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Sample records for alder flycatcher empidonax

  1. Habitat and sex differences in physiological condition of breeding Southwestern Willow Flycatchers (Empidonax traillii extimus)

    USGS Publications Warehouse

    Owen, J.C.; Sogge, M.K.; Kern, M.D.

    2005-01-01

    The Southwestern Willow Flycatcher (Empidonax traillii extimus; hereafter "flycatcher") is a federally listed endangered species that breeds in densely vegetated riparian habitats dominated by native and exotic plants, including introduced monotypic saltcedar (Tamarix ramosissima). Some workers have theorized that saltcedar is unsuitable habitat for the flycatcher, primarily because it generally supports a smaller and less diverse invertebrate community (the flycatcher's food base) than native habitats (e.g. Salix spp.). However, differences in insect communities between native and saltcedar habitats are not proof that saltcedar habitats are inferior. The only way to evaluate whether the habitats differ in dietary or energetic quality is to document actual food limitation or its manifestations. Measurements of an individual's body condition and metabolic state can serve as indicators of environmental stressors, such as food limitation and environmental extremes. We captured 130 flycatchers breeding in native and saltcedar habitats in Arizona and New Mexico and measured 12 variables of physiological condition. These variables included body mass, fat level, body condition index, hematocrit, plasma triglycerides, plasma free fatty acids and glycerol, plasma glucose and beta-hydroxybutyrate, plasma uric acid, total leukocyte count, and heterophil-to-lymphocyte ratio. We found substantial sex-based differences in the condition of male and female flycatchers. Ten of the 12 measures of physiological condition differed significantly between the sexes. In all cases where male and female condition differed (except mass), the differences suggest that males were in poorer condition than females. We found few habitat-based differences in flycatcher condition. Only 3 of the 12 physiological condition indices differed significantly between habitats. Our data show that, at least in some parts of the flycatcher's range, there is no evidence that flycatchers breeding in saltcedar

  2. A survey protocol for the Southwestern Willow Flycatcher (Empidonax traillii extimus)

    USGS Publications Warehouse

    Tibbitts, Timothy J.; Sogge, Mark K.; Sferra, Susan J.

    1994-01-01

    The southwestern willow flycatcher (Empidonax traillii extimus) is a riparian obligate neotropical migrant, nesting in cottonwood-willow associations and structurally similar riparian vegetation associations. The southwestern willow flycatcher has declined through the twentieth century, primarily due to a number of factors, including loss and fragmentation of riparian habitat, brood parasitism by brown-headed cowbirds (Molothrus ater), invasion of riparian habitat by the exotic tamarisk (Tamarix sp.), and predation (Hunter et al. 1987), Unitt 1987, Hunter et al. 1988, Whitfield 1990, Harris 1991, Rosenberg et al. 1991). In 1991 the U.S. Fish and Wildlife Service (USFWS) designated the southwestern willow flycatcher as a candidate category 1 species (USFWS 1991), indicating that the USFWS had sufficient information to support listing under the Endangered Species Act of 1973, as amended (Act), but that a proposal to list was precluded by other listing actions of higher priority. In July 1993, the USFWS proposed to list E. t. extimus as an endangered species and to designate critical habitat under the Act (USFWS 1993). The states of Arizona, New Mexico, and California comprise most of the southwestern willow flycatcher's historic and current range. Each of these states lists the species as endangered [Arizona Game and Fish Department (AGFD) 1988, New Mexico Department of Game and Fish (NMDGF) 1988, California Department of Game and Fish 1991]. Because of the precarious status of the southwestern willow flycatcher (Unitt 1987, USFWS 1993), there is a need to identify as many remaining breeding locations as possible. This survey protocol was developed to facilitate and standardize breeding surveys, and is based primarily on extensive 1992 and 1993 field surveys. It was developed at the request of the Arizona Partners in flight, and organization of Federal and State agencies, nongovernmental organizations, and individuals. This protocol is intended to be useful

  3. Geographic variation in the plumage coloration of willow flycatchers Empidonax traillii

    USGS Publications Warehouse

    Paxton, Eben H.; Sogge, Mark K.; Koronkiewicz, Thomas J.; McLeod, Mary Anne; Theimer, Tad C.

    2010-01-01

    The ability to identify distinct taxonomic groups of birds (species, subspecies, geographic races) can advance ecological research efforts by determining connectivity between the non-breeding and breeding grounds for migrant species, identifying the origin of migrants, and helping to refine boundaries between subspecies or geographic races. Multiple methods are available to identify taxonomic groups (e.g., morphology, genetics), and one that has played an important role for avian taxonomists over the years is plumage coloration. With the advent of electronic devices that can quickly and accurately quantify plumage coloration, the potential of using coloration as an identifier for distinct taxonomic groups, even when differences are subtle, becomes possible. In this study, we evaluated the degree to which plumage coloration differs among the four subspecies of the willow flycatcher Empidonax traillii, evaluated sources of variation, and considered the utility of plumage coloration to assign subspecies membership for individuals of unknown origin. We used a colorimeter to measure plumage coloration of 374 adult willow flycatchers from 29 locations across their breeding range in 2004 and 2005. We found strong statistical differences among the mean plumage coloration values of the four subspecies; however, while individuals tended to group around their respective subspecies' mean color value, the dispersion of individuals around such means overlapped. Mean color values for each breeding site of the three western subspecies clustered together, but the eastern subspecies' color values were dispersed among the other subspecies, rather than distinctly clustered. Additionally, sites along boundaries showed evidence of intergradation and intermediate coloration patterns. We evaluated the predictive power of colorimeter measurements on flycatchers by constructing a canonical discriminant model to predict subspecies origin of migrants passing through the southwestern U

  4. Preliminary Risk Assessment of the Southwestern Willow Flycatcher (Empidonax traillii extimus) at the Los Alamos National Laboratory

    SciTech Connect

    Gallegos, A.F.; Gonzales, G.J.; Bennett, K.D.; Mullen, M.A.; Foxx, T.S.

    1998-10-01

    The southwestern willow flycatcher (Empidonax traillii extimus) is the fourth threatened or endangered species to undergo a preliminary assessment for estimating potential risk from environmental contaminants at the Los Alamos National Laboratory. The assessments are being conducted as part of a three-year project to develop a habitat management plan for threatened and endangered species and species of concern at the Laboratory. For the preliminary assessment, estimated doses were compared against toxicity reference values to generate hazard indices (HIs). This assessment included a measure of cumulative effects from multiple contaminants (radionuclides, metals, and organic chemicals) to 100 simulated nest sites located within flycatcher potential habitat. Sources of contaminant values were 10,000-ft{sup 2} grid cells within an Ecological Exposure Unit (EEU). This EEU was estimated around the potential habitat and was based on the maximum home range for the fly catcher identified in the scientific literature. The tools used included a custom FORTRAN program, ECORSK5, and a geographic information system. Food consumption and soil ingestion contaminant pathways were addressed in the assessment. Using a four-category risk evaluation, HI results indicate no appreciable impact is expected to the southwestern willow flycatcher. Information on risk by specific geographical location was generated, which can be used to manage contaminated areas, flycatcher habitat, facility siting, and/or facility operations in order to maintain low levels of risk from contaminants.

  5. The role of ecologic diversification in sibling speciation of Empidonax flycatchers (Tyrannidae): multigene evidence from mtDNA.

    PubMed

    Johnson, N K; Cicero, C

    2002-10-01

    Avian genera characterized by sibling species with distinctive habitat preferences present an evolutionary enigma in view of the more commonplace occurrence of syntopic congeners that differ strikingly in colour and pattern. No existing theory has explained the evolutionary background that led to these differences. Here we propose that great phenotypic similarity among some groups of sibling species limits their coexistence and that clues to their radiation can be seen in patterns of geographical occurrence. To illustrate our thesis we focused on the New World flycatcher genus Empidonax, a group of 15 species notorious for their great phenotypic similarity. Using 3069 base pairs of mitochondrial DNA from four genes, we produced a complete molecular phylogeny that identified four clades, three of which represent close relatives. The fourth clade includes only E. virescens, which apparently has no close living relatives. The majority of species, including many distant relatives, are completely (58.1%) or essentially (6.7%) allopatric in breeding distribution and exhibit striking ecological segregation into distinctive climate-vegetation zones. Even where ranges overlap, occupancy of the same habitat by different species is rare. Phylogenetic and distributional patterns in Empidonax suggest a peripatric model of stepwise colonization and then range expansion of small groups of pioneers during glacial periods into initially enlarging, distinctive habitats destined to be widespread during interglacials. Vicariance is not indicated in the absence of barriers of appropriate age and geographical position. Rapoport's rule that northern species have larger ranges than southern species is strongly supported. PMID:12296949

  6. A satellite model of Southwestern Willow Flycatcher (Empidonax traillii extimus) breeding habitat and a simulation of potential effects of tamarisk leaf beetles (Diorhabda spp.), southwestern United States

    USGS Publications Warehouse

    Hatten, James R.

    2016-01-01

    The study described in this report represents the first time that a satellite model has been used to identify potential Southwestern Willow Flycatcher (Empidonax traillii extimus) (hereinafter referred to as “flycatcher”) breeding habitat rangewide for 2013–15. Fifty-seven Landsat scenes were required to map the entire range of the flycatcher, encompassing parts of six States and more than 1 billion 30-meter pixels. Predicted flycatcher habitat was summarized in a hierarchical fashion from largest to smallest: regionwide, State, U.S. Fish and Wildlife Service (FWS) management unit, 7.5-minute quadrangle, and critical-habitat reach. The term “predicted habitat” is used throughout this report to distinguish areas the satellite model predicts as suitable flycatcher habitat from what may actually exist on the ground. A rangewide accuracy assessment was done with 758 territories collected in 2014, and change detection was done with yearly habitat maps to identify how and where habitat changed over time. Additionally, effects of tamarisk leaf beetles (Diorhabda spp.) on flycatcher habitat were summarized for the lower Virgin River from 2010 to 2015, and simulations of how tamarisk leaf beetles may affect flycatcher habitat in the lower Colorado and upper Gila Rivers were done for 2015. Model results indicated that the largest areas of predicted flycatcher habitat at elevations below 1,524 meters were in New Mexico and Arizona, areas followed in descending order by California, Texas, Nevada, Utah, and Colorado. By FWS management unit, the largest area of flycatcher habitat during all 3 years were the Middle Rio Grande (New Mexico), followed by the Upper Gila (Arizona and New Mexico) and Middle Gila/San Pedro (Arizona) management units. The area of predicted flycatcher habitat varied considerably in 7.5-minute quadrangles, ranging from 0 to1,398 hectares (ha). Averaged across 3 years, the top three producing quadrangles were Paraje Well (New Mexico), San Marcial

  7. A high incidence of brown-headed cowbird parasitism of willow flycatchers

    USGS Publications Warehouse

    Sedgwick, James A.; Knopf, Fritz L.

    1988-01-01

    Brown-headed Cowbirds (Molothrus ater) parasitize both Willow (Empidonax traillii) and Alder (E. alnorum) flycatchers (Friedmann et al. 1977, Friedmann and Kiff 1985). These two flycatchers were considered a single species until 1973 (AOU 1973), which has masked information about the frequency with which each is parasitized. Whereas several studies of the superspecies (Traill's Flycatcher) have focused on or included details of cowbird parasitism, most were of eastern populations, and most reported frequencies of parasitism ≤21% (Hicks 1934, Berger 1951, Berger and Parmalee 1952, Walkinshaw 1966, Holcomb 1972). Friedmann et al. (1977:13) suggested that western populations (Willow Flycatchers) are parasitized only about half as much (ca. 10%) as eastern populations (Traill's Flycatcher superspecies). This note described a high rate of cowbird parasitism within a population of Willow Flycatchers in northcentral Colorado. We include details of responses to parasitism and host vs. cowbird fledgling success.

  8. Regionwide polygyny in willow flycatchers

    USGS Publications Warehouse

    Sedgwick, James A.; Knopf, Fritz L.

    1989-01-01

    Most species of North American flycatchers (Tyranidae) are believed to be normally monogamous (Skutch 1960, Verner and Willson 1969). Some instances of bigamy are known for the Eastern Phoebe (Sayornis phoebe; Sherman 1952), Eastern Wood-Pewee (Contopus virens; W. J. Smith, cited in Eckhardt 1976), Western Wood-Pewee (C. sordidulus; Eckhardt 1976), and Acadian Flycatcher (Empidonax viriscens; Mumford 1964). Recently, local incidences of polygyny have also been reported for the Least (E. minimus; Briskie and Sealy 1987) and Willow (E. traillii; Prescott 1986) flycatchers. Here, we present details on two additional instances of polygyny in Willow Flycatchers in different regions of North America, including information on the behavior and nesting ecology of polygynous trios.

  9. Primary song by a juvenile willow flycatcher

    USGS Publications Warehouse

    Sogge, M.K.

    1997-01-01

    The timing of song development in suboscines, in which song appears not to be learned from other adults is poorly known. The Willow Flycatcher (Empidonax traillii) is a suboscine with a primary song typically referred to as fitz-bew. I report here an instance of very early singing by a 6-8-wk-old Willow Flycatcher, which sang in an aggressive context in response to a recording of adult flycatcher song. This is exceptionally early development of primary song, even among suboscines. Early song development may assist in the defense of winter territories.

  10. Southwestern Willow Flycatcher Breeding Site and Territory Summary - 2006

    USGS Publications Warehouse

    Durst, Scott L.; Sogge, Mark K.; Stump, Shay D.; Williams, Sartor O.; Kus, Barbara E.; Sferra, Susan J.

    2007-01-01

    Introduction The Southwestern Willow Flycatcher (Empidonax traillii extimus) is an endangered bird that breeds only in dense riparian habitats in six southwestern states (southern California, extreme southern Nevada, southern Utah, southwestern Colorado, Arizona, and New Mexico). Since 1993, hundreds of Southwestern Willow Flycatcher surveys have been conducted each year, and many new flycatcher breeding sites located. This document synthesizes information on all known Southwestern Willow Flycatcher breeding sites. This rangewide data synthesis was designed to meet these objectives: * identify all known Southwestern Willow Flycatcher breeding sites, and * assemble data on population size, location, habitat, and other information for all breeding sites, for as many years as possible, from 1993 through 2006. This report provides data summaries in terms of the number of flycatcher sites and the number of territories.

  11. Sex determination of the Acadian Flycatcher using discriminant analysis

    USGS Publications Warehouse

    Wilson, R.R.

    1999-01-01

    I used five morphometric variables from 114 individuals captured in Arkansas to develop a discriminant model to predict the sex of Acadian Flycatchers (Empidonax virescens). Stepwise discriminant function analyses selected wing chord and tail length as the most parsimonious subset of variables for discriminating sex. This two-variable model correctly classified 80% of females and 97% of males used to develop the model. Validation of the model using 19 individuals from Louisiana and Virginia resulted in 100% correct classification of males and females. This model provides criteria for sexing monomorphic Acadian Flycatchers during the breeding season and possibly during the winter.

  12. Willow Flycatcher nonbreeding territory defense behavior in Costa Rica

    USGS Publications Warehouse

    Sogge, M.K.; Koronkiewicz, T.J.; van Riper, Charles, III; Durst, S.L.

    2007-01-01

    We studied the intraspecific territorial defense behavior of wintering Willow Flycatchers (Empidonax traillii) in Costa Rica using a randomized playback experiment that exposed male and female birds to recordings of Willow Flycatcher songs and calls, Lesser Ground Cuckoo (Morococcyx erythropygius) vocalizations, and random noise. Flycatchers of both sexes responded most strongly to simulated conspecific territory intrusion, and the agonistic behaviors that we observed were similar to those seen during natural intraspecific encounters in winter. Both males and females engaged in song and aggressive behaviors in defense of territories, and there was no significant difference between the sexes in scored agonistic responses. The similarity between the sexes in intraspecific territorial defense behaviors and aggressiveness may account for both sexes of flycatchers using the same habitats at our study sites in Costa Rica, and wintering females defending territories against males. The Willow Flycatcher, a sexually monomorphic species, differs in this way from a number of sexually dimorphic passerines, in which behaviorally dominant males occur in more optimal winter habitats. ?? The Cooper Ornithological Society 2007.

  13. Nestling sex ratio in the Southwestern Willow Flycatcher

    USGS Publications Warehouse

    Paxton, E.H.; Sogge, M.K.; McCarthey, T.D.; Keim, P.

    2002-01-01

    Using molecular-genetic techniques, we determined the gender of 202 Southwestern Willow Flycatcher (Empidonax traillii extimus) nestlings from 95 nests sampled over a five-year period. Overall nestling sex ratio did not vary significantly from 50:50 among years, by clutch order, or by mating strategy (monogamous vs. polygamous pairings). However, we did observe significant differences among the four sites sampled, with sex ratios biased either toward males or females at the different sites. Given the small population sizes and geographic isolation of many of the endangered subspecies' breeding populations, sex-ratio differences may have localized negative impacts. ?? The Cooper Ornithological Society 2002.

  14. Nestling sex ratios in the southwestern willow flycatcher

    USGS Publications Warehouse

    Paxton, E.H.; Sogge, M.K.; McCarthey, Tracy; Keim, Paul

    2002-01-01

    Using molecular-genetic techniques, we determined the gender of 202 Southwestern Willow Flycatcher (Empidonax traillii extimus) nestlings from 95 nests sampled over a five-year period. Overall nestling sex ratio did not vary significantly from 50:50 among years, by clutch order, or by mating strategy (monogamous vs. polygamous pairings). However, we did observe significant differences among the four sites sampled, with sex ratios biased either toward males or females at the different sites. Given the small population sizes and geographic isolation of many of the endangered subspecies' breeding populations, sex-ratio differences may have localized negative impacts.

  15. Available data support protection of the Southwestern Willow Flycatcher under the Endangered Species Act

    USGS Publications Warehouse

    Theimer, Tad C.; Smith, Aaron D.; Mahoney, Sean M.; Ironside, Kirsten E.

    2016-01-01

    Zink (2015) argued there was no evidence for genetic, morphological, or ecological differentiation between the federally endangered Southwestern Willow Flycatcher (Empidonax traillii extimus) and other Willow Flycatcher subspecies. Using the same data, we show there is a step-cline in both the frequency of a mtDNA haplotype and in plumage variation roughly concordant with the currently recognized boundary between E. t. extimus and E. t adastus, the subspecies with which it shares the longest common boundary. The geographical pattern of plumage variation is also concordant with previous song analyses differentiating those 2 subspecies and identified birds in one low-latitude, high-elevation site in Arizona as the northern subspecies. We also demonstrate that the ecological niche modeling approach used by Zink yields the same result whether applied to the 2 flycatcher subspecies or to 2 unrelated species, E. t. extimus and Yellow Warbler (Setophaga petechia). As a result, any interpretation of those results as evidence for lack of ecological niche differentiation among Willow Flycatcher subspecies would also indicate no differentiation among recognized species and would therefore be an inappropriate standard for delineating subspecies. We agree that many analytical techniques now available to examine genetic, morphological, and ecological differentiation would improve our understanding of the distinctness (or lack thereof) of Willow Flycatcher subspecies, but we argue that currently available evidence supports protection of the Southwestern Willow Flycatcher under the Endangered Species Act.

  16. Elucidating spatially explicit behavioral landscapes in the Willow Flycatcher

    USGS Publications Warehouse

    Bakian, Amanda V.; Sullivan, Kimberly A.; Paxton, Eben H.

    2012-01-01

    Animal resource selection is a complex, hierarchical decision-making process, yet resource selection studies often focus on the presence and absence of an animal rather than the animal's behavior at resource use locations. In this study, we investigate foraging and vocalization resource selection in a population of Willow Flycatchers, Empidonax traillii adastus, using Bayesian spatial generalized linear models. These models produce “behavioral landscapes” in which space use and resource selection is linked through behavior. Radio telemetry locations were collected from 35 adult Willow Flycatchers (n = 14 males, n = 13 females, and n = 8 unknown sex) over the 2003 and 2004 breeding seasons at Fish Creek, Utah. Results from the 2-stage modeling approach showed that habitat type, perch position, and distance from the arithmetic mean of the home range (in males) or nest site (in females) were important factors influencing foraging and vocalization resource selection. Parameter estimates from the individual-level models indicated high intraspecific variation in the use of the various habitat types and perch heights for foraging and vocalization. On the population level, Willow Flycatchers selected riparian habitat over other habitat types for vocalizing but used multiple habitat types for foraging including mountain shrub, young riparian, and upland forest. Mapping of observed and predicted foraging and vocalization resource selection indicated that the behavior often occurred in disparate areas of the home range. This suggests that multiple core areas may exist in the home ranges of individual flycatchers, and demonstrates that the behavioral landscape modeling approach can be applied to identify spatially and behaviorally distinct core areas. The behavioral landscape approach is applicable to a wide range of animal taxa and can be used to improve our understanding of the spatial context of behavior and resource selection.

  17. Describing Willow Flycatcher habitats: scale perspectives and gender differences

    USGS Publications Warehouse

    Sedgwick, James A.; Knopf, Fritz L.

    1992-01-01

    We compared habitat characteristics of nest sites (female-selected sites) and song perch sites (male-selected sites) with those of sites unused by Willow Flycatchers (Empidonax traillii) at three different scales of vegetation measurement: (1) microplot (central willow [Salix spp.] bush and four adjacent bushes); (2) mesoplot (0.07 ha); and, (3) macroplot (flycatcher territory size). Willow Flycatchers exhibited vegetation preferences at all three scales. Nest sites were distinguished by high willow density and low variability in willow patch size and bush height. Song perch sites were characterized by large central shrubs, low central shrub vigor, and high variability in shrub size. Unused sites were characterized by greater distances between willows and willow patches, less willow coverage, and a smaller riparian zone width than either nest or song perch sites. At all scales, nest sites were situated farther from unused sites in multivariate habitat space than were song perch sites, suggesting (1) a correspondence among scales in their ability to describe Willow Flycatcher habitat, and (2) females are more discriminating in habitat selection than males. Microhabitat differences between male-selected (song perch) and female-selected (nest) sites were evident at the two smaller scales; at the finest scale, the segregation in habitat space between male-selected and female-selected sites was greater than that between male-selected and unused sites. Differences between song perch and nest sites were not apparent at the scale of flycatcher territory size, possibly due to inclusion of (1) both nest and song perch sites, (2) defended, but unused habitat, and/or (3) habitat outside of the territory, in larger scale analyses. The differences between nest and song perch sites at the finer scales reflect their different functions (e.g., nest concealment and microclimatic requirements vs. advertising and territorial defense, respectively), and suggest that the exclusive use

  18. Vocal frequency change reflects different responses to anthropogenic noise in two suboscine tyrant flycatchers

    PubMed Central

    Francis, Clinton D.; Ortega, Catherine P.; Cruz, Alexander

    2011-01-01

    Anthropogenic noise is prevalent across the globe and can exclude birds from otherwise suitable habitat and negatively influence fitness; however, the mechanisms responsible for species' responses to noise are not always clear. One effect of noise is a reduction in effective acoustic communication through acoustic masking, yet some urban songbirds may compensate for masking by noise through altering their songs. Whether this vocal flexibility accounts for species persistence in noisy areas is unknown. Here, we investigated the influence of noise on habitat use and vocal frequency in two suboscine flycatchers using a natural experiment that isolated effects of noise from confounding stimuli common to urban habitats. With increased noise exposure, grey flycatcher (Empidonax wrightii) occupancy declined, but vocal frequency did not change. By contrast, ash-throated flycatcher (Myiarchus cinerascens) occupancy was uninfluenced by noise, but individuals in areas with greater noise amplitudes vocalized at a higher frequency, although the increase (≈200 kHz) may only marginally improve communication and may represent a secondary effect from increased vocal amplitude. Even so, the different flycatcher behavioural responses suggest that signal change may help some species persist in noisy areas and prompt important questions regarding which species will cope with an increasingly noisy world. PMID:21123268

  19. Acadian flycatcher nest placement: Does placement influence reproductive success?

    USGS Publications Warehouse

    Wilson, R.R.; Cooper, R.J.

    1998-01-01

    We located 511 Acadian Flycatcher (Empidonax virescens) nests in bottomland hardwood forest of eastern Arkansas. Microhabitat characteristics were measured and their relationship with nest success evaluated. Fifty-two percent of all nesting attempts resulted in predation. Attributes of nest placement were similar between successful and unsuccessful nests, although successful nests were placed higher. Similarly, nonparasitized nests were typically higher than parasitized nests. Nests initiated late in the breeding season were placed in larger trees with higher canopy bases resulting in increased vegetation around the nest. Fifteen different tree species were used for nesting. Acadian Flycatchers chose nest trees in a nonrandom fashion, selecting Nuttall oak (Quercus nuttallii) and possumhaw (Ilex decidua) in greater proportions than their availability. However, there was no relationship between tree species used for nesting and nest success. Nest height was positively correlated with concealment at the nest site, supporting the predator-avoidance theory. No other attribute of nest placement differentiated successful nest sites, suggesting that nest predation is likely a function of random events in space and time.

  20. Genetic variation in the endangered Southwestern Willow Flycatcher

    USGS Publications Warehouse

    Busch, Joseph; Miller, Mark P.; Paxton, E.H.; Sogge, M.K.; Keim, Paul

    2000-01-01

    The Southwestern Willow Flycatcher(Empidonax trailii extimus) is an endangered Neotropical migrant that breeds in isolated remnants of dense riparian habitat in the southwestern United States. We estimated genetic variation at 20 breedings sites of the Southwestern Willow Flycatcher(290 individuals) using 38 amplified fragment length polymorphisms(AFLPs). Our results suggest that considerable genetic diversity exists within the subspecies and within local breeding sites. Statistical analyses of genetic variation revealed only slight, although significant, differentiation among breeding sites( Mantel's r = 0.0705, P < 0.0005; 0 = 0.0816, 95% CI = 0.0608 to 0.1034; a??sr = 0.0458, P < 0.001). UPGMA cluster analysis of the AFLP markers indicates that extensive gene flow has occurred among breeding sites. No one site stood out as being genetically unique or isolated. Therefore the small level of genetic structure that we detected may not be biologically significant. Ongoing field studies are consistent with this conclusion. Of the banded birds that were resighted or recaptured in Arizona during the 1996 to 1998 breeding seasons, one-third moved between breeding sites and two-thirds were philopatric. Low differentiation maybe the result of historically high rangewide diversity followed by recent geographic isolation of breeding sites, although observational data indicate that gene flow is a current phenomenon. Our data suggest that breeding groups of E. t. extimus act as a metapopulation.

  1. Injury due to leg bands in willow flycatchers

    USGS Publications Warehouse

    Sedgwick, J.A.; Klus, R.J.

    1997-01-01

    We report an apparently unusually high incidence of leg injury in Willow Flycatchers (Empidonax traillii) as a result of banding and color banding. Color bands and U.S. Fish and Wildlife Service (USFWS) bands applied to Willow Flycatchers from 1988-1995 resulted in an overall leg injury rate of 9.6% to birds returning to our study areas in subsequent years. Most injuries occurred on legs with only color band(s) (58.3%) or on legs with both a USFWS band and a color band (35%); only 6.7% of injuries (4/60) were due to USFWS bands alone, yielding an overall USFWS band injury rate of only 0.6%. Injuries ranged from severe (swollen, bleeding legs; a missing foot) to relatively minor (irritations on the tarsus). Amputation of the foot occurred in 33.9% of the cases. Return rates of adult injured birds in the year(s) following injury were significantly lower than for the population at large.

  2. A habitat overlap analysis derived from maxent for tamarisk and the south-western willow flycatcher

    NASA Astrophysics Data System (ADS)

    York, Patricia; Evangelista, Paul; Kumar, Sunil; Graham, James; Flather, Curtis; Stohlgren, Thomas

    2011-06-01

    Biologic control of the introduced and invasive, woody plant tamarisk ( Tamarix spp, saltcedar) in south-western states is controversial because it affects habitat of the federally endangered South-western Willow Flycatcher ( Empidonax traillii extimus). These songbirds sometimes nest in tamarisk where floodplain-level invasion replaces native habitats. Biologic control, with the saltcedar leaf beetle ( Diorhabda elongate), began along the Virgin River, Utah, in 2006, enhancing the need for comprehensive understanding of the tamarisk-flycatcher relationship. We used maximum entropy (Maxent) modeling to separately quantify the current extent of dense tamarisk habitat (>50% cover) and the potential extent of habitat available for E. traillii extimus within the studied watersheds. We used transformations of 2008 Landsat Thematic Mapper images and a digital elevation model as environmental input variables. Maxent models performed well for the flycatcher and tamarisk with Area Under the ROC Curve (AUC) values of 0.960 and 0.982, respectively. Classification of thresholds and comparison of the two Maxent outputs indicated moderate spatial overlap between predicted suitable habitat for E. traillii extimus and predicted locations with dense tamarisk stands, where flycatcher habitat will potentially change flycatcher habitats. Dense tamarisk habitat comprised 500 km2 within the study area, of which 11.4% was also modeled as potential habitat for E. traillii extimus. Potential habitat modeled for the flycatcher constituted 190 km2, of which 30.7% also contained dense tamarisk habitat. Results showed that both native vegetation and dense tamarisk habitats exist in the study area and that most tamarisk infestations do not contain characteristics that satisfy the habitat requirements of E. traillii extimus. Based on this study, effective biologic control of Tamarix spp. may, in the short term, reduce suitable habitat available to E. traillii extimus, but also has the potential

  3. A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

    USGS Publications Warehouse

    Sogge, Mark K.; U.S. Geological Survey; Ahlers, Darrell; Bureau of Reclamation; Sferra, Susan J.; U.S. Fish and Wildlife Service

    2010-01-01

    The Southwestern Willow Flycatcher (Empidonax traillii extimus) has been the subject of substantial research, monitoring, and management activity since it was listed as an endangered species in 1995. When proposed for listing in 1993, relatively little was known about the flycatcher's natural history, and there were only 30 known breeding sites supporting an estimated 111 territories rangewide (Sogge and others, 2003a). Since that time, thousands of presence/absences surveys have been conducted throughout the historical range of the flycatcher, and many studies of its natural history and ecology have been completed. As a result, the ecology of the flycatcher is much better understood than it was just over a decade ago. In addition, we have learned that the current status of the flycatcher is better than originally thought: as of 2007, the population was estimated at approximately 1,300 territories distributed among approximately 280 breeding sites (Durst and others, 2008a). Concern about the Southwestern Willow Flycatcher on a rangewide scale was brought to focus by Unitt (1987), who described declines in flycatcher abundance and distribution throughout the Southwest. E. t. extimus populations declined during the 20th century, primarily because of habitat loss and modification from activities, such as dam construction and operation, groundwater pumping, water diversions, and flood control. In 1991, the U.S. Fish and Wildlife Service (USFWS) designated the Southwestern Willow Flycatcher as a candidate category 1 species (U.S. Fish and Wildlife Service, 1991). In July 1993, the USFWS proposed to list E. t. extimus as an endangered species and to designate critical habitat under the Act (U.S. Fish and Wildlife Service, 1993). A final rule listing E. t. extimus as endangered was published in February 1995 (U.S. Fish and Wildlife Service, 1995); critical habitat was designated in 1997 (U.S. Fish and Wildlife Service, 1997). The USFWS Service released a Recovery Plan for

  4. Risky business: Site selection by Acadian Flycatchers under threat of nest predation and brood parasitism

    USGS Publications Warehouse

    HazIer, K.R.; Cooper, R.J.; Twedt, D.J.

    2006-01-01

    Habitat quality is determined not only by habitat structure and the availability of resources, but also by competitors, cooperators, predators, and parasites. We hypothesized that, for passerines, minimizing risk from avian nest predators and brood parasites is an important factor in selecting a breeding site. Through the early part of two breeding seasons, we spot-mapped locations of Acadian Flycatchers (Empidonax virescens, territory selectors), Red-bellied Woodpeckers (Melanerpes carolinus, nest predators) and Brown-headed Cowbirds (Molothrus ater, brood parasites) in a 56-ha study area within an extensive bottomland hardwood forest. We were thereby able to determine the order of flycatcher territory settlement and nest initiation in relation to risk of predation and parasitism, while accounting for habitat structure. Male settlement was influenced by both habitat structure and risk avoidance. However, risk trom woodpeckers was relatively more important in the first season and risk from cowbirds in the second, evidently due to differences in the relative abundance of predator and brood-parasite in each year. For male flycatchers, settlement choices appear to be flexible in the face of changing 'risk landscapes.' For females, habitat structure was the most important predictor of nest site selection. Even so, there was evidence that females avoided cowbirds. Surprisingly, nest site selection was positively associated with woodpecker abundance in the first season when woodpeckers were present in greater numbers. Possible explanations for this contradictory result are discussed.

  5. Territoriality, site fidelity, and survivorship of willow flycatchers wintering in Costa Rica

    USGS Publications Warehouse

    Koronkiewicz, T.J.; Sogge, M.K.; van Riper, Charles, III; Paxton, E.H.

    2006-01-01

    We studied wintering Willow Flycatchers (Empidonax traillii) in two seasonal freshwater wetland habitats in northwestern Costa Rica during five boreal winters, to determine habitat occupancy, overwinter and between-year site and territory fidelity, and the degree to which the sexes maintain and defend winter territories. Both males and females used agonistic displays, song, and other vocalizations to maintain and defend mutually exclusive winter territories. Males were generally more abundant than females, but this varied by site and year. There was no significant difference in male and female territory size, nor any indication of sexual habitat segregation. Similarity in morphology and aggressiveness between the sexes may account for the lack of habitat segregation and the ability of females to maintain territories at wintering sites. Each year, 80%-92% of banded flycatchers that were present in midwinter remained at the site until late winter; of these, 86%-100% of individuals maintained the same territories throughout the entire period. We also observed nonterritorial floaters that subsequently established and held winter territories. Between-year site fidelity averaged 68%, and almost all returning birds established territories with boundaries similar to the previous year. Between-year apparent survivorship estimates ranged annually from 54%-72%, with no difference between sites but weak support for higher survivorship of males compared to females. Values for winter site and territory fidelity were generally higher than those reported for other species and for Willow Flycatchers on the breeding grounds; between-year survivorship estimates were similar to those reported for breeding flycatchers. ?? The Cooper Ornithological Society 2006.

  6. Breeding biology of Acadian flycatchers in a bottomland hardwood forest

    USGS Publications Warehouse

    Wilson, R.R.; Cooper, R.J.

    1998-01-01

    From 1993-1995, we located and monitored 601 Acadian Flycatcher (Empidonax virescens) nests in a large contiguous tract of bottomland hardwood forest on the White River National Wildlife Refuge, Arkansas. Annual reproductive success was significantly different among years; ranging from 10-25% (Mayfield estimate) over the three years of the study. There was no significant difference in nest success among study plots, with nesting success showing a trend of increasing late in the breeding season. Clutch size for non-parasitized nests averaged 2.9 ? 0.02 (SE) eggs with a mode of 3. Rates of Brown-headed Cowbird (Molothrus ater) parasitism were low (21%), accounting for 7% of all nest failures. However, parasitism by cowbirds resulted in a reduction of clutch size for nests initiated early (i.e., first nests and replacements) in the breeding season. Predation was the leading cause of nest failures, accounting for 75% of all failures. Snakes and avian predators were thought to be the leading cause of nest failures. Although additional factors must be investigated, preliminary results indicate that nest predation is a major influence on this population, despite the size of the forest tract.

  7. Rivers, dams, and willow flycatchers: a summary of their science and policy connections

    NASA Astrophysics Data System (ADS)

    Graf, William L.; Stromberg, Julie; Valentine, Brad

    2002-10-01

    The southwestern willow flycatcher ( Empidonax traillii extimus) is a riparian bird that spends winter months in Central and South America and summer breeding months in riparian zones of the American Southwest. Decline of the willow flycatcher population to less than 1000 breeding pairs prompted the Federal government to declare the species endangered, triggering a major recovery effort. The most important aspect of recovery is management and improvement of the riparian habitat of the bird population. Although the direct management of the species is primarily a biological issue, fluvial hydrology and geomorphology play an important role in understanding the dynamics of the present bird population and in designing a recovery plan because these physical systems are the substrates for the living communities which include the birds. Contributions of geomorphology and hydrology to the recovery plan include the use of watersheds and river basins as planning and evaluation units; understanding the connections between fluvial forms and riparian vegetation; implications for the bird population of the magnitude, frequency, duration, timing, and rate of change for various river discharges. The installation and operation of dams are the most important causes of hydro-geomorphic and ecological change in the region, so that management of these structures offers primary opportunities to improve the physical and biological conditions for the endangered species.

  8. A multiscaled model of southwestern willow flycatcher breeding habitat

    USGS Publications Warehouse

    Hatten, J.R.; Paradzick, C.E.

    2003-01-01

    The southwestern willow flycatcher (SWFL; Empidonax traillii extimus) is an endangered songbird whose habitat has declined dramatically over the last century. Understanding habitat selection patterns and the ability to identify potential breeding areas for the SWFL is crucial to the management and conservation of this species. We developed a multiscaled model of SWTL breeding habitat with a Geographic Information System (GIS), survey data, GIS variables, and multiple logistic regressions. We obtained presence and absence survey data from a riverine ecosystem and a reservoir delta in south-central Arizona, USA, in 1999. We extracted the GIS variables from satellite imagery and digital elevation models to characterize vegetation and floodplain within the project area. We used multiple logistic regressions within a cell-based (30 X 30 m) modeling environment to (1) determine associations between GIS variables and breeding-site occurrence at different spatial scales (0.09-72 ha), and (2) construct a predictive model. Our best model explained 54% of the variability in breeding-site occurrence with the following variables: vegetation density at the site (0.09 ha), proportion of dense vegetation and variability in vegetation density within a 4.5-ha neighborhood, and amount of floodplain or flat terrain within a 41-ha neighborhood. The density of breeding sites was highest in areas that the model predicted to be most suitable within the project area and at an external test site 200 km away. Conservation efforts must focus on protecting not only occupied patches, but also surrounding riparian forests and floodplain to ensure long-term viability of SWTL. We will use the multiscaled model to map SWTL breeding habitat in Arizona, prioritize future survey effort, and examine changes in habitat abundance and quality over time.

  9. Relative performance of hybrid nestlings in Ficedula flycatchers: a translocation experiment.

    PubMed

    Vallin, Niclas; Nonaka, Yuki; Feng, Jue; Qvarnström, Anna

    2013-02-01

    Ecological speciation predicts that hybrids should experience relatively low fitness in the local environments of their parental species. In this study, we performed a translocation experiment of nestling hybrids between collared and pied flycatchers into the nests of conspecific pairs of their parental species. Our aim was to compare the performance of hybrids with purebred nestlings. Nestling collared flycatchers are known to beg and grow faster than nestling pied flycatchers under favorable conditions, but to experience higher mortality than nestling pied flycatchers under food limitation. The experiment was performed relatively late in the breeding season when food is limited. If hybrid nestlings have an intermediate growth potential and begging intensity, we expected them to beg and grow faster, but also to experience lower survival than pied flycatchers. In comparison with nestling collared flycatchers, we expected them to beg and grow slower, but to survive better. We found that nestling collared flycatchers indeed begged significantly faster and experienced higher mortality than nestling hybrids. Moreover, nestling hybrids had higher weight and tended to beg faster than nestling pied flycatchers, but we did not detect a difference in survival between the latter two groups of nestlings. We conclude that hybrid Ficedula nestlings appear to have a better intrinsic adaptation to food limitation late in the breeding season compared with nestling collared flycatchers. We discuss possible implications for gene flow between the two species. PMID:23467681

  10. Song discrimination by nestling collared flycatchers during early development.

    PubMed

    McFarlane, S Eryn; Söderberg, Axel; Wheatcroft, David; Qvarnström, Anna

    2016-07-01

    Pre-zygotic isolation is often maintained by species-specific signals and preferences. However, in species where signals are learnt, as in songbirds, learning errors can lead to costly hybridization. Song discrimination expressed during early developmental stages may ensure selective learning later in life but can be difficult to demonstrate before behavioural responses are obvious. Here, we use a novel method, measuring changes in metabolic rate, to detect song perception and discrimination in collared flycatcher embryos and nestlings. We found that nestlings as early as 7 days old respond to song with increased metabolic rate, and, by 9 days old, have increased metabolic rate when listening to conspecific when compared with heterospecific song. This early discrimination between songs probably leads to fewer heterospecific matings, and thus higher fitness of collared flycatchers living in sympatry with closely related species. PMID:27405379

  11. Song discrimination by nestling collared flycatchers during early development

    PubMed Central

    Söderberg, Axel; Wheatcroft, David; Qvarnström, Anna

    2016-01-01

    Pre-zygotic isolation is often maintained by species-specific signals and preferences. However, in species where signals are learnt, as in songbirds, learning errors can lead to costly hybridization. Song discrimination expressed during early developmental stages may ensure selective learning later in life but can be difficult to demonstrate before behavioural responses are obvious. Here, we use a novel method, measuring changes in metabolic rate, to detect song perception and discrimination in collared flycatcher embryos and nestlings. We found that nestlings as early as 7 days old respond to song with increased metabolic rate, and, by 9 days old, have increased metabolic rate when listening to conspecific when compared with heterospecific song. This early discrimination between songs probably leads to fewer heterospecific matings, and thus higher fitness of collared flycatchers living in sympatry with closely related species. PMID:27405379

  12. Demographic Divergence History of Pied Flycatcher and Collared Flycatcher Inferred from Whole-Genome Re-sequencing Data

    PubMed Central

    Nadachowska-Brzyska, Krystyna; Burri, Reto; Olason, Pall I.; Kawakami, Takeshi; Smeds, Linnéa; Ellegren, Hans

    2013-01-01

    Profound knowledge of demographic history is a prerequisite for the understanding and inference of processes involved in the evolution of population differentiation and speciation. Together with new coalescent-based methods, the recent availability of genome-wide data enables investigation of differentiation and divergence processes at unprecedented depth. We combined two powerful approaches, full Approximate Bayesian Computation analysis (ABC) and pairwise sequentially Markovian coalescent modeling (PSMC), to reconstruct the demographic history of the split between two avian speciation model species, the pied flycatcher and collared flycatcher. Using whole-genome re-sequencing data from 20 individuals, we investigated 15 demographic models including different levels and patterns of gene flow, and changes in effective population size over time. ABC provided high support for recent (mode 0.3 my, range <0.7 my) species divergence, declines in effective population size of both species since their initial divergence, and unidirectional recent gene flow from pied flycatcher into collared flycatcher. The estimated divergence time and population size changes, supported by PSMC results, suggest that the ancestral species persisted through one of the glacial periods of middle Pleistocene and then split into two large populations that first increased in size before going through severe bottlenecks and expanding into their current ranges. Secondary contact appears to have been established after the last glacial maximum. The severity of the bottlenecks at the last glacial maximum is indicated by the discrepancy between current effective population sizes (20,000–80,000) and census sizes (5–50 million birds) of the two species. The recent divergence time challenges the supposition that avian speciation is a relatively slow process with extended times for intrinsic postzygotic reproductive barriers to evolve. Our study emphasizes the importance of using genome-wide data to

  13. The effect of alder forest cover and alder forest conversion on site fertility and productivity

    SciTech Connect

    Van Miegroet, H.; Cole, D.W.; Homann, P.S.

    1988-01-01

    Red alder (Alnus rubra Bong.) is known for its ability to improve the status of soil N through symbiotic N fixation. The objective of this paper is to assess the effect of red alder forests and their removal on soil and solution chemistry and on the growth of trees subsequently established on such sites. This was achieved through a series of paired field comparisons at two locations in Washington, involving similar-aged pure alder and Douglas-fir forests on soils that were essentially the same prior to stand establishment. At Pack Forest alder and Douglas-fir stands on high- and low-productivity sites were subjected to three levels of harvesting: bore only removal, whole tree (aboveground) harvesting, and complete removal of all vegetation and forest floor. The effect of harvesting intensity was examined on nutrient removal with biomass and through leaching, and on subsequent seedling growth. At Thompson Research Center adjacent Douglas-fir and alder forests were harvested, and half of each area was replanted with either Douglas-fir or red alder seedlings, yielding four forest conversion units. Differences in growth patterns, tree nutrient status, and leaching losses between these conversion plots were examined. Compared with adjacent Douglas-fir forests, substantially more N, P, K, and Ca are tied up in aboveground vegetation and on the forest floor of alder forests, and these elements also cycle faster in alder ecosystems primarily due to the deciduous nature of alder.

  14. A New Species of Muscicapa Flycatcher from Sulawesi, Indonesia

    PubMed Central

    Yong, Ding Li; Prawiradilaga, Dewi M.; Putra, Dadang Dwi; Round, Philip D.; Rheindt, Frank E.

    2014-01-01

    The Indonesian island of Sulawesi, a globally important hotspot of avian endemism, has been relatively poorly studied ornithologically, to the extent that several new bird species from the region have been described to science only recently, and others have been observed and photographed, but never before collected or named to science. One of these is a new species of Muscicapa flycatcher that has been observed on several occasions since 1997. We collected two specimens in Central Sulawesi in 2012, and based on a combination of morphological, vocal and genetic characters, we describe the new species herein, more than 15 years after the first observations. The new species is superficially similar to the highly migratory, boreal-breeding Gray-streaked Flycatcher Muscicapa griseisticta, which winters in Sulawesi; however, the new species differs strongly from M. griseisticta in several morphological characters, song, and mtDNA. Based on mtDNA, the new species is only distantly related to M. griseisticta, instead being a member of the M. dauurica clade. The new species is evidently widely distributed in lowland and submontane forest throughout Sulawesi. This wide distribution coupled with the species' apparent tolerance of disturbed habitats suggests it is not currently threatened with extinction. PMID:25419968

  15. Sympatric divergence and clinal variation in multiple coloration traits of Ficedula flycatchers.

    PubMed

    Laaksonen, T; Sirkiä, P M; Calhim, S; Brommer, J E; Leskinen, P K; Primmer, C R; Adamík, P; Artemyev, A V; Belskii, E; Both, C; Bureš, S; Burgess, M D; Doligez, B; Forsman, J T; Grinkov, V; Hoffmann, U; Ivankina, E; Král, M; Krams, I; Lampe, H M; Moreno, J; Mägi, M; Nord, A; Potti, J; Ravussin, P-A; Sokolov, L

    2015-04-01

    Geographic variation in phenotypes plays a key role in fundamental evolutionary processes such as local adaptation, population differentiation and speciation, but the selective forces behind it are rarely known. We found support for the hypothesis that geographic variation in plumage traits of the pied flycatcher Ficedula hypoleuca is explained by character displacement with the collared flycatcher Ficedula albicollis in the contact zone. The plumage traits of the pied flycatcher differed strongly from the more conspicuous collared flycatcher in a sympatric area but increased in conspicuousness with increasing distance to there. Phenotypic differentiation (PST ) was higher than that in neutral genetic markers (FST ), and the effect of geographic distance remained when statistically controlling for neutral genetic differentiation. This suggests that a cline created by character displacement and gene flow explains phenotypic variation across the distribution of this species. The different plumage traits of the pied flycatcher are strongly to moderately correlated, indicating that they evolve non-independently from each other. The flycatchers provide an example of plumage patterns diverging in two species that differ in several aspects of appearance. The divergence in sympatry and convergence in allopatry in these birds provide a possibility to study the evolutionary mechanisms behind the highly divergent avian plumage patterns. PMID:25683091

  16. Female ornamentation and territorial conflicts in collared flycatchers ( Ficedula albicollis)

    NASA Astrophysics Data System (ADS)

    Hegyi, Gergely; Garamszegi, László Zsolt; Eens, Marcel; Török, János

    2008-10-01

    Female ornaments in species with conventional sex roles often indicate individual quality, but the evolutionary forces maintaining them are less clear. Sexual competition for breeding opportunities may represent an important role for female signals, especially in polygynous species, but there is little experimental evidence for this. The wing patch size (WPS) of female collared flycatchers indicates age and body condition and predicts social mating patterns. We challenged nest-building females with decoy females of varying WPS and found that the aggressive response of residents increased with decoy WPS, suggesting a role for this female ornament in territorial competition. Our results explain why female WPS predicts territorial distances when mated to a polygynous male and indicate that the role of WPS in female competitive interactions is similar to that in males of the same population.

  17. The pentadehydro-Diels-Alder reaction.

    PubMed

    Wang, Teng; Naredla, Rajasekhar Reddy; Thompson, Severin K; Hoye, Thomas R

    2016-04-28

    In the classic Diels-Alder [4 + 2] cycloaddition reaction, the overall degree of unsaturation (or oxidation state) of the 4π (diene) and 2π (dienophile) pairs of reactants dictates the oxidation state of the newly formed six-membered carbocycle. For example, in the classic Diels-Alder reaction, butadiene and ethylene combine to produce cyclohexene. More recent developments include variants in which the number of hydrogen atoms in the reactant pair and in the resulting product is reduced by, for example, four in the tetradehydro-Diels-Alder (TDDA) and by six in the hexadehydro-Diels-Alder (HDDA) reactions. Any oxidation state higher than tetradehydro (that is, lacking more than four hydrogens) leads to the production of a reactive intermediate that is more highly oxidized than benzene. This increases the power of the overall process substantially, because trapping of the reactive intermediate can be used to increase the structural complexity of the final product in a controllable and versatile manner. Here we report an unprecedented overall 4π + 2π cycloaddition reaction that generates a different, highly reactive intermediate known as an α,3-dehydrotoluene. This species is in the same oxidation state as a benzyne. Like benzynes, α,3-dehydrotoluenes can be captured by various trapping agents to produce structurally diverse products that are complementary to those arising from the HDDA process. We call this new cycloisomerization process a pentadehydro-Diels-Alder (PDDA) reaction-a nomenclature chosen for chemical taxonomic reasons rather than mechanistic ones. In addition to alkynes, nitriles (RC≡N), although non-participants in aza-HDDA reactions, readily function as the 2π component in PDDA cyclizations to produce, via trapping of the α,3-(5-aza)dehydrotoluene intermediates, pyridine-containing products. PMID:27088605

  18. Origins of Stereoselectivity in the trans-Diels-Alder Paradigm

    PubMed Central

    Paton, Robert S.; Mackey, Joel L.; Kim, Woo Han; Lee, Jun Hee; Danishefsky, Samuel J.; Houk, K. N.

    2010-01-01

    The regioselectivity and stereoselectivity aspects of the Diels-Alder/radical hydrodenitration reaction sequence leading to trans-fused ring systems have been investigated with density functional calculations. A continuum of transition structures representing Diels-Alder and hetero-Diels-Alder cycloadditions as well as a sigmatropic rearrangement have been located, and they all lie very close in energy on the potential energy surface. All three pathways are found to be important in the formation of the Diels-Alder adduct. Reported regioselectivities are reproduced by the calculations. The stereoselectivity of radical hydrodenitration of the cis-Diels-Alder adduct is found to be related to the relative conformational stabilities of bicyclic radical intermediates. Overall, the computations provide understanding of the regioselectivities and stereoselectivities of the trans-Diels-Alder paradigm. PMID:20557046

  19. Molecular phylogeny of the Indian Ocean Terpsiphone paradise flycatchers: undetected evolutionary diversity revealed amongst island populations.

    PubMed

    Bristol, Rachel M; Fabre, Pierre-Henri; Irestedt, Martin; Jønsson, Knud A; Shah, Nirmal J; Tatayah, Vikash; Warren, Ben H; Groombridge, Jim J

    2013-05-01

    We construct a molecular phylogeny of Terpsiphone flycatchers of the Indian Ocean and use this to investigate their evolutionary relationships. A total of 4.4 kb of mitochondrial (cyt-b, ND3, ND2, control region) and nuclear (G3PDH, MC1R) sequence data were obtained from all species, sub-species and island populations of the region. Colonisation of the western Indian Ocean has been within the last two million years and greatly postdates the formation of the older islands of the region. A minimum of two independent continent-island colonisation events must have taken place in order to explain the current distribution and phylogenetic placement of Terpsiphone in this region. While five well-diverged Indian Ocean clades are detected, the relationship between them is unclear. Short intermodal branches are indicative of rapid range expansion across the region, masking exact routes and chronology of colonisation. The Indian Ocean Terpsiphone taxa fall into five well supported clades, two of which (the Seychelles paradise flycatcher and the Mascarene paradise flycatcher) correspond with currently recognised species, whilst a further three (within the Madagascar paradise flycatcher) are not entirely predicted by taxonomy, and are neither consistent with distance-based nor island age-based models of colonisation. We identify the four non-Mascarene clades as Evolutionarily Significant Units (ESUs), while the Mascarene paradise flycatcher contains two ESUs corresponding to the Mauritius and Réunion subspecies. All six ESUs are sufficiently diverged to be worthy of management as if they were separate species. This phylogenetic reconstruction highlights the importance of sub-specific molecular phylogenetic reconstructions in complex island archipelago settings in clarifying phylogenetic history and ESUs that may otherwise be overlooked and inadvertently lost. Our phylogenetic reconstruction has identified hidden pockets of evolutionary distinctiveness, which provide a valuable

  20. Correcting the "correct" name for the Asian Brown Flycatcher (Aves: Passeriformes, Muscicapidae, Muscicapa).

    PubMed

    Dickinson, Edward C; Schodde, Richard; Kullander, Sven; Crochet, Pierre André; Elliott, Andy; Kirwan, Guy M

    2014-01-01

    Mlíkovský (2012) claimed that Muscicapa latirostris Raffles, 1822 was the correct name for the Asian Brown Flycatcher, and rejected its senior synonym, Muscicapa dauurica Pallas, 1811. Muscicapa dauurica is in equal or greater use today for this flycatcher, to which the references to it in Mlíkovský (2012) testify even though they are far from comprehensive. Other major references using dauurica Pallas are Sibley & Monroe (1990), Inskipp et al. (1996), Kennedy et al. (2000), Dickinson (2003), Rasmussen & Anderton (2005), Clement (2006), Wells (2007) and Mann (2008). PMID:25283921

  1. Enantio- and periselective nitroalkene Diels-Alder reaction.

    PubMed

    Narcis, Maurice J; Sprague, Daniel J; Captain, Burjor; Takenaka, Norito

    2012-12-14

    The periselective Diels-Alder reaction of 5-substituted pentamethylcyclopentadienes and nitroethylene has been realized by helical-chiral hydrogen bond donor catalysts. To our knowledge, this represents the first asymmetric catalytic nitroalkene Diels-Alder reaction via activation of nitroalkene, and thus establishes its proof-of-principle. PMID:23104427

  2. Covalently crosslinked diels-alder polymer networks.

    SciTech Connect

    Bowman, Christopher; Adzima, Brian J.; Anderson, Benjamin John

    2011-09-01

    This project examines the utility of cycloaddition reactions for the synthesis of polymer networks. Cycloaddition reactions are desirable because they produce no unwanted side reactions or small molecules, allowing for the formation of high molecular weight species and glassy crosslinked networks. Both the Diels-Alder reaction and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) were studied. Accomplishments include externally triggered healing of a thermoreversible covalent network via self-limited hysteresis heating, the creation of Diels-Alder based photoresists, and the successful photochemical catalysis of CuAAC as an alternative to the use of ascorbic acid for the generation of Cu(I) in click reactions. An analysis of the results reveals that these new methods offer the promise of efficiently creating robust, high molecular weight species and delicate three dimensional structures that incorporate chemical functionality in the patterned material. This work was performed under a Strategic Partnerships LDRD during FY10 and FY11 as part of a Sandia National Laboratories/University of Colorado-Boulder Excellence in Science and Engineering Fellowship awarded to Brian J. Adzima, a graduate student at UC-Boulder. Benjamin J. Anderson (Org. 1833) was the Sandia National Laboratories point-of-contact for this fellowship.

  3. Nest box use and productivity of great crested flycatchers in prescribed-burned longleaf pine forests

    USGS Publications Warehouse

    White, D.H.; Seginak, J.T.

    2000-01-01

    Managing for the endangered Red-cockaded Woodpecker (Picoides borealis) on federal lands requires burning large tracts of mature pine forests every 3-5 yr. Many cavity trees that serve as potential nest sites for primary and secondary hole-nesting birds are destroyed by fire. We assessed the efficacy of a nest box program for the Great Crested Flycatcher (Myiarchus crinitus) at Carolina Sandhills National Wildlife Refuge, an area intensively managed for Red-cockaded Woodpeckers. During 1996-1998, we installed and monitored 330 (30 in each of 11 sites) nest boxes in mature (>60 yr) longleaf pine (Pinus palustris) tracts that were burned either in April-June (warm season) or December-March (cool season). Prescribed-burned sites were nearly devoid of snags; we estimated only 0.8/ ha in cool-season burns and 1.7/ha in warm-season burns. Great Crested Flycatchers built nests in 20% of the boxes available to them. Clutch sizes were larger in warm-season burns than in cool-season burns, but fledging success (fledglings/nest hatching -1 egg) was lower. Twenty-two of 59 Great Crested Flycatcher nests were depredated and the proportions in each burn class were similar. We recommend the installation of nest boxes for Great Crested Flycatchers in prescribed-burned pine forests, but additional research is needed in these habitats on nest depredation rates and causes.

  4. Oxidative stress in pied flycatcher (Ficedula hypoleuca) nestlings from metal contaminated environments in northern Sweden

    SciTech Connect

    Berglund, A.M.M. Sturve, J.; Foerlin, L.; Nyholm, N.E.I.

    2007-11-15

    Metals have been shown to induce oxidative stress in animals. One of the most metal polluted terrestrial environments in Sweden is the surroundings of a sulfide ore smelter plant located in the northern part of the country. Pied flycatcher nestlings (Ficedula hypoleuca) that grew up close to the industry had accumulated amounts of arsenic, cadmium, mercury, lead, iron and zinc in their liver tissue. The aim of this study was to investigate if pied flycatcher nestlings in the pollution gradient of the industry were affected by oxidative stress using antioxidant molecules and enzyme activities. The antioxidant assays were also evaluated in search for useful biomarkers in pied flycatchers. This study indicated that nestlings in metal contaminated areas showed signs of oxidative stress evidenced by up regulated hepatic antioxidant defense given as increased glutathione reductase (GR) and catalase (CAT) activities and slightly but not significantly elevated lipid peroxidation and glutathione-S-transferase (GST) activities. Stepwise linear regression indicated that lipid peroxidation and CAT activities were influenced mostly by iron, but iron and lead influenced the CAT activity to a higher degree. Positive relationships were found between GST and lead as well as GR activities and cadmium. We conclude that GR, CAT, GST activities and lipid peroxidation levels may function as useful biomarkers for oxidative stress in free-living pied flycatcher nestlings exposed to metal contaminated environments.

  5. Microwave-Based Reaction Screening: Tandem Retro-Diels-Alder/Diels-Alder Cycloadditions of ortho-Quinol Dimers

    PubMed Central

    Dong, Suwei; Cahill, Kath arine J.; Kang, Moon -Il; Colburn, Nancy H.; Henrich, Curtis J.; Wilson, Jennifer A.; Beutler, John A.; Johnson, Richard P.; Porco, John A.

    2011-01-01

    We have accomplished a parallel screen of cycloaddition partners for ortho-quinols utilizing a plate-based microwave system. Microwave irradiation improves the efficiency of retro-Diels-Alder/Diels-Alder cascades of ortho-quinol dimers which generally proceed in a diastereoselective fashion. Computational studies indicate that asynchronous transition states are favored in Diels-Alder cycloadditions of ortho-quinols. Subsequent biological evaluation of a collection of cycloadducts has identified an inhibitor of activator protein-1 (AP-1), an oncogenic transcription factor. PMID:21942286

  6. Effects of Alder Mine on the Water, Sediments, and Benthic Macroinvertebrates of Alder Creek, 1998 Annual Report.

    SciTech Connect

    Peplow, Dan

    1999-05-28

    The Alder Mine, an abandoned gold, silver, copper, and zinc mine in Okanogan County, Washington, produces heavy metal-laden effluent that affects the quality of water in a tributary of the Methow River. The annual mass loading of heavy metals from two audits at the Alder Mine was estimated to exceed 11,000 kg per year. In this study, water samples from stations along Alder Creek were assayed for heavy metals by ICP-AES and were found to exceed Washington State's acute freshwater criteria for cadmium (Cd), copper (Cu), selenium (Se), and zinc (Zn).

  7. 54. ALDER CREEK DIVERSION, PROJECT 1933, EXHIBIT F, SANTA ANA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    54. ALDER CREEK DIVERSION, PROJECT 1933, EXHIBIT F, SANTA ANA POWERHOUSE NO. 2 SCE drawing no. 5206858, no date (FERC no. 1933-48). - Santa Ana River Hydroelectric System, Redlands, San Bernardino County, CA

  8. Vortex wake, downwash distribution, aerodynamic performance and wingbeat kinematics in slow-flying pied flycatchers

    PubMed Central

    Muijres, Florian T.; Bowlin, Melissa S.; Johansson, L. Christoffer; Hedenström, Anders

    2012-01-01

    Many small passerines regularly fly slowly when catching prey, flying in cluttered environments or landing on a perch or nest. While flying slowly, passerines generate most of the flight forces during the downstroke, and have a ‘feathered upstroke’ during which they make their wing inactive by retracting it close to the body and by spreading the primary wing feathers. How this flight mode relates aerodynamically to the cruising flight and so-called ‘normal hovering’ as used in hummingbirds is not yet known. Here, we present time-resolved fluid dynamics data in combination with wingbeat kinematics data for three pied flycatchers flying across a range of speeds from near hovering to their calculated minimum power speed. Flycatchers are adapted to low speed flight, which they habitually use when catching insects on the wing. From the wake dynamics data, we constructed average wingbeat wakes and determined the time-resolved flight forces, the time-resolved downwash distributions and the resulting lift-to-drag ratios, span efficiencies and flap efficiencies. During the downstroke, slow-flying flycatchers generate a single-vortex loop wake, which is much more similar to that generated by birds at cruising flight speeds than it is to the double loop vortex wake in hovering hummingbirds. This wake structure results in a relatively high downwash behind the body, which can be explained by the relatively active tail in flycatchers. As a result of this, slow-flying flycatchers have a span efficiency which is similar to that of the birds in cruising flight and which can be assumed to be higher than in hovering hummingbirds. During the upstroke, the wings of slowly flying flycatchers generated no significant forces, but the body–tail configuration added 23 per cent to weight support. This is strikingly similar to the 25 per cent weight support generated by the wing upstroke in hovering hummingbirds. Thus, for slow-flying passerines, the upstroke cannot be regarded as

  9. Myiarchus flycatchers are the primary seed dispersers of Bursera longipes in a Mexican dry forest

    PubMed Central

    Almazán-Núñez, R. Carlos; Eguiarte, Luis E.; Arizmendi, María del Coro

    2016-01-01

    We evaluated the seed dispersal of Bursera longipes by birds along a successional gradient of tropical dry forest (TDF) in southwestern Mexico. B. longipes is an endemic tree to the TDF in the Balsas basin. The relative abundance of frugivorous birds, their frequency of visits to B. longipes and the number of removed fruits were recorded at three study sites with different stages of forest succession (early, intermediate and mature) characterized by distinct floristic and structural elements. Flycatchers of the Myiarchus and Tyrannus genera removed the majority of fruits at each site. Overall, visits to B. longipes were less frequent at the early successional site. Birds that function as legitimate dispersers by consuming whole seeds and regurgitating or defecating intact seeds in the process also remove the pseudoaril from seeds, thereby facilitating the germination process. The highest germination percentages were recorded for seeds that passed through the digestive system of two migratory flycatchers: M. cinerascens and M. nutingii. Perch plants, mainly composed of legumes (e.g., Eysenhardtia polystachya, Acacia cochliacantha, Calliandra eryophylla, Mimosa polyantha), serve also as nurse plants since the number of young individuals recruited from B. longipes was higher under these than expected by chance. This study shows that Myiarchus flycatchers are the most efficient seed dispersers of B. longipes across all successional stages. This suggests a close mutualistic relationship derived from adaptive processes and local specializations throughout the distribution of both taxa, as supported by the geographic mosaic theory of coevolution. PMID:27326382

  10. Myiarchus flycatchers are the primary seed dispersers of Bursera longipes in a Mexican dry forest.

    PubMed

    Almazán-Núñez, R Carlos; Eguiarte, Luis E; Arizmendi, María Del Coro; Corcuera, Pablo

    2016-01-01

    We evaluated the seed dispersal of Bursera longipes by birds along a successional gradient of tropical dry forest (TDF) in southwestern Mexico. B. longipes is an endemic tree to the TDF in the Balsas basin. The relative abundance of frugivorous birds, their frequency of visits to B. longipes and the number of removed fruits were recorded at three study sites with different stages of forest succession (early, intermediate and mature) characterized by distinct floristic and structural elements. Flycatchers of the Myiarchus and Tyrannus genera removed the majority of fruits at each site. Overall, visits to B. longipes were less frequent at the early successional site. Birds that function as legitimate dispersers by consuming whole seeds and regurgitating or defecating intact seeds in the process also remove the pseudoaril from seeds, thereby facilitating the germination process. The highest germination percentages were recorded for seeds that passed through the digestive system of two migratory flycatchers: M. cinerascens and M. nutingii. Perch plants, mainly composed of legumes (e.g., Eysenhardtia polystachya, Acacia cochliacantha, Calliandra eryophylla, Mimosa polyantha), serve also as nurse plants since the number of young individuals recruited from B. longipes was higher under these than expected by chance. This study shows that Myiarchus flycatchers are the most efficient seed dispersers of B. longipes across all successional stages. This suggests a close mutualistic relationship derived from adaptive processes and local specializations throughout the distribution of both taxa, as supported by the geographic mosaic theory of coevolution. PMID:27326382

  11. The Rusty-tailed Flycatcher (Muscicapa ruficauda; Aves: Muscicapidae) is a member of the genus Ficedula.

    PubMed

    Hooper, Daniel M; Olsson, Urban; Alström, Per

    2016-09-01

    The phylogenetic relationships of the avian family Muscicapidae (Old World chats and flycatchers) have historically been enigmatic and remain an active area of study. Widespread instances of non-monophyly resulting from misleading morphological and behavioral similarities have merited numerous taxonomic revisions to the group. Here we report one such instance with regard to the Rusty-tailed Flycatcher Muscicapa ruficauda, which has recently been placed in the newly proposed monotypic genus Ripleyia, due to inferred sister relationship to the genus Muscicapa and related genera (Voelker et al., 2016a). This name was later replaced by Ripleyornis, as it was realized that Ripleyia is a junior homonym of a genus of Mollusca (Voelker et al., 2016b). Using a Bayesian phylogenetic assessment of the Muscicapidae with near-complete taxon sampling of the genus Ficedula for five loci, along with an acoustic comparison of M. ruficauda to a subset of other flycatcher species, we show that this species should be reassigned to the genus Ficedula and accordingly that the names Ripleyia and Ripleyornis are both junior synonyms of Ficedula. PMID:27246102

  12. Divergence in gene expression within and between two closely related flycatcher species.

    PubMed

    Uebbing, Severin; Künstner, Axel; Mäkinen, Hannu; Backström, Niclas; Bolivar, Paulina; Burri, Reto; Dutoit, Ludovic; Mugal, Carina F; Nater, Alexander; Aken, Bronwen; Flicek, Paul; Martin, Fergal J; Searle, Stephen M J; Ellegren, Hans

    2016-05-01

    Relatively little is known about the character of gene expression evolution as species diverge. It is for instance unclear if gene expression generally evolves in a clock-like manner (by stabilizing selection or neutral evolution) or if there are frequent episodes of directional selection. To gain insights into the evolutionary divergence of gene expression, we sequenced and compared the transcriptomes of multiple organs from population samples of collared (Ficedula albicollis) and pied flycatchers (F. hypoleuca), two species which diverged less than one million years ago. Ordination analysis separated samples by organ rather than by species. Organs differed in their degrees of expression variance within species and expression divergence between species. Variance was negatively correlated with expression breadth and protein interactivity, suggesting that pleiotropic constraints reduce gene expression variance within species. Variance was correlated with between-species divergence, consistent with a pattern expected from stabilizing selection and neutral evolution. Using an expression PST approach, we identified genes differentially expressed between species and found 16 genes uniquely expressed in one of the species. For one of these, DPP7, uniquely expressed in collared flycatcher, the absence of expression in pied flycatcher could be associated with a ≈20-kb deletion including 11 of 13 exons. This study of a young vertebrate speciation model system expands our knowledge of how gene expression evolves as natural populations become reproductively isolated. PMID:26928872

  13. 3D Photofixation Lithography in Diels–Alder Networks

    PubMed Central

    Adzima, Brian J.; Kloxin, Christopher J.; DeForest, Cole A.; Anseth, Kristi S.

