Wildfire Promotes Dominance of Invasive Giant Reed (Arundo donax) in Riparian Ecosystems

Widespread invasion of riparian ecosystems by the large bamboo-like grass Arundo donax L. has altered community structure and ecological function of streams in California. This study evaluated the influence of wildfire on A. donax invasion by investigating its relative rate of reestablishment versus native riparian species after wildfire burned 300 ha of riparian woodlands along the Santa Clara River in southern California in October 2003. Post-fire A. donax growth rates and productivity were compared to those of native woody riparian species in plots established before and after the fire. Arundo donax resprouted within days after the fire and exhibited higher growth rates and productivity compared to native riparian plants. Arundo donax grew 3–4 times faster than native woody riparian plants—up to a mean of 2.62 cm day−1—and reached up to 2.3 m in height less than 3 months after the fire. One year post-fire, A. donax density was nearly 20 times higher and productivity was 14–24 times higher than for native woody species. Three mechanisms—fire-adapted phenology, high growth rate, and growth response to nutrient enrichment—appear to promote the preemption of native woody riparian species by A. donax after fire. This greater dominance of A. donax after wildfire increased the susceptibility of riparian woodlands along the Santa Clara River to subsequent fire, potentially creating an invasive plant-fire regime cycle. Moreover, A. donax infestations appear to have allowed the wildfire to cross the broad bed of the Santa Clara River from the north, allowing thousands of acres of shrubland to the south to burn

Rare Kaon Decays

The current status of rare kaon decay experiments is reviewed. New limits in the search for Lepton Flavor Violation are discussed, as are new measurements of the CKM matrix.Comment: 8 pages, 3 figures, LaTeX, presented at the 3rd International Conference on B Phyiscs and CP Violation, Taipei December 3-7, 199

Finite-size scaling in thin Fe/Ir(100) layers

The critical temperature of thin Fe layers on Ir(100) is measured through M\"o{\ss}bauer spectroscopy as a function of the layer thickness. From a phenomenological finite-size scaling analysis, we find an effective shift exponent lambda = 3.15 +/- 0.15, which is twice as large as the value expected from the conventional finite-size scaling prediction lambda=1/nu, where nu is the correlation length critical exponent. Taking corrections to finite-size scaling into account, we derive the effective shift exponent lambda=(1+2\Delta_1)/nu, where Delta_1 describes the leading corrections to scaling. For the 3D Heisenberg universality class, this leads to lambda = 3.0 +/- 0.1, in agreement with the experimental data. Earlier data by Ambrose and Chien on the effective shift exponent in CoO films are also explained.Comment: Latex, 4 pages, with 2 figures, to appear in Phys. Rev. Lett

New radioiodinated methyl-branched fatty acids for cardiac studies

The effects of 3-methyl-substitution on the heart retention and metabolism of 3-R,S-methyl-(BMIPP) and 3,3-dimethyl-(DMIPP) analogues of 15-(p-iodophenyl)-pentadecanoic acid (IPP) have been studied in rats. Methyl-substitution considerably increased the myocardial half-time values in fasted rats: IPP, 5 to 10 min; BMIPP, 30 to 45 min; DMIPP, 6 to 7 h. Because of the observed differences in the relative myocardial uptake and retention of these agents, an evaluation of the subcellular distribution profiles and the distribution of radioactivity within various lipid pools extracted from cell components was performed. Studies with DMIPP in fasted rats have shown high levels of the free fatty acid and only slow conversion to triglycerides. These data are in contrast to the rapid clearance of the straight chain IPP analogue and rapid incorporation into triglycerides. These data suggest that the prolonged myocardial retention observed with DMIPP in vivo may result from inhibition of US -oxidation. Subcellular distribution studies have shown predominate association of DMIPP and BMIPP with the mitochondrial and microsomal fractions, while IPP was primarily found in the cytoplasm. Because of the unique ''trapping'' properties and the high heart:blood ratios, ( STI)DMIPP should be useful for evaluation of aberrations in regional myocardial uptake. 7 refs., 9 figs., 1 tab

Nuclear medicine program. Progress report for quarter ending June 30, 1995

In this report we describe the first synthesis of the (-)(-) and (-)(+) isomers of 1-azabicyclo oct-3-yl {alpha}-(1-fluoropent-5-yl)-{alpha}-hydroxy-{alpha}-phenylacetate ({open_quotes}FQNPe{close_quotes}). Earlier studies with the racemic FQNPe mixture had demonstrated high in vitro binding affinity for the muscarinic-cholinergic receptor and showed that pre-treatment of rats with this new agent significantly blocked receptor localization of subsequently injected -Z-(-,-)-IQNP. Because of the potential important use of fluorine-18-labeled analogues for clinical evaluation of changes in muscarinic-cholinergic receptors by positron emission tomography (PET), we have now synthesized the diastereomeric isomers of FQNPe. Multi-gram quantities of ethyl-{alpha}- (1-chloropent-5-yl)-{alpha}-hydroxy-{alpha}-phenylacetate were prepared and then saponified into the racemic {alpha}-(1-chloropent-5-yl)-{alpha}-hydroxy-{alpha}-phenylacetic acid mixture. The racemic acid was resolved into (-)- and (+)-{alpha}-(1-chloropent-5-yl)-{alpha}-hydroxy-{alpha}-phenylacetic acid enantiomers by isolation of the (-) salt of (S-)-(-)-{alpha}-methylbenzylamine and the (+) salt of (R)-(+)-{alpha}-methylbenzylamine. The resolved (-)- ([{alpha}]{sub D} = -12.1{degrees}, c = 5.8, chloroform) and (+)-acetic acids ([{alpha}]{sub D} = + 11.6{degrees}, c = 6.0, chloroform) were fully characterized and then converted to the enantiomeric ethyl-{alpha}-(1-fluoropent-5-yl)-{alpha}-hydroxy-{alpha}-phenylacetates by a four-step reaction sequence. The (-)- and (+)-ethyl-{alpha}-(1-fluoropent-5-yl)-{alpha}-hydroxy-{alpha}-phenylacetates were then each transesterified with (-)-quinuclidinol to form the (-)(-) FQNPe and (-)(+) FQNPe diastereomers. These diastereomeric esters will now be evaluated in in vitro studies. The availability of the substrates for preparation of the fluorine-18-labeled enantiomers will now allow evaluation of the radiolabeled compounds in animals

