Analysis of internal conversion coefficients
Coursol; Gorozhankin; Yakushev; Briancon; Vylov
2000-03-01
An extensive database has been assembled that contains the three most widely used sets of calculated internal conversion coefficients (ICC): [Hager R.S., Seltzer E.C., 1968. Internal conversion tables. K-, L-, M-shell Conversion coefficients for Z = 30 to Z = 103, Nucl. Data Tables A4, 1-237; Band I.M., Trzhaskovskaya M.B., 1978. Tables of gamma-ray internal conversion coefficients for the K-, L- and M-shells, 10 < or = Z < or = 104, Special Report of Leningrad Nuclear Physics Institute; Rosel F., Fries H.M., Alder K., Pauli H.C., 1978. Internal conversion coefficients for all atomic shells, At. Data Nucl. Data Tables 21, 91-289] and also includes new Dirac Fock calculations [Band I.M. and Trzhaskovskaya M.B., 1993. Internal conversion coefficients for low-energy nuclear transitions, At. Data Nucl. Data Tables 55, 43-61]. This database is linked to a computer program to plot ICCs and their combinations (sums and ratios) as a function of Z and energy, as well as relative deviations of ICC or their combinations for any pair of tabulated data. Examples of these analyses are presented for the K-shell and total ICCs of the gamma-ray standards [Hansen H.H., 1985. Evaluation of K-shell and total internal conversion coefficients for some selected nuclear transitions, Eur. Appl. Res. Rept. Nucl. Sci. Tech. 11.6 (4) 777-816] and for the K-shell and total ICCs of high multipolarity transitions (total, K-, L-, M-shells of E3 and M3 and K-shell of M4). Experimental data sets are also compared with the theoretical values of these specific calculations. PMID:10724406
Ratios of internal conversion coefficients
Raman, S.; Ertugrul, M.; Nestor, C.W. . E-mail: CNestorjr@aol.com; Trzhaskovskaya, M.B.
2006-03-15
We present here a database of available experimental ratios of internal conversion coefficients for different atomic subshells measured with an accuracy of 10% or better for a number of elements in the range 26 {<=} Z {<=} 100. The experimental set involves 414 ratios for pure and 1096 ratios for mixed-multipolarity nuclear transitions in the transition energy range from 2 to 2300 keV. We give relevant theoretical ratios calculated in the framework of the Dirac-Fock method with and without regard for the hole in the atomic subshell after conversion. For comparison, the ratios obtained within the relativistic Hartree-Fock-Slater approximation are also presented. In cases where several ratios were measured for the same transition in a given isotope in which two multipolarities were involved, we present the mixing ratio {delta} {sup 2} obtained by a least squares fit.
Dirac-Fock Internal Conversion Coefficients
NASA Astrophysics Data System (ADS)
Band, I. M.; Trzhaskovskaya, M. B.; Nestor, C. W.; Tikkanen, P. O.; Raman, S.
2002-05-01
Internal conversion coefficients (ICCs) obtained from relativistic self-consistent-field Dirac-Fock (DF) calculations are presented. The exchange terms of DF equations are included exactly, both for the interaction between bound electrons and for the interaction between bound and free electrons. Static and dynamic effects resulting from finite nuclear size are taken into account, the latter using the surface current model. Experimental electron-binding energies are used wherever possible. The hole in the atomic shell from which an electron was emitted is not taken into consideration because there is no compelling experimental evidence to warrant it. ICCs are given here for each Z between Z=10 and Z=126; for K, L1, L2, and L3 atomic shells; for nuclear-transition multipolarities E1… E5, M1… M5; and for nuclear-transition energies from ˜1 keV above the L1 threshold to 2000 keV. Also given are the total ICCs. Accurate (≤5%) experimental ICCs ( K and total) are known for 77 transitions with multipolarities E2, M3, E3, M4, or E5. For these transitions, the theoretical DF values are, on average, about 3% lower than the theoretical relativistic Hartree-Fock-Slater (RHFS) values. The DF values are in better agreement with experimental results than the RHFS values.
Determination of absolute internal conversion coefficients using the SAGE spectrometer
NASA Astrophysics Data System (ADS)
Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.
2016-03-01
A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.
INTERNAL CONVERSION COEFFICIENTS - HOW GOOD ARE THEY NOW?
KIBEDI,T.; BURROWS, T.W.; TRZHASKOVSKAYA, M.B.; NESTOR, JR., C.W.; DAVIDSON, P.M.
2007-04-22
Internal conversion coefficients involving atomic electrons (ICC) and electron-positron pairs (IPC) are often required to determine transition multipolarities and total transition rates. A new internal conversion coefficient data base, BrIcc has been developed which integrates a number of tabulations on ICC and IPC, as well as {Omega}(E0) electronic factors. To decide which theoretical internal conversion coefficient table to use, the accurately determined experimental {alpha}{sub K}, {alpha}{sub L}, {alpha}{sub Total} and {alpha}{sub K}/{alpha}{sub L} values were compared with the new Dirac-Fock calculations using extreme assumptions on the effect of the atomic vacancy. While the overall difference between experiment and theory is less than 1%, our analysis shows preference towards the so called ''Frozen Orbital'' approximation, which takes into account the effect of the atomic vacancy.
Internal Conversion Coefficients for Low-Energy Nuclear Transitions
NASA Astrophysics Data System (ADS)
Band, I. M.; Trzhaskovskaya, M. B.
1993-09-01
Presented here are calculated internal conversion coefficients (ICCs) of gamma rays for 35 observed low-energy nuclear transitions having Eγ ≲ 3 keV. Additionally, the ICCs for 24 high-multipole-order transitions which have been measured extensively are also given. The ICC calculations have been performed using Dirac-Fock electron wave functions, the exchange terms of the Dirac-Fock equations being included wthout any approximations both for the interaction between bound electrons and the interaction between bound and free electrons. Our previous studies have shown that the Dirac-Fock method allows ICC values to be obtained in best agreement with experimental data.
Internal conversion coefficients of high multipole transitions: Experiment and theories
NASA Astrophysics Data System (ADS)
Gerl, J.; Vijay Sai, K.; Sainath, M.; Gowrishankar, R.; Venkataramaniah, K.
2008-09-01
A compilation of the available experimental internal conversion coefficients (ICCs), αT, αK, αL, and ratios K/L and K/LM of high multipole ( L > 2) transitions for a number of elements in the range 21 ⩽ Z ⩽ 94 is presented. Our listing of experimental data includes 194 data sets on 110 E3 transitions, 10 data sets on 6 E4 transitions, 11 data sets on 7 E5 transitions, 38 data sets on 21 M3 transitions, and 132 data sets on 68 M4 transitions. Data with less than 10% experimental uncertainty have been selected for comparison with the theoretical values of Hager and Seltzer [R.S. Hager, E.C. Seltzer, Nucl. Data Tables A 4 (1968) 1], Rosel et al. [F. Rösel, H.M. Fries, K. Alder, H.C. Pauli, At. Data Nucl. Data Tables 21 (1978) 91], and BRICC. The relative percentage deviations (%Δ) have been calculated for each of the above theories and the averages (%Δ¯) are estimated. The Band et al. [I.M. Band, M.B. Trzhaskovskaya, C.W. Nestor Jr., P.O. Tikkanen, S. Raman, At. Data Nucl. Data Tables 81 (2002) 1] tables, using the BRICC interpolation code, are seen to give theoretical ICCs closest to experimental values.
New features of the IC(4) code and comparison of internal conversion coefficient calculations.
Gorozhankin, V M; Coursol, N; Yakushev, E A; Vylov, Ts; Briançon, C
2002-01-01
The IC(4) software developed to compare calculated internal conversion coefficients (ICC) has been enhanced by adding new features through the use of Borland Delphi and TeeChart. Particularly, the 3D-graph option enhances the possibilities of analyzing calculated ICC values. For example, the comparison between the results given by three sets of theoretical ICC tables for any arbitrary pair of calculated ICC can be presented in a much clearer manner. Their differences can be displayed as energy vs. atomic number surfaces. Results from the analyses of K-shell and total ICCs for E2, E3, M2, M3, and M4 multipolarity are discussed. PMID:11839014
NASA Astrophysics Data System (ADS)
Németh, Zsolt
1992-02-01
A large set of accurately measured E3, M3, E4 and M4 internal conversion coefficients (ICCs) has been compared with various theoretical values. ICCs calculated by considering Dirac-Fock wave functions are found in best agreement with the experimental values, although dependence of their discrepancies on transition energy, multipolarity and parity, as well as on nuclear charge and shell, has been revealed. The ICCs of Rösel et al., after the adjustment of Németh and Veres, proved to be the most successful in reproducing the experimental values. The adjusted ICCs of Rösel et al. are recommended and revision of the ICCs and γ-emission probabilities of isomeric transitions in evaluated data compilations such as Nuclear Data Sheets is suggested. Selection from the contradicting K and total ICCs of the 661.66 keV transition of 137Ba is proposed.
Resonance behavior of internal conversion coefficients at low γ-ray energy
NASA Astrophysics Data System (ADS)
Trzhaskovskaya, M. B.; Kibédi, T.; Nikulin, V. K.
2010-02-01
A resonance-like structure of internal conversion coefficients (ICCs) at low γ-ray energy (≲100 keV) is studied. Our calculations revealed new, previously unknown resonance minima in the energy dependence of ICCs for the ns shells at E2-E5 transitions. The resonances are the most defined for ICCs in light and medium elements with Z≲ 50. It is shown that ICCs may have up to four resonances for outer shells while it has been assumed so far that only one resonance exists. Well-pronounced resonances in ICCs at E1 transition were discovered for the ns shells with n⩾2 as well as for the np shells with n⩾3 and the nd shells with n⩾4 of all elements up to superheavy ones. Simple expressions for approximate values of the E1 resonance energy were obtained which are of importance for determination of the resonance energy range where the interpolation of ICCs taken from tables or databases may give significant errors. The occurrence of resonances in ICCs is explained by vanishing conversion matrix elements under changes of sign. The peculiarities of the behavior of the matrix elements and electron wave functions at the resonance energy are considered. Available experimental ICCs for electric transitions with energies near the expected position of resonances satisfactory agree with our calculations.
Comparison of experimental and theoretical high multipole-order internal conversion coefficients
NASA Astrophysics Data System (ADS)
Németh, Zs.; Veres, Á.
1990-01-01
Sixty-four accurately measured (1 σ ⩽ 5%) internal conversion coefficients (ICCs) of high multipole-order (E3, M3, E4, M4) gamma-transitions have been compared with the theoretical values of Rösel et al. and Hager and Seltzer. Individual measurements were carefully examined and modified, if necessary. The discrepancies among the experimental values and the Rösel calculations tend to fall within a narrow band and do not reveal any dependence on atomic number, shell or transition energy. However, discrepancies between the experimental data and the calculations of Hager and Seltzer depend on transition energy, viz., increases up to 10% occur when the transition energy approaches the K binding energy. The calculations of Rösel et al. are preferred, and it is proposed that their third and fourth order ICCs are multiplied by factors of 0.975±0.010 and 0.975±0.005 respectively, to give better agreement with the experimental data. The accuracy of the corrected theoretical values is higher than most of the experimental data. This comparison also implies that the recommended source of ICCs and total transition probabilities needs to be reconsidered by the International Nuclear Structure and Decay Data Network.
Pure E2 transitions: A test for BRICC Internal Conversion Coefficients
NASA Astrophysics Data System (ADS)
Gerl, J.; Sai, K. Vijay; Sainath, M.; Gowrishankar, R.; Venkataramaniah, K.
2009-01-01
The most widely used theoretical internal conversion coefficient (ICC) tables are of Hager and Seltzer (HS), Rosel et al. and BRICC (Band et al. tables using BRICC interpolation code). A rigorous comparison of experimental ICCs with various theoretical tabulations is possible only when a large data on experimental ICCs is available at one place. For this reason, a compilation of all the available experimental ICCs, αT, αK, αL of E2 transitions for a number of elements in the range of 24⩽Z⩽94 is presented. Listing of experimental data includes 595 datasets corresponding to 505 E2 transitions in 165 nuclei across the nuclear chart. Data with less than 10% experimental uncertainty have been selected for comparison with the theoretical values of Hager and Seltzer, Rosel et al. and BRICC. The relative percentage deviation (%Δ) have been calculated for each of the above theories and the average (%Δ¯) are estimated. The Band et al. tables, using the BRICC interpolation code are seen to give theoretical ICCs closest to experimental values.
Nica, N.; Hardy, J. C.; Iacob, V. E.; Balonek, C.; Trzhaskovskaya, M. B.
2008-03-15
Recently we measured the ratio of K-shell internal conversion coefficients, {alpha}{sub K}, for the 127.5-keV E3 transition in {sup 134}Cs and the 661.7-keV M4 transition in {sup 137}Ba. We here report a measurement of the 165.9-keV M1 transition in {sup 139}La, based on which we convert our earlier ratio measurement into individual {alpha}{sub K} values for the transitions in {sup 134}Cs and {sup 137}Ba. These results continue to confirm the Dirac-Fock calculations of internal conversion coefficients that incorporate the atomic K-shell vacancy.
Averaging Internal Consistency Reliability Coefficients
ERIC Educational Resources Information Center
Feldt, Leonard S.; Charter, Richard A.
2006-01-01
Seven approaches to averaging reliability coefficients are presented. Each approach starts with a unique definition of the concept of "average," and no approach is more correct than the others. Six of the approaches are applicable to internal consistency coefficients. The seventh approach is specific to alternate-forms coefficients. Although the…
Lattice effect in solid state internal conversion
Kalman, Peter; Keszthelyi, Tamas
2009-03-15
The effect of the crystal lattice on nuclear fusion reactions p+d{yields}{sup 3}He taking place in internal conversion channels is studied. Fusionable particles solved in the investigated crystalline material form a sublattice. Fusion reaction is generated by a flux of incoming fusionable particles. The calculated cross sections are compared with those of an ordinary fusion reaction. The internal conversion coefficients are also calculated.
Personal Dose Equivalent Conversion Coefficients For Photons To 1 GEV
Veinot, K. G.; Hertel, N. E.
2010-09-27
The personal dose equivalent, H{sub p}(d), is the quantity recommended by the International Commission on Radiation Units and Measurements (ICRU) to be used as an approximation of the protection quantity Effective Dose when performing personal dosemeter calibrations. The personal dose equivalent can be defined for any location and depth within the body. Typically, the location of interest is the trunk where personal dosemeters are usually worn and in this instance a suitable approximation is a 30 cm X 30 cm X 15 cm slab-type phantom. For this condition the personal dose equivalent is denoted as H{sub p,slab}(d) and the depths, d, are taken to be 0.007 cm for non-penetrating and 1 cm for penetrating radiation. In operational radiation protection a third depth, 0.3 cm, is used to approximate the dose to the lens of the eye. A number of conversion coefficients for photons are available for incident energies up to several MeV, however, data to higher energies are limited. In this work conversion coefficients up to 1 GeV have been calculated for H{sub p,slab}(10) and H{sub p,slab}(3) using both the kerma approximation and by tracking secondary charged particles. For H{sub p}(0.07) the conversion coefficients were calculated, but only to 10 MeV due to computational limitations. Additionally, conversions from air kerma to H{sub p,slab}(d) have been determined and are reported. The conversion coefficients were determined for discrete incident energies, but analytical fits of the coefficients over the energy range are provided. Since the inclusion of air can influence the production of secondary charged particles incident on the face of the phantom conversion coefficients have been determined both in vacuo and with the source and slab immersed within a sphere in air. The conversion coefficients for the personal dose equivalent are compared to the appropriate protection quantity, calculated according to the recommendations of the latest International Commission on
Personal dose-equivalent conversion coefficients for 1252 radionuclides.
Otto, Thomas
2016-01-01
Dose conversion coefficients for radionuclides are useful for routine calculations in radiation protection in industry, medicine and research. They give a simple and often sufficient estimate of dose rates during production, handling and storage of radionuclide sources, based solely on the source's activity. The latest compilation of such conversion coefficients dates from 20 y ago, based on nuclear decay data published 30 y ago. The present publication provides radionuclide-specific conversion coefficients to personal dose based on the most recent evaluations of nuclear decay data for 1252 radionuclides and fluence-to-dose-equivalent conversion coefficients for monoenergetic radiations. It contains previously unknown conversion coefficients for >400 nuclides and corrects those conversion coefficients that were based on erroneous decay schemes. For the first time, estimates for the protection quantity Hp(3) are included. PMID:25349458
Conversion coefficients of the isomeric state in {sup 72}Br
Briz, J. A.; Borge, M. J. G.; Maira, A.; Perea, A.; Tengblad, O.; Agramunt, J.; Algora, A.; Estevez, E.; Nacher, E.; Rubio, B.; Fraile, L. M.; Deo, A.; Farrelly, G.; Gelletly, W.; Podolyak, Z.
2010-04-26
In order to determine the Gamow-Teller strength distribution for the N Z nucleus {sup 72}Kr an experiment was performed with a Total Absorption Gamma Spectrometer. To fully accomplish this task it is crucial to determine the multipolarity of the low energy transitions as the spin-parity of the daughter ground state has been debated. This is done by experimental determination of the conversion coefficients. Preliminary results for the multipolarity and conversion coefficients of the transition connecting the isomeric state at 101 keV with the {sup 72}Br ground state are presented.
Personal dose equivalent conversion coefficients for electrons to 1 Ge V.
Veinot, K G; Hertel, N E
2012-04-01
In a previous paper, conversion coefficients for the personal dose equivalent, H(p)(d), for photons were reported. This note reports values for electrons calculated using similar techniques. The personal dose equivalent is the quantity used to approximate the protection quantity effective dose when performing personal dosemeter calibrations and in practice the personal dose equivalent is determined using a 30×30×15 cm slab-type phantom. Conversion coefficients to 1 GeV have been calculated for H(p)(10), H(p)(3) and H(p)(0.07) in the recommended slab phantom. Although the conversion coefficients were determined for discrete incident energies, analytical fits of the conversion coefficients over the energy range are provided using a similar formulation as in the photon results previously reported. The conversion coefficients for the personal dose equivalent are compared with the appropriate protection quantity, calculated according to the recommendations of the latest International Commission on Radiological Protection guidance. Effects of eyewear on H(p)(3) are also discussed. PMID:21715410
Comparison of fluence-to-dose conversion coefficients for deuterons, tritons and helions.
Copeland, Kyle; Friedberg, Wallace; Sato, Tatsuhiko; Niita, Koji
2012-02-01
Secondary radiation in aircraft and spacecraft includes deuterons, tritons and helions. Two sets of fluence-to-effective dose conversion coefficients for isotropic exposure to these particles were compared: one used the particle and heavy ion transport code system (PHITS) radiation transport code coupled with the International Commission on Radiological Protection (ICRP) reference phantoms (PHITS-ICRP) and the other the Monte Carlo N-Particle eXtended (MCNPX) radiation transport code coupled with modified BodyBuilder™ phantoms (MCNPX-BB). Also, two sets of fluence-to-effective dose equivalent conversion coefficients calculated using the PHITS-ICRP combination were compared: one used quality factors based on linear energy transfer; the other used quality factors based on lineal energy (y). Finally, PHITS-ICRP effective dose coefficients were compared with PHITS-ICRP effective dose equivalent coefficients. The PHITS-ICRP and MCNPX-BB effective dose coefficients were similar, except at high energies, where MCNPX-BB coefficients were higher. For helions, at most energies effective dose coefficients were much greater than effective dose equivalent coefficients. For deuterons and tritons, coefficients were similar when their radiation weighting factor was set to 2. PMID:21474471
Endo, Akira; Petoussi-Henss, Nina; Zankl, Maria; Bolch, Wesley E; Eckerman, Keith F; Hertel, Nolan E; Hunt, John G; Pelliccioni, Maurizio; Schlattl, Helmut; Menzel, Hans-Georg
2014-10-01
This paper reviews the ICRP Publications 110 and 116 describing the reference computational phantoms and dose conversion coefficients for external exposures. The International Commission on Radiological Protection (ICRP) in its 2007 Recommendations made several revisions to the methods of calculation of the protection quantities. In order to implement these recommendations, the DOCAL task group of the ICRP developed computational phantoms representing the reference adult male and female and then calculated a set of dose conversion coefficients for various types of idealised external exposures. This paper focuses on the dose conversion coefficients for neutrons and investigates their relationship with the conversion coefficients of the protection and operational quantities of ICRP Publication 74. Contributing factors to the differences between these sets of conversion coefficients are discussed in terms of the changes in phantoms employed and the radiation and tissue weighting factors. PMID:24285286
NASA Astrophysics Data System (ADS)
Chang, Lienard A.
In the event of a radiological accident or attack, it is important to estimate the organ doses to those exposed. In general, it is difficult to measure organ dose directly in the field and therefore dose conversion coefficients (DCC) are needed to convert measurable values such as air kerma to organ dose. Previous work on these coefficients has been conducted mainly for adults with a focus on radiation protection workers. Hence, there is a large gap in the literature for pediatric values. This study coupled a Monte Carlo N-Particle eXtended (MCNPX) code with International Council of Radiological Protection (ICRP)-adopted University of Florida and National Cancer Institute pediatric reference phantoms to calculate a comprehensive list of dose conversion coefficients (mGy/mGy) to convert air-kerma to organ dose. Parameters included ten phantoms (newborn, 1-year, 5-year, 10-year, 15-year old male and female), 28 organs over 33 energies between 0.01 and 20 MeV in six (6) irradiation geometries relevant to a child who might be exposed to a radiological release: anterior-posterior (AP), posterior-anterior (PA), right-lateral (RLAT), left-lateral (LLAT), rotational (ROT), and isotropic (ISO). Dose conversion coefficients to the red bone marrow over 36 skeletal sites were also calculated. It was hypothesized that the pediatric organ dose conversion coefficients would follow similar trends to the published adult values as dictated by human anatomy, but be of a higher magnitude. It was found that while the pediatric coefficients did yield similar patterns to that of the adult coefficients, depending on the organ and irradiation geometry, the pediatric values could be lower or higher than that of the adult coefficients.
Neutron fluence-to-dose conversion coefficients for embryo and fetus.
Chen, Jing; Meyerhof, Dorothy; Vlahovich, Slavica
2004-01-01
A problem of concern in radiation protection is the exposure of pregnant women to ionising radiation, because of the high radiosensitivity of the embryo and fetus. External neutron exposure is of concern when pregnant women travel by aeroplane. Dose assessments for neutrons frequently rely on fluence-to-dose conversion coefficients. While neutron fluence-to-dose conversion coefficients for adults are recommended in International Commission on Radiological Protection publications and International Commission on Radiological Units and Measurements reports, conversion coefficients for embryos and fetuses are not given in the publications. This study undertakes Monte Carlo calculations to determine the mean absorbed doses to the embryo and fetus when the mother is exposed to neutron fields. A new set of mathematical models for the embryo and fetus has been developed at Health Canada and is used together with mathematical phantoms of a pregnant female developed at Oak Ridge National Laboratory. Monoenergetic neutrons from 1 eV to 10 MeV are considered in this study. The irradiation geometries include antero-posterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT) and isotropic (ISO) geometries. At each of these standard irradiation geometries, absorbed doses to the fetal brain and body are calculated; for the embryo at 8 weeks and the fetus at 3, 6 or 9 months. Neutron fluence-to-absorbed dose conversion coefficients are derived for the four age groups. Neutron fluence-to-equivalent dose conversion coefficients are given for the AP irradiations which yield the highest radiation dose to the fetal body in the neutron energy range considered here. The results indicate that for neutrons <10 MeV more protection should be given to pregnant women in the first trimester due to the higher absorbed dose per unit neutron fluence to the fetus. PMID:15353732
Personal dose equivalent conversion coefficients for photons to 1 GeV.
Veinot, K G; Hertel, N E
2011-04-01
The personal dose equivalent, H(p)(d), is the quantity recommended by the International Commission on Radiation Units and Measurements (ICRU) to be used as an approximation of the protection quantity effective dose when performing personal dosemeter calibrations. The personal dose equivalent can be defined for any location and depth within the body. Typically, the location of interest is the trunk, where personal dosemeters are usually worn, and in this instance a suitable approximation is a 30 × 30 × 15 cm(3) slab-type phantom. For this condition, the personal dose equivalent is denoted as H(p,slab)(d) and the depths, d, are taken to be 0.007 cm for non-penetrating and 1 cm for penetrating radiation. In operational radiation protection a third depth, 0.3 cm, is used to approximate the dose to the lens of the eye. A number of conversion coefficients for photons are available for incident energies up to several megaelectronvolts, however, data to higher energies are limited. In this work, conversion coefficients up to 1 GeV have been calculated for H(p,slab)(10) and H(p,slab)(3) both by using the kerma approximation and tracking secondary charged particles. For H(p)(0.07), the conversion coefficients were calculated, but only to 10 MeV due to computational limitations. Additionally, conversions from air kerma to H(p,slab)(d) have been determined and are reported. The conversion coefficients were determined for discrete incident energies, but analytical fits of the coefficients over the energy range are provided. Since the inclusion of air can influence the production of secondary charged particles incident on the face of the phantom, conversion coefficients have been determined both in vacuo and with the source and slab immersed within a sphere in air. The conversion coefficients for the personal dose equivalent are compared with the appropriate protection quantity, calculated according to the recommendations of the latest International Commission on Radiological
Converse magneto-electric coefficient of concentric multiferroic composite ring
NASA Astrophysics Data System (ADS)
Chavez, Andres C.; Lopez, Mario; Youssef, George
2016-06-01
The converse magnetoelectric (CME) coefficient of an artificial, multiferroic composite cylinder was determined for two interface boundary conditions; specifically epoxy-bonded and shrink-fit. The composite consists of two concentrically bonded rings with the inner and outer rings made from Terfenol-D and lead zirconate titanate, respectively. The diameter of the inner annulus was 25 mm, and the outer ring diameter was 30 mm. Electric fields ranging from 20 kV/m to 80 kV/m with AC components cycling at frequencies from 4 kHz to 50 kHz were applied for actuation of the composite. A magnetic bias field from 0 Oe to 2300 Oe was applied for enhancement of the CME coefficient. It has been found that the maximum CME for epoxy-bonded rings occurs at lower bias magnetic field than shrink-fitted rings. Resonance for the epoxy-bonded composite was found to be 36 kHz whereas the resonant frequency for the shrink-fit structure was 34 kHz. The maximum CME coefficients were approximately 535 mG/V at 100 Vpp and 330 mG/V at 400 Vpp for the epoxy-bonded and shrink-fit configurations, respectively.
ERIC Educational Resources Information Center
Green, Samuel B.; Yang, Yanyun
2015-01-01
In the lead article, Davenport, Davison, Liou, & Love demonstrate the relationship among homogeneity, internal consistency, and coefficient alpha, and also distinguish among them. These distinctions are important because too often coefficient alpha--a reliability coefficient--is interpreted as an index of homogeneity or internal consistency.…
Qiu, Rui; Li, Junli; Zhang, Zhan; Liu, Liye; Bi, Lei; Ren, Li
2009-02-01
A set of conversion coefficients from kerma free-in-air to the organ-absorbed dose are presented for external monoenergetic photon beams from 10 keV to 10 MeV based on the Chinese mathematical phantom, a whole-body mathematical phantom model. The model was developed based on the methods of the Oak Ridge National Laboratory mathematical phantom series and data from the Chinese Reference Man and the Reference Asian Man. This work is carried out to obtain the conversion coefficients based on this model, which represents the characteristics of the Chinese population, as the anatomical parameters of the Chinese are different from those of Caucasians. Monte Carlo simulation with MCNP code is carried out to calculate the organ dose conversion coefficients. Before the calculation, the effects from the physics model and tally type are investigated, considering both the calculation efficiency and precision. In the calculation irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational and isotropic geometries. Conversion coefficients from this study are compared with those recommended in the Publication 74 of International Commission on Radiological Protection (ICRP74) since both the sets of data are calculated with mathematical phantoms. Overall, consistency between the two sets of data is observed and the difference for more than 60% of the data is below 10%. However, significant deviations are also found, mainly for the superficial organs (up to 65.9%) and bone surface (up to 66%). The big difference of the dose conversion coefficients for the superficial organs at high photon energy could be ascribed to kerma approximation for the data in ICRP74. Both anatomical variations between races and the calculation method contribute to the difference of the data for bone surface. PMID:19376886
Lee, Choonsik; Lee, Choonik; Lee, Jai-Ki
2007-05-01
International Commission on Radiological Protection (ICRP) reported comprehensive dose conversion coefficients for adult population, which is exposed to external photon sources in the Publication 74. However, those quantities were calculated from so-called stylized (or mathematical) phantoms composed of simplified mathematical surface equations so that the discrepancy between the phantoms and real human anatomy has been investigated by several authors using Caucasian-based voxel phantoms. To address anatomical and racial limitations of the stylized phantoms, several Asian-based voxel phantoms have been developed by Korean and Japanese investigators, independently. In the current study, photon dose conversion coefficients of ICRP 74 were compared with those from a total of five Asian-based male voxel phantoms, whose body dimensions were almost identical. Those of representative radio-sensitive organs (testes, red bone marrow, colon, lungs, and stomach), and effective dose conversion coefficients were obtained for comparison. Even though organ doses for testes, colon and lungs, and effective doses from ICRP 74 agreed well with those from Asian voxel phantoms within 10%, absorbed doses for red bone marrow and stomach showed significant discrepancies up to 30% which was mainly attributed to difference of phantom description between stylized and voxel phantoms. This study showed that the ICRP 74 dosimetry data, which have been reported to be unrealistic compared to those from Caucasian-based voxel phantoms, are also not appropriate for Asian population. PMID:17337194
Delimiting Coefficient a from Internal Consistency and Unidimensionality
ERIC Educational Resources Information Center
Sijtsma, Klaas
2015-01-01
I discuss the contribution by Davenport, Davison, Liou, & Love (2015) in which they relate reliability represented by coefficient a to formal definitions of internal consistency and unidimensionality, both proposed by Cronbach (1951). I argue that coefficient a is a lower bound to reliability and that concepts of internal consistency and…
Behrens, R
2012-09-01
The International Organization for Standardization (ISO) has issued a standard series on photon reference radiation qualities (ISO 4037). In this series, no conversion coefficients are contained for the quantity personal dose equivalent at a 3 mm depth, H(p)(3). In the past, for this quantity, a slab phantom was recommended as a calibration phantom; however, a cylinder phantom much better approximates the shape of a human head than a slab phantom. Therefore, in this work, the conversion coefficients from air kerma to H(p)(3) for the cylinder phantom are supplied for X- and gamma radiation qualities defined in ISO 4037. PMID:22434922
A Method for Maximizing the Internal Consistency Coefficient Alpha.
