3,306 research outputs found
Comparative Analysis of Systems of Domestic Taxation of Controlled Foreign Corporations
This Note outlines the existing law and practice of the domestic taxation of CFC\u27s in the United States, United Kingdom, France, West Germany, and Japan, each of which exhibits a high level of economic and industrial advancement. United States developments are important because the statutory provisions of Subpart F have been adopted, with modifications, by other nations, including West Germany and Japan. The United Kingdom and France, on the other hand, have not yet adopted an integrated statutory scheme providing for domestic taxation of CFC\u27s. These countries attack tax evasion schemes utilizing foreign controlled companies primarily through general laws, exchange controls, and the requirement of government consent for certain international transactions
Chi hotspots trigger a conformational change in the helicase-like domain of AddAB to activate homologous recombination
In bacteria, the repair of double-stranded DNA breaks is modulated by Chi sequences. These are recognised by helicase-nuclease complexes that process DNA ends for homologous recombination. Chi activates recombination by changing the biochemical properties of the helicase-nuclease, transforming it from a destructive exonuclease into a recombination-promoting repair enzyme. This transition is thought to be controlled by the Chi-dependent opening of a molecular latch, which enables part of the DNA substrate to evade degradation beyond Chi. Here, we show that disruption of the latch improves Chi recognition efficiency and stabilizes the interaction of AddAB with Chi, even in mutants that are impaired for Chi binding. Chi recognition elicits a structural change in AddAB that maps to a region of AddB which resembles a helicase domain, and which harbours both the Chi recognition locus and the latch. Mutation of the latch potentiates the change and moderately reduces the duration of a translocation pause at Chi. However, this mutant displays properties of Chi-modified AddAB even in the complete absence of bona fide hotspot sequences. The results are used to develop a model for AddAB regulation in which allosteric communication between Chi binding and latch opening ensures quality control during recombination hotspot recognition
Star-Forming or Starbursting? The Ultraviolet Conundrum
Compared to starburst galaxies, normal star forming galaxies have been shown
to display a much larger dispersion of the dust attenuation at fixed reddening
through studies of the IRX-beta diagram (the IR/UV ratio "IRX" versus the UV
color "beta"). To investigate the causes of this larger dispersion and attempt
to isolate second parameters, we have used GALEX UV, ground-based optical, and
Spitzer infrared imaging of 8 nearby galaxies, and examined the properties of
individual UV and 24 micron selected star forming regions. We concentrated on
star-forming regions, in order to isolate simpler star formation histories than
those that characterize whole galaxies. We find that 1) the dispersion is not
correlated with the mean age of the stellar populations, 2) a range of dust
geometries and dust extinction curves are the most likely causes for the
observed dispersion in the IRX-beta diagram 3) together with some potential
dilution of the most recent star-forming population by older unrelated bursts,
at least in the case of star-forming regions within galaxies, 4) we also
recover some general characteristics of the regions, including a tight positive
correlation between the amount of dust attenuation and the metal content.
