26 research outputs found

    Automorphism Modular Invariants of Current Algebras

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    We consider those two-dimensional rational conformal field theories (RCFTs) whose chiral algebras, when maximally extended, are isomorphic to the current algebra formed from some affine non-twisted Kac--Moody algebra at fixed level. In this case the partition function is specified by an automorphism of the fusion ring and corresponding symmetry of the Kac--Peterson modular matrices. We classify all such partition functions when the underlying finite-dimensional Lie algebra is simple. This gives all possible spectra for this class of RCFTs. While accomplishing this, we also find the primary fields with second smallest quantum dimension.Comment: 32 pages, plain Te

    Quasi-Quantum Groups, Knots, Three-Manifolds, and Topological Field Theory

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    We show how to construct, starting from a quasi-Hopf algebra, or quasi-quantum group, invariants of knots and links. In some cases, these invariants give rise to invariants of the three-manifolds obtained by surgery along these links. This happens for a finite-dimensional quasi-quantum group, whose definition involves a finite group GG, and a 3-cocycle \om, which was first studied by Dijkgraaf, Pasquier and Roche. We treat this example in more detail, and argue that in this case the invariants agree with the partition function of the topological field theory of Dijkgraaf and Witten depending on the same data G, \,\om.Comment: 30 page

    Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices

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    The luminescence properties of highly strained, Sb-doped Ge/Si multi-layer heterostructures with incorporated Ge quantum dots (QDs) are studied. Calculations of the electronic band structure and luminescence measurements prove the existence of an electron miniband within the columns of the QDs. Miniband formation results in a conversion of the indirect to a quasi-direct excitons takes place. The optical transitions between electron states within the miniband and hole states within QDs are responsible for an intense luminescence in the 1.4–1.8 µm range, which is maintained up to room temperature. At 300 K, a light emitting diode based on such Ge/Si QD superlattices demonstrates an external quantum efficiency of 0.04% at a wavelength of 1.55 µm

    Frailty and sarcopenia within the earliest national Dutch childhood cancer survivor cohort (DCCSS-LATER): a cross-sectional study.

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    BACKGROUND: Childhood cancer survivors appear to be at increased risk of frailty and sarcopenia, but evidence on the occurrence of and high-risk groups for these aging phenotypes is scarce, especially in European survivors. The aim of this cross-sectional study was to assess the prevalence of and explore risk factors for pre-frailty, frailty, and sarcopenia in a national cohort of Dutch childhood cancer survivors diagnosed between 1963 and 2001. METHODS: Eligible individuals (alive at the time of study, living in the Netherlands, age 18-45 years, and had not previously declined to participate in a late-effects study) from the Dutch Childhood Cancer Survivor Study (DCCSS-LATER) cohort were invited to take part in this cross-sectional study. We defined pre-frailty and frailty according to modified Fried criteria, and sarcopenia according to the European Working Group on Sarcopenia in Older People 2 definition. Associations between these conditions and demographic and treatment-related as well as endocrine and lifestyle-related factors were estimated with two separate multivariable logistic regression models in survivors with any frailty measurement or complete sarcopenia measurements. FINDINGS: 3996 adult survivors of the DCCSS-LATER cohort were invited to participate in this cross-sectional study. 1993 non-participants were excluded due to lack of response or a decline to participate and 2003 (50·1%) childhood cancer survivors aged 18-45 years were included. 1114 (55·6%) participants had complete frailty measurements and 1472 (73·5%) participants had complete sarcopenia measurements. Mean age at participation was 33·1 years (SD  7·2). 1037 (51·8%) participants were male, 966 (48·2%) were female, and none were transgender. In survivors with complete frailty measurements or complete sarcopenia measurements, the percentage of pre-frailty was 20·3% (95% CI 18·0-22·7), frailty was 7·4% (6·0-9·0), and sarcopenia was 4·4% (3·5-5·6). In the models for pre-frailty, underweight (odds ratio [OR] 3·38 [95% CI 1·92-5·95]) and obesity (OR 1·67 [1·14-2·43]), cranial irradiation (OR 2·07 [1·47-2·93]), total body irradiation (OR 3·17 [1·77-5·70]), cisplatin dose of at least 600 mg/m(2) (OR 3·75 [1·82-7·74]), growth hormone deficiency (OR 2·25 [1·23-4·09]), hyperthyroidism (OR 3·72 [1·63-8·47]), bone mineral density (Z score ≤-1 and >-2, OR 1·80 [95% CI 1·31-2·47]; Z score ≤-2, OR 3·37 [2·20-5·15]), and folic acid deficiency (OR 1·87 [1·31-2·68]) were considered significant. For frailty, associated factors included age at diagnosis between 10-18 years (OR 1·94 [95% CI 1·19-3·16]), underweight (OR 3·09 [1·42-6·69]), cranial irradiation (OR 2·65 [1·59-4·34]), total body irradiation (OR 3·28 [1·48-7·28]), cisplatin dose of at least 600 mg/m(2) (OR 3·93 [1·45-10·67]), higher carboplatin doses (per g/m(2); OR 1·15 [1·02-1·31]), cyclophosphamide equivalent dose of at least 20 g/m(2) (OR 3·90 [1·65-9·24]), hyperthyroidism (OR 2·87 [1·06-7·76]), bone mineral density Z score ≤-2 (OR 2·85 [1·54-5·29]), and folic acid deficiency (OR 2·04 [1·20-3·46]). Male sex (OR 4·56 [95%CI 2·26-9·17]), lower BMI (continuous, OR 0·52 [0·45-0·60]), cranial irradiation (OR 3·87 [1·80-8·31]), total body irradiation (OR 4·52 [1·67-12·20]), hypogonadism (OR 3·96 [1·40-11·18]), growth hormone deficiency (OR 4·66 [1·44-15·15]), and vitamin B12 deficiency (OR 6·26 [2·17-1·81]) were significantly associated with sarcopenia. INTERPRETATION: Our findings show that frailty and sarcopenia occur already at a mean age of 33 years in childhood cancer survivors. Early recognition and interventions for endocrine disorders and dietary deficiencies could be important in minimising the risk of pre-frailty, frailty, and sarcopenia in this population. FUNDING: Children Cancer-free Foundation, KiKaRoW, Dutch Cancer Society, ODAS Foundation
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