ERIC Educational Resources Information Center
Pepin, Michel
This paper presents three different ways of computing the internal consistency coefficient alpha for a same set of data. The main objective of the paper is the illustration of a method for maximizing coefficient alpha. The maximization of alpha can be achieved with the aid of a principal component analysis. The relation between alpha max. and the…
Dose conversion coefficients for electron exposure of the human eye lens.
Behrens, R; Dietze, G; Zankl, M
2009-07-01
Recent epidemiological studies suggest a rather low dose threshold (below 0.5 Gy) for the induction of a cataract of the eye lens. Some other studies even assume that there is no threshold at all. Therefore, protection measures have to be optimized and current dose limits for the eye lens may be reduced in the future. Two questions arise from this situation: first, which dose quantity is related to the risk of developing a cataract, and second, which personal dose equivalent quantity is appropriate for monitoring this dose quantity. While the dose equivalent quantity H(p)(0.07) has often been seen as being sufficiently accurate for monitoring the dose to the lens of the eye, this would be questionable in the case when the dose limits were reduced and, thus, it may be necessary to generally use the dose equivalent quantity H(p)(3) for this purpose. The basis for a decision, however, must be the knowledge of accurate conversion coefficients from fluence to equivalent dose to the lens. This is especially important for low-penetrating radiation, for example, electrons. Formerly published values of conversion coefficients are based on quite simple models of the eye. In this paper, quite a sophisticated model of the eye including the inner structure of the lens was used for the calculations and precise conversion coefficients for electrons with energies between 0.2 MeV and 12 MeV, and for angles of radiation incidence between 0 degrees and 45 degrees are presented. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are up to 1000 times smaller for electron energies below 1 MeV, nearly equal at 1 MeV and above 4 MeV, and by a factor of 1.5 larger at about 1.5 MeV electron energy. PMID:19502705
Dose conversion coefficients for photon exposure of the human eye lens.
Behrens, R; Dietze, G
2011-01-21
In recent years, several papers dealing with the eye lens dose have been published, because epidemiological studies implied that the induction of cataracts occurs even at eye lens doses of less than 500 mGy. Different questions were addressed: Which personal dose equivalent quantity is appropriate for monitoring the dose to the eye lens? Is a new definition of the dose quantity H(p)(3) based on a cylinder phantom to represent the human head necessary? Are current conversion coefficients from fluence to equivalent dose to the lens sufficiently accurate? To investigate the latter question, a realistic model of the eye including the inner structure of the lens was developed. Using this eye model, conversion coefficients for electrons have already been presented. In this paper, the same eye model-with the addition of the whole body-was used to calculate conversion coefficients from fluence (and air kerma) to equivalent dose to the lens for photon radiation from 5 keV to 10 MeV. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are similar between 40 keV and 1 MeV and lower by up to a factor of 5 and 7 for photon energies at about 10 keV and 10 MeV, respectively. Above 1 MeV, the new values (calculated without kerma approximation) should be applied in pure photon radiation fields, while the values adopted by the ICRP in 1996 (calculated with kerma approximation) should be applied in case a significant contribution from secondary electrons originating outside the body is present. PMID:21178237
NASA Astrophysics Data System (ADS)
Schlattl, H.; Zankl, M.; Petoussi-Henss, N.
2007-04-01
A new series of organ equivalent dose conversion coefficients for whole body external photon exposure is presented for a standardized couple of human voxel models, called Rex and Regina. Irradiations from broad parallel beams in antero-posterior, postero-anterior, left- and right-side lateral directions as well as from a 360° rotational source have been performed numerically by the Monte Carlo transport code EGSnrc. Dose conversion coefficients from an isotropically distributed source were computed, too. The voxel models Rex and Regina originating from real patient CT data comply in body and organ dimensions with the currently valid reference values given by the International Commission on Radiological Protection (ICRP) for the average Caucasian man and woman, respectively. While the equivalent dose conversion coefficients of many organs are in quite good agreement with the reference values of ICRP Publication 74, for some organs and certain geometries the discrepancies amount to 30% or more. Differences between the sexes are of the same order with mostly higher dose conversion coefficients in the smaller female model. However, much smaller deviations from the ICRP values are observed for the resulting effective dose conversion coefficients. With the still valid definition for the effective dose (ICRP Publication 60), the greatest change appears in lateral exposures with a decrease in the new models of at most 9%. However, when the modified definition of the effective dose as suggested by an ICRP draft is applied, the largest deviation from the current reference values is obtained in postero-anterior geometry with a reduction of the effective dose conversion coefficient by at most 12%.
Schlattl, H; Zankl, M; Petoussi-Henss, N
2007-04-21
A new series of organ equivalent dose conversion coefficients for whole body external photon exposure is presented for a standardized couple of human voxel models, called Rex and Regina. Irradiations from broad parallel beams in antero-posterior, postero-anterior, left- and right-side lateral directions as well as from a 360 degrees rotational source have been performed numerically by the Monte Carlo transport code EGSnrc. Dose conversion coefficients from an isotropically distributed source were computed, too. The voxel models Rex and Regina originating from real patient CT data comply in body and organ dimensions with the currently valid reference values given by the International Commission on Radiological Protection (ICRP) for the average Caucasian man and woman, respectively. While the equivalent dose conversion coefficients of many organs are in quite good agreement with the reference values of ICRP Publication 74, for some organs and certain geometries the discrepancies amount to 30% or more. Differences between the sexes are of the same order with mostly higher dose conversion coefficients in the smaller female model. However, much smaller deviations from the ICRP values are observed for the resulting effective dose conversion coefficients. With the still valid definition for the effective dose (ICRP Publication 60), the greatest change appears in lateral exposures with a decrease in the new models of at most 9%. However, when the modified definition of the effective dose as suggested by an ICRP draft is applied, the largest deviation from the current reference values is obtained in postero-anterior geometry with a reduction of the effective dose conversion coefficient by at most 12%. PMID:17404459
Dose conversion coefficients for ICRP110 voxel phantom in the Geant4 Monte Carlo code
NASA Astrophysics Data System (ADS)
Martins, M. C.; Cordeiro, T. P. V.; Silva, A. X.; Souza-Santos, D.; Queiroz-Filho, P. P.; Hunt, J. G.
2014-02-01
The reference adult male voxel phantom recommended by International Commission on Radiological Protection no. 110 was implemented in the Geant4 Monte Carlo code. Geant4 was used to calculate Dose Conversion Coefficients (DCCs) expressed as dose deposited in organs per air kerma for photons, electrons and neutrons in the Annals of the ICRP. In this work the AP and PA irradiation geometries of the ICRP male phantom were simulated for the purpose of benchmarking the Geant4 code. Monoenergetic photons were simulated between 15 keV and 10 MeV and the results were compared with ICRP 110, the VMC Monte Carlo code and the literature data available, presenting a good agreement.
Photon extremity absorbed dose and kerma conversion coefficients for calibration geometries.
Veinot, K G; Hertel, N E
2007-02-01
Absorbed dose and dose equivalent conversion coefficients are routinely used in personnel dosimetry programs. These conversion coefficients can be applied to particle fluences or to measured air kerma values to determine appropriate operational monitoring quantities such as the ambient dose equivalent or personal dose equivalent for a specific geometry. For personnel directly handling materials, the absorbed dose to the extremities is of concern. This work presents photon conversion coefficients for two extremity calibration geometries using finger and wrist/arm phantoms described in HPS N13.32. These conversion coefficients have been calculated as a function of photon energy in terms of the kerma and the absorbed dose using Monte Carlo techniques and the calibration geometries specified in HPS N13.32. Additionally, kerma and absorbed dose conversion coefficients for commonly used x-ray spectra and calibration source fields are presented. The kerma values calculated in this work for the x-ray spectra and calibration sources compare well to those listed in HPS N13.32. The absorbed dose values, however, differ significantly for higher energy photons because charged particle equilibrium conditions have not been satisfied for the shallow depth. Thus, the air-kerma-to-dose and exposure-to-dose conversion coefficients for Cs and Co listed in HPS N13.32 overestimate the absorbed dose to the extremities. Applying the conversion coefficients listed in HPS N13.32 for Cs, for example, would result in an overestimate of absorbed dose of 62% for the finger phantom and 55% for the wrist phantom. PMID:17220720
Test of internal-conversion theory with measurements in {sup 134}Cs and {sup 137}Ba
Nica, N.; Hardy, J. C.; Iacob, V. E.; Rockwell, W. E.; Trzhaskovskaya, M. B.
2007-02-15
We have measured the ratio of K-shell internal conversion coefficients, {alpha}{sub K}, for the 127.5-keV E3 transition in {sup 134}Cs and the 661.7-keV M4 transition in {sup 137}Ba. Previous measurements of these {alpha}{sub K} values led to a ratio that differed from calculated internal conversion coefficients. Our measured result, 30.01(15), disagrees with, but is a factor of three more precise than, the previous average of all experimental results. Our new result is consistent with calculations.
International and American Students' Perceptions of Informal English Conversations
ERIC Educational Resources Information Center
Lee, Eun Jeong
2016-01-01
This study investigated international and American students' perceptions of structured but informal English conversations with each other. American and international students perceived the effects of these conversations differently. While the international students claimed increased linguistic and cultural competence, the Americans identified…
Chang, S J; Hung, S Y; Liu, Y L; Jiang, S H; Wu, J
2015-11-01
Reference man has been widely used for external and internal dose evaluation of radiation protection. The parameters of the mathematical model of organs suggested by the International Commission of Radiological Protection (ICRP) are adopted from the average data of Caucasians. However, the organ masses of Asians are significantly different from the data of Caucasians, leading to potentially dosimetric errors. In this study, a total of 40 volunteers whose heights and weights corresponded to the statistical average of Taiwanese adults were recruited. Magnetic resonance imaging was performed, and T2-weighted images were acquired. The Taiwanese reference man and woman were constructed according to the measured organ masses. The dose conversion coefficients (DCFs) for anterior-posterior (AP), posterior-anterior (PA), right lateral (RLAT) and left lateral (LLAT) irradiation geometries were simulated. For the Taiwanese reference man, the average differences of the DCFs compared with the results of ICRP-74 were 7.6, 5.1 and 11.1 % for 0.1, 1 and 10 MeV photons irradiated in the AP direction. The maximum difference reached 51.7 % for the testes irradiated by 10 MeV photons. The size of the trunk, the volume and the geometric position of organs can cause a significant impact on the DCFs for external exposure of radiation. The constructed Taiwanese reference man and woman can be used in radiation protection to increase the accuracy of dose evaluation for the Taiwanese population. PMID:25944957
Calculation of conversion coefficients for clinical photon spectra using the MCNP code.
Lima, M A F; Silva, A X; Crispim, V R
2004-01-01
In this work, the MCNP4B code has been employed to calculate conversion coefficients from air kerma to the ambient dose equivalent, H*(10)/Ka, for monoenergetic photon energies from 10 keV to 50 MeV, assuming the kerma approximation. Also estimated are the H*(10)/Ka for photon beams produced by linear accelerators, such as Clinac-4 and Clinac-2500, after transmission through primary barriers of radiotherapy treatment rooms. The results for the conversion coefficients for monoenergetic photon energies, with statistical uncertainty <2%, are compared with those in ICRP publication 74 and good agreements were obtained. The conversion coefficients calculated for real clinic spectra transmitted through walls of concrete of 1, 1.5 and 2 m thick, are in the range of 1.06-1.12 Sv Gy(-1). PMID:15367760
Zhang, Xiaomin; Xie, Xiangdong; Qu, Decheng; Ning, Jing; Zhou, Hongmei; Pan, Jie; Yang, Guoshan
2016-03-01
A set of fluence-to-dose conversion coefficients has been calculated for neutrons with energies <20 MeV using a developed voxel mouse model and Monte Carlo N-particle code (MCNP), for the purpose of neutron radiation effect evaluation. The calculation used 37 monodirectional monoenergetic neutron beams in the energy range 10(-9) MeV to 20 MeV, under five different source irradiation configurations: left lateral, right lateral, dorsal-ventral, ventral-dorsal, and isotropic. Neutron fluence-to-dose conversion coefficients for selected organs of the body were presented in the paper, and the effect of irradiation geometry conditions, neutron energy and the organ location on the organ dose was discussed. The results indicated that neutron dose conversion coefficients clearly show sensitivity to irradiation geometry at neutron energy below 1 MeV. PMID:26661852
Zhang, Xiaomin; Xie, Xiangdong; Qu, Decheng; Ning, Jing; Zhou, Hongmei; Pan, Jie; Yang, Guoshan
2016-01-01
A set of fluence-to-dose conversion coefficients has been calculated for neutrons with energies <20 MeV using a developed voxel mouse model and Monte Carlo N-particle code (MCNP), for the purpose of neutron radiation effect evaluation. The calculation used 37 monodirectional monoenergetic neutron beams in the energy range 10−9 MeV to 20 MeV, under five different source irradiation configurations: left lateral, right lateral, dorsal–ventral, ventral–dorsal, and isotropic. Neutron fluence-to-dose conversion coefficients for selected organs of the body were presented in the paper, and the effect of irradiation geometry conditions, neutron energy and the organ location on the organ dose was discussed. The results indicated that neutron dose conversion coefficients clearly show sensitivity to irradiation geometry at neutron energy below 1 MeV. PMID:26661852
Further Test of Internal-conversion Theory with a Measurement in 119Sn
NASA Astrophysics Data System (ADS)
Nica, N.; Hardy, J. C.; Iacob, V. E.
2014-06-01
Precise measurements are being used to test theoretical K-shell internal conversion coefficients (ICCs): in particular, our program has focused on examining whether the atomic K-vacancy formed during the conversion process must be incorporated into the calculations. We report here a measurement on the 65.66-keV, M4 isomeric transition in 119Sn. Our preliminary result is αK = 1610 (27), which confirms the importance of including the vacancy in the ICC calculations.
Chapter 4: Ultrafast Internal Conversion of Pyrazine via Conical Intersection
NASA Astrophysics Data System (ADS)
Suzuki, T.; Suzuki, Y. I.
2014-04-01
We describe recent experimental studies of internal conversion via conical intersection in pyrazine. Ultrafast S2 - S1 internal conversion is observed in real time using a time-resolved photoelectron imaging (TRPEI) method with a time resolution of 22 fs. This method enables us to obtain a time-energy map of the photoelectron angular anisotropy, which unambiguously reveals the signature of internal conversion. Furthermore, the time-energy map of the photoelectron kinetic energy distribution (PKED) exhibits vibrational quantum beats of totally symmetric modes in S1 after internal conversion. We also studied similar conical intersections between D1(π-1) and D0(n-1) by He(I) photoelectron spectroscopy and pulsed field ionization photoelectron spectroscopy. The existence of ultrafast internal conversion from D1 to D0 is confirmed by broadening of He(I) photoelectron spectra of pyrazine and deuterated pyrazine. Comparison of these spectra with one-color resonance-enhanced multiphoton ionization (REMPI) spectra of the 3s Rydberg states clearly indicates that the conical intersection between D1 and D0 induces ultrafast internal conversion from the Rydberg state with a D1 ion core to that with a D0 ion core.
Taranenko, Valery; Xu, X George
2009-01-01
Protection of pregnant women and their foetus against external proton irradiations poses a unique challenge. Assessment of foetal dose due to external protons in galactic cosmic rays and as secondaries generated in aircraft walls is especially important during high-altitude flights. This paper reports a set of fluence to absorbed dose conversion coefficients for the foetus and its brain for external monoenergetic proton beams of six standard configurations (the antero-posterior, the postero-anterior, the right lateral, the left lateral, the rotational and the isotropic). The pregnant female anatomical definitions at each of the three gestational periods (3, 6 and 9 months) are based on newly developed RPI-P series of models whose organ masses were matched within 1% with the International Commission on Radiological Protection reference values. Proton interactions and the transport of secondary particles were carefully simulated using the Monte Carlo N-Particle eXtended code (MCNPX) and the phantoms consisting of several million voxels at 3 mm resolution. When choosing the physics models in the MCNPX, it was found that the advanced Cascade-Exciton intranuclear cascade model showed a maximum of 9% foetal dose increase compared with the default model combination at intermediate energies below 5 GeV. Foetal dose results from this study are tabulated and compared with previously published data that were based on simplified anatomy. The comparison showed a strong dependence upon the source geometry, energy and gestation period: the dose differences are typically less than 20% for all sources except ISO where systematically 40-80% of higher doses were observed. Below 200 MeV, a larger discrepancy in dose was found due to the Bragg peak shift caused by different anatomy. The tabulated foetal doses represent the latest and most detailed study to date offering a useful set of data to improve radiation protection dosimetry against external protons. PMID:19246483
NASA Astrophysics Data System (ADS)
Ma, A. K.; Altaher, K.; Hussein, M. A.; Amer, M.; Farid, K. Y.; Alghamdi, A. A.
2014-02-01
In this work we will present a new set of photon fluence-to-effective dose conversion coefficients using the Saudi population-based voxel phantom developed recently by our group. The phantom corresponds to an average Saudi male of 173 cm tall weighing 77 kg. There are over 125 million voxels in the phantom each of which is 1.37×1.37×1.00 mm3. Of the 27 organs and tissues of radiological interest specified in the recommendations of ICRP Publication 103, all but the oral mucosa, extrathoracic tissue and the lymph nodes were identified in the current version of the phantom. The bone surface (endosteum) is too thin to be identifiable; it is about 10 μm thick. The dose to the endosteum was therefore approximated by the dose to the bones. Irradiation geometries included anterior-posterior (AP), left (LLAT) and rotational (ROT). The simulations were carried out with the MCNPX code version 2.5.0. The fluence in free air and the energy depositions in each organ were calculated for monoenergetic photon beams from 10 keV to 10 MeV to obtain the conversion coefficients. The radiation and tissue weighting factors were taken from ICRP Publication 60 and 103. The results from this study will also be compared with the conversion coefficients in ICRP Publication 116.
Li, Junli; Qiu, Rui; Zhang, Zhan; Liu, Liye; Zeng, Zhi; Bi, Lei; Li, Wenqian
2009-07-01
A set of conversion coefficients from kerma free-in-air to the organ absorbed dose are presented for external monoenergetic photon beams from 10 keV to 10 MeV based on a whole-body, Chinese adult male voxel phantom. This computational phantom, called the Chinese voxel phantom (CVP), including totally 23 organs, was developed from magnetic resonance imaging of a young healthy Chinese man at a resolution of 2 x 2 mm. Compared with the ICRP Reference Man, more than half of the organs or tissues in the CVP show mass differences of more than 20. Monte Carlo simulations with MCNP code were carried out to calculate the organ dose conversion coefficients. Irradiation conditions include anterior-posterior, posterior-anterior (PA), right-lateral, left-lateral, rotational and isotropic geometries. Organ dose conversion coefficients from this study are compared with the data from the Asian voxel phantoms Visible Chinese Human and KORMAN. These data sets agree with each other within 10% for photon energy >5 MeV. However, discrepancies of 34-63% were observed for organs of the alimentary tract, such as the oesophagus and stomach, those of the urinary system, such as the bladder wall and thyroid, especially at low photon energy range and PA geometry. These results suggest that the anatomical variation within the Chinese population, as represented by these adult male voxel phantoms, can lead to uncertainties when a standard phantom is used for the entire population. PMID:19457976
Xiao, Pingping; Wang, Xianping; Sun, Jingjing; Huang, Meizhen; Chen, Xianfeng; Cao, Zhuangqi
2012-06-18
A new scheme is proposed to measure the electro-optical (EO) and converse-piezoelectric (CPE) coefficients of the PMN-PT ceramics simultaneously, in which the PMN-PT ceramics acts as the guiding layer of a symmetrical metal-cladding waveguide. As the applied electric field exerts on the waveguide, the effective refractive index (RI) (or synchronous angle) can be effectively tuned from a selected mode to another adjacent mode owing to the high sensitivity and the small spacing of the ultra-high order modes. Subsequently, a correlation between EO and CPE coefficients is established. With this correlation and the measurement of the effective RI change to the applied voltage, the quadratic EO and CPE coefficients of PMN-PT ceramics are obtained simultaneously. The obtained results are further checked by fitting the variations of effective RI to a quadratic function. Our measurement method can be extended to a wide range of other materials. PMID:22714448
Conversion Intentions of Interns: What Are the Motivating Factors?
ERIC Educational Resources Information Center
Hurst, Jessica L.; Good, Linda K.; Gardner, Phil
2012-01-01
Purpose: The purpose of this study is to investigate interns' supervisory support expectations, psychological contract obligations, job satisfaction, perception of advancement opportunities and affective organisational commitment in an attempt to gain a better understanding of how these variables influence interns' conversion intentions.…
Organ dose conversion coefficients for tube current modulated CT protocols for an adult population
NASA Astrophysics Data System (ADS)
Fu, Wanyi; Tian, Xiaoyu; Sahbaee, Pooyan; Zhang, Yakun; Segars, William Paul; Samei, Ehsan
2016-03-01
In computed tomography (CT), patient-specific organ dose can be estimated using pre-calculated organ dose conversion coefficients (organ dose normalized by CTDIvol, h factor) database, taking into account patient size and scan coverage. The conversion coefficients have been previously estimated for routine body protocol classes, grouped by scan coverage, across an adult population for fixed tube current modulated CT. The coefficients, however, do not include the widely utilized tube current (mA) modulation scheme, which significantly impacts organ dose. This study aims to extend the h factors and the corresponding dose length product (DLP) to create effective dose conversion coefficients (k factor) database incorporating various tube current modulation strengths. Fifty-eight extended cardiac-torso (XCAT) phantoms were included in this study representing population anatomy variation in clinical practice. Four mA profiles, representing weak to strong mA dependency on body attenuation, were generated for each phantom and protocol class. A validated Monte Carlo program was used to simulate the organ dose. The organ dose and effective dose was further normalized by CTDIvol and DLP to derive the h factors and k factors, respectively. The h factors and k factors were summarized in an exponential regression model as a function of body size. Such a population-based mathematical model can provide a comprehensive organ dose estimation given body size and CTDIvol. The model was integrated into an iPhone app XCATdose version 2, enhancing the 1st version based upon fixed tube current modulation. With the organ dose calculator, physicists, physicians, and patients can conveniently estimate organ dose.
NASA Astrophysics Data System (ADS)
Zhu, Z.; Toksoz, M. N.
2014-12-01
Theoretical calculation of seismoelectric conversion coefficients is difficult because it requires a large number of parameters that are hard to obtain. Much laboratory data are needed to validate the theoretical results. The most critical issue is determining independently the effect of porosity and permeability on seismoelectric coefficients. In general, when the rock porosity increases, the permeability increases too, and vice versa. In this study, we make measurements on both synthetic sandstone and two Berea (500 and 100) samples. We built a man-made "sandstone" sample with round cracks which are distributed in a horizontal plane. Thus the small cube (1.7 cm^3 ) only has one value of porosity and different permeabilities in the three directions. It is a sample with anisotropy in permeability. Laboratory experiments in a water tank show that the seismoelectric conversion coefficient is related to permeabilities in the three directions. The seismoelectric coefficient is highest in the direction of maximum permeability and lowest in the direction of minimum permeability. The measurements with the isotropic Berea samples show that seismoelectric coefficient increases with both porosity and permeability. Application of the result to borehole logging measurements requires analysis of the data from P, S, and Stoneley waves. P and Stoneley waves give large seismoelectric signals in the presence of fractures or high permeability zones. Shear waves, that do not induce fluid flow, provide very small seismoelectric signals. If the fracture strike in the formation is along the borehole axis, the P-wave induces stronger seismoelectric signal. Seismoelectric well logging might prove help for exploring the fractures or micro fractures in a borehole wall.
Miri Hakimabad, H; Rafat Motavalli, L; Karimi Shahri, K
2009-03-01
Neutron fluence to absorbed dose conversion coefficients have been evaluated for the analytical ORNL modified adult phantom in 21 body organs using MCNP4C Monte Carlo code. The calculation used 20 monodirectional monoenergetic neutron beams in the energy range 10(-9)-20 MeV, under four irradiation conditions: anterior-posterior (AP), posterior-anterior (PA), left-lateral (LLAT) and right-lateral (RLAT). Then the conversion coefficients are compared with the data reported in ICRP publication 74 for mathematical MIRD type phantoms and by Bozkurt et al for the VIPMAN voxel model. Although the ORNL results show fewer differences with the ICRP results than the Bozkurt et al data, one can deduce neither complete agreement nor disparity between this study and other data sets. This comparison shows that in some cases any differences in applied Monte Carlo codes or simulated body models could significantly change the organ dose conversion factors. This sensitivity should be considered for radiological protection programmes. For certain organs, the results of two models with major differences can be in a satisfactory agreement because of the similarity in those organ models. PMID:19225185
Further test of internal-conversion theory with a measurement in {sup 197}Pt
Nica, N.; Hardy, J. C.; Iacob, V. E.; Goodwin, J.; Balonek, C.; Hernberg, M.; Nolan, J.; Trzhaskovskaya, M. B.
2009-12-15
We have measured the K-shell internal conversion coefficient, {alpha}{sub K}, for the 346.5-keV M4 transition in {sup 197}Pt to be 4.23(7). This result differs from a previous value, which disagreed significantly from theory. Our new value agrees well with Dirac-Fock calculations and removes the earlier discrepancy as a source of concern.
Actinide co-conversion by internal gelation
Robisson, Anne-Charlotte; Dauby, Jacques; Dumont-Shintu, Corinne; Machon, Estelle; Grandjean, Stephane
2007-07-01
Suitable microstructures and homogenous microspheres of actinide compounds are of interest for future nuclear fuel or transmutation target concepts to prevent the generation and dispersal of actinide powder. Sol-gel routes are being investigated as one of the possible solutions for producing these compounds. Preliminary work is described involving internal gelation to synthesize mixed compounds including minor actinides, particularly mixed actinide or mixed actinide-inert element compounds. A parameter study is discussed to highlight the importance of the initial broth composition for obtaining gel microspheres without major defects (cracks, craters, etc.). In particular, conditions are defined to produce gel beads from Zr(IV)/Y(III)/Ce(III) or Zr(IV)/An(III) systems. After gelation, the heat treatment of these microspheres is described for the purpose of better understanding the formation of cracks after calcination and verifying the effective synthesis of an oxide solid-solution. (authors)
Further Test of Internal-conversion Theory with a Measurement in {sup 119}Sn
Nica, N. Hardy, J.C.; Iacob, V.E.
2014-06-15
Precise measurements are being used to test theoretical K-shell internal conversion coefficients (ICCs): in particular, our program has focused on examining whether the atomic K-vacancy formed during the conversion process must be incorporated into the calculations. We report here a measurement on the 65.66-keV, M4 isomeric transition in {sup 119}Sn. Our preliminary result is α{sub K}=1610(27), which confirms the importance of including the vacancy in the ICC calculations.
Internal conversion in highly-stripped {sup 83}Kr ions
Rehm, K.E.; Ahmad, I.; Gehring, J.
1995-08-01
The transition probability per unit time for the decay of a nuclear level via internal conversion (IC), {lambda}IC, depends on the electron environment of the nucleus. For example, inner-shell conversion in highly-charged ions can change appreciably as electrons are successively removed from the ion. Magnetic dipole (Ml) transitions are especially sensitive to this effect since the internal conversion depends strongly on the electron density at the nucleus. Hence, measurements of {lambda}IC,q, the internal conversion rate in an ion with charge state q, can provide good tests of theoretical electron wave functions if the electron configuration in the ions is known. In a previous experiment, a new method which identifies charge-changing events during passage of ion beams through a magnetic spectrometer was used to determine {lambda}IC,q for the 14.4-keV isomer in {sup 57}Fe. This contribution reports measurements made using the same technique for the 9.4-keV isomer in {sup 83}Kr. A beam of {sup 83}Kr with energy 650 MeV bombarded a Au target with a thickness 300 {mu}g cm{sup -2}. Secondary scattered beams were accepted and analyzed by an Enge magnetic spectrometer. The numbers of excited nuclei decaying during passage through the spectrometer and their internal conversion rates were deduced from the pattern of events measured in the spectrometer focal plane.
