333 research outputs found
A model for co-clusters and their strengthening in Al-Cu-Mg based alloys: a comparison with experimental data
A model for the thermodynamics of and strengthening due to CuâMg co-clusters in AlâCuâMg based alloys is analysed and tested. The formulation uses a single interaction enthalpy between dissimilar alloying elements (e.g. Cu and Mg atoms in an AlâCuâMg based alloy) combined with the configurational entropy. The metastable solvus in AlâCuâMg based alloys is calculated. Recently published small angle X-ray scattering experiments, 3 dimensional atom probe and yield strength data on these type of alloys support the model. The small angle X-ray scattering and hardness experiments, as well as calorimetry experiments, are sensitive to the main free energy (or enthalpy) changes, which are dominated by CuâMg bonds formed by the dimers and the local electron densities related to these bonds. 3 dimensional atom probe is less sensitive to dimers, and will detect agglomeration of dimers to form larger clusters
Acremonium phylogenetic overview and revision of Gliomastix, Sarocladium, and Trichothecium
AbstractOver 200 new sequences are generated for members of the genus Acremonium and related taxa including ribosomal small subunit sequences (SSU) for phylogenetic analysis and large subunit (LSU) sequences for phylogeny and DNA-based identification. Phylogenetic analysis reveals that within the Hypocreales, there are two major clusters containing multiple Acremonium species. One clade contains Acremonium sclerotigenum, the genus Emericellopsis, and the genus Geosmithia as prominent elements. The second clade contains the genera Gliomastix sensu stricto and Bionectria. In addition, there are numerous smaller clades plus two multi-species clades, one containing Acremonium strictum and the type species of the genus Sarocladium, and, as seen in the combined SSU/LSU analysis, one associated subclade containing Acremonium breve and related species plus Acremonium curvulum and related species. This sequence information allows the revision of three genera. Gliomastix is revived for five species, G. murorum, G. polychroma, G. tumulicola, G. roseogrisea, and G. masseei. Sarocladium is extended to include all members of the phylogenetically distinct A. strictum clade including the medically important A. kiliense and the protective maize endophyte A. zeae. Also included in Sarocladium are members of the phylogenetically delimited Acremonium bacillisporum clade, closely linked to the A. strictum clade. The genus Trichothecium is revised following the principles of unitary nomenclature based on the oldest valid anamorph or teleomorph name, and new combinations are made in Trichothecium for the tightly interrelated Acremonium crotocinigenum, Spicellum roseum, and teleomorph Leucosphaerina indica. Outside the Hypocreales, numerous Acremonium-like species fall into the Plectosphaerellaceae, and A. atrogriseum falls into the Cephalothecaceae
Fundamentals of interface phenomena in advanced bulk nanoscale materials
The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materials processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by TEM, high-resolution x-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studied. Also enhanced grain boundary diffusivity is addressed. Structure recovery and dislocation emission from grain boundaries in nanocrystalline materials have been investigated by analytical methods and modeling
Species and ecological diversity within the Cladosporium cladosporioides complex (Davidiellaceae, Capnodiales)
The genus Cladosporium is one of the largest genera of
dematiaceous hyphomycetes, and is characterised by a coronate scar structure,
conidia in acropetal chains and Davidiella teleomorphs. Based on
morphology and DNA phylogeny, the species complexes of C. herbarum
and C. sphaerospermum have been resolved, resulting in the
elucidation of numerous new taxa. In the present study, more than 200 isolates
belonging to the C. cladosporioides complex were examined and
phylogenetically analysed on the basis of DNA sequences of the nuclear
ribosomal RNA gene operon, including the internal transcribed spacer regions
ITS1 and ITS2, the 5.8S nrDNA, as well as partial actin and translation
elongation factor 1-α gene sequences. For the saprobic, widely
distributed species Cladosporium cladosporioides, both a neotype and
epitype are designated in order to specify a well established circumscription
and concept of this species. Cladosporium tenuissimum and C.
oxysporum, two saprobes abundant in the tropics, are epitypified and
shown to be allied to, but distinct from C. cladosporioides.
Twenty-two species are newly described on the basis of phylogenetic characters
and cryptic morphological differences. The most important phenotypic
characters for distinguishing species within the C. cladosporioides
complex, which represents a monophyletic subclade within the genus, are shape,
width, length, septation and surface ornamentation of conidia and
conidiophores; length and branching patterns of conidial chains and hyphal
shape, width and arrangement. Many of the treated species, e.g.,
C. acalyphae, C. angustisporum, C. australiense,
C. basiinflatum, C. chalastosporoides, C.
colocasiae, C. cucumerinum, C. exasperatum, C. exile,
C. flabelliforme, C. gamsianum, and C. globisporum
are currently known only from specific hosts, or have a restricted
geographical distribution. A key to all species recognised within the C.
