1,072 research outputs found
Generalised Lyndon-Schützenberger Equations
We fully characterise the solutions of the generalised Lyndon-Schützenberger word equations , where for all , for all , for all , and is an antimorphic involution. More precisely, we show for which , , and such an equation has only -periodic solutions, i.e., , , and are in for some word , closing an open problem by Czeizler et al. (2011)
Control of electron dynamics, radical and metastable species generation in atmospheric pressure RF plasma jets by Voltage Waveform Tailoring
Atmospheric pressure capacitively coupled radio frequency discharges operated in He/N2 mixtures and driven by tailored voltage waveforms are investigated experimentally using a COST microplasma reference jet and by means of kinetic simulations as a function of the reactive gas admixture and the number of consecutive harmonics used to drive the plasma. Pulse-type 'peaks'-waveforms, that consist of up to four consecutive harmonics of the fundamental frequency (f = 13.56 MHz), are used at a fixed peak-to-peak voltage of 400 V. Based on an excellent agreement between experimental and simulation results with respect to the DC self-bias and the spatio-temporal electron impact excitation dynamics, we demonstrate that Voltage Waveform Tailoring allows for the control of the dynamics of energetic electrons, the electron energy distribution function in distinct spatio-temporal regions of interest, and, thus, the generation of atomic nitrogen as well as helium metastables, which are highly relevant for a variety of technological and biomedical applications. By tuning the number of driving frequencies and the reactive gas admixture, the generation of these important species can be optimised. The behaviour of the DC self-bias, which is different compared to that in low pressure capacitive radio frequency plasmas, is understood based on an analytical model
Efeitos do processo industrial no potencial antioxidante de quatro cultivares brasileiras de feijão carioca.
No Brasil, o feijão é atualmente comercializado na forma in natura para o cozimento, diferente de outros países onde o processado na forma de enlatado é superior à forma seca. No país, o consumo do grão processado ainda é pequeno, mas vem ganhando a mesa dos brasileiros aos poucos. Objetivou-se então avaliar o efeito do processamento industrial no potencial antioxidante do feijão carioca.CONAF
Helium metastable species generation in atmospheric pressure RF plasma jets driven by tailored voltage waveforms in mixtures of He and N2
Spatially resolved tunable diode-laser absorption measurements of the absolute densities of He-I (23S1) metastables in a micro atmospheric pressure plasma jet operated in He/N2 and driven by 'peaks'- and 'valleys'-type tailored voltage waveforms are presented. The measurements are performed at different nitrogen admixture concentrations and peak-to-peak voltages with waveforms that consist of up to four consecutive harmonics of the fundamental frequency of 13.56 MHz. Comparisons of the measured metastable densities with those obtained from particle-in-cell/Monte Carlo collision simulations show a good quantitative agreement. The density of helium metastables is found to be significantly enhanced by increasing the number of consecutive driving harmonics. Their generation can be further optimized by tuning the peak-to-peak voltage amplitude and the concentration of the reactive gas admixture. These findings are understood based on detailed fundamental insights into the spatio-temporal electron dynamics gained from the simulations, which show that voltage waveform tailoring allows to control the electron energy distribution function to optimize the metastable generation. A high degree of correlation between the metastable creation rate and the electron impact excitation rate from the helium ground state into the He-I ((3s)3S1) level is observed for some conditions which may facilitate an estimation of the metastable densities based on phase resolved optical emission spectroscopy measurements of the 706.5 nm He-I line originating from the above level and metastable density values at proper reference conditions
NMR and LC-MS assessment of compound variability of common bean (Phaseolus vulgaris) stored under controlled atmosphere.