Santos, J C; Mariano, L; Tomal, A; Costa, P R
2016-03-01
According to the International Commission on Radiation Units and Measurements (ICRU), the relationship between effective dose and incident air-kerma is complex and depends on the attenuation of x-rays in the body. Therefore, it is not practical to use this quantity for shielding design purposes. This correlation is adopted in practical situations by using conversion coefficients calculated using validated mathematical models by the ICRU. The ambient dose equivalent, H*(10), is a quantity adopted by the IAEA for monitoring external exposure. Dose constraint levels are established in terms of H*(10), while the radiation levels in radiometric surveys are calculated by means of the measurements of air-kerma with ion chambers. The resulting measurements are converted into ambient dose equivalents by conversion factors. In the present work, an experimental study of the relationship between the air-kerma and the operational quantity ambient dose equivalent was conducted using different experimental scenarios. This study was done by measuring the primary x-ray spectra and x-ray spectra transmitted through materials used in dedicated chest radiographic facilities, using a CdTe detector. The air-kerma to ambient dose equivalent conversion coefficients were calculated from these measured spectra. The resulting values of the quantity ambient dose equivalent using these conversion coefficients are more realistic than those available in the literature, because they consider the real energy distribution of primary and transmitted x-ray beams. The maximum difference between the obtained conversion coefficients and the constant value recommended in national and international radiation protection standards is 53.4%. The conclusion based on these results is that a constant coefficient may not be adequate for deriving the ambient dose equivalent. PMID:26835613
Dong, Liang; Li, Taosheng; Liu, Chunyu
2015-04-01
A set of fluence-to-effective dose conversion coefficients of external exposure to muons were investigated for Chinese hybrid phantom references, which include both male and female. Both polygon meshes and Non-Uniform Rational B-Spline (NURBS) surfaces were used to descried the boundary of the organs and tissues in these phantoms. The 3D-DOCTOR and Rhinoceros software were used to polygonise the colour slice images and generate the NURBS surfaces, respectively. The voxelisation is completed using the BINVOX software and the assembly finished by using MATLAB codes. The voxel resolutions were selected to be 0.22 × 0.22 × 0.22 cm(3) and 0.2 × 0.2 × 0.2 cm(3) for male and female phantoms, respectively. All parts of the final phantoms were matched to their reference organ masses within a tolerance of ±5%. The conversion coefficients for negative and positive muons were calculated with the FLUKA transport code. There were 21 external monoenergetic beams ranging from 0.01 GeV to 100 TeV in 5 different geometrical conditions of irradiation. PMID:25313173
Optimised geometry to calculate dose rate conversion coefficient for external exposure to photons.
Askri, B; Manai, K; Trabelsi, A; Baccari, B
2008-01-01
A single-parameter geometry to describe soil is achieved for Monte Carlo calculation of absorbed dose rate in air for photon emitters from natural radionuclides. This optimised geometry based on physical assumptions consists of the soil part whose emitted radiation has a given minimum probability to reach the detector. This geometry was implemented in Geant4 toolkit and a significant reduction in computation time was achieved. Simulation tests have shown that for soil represented by a cylinder of 40 m radius and 1 m deep, >98% of the calculated dose rate conversion coefficients in air at 1 m above the ground is generated by only 6% of the soil volume in the case of uniform distribution of radioactivity, and >99.2% of the calculated dose rate for an exponential distribution. When the soil is represented by the entire optimised geometry, 99% of the conversion coefficients values are reached for a soil depth of 1 m and 100% for that of approximately 2 m. PMID:17959610
NASA Astrophysics Data System (ADS)
Hu, Shougeng; Wang, Jue; Wang, Zhanqi
2010-11-01
Relating supplementary cultivated land (SCL) quantity and quality with the occupied cultivated land (OCL) grade as well as realizing conversion between them are crucial to keep the balance between SCL and OCL, to protect the limited farming resources, to guarantee the security of national food, to harmonize the relationship between human and land resources, and to promote sustainable economic development. The Jianhan plain, one of China's grain production bases, was chosen for a case study to quantify the relationships between the grade index of farmland utilization and standard food output based on the resulting grade of agricultural land. Linear regression is used to model the relationships for 2778 samples from the grade of agricultural land obtained by field mapping. The average of grade index for different utilization grades was estimated by the area weighted average method. The results demonstrate that quantity-quality grade conversion coefficient of supplementary cultivated land, and the method used in this study are powerful tools to quantify the relationship between the quantity and quality of the SCL and the grade and realize conversion of OCL. Theses results can be used for protecting the quantity and quality of cultivated land and optimizing design for land consolidation project as well as determining the reasonable scale and layout of land use planning in the Jianghan plain.
NASA Astrophysics Data System (ADS)
Hu, Shougeng; Wang, Jue; Wang, Zhanqi
2009-09-01
Relating supplementary cultivated land (SCL) quantity and quality with the occupied cultivated land (OCL) grade as well as realizing conversion between them are crucial to keep the balance between SCL and OCL, to protect the limited farming resources, to guarantee the security of national food, to harmonize the relationship between human and land resources, and to promote sustainable economic development. The Jianhan plain, one of China's grain production bases, was chosen for a case study to quantify the relationships between the grade index of farmland utilization and standard food output based on the resulting grade of agricultural land. Linear regression is used to model the relationships for 2778 samples from the grade of agricultural land obtained by field mapping. The average of grade index for different utilization grades was estimated by the area weighted average method. The results demonstrate that quantity-quality grade conversion coefficient of supplementary cultivated land, and the method used in this study are powerful tools to quantify the relationship between the quantity and quality of the SCL and the grade and realize conversion of OCL. Theses results can be used for protecting the quantity and quality of cultivated land and optimizing design for land consolidation project as well as determining the reasonable scale and layout of land use planning in the Jianghan plain.
The non-ergodic nature of internal conversion.
Sølling, Theis I; Kuhlman, Thomas S; Stephansen, Anne B; Klein, Liv B; Møller, Klaus B
2014-02-01
The absorption of light by molecules can induce ultrafast dynamics and coupling of electronic and nuclear vibrational motion. The ultrafast nature in many cases rests on the importance of several potential energy surfaces in guiding the nuclear motion-a concept of central importance in many aspects of chemical reaction dynamics. This Minireview focuses on the non-ergodic nature of internal conversion, that is, on the concept that the nuclear dynamics only sample a reduced phase space, potentially resulting in localization of the dynamics in real space. A series of results that highlight the nonstatistical nature of the excited-state deactivation process is presented. The examples are categorized into four groups. 1) Localization of the energy in one degree of freedom in S2 →S1 transitions, in which the transition is either determined by the time spent in the S2 →S1 coupling region or by the time it takes to reach it. 2) Localization of energy into a single reactive mode, which is dictated by the internal conversion process. 3) Initiation of the internal conversion by activation of a single complex motion, which then specifically couples to a reactive mode. 4) Nonstatistical internal conversion as a tool to accomplish biomolecular stability. Herein, the discussion on nonstatistical internal conversion in DNA as a mechanism to eliminate electronic excitation energy is extended to include molecules with an S-S bond as a model of the disulfide bridge in peptides. All of these examples are summed up in Kasha's rule. For systems with multiple degrees of freedom it will be possible to locate an appropriate motion somewhere in phase space that will take the wavepacket to the coupling region and facilitate an ultrafast transition to S1. Once at S1, the momentum of the wavepacket is lost and the only options left are the statistical processes of reaction or light emission. PMID:24375886
Miao, L; Tanemura, S; Huang, R; Liu, C Y; Huang, C M; Xu, G
2010-08-01
Titanate nanotubes Na(2-x)H(x)Ti(3)O(7) produced by alkali hydrothermally treated ground TiO(2) aerogels are investigated as possible materials for high-temperature thermoelectric conversion by measuring their thermoelectric properties. Strikingly, the Seebeck coefficients increased sharply in the temperature range 745 to 1032 K, reaching a maximum of 302 muV/K. The electrical resistivity of the TNNTs ranged from 325 to 525 Omegam, which is lower than that of bulk TiO(2), and thermal conductivities at room temperature were also very low, ranging from 0.55 to 0.75 Wm(-1) K(-1). The hollow structure of the titanate nanotubes, with small, uniform diameters, is thought to be responsible for the ultralow thermal conductivity. The large thermoelectric power and ultralow thermal conductivity suggest that titanate nanotubes represent a new kind of p-type oxide thermoelectric material. PMID:20735107
Dose conversion coefficients for neutron exposure to the lens of the human eye
Manger, Ryan P; Bellamy, Michael B; Eckerman, Keith F
2011-01-01
Dose conversion coefficients for the lens of the human eye have been calculated for neutron exposure at energies from 1 x 10{sup -9} to 20 MeV and several standard orientations: anterior-to-posterior, rotational and right lateral. MCNPX version 2.6.0, a Monte Carlo-based particle transport package, was used to determine the energy deposited in the lens of the eye. The human eyeball model was updated by partitioning the lens into sensitive and insensitive volumes as the anterior portion (sensitive volume) of the lens being more radiosensitive and prone to cataract formation. The updated eye model was used with the adult UF-ORNL mathematical phantom in the MCNPX transport calculations.
Khailov, A M; Ivannikov, A I; Skvortsov, V G; Stepanenko, V F; Tsyb, A F; Trompier, F; Hoshi, M
2010-02-01
In the present study, MCNP4B simulation code is used to simulate neutron and photon transport. It gives the conversion coefficients that relate neutron fluence to the dose in tooth enamel (molars and pre-molars only) for 20 energy groups of monoenergetic neutrons with energies from 10-9 to 20 MeV for five different irradiation geometries. The data presented are intended to provide the basis for connection between EPR dose values and standard protection quantities defined in ICRP Publication 74. The results of the calculations for critical organs were found to be consistent with ICRP data, with discrepancies generally less than 10% for the fast neutrons. The absorbed dose in enamel was found to depend strongly on the incident neutron energy for neutrons over 10 keV. The dependence of the data on the irradiation geometry is also shown. Lower bound estimates of enamel radiation sensitivity to neutrons were made using obtained coefficients for the secondary photons. Depending on neutron energy, tooth enamel was shown to register 10-120% of the total neutron dose in the human body in the case of pure neutron exposure and AP irradiation geometry. PMID:20065707
Internal-conversion process in superintense ultrashort x-ray pulses
Kis, Daniel; Kalman, Peter; Keszthelyi, Tamas; Szivos, Janos
2010-01-15
The electron-nucleus interaction in a super-intense few-cycle x-ray pulse is investigated. The super-intense few-cycle x-ray pulse-induced internal conversion (IC) process is discussed in detail. The x-ray laser-pulse induced IC coefficient is calculated, and in particular, it is derived in the case of a pulse of Gaussian shape and for a bound-free electron transition. The IC coefficient of the IC process induced by a super-intense few-cycle soft-x-ray laser pulse in the case of the {sup 99m}Tc isomer is determined numerically. The results obtained for the IC coefficient show significant carrier angular frequency, carrier-envelope phase, and pulse-length dependencies. The infinite pulse-length limit and experimental aspects are also discussed.
Hursin, M.; Koeberl, O.; Perret, G.
2012-07-01
High Conversion Light Water Reactors (HCLWR) allows a better usage of fuel resources thanks to a higher breeding ratio than standard LWR. Their uses together with the current fleet of LWR constitute a fuel cycle thoroughly studied in Japan and the US today. However, one of the issues related to HCLWR is their void reactivity coefficient (VRC), which can be positive. Accurate predictions of void reactivity coefficient in HCLWR conditions and their comparisons with representative experiments are therefore required. In this paper an inter comparison of modern codes and cross-section libraries is performed for a former Benchmark on Void Reactivity Effect in PWRs conducted by the OECD/NEA. It shows an overview of the k-inf values and their associated VRC obtained for infinite lattice calculations with UO{sub 2} and highly enriched MOX fuel cells. The codes MCNPX2.5, TRIPOLI4.4 and CASMO-5 in conjunction with the libraries ENDF/B-VI.8, -VII.0, JEF-2.2 and JEFF-3.1 are used. A non-negligible spread of results for voided conditions is found for the high content MOX fuel. The spread of eigenvalues for the moderated and voided UO{sub 2} fuel are about 200 pcm and 700 pcm, respectively. The standard deviation for the VRCs for the UO{sub 2} fuel is about 0.7% while the one for the MOX fuel is about 13%. This work shows that an appropriate treatment of the unresolved resonance energy range is an important issue for the accurate determination of the void reactivity effect for HCLWR. A comparison to experimental results is needed to resolve the presented discrepancies. (authors)
Gualdrini, G; Ferrari, P
2007-01-01
Effective dose is the main radiation protection quantity. Progresses in radiation studies brought ICRP to revise ICRP 60 recommendations. A new publication, already circulated in form of draft, is expected to change some aspects of effective dose evaluation method. The organ absorbed doses for neutrons at various energies and incidence angles, necessary to estimate the effective dose, have been published in ICRU 57 and ICRP 74 reports for ADAM and EVA analytical male and female phantoms and similar calculations were also performed, based on the MCNP code, for VIP-MAN voxel phantom. The NORMAN voxel phantom, developed on the basis of magnetic resonance data of an adult male at HPA (formerly NRPB), is an accurate model (with a voxel element of approximately 8 mm(3)), which well approximates the standard man and has been already employed for radiation protection studies with photons. In the present paper, a modified version, called NORMAN-05, including a new organ, the salivary glands (as suggested in the mentioned ICRP draft), and a more detailed skeletal description, especially devoted to red bone marrow dose evaluation, has been employed with the Monte Carlo code MCNPX to calculate neutron conversion coefficients from thermal energies to 20 MeV. Some preliminary results, for antero-posterior and postero-anterior irradiation conditions, are presented and compared with the available published data. PMID:17502319
Observation of internal wave polarity conversion generated by a rising tide
NASA Astrophysics Data System (ADS)
Li, Lan; Wang, Caixia; Grimshaw, Roger
2015-05-01
The observations reported here are based on time series of in situ observation data in Laoshan Bay off the Qingdao coast. A chain of thermistors (T-chain) at a fixed location recorded a sequence of elevation internal waves followed by depression internal waves passing by over an elapsed time of about 1 h. This observed polarity conversion at a fixed location is caused by the vertical stratification variation mainly induced by the rising tide, which is believed to be the first reported observation of this kind. The process of an elevation internal wave train converting to a depression wave train is simulated using the variable-coefficient extended Korteweg-de Vries (veKdV) equation, which also provides a further comparison between theory and the reported observations.
Intense few-cycle hard-UV-pulse-induced internal conversion processes
Kis, Daniel; Kalman, Peter; Keszthelyi, Tamas
2010-08-15
The internal conversion coefficient for bound-free electron transition of originally energetically forbidden internal conversion processes induced by intense, few-cycle UV laser pulse of Gaussian shape in the case of isomers {sup 107}Ag{sup m} (K shell, E3, 25.47 keV), {sup 90}Nb{sup m} (L{sub 2} shell, M2+E3, 2.3 keV), {sup 183}W{sup m1}(M{sub 5} shell, E2, 1.79 keV), {sup 183}W{sup m2} (N{sub 1} shell, E1, 548 eV), and {sup 188}Re{sup m} (M{sub 2} shell, M3+E4, 2.63 keV), and {sup 235}U{sup m} (O{sub 4} and O{sub 5} shells, E3, 73.5 eV) is determined numerically. Experimental conditions and possibilities of the laser-induced internal conversion process of {sup 183}W{sup m2} from the N{sub 1} shell are discussed in more detail.
Alcohol fuel conversion apparatus for internal combustion engines
Carroll, B.I.
1987-01-13
An alcohol fuel conversion apparatus is described for internal combustion engines comprising: fuel storage means containing an alcohol fuel; primary heat exchanger means in fluid communication with the fuel storage means for transferring heat to pressurized alcohol contained within the heat exchanger means; a heat source for heating the heat exchange means; pressure relief valve means, in closed fluid communication with the primary heat exchange means, operable to release heated pressurized alcohol into an expansion chamber; converter means, including the expansion chamber, in fluid communication with the pressure relief valve means for receiving the heated pressurized alcohol and for the vaporization of the alcohol; carburetor means in fluid communication with the converter means for metering and mixing vaporized alcohol with air for proper combustion and for feeding the mixture to an internal combustion engine; and pump means for pressurized pumping of alcohol from the fuel storage means to the heat exchanger means, converter means, carburetor means, and to the engine.
Yamashita, Osamu Odahara, Hirotaka; Ochi, Takahiro; Satou, Kouji
2007-10-02
The thermo-emf {delta}V and current {delta}I generated by imposing the alternating temperature gradients (ATG) at a period of T and the steady temperature gradient (STG) on a thermoelectric (TE) composite were measured as a function of t, where t is the lapsed time and T was varied from 60 to or {infinity} s. The STG and ATG were produced by imposing steadily and alternatively a source voltage V in the range from 1.0 to 4.0 V on two Peltier modules sandwiching a composite. {delta}T, {delta}V, {delta}I and V{sub P} oscillate at a period T and their waveforms vary significantly with a change of T, where {delta}V and V{sub P} are the voltage drops in a load resistance R{sub L} and in resistance R{sub P} of two modules. The resultant Seebeck coefficient |{alpha}| = |{delta}V|/{delta}T of a composite under the STG was found to be expressed as |{alpha}| = |{alpha}{sub 0}|(1 - R{sub comp}/R{sub T}), where R{sub T} is the total resistance of a circuit for measuring the output signals and R{sub comp} is the resistance of a composite. The effective generating power {delta}W{sub eff} has a local maximum at T = 960 s for the p-type composite and at T = 480 s for the n-type one. The maximum energy conversion efficiency {eta} of the p- and n-type composites under the ATG produced by imposing a voltage of 4.0 V at an optimum period were 0.22 and 0.23% at {delta}T{sub eff} = 50 K, respectively, which are 42 and 43% higher than those at {delta}T = 42 K under the STG. These maximum {eta} for a TE composite sandwiched between two Peltier modules, were found to be expressed theoretically in terms of R{sub P}, R{sub T}, R{sub L}, {alpha}{sub P} and {alpha}, where {alpha}{sub P} and {alpha} are the resultant Seebeck coefficients of Peltier modules and a TE composite.
Conversion coefficients for the estimation of effective dose in cone-beam CT
Kim, Dong-Soo; Rashsuren, Oyuntugs
2014-01-01
Purpose To determine the conversion coefficients (CCs) from the dose-area product (DAP) value to effective dose in cone-beam CT. Materials and Methods A CBCT scanner with four fields of view (FOV) was used. Using two exposure settings of the adult standard and low dose exposure, DAP values were measured with a DAP meter in C mode (200mm×179 mm), P mode (154 mm×154 mm), I mode (102 mm×102 mm), and D mode (51 mm×51 mm). The effective doses were also investigated at each mode using an adult male head and neck phantom and thermoluminescent chips. Linear regressive analysis of the DAP and effective dose values was used to calculate the CCs for each CBCT examination. Results For the C mode, the P mode at the maxilla, and the P mode at the mandible, the CCs were 0.049 µSv/mGycm2, 0.067 µSv/mGycm2, and 0.064 µSv/mGycm2, respectively. For the I mode, the CCs at the maxilla and mandible were 0.076 µSv/mGycm2 and 0.095 µSv/mGycm2, respectively. For the D mode at the maxillary incisors, molars, and mandibular molars, the CCs were 0.038 µSv/mGycm2, 0.041 µSv/mGycm2, and 0.146 µSv/mGycm2, respectively. Conclusion The CCs in one CBCT device with fixed 80 kV ranged from 0.038 µSv/mGycm2 to 0.146 µSv/mGycm2 according to the imaging modes and irradiated region and were highest for the D mode at the mandibular molar. PMID:24701455
NASA Astrophysics Data System (ADS)
Nogueira, P.; Zankl, M.; Schlattl, H.; Vaz, P.
2011-11-01
The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation—the germinative cells—absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.
NASA Astrophysics Data System (ADS)
Krstic, D.; Nikezic, D.
2007-09-01
Dose conversion coefficients for different organs of age-dependent ORNL phantoms, due to the 137Cs in soil have been calculated using the MCNP-4B code. A cylindrical source at a depth of 20 cm was subdivided into 10 smaller cylinders, each of height 2 cm. Any one of these smaller cylinders could be considered as a source of photons with the energies of 661.6 keV. The ORNL phantoms stand exactly above the center of the cylinders. MCNP-4B energy deposition tally (F6) in MeV/g per one emitted photon was used to calculate absorbed doses in organs of phantoms. Then, conversion of units was made to obtain absorbed dose in fGy (femto-Gray) per Bq s kg -1. Absorbed doses in all major organs and the remainder, defined in reports ICRP60 and 74, were calculated as a function of the 137Cs source depth. Conversion coefficients decrease as the phantom age increases.
Electron-nucleus interaction in laser fields: The laser-assisted internal conversion process
NASA Astrophysics Data System (ADS)
Kálmán, Péter; Bükki, Tamás
2002-05-01
We present a general formalism for an efficient treatment of a broad range of electron-nucleus laser processes. The interaction with the laser beam is taken into account by transforming the system into an oscillating frame, called the Henneberger picture. General expressions for the transition probability per unit time are given in the weak laser field and in the n photonic cases, and connection to previous methods is demonstrated in the appropriate limits. As an example, the transition probability per unit time of laser-induced internal conversion (IC) processes is presented. The conservation of angular momentum in the multiphoton process can be traced well in our calculation. Numerical values of the IC coefficient of the energetically forbidden IC process in case of 99mTc ignited by the absorption of up to three soft-x-ray laser photons are also given. The increase in the rate of IC decay is found comparable to or greater than the natural decay rate of the isomer in case of appropriate intensity and photon energy of the laser. Hard UV laser-induced internal conversion coefficients (ICCs) are also calculated for energetically forbidden shells of 107Agm (K shell, E3, 25.47 keV), 90Nbm (L2 shell, M2+E3, 2.3 keV), 183Wm (N1 shell, E1, 544 eV and M5 shell, E2, 1.79 keV), 188Rem (M2 shell, M3+E4, 2.63 keV), 205Pbm (M5 shell, E2, 2.4 keV), and 235Um (O4 and O5 shells, E3, 73.5 eV). Measurable induced ICCs are found in case of available intensities and photon energies of the laser beam for the above isomers. Experiments, that may demonstrate the effect and may be tools for determination of nuclear transition energies, are also suggested.
Technology Transfer Automated Retrieval System (TEKTRAN)
An empirical correlation of volumetric mass transfer coefficient was developed for a pilot scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s pen...
Nogueira, P; Zankl, M; Schlattl, H; Vaz, P
2011-11-01
The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV. PMID:21983644
NASA Astrophysics Data System (ADS)
Glownia, J. H.; Misewich, J.; Sorokin, P. P.
1987-09-01
An apparatus combining subpicosecond 248.5 nm pump pulses with a time-resolved subpicosecond broadband infrared absorption spectroscopy probe has been utilized to measure an internal conversion rate in 1,4-diazabicyclo[2.2.2]octane vapor. A subpicosecond (⪅ 500 fs) internal conversion rate has been determined.
NASA Astrophysics Data System (ADS)
Chidambaram, N.; Balma, D.; Nigon, R.; Mazzalai, A.; Matloub, R.; Sandu, C. S.; Muralt, P.
2015-04-01
The use of interdigitated electrodes (IDEs) in conjunction with ferroelectric thin films shows many attractive features for piezoelectric MEMS applications. In this work, growth of {1 0 0}-textured lead zirconate titanate (PZT) thin films was achieved on insulating MgO buffered, oxidized silicon substrates. IDEs were fabricated by lift-off techniques and cantilevers were formed by dicing. The deflection upon application of a sweeping voltage was measured as large signal response in parallel to the ferroelectric polarization (PV loop). Likewise, the small signal piezoelectric response was measured in parallel to the capacitance-voltage (CV) measurement. In this way, a complete picture of the ferroelectric-piezoelectric element was obtained. From the deflection, the in-plane piezoelectric stress in the PZT thin film was derived and, from this, the effective piezoelectric coefficients. For the latter, two types were defined: an engineering type corresponding to the average value along the IDE, which can directly be compared to coefficient of a parallel plate electrode (PPE) capacitor and a second one that approximately yields the idealized coefficient governing between the electrode fingers. The IDE structures were experimentally compared with PPE structures of identical film thickness. The resulting coefficients were of opposite sign, as expected. In spite of a much better polarization loop, the IDE device showed a lower average piezoelectric stress. The estimated peak value between the fingers was about the same as in the PPE device, corresponding to about 20 C m-2. Nevertheless, the result is very promising for cases where compressive piezoelectric stresses are required and for preventing cracking due to large piezoelectric tensile stresses in PPE systems.
Coherent phase control of internal conversion in pyrazine
Gordon, Robert J. Singha, Sima; Zhao, Youbo; Hu, Zhan; Seideman, Tamar; Sukharev, Maxim
2015-04-14
Shaped ultrafast laser pulses were used to study and control the ionization dynamics of electronically excited pyrazine in a pump and probe experiment. For pump pulses created without feedback from the product signal, the ion growth curve (the parent ion signal as a function of pump/probe delay) was described quantitatively by the classical rate equations for internal conversion of the S{sub 2} and S{sub 1} states. Very different, non-classical behavior was observed when a genetic algorithm (GA) employing phase-only modulation was used to minimize the ion signal at some pre-determined target time, T. Two qualitatively different control mechanisms were identified for early (T < 1.5 ps) and late (T > 1.5 ps) target times. In the former case, the ion signal was largely suppressed for t < T, while for t ≫ T, the ion signal produced by the GA-optimized pulse and a transform limited (TL) pulse coalesced. In contrast, for T > 1.5 ps, the ion growth curve followed the classical rate equations for t < T, while for t ≫ T, the quantum yield for the GA-optimized pulse was much smaller than for a TL pulse. We interpret the first type of behavior as an indication that the wave packet produced by the pump laser is localized in a region of the S{sub 2} potential energy surface where the vertical ionization energy exceeds the probe photon energy, whereas the second type of behavior may be described by a reduced absorption cross section for S{sub 0} → S{sub 2} followed by incoherent decay of the excited molecules. Amplitude modulation observed in the spectrum of the shaped pulse may have contributed to the control mechanism, although this possibility is mitigated by the very small focal volume of the probe laser.
Coherent phase control of internal conversion in pyrazine.
Gordon, Robert J; Hu, Zhan; Seideman, Tamar; Singha, Sima; Sukharev, Maxim; Zhao, Youbo
2015-04-14
Shaped ultrafast laser pulses were used to study and control the ionization dynamics of electronically excited pyrazine in a pump and probe experiment. For pump pulses created without feedback from the product signal, the ion growth curve (the parent ion signal as a function of pump/probe delay) was described quantitatively by the classical rate equations for internal conversion of the S2 and S1 states. Very different, non-classical behavior was observed when a genetic algorithm (GA) employing phase-only modulation was used to minimize the ion signal at some pre-determined target time, T. Two qualitatively different control mechanisms were identified for early (T < 1.5 ps) and late (T > 1.5 ps) target times. In the former case, the ion signal was largely suppressed for t < T, while for t ≫ T, the ion signal produced by the GA-optimized pulse and a transform limited (TL) pulse coalesced. In contrast, for T > 1.5 ps, the ion growth curve followed the classical rate equations for t < T, while for t ≫ T, the quantum yield for the GA-optimized pulse was much smaller than for a TL pulse. We interpret the first type of behavior as an indication that the wave packet produced by the pump laser is localized in a region of the S2 potential energy surface where the vertical ionization energy exceeds the probe photon energy, whereas the second type of behavior may be described by a reduced absorption cross section for S0 → S2 followed by incoherent decay of the excited molecules. Amplitude modulation observed in the spectrum of the shaped pulse may have contributed to the control mechanism, although this possibility is mitigated by the very small focal volume of the probe laser. PMID:25877582
Coherent phase control of internal conversion in pyrazine
NASA Astrophysics Data System (ADS)
Gordon, Robert J.; Hu, Zhan; Seideman, Tamar; Singha, Sima; Sukharev, Maxim; Zhao, Youbo
2015-04-01
Shaped ultrafast laser pulses were used to study and control the ionization dynamics of electronically excited pyrazine in a pump and probe experiment. For pump pulses created without feedback from the product signal, the ion growth curve (the parent ion signal as a function of pump/probe delay) was described quantitatively by the classical rate equations for internal conversion of the S2 and S1 states. Very different, non-classical behavior was observed when a genetic algorithm (GA) employing phase-only modulation was used to minimize the ion signal at some pre-determined target time, T. Two qualitatively different control mechanisms were identified for early (T < 1.5 ps) and late (T > 1.5 ps) target times. In the former case, the ion signal was largely suppressed for t < T, while for t ≫ T, the ion signal produced by the GA-optimized pulse and a transform limited (TL) pulse coalesced. In contrast, for T > 1.5 ps, the ion growth curve followed the classical rate equations for t < T, while for t ≫ T, the quantum yield for the GA-optimized pulse was much smaller than for a TL pulse. We interpret the first type of behavior as an indication that the wave packet produced by the pump laser is localized in a region of the S2 potential energy surface where the vertical ionization energy exceeds the probe photon energy, whereas the second type of behavior may be described by a reduced absorption cross section for S0 → S2 followed by incoherent decay of the excited molecules. Amplitude modulation observed in the spectrum of the shaped pulse may have contributed to the control mechanism, although this possibility is mitigated by the very small focal volume of the probe laser.
Internal Conversion and Vibrational Energy Redistribution in Chlorophyll A.
Shenai, Prathamesh M; Fernandez-Alberti, Sebastian; Bricker, William P; Tretiak, Sergei; Zhao, Yang
2016-01-14
We have computationally investigated the role of intramolecular vibrational modes in determining nonradiative relaxation pathways of photoexcited electronic states in isolated chlorophyll A (ChlA) molecules. To simulate the excited state relaxation from the initially excited Soret state to the lowest excited state Qy, the approach of nonadiabatic excited state molecular dynamics has been adopted. The intramolecular vibrational energy relaxation and redistribution that accompany the electronic internal conversion process is followed by analyzing the excited state trajectories in terms of the ground state equilibrium normal modes. The time dependence of the normal mode velocities is determined by projecting instantaneous Cartesian velocities onto the normal mode vectors. Our analysis of the time evolution of the average mode energies uncovers that only a small subset of the medium-to-high frequency normal modes actively participate in the electronic relaxation processes. These active modes are characterized by the highest overlap with the nonadiabatic coupling vectors (NACRs) during the electronic transitions. Further statistical analysis of the nonadiabatic transitions reveals that the electronic and vibrational energy relaxation occurs via two distinct pathways with significantly different time scales on which the hopping from Soret to Qx occurs thereby dictating the overall dynamics. Furthermore, the NACRs corresponding to each of the transitions have been consistently found to be predominantly similar to a set of normal modes that vary depending upon the transition and the identified categories. Each pathway exhibits a differential time scale of energy transfer and also a differential set of predominant active modes. Our present analysis can be considered as a general approach allowing identification of a reduced subset of specific vibrational coordinates associated with nonradiative relaxation pathways. Therefore, it represents an adequate prior strategy that
Internal Evaluation a Quarter-Century Later: A Conversation with Arnold J. Love
ERIC Educational Resources Information Center
Volkov, Boris B.
