sub 25}FeO{sub 39}, and Bi{sub 25}InO{sub 39} synthesized using the solid-state method. We explore a hypothesis, inspired by optical studies in the literature, that suggests that trivalent sillenites have additional disorder not present in the tetravalent compounds. Electron diffraction patterns of Bi{sub 25}FeO{sub 39} and Bi{sub 25}InO{sub 39} show streaks that confirm deviations from the ideal sillenite structure. Multi-slice simulations of electron-diffraction patterns are presented for different perturbations to the sillenite structure - partial substitution of the M site by Bi{sup 3+}, random and ordered oxygen-vacancies, and amore » frozen-phonon model. Although comparison of experimental data to simulations cannot be conclusive, we consider the streaks as evidence of short-range ordered oxygen-vacancies.« less

  18. Electron Matter Optics and the Quantum Electron Stern-Gerlach Magnet

    NASA Astrophysics Data System (ADS)

    McGregor, Scot; Bach, Roger; Yin, Xiaolu; Liou, Sy-Hwang; Batelaan, Herman; Gronniger, Glen

    2011-05-01

    We explore electron interferometry for the purpose of performing fundamental quantum mechanical experiments and sensing applications. To this end electron matter optics elements, in particular, a diffraction limited single slit, a double slit, and a nano-fabricated grating diffraction apparatus as well as a Mach-Zehnder IFM were previously developed. The double slit diffraction pattern has been recorded one electron at a time. Furthermore, the capability of closing each slit on demand has been developed, in that way realizing the thought experiment that Feynman explains in his lectures. The capability of the Mach-Zehnder interferometer to sense DC and AC electromagnetic fields for industrial applications is currently under investigation. Also, the construction of a new type of interferometer that has the potential to significantly increase the enclosed area and thus its sensitivity is in progress. Finally an idea to separate an electron beam fully into its two spin component using an electron interferometer is presented. We gratefully acknowledge funding by NSF Grant No. 0969506 and R. B. and S. M. acknowledge DOE-GAANN fellowships.

  19. A protocol for searching the most probable phase-retrieved maps in coherent X-ray diffraction imaging by exploiting the relationship between convergence of the retrieved phase and success of calculation.

    PubMed

    Sekiguchi, Yuki; Hashimoto, Saki; Kobayashi, Amane; Oroguchi, Tomotaka; Nakasako, Masayoshi

    2017-09-01

    Coherent X-ray diffraction imaging (CXDI) is a technique for visualizing the structures of non-crystalline particles with size in the submicrometer to micrometer range in material sciences and biology. In the structural analysis of CXDI, the electron density map of a specimen particle projected along the direction of the incident X-rays can be reconstructed only from the diffraction pattern by using phase-retrieval (PR) algorithms. However, in practice, the reconstruction, relying entirely on the computational procedure, sometimes fails because diffraction patterns miss the data in small-angle regions owing to the beam stop and saturation of the detector pixels, and are modified by Poisson noise in X-ray detection. To date, X-ray free-electron lasers have allowed us to collect a large number of diffraction patterns within a short period of time. Therefore, the reconstruction of correct electron density maps is the bottleneck for efficiently conducting structure analyses of non-crystalline particles. To automatically address the correctness of retrieved electron density maps, a data analysis protocol to extract the most probable electron density maps from a set of maps retrieved from 1000 different random seeds for a single diffraction pattern is proposed. Through monitoring the variations of the phase values during PR calculations, the tendency for the PR calculations to succeed when the retrieved phase sets converged on a certain value was found. On the other hand, if the phase set was in persistent variation, the PR calculation tended to fail to yield the correct electron density map. To quantify this tendency, here a figure of merit for the variation of the phase values during PR calculation is introduced. In addition, a PR protocol to evaluate the similarity between a map of the highest figure of merit and other independently reconstructed maps is proposed. The protocol is implemented and practically examined in the structure analyses for diffraction patterns from aggregates of gold colloidal particles. Furthermore, the feasibility of the protocol in the structure analysis of organelles from biological cells is examined.

  20. Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells

    NASA Astrophysics Data System (ADS)

    Dongol, Amit

    The intensity dependent diffraction efficiency of a phase coherent photorefractive (PCP) ZnSe quantum well (QW) is investigated at 80 K in a two-beam four-wave mixing (FWM) configuration using 100 fs laser pulses with a repetition rate of 80 MHz. The observed diffraction efficiencies of the first and second-order diffracted beam are on the order of 10-3 and 10-5, respectively, revealing nearly no intensity dependence. The first-order diffraction is caused by the PCP effect where the probe-pulse is diffracted due to a long-living incoherent electron density grating in the QW. The second-order diffraction is created by a combination of diffraction processes. For negative probe-pulse delay, the exciton polarization is diffracted at the electron grating twice by a cascade effect. For positive delay, the diffracted signal is modified by the destructive interference with a chi(5) generated signal due to a dynamical screening effect. Model calculations of the signal traces based on the optical Bloch equations considering inhomogeneous broadening of exciton energies are in good agreement with the experimental data. To study the carrier dynamics responsible for the occurrence of the PCP effect, threebeam FWM experiments are carried out. The non-collinear wave-vectors k1 , k2 and k3 at central wavelength of 441 nm (~2.81 eV) were resonantly tuned to the heavy-hole exciton transition energy at 20 K. In the FWM experiment the time coincident strong pump pulses k1 and k2 create both an exciton density grating in the QW and an electron-hole pair grating in the GaAs while the delayed weak pulse k3 simultaneously probes the exciton lifetime as well as the electron grating capture time. The model calculations are in good agreement with the experimental results also providing information about the transfer delay of electrons arriving from the substrate to the QW. For negative probe-pulse delay we still observe a diffracted signal due to the long living electron density grating in the QW. The electron grating build-up and decay times are also studied with the modified three-beam FWM set-up. Using an optical shutter for pump pulses k1and k2, the dynamics of the electron grating formation and its decay is continuously probed by a delayed pulse k3. The obtained build-up and decay times are found to depend nearly linearly on the intensity of incident pulses k1 and k2 being on the order of several microseconds at low pump intensities. The PCP effect in ZnSe QW possesses a time-gating capability which can be used for real-time holographic imaging. In this work we demonstrate contrast enhanced real time holographic imaging (CEHI) of floating glass beads and of living unicellular animals (Paramecium and Euglena cells) in aqueous solution. We also demonstrate CEHI of a ~100 im thick wire concealed behind a layer of chicken skin. The results demonstrate the potential of PCP QWs for real-time and depth-resolved imaging of moving micrometer sized biological objects in transparent media or of obscured objects in turbid media.

  1. Structure Evolution and Distributions of Grain-Boundary Misorientainons in Submicrocrystalline Molybdenum Irradiated with a Pulsed Electron Beam

    NASA Astrophysics Data System (ADS)

    Stepanova, E. N.; Grabovetskaya, G. P.; Teresov, A. D.; Mishin, I. P.

    2018-05-01

    Using the methods of electron backscatter diffraction, electron microscopy and X-ray diffraction analysis, it is demonstrated that irradiation of the surface of a submicrocrystalline molybdenum specimen with a pulsed electron beam in a non-melt regime results in the formation of a gradient structure in its bulk. The irradiation temperature is shown to affect the density of defects, the value of stress, and the distributions of grain-boundary misorientations in the surface and bulk of the submicrocrystalline molybdenum specimens.

  2. A Public Relations Nightmare: ACLU Class Action Lawsuit Exposes Inaccurate and Inequitable High School Graduation Rates

    ERIC Educational Resources Information Center

    Watson, Terri N.; Brown, Kathleen M.

    2010-01-01

    Florida's decision to equate a GED to a high school diploma undermines the attempt of No Child Left Behind to close the achievement gap, while infringing on the public's trust. Public trust fosters a culture of systemic equity and social justice, which are necessary for academic excellence (Byrk & Schneider, 2003). Florida's code of ethics for…

  3. Analysis of the Marine Corps Educational Tier System

    DTIC Science & Technology

    2013-03-01

    Accounting Office GED General Educational Development HSDG High School Diploma Graduate HumRRO Human Resources Research Organization JAMERS...Tier III: Non- High School Diploma Graduate (NHSDG) In 1997, research by Laurence, Ramsberger, and Arabian examined yet again the first-term...recruiting and first-term attrition. E. FINAL REMARKS A reoccurring theme in attrition research is that the high school diploma is the most

  4. International Assessment of Unmanned Ground Vehicles

    DTIC Science & Technology

    2008-02-01

    research relevant to ground robotics include • Multi-sensor data fusion • Stereovision • Dedicated robots, including legged robots, tracked robots...Technology Laboratory has developed several mobile robots with leg - ged, wheeled, rolling, rowing, and hybrid locomotion. Areas of particular emphasis...117 UK Department of Trade and Industry ( DTI ) Global Watch Mission. November 2006. Mechatronics in Russia. 118 CRDI Web Site: http

  5. The Joliet Junior College Center for Adult Basic Education and Literacy's "Families about Success": Intergenerational Programming That Works.

    ERIC Educational Resources Information Center

    Irby, Terry R.; And Others

    Joliet Junior College's Center for Adult Basic Education and Literacy (CABEL) is responsible for providing adult basic education and support services for adults whose skills in reading and mathematics are below the 12th grade level. Its offerings include instruction in Adult Basic Education (ABE), General Educational Development (GED), English as…

  6. A Comparison of Three Groups of Young Fathers and Program Outcomes

    ERIC Educational Resources Information Center

    Weinman, Maxine L.; Buzi, Ruth S.; Smith, Peggy B.; Nevarez, Lucinda

    2007-01-01

    The purpose of this study was to examine the impact of a fatherhood program on risk behaviors among three groups of young fathers: those still in school (21%), those who had dropped out (52%), and those who graduated from high school or completed a GED (27%). The sample consisted of 198 young fathers who participated in a school-linked…

  7. Educating the Incarcerated: Perspectives from Inmate Students Regarding Education as a Means to Reduce Recidivism

    ERIC Educational Resources Information Center

    Dunn, Terri Cauley

    2014-01-01

    The purpose of this phenomenological research study was to describe how inmate students incarcerated in an Alabama Department of Correctional Services (ADOC) work release facility, and who are enrolled in a prison-based GED program, perceive the role of education in curtailing criminal activity among prisoners who are released back into society.…

  8. Transitioning Adults to College: Adult Basic Education Program Models. NCSALL Occasional Paper

    ERIC Educational Resources Information Center

    Zafft, Cynthia; Kallenbach, Silja; Spohn, Jessica

    2006-01-01

    While the majority of adults who take the General Educational Development (GED) test do so in order to continue their education, few go on to enter postsecondary education. Yet, these same adults stand to make substantial economic and personal gains when they use their adult secondary credential to move from the ranks of high school dropout to…

  9. Recidivism Study: Positive Terminations from J. F. Ingram State Technical College, 1976-1986.

    ERIC Educational Resources Information Center

    Cogburn, Helen E.

    In 1988, a study was conducted by the J. F. Ingram State Technical College (ISTC) to determine recidivism rates for incarcerated individuals who earned a diploma and/or a General Educational Development (GED) certificate at ISTC during the years 1976 through 1986. The identification numbers of 2,844 students who had completed programs at ISTC were…

  10. A Critical Review of Concept Mapping Research Literature: Informing Teaching and Learning Practices in GED Preparation Programs

    ERIC Educational Resources Information Center

    Martin, Larry G.; Martin, Fatima A.; Southworth, Erica

    2015-01-01

    Concept maps (Cmaps) are still underutilized in adult literacy programs and classes. The teaching and learning approaches that have been used historically in adult literacy programs to address the learning needs of these students have not kept pace with the literacy skill demands that have sprung from the increased pace of technological…

  11. ABE/GED Instruction of High School Dropouts. "353" Special Demonstration Project.

    ERIC Educational Resources Information Center

    Norwood, Dianne

    One hundred individuals who dropped out of high school in Lawrence County, Alabama, during the 1986-87 school year were studied in order to help formulate ways schools could prevent students from dropping out and ideas on how to create advertising about available adult education to which such dropouts would be receptive. A former in-home adult…

  12. Inhibition of fetal bone development through epigenetic down- regulation of HoxA10 in obese rats fed high fat diet

    USDA-ARS?s Scientific Manuscript database

    Epidemiological studies show that maternal obesity during intrauterine and early postnatal life increases the risk of low bone mass and fracture later in life. Here, we show that bone development is inhibited in GED 18.5 embryos from rat dams made obese by feeding a high fat diet (HFD). Moreover, fe...

  13. A Follow-Up Appraisal of Selected General Educational Development Test Examinees at McLennan Community College, Waco, Texas.

    ERIC Educational Resources Information Center

    Nelson, Jack Jay

    The report describes a study designed to follow up successful examinees of the General Educational Development (GED) test administered at McLennan Community College. The study's purpose was to determine the trends, traits, and effects of specific aspects related to their receipt of a high school equivalency certificate. Of the 1,065 successful…

  14. Social Networks and Community Support: Sustaining Women in Need of Community-Based Adult Education Programs

    ERIC Educational Resources Information Center

    Albertini, Velmarie L.

    2009-01-01

    Life for uneducated women involves contending with myriad barriers to economic self-sufficiency. The average income for individuals without at least a high school diploma or GED is about $18,734. That income level falls close to the poverty line established by the federal government for a family of three or more. Further compounding the problem…

  15. Cognitive Skills Matter in the Labor Market, Even for School Dropouts. NCSALL Reports #15.

    ERIC Educational Resources Information Center

    Tyler, John H.; Murnane, Richard J.; Willett, John B.

    A study examined evidence of any labor market payoff for school dropouts and if they acquire cognitive skills, and studied whether the payoff differs by gender and race/ethnicity. It analyzed data containing information on the universe of school dropouts in New York and Florida who took the General Educational Development (GED) exams between…

  16. How Is Education Perceived on the Inside?: A Preliminary Study of Adult Males in a Correctional Setting

    ERIC Educational Resources Information Center

    Moeller, Michelle; Day, Scott L.; Rivera, Beverly D.

    2004-01-01

    This study explores a group of inmates' perceptions of their correctional education and environment based on Fetterman's 1994 idea of empowerment evaluation. A group of 16 male inmates were randomly selected from GED and ABE courses in a high minimum correctional facility in Illinois. A self-administered questionnaire included 5 topics:…

  17. Being a (Good) Student: Conceptions of Identity of Adult Basic Education Participants Transitioning to College

    ERIC Educational Resources Information Center

    Reddy, Mina

    2012-01-01

    This study examines the perceptions of identity of a category of students that has rarely been studied in the context of higher education. These are adults who have participated in GED preparation or English for Speakers of Other Languages (ESOL) courses in Adult Basic Education (ABE) programs. A college education is increasingly necessary for…

  18. Effective Literacy Instruction for Adults with Specific Learning Disabilities: Implications for Adult Educators

    ERIC Educational Resources Information Center

    Hock, Michael F.

