1,536 research outputs found
Integrable Supersymmetric Fluid Mechanics from Superstrings
Following the construction of a model for the planar supersymmetric Chaplygin
gas, supersymmetric fluid mechanics in (1+1)-dimensions is obtained from the
light-cone parametrized Nambu-Goto superstring in (2+1)-dimensions. The lineal
model is completely integrable and can be formulated neatly using Riemann
coordinates. Infinite towers of conserved charges and supercharges are
exhibited. They form irreducible representations of a dynamical (hidden)
SO(2,1) symmetry group.Comment: 11 pages, LaTex; typographical errors correcte
CO diffusion and desorption kinetics in CO ices
Diffusion of species in icy dust grain mantles is a fundamental process that
shapes the chemistry of interstellar regions; yet measurements of diffusion in
interstellar ice analogs are scarce. Here we present measurements of CO
diffusion into CO ice at low temperatures (T=11--23~K) using CO
longitudinal optical (LO) phonon modes to monitor the level of mixing of
initially layered ices. We model the diffusion kinetics using Fick's second law
and find the temperature dependent diffusion coefficients are well fit by an
Arrhenius equation giving a diffusion barrier of 300 40 K. The low
barrier along with the diffusion kinetics through isotopically labeled layers
suggest that CO diffuses through CO along pore surfaces rather than through
bulk diffusion. In complementary experiments, we measure the desorption energy
of CO from CO ices deposited at 11-50 K by temperature-programmed
desorption (TPD) and find that the desorption barrier ranges from 1240 90
K to 1410 70 K depending on the CO deposition temperature and
resultant ice porosity. The measured CO-CO desorption barriers demonstrate
that CO binds equally well to CO and HO ices when both are compact. The
CO-CO diffusion-desorption barrier ratio ranges from 0.21-0.24 dependent on
the binding environment during diffusion. The diffusion-desorption ratio is
consistent with the above hypothesis that the observed diffusion is a surface
process and adds to previous experimental evidence on diffusion in water ice
that suggests surface diffusion is important to the mobility of molecules
within interstellar ices
Enriched functor categories for functor calculus
In this paper we present background results in enriched category theory and enriched model category theory necessary for developing model categories of enriched functors suitable for doing functor calculus
Genotoxicity of nitroso compounds and sodium dichromate in a model combining organ cultures of human nasal epithelia and the comet assay
Genotoxic effects of xenobiotics are a possible step in tumor initiation in the mucosa of the upper aerodigestive tract. Using the comet assay, detecting genotoxicity in human tissue has been restricted to single incubations in vitro, but in vivo most xenobiotics harm their target in a repetitive or chronic manner. Therefore, we propose a model, which provides repetitive incubations in human upper aerodigestive tract mucosa cultures. Samples of human inferior nasal turbinate mucosa (n = 25) were cultured according to a modified version of a technique originally described by Steinsvag. On day 1 fresh samples and on days 7, 9 and 11 organ cultures were incubated with N-nitrosodiethylamine (NDEA), sodium dichromate (Na2Cr2O7) and N'-methyl-N-nitro-N-nitrosoguanidine(MNNG). Mucosa samples and organ cultures, respectively, underwent a modified comet assay on days 1, 7 and 11. Genotoxicity could be shown for NDEA, Na2Cr2O7 and MNNG on days 1, 7 and 11. Duration of tissue culture and repetitive incubations did not significantly influence the results for NDEA. Nevertheless, Na2Cr2O7 and MNNG caused higher genotoxic effects on cultures subjected to the comet assay on day 11. This model may help to assess genotoxic hazards posed by environ mental pollutants that have a cumulative character in repetitive or chronic exposure in vivo. Copyright (C) 2001 S. Karger AG, Basel
A colimit decomposition for homotopy algebras in Cat
Badzioch showed that in the category of simplicial sets each homotopy algebra
of a Lawvere theory is weakly equivalent to a strict algebra. In seeking to
extend this result to other contexts Rosicky observed a key point to be that
each homotopy colimit in simplicial sets admits a decomposition into a homotopy
sifted colimit of finite coproducts, and asked the author whether a similar
decomposition holds in the 2-category of categories Cat. Our purpose in the
present paper is to show that this is the case.Comment: Some notation changed; small amount of exposition added in intr
Neural pattern similarity differentially affects memory performance of younger and older adults: age differences in neural similarity and memory
