2,564 research outputs found
Waking up dormant tumors
As appreciation grows for the contribution of the tumor microenvironment to the progression of cancer, new evidence accumulates to support that the participation of stromal cells can extend beyond the local environment. Recently, Elkabets and colleagues demonstrated a systemic interaction between cancer cells and distant bone marrow cells to support the growth of otherwise indolent tumor cells at a secondary site, raising thought-provoking questions regarding the involvement of stromal cells in maintaining metastatic dormancy.National Institutes of Health (U.S.) (NIH grant CA125550)National Institutes of Health (U.S.) (NIH grant CA155370)National Institutes of Health (U.S.) (NIH grant CA151925)National Institutes of Health (U.S.) (NIH grant DK081576)United States. Dept. of Defense (Breast Cancer Research Program Predoctoral Traineeship Award
Organic Food and Agriculture - Ethics
Organic food is produced without the use of synthetic fertilizers and pesticides. Four further exclusions in organic production are: genetically modified organisms (GMOs), irradiation, prophylactic antibiotics, and engineered nanoparticles. These six exclusions differentiate organic agriculture from chemical agriculture. Agriculture and food harvesting and production date back millennia, and until about a century ago that history is de facto organic. The Industrial Revolution ushered in an era of novel production strategies. Agriculture was not immune to new views of industrialization and reductionism. Advances in chemistry enabled some implementation of such views. Early in the diffusion of chemical farming practices, the Austrian mystic Rudolf Steiner (1865â1924) called for a differentiated agriculture free of these new synthetic chemical inputs. The terminology, theory, and practices of biodynamic agriculture evolved (in the 1920s and 1930s) from Steinerâs Agriculture Course of 1924. It was a guided evolution, coordinated by Ehrenfried Pfeiffer (1899â1961) in Switzerland. The UK agriculturist, Lord Northbourne (1896â1982), invited Pfeiffer to lead a conference on biodynamics at his farm in Kent (in 1939). The following year Northbourne published his manifesto of organic farming, âLook to the Land.â In that book, he coined the term âorganic farmingâ and wrote of a contest of âorganic versus chemical farmingâ.The ideas and ideals of organic farming quickly proliferated internationally off the back of Northbourneâs 1940 book. Organic farming is now practiced in at least 179 countries, accounts for 50.9 million agricultural hectares, and a market value of US$ 81.6 billion (âŹ75 billion)
PMH15 BURDEN OF ILLNESS AMONG PATIENTS WITH ALZHEIMER'S DISEASE IN A COMMERCIALLY-INSURED POPULATION
ARDebug: an augmented reality tool for analysing and debugging swarm robotic systems
Despite growing interest in collective robotics over the past few years, analysing and debugging the behaviour of swarm robotic systems remains a challenge due to the lack of appropriate tools. We present a solution to this problem-ARDebug: an open-source, cross-platform, and modular tool that allows the user to visualise the internal state of a robot swarm using graphical augmented reality techniques. In this paper we describe the key features of the software, the hardware required to support it, its implementation, and usage examples. ARDebug is specifically designed with adoption by other institutions in mind, and aims to provide an extensible tool that other researchers can easily integrate with their own experimental infrastructure
Fast Room-Temperature Detection of Terahertz Quantum Cascade Lasers with Graphene-Loaded Bow-Tie Plasmonic Antenna Arrays
We present a fast room-temperature terahertz detector based on interdigitated bow-tie antennas contacting graphene. Highly efficient photodetection was achieved by using two metals with different work functions as the arms of a bow-tie antenna contacting graphene. Arrays of the bow-ties were fabricated in order to enhance the responsivity and coupling of the incoming light to the detector, realizing an efficient imaging system. The device has been characterized and tested with a terahertz quantum cascade laser emitting in single frequency around 2 THz, yielding a responsivity of âŒ34 ÎŒA/W and a noise-equivalent power of âŒ1.5 Ă 10 W/Hz.R.D., Y.R., and H.E.B. acknowledge financial support from the Engineering and Physical Sciences Research Council (Grant No. EP/J017671/1, Coherent Terahertz Systems). S.H. acknowledges funding from EPSRC (Grant No. EP/K016636/1, GRAPHTED). H.L. and J.A.Z. acknowledge financial support from the EPSRC (Grant No. EP/L019922/1). J.A.A.-W. acknowledges a Research Fellowship from Churchill College, Cambridge. H.J.J. thanks the Royal Commission for the Exhibition of 1851 for her Research Fellowship.This is the final version of the article. It first appeared from American Chemical Society via https://doi.org/10.1021/acsphotonics.6b0040
An Extended Model for the Evolution of Prebiotic Homochirality: A Bottom-Up Approach to the Origin of Life
A generalized autocatalytic model for chiral polymerization is investigated
in detail. Apart from enantiomeric cross-inhibition, the model allows for the
autogenic (non-catalytic) formation of left and right-handed monomers from a
substrate with reaction rates and , respectively. The
spatiotemporal evolution of the net chiral asymmetry is studied for models with
