3,491 research outputs found
Screened self-energy correction to the 2p3/2-2s transition energy in Li-like ions
We present an ab initio calculation of the screened self-energy correction
for (1s)^2 2p3/2 and (1s)^2 2s states of Li-like ions with nuclear charge
numbers in the range Z = 12-100. The evaluation is carried out to all orders in
the nuclear-strength parameter Z \alpha. This investigation concludes our
calculations of all two-electron QED corrections for the 2p3/2-2s transition
energy in Li-like ions and thus considerably improves theoretical predictions
for this transition for high-Z ions
Recoil correction to the bound-electron g factor in H-like atoms to all orders in
The nuclear recoil correction to the bound-electron g factor in H-like atoms
is calculated to first order in and to all orders in . The
calculation is performed in the range Z=1-100. A large contribution of terms of
order and higher is found. Even for hydrogen, the higher-order
correction exceeds the term, while for uranium it is above the
leading correction.Comment: 6 pages, 3 tables, 1 figur
‘Scots and Scabs from North-by-Tweed’:Undesirable Scottish Migrants in Seventeenth- and Early Eighteenth-Century England
While very prominent in the contemporary world, anxiety about the potentially negative impact that immigrants might have on their host communities has deep historical roots. In a British context, such fears were particularly heightened following the regal union of 1603 when large numbers of Scots began settling in England. This article offers a fresh perspective on these issues by exploring the experiences and reception of poor, deviant or otherwise ‘undesirable’ Scottish migrants to England during the seventeenth and eighteenth centuries. Focusing in particular on chapmen, vagrants and criminals, it suggests that, while in general Scots were able to integrate relatively easily into English society, there existed an unwelcome subset surviving by dubious means. Though not usually attracting unduly severe treatment on account of their nationality, these unwelcome migrants had a disproportionate effect on English perceptions of and attitudes towards the broader cohort of Scottish migrants in their midst
Evidence for the absence of regularization corrections to the partial-wave renormalization procedure in one-loop self energy calculations in external fields
The equivalence of the covariant renormalization and the partial-wave
renormaliz ation (PWR) approach is proven explicitly for the one-loop
self-energy correction (SE) of a bound electron state in the presence of
external perturbation potentials. No spurious correctio n terms to the
noncovariant PWR scheme are generated for Coulomb-type screening potentia ls
and for external magnetic fields. It is shown that in numerical calculations of
the SE with Coulombic perturbation potential spurious terms result from an
improper treatment of the unphysical high-energy contribution. A method for
performing the PWR utilizing the relativistic B-spline approach for the
construction of the Dirac spectrum in external magnetic fields is proposed.
This method is applied for calculating QED corrections to the bound-electron
-factor in H-like ions. Within the level of accuracy of about 0.1% no
spurious terms are generated in numerical calculations of the SE in magnetic
fields.Comment: 22 pages, LaTeX, 1 figur
Deletion of Glycogen Synthase Kinase-3β in Cartilage Results in Up-Regulation of Glycogen Synthase Kinase-3α Protein Expression
The rate of endochondral bone growth determines final height in humans and is tightly controlled. Glycogen synthase kinase-3 (GSK-3) is a negative regulator of several signaling pathways that govern bone growth, such as insulin/IGF and Wnt/β-catenin. The two GSK-3 proteins, GSK-3 and GSK-3β, display both overlapping and distinct roles in different tissues. Here we show that pharmacological inhibition of GSK-3 signaling in a mouse tibia organ culture system results in enhanced bone growth, accompanied by increased proliferation of growth plate chondrocytes and faster turnover of hypertrophic cartilage to bone. GSK-3 inhibition rescues some, but not all, effects of phosphatidylinositide 3-kinase inhibition in this system, in agreement with the antagonistic role of these two kinases in response to signals such as IGF. However, cartilage-specific deletion of the Gsk3b gene in mice has minimal effects on skeletal growth or development. Molecular analyses demonstrated that compensatory up-regulation of GSK-3 protein levels in cartilage is the likely cause for this lack of effect. To our knowledge, this is the first tissue in which such a compensatory mechanism is described. Thus, our study provides important new insights into both skeletal development and the biology of GSK-3 proteins. (Endocrinology 152: 1755–1766, 2011
p38 MAPK signaling during murine preimplantation development.
