941 research outputs found
1000-MWe LMFBR ACCIDENT ANALYSIS AND SAFETY SYSTEM DESIGN STUDY. TOPICAL REPORT. ACCIDENT ANALYSIS METHODS.
Supporting researchers conducting qualitative research into sensitive, challenging, and difficult topics: Experiences and practical applications.
Qualitative researchers often engage in work addressing challenging, difficult, or sensitive topics and are consequently exposed to the participantsâ narratives which may be emotionally charged, distressing, or compromising. These narratives occasionally rest heavy on a researcherâs conscience or may linger in the mind. Much literature has assessed how best to keep participants safe, but less attention has been given to how we keep researchers safe. We therefore document the following: (1) Our experiences of the issues presented by undertaking qualitative research involving challenging, difficult, or sensitive topics; and (2) Practical principles devised to overcome these issues, ensuring safety and wellbeing amongst researchers engaging in these types of qualitative research. We provide guidance for qualitative researchers of all levels of experience and expertise on how best to protect and support themselves, their colleagues, and other collaborating research staff, when undertaking qualitative research which might otherwise feel uncomfortable or overwhelming to tackle
Outstanding Questions in Flower Metabolism
The great diversity of flowers, their color, odor, taste, and shape, is mostly a result of the metabolic processes that occur in this reproductive organ when the flower and its tissues develop, grow, and finally die. Some of these metabolites serve to advertise flowers to animal pollinators, other confer protection towards abiotic stresses, and a large proportion of the molecules of the central metabolic pathways have bioenergetic and signaling functions that support growth and the transition to fruits and seeds. Although recent studies have advanced our general understanding of flower metabolism, several questions still await an answer. Here, we have compiled a list of open questions on flower metabolism encompassing molecular aspects, as well as topics of relevance for agriculture and the ecosystem. These questions include the study of flower metabolism through development, the biochemistry of nectar and its relevance to promoting plantâpollinator interaction, recycling of metabolic resources after flowers whiter and die, as well as the manipulation of flower metabolism by pathogens. We hope with this review to stimulate discussion on the topic of flower metabolism and set a reference point to return to in the future when assessing progress in the field
Failure in Internally Pressurized Bent Tubes
The analysis and modeling of tube-hydroformed components is more complicated than that employed for sheet-metal panels, due to the lengthier process sequence and variable strain path - from flat-rolled sheet to tube; from straight tube to bent tube; and from bent tube to hydroformed component. These additional process steps make it difficult to determine whether post mortem analyses of tube failure during hydroforming can, and should, be conducted with the same tools and databases as used for simple stampings. To provide a partial answer, the properties of commercially fabricated welded straight tubes were evaluated using a free-expansion internal pressure test and compared with those of free-expansion internal pressure tests on bent tubes. The results demonstrated that the behavior of the bent tube was consistent with the mechanical properties of the as-received tube, provided due notice was accorded to the complex strain history of the bent tube. However, due to the strain-path changes occurring at the failure location, conventional approaches for monitoring strain history would yield (apparently) anomalous results
A Phenomenological Analysis of Gluon Mass Effects in Inclusive Radiative Decays of the and $\Upsilon
The shapes of the inclusive photon spectra in the processes \Jp \to \gamma
X and \Up \to \gamma X have been analysed using all available experimental
data.
