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Artículos de revistas sobre el tema "17O(p,p)"

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Publicado: 25 de mayo de 2024

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1

Scott, D. A., C. Bruno y A. Caciolli. "17O(p, α) 14N study at the LUNA accelerator". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 718 (agosto de 2013): 481–82. http://dx.doi.org/10.1016/j.nima.2012.11.079.

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2

Seliger, J. y V. Žagar. "1H17O nuclear quadrupole double resonance in phenylphosphinic acid and phenylphosphonic acid.17O quadrupole coupling in P = O and POH bonds". Magnetic Resonance in Chemistry 46, n.º 10 (octubre de 2008): 969–73. http://dx.doi.org/10.1002/mrc.2296.

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3

Mea, G. Della, A. Patelli, S. Restello, V. Rigato y A. Vomiero. "14N(α,p)17O nuclear reaction cross-section at 4.9–6.1MeV". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 240, n.º 4 (diciembre de 2005): 803–9. http://dx.doi.org/10.1016/j.nimb.2005.06.213.

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4

Lin, Z., L. C. McIntyre, J. A. Leavitt, M. D. Ashbaugh y R. P. Cox. "Determination of nitrogen using the 14N(α, p)17O nuclear reaction". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 79, n.º 1-4 (junio de 1993): 498–500. http://dx.doi.org/10.1016/0168-583x(93)95398-o.

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5

Hosokawa, Yoshiaki, Tomohiro Onodera, Kentaro Homan, Jun Yamaguchi, Kohsuke Kudo, Hiroyuki Kameda, Hiroyuki Sugimori y Norimasa Iwasaki. "Establishment of a New Qualitative Evaluation Method for Articular Cartilage by Dynamic T2w MRI Using a Novel Contrast Medium as a Water Tracer". CARTILAGE 13, n.º 3 (julio de 2022): 194760352211115. http://dx.doi.org/10.1177/19476035221111503.

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Objective In the early stages of cartilage damage, diagnostic methods focusing on the mechanism of maintaining the hydrostatic pressure of cartilage are thought to be useful. 17O-labeled water, which is a stable isotope of oxygen, has the advantage of no radiation exposure or allergic reactions and can be detected by magnetic resonance imaging (MRI). This study aimed to evaluate MRI images using 17O-labeled water in a rabbit model. Design Contrast MRI with 17O-labeled water and macroscopic and histological evaluations were performed 4 and 8 weeks after anterior cruciate ligament transection surgery in rabbits. A total of 18 T2-weighted images were acquired, and 17O-labeled water was manually administered on the third scan. The 17O concentration in each phase was calculated from the signal intensity at the articular cartilage. Macroscopic and histological grades were evaluated and compared with the 17O concentration. Results An increase in 17O concentration in the macroscopic and histologically injured areas was observed by MRI. Macroscopic evaluation showed that the 17O concentration significantly increased in the damaged site group. Histological evaluations also showed that 17O concentrations significantly increased at 36 minutes 30 seconds after initiating MRI scanning in the Osteoarthritis Research Society International (OARSI) grade 3 (0.493 in grade 0, 0.659 in grade 1, 0.4651 in grade 2, and 0.9964 in grade 3, P < 0.05). Conclusion 17O-labeled water could visualize earlier articular cartilage damage, which is difficult to detect by conventional methods.
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6

Wrackmeyer, Bernd y Oleg L. Tok. "Indirect Nuclear Spin-Spin Coupling Constants 1J(17O,11B). First Observation And Calculation Using Density Functional Theory (Dft)". Zeitschrift für Naturforschung B 61, n.º 8 (1 de agosto de 2006): 949–55. http://dx.doi.org/10.1515/znb-2006-0804.

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Coupling constants 1J(17O,11B) of borates, borane adducts and boranes with boron-oxygen bonds have been calculated on the basis of optimised molecular structures using the B3LYP/6-311+G(d,p) level of theory. This indicates that such coupling constants can be of either sign and that their magnitudes can be rather small. Since both 11B and 17O are quadrupole nuclei, it is therefore difficult to measure representative data. In the cases of trimethoxyborane and tetraethyldiboroxanes, it proved possible to obtain experimental data 1J(17O,11B) (22 and 18 Hz) by measurement of 17O NMR spectra at high temperature (120 °C and 160 °C) respectively. The magnitude of these coupling constants is in reasonable agreement with calculated data. In the case of the diboroxane, this points towards a bond angle B-O-B more close to 180◦ than to 140°
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7

Kong, Xianqi, Aaron Tang, Ruiyao Wang, Eric Ye, Victor Terskikh y Gang Wu. "Are the amide bonds in N-acyl imidazoles twisted? A combined solid-state 17O NMR, crystallographic, and computational study". Canadian Journal of Chemistry 93, n.º 4 (abril de 2015): 451–58. http://dx.doi.org/10.1139/cjc-2014-0397.

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We report synthesis of 17O-labeling and solid-state 17O NMR measurements of three N-acyl imidazoles of the type R-C(17O)-Im: R = p-methoxycinnamoyl (MCA-Im), R = 4-(dimethylamino)benzoyl (DAB-Im), and R = 2,4,6-trimethylbenzoyl (TMB-Im). Solid-state 17O NMR experiments allowed us to determine for the first time the 17O quadrupole coupling and chemical shift tensors in this class of organic compounds. We also determined the crystal structures of these compounds using single-crystal X-ray diffraction. The crystal structures show that, while the C(O)–N amide bond in DAB-Im exhibits a small twist, those in MCA-Im and TMB-Im are essentially planar. We found that, in these N-acyl imidazoles, the 17O quadrupole coupling and chemical shift tensors depend critically on the torsion angle between the conjugated acyl group and the C(O)–N amide plane. The computational results from a plane-wave DFT approach, which takes into consideration the entire crystal lattice, are in excellent agreement with the experimental solid-state 17O NMR results. Quantum chemical computations also show that the dependence of 17O NMR parameters on the Ar–C(O) bond rotation is very similar to that previously observed for the C(O)–N bond rotation in twisted amides. We conclude that one should be cautious in linking the observed NMR chemical shifts only to the twist of the C(O)–N amide bond.
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8

Blinc, R. "17O NQR and the Mechanism of the Phase Transition in KH2PO4 Type H-bonded Systems". Zeitschrift für Naturforschung A 41, n.º 1-2 (1 de febrero de 1986): 249–55. http://dx.doi.org/10.1515/zna-1986-1-244.