Although generalizing our results to whole galaxies may not be immediate, the
possibility of a range of dust extinction laws and geometries should be
accounted for in the latter systems as well.Comment: 18 pages, 17 figures, accepted for publication in Ap
Star formation and dust extinction properties of local galaxies from AKARI-GALEX All-Sky Surveys: First results from most secure multiband sample from FUV to FIR
The AKARI All-Sky Survey provided the first bright point source catalog
detected at 90um. Starting from this catalog, we selected galaxies by matching
AKARI sources with those in the IRAS PSCz. Next, we have measured total GALEX
FUV and NUV flux densities. Then, we have matched this sample with SDSS and
2MASS galaxies. By this procedure, we obtained the final sample which consists
of 607 galaxies. If we sort the sample with respect to 90um, their average SED
shows a coherent trend: the more luminous at 90um, the redder the global SED
becomes. The M_r--NUV-r color-magnitude relation of our sample does not show
bimodality, and the distribution is centered on the green valley between the
blue cloud and red sequence seen in optical surveys. We have established
formulae to convert FIR luminosity from AKARI bands to the total infrared (IR)
luminosity L_TIR. With these formulae, we calculated the star formation
directly visible with FUV and hidden by dust. The luminosity related to star
formation activity (L_SF) is dominated by L_TIR even if we take into account
the far-infrared (FIR) emission from dust heated by old stars. At high star
formation rate (SFR) (> 20 Msun yr^-1), the fraction of directly visible SFR,
SFR_FUV, decreases. We also estimated the FUV attenuation A_FUV from
FUV-to-total IR (TIR) luminosity ratio. We also examined the L_TIR/L_FUV-UV
slope (FUV- NUV) relation. The majority of the sample has L_TIR/L_FUV ratios 5
to 10 times lower than expected from the local starburst relation, while some
LIRGs and all the ULIRGs of this sample have higher L_TIR/L_FUV ratios. We
found that the attenuation indicator L_TIR/L_FUV is correlated to the stellar
mass of galaxies, M*, but there is no correlation with specific SFR (SSFR),
SFR/M*, and dust attenuation L_TIR/L_FUV. (abridged)Comment: 13 pages, 18 figures, accepted for publication in A&
Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator
HII regions are the birth places of stars, and as such they provide the best
measure of current star formation rates (SFRs) in galaxies. The close proximity
of the Magellanic Clouds allows us to probe the nature of these star forming
regions at small spatial scales. We aim to determine the monochromatic IR band
that most accurately traces the bolometric IR flux (TIR), which can then be
used to estimate an obscured SFR. We present the spatial analysis, via
aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using
the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are
also included. We find that nearly all of the LMC and SMC HII region SEDs peak
around 70um, from ~10 to ~400 pc from the central sources. As a result, the
sizes of HII regions as probed by 70um is approximately equal to the sizes as
probed by TIR (about 70 pc in radius); the radial profile of the 70um flux,
normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma
standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction
of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um
normalized fluxes (0.12 to 0.52); and these results are invariant between the
LMC and SMC. From these results, we argue that 70um is the most suitable IR
band to use as a monochromatic obscured star formation indicator because it
most accurately reproduces the TIR of HII regions in the LMC and SMC and over
large spatial scales. We also explore the general trends of the 8, 24, 70, and
160um bands in the LMC and SMC HII region SEDs, radial surface brightness
profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an
obscured SFR equation that is modified from the literature to use 70um
luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable
from 10 to 300 pc distance from the center of an HII region.Comment: 21 pages, 12 figures, 4 tables. Will be published in ApJ
Corn stover harvest increases herbicide movement to subsurface drains – Root Zone Water QualityModel simulations
BACKGROUND: Crop residue removal for bioenergy production can alter soil hydrologic properties and the movement of agrochemicals to subsurface drains. The Root Zone Water Quality Model (RZWQM), previously calibrated using measured flow and atrazine concentrations in drainage from a 0.4 ha chisel-tilled plot, was used to investigate effects of 50 and 100% corn (Zea mays L.) stover harvest and the accompanying reductions in soil crust hydraulic conductivity and total macroporosity on transport of atrazine, metolachlor andmetolachlor oxanilic acid (OXA).
RESULTS: The model accurately simulated field-measured metolachlor transport in drainage. A 3 year simulation indicated that 50% residue removal reduced subsurface drainage by 31% and increased atrazine and metolachlor transport in drainage 4–5-fold when surface crust conductivity and macroporosity were reduced by 25%. Based on itsmeasured sorption coefficient, approximately twofold reductions in OXA losses were simulated with residue removal.
CONCLUSION: The RZWQM indicated that, if corn stover harvest reduces crust conductivity and soil macroporosity, losses of atrazine andmetolachlor in subsurface drainagewill increase owing to reduced sorption related tomorewatermoving through fewermacropores. Losses of the metolachlor degradation product OXA will decrease as a result of themore rapid movement of the parent compound into the soil
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