1,049 research outputs found
P-T-t path for the Archean Pikwitonei Granulite Domain and Cross Lake Subprovince, Manitoba, Canada
The rationale was outlined for constructing pressure-temperature-time (P-T-t) paths by using U-Pb dating of garnet produced in thermobarometrically sensitive reactions. In an example from the Pikwitonei granulites of the Northwestern Superior Province of the Canadian Shield, garnets were formed at 2744-2742 Ma, 2700-2689 Ma, and 2605-2590 Ma, the latter events coinciding with times recorded by U-Pb zircon systems. Garnet grew during metamorphism at 6.5 kbar, 630 to 750 C and later at 7.2 to 7.5 kbar, 800 C; the later metamorphism apparently did not exceed the U-Pb closure temperature. The resultant P-T-t path is counterclockwise, with late isobaric cooling, interpreted to result from magmatic heating at an Andean margin
Age Moderates the Effect of Self-Paced Exercise on Exercise Adherence among Overweight Adults
Objective: The present study tested the hypothesis that the effect of self-paced exercise on adherence to exercise programs is more pronounced with increasing age. Method: Fifty-nine low-active overweight adults (18-65 years) were encouraged to walk 30 to 60 min/day and randomized to either self-paced (n = 30) or prescribed moderate-intensity (n = 29) conditions. Results: The effect of study condition was moderated by age (main effect: b = 6.14, SE = 2.54, p = .02; Condition × Age: b = −11.55, SE = 3.77, p \u3c .01), such that among participants \u3e50 years, those in the self-paced condition exercised 6 more min/day than participants in the prescribed moderate-intensity condition (p = .02), whereas among participants \u3c50 \u3eyears, those in the self-paced condition exercised 5.4 fewer min/day compared with those in the moderate-intensity condition (p = .05). Affective response to physical activity did not mediate the moderating effect of age. Discussion: As age increases, adults may be more likely to adhere to self-paced versus prescribed moderate-intensity exercise
Linking the exotic structure of C to its unbound mirror Na
The structure of C is used to define a nuclear interaction that,
when used in a multichannel algebraic scattering theory for the C
system, gives a credible definition of the (compound) excitation spectra. When
couplings to the low-lying collective excitations of the C-core are
taken into account, both sub-threshold and resonant states about the
C threshold are found. Adding Coulomb potentials to that nuclear
interaction, the method is used for the mirror system of Ne to
specify the low-excitation spectrum of the particle unstable Na. We
compare the results with those of a microscopic cluster model. A spectrum of
low excitation resonant states in Na is found with some differences to
that given by the microscopic-cluster model. The calculated resonance
half-widths (for proton emission) range from to keV.Comment: 13 pages, 5 figure
Affective response as a mediator of the association between the physical and social environment and physical activity behavior
Perceptions of the physical and social environment have been shown to be predictive of physical activity (PA) behavior. However, the mechanisms of this association have not been examined. Affective response to PA was examined as a putative mediator of the association between perceptions of the PA environment and subsequent PA behavior. As part of a PA promotion study, 59 low-active overweight or obese but otherwise healthy adults completed real-time assessments of the perceived physical and social PA environment, affective response to PA, and PA behavior over a 6-month period. As hypothesized, decreased latency to and greater duration of subsequent PA was predicted by engaging in PA with a partner (b = 17.24, SE = .45, p \u3c .01), engaging in PA outdoors versus indoors (b = 3.70, SE = 0.67, p \u3c .01), and perceived pleasantness of the physical (b = 0.59, SE = .17, p \u3c .01) and social settings (b = 0.68, SE = .16, p \u3c .01). Affective response to PA (a shift toward feeling good versus bad during PA) mediated the association between engaging in PA with a partner (a path: 0.53(.11), p \u3c .01, b path: 0.42(.12), p \u3c .01, ab path: 0.22(.08), 95% CI .09–.41) and perceived pleasantness of the physical (a path: .38(.02), p \u3c .01; b path: .65(.23), p = .01; ab path: .25(.09), 95% CI .08–.43) and social setting (apath: .35(.02), p \u3c .01; b path: .57(.23), p = .01; ab path: .20(.08), 95% CI .03–.37) and PA behavior, but not the association between engaging in PA outdoors versus indoors and PA behavior. These findings suggest that perceived environmental variables may have their effects on PA through the process of psychological hedonism
Real-time dynamics of the formation of hydrated electrons upon irradiation of water clusters with extreme ultraviolet light
