1,517 research outputs found
Spatially fractional-order viscoelasticity, non-locality and a new kind of anisotropy
Spatial non-locality of space-fractional viscoelastic equations of motion is
studied. Relaxation effects are accounted for by replacing second-order time
derivatives by lower-order fractional derivatives and their generalizations. It
is shown that space-fractional equations of motion of an order strictly less
than 2 allow for a new kind anisotropy, associated with angular dependence of
non-local interactions between stress and strain at different material points.
Constitutive equations of such viscoelastic media are determined. Explicit
fundamental solutions of the Cauchy problem are constructed for some cases
isotropic and anisotropic non-locality
Diffusion in multiscale spacetimes
We study diffusion processes in anomalous spacetimes regarded as models of
quantum geometry. Several types of diffusion equation and their solutions are
presented and the associated stochastic processes are identified. These results
are partly based on the literature in probability and percolation theory but
their physical interpretation here is different since they apply to quantum
spacetime itself. The case of multiscale (in particular, multifractal)
spacetimes is then considered through a number of examples and the most general
spectral-dimension profile of multifractional spaces is constructed.Comment: 23 pages, 5 figures. v2: discussion improved, typos corrected,
references adde
Retarding Sub- and Accelerating Super-Diffusion Governed by Distributed Order Fractional Diffusion Equations
We propose diffusion-like equations with time and space fractional
derivatives of the distributed order for the kinetic description of anomalous
diffusion and relaxation phenomena, whose diffusion exponent varies with time
and which, correspondingly, can not be viewed as self-affine random processes
possessing a unique Hurst exponent. We prove the positivity of the solutions of
the proposed equations and establish the relation to the Continuous Time Random
Walk theory. We show that the distributed order time fractional diffusion
equation describes the sub-diffusion random process which is subordinated to
the Wiener process and whose diffusion exponent diminishes in time (retarding
sub-diffusion) leading to superslow diffusion, for which the square
displacement grows logarithmically in time. We also demonstrate that the
distributed order space fractional diffusion equation describes super-diffusion
phenomena when the diffusion exponent grows in time (accelerating
super-diffusion).Comment: 11 pages, LaTe
Impacts of Co-Solvent Flushing on Microbial Populations Capable of Degrading Trichloroethylene
With increased application of co-solvent flushing technologies for removal of nonaqueous phase liquids from groundwater aquifers, concern over the effects of the solvent on native microorganisms and their ability to degrade residual contaminant has also arisen. This study assessed the impact of ethanol flushing on the numbers and activity potentials of trichloroethylene (TCE)-degrading microbial populations present in aquifer soils taken immediately after and 2 years after ethanol flushing of a former dry cleaners site. Polymerase chain reaction analysis revealed soluble methane monooxygenase genes in methanotrophic enrichments, and 16S rRNA analysis identified Methylocystis parvus with 98% similarity, further indicating the presence of a type II methanotroph. Dissimilatory sulfite reductase genes in sulfate-reducing enrichments prepared were also observed. Ethanol flushing was simulated in columns packed with uncontaminated soils from the dry cleaners site that were dosed with TCE at concentrations observed in the field; after flushing, the columns were subjected to a continuous flow of 500 pore volumes of groundwater per week. Total acridine orange direct cell counts of the flushed and nonflushed soils decreased over the 15-week testing period, but after 5 weeks, the flushed soils maintained higher cell counts than the nonflushed soils. Inhibition of methanogenesis by sulfate reduction was observed in all column soils, as was increasing removal of total methane by soils incubated under methanotrophic conditions. These results showed that impacts of ethanol were not as severe as anticipated and imply that ethanol may mitigate the toxicity of TCE to the microorganisms
Infrared spectroscopy of phytochrome and model pigments
Fourier-transform infrared difference spectra between the red-absorbing and far-red-absorbing forms of oat phytochrome have been measured in H2O and 2H2O. The difference spectra are compared with infrared spectra of model compounds, i.e. the (5Z,10Z,15Z)- and (5Z,10Z,15E)-isomers of 2,3,7,8,12,13,17,18-octaethyl-bilindion (Et8-bilindion), 2,3-dihydro-2,3,7,8,12,13,17,18-octaethyl-bilindion (H2Et8-bilindion), and protonated H2Et8-bilindion in various solvents. The spectra of the model compounds show that only for the protonated forms can clear differences between the two isomers be detected. Since considerable differences are present between the spectra of Et8-bilindion and H2Et8-bilindion, it is concluded that only the latter compound can serve as a model system of phytochrome. The 2H2O effect on the difference spectrum of phytochrome supports the view that the chromophore in red-absorbing phytochrome is protonated and suggests, in addition, that it is also protonated in far-red-absorbing phytochrome. The spectra show that protonated carboxyl groups are influenced. The small amplitudes in the difference spectra exclude major changes of protein secondary structure
Ensuring young voices are heard in core outcome set development: international workshops with 70 children and young people.
