10,174 research outputs found
EFFECTS OF TRADE BARRIERS ON U.S. APPLE EXPORTS
We build a spatial equilibrium trade model for apples using demand and supply relations for each importing and exporting country. The model maximizes welfare subject to demand and production constraints. A trade barrier (free trade) scenario which incorporates (removes) import quotas and tariffs is run. Comparison of the solutions of the two scenarios quantifies the impacts of trade barriers on US apple exports.apples, spatial equilibrium model, trade barriers, International Relations/Trade, F10,
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Process length variation in cysts of a dinoflagellate, Lingulodinium machaerophorum, in surface sediments: Investigating its potential as salinity proxy
“Many authors have contributed to writing this paper. Those listed in the metadata are: the main/contact author, the first listed author and Brunel University author(s). For a full list of the authors, please see the PDF version.”A biometrical analysis of the dinoflagellate cyst Lingulodinium machaerophorum (Deflandre and Cookson 1955) Wall, 1967 in 144 globally distributed surface sediment samples revealed that the average process length is related to summer salinity and temperature at a water depth of 30 m by the equation (salinity/temperature) = (0.078*average process length + 0.534) with R² = 0.69. This relationship can be used to reconstruct palaeosalinities, albeit with caution. The particular ecological window can be associated with known distributions of the corresponding motile stage Lingulodinium polyedrum (Stein) Dodge, 1989. Confocal laser microscopy showed that the average process length is positively related to the average distance between process bases (R²=0.78), and negatively related to the number of processes (R²=0.65). These results document the existence of two end members in cyst formation: one with many short, densely distributed processes and one with a few, long, widely spaced processes, which can be respectively related to low and high salinity/temperature ratios. Obstruction during formation of the cysts causes anomalous distributions of the processes. From a biological perspective, processes function to facilitate sinking of the cysts through clustering
Encapsulation of a {Cu16} cluster containing four [Cu4O4] cubanes within an isopolyoxometalate {W44} cluster
We report a {Cu16} embedded within a {W44} cluster containing four cubane-like [Cu4O4] units within an isopolyoxotungstate (isoPOT) in a {Na4Cu4[(H2W11O38) (CH3COO)(OH)3]}4·88H2O (1) and a polyanion Cu-linked {W11} chain Na6Cu2[(H2W11O38)(CH3COO)(OH)]·26H2O (2). Electronically, the redox properties show that both compounds 1 and 2 undergo irreversible reductions resulting in the demetalation of the compounds, whilst the magnetic behavior of 1 and 2 shows a weak antiferromagnetic and a stronger ferromagnetic coupling, respectively
Annealing of radiation induced defects in silicon in a simplified phenomenological model
The concentration of primary radiation induced defects has been previously
estimated considering both the explicit mechanisms of the primary interaction
between the incoming particle and the nuclei of the semiconductor lattice, and
the recoil energy partition between ionisation and displacements, in the frame
of the Lindhard theory. The primary displacement defects are vacancies and
interstitials, that are essentially unstable in silicon. They interact via
migration, recombination, annihilation or produce other defects. In the present
work, the time evolution of the concentration of defects induced by pions in
medium and high resistivity silicon for detectors is modelled, after
irradiation. In some approximations, the differential equations representing
the time evolution processes could be decoupled. The theoretical equations so
obtained are solved analytically in some particular cases, with one free
parameter, for a wide range of particle fluences and/or for a wide energy range
of the incident particles, for different temperatures; the corresponding
stationary solutions are also presented.Comment: 14 pages, 5 figures, accepted to Nuclear Instruments and Methods in
Physics Research B second version, major revisio
Expression of PIK3CA mutant E545K in the mammary gland induces heterogeneous tumors but is less potent than mutant H1047R.
The phosphoinositide 3-kinase (PI3K) signaling cascade is a key mediator of cellular growth, survival and metabolism and is frequently subverted in human cancer. The gene encoding for the alpha catalytic subunit of PI3K (PIK3CA) is mutated and/or amplified in ∼30% of breast cancers. Mutations in either the kinase domain (H1047R) or the helical domain (E545K) are most common and result in a constitutively active enzyme with oncogenic capacity. PIK3CA(H1047R) was previously demonstrated to induce tumors in transgenic mouse models; however, it was not known whether overexpression of PIK3CA(E545K) is sufficient to induce mammary tumors and whether tumor initiation by these two types of mutants differs. Here, we demonstrate that expression of PIK3CA(E545K) in the mouse mammary gland induces heterogenous mammary carcinomas but with a longer latency than PIK3CA(H1047R)-expressing mice. Our results suggest that the helical domain mutant PIK3CA(E545K) is a less potent inducer of mammary tumors due to less efficient activation of downstream Akt signaling
Type III and N Einstein spacetimes in higher dimensions: general properties
The Sachs equations governing the evolution of the optical matrix of geodetic
WANDs (Weyl aligned null directions) are explicitly solved in n-dimensions in
several cases which are of interest in potential applications. This is then
used to study Einstein spacetimes of type III and N in the higher dimensional
Newman-Penrose formalism, considering both Kundt and expanding (possibly
twisting) solutions. In particular, the general dependence of the metric and of
the Weyl tensor on an affine parameter r is obtained in a closed form. This
allows us to characterize the peeling behaviour of the Weyl "physical"
components for large values of r, and thus to discuss, e.g., how the presence
of twist affects polarization modes, and qualitative differences between four
and higher dimensions. Further, the r-dependence of certain non-zero scalar
curvature invariants of expanding spacetimes is used to demonstrate that
curvature singularities may generically be present. As an illustration, several
explicit type N/III spacetimes that solve Einstein's vacuum equations (with a
possible cosmological constant) in higher dimensions are finally presented.Comment: 19 page
Rotational cooling of molecules using lamps
We investigate theoretically the application of tailored incoherent
far-infrared fields in combination with laser excitation of a single
rovibrational transition for rotational cooling of translationally cold polar
diatomic molecules. The cooling schemes are effective on a timescale shorter
than typical unperturbed trapping times in ion traps and comparable to
obtainable confinement times of neutral molecules.Comment: 5 pages, 2 figure
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