2011-01-01
This chapter features a recent conversation with Dr. Arnold J. Love, a long-time proponent of internal evaluation and one of the most cited internal evaluation authors. In 1983, Love edited the first issue of "New Directions for Program Evaluation" on the topic of internal evaluation. He is the author of the book "Internal Evaluation: Building…
Measurement of K-shell fluorescent yield in iridium: testing internal-conversion theory
NASA Astrophysics Data System (ADS)
Montague, J. R.; Nica, N.; Iacob, V. E.; Hardy, J. C.
2004-10-01
Internal conversion coefficients (ICC) play an essential role in nuclear decay schemes. Even so, calculated ICCs agree with experiment only to within a few percent and, for transitions with high multipolarity and energies close to the electron binding energies, they depend strongly on whether the final state is taken to include the atomic vacancy created by the conversion process. Recently, we measured the ratio of K X-rays to γ -rays for the 80.2-keV M4 transition in ^193mIr, determined the product ω _Kα K and extracted α K using the value ω _K=0.958(4) taken from a global fit to a set of elements not including iridium. The result strongly supported the calculation that includes the vacancy. To solidify this result, we now report a new experiment to determine directly the ω K for iridium. We selected the 129.4-keV M1+E2 transition in ^191Ir for which the α K calculation is nearly independent of the vacancy treatment. We again used the X-to-γ decay-rate ratio but this time divided the result by the calculated α K to obtain ω _K. Our preliminary result is ω _K=0.948(8), in good agreement with the value taken from the global fit.
Olsher, R H; McLean, T D; Justus, A L; Devine, R T; Gadd, M S
2010-03-01
Monte Carlo simulations were performed to extend existing neutron personal dose equivalent fluence-to-dose conversion coefficients to an energy of 250 MeV. Presently, conversion coefficients, H(p,slab)(10,alpha)/Phi, are given by ICRP-74 and ICRU-57 for a range of angles of radiation incidence (alpha = 0, 15, 30, 45, 60 and 75 degrees ) in the energy range from thermal to 20 MeV. Standard practice has been to base operational dose quantity calculations <20 MeV on the kerma approximation, which assumes that charged particle secondaries are locally deposited, or at least that charged particle equilibrium exists within the tally cell volume. However, with increasing neutron energy the kerma approximation may no longer be valid for some energetic secondaries such as protons. The Los Alamos Monte Carlo radiation transport code MCNPX was used for all absorbed dose calculations. Transport models and collision-based energy deposition tallies were used for neutron energies >20 MeV. Both light and heavy ions (HIs) (carbon, nitrogen and oxygen recoil nuclei) were transported down to a lower energy limit (1 keV for light ions and 5 MeV for HIs). Track energy below the limit was assumed to be locally deposited. For neutron tracks <20 MeV, kerma factors were used to obtain absorbed dose. Results are presented for a discrete set of angles of incidence on an ICRU tissue slab phantom. PMID:19887515
NASA Astrophysics Data System (ADS)
Johnson, Perry; Lee, Choonsik; Johnson, Kevin; Siragusa, Daniel; Bolch, Wesley E.
2009-06-01
In this study, the influence of patient size on organ and effective dose conversion coefficients (DCCs) was investigated for a representative interventional fluoroscopic procedure—cardiac catheterization. The study was performed using hybrid phantoms representing an underweight, average and overweight American adult male. Reference body sizes were determined using the NHANES III database and parameterized based on standing height and total body mass. Organ and effective dose conversion coefficients were calculated for anterior-posterior, posterior-anterior, left anterior oblique and right anterior oblique projections using the Monte Carlo code MCNPX 2.5.0 with the metric dose area product being used as the normalization factor. Results show body size to have a clear influence on DCCs which increased noticeably when body size decreased. It was also shown that if patient size is neglected when choosing a DCC, the organ and effective dose will be underestimated to an underweight patient and will be overestimated to an underweight patient, with errors as large as 113% for certain projections. Results were further compared with those published for a KTMAN-2 Korean patient-specific tomographic phantom. The published DCCs aligned best with the hybrid phantom which most closely matched in overall body size. These results highlighted the need for and the advantages of phantom-patient matching, and it is recommended that hybrid phantoms be used to create a more diverse library of patient-dependent anthropomorphic phantoms for medical dose reconstruction.
Mclean, Thomas D; Justus, Alan L; Gadd, S Milan; Olsher, Richard H; Devine, Robert T
2009-01-01
Monte Carlo simulations were performed to extend existing neutron personal dose equivalent fluence-to-dose conversion coefficients to an energy of 250 MeV. Presently, conversion coefficients, H(p,slab)(10,alpha)/Phi, are given by ICRP-74 and ICRU-57 for a range of angles of radiation incidence (alpha = 0, 15, 30, 45, 60 and 75 degrees ) in the energy range from thermal to 20 MeV. Standard practice has been to base operational dose quantity calculations <20 MeV on the kerma approximation, which assumes that charged particle secondaries are locally deposited, or at least that charged particle equilibrium exists within the tally cell volume. However, with increasing neutron energy the kerma approximation may no longer be valid for some energetic secondaries such as protons. The Los Alamos Monte Carlo radiation transport code MCNPX was used for all absorbed dose calculations. Transport models and collision-based energy deposition tallies were used for neutron energies >20 MeV. Both light and heavy ions (HIs) (carbon, nitrogen and oxygen recoil nuclei) were transported down to a lower energy limit (1 keV for light ions and 5 MeV for HIs). Track energy below the limit was assumed to be locally deposited. For neutron tracks <20 MeV, kerma factors were used to obtain absorbed dose. Results are presented for a discrete set of angles of incidence on an ICRU tissue slab phantom.
NASA Astrophysics Data System (ADS)
Fujii, Ritsuko; Inaba, Toru; Watanabe, Yasutaka; Koyama, Yasushi; Zhang, Jian-Ping
2003-02-01
Near-infrared, subpicosecond time-resolved absorption spectroscopy of all- trans carotenoids having the number of conjugated double bonds, n=9-13, identified two different pathways of internal conversion in accordance with the energy diagram recently determined by measurements of resonance-Raman excitation profiles (RREPs) [K. Furuichi, T. Sashima, Y. Koyama, Chem. Phys. Lett. 356 (2002) 547]: the 1B u+→1B u-→2A g- internal conversion for neurosporene ( n=9) and spheroidene ( n=10), whereas the 1B u+→3A g-→2A g- internal conversion for lycopene ( n=11), anhydrorhodovibrin ( n=12) and spirilloxanthin ( n=13).
Conversion coefficients from fluence to effective dose for heavy ions with energies up to 3 GeV/A.
Sato, T; Tsuda, S; Sakamoto, Y; Yamaguchi, Y; Niita, K
2003-01-01
Radiological protection against high-energy heavy ions has been an essential issue in the planning of long-term space missions. The fluence to effective dose conversion coefficients have been calculated for heavy ions using the particle and heavy ion transport code system PHITS coupled with an anthropomorphic phantom of the MIRD5 type. The calculations were performed for incidences of protons and typical space heavy ions--deuterons, tritons, 3He, alpha particles, 12C, 20Ne, 40Ar, 40Ca and 56Fe--with energies up to 3 GeV/A in the isotropic and anterior-posterior irradiation geometries. A simple fitting formula that can predict the effective dose from almost all kinds of space heavy ions below 3 GeV/A within an accuracy of 30% is deduced from the results. PMID:14653334
5 CFR 315.712 - Conversion based on service as a Federal Career Intern.
Code of Federal Regulations, 2010 CFR
2010-01-01
... Career Intern. 315.712 Section 315.712 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS CAREER AND CAREER-CONDITIONAL EMPLOYMENT Conversion to Career or Career-Conditional Employment From Other Types of Employment § 315.712 Conversion based on service as a Federal Career...
5 CFR 315.712 - Conversion based on service as a Federal Career Intern.
Code of Federal Regulations, 2011 CFR
2011-01-01
... Career Intern. 315.712 Section 315.712 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS CAREER AND CAREER-CONDITIONAL EMPLOYMENT Conversion to Career or Career-Conditional Employment From Other Types of Employment § 315.712 Conversion based on service as a Federal Career...
5 CFR 315.712 - Conversion based on service as a Federal Career Intern.
Code of Federal Regulations, 2012 CFR
2012-01-01
... Career Intern. 315.712 Section 315.712 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS CAREER AND CAREER-CONDITIONAL EMPLOYMENT Conversion to Career or Career-Conditional Employment From Other Types of Employment § 315.712 Conversion based on service as a Federal Career...
NASA Astrophysics Data System (ADS)
Liu, Liye; Zeng, Zhi; Li, Junli; Qiu, Rui; Zhang, Binquan; Ma, Jizeng; Li, Ren; Li, Wenqian; Bi, Lei
2009-11-01
A high-resolution whole-body voxel model called CAM representing the Chinese adult male was constructed in this paper based on a previous individual voxel model. There are more than 80 tissues and organs in CAM, including almost all organs required in the ICRP new recommendation. The mass of individual organs has been adjusted to the Chinese reference data. Special considerations were given to representing the gross spatial distribution of various bone constituents as realistically as possible during the construction of the site-specific skeleton. Organ dose conversion coefficients were calculated for six idealized external photon exposures from 10 keV to 10 MeV by using Monte Carlo simulation. The resulting dose coefficients were then compared with those from other models, e.g. CMP, ICRP 74, Rex, HDRK-man and VIP-man. Old and new effective male doses of CAM were calculated by using the tissue weighting factors from ICRP 60 and 103 Publications, respectively. Dosimetric differences between mathematical and voxel models, and the differences between Asian and Caucasian models are also discussed in this paper.
Liu, Liye; Zeng, Zhi; Li, Junli; Qiu, Rui; Zhang, Binquan; Ma, Jizeng; Li, Ren; Li, Wenqian; Bi, Lei
2009-11-01
A high-resolution whole-body voxel model called CAM representing the Chinese adult male was constructed in this paper based on a previous individual voxel model. There are more than 80 tissues and organs in CAM, including almost all organs required in the ICRP new recommendation. The mass of individual organs has been adjusted to the Chinese reference data. Special considerations were given to representing the gross spatial distribution of various bone constituents as realistically as possible during the construction of the site-specific skeleton. Organ dose conversion coefficients were calculated for six idealized external photon exposures from 10 keV to 10 MeV by using Monte Carlo simulation. The resulting dose coefficients were then compared with those from other models, e.g. CMP, ICRP 74, Rex, HDRK-man and VIP-man. Old and new effective male doses of CAM were calculated by using the tissue weighting factors from ICRP 60 and 103 Publications, respectively. Dosimetric differences between mathematical and voxel models, and the differences between Asian and Caucasian models are also discussed in this paper. PMID:19841518
Topical applications of resonance internal conversion in laser produced plasma
NASA Astrophysics Data System (ADS)
Karpeshin, F. F.
2007-04-01
Physical aspects of resonance effects arising in plasma due to interactions of nuclei with the electrons are considered. Among them are resonance conversion (TEEN) and the reverse process of NEET. These processes are of great importance for pumping the excited nuclear states (isomers) and for accelerating their decay. Experiment is discussed on studying the unique 3.5-eV 229m Th nuclide.
Sato, Motoki; Adachi, Shunsuke; Suzuki, Toshinori
2016-07-14
Isomerization of tetramethylethylene (TME) following ultrafast internal conversion was investigated using time-resolved photoelectron spectroscopy with vacuum-ultraviolet probe pulses. The difference photoelectron spectrum at τ = 15 ps was reasonably well reproduced using a linear combination of static photoelectron spectra of TME and its isomers. The isomers were produced as a consequence of unimolecular reaction of vibrationally hot TME, created by internal conversion from the excited state. PMID:27030934
Wiebke, Jonas; Pahl, Elke; Schwerdtfeger, Peter
2012-07-01
A simple and efficient internal-coordinate importance sampling protocol for the Monte Carlo computation of (up to fourth-order) virial coefficients ̅B(n) of atomic systems is proposed. The key feature is a multivariate sampling distribution that mimics the product structure of the dominating pairwise-additive parts of the ̅B(n). This scheme is shown to be competitive over routine numerical methods and, as a proof of principle, applied to neon: The second, third, and fourth virial coefficients of neon as well as equation-of-state data are computed from ab initio two- and three-body potentials; four-body contributions are found to be insignificant. Kirkwood-Wigner quantum corrections to first order are found to be crucial to the observed agreement with recent ab initio and experimental reference data sets but are likely inadequate at very low temperatures. PMID:22779666
The maximum coefficient of performance of internally irreversible refrigerators and heat pumps
NASA Astrophysics Data System (ADS)
Ait-Ali, Mohand A.
1996-04-01
A class of irreversible refrigeration cycles is investigated to determine the maximum coefficient of performance in the heat pump mode and the refrigerator mode. For the purpose of generality and simplicity of the results, finite-time heat transfer in the condenser and evaporator is expressed in terms of arithmetic mean temperature differences. The generic source of internal irreversibility is measured by a single irreversibility factor which transforms the Clausius inequality into an equality to simplify the cycle model. These optimum cycle performances are obtained as closed form analytical expressions in which the irreversibility factor has been shown to be simply related to the ratio of the actual and endoreversible cycle coefficients of performance.
Bourgois, L; Antoni, R
2016-01-01
Conversion coefficients fluence to local skin equivalent dose, as introduced in ICRP Publication 116, 2010, are calculated for positrons of energies ranging from 10 keV to 10 MeV using the code MCNP6. Fluence to dose equivalent conversion coefficients H'(0.07,0°)/Φ are calculated for positrons of energy ranging between 20 keV and 10 MeV. A comparison between operational dose quantity H'(0.07,0°) and the Local-Skin equivalent Dose shows an overall good agreement between these two quantities, except between 60 keV and 100 keV. PMID:26623930
Suzuki, Toshinori
2014-01-01
This article describes our recent experimental studies on internal conversion via a conical intersection using photoelectron spectroscopy. Ultrafast S2(ππ*)-S1(nπ*) internal conversion in pyrazine is observed in real time using sub-20 fs deep ultraviolet pulses (264 and 198 nm). While the photoelectron kinetic energy distribution does not exhibit a clear signature of internal conversion, the photoelectron angular anisotropy unambiguously reveals the sudden change of electron configuration upon internal conversion. An explanation is presented as to why these two observables have different sensitivities to internal conversion. The 198 nm probe photon energy is insufficient for covering the entire Franck-Condon envelopes upon photoionization from S2/S1 to D1/D0. A vacuum ultraviolet free electron laser (SCSS) producing 161 nm radiation is employed to solve this problem, while its pulse-to-pulse timing jitter limits the time resolution to about 1 ps. The S2-S1 internal conversion is revisited using the sub-20 fs 159 nm pulse created by filamentation four-wave mixing. Conical intersections between D1(π-1) and D0(n-1) and also between the Rydberg state with a D1 ion core and that with a D0 ion core of pyrazine are studied by He(I) photoelectron spectroscopy, pulsed field ionization photoelectron spectroscopy and one-color resonance-enhanced multiphoton ionization spectroscopy. Finally, ultrafast S2(ππ*)-S1(ππ*) internal conversion in benzene and toluene are compared with pyrazine. PMID:24566311
Inequalities, the arts and public health: Towards an international conversation
Parkinson, Clive; White, Mike
2014-01-01
This paper considers how participatory arts informed by thinking in public health can play a significant part internationally in addressing inequalities in health. It looks beyond national overviews of arts and health to consider what would make for meaningful international practice, citing recent initiatives of national networks in English-speaking countries and examples of influential developments in South America and the European Union. In the context of public health thinking on inequalities and social justice, the paper posits what would make for good practice and appropriate research that impacts on policy. As the arts and health movement gathers momentum, the paper urges the arts to describe their potency in the policy-making arena in the most compelling ways to articulate their social, economic and cultural values. In the process, it identifies the reflexive consideration of participatory practice – involving people routinely marginalised from decision-making processes – as a possible avenue into this work. PMID:25729409
Patni, H K; Nadar, M Y; Akar, D K; Bhati, S; Sarkar, P K
2011-11-01
The adult reference male and female computational voxel phantoms recommended by ICRP are adapted into the Monte Carlo transport code FLUKA. The FLUKA code is then utilised for computation of dose conversion coefficients (DCCs) expressed in absorbed dose per air kerma free-in-air for colon, lungs, stomach wall, breast, gonads, urinary bladder, oesophagus, liver and thyroid due to a broad parallel beam of mono-energetic photons impinging in anterior-posterior and posterior-anterior directions in the energy range of 15 keV-10 MeV. The computed DCCs of colon, lungs, stomach wall and breast are found to be in good agreement with the results published in ICRP publication 110. The present work thus validates the use of FLUKA code in computation of organ DCCs for photons using ICRP adult voxel phantoms. Further, the DCCs for gonads, urinary bladder, oesophagus, liver and thyroid are evaluated and compared with results published in ICRP 74 in the above-mentioned energy range and geometries. Significant differences in DCCs are observed for breast, testis and thyroid above 1 MeV, and for most of the organs at energies below 60 keV in comparison with the results published in ICRP 74. The DCCs of female voxel phantom were found to be higher in comparison with male phantom for almost all organs in both the geometries. PMID:21147784
Experimental demonstration of internal wavelength conversion in the magnesium atomic filter.
Chan, Y C; Tabat, M D; Gelbwachs, J A
1989-07-15
We describe what is to our knowledge the first experimental demonstration of internal wavelength conversion in the metastable Mg atomic filter. The filter operates at a Fraunhofer line, thereby offering intrinsic solar background rejection. Incoming green Fraunhofer photons (518 nm) are absorbed by metastable Mg atoms in an oven cell and are converted into UV (384-nm) photons. We observed a green-to-UV conversion efficiency of greater than 50%. PMID:19752947
NASA Technical Reports Server (NTRS)
Paden, Jack; Pandey, Dhirendra K.; Shivakumar, Netra D.; Stassi, Joseph C.; Wilson, Robert; Bolden, William; Thomas, Susan; Gibson, M. Alan
1991-01-01
A compendium is presented of the ground and inflight scanner and nonscanner offsets and count conversion (gain) coefficients used for the Earth Radiation Budget Experiment (ERBE) production processing of data from the ERBS, NOAA-9, and NOAA-10 satellites for the 1 Nov. 1984 to 31 Dec. 1986.
ERIC Educational Resources Information Center
Tozer, Erinn E.; Hayes, Jeffrey A.
2004-01-01
This study examined the potential influence of religiosity, sexual orientation identity development, and internalized homonegativity on the propensity to seek conversion therapy to change one's sexual orientation. An Internet sample of 76 women and 130 men who were gay-identified, lesbian-identified, same-sex attracted, and "questioning" was…
Leenheer, Andrew J.; Narang, Prineha; Atwater, Harry A.; Lewis, Nathan S.
2014-04-07
Collection of hot electrons generated by the efficient absorption of light in metallic nanostructures, in contact with semiconductor substrates can provide a basis for the construction of solar energy-conversion devices. Herein, we evaluate theoretically the energy-conversion efficiency of systems that rely on internal photoemission processes at metal-semiconductor Schottky-barrier diodes. In this theory, the current-voltage characteristics are given by the internal photoemission yield as well as by the thermionic dark current over a varied-energy barrier height. The Fowler model, in all cases, predicts solar energy-conversion efficiencies of <1% for such systems. However, relaxation of the assumptions regarding constraints on the escape cone and momentum conservation at the interface yields solar energy-conversion efficiencies as high as 1%–10%, under some assumed (albeit optimistic) operating conditions. Under these conditions, the energy-conversion efficiency is mainly limited by the thermionic dark current, the distribution of hot electron energies, and hot-electron momentum considerations.
Jacques, S L; McAuliffe, D J
1991-06-01
The explosive vaporization of melanosomes in situ in skin during pulsed laser irradiation (pulse duration less than 1 microsecond) is observed as a visible whitening of the superficial epidermal layer due to stratum corneum disruption. In this study, the ruby laser (694 nm) was used to determine the threshold radiant exposure, H0 (J/cm2), required to elicit whitening for in vitro black (Negroid) human skin samples which were pre-equilibrated at an initial temperature, Ti, of 0, 20, or 50 degrees C. A plot of H0 vs Ti yields a straight line whose x-intercept indicates the threshold temperature of explosive vaporization to be 112 +/- 7 degrees C (SD, N = 3). The slope, delta H0/delta Ti, specifies the internal absorption coefficient, mua, within the melanosome: mua = -rho C/(slope(1 + 7.1 Rd)), where rho C is the product of density and specific heat, and Rd is the total diffuse reflectance from the skin. A summary of the absorption spectrum (mua) for the melanosome interior (351-1064 nm) is presented based on H0 data from this study and the literature. The in vivo absorption spectrum (380-820 nm) for human epidermal melanin was measured by an optical fiber spectrophotometer and is compared with the melanosome spectrum. PMID:1886936
NASA Technical Reports Server (NTRS)
Paden, Jack; Pandey, Dhirendra K.; Stassi, Joseph C.; Wilson, Robert; Bolden, William; Thomas, Susan; Gibson, M. Alan
1993-01-01
This document contains a compendium of the ground and in-flight scanner and non-scanner offsets and count conversion (gain) coefficients used for the Earth Radiation Budget Experiment (ERBE) production processing of data from the ERBS satellite for the period from 1 January 1987 to 31 December 1989; for the NOAA-9 satellite, for the month of January 1987; and for the NOAA-10 satellite, for the period from 1 January 1987 to 31 May 1989.
NASA Astrophysics Data System (ADS)
Alves, M. C.; Santos, W. S.; Lee, Choonsik; Bolch, Wesley E.; Hunt, John G.; Carvalho Júnior, A. B.
2014-12-01
The conversion coefficients (CCs) relate protection quantities, mean absorbed dose (DT) and effective dose (E), with physical radiation field quantities, such as fluence (Φ). The calculation of CCs through Monte Carlo simulations is useful for estimating the dose in individuals exposed to radiation. The aim of this work was the calculation of conversion coefficients for absorbed and effective doses per fluence (DT/ Φ and E/Φ) using a sitting and standing female hybrid phantom (UFH/NCI) exposure to monoenergetic protons with energy ranging from 2 MeV to 10 GeV. The radiation transport code MCNPX was used to develop exposure scenarios implementing the female UFH/NCI phantom in sitting and standing postures. Whole-body irradiations were performed using the recommended irradiation geometries by ICRP publication 116 (AP, PA, RLAT, LLAT, ROT and ISO). In most organs, the conversion coefficients DT/Φ were similar for both postures. However, relative differences were significant for organs located in the abdominal region, such as ovaries, uterus and urinary bladder, especially in the AP, RLAT and LLAT geometries. Anatomical differences caused by changing the posture of the female UFH/NCI phantom led an attenuation of incident protons with energies below 150 MeV by the thigh of the phantom in the sitting posture, for the front-to-back irradiation, and by the arms and hands of the phantom in the standing posture, for the lateral irradiation.
Beidler, C. D.; Allmaier, K.; Isaev, Maxim Yu; Kasilov, K.; Kernbichler, W.; Leitold, G.; Maassberg, H.; Mikkelsen, D. R.; Murakami, Masanori; Schmidt, M.; Spong, Donald A; Tribaidos, V.; Wakasa, A.
2011-01-01
Numerical results for the three mono-energetic transport coefficients required for a complete neoclassical description of stellarator plasmas have been benchmarked within an international collaboration. These transport coefficients are flux-surface-averaged moments of solutions to the linearized drift kinetic equation which have been determined using field-line-integration techniques, Monte Carlo simulations, a variational method employing Fourier-Legendre test functions and a finite-difference scheme. The benchmarking has been successfully carried out for past, present and future devices which represent different optimization strategies within the extensive configuration space available to stellarators. A qualitative comparison of the results with theoretical expectations for simple model fields is provided. The behaviour of the results for the mono-energetic radial and parallel transport coefficients can be largely understood from such theoretical considerations but the mono-energetic bootstrap current coefficient exhibits characteristics which have not been predicted.
NASA Astrophysics Data System (ADS)
Bachilo, S. M.; Spangler, C. W.; Gillbro, T.
1998-02-01
Time-resolved and steady-state fluorescence investigations on a series of α,ω-diphenylpolyenes have been made. Dual S 1/S 2 fluorescence was observed for polyenes with more than three double bonds in the polyene chain and the intensity and lifetime of the S 1 fluorescence decreased with increasing chain length. The 1B u energy was almost inversely proportional to the square root of the total molecular length. A similar dependence was found for the energy of the 1A g level, but the length without the phenyl rings was used. The logarithm of the S 1→S 0 internal conversion rate in long-chain diphenylpolyenes exhibits a linear dependence on the S 1 energy. The rate in diphenylhexatriene is slightly higher than the value predicted from the linear dependence, while the internal conversion of diphenylbutadiene is much faster due to stronger S 1-S 2 interaction.
A new interpretation of internal heat transfer coefficients of porous media
NASA Technical Reports Server (NTRS)
Dybbs, A.; Kar, K.; Groeneweg, M.; Ling, J. X.; Naraghi, M.
1984-01-01
The results of laser anemometer and flow visualization based fluid mechanics studies of porous media are used to obtain heat transfer coefficients for porous materials. Average pore flow Re ranging from 0.16-700 were examined. Darcy, inertial steady laminar, unsteady laminar and turbulent flow regimes were detected. A passage length model was devised to derive the heat transfer coefficient. Sample data from flows through porous metals composed of powders and fibers validated the passage length for Darcy and inertial flow regimes. Unsteady laminar and turbulent flow coefficients require the identification of new parameters.
Raffo-Caiado, Ana Claudia; Begovich, John M; Ferrada, Juan J
2009-11-01
This is the final report that closed a joint collaboration effort between DOE and the National Nuclear Energy Commission of Brazil (CNEN). In 2005, DOE and CNEN started a collaborative effort to evaluate measures that can strengthen the effectiveness of international safeguards at a natural uranium conversion plant (NUCP). The work was performed by DOE s Oak Ridge National Laboratory and CNEN. A generic model of a NUCP was developed and typical processing steps were defined. Advanced instrumentation and techniques for verification purposes were identified and investigated. The scope of the work was triggered by the International Atomic Energy Agency s 2003 revised policy concerning the starting point of safeguards at uranium conversion facilities. Prior to this policy only the final products of the uranium conversion plant were considered to be of composition and purity suitable for use in the nuclear fuel cycle and therefore, subject to the IAEA safeguards control. DOE and CNEN have explored options for implementing the IAEA policy, although Brazil understands that the new policy established by the IAEA is beyond the framework of the Quadripartite Agreement of which it is one of the parties, together with Argentina, the Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials (ABACC) and the IAEA. Two technical papers on this subject were published at the 2005 and 2008 INMM Annual Meetings.
Psychometric Inferences from a Meta-Analysis of Reliability and Internal Consistency Coefficients
ERIC Educational Resources Information Center
Botella, Juan; Suero, Manuel; Gambara, Hilda
2010-01-01
A meta-analysis of the reliability of the scores from a specific test, also called reliability generalization, allows the quantitative synthesis of its properties from a set of studies. It is usually assumed that part of the variation in the reliability coefficients is due to some unknown and implicit mechanism that restricts and biases the…
NASA Astrophysics Data System (ADS)
Nolan, J.; Nica, N.; Hardy, J. C.; Hernberg, M.; Goodwin, J. R.; Iacob, V. E.
2008-10-01
Precise values for internal conversion coefficients (ICCs) are important in the study of nuclear decay schemes; they are also useful for detector efficiency calibration. A recent survey revealed that few measured ICCs are known to a high precision (˜ 1%); in addition, there is some theoretical uncertainty over how to deal with the atomic vacancy left by the departing electron during the internal conversion process. Texas A&M has previously precisely measured the ICCs for ^193Ir, ^137Ba, and ^134Cs as a test of internal conversion theory; we now consider the ICC for ^197Pt^m as a further test. The ^197Pt^m was produced by thermal neutron activation of separated ^196Pt (97.43% pure). Two separate sources were produced; x-ray and gamma-ray emissions from each source were recorded by a High Purity Germanium Detector (+/- 0.20% absolute efficiency uncertainty). After impurity subtraction and attenuation correction, preliminary results for the αk value for the two sources have now been obtained. The αk from source one is 4.24 (13); the αk from source two is 4.26 (8). While these values are still tentative, the results show agreement with the theory that considers the atomic vacancy.
Mokhtari, Arash; Preußler, Stefan; Jamshidi, Kambiz; Akbari, Mahmood; Schneider, Thomas
2012-09-24
A fully electrically tunable microwave photonic filter is realized by the implementation of delay lines based on frequency-time conversion. The frequency response and free spectral range (FSR) of the filter can be engineered by a simple electrical tuning of the delay lines. The method has the capability of being integrated on a silicon photonic platform. In the experiment, a 2-tap tunable microwave photonic filter with a 3-dB bandwidth of 2.55 GHz, a FSR of 4.016 GHz, a FSR maximum tuning range from -354 MHz to 354 MHz and a full FSR translation range is achieved. PMID:23037423
Huix-Rotllant, Miquel; Tamura, Hiroyuki; Burghardt, Irene
2015-05-01
Quantum-dynamical simulations are used to investigate the interplay of exciton delocalization and vibronically induced internal conversion processes in the elementary charge separation steps at regioregular donor-acceptor heterojunctions. Ultrafast internal conversion leads to efficient deexcitation within the excitonic and charge transfer manifolds, thus modifying the charge separation dynamics. We address a model donor-acceptor junction representative of regioregular P3HT-PCBM, using high-dimensional quantum dynamics simulations by multiconfigurational methods. While partial trapping into an interfacial charge separated state occurs, long-range charge-separated states are accessed as previously demonstrated in the work of Tamura and Burghardt [J. Am. Chem. Soc. 2013, 135, 16364]. For an H-aggregate type, stacked donor species, the initial bright state undergoes ultrafast internal conversion within the excitonic manifold, creating multiple charge transfer pathways before reaching the lowest-energy dark exciton, which is uncoupled from the charge transfer manifold. This process profoundly affects the charge separation mechanism and efficiency. For small energetic offsets between the interfacial excitonic and charge transfer states, a delocalized initial bright state proves less prone to electron-hole capture by the interfacial trap than a localized, vibronic wavepacket close to the interface. For both delocalized and localized initial states, a comparable yield of free carriers is obtained, which is found to be optimal for energetic offsets of the order of the Coulomb barrier to charge separation. Interfacial trapping is significantly reduced as the barrier height decreases with fullerene aggregation. Despite the high-dimensional nature of the system, charge separation is an ultrafast coherent quantum process exhibiting oscillatory features as observed in recent experiments. PMID:26263337
NASA Astrophysics Data System (ADS)
Curchod, Basile F. E.; Rauer, Clemens; Marquetand, Philipp; González, Leticia; Martínez, Todd J.
