13,840 research outputs found
Extreme(ly) mean(ingful): Sequential formation of a quality group
The present paper studies the limiting behavior of the average score of a
sequentially selected group of items or individuals, the underlying
distribution of which, , belongs to the Gumbel domain of attraction of
extreme value distributions. This class contains the Normal, Lognormal, Gamma,
Weibull and many other distributions. The selection rules are the "better than
average" () and the "-better than average" rule, defined as
follows. After the first item is selected, another item is admitted into the
group if and only if its score is greater than times the average score
of those already selected. Denote by the average of the first
selected items, and by the time it takes to amass them. Some of the key
results obtained are: under mild conditions, for the better than average rule,
less a suitable chosen function of converges almost surely
to a finite random variable. When ,
and , then
is of approximate order . When , the asymptotic results for
are of a completely different order of magnitude. Interestingly,
for a class of distributions, , suitably normalized, asymptotically
approaches 1, almost surely for relatively small , in probability
for moderate sized and in distribution when is large.Comment: Published in at http://dx.doi.org/10.1214/10-AAP684 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
A new code for Fourier-Legendre analysis of large datasets: first results and a comparison with ring-diagram analysis
Fourier-Legendre decomposition (FLD) of solar Doppler imaging data is a
promising method to estimate the sub-surface solar meridional flow. FLD is
sensible to low-degree oscillation modes and thus has the potential to probe
the deep meridional flow. We present a newly developed code to be used for
large scale FLD analysis of helioseismic data as provided by the Global
Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI)
instrument, and the upcoming Helioseismic and Magnetic Imager (HMI) instrument.
First results obtained with the new code are qualitatively comparable to those
obtained from ring-diagram analyis of the same time series.Comment: 4 pages, 2 figures, 4th HELAS International Conference "Seismological
Challenges for Stellar Structure", 1-5 February 2010, Arrecife, Lanzarote
(Canary Islands
The Critical Exponent is Computable for Automatic Sequences
The critical exponent of an infinite word is defined to be the supremum of
the exponent of each of its factors. For k-automatic sequences, we show that
this critical exponent is always either a rational number or infinite, and its
value is computable. Our results also apply to variants of the critical
exponent, such as the initial critical exponent of Berthe, Holton, and Zamboni
and the Diophantine exponent of Adamczewski and Bugeaud. Our work generalizes
or recovers previous results of Krieger and others, and is applicable to other
situations; e.g., the computation of the optimal recurrence constant for a
linearly recurrent k-automatic sequence.Comment: In Proceedings WORDS 2011, arXiv:1108.341
Liquid-liquid phase separation and morphology of internally mixed dicarboxylic acids/ammonium sulfate/water particles
Knowledge of the physical state and morphology of internally mixed organic/inorganic aerosol particles is still largely uncertain. To obtain more detailed information on liquid-liquid phase separation (LLPS) and morphology of the particles, we investigated complex mixtures of atmospherically relevant dicarboxylic acids containing 5, 6, and 7 carbon atoms (C5, C6 and C7) having oxygen-to-carbon atomic ratios (O:C) of 0.80, 0.67, and 0.57, respectively, mixed with ammonium sulfate (AS). With micrometer-sized particles of C5/AS/H_2O, C6/AS/H_2O and C7/AS/H_2O as model systems deposited on a hydrophobically coated substrate, laboratory experiments were conducted for various organic-to-inorganic dry mass ratios (OIR) using optical microscopy and Raman spectroscopy. When exposed to cycles of relative humidity (RH), each system showed significantly different phase transitions. While the C5/AS/H_2O particles showed no LLPS with OIR = 2:1, 1:1 and 1:4 down to 20% RH, the C6/AS/H_2O and C7/AS/H_2O particles exhibit LLPS upon drying at RH 50 to 85% and ~90%, respectively, via spinodal decomposition, growth of a second phase from the particle surface or nucleation-and-growth mechanisms depending on the OIR. This suggests that LLPS commonly occurs within the range of O:C < 0.7 in tropospheric organic/inorganic aerosols. To support the comparison and interpretation of the experimentally observed phase transitions, thermodynamic equilibrium calculations were performed with the AIOMFAC model. For the C7/AS/H_2O and C6/AS/H_2O systems, the calculated phase diagrams agree well with the observations while for the C5/AS/H_2O system LLPS is predicted by the model at RH below 60% and higher AS concentration, but was not observed in the experiments. Both core-shell structures and partially engulfed structures were observed for the investigated particles, suggesting that such morphologies might also exist in tropospheric aerosols