    2012-01-01

    Adults with learning disabilities (LD) attending adult basic education, GED programs, or community colleges are among the lowest performers on measures of literacy. For example, on multiple measures of reading comprehension, adults with LD had a mean reading score at the third grade level, whereas adults without LD read at the fifth grade level.…

  19. Spatial aspects of building and population exposure data and their implications for global earthquake exposure modeling

    USGS Publications Warehouse

    Dell’Acqua, F.; Gamba, P.; Jaiswal, K.

    2012-01-01

    This paper discusses spatial aspects of the global exposure dataset and mapping needs for earthquake risk assessment. We discuss this in the context of development of a Global Exposure Database for the Global Earthquake Model (GED4GEM), which requires compilation of a multi-scale inventory of assets at risk, for example, buildings, populations, and economic exposure. After defining the relevant spatial and geographic scales of interest, different procedures are proposed to disaggregate coarse-resolution data, to map them, and if necessary to infer missing data by using proxies. We discuss the advantages and limitations of these methodologies and detail the potentials of utilizing remote-sensing data. The latter is used especially to homogenize an existing coarser dataset and, where possible, replace it with detailed information extracted from remote sensing using the built-up indicators for different environments. Present research shows that the spatial aspects of earthquake risk computation are tightly connected with the availability of datasets of the resolution necessary for producing sufficiently detailed exposure. The global exposure database designed by the GED4GEM project is able to manage datasets and queries of multiple spatial scales.

  20. Detection of expansion at large angle grain boundaries using electron diffraction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Balluffi, R.W.; Bristowe, P.D.

    1984-02-01

    Lamarre and Sass (LS) (Scripta Metall. 17: 1141(1983)) observed a grain boundary electron diffraction effect from a large angle twist boundary which they claim can be used to obtain the volume expansion at the grain boundary in a direction normal to it. This paper considers the case where the intensity from the grain boundary region, is close to lattice reflections on the same element of the boundary diffraction lattice. Analysis of this complex problem show that the simplified model of LS is misleading in this case. (DLC)

  1. Graphene unit cell imaging by holographic coherent diffraction.

    PubMed

    Longchamp, Jean-Nicolas; Latychevskaia, Tatiana; Escher, Conrad; Fink, Hans-Werner

    2013-06-21

    We have imaged a freestanding graphene sheet of 210 nm in diameter with 2 Å resolution by combining coherent diffraction and holography with low-energy electrons. The entire sheet is reconstructed from a single diffraction pattern displaying the arrangement of 660.000 individual graphene unit cells at once. Given the fact that electrons with kinetic energies of the order of 100 eV do not damage biological molecules, it will now be a matter of developing methods for depositing individual proteins onto such graphene sheets.

  2. Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution.

    PubMed

    Pennacchio, Francesco; Vanacore, Giovanni M; Mancini, Giulia F; Oppermann, Malte; Jayaraman, Rajeswari; Musumeci, Pietro; Baum, Peter; Carbone, Fabrizio

    2017-07-01

    Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 10 5 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect). Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons.

  3. Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution

    PubMed Central

    Pennacchio, Francesco; Vanacore, Giovanni M.; Mancini, Giulia F.; Oppermann, Malte; Jayaraman, Rajeswari; Musumeci, Pietro; Baum, Peter; Carbone, Fabrizio

    2017-01-01

    Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 105 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect). Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons. PMID:28713841

  4. Quantitative Analysis of Electron Beam Damage in Organic Thin Films

    PubMed Central

    2017-01-01

    In transmission electron microscopy (TEM) the interaction of an electron beam with polymers such as P3HT:PCBM photovoltaic nanocomposites results in electron beam damage, which is the most important factor limiting acquisition of structural or chemical data at high spatial resolution. Beam effects can vary depending on parameters such as electron dose rate, temperature during imaging, and the presence of water and oxygen in the sample. Furthermore, beam damage will occur at different length scales. To assess beam damage at the angstrom scale, we followed the intensity of P3HT and PCBM diffraction rings as a function of accumulated electron dose by acquiring dose series and varying the electron dose rate, sample preparation, and the temperature during acquisition. From this, we calculated a critical dose for diffraction experiments. In imaging mode, thin film deformation was assessed using the normalized cross-correlation coefficient, while mass loss was determined via changes in average intensity and standard deviation, also varying electron dose rate, sample preparation, and temperature during acquisition. The understanding of beam damage and the determination of critical electron doses provides a framework for future experiments to maximize the information content during the acquisition of images and diffraction patterns with (cryogenic) transmission electron microscopy. PMID:28553431

  5. Development of splitting convergent beam electron diffraction (SCBED).

    PubMed

    Houdellier, Florent; Röder, Falk; Snoeck, Etienne

    2015-12-01

    Using a combination of condenser electrostatic biprism with dedicated electron optic conditions for sample illumination, we were able to split a convergent beam electron probe focused on the sample in two half focused probes without introducing any tilt between them. As a consequence, a combined convergent beam electron diffraction pattern is obtained in the back focal plane of the objective lens arising from two different sample areas, which could be analyzed in a single pattern. This splitting convergent beam electron diffraction (SCBED) pattern has been tested first on a well-characterized test sample of Si/SiGe multilayers epitaxially grown on a Si substrate. The SCBED pattern contains information from the strained area, which exhibits HOLZ lines broadening induced by surface relaxation, with fine HOLZ lines observed in the unstrained reference part of the sample. These patterns have been analyzed quantitatively using both parts of the SCBED transmitted disk. The fine HOLZ line positions are used to determine the precise acceleration voltage of the microscope while the perturbed HOLZ rocking curves in the stained area are compared to dynamical simulated ones. The combination of these two information leads to a precise evaluation of the sample strain state. Finally, several SCBED setups are proposed to tackle fundamental physics questions as well as applied materials science ones and demonstrate how SCBED has the potential to greatly expand the range of applications of electron diffraction and electron holography. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Zemax simulations describing collective effects in transition and diffraction radiation.

    PubMed

    Bisesto, F G; Castellano, M; Chiadroni, E; Cianchi, A

    2018-02-19

    Transition and diffraction radiation from charged particles is commonly used for diagnostics purposes in accelerator facilities as well as THz sources for spectroscopy applications. Therefore, an accurate analysis of the emission process and the transport optics is crucial to properly characterize the source and precisely retrieve beam parameters. In this regard, we have developed a new algorithm, based on Zemax, to simulate both transition and diffraction radiation as generated by relativistic electron bunches, therefore considering collective effects. In particular, unlike other previous works, we take into account electron beam physical size and transverse momentum, reproducing some effects visible on the produced radiation, not observable in a single electron analysis. The simulation results have been compared with two experiments showing an excellent agreement.

  7. On the Use of Dynamical Diffraction Theory To Refine Crystal Structure from Electron Diffraction Data: Application to KLa5O5(VO4)2, a Material with Promising Luminescent Properties.

    PubMed

    Colmont, Marie; Palatinus, Lukas; Huvé, Marielle; Kabbour, Houria; Saitzek, Sébastien; Djelal, Nora; Roussel, Pascal

    2016-03-07

    A new lanthanum oxide, KLa5O5(VO4)2, was synthesized using a flux growth technique that involved solid-state reaction under an air atmosphere at 900 °C. The crystal structure was solved and refined using an innovative approach recently established and based on three-dimensional (3D) electron diffraction data, using precession of the electron beam and then validated against Rietveld refinement and denisty functional theory (DFT) calculations. It crystallizes in a monoclinic unit cell with space group C2/m and has unit cell parameters of a = 20.2282(14) Å, b = 5.8639(4) Å, c = 12.6060(9) Å, and β = 117.64(1)°. Its structure is built on Cresnel-like two-dimensional (2D) units (La5O5) of 4*3 (OLa4) tetrahedra, which run parallel to (001) plane, being surrounded by isolated VO4 tetrahedra. Four isolated vanadate groups create channels that host K(+) ions. Substitution of K(+) cations by another alkali metal is possible, going from lithium to rubidium. Li substitution led to a similar phase with a primitive monoclinic unit cell. A complementary selected area electron diffraction (SAED) study highlighted diffuse streaks associated with stacking faults observed on high-resolution electron microscopy (HREM) images of the lithium compound. Finally, preliminary catalytic tests for ethanol oxidation are reported, as well as luminescence evidence. This paper also describes how solid-state chemists can take advantages of recent progresses in electron crystallography, assisted by DFT calculations and powder X-ray diffraction (PXRD) refinements, to propose new structural types with potential applications to the physicist community.

  8. Strain analysis from nano-beam electron diffraction: Influence of specimen tilt and beam convergence.

    PubMed

    Grieb, Tim; Krause, Florian F; Schowalter, Marco; Zillmann, Dennis; Sellin, Roman; Müller-Caspary, Knut; Mahr, Christoph; Mehrtens, Thorsten; Bimberg, Dieter; Rosenauer, Andreas

    2018-07-01

    Strain analyses from experimental series of nano-beam electron diffraction (NBED) patterns in scanning transmission electron microscopy are performed for different specimen tilts. Simulations of NBED series are presented for which strain analysis gives results that are in accordance with experiment. This consequently allows to study the relation between measured strain and actual underlying strain. A two-tilt method which can be seen as lowest-order electron beam precession is suggested and experimentally implemented. Strain determination from NBED series with increasing beam convergence is performed in combination with the experimental realization of a probe-forming aperture with a cross inside. It is shown that using standard evaluation techniques, the influence of beam convergence on spatial resolution is lower than the influence of sharp rings around the diffraction disc which occur at interfaces and which are caused by the tails of the intensity distribution of the electron probe. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Applications of the diffraction and interference of light and electronic waves

    NASA Astrophysics Data System (ADS)

    Bahrim, Cristian; Lanning, Robert

    2010-10-01

    As part of a NSF sponsored program, called STAIRSTEP, at Lamar University we work on improving the basic knowledge of our physics majors in topics with broader impact in various areas of science and engineering [1]. The purpose is to facilitate a deeper understanding of some fundamental concepts in the field of optics through hands-on experience [2]. We choose to study the interference/diffraction of light and matter waves, because of its fundamental importance in physics with many applications. We target multiple goals in our field of study such as to understand the formation of electronic waves (wave packets) and their interaction with atoms in crystals (electron diffraction); the Fourier analysis of light with applications in spectroscopy, etc. We can show that a crystal lattice Fourier transforms the sinusoidal waves associated to free electrons fired toward the crystal. Our studies led to a simple and instructive recipe for discovering the arrangement of atoms in crystals from the analysis of the diffraction patterns produced by radiation or by electrons transmitted through crystals. [1] Doerschuk P. et al., 39th ASEE/IEEE Frontiers in Education Conference, San Antonio 2009, M3F-1. [2] Bahrim C, Innovation 2006 -- World Innovations in Engineering Education and Research, Chapter 17, iNEER Innovation Series, ISBN 0-9741252-5-3.

  10. Diffraction contrast as a sensitive indicator of femtosecond sub-nanoscale motion in ultrafast transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Cremons, Daniel R.; Schliep, Karl B.; Flannigan, David J.

    2013-09-01

    With ultrafast transmission electron microscopy (UTEM), access can be gained to the spatiotemporal scales required to directly visualize rapid, non-equilibrium structural dynamics of materials. This is achieved by operating a transmission electron microscope (TEM) in a stroboscopic pump-probe fashion by photoelectrically generating coherent, well-timed electron packets in the gun region of the TEM. These probe photoelectrons are accelerated down the TEM column where they travel through the specimen before reaching a standard, commercially-available CCD detector. A second laser pulse is used to excite (pump) the specimen in situ. Structural changes are visualized by varying the arrival time of the pump laser pulse relative to the probe electron packet at the specimen. Here, we discuss how ultrafast nanoscale motions of crystalline materials can be visualized and precisely quantified using diffraction contrast in UTEM. Because diffraction contrast sensitively depends upon both crystal lattice orientation as well as incoming electron wavevector, minor spatial/directional variations in either will produce dynamic and often complex patterns in real-space images. This is because sections of the crystalline material that satisfy the Laue conditions may be heterogeneously distributed such that electron scattering vectors vary over nanoscale regions. Thus, minor changes in either crystal grain orientation, as occurs during specimen tilting, warping, or anisotropic expansion, or in the electron wavevector result in dramatic changes in the observed diffraction contrast. In this way, dynamic contrast patterns observed in UTEM images can be used as sensitive indicators of ultrafast specimen motion. Further, these motions can be spatiotemporally mapped such that direction and amplitude can be determined.

  11. Electron-beam-irradiation-induced crystallization of amorphous solid phase change materials

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Wu, Liangcai; Wen, Lin; Ma, Liya; Zhang, Xingyao; Li, Yudong; Guo, Qi; Song, Zhitang

    2018-04-01

    The electron-beam-irradiation-induced crystallization of phase change materials in a nano sized area was studied by in situ transmission electron microscopy and selected area electron diffraction. Amorphous phase change materials changed to a polycrystalline state after being irradiated with a 200 kV electron beam for a long time. The results indicate that the crystallization temperature strongly depends on the difference in the heteronuclear bond enthalpy of the phase change materials. The selected area electron diffraction patterns reveal that Ge2Sb2Te5 is a nucleation-dominated material, when Si2Sb2Te3 and Ti0.5Sb2Te3 are growth-dominated materials.

  12. Electron crystallography with the EIGER detector

    PubMed Central

    Tinti, Gemma; Fröjdh, Erik; van Genderen, Eric; Gruene, Tim; Schmitt, Bernd; de Winter, D. A. Matthijs; Weckhuysen, Bert M.; Abrahams, Jan Pieter

    2018-01-01

    Electron crystallography is a discipline that currently attracts much attention as method for inorganic, organic and macromolecular structure solution. EIGER, a direct-detection hybrid pixel detector developed at the Paul Scherrer Institut, Switzerland, has been tested for electron diffraction in a transmission electron microscope. EIGER features a pixel pitch of 75 × 75 µm2, frame rates up to 23 kHz and a dead time between frames as low as 3 µs. Cluster size and modulation transfer functions of the detector at 100, 200 and 300 keV electron energies are reported and the data quality is demonstrated by structure determination of a SAPO-34 zeotype from electron diffraction data. PMID:29765609

  13. Non-destructive detection of cross-sectional strain and defect structure in an individual Ag five-fold twinned nanowire by 3D electron diffraction mapping.

    PubMed

    Fu, Xin; Yuan, Jun

    2017-07-24

    Coherent x-ray diffraction investigations on Ag five-fold twinned nanowires (FTNWs) have drawn controversial conclusions concerning whether the intrinsic 7.35° angular gap could be compensated homogeneously through phase transformation or inhomogeneously by forming disclination strain field. In those studies, the x-ray techniques only provided an ensemble average of the structural information from all the Ag nanowires. Here, using three-dimensional (3D) electron diffraction mapping approach, we non-destructively explore the cross-sectional strain and the related strain-relief defect structures of an individual Ag FTNW with diameter about 30 nm. The quantitative analysis of the fine structure of intensity distribution combining with kinematic electron diffraction simulation confirms that for such a Ag FTNW, the intrinsic 7.35° angular deficiency results in an inhomogeneous strain field within each single crystalline segment consistent with the disclination model of stress-relief. Moreover, the five crystalline segments are found to be strained differently. Modeling analysis in combination with system energy calculation further indicates that the elastic strain energy within some crystalline segments, could be partially relieved by the creation of stacking fault layers near the twin boundaries. Our study demonstrates that 3D electron diffraction mapping is a powerful tool for the cross-sectional strain analysis of complex 1D nanostructures.