2016-03-01
Full multiple spawning is a formally exact method to describe the excited-state dynamics of molecular systems beyond the Born-Oppenheimer approximation. However, it has been limited until now to the description of radiationless transitions taking place between electronic states with the same spin multiplicity. This Communication presents a generalization of the full and ab initio multiple spawning methods to both internal conversion (mediated by nonadiabatic coupling terms) and intersystem crossing events (triggered by spin-orbit coupling matrix elements) based on a spin-diabatic representation. The results of two numerical applications, a model system and the deactivation of thioformaldehyde, validate the presented formalism and its implementation.
Liebel, M; Schnedermann, C; Kukura, P
2014-05-16
Coupling of nuclear and electronic degrees of freedom mediates energy flow in molecules after optical excitation. The associated coherent dynamics in polyatomic systems, however, remain experimentally unexplored. Here, we combined transient absorption spectroscopy with electronic population control to reveal nuclear wave packet dynamics during the S2 → S1 internal conversion in β-carotene. We show that passage through a conical intersection is vibrationally coherent and thereby provides direct feedback on the role of different vibrational coordinates in the breakdown of the Born-Oppenheimer approximation. PMID:24877970
Lai, M.; Botsis, J.; Coric, D.; Cugnoni, J.
2008-08-28
The increasing needs of extending the lifetime in high-technology fields, such as space and aerospace, rail transport and naval systems, require quality enhancing of the composite materials either from a processing standing point or in the sense of resistance to service conditions. It is well accepted that the final quality of composite materials and structures is strongly influenced by processing parameters like curing and post-curing temperatures, rate of heating and cooling, applied vacuum, etc. To optimize manufacturing cycles, residual strains evolution due to chemical shrinkage and other physical parameters of the constituent materials must be characterized in situ. Such knowledge can lead to a sensible reduction in defects and to improved physical and mechanical properties of final products. In this context continuous monitoring of strains distribution developed during processing is important in understanding and retrieving components' and materials' characteristics such as local strains gradients, degree of curing, coefficient of thermal expansion, moisture absorption, etc.
NASA Astrophysics Data System (ADS)
Werner, Ute; Mitrić, Roland; Bonačić-Koutecký, Vlasta
2010-05-01
We present an approach for the simulation of time resolved photoelectron spectra based on the combination of the ab initio nonadiabatic molecular dynamics "on the fly" with the Stieltjes imaging method utilizing discrete neutral states above the ionization limit for the approximate description of the ionization continuum. Our approach has been implemented in the framework of the time-dependent density functional theory and has been applied to interrogate the ultrafast internal conversion between the S2 and S1 states in pyrazine. The simulations reveal that, parallel to the S2→S1 internal conversion, a change in the dominant ionization process (S2→D1 versus S1→D0) occurs on the time scale of 20 fs such that no significant change in the photoelectron kinetic energy distribution is observed. The presented results are in full agreement with the experimental results presented in the accompanying paper [Suzuki et al., J. Chem. Phys. 132, 174302 (2010)] and provide an insight into the interplay between the nonradiative relaxation and the photoionization process in pyrazine as reflected in the time resolved photoelectron spectrum. Our approach represents a general tool for the investigation of ultrafast photoionization processes in complex systems and thus can be used to investigate the ultrafast femtochemistry of complex molecular systems including all degrees of freedom.
Nica, N.; Hardy, J.C.; Iacob, V.E.; Montague, J.R.; Trzhaskovskaya, M.B.
2005-05-01
We have measured the total intensity of K x rays relative to 129.4-keV {gamma} rays from decay of the second excited state in {sup 191}Ir. This (M1+E2) transition was observed following the {beta} decay of 15.4-d {sup 191}Os. Our measured ratio yields the result {alpha}{sub K}{omega}{sub K}=2.044(11). When combined with a recent measurement of the same ratio for the 80.2-keV M4 transition from {sup 193}Ir{sup m}, this result strongly confirms the need for the K-shell hole to be included in calculations of internal-conversion coefficients {alpha}{sub K}. Since the {alpha}{sub K} value calculated for the {sup 191}Ir transition is virtually independent of the hole treatment, our result also yields a model-independent value for the iridium fluorescence yield, {omega}{sub K}=0.954(9)
Masuda, Ryo Kobayashi, Yasuhiro; Kitao, Shinji; Kurokuzu, Masayuki; Saito, Makina; Mitsui, Takaya; Iga, Fumitoshi; Seto, Makoto
2014-02-24
A detection system for synchrotron-radiation (SR)-based Mössbauer spectroscopy was developed to enhance the nuclear resonant scattering counting rate and thus increase the available nuclides. In the system, a windowless avalanche photodiode (APD) detector was combined with a vacuum cryostat to detect the internal conversion (IC) electrons and fluorescent X-rays accompanied by nuclear de-excitation. As a feasibility study, the SR-based Mössbauer spectrum using the 76.5 keV level of {sup 174}Yb was observed without {sup 174}Yb enrichment of the samples. The counting rate was five times higher than that of our previous system, and the spectrum was obtained within 10 h. This result shows that nuclear resonance events can be more efficiently detected by counting IC electrons for nuclides with high IC coefficients. Furthermore, the windowless detection system enables us to place the sample closer to the APD elements and is advantageous for nuclear resonant inelastic scattering measurements. Therefore, this detection system can not only increase the number of nuclides accessible in SR-based Mössbauer spectroscopy but also allows the nuclear resonant inelastic scattering measurements of small single crystals or enzymes with dilute probe nuclides that are difficult to measure with the previous detection system.
DOE R&D Accomplishments Database
Sibener, S. J.; Lee, Y. T.
1978-05-01
An experiment was performed which confirms the existence of an internal mode dependence of molecular sticking probabilities for collisions of molecules with a cold surface. The scattering of a velocity selected effusive beam of CCl{sub 4} from a 90 K CC1{sub 4} ice surface has been studied at five translational velocities and for two different internal temperatures. At a surface temperature of 90 K (approx. 99% sticking probability) a four fold increase in reflected intensity was observed for the internally excited (560 K) CC1{sub 4} relative to the room temperature (298 K) CC1{sub 4} at a translational velocity of 2.5 X 10{sup 4} cm/sec. For a surface temperature of 90 K all angular distributions were found to peak 15{sup 0} superspecularly independent of incident velocity.
ERIC Educational Resources Information Center
Colombani, Olivier; Langelier, Ophelie; Martwong, Ekkachai; Castignolles, Patrice
2011-01-01
The use of an internal standard is a conventional and convenient way to monitor the conversion of one or several monomers during a controlled radical polymerization. However, the validity of this technique relies on an accurate determination of the initial monomer-to-internal standard ratio, A[subscript 0], because all subsequent calculations of…
NASA Astrophysics Data System (ADS)
Galeano, D. C.; Santos, W. S.; Alves, M. C.; Souza, D. N.; Carvalho, A. B.
2016-04-01
The aim of this work was to modify the standing posture of the anthropomorphic reference phantoms of ICRP publication 110, AM (Adult Male) and AF (Adult Female), to the sitting posture. The change of posture was performed using the Visual Monte Carlo software (VMC) to rotate the thigh region of the phantoms and position it between the region of the leg and trunk. Scion Image software was used to reconstruct and smooth the knee and hip contours of the phantoms in a sitting posture. For 3D visualization of phantoms, the VolView software was used. In the change of postures, the organ and tissue masses were preserved. The MCNPX was used to calculate the equivalent and effective dose conversion coefficients (CCs) per fluence for photons for six irradiation geometries suggested by ICRP publication 110 (AP, PA, RLAT, LLAT, ROT and ISO) and energy range 0.010-10 MeV. The results were compared between the standing and sitting postures, for both sexes, in order to evaluate the differences of scattering and absorption of radiation for different postures. Significant differences in the CCs for equivalent dose were observed in the gonads, colon, prostate, urinary bladder and uterus, which are present in the pelvic region, and in organs distributed throughout the body, such as the lymphatic nodes, muscle, skeleton and skin, for the phantoms of both sexes. CCs for effective dose showed significant differences of up to 16% in the AP irradiation geometry, 27% in the PA irradiation geometry and 13% in the ROT irradiation geometry. These results demonstrate the importance of using phantoms in different postures in order to obtain more precise conversion coefficients for a given exposure scenario.
Kölle, Patrick; Schnappinger, Thomas; de Vivie-Riedle, Regina
2016-03-21
Oligothiophenes and polythiophenes are building blocks of organic-based energy conversion materials. Therefore the lifetime of the excited states plays a central role. As a first step to understand the factors influencing the performance, we investigated the deactivation processes from the first excited state S1 of thiophene and small oligothiophenes containing up to four rings using quantum chemical calculations. For thiophene a low-lying S1/S0 conical intersection seam is easily accessible and drives the fast internal conversion. In oligothiophenes barriers inhibit this passage while deactivation pathways via intersystem crossing channels open. The first one is responsible for the high triplet quantum yields and takes place shortly after the Franck-Condon region. The second one occurs in the vicinity of a local S1 minimum. The calculated spin-orbit coupling strength together with the singlet-triplet energy gaps can explain the decreasing triplet and increasing fluorescence quantum yields for growing chain length. From the triplets the ground state is reachable by inter-ring torsions and T1/S0 intersections. The present results allow a deeper understanding of the deactivation pathways of thiophene and small oligothiophenes and are of potential interest for the photophysics of longer oligothiophenes and polythiophenes used in optical devices. PMID:26914290
Curchod, Basile F. E.; Rauer, Clemens; Marquetand, Philipp; Gonzalez, Leticia; Martinez, Todd J.
2016-03-11
Full Multiple Spawning is a formally exact method to describe the excited-state dynamics of molecular systems beyond the Born-Oppenheimer approximation. However, it has been limited until now to the description of radiationless transitions taking place between electronic states with the same spin multiplicity. This Communication presents a generalization of the full and ab initio Multiple Spawning methods to both internal conversion (mediated by nonadiabatic coupling terms) and intersystem crossing events (triggered by spin-orbit coupling matrix elements) based on a spin-diabatic representation. Lastly, the results of two numerical applications, a model system and the deactivation of thioformaldehyde, validate the presented formalismmore » and its implementation.« less
Cyr, D.R.; Hayden, C.C.
1995-08-01
The authors have studied the dynamics of ultrafast internal conversion processes using femtosecond time-resolved photoionization and photoelectron spectroscopy. In hexatriene, following femtosecond pulse excitation at 250 nm, they use time-delayed photoionization to observe the formation and decay of an intermediate species on the subpicosecond time scale. With time-resolved photoelectron spectroscopy, the rapid evolution of vibrational excitation in this intermediate is observed, as electronic energy is converted to vibrational energy in the molecule. The photodynamics of cis and trans isomers of hexatriene are compared and found to be surprisingly different on the 2-3 psec time scale. These results are important for understanding the fundamental photochemical processes in linear polyenes, which have served as models for the active chromophores of many biological photosystems.
NASA Astrophysics Data System (ADS)
1993-03-01
With regard to accelerated introduction of high efficient energy conversion technology to developing countries, the paper investigates the countries' thoughts of the introduction of the technology and the status of the introduction bases. The countries for survey are the Philippines, Indonesia, Malaysia and Thailand. The Philippine government expects to develop cogeneration as well as large power sources and to widen effective use of natural energy. In Indonesia, they largely expect effective use of biomass energy using Stirling engines by international cooperation and the promoted local electrification using standalone distributed fuel cells. In Malaysia, they have great expectations of the introduction of air conditioning facilities using Stirling engines and the use of standalone distributed fuel cells for promotion of local electrification. Thailand hopes for the use of Stirling engines to air conditioning systems, and the development of solar Stirling generators with solar energy as a heat source and electric vehicles.
NASA Astrophysics Data System (ADS)
Stock, K.; Bizjak, T.; Lochbrunner, S.
2002-03-01
The intramolecular excited-state proton transfer (ESIPT) and internal conversion (IC) of o-hydroxybenzaldehyde was investigated by transient absorption measurements with 30 fs time resolution and quantitative fluorescence spectroscopy. A 45 fs delayed rise of the product emission and coherently excited vibrations indicate that the ESIPT is a ballistic motion of a well defined wavepacket along skeletal coordinates of the H-chelate ring. The IC proceeds as thermally activated process over an energy barrier of about 200 meV caused by an avoided crossing between the ππ∗- and πσ∗-state. The coordinates involved in the ESIPT and in the IC are found to be orthogonal.
Wang, Hsin; Porter, Wallace D; Bottner, Harold; Konig, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolett, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Partricia; Sharp, Jeff; Lo, Jason; Keinke, Holger; Kiss, Laszlo I.
2013-01-01
Recent research and development of high temperature thermoelectric materials has demonstrated great potential of converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as an important area for improving energy efficiency. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is Part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main focuses in Part I are on two electronic transport properties: Seebeck coefficient and electrical resistivity.
NASA Astrophysics Data System (ADS)
Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff W.; Lo, Jason; Kleinke, Holger; Kiss, Laszlo
2013-04-01
Recent research and development of high-temperature thermoelectric materials has demonstrated great potential for converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air-conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The dimensionless figure of merit, ZT, still needs to be improved from the current value of 1.0 to 1.5 to above 2.0 to be competitive with other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods, and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as a key component for improving energy efficiency. The International Energy Agency (IEA) group under the Implementing Agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main foci in part I are the measurement of two electronic transport properties: Seebeck coefficient and electrical resistivity.
Daures, J; Gouriou, J; Bordy, J M
2011-03-01
This work has been performed within the frame of the European Union ORAMED project (Optimisation of RAdiation protection for MEDical staff). The main goal of the project is to improve standards of protection for medical staff for procedures resulting in potentially high exposures and to develop methodologies for better assessing and for reducing, exposures to medical staff. The Work Package WP2 is involved in the development of practical eye-lens dosimetry in interventional radiology. This study is complementary of the part of the ENEA report concerning the calculations with the MCNP-4C code of the conversion factors related to the operational quantity H(p)(3). In this study, a set of energy- and angular-dependent conversion coefficients (H(p)(3)/K(a)), in the newly proposed square cylindrical phantom made of ICRU tissue, have been calculated with the Monte-Carlo code PENELOPE and MCNP5. The H(p)(3) values have been determined in terms of absorbed dose, according to the definition of this quantity, and also with the kerma approximation as formerly reported in ICRU reports. At a low-photon energy (up to 1 MeV), the two results obtained with the two methods are consistent. Nevertheless, large differences are showed at a higher energy. This is mainly due to the lack of electronic equilibrium, especially for small angle incidences. The values of the conversion coefficients obtained with the MCNP-4C code published by ENEA quite agree with the kerma approximation calculations obtained with PENELOPE. We also performed the same calculations with the code MCNP5 with two types of tallies: F6 for kerma approximation and *F8 for estimating the absorbed dose that is, as known, due to secondary electrons. PENELOPE and MCNP5 results agree for the kerma approximation and for the absorbed dose calculation of H(p)(3) and prove that, for photon energies larger than 1 MeV, the transport of the secondary electrons has to be taken into account. PMID:21242167
NASA Astrophysics Data System (ADS)
Rosikhin, Ahmad; Winata, Toto
2016-04-01
Internal transmission profile in charges carrier generation layer of graphene/Si based solar cell has been explored theoretically. Photovoltaic device was constructed from graphene/Si heterojunction forming a multilayer stuck with Si as generation layer. The graphene/Si sheet was layered on ITO/glass wafer then coated by Al forming Ohmic contact with Si. Photon incident propagate from glass substrate to metal electrode and assumed that there is no transmission in Al layer. The wavelength range spectra used in this calculation was 200 - 1000 nm. It found that transmission intensity in the generation layer show non-linear behavior and partitioned by few areas which related with excitation process. According to this information, it may to optimize the photons absorption to create more excitation process by inserting appropriate material to enhance optical properties in certain wavelength spectra because of the exciton generation is strongly influenced by photon absorption.
Spin-symmetry conversion and internal rotation in high J molecular systems
NASA Astrophysics Data System (ADS)
Mitchell, Justin; Harter, William
2006-05-01
Dynamics and spectra of molecules with internal rotation or rovibrational coupling is approximately modeled by rigid or semi-rigid rotors with attached gyroscopes. Using Rotational Energy (RE)^1 surfaces, high resolution molecular spectra for high angular momentum show two distinct but related phenomena; spin-symmetry conversion and internal rotation. For both cases the high total angular momentum allows for transitions that would otherwise be forbidden. Molecular body-frame J-localization effects associated with tight energy level-clusters dominate the rovibronic spectra of high symmetry molecules, particularly spherical tops at J>10. ^2 The effects include large and widespread spin-symmetry mixing contrary to conventional wisdom^3 about weak nuclear moments. Such effects are discussed showing how RE surface plots may predict them even at low J. Classical dynamics of axially constrained rotors are approximated by intersecting rotational-energy-surfaces (RES) that have (J-S).B.(J-S) forms in the limit of constraints that do no work. Semi-classical eigensolutions are compared to those found by direct diagonalization. ^1 W.G Hater, in Handbook of Atomic, Molecular and Optical Physics, edited by G.W.F Drake (Springer, Germany 2006) ^2 W. G. Harter, Phys. Rev. A24,192-262(1981). ^3 G. Herzberg, Infrared and Raman Spectra (VanNostrand 1945) pp. 458,463.
NASA Astrophysics Data System (ADS)
1994-03-01
Following cooperative researches on fuel cell jointly conducted by NEDO and EGAT (Electricity Generating Authority of Thailand), the survey on international cooperation relating to high efficiency energy conversion technology was carried out for the ASEAN countries. The paper summed up the results of the survey. The study of the international cooperation is made for the following three items: a program for periodical exchange of information with EGAT, a project for cooperative research on phosphoric acid fuel cell in Indonesia, and a project for cooperative research with EGAT on electric power storage by advanced battery. In Malaysia, which is small in scale of state, part of the Ministry of Energy, Telecommunication and Posts is only in charge of the energy issue. Therefore, the situation is that they cannot answer well to many items of research/development cooperation brought in from Japan. The item of medium- and long-term developmental research in the Philippines is about the problems which are seen subsequently in the Manila metropolitan area where the problem of outage is being settled. Accordingly, it is essential to promote the cooperative research, well confirming policies and systems of the Ministry of Energy and the national electricity corporation.
NASA Astrophysics Data System (ADS)
Schell, W. R.; Vives-Batlle, J.; Yoon, S. R.; Tobin, M. J.
1999-02-01
Low levels of radioactive gases are released from nuclear electric power generation, nuclear fuel reprocessing plants, nuclear weapons tests and from diagnostic medical uses of radioactive gas tracers. A prototype model of an inorganic scintillator - Crystal Gas Electron Detector (CGED) - was built for measurements of xenon isotopes in-line by detecting the beta and internal conversion (IC) electrons present in atmospheric samples. The detection and quantification of the radionuclide spectra are accomplished, during air flow, without complete purification of the fission gases. Initial operational tests and calibrations made permit the integration of the CGED into a portable Gas Analysis, Separation and Purification (GASP) system [1-3]. The CGED detector, Pulse Shaping and Timing (PSA) electronics, and mathematical treatment of the accumulated spectra are used to resolve the K and LMNO-IC electrons and beta continuum. These data are used, in-line, for dating the age of an air parcel containing fission gases released from nuclear reactors and/or from nuclear weapons tests, as part of the monitoring equipment required to enforce the Comprehensive Test Ban Treaty, CTBT. This report is one of a series of papers providing the design features, operational methods, calibration, and applications of radioactive gas analysis system to the International CTBT.
Keum, Mihyun; Park, Jae Hong; Park, Sung Ho; Ahn, Seung Do
2014-03-01
A Monte Carlo program for calculating organ doses for patients undergoing medical x-ray examination (PCXMC) was used to calculate effective dose conversion coefficients for Korean adults. Two sets of effective dose results were calculated based on tissue weighting factors recommended in International Commission on Radiological Protection (ICRP) Publications 60 and 103 for monochromatic energy photons of 10, 15, 20, 30, 40, 50, 60, 70, 80, 100 and 150 keV. The results were obtained for monoenergetic photons, since effective dose conversion coefficients recommended in ICRP Publications 74 and 116 were given for monochromatic energies, thereby enabling the comparison of our result to those suggested by the ICRP publications. The areas of comparison include: to observe effects due to changes in tissue weighting factors, modification within Medical Internal Radiation Dose (MIRD) phantoms and differences in phantom types. The phantom employed in the PCXMC program is a modified version of the phantom used in ICRP Publication 74, with additional organs that were added in order to take into account the updated tissue weighting factors given in ICRP Publication 103. Both use MIRD phantoms but our study modified the phantom size to the average physical condition of Korean adults, while ICRP Publication 74 uses the phantom size of the reference man defined in ICRP Publication 23. On the other hand, the effective dose suggested in ICRP 116 was calculated using an entirely different type of phantom: a voxel phantom with the size of reference man. Although significant differences were observed for certain organ doses in the lateral beam directions, differences in the effective doses were within 5% for the anterior-posterior (AP) and posterior-anterior (PA) directions, and within 16% in lateral directions when tissue weighting factors were applied and the variations were adjusted for all three comparisons. The results show that calculation of effective doses for Korean adults
Bradley, E.; Adelfang, P.; Goldman, I.N.
2008-07-15
The IAEA has been involved for more than twenty years in supporting international nuclear non- proliferation efforts associated with reducing the amount of highly enriched uranium (HEU) in international commerce. IAEA projects and activities have directly supported the Reduced Enrichment for Research and Test Reactors (RERTR) programme, as well as directly assisted efforts to convert research reactors from HEU to LEU fuel. HEU to LEU fuel conversion projects differ significantly depending on several factors including the design of the reactor and fuel, technical needs of the member state, local nuclear infrastructure, and available resources. To support such diverse endeavours, the IAEA tailors each project to address the relevant constraints. This paper presents the different approaches taken by the IAEA to address the diverse challenges involved in research reactor HEU to LEU fuel conversion projects. Examples of conversion related projects in different Member States are fully detailed. (author)
McCaffery, Anthony J
2015-09-14
Little is known of the mechanism by which H and H2, the principal constituents of the post-re-combination early Universe, cooled sufficiently to permit cluster formation, nucleosynthesis, and, eventually, the formation of structured objects. Radiative decay primarily cools the internal modes of H2, as Δj = - 2 jumps accompany quadrupolar emission. This, however, would be a self-limiting mechanism. In this work, a translational energy cooling mechanism based on collision-induced, translation-to-internal mode conversion, is extended, following an earlier study [A. J. McCaffery and R. J. Marsh, J. Chem. Phys. 139, 234310 (2013)] of ensembles comprising H2 in a H atom bath gas. Here, the possible influence of minor species, such as HD, on this cooling mechanism is investigated. Results suggest that the influence of HD is small but not insignificant. Conversion is very rapid and an overall translation-to-internal energy conversion efficiency of some 5% could be expected. This finding may be of use in the further development of models of this complex phase of early Universe evolution. An unexpected finding in this study was that H2 + HD ensembles are capable of very rapid translation-to-internal conversion with efficiencies of >40% and relaxation rates that appear to be relatively slow. This may have potential as an energy storage mechanism. PMID:26374034
McCaffery, Anthony J.
2015-09-14
Little is known of the mechanism by which H and H{sub 2}, the principal constituents of the post-re-combination early Universe, cooled sufficiently to permit cluster formation, nucleosynthesis, and, eventually, the formation of structured objects. Radiative decay primarily cools the internal modes of H{sub 2}, as Δj = − 2 jumps accompany quadrupolar emission. This, however, would be a self-limiting mechanism. In this work, a translational energy cooling mechanism based on collision-induced, translation-to-internal mode conversion, is extended, following an earlier study [A. J. McCaffery and R. J. Marsh, J. Chem. Phys. 139, 234310 (2013)] of ensembles comprising H{sub 2} in a H atom bath gas. Here, the possible influence of minor species, such as HD, on this cooling mechanism is investigated. Results suggest that the influence of HD is small but not insignificant. Conversion is very rapid and an overall translation-to-internal energy conversion efficiency of some 5% could be expected. This finding may be of use in the further development of models of this complex phase of early Universe evolution. An unexpected finding in this study was that H{sub 2} + HD ensembles are capable of very rapid translation-to-internal conversion with efficiencies of >40% and relaxation rates that appear to be relatively slow. This may have potential as an energy storage mechanism.
Stereo-selective partitioning of translation-to-internal energy conversion in gas ensembles
McCaffery, Anthony J.
2014-11-07
A recent computational study of translation-to-internal energy transfer to H{sub 2} (v = 0,j = 0), hereinafter denoted H{sub 2} (0;0), in a bath of H atoms [A. J. McCaffery and R. J. Marsh, J. Chem. Phys. 139, 234310 (2013)] revealed an unexpected energy partitioning in which the H{sub 2} vibrational temperature greatly exceeds that of rotation. This occurs despite rotation and vibration distributions being close to Boltzmann from early in ensemble evolution. In this work, the study is extended to include H{sub 2} (0;0), O{sub 2} (0;0), and HF (0;0) in a wide range of atomic bath gases comprising some 22 ensembles in all. Translation-to-internal energy conversion in the systems studied was found to be relatively inefficient, falling approximately with (√μ′){sup −1} as bath gas mass increases, where μ′ is the reduced mass of the diatomic–bath gas pair. In all 22 systems studied, T{sub v} exceeds T{sub r} – by a factor > 4 for some pairs. Analysis of the constraints that influence (0;0) → (1;j) excitation for each diatomic–atom pair in momentum–angular momentum space demonstrates that a vibrational preference results from energy constraints that limit permitted collision trajectories to those of low effective impact parameter, i.e., to those that are axial or near axial on impact with the Newton surface. This implies that a steric constraint is an inherent feature of vibration-rotation excitation and arises because momentum and energy barriers must be overcome before rotational states may be populated in the higher vibrational level.
Guo, Yuanqing; Bhattacharya, Atanu; Bernstein, Elliot R
2011-09-01
Electronically nonadiabatic processes such as ultrafast internal conversion (IC) from an upper electronic state (S(1)) to the ground electronic state (S(0)) though a conical intersection (CI), can play an essential role in the initial steps of the decomposition of energetic materials. Such nonradiative processes following electronic excitation can quench emission and store the excitation energy in the vibrational degrees of freedom of the ground electronic state. This excess vibrational energy in the ground electronic state can dissociate most of the chemical bonds of the molecule and can generate stable, small molecule products. The present study determines ultrafast IC dynamics of a model nitramine energetic material, dimethylnitramine (DMNA). Femtosecond (fs) pump-probe spectroscopy, for which a pump pulse at 271 nm and a probe pulse at 405.6 nm are used, is employed to elucidate the IC dynamics of this molecule from its S(1) excited state. A very short lifetime of the S(1) excited state (∼50 ± 16 fs) is determined for DMNA. Complete active space self-consistent field (CASSCF) calculations show that an (S(1)/S(0))(CI) CI is responsible for this ultrafast decay from S(1) to S(0). This decay occurs through a reaction coordinate involving an out-of-plane bending mode of the DMNA NO(2) moiety. The 271 nm excitation of DMNA is not sufficient to dissociate the molecule on the S(1) potential energy surface (PES) through an adiabatic NO(2) elimination pathway. PMID:21351779
Visualizing competing intersystem crossing and internal conversion with a complementary measurement
NASA Astrophysics Data System (ADS)
Liu, Yuzhu; Gerber, Thomas; Qin, Chaochao; Jin, Feng; Knopp, Gregor
2016-02-01
A complementary measurement method based on a home-built double-sided velocity map imaging setup is introduced. This method can simultaneously obtain time-resolved photoelectron imaging and fragment ion imaging. It has been successfully applied to investigate the ultrafast dynamics of the second singlet electronically excited state (S2) in m-xylene. Time-resolved photoelectron and ion signals derived from the initial populated S2 state are tracked following two-photon absorption of a pump pulse. Time-of-flight mass spectra (TOFMS) show that there are dominant parent ions and one fragment ions with methyl loss during such a process. According to the measured photoelectron images and fragment ions images, transient kinetic energy distributions and angular distributions of the generated photoelectrons and fragments are obtained and analyzed. Compared to stand-alone photoelectron imaging, the obtained fragment ion imaging is powerful for further understanding the mechanisms especially when the dissociation occurs during the pump-probe ionization. Two competing channels intersystem crossing T3←S2 and internal conversion S1←S2 are attributed to the deactivation of the S2 state. A lifetime of ˜50 fs for the initially excited S2 state, of ˜276 fs for the secondary populated S1 state, and of 5.76 ps for the T3 state is inferred.
NASA Astrophysics Data System (ADS)
Bozkurt, A.; Chao, T. C.; Xu, X. G.; Bozkurt, A.; Chao, T. C.
2000-10-01
A new set of fluence-to-absorbed dose and fluence-to-effective dose conversion coefficients have been calculated for neutrons below 20 MeV using a whole-body anatomical model, VIP-Man, developed from the high-resolution transverse colour photographic images of the National Library of Medicine's Visible Human Project®. Organ dose calculations were performed using the Monte Carlo code MCNP for 20 monoenergetic neutron beams between 1×10-9 MeV and 20 MeV under six different irradiation geometries: anterior-posterior, posterior-anterior, right lateral, left lateral, rotational and isotropic. The absorbed dose for 24 major organs and effective dose results based on the realistic VIP-Man are presented and compared with those based on the simplified MIRD-based phantoms reported in the literature. Effective doses from VIP-Man are not significantly different from earlier results for neutrons in the energy range studied. There are, however, remarkable deviations in organ doses due to the anatomical differences between the image-based and the earlier mathematical models.
