From bare interactions, low--energy constants and unitary gas to nuclear density functionals without free parameters: application to neutron matter

We further progress along the line of Ref. [Phys. Rev. {\bf A 94}, 043614 (2016)] where a functional for Fermi systems with anomalously large $s$-wave scattering length $a_s$ was proposed that has no free parameters. The functional is designed to correctly reproduce the unitary limit in Fermi gases together with the leading-order contributions in the s- and p-wave channels at low density. The functional is shown to be predictive up to densities $\sim0.01$ fm$^{-3}$ that is much higher densities compared to the Lee-Yang functional, valid for $\rho < 10^{-6}$ fm$^{-3}$. The form of the functional retained in this work is further motivated. It is shown that the new functional corresponds to an expansion of the energy in $(a_s k_F)$ and $(r_e k_F)$ to all orders, where $r_e$ is the effective range and $k_F$ is the Fermi momentum. One conclusion from the present work is that, except in the extremely low--density regime, nuclear systems can be treated perturbatively in $-(a_s k_F)^{-1}$ with respect to the unitary limit. Starting from the functional, we introduce density--dependent scales and show that scales associated to the bare interaction are strongly renormalized by medium effects. As a consequence, some of the scales at play around saturation are dominated by the unitary gas properties and not directly to low-energy constants. For instance, we show that the scale in the s-wave channel around saturation is proportional to the so-called Bertsch parameter $\xi_0$ and becomes independent of $a_s$. We also point out that these scales are of the same order of magnitude than those empirically obtained in the Skyrme energy density functional. We finally propose a slight modification of the functional such that it becomes accurate up to the saturation density $\rho\simeq 0.16$ fm$^{-3}$

Magnetic and electrical properties of dhcp NpPd3 and U(1-x)Np(x)Pd3

We have made an extensive study of the magnetic and electrical properties of double-hexagonal closepacked NpPd3 and a range of U(1-x)Np(x)Pd3 compounds with x=0.01, 0.02, 0.05, and 0.50 using magnetization, magnetic susceptibility, electrical resistivity, and heat capacity measurements on polycrystalline samples, performed in the temperature range 2-300 K and in magnetic fields up to 9 T. Two transitions are observed in NpPd3 at T=10 and 30 K. Dilute Np samples (x<0.05) exhibit quadrupolar transitions, with the transition temperatures reduced from those of pure UPd3.Comment: 10 pages, 18 figure

Structural Modeling of the Next Generation Space Telescope's Primary Mirror

In recent years, astronomical observations made with space telescopes have dramatically increased our understanding of the history of the universe. In particular, the cosmic Background Explorer (COBE) and the Hubble Space Telescope (HST) have yielded observations that cannot be achieved at ground-based observatories. We now have views of the universe before galaxies existed (from COBE) and views of young galaxies (from HST). But none of the existing observatories can provide views of the period in which the galaxies were born, about 100 million to one billion years after the "big bang". NASA expects the Next Generation Space Telescope (NGST) to fill this gap. An investigation into the structural modeling of the primary mirror of the NGST, its methodology and results are presented

A contribution to an understanding of landscape development through three-dimensional morphological analysis of a pedological cover (Paulinia, State of Sao Paulo, Brazil) = Contribution à l'analyse morphologique tridimensionnelle de la couverture pédologique à la reconstitution de l'évolution du modelé (Paulinia, Etat de Sao Paulo, Brésil)

L'organisation tridimensionnelle d'une couverture pédologique, comprenant l'étude des relations géométriques entre horizons, et particulièrement des relations de concordance ou de discordance, permet de reconstituer certaines étapes de l'évolution du modelé. Le versant étudié, situé en zone tropicale humide (Brésil atlantique), présente à l'amont une couverture ferrallitique très épaisse (> 10 m) constituée d'horizons à limites subhorizontales. La partie supérieure de cette couverture est recoupée par une différenciation pédologique moins développée. Cette dernière est concordante à la topographie actuelle et s'est développée le long du versant à partir des horizons successifs de la couverture ferrallitique jusqu'au substratum. Lorsque ce substratum est atteint, des sols lithodépendants se forment à partir des grès, siltites et argilites de la "formation Tubarao" (permo-carbonifère). Cette discordance entre la différenciation superficielle et les horizons de la couverture ferrallitique implique que la première est plus récente que la seconde. Plus à l'aval, une couverture épaisse réapparaît qui a pu être raccordée à celle de l'amont par l'étude selon le plan horizontal. En considérant que la géométrie de la couverture ferrallitique (limites entre horizons et front de structuration pédologique) est conforme à la surface topographique contemporaine de sa formation, il est possible de reconstituer cette dernière. La topographie actuelle apparaît alors comme partiellement incisée dans cette topographie ancienne. (Résumé d'auteur

