15,267 research outputs found

    Restoration of eucalypt grassy woodland: effects of experimental interventions on ground-layer vegetation

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    We report on the effects of broad-scale restoration treatments on the ground layer of eucalypt grassy woodland in south-eastern Australia. The experiment was conducted in two conservation reserves from which livestock grazing had previously been removed. Changes in biomass, species diversity, ground-cover attributes and life-form were analysed over a 4-year period in relation to the following experimental interventions: (1) reduced kangaroo density, (2) addition of coarse woody debris and (3) fire (a single burn). Reducing kangaroo density doubled total biomass in one reserve, but no effects on exotic biomass, species counts or ground cover attributes were observed. Coarse woody debris also promoted biomass, particularly exotic annual forbs, as well as plant diversity in one of the reserves. The single burn reduced biomass, but changed little else. Overall, we found the main driver of change to be the favourable growth seasons that had followed a period of drought. This resulted in biomass increasing by 67%, (mostly owing to the growth of perennial native grasses), whereas overall native species counts increased by 18%, and exotic species declined by 20% over the 4-year observation period. Strategic management of grazing pressure, use of fire where biomass has accumulated and placement of coarse woody debris in areas of persistent erosion will contribute to improvements in soil and vegetation condition, and gains in biodiversity, in the future.Funding and in-kind logistic support for this project was provided by the ACT Government as part of an Australian Research Council Linkage Grant (LP0561817; LP110100126). Drafts of the manuscript were read by Saul Cunningham and Ben Macdonald

    Compression Drying of Sapwood

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    A compression drying experiment carried out on small blocks of sapwood from Pinus radiata, Araucaria cunninghamii. Eucalyptus regnans, and E. obliqua is described. Effects of initial moisture content, speed of compression, specimen thickness and orientation on moisture loss and energy input were studied. All specimens were compressed perpendicular to the grain to the same stress in either a radial or tangential direction in a jig that prevented lateral expansion. Force and deformation changes of the specimens were recorded during compression, and water loss at the end of the process was measured. From these data, volumetric compressions, moisture losses, energy inputs, and energy efficiencies of water removal were calculated.The analyses of variance confirmed that initial moisture content, species and wood specific gravity, amount of volumetric strain, rate of compression, and specimen orientation all affected unit water removal; specimen thickness did not. The lower density softwoods deformed to a greater extent than the hardwoods and lost more water. More water was removed from wetter specimens than drier ones at the same stress, and a slow compression rate caused a greater water loss than a more rapid rate. Specimens compressed tangentially lost more water than those compressed radially. Energy efficiency of water removal was greatest in the relatively low specific gravity Pinus radiata specimens with high moisture contents which were compressed tangentially at a slow rate

    Synthesis Imaging of Dense Molecular Gas in the N113 HII Region of the Large Magellanic Cloud

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    We present aperture synthesis imaging of dense molecular gas in the Large Magellanic Cloud, taken with the prototype millimeter receivers of the Australia Telescope Compact Array (ATCA). Our observations of the N113 HII region reveal a condensation with a size of ~6" (1.5 pc) FWHM, detected strongly in the 1-0 lines of HCO+, HCN and HNC, and weakly in C_2H. Comparison of the ATCA observations with single-dish maps from the Mopra Telescope and sensitive spectra from the Swedish-ESO Submillimetre Telescope indicates that the condensation is a massive clump of ~10^4 solar masses within a larger ~10^5 solar mass molecular cloud. The clump is centered adjacent to a compact, obscured HII region which is part of a linear structure of radio continuum sources extending across the molecular cloud. We suggest that the clump represents a possible site for triggered star formation. Examining the integrated line intensities as a function of interferometer baseline length, we find evidence for decreasing HCO+/HCN and HCN/HNC ratios on longer baselines. These trends are consistent with a significant component of the HCO+ emission arising in an extended clump envelope and a lower HCN/HNC abundance ratio in dense cores.Comment: 10 pages, 6 figures, to appear in Ap

    Observation of HCN hyperfine line anomalies towards low- and high-mass star-forming cores