  14. In situ investigation of deformation mechanisms in magnesium-based metal matrix composites

    NASA Astrophysics Data System (ADS)

    Farkas, Gergely; Choe, Heeman; Máthis, Kristián; Száraz, Zoltán; Noh, Yoonsook; Trojanová, Zuzanka; Minárik, Peter

    2015-07-01

    We studied the effect of short fibers on the mechanical properties of a magnesium alloy. In particular, deformation mechanisms in a Mg-Al-Sr alloy reinforced with short alumina fibers were studied in situ using neutron diffraction and acoustic emission methods. The fibers' plane orientation with respect to the loading axis was found to be a key parameter, which influences the acting deformation processes, such as twinning or dislocation slip. Furthermore, the twinning activity was much more significant in samples with parallel fiber plane orientation, which was confirmed by both acoustic emission and electron backscattering diffraction results. Neutron diffraction was also used to assist in analyzing the acoustic emission and electron backscattering diffraction results. The simultaneous application of the two in situ methods, neutron diffraction and acoustic emission, was found to be beneficial for obtaining complementary datasets about the twinning and dislocation slip in the magnesium alloys and composites used in this study.

  15. Transmission Electron Microscopy of Single Wall Carbon Nanotube/Polymer Nanocomposites: A First-Principles Study

    NASA Technical Reports Server (NTRS)

    Sola, Francisco; Xia, Zhenhai; Lebrion-Colon, Marisabel; Meador, Michael A.

    2012-01-01

    The physics of HRTEM image formation and electron diffraction of SWCNT in a polymer matrix were investigated theoretically on the basis of the multislice method, and the optics of a FEG Super TWIN Philips CM 200 TEM operated at 80 kV. The effect of nanocomposite thickness on both image contrast and typical electron diffraction reflections of nanofillers were explored. The implications of the results on the experimental applicability to study dispersion, chirality and diameter of nanofillers are discussed.

  16. Diffracted diffraction radiation and its application to beam diagnostics

    NASA Astrophysics Data System (ADS)

    Goponov, Yu. A.; Shatokhin, R. A.; Sumitani, K.; Syshchenko, V. V.; Takabayashi, Y.; Vnukov, I. E.

    2018-03-01

    We present theoretical considerations for diffracted diffraction radiation and also propose an application of this process to diagnosing ultra-relativistic electron (positron) beams for the first time. Diffraction radiation is produced when relativistic particles move near a target. If the target is a crystal or X-ray mirror, diffraction radiation in the X-ray region is expected to be diffracted at the Bragg angle and therefore be detectable. We present a scheme for applying this process to measurements of the beam angular spread, and consider how to conduct a proof-of-principle experiment for the proposed method.

  17. In-Depth View of the Structure and Growth of SnO2 Nanowires and Nanobrushes.

    PubMed

    Stuckert, Erin P; Geiss, Roy H; Miller, Christopher J; Fisher, Ellen R

    2016-08-31

    Strategic application of an array of complementary imaging and diffraction techniques is critical to determine accurate structural information on nanomaterials, especially when also seeking to elucidate structure-property relationships and their effects on gas sensors. In this work, SnO2 nanowires and nanobrushes grown via chemical vapor deposition (CVD) displayed the same tetragonal SnO2 structure as revealed via powder X-ray diffraction bulk crystallinity data. Additional characterization using a range of electron microscopy imaging and diffraction techniques, however, revealed important structure and morphology distinctions between the nanomaterials. Tailoring scanning transmission electron microscopy (STEM) modes combined with transmission electron backscatter diffraction (t-EBSD) techniques afforded a more detailed view of the SnO2 nanostructures. Indeed, upon deeper analysis of individual wires and brushes, we discovered that, despite a similar bulk structure, wires and brushes grew with different crystal faces and lattice spacings. Had we not utilized multiple STEM diffraction modes in conjunction with t-EBSD, differences in orientation related to bristle density would have been overlooked. Thus, it is only through a methodical combination of several structural analysis techniques that precise structural information can be reliably obtained.

  18. Diffraction efficiency of plasmonic gratings fabricated by electron beam lithography using a silver halide film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sudheer,, E-mail: sudheer@rrcat.gov.in, E-mail: sudheer.rrcat@gmail.com; Tiwari, P.; Srivastava, Himanshu

    2016-07-28

    The silver nanoparticle surface relief gratings of ∼10 μm period are fabricated using electron beam lithography on the silver halide film substrate. Morphological characterization of the gratings shows that the period, the shape, and the relief depth in the gratings are mainly dependent on the number of lines per frame, the spot size, and the accelerating voltage of electron beam raster in the SEM. Optical absorption of the silver nanoparticle gratings provides a broad localized surface plasmon resonance peak in the visible region, whereas the intensity of the peaks depends on the number density of silver nanoparticles in the gratings. Themore » maximum efficiency of ∼7.2% for first order diffraction is observed for the grating fabricated at 15 keV. The efficiency is peaking at 560 nm with ∼380 nm bandwidth. The measured profiles of the diffraction efficiency for the gratings are found in close agreement with the Raman-Nath diffraction theory. This technique provides a simple and efficient method for the fabrication of plasmonic nanoparticle grating structures with high diffraction efficiency having broad wavelength tuning.« less

  19. Coincidence studies of diffraction structures in binary encounter electron spectra

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liao, C.; Hagmann, S.; Richard, P.

    The authors have measured binary encounter electron (BEe) production in collisions of 0.3 MeV/u Cu{sup q+} (q=4,12) projectiles on H{sub 2} targets from 0 to 70 degrees with respect to the beam direction. Prominent features are the appearance of the BEe peak splitting and a very strong forward peaked angular distribution which are attributed to the diffractive scattering of the quasifree target electrons in the short range potential of the projectile. Using electron-projectile final charge state coincidence techniques, different collision reaction channels can be separated. Measurements of this type are being pursued.

  20. High current table-top setup for femtosecond gas electron diffraction.

    PubMed

    Zandi, Omid; Wilkin, Kyle J; Xiong, Yanwei; Centurion, Martin

    2017-07-01

    We have constructed an experimental setup for gas phase electron diffraction with femtosecond resolution and a high average beam current. While gas electron diffraction has been successful at determining molecular structures, it has been a challenge to reach femtosecond resolution while maintaining sufficient beam current to retrieve structures with high spatial resolution. The main challenges are the Coulomb force that leads to broadening of the electron pulses and the temporal blurring that results from the velocity mismatch between the laser and electron pulses as they traverse the sample. We present here a device that uses pulse compression to overcome the Coulomb broadening and deliver femtosecond electron pulses on a gas target. The velocity mismatch can be compensated using laser pulses with a tilted intensity front to excite the sample. The temporal resolution of the setup was determined with a streak camera to be better than 400 fs for pulses with up to half a million electrons and a kinetic energy of 90 keV. The high charge per pulse, combined with a repetition rate of 5 kHz, results in an average beam current that is between one and two orders of magnitude higher than previously demonstrated.

  1. High current table-top setup for femtosecond gas electron diffraction

    DOE PAGES

    Zandi, Omid; Wilkin, Kyle J.; Xiong, Yanwei; ...

    2017-05-08

    Here, we have constructed an experimental setup for gas phase electron diffraction with femtosecond resolution and a high average beam current. While gas electron diffraction has been successful at determining molecular structures, it has been a challenge to reach femtosecond resolution while maintaining sufficient beam current to retrieve structures with high spatial resolution. The main challenges are the Coulomb force that leads to broadening of the electron pulses and the temporal blurring that results from the velocity mismatch between the laser and electron pulses as they traverse the sample. We also present here a device that uses pulse compression tomore » overcome the Coulomb broadening and deliver femtosecond electron pulses on a gas target. The velocity mismatch can be compensated using laser pulses with a tilted intensity front to excite the sample. The temporal resolution of the setup was determined with a streak camera to be better than 400 fs for pulses with up to half a million electrons and a kinetic energy of 90 keV. Finally, the high charge per pulse, combined with a repetition rate of 5 kHz, results in an average beam current that is between one and two orders of magnitude higher than previously demonstrated.« less

  2. Measuring the Shock Stage of Asteroid Regolith Grains by Electron Back-Scattered Diffraction

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Martinez, James; Sitzman, Scott; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Terada, Yasuko; Yagi, Naoto; Komatsu, Mutsumi; Ozawa, Hikaru; hide

    2018-01-01

    We have been analyzing Itokawa samples in order to definitively establish the degree of shock experienced by the regolith of asteroid Itokawa, and to devise a bridge between shock determinations by standard light optical petrography, crystal structures as determined by electron and X-ray diffraction. These techniques would then be available for samples returned from other asteroid regoliths.

  3. "They Never Really Tried to Reach out to Us": Examining Identities and Confronting the Emotional Distance between Urban Youth and Urban Schools

    ERIC Educational Resources Information Center

    McKnight, Andrew N.

    2015-01-01

    This paper looks at the perspectives of 22 young adults concerning their upbringings and life experiences, experiences in inner city and suburban schools, after leaving school, and later in a privately funded urban GED preparation facility in a large southern city. Specifically it addresses the conceptions students have about school and their…

  4. The Devil's in the Details: Evidence from the GED on Large Effects of Small Differences in High Stakes Exams

    ERIC Educational Resources Information Center

    Tyler, John H.; Murnane, Richard J.; Willett, John B.

    2004-01-01

    As part of standards-based educational reform efforts, more than 40 states will soon require students to achieve passing scores on standardized exams in order to obtain a high school diploma. Currently, many states are struggling with the design of their examination systems, debating such questions as which subjects should be tested, what should…

  5. Recruiting 21st Century Army Warriors: A Task Requiring National Attention

    DTIC Science & Technology

    2007-02-04

    Millennials , Advertising, GED, Obesity CLASSIFICATION: Unclassified Following the terrorist attacks on September 11, 2001, the United States...are barring recruiters from gaining access to some campuses. The Millennial Generation Generational attitudes also negatively impact the Army’s...recruiting efforts. The majority of the young men and women the Army seeks to recruit today are often referred to as the “ Millennial Generation

  6. A Study To Determine the Effect of Skill-Focused Curriculum & Instruction on Student Achievement as Evidenced by GED & ACT Pre/Post Scores.

    ERIC Educational Resources Information Center

    Hinterer, Sally A.

    This study explored the effect of skill-based curricula (based on Bloom's Taxonomy) on the academic performance of incarcerated youth. It investigated the impact of teaching thinking skills as a model for designing curricula at the West Virginia Industrial Home for Youth's Johnston High School, a maximum-security juvenile facility. The Graduate…

  7. Enhancing the Instructional Program with Creative Arts: Q&A with Susan Riley, M.Ed. Educator Effectiveness Webinar Series

    ERIC Educational Resources Information Center

    Regional Educational Laboratory Mid-Atlantic, 2016

    2016-01-01

    This document provides Q&A with webinar presenter, Susan Riley. Riley's presentation looks at broad ideas of clarifying best practices in using arts integration (AI) and/or STEAM at any grade level. Questions cover topics such as: the creativity crisis in US schools, integrating art into math adult education (GED and ESL), theater arts in the…

  8. Using Modern Statistical Methods to Analyze Demographics of Kansas ABE/GED Students Who Transition to Community or Technical College Programs

    ERIC Educational Resources Information Center

    Zacharakis, Jeff; Wang, Haiyan; Patterson, Margaret Becker; Andersen, Lori

    2015-01-01

    This research analyzed linked high-quality state data from K-12, adult education, and postsecondary state datasets in order to better understand the association between student demographics and successful completion of a postsecondary program. Due to the relatively small sample size compared to the large number of features, we analyzed the data…

  9. Examination of Urban High School Dropouts with High Self-Efficacy: A Phenomenological Study

    ERIC Educational Resources Information Center

    Bayles, Ronald

    2012-01-01

    The purpose of this study was to explore the lived experience of urban students in Central Alabama with high self-efficacy who have dropped out of school to pursue a GED. This study: (a) provided a platform that gave voice to students to share their lived experience as they made the decision to drop out of high school, (b) identified the character…

  10. The Development and Validation of a Domestic Violence Scale Administered to GED Program Participants to Determine the Effect on Test Performance

    ERIC Educational Resources Information Center

    Muro, Andres

    2013-01-01

    Overwhelming evidence shows that domestic violence is a very serious problem affecting women in the United States. Black et al. (2010) report that approximately 34 million women in the United States, or approximately 30%, have experienced some form of violence including rape, physical, violence, and/or stalking in their lifetimes. Twenty-two…

  11. 20 CFR 664.300 - Who is an “out-of-school youth”?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... school dropout; or (b) Is an eligible youth who has either graduated from high school or holds a GED, but... 20 Employees' Benefits 4 2012-04-01 2012-04-01 false Who is an âout-of-school youthâ? 664.300...) YOUTH ACTIVITIES UNDER TITLE I OF THE WORKFORCE INVESTMENT ACT Out-of-School Youth § 664.300 Who is an...

  12. 20 CFR 664.300 - Who is an “out-of-school youth”?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... school dropout; or (b) Is an eligible youth who has either graduated from high school or holds a GED, but... 20 Employees' Benefits 4 2013-04-01 2013-04-01 false Who is an âout-of-school youthâ? 664.300...) YOUTH ACTIVITIES UNDER TITLE I OF THE WORKFORCE INVESTMENT ACT Out-of-School Youth § 664.300 Who is an...

  13. 20 CFR 664.300 - Who is an “out-of-school youth”?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... school dropout; or (b) Is an eligible youth who has either graduated from high school or holds a GED, but... 20 Employees' Benefits 4 2014-04-01 2014-04-01 false Who is an âout-of-school youthâ? 664.300...) YOUTH ACTIVITIES UNDER TITLE I OF THE WORKFORCE INVESTMENT ACT Out-of-School Youth § 664.300 Who is an...

  14. Direct analysis of ultra-trace semiconductor gas by inductively coupled plasma mass spectrometry coupled with gas to particle conversion-gas exchange technique.

