8,882 research outputs found
Hyperonic crystallization in hadronic matter
Published in Hadrons, Nuclei and Applications, World Scientific, Singapore,
Proc.of the Conference Bologna2000. Structure of the Nucleus at the Dawn of the
Century, G. Bonsignori, M. Bruno, A. Ventura, D. Vretenar Editors, pag. 319.Comment: 4 pages, 2figure
Structure formation in the presence of relativistic heat conduction: corrections to the Jeans wave number with a stable first order in the gradients formalism
The problem of structure formation in relativistic dissipative fluids was
analyzed in a previous work within Eckart's framework, in which the heat flux
is coupled to the hydrodynamic acceleration, additional to the usual
temperature gradient term. It was shown that in such case, the pathological
behavior of fluctuations leads to the disapperance of the gravitational
instability responsible for structure formation. In the present work the
problem is revisited now using a constitutive equation derived from
relativistic kinetic theory. The new relation, in which the heat flux is not
coupled to the hydrodynamic acceleration, leads to a consistent first order in
the gradients formalism. In this case the gravitational instability remains,
and only relativistic corrections to the Jeans wave number are obtained. In the
calculation here shown the non-relativistc limit is recovered, opposite to what
happens in Eckart's case.Comment: 10 pages, no figure
Enhancement of metabolite production in high-altitude microalgal strains by optimized C/N/P ratio
This study evaluated the role of C/N/P in the increase in the synthesis of carbohydrates, proteins, and lipids in two high-mountain strains of algae (Chlorella sp. UFPS019 and Desmodesmus sp. UFPS021). Three carbon sources (sodium acetate, sodium carbonate, and sodium bicarbonate), and the sources of nitrogen (NaNO3) and phosphate (KH2PO4 and K2HPO4) were analyzed using a surface response (3 factors, 2 levels). In Chlorella sp. UFPS019, the optimal conditions to enhance the synthesis of carbohydrates were high sodium carbonate content (3.53 g/L), high KH2PO4 and K2HPO4 content (0.06 and 0.14 g/L, respectively), and medium-high NaNO3 (0.1875 g/L). In the case of lipids, a high concentration of sodium acetate (1.19 g/L) coupled with high KH2PO4 and K2HPO4 content (0.056 and 0.131 g/L, respectively) and a low concentration of NaNO3 (0.075 g/L) drastically induced the synthesis of lipids. In the case of Desmodesmus sp. UFPS021, the protein content was increased using high sodium acetate (2 g/L), high KH2PO4 and K2HPO4 content (0.056 and 0.131 g/L, respectively), and high NaNO3 concentration (0.25 g/L). These results demonstrate that the correct adjustment of the C/N/P ratio can enhance the capacity of high-mountain strains of algae to produce high concentrations of carbohydrates, proteins, and lipids
GOLLUM: a next-generation simulation tool for electron, thermal and spin transport
We have developed an efficient simulation tool 'GOLLUM' for the computation
of electrical, spin and thermal transport characteristics of complex
nanostructures. The new multi-scale, multi-terminal tool addresses a number of
new challenges and functionalities that have emerged in nanoscale-scale
transport over the past few years. To illustrate the flexibility and
functionality of GOLLUM, we present a range of demonstrator calculations
encompassing charge, spin and thermal transport, corrections to density
functional theory such as LDA+U and spectral adjustments, transport in the
presence of non-collinear magnetism, the quantum-Hall effect, Kondo and Coulomb
blockade effects, finite-voltage transport, multi-terminal transport, quantum
pumps, superconducting nanostructures, environmental effects and pulling curves
and conductance histograms for mechanically-controlled-break-junction
experiments.Comment: 66 journal pages, 57 figure
The Zagros Epipalaeolithic revisited: New excavations and 14C dates from Palegawra cave in Iraqi Kurdistan
Palegawra cave, alongside its neighbouring Zarzi, has been an emblematic site of the Epipalaeolithic (Zarzian) cultural horizon in the NW Zagros of Southwest Asia ever since its first exploration in 1951 by Bruce Howe and Robert Braidwood in the context of the Iraq-Jarmo project. At the time scientific excavation, sampling and analysis methods were either underdeveloped or did not exist. In this paper we present the first results of new excavations at Palegawra conducted in 2016–2017 by the Eastern Fertile Crescent (EFEC) project, a research collaboration of the University of Liverpool and the Sulaymaniyah Directorate of Antiquities and Heritage. Our research has produced the first radiometric evidence pushing back the chronology of the NW Zagros Epipalaeolithic to the Last Glacial Maximum, thus fully aligning it with Epipalaeolithic facies until now known only from the Levant and the south Anatolian coast. We have also unearthed, for the first time in the Palaeolithic of the Zagros, direct archaeobotanical evidence for hitherto elusive Zarzian plant exploitation and the vegetation of the NW Zagros piedmont zone from the LGM to the end of the Lateglacial (~19,600–13,000 cal BP). The new Palegawra chronology alongside our detailed studies of its material culture and faunal and botanical assemblages suggest that the prevailing Epipalaeolithic habitation pattern in the NW Zagros (centred on generalised persistent occupations of small caves and rock-shelters alongside task-oriented ephemeral open-air campsites) remained an enduring characteristic of the Zarzian horizon throughout this period. The Palegawra data clearly show that neither resource levels and climate conditions nor geographic and/or cultural isolation provide adequate explanations for the stability and longevity of Zarzian lifeways during this long timespan. More fieldwork is required, including the discovery, excavation and intensive sampling of other Zarzian sites, for reaching a datainformed understanding of the nature and evolution of the NW Zagros Epipalaeolithic
Detecting individual gravity modes in the Sun: Chimera or reality?
Over the past 15 years, our knowledge of the interior of the Sun has
tremendously progressed by the use of helioseismic measurements. However, to go
further in our understanding of the solar core, we need to measure gravity (g)
modes. Thanks to the high quality of the Doppler-velocity signal measured by
GOLF/SoHO, it has been possible to unveil the signature of the asymptotic
properties of the solar g modes, thus obtaining a hint of the rotation rate in
the core. However, the quest for the detection of individual g modes is not yet
over. In this work, we apply the latest theoretical developments to guide our
research using GOLF velocity time series. In contrary to what was thought till
now, we are maybe starting to identify individual low-frequency g modes...Comment: Highlight of Astronomy (HoA) proceedings of the JD-11, IAU 2009. 2
pages, 1 figur
Study of the volume and spin collapse in orthoferrite LuFeO_3 using LDA+U
Rare earth (R) orthoferrites RFeO_3 exhibit large volume transitions
associated with a spin collapse. We present here ab initio calculations on
LuFeO_3. We show that taking into account the strong correlation among the
Fe-3d electrons is necessary. Indeed, with the LDA+U method in the Projector
Augmented Wave (PAW), we are able to describe the isostructural phase
transition at 50 GPa, as well as a volume discontinuity of 6.0% at the
transition and the considerable reduction of the magnetic moment on the Fe
ions. We further investigate the effect of the variation of U and J and find a
linear dependence of the transition pressure on these parameters. We give an
interpretation for the non-intuitive effect of J. This emphasizes the need for
a correct determination of these parameters especially when the LDA+U is
applied to systems (e.g in geophysical investigations) where the transition
pressure is a priori unknown
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