Mitogen-activated protein kinase (MAPK) pathways mediate some important cellular processes and are likely to also regulate preimplantation development. The role of p38 MAP kinase signaling during murine preimplantation development was investigated in the present study. p38 MAPK, p38-regulated or -activated kinase (PRAK; MK5), map kinase-activated protein kinase 2 (MK2), and heat shock protein 25 (hsp25) mRNAs and proteins were detected throughout preimplantation development. Two-cell stage embryos cultured in the presence of SB220025 and SB203580 (specific inhibitors of p38 MAPK alpha/beta), progressed to the eight-cell stage with the same frequency as controls; however, treated embryos halted their development at the 8- to 16-cell stage. In addition, embryos treated with p38 MAPK inhibitors displayed a complete loss of MK2 and hsp25 phosphorylation and also a complete loss of filamentous actin as indicated by the absence of rhodamine-phalloidin staining. In these inhibitor-treated groups, the embryos were composed of a mixture of compacting and noncompacting cells, and the embryos were one to two cell divisions behind controls. Treated embryos remained viable as the developmental blockade was rescued by removing embryos from the drug treatment and placing them in drug-free medium until they progressed to the blastocyst stage. This study demonstrates that p38 MAPK activity is required to support development through the murine preimplantation interval
QED theory of the nuclear recoil effect on the atomic g factor
The quantum electrodynamic theory of the nuclear recoil effect on the atomic
g factor to all orders in \alpha Z and to first order in m/M is formulated. The
complete \alpha Z-dependence formula for the recoil correction to the
bound-electron g factor in a hydrogenlike atom is derived. This formula is used
to calculate the recoil correction to the bound-electron g factor in the order
(\alpha Z)^2 m/M for an arbitrary state of a hydrogenlike atom.Comment: 17 page
Balancing precision and risk: Should multiple detection methods be analyzed separately in N-mixture models?
Using multiple detection methods can increase the number, kind, and distribution of individuals sampled, which may increase accuracy and precision and reduce cost of population abundance estimates. However, when variables influencing abundance are of interest, if individuals detected via different methods are influenced by the landscape differently, separate analysis of multiple detection methods may be more appropriate. We evaluated the effects of combining two detection methods on the identification of variables important to local abundance using detections of grizzly bears with hair traps (systematic) and bear rubs (opportunistic). We used hierarchical abundance models (N-mixture models) with separate model components for each detection method. If both methods sample the same population, the use of either data set alone should (1) lead to the selection of the same variables as important and (2) provide similar estimates of relative local abundance. We hypothesized that the inclusion of 2 detection methods versus either method alone should (3) yield more support for variables identified in single method analyses (i.e. fewer variables and models with greater weight), and (4) improve precision of covariate estimates for variables selected in both separate and combined analyses because sample size is larger. As expected, joint analysis of both methods increased precision as well as certainty in variable and model selection. However, the single-method analyses identified different variables and the resulting predicted abundances had different spatial distributions. We recommend comparing single-method and jointly modeled results to identify the presence of individual heterogeneity between detection methods in N-mixture models, along with consideration of detection probabilities, correlations among variables, and tolerance to risk of failing to identify variables important to a subset of the population. The benefits of increased precision should be weighed against those risks. The analysis framework presented here will be useful for other species exhibiting heterogeneity by detection method
HITRAP: A facility at GSI for highly charged ions
An overview and status report of the new trapping facility for highly charged
ions at the Gesellschaft fuer Schwerionenforschung is presented. The
construction of this facility started in 2005 and is expected to be completed
in 2008. Once operational, highly charged ions will be loaded from the
experimental storage ring ESR into the HITRAP facility, where they are
decelerated and cooled. The kinetic energy of the initially fast ions is
reduced by more than fourteen orders of magnitude and their thermal energy is
cooled to cryogenic temperatures. The cold ions are then delivered to a broad
range of atomic physics experiments.Comment: 8 pages, 11 figure
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