    PubMed

    Ohata, Masaki; Sakurai, Hiromu; Nishiguchi, Kohei; Utani, Keisuke; Günther, Detlef

    2015-09-03

    An inductively coupled plasma mass spectrometry (ICPMS) coupled with gas to particle conversion-gas exchange technique was applied to the direct analysis of ultra-trace semiconductor gas in ambient air. The ultra-trace semiconductor gases such as arsine (AsH3) and phosphine (PH3) were converted to particles by reaction with ozone (O3) and ammonia (NH3) gases within a gas to particle conversion device (GPD). The converted particles were directly introduced and measured by ICPMS through a gas exchange device (GED), which could penetrate the particles as well as exchange to Ar from either non-reacted gases such as an air or remaining gases of O3 and NH3. The particle size distribution of converted particles was measured by scanning mobility particle sizer (SMPS) and the results supported the elucidation of particle agglomeration between the particle converted from semiconductor gas and the particle of ammonium nitrate (NH4NO3) which was produced as major particle in GPD. Stable time-resolved signals from AsH3 and PH3 in air were obtained by GPD-GED-ICPMS with continuous gas introduction; however, the slightly larger fluctuation, which could be due to the ionization fluctuation of particles in ICP, was observed compared to that of metal carbonyl gas in Ar introduced directly into ICPMS. The linear regression lines were obtained and the limits of detection (LODs) of 1.5 pL L(-1) and 2.4 nL L(-1) for AsH3 and PH3, respectively, were estimated. Since these LODs revealed sufficiently lower values than the measurement concentrations required from semiconductor industry such as 0.5 nL L(-1) and 30 nL L(-1) for AsH3 and PH3, respectively, the GPD-GED-ICPMS could be useful for direct and high sensitive analysis of ultra-trace semiconductor gas in air. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. An adaptive modeling and simulation environment for combined-cycle data reconciliation and degradation estimation

    NASA Astrophysics Data System (ADS)

    Lin, Tsungpo

    Performance engineers face the major challenge in modeling and simulation for the after-market power system due to system degradation and measurement errors. Currently, the majority in power generation industries utilizes the deterministic data matching method to calibrate the model and cascade system degradation, which causes significant calibration uncertainty and also the risk of providing performance guarantees. In this research work, a maximum-likelihood based simultaneous data reconciliation and model calibration (SDRMC) is used for power system modeling and simulation. By replacing the current deterministic data matching with SDRMC one can reduce the calibration uncertainty and mitigate the error propagation to the performance simulation. A modeling and simulation environment for a complex power system with certain degradation has been developed. In this environment multiple data sets are imported when carrying out simultaneous data reconciliation and model calibration. Calibration uncertainties are estimated through error analyses and populated to performance simulation by using principle of error propagation. System degradation is then quantified by performance comparison between the calibrated model and its expected new & clean status. To mitigate smearing effects caused by gross errors, gross error detection (GED) is carried out in two stages. The first stage is a screening stage, in which serious gross errors are eliminated in advance. The GED techniques used in the screening stage are based on multivariate data analysis (MDA), including multivariate data visualization and principal component analysis (PCA). Subtle gross errors are treated at the second stage, in which the serial bias compensation or robust M-estimator is engaged. To achieve a better efficiency in the combined scheme of the least squares based data reconciliation and the GED technique based on hypotheses testing, the Levenberg-Marquardt (LM) algorithm is utilized as the optimizer. To reduce the computation time and stabilize the problem solving for a complex power system such as a combined cycle power plant, meta-modeling using the response surface equation (RSE) and system/process decomposition are incorporated with the simultaneous scheme of SDRMC. The goal of this research work is to reduce the calibration uncertainties and, thus, the risks of providing performance guarantees arisen from uncertainties in performance simulation.

  16. Individual analysis of inter and intragrain defects in electrically characterized polycrystalline silicon nanowire TFTs by multicomponent dark-field imaging based on nanobeam electron diffraction two-dimensional mapping

    NASA Astrophysics Data System (ADS)

    Asano, Takanori; Takaishi, Riichiro; Oda, Minoru; Sakuma, Kiwamu; Saitoh, Masumi; Tanaka, Hiroki

    2018-04-01

    We visualize the grain structures for individual nanosized thin film transistors (TFTs), which are electrically characterized, with an improved data processing technique for the dark-field image reconstruction of nanobeam electron diffraction maps. Our individual crystal analysis gives the one-to-one correspondence of TFTs with different grain boundary structures, such as random and coherent boundaries, to the characteristic degradations of ON-current and threshold voltage. Furthermore, the local crystalline uniformity inside a single grain is detected as the difference in diffraction intensity distribution.

  17. Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

    DOE PAGES

    Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth; ...

    2016-11-18

    A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO 3 single crystals. Furthermore, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system.

  18. Space charge effects in ultrafast electron diffraction and imaging

    NASA Astrophysics Data System (ADS)

    Tao, Zhensheng; Zhang, He; Duxbury, P. M.; Berz, Martin; Ruan, Chong-Yu

    2012-02-01

    Understanding space charge effects is central for the development of high-brightness ultrafast electron diffraction and microscopy techniques for imaging material transformation with atomic scale detail at the fs to ps timescales. We present methods and results for direct ultrafast photoelectron beam characterization employing a shadow projection imaging technique to investigate the generation of ultrafast, non-uniform, intense photoelectron pulses in a dc photo-gun geometry. Combined with N-particle simulations and an analytical Gaussian model, we elucidate three essential space-charge-led features: the pulse lengthening following a power-law scaling, the broadening of the initial energy distribution, and the virtual cathode threshold. The impacts of these space charge effects on the performance of the next generation high-brightness ultrafast electron diffraction and imaging systems are evaluated.

  19. Defect ordering in YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6: Synthesis and characterization by neutron and electron diffraction

    NASA Astrophysics Data System (ADS)

    Lin, Y. P.; Greedan, J. E.; O'Reilly, A. H.; Reimers, J. N.; Stager, C. V.; Post, M. L.

    1990-02-01

    Polycrystalline samples of YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6 were prepared by oxygen titration of YBa 2 Cu 3O 6.0 at 450°C followed by slow cooling to room temperature. Both samples showed evidence for the a' = 2a supercell in individual grains by electron diffraction as reported previously. In addition the superlattice was observed in neutron powder diffraction indicating that the bulk material is also well ordered. In this study the YBa 2Cu 3O 6.6 phase showed longer correlation lengths for ordering along both a* and b* than YBa 2Cu 3O 6.5. For the former compound the powder-averaged, sample-averaged a* correlation distance is 26A˚from neutron diffraction. Analysis of electron diffraction profiles on selected single crystals give correlation lengths along a*, b*, and c* of 100, 200, and 50A˚, respectively. Dark field imaging discloses the presence of striped, ordered domains elongated along b* with a distribution of sizes. Both neutron diffraction and dark field imaging indicate that the volume fraction of the ordered domains is about 50%. A correlation is noted between the Meissner Effect and the extent of defect ordering in the bulk samples of the two phases.

  20. Ultrafast molecular processes mapped by femtosecond x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Elsaesser, Thomas

    2012-02-01

    X-ray diffraction with a femtosecond time resolution allows for mapping photoinduced structural dynamics on the length scale of a chemical bond and in the time domain of atomic and molecular motion. In a pump-probe approach, a femtosecond excitation pulse induces structural changes which are probed by diffracting a femtosecond hard x-ray pulse from the excited sample. The transient angular positions and intensities of diffraction peaks give insight into the momentary atomic or molecular positions and into the distribution of electronic charge density. The simultaneous measurement of changes on different diffraction peaks is essential for determining atom positions and charge density maps with high accuracy. Recent progress in the generation of ultrashort hard x-ray pulses (Cu Kα, wavelength λ=0.154 nm) in laser-driven plasma sources has led to the implementation of the powder diffraction and the rotating crystal method with a time resolution of 100 fs. In this contribution, we report new results from powder diffraction studies of molecular materials. A first series of experiments gives evidence of a so far unknown concerted transfer of electrons and protons in ammonium sulfate [(NH4)2SO4], a centrosymmetric structure. Charge transfer from the sulfate groups results in the sub-100 fs generation of a confined electron channel along the c-axis of the unit cell which is stabilized by transferring protons from the adjacent ammonium groups into the channel. Time-dependent charge density maps display a periodic modulation of the channel's charge density by low-frequency lattice motions with a concerted electron and proton motion between the channel and the initial proton binding site. A second study addresses atomic rearrangements and charge dislocations in the non-centrosymmetric potassium dihydrogen phosphate [KH2PO4, KDP]. Photoexcitation generates coherent low-frequency motions along the LO and TO phonon coordinates, leaving the average atomic positions unchanged. The time-dependent maps of electron density demonstrate a concomitant oscillatory relocation of electronic charge with a spatial amplitude of the order of a chemical bond length, two orders of magnitude larger than the vibrational amplitudes. The coherent phonon motions drive the charge relocation, similar to a soft mode driven phase transition between the ferro- and paraelectric phase of KDP.

  1. Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

    PubMed

    Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

    2013-01-01

    Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

  2. Measurements of Auger Electron Diffraction Using a 180° Deflection Toroidal Analyzer

    NASA Astrophysics Data System (ADS)

    Shiraki, Susumu; Ishii, Hideshi; Nihei, Yoshimasa; Owari, Masanori

    A 180° deflection toroidal analyzer is a novel electron spectrometer, which allows the simultaneous registration of the wide range of polar angles in a given azimuth of the sample. Therefore, measurements of photo- and Auger electron intensities over π steradians can be performed rapidly by azimuthal rotation of the sample. Using this analyzer, two-dimensional patterns of electron-beam-excited O KVV and Mg KVV Auger electron diffraction (AED) from a MgO(001) surface were measured in short acquisition times. The AED patterns obtained were compared with theoretical ones calculated by the multiple-scattering scheme. The agreement between experimental and theoretical data was good for both O KVV and Mg KVV transitions.

  3. Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Weathersby, S. P.; Brown, G.; Chase, T. F.

    Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition ratemore » with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.« less

  4. Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory.

    PubMed

    Weathersby, S P; Brown, G; Centurion, M; Chase, T F; Coffee, R; Corbett, J; Eichner, J P; Frisch, J C; Fry, A R; Gühr, M; Hartmann, N; Hast, C; Hettel, R; Jobe, R K; Jongewaard, E N; Lewandowski, J R; Li, R K; Lindenberg, A M; Makasyuk, I; May, J E; McCormick, D; Nguyen, M N; Reid, A H; Shen, X; Sokolowski-Tinten, K; Vecchione, T; Vetter, S L; Wu, J; Yang, J; Dürr, H A; Wang, X J

    2015-07-01

    Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

  5. Highlighting material structure with transmission electron diffraction correlation coefficient maps.

    PubMed

    Kiss, Ákos K; Rauch, Edgar F; Lábár, János L

    2016-04-01

    Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Symposium LL: Nanowires--Synthesis Properties Assembly and Application

    DTIC Science & Technology

    2010-09-10

    dedicated hard x - ray microscopy beamline is operated in partnership with the Advanced Photon Source to provide fluorescence, diffraction, and...characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X - ray diffraction (XRD) measurements, proving it to be...Investigation of Preferred Growth Direction of GaN Nanorods by Synchrotron X - ray Reciprocal Space Mapping. Yuri Sohn1, Sanghwa Lee1, Chinkyo Kim1 and Dong

  7. Quantitative measurements of magnetic vortices using position resolved diffraction in Lorentz STEM

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zaluzec, N. J.

    2002-03-05

    A number of electron column techniques have been developed over the last forty years to permit visualization of magnetic fields in specimens. These include: Fresnel imaging, Differential Phase Contrast, Electron Holography and Lorentz STEM. In this work we have extended the LSTEM methodology using Position Resolved Diffraction (PRD) to quantitatively measure the in-plane electromagnetic fields of thin film materials. The experimental work reported herein has been carried out using the ANL AAEM HB603Z 300 kV FEG instrument 5. In this instrument, the electron optical column was operated in a zero field mode, at the specimen, where the objective lens ismore » turned off and the probe forming lens functions were reallocated to the C1, C2, and C3 lenses. Post specimen lenses (P1, P2, P3, P4) were used to magnify the transmitted electrons to a YAG screen, which was then optically transferred to a Hamamatsu ORCA ER CCD array. This CCD was interfaced to an EmiSpec Data Acquisition System and the data was subsequently transferred to an external computer system for detailed quantitative analysis. In Position Resolved Diffraction mode, we digitally step a focused electron probe across the region of interest of the specimen while at the same time recording the complete diffraction pattern at each point in the scan.« less

  8. Application of a real-space three-dimensional image reconstruction method in the structural analysis of noncrystalline biological macromolecules enveloped by water in coherent x-ray diffraction microscopy.

    PubMed

    Kodama, Wataru; Nakasako, Masayoshi

    2011-08-01

    Coherent x-ray diffraction microscopy is a novel technique in the structural analyses of particles that are difficult to crystallize, such as the biological particles composing living cells. As water is indispensable for maintaining particles in functional structures, sufficient hydration of targeted particles is required during sample preparation for diffraction microscopy experiments. However, the water enveloping particles also contributes significantly to the diffraction patterns and reduces the electron-density contrast of the sample particles. In this study, we propose a protocol for the structural analyses of particles in water by applying a three-dimensional reconstruction method in real space for the projection images phase-retrieved from diffraction patterns, together with a developed density modification technique. We examined the feasibility of the protocol through three simulations involving a protein molecule in a vacuum, and enveloped in either a droplet or a cube-shaped water. The simulations were carried out for the diffraction patterns in the reciprocal planes normal to the incident x-ray beam. This assumption and the simulation conditions corresponded to experiments using x-ray wavelengths of shorter than 0.03 Å. The analyses demonstrated that our protocol provided an interpretable electron-density map. Based on the results, we discuss the advantages and limitations of the proposed protocol and its practical application for experimental data. In particular, we examined the influence of Poisson noise in diffraction patterns on the reconstructed three-dimensional electron density in the proposed protocol.

  9. Electromagnetic diffraction radiation of a subwavelength-hole array excited by an electron beam.

    PubMed

    Liu, Shenggang; Hu, Min; Zhang, Yaxin; Li, Yuebao; Zhong, Renbin

    2009-09-01

    This paper explores the physics of the electromagnetic diffraction radiation of a subwavelength holes array excited by a set of evanescent waves generated by a line charge of electron beam moving parallel to the array. Activated by a uniformly moving line charge, numerous physical phenomena occur such as the diffraction radiation on both sides of the array as well as the electromagnetic penetration or transmission below or above the cut-off through the holes. As a result the subwavelength holes array becomes a radiation array. Making use of the integral equation with relevant Green's functions, an analytical theory for such a radiation system is built up. The results of the numerical calculations based on the theory agree well with that obtained by the computer simulation. The relation among the effective surface plasmon wave, the electromagnetic penetration or transmission of the holes and the diffraction radiation is revealed. The energy dependence of and the influence of the hole thickness on the diffraction radiation and the electromagnetic penetration or transmission are investigated in detail. Therefore, a distinct diffraction radiation phenomenon is discovered.

  10. Dark-field transmission electron microscopy and the Debye-Waller factor of graphene

    PubMed Central

    Hubbard, William A.; White, E. R.; Dawson, Ben; Lodge, M. S.; Ishigami, Masa; Regan, B. C.

    2014-01-01

    Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary. PMID:25242882

  11. Extracting conformational structure information of benzene molecules via laser-induced electron diffraction

    DOE PAGES

    Ito, Yuta; Wang, Chuncheng; Le, Anh-Thu; ...

