25,261 research outputs found
Active Learning Techniques to Build Problem Solving Skills in Chemistry Students
Through the introduction of Team-Based Learning problem classes and a ‘Purple Pens’ feedback intervention in which students write their own feedback on a mixed formative and summative class test we have been able to observe a significant increase in exam performance in Foundation Year students. Both Science and Health students improved their exam performance by 13% and 11% respectively and both interventions were positively received by students
Metamaterial-based graphene thermal emitter
This is the final version of the article. Available from Tsinghua University Press / Springer Verlag via the DOI in this record.The publisher's erratum to this article is in ORE: http://hdl.handle.net/10871/34353A thermal emitter composed of a frequency-selective surface metamaterial layer and a hexagonal boron nitride-encapsulated graphene filament is demonstrated. The broadband thermal emission of the metamaterial (consisting of ring resonators) was tailored into two discrete bands, and the measured reflection and emission spectra agreed well with the simulation results. The high modulation frequencies that can be obtained in these devices, coupled with their operation in air, confirm their feasibility for use in applications such as gas sensing.C.S., I.J.L. and G.R.N. acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via the Centre for Doctoral Training in Electromagnetic Metamaterials (No. EP/L015331/1). G.R.N. also acknowledges the support of EPSRC via a Fellowship in Frontier Manufacturing (No. EP/J018651/1)
A Thermal Management System to Reuse Thermal Waste Released by High-Power Light-Emitting Diodes
© 1963-2012 IEEE. In this article, a comprehensive and efficient thermal management system is proposed to harvest and reuse the thermal waste of high-power light-emitting diodes (HP-LEDs) for the first time. Besides a conventional cooling system, including a thermoelectric (TE) cooler (TEC), a heatsink, and a fan, the proposed thermal management system also employs a TE generator (TEG), a temperature sensor, a voltage boost converter, and a microcontroller for thermal waste recycling. In this system, some of the thermal waste released by the HP-LED is harvested by the TEG and converted into electrical energy. With the help of a voltage boost converter, the harvested electrical power is used to power a temperature sensor for monitoring the surface temperature of the HP-LED. The entire system is regulated by the microcontroller. The system is elaborately established, tested, and the results are discussed. The experimental results show that the proposed system has an output electrical power of approximately 696.5μW , which is used to power a temperature sensor as a demonstration. The sensor works well, and the discrepancy of the surface temperature of the HP-LED measured by the sensor and by a thermometer is less than 5.38%, which validates the proposed thermal management system
Self-avoiding walks and connective constants
The connective constant of a quasi-transitive graph is the
asymptotic growth rate of the number of self-avoiding walks (SAWs) on from
a given starting vertex. We survey several aspects of the relationship between
the connective constant and the underlying graph .
We present upper and lower bounds for in terms of the
vertex-degree and girth of a transitive graph.
We discuss the question of whether for transitive
cubic graphs (where denotes the golden mean), and we introduce the
Fisher transformation for SAWs (that is, the replacement of vertices by
triangles).
We present strict inequalities for the connective constants
of transitive graphs , as varies.
As a consequence of the last, the connective constant of a Cayley
graph of a finitely generated group decreases strictly when a new relator is
added, and increases strictly when a non-trivial group element is declared to
be a further generator.
We describe so-called graph height functions within an account of
"bridges" for quasi-transitive graphs, and indicate that the bridge constant
equals the connective constant when the graph has a unimodular graph height
function.
A partial answer is given to the question of the locality of
connective constants, based around the existence of unimodular graph height
functions.
Examples are presented of Cayley graphs of finitely presented
groups that possess graph height functions (that are, in addition, harmonic and
unimodular), and that do not.
The review closes with a brief account of the "speed" of SAW.Comment: Accepted version. arXiv admin note: substantial text overlap with
arXiv:1304.721
An ecological approach to problems of Dark Energy, Dark Matter, MOND and Neutrinos
Modern astronomical data on galaxy and cosmological scales have revealed
powerfully the existence of certain dark sectors of fundamental physics, i.e.,
existence of particles and fields outside the standard models and inaccessible
by current experiments. Various approaches are taken to modify/extend the
standard models. Generic theories introduce multiple de-coupled fields A, B, C,
each responsible for the effects of DM (cold supersymmetric particles), DE
(Dark Energy) effect, and MG (Modified Gravity) effect respectively. Some
theories use adopt vanilla combinations like AB, BC, or CA, and assume A, B, C
belong to decoupled sectors of physics. MOND-like MG and Cold DM are often
taken as opposite frameworks, e.g. in the debate around the Bullet Cluster.