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17O quadrupole and 17O-proton magnetic dipolar coupling data are used to discriminate between three alternative phase transition driving mechanisms in KH2PO4 type H-bonded systems: (i) the proton order-disorder model; (ii) the P (or Se) ion order-disorder model, and (iii) the PO4 (or SeO3) orientational order-disorder model.The data for KH3(SeO3)2, CsH2PO4 and KH2PO4 definitely exclude models (ii) and (iii) and agree with the predictions of model (i).
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9

Salimi, M., O. Kakuee, S. F. Masoudi, H. Rafi-kheiri, E. Briand, J. J. Ganem y I. Vickridge. "Measurement of (p,p) elastic differential cross sections for 17O in the 0.6–2 MeV range at 165°". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 516 (abril de 2022): 15–22. http://dx.doi.org/10.1016/j.nimb.2022.01.002.

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10

Smithson, M. J., D. L. Watson y H. T. Fortune. "A study of the12C(6Li,p)17O reaction at E=28 MeV". Journal of Physics G: Nuclear Physics 12, n.º 10 (octubre de 1986): 985–1000. http://dx.doi.org/10.1088/0305-4616/12/10/010.

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11

Xu, Huizhong, Zhuying Zhou, Chao Zhang, Guoqing Zhao y Liqun Shi. "Excitation function and angular distribution for the 14N(α,p)17O reaction". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 149, n.º 4 (marzo de 1999): 390–94. http://dx.doi.org/10.1016/s0168-583x(98)00959-8.

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12

Sergi, M. L., C. Spitaleri, A. Coc, A. Mukhamedzhanov, S. V. Burjan, M. Gulino, F. Hammache et al. "The 65 keV resonance in the 17O(p,α)14N thermonuclear reaction". Nuclear Physics A 834, n.º 1-4 (marzo de 2010): 676c—678c. http://dx.doi.org/10.1016/j.nuclphysa.2010.01.122.

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13

Taskinen, Esko. "17O NMR study of p-π conjugation in methoxybutadienes and related compounds". Magnetic Resonance in Chemistry 33, n.º 4 (abril de 1995): 256–59. http://dx.doi.org/10.1002/mrc.1260330406.

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14

Ma, T. L., B. Guo, Z. H. Li, Y. J. Li, D. Y. Pang, Y. L. Han, Y. P. Shen et al. "Precision measurement of the angular distribution for the 16O(d, p)17O transfer reaction to the ground state of 17O". Nuclear Physics A 986 (junio de 2019): 26–33. http://dx.doi.org/10.1016/j.nuclphysa.2019.03.004.

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15

Wagemans, J., C. Wagemans, G. Goeminne y P. Geltenbort. "Detailed investigation of the 14N(n,p)14C, 17O(n,α)14C, 26Al(n,p)26Mg and 26Al(n,α)23Na reactions". Nuclear Physics A 688, n.º 1-2 (mayo de 2001): 490–92. http://dx.doi.org/10.1016/s0375-9474(01)00765-5.

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16

Yamamoto, K., H. Masui, K. Kato, T. Wada y M. Ohta. "Radiative Capture Cross Section for 16O(n, )17O and 16O(p, )17F below Astrophysical Energies". Progress of Theoretical Physics 121, n.º 2 (1 de febrero de 2009): 375–90. http://dx.doi.org/10.1143/ptp.121.375.

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17

Chafa, A., F. Z. Messili y S. Barhoumi. "194.1 keV resonance contribution on 17O(p,α)14N reaction rate using R matrix code". Astrophysics and Space Science 349, n.º 1 (18 de septiembre de 2013): 373–77. http://dx.doi.org/10.1007/s10509-013-1609-9.

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18

Chai, C. L. L., W. A. Loughlin y G. Lowe. "The stereochemical course of sulphuryl transfer catalysed by arylsulphatase II from Aspergillus oryzae". Biochemical Journal 287, n.º 3 (1 de noviembre de 1992): 805–12. http://dx.doi.org/10.1042/bj2870805.

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Phenyl [(R)-16O,17O,18O]sulphate was synthesized and used to study the stereochemical course of sulphuryl transfer to p-cresol catalysed by arylsulphatase II from Aspergillus oryzae. The reaction was shown to proceed with retention of configuration at the sulphur atom, providing evidence for the involvement of a sulpho-enzyme intermediate on the reaction pathway.
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19

Lagostina, Valeria, Loredana Leone, Fabio Carniato, Giuseppe Digilio, Lorenzo Tei y Mauro Botta. "Electronic Effects of the Substituents on Relaxometric and CEST Behaviour of Ln(III)-DOTA-Tetraanilides". Inorganics 7, n.º 4 (27 de marzo de 2019): 43. http://dx.doi.org/10.3390/inorganics7040043.

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Three different 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetamide (DOTAM) derivatives bearing as amide N-substituents phenyl, p-methoxyphenyl and p-ethylbenzoate groups were synthesized and the 1H and 17O NMR relaxometric behaviour of the Gd(III)-chelates and chemical exchange saturation transfer (CEST) effect of the Eu(III) complexes were evaluated. The electronic properties of the substituents were shown to strongly influence the coordinated water exchange rate (kex), resulting in five times faster kex for the electron donating phenylmethoxy group compared to the electron withdrawing ethylbenzoate group.
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20

Gisler, Andreas, Martina Schaade, Eric J. M. Meier, Anthony Linden y Wolfgang von Philipsborn. "187Os, 31P and 17O NMR study of carbonylated and alkylated (p-cymene)OsI (L)PR3 complexes". Journal of Organometallic Chemistry 545-546 (enero de 1997): 315–26. http://dx.doi.org/10.1016/s0022-328x(97)00376-8.