cladosporioides complex is provided
Topical rapamycin as a treatment for fibrofolliculomas in Birt-Hogg-Dubé syndrome:a double-blind placebo-controlled randomized split-face trial
Background: Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder characterised by the occurrence of benign, mostly facial, skin tumours called fibrofolliculomas, multiple lung cysts, spontaneous pneumothorax and an increased renal cancer risk. Current treatments for fibrofolliculomas have high rates of recurrence and carry a risk of complications. It would be desirable to have a treatment that could prevent fibrofolliculomas from growing. Animal models of BHD have previously shown deregulation of mammalian target of rapamycin (mTOR). Topical use of the mTOR inhibitor rapamycin is an effective treatment for the skin tumours (angiofibromas) in tuberous sclerosis complex, which is also characterised by mTOR deregulation. In this study we aimed to determine if topical rapamycin is also an effective treatment for fibrofolliculomas in BHD. Methods: We performed a double blinded, randomised, facial left-right controlled trial of topical rapamycin 0.1% versus placebo in 19 BHD patients. Trial duration was 6 months. The primary outcome was cosmetic improvement as measured by doctors and patients. Changes in fibrofolliculoma number and size were also measured, as was occurrence of side effects. Results: No change in cosmetic status of fibrofolliculomas was reported in the majority of cases for the rapamycin treated (79% by doctors, 53% by patients) as well as the placebo treated facial sides (both 74%). No significant differences between rapamycin and placebo treated facial halves were observed (p = 1.000 for doctors opinion, p = 0.344 for patients opinion). No significant difference in fibrofolliculoma number or change in size of the fibrofolliculomas was seen after 6 months. Side effects occurred more often after rapamycin treatment (68% of patients) than after placebo (58% of patients; p = 0.625). A burning sensation, erythema, itching and dryness were most frequently reported. Conclusions: This study provides no evidence that treatment of fibrofolliculomas with topical rapamycin in BHD results in cosmetic improvement. Trial Registration: ClinicalTrials.gov NCT00928798</p
Investigation of the Exclusive 3He(e,e'pp)n Reaction
Cross sections for the 3He(e,e'pp)n reaction were measured over a wide range
of energy and three- momentum transfer. At a momentum transfer q=375 MeV/c,
data were taken at transferred energies omega ranging from 170 to 290 MeV. At
omega=220 MeV, measurements were performed at three q values (305, 375, and 445
MeV/c). The results are presented as a function of the neutron momentum in the
final-state, as a function of the energy and momentum transfer, and as a
function of the relative momentum of the two-proton system. The data at neutron
momenta below 100 MeV/c, obtained for two values of the momentum transfer at
omega=220 MeV, are well described by the results of continuum-Faddeev
calculations. These calculations indicate that the cross section in this domain
is dominated by direct two-proton emission induced by a one-body hadronic
current. Cross section distributions determined as a function of the relative
momentum of the two protons are fairly well reproduced by continuum-Faddeev
calculations based on various realistic nucleon-nucleon potential models. At
higher neutron momentum and at higher energy transfer, deviations between data
and calculations are observed that may be due to contributions of isobar
currents.Comment: 14 pages, 1 table, 17 figure
Ground-state correlations and final state interactions in the process 3He(e,e'pp)n
The two-proton emission process is theoretically investigated
using realistic three-nucleon wave functions and taking the final state
interaction into account by an approach which can be used when the value of the
three-nucleon invariant mass is either below or above the pion emission
threshold. Various kinematical conditions which enhance or minimize the effects
of the final state interaction are thoroughly analyzed.Comment: 26 pages, 12 eps-figures. Introduction and abstract updated, few
references added and Apendix A remove
First measurements of the ^16O(e,e'pn)^14N reaction
This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction.
Data were measured in kinematics centred on a super-parallel geometry at energy
and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution
was sufficient to distinguish groups of states in the residual nucleus but not
good enough to separate individual states. The data show a strong dependence on
missing momentum and this dependence appears to be different for two groups of
states in the residual nucleus. Theoretical calculations of the reaction using
the Pavia code do not reproduce the shape or the magnitude of the data.Comment: 10 pages, 11 figures, 2 tables, Accepted for publication in EPJ
One Body Density Matrix, Natural Orbits and Quasi Hole States in 16O and 40Ca
The one body density matrix, momentum distribution, natural orbits and quasi
hole states of 16O and 40Ca are analyzed in the framework of the correlated
basis function theory using state dependent correlations with central and
tensor components. Fermi hypernetted chain integral equations and single
operator chain approximation are employed to sum cluster diagrams at all
orders. The optimal trial wave function is determined by means of the
variational principle and the realistic Argonne v8' two-nucleon and Urbana IX
three-nucleon interactions. The correlated momentum distributions are in good
agreement with the available variational Monte Carlo results and show the well
known enhancement at large momentum values with respect to the independent
particle model. Diagonalization of the density matrix provides the natural
orbits and their occupation numbers. Correlations deplete the occupation number
of the first natural orbitals by more than 10%. The first following ones result
instead occupied by a few percent. Jastrow correlations lower the spectroscopic
factors of the valence states by a few percent (~1-3%) and an additional ~8-12%
depletion is provided by tensor correlations. It is confirmed that short range
correlations do not explain the spectroscopic factors extracted from (e,e'p)
experiments. 2h-1p perturbative corrections in the correlated basis are
expected to provide most of the remaining strength, as in nuclear matter.Comment: 25 pages, 9 figures. Submitted to Phys.Rev.
- âŠ