2,184 research outputs found
Ryhiner-Kartensammlung / 21/B Ville de Tong cheu : ; Pellerinage pour obtenir une année fertile
No full textChedel inv. sc.Ansicht oben ("Ville de Tong cheu", 9 x 12 cm), Bild unten ("Pellerinage ...", 9 x 12 cm)Numerierung unten rechts: "T. V. No. IX."Ursprungswerk: "Histoire générale des voyages" von A.F. Prévost (Paris : Didot, 1746-1761
Spin-spin coupling measurements in solid-state NMR and applications to rhodospin
No full textThis thesis discusses some recently developed symmetry-based rotor-synchronised re-coupling sequences in magic-angle-spinning solid-state NMR and their applications to biological samples. Symmetry theorems are applied to the problem of spin-spin couplings in the presence of magic-angle-spinning in the solid-state. Homonuclear dipolar and J-coupling measurements are achieved on multiple 13C labelled systems. J-coupling measurements have been performed on a G-protein coupled receptor - rhodopsin. Accurate distance measurements and J-coupling are obtained through rare spin signal build-up curves and J-modulated curves. The data collected for the G- protein coupled receptor includes the use of a new technique without decoupling. A general introduction to solid-state NMR and its uses in molecular structure determination are discussed. This includes a description of symmetry-based pulse sequences. The emphasis is put on applications of such sequences for the establishment of an accurate methodology to measure spin-spin couplings. The techniques are demonstrated on model systems of known structure and then applied to the investigation of the chemical bonding in the membrane protein rhodopsin, where the retinylidene chromophore is selectively labelled. In the context of this thesis the main focus is on a particular class of biomolecule, the trans-membrane G-protein coupled receptor, rhodopsin. A general description of the functionality of these proteins is also discussed.</p
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Study of the rare decay K(L) →e⁺e⁻μ⁺μ⁻ at KTeV
No full textThe rare decay K(L) → e⁺e⁻μ⁺μ⁻ offers the best opportunity to study the dynamics behind the KL γ*γ* vertex. This information is needed to subtract the long-distance contribution to the decay K(L) → μ⁺μ⁻, allowing for a calculation of rho, the real part of the CKM matrix element Vtd. Analysis of data from the 1997 and 1999 runs of the KTeV experiment has isolated a sample of 132 K(L) → e⁺e⁻μ⁺μ⁻ events, with an estimated background of 0.8 events. Based on this data, the branching ratio for this mode was calculated to be B(K(L) → e⁺e⁻μ⁺μ⁻) = (2.63 ± 0.23(stat) ± 0.13(syst)) x 10⁻⁹, where a radiative cutoff has been imposed at x(e⁺e⁻μ⁺μ⁻) > 0.95. The D'Ambrosio, Isidori, and Portoles K(L) γ*γ* linear form factor parameter alpha was measured to be -1.52 ± 0.38, consistent with previous experimental results. Little sensitivity was found to the quadratic parameter beta, resulting in a measured value of +12.3 ± 77.1. The asymmetry in the angular distribution of the K(L) → e⁺e⁻μ⁺μ⁻ decay products was measured to be A < 25.5% with 90% confidence, constraining the size of any CP-violating contribution to the K(L) gamma*gamma* interaction. Finally, a 90% C.L. upper limit of 4.12 x 10⁻¹¹ was placed on the branching ratio of the lepton flavor-violating mode K(L) → e⁺/⁻ e⁺/⁻μ⁺/⁻μ⁺/⁻, a full factor of 3 improvement over the current limit
A robust pulse sequence for the determination of small homonuclear dipolar couplings in magic-angle spinning NMR
No full textWe present a new solid-state NMR pulse sequence that accomplishes efficient broad-band dipolar recoupling in systems with small dipolar couplings and large chemical shift anisotropies. The method involves a supercycled symmetry-based recoupling sequence incorporated in a constant-interval data acquisition strategy. The supercycle removes destructive higher-order average Hamiltonian terms, and makes the method more robust at long time intervals. We demonstrate 38.4% double-quantum filtering efficiency on diammonium [1,4-13C2]-fumarate in which the internuclear distance, as estimated by X-ray diffraction, is 387.8 pm. The estimated 13C-13C dipolar coupling was -136.5±5.1 Hz, corresponding to an internuclear distance of 382.5±4 pm
Estudos sobre propriedades mecanicas do colmo da cana-de-açucar
No full textOrientador : Cheu-Shang ChangDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos e AgricolaMestradoMestre em Engenharia Agrícol
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Growth patterns of uninfected children born to women living with perinatally versus nonperinatally acquired HIV
No full textThe aim of this study was to compare long-term growth between HIV-exposed uninfected children (CHEU) born to women with perinatally acquired HIV (CHEU-PHIV) and CHEU born to women with nonperinatally acquired HIV (CHEU-NPHIV).
