2,796 research outputs found
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Chemical underpinning of the tea bag index: An examination of the decomposition of tea leaves
Decomposition is a key flux of terrestrial carbon to the atmosphere. Therefore, gaining a better understanding of how plant litter decomposes in soil, and what governs this process, is vital for global climate models. The Tea Bag Index (TBI) was introduced by Keuskamp et al. (2013) as a novel method for measuring litter decomposition rate and stabilisation. The TBI uses two types of tea bags representing fast (green tea) and slow (rooibos tea) decomposition substrates as standardised litter bags. To date, the TBI method has been used in over 2000 locations across the globe. However, before now, there has been no information on how the composition of the tea leaves change during incubation. These data are crucial in determining the validity of the use of the TBI method globally, to ensure the tea leaves decompose in a way that is representative of so-called “native” litters. To provide chemical underpinning of the TBI method, a laboratory incubation of the tea bags was conducted with destructive sampling at 0, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, and 91 d. The incubated tea was analysed for total C and N. In addition, C was characterised as alkyl, O-alkyl, aromatic, or carbonyl C using solid-state 13C nuclear magnetic resonance spectroscopy with cross-polarization and magic angle spinning (CPMAS NMR). The results suggest that changes in carbon in both tea types are comparable to other litter studies, with a net decrease in total C and relative proportion of O-alkyl C fraction, which contains carbohydrates and cellulose. We conclude that the decomposition of tea leaves in the bags used in the TBI is representative of other litters
Regulation of cAMP responses by the G12/13 pathway converges on adenylyl cyclase VII
Regulation of intracellular cyclic adenosine 3’, 5’-monophosphate (cAMP) by multiple pathways enables differential function of this ubiquitous second messenger in a context dependent manner. Modulation of Gs-stimulated intracellular cAMP has long been known to be modulated by the Gi and Gq/Ca2+ pathways. Recently, the G13 pathway was also shown to facilitate cAMP responses in murine macrophage cells. We report here that this synergistic regulation of cAMP synthesis by the Gs and G13 pathways is mediated by a specific isoform of adenylyl cyclase, AC7. Furthermore, this signaling paradigm exists in several hematopoietic lineages and can be recapitulated by exogenous expression of AC7 in HEK 293 cells. Mechanistic characterization of this synergistic interaction indicates that it occurs downstream of receptor activation and it can be mediated by the alpha subunit of either G12 or G13. Our results demonstrate that AC7 is a specific downstream effector of the G12/13 pathway
Scaled Physical Prototyping of Construction Processes Using 3D Printing
3D printing and Building Information Modelling (BIM) are two technologies that have become increasingly popular and changed a wide variety of applications in a significant manner. 3D printing enables the design, prototyping and manufacture of items that were previously impossible or infeasible to do. Similarly, BIM is changing the way building and civil infrastructure projects are conceived, designed, delivered and maintained with a push towards a digital, wholly collaborative construction environment.This paper examines how 3D printing and BIM can be used in a complimentary manner to help visualise and communicate important aspects of a project to the relevant stakeholders and personnel involved. By using the BIM model that has been developed for a specific project and segmenting key components of this model we can then use 3D printers to create a scaled model of the job and educate the concerned parties in the construction methodology, main risk areas, and ongoing concerns for maintenance and end-of-life deconstruction.
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Frio pilot in CO2 sequestration in brine-bearing sandstones: The University of Texas at Austin, Bureau of Economic Geology, report to the Texas Commission on Environmental Quality to accompany a class V application for an experimental technology pilot injection well.
GEOSEQ project (LBNL, LLNL, ORNL), NETL, Schlumberger–Doll Research Center, Transpetco, Sandia TechnologiesJackson School of Geoscience
Impact of the Algebra I End of Course Examination on African American Students Obtaining a Standard High School Diploma
The state of Florida requires all students complete Algebra I and pass the End of Course Examination (EOCE) to graduate with a standard high school diploma. Algebra I EOCE results indicate that many African American students do not pass the examination. This research sought to determine if there is a relationship between African American students’ failure to pass the Algebra I EOCE and graduate with a standard diploma. Four hypotheses, null and alternative were tested. Two ninth-grade cohorts, 2013-2014 and 2014-2015 comprised the sample. Data were analyzed using t test and one-way analyses of variance (ANOVA). Results indicate a significant relationship between African American students’ failure to pass the Algebra I EOCE and graduation with a standard high school diploma
Hard diffraction from parton rescattering in QCD
We analyze the QCD dynamics of diffractive deep inelastic scattering. The
presence of a rapidity gap between the target and diffractive system requires
that the target remnant emerges in a color singlet state, which we show is made
possible by the soft rescattering of the struck quark. This rescattering is
described by the path-ordered exponential (Wilson line) in the expression for
the parton distribution function of the target. The multiple scattering of the
struck parton via instantaneous interactions in the target generates dominantly
imaginary diffractive amplitudes, giving rise to an "effective pomeron"
exchange. The pomeron is not an intrinsic part of the proton but a dynamical
effect of the interaction. This picture also applies to diffraction in
hadron-initiated processes. Due to the different color environment the
rescattering is different in virtual photon- and hadron-induced processes,
explaining the observed non-universality of diffractive parton distributions.
This framework provides a theoretical basis for the phenomenologically
successful Soft Color Interaction model which includes rescattering effects and
thus generates a variety of final states with rapidity gaps. We discuss
developments of the SCI model to account for the color coherence features of
the underlying subprocesses.Comment: 12 pages, 9 figures, REVTeX4. Somewhat expanded and modified version,
two new subsections added. To appear in PR
Quantum Key Distribution in a Multi-User Network at Gigahertz Clock rates
In recent years quantum information research has lead to the discovery of a
number of remarkable new paradigms for information processing and
communication. These developments include quantum cryptography schemes that
offer unconditionally secure information transport guaranteed by
quantum-mechanical laws. Such potentially disruptive security technologies
could be of high strategic and economic value in the future. Two major issues
confronting researchers in this field are the transmission range (typically
<100km) and the key exchange rate, which can be as low as a few bits per second
at long optical fiber distances. This paper describes further research of an
approach to significantly enhance the key exchange rate in an optical fiber
system at distances in the range of 1-20km. We will present results on a number
of application scenarios, including point-to-point links and multi-user
networks. Quantum key distribution systems have been developed, which use
standard telecommunications optical fiber, and which are capable of operating
at clock rates of up to 2GHz. They implement a polarization-encoded version of
the B92 protocol and employ vertical-cavity surface-emitting lasers with
emission wavelengths of 850 nm as weak coherent light sources, as well as
silicon single-photon avalanche diodes as the single photon detectors. The
point-to-point quantum key distribution system exhibited a quantum bit error
rate of 1.4%, and an estimated net bit rate greater than 100,000 bits- per
second for a 4.2 km transmission range.Comment: Presented at SPIE Symposium on Microtechnologies for the New
Millennium, Sevilla, Spain (May 2005
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