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21

Gesuè, Riccardo Maria. "The challenging direct measurement of the 65 keV resonance strength of the 17O(p, γ)18F reaction at LUNA". EPJ Web of Conferences 275 (2023): 02004. http://dx.doi.org/10.1051/epjconf/202327502004.

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The 17O(p, γ)18F reaction plays a crucial role in AGB nucleosynthesis as well as in explosive hydrogen burning occurring in type Ia novae. At the temperatures of interest for the former scenario ( 20MK < T < 80MK) the main contribution to the astrophysical reaction rate comes from the poorly constrained ER = 65 keV resonance. The strength of this resonance is presently determined only through indirect measurements, with an adopted value ωγ =(16 ± 3) peV. A new high sensitivity setup was installed at LUNA, located at LNGS. The underground location of the LUNA 400kV accelerator guarantees a reduction of the cosmic ray background by several orders of magnitude. The residual background was further reduced installing a devoted shielding. On the other hand, to increase the efficiency, the 4π BGO detector was coupled with Al target chamber and holder. With more than 400C accumulated on Ta2O5 targets, nominal 17O enrichment of 90%, the LUNA collaboration has performed the first direct measurement of the 65 keV resonance strength.
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22

Sopchik, Alan E., S. Matthew Cairns y Wesley G. Bentrude. "17O NMR of diastereomeric 3′,5′-cyclic thymidine methyl phosphates, methylphosphonates, and N,N-dimethyl phosphoramidates. Phosphorus configuration of P-chiral [17O, 18O]-nucleoside phosphate diesters". Tetrahedron Letters 30, n.º 10 (enero de 1989): 1221–24. http://dx.doi.org/10.1016/s0040-4039(00)72720-1.

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23

Bzhezovskii, V. M., R. B. Valeev, G. A. Kalabin, I. A. Aliev y B. A. Trofimov. "Study of conjugation effects. Communication 26.13C,17O, and33S NMR spectra of P-chlorophenyl alkyl sulfides and sulfones". Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 36, n.º 9 (septiembre de 1987): 1819–24. http://dx.doi.org/10.1007/bf00958321.

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24

Piskoř, Š. y W. Schäferlingová. "Spectroscopic information on 13,14C, 15N, 17O, 29–31Si, 33S, 28Cl and 111,113,115,117Cd from the (d,p) reaction". Nuclear Physics A 510, n.º 2 (abril de 1990): 301–21. http://dx.doi.org/10.1016/0375-9474(90)90241-d.

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25

Piatti, D. y G. F. Ciani. "Towards a direct measurement of the 17O(p, γ)18F 65 keV resonance strength at LUNA". EPJ Web of Conferences 279 (2023): 11002. http://dx.doi.org/10.1051/epjconf/202327911002.

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The 17O(p, γ)18F reaction plays a crucial role in the hydrogen burning phases of different stellar scenarios. At temperature of interest for AGB nucleosynthesis (20 MK < T < 80 MK) the main contribution to the astrophysical reaction rate comes from the poorly constrained 65 keV resonance. The strength of this resonance is presently determined only through indirect measurements, with a reported value of ωγ = (1.6 ± 0.3) 10−11 eV. With typical experimental quantities for beam current, isotopic enrichment and detection efficiency, this strength yields to an expected count rate of less than one count per Coulomb, making the direct measurement of this resonance extremely challenging. A new high sensitivity setup has been installed at LUNA (Laboratory for Underground Nuclear Astrophysics) of Laboratori Nazionali del Gran Sasso. The high performance LUNA 400kV accelerator underground location guarantees, indeed, a reduction of cosmic ray background by several orders of magnitude. The residual background was further reduced by a devoted shielding of lead and borated (5%) polyethylene. On the other hand, the 4π BGO detector efficiency was optimized installing aluminum target chamber and holder. With about 400 C accumulated on Ta2O5 targets, with nominal 17O enrichment of 90%, the LUNA collaboration has performed the first direct measurement of the 65 keV resonance strength.
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26

Brownlee, RTC, MJ Oconnor, BP Shehan y AG Wedd. "Applications of 95Mo N.M.R-Spectroscopy. XVI. Structure and Bonding in [Mo(Co)3(η6-Arene)] Complexes From 95Mo,13C and 17O Relaxation-Times". Australian Journal of Chemistry 39, n.º 7 (1986): 931. http://dx.doi.org/10.1071/ch9860931.

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Spin-lattice relaxation times (T1) have been measured for the 95Mo, 17O and methine and carbonyl 13C nuclei for a series of [Mo(CO)3(η6-C6H6- nMen)] complexes. In addition to the expected decrease in T1 with increasing molecular volume, the 95Mo and methine 13C data are interpreted in terms of variations in arene -molybdenum bonding. The methine 13C T1 values decrease in the order o- xylene > toluene > p- xylene > m- xylene > mesitylene . The methyl substitution pattern determines the distribution of electron-rich sites on the arene ligand , affecting the molybdenum- arene bond strength and the barrier to arene rotation. These observations support an earlier proposal that downfield 95Mo chemical shifts are associated with increased molybdenum- arene bond strength. 95Mo T1 values are unaffected by the rotational barriers, since they depend only on molecular tumbling perpendicular to the pseudo C3v symmetry axis. While these T1 values decrease as the number of methyl groups increases, an effect due to increasing molecular volume, the order of 95Mo T1 for the xylene complexes is opposite to that of the 13C T1, due to a reduction in the electric field gradient at the 95Mo nucleus. 95Mo quadrupole coupling constants for the series are 1.2�0.2 MHz. The 17O T1 values have also been measured for this series. They are considerably longer, and quadrupole coupling constants smaller (0.87�0.07 MHz), than those of other metallocarbonyls , indicating a significant increase in metal- ligand dπ-pπ - back bonding in the present system. A correlation between carbonyl force constants and 17O quadrupole coupling constants is presented.
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27

Malová Križková, Petra, Alexander Roller y Friedrich Hammerschmidt. "Formal synthesis of P-chiral [16O,17O,18O]phosphoenol pyruvates by means of the α-hydroxyphosphonate-phosphate rearrangement". Phosphorus, Sulfur, and Silicon and the Related Elements 193, n.º 8 (19 de abril de 2018): 515–19. http://dx.doi.org/10.1080/10426507.2018.1452235.