    2013-01-01

    3D structures were written and developed in a crosslinked polymer initially formed by a Diels–Alder reaction. Unlike conventional liquid resists, small features cannot sediment, as the reversible crosslinks function as a support, and the modulus of the material is in the MPa range at room temperature. The support structure, however, can be easily removed by heating the material which depolymerizes the polymer into a mixture of low-viscosity monomers. Complex shapes were written into the polymer network using two-photon techniques to spatially control the photoinitiation and subsequent thiol–ene reaction to selectively convert the Diels–Alder adducts into irreversible crosslinks. PMID:23080017

  14. Zero prevalence of extended spectrum beta-lactamase-producing bacteria in 300 breeding Collared Flycatchers in Sweden.

    PubMed

    Järhult, Josef D; Stedt, Johan; Gustafsson, Lars

    2013-01-01

    Wild birds are important indicators and potential spreaders of antibiotic resistance. The order Passerines is scarcely studied apart from Corvus sp. but extended spectrum beta-lactamases (ESBLs) has been found in Blackbirds. We tested 300 fecal samples from a well-studied population of Collared Flycatchers (Ficedula albicollis) at the Island of Gotland in Sweden and found no ESBL-producing bacteria. These results support the idea of 'ecological guild' as Blackbirds are ground-foraging invertebrate feeders, whereas Collared Flycatchers are aerial insectivores not regularly coming into contact with fecal contaminations and therefore less prone to acquire pathogens spread by the fecal-oral route. PMID:23898397

  15. Malaria-Infected Female Collared Flycatchers (Ficedula albicollis) Do Not Pay the Cost of Late Breeding

    PubMed Central

    Kulma, Katarzyna; Low, Matthew; Bensch, Staffan; Qvarnström, Anna

    2014-01-01

    Life-history theory predicts that the trade-off between parasite defense and other costly traits such as reproduction may be most evident when resources are scarce. The strength of selection that parasites inflict on their host may therefore vary across environmental conditions. Collared flycatchers (Ficedula albicollis) breeding on the Swedish island Öland experience a seasonal decline in their preferred food resource, which opens the possibility to test the strength of life-history trade-offs across environmental conditions. We used nested-PCR and quantitative-PCR protocols to investigate the association of Haemosporidia infection with reproductive performance of collared flycatcher females in relation to a seasonal change in the external environment. We show that despite no difference in mean onset of breeding, infected females produced relatively more of their fledglings late in the season. This pattern was also upheld when considering only the most common malaria lineage (hPHSIB1), however there was no apparent link between the reproductive output and the intensity of infection. Infected females produced heavier-than-average fledglings with higher-than-expected recruitment success late in the season. This reversal of the typical seasonal trend in reproductive output compensated them for lower fledging and recruitment rates compared to uninfected birds earlier in the season. Thus, despite different seasonal patterns of reproductive performance the overall number of recruits was the same for infected versus uninfected birds. A possible explanation for our results is that infected females breed in a different microhabitat where food availability is higher late in the season but also is the risk of infection. Thus, our results suggest that another trade-off than the one we aimed to test is more important for explaining variation in reproductive performance in this natural population: female flycatchers appear to face a trade-off between the risk of infection and

  16. The skeleton flight apparatus of North American bluebirds (Sialia): phylogenetic thrushes or functional flycatchers?

    PubMed

    Corbin, Clay E; Lowenberger, Lauren K; Dorkoski, Ryan P

    2013-08-01

    To better understand ecological traits of organisms, one can study them from two, not necessarily mutually exclusive perspectives: how the traits evolved, and their current adaptive utility. In birds, foraging behavior and associated morphological traits generally are explained by a combination of adaptive and phylogenetic predictors. The avian skeleton and more specifically, the skeletal flight apparatus is under well-known functional and phylogenetic constraints. This is an interesting area to partition the relative contributions of adaptive correlated evolution and phylogenetic constraint to species clustering in morphological space. A prediction of convergent evolution is that nonphylogenetic morphological clustering is a characteristic of ecological similarity. We tested this using representatives of North American birds from two clades, one with a mixture of foraging modes (Turdid thrushes, solitaires, and bluebirds) and one with more canalized foraging behaviors (Tyrannid flycatchers). Nine characters on the skeletal flight apparatus from 19 species were used to characterize the morphological space and test for ecomorphological clustering. When body size and phylogeny are considered, the three bluebird species and Townsend's solitaire cluster with the ecologically similar flycatchers rather than with their phylogenetic close relatives. Furthermore, sit-and-wait foragers tend to exhibit relatively long distal elements and a long keel while active ground foragers have deeper keels and a longer humerus. Distal elements, expected to be relatively shorter and more bowed in the flycatchers and bluebirds, were actually longer and narrower. A reduction of distal element mass may be more important for facilitating maneuverability than surface area for insertion of wing-rotational musculature. PMID:23576285

  17. 61. Photocopy of Engine Room Floor Plan, White Alder. The ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. Photocopy of Engine Room Floor Plan, White Alder. The Niagara Shipbuilding Corp. Engineering Department, Buffalo, New York. Coast Guard Headquarters Drawing No. 540-WAGL-1604-10, dated February 1943; revised January 1963. Original drawing property of the U.S. Coast Guard. - U.S. Coast Guard Cutter WHITE HEATH, USGS Integrated Support Command Boston, 427 Commercial Street, Boston, Suffolk County, MA

  18. N2-fixing red alder indirectly accelerates ecosystem nitrogen cycling

    USGS Publications Warehouse

    Perakis, Steven S.; Matkins, Joselin J.; Hibbs, David E.

    2012-01-01

    Symbiotic N2-fixing tree species can accelerate ecosystem N dynamics through decomposition via direct pathways by producing readily decomposed leaf litter and increasing N supply to decomposers, as well as via indirect pathways by increasing tissue and detrital N in non-fixing vegetation. To evaluate the relative importance of these pathways, we compared three-year decomposition and N dynamics of N2-fixing red alder leaf litter (2.34 %N) to both low-N (0.68 %N) and high-N (1.21 %N) litter of non-fixing Douglas-fir, and decomposed each litter source in four forests dominated by either red alder or Douglas-fir. We also used experimental N fertilization of decomposition plots to assess elevated N availability as a potential mechanism of N2-fixer effects on litter mass loss and N dynamics. Direct effects of N2-fixing red alder on decomposition occurred primarily as faster N release from red alder than Douglas-fir litter, but direct increases in N supply to decomposers via fertilization did not stimulate decomposition of any litter. Fixed N indirectly influenced detrital dynamics by increasing Douglas-fir tissue and litter N concentrations, which accelerated litter N release without accelerating mass loss. By increasing soil N, tissue N, and the rate of N release from litter of non-fixers, we conclude that N2-fixing vegetation can indirectly foster plant-soil feedbacks that contribute to the persistence of elevated N availability in terrestrial ecosystems.

  19. Continuous Flow of Nitroso Diels-Alder Reaction

    PubMed Central

    2015-01-01

    Our flow reaction systems have provided quantitative yields of nitroso Diels-Alder products with no byproducts in cases of cyclic dienes without temperature and pressure controls. Additionally, the reaction times were significantly shortened by using homogeneous catalyst (CuCl) or heterogeneous reagent (MnO2) in comparison with batch reaction. PMID:26138229

  20. High stereoselectivity on low temperature Diels-Alder reactions

    PubMed Central

    da Silva Filho, Luiz Carlos; Lacerda Júnior, Valdemar; Constantino, Mauricio Gomes; da Silva, Gil Valdo José; Invernize, Paulo Roberto

    2005-01-01

    We have found that some of the usually poor dienophiles (2-cycloenones) can undergo Diels-Alder reaction at -78°C with unusually high stereoselectivity in the presence of niobium pentachloride as a Lewis acid catalyst. A remarkable difference in reaction rates for unsubstituted and α- or β-methyl substituted 2-cycloenones was also observed. PMID:16542029

  1. High stereoselectivity on low temperature Diels-Alder reactions.

    PubMed

    da Silva Filho, Luiz Carlos; Lacerda Júnior, Valdemar; Constantino, Mauricio Gomes; da Silva, Gil Valdo José; Invernize, Paulo Roberto

    2005-01-01

    We have found that some of the usually poor dienophiles (2-cycloenones) can undergo Diels-Alder reaction at -78 degrees C with unusually high stereoselectivity in the presence of niobium pentachloride as a Lewis acid catalyst. A remarkable difference in reaction rates for unsubstituted and alpha- or beta-methyl substituted 2-cycloenones was also observed. PMID:16542029

  2. Climate adaptation and speciation: particular focus on reproductive barriers in Ficedula flycatchers.

    PubMed

    Qvarnström, Anna; Ålund, Murielle; McFarlane, S Eryn; Sirkiä, Päivi M

    2016-01-01

    Climate adaptation is surprisingly rarely reported as a cause for the build-up of reproductive isolation between diverging populations. In this review, we summarize evidence for effects of climate adaptation on pre- and postzygotic isolation between emerging species with a particular focus on pied (Ficedula hypoleuca) and collared (Ficedula albicollis) flycatchers as a model for research on speciation. Effects of climate adaptation on prezygotic isolation or extrinsic selection against hybrids have been documented in several taxa, but the combined action of climate adaptation and sexual selection is particularly well explored in Ficedula flycatchers. There is a general lack of evidence for divergent climate adaptation causing intrinsic postzygotic isolation. However, we argue that the profound effects of divergence in climate adaptation on the whole biochemical machinery of organisms and hence many underlying genes should increase the likelihood of genetic incompatibilities arising as side effects. Fast temperature-dependent co-evolution between mitochondrial and nuclear genomes may be particularly likely to lead to hybrid sterility. Thus, how climate adaptation relates to reproductive isolation is best explored in relation to fast-evolving barriers to gene flow, while more research on later stages of divergence is needed to achieve a complete understanding of climate-driven speciation. PMID:27087843

  3. Experimentally increased badge size increases male competition and reduces male parental care in the collared flycatcher

    PubMed Central

    Qvarnstroöm, A.

    1997-01-01

    Experimental enlargement of sexually selected traits that are energetically cheap to produce is expected to reveal costs resulting from increased risk of predation or social competition. Given a trade-off between sexually selected traits and life history traits such costs may be expected to affect not only the males themselves but also their offspring. In this study I manipulated the size of the forehead patch, a sexually selected trait that functions as a badge of status in male collared flycatchersFicedula albicollis). First, I found that a male's likelihood to establish a breeding territory with respect to his original badge size was affected by the treatment such that old males (older than or equal to two years) with relatively small original badges enjoyed an increased likelihood of establishing a breeding territory while young males (yearlings) suffered a reduced likelihood of establishment when their badges were enlarged as compared to unchanged. Second, young males with enlarged badges that were able to establish a territory fed their nestlings less in relation to their females compared to the control males. However, the females adjusted their parental effort to such an extent that no significant differences were observed in total feeding rate nor in reproductive success between the two groups of males. These results suggest that experimentally enlarged badge size in the collared flycatcher may result in increased male competition and that males have to trade their effort spent in male contest against their parental effort.

  4. Experimental manipulation shows that the white wing patch in collared flycatchers is a male sexual ornament

    PubMed Central

    de Heij, Maaike E; Gustafsson, Lars; Brommer, Jon E

    2011-01-01

    Descriptive analysis suggests that a conspicuous white wing patch in dichromatic (black and white) pied and collared flycatchers is under sexual selection. Here, we use an experimental approach to test whether this trait is indeed the target of selection. We caught 100 collared flycatcher Ficedula albicollis males soon after their arrival on the breeding site. We reduced (blackened) part of the white wing patch in half of these males and recorded their mating success and within and extra-pair offspring production. Reduction of the size of the white wing patch lowered a male's probability to attract a secondary social female, but not a primary female. However, primary females paired to males with a reduced wing patch were smaller (in tarsus), suggesting that male choice of partner or female–female competition over mates occurs in this species. The probability of pairing with a primary female (but not other components of male reproductive success) declined with arrival time (proxied by the date of capture). Males with a reduced wing patch size tended to sire less extra-pair offspring, although this relationship was reversed in one of the three study plots, suggesting that mating dynamics are context dependent. While our findings show that wing patch size is the target of sexual selection, the pathways and the strength of selection on this ornament differed markedly from a previous descriptive study. Nonexperimental studies of sexual selection in the wild may overestimate its importance because male fitness and ornamentation both depend positively on environmental conditions. PMID:22393521

  5. Enhanced stereocontrol in Diels-Alder reactions of chiral dienols.

    PubMed

    Cayzer, Tory N; Miller, Natalie A; Paddon-Row, Michael N; Sherburn, Michael S

    2006-05-21

    This combined experimental-computational investigation demonstrates that the presence of a removable bromine substituent on a diene leads to complete pi-diastereofacial and endo/exo stereoselection in both intermolecular and intramolecular Diels-Alder reactions. The influence of the bromine upon stereoselectivity is dramatic: the cycloaddition of nonbrominated precursor 18E, for example, gives four diastereomeric products in a 55:13:16:16 ratio; the bromine-containing analogue gives one stereoisomer within the limits of detection. The examination of B3LYP/6-31+G(d) transition structures allows an interpretation of these experimental findings. A method for the completely stereoselective synthesis of complimentary diastereomeric products (30Z and 31Z) from the same simple starting materials (28 and 2) is reported. Discrepancies between calculation and experiment in an earlier investigation into the Diels-Alder reaction are explained. PMID:16688346

  6. Recent Progress in Dehydro(genative) Diels-Alder Reaction.

    PubMed

    Li, Wenbo; Zhou, Liejin; Zhang, Junliang

    2016-01-26

    In recent years, remarkable progress has been made in dehydro or dehydrogenative Diels-Alder (D-A) reactions. This Minireview gives an overview of the major two strategies for dehydro(genative) Diels-Alder reactions, which differ in dehydrogenation and D-A cyclization sequence. Reactions in which D-A cycloaddition is followed by dehydrogenation are useful methods for the synthesis of various aromatic compounds, whereas advancements in dehydro genative procedures with oxidants or catalysts prior to D-A cycloaddition offer yet further new routes to functionalized cycloadducts. Recent leading findings are highlighted and the current state of the art, scope, and limitations of these processes are discussed in this Minireview. PMID:26786814

  7. Field trial with redtop flycatcher baited with ready made protein meal for the control of houseflies in Gazipur dairy farm, Delhi.

    PubMed

    Das, B P

    1994-03-01

    A field trial with Redtop Flycatcher having bait formulated as ready made protein meal a.i 977 gms/kg was carried out for the control of adult housefly Musca domestica domestica L. in Gazipur dairy farm situated at eastern corner of Delhi and observation compared with another field trial with commonly available Baygon bait using scattering method. The observation recorded during the field trial revealed that the new flycatcher was capable of retaining the trapped flies and the protein bait remained active for a period of 35 to 42 days (with peak attractability around the ninth day) without requiring refilling the flycatcher with bait during this period. The flycatcher installed in indoor situation was found to be more effective than that kept outside. Parallel tests with Baygon bait containing 2 per cent Propoxur scattered @ 40 gms a.i/100 m2 were found to kill more flies than the new protein baited flycatcher but required daily replenishment of the insecticide. Fly attractancy of the protein sample was also compared with that of other food sources for the flies available in the study area over a period of five days, independently using the same flycatcher. Wheat flour dough was observed to be the most efficient fly attractant compared to other food sources including protein bait. PMID:7963378

  8. Alternate non-stop migration strategies of pied flycatchers to cross the Sahara desert.

    PubMed

    Ouwehand, Janne; Both, Christiaan

    2016-04-01

    Each year more than two billion songbirds cross the Sahara, but how they perform this formidable task is largely unknown. Using geolocation tracks from 27 pied flycatchers, a nocturnally migrating passerine, we show that most birds made diurnal flights in both autumn and spring. These diurnal flights were estimated to be part of non-stop flights of mostly 40-60 h. In spring, birds flew across the Sahara, while autumn migration probably circumpassed part of the desert, through a long oversea flight. Our data contradict claims that passerines cross the Sahara by intermittent flight and daytime resting. The frequent occurrence of long non-stop flights to cross the desert shows migrants' physiological abilities and poses the question why this would not be the general migration strategy to cross the Sahara. PMID:27072404

  9. Hybrid Dysfunction Expressed as Elevated Metabolic Rate in Male Ficedula Flycatchers.

    PubMed

    McFarlane, S Eryn; Sirkiä, Päivi M; Ålund, Murielle; Qvarnström, Anna

    2016-01-01

    Studies of ecological speciation are often biased towards extrinsic sources of selection against hybrids, resulting from intermediate hybrid morphology, but the knowledge of how genetic incompatibilities accumulate over time under natural conditions is limited. Here we focus on a physiological trait, metabolic rate, which is central to life history strategies and thermoregulation but is also likely to be sensitive to mismatched mitonuclear interactions. We measured the resting metabolic rate of male collared, and pied flycatchers as well as of naturally occurring F1 hybrid males, in a recent hybrid zone. We found that hybrid males had a higher rather than intermediate metabolic rate, which is indicative of hybrid physiological dysfunction. Fitness costs associated with elevated metabolic rate are typically environmentally dependent and exaggerated under harsh conditions. By focusing on male hybrid dysfunction in an eco-physiological trait, our results contribute to the general understanding of how combined extrinsic and intrinsic sources of hybrid dysfunction build up under natural conditions. PMID:27583553

  10. Breeding Experience and the Heritability of Female Mate Choice in Collared Flycatchers

    PubMed Central

    Hegyi, Gergely; Herényi, Márton; Wilson, Alastair J.; Garamszegi, László Zsolt; Rosivall, Balázs; Eens, Marcel; Török, János

    2010-01-01

    Background Heritability in mate preferences is assumed by models of sexual selection, and preference evolution may contribute to adaptation to changing environments. However, mate preference is difficult to measure in natural populations as detailed data on mate availability and mate sampling are usually missing. Often the only available information is the ornamentation of the actual mate. The single long-term quantitative genetic study of a wild population found low heritability in female mate ornamentation in Swedish collared flycatchers. One potentially important cause of low heritability in mate ornamentation at the population level is reduced mate preference expression among inexperienced individuals. Methodology/Principal Findings Applying animal model analyses to 21 years of data from a Hungarian collared flycatcher population, we found that additive genetic variance was 50 percent and significant for ornament expression in males, but less than 5 percent and non-significant for mate ornamentation treated as a female trait. Female breeding experience predicted breeding date and clutch size, but mate ornamentation and its variance components were unrelated to experience. Although we detected significant area and year effects on mate ornamentation, more than 85 percent of variance in this trait remained unexplained. Moreover, the effects of area and year on mate ornamentation were also highly positively correlated between inexperienced and experienced females, thereby acting to remove difference between the two groups. Conclusions/Significance The low heritability of mate ornamentation was apparently not explained by the presence of inexperienced individuals. Our results further indicate that the expression of mate ornamentation is dominated by temporal and spatial constraints and unmeasured background factors. Future studies should reduce unexplained variance or use alternative measures of mate preference. The heritability of mate preference in the wild

  11. Alder (alnus crispa) effects on soils in ecosystems of the agashashok river valley, northwest Alaska

    USGS Publications Warehouse

    Rhoades, C.; Oskarsson, H.; Binkley, D.; Stottlemyer, B.

    2001-01-01

    At the northern limit of the boreal forest biome, alder (Alnus crispa [Ait.] Pursh) shrubs occur in a variety of ecosystems. We assessed the effects of individual alder shrubs on soil properties and understory plant tissue nitrogen in floodplain terraces, valley slopes and tussock tundra ridges. The three ecosystems differed with respect to soil properties and abiotic conditions and supported distinct plant communities. Alder increased resin-exchangeable soil N and NO3 production significantly in each ecosystem. The greatest difference between alder canopy and surrounding soil NO3 measured both under field and laboratory conditions occured in floodplain sites. The shrub effect on soil pH and soil organic matter was greatest on tundra ridges. Alder shrubs also influenced the nitrogen nutrition of plants growing beneath their canopies. Plants growing below alder canopies had higher foliar nitrogen concentration and natural abundance 15N composition and lower carbon to nitrogen ratio than open-grown plants. Similar to soil N availability, understory plant leaf chemistry responded more to alder on floodplains than on slope or tundra ecosystems. This pattern suggests that understory plants rely more heavily on alder-fixed-N in this resource-poor ecosystem.

  12. Enantioselective and regioselective pyrone Diels-Alder reactions of vinyl sulfones: total synthesis of (+)-cavicularin.

    PubMed

    Zhao, Peng; Beaudry, Christopher M

    2014-09-22

    The total synthesis of (+)-cavicularin is described. The synthesis features an enantio- and regioselective pyrone Diels-Alder reaction of a vinyl sulfone to construct the cyclophane architecture of the natural product. The Diels-Alder substrate was prepared by a regioselective one-pot three-component Suzuki reaction of a non-symmetric dibromoarene. PMID:25082270

  13. Flycatchers copy conspecifics in nest-site selection but neither personal experience nor frequency of tutors have an effect.

    PubMed

    Jaakkonen, Tuomo; Kari, Annemari; Forsman, Jukka T

    2013-01-01

    Using the behavior of others in guiding one's own behavior is a common strategy in animals. The prevailing theory predicts that young age and the inexperience of an individual are expected to increase the probability of adopting the behaviors of others. Also, the most common behavior in the population should be copied. Here, we tested the above predictions by examining social information use in the selection of nest-site features with a field experiment using a wild cavity nesting bird, the collared flycatcher (Ficedula albicollis). We used an experimental design in which geometric symbols depict nest-site features. By manipulating the apparent symbol choices of early settled individuals and monitoring the choices of later arriving birds, we can study social information use without bias from learned or innate preferences. Flycatchers were found to use social information in the selection of nest-site features, with about 60% of the population preferring the manipulated conspecific choices. However, age and experience as explanatory factors suggested by the social information use theory did not explain the choices. The present result, in concert with earlier similar experiments, implies that flycatchers may in some situations rely more on interspecific information in the selection of nest-site characteristics. PMID:23544136

  14. Ectomycorrhizal root development in wet Alder carr forests in response to desiccation and eutrophication.

    PubMed

    Baar, J; Bastiaans, T; van de Coevering, M A; Roelofs, J G M

    2002-06-01

    Effects of desiccation and eutrophication on ectomycorrhizal (ECM) root development in wet Alder carr forests in The Netherlands were studied. In northwestern Europe, wet Alder carr forests are found mostly in peatlands and along streams, forming an important component of wetland ecosystems. The dominant tree species in wet Alder carr forests is Alnus glutinosa (L.) Gaertn. (Black alder), which associates with ectomycorrhizal fungi. During recent decades, wet Alder carr forests in Europe have declined because of desiccation and eutrophication, particularly in The Netherlands. In the present study, the number of root tips of A. glutinosa trees was highest in an undisturbed wet Alder carr forest in a peatland area. Eutrophication in the peatland area significantly inhibited ectomycorrhizal (ECM) root development of A. glutinosa. In the eutrophied forest, ECM root tips were observed only close to A. glutinosa trees growing on hummocks. The concentrations of nitrate and potassium in soil water of the eutrophied forest were significantly higher than in the undisturbed forest, while magnesium and iron concentrations and the pH were significantly lower. The number of ECM root tips of A. glutinosa in a desiccated forest along a stream was generally lower than in an undisturbed wet Alder carr forest on waterlogged soil in the same area. The sulphate concentration in soil water in the desiccated forest was significantly higher than in the forest on waterlogged soil. ECM root development of A. glutinosa may have been negatively affected by the chemical composition of the soil water. PMID:12072985

  15. Trade-offs between sexual advertisement and immune function in the pied flycatcher (Ficedula hypoleuca).

    PubMed Central

    Kilpimaa, Janne; Alatalo, Rauno V.; Siitari, Heli

    2004-01-01

    Good genes models of sexual selection assume that sexual advertisement is costly and thus the level of advertisement honestly reveals heritable viability. Recently it has been suggested that an important cost of sexual advertisement might be impairment of the functioning of the immune system. In this field experiment we investigated the possible trade-offs between immune function and sexual advertisement by manipulating both mating effort and activity of immune defence in male pied flycatchers. Mating effort was increased in a non-arbitrary manner by removing females from mated males during nest building. Widowed males sustained higher haematocrit levels than control males and showed higher expression of forehead patch height, suggesting that manipulation succeeded in increasing mating effort. Males that were experimentally forced to increase mating effort had reduced humoral immune responsiveness compared with control males. In addition, experimental activation of immune defence by vaccination with novel antigens reduced the expression of male ornament dimensions. To conclude, our results indicate that causality behind the trade-off between immune function and sexual advertisement may work in both directions: sexual activity suppresses immune function but immune challenge also reduces sexual advertisement. PMID:15058434

  16. Unexpected divergence and lack of divergence revealed in continental Asian Cyornis flycatchers (Aves: Muscicapidae).

    PubMed

    Zhang, Zhen; Wang, Xiaoyang; Huang, Yuan; Olsson, Urban; Martinez, Jonathan; Alström, Per; Lei, Fumin

    2016-01-01

    The flycatcher genus Cyornis (Aves: Muscicapidae) comprises 25 species with Oriental distributions. Their relationships are poorly known. We analyzed the phylogenetic relationships of 70 individuals from 12 species and several subspecies of Cyornis based on three mitochondrial genes and five nuclear introns, with special focus on Chinese and Vietnamese populations of the monotypic C. hainanus and polytypic C. rubeculoides. We found no support for inclusion of C. concretus in Cyornis. Deep divergences were observed among different subspecies of C. banyumas and C. rubeculoides. C. rubeculoides glaucicomans was also shown to have a highly distinctive song, and we propose that it is treated as a distinctive Chinese endemic species, C. glaucicomans. In contrast, the south Vietnamese C. rubeculoides klossi, which has a disjunct distribution from the other subspecies of C. rubeculoides, along with a recently discovered population in Guangdong Province (China) with several plumage features reminiscent of C. r. klossi, were indistinguishable in all loci analyzed from the phenotypically markedly different C. hainanus. More research is needed to elucidate the reasons for this unexpected pattern. PMID:26358612

  17. Nutritional correlates and mate acquisition role of multiple sexual traits in male collared flycatchers

    NASA Astrophysics Data System (ADS)

    Hegyi, Gergely; Szöllősi, Eszter; Jenni-Eiermann, Susanne; Török, János; Eens, Marcel; Garamszegi, László Zsolt

    2010-06-01

    The information content of a sexual signal may predict its importance in a multiple signal system. Many studies have correlated sexual signal expression with the absolute levels of nutrient reserves. In contrast, the changes of nutrient reserves associated with signal expression are largely unknown in the wild due to technical limitations although they are important determinants of signal information content. We compared two visual and eight acoustic sexual traits in male collared flycatchers to see whether the nutritional correlates of expression predict the role of the signal in sexual selection. We used single point assays of plasma lipid metabolites to estimate short-term changes in nutritional state in relation to sexual trait expression during courtship. As a measure of sexual selection, we estimated the relationship with pairing latency after arrival in a 4-year dataset. Males which found a mate rapidly were characterized by large wing and forehead patches, but small song strophe complexity and small figure repertoire size. Traits more strongly related to pairing latency were also more closely related to changes in nutrient reserves. This indicates a link between signal role and information content. Small wing patches and, surprisingly, complex songs seemed to indicate poor phenotypic quality and were apparently disfavoured at mate acquisition in our population. Future studies of the information content of sexual traits, especially dynamic traits such as song, may benefit from the use of plasma metabolite profiles as non-invasive indicators of short-term changes in body condition.

  18. PSMC analysis of effective population sizes in molecular ecology and its application to black-and-white Ficedula flycatchers.

    PubMed

    Nadachowska-Brzyska, Krystyna; Burri, Reto; Smeds, Linnéa; Ellegren, Hans

    2016-03-01

    Climatic fluctuations during the Quaternary period governed the demography of species and contributed to population differentiation and ultimately speciation. Studies of these past processes have previously been hindered by a lack of means and genetic data to model changes in effective population size (Ne ) through time. However, based on diploid genome sequences of high quality, the recently developed pairwise sequentially Markovian coalescent (PSMC) can estimate trajectories of changes in Ne over considerable time periods. We applied this approach to resequencing data from nearly 200 genomes of four species and several populations of the Ficedula species complex of black-and-white flycatchers. Ne curves of Atlas, collared, pied and semicollared flycatcher converged 1-2 million years ago (Ma) at an Ne of ≈ 200 000, likely reflecting the time when all four species last shared a common ancestor. Subsequent separate Ne trajectories are consistent with lineage splitting and speciation. All species showed evidence of population growth up until 100-200 thousand years ago (kya), followed by decline and then start of a new phase of population expansion. However, timing and amplitude of changes in Ne differed among species, and for pied flycatcher, the temporal dynamics of Ne differed between Spanish birds and central/northern European populations. This cautions against extrapolation of demographic inference between lineages and calls for adequate sampling to provide representative pictures of the coalescence process in different species or populations. We also empirically evaluate criteria for proper inference of demographic histories using PSMC and arrive at recommendations of using sequencing data with a mean genome coverage of ≥18X, a per-site filter of ≥10 reads and no more than 25% of missing data. PMID:26797914

  19. New quill mites (Cheyletoidea: Syringophilidae) parasitizing the black-headed paradise-flycatcher Terpsiphone rufiventer (Passeriformes: Monarchidae) in Gabon.

    PubMed

    Glowska, Eliza; Schmidt, Brian K

    2014-01-01

    A new genus of quill mites (Cheyletoidea: Syringophilidae) and two new species Pipicobia terpsiphoni gen. nov. and sp. nov. and Syringophiloidus furthi sp. nov. parasitizing the black-headed paradise-flycatcher Terpsiphone rufiventer (Swainson) (Passeriformes: Monarchidae) in Gabon are described. Three species of the Neopicobia Skoracki, 2011 are moved to the newly established genus: Pipicobia locustella (Skoracki, Bochkov and Wauthy, 2004) comb. nov., Pipicobia pyrrholaemus (Skoracki and Glowska, 2008) comb.nov., and Pipicobia glossopsitta (Skoracki, Glowska and Sikora, 2008) comb.nov. Syringophilids are recorded on hosts of the family Monarchidae and in Gabon for the first time. A key to the genera of the subfamily Picobiinae is proposed. PMID:24869522

  20. Electron transfer-initiated Diels-Alder cycloadditions of 2'-hydroxychalcones.

    PubMed

    Cong, Huan; Ledbetter, Dustin; Rowe, Gerard T; Caradonna, John P; Porco, John A

    2008-07-23

    An efficient approach to cyclohexenyl chalcones employing highly electron rich 2'-hydroxychalcone dienophiles via electron transfer-initiated Diels-Alder cycloaddition is described. Using the methodology, the total synthesis of nicolaiodesin C has been accomplished. PMID:18576647

  1. Habitat shifts in the evolutionary history of a Neotropical flycatcher lineage from forest and open landscapes

    PubMed Central

    2008-01-01

    Background Little is known about the role ecological shifts play in the evolution of Neotropical radiations that have colonized a variety of environments. We here examine habitat shifts in the evolutionary history of Elaenia flycatchers, a Neotropical bird lineage that lives in a range of forest and open habitats. We evaluate phylogenetic relationships within the genus based on mitochondrial and nuclear DNA sequence data, and then employ parsimony-based and Bayesian methods to reconstruct preferences for a number of habitat types and migratory behaviour throughout the evolutionary history of the genus. Using a molecular clock approach, we date the most important habitat shifts. Results Our analyses resolve phylogenetic relationships among Elaenia species and confirm several species associations predicted by morphology while furnishing support for other taxon placements that are in conflict with traditional classification, such as the elevation of various Elaenia taxa to species level. While savannah specialism is restricted to one basal clade within the genus, montane forest was invaded from open habitat only on a limited number of occasions. Riparian growth may have been favoured early on in the evolution of the main Elaenia clade and subsequently been deserted on several occasions. Austral long-distance migratory behaviour evolved on several occasions. Conclusion Ancestral reconstructions of habitat preferences reveal pronounced differences not only in the timing of the emergence of certain habitat preferences, but also in the frequency of habitat shifts. The early origin of savannah specialism in Elaenia highlights the importance of this habitat in Neotropical Pliocene and late Miocene biogeography. While forest in old mountain ranges such as the Tepuis and the Brazilian Shield was colonized early on, the most important colonization event of montane forest was in conjunction with Pliocene Andean uplift. Riparian habitats may have played an important role in

  2. Mutations in different pigmentation genes are associated with parallel melanism in island flycatchers.

    PubMed

    Uy, J Albert C; Cooper, Elizabeth A; Cutie, Stephen; Concannon, Moira R; Poelstra, Jelmer W; Moyle, Robert G; Filardi, Christopher E

    2016-07-13

    The independent evolution of similar traits across multiple taxa provides some of the most compelling evidence of natural selection. Little is known, however, about the genetic basis of these convergent or parallel traits: are they mediated by identical or different mutations in the same genes, or unique mutations in different genes? Using a combination of candidate gene and reduced representation genomic sequencing approaches, we explore the genetic basis of and the evolutionary processes that mediate similar plumage colour shared by isolated populations of the Monarcha castaneiventris flycatcher of the Solomon Islands. A genome-wide association study (GWAS) that explicitly controlled for population structure revealed that mutations in known pigmentation genes are the best predictors of parallel plumage colour. That is, entirely black or melanic birds from one small island share an amino acid substitution in the melanocortin-1 receptor (MC1R), whereas similarly melanic birds from another small island over 100 km away share an amino acid substitution in a predicted binding site of agouti signalling protein (ASIP). A third larger island, which separates the two melanic populations, is inhabited by birds with chestnut bellies that lack the melanic MC1R and ASIP allelic variants. Formal FST outlier tests corroborated the results of the GWAS and suggested that strong, directional selection drives the near fixation of the MC1R and ASIP variants across islands. Our results, therefore, suggest that selection acting on different mutations with large phenotypic effects can drive the evolution of parallel melanism, despite the relatively small population size on islands. PMID:27412275

  3. Geographical trends in the yolk carotenoid composition of the pied flycatcher (Ficedula hypoleuca).

    PubMed

    Eeva, Tapio; Ruuskanen, Suvi; Salminen, Juha-Pekka; Belskii, Eugen; Järvinen, Antero; Kerimov, Anvar; Korpimäki, Erkki; Krams, Indrikis; Moreno, Juan; Morosinotto, Chiara; Mänd, Raivo; Orell, Markku; Qvarnström, Anna; Siitari, Heli; Slater, Fred M; Tilgar, Vallo; Visser, Marcel E; Winkel, Wolfgang; Zang, Herwig; Laaksonen, Toni

    2011-02-01

    Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female's diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards. The most southern population (which is also the one found at the highest altitude) also showed relatively low carotenoid levels. Concentrations of β-carotene and zeaxanthin did not show any obvious geographical gradients. Egg yolks also contained proportionally more lutein and other xanthophylls in deciduous than in mixed or coniferous habitats. We suggest that latitudinal gradients in lutein and xanthophylls reflect the lower availability of lutein-rich food items in the northern F. hypoleuca populations and in montane southern populations, which start egg-laying earlier relative to tree phenology than the Central European populations. Similarly, among-habitat variation is likely to reflect the better availability of lutein-rich food in deciduous forests. Our study is the first to indicate that the concentration and profile of yolk carotenoids may show large-scale spatial variation among populations in different parts of the species' geographical range. Further studies are needed to test the fitness effects of this geographical variation. PMID:20848135

  4. Changing climate and the phenological response of great tit and collared flycatcher populations in floodplain forest ecosystems in Central Europe

    NASA Astrophysics Data System (ADS)

    Bauer, Zdeněk; Trnka, Miroslav; Bauerová, Jana; Možný, Martin; Štěpánek, Petr; Bartošová, Lenka; Žalud, Zdeněk

    2010-01-01

    This study is based on 47 years of observations (1961-2007) on two common bird species, the Great Tit ( Parus major) and the Collared Flycatcher ( Ficedula albicollis), and a dominant tree species in their habitat, the English Oak ( Quercus robur). The study took place at four research sites in the Czech Republic located in full-grown, multi-aged floodplain forests with no forestry management. An increase in air temperature over the evaluated period clearly influenced the length of phenological phases. The full foliage date of English Oak has advanced by 8.7 days during the past 47 years. Great Tit and Collared Flycatcher populations have reacted to the changing climate in the same way, with first laying date and mean laying date advancing by between 6.0 and 9.0 days. In all cases, the trends are highly significant and consistent over all sites. Despite the ongoing shift in phenological stages toward the beginning of the year, the change does not appear to have led to mistiming in the trophic food chain. Overall, this study shows almost identical rates of change in egg laying dates for both bird species in all the floodplain forests studied, and these trends are coherent with those of English Oak and peak herbivorous caterpillar activity.

  5. Differentiation in neutral genes and a candidate gene in the pied flycatcher: using biological archives to track global climate change

    PubMed Central

    Kuhn, Kerstin; Schwenk, Klaus; Both, Christiaan; Canal, David; Johansson, Ulf S; van der Mije, Steven; Töpfer, Till; Päckert, Martin

    2013-01-01

    Global climate change is one of the major driving forces for adaptive shifts in migration and breeding phenology and possibly impacts demographic changes if a species fails to adapt sufficiently. In Western Europe, pied flycatchers (Ficedula hypoleuca) have insufficiently adapted their breeding phenology to the ongoing advance of food peaks within their breeding area and consequently suffered local population declines. We address the question whether this population decline led to a loss of genetic variation, using two neutral marker sets (mitochondrial control region and microsatellites), and one potentially selectively non-neutral marker (avian Clock gene). We report temporal changes in genetic diversity in extant populations and biological archives over more than a century, using samples from sites differing in the extent of climate change. Comparing genetic differentiation over this period revealed that only the recent Dutch population, which underwent population declines, showed slightly lower genetic variation than the historic Dutch population. As that loss of variation was only moderate and not observed in all markers, current gene flow across Western and Central European populations might have compensated local loss of variation over the last decades. A comparison of genetic differentiation in neutral loci versus the Clock gene locus provided evidence for stabilizing selection. Furthermore, in all genetic markers, we found a greater genetic differentiation in space than in time. This pattern suggests that local adaptation or historic processes might have a stronger effect on the population structure and genetic variation in the pied flycatcher than recent global climate changes. PMID:24363905

  6. Candidate genes for colour and vision exhibit signals of selection across the pied flycatcher (Ficedula hypoleuca) breeding range

    PubMed Central

    Lehtonen, P K; Laaksonen, T; Artemyev, A V; Belskii, E; Berg, P R; Both, C; Buggiotti, L; Bureš, S; Burgess, M D; Bushuev, A V; Krams, I; Moreno, J; Mägi, M; Nord, A; Potti, J; Ravussin, P-A; Sirkiä, P M; Sætre, G-P; Winkel, W; Primmer, C R

    2012-01-01

    The role of natural selection in shaping adaptive trait differentiation in natural populations has long been recognized. Determining its molecular basis, however, remains a challenge. Here, we search for signals of selection in candidate genes for colour and its perception in a passerine bird. Pied flycatcher plumage varies geographically in both its structural and pigment-based properties. Both characteristics appear to be shaped by selection. A single-locus outlier test revealed 2 of 14 loci to show significantly elevated signals of divergence. The first of these, the follistatin gene, is expressed in the developing feather bud and is found in pathways with genes that determine the structure of feathers and may thus be important in generating variation in structural colouration. The second is a gene potentially underlying the ability to detect this variation: SWS1 opsin. These two loci were most differentiated in two Spanish pied flycatcher populations, which are also among the populations that have the highest UV reflectance. The follistatin and SWS1 opsin genes thus provide strong candidates for future investigations on the molecular basis of adaptively significant traits and their co-evolution. PMID:22027894

  7. Heavy metal stress in alders: Tolerance and vulnerability of the actinorhizal symbiosis.

    PubMed

    Bélanger, Pier-Anne; Bellenger, Jean-Philippe; Roy, Sébastien

    2015-11-01

    Alders have already demonstrated their potential for the revegetation of both mining and industrial sites. These actinorhizal trees and shrubs and the actinobacteria Frankia associate in a nitrogen-fixing symbiosis which could however be negatively affected by the presence of heavy metals, and accumulate them. In our hydroponic assay with black alders, quantification of the roots and shoots metal concentrations showed that, in the absence of stress, symbiosis increases Mo and Ni root content and simultaneously decreases Mo shoot content. Interestingly, the Mo shoot content also decreases in the presence of Ni, Cu, Pb, Zn and Cd for symbiotic alders. In symbiotic alders, Pb shoot translocation was promoted in presence of Pb. On the other hand, Cd exclusion in symbiotic root tissues was observed with Pb and Cd. In the presence of symbiosis, only Cd and Pb showed translocation into aerial tissues when present in the nutrient solution. Moreover, the translocation of Ni to shoot was prevented by symbiosis in the presence of Cd, Ni and Pb. The hydroponic experiment demonstrated that alders benefit from the symbiosis, producing more biomass (total, root and shoot) than non nodulated alders in control condition, and in the presence of metals (Cu, Ni, Zn, Pb and Cd). Heavy metals did not reduce the nodule numbers (SNN), but the presence of Zn or Cd did reduce nodule allocation. Our study suggests that the Frankia-alder symbiosis is a promising (and a compatible) plant-microorganism association for the revegetation of contaminated sites, with minimal risk of metal dispersion. PMID:26091871

  8. Resolving taxonomic uncertainty and historical biogeographic patterns in Muscicapa flycatchers and their allies.

    PubMed

    Voelker, Gary; Huntley, Jerry W; Peñalba, Joshua V; Bowie, Rauri C K

    2016-01-01

    Muscicapa flycatchers and their allies (Bradornis, Dioptornis, Empidornis, Fraseria, Myioparus, Namibornis, and Sigelus) are widely distributed in Africa, Europe and Asia. This broad distribution and the wide variety of habitats occupied by the group, ranging from arid to tropical forests, presents an interesting opportunity to explore the evolution of biogeographic patterns and habitat associations. Sequence data (up to 3310 base pairs from two mitochondrial and two nuclear genes) were generated for 36 of 42 species which comprise the assemblage. Complementary data from an additional species was retrieved from GenBank, as was an additional gene which was available for 21 of our included taxa. Using model-based phylogenetic methods and molecular clock dating, we constructed a time-calibrated molecular phylogenetic hypothesis for the lineage. Ancestral area reconstructions were performed on the phylogeny using LaGrange and BioGeoBEARS. Our results indicate that Bradornis, Fraseria, and Muscicapa are each non-monophyletic, with the latter being shown to comprise five separate clades each more closely related to other genera. Two new genera (Chapinia and Ripleyia) are erected to account for these results. Muscicapa and allies originated c. 7.4 Ma, most likely in Africa given that their sister lineage is almost entirely from there, and rapidly achieved a Eurasian distribution by c. 7.1 Ma. A second divergence at c. 6.1 Ma resulted in two clades. The first is a largely Eurasian clade that subsequently recolonized Africa, perhaps as the result of the loss of migration. The second is an African clade, and ancestral reconstructions suggest a Congolian (e.g. tropical forest) origin for this clade, with several subsequent diversifications into more arid habitats. This is a unique result, as most tropical forest lineages are confined to that habitat. As with other studies of African bird lineages, Afrotropical forest dynamics appear to have played a significant role in

  9. The Influence of Speckled Alder on Nitrogen Accumulation in Adirondack Wetlands

    NASA Astrophysics Data System (ADS)

    Kiernan, B. D.; Hurd, T. M.; Raynal, D. J.

    2001-05-01

    Shrub-dominated wetlands of the Adirondacks typically support vigorous populations of nitrogen-fixing speckled alder Alnus incana (L.) Moench var. americana Regel), and are the second most abundant wetland type in the Adirondack region. In symbiotic association with an actinomycete of the genus Frankia, this shrub fixes 37-43 kg N/ha/yr in monotypic stands. This study was undertaken to quantify the abundance of alder in wetlands typed as "Scrub-shrub 1" (SS1; known as alder/willow wetlands) in the National Wetlands Inventory, and to determine the accumulation of nitrate and ammonium in alder wetland substrates. Twenty wetlands from the Oswegatchie-Black (OB) and Upper Hudson (UH) watersheds were randomly selected using the Adirondack Park Agency's GIS data base which includes wetland cover types assigned using remotely sensed data. Wetlands designated as "SS1" (scrub-shrub vegetation) and "SS1/EM1" (scrub-shrub with emergent herbaceous vegetation) were included in the sample. Six wetlands varying in alder abundance were chosen to estimate N accumulation in the substrate, with measurement of dissolved inorganic N in groundwater and ion exchange resin extracts. In the OB watershed, A. incana averaged 30 % of total shrub density in SS1 wetlands and 36 % in SS1/EM1 wetlands. Alder accounted for 49 % of all stems in UH SS1 wetlands, 28 % in the SS1/EM1 wetlands and in total accounted for 35 % of all stems in this study. Nitrate in IER extracts and groundwater was significantly higher in high-density alder wetlands (p < 0.05). Eight of the 20 wetlands included in this study were estimated to have less than 3,000 alder stems/ha, and five were estimated to have greater than 10,000 stems/ha. The other seven wetlands averaged 6,000 stems/ha. At nine sites, foliar N equaled or exceeded estimated atmospheric deposition (~10 kg/ha/yr), and was likely derived from N fixation. We conclude that 50 % of the SS1/EM1 wetlands and at least 75 % of the SS1 wetlands in these watersheds

  10. Linking Landscape Characteristics and High Stream Nitrogen in the Oregon Coast Range: Red Alder Complicates Use of Nutrient Criteria

    EPA Science Inventory

    Red alder (a nitrogen-fixing tree) and sea salt inputs can strongly influence stream nitrogen concentrations in western Oregon and Washington. We compiled a database of stream nitrogen and landscape characteristics in the Oregon Coast Range. Basal area of alder, expressed as a ...

  11. Diels-Alder reactions: The effects of catalyst on the addition reaction

    NASA Astrophysics Data System (ADS)

    Yilmaz, Özgür; Kus, Nermin Simsek; Tunç, Tuncay; Sahin, Ertan

    2015-10-01

    The reaction between 2,3-dimethyl-1,3-butadiene and dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate is efficiently achieved with small amounts of catalyst, i.e. phenol, AcOH, nafion, and β-cyclodextrin. Exo-diastereoselective cycloaddition reactions were observed both without catalyst and different catalysts for 48 days. As a result, different products (tricyclicmolecule 5, retro-Diels-Alder product 6, and oxidation product 7) were obtained with different catalysts. In addition, we synthesized Diels-Alders product 8 and tricyclocyclitol 10 via Diels-Alder reaction. The structures of these products were characterized by 1H NMR, 13C NMR, MS and IR spectroscopy.

  12. Electrostatic catalysis of a Diels-Alder reaction

    NASA Astrophysics Data System (ADS)

    Aragonès, Albert C.; Haworth, Naomi L.; Darwish, Nadim; Ciampi, Simone; Bloomfield, Nathaniel J.; Wallace, Gordon G.; Diez-Perez, Ismael; Coote, Michelle L.

    2016-03-01

    It is often thought that the ability to control reaction rates with an applied electrical potential gradient is unique to redox systems. However, recent theoretical studies suggest that oriented electric fields could affect the outcomes of a range of chemical reactions, regardless of whether a redox system is involved. This possibility arises because many formally covalent species can be stabilized via minor charge-separated resonance contributors. When an applied electric field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the molecule or transition state. This means that it should be possible to manipulate the kinetics and thermodynamics of non-redox processes using an external electric field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide experimental evidence that the formation of carbon-carbon bonds is accelerated by an electric field. We have designed a surface model system to probe the Diels-Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach. This technique, performed at the single-molecule level, is perfectly suited to deliver an electric-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-molecule junctions, resulting from the reaction that occurs when the electric field is present and aligned so as to favour electron flow from the dienophile to the diene. Our results are qualitatively consistent with those predicted by quantum-chemical calculations in a theoretical model of this system, and herald a new approach to chemical catalysis.

  13. Interactions between the Avian Parasite, Philornis downsi (Diptera: Muscidae) and the Galapagos Flycatcher, Myiarchus magnirostris Gould (Passeriformes: Tyrannidae).

    PubMed

    Lincango, Piedad; Causton, Charlotte; Cedeño, Daniel; Castañeda, Johanna; Hillstrom, Alexandra; Freund, Deborah

    2015-10-01

    An incidental observation of the fly Philornis downsi parasitizing a Galapagos Flycatcher (Myiarchus magnirostris) nest has revealed new insights into the searching behavior and biology of this invasive fly parasite and its interactions with endemic landbirds in the Galapagos Islands. Observations suggest that P. downsi relies on olfactory cues, or olfactory cues combined with the activity of adult birds, to locate nests and that flies continue to visit nests when chicks are >3 d old. At least 200 eggs were laid by P. downsi in different parts of the nest and >40 early-instar larvae were found inside the head of one chick, with additional larvae found in the base of the nest. Parasitism was the likely cause of mortality of both chicks found in or near the nest. This description of P. downsi parasitizing chicks of M. magnirostris highlights the vulnerability of this endemic bird species to this invasive fly. PMID:26267462

  14. Ecophysiological characteristics of Taiwan alder (Alnus formosana) seedlings adapted to the subtropical region.

    PubMed

    Liao, Tien-Szu; Weng, Jen-Hsien

    2002-04-01

    We investigated several ecophysiological characteristics of seedlings of a low-elevation (100-200 m) and a high-elevation (2000-2400 m) population of Taiwan alder (Alnus formosana Makino) from subtropical Taiwan. Both populations had a wide optimal temperature range for photosynthesis, and there was little difference in the optimal temperature range for photosynthesis between populations. Photosynthetic rate (P(N)) was near maximal from 20 to 35 degrees C when seedlings of both the low-elevation and the high-elevation populations were acclimated at a day/night temperature of 30/23 degrees C. When seedlings were acclimated at a day/night temperature of 20/10 degrees C, P(N) was near maximal over the range 15-35 degrees C in the low-elevation population and 15-30 degrees C in the high-elevation population. Compared with nine other tree species native to Taiwan, Taiwan alder had a high P(N) and stomatal conductance (g(s)) under well-watered conditions. Reflecting its higher transpiration rate, Taiwan alder had a significantly greater leaf-air temperature difference than camphor (Cinnamomum camphora (L.) J. Presl), a co-occurring lowland tree species with leaves similar in shape and size to those of Taiwan alder. Despite higher g(s), high root and shoot hydraulic conductances enabled Taiwan alder to maintain higher leaf water potentials than camphor under well-watered conditions. We conclude that both photosynthetic characteristics and water relations are important factors enabling Taiwan alder to adapt to a wide temperature range, thereby ensuring its success at both high and low elevations in subtropical Taiwan. PMID:11960760

  15. Phylogeny of the monarch flycatchers reveals extensive paraphyly and novel relationships within a major Australo-Pacific radiation.

    PubMed

    Andersen, Michael J; Hosner, Peter A; Filardi, Christopher E; Moyle, Robert G

    2015-02-01

    Monarch flycatchers are a major component of Australo-Pacific and Wallacean avifaunas. To date, the family has received incomplete attention by molecular systematists who focused on subclades with minimal character and/or taxon sampling. As a result, Monarchidae taxonomy is still out-of-date, and biogeographic reconstructions have been based on poorly-resolved phylogenies, limiting their interpretation. Here, we produced a comprehensive, molecular phylogeny of the Monarchidae inferred from mitochondrial and nuclear loci using both concatenated and multilocus coalescent frameworks. We sampled 92% of the 99 recognized monarchid biological species and included deeper sampling within several phylogenetic species complexes, including Monarcha castaneiventris, Symposiachrus barbatus, and Terpsiphone rufiventer. Melampitta is identified as sister to the monarch flycatchers, which themselves comprise four major lineages. The first lineage comprises Terpsiphone and allies, the second lineage is Grallina, the third is Arses and Myiagra, and the fourth lineage comprises a diverse assemblage of genera including the "core monarchs" and the most geographically isolated groups like Chasiempis (Hawaii) and Pomarea (eastern Polynesia). Gene tree discordance was evident in Myiagra, which has implications for basal lineages in the genus (e.g., M. azureocapilla, M. hebetior, and M. alecto). Numerous genera within the core monarchs are paraphyletic, including Mayrornis and Pomarea, whereas the validity of others such as Metabolus are questionable. We recognize polytypic taxa as multiple species, including Lamprolia victoriae and Myiagra azureocapilla. In general, the topology of species complexes included short internodes that were not well resolved, owing to their rapid diversification across island archipelagos. Terpsiphone rufiventer comprises multiple lineages, including a heretofore-unappreciated West African lineage, but relationships within these rapid radiations will require

  16. Stereoselection in Intramolecular Diels-Alder Reactions of 2-Cyano-1-azadienes: Indolizidine and Quinolizidine Synthesis.

    PubMed

    Tay, Gidget C; Sizemore, Nicholas; Rychnovsky, Scott D

    2016-07-01

    Progress toward understanding the scope and diastereoselectivity of intramolecular Diels-Alder reactions using 2-cyano-1-azadienes is described herein. The resulting cyanoenamine products are underutilized intermediates in organic synthesis. Assembly of the Diels-Alder precursors was achieved using an improved imine condensation/oxidative cyanation protocol. By this method, several highly substituted indolizidine and quinolizidine architectures were constructed. Quantum mechanical DFT calculations at the B3LYP/6-31+G(d) level of theory were performed for these cyclizations and provide insights into the origins of the observed diastereoselectivities. PMID:27295460

  17. Schleyer hyperconjugative aromaticity and Diels-Alder reactivity of 5-substituted cyclopentadienes.

    PubMed

    Levandowski, Brian J; Zou, Lufeng; Houk, K N

    2016-01-01

    Schleyer's discovery of hyperconjugative aromaticity and antiaromaticity in 5-substituted cyclopentadienes further expanded our understanding of the pervasive influence of aromaticity. Acceptors induce antiaromatic character by Schleyer's negative hyperconjugative aromaticity, and donors have the opposite effect. We computationally explored the Diels-Alder reactivity of 5-substituted cyclopentadienes with ethylene and maleic anhydride. The predicted billionfold difference in the computed gas phase rate constants at room temperature for the Diels-Alder reactions of 5-substituted cyclopentadienes with ethylene or maleic anhydride results from differences in the transition state distortion energies, which are directly related to the hyperconjugative aromaticity of these molecules. PMID:26444427

  18. Preparation and Diels-Alder reactions of 1′-heterosubsituted vinylimidazoles

    PubMed Central

    Ray, Abhisek; Mukherjee, Sabuj; Das, Jayanta; Bhandari, Manoj K.; Du, Hongwang; Yousufuddin, Muhammed; Lovely, Carl J.

    2015-01-01

    A Diels-Alder/rearrangement sequence has been pursued in our lab en route to a number of oroidin dimers. In order to access the fully substituted core of these molecules, 1′,2′-disubstituted 4-vinylimidazoles were required as dienes. The preparation of a series of a 4-vinylimidazoles containing substituents on the vinyl moiety via hydroalumination/electrophilic trapping or hydrosilylation are described. These derivatives undergo Diels-Alder reactions with N-phenylmaleimide to provide the tetrahydrobenzimidazole derivatives. The cycloadducts derived from halosubstituted systems generally undergo elimination, leading to the corresponding dihydrobenzimidazole, whereas the silyl and stannyl derivatives provide the corresponding 4-substituted tetrahydrobenzimidazole. PMID:26139945

  19. Enantioselective Organocatalytic Diels–Alder Trapping of Photochemically Generated Hydroxy‐o‐Quinodimethanes

    PubMed Central

    Dell'Amico, Luca; Vega‐Peñaloza, Alberto; Cuadros, Sara

    2016-01-01

    Abstract The photoenolization/Diels–Alder strategy offers straightforward access to synthetically valuable benzannulated carbocyclic products. This historical light‐triggered process has never before succumbed to efforts to develop an enantioselective catalytic approach. Herein, we demonstrate how asymmetric organocatalysis provides simple yet effective catalytic tools to intercept photochemically generated hydroxy‐o‐quinodimethanes with high stereoselectivity. We used a chiral organic catalyst, derived from natural cinchona alkaloids, to activate maleimides toward highly stereoselective Diels–Alder reactions. An unconventional mechanism of stereocontrol is operative, wherein the organocatalyst is actively involved in both the photochemical pathway, by leveraging the formation of the reactive photoenol, and the stereoselectivity‐defining event. PMID:26797768

  20. Competition between classical and hexadehydro-Diels–Alder (HDDA) reactions of HDDA triynes with furan

    PubMed Central

    Nguyen, Quang Luu; Baire, Beeraiah; Hoye, Thomas R.

    2015-01-01

    We report here thermal reactions between furan and one of three related triyne substrates. Each triyne is capable of reacting initially in two modes: (i) unimolecular hexadehydro-Diels-Alder (HDDA) reaction or (ii) bimolecular Diels-Alder reaction between one of its alkynes with furan. The relative rates of these initial events are such that two of the substrates react essentially in only one of modes (i) or (ii). The third is intermediate in behavior; its bifurcation is dependent on the concentration of the furan reactant. These results teach, more generally, principles relevant to the design of efficient HDDA-based reaction cascades. PMID:26028780

  1. A high-density linkage map enables a second-generation collared flycatcher genome assembly and reveals the patterns of avian recombination rate variation and chromosomal evolution

    PubMed Central

    Kawakami, Takeshi; Smeds, Linnéa; Backström, Niclas; Husby, Arild; Qvarnström, Anna; Mugal, Carina F; Olason, Pall; Ellegren, Hans

    2014-01-01

    Detailed linkage and recombination rate maps are necessary to use the full potential of genome sequencing and population genomic analyses. We used a custom collared flycatcher 50 K SNP array to develop a high-density linkage map with 37 262 markers assigned to 34 linkage groups in 33 autosomes and the Z chromosome. The best-order map contained 4215 markers, with a total distance of 3132 cm and a mean genetic distance between markers of 0.12 cm. Facilitated by the array being designed to include markers from most scaffolds, we obtained a second-generation assembly of the flycatcher genome that approaches full chromosome sequences (N50 super-scaffold size 20.2 Mb and with 1.042 Gb (of 1.116 Gb) anchored to and mostly ordered and oriented along chromosomes). We found that flycatcher and zebra finch chromosomes are entirely syntenic but that inversions at mean rates of 1.5–2.0 event (6.6–7.5 Mb) per My have changed the organization within chromosomes, rates high enough for inversions to potentially have been involved with many speciation events during avian evolution. The mean recombination rate was 3.1 cm/Mb and correlated closely with chromosome size, from 2 cm/Mb for chromosomes >100 Mb to >10 cm/Mb for chromosomes <10 Mb. This size dependence seemed entirely due to an obligate recombination event per chromosome; if 50 cm was subtracted from the genetic lengths of chromosomes, the rate per physical unit DNA was constant across chromosomes. Flycatcher recombination rate showed similar variation along chromosomes as chicken but lacked the large interior recombination deserts characteristic of zebra finch chromosomes. PMID:24863701

  2. Identifying the African Wintering Grounds of Hybrid Flycatchers Using a Multi–Isotope (δ2H, δ13C, δ15N) Assignment Approach

    PubMed Central

    Van Wilgenburg, Steven L.; Hobson, Keith A.; Folmer, Eelke; Font, Laura; Klaassen, Marcel

    2014-01-01

    Migratory routes and wintering grounds can have important fitness consequences, which can lead to divergent selection on populations or taxa differing in their migratory itinerary. Collared (Ficedula albicollis) and pied (F. hypoleuca) flycatchers breeding in Europe and wintering in different sub-Saharan regions have distinct migratory routes on the eastern and western sides of the Sahara desert, respectively. In an earlier paper, we showed that hybrids of the two species did not incur reduced winter survival, which would be expected if their migration strategy had been a mix of the parent species' strategies potentially resulting in an intermediate route crossing the Sahara desert to different wintering grounds. Previously, we compared isotope ratios and found no significant difference in stable-nitrogen isotope ratios (δ15N) in winter-grown feathers between the parental species and hybrids, but stable-carbon isotope ratios (δ13C) in hybrids significantly clustered only with those of pied flycatchers. We followed up on these findings and additionally analyzed the same feathers for stable-hydrogen isotope ratios (δ2H) and conducted spatially explicit multi-isotope assignment analyses. The assignment results overlapped with presumed wintering ranges of the two species, highlighting the efficacy of the method. In contrast to earlier findings, hybrids clustered with both parental species, though most strongly with pied flycatcher. PMID:24847717

  3. A Gene-Based Genetic Linkage Map of the Collared Flycatcher (Ficedula albicollis) Reveals Extensive Synteny and Gene-Order Conservation During 100 Million Years of Avian Evolution

    PubMed Central

    Backström, Niclas; Karaiskou, Nikoletta; Leder, Erica H.; Gustafsson, Lars; Primmer, Craig R.; Qvarnström, Anna; Ellegren, Hans

    2008-01-01

    By taking advantage of a recently developed reference marker set for avian genome analysis we have constructed a gene-based genetic map of the collared flycatcher, an important “ecological model” for studies of life-history evolution, sexual selection, speciation, and quantitative genetics. A pedigree of 322 birds from a natural population was genotyped for 384 single nucleotide polymorphisms (SNPs) from 170 protein-coding genes and 71 microsatellites. Altogether, 147 gene markers and 64 microsatellites form 33 linkage groups with a total genetic distance of 1787 cM. Male recombination rates are, on average, 22% higher than female rates (total distance 1982 vs. 1627 cM). The ability to anchor the collared flycatcher map with the chicken genome via the gene-based SNPs revealed an extraordinary degree of both synteny and gene-order conservation during avian evolution. The great majority of chicken chromosomes correspond to a single linkage group in collared flycatchers, with only a few cases of inter- and intrachromosomal rearrangements. The rate of chromosomal diversification, fissions/fusions, and inversions combined is thus considerably lower in birds (0.05/MY) than in mammals (0.6–2.0/MY). A dearth of repeat elements, known to promote chromosomal breakage, in avian genomes may contribute to their stability. The degree of genome stability is likely to have important consequences for general evolutionary patterns and may explain, for example, the comparatively slow rate by which genetic incompatibility among lineages of birds evolves. PMID:18562642

  4. Genetic Mapping in a Natural Population of Collared Flycatchers (Ficedula albicollis): Conserved Synteny but Gene Order Rearrangements on the Avian Z Chromosome

    PubMed Central

    Backström, Niclas; Brandström, Mikael; Gustafsson, Lars; Qvarnström, Anna; Cheng, Hans; Ellegren, Hans

    2006-01-01

    Data from completely sequenced genomes are likely to open the way for novel studies of the genetics of nonmodel organisms, in particular when it comes to the identification and analysis of genes responsible for traits that are under selection in natural populations. Here we use the draft sequence of the chicken genome as a starting point for linkage mapping in a wild bird species, the collared flycatcher—one of the most well-studied avian species in ecological and evolutionary research. A pedigree of 365 flycatchers was established and genotyped for single nucleotide polymorphisms in 23 genes selected from (and spread over most of) the chicken Z chromosome. All genes were also found to be located on the Z chromosome in the collared flycatcher, confirming conserved synteny at the level of gene content across distantly related avian lineages. This high degree of conservation mimics the situation seen for the mammalian X chromosome and may thus be a general feature in sex chromosome evolution, irrespective of whether there is male or female heterogamety. Alternatively, such unprecedented chromosomal conservation may be characteristic of most chromosomes in avian genome evolution. However, several internal rearrangements were observed, meaning that the transfer of map information from chicken to nonmodel bird species cannot always assume conserved gene orders. Interestingly, the rate of recombination on the Z chromosome of collared flycatchers was only ∼50% that of chicken, challenging the widely held view that birds generally have high recombination rates. PMID:16783008

  5. Assembly of the Isoindolinone Core of Muironolide A by Asymmetric Intramolecular Diels-Alder Cycloaddition

    PubMed Central

    Flores, Beatris; Molinski, Tadeusz F.

    2011-01-01

    The hexahydro-1H-isoindolin-1-one core of muironolide A was prepared by asymmetric intramolecular Diels Alder cycloaddition using a variant of the MacMillan organocatalyst which sets the C4,C5 and C11 stereocenters. PMID:21751773

  6. WATERSHED BIOGEOCHEMISTRY IN THE OREGON COAST RANGE: THE ROLE OF RED ALDER AND SALMON

    EPA Science Inventory

    Variations in plant community composition across the landscape can influence nutrient retention and loss at the watershed scale. A striking example of plant species influence is the role of N2-fixing red alder (Alnus rubra) in the biogeochemistry of Pacific Northwest forests. T...

  7. The Phytophthora species assemblage and diversity in riparian alder ecosystems of western Oregon, USA.

    PubMed

    Sims, Laura Lee; Sutton, Wendy; Reeser, Paul; Hansen, Everett M

    2015-01-01

    Phytophthora species were systematically sampled, isolated, identified and compared for presence in streams, soil and roots of alder (Alnus species) dominated riparian ecosystems in western Oregon. We describe the species assemblage and evaluate Phytophthora diversity associated with alder. We recovered 1250 isolates of 20 Phytophthora species. Only three species were recovered from all substrates (streams, soil, alder roots): P. gonapodyides, the informally described "P. taxon Pgchlamydo", and P. siskiyouensis. P. alni ssp. uniformis along with five other species not previously recovered in Oregon forests are included in the assemblage: P.citricola s.l., P. gregata, P. gallica, P. nicotianae and P. parsiana. Phytophthora species diversity was greatest in downstream riparian locations. There was no significant difference in species diversity comparing soil and unwashed roots (the rhizosphere) to stream water. There was a difference between the predominating species from the rhizosphere compared to stream water. The most numerous species was the informally described "P. taxon Oaksoil", which was mainly recovered from, and most predominant in, stream water. The most common species from riparian forest soils and alder root systems was P. gonapodyides. PMID:26240311

  8. The role of curvature in Diels-Alder functionalization of carbon-based materials.

    PubMed

    Willocq, B; Lemaur, V; El Garah, M; Ciesielski, A; Samorì, P; Raquez, J-M; Dubois, Ph; Cornil, J

    2016-06-18

    We have estimated theoretically the impact of curvature on the free energies of activation and reaction associated with Diels-Alder reactions on carbon-based materials. Significant reduction is observed for both energy values with increasing curvature for core-functionalization, while the opposite trend prevails for edge-functionalization, as further supported by SEM/fluorescence measurements. PMID:27226252

  9. Enantioselective Synthesis of (+)-Estrone Exploiting a Hydrogen Bond-Promoted Diels−Alder Reaction

    PubMed Central

    2010-01-01

    Starting from Dane’s diene and methylcyclopentenedione, (+)-estrone is synthesized along the Quinkert−Dane route in 24% total yield. The key step is an enantioselective Diels−Alder reaction promoted by an amidinium catalyst as efficiently as by a traditional Ti-TADDOLate Lewis acid. PMID:20302330

  10. Reactions of nitroso hetero-Diels-Alder cycloadducts with azides: stereoselective formation of triazolines and aziridines.