    2016-05-01

    Here, we have measured the angular distributions of high energy photoelectrons of benzene molecules generated by intense infrared femtosecond laser pulses. These electrons arise from the elastic collisions between the benzene ions with the previously tunnel-ionized electrons that have been driven back by the laser field. Theory shows that laser-free elastic differential cross sections (DCSs) can be extracted from these photoelectrons, and the DCS can be used to retrieve the bond lengths of gas-phase molecules similar to the conventional electron diffraction method. From our experimental results, we have obtained the C-C and C-H bond lengths of benzene with a spatialmore » resolution of about 10 pm. Our results demonstrate that laser induced electron diffraction (LIED) experiments can be carried out with the present-day ultrafast intense lasers already. Looking ahead, with aligned or oriented molecules, more complete spatial information of the molecule can be obtained from LIED, and applying LIED to probe photo-excited molecules, a “molecular movie” of the dynamic system may be created with sub-A°ngstrom spatial and few-ten femtosecond temporal resolutions.« less

  12. Dark-field transmission electron microscopy and the Debye-Waller factor of graphene.

    PubMed

    Shevitski, Brian; Mecklenburg, Matthew; Hubbard, William A; White, E R; Dawson, Ben; Lodge, M S; Ishigami, Masa; Regan, B C

    2013-01-15

    Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary.

  13. Flat ion milling: a powerful tool for preparation of cross-sections of lead-silver alloys.

    PubMed

    Brodusch, Nicolas; Boisvert, Sophie; Gauvin, Raynald

    2013-06-01

    While conventional mechanical and chemical polishing results in stress, deformation and polishing particles embedded on the surface, flat milling with Ar+ ions erodes the material with no mechanical artefacts. This flat milling process is presented as an alternative method to prepare a Pb-Ag alloy cross-section for scanning electron microscopy. The resulting surface is free of scratches with very little to no stress induced, so that electron diffraction and channelling contrast are possible. The results have shown that energy dispersive spectrometer (EDS) mapping, electron channelling contrast imaging and electron backscatter diffraction can be conducted with only one sample preparation step. Electron diffraction patterns acquired at 5 keV possessed very good pattern quality, highlighting an excellent surface condition. An orientation map was acquired at 20 keV with an indexing rate of 90.1%. An EDS map was performed at 5 keV, and Pb-Ag precipitates of sizes lower than 100 nm were observed. However, the drawback of the method is the generation of a noticeable surface topography resulting from the interaction of the ion beam with a polycrystalline and biphasic sample.

  14. Soft-template synthesis of single-crystalline CdS dendrites.

    PubMed

    Niu, Haixia; Yang, Qing; Tang, Kaibin; Xie, Yi; Zhu, Yongchun

    2006-01-01

    The single-crystalline CdS dendrites have been fabricated from the reaction of CdCl2 and thiourea at 180 degrees C, in which glycine was employed as a soft template. The obtained products were explored by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electronic diffraction. The optical properties of CdS dendrites have been investigated by ultraviolet and visible light (UV-vis) and photoluminescence techniques. The investigations indicated that the dendrites were grown due to the anisotropic properties enhanced by the use of Glycine in the route.

  15. Room temperature chemical synthesis of lead selenide thin films with preferred orientation

    NASA Astrophysics Data System (ADS)

    Kale, R. B.; Sartale, S. D.; Ganesan, V.; Lokhande, C. D.; Lin, Yi-Feng; Lu, Shih-Yuan

    2006-11-01

    Room temperature chemical synthesis of PbSe thin films was carried out from aqueous ammoniacal solution using Pb(CH3COO)2 as Pb2+ and Na2SeSO3 as Se2- ion sources. The films were characterized by a various techniques including, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), Fast Fourier transform (FFT) and UV-vis-NIR techniques. The study revealed that the PbSe thin film consists of preferentially oriented nanocubes with energy band gap of 0.5 eV.

  16. Neutron powder diffraction study on the iron-based nitride superconductor ThFeAsN

    NASA Astrophysics Data System (ADS)

    Mao, Huican; Wang, Cao; Maynard-Casely, Helen E.; Huang, Qingzhen; Wang, Zhicheng; Cao, Guanghan; Li, Shiliang; Luo, Huiqian

    2017-03-01

    We report neutron diffraction and transport results on the newly discovered superconducting nitride ThFeAsN with T_c= 30 \\text{K} . No magnetic transition, but a weak structural distortion around 160 K, is observed by cooling from 300 K to 6 K. Analysis on the resistivity, Hall transport and crystal structure suggests that this material behaves as an electron optimally doped pnictide superconductor due to extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen site, which, together with the low arsenic height, may enhance the electron itinerancy and reduce the electron correlations, thus suppressing the static magnetic order.

  17. Ultrafast electron diffraction study of ab-plane dynamics in superconducting Bi2Sr<2CaCu2O8+d

    NASA Astrophysics Data System (ADS)

    Konstantinova, Tatiana; Reid, Alexander; Wu, Lijun; Durr, Hermann; Wang, Xijie; Zhu, Yimei

    The role of phonons and other collective modes in cooperative electron phenomena in high-TC cuprate superconductors is an extensively interesting topic. Time-resolved experiments provide temporal hierarchy of the bosonic modes interacting with electrons. However, majority of research in this field explore dynamics of electronic states and can only make indirect conclusion about involvement of the lattice. We report time-resolved study of optimally doped Bi2Sr2CaCu2O8+d lattice response to photo-excitation by means of ultrafast electron diffraction that is directly sensitive to atomic motion. Data analysis utilizing Bloch-wave calculation of diffraction peak intensity allows separation of Cu-O in-plane vibration building up on the sub picosecond time scale from the low energy phonon population growth with a much slower rate. This study confirms the assumption of strong electron coupling to the Cu-O plane phonons. This work was supported by the US DOE, Office of Science, Basic Energy Science, Materials Science and Engineering Division under Contract No: DE-AC02-98CH10886; DOE LDRD funding under contract DE-AC02-76SF00515 and BNL.

  18. Routes and Reasons Out, Paths Back: The Influence of Push and Pull Reasons for Leaving School on Students' School Reengagement

    ERIC Educational Resources Information Center

    Boylan, Rebecca L.; Renzulli, Linda

    2017-01-01

    Dropout is a major issue facing our country's schools; however, many students who drop out of school later go on to finish their degree either by returning to high school or by earning a General Education Development (GED) credential. Despite this, there has been relatively little research on these students who "stopout" of high school.…

  19. Craftsmanship and Technology: Level I, Unit 5, Lesson 1; Government Separation of Powers: Lesson 2; Comparisons in Literature: Lesson 3. Advanced General Education Program. A High School Self-Study Program.

    ERIC Educational Resources Information Center

    Manpower Administration (DOL), Washington, DC. Job Corps.

    An advanced General Education Program has been designed to prepare an individual with the information, concepts, and general knowledge required to successfully pass the American Council on Education's High School General Education Development (GED) Test. The Advanced General Education Program provides comprehensive self-instruction in each of the…

  20. A Hybrid Neuromechanical Ambulatory Assist System

    DTIC Science & Technology

    2016-08-01

    provide real- time closed-loop control using brace mounted sensors to deliver the stimulation needed to stand up and walk while coordinating exoskeletal...target PC during real- time implementation. The muscle stimulator unit delivered the NES to target paralyzed muscles to drive limb motion. The activity...manual adjustment of thresholds used in the GED and stimulation pattern lengths (Figure 26b). The time for a right or left step could be decreased

  1. 20 CFR 664.300 - Who is an “out-of-school youth”?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... dropout; or (b) Is an eligible youth who has either graduated from high school or holds a GED, but is... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Who is an âout-of-school youthâ? 664.300... ACTIVITIES UNDER TITLE I OF THE WORKFORCE INVESTMENT ACT Out-of-School Youth § 664.300 Who is an “out-of...

  2. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders.

    PubMed

    Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

    2015-03-01

    Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni-Se-O-Cl crystals, zeolites, germanates, metal-organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED methods will become crucially important in the near future.

  3. The Greening after Extended Darkness1 Is an N-End Rule Pathway Mutant with High Tolerance to Submergence and Starvation1[OPEN

    PubMed Central

    Riber, Willi; Müller, Jana T.; Visser, Eric J.W.; Sasidharan, Rashmi; Voesenek, Laurentius A.C.J.; Mustroph, Angelika

    2015-01-01

    Plants respond to reductions in internal oxygen concentrations with adaptive mechanisms (for example, modifications of metabolism to cope with reduced supply of ATP). These responses are, at the transcriptional level, mediated by the group VII Ethylene Response Factor transcription factors, which have stability that is regulated by the N-end rule pathway of protein degradation. N-end rule pathway mutants are characterized by a constitutive expression of hypoxia response genes and abscisic acid hypersensitivity. Here, we identify a novel proteolysis6 (prt6) mutant allele, named greening after extended darkness1 (ged1), which was previously discovered in a screen for genomes uncoupled-like mutants and shows the ability to withstand long periods of darkness at the seedling stage. Interestingly, this ethyl methanesulfonate-derived mutant shows unusual chromosomal rearrangement instead of a point mutation. Furthermore, the sensitivity of N-end rule pathway mutants ged1 and prt6-1 to submergence was studied in more detail to understand previously contradicting experiments on this topic. Finally, it was shown that mutants for the N-end rule pathway are generally more tolerant to starvation conditions, such as prolonged darkness or submergence, which was partially associated with carbohydrate conservation. PMID:25667318

  4. Auger electron diffraction study of the growth of Fe(001) films on ZnSe(001)

    NASA Astrophysics Data System (ADS)

    Jonker, B. T.; Prinz, G. A.

    1991-03-01

    The growth of Fe films on ZnSe(001) epilayers and bulk GaAs(001) substrates has been studied to determine the mode of film growth, the formation of the interface, and the structure of the overlayer at the 1-10 monolayer level. Auger electron diffraction (AED), x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction data are obtained for incremental deposition of the Fe(001) overlayer. The coverage dependence of the AED forward scattering peaks reveals a predominantly layer-by-layer mode of film growth at 175 °C on ZnSe, while a more three-dimensional growth mode occurs on the oxide-desorbed GaAs(001) substrate. XPS studies of the semiconductor 3d levels indicate that the Fe/ZnSe interface is less reactive than the Fe/GaAs interface.

  5. Determination of dislocation density by electron backscatter diffraction and X-ray line profile analysis in ferrous lath martensite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Berecz, Tibor, E-mail: berecz@eik.bme.hu; Jenei, Péter, E-mail: jenei@metal.elte.hu; Csóré, András, E-mail: csorean@gmail.com

    2016-03-15

    The microstructure and the dislocation density in as-quenched ferrous lath martensite were studied by different methods. The blocks, packets and variants formed due to martensitic transformation were identified and their sizes were determined by electron backscatter diffraction (EBSD). Concomitant transmission electron microscopy (TEM) investigation revealed that the laths contain subgrains with the size between 50 and 100 nm. A novel evaluation procedure of EBSD images was elaborated for the determination of the density and the space distribution of geometrically necessary dislocations from the misorientation distribution. The total dislocation density obtained by X-ray diffraction line profile analysis was in good agreementmore » with the value determined by EBSD, indicating that the majority of dislocations formed due to martensitic transformation during quenching are geometrically necessary dislocations.« less

  6. Room Temperature Ferromagnetism of Fe Doped Indium Tin Oxide Based on Dispersed Fe3O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Okada, Koichi; Kohiki, Shigemi; Nishi, Sachio; Shimooka, Hirokazu; Deguchi, Hiroyuki; Mitome, Masanori; Bando, Yoshio; Shishido, Toetsu

    2007-09-01

    Transmission electron microscopy revealed that Fe3O4 nanoparticles with diameter of ≈200 nm dispersed in Fe doped indium tin oxide (Fe@ITO) powders exhibiting co-occurrence of room temperature ferromagnetism and superparamagnetism. Although we observed no X-ray diffraction peak from Fe related compounds for Fe0.19@ITO (ITO: In1.9Sn0.1O3) powders, the powders showed both hysteresis loop in field dependent magnetization at 300 K and divergence of zero-field-cooled magnetization from field-cooled magnetization. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy demonstrated that the nanoparticle with diameter of ≈200 nm consists of Fe and oxygen. Transmission electron diffraction revealed that crystal structure of the nanoparticle is inverse spinel type Fe3O4. The Fe3O4 crystalline phase by electron diffraction is consistent with the saturation magnetization of 1.3 μB/Fe and magnetic anomaly at ≈110 K observed for the powders.

  7. Ultrafast structural dynamics of boron nitride nanotubes studied using transmitted electrons.

    PubMed

    Li, Zhongwen; Sun, Shuaishuai; Li, Zi-An; Zhang, Ming; Cao, Gaolong; Tian, Huanfang; Yang, Huaixin; Li, Jianqi

    2017-09-14

    We investigate the ultrafast structural dynamics of multi-walled boron nitride nanotubes (BNNTs) upon femtosecond optical excitation using ultrafast electron diffraction in a transmission electron microscope. Analysis of the time-resolved (100) and (002) diffraction profiles reveals highly anisotropic lattice dynamics of BNNTs, which can be attributed to the distinct nature of the chemical bonds in the tubular structure. Moreover, the changes in (002) diffraction positions and intensities suggest that the lattice response of BNNTs to the femtosecond laser excitation involves a fast and a slow lattice dynamic process. The fast process with a time constant of about 8 picoseconds can be understood to be a result of electron-phonon coupling, while the slow process with a time constant of about 100 to 300 picoseconds depending on pump laser fluence is tentatively associated with an Auger recombination effect. In addition, we discuss the power-law relationship of a three-photon absorption process in the BNNT nanoscale system.

  8. Free-electron-laser coherent diffraction images of individual drug-carrying liposome particles in solution.

    PubMed

    Huang, Chi-Feng; Liang, Keng S; Hsu, Tsui-Ling; Lee, Tsung-Tse; Chen, Yi-Yun; Yang, Shun-Min; Chen, Hsiang-Hsin; Huang, Shih-Hsin; Chang, Wei-Hau; Lee, Ting-Kuo; Chen, Peilin; Peng, Kuei-En; Chen, Chien-Chun; Shi, Cheng-Zhi; Hu, Yu-Fang; Margaritondo, Giorgio; Ishikawa, Tetsuya; Wong, Chi-Huey; Hwu, Y

    2018-02-08

    Using the excellent performances of a SACLA (RIKEN/HARIMA, Japan) X-ray free electron laser (X-FEL), coherent diffraction imaging (CDI) was used to detect individual liposome particles in water, with or without inserted doxorubicin nanorods. This was possible because of the electron density differences between the carrier, the liposome, and the drug. The result is important since liposome nanocarriers at present dominate drug delivery systems. In spite of the low cross-section of the original ingredients, the diffracted intensity of drug-free liposomes was sufficient for spatial reconstruction yielding quantitative structural information. For particles containing doxorubicin, the structural parameters of the nanorods could be extracted from CDI. Furthermore, the measurement of the electron density of the solution enclosed in each liposome provides direct evidence of the incorporation of ammonium sulphate into the nanorods. Overall, ours is an important test for extending the X-FEL analysis of individual nanoparticles to low cross-sectional systems in solution, and also for its potential use to optimize the manufacturing of drug nanocarriers.