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28

Jeong, Junho, Tina M. Briere, N. Sahoo, T. P. Das, S. Ohira, K. Nishiyama y K. Nagamine. "Theory of Nuclear Quadrupole Interactions of 14N, 17O, and 35Cl Nuclei in p-Cl-Ph-CH-N=TEMPO". Zeitschrift für Naturforschung A 57, n.º 6-7 (1 de julio de 2002): 527–31. http://dx.doi.org/10.1515/zna-2002-6-744.

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The nuclear quadrupole coupling constants and asymmetry parameters have been studied for the 35Cl, 17O, and 14N nuclei in the molecular ferromagnet 4-(p-chlorobenzylideneamino)-TEMPO (2,2,6,6-tetramethyl- piperidin-1-yloxyl) using elctronic stuctures obtained by the Hartree-Fock procedure for the bare system and systems with trapped muon and muonium. Trends in the sizes of the coupling constants and asymmetry parameters for the various nuclei have been studied, and possible physical explanations have been proposed. For the systems with trapped muon or muonium, very substantial influences of the muon and muonium on the coupling constants and asymmetry parameters for the nuclei close to the trapping sites have been observed. The coupling constants and asymmetry parameters are found to be very different for the various nuclei, for the two cases where muon is trapped near chlorine and muonium near oxygen, indicating that, if experimental data were available to compare with theory, one could make conclusions about which of these two centers is responsible for the observed muon spin rotation frequency associated with the muon magnetic hyperfine interactions in these two trapped systems
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29

Ornelas, A., Gy Gyürky, Z. Halász, Cs M. Oláh, Zs Fülöp, I. Rajta y I. Vajda. "Towards an activation cross section measurement of the 17O(p,γ)18F reaction in a wide energy range". Journal of Physics: Conference Series 940 (enero de 2018): 012052. http://dx.doi.org/10.1088/1742-6596/940/1/012052.

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30

O'Malley, Patrick J. "1H, 13C and 17O principal hyperfine tensor determination for the p-benzosemiquinone anion radical using hybrid density functional methods". Chemical Physics Letters 262, n.º 6 (noviembre de 1996): 797–800. http://dx.doi.org/10.1016/s0009-2614(96)01146-3.

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31

Petry, Pascale, Mario Dicato, Fernand Ries, Pascale Molitor y Elisabeth Poeckes. "MEMBRANE P-GLYCOPROTEIN (PG-17O) EXPRESSION CORRELATES TO DRUG RESISTANCE IN BLAST CRISIS OF CHRONIC MYELOGENOUS LEUKEMIA (BC-CML)". Biology of the Cell 73, n.º 2-3 (enero de 1991): 49a. http://dx.doi.org/10.1016/0248-4900(91)90258-o.

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32

Ciani, G. F. y D. Piatti. "Towards a direct measurement of the E cm = 65 keV resonance strength in 17O(p, γ)18F at LUNA". Journal of Physics: Conference Series 2586, n.º 1 (1 de septiembre de 2023): 012095. http://dx.doi.org/10.1088/1742-6596/2586/1/012095.

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Abstract The 17O(p, γ)18F reaction plays a crucial role in several stellar scenarios where the hydrogen burning phases takes place. In particular, in the temperature energy range of interest for AGB nucleosynthesis (20 MK< T <80 MK) the main contribution to the astrophysical reaction rate comes from the elusive 65 keV resonance. Indeed, this resonance strength is at the moment determined only through indirect measurements, with a reported value of ωγ = (1.6 ± 0.3) × 10−11 eV. With typical experimental quantities for beam current, isotopic enrichment and detection efficiency, this strength yields an expected count rate of less than one count per Coulomb, making the direct measurement of this resonance extremely challenging. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400kV accelerator installed in Laboratori Nazionali del Gran Sasso (Italy) provides a unique possibility to directly measure this low resonance thanks to the reduction of cosmic ray background by six orders of magnitude with respect surface laboratories and thanks to an intense, narrow proton beam. To improve the experimental sensitivity, the environmental background was further reduced designing a lead and borated (5%) polyethylene shielding and the absorption of γ − rays emitted by the reaction was minimised by the installation of target chamber and holder made of aluminum. With about 400 Coulomb accumulated on Ta2O5 targets, with nominal 17O enrichment of 90%, the LUNA collaboration has performed the first direct measurement of the 65 keV resonance strength.
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33

Milton, G. M., S. J. Kramer, R. M. Brown, C. J. W. Repta, K. J. King y R. R. Rao. "Radiocarbon Dispersion around Canadian Nuclear Facilities". Radiocarbon 37, n.º 2 (1995): 485–96. http://dx.doi.org/10.1017/s0033822200030964.