    PubMed

    Bodnar, Brian S; Miller, Marvin J

    2007-05-11

    The addition of azides to acylnitroso hetero-Diels-Alder cycloadducts derived from cyclopentadiene affords exo-triazolines in excellent yield. The reaction is greatly affected by the level of alkene strain, while sterically demanding azides do not hinder the reaction. Conversion of the triazolines to aziridines is also described. PMID:17429998

  11. Reactions of Nitroso Hetero Diels-Alder Cycloadducts with Azides: Stereoselective Formation of Triazolines and Aziridines

    PubMed Central

    Bodnar, Brian S.

    2011-01-01

    The addition of azides to acylnitroso hetero Diels-Alder cycloadducts derived from cyclopentadiene affords exo triazolines in excellent yield. The reaction is greatly affected by reducing the level of alkene strain, while sterically demanding azides do not hinder the reaction. Conversion of the triazolines to aziridines is also described. PMID:17429998

  12. A solvent-free Diels-Alder reaction of graphite into functionalized graphene nanosheets.

    PubMed

    Seo, Jeong-Min; Baek, Jong-Beom

    2014-12-01

    A solvent-free Diels-Alder reaction was carried out by heating a mixture of graphite and a typical dienophile, maleic anhydride (MA) or maleimide (MI), in a sealed glass ampoule of argon. The functionalization of graphite with dienophiles was confirmed by various characterization techniques, suggesting the efficient functionalization and delamination of graphite into a few layers of graphitic nanosheets. PMID:25314623

  13. Hydrogen-Bonding Catalysis of Tetraalkylammonium Salts in an Aza-Diels-Alder Reaction.

    PubMed

    Kumatabara, Yusuke; Kaneko, Shiho; Nakata, Satoshi; Shirakawa, Seiji; Maruoka, Keiji

    2016-08-01

    A piperidine-derived tetraalkylammonium salt with a non-coordinating counteranion worked as an effective hydrogen-bonding catalyst in an aza-Diels-Alder reaction of imines and a Danishefsky diene. The hydrogen-bonding interaction between the ammonium salt and an imine was observed as part of a (1) H NMR titration study. PMID:27311924

  14. Synthesis of a natural chromenoquinone via the Diels-Alder reaction of pyranobenzyne and furan.

    PubMed

    Katakawa, Kazuaki; Sato, Ayaka; Iwasaki, Mari; Horikawa, Tomofumi; Kumamoto, Takuya

    2014-01-01

    We describe the total synthesis of angular chromenoquinone 1 isolated from Conospermum plants. Iodophenol, a precursor of pyranobenzyne, was prepared by Claisen rearrangement of an iodoresorcinol derivative. Diels-Alder reaction of the pyranobenzyne and a substituted furan proceeded in low regioselectivity to afford desired 1 and its regioisomer. PMID:25087635

  15. A Computational Experiment of the Endo versus Exo Preference in a Diels-Alder Reaction

    ERIC Educational Resources Information Center

    Rowley, Christopher N.; Woo, Tom K.

    2009-01-01

    We have developed and tested a computational laboratory that investigates an endo versus exo Diels-Alder cycloaddition. This laboratory employed density functional theory (DFT) calculations to study the cycloaddition of N-phenylmaleimide to furan. The endo and exo stereoisomers of the product were distinguished by building the two isomers in a…

  16. Changes in sediment volume in Alder Lake, Nisqually River Basin, Washington, 1945-2011

    USGS Publications Warehouse

    Czuba, Jonathan A.; Olsen, Theresa D.; Czuba, Christiana R.; Magirl, Christopher S.; Gish, Casey C.

    2012-01-01

    The Nisqually River drains the southwest slopes of Mount Rainier, a glaciated stratovolcano in the Cascade Range of western Washington. The Nisqually River was impounded behind Alder Dam when the dam was completed in 1945 and formed Alder Lake. This report quantifies the volume of sediment deposited by the Nisqually and Little Nisqually Rivers in their respective deltas in Alder Lake since 1945. Four digital elevation surfaces were generated from historical contour maps from 1945, 1956, and 1985, and a bathymetric survey from 2011. These surfaces were used to compute changes in sediment volume since 1945. Estimates of the volume of sediment deposited in Alder Lake between 1945 and 2011 were focused in three areas: (1) the Nisqually River delta, (2) the main body of Alder Lake, along a 40-meter wide corridor of the pre-dam Nisqually River, and (3) the Little Nisqually River delta. In each of these areas the net deposition over the 66-year period was 42,000,000 ± 4,000,000 cubic meters (m3), 2,000,000 ± 600,000 m3, and 310,000 ± 110,000 m3, respectively. These volumes correspond to annual rates of accumulation of 630,000 ± 60,000 m3/yr, 33,000 ± 9,000 m3/yr, and 4,700 ± 1,600 m3/yr, respectively. The annual sediment yield of the Nisqually (1,100 ± 100 cubic meters per year per square kilometer [(m3/yr)/km2]) and Little Nisqually River basins [70 ± 24 (m3/yr)/km2] provides insight into the yield of two basins with different land cover and geomorphic processes. These estimates suggest that a basin draining a glaciated stratovolcano yields approximately 15 times more sediment than a basin draining forested uplands in the Cascade Range. Given the cumulative net change in sediment volume in the Nisqually River delta in Alder Lake, the total capacity of Alder Lake since 1945 decreased about 3 percent by 1956, 8 percent by 1985, and 15 percent by 2011.

  17. Problems in separating species with similar habits and vocalizations

    USGS Publications Warehouse

    Robbins, C.S.; Stallcup, R.W.

    1981-01-01

    The possibilities for species misidentification based on vocalization or habitat association are high. However, the magnitude of the errors actually perpetrated is generally within an acceptable range in most types of bird survey work. Examples of problems discussed are: congeners that are similar in appearance or in song (such as Chimney and Vaux's Swifts, Chaetura pelagica, C. vauxi; Hammond's, Dusky and Gray Flycatchers, Empidonax hammondii, E. oberholseri, E. wrightii; Willow and Alder Flycatchers, E. traillii, E. alnorum; Common and Fish Crows, Corvus brachyrhynchos, C. ossifragus); birds that are misidentified because they are not expected by the observer (House Finches, Carpodacus mexicanus, invading new areas of eastern U.S.); birds that imitate other species (especially Starling, Sturnus vulgaris, and Mockingbird, Mimus polyglottos); birds in mixed flocks; birds with geographic differences in vocalizations (Solitary Vireo, Vireo solitarius); woodpeckers that are only heard drumming; and nests or eggs that are misidentified. Equally serious problems are the errors resulting from undetected species and from careless recording or failure to check manuscripts against original data. The quality of published count work can be improved considerably by (1) recognizing the problems that exist, (2) standardizing techniques for dealing with situations where not all birds can be identified, and (3) routinely applying all appropriate safeguards such as verification by mist netting and measuring, photography, tape recording or playback, additional observations, and careful verification of all entries in the final manuscript.

  18. Dendrochronology and lakes: using tree-rings of alder to reconstruct lake levels

    NASA Astrophysics Data System (ADS)

    van der Maaten, Ernst; Buras, Allan; Scharnweber, Tobias; Simard, Sonia; Kaiser, Knut; Lorenz, Sebastian; van der Maaten-Theunissen, Marieke; Wilmking, Martin

    2014-05-01

    Climate change is considered a major threat for ecosystems around the world. Assessing its effects is challenging, amongst others, as we are unsure how ecosystems may respond to climate conditions they were not exposed to before. However, increased insight may be obtained by analyzing responses of ecosystems to past climate variability. In this respect, lake ecosystems appear as valuable sentinels, because they provide direct and indirect indicators of change through effects of climate. Lake-level fluctuations of closed catchments, for example, reflect a dynamic water balance, provide detailed insight in past moisture variations, and thereby allow for assessments of effects of anticipated climate change. Up to now, lake-level data are mostly obtained from gauging records and reconstructions from sediments and landforms. However, these records are in many cases only available over relatively short time periods, and, since geoscientific work is highly demanding, lake-level reconstructions are lacking for many regions. Here, we present and discuss an alternative method to reconstruct lake levels, which is based on tree-ring data of black alder (Alnus glutinosa L.). This tree species tolerates permanently waterlogged and temporally flooded conditions (i.e. riparian vegetation), and is often found along lakeshores. As the yearly growth of trees varies depending upon the experienced environmental conditions, annual rings of black alder from lakeshore vegetation likely capture information on variations in water table, and may therefore be used to reconstruct lake levels. Although alder is a relatively short-lived tree species, the frequent use of its' decay-resistant wood in foundations of historical buildings offers the possibility of extending living tree-chronologies back in time for several centuries. In this study, the potential to reconstruct lake-level fluctuations from tree-ring chronologies of black alder is explored for three lake ecosystems in the Mecklenburg

  19. Out of Amazonia again and again: episodic crossing of the Andes promotes diversification in a lowland forest flycatcher

    PubMed Central

    Miller, Matthew J; Bermingham, Eldredge; Klicka, John; Escalante, Patricia; do Amaral, Fabio S. Raposo; Weir, Jason T; Winker, Kevin

    2008-01-01

    Most Neotropical lowland forest taxa occur exclusively on one side of the Andes despite the availability of appropriate habitat on both sides. Almost all molecular phylogenies and phylogenetic analyses of species assemblages (i.e. area cladograms) have supported the hypothesis that Andean uplift during the Late Pliocene created a vicariant barrier affecting lowland lineages in the region. However, a few widespread plant and animal species occurring in lowland forests on both sides of the Andes challenge the generality of this hypothesis. To understand the role of the Andes in the history of such organisms, we reconstructed the phylogeographic history of a widespread Neotropical flycatcher (Mionectes oleagineus) in the context of the other four species in the genus. A molecular phylogeny based on nuclear and mitochondrial sequences unambiguously showed an early basal split between montane and lowland Mionectes. The phylogeographic reconstruction of lowland taxa revealed a complex history, with multiple cases in which geographically proximate populations do not represent sister lineages. Specifically, three populations of M. oleagineus west of the Andes do not comprise a monophyletic clade; instead, each represents an independent lineage with origins east of the Andes. Divergence time estimates suggest that at least two cross-Andean dispersal events post-date Andean uplift. PMID:18285279

  20. Integrated plumage colour variation in relation to body condition, reproductive investment and laying date in the collared flycatcher

    NASA Astrophysics Data System (ADS)

    Laczi, Miklós; Hegyi, Gergely; Herényi, Márton; Kiss, Dorottya; Markó, Gábor; Nagy, Gergely; Rosivall, Balázs; Szöllősi, Eszter; Török, János

    2013-10-01

    The possible integration of different sexual ornaments into a composite system, and especially the information content of such ornament complexes, is poorly investigated. Many bird species display complex plumage coloration, but whether this represents one integrated or several independent sexual traits can be unclear. Collared flycatchers ( Ficedula albicollis) display melanised and depigmented plumage areas, and the spectral features (brightness and UV chroma) of these are correlated with each other across the plumage. In a 5-year dataset of male and female plumage reflectance, we examined some of the potential information content of integrated, plumage-level colour attributes by estimating their relationships to previous and current year body condition, laying date and clutch size. Females were in better condition the year before they became darker pigmented, and males in better current year condition were also darker pigmented. Female pigment-based brightness was positively, while male structurally based brightness was negatively related to current laying date. Finally, the overall UV chroma of white plumage areas in males was positively associated with current clutch size. Our results show that higher degree of pigmentation is related to better condition, while the structural colour component is associated with some aspects of reproductive investment. These results highlight the possibility that correlated aspects of a multiple plumage ornamentation system may reflect together some aspects of individual quality, thereby functioning as a composite signal.

  1. δ15N patterns of Douglas-fir and red alder riparian forests in the Oregon Coast Range

    USGS Publications Warehouse

    Scott, E.E.; Perakis, S.S.; Hibbs, D.E.

    2008-01-01

    We used naturally occurring stable isotopes of N to compare N dynamics in near-stream and upslope environments along riparian catenas in N-fixing red alder (Alnus rubra) and Douglas-fir (Pseudotsuga menziesii) forests in the Coast Range of western Oregon. Based on the existing literature, we expected soil δ15N to be enriched closer to streams owing to inputs of isotopically heavy, marine-derived N by spawning salmon, higher rates of denitrification near the stream, or both. However, it has been unclear what effect red alder might have on soil δ15N patterns near streams. We found a consistent −1‰ δ15N signature in red alder foliage, and δ15N of total N in soils under red alder averaged 2.2‰ along sampling transects extending 20 m upslope from the stream. Surprisingly, δ15N of total N in soil under Douglas-fir was progressively depleted nearer to streams, opposite from the pattern expected from N losses by denitrification or N inputs from anadromous salmon. Instead, δ15N of total N in soil under Douglas-fir converged toward soil δ15N values typical of red alder sites. We consider that the historic presence of red alder may have contributed a legacy of lower soil δ15N nearer to streams on sites that are currently dominated by young Douglas-fir forest.

  2. Headwater riparian invertebrate communities associated with red alder and conifer wood and leaf litter in southeastern Alaska

    USGS Publications Warehouse

    LeSage, C.M.; Merritt, R.W.; Wipfli, M.S.

    2005-01-01

    We examined how management of young upland forests in southeastern Alaska affect riparian invertebrate taxa richness, density, and biomass, in turn, potentially influencing food abundance for fish and wildlife. Southeastern Alaska forests are dominated by coniferous trees including Sitka spruce (Picea sitchensis (Bong.) Carr.), western hemlock (Tsuga heterophylla (Raf.) Sarg.), with mixed stands of red cedar (Thuja plicata Donn.). Red alder (Alnus rubra Bong.) is hypothesized to influence the productivity of young-growth conifer forests and through forest management may provide increased riparian invertebrate abundance. To compare and contrast invertebrate densities between coniferous and alder riparian habitats, leaf litter and wood debris (early and late decay classes) samples were collected along eleven headwater streams on Prince of Wales Island, Alaska, during the summers of 2000 and 2001. Members of Acarina and Collembola were the most abundant taxa collected in leaf litter with alder litter having significantly higher mean taxa richness than conifer litter. Members of Acarina were the most abundant group collected on wood debris and alder wood had significantly higher mean taxa richness and biomass than conifer wood. Alder wood debris in more advanced decay stages had the highest mean taxa richness and biomass, compared to other wood types, while conifer late decay wood debris had the highest densities of invertebrates. The inclusion of alder in young-growth conifer forests can benefit forest ecosystems by enhancing taxa richness and biomass of riparian forest invertebrates. ?? 2005 by the Northwest Scientific Association. All rights reserved.

  3. Distortion-Controlled Reactivity and Molecular Dynamics of Dehydro-Diels-Alder Reactions.

    PubMed

    Yu, Peiyuan; Yang, Zhongyue; Liang, Yong; Hong, Xin; Li, Yanwei; Houk, K N

    2016-07-01

    We report density functional theory (M06-2X) studies of a series of dehydro-Diels-Alder (DDA) reactions. For these and the parent reaction, the stepwise mechanisms have similar barriers, whereas the barriers of the concerted mechanisms differ significantly. The reactivity of DDA reactions is controlled by distortion energy. The concerted and stepwise mechanisms of the hexadehydro-Diels-Alder (HDDA) reaction are competitive with activation barriers of ∼36 kcal/mol. This is because a large distortion energy (∼43 kcal/mol) is required to achieve the concerted transition state geometry. MD simulations reveal that productive concerted trajectories display a strong angle bending oscillation (∼25° oscillation amplitude), while the stepwise trajectories show only a chaotic pattern and less pronounced bending vibrations. PMID:27286801

  4. Use of wetlands for production of woody plants for fuels and petrochemical substitutes. [Alders, willows, poplars

    SciTech Connect

    Farnham, R.S.; Read, P.

    1981-03-01

    Work performed on this project in the past year has included the evaluations of natural stands productivity for wetland biomass species; propagation studies with alder, willow and poplar species; nursery establishment for production of cultivars and evaluation of wetland soils suitable for production of woody biomass species. Also a biomass research facility has been established in N. Minnesota suitable for long-term research and demonstration. Propagation research has included both micro and macro propagation techniques with native willows, selected willow clones from Sweden, alder seed selection from Finland and hybrid poplar clones from US Forest Service, Rhinelander, Wisconsin. Approximately 100,000 rooted plants will be available for field research by June 1, 1981.

  5. Cyclodextrin-promoted Diels Alder reactions of a polycyclic aromatic hydrocarbon under mild reaction conditions

    PubMed Central

    Chaudhuri, Sauradip; Phelan, Tyler; Levine, Mindy

    2015-01-01

    Reported herein is the effect of cyclodextrins on the rates of aqueous Diels Alder reactions of 9-anthracenemethanol with a variety of N-substituted maleimides. These reactions occurred under mild reaction conditions (aqueous solvent, 40 °C), and were most efficient for the reaction of N-cyclohexylmaleimide with a methyl-β-cyclodextrin additive (94% conversion in 24 hours). These results can be explained on the basis of a model wherein the cyclodextrins bind the hydrophobic substituents on the maleimides and activate the dienophile via electronic modulation of the maleimide double bond. The results reported herein represent a new mechanism for cyclodextrin-promoted Diels Alder reactions, and have significant potential applications in the development of other cyclodextrin-promoted organic transformations. Moreover, the ability to deplanarize polycyclic aromatic hydrocarbons (PAHs) under mild conditions, as demonstrated herein, has significant applications for PAH detoxification. PMID:26692588

  6. Total synthesis of Elisabethin A: intramolecular Diels-Alder reaction under biomimetic conditions.

    PubMed

    Heckrodt, Thilo J; Mulzer, Johann

    2003-04-23

    We describe the first total synthesis of the marine diterpenoid elisabethin A. The synthesis uses (S)-hydroxy-2-methyl-propionate as the chiral starting material, which is elaborated into a dienyl-iodide and added to an aryl acetic acid ester via enolate alkylation. The hydroquinoid system is oxidized to the quinone which serves as the dienophile in a highly stereocontrolled intramolecular Diels-Alder addition. This IMDA reaction, which to our knowledge is the first one to employ a terminal (Z)-diene, proceeds under biomimetic conditions (water, ferrichloride as the oxidant, room temperature) with high yield and stereoselectivity. The Diels-Alder adduct is transformed into the natural product via a three-step sequence including selective hydrogenation, base-catalyzed epimerization of the cis- into the trans-decalin system and O-demethylation. PMID:12696865

  7. Biomass of Speckled Alder on an Air-Polluted Mountain Site and its Response to Fertilization

    NASA Astrophysics Data System (ADS)

    Kuneš, Ivan; Baláš, Martin; Koňasová, Tereza; Špulák, Ondřej; Balcar, Vratislav; Millerová, Kateřina Bednářová; Kacálek, Dušan; Jakl, Michal; Zahradník, Daniel; Vítámvás, Jan; Š´astná, Jaroslava; Jaklová Dytrtová, Jana

    2014-12-01

    The article summarizes outcomes of a biomass study conducted in a young speckled alder plantation on a cold mountain site. At this location, the previously existing old forest was clear felled because of damage from air pollution, and present-day surface humus is in need of restoration. The intention of this study was to quantify the biomass and nutrients accumulated by alders and their components and assess whether the initial fertilization resulted in increased biomass production and nutrient accumulation in the biomass. Besides the control, two fertilized treatments were installed. In the surface treatment (SUT), the amendment was applied as a base dressing in small circles around trees. In the planting-hole treatment (PHT), the amendment was incorporated into soil inside the planting holes. Five growth seasons after planting and fertilization, six alders from each treatment were harvested including roots. Their biomass was quantified and analyzed for macroelements. The greatest pool of dry mass (DM) was branches in the control and stem wood in the fertilized treatments. The greatest pools of macroelements were leaves and branches. The most pronounced effects of fertilization were recorded in the DM and consequently in the absolute quantities of nutrients. The DM of an average tree in the control, SUT, and PHT was 85, 226, and 231 g, respectively. The absolute contents of nutrients per tree in the fertilized treatments showed the following increases, as compared with the control: (N) 2.5-2.6 times; (P) 1.6-2.4 times; (K) 1.8-2.1 times; and (Mg) 1.8-2.0 times, respectively. Speckled alder responded positively to fertilization.

  8. Biomass of speckled alder on an air-polluted mountain site and its response to fertilization.

    PubMed

    Kuneš, Ivan; Baláš, Martin; Koňasová, Tereza; Spulák, Ondřej; Balcar, Vratislav; Millerová, Kateřina Bednářová; Kacálek, Dušan; Jakl, Michal; Zahradník, Daniel; Vítámvás, Jan; Stastná, Jaroslava; Jaklová Dytrtová, Jana

    2014-12-01

    The article summarizes outcomes of a biomass study conducted in a young speckled alder plantation on a cold mountain site. At this location, the previously existing old forest was clear felled because of damage from air pollution, and present-day surface humus is in need of restoration. The intention of this study was to quantify the biomass and nutrients accumulated by alders and their components and assess whether the initial fertilization resulted in increased biomass production and nutrient accumulation in the biomass. Besides the control, two fertilized treatments were installed. In the surface treatment (SUT), the amendment was applied as a base dressing in small circles around trees. In the planting-hole treatment (PHT), the amendment was incorporated into soil inside the planting holes. Five growth seasons after planting and fertilization, six alders from each treatment were harvested including roots. Their biomass was quantified and analyzed for macroelements. The greatest pool of dry mass (DM) was branches in the control and stem wood in the fertilized treatments. The greatest pools of macroelements were leaves and branches. The most pronounced effects of fertilization were recorded in the DM and consequently in the absolute quantities of nutrients. The DM of an average tree in the control, SUT, and PHT was 85, 226, and 231 g, respectively. The absolute contents of nutrients per tree in the fertilized treatments showed the following increases, as compared with the control: (N) 2.5-2.6 times; (P) 1.6-2.4 times; (K) 1.8-2.1 times; and (Mg) 1.8-2.0 times, respectively. Speckled alder responded positively to fertilization. PMID:25294419

  9. TEMPO-Mediated Aza-Diels-Alder Reaction: Synthesis of Tetrahydropyridazines Using Ketohydrazones and Olefins.

    PubMed

    Yang, Xiu-Long; Peng, Xie-Xue; Chen, Fei; Han, Bing

    2016-05-01

    A novel, facile, and efficient method for the synthesis of tetrahydropyridazines by a one-pot tandem reaction of easily accessible ketohydrazones and olefins in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been successfully developed. The reaction involves the initial generation of azoalkenes from direct oxidative dehydrogenation of ketohydrazones using TEMPO as the commercially available oxidant, followed by a subsequent aza-Diels-Alder reaction with olefins. PMID:27120574

  10. Diels-Alder Reactions of Furans with Itaconic Anhydride: Overcoming Unfavorable Thermodynamics.

    PubMed

    Pehere, Ashok D; Xu, Shu; Thompson, Severin K; Hillmyer, Marc A; Hoye, Thomas R

    2016-06-01

    Unfavorable thermodynamics often render furans reluctant to engage in high-yielding Diels-Alder (DA) cycloaddition reactions. Here, we report the highly efficient conversion of the biosourced reactants itaconic anhydride (IA) and furfuryl alcohol (FA) to a single DA adduct. The free energy advantages provided by anhydride ring opening and crystal lattice energy of the product overcome the loss of aromaticity of the furanoid diene. Detailed (1)H NMR studies provided valuable insights about relevant kinetic and thermodynamic features. PMID:27214494

  11. New L-Serine Derivative Ligands as Cocatalysts for Diels-Alder Reaction

    PubMed Central

    Sousa, Carlos A. D.; Rodríguez-Borges, José E.; Freire, Cristina

    2013-01-01

    New L-serine derivative ligands were prepared and tested as cocatalyst in the Diels-Alder reactions between cyclopentadiene (CPD) and methyl acrylate, in the presence of several Lewis acids. The catalytic potential of the in situ formed complexes was evaluated based on the reaction yield. Bidentate serine ligands showed good ability to coordinate medium strength Lewis acids, thus boosting their catalytic activity. The synthesis of the L-serine ligands proved to be highly efficient and straightforward. PMID:24383009

  12. Molecular Complexity via C–H Activation: A Dehydrogenative Diels-Alder Reaction

    PubMed Central

    Stang, Erik M.; White, M. Christina

    2011-01-01

    Traditionally, C–H oxidation reactions install oxidized functionality onto a preformed molecular skeleton, resulting in a local molecular change. The use of C–H activation chemistry to construct complex molecular scaffolds is a new area with tremendous potential in synthesis. We report a Pd(II)/bis-sulfoxide catalyzed dehydrogenative Diels-Alder reaction that converts simple terminal olefins into complex cycloadducts in a single operation. PMID:21842902

  13. Can an Alder Disease Influence the Controls of Ecosystem Water Flux?

    NASA Astrophysics Data System (ADS)

    Rohrs-Richey, J. K.; Mulder, C. P.; Ruess, R. W.; Winton, L. M.; Stanosz, G. R.

    2007-12-01

    In Alaska, nitrogen-fixing shrubs (Alnus spp.) comprise a large component of the vegetation and are important for water and energy flux in the Alaskan tundra, the Interior boreal forest, and south-central Alaska. Recently there has been high incidence and severity of a canker disease on Alnus which alters small scale controls (e.g., leaves, branches) of water and carbon flux and may have ecosystem scale effects in severely diseased areas. The fungal pathogen, Valsa melanodiscus (anamorph =Cytospora umbrina), kills active xylem and phloem, causes long, girdling cankers on stems, and is frequently associated with stem mortality in the thin leaf alder (Alnus tenuifolia) and green alder (Alnus crispa). We are just beginning to understand how this canker disease affects the physiology of its host and the implications for water loss and carbon fixation. An inoculation experiment at the University of Alaska is currently being conducted on well-watered and water-limited green alders to: 1) monitor the response of the water transport system to infection and canker development; 2) assess the ability of colonized alders to adjust water use efficiency; and 3) measure the effect of canker development on photosynthesis. Only 4 weeks after inoculation, stems (3-5 mm diam.) with incipient cankers had an overall reduction in total daily water loss and up to 50 percent decrease in daily peak water loss. Stems with incipient cankers were also unable to attain the maximum photosynthetic rate of healthy stems, and had lower light saturation points and quantum efficiencies. Further quantification of these relationships is underway. This study, in combination with recent field measurements of sapflow, will allow us to estimate the impact of varying degrees of disease severity on stand-level water flux. Alders are a keystone species and are currently responding to climate change by expanding into the Alaska tundra, increasing abundance in northern Alaska, and migrating into river

  14. Male-male competition and parental care in collared flycatchers (Ficedula albicollis): an experiment controlling for differences in territory quality.

    PubMed

    Qvarnström, A; Grifffith, S C; Gustafsson, L

    2000-12-22

    Females are known to benefit from mate choice in several different ways but the relationship between these benefits has received little attention. The quality of resources provided by males, such as nest sites, and paternal care are often assumed to covary positively However, because the location of the nest affects the cost of parental care, these two benefits from mate choice can easily be confounded. To investigate the provisioning ability of successful competitors while controlling for differences in territory quality we removed early-settled pairs of collared flycatchers (Ficedula albicollis) and allowed replacement by later-arriving males or floaters (i.e.'poor competitors'). A control group of early-settled males (i.e. 'good competitors') had their females removed. Females paired to good competitors enjoyed a significantly higher reproductive success and tended to receive more parental assistance from their mates compared with females mated to poor competitors. Thus, some males seem able not only to compete successfully over resources but also to feed their offspring at a relatively higher rate. An alternative explanation, that poor competitors invested less in offspring quality in response to a lower share of paternity, could be rejected. The rate of extra-pair paternity did not differ between the two treatment groups. Our results suggest that male- male competition can sometimes facilitate female choice of superior care-givers. Thus, a female's benefit from choosing a competitive male may not be restricted to the quality of the resource he defends but can also include superior paternal care. PMID:11197133

  15. Effects of brood size manipulation and common origin on phenotype and telomere length in nestling collared flycatchers

    PubMed Central

    2012-01-01

    Background Evidence is accumulating that telomere length is a good predictor of life expectancy, especially early in life, thus calling for determining the factors that affect telomere length at this stage. Here, we investigated the relative influence of early growth conditions and origin (genetics and early maternal effects) on telomere length of collared flycatchers (Ficedula albicollis) at fledging. We experimentally transferred hatchlings among brood triplets to create reduced, control (i.e. unchanged final nestling number) and enlarged broods. Results Although our treatment significantly affected body mass at fledging, we found no evidence that increased sibling competition affected nestling tarsus length and telomere length. However, mixed models showed that brood triplets explained a significant part of the variance in body mass (18%) and telomere length (19%), but not tarsus length (13%), emphasizing that unmanipulated early environmental factors influenced telomere length. These models also revealed low, but significant, heritability of telomere length (h2 = 0.09). For comparison, the heritability of nestling body mass and tarsus length was 0.36 and 0.39, respectively, which was in the range of previously published estimates for those two traits in this species. Conclusion Those findings in a wild bird population demonstrate that telomere length at the end of the growth period is weakly, but significantly, determined by genetic and/or maternal factors taking place before hatching. However, we found no evidence that the brood size manipulation experiment, and by extension the early growth conditions, influenced nestling telomere length. The weak heritability of telomere length suggests a close association with fitness in natural populations. PMID:22901085

  16. Dimerization of quercetin, Diels-Alder vs. radical-coupling approach: a joint thermodynamics, kinetics, and topological study.

    PubMed

    Fourré, Isabelle; Di Meo, Florent; Podloucká, Pavlína; Otyepka, Michal; Trouillas, Patrick

    2016-08-01

    Quercetin is a prototypical antioxidant and prominent member of flavonoids, a large group of natural polyphenols. The oxidation of quercetin may lead to its dimerization, which is a paradigm of the more general polyphenol oligomerization. There exist two opposing mechanisms to describe the dimerization process, namely radical-coupling or Diels-Alder reactions. This work presents a comprehensive rationalization of this dimerization process, acquired from density functional theory (DFT) calculations. It is found that the two-step radical-coupling pathway is thermodynamically and kinetically preferred over the Diels-Alder reaction. This is in agreement with the experimental results showing the formation of only one isomer, whereas the Diels-Alder mechanism would yield two isomers. The evolution in bonding, occurring during these two processes, is investigated using the atoms in molecules (AIM) and electron localization function (ELF) topological approaches. It is shown that some electron density is accumulated between the fragments in the transition state of the radical-coupling reaction, but not in the transition state of the Diels-Alder process. Graphical Abstract Quantum chemistry calculations of the dimerization process of quercetin show that a radical coupling approach is preferred to a Diels-Alder type reaction, in agreement with experimental results. Analysis of the bonding evolution highlights the reaction mechanism. PMID:27449669

  17. Linked selection and recombination rate variation drive the evolution of the genomic landscape of differentiation across the speciation continuum of Ficedula flycatchers

    PubMed Central

    Burri, Reto; Nater, Alexander; Kawakami, Takeshi; Mugal, Carina F.; Olason, Pall I.; Smeds, Linnea; Suh, Alexander; Dutoit, Ludovic; Bureš, Stanislav; Garamszegi, Laszlo Z.; Hogner, Silje; Moreno, Juan; Qvarnström, Anna; Ružić, Milan; Sæther, Stein-Are; Sætre, Glenn-Peter; Török, Janos; Ellegren, Hans

    2015-01-01

    Speciation is a continuous process during which genetic changes gradually accumulate in the genomes of diverging species. Recent studies have documented highly heterogeneous differentiation landscapes, with distinct regions of elevated differentiation (“differentiation islands”) widespread across genomes. However, it remains unclear which processes drive the evolution of differentiation islands; how the differentiation landscape evolves as speciation advances; and ultimately, how differentiation islands are related to speciation. Here, we addressed these questions based on population genetic analyses of 200 resequenced genomes from 10 populations of four Ficedula flycatcher sister species. We show that a heterogeneous differentiation landscape starts emerging among populations within species, and differentiation islands evolve recurrently in the very same genomic regions among independent lineages. Contrary to expectations from models that interpret differentiation islands as genomic regions involved in reproductive isolation that are shielded from gene flow, patterns of sequence divergence (dxy and relative node depth) do not support a major role of gene flow in the evolution of the differentiation landscape in these species. Instead, as predicted by models of linked selection, genome-wide variation in diversity and differentiation can be explained by variation in recombination rate and the density of targets for selection. We thus conclude that the heterogeneous landscape of differentiation in Ficedula flycatchers evolves mainly as the result of background selection and selective sweeps in genomic regions of low recombination. Our results emphasize the necessity of incorporating linked selection as a null model to identify genome regions involved in adaptation and speciation. PMID:26355005

  18. The Mouse-colored Tyrannulet (Phaeomyias murina) is a species complex that includes the Cocos Flycatcher (Nesotriccus ridgwayi), an island form that underwent a population bottleneck.

    PubMed

    Zucker, Marc R; Harvey, Michael G; Oswald, Jessica A; Cuervo, Andrés; Derryberry, Elizabeth; Brumfield, Robb T

    2016-08-01

    Simultaneous examination of evolutionary history in island forms and closely related mainland relatives can provide reciprocal insight into the evolution of island and mainland faunas. The Cocos Flycatcher (Nesotriccus ridgwayi) is a small tyrant flycatcher (Tyrannidae) endemic to Cocos Island, an oceanic island in the eastern Pacific Ocean. We first established its close relationship to the mainland species Mouse-colored Tyrannulet (Phaeomyias murina) using a phylogeny from genome-wide ultraconserved elements and exons. We then used mitochondrial DNA to explore the relationships between Nesotriccus and Phaeomyias populations from across its distribution in Central and South America. We found that Nesotriccus is nested within the Phaeomyias evolutionary tree, and that Phaeomyias represents a complex of at least four evolutionarily distinct species that differ in plumage, voice, and habitat association. Nesotriccus underwent a population bottleneck subsequent to its divergence from Central American and northern South American Phaeomyias populations in the middle Pleistocene. The 46 UCE loci containing alleles that are fixed between the two species are widely distributed across the genome, which suggests that selective or neutral processes responsible for divergence have occurred genome-wide. Overall, our simultaneous examination of Phaeomyias and Nesotriccus revealed divergent levels of genetic diversity and evolutionary histories between island and mainland forms. PMID:27126184

  19. Total Synthesis of the Galbulimima Alkaloids Himandravine and GB17 Using Biomimetic Diels–Alder Reactions of Double Diene Precursors

    PubMed Central

    Larson, Reed T.; Pemberton, Ryan P.; Franke, Jenna M.; Tantillo, Dean J.; Thomson, Regan J.

    2015-01-01

    The enantioselective total syntheses of himandravine and GB17 were completed through a common biomimetic strategy involving Diels–Alder reactions of unusual double diene containing linear precursors. The double diene precursors, containing or lacking a C12 substituent as required to produce GB17 or himandravine, respectively, were found to undergo Diels–Alder reactions to afford mixtures of regioisomeric cycloadducts that map onto the alternative carbocyclic frameworks of both himandravine and GB17. Computational investigations revealed that these Diels–Alder reactions proceed via transition state structures of similar energy that have a high degree of bispericyclic character and that the low levels of regioselectivity observed in the reactions are a consequence of competing orbital interaction and distortion energies. The combined experimental and computational results provide valuable insights into the biosynthesis of the Galbulimima alkaloids. PMID:26305231

  20. Total Synthesis of the Galbulimima Alkaloids Himandravine and GB17 Using Biomimetic Diels-Alder Reactions of Double Diene Precursors.

    PubMed

    Larson, Reed T; Pemberton, Ryan P; Franke, Jenna M; Tantillo, Dean J; Thomson, Regan J

    2015-09-01

    The enantioselective total syntheses of himandravine and GB17 were completed through a common biomimetic strategy involving Diels-Alder reactions of unusual double diene containing linear precursors. The double diene precursors, containing or lacking a C12 substituent as required to produce GB17 or himandravine, respectively, were found to undergo Diels-Alder reactions to afford mixtures of regioisomeric cycloadducts that map onto the alternative carbocyclic frameworks of both himandravine and GB17. Computational investigations revealed that these Diels-Alder reactions proceed via transition state structures of similar energy that have a high degree of bispericyclic character and that the low levels of regioselectivity observed in the reactions are a consequence of competing orbital interaction and distortion energies. The combined experimental and computational results provide valuable insights into the biosynthesis of the Galbulimima alkaloids. PMID:26305231

  1. Recent Advances in Inverse-Electron-Demand Hetero-Diels-Alder Reactions of 1-Oxa-1,3-Butadienes.

    PubMed

    Pałasz, Aleksandra

    2016-06-01

    This review is an endeavor to highlight the progress in the inverse-electron-demand hetero-Diels-Alder reactions of 1-oxa-1,3-butadienes in recent years. The huge number of examples of 1-oxadienes cycloadditions found in the literature clearly demonstrates the incessant importance of this transformation in pyran ring synthesis. This type of reaction is today one of the most important methods for the synthesis of dihydropyrans which are the key building blocks in structuring of carbohydrate and other natural products. Two different modes, inter- and intramolecular, of inverse-electron-demand hetero-Diels-Alder reactions of 1-oxadienes are discussed. The domino Knoevenagel hetero-Diels-Alder reactions are also described. In recent years the use of chiral Lewis acids, chiral organocatalysts, new optically active heterodienes or dienophiles have provided enormous progress in asymmetric synthesis. Solvent-free and aqueous hetero-Diels-Alder reactions of 1-oxabutadienes were also investigated. The reactivity of reactants, selectivity of cycloadditions, and chemical stability in aqueous solutions and under physiological conditions were taken into account to show the potential application of the described reactions in bioorthogonal chemistry. New bioorthogonal ligation by click inverse-electron-demand hetero-Diels-Alder cycloaddition of in situ-generated 1-oxa-1,3-butadienes and vinyl ethers was developed. It seems that some of the hetero-Diels-Alder reactions described in this review can be applied in bioorthogonal chemistry because they are selective, non-toxic, and can function in biological conditions taking into account pH, an aqueous environment, and temperature. PMID:27573264

  2. Diarylheptanoids from green alder bark and their potential for DNA protection.

    PubMed

    Novaković, Miroslav; Stanković, Miroslava; Vučković, Ivan; Todorović, Nina; Trifunović, Snežana; Apostolović, Danijela; Mandić, Boris; Veljić, Milan; Marin, Petar; Tešević, Vele; Vajs, Vlatka; Milosavljević, Slobodan

    2014-06-01

    Nine diarylheptanoids, 1-9, catechin (11), and a phenolic glucoside, 10, were isolated from the bark of green alder (Alnus viridis). Four of the isolated compounds, i.e., 2, 5, 8, 10, are new. The structures of 1-11 were determined on the basis of spectroscopic data. All isolated compounds were evaluated for their in vitro protective effects on chromosome aberrations in peripheral human lymphocytes using cytokinesis-block micronucleus (CBMN) assay. Almost all of them exerted a pronounced effect of decreasing DNA damage of human lymphocytes, acting stronger than the known synthetic protector amifostine. PMID:24934673

  3. Hetero-Diels-Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles.

    PubMed

    Mlostoń, Grzegorz; Grzelak, Paulina; Mikina, Maciej; Linden, Anthony; Heimgartner, Heinz

    2015-01-01

    Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels-Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones. PMID:26124858

  4. On the theory of Brownian motion with the Alder-Wainwright effect

    NASA Astrophysics Data System (ADS)

    Okabe, Yasunori

    1986-12-01

    The Stokes-Boussinesq-Langevin equation, which describes the time evolution of Brownian motion with the Alder-Wainwright effect, can be treated in the framework of the theory of KMO-Langevin equations which describe the time evolution of a real, stationary Gaussian process with T-positivity (reflection positivity) originating in axiomatic quantum field theory. After proving the fluctuation-dissipation theorems for KMO-Langevin equations, we obtain an explicit formula for the deviation from the classical Einstein relation that occurs in the Stokes-Boussinesq-Langevin equation with a white noise as its random force. We are interested in whether or not it can be measured experimentally.

  5. Conformations of allylic fluorides and stereoselectivities of their diels-alder cycloadditions.

    PubMed

    Grée, D; Vallerie, L; Grée, R; Toupet, L; Washington, I; Pelicier, J P; Villacampa, M; Pérez, J M; Houk, K N

    2001-04-01

    The preparations of new allylic fluorides from the corresponding alcohols are reported. Conformational analysis is achieved by comparison of experimental NMR measurements with theoretical (B3LYP) calculations of relative energies of conformers and J(H,H) and J(H,F) coupling constants. The Diels-Alder reactions of allylic fluorides are investigated experimentally and theoretically. The stereoselectivities of the reactions were determined by NMR analysis and, in one case, by X-ray crystallography. Theoretical predictions of stereoselectivity based upon transition state modeling provided good agreement with experiment. Theoretical models for allylic fluorides and transition state conformations are reported. PMID:11281778

  6. The Nitrosocarbonyl Hetero-Diels–Alder Reaction as a Useful Tool for Organic Syntheses

    PubMed Central

    Bodnar, Brian S.

    2014-01-01

    Organic transformations that result in the formation of multiple covalent bonds within the same reaction are some of the most powerful tools in synthetic organic chemistry. Nitrosocarbonyl hetero-Diels–Alder (HDA) reactions allow for the simultaneous stereospecific introduction of carbon–nitrogen and carbon–oxygen bonds in one synthetic step, and provide direct access to 3,6-dihydro-1,2-oxazines. This Review describes the development of the nitrosocarbonyl HDA reaction and the utility of the resulting oxazine ring in the synthesis of a variety of important, biologically active molecules. PMID:21520360

  7. Insight on mendable resin made by combining Diels-Alder epoxy adducts with DGEBA

    NASA Astrophysics Data System (ADS)

    Dello Iacono, S.; Martone, A.; Filippone, G.; Acierno, D.; Zarrelli, M.; Giordano, M.; Amendola, E.

    2016-05-01

    Formation of micro-cracks is a critical problem in polymers and polymer composites during their service in structural applications. In this context, materials endowed with self-healing features would lead to the next polymers generation. In the present paper, an epoxy system integrating Diels-Alder epoxy adducts is investigated by thermal and spectroscopic analysis. The direct and retro D-A reaction have been studied by FTIR and specific absorption bands have been identified. Finally, mechanical tests have been performed on the system. The polymer is able to heal fracture and micro-cracks recovering its stiffness after a thermal treatment.

  8. Silver Nanoparticle-Catalyzed Diels-Alder Cycloadditions of 2′-Hydroxychalcones

    PubMed Central

    Cong, Huan; Becker, Clinton F.; Elliott, Sean J.; Grinstaff, Mark W.; Porco, John A.

    2010-01-01

    Metal nanoparticles are currently being employed as catalysts for a number of classical chemical transformations. In contrast, identification of novel reactions of nanoparticles, especially towards the synthesis of complex natural products and derivatives, is highly underdeveloped and represents a bourgeoning area in chemical synthesis. Herein, we report silica-supported silver nanoparticles as solid, recyclable catalysts for Diels-Alder cycloadditions of 2′-hydroxychalcones and dienes in high yield and turnover number. The use of silver nanoparticle catalysts is further demonstrated by the total synthesis of the cytotoxic natural product panduratin A employing a highly electron-rich dienophile and Lewis acid-sensitive diene. PMID:20443601

  9. Diels-Alder reactions of five-membered heterocycles containing one heteroatom

    PubMed Central

    Ding, Xiaoyuan; Nguyen, Son T.; Williams, John D.; Peet, Norton P.

    2015-01-01

    Diels-Alder reactions of five-membered heterocycles containing one heteroatom with an N-arylmaleimide were studied. Cycloaddition of 2,5-dimethylfuran (4) with 2-(4-methylphenyl)maleimide (3) in toluene at 60 °C gave bicyclic adduct 5. Cycloadditions of 3 with 2,5-dimethylthiophene (11) and 1,2,5-trimethylpyrrole (14) were also studied. Interestingly, the bicyclic compound 5 cleanly rearranged, with loss of water, when treated with p-toluenesulfonic acid in toluene at 80 °C to give 4,7-dimethyl-2-p-tolylisoindoline-1,3-dione (6). PMID:25838605

  10. Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction

    SciTech Connect

    SHALTOUT,RAAFAT M.; LOY,DOUGLAS A.; MCCLAIN,MARK D.; PRABAKAR,SHESHASAYANA; GREAVES,JOHN; SHEA,KENNETH J.

    1999-12-08

    Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems by incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the

  11. Energy storage capacity of reversible liquid phase Diels-Alder reactions as determined by drop calorimetry

    SciTech Connect

    Chung, C.P.

    1983-01-01

    Several Diels-Alder reactions were evaluated as possible candidates for energy storage. The goal was to use simple drop calorimetry to screen reactions and to identify those with high energy storage capacities. The dienes used were furan and substituted furans. The dienophiles used were maleic anhydride and substituted maleic anhydrides. Sixteen reactions have been examined. Three had energy storage capacities that were increased due to reaction (maleic anhydride and 2-methyl furan, maleic anhydride and 2-ethyl furan, maleic anhydride and 2,5-dimethyl furan). The remaining thirteen showed no increase in apparent heat capacity due to reaction.

  12. Continuous-flow stereoselective organocatalyzed Diels-Alder reactions in a chiral catalytic "homemade" HPLC column.

    PubMed

    Chiroli, Valerio; Benaglia, Maurizio; Cozzi, Franco; Puglisi, Alessandra; Annunziata, Rita; Celentano, Giuseppe

    2013-07-19

    Continuous-flow organocatalyzed Diels-Alder reactions have been performed with excellent enantioselectivity for the first time in a chiral "homemade" HPLC column, packed with silica on which a MacMillan catalyst has been supported by a straightforward immobilization procedure. The versatility of the system was also proven by running with the same column continuous-flow stereoselective reactions with three different substrates, showing that the catalytic reactor may efficiently work in continuo for more than 150 h; the regeneration of the HPLC column was also demonstrated, allowing to further extend the activity of the reactor to more than 300 operating hours. PMID:23808663

  13. Control of femtosecond laser driven retro-Diels-Alder-like reaction of dicyclopentadiene

    PubMed Central

    Das, Dipak Kumar; Goswami, Tapas; Goswami, Debabrata

    2013-01-01

    Using femtosecond time resolved degenerate pump-probe mass spectrometry coupled with simple linearly chirped frequency modulated pulse, we elucidate that the dynamics of retro-Diels-Alder-like reaction of diclopentadiene (DCPD) to cyclopentadiene (CPD) in supersonic molecular beam occurs in ultrafast time scale. Negatively chirped pulse enhances the ion yield of CPD, as compared to positively chirped pulse. This indicates that by changing the frequency (chirp) of the laser pulse we can control the ion yield of a chemical reaction. PMID:23814449

  14. Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

    PubMed Central

    Grzelak, Paulina; Mikina, Maciej; Linden, Anthony

    2015-01-01

    Summary Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones. PMID:26124858

  15. The Inverse Demand Oxa-Diels-Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity.

    PubMed

    Stefańska, Karolina; Jędrzejewska, Hanna; Wierzbicki, Michał; Szumna, Agnieszka; Iwanek, Waldemar

    2016-07-15

    The Diels-Alder reaction enables introduction of new functionalities onto the resorcinarene skeleton with simultaneous generation of new stereogenic centers and expansion of the internal cavity. We present highly regio- and diastereoselective inverse electron demand oxa-Diels-Alder reactions of resorcinarene ortho-quinone methide with benzofuran and indene, each generating 12 new stereogenic centers. The mechanism and reasons for regioselectivity and diastereoselectivity were analyzed using theoretical calculations (NBO charges, Fukui functions, transition state energies, and thermodynamic stability of the products). Enantiomers were separated, and their configurations were determined by comparison of experimental and theoretical electronic circular dichroism spectra. PMID:27336857

  16. Chiral Pyridinium Phosphoramide as a Dual Brønsted Acid Catalyst for Enantioselective Diels-Alder Reaction.

    PubMed

    Nishikawa, Yasuhiro; Nakano, Saki; Tahira, Yuu; Terazawa, Kanako; Yamazaki, Ken; Kitamura, Chitoshi; Hara, Osamu

    2016-05-01

    Chiral pyridinium phosphoramide 1·HX was designed to be a new class of chiral Brønsted acid catalyst in which both the pyridinium proton and the adjacent imide-like proton activated by the electron-withdrawing pyridinium moiety could work cooperatively as strong dual proton donors. The potential of 1·HX was shown in the enantioselective Diels-Alder reactions of 1-amino dienes with various dienophiles including N-unsubstituted maleimide, which has yet to be successfully used in an asymmetric Diels-Alder reaction. PMID:27093584

  17. Medium-Ring Effects on the Endo/Exo Selectivity of the Organocatalytic Intramolecular Diels-Alder Reaction.

    PubMed

    Hooper, Joel F; James, Natalie C; Bozkurt, Esra; Aviyente, Viktorya; White, Jonathan M; Holland, Mareike C; Gilmour, Ryan; Holmes, Andrew B; Houk, K N

    2015-12-18

    The intramolecular Diels-Alder reaction has been used as a powerful method to access the tricyclic core of the eunicellin natural products from a number of 9-membered-ring precursors. The endo/exo selectivity of this reaction can be controlled through a remarkable organocatalytic approach, employing MacMillan's imidazolidinone catalysts, although the mechanistic origin of this selectivity remains unclear. We present a combined experimental and density functional theory investigation, providing insight into the effects of medium-ring constraints on the organocatalyzed intramolecular Diels-Alder reaction to form the isobenzofuran core of the eunicellins. PMID:26560246

  18. Enantio- and periselective nitroalkene Diels-Alder reactions catalyzed by helical-chiral hydrogen bond donor catalysts.

    PubMed

    Peng, Zhili; Narcis, Maurice J; Takenaka, Norito

    2013-01-01

    Helical-chiral double hydrogen bond donor catalysts promote the nitroalkene Diels-Alder reaction in an enantio- and periselective manner. This represents the first asymmetric catalytic nitroalkene Diels-Alder reaction via LUMO-lowering catalysis. To gain an insight into this new process, the substrate scope of our catalyst was investigated by exploiting readily available 5-substituted pentamethylcyclopentadienes. The catalyst was found to tolerate dienes with different steric demands as well as dienes substituted with heteroatoms. The synthetic utility of 5-substituted pentamethylcyclopentadienes is rather limited, and thus we have developed a three-step route to 1,4,5,5-tetrasubstituted cyclopentadienes from commercially available ketones. PMID:23966083

  19. The Hexadehydro-Diels-Alder Cycloisomerization Reaction Proceeds by a Stepwise Mechanism.

    PubMed

    Wang, Tao; Niu, Dawen; Hoye, Thomas R

    2016-06-29

    We report here experiments showing that the hexadehydro-Diels-Alder (HDDA) cycloisomerization reaction proceeds in a stepwise manner-i.e., via a diradical intermediate. Judicious use of substituent effects was decisive. We prepared (i) a series of triyne HDDA substrates that differed only in the R group present on the remote terminus of the diynophilic alkyne and (ii) an analogous series of dienophilic alkynes (n-C7H15COC≡CR) for use in classical Diels-Alder (DA) reactions (with 1,3-cyclopentadiene). The R groups were CF3, CHO, COMe/Et, CO2Me, CONMe2/Et2, H, and 1-propynyl. The relative rates of both the HDDA cyclization reactions and the simple DA cycloadditions were measured. The reactivity trends revealed a dramatic difference in the behaviors of the CF3 (slowest HDDA and nearly fastest DA) and 1-propynyl (fastest HDDA and slowest DA) containing members of each series. These differences can be explained by invoking radical-stabilizing energies rather than electron-withdrawing effects as the dominating feature of the HDDA reaction. PMID:27266843

  20. New Insights into the Diels-Alder Reaction of Graphene Oxide.

    PubMed

    Brisebois, Patrick P; Kuss, Christian; Schougaard, Steen B; Izquierdo, Ricardo; Siaj, Mohamed

    2016-04-18

    Graphene oxide is regarded as a major precursor for graphene-based materials. The development of graphene oxide based derivatives with new functionalities requires a thorough understanding of its chemical reactivity, especially for canonical synthetic methods such as the Diels-Alder cycloaddition. The Diels-Alder reaction has been successfully extended with graphene oxide as a source of diene by using maleic anhydride as a dienophile, thereby outlining the presence of the cis diene present in the graphene oxide framework. This reaction provides fundamental information for understanding the exact structure and chemical nature of graphene oxide. On the basis of high-resolution (13) C-SS NMR spectra, we show evidence for the formation of new sp(3) carbon centers covalently bonded to graphene oxide following hydrolysis of the reaction product. DFT calculations are also used to show that the presence of a cis dihydroxyl and C vacancy on the surface of graphene oxide are promoting the reaction with significant negative reaction enthalpies. PMID:26953926

  1. NITROGEN EXPORT FROM FORESTED WATERSHEDS IN THE OREGON COAST RANGE: THE ROLE OF N2-FIXING RED ALDER

    EPA Science Inventory

    Variations in plant community composition across the landscape can influence nutrient retention and loss at the watershed scale. A striking example of plant species influence is the role of N2-fixing red alder (Alnus rubra) in the biogeochemistry of Pacific Northwest forests. T...

  2. Anomalous Reactivity and Selectivity in the Intermolecular Diels-Alder Reactions of Multisubstituted Acyclic Dienes with Geometrical Isomers of Enals.

    PubMed

    Zhou, Jia-Hui; Cai, Sai-Hu; Xu, Yun-He; Loh, Teck-Peng

    2016-05-20

    A Lewis-acid catalyzed intermolecular Diels-Alder reaction between multisubstituted acyclic dienes and the E and Z isomers of α,β-enals was studied. It was found that the diene reacted selectively with the Z-isomer of the α,β-enal. PMID:27132468

  3. A Kinetic Study of the Diels-Alder Reaction. An Experiment Illustrating Simple Second-Order Reaction Kinetics.

    ERIC Educational Resources Information Center

    Silvestri, Michael G.; Dills, Charles E.

    1989-01-01

    Describes an organic chemistry experiment for teaching the basic concepts of chemical kinetics. Provides background information about first- and second-order reactions, experimental procedures of the Diels-Alder reaction between cyclopentadiene and dimethyl fumarate, and the experimental results. (YP)

  4. Microwave-Enhanced Organic Syntheses for the Undergraduate Laboratory: Diels-Alder Cycloaddition, Wittig Reaction, and Williamson Ether Synthesis

    ERIC Educational Resources Information Center

    Baar, Marsha R.; Falcone, Danielle; Gordon, Christopher

    2010-01-01

    Microwave heating enhanced the rate of three reactions typically performed in our undergraduate organic chemistry laboratory: a Diels-Alder cycloaddition, a Wittig salt formation, and a Williamson ether synthesis. Ninety-minute refluxes were shortened to 10 min using a laboratory-grade microwave oven. In addition, yields improved for the Wittig…

  5. The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry.

    PubMed

    Polgar, Lorenzo Massimo; van Duin, Martin; Picchioni, Francesco

    2016-01-01

    A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified with furfurylamine to graft furan groups to the rubber backbone. These pendant furan groups are then cross-linked with a bis-maleimide via a Diels-Alder coupling reaction. Both reactions can be performed under a broad range of experimental conditions and can easily be applied on a large scale. The material properties of the resulting Diels-Alder cross-linked rubbers are similar to a peroxide-cured ethylene/propylene/diene rubber (EPDM) reference. The cross-links break at elevated temperatures (> 150 °C) via the retro-Diels-Alder reaction and can be reformed by thermal annealing at lower temperatures (50-70 °C). Reversibility of the system was proven with infrared spectroscopy, solubility tests and mechanical properties. Recyclability of the material was also shown in a practical way, i.e., by cutting a cross-linked sample into small parts and compression molding them into new samples displaying comparable mechanical properties, which is not possible for conventionally cross-linked rubbers. PMID:27583665

  6. Asymmetric synthesis of bicyclic dihydropyrans via organocatalytic inverse-electron-demand oxo-Diels-Alder reactions of enolizable aliphatic aldehydes.

    PubMed

    Li, Jun-Long; Yang, Kai-Chuan; Li, Yi; Li, Qiang; Zhu, Hong-Ping; Han, Bo; Peng, Cheng; Zhi, Yong-Gang; Gou, Xiao-Jun

    2016-08-23

    A highly enantioselective organocatalytic inverse-electron-demand oxo-Diels-Alder reaction involving aqueous acetaldehyde has been discovered. The reaction, in which cyclic enones serve as dienes in the presence of readily available secondary amine catalysts, allows facile construction of optically active bicyclic dihydropyrans. Other typical enolizable aliphatic aldehydes can also serve as competent dienophiles in the reaction. PMID:27436351

  7. Sorocenols G and H, Anti-MRSA Oxygen Heterocyclic Diels-Alder-type Adducts from Sorocea muriculata Roots

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bioassay-guided fractionation of a root extract of Sorocea muriculata led to the isolation and identification of two new oxygen heterocyclic Diels-Alder-type adducts, sorocenols G (1) and H (2), along with lupeol-3-(3'R-hydroxytetradecanoate) and oxyresveratrol. The structures of 1 and 2 were eluci...

  8. Optimizing the trade-off between offspring number and quality in unpredictable environments: testing the role of differential androgen transfer to collared flycatcher eggs.

    PubMed

    Rice, Amber M; Vallin, Niclas; Kulma, Katarzyna; Arntsen, Hanna; Husby, Arild; Tobler, Michael; Qvarnström, Anna

    2013-05-01

    According to the brood reduction hypothesis, parents adjust their brood size in response to current environmental conditions. When resources are abundant, parents can successfully raise all hatched offspring, but when resources are scarce, brood reduction, i.e., the sacrifice of some siblings to secure the quality of a subset of offspring, may maximize fitness. Differential transfer of maternal androgens is one potential proximate mechanism through which female birds may facilitate brood reduction because it may alter the relative competitive ability of sibling nestlings. We tested the hypothesis that female collared flycatchers (Ficedula albicollis) manipulate sibling competition by transferring less androgens to eggs late in the laying sequence. We experimentally elevated androgen levels in i) whole clutches and ii) only the two last laid eggs, and compared growth and begging behavior of offspring from these treatments with a control treatment. By using three treatments and video assessment of begging, we examined the effects of within-clutch patterns of yolk androgen transfer on levels of sibling competition in situ. When androgens were elevated in only the two last laid eggs, begging was more even among siblings compared to control nests. We also found that female nestlings receiving additional yolk androgens showed higher mass gain later in the breeding season, while their male counterparts did not. Our results suggest that females may improve reproductive success in unpredictable environments by altering within-clutch patterns of yolk androgen transfer. We discuss the possibility that life-history divergence between the co-occurring collared and pied flycatcher (Ficedula hypoleuca) is amplified by patterns of yolk androgen transfer. PMID:23602767

  9. Climate change, breeding date and nestling diet: how temperature differentially affects seasonal changes in pied flycatcher diet depending on habitat variation.

    PubMed

    Burger, Claudia; Belskii, Eugen; Eeva, Tapio; Laaksonen, Toni; Mägi, Marko; Mänd, Raivo; Qvarnström, Anna; Slagsvold, Tore; Veen, Thor; Visser, Marcel E; Wiebe, Karen L; Wiley, Chris; Wright, Jonathan; Both, Christiaan

    2012-07-01

    1. Climate warming has led to shifts in the seasonal timing of species. These shifts can differ across trophic levels, and as a result, predator phenology can get out of synchrony with prey phenology. This can have major consequences for predators such as population declines owing to low reproductive success. However, such trophic interactions are likely to differ between habitats, resulting in differential susceptibility of populations to increases in spring temperatures. A mismatch between breeding phenology and food abundance might be mitigated by dietary changes, but few studies have investigated this phenomenon. Here, we present data on nestling diets of nine different populations of pied flycatchers Ficedula hypoleuca, across their breeding range. This species has been shown to adjust its breeding phenology to local climate change, but sometimes insufficiently relative to the phenology of their presumed major prey: Lepidoptera larvae. In spring, such larvae have a pronounced peak in oak habitats, but to a much lesser extent in coniferous and other deciduous habitats. 2. We found strong seasonal declines in the proportions of caterpillars in the diet only for oak habitats, and not for the other forest types. The seasonal decline in oak habitats was most strongly observed in warmer years, indicating that potential mismatches were stronger in warmer years. However, in coniferous and other habitats, no such effect of spring temperature was found. 3. Chicks reached somewhat higher weights in broods provided with higher proportions of caterpillars, supporting the notion that caterpillars are an important food source and that the temporal match with the caterpillar peak may represent an important component of reproductive success. 4. We suggest that pied flycatchers breeding in oak habitats have greater need to adjust timing of breeding to rising spring temperatures, because of the strong seasonality in their food. Such between-habitat differences can have

  10. Diversity-Oriented Approaches to Polycyclics and Bioinspired Molecules via the Diels-Alder Strategy: Green Chemistry, Synthetic Economy, and Beyond.

    PubMed

    Kotha, Sambasivarao; Chavan, Arjun S; Goyal, Deepti

    2015-05-11

    We describe diverse approaches to various dienes and their utilization in the Diels-Alder reaction to produce a variety of polycycles. The dienes covered here are prepared by simple alkylation reaction or via the Claisen rearrangement or by enyne metathesis of alkyne or enyne building blocks. Here, we have also included the Diels-Alder chemistry of dendralenes, a higher analog of cross-conjugated dienes. The present article is inclusive of o-xylylene derivatives that are generated in situ starting with benzosultine or benzosulfone derivatives. The Diels-Alder reaction of these dienes with various dienophiles gave diverse polycyclic systems and biologically important targets. PMID:25875156

  11. The impact of a pulsing groundwater table on greenhouse gas emissions in riparian grey alder stands.

    PubMed

    Mander, Ülo; Maddison, Martin; Soosaar, Kaido; Teemusk, Alar; Kanal, Arno; Uri, Veiko; Truu, Jaak

    2015-02-01

    Floods control greenhouse gas (GHG) emissions in floodplains; however, there is a lack of data on the impact of short-term events on emissions. We studied the short-term effect of changing groundwater (GW) depth on the emission of (GHG) carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in two riparian grey alder (Alnus incana) stands of different age in Kambja, southern Estonia, using the opaque static chamber (five replicates in each site) and gas chromatography methods. The average carbon and total nitrogen content in the soil of the old alder (OA) stand was significantly higher than in the young alder (YA) stand. In both stands, one part was chosen for water table manipulation (Manip) and another remained unchanged with a stable and deeper GW table. Groundwater table manipulation (flooding) significantly increases CH4 emission (average: YA-Dry 468, YA-Manip 8,374, OA-Dry 468, OA-Manip 4,187 μg C m(-2) h(-1)) and decreases both CO2 (average: OA-Dry 138, OA-Manip 80 mg C m(-2) h(-1)) and N2O emissions (average: OA-Dry 23.1, OA-Manip 11.8 μg N m(-2) h(-1)) in OA sites. There was no significant difference in CO2 and CH4 emissions between the OA and YA sites, whereas in OA sites with higher N concentration in the soil, the N2O emission was significantly higher than at the YA sites. The relative CO2 and CH4 emissions (the soil C stock-related share of gaseous losses) were higher in manipulated plots showing the highest values in the YA-Manip plot (0.03 and 0.0030 % C day(-1), respectively). The soil N stock-related N2O emission was very low achieving 0.000019 % N day(-1) in the OA-Dry plot. Methane emission shows a negative correlation with GW, whereas the 20 cm depth is a significant limit below which most of the produced CH4 is oxidized. In terms of CO2 and N2O, the deeper GW table significantly increases emission. In riparian zones of headwater streams, the short-term floods (e.g. those driven by extreme climate events) may significantly enhance

  12. Poly /Diels-Alder/ matrix resins. [high temperature resistant graphite reinforced composites

    NASA Technical Reports Server (NTRS)

    Jones, R. J.; Orell, M. K.; Sheppard, C. H.; Vaughan, R. W.

    1977-01-01

    A poly (Diels-Alder) (PDA) resin approach was investigated as a means to achieve autoclavability of high-temperature resistant resin/fiber composites under mild fabrication conditions. The results of the study were highly promising and program objectives were achieved. Low-void content Type A-S graphite reinforced composites were autoclave fabricated from a PDA resin/fiber prepreg prepared from an acetone:methanol:dioxane varnish. Autoclave conditions were 400 F and 100 psi for up to two hours duration. After postcure at temperatures up to 600 F, the composites demonstrated high initial mechanical properties at temperatures up to 550 F. The results from isothermal aging studies in air for 1000 hours indicated potential for long-term (over 1000 hours) use at 500 F and shorter-term use at 550 F.

  13. Characterization of vanadium ion uptake in sulfonated diels alder poly(phenylene) membranes

    DOE PAGESBeta

    Lawton, Jamie; Jones, Amanda; Tang, Zhijiang; Lindsey, Melanie; Zawodzinski, Thomas A

    2015-11-28

    Sulfonated diels alder poly(phenylene) (SDAPP), alternative aromatic hydrocarbon membranes for vanadium redox flow batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). Membranes soaked in sulfuric acid and vanadyl sulfate are analyzed to determine the membrane environment in which the vanadyl ion (VO2+) diffuses in the membranes. These results are compared to Nafion 117 membranes. In contrast to Nafion, the VO2+ in SDAPP membranes exists in two different environments. The results of analysis of rotational diffusion determined from fits the EPR spectral lineshapes in comparison with previously reported permeation studies and measurements of partitioning functions reported here suggest that themore » diffusion pathways in SDAPP are very different than in Nafion.« less

  14. Economic considerations in establishing European alder in herbaceous cover on surface-mined land

    SciTech Connect

    Ringe, J.M.; Graves, D.H.

    1985-12-09

    Herbicides are a practical tool for selectively controlling vegetative competition during tree seedling establishment. A study to investigate the effects of eight herbicide treatments on the survival and height growth of European alder (Alnus glutinosa) seedlings established in herbaceous cover indicated a positive treatment effect, but very little difference between the herbicide treatments themselves. Since the costs of the herbicides varied considerably, similar results could be obtained using the different herbicides, but at substantially different costs. Biological data were combined with the economic data to derive a modified benefit/cost ratio. This ratio facilitates herbicide treatment choice by comparing the amount of added survival or growth obtained per dollar spent on herbicides. 5 references, 6 tables.

  15. Description and identification of Alnus acuminata ectomycorrhizae from Argentinean alder stands.

    PubMed

    Pritsch, Karin; Becerra, Alejandra; Põlme, Sergei; Tedersoo, Leho; Schloter, Michael; Agerer, Reinhard

    2010-01-01

    The objective of this study was to describe the morphological and anatomical features of five unidentified ectomycorrhizal types of Alnus acuminata and to complement their identification based on ITS-rDNA sequence analysis. The combined approach of morphotyping and sequence analysis based on ITS sequence comparison with sequences contained in GenBank and the UNITE database let us assign three of the five field-collected ectomycorrhiza morphotypes to the tomentella-thelephora lineage that closely matched European and North American species. The sequencing results within Tomentella point toward alder specific clades within T. sublilacina, T. ellisii and T. stuposa sensu lato. The two other EcM morphotypes matched Lactarius omphaliiformis and a Russula sp. Better focused, concomitant fruit body surveys are needed for accurate identification of South American ectomycorrhizal fungi because of the evidence of cryptic speciation in both agaricoid and resupinate mycobionts. PMID:20943556

  16. Kondrat'eva ligation: Diels-Alder-based irreversible reaction for bioconjugation.

    PubMed

    Jouanno, Laurie-Anne; Chevalier, Arnaud; Sekkat, Nawal; Perzo, Nicolas; Castel, Hélène; Romieu, Anthony; Lange, Norbert; Sabot, Cyrille; Renard, Pierre-Yves

    2014-11-01

    Diversification of existing chemoselective ligations is required to efficiently access complex and well-defined biomolecular assemblies with unique and valuable properties. The development and bioconjugation applications of a novel Diels-Alder-based irreversible site-specific ligation are reported. The strategy is based on a Kondrat'eva cycloaddition between bioinert and readily functionalizable 5-alkoxyoxazoles and maleimides that readily react together under mild and easily tunable reaction conditions to afford a fully stable pyridine scaffold. The potential of this novel bioconjugation is demonstrated through the preparation of fluorescent conjugates of biomolecules and a novel Förster resonance energy transfer (FRET)-based probe suitable for the in vivo detection and imaging of urokinase-like plasminogen activator (uPA), which is a key protease involved in cancer invasion and metastasis. PMID:25346140

  17. A mechanochemical study of the effects of compression on a Diels-Alder reaction.

    PubMed

    Jha, Sanjiv K; Brown, Katie; Todde, Guido; Subramanian, Gopinath

    2016-08-21

    We examine the effects of compressive external forces on the mechanisms of the parent Diels-Alder (DA) reaction between butadiene and ethylene. Reaction pathways and transition states were calculated using the nudged elastic band method within a mechanochemical framework at the CASSCF(6,6)/6-31G**, as well as the B3LYP/6-311++G** levels of theory. Our results suggest that compressive hydrostatic pressure lowers the energy barrier for the parent DA reaction while suppressing the undesirable side reaction, thereby leading to a direct increase in the yield of cyclohexene. Compressive pressure also increases the exothermicity of the parent DA reaction, which would lead to increased temperatures in a reaction vessel and thereby indirectly increase the yield of cyclohexene. Our estimates indicate that the compression used in our study corresponds to a range of 68 MPa-1410 MPa. PMID:27544105

  18. Dynamics of methane production, sulfate reduction, and denitrification in a permanently waterlogged alder swamp

    SciTech Connect

    Westermann, P.; Ahring, B.K.

