University of Hamburg

About: University of Hamburg is a education organization based out in Hamburg, Germany. It is known for research contribution in the topics: Population & Laser. The organization has 45564 authors who have published 89286 publications receiving 2850161 citations. The organization is also known as: Hamburg University.

Time-resolved serial crystallography captures high-resolution intermediates of photoactive yellow protein

Abstract: Serial femtosecond crystallography using ultrashort pulses from x-ray free electron lasers (XFELs) enables studies of the light-triggered dynamics of biomolecules. We used microcrystals of photoactive yellow protein (a bacterial blue light photoreceptor) as a model system and obtained high-resolution, time-resolved difference electron density maps of excellent quality with strong features; these allowed the determination of structures of reaction intermediates to a resolution of 1.6 angstroms. Our results open the way to the study of reversible and nonreversible biological reactions on time scales as short as femtoseconds under conditions that maximize the extent of reaction initiation throughout the crystal.

Experimental tests of factorization in charmless nonleptonic two-body B decays

Abstract: Using a theoretical framework based on the next-to-leading-order QCD-improved effective Hamiltonian and a factorization ansatz for the hadronic matrix elements of the four-quark operators, we reassess branching fractions in two-body nonleptonic decays $\stackrel{\ensuremath{\rightarrow}}{B}PP,PV,VV,$ involving the lowest-lying light pseudoscalar $(P)$ and vector $(V)$ mesons in the standard model. We work out the parametric dependence of the decay rates, making use of the currently available information on the weak mixing matrix elements, form factors, decay constants, and quark masses. Using the sensitivity of the decay rates on the effective number of colors, ${N}_{c},$ as a criterion of theoretical predictivity, we classify all the current-current (tree) and penguin transitions in five different classes. The recently measured charmless two-body $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PP}$ decays ${(B}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\eta}}^{\ensuremath{'}}, {B}^{0}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\eta}}^{\ensuremath{'}}, {B}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}, {B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{0},$ and charge conjugates) are dominated by the ${N}_{c}$-stable QCD penguin transitions (class-IV transitions) and their estimates are consistent with the data. The measured charmless $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PV} {(B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{K}^{+}, {B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{h}^{+})$ and $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{VV}$ transition $(\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{K}^{*}),$ on the other hand, belong to the penguin (class-V) and tree (class-III) transitions. The class-V penguin transitions are ${N}_{c}$ sensitive and/or involve large cancellations among competing amplitudes, making their decay rates in general more difficult to predict. Some of these transitions may also receive significant contributions from annihilation and/or final state interactions. We propose a number of tests of the factorization framework in terms of the ratios of branching ratios for some selected $\stackrel{\ensuremath{\rightarrow}}{B}{h}_{1}{h}_{2}$ decays involving light hadrons ${h}_{1}$ and ${h}_{2},$ which depend only moderately on the form factors. We also propose a set of measurements to determine the effective coefficients of the current-current and QCD penguin operators. The potential impact of $\stackrel{\ensuremath{\rightarrow}}{B}{h}_{1}{h}_{2}$ decays on the CKM phenomenology is emphasized by analyzing a number of decay rates in the factorization framework.

The World Health Organization Fetal Growth Charts: A Multinational Longitudinal Study of Ultrasound Biometric Measurements and Estimated Fetal Weight

Abstract: Background Perinatal mortality and morbidity continue to be major global health challenges strongly associated with prematurity and reduced fetal growth, an issue of further interest given the mounting evidence that fetal growth in general is linked to degrees of risk of common noncommunicable diseases in adulthood. Against this background, WHO made it a high priority to provide the present fetal growth charts for estimated fetal weight (EFW) and common ultrasound biometric measurements intended for worldwide use. Methods and Findings We conducted a multinational prospective observational longitudinal study of fetal growth in low-risk singleton pregnancies of women of high or middle socioeconomic status and without known environmental constraints on fetal growth. Centers in ten countries (Argentina, Brazil, Democratic Republic of the Congo, Denmark, Egypt, France, Germany, India, Norway, and Thailand) recruited participants who had reliable information on last menstrual period and gestational age confirmed by crown–rump length measured at 8–13 wk of gestation. Participants had anthropometric and nutritional assessments and seven scheduled ultrasound examinations during pregnancy. Fifty-two participants withdrew consent, and 1,387 participated in the study. At study entry, median maternal age was 28 y (interquartile range [IQR] 25–31), median height was 162 cm (IQR 157–168), median weight was 61 kg (IQR 55–68), 58% of the women were nulliparous, and median daily caloric intake was 1,840 cal (IQR 1,487–2,222). The median pregnancy duration was 39 wk (IQR 38–40) although there were significant differences between countries, the largest difference being 12 d (95% CI 8–16). The median birthweight was 3,300 g (IQR 2,980–3,615). There were differences in birthweight between countries, e.g., India had significantly smaller neonates than the other countries, even after adjusting for gestational age. Thirty-one women had a miscarriage, and three fetuses had intrauterine death. The 8,203 sets of ultrasound measurements were scrutinized for outliers and leverage points, and those measurements taken at 14 to 40 wk were selected for analysis. A total of 7,924 sets of ultrasound measurements were analyzed by quantile regression to establish longitudinal reference intervals for fetal head circumference, biparietal diameter, humerus length, abdominal circumference, femur length and its ratio with head circumference and with biparietal diameter, and EFW. There was asymmetric distribution of growth of EFW: a slightly wider distribution among the lower percentiles during early weeks shifted to a notably expanded distribution of the higher percentiles in late pregnancy. Male fetuses were larger than female fetuses as measured by EFW, but the disparity was smaller in the lower quantiles of the distribution (3.5%) and larger in the upper quantiles (4.5%). Maternal age and maternal height were associated with a positive effect on EFW, particularly in the lower tail of the distribution, of the order of 2% to 3% for each additional 10 y of age of the mother and 1% to 2% for each additional 10 cm of height. Maternal weight was associated with a small positive effect on EFW, especially in the higher tail of the distribution, of the order of 1.0% to 1.5% for each additional 10 kg of bodyweight of the mother. Parous women had heavier fetuses than nulliparous women, with the disparity being greater in the lower quantiles of the distribution, of the order of 1% to 1.5%, and diminishing in the upper quantiles. There were also significant differences in growth of EFW between countries. In spite of the multinational nature of the study, sample size is a limiting factor for generalization of the charts. Conclusions This study provides WHO fetal growth charts for EFW and common ultrasound biometric measurements, and shows variation between different parts of the world.