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Canadian deuterium uranium (CANDU) pressurized heavy-water reactors produce 14C by neutron activation of trace quantities of nitrogen in annular gas and reactor components (14N(n,p)14C), and from 17O in the heavy water moderator by (17O(n,α)14C). The radiocarbon produced in the moderator is removed on ion exchange resins incorporated in the water purification systems; however, a much smaller gaseous portion is vented from reactor stacks at activity levels considerably below 1% of permissible derived emission limits. Early measurements of the carbon speciation indicated that >90% of the 14C emitted was in the form of CO2. We conducted surveys of the atmospheric dispersion of 14CO2 at the Chalk River Laboratories and at the Pickering Nuclear Generating Station. We analyzed air, vegetation, soils and tree rings to add to the historical record of 14C emissions at these sites, and to gain an understanding of the relative importance of the various carbon pools that act as sources/sinks within the total 14C budget. Better model parameters than those currently available for calculating the dose to the critical group can be obtained in this manner. Global dose estimates may require the development of techniques for estimating emissions occurring outside the growing season.
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34

Conner, John K., Johanna Haider, MN Stuart Hill, Howard Maskill y Monique Pestman. "The mechanism of solvolysis of 2-adamantyl azoxytosylate: isotopic labelling, medium effect, and attempted deoxygenation studies". Canadian Journal of Chemistry 76, n.º 6 (1 de junio de 1998): 862–68. http://dx.doi.org/10.1139/v98-071.

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Rates of solvolysis of 2-adamantyl azoxytosylate (1) have been measured over a range of temperatures in ethanoic acid, methanoic acid, 50:50 (v/v) trifluoroethanol:water, 80:20 (v/v) trifluoroethanol:water, 97:3 (w/w) trifluoroethanol:water, and 70:30 (v/v) ethanol:water. For comparison, rates of solvolysis of 2-adamantyl tosylate (2) have also been measured in 50:50, 80:20, and 90:10 (v/v) trifluoroethanol:water, and for both compounds, activation parameters have been determined. These and results published earlier allow a correlation of the two reactions and indicate that the m value for 2-adamantyl azoxytosylate solvolysis is only 0.46. This is one of the lowest m values for a reaction that is unambiguously an SN1 solvolysis. We have also recorded the 17O NMR spectrum of the 2-adamantyl tosylate formed from 17O-labelled 2-adamantyl azoxytosylate in deuteriochloroform, and the millimeter-wave spectrum of the nitrous oxide evolved in the hydrolysis of 18O-labelled 2-adamantyl azoxytosylate. These labelling studies have provided more detailed knowledge of the SN1 fragmentation mechanism of 1 and exclude a mechanism of reaction via rearrangement to N-nitroso,N-(2-adamantyl),O-(p-toluenesulfonyl)hydroxylamine (5). Attempted deoxygenation of 1 to give 2-adamantyl diazotosylate (8) and a subsequent fragmentation proved unsuccessful.Key words: nitrous oxide, carbenium ion, isotopic labelling, solvolysis, m value.
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35

BASIOURA, A., I. MICHOS, A. NTEMKA, I. KARAGIANNIS y C. M. BOSCOS. "Effect of iron oxide and silver nanoparticles on boar semen CASA motility and kinetics". Journal of the Hellenic Veterinary Medical Society 71, n.º 3 (15 de octubre de 2020): 2331. http://dx.doi.org/10.12681/jhvms.25084.

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The objective of the study was to investigate the potential toxic effect of iron oxide (Fe3O4) and silver (Ag/Fe) spherical nanoparticles (NPs) as alternative antimicrobial compounds on boar semen. The NPs’ minimum inhibitory concentration was determined applying the in vitro antimicrobial activity evaluation test and included in the experiment. Totally, 9 ejaculates (3 boars; 3 ejaculates/boar) were extended in BTS without antibiotics at 30×106 spermatozoa/mL and divided in 3 aliquots corresponding to the following groups: 1) Control group (C): extended semen without treatment; 2) Iron oxide group (Fe): extended semen with Fe3O4 NPs of diameter 40 nm (0.192 mg/mL semen); and 3) Silver group (Ag): extended semen with Ag/Fe NPs of diameter 30 nm, consisted of Ag and a 5% of zero-valent Fe (0.128 mg/mL semen). Semen samples of all groups were incubated at 17o C for 30 min following NPs’ removal through a magnetic field. All post treated samples were stored at 17o C for 48 h. Total motility (TM) and kinetics (progressive motility PM; rapid/medium/slow movement spermatozoa; static spermatozoa; VCL; VSL; VAP; LIN; STR; WOB; ALH; BCF; hyperactive spermatozoa) were evaluated by CASA system at 0, 24 and 48 h post treatment. Data were analyzed with a repeated measures mixed model. Group Fe did not differ from group C at any time point. TM and PM were lower at 24 h of storage in group Ag compared to groups C and Fe (all P<0.001). By 48 h of storage spermatozoa of group Ag were totally immotile and thus excluded from analysis. The comparison within groups and between storage time points showed that the values of TM, PM, VCL, VAP, ALH and BCF decreased after 24 h of storage in group Ag (all P<0.05), but not in groups C and Fe, while no significant differences were observed for the remaining parameters between successive time points within any group (P>0.05). In conclusion, Ag/Fe NPs demonstrated a harmful effect on boar spermatozoa, while the used concentration of the examined Fe3O4 NPs did not affect boar sperm CASA motility parameters enhancing further research about their application on semen handling.
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36

Dahn, Hans, Vien Van Toan y My-Ngoc Ung-Truong. "NMR of terminal oxygen. 9—17O NMR of the PO ‘double bond’: Phosphine oxides, phosphinates, phosphonates, acylphosphonates and related compounds". Magnetic Resonance in Chemistry 30, n.º 11 (noviembre de 1992): 1089–96. http://dx.doi.org/10.1002/mrc.1260301112.

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37

Fedorova, O. M., Anatoly Yakovlevich Fishman, Tatiana Eugenievna Kurennykh, Vladimir Borisovich Vykhodets y V. B. Vykhodets. "Isotope Exchange between 18O2 Gas and Mechanoactivated Oxide NdMnO3+δ". Defect and Diffusion Forum 333 (enero de 2013): 193–98. http://dx.doi.org/10.4028/www.scientific.net/ddf.333.193.

