647 research outputs found
Recommended from our members
Predominant variable region gene usage by gamma/delta T cell receptor-bearing cells in the adult thymus.
Previous studies have indicated that the diversity of gamma genes expressed by gamma/delta-bearing murine T cells is limited, but comparable information concerning the expressed diversity of delta genes is lacking. In this study, we have investigated the rearrangement and expression of delta and gamma genes in T cell hybridomas that express gamma/delta T cell receptors. Three productive delta chain cDNA clones were isolated (delta 7.3, delta 7.1, and delta 2.3) that encode new variable region sequences. Two of the delta cDNAs differ significantly from those observed in the V alpha repertoire. In addition, one cDNA expressed a new J delta region (J delta 2), which was localized between J delta 1 and C delta genes. Using these and other delta gene probes and gamma gene probes, we found that five independent hybridomas expressed four different V delta s and three different V gamma s. However, analysis of an enriched population of gamma/delta-expressing cells from the adult thymus suggests that only a few V delta genes and one V gamma gene are used by the majority of the cells. These results suggest that important components of receptor chain that contribute to specificity (i.e., the germline V gene sequences) are relatively nondiverse in the thymic gamma/delta population
Wall-bounded turbulent flows at high Reynolds numbers: Recent advances and key issues
Wall-bounded turbulent flows at high Reynolds numbers have become an increasingly active area of
research in recent years. Many challenges remain in theory, scaling, physical understanding,
experimental techniques, and numerical simulations. In this paper we distill the salient advances of
recent origin, particularly those that challenge textbook orthodoxy. Some of the outstanding
questions, such as the extent of the logarithmic overlap layer, the universality or otherwise of the
principal model parameters such as the von Kármán “constant,” the parametrization of roughness
effects, and the scaling of mean flow and Reynolds stresses, are highlighted. Research avenues that
may provide answers to these questions, notably the improvement of measuring techniques and the
construction of new facilities, are identified. We also highlight aspects where differences of opinion
persist, with the expectation that this discussion might mark the beginning of their resolution
Statistics of turbulence in the energy-containing range of Taylor-Couette compared to canonical wall-bounded flows
Considering structure functions of the streamwise velocity component in a
framework akin to the extended self-similarity hypothesis (ESS), de Silva
\textit{et al.} (\textit{J. Fluid Mech.}, vol. 823,2017, pp. 498-510) observed
that remarkably the \textit{large-scale} (energy-containing range) statistics
in canonical wall bounded flows exhibit universal behaviour. In the present
study, we extend this universality, which was seen to encompass also flows at
moderate Reynolds number, to Taylor-Couette flow. In doing so, we find that
also the transversal structure function of the spanwise velocity component
exhibits the same universal behaviour across all flow types considered. We
further demonstrate that these observations are consistent with predictions
developed based on an attached-eddy hypothesis. These considerations also yield
a possible explanation for the efficacy of the ESS framework by showing that it
relaxes the self-similarity assumption for the attached eddy contributions. By
taking the effect of streamwise alignment into account, the attached eddy model
predicts different behaviour for structure functions in the streamwise and in
the spanwise directions and that this effect cancels in the ESS-framework ---
both consistent with the data. Moreover, it is demonstrated here that also the
additive constants, which were previously believed to be flow dependent, are
indeed universal at least in turbulent boundary layers and pipe flow where
high-Reynolds number data are currently available.Comment: accepted in J. Fluid Mec
Continuous measurement of global difference coupling using a phase-locked-loop tune meter in the Relativistic Heavy Ion Collider
We present a new technique to continuously measure and compensate the global difference coupling coefficient through the continuous measurements of eigenmode projection parameters, using a high resolution phase-locked-loop tune meter. First, four eigenmode projection parameters are defined as the observables for weak difference coupling. Then, their analytical expressions are obtained using the strict matrix treatment and the Hamiltonian perturbation theory of linear coupling. From these parameters, the complex global coupling coefficient can be fully determined and compensated. This method was successfully demonstrated in the Relativistic Heavy Ion Collider (RHIC) 2006 run
Attitudes of editors of core clinical journals about whether systematic reviews are original research: a mixed-methods study.
In 2009, not all journal editors considered systematic reviews (SRs) to be original research studies, and not all PubMed Core Clinical Journals published SRs. The aim of this study was to conduct a new analysis about editors' opinion regarding SRs as original research.
We conducted a survey and qualitative interview study of journal editors.
All editors listed as editor-in chief of 118 PubMed Core Clinical Journals.
We contacted editors via email and asked them whether they considered SRs original research, whether they published SRs in the journal and, if yes, in which section. We searched PubMed for any SRs (or meta-analyses) published in the included journals in 2017; if we did not find any, we hand-searched these journals. Editors were invited to participate in a follow-up qualitative interview study.
We received responses from 73 editors representing 72 (62%) journals. Fifty-two (80%) editors considered SRs original research, either for any type of SR (65%) or only for SRs with a meta-analysis (15%) and almost all (91%) of editors published SRs. Compared with the results of the 2009 study of Core Clinical Journals, a similar proportion of editors considered SRs to be original studies (71%), accepted SRs as original on certain condition such as presence of meta-analysis (14%) or published SRs (94%). Interviews with editors showed that they used various criteria to decide whether a SR is original research, including methodology, reproducibility, originality of idea and level of novelty.
The majority of editors of core clinical journals consider that SRs are original research. Among editors, there was no uniform approach to defining what makes a SR, or any study, original. This indicates that the concepts of originality of SRs and research are evolving and that this would be a relevant topic for further discussion
- …