451 research outputs found
Up-Down Quark Mass Difference Effect in Nuclear Many-Body Systems
A charge-symmetry-breaking nucleon-nucleon force due to the up-down quark
mass difference is evaluated in the quark cluster model. It is applied to the
shell-model calculation for the isovector mass shifts of isospin multiplets and
the isospin-mixing matrix elements in 1s0d-shell nuclei. We find that the
contribution of the quark mass difference effect is large and agrees with
experiment. This contribution may explain the Okamoto-Nolen-Schiffer anomaly,
alternatively to the meson-mixing contribution, which is recently predicted to
be reduced by the large off-shell correction
New representation of orbital motion with arbitrary angular momenta
A new formulation is presented for a variational calculation of -body
systems on a correlated Gaussian basis with arbitrary angular momenta. The
rotational motion of the system is described with a single spherical harmonic
of the total angular momentum , and thereby needs no explicit coupling of
partial waves between particles. A simple generating function for the
correlated Gaussian is exploited to derive the matrix elements. The formulation
is applied to various Coulomb three-body systems such as , and up to in order to show its usefulness and
versatility. A stochastic selection of the basis functions gives good results
for various angular momentum states.Comment: Revte
SHEDDING SOME LIGHT ON THISMIA RODWAYI F. MUELL. (FAIRY LANTERNS) IN TASMANIA: DISTRIBUTION, HABITAT AND CONSERVATION STATUS
Thismia rodwayi is a seldom-seen, subterranean plant that occurs i
A comparative study on wear and corrosion behaviour of tungsten carbide-nickel and tungsten carbide-cobalt high velocity oxy-fuel (HVOF) for carbon steel blade
Nowadays, the demand of high wear and corrosion resistance of the components in
various industry is increasing from time to time. Therefore, high velocity oxy-fuel
(HVOF) thermal spray was introduced to protect machine components from wear and
corrosion, to restore worn components and to improve the durability of the
components. HVOF is one of the process of depositing a material layer over a base
metal or substrate with characteristics of high flame velocity and moderate
temperature. The main purpose of this present study is to characterize the structure of
the tungsten carbide 10 wt.% nickel (WC-10Ni) and tungsten carbide 12 wt.% w cobalt
(WC-12Co) coating deposited by means of HVOF thermal spray onto a continuous
digester (CD) blade that made up from carbon steel. The morphology and chemical
composition of the coating were characterized by scanning electron microscope
(SEM), electron dispersive spectrometer (EDS), and x-ray diffraction (XRD). The
hardness test was carried out by using Vickers micro-hardness tester with load of 490.3
mN (0.05 HV). The wear and corrosion behavior and mechanism for both coatings
was compared. Three body wear test was carried out in term of weight loss and
electrochemical test was performed in acidic media (mixture of sulfuric acid, H2SO4
and ilmenite) to obtain the corrosion rate of the coating. From the result, it shows that
WC-12Co coating has finer grain size that is around 2.3 μm. WC-12Co has higher
wear resistance due to high volume friction, low mean free path, high hardness and
lower porosity distribution compared to WC-10Ni. Besides, the formation of
secondary phase, W2C also affected the hardness of both coating, where this phase is
harder than WC phase. For corrosion test, WC-12Co shows good corrosion resistance
with small differences of corrison rate with WC-10Ni, that is only 0.7016 mm/y. As a
conclusion, WC-12Co HVOF coating shows high potential on replacement of CD
blade
The influence of depth of anesthesia and blood pressure on muscle recorded motor evoked potentials in spinal surgery. A prospective observational study protocol
For high-risk spinal surgeries, intraoperative neurophysiological monitoring (IONM) is used to detect and prevent intraoperative neurological injury. The motor tracts are monitored by recording and analyzing muscle transcranial electrical stimulation motor evoked potentials (mTc-MEPs). A mTc-MEP amplitude decrease of 50-80% is the most common warning criterion for possible neurological injury. However, these warning criteria often result in false positive warnings. False positives may be caused by inadequate depth of anesthesia and blood pressure on mTc-MEP amplitudes. The aim of this paper is to validate the study protocol in which the goal is to investigate the effects of depth of anesthesia (part 1) and blood pressure (part 2) on mTc-MEPs. Per part, 25 patients will be included. In order to investigate the effects of depth of anesthesia, a processed electroencephalogram (pEEG) monitor will be used. At pEEG values of 30, 40 and 50, mTc-MEP measurements will be performed. To examine the effect of blood pressure on mTc-MEPs the mean arterial pressure will be elevated from 60 to 100 mmHg during which mTc-MEP measurements will be performed. We hypothesize that by understanding the effects of depth of anesthesia and blood pressure on mTc-MEPs, the mTc-MEP monitoring can be interpreted more reliably. This may contribute to fewer false positive warnings. By performing this study after induction and prior to incision, this protocol provides a unique opportunity to study the effects of depths of anesthesia and blood pressure on mTc-MEPs alone with as little confounders as possible. Trial registration number NL7772