  9. In cellulo serial crystallography of alcohol oxidase crystals inside yeast cells

    DOE PAGES

    Jakobi, Arjen J.; Passon, Daniel M.; Knoops, Kevin; ...

    2016-03-01

    The possibility of using femtosecond pulses from an X-ray free-electron laser to collect diffraction data from protein crystals formed in their native cellular organelle has been explored. X-ray diffraction of submicrometre-sized alcohol oxidase crystals formed in peroxisomes within cells of genetically modified variants of the methylotrophic yeast Hansenula polymorpha is reported and characterized. Furthermore, the observations are supported by synchrotron radiation-based powder diffraction data and electron microscopy. Based on these findings, the concept of in cellulo serial crystallography on protein targets imported into yeast peroxisomes without the need for protein purification as a requirement for subsequent crystallization is outlined.

  10. In cellulo serial crystallography of alcohol oxidase crystals inside yeast cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jakobi, Arjen J.; Passon, Daniel M.; Knoops, Kevin

    The possibility of using femtosecond pulses from an X-ray free-electron laser to collect diffraction data from protein crystals formed in their native cellular organelle has been explored. X-ray diffraction of submicrometre-sized alcohol oxidase crystals formed in peroxisomes within cells of genetically modified variants of the methylotrophic yeast Hansenula polymorpha is reported and characterized. Furthermore, the observations are supported by synchrotron radiation-based powder diffraction data and electron microscopy. Based on these findings, the concept of in cellulo serial crystallography on protein targets imported into yeast peroxisomes without the need for protein purification as a requirement for subsequent crystallization is outlined.

  11. In cellulo serial crystallography of alcohol oxidase crystals inside yeast cells

    PubMed Central

    Jakobi, Arjen J.; Passon, Daniel M.; Knoops, Kèvin; Stellato, Francesco; Liang, Mengning; White, Thomas A.; Seine, Thomas; Messerschmidt, Marc; Chapman, Henry N.; Wilmanns, Matthias

    2016-01-01

    The possibility of using femtosecond pulses from an X-ray free-electron laser to collect diffraction data from protein crystals formed in their native cellular organelle has been explored. X-ray diffraction of submicrometre-sized alcohol oxidase crystals formed in peroxisomes within cells of genetically modified variants of the methylotrophic yeast Hansenula polymorpha is reported and characterized. The observations are supported by synchrotron radiation-based powder diffraction data and electron microscopy. Based on these findings, the concept of in cellulo serial crystallography on protein targets imported into yeast peroxisomes without the need for protein purification as a requirement for subsequent crystallization is outlined. PMID:27006771

  12. Diffraction-controlled backscattering threshold and application to Raman gap

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rose, Harvey A.; Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544; Mounaix, Philippe

    2011-04-15

    In most classic analytical models of linear stimulated scatter, light diffraction is omitted, a priori. However, modern laser optic typically includes a variant of the random phase plate [Y. Kato et al., Phys. Rev. Lett. 53, 1057 (1984)], resulting in diffraction limited laser intensity fluctuations - or localized speckles - which may result in explosive reflectivity growth as the average laser intensity approaches a critical value [H. A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883 (1994)]. Among the differences between stimulated Raman scatter (SRS) and stimulated Brillouin scatter is that the SRS scattered light diffracts more stronglymore » than the laser light with increase of electron density. This weakens the tendency of the SRS light to closely follow the most amplified paths, diminishing gain. Let G{sub 0} be the one-dimensional power gain exponent of the stimulated scatter. In this paper we show that differential diffraction gives rise to an increase of G{sub 0} at the SRS physical threshold with increase of electron density up to a drastic disruption of SRS as electron density approaches one fourth of its critical value from below. For three wave interaction lengths not small compared to a speckle length, this is a physically robust Raman gap mechanism.« less

  13. Nanoscale monoclinic domains in epitaxial SrRuO{sub 3} thin films deposited by pulsed laser deposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ghica, C., E-mail: cghica@infim.ro; Negrea, R. F.; Nistor, L. C.

    2014-07-14

    In this paper, we analyze the structural distortions observed by transmission electron microscopy in thin epitaxial SrRuO{sub 3} layers used as bottom electrodes in multiferroic coatings onto SrTiO{sub 3} substrates for future multiferroic devices. Regardless of the nature and architecture of the multilayer oxides deposited on the top of the SrRuO{sub 3} thin films, selected area electron diffraction patterns systematically revealed the presence of faint diffraction spots appearing in forbidden positions for the SrRuO{sub 3} orthorhombic structure. High-resolution transmission electron microscopy (HRTEM) combined with Geometric Phase Analysis (GPA) evidenced the origin of these forbidden diffraction spots in the presence ofmore » structurally disordered nanometric domains in the SrRuO{sub 3} bottom layers, resulting from a strain-driven phase transformation. The local high compressive strain (−4% ÷ −5%) measured by GPA in the HRTEM images induces a local orthorhombic to monoclinic phase transition by a cooperative rotation of the RuO{sub 6} octahedra. A further confirmation of the origin of the forbidden diffraction spots comes from the simulated diffraction patterns obtained from a monoclinic disordered SrRuO{sub 3} structure.« less

  14. Facing the phase problem in Coherent Diffractive Imaging via Memetic Algorithms.

    PubMed

    Colombo, Alessandro; Galli, Davide Emilio; De Caro, Liberato; Scattarella, Francesco; Carlino, Elvio

    2017-02-09

    Coherent Diffractive Imaging is a lensless technique that allows imaging of matter at a spatial resolution not limited by lens aberrations. This technique exploits the measured diffraction pattern of a coherent beam scattered by periodic and non-periodic objects to retrieve spatial information. The diffracted intensity, for weak-scattering objects, is proportional to the modulus of the Fourier Transform of the object scattering function. Any phase information, needed to retrieve its scattering function, has to be retrieved by means of suitable algorithms. Here we present a new approach, based on a memetic algorithm, i.e. a hybrid genetic algorithm, to face the phase problem, which exploits the synergy of deterministic and stochastic optimization methods. The new approach has been tested on simulated data and applied to the phasing of transmission electron microscopy coherent electron diffraction data of a SrTiO 3 sample. We have been able to quantitatively retrieve the projected atomic potential, and also image the oxygen columns, which are not directly visible in the relevant high-resolution transmission electron microscopy images. Our approach proves to be a new powerful tool for the study of matter at atomic resolution and opens new perspectives in those applications in which effective phase retrieval is necessary.

  15. Role of Emission Character in Auger Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Idzerda, Y. U.

    A review of the interpretation of the angle-dependent Auger intensity pattern by both Auger electron diffraction (AED), which is concerned with identifying the nearby atomic structure, and angle-resolved Auger electron spectroscopy (ARAES), which is concerned with identifying the character of the emitted electron source function, is presented. The importance of the emission character of the Auger electron (in terms of its angular momentum, l, and its magnetic quantum number, m) in understanding the generation of the AED and ARAES patterns is described. Understanding of how the various direct and secondary mechanisms for the Auger electron generation can affect the populations of these states can also be used to help identify the multiplet structure within the Auger lineshape as well as elucidate the core hole generation process.

  16. Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Godec, Matjaz, E-mail: matjaz.godec@imt.si; Batic, Barbara Setina; Mandrino, Djordje

    2010-04-15

    A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M{sub 6}C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V{sub 6}C{sub 5}, while the tungsten-rich carbidesmore » were M{sub 6}C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.« less

  17. Structural dynamics of surfaces by ultrafast electron crystallography: experimental and multiple scattering theory.

    PubMed

    Schäfer, Sascha; Liang, Wenxi; Zewail, Ahmed H

    2011-12-07

    Recent studies in ultrafast electron crystallography (UEC) using a reflection diffraction geometry have enabled the investigation of a wide range of phenomena on the femtosecond and picosecond time scales. In all these studies, the analysis of the diffraction patterns and their temporal change after excitation was performed within the kinematical scattering theory. In this contribution, we address the question, to what extent dynamical scattering effects have to be included in order to obtain quantitative information about structural dynamics. We discuss different scattering regimes and provide diffraction maps that describe all essential features of scatterings and observables. The effects are quantified by dynamical scattering simulations and examined by direct comparison to the results of ultrafast electron diffraction experiments on an in situ prepared Ni(100) surface, for which structural dynamics can be well described by a two-temperature model. We also report calculations for graphite surfaces. The theoretical framework provided here allows for further UEC studies of surfaces especially at larger penetration depths and for those of heavy-atom materials. © 2011 American Institute of Physics

  18. Multiobjective optimizations of a novel cryocooled dc gun based ultrafast electron diffraction beam line

    NASA Astrophysics Data System (ADS)

    Gulliford, Colwyn; Bartnik, Adam; Bazarov, Ivan

    2016-09-01

    We present the results of multiobjective genetic algorithm optimizations of a single-shot ultrafast electron diffraction beam line utilizing a 225 kV dc gun with a novel cryocooled photocathode system and buncher cavity. Optimizations of the transverse projected emittance as a function of bunch charge are presented and discussed in terms of the scaling laws derived in the charge saturation limit. Additionally, optimization of the transverse coherence length as a function of final rms bunch length at the sample location have been performed for three different sample radii: 50, 100, and 200 μ m , for two final bunch charges: 1 05 electrons (16 fC) and 1 06 electrons (160 fC). Example optimal solutions are analyzed, and the effects of disordered induced heating estimated. In particular, a relative coherence length of Lc ,x/σx=0.27 nm /μ m was obtained for a final bunch charge of 1 05 electrons and final bunch length of σt≈100 fs . For a final charge of 1 06 electrons the cryogun produces Lc ,x/σx≈0.1 nm /μ m for σt≈100 - 200 fs and σx≥50 μ m . These results demonstrate the viability of using genetic algorithms in the design and operation of ultrafast electron diffraction beam lines.

  19. Quantum games with a multi-slit electron diffraction set-up

    NASA Astrophysics Data System (ADS)

    Iqbal, A.

    2003-05-01

    A set-up is proposed to play a quantum version of the famous bimatrix game of Prisoners' Dilemma. Multi-slit electron diffraction with each player's pure strategy consisting of opening one of the two slits at his/her disposal are essential features of the set-up. Instead of entanglement the association of waves with travelling material objects is suggested as another resource to play quantum games.

  20. Measurement and Interpretation of Diffuse Scattering in X-Ray Diffraction for Macromolecular Crystallography

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wall, Michael E.

    X-ray diffraction from macromolecular crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering reflects the mean electron density in the unit cells of the crystal. The diffuse scattering arises from correlations in the variations of electron density that may occur from one unit cell to another, and therefore contains information about collective motions in proteins.

  1. X-ray laser–induced electron dynamics observed by femtosecond diffraction from nanocrystals of Buckminsterfullerene

    PubMed Central

    Abbey, Brian; Dilanian, Ruben A.; Darmanin, Connie; Ryan, Rebecca A.; Putkunz, Corey T.; Martin, Andrew V.; Wood, David; Streltsov, Victor; Jones, Michael W. M.; Gaffney, Naylyn; Hofmann, Felix; Williams, Garth J.; Boutet, Sébastien; Messerschmidt, Marc; Seibert, M. Marvin; Williams, Sophie; Curwood, Evan; Balaur, Eugeniu; Peele, Andrew G.; Nugent, Keith A.; Quiney, Harry M.

    2016-01-01

    X-ray free-electron lasers (XFELs) deliver x-ray pulses with a coherent flux that is approximately eight orders of magnitude greater than that available from a modern third-generation synchrotron source. The power density of an XFEL pulse may be so high that it can modify the electronic properties of a sample on a femtosecond time scale. Exploration of the interaction of intense coherent x-ray pulses and matter is both of intrinsic scientific interest and of critical importance to the interpretation of experiments that probe the structures of materials using high-brightness femtosecond XFEL pulses. We report observations of the diffraction of extremely intense 32-fs nanofocused x-ray pulses by a powder sample of crystalline C60. We find that the diffraction pattern at the highest available incident power significantly differs from the one obtained using either third-generation synchrotron sources or XFEL sources operating at low output power and does not correspond to the diffraction pattern expected from any known phase of crystalline C60. We interpret these data as evidence of a long-range, coherent dynamic electronic distortion that is driven by the interaction of the periodic array of C60 molecular targets with intense x-ray pulses of femtosecond duration. PMID:27626076

  2. A pseudo-tetragonal tungsten bronze superstructure: a combined solution of the crystal structure of K6.4(Nb,Ta)(36.3)O94 with advanced transmission electron microscopy and neutron diffraction.

    PubMed

    Paria Sena, Robert; Babaryk, Artem A; Khainakov, Sergiy; Garcia-Granda, Santiago; Slobodyanik, Nikolay S; Van Tendeloo, Gustaaf; Abakumov, Artem M; Hadermann, Joke

    2016-01-21

    The crystal structure of the K6.4Nb28.2Ta8.1O94 pseudo-tetragonal tungsten bronze-type oxide was determined using a combination of X-ray powder diffraction, neutron diffraction and transmission electron microscopy techniques, including electron diffraction, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), annular bright field STEM (ABF-STEM) and energy-dispersive X-ray compositional mapping (STEM-EDX). The compound crystallizes in the space group Pbam with unit cell parameters a = 37.468(9) Å, b = 12.493(3) Å, c = 3.95333(15) Å. The structure consists of corner sharing (Nb,Ta)O6 octahedra forming trigonal, tetragonal and pentagonal tunnels. All tetragonal tunnels are occupied by K(+) ions, while 1/3 of the pentagonal tunnels are preferentially occupied by Nb(5+)/Ta(5+) and 2/3 are occupied by K(+) in a regular pattern. A fractional substitution of K(+) in the pentagonal tunnels by Nb(5+)/Ta(5+) is suggested by the analysis of the HAADF-STEM images. In contrast to similar structures, such as K2Nb8O21, also parts of the trigonal tunnels are fractionally occupied by K(+) cations.

  3. Structural phase transitions and time-resolved dynamics of solid-supported interfacial methanol observed by reflection electron diffraction

    NASA Astrophysics Data System (ADS)

    Yang, Ding-Shyue; He, Xing; Wu, Chengyi

    Due to their large scattering cross sections with matter, electrons are suitable for contactless probing of solid-supported surface assemblies, especially in a reflection geometry. Direct visualization of assembly structures through electron diffraction further enables studies of ultrafast structural dynamics through the pump-probe scheme as well as discoveries of hidden phase changes in equilibrium that have been obscure in spectroscopic measurements. In this presentation, we report our first observation of unique two-stage transformations of interfacial methanol on smooth hydrophobic surfaces. The finding may reconcile the inconsistent previous reports of the crystallization temperature using various indirect methods. Dynamically, energy transfer across a solid-molecule interface following photoexcitation of the substrate is found to be highly dependent on the structure of interfacial methanol. If it is only 2-dimensionally ordered, as the film thickness increases, a prolonged time in the decrease of diffraction intensity is seen, signifying an inefficient vibrational coupling in the surface normal direction. Implications of the dynamics results and an outlook of interfacial studies using time-resolved and averaged electron diffraction will be discussed. We gratefully acknowledge the support from the R. A. Welch Foundation (Grant No. E-1860), the Donors of the American Chemical Society Petroleum Research Fund (ACS-PRF), and the University of Houston.