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    HCN is becoming a popular choice of molecule for studying star formation in both low- and high-mass regions and for other astrophysical sources from comets to high-redshift galaxies. However, a major and often overlooked difficulty with HCN is that it can exhibit non-local thermodynamic equilibrium (non-LTE) behaviour in its hyperfine line structure. Individual hyperfine lines can be strongly boosted or suppressed. In low-mass star-forming cloud observations, this could possibly lead to large errors in the calculation of opacity and excitation temperature, while in massive star-forming clouds, where the hyperfine lines are blended due to turbulent broadening, errors will arise in infall measurements that are based on the separation of the peaks in a self-absorbed profile. The underlying line shape cannot be known for certain if hyperfine anomalies are present. We present a first observational investigation of these anomalies across a range of conditions and transitions by carrying out a survey of low-mass starless cores (in Taurus & Ophiuchus) and high-mass protostellar objects (in the G333 giant molecular cloud) using hydrogen cyanide (HCN) J=1-0 and J=3-2 emission lines. We quantify the degree of anomaly in these two rotational levels by considering ratios of individual hyperfine lines compared to LTE values. We find that all the cores observed show some degree of anomaly while many of the lines are severely anomalous. We conclude that HCN hyperfine anomalies are common in both lines in both low-mass and high-mass protostellar objects, and we discuss the differing hypotheses for the generation of the anomalies. In light of the results, we favour a line overlap effect for the origins of the anomalies. We discuss the implications for the use of HCN as a dynamical tracer and suggest in particular that the J=1-0, F=0-1 hyperfine line should be avoided in quantitative calculations.Comment: 17 pages, 8 figure