Beta-delayed proton emission in the 100Sn region
Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was
studied at the National Superconducting Cyclotron Laboratory. The nuclei were
produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be
target. Beam purification was provided by the A1900 Fragment Separator and the
Radio Frequency Fragment Separator. The fragments of interest were identified
and their decay was studied with the NSCL Beta Counting System (BCS) in
conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing,
98Inm and 99In were identified as beta-delayed proton emitters, with branching
ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for
89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9
-1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for
101Sn was deduced with higher precision than previously reported. The impact of
the newly measured bp values on the composition of the type-I X-ray burst ashes
was studied.Comment: 15 pages, 14 Figures, 4 Table
Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses
Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant =1.138 fm and binding energy per nucleon = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility to be 288 28 MeV using
the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy.
Rev. C
Evolutionary History and Novel Biotic Interactions Determine Plant Responses to Elevated CO2 and Nitrogen Fertilization
A major frontier in global change research is predicting how multiple agents of global change will alter plant productivity, a critical component of the carbon cycle. Recent research has shown that plant responses to climate change are phylogenetically conserved such that species within some lineages are more productive than those within other lineages in changing environments. However, it remains unclear how phylogenetic patterns in plant responses to changing abiotic conditions may be altered by another agent of global change, the introduction of non-native species. Using a system of 28 native Tasmanian Eucalyptus species belonging to two subgenera, Symphyomyrtus and Eucalyptus, we hypothesized that productivity responses to abiotic agents of global change (elevated CO2 and increased soil N) are unique to lineages, but that novel interactions with a nonnative species mediate these responses. We tested this hypothesis by examining productivity of 1) native species monocultures and 2) mixtures of native species with an introduced hardwood plantation species, Eucalyptus nitens, to experimentally manipulated soil N and atmospheric CO2. Consistent with past research, we found that N limits productivity overall, especially in elevated CO2 conditions. However, monocultures of species within the Symphyomyrtus subgenus showed the strongest response to N (gained 127% more total biomass) in elevated CO2 conditions, whereas those within the Eucalyptus subgenus did not respond to N. Root:shoot ratio (an indicator of resource use) was on average greater in species pairs containing Symphyomyrtus species, suggesting that functional traits important for resource uptake are phylogenetically conserved and explaining the phylogenetic pattern in plant response to changing environmental conditions. Yet, native species mixtures with E. nitens exhibited responses to CO2 and N that differed from those of monocultures, supporting our hypothesis and highlighting that both plant evolutionary history and introduced species will shape community productivity in a changing world
Long-term monitoring of the threatened lesser guineaflower Hibbertia calycina (DC.) N.A.Wakef. (Dilleniaceae) in Tasmania
This paper describes the distribution of the threatened shrub Hibbertia calycina (DC.) N.A.Wakef., a distinctive plant restricted to northeast Tasmania. It compares changes over time in population size and evaluates the species response to disturbance. Results found H. calycina distribution is restricted to isolated clumps on highly insolated ridges and steep upper slopes of fine-grained Mathinna-series sedimentary rocks in dry sclerophyll forest dominated by Eucalyptus sieberi L.Johnson. Nine populations were documented with an estimated area of occupancy of 0.43 km2 and area of extent measuring 95 km2, demonstrating that the current listing of H. calycina as vulnerable is appropriate on Tasmania’s Threatened Species Protection Act 1995. We believe that the distribution of the present population is a result of natural factors (i.e., restricted habitat range and natural fire events) and anthropogenic factors (managed fire regime and illegal firewood cutting). Although frequent fire and roading have the potential to impact populations, H. calycina appears to be stable without active management in a landscape of patchy, regular, low severity fire. Our results indicate susceptibility to the soil-borne pathogen Phytophthora cinnamomi is likely less problematic than previously postulated, yet more data and research is required before management is changed
- …