    1987-10-01

    The dynamics of sulfate reduction, methane production, and denitrification were investigated in a permanently waterlogged alder swamp. Molybdate, an inhibitor of sulfate reduction, stimulated methane production in soil slurries, thus suggesting competition for common substrates between sulfate-reducing and methane-producing bacteria. Acetate, hydrogen, and methanol were found to stimulate both sulfate reduction and methane production, while trimethylamine mainly stimulated methane production. Nitrate addition reduced both methane production and sulfate reduction, either as a consequence of competition of poisoning of the bacteria. Sulfate-reducing bacteria were only slightly limited by the availability of electron acceptors, while denitrifying bacteria were seriously limited by low nitrate concentrations. Arrhenius plots of the three processes revealed different responses to temperature changes in the slurries. Methane production was most sensitive to temperature changes, followed by denitrification and sulfate reduction. No significant differences between slope patterns were observed when comparing summer and winter measurements, indicating similar populations regarding temperature responses.

  19. Characterization of vanadium ion uptake in sulfonated diels alder poly(phenylene) membranes

    SciTech Connect

    Lawton, Jamie; Jones, Amanda; Tang, Zhijiang; Lindsey, Melanie; Zawodzinski, Thomas A

    2015-11-28

    Sulfonated diels alder poly(phenylene) (SDAPP), alternative aromatic hydrocarbon membranes for vanadium redox flow batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). Membranes soaked in sulfuric acid and vanadyl sulfate are analyzed to determine the membrane environment in which the vanadyl ion (VO2+) diffuses in the membranes. These results are compared to Nafion 117 membranes. In contrast to Nafion, the VO2+ in SDAPP membranes exists in two different environments. The results of analysis of rotational diffusion determined from fits the EPR spectral lineshapes in comparison with previously reported permeation studies and measurements of partitioning functions reported here suggest that the diffusion pathways in SDAPP are very different than in Nafion.

  20. Click and Patterned Functionalization of Graphene by Diels-Alder Reaction.

    PubMed

    Li, Jing; Li, Meng; Zhou, Li-Li; Lang, Shuang-Yan; Lu, Hai-Yan; Wang, Dong; Chen, Chuan-Feng; Wan, Li-Jun

    2016-06-22

    Chemical functionalization is a promising approach to controllably manipulate the characteristics of graphene. Here, we designed cis-dienes, featuring two dihydronaphthalene backbones, to decorate a graphene surface via Diels-Alder (DA) click reaction. The installation of a diene moiety into a nonplanar molecular structure to form cis-conformation enables a rapid (∼5 min) DA reaction between graphene and diene groups. Patterned graphene of sub-micrometer resolution can be obtained by easily soaking poly(methyl methacrylate)-masked graphene in solution of hydroxyl-substituted cis-diene at room temperature. The functionalization degree can be further controlled by carrying out the reaction at higher temperature. The present result gives important insight into the effect of molecular conformation on the graphene functionalization process, and provides an effective and facile method for graphene functionalization. PMID:27264112

  1. Total synthesis of (+)-gelsemine via an organocatalytic Diels-Alder approach.

    PubMed

    Chen, Xiaoming; Duan, Shengguo; Tao, Cheng; Zhai, Hongbin; Qiu, Fayang G

    2015-01-01

    The structurally complex alkaloid gelsemine was previously thought to have no significant biological activities, but a recent study has shown that it has potent and specific antinociception in chronic pain. While this molecule has attracted significant interests from the synthetic community, an efficient synthetic strategy is still the goal of many synthetic chemists. Here we report the asymmetric total synthesis of (+)-gelsemine, including a highly diastereoselective and enantioselective organocatalytic Diels-Alder reaction, an efficient intramolecular trans-annular aldol condensation furnishing the prolidine ring and establishing the configuration of the C20 quaternary carbon stereochemical centre. The entire gelsemine skeleton was constructed through a late-stage intramolecular SN2 substitution. The enantiomeric excess of this total synthesis is over 99%, and the overall yield is around 5%. PMID:25995149

  2. Total synthesis of (+)-gelsemine via an organocatalytic Diels–Alder approach

    PubMed Central

    Chen, Xiaoming; Duan, Shengguo; Tao, Cheng; Zhai, Hongbin; Qiu, Fayang G.

    2015-01-01

    The structurally complex alkaloid gelsemine was previously thought to have no significant biological activities, but a recent study has shown that it has potent and specific antinociception in chronic pain. While this molecule has attracted significant interests from the synthetic community, an efficient synthetic strategy is still the goal of many synthetic chemists. Here we report the asymmetric total synthesis of (+)-gelsemine, including a highly diastereoselective and enantioselective organocatalytic Diels–Alder reaction, an efficient intramolecular trans-annular aldol condensation furnishing the prolidine ring and establishing the configuration of the C20 quaternary carbon stereochemical centre. The entire gelsemine skeleton was constructed through a late-stage intramolecular SN2 substitution. The enantiomeric excess of this total synthesis is over 99%, and the overall yield is around 5%. PMID:25995149

  3. Synthesis of tetrasubstituted 1-silyloxy-3-aminobutadienes and chemistry beyond Diels–Alder reactions

    PubMed Central

    Li, Xijian; Peng, Siyu; Li, Li; Huang, Yong

    2015-01-01

    Electron-rich dienes have revolutionized the synthesis of complex compounds since the discovery of the legendary Diels–Alder cycloaddition reaction. This highly efficient bond-forming process has served as a fundamental strategy to assemble many structurally formidable molecules. Amino silyloxy butadienes are arguably the most reactive diene species that are isolable and bottleable. Since the pioneering discovery by Rawal, 1-amino-3-silyloxybutadienes have been found to undergo cycloaddition reactions with unparalleled mildness, leading to significant advances in both asymmetric catalysis and total synthesis of biologically active natural products. In sharp contrast, this class of highly electron-rich conjugated olefins has not been studied in non-cycloaddition reactions. Here we report a simple synthesis of tetrasubstituted 1-silyloxy-3-aminobutadienes, a complementarily substituted Rawal's diene. This family of molecules is found to undergo a series of intriguing chemical transformations orthogonal to cycloaddition reactions. Structurally diverse polysubstituted ring architectures are established in one step from these dienes. PMID:25898310

  4. Dynamics of Methane Production, Sulfate Reduction, and Denitrification in a Permanently Waterlogged Alder Swamp

    PubMed Central

    Westermann, Peter; Ahring, Birgitte Kiær

    1987-01-01

    The dynamics of sulfate reduction, methane production, and denitrification were investigated in a permanently waterlogged alder swamp. Molybdate, an inhibitor of sulfate reduction, stimulated methane production in soil slurries, thus suggesting competition for common substrates between sulfate-reducing and methane-producing bacteria. Acetate, hydrogen, and methanol were found to stimulate both sulfate reduction and methane production, while trimethylamine mainly stimulated methane production. Nitrate addition reduced both methane production and sulfate reduction, either as a consequence of competition or poisoning of the bacteria. Sulfate-reducing bacteria were only slightly limited by the availability of electron acceptors, while denitrifying bacteria were seriously limited by low nitrate concentrations. Arrhenius plots of the three processes revealed different responses to temperature changes in the slurries. Methane production was most sensitive to temperature changes, followed by denitrification and sulfate reduction. No significant differences between slope patterns were observed when comparing summer and winter measurements, indicating similar populations regarding temperature responses. PMID:16347472

  5. Diels-Alder Trapping of Photochemically Generated Dienes with Acrylic Esters: A Novel Approach to Photocured Polymer Film Development

    NASA Technical Reports Server (NTRS)

    Ilhan, Faysal; Tyson, Daniel S.; Smith, Deedee; Meador, Mary Ann; Meador, Michael A.

    2004-01-01

    Diels-Alder cycloadditions have often been utilized in polymer synthesis as an alternative to condensation reactions. In our earlier efforts, we developed a new method for the preparation of linear aromatic polyimides, which employs o-quionodimethanes (o-QDMs), generated by a well-known photochemical reaction: the photoenolization of o-methylphenyl ketones. Photolysis of o-methylbenzophenone 1 produces hydroxy-o-quino- diemthane 2, which can be trapped with dienophiles, such as dimethyl acetylenedicarboxylate, to efficiently yield the corresponding cycloadduct (Scheme 1). Here we extend this approach to a novel photocuring process for development of polymer films. We synthesized a series of molecules with multi o-mehtylphenyl ketone functionalities. We further investigated these molecules as photoreactive monomers to obtain polyester films through Diels-Alder cycloadditions.

  6. Exploring Reaction Mechanism on Generalized Force Modified Potential Energy Surfaces (G-FMPES) for Diels-Alder Reaction

    NASA Astrophysics Data System (ADS)

    Jha, Sanjiv; Brown, Katie; Subramanian, Gopinath

    We apply a recent formulation for searching minimum energy reaction path (MERP) and saddle point to atomic systems subjected to an external force. We demonstrate the effect of a loading modality resembling hydrostatic pressure on the trans to cis conformational change of 1,3-butadiene, and the simplest Diels-Alder reaction between ethylene and 1,3-butadiene. The calculated MERP and saddle points on the generalized force modified potential energy surface (G-FMPES) are compared with the corresponding quantities on an unmodified potential energy surface. Our study is performed using electronic structure calculations at the HF/6-31G** level as implemented in the AIMS-MOLPRO code. Our calculations suggest that the added compressive pressure lowers the energy of cis butadiene. The activation energy barrier for the concerted Diels-Alder reaction is found to decrease progressively with increasing compressive pressure.

  7. Studies on the synthesis of (-)-spinosyn a: application of the steric directing group strategy to transannular Diels-Alder reactions.

    PubMed

    Frank, Scott A; Roush, William R

    2002-06-14

    A highly diastereoselective and enantioselective synthesis of the decahydro-as-indacene nucleus 12 of (-)-spinosyn A (1) is reported. By implementing the steric directing group strategy, tricyclic lactone 37 was produced from a remarkably diastereoselective transannular Diels-Alder reaction of lactone 9. The tricyclic core of the natural product was then obtained by using an Ireland-Claisen ring contraction of 37. Reversal of the order of these two steps resulted in an almost complete loss of diastereoselectivity. PMID:12054969

  8. Copper-Catalyzed Aza-Diels-Alder Reaction and Halogenation: An Approach To Synthesize 7-Halogenated Chromenoquinolines.

    PubMed

    Yu, Xiaoqiang; Wang, Jiao; Xu, Zhanwei; Yamamoto, Yoshinori; Bao, Ming

    2016-05-20

    A new halogenation method to construct halogen-substituted quinoline moieties is described. The Cu-catalyzed intramolecular aza-Diels-Alder reaction and halogenation reaction proceeded smoothly under mild conditions to produce the corresponding 7-chloro-6H-chromeno[4,3-b]quinolines and 7-chloro-6H-thiochromeno[4,3-b]quinolines in satisfactory yields. PMID:27145113

  9. Quantitative structure-activation barrier relationship modeling for Diels-Alder ligations utilizing quantum chemical structural descriptors

    PubMed Central

    2013-01-01

    Background In the present study, we show the correlation of quantum chemical structural descriptors with the activation barriers of the Diels-Alder ligations. A set of 72 non-catalysed Diels-Alder reactions were subjected to quantitative structure-activation barrier relationship (QSABR) under the framework of theoretical quantum chemical descriptors calculated solely from the structures of diene and dienophile reactants. Experimental activation barrier data were obtained from literature. Descriptors were computed using Hartree-Fock theory using 6-31G(d) basis set as implemented in Gaussian 09 software. Results Variable selection and model development were carried out by stepwise multiple linear regression methodology. Predictive performance of the quantitative structure-activation barrier relationship (QSABR) model was assessed by training and test set concept and by calculating leave-one-out cross-validated Q2 and predictive R2 values. The QSABR model can explain and predict 86.5% and 80% of the variances, respectively, in the activation energy barrier training data. Alternatively, a neural network model based on back propagation of errors was developed to assess the nonlinearity of the sought correlations between theoretical descriptors and experimental reaction barriers. Conclusions A reasonable predictability for the activation barrier of the test set reactions was obtained, which enabled an exploration and interpretation of the significant variables responsible for Diels-Alder interaction between dienes and dienophiles. Thus, studies in the direction of QSABR modelling that provide efficient and fast prediction of activation barriers of the Diels-Alder reactions turn out to be a meaningful alternative to transition state theory based computation. PMID:24171724

  10. A Catalyst-Enabled Diastereodivergent Aza-Diels-Alder Reaction: Complementarity of N-Heterocyclic Carbenes and Chiral Amines.

    PubMed

    Rong, Zi-Qiang; Wang, Min; Chow, Chi Hao Eugene; Zhao, Yu

    2016-07-01

    Highly efficient and diastereodivergent aza-Diels-Alder reactions have been developed to access either diastereomeric series of benzofuran-fused δ-lactams and dihydropyridines in nearly perfect stereoselectivity (d.r. >20:1, >99 % ee for all examples). The complementarity of N-heterocyclic carbene and chiral amine as the catalyst was demonstrated for the first time, together with an excellent level of catalytic efficiency (1 mol % loading). PMID:27219298

  11. Phylogeography of the Vermilion Flycatcher species complex: Multiple speciation events, shifts in migratory behavior, and an apparent extinction of a Galápagos-endemic bird species.

    PubMed

    Carmi, Ore; Witt, Christopher C; Jaramillo, Alvaro; Dumbacher, John P

    2016-09-01

    The Vermilion Flycatcher (Pyrocephalus rubinus) is a widespread species found in North and South America and the Galápagos. Its 12 recognized subspecies vary in degree of geographic isolation, phenotypic distinctness, and migratory status. Some authors suggest that Galápagos subspecies nanus and dubius constitute one or more separate species. Observational reports of distinct differences in song also suggest separate species status for the austral migrant subspecies rubinus. To evaluate geographical patterns of diversification and taxonomic limits within this species complex, we carried out a molecular phylogenetic analysis encompassing 10 subspecies and three outgroup taxa using mitochondrial (ND2, Cyt b) and nuclear loci (ODC introns 6 through 7, FGB intron 5). We used samples of preserved tissues from museum collections as well as toe pad samples from museum skins. Galápagos and continental clades were recovered as sister groups, with initial divergence at ∼1mya. Within the continental clade, North and South American populations were sister groups. Three geographically distinct clades were recovered within South America. We detected no genetic differences between two broadly intergrading North American subspecies, mexicanus and flammeus, suggesting they should not be recognized as separate taxa. Four western South American subspecies were also indistinguishable on the basis of loci that we sampled, but occur in a region with patchy habitat, and may represent recently isolated populations. The austral migrant subspecies, rubinus, comprised a monophyletic mitochondrial clade and had many unique nuclear DNA alleles. In combination with its distinct song, exclusive song recognition behavior, different phenology, and an isolated breeding range, our data suggests that this taxon represents a separate species from other continental populations. Mitochondrial and nuclear genetic data, morphology, and behavior suggest that Galápagos forms should be elevated to two

  12. A new approach to the synthesis of monomers and polymers incorporating furan/maleimide Diels-Alder adducts

    NASA Astrophysics Data System (ADS)

    Banella, Maria Barbara; Gioia, Claudio; Vannini, Micaela; Colonna, Martino; Celli, Annamaria; Gandini, Alessandro

    2016-05-01

    The Diels-Alder reaction between furan and maleimide moieties is a well-known and widely used strategy to build bio-based macromolecular structures with peculiar properties. The furan-maleimide adducts are thermally reversible because they can be broken above about 120°C and recombined at lower temperatures. At the moment only the monomers exhibiting the furan or the maleimide moieties on their extremity are used in order to get linear or cross-linked polymeric structures. The innovative idea described here consists in using a monomer bearing two carboxylic acidic groups on its extremities and a furan-maleimide Diels-Alder adduct within its structure. This monomer can give rise to classical polycondensation reactions leading to polymers. These polymers (which are polyesters in the present case) can be broken at high temperatures in correspondence of the furane-maleimide Diels-Alder adduct leading to segments exhibiting furan or maleimide moieties at their extremities, which at lower temperature recombine leading to random or block copolymers.

  13. Performance of ectomycorrhizal alders exposed to specific Canadian oil sands tailing stressors under in vivo bipartite symbiotic conditions.

    PubMed

    Beaudoin-Nadeau, Martin; Gagné, André; Bissonnette, Cyntia; Bélanger, Pier-Anne; Fortin, J André; Roy, Sébastien; Greer, Charles W; Khasa, Damase P

    2016-07-01

    Canadian oil sands tailings are predominately sodic residues contaminated by hydrocarbons such as naphthenic acids. These conditions are harsh for plant development. In this study, we evaluated the effect of inoculating roots of Alnus viridis ssp. crispa and Alnus incana ssp. rugosa with ectomycorrhizal fungi in the presence of tailings compounds. Seedlings were inoculated with 7 different strains of Paxillus involutus and Alpova diplophloeus and were grown under different treatments of NaCl, Na2SO4, and naphthenic acids in a growth chamber. Afterwards, seedling survival, height, dry biomass, leaf necrosis, and root mycorrhization rate were measured. Paxillus involutus Mai was the most successful strain in enhancing alder survival, health, and growth. Seedlings inoculated with this strain displayed a 25% increase in survival rate, 2-fold greater biomass, and 2-fold less leaf necrosis compared with controls. Contrary to our expectations, A. diplophloeus was not as effective as P. involutus in improving seedling fitness, likely because it did not form ectomycorrhizae on roots of either alder species. High intraspecific variation characterized strains of P. involutus in their ability to stimulate alder height and growth and to minimize leaf necrosis. We conclude that in vivo selection under bipartite symbiotic conditions is essential to select effective strains that will be of use for the revegetation and reclamation of derelict lands. PMID:27170470

  14. Design Paradigm Utilizing Reversible Diels-Alder Reactions to Enhance the Mechanical Properties of 3D Printed Materials.

    PubMed

    Davidson, Joshua R; Appuhamillage, Gayan A; Thompson, Christina M; Voit, Walter; Smaldone, Ronald A

    2016-07-01

    A design paradigm is demonstrated that enables new functional 3D printed materials made by fused filament fabrication (FFF) utilizing a thermally reversible dynamic covalent Diels-Alder reaction to dramatically improve both strength and toughness via self-healing mechanisms. To achieve this, we used as a mending agent a partially cross-linked terpolymer consisting of furan-maleimide Diels-Alder (fmDA) adducts that exhibit reversibility at temperatures typically used for FFF printing. When this mending agent is blended with commercially available polylactic acid (PLA) and printed, the resulting materials demonstrate an increase in the interfilament adhesion strength along the z-axis of up to 130%, with ultimate tensile strength increasing from 10 MPa in neat PLA to 24 MPa in fmDA-enhanced PLA. Toughness in the z-axis aligned prints increases by up to 460% from 0.05 MJ/m(3) for unmodified PLA to 0.28 MJ/m(3) for the remendable PLA. Importantly, it is demonstrated that a thermally reversible cross-linking paradigm based on the furan-maleimide Diels-Alder (fmDA) reaction can be more broadly applied to engineer property enhancements and remending abilities to a host of other 3D printable materials with superior mechanical properties. PMID:27299858

  15. Effects of fungal inocula and habitat conditions on alder and eucalyptus leaf litter decomposition in streams of northern Spain.

    PubMed

    Pérez, Javier; Galán, Javier; Descals, Enrique; Pozo, Jesús

    2014-02-01

    We investigated how fungal decomposer (aquatic hyphomycetes) communities colonizing alder and eucalyptus leaf litter respond to changes in habitat characteristics (transplantation experiment). We examined the breakdown of leaf materials and the associated fungal communities at two contrasting sites, a headwater stream (H) and a midreach (M). Agroforestry increased from headwater to midreach. One month after the start of experiments at both sites, some leaf samples from the midreach site were transplanted to the headwater site (M-H treatment). Although both sites showed similar dissolved inorganic nutrient concentrations, eucalyptus leaves initially incubated at the midreach site (M, M-H) increased their breakdown rate compared to those incubated along the experiment at the headwater site (H). Alder breakdown rate was not enhanced, suggesting that their consumption was not limited by nutrient availability. Sporulation rates clearly differed between leaf types (alder > eucalyptus) and streams (H > M), but no transplantation effect was detected. When comparing conidial assemblages after transplantation, an inoculum effect (persistence of early colonizing species) was clear in both leaf species. Substrate preference and shifts in the relative importance of some fungal species along the process were also observed. Overall, our results support the determining role of the initial conditioning phase on the whole litter breakdown process, highlighting the importance of intrinsic leaf characteristics and those of the incubation habitat. PMID:24141942

  16. Short-term influence of nitrate on acetylene reduction, photosynthesis and nodule respiration of black alder seedlings

    SciTech Connect

    Cazell, B.H.; Samuelson, L.J.; Seiler, J.R. )

    1990-05-01

    Black alder (Alnus glutinosa L. Gaernt.) has shown significant benefits in several silvicultural applications such as nurse-trees. However, little is known concerning the nitrate/N-fixing interactions. Our objections were to examine the effects of three nitrate levels on acetylene reduction (AR), net photosynthesis (Ps) and nodule respiration (NR). Fifteen month-old black alder rooted cuttings were inoculated with one strain of Frankia inoculum (ARgN22D) at six months, maintained under 16h photoperiod at ambient greenhouse conditions, and fertilized for two months prior to study with a modified Crone's N-free solution. At study initiation seedlings were fertilized for six days with 0, 7.5 or 15 mM NO{sub 3}{sup {minus}}. Measurements of AR, Ps and NR were collected on the second, fourth and sixth day of NO{sub 3}{sup {minus}} application. By day four AR was significantly lowered by 75% for the 15 mM NO{sub 3}{sup {minus}} treatment when compared with the controls. On day six, Ps and NR were lowered significantly by 29% and 59%, respectively, for the 15 mM NO{sub 3}{sup {minus}} treatments when compared to control values. Results suggest any benefit from black alder N-fixation might be negated by nitrate fertilization.

  17. A Soil Moisture-Heat Based Early Establishment Model of Riparian White Alder (Alnus rhombifolia)

    NASA Astrophysics Data System (ADS)

    Jablkowski, P.; Johnson, E. A.; Martin, Y. E.

    2013-12-01

    Establishment of fluvially dispersed seeds on accreted gravel-sand bars is limited by water availability in streams. Past establishment models have used the stream/water table recession rate, and maximum root growth rate to determine the elevation limit of seedling establishment. This approach neglects the role of the saturated-unsaturated vadose zone in providing water to recently germinated seedlings, the physical processes that determine the soil moisture content, and the effect moisture deficit has on seedling root growth. This study combines a soil moisture-heat budget and a seedling root growth model that responds to soil moisture availability to find the elevation limit of establishment of white alder (Alnus rhombifolia) on vertically accreted bars along the south fork Eel River in the Angelo Coast Range Reserve, California. To establish successfully, seedling roots must maintain a connection with sufficient moisture to avoid water stress. This will depend on the elevation of the bar, the stream recession rate, the root growth rate, and the diurnal cycle of soil moisture. A one-dimensional moisture-heat budget of the top 15 centimeters of sediment was validated at two locations characterized by sand and clay-gravel textures respectively, using soil moisture and temperature measurements at 5, 10 and 15 cm, net radiation, air temperature, humidity, wind velocity and precipitation measured during spring-summer stream recession. Two patterns in soil water content were apparent: an average daily moisture decrease at each depth driven by stream/water table recession, and a diurnal pattern of isothermal liquid and vapour flux increasing soil water content in the upper 15 cm between 12:00 pm and 5:00 pm PDT. To determine seedling root growth rates, white alder seedlings were grown in growth chambers under a range of reduced matric potentials using polyethylene glycol. Root length measurements were made at 4 hour intervals and a quadratic equation was fit to the root

  18. Silylium ion-catalyzed challenging Diels-Alder reactions: the danger of hidden proton catalysis with strong Lewis acids.

    PubMed

    Schmidt, Ruth K; Müther, Kristine; Mück-Lichtenfeld, Christian; Grimme, Stefan; Oestreich, Martin

    2012-03-01

    The pronounced Lewis acidity of tricoordinate silicon cations brings about unusual reactivity in Lewis acid catalysis. The downside of catalysis with strong Lewis acids is, though, that these do have the potential to mediate the formation of protons by various mechanisms, and the thus released Brønsted acid might even outcompete the Lewis acid as the true catalyst. That is an often ignored point. One way of eliminating a hidden proton-catalyzed pathway is to add a proton scavenger. The low-temperature Diels-Alder reactions catalyzed by our ferrocene-stabilized silicon cation are such a case where the possibility of proton catalysis must be meticulously examined. Addition of the common hindered base 2,6-di-tert-butylpyridine resulted, however, in slow decomposition along with formation of the corresponding pyridinium ion. Quantitative deprotonation of the silicon cation was observed with more basic (Mes)(3)P to yield the phosphonium ion. A deuterium-labeling experiment verified that the proton is abstracted from the ferrocene backbone. A reasonable mechanism of the proton formation is proposed on the basis of quantum-chemical calculations. This is, admittedly, a particular case but suggests that the use of proton scavengers must be carefully scrutinized, as proton formation might be provoked rather than prevented. Proton-catalyzed Diels-Alder reactions are not well-documented in the literature, and a representative survey employing TfOH is included here. The outcome of these catalyses is compared with our silylium ion-catalyzed Diels-Alder reactions, thereby clearly corroborating that hidden Brønsted acid catalysis is not operating with our Lewis acid. Several simple-looking but challenging Diels-Alder reactions with exceptionally rare dienophile/enophile combinations are reported. Another indication is obtained from the chemoselectivity of the catalyses. The silylium ion-catalyzed Diels-Alder reaction is general with regard to the oxidation level of the

  19. Laying date and polygyny as determinants of annual reproductive success in male collared flycatchers ( Ficedula albicollis): a long-term study

    NASA Astrophysics Data System (ADS)

    Herényi, Márton; Garamszegi, László Zsolt; Hargitai, Rita; Hegyi, Gergely; Rosivall, Balázs; Szöllősi, Eszter; Török, János

    2014-04-01

    Annual reproductive success (ARS) is one of the main components of lifetime reproductive success, a reliable measure of individual fitness. Previous studies often dealt with ARS and variables potentially affecting it. Among them, long-term studies that consider multiple factors at the same time are particularly important in understanding the adaptive value of different phenotypes. Here, we used an 18-year dataset to quantify the ARS of male collared flycatchers ( Ficedula albicollis) on the basis of recruited offspring. We simultaneously assessed the effect of start of breeding, age, polygyny, body size and the expression of forehead patch (a sexually selected trait). The success of early breeding individuals was appreciably higher than late birds; however, breeding too early was also disadvantaged, and males that bred around the yearly median breeding date had the highest ARS. Polygynous males were more successful in years with good food supply, while in years with low food availability, they did not produce more recruits than monogamous males. The age of males, their forehead patch size and body size did not affect the number of recruits. Our findings support the importance of breeding date and suggest stabilizing selection on it in the long term. We also show that polygyny is not always advantageous for males, and its fitness pay-off may depend on environmental quality.

  20. A Single Molecular Diels-Alder Crosslinker for Achieving Recyclable Cross-Linked Polymers.

    PubMed

    Chen, Shengli; Wang, Fenfen; Peng, Yongjin; Chen, Tiehong; Wu, Qiang; Sun, Pingchuan

    2015-09-01

    A triol-functional crosslinker combining the thermoreversible properties of Diels-Alder (DA) adducts in one molecule is designed, synthesized, and used as an ideal substitute of a traditional crosslinker to prepare thermal recyclable cross-linked polyurethanes with excellent mechanical properties and recyclability in a very simple and efficient way. The recycle property of these materials achieved by the DA/retro-DA reaction at a suitable temperature is verified by differential scanning calorimetry and in situ variable temperature solid-state NMR experiments during the cyclic heating and cooling processes. The thermal recyclability and remending ability of the bulk polyurethanes is demonstrated by three polymer processing methods, including hot-press molding, injection molding, and solution casting. It is notable that all the recycled cross-linked polymers display nearly invariable elongation/stress at break compared to the as-synthesized samples. Further end-group functionalization of this single molecular DA crosslinker provides the potential in preparing a wide range of recyclable cross-linked polymers. PMID:26248230

  1. Artificial Metalloenzymes with the Neocarzinostatin Scaffold: Toward a Biocatalyst for the Diels-Alder Reaction.

    PubMed

    Ghattas, Wadih; Cotchico-Alonso, Lur; Maréchal, Jean-Didier; Urvoas, Agathe; Rousseau, Maëva; Mahy, Jean-Pierre; Ricoux, Rémy

    2016-03-01

    A copper(II) cofactor coupled to a testosterone anchor, copper(II)-(5-(Piperazin-1-yl)-1,10-phenanthroline)testosterone-17-hemisuccinamide (10) was synthesized and associated with a neocarzinostatin variant, NCS-3.24 (KD =3 μm), thus generating a new artificial metalloenzyme by following a "Trojan horse" strategy. Interestingly, the artificial enzyme was able to efficiently catalyze the Diels-Alder cyclization reaction of cyclopentadiene (1) with 2-azachalcone (2). In comparison with what was observed with cofactor 10 alone, the artificial enzymes favored formation of the exo products (endo/exo ratios of 84:16 and 62:38, respectively, after 12 h). Molecular modeling studies assigned the synergy between the copper complex and the testosterone (KD =13 μm) moieties in the binding of 10 to good van der Waals complementarity. Moreover, by pushing the modeling exercise to its limits, we hypothesize on the molecular grounds that are responsible for the observed selectivity. PMID:26677011

  2. Combinatorial Synthesis of Linearly Condensed Polycyclic Compounds, Including Anthracyclinones, Through Tandem Diels-Alder Additions

    NASA Astrophysics Data System (ADS)

    Vogel, Pierre

    Double exocyclic 1,3-dienes such as 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane and its 1-substituted derivatives undergo two successive Diels-Alder additions with large reactivity difference between the addition of the first equivalent (k 1) and the second equivalent (k 2) of dienophile. This allows one to prepare, through parallel synthesis, a large number of linearly condensed polycyclic systems containing three annulated six-membered rings, including naphthacenyl systems and anthracyclinones. The large k 1/k 2 rate constant ratio is a consequence of the Dimroth principle, the first cycloaddition being significantly more exothermic then the second one. Control of regio- and stereoselectivity of the two successive cycloadditions is possible by 1-substitution of the 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane, for instance by a 1-(dimethoxymethyl) group, or by stereoselective disubstitution of the double diene by arenesulfenyl substituents. Enantiomerically pure anthracyclinones and analogues are obtained using enantiomerically pure dienophiles such as 3-oxo-but-2-en-2-yl esters. The chemistry so-developed has allowed the preparation of enantiomerically pure 6-((aminoalkoxy)oxy)methyl-6,7-dideoxyidarubicinones that are DNA intercalators and inhibitors of topoisomerase II-induced DNA strained religation.

  3. Vanadium redox flow battery efficiency and durability studies of sulfonated Diels Alder poly(phenylene)s

    SciTech Connect

    Fujimoto, Cy H.; Kim, Soowhan; Stains, Ronald; Wei, Xiaoliang; Li, Liyu; Yang, Zhenguo

    2012-07-01

    Sulfonated Diels Alder poly(phenylene) (SDAPP) was examined for vanadium redox flow battery (VRFB) use. The ion exchange capacity (IEC) was varied from 1.4, 1.6 and 2.0 meq/g in order to tune the proton conductivity and vanadium permeability. Coulombic efficiencies between 92 to 99% were observed, depending on IEC (lower IEC, higher coulombic efficiencies). In all cases the SDAPP displayed comparable energy efficiencies (88 - 90%) to Nafion 117 (88%) at 50mA/cm2. Membrane durability also was dependent on IEC; SDAPP with the highest IEC lasted slightly over 50 cycles while SDAPP with the lowest IEC lasted over 400 cycles and testing was discontinued only due to time constraints. Accelerated vanadium lifetime studies were initialed with SDAPP, by soaking films in a 0.1 M V5+ and 5.0 M total SO4-2 solution. The rate of degradation was also proportional with IEC; the 2 meq/g sample dissolved within 376 hours, the 1.6 meq/g sample dissolved after 860 hours, while the 1.4 meq/g sample broke apart after 1527 hours.

  4. Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

    SciTech Connect

    Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; Anderson, Travis M.

    2015-10-23

    Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediate ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. As a result, improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.

  5. Storing solar energy with liquid phase Diels-Alder reactions. Final report

    SciTech Connect

    Poling, B.E.

    1983-07-28

    At the beginning of this project, a preliminary study was completed that indicated the Diels-Alder reaction between maleic anhydride and 2 methyl furan had an energy storage capacity greater than water. During the last two years when this grant was in effect, three additional projects have been completed. First, an improved calorimetric techniques was developed for determination of the energy storage capacity of a reversible liquid phase chemical reaction. This technique confirmed the validity of the earlier results for the maleic anhydride-methyl furan reaction. Second, a technique was developed for characterizing solution nonidealities for mixtures in which reversible chemical reactions occur. It was found that for the maleic anhydride-2 methyl furan reaction, these non idealities could affect equilibrium compositions by nearly 40%. Third, drop calorimetry was used as a screening method to examine sixteen reactions for their potential as energy storage candidates. Of the sixteen examined, three (all involving maleic anhydride and substituted furan) showed an increased energy storage capacity due to reaction while the remaining thirteen showed no increase. In the following report, results of these three studies are summarized. Finally, a general summary of the status of energy storage by chemical reactions is presented.

  6. Surface confined retro Diels-Alder reaction driven by the swelling of weak polyelectrolytes.

    PubMed

    Lyu, Beier; Cha, Wenli; Mao, Tingting; Wu, Yuanzi; Qian, Hujun; Zhou, Yitian; Chen, Xiuli; Zhang, Shen; Liu, Lanying; Yang, Guang; Lu, Zhongyuan; Zhu, Qiang; Ma, Hongwei

    2015-03-25

    Recently, the type of reactions driven by mechanical force has increased significantly; however, the number of methods for activating those mechanochemical reactions stays relatively limited. Furthermore, in situ characterization of a reaction is usually hampered by the inherent properties of conventional methods. In this study, we report a new platform that utilizes mechanical force generated by the swelling of surface tethered weak polyelectrolytes. An initiator with Diels-Alder (DA) adduct structure was applied to prepare the polyelectrolyte-carboxylated poly(OEGMA-r-HEMA), so that the force could trigger the retro DA reaction. The reaction was monitored in real time by quartz crystal microbalance and confirmed with atomic force microscopy and X-ray photoelectron spectroscopy. Compared with the conventional heating method, the swelling-induced retro DA reaction proceeded rapidly with high conversion ratio and selectivity. A 23.61 kcal/mol theoretical energy barrier supported the practicability of this retro DA reaction being triggered mechanically at ambient temperature. During swelling, the tensile force was controllable and persistent. This unique feature imparts this mechanochemical platform the potential to "freeze" an intermediate state of a reaction for in situ spectroscopic observations, such as surface-enhanced Raman spectroscopy and frequency generation spectroscopy. PMID:25734373

  7. Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

    DOE PAGESBeta

    Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; Anderson, Travis M.

    2015-10-23

    Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediatemore » ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. As a result, improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.« less

  8. Factors affecting distribution of wood, detritus, and sediment in headwater streams draining managed young-growth red alder - Conifer forests in southeast Alaska

    USGS Publications Warehouse

    Gomi, T.; Johnson, A.C.; Deal, R.L.; Hennon, P.E.; Orlikowska, E.H.; Wipfli, M.S.

    2006-01-01

    Factors (riparian stand condition, management regimes, and channel properties) affecting distributions of wood, detritus (leaves and branches), and sediment were examined in headwater streams draining young-growth red alder (Alnus rubra Bong.) - conifer riparian forests (40 years old) remained in channels and provided sites for sediment and organic matter storage. Despite various alder-conifer mixtures and past harvesting effects, the abundance of large wood, fine wood, and detritus accumulations significantly decreased with increasing channel bank-full width (0.5-3.5 m) along relatively short channel distances (up to 700 m). Changes in wood, detritus, and sediment accumulations together with changes in riparian stand characteristics create spatial and temporal variability of in-channel conditions in headwater systems. A component of alder within young-growth riparian forests may benefit both wood production and biological recovery in disturbed headwater stream channels. ?? 2006 NRC.

  9. Ross operation in children and young adults: the Alder Hey case series

    PubMed Central

    Raja, Shahzad Gull; Pozzi, Marco

    2004-01-01

    Background The ideal prosthesis for aortic valve replacement in children and young adults has not been found yet. In recent years there has been a renewed interest in the replacement of aortic valve with the pulmonary autograft owing to its advantages of lack of anticoagulation, potential for growth and excellent haemodynamic performance. The purpose of this study was to review our institutional experience at Alder Hey hospital with the Ross procedure in children and young adults. Methods From November 1996 to September 2003, 38 patients (mean age, 13.1 ± 5.7 years) underwent the Ross procedure for various aortic valve diseases using the root replacement technique. Clinical and echocardiographic follow-up was performed early (within 30 days), 3 to 6 months, and yearly after surgery. Medical records of all patients were reviewed retrospectively. Results There was 1 perioperative death. The patients were followed-up for a median interval of 36 months and up to 7 years. One patient died 3 years after surgery secondary to ventricular arrhythmia with overall mortality of 5.3%. Actuarial survival at 7 years was 94 ± 2.5% and there was 100% freedom from reoperation for autograft valve dysfunction or any other cause. Balloon dilatation was required in 2 patients for pulmonary homograft stenosis. The haemodynamics at the latest follow-up were also similar to those at the time of discharge after surgery. There was no progression in the degree of aortic regurgitation for 11 patients with trivial and 3 with mild regurgitation. Conclusion Our experience demonstrates that Ross operation is an attractive option for aortic valve replacement in children and young adults. Not only can the operation be accomplished with a low operative risk but the valve function stays normal over a long period of time with minimal alteration in lifestyle and no need for repeated operations to replace the valve as a result of somatic growth of the children. PMID:15096281

  10. Harnessing the bioorthogonal inverse electron demand Diels-Alder cycloaddition for pretargeted PET imaging.

    PubMed

    Reiner, Thomas; Lewis, Jason S; Zeglis, Brian M

    2015-01-01

    Due to their exquisite affinity and specificity, antibodies have become extremely promising vectors for the delivery of radioisotopes to cancer cells for PET imaging. However, the necessity of labeling antibodies with radionuclides with long physical half-lives often results in high background radiation dose rates to non-target tissues. In order to circumvent this issue, we have employed a pretargeted PET imaging strategy based on the inverse electron demand Diels-Alder cycloaddition reaction. The methodology decouples the antibody from the radioactivity and thus exploits the positive characteristics of antibodies, while eschewing their pharmacokinetic drawbacks. The system is composed of four steps: (1) the injection of a mAb-trans-cyclooctene (TCO) conjugate; (2) a localization time period during which the antibody accumulates in the tumor and clears from the blood; (3) the injection of the radiolabeled tetrazine; and (4) the in vivo click ligation of the components followed by the clearance of excess radioligand. In the example presented in the work at hand, a (64)Cu-NOTA-labeled tetrazine radioligand and a trans-cyclooctene-conjugated humanized antibody (huA33) were successfully used to delineate SW1222 colorectal cancer tumors with high tumor-to-background contrast. Further, the pretargeting methodology produces high quality images at only a fraction of the radiation dose to non-target tissue created by radioimmunoconjugates directly labeled with (64)Cu or (89)Zr. Ultimately, the modularity of this protocol is one of its greatest assets, as the trans-cyclooctene moiety can be appended to any non-internalizing antibody, and the tetrazine can be attached to a wide variety of radioisotopes. PMID:25742199

  11. QM/QM' Direct Molecular Dynamics of Water-Accelerated Diels-Alder Reaction.

    PubMed

    Liu, Fengjiao; Yang, Zhongyue; Mei, Ye; Houk, K N

    2016-07-01

    A QM/QM' direct molecular dynamics study of a water-accelerated Diels-Alder reaction in aqueous solution is reported. Cyclopentadiene and methyl vinyl ketone are known to react faster in water than in nonpolar solvents. We have explored how polarization of water molecules afforded by PM3 influences the nature of the transition state, and the reaction dynamics. We compare the results with previous studies on QM/MM and QM/MM+3QM water simulations from our laboratory. Transition state sampling in vacuum PM3 water boxes indicates that the asynchronicity is 0.54 Å in QM/QM', as compared to 0.48 Å in QM/MM, and 0.54 Å in QM/MM+3QM water. The mean time gap between the formation of two C-C bonds is 19 fs for QM/QM', compared to 20 fs for QM/MM, and 25 fs for QM/MM+3QM water. The samplings and time gaps are qualitatively consistent, indicating that water polarization is not significant in sampling and dynamics of bonding changes. The dynamics of hydrogen bonding between reacting molecules and water molecules was also analyzed. From reactants to transition states, H-bond shortening is 0.4 Å by QM/QM', while only 0.15 Å for QM/MM and QM/MM+3QM water. From reactants to transition states, the mean value of the H-bond angle increases by 19° in QM/QM', but only 4° in QM/MM, and 10° in QM/MM+3QM water. These suggest that water polarization is essential for the correct representation of dynamical formation of hydrogen bonds in the transition state by water reorientation. QM/QM' overestimates the hydrogen bonding enhancement because of its underestimation of neutral hydrogen bonding within the reactants, a general deficiency of PM3. PMID:27092967

  12. Harnessing the Bioorthogonal Inverse Electron Demand Diels-Alder Cycloaddition for Pretargeted PET Imaging

    PubMed Central

    Lewis, Jason S.

    2015-01-01

    Due to their exquisite affinity and specificity, antibodies have become extremely promising vectors for the delivery of radioisotopes to cancer cells for PET imaging. However, the necessity of labeling antibodies with radionuclides with long physical half-lives often results in high background radiation dose rates to non-target tissues. In order to circumvent this issue, we have employed a pretargeted PET imaging strategy based on the inverse electron demand Diels-Alder cycloaddition reaction. The methodology decouples the antibody from the radioactivity and thus exploits the positive characteristics of antibodies, while eschewing their pharmacokinetic drawbacks. The system is composed of four steps: (1) the injection of a mAb-trans-cyclooctene (TCO) conjugate; (2) a localization time period during which the antibody accumulates in the tumor and clears from the blood; (3) the injection of the radiolabeled tetrazine; and (4) the in vivo click ligation of the components followed by the clearance of excess radioligand. In the example presented in the work at hand, a 64Cu-NOTA-labeled tetrazine radioligand and a trans-cyclooctene-conjugated humanized antibody (huA33) were successfully used to delineate SW1222 colorectal cancer tumors with high tumor-to-background contrast. Further, the pretargeting methodology produces high quality images at only a fraction of the radiation dose to non-target tissue created by radioimmunoconjugates directly labeled with 64Cu or 89Zr. Ultimately, the modularity of this protocol is one of its greatest assets, as the trans-cyclooctene moiety can be appended to any non-internalizing antibody, and the tetrazine can be attached to a wide variety of radioisotopes. PMID:25742199

  13. Novel Diels-Alder based self-healing epoxies for aerospace composites

    NASA Astrophysics Data System (ADS)

    Coope, T. S.; Turkenburg, D. H.; Fischer, H. R.; Luterbacher, R.; van Bracht, H.; Bond, I. P.

    2016-08-01

    Epoxy resins containing Diels-Alder (DA) furan and maleimide moieties are presented with the capability to self-heal after exposure to an external heat source. A conventional epoxy amine system has been combined with furfuryl and maleimide functional groups in a two-step process, to avoid major side-reactions, and the concentration of a thermo-reversibly binding cross-linker was considered to balance thermoset and thermoplastic behaviours, and the subsequent self-healing performance. In the context of self-repair technologies an inbuilt ‘intrinsic’ self-healing system is deemed favourable as the healing agent can be placed in known ‘hot spot’ regions (i.e. skin-stringer run outs, ply drops and around drilled holes) where operational damage predominately occurs in load bearing aerospace structures. In this study, the mechanical and self-healing performance of furan functionalised epoxy resins containing varying amounts (10, 20, 30 or 40 pph) of bismaleimide were investigated using a bulk epoxy polymer tapered double cantilever beam test specimen geometry. Two forms, a thin film and a bulk material, were evaluated to account for future integration methods into fibre reinforced polymer (FRP) composites. The highest healing efficiency, with respect to the obtained initial load value, was observed from the 20 pph bulk material derivative. The polymers were successful in achieving consistent multiple (three) healing cycles when heated at 150 °C for 5 min. This novel investigated DA material exhibits favourable processing characteristics for FRP composites as preliminary studies have shown successful coextrution with reinforcing fibres to form free standing films and dry fibre impregnation.

  14. The mechanism of the retro-Diels-Alder reaction in 4-vinylcyclohexene cation radical

    NASA Astrophysics Data System (ADS)

    Pancíř, J.; Tureček, F.

    1984-06-01

    Butadiene cation radicals are produced symmetrically from the ring and side-chain of the vinylcyclohexene cation radical near the onset of the fragmentation. The appearance energies of C 4H 6+- and C 4H 2D 4+- from (3,3,6,6-D 4)vinylcyclohex ene were measured as 11.07 ± 0.05 and 11.06 ± 0.06 eV, respectively. This sets the barrier to retro-Diels-Alder decomposition at 1140 kJ mol -1 above the energy of 1 and 44 kJ mol -1 above the thermochemical threshold corresponding to C 4H 6+- + C 4H 6. Topological molecular orbital calculations indicate that this lowest-energy path involves a sequential rupture of the C 3C 4 and C 5C 6 bonds, with a calculated barrier of 211 kJ mol -1. The second, two-step reaction channel proceeds by subsequent fission of the C 5C 6 and C 3C 4 bonds with a barrier of 299 kJ mol -1. This channel is found experimentally as a break on the ionization efficiency curve at 12.1 eV. Both the supra-supra and the supra-antara pericyclic reactions go through energy maxima and are therefore forbidden. The supra-supra process is the most favorable route for decomposition from the first excited state, the activation energy being 333 kJ mol -1. The preference for the two-step mechanism is due to hyperconjugative stabilization of intermediate molecular configurations.

  15. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study

    PubMed Central

    Callender, Katrina L.; Roy, Sébastien; Khasa, Damase P.; Whyte, Lyle G.; Greer, Charles W.

    2016-01-01

    Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM) fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal) alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI), and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS) region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas), metal sequestration (Brevundimonas and Caulobacter) and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas) increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN) assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude) and mineralization (five-fold). Genomic techniques proved useful in investigating

  16. Synthesis of terephthalic acid via Diels-Alder reactions with ethylene and oxidized variants of 5-hydroxymethylfurfural

    PubMed Central

    Pacheco, Joshua J.; Davis, Mark E.

    2014-01-01

    Terephthalic acid (PTA), a monomer in the synthesis of polyethylene terephthalate (PET), is obtained by the oxidation of petroleum-derived p-xylene. There is significant interest in the synthesis of renewable, biomass-derived PTA. Here, routes to PTA starting from oxidized products of 5-hydroxymethylfurfural (HMF) that can be produced from biomass are reported. These routes involve Diels-Alder reactions with ethylene and avoid the hydrogenation of HMF to 2,5-dimethylfuran. Oxidized derivatives of HMF are reacted with ethylene over solid Lewis acid catalysts that do not contain strong Brønsted acids to synthesize intermediates of PTA and its equally important diester, dimethyl terephthalate (DMT). The partially oxidized HMF, 5-(hydroxymethyl)furoic acid (HMFA), is reacted with high pressure ethylene over a pure-silica molecular sieve containing framework tin (Sn-Beta) to produce the Diels-Alder dehydration product, 4-(hydroxymethyl)benzoic acid (HMBA), with 31% selectivity at 61% HMFA conversion after 6 h at 190 °C. If HMFA is protected with methanol to form methyl 5-(methoxymethyl)furan-2-carboxylate (MMFC), MMFC can react with ethylene in the presence of Sn-Beta for 2 h to produce methyl 4-(methoxymethyl)benzenecarboxylate (MMBC) with 46% selectivity at 28% MMFC conversion or in the presence of a pure-silica molecular sieve containing framework zirconium (Zr-Beta) for 6 h to produce MMBC with 81% selectivity at 26% MMFC conversion. HMBA and MMBC can then be oxidized to produce PTA and DMT, respectively. When Lewis acid containing mesoporous silica (MCM-41) and amorphous silica, or Brønsted acid containing zeolites (Al-Beta), are used as catalysts, a significant decrease in selectivity/yield of the Diels-Alder dehydration product is observed. PMID:24912153

  17. Synthesis of terephthalic acid via Diels-Alder reactions with ethylene and oxidized variants of 5-hydroxymethylfurfural.

    PubMed

    Pacheco, Joshua J; Davis, Mark E

    2014-06-10

    Terephthalic acid (PTA), a monomer in the synthesis of polyethylene terephthalate (PET), is obtained by the oxidation of petroleum-derived p-xylene. There is significant interest in the synthesis of renewable, biomass-derived PTA. Here, routes to PTA starting from oxidized products of 5-hydroxymethylfurfural (HMF) that can be produced from biomass are reported. These routes involve Diels-Alder reactions with ethylene and avoid the hydrogenation of HMF to 2,5-dimethylfuran. Oxidized derivatives of HMF are reacted with ethylene over solid Lewis acid catalysts that do not contain strong Brønsted acids to synthesize intermediates of PTA and its equally important diester, dimethyl terephthalate (DMT). The partially oxidized HMF, 5-(hydroxymethyl)furoic acid (HMFA), is reacted with high pressure ethylene over a pure-silica molecular sieve containing framework tin (Sn-Beta) to produce the Diels-Alder dehydration product, 4-(hydroxymethyl)benzoic acid (HMBA), with 31% selectivity at 61% HMFA conversion after 6 h at 190 °C. If HMFA is protected with methanol to form methyl 5-(methoxymethyl)furan-2-carboxylate (MMFC), MMFC can react with ethylene in the presence of Sn-Beta for 2 h to produce methyl 4-(methoxymethyl)benzenecarboxylate (MMBC) with 46% selectivity at 28% MMFC conversion or in the presence of a pure-silica molecular sieve containing framework zirconium (Zr-Beta) for 6 h to produce MMBC with 81% selectivity at 26% MMFC conversion. HMBA and MMBC can then be oxidized to produce PTA and DMT, respectively. When Lewis acid containing mesoporous silica (MCM-41) and amorphous silica, or Brønsted acid containing zeolites (Al-Beta), are used as catalysts, a significant decrease in selectivity/yield of the Diels-Alder dehydration product is observed. PMID:24912153

  18. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study.

    PubMed

    Callender, Katrina L; Roy, Sébastien; Khasa, Damase P; Whyte, Lyle G; Greer, Charles W

    2016-01-01

    Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM) fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal) alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI), and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS) region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas), metal sequestration (Brevundimonas and Caulobacter) and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas) increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN) assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude) and mineralization (five-fold). Genomic techniques proved useful in investigating

  19. Can We Use Tree Rings of Black Alder to Reconstruct Lake Levels? A Case Study for the Mecklenburg Lake District, Northeastern Germany

    PubMed Central

    van der Maaten, Ernst; van der Maaten-Theunissen, Marieke; Buras, Allan; Scharnweber, Tobias; Simard, Sonia; Kaiser, Knut; Lorenz, Sebastian; Wilmking, Martin

    2015-01-01

    In this study, we explore the potential to reconstruct lake-level (and groundwater) fluctuations from tree-ring chronologies of black alder (Alnus glutinosa L.) for three study lakes in the Mecklenburg Lake District, northeastern Germany. As gauging records for lakes in this region are generally short, long-term reconstructions of lake-level fluctuations could provide valuable information on past hydrological conditions, which, in turn, are useful to assess dynamics of climate and landscape evolution. We selected black alder as our study species as alder typically thrives as riparian vegetation along lakeshores. For the study lakes, we tested whether a regional signal in lake-level fluctuations and in the growth of alder exists that could be used for long-term regional hydrological reconstructions, but found that local (i.e. site-specific) signals in lake level and tree-ring chronologies prevailed. Hence, we built lake/groundwater-level reconstruction models for the three study lakes individually. Two sets of models were considered based on (1) local tree-ring series of black alder, and (2) site-specific Standardized Precipitation Evapotranspiration Indices (SPEI). Although the SPEI-based models performed statistically well, we critically reflect on the reliability of these reconstructions, as SPEI cannot account for human influence. Tree-ring based reconstruction models, on the other hand, performed poor. Combined, our results suggest that, for our study area, long-term regional reconstructions of lake-level fluctuations that consider both recent and ancient (e.g., archaeological) wood of black alder seem extremely challenging, if not impossible. PMID:26317768

  20. Can We Use Tree Rings of Black Alder to Reconstruct Lake Levels? A Case Study for the Mecklenburg Lake District, Northeastern Germany.

    PubMed

    van der Maaten, Ernst; van der Maaten-Theunissen, Marieke; Buras, Allan; Scharnweber, Tobias; Simard, Sonia; Kaiser, Knut; Lorenz, Sebastian; Wilmking, Martin

    2015-01-01

    In this study, we explore the potential to reconstruct lake-level (and groundwater) fluctuations from tree-ring chronologies of black alder (Alnus glutinosa L.) for three study lakes in the Mecklenburg Lake District, northeastern Germany. As gauging records for lakes in this region are generally short, long-term reconstructions of lake-level fluctuations could provide valuable information on past hydrological conditions, which, in turn, are useful to assess dynamics of climate and landscape evolution. We selected black alder as our study species as alder typically thrives as riparian vegetation along lakeshores. For the study lakes, we tested whether a regional signal in lake-level fluctuations and in the growth of alder exists that could be used for long-term regional hydrological reconstructions, but found that local (i.e. site-specific) signals in lake level and tree-ring chronologies prevailed. Hence, we built lake/groundwater-level reconstruction models for the three study lakes individually. Two sets of models were considered based on (1) local tree-ring series of black alder, and (2) site-specific Standardized Precipitation Evapotranspiration Indices (SPEI). Although the SPEI-based models performed statistically well, we critically reflect on the reliability of these reconstructions, as SPEI cannot account for human influence. Tree-ring based reconstruction models, on the other hand, performed poor. Combined, our results suggest that, for our study area, long-term regional reconstructions of lake-level fluctuations that consider both recent and ancient (e.g., archaeological) wood of black alder seem extremely challenging, if not impossible. PMID:26317768

  1. Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

    PubMed Central

    Gunta, Rama

    2015-01-01

    Summary Here, we describe a new and simple synthetic strategy to various polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis (RRM) as the key steps. This approach delivers tri- and tetracyclic sulfones with six (n = 1), seven (n = 2) or eight-membered (n = 3) fused-ring systems containing trans-ring junctions unlike the conventional all cis-ring junctions generally obtained during the RRM sequence. Interestingly the starting materials used are simple and commercially available. PMID:26425192

  2. Nitroso Diels-Alder (NDA) Reaction as an Efficient Tool for the Functionalization of Diene-Containing Natural Products

    PubMed Central

    Carosso, Serena; Miller, Marvin J.

    2014-01-01

    This review describes the use of nitroso Diels-Alder reactions for the functionalization of complex diene-containing natural products in order to generate libraries of compounds with potential biological activity. The application of this methodology to the structural modification of a series of natural products (thebaine, steroidal dienes, rapamycin, leucomycin, colchicine, isocolchicine and piperine) is discussed using relevant examples from the literature from 1973 onwards. The biological activity of the resulting compounds is also discussed. Additional comments are provided that evaluate the methodology as a useful tool in organic, bioorganic and medicinal chemistry. PMID:25119424

  3. Concise Approach to (ent)-14 β-Hydroxysteroids through Highly Diastereo-/Enantioselective Diels-Alder Reactions.

    PubMed

    Peter, Clovis; Ressault, Blandine; Geoffroy, Philippe; Miesch, Michel

    2016-07-25

    14β-Hydroxysteroids, especially 14β-hydroxyandrostane derivatives are closely related to the cardenolide skeletons. The latter were readily available through highly diastero/enantioselective Diels-Alder (DA) reactions requiring high pressure or Lewis acid activation. Moreover, in the presence of (R)- or (S)-carvone as a chiral dienophile, the DA-reaction takes place under chemodivergent parallel kinetic resolution control affording highly enantiomerically enriched 14β-hydroxysteroid derivatives or the corresponding (ent)-14β-hydroxysteroid derivatives. PMID:27192692

  4. Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

    PubMed Central

    Miró, Javier; Sánchez-Roselló, María; Sanz, Álvaro; Rabasa, Fernando

    2015-01-01

    Summary A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols. PMID:26425205

  5. Retrospective multicenter evaluation of the "fly-catching syndrome" in 24 dogs: EEG, BAER, MRI, CSF findings and response to antiepileptic and antidepressant treatment.

    PubMed

    Wrzosek, Marcin; Płonek, Marta; Nicpoń, Józef; Cizinauskas, Sigitas; Pakozdy, Akos

    2015-12-01

    The fly-catching syndrome (FCS) is a rare canine condition of sudden, occasional, or constant episodes of biting the air. It may be accompanied by jumping, licking, and swallowing. The etiology of FCS is unknown and controversial. Various explanations for its occurrence have included epileptoid disorders such as visual cortex epileptiform disturbances and simple and complex partial seizures as well as compulsive disorders, hallucinatory behavior, and stereotypy. A retrospective multicenter analysis of 24 dogs with clinical symptoms of FCS is presented. Clinical signs at the time of presentation, the mean age at onset of the disease, the response to treatment, and the clinical outcome were recorded and analyzed in all patients. All dogs underwent clinical, neurological, and otoscopic examinations. Complete blood cell counts (CBCs) and serum chemistry panels were obtained from each dog. Diagnostic testing included MRI and EEG examinations in 21 cases, BAER in 19 cases, and CSF analysis in 20 cases. The EEG revealed spike activity in 8 (38%) of the 21 cases, 7 of which had activity in the occipital lobes. The brainstem auditory evoked response (BAER) revealed three cases of bilateral deafness. The MRI revealed six cases of Chiari malformation (CM), one case of syringohydromyelia (SM), and one case of a falx cerebri meningioma. The dogs were divided into groups according to their treatment protocol. Group A included dogs treated with phenobarbital (PB), and group B consisted of dogs treated with fluoxetine (FLX). Thirty-six percent of the dogs in group A responded to PB, while 100% of the dogs in group B responded to FLX. The results suggest that FCS is more responsive to FLX than PB. However, the etiology of this behavior remains unclear in most cases. PMID:26584225

  6. Copper(II)-catalyzed room temperature aerobic oxidation of hydroxamic acids and hydrazides to acyl-nitroso and azo intermediates, and their Diels-Alder trapping.

    PubMed

    Chaiyaveij, Duangduan; Cleary, Leah; Batsanov, Andrei S; Marder, Todd B; Shea, Kenneth J; Whiting, Andrew

    2011-07-01

    CuCl(2), in the presence of a 2-ethyl-2-oxazoline ligand, is an effective catalyst for the room temperature, aerobic oxidation of hydroxamic acids and hydrazides, to acyl-nitroso and azo dienophiles respectively, which are efficiently trapped in situ via both inter- and intramolecular hetero-Diels-Alder reactions with dienes. Both inter- and intramolecular variants of the Diels-Alder reaction are suitable under the reaction conditions using a variety of solvents. Under the same conditions, an acyl hydrazide was also oxidized to give an acyl-azo dienophile which was trapped intramolecularly by a diene. PMID:21644530

  7. Humus bacteria of Norway spruce stands: plant growth promoting properties and birch, red fescue and alder colonizing capacity.

    PubMed

    Elo; Maunuksela; Salkinoja-Salonen; Smolander; Haahtela

    2000-02-01

    We studied the potential of the humus layer of the Norway spruce stands to supply beneficial rhizobacteria to birch (Betula pendula), alder (Alnus incana) and fescue grass (Festuca rubra), representatives of pioneer vegetation after clear-cutting of the coniferous forest. Axenically grown seedlings of these species were inoculated with the acid spruce humus, pH 3.7-5.3. Actinorhizal propagules, capable of nodulating alder, were present in high density (10(3) g(-1)) in humus of long-term limed plots, whereas plots with nitrogen fertilization contained almost none (

  8. Insight into the informational-structure behavior of the Diels-Alder reaction of cyclopentadiene and maleic anhydride.

    PubMed

    Molina-Espíritu, Moyocoyani; Esquivel, Rodolfo O; Kohout, Miroslav; Angulo, Juan Carlos; Dobado, José A; Dehesa, Jesús S; LópezRosa, Sheila; Soriano-Correa, Catalina

    2014-08-01

    The course of the Diels-Alder reactions of cyclopentadiene and maleic anhydride were studied. Two reaction paths were modelled: endo- and exo-selective paths. All structures within the transient region were characterized and analyzed by means of geometrical descriptors, physicochemical parameters and information-theoretical measures in order to observe the linkage between chemical behavior and the carriage of information. We have shown that the information-theoretical characterization of the chemical course of the reaction is in complete agreement with its phenomenological behavior in passing from reactants to products. In addition, we were able to detect the main differences between the two reaction mechanisms. This type of informational analysis serves to provide tools to help understand the chemical reactivity of the two simplest Diels-Alder reactions, which permits the establishment of a connection between the quantum changes that molecular systems exert along reaction coordinates and standard physicochemical phenomenology. In the present study, we have shown that every reaction stage has a family of subsequent structures that are characterized not solely by their phenomenological behavior but also by informational properties of their electronic density distribution (localizability, order, uniformity). Moreover, we were able to describe the main differences between endo-adduct and exo-adduct pathways. With the advent of new experimental techniques, it is in principle possible to observe the structural changes in the transient regions of chemical reactions. Indeed, through this work we have provided the theoretical concepts needed to unveil the concurrent processes associated with chemical reactions. PMID:25086767

  9. An interpenetrating HA/G/CS biomimic hydrogel via Diels-Alder click chemistry for cartilage tissue engineering.

    PubMed

    Yu, Feng; Cao, Xiaodong; Zeng, Lei; Zhang, Qing; Chen, Xiaofeng

    2013-08-14

    In order to mimic the natural cartilage extracellular matrix, a novel biological degradable interpenetrating network hydrogel was synthesized from the gelatin (G), hyaluronic acid (HA) and chondroitin sulfate (CS) by Diels-Alder "click" chemistry. HA was modified with furylamine and G was modified with furancarboxylic acid respectively. (1)H NMR spectra and elemental analysis showed that the substitution degrees of HA-furan and G-furan were 71.5% and 44.5%. Then the hydrogels were finally synthesized by cross-linking furan-modified HA and G derivatives with dimaleimide poly(ethylene glycol) (MAL-PEG-MAL). The mechanical and degradation properties of the hydrogels could be tuned simply through varying the molar ratio between furan and maleimide. Rheological, mechanical and degradation studies demonstrated that the Diels-Alder "click" chemistry is an efficient method for preparing high performance biological interpenetrating hydrogels. This biomimic hydrogel with improved mechanical properties could have great potential applications in cartilage tissue engineering. PMID:23769536

  10. Synthesis of the Reported Pyranonaphthoquinone Structure of the Indoleamine-2,3-dioxygenase Inhibitor Annulin B by Regioselective Diels-Alder Reaction.

    PubMed

    Inman, Martyn; Carvalho, Catarina; Lewis, William; Moody, Christopher J

    2016-09-01

    Annulin B, isolated from the marine hydroid isolated from Garveia annulata, is a potent inhibitor of the tryptophan catabolizing enzyme indoleamine-2,3-dioxygenase (IDO). A synthesis of the reported pyranonaphthoquinone structure is described, in which the key step is a regioselective Diels-Alder reaction between a pyranobenzoquinone dienophile and a silyl ketene acetal diene. PMID:27513176

  11. Integration of Computational and Preparative Techniques to Demonstrate Physical Organic Concepts in Synthetic Organic Chemistry: An Example Using Diels-Alder Reaction

    ERIC Educational Resources Information Center

    Palmer, David R. J.

    2004-01-01

    The Diels-Alder reaction is used as an example for showing the integration of computational and preparative techniques, which help in demonstrating the physical organic concepts in synthetic organic chemistry. These experiments show that the students should not accept the computational results without questioning them and in many Diels-Alder…

  12. Bicyclic Guanidine Catalyzed Asymmetric Tandem Isomerization Intramolecular-Diels-Alder Reaction: The First Catalytic Enantioselective Total Synthesis of (+)-alpha-Yohimbine.

    PubMed

    Feng, Wei; Jiang, Danfeng; Kee, Choon-Wee; Liu, Hongjun; Tan, Choon-Hong

    2016-02-01

    Hydroisoquinoline derivatives were prepared in moderate to good enantioselectivities via a bicyclic guanidine-catalyzed tandem isomerization intramolecular-Diels-Alder (IMDA) reaction of alkynes. With this synthetic method, the first enantioselective synthesis of (+)-alpha-yohimbine was completed in 9 steps from the IMDA products. PMID:25932622

  13. Diels-Alder Synthesis of endo-cis-N-phenylbicyclo[2.2.2]oct-5-en-2,3-dicarboximide

    ERIC Educational Resources Information Center

    Baar, Marsha R.; Wustholz, Kristin

    2005-01-01

    A study investigated the Diels-Alder synthesis of endo-cis-N-phenylbicyclo [2.2.2]oct-5-en-2,3-dicarboximide. The amount of time taken by a reaction between the 1,3-cyclohexadiene and N-phenylmaleimide at room temperature and also whether the desired cycloadduct would precipitate directly from the reaction mixture was examined.

  14. Fast Hetero-Diels-Alder Reactions Using 4-Phenyl-1,2,4-Triazoline-3,5-Dione (PTAD) as the Dienophile

    ERIC Educational Resources Information Center

    Celius, Tevye C.

    2010-01-01

    A hetero-Diels-Alder reaction that proceeds rapidly and only requires a simple filtration to purify the product is presented. The dienophile, 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), is prepared by the heterogeneous oxidation of 4-phenylurazole by the bromenium ion, Br[superscript +], generated in situ by the oxidation of potassium bromide by…

  15. Illustrating the Utility of X-Ray Crystallography for Structure Elucidation through a Tandem Aldol Condensation/Diels-Alder Reaction Sequence

    ERIC Educational Resources Information Center

    Hoang, Giang T.; Kubo, Tomohiro; Young, Victor G., Jr.; Kautzky, Jacob A.; Wissinger, Jane E.

