5,439 research outputs found
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Identification of strategic molecules for future circular supply chains using large reaction networks
Networks of chemical reactions represent relationships between molecules within chemical supply chains and promise to enhance planning of multi-step synthesis routes from bio-renewable feedstocks.</p
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Teaching sustainability as complex systems approach: a sustainable development goals workshop
Purpose
Approaches to solving sustainability problems require a specific problem-solving mode, encompassing the complexity, fuzziness and interdisciplinary nature of the problem. This paper aims to promote a complex systems’ view of addressing sustainability problems, in particular through the tool of network science, and provides an outline of an interdisciplinary training workshop.
Design/methodology/approach
The topic of the workshop is the analysis of the Sustainable Development Goals (SDGs) as a political action plan. The authors are interested in the synergies and trade-offs between the goals, which are investigated through the structure of the underlying network. The authors use a teaching approach aligned with sustainable education and transformative learning.
Findings
Methodologies from network science are experienced as valuable tools to familiarise students with complexity and to handle the proposed case study.
Originality/value
To the best of the authors’ knowledge, this is the first work which uses network terminology and approaches to teach sustainability problems. This work highlights the potential of network science in sustainability education and contributes to accessible material.
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Gravitational Waves Astronomy: a cornerstone for gravitational theories
Realizing a gravitational wave (GW) astronomy in next years is a great
challenge for the scientific community. By giving a significant amount of new
information, GWs will be a cornerstone for a better understanding of
gravitational physics. In this paper we re-discuss that the GW astronomy will
permit to solve a captivating issue of gravitation. In fact, it will be the
definitive test for Einstein's general relativity (GR), or, alternatively, a
strong endorsement for extended theories of gravity (ETG).Comment: To appear in Proceedings of the Workshop "Cosmology, the Quantum
Vacuum and Zeta Functions" for the celebration of Emilio Elizalde's sixtieth
birthday, Barcelona, March 8-10, 201
Impact of platelet count on results obtained from multiple electrode platelet aggregometry (Multiplate™)
<p>Abstract</p> <p>Objectives</p> <p>Use of potent antiplatelet drugs requires evaluation of platelet function. While platelet function in elective cases is usually assessed in a central laboratory environment, there is also an urgent need for rapid perioperative point-of-care assessment. Recently, multiple electrode platelet aggregometry has been developed and assumed to measure platelet function independent from platelet count. We tested the hypothesis that results of multiple electrode platelet aggregometry are affected by platelet count, in particular if platelet count is below normal range.</p> <p>Methods</p> <p>Whole blood samples from 20 healthy volunteers were prepared containing platelet concentrations of 50,000, 100,000, 150,000, 200,000, and 250,000 μl<sup>-1 </sup>while maintaining hematocrit. Platelet aggregation was induced by collagen, thrombin receptor activating peptide 6 (TRAP-6), adenosine-diphoshate (ADP), and arachidonic acid, respectively, and aggregation was measured by multiple electrode platelet aggregometry (Multiplate™).</p> <p>Results</p> <p>Results of multiple electrode platelet aggregometry significantly decreased in blood samples with platelet count below normal range. Compared to results measured in blood samples with platelet count within normal range, aggregometry results decreased by 18.4% (p < 0.001) and 37.2% (p < 0.001) in blood samples with a platelet count of 100.000 and 50.000 μl<sup>-1</sup>, respectively. On the other hand, large interindividual variation has been observed and some blood samples showed normal results even with platelet counts of 50.000 μl<sup>-1</sup>.</p> <p>Conclusion</p> <p>The results obtained with Multiplate™ Analyzer are influenced by platelet function as well as platelet count thus displaying the overall platelet aggregability within the blood sample rather than platelet function alone.</p
Doppler velocimetry of spin propagation in a two-dimensional electron gas
Controlling the flow of electrons by manipulation of their spin is a key to
the development of spin-based electronics. While recent demonstrations of
electrical-gate control in spin-transistor configurations show great promise,
operation at room temperature remains elusive. Further progress requires a
deeper understanding of the propagation of spin polarization, particularly in
the high mobility semiconductors used for devices. Here we report the
application of Doppler velocimetry to resolve the motion of spin-polarized