Nica, N.; Hardy, J.C.; Iacob, V.E.; Raman, S.; Nestor, C.W. Jr.; Trzhaskovskaya, M.B.
2004-11-01
The 10.5-day isomer in {sup 193}Ir decays by a single 80.2-keV M4 transition directly to the ground state of that nucleus. We have measured the total intensity of K x rays relative to 80.2-keV {gamma} rays for this transition to be 98.7(6). With the K-shell fluorescent yield for iridium taken to be 0.958(4), this result yields {alpha}{sub K}=103.0(8) for the K-shell internal conversion coefficient (ICC). The calculated {alpha}{sub K} for this transition is particularly sensitive to the treatment of the hole that is created by conversion in the atomic K shell. Recent ICC tables, which ignore the hole, yield {alpha}{sub K}=92.0. We demonstrate that calculations incorporating the hole produce values between 99.6 and 103.3 depending on the approximation used. Our result strongly supports the need to include the hole.
Taprogge, J.; Jungclaus, A.; Grawe, H.; Nishimura, S.; Xu, Z. Y.; Doornenbal, P.; Lorusso, G.; Nacher, E.; Simpson, G. S.; Soderstrom, P. A.; Sumikama, T.; Kondev, F. G.
2014-11-10
The decay of an isomeric state in the neutron-rich nucleus 129Cd has been observed via the detection of internal conversion and Compton electrons providing first experimental information on excited states in this nucleus. The isomer was populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. From the measured yields of γ-rays and internal conversion electrons, a multipolarity of E 3 was tentatively assigned to the isomeric transition. A half-life of T1/2=3.6(2) msT1/2=3.6(2) ms was determined for the new state which was assigned a spin of (21/2+)(21/2+), based on a comparison to shell model calculations performed using state-of-the-art realistic effective interactions.
Precise αK Measurement of 346.5 keV Transition in ^197Pt as a Test of Internal Conversion Theory
NASA Astrophysics Data System (ADS)
Hernberg, Mark; Hardy, John; Nica, Ninel; Goodwin, John; Iacob, Victor
2007-10-01
We have determined the K-shell internal conversion coefficient (ICC) of the 346.5 keV M4 transition in ^197Pt using an HPGe detector at the Texas A&M University Cyclotron. ICCs are used in the study of nuclear decay schemes, branching ratios and transition rates, as well as spin and parity assignments. We have recently been measuring ICCs (in ^193Ir , ^137Ba, ^134Cs) with the specific purpose of testing the method used to treat the atomic vacancy in calculating ICCs. Previous measurements of the ICC for the 346.5 keV transition in ^197Pt have disagreed significantly from calculated coefficients regardless of the method used to consider the vacancy. This could have indicated some other unknown factor causing a problem in the calculations. Our preliminary result, determined with an uncertainty of 3% is αK= 4.24(13). This disagrees with previous measurements (αK= 4.02(8)) and is now consistent with the calculated ICCs.
Kulkarni, A.; Saluja, J.
1987-06-30
The United States Agency for International Development (AID), in joint collaboration with the Government of India (GOI), supported a research and development program in Alternate Energy Resources during the period March 1983 to June 1987. The primary emphasis of this program was to develop new and advanced coal and biomass conversion technologies for the efficient utilization of coal and biomass feedstocks in India. This final ''summary'' report is divided into two volumes. This Report, Volume I, covers the program overview and coal projects and Volume II summarizes the accomplishments of the biomass projects. The six projects selected in the area of coal were: Evaluation of the Freeboard Performance in a Fluidized-Bed Combustor; Scale-up of AFBC boilers; Rheology, Stability and Combustion of Coal-Water Slurries; Beneficiation of Fine Coal in Dense Medium Cyclones; Hot Gas Cleanup and Separation; and Cold Gas Cleanup and Separation.
NASA Astrophysics Data System (ADS)
Fairall, C. W.; Bariteau, L.; Grachev, A. A.; Hill, R. J.; Wolfe, D. E.; Brewer, W. A.; Tucker, S. C.; Hare, J. E.; Angevine, W. M.
2006-12-01
In this paper, we examine observations of shallow, stable boundary layers in the cool waters of the Gulf of Maine between Cape Cod, Massachusetts, and Nova Scotia, obtained in the 2004 New England Air Quality Study (NEAQS-04), which was part of the International Consortium for Atmospheric Research into Transport and Transformation (ICARTT). The observations described herein were made from the NOAA Research Vessel Ronald H. Brown. The ship was instrumented for measurements of meteorological, gas-phase and aerosol atmospheric chemistry variables. Meteorological instrumentation included a Doppler lidar, a radar wind profiler, rawinsonde equipment, and a surface flux package. In this study, we focus on direct comparisons of the NEAQS-04 flux observations with the COARE bulk flux algorithm to investigate possible coastal influences on air-sea interactions. We found significant suppression of the transfer coefficients for momentum, sensible heat, and latent heat; the suppression was correlated with lighter winds, more stable surface layers, S-SE wind direction, and lower boundary layer heights. Analysis of the details shows the suppression is not a measurement, stability correction, or surface wave effect. The correlation with boundary layer height is consistent with an interpretation that our measurements at 18-m height do not realize the full surface flux in shallow boundary layers. We also find that a bulk Richardson number threshold of 0.1 gives a better estimate of boundary layer height than 0.25 or 0.5. Mean ozone deposition velocity is estimated as 0.44 mm s-1, corresponding to a boundary removal timescale of about 1 day.
The multivesicular body is the major internal site of prion conversion
Yim, Yang-In; Park, Bum-Chan; Yadavalli, Rajgopal; Zhao, Xiaohong; Eisenberg, Evan; Greene, Lois E.
2015-01-01
ABSTRACT The conversion of the properly folded prion protein, PrPc, to its misfolded amyloid form, PrPsc, occurs as the two proteins traffic along the endocytic pathway and PrPc is exposed to PrPsc. To determine the specific site of prion conversion, we knocked down various proteins in the endocytic pathway including Rab7a, Tsg101 and Hrs (also known as HGS). PrPsc was markedly reduced in two chronically infected cell lines by preventing the maturation of the multivesicular body, a process that begins in the early endosome and ends with the sorting of cargo to the lysosome. By contrast, knocking down proteins in the retromer complex, which diverts cargo away from the multivesicular body caused an increase in PrPsc levels. These results suggest that the multivesicular body is the major site for intracellular conversion of PrPc to PrPsc. PMID:25663703
NASA Astrophysics Data System (ADS)
Chen, Jing
2008-08-01
This study used the Monte-Carlo code MCNPX to determine mean absorbed doses to the embryo and foetus when the mother is exposed to external muon fields. Monoenergetic muons ranging from 20 MeV to 50 GeV were considered. The irradiation geometries include anteroposterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT), isotropic (ISO), and top-down (TOP). At each of these irradiation geometries, absorbed doses to the foetal body were calculated for the embryo of 8 weeks and the foetus of 3, 6 or 9 months, respectively. Muon fluence-to-absorbed-dose conversion coefficients were derived for the four prenatal ages. Since such conversion coefficients are yet unknown, the results presented here fill a data gap.
Chen Jing
2008-08-07
This study used the Monte-Carlo code MCNPX to determine mean absorbed doses to the embryo and foetus when the mother is exposed to external muon fields. Monoenergetic muons ranging from 20 MeV to 50 GeV were considered. The irradiation geometries include anteroposterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT), isotropic (ISO), and top-down (TOP). At each of these irradiation geometries, absorbed doses to the foetal body were calculated for the embryo of 8 weeks and the foetus of 3, 6 or 9 months, respectively. Muon fluence-to-absorbed-dose conversion coefficients were derived for the four prenatal ages. Since such conversion coefficients are yet unknown, the results presented here fill a data gap.
Comparison of 50-year and 70-year internal-dose-conversion factors
Ryan, M.T.; Dunning, D.E. Jr.
1981-03-01
The 50-year inhalation and ingestion dose commitments associated with an acute intake (of a radionuclide) of 3.7 x 10/sup 4/ Bq (1 ..mu..Ci) in one day were compared with the corresponding dose commitments calculated for a 70-year integration period resulting from a chronic intake of the same amount at a rate of 101 Bq/d (0.00274 ..mu..Ci/d) for one year. These values, known as dose conversion factors, estimate the dose accumulated during a given period of time following a unit of intake of a radionuclide. It was demonstrated that the acute intake of 3.7 x 10/sup 4/ Bq in one day and the chronic intake of 101 Bq/d for one year (a total intake of 3.7 x 10/sup 4/ Bq) result in essentially the same dose commitment for a relatively long integration period. Therefore, the comparison of 50-year acute dose conversion factors and 70-year chronic dose conversion factors is essentially only a measure of the additional dose accumulated in the 50 to 70 year period. It was found that for radionuclides with atomic mass less than 200 the percent difference in the 70-year and 50-year dose conversion factors was essentially zero in most cases. Differences of approximately 5 to 50% were obtained for dose conversion factors for most alpha emitters with atomic masses of greater than 200. Comparisons were made on the basis of both organ dose equivalent and effective dose equivalent. The implications and significance of these results are discussed.
NASA Astrophysics Data System (ADS)
Grunnet-Jepsen, A.; Aubrecht, I.; Solymar, L.
1995-05-01
An experimental investigation of the electric field in the bulk of a Bi12SiO20 crystal is carried out, and a two-region model is developed that can account for the buildup of screening charges near the electrodes. In light of our results, a simple method is proposed for the determination of the effective electro-optic coefficients based on applying a sufficiently high-frequency square-wave voltage to prevent screening charge buildup. A demonstration of this method for Bi12SiO20 leads to a value of 4.4 pm / V for the stress-free (unclamped) coefficient, and a subsequent consideration of piezoelastic contributions allows the strain-free (clamped) coefficient to be estimated at 3.7 pm / V.
ERIC Educational Resources Information Center
Kerridge, Richard; Cinnamond, Sacha
2012-01-01
Richard Kerridge and Sacha Cinnamond explain how their history department built a culture of international dialogue and collaboration that enriches their students' historical learning. Video-conferencing is at the centre of these activities. Their story begins with an initial, moving encounter with the First World War battlefields that soon turned…
ERIC Educational Resources Information Center
Abasi, Ali R.; Graves, Barbara
2008-01-01
In this study we examine how university plagiarism policies interact with international graduate students' academic writing in English as they develop identities as authors and students. The study is informed by the sociocultural theoretical perspective [Vygotsky, L. (1978). "Mind in society: The development of higher mental processes." Cambridge,…
ERIC Educational Resources Information Center
Bauer, Patricia J.; Stark, Emily N.; Lukowski, Angela F.; Rademacher, Jennifer; Van Abbema, Dana L.; Ackil, Jennifer K.
2005-01-01
Mother-child conversations about a devastating tornado and about 2 nontraumatic events were examined to determine whether there were (a) differences in use of internal states language when talking about traumatic and nontraumatic events and (b) similarities in mothers' and children's use of internal states language. At Session 1, which took place…
NASA Astrophysics Data System (ADS)
Cavalcante, F. R.; Galeano, D. C.; Carvalho Júnior, A. B.; Hunt, J.
2014-02-01
Due to the difficulty in implementing invasive techniques for calculations of dose for some exposure scenarios, computational simulators have been created to represent as realistically as possible the structures of the human body and through radiation transport simulations to obtain conversion coefficients (CCs) to estimate dose. In most published papers simulators are implemented in the standing posture and this may not describe a real scenario of exposure. In this work we developed exposure scenarios in the Visual Monte Carlo (VMC) code using a female simulator in standing and sitting postures. The simulator was irradiated in the antero-posterior (AP) geometry by a plane source of monoenergetic photons with energy from 10 keV to 2 MeV. The conversion coefficients for equivalent dose in terms of air kerma (HT/Kair) were calculated for both scenarios and compared. The results show that the percentage difference of CCs for the organs of the head and thorax was not significant (less than 5%) since the anatomic position of the organs is the same in both postures. The percentage difference is more significant to the ovaries (71% for photon energy of 20 keV), to the bladder (39% at 60 keV) and to the uterus (37% at 100 keV) due to different processes of radiation interactions in the legs of the simulator when its posture is changed. For organs and tissues that are distributed throughout the entire body, such as bone (21% at 100 keV) and muscle (30% at 80 keV) the percentage difference of CCs reflects a reduction of interaction of photons with the legs of the simulator. Therefore, the calculation of conversion coefficients using simulators in the sitting posture is relevant for a more accurate dose estimation in real exposures to radiation.
Yu, G.; Heeger, A.J.
1995-10-01
The photosensitivity of semiconducting polymers can be enhanced by blending donor and acceptor polymers to optimize photoinduced charge separation. We describe a novel phase-separated polymer blend (composite) made with poly[2-methoxy-5-(2{prime}-ethyl-hexyloxy)-1,4-phenylene vinylene], MEH-PPV, as donor and cyano-PPV, CN-PPV, as acceptor. The photoluminescence and electroluminescence of both component polymers are quenched in the blend, indicative of rapid and efficient separation of photogenerated electron-hole pairs with electrons on the acceptor and holes on the donor. Diodes made with such a composite semiconducting polymer as the photosensitive medium show promising photovoltaic characteristics with carrier collection efficiency of 5% electrons/photon and energy conversion efficiency of 0.9%, {similar_to}20 times larger than in diodes made with pure MEH-PPV and {similar_to}100 times larger than in diodes made with CN-PPV. The photosensitivity and the quantum yield increase with reverse bias voltage, to 0.3 A/W and 80% electrons/photon respectively at {minus}10 V, comparable to results obtained from photodiodes made with inorganic semiconductors. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
NASA Astrophysics Data System (ADS)
Suzuki, Yuji
2006-09-01
This special issue of Journal of Micromechanics and Microengineering contains a selection of papers from the Fifth International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2005). The meeting was held on 28-30 November 2005 in Tokyo, Japan, and was supported by the 21COE Program 'Mechanical Systems Innovation' at the University of Tokyo. Power MEMS is one of the newest categories of MEMS, encompassing microdevices and microsystems for power generation, energy conversion and propulsion. The series of PowerMEMS workshops started in 2000 in Sendai, Japan and then moved to Tsukuba, Makuhari, Kyoto and Tokyo. At the 2005 meeting there were four invited, 25 oral and 26 poster presentations from 14 different countries. From the 55 papers in the proceedings, 18 papers have been selected for this special issue. The papers were chosen on the basis of their quality, scientific impact and relevance to the scope of the journal. The authors of the selected papers were invited to expand their manuscripts beyond the workshop page limitation and to revise the papers to meet the criteria of archival journal publication. All papers have been subjected to the journal's standard peer review process. The papers included herein are ordered according to four areas: energy harvesting, micro combustors and fuel processors, micro fuel cells, and micro engines and generators. It is my pleasure to present these selected papers from PowerMEMS 2005, and I hope that this special issue provides a valuable overview of the latest research in micro and nanotechnology for power generation and energy conversion.
Zhu, Lin; Mochizuki, Toshimitsu; Yoshita, Masahiro; Chen, Shaoqiang; Kim, Changsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko
2016-05-16
We calculated the conversion-efficiency limit ηsc and the optimized subcell bandgap energies of 1 to 5 junction solar cells without and with intermediate reflectors under 1-sun AM1.5G and 1000-sun AM1.5D irradiations, particularly including the impact of internal radiative efficiency (ηint) below unity for realistic subcell materials on the basis of an extended detailed-balance theory. We found that the conversion-efficiency limit ηsc significantly drops when the geometric mean ηint* of all subcell ηint in the stack reduces from 1 to 0.1, and that ηsc degrades linearly to logηint* for ηint* below 0.1. For ηint*<0.1 differences in ηsc due to additional intermediate reflectors became very small if all subcells are optically thick for sun light. We obtained characteristic optimized bandgap energies, which reflect both ηint* decrease and AM1.5 spectral gaps. These results provide realistic efficiency targets and design principles. PMID:27409948
Zhu, Lin Kim, Changsu; Yoshita, Masahiro; Chen, Shaoqiang; Sato, Shintaroh; Mochizuki, Toshimitsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko
2014-01-20
To develop a realistic design principle, we calculated the maximum conversion efficiency η{sub sc} and optimized sub-cell band-gap energies E{sub g} in double-junction tandem solar cells via a detailed-balance theory, paying particular attention to their dependence on internal luminescence quantum yields y{sub int} of the top and bottom sub-cell materials. A strong drop in the maximum η{sub sc} occurs when y{sub int} slightly drops from 1 to 0.9, where the drop in y{sub int} of the bottom cell causes a stronger effect than that of the top cell. For low values of y{sub int}, the maximum η{sub sc} has a simple logarithmic dependence on the geometric mean of the two sub-cells'y{sub int}.
Giacomelli, L.; Hjalmarsson, A.; Hellesen, C.; Conroy, S.; Sunden, E. Andersson; Ericsson, G.; Johnson, M. Gatu; Sjoestrand, H.; Weiszflog, M.; Kaellne, J.; Tardocchi, M.; Gorini, G.
2008-10-15
The effect of ion cyclotron resonance heating (ICRH) on ({sup 3}He)D plasmas at JET was studied with the time of flight optimized rate (TOFOR) spectrometer dedicated to 2.5 MeV dd neutron measurements. In internal transport barrier (ITB) plasma experiments with large {sup 3}He concentrations (X({sup 3}He)>15%) an increase in neutron yield was observed after the ITB disappeared but with the auxiliary neutral beam injection and ICRH power still applied. The analysis of the TOFOR data revealed the formation of a high energy (fast) D population in this regime. The results were compared to other mode conversion experiments with similar X({sup 3}He) but slightly different heating conditions. In this study we report on the high energy neutron tails originating from the fast D ions and their correlation with X({sup 3}He) and discuss the light it can shed on ICRH-plasma power coupling mechanisms.
NASA Astrophysics Data System (ADS)
Grinev, Timur; Brumer, Paul
2015-12-01
Molecular excitation with incoherent light is examined using realistic turn-on time scales, and results are compared to those obtained via commonly used sudden turn-on, or pulses. Two significant results are obtained. First, in contrast to prior studies involving sudden turn-on, realistic turn-on is shown to lead to stationary coherences for natural turn-on time scales. Second, the time to reach the final stationary mixed state, known to result from incoherent excitation, is shown to depend directly on the inverse of the molecular energy level spacings, in both sudden and realistic turn-on cases. The S0 → S2/S1 internal conversion process in pyrazine is used as an example throughout. Implications for studies of natural light harvesting systems are noted.
Yu, Hui; Sanchez-Rodriguez, Jose A; Pollum, Marvin; Crespo-Hernández, Carlos E; Mai, Sebastian; Marquetand, Philipp; González, Leticia; Ullrich, Susanne
2016-07-27
The photodynamic properties of molecules determine their ability to survive in harsh radiation environments. As such, the photostability of heterocyclic aromatic compounds to electromagnetic radiation is expected to have been one of the selection pressures influencing the prebiotic chemistry on early Earth. In the present study, the gas-phase photodynamics of uracil, 5-methyluracil (thymine) and 2-thiouracil-three heterocyclic compounds thought to be present during this era-are assessed in the context of their recently proposed intersystem crossing pathways that compete with internal conversion to the ground state. Specifically, time-resolved photoelectron spectroscopy measurements evidence femtosecond to picosecond timescales for relaxation of the singlet (1)ππ* and (1)nπ* states as well as for intersystem crossing to the triplet manifold. Trapping in the excited triplet state and intersystem crossing back to the ground state are investigated as potential factors contributing to the susceptibility of these molecules to ultraviolet photodamage. PMID:27189184
Grinev, Timur; Brumer, Paul
2015-12-28
Molecular excitation with incoherent light is examined using realistic turn-on time scales, and results are compared to those obtained via commonly used sudden turn-on, or pulses. Two significant results are obtained. First, in contrast to prior studies involving sudden turn-on, realistic turn-on is shown to lead to stationary coherences for natural turn-on time scales. Second, the time to reach the final stationary mixed state, known to result from incoherent excitation, is shown to depend directly on the inverse of the molecular energy level spacings, in both sudden and realistic turn-on cases. The S{sub 0} → S{sub 2}/S{sub 1} internal conversion process in pyrazine is used as an example throughout. Implications for studies of natural light harvesting systems are noted.
Internal dose conversion factors for calculation of dose to the public
Not Available
1988-07-01
This publication contains 50-year committed dose equivalent factors, in tabular form. The document is intended to be used as the primary reference by the US Department of Energy (DOE) and its contractors for calculating radiation dose equivalents for members of the public, resulting from ingestion or inhalation of radioactive materials. Its application is intended specifically for such materials released to the environment during routine DOE operations, except in those instances where compliance with 40 CFR 61 (National Emission Standards for Hazardous Air Pollutants) requires otherwise. However, the calculated values may be equally applicable to unusual releases or to occupational exposures. The use of these committed dose equivalent tables should ensure that doses to members of the public from internal exposures are calculated in a consistent manner at all DOE facilities.
Ören, Ünal; Andersson, Martin; Rääf, Christopher L; Mattsson, Sören
2016-06-01
The purpose of this study was to derive calibration coefficients (in terms of cps kBq(-1)) and minimum detectable activities, MDA, (in terms of kBq and corresponding dose rate) for the dual head gamma camera part of an SPECT/CT-instrument when used for in vivo internal contamination measurements in radiation emergency situations. A cylindrical-conical PMMA phantom with diameters in the range of 7-30 cm was developed in order to simulate different body parts and individuals of different sizes. A series of planar gamma camera investigations were conducted using an SPECT/CT modality with the collimators removed for (131)I and (137)Cs, radionuclides potentially associated with radiation emergencies. Energy windows of 337-391 and 490-690 keV were selected for (131)I and (137)Cs, respectively. The measurements show that the calibration coefficients for (137)Cs range from 10 to 19 cps kBq(-1) with MDA values in the range of 0.29-0.55 kBq for phantom diameters of 10-30 cm. The corresponding values for (131)I are 12-37 cps kBq(-1) with MDA values of 0.08-0.26 kBq. An internal dosimetry computer program was used for the estimation of minimum detectable dose rates. A thyroid uptake of 0.1 kBq (131)I (representing MDA) corresponds to an effective dose rate of 0.6 µSv d(-1) A (137)Cs source position representing the colon with an MDA of 0.55 kBq corresponds to an effective dose rate was 1 µSv y(-1) This method using a simple phantom for the determination of calibration coefficients, and MDA levels can be implemented within the emergency preparedness plans in hospitals with nuclear medicine departments. The derived data will help to quickly estimate the internal contamination of humans following radiation emergencies. PMID:26769903
NASA Astrophysics Data System (ADS)
Taranenko, Valery; Xu, X. George
2008-03-01
Protection of fetuses against external neutron exposure is an important task. This paper reports a set of absorbed dose conversion coefficients for fetal and maternal organs for external neutron beams using the RPI-P pregnant female models and the MCNPX code. The newly developed pregnant female models represent an adult female with a fetus including its brain and skeleton at the end of each trimester. The organ masses were adjusted to match the reference values within 1%. For the 3 mm cubic voxel size, the models consist of 10-15 million voxels for 35 organs. External monoenergetic neutron beams of six standard configurations (AP, PA, LLAT, RLAT, ROT and ISO) and source energies 0.001 eV-100 GeV were considered. The results are compared with previous data that are based on simplified anatomical models. The differences in dose depend on source geometry, energy and gestation periods: from 20% up to 140% for the whole fetus, and up to 100% for the fetal brain. Anatomical differences are primarily responsible for the discrepancies in the organ doses. For the first time, the dependence of mother organ doses upon anatomical changes during pregnancy was studied. A maximum of 220% increase in dose was observed for the placenta in the nine months model compared to three months, whereas dose to the pancreas, small and large intestines decreases by 60% for the AP source for the same models. Tabulated dose conversion coefficients for the fetus and 27 maternal organs are provided.
Blancafort, Lluís; Ovejas, Virginia; Montero, Raúl; Fernández-Fernández, Marta; Longarte, Asier
2016-04-01
The photochemical and photophysical pathways operative in N-methylpyrrole, after excitation in the near part of its ultraviolet absorption spectrum, have been investigated by the combination of time-resolved total ion yield and photoelectron spectroscopies with high-level ab initio calculations. The results collected are remarkably different from the observations made for pyrrole and other aromatic systems, whose dynamics is dictated by the presence of πσ* excitations on X-H (X: N, O, S, ...) bonds. The presence of a barrier along the C-N dissociation coordinate that can not be tunneled triggers two alternative decay mechanisms for the S1 A″ πσ* state. While at low vibrational content the C-N dissociation occurs on the surface of a lower (3)ππ* state reached after efficient intersystem crossing, at higher excitation energies, the A″ πσ* directly internally converts to the ground state through a ring-twisted S1/S0 conical intersection. The findings explain previous observations on the molecule and may be relevant for more complex systems containing similar C-N bonds, such as the DNA nucleotides. PMID:26978190
ERIC Educational Resources Information Center
Jones, Diane Carlson; Vigfusdottir, Thorbjorg Helga; Lee, Yoonsun
2004-01-01
This research evaluates the contributions of three dimensions of appearance culture (appearance magazine exposure, appearance conversations with friends, and peer appearance criticism) and body mass index (BMI) to internalization of appearance ideals and body image dissatisfaction. Four hundred thirty-three girls and 347 boys in Grades 7 through…
McCamant, David W.; Kukura, Philipp; Mathies, Richard A.
2005-01-01
We have developed the technique of femtosecond stimulated Raman spectroscopy (FSRS), which allows the rapid collection of high-resolution vibrational spectra on the femtosecond time scale. FSRS combines a sub-50 fs actinic pump pulse with a two-pulse stimulated Raman probe to obtain vibrational spectra whose frequency resolution limits are uncoupled from the time resolution. This allows the acquisition of spectra with <100 fs time resolution and <30 cm−1 frequency resolution. Additionally, FSRS is unaffected by background fluorescence, provides rapid (100 ms) acquisition times, and exhibits traditional spontaneous Raman line shapes. FSRS is used here to study the relaxation dynamics of β-carotene. Following optical excitation to S2 (1Bu+) the molecule relaxes in 160 fs to S1 (2Ag−) and then undergoes two distinct stages of intramolecular vibrational energy redistribution (IVR) with 200 and 450 fs time constants. These processes are attributed to rapid (200 fs) distribution of the internal conversion energy from the S1 C=C modes into a restricted bath of anharmonically coupled modes followed by complete IVR in 450 fs. FSRS is a valuable new technique for studying the vibrational structure of chemical reaction intermediates and transition states. PMID:16710440
Cao, Jun; Xie, Zhi-Zhong
2016-03-01
The ab initio electronic structure calculations and CASSCF-based nonadiabatic dynamics simulations have been used to investigate the internal conversion and intersystem crossing process of both trans-acrolein and 2-cyclopentenone in the gas phase. Our calculation results show that relaxation from the Franck-Condon region to an S1 minimum is ultrafast and that the S1 state will dominantly undergo intersystem crossing to triplet states due to the existence of significant barriers to access the S1/S0 intersection points and of energetically close-lying triplet states. The S1/T2/T1 three-state intersection is observed in our dynamics simulations to play an important role in the population of the lowest triplet state, which is consistent with previous suggestions. Although the evolution into triplet states involves a similar path and gives rise to a similar triplet quantum yield for these two molecules, the intersystem crossing rate of 2-cyclopentenone is lower owing to the ring constraint that results in a smaller spin-orbital coupling in the singlet-triplet crossing region. The present theoretical study reproduces the experimental results and gives an explanation about the structural factors that govern the excited-state decay of some types of α,β-enones. PMID:26882275
NASA Astrophysics Data System (ADS)
Ao, Guanghong; Qian, Xuemin; Xiao, Zhengguo; Li, Zhongguo; Nie, Zhongquan; Wang, Yuxiao; Zhang, Xueru; Song, Yinglin
2015-08-01
Meso-tetraphenylporphyrin (TPP), (meso-tetrakis(4-cyanophenyl)porphyrin [TPP(CN)4)] and (meso-tetrakis(4-methoxyphenyl)porphyrin [TPP(OMe)4]) are synthesized. The donor methoxy substitute (OMe) and acceptor cyano substitute (CN) are introduced into TPP in order to examine their influence on the photophysical properties of TPP. The nonlinear absorption properties of these three porphyrins are studied using open-aperture Z-scan and time-resolved pump-probe techniques in picosecond and nanosecond regimes, and the results are elucidated successfully by a five-level model. As compared to TPP, TPP(OMe)4 exhibits an accelerated internal conversion from S1 to S0 state (0.02 ns), and S1 to T1 state (0.03 ns). Moreover, a changeover from saturable absorption to reverse saturable absorption is observed in TPP(OMe)4 in the ps regime. Whereas the nonlinear absorption behavior of TPP(CN)4 is similar to that of TPP. The results imply that these two substituents, especially the OMe group, could modulate the photophysical properties of TPP, which may provide a useful option for porphyrin-related applications.
NASA Astrophysics Data System (ADS)
Chang, Yin-Jung; Shih, Ko-Han
2016-05-01
Internal photoemission (IPE) across an n-type Schottky junction due to standard AM1.5G solar illumination is quantified with practical considerations for Cu, Ag, and Al under direct and fully nondirect transitions, all in the context of the constant matrix element approximation. Under direct transitions, photoemitted electrons from d bands dominate the photocurrent and exhibit a strong dependence on the barrier energy ΦB but are less sensitive to the change in the metal thickness. Photocurrent is shown to be nearly completely contributed by s-state electrons in the fully nondirect approximation that offers nearly identical results as in the direct transition for metals having a free-electron-like band structure. Compared with noble metals, Al-based IPE has the highest quantum yield up to about 5.4% at ΦB = 0.5 eV and a maximum power conversion efficiency of approximately 0.31% due mainly to its relatively uniform and wide Pexc energy spectral width. Metals (e.g., Ag) with a larger interband absorption edge are shown to outperform those with shallower d-bands (e.g., Cu and Au).
