Modality effects in vocabulary acquisition

It is unknown whether modality affects the efficiency with which humans learn novel word forms and their meanings, with previous studies reporting both written and auditory advantages. The current study implements controls whose absence in previous work likely offers explanation for such contradictory findings. In two novel word learning experiments, participants were trained and tested on pseudoword - novel object pairs, with controls on: modality of test, modality of meaning, duration of exposure and transparency of word form. In both experiments word forms were presented in either their written or spoken form, each paired with a pictorial meaning (novel object). Following a 20-minute filler task, participants were tested on their ability to identify the picture-word form pairs on which they were trained. A between subjects design generated four participant groups per experiment 1) written training, written test; 2) written training, spoken test; 3) spoken training, written test; 4) spoken training, spoken test. In Experiment 1 the written stimulus was presented for a time period equal to the duration of the spoken form. Results showed that when the duration of exposure was equal, participants displayed a written training benefit. Given words can be read faster than the time taken for the spoken form to unfold, in Experiment 2 the written form was presented for 300 ms, sufficient time to read the word yet 65% shorter than the duration of the spoken form. No modality effect was observed under these conditions, when exposure to the word form was equivalent. These results demonstrate, at least for proficient readers, that when exposure to the word form is controlled across modalities the efficiency with which word form-meaning associations are learnt does not differ. Our results therefore suggest that, although we typically begin as aural-only word learners, we ultimately converge on developing learning mechanisms that learn equally efficiently from both written and spoken materials

Spatiotemporal variation of methane and other trace hydrocarbon concentrations in the valley of Mexico

Mexico City is the world's largest and most polluted urban center. We examine the distribution of methane and other hydrocarbons within the Valley of Mexico, using it as a model for the role developing megacities will play in the next century of geochemical cycling. Seventy-five whole air samples were analyzed with multivariate statistical techniques, including factor analysis using principal components. Methane concentrations are highly variable in space and time, due to air circulations and source distribution. Landfills and open sewage canals are major inputs. Emissions into and out from the valley are modeled to be ∼515 t per day. Per capita emission is 0.01 t per annum per person, consistent with the global average for human related anaerobic generation. Natural gas leaks are small, and likely to be higher in other developing megacities; Mexican natural gas use has been discouraged out of earthquake safety concerns. In contrast, liquefied petroleum gas loss constitutes the major emission of propane and butane estimated at a leak rate of 5-10%. Kyoto and other environmental conventions have ignored methane as a greenhouse gas. Our analysis underscores the need to consider methane and other hydrocarbons, and the urbanization process, in future emission protocols. © 2002 Elsevier Science Ltd. All rights reserved

Nonmethane hydrocarbon and halocarbon distributions during Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange, June 1992

Aircraft measurements of selected nonmethane hydrocarbon and halocarbon species were made in the lower troposphere of the NE Atlantic near the Azores, Portugal, during June 1992 as part of the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange. In this paper, the impact of continental outflow from both Europe and North America on the study region were assessed. Four main air mass types were characterized from trajectories and trace gas concentrations: clean marine from the Atlantic, and continental air from the Iberian Peninsula, the British Isles and Northern Europe, and North America. Each classification exhibited trace gas concentrations that had been modified en route by photochemical processes and mixing. Comparison with the clean marine boundary layer (MBL) shows that the boundary layer of the predominantly continental air masses were enhanced in hydrocarbons and halocarbons by factors of approximately 2 for ethane, 5 for propane, 2-6 for ethyne and benzene, and 2-3 for C2Cl4. The same air masses also exhibited large ozone enhancements, with 2 to 3 times higher mixing ratios in the continental boundary layer air compared to the clean MBL. This indicates a primarily anthropogenic photochemical source for a significant fraction of the lower tropospheric ozone in this region. Methyl bromide exhibited on average 10-20% higher concentrations in the boundary layer affected by continental outflow than in the clean MBL, and was seen to be enhanced in individual plumes of air of continental origin. This is consistent with significant anthropogenic sources for methyl bromide. In addition, median MBL concentrations of ethene and methyl iodide showed enhancements of approximately a factor of 2 above free tropospheric values, suggesting primarily coastal/oceanic sources for these species. Copyright 1996 by the American Geophysical Union