electrons in GaAs quantum wells driven by a drifting Fermi sea. We find that
the spin mobility tracks the high electron mobility precisely as a function of
T. However, we also observe that the coherent precession of spins driven by
spin-orbit interaction, which is essential for the operation of a broad class
of spin logic devices, breaks down at temperatures above 150 K for reasons that
are not understood theoretically
Resonant and bound states of charged defects in two-dimensional semiconductors
A detailed understanding of charged defects in two-dimensional semiconductors is needed for the development of ultrathin electronic devices. Here, we study negatively charged acceptor impurities in monolayer WS2 using a combination of scanning tunneling spectroscopy and large-scale atomistic electronic structure calculations. We observe several localized defect states of hydrogenic wave function character in the vicinity of the valence band edge. Some of these defect states are bound, while others are resonant. The resonant states result from the multivalley valence band structure of WS2, whereby localized states originating from the secondary valence band maximum at Γ hybridize with continuum states from the primary valence band maximum at K/K′. Resonant states have important consequences for electron transport as they can trap mobile carriers for several tens of picoseconds
Perovskite solar cells: a deep analysis using current–voltage and capacitance–voltage techniques
Perovskite solar cells exhibiting~14–15% efficiency were experimentally measured using current–voltage (I–V) and capacitance–voltage (C–V) techniques in order to extract material and device properties, and understand the action of photovoltaic
(PV) operation. Deep analyses were carried out on dark- and illuminated I–V curves, and dark C–V curves. Results were
compared with those of graded bandgap solar cells fabricated on inorganic n-type window layers. These analyses according
to a physicist’s point of view lead to understand the perovskite solar cell as a graded bandgap solar cell built on a p-type
window layer. I–V and C–V results show very similar behaviour and the principle of PV action is identical. Once the stability
issues with perovskites are solved, these devices have very high potential of producing next generation solar cells reaching
at least mid-20% efficiency values
Linear magnetoresistance in commercial n-type silicon due to inhomogeneous doping
Free electron theory tells us that resistivity is independent of magnetic
field. In fact, most observations match the semiclassical prediction of a
magnetoresistance that is quadratic at low fields before saturating. However, a
non-saturating linear magnetoresistance has been observed in exotic
semiconductors such as silver chalcogenides, lightly-doped InSb, N-doped InAs,
MnAs-GaAs composites, PrFeAsO, and epitaxial graphene. Here we report the
observation of a large linear magnetoresistance in the ohmic regime in
commonplace commercial n-type silicon wafer. It is well-described by a
classical model of spatially fluctuating donor densities, and may be amplified
by altering the aspect ratio of the sample to enhance current-jetting:
increasing the width tenfold increased the magnetoresistance at 8 T from 445 %
to 4707 % at 35 K. This physical picture may well offer insights into the large
magnetoresistances recently observed in n-type and p-type Si in the non-ohmic
regime.Comment: submitted to Nature Material
Quantum nondemolition measurement of mechanical motion quanta
The fields of opto- and electromechanics have facilitated numerous advances
in the areas of precision measurement and sensing, ultimately driving the
studies of mechanical systems into the quantum regime. To date, however, the
quantization of the mechanical motion and the associated quantum jumps between
phonon states remains elusive. For optomechanical systems, the coupling to the
environment was shown to preclude the detection of the mechanical mode
occupation, unless strong single photon optomechanical coupling is achieved.
Here, we propose and analyse an electromechanical setup, which allows to
overcome this limitation and resolve the energy levels of a mechanical
oscillator. We find that the heating of the membrane, caused by the interaction
with the environment and unwanted couplings, can be suppressed for carefully
designed electromechanical systems. The results suggest that phonon number
measurement is within reach for modern electromechanical setups.Comment: 8 pages, 5 figures plus 24 pages, 11 figures supplemental materia
Heavy Meson Production in Proton-Nucleus Reactions with Empirical Spectral Functions
We study the production of and mesons in reactions on the basis of empirical spectral functions. The high
momentum, high removal energy part of the spectral function is found to be
negligible in all cases close to the absolute threshold. Furthermore, the
two-step process () dominates the cross section at threshold energies in line with
earlier calculations based on the folding model.Comment: 18 pages, LaTeX, plus 14 postscript figures, submitted to Z. Phys.
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