    2015-01-01

    Two introductory organic chemistry laboratory experiments are described based on the Diels-Alder reaction of 2,3,4,5-tetraphenylcyclopentadienone, which is synthesized prior to or in a one-pot reaction, with styrene. Students are presented with three possible products, the "endo" and "exo" diastereomers and the decarbonylated…

  16. The Synthesis of "N"-Benzyl-2-Azanorbornene via Aqueous Hetero Diels-Alder Reaction: An Undergraduate Project in Organic Synthesis and Structural Analysis

    ERIC Educational Resources Information Center

    Sauvage, Xavier; Delaude, Lionel

    2008-01-01

    The synthesis of "N"-benzyl-2-azanorbornene via aqueous hetero Diels-Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described. Characterization of the product was achieved by IR and NMR spectroscopies. The spectral data acquired are thoroughly discussed. Numerous…

  17. Diels-Alder Cycloadditions: A MORE Experiment in the Organic Laboratory Including a Diene Identification Exercise Involving NMR Spectroscopy and Molecular Modeling

    ERIC Educational Resources Information Center

    Shaw, Roosevelt; Severin, Ashika; Balfour, Miguel; Nettles, Columbus

    2005-01-01

    Two Diels-Alder reactions are described that are suitable for a MORE (microwave-induced organic reaction enhanced) experiment in the organic chemistry laboratory course. A second experiment in which the splitting patterns of the vinyl protons in the nuclear magnetic resonance (NMR) spectra of two MORE adducts are used in conjunction with molecular…

  18. Synthesis of a Self-Healing Polymer Based on Reversible Diels-Alder Reaction: An Advanced Undergraduate Laboratory at the Interface of Organic Chemistry and Materials Science

    ERIC Educational Resources Information Center

    Weizman, Haim; Nielsen, Christian; Weizman, Or S.; Nemat-Nasser, Sia

    2011-01-01

    This laboratory experiment exposes students to the chemistry of self-healing polymers based on a Diels-Alder reaction. Students accomplish a multistep synthesis of a monomer building block and then polymerize it to form a cross-linked polymer. The healing capability of the polymer is verified by differential scanning calorimetry (DSC) experiments.…

  19. N,N'-Dioxide/nickel(ii)-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene with 2,3-dioxopyrrolidines and 2-alkenoyl pyridines.

    PubMed

    Lu, Yan; Zhou, Yuhang; Lin, Lili; Zheng, Haifeng; Fu, Kai; Liu, Xiaohua; Feng, Xiaoming

    2016-07-01

    A chiral N,N'-dioxide/Ni(OTf)2 complex-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene with 2,3-dioxopyrrolidines and 2-alkenoyl pyridines has been achieved. The corresponding chiral bridged compounds were obtained in high yields with excellent dr and ee values (up to 97% yield, 95 : 5 dr and 97% ee). PMID:27284594

  20. A π-electronic covalent organic framework catalyst: π-walls as catalytic beds for Diels-Alder reactions under ambient conditions.

    PubMed

    Wu, Yang; Xu, Hong; Chen, Xiong; Gao, Jia; Jiang, Donglin

    2015-06-25

    We report a strategy for developing π-electronic covalent organic frameworks as heterogeneous catalysts that enable the use of columnar π-walls as catalytic beds to facilitate organic transformations in their one-dimensional open channels. The π-frameworks exhibit outstanding catalytic activity, promote Diels-Alder reactions under ambient conditions and are robust for cycle use. PMID:26000867

  1. Diels-Alder attachment of a planar organic molecule to a dangling bond dimer on a hydrogenated semiconductor surface.

    PubMed

    Godlewski, Szymon; Kawai, Hiroyo; Engelund, Mads; Kolmer, Marek; Zuzak, Rafal; Garcia-Lekue, Aran; Novell-Leruth, Gerard; Echavarren, Antonio M; Sanchez-Portal, Daniel; Joachim, Christian; Saeys, Mark

    2016-06-22

    Construction of single-molecule electronic devices requires the controlled manipulation of organic molecules and their properties. This could be achieved by tuning the interaction between the molecule and individual atoms by local "on-surface" chemistry, i.e., the controlled formation of chemical bonds between the species. We demonstrate here the reversible attachment of a planar conjugated polyaromatic molecule to a pair of unpassivated dangling bonds on a hydrogenated Ge(001):H surface via a Diels-Alder [4+2] addition using the tip of a scanning tunneling microscope (STM). Due to the small stability difference between the covalently bonded and a nearly undistorted structure attached to the dangling bond dimer by long-range dispersive forces, we show that at cryogenic temperatures the molecule can be switched between both configurations. The reversibility of this covalent bond forming reaction may be applied in the construction of complex circuits containing organic molecules with tunable properties. PMID:27271337

  2. Pyrone Diels-Alder Routes to Indolines and Hydroindolines: Syntheses of Gracilamine, Mesembrine, and Δ(7) -Mesembrenone.

    PubMed

    Gan, Pei; Smith, Myles W; Braffman, Nathaniel R; Snyder, Scott A

    2016-03-01

    Although the Diels-Alder reaction has long been utilized for the preparation of numerous heterocycles, opportunities to extend its power remain. Herein, we detail a simple, modular, and robust approach that combines various amines regioselectively with 4,6-dichloropyrone to create substrates which, under appropriate conditions, can directly deliver varied indolines and hydroindolines through [4+2] cycloadditions with substitution patterns difficult to access otherwise. As an initial demonstration of the power of the strategy, several different natural products have been obtained either formally or by direct total synthesis, with efforts toward one of these-the complex amaryllidaceae alkaloid gracilamine-affording the shortest route to date in terms of linear step count. PMID:26865400

  3. Catalytic Effects of Oxide Surfaces on Diels-Alder Cycloaddition between Furan and Methyl Acrylate: A DFT Study

    NASA Astrophysics Data System (ADS)

    Salavati-Fard, Taha; Jenness, Glen; Caratzoulas, Stavros; Doren, Douglas

    Using density functional theory with periodic boundary conditions, we study the catalytic effects of oxide surfaces such as ZrO_2 and HfO_2 on Diels-Alder reaction between furan and methyl acrylate. The cycloadduct can be dehydrated later to produce methyl benzoic which is an important step toward benzoic acid production. The gas-phase and on-surface reaction mechanisms are studied in detail. The surface hydration effects on the reaction mechanism and energy profile are studied as well. Our calculations show that the oxide surfaces catalyze the reaction significantly through the interaction of metal sites with methyl acrylate. The calculations are interpreted by making use of electronic density of states and band structure of the catalyst.

  4. Factors Controlling the Reactivity and Selectivity of the Diels-Alder Reactions Involving 1,2-Azaborines.

    PubMed

    García-Rodeja, Yago; Fernández, Israel

    2016-08-01

    The factors controlling the reactivity and endo/exo selectivity of the Diels-Alder reactions involving 1,2-azaborines have been computationally explored within the density functional theory framework. It is found that the AlCl3-catalyzed [4 + 2]-cycloaddition reaction between these dienes and N-methylmaleimide proceeds concertedly and leads almost exclusively to the corresponding endo cycloadduct, which is in good agreement with previous experimental observations. In addition, the effect of the substituent directly attached to the boron atom of the 1,2-azaborine on the process is also analyzed in detail. To this end, the combination of the activation strain model of reactivity and the energy decomposition analysis methods has been applied to gain a quantitative understanding into the origins of the endo selectivity of the process as well as the influence of the boron and nitrogen substituent on the barrier heights of the transformations. PMID:27383907

  5. Full cell study of Diels Alder poly(phenylene) anion and cation exchange membranes in vanadium redox flow batteries

    DOE PAGESBeta

    Pezeshki, Alan M.; Fujimoto, Cy; Sun, Che -Nan; Mench, Matthew M.; Zawodzinski, Thomas A.; Tang, Z. J.

    2015-11-14

    In this paper, we report on the performance of Diels Alder poly(phenylene) membranes in vanadium redox flow batteries. The membranes were functionalized with quaternary ammonium groups to form an anion exchange membrane (QDAPP) and with sulfonic acid groups to form a cation exchange membrane (SDAPP). Both membrane classes showed similar conductivities in the battery environment, suggesting that the ion conduction mechanism in the material is not strongly affected by the moieties along the polymer backbone. The resistance to vanadium permeation in QDAPP was not improved relative to SDAPP, further suggesting that the polarity of the functional groups do not playmore » a significant role in the membrane materials tested. Both QDAPP and SDAPP outperformed Nafion membranes in cycling tests, with both achieving voltage efficiencies above 85% while maintaining 95% coulombic efficiency while at a current density of 200 mA/cm2.« less

  6. Full cell study of Diels Alder poly(phenylene) anion and cation exchange membranes in vanadium redox flow batteries

    SciTech Connect

    Pezeshki, Alan M.; Fujimoto, Cy; Sun, Che -Nan; Mench, Matthew M.; Zawodzinski, Thomas A.; Tang, Z. J.

    2015-11-14

    In this paper, we report on the performance of Diels Alder poly(phenylene) membranes in vanadium redox flow batteries. The membranes were functionalized with quaternary ammonium groups to form an anion exchange membrane (QDAPP) and with sulfonic acid groups to form a cation exchange membrane (SDAPP). Both membrane classes showed similar conductivities in the battery environment, suggesting that the ion conduction mechanism in the material is not strongly affected by the moieties along the polymer backbone. The resistance to vanadium permeation in QDAPP was not improved relative to SDAPP, further suggesting that the polarity of the functional groups do not play a significant role in the membrane materials tested. Both QDAPP and SDAPP outperformed Nafion membranes in cycling tests, with both achieving voltage efficiencies above 85% while maintaining 95% coulombic efficiency while at a current density of 200 mA/cm2.

  7. Elucidation of Diels-Alder Reaction Network of 2,5-Dimethylfuran and Ethylene on HY Zeolite Catalyst.

    PubMed

    Do, Phuong T M; McAtee, Jesse R; Watson, Donald A; Lobo, Raul F

    2013-01-01

    The reaction of 2,5-dimethylfuran and ethylene to produce p-xylene represents a potentially important route for the conversion of biomass to high-value organic chemicals. Current preparation methods suffer from low selectivity and produce a number of byproducts. Using modern separation and analytical techniques, the structure of many of the byproducts produced in this reaction when HY zeolite is employed as a catalyst has been identified. From these data, a detailed reaction network is proposed demonstrating that hydrolysis and electrophilic alkylation reactions compete with the desired Diels-Alder/dehydration sequence. This information will allow the rational identification of more selective catalysts and more selective reaction conditions. PMID:23316419

  8. Elucidation of Diels-Alder Reaction Network of 2,5-Dimethylfuran and Ethylene on HY Zeolite Catalyst

    PubMed Central

    Do, Phuong T.M.; McAtee, Jesse R.; Watson, Donald A.; Lobo, Raul F.

    2012-01-01

    The reaction of 2,5-dimethylfuran and ethylene to produce p-xylene represents a potentially important route for the conversion of biomass to high-value organic chemicals. Current preparation methods suffer from low selectivity and produce a number of byproducts. Using modern separation and analytical techniques, the structure of many of the byproducts produced in this reaction when HY zeolite is employed as a catalyst has been identified. From these data, a detailed reaction network is proposed demonstrating that hydrolysis and electrophilic alkylation reactions compete with the desired Diels-Alder/dehydration sequence. This information will allow the rational identification of more selective catalysts and more selective reaction conditions. PMID:23316419

  9. Irreversible endo-Selective Diels–Alder Reactions of Substituted Alkoxyfurans: A General Synthesis of endo-Cantharimides

    PubMed Central

    Foster, Robert W; Benhamou, Laure; Porter, Michael J; Bučar, Dejan-Krešimir; Hailes, Helen C; Tame, Christopher J; Sheppard, Tom D

    2015-01-01

    The [4+2] cycloaddition of 3-alkoxyfurans with N-substituted maleimides provides the first general route for preparing endo-cantharimides. Unlike the corresponding reaction with 3H furans, the reaction can tolerate a broad range of 2-substitued furans including alkyl, aromatic, and heteroaromatic groups. The cycloaddition products were converted into a range of cantharimide products with promising lead-like properties for medicinal chemistry programs. Furthermore, the electron-rich furans are shown to react with a variety of alternative dienophiles to generate 7-oxabicyclo[2.2.1]heptane derivatives under mild conditions. DFT calculations have been performed to rationalize the activation effect of the 3-alkoxy group on a furan Diels–Alder reaction. PMID:25756502

  10. Diels-Alder functionalized carbon nanotubes for bone tissue engineering: in vitro/in vivo biocompatibility and biodegradability

    NASA Astrophysics Data System (ADS)

    Mata, D.; Amaral, M.; Fernandes, A. J. S.; Colaço, B.; Gama, A.; Paiva, M. C.; Gomes, P. S.; Silva, R. F.; Fernandes, M. H.

    2015-05-01

    The risk-benefit balance for carbon nanotubes (CNTs) dictates their clinical fate. To take a step forward at this crossroad it is compulsory to modulate the CNT in vivo biocompatibility and biodegradability via e.g. chemical functionalization. CNT membranes were functionalised combining a Diels-Alder cycloaddition reaction to generate cyclohexene (-C6H10) followed by a mild oxidisation to yield carboxylic acid groups (-COOH). In vitro proliferation and osteogenic differentiation of human osteoblastic cells were maximized on functionalized CNT membranes (p,f-CNTs). The in vivo subcutaneously implanted materials showed a higher biological reactivity, thus inducing a slighter intense inflammatory response compared to non-functionalized CNT membranes (p-CNTs), but still showing a reduced cytotoxicity profile. Moreover, the in vivo biodegradation of CNTs was superior for p,f-CNT membranes, likely mediated by the oxidation-induced myeloperoxidase (MPO) in neutrophil and macrophage inflammatory milieus. This proves the biodegradability faculty of functionalized CNTs, which potentially avoids long-term tissue accumulation and triggering of acute toxicity. On the whole, the proposed Diels-Alder functionalization accounts for the improved CNT biological response in terms of the biocompatibility and biodegradability profiles. Therefore, CNTs can be considered for use in bone tissue engineering without notable toxicological threats.The risk-benefit balance for carbon nanotubes (CNTs) dictates their clinical fate. To take a step forward at this crossroad it is compulsory to modulate the CNT in vivo biocompatibility and biodegradability via e.g. chemical functionalization. CNT membranes were functionalised combining a Diels-Alder cycloaddition reaction to generate cyclohexene (-C6H10) followed by a mild oxidisation to yield carboxylic acid groups (-COOH). In vitro proliferation and osteogenic differentiation of human osteoblastic cells were maximized on functionalized CNT

  11. Enantio- and Diastereoselective Formal Hetero-Diels-Alder Reactions of Trifluoromethylated Enones Catalyzed by Chiral Primary Amines.

    PubMed

    Lin, Yong-Jun; Du, Li-Na; Kang, Tai-Ran; Liu, Quan-Zhong; Chen, Ze-Qin; He, Long

    2015-08-10

    Enantioselective formal hetero-Diels-Alder reactions of trifluoromethylated enones and 2-amino-1,3-butadienes generated in situ from aliphatic acyclic enones and chiral primary amines are reported. The corresponding tetrahydropyran-4-ones are formed in up to 94 % yield and with up to 94 % ee. The reaction was carried out through a stepwise mechanism, including initial aminocatalytic aldol condensation of 2-amino-1,3-butadiene to the trifluoromethylated carbonyl group followed by an intramolecular oxa-Michael addition. Both NMR investigation and theoretical calculations on the transition state indicate that the protonated tertiary amine could effectively activate the carbonyl group of the trifluoromethyl ketone to promote the addition process through hydrogen-bonding interaction of N-H⋅⋅⋅F and N-H⋅⋅⋅O simultaneously, and thus provide a chiral environment for the approach of amino-1,3-butadienes to the activated trifluoromethyl ketone, resulting in high enantioselectivity. PMID:26179273

  12. Enhancement of the Click Chemistry for the Inverse Diels Alder Technology by Functionalization of Amide-Based Monomers

    PubMed Central

    Pipkorn, Ruediger; Wiessler, Manfred; Waldeck, Waldemar; Lorenz, Peter; Muehlhausen, Ute; Fleischhacker, Heinz; Koch, Mario; Braun, Klaus

    2011-01-01

    In the near future personalized medicine with nucleic acids will play a key role in molecular diagnostics and therapy, which require new properties of the nucleic acids, like stability against enzymatic degradation. Here we demonstrate that the replacement of nucleobases with PNA by functional molecules harbouring either a dienophile or a diene reactivity is feasible and confers all new options for functionalization. These newly developed derivatives allow independent multi-ligations of multi-faceted components by use of the inverse Diels Alder technology. The high chemical stability and the ease of synthesis qualify these polyamide building blocks as favourites for intracellular delivery and targeting applications. This allows local drug concentrations sufficient for imaging and therapy and simultaneously a reduction of the application doses. It is important to point out that this technology is not restricted to ligation of medicament material; it is also a candidate to develop new and highly efficient active compounds for a “sustainable pharmacy”. PMID:21750642

  13. Diels-Alder Trapping of Photochemically Generated o-Quinodimethane Intermediates: An Alternative Route to Photocured Polymer Film Development

    NASA Technical Reports Server (NTRS)

    Tyson, Daniel S.; Ilhan, Faysal; Meador, Mary Ann B.; Smith, Dee Dee; Scheiman, Daniel A.; Meador, Michael A.

    2004-01-01

    Photolysis of o-methylphenyl ketones generates bis-o-quinodimethane intermediates that can be trapped in situ by dienophiles through Diels-Alder cycloadditions. This well-known photochemical process is applied to a series of six new photoreactive monomers containing bis-(o-methylphenyl ketone) functionalities combined with diacrylate and triacrylate ester monomers for the development of acrylic ester copolymer blends. Irradiation of cyclohexanone solutions of the bis-(o-methylphenyl ketone)s and acrylate esters produce thin polymer films. Solid state 13C NMR data indicated 47- 100% reaction of the bis-(o-methylphenyl ketone)s, depending on experimental conditions, to yield the desired products. DSC and TGA analyses were performed to determine the glass transition temperature, T,, and onset of decomposition, Td, of the resulting polymer films. A statistical Design of Experiments approach was used to obtain a systematic understanding of the effects of experimental variables on the extent of polymerization and the final polymer properties.

  14. Regioselective Synthesis of C-3-Functionalized Quinolines via Hetero-Diels-Alder Cycloaddition of Azadienes with Terminal Alkynes.

    PubMed

    Saunthwal, Rakesh K; Patel, Monika; Verma, Akhilesh K

    2016-08-01

    A highly efficient metal and protection-free approach for the regioselective synthesis of C-3-functionalized quinolines from azadienes (in situ generated from 2-aminobenzyl alcohol) and terminal alkynes through [4 + 2] cycloaddition has been developed. An unprecedented reaction of 2-aminobenzyl alcohol with 1,3- and 1,4-diethynylbenzene provided the C-3 tolylquinolines via [4 + 2] HDA and oxidative decarboxylation. The -NH2 group directed mechanistic approach was well supported by the control experiments and deuterium-labeling studies and by isolating the azadiene intermediate. The reactivity and selectivity of unprotected azadiene in metal-free base-assisted hetero-Diels-Alder reaction is exploited to quickly assemble an important class of C-3-functionalized quinolines, which are difficult to access. PMID:27380814

  15. Diels-Alder reactions for the rational design of benzo[b]thiophenes: DFT-based guidelines for synthetic chemists

    NASA Astrophysics Data System (ADS)

    Brasca, Romina; Kneeteman, María N.; Mancini, Pedro M. E.; Fabian, Walter M. F.

    2012-02-01

    In this work we studied the capability of several diene/dienophile pairs to undergo Diels-Alder (DA) reactions leading to benzo[b]thiophenes. A variety of synthetically and commercially available nitrothiophenes were chosen as dienophiles. Methyl 5-nitro-3-thiophenecarboxylate was selected as a potential strong electrophilic candidate based on some DFT-based properties and the substitution pattern of the expected product. The mechanistic details concerning the participation of this dienophile in polar DA reactions were investigated through a theoretical point of view. The results were compared with the experimental outcomes. This methodology should allow synthetic chemists to analyze DA reactions in detail in a stage prior to the synthetic job.

  16. Effects of surface inactivation, high temperature drying and preservative treatment on surface roughness and colour of alder and beech wood

    NASA Astrophysics Data System (ADS)

    Aydin, Ismail; Colakoglu, Gursel

    2005-10-01

    Although extensive research has been conducted in wood surface quality analysis, a unified approach to surface quality characterisation does not exist. Measurements of the variation in surface roughness and surface colour are used widely for the evaluation of wood surface quality. Colour is a basic visual feature for wood and wood-based products. Colour measurement is one of the quality control tests that should be carried out because the colour deviations are spotted easily by the consumers. On the other hand, a common problem faced by plywood manufacturers is panel delamination, for which a major cause is poor quality glue-bonds resulting from rough veneer. Rotary cut veneers with dimensions of 500 mm × 500 mm × 2 mm manufactured from alder ( Alnus glutinosa subsp. barbata) and beech ( Fagus orientalis Lipsky) logs were used as materials in this study. Veneer sheets were oven-dried in a veneer dryer at 110 °C (normal drying temperature) and 180 °C (high drying temperature) after peeling process. The surfaces of some veneers were then exposed at indoor laboratory conditions to obtain inactive wood surfaces for glue bonds, and some veneers were treated with borax, boric acid and ammonium acetate solutions. After these treatments, surface roughness and colour measurements were made on veneer surfaces. High temperature drying process caused a darkening on the surfaces of alder and beech veneers. Total colour change value (Δ E*) increased linear with increasing exposure time. Among the treatment solutions, ammonium acetate caused the biggest colour change while treatment with borax caused the lowest changes in Δ E* values. Considerable changes in surface roughness after preservative treatment did not occur on veneer surfaces. Generally, no clear changes were obtained or the values mean roughness profile ( Ra) decreased slightly in Ra values after the natural inactivation process.

  17. Tyrosine-Lipid Peroxide Adducts from Radical Termination: Para-Coupling and Intramolecular Diels-Alder Cyclization

    PubMed Central

    Shchepin, Roman; Möller, Matias N.; Kim, Hye-young H.; Hatch, Duane M.; Bartesaghi, Silvina; Kalyanaraman, Balaraman; Radi, Rafael

    2013-01-01

    Free radical co-oxidation of polyunsaturated lipids with tyrosine or phenolic analogs of tyrosine gave rise to lipid peroxide-tyrosine (phenol) adducts in both aqueous micellar and organic solutions. The novel adducts were isolated and characterized by 1D and 2D NMR as well as by mass spectrometry. The spectral data suggest that the polyunsaturated lipid peroxyl radicals give stable peroxide coupling products exclusively at the para position of the tyrosyl (phenoxy) radicals. These adducts have characteristic 13C chemical shifts at 185 ppm due to the cross-conjugated carbonyl of the phenol-derived cyclohexadienone. The primary peroxide adducts subsequently undergo intramolecular Diels-Alder (IMDA) cyclization, affording a number of diastereomeric tricyclic adducts that have characteristic carbonyl 13C chemical shifts at ~198 ppm. All NMR HMBC and HSQC correlations support the structure assignment of the primary and Diels-Alder adducts, as does MS collision induced dissociation. Kinetic rate constants and activation parameters for the IMDA reaction were determined and the primary adducts were reduced with cuprous ion giving a phenol-derived 4-hydroxycyclohexa-2,5-dienone. No products from adduction of peroxyls at the phenolic ortho position were found either in the primary or the cuprous reduction product mixtures. These studies provide a framework for understanding the nature of lipid-protein adducts formed by peroxyl-tyrosyl radical-radical termination processes. Coupling of lipid peroxyl radicals with tyrosyl radicals leads to cyclohexenone and cyclohexadienone adducts which are of interest in and of themselves since, as electrophiles, they are likely targets for protein nucleophiles. One consequence of lipid peroxyl reactions with tyrosyls may therefore be protein-protein crosslinks via interprotein Michael adducts. PMID:21090613

  18. Chemo-protective and regenerative effects of diarylheptanoids from the bark of black alder (Alnus glutinosa) in human normal keratinocytes.

    PubMed

    Dinić, Jelena; Ranđelović, Teodora; Stanković, Tijana; Dragoj, Miodrag; Isaković, Aleksandra; Novaković, Miroslav; Pešić, Milica

    2015-09-01

    Medicinal plants are recognized from ancient times as a source of diverse therapeutic agents and many of them are used as dietary supplements. Comprehensive approaches are needed that would identify bioactive components with evident activity against specific indications and provide a better link between science (ethno-botany, chemistry, biology and pharmacology) and market. Recently, the bark of black alder (Alnus glutinosa) appeared at market in the form of food supplement for treatment of different skin conditions. This study aimed to evaluate protective effects of two diarylheptanoids isolated from the bark of black alder: platyphylloside, 5(S)-1,7-di(4-hydroxyphenyl)-3-heptanone-5-O-β-D-glucopyranoside (1) and its newly discovered analog 5(S)-1,7-di(4-hydroxyphenyl)-5-O-β-D-[6-(E-p-coumaroylglucopyranosyl)]heptane-3-one (2) towards doxorubicin damaging activity. To that end, we employed HaCaT cells, non-cancerous human keratinocytes commonly used for skin regenerative studies. Diarylheptanoids significantly antagonized the effects of doxorubicin by lowering the sensitivity of HaCaT cells to this drug. Compound 2 prevented doxorubicin-induced cell death by activating autophagy. Both 1 and 2 protected HaCaT cells against doxorubicin-induced DNA damage. They significantly promoted migration and affected F-actin distribution. These results indicate that chemo-protective effects of diarylheptanoids may occur at multiple subcellular levels. Therefore, diarylheptanoids 1 and 2 could be considered as protective agents for non-cancerous dividing cells during chemotherapy. PMID:26162555

  19. 40Ar/39Ar ages from the rhyolite of Alder Creek, California: age of the Cobb Mountain normal-polarity subchron revisited

    USGS Publications Warehouse

    Turrin, B.D.; Donnelly-Nolan, J. M.; Hearn, B.C., Jr.

    1994-01-01

    New 40Ar/39Ar age determinations on sanidine from the rhyolite of Alder Creek, California, indicate a 1.186 ?? 0.006 Ma age for the Cobb Mountain Normal-Polarity Subchron. The hew age is statistically older (?? = 0.05) than the previously reported K-Ar age (1.12 ?? 0.02 Ma) and agrees with the age suggested by the astronomical polarity time scale. Incomplete extraction of radiogenic 40Ar (40Ar*) from the sanidine is the most likely reason for the disparity between the 40Ar/39Ar and K-Ar ages. Because the Cobb Mountain subchron is a worldwide, short-duration event, and because no widely used interlaboratory 40Ar/39Ar standard younger than 27 Ma exists, it is proposed that sanidine from the rhyolite of Alder Creek be considered for use as a new Quaternary 40Ar/39Ar mineral standard. -Authors

  20. On the Diels-Alder approach to solely biomass-derived polyethylene terephthalate (PET): conversion of 2,5-dimethylfuran and acrolein into p-xylene.

    PubMed

    Shiramizu, Mika; Toste, F Dean

    2011-10-24

    Polyethylene terephthalate (PET) is a polymeric material with high global demand. Conventionally, PET is produced from fossil-fuel-based materials. Herein, we explored the feasibility of a sustainable method for PET production by using solely bio-renewable resources. Specifically, 2,5-dimethylfuran (derived from lignocellulosic biomass through 5-(hydroxymethyl)furfural) and acrolein (produced from glycerol, a side product of biodiesel production) were converted into the key intermediate p-xylene (a precursor of terephthalic acid). This synthesis consists of a sequential Diels-Alder reaction, oxidation, dehydration, and decarboxylation. In particular, the pivotal first step, the Diels-Alder reaction, was studied in detail to provide useful kinetic and thermodynamic data. Although it was found that this reaction requires low temperature to proceed efficiently, which presents a limitation on economic feasibility on an industrial scale, the concept was realized and bio-derived p-xylene was obtained in 34% overall yield over four steps. PMID:21922576

  1. Cyclopropanation of nitroso Diels–Alder cycloadducts and application to the synthesis of a 2’,3’-methano carbocyclic nucleoside

    PubMed Central

    Ji, Cheng; Miller, Marvin J.

    2010-01-01

    Treatment of nitroso Diels–Alder cycloadducts 1 with diazomethane in the presence of palladium acetate gives synthetically useful exo-6-oxa-7-azatricyclo[3.2.1.02,4]octane derivatives 7 in good to excellent yield. Using this methodology, a conformationally restricted 2’,3’-methano carbocyclic nucleoside was efficiently synthesized from nitroso cycloadduct 1a in 7 steps. PMID:20607121

  2. Adaptation of a Small-Molecule Hydrogen-Bond Donor Catalyst to an Enantioselective Hetero-Diels–Alder Reaction Hypothesized for Brevianamide Biosynthesis

    PubMed Central

    2015-01-01

    Chiral diamine-derived hydrogen-bond donors were evaluated for their ability to effect stereocontrol in an intramolecular hetero-Diels–Alder (HDA) reaction hypothesized in the biosynthesis of brevianamides A and B. Collectively, these results provide proof of principle that small-molecule hydrogen-bond catalysis, if even based on a hypothetical biosynthesis construct, holds significant potential within enantioselective natural product synthesis. PMID:25697748

  3. New and Concise Syntheses of the Bicyclic Oxamazin Core Using an Intramolecular Nitroso Diels-Alder Reaction and Ring-Closing Olefin Metathesis

    PubMed Central

    Watson, Kyle D.; Carosso, Serena

    2013-01-01

    Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels-Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems. PMID:23276301

  4. Comparative phylogenies and host specialization in the alder ectomycorrhizal fungi Alnicola, Alpova and Lactarius (Basidiomycota) in Europe

    PubMed Central

    2011-01-01

    Background Mycorrhizal fungi form intimate associations with their host plants that constitute their carbon resource and habitat. Alnus spp. (Betulaceae) are known to host an exceptional species-poor and specialized ectomycorrhizal (ECM) fungal community compared to other tree species, but the host-specificity pattern and its significance in terms of fungal diversification and speciation remain poorly documented. The degree of parallel speciation, host switching, and patterns of biogeography were explored in the historical associations between alders and three ECM taxa of Basidiomycetes: Alnicola (Agaricales), Alpova (Boletales), and Lactarius (Russulales). The aim was to develop an evolutionary framework on host specificity and diversification of Basidiomycetes in this highly specialized plant-fungus symbiosis. Results Sporocarps of Alnicola (220), Lactarius (61) and Alpova (29) were collected from stands of the four European alder species (A. alnobetula including the endemic subsp. suaveolens in Corsica, A. cordata, A. glutinosa, A. incana) in Western Europe (mainly in France and Austria), from 1995 to 2009. Specimens were morphologically identified to the species level. From these, 402 sequences of four DNA regions (ITS, rpb2, gpd, and the V9 domain of the mit-SSU rDNA) were successfully obtained and analyzed in addition with 89 sequences available in GenBank and UNITE databases. Phylogenetic analyses were conducted on all sequence data sets (individual and combined) using maximum likelihood reconstruction and Bayesian inference. Fungal phylogenies are compared and discussed in relation to the host, with a focus on species boundaries by associating taxonomic, systematic and molecular information. Conclusions Patterns of host specificity and phylogenies of Alnicola and Lactarius suggest coevolution as a basal factor of speciation in relation with the subgeneric diversification of Alnus, possibly due to the very selective pressure of the host. A second element of

  5. Stem Photosynthesis not Pressurized Ventilation is Responsible for Light-enhanced Oxygen Supply to Submerged Roots of Alder (Alnus glutinosa)

    PubMed Central

    ARMSTRONG, WILLIAM; ARMSTRONG, JEAN

    2005-01-01

    • Background and Aims Claims that submerged roots of alder and other wetland trees are aerated by pressurized gas flow generated in the stem by a light-induced thermo-osmosis have seemed inconsistent with root anatomy. Our aim was to seek a verification using physical root–stem models, stem segments with or without artificial roots, and rooted saplings. • Methods Radial O2 loss (ROL) from roots was monitored polarographically as the gas space system of the models, and stems were pressurized artificially. ROL and internal pressurization were also measured when stems were irradiated and the xylem stream was either CO2 enriched or not. Stem photosynthesis and respiration were measured polarographically. Stem and root anatomy were examined by light and fluorescence microscopy. • Key Results Pressurizing the models and stems to ≤10 kPa, values much higher than those reportedly generated by thermo-osmosis, created only a negligible density-induced increase in ROL, but ROL increased rapidly when ambient O2 concentrations were raised. Internal pressures rose by several kPa when shoots were exposed to high light flux and ROL increased substantially, but both were due to O2 accumulation from stem photosynthesis using internally sourced CO2. Increased stem pressures had little effect on O2 transport, which remained largely diffusive. Oxygen flux from stems in high light periods indicated a net C gain by stem photosynthesis. Chloroplasts were abundant in the secondary cortex and secondary phloem, and occurred throughout the secondary xylem rays and medulla of 3-year-old stems. Diurnal patterns of ROL, most marked when light reached submerged portions of the stem, were modified by minor variations in light flux and water level. Low root temperatures also helped improve root aeration. • Conclusions Pressurized gas flow to submerged roots does not occur to any significant degree in alder, but stem photosynthesis, using internally sourced CO2 from respiration and the

  6. Revisiting the concept of the (a)synchronicity of diels-alder reactions based on the dynamics of quasiclassical trajectories.

    PubMed

    de Souza, Miguel A F; Ventura, Elizete; do Monte, Silmar A; Riveros, José M; Longo, Ricardo L

    2016-03-30

    A number of model Diels-Alder (D-A) cycloaddition reactions (H2 CCH2  + cyclopentadiene and H2 CCHX + 1,3-butadiene, with X = H, F, CH3 , OH, CN, NH2 , and NO) were studied by static (transition state - TS and IRC) and dynamics (quasiclassical trajectories) approaches to establish the (a)synchronous character of the concerted mechanism. The use of static criteria, such as the asymmetry of the TS geometry, for classifying and quantifying the (a)synchronicity of the concerted D-A reaction mechanism is shown to be severely limited and to provide contradictory results and conclusions when compared to the dynamics approach. The time elapsed between the events is shown to be a more reliable and unbiased criterion and all the studied D-A reactions, except for the case of H2 CCHNO, are classified as synchronous, despite the gradual and quite distinct degrees of (a)symmetry of the TS structures. © 2015 Wiley Periodicals, Inc. PMID:26575321

  7. Role of encapsulated metal cation in the reactivity and regioselectivity of the C₆₀ Diels-Alder reaction.

    PubMed

    Cui, Cheng-Xing; Liu, Ya-Jun

    2015-03-26

    Endohedral metallofullerene has novel properties because of the interaction between the encapsulated metal atom or cation and fullerene. Experiments have demonstrated that the insertion of Li(+) into C60 can greatly promote the reactivity of the Diels-Alder (DA) cycloaddition of cyclopentadiene (CpH) to C60. However, the reaction is sufficiently fast that its quantitative kinetic data cannot be obtained experimentally. In addition, knowledge regarding the effects of other alkali metal cations and metal cations with more charges on the reactivity and regioselectivity of C60 is almost nonexistent. In the current study, DA cycloadditions of CpH to M(+)@C60 (where M = Li, Na, K, Rb, and Cs) and Ca(2+)@C60 were investigated via density functional theory in the gas phase and in solvent. Via careful discussion and comparison with the results of C60, we concluded the following for the DA reaction of CpH to C60 and, more generally, for DA reactions of other fullerenes: (1) the encapsulated metal cations enhance the reactivity; (2) among alkali metal cations, Na(+) could be the best catalyst; (3) Ca(2+) is more favorable in promoting the reactivity than any alkali metal cation; (4) encapsulated metal cations with more positive charges enhance the reactivity of the 6-5 bond in C60, which is significant when the 6-5 adduct is the target product. PMID:25714730

  8. N-(furfural) chitosan hydrogels based on Diels-Alder cycloadditions and application as microspheres for controlled drug release.

    PubMed

    Montiel-Herrera, Marcelino; Gandini, Alessandro; Goycoolea, Francisco M; Jacobsen, Neil E; Lizardi-Mendoza, Jaime; Recillas-Mota, Maricarmen; Argüelles-Monal, Waldo M

    2015-09-01

    In this study, chitosan was chemically modified by reductive amination in a two-step process. The synthesis of N-(furfural) chitosan (FC) was confirmed by FT-IR and (1)H NMR analysis, and the degrees of substitution were estimated as 8.3 and 23.8%. The cross-linkable system of bismaleimide (BM) and FC shows that FC shared properties of furan-maleimide chemistry. This system produced non-reversible hydrogel networks by Diels-Alder cycloadditions at 85 °C. The system composed of BM and FC (23.8% substitution) generated stronger hydrogel networks than those of FC with an 8.3% degree of substitution. Moreover, the FC-BM system was able to produce hydrogel microspheres. Environmental scanning electron microscopy revealed the surface of the microspheres to be non-porous with small protuberances. In water, the microspheres swelled, increasing their volume by 30%. Finally, microspheres loaded with methylene blue were able to release the dye gradually, obeying second-order kinetics for times less than 600 min. This behavior suggests that diffusion is governed by the relaxation of polymer chains in the swelled state, thus facilitating drug release outside the microspheres. PMID:26005158

  9. Self-healable interfaces based on thermo-reversible Diels-Alder reactions in carbon fiber reinforced composites.

    PubMed

    Zhang, W; Duchet, J; Gérard, J F

    2014-09-15

    Thermo-reversible Diels-Alder (DA) bonds formed between maleimide and furan groups have been used to generate an interphase between carbon fiber surface and an epoxy matrix leading to the ability of interfacial self-healing in carbon:epoxy composite materials. The maleimide groups were grafted on an untreated T700 carbon fiber from a three step surface treatment: (i) nitric acid oxidization, (ii) tetraethylenepentamine amination, and (iii) bismaleimide grafting. The furan groups were introduced in the reactive epoxy system from furfuryl glycidyl ether. The interface between untreated carbon fiber and epoxy matrix was considered as a reference. The interfacial shear strength (IFSS) was evaluated by single fiber micro-debonding test. The debonding force was shown to have a linear dependence with embedded length. The highest healing efficiency calculated from the debonding force was found to be about 82% more compared to the value for the reference interface. All the interphases designed with reversible DA bonds have a repeatable self-healing ability. As after the fourth healing, they can recover a relatively high healing efficiency (58% for the interphase formed by T700-BMI which is oxidized for 60 min during the first treatment step). PMID:24998055

  10. Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

    PubMed Central

    Kocsis, Laura S.; Benedetti, Erica; Brummond, Kay M.

    2013-01-01

    Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields. PMID:23609566

  11. Avian use of forest habitats in the Pembina Hills of northeastern North Dakota

    USGS Publications Warehouse

    Faanes, C.A.; Andrew, J.M.

    1983-01-01

    North Dakota has the least extensive total area of forested habitats of any of the 50 United States. Although occurring in limited area, forest communities add considerably to the total ecological diversity of the State. The forests of the Pembina Hills region in northeastern North Dakota are one of only three areas large enough to be considered of commercial value. During 1981 we studied the avifauna of the upper valley of the Pembina River in the Pembina Hills. Field work extended from 20 April to 23 July; breeding bird censuses were conducted 7 June to 2 July. Of the 120 bird species recorded during the study period, 79 species were recorded during the breeding season. The total breeding population was estimated at nearly 76,000 breeding pairs. The wood warblers (Parulidae) were the most numerous family, accounting for about 28,000 breeding pairs. The yellow warbler (Dendroica petechia) was the most abundant breeding species, making up 19.4% of the population. American redstart (Setophaga ruticilla) was second in abundance, accounting for 10.5% of the breeding population. Largest breeding densities occurred in the willow (Salix sp.) shrub community. Although supporting the lowest mean breeding density, quaking aspen (Populus tremuloides) forests supported the highest species diversity. First State breeding records were recorded for alder flycatcher (Empidonax alnorum) and golden-winged warbler (Vermivora chrysoptera). Records were obtained for 12 species considered rare or unusual in North Dakota during the breeding season. The status of all species known to have occurred in the study area is described in an annotated species list.

  12. Antioxidative activity of diarylheptanoids from the bark of black alder (Alnus glutinosa) and their interaction with anticancer drugs.

    PubMed

    Dinić, Jelena; Novaković, Miroslav; Podolski-Renić, Ana; Stojković, Sonja; Mandić, Boris; Tešević, Vele; Vajs, Vlatka; Isaković, Aleksandra; Pešić, Milica

    2014-08-01

    Diarylheptanoids belong to polyphenols, a group of plant secondary metabolites with multiple biological properties. Many of them display antioxidative, cytotoxic, or anticancer actions and are increasingly recognized as potential therapeutic agents. The aim of this study was to evaluate antioxidant and cytoprotective activity of two diarylheptanoids: platyphylloside 5(S)-1,7-di(4-hydroxyphenyl)-3-heptanone-5-O-β-D-glucopyranoside (1) and its newly discovered analog 5(S)-1,7-di(4-hydroxyphenyl)-5-O-β-D-[6-(E-p-coumaroylglucopyranosyl)]heptane-3-one (2), both isolated from the bark of black alder (Alnus glutinosa). To that end, we have employed a cancer cell line (NCI-H460), normal human keratinocytes (HaCaT), and peripheral blood mononuclear cells. The effects on cell growth were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. Cell death was examined by annexin V/propidium iodide staining on a flow cytometer. Reactive oxygen species production was examined by dihydroethidium staining. Mitochondrial structure and doxorubicin localization were visualized by fluorescent microscopy. Gene expression of manganese superoxide dismutase and hypoxia-inducible factor-1α was determined by reverse transcription polymerase chain reaction. Diarylheptanoids antagonized the effects of either doxorubicin or cisplatin, significantly increasing their IC50 values in normal cells. Diarylheptanoid 1 induced the retention of doxorubicin in cytoplasm and reduced mitochondrial fragmentation associated with doxorubicin application. Diarylheptanoid 2 reduced the reactive oxygen species production induced by cisplatin. Both compounds increased the messenger ribonucleic acid expression of enzymes involved in reactive oxygen species elimination (manganese superoxide dismutase and hypoxia-inducible factor-1α). These results indicate that neutralization of reactive oxygen species is an important mechanism of diarylheptanoid action, although these

  13. A new insight on the gas phase retro-Diels-Alder reaction of bicyclic compounds: density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Mora, Jose R.; Lezama, Jesús; Córdova-Sintjago, Tania C.; Chuchani, Gabriel

    2015-11-01

    The mechanisms of the gas-phase thermal decomposition of bicyclo[2.2.1]heptadiene and 3,7,7-trimethylbicyclo[2.2.1]hept-2-ene were examined by density functional theory calculations with the hybrid functionals: B3LYP, CAM-B3LYP, MPW1PW91, and PBEPBE. Reasonable agreements were found between theoretical and experimental values with the B3LYP hybrid functional. Three molecular concerted pathways for bicyclo[2.2.1]heptadiene decomposition are proposed. The retro-Diels-Alder (retro-DA) pathway yields cyclopentadiene and acetylene through a nearly synchronous transition state structure (Sy = 0.97). The other two reaction channels are stepwise with a common step with the formation of the intermediate bicyclo[4.1.0] heptadiene. This reaction is dominated by C-C bond breaking leading to the methylene migration by an early transition state in the reaction coordinate (Sy = 0.91). The rearrangements of the latter intermediate producing toluene were also studied. The retro-DA elimination of 3,7,7-trimethylbicyclo[2.2.1]hept-2-ene gives 1,5,5-trimethyl-cyclopenta-1,3-diene in a less synchronous process (Sy = 0.77). This fact may be due to the electronic effects of the methyl substituent. The latter product is unstable and undergoes methyl migrations to give a more stable isomer 1,2,3-trimethylcyclopenta-1,3-diene. The stepwise mechanism for the retro-DA reaction through a biradical intermediate appears to be unfavourable because the barrier is bigger than that for the concerted reaction.

  14. Short Rotation Woody Crops Program. Quarterly progress report, March 1-May 31, 1985. [Sycamore, alders, black locust, larch, poplars, saltbush

    SciTech Connect

    Wright, L.L.; Perlack, R.D.; Wenzel, C.R.; Trimble, J.L.; Ranney, J.W.

    1985-08-01

    This report covers the progress of the Short Rotation Woody Crops Program (SRWCP) during the third quarter of fiscal year 1985. This report summarizes ORNL management activities, technical activities at ORNL and subcontract institutions, and the technology transfer that is occurring as a result of subcontractor and ORNL activities. Third-year results of a nutrient utilization study confirmed that there were no benefits to quarterly fertilization with urea nitrogen. Testing of one prototype short-rotation intensive culture harvester was conducted on a sycamore plantation on Scott Paper Company land in southern Alabama. Coppice yields of European black alder reported by Iowa State University indicate potential productivity of about 7.2 dry Mg . ha/sup -1/ . year/sup -1/ if the best trees are selected. Coppice yields were more than double first-rotation yields. About 31,000 black locust and larch trees were established in 12 genetic tests at 4 sites in Michigan. Seedling rotation productivity rates of 4-year-old hybrid poplar, based on harvest data, were reported by Pennsylvania State University. Rates varied from 4.8 dry Mg . ha/sup -1/ . year/sup -1/ to 10.7 dry Mg . ha/sup -1/ . year/sup -1/, depending on site, management strategy, and planting year. An efficient method for in vitro micropropagation of elite genotypes of fourwing saltbush was developed by Plant Resources Institute. A new study to evaluate yield/density relationships was established by the USDA Forest Service, Pacific Northwest Forest and Range Experiment Station. Dissertation research on the crown geometry of plantation-grown American sycamore was completed.

  15. Multicomponent Double Diels-Alder/Nazarov Tandem Cyclization of Symmetric Cross-Conjugated Diynones to Generate [6-5-6] Tricyclic Products.

    PubMed

    Carmichael, Rachael A; Chalifoux, Wesley A

    2016-06-20

    The construction of complex polycyclic terpenoid products in an efficient and step-economical manner using multicomponent and tandem processes is highly valuable. Herein, we report a tandem cyclization sequence that initiates with a multicomponent double Diels-Alder reaction of cross-conjugated diynones, followed by a Nazarov cyclization to efficiently produce [6-5-6] tricyclic products with excellent regio- and diastereoselectivity. This methodology generates five new carbon-carbon bonds, three rings, quaternary or vicinal quaternary carbons, and stereogenic centers in a one-pot reaction. PMID:27124516

  16. Regio- and stereochemically controlled formation of hydroxamic acids from indium triflate-mediated nucleophilic ring-opening reactions with acylnitroso-Diels–Alder adducts

    PubMed Central

    Yang, Baiyuan; Miller, Marvin J.

    2010-01-01

    Treatment of acylnitroso-Diels–Alder [2.2.1] bicyclic adducts 2a–b with indium triflate in an alcohol solvent induces ring opening reactions to afford monocyclic anti-1,2-, anti-1,4- and syn-1,4-hydroxamic acids with good to excellent regio- and stereoselectivity (up to 7:86:7). Treatment of [2.2.2] bicyclic nitroso adducts 2c–d under similar reaction conditions generates only anti-1,2- and anti-1,4-hydroxamic acids with anti-1,4-product predominant (up to 17:83). PMID:20209116

  17. Enantioselective synthesis of allenylenol silyl ethers via chiral lithium amide mediated reduction of ynenoyl silanes and their Diels-Alder reactions.

    PubMed

    Sasaki, Michiko; Kondo, Yasuhiro; Moto-ishi, Ta-ichi; Kawahata, Masatoshi; Yamaguchi, Kentaro; Takeda, Kei

    2015-03-01

    An enantioselective Meerwein-Ponndorf-Verley-type reduction of ynenoylsilanes by a chiral lithium amide followed by a Brook rearrangement and anti-mode protonation across conjugated 1,3-enynes provides allene derivatives bearing a 2-siloxyvinyl moiety in high enantioselectivity. The E/Z geometry of enol silyl ethers is controlled by the geometry of the starting enyne moiety. Thus, (E)- and (Z)-enol silyl ethers are obtained from (Z)- and (E)-ynenoylsilans, respectively. The 2-siloxyvinylallene products can participate in Diels-Alder reactions with reactive dienophiles such as PTAD, which can be achieved in a one-pot operation from ynenoylsilanes. PMID:25689472

  18. A Base-Catalyzed, Domino Aldol/hetero-Diels-Alder Synthesis of Tricyclic Pyrano[3,4-c]chromenes in Glycerol.

    PubMed

    Parmar, Bhagyashri D; Sutariya, Tushar R; Brahmbhatt, Gaurangkumar C; Parmar, Narsidas J; Kant, Rajni; Gupta, Vivek K

    2016-06-17

    The domino aldol/hetero-Diels-Alder synthesis of some new tricyclic pyrano[3,4-c]chromene derivatives has been achieved successfully after assembling a variety of acyclic or cyclic monoketones with prenyl ether-tethered aldehydes in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene in glycerol at 120 °C. The hitherto unreported stereochemical outcome of this synthetic sequence was studied and established on the basis of single-crystal X-ray diffraction data and 2D NMR NOESY spectroscopy along with the isolation and characterization of the intermediate Aldol condensation product. PMID:27171909

  19. Bisadducts from the Diels-Alder Trapping of Bis(o-Xylenols) Photochemically Generated from 2,5-Dibenzoyl-p-xylene

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.; Kinder, James D.; Kirby, James P.

    2003-01-01

    Photolysis of 2,5-dibenzoyl-p-xylene produces two discrete o-xylenols which undergo Diels-Alder cycloadditions with standard dienophiles, such as methyl acrylate, to produce 1,5-dihydroxy-1,5-diphenyl-l,2,3,4,5,6,7,8-octahydroanthracenes, 2a, in good yield (greater than 80%). The anti bisadduct crystallizes into hydrogen bonded stacks. Conversion of both syn- and anti-bisadducts to the corresponding anthracenes was achieved through the use of standard dehydration and aromatization chemistry.

  20. The Holocene vegetation history of the Khibiny Mountains: implications for the post-glacial expansion of spruce and alder on the Kola Peninsula, northwestern Russia

    NASA Astrophysics Data System (ADS)

    Kremenetski, Constantin; Vaschalova, Tatiana; Sulerzhitsky, Leopold

    1999-02-01

    Pollen and peat botanical investigations of the Lutnermayok peat bog, Kola Peninsula, northwestern Russia, were carried out, and 21 surface pollen samples were studied. Combined with previous studies our data form the basis for the vegetation history over the last 7000 yr of the Khibiny Mountains. Pinus sylvestris was the dominant species between 7000 and 5000 yr BP and Picea obovata penetrated to the Khibiny Mountains ca. 5500/5300 yr BP. Since 4500 yr BP, Picea replaced Pinus in major parts of the area and dominated the forest cover. Picea immigrated to the Kola Peninsula after 7000 yr BP. There were two paths of spruce migration: from the southeast and the southwest. Grey alder, Alnusincana, immigrated to the Kola Peninsula from the southwest and northwest about ca. 8000 yr BP. Grey alder has been restricted to its modern range since 4000 yr BP. The range of vertical movement of the treeline in Khibiny Mountains during the last 700 yr was 240-260 m, which corresponds to an amplitude of summer temperature change of 2°C.

  1. Application of an enyne metathesis/Diels-Alder cycloaddition sequence: a new versatile approach to the syntheses of C-aryl glycosides and spiro-C-aryl glycosides.

    PubMed

    Subrahmanyam, Ayyagari V; Palanichamy, Kalanidhi; Kaliappan, Krishna P

    2010-07-26

    An efficient approach for the synthesis of a variety of C-aryl and spiro-C-aryl glycosides is described. This diversity-oriented strategy employed here relies on a sequential enyne metathesis to generate the 1,3-diene moiety and Diels-Alder reaction with different dienophiles followed by aromatisation. Whereas cross-enyne metathesis with ethylene gas is used to install the 1,3-diene moiety at the anomeric centre for the synthesis of C-aryl glycosides, an intramolecular enyne metathesis on the sugar enyne is performed to generate the 1,3-diene moiety for the synthesis of spiro-C-aryl glycosides. Efforts to extend this strategy to the synthesis of the core structure of natural C-aryl glycoside gilvocarcin are also described. A combination of both C-aryl and spiro-C-aryl glycosides in the same moiety to combine the features thereof has also been accomplished. A tandem enyne metathesis/Diels-Alder reaction/aromatisation has also been attempted to directly access the C-aryl glycosides in one pot albeit in low yield. PMID:20549721

  2. Paxillus rubicundulus (Boletales, Paxillaceae) and two new alder-specific ectomycorrhizal species, Paxillus olivellus and Paxillus adelphus, from Europe and North Africa.

    PubMed

    Jargeat, Patricia; Moreau, Pierre-Arthur; Gryta, Hervé; Chaumeton, Jean-Paul; Gardes, Monique

    2016-05-01

    Paxillus rubicundulus P.D. Orton has been shown to be a complex of at least three ectomycorrhizal taxa strictly associated with alders (Alnus) in Europe, P. rubicundulus s. str., and two undescribed clades. To assess the taxonomic status of these three clades and their phylogenetic relationships, phylogenetic analyses of two independent gene regions (ITS and gpd), combined with macro- and micromorphological comparisons of genetically identified specimens, were carried out. A total of 85 sequences were successfully obtained from basidiomata and alder mycorrhizae collected in France and Algeria and combined with GenBank and UNITE sequences. The phylogenetic results and estimates of genetic diversity confirmed that the three clades are distinct species, often found in sympatry. As a result, P. rubicundulus s. str. was redefined based on the revision of type material, and Paxillus adelphus and Paxillus olivellus are introduced as new Linnaean names. The often used name Paxillus filamentosus is rejected since it could not be applied to any of the new species. The three species are distinguished micromorphologically by spore size and shape. They are widely distributed in Europe, North Africa and western Asia; P. rubicundulus is rare, and all species have a limited host range. PMID:27109368

  3. Total synthesis of (-)-spinosyn A: examination of structural features that govern the stereoselectivity of the key transannular Diels-Alder reaction.

    PubMed

    Winbush, SusAnn M; Mergott, Dustin J; Roush, William R

    2008-03-01

    A study of elements of stereochemical control in transannular Diels-Alder reactions leading to the decahydro-as-indacene core of (-)-spinosyn A is described. Initial studies focused on macrocyclic pentaene 9, which includes C(6)-Br and C(8)-OTBS substituents. Excellent selectivity (>95:5) was observed in the cycloaddition of 9 as a consequence of 1,3-allylic strain interactions involving the C(6) and C(8) substituents in the disfavored TS-2. The major cycloadduct 22 was used in a formal synthesis of (-)-spinosyn A. The TDA cyclizations of 12 (which lacks the C(8)-OTBS unit of 9), 13 (which lacks the C(6)-Br substituent of 12), and 14 (which lacks the C(6)-Br and C(21)-Et substituents of 12) were also studied. Macrocycles 12 and 13 served as precursors to (-)-spinosyn A and the (-)-spinosyn A aglycon (34), respectively. It is striking that substrates 12-14 give very similar distributions of transannular Diels-Alder cycloadducts, indicating that the C(6)-Br and C(21)-stereocenter do not play a significant role in the diastereoselectivity of the TDA cycloaddition of spinosyn A precursor 12. It is likely that some as yet unidentified conformational or structural features of macrocycles 12-14 contribute to the levels of diastereoselectivity achieved, since these TDA reactions are more selective for the C(7)-C(9) stereochemical relationship found in the natural product than are the IMDA reactions of trienes 4 and 7. PMID:18215065

  4. Isotopologue ratios of N2O and N2 measurements underpin the importance of denitrification in differently N-loaded riparian alder forests.

    PubMed

    Mander, Ulo; Well, Reinhard; Weymann, Daniel; Soosaar, Kaido; Maddison, Martin; Kanal, Arno; Lõhmus, Krista; Truu, Jaak; Augustin, Jürgen; Tournebize, Julien

    2014-10-21

    Known as biogeochemical hotspots in landscapes, riparian buffer zones exhibit considerable potential concerning mitigation of groundwater contaminants such as nitrate, but may in return enhance the risk for indirect N2O emission. Here we aim to assess and to compare two riparian gray alder forests in terms of gaseous N2O and N2 fluxes and dissolved N2O, N2, and NO3(-) in the near-surface groundwater. We further determine for the first time isotopologue ratios of N2O dissolved in the riparian groundwater in order to support our assumption that it mainly originated from denitrification. The study sites, both situated in Estonia, northeastern Europe, receive contrasting N loads from adjacent uphill arable land. Whereas N2O emissions were rather small at both sites, average gaseous N2-to-N2O ratios inferred from closed-chamber measurements and He-O laboratory incubations were almost four times smaller for the heavily loaded site. In contrast, groundwater parameters were less variable among sites and between landscape positions. Campaign-based average (15)N site preferences of N2O (SP) in riparian groundwater ranged between 11 and 44 ‰. Besides the strong prevalence of N2 emission over N2O fluxes and the correlation pattern between isotopologue and water quality data, this comparatively large range highlights the importance of denitrification and N2O reduction in both riparian gray alder stands. PMID:25264900

  5. DFT Study of Solvent Effects in Acid-Catalyzed Diels-Alder Cycloadditions of 2,5-Dimethylfuran and Maleic Anhydride.

    PubMed

    Salavati-fard, Taha; Caratzoulas, Stavros; Doren, Douglas J

    2015-09-24

    Density functional theory electronic structure calculations were used to explore the mechanism for the Diels-Alder reaction between 2,5-dimethylfuran and maleic anhydride (MA). Reaction paths are reported for uncatalyzed and Lewis and Brønsted acid-catalyzed reactions in vacuum and in a broad range of solvents. The calculations show that, while the uncatalyzed Diels-Alder reaction is thermally feasible in vacuum, a Lewis acid (modeled as Na(+)) lowers the activation barrier by interacting with the dienophile (MA) and decreasing the HOMO-LUMO gap of the reactants. A Brønsted acid (modeled as a proton) can bind to a carbonyl oxygen in MA, changing the reaction mechanism from concerted to stepwise and eliminating the activation barrier. Solvation effects were studied with the SMD model. Electrostatic effects play the largest role in determining the solvation energy of the transition state, which tracks the net dipole moment at the transition state. For the uncatalyzed reaction, the dipole moment is largely determined by charge transfer between the reactants, but in the reactions with ionic catalysts, there is no simple relationship between solvation of the transition state and charge transfer between the reactants. Nonelectrostatic contributions to solvation of the reactants and transition state also make significant contributions to the activation energy. PMID:26331220

  6. Cross-Linked Hydrogels Formed through Diels-Alder Coupling of Furan- and Maleimide-Modified Poly(methyl vinyl ether-alt-maleic acid).

    PubMed

    Stewart, S Alison; Backholm, Matilda; Burke, Nicholas A D; Stöver, Harald D H

    2016-02-23

    The Diels-Alder [4 + 2] cycloaddition between furan- and maleimide-functional polyanions was used to form cross-linked synthetic polymer hydrogels. Poly(methyl vinyl ether-alt-maleic anhydride) was reacted with furfurylamine or N-(2-aminoethyl)maleimide in acetonitrile to form pairs of furan- and maleimide-functionalized poly(methyl vinyl ether-alt-maleic acid)s. Mixtures of these mutually reactive polyanions in water gelled within 15 min to 18 h, depending on degree of functionalization and polymer concentrations. Solution and magic-angle spinning (1)H NMR were used to confirm the formation of the Diels-Alder adduct, to analyze competing hydrolytic side reactions, and demonstrate postgelation functionalization. The effect of the degree of furan and maleimide functionalization, polymer concentration, pH, and calcium ion concentration, on gelation time, gel mechanical properties, and equilibrium swelling, are described. Release of dextran as a model drug was studied using fluorescence spectroscopy, as a function of gel composition and calcium treatment. PMID:26800849

  7. Reactivity of Single-Walled Carbon Nanotubes in the Diels-Alder Cycloaddition Reaction: Distortion-Interaction Analysis along the Reaction Pathway.

    PubMed

    Li, Yingzi; Osuna, Sílvia; Garcia-Borràs, Marc; Qi, Xiaotian; Liu, Song; Houk, Kendall N; Lan, Yu

    2016-08-26

    Diels-Alder cycloaddition is one of the most powerful tools for the functionalization of single-walled carbon nanotubes (SWCNTs). Density functional theory at the B3-LYP level of theory has been used to investigate the reactivity of different-diameter SWCNTs (4-9,5) in Diels-Alder reactions with 1,3-butadiene; the reactivity was found to decrease with increasing SWCNT diameter. Distortion/interaction analysis along the whole reaction pathway was found to be a better way to explore the reactivity of this type of reaction. The difference in interaction energy along the reaction pathway is larger than that of the corresponding distortion energy. However, the distortion energy plots for these reactions show the same trend. Therefore, the formation of the transition state can be determined from the interaction energy. A lower interaction energy leads to an earlier transition state, which indicates a lower activation energy. The computational results also indicate that the original distortion of the SWCNTs leads to an increase in the reactivity of the SWCNTs. PMID:27465519

  8. Intramolecular didehydro-Diels-Alder reaction and its impact on the structure-function properties of environmentally sensitive fluorophores.

    PubMed

    Brummond, Kay M; Kocsis, Laura S

    2015-08-18

    Reaction discovery plays a vital role in accessing new chemical entities and materials possessing important function.1 In this Account, we delineate our reaction discovery program regarding the [4 + 2] cycloaddition reaction of styrene-ynes. In particular, we highlight our studies that lead to the realization of the diverging reaction mechanisms of the intramolecular didehydro-Diels-Alder (IMDDA) reaction to afford dihydronaphthalene and naphthalene products. Formation of the former involves an intermolecular hydrogen atom abstraction and isomerization, whereas the latter is formed via an unexpected elimination of H2. Forming aromatic compounds by a unimolecular elimination of H2 offers an environmentally benign alternative to typical oxidation protocols. We also include in this Account ongoing work focused on expanding the scope of this reaction, mainly its application to the preparation of cyclopenta[b]naphthalenes. Finally, we showcase the synthetic utility of the IMDDA reaction by preparing novel environmentally sensitive fluorophores. The choice to follow this path was largely influenced by the impact this reaction could have on our understanding of the structure-function relationships of these molecular sensors by taking advantage of a de novo construction and functionalization of the aromatic portion of these compounds. We were also inspired by the fact that, despite the advances that have been made in the construction of small molecule fluorophores, access to rationally designed fluorescent probes or sensors possessing varied and tuned photophysical, spectral, and chemical properties are still needed. To this end, we report our studies to correlate fluorophore structure with photophysical property relationships for a series of solvatochromic PRODAN analogs and viscosity-sensitive cyanoacrylate analogs. The versatility of this de novo strategy for fluorophore synthesis was demonstrated by showing that a number of functional groups could be installed at

  9. endo/exo stereoselectivity in Diels-Alder reactions of α,β-dialkylated conjugated enals to cyclic 1,3-dienes: intermediates in the synthesis of (-)-β-santalol and its analogs.

    PubMed

    Chapuis, Christian; Skuy, David; de Saint Laumer, Jean-Yves; Brauchli, Robert

    2014-10-01

    Highly exo-selective [4+2] cycloadditions of cyclopenta-1,3-diene 2a to α,β-dialkyl conjugated enals 5 are compared with the analogous endo-favored Diels-Alder reaction of cyclohexa-1,3-diene 7. The exo-stereoselectivity is lower in the homologous case of methylcyclopenta-1,3-diene 9. This diastereoselectivity is discussed either in terms of a retro-homo-Diels-Alder reaction, associated with thermodynamic control, or with respect to either a competing hetero-Diels-Alder/Claisen or Cope domino pathway, or retro-Claisen/retro-hetero-Diels-Alder of the endo-homo-cycloadducts. These hypothetical mechanisms have been examined by DFT calculations at the MPW1K(CH2 Cl2 )/6-31+G** level of theory for the AlCl3 -mediated cycloadditions of 5d to 2a and 7. Application of Corey's methodology to the γ-halogeno-α-methyl-substituted dienophiles 5a and 5b allowed an enantioselective preparation of known and useful intermediates for the synthesis of either the naturally occurring (-)-β-santalol or its potentially olfactive structural analogs. PMID:25329781

  10. Design of cross-linked semicrystalline poly(ε-caprolactone)-based networks with one-way and two-way shape-memory properties through Diels-Alder reactions.

    PubMed

    Raquez, Jean-Marie; Vanderstappen, Sophie; Meyer, Franck; Verge, Pierre; Alexandre, Michael; Thomassin, Jean-Michel; Jérôme, Christine; Dubois, Philippe

    2011-08-29

    Cross-linked poly(ε-caprolactone) (PCL)-based polyesterurethane (PUR) systems have been synthesized through Diels-Alder reactions by reactive extrusion. The Diels-Alder and retro-Diels-Alder reactions proved to be useful for enhancing the molecular motion of PCL-based systems, and therefore their crystallization ability, in the design of cross-linked semicrystalline polymers with one-way and two-way shape-memory properties. Successive reactions between α,ω-diol PCL (PCL(2) ), furfuryl alcohol, and methylene diphenyl 4,4'-diisocyanate straightforwardly afforded the α,ω-furfuryl PCL-based PUR systems, and subsequent Diels-Alder reactions with N,N-phenylenedimaleimide afforded the thermoreversible cycloadducts. The cross-linking density could be modulated by partially replacing PCL-diol with PCL-tetraol. Interestingly, the resulting PUR systems proved to be semicrystalline cross-linked polymers, the melting temperature of which (close to 45 °C) represented the switching temperature for their shape-memory properties. Qualitative and quantitative measurements demonstrated that these PUR systems exhibited one-way and two-way shape-memory properties depending on their cross-linking density. PMID:21744399

  11. Social information and community dynamics: nontarget effects from simulating social cues for management.

    PubMed

    Fletcher, Robert J

    2008-10-01

    Artificially creating social stimuli may be an effective tool for facilitating settlement by rare and/or declining species into suitable habitat. However, the potential consequences for other community members have not been explored and should be considered when evaluating the overall utility of using such management strategies. I report on nontarget, community-wide effects that occurred when manipulating social cues of two competitors that are species of concern in the western United States, the dominant Least Flycatcher (Empidonax minimus) and the subordinate American Redstart (Setophaga ruticilla). The experiment consisted of surveying birds during a pretreatment year, which allows for the control of baseline communities, and a treatment year, in which treatments were applied just prior to settlement by migratory birds. Treatments included broadcasting songs of flycatchers and redstarts and were compared to controls. While the addition of redstart cues did not significantly influence community structure, the addition of flycatcher cues reduced species richness of migratory birds by approximately 30%. This pattern was driven by an absence of local colonizations of small-bodied migrants to sites with added flycatcher cues, rather than by local extinctions occurring from manipulations. The artificial flycatcher stimuli were more responsible for declines in species richness than were changes in actual flycatcher densities. I conclude by identifying some fundamental issues that managers and conservation practitioners should weigh when considering simulating social cues for species conservation prior to implementation. PMID:18839770

  12. Diels-Alder Reaction of Anthranilic Acids: A Versatile Route to Dense Monolayers on Flat Edge and Basal Plane Graphitic Carbon Substrates.

