442 research outputs found
Three Applications of the String-Inspired Technique to Quantum Electrodynamics
We discuss the following recent applications of the ``string-inspired''
worldline technique to calculations in quantum electrodynamics: i) Photon
splitting in a constant magnetic field, ii) The two-loop Euler-Heisenberg
Lagrangian, iii) A progress report on a recalculation of the three-loop QED
beta -- function.Comment: 10 pages, uuencoded Postscript-File, talk given by C. Schubert at the
Zeuthen Workshop on Elementary Particle Theory: QCD and QED in Higher Orders,
Rheinsberg, Germany, 21-26 Apr 199
Reduced Serum Levels of Bone Formation Marker P1NP in Psoriasis
Psoriasis is a chronic inflammatory disease of the skin and joints. More recent data
emphasize an association with dysregulated glucose and fatty acid metabolism, obesity,
elevated blood pressure and cardiac disease, summarized as metabolic syndrome.
TNF-a and IL-17, central players in the pathogenesis of psoriasis, are known to
impair bone formation. Therefore, the relation between psoriasis and bone metabolism
parameters was investigated. Two serum markers of either bone formation—N-terminal
propeptide of type I procollagen (P1NP) or bone resorption—C-terminal telopeptide
of type I collagen (CTX-I)—were analyzed in a cohort of patients with psoriasis
vulgaris. In patients with psoriasis, P1NP serum levels were reduced compared to
gender-, age-, and body mass index-matched healthy controls. CTX-I levels were
indistinguishable between patients with psoriasis and controls. Consistently, induction
of psoriasis-like skin inflammation in mice decreases bone volume and activity of
osteoblasts. Moreover, efficient anti-psoriatic treatment improved psoriasis severity, but
did not reverse decreased P1NP level suggesting that independent of efficient skin
treatment psoriasis did affect bone metabolism and might favor the development of
osteoporosis. Taken together, evidence is provided that bone metabolism might be
affected by psoriatic inflammation, which may have consequences for future patient
counseling and disease monitoring
Measuring Charge Transport in an Amorphous Semiconductor Using Charge Sensing
We measure charge transport in hydrogenated amorphous silicon (a-Si:H) using
a nanometer scale silicon MOSFET as a charge sensor. This charge detection
technique makes possible the measurement of extremely large resistances. At
high temperatures, where the a-Si:H resistance is not too large, the charge
detection measurement agrees with a direct measurement of current. The device
geometry allows us to probe both the field effect and dispersive transport in
the a-Si:H using charge sensing and to extract the density of states near the
Fermi energy.Comment: 4 pages, 4 figure
Bistability in the Tunnelling Current through a Ring of Coupled Quantum Dots
We study bistability in the electron transport through a ring of N coupled
quantum dots with two orbitals in each dot. One orbital is localized (called b
orbital) and coupling of the b orbitals in any two dots is negligible; the
other is delocalized in the plane of the ring (called d orbital), due to
coupling of the d orbitals in the neighboring dots, as described by a
tight-binding model. The d orbitals thereby form a band with finite width. The
b and d orbitals are connected to the source and drain electrodes with a
voltage bias V, allowing the electron tunnelling. Tunnelling current is
calculated by using a nonequilibrium Green function method recently developed
to treat nanostructures with multiple energy levels. We find a bistable effect
in the tunnelling current as a function of bias V, when the size N>50; this
effect scales with the size N and becomes sizable at N~100. The temperature
effect on bistability is also discussed. In comparison, mean-field treatment
tends to overestimate the bistable effect.Comment: Published in JPSJ; minor typos correcte
Calcifying fibrous tumor and inflammatory myofibroblastic tumor are epigenetically related: A comparative genome-wide methylation study
Item does not contain fulltextBased on histological findings, calcifying fibrous tumor (CFT) may be a late (burned out) stage of inflammatory myofibroblastic tumor (IMT). This concept, however, has not been proven by molecular means. Five CFTs were analyzed for IMT-related rearrangements in ALK, ROS1 and RET using fluorescence in situ hybridization (FISH). Additionally, genome-wide methylation patterns were investigated and compared with IMT (n=7), leiomyoma (n=7), angioleiomyoma (n=9), myopericytoma (n=7) and reactive soft tissue lesions (n=10) using unsupervised hierarchical cluster analysis and t distributed stochastic neighbor embedding. CFT patients, 4 females and 1 male, had a median age of 20years ranging from 7 to 43years. Two patients were younger than 18years old. The tumors originated in the abdomen (n=4) and axilla (n=1). Histologically, all lesions were (multi) nodular and hypocellular consisting of bland looking (myo)fibroblasts embedded in a collagenous matrix with calcifications. FISH analysis brought up negative results for ALK, RET and ROS1 rearrangements. However, genome-wide methylation analysis revealed overlapping methylation patterns of CFT and IMT forming a distinct homogeneous methylation cluster with exception of one case clustering with myopericytoma/angioleiomyoma. In conclusion, DNA methylation profiling supports the concept that CFT and IMT represent both ends of a spectrum of one entity with CFT being the burn out stage of IMT
