Quantum approach to nucleation times of kinetic Ising ferromagnets

Low temperature dynamics of Ising ferromagnets under finite magnetic fields are studied in terms of quantum spin representations of stochastic evolution operators. These are constructed for the Glauber dynamic as well as for a modification of this latter, introduced by K. Park {\it et al.} in Phys. Rev. Lett. {\bf 92}, 015701 (2004). In both cases the relaxation time after a field quench is evaluated both numerically and analytically using the spectrum gap of the corresponding operators. The numerical work employs standard recursive techniques following a symmetrization of the evolution operator accomplished by a non-unitary spin rotation. The analytical approach uses low temperature limits to identify dominant terms in the eigenvalue problem. It is argued that the relaxation times already provide a measure of actual nucleation lifetimes under finite fields. The approach is applied to square, triangular and honeycomb lattices.Comment: 14 pages, 6 figure

Class Attendance and Students’ Evaluations of Teaching: Do No-Shows Bias Course Ratings and Rankings?

Background: Many university departments use students’ evaluations of teaching (SET) to compare and rank courses. However, absenteeism from class is often nonrandom and, therefore, SET for different courses might not be comparable. Objective: The present study aims to answer two questions. Are SET positively biased due to absenteeism? Do procedures, which adjust for absenteeism, change course rankings? Research Design: The author discusses the problem from a missing data perspective and present empirical results from regression models to determine which factors are simultaneously associated with students’ class attendance and course ratings. In order to determine the extent of these biases, the author then corrects average ratings for students’ absenteeism and inspect changes in course rankings resulting from this adjustment. Subjects: The author analyzes SET data on the individual level. One or more course ratings are available for each student. Measures: Individual course ratings and absenteeism served as the key outcomes. Results: Absenteeism decreases with rising teaching quality. Furthermore, both factors are systematically related to student and course attributes. Weighting students’ ratings by actual absenteeism leads to mostly small changes in ranks, which follow a power law. Only a few, average courses are disproportionally influenced by the adjustment. Weighting by predicted absenteeism leads to very small changes in ranks. Again, average courses are more strongly affected than courses of very high or low in quality. Conclusions: No-shows bias course ratings and rankings. SET are more appropriate to identify high- and low-quality courses than to determine the exact ranks of average courses

Low-temperature nucleation in a kinetic Ising model with soft stochastic dynamics

We study low-temperature nucleation in kinetic Ising models by analytical and simulational methods, confirming the general result for the average metastable lifetime, = A*exp(beta*Gamma) (beta = 1/kT) [E. Jordao Neves and R.H. Schonmann, Commun. Math. Phys. 137, 209 (1991)]. Contrary to common belief, we find that both A and Gamma depend significantly on the stochastic dynamic. In particular, for a ``soft'' dynamic, in which the effects of the interactions and the applied field factorize in the transition rates, Gamma does NOT simply equal the energy barrier against nucleation, as it does for the standard Glauber dynamic, which does not have this factorization property.Comment: 4 pages RevTex4, 2 figures. Phys. Rev. Lett., in pres

Pulsation of M-type Mira variables with moderately different mass: search for observable mass effects

Models of M-type Miras with masses of 1 $M_\odot$ and 1.2 $M_\odot$, i.e. with envelope masses of about 0.4 $M_\odot$ and 0.6 $M_\odot$, have been constructed, and a comparison has been made of their observable properties. Geometric pulsation of continuum-forming layers is found to be little affected by the mass difference. The influence of molecular contamination of near-infrared continuum bandpasses upon interferometrically measured fit diameters ranges from undetectable to quite significant. Some pulsation cycles of the lower-mass model Mira show substantially stronger contamination than that found in any cycle of the higher-mass star. Observations which sample pulsation phase well and continuously are crucial for avoiding misinterpretations, because the assignment of absolute pulsation phases is inherently uncertain by at least 0.1 cycles, diameter changes may be strongly phase-dependent, and cycle-to-cycle variations may be substantial. In accord with expectations, we find that cycle-to-cycle variations that show up in light curves and in near-continuum diameters tend to be larger and more common in the low-mass models, leading to one possible way to discriminate mass. Two other methods, based on high-precision measurements of the pulsation amplitude and on derivation of pre-maximum effective temperatures from diameter measurements, are also discussed. High-layer features that may be strongly affected by mass are not well described by present dust-free models.Comment: Accepted for MNRAS, 8 Pages, 8 Figure

Excited States of Proton-bound DNA/RNA Base Homo-dimers: Pyrimidines

We are presenting the electronic photo fragment spectra of the protonated pyrimidine DNA bases homo-dimers. Only the thymine dimer exhibits a well structured vibrational progression, while protonated monomer shows broad vibrational bands. This shows that proton bonding can block some non radiative processes present in the monomer.Comment: We acknowledge the use of the computing facility cluster GMPCS of the LUMAT federation (FR LUMAT 2764

