1,349 research outputs found
Spin-stiffness of anisotropic Heisenberg model on square lattice and possible mechanism for pinning of the electronic liquid crystal direction in YBCO
Using series expansions and spin-wave theory we calculate the spin-stiffness
anisotropy in Heisenberg models on the square lattice
with anisotropic couplings . We find that for the weakly anisotropic
spin-half model (), deviates
substantially from the naive estimate . We
argue that this deviation can be responsible for pinning the electronic liquid
crystal direction, a novel effect recently discovered in YBCO. For
completeness, we also study the spin-stiffness for arbitrary anisotropy
for spin-half and spin-one models. In the limit of ,
when the model reduces to weakly coupled chains, the two show dramatically
different behavior. In the spin-one model, the stiffness along the chains goes
to zero, implying the onset of Haldane-gap phase, whereas for spin-half the
stiffness along the chains increases monotonically from a value of
for towards for . Spin-wave theory is
extremely accurate for spin-one but breaks down for spin-half presumably due to
the onset of topological terms.Comment: 6 pages, 3 figure
Perfectionism or Perfectionisms in Orthorexia Nervosa
Purpose: Perfectionism is considered a transdiagnostic construct that characterises eating disorders (EDs) and obsessive-compulsive disorder (OCD) and that could also depict orthorexia nervosa (ON). The principal aim of this study was to investigate what dimensions of perfectionism mostly represent ON. Moreover, it was evaluated if dieting impacted the presence of orthorexic features and perfectionistic behaviour. Methods: The sample consisted of two groups-the "Diet" (n = 93), and the "No Diet" (n = 94) groups-composed of people with high and low orthorexic tendencies, respectively. Participants filled out self-report questionnaires to investigate orthorexic tendencies and different facets of perfectionism. Results: Analyses highlighted that people with high orthorexic tendencies showed higher perfectionistic features and that ON had a significant relationship with different facets of perfectionism. No interactions with diet were found. Therefore, no other differences were highlighted when the group type (Diet/No Diet) was considered. Conclusions: Regardless of diet, different facets of perfectionism characterise ON: perfectionism as a personality trait and perfectionism related to EDs and to obsessive-compulsive features. Our results evidenced that perfectionism could also be considered a useful construct in the conceptualization of orthorexia nervosa
I-surfaces with one T-singularity
We classify normal stable surfaces with KX2=1, pg= 2 and q= 0 with a unique singular point which is a non-canonical T-singularity, thus exhibiting two divisors in the main component and a new irreducible component of the moduli space of stable surfaces M¯ 1 , 3
Chen-Ruan cohomology of ADE singularities
We study Ruan's \textit{cohomological crepant resolution conjecture} for
orbifolds with transversal ADE singularities. In the -case we compute both
the Chen-Ruan cohomology ring and the quantum corrected
cohomology ring . The former is achieved in general, the
later up to some additional, technical assumptions. We construct an explicit
isomorphism between and in the -case,
verifying Ruan's conjecture. In the -case, the family
is not defined for . This implies that
the conjecture should be slightly modified. We propose a new conjecture in the
-case which we prove in the -case by constructing an explicit
isomorphism.Comment: This is a short version of my Ph.D. Thesis math.AG/0510528. Version
2: chapters 2,3,4 and 5 has been rewritten using the language of groupoids; a
link with the classical McKay correpondence is given. International Journal
of Mathematics (to appear
Use of Annual Self-Reseeding Legumes in an Oak Forest in Central Italy
A trial has been carried out for three years in an oak coppice geometrically thinned out of Mediterranean Central Italy, about the functioning of a pastoral system made by four different resources: native pasture, subterranean clover (Trifolium brachycalycinum Katzn. et Morley) in pure stand, strips thinned out and firebreaks improved with oversown subclover, all grazed by sheep. Subclover increased the forage yield and improved the palatabilty of the pasture and the regularity of grazing; the higher biomass intake by animals reduced the quantity of dried biomass in summer and contributed to keep low either fire hazards or flame diffusion speed. Data underlined the importance of deferred grazing and of the combination of different native or improved resources on the seasonal distribution of production and animal intake
Magnetic order in coupled spin-half and spin-one Heisenberg chains in anisotropic triangular-lattice geometry
We study spin-half and spin-one Heisenberg models in the limit where one
dimensional (1-D) linear chains, with exchange constant J1, are weakly coupled
in an anisotropic triangular lattice geometry. Results are obtained by means of
linked-cluster series expansions at zero temperature around different
magnetically ordered phases. We study the non-colinear spiral phases that arise
classically in the model and the colinear antiferromagnet that has been
recently proposed for the spin-half model by Starykh and Balents using a
Renormalization Group approach. We find that such phases can be stabilized in
the spin-half model for arbitrarily small coupling between the chains. For