Li, Shengquan; Zhang, Kezhao; Li, Juan; Liu, Chao
2016-03-01
This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach. PMID:26775089
NASA Astrophysics Data System (ADS)
Galeano, D. C.; Cavalcante, F. R.; Carvalho, A. B.; Hunt, J.
2014-02-01
The dose conversion coefficient (DCC) is important to quantify and assess effective doses associated with medical, professional and public exposures. The calculation of DCCs using anthropomorphic simulators and radiation transport codes is justified since in-vivo measurement of effective dose is extremely difficult and not practical for occupational dosimetry. DCCs have been published by the ICRP using simulators in a standing posture, which is not always applicable to all exposure scenarios, providing an inaccurate dose estimation. The aim of this work was to calculate DCCs for equivalent dose in terms of air kerma (H/Kair) using the Visual Monte Carlo (VMC) code and the VOXTISS8 adult male voxel simulator in sitting and standing postures. In both postures, the simulator was irradiated by a plane source of monoenergetic photons in antero-posterior (AP) geometry. The photon energy ranged from 15 keV to 2 MeV. The DCCs for both postures were compared and the DCCs for the standing simulator were higher. For certain organs, the difference of DCCs were more significant, as in gonads (48% higher), bladder (16% higher) and colon (11% higher). As these organs are positioned in the abdominal region, the posture of the anthropomorphic simulator modifies the form in which the radiation is transported and how the energy is deposited. It was also noted that the average percentage difference of conversion coefficients was 33% for the bone marrow, 11% for the skin, 13% for the bone surface and 31% for the muscle. For other organs, the percentage difference of the DCCs for both postures was not relevant (less than 5%) due to no anatomical changes in the organs of the head, chest and upper abdomen. We can conclude that is important to obtain DCCs using different postures from those present in the scientific literature.
NASA Astrophysics Data System (ADS)
2014-11-01
It is our great pleasure to welcome you to the 14th International Conference on Micro- and Nano-Technology for Power Generation and Energy Conversion Applications, or PowerMEMS 2014, in Awaji Island, Japan. The aim of PowerMEM is to present the latest research results in the field of miniature, micro- and nano-scale technologies for power generation and energy conversion. The conference will also- give us the opportunity to exchange informations and new ideas in the field of Power MEMS/NEMS. The current status of the field of PowerMEMS spans the full spectrum from basic research to practical applications. We will enjoy valuable discussions not only from the viewpoint of academia but from commercial and industrial perspectives. In the conference, three invited speakers lead the technical program. We received 172 abstracts and after a careful reviewing process by the Technical Program Committee a total of 133 papers were selected for presentation. These have been organized into 16 Oral sessions in two parallel streams and two poster sessions including some late-news papers. The oral and regular poster papers are published by the Institute of Physics (IOP). We have also organized a PowerMEMS School in Kobe-Sannomiya contiguous to the main conference. This two-day school will cover various topics of energy harvesting. World leading experts will give invited lectures on their main topics. This is a new experiment to broaden the technology remit of our conference by organizing mini symposiums that aim to gather the latest research on the following topics by the organizers: Microscale Combustion, Wideband Vibration Energy Harvesting, RF Energy Transfer and Industrial Application. We hope this, and other activities will make PowerMEMS2014 a memorable success. One of the important programs in an international conference is the social program, and we prepare the PowerMEMS2014 banquet in the banquet room at the Westin Awaji Island Hotel. This will provide an opportunity to
NASA Astrophysics Data System (ADS)
Tanaka, Shuji; Toriyama, Toshiyuki
2005-09-01
This special issue of the Journal of Micromechanics and Microengineering features papers selected from the Fourth International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2004). The workshop was held in Kyoto, Japan, on 28-30 November 2004, by The Ritsumeikan Research Institute of Micro System Technology in cooperation with The Global Emerging Technology Institute, The Institute of Electrical Engineers of Japan, The Sensors and Micromachines Society, The Micromachine Center and The Kyoto Nanotech Cluster. Power MEMS is one of the newest categories of MEMS, which encompasses microdevices and microsystems for power generation, energy conversion and propulsion. The first concept of power MEMS was proposed in the late 1990s by Epstein's group at the Massachusetts Institute of Technology, where they continue to study MEMS-based gas turbine generators. Since then, the research and development of power MEMS have been promoted by the need for compact power sources with high energy and power density. Since its inception, power MEMS has expanded to include not only various MEMS-based power generators but also small energy machines and microdevices for macro power generators. At the last workshop, various devices and systems, such as portable fuel cells and their peripherals, micro and small turbo machinery, energy harvesting microdevices, and microthrusters, were presented. Their power levels vary from ten nanowatts to hundreds of watts, spanning ten orders of magnitude. The first PowerMEMS workshop was held in 2000 in Sendai, Japan, and consisted of only seven invited presentations. The workshop has grown since then, and in 2004 there were 5 invited, 20 oral and 29 poster presentations. From the 54 papers in the proceedings, 12 papers have been selected for this special issue. I would like to express my appreciation to the members of the Organizing Committee and Technical Program Committee. This special issue was
NASA Astrophysics Data System (ADS)
Mitcheson, Paul; Beeby, Steve
2013-12-01
It is a pleasure to welcome you to The Royal Society in London and the 13th International Conference on Micro- and Nano-Technology for Power Generation and Energy Conversion Applications, or PowerMEMS 2013. The objective of PowerMEMS 2013 is to catalyse innovation in miniature, micro- and nano-scale technologies for power generation and energy conversion. The conference aims to stimulate the exchange of insights and information, and the development of new ideas in the Power MEMS/NEMS field as well as at the meso-scale. It will allow the attendees to interact and network within our multidisciplinary community that includes professionals from many branches of science and engineering. The technical program is led by four invited speakers covering inductive power transfer, chip scale power sources, thermal energy harvesting and implantable biofuel cells. We received 177 abstracts and following a careful reviewing process by the Technical Program Committee a total of 137 papers were selected for presentation. These have been organised into 16 oral sessions in two parallel streams and two poster sessions that have been augmented by 10 late news papers. The oral and regular poster papers are, for the first time, being published by the Institute of Physics. We have made every effort to make PowerMEMS 2013 the busiest yet and have included for the first time the PowerMEMS School. This two-day school held at Imperial College London covered a wide range of power-MEMS topics including technologies for power generation, power transmission, energy storage, power electronics interfaces and metrology. Registrations for the School exceeded our expectations and it was full by early November. We hope this, and other activities such as the Discussion Panel and the inclusion of late news papers, will make PowerMEMS 2013 a memorable success. We have also reached out to new communities, such as those working in wireless power transfer and RF harvesting to broaden the technology remit of
NASA Astrophysics Data System (ADS)
Mitcheson, Paul; Beeby, Steve
2013-12-01
It is a pleasure to welcome you to The Royal Society in London and the 13th International Conference on Micro- and Nano-Technology for Power Generation and Energy Conversion Applications, or PowerMEMS 2013. The objective of PowerMEMS 2013 is to catalyse innovation in miniature, micro- and nano-scale technologies for power generation and energy conversion. The conference aims to stimulate the exchange of insights and information, and the development of new ideas in the Power MEMS/NEMS field as well as at the meso-scale. It will allow the attendees to interact and network within our multidisciplinary community that includes professionals from many branches of science and engineering. The technical program is led by four invited speakers covering inductive power transfer, chip scale power sources, thermal energy harvesting and implantable biofuel cells. We received 177 abstracts and following a careful reviewing process by the Technical Program Committee a total of 137 papers were selected for presentation. These have been organised into 16 oral sessions in two parallel streams and two poster sessions that have been augmented by 10 late news papers. The oral and regular poster papers are, for the first time, being published by the Institute of Physics. We have made every effort to make PowerMEMS 2013 the busiest yet and have included for the first time the PowerMEMS School. This two-day school held at Imperial College London covered a wide range of power-MEMS topics including technologies for power generation, power transmission, energy storage, power electronics interfaces and metrology. Registrations for the School exceeded our expectations and it was full by early November. We hope this, and other activities such as the Discussion Panel and the inclusion of late news papers, will make PowerMEMS 2013 a memorable success. We have also reached out to new communities, such as those working in wireless power transfer and RF harvesting to broaden the technology remit of
McGuire, Lynne I; Poleggi, Anna; Poggiolini, Ilaria; Suardi, Silvia; Grznarova, Katarina; Shi, Song; de Vil, Bart; Sarros, Shannon; Satoh, Katsuya; Cheng, Keding; Cramm, Maria; Fairfoul, Graham; Schmitz, Matthias; Zerr, Inga; Cras, Patrick; Equestre, Michele; Tagliavini, Fabrizio; Atarashi, Ryuichiro; Knox, David; Collins, Steven; Haïk, Stéphane; Parchi, Piero; Pocchiari, Maurizio; Green, Alison
2016-07-01
Real-time quaking-induced conversion (RT-QuIC) has been proposed as a sensitive diagnostic test for sporadic Creutzfeldt-Jakob disease; however, before this assay can be introduced into clinical practice, its reliability and reproducibility need to be demonstrated. Two international ring trials were undertaken in which a set of 25 cerebrospinal fluid samples were analyzed by a total of 11 different centers using a range of recombinant prion protein substrates and instrumentation. The results show almost complete concordance between the centers and demonstrate that RT-QuIC is a suitably reliable and robust technique for clinical practice. Ann Neurol 2016;80:160-165. PMID:27130376
McGuire, Lynne I.; Poleggi, Anna; Poggiolini, Ilaria; Suardi, Silvia; Grznarova, Katarina; Shi, Song; de Vil, Bart; Sarros, Shannon; Satoh, Katsuya; Cheng, Keding; Cramm, Maria; Fairfoul, Graham; Schmitz, Matthias; Zerr, Inga; Cras, Patrick; Equestre, Michele; Tagliavini, Fabrizio; Atarashi, Ryuichiro; Knox, David; Collins, Steven; Haïk, Stéphane; Parchi, Piero; Pocchiari, Maurizio
2016-01-01
Real‐time quaking‐induced conversion (RT‐QuIC) has been proposed as a sensitive diagnostic test for sporadic Creutzfeldt–Jakob disease; however, before this assay can be introduced into clinical practice, its reliability and reproducibility need to be demonstrated. Two international ring trials were undertaken in which a set of 25 cerebrospinal fluid samples were analyzed by a total of 11 different centers using a range of recombinant prion protein substrates and instrumentation. The results show almost complete concordance between the centers and demonstrate that RT‐QuIC is a suitably reliable and robust technique for clinical practice. Ann Neurol 2016;80:160–165 PMID:27130376
Anderson, John L
2011-01-01
Om July 18, 2010, the eve of the 21st International Congress on the Education of the Deaf (ICED 2010), the International Leaders Summit was held at the Center for Dialogue at Simon Fraser University, Vancouver, Canada. A total of 120 world leaders from 32 countries participated. Presenters, including students, led the conversation on current perspectives, teacher preparation, worldwide resources, and major issues affecting the education of d/Deaf and hard of hearing infants, children, and youth. Summit participants recognized that advances in detection, early intervention, and technology present challenges in meeting the needs of a student population more diverse than at any other stage in history. While it was acknowledged that needs differ in various parts of the world, there was a consensus that change is required to prepare students to handle challenges in the 21st century. PMID:21949967
Fujimura, Miki; Tominaga, Teiji
2015-01-01
Moyamoya disease is a chronic cerebrovascular disease with unknown etiology, which is characterized by bilateral steno-occlusive changes at the terminal portion of the internal carotid artery and an abnormal vascular network formation at the base of the brain. Moyamoya disease is known to have unique and dynamic nature to convert the vascular supply for the brain from internal carotid (IC) system to the external carotid (EC) system, as indicated by Suzuki's angiographic staging established in 1969. Insufficiency of this 'IC-EC conversion system' may result in cerebral ischemia, as well as in intracranial hemorrhage from inadequate collateral vascular network, both of which represent the clinical presentation of moyamoya disease. Therefore, surgical revascularization by extracranial-intracranial bypass is the preferred procedure for moyamoya disease to complement 'IC-EC conversion' and thus to avoid cerebral infarction and/or intracranial hemorrhage. Long-term outcome of revascularization surgery for moyamoya disease is favorable, but rapid increase in cerebral blood flow on the affected hemisphere could temporarily cause unfavorable phenomenon such as cerebral hyperperfusion syndrome. We would review the current status of revascularization surgery for moyamoya disease based on its basic pathology, and sought to discuss the significance of measuring cerebral blood flow in the acute stage and intensive perioperative management. PMID:25971859
Lee, Jae Hoon; Chung, Duke Whan; Han, Chung Soo
2012-09-01
The purpose of this study was to analyze the utility and the clinical outcomes of anterolateral thigh (ALT)-free flaps and conversion from external to internal fixation with plating and bone grafting in Gustilo type IIIB open tibial fractures. A total of 21 patients were analyzed retrospectively. The mean follow-up period was 18 months and the mean age was 46.7 years. There were 18 men and three women. The mean time from injury to flap coverage was 11.6 days. The mean size of flaps used was 15.3 × 8.2 cm. The mean size of bone defects was 2.26 cm. Segmental bone defects were observed in 5 five cases, for which bone transport or vascularized fibular graft were performed. When flaps were successful and the fracture sites did not have any evidence of infection, internal fixation with plates and bone grafting were performed. Flaps survived in 20 cases. In the 20 cases with successful flaps, two cases developed osteomyelitis, but the 20 cases achieved solid bone union at a mean of 8.6 months after the injury, salvaging the lower extremity in 100% of the cases. At the last follow-up, 9 nine cases were measured excellent or good; 6, fair; and 6, poor in the functional assessment based on the method developed by Puno et al. ALT- free flaps to cover soft tissue defects in Gustilo type IIIB open tibial fractures are considered as useful option for the treatment of composite defects. In addition, conversion to internal fixation and bone grafting can be an alternative method in order to reduce the risk of complications and inconvenience of external fixators. PMID:22434519
Law, Ryan; Grimm, Ian S; Stavas, Joseph M; Baron, Todd H
2016-03-01
Patients with acute cholecystitis sometimes require placement of percutaneous cholecystostomy catheters, either as a bridge to surgery or as primary therapy. In patients who cannot undergo surgery, subsequent removal of the catheter can lead to recurrence of cholecystitis, whereas leaving the drain in place can cause adverse events. We investigated internalization of percutaneous cholecystostomy drainage catheters, using endoscopic ultrasound (EUS)-guided placement of lumen-apposing metal stents (LAMS) as an alternative treatment strategy. Seven patients (median age, 57 years; 6 men) underwent EUS-guided cholecystoenterostomy for internalization of gallbladder drainage with EUS-guided placement of a 10- or 15-mm LAMS. All had initially been treated with placement of a percutaneous cholecystostomy catheter for cholecystitis and were later deemed unfit for cholecystectomy. Technical success was achieved in all patients in 1 endoscopic session, with subsequent removal of all percutaneous drains. Two patients required placement of self-expandable metal stents within the LAMS to successfully bridge the gallbladder and gastrointestinal lumen. No adverse events occurred after a median follow-up of 2.5 months. EUS-guided cholecystoenterostomy using a LAMS is therefore a viable option for internal gallbladder drainage in patients who have a percutaneous cholecystostomy catheter and are poor candidates for cholecystectomy. PMID:26528802
Solvent-mediated internal conversion in diphenoxyethane-(H{sub 2}O){sub n}clusters, n = 2-4
Walsh, Patrick S.; Buchanan, Evan G.; Gord, Joseph R.; Zwier, Timothy S.
2015-04-21
1,2-diphenoxyethane (DPOE) is a flexible bichromophore whose excited states come in close-lying pairs whose splitting and vibronic coupling can be modulated by solvent. Building on the ground state infrared spectroscopy of DPOE-(H{sub 2}O){sub n} clusters with n = 2-4 from the adjoining paper [Walsh et al., J. Chem. Phys. 142, 154303 (2015)], the present work focuses on the vibronic and excited state infrared spectroscopies of the clusters. The type and degree of asymmetry of the water cluster binding to DPOE is reflected in the variation in the magnitude of the S{sub 1}/S{sub 2} splitting with cluster size. Excited state resonant ion-dip infrared spectroscopy was performed at the electronic origins of the first two excited states in order to explore how the water clusters’ OH stretch spectra report on the nature of the two excited states, and the interaction of the S{sub 2} state with nearby S{sub 1} vibronic levels mediated by the water clusters. The data set, when taken as a whole, provides a state-to-state view of internal conversion and the role of solvent in mediating conversion of electronic excitation between two chromophores, providing a molecular-scale view of Kasha’s rule.
NASA Astrophysics Data System (ADS)
Kakitani, Yoshinori; Miki, Takeshi; Koyama, Yasushi; Nagae, Hiroyoshi; Nakamura, Ryosuke; Kanematsu, Yasuo
2009-07-01
The time constants of the vibrational relaxation, υ = 2 → υ = 1 and υ = 1 → υ = 0, in the 1Bu+ manifold and those of internal conversion from the 1Bu+(0) level, which is isoenergetic (so-called 'diabatic') with the 1Bu- vibronic levels in neurosporene and spheroidene and with the 3Ag- vibronic levels in lycopene and anhydrorhodovibrin, were determined by Kerr-gate fluorescence spectroscopy. The time constants of the vibrational relaxation were in the ˜1:2 ratio, and those of internal conversion agreed with the lifetimes of the diabatic counterparts, i.e., the 1Bu- and 3Ag- electronic states, respectively.
NASA Astrophysics Data System (ADS)
Livermore, C.; Velásquez-García, L. F.
2015-12-01
Greetings, and welcome to Boston, MA and PowerMEMS 2015 - the 15th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications! The objective of PowerMEMS 2015 is to catalyze innovation in micro- and nano-scale technologies for the energy domain. The scope of the meeting ranges from basic principles, to materials and fabrication, to devices and systems, to applications. The many applications of Power MEMS range from the harvesting, storage, conversion and conditioning of energy, to integrated systems that manage these processes, to actuation, pumping, and propulsion. Our Conference aims to stimulate the exchange of insights and information, as well as the development of new ideas, in the Power MEMS field. Our goal is to allow the attendees to interact and network within our multidisciplinary community that includes professionals from many branches of science and engineering, as well as energy, policy, and entrepreneurial specialists interested in the commercialization of Power MEMS technologies. Since the first PowerMEMS in Sendai, Japan in 2000, the Conference has grown in size, reputation, impact, and technical breadth. This continuing growth is evident in this year's technical program, which includes an increasing number of papers on nanomaterials, additive manufacturing for energy systems, actuators, energy storage, harvesting strategies and integrated energy harvesting systems, for example. This year's technical program is highlighted by six plenary talks from prominent experts on piezoelectrics, robotic insects, thermoelectrics, photovoltaics, nanocomposite cathodes, and thermal energy conversion systems. The contributed program received a large number of abstract submissions this year, 169 in total. After careful review by the 34-member Technical Program Committee, a total of 135 papers were selected for presentation. The 60 contributed oral presentations are arranged in two parallel sessions. The 75 posters
NASA Astrophysics Data System (ADS)
Rondonuwu, Ferdy S.; Watanabe, Yasutaka; Fujii, Ritsuko; Koyama, Yasushi
2003-07-01
Subpicosecond time-resolved absorption spectra were recorded in the visible region for a set of photosynthetic carotenoids having different numbers of conjugated double bonds ( n), which include neurosporene ( n=9), spheroidene ( n=10), lycopene ( n=11), anhydrorhodovibrin ( n=12) and spirilloxanthin ( n=13). Singular-value decomposition and global fitting of the spectral-data matrices lead us to a branched relaxation scheme including both (1) the singlet internal conversion in the sequence of 1 1B u+ → 1 1B u- → 2 1A g- → 1 1A g-(ground), and (2) the singlet-to-triplet conversion of 1 1B u- → 1 3A g followed by triplet internal conversion of 1 3A g → 1 3B u.
NASA Astrophysics Data System (ADS)
Cho, Young-Ho
2012-09-01
This special section of Journal of Micromechanics and Microengineering features papers selected from the 11th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2011), held at Sejong Hotel in Seoul, Korea during 15-18 November 2011. Since the first PowerMEMS workshop held in Sendai, Japan in 2000, the workshop has developed as the premier forum for reporting research results in micro and nanotechnology for power generation, energy conversion, harvesting and processing applications, including in-depth technical issues on nanostructures and materials for small-scale high-density energy and thermal management. Potential PowerMEMS applications cover not only portable power devices for consumer electronics and remote sensors, but also micro engines, impulsive thrusters and fuel cells for systems ranging from the nanometer to the millimeter scale. The 2011 technical program consists of 1 plenary talk, 4 invited talks and 118 contributed presentations. The 48 oral and 70 poster presentations, selected by 27 Technical Program Committee Members from 131 submitted abstracts, have stimulated lively discussion maximizing the interaction between participants. Among them, this special section includes 9 papers covering micro-scale power generators, energy converters, harvesters, thrusters and thermal coolers. Finally, we are grateful to the members of the International Steering Committee, the Technical Program Committee, and the Local Organizing Committee for their efforts and contributions to PowerMEMS 2011. We also thank the two companies Samsung Electro-Mechanics and LG Elite for technical tour arrangements. Special thanks go to Dr Ian Forbes, the editorial staff of the Journal of Micromechanics and Microengineering, as well as to the staff of IOP Publishing for making this special section possible.
NASA Astrophysics Data System (ADS)
Tanaka, Shuji
2009-09-01
This special issue of the Journal of Micromechanics and Microengineering features papers selected from The 8th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2008) with the 2nd Symposium on Micro Environmental Machine Systems (μMEMS 2008). The workshop was held in Sendai, Japan on 9-12 November 2008 by Tohoku University. This is the second time that the PowerMEMS workshop has been held in Sendai, following the first workshop in 2000. Power MEMS is one of the newest categories of MEMS, which encompasses microdevices and microsystems for power generation, energy conversion and propulsion. The first concept of Power MEMS was born in the late 1990's from a MEMS-based gas turbine project at Massachusetts Institute of Technology. After that, the research and development of Power MEMS have been promoted by the strong need for compact power sources with high energy and/or power density. Since its inception, Power MEMS has expanded to include not only various MEMS-based power generators but also small energy machines and microdevices for macro power generators. Previously, the main topics of the PowerMEMS workshop were miniaturized gas turbines and micro fuel cells, but recently, energy harvesting has been the hottest topic. In 2008, energy harvesting had a 41% share in the 118 accepted regular papers. This special issue includes 19 papers on various topics. Finally, I would like to express my sincere appreciation to the members of the International Steering Committee, the Technical Program Committee, the Local Organizing Committee and financial supporters. This special issue was edited in collaboration with the staff of IOP Publishing.
Factor Scores, Structure Coefficients, and Communality Coefficients
ERIC Educational Resources Information Center
Goodwyn, Fara
2012-01-01
This paper presents heuristic explanations of factor scores, structure coefficients, and communality coefficients. Common misconceptions regarding these topics are clarified. In addition, (a) the regression (b) Bartlett, (c) Anderson-Rubin, and (d) Thompson methods for calculating factor scores are reviewed. Syntax necessary to execute all four…
Yasin, Muhammad; Park, Shinyoung; Jeong, Yeseul; Lee, Eun Yeol; Lee, Jinwon; Chang, In Seop
2014-10-01
This study proposed a submerged hollow fibre membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) membrane fibres were used to fabricate a membrane module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen (P) and membrane surface area per unit working volume of the liquid (A(S)/V(L)) were used as controllable parameters to determine gas-liquid volumetric mass transfer coefficient (k(L)a) values. We found a k(L)a of 135.72 h(-1) when P was 93.76 kPa and AS/VL was fixed at 27.5m(-1). A higher k(L)a of 155.16 h(-1) was achieved by increasing AS/VL to 62.5m(-1) at a lower P of 37.23 kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO2 fermentation using Eubacterium limosum KIST612. PMID:25105269
Kobayashi, Masanao; Ootsuka, Tomoko; Suzuki, Syoichi
2013-01-01
The purpose of this paper is to reappraise the accuracy of a conversion coefficient (k) reported by International Commission on Radiological Protection Publication 102 Table A.2. The effective doses of the routine head computed tomography (CT), the routine chest CT, the perfusion CT, and the coronary CT were evaluated using the conversion coefficient (adult head: 0.021 mSv·mGy⁻¹·cm⁻¹, adult chest: 0.014 mSv·mGy⁻¹·cm⁻¹). The dose length product (DLP) used the value displayed on the console on each scanning condition. The effective doses were evaluated using a human body type phantom (Alderson Rando phantom) and thermoluminescent dosimeter (TLD) elements for comparison with the converted value. This paper reported that the effective doses evaluated from conversion coefficient became different by 0.3 mSv (17%) compared with measurements, the effective dose computed with the conversion coefficient of the adult chest may be underestimated by 45%, and the bolus-tracking which scans the narrow beams should not use a conversion coefficient. PMID:23358334
Felder, W.
1980-09-01
Reliable kinetic data on isolated elementary combustion reactions spanning a broad temperature range are required for modeling and scaling studies aimed at improving the performance of, and reducing the pollutant formation from, fossil-fuel burning devices. Such data are generally not available. In the present work a new technique, High Temperature Photochemistry (HTP), has been developed to provide such data. It combines the technology of the high-temperature, fast-flow reactors (HTFFR) we developed to study kinetics of metal atom/oxide reactions in the 300 to 1900 K range with the methodology of the flash photolysis technique which, although used widely for study of such combustion reactions, has previously been limited to studies at or near room temperature. This report discusses aspects of the complete HTP study on the benchmark reaction, O + CH/sub 4/ ..-->../sup (1)/ OH + CH/sub 3/, including new data in the 1500 to 1700 K range obtained in the present contract year. The data which extend from 400 to 1700 K overlap the previous low temperature (250 to 950 K) and high temperature (1200 to 2600 K) measurements of k/sub 1/(T) and show a curved Arrhenius plot, in excellent agreement with the more reliable work of others and with recent theoretical work. The HTP data can be fit by an empirical rate coefficient expression which is given. The HTP apparatus has been modified to conduct measurements on the reaction OH + C/sub 6/H/sub 6/ and these experiments have been initiated.
Coefficient Alpha and Reliability of Scale Scores
ERIC Educational Resources Information Center
Almehrizi, Rashid S.
2013-01-01
The majority of large-scale assessments develop various score scales that are either linear or nonlinear transformations of raw scores for better interpretations and uses of assessment results. The current formula for coefficient alpha (a; the commonly used reliability coefficient) only provides internal consistency reliability estimates of raw…
Preliminary Neutronic Study of D2O-cooled High Conversion PWRs
Hikaru Hiruta; Gilles Youinou
2013-10-01
This paper presents a preliminary neutronics analysis of tight-pitch D2O-cooled high-conversion PWRs loaded with MOX fuel aiming at high Pu conversion and negative void coefficient. SCALE6.1 has been exclusively utilized for this study. The analyses are performed in two separate parts. The first part of this paper investigates the performance of axial and internal blankets and seeks break-even or near-breeder core even without the presence of radial blankets. The second part of this paper performs sensitivity and uncertainty analyses of integral parameters (keff and void coefficient) for selected systems in order to analyze the characters of this high-conversion PWR from different aspects.
Recirculation in multiple wave conversions
Kaufman, A. N.; Brizard, A.J.; Kaufman, A.N.; Tracy, E.R.
2008-07-30
A one-dimensional multiple wave-conversion model is constructed that allows energy recirculation in ray phase space. Using a modular eikonal approach, the connection coefficients for this model are calculated by ray phase-space methods. Analytical results (confirmed numerically) show that all connection coefficients exhibit interference effects that depend on an interference phase, calculated from the coupling constants and the area enclosed by the intersecting rays. This conceptual model, which focuses on the topology of intersecting rays in phase space, is used to investigate how mode conversion between primary and secondary waves is modified by the presence of a tertiary wave.
Coefficients for Interrater Agreement.
ERIC Educational Resources Information Center
Zegers, Frits E.
1991-01-01
The degree of agreement between two raters rating several objects for a single characteristic can be expressed through an association coefficient, such as the Pearson product-moment correlation. How to select an appropriate association coefficient, and the desirable properties and uses of a class of such coefficients--the Euclidean…
NASA Astrophysics Data System (ADS)
Ghodssi, Reza; Livermore, Carol; Arnold, David
2010-10-01
This special section of the Journal of Micromechanics and Microengineering presents papers selected from the 9th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2009), which was held in Washington DC, USA from 1-4 December 2009. Since it was first held in Sendai, Japan in 2000, the PowerMEMS workshop has focused on small-scale systems that process, convert, or generate macroscopically significant amounts of power, typically with high power density or high energy density. In the workshop's early years, much of the research presented was on small-scale fueled systems, such as micro heat engines and micro fuel cells. The past nine years have seen a dramatic expansion in the range of technologies that are brought to bear on the challenge of high-power, small-scale systems, as well as an increase in the applications for such technologies. At this year's workshop, 158 contributed papers were presented, along with invited and plenary presentations. The papers focused on applications from micro heat engines and fuel cells, to energy harvesting and its enabling electronics, to thermal management and propulsion. Also presented were the technologies that enable these applications, such as the structuring of microscale, nanoscale and biological systems for power applications, as well as combustion and catalysis at small scales. This special section includes a selection of 12 expanded papers representing energy harvesting, chemical and fueled systems, and elastic energy storage at small scales. We would like to express our appreciation to the members of the International Steering Committee, the Technical Program Committee, the Local Organizing Committee, and to the workshop's financial supporters. We are grateful to the referees for their contributions to the review process. Finally, we would like to thank Dr Ian Forbes, the editorial staff of the Journal of Micromechanics and Microengineering, and the staff
Atmospheric Science Data Center
2013-03-12
... 1,000,000 1,000,000 micrometers nano- 1,000,000,000 1,000,000,000 nanometers ... conversions, see the National Institute of Standards and Technology (NIST) Special Publications: NIST Guide to SI Units: ...