Amorphous alumina in the extended atmosphere of Alpha Orionis

In this paper we study the extended atmosphere of the late-type supergiant Alpha Orionis. Infrared spectroscopy of red supergiants reveals strong molecular bands, some of which do not originate in the photosphere but in a cooler layer of molecular material above it. Lately, these layers have been spatially resolved by near and mid-IR interferometry. In this paper, we try to reconcile the IR interferometric and ISO-SWS spectroscopic results on Alpha Orionis with a thorough modelling of the photosphere, molecular layer(s) and dust shell. From the ISO and near-IR interferometric observations, we find that Alpha Orionis has only a very low density water layer close above the photosphere. However, mid-IR interferometric observations and a narrow-slit N-band spectrum suggest much larger extra-photospheric opacity close to the photosphere at those wavelengths, even when taking into account the detached dust shell. We argue that this cannot be due to the water layer, and that another source of mid-IR opacity must be present. We show that this opacity source is probably neither molecular nor chromospheric. Rather, we present amorphous alumina (Al2O3) as the best candidate and discuss this hypothesis in the framework of dust-condensation scenarios.Comment: 15 pages, 18 figures, accepted for publication in A&

The relationship between facial skeletal class and expert-rated interpersonal skill: an epidemiological survey on young Italian adults

BACKGROUND: The facial region plays a major role in determining physical attractiveness, so we assessed the hypothesis that the capability of successfully managing interpersonal relationships in young adults might be related to the facial skeletal class. METHODS: 1,014 young subjects applying to the Military Academy of Pozzuoli, Italy, were enrolled and the cephalometric evaluation was performed by calculating the angular relationships between skeletal points localized by the lateral cephalogram of the face, sorting the subjects in three groups corresponding to each major facial skeletal class. Concurrently, the subjects were evaluated by a team of psychiatrists administering the MMPI-2 test followed by a brief colloquium with each candidate, in order to identify those subjects characterized by low skills for managing interpersonal relationships. RESULTS: According to the psychiatric evaluation about 20% of the subjects were considered potentially unable to manage successfully interpersonal relationships (NS). Males displayed an about two-fold increased risk of being NS. No differences were shown in the distribution of the NS male subjects among the three different facial skeletal classes. On the other hand, NS females displayed a different distribution among the three facial skeletal classes, with a trend of about two-fold and four-fold, respectively, for those subjects belonging to classes II and III, respect to those belonging to class I. CONCLUSION: Females may be more sensitive to physical factors determining beauty, such as the facial morphology certainly is. This finding appears to be interesting especially when thinking about possible orthodontic interventions, although further study is certainly needed to confirm these results

Dust in brown dwarfs and extra-solar planets IV. Assessing TiO2 and SiO nucleation for cloud formation modeling

Clouds form in atmospheres of brown dwarfs and planets. The cloud particle formation processes are similar to the dust formation process studied in circumstellar shells of AGB stars and in Supernovae. Cloud formation modelling in substellar objects requires gravitational settling and element replenishment in addition to element depletion. All processes depend on the local conditions, and a simultaneous treatment is required. We apply new material data in order to assess our cloud formation model results regarding the treatment of the formation of condensation seeds. We re-address the question of the primary nucleation species in view of new (TiO2)_N-cluster data and new SiO vapour pressure data. We apply the density functional theory using the computational chemistry package Gaussian 09 to derive updated thermodynamical data for (TiO2)_N-clusters as input for our TiO2 seed formation model. We test different nucleation treatments and their effect on the overall cloud structure by solving a system of dust moment equations and element conservation or a pre-scribed Drift-Phoenix atmosphere structure. Updated Gibbs free energies for the (TiO2)_N-clusters are presented, and a slightly temperature dependent surface tension for T=500 ... 2000K with an average value of sigma_infty = 480.6 erg 1/cm2. The TiO2-seed formation rate changes only slightly with the updated cluster data. A considerably larger effect on the rate of seed formation, and hence on grain size and dust number density, results from a switch to SiO-nucleation. Despite the higher abundance of SiO over TiO2 in the gas phase, TiO2 remains considerably more efficient in forming condensation seeds by homogeneous nucleation followed by heterogeneous grain growth. The paper discussed the effect on the cloud structure in more detail.Comment: accepted for publication in A&A (abstract abridged

What patients think doctors know: Beliefs about provider knowledge as barriers to safe medication use

We examined patient beliefs about provider awareness of medication use, patient-reported prevalence and nature of provider counseling about medications, and the impact of health literacy on these outcomes