  4. Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

    DOE PAGES

    Pekin, Thomas C.; Gammer, Christoph; Ciston, Jim; ...

    2017-01-28

    Scanning nanobeam electron diffraction strain mapping is a technique by which the positions of diffracted disks sampled at the nanoscale over a crystalline sample can be used to reconstruct a strain map over a large area. However, it is important that the disk positions are measured accurately, as their positions relative to a reference are directly used to calculate strain. Here in this study, we compare several correlation methods using both simulated and experimental data in order to directly probe susceptibility to measurement error due to non-uniform diffracted disk illumination structure. We found that prefiltering the diffraction patterns with amore » Sobel filter before performing cross correlation or performing a square-root magnitude weighted phase correlation returned the best results when inner disk structure was present. Lastly, we have tested these methods both on simulated datasets, and experimental data from unstrained silicon as well as a twin grain boundary in 304 stainless steel.« less

  5. Direct single-shot phase retrieval from the diffraction pattern of separated objects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leshem, Ben; Xu, Rui; Dallal, Yehonatan

    The non-crystallographic phase problem arises in numerous scientific and technological fields. An important application is coherent diffractive imaging. Recent advances in X-ray free-electron lasers allow capturing of the diffraction pattern from a single nanoparticle before it disintegrates, in so-called ‘diffraction before destruction’ experiments. Presently, the phase is reconstructed by iterative algorithms, imposing a non-convex computational challenge, or by Fourier holography, requiring a well-characterized reference field. Here we present a convex scheme for single-shot phase retrieval for two (or more) sufficiently separated objects, demonstrated in two dimensions. In our approach, the objects serve as unknown references to one another, reducing themore » phase problem to a solvable set of linear equations. We establish our method numerically and experimentally in the optical domain and demonstrate a proof-of-principle single-shot coherent diffractive imaging using X-ray free-electron lasers pulses. Lastly, our scheme alleviates several limitations of current methods, offering a new pathway towards direct reconstruction of complex objects.« less

  6. Direct single-shot phase retrieval from the diffraction pattern of separated objects

    DOE PAGES

    Leshem, Ben; Xu, Rui; Dallal, Yehonatan; ...

    2016-02-22

    The non-crystallographic phase problem arises in numerous scientific and technological fields. An important application is coherent diffractive imaging. Recent advances in X-ray free-electron lasers allow capturing of the diffraction pattern from a single nanoparticle before it disintegrates, in so-called ‘diffraction before destruction’ experiments. Presently, the phase is reconstructed by iterative algorithms, imposing a non-convex computational challenge, or by Fourier holography, requiring a well-characterized reference field. Here we present a convex scheme for single-shot phase retrieval for two (or more) sufficiently separated objects, demonstrated in two dimensions. In our approach, the objects serve as unknown references to one another, reducing themore » phase problem to a solvable set of linear equations. We establish our method numerically and experimentally in the optical domain and demonstrate a proof-of-principle single-shot coherent diffractive imaging using X-ray free-electron lasers pulses. Lastly, our scheme alleviates several limitations of current methods, offering a new pathway towards direct reconstruction of complex objects.« less

  7. Three-dimensional reconstruction for coherent diffraction patterns obtained by XFEL.

    PubMed

    Nakano, Miki; Miyashita, Osamu; Jonic, Slavica; Song, Changyong; Nam, Daewoong; Joti, Yasumasa; Tama, Florence

    2017-07-01

    The three-dimensional (3D) structural analysis of single particles using an X-ray free-electron laser (XFEL) is a new structural biology technique that enables observations of molecules that are difficult to crystallize, such as flexible biomolecular complexes and living tissue in the state close to physiological conditions. In order to restore the 3D structure from the diffraction patterns obtained by the XFEL, computational algorithms are necessary as the orientation of the incident beam with respect to the sample needs to be estimated. A program package for XFEL single-particle analysis based on the Xmipp software package, that is commonly used for image processing in 3D cryo-electron microscopy, has been developed. The reconstruction program has been tested using diffraction patterns of an aerosol nanoparticle obtained by tomographic coherent X-ray diffraction microscopy.

  8. Three dimensional X-ray Diffraction Contrast Tomography Reconstruction of Polycrystalline Strontium Titanate during Sintering and Electron Backscatter Diffraction Validation

    NASA Astrophysics Data System (ADS)

    Syha, M.; Rheinheimer, W.; Loedermann, B.; Graff, A.; Trenkle, A.; Baeurer, M.; Weygand, D.; Ludwig, W.; Gumbsch, P.

    The microstructural evolution of polycrystalline strontium titanate was investigated in three dimensions (3D) using X-ray diffraction contrast tomography (DCT) before and after ex-situ annealing at 1600°C. Post-annealing, the specimen was additionally subjected to phase contrast tomography (PCT) in order to finely resolve the porosities. The resulting microstructure reconstructions were studied with special emphasis on morphology and interface orientation during microstructure evolution. Subsequently, cross-sections of the specimen were studied using electron backscatter diffraction (EBSD). Corresponding cross-sections through the 3D reconstruction were identified and the quality of the reconstruction is validated with special emphasis on the spatial resolution at the grain boundaries, the size and location of pores contained in the material and the accuracy of the orientation determination.

  9. Three-dimensional nanostructure determination from a large diffraction data set recorded using scanning electron nanodiffraction.

    PubMed

    Meng, Yifei; Zuo, Jian-Min

    2016-09-01

    A diffraction-based technique is developed for the determination of three-dimensional nanostructures. The technique employs high-resolution and low-dose scanning electron nanodiffraction (SEND) to acquire three-dimensional diffraction patterns, with the help of a special sample holder for large-angle rotation. Grains are identified in three-dimensional space based on crystal orientation and on reconstructed dark-field images from the recorded diffraction patterns. Application to a nanocrystalline TiN thin film shows that the three-dimensional morphology of columnar TiN grains of tens of nanometres in diameter can be reconstructed using an algebraic iterative algorithm under specified prior conditions, together with their crystallographic orientations. The principles can be extended to multiphase nanocrystalline materials as well. Thus, the tomographic SEND technique provides an effective and adaptive way of determining three-dimensional nanostructures.

  10. Structure determination of Ba5AlF13 by coupling electron, synchrotron and neutron powder diffraction, solid-state NMR and ab initio calculations.

    PubMed

    Martineau, Charlotte; Allix, Mathieu; Suchomel, Matthew R; Porcher, Florence; Vivet, François; Legein, Christophe; Body, Monique; Massiot, Dominique; Taulelle, Francis; Fayon, Franck

    2016-10-04

    The room temperature structure of Ba 5 AlF 13 has been investigated by coupling electron, synchrotron and neutron powder diffraction, solid-state high-resolution NMR ( 19 F and 27 Al) and first principles calculations. An initial structural model has been obtained from electron and synchrotron powder diffraction data, and its main features have been confirmed by one- and two-dimensional NMR measurements. However, DFT GIPAW calculations of the 19 F isotropic shieldings revealed an inaccurate location of one fluorine site (F3, site 8a), which exhibited unusual long F-Ba distances. The atomic arrangement was reinvestigated using neutron powder diffraction data. Subsequent Fourier maps showed that this fluorine atom occupies a crystallographic site of lower symmetry (32e) with partial occupancy (25%). GIPAW computations of the NMR parameters validate the refined structural model, ruling out the presence of local static disorder and indicating that the partial occupancy of this F site reflects a local motional process. Visualisation of the dynamic process was then obtained from the Rietveld refinement of neutron diffraction data using an anharmonic description of the displacement parameters to account for the thermal motion of the mobile fluorine. The whole ensemble of powder diffraction and NMR data, coupled with first principles calculations, allowed drawing an accurate structural model of Ba 5 AlF 13 , including site-specific dynamical disorder in the fluorine sub-network.

  11. The structure of denisovite, a fibrous nanocrystalline polytypic disordered ‘very complex’ silicate, studied by a synergistic multi-disciplinary approach employing methods of electron crystallography and X-ray powder diffraction

    PubMed Central

    Schowalter, Marco; Schmidt, Martin U.; Czank, Michael; Depmeier, Wulf; Rosenauer, Andreas

    2017-01-01

    Denisovite is a rare mineral occurring as aggregates of fibres typically 200–500 nm diameter. It was confirmed as a new mineral in 1984, but important facts about its chemical formula, lattice parameters, symmetry and structure have remained incompletely known since then. Recently obtained results from studies using microprobe analysis, X-ray powder diffraction (XRPD), electron crystallography, modelling and Rietveld refinement will be reported. The electron crystallography methods include transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-angle annular dark-field imaging (HAADF), high-resolution transmission electron microscopy (HRTEM), precession electron diffraction (PED) and electron diffraction tomography (EDT). A structural model of denisovite was developed from HAADF images and later completed on the basis of quasi-kinematic EDT data by ab initio structure solution using direct methods and least-squares refinement. The model was confirmed by Rietveld refinement. The lattice parameters are a = 31.024 (1), b = 19.554 (1) and c = 7.1441 (5) Å, β = 95.99 (3)°, V = 4310.1 (5) Å3 and space group P12/a1. The structure consists of three topologically distinct dreier silicate chains, viz. two xonotlite-like dreier double chains, [Si6O17]10−, and a tubular loop-branched dreier triple chain, [Si12O30]12−. The silicate chains occur between three walls of edge-sharing (Ca,Na) octahedra. The chains of silicate tetrahedra and the octahedra walls extend parallel to the z axis and form a layer parallel to (100). Water molecules and K+ cations are located at the centre of the tubular silicate chain. The latter also occupy positions close to the centres of eight-membered rings in the silicate chains. The silicate chains are geometrically constrained by neighbouring octahedra walls and present an ambiguity with respect to their z position along these walls, with displacements between neighbouring layers being either Δz = c/4 or −c/4. Such behaviour is typical for polytypic sequences and leads to disorder along [100]. In fact, the diffraction pattern does not show any sharp reflections with l odd, but continuous diffuse streaks parallel to a* instead. Only reflections with l even are sharp. The diffuse scattering is caused by (100) nano­lamellae separated by stacking faults and twin boundaries. The structure can be described according to the order–disorder (OD) theory as a stacking of layers parallel to (100). PMID:28512570

  12. Realizing Ultrafast Electron Pulse Self-Compression by Femtosecond Pulse Shaping Technique.

    PubMed

    Qi, Yingpeng; Pei, Minjie; Qi, Dalong; Yang, Yan; Jia, Tianqing; Zhang, Shian; Sun, Zhenrong

    2015-10-01

    Uncorrelated position and velocity distribution of the electron bunch at the photocathode from the residual energy greatly limit the transverse coherent length and the recompression ability. Here we first propose a femtosecond pulse-shaping method to realize the electron pulse self-compression in ultrafast electron diffraction system based on a point-to-point space-charge model. The positively chirped femtosecond laser pulse can correspondingly create the positively chirped electron bunch at the photocathode (such as metal-insulator heterojunction), and such a shaped electron pulse can realize the self-compression in the subsequent propagation process. The greatest advantage for our proposed scheme is that no additional components are introduced into the ultrafast electron diffraction system, which therefore does not affect the electron bunch shape. More importantly, this scheme can break the limitation that the electron pulse via postphotocathode static compression schemes is not shorter than the excitation laser pulse due to the uncorrelated position and velocity distribution of the initial electron bunch.

  13. Dynamics of reflection high-energy electron diffraction intensity oscillations during molecular beam epitaxial growth of GaAs on (111)B GaAs substrates

    NASA Astrophysics Data System (ADS)

    Yen, M. Y.; Haas, T. W.

    1990-06-01

    We have observed intensity oscillations in reflection high-energy electron diffraction during molecular beam epitaxial growth of GaAs on (111)B GaAs substrates. These oscillations only exist over a narrow range of growth conditions and their behavior is strongly dependent on the migration kinetics of group III and the molecular dissociative reaction of group V elements.

  14. Stress Corrosion Cracking Facet Crystallography of Ti-8Al-1Mo-1V (Preprint)

    DTIC Science & Technology

    2011-05-01

    fractography and electron backscatter diffraction. The results indicate that most facets are formed nearly perpendicular to the loading direction on...of Ti-8Al- 1Mo-1V have been characterized using quantitative fractography and electron backscatter diffraction. The results indicate that most facets...EBSD and quantitative tilt fractography [27;29] allow for determination of the crystallographic fracture plane to an accuracy between 1o [29] and

  15. Nanostructure size determination in p-type porous silicon by the use of transmission electron diffraction image processing

    NASA Astrophysics Data System (ADS)

    Ramirez-Porras, A.

    2005-06-01

    The structure of p-type porous silicon (PS) has been investigated by the use of transmission electron diffraction (TED) microscopy and image processing. The results suggest the presence of well oriented crystalline phases and polycrystalline phases characterized by random orientation. These phases are believed to be formed by spheres with a mean diameter of 4.3 nm and a standard deviation of 1.3 nm.

  16. Crystallographic data processing for free-electron laser sources

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    White, Thomas A., E-mail: taw@physics.org; Barty, Anton; Stellato, Francesco

    2013-07-01

    A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A processing pipeline for diffraction data acquired using the ‘serial crystallography’ methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A detailed analysis of the nature and impact of indexing ambiguities is presented. Simulations of the Monte Carlo integration scheme, which accounts for the partially recorded nature of the diffraction intensities, are presented and show thatmore » the integration of partial reflections could be made to converge more quickly if the bandwidth of the X-rays were to be increased by a small amount or if a slight convergence angle were introduced into the incident beam.« less

  17. A method to correct coordinate distortion in EBSD maps

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Y.B., E-mail: yubz@dtu.dk; Elbrønd, A.; Lin, F.X.

    2014-10-15

    Drift during electron backscatter diffraction mapping leads to coordinate distortions in resulting orientation maps, which affects, in some cases significantly, the accuracy of analysis. A method, thin plate spline, is introduced and tested to correct such coordinate distortions in the maps after the electron backscatter diffraction measurements. The accuracy of the correction as well as theoretical and practical aspects of using the thin plate spline method is discussed in detail. By comparing with other correction methods, it is shown that the thin plate spline method is most efficient to correct different local distortions in the electron backscatter diffraction maps. -more » Highlights: • A new method is suggested to correct nonlinear spatial distortion in EBSD maps. • The method corrects EBSD maps more precisely than presently available methods. • Errors less than 1–2 pixels are typically obtained. • Direct quantitative analysis of dynamic data are available after this correction.« less

  18. Reflection high energy electron diffraction observation of surface mass transport at the two- to three-dimensional growth transition of InAs on GaAs(001)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Patella, F.; Arciprete, F.; Fanfoni, M.