    PubMed

    Farquhar, Anna K; Fitchett, Christopher M; Dykstra, Haidee M; Waterland, Mark R; Brooksby, Paula A; Downard, Alison J

    2016-09-01

    Methods that reliably yield monolayers of covalently anchored modifiers on graphene and other planar graphitic materials are in demand. Covalently bonded groups can add functionality to graphitic carbon for applications ranging from sensing to supercapacitors and can tune the electronic and optical properties of graphene. Limiting modification to a monolayer gives a layer with well-defined concentration and thickness providing a minimum barrier to charge transfer. Here we investigate the use of anthranilic acid derivatives for grafting aryl groups to few layer graphene and pyrolyzed photoresist film (PPF). Under mild conditions, anthranilic acids generate arynes, which undergo Diels-Alder cycloadditions. Using spectroscopy, electrochemistry, and atomic force microscopy, we demonstrate that the reaction yields monolayers of aryl groups on graphene and PPF with maximum surface coverages consistent with densely packed layers. Our study confirms that anthranilic acids offer a convenient route to covalent modification of planar graphitic carbons (both basal and edge plane materials). PMID:27529723

  13. An enantioselective central-axial-central chiral element transfer process leading to a concise synthesis of (+)-sterpurene: Intramolecular Diels-Alder reactions of vinylallene sulfoxides

    SciTech Connect

    Gibbs, R.A.; Bartels, K.; Lee, R.W.K.; Okamura, W.H. )

    1989-05-10

    The intramolecular Diels-Alder (IMDA) reaction of vinylallene sulfoxide 19 as the diene component occurs in a rapid and stereoselective manner at room temperature to give tricyclic 20 in good yield. Sulfoxide 19 cyclizes {approximately} 140 times faster than the corresponding hydrocarbon 15a. It was also shown that gem-dimethyl substitution on the tether linking the vinylallene and vinyl group accelerates the rate of cyclization by only a factor of {approximately} 2.6. Treatment of enantiomerically enriched diene propargyl alcohol 6 with benzenesulfenyl chloride gave vinyallene sulfoxide 4 which cyclized in a highly enantio- and diastereoselective fashion to afford optically active tricyclic sulfoxide 5. Sulfoxide 5 was converted in two steps to the novel sesquiterpene fungal metabolite (+)-sterpurene, thus establishing its absolute configuration. By use of 2D NMR techniques, most of the proton and carbon signals in the {sup 1}H and {sup 13}C NMR spectra of sterpurene (8) and the precursor diene 33 were assigned.

  14. Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

    PubMed Central

    Chou, Ting-Yi; ALJaroudi, Zainab; Ellis, Bobby D; Cameron, T Stanley

    2014-01-01

    Summary The synthesis of 5-substituted 6,6a-dihydroisoindolo[2,1-a]quinolin-11(5H)-ones via [4 + 2] imino-Diels–Alder cyclization from N-aryl-3-hydroxyisoindolinones and N-vinyl lactams under Lewis acid-catalysed anhydrous conditions is reported. Reactions of N-(2-substituted-aryl)-3-hydroxyisoindolinones with N-vinylpyrrolidone under identical conditions resulted in the formation of 2-(2-substitued-aryl)-3-(2-(2-oxopyrrolidin-1-yl)vinyl)isoindolin-1-one analogues indicating steric hinderance as the cause of deviation. The probable mechanism of the reaction based on the results from X-ray crystallography and molecular modelling is discussed. PMID:24778740

  15. ent-Kaurane-Based Regio- and Stereoselective Inverse Electron Demand Hetero-Diels-Alder Reactions: Synthesis of Dihydropyran-Fused Diterpenoids†

    PubMed Central

    Ding, Chunyong; Wang, Lili; Chen, Haijun; Wild, Christopher; Ye, Na; Ding, Ye; Wang, Tianzhi; White, Mark A.; Shen, Qiang; Zhou, Jia

    2014-01-01

    A mild and concise approach for the construction of 3,4-dihydro-2H-pyran ring integrated into the A-ring of the natural product oridonin using an optimized inverse electron demand hetero-Diels-Alder (IED HDA) reaction is reported herein. A self-dimerization of the exocyclic enone installed in the A-ring through a homo-HDA reaction was identified to exclusively give a dimeric ent-kaurane diterpenoid with the spirochroman core. Moreover, the efficient cross-HDA cycloadditions of this enone with various vinyl ethers or vinyl sulfides, instead of its own homo-HDA dimerization, were achieved in regio- and stereoselective manners, thus providing the access to novel dihydropyran-fused diterpenoids as potential anticancer agents to overcome chemoresistance. PMID:25225052

  16. Phomanolides A and B from the Fungus Phoma sp.: Meroterpenoids Derived from a Putative Tropolonic Sesquiterpene via Hetero-Diels-Alder Reactions.

    PubMed

    Zhang, Jinyu; Liu, Ling; Wang, Bo; Zhang, Yang; Wang, Lili; Liu, Xingzhong; Che, Yongsheng

    2015-12-24

    Phomanolides A (1) and B (2), unique meroterpenoids with new pentacyclic and tetracyclic skeletons, respectively, and phomanoxide (3), the double-epoxidation product of a putative biosynthetic precursor of 1 and 2, were isolated from the solid substrate fermentation cultures of the fungus Phoma sp., along with the known compound eupenifeldin (4). The structures of 1-3 were elucidated based on NMR spectroscopic data and electronic circular dichroism calculations and further secured by X-ray crystallography. Biogenetically, compounds 1 and 2 could be derived from a hypothetical monotropolonic sesquiterpene intermediate via hetero-Diels-Alder reactions. Compound 4 showed potent antiproliferative effects against three human glioma cell lines, with IC50 values of 0.08-0.13 μM. PMID:26651221

  17. Metalloporphyrin-Based Hypercrosslinked Polymers Catalyze Hetero-Diels-Alder Reactions of Unactivated Aldehydes with Simple Dienes: A Fascinating Strategy for the Construction of Heterogeneous Catalysts.

    PubMed

    Dou, Zhiyu; Xu, Li; Zhi, Yongfeng; Zhang, Yuwei; Xia, Hong; Mu, Ying; Liu, Xiaoming

    2016-07-11

    We describe a novel and intriguing strategy for the construction of efficient heterogeneous catalysts by hypercrosslinking catalyst molecules in a one-pot Friedel-Crafts alkylation reaction. The new hypercrosslinked polymers (HCPs) as porous solid catalysts exhibit the combined advantages of homogeneous and heterogeneous catalysis, owing to their high surface area, good stability, and tailoring of catalytic centers on the frameworks. Indeed, a new class of metalloporphyrin-based HCPs were successfully synthesized using modified iron(III) porphyrin complexes as building blocks, and the resulting networks were found to be excellent recyclable heterogeneous catalysts for the hetero-Diels-Alder reaction of unactivated aldehydes with 1,3-dienes. Moreover, this new strategy showed wide adaptability, and many kinds of homogeneous-like solid-based catalysts with high catalytic performance and excellent recyclability were also constructed. PMID:27147500

  18. Catalytic effect of gallium chloride in the diels-alder reaction between maleic anhydride and its derivatives and unsubstituted and substituted anthracenes

    SciTech Connect

    Kiselev, V.D.; Konovalov, A.I.; Shakirov, I.M.

    1985-11-10

    The stability of n, v complexes between gallium chloride and unsubstituted and substituted maleic anhydrides was determined in benzene by a thermochemical method; it was shown that the stability of the complexes decreases in the transition from maleic anhydrides with electron-donating substituents to maleic anhydrides with electron-withdrawing substituents. The reactivity of these dienophiles in the uncatalyzed Diels-Alder reactions with unsubstituted and substituted anthracenes in benzene and in the reactions catalyzed by gallium chloride was studied. The reactivity of the dienophiles varies similarly in the reactions with the investigated dienes, and this rules out treatment of steric hindrances as the reason for the reduced reactivity of the substituted dienophiles. A decrease in the catalytic effect was observed for the unreactive diene-dienophile pairs.

  19. ent-Kaurane-based regio- and stereoselective inverse electron demand hetero-Diels-Alder reactions: synthesis of dihydropyran-fused diterpenoids.

    PubMed

    Ding, Chunyong; Wang, Lili; Chen, Haijun; Wild, Christopher; Ye, Na; Ding, Ye; Wang, Tianzhi; White, Mark A; Shen, Qiang; Zhou, Jia

    2014-11-14

    A mild and concise approach for the construction of a 3,4-dihydro-2H-pyran ring integrated into the A-ring of the natural product oridonin using an optimized inverse electron demand hetero-Diels-Alder (IED HDA) reaction is reported herein. A self-dimerization of the exocyclic enone installed in the A-ring through a homo-HDA reaction was identified to exclusively give a dimeric ent-kaurane diterpenoid with the spirochroman core. Moreover, efficient cross-HDA cycloadditions of this enone with various vinyl ethers or vinyl sulfides, instead of its own homo-HDA dimerization, were achieved in a regio- and stereoselective manner, thus providing access to novel dihydropyran-fused diterpenoids as potential anticancer agents to overcome chemoresistance. PMID:25225052

  20. Development of an Enyne Metathesis/Isomerization/Diels-Alder One-Pot Reaction for the Synthesis of a Novel Near-Infrared (NIR) Dye Core.

    PubMed

    Yamashita, Kohei; Fujii, Yuki; Yoshioka, Shohei; Aoyama, Hiroshi; Tsujino, Hirofumi; Uno, Tadayuki; Fujioka, Hiromichi; Arisawa, Mitsuhiro

    2015-11-23

    N-Alkyl-N-allyl-2-alkynylaniline derivatives undergo a tandem ring-closing enyne metathesis/isomerization/Diels-Alder cycloaddition sequence in the presence of a second-generation Grubbs catalyst and dienophiles. In practice, the acyclic enyne in the presence of the ruthenium alkylidene first undergoes ring-closing metathesis to generate cyclic 4-vinyl-1,2-dihydroquinolines; following diene isomerization and then the addition of a dienophile, these ring-closing metathesis products are selectively converted into a 7-methyl-4H-naphtho[3,2,1-de]quinoline-8,11-dione core. Overall, the reaction sequence converts simple aniline derivatives into π-conjugated small molecules, which have characteristic absorption in the near-infrared region, in a single operation through three unique ruthenium-catalyzed transformations. PMID:26449517

  1. Understanding reactivity and regioselectivity in Diels-Alder reactions of a sugar-derived dienophile bearing two competing EWGs. An experimental and computational study.

    PubMed

    Giri, Germán F; Sarotti, Ariel M; Spanevello, Rolando A

    2015-10-13

    The effect of an extra EWG in the reactivity and regioselectivity in Diels-Alder reactions of β-cyanolevoglucosenone and 4 different dienes was studied by a joint computational and experimental study. Conceptual DFT analysis successfully predicted an important enhancement in the reactivity, and correctly anticipated the regioselectivity in the reactions with isoprene. However, this static treatment failed when dealing the regiochemical preference of the reactions involving a substituted anthracene as diene. MPW1K/6-31G* calculations correctly reproduced the experimental observations. Based on the collected data, we found that when dealing with dienes and dienophiles with no clear electronically activated position, the ease of pyramidalization of the interacting atoms dictates the regioselectivity of the DA reaction. PMID:26318382

  2. Effect on tumor necrosis factor-α production and antioxidant ability of black alder, as factors related to its anti-inflammatory properties.

    PubMed

    Acero, Nuria; Muñoz-Mingarro, Dolores

    2012-06-01

    Alders exhibit several uses in different areas and also offer some nutritional and medicinal values. The bark and leaves from black alder [Alnus glutinosa (L.) Gaertn] are used in folk medicine for the treatment of inflammatory processes and other health disorders. This study assessed if an extract of A. glutinosa stem bark exhibits some biological properties linked to improving the inflammatory state, which could partly justify its ethnopharmacological use. Therefore, various aspects of antioxidant activity as well as the effect on tumor necrosis factor-α (TNF-α) production were evaluated. The phytochemical study revealed the presence of terpenes, saponins, tannins, flavonoids, and anthraquinones (by high-performance thin-layer chromatography). The betulinic acid content in the extract, determined by reversed-phase high-performance liquid chromatography (validated method), was 0.72±0.027%. In addition, high amounts for total phenols as well as flavonoids were determined. The extract exhibited a 2,2'-diphenylpicrylhydrazyl radical scavenging capacity similar to that of ascorbic acid and had a significant effect on superoxide anion scavenging, superior to that of ascorbic acid. It was also able to protect HeLa cells from induced oxidative stress. In the TNF-α assay, levels of this citokine were depressed by the extract in HL-60 cells. To test the effect of the extract on cell proliferation, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed. According to the results, the antioxidant properties displayed by the extract of A. glutinosa stem bark, together with the effect on TNF-α levels, suggest that these activities, linked to a successful reduction in inflammatory processes, may support, in part, its ethnopharmacological use. PMID:22424456

  3. Effect on Tumor Necrosis Factor-α Production and Antioxidant Ability of Black Alder, as Factors Related to Its Anti-Inflammatory Properties

    PubMed Central

    Acero, Nuria

    2012-01-01

    Abstract Alders exhibit several uses in different areas and also offer some nutritional and medicinal values. The bark and leaves from black alder [Alnus glutinosa (L.) Gaertn] are used in folk medicine for the treatment of inflammatory processes and other health disorders. This study assessed if an extract of A. glutinosa stem bark exhibits some biological properties linked to improving the inflammatory state, which could partly justify its ethnopharmacological use. Therefore, various aspects of antioxidant activity as well as the effect on tumor necrosis factor-α (TNF-α) production were evaluated. The phytochemical study revealed the presence of terpenes, saponins, tannins, flavonoids, and anthraquinones (by high-performance thin-layer chromatography). The betulinic acid content in the extract, determined by reversed-phase high-performance liquid chromatography (validated method), was 0.72±0.027%. In addition, high amounts for total phenols as well as flavonoids were determined. The extract exhibited a 2,2′-diphenylpicrylhydrazyl radical scavenging capacity similar to that of ascorbic acid and had a significant effect on superoxide anion scavenging, superior to that of ascorbic acid. It was also able to protect HeLa cells from induced oxidative stress. In the TNF-α assay, levels of this citokine were depressed by the extract in HL-60 cells. To test the effect of the extract on cell proliferation, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed. According to the results, the antioxidant properties displayed by the extract of A. glutinosa stem bark, together with the effect on TNF-α levels, suggest that these activities, linked to a successful reduction in inflammatory processes, may support, in part, its ethnopharmacological use. PMID:22424456

  4. The Diels-Alder-Reaction with inverse-Electron-Demand, a very efficient versatile Click-Reaction Concept for proper Ligation of variable molecular Partners

    PubMed Central

    Wiessler, Manfred; Waldeck, Waldemar; Kliem, Christian; Pipkorn, Ruediger; Braun, Klaus

    2010-01-01

    The ligation of active pharmaceutical ingredients (API) for working with image processing systems in diagnostics (MRT) attracts increasing notice and scientific interest. The Diels-Alder ligation Reaction with inverse electron demand (DARinv) turns out to be an appropriate candidate. The DARinv is characterized by a specific distribution of electrons of the diene and the corresponding dienophile counterpart. Whereas the reactants in the classical Diels-Alder Reaction feature electron-rich diene and electron-poor dienophile compounds, the DARinv exhibits exactly the opposite distribution of electrons. Substituents with pushing electrones increase and, with pulling electrons reduce the electron density of the dienes as used in the DARinv. We report here that the DARinv is an efficient route for coupling of multifunctional molecules like active peptides, re-formulated drugs or small molecules like the alkyalting agent temozolomide (TMZ). This is an example of our contribution to the "Click chemistry" technology. In this case TMZ is ligated by DARinv as a cargo to transporter molecules facilitating the passage across the cell membranes into cells and subsequently into subcellular components like the cell nucleus by using address molecules. With such constructs we achieved high local concentrations at the desired target site of pharmacological action. The DARinv ligation was carried out using the combination of several technologies, namely: the organic chemistry and the solid phase peptide synthesis which can produce 'tailored' solutions for questions not solely restricted to the medical diagnostics or therapy, but also result in functionalizations of various surfaces qualified amongst others also for array development. We like to acquaint you with the DARinv and we like to exemplify that all ligation products were generated after a rapid and complete reaction in organic solutions at room temperature, in high purity, but also, hurdles and difficulties on the way to the

  5. Healable capacitive touch screen sensors based on transparent composite electrodes comprising silver nanowires and a furan/maleimide diels-alder cycloaddition polymer.

    PubMed

    Li, Junpeng; Liang, Jiajie; Li, Lu; Ren, Fengbo; Hu, Wei; Li, Juan; Qi, Shuhua; Pei, Qibing

    2014-12-23

    A healable transparent capacitive touch screen sensor has been fabricated based on a healable silver nanowire-polymer composite electrode. The composite electrode features a layer of silver nanowire percolation network embedded into the surface layer of a polymer substrate comprising an ultrathin soldering polymer layer to confine the nanowires to the surface of a healable Diels-Alder cycloaddition copolymer and to attain low contact resistance between the nanowires. The composite electrode has a figure-of-merit sheet resistance of 18 Ω/sq with 80% transmittance at 550 nm. A surface crack cut on the conductive surface with 18 Ω is healed by heating at 100 °C, and the sheet resistance recovers to 21 Ω in 6 min. A healable touch screen sensor with an array of 8×8 capacitive sensing points is prepared by stacking two composite films patterned with 8 rows and 8 columns of coupling electrodes at 90° angle. After deliberate damage, the coupling electrodes recover touch sensing function upon heating at 80 °C for 30 s. A capacitive touch screen based on Arduino is demonstrated capable of performing quick recovery from malfunction caused by a razor blade cutting. After four cycles of cutting and healing, the sensor array remains functional. PMID:25486240

  6. Mechanism and regioselectivity of the reversible Diels-Alder cycloaddition of 2-methyl-1,3 butadiene with C48B6N6 heterofullerene: a DFT approach.

    PubMed

    Zahedi, Ehsan

    2014-09-01

    A theoretical study of the mechanism and regioslectivity of Diels-Alder [4+2] cycloaddition reactions between 2-methyl-1,3 butadiene and hetero bonds of the most stable isomer of C48B6N6 heterofullerene have been studied at the B3LYP/6-31G(*) level. Three heterobond pathways BC, BN and NC including two regioisomers for each one are considered by different approaches. All studied reactions have normal electron demand nature and corresponding regioisomers are produced via asynchronous processes. Predicted regioselectivities using electronic and energetic results are in complete agreement with each other and show that BC heterobond pathway is more active than others and regioisomer 16 is the major. The local reactivity difference values (Rk) show that all reaction sites at C48B6N6 present ambiphilic activation while reaction sites at 2-methyl-1,3 butadiene show nucleophilic activation. Therefore, it is predictable that C48B6N6 should present electrophilic nature. Plotting of ΔRk and Δs values of six studied channels toward corresponding activation Gibbs free energies showed that the regioisomeric channel with lower ΔRk and Δs values is faster and vice versa. PMID:25203975

  7. A Near-Infrared Photothermal Effect-Responsive Drug Delivery System Based on Indocyanine Green and Doxorubicin-Loaded Polymeric Micelles Mediated by Reversible Diels-Alder Reaction.

    PubMed

    Li, Hui; Li, Junjie; Ke, Wendong; Ge, Zhishen

    2015-10-01

    Near-infrared light (NIR) possesses great advantages for light-responsive controllable drug release, such as deep tissue penetration and low damage to healthy tissues. Herein, a NIR-responsive drug delivery system is developed based on a NIR dye, indocyanine green (ICG), and anticancer drug, doxorubicin (DOX)-loaded thermoresponsive block copolymer micelles, in which the drug release can be controlled via NIR irradiation. First, block copolymers, poly(oligo(ethylene glycol) methacrylate)-block-poly(furfuryl methacrylate) (POEGMA-b-PFMA), are synthesized by sequential reversible addition-fragmentation chain-transfer (RAFT) polymerization, followed by modification with N-octyl maleimide through Diels-Alder (DA) reaction to produce POEGMA-b-POMFMA. The self-assembly of POEGMA-b-POMFMA by nano-precipitation in aqueous solution affords the polymeric micelles which are used to simultaneously encapsulate ICG and DOX. Upon irradiation by NIR light (805 nm), the loaded DOX is released rapidly from the micelles due to partial retro DA reaction and local temperature increase-induced faster drug diffusion by the photothermal effect. Cytotoxicity evaluation and intracellular distribution observation demonstrate significant synergistic effects of NIR-triggered drug release, photothermal, and chemotherapy toward cancer cells under NIR irradiation. PMID:26274805

  8. Kinetic and spectrophotometric investigation of the diels-alder reaction between maleic anhydride derivatives and substituted anthracenes in the presence of gallium and aluminum chlorides

    SciTech Connect

    Kiselev, V.D.; Konovalov, A.I.; Shakirov, I.M.

    1986-10-01

    A comparison was made of the kinetic data for the normal Diels-Alder reaction of para-substituted N-arylmaleimides and substituted maleic anhydrides with meso-substituted anthracenes and of the reaction catalyzed by gallium and aluminum chlorides. The largely constant effects of gallium chloride (10/sup 4/) and aluminum chloride (10/sup 5/) in the acceleration of the reactions between the various pairs were demonstrated. The energies of charge transfer in the complexes between hexamethylbenzene and the dienophiles in the presence and absence of Lewis acids were determined by spectrophotometry. A significant decrease (to 1.2 eV) of the charge-transfer energy was found in the ..pi.., ..pi..-complexes and was attributed to the stabilization of the LUMO of the dienophile. From analysis of the obtained data it was concluded that the observed catalytic effect in the presence of Lewis acids can be explained by the approach of the frontier orbital levels and by a favorable change in the coefficients at the atomic orbitals responsible for the reaction.

  9. Determination of the energy storage capacity of the Diels-Alder reaction between methylfuran and maleic anhydride as applied to storing solar energy

    SciTech Connect

    Sparks, B.G.

    1981-01-01

    The heat storage capacity of the Diels-Alder reaction between 2-methylfuran and maleic anhydride is calculated using reaction parameters obtained from solution calorimetry. An equilibrium constant of .614 1/mol and a heat of reaction of 14.33 kcal/mole were obtained from experiments at 45/sup 0/C. A reaction ..delta..C/sub p/ of -21.8 cal/mole was calculated from heat capacity information at 25/sup 0/C. From these parameters, a solution initially seven molar in methylfuran and maleic anhydride was found to have a maximum apparent volumetric heat capacity of about 1.85 times that of water. This maximum occurs at about 335/sup 0/K. Typical active solar energy schemes operate between 300 and 400/sup 0/K. When cycled between these temperatures, this system has an overall apparent heat capacity about 1.5 times that of water. The apparent heat capacity increases as the temperature range is narrowed.

  10. Origin of the synchronicity in bond formation in polar Diels-Alder reactions: an ELF analysis of the reaction between cyclopentadiene and tetracyanoethylene.

    PubMed

    Domingo, Luis R; Pérez, Patricia; Sáez, Jose A

    2012-05-21

    The origin of the synchronicity in C-C bond formation in polar Diels-Alder (P-DA) reactions involving symmetrically substituted electrophilic ethylenes has been studied by an ELF analysis of the electron reorganization along the P-DA reaction of cyclopentadiene (Cp) with tetracyanoethylene (TCE) at the B3LYP/6-31G* level. The present study makes it possible to establish that the synchronicity in C-C bond formation in P-DA reactions is controlled by the symmetric distribution of the electron-density excess reached in the electrophile through the charge transfer process, which can be anticipated by an analysis of the spin electron-density at the corresponding radical anion. The ELF comparative analysis of bonding along the DA reactions of Cp with ethylene and with TCE asserts that these DA reactions, which have a symmetric electron reorganization, do not have a cyclic electron reorganization as the pericyclic mechanism states. Due to the very limited number of cases of symmetrically substituted ethylenes, we can conclude that the synchronous mechanism is an exception of DA reactions. PMID:22527420

  11. On-resin Diels-Alder reaction with inverse electron demand: an efficient ligation method for complex peptides with a varying spacer to optimize cell adhesion.

    PubMed

    Pagel, Mareen; Meier, René; Braun, Klaus; Wiessler, Manfred; Beck-Sickinger, Annette G

    2016-06-01

    Solid phase peptide synthesis (SPPS) is the method of choice to produce peptides. Several protecting groups enable specific modifications. However, complex peptide conjugates usually require a rather demanding conjugation strategy, which is mostly performed in solution. Herein, an efficient strategy is described using an on-resin Diels-Alder reaction with inverse electron demand (DARinv). This method is compatible with the standard Fmoc/tBu strategy and is easy to monitor. As a proof of concept a titanium binding peptide was modified with a cyclic cell binding peptide (RGD) by DARinv on a solid support applying different tetrazines and alkenes. The generated bulky DARinv linkers were employed to act as the required spacer for RGD mediated cell adhesion on titanium. In vitro studies demonstrated improved cell spreading on DARinv-conjugated peptides and revealed, in combination with molecular dynamics-simulation, new insights into the design of spacers between the RGD peptide and the surface. Performing the DARinv on resin expands the toolbox of SPPS to produce complex peptide conjugates under mild, catalyst free conditions with reduced purification steps. The resulting conjugate can be effectively exploited to promote cell adhesion on biomaterials. PMID:27117044

  12. Dark CO/sub 2/ fixation and amino acid metabolism in symbiotic N/sub 2/-fixing systems. Labeling studies with /sup 14/C and /sup 13/N-labeled tracers. [Roots of soybean plants and alders

    SciTech Connect

    Coker, G.T. III

    1982-01-01

    Amino acid metabolism was examined by monitoring the amino acids labeled with (/sup 14/C) incorporated during dark CO/sub 2/ fixation and with (/sup 13/N) incorporated from /sup 13/NH/sub 4/+, /sup 13/NO/sub 3/- or (/sup 13/N)N/sub 2/. Label from /sup 14/CO/sub 2/ was directly incorporated in soybean roots and the N/sub 2/-fixing root nodules of soybeans and alders. The products of dark CO/sub 2/ fixation were primarily amino and organic acids. The distribution of label incorporated from /sup 14/CO/sub 2/ into amino acids depended on the plant species and the nitrigen source. The major labeled amino acids in roots and nodules of soybean plants dependent on N/sub 2/ were aspartate and glutamate; in alder nodules, citrulline; in roots of soybean plants treated with NO/sub 3/-, asparagine; and in roots of soybean plants treated with NH/sub 4/+, asparagine and glutamine. Asparagine was the major amino acid transported out of the soybean root system. Experiments indicated that asparagine was synthesized directly from aspartate. After exposure to /sup 14/CO/sub 2/, the specific activity of glutamine was consistently higher than that of glutamate in soybean nodules and roots of plants treated with NO/sub 3/-. This was taken as evidence that there were two pools of glutamate, only one of which was associated with glutamine synthesis. Alder and soybean nodules and roots were incubated with /sup 13/N-labeled tracers. Those tissues incubated with /sup 13/NH/sub 4/+ had a higher ratio of (/sup 13/N)glutamine to (/sup 13/N)glutamate that similar tissues exposed to /sup 13/NO/sub 3/- or (/sup 13/N)N/sub 2/. An explanation for these results based on the relative rates of glutamine and glutamate synthesis is discussed.

  13. An unexpected double Diels-Alder reaction of (E)-2-bromo-4-aryl-1,3-pentadiene involving [1,5]-hydrogen migration and HBr elimination: synthesis of bicyclo[2.2.2]octene derivatives.

    PubMed

    Huang, Pingping; Liu, Lingyan; Chang, Weixing; Li, Jing

    2015-03-01

    An unexpected double Diels-Alder (DDA) reaction of (E)-2-bromo-4-aryl-1,3-pentadiene was developed and resulted in a series of "butterfly-like" bicyclo[2.2.2]octene derivatives in moderate to good yields without the need for a metal catalyst. The proposed mechanism involves a [1,5]-sigmatropic hydrogen migration and HBr elimination. Through this decisive [1,5]-hydrogen shift step, the electronic properties and steric hindrance of the conjugated diene substrate are completely altered and the DDA reaction of this potential diene synthon is successfully achieved. PMID:25620015

  14. A technique to produce aluminum color bands for avian research

    USGS Publications Warehouse

    Koronkiewicz, T.J.; Paxton, E.H.; Sogge, M.K.

    2005-01-01

    We developed a technique to produce metal (aluminum) color bands, in response to concerns about leg injuries caused by celluloid-plastic color bands applied to Willow Flycatchers (Empidonax traillii). The technique involves color-anodized aluminum bands (unnumbered blanks and federal numbered bands), with auto pin-striping tape and flexible epoxy sealant, to create a variety of solid, half- and triple-split colors. This allows for hundreds of unique, high-contrast color combinations. During six consecutive years of application, these colored metal bands have resisted color fade compared to conventional celluloid-plastic bands, and have reduced leg injuries in the flycatcher. Although not necessarily warranted for all color-banding studies, these metal bands may provide a lower-impact option for studies of species known to be impacted by plastic color bands.

  15. Linear-dendritic supramolecular complexes as nanoscale reaction vessels for "green" chemistry. Diels-Alder reactions between fullerene C60 and polycyclic aromatic hydrocarbons in aqueous medium.

    PubMed

    Simonyan, Arsen; Gitsov, Ivan

    2008-10-21

    This study describes the first Diels-Alder (DA) reaction performed in aqueous medium with highly hydrophobic compounds-fullerene (C 60) as the dienophile and anthracene (An) or tetracene (Tet) as the dienes, respectively. The reactions are performed in nanocontainers, constructed by self-assembly of linear-dendritic amphiphilic copolymers with poly(ethylene glycol), PEG or poly(ethylene oxide), PEO as the hydrophilic blocks and poly(benzyl ether) monodendrons as the hydrophobic fragments: G3PEO13k, dG3 and dG2. Comparative studies under identical conditions are carried out with an amphiphilic linear-linear copolymer, poly(styrene)1800- block-PEO2100, PSt-PEO, and the nonionic surfactant Igepal CO-720, IP720. The binding affinity of supermolecules built of these amphiphiles toward the DA reagents decreases in the following order: G3PEO13k > dG3 > PSt-PEO > dG2 > IP720. The kinetic constant of binding is evaluated for tetracene and decreases in a similar fashion: 5 x 10 (-7) M/min (G3PEO13k), through 4 x 10 (-7) M/min (PSt-PEO) down to 1.5 x 10 (-7) M/min for IP720. The mobility of substrates encapsulated in the micellar core, estimated by pyrene fluorescence decay, is 95-121 ns for the micelles of the linear-dendritic copolymers and notably higher for PSt-PEO (152 ns), revealing the much denser interior of the linear analogue. The apparent kinetic constant for the DA reaction of C 60 and Tet within the G3PEO13k supermolecule in aqueous medium is markedly higher than in organic solvent (toluene), 208 vs 1.82 M /min. With G3PEO13k the conversions reach 49% for the DA reaction between C 60 and An, and 55% for C 60 and Tet. Besides the monoadduct (26.5% yield) the reaction with An produces exclusively increasing amounts of D 2 h -symmetric antipodal bis-adduct, whose yield reaches up to 22.5% after 48 h. In addition to the environmentally friendly conditions notable advantages of the synthetic strategy described are the extended stability of the linear

  16. Direct and Indirect Determinations of Elementary Rate Constants H + O2: Chain Branching; the Dehydration of tertiary-Butanol; the Retro Diels-Alder Reaction of Cyclohexene; the Dehydration of Isopropanol

    NASA Astrophysics Data System (ADS)

    Heyne, Joshua S.

    Due to growing environmental concern over the continued use of fossil fuels, methods to limit emissions and partially replace fossil fuel use with renewable biofuels are of considerable interest. Developing chemical kinetic models for the chemistry that affects combustion properties is important to understanding how new fuels affect combustion energy conversion processes in transportation devices. This thesis reports the experimental study of several important reactions (the H + O2 branching reaction, the key decomposition reactions of tertiary-butanol, the dehydration reaction of isopropanol, and the retro Diels-Alder reaction of cyclohexene) and develops robust analysis methods to estimate the absolute uncertainties of specific elementary rate constants derived from the experimental data. In the study of the above reactions, both a direct and indirect rate constant determination technique with associated uncertainty estimation methodologies are developed. In the study of the decomposition reactions, a direct determination technique is applied to experimental data gathered in preparation of this thesis. In the case of the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, both of which are used as internal standards for relative rate studies (Herzler et al. 1997) and chemical thermometry (Rosado-Reyes et al. 2013) , analysis showed an ˜20 K difference in the reaction rate between the reported results and the previous recommendations. In light of these discrepancies, an uncertainty estimation of previous recommendations illuminated an uncertainty of at least 20 K for the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, thus resolving the discrepancies. The determination of the H + O2 branching reaction and decomposition reactions of isopropanol used an indirect determination technique. The uncertainty of the H + O2 branching reaction rate is shown to be underestimated by previous

  17. Dehydrogenative Diels-Alder reaction.

    PubMed

    Ozawa, Takuya; Kurahashi, Takuya; Matsubara, Seijiro

    2011-10-01

    The dehydrogenative cycloaddition of dieneynes, which possess a diene in the form of a styrene moiety and a dienophile in the form of an alkyne moiety, produces naphthalene derivatives when heated. It was found that a key requirement of this process is the presence of a silyl group attached to the alkyne moiety, which forces a dehydrogenation reaction to occur. PMID:21905638

  18. Pressure Dependent Mass Fraction in Noble Gas Mass Spectrometers: A Possible Explanation for the Excessive Dispersion in the EARTHTIME Fish Canyon/Alder Creek Inter-Calibration Experiment

    NASA Astrophysics Data System (ADS)

    Turrin, B. D.; Swisher, C. C.; Mana, S.

    2011-12-01

    Mass spectrometer fractionation bias (mass discrimination) is a ubiquitous phenomenon in noble gas mass spectroscopy and must be corrected for in order to obtain accurate-high precision isotopic ratios that are used in isotopic age calculations. Temporal variations in mass fractionation are well known phenomena and have been reported in several studies (eg. Turrin et al., 2010 and references therein). Here we report on the pressure dependency on mass spectrometer fractionation bias. In our experiment, we varied by a factor of five the signal size of aliquots of atmospheric argon delivered from an automated air pipette system. The measured mass discrimination difference (MD) as determined by the 40Ar/36Ar ratio between the 1-fold and 5-fold air pipette shots is ~5%. The air 40Ar/36Ar aliquots were measured using a MAP 215-50 operating in pulse counting mode. The air measurements were interspersed with measurements of Alder Creek (AC) sanidine and Fish Canyon (FC) sanidine that were co-irradiated for 0.75 hours. The grain sizes for the two mineral standards were chosen such that the AC sample yielded 40Ar signals of about 50 kcps, similar to that delivered by a single aliquot delivered by the air pipette. The FC grains were about 5-10 times greater (150-600 kcps) than the single air aliquot. Following the analyses, we applied the MD correction to both the FC and AC analyses. When the MD as determined from the single pipette data (which matches 40Ar beam intensity of the AC sample) is applied to both the AC and FC data a "J" of 1.579±0.001x10-4 is obtained from the FC data and an age of 1183 ±4 ka for AC. However, when the MD as determined from the multiple aliquot pipette data (with an 40Ar beam similar to that of the FC analyses) is applied to the FC data a "J" of 1.588±0.001x10-4 is obtained and an AC age of 1189 ±4 ka the same age at the 95% confidence level, the reported age for AC. We conclude that variation in MD over signal sizes typically analyzed in 40Ar

  19. Root tensile strength of grey alder and mountain maple grown on a coarse grained eco-engineered slope in the Swiss Alps related to wood anatomical features

    NASA Astrophysics Data System (ADS)

    Kink, Dimitri; Bast, Alexander; Meyer, Christine; Meier, Wolfgang; Egli, Markus; Gärtner, Holger

    2014-05-01

    . In order to confirm this assumption and possibly find more important root properties which have an influence on soil stabilization, the root systems of seven trees (three grey alder, four mountain maple) were excavated and analyzed. The study site is a catchment, where shallow landslides are common. It is located in the Prättigau valley in the Eastern Swiss Alps and was eco-engineered in 1997. The substrate is coarse-grained morainic material, mean annual air temperature reaches 4.64°C, average precipitation is 1170 mm, and the altitude is about 1000 m a.s.l.. The root system of each tree was uncovered carefully by hand to keep the roots undamaged, before removal it was photographed in situ to document the root distribution. The root systems were then cut into single root pieces of about 20 cm length and the position of each sample was documented. The root samples were then hierarchically classified in several root classes. The tensile strength of more than 500 samples was determined. In addition, the values for age, diameter, and root moisture were ascertained. Since it was assumed, that the cellular structure of the roots has an influence on the tensile strength, two microscopic thin-sections were prepared from all successfully tested root samples. The microscopic analysis focused on anatomical parameters such as the size and number of vessels, their distribution as well as their conductivity. The results for the final correlation between the anatomical characteristics and the root's tensile strength are presented for both tree species.

  20. High performance addition-type thermoplastics (ATTs) - Evidence for the formation of a Diels-Alder adduct in the reaction of an acetylene-terminated material and a bismaleimide

    NASA Technical Reports Server (NTRS)

    Pater, R. H.; Soucek, M. D.; Chang, A. C.; Partos, R. D.

    1991-01-01

    Recently, the concept and demonstration of a new versatile synthetic reaction for making a large number of high-performance addition-type thermoplastics (ATTs) were reported. The synthesis shows promise for providing polymers having an attractive combination of easy processability, good toughness, respectable high temperature mechanical performance, and excellent thermo-oxidative stability. The new chemistry involves the reaction of an acetylene-terminated material with a bismaleimide or benzoquinone. In order to clarify the reaction mechanism, model compound studies were undertaken in solutions as well as in the solid state. The reaction products were purified by flash chromatography and characterized by conventional analytical techniques including NMR, FT-IR, UV-visible, mass spectroscopy, and high pressure liquid chromatography. The results are presented of the model compound studies which strongly support the formation of a Diels-Alder adduct in the reaction of an acetylene-terminated compound and a bismaleimide or benzoquinone.

  1. High pressure Diels-Alder approach to hydroxy-substituted 6a-cyano-tetrahydro-6H-benzo[c]chromen-6-ones: a route to delta(6)-cis-cannabidiol.

    PubMed

    Ballerini, Eleonora; Minuti, Lucio; Piermatti, Oriana; Pizzo, Ferdinando

    2009-06-01

    Diels-Alder cycloaddition reactions of 3-cyanocoumarin, hydroxy-substituted 3-cyanocoumarins and mesyl-substituted 3-cyano-coumarins with methyl-1,3-butadienes carried out under high pressure (11 kbar) are reported. Activation by high pressure allows these reactions to proceed satisfactorily under mild conditions to produce 6a-cyano-hydroxy- and 6a-cyano-mesyl-tetrahydro-6H-benzo[c]chromen-6-ones in moderate to excellent yield. The synthesis of cis-1-hydroxy-9-methyl-3-pentyl-6a,7,10,10a-tetrahydro-benzo[c]chromen-6-one as precursor of Delta(6)-3,4-cis-cannabidiol (Delta(6)-cis-CBD) and Delta(8)-cis-tetrahydrocannabinol (Delta(8)-cis-THC) is outlined. PMID:19402693

  2. Multilocus Sequence Typing Confirms the Close Genetic Interrelatedness of Three Distinct Flavescence Dorée Phytoplasma Strain Clusters and Group 16SrV Phytoplasmas Infecting Grapevine and Alder in Europe▿

    PubMed Central

    Arnaud, Guillaume; Malembic-Maher, Sylvie; Salar, Pascal; Bonnet, Patrick; Maixner, Michael; Marcone, Carmine; Boudon-Padieu, Elisabeth; Foissac, Xavier

    2007-01-01

    Vineyards of southern France and northern Italy are affected by the flavescence dorée (FD) phytoplasma, a quarantine pathogen transmitted by the leafhopper of Nearctic origin Scaphoideus titanus. To better trace propagation of FD strains and identify possible passage between the vineyard and wild plant compartments, molecular typing of phytoplasma strains was applied. The sequences of the two genetic loci map and uvrB-degV, along with the sequence of the secY gene, were determined among a collection of FD and FD-related phytoplasmas infecting grapevine, alder, elm, blackberry, and Spanish broom in Europe. Sequence comparisons and phylogenetic analyses consistently indicated the existence of three FD phytoplasma strain clusters. Strain cluster FD1 (comprising isolate FD70) displayed low variability and represented 17% of the disease cases in the French vineyard, with a higher incidence of the cases in southwestern France. Strain cluster FD2 (comprising isolates FD92 and FD-D) displayed no variability and was detected both in France (83% of the cases) and in Italy, whereas the more-variable strain cluster FD3 (comprising isolate FD-C) was detected only in Italy. The clonal property of FD2 and its wide distribution are consistent with diffusion through propagation of infected-plant material. German Palatinate grapevine yellows phytoplasmas (PGY) appeared variable and were often related to some of the alder phytoplasmas (AldY) detected in Italy and France. Finally, phylogenetic analyses concluded that FD, PGY, and AldY were members of the same phylogenetic subclade, which may have originated in Europe. PMID:17468266

  3. N-O Chemistry for Antibiotics: Discovery of N-Alkyl-N-(pyridin-2-yl)hydroxylamine Scaffolds as Selective Antibacterial Agents Using Nitroso Diels-Alder and Ene Chemistry

    PubMed Central

    Wencewicz, Timothy A.; Yang, Baiyuan; Rudloff, James R.; Oliver, Allen G.; Miller, Marvin J.

    2011-01-01

    The discovery, syntheses, and structure-activity relationships (SAR) of a new family of heterocyclic antibacterial compounds based on N-alkyl-N-(pyridin-2-yl)hydroxylamine scaffolds are described. A structurally diverse library of ~100 heterocyclic molecules generated from Lewis acid-mediated nucleophilic ring opening reactions with nitroso Diels-Alder cycloadducts and nitroso ene reactions with substituted alkenes was evaluated in whole cell antibacterial assays. Compounds containing the N-alkyl-N-(pyridin-2-yl)hydroxylamine structure demonstrated selective and potent antibacterial activity against the Gram-positive bacterium Micrococcus luteus ATCC 10240 (MIC90 = 2.0 μM or 0.41 μg/mL) and moderate activity against other Gram-positive strains including antibiotic resistant strains of Staphylococcus aureus (MRSA) and Enterococcus faecalis (VRE). A new synthetic route to the active core was developed using palladium-catalyzed Buchwald-Hartwig amination reactions of N-alkyl-O-(4-methoxybenzyl)hydroxylamines with 2-halo-pyridines that facilitated SAR studies and revealed the simplest active structural fragment. This work shows the value of using a combination of diversity-oriented synthesis (DOS) and parallel synthesis for identifying new antibacterial scaffolds. PMID:21859126

  4. Species interactions and population density mediate the use of social cues for habitat selection.

    PubMed

    Fletcher, Robert J

    2007-05-01

    1. The perspective that populations and communities are structured by antagonistic interactions among individuals has dominated much of ecology. Yet how animals use social information to guide decisions, such as habitat selection, may be influenced by both positive and negative interactions among individuals. Recent theory also suggests that the way animals use social information may be substantially influenced by population density, which alters the potential costs and benefits of such behaviours. 2. I manipulated cues of two competitors, the dominant least flycatcher Empidonax minimus (Baird & Baird) and the subordinate American redstart Setophaga ruticilla (Linnaeus), to assess the use of conspecific and heterospecific cues during habitat selection, and if population density influences these strategies. The experiment consisted of surveying birds during a pre-treatment year, which allows for the control and testing the effect of baseline densities, and a treatment year, in which treatments were applied just prior to settlement. Treatments included broadcasting songs of flycatchers and redstarts, and were compared with controls. 3. When controlling for pre-treatment densities, bird densities, and to a lesser extent arrival dates, during the treatment year suggested that flycatchers were attracted to both conspecific and heterospecific cues during settlement. Furthermore, attraction was strongest for flycatchers in plots with moderate pre-treatment densities. American redstarts were rare in the study area but showed apparent attraction to conspecifics and avoidance of heterospecifics. 4. These results provide experimental evidence for the use of multiple social cues in habitat selection and suggest that heterospecific attraction may operate under broader contexts than originally envisioned. In such instances, nontarget effects can potentially occur when manipulating social cues to elicit settlement in conservation strategies. The impact of population density on

  5. Does nonrandom nest placement imply nonrandom nest predation? - A reply

    USGS Publications Warehouse

    Cooper, R.J.; Wilson, R.R.; Zenitsky, G.D.; Mullin, S.J.; Dececco, J.D.; Marshall, M.R.; Wolf, D.J.; Pomara, L.Y.

    1999-01-01

    In response to the critique by Schmidt and Whelan (Condor 101(4):916-920, 1999), we find that the relationship between nest success and tree selectivity is dependent upon inclusion or exclusion of particular tree species, whether or not years are pooled, and the selectivity index used. We question their use of point estimates of nest success with extremely high variances, defend our index, question the application of the Chesson (1983) index to our data, and explain the need to analyze years separately. Bottomland hardwood forest systems are extremely variable; hydroperiods alter the suitability of nesting substrates, availability of alternative food, and behavior of predators and their prey. Given these features, actively searching for Acadian Flycatcher (Empidonax virescens) nests is seldom an efficient predator foraging strategy. Therefore, these predation events are best described as random; nests are principally encountered opportunistically by generalist predators while searching for other prey.

  6. Temperature can interact with landscape factors to affect songbird productivity.

    PubMed

    Cox, W Andrew; Thompson, Frank R; Reidy, Jennifer L; Faaborg, John

    2013-04-01

    Increased temperatures and more extreme weather patterns associated with global climate change can interact with other factors that regulate animal populations, but many climate change studies do not incorporate other threats to wildlife in their analyses. We used 20 years of nest-monitoring data from study sites across a gradient of habitat fragmentation in Missouri, USA, to investigate the relative influence of weather variables (temperature and precipitation) and landscape factors (forest cover and edge density) on the number of young produced per nest attempt (i.e., productivity) for three species of songbirds. We detected a strong forest cover × temperature interaction for the Acadian Flycatcher (Empidonax virescens) on productivity. Greater forest cover resulted in greater productivity because of reduced brood parasitism and increased nest survival, whereas greater temperatures reduced productivity in highly forested landscapes because of increased nest predation but had no effect in less forested landscapes. The Indigo Bunting (Passerina cyanea) exhibited a similar pattern, albeit with a marginal forest cover × temperature interaction. By contrast, productivity of the Northern Cardinal (Cardinalis cardinalis) was not influenced by landscape effects or temperature. Our results highlight a potential difficulty of managing wildlife in response to global change such as habitat fragmentation and climate warming, as the habitat associated with the greatest productivity for flycatchers was also that most negatively influenced by high temperatures. The influence of high temperatures on nest predation (and therefore, nest predators) underscores the need to acknowledge the potential complexity of species' responses to climate change by incorporating a more thorough consideration of community ecology in the development of models of climate impacts on wildlife. PMID:23504884

  7. Effects of reintroduced beaver (Castor canadensis) on riparian bird community structure along the upper San Pedro River, southeastern Arizona and northern Sonora, Mexico

    USGS Publications Warehouse

    Johnson, Glenn E.; van Riper, Charles, III

    2014-01-01

    Chapter 1.—We measured bird abundance and richness along the upper San Pedro River in 2005 and 2006, in order to document how beavers (Castor canadensis) may act as ecosystem engineers after their reintroduction to a desert riparian area in the Southwestern United States. In areas where beavers colonized, we found higher bird abundance and richness of bird groups, such as all breeding birds, insectivorous birds, and riparian specialists, and higher relative abundance of many individual species—including several avian species of conservation concern. Chapter 2.—We conducted bird surveys in riparian areas along the upper San Pedro River in southeastern Arizona (United States) and northern Sonora (Mexico) in order to describe factors influencing bird community dynamics and the distribution and abundance of species, particularly those of conservation concern. These surveys were also used to document the effects of the ecosystem-altering activities of a recently reintroduced beavers (Castor canadensis). Chapter 3.—We reviewed Southwestern Willow Flycatcher (Empidonax traillii extimus) nest records and investigated the potential for future breeding along the upper San Pedro River in southeastern Arizona, where in July 2005 we encountered the southernmost verifiable nest attempt for the species. Continued conservation and management of the area’s riparian vegetation and surface water has potential to contribute additional breeding sites for this endangered Willow Flycatcher subspecies. Given the nest record along the upper San Pedro River and the presence of high-density breeding sites to the north, the native cottonwood-willow forests of the upper San Pedro River could become increasingly important to E. t. extimus recovery, especially considering the anticipated effect of the tamarisk leaf beetle (Diorhabda carinulata) on riparian habitat north of the region.

  8. Presumed consent for transplantation: a dead issue after Alder Hey?

    PubMed

    English, V; Sommerville, A

    2003-06-01

    In the wake of scandals about the unauthorised retention of organs following postmortem examination, the issue of valid consent (or the lack of it) has returned to the forefront. Emphasis is put on obtaining explicit authorisation from the patient or family prior to any medical intervention, including those involving the dead. Although the controversies in the UK arose from the retention of human material for education or research rather than therapy, concern has been expressed that public mistrust could also adversely affect organ donation for transplantation. At the same time, however, the British Medical Association (BMA) continues to call for a shift to a system of presumed consent for organ transplantation. This apparent inconsistency can be justified because valid distinctions exist between the reasons requiring explicit consent for retention and the acceptability of presumed consent for transplantation. This paper argues for introducing a system of presumed consent for organ donation, given the overwhelming expressions of public support for transplantation. Ongoing legislative review in the UK provides an ideal chance to alter the default position to one where potential donors can simply acquiesce or opt out of donation. Combined with consultation with their relatives, this could be a much better method of realising individuals' wishes. It would also achieve a better balance between the duties owed to the deceased and those owed to people awaiting a transplant. PMID:12796433

  9. Recommendations for cowbird management in recovery efforts for the southwestern willow flycatcher

    USGS Publications Warehouse

    Rothstein, S.I.; Kus, B.E.; Whitfield, M.J.; Sferra, S.J.

    2003-01-01

    Three generations of mallard ducks (Anas platyrhynchos) were fed either a control diet or a diet containing 0.5 ppm mercury in the form of methylmercury. The levels of mercury in adult tissues and eggs remained about the same over 3 generations. The methylmercury diet had no effect on adult weights or weight changes during the reproductive season. Females fed a diet containing 0.5 ppm mercury laid a greater percentage of their eggs outside their nestboxes than did controls, and also laid fewer eggs and produced fewer ducklings. Methylmercury in the diet appeared to result in a small amount of eggshell thinning. Ducklings from parents fed methylmercury were less responsive than, controls to tape-recorded maternal calls, but were hyper-responsive to a frightening stimulus in avoidance tests; there were no significant differences in locomotor activity in an open-field test.

  10. Tamarisk biocontrol using tamarisk beetles: Potential consequences for riparian birds in the southwestern United States

    USGS Publications Warehouse

    Paxton, Eben H.; Theimer, Tad C.; Sogge, Mark K.

    2011-01-01

    The tamarisk beetle (Diorhabda spp.), a non-native biocontrol agent, has been introduced to eradicate tamarisk (Tamarix spp.), a genus of non-native tree that has become a dominant component of riparian woodlands in the southwestern United States. Tamarisk beetles have the potential to spread widely and defoliate large expanses of tamarisk habitat, but the effects of such a widespread loss of riparian vegetation on birds remains unknown. We reviewed literature on the effects of other defoliating insects on birds to investigate the potential for tamarisk beetles to affect birds positively or negatively by changing food abundance and vegetation structure. We then combined data on the temporal patterns of tamarisk defoliation by beetles with nest productivity of a well-studied riparian obligate, the Southwestern Willow Flycatcher (Empidonax traillii extimus), to simulate the potential demographic consequences of beetle defoliation on breeding riparian birds in both the short and long term. Our results highlight that the effects of tamarisk biocontrol on birds will likely vary by species and population, depending upon its sensitivity to seasonal defoliation by beetles and net loss of riparian habitat due to tamarisk mortality. Species with restricted distributions that include areas dominated by tamarisk may be negatively affected both in the short and long term. The rate of regeneration and/or restoration of native cottonwoods (Populus spp.) and willows (Salix spp.) relative to the rate of tamarisk loss will be critical in determining the long-term effect of this large-scale ecological experiment.

  11. Avian habitat relationships in pinyon-juniper woodland

    USGS Publications Warehouse

    Sedgwick, James A.

    1987-01-01

    Habitat relationships of breeding birds were examined in northwestern Colorado in pinyon-juniper (Pinus edulis-Juniperus osteosperma) woodland and in openings where most overstory trees had been knocked down by anchor chaining. Vegetation characteristics and physical habitat features were measured in 233 0.04-ha circular plots around singing males of 13 species of birds from 15 May to 15 July 1980. Thirteen-group discriminant function analysis ordinated bird species along three habitat dimensions described by (1) canopy height; (2) slope, shrub size, and shrub species diversity; and (3) percentage canopy cover, large tree density, distance from a habitat edge, litter cover, and green cover. Woodland, open-area, and intermediate edge species were clearly segregated along the first discriminant axis, and species' associations with shrubs, inclination, ground cover, and edges were revealed by the ordinations along the second and third discriminant axes. Two-group discriminant analyses comparing occupied and available plots identified additional and more specific habitat associations. For example, Hermit Thrushes (Catharus guttatus) were associated with mature forested habitats and forest interiors, Virginia's Warblers (Vermivora virginiae) favored steep, oak-covered draws, Rock Wrens (Salpinctes obsoletus) selected areas where percentage log cover and small tree density were high, and Dusky Flycatchers (Empidonax oberholseri) preferred shrubby slopes with scattered large trees near woodland edges.

  12. Nesting success of grassland and savanna birds on reclaimed surface coal mines of the midwestern United States

    SciTech Connect

    Galligan, E.W.; DeVault, T.L.; Lima, S.L.

    2006-12-15

    Reclaimed surface coal mines in southwestern Indiana support many grassland and shrub/savanna bird species of conservation concern. We examined the nesting success of birds on these reclaimed mines to assess whether such 'unnatural' places represent productive breeding habitats for such species. We established eight study sites on two large, grassland-dominated mines in southwestern Indiana and classified them into three categories (open grassland, shrub/savanna, and a mixture of grassland and shrub/savanna) based on broad vegetation and landscape characteristics. During the 1999 and 2000 breeding seasons, we found and monitored 911 nests of 31 species. Daily nest survival for the most commonly monitored grassland species ranged from 0.903 (Dickcissel, Spiza americana) to 0.961 (Grasshopper Sparrow, Ammodramus savannarum). Daily survival estimates for the dominant shrub/savanna nesting species ranged from 0.932 (Brown Thrasher, Toxostoma rufum) to 0.982 (Willow Flycatcher, Empidonax traillii). Vegetation and landscape effects on nesting success were minimal, and only Eastern Meadowlarks (Sturnella magna) showed a clear time-of-season effect, with greater nesting success in the first half of the breeding season. Rates of Brown-headed Cowbird (Molothrus ater) parasitism were only 2.1% for grassland species and 12.0% for shrub/savanna species. The nesting success of birds on reclaimed mine sites was comparable to that in other habitats, indicating that reclaimed habitats on surface mines do not necessarily represent reproductive traps for birds.

  13. Tamarix and Diorhabda leaf beetle interactions: implications for Tamarix water use and riparian habitat

    USGS Publications Warehouse

    Nagler, Pamela; Glenn, Edward P.

    2013-01-01

    Tamarix leaf beetles (Diorhabda carinulata) have been widely released on western United States rivers to control introduced shrubs in the genus Tamarix, with the goals of saving water through removal of an assumed high water-use plant, and of improving habitat value by removing a competitor of native riparian trees. We review recent studies addressing three questions: (1) to what extent are Tamarix weakened or killed by recurrent cycles of defoliation; (2) can significant water salvage be expected from defoliation; and (3) what are the effects of defoliation on riparian ecology, particularly on avian habit? Defoliation has been patchy at many sites, and shrubs at some sites recover each year even after multiple years of defoliation. Tamarix evapotranspiration (ET) is much lower than originally assumed in estimates of potential water savings, and are the same or lower than possible replacement plants. There is concern that the endangered southwestern willow flycatcher (Empidonax trailli extimus) will be negatively affected by defoliation because the birds build nests early in the season when Tamarix is still green, but are still on their nests during the period of summer defoliation. Affected river systems will require continued monitoring and development of adaptive management practices to maintain or enhance riparian habitat values. Multiplatform remote sensing methods are playing an essential role in monitoring defoliation and rates of ET on affected river systems.

  14. Breeding Phenology of Birds: Mechanisms Underlying Seasonal Declines in the Risk of Nest Predation

    PubMed Central

    Borgmann, Kathi L.; Conway, Courtney J.; Morrison, Michael L.

    2013-01-01

    Seasonal declines in avian clutch size are well documented, but seasonal variation in other reproductive parameters has received less attention. For example, the probability of complete brood mortality typically explains much of the variation in reproductive success and often varies seasonally, but we know little about the underlying cause of that variation. This oversight is surprising given that nest predation influences many other life-history traits and varies throughout the breeding season in many songbirds. To determine the underlying causes of observed seasonal decreases in risk of nest predation, we modeled nest predation of Dusky Flycatchers (Empidonax oberholseri) in northern California as a function of foliage phenology, energetic demand, developmental stage, conspecific nest density, food availability for nest predators, and nest predator abundance. Seasonal variation in the risk of nest predation was not associated with seasonal changes in energetic demand, conspecific nest density, or predator abundance. Instead, seasonal variation in the risk of nest predation was associated with foliage density (early, but not late, in the breeding season) and seasonal changes in food available to nest predators. Supplemental food provided to nest predators resulted in a numerical response by nest predators, increasing the risk of nest predation at nests that were near supplemental feeders. Our results suggest that seasonal changes in foliage density and factors associated with changes in food availability for nest predators are important drivers of temporal patterns in risk of avian nest predation. PMID:23776566

  15. Building hierarchical models of avian distributions for the State of Georgia

    USGS Publications Warehouse

    Howell, J.E.; Peterson, J.T.; Conroy, M.J.

    2008-01-01

    To predict the distributions of breeding birds in the state of Georgia, USA, we built hierarchical models consisting of 4 levels of nested mapping units of decreasing area: 90,000 ha, 3,600 ha, 144 ha, and 5.76 ha. We used the Partners in Flight database of point counts to generate presence and absence data at locations across the state of Georgia for 9 avian species: Acadian flycatcher (Empidonax virescens), brownheaded nuthatch (Sitta pusilla), Carolina wren (Thryothorus ludovicianus), indigo bunting (Passerina cyanea), northern cardinal (Cardinalis cardinalis), prairie warbler (Dendroica discolor), yellow-billed cuckoo (Coccyxus americanus), white-eyed vireo (Vireo griseus), and wood thrush (Hylocichla mustelina). At each location, we estimated hierarchical-level-specific habitat measurements using the Georgia GAP Analysis18 class land cover and other Geographic Information System sources. We created candidate, species-specific occupancy models based on previously reported relationships, and fit these using Markov chain Monte Carlo procedures implemented in OpenBugs. We then created a confidence model set for each species based on Akaike's Information Criterion. We found hierarchical habitat relationships for all species. Three-fold cross-validation estimates of model accuracy indicated an average overall correct classification rate of 60.5%. Comparisons with existing Georgia GAP Analysis models indicated that our models were more accurate overall. Our results provide guidance to wildlife scientists and managers seeking predict avian occurrence as a function of local and landscape-level habitat attributes.

  16. Tamarisk biocontrol using tamarisk beetles: Potential consequences for riparian birds in the southwestern United States

    USGS Publications Warehouse

    Paxton, E.H.; Theimer, T.C.; Sogge, M.K.

    2011-01-01

    The tamarisk beetle (Diorhabda spp.), a non-native biocontrol agent, has been introduced to eradicate tamarisk (Tamarix spp.), a genus of non-native tree that has become a dominant component of riparian woodlands in the southwestern United States. Tamarisk beetles have the potential to spread widely and defoliate large expanses of tamarisk habitat, but the effects of such a widespread loss of riparian vegetation on birds remains unknown. We reviewed literature on the effects of other defoliating insects on birds to investigate the potential for tamarisk beetles to affect birds positively or negatively by changing food abundance and vegetation structure. We then combined data on the temporal patterns of tamarisk defoliation by beetles with nest productivity of a wellstudied riparian obligate, the Southwestern Willow Flycatcher (Empidonax traillii extimus), to simulate the potential demographic consequences of beetle defoliation on breeding riparian birds in both the short and long term. Our results highlight that the effects of tamarisk biocontrol on birds will likely vary by species and population, depending upon its sensitivity to seasonal defoliation by beetles and net loss of riparian habitat due to tamarisk mortality. Species with restricted distributions that include areas dominated by tamarisk may be negatively affected both in the short and long term. The rate of regeneration and/or restoration of native cottonwoods (Populus spp.) and willows (Salix spp.) relative to the rate of tamarisk loss will be critical in determining the long-term effect of this large-scale ecological experiment. ?? The Cooper Ornithological Society 2011.

  17. Management by assertion: beavers and songbirds at Lake Skinner (Riverside County, California).

    PubMed

    Longcore, Travis; Rich, Catherine; Müller-Schwarze, Dietland

    2007-04-01

    Management of ecological reserve lands should rely on the best available science to achieve the goal of biodiversity conservation. "Adaptive Resource Management" is the current template to ensure that management decisions are reasoned and that decisions increase understanding of the system being managed. In systems with little human disturbance, certain management decisions are clear; steps to protect native species usually include the removal of invasive species. In highly modified systems, however, appropriate management steps to conserve biodiversity are not as readily evident. Managers must, more than ever, rely upon the development and testing of hypotheses to make rational management decisions. We present a case study of modern reserve management wherein beavers (Castor canadensis) were suspected of destroying habitat for endangered songbirds (least Bell's vireo, Vireo bellii pusillus, and southwestern willow flycatcher, Empidonax traillii extimus) and for promoting the invasion of an exotic plant (tamarisk, Tamarix spp.) at an artificial reservoir in southern California. This case study documents the consequences of failing to follow the process of Adaptive Resource Management. Managers made decisions that were unsupported by the scientific literature, and actions taken were likely counterproductive. The opportunity to increase knowledge of the ecosystem was lost. Uninformed management decisions, essentially "management by assertion," undermine the long-term prospects for biodiversity conservation. PMID:17318698

  18. Planned flooding and Colorado River riparian trade-offs downstream from Glen Canyon Dam, Arizona

    USGS Publications Warehouse

    Stevens, Lawrence E.; Ayers, T.J.; Bennett, J.B.; Christensen, K.; Kearsley, M.J.C.; Meretsky, V.J.; Phillips, A. M., III; Parnell, R.A.; Spence, J.; Sogge, M.K.; Springer, A.E.; Wegner, D.L.

    2001-01-01

    Regulated river restoration through planned flooding involves trade-offs between aquatic and terrestrial components, between relict pre-dam and novel post-dam resources and processes, and between management of individual resources and ecosystem characteristics. We review the terrestrial (wetland and riparian) impacts of a 1274 m3/s test flood conducted by the U.S. Bureau of Reclamation in March/April 1996, which was designed to improve understanding of sediment transport and management downstream from Glen Canyon Dam in the Colorado River ecosystem. The test flood successfully restored sandbars throughout the river corridor and was timed to prevent direct impacts to species of concern. A total of 1275 endangered Kanab ambersnail (Oxyloma haydeni kanabensis) were translocated above the flood zone at Vaseys Paradise spring, and an estimated 10.7% of the total snail habitat and 7.7% of the total snail population were lost to the flood. The test flood scoured channel margin wetlands, including potential foraging habitats of endangered Southwestern Willow Flycatcher (Empidonax traillii extimus). It also buried ground-covering riparian vegetation under >1 m of fine sand but only slightly altered woody sandbar vegetation and some return-current channel marshes. Pre-flood control efforts and appropriate flood timing limited recruitment of four common nonnative perennial plant species. Slight impacts on ethnobotanical resources were detected >430 km downstream, but those plant assemblages recovered rapidly. Careful design of planned flood hydrograph shape and seasonal timing is required to mitigate terrestrial impacts during efforts to restore essential fluvial geomorphic and aquatic habitats in regulated river ecosystems.

  19. A removal model for estimating detection probabilities from point-count surveys

    USGS Publications Warehouse

    Farnsworth, G.L.; Pollock, K.H.; Nichols, J.D.; Simons, T.R.; Hines, J.E.; Sauer, J.R.

    2002-01-01

    Use of point-count surveys is a popular method for collecting data on abundance and distribution of birds. However, analyses of such data often ignore potential differences in detection probability. We adapted a removal model to directly estimate detection probability during point-count surveys. The model assumes that singing frequency is a major factor influencing probability of detection when birds are surveyed using point counts. This may be appropriate for surveys in which most detections are by sound. The model requires counts to be divided into several time intervals. Point counts are often conducted for 10 min, where the number of birds recorded is divided into those first observed in the first 3 min, the subsequent 2 min, and the last 5 min. We developed a maximum-likelihood estimator for the detectability of birds recorded during counts divided into those intervals. This technique can easily be adapted to point counts divided into intervals of any length. We applied this method to unlimited-radius counts conducted in Great Smoky Mountains National Park. We used model selection criteria to identify whether detection probabilities varied among species, throughout the morning, throughout the season, and among different observers. We found differences in detection probability among species. Species that sing frequently such as Winter Wren (Troglodytes troglodytes) and Acadian Flycatcher (Empidonax virescens) had high detection probabilities (~90%) and species that call infrequently such as Pileated Woodpecker (Dryocopus pileatus) had low detection probability (36%). We also found detection probabilities varied with the time of day for some species (e.g. thrushes) and between observers for other species. We used the same approach to estimate detection probability and density for a subset of the observations with limited-radius point counts.

  20. Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures.

    PubMed

    Friggens, Megan M; Finch, Deborah M

    2015-01-01

    Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy's warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be used

  1. Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures

    PubMed Central

    Friggens, Megan M.; Finch, Deborah M.

    2015-01-01

    Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy’s warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be

  2. ADVANCED INTRAMOLECULAR DIELS-ALDER STUDY TOWARD THE SYNTHESIS OF (-)-MORPHINE: STRUCTURE CORRECTION OF A PREVIOUSLY REPORTED DIELS-ALDER PRODUCT. (R826113)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  3. Synthesis and Evaluation of 5-Lipoxygenase Translocation Inhibitors from Acylnitroso Hetero-Diels-Alder Cycloadducts†

    PubMed Central

    Bolger, Joshua K.; Tian, Wen; Wolter, William R.; Cho, Wonhwa; Suckow, Mark A.

    2012-01-01

    Acylnitroso cycloadducts have proven to be valuable intermediates in the syntheses of a plethora of biologically active molecules. Recently, organometallic reagents were shown to open bicyclic acylnitroso cycloadducts and, more interestingly, the prospect of highly regioselective openings was raised. This transformation was employed in the synthesis of a compound with excellent inhibitory activity against 5-lipoxygenase ((±)-4a, IC50 51 nM), an important mediator of inflammation intimately involved in a number of disease states including asthma and cancer. Optimization of the copper-mediated organometallic ring opening reaction was accomplished allowing the further exploration of the biological activity. Synthesis of a number of derivatives with varying affinity for metal binding as well as pendant groups in a range of sizes was accomplished. Analogues were tested in a whole cell assay which revealed a subset of the compounds to be inhibitors of enzyme translocation, a mode of action not previously known and, potentially, extremely important for better understanding of the enzyme and inhibitor development. Additionally, the lead compound was tested in vivo in an established colon cancer model and showed very encouraging anti-tumorogenic properties. PMID:21365098

  4. FATE AND EFFECTS OF PHOSPHORUS ADDITIONS IN SOILS UNDER N2-FIXING RED ALDER

    EPA Science Inventory

    Soil phosphorus (P) dynamics are controlled by the interaction of geochemical, biochemical and biological processes, and changing species composition or management may alter the relative importance of these processes. We examined the role of these processes in two plantations of...

  5. AQUEOUS AZA-DIELS-ALDER REACTIONS CATALYZED BY LANTHANIDE(III) TRIFLUOROMETHANESULFONATES. (R826123)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  6. Holocene changes of Andean alder (Alnus acuminata) in highland Ecuador and Peru

    NASA Astrophysics Data System (ADS)

    Weng, Chengyu; Bush, Mark B.; Chepstow-Lusty, Alex J.

