154 research outputs found
Strain and band-mixing effects on the excitonic Aharonov-Bohm effect in In(Ga)As/GaAs ringlike quantum dots
Neutral excitons in strained axially symmetric In(Ga)As/GaAs quantum dots
with ringlike shape are investigated. Similar to experimental self-assembled
quantum rings, the analyzed quantum dots have volcano-like shapes. The
continuum mechanical model is employed to determine the strain distribution,
and the single-band envelope function approach is adopted to compute the
electron states. The hole states are determined by the axially symmetric
multiband Luttinger-Kohn Hamiltonian, and the exciton states are obtained from
an exact diagonalization. We found that the presence of the inner layer
covering the ring opening enhances the excitonic Aharonov-Bohm (AB)
oscillations. The reason is that the hole becomes mainly localized in the inner
part of the quantum dot due to strain, whereas the electron resides mainly
inside the ring-shaped rim. Interestingly, larger AB oscillations are found in
the analyzed quantum dot than in a fully opened quantum ring of the same width.
Comparison with the unstrained ring-like quantum dot shows that the amplitude
of the excitonic Aharonov-Bohm oscillations are almost doubled in the presence
of strain. The computed oscillations of the exciton energy levels are
comparable in magnitude to the oscillations measured in recent experiments.Comment: 16 pages, 9 figures, accepted for publication in Physical Review
On unitarizability in the case of classical p-adic groups
In the introduction of this paper we discuss a possible approach to the
unitarizability problem for classical p-adic groups. In this paper we give some
very limited support that such approach is not without chance. In a forthcoming
paper we shall give additional evidence in generalized cuspidal rank (up to)
three.Comment: This paper is a merged and revised version of ealier preprints
arXiv:1701.07658 and arXiv:1701.07662. The paper is going to appear in the
Proceedings of the Simons Symposium on Geometric Aspects of the Trace Formul
Scaling of avalanche queues in directed dissipative sandpiles
We simulate queues of activity in a directed sandpile automaton in 1+1
dimensions by adding grains at the top row with driving rate .
The duration of elementary avalanches is exactly described by the distribution
, limited either by the system size or by
dissipation at defects . Recognizing the probability
as a distribution of service time of jobs arriving at a server with frequency
, the model represents a new example of the server
queue in the queue theory. We study numerically and analytically the tail
behavior of the distributions of busy periods and energy dissipated in the
queue and the probability of an infinite queue as a function of driving rate.Comment: 11 pages, 9 figures; To appear in Phys. Rev.
A FUNCTION PROPERTY OF POLYTROPHIC PROCESS WITH ASPECT OF TANGENT CONSTRUCTION
In this paper, starting from general tangent equation in arbitrary point of specified curve, using principles of differential geometry and given mathematical transformation tangent equation of polytrophic function in p – v diagram was obtained. This form is convenient for solving numerous practical and theoretical problems in engineering thermodynamic by means of graphical method. It was shown that tangent can be constructed easily, using polytrophic equation only, but it is not example with other functions appearing in thermodynamics. Later, in this paper, we have given some methods, which refer to more exact construction of polytrophic and graphical analyze of polytrophic process
Nonuniversal scaling behavior of Barkhausen noise
We simulate Barkhausen avalanches on fractal clusters in a two-dimensional
diluted Ising ferromagnet with an effective Gaussian random field. We vary the
concentration of defect sites and find a scaling region for moderate
disorder, where the distribution of avalanche sizes has the form . The exponents for size
and for length distribution, and the fractal dimension of
avalanches satisfy the scaling relation .
For fixed disorder the exponents vary with driving rate in agreement with
experiments on amorphous Si-Fe alloys.Comment: 5 pages, Latex, 4 PostScript figures include
Influence of pressure and time on extraction process using supercritical CO2
The supercritical fluid extraction (SFE) by carbon dioxide (CO2) of Salvia officinalis L. was investigated. SFE by CO2 was performed at different pressure (80, 100, 150, 200 and 300 bar) and constant temperature of 40ºC (all other extraction conditions, such are flow rate, particle diameter of Salvia officinalis, extraction time were kept constant. The GC-MS method was used for determination of qualitative and quantitative composition of obtained extracts and essential oils
Effect of starter cultures on survival of Listeria monocytogenes in Cajna sausage
The aim of the study was to evaluate the survival of Listeria monocytogenes during the production of Cajna sausage with short maturation time. Sausage batter was inoculated with three different serotypes 4b and serotype 1/2. of L. monocytogenes. Control sausages were without any starter culture added; the second batch was inoculated with strains of Lactobacillus sakei, Staphylococcus carnosus and Staphylococcus xylosus, and the third batch was inoculated with strains of Debaryomyces hansenii, Lactobacillus sakei, Pediococcus acidilactici, Pediococcus pentosaceus, Staphylococcus carnosus and Staphylococcus xylosus. After 18 days of ripening, L. monocytogenes was not detected in any of the sausages, but during this fermentation and drying, the numbers of this pathogen was lower in the sausages inoculated with starter cultures
Differences in Self-Rated Versus Parent Proxy–Rated Vision-Related Quality of Life and Functional Vision of Visually Impaired Children
PURPOSE: To investigate disagreement between children's self-reported vision-related quality of life (VQoL) and functional vision (FV), and their parents' proxy-reports. DESIGN: Cross-sectional study. METHODS: 152 children aged 7-18 years with visual impairment (VI) (defined by the World Health Organization), and their parents, were recruited from 22 National Health Service (NHS) Ophthalmology Departments in the United Kingdom. Age-appropriate versions of 2 vision-specific instruments capturing VQoL and FV, were administered to children alongside modified versions for completion by parents on behalf of their child (i.e. parent proxy-report). Disagreement between self- and parent proxy-report was examined using the Bland-Altman (BA) method, and a threshold of disagreement based on 0.5 standard deviation. Disagreement was analysed according to participants' age, gender and clinical characteristics, using logistic regression analyses. RESULTS: Children rated themselves as having better outcomes than their parents did, although parents both under- and over-estimated their child's VQoL (mean score difference = 7.7). With each year of increasing age, there was a 1.18 (1.04 - 1.35) higher odds of children self-rating their VQoL better than their parents (p = 0.013). Although parents consistently under-estimated their child's FV (mean score difference = -4.7), no characteristics were significantly associated with differences in disagreement. CONCLUSIONS: Disagreement between child self-report on the impact of VI, and their parents' proxy-reports varies by age. This implies that self-report from children must remain the gold standard. Where self-reporting is not possible, parent proxy-reports may provide useful insights, but must be interpreted with caution
Asymmetric versus symmetric double quantum wells: Band gap tuning without electric field
We investigate the electron states in double asymmetric
quantum wells grown along the direction.
The subbands are computed by means of the envelope function approximation
applied to the 8-band Kane model. The asymmetry of the
confining potential of the double quantum wells results in a gap opening which
is absent in the symmetric system where it can only be induced by an applied
electric field. The band gap and the subbands are affected by spin-orbit
coupling which is a consequence of the asymmetry of the confining potential.
The electron-like and hole-like states are mainly confined in different quantum
wells, and the enhanced hybridization between them opens a spin-dependent
hybridization gap at a finite in-plane wavevector. We show that both the ratio
of the widths of the two quantum wells and the mole fraction of the
barrier control both the energy gap between the
hole-like states and the hybridization gap. The energy subbands are shown to
exhibit inverted ordering, and therefore a nontrivial topological phase could
emerge in the system.Comment: 16 pages, 5 figures, The following article has been accepted by
Journal of Applied Physics; After it is published, it will be found at
https://doi.org/10.1063/5.001606
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