The anisotropic quantum antiferromagnet on the Sierpinski gasket: Ground state and thermodynamics

We investigate an antiferromagnetic s=1/2 quantum spin system with anisotropic spin exchange on a fractal lattice, the Sierpinski gasket. We introduce a novel approximative numerical method, the configuration selective diagonalization (CSD) and apply this method to the Sierpinski gasket with N=42. Using this and other methods we calculate ground state energies, spin gap, spin-spin correlations and specific heat data and conclude that the s=1/2 quantum antiferromagnet on the Sierpinski gasket shows a disordered magnetic ground state with a very short correlation length of about 1 and an, albeit very small, spin gap. This conclusion holds for Heisenberg as well a for XY exchange.Comment: LaTeX: 16 pages, 9 figures, 1 tabl

Low-lying excitations and thermodynamics of an antiferromagnetic Heisenberg fractal system of a dimension between one and two

We investigate a frustrated Heisenberg spin-1/2 antiferromagnet on a fractal lattice of dimension d=ln3/ln2 (Sierpinski gasket). Calculations were performed using (a) exact diagonalization of all eigenstates and eigenvectors for systems up to N=15 and (b) the Decoupled-Cell Quantum-Monte-Carlo method for systems up to N=366. We present the low-lying spectrum and the specific heat. The specific heat shows a second maximum in the low-temperature region. This behavior is similar to the behavior of the quantum Heisenberg antiferromagnet on a kagome lattice and suggests a disordered ground state and a spin gap in the considered system.Comment: 2 pages, LaTeX, 3 eps figures, to appear in JMM

The need for culture swabs in laparoscopically treated appendicitis

INTRODUCTION: Appendicitis remains the most common cause of an acute abdomen. Obtaining intra-abdominal cultures is routine surgical practice. There are studies showing no efficacy of such procedures in cases where open appendectomies are performed. AIM: The goal of this study was to assess the need for obtaining intra-abdominal cultures during laparoscopic appendectomies. MATERIAL AND METHODS: Between 2007 and 2012, 369 patients were operated on with the diagnosis of histopathologically proven acute appendicitis. Sixty-two percent of them were operated on using laparoscopic techniques. The microbiological assessment was routinely done for the open procedures and in 42% of cases that underwent a laparoscopic operation. RESULTS: In 57% (134) the swabbing results were negative. Among 43% (102) of the patients with a positive result, Escherichia coli was isolated in 76.5% (78), Proteus mirabilis in 13.7% (14), Pseudomonas aeruginosa in 4.9% (5) and Citrobacter freundii in 4.9% (5). Five cases had bacteria resistant to the antibiotic given preoperatively (that is 4.9% of all positive cultures and 1.4% of all operated patients). However, these cases did not affect the incidence of postoperative complications. Consideration of the postoperative morbidity showed that there was no statistically significant difference between the laparoscopic group with and without intra-operative swabbing (p > 0.05). CONCLUSIONS: The postoperative patient outcome was more dependent on the pathology of the appendix than on the results of the microbiological assessment at the time of surgery. Hence, routine intra-operative cultures during laparoscopic appendectomies appear to have little value in patient management. Swabbing during laparoscopic procedures should be limited to only selected high-risk groups

Pancreatoduodenectomy due to cancer in the older population

By 2030, 70% of all pancreatic cancer will be diagnosed in the older population. However, pancreas operations are a complex surgical procedure with a high rate of morbidity and mortality. Therefore, the benefits of surgical resection in older patients are controversial and decisions about treatment for this group must be well balanced. Chronological age alone should not be a contraindication for multimodal radical treatment in older patients. Fit patients, according to the comprehensive geriatric assessment (SGA), should be qualified for the same treatment as younger patients to benefit the same outcomes. However, they should be operated on in high-volume hospitals by experienced surgeons. Prefrail patients should undergo prehabilitation, during neoadjuvant treatment also, and then reevaluated. Frail patients should be discussed in an oncogeriatric meeting. We still do not have evidence-based data to design a tailored approach for them so as to balanced good oncologic outcomes and the appropriate postoperative quality of life