Age-related memory decline is associated with changes in neural functioning but little is known about how aging affects the quality of information representation in the brain. Whereas a long-standing hypothesis of the aging literature links cognitive impairments to less distinct neural representations in old age, memory studies have shown that high similarity between activity patterns benefits memory performance for the respective stimuli. Here, we addressed this apparent conflict by investigating between-item representational similarity in 50 younger (19–27 years old) and 63 older (63–75 years old) human adults (male and female) who studied scene-word associations using a mnemonic imagery strategy while electroencephalography was recorded. We compared the similarity of spatiotemporal frequency patterns elicited during encoding of items with different subsequent memory fate. Compared to younger adults, older adults’ memory representations were more similar to each other but items that elicited the most similar activity patterns early in the encoding trial were those that were best remembered by older adults. In contrast, young adults’ memory performance benefited from decreased similarity between earlier and later periods in the encoding trials, which might reflect their better success in forming unique memorable mental images of the joint picture–word pair. Our results advance the understanding of the representational properties that give rise to memory quality as well as how these properties change in the course of aging
Cohesive energies of cubic III-V semiconductors
Cohesive energies for twelve cubic III-V semiconductors with zincblende
structure have been determined using an ab-initio scheme. Correlation
contributions, in particular, have been evaluated using the coupled-cluster
approach with single and double excitations (CCSD). This was done by means of
increments obtained for localized bond orbitals and for pairs and triples of
such bonds. Combining these results with corresponding Hartree-Fock data, we
recover about 92 \% of the experimental cohesive energies.Comment: 16 pages, 1 figure, late
THU0366 SYSTEMATIC CORONARY RISK EVALUATION (SCORE) MISCLASSIFIES CARDIOVASCULAR RISK IN ANTISYNTHETASE SYNDROME: RESULTS OF THE PILOT MULTICENTRIC STUDY RI.CAR.D.A.
Background:Antisynthetase Syndrom (ASyS) is an autoimmune overlap disease characterized by antiaminoacyl-tRNA-synthetase (anti-ARS) antibodies and the classic triad of arthritis, myositis and interstitial lung disease (ILD) (1). Markers of cardiovascular (CV) or cerebrovascular (CVB) risk have never been examined in ASyS.Objectives:Aim of this study (RIsk of CARdiovascular Disease in ASyS: RI.CAR.D.A.) was to test the ability of an established traditional CV risk prediction score (Systematic Coronary Risk Evaluation-SCORE) and its EULAR modified version (mSCORE) to identify ASyS patients at high CV risk. Moreover, we sought to examine for the first time associations of CV surrogate markers with clinical and immunological ASyS parameters.Methods:SCORE/mSCORE and the gold standard marker of aortic stiffness (carotid-femoral pulse wave velocity-cfPWV) were examined in patients with ASyS and healthy controls in a multicenter setting (6 Rheumatology Centers). Moreover, sonography of the common- (CCA), internal- (ICA) and external- (ECA) carotid arteries was performed in subsets of both groups, evaluating carotid intima-media-thickness (cIMT), plaques and duplex-sonographic indices of CBV risk such as the resistance- (RI) and pulsatility-index (PI).Figure 1.Carotid Doppler surrogate markers of cardiovascular and cerebrovascular risk in controls and ASyS (case).cIMTCarotid intima media thickness;CAA(common-),ICA(internal),ECA(external) carotid artery;RIresistance index;PIpulsatility index. (all;p0.9 mm) (SCA) in85.7%of the patients respectively. ROC analyses showed similarly poor diagnostic performances of SCORE/mSCORE in comparison to cfPWV(>10 m/s) and SAC by areas under the curve (AUC) of0.56 (95%CI=0.39-0.73) and0.63 (95%CI=0.3-0.96),respectively. cfPWV and SCA were higher in ASyS patients compared to controls (padj=0.021andp=0.003, respectively). cfPWV and cIMT correlated in the patient group significantly with age (r=0.679; p<0.001 and r=0.664; p<0.001,respectively).Moreover, cfPWV correlated with BMI (padj=0.001) and diabetes(padj=0.043). ACC-RI and ACC-PI showed significant associations with a marker of myositis activity [creatine phosphokinase (CPK):r=0.629;p=0.012andr=0.574;p=0.032, respectively]. Finally, ACI-RI and ACI-PI values were higher in patients with ILD (both;p=0.039).Conclusion:This is the first report of higher aortic stiffness and SCA in ASyS patients compared to controls. Active myositis and presence of ILD were associated with higher CVB risk parameters. Furthermore, SCORE/mSCORE performed poorly in identifying patients at high CV risk and carotid arteriosclerosis compared to cfPWV and CS respectively. Thus, cfPWV and CS could improve CV and CBV screening in ASyS patients.References:[1]Cavagna L, et al. Clinical Spectrum Time Course in Anti Jo-1 Positive Antisynthetase Syndrome.Medicine2015;94:1144.Disclosure of Interests:None declare
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