Surgical treatment of a giant tibial high-grade mixofibrosarcoma with preservation of limb function: a case report
Myxofibrosarcoma is one of the most common sarcomas in elderly patients showing a slight male prevalence. The tumor is mainly located in lower and upper extremities and rarely in trunk, neck and feet. We present a case of a 84-year-old man referred to our tumour center with a giant and neglected high-grade tibial myxofibrosarcoma in the anteromedial side of tibial mid-diaphysis. Large size lesions in association with older age may jeopardise the maintenance of limb vitality, vascularity and stability
Fibrous Hamartoma of Infancy: A Series of 21 Cases and Review of the Literature
IntroducciĂłn: El hamartoma fibroso de la infancia (HFI) es tumor poco frecuente de tejidos blandos en lactantes y niños, caracterizado histopatĂłlogicamente por su morfologĂa trifásica y curso benigno. MĂ©todos: Presentamos las caracterĂsticas histopatolĂłgicas e inmunohistoquĂmicas de una serie de 21 casos de HFI y revisamos sus principales diagnĂłsticos diferenciales. Resultados: Las lesiones predominaron en varones con una edad media de 3,7 años (5 meses24 años) en localizaciones previamente descritas. HistopatolĂłgicamente, se caracterizaron por
proporciones variables de tejido fibroblástico, mesenquimal y adiposo maduro. Tres casos (21%) mostraron zonas hialinizadas con artefactos en grietas, que imitaban al fibroblastoma de células gigantes. Presentaron tinción positiva para actina de músculo liso 8/13 (61%) en el componente fibroblástico, CD34 en 6/8 (75%) en el mesenquimal inmaduro y fibroblástico; y S100 en el tejido adiposo en 7/7 (100%).
ConclusiĂłn: Nuestros hallazgos histopatolĂłgicos son superponibles a los descritos en series amplias. No obstante, la heterogeneidad clĂnica obliga a conocer las variantes de esta entidad dentro de su tĂpica histomorfologĂa trifásica, para lograr un correcto diagnĂłstico y manejo terapĂ©utico.Background: Fibrous hamartoma of infancy (FHI) is a rare soft-tissue tumor usually seen in infants and young children. Histologically, the tumor is characterized by a triphasic morphology, and the clinical course is benign. Methods: We described the histopathologic and immunohistochemical features in a series of 21 cases of FHI and reviewed the main entities to consider in differential diagnosis. Results: Most patients in the series were male. The mean age was 3.7 years (range, 5 months---24 years), and lesions were found in locations that have been previously reported. Histopathologically, the tumors were composed of variable proportions of fibroblastic, mesenchymal, and mature adipose tissue. Three of the 13 immunohistochemically stained biopsies (14%) contained hyalinized zones with cracking artifacts, mimicking giant cell fibroblastoma. Eight of the 13 stained with smooth-muscle actin (61%) were positive in the fibroblastic component, 6 of the 8 stained with CD34 (75%) were positive in the immature mesenchymal and fibroblastic components, and all 7 stained with S100 were positive (100%) in adipose tissue. Conclusions: Our histopathologic findings are consistent with those described in larger series. However, in order to reach a precise diagnosis and plan treatment, clinical heterogeneity obliges us to become familiar with variations in the characteristic triphasic histology of FHI
Magnetic Photon Splitting: the S-Matrix Formulation in the Landau Representation
Calculations of reaction rates for the third-order QED process of photon
splitting in strong magnetic fields traditionally have employed either the
effective Lagrangian method or variants of Schwinger's proper-time technique.
Recently, Mentzel, Berg and Wunner (1994) presented an alternative derivation
via an S-matrix formulation in the Landau representation. Advantages of such a
formulation include the ability to compute rates near pair resonances above
pair threshold. This paper presents new developments of the Landau
representation formalism as applied to photon splitting, providing significant
advances beyond the work of Mentzel et al. by summing over the spin quantum
numbers of the electron propagators, and analytically integrating over the
component of momentum of the intermediate states that is parallel to field. The
ensuing tractable expressions for the scattering amplitudes are satisfyingly
compact, and of an appearance familiar to S-matrix theory applications. Such
developments can facilitate numerical computations of splitting considerably
both below and above pair threshold. Specializations to two regimes of interest
are obtained, namely the limit of highly supercritical fields and the domain
where photon energies are far inferior to that for the threshold of
single-photon pair creation. In particular, for the first time the
low-frequency amplitudes are simply expressed in terms of the Gamma function,
its integral and its derivatives. In addition, the equivalence of the
asymptotic forms in these two domains to extant results from effective
Lagrangian/proper-time formulations is demonstrated.Comment: 19 pages, 3 figures, REVTeX; accepted for publication in Phys. Rev.
An alternative pathway for production of acetonitrile: ruthenium catalysed aerobic dehydrogenation of ethylamine
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