3,498 research outputs found
Reducing Deforestation and Trading Emissions: Economic Implications for the post-Kyoto Carbon Market
This paper quantitatively assesses the economic implications of crediting carbon abatement from reduced deforestation for the emissions market in 2020 by linking a numerical equilibrium model of the global carbon market with a dynamic partial equilibrium model of the forestry sector. We find that integrating avoided deforestation in international emissions trading considerably decreases the costs of post-Kyoto climate policy – even when accounting for conventional abatement options of developing countries under the CDM. At the same time, tropical rainforest regions receive substantial net revenues from exporting carbon-offset credits to the industrialized world. Moreover, reduced deforestation can increase environmental effectiveness by enabling industrialized countries to tighten their carbon constraints without increasing mitigation costs. Regarding uncertainties of this future carbon abatement option, we find both forestry transaction costs and deforestation baselines to play an important role for the post-Kyoto carbon market. --Climate Change,Kyoto Protocol,Emissions Trading,Deforestation
Optical evidence for intermolecular coupling in mixed films of pentacene and perfluoropentacene
We present optical absorption spectra of mixed films of pentacene (PEN) and
perfluoropentacene (PFP) grown on SiO2. We investigated the influence of
intermolecular coupling between PEN and PFP on the optical spectra by analyzing
samples with five different mixing ratios of PFP:PEN with variable angle
spectroscopic ellipsometry (VASE) and differential reflectance spectroscopy
(DRS). The data show how the spectral shape is influenced by changes in the
volume ratio of the two components. By comparison with the pure film spectra an
attempt is made to distinguish transitions due to intermolecular coupling
between PEN and PFP from transitions caused by interactions of PEN (PFP) with
other molecules of the same type. We observe a new transition at 1.6 eV which
is not found in the pure film spectra and which we assign to coupling of PFP
and PEN.Comment: 6 pages, 6 figures, 1 table, accepted for publication in Phys. Rev.
Postsettlement growth of two estuarine crab species, Chasmagnathus granulata and Cyrtograpsus angulatus (Crustacea, Decapoda, Grapsidae): laboratory and field observations
The estuarine grapsid crabs Chasmagnathus granulata and Cyrtograpsus angulatus belong to the most typical and dominant inhabitants of brackish coastal lagoons in southeastern South America. In a combined laboratory and field investigation of juvenile growth, we measured the increase in body size in these species under controlled conditions as well as in field experiments (in Mar Chiquita lagoon, Argentina), seasonal changes in size frequency distribution of a natural population, and growth related changes in selected morphometric traits of male and female juveniles (relations between carapace width, carapace length, propodus height and length of the cheliped, and pleon width). At 24°C, Cy. angulatus grew faster than Ch. granulata; it reached the crab-9 instar (C9; 13 mm carapace width) after 92 days, while Ch. granulata required 107 days to reach the C8 instar (7.4 mm). At 12°C, growth ceased in both species. The pleon begins to show sexual differences in the C5 (Cy. angulatus) and C8 instar (Ch. granulata), respectively, while the chelae differentiate earlier in Ch. granulata than in Cy. angulatus (in C4 vs C6). In the field, growth was maximal in summer, and was generally faster than in laboratory cultures. However, there is great individual variability in size (about 25% even in the first crab instar) and in size increments at ecdysis, increasing throughout juvenile growth. Our data indicate that, in the field, small-scale and short-term variations in feeding conditions, temperature, and salinity account for an extremely high degree of variability in the absolute and relative rates of growth as well as in the time to sexual differentiation
Implikationen der gestuften Hochschul-Curricula auf die Innovationsfähigkeit Deutschlands: Qualitiative Untersuchungen zur Umstellung der Studien-Curricula in Deutschland
Gegenstand der Untersuchung sind die Studiencurricula der Fächer Chemie, Maschinenbau und Soziologie. Analysiert wurden das Studienangebot und der jeweils zentrale Studiengang der drei Fächer an drei Universitäten vor und nach der Bologna-Reform. Außerdem wurden Vertreter aus Verbänden und potenzielle Arbeitgeber von Absolventen nach ihrer Einschätzung zu den Studiengängen in Chemie, Maschinenbau und Soziologie und zur Studienreform befragt. Das grundlegende Projektdesign ist weitgehend von der Expertenkommission für Forschung und Innovation vorgegeben worden. Empirisch basiert die Untersuchung erstens auf einer Dokumentenanalyse, die sich auf die Studien- und Prüfungsordnungen und sonstige Studieninformationen konzentriert. Dieser Blick auf die Studiencurricula der Fächer wird zweitens ergänzt durch leitfadengestützte Experteninterviews der Anbieter dieser Studiengänge. Dazu wurden vor Ort zwölf Interviews geführt, für jedes Fach wurde jeweils ein Fachvertreter und für jede Universität ein Studienkoordinator auf Universitätsebene befragt. Drittens wurden in 23 Interviews mit Vertretern von Unternehmen, Forschungseinrichtungen, Arbeitgeber- und Fachverbände vor Ort oder telefonisch geführt, um sie nach ihren Einschätzungen zu Studium und Studienreform zu befragen
Las centollas colonizan la Antartida
Es conocido que en Antartida no viven cangrejos. El hallazgo en los ultimo años de centolla podria estar anunciando la futura conquista de la Antartida por los cangrejos
Photoluminescence spectroscopy of pure pentacene, perfluoropentacene and mixed thin films
We report detailed temperature dependent photoluminescence (PL) spectra of
pentacene (PEN), perfluoropentacene (PFP), and PEN:PFP mixed thin films grown
on SiO2. PEN and PFP are particularly suitable for this study, since they are
structurally compatible for good intermixing and form a model donor/acceptor
system. The PL spectra of PEN are discussed in the context of existing
literature and compared to the new findings for PFP. We analyze the optical
transitions observed in the spectra of PEN and PFP using time-dependent density
functional theory (TD-DFT) calculations. Importantly, for the mixed PEN:PFP
film we observe an optical transition in PL at 1.4 eV providing evidence for
coupling effects in the blend. We discuss a possible charge-transfer (CT) and
provide a tentative scheme of the optical transitions in the blended films.Comment: 9 pages, 6 figures, accepted for publication in J. Chem. Phy
On the use of Purcell factors for plasmon antennas
The Purcell factor is the standard figure of merit for spontaneous emission
enhancement in microcavities, that has also been proposed to describe emission
enhancements for plasmonic resonances. A comparison is made of quality factor,
mode volume and Purcell factor for single and coupled plasmon spheres to exact
calculations of emission rates. The paper explains why the Purcell factor is
not appropriate for plasmon antennas.Comment: 3 pages, 2 figure
Optimization of DNA extraction from human urinary samples for mycobiome community profiling.