Plain english summaryResearchers test treatments to ensure these work and are safe. They do this by studying the effects that treatments have on patients by measuring outcomes, such as pain and quality of life. Often research teams measure different outcomes even though each team is studying the same condition. This makes it hard to compare the findings from different studies and it can reduce the accuracy of the treatment advice available to patients. Increasingly, researchers are tackling this problem by developing 'core outcome sets'. These are lists of outcomes that all researchers working on a given condition should measure in their studies. It is important that patients have a voice in the development of core outcome sets and children and young people are no exception. But their voices have rarely been heard when core outcome sets are developed. Researchers are trying to address this problem and make sure that core outcome sets are developed in ways that are suitable for children and young people. As a first step, we held two international workshops with children and young people to listen to their views. They emphasised the importance of motivating young people to participate in developing core outcome sets, making them feel valued, and making the development process more interactive, enjoyable and convenient. We hope this commentary will encourage researchers to include children and young people when developing core outcome sets and to adapt their methods so these are suitable for young participants. Future research is important to examine whether these adaptations are effective.AbstractBackground Different research teams looking at treatments for the same condition often select and measure inconsistent treatment outcomes. This makes it difficult to synthesise the results of different studies, leads to selective outcome reporting and impairs the quality of evidence about treatments. 'Core outcome sets' (COS) can help to address these problems. A COS is an agreed, minimum list of outcomes that researchers are encouraged to consistently measure and report in their studies. Including children and young people (CYP) as participants in the development of COS for paediatric conditions ensures that clinically meaningful outcomes are measured and reported. However, few published COS have included CYP as participants. COS developers have described difficulties in recruiting and retaining CYP and there is a lack of guidance on optimising COS methods for them. We aimed to explore CYP's views on the methods used to develop COS and identify ways to optimise these methods.Main body This commentary summarises discussions during two workshops with approximately 70 CYP (aged 10-18 years old) at the International Children's Advisory Network Research and Advocacy Summit, 2018. Delegates described what might motivate them to participate in a COS study, including feeling valued, understanding the need for COS and the importance of input from CYP in their development, and financial and other incentives (e.g. certificates of participation). For Delphi surveys, delegates suggested that lists of outcomes should be as brief as possible, and that scoring and feedback methods should be simplified. For consensus meetings, delegates advised preparing CYP in advance, supporting them during meetings (e.g. via mentors) and favoured arrangements whereby CYP could meet separately from parents and other stakeholders. Overall, they wanted COS methods that were convenient, enjoyable and engaging.Conclusion This commentary points to the limitations of the methods currently used to develop COS with CYP. It also points to ways to motivate CYP to participate in COS studies and to enhancements of methods to make participation more engaging for CYP. Pending much needed research on COS methods for CYP, the perspectives offered in the workshops should help teams developing COS in paediatrics and child health
The meaning of life in a developing universe
The evolution of life on Earth has produced an organism that is beginning to model and understand its own evolution and the possible future evolution of life in the universe. These models and associated evidence show that evolution on Earth has a trajectory. The scale over which living processes are organized cooperatively has increased progressively, as has its evolvability. Recent theoretical advances raise the possibility that this trajectory is itself part of a wider developmental process. According to these theories, the developmental process has been shaped by a larger evolutionary process that involves the reproduction of universes. This evolutionary process has tuned the key parameters of the universe to increase the likelihood that life will emerge and develop to produce outcomes that are successful in the larger process (e.g. a key outcome may be to produce life and intelligence that intentionally reproduces the universe and tunes the parameters of ‘offspring’ universes). Theory suggests that when life emerges on a planet, it moves along this trajectory of its own accord. However, at a particular point evolution will continue to advance only if organisms emerge that decide to advance the evolutionary process intentionally. The organisms must be prepared to make this commitment even though the ultimate nature and destination of the process is uncertain, and may forever remain unknown. Organisms that complete this transition to intentional evolution will drive the further development of life and intelligence in the universe. Humanity’s increasing understanding of the evolution of life in the universe is rapidly bringing it to the threshold of this major evolutionary transition
A Mixture of LBG Overdensities in the Fields of Three Quasars: Implications for the Robustness of Photometric Selection
The most luminous quasars at are suspected to be both highly
clustered and reside in the most massive dark matter halos in the early
Universe, making them prime targets to search for galaxy overdensities and/or
protoclusters. We search for Lyman-break dropout-selected galaxies using HST
WFC3/ACS broadband imaging in the fields of three quasars, as well
as their simultaneously observed coordinated-parallel fields, and constrain
their photometric redshifts using EAZY. One field, J0305-3150, shows a volume
density 10 higher than the blank-field UV luminosity function (UVLF) at
M, with tentative evidence of a 3 overdensity in its
parallel field located 15 cMpc away. Another field, J2054-0005, shows an
angular overdensity within 500 ckpc from the quasar but still consistent with
UVLF predictions within 3, while the last field, J2348-3054, shows no
enhancement. We discuss methods for reducing uncertainty in overdensity
measurements when using photometric selection and show that we can robustly
select LBGs consistent with being physically associated with the quasar,
corroborated by existing JWST/NIRCam WFSS data in the J0305 field. Even
accounting for incompleteness, the overdensities in J0305 and J2054 are higher
for brighter galaxies at short angular separations, suggesting preferential
enhancement of more massive galaxies in the immediate vicinity of the quasar.
Finally, we compare the LBG population with previously-identified [CII] and
mm-continuum companions; the LBG overdensities are not accompanied by an
enhanced number of dusty galaxies, suggesting that the overdense quasar fields
are not in the bursty star-forming phase sometimes seen in high-redshift
protoclusters.Comment: 22 pages (main text), 12 figures, 10 tables, 2 appendices. Final
version after addressing referee report, accepted to ApJ May 202
Electrical properties of a-antimony selenide
This paper reports conduction mechanism in a-\sbse over a wide range of
temperature (238K to 338K) and frequency (5Hz to 100kHz). The d.c. conductivity
measured as a function of temperature shows semiconducting behaviour with
activation energy E= 0.42 eV. Thermally induced changes in the
electrical and dielectric properties of a-\sbse have been examined. The a.c.
conductivity in the material has been explained using modified CBH model. The
band conduction and single polaron hopping is dominant above room temperature.
However, in the lower temperature range the bipolaron hopping dominates.Comment: 9 pages (RevTeX, LaTeX2e), 9 psfigures, also at
http://pu.chd.nic.in/ftp/pub/san16 e-mail: gautam%[email protected]
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