NASA Astrophysics Data System (ADS)
Hebling, C.; Woias, P.
2008-10-01
This special issue of Journal of Micromechanics and Microengineering (JMM) contains a selection of papers from the 7th International Workshop on Micro and Nanotechnologies for Power Generation and Energy Conversion (PowerMEMS 2007). The workshop was held in Freiburg, Germany on 27-29 November 2007 under the joint organization of the Fraunhofer Institute for Solar Energy Systems (FhG-ISE), Freiburg and the Department of Microsystems Engineering (IMTEK) of the Albert-Ludwig-University of Freiburg. PowerMEMS 2007 continues a series of workshops initiated in 2000 in Japan to create an annual discussion forum in the emerging field of micro energy technology. With a single exception in 2001, the workshop has continued as an annual meeting ever since, with a continuous increase in the number of presentations and participants. The program of PowerMEMS 2007 was composed of 2 invited talks, 25 oral talks and 61 poster presentations. From these 88 presentations 16 have been selected for this special issue. It was at the end of 1959 when the Caltech physicist Richard Feynman gave his famous lecture entitled 'There Is Plenty of Room at the Bottom' in which he discussed the possibilities of miniaturization for both storage capacity ('Encyclopaedia Britannica on the head of a pin') as well as micro machining ('rearranging the atoms'), although there were absolutely no technological possibilities in sight for an adequate realization of such ideas. Now, nearly 50 years later, we not only have incredible knowledge about the nanoworld, but even more we are now able to generate microelectromechanical devices which, next to their electronic properties, can integrate physical and analytical functions. Today, Feynman might easily have added a second lecture entitled 'There is Plenty of Energy at the Bottom'. Micro energy technology has seen a tremendous rise in MEMS and material sciences and is regarded today as one of their hot topics. Also, there are more and more companies in this
New calculations of neutron kerma coefficients and dose equivalent.
Liu, Zhenzhou; Chen, Jinxiang
2008-06-01
For neutron energies ranging from 1 keV to 20 MeV, the kerma coefficients for elements H, C, N, O, light water, and ICRU tissue were deduced respectively from microscopic cross sections and Monte Carlo simulation (MCNP code). The results are consistent within admitted uncertainties with values evaluated by an international group (Chadwick et al 1999 Med. Phys. 26 974-91). The ambient dose equivalent generated in the ISO-recommended neutron field for an Am-Be neutron source (ISO 8529-1: 2001(E)) was obtained from the kerma coefficients and Monte Carlo calculation. In addition, it was calculated directly by multiplying the neutron fluence by the fluence-to-ambient dose conversion coefficients recommended by ICRP (ICRP 1996 ICRP Publication 74 (Oxford: Pergamon)). The two results agree well with each other. The main feature of this work is our Monte Carlo simulation design and the treatments differing from the work of others in the calculation of neutron energy transfer in non-elastic processes. PMID:18495982
ERIC Educational Resources Information Center
Xia, Jiang
1998-01-01
Describes an activity for use in the conversational English-as-a-foreign-language classroom. The activity involves having each student say one or two sentences that continues a story being made up as the activity goes along. Students were positive about the activity, because saying only one or two sentences helped them not to feel pressured or…
NASA Astrophysics Data System (ADS)
Preece, Alun; Webberley, Will; Braines, Dave
2015-05-01
Recent advances in natural language question-answering systems and context-aware mobile apps create opportunities for improved sensemaking in a tactical setting. Users equipped with mobile devices act as both sensors (able to acquire information) and effectors (able to act in situ), operating alone or in collectives. The currently- dominant technical approaches follow either a pull model (e.g. Apple's Siri or IBM's Watson which respond to users' natural language queries) or a push model (e.g. Google's Now which sends notifications to a user based on their context). There is growing recognition that users need more flexible styles of conversational interaction, where they are able to freely ask or tell, be asked or told, seek explanations and clarifications. Ideally such conversations should involve a mix of human and machine agents, able to collaborate in collective sensemaking activities with as few barriers as possible. Desirable capabilities include adding new knowledge, collaboratively building models, invoking specific services, and drawing inferences. As a step towards this goal, we collect evidence from a number of recent pilot studies including natural experiments (e.g. situation awareness in the context of organised protests) and synthetic experiments (e.g. human and machine agents collaborating in information seeking and spot reporting). We identify some principles and areas of future research for "conversational sensemaking".
NASA Astrophysics Data System (ADS)
Preece, Alun; Gwilliams, Chris; Parizas, Christos; Pizzocaro, Diego; Bakdash, Jonathan Z.; Braines, Dave
2014-05-01
Recent developments in sensing technologies, mobile devices and context-aware user interfaces have made it pos- sible to represent information fusion and situational awareness for Intelligence, Surveillance and Reconnaissance (ISR) activities as a conversational process among actors at or near the tactical edges of a network. Motivated by use cases in the domain of Company Intelligence Support Team (CoIST) tasks, this paper presents an approach to information collection, fusion and sense-making based on the use of natural language (NL) and controlled nat- ural language (CNL) to support richer forms of human-machine interaction. The approach uses a conversational protocol to facilitate a ow of collaborative messages from NL to CNL and back again in support of interactions such as: turning eyewitness reports from human observers into actionable information (from both soldier and civilian sources); fusing information from humans and physical sensors (with associated quality metadata); and assisting human analysts to make the best use of available sensing assets in an area of interest (governed by man- agement and security policies). CNL is used as a common formal knowledge representation for both machine and human agents to support reasoning, semantic information fusion and generation of rationale for inferences, in ways that remain transparent to human users. Examples are provided of various alternative styles for user feedback, including NL, CNL and graphical feedback. A pilot experiment with human subjects shows that a prototype conversational agent is able to gather usable CNL information from untrained human subjects.
Coefficients of Effective Length.
ERIC Educational Resources Information Center
Edwards, Roger H.
1981-01-01
Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)
Factors Affecting Coefficient Alpha: A Mini Monte Carlo Study.
ERIC Educational Resources Information Center
Reinhardt, Brian M.
Factors affecting a lower-bound estimate of internal consistency reliability, Cronbach's coefficient alpha, are explored. Theoretically, coefficient alpha is an estimate of the correlation between two tests drawn at random from a pool of items like the items in the test under consideration. As a practical matter, coefficient alpha can be an index…
My Current Thoughts on Coefficient Alpha and Successor Procedures
ERIC Educational Resources Information Center
Cronbach, Lee J.; Shavelson, Richard J.
2004-01-01
In 1997, noting that the 50th anniversary of the publication of "Coefficient Alpha and the Internal Structure of Tests" was fast approaching, Lee Cronbach planned what have become the notes published here. His aim was to point out the ways in which his views on coefficient alpha had evolved, doubting now that the coefficient was the best way of…
NASA Astrophysics Data System (ADS)
Reynaerts, Dominiek; Vullers, Ruud
2011-10-01
This special section of Journal of Micromechanics and Microengineering features papers selected from the 10th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2010). The workshop was organized in Leuven, Belgium from 30 November to 3 December 2010 by Katholieke Universiteit Leuven and the imec/Holst Centre. This was a special PowerMEMS Workshop, for several reasons. First of all, we celebrated the 10th anniversary of the workshop: the first PowerMEMS meeting was organized in Sendai, Japan in 2000. None of the organizers or participants of this first meeting could have predicted the impact of the workshop over the next decade. The second reason was that, for the first time, the conference organization spanned two countries: Belgium and the Netherlands. Thanks to the advances in information technology, teams from Katholieke Universiteit Leuven (Belgium) and the imec/Holst Centre in Eindhoven (the Netherlands) have been able to work together seamlessly as one team. The objective of the PowerMEMS Workshop is to stimulate innovation in micro and nanotechnology for power generation and energy conversion applications. Its scope ranges from integrated microelectromechanical systems (MEMS) for power generation, dissipation, harvesting, and management, to novel nanostructures and materials for energy-related applications. True to the objective of the PowerMEMSWorkshop, the 2010 technical program covered a broad range of energy related research, ranging from the nanometer to the millimeter scale, discussed in 5 invited and 52 oral presentations, and 112 posters. This special section includes 14 papers covering vibration energy harvesters, thermal applications and micro power systems. Finally, we wish to express sincere appreciation to the members of the International Steering Committee, the Technical Program Committee and last but not least the Local Organizing Committee. This special issue was edited in
NASA Astrophysics Data System (ADS)
Naqvi, K. Razi; Jávorfi, Tamás; Melø, T. B.; Garab, Gyözö
1998-12-01
Wavelength-selective photo-excitation of samples containing a detergent and LHCII (the main light-harvesting complex pertaining to photosystem II of green plants) is used for recording time-resolved triplet-minus-singlet (TmS) difference spectra, with a view to probing interactions between chlorophyll a (Chl a) and chlorophyll b (Chl b), and between Chl a and lutein (Lut). Once the detergent concentration ( CD) exceeds a threshold, C©, the TmS spectrum becomes sensitive to λ⊗, the wavelength of excitation, and to t, the delay between excitation and observation. Each increment in CD brings about a diminution in the efficiency of a†→ x† transfer (triplet-triplet transfer from Chl a to Lut) and a rise in both the triplet formation yield and the fluorescence yield of Chl a. What is more, b*→ a* transfer (singlet-singlet transfer from Chl b to Chl a) slackens to such an extent that Chl b*→Chl b† intersystem crossing, negligible when CD is below C©, begins to vie with transfer, for the deactivation of Chl b* (in the foregoing an asterisk/dagger denotes singlet/triplet excitation). The reduction in the efficiencies of the two transfers is easily understood by: (i) invoking the Kühlbrandt-Wang-Fujiyoshi model of LHCII, which posits each Chl b in contact with a Chl a and each Chl a in contact with a Lut, and (ii) assuming that the detergent severs contact between adjacent chromophores. That a growth in the triplet yield of Chl a* accompanies the detergent-induced decrease in the efficiency of a†→ x† transfer becomes intelligible if one assumes, further, that internal conversion in Chla* is faster than that in overlineChla * , where under or over lining betokens the presence or absence of a carotenoid neighbour. When CD is close to C©, most Chl a molecules are adjacent to a Lut, internal conversion dominates, and the overall triplet yield is low. As CD is gradually raised the Chla → overlineChla transformation sets in, causing concomitant drops in
NASA Astrophysics Data System (ADS)
Springborg, Michael; Kirtman, Bernard
2013-03-01
Piezoelectricity results from a coupling between responses to mechanical and electric perturbations and leads to changes in the polarization due to strain or stress or, alternatively, the occurrence of strain as a function of an applied external, electrostatic field (i.e., converse piezoelectricity). Theoretical studies of those properties for extended systems require accordingly that their dipole moment or polarization can be calculated. However, whereas the definition of the operator for the dipole moment for any finite system is trivial, it is only within the last 2 decades that the expressions for the equivalent operator in the independent-particle approximation for the infinite and periodic system have been presented. Here, we demonstrate that the so called branch dependence of the polarization for the infinite, periodic system is related to physical observables in contrast to what often is assumed. This is related to the finding that converse piezoelectric properties depend both on the surfaces of the samples of interest even for samples with size well above the thermodynamic limit. However, we shall demonstrate that these properties can be calculated without explicitly taking the surfaces into account. Both the foundations and results for real system shall be presented.
NASA Technical Reports Server (NTRS)
Snyder, G. Jeffrey (Inventor)
2015-01-01
A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.
ERIC Educational Resources Information Center
Slapac, Alina; Kim, Sujin
2014-01-01
Building a culturally responsive learning community begins with global awareness and cultural responsiveness. Preservice and PreK-12 practicing teachers can use the interactive questions showcased here to enhance their intercultural competence by drawing on the knowledge, skills, and experiences of international faculty and colleagues.
Bounding the Bogoliubov coefficients
Boonserm, Petarpa; Visser, Matt
2008-11-15
While over the last century or more considerable effort has been put into the problem of finding approximate solutions for wave equations in general, and quantum mechanical problems in particular, it appears that as yet relatively little work seems to have been put into the complementary problem of establishing rigourous bounds on the exact solutions. We have in mind either bounds on parametric amplification and the related quantum phenomenon of particle production (as encoded in the Bogoliubov coefficients), or bounds on transmission and reflection coefficients. Modifying and streamlining an approach developed by one of the present authors [M. Visser, Phys. Rev. A 59 (1999) 427-438, (arXiv:quant-ph/9901030)], we investigate this question by developing a formal but exact solution for the appropriate second-order linear ODE in terms of a time-ordered exponential of 2x2 matrices, then relating the Bogoliubov coefficients to certain invariants of this matrix. By bounding the matrix in an appropriate manner, we can thereby bound the Bogoliubov coefficients.
Woodall, J.M.
1982-02-16
Energy conversion capable of receiving input energy in thermal or radiant form at a variable rate and releasing energy in thermal, radiant or electrical form independent of rate is accomplished by providing a buffer member of a material that has three criteria: a melting temperature above 1300/sup degree/ K, a thermal conductance greater than 0.1 in calories per square centimeter per centimeter per degree per second and a latent heat of fusion of the order of 1 kilocalorie per mole. The converter can absorb energy of multiple types, store it and then release it in a form compatible with the prospective use. Sunlight of daylight duration and varying intensity is converted to steady 24 hour a day electrical output.
Effectiveness Factors and Conversion in a Biocatalytic Membrane Reactor
Godongwana, Buntu
2016-01-01
Analytical expressions of the effectiveness factor of a biocatalytic membrane reactor, and its asymptote as the Thiele modulus becomes large, are presented. The evaluation of the effectiveness factor is based on the solution of the governing equations for solute transport in the two regions of the reactor, i.e. the lumen and the matrix (with the biofilm immobilized in the matrix). The lumen solution accounts for both axial diffusion and radial convective flow, while the matrix solution is based on Robin-type boundary conditions. The effectiveness factor is shown to be a function of the Thiele modulus, the partition coefficient, the Sherwood number, the Peclet number, and membrane thickness. Three regions of Thiele moduli are defined in the effectiveness factor graphs. These correspond with reaction rate limited, internal-diffusion limited, and external mass transfer limited solute transport. Radial convective flows were shown to only improve the effectiveness factor in the region of internal diffusion limitation. The assumption of first order kinetics is shown to be applicable only in the Thiele modulus regions of internal and external mass transfer limitation. An iteration scheme is also presented for estimating the effectiveness factor when the solute fractional conversion is known. The model is validated with experimental data from a membrane gradostat reactor immobilised with Phanerochaete chrysosporium for the production of lignin and manganese peroxidases. The developed model and experimental data allow for the determination of the Thiele modulus at which the effectiveness factor and fractional conversion are optimal. PMID:27104954
"The Clearing": Conversations at the Wabash Center
ERIC Educational Resources Information Center
Pence, Nadine S.
2007-01-01
The study of religion seeks to understand life and life practices, which means that it is internally suited to dynamic teaching-learning methods such as exploration, conversation, and imaginative construction. Wabash Center hospitality enables reflective conversations about the nature of our craft, the shape of our vocation, and the direction of…
How Metric Conversion Affects Administrative Practices
ERIC Educational Resources Information Center
Straka, M. K.
1977-01-01
Changes necessary in the administrative activities of educational institutions following conversion to the metric system are outlined for secretarial practices, purchasing, internal reporting and forms, computer operations, travel, publications, buildings and plant, new buildings, sport facilities, and health services. (MF)
Cupola Corner 1 - Conversation With Chris Ferguson
Atlantis Commander Chris Ferguson joined Expedition 28 Flight Engineer Ron Garan in the International Space Station cupola for some conversation about the space shuttle, and how the astronauts can ...
Optical Control of Internal Conversion in Pyrazine
NASA Astrophysics Data System (ADS)
Barry, Grant; Singha, Sima; Hu, Zhan; Seideman, Tamar; Gordon, Robert
2014-03-01
We apply quantum control schemes previously reserved for atoms and small molecules to more complex polyatomic molecules. Pyrazine was chosen as a model polyatomic molecule for its well-studied conical intersection seam between the S1 and S2 potential energy surfaces (PESs). Using shaped ultraviolet femtosecond laser pulses, we demonstrate optical control of the excited state dynamics of this molecule under collisionless conditions. This was achieved in a pump-probe experiment by employing a genetic algorithm programmed to suppress ionization of the pyrazine molecules at a preselected time. Our findings indicate that the optimized pulses localize the wave packet for times up to 1.5 ps at a location on the coupled S1/S2 PESs where ionization is energetically forbidden. Our approach is general and does not require knowledge of the molecular Hamiltonian. Funding provided by National Science Foundation grant no. CHE-0848198.
Document Conversion Methodology.
ERIC Educational Resources Information Center
Bovee, Donna
1990-01-01
Discusses digital imaging technology and examines document database conversion considerations. Two types of document imaging systems are described: (1) a work in process system, and (2) a storage and retrieval system. Conversion methodology is outlined, and a document conversion scenario is presented as a practical guide to conversion. (LRW)
Drag Coefficient of Hexadecane Particles
NASA Astrophysics Data System (ADS)
Nakao, Yoshinobu; Hishida, Makoto; Kajimoto, Sadaaki; Tanaka, Gaku
This paper deals with the drag coefficient of solidified hexadecane particles and their free rising velocity in liquid. The drag coefficient was experimentally investigated in Reynolds number range of about 40-300. The present experimental results are summarized in the following; (1) the drag coefficient of solidified hexadecane particles formed in liquid coolant by direct contact cooling is higher than that of a smooth surface sphere, this high drag coefficient seems to be attributed to the non-smooth surface of the solidified hexadecane particles, (2) experimental correlation for the drag coefficient of the solidified hexadecane particles was proposed, (3 ) the measured rising velocity of the solidified hexadecane particle agrees well with the calculated one, (4) the drag coefficients of hexadecane particles that were made by pouring hexadecane liquid into a solid hollow sphere agreed well with the drag coefficient of smooth surface sphere.
NASA Astrophysics Data System (ADS)
Allen, Mark G.; Lang, Jeffrey
2013-11-01
Welcome to this special section of the Journal of Micromechanics and Microengineering (JMM). This section, co-edited by myself and by Professor Jeffrey Lang of the Massachusetts Institute of Technology, contains expanded versions of selected papers presented at the Power MEMS meeting held in Atlanta, GA, USA, in December of 2012. Professor Lang and I had the privilege of co-chairing Power MEMS 2012, the 12th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications. The scope of the PowerMEMS series of workshops ranges from basic principles, to materials and fabrication, to devices and systems, to applications. The many applications of power MEMS (microelectromehcanical systems) range from MEMS-enabled energy harvesting, storage, conversion and conditioning, to integrated systems that manage these processes. Why is the power MEMS field growing in importance? Smaller-scale power and power supplies (microwatts to tens of watts) are gaining in prominence due to many factors, including the ubiquity of low power portable electronic equipment and the proliferation of wireless sensor nodes that require extraction of energy from their embedding environment in order to function. MEMS manufacturing methods can be utilized to improve the performance of traditional power supply elements, such as allowing batteries to charge faster or shrinking the physical size of passive elements in small-scale power supplies. MEMS technologies can be used to fabricate energy harvesters that extract energy from an embedding environment to power wireless sensor nodes, in-body medical implants and other devices, in which the harvesters are on the small scales that are appropriately matched to the overall size of these microsystems. MEMS can enable the manufacturing of energy storage elements from nontraditional materials by bringing appropriate structure and surface morphology to these materials as well as fabricating the electrical interfaces
26 CFR 1.1001-5 - European Monetary Union (conversion to the euro).
Code of Federal Regulations, 2010 CFR
2010-04-01
... 26 Internal Revenue 11 2010-04-01 2010-04-01 true European Monetary Union (conversion to the euro). 1.1001-5 Section 1.1001-5 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... § 1.1001-5 European Monetary Union (conversion to the euro). (a) Conversion of currencies....
NASA Astrophysics Data System (ADS)
Zhuravlev, M. V.; Solis, N. W.; Peretyagin, P. Yu.; Okun'kova, A. A.; Torrecillas, R.
2016-04-01
Using quantum and semiclassical approaches, the energy excitation threshold for induced Raman scattering is estimated and a relationship between the excitation threshold and the concentration of optically active molecules in a bilayer microresonator is established. Estimates are made during the formation of specially configured optical fields: internal and external photonic nanojets. Based on the amount of stored energy per mode and the value of the threshold intensity, an additional generalized selection rule for whispering gallery modes is suggested. It is shown that the bilayer microresonator can focus incident radiation (laser pumping) into a submicron focal volume at a low threshold intensity.
Conversion electron study of 110Cd: Evidence of new E0 branches
NASA Astrophysics Data System (ADS)
Jigmeddorj, B.; Garrett, P. E.; Diaz Varela, A.; Ball, G. C.; Bangay, J. C.; Cross, D. S.; Demand, G. A.; Garnsworthy, A. B.; Green, K. L.; Hackman, G.; Kulp, W. D.; Leach, K. G.; Orce, J. N.; Rand, E. T.; Sumithrarachchi, C.; Svensson, C. E.; Triambak, S.; Wong, J.; Wood, J. L.; Yates, S. W.
2016-02-01
Excited states of 110Cd were studied with conversion electron spectroscopy following the β+/EC decay of 110In. Internal conversion coefficients from K-shell electrons are extracted from γ- e- coincidences and compared with expected values for E1, M1, and E2 transitions, allowing the assignment of the transition multipolarities. The αK values for transitions connecting the 4+ and 6+ members of the deformed intruder band and the ground-state band show evidence for E0 components. The extracted ρ2(E0)\\cdot 103 value for the 4+3→ 4+1 708 keV transition is determined to be 106^{+98}_{-91}.
Pashto Conversation Manual and Pashto Conversation Tapescript.
ERIC Educational Resources Information Center
Tegey, Habibullah; Robson, Barbara
This conversation manual and tapescript are part of a set of materials that have been developed to teach oral and written Afghan Pashto to English speakers. In addition to the conversation manual and tapescript, the set consists of a beginning textbook, an intermediate textbook, a reader, and a set of taped lessons that correlate with the…
Quadrature formulas for Fourier coefficients
NASA Astrophysics Data System (ADS)
Bojanov, Borislav; Petrova, Guergana
2009-09-01
We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node formula for the Fourier-Tchebycheff coefficients given by Micchelli and Sharma and construct new Gaussian formulas for the Fourier coefficients of a function, based on the values of the function and its derivatives.
Coefficient Alpha: A Reliability Coefficient for the 21st Century?
ERIC Educational Resources Information Center
Yang, Yanyun; Green, Samuel B.
2011-01-01
Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…
Thermal Energy Conversion Branch
NASA Technical Reports Server (NTRS)
Bielozer, Matthew C.; Schreiber, Jeffrey, G.; Wilson, Scott D.
2004-01-01
The Thermal Energy Conversion Branch (5490) leads the way in designing, conducting, and implementing research for the newest thermal systems used in space applications at the NASA Glenn Research Center. Specifically some of the most advanced technologies developed in this branch can be broken down into four main areas: Dynamic Power Systems, Primary Solar Concentrators, Secondary Solar Concentrators, and Thermal Management. Work was performed in the Dynamic Power Systems area, specifically the Stirling Engine subdivision. Today, the main focus of the 5490 branch is free-piston Stirling cycle converters, Brayton cycle nuclear reactors, and heat rejection systems for long duration mission spacecraft. All space exploring devices need electricity to operate. In most space applications, heat energy from radioisotopes is converted to electrical power. The Radioisotope Thermoelectric Generator (RTG) already supplies electricity for missions such as the Cassini Spacecraft. The focus of today's Stirling research at GRC is aimed at creating an engine that can replace the RTG. The primary appeal of the Stirling engine is its high system efficiency. Because it is so efficient, the Stirling engine will significantly reduce the plutonium fuel mission requirements compared to the RTG. Stirling is also being considered for missions such as the lunar/Mars bases and rovers. This project has focused largely on Stirling Engines of all types, particularly the fluidyne liquid piston engine. The fluidyne was developed by Colin D. West. This engine uses the same concepts found in any type of Stirling engine, with the exception of missing mechanical components. All the working components are fluid. One goal was to develop and demonstrate a working Stirling Fluidyne Engine at the 2nd Annual International Energy Conversion Engineering Conference in Providence, Rhode Island.
Transfer having a coupling coefficient higher than its active material
NASA Technical Reports Server (NTRS)
Lesieutre, George A. (Inventor); Davis, Christopher L. (Inventor)
2001-01-01
A coupling coefficient is a measure of the effectiveness with which a shape-changing material (or a device employing such a material) converts the energy in an imposed signal to useful mechanical energy. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. This invention describes a class of devices wherein the apparent coupling coefficient can, in principle, approach 1.0, corresponding to perfect electromechanical energy conversion. The key feature of this class of devices is the use of destabilizing mechanical pre-loads to counter inherent stiffness. The approach is illustrated for piezoelectric and thermoelectrically actuated devices. The invention provides a way to simultaneously increase both displacement and force, distinguishing it from alternatives such as motion amplification, and allows transducer designers to achieve substantial performance gains for actuator and sensor devices.
Biotechnology of biomass conversion
Wayman, M.; Parekh, S.R.
1990-01-01
This book covers: An introduction to biomass crops; The microbiology of fermentation processes; The production of ethanol from biomass crops, such as sugar cane and rubbers; The energy of biomass conversion; and The economics of biomass conversion.
NASA Astrophysics Data System (ADS)
Rondonuwu, Ferdy S.; Kakitani, Yoshinori; Tamura, Hiroshi; Koyama, Yasushi
2006-09-01
Key Raman lines ascribable to the 1Bu+, 3Ag-, 1Bu- and 2Ag- states were identified in the subpicosecond time-resolved Raman spectra of spheroidene and lycopene having 10 and 11 conjugated double bonds, respectively. The sequential rise-and-decay of the key Raman lines showed the internal conversion processes of 1Bu+→3Ag-→1Bu-→2Ag-→1Ag- (ground). The time constant in each step of internal conversion reflects the energy gap between the relevant states that had been determined by measurement of resonance - Raman excitation profiles [K. Furuichi, T. Sashima, Y. Koyama, Chem. Phys. Lett. 356 (2002) 547].
RADIONUCLIDE RISK COEFFICIENT UNCERTAINTY REPORT
EPA has published excess cancer risk coefficients for the US population in Federal Guidance Report 13 (FGR 13). FGR 13 gives separate risk coefficients for food ingestion, water ingestion, inhalation, and external exposure for each of over 800 radionuclides. Some information on...
Standardized Discriminant Coefficients: A Rejoinder.
ERIC Educational Resources Information Center
Mueller, Ralph O.; Cozad, James B.
1993-01-01
Although comments of D.J. Nordlund and R. Nagel are welcomed, their arguments are not sufficient to accept the recommendation of using total variance estimates to standardize canonical discriminant function coefficients. If standardized coefficients are used to help interpret a discriminant analysis, pooled within-group variance estimates should…
ERIC Educational Resources Information Center
Corliss, William R.
This publication is one of a series of information booklets for the general public published by the United States Atomic Energy Commission. Direct energy conversion involves energy transformation without moving parts. The concepts of direct and dynamic energy conversion plus the laws governing energy conversion are investigated. Among the topics…
Thermionic Energy Conversion (TEC) topping thermoelectrics
NASA Technical Reports Server (NTRS)
Morris, J. F.
1981-01-01
Performance expectations for thermionic and thermoelectric energy conversion systems are reviewed. It is noted that internal radiation effects diminish thermoelectric figures of merit significantly at 1000 K and substantially at 2000 K; the effective thermal conductivity contribution of intrathermoelectric radiative dissipation increases with the third power of temperature. It is argued that a consideration of thermoelectric power generation with high temperature heat sources should include utilization of thermionic energy conversion (TEC) topping thermoelectrics. However TEC alone or TEC topping more efficient conversion systems like steam or gas turbines, combined cycles, or Stirling engines would be more desirable generally.
Iterated multidimensional wave conversion
NASA Astrophysics Data System (ADS)
Brizard, A. J.; Tracy, E. R.; Johnston, D.; Kaufman, A. N.; Richardson, A. S.; Zobin, N.
2011-12-01
Mode conversion can occur repeatedly in a two-dimensional cavity (e.g., the poloidal cross section of an axisymmetric tokamak). We report on two novel concepts that allow for a complete and global visualization of the ray evolution under iterated conversions. First, iterated conversion is discussed in terms of ray-induced maps from the two-dimensional conversion surface to itself (which can be visualized in terms of three-dimensional rooms). Second, the two-dimensional conversion surface is shown to possess a symplectic structure derived from Dirac constraints associated with the two dispersion surfaces of the interacting waves.
NASA Technical Reports Server (NTRS)
Morris, J. F.
1981-01-01
Thermionic energy conversion (TEC) and metallic-fluid heat pipes (MFHPs), offering unique advantages in terrestrial and space energy processing by virtue of operating on working-fluid vaporization/condensation cycles that accept great thermal power densities at high temperatures, share complex materials problems. Simplified equations are presented that verify and solve such problems, suggesting the possibility of cost-effective applications in the near term for TEC and MFHP devices. Among the problems discussed are: the limitation of alkali-metal corrosion, protection against hot external gases, external and internal vaporization, interfacial reactions and diffusion, expansion coefficient matching, and creep deformation.
Wrong Signs in Regression Coefficients
NASA Technical Reports Server (NTRS)
McGee, Holly
1999-01-01
When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.
Fuel Temperature Coefficient of Reactivity
Loewe, W.E.
2001-07-31
A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.
26 CFR 1.1001-5 - European Monetary Union (conversion to the euro).
Code of Federal Regulations, 2014 CFR
2014-04-01
... 26 Internal Revenue 11 2014-04-01 2014-04-01 false European Monetary Union (conversion to the euro... Gain Or Loss § 1.1001-5 European Monetary Union (conversion to the euro). (a) Conversion of currencies. For purposes of § 1.1001-1(a), the conversion to the euro of legacy currencies (as defined in §...