Here we argue that these ad hoc divisions of sectors miss important clues from
the data. The data actually suggest that the physics of all dark sectors is
likely linked together by a self-interacting oscillating field, which governs a
chameleon-like dark fluid, appearing as DM, DE and MG in different settings. It
is timely to consider an interdisciplinary approach across all semantic
boundaries of dark sectors, treating the dark stress as one identity, hence
accounts for several "coincidences" naturally.Comment: 12p, Proceedings to the 6-th Int. Conf. of Gravitation and Cosmology.
Neutrino section expande
A Pressure-Robust Discretization of Oseen's Equation Using Stabilization in the Vorticity Equation
Discretization of Navier--Stokes equations using pressure-robust finite element methods is considered for the high Reynolds number regime. To counter oscillations due to dominating convection we add a stabilization based on a bulk term in the form of a residual-based least squares stabilization of the vorticity equation supplemented by a penalty term on (certain components of) the gradient jump over the elements faces. Since the stabilization is based on the vorticity equation, it is independent of the pressure gradients, which makes it pressure-robust. Thus, we prove pressure-independent error estimates in the linearized case, known as Oseen's problem. In fact, we prove an error estimate in the -norm that is known to be the best that can be expected for this type of problem. Numerical examples are provided that, in addition to confirming the theoretical results, show that the present method compares favorably to the classical residual-based streamline upwind Petrov--Galerkin stabilization
A customized monocyte cDNA microarray for diagnosis of rheumatoid arthritis and prognosis of anti-TNF-α therapy
Background
In rheumatoid arthritis (RA) macrophages (Mf) play a pivotal role. They become highly activated in synovitis and at the cartilage–pannus junction. Furthermore, therapeutic neutralization of molecules produced by activated Mf lead to clinical improvement in RA, and circulating monocytes (MO) of the peripheral blood in patients with RA spontaneously express proinflammatory genes (IL-1β, IL-6, TNF).
Methods
A custom RA-MO cDNA microarray was generated using differentially expressed genes obtained from gene subtraction and from comparative whole genome wide U133A analysis in normal donors, active and anti-TNF-α created RA patients. Genes were selected using MAS 5.0, multtest and PAM. The custom microarray consists of 313 genes including guide dots, and positive (housekeeping genes and spike controls) and negative controls for image and statistical analysis. Each probe was spotted in 16 replicates.
Results
The RA-MO chipset-II was validated using the following: non-stimulated and LPS, PMA, Vit.D3+LPS, PMA+LPS stimulated U937 cells; nonstimulated and LPS stimulated healthy donor MO; MO from normal donors (n = 3) and RA patients before and during anti-TNF-α treatment (n = 5 each); and synovial tissue from normal individuals (n = 2) and RA patients (n = 2). Not only LPS/PMA regulated genes but also RA specific and anti-TNF-α regulated genes were validated. In addition, we could clarify whether these genes are differentially transcribed only in MO or whether they can also be found in RA tissue Mf. Our data indicate a high degree of reproducibility that is sufficient for diagnostic applications and therapy monitoring.
Conclusion
The RA-MO chipset-II microarray is competitive and flexible for enlargement of the number of genes. The current gene selection will contribute to validating the role of monocytes in disease activity, to therapeutic interventions, and may improve the knowledge on the regulation of pathways in activated monocytes in chronic inflammation
Pattern Avoidance in Poset Permutations
We extend the concept of pattern avoidance in permutations on a totally
ordered set to pattern avoidance in permutations on partially ordered sets. The
number of permutations on that avoid the pattern is denoted
. We extend a proof of Simion and Schmidt to show that for any poset , and we exactly classify the posets for which
equality holds.Comment: 13 pages, 1 figure; v2: corrected typos; v3: corrected typos and
improved formatting; v4: to appear in Order; v5: corrected typos; v6: updated
author email addresse
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