THE IMPACT OF COGNITIVE FUNCTION ON PATIENT LANGUAGE AND QUALITY OF LIFE OUTCOMES FOR STROKE SURVIVORS WITH APHASIA WHO PARTICIPATE IN AN INTENSIVE COMPREHENSIVE APHASIA PROGRAM (ICAP)
Background: Aphasia is an acquired language disorder that impairs communication, across all modalities of language (i.e., reading, writing, speaking, and comprehension). Aphasia most commonly results from damage to the left hemisphere of the brain (e.g., stroke, traumatic brain injury). Cognitive function including attention, memory, and executive functioning may negatively impact patient outcomes during post-acute rehabilitation of aphasia. Intensive Comprehensive Aphasia Programs (ICAPs) provide intensive, evidence-based and holistic treatment for a cohort of stroke survivors. The impact of these cognitive functions on language outcomes following participation in an ICAP has not been explored.
Aims: To investigate the impact of extralinguistic cognition and the implementation of a novel cognitive education intervention on language outcomes following for stroke survivors with aphasia who participate in an ICAP.
Methods & Procedures: Eight adult stroke survivors with chronic aphasia participated in a 4-week ICAP implemented by graduate students during the Summer of 2022. Participants in the experimental group received cognitive education about attention, memory, executive functioning domains, external cognitive strategies, and internal cognitive strategies. Participants were matched by age and gender into a control or experimental group. Cognitive function, linguistic function, communicative participation, and quality of life was assessed before and after the ICAP.
Outcomes & Results: Paired sample t-tests were used to compare pre- and post-ICAP performance on language measures within and across groups. Pearson’s r correlation coefficients were used to evaluate the relationship between pre-ICAP extralinguistic cognition and language-based outcomes. Statistically significant change was observed in the experimental group pre- to post- ICAP language outcomes and between the experimental group and the experimental group for language change scores. Low and moderate correlation between the pre-ICAP extralinguistic cognitive abilities and language change scores was observed.
Conclusions: This pilot study suggests that providing cognitive education during an ICAP may positively impact language outcomes for participants with post-stroke aphasia
Experimental evidence for excess entropy discontinuities in glass-forming solutions
Glass transition temperatures T_g are investigated in aqueous binary and multi-component solutions consisting of citric acid, calcium nitrate (Ca(NO_3)_2), malonic acid, raffinose, and ammonium bisulfate (NH_4HSO_4) using a differential scanning calorimeter. Based on measured glass transition temperatures of binary aqueous mixtures and fitted binary coefficients, the T_g of multi-component systems can be predicted using mixing rules. However, the experimentally observed T_g in multi-component solutions show considerable deviations from two theoretical approaches considered. The deviations from these predictions are explained in terms of the molar excess mixing entropy difference between the supercooled liquid and glassy state at T_g. The multi-component mixtures involve contributions to these excess mixing entropies that the mixing rules do not take into account
Electron donor contributions to denitrification in the Elk Valley Aquifer, North Dakota
Six denitrification tracer tests were performed over eight and a half years in in situ mesocosms (ISMs) in the Elk Valley Aquifer (EVA) in east-central North Dakota. Groundwater samples were analyzed to determine how much nitrate was lost beyond that explained by dilution of the bromide tracer. Additional losses were attributed to denitrification. The denitrification rates varied from 0.10 to 0.23 mg N/L/day for the six tests. In general, the major electron donors for denitrification are organic carbon (OC), pyrite (FeS2), and ferrous iron silicate minerals. In the EVA tracer tests, increases in sulfate indicated that the oxidation of pyrite explained a significant of the denitrification. The contributions of the three electron donors varied between tests and from test to test with pyrite, ferrous iron from silicate minerals, and OC apparently contributing 38-84%, 1-3%, and 14-59% to denitrification, respectively
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