vanishing coupling between the chains the energy of each phase must approach
that of decoupled linear chains. With increasing inter-chain coupling, the
non-colinear phase appears to have a lower energy in our calculations. For the
spin-one chain, we find that there is a critical interchain coupling needed to
overcome the Haldane gap. When spin-one chains are coupled in an unfrustrated
manner, the critical coupling is very small (~0.01J1) and agrees well with
previous chain mean-field studies. When they are coupled in the frustrated
triangular-lattice geometry, the critical coupling required to develop magnetic
order is substantially larger (> 0.3J1). The colinear phase is not obtained for
the spin-one Heisenberg model.Comment: 7 pages, 8 figure
Characteristics of drug-resistant tuberculosis in Abkhazia (Georgia), a high-prevalence area in Eastern Europe
Although multidrug-resistant (MDR) tuberculosis (TB) is a major public health problem in Eastern Europe, the factors contributing to emergence, spread and containment of MDR-TB are not well defined. Here, we analysed the characteristics of drug-resistant TB in a cross-sectional study in Abkhazia (Georgia) between 2003 and 2005, where standard short-course chemotherapy is supplemented with individualized drug-resistance therapy. Drug susceptibility testing (DST) and molecular typing were carried out for Mycobacterium tuberculosis complex strains from consecutive smear-positive TB patients. Out of 366 patients, 60.4% were resistant to any first-line drugs and 21% had MDR-TB. Overall, 25% of all strains belong to the Beijing genotype, which was found to be strongly associated with the risk of MDR-TB (OR 25.9, 95% CI 10.2-66.0) and transmission (OR 2.8, 95% CI 1.6-5.0). One dominant MDR Beijing clone represents 23% of all MDR-TB cases. The level of MDR-TB did not decline during the study period, coinciding with increasing levels of MDR Beijing strains among previously treated cases. Standard chemotherapy plus individualized drug-resistance therapy, guided by conventional DST, might be not sufficient to control MDR-TB in Eastern Europe in light of the spread of "highly transmissible" MDR Beijing strains circulating in the community
Treatment of tuberculosis in a region with high drug resistance: Outcomes, drug resistance amplification and re-infection
Introduction: Emerging antituberculosis drug resistance is a serious threat for tuberculosis (TB) control, especially in Eastern
European countries.
Methods: We combined drug susceptibility results and molecular strain typing data with treatment outcome reports to
assess the influence of drug resistance on TB treatment outcomes in a prospective cohort of patients from Abkhazia
(Georgia). Patients received individualized treatment regimens based on drug susceptibility testing (DST) results. Definitions
for antituberculosis drug resistance and treatment outcomes were in line with current WHO recommendations. First and
second line DST, and molecular typing were performed in a supranational laboratory for Mycobacterium tuberculosis (MTB)
strains from consecutive sputum smear-positive TB patients at baseline and during treatment.
Results: At baseline, MTB strains were fully drug-susceptible in 189/326 (58.0%) of patients. Resistance to at least H or R
(PDR-TB) and multidrug-resistance (MDR-TB) were found in 69/326 (21.2%) and 68/326 (20.9%) of strains, respectively. Three
MDR-TB strains were also extensively resistant (XDR-TB). During treatment, 3/189 (1.6%) fully susceptible patients at baseline
were re-infected with a MDR-TB strain and 2/58 (3.4%) PDR-TB patients became MDR-TB due to resistance amplification. 5/
47 (10.6%) MDR- patients became XDR-TB during treatment. Treatment success was observed in 161/189 (85.2%), 54/69
(78.3%) and 22/68 (32.3%) of patients with fully drug susceptible, PDR- and MDR-TB, respectively. Development of ofloxacin
resistance was significantly associated with a negative treatment outcome.
Conclusion: In Abkhazia, a region with high prevalence of drug resistant TB, the use of individualized MDR-TB treatment
regimens resulted in poor treatment outcomes and XDR-TB amplification. Nosocomial transmission of MDR-TB emphasizes
the importance of infection control in hospitals
Treatment of tumours with the combination of WR-2721 and cis-dichlorodiammineplatinum (II) or cyclophosphamide.
The ability of WR-2721 [S-2(3-aminopropylamino)ethyl-phosporothioic acid] to selectively protect the host against the toxic effects of multiple doses of cis-dichlorodiammineplatinum [cis-Pt] or cyclophosphamide [CY] has been studied in mice and rats bearing 3 different tumours. Selective protection against cis-Pt induced nephrotoxicity has been demonstrated under all conditions studied, with the extent of protection being inversely related to the size of the cis-Pt dose. For example, pre-treatment with 200 mg/kg of WR-2721 30 min before each weekly dose of 2 mg/kg of cis-Pt allows the administration of this cytotoxic agent for 3 times longer before nephrotoxic injury. In none of these studies was there tumour protection. The same pattern was observed with CY, but quantitation of the extent of marrow protection was not possible for the multiple treatment studies, due to the longer latent period between induced and observed death with this drug. We conclude, therefore, that for both of these drugs, selective protection of the kidney and marrow is not only maintained under conditions of multiple treatment, but actually enhanced due to the need for smaller doses of cytotoxic agents in these protocols
- …