305 research outputs found
Photodetachment study of the 1s3s4s ^4S resonance in He^-
A Feshbach resonance associated with the 1s3s4s ^{4}S state of He^{-} has
been observed in the He(1s2s ^{3}S) + e^- (\epsilon s) partial photodetachment
cross section. The residual He(1s2s ^{3}S) atoms were resonantly ionized and
the resulting He^+ ions were detected in the presence of a small background. A
collinear laser-ion beam apparatus was used to attain both high resolution and
sensitivity. We measured a resonance energy E_r = 2.959 255(7) eV and a width
\Gamma = 0.19(3) meV, in agreement with a recent calculation.Comment: LaTeX article, 4 pages, 3 figures, 21 reference
Optofluidic distributed feedback lasers with evanescent pumping : reduced threshold and angular dispersion analysis
The authors acknowledge financial support from the European Research Council (ERC StG ABLASE, 640012), the Scottish Funding Council (via SUPA) and the European Union Marie Curie Career Integration Grant (PCIG12-GA-2012-334407). M.K. and G.L.W. acknowledge funding from the EPSRC DTG (EP/M506631/1 and EP/K503162/1). M.S. acknowledges funding from the European Commission for a Marie Sklodowska-Curie Individual Fellowship (659213). I.D.W.S. acknowledges funding from a Royal Society Wolfson research merit award. The research data supporting this publication can be accessed at http://dx.doi.org/10.17630/0ed7dad7-75e1-4ab9-9845-c455d1a7c6a4.We demonstrate an evanescently pumped water-based optofluidic DFB laser with a record low pump threshold of ETH = 520 nJ. The low threshold results from an optimized mode shape, which is achieved by a low refractive index substrate, and from the use of a mixed-order DFB grating. Investigating the photonic band structure via angular dispersion analysis both above and below lasing threshold allows us to measure the refractive index of the liquid gain layer and to determine device parameters such as the waveguide core layer thickness. We show that it is possible to tailor the divergence of the lasing emission by varying the number of second order grating periods used for outcoupling.Publisher PDFPeer reviewe
Systemic multilineage engraftment in mice after in utero transplantation with human hematopoietic stem cells
In utero hematopoietic cell transplantation (IUHCT) is a potential therapy for the treatment of numerous
genetic diseases such as hemoglobinopathies, immunodeficiencies, and inborn errors of metabolism.1 In
utero therapy offers the benefit of avoiding host myeloablation and immunosuppression and has been
shown to be successful in multiple animal models, including mice,2-5 dogs,6,7 pigs,8,9 and sheep.10-12
The timing of IUHCT exposes the transplanted human cells to the normal fetal migratory and
developmental cues that facilitate proper stem cell distribution and differentiation.11,12 Clinically, IUHCT
has been successful for fetuses with severe combined immunodeficiency (SCID),13,14 but therapeutic
uses for other diseases, including hemoglobinopathies, have seen limited success.15 Further
investigations identified multiple barriers to successful engraftment, including lack of space within the
hematopoietic niche16,17 and the maternal immune system.2,18 Among available animal models of
IUHCT, the fetal mouse remains an efficient and reproducible model to study the differentiation of stem
cells in a nonirradiated host. NSG (NOD-SCID IL2Rg-null) mice, which are developed with SCID and
IL-2Rg-null chain mutations, are a robust platform for the engraftment of human hematopoietic cells
because they have no endogenous T, B, or natural killer cells.19-22 In this study, we used IUHCT of
human CD341 cells in NSG mice to create a reproducible mouse model to study stem cell engraftment,
differentiation, and systemic repopulation after IUHCT
Total cross sections for electron scattering by 1-propanol at impact energies in the range 40-500 eV
Absolute total cross section (TCS) measurements for electron scattering from 1-propanol molecules are reported for impact energies from 40 to 500 eV. These measurements were obtained using a new apparatus developed at Juiz de Fora Federal University—Brazil, which is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the molecules to be studied at a given pressure. Besides these experimental measurements, we have also calculated TCS using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference (IAM-SCAR+I) approach with the level of agreement between them being typically found to be very good.M.C.A.L. acknowledges financial support from Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Fundac¸ ´ ao de Amparo ˜ a Pesquisa do Estado `
de Minas Gerais (FAPEMIG), and FINEP, while M.J.B. thanks
CNPq for his “Special Visiting Professor” award. Some financial assistance from the Australian Research Council through