A longitudinal analysis of anthropometric measurements from a U.S.-based multisite prospective cohort study enrolling CHEU and their mothers since April 2007.
CHEU were evaluated for growth annually from birth through age 5 and again at age 7 years. Z-scores were calculated using U.S. growth references for weight (WTZ), height (HTZ), and weight-for-length or BMI-for-age (WLZ/BMIZ). Mid-upper arm circumference (MUACZ) and triceps skinfold thickness (TSFZ) Z-scores were obtained from ages 1 and 2, respectively, through age 7 years. Piecewise mixed-effects models, overall and stratified by race and sex, were fit to assess differential growth patterns across age by maternal PHIV status.
One thousand four hundred fifty-four singleton infants (286 CHEU-PHIV and 1168 CHEU-NPHIV) were included. CHEU-PHIV had slower growth rates than CHEU-NPHIV for WTZ and WLZ/BMIZ at earlier ages and continued to have lower mean WTZ [-0.27, 95% confidence interval (95% CI): -0.50, -0.04] and WLZ/BMIZ (-0.39, 95% CI: -0.67, -0.11) through age 7. Among non-Black boys, CHEU-PHIV had slightly lower WTZ and WLZ/BMIZ at birth than CHEU-NPHIV and these growth deficits persisted through age 7 years.
Compared with CHEU-NPHIV, CHEU-PHIV had diminished growth in early childhood with differences most pronounced among non-Black male children. Further longitudinal follow-up of CHEU-PHIV into young adulthood is needed to understand whether these early effects of maternal PHIV status on growth persist and have other health consequences
Growth Patterns of Uninfected Children Born to Women Living with Perinatally- Versus Non-Perinatally-Acquired HIV
No full textObjective: The aim of this study was to compare long-term growth between HIV-exposed uninfected children (CHEU) born to women with perinatally acquired HIV (CHEU-PHIV) and CHEU born to women with nonperinatally acquired HIV (CHEU-NPHIV).
Design: A longitudinal analysis of anthropometric measurements from a U.S.-based multisite prospective cohort study enrolling CHEU and their mothers since April 2007.
Methods: CHEU were evaluated for growth annually from birth through age 5 and again at age 7 years. Z-scores were calculated using U.S. growth references for weight (WTZ), height (HTZ), and weight-for-length or BMI-for-age (WLZ/BMIZ). Mid-upper arm circumference (MUACZ) and triceps skinfold thickness (TSFZ) Z-scores were obtained from ages 1 and 2, respectively, through age 7 years. Piecewise mixed-effects models, overall and stratified by race and sex, were fit to assess differential growth patterns across age by maternal PHIV status.
Results: One thousand four hundred fifty-four singleton infants (286 CHEU-PHIV and 1168 CHEU-NPHIV) were included. CHEU-PHIV had slower growth rates than CHEU-NPHIV for WTZ and WLZ/BMIZ at earlier ages and continued to have lower mean WTZ [-0.27, 95% confidence interval (95% CI): -0.50, -0.04] and WLZ/BMIZ (-0.39, 95% CI: -0.67, -0.11) through age 7. Among non-Black boys, CHEU-PHIV had slightly lower WTZ and WLZ/BMIZ at birth than CHEU-NPHIV and these growth deficits persisted through age 7 years.