Free electrons in a polar liquid can form a bound state via interaction with the molecular environment. This so-called hydrated electron state in water is of fundamental importance e.g.~in cellular biology or radiation chemistry. Hydrated electrons are highly reactive radicals that can either directly interact with DNA or enzymes, or form highly excited hydrogen (H∗) after being captured by protons. Here, we investigate the formation of the hydrated electron in real-time employing XUV femtosecond pulses from a free electron laser, in this way observing the initial steps of the hydration process. Using time-resolved photoelectron spectroscopy we find formation timescales in the low picosecond range and resolve the prominent dynamics of forming excited hydrogen states
Particle-unstable nuclei in the Hartree-Fock theory
Ground state energies and decay widths of particle unstable nuclei are
calculated within the Hartree-Fock approximation by performing a complex
scaling of the many-body Hamiltonian. Through this transformation, the wave
functions of the resonant states become square integrable. The method is
implemented with Skyrme effective interactions. Several Skyrme parametrizations
are tested on four unstable nuclei: 10He, 12O, 26O and 28O.Comment: 5 pages, LaTeX, submitted to Phys. Rev. Let
Three-body Faddeev Calculation for 11Li with Separable Potentials
The halo nucleus Li is treated as a three-body system consisting of an
inert core of Li plus two valence neutrons. The Faddeev equations are
solved using separable potentials to describe the two-body interactions,
corresponding in the n-Li subsystem to a p resonance plus a
virtual s-wave state. The experimental Li energy is taken as input and
the Li transverse momentum distribution in Li is studied.Comment: 6 pages, RevTeX, 1 figur
Large-basis shell-model calculations for p-shell nuclei
Results of large-basis shell-model calculations for nuclei with A=7-11 are
presented. The effective interactions used in the study were derived
microscopically from the Reid93 potential and take into account the Coulomb
potential as well as the charge dependence of T=1 partial waves. For A=7, a
model space was used, while for the rest of the studied
nuclides, the calculations were performed in a model space. It
is demonstrated that the shell model combined with microscopic effective
interactions derived from modern nucleon-nucleon potentials is capable of
providing good agreement with the experimental properties of the ground state
as well as with those of the low-lying excited states.Comment: 17 pages. REVTEX. 16 PostScript figure
Simple transfer functions for calculating benthic fixed nitrogen losses and C:N:P regeneration ratios in global biogeochemical models
Empirical transfer functions are derived for predicting the total benthic nitrate loss(LNO3) and the net loss of dissolved inorganic nitrogen (LDIN) in marine sediments,equivalent to sedimentary denitrification. The functions are dynamic vertically integratedsediment models which require the rain rate of particulate organic carbon to the seafloor(RRPOC) and a proposed new variable(O2-NO3)bw (bottom water O2 concentration minus NO3-concentration) as the only input parameters. Applied globally to maps of RRPOC and(O2-NO3)bw on a 1° x 1° spatial resolution, the models predict a NO3- drawdown of 196 Tg yr-1 (LNO3)of which 153 – 155 Tg yr-1 is denitrified to N2 (LDIN). This is in good agreement with previous estimates using very different methods. Our approach implicitly accounts for fixed N loss via anammox, such that our findings do not support the idea that the relatively recent discovery of anammox in marine sediments might require current estimates of the global benthic marine N budget to be revised. The continental shelf (0 – 200 m) accounts for >50% of global LNO3 and LDIN, with slope (200 – 2000 m) and deep-sea (>2000 m) sediments contributing ca. 30% and 20%, respectively.
Denitrification in high-nitrate/low-oxygen regions such as oxygen minimum zones is significant (ca. 15 Tg N yr-1; 10% of global) despite covering only 1% of the seafloor. The data are used to estimate the net fluxes of nitrate (18 Tg N yr-1) and phosphate(27 Tg P yr-1) across the sediment-water interface. The benthic fluxes strongly deviate from Redfield composition, with globally averaged N:P, N:C and C:P values of 8.3, 0.067 and 122, respectively, indicating world-wide fixed N losses (by denitrification) relative to C and P. The transfer functions are designed to be coupled dynamically to general circulation models to better predict the feedback of sediments on pelagic nutrient cycling and dissolved O2 distributions
Evidence of a new state in Be observed in the Li -decay
Coincidences between charged particles emitted in the -decay of
Li were observed using highly segmented detectors. The breakup channels
involving three particles were studied in full kinematics allowing for the
reconstruction of the excitation energy of the Be states participating
in the decay. In particular, the contribution of a previously unobserved state
at 16.3 MeV in Be has been identified selecting the +
He + He+n channel. The angular correlations between the
particle and the center of mass of the He+n system favors spin and
parity assignment of 3/2 for this state as well as for the previously known
state at 18 MeV.Comment: 13 pages, 6 figure
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