Grant No. DP160102787 is also noted. Finally, S. Ghosh
acknowledges for his grant from PNPD/CAPES, while G. Garcia thanks the Spanish Ministerio de Economia, Industria y
Competitividad for his project Grant No. FIS 2016-80440 and
the EU Project No. FP7–ITN–ARGENT-608163
Total cross sections for electron scattering by 1-propanol at impact energies in the range 40-500 eV
Absolute total cross section (TCS) measurements for electron scattering from 1-propanol molecules are reported for impact energies from 40 to 500 eV. These measurements were obtained using a new apparatus developed at Juiz de Fora Federal University-Brazil, which is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the molecules to be studied at a given pressure. Besides these experimental measurements, we have also calculated TCS using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference (IAM-SCAR+I) approach with the level of agreement between them being typically found to be very good. Published by AIP Publishing
Low-energy positron interactions with krypton
Cross sections for positron scattering from krypton have been measured with an energy resolution of ∼60 meV over the energy range 0.5–60 eV. Absolute values of the grand total (σGT), positronium formation (σPs), and grand total minus positronium formation (σGT-σPs,) cross sections are presented. Theoretical estimations of σGT and σGT-σPs are also performed for this target using the convergent close-coupling method and the relativistic optical potential approach. We also provide experimental and theoretical results for elastic differential cross sections, for selected energies both below and above the Ps threshold. Where available, the present results are compared to both experimental and theoretical values from the literature.C. Makochekanwa, J. R. Machacek, A. C. L. Jones, P. Caradonna, D. S. Slaughter, R. P. McEachran, J. P. Sullivan, and S. J. Buckman, S. Bellm and B. Lohmann, D. V. Fursa and I. Bray, D.W. Mueller, A. D. Stauffer, M. Hoshin
Reductions in hypothalamic Gfap expression, glial cells and α-tanycytes in lean and hypermetabolic Gnasxl-deficient mice
BACKGROUND: Neuronal and glial differentiation in the murine hypothalamus is not complete at birth, but continues over the first two weeks postnatally. Nutritional status and Leptin deficiency can influence the maturation of neuronal projections and glial patterns, and hypothalamic gliosis occurs in mouse models of obesity. Gnasxl constitutes an alternative transcript of the genomically imprinted Gnas locus and encodes a variant of the signalling protein Gαs, termed XLαs, which is expressed in defined areas of the hypothalamus. Gnasxl-deficient mice show postnatal growth retardation and undernutrition, while surviving adults remain lean and hypermetabolic with increased sympathetic nervous system (SNS) activity. Effects of this knock-out on the hypothalamic neural network have not yet been investigated. RESULTS: RNAseq analysis for gene expression changes in hypothalami of Gnasxl-deficient mice indicated Glial fibrillary acid protein (Gfap) expression to be significantly down-regulated in adult samples. Histological analysis confirmed a reduction in Gfap-positive glial cell numbers specifically in the hypothalamus. This reduction was observed in adult tissue samples, whereas no difference was found in hypothalami of postnatal stages, indicating an adaptation in adult Gnasxl-deficient mice to their earlier growth phenotype and hypermetabolism. Especially noticeable was a loss of many Gfap-positive α-tanycytes and their processes, which form part of the ependymal layer that lines the medial and dorsal regions of the 3(rd) ventricle, while β-tanycytes along the median eminence (ME) and infundibular recesses appeared unaffected. This was accompanied by local reductions in Vimentin and Nestin expression. Hypothalamic RNA levels of glial solute transporters were unchanged, indicating a potential compensatory up-regulation in the remaining astrocytes and tanycytes. CONCLUSION: Gnasxl deficiency does not directly affect glial development in the hypothalamus, since it is expressed in neurons, and Gfap-positive astrocytes and tanycytes appear normal during early postnatal stages. The loss of Gfap-expressing cells in adult hypothalami appears to be a consequence of the postnatal undernutrition, hypoglycaemia and continued hypermetabolism and leanness of Gnasxl-deficient mice, which contrasts with gliosis observed in obese mouse models. Since α-tanycytes also function as adult neural progenitor cells, these findings might indicate further developmental abnormalities in hypothalamic formations of Gnasxl-deficient mice, potentially including neuronal composition and projections
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