    2004-10-01

    Fossil pollen records from the high Andes of Ecuador and northern Peru show that Alnus increased in abundance at most sites following warming associated with the onset of the Holocene. The peak of Alnus pollen abundance occurred between 9000 and 5000 yr BP. However, between 6500 and 4500 yr BP, the abundance of Alnus pollen declined markedly in all of the available records, including sites both within and above its modern distribution range. Even though the beginning of this decline may have been time-transgressive, the greatest reduction of Alnus abundance is consistent between sites, occurring at ca. 4500 yr BP. This synchrony suggests that one or more factors affected Alnus populations across the whole region. A cooler climate, droughts and anthropogenic activity are discussed as possible causes on such a large spatial scale. A scenario is suggested in which the early-mid Holocene increase in Alnus populations was curtailed by droughts, and then further impacted by major regional cooling from ca. 5000 yr BP onwards. Human agricultural activities in this wetter interval may also have delayed Alnus recovery. A resurgence of Alnus populations at 2000-1000 yr BP may have been a response to regional warming coupled with human land management practices. Copyright

  7. Multistep Synthesis of a Terphenyl Derivative Showcasing the Diels-Alder Reaction

    ERIC Educational Resources Information Center

    Davie, Elizabeth A. Colby

    2015-01-01

    An adaptable multistep synthesis project designed for the culmination of a second-year organic chemistry laboratory course is described. The target compound is a terphenyl derivative that is an intermediate in the synthesis of compounds used in organic light-emitting devices. Students react a conjugated diene with dimethylacetylene dicarboxylate…

  8. Red Alder (Alnus rubra) Distribution Influences Nitrate Discharge to Coastal Estuaries: Comparison of Two Oregon Watersheds

    EPA Science Inventory

    We determined nutrient export from the Yaquina and Alsea Rivers as part of a larger program for evaluating nutrient sources to coastal waters. The Yaquina and Alsea data indicated that one river typically contained twice the amount of dissolved nitrate-N, although temperature, co...

  9. Discussion of Alfred Alder's preface to The Diary of Vaslav Nijinsky.

    PubMed

    Ansbacher, H L

    1981-07-01

    In his preface to The Diary of Vaslav Nijinsky, Alfred Adler (1) found his theory of the dynamics of schizophrenia supported in the Diary, (2) alluded to Nijinsky's prepsychotic personality, and (3) briefly touched on the possibility and conditions of recovery. To add to the understanding of Adler's "Preface," this discussion (1) expands his theory of schizophrenia, (2) gives some concrete data of Nijinsky's prepsychotic personality, (3) describes two episodes of recovery subsequent to the "Preface," and (4) introduces an important aspect of Adler's theory, which he had to omit out of consideration for Nijinsky's wife, Romola-namely, her role in her husband's disorder. With the larger theoretical and historical context established. Adler's "Preface" can be appreciated for its predictive validity. PMID:7018451

  10. Alder Expansion as a Coastal Warming Signal - Linking Coastal Alaskan Carbon to Vegetation Change with Climate

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Moy, C. M.; McGeachy, A.

    2014-12-01

    Corser Bog (60.5296364oN, 145.453858oW), 21 km east of Cordova, AK is a sphagnum-dominated peatland 42 m asl. adjacent to Sheridan Glacier and the Copper River Delta. Deglaciation at 11.5 ka began with shallow pond deposition, reflecting regional warmth with the pioneers Alnus crispa subsp. sinuata, Salix, and ferns colonizing the fresh, mineral soils on the landscape. Continued early Holocene warming/melting of glaciers led to the foundation species Alnus dominance and peatland formation, surrounded by shrubs such as Rubus spectabilis, Sambucus racemosa, and wetland species such as Myrica gale and Potentilla palustris. As Sphagnum peat accumulated, the highest rates of carbon accumulation for a few centuries are represented at 50 g/m2/a, similar to short-term very high rates in the early Holocene throughout the circumboreal region but varying within the early Holocene due to development of local wet, bryophytic environments. A shift to sedge peat regionally along the South-Central Alaskan coast 7.6 - 3.7 ka is paralleled by a more evaporative, drier climate with Rhododendron groenlandicum presence, lower carbon accumulation (13 g/m2/a), and minimal macrofossil preservation, which is paralleled regionally in coastal muskegs both to the northwest and southeast and by a hiatus in a nearby lake record. A cooler, moister climate is evident in Corser Bog with the shift to Sphagnum peat at 3.7 ka, regional shifts from sedge to Sphagnum peat throughout the entire coastline from Yakutat to Girdwood, AK and the demonstration of glacial advances in the region. Alnus pollen markedly increases to 60% in the uppermost sample, indicative of a major signal for glacial recession in this region.

  11. ISOPRENE/METHYL ACRYLATE DIELS-ALDER REACTION IN SUPERCRITICAL CARBON DIOXIDE. (R822721C640)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. Synthesis of novel plant oil derivatives: Furan and Diels-Alder reaction products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant oils are useful sustainable raw materials for the development of new chemical products. In this work epoxidized soybean oil was treated with different acids, and variable amounts of furan structures were produced from the epoxidized linoleate moiety. From process studies, the highest yields of...

  13. An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

    PubMed Central

    Ma, Zhiyuan; Ni, Feng; Woo, Grace H C; Lo, Sie-Mun; Roveto, Philip M; Schaus, Scott E

    2012-01-01

    Summary Intramolecular inverse electron demand cycloadditions of isatin-derived 1,2,4-triazines with acetylenic dienophiles tethered by amidations or transesterifications proceed in excellent yields to produce lactam- or lactone-fused α-carbolines. Beginning with various isatins and alkynyl dienophiles, a pilot-scale library of eighty-eight α-carbolines was prepared by using this robust methodology for biological evaluation. PMID:23015831

  14. Chiral holmium complex-catalyzed Diels-Alder reaction of silyloxyvinylindoles: stereoselective synthesis of hydrocarbazoles.

    PubMed

    Harada, Shinji; Morikawa, Takahiro; Nishida, Atsushi

    2013-10-18

    The catalytic and asymmetric cycloaddition between 3-[1-(silyloxy)vinyl]indoles and electron-deficient olefins gave substituted hydrocarbazoles in up to 99% yield and 94% ee. This reaction was catalyzed by a novel chiral holmium(III) complex. Alkylation of the cycloadduct gave a tricyclic compound with four continuous chiral centers, one of which was a quaternary carbon. PMID:24079531

  15. Catalysis of the Aza-Diels-Alder Reaction by Hydrogen and Halogen Bonds.

    PubMed

    Nziko, Vincent de Paul N; Scheiner, Steve

    2016-03-18

    The combination of H2C═NH and cis-1,3-butadiene to form a six-membered ring was examined by quantum calculations. The energy barrier for this reaction is substantially lowered by the introduction of an imidazolium catalyst with either a H or halogen (X) atom in the 2-position, which acts via a H or halogen bond to the N atom of the imine, respectively. X = I has the largest effect, and Cl the smallest; Br and H are roughly equivalent. The catalyst retards the formation of the incipient N-C bond from imine to diene while simultaneously accelerating the C-C bond formation. The energy of the π* LUMO of the imine is lowered by the catalyst, which thereby enhances charge transfer from the diene to the imine. Assessment of free energies suggests catalytic rate acceleration by as much as 4-6 orders of magnitude. PMID:26907727

  16. Evidence contrary to the accepted Diels-Alder mechanism in the thermal modification of vegetable oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A transesterified oleochemical product has been made using two routes. Soybean oil was thermally polymerized anaerobically at 330 deg C. and the material was then transesterified using base catalyst and methanol. Alternatively, a similar product can be obtained by heating methyl linoleate to the sam...

  17. 76 FR 50541 - Endangered and Threatened Wildlife and Plants; Designation of Revised Critical Habitat for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-15

    ... flycatcher critical habitat rule published in the Federal Register on October 19, 2005 (70 FR 60886); our October 12, 2004, proposed critical habitat rule (69 FR 60706); the Southwestern Willow Flycatcher... July 22, 1997 (62 FR 39129), and August 20, 1997 (62 FR 44228); the final flycatcher listing rule...

  18. Seasonal differences in riparian consumer diet and insect communities in an Oregon Coast Range watershed food web.

    NASA Astrophysics Data System (ADS)

    Robillard, A.; Li, J.

    2005-05-01

    In riparian areas, terrestrial and aquatic habitats overlap creating zones where they interact as an aquatic-terrestrial interface. This coupling allows energy to move between systems and generates intertwining food webs. Thus, vertebrate riparian consumers, such as fish or birds, potentially have alternative prey from sources external to their habitats. The purpose of our study was to explore this reciprocal exchange in an alder dominated riparian forest of the Oregon Coast Range. Diet samples were collected from birds and fish in summer and fall 2003 with a suite of insect samples at Honeygrove Creek and two of its small tributaries. In a comparison of emerging aquatic insects and flying terrestrial insects during June and again in September, we detected seasonal differences in terrestrial and aquatic insects available to riparian consumers. Despite this availability of externally derived prey, fish depended more on resources derived from within their respective habitats during summer. Cutthroat trout (Oncorhynchus clarkii) and Coho salmon (Oncorhynchus kitsutch) ate more juvenile aquatic than adult aquatic or terrestrial insects. During fall, the same pattern was exhibited by Coho but Cutthroat trout appeared to consume a slightly greater number of terrestrial insects. The preliminary analysis of bird diet samples from commonly encountered species such as, Swainson's thrush, Song Sparrow, and Pacific-slope Flycatcher, showed more terrestrial derived prey in their diets than aquatic during the summer sampling season.

  19. Factors affecting songbird nest survival in riparian forests in a Midwestern agricultural landscape

    USGS Publications Warehouse

    Peak, R.G.; Thompson, F. R., III; Shaffer, T.L.

    2004-01-01

    We investigated factors affecting nest success of songbirds in riparian forest and buffers in northeastern Missouri. We used an information-theoretic approach to determine support for hypotheses concerning effects of nest-site, habitat-patch, edge, and temporal factors on nest success of songbirds in three narrow (55DS95 m) and three wide (400DS530 m) riparian forests with adjacent grasslandDSshrub buffer strips and in three narrow and three wide riparian forests without adjacent grasslandDSshrub buffer strips. We predicted that temporal effects would have the most support and that habitat-patch and edge effects would have little support, because nest predation would be great across all sites in the highly fragmented, predominantly agricultural landscape. Interval nest success was 0.404, 0.227, 0.070, and 0.186, respectively, for Gray Catbird (Dumetella carolinensis), Northern Cardinal (Cardinalis cardinalis), Indigo Bunting (Passerina cyanea), and forest interior species pooled (Acadian Flycatcher [Empidonax virescens], Wood Thrush [Hylocichla mustelina], Ovenbird [Seiurus aurocapillus], and Kentucky Warbler [Oporornis formosus]). The effect of nest stage on nest success had the most support; daily nest success for Gray Catbird and Indigo Bunting were lowest in the laying stage. We found strong support for greater nest success of Gray Catbird in riparian forests with adjacent buffer strips than in riparian forests without adjacent buffer strips. Patch width also occurred in the most supported model for Gray Catbird, but with very limited support. The null model received the most support for Northern Cardinal. Riparian forests provided breeding habitat for areas sensitive forest species and grassland-shrub nesting species. Buffer strips provided additional breeding habitat for grassland-shrub nesting species. Interval nest success for Indigo Bunting and area-sensitive forest species pooled, however, fell well below the level that is likely necessary to balance

  20. Factors affecting songbird nest survival in riparian forests in a midwestern agricultural landscape

    USGS Publications Warehouse

    Peak, R.G.; Thompson, F. R., III; Shaffer, T.L.

    2004-01-01

    We investigated factors affecting nest success of songbirds in riparian forest and buffers in northeastern Missouri. We used an information-theoretic approach to determine support for hypotheses concerning effects of nest-site, habitat-patch, edge, and temporal factors on nest success of songbirds in three narrow (55-95 m) and three wide (400-530 m) riparian forests with adjacent grassland-shrub buffer strips and in three narrow and three wide riparian forests without adjacent grassland-shrub buffer strips. We predicted that temporal effects would have the most support and that habitat-patch and edge effects would have little support, because nest predation would be great across all sites in the highly fragmented, predominantly agricultural landscape. Interval nest success was 0.404, 0.227, 0.070, and 0.186, respectively, for Gray Catbird (Dumetella carolinensis), Northern Cardinal (Cardinalis cardinalis), Indigo Bunting (Passerina cyanea), and forest interior species pooled (Acadian Flycatcher [Empidonax virescens], Wood Thrush [Hylocichla mustelina], Ovenbird [Seiurus aurocapillus], and Kentucky Warbler [Oporornis formosus]). The effect of nest stage on nest success had the most support; daily nest success for Gray Catbird and Indigo Bunting were lowest in the laying stage. We found strong support for greater nest success of Gray Catbird in riparian forests with adjacent buffer strips than in riparian forests without adjacent buffer strips. Patch width also occurred in the most-supported model for Gray Catbird, but with very limited support. The null model received the most support for Northern Cardinal. Riparian forests provided breeding habitat for area-sensitive forest species and grassland-shrub nesting species. Buffer strips provided additional breeding habitat for grassland-shrub nesting species. Interval nest success for Indigo Bunting and area-sensitive forest species pooled, however, fell well below the level that is likely necessary to balance juvenile

  1. Landscape structure in a managed forest mosaic of the Southern Appalachian Mountains and its influence on songbirds and small mammals

    NASA Astrophysics Data System (ADS)

    Leimgruber, Peter

    Forests in the Appalachian Mountains have been severely affected by logging in the past and little old-growth is left. The remaining forests form a heterogeneous mosaic of different forest successions. A concern for conservation is how additional logging will alter the mosaic and its fauna. I studied the effects of logging on the landscape mosaic and how changes in the landscape structure influence small mammals and birds in the George Washington National Forest, Virginia. My dissertation also included research on how to improve techniques for landscape ecological studies, such as roadside monitoring of birds and mapping of forest resources using remote sensing and Geographic Information Systems (GIS). Because of the scale dependency of landscape-ecological relationships, I investigated how landscape structure in the forest mosaic changes with increasing scales. I determined threshold scales at which structure changed markedly. After establishing a baseline, I examined how logging affected the intensity and location of such thresholds. I found thresholds in landscape structure exist at 400-, 500-, and 800-m intervals from the outer edge of the cut. While logging did not change threshold location and intensity for global landscape indices, such as dominance and contagion, thresholds for focal indices, such as mean patch size and percent cover for early-successional forest, changed markedly. Using GIS, I determined how logging affected small mammals and birds at the landscape scale. I divided the landscape into three zones (zone 1, inside logged areas; zone 2, 20--400 m from logged areas; zone 3, 1000--1500 m from logged areas). Logging changed species presence and richness more drastically in close proximity of cuts than on the landscape and influenced birds more strongly than mammals. In the cuts, edge-adapted birds, such as the indigo bunting (Passerina cyanea), replaced forest interior species, such as the Acadian flycatcher (Empidonax virescens). Most

  2. Design and preparation of novel polyarylene ether materials based on Diels-Alder reaction as the crosslinker for electrooptical modulators

    NASA Astrophysics Data System (ADS)

    Gao, Wu; Hou, Wenjun; Zhen, Zhen; Liu, Xinhou; Liu, Jialei; Fedorchuk, A. A.; Czaja, P.

    2016-07-01

    Novel crosslinkable organic linear electro-optical (EO) material based on polyarylene ether as the main chain host polymer was designed and prepared. The host polymer with rigid aromatic has demonstrated a good compatibility with the guest chromophore. Long side chain with anthracene ensured the crosslinkable reaction and appropriate glass transition temperature of the host polymer (55 °C). The EO r33 tensor coefficient for this novel EO material has been magnitude of 66 pm/V at 1310 nm and the excellent long term stability at 85 °C. These parameters permit to consider their application in fabrication of organic electro optical devices. The semi-empirical and DFT quantum chemical simulations were performed for 4 principal chromophores to clarify a role of cross-linker in the enhancement of the ground state dipole moments and effective hyperpolarizabilities.

  3. Diels-Alder Trapping of Photochemically Generated o-Xylenols: Application in the Synthesis of Novel Organic Molecules and Polymers

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.

    2003-01-01

    Bis(o-xylenol) equivalents are useful synthetic intermediates in the construction of polymers and hydroxyl substituted organic molecules which can organize by hydrogen bonded self-assembly into unique supramolecular structures. These polymers and supramolecular materials have potential use as coatings and thin films in aerospace, electronic and biomedical applications.

  4. Energy storage capacity of reversible liquid-phase Diels Alder reaction between maleic anhydride and 2- methyl furan

    SciTech Connect

    Sparks, B.G.; Poling, B.E.

    1983-07-01

    Calorimetry was used to determine the heat of reaction and equilibrium constant at 318 K for the reaction between maleic anhydride (A) and 2-methyl furan (B). The values were-60 kJ/gmol and 614 cm/sup 3//gmol, respectively. The motivation for this work was to find a single phase-reacting system that could be used to store solar energy. Thus, the energy storage capacity was calculated for a mixture of A and B, both initially at 7 kmol/m/sup 3/, in dioxane. The maximum apparent heat capacity of 7.37 J/cm/sup 3/ X K occurred at 334 K. This maximum value is 76% higher than the heat capacity of pure water.

  5. Treatment of glioblastoma multiforme cells with temozolomide-BioShuttle ligated by the inverse Diels-Alder ligation chemistry

    PubMed Central

    Braun, Klaus; Wiessler, Manfred; Ehemann, Volker; Pipkorn, Ruediger; Spring, Herbert; Debus, Juergen; Didinger, Bernd; Koch, Mario; Muller, Gabriele; Waldeck, Waldemar

    2008-01-01

    Recurrent glioblastoma multiforme (GBM), insensitive against most therapeutic interventions, has low response and survival rates. Temozolomide (TMZ) was approved for second-line therapy of recurrent anaplastic astrocytoma. However, TMZ therapy in GBM patients reveals properties such as reduced tolerability and inauspicious hemogram. The solution addressed here concerning GBM therapy consolidates and uses the potential of organic and peptide chemistry with molecular medicine. We enhanced the pharmacologic potency with simultaneous reduction of unwanted adverse reactions of the highly efficient chemotherapeutic TMZ. The TMZ connection to transporter molecules (TMZ-BioShuttle) was investigated, resulting in a much higher pharmacological effect in glioma cell lines and also with reduced dose rate. From this result we can conclude that a suitable chemistry could realize the ligation of pharmacologically active, but sensitive and highly unstable pharmaceutical ingredients without functional deprivation. The TMZ-BioShuttle dramatically enhanced the potential of TMZ for the treatment of brain tumors and is an attractive drug for combination chemotherapy. PMID:19920915

  6. Extension of the PNA world by functionalized PNA monomers eligible candidates for inverse Diels Alder Click Chemistry

    PubMed Central

    Wiessler, Manfred; Waldeck, Waldemar; Pipkorn, Ruediger; Kliem, Christian; Lorenz, Peter; Fleischhacker, Heinz; Hafner, Manuel; Braun, Klaus

    2010-01-01

    Progress in genome research led to new perspectives in diagnostic applications and to new promising therapies. On account of their specificity and sensitivity, nucleic acids (DNA/RNA) increasingly are in the focus of the scientific interest. While nucleic acids were a target of therapeutic interventions up to now, they could serve as excellent tools in the future, being highly sequence-specific in molecular diagnostics. Examples for imaging modalities are the representation of metabolic processes (Molecular Imaging) and customized therapeutic approaches (“Targeted Therapy”). In the individualized medicine nucleic acids could play a key role; this requires new properties of the nucleic acids, such as stability. Due to evolutionary reasons natural nucleic acids are substrates for nucleases and therefore suitable only to a limited extent as a drug. To use DNA as an excellent drug, modifications are required leading e.g. to a peptide nucleic acid (PNA). Here we show that an easy substitution of nucleobases by functional molecules with different reactivity like the Reppe anhydride and pentenoic acid derivatives is feasible. These derivatives allow an independent multi-ligation of functionalized compounds, e.g. pharmacologically active ones together with imaging components, leading to local concentrations sufficient for therapy and diagnostics at the same time. The high chemical stability and ease of synthesis could enhance nucleic chemistry applications and qualify PNA as a favourite for delivery. This system is not restricted to medicament material, but appropriate for the development of new and highly efficient drugs for a sustainable pharmacy. PMID:20617125

  7. LANDSCAPE CHARACTERISTICS AND HIGH STREAM NITROGEN IN THE OREGON COAST RANGE: RED ALDER COMPLICATES USE OF NUTRIENT CRITERIA

    EPA Science Inventory

    Stream nitrogen concentrations are variable and often high in the Oregon Coast Range, uncharacteristic for a predominantly forested region. We compiled stream nitrogen data and GIS-derived landscape characteristics in order to examine variation in nitrogen across the region. In s...

  8. Nest survival of forest birds in the Mississippi Alluvial Valley

    USGS Publications Warehouse

    Twedt, D.J.; Wilson, R.R.; Henne-Kerr, J.L.; Hamilton, R.B.

    2001-01-01

    vimns, 7%), eastern towhee (14%), indigo bunting (14%), and northern cardinal (17%) did not differ from nest success in cottonwood plantations that were coppiced from root sprouts following pulpwood harvest. Within bottomland hardwood forests, uneven-aged group-selection timber harvest reduced the combined daily nest survival of all species from 0.958 to 0.938, which reduced nest success by about 14%. Specifically, timber harvest reduced nest success of species that nest in the forest midstory and canopy, such as Acadian flycatcher (Empidonax virescens)--from 32% before harvest to 14% after harvest. Conversely, those species that nest primarily in the shrubby understory--such as northern cardinal--were not affected by timber harvest and maintained an overall nest success of about 33%. Thus, birds nesting in the understory of bottomland hardwood forests are not adversely impacted by selective timber harvest, but there is a short-term reduction in nest success for birds that nest in the canopy and midstory.

  9. Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

    PubMed Central

    Pipic, Alma; Zeller, Matthias; Tsetsakos, Panagiota

    2013-01-01

    Summary The tin(IV)-catalyzed reaction of β-nitrostyrene with (E)-3-methyl-1,3-pentadiene in toluene afforded two major nitronic ester cycloadducts in 27% and 29% yield that arise from the reaction at the less substituted diene double bond. Also present were four cycloadducts from the reaction at the higher substituted diene double bond, two of which were the formal cycloadducts of (Z)-3-methyl-1,3-pentadiene. A Friedel–Crafts alkylation product from the reaction of the diene, β-nitrostyrene, and toluene was also obtained in 10% yield. The tin(IV)-catalyzed reaction of β-nitrostyrene with (Z)-3-methyl-1,3-pentadiene in dichloromethane afforded four nitronic ester cycloadducts all derived from the reaction at the higher substituted double bond. One cycloadduct was isolated in 45% yield and two others are formal adducts of the E-isomer of the diene. The product formation in these reactions is consistent with a stepwise mechanism involving a zwitterionic intermediate. The initially isolated nitronic ester cycloadducts underwent tin(IV)-catalyzed interconversion, presumably via zwitterion intermediates. Cycloadducts derived from the reaction at the less substituted double bond of (E)-3-methyl-1,3-pentadiene underwent a [3,3]-sigmatropic rearrangement on heating to afford 4-nitrocyclohexenes. Cycloadducts derived from the reaction at the higher substituted diene double bond of either diene failed to undergo a thermal rearrangement. Rates and success of the rearrangement are consistent with a concerted mechanism possessing a dipolar transition state. An initial assessment of substituent effects on the rearrangement process is presented. PMID:24204426

  10. Identifying important spatial and temporal scales and patterns of soil properties in a tidal saltmarsh situated in a mixed red alder and Douglas fir watershed

    EPA Science Inventory

    Sea level rise is expected to drive a loss in salt marsh area and a change in marsh habitat composition, potentially leading to changes in the nitrogen source/sink dynamics of these systems. Estuaries in the Pacific Northwest might be particularly vulnerable to the effect of sal...

  11. Metabolic Profiling of Major Vitamin D Metabolites Using Diels-Alder Derivatization and Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biologically active forms of vitamin D are important analytical targets both in research and in clinical practice. Typically, each of the vitamin D metabolites is best analyzed by individual assay. However, current LC-MS technologies allow simultaneous metabolic profiling of entire biochemical pathw...

  12. Use of a Monoclonal Antibody-Based Immunoassay for the Detection and Quantification of Heliscus lugdunensis Colonizing Alder Leaves and Roots.

    PubMed

    Bermingham, S.; Dewey, F.M.; Fisher, P.J.; Maltby, L.

    2001-12-01

    A genus-specific monoclonal antibody, NG-CF10, raised in a previous study to the fungal pathogen Nectria galligena, was found to recognize the aquatic hyphomycete Heliscus lugdunensis (anamorph) and its teleomorph Nectria lugdunensis. Using this MAb in a plate trapped antigen- ELISA we could detect and determine the biomass of Heliscus lugdunensis in mixed assemblages in both naturally occurring and artificially inoculated leaves and roots of Alnus glutinosa trees. Initial studies indicate that the biomass associated with naturally occurring leaf material is significantly lower than that recorded with laboratory inoculated leaves, suggesting that biomass production is limited in the natural environment. Significantly lower biomass was associated with roots when compared with leaf material, which supports the proposition that rather than a major substrate for the growth of aquatic hyphomycetes, roots act as a refugium for fungal growth. PMID:12024233

  13. Iptycene synthesis: A new method for attaching a 2,3-anthracene moiety to the 9,10-positions of another anthracene moiety - Exceptional conditions for a Lewis acid catalyzed Diels-Alder reaction

    NASA Technical Reports Server (NTRS)

    Chen, Yong-Shing; Hart, Harold

    1989-01-01

    An efficient three-step method for appending a 2,3-anthracene moiety to the 9,10-positions of an existing anthracene moiety is described. The first step uses excess 1,4-anthraquinone (3 equiv) and aluminum chloride (6 equiv) to obtain the anthracene-quinone cycloadduct (omission of the AlCl3 resulted in no adduct). The resulting diketone was reduced to the corresponding diol (excess LiAlH4), which was dehydrated to the arene with phosphorus oxychloride and pyridine. Specific examples include the preparation of heptipycene 8 from pentiptycene 6 (66 percent overall yield) and a similar conversion of 8 to the noniptycene 13 (75 percent overall yield). The methodology led to a markedly improved synthesis of tritriptycene 9 and the first synthesis of undecaiptycene 14.

  14. Protective and therapeutic effects of an extract mixture of alder tree, labiate herb, milk thistle green bean-rice bran fermentation, and turnip against ethanol-induced toxicity in the rat

    PubMed Central

    Baek, Min-Won; Seok, Seung-Hyeok; Lee, Hui-Young; Kim, Dong Jae; Lee, Byoung-Hee; Ahn, Young-Tae; Lim, Kwang-Sei; Huh, Chul-Sung

    2008-01-01

    An herbal extract mixture and yogurt added to the herbal extract mixture were tested for their protective and therapeutic effects on ethanol-induced liver injury. The herbal extract mixture, yogurt and commercial drugs were used for treatment for two weeks prior to administering a single oral dose of ethanol (3 g/kg body weight). The herbal extract mixture and yogurt added to the herbal extract mixture were found to provide protection against ethanol-induced toxicity comparable to the commercial drug treatment, according to the serum and histopathological analysis. It was also shown that co-treatment with herbal extract mixture and yogurt against a triple oral dose of ethanol (2 g/kg body weight, over one week) provided protection against ethanol toxicity. After the initial set of experiments, the herbal extract mixture and yogurt treatments were extended for three more weeks. When compared to the positive control, further treatment with both the herbal extract and yogurt significantly reduced liver injury and resulted in a lower grade of lipid deposition. PMID:18296886

  15. Pedagogical Comparison of Five Reactions Performed under Microwave Heating in Multi-Mode versus Mono-Mode Ovens: Diels-Alder Cycloaddition, Wittig Salt Formation, E2 Dehydrohalogenation to Form an Alkyne, Williamson Ether Synthesis, and Fischer Esterification

    ERIC Educational Resources Information Center

    Baar, Marsha R.; Gammerdinger, William; Leap, Jennifer; Morales, Erin; Shikora, Jonathan; Weber, Michael H.

    2014-01-01

    Five reactions were rate-accelerated relative to the standard reflux workup in both multi-mode and mono-mode microwave ovens, and the results were compared to determine whether the sequential processing of a mono-mode unit could provide for better lab logistics and pedagogy. Conditions were optimized so that yields matched in both types of…

  16. Abundance of Alnus incana ssp. rugosa in Adirondack Mountain shrub wetlands and its influence on inorganic nitrogen.

    PubMed

    Kiernan, B D; Hurd, T M; Raynal, D J

    2003-01-01

    The purpose of this research was to determine the abundance of the nitrogen-fixing shrub, Alnus incana ssp. rugosa (speckled alder), in shrub wetlands of the Adirondack Mountain region of New York State and to determine whether its abundance affects the concentration or accumulation of inorganic nitrogen in wetland substrates. Alder/willow wetlands are the second most common wetland type in the Adirondack region. The Adirondack Park Agency's digital GIS database of wetland types was used to determine the areal extent of alder/willow wetlands in the Adirondacks. Randomly selected wetlands were sampled to determine the size and abundance of alder. Alder densities averaged approximately 7000 stems ha(-1) and alder was present in 75% of the wetlands. As an indication of short-term accumulation of NO(3-) and NH4(+) in wetland substrates, ion exchange resins were used to sample ground water in high and low alder density wetlands as well as from wetlands lacking alder and dominated by conifers. Additionally, NO(3-) and NH(4+) concentrations in ground water samples were measured. NH(4+) accumulation levels from exchange resins were low for all wetland types while groundwater NH(4+) concentration was highest in the low-density alder sites. Wetlands with high alder density had approximately six times higher NO(3-) accumulation than other wetlands. Substrate groundwater NO(3-) concentrations in wetlands of high-density alder exceeded by three times levels in low or no alder wetlands, showing the importance of alder to local N budgets. To assess the recovery of shrub wetlands from acidification, future studies should determine the fate of fixed N in wetland systems. PMID:12667762

  17. Nasal mites from birds of a Guatemalan cloud forest (Acarina: rhinonyssidae)

    SciTech Connect

    Spicer, G.S.

    1984-01-01

    A survey of the nasal mites from Guatemalan cloud forest birds is reported. Seventy-eight birds, representing 10 families and 18 species, were examined. Prevalence of infection was 24%. Two new species are described: Sternostoma darlingi from Mitrephanes phaeocercus (Tyrannidae) and S. pencei from Empidonax flavescens (Tyrannidae). New host records are reported for S. priangae from Chlorospingus opthalmicus (Thraupidae), S. hutsoni from Catharus dryas (Turdidae), Ptilonyssus sairae from Chlorospingus opthalmicus (Thraupidae), and Myioborus miniatus (Parulidae), P. euroturdi from Catharus dryas (Turdidae), P. tyrannus from Empidonax flavescens and Mitrephanes phaeocercus (both Tyannidae), and Tinaminyssus ixoreus from Catharus dryas (Turdidae). The subspecies Ptilonyssus euroturdi mimicola Fain and Hyland is synonymized with the nominate subspecies. Data are presented to suggest that the Rhinonyssidae may be a polyphyletic assemblage. 35 references, 12 figures, 1 table.

  18. Total synthsis of (+)-ambuic acid: α-bromination with 1,2-dibromotetrachloroethane.

    PubMed

    Jung, Sun Hee; Hwang, Geum-Sook; Lee, Sung Il; Ryu, Do Hyun

    2012-03-01

    Total synthesis of (+)-ambuic acid has been accomplished from the readily available stereocontrolled Diels-Alder adduct of cyclopentadiene and iodo-1,4-benzoquinone monoketal through an efficient series of steps. A new method for the highly commendable synthesis of α-brominated Diels-Alder adduct is described. PMID:22280015

  19. Great price spike of '93: An analysis of lumber and stumpage prices in the pacific northwest. Forest Service research paper

    SciTech Connect

    Sohngen, B.L.; Haynes, R.W.

    1994-08-01

    The report includes prices for red alder hardwood logs which are published and analyzed for reliability consistency, and robustness. Timberland managers can use these prices to make decisions regarding land management. They show that values for red alder logs have been increasing steadily for the past 11 years.

  20. 77 FR 41147 - Endangered and Threatened Wildlife and Plants; Designation of Revised Critical Habitat for the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-12

    ... the Federal Register on August 15, 2011 (76 FR 50542). We are accepting comments regarding additional... flycatcher critical habitat designation (70 FR 60886, October 19, 2005) and lands to be newly considered for... complete and accurate. If you submitted comments or information on the proposed revised rule (76 FR...

  1. 78 FR 343 - Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Southwestern...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-03

    ... analysis and draft environmental assessment in the Federal Register on July 12, 2012 (77 FR 41147... seq.) on February 27, 1995 (60 FR 10694). On July 22, 1997, we published a final critical habitat designation for the flycatcher along 964 river km (599 river mi) in Arizona, California, and New Mexico (62...

  2. Females discriminate against heterospecific sperm in a natural hybrid zone.

    PubMed

    Cramer, Emily R A; Ålund, Murielle; McFarlane, S Eryn; Johnsen, Arild; Qvarnström, Anna

    2016-08-01

    When hybridization is maladaptive, species-specific mate preferences are selectively favored, but low mate availability may constrain species-assortative pairing. Females paired to heterospecifics may then benefit by copulating with multiple males and subsequently favoring sperm of conspecifics. Whether such mechanisms for biasing paternity toward conspecifics act as important reproductive barriers in socially monogamous vertebrate species remains to be determined. We use a combination of long-term breeding records from a natural hybrid zone between collared and pied flycatchers (Ficedula albicollis and F. hypoleuca), and an in vitro experiment comparing conspecific and heterospecific sperm performance in female reproductive tract fluid, to evaluate the potential significance of female cryptic choice. We show that the females most at risk of hybridizing (pied flycatchers) frequently copulate with multiple males and are able to inhibit heterospecific sperm performance. The negative effect on heterospecific sperm performance was strongest in pied flycatcher females that were most likely to have been previously exposed to collared flycatcher sperm. We thus demonstrate that a reproductive barrier acts after copulation but before fertilization in a socially monogamous vertebrate. While the evolutionary history of this barrier is unknown, our results imply that there is opportunity for it to be accentuated via a reinforcement-like process. PMID:27312694

  3. A Field Guide to Common Educator Birds.

    ERIC Educational Resources Information Center

    Smock, Judith N.

    1990-01-01

    Teaching may be for the birds, but many educator birds have been abandoning the field of late for downier nests. Several species still remain, including the crown-tufted superintendent bird, the red-throated assistant superintendent bird, the crested fly-catcher principal bird, the exotic scenery bird, the roadrunner psychologist bird, and the…

  4. Vigilance against predators induced by eavesdropping on heterospecific alarm calls in a non-vocal lizard Oplurus cuvieri cuvieri (Reptilia: Iguania).

    PubMed

    Ito, Ryo; Mori, Akira

    2010-04-22

    Prey animals can reduce their risk of predation by detecting potential predators before encounters occur. Some animals gain information about nearby predators by eavesdropping on heterospecific alarm calls. Despite having well-developed ears, most lizards do not use vocal information for intraspecific communication, and few studies have shown practical use of the ears in wild lizards. Here, we show that the Madagascan spiny-tailed iguana (Oplurus cuvieri cuvieri) obtains auditory signals for predator detection. The Madagascan spiny-tailed iguana and the Madagascar paradise flycatcher (Terpsiphone mutata) are syntopic inhabitants of the Ampijoroa dry deciduous forest of Madagascar. The iguana and the flycatcher have neither a predator-prey relationship nor resource competition, but they have shared predators such as raptors and snakes. Using playback experiments, we demonstrated that the iguana discriminates mobbing alarm calls of the flycatcher from its songs and then enhances its vigilance behaviour. Our results demonstrate the occurrence of an asymmetrical ecological relationship between the Madagascan spiny-tailed iguana and the paradise flycatcher through eavesdropping on information about the presence of predators. This implies that indirect interspecific interactions through information recognition may be more common than generally thought in an animal community. PMID:20031993

  5. Positive fitness consequences of interspecific interaction with a potential competitor.

    PubMed Central

    Forsman, J T; Seppänen, J -T; Mönkkönen, M

    2002-01-01

    The coexistence of species sharing mutual resources is usually thought to be limited by negative processes such as interspecific competition. This is because an overlap in resource use leads to negative fitness consequences, and traits favouring avoidance of potential competitors, for example in habitat selection, are therefore selected for. However, species interactions are acknowledged to vary from negative (competition) to mutualism, although empirical evidence for positive interspecific interactions from natural communities of other than plants and sessile animals is scarce. Here, we experimentally examined the habitat selection and its fitness consequences of a migrant bird, the pied flycatcher (Ficedula hypoleuca), in relation to the presence of competitively superior birds, resident titmice (Parus spp.). Experiments were conducted on two spatial scales: landscape and nest-site scale. We demonstrate that pied flycatchers were attracted to and accrued fitness benefits from the presence of titmice. Flycatchers breeding in tight association with titmice initiated breeding earlier, had larger broods and heavier young than solitarily breeding flycatchers. This paradoxical result indicates that species interactions may switch from negative to positive and that the coexistence of species is not always restricted by negative costs caused by other species. PMID:12184832

  6. The Role of MC1R in Speciation & Phylogeny

    ERIC Educational Resources Information Center

    Offner, Susan

    2013-01-01

    A point mutation in the MC1R gene, a G-protein-coupled receptor, has been found that could have led to the formation of two subspecies of Solomon Island flycatcher from a single ancestral population. I discuss the many roles that G-protein-coupled receptors play in vertebrate physiology and how one particular point mutation can have enormous…

  7. Relative fitness of a generalist parasite on two alternative hosts: a cross-infestation experiment to test host specialization of the hen flea Ceratophyllus gallinae (Schrank).

    PubMed

    Appelgren, A; McCoy, K D; Richner, H; Doligez, B

    2016-05-01

    Host range is a key element of a parasite's ecology and evolution and can vary greatly depending on spatial scale. Generalist parasites frequently show local population structure in relation to alternative sympatric hosts (i.e. host races) and may thus be specialists at local scales. Here, we investigated local population specialization of a common avian nest-based parasite, the hen flea Ceratophyllus gallinae (Schrank), exploiting two abundant host species that share the same breeding sites, the great tit Parus major (Linnaeus) and the collared flycatcher Ficedula albicollis (Temminck). We performed a cross-infestation experiment of fleas between the two host species in two distinct study areas during a single breeding season and recorded the reproductive success of both hosts and parasites. In the following year, hosts were monitored again to assess the long-term impact of cross-infestation. Our results partly support the local specialization hypothesis: in great tit nests, tit fleas caused higher damage to their hosts than flycatcher fleas, and in collared flycatcher nests, flycatcher fleas had a faster larval development rates than tit fleas. However, these results were significant in only one of the two studied areas, suggesting that the location and history of the host population can modulate the specialization process. Caution is therefore called for when interpreting single location studies. More generally, our results emphasize the need to explicitly account for host diversity in order to understand the population ecology and evolutionary trajectory of generalist parasites. PMID:26910399

  8. A new species of Isospora Schneider, 1881 (Apicomplexa: Eimeiriidae) from the grey-hooded attila Attila rufus Vieillot, 1819 (Passeriformes: Tyrannidae) on the Marambaia island, Brazil.

    PubMed

    Rodrigues, Mariana Borges; Da Silva, Lidiane Maria; Lopes, Bruno Do Bomfim; Berto, Bruno Pereira; Luz, Hermes Ribeiro; Ferreira, Ildemar; Lopes, Carlos Wilson Gomes

    2015-01-01

    The New World tyrant-flycatcher (Tyrannidae) Attila rufus (Vieillot, 1819) is commonly known as grey-hooded attila or 'capitão-de-saíra' in Brazil (Sick 1997; CBRO 2014). This species has a wide distribution and their population trends appear to be stable; therefore, it is least concern according to IUCN (2015) criteria. PMID:26624438

  9. Tall shrub expansion facilitated by patterned ground in the northwest Siberian Low Arctic

    NASA Astrophysics Data System (ADS)

    Frost, G. V.; Epstein, H. E.; Walker, D. A.; Matyshak, G.; Ermokhina, K.

    2011-12-01

    We integrated field observations with a time-series of satellite imagery to identify key biophysical attributes associated with tall shrub expansion and increased vegetation productivity within a forest-tundra ecotone near Kharp, northwest Siberia. Comparison of high-resolution Corona and QuickBird satellite photography indicates that alder (Alnus fruticosa) cover increased by ~10% since 1968. Additionally, areas of sharply increasing productivity detected using a Landsat TM/ETM+ time-series for 1985-2009 are consistently co-located with expanding shrub stands. Field observations made in 2011 revealed that most of the shrub expansion has occurred in areas of patterned ground in which abundant mineral-dominated microsites ("circles") have been maintained by cryogenic disturbance. In order to test whether shrub expansion was facilitated by circles, we established a series of transects according to categories of alder stand age and circle density. Along the transects, we mapped the location of alders and circles, measured soil organic depth and leaf area index (LAI), and characterized plant communities. In recent expansion areas, young alders occur almost exclusively on silt-rich circles that lack vegetation and surface organic matter. Alder abundance and LAI increased with the total area occupied by exposed circles. Analyses using spatial statistics indicate that young alders tend to occur in evenly-spaced groups that mirror the spacing of circles. This distribution pattern persists in older alder stands, especially where circles are large and widely-spaced. Stands on closely-spaced circles quickly develop dense canopies and low species-diversity. Based on ground- and satellite-based observations, we conclude that the abundance of mineral-dominated circles at Kharp has facilitated rapid alder expansion and associated alterations in plant community structure, composition, and productivity. Physical processes in areas of patterned ground promote continuous, rather than

  10. Cycloaddition Chemistry of Tetrafluorothiophene S,S-Dioxide.

    PubMed

    Lemal, David M

    2016-06-17

    Tetrafluorothiophene S,S-dioxide has been found to be a powerful and versatile cycloaddend that undergoes a wide range of reactions as a Diels-Alder diene, dienophile, and [2 + 2] addend. Because it dimerizes only slowly at high temperatures, a broad range of conditions are available for these transformations. Reactions with terminal alkynes yield products of both Diels-Alder and [2 + 2] cycloaddition. Remarkably, the orbital topology-forbidden [2 + 2] process sometimes dominates over the allowed Diels-Alder reaction. PMID:27246658

  11. Synthetic applications of aqueous accelerated [3,3] sigmatropic rearrangements of allyl vinyl ethers. [1,3] sigmatropic rearrangements of allyl vinyl ethers in 3 M lithium perchlorate-diethyl ether at ambient temperature. New methods to effect the retro Diels-Alder reaction of N-alkyl-2-azanorbornenes

    SciTech Connect

    Clark, J.D.

    1992-01-01

    Claisen rearrangements employed in the synthesis of natural and unnatural products that were heretofore difficult or impossible using conventional means are realized through the agency of water. Allyl vinyl ether 35, the unprotected form of McMurry's aphidicolin intermediate 7, rearranged after 24 h in 2.5:1 water/methanol at 80[degrees]C, affording aldehyde 40 in 70--85% yield. Acetaldehyde elimination witnessed using conventional reaction conditions was suppressed when employing water. The application of a Claisen rearrangement within the molecular framework of fenestranes was realized for the first time. Fenestrene vinyl ethers 28 and 30 rearranged to form the fenestrenes 29 and 31, respectively. Noteworthy is fenestrene 29, the first fenestrane synthesized possessing a trans-ring fusion common to two five-membered rings. The medium of 3.0 M lithium perchlorate-diethyl ether has been found to induce the rarely witnessed rearrangement of allyl vinyl ethers, despite the fact that the corresponding sigmatropic rearrangement is energetically more favorable. Yields are very good; however, in some instances the sigmatropic rearrangement and elimination processes compete slightly. Results from the observed stereoselectivities, concentration effects on reaction rate, and a crossover study indicate that these shifts take place via dissociated ions followed by recombination, and that the observed stereoselectivities are a result of unequal steric effects in the transition states for recombination. Copper(II) and sulfonic acid ion exchange resins have been found to readily catalyze the heterocycloreversion of N-alkyl-2-azanorbornenes to the corresponding primary amines, eliminating the necessity of employing a reactive dienophile to trap out the released cyclopentadiene.

  12. Preliminary correlation of organic molecular tracers in residential wood smoke with the source of fuel

    NASA Astrophysics Data System (ADS)

    Standley, Laurel J.; Simoneit, Bernd R. T.

    Polar cyclic di- and triterpenoids were analyzed in the extracts of residential wood combustion aerosols collected in suburban sections of Eugene, Oakridge and Corvallis, Oregon. Additional samples collected included alder wood, smoke from two wood stoves burning only alder or pine as fuel, soot from a stove burning alder and a fireplace where oak was the predominant fuel. Due to the relatively cooler temperatures present under the smoldering conditions of residential wood combustion, as compared to the active burning of forest fires and slash burns, incomplete combustion resulted in the preservation of high levels of the natural products. There were three distinct signatures which could be used to trace relative input from coniferous, alder and oak combustion products, i.e. diterpenoids, lupane-derived triterpenoids and friedelin, respectively. Conifer combustion products dominated the suburban smoke aerosols.

  13. "Inosaminoacids": novel inositol-amino acid hybrid structures accessed by microbial arene oxidation.

    PubMed

    Pilgrim, Sarah; Kociok-Köhn, Gabriele; Lloyd, Matthew D; Lewis, Simon E

    2011-04-28

    Microbial 1,2-dihydroxylation of sodium benzoate permits the rapid construction of novel inositol-amino acid hybrid structures. Both β- and γ-amino acids are accessible by means of an acylnitroso Diels-Alder cycloaddition. PMID:21409268

  14. Studying the effect of high pressure on the cycloaddition reactions of maleic anhydride and substituted anthracenes

    NASA Astrophysics Data System (ADS)

    Kiselev, V. D.; Shakirova, I. I.; Kornilov, D. A.; Kashaeva, E. A.; Potapova, L. N.; Konovalov, A. I.

    2013-01-01

    The kinetics (rate, activation, and volume) of the high-pressure (up to 2500 bar) Diels-Alder reactions of maleic anhydride with 9-phenylanthracene and 9,10-dimethylanthracene in toluene is investigated.

  15. 75 FR 870 - Granting of Request for Early Termination of the Waiting Period Under the Premerger Notification...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ... Squibb Company. G Alder Biopharmaceuticals Inc. G AiderBio Holdings, LLC. 20100149 G JLL Partners Fund V... Intuit Inc. G Intuit Inc. 20100211 G Jacobs Engineering Group Inc. G TYBRIN Corporation. G...

  16. Senna

    MedlinePlus

    ... might drop too low. Stimulant laxative herbs include aloe, alder buckthorn, black root, blue flag, butternut bark, colocynth, European buckthorn, fo ti, gamboge, gossypol, greater bindweed, jalap, manna, Mexican scammony root, rhubarb, senna, and yellow dock.

  17. Total synthesis of a thromboxane receptor antagonist, terutroban.

    PubMed

    Ahmed, Wasim; Mainkar, Prathama S; Pabbaraja, Srihari; Chandrasekhar, Srivari

    2015-03-14

    A total synthesis of terutroban is achieved using the Claisen rearrangement, Friedel-Crafts acylation and Heck coupling as key reactions, avoiding the classical Diels-Alder approach used before. PMID:25611989

  18. A Valence Isomer Trapping Procedure for Introductory Organic Laboratory.

    ERIC Educational Resources Information Center

    Kurtz, David W.; Johnson, Richard P.

    1989-01-01

    Described is an experiment which illustrates valence isomerization, the trapping of a reactive intermediate and retrosynthetic analysis applied to the Diels-Alder reaction. Included is a background discussion, experimental procedures, and a discussion of the analysis. (CW)

  19. The patterns of Corylus and Alnus pollen seasons and pollination periods in two Polish cities located in different climatic regions.

    PubMed

    Puc, Małgorzata; Kasprzyk, Idalia

    2013-01-01

    This study compares phenological observations of Corylus (hazel) and Alnus (alder) flowering with airborne pollen counts of these taxa recorded using volumetric spore traps (2009-2011). The work was carried out in the Polish cities of Szczecin and Rzeszów that are located in different climatic regions. Correlations between pollen concentrations and meteorological data were investigated using Spearman's rank correlation analysis. The timings of hazel and alder pollination and the occurrence of airborne pollen varied greatly and were significantly influenced by meteorological conditions (p < 0.05). The flowering synchronization of hazel and alder pollination in Szczecin and Rzeszów varied over the study period. Hazel and alder trees flowered notably earlier in stands located in places that were exposed to sunlight (insolated) and sheltered from the wind. On the other hand, a delay in the timing of pollination was observed in quite sunny but very windy sites. In Rzeszów, maximum hazel pollen concentrations did not coincide with the period of full pollination (defined as between 25 % hazel and alder and 75 % of flowers open). Conversely, in Szczecin, the highest hazel pollen concentrations were recorded during phenophases of the full pollination period. The period when the highest alder pollen concentrations were recorded varied between sites, with Rzeszów recording the highest concentrations at the beginning of pollination and Szczecin recording alder pollen throughout the full pollination period. Substantial amounts of hazel and alder pollen grains were recorded in the air of Rzeszów (but not Szczecin) before the onset of the respective pollen seasons. PMID:24098067

  20. How can effect the synergy of climate change, soil units and vegetation groups the potential global distribution of plants up to 2300: a modelling study for prediction of potential global distribution and migration of the N2 fixing species Alnus spp.

    NASA Astrophysics Data System (ADS)

    Sakalli, A.

    2015-01-01

    Plant migration is a well known adaptation strategy of plant groups or species with evidence from historical to present observation and monitoring studies. Importance of N2-fixing plants has increased in last decades. Alnus (alder) is an important plant group because of its nitrogen fixation ability. Alders are generally distributed in humid locations of boreal, temperate and tropical climate zones, where the nitrogen fixation is an important nitrogen source for other plants. To model the nitrogen fixation by alder, data about the global distribution of alder is absolutely required. In this study a new method and model are presented to predict the distribution of N2-fixing genus on global scale and its migration in the future by using climate change scenarios. Three linear functions were defined for the determination of climate niche of alders. The distribution and migration model (Alnus-Distribution-Model (ADM)) was improved with the aid of the soil units from FAO-Unesco Soil Database, and vegetation types from Schmithüsen's biogeographical atlas. The model was also developed to predict the impact of climate change on alder distribution by using climate data from experiments performed by the Community Climate System Model version 4 (CCSM4) including the representative concentration pathways (RCPs) mitigation scenarios, and extensions of the scenarios beyond 2100 to 2300. The model covered basic approaches to understand the combine effect of climate, soil and vegetation on plant distribution and migration in the current time and future.

  1. Evidence of involvement of aluminum in causation of defective formation of eggshells and of impaired breeding in wild passerine birds

    SciTech Connect

    Nyholm, N.E.I.

    1981-12-01

    Aluminum was found in the bone marrow tissue of humeri of wild pied flycatchers (Ficedula hypoleuca), specifically in birds with impaired breeding. Production of only small cluthes, defective eggshell formation, and intrauterine bleeding were characteristic impairments shown by the aluminum-contaminated birds. These impairments agree with the symptoms of aluminum intoxication of mammals (including man) reported in the literature. A possible route of transport of aluminum to the birds is presented, in which acid precipitation is the proximate link.

  2. Spatial and temporal controls on Alnus-derived nutrients and stream stoichiometry: Implications for aquatic ecosystem productivity

    NASA Astrophysics Data System (ADS)

    Devotta, D.; Fraterrigo, J.; Walsh, P.; Hu, F.

    2015-12-01

    Predicting how nutrient fluxes that cross ecosystem boundaries will respond to future climate change is one of the greatest challenges for ecology in the 21st century. In southwestern (SW) Alaska, Pacific salmon (Oncorhynchus spp.) and nitrogen (N)-fixation by alder (Alnus spp.) provide key nutrient subsidies to freshwater systems. The importance of alder-derived nutrients (ADN) to aquatic systems will increase as alder cover expands under climate warming and salmon harvesting reduces marine-derived nutrients. We investigate broad-scale spatial and temporal drivers of ADN and stream N:P in 26 streams in SW Alaska. Alder cover and watershed features were measured using satellite images and topographic maps in ArcGIS. Stream water samples were collected in each spring and summer from 2010-2013 and analyzed for dissolved N and total phosphorus (TP). We obtained annual growing season length (AGSL) and sum of growing degree days (GDD) data from weather stations. Elevation was inversely related to alder cover, stream N, and N:P (ρ=-0.802, -0.65, and -0.71 resp., p<0.01, n=208). Alder cover had the largest influence on stream N (mean β estimate=0.402, 90% CIs). Stream N increased with alder cover, under longer AGSL, and lower GDD (interaction effect sizes between alder and stream N=0.196 and -0.185 resp., 90% CIs), suggesting that long growing seasons with minimal heat accumulation during the spring and fall increased ADN export. Higher P was associated with lower temperatures, possibly reflecting reduced P demand under low rates of metabolic activity. Structural equation modeling revealed significant causal relationships among elevation, alder cover, and stream N:P across multiple years (r2=0.94, X2=742.8, df=9, p<0.01). All paths in the model were significant (p<0.01) except between stream N:P and weather (p=0.165). These results demonstrate that spatial variation in alder cover associated with elevation is a stronger regulator of ADN fluxes and stream N:P than

  3. Effects of invasive European bird cherry (Prunus padus) on leaf litter processing by aquatic invertebrate shredder communities in urban Alaskan streams

    USGS Publications Warehouse

    Roon, David A.; Wipfli, Mark S.; Wurtz, Tricia L.

    2014-01-01

    European bird cherry (Prunus padus) (EBC) is an invasive ornamental tree that is spreading rapidly in riparian forests of urban Alaska. To determine how the spread of EBC affects leaf litter processing by aquatic invertebrate shredders, we conducted complementary leaf pack experiments in two streams located in Anchorage, Alaska. The first experiment contrasted invasive EBC with three native tree species—thin-leaf alder (Alnus tenuifolia), paper birch (Betula neoalaskana), and black cottonwood (Populus trichocarpa)—in one reach of Chester Creek; finding that EBC leaf litter broke down significantly faster than birch and cottonwood, but at a similar rate to alder. The second experiment contrasted EBC with alder in four reaches of Campbell and Chester creeks; finding that while EBC leaf litter broke down significantly faster than alder in Chester Creek, EBC broke down at a similar rate to alder in Campbell Creek. Although EBC sometimes supported fewer shredders by both count and mass, shredder communities did not differ significantly between EBC and native plants. Collectively, these data suggest that invasive EBC is not currently exhibiting strong negative impacts on leaf litter processing in these streams, but could if it continues to spread and further displaces native species over time.

  4. Growth and N2 fixation in an Alnus hirsuta (Turcz.) var. sibirica stand in Japan.

    PubMed

    Tobita, Hiroyuki; Hasegawa, Shigeaki F; Yazaki, Kenichi; Komatsu, Masabumi; Kitao, Mitsutoshi

    2013-11-01

    To estimate the N2 fixation ability of the alder (Alnus hirsuta (Turcz.) var. sibirica), we examined the seasonal variation in nitrogenase activity of nodules using the acetylene reduction method in an 18-year-old stand naturally regenerated after disturbance by road construction in Japan. To evaluate the contribution of N2 fixation to the nitrogen (N) economy in this alder stand, we also measured the phenology of the alder, the litterfall, the decomposition rate of the leaf litter, and N accumulation in the soil. The acetylene reduction activity per unit nodule mass (ARA) under field conditions appeared after bud break, peaked the maximum in midsummer after full expansion of the leaves, and disappeared after all leaves had fallen. There was no consistent correlation between ARA and tree size (dbh). The amount of N2 fixed in this alder stand was estimated at 56.4 kg ha-1 year-1 when a theoretical molar ratio of 3 was used to convert the amount of reduced acetylene to the amount of fixed N2. This amount of N2 fixation corresponded to the 66.4 percent of N in the leaf litter produced in a year. These results suggested that N2 fixation still contributed to the large portion of N economy in this alder stand. PMID:24287656

  5. Controlling porosity in bridged polysilsesquioxanes through elimination reactions

    SciTech Connect

    McClain, M.D.; Loy, D.A.; Prabakar, S.

    1996-06-01

    The retro Diels-Alder reaction was used to modify porosity in hydrocarbon-bridged polysilsesquioxane gels. Microporous polysilsesquioxanes incorporating a thermally labile Diels-Alder adduct as the hydrocarbon bridging group were prepared by sol-gel polymerization of trans-2,3-bis(triethoxysilyl)norbornene. Upon heating the 2,3-norbornenylene-bridges polymers at temperatures above 250 C, the norbornenylene-bridging group underwent a retro Diels-Alder reaction losing cyclopentadiene and leaving behind a ethenylene-bridged polysilsesquioxane. Less than theoretical quantities of cyclopentadiene were volatilized indicating that some of the diene was either reacting with the silanol and olefinic rich material or undergoing oligomerization. Both scanning electron microscopy and nitrogen sorption porosimetry revealed net coarsening of pores (and reduction of surface area) in the materials with thermolysis.

  6. Benthic invertebrate community structure is influenced by forest succession after clearcut logging in southeastern Alaska

    USGS Publications Warehouse

    Hernandez, O.; Merritt, R.W.; Wipfli, M.S.

    2005-01-01

    To assess the effects of timber harvesting on headwater streams in upland forests, benthic community structure was contrasted among four dominant forest management types (old growth, red alder-dominated young growth, conifer-dominated young growth, clearcut) and instream habitats (woody debris, cobble, gravel) in southeastern Alaska. Benthos in streams of previously harvested areas resulted in increased richness, densities and biomass relative to old growth types, particularly in young growth stands with a red alder-dominated riparian canopy. Woody debris and gravel habitats supported a combination of higher densities and biomass of invertebrates than cobble habitats. In addition, woody debris also supported a richer and more diverse invertebrate fauna than either cobble or gravel substrates. Maintaining both a woody debris source and a red alder component in regenerating riparian forests following timber harvesting should support greater invertebrate densities and diversity following clearcutting. ?? Springer 2005.

  7. Widespread Expansion of Boreal Shrublands in the Siberian Low Arctic Is Linked to Cryogenic Disturbance and Geomorphology

    NASA Astrophysics Data System (ADS)

    Frost, G. V.; Epstein, H. E.; Walker, D. A.

    2012-12-01

    Declassified imagery from the KH-4B "Corona" and KH-7 "Gambit" Cold War satellite surveillance systems (1963-1972) are a unique, high-resolution dataset that establishes a baseline for landcover-change studies in the Russian Arctic spanning 6 decades. We co-registered Corona/Gambit and modern high-resolution imagery for seven ~65 km2 Low Arctic sites in northwest Siberia and Chukotka and quantified changes in the extent of tall shrublands dominated by Siberian alder (Alnus fruticosa) using a point-intercept sampling approach. We made ground observations at two sites to identify important geomorphic processes and physiographic units associated with shrub expansion. Alder shrubland cover increased at all sites; relative to the 1960s extent, shrubland extent increased by 5-31% at the northwest Siberian sites and by 9% at both Chukotkan sites,. In northwest Siberia, alder expansion was closely linked to cryogenic disturbances related to patterned-ground and active-layer detachments. At the Chukotkan sites, most alder expansion occurred on hillslope colluvium and floodplains; we also observed modest increases in Siberian dwarf pine (Pinus pumila). The close correspondence between expanding shrub patches and disturbance processes indicates that sparsely-vegetated, mineral-rich seedbeds strongly facilitate alder recruitment, and that the spatio-temporal attributes of disturbance mechanisms are a key determinant of landscape susceptibility to shrub expansion. Shrub expansion, in turn, initiates a cascade of effects on permafrost thermal regime and disturbance, promoting the accumulation of biomass and potentially buffering permafrost from climate warming.; Recently-established alder shrubs growing on non-sorted circles in patterned ground near Obskaya, northwest Siberia.

  8. Parameterised local spin density exchange-correlation energies and potentials for electronic structure calculations I. Zero temperature formalism

    NASA Astrophysics Data System (ADS)

    MacLaren, J. M.; Clougherty, D. P.; McHenry, M. E.; Donovan, M. M.

    1991-09-01

    Commonly used approximate forms for the exchange-correlation energy and potential within the local density approximation are summarised, and FORTRAN code is included for the evaluation of these various forms. Included are the following: Xα, Kohn-Sham-Gaspàr, Hedin-Lundqvist-Wilkins, Janak-Moruzzi-Williams, Von Barth-Hedin, Ceperley-Alder (Perdew-Zunger), and Ceperley-Alder (Vosko-Wilk-Nusair). Both the Vosko-Wilk-Nusair and the Von Barth-Hedin expressions for spin interpolation between paramagnetic and ferromagnetic limits are also provided.

  9. Ynamide Carbopalladation: A Flexible Route to Mono-, Bi- and Tricyclic Azacycles

    PubMed Central

    Campbell, Craig D; Greenaway, Rebecca L; Holton, Oliver T; Walker, P Ross; Chapman, Helen A; Russell, C Adam; Carr, Greg; Thomson, Amber L; Anderson, Edward A

    2015-01-01

    Bromoenynamides represent precursors to a diversity of azacycles by a cascade sequence of carbopalladation followed by cross-coupling/electrocyclization, or reduction processes. Full details of our investigations into intramolecular ynamide carbopalladation are disclosed, which include the first examples of carbopalladation/cross-coupling reactions using potassium organotrifluoroborate salts; and an understanding of factors influencing the success of these processes, including ring size, and the nature of the coupling partner. Additional mechanistic observations are reported, such as the isolation of triene intermediates for electrocyclization. A variety of hetero-Diels–Alder reactions using the product heterocycles are also described, which provide insight into Diels–Alder regioselectivity. PMID:26189754

  10. Studies toward the total syntheses of cucurbitacins B and D.

    PubMed

    Jung, Michael E; Lui, Rebecca M

    2010-11-01

    Synthetic efforts toward the convergent construction of the tetracyclic triterpenoids cucurbitacins B and D are described. The results of a Diels-Alder study examining the effects of steric and electronic variations of 2-methyl-2-cyclohexenone on the endo/exo-diastereoselectivity of the reaction are presented. The diastereomer of the core of the cucurbitacins, epimeric at C8, C9, and C10, 51, was synthesized via a highly regio- and stereoselective Diels-Alder reaction of the diene 4 and the novel dienophile 50. PMID:20873743

  11. β-Aryl-α-nitro-α,β-enals as heterodienes and dienophiles.

    PubMed

    Lago-Santomé, Hugo; Martínez-Bescos, Patricia; Fernández-González, Marta; Ozores-Viturro, Lidia; Cagide-Fagín, Fernando; Alonso, Ricardo

    2014-09-19

    As demonstrated with the β-(2-furyl)-substituted analogue 1b, β-aryl-α-nitro-α,β-enals (1) behave as heterodienes against enamines and enol ethers using their enal unit (e.g., 1b → 12). α-Nitro-α,β-enals can act as well as highly reactive dienophiles to render adducts endowed with nitrogenated quaternary centers (e.g., 1b → 15a). A hetero-Diels-Alder (HDA)/Diels-Alder (DA) sequence from 1b also proved feasible on serial treatment with ethyl vinyl ether and Danishefsky's diene (1b → 14). PMID:25181678

  12. Triple Benzannulation of Naphthalene via a 1,3,6-Naphthotriyne Synthetic Equivalent. Synthesis of Dibenz[a,c]anthracene.

    PubMed

    Mannes, Philip Z; Onyango, Evans O; Gribble, Gordon W

    2015-11-01

    A new synthesis of dibenzo[a,c]anthracene (4) is described that features the generation, from tetrabromo-bis-triflate 1 and phenyllithium, of a 1,3,6-naphthotriyne (2) synthetic equivalent that is trapped with 3 equiv of furan to form Diels-Alder tris-adduct 3. A subsequent two-step deoxygenation of 3 represents the first synthesis of dibenz[a,c]anthracene (4) that involves a tandem aryne Diels-Alder cycloaddition-deoxygenation strategy. PMID:26452053

  13. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2009-11-24

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments or the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  14. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2006-04-04

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments and the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  15. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2009-09-29

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments or the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  16. Guild structure of a riparian avifauna relative to seasonal cattle grazing

    USGS Publications Warehouse

    Knopf, F.L.; Sedgwick, J.A.; Cannon, R. W.

    1988-01-01

    Knopf et al. found that summer cattle grazing has an adverse effect on the presence of certain willow-dependent songbirds. Pastures that have historical summer grazing no longer have the Willow flycatcher, Lincoln's sparrow and the White-crowned sparrow present. Yet in these same areas, birds like the American Robin, Brown-headed cowbird and the Red-winged blackbird have increased in density. One possible answer for the decrease in some songbirds is the fact that the main focus of the Arapaho National Wildlife Refuge is on waterfowl habitat, which requires large amounts of open space (opposite of desirable songbird habitat).

  17. Large-scale geographical variation confirms that climate change causes birds to lay earlier.

    PubMed

    Both, Christiaan; Artemyev, Aleksandr V; Blaauw, Bert; Cowie, Richard J; Dekhuijzen, Aarnoud J; Eeva, Tapio; Enemar, Anders; Gustafsson, Lars; Ivankina, Elena V; Järvinen, Antero; Metcalfe, Neil B; Nyholm, N Erik I; Potti, Jaime; Ravussin, Pierre-Alain; Sanz, Juan Jose; Silverin, Bengt; Slater, Fred M; Sokolov, Leonid V; Török, János; Winkel, Wolfgang; Wright, Jonathan; Zang, Herwig; Visser, Marcel E

    2004-08-22

    Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long-term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement. PMID:15306284

  18. A neotropical migrant bird's dilemma: where to stop for a good meal

    USGS Publications Warehouse

    Fontaine, Joseph J.; van Riper, Charles, III

    2009-01-01

    To learn how migrating birds determine where to stop and find food, scientists from the U.S. Geological Survey, Northern Arizona University, and The University of Arizona studied the behavior of 28 species of neotropical migrant songbirds - warblers, flycatchers, tanagers, and vireos - along the lower Colorado River from 2001 to 2004. They found that, like interstate travelers greeted by restaurant billboards, songbirds flying over Cibola National Wildlife Refuge, Arizona, relied on the flowering of honey mesquite (Prosopis glandulosa) to detect the availability of insects that they prey on. Understanding where and why migrant birds stop will help land managers better protect key habitats used by these tiny travelers.

  19. Replacement names for Chapinia and Ripleyia (Aves: Passeriformes: Muscicapidae).

    PubMed

    Voelker, Gary; Bowie, Rauri C K; Conway, Kevin W

    2016-01-01

    Earlier this year, two of us (GV & RB) introduced the genus-group names Chapinia and Ripleyia (in Voelker et al. 2016) for two species of African flycatchers allied to Muscicapa. We recently became aware that both of these genus-group names are preoccupied within Animalia (Chapinia by Chapinia Ewing, 1927 [Insecta: Phthiraptera] and Ripleyia by Ripleyia Cossman, 1920 [Mollusca]), rendering them junior homonyms. Following Article 60 of the International Code of Zoological Nomenclature (ICZN 1999) we herein provide replacement names for the two generic names introduced in Voelker et al. (2016). PMID:27394844

  20. Nitrogen fixation in forested soils by non-leguminous nitrogen-fixing plants and by non-symbiotic soil organisms. Final report, October 1, 1977-September 30, 1982

    SciTech Connect

    Lane, C.L.

    1982-01-01

    Studies using mixtures of nitrogen-fixing plants mixed with loblolly pine showed no growth increase on a good site but a growth increase on a poor site. Soil nutrient studies showed that soils beneath alder, eleagnus, wax myrtle and red cedar had a higher nutrient concentration than soils not influenced by the crown. Monthly nutrient concentrations were quite variable.

