371 research outputs found
Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. II: Role of the effective mass
We have constructed four new complete mass tables, referred to as HFB-4 to
HFB-7, each one including all the 9200 nuclei lying between the two drip lines
over the range of Z and N>8 and Z<120. HFB-4 and HFB-5 have the isoscalar
effective mass M*_s$ constrained to the value 0.92 M, with the former having a
density-independent pairing, and the latter a density-dependent pairing. HFB-6
and HFB-7 are similar, except that M*_s is constrained to 0.8 M. The rms errors
of the mass-data fits are 0.680, 0.675, 0.686, and 0.676 MeV, respectively,
almost as good as for the HFB-2 mass formula, for which M*_s was unconstrained.
However, as usual, the single-particle spectra depend significantly on M*_s.
This decoupling of the mass fits from the fits to the single-particle spectra
has been achieved only by making the cutoff parameter of the delta-function
pairing force a free parameter. An improved treatment of the center-of-mass
correction was adopted, but although this makes a difference to individual
nuclei it does not reduce the overall rms error of the fit. The extrapolations
of all four new mass formulas out to the drip lines are essentially the same as
for the original HFB-2 mass formula.Comment: 12 pages revtex, 9 eps figures, accepted for publication in Phys.
Rev.
Pyrolysis of organic side stream materials for the production of biochar as an amendment in green roofs: Characterization and field experiments
Green roofs offer a solution to worldwide problems in cities like: the urban heat island effect, floods and the loss of rural regions. Nevertheless, the widespread application of green roofs still faces some serious challenges, e.g. an excessive amount of drainage water, an excess of nutrients in this water, and plant mortality in periods of severe drought. Also, the production process of the components of these substrates, such as expanded clay, is not environmentally and energy-friendly. Biochar amendment in green roof substrates can help to overcome these problems because of its valuable properties like a high nutrient content, high waterholding capacity (WHC), low density and its self-sustaining production process.
In this research, biochar is produced from six different side streams in a pilot-scale rotating kiln carbonization reactor (kg/hour input). These side streams consists out of: MDF, date palm, coffee skins, tree bark, olive stones and a waste wood mix. The produced biochars are characterized with multiple physico-chemical analyses like biochar yield, elemental composition, surface functional groups, morphology, WHC, cation exchange capacity and polyaromatic hydrocarbons (PAH’s). Furthermore, a techno-economical analysis is performed on the large-scale production of these biochars.
Small scale (0,25 m2) and field experiments (2.5 m2) with biochar incorporated in commercially available green roof substrates in the temperate climate of the Netherlands and Belgium examine whether biochar can offer a solution to the described problems. Based on the analyses of the biochar, in particular the PAH’s and elemental composition, and the small scale growth experiments, two different biochars made from the waste wood mix and tree bark in concentrations of 1 and 5 % are selected for the field experiments.
Growth of Sedum plants is monitored with digital imaging processing over a period of several months, starting from November 2018. Several chemical and physical parameters are monitored and linked to the properties of the biochar incorporated substrate like pH, conductivity, nutrient leaching and waterholding capacity
Projection and ground state correlations made simple
We develop and test efficient approximations to estimate ground state
correlations associated with low- and zero-energy modes. The scheme is an
extension of the generator-coordinate-method (GCM) within Gaussian overlap
approximation (GOA). We show that GOA fails in non-Cartesian topologies and
present a topologically correct generalization of GOA (topGOA). An RPA-like
correction is derived as the small amplitude limit of topGOA, called topRPA.
