2,021 research outputs found
Kaon photoproduction: background contributions, form factors and missing resonances
The photoproduction p(gamma, K+)Lambda process is studied within a
field-theoretic approach. It is shown that the background contributions
constitute an important part of the reaction dynamics. We compare predictions
obtained with three plausible techniques for dealing with these background
contributions. It appears that the extracted resonance parameters drastically
depend on the applied technique. We investigate the implications of the
corrections to the functional form of the hadronic form factor in the contact
term, recently suggested by Davidson and Workman (Phys. Rev. C 63, 025210). The
role of background contributions and hadronic form factors for the
identification of the quantum numbers of ``missing'' resonances is discussed.Comment: 11 pages, 7 eps figures, submitted to Phys. Rev.
Spin-dependent correlations and the semi-exclusive ^{16}O(e,e'p) reaction
The effect of central, tensor and spin-isospin nucleon-nucleon correlations
upon semi-exclusive ^{16}O(e,e'p) reactions is studied for Q^2 and Bjorken x
values in the range and 0.15
x 2. The fully unfactorized calculations are performed in
a framework that accounts not only for the dynamical coupling of virtual
photons to correlated nucleon pairs but also for meson-exchange and
-isobar currents. Tensor correlations are observed to produce
substantially larger amounts of semi-exclusive ^{16}O(e,e'p) strength than
central correlations do and are predominantly manifest in the proton-neutron
knockout channel. With the exception of the case, in all
kinematical situations studied the meson-exchange and isobar currents are a
strong source of A(e,e'p) strength at deep missing energies. This feature gives
the A(e,e'p) strength at deep missing energies a pronounced transverse
character.Comment: 14 pages, 6 figure
Pediatric Microdose Study of [14C]Paracetamol to Study Drug Metabolism Using Accelerated Mass Spectrometry: Proof of Concept
Results: Ten infants (aged 0.1–83.1 months) were included; one was excluded as he vomited shortly after administration. In nine patients, [14C]AAP and metabolites in blood samples were detectable at expected concentrations: median (range) maximum concentration (Cmax) [14C]AAP 1.68 (0.75–4.76) ng/L, [14C]AAP-Glu 0.88 (0.34–1.55) ng/L, and [14C]AAP-4Sul 0.81 (0.29–2.10) ng/L. Dose-normalized oral [14C]AAP Cmax approached median intravenous average concentrations (Cav): 8.41 mg/L (3.75–23.78 mg/L) and 8.87 mg/L (3.45–12.9 mg/L), respectively.Conclusions: We demonstrate the feasibility of using a [14C]labeled microdose to study AAP pharmacokinetics, including metabolite disposition, in young children.Background: Pediatric drug development is hampered by practical, ethical, and scientific challenges. Microdosing is a promising new method to obtain pharmacokinetic data in children with minimal burden and minimal risk. The use of a labeled oral microdose offers the added benefit to study intestinal and hepatic drug disposition in children already receiving an intravenous therapeutic drug dose for clinical reasons.Methods: In an open-label microdose pharmacokinetic pilot study, infants (0–6 years of age) received a single oral [14C]AAP microdose (3.3 ng/kg, 60 Bq/kg) in addition to intravenous therapeutic doses of AAP (15 mg/kg intravenous every 6 h). Blood samples were taken from an indwelling catheter. AAP blood concentrations were measured by liquid chromatography–tandem mass spectrometry (LC-MS/MS) and [14C]AAP and metabolites ([14C]AAP-Glu and [14C]AAP-4Sul) were measured by accelerator mass spectrometry.Objective: The objective of this study was to present pilot data of an oral [14C]paracetamol [acetaminophen (AAP)] microdosing study as proof of concept to study developmental pharmacokinetics in children
The combined and interactive effects of zinc, temperature, and phosphorus on the structure and functioning of a freshwater community
Ecotoxicological studies mainly consist of single-species experiments evaluating the effects of a single stressor. However, under natural conditions aquatic communities are exposed to a mixture of stressors. The present study aimed to identify how the toxicity of zinc (Zn) is affected by increased temperature and increased phosphorus (P) supply and how these interactions vary among species, functional groups, and community structure and function. Aquatic microcosms were subjected to 3 Zn concentrations (background, no Zn added, and 75 and 300 μg Zn/L), 2 temperatures (16–19 and 21–24 °C), and 2 different P additions (low, 0.02, and high, 0.4 mg P L−1 wk−1) for 5 wk using a full factorial design. During the study, consistent interactions between Zn and temperature were only rarely found at the species level (4%), but were frequently found at the functional group level (36%), for community structure (100%) and for community function (100%; such as dissolved organic carbon concentrations and total chlorophyll). The majority of the Zn × temperature interactions were observed at 300 μg Zn/L and generally indicated a smaller effect of Zn at higher temperature. Furthermore, no clear indication was found that high P addition by itself significantly affected the overall effects of Zn on the community at any level of organization. Interestingly, though, 90% of all the Zn × temperature interactions observed at the species, group, and community composition level were found under high P addition. Collectively, the results of our study with the model chemical Zn suggest that temperature and phosphorus loading to freshwater systems should be accounted for in risk assessment, because these factors may modify the effects of chemicals on the structure and functioning of aquatic communities, especially at higher levels of biological organization. Environ Toxicol Chem 2018;37:2413–2427.</p
Meson and Isobar Degrees of Freedom in A() reactions at
The effect of meson and isobar degrees of freedom in A()
and A(e,e'n) is studied for four-momentum transfers Q^2 in the range between
0.2 and 0.8 (GeV/c)^2. The calculations are performed in a non-relativistic
framework with explicit (N,\Delta,\pi) degrees-of-freedom. For the whole range
of momentum transfers under investigation the relative effect of the
meson-exchange and isobar degrees of freedom is significant. At low missing
momenta and quasi-elastic conditions, a tendency to reduce the (e,e'p) and
(e,e'n) differential cross sections is noticed. The greatest sensitivity is
found in the interference structure functions and . The recoil
polarization observables, on the other hand, are moderately affected by the
meson-exchange and -isobar currents.Comment: 16 pages (Revtex) + 18 figures (eps file
Consensus on the reporting and experimental design of clinical and cognitive-behavioural neurofeedback studies (CRED-nf checklist)
Neurofeedback has begun to attract the attention and scrutiny of the scientific and medical mainstream. Here, neurofeedback researchers present a consensus-derived checklist that aims to improve the reporting and experimental design standards in the field.</p
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