The spectral gap for some spin chains with discrete symmetry breaking

We prove that for any finite set of generalized valence bond solid (GVBS) states of a quantum spin chain there exists a translation invariant finite-range Hamiltonian for which this set is the set of ground states. This result implies that there are GVBS models with arbitrary broken discrete symmetries that are described as combinations of lattice translations, lattice reflections, and local unitary or anti-unitary transformations. We also show that all GVBS models that satisfy some natural conditions have a spectral gap. The existence of a spectral gap is obtained by applying a simple and quite general strategy for proving lower bounds on the spectral gap of the generator of a classical or quantum spin dynamics. This general scheme is interesting in its own right and therefore, although the basic idea is not new, we present it in a system-independent setting. The results are illustrated with an number of examples.Comment: 48 pages, Plain TeX, BN26/Oct/9

Practical issues in early switching from intravenous to oral antibiotic therapy in children with uncomplicated acute hematogenous osteomyelitis: Results from an italian survey

Background: The European Society of Pediatric Infectious Diseases (ESPID) guidelines for acute hematogenous osteomyelitis (AHOM) have been published recently. In uncomplicated cases, an early (2-4 days) switch to oral empirical therapy, preferentially with flucloxacillin, is recommended in low methicillin-resistant Staphylococcus aureus settings. We conducted a survey with the aim of evaluating the behaviors of Italian pediatricians at this regard. Methods: An open-ended questionnaire investigating the empiric therapy adopted in uncomplicatedAHOMchildren according to age was sent by email to 31 Italian pediatric clinics taking care of children with infectious diseases, and results were analyzed. Results: The preferred intravenous (IV) regimen was a penicillin plus an aminoglycoside (n = 10; 32.3%) in children aged <3 months, and a combination of a third-generation cephalosporin plus oxacillin (n = 7; 22.6%), or oxacillin alone (n = 6; 19.4%) in those 653 months. In every age class, amoxicillin-clavulanate was the first-choice oral antibiotic. Other antibiotics largely used orally included clindamycin, rifampicin, and trimethoprim/sulfamethoxazole. Flucloxacillin was never prescribed. Only 3 centers switched to oral therapy within 7 days in children 653 months of age. The most commonly reported reason influencing the time to switch to oral therapy concerned caregivers\u2019 adherence to oral therapy. Conclusion: Adherence to guidelines was poor, and early transition to oral therapy in the clinical practice was rarely adopted. Given the large use of potentially effective, but poorly studied, oral antibiotics such as amoxicillin/clavulanate, trimethoprim/sulfamethoxazole, and rifampicin, our data may stimulate further studies of this regard