    2005-12-19

    We have followed by reflection high-energy electron diffraction the nucleation of InAs quantum dots on GaAs(001), grown by molecular-beam epitaxy with growth interruptions. Surface mass transport gives rise, at the critical InAs thickness, to a huge nucleation of three-dimensional islands within 0.2 monolayers (ML). Such surface mass diffusion has been evidenced by observing the transition of the reflection high-energy electron diffraction pattern from two- to three-dimensional during the growth interruption after the deposition of 1.59 ML of InAs. It is suggested that the process is driven by the As{sub 2} adsorption-desorption process and by the lowering of the In bindingmore » energy due to compressive strain. The last condition is met first in the region surrounding dots at step edges where nucleation predominantly occurs.« less

  19. Trans-pent-2-ene. Electron diffraction, vibrational analysis and molecular mechanics

    NASA Astrophysics Data System (ADS)

    Ter Brake, J. H. M.; Mijlhoff, F. C.

    1981-12-01

    The molecular structure of trans-pent-2-ene has been investigated, using electron diffraction, vibrational analysis and molecular mechanics. It is possible to Fit a model, describing trans-pent-2-ene as a semi-rigid molecule with one conformer only, to the electron diffraction data. However, molecular mechanics shows that trans-pent-2-ene is not a semi-rigid molecule. The large-amplitude motion is described, using all pseudo-conformers at 10° intervals around the circle of rotation. The resulting rα structure is: r[-C-C] = 148.4(1), r[-CC-] = 133.4(2), r[-C-C-] = 157.6(5), r[C-H] = 108.2(1)pm; ∠[-C-CC-] = 125.4(3), ∠[C-C-C-] = 115.6(6), ∠[-C-C-H] = 12.7(6), ∠[-CC-H] = 129(2)°. Standard deviations given in parentheses refer to the last significant digit.

  20. Automated grain mapping using wide angle convergent beam electron diffraction in transmission electron microscope for nanomaterials.

    PubMed

    Kumar, Vineet

    2011-12-01

    The grain size statistics, commonly derived from the grain map of a material sample, are important microstructure characteristics that greatly influence its properties. The grain map for nanomaterials is usually obtained manually by visual inspection of the transmission electron microscope (TEM) micrographs because automated methods do not perform satisfactorily. While the visual inspection method provides reliable results, it is a labor intensive process and is often prone to human errors. In this article, an automated grain mapping method is developed using TEM diffraction patterns. The presented method uses wide angle convergent beam diffraction in the TEM. The automated technique was applied on a platinum thin film sample to obtain the grain map and subsequently derive grain size statistics from it. The grain size statistics obtained with the automated method were found in good agreement with the visual inspection method.

  1. Experimental determination of spin-dependent electron density by joint refinement of X-ray and polarized neutron diffraction data.

    PubMed

    Deutsch, Maxime; Claiser, Nicolas; Pillet, Sébastien; Chumakov, Yurii; Becker, Pierre; Gillet, Jean Michel; Gillon, Béatrice; Lecomte, Claude; Souhassou, Mohamed

    2012-11-01

    New crystallographic tools were developed to access a more precise description of the spin-dependent electron density of magnetic crystals. The method combines experimental information coming from high-resolution X-ray diffraction (XRD) and polarized neutron diffraction (PND) in a unified model. A new algorithm that allows for a simultaneous refinement of the charge- and spin-density parameters against XRD and PND data is described. The resulting software MOLLYNX is based on the well known Hansen-Coppens multipolar model, and makes it possible to differentiate the electron spins. This algorithm is validated and demonstrated with a molecular crystal formed by a bimetallic chain, MnCu(pba)(H(2)O)(3)·2H(2)O, for which XRD and PND data are available. The joint refinement provides a more detailed description of the spin density than the refinement from PND data alone.

  2. Electron transfer in a virtual quantum state of LiBH4 induced by strong optical fields and mapped by femtosecond x-ray diffraction.

    PubMed

    Stingl, J; Zamponi, F; Freyer, B; Woerner, M; Elsaesser, T; Borgschulte, A

    2012-10-05

    Transient polarizations connected with a spatial redistribution of electronic charge in a mixed quantum state are induced by optical fields of high amplitude. We determine for the first time the related transient electron density maps, applying femtosecond x-ray powder diffraction as a structure probe. The prototype ionic material LiBH4 driven nonresonantly by an intense sub-40 fs optical pulse displays a large-amplitude fully reversible electron transfer from the BH4(-) anion to the Li+ cation during excitation. Our results establish this mechanism as the source of the strong optical polarization which agrees quantitatively with theoretical estimates.

  3. Diffractive optical elements on non-flat substrates using electron beam lithography

    NASA Technical Reports Server (NTRS)

    Maker, Paul D. (Inventor); Muller, Richard E. (Inventor); Wilson, Daniel W. (Inventor)

    2002-01-01

    The present disclosure describes a technique for creating diffraction gratings on curved surfaces with electron beam lithography. The curved surface can act as an optical element to produce flat and aberration-free images in imaging spectrometers. In addition, the fabrication technique can modify the power structure of the grating orders so that there is more energy in the first order than for a typical grating. The inventors noticed that by using electron-beam lithography techniques, a variety of convex gratings that are well-suited to the requirements of imaging spectrometers can be manufactured.

  4. Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dzhumagulova, K. N., E-mail: dzhumagulova.karlygash@gmail.com; Shalenov, E. O.; Ramazanov, T. S.

    2015-08-15

    Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

  5. Convergent beam electron-diffraction investigation of lattice mismatch and static disorder in GaAs/GaAs1-xNx intercalated GaAs/GaAs1-xNx:H heterostructures

    NASA Astrophysics Data System (ADS)

    Frabboni, S.; Grillo, V.; Gazzadi, G. C.; Balboni, R.; Trotta, R.; Polimeni, A.; Capizzi, M.; Martelli, F.; Rubini, S.; Guzzinati, G.; Glas, F.

    2012-09-01

    Hydrogen incorporation in diluted nitride semiconductors dramatically modifies the electronic and structural properties of the crystal through the creation of nitrogen-hydrogen complexes. We report a convergent beam electron-diffraction characterization of diluted nitride semiconductor-heterostructures patterned at a sub-micron scale and selectively exposed to hydrogen. We present a method to determine separately perpendicular mismatch and static disorder in pristine and hydrogenated heterostructures. The roles of chemical composition and strain on static disorder have been separately assessed.

  6. Electron irradiation induced effects on the physico-chemical properties of L-Arginine Maleate Dihydrate (LAMD) single crystals

    NASA Astrophysics Data System (ADS)

    Thomas, Prince; Dhole, S. D.; Joseph, Ginson P.

    2018-07-01

    Single crystals of L-Arginine Maleate Dihydrate (LAMD) have been synthesized by slow solvent evaporation technique and irradiated with 6 MeV electrons at fluences of 0.5 ×1015e /cm2 , 1.0 ×1015e /cm2 and 1.5 ×1015e /cm2 . The Powder X-ray Diffraction (PXRD) studies showed that the intensity of the diffraction peaks of the Electron Beam (EB) irradiated crystals decreases with irradiation fluence. The electron irradiation induced effects on the optical parameters such as cut-off wavelength, band gap, Urbach energy and refractive index have been studied and the results are tabulated. The electronic parameters such as valence electron plasma energy, ℏωp , Penn gap, Ep , Fermi energy, EF and Electronic polarizability, α for pure and irradiated LAMD crystals are calculated. The electrical and thermal properties of the pure and irradiated LAMD crystals are also investigated.

  7. Compression of high-density 0.16 pC electron bunches through high field gradients for ultrafast single shot electron diffraction: The Compact RF Gun

    PubMed Central

    Daoud, Hazem; Floettmann, Klaus; Dwayne Miller, R. J.

    2017-01-01

    We present an RF gun design for single shot ultrafast electron diffraction experiments that can produce sub-100 fs high-charge electron bunches in the 130 keV energy range. Our simulations show that our proposed half-cell RF cavity is capable of producing 137 keV, 27 fs rms (60 fs FWHM), 106 electron bunches with an rms spot size of 276 μm and a transverse coherence length of 2.0 nm. The required operation power is 9.2 kW, significantly lower than conventional rf cavity designs and a key design feature. This electron source further relies on high electric field gradients at the cathode to simultaneously accelerate and compress the electron bunch to open up new space-time resolution domains for atomically resolved dynamics. PMID:28428973

  8. Validation of Passive Sampling Devices for Monitoring of Munitions Constituents in Underwater Environments

    DTIC Science & Technology

    2017-09-01

    information provided from the GED (Peggy Harris, personal communication ), but unprecedented high rainfall (including 20” of rain April 29–30, 2014...Alexandria, VA, by the Energy and Environmental Sustainability Branch (71760) of the Advanced Systems and Applied Sciences Division (71700), Space ...sampling and analyses. These challenges include a high level of effort or difficulty required to (1) measure MC at very low (ng/L) concentrations; (2

  9. Voluntary Release Pilot Program: Effects on Attrition of General Detail Personnel

    DTIC Science & Technology

    1978-07-01

    compared to 45 percent for Great Lakes. Within the control group, the distribution of recruits in quality group B was nearly equivalent at all RTCs. Also...for the control group). Loss group data were related to educational level in the control group onlyi Holders of GED certificates and non -high school...within the control group, represent no greater an attri- tion, disciplinary, or desertion risk than non -DELTAs. No significant differences associated

  10. Learning To Think, Learning To Learn: What the Science of Thinking and Learning Has To Offer Adult Education. NIFL Literacy Leader Fellowship, Program Reports, Volume IV, Number 1.

    ERIC Educational Resources Information Center

    Cromley, Jennifer

    This book, developed for adult educators who teach or tutor reading in General Educational Development (GED) classrooms and for teacher trainers, contains 18 fact sheets on learning and thinking, each about 10 pages long. The following fact sheets are included: (1) Literature Is Not Science; (2) Making Connections; (3) Mental Models; (4) Thinking…

  11. Distance in War: The Experience of MQ-1 and MQ-9 Aircrew

    DTIC Science & Technology

    2015-01-01

    ged, and psychologically impacted by the work they perform. The continuing ethical and moral relativism society uses to place new weapons and methods...outcome of such ignorance results in moral disengagement for the RPA aircrew. Within her article titled, “The End of Military Virtue,” author Laurie...imaginary precipice that we should attempt to turn back from. Based upon centuries of military technological and cultural advancements, we should

  12. Cumberland Valley School District's "High School Diploma Program for Adults." Extension of 1995-96 "353 Grant." Earning a Regular High School Diploma with or without a GED. Final Report, 1997-98.

    ERIC Educational Resources Information Center

    Gruber, Samuel C.

    This document consists of a final report, informational packet, and training manual. These materials are from a 1997-98 extension of a project during which several educational agencies used the Cumberland Valley (Pennsylvania) diploma model to develop their own high school diploma program for implementation. The report itself describes the diploma…

  13. The Impact of the State-Wide and District Dropout Prevention Plans on the Dropout Rates, Graduation Rates, GED Completions, and Truancy Rates of High School Teens in Mississippi

    ERIC Educational Resources Information Center

    Spencer, Amanda Jean Martin

    2011-01-01

    In 2006, as part of the compliance with the No Child Left Behind Act of 2001, Mississippi implemented a state-wide dropout prevention plan. The Mississippi Department of Education through the Office of Dropout Prevention supplied a skeletal format to serve as a guideline for all 152 individual school districts within the state. The school…

  14. Empirical Bayes Estimation of Proportions in Several Groups.

    DTIC Science & Technology

    1981-01-01

    Street NW Washington, DC 20208 Dr. William Graham Testing Directorate 1 Dr. Lorraine D. Eyde MEPCOM/MEPCT-P Personnel R&D Center Ft. Sheridan, IL...D-53 BONN 1, GERMANY Princeton, NJ 08540 1 Dr. Mark D. Reckase Dr. Gary Marco Educational Psychology Dept. Educational Testing Service University of...GED Testing Service, Suite 20 Columbia, SC 29208 One Dupont Cirle, NW Washington, DC 20036 1 PROF. FUMIKO SAMEJIMA DEPT. OF PSYCHOLOGY UNIVERSITY OF

  15. "Our Success Is Our Graduates" Case Study of Year Up: A Career Advancement Model for Low-Income Young Adults. Advancement for Low-Wage Workers Report Series

    ERIC Educational Resources Information Center

    Biswas, Radha Roy

    2005-01-01

    This report describes the "Year Up" program, an innovative technology training program, that prepares and places low-income, urban young adults in entry-level IT jobs while also preparing them for college. The program targets recent high school graduates and GED recipients between the ages of 18 and 24 who are either unemployed or…

  16. Action Research Monographs. Complete Set. Pennsylvania Action Research Network, 1998-99. A Section 353 Project of the Pennsylvania Department of Education, Bureau of Adult Basic and Literacy Education. A Learning from Practice Project.

    ERIC Educational Resources Information Center

    Pennsylvania State Univ., McKeesport.

    This publication consists of the complete set of 23 monographs developed by the Pennsylvania Action Research Network to supplement the 67 monographs produced over the past 3 years. The specific audience are literacy, General Educational Development (GED), and English-as-a Second Language (ESL) practitioners. The titles are: "Use of…

  17. Bunch evolution study in optimization of MeV ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Lu, Xian-Hai; Du, Ying-Chao; Huang, Wen-Hui; Tang, Chuan-Xiang

    2014-12-01

    Megaelectronvolt ultrafast electron diffraction (UED) is a promising detection tool for ultrafast processes. The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled.

  18. Ballistic protons in incoherent exclusive vector meson production as a measure of rare parton fluctuations at an electron-ion collider

    DOE PAGES

    Lappi, T.; Venugopalan, R.; Mantysaari, H.

    2015-02-25

    We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multi-parton Fock states in the nuclear wavefunctions. In particular, the saturation scale that characterizes this multi-parton dynamics is significantly larger in central events relative to minimum bias events. As an application, we examine the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.

  19. Tests of Si(111)-7 × 7 structural models by comparison with transmission electron diffraction patterns

    NASA Astrophysics Data System (ADS)

    McRae, E. G.; Petroff, P. M.

    1984-11-01

    Several structural models of the Si(111)-7 × 7 surface are tested by comparing calculated and observed transmission electron diffraction (TED) patterns. The models comprise "adatom" models where the unit mesh contains 12 adatoms or atom clusters in a locally (2 × 2) arrangement, and "triangle-dimer" models where the unit mesh contains 9 dimers or pairs of dimers bordering a triangular subunit of the unit mesh. The distribution of diffraction intensity among fractional-order spots is calculated kinematically and compared with TED patterns observed by Petroff and Wilson and others. No agreement is found for adatom models. Good but not perfect agreement is found for one triangle-dimer model.

  20. Thin Film Research. Volume 1

    DTIC Science & Technology

    1985-05-30

    Order (FECO) ......... 23 3. X -Ray Diffraction ............................... 26 4. Transmission Electron Microscopy (TEM) ............... 26 5...remained amorphous after bombardment, as evidenced by X - ray diffraction, and showed no other changes. 0 (2) For Sb203, the crystallite size was reduced...main effect on MgF2 was the reduction in crystallite size. The films were too thir. for meaningful x - ray diffraction analysis. Durability and

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