Relativistic, higher order QCD and gluon mass corrections were taken into
account in the fitted functions. Only on including the gluon mass corrections,
were consistent and acceptable fits obtained. Values of
GeV and GeV were found for the
effective gluon masses (corresponding to Born level diagrams) for the \Jp and
\Up respectively. The width ratios \Gamma(V \to {\rm hadrons})/\Gamma(V \to
\gamma+ {\rm hadrons}) V=\Jp, \Up were used to determine and . Values consistent with the current world
average were obtained only when gluon mass correction factors,
calculated using the fitted values of the effective gluon mass, were applied. A
gluon mass GeV, as suggested with these results, is consistent with
previous analytical theoretical calculations and independent phenomenological
estimates, as well as with a recent, more accurate, lattice calculation of the
gluon propagator in the infra-red region.Comment: 50 pages, 11 figures, 15 table
Electronic Structure of Transition-Metal Dicyanamides Me[N(CN)] (Me = Mn, Fe, Co, Ni, Cu)
The electronic structure of Me[N(CN)] (Me=Mn, Fe, Co, Ni, Cu)
molecular magnets has been investigated using x-ray emission spectroscopy (XES)
and x-ray photoelectron spectroscopy (XPS) as well as theoretical
density-functional-based methods. Both theory and experiments show that the top
of the valence band is dominated by Me 3d bands, while a strong hybridization
between C 2p and N 2p states determines the valence band electronic structure
away from the top. The 2p contributions from non-equivalent nitrogen sites have
been identified using resonant inelastic x-ray scattering spectroscopy with the
excitation energy tuned near the N 1s threshold. The binding energy of the Me
3d bands and the hybridization between N 2p and Me 3d states both increase in
going across the row from Me = Mn to Me = Cu. Localization of the Cu 3d states
also leads to weak screening of Cu 2p and 3s states, which accounts for shifts
in the core 2p and 3s spectra of the transition metal atoms. Calculations
indicate that the ground-state magnetic ordering, which varies across the
series is largely dependent on the occupation of the metal 3d shell and that
structural differences in the superexchange pathways for different compounds
play a secondary role.Comment: 20 pages, 11 figures, 2 table
Exact two-particle eigenstates in partially reduced QED
We consider a reformulation of QED in which covariant Green functions are
used to solve for the electromagnetic field in terms of the fermion fields. It
is shown that exact few-fermion eigenstates of the resulting Hamiltonian can be
obtained in the canonical equal-time formalism for the case where there are no
free photons. These eigenstates lead to two- and three-body Dirac-like
equations with electromagnetic interactions. Perturbative and some numerical
solutions of the two-body equations are presented for positronium and
muonium-like systems, for various strengths of the coupling.Comment: 33 pages, LaTex 2.09, 4 figures in EPS forma
Multiloop Calculations: towards R at Order alpha_s^4
We discuss recent developments in multiloop calculations aiming eventually in
computing the total cross section for e^+e^- annihilation into hadrons in order
alpha_s^4.Comment: Comments: 5 pages, presented at the 7-th International Symposium on
Radiative Corrections, Shonan Village (Japan), October 2005. The complete
paper is also available via the www at
http://www-ttp.physik.uni-karlsruhe.de/Preprints
Insights into the complex regulation of rpoS in Borrelia burgdorferi
Co-ordinated regulation of gene expression is required for the transmission and survival of Borrelia burgdorferi in different hosts. The sigma factor RpoS (ÏS), as regulated by RpoN (Ï54), has been shown to regulate key virulence factors (e.g. OspC) required for these processes. As important, multiple signals (e.g. temperature, pH, cell density, oxygen) have been shown to increase the expression of ÏS-dependent genes; however, little is known about the signal transduction mechanisms that modulate the expression of rpoS. In this report we show that: (i) rpoS has a Ï54-dependent promoter that requires Rrp2 to activate transcription; (ii) Rrp2Î123, a constitutively active form of Rrp2, activated Ï54-dependent transcription of rpoS/P-lacZ reporter constructs in Escherichia coli; (iii) quantitative reverse transcription polymerase chain reaction (QRT-PCR) experiments with reporter cat constructs in B. burgdorferi indicated that Rrp2 activated transcription of rpoS in an enhancer-independent fashion; and finally, (iv) rpoN is required for cell density- and temperature-dependent expression of rpoS in B. burgdorferi, but histidine kinase Hk2, encoded by the gene immediately upstream of rrp2, is not essential. Based on these findings, a model for regulation of rpoS has been proposed which provides mechanisms for multiple signalling pathways to modulate the expression of the ÏS regulon in B. burgdorferi
A terminal assessment of stages theory : introducing a dynamic states approach to entrepreneurship
Stages of Growth models were the most frequent theoretical approach to understanding entrepreneurial business growth from 1962 to 2006; they built on the growth imperative and developmental models of that time. An analysis of the universe of such models (N=104) published in the management literature shows no consensus on basic constructs of the approach, nor is there any empirical confirmations of stages theory. However, by changing two propositions of the stages models, a new dynamic states approach is derived. The dynamic states approach has far greater explanatory power than its precursor, and is compatible with leading edge research in entrepreneurship
- âŠ