Mixings of 4-quark components in light non-singlet scalar mesons in QCD sum rules

Mixings of 4-quark components in the non-singlet scalar mesons are studied in the QCD sum rules. We propose a formulation to evaluate the cross correlators of q\bar q and qq\bar q \bar q operators and to define the mixings of different Fock states in the sum rule. It is applied to the non-singlet scalar mesons, a_0 and K_0^\ast. It is found that the 4-quark operators predict lower masses than the q\bar q operators and that the 4-quark states occupy about 70-90% of the lowest mass states.Comment: 8 pages, 9 figure

A Mathematical Justification for the Herman-Kluk Propagator

A class of Fourier Integral Operators which converge to the unitary group of the Schrödinger equation in the semiclassical limit ε → 0 in the uniform operator norm is constructed. The convergence allows for an error bound of order O(ε), which can be improved to arbitrary order in ε upon the introduction of corrections in the symbol. On the Ehrenfest-timescale, the result holds with a slightly weaker error bound. In the chemical literature the approximation is known as the Herman-Kluk propagator

Single switch surface hopping for a model of pyrazine

The single switch trajectory surface hopping algorithm is tested for numerical simulations of a two-state three-mode model for the internal conversion of pyrazine through a conical intersection of potential energy surfaces. The algorithm is compared to two other surface hopping approaches, namely, Tully’s method of the fewest switches [J. Chem. Phys. 93, 1061 (1990)] and the method by Voronin et al. [J. Phys. Chem. A 102, 6057 (1998)] . The single switch algorithm achieves the most accurate results. Replacing its deterministic nonadiabatic branching condition by a probabilistic accept-reject criterion, one obtains the method of Voronin et al. without momentum adjustment. This probabilistic version of the single switch approach outperforms the considered algorithms in terms of accuracy, memory requirement, and runtime

Renormalization of the Deuteron with One Pion Exchange

We analyze the deuteron bound state through the One Pion Exchange Potential. We pay attention to the short distance peculiar singularity structure of the bound state wave functions in coordinate space and the elimination of short distance ambiguities by selecting the regular solution at the origin. We determine the so far elusive amplitude of the converging exponential solutions at the origin. All bound state deuteron properties can then be uniquely deduced from the deuteron binding energy, the pion-nucleon coupling constant and pion mass. This generates correlations among deuteron properties. Scattering phase shifts and low energy parameters in the 3S1-3D1 channel are constructed by requiring orthogonality of the positive energy states to the deuteron bound state, yielding an energy independent combination of boundary conditions. We also analyze from the viewpoint of short distance boundary conditions the weak binding regime on the light of long distance perturbation theory and discuss the approach to the chiral limit.Comment: 22 pages, 11 figure

Construction and validation of a rigorous surface hopping algorithm for conical crossings

This article presents and evaluates a surface hopping algorithm for time-dependent two-level Schr¨odinger systems with conically intersecting eigenvalues. The algorithm implements an asymptotic semigroup for approximating the solution’s Wigner function, that was rigorously defined and derived from the Schr¨odinger equation by two of the authors in previous work. It is applied to two-dimensional isotropic systems, which include linear Jahn-Teller Hamiltonians, and Gaussian initial data. It reproduces energy level populations and expectation values with an accuracy of two to three percent

Undergraduate Student Perceptions Regarding the Use of Educational Technology – A Case Study in a Statistics Service Course

Published ArticleIntegrating theory with practice has become a mandatory requirement for universities of technology. Using educational technology to supplement traditional pedagogical approaches has contributed significantly to achieving this mandate. However, which educational technologies could help improve the educational experience of students in a statistical service course? This research uses an exploratory design, where one large group of undergraduate students were polled using a questionnaire as the main data collection tool. Microsoft Excel and PowerPoint presentations were viewed as a very good supplemental educational tool, while YouTube clips, myVUT (institutional learning management system using Sakai) and the business/financial calculator were not fully utilised by the students. However, the majority of students selected the prescribed textbook as the most useful educational tool in understanding first year statistics, as it was a locally published textbook with many native examples. A blend of all these educational technologies helped to enrich student understanding and satisfaction in learning statistical concepts

Cognitive animacy and its relation to linguistic animacy: Evidence from Japanese and Persian

Animacy, commonly defined as the distinction between living and non-living entities, is a useful notion in cognitive science and linguistics employed to describe and predict variation in psychological and linguistic behaviour. In the (psycho)linguistics literature we find linguistic animacy dichotomies which are (implicitly) assumed to correspond to biological dichotomies. We argue this is problematic, as it leaves us without a cognitively grounded, universal description for non-prototypical cases. We show that ‘animacy’ in language can be better understood as universally emerging from a gradual, cognitive property by collecting animacy ratings for a great range of nouns from Japanese and Persian. We used these cognitive ratings in turn to predict linguistic variation in these languages traditionally explained through dichotomous distinctions. We show that whilst (speakers of) languages may subtly differ in their conceptualisation of animacy, universality may be found in the process of mapping conceptual animacy to linguistic variation

The role of treatment delays in surgical site infection after appendicectomy in a South African rural regional hospital

Background. Delays to surgery for acute appendicitis in low- and middle-income countries lead to significant morbidity.Objectives. To investigate the role of time to surgery in the development of complicated appendicitis and surgical site infection (SSI) in a rural referral hospital in South Africa (SA).Methods. A prospective cohort study was conducted of all patients presenting to a regional hospital in SA with acute appendicitis during 2017. Inpatient interview and data collection were followed by 30-day post-surgical follow-up to assess time periods to surgery and operative outcomes.Results. A total of 188 patients underwent surgery for acute appendicitis. The median (interquartile range (IQR)) age was 19 (3 - 73) years, and 62% were male. The median (IQR) time from symptoms to surgery was 60 (42 - 86) hours and from hospital admission to surgery 8 (4 - 16) hours. Forty-one percent were managed laparoscopically, 62% had complicated appendicitis, and 25% developed SSI. Time from symptoms to surgery >72 hours was associated with an increased risk of complicated appendicitis (odds ratio (OR) 4.32; 95% confidence interval (CI) 1.36 - 13.75; p=0.013). Patients with SSI had an increased median delay of 15 hours (p=0.05) compared with those without SSI. Multivariable analysis showed that the risk of SSI increased with complicated appendicitis (OR 8.96; 95% CI 2.73 - 29.41; p<0,001) and decreased with laparoscopic surgery (OR 0.21; 95% CI 0.07 - 0.59; p=0.003). Time to surgery had no effect on the risk of SSI in adjusted analyses.Conclusions. Delays to surgery beyond 72 hours significantly increased complicated appendicitis, an important risk factor for SSI. Access to facilities with surgical capability and the use of laparoscopic surgery are modifiable risk factors for SSI

Energy Level Crossings in Molecular Dynamics

Energy level crossings are the landmarks that separate classical from quantum mechanical modeling of molecular systems. They induce non-adiabatic transitions between the otherwise adiabatically decoupled electronic level spaces. This review covers results on the analysis of propagation through level crossings of codimension two, a mathematical justification of surface hopping algorithms, and a spectral study of a linear isotropic system