6,037 research outputs found
Beyond differences in means:robust graphical methods to compare two groups in neuroscience
If many changes are necessary to improve the quality of neuroscience research, one relatively
simple step could have great pay-offs: to promote the adoption of detailed graphical methods,
combined with robust inferential statistics. Here we illustrate how such methods can lead to a
much more detailed understanding of group differences than bar graphs and t-tests on means.
To complement the neuroscientist’s toolbox, we present two powerful tools that can help us
understand how groups of observations differ: the shift function and the difference asymmetry
function. These tools can be combined with detailed visualisations to provide complementary
perspectives about the data. We provide implementations in R and Matlab of the graphical
tools, and all the examples in the article can be reproduced using R scripts
Interconnected alchemy: an apparatus for alchemical algorithms
The trope of the fraudulent or occult alchemist, prevalent since the mediaeval period of alchemy’s introduction into European thought, belies the endeavour of practitioners from ancient Egypt onwards. Alchemists used observation, experimentation, and drew conclusions to understand the world around them. Notions of interconnectedness, harmoniousness and codification pervade the alchemical pursuit—and alchemy interconnects literature, art, mathematics, and music....One of our tools is "numbers into notes", a web app for algorithmic composition based on early mathematics, in which the role of the human is to parameterize the algorithm and map number ranges to musical note
The Management Of Research And Development And The Relevance Of Financial Accounting
This study investigates alternatives to current financial accounting treatment of research and development expenditures in United States public corporations. A questionnaire survey was sent to members of the Financial Directors Network of the Industrial Research Institute of America, representing over forty percent of private research and development in the United States. Background research and the survey indicate that if the financial reporting of research and development is modified, research and development will increase and a shift from short?term to long?term projects will occur; and finally United States public corporations will more effectively compete in the international markets
Nonlinear modeling of thermoacoustic systems
Thermoacoustic systems convert energy from heat to acoustic power and vice versa. These systems have commercial interest due to the high potential efficiency and low number of moving parts. To numerically predict the performance of a thermoacoustic device inherent nonlinearities in the system, such as thermoacoustic streaming and generation of harmonics need to be taken into account. We present a nonlinear frequency domain method with which these nonlinearities in thermoacoustic systems are modeled in a computationally efficient manner. Using this method, the nonlinear periodic steady state of a thermoacoustic engine can directly be computed, without computing the long initial transient of the system. In this publication, the developed method is applied to compute the periodic steady state of an experimental standing wave engine. The results obtained match well with experimental data
Examination of an in-vitro methodology to evaluate the biomechanical performance of nucleus augmentation in axial compression
Intervertebral disc degeneration is one of the leading causes of back pain, but treatment options remain limited. Recently, there have been advances in the development of biomaterials for nucleus augmentation; however, the testing of such materials preclinically has proved challenging. The aim of this study was to develop methods for fabricating and testing bone-disc-bone specimens in vitro for examining the performance of nucleus augmentation procedures. Control, nucleotomy and treated intervertebral disc specimens were fabricated and tested under static load. The nucleus was removed from nucleotomy specimens using a trans-endplate approach with a bone plug used to restore bony integrity. Specimen-specific finite element models were developed to elucidate the reasons for the variations observed between control specimens. Although the computational models predicted a statistically significant difference between the healthy and nucleotomy groups, the differences found experimentally were not significantly different. This is likely due to variations in the material properties, hydration and level of annular collapse. The deformation of the bone was also found to be non-negligible. The study provides a framework for the development of testing protocols for nucleus augmentation materials and highlights the need to control disc hydration and the length of bone retained to reduce inter-specimen variability
The nucleon's strange electromagnetic and scalar matrix elements
Quenched lattice QCD simulations and quenched chiral perturbation theory are
used together for this study of strangeness in the nucleon. Dependences of the
matrix elements on strange quark mass, valence quark mass and momentum transfer
are discussed in both the lattice and chiral frameworks. The combined results
of this study are in good agreement with existing experimental data and
predictions are made for upcoming experiments. Possible future refinements of
the theoretical method are suggested.Comment: 24 pages, 9 figure
Peptide:glycosaminoglycan hybrid hydrogels as an injectable intervention for spinal disc degeneration
Degeneration of the spinal discs is a major cause of back pain. During the degeneration process, there is a loss of glycosaminoglycans (GAGs) from the proteoglycan-rich gel in the disc’s nucleus, which adversely alters biomechanical performance. Current surgical treatments for back pain are highly invasive and have low success rates; there is an urgent need for minimally-invasive approaches that restore the physiological mechanics of the spine. Here we present an injectable peptide:GAG hydrogel that rapidly self-assembles in situ and restores the mechanics of denucleated intervertebral discs. It forms a gel with comparable mechanical properties to the native tissue within seconds to minutes depending on the peptide chosen. Unlike other biomaterials that have been proposed for this purpose, these hybrid hydrogels can be injected through a very narrow 25 G gauge needle, minimising damage to the surrounding soft tissue, and they mimic the ability of the natural tissue to draw in water by incorporating GAGs. Furthermore, the GAGs enhance the gelation kinetics and thermodynamic stability of peptide hydrogels, significantly reducing effusion of injected material from the intervertebral disc (GAG leakage of 8 ± 3% after 24 hrs when peptide present, compared to 39 ± 3% when no peptide present). In an ex vivo model, we demonstrate that the hydrogels can restore the compressive stiffness of denucleated bovine intervertebral discs. Compellingly, this novel biomaterial has the potential to transform the clinical treatment of back pain by resolving current surgical challenges, thus improving patient quality of life
Decay rate and decoherence control in coupled dissipative cavities
We give a detailed account of the derivation of a master equation for two
coupled cavities in the presence of dissipation. The analytical solution is
presented and physical limits of interest are discussed. Firstly we show that
the decay rate of initial coherent states can be significantly modified if the
two cavities have different decay rates and are weakly coupled through a wire.
Moreover, we show that also decoherence rates can be substantially altered by
manipulation of physical parameters. Conditions for experimental realizations
are discussed.Comment: 19 pages, 1 table, accepted by Physica
Time evolution of the classical and quantum mechanical versions of diffusive anharmonic oscillator: an example of Lie algebraic techniques
We present the general solutions for the classical and quantum dynamics of
the anharmonic oscillator coupled to a purely diffusive environment. In both
cases, these solutions are obtained by the application of the
Baker-Campbell-Hausdorff (BCH) formulas to expand the evolution operator in an
ordered product of exponentials. Moreover, we obtain an expression for the
Wigner function in the quantum version of the problem. We observe that the role
played by diffusion is to reduce or to attenuate the the characteristic quantum
effects yielded by the nonlinearity, as the appearance of coherent
superpositions of quantum states (Schr\"{o}dinger cat states) and revivals.Comment: 21 pages, 6 figures, 2 table
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