  1. Total synthesis of (-)-depyranoversicolamide B.

    PubMed

    Qin, Wen-Fang; Xiao, T; Zhang, D; Deng, Lin-Feng; Wang, Y; Qin, Y

    2015-11-18

    Starting from easily prepared (R)-C3-isoprenylated pyrroloindoline, the C3-isoprenylated indolyl diketopiperazine is prepared by an efficient reductive opening of the pyrrolo ring, and undergoes biomimetic Diels-Alder reaction to generate an anti-adduct as a sole stereoisomer. Oxidation of the indoline moiety to oxindole completes the synthesis of (-)-depyranoversicolamide B. PMID:26393932

  2. The implications of the Human Tissue Act 2004 for dentistry.

    PubMed

    Forsyth, Laura; Woof, Marcus

    2006-12-23

    Partly as a consequence of the inquiries into the events at the Bristol Royal Infirmary and the Royal Liverpool Children's Hospital (Alder Hey), the Government recently enacted the Human Tissue Act 2004. The main provisions of the Act came into force on 1 September 2006 and have potential implications for dentists. PMID:17183410

  3. Application of the intramolecular vinylogous Morita-Baylis-Hillman reaction toward the synthesis of the spinosyn A tricyclic nucleus.

    PubMed

    Mergott, Dustin J; Frank, Scott A; Roush, William R

    2002-09-01

    [reaction: see text] A concise synthesis of the spinosyn A tricyclic nucleus 27 has been developed by a route featuring a one-pot tandem intramolecular Diels-Alder reaction and intramolecular vinylogous Morita-Baylis-Hillman cyclization in which five stereocenters in tricycle 10 are set with excellent selectivity. PMID:12201741

  4. DIRECT-SEEDING OF COMMERCIAL TREES ON SURFACE-MINE SPOIL

    EPA Science Inventory

    Two small-seeded species, Paulownia (Paulownia tomentosa), and European alder (Alnus glutinosa) and three large seeded species, northern red oak (Quercus rubra), pin oak (Quercus palustris), and bur oak (Quercus macrocarpa) were direct-seeded on three aspects on minesoil in easte...

  5. EFFECTS OF SULFURIC ACID RAIN ON TWO MODEL HARDWOOD FORESTS: THROUGHFALL, LITTER LEACHATE, AND SOIL SOLUTION

    EPA Science Inventory

    Simulated sulfuric acid rain (pH 3.0, 3.5, 4.5, and 5.6) was applied to model forests containing either sugar maple (Acer saccharum) or red alder (Alnus rubra). Water samples were collected above and below the canopy, below the litter, and from 20 cm and 1 m below the surface of ...

  6. Asymmetric Total Syntheses of (+)- and (−)-Versicolamide B and Biosynthetic Implications

    PubMed Central

    Miller, Kenneth A.; Tsukamoto, Sachiko; Williams, Robert M.

    2010-01-01

    The Diels-Alder reaction is one of the most well-studied, synthetically useful organic transformations. While a significant number of naturally occurring substances are postulated to arise by biosynthetic Diels-Alder reactions, rigorous confirmation of a mechanistically distinct natural Diels-Alderase enzyme remains elusive. Within this context, several related fungi within the Aspergillus genus produce a number of metabolites of opposite absolute configuration including (+)- or (−)-versicolamide B. These alkaloids are hypothesized to arise via biosynthetic Diels-Alder reactions implying that each Aspergillus species possesses enantiomerically distinct Diels-Alderases. Herein, experimental validation of these biosynthetic proposals via deployment of the IMDA reaction as a key step in the asymmetric total syntheses of (+)- and (−)-versicolamide B is described. Laboratory validation of the proposed biosynthetic Diels-Alder construction, coupled with the secondary metabolite profile of the producing fungi, reveals that each Aspergillus species has evolved enantiomerically distinct indole oxidases, as well as enantiomerically distinct Diels-Alderases. PMID:20300443

  7. A self-crosslinking thermosetting monomer with both epoxy and anhydride groups derived from Tung oil fatty acids: Synthesis and properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A self-crosslinking compound with epoxy groups and anhydride groups (GEMA) has been successfully synthesized from Tung oil fatty acid by reacting with maleic anhydride via the Diels-Alder reaction. GEMA has very good storage stability and can be cured with trace amounts of tertiary amine. This advan...

  8. Total Synthesis and Structural Revision of Antibiotic CJ-16,264**

    PubMed Central

    Nicolaou, K. C.; Shah, Akshay A.; Korman, Henry; Khan, Tabrez; Shi, Lei; Worawalai, Wisuttaya; Theodorakis, Emmanuel A.

    2015-01-01

    The total synthesis and structural revision of antibiotic CJ-16,264 is described. Starting with citronellal, the quest for the target molecule featured a novel bis-transannular Diels–Alder reaction that casted stereoselectively the decalin system and included the synthesis of six isomers before demystification of its true structure. PMID:26096055

  9. Synthesis of (±)-Nosyberkol (Isotuberculosinol, Revised Structure of Edaxadiene) and (±)-Tuberculosinol

    PubMed Central

    Maugel, Nathan; Mann, Francis M.; Hillwig, Matthew L.; Peters, Reuben J.

    2010-01-01

    Me2AlCl-catalyzed Diels–Alder reaction of N-tigloyloxazolidinone with 6,6-dimethyl-1-vinylcyclohexene selectively provided the exo adduct, which was converted to nosyberkol (isotuberculosinol) and tuberculosinol. The spectral data for nosyberkol are identical to those reported for edaxadiene, whose structure is revised accordingly. PMID:20462237

  10. Synthesis of (+/-)-nosyberkol (isotuberculosinol, revised structure of edaxadiene) and (+/-)-tuberculosinol.

    PubMed

    Maugel, Nathan; Mann, Francis M; Hillwig, Matthew L; Peters, Reuben J; Snider, Barry B

    2010-06-01

    Me(2)AlCl-catalyzed Diels-Alder reaction of N-tigloyloxazolidinone with 6,6-dimethyl-1-vinylcyclohexene selectively provided the exo adduct, which was converted to nosyberkol (isotuberculosinol) and tuberculosinol. The spectral data for nosyberkol are identical with those reported for edaxadiene, whose structure is revised accordingly. PMID:20462237

  11. 36 CFR 293.16 - Special provisions governing the Boundary Waters Canoe Area Wilderness, Superior National Forest...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... on Trout Lake in Saint Louis County, Fall Lake, Moose Lake, Newfound Lake, Newton Lake, Sucker Lake... between Ottawa Island and Washington Island, all in Lake County, and East Bearskin Lake and Saganaga Lake... Lake, Alder Lake, Canoe Lake, Sea Gull Lake, and Island River east of......

  12. 36 CFR 293.16 - Special provisions governing the Boundary Waters Canoe Area Wilderness, Superior National Forest...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... on Trout Lake in Saint Louis County, Fall Lake, Moose Lake, Newfound Lake, Newton Lake, Sucker Lake... between Ottawa Island and Washington Island, all in Lake County, and East Bearskin Lake and Saganaga Lake... Lake, Alder Lake, Canoe Lake, Sea Gull Lake, and Island River east of......

  13. 36 CFR 293.16 - Special provisions governing the Boundary Waters Canoe Area Wilderness, Superior National Forest...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... on Trout Lake in Saint Louis County, Fall Lake, Moose Lake, Newfound Lake, Newton Lake, Sucker Lake... between Ottawa Island and Washington Island, all in Lake County, and East Bearskin Lake and Saganaga Lake... Lake, Alder Lake, Canoe Lake, Sea Gull Lake, and Island River east of......

  14. A biosynthesis-inspired approach to over twenty diverse natural product-like scaffolds.

    PubMed

    Firth, James D; Craven, Philip G E; Lilburn, Matthew; Pahl, Axel; Marsden, Stephen P; Nelson, Adam

    2016-07-28

    A synthetic approach to diverse scaffolds was developed that was inspired by diterpene biosynthesis. Initial scaffolds, generated using Diels-Alder reactions of furyl-functionalised amines, were transformed into alternative scaffolds using cleavage, ring expansion, annulation and rearrangement reactions. In total, 25 diverse scaffolds were prepared that were shown to have high natural product-likeness. PMID:27424656

  15. Allergenic airborne pollen and spores in Anchorage, Alaska

    SciTech Connect

    Anderson, J.H.

    1985-05-01

    Major aeroallergens in Anchorage are birch, alder, poplar, spruce, grass pollen, Cladosporium, and unspecified fungus spores. Lesser pollens are sorrel, willow, pine, juniper, sedge, lamb's-quarters, wormwood, plantain, and others. The aero-flora is discussed in terms of the frequency of allergenically significant events and within-season and year-to-year dynamics.

  16. TERRESTRIAL AND MARINE SOURCES OF NUTRIENTS TO AN OREGON COASTAL RIVER

    EPA Science Inventory

    In the Pacific Northwest of North America, anadromous fish can transport significant quantities of nutrients and energy from the ocean to the watersheds where they return, reproduce and die. In addition, the widespread distribution of N2-fixing alders (Alnus spp.) can influence ...

  17. A cyclopropene-modified nucleotide for site-specific RNA labeling using genetic alphabet expansion transcription.

    PubMed

    Eggert, F; Kath-Schorr, S

    2016-06-01

    Site-specific RNA modification with methyl cyclopropene moieties is performed by T7 in vitro transcription. An existing unnatural base is functionalized with a cyclopropene moiety and used in transcription reactions to produce site-specifically cyclopropene-modified RNA molecules. The posttranscriptional inverse electron demand Diels-Alder cycloaddition reaction with a selected tetrazine-fluorophore conjugate is demonstrated. PMID:27181840

  18. Design of a Brønsted acid with two different acidic sites: synthesis and application of aryl phosphinic acid-phosphoric acid as a Brønsted acid catalyst.

    PubMed

    Momiyama, N; Narumi, T; Terada, M

    2015-12-11

    A Brønsted acid with two different acidic sites, aryl phosphinic acid-phosphoric acid, has been synthesized. Its catalytic performance was assessed in the hetero-Diels-Alder reaction of aldehyde hydrates with Danishefsky's diene, achieving high reaction efficiency. PMID:26445921

  19. From the forest to the sea and back again: Biogeochemistry in the Oregon Coast Range

    EPA Science Inventory

    Variations in plant community composition across the landscape can influence nutrient retention and loss at the watershed scale. A striking example of plant species influence is the role of N2-fixing red alder (Alnus rubra) in the biogeochemistry of Pacific Northwest forests. A...

  20. 75 FR 4056 - Claire Fay and Charlie Hotchkin; Notice of Application Accepted for Filing, Soliciting Motions To...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Claire Fay and Charlie Hotchkin; Notice of Application Accepted for Filing...: August 4, 2009. d. Applicant: Claire Fay and Charlie Hotchkin. e. Name of Project: Alder Brook Mini...

  1. Study of improved methods for predicting chemical equilibria: Technical progress report for the period July 1, 1986 to September 1, 1987

    SciTech Connect

    Lenz, T.G.; Vaughan, J.D.

    1987-01-01

    We carried out a detailed study of the capabilities and limitations of two force field models (MMP2 and MOLBD3) for calculating thermodynamic properties of -diene and -ene hydrocarbons. New force field parameters were introduced for the MOLBD3 program for unsaturated five-member rings and for methylene-bridged compounds. We investigated the Diels-Alder condensation of 1,3-cyclopentadiene in the temperature range 273 to 500K by use of MOLBD3. Equilibrium constants, standard enthalpies of reaction, and standard entropies of reaction were calculated. The calculated results were compared with experimental data reported in the literature. Anthracene derivatives, maleic anhydride derivatives, and Diels-Alder adducts were synthesized and purified in preparation for future experimental determination of equilibrium constants for various Diels-Alder reactions. The structure of the 9-phenylanthracene-maleic anhydride adduct was determined by x-ray crystallography. Equilibrium constants for the Diels-Alder reaction of 9-phenylanthracene and maleic anhydride in 1,2,4-trichlorobenzene were determined for seven temperatures between 124 and 175/sup 0/C. 27 refs., 1 fig., 13 tabs.

  2. Chiral 1,3,2-oxazaborolidines in asymmetric synthesis: recent advances

    NASA Astrophysics Data System (ADS)

    Glushkov, Vladimir A.; Tolstikov, Alexander G.

    2004-06-01

    The use of chiral 1,3,2-oxazaborolidines in asymmetric organic synthesis, particularly, in enantioselective reduction of ketones, imines and oxime ethers, asymmetric Diels-Alder reactions, aldol condensation and atroposelective reduction of lactones is reviewed. Reactions of immobilised 1,3,2-oxazaborolidines are also considered.

  3. Linking landscape characteristics and stream nitrogen in the Oregon Coast Range: Empirical modeling of water quality monitoring data

    EPA Science Inventory

    Background sources of nitrogen (N) provide a challenge for setting stream nutrient criteria in the Pacific Northwest US. Red alder (Alnus rubra), an early successional nitrogen fixing tree, and sea salt inputs can strongly influence stream N concentrations observed in individual...

  4. Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

    PubMed Central

    Dipak, Mirtunjay Kumar

    2014-01-01

    Summary Intricate caged molecular frameworks are assembled by an atom economical process via a Diels–Alder (DA) reaction, a Claisen rearrangement, a ring-closing metathesis (RCM) and an alkenyl Grignard addition. The introduction of olefinic moieties in the pentacycloundecane (PCUD) framework at appropriate positions followed by RCM led to the formation of novel heptacyclic cage systems. PMID:25550729

  5. Recycling tires? Reversible crosslinking of poly(butadiene).

    PubMed

    Trovatti, Eliane; Lacerda, Talita M; Carvalho, Antonio J F; Gandini, Alessandro

    2015-04-01

    Furan-modified poly(butadiene) prepared by the thiol-ene click reaction is crosslinked with bismaleimides through the Diels-Alder reaction, giving rise to a novel recyclable elastomer. This is possible because of the thermal reversibility of the adducts responsible for the formation of the network. The use of this strategy provides the possibility to produce recyclable tires. PMID:25689366

  6. Nanoparticle fillers obtained from wood processing wastes for reinforcing of paper

    NASA Astrophysics Data System (ADS)

    Laka, Marianna; Vikele, Laura; Rozenberga, Linda; Janceva, Sarmite

    2016-05-01

    Paper sheets were produced from bleached kraft pulp, and office and newsprint waste paper. Nanoparticles from black alder bark, grey alder bark and pine bark as well as birch sawdust were obtained for using them as reinforcing fillers in paper. Non-extracted bark and that extracted in biorefinery were used. For producing nanoparticles, the materials were destructed using the thermocatalytic destruction method and then dispersed in water medium in a ball mill. At a sufficient concentration, gel-like dispersions were obtained, which contained nanoparticles with the size ~300 nm. The dispersions were introduced in paper furnish in different amounts. It has been established that all the nanoparticle fillers increase the tensile index and burst index in dry and wet states. The nanoparticle fillers from extracted bark increase the mechanical indices to a higher extent. At 20% filler content, tensile index in a dry state increases in the case of non-extracted grey alder bark, black alder bark and pine bark by 28, 30 and 15%, and in the case of extracted ones - by 44, 40 and 30%, respectively; the burst index increases by 78, 19 and 4%, and 91, 25 and 14%, respectively. The nanoparticle filler from birch sawdust increases the tensile strength in a dry state by 9% and burst index by 20%. The obtained nanoparticle fillers slightly improve also the water resistance of paper.

  7. Total Synthesis of (±)-Maoecrystal V

    PubMed Central

    Peng, Feng; Danishefsky, Samuel J.

    2012-01-01

    The total synthesis of racemic maoecrystal V has been accomplished. Key steps include an intramolecular Diels-Alder cyclization to rapidly construct the core system from simple starting materials and the creation of the A–C ring trans-fusion through intramolecular delivery of a hydrogen to the hindered β-face of the ring system. PMID:23126440

  8. Progenesis in the evolution of the nudibranch mollusks genus Dendronotus (Gastropoda: Nudibranchia).

    PubMed

    Ekimova, I A; Malakhov, V V

    2016-03-01

    The morphology and postlarval ontogenesis of the radula in 11 species of the genus Dendronotus Alder et Hancock, 1845, has been studied. Four types of radula are recognized in adult mollusks. Proposed evidence suggests that small species of Dendronotus have evolved by progenesis. PMID:27193883

  9. Bounding salt marsh nitrogen fluxes: development of an ecohydrological salt marsh model

    EPA Science Inventory

    A mass-balance approach to characterize nitrogen flux in a 2-hectare, meso-haline saltmarsh yielded extensive flow and water chemistry data. However, a significant, unevenly distributed population of the nitrogen fixer Alnus rubra (red alder) in the 20-hectare upland catchment l...

  10. Synthesis of cyclic sulfones by ring-closing metathesis.

    PubMed

    Yao, Qingwei

    2002-02-01

    A general and highly efficient synthesis of cyclic sulfones based on ring-closing metathesis has been developed. The synthetic utility of the resulting cyclic sulfones was demonstrated by their participation in stereoselective Diels-Alder reactions and transformation to cyclic dienes by the Ramberg-Bäcklund reaction. PMID:11820896

  11. A click chemistry-based microRNA maturation assay optimized for high-throughput screening.

    PubMed

    Lorenz, Daniel A; Garner, Amanda L

    2016-07-01

    Catalytic enzyme-linked click-chemistry assays (cat-ELCCA) are an emerging class of biochemical assay. Herein we report on expanding the toolkit of cat-ELCCA to include the kinetically superior inverse-electron demand Diels-Alder (IEDDA) reaction. The result is a technology with improved sensitivity and reproducibility, enabling automated high-throughput screening. PMID:27284591

  12. A Synthesis of the Carbon Skeleton of Maoecrystal V

    PubMed Central

    Krawczuk, Paul J.; Schöne, Niklas; Baran, Phil S.

    2009-01-01

    An enantioselective synthesis of the maoecrystal V (1) carbon skeleton is described. The key transformations include arylation of a 1,3-dicarbonyl compound with a triarylbismuth(V)dichloride species, oxidative dearomatization of a phenol, and a subsequent intramolecular Diels-Alder reaction. PMID:19795876

  13. Using soil island plantings as dispersal vectors in large area copper tailings reforestation

    SciTech Connect

    Scherer, G.; Everett, R.

    1998-12-31

    The Wenatchee National Forest undertook the reforestation of the 80 acre (35 ha) Holden copper mine tailings of Washington State in 1989 by using 20, one-fourth acre, triangular shaped soil islands as a source of plant propagules targeted for gravel-covered tailings surfaces. The islands were constructed of soil and surface litter transported from a nearby gravel pit, and planted with four species of conifer seedlings, the shrub Sitka alder (Alnus sinuata) and eight species of grasses. Conifer and alder seedlings were also planted in graveled covered tailings with amendments. Since reproductive status of the conifers would not occur for several years, this propagule vector hypothesis was tested by measuring the distances traveled onto the tailings surface by grass seeds. The number of grass shoots established in four treatment blocks in target plots downwind from the soil island source plantings was also determined. After 36 months, grass seed had migrated to a distance of 32 feet (11 m) from the soil island source. Grass shoots were present within 10 feet (3 m) downwind of the soil island, the most frequent being Mountain brome (Bromus marginatus). Among the tree species, lodgepole pine (Pinus contorta) and Sitka alder grew an average of 6 inches (15--16 cm) after 40 months on the soil islands but somewhat less on the tailing surface. By the third growing season, the only tree species in reproductive condition on the tailings was alder. The soil-island technique is successful for grass dispersal and may have potential for conifer and alder migration.

  14. Effects of experimental calcium availability and anthropogenic metal pollution on eggshell characteristics and yolk carotenoid and vitamin levels in two passerine birds.

    PubMed

    Espín, Silvia; Ruiz, Sandra; Sánchez-Virosta, Pablo; Salminen, Juha-Pekka; Eeva, Tapio

    2016-05-01

    The maternal investment into egg quality depends on the condition of the female, the quality of the mate, and the quality of the environment. In that sense, availability of nutrients and exposure to pollutants are essential parameters to consider. The main aim of this study is to assess the effects of calcium (Ca) availability and anthropogenic metal pollution on early-stage reproduction in two passerine species, great tits (Parus major) and pied flycatchers (Ficedula hypoleuca), inhabiting a Ca-poor and metal-polluted area in SW Finland. Both species were able to obtain sufficient Ca for eggshell formation, and metal pollution was below the level of having negative effects in the egg size and eggshell characteristics. However, metal polluted environment negatively affected yolk lutein and vitamin D3 levels in both species, probably because of a lower access to carotenoid-rich diet and higher metal interference with vitamin D3 metabolism. The higher levels of vitamin D3 in yolks in the unpolluted zone could also be due to upregulated D3 levels as a response to the lower natural Ca availability. Yolk carotenoids and vitamin D3 were positively associated with nestling growth and size, supporting their importance for the appropriate chick development. The interspecific differences in yolk nutrient concentrations possibly reflect the different growth rate of these species. Pied flycatchers are likely adapted to low Ca availability through an efficient vitamin D3 metabolism, but their Ca intake could be close to a deficient level. PMID:26943740

  15. Sex chromosome linked genetic variance and the evolution of sexual dimorphism of quantitative traits.

    PubMed

    Husby, Arild; Schielzeth, Holger; Forstmeier, Wolfgang; Gustafsson, Lars; Qvarnström, Anna

    2013-03-01

    Theory predicts that sex chromsome linkage should reduce intersexual genetic correlations thereby allowing the evolution of sexual dimorphism. Empirical evidence for sex linkage has come largely from crosses and few studies have examined how sexual dimorphism and sex linkage are related within outbred populations. Here, we use data on an array of different traits measured on over 10,000 individuals from two pedigreed populations of birds (collared flycatcher and zebra finch) to estimate the amount of sex-linked genetic variance (h(2)z ). Of 17 traits examined, eight showed a nonzero h(2)Z estimate but only four were significantly different from zero (wing patch size and tarsus length in collared flycatchers, wing length and beak color in zebra finches). We further tested how sexual dimorphism and the mode of selection operating on the trait relate to the proportion of sex-linked genetic variance. Sexually selected traits did not show higher h(2)Z than morphological traits and there was only a weak positive relationship between h(2)Z and sexual dimorphism. However, given the relative scarcity of empirical studies, it is premature to make conclusions about the role of sex chromosome linkage in the evolution of sexual dimorphism. PMID:23461313

  16. ‘Heritability’ of dispersal propensity in a patchy population

    PubMed Central

    Doligez, Blandine; Gustafsson, Lars; Pärt, Tomas

    2009-01-01

    Although dispersal is often considered to be a plastic, condition-dependent trait with low heritability, growing evidence supports medium to high levels of dispersal heritability. Obtaining unbiased estimates of dispersal heritability in natural populations nevertheless remains crucial to understand the evolution of dispersal strategies and their population consequences. Here we show that dispersal propensity (i.e. the probability of dispersal between habitat patches) displays a significant heritability in the collared flycatcher Ficedula albicollis, as estimated by within-family resemblance when accounting for environmental factors. Offspring of dispersing mothers or fathers had a higher propensity to disperse to a new habitat patch themselves. The effect of parental dispersal status was additional to that of local habitat quality, as measured by local breeding population size and success, confirming previous results about condition-dependent dispersal in this population. The estimated levels of heritability varied between 0.30±0.07 and 0.47±0.10, depending on parent–offspring comparisons made and correcting for a significant assortative mating with respect to dispersal status. Siblings also displayed a significant resemblance in dispersal propensity. These results suggest that variation in between-patch natal dispersal in the collared flycatcher is partly genetically determined, and we discuss ways to quantify this genetic basis and its implications. PMID:19419988

  17. Molecular phylogeny of African bush-shrikes and allies: tracing the biogeographic history of an explosive radiation of corvoid birds.

    PubMed

    Fuchs, Jérôme; Irestedt, Martin; Fjeldså, Jon; Couloux, Arnaud; Pasquet, Eric; Bowie, Rauri C K

    2012-07-01

    The Malaconotidea (e.g., butcherbirds, bush-shrikes, batises, vangas) represent an Old World assemblage of corvoid passerines that encompass many different foraging techniques (e.g., typical flycatchers, flycatcher-shrikes, canopy creepers, undergrowth skulkers). At present, relationships among the primary Malaconotidea clades are poorly resolved, a result that could either be attributed to a rapid accumulation of lineages over a short period of time (hard polytomy) or to an insufficient amount of data having been brought to bear on the problem (soft polytomy). Our objective was to resolve the phylogenetic relationships and biogeographic history of the Malaconotidea using DNA sequences gathered from 10 loci with different evolutionary properties. Given the range of substitution rates of molecular markers we sequenced (mitochondrial, sex-linked, autosomal), we also sought to explore the effect of altering the branch-length prior in Bayesian tree estimation analyses. We found that changing the branch-length priors had no major effect on topology, but clearly improved mixing of the chains for some loci. Our phylogenetic analyses clarified the relationships of several genera (e.g., Pityriasis, Machaerirhynchus) and provide for the first time strong support for a sister-group relationship between core platysteirids and core vangids. Our biogeographic reconstruction somewhat unexpectedly suggests that the large African radiation of malaconotids originated after a single over-water dispersal from Australasia around 45-33.7 mya, shedding new light on the origins of the Afrotropical avifauna. PMID:22475817

  18. Effects of nocturnal illumination on life-history decisions and fitness in two wild songbird species

    PubMed Central

    de Jong, Maaike; Ouyang, Jenny Q.; Da Silva, Arnaud; van Grunsven, Roy H. A.; Kempenaers, Bart; Visser, Marcel E.; Spoelstra, Kamiel

    2015-01-01

    The effects of artificial night lighting on animal behaviour and fitness are largely unknown. Most studies report short-term consequences in locations that are also exposed to other anthropogenic disturbance. We know little about how the effects of nocturnal illumination vary with different light colour compositions. This is increasingly relevant as the use of LED lights becomes more common, and LED light colour composition can be easily adjusted. We experimentally illuminated previously dark natural habitat with white, green and red light, and measured the effects on life-history decisions and fitness in two free-living songbird species, the great tit (Parus major) and pied flycatcher (Ficedula hypoleuca) in two consecutive years. In 2013, but not in 2014, we found an effect of light treatment on lay date, and of the interaction of treatment and distance to the nearest lamp post on chick mass in great tits but not in pied flycatchers. We did not find an effect in either species of light treatment on breeding densities, clutch size, probability of brood failure, number of fledglings and adult survival. The finding that light colour may have differential effects opens up the possibility to mitigate negative ecological effects of nocturnal illumination by using different light spectra. PMID:25780240

  19. Natural selection for earlier male arrival to breeding grounds through direct and indirect effects in a migratory songbird

    PubMed Central

    Velmala, William; Helle, Samuli; Ahola, Markus P; Klaassen, Marcel; Lehikoinen, Esa; Rainio, Kalle; Sirkiä, Päivi M; Laaksonen, Toni

    2015-01-01

    For migratory birds, the earlier arrival of males to breeding grounds is often expected to have fitness benefits. However, the selection differential on male arrival time has rarely been decomposed into the direct effect of male arrival and potential indirect effects through female traits. We measured the directional selection differential on male arrival time in the pied flycatcher (Ficedula hypoleuca) using data from 6 years and annual number of fledglings as the fitness proxy. Using structural equation modeling, we were able to take into account the temporal structure of the breeding cycle and the hierarchy between the examined traits. We found directional selection differentials for earlier male arrival date and earlier female laying date, as well as strong selection differential for larger clutch size. These selection differentials were due to direct selection only as indirect selection for these traits was nonsignificant. When decomposing the direct selection for earlier male arrival into direct and indirect effects, we discovered that it was almost exclusively due to the direct effect of male arrival date on fitness and not due to its indirect effects via female traits. In other words, we showed for the first time that there is a direct effect of male arrival date on fitness while accounting for those effects that are mediated by effects of the social partner. Our study thus indicates that natural selection directly favored earlier male arrival in this flycatcher population. PMID:25859326

  20. Effects of nocturnal illumination on life-history decisions and fitness in two wild songbird species.

    PubMed

    de Jong, Maaike; Ouyang, Jenny Q; Da Silva, Arnaud; van Grunsven, Roy H A; Kempenaers, Bart; Visser, Marcel E; Spoelstra, Kamiel

    2015-05-01

    The effects of artificial night lighting on animal behaviour and fitness are largely unknown. Most studies report short-term consequences in locations that are also exposed to other anthropogenic disturbance. We know little about how the effects of nocturnal illumination vary with different light colour compositions. This is increasingly relevant as the use of LED lights becomes more common, and LED light colour composition can be easily adjusted. We experimentally illuminated previously dark natural habitat with white, green and red light, and measured the effects on life-history decisions and fitness in two free-living songbird species, the great tit (Parus major) and pied flycatcher (Ficedula hypoleuca) in two consecutive years. In 2013, but not in 2014, we found an effect of light treatment on lay date, and of the interaction of treatment and distance to the nearest lamp post on chick mass in great tits but not in pied flycatchers. We did not find an effect in either species of light treatment on breeding densities, clutch size, probability of brood failure, number of fledglings and adult survival. The finding that light colour may have differential effects opens up the possibility to mitigate negative ecological effects of nocturnal illumination by using different light spectra. PMID:25780240

  1. Leading edge vortex in a slow-flying passerine

    PubMed Central

    Muijres, Florian T.; Johansson, L. Christoffer; Hedenström, Anders

    2012-01-01

    Most hovering animals, such as insects and hummingbirds, enhance lift by producing leading edge vortices (LEVs) and by using both the downstroke and upstroke for lift production. By contrast, most hovering passerine birds primarily use the downstroke to generate lift. To compensate for the nearly inactive upstroke, weight support during the downstroke needs to be relatively higher in passerines when compared with, e.g. hummingbirds. Here we show, by capturing the airflow around the wing of a freely flying pied flycatcher, that passerines may use LEVs during the downstroke to increase lift. The LEV contributes up to 49 per cent to weight support, which is three times higher than in hummingbirds, suggesting that avian hoverers compensate for the nearly inactive upstroke by generating stronger LEVs. Contrary to other animals, the LEV strength in the flycatcher is lowest near the wing tip, instead of highest. This is correlated with a spanwise reduction of the wing's angle-of-attack, partly owing to upward bending of primary feathers. We suggest that this helps to delay bursting and shedding of the particularly strong LEV in passerines. PMID:22417792

  2. Natural selection for earlier male arrival to breeding grounds through direct and indirect effects in a migratory songbird.

    PubMed

    Velmala, William; Helle, Samuli; Ahola, Markus P; Klaassen, Marcel; Lehikoinen, Esa; Rainio, Kalle; Sirkiä, Päivi M; Laaksonen, Toni

    2015-03-01

    For migratory birds, the earlier arrival of males to breeding grounds is often expected to have fitness benefits. However, the selection differential on male arrival time has rarely been decomposed into the direct effect of male arrival and potential indirect effects through female traits. We measured the directional selection differential on male arrival time in the pied flycatcher (Ficedula hypoleuca) using data from 6 years and annual number of fledglings as the fitness proxy. Using structural equation modeling, we were able to take into account the temporal structure of the breeding cycle and the hierarchy between the examined traits. We found directional selection differentials for earlier male arrival date and earlier female laying date, as well as strong selection differential for larger clutch size. These selection differentials were due to direct selection only as indirect selection for these traits was nonsignificant. When decomposing the direct selection for earlier male arrival into direct and indirect effects, we discovered that it was almost exclusively due to the direct effect of male arrival date on fitness and not due to its indirect effects via female traits. In other words, we showed for the first time that there is a direct effect of male arrival date on fitness while accounting for those effects that are mediated by effects of the social partner. Our study thus indicates that natural selection directly favored earlier male arrival in this flycatcher population. PMID:25859326

  3. Interspecific variation in the relationship between clutch size, laying date and intensity of urbanization in four species of hole-nesting birds.

    PubMed

    Vaugoyeau, Marie; Adriaensen, Frank; Artemyev, Alexandr; Bańbura, Jerzy; Barba, Emilio; Biard, Clotilde; Blondel, Jacques; Bouslama, Zihad; Bouvier, Jean-Charles; Camprodon, Jordi; Cecere, Francesco; Charmantier, Anne; Charter, Motti; Cichoń, Mariusz; Cusimano, Camillo; Czeszczewik, Dorota; Demeyrier, Virginie; Doligez, Blandine; Doutrelant, Claire; Dubiec, Anna; Eens, Marcel; Eeva, Tapio; Faivre, Bruno; Ferns, Peter N; Forsman, Jukka T; García-Del-Rey, Eduardo; Goldshtein, Aya; Goodenough, Anne E; Gosler, Andrew G; Grégoire, Arnaud; Gustafsson, Lars; Harnist, Iga; Hartley, Ian R; Heeb, Philipp; Hinsley, Shelley A; Isenmann, Paul; Jacob, Staffan; Juškaitis, Rimvydas; Korpimäki, Erkki; Krams, Indrikis; Laaksonen, Toni; Lambrechts, Marcel M; Leclercq, Bernard; Lehikoinen, Esa; Loukola, Olli; Lundberg, Arne; Mainwaring, Mark C; Mänd, Raivo; Massa, Bruno; Mazgajski, Tomasz D; Merino, Santiago; Mitrus, Cezary; Mönkkönen, Mikko; Morin, Xavier; Nager, Ruedi G; Nilsson, Jan-Åke; Nilsson, Sven G; Norte, Ana C; Orell, Markku; Perret, Philippe; Perrins, Christopher M; Pimentel, Carla S; Pinxten, Rianne; Richner, Heinz; Robles, Hugo; Rytkönen, Seppo; Senar, Juan Carlos; Seppänen, Janne T; Pascoal da Silva, Luis; Slagsvold, Tore; Solonen, Tapio; Sorace, Alberto; Stenning, Martyn J; Tryjanowski, Piotr; von Numers, Mikael; Walankiewicz, Wieslaw; Møller, Anders Pape

    2016-08-01

    The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole-nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large-scale study showing a species-specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and

  4. Use of on-site mycorrhizal inoculum for plant establishment on abandoned mined lands. Final report, 31 May 1988-31 March 1990

    SciTech Connect

    Helm, D.J.; Carling, D.E.

    1990-04-27

    Natural vegetation succession on abandoned coal-mined lands does not provide sufficient plant cover to control soil erosion in the short term. Soil inoculum of mycorrhizal fungi from an adjacent undisturbed area was used to inoculate balsam poplar cuttings and alder seedlings to improve plant growth. Soil inoculum contains the species of mycorrhizal fungi indigenous to the area as well as other beneficial organisms. An initial survey of mycorrhizal fungi in soils was conducted to determine the existing levels of mycorrhizal infection on native and disturbed soils. Four experiments were implemented to determine (1) fertilizer and mycorrhizal effects, (2) effects of successional stage of inoculum source, (3) effects of nitrogen sources in conjunction with mycorrhizae, and (4) the combinations of microsites, fertilizer, and mycorrhizae needed to establish vegetation on a steep slope. Soil-borne inoculum improved the growth of balsam poplar cuttings and alder seedlings over the 2-yr period.

  5. Europe's first children's hospital in a park.

    PubMed

    Baillie, Jonathan

    2015-09-01

    Just a year after the centenary of the completion of the 1914-built children's hospital which it will soon replace, this autumn will see the opening of a new Alder Hey Children's Hospital in Liverpool, dubbed Alder Hey in the Park thanks to its attractive parkland setting. The 270-bedded hospital, designed by architects, landscape architects, and interior designers, BDP, and built by Laing O'Rourke, is located in Springfield Park on Liverpool's northern fringes, and features a highly striking external design, with the three distinctive 'fingers' housing the wards bordered by extensive greenery, and the buildings topped by green undulating roofs. All the inpatient bedrooms, and indeed many other internal spaces, will enjoy parkland views. The new hospital will also reportedly offer some of Europe's most advanced children's healthcare. HEJ editor, Jonathan Baillie, reports on the construction of this stunning new healthcare facility, where children's views were key in shaping the design. PMID:26548125

  6. Dynamically Complex [6+4] and [4+2] Cycloadditions in the Biosynthesis of Spinosyn A.

    PubMed

    Patel, Ashay; Chen, Zhuo; Yang, Zhongyue; Gutiérrez, Osvaldo; Liu, Hung-Wen; Houk, K N; Singleton, Daniel A

    2016-03-23

    SpnF, an enzyme involved in the biosynthesis of spinosyn A, catalyzes a transannular Diels-Alder reaction. Quantum mechanical computations and dynamic simulations now show that this cycloaddition is not well described as either a concerted or stepwise process, and dynamical effects influence the identity and timing of bond formation. The transition state for the reaction is ambimodal and leads directly to both the observed Diels-Alder and an unobserved [6+4] cycloadduct. The potential energy surface bifurcates and the cycloadditions occur by dynamically stepwise modes featuring an "entropic intermediate". A rapid Cope rearrangement converts the [6+4] adduct into the observed [4+2] adduct. Control of nonstatistical dynamical effects may serve as another way by which enzymes control reactions. PMID:26909570

  7. Characterisation of the aroma profiles of different honeys and corresponding flowers using solid-phase microextraction and gas chromatography-mass spectrometry/olfactometry.

    PubMed

    Seisonen, Sirli; Kivima, Evelin; Vene, Kristel

    2015-02-15

    The aroma profiles of thirteen different honey samples from four botanical origins: heather (Calluna vulgaris), raspberry (Rubus idaeus), rape (Brassica napus), alder buckthorn (Frangula alnus) and the blossoms of the four corresponding flowers were investigated to find odour-active compounds exclusively representing specific honeys based on odour-active compounds from the blossoms. Gas-chromatography-mass spectrometry (GC-MS) and gas-chromatography-olfactometry were used to determine and identify the odour-active compounds. Data was analysed using agglomerative hierarchical clustering and correspondence analysis. Honeys from the same botanical origin clustered together; however, none of the identified compounds were exclusive to a particular honey/blossom combination. Heather honey had the flavour profile most different to the others. Isophorone and 2-methylbutyric acid were found only in heather honeys. Heather honey was characterised by having more "sweet" and "candy-like" notes, raspberry honeys had more "green" notes, while alder buckthorn had more "honey" and "floral" notes. PMID:25236195

  8. Studies Toward the Syntheses of Pluramycin Natural Products. The First Total Synthesis of Isokidamycin.

    PubMed Central

    O'Keefe, B. Michael; Mans, Douglas M.; Kaelin, David E.; Martin, Stephen F.

    2011-01-01

    We report the first total synthesis of the complex C-aryl glycoside isokidamycin, the epimer of the naturally-occurring pluramycin antibiotic kidamycin. The synthesis features a highly efficientDiels-Alder reaction between a substituted naphthyne and a glycosylatedfuran to form the anthracene core bearing a pendant angolosamine C-glycoside. The regiochemical outcome of the Diels-Alder reaction was controlled by employing a disposable silicon-tether to link the reactive napthyne and the glycosyl furan, rendering the cycloaddition intramolecular. The benzopyranone moietyof the aromatic nucleus was appended by cyclization of a functionalized vinylogous amide onto an advanced anthrol intermediate. The vancosamine amino glycoside was introduced by an O→C-glycoside rearrangement that produced the β-anomer. Subsequent refunctionalizations then led to isokidamycin. PMID:21804649

  9. Production of Diethyl Terephthalate from Biomass-Derived Muconic Acid.

    PubMed

    Lu, Rui; Lu, Fang; Chen, Jiazhi; Yu, Weiqiang; Huang, Qianqian; Zhang, Junjie; Xu, Jie

    2016-01-01

    We report a cascade synthetic route to directly obtain diethyl terephthalate, a replacement for terephthalic acid, from biomass-derived muconic acid, ethanol, and ethylene. The process involves two steps: First, a substituted cyclohexene system is built through esterification and Diels-Alder reaction; then, a dehydrogenation reaction provides diethyl terephthalate. The key esterification reaction leads to improved solubility and modulates the electronic properties of muconic acid, thus promoting the Diels-Alder reaction with ethylene. With silicotungstic acid as the catalyst, nearly 100% conversion of muconic acid was achieved, and the cycloadducts were formed with more than 99.0% selectivity. The palladium-catalyzed dehydrogenation reaction preferentially occurs under neutral or mildly basic conditions. The total yield of diethyl terephthalate reached 80.6% based on the amount of muconic acid used in the two-step synthetic process. PMID:26592149

  10. Poly(2-vinyl pyridine)-block-poly(ethylene oxide) featuring a furan group at the block junction-synthesis and functionalization.

    PubMed

    Rudolph, Tobias; Barthel, Markus J; Kretschmer, Florian; Mansfeld, Ulrich; Hoeppener, Stephanie; Hager, Martin D; Schubert, Ulrich S; Schacher, Felix H

    2014-05-01

    Furfuryl glycidyl ether (FGE) represents a highly versatile monomer for the preparation of reversibly cross-linkable nanostructured materials via Diels-Alder reactions. Here, the use of FGE for the mid-chain functionalization of a P2VP-b-PEO diblock copolymer is reported. The material features one furan moiety at the block junction, P2VP68 -FGE-b-PEO390 , which can be subsequently addressed in Diels-Alder reactions using maleimide-functionalized counterparts. The presence of the FGE moiety enables the introduction of dyes as model labels or the formation of hetero-grafted brushes as shell on hybrid Au@Polymer nanoparticles. This renders P2VP68 -FGE-b-PEO390 , a powerful tool for selective functionalization reactions, including the modification of surfaces. PMID:24615738

  11. Ectomycorrhizae between Alnus acuminata H.B.K. and Naucoria escharoides (Fr.:Fr.) Kummer from Argentina.

    PubMed

    Becerra, Alejandra; Daniele, Graciela; Domínguez, Laura; Nouhra, Eduardo; Horton, Tom

    2002-04-01

    Field ectomycorrhizae of Naucoria escharoides on Alnus acuminata ("andean alder", "aliso del cerro") are described in detail for the first time. Naturally occurring ectomycorrhizal roots were sampled beneath sporocarps of N. escharoides. The samples were taken from four natural forest plots at two homogeneous A. acuminata sites (Tucumán and Catamarca Provinces, Argentina). The ectomycorrhizae were characterized morphologically and compared by means of PCR/RFLP analysis of the internal transcribed spacer region of the nuclear rDNA. The most important morphological features of the ectomycorrhizae are a white to pale yellow mantle, simple to monopodial branches, hyaline emanating hyphae, abundant hyphal bundles emerging more or less perpendicularly from a plectenchymatous mantle, and an acute or rounded apex with or without a mantle. N. escharoides fruitbodies have white basal mycelium with emanating hyphae similar to those of andean alder ectomycorrhizae. The RFLP profiles of sporocarps and mycorrhizae were the same. PMID:12035728

  12. Maleimide-grafted cellulose nanocrystals as cross-linkers for bionanocomposite hydrogels.

    PubMed

    García-Astrain, C; González, K; Gurrea, T; Guaresti, O; Algar, I; Eceiza, A; Gabilondo, N

    2016-09-20

    This article deals with the preparation of bionanocomposite hydrogels from natural polymers and nanoentities, an emerging class of materials for biotechnological and biomedical applications. Herein, the applicability of the Diels-Alder "click" reaction to the design of bionanocomposite hydrogels from furan modified gelatin using maleimide-functionalized cellulose nanocrystals as multifunctional cocross-linkers is demonstrated. The functionalization of cellulose nanocrystals with maleimide moieties was confirmed by XPS. The swelling and rheological properties of the resulting bionanocomposite confirmed the formation of hydrogel networks with covalently embedded nanoentities. The Diels-Alder reaction resulted in the formation of stiffer networks with lower swelling ratios due to the formation of additional cross-linking points. The designed "click" strategy proved to be a promising candidate for the formation of fully renewable bionanocomposite hydrogels. PMID:27261734

  13. Synthesis of allocolchicinoids: a 50 year journey

    NASA Astrophysics Data System (ADS)

    Sitnikov, N. S.; Fedorov, A. Yu

    2013-05-01

    Published data on the stereo- and enantioselective synthesis of allocolchicinoids, which are of interest as antitumour agents, are summarized. The stereochemistry of these compounds is described. Two key approaches to their preparation are considered, namely, the synthesis from natural colchicine and total synthesis from commercially available reagents. Various total syntheses of N-acetylcolchicinol are performed using biaryl oxidative and reductive coupling, cyclopropanation-ring expansion and Nicholas reaction. The synthetic routes to allocolchicine are based on Diels-Alder cycloaddition, combination of metathesis and Diels-Alder reaction and direct catalytic CH-arylation. Analogues of the colchicine site ligands incorporating heteroaromatic rings are briefly considered; their structural features and methods of synthesis are discussed. The bibliography includes 144 references.

  14. Addition polymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and Bis-dienes. 2: Evidence for thermal dehydration occurring in the cure process

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Olshavsky, Michael A.; Meador, Michael A.; Ahn, Myong-Ku

    1988-01-01

    Diels-Alder cycloaddition copolymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and anthracene end-capped polyimide oligomers appear, by thermogravimetric analysis (TGA), to undergo dehydration at elevated temperatures. This would produce thermally stable pentiptycene units along the polymer backbone, and render the polymers incapable of unzipping through a retro-Diels-Alder pathway. High resolution solid 13C nuclear magnetic resonance (NMR) of one formulation of the polymer system before and after heating at elevated temperatures, shows this to indeed be the case. NMR spectra of solid samples of the polymer before and after heating correlated well with those of the parent pentiptycene model compound before and after acid-catalyzed dehydration. Isothermal gravimetric analyses and viscosities of the polymer before and after heat treatment support dehydration as a mechanism for the cure reaction.

  15. Pathway-Dependent Post-assembly Modification of an Anthracene-Edged M(II)4L6 Tetrahedron.

    PubMed

    Ronson, Tanya K; Pilgrim, Ben S; Nitschke, Jonathan R

    2016-08-24

    Fe(II)4L6 tetrahedral cage 1 undergoes post-assembly modification (PAM) via a Diels-Alder cycloaddition of the anthracene panels of the cage with tetracyanoethylene (TCNE). The modified cage 2 possesses an enclosed cavity suitable for encapsulation of the fullerene C60, whereas original cage 1 forms a unique covalent adduct through a Diels-Alder cycloaddition of three of its anthracene ligands with C60. This adduct undergoes further PAM via reaction of the remaining three ligands with TCNE, enabling the isolation of two distinct products depending on the order of addition of C60 and TCNE. Modified cage 2 was also able to bind an anionic guest, [Co(C2B9H11)2](-), which was not encapsulated by the original cage, demonstrating the potential of PAM for tuning the binding properties of supramolecular hosts. PMID:27500974

  16. UNIFAC parameters for maleic anhydride and 2-methyl furan in p-dioxane system

    SciTech Connect

    Daumn, K.J.

    1983-01-01

    The purpose of this work was to develop a method for calculating equilibrium concentrations for reversible liquid phase reactions from a minimum of experimental data. The example reaction studied was the Diels Alder reaction between 2-methyl furan and maleic anhydride. Specifically, interaction parameters of the UNIFAC model for groups in the compounds 2-methyl furan, maleic anhydride and the solvent, p-dioxane, were determined. The activity coefficient of each substance was then predicted by the UNIFAC method. Equilibrium constants at 45/sup 0/C for the Diels Alder reaction between 2-methyl furan and maleic anhydride were then calculated from these activity coefficients and two previously determined sets of equilibrium concentrations at 45/sup 0/C. These two equilibrium constants were within 12% of each other, which demonstrated the validity of the method.

  17. Polyimides by Photochemical Cyclopolymerization

    NASA Technical Reports Server (NTRS)

    Meador, Michael A. (Inventor)

    2005-01-01

    The novel polyimides of this invention are derived from Diels-Alder cyclopolymerization of photochemically generated bisdienes with dienophiles, such as bismaleimides, trismaleimides and mixtures thereof with maleimide endcaps. Irradiation of one or more diketones produces two distinct hydroxy o-quinodimethane (photoenol) intermediates. These intermediates are trapped via Diels-Alder cycloaddition with appropriate dienophiles, e.g., bismaleimide and/or trismaleimides to give the corresponding polyimides in quantitative yields. When bismaleimides, trismaleimides or mixtures thereof with maleimide end-caps are used as the dienophile, the resulting polyimides have glass transition temperatures (Tg) as high as 300 C. Polyimide films can be prepared by ultraviolet irradiation of high solids content varnishes of the monomers in a small amount of solvent, e.g., cyclohexanone, dimethyl formamide, N-methylpyrollidone and the like. These novel polyimides are characterized as having high glass transition temperatures, good mechanical properties and improved processing in the manufacture of adhesives, electronic materials and films.

  18. Polyimides by photochemical cyclopolymerization

    NASA Technical Reports Server (NTRS)

    Meador, Michael A. (Inventor)

    2005-01-01

    The novel polyimides of this invention are derived from Diels-Alder cyclopolymerization of photochemically generated bisdienes with dienophiles, such as bismaleimides, trismaleimides and mixtures thereof with maleimide end-caps. Irradiation of one or more diketones produces two distinct hydroxy o-quinodimethane (photoenol) intermediates. These intermediates are trapped via Diels-Alder cycloaddition with appropriate dienophiles, e.g., bismaleimide and/or trismaleimides to give the corresponding polyimides in quantitative yields. When bismaleimides, trismaleimides or mixtures thereof with maleimide end-caps are used as the dienophile, the resulting polyimides have glass transition temperatures (Tg) as high as 300? C. Polyimide films can be prepared by ultraviolet irradiation of high solids content varnishes of the monomers in a small amount of solvent, e.g., cyclohexanone, dimethyl formamide, N-methylpyrollidone and the like. These novel polyimides are characterized as having high glass transition temperatures, good mechanical properties and improved processing in the manufacture of adhesives, electronic materials and films.

  19. Intramolecular cycloaddition in 6,6-spiroepoxycyclohexa-2,4-dienone: simple aromatics to (+/-)-platencin.

    PubMed

    Singh, Vishwakarma; Sahu, Bharat Chandra; Bansal, Varsha; Mobin, Shaikh M

    2010-10-01

    A formal total synthesis of platencin from a simple aromatic precursor is described. Transformation of the aromatic compound into reactive spiroepoxycyclohexa-2,4-dienone and intramolecular cycloaddition are the key features of our methodology. 2-Hydroxymethyl-6-(3-hydroxy-hex-5-enyl)-phenol was oxidized with NaIO(4) to give a dimer that, upon a retro-Diels-Alder reaction, generated the spiroepoxycyclohexa-2,4-dienone that underwent intramolecular Diels-Alder reaction to give a tricyclic adduct having a core structure of platencin and appropriately disposed functional groups in a single step. Reduction of the double bond present in the ethano-bridge, manipulation of the oxirane ring and introduction of a double bond in the six-membered ring furnished a tricyclic intermediate which has already been converted into platencin. PMID:20683538

  20. The 2.5-diacyl-1,4-dimethylbenzenes: Examples of bisphotoenol equivalents

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.

    1987-01-01

    The photochemistry of 2,5-dibenzoyl(DBX)-and 2,5-diacetyl-1,4-dimethylbenzene (DAX) has been investigated. Both compounds readily undergo photoenolization similar to 0-alkylphenyl ketones. However, unlike 0-alkylphenyl ketones DAX and DBX are each capable of undergoing two tandem photoenolizations. Photoenols derived from o-alkylphenyl ketones have been successfully trapped with Diels-Alder dienophiles to provide a convenient synthesis of substituted tetralins. Similarly, Diels-Alder trapping of DBX photoenils afforded substituted tetra- and octahydro anthracenes. Further mainpulation of these photadducts provided the corresponding anthracenes in good yield. The photochemistry of DAX and DBX will be discussed, in particular their use in the synthesis of substituted anthracenes.

  1. Nearby Supernova Factory II classification of the SN Ia LSQ13ads and non-detection of LSQ13acp

    NASA Astrophysics Data System (ADS)

    Baugh, D.; Chen, J.; Chotard, N.; Wu, C.; Tao, C.; Fouchez, D.; Tilquin, A.; Hadjiyska, E.; Rabinowitz, D.; Baltay, C.; Ellman, N.; McKinnon, R.; Walker, E.; Effron, A.; Cellier-Holzem, F.; Canto, A.; Antilogus, P.; Bongard, S.; Pain, R.; Copin, Y.; Gangler, E.; Pereira, R.; Rigault, M.; Smadja, G.; Aldering, G.; Birchall, D.; Fakhouri, H.; Kim, A.; Nordin, J.; Nugent, P.; Perlmutter, S.; Runge, K.; Saunders, C.; Suzuki, N.; Pecontal, R. C. Thomas E.; Feindt, U.; Kowalski, M.; Benitez, S.; Hillebrandt, W.; Kromer, M.; Sasdelli, M.; Sternberg, A.; Taubenberger, S.

    2013-04-01

    The Nearby Supernova Factory II (http://snfactory.lbl.gov) reports the following spectroscopic observations of supernovae based on spectra (range 320-1000 nm) obtained with the SuperNova Integral Field Spectrograph (Aldering et al 2002, SPIE, 4836, 61) on the University of Hawaii 2.2-meter telescope. Classifications were performed using Superfit (Howell et al 2002, BAAS, 34, 1256) or SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

  2. Nearby Supernova Factory II classification of the SN Ia LSQ13yd

    NASA Astrophysics Data System (ADS)

    Feindt, U.; Kowalski, M.; Benitez, S.; Hillebrandt, W.; Kromer, M.; Sasdelli, M.; Sternberg, A.; Taubenberger, S.; Baugh, D.; Chen, J.; Chotard, N.; Wu, C.; Tao, C.; Fouchez, D.; Tilquin, A.; Hadjiyska, E.; Rabinowitz, D.; Baltay, C.; Ellman, N.; McKinnon, R.; Walker, E.; Effron, A.; Cellier-Holzem, F.; Canto, A.; Antilogus, P.; Bongard, S.; Pain, R.; Copin, Y.; Gangler, E.; Pereira, R.; Rigault, M.; Smadja, G.; Aldering, G.; Birchall, D.; Fakhouri, H.; Kim, A.; Nordin, J.; Nugent, P.; Perlmutter, S.; Runge, K.; Saunders, C.; Suzuki, N.; Pecontal, R. C. Thomas E.

    2013-04-01

    The Nearby Supernova Factory II (http://snfactory.lbl.gov) reports the following spectroscopic observations of supernovae based on spectra (range 320-1000 nm) obtained with the SuperNova Integral Field Spectrograph (Aldering et al 2002, SPIE, 4836, 61) on the University of Hawaii 2.2-meter telescope. Classifications were performed using Superfit (Howell et al 2002, BAAS, 34, 1256) or SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

  3. Nearby Supernova Factory II classification of CSS130502:114010+3001461 and LSQ13afs

    NASA Astrophysics Data System (ADS)

    Tao, C.; Fouchez, D.; Tilquin, A.; Hadjiyska, E.; Rabinowitz, D.; Baltay, C.; Ellman, N.; McKinnon, R.; Walker, E.; Effron, A.; Cellier-Holzem, F.; Canto, A.; Antilogus, P.; Bongard, S.; Pain, R.; Copin, Y.; Gangler, E.; Pereira, R.; Rigault, M.; Smadja, G.; Aldering, G.; Birchall, D.; Fakhouri, H.; Kim, A.; Nordin, J.; Nugent, P.; Perlmutter, S.; Runge, K.; Saunders, C.; Suzuki, N.; Pecontal, R. C. Thomas E.; Feindt, U.; Kowalski, M.; Benitez, S.; Hillebrandt, W.; Kromer, M.; Sasdelli, M.; Sternberg, A.; Taubenberger, S.; Baugh, D.; Chen, J.; Chotard, N.; Wu, C.

    2013-05-01

    The Nearby Supernova Factory II (http://snfactory.lbl.gov) reports the following spectroscopic observations of supernovae based on spectra (range 320-1000 nm) obtained with the SuperNova Integral Field Spectrograph (Aldering et al 2002, SPIE, 4836, 61) on the University of Hawaii 2.2-meter telescope. Classifications were performed using Superfit (Howell et al 2002, BAAS, 34, 1256) or SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

  4. Nearby Supernova Factory II classification of five SNe Ia

    NASA Astrophysics Data System (ADS)

    Pecontal, E.; Feindt, U.; Greskovic, P.; Kowalski, M.; Lombardo, S.; Benitez, S.; Hillebrandt, W.; Kromer, M.; Sasdelli, M.; Sternberg, A.; Taubenberger, S.; Baugh, D.; Chen, J.; Wu, C.; Tao, C.; Fouchez, D.; Tilquin, A.; Hadjiyska, E.; Rabinowitz, D.; Baltay, C.; Ellman, N.; McKinnon, R.; Walker, E.; Effron, A.; Cellier-Holzem, F.; Canto, A.; Antilogus, P.; Bongard, S.; Fleury, M.; Copin, R. Pain Y.; Chotard, N.; Gangler, E.; Pereira, R.; Rigault, M.; Smadja, G.; Aldering, G.; Birchall, D.; Fakhouri, H.; Kim, A.; Nordin, J.; Nugent, P.; Perlmutter, S.; Rubin, D.; Runge, K.; Saunders, C.; Sofiatti, C.; Suzuki, N.; Thomas, R. C.

    2013-08-01

    The Nearby Supernova Factory II (http://snfactory.lbl.gov) reports the following spectroscopic observations of supernovae based on spectra (range 320-1000 nm) obtained with the SuperNova Integral Field Spectrograph (Aldering et al 2002, SPIE, 4836, 61) on the University of Hawaii 2.2-meter telescope. Classifications were performed using Superfit (Howell et al 2002, BAAS, 34, 1256) or SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

  5. Nearby Supernova Factory II classification of three SNe and two non-detections

    NASA Astrophysics Data System (ADS)

    Aldering, G.; Birchall, D.; Fakhouri, H.; Kim, A.; Nordin, J.; Nugent, P.; Perlmutter, S.; Rubin, D.; Runge, K.; Saunders, C.; Sofiatti, C.; Suzuki, N.; Thomas, R. C.; Pecontal, E.; Feindt, U.; Greskovic, P.; Kowalski, M.; Lombardo, S.; Benitez, S.; Hillebrandt, W.; Kromer, M.; Sasdelli, M.; Sternberg, A.; Taubenberger, S.; Baugh, D.; Chen, J.; Wu, C.; Tao, C.; Fouchez, D.; Tilquin, A.; Hadjiyska, E.; Rabinowitz, D.; Baltay, C.; Ellman, N.; McKinnon, R.; Walker, E.; Effron, A.; Cellier-Holzem, F.; Canto, A.; Antilogus, P.; Bongard, S.; Fleury, M.; Copin, R. Pain Y.; Chotard, N.; Gangler, E.; Pereira, R.; Rigault, M.; Smadja, G.

    2013-07-01

    The Nearby Supernova Factory II (http://snfactory.lbl.gov) reports the following spectroscopic observations of supernovae based on spectra (range 320-1000 nm) obtained with the SuperNova Integral Field Spectrograph (Aldering et al 2002, SPIE, 4836, 61) on the University of Hawaii 2.2-meter telescope. Classifications were performed using Superfit (Howell et al 2002, BAAS, 34, 1256) or SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

  6. Synthesis of sp(3)-rich scaffolds for molecular libraries through complexity-generating cascade reactions.

    PubMed

    Flagstad, T; Min, G; Bonnet, K; Morgentin, R; Roche, D; Clausen, M H; Nielsen, T E

    2016-06-01

    An efficient strategy for the synthesis of complex small molecules from simple building blocks is presented. Key steps of the strategy include tandem Petasis and Diels-Alder reactions, and divergent complexity-generating cyclization cascades from a key dialdehyde intermediate. The methodology is validated through the synthesis of a representative compound set, which has been used in the production of 1617 molecules for the European Lead Factory. PMID:27171614

  7. Modular Synthesis of the Pentacyclic Core of Batrachotoxin and Select Batrachotoxin Analogue Designs

    PubMed Central

    Devlin, A. Sloan

    2012-01-01

    Pentacyclic analogues of the potent voltage-gated sodium ion channel agonist batrachotoxin can be accessed through an intermediate furan by exploiting Diels-Alder cycloaddition reactions with ring-strained dienophiles. The use of 3-bromofuran as a 1,2-dianion equivalent, the application of carbamate reductive N-alkylation for homomorpholine ring assembly, and the demonstration of CsF as an effective reagent for generating benzyne, cyclohexyne, and related dienophiles underscore this work. PMID:23641312

  8. Of parachuting spiders and meat-eating beetles

    USGS Publications Warehouse

    Booth, W.

    1990-01-01

    Here and there on the rolling hills of gray volcanic ash around the volcano are clumps of invading fireweed and another pioneer called pearly everlasting. Alder and Willow saplings grow sporadically along the otherwise barren stream courses. Plugs of grass sprout in piles of elk droppings. And deer mic and pocket gophers, the survivialists of the animal world, also have managed to gain foothold. 

  9. C2-Symmetric diamines and their derivatives as promising organocatalysts for asymmetric synthesis

    NASA Astrophysics Data System (ADS)

    Zlotin, S. G.; Kochetkov, S. V.

    2015-11-01

    The review is devoted to the application of C2-symmetric diamines and their derivatives as organocatalysts for asymmetric reactions (aldol, Michael, Mannich, Diels-Alder reactions, desymmetrization, allylation, etc.). Amino acid derivatives, di- and polyamides (sulfamides), bisureas, bisthioureas, bisamidines and bisguanidines are considered. Significant attention is given to the effect of the catalyst structure on the mechanism of catalytic action. Successful applications of such catalysts in enantioselective synthesis of chiral biologically active compounds are summarized. The bibliography includes 181 references.

  10. Total synthesis of (-)-spinosyn A.

    PubMed

    Mergott, Dustin J; Frank, Scott A; Roush, William R

    2004-08-17

    A convergent, highly stereoselective total synthesis of (-)-spinosyn A (1) is described. Key features of the synthesis include the transannular Diels-Alder reaction of macrocyclic pentaene 11 and the transannular Morita-Baylis-Hillman cyclization of 12 that generates tetracycle 26. The total synthesis of (-)-spinosyn A was completed by a sequence involving the highly beta-selective glycosidation reaction of 13 and glycosyl imidate 30. PMID:15173590

  11. Total Synthesis of (−)-Calyciphylline N

    PubMed Central

    Shvartsbart, Artem; Smith, Amos B.

    2014-01-01

    The total synthesis of the architecturally complex Daphniphyllum alkaloid (−)-calyciphylline N has been achieved. Highlights of the synthesis include a Et2AlCl promoted, highly stereoselective susbtrate controlled intramolecular Diels-Alder reaction, a transannular enolate alkylation, an effective Stille carbonylation/Nazarov cyclization sequence, and a high risk dia-stereoselective hydrogenation of a fully substituted conjugated diene ester. PMID:24319987

  12. The Daphniphyllum Alkaloids: Total Synthesis of (−)-Calyciphylline N

    PubMed Central

    2016-01-01

    Presented here is a full account on the development of a strategy culminating in the first total synthesis of the architecturally complex daphniphyllum alkaloid, (−)-calyciphylline N. Highlights of the approach include a highly diastereoselective, intramolecular Diels–Alder reaction of a silicon-tethered acrylate; an efficient Stille carbonylation of a sterically encumbered vinyl triflate; a one-pot Nazarov cyclization/proto-desilylation sequence; and the chemoselective hydrogenation of a fully substituted diene ester. PMID:25756504

  13. Nitrogen fixation in forested soils by non-leguminous nitrogen-fixing plants and by non-symbiotic soil organisms. Progress report, June 1, 1979-May 31, 1980

    SciTech Connect

    Lane, C.L.

    1980-05-01

    Field plantings of several species of nitrogen-fixing plants mixed with loblolly pine were measured after two growing seasons on three sites. Survival of loblolly pine was 86%; thorny eleagnus 97%; black alder 58%; and wax myrtle 88%. There was no evidence of an increase in the growth of the loblolly pine caused by the nitrogen-fixing species. Considerable deer browse damage was evident on the thorny eleagnus planted on a deep sand.

  14. Biomimetic Total Syntheses of (−)-Leucoridines A and C through the Dimerization of (−)-Dihydrovalparicine

    PubMed Central

    Kokkonda, Praveen; Brown, Keaon R.; Seguin, Trevor J.; Wheeler, Steven E.; Vaddypally, Shivaiah; Zdilla, Michael J.; Andrade, Rodrigo B.

    2016-01-01

    Concise biomimetic syntheses of the Strychnos-Strychnos-type bis-indole alkaloids (−)-leucoridine A (1) and C (2) were accomplished through the biomimetic dimerization of (−)-dihydrovalparicine (3). En route to 3, the known alkaloids (+)-geissoschizoline (8) and (−)-dehydrogeissoschizoline (10) were also prepared. DFT calculations were employed to elucidate the mechanism, which favors a stepwise aza-Michael/spirocyclization sequence over the alternate hetero-Diels–Alder cycloaddition reaction. PMID:26315453

  15. EFFECT OF SIMULATED SULFURIC ACID RAIN ON THE CHEMISTRY OF A SULFATE-ADSORBING FOREST SOIL

    EPA Science Inventory

    Simulated H2SO4 rain (pH 3.0, 3.5, 4.0) or control rain (pH 5.6) was applied for 3.5 yr to large lysimeter boxes containing a sulfate-adsorbing forest soil and either red alder (Alnus rubra) or sugar maple (Acer saccharum) seedlings. After removal of the plants and the litter lay...

  16. Simultaneous introduction of trifluoromethyl and λ(6)-pentafluorosulfanyl substituents using F5S-C≡C-CF3 as a dienophile.

    PubMed

    Duda, Blazej; Lentz, Dieter

    2015-05-28

    F5S-C≡C-CF3 can be easily prepared in high yields in two steps from 3,3,3-trifluoropropyne. It is a powerful, versatile dienophile in Diels-Alder reactions. Reactions at room temperature provide the corresponding products in up to quantitative yields allowing the introduction of the pentafluorosulfanyl group and trifluoromethyl group at the 1,2 position. PMID:25906359

  17. Preparations and properties of anti-corrosion additives of water-soluble metal working fluids for aluminum alloy materials.

    PubMed

    Watanabe, Shoji

    2008-01-01

    This short review describes various types of anti-corrosion additives of water-soluble metal working fluids for aluminum alloy materials. It is concerned with synthetic additives classified according to their functional groups; silicone compounds, carboxylic acids and dibasic acids, esters, Diels-Alder adducts, various polymers, nitrogen compounds, phosphoric esters, phosphonic acids, and others. Testing methods for water-soluble metal working fluids for aluminum alloy materials are described for a practical application in a laboratory. PMID:18075217

  18. Asymmetric Total Synthesis of (-)-Maoecrystal V.

    PubMed

    Zhang, Wei-bin; Shao, Wen-bin; Li, Fu-zhuo; Gong, Jian-xian; Yang, Zhen

    2015-09-01

    The asymmetric total synthesis of (-)-maoecrystal V, a novel cytotoxic pentacyclic ent-kaurane diterpene, has been accomplished. Key steps of the current strategy involve an early-stage semipinacol rearrangement reaction for the construction of the C10 quaternary stereocenter, a rhodium-catalyzed intramolecular O-H insertion reaction, and a sequential Wessely oxidative dearomatization/intramolecular Diels-Alder reaction to forge the pentacyclic framework of maoecrystal V. PMID:26136342

  19. Bisannelation with a benzo(1,2-c:4,5-c-prime) difuran equivalent - A new route to linear acene derivatives

    NASA Technical Reports Server (NTRS)

    Luo, Jihmei; Hart, Harold

    1988-01-01

    It was observed that the base peak in the mass spectra of all the Diels-Alder bis adducts of anthracene diendoxide as well as of its tetrahydro derivative appear at m/e 158, corresponding to the radical cation of benzo(1,2-c:4,5-c-prime) difuran (BDF). This paper describes a synthetic equivalent of BDF and demonstrates its utility for obtaining linear acene derivatives.

  20. Supercritical fluid reactions for coal processing. Quarterly report, July 1--September 30, 1996

    SciTech Connect

    Eckert, C.A.

    1996-12-31

    Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we propose to develop a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The Diels-Alder reaction of anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) was chosen as the model system and was investigated in supercritical carbon dioxide.