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Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei
UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting
sporadic occultation of stellar light by circumstellar dust. GM\,Cephei is such
a UXor in the young (~Myr) open cluster Trumpler\,37, showing prominent
infrared excess, emission-line spectra, and flare activity. Our photometric
monitoring (2008--2018) detects (1)~an 3.43~day period, likely arising
from rotational modulation by surface starspots, (2)~sporadic brightening on
time scales of days due to accretion, (3)~irregular minor flux drops due to
circumstellar dust extinction, and (4)~major flux drops, each lasting for a
couple of months with a recurrence time, though not exactly periodic, of about
two years. The star experiences normal reddening by large grains, i.e., redder
when dimmer, but exhibits an unusual "blueing" phenomenon in that the star
turns blue near brightness minima. The maximum extinction during relatively
short (lasting ~days) events, is proportional to the duration, a
consequence of varying clump sizes. For longer events, the extinction is
independent of duration, suggestive of a transverse string distribution of
clumps. Polarization monitoring indicates an optical polarization varying
--8, with the level anticorrelated with the slow brightness
change. Temporal variation of the unpolarized and polarized light sets
constraints on the size and orbital distance of the circumstellar clumps in the
interplay with the young star and scattering envelope. These transiting clumps
are edge-on manifestations of the ring- or spiral-like structures found
recently in young stars with imaging in infrared of scattered light, or in
submillimeter of thermalized dust emission.Comment: 20 pages, 9 figure
Experiences of refugees and asylum seekers in general practice: a qualitative study
Background: There has been much debate regarding the refugee health situation in the UK. However most of the existing literature fails to take account of the opinions of refugees themselves. This study was established to determine the views of asylum seekers and refugees on their overall experiences in primary care and to suggest improvements to their care. Methods: Qualitative study of adult asylum seekers and refugees who had entered the UK in the last 10 years. The study was set in Barnet Refugee Walk in Service, London. 11 Semi structured interviews were conducted and analysed using framework analysis. Results: Access to GPs may be more difficult for failed asylum seekers and those without support from refugee agencies or family. There may be concerns amongst some in the refugee community regarding the access to and confidentiality of professional interpreters. Most participants stated their preference for GPs who offered advice rather than prescriptions. The stigma associated with refugee status in the UK may have led to some refugees altering their help seeking behaviour. Conclusion: The problem of poor access for those with inadequate support may be improved by better education and support for GPs in how to provide for refugees. Primary Care Trusts could also supply information to newly arrived refugees on how to access services. GPs should be aware that, in some situations, professional interpreters may not always be desired and that instead, it may be advisable to reach a consensus as to who should be used as an interpreter. A better doctor-patient experience resulting from improvements in access and communication may help to reduce the stigma associated with refugee status and lead to more appropriate help seeking behaviour. Given the small nature of our investigation, larger studies need to be conducted to confirm and to quantify these results
Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XV. Long-Term Optical Monitoring of NGC 5548
We present the results of three years of ground-based observations of the
Seyfert 1 galaxy NGC 5548, which combined with previously reported data, yield
optical continuum and broad-line H-beta light curves for a total of eight
years. The light curves consist of over 800 points, with a typical spacing of a
few days between observations. During this eight-year period, the nuclear
continuum has varied by more than a factor of seven, and the H-beta emission
line has varied by a factor of nearly six. The H-beta emission line responds to
continuum variations with a time delay or lag of 10-20 days, the precise value
varying somewhat from year to year. We find some indications that the lag
varies with continuum flux in the sense that the lag is larger when the source
is brighter.Comment: 29 pages, 6 figures. Accepted for publication in ApJ (1999 Jan 10
Large tunable valley splitting in edge-free graphene quantum dots on boron nitride
Coherent manipulation of binary degrees of freedom is at the heart of modern
quantum technologies. Graphene offers two binary degrees: the electron spin and
the valley. Efficient spin control has been demonstrated in many solid state
systems, while exploitation of the valley has only recently been started, yet
without control on the single electron level. Here, we show that van-der Waals
stacking of graphene onto hexagonal boron nitride offers a natural platform for
valley control. We use a graphene quantum dot induced by the tip of a scanning
tunneling microscope and demonstrate valley splitting that is tunable from -5
to +10 meV (including valley inversion) by sub-10-nm displacements of the
quantum dot position. This boosts the range of controlled valley splitting by
about one order of magnitude. The tunable inversion of spin and valley states
should enable coherent superposition of these degrees of freedom as a first
step towards graphene-based qubits
Fate specification and tissue-specific cell cycle control of the <i>Caenorhabditis elegans</i> intestine
Coordination between cell fate specification and cell cycle control in multicellular organisms is essential to regulate cell numbers in tissues and organs during development, and its failure may lead to oncogenesis. In mammalian cells, as part of a general cell cycle checkpoint mechanism, the F-box protein β-transducin repeat-containing protein (β-TrCP) and the Skp1/Cul1/F-box complex control the periodic cell cycle fluctuations in abundance of the CDC25A and B phosphatases. Here, we find that the Caenorhabditis elegans β-TrCP orthologue LIN-23 regulates a progressive decline of CDC-25.1 abundance over several embryonic cell cycles and specifies cell number of one tissue, the embryonic intestine. The negative regulation of CDC-25.1 abundance by LIN-23 may be developmentally controlled because CDC-25.1 accumulates over time within the developing germline, where LIN-23 is also present. Concurrent with the destabilization of CDC-25.1, LIN-23 displays a spatially dynamic behavior in the embryo, periodically entering a nuclear compartment where CDC-25.1 is abundant
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