IntroductionRecent data suggest the urinary tract hosts a microbial community of varying composition, even in the absence of infection. Culture-independent methodologies, such as next-generation sequencing of conserved ribosomal DNA sequences, provide an expansive look at these communities, identifying both common commensals and fastidious organisms. A fundamental challenge has been the isolation of DNA representative of the entire resident microbial community, including fungi.Materials and methodsWe evaluated multiple modifications of commonly-used DNA extraction procedures using standardized male and female urine samples, comparing resulting overall, fungal and bacterial DNA yields by quantitative PCR. After identifying protocol modifications that increased DNA yields (lyticase/lysozyme digestion, bead beating, boil/freeze cycles, proteinase K treatment, and carrier DNA use), all modifications were combined for systematic confirmation of optimal protocol conditions. This optimized protocol was tested against commercially available methodologies to compare overall and microbial DNA yields, community representation and diversity by next-generation sequencing (NGS).ResultsOverall and fungal-specific DNA yields from standardized urine samples demonstrated that microbial abundances differed significantly among the eight methods used. Methodologies that included multiple disruption steps, including enzymatic, mechanical, and thermal disruption and proteinase digestion, particularly in combination with small volume processing and pooling steps, provided more comprehensive representation of the range of bacterial and fungal species. Concentration of larger volume urine specimens at low speed centrifugation proved highly effective, increasing resulting DNA levels and providing greater microbial representation and diversity.ConclusionsAlterations in the methodology of urine storage, preparation, and DNA processing improve microbial community profiling using culture-independent sequencing methods. Our optimized protocol for DNA extraction from urine samples provided improved fungal community representation. Use of this technique resulted in equivalent representation of the bacterial populations as well, making this a useful technique for the concurrent evaluation of bacterial and fungal populations by NGS
Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface
We report on two orders of magnitude reduction in the fluorescence lifetime
when a single molecule placed in a thin film is surrounded by two gold
nanospheres across the film interface. By attaching one of the gold particles
to the end of a glass fiber tip, we could control the modification of the
molecular fluorescence at will. We find a good agreement between our
experimental data and the outcome of numerical calculations
The qWR star HD 45166. II. Fundamental stellar parameters and evidence of a latitude-dependent wind
The enigmatic object HD 45166 is a qWR star in a binary system with an
orbital period of 1.596 day, and presents a rich emission-line spectrum in
addition to absorption lines from the companion star (B7 V). As the system
inclination is very small (i=0.77 +- 0.09 deg), HD 45166 is an ideal laboratory
for wind-structure studies. The goal of the present paper is to determine the
fundamental stellar and wind parameters of the qWR star. A radiative transfer
model for the wind and photosphere of the qWR star was calculated using the
non-LTE code CMFGEN. The wind asymmetry was also analyzed using a
recently-developed version of CMFGEN to compute the emerging spectrum in
two-dimensional geometry. The temporal-variance spectrum (TVS) was calculated
for studying the line-profile variations. Abundances, stellar and wind
parameters of the qWR star were obtained. The qWR star has an effective
temperature of Teff=50000 +- 2000 K, a luminosity of log(L/Lsun)=3.75 +- 0.08,
and a corresponding photospheric radius of Rphot=1.00 Rsun. The star is
helium-rich (N(H)/N(He) = 2.0), while the CNO abundances are anomalous when
compared either to solar values, to planetary nebulae, or to WR stars. The
mass-loss rate is Mdot = 2.2 . 10^{-7} Msun/yr, and the wind terminal velocity
is vinf=425 km/s. The comparison between the observed line profiles and models
computed under different latitude-dependent wind densities strongly suggests
the presence of an oblate wind density enhancement, with a density contrast of
at least 8:1 from equator to pole. If a high velocity polar wind is present
(~1200 km/s), the minimum density contrast is reduced to 4:1. The wind
parameters determined are unusual when compared to O-type stars or to typical
WR stars. (abridged)Comment: 16 pages, 13 figures, accepted for publication in A&
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