Using exactly solvable models, the topGOA and topRPA schemes are compared with
conventional approaches (GCM-GOA, RPA, Lipkin-Nogami projection) for
rotational-vibrational motion and for particle number projection. The results
shows that the new schemes perform very well in all regimes of coupling.Comment: RevTex, 12 pages, 7 eps figure
The r-Process in Supernovae: Impact of New Microscopic Mass Formulas
The astrophysical origin of -process nuclei remains a long-standing
mystery. Although some astrophysical scenarios show some promise, many
uncertainties involved in both the astrophysical conditions and in the nuclear
properties far from the -stability have inhibited us from understanding
the nature of the -process. The purpose of the present paper is to examine
the effects of the newly-derived microscopic Hartree-Fock-Bogoliubov (HFB) mass
formulas on the -process nucleosynthesis and analyse to what extent a
solar-like -abundance distribution can be obtained. The -process
calculations with the HFB-2 mass formula are performed, adopting the
parametrized model of the prompt explosion from a collapsing O-Ne-Mg core for
the physical conditions and compared with the results obtained with the HFB-7
and droplet-type mass formulas. Due to its weak shell effect at the neutron
magic numbers in the neutron-rich region, the microscopic mass formulas (HFB-2
and HFB-7) give rise to a spread of the abundance distribution in the vicinity
of the -process peaks ( and 195). While this effect resolves the
large underproduction at and 140 obtained with droplet-type
mass formulas, large deviations compared to the solar pattern are found near
the third -process peak. It is shown that a solar-like -process pattern
can be obtained if the dynamical timescales of the outgoing mass trajectories
are increased by a factor of about 2-3, or if the -decay rates are
systematically increased by the same factor.Comment: 22 pages, 12 figures, accepted for publication in ApJ, some color
figures converted to B&W due to size constraint
High-resolution record of the Northern Hemisphere climate extending into the last interglacial period
Role of Esrrg in the Fibrate-Mediated Regulation of Lipid Metabolism Genes in Human ApoA-I Transgenic Mice
We have used a new ApoA-I transgenic mouse model to identify by global gene expression profiling, candidate genes that affect lipid and lipoprotein metabolism in response to fenofibrate treatment. Multilevel bioinformatical analysis and stringent selection criteria (2-fold change, 0% false discovery rate) identified 267 significantly changed genes involved in several molecular pathways. The fenofibrate-treated group did not have significantly altered levels of hepatic human APOA-I mRNA and plasma ApoA-I compared with the control group. However, the treatment increased cholesterol levels to 1.95-fold mainly due to the increase in high-density lipoprotein (HDL) cholesterol. The observed changes in HDL are associated with the upregulation of genes involved in phospholipid biosynthesis and lipid hydrolysis, as well as phospholipid transfer protein. Significant upregulation was observed in genes involved in fatty acid transport and β-oxidation, but not in those of fatty acid and cholesterol biosynthesis, Krebs cycle and gluconeogenesis. Fenofibrate changed significantly the expression of seven transcription factors. The estrogen receptor-related gamma gene was upregulated 2.36-fold and had a significant positive correlation with genes of lipid and lipoprotein metabolism and mitochondrial functions, indicating an important role of this orphan receptor in mediating the fenofibrate-induced activation of a specific subset of its target genes.National Institutes of Health (HL48739 and HL68216); European Union (LSHM-CT-2006-0376331, LSHG-CT-2006-037277); the Biomedical Research Foundation of the Academy of Athens; the Hellenic Cardiological Society; the John F Kostopoulos Foundatio
Individual differences in newborn visual attention associate with temperament and behavioral difficulties in later childhood
Recently it was shown that individual differences in attention style in infants are
associated with childhood effortful control, surgency, and hyperactivity-inattention. Here we
investigated whether effortful control, surgency and behavioral problems in childhood can be
predicted even earlier, from individual differences in newborns’ average duration of gaze to
stimuli. Eighty newborns participated in visual preference and habituation studies. Parents
completed questionnaires at follow up (mean age = 7.5 years, SD = 1.0 year). Newborns’
average dwell time was negatively associated with childhood surgency (β = -.25, R2 = .04, p =
.02) and total behavioral difficulties (β = -.28, R2 = .05, p = .04) but not with effortful control (β
= .03, R2 = .001, p = .76). Individual differences in newborn visual attention significantly
associated with individual variation in childhood surgency and behavioral problems, showing
that some of the factors responsible for this variation are present at birth
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