Hydrocarbon and halocarbon measurements as photochemical and dynamical indicators of atmospheric hydroxyl, atomic chlorine, and vertical mixing obtained during Lagrangian flights

Nonmethane hydrocarbons and halocarbons were measured during two Lagrangian experiments conducted in the lower troposphere of the North Atlantic as part of the June 1992, Atlantic Stratosphere Transition Experiment/Marine Aerosol and Gas Exchange (ASTEX/MAGE) expedition. The first experiment was performed in very clean marine air. Meteorological observations indicate that the height of the marine boundary layer rose rapidly, entraining free tropospheric air. However, the free tropospheric and marine boundary layer halocarbon concentrations were too similar to allow this entrainment to be quantified by these measurements. The second Lagrangian experiment took place along the concentration gradient of an aged continental air mass advecting from Europe. The trace gas measurements confirm that the National Center for Atmospheric Research (NCAR) Electra aircraft successfully intercepted the same air mass on consecutive days. Two layers, a surface layer and a mixed layer with chemically distinct compositions, were present within the marine boundary layer. The composition of the free troposphere was very different from that of the mixed layer, making entrainment from the free troposphere evident Concentrations of the nonmethane hydrocarbons in the Lagrangian surface layer were observed to become depleted relative to the longer-lived tetrachloroethene. A best fit to the observations was calculated using various combinations of the three parameters, loss by reaction with hydroxyl, loss by reaction with chlorine, and/or dilution from the mixed layer. These calculations provided estimated average concentrations in the surface layer for a 5-hour period from dawn to 11 UT of 0.3±0.5 ×106 molecules cm-3 for HO, and 3.3±;1.1 ×104 molecules cm-3 for Cl. Noontime concentration estimates were 2.6±0.7 ×106 molecules cm-3 for HO and 6.5±1.4 ×104 molecules cm-3 for Cl. Copyright 1996 by the American Geophysical Union

Expanded concept and revised taxonomy of the milliped family Xystodesmidae Cook, 1895 (Polydesmida: Leptodesmidea: Xystodesmoidea): incorporations of Euryuridae Pocock, 1909 and Eurymerodesmidae Causey, 1951, taxon revivals/proposals/transferrals, and a distributional update