International Medical Graduates in the Pediatric Workforce in the United States

Through the analysis of health workforce databases, in this study, we summarize the supply, distribution and characteristics of international medical graduates in the US pediatric workforce. BACKGROUND AND OBJECTIVES: To describe the supply, distribution, and characteristics of international medical graduates (IMGs) in pediatrics who provide patient care in the United States. METHODS: Cross-sectional study, combining data from the 2019 Physician Masterfile of the American Medical Association and the Educational Commission for Foreign Medical Graduates database. RESULTS: In total, 92 806 pediatric physicians were identified, comprising 9.4% of the entire US physician workforce. Over half are general pediatricians. IMGs account for 23.2% of all general pediatricians and pediatric subspecialists. Of all IMGs in pediatrics, 22.1% or 4775 are US citizens who obtained their medical degree outside the United States or Canada, and 15.4% (3246) attended medical school in the Caribbean. Fifteen non-US medical schools account for 29.9% of IMGs currently in active practice in pediatrics in the United States. IMGs are less likely to work in group practice or hospital-based practice and are more likely to be employed in solo practice (compared with US medical school graduates). CONCLUSIONS: With this study, we provide an overview of the pediatric workforce, quantifying the contribution of IMGs. Many IMGs are US citizens who attend medical school abroad and return to the United States for postgraduate training. Several factors, including the number of residency training positions, could affect future numbers of IMGs entering the United States. Longitudinal studies are needed to better understand the implications that workforce composition and distribution may have for the care of pediatric patients

A comparison of physician emigration from Africa to the United States of America between 2005 and 2015

BACKGROUND: Migration of health professionals has been a cause for global concern, in particular migration from African countries with a high disease burden and already fragile health systems. An estimated one fifth of African-born physicians are working in high-income countries. Lack of good data makes it difficult to determine what constitutes "African" physicians, as most studies do not distinguish between their country of citizenship and country of training. Thus, the real extent of migration from African countries to the United States (US) remains unclear. This paper quantifies where African migrant physicians come from, where they were educated, and how these trends have changed over time. METHODS: We combined data from the Educational Commission for Foreign Medical Graduates with the 2005 and 2015 American Medical Association Physician Masterfiles. Using a repeated cross-sectional study design, we reviewed the available data, including medical school attended, country of medical school, and citizenship when entering medical school. RESULTS: The outflow of African-educated physicians to the US has increased over the past 10 years, from 10 684 in 2005 to 13 584 in 2015 (27.1% increase). This represents 5.9% of all international medical graduates in the US workforce in 2015. The number of African-educated physicians who graduated from medical schools in sub-Saharan countries was 2014 in 2005 and 8150 in 2015 (304.6% increase). We found four distinct categorizations of African-trained physicians migrating to the US: (1) citizens from an African country who attended medical school in their own country (86.2%, n = 11,697); (2) citizens from an African country who attended medical school in another African country (2.3%, n = 317); (3) US citizens who attended medical school in an African country (4.0%, n = 537); (4) citizens from a country outside Africa, and other than the United States, who attended medical school in an African country (7.5%, n = 1013). Overall, six schools in Africa provided half of all African-educated physicians. CONCLUSIONS: The number of African-educated physicians in the US has increased over the past 10 years. We have distinguished four migration patterns, based on citizenship and country of medical school. The majority of African graduates come to the US from relatively few countries, and from a limited number of medical schools. A proportion are not citizens of the country where they attended medical school, highlighting the internationalization of medical education

Dry-Spun Silk Produces Native-Like Fibroin Solutions

Silk's outstanding mechanical properties and energy efficient solidification mechanisms provide inspiration for biomaterial self-assembly as well as offering a diverse platform of materials suitable for many biotechnology applications. Experiments now reveal that the mulberry silkworm Bombyx mori secretes its silk in a practically "unspun" state that retains much of the solvent water and exhibits a surprisingly low degree of molecular order (β-sheet crystallinity) compared to the state found in a fully formed and matured fiber. These new observations challenge the general understanding of silk spinning and in particular the role of the spinning duct for structure development. Building on this discovery we report that silk spun in low humidity appears to arrest a molecular annealing process crucial for β-sheet formation. This, in turn, has significant positive implications, enabling the production of a high fidelity reconstituted silk fibroin with properties akin to the gold standard of unspun native silk