832 research outputs found
On the photon Green functions in curved space-time
Quantization of electrodynamics in curved space-time in the Lorenz gauge and
with arbitrary gauge parameter makes it necessary to study Green functions of
non-minimal operators with variable coefficients. Starting from the integral
representation of photon Green functions, we link them to the evaluation of
integrals involving Gamma functions. Eventually, the full asymptotic expansion
of the Feynman photon Green function at small values of the world function, as
well as its explicit dependence on the gauge parameter, are obtained without
adding by hand a mass term to the Faddeev--Popov Lagrangian. Coincidence limits
of second covariant derivatives of the associated Hadamard function are also
evaluated, as a first step towards the energy-momentum tensor in the
non-minimal case.Comment: 22 pages, plain Tex. All sections and appendices have been improve
Towards weighing the condensation energy to ascertain the Archimedes force of vacuum
The force exerted by the gravitational field on a Casimir cavity in terms of
Archimedes force of vacuum is discussed, the force that can be tested against
observation is identified, and it is shown that the present technology makes it
possible to perform the first experimental tests. The use of suitable high-Tc
superconductors as modulators of Archimedes force is motivated. The possibility
is analyzed of using gravitational wave interferometers as detectors of the
force, transported through an optical spring from the Archimedes vacuum force
apparatus to the gravitational interferometer test masses to maintain the two
systems well separated. The use of balances to actuate and detect the force is
also analyzed, the different solutions are compared, and the most important
experimental issues are discussed.Comment: Revtex, 33 pages, 8 figures. In the final version, the title has been
changed, and all sections have been improved, while 2 appendices have been
adde
The stratigraphic and structural setting of metamorphic continental units from Alpine Corsica: clues from the area between Asco and Golo valleys (Central Corsica, France)
Mitogen-activated kinase kinase kinase 1 inhibits hedgehog signaling and medulloblastoma growth through GLI1 phosphorylation
The aberrant activation of hedgehog (HH) signaling is a leading cause of the development of medulloblastoma, a pediatric tumor of the cerebellum. The FDA‑approved HH inhibitor, Vismodegib, which targets the transmembrane transducer SMO, has shown limited efficacy in patients with medulloblastoma, due to compensatory mechanisms that maintain an active HH‑GLI signaling status. Thus, the identification of novel actionable mechanisms, directly affecting the activity of the HH‑regulated GLI transcription factors is an important goal for these malignancies. In this study, using gene expression and reporter assays, combined with biochemical and cellular analyses, we demonstrate that mitogen‑activated kinase kinase kinase 1 (MEKK1), the most upstream kinase of the mitogen‑activated protein kinase (MAPK) phosphorylation modules, suppresses HH signaling by associating and phosphorylating GLI1, the most potent HH‑regulated transcription factor. Phosphorylation occurred at multiple residues in the C‑terminal region of GLI1 and was followed by an increased association with the cytoplasmic proteins 14‑3‑3. Of note, the enforced expression of MEKK1 or the exposure of medulloblastoma cells to the MEKK1 activator, Nocodazole, resulted in a marked inhibitory effect on GLI1 activity and tumor cell proliferation and viability. Taken together, the results of this study shed light on a novel regulatory mechanism of HH signaling, with potentially relevant implications in cancer therapy
Type III pleuropulmonary blastoma in a 7-month-old female baby with impending respiratory failure: a case report
INTRODUCTION: Pleuropulmonary blastoma is a very rare, aggressive, embryonal pulmonary neoplasm which mostly affects children under the age of 5. According to the histopathological features, three subtypes of pleuropulmonary blastoma have been recognized: type I (purely cystic), type II (grossly visible cystic and solid elements) and type III (purely solid). Characteristics of type I and type II blastoma allow an earlier diagnosis compared with type III. Here we present a case report of an unusual presentation of type III pleuropulmonary blastoma. CASE PRESENTATION: We describe the case of a 7-month-old female baby of Italian mother and Kurdish father who was diagnosed with type III pleuropulmonary blastoma, which entirely occupied her right hemithorax. CONCLUSIONS: The reported case is an unusual presentation because type III pleuropulmonary blastoma typically occurs in older children. The complete re-expansion of her residual, previously totally compressed, right lung observed immediately after the resection of the lesion suggests an atypical rapid growth of this embryonal tumor in the late phase of gestation or after delivery. This case report suggests that, in addition to other childhood tumors, type III pleuropulmonary blastoma should be included in the differential diagnosis of solid nonhomogeneous thoracic large masses, compressing the mediastinal and chest wall structures in infants. This is an original case report of interest for several specialities such us pediatrics, radiology, surgery and oncology
Significance of persistence of antibodies against Leishmania infantum in sicilian patients affected by acute visceral leishmaniasis.
New Insight into Immunity and Immunopathology of Rickettsial Diseases
Human rickettsial diseases comprise a variety of clinical entities caused by microorganisms belonging to the genera Rickettsia, Orientia, Ehrlichia, and Anaplasma. These microorganisms are characterized by a strictly intracellular location which has, for long, impaired their detailed study. In this paper, the critical steps taken by these microorganisms to play their pathogenic roles are discussed in detail on the basis of recent advances in our understanding of molecular Rickettsia-host interactions, preferential target cells, virulence mechanisms, three-dimensional structures of bacteria effector proteins, upstream signalling pathways and signal transduction systems, and modulation of gene expression. The roles of innate and adaptive immune responses are discussed, and potential new targets for therapies to block host-pathogen interactions and pathogen virulence mechanisms are considered
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