Euryuridae Pocock 1909 and Eurymerodesmidae Causey 1951, both endemic to the eastern/central United States (US), are incorporated into Xystodesmidae Cook 1895 and reduced to subfamilies and (sub)tribes n. stats. Euryurina and Melaphina Brolemann 1916, n. stats., are sister-taxa that differ primarily in epiproctal configurations and comprise Euryurini; sister-taxa Eurymerodesmina and Nannariina Hoffman 1964, n. stats., the latter transferred from Xystodesminae, comprise Eurymerodesmini, n. stat., in which plesiomorphic forms exhibit sublinear, “stick-like,” and subapically curved/bent gonopodal acropodites with moderately-long to long hairs, often with distal tufts, on their “inner” surfaces. Additional transferrals include Wamokia Chamberlin from the xystodesmine tribe Xystocheirini to Xystodesmini (= Harpaphini), and Macellolophus Attems, from Xystodesmidae to Chelodesmidae. Except for Chonaphini, the term, “prefemoral process,” has traditionally been assigned to the secondary and shorter telopodital projection regardless of its position, origin, or configuration. Homology of these different structures has never been demonstrated and requires investigation, but the multitude of differences suggests that they are not such and warrant different names, for example “femoral process,” for the similarly positioned branches in Devillea Brölemann and Rhysodesmus Cook (Xystodesminae: Devilleini, Rhysodesmini). The latter tribe may be polyphyletic, and new tribes may be required for components with acicular “prefemoral processes” (Boraria and Cherokia, both by Chamberlin, Gyalostethus and Erdelyia, both by Hoffman, and Pleuroloma Rafinesque) and the southeastern US genera with small-bodied species (Caralinda Hoffman and Gonoessa, Parvulodesmus, and Lourdesia, all by Shelley). Taxonomic value is accorded the “prefemoral extension/elongation,” which is absent from Eurymerodesmina; complete, encircles the acropodite, and extends for ~1/3 to 1/2 of the latter’s lengths in Euryurini; and incomplete and extends for ~1/4 to 1/3 of the “outer” acropodital surfaces in Nannariina and xystodesmine tribes. Other newly recognized taxonomic characters include the “inner” and “outer” acropodital surfaces/margins, the position on the acropodital stem of the “distal curve/bend,” and the length of the “distal zone.” Rhysodesmus and Sigmoria (Rudiloria) t. trimaculata (Wood) (Xystodesminae: Rhysodesmini, Apheloriini) are recorded from, respectively, Chihuahua, Mexico, and Québec, Canada, as are Xystodesmidae/-inae and, provisionally, Chonaphini, Montaphe Chamberlin, and M. elrodi(Chamberlin), the only plausible taxa for an unidentifiable juvenile from near Yahk and only 2.5 km (1.6 mi) north of the International Border. The southern periphery of interior British Columbia (BC) thus represents the second xystodesmid faunal region in BC and the third in Canada. While incorporation of Euryuridae does not affect the family’s overall distribution, that of Eurymerodesmidae fundamentally alters it by joining the formerly separate East-Nearctic and Meso-American regions into a continuous one extending, north-south, from Montréal Island, Québec, to Santa Ana Department, El Salvador, a distance of around 4,944 km (3,090 mi). Xystodesmidae also inhabit two West-Nearctic regions, one in the interior stretching from southernmost BC to northeastern Oregon and the other running along the Pacific Coast from southern Alaska to southern California. The family also occupies two Palearctic regions, each with three subregions, an eastern one spreading from Hokkaido, Japan, and the southern Maritime Province, Russia, to Taiwan; a point locality in northern Vietnam; and southern/eastern China. The second Palearctic area extends along the Mediterranean and adjoining seas from Morocco, Sardinia, and the southeastern corner of France to Cyprus and southern coastal Turkey. New locality data, references, and maps are provided along with diagnostic accounts of all reconceptualized taxa and new/revived statuses. A simple, sublinear, “stick-like” acropodite with a curve or bend near midlength or subapically and without a secondary telopodital projection is the hypothesized plesiomorphic gonopodal condition in Xystodesmidae. This form has undergone multitudinous modifications/alterations – twists, curls, variably configured thickened and laminate expansions, reductions, bi-/trifurcations, enlargements, ornamentations, etc. that are manifested in today’s xystodesmine tribes. When Avalonia collided with Baltica 450 million years ago, ancestral xystodesmoideans on the former dispersed into the latter, penetrated and occupied vacant niches, and evolved into today’s Melaphina (Euryurinae: Euryurini) and Devilleina (Xystodesminae). A similar evolutionary burst leading to today’s Nearctic and East-Palearctic faunas occurred 10 million years later when Avalonia + Baltica collided with Laurentia to form Euramerica. Ancestral forms of Euryurinae and Xystodesminae again penetrated vacant niches and evolved; the former maintained the general gonopodal structural pattern of Melaphina but changed the epiproct from triangular to broad and spatulate, thereby creating Euryurina. The earliest xystodesmine taxa to evolve in Laurentia were Rhysodesmini and Rhysodesmus, which spread southwestward, penetrated “proto- Mexico, and left relict populations in today’s southern Appalachians. Eurymerodesmina and Nannariina arose from ancestral euryurine stock prior to the Cretaceous in western Appalachia in their present area of overlap. The former dispersed to the west and south while the latter expanded to the east and north; consequently, the Western Inland Seaway minimally impacted Nannariina while eradicating Eurymerodesmina from the inundated area. Today’s populations in the Plains and south-southeastern states therefore represent secondary dispersion in the past 50-60 million years. The Seaway also eradicated Rhysodesmus from these areas, but enough forms survived in high mountain refugia to replenish the fauna when the embayment receded