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sotope exchange of oxygen 18О2 with oxides NdMnO3+δ was investigated. The oxide was obtained from oxides Nd2O3 and Mn2O3 using a ceramic technology with annealing in air at 1400°C for 90 hours followed by cooling in a furnace. A planetary mill AGO-2 with a centrifugal factor of g = 60 was used for mechanical treatment of oxides. The study of isotope exchange was carried out by nuclear microanalysis. The concentration of the isotopes 18O and 16O in oxides was determined using a Van de Graaff accelerator and 18O(p, α)15N and 16O(d, p)17O* reactions at the energies of incident beams 762 and 900 keV. Isothermal annealing of powders was carried out in oxygen, enriched to 80% by the isotope 18O. It was established that the concentration of the isotope 18O in mechanically activated powders was several times higher than in the initial micropowder under the same conditions of annealing. The effect increased with increasing of mechanical activation time (30 - 300 s). The isotope exchange parameters connected with the processes at the boundaries of the particles of mechano-activated powder and within their volume were analyzed.
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38

Duarte, R., A. R. Bagaldo, R. Matoso Silva, R. L. Oliveira, T. M. Silva, R. Ribeiro y F. L. Araújo. "Torta de amendoim em substituição ao farelo de soja na alimentação de cordeiros ½ sangue dorper". Archivos de Zootecnia 64, n.º 247 (10 de diciembre de 2015): 317–22. http://dx.doi.org/10.21071/az.v64i248.415.

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Objetivou-se determinar o melhor nível de inclusão de torta de amendoim (Arachis hypogaea), no suplemento concentrado de cordeiros. Foram utilizados 20 cordeiros mestiços ½ sangue Dorper, com idade média de 7 meses, mantidos em baias individuais. Os tratamentos consistiram em níveis de substituição do farelo de soja pela torta de amendoim em 0; 33,33; 66,67; e 100 %. O período experimental foi de 32 dias, dos quais 14 dias para adaptação e 18 entre rotina e coleta de dados. Durante os últimos 5 dias experimentais foram coletadas amostras diárias do ofertado, sobras e fezes, duas vezes ao dia, as 8 e 15 horas, as quais foram secas e moídas para as análises bromatológicas. Nos 8º, 9º e 10º dias do período experimental, os animais foram submetidos à observação visual para avaliação do comportamento ingestivo em reposta a dieta e as respostas fisiológicas dos animais ao ambiente. Nos dias 13o, 15o e 17o, realizou-se a medição do consumo de água em resposta a dieta oferecida. Os consumos de matéria seca, proteína bruta, nutrientes digestíveis totais, fibra em detergente neutro e fibra em detergente ácido, não foram significativos (p>0,05) com a inclusão da torta de amendoim. Os coeficientes de digestibilidade da matéria seca, fibra em detergente neutro e carboidratos não fibrosos não apresentaram diferenças (p>0,05) e o consumo de água foi similar (p>0,05) com a inclusão da torta de amendoim em substituição ao farelo de soja. A frequência cardíaca , temperatura retal e temperatura corpórea foram semelhantes (p>0,05) no período da manhã e tarde, exceto para a frequência respiratória no período da tarde que apresentou um efeito quadrático (p
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39

Kobayashi, Takuya, Fumitaka Nishiyama y Katsumi Takahiro. "Chromatic Change in Copper Oxide Layers Irradiated with Low Energy Ions". Quantum Beam Science 5, n.º 1 (10 de marzo de 2021): 7. http://dx.doi.org/10.3390/qubs5010007.

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The color of a thin copper oxide layer formed on a copper plate was transformed from reddish-brown into dark blue-purple by irradiation with 5 keV Ar+ ions to a fluence as low as 1 × 1015 Ar+ cm−2. In the unirradiated copper oxide layer, the copper valence state of Cu2+ and Cu+ and/or Cu0 was included as indicated by the presence of a shake-up satellite line in a photoemission spectrum. While for the irradiated one, the satellite line decreased in intensity, indicating that irradiation resulted in the reduction from Cu2+ to Cu+ and/or Cu0. Furthermore, nuclear reaction analysis using a 16O(d, p)17O reaction with 0.85 MeV deuterons revealed a significant loss of oxygen (5 × 1015 O atoms cm−2) in the irradiated layer. Thus, the chromatic change observed in the present work originated in the irradiation-induced reduction of a copper oxide.
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40

Noli, F., P. Misaelides, A. Lagoyannis y J. P. Riviere. "Application of RBS and NRA for the Investigation of Corrosion Resistance of Nitrogen‐Implanted Steel." HNPS Proceedings 18 (23 de noviembre de 2019): 113. http://dx.doi.org/10.12681/hnps.2557.

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Austenitic stainless steel AISI 304L was implanted with low energy, high current nitrogen iοns at moderate temperatures extracted from a Kaufman type iοn source (Extraction voltage: 1.2 keV; Extracted current: 1 mA/cm2; Ion dose: about 4x1019 ions /cm2). The temperature during the implantation (duration 1 hour) was 400 and 500 oC respectively for the two series of samples prepared. The characterization of the samples by X‐Ray Diffraction, Transmission Electron Microscopy and Scanning Electron Microscopy showed that a metastable fcc solid solution with a high nitrogen content (about wt. 30%) was formed resulting in an increase of its Vickers hardness. Rutherford Backscattering Spectrometry (Ed: 1.75 MeV) was applied in combination with Nuclear Reaction Analysis (NRA) in order to obtain information about the N‐, O‐ and C‐ depth distribution in the near‐surface layers of the samples. The nitrogen depth distribution was determined using the 14N(d,α)12C and the 14N(d,p)15N nuclear reactions whereas the oxygen and carbon ones by the 16O(d,p)17O and 12C(d,p)13C (Ed: 1.35 MeV). Investigation of the corrosion behaviour of the samples was performed under strong aggressive conditions (hydrochloric acid 2% at 50 oC) using electrochemical techniques (potentiodynamic polarization and cyclic voltammetry). The samples implanted at 400 oC exhibited remarkable resistance to corrosion compared to those implanted at 500 oC and the untreated material. This could be attributed to the modified surface region and its high nitrogen content.
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41

Ciani, Giovanni Francesco, Denise Piatti y Riccardo Maria Gesuè. "The challenging direct measurement of the 65 keV resonance strength of the 17O(p,γ)18F reaction at LUNA". EPJ Web of Conferences 260 (2022): 11003. http://dx.doi.org/10.1051/epjconf/202226011003.

