1,114 research outputs found
Direct writing of optical microresonators in a lab-on-a-chip for label-free biosensing
Whispering gallery mode (WGM) resonators are promising optical structures for microfluidic label-free bio-sensors mainly due to their high sensitivity, but from a practical point of view they present numerous constraints that make their use in real laboratory diagnosis application difficult. Herein we report on a monolithic lab on a chip fabricated by a hybrid femtosecond laser micromachining approach, for label-free biosensing. It consists of a polymer WGM microresonator sensor integrated inside a glass microfluidic chip, presenting a refractive index change sensitivity of 61 nm per RIU. The biosensing capabilities of the device have been demonstrated by exploiting the biotin-streptavidin binding affinity, obtaining a measurable minimum surface density increase of 67 x 10(3) molecules per mu m(2)
Diapirs as the source of the sediment signature in arc lavas
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Geoscience 4 (2011): 641-646, doi:10.1038/ngeo1214Many arc lavas show evidence for the involvement of subducted sediment in the melting process. There is debate whether this âsediment meltâ signature forms at relatively low temperature near the fluid-saturated solidus or at higher temperature beyond the breakdown of trace-element-rich accessory minerals. We present new geochemical data from high- to ultrahigh-pressure rocks that underwent subduction and show no significant depletion of key trace elements in the sediment melt component until peak metamorphic temperatures exceeded ~1050ÂșC from 2.7 to 5 GPa. These temperatures are higher than for the top of the subducting plate at similar pressures based on thermal models. To address this discrepancy, we use instability calculations for a non-Newtonian buoyant layer in a viscous half-space to show that, in typical subduction zones, solid-state sediment diapirs initiate at temperatures between 500â850ÂșC. Based on these calculations, we propose that the sediment melt component in arc magmas is produced by high degrees of dehydration melting in buoyant diapirs of metasediment that detach from the slab and rise into the hot mantle wedge. Efficient recycling of sediments into the wedge by this mechanism will alter volatile fluxes into the deep mantle compared to estimates based solely on devolatilization of the slab.Funding for this work was provided by NSF and WHOIâs Deep Ocean Exploration Institute
Activity of 50 Long-Period Comets Beyond 5.2 AU
Remote investigations of the ancient solar system matter has been
traditionally carried out through the observations of long-period (LP) comets
that are less affected by solar irradiation than the short-period counterparts
orbiting much closer to the Sun. Here we summarize the results of our
decade-long survey of the distant activity of LP comets. We found that the most
important separation in the dataset is based on the dynamical nature of the
objects. Dynamically new comets are characterized by a higher level of activity
on average: the most active new comets in our sample can be characterized by
afrho values >3--4 higher than that of our most active returning comets. New
comets develop more symmetric comae, suggesting a generally isotropic outflow.
Contrary to this, the coma of recurrent comets can be less symmetrical,
ocassionally exhibiting negative slope parameters, suggesting sudden variations
in matter production. The morphological appearance of the observed comets is
rather diverse. A surprisingly large fraction of the comets have long, teniouos
tails, but the presence of impressive tails does not show a clear correlation
with the brightness of the comets.Comment: 21 pages, 4 figures, accepted for publication in A
A detailed geochemical study of island arc crust : the Talkeetna Arc section, southâcentral Alaska
Author Posting. © The Author, 2006. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Journal of Petrology 47 (2006): 1051-1093, doi:10.1093/petrology/egl002.The Early to Middle Jurassic Talkeetna Arc section exposed in the Chugach Mountains
of south central Alaska is 5-18 km wide and extends for over 150 km. This accreted
island arc includes exposures of upper mantle to volcanic upper crust. The section
comprises six lithologic units, in order of decreasing depth: (1) residual upper mantle
harzburgite (with lesser proportions of dunite); (2) pyroxenite; (3) basal gabbronorite; (4)
lower crustal gabbronorite; (5) mid-crustal plutonic rocks; and (6) volcanic rocks. The
pyroxenites overlie residual mantle peridotite, with some interfingering of the two along
the contact. The basal gabbronorite overlies pyroxenite, again with some interfingering of
the two different units along their contact. Lower crustal gabbronorite (â€10 km thick)
includes abundant rocks with well developed modal layering. The mid-crustal plutonic
rocks include a heterogeneous assemblage of gabbroic rocks, dioritic to tonalitic rocks
(30-40% area), and concentrations of mafic dikes and chilled mafic inclusions. The
volcanic rocks (~7 km thick) range from basalt to rhyolite.
Many of the evolved volcanic compositions are a result of fractional crystallisation
processes whose cumulate products are directly observable in the lower crustal
gabbronorites. For example, Ti and Eu enrichments in lower crustal gabbronorites are
mirrored by Ti and Eu depletions in evolved volcanics. In addition, calculated parental
liquids from ion microprobe analyses of clinopyroxene in lower crustal gabbronorites
indicate that the clinopyroxenes crystallised in equilibrium with liquids whose
compositions were the same as the compositions of volcanic rocks. The compositional
variation of the main series of volcanic and chilled mafic rocks can be modeled through
fractionation of observed phase compositions and phase proportions in lower crustal
gabbronorite (i.e. cumulates).
