492 research outputs found
Zorgen rondom IVF
De vraag naar dit onderzoek kwam vanuit de patiëntenvereniging Freya terecht bij de Wetenschapswinkel Geneeskunde en Volksgezondheid van de Rijksuniversiteit Groningen.
Deze vraag is vertaald in een wetenschappelijk te beantwoorden probleemstelling. Het onderzoek dat hieruit is voort gekomen, is uitgevoerd in het kader van een afstudeeronderzoek.
De probleemstelling van het onderzoek luidt:
In welke opzichten en in hoeverre hebben vrouwen die kiezen voor IVF (in vitro fertilisatie), behoefte aan steun en begeleiding bij keuzen en ervaringen die zich in het behandelingstraject voordoen...
Deep-inelastic production of heavy quarks
Deep-inelastic production of heavy quarks at HERA, especially charm, is an
excellent signal to measure the gluon distribution in the proton at small
values. By measuring various differential distributions of the heavy quarks
this reaction permits additional more incisive QCD analyses due to the many
scales present. Furthermore, the relatively small mass of the charm quark,
compared to the typical momentum transfer , allows one to study whether and
when to treat this quark as a parton. This reaction therefore sheds light on
some of the most fundamental aspects of perturbative QCD. We discuss the above
issues and review the feasibility of their experimental investigation in the
light of a large integrated luminosity.Comment: 10 pages, uses epsfig.sty, five ps figures included. To appear in the
proceedings of the workshop Future Physics at HERA, eds. G. Ingelman, A. De
Roeck and R. Klanner, DESY, Hamburg, 199
The non-concept of âwar-pronenessâ: Naar aanleiding van H. W. Houweling and J. G. Siccama, War in the foreign policies of nations, Acta Politica, 1981 nr. 1, 67-99
Vector competence of Aedes aegypti, Culex tarsalis, and Culex quinquefasciatus from California for Zika virus.
Zika virus (ZIKV) has emerged since 2013 as a significant global human health threat following outbreaks in the Pacific Islands and rapid spread throughout South and Central America. Severe congenital and neurological sequelae have been linked to ZIKV infections. Assessing the ability of common mosquito species to transmit ZIKV and characterizing variation in mosquito transmission of different ZIKV strains is important for estimating regional outbreak potential and for prioritizing local mosquito control strategies for Aedes and Culex species. In this study, we evaluated the laboratory vector competence of Aedes aegypti, Culex quinquefasciatus, and Culex tarsalis that originated in areas of California where ZIKV cases in travelers since 2015 were frequent. We compared infection, dissemination, and transmission rates by measuring ZIKV RNA levels in cohorts of mosquitoes that ingested blood meals from type I interferon-deficient mice infected with either a Puerto Rican ZIKV strain from 2015 (PR15), a Brazilian ZIKV strain from 2015 (BR15), or an ancestral Asian-lineage Malaysian ZIKV strain from 1966 (MA66). With PR15, Cx. quinquefasciatus was refractory to infection (0%, N = 42) and Cx. tarsalis was infected at 4% (N = 46). No ZIKV RNA was detected in saliva from either Culex species 14 or 21 days post feeding (dpf). In contrast, Ae. aegypti developed infection rates of 85% (PR15; N = 46), 90% (BR15; N = 20), and 81% (MA66; N = 85) 14 or 15 dpf. Although MA66-infected Ae. aegypti showed higher levels of ZIKV RNA in mosquito bodies and legs, transmission rates were not significantly different across virus strains (P = 0.13, Fisher's exact test). To confirm infectivity and measure the transmitted ZIKV dose, we enumerated infectious ZIKV in Ae. aegypti saliva using Vero cell plaque assays. The expectorated plaque forming units PFU varied by viral strain: MA66-infected expectorated 13±4 PFU (mean±SE, N = 13) compared to 29±6 PFU for PR15-infected (N = 13) and 35±8 PFU for BR15-infected (N = 6; ANOVA, df = 2, F = 3.8, P = 0.035). These laboratory vector competence results support an emerging consensus that Cx. tarsalis and Cx. quinquefasciatus are not vectors of ZIKV. These results also indicate that Ae. aegypti from California are efficient laboratory vectors of ancestral and contemporary Asian lineage ZIKV
The curvature of as a probe of the range of validity of perturbative QCD evolutions in the small- region
Perturbative NLO and NNLO QCD evolutions of parton distributions are studied,
in particular in the (very) small- region, where they are in very good
agreement with all recent precision measurements of . These
predictions turn out to be also rather insensitive to the specific choice of
the factorization scheme ( or DIS). A characteristic feature of
perturbative QCD evolutions is a {\em{positive}} curvature of which
increases as decreases. This perturbatively stable prediction provides a
sensitive test of the range of validity of perturbative QCD.Comment: 17 pages, 6 figures, 2 tables; minor corrections, to appear in EPJ
Bottom quark electroproduction in variable flavor number schemes
Two variable flavor number schemes are used to describe bottom quark
production in deep inelastic electron-proton scattering. In these schemes the
coefficient functions are derived from mass factorization of the heavy quark
coefficient functions presented in a fixed flavor number scheme. Also one has
to construct a parton density set with five light flavors (u,d,s,c,b) out of a
set which only contains four light flavors (u,d,s,c). In order the
two sets are discontinuous at which follows from mass factorization
of the heavy quark coefficient functions when it is carried out in the -scheme. Both variable flavor number schemes give almost identical
predictions for the bottom structure functions and . Also
they both agree well with the corresponding results based on fixed order
four-flavor perturbation theory over a wide range in and .Comment: Latex with seventeen PostScript figure
Order \alpha_s^2 Contributions to charm production in charged-current deep-inelastic lepton-hadron scattering
The most important part of the order corrections to the charm
component of the charged-current structure functions and
have been calculated. This calculation is based on the asymptotic
form of the heavy-quark coefficient functions corresponding to the higher order
corrections to the W-boson-gluon fusion process. These coefficient functions
which are in principle only valid for can be also used to
estimate the order contributions at lower values provided . It turns out that the above corrections are appreciable in the large
-region and they explain the discrepancy found for the structure functions
between the fixed-flavour scheme (FFS) and the variable-flavour-number scheme
(VFNS). These corrections also hamper the extraction of the strange-quark
density from the data obtained for the charged-current and the
electromagnetic-current processes.Comment: 45 pages LaTeX, 17 Postscript Figure
On the Resummation of the epe^+e^-$ Annihilation
The resummation of the non-singlet contributions is
performed for initial state QED corrections. As examples, the effect of the
resummation on neutral-current deep-inelastic scattering and the scattering cross section near the -peak is
investigated.Comment: 11 pages Latex, including 3 eps-figure
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