several values of the maximum polymer length, N. For N=2, we study the validity
of the adiabatic approximation often cited in the literature. We show that the
approximation obtains the correct equilibrium values of the net chirality, but
fails to reproduce the short time behavior. We show also that the autogenic
term in the full N=2 model behaves as a control parameter in a chiral symmetry-
breaking phase transition leading to full homochirality from racemic initial
conditions. We study the dynamics of the N -> infinity model with symmetric
() autogenic formation, showing that it only achieves
homochirality for , where is an N-dependent
critical value. For we investigate the behavior of
models with several values of N, showing that the net chiral asymmetry grows as
tanh(N). We show that for a given symmetric autogenic reaction rate, the net
chirality and the concentrations of chirally pure polymers increase with the
maximum polymer length in the model. We briefly discuss the consequences of our
results for the development of homochirality in prebiotic Earth and possible
experimental verification of our findings
Direct interaction between the Gulf Stream and the shelfbreak south of New England
© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 2 (2012): 553, doi:10.1038/srep00553.Sea surface temperature imagery, satellite altimetry, and a surface drifter track reveal an unusual tilt in the Gulf Stream path that brought the Gulf Stream to 39.9°N near the Middle Atlantic Bight shelfbreakâ200 km north of its mean positionâin October 2011, while a large meander brought Gulf Stream water within 12 km of the shelfbreak in December 2011. Near-bottom temperature measurements from lobster traps on the outer continental shelf south of New England show distinct warming events (temperature increases exceeding 6°C) in November and December 2011. Moored profiler measurements over the continental slope show high salinities and temperatures, suggesting that the warm water on the continental shelf originated in the Gulf Stream. The combination of unusual water properties over the shelf and slope in late fall and the subsequent mild winter may affect seasonal stratification and habitat selection for marine life over the continental shelf in 2012.Profiler data were made available by the Ocean
Observatory Initiative (OOI) during the construction phase of the project. The OOI is
funded by the National Science Foundation and managed by the Consortium for Ocean
Leadership. Drifter data were provided by Tim Shaw and David Calhoun at Cape Fear
Community College.GGGwas supported by NSFGrant OCE-1129125. RET was supported
by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with
funding provided by the Cooperative Institute for the North Atlantic Region. MA was
supported by the Penzance Endowed Fund in Support of Assistant Scientists
Cohomological Donaldson-Thomas theory of a quiver with potential and quantum enveloping algebras
This paper concerns the cohomological aspects of Donaldson-Thomas theory for
Jacobi algebras and the associated cohomological Hall algebra, introduced by
Kontsevich and Soibelman. We prove the Hodge-theoretic categorification of the
integrality conjecture and the wall crossing formula, and furthermore realise
the isomorphism in both of these theorems as Poincar\'e-Birkhoff-Witt
isomorphisms for the associated cohomological Hall algebra. We do this by
defining a perverse filtration on the cohomological Hall algebra, a result of
the "hidden properness" of the semisimplification map from the moduli stack of
semistable representations of the Jacobi algebra to the coarse moduli space of
polystable representations. This enables us to construct a degeneration of the
cohomological Hall algebra, for generic stability condition and fixed slope, to
a free supercommutative algebra generated by a mixed Hodge structure
categorifying the BPS invariants. As a corollary of this construction we
furthermore obtain a Lie algebra structure on this mixed Hodge structure - the
Lie algebra of BPS invariants - for which the entire cohomological Hall algebra
can be seen as the positive part of a Yangian-type quantum group.Comment: v5 final version, 64 pages, to appear in Invent. Math. Many thanks to
the anonymous referee for helpful suggestion
The Effects of Surfaces and Surface Passivation on the Electrical Properties of Nanowires and Other Nanostructures: Time-Resolved Terahertz Spectroscopy Studies
The electrical properties of nanomaterials are strongly influenced by their surfaces, which in turn are strongly influenced by device processing and passivation procedures. Optical pump-terahertz probe spectroscopy is ideal for measuring the native properties of these materials, determining the changes induced by device processing, and studying the effectiveness of surface passivation procedures. Here we study the electronic properties of III-V nanowires and other nanomaterials in both their native and encapsulated/integrated states, which is uniquely possible with terahertz spectroscopy
Tin(iv) dopant removal through anti-solvent engineering enabling tin based perovskite solar cells with high charge carrier mobilities
We report the need for careful selection of anti-solvents for Sn-based perovskite solar cells fabricated through the commonly used anti-solvent method, compared to their Pb-based counterparts.</p
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