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A precise determination of proton capture rates on oxygen is mandatory to predict the abundance ratios of the oxygen isotopes in a stellar environment where hydrogen burning is active. The 17O(p,γ)18F reaction, specifically, plays a crucial role in AGB nucleosynthesis as well as in explosive hydrogen burning occurring in type Ia novae. At temperatures of interest for the former scenario (20 MK ≤ T ≤ 80 MK) the main contribution to the astrophysical reaction rate comes from the Ec.m. = 65 keV resonance. The strength of this resonance is presently determined only through indirect measurements, with an adopted value of ωγ = (1.6 ± 0.3) × 10−11 eV. Thanks to the low background environment of the Laboratori Nazionali del Gran Sasso, the intense and stable beam provided by the LUNA 400 kV accelerator and the experience in oxygen target production, the LUNA collaboration is aiming the first direct measurement of the above mentioned resonance strength. In the present work details of challenging direct measurement planned at LUNA will be described.
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42

Chronister, Aaron, Andrej Pustogow, Naoki Kikugawa, Dmitry A. Sokolov, Fabian Jerzembeck, Clifford W. Hicks, Andrew P. Mackenzie, Eric D. Bauer y Stuart E. Brown. "Evidence for even parity unconventional superconductivity in Sr2RuO4". Proceedings of the National Academy of Sciences 118, n.º 25 (14 de junio de 2021): e2025313118. http://dx.doi.org/10.1073/pnas.2025313118.

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Unambiguous identification of the superconducting order parameter symmetry in Sr2RuO4 has remained elusive for more than a quarter century. While a chiral p-wave ground state analogue to superfluid 3He-A was ruled out only very recently, other proposed triplet-pairing scenarios are still viable. Establishing the condensate magnetic susceptibility reveals a sharp distinction between even-parity (singlet) and odd-parity (triplet) pairing since the superconducting condensate is magnetically polarizable only in the latter case. Here field-dependent 17O Knight shift measurements, being sensitive to the spin polarization, are compared to previously reported specific heat measurements for the purpose of distinguishing the condensate contribution from that due to quasiparticles. We conclude that the shift results can be accounted for entirely by the expected field-induced quasiparticle response. An upper bound for the condensate magnetic response of <10% of the normal state susceptibility is sufficient to exclude all purely odd-parity candidates.
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43

Quin, Louis D., En-Yun Yao y Jerzy Szewczyk. "Special Properties Imparted to the 9-Phosphabicyclo[6.1.0]nonatriene system by a P-(2,4,6-tri-t-butylphenyl) substituent; 17O NMR spectrum of a bicyclic phosphirane oxide". Tetrahedron Letters 28, n.º 10 (enero de 1987): 1077–80. http://dx.doi.org/10.1016/s0040-4039(00)95915-x.

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44

Bund, G. W. y K. Ueta. "Simulation of the exclusion principle in the neutron−16O interaction through a repulsive term and application to a three-body calculation of theO16(d,p)17O reaction". Physical Review C 51, n.º 5 (1 de mayo de 1995): 2819–22. http://dx.doi.org/10.1103/physrevc.51.2819.

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45

Hedrick, Brittany, Anthony Riccio, Matthew Siebert, Claire Shivers, Mitchell Harris, William A. Pierce, Danielle M. Thomas y Jacob R. Zide. "Do We Really Need to Worry About Calcaneocuboid Subluxation During Lateral Column Lengthening for Planovalgus Foot Deformity?" Foot & Ankle Orthopaedics 5, n.º 4 (1 de octubre de 2020): 2473011420S0024. http://dx.doi.org/10.1177/2473011420s00244.

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Category: Midfoot/Forefoot; Other Introduction/Purpose: While lengthening of the lateral column through a calcaneal neck osteotomy is an integral component of flatfoot reconstruction in younger patients with flexible planovalgus deformities, the procedure has been implicated in iatrogenic calcaneocuboid (CC) subluxation and subsequent degenerative changes at the CC articulation. The purpose of this study is to characterize alterations at the CC joint following lateral column lengthening (LCL) as well as to determine if Steinman pin stabilization of the CC joint prior to distraction maintains a normal CC relationship. Methods: Seven matched pairs of fresh frozen cadaveric feet underwent pre-procedure plain radiography and cross-sectional computed tomography (CT) imaging. LCL via a calcaneal neck osteotomy was then performed. One foot of each matched pair had a single smooth Steinman pin placed centrally across the CC joint prior to osteotomy distraction. Distraction across each osteotomy was then performed and maintained with a 12mm porous titanium wedge. Repeat imaging was obtained and compared to pre-procedure studies to quantify sagittal and rotational differences at the CC articulation Results: Following LCL, plain radiography demonstrated statistically significant increases in the percentage of the calcaneal articular surface dorsal to the superior aspect of the cuboid in both the pinned (8.2% vs 17.6%, p=0.02) and unpinned (12.5% vs 16.3%, p=0.04) specimens. No difference in the percentage of subluxation was found between the two groups following LCL. CT imaging demonstrated statistically significant increases in rotation between the calcaneus and cuboid following LCL in both the pinned (7.6O +- 5.6O, p=0.01) and unpinned (17O +- 12.3O, p=0.01) specimens. Though a greater degree of rotation was present in the unpinned specimens following LCL, this difference was not statistically significant (p=0.28). Conclusion: Both sagittal and rotatory subluxation seem to occur at the CC joint following LCL regardless of pin stabilization. As a single pin would be expected to limit pure translation while having little effect on rotation, it is possible that the rotational changes identified on three-dimensional imaging are interpreted as dorsal translation when viewed two dimensionally using plain radiography. Consideration should therefore be given to CC stabilization with two pins during LCL to prevent this rotatory subluxation.
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46