    Textualism and Tax Shelters

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    A substantial debate about the approaches employed by courts to interpret statutes and regulations has developed during the last decade. Some have argued that the search for a statute\u27s meaning and purpose should focus on the text, itself, and should not include consulting legislative history. In contrast, others have argued that it is difficult to determine the meaning of a statute without consulting legislative history to determine the legislature\u27s purpose for the statute. The debate about the appropriate method for interpreting statutes underlies a crisis in the administration of tax law. The recent proliferation of tax shelters has at least in part been facilitated by the ascendancy of textualism. Our conversations with practitioners indicate that tax advisors have become more aggressive in structuring transactions that comply with the form of the tax statutes even though the transactions may be highly questionable in light of the legislation\u27s history or underlying purpose. The result has been a cottage industry where investment banks and accounting firms market tax shelters that triumph in form, but not substance, at the expense of the fisc. Because most tax shelter activity is hidden, it is difficult to ascertain its revenue impact. It is estimated that tax shelters reduced tax revenues by approximately 10to10 to 24 billion in 1999. In addition, practitioners and government officials worry that the use of shelters is eroding confidence in the tax system. Although the majority of courts have not adopted textualism, the legal community\u27s acceptance of textualism as a plausible method of interpretation has dramatically affected the practice of tax law. Taxpayers often invest in tax shelters based upon the opinion of counsel assessing the probability that the desired tax results from the transaction, if challenged, will be sustained. These opinion letters are essential to attract investors because they protect taxpayers from various penalties that otherwise might be imposed if the Service successfully challenges the transaction. Under the textualist approach, it is much easier for an attorney to write a favorable opinion for transactions that are designed to comply with the letter of the law, but not its spirit, for at least two reasons. First, the attorney is permitted to ignore, or at least downplay, any legislative history that would argue against, or undercut, the desired tax results. Second, under a textualist approach, it is arguable that various well-accepted judicial doctrines, such as the business purpose doctrine, are suspect. At the extreme, a textualist might argue that these doctrines are the product of judicial activism and either should no longer be followed, or at a minimum should not be extended into new areas of the law. Tax shelter promoters have exploited the move towards textualism by designing transactions that comply with the letter of the law, but that generate results clearly never contemplated by Congress or the Treasury. Some promoters believe that the more detailed and complex the underlying law is, the more likely it is that a transaction complying with the letter of the law will be respected. One area in tax law that is particularly detailed and complex is Subchapter K, the partnership tax provisions. Subchapter K also has several special rules not otherwise available in the Internal Revenue Code. It is, therefore, not surprising that Subchapter K has become the vehicle of choice for a wide variety of abusive transactions. Transactions are designed so that a partnership is created or joined just to take advantage of these special rules (reverse engineered transactions). In an attempt to stem the tide, the IRS adopted a general anti-abuse rule for Subchapter K. This rule requires that the provisions of Subchapter K be interpreted consistent with the intent of subchapter K. Oversimplified, the regulations assert that there is an overall legislative intent underlying Subchapter K, and if a partnership is formed or availed of in connection with a transaction to substantially reduce federal taxes in a manner inconsistent with this intent, the transaction may be recast. The regulations make clear that for a transaction to pass muster, doctrines that originated with the judiciary, i.e., the requirements of a business purpose, economic substance, and substance over form, must be taken into account. In addition, the regulations require that the purposivist method of statutory interpretation be used to interpret Subchapter K. The anti-abuse regulations caused an unprecedented furor within the tax bar. They have been severely criticized by academics and practitioners alike on a variety of bases, the most damning of which is that Treasury lacked the authority to promulgate the rules and that therefore they are not valid. Indeed, it is fair to say that there is a general consensus that the partnership anti-abuse regulations are an extreme example of administrative overreaching. We disagree. Although we do not endorse all the policy choices in the anti-abuse regulations, we believe that they are not only valid, but suggest a way in which transactions that are the product of reverse engineering can and should be attacked, both within and without Subchapter K. Initially, it may seem inappropriate for Treasury to instruct the judiciary on how and when the courts should apply judicial doctrines and what tools they should use in interpreting statutes. After all, as every law student knows, [i]t is emphatically the province and duty of the judicial department to say what the law is. Marbury v. Madison, 5 U.S. 137, 177 (1803). Where does Treasury get the authority to instruct a court as to which method of interpretation it should use to interpret a tax statute? On reflection, however, we believe that Treasury acted well within its authority under Chevron, U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984) and was simply filling a gap in the statute left by Congress. The judicial doctrines that are implicit in the intent of subchapter K were well-developed when Subchapter K was first enacted in 1954 and continue to be applied in a variety of contexts by the courts. At that time, however, it was not clear exactly how and when these doctrines should be applied in the context of Subchapter K. There is little doubt Congress could have clarified this issue by statute. It could have insisted that these doctrines (or variations thereof) be applied with full force, or it could have forbidden their application altogether. Congress, however, chose not to address this issue, leaving a gap in the statute. Under current administrative law principles, this silence constitutes an implied delegation of authority by Congress to Treasury to fill that gap. In addition to being valid, we also believe that, as a general proposition, it is sound tax policy to use broad standards to administer the tax law. Historically this had been accomplished by the courts through the use of these judicial doctrines. Although the ascendancy of textualism cast doubt on the continuing viability of the doctrines, Treasury eliminated that doubt by promulgating these regulations (if valid), and requiring lawyers and courts to consider the intent of subchapter K. This approach allows the IRS to use broad standards to administer the tax law in place of a collection of narrow rules that must be constantly changed in a hopeless attempt to keep pace with the latest tax gimmick. To assure proper consideration of these doctrines by tax advisors, we recommend that the IRS amend its standards for practice to require advisors opining on the validity of tax shelters to apply the doctrines to the specific facts of the tax shelter in their opinion letter

    System remotely inspects, measures, and records internal irregularities in piping

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    Video electromechanical probe visually inspects and measures internal offset and peaking of welds in relatively large piping. Irregularity dimensions are recorded on peripheral equipment consisting of video tape and X-Y plotter. The probe is used for inspection of vacuum-jacketed liquid lines that cannot be inspected externally

    Between Treewidth and Clique-width

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    Many hard graph problems can be solved efficiently when restricted to graphs of bounded treewidth, and more generally to graphs of bounded clique-width. But there is a price to be paid for this generality, exemplified by the four problems MaxCut, Graph Coloring, Hamiltonian Cycle and Edge Dominating Set that are all FPT parameterized by treewidth but none of which can be FPT parameterized by clique-width unless FPT = W[1], as shown by Fomin et al [7, 8]. We therefore seek a structural graph parameter that shares some of the generality of clique-width without paying this price. Based on splits, branch decompositions and the work of Vatshelle [18] on Maximum Matching-width, we consider the graph parameter sm-width which lies between treewidth and clique-width. Some graph classes of unbounded treewidth, like distance-hereditary graphs, have bounded sm-width. We show that MaxCut, Graph Coloring, Hamiltonian Cycle and Edge Dominating Set are all FPT parameterized by sm-width
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