The Design and Validation of the Quantum Mechanics Conceptual Survey

The Quantum Mechanics Conceptual Survey (QMCS) is a 12-question survey of students' conceptual understanding of quantum mechanics. It is intended to be used to measure the relative effectiveness of different instructional methods in modern physics courses. In this paper we describe the design and validation of the survey, a process that included observations of students, a review of previous literature and textbooks and syllabi, faculty and student interviews, and statistical analysis. We also discuss issues in the development of specific questions, which may be useful both for instructors who wish to use the QMCS in their classes and for researchers who wish to conduct further research of student understanding of quantum mechanics. The QMCS has been most thoroughly tested in, and is most appropriate for assessment of (as a posttest only), sophomore-level modern physics courses. We also describe testing with students in junior quantum courses and graduate quantum courses, from which we conclude that the QMCS may be appropriate for assessing junior quantum courses, but is not appropriate for assessing graduate courses. One surprising result of our faculty interviews is a lack of faculty consensus on what topics should be taught in modern physics, which has made designing a test that is valued by a majority of physics faculty more difficult than expected.Comment: Submitted to Physical Review Special Topics: Physics Education Researc

Gene flow between island populations of the malaria mosquito, Anopheles hinesorum, may have contributed to the spread of divergent host preference phenotypes

Anopheles hinesorum is a mosquito species with variable host preference. Throughout New Guinea and northern Australia, An. hinesorum feeds on humans (it is opportunistically anthropophagic) while in the south-west Pacific's Solomon Archipelago, the species is abundant but has rarely been found biting humans (it is exclusively zoophagic in most populations). There are at least two divergent zoophagic (nonhuman biting) mitochondrial lineages of An. hinesorum in the Solomon Archipelago representing two independent dispersals. Since zoophagy is a derived (nonancestral) trait in this species, this leads to the question: has zoophagy evolved independently in these two populations? Or conversely: has nuclear gene flow or connectivity resulted in the transfer of zoophagy? Although we cannot conclusively answer this, we find close nuclear relationships between Solomon Archipelago populations indicating that recent nuclear gene flow has occurred between zoophagic populations from the divergent mitochondrial lineages. Recent work on isolated islands of the Western Province (Solomon Archipelago) has also revealed an anomalous, anthropophagic island population of An. hinesorum. We find a common shared mitochondrial haplotype between this Solomon Island population and another anthropophagic population from New Guinea. This finding suggests that there has been recent migration from New Guinea into the only known anthropophagic population from the Solomon Islands. Although currently localized to a few islands in the Western Province of the Solomon Archipelago, if anthropophagy presents a selective advantage, we may see An. hinesorum emerge as a new malaria vector in a region that is now working on malaria elimination

Artificial reefs: from ecological processes to fishing enhancement tools

info:eu-repo/semantics/publishedVersio

Phase transitions for suspension flows

This paper is devoted to study thermodynamic formalism for suspension flows defined over countable alphabets. We are mostly interested in the regularity properties of the pressure function. We establish conditions for the pressure function to be real analytic or to exhibit a phase transition. We also construct an example of a potential for which the pressure has countably many phase transitions.Comment: Example 5.2 expanded. Typos corrected. Section 6.1 superced the note "Thermodynamic formalism for the positive geodesic flow on the modular surface" arXiv:1009.462

Nuclear medicine program progress report for quarter ending September 30, 1996

The reactor production yields of tungsten-188 produced by neutron capture by enriched tungsten-186 in the HFIR and other reactors are nearly an order of magnitude lower than expected by calculation using established cross section values. Since neutron capture of tungsten-188 may be the major factor which significantly reduces the observed yields of tungsten-188, the authors have evaluated the possible burn-up cross section of the tungsten-188 product. Tungsten-189 was produced by irradiating a radioactive target containing a known amount of {sup 188}W. In order to reduce the radiation level to an acceptable level (90% of {sup 188}Re, which is the decay product of {sup 188}W, prior to irradiation. They were able to confirm the two predominant {gamma}-rays in the decay of {sup 189}W, 260.1 {+-} 1.4 and 421.5 {+-} 1.6 keV. By following the decay of these {gamma}-rays in two sets of experiments, a half-life of 10.8 {+-} 0.3 m was obtained for {sup 189}W. Based on a knowledge of the {sup 188}W content of target (52.6 mBq), neutron flux of 5 {times} 10{sup 13} n {center_dot} s{sup {minus}1} {center_dot} cm{sup {minus}2}, irradiation time of 10 min and with the assumption of 100% intensity for 260.1 and 421.5 keV {gamma}-rays, a cross-section of 12.0 {+-} 2.5 b was calculated for burn-up cross-section of {sup 188}W, which helps explain the greatly reduced production yields of {sup 188}W