Ozsváth, Bíró, Nagy, Buglyó, Sanna y Farkas. "Trends and Exceptions in the Interaction of Hydroxamic Acid Derivatives of Common Di- and Tripeptides with Some 3d and 4d Metal Ions in Aqueous Solution". Molecules 24, n.º 21 (31 de octubre de 2019): 3941. http://dx.doi.org/10.3390/molecules24213941.

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By using various techniques (pH-potentiometry, UV-Visible spectrophotometry, 1H and 17O-NMR, EPR, ESI-MS), first time in the literature, solution equilibrium study has been performed on complexes of dipeptide and tripeptide hydroxamic acids—AlaAlaNHOH, AlaAlaN(Me)OH, AlaGlyGlyNHOH, and AlaGlyGlyN(Me)OH—with 4d metals: the essential Mo(VI) and two half-sandwich type cations, [(η6-p-cym)Ru(H2O)3]2+ as well as [(η5-Cp*)Rh(H2O)3]2+, the latter two having potential importance in cancer therapy. The tripeptide derivatives have also been studied with some biologically important 3d metals, such as Fe(III), Ni(II), Cu(II), and Zn(II), in order to compare these new results with the corresponding previously obtained ones on dipeptide hydroxamic acids. Based on the outcomes, the effects of the type of metal ions, the coordination number, the number and types of donor atoms, and their relative positions to each other on the complexation have been evaluated in the present work. We hope that these collected results might be used when a new peptide-based hydroxamic acid molecule is planned with some purpose, e.g. to develop a potential metalloenzyme inhibitor.
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47

Papadogianakis, Georgios, Joop A. Peters, Leendert Maat y Roger A. Sheldon. "Catalytic conversions in water: 17O, {1H}31P and 35Cl NMR study of a novel stoichiometric redox reaction between PdCl2, tppts and H2O [tppts = P(C6H4-m-SO3Na)3]". Journal of the Chemical Society, Chemical Communications, n.º 11 (1995): 1105. http://dx.doi.org/10.1039/c39950001105.

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48

Quillet, V., F. Abel y M. Schott. "Absolute cross section measurements for H and D elastic recoil using 1 to 2.5 MeV 4He ions, and for the 12C(d,p)13C and 16O(d,p1)17O nuclear reactions". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 83, n.º 1-2 (octubre de 1993): 47–61. http://dx.doi.org/10.1016/0168-583x(93)95906-l.

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49

Gray, Gary M. y Keith A. Redmill. "Chemical shift correlations in the 13C, 17O and 31P NMR spectra of some Mo(CO)4((PPh2O)2Y(R)R′) (Y(R) = P(O), Si(Me); R′ = alkyl, haloalkyl, aryl) and [Mo(CO)4(PPh2O)2]2Si complexes". Journal of Organometallic Chemistry 280, n.º 1 (enero de 1985): 105–14. http://dx.doi.org/10.1016/0022-328x(85)87067-4.

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50

Cheng, Christopher, Jon Hedgecock, Matthew Solomito, Sheeba Joseph y J. Lee Pace. "DEFINING TROCHLEAR DYSPLASIA VIA THE LATERAL TROCHLEAR INCLINATION ANGLE". Orthopaedic Journal of Sports Medicine 8, n.º 4_suppl3 (1 de abril de 2020): 2325967120S0017. http://dx.doi.org/10.1177/2325967120s00179.

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Background: Trochlear dysplasia (TD) is the principle anatomic risk factor for patellar instability (PI). The lateral trochlear inclination (LTI) is a quantitative measure of trochlear morphology on axial magnetic resonance imaging (MRI). Threshold values for patients at risk for PI via LTI measurement have ranged from 11o to 17o. Our group recently described a new technique for characterizing LTI by referencing the fully-formed posterior femoral condyles. This novel measurement technique revealed that the historically-used method was comparable in reliability but significantly underestimated TD. Purpose: The purpose of this study was to define, with high specificity, a LTI value cutoff value consistent with patellar instability using the new LTI measurement technique. Methods: MRI scans of 95 patients aged 9 to 18 years treated for PI at our tertiary referral center were compared with a control cohort of 98 age- and gender- matched patients with knee imaging but no clinical evidence of PI. LTI was measured as the angle formed between a line subtended from the cartilaginous surface of the lateral trochlea at its most proximal extent and a line parallel to the fully-formed posterior condyles. Receiver operator characteristic (ROC) curve analysis was conducted to establish a cutoff value with optimal specificity and sensitivity. Results: Average LTI was significantly lower in the study group (5.9±10.4o) than control (18.9±5.8o) (p<0.001). Area under the ROC curve was 0.86. A proposed 8.9o LTI threshold angle achieves good discrimination between the two groups, with specificity of 0.904 and sensitivity of 0.684. Conclusion: Re-examination of previously described threshold values using ROC curve analysis of LTI measured in reference to the posterior condyles found 8.9o as the optimal threshold value to achieve good discrimination between patients with and without PI. The novel technique has previously been established to have excellent intra- and inter-observer reliability and produced significantly lower LTI values than the historically-used technique. Taken in concert, this new cutoff is valuable to improve future clinical decision making in regards to risk stratification, treatment algorithms and research purposes.
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