Primary, mantle-derived melts in the Talkeetna Arc underwent fractionation of
pyroxenite at the base of the crust. Our calculations suggest that more than 25 wt % of the
primary melts crystallised as pyroxenites at the base of the crust. The discrepancy
between the observed proportion of pyroxenites (less than 5% of the arc section) and the
proportion required by crystal fractionation modeling (more than 25%) may be best understood as the result of gravitational instability, with dense ultramafic cumulates,
probably together with dense garnet granulites, foundering into the underlying mantle
during the time when the Talkeetna Arc was magmatically active, or in the initial phases
of slow cooling (and sub-solidus garnet growth) immediately after the cessation of arc
activity.This study was supported by National Science Foundation Grant EAR-9910899
Reconstruction of the Talkeetna intraoceanic arc of Alaska through thermobarometry
Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): B03204, doi:10.1029/2007JB005208.The Talkeetna arc is one of two intraoceanic arcs where much of the section from the upper mantle through the volcanic carapace is well exposed. We reconstruct the vertical section of the Talkeetna arc by determining the (re)crystallization pressures at various structural levels. The thermobarometry shows that the tonalites and quartz diorites intruded at âŒ5â9 km into a volcanic section estimated from stratigraphy to be 7 km thick. The shallowest, Tazlina and Barnette, gabbros crystallized at âŒ17â24 km; the Klanelneechena Klippe crystallized at âŒ24â26 km; and the base of the arc crystallized at âŒ35 km depth. The arc had a volcanic:plutonic ratio of âŒ1:3â1:4. However, many or most of the felsic plutonic rocks may represent crystallized liquids rather than cumulates so that the liquid:cumulate ratio might be 1:2 or larger. The current 5- to 7-km structural thickness of the plutonic section of the arc is âŒ15â30% of the original 23- to 28-km thickness. The bulk composition of the original Talkeetna arc section was âŒ51â58 wt % SiO2.Funded by NSF EAR-9910899
Meat production and maintaining biodiversity: Grazing by traditional breeds and crossbred beef cattle in marshes and grasslands
Questions: Sustainable rangeland utilization considering traditions and economic reasons is compulsory for harmonising the needs of the agricultural and nature conservation sectors. For proper rangeland management it is crucial to compare the grazing
effects of traditional breeds and crossbred animals of the same species that might have
different effects on the rangelands. To fill this knowledge gap, in a grazing experiment,
we investigated the effect of cattle breeds on the vegetation to test the effects on
nature conservation value and agricultural production value. We hypothesized that the
effects of cattle grazing on habitat conservation values and forage quality depend on
the grazing breed, because breeds differ in selectivity, body size and trampling effect.
Location: Marshes and alkaline wet grasslands in HortobĂĄgy National Park, Hungary.
Methods: We recorded the percentage cover of vascular plants in three consecutive
years in a total of 60 plots in 12 areas grazed by traditional (0.61 AU/ha) and largesized crossbred beef cattle (0.68 AU/ha).
Results: We found that the effect of cattle breed on the habitat conservation values
and forage quality is dependent on the habitat type. The traditional breed maintained
a significantly higher species number and Shannon diversity in marshes than the
crossbred beef cattle. Grazing of crossbred cattle led to decreasing moisture indicator values in marsh habitats.
Conclusions: Our findings revealed that traditional breeds should be prioritized in the
management of wet alkaline grasslands and marshes. Crossbred beef cattle might be
a substitute but only in case traditional breeds are not available for the management
of alkaline wet grasslands. In marshes, however, we recommend prioritizing the traditional breeds as they maintain higher diversity compared to crossbred beef cattle
Extensive Spectroscopy and Photometry of the Type IIP Supernova 2013ej
We present extensive optical (, , and open CCD) and
near-infrared () photometry for the very nearby Type IIP SN ~2013ej
extending from +1 to +461 days after shock breakout, estimated to be MJD
. Substantial time series ultraviolet and optical spectroscopy
obtained from +8 to +135 days are also presented. Considering well-observed SNe
IIP from the literature, we derive bolometric calibrations from
and unfiltered measurements that potentially reach 2\% precision with a
color-dependent correction. We observe moderately strong Si II
as early as +8 days. The photospheric velocity () is
determined by modeling the spectra in the vicinity of Fe II
whenever observed, and interpolating at photometric epochs based on a
semianalytic method. This gives km s at +50
days. We also observe spectral homogeneity of ultraviolet spectra at +10--12
days for SNe IIP, while variations are evident a week after explosion. Using
the expanding photosphere method, from combined analysis of SN 2013ej and SN
2002ap, we estimate the distance to the host galaxy to be
Mpc, consistent with distance estimates from other methods. Photometric and
spectroscopic analysis during the plateau phase, which we estimated to be
days long, yields an explosion energy of
ergs, a final pre-explosion progenitor mass of ~M and a
radius of ~R. We observe a broken exponential profile beyond
+120 days, with a break point at + days. Measurements beyond this
break time yield a Ni mass of ~M.Comment: 29 pages, 23 figures, 15 tables, Published in The Astrophisical
Journa
Feature integration in natural language concepts
Two experiments measured the joint influence of three key sets of semantic features on the frequency with which artifacts (Experiment 1) or plants and creatures (Experiment 2) were categorized in familiar categories. For artifacts, current function outweighed both originally intended function and current appearance. For biological kinds, appearance and behavior, an inner biological function, and appearance and behavior of offspring all had similarly strong effects on categorization. The data were analyzed to determine whether an independent cue model or an interactive model best accounted for how the effects of the three feature sets combined. Feature integration was found to be additive for artifacts but interactive for biological kinds. In keeping with this, membership in contrasting artifact categories tended to be superadditive, indicating overlapping categories, whereas for biological kinds, it was subadditive, indicating conceptual gaps between categories. It is argued that the results underline a key domain difference between artifact and biological concepts
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