Conclusion: Compared with CHEU-NPHIV, CHEU-PHIV had diminished growth in early childhood with differences most pronounced among non-Black male children. Further longitudinal follow-up of CHEU-PHIV into young adulthood is needed to understand whether these early effects of maternal PHIV status on growth persist and have other health consequences
Ryhiner-Kartensammlung / 19/A Cité de Chau cheu fu
No full texttirée de NieuhofTitelkartusche oben MitteNumerierung unten rechts: "T. V. No. VI."Ursprungswerk: "Histoire générale des voyages" von A. F. Prévost (Paris : Didot, 1746-1761
Theory and applications of supercycled symmetry-based recoupling sequences in solid-state NMR
No full textWe present the theoretical principles of supercycled symmetry-based recoupling sequences in solid-state magic-angle-spinning NMR. We discuss the construction procedure of the SR26 pulse sequence, which is a particularly robust sequence for double-quantum homonuclear dipole-dipole recoupling. The supercycle removes destructive higher-order average Hamiltonian terms and renders the sequence robust over long time intervals. We demonstrate applications of the SR26 sequence to double-quantum spectroscopy, homonuclear spin counting, and determination of the relative orientations of chemical shift anisotropy tensors
Impact of antenatal antiretroviral drug exposure on the growth of children who are HIV-exposed uninfected: the national South African Prevention of Mother to Child Evaluation cohort study
No full textBACKGROUND: The relationship between in-utero antiretroviral (ARV) drug exposure and child growth needs further study as current data provide mixed messages. We compared postnatal growth in the first 18-months of life between children who are HIV-exposed uninfected (CHEU) with fetal exposure to ARV drugs (prophylaxis or triple-drug therapy (ART)) and CHEU not exposed to ARVs. We also examined other independent predictors of postnatal growth. METHODS: We analysed data from a national prospective cohort study of 2526 CHEU enrolled at 6-weeks and followed up 3-monthly till 18-months postpartum, between October 2012 and September 2014. Infant anthropometry was measured, and weight-for-age (WAZ) and length-for-age (LAZ) Z-scores calculated. Generalized estimation equation models were used to compare Z-scores between groups. RESULTS: Among 2526 CHEU, 617 (24.4%) were exposed to ART since -pregnancy (pre-conception ART), 782 (31.0%) to ART commencing post-conception, 879 (34.8%) to maternal ARV prophylaxis (Azidothymidine (AZT)), and 248 (9.8%) had no ARV exposure. In unadjusted analyses, preterm birth rates were higher among CHEU with no ARV exposure than in other groups. Adjusting for infant age, the mean WAZ profile was lower among CHEU exposed to pre-conception ART [-0.13 (95% confidence interval − 0.26; − 0.01)] than the referent AZT prophylaxis group; no differences in mean WAZ profiles were observed for the post-conception ART (− 0.05 (− 0.16; 0.07)), None (− 0.05 (− 0.26; 0.16)) and newly-infected (− 0.18 (− 0.48; 0.13)) groups. Mean LAZ profiles were similar across all groups. In multivariable analyses, mean WAZ and LAZ profiles for the ARV exposure groups were completely aligned. Several non-ARV factors including child, maternal, and socio-demographic factors independently predicted mean WAZ. These include child male (0.45 (0.35; 0.56)) versus female, higher maternal education grade 7–12 (0.28 (0.14; 0.42) and 12 + (0.36 (0.06; 0.66)) versus ≤ grade7, employment (0.16 (0.04; 0.28) versus unemployment, and household food security (0.17 (0.03; 0.31). Similar predictors were observed for mean LAZ. CONCLUSION: Findings provide evidence for initiating all pregnant women living with HIV on ART as fetal exposure had no demonstrable adverse effects on postnatal growth. Several non-HIV-related maternal, child and socio-demographic factors were independently associated with growth, highlighting the need for multi-sectoral interventions. Longer-term monitoring of CHEU children is recommended. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12879-022-07847-9
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