Rota-Baxter algebras and new combinatorial identities

The word problem for an arbitrary associative Rota-Baxter algebra is solved. This leads to a noncommutative generalization of the classical Spitzer identities. Links to other combinatorial aspects, particularly of interest in physics, are indicated.Comment: 8 pages, improved versio

Renormalization: a quasi-shuffle approach

In recent years, the usual BPHZ algorithm for renormalization in perturbative quantum field theory has been interpreted, after dimensional regularization, as a Birkhoff decomposition of characters on the Hopf algebra of Feynman graphs, with values in a Rota-Baxter algebra of amplitudes. We associate in this paper to any such algebra a universal semi-group (different in nature from the Connes-Marcolli "cosmical Galois group"). Its action on the physical amplitudes associated to Feynman graphs produces the expected operations: Bogoliubov's preparation map, extraction of divergences, renormalization. In this process a key role is played by commutative and noncommutative quasi-shuffle bialgebras whose universal properties are instrumental in encoding the renormalization process

Minimum energy states of the plasma pinch in standard and Hall magnetohydrodynamics

Axisymmetric relaxed states of a cylindrical plasma column are found analytically in both standard and Hall magnetohydrodynamics (MHD) by complete minimization of energy with constraints imposed by invariants inherent in corresponding models. It is shown that the relaxed state in Hall MHD is the force-free magnetic field with uniform axial flow and/or rigid azimuthal rotation. The relaxed states in standard MHD are more complex due to the coupling between velocity and magnetic field. Application of these states for reversed-field pinches (RFP) is discussed

Self esteem and organizational commitment among health information management staff in tertiary care hospitals in Tehran

BACKGROUND: Self esteem (SE) and organizational commitment (OC)? have significant impact on the quality of work life. AIM: This study aims to gain a better understanding of the relationships between SE and OC among health information management staff in tertiary care hospitals in Tehran (Iran). METHODS: This was a descriptive correlational and cross sectional study conducted on the health information management staff of tertiary care hospitals in Tehran, Iran. A total of 155 participants were randomly selected from 400 staff. Data were collected by two standard questionnaires. The SE and OC was measured using Eysenck SE scale and Meyer and Allen's three component model, respectively. The collected data were analyzed with the SPSS (version 16) using statistical tests of of independent T-test, Pearson Correlation coefficient, one way ANOVA and F tests. RESULTS: The OC and SE of the employees' were 67.8?, out of 120 (weak) and 21.0 out of 30 (moderate), respectively. The values for affective commitment, normative commitment, and continuance commitment were respectively 21.3 out of 40 (moderate), 23.9 out of 40 (moderate), and 22.7 out of 40 (moderate). The Pearson correlation coefficient test showed a significant OC and SE was statistically significant (P<0.05). The one way ANOVA test (P<0.05) did not show any significant difference between educational degree and work experience with SE and OC. CONCLUSION: This research showed that SE and OC ?are moderate. SE and OC have strong correlation with turnover, critical thinking, job satisfaction, and individual and organizational improvement. Therefore, applying appropriate human resource policies is crucial to reinforce these measures

Distribution and abundance of phytoplankton in Hormuzgan province, Hormuz Strait and the Persian Gulf waters

Distribution and density of different phytoplankton groups in Hormuzgan province along the Persian Gulf, from Sirik Harbor to Nayband Bay were studied during winter 2004. Sampling was carried out on board of Ferdous-1 research vessel in seven transects (21 stations) in three lines including surface layer (0-20m), middle and bottom layers (20-50m and more than 50m, respectively). We found 46 genera of diatoms (Bacillariophyceae), 19 genera of dinoflagellates, 6 genera of blue-green algae (Cyanophyceae), 1 genus of Euglenophyceae and 1 genus of Chrysophyceae. We recorded maximum and minimum phytoplankton density in different transects at 37665583 and 2433208 cells/m3 respectively. The maximum density was 62762083 cells/m3 for Bacillariophyceae group that was sampled in surface layer (0-20m) of the station 9. Also, we found that average total number of phytoplankton in three lines of seven transects was 11728973 cells/m3. One way ANOVA showed a significant difference for average number of phytoplankton for each transect (P0.05)