Dynamical Casimir effect with cylindrical waveguides

I consider the quantum electromagnetic field in a coaxial cylindrical waveguide, such that the outer cylindrical surface has a time-dependent radius. The field propagates parallel to the axis, inside the annular region between the two cylindrical surfaces. When the mechanical frequency and the thickness of the annular region are small enough, only Transverse Electromagnetic (TEM) photons may be generated by the dynamical Casimir effect. The photon emission rate is calculated in this regime, and compared with the case of parallel plates in the limit of very short distances between the two cylindrical surfaces. The proximity force approximation holds for the transition matrix elements in this limit, but the emission rate scales quadratically with the mechanical frequency, as opposed to the cubic dependence for parallel plates.Comment: 6 page

Quantum radiation in a plane cavity with moving mirrors

We consider the electromagnetic vacuum field inside a perfect plane cavity with moving mirrors, in the nonrelativistic approximation. We show that low frequency photons are generated in pairs that satisfy simple properties associated to the plane geometry. We calculate the photon generation rates for each polarization as functions of the mechanical frequency by two independent methods: on one hand from the analysis of the boundary conditions for moving mirrors and with the aid of Green functions; and on the other hand by an effective Hamiltonian approach. The angular and frequency spectra are discrete, and emission rates for each allowed angular direction are obtained. We discuss the dependence of the generation rates on the cavity length and show that the effect is enhanced for short cavity lengths. We also compute the dissipative force on the moving mirrors and show that it is related to the total radiated energy as predicted by energy conservation.Comment: 17 pages, 1 figure, published in Physical Review

Inertial forces in the Casimir effect with two moving plates

We combine linear response theory and dimensional regularization in order to derive the dynamical Casimir force in the low frequency regime. We consider two parallel plates moving along the normal direction in $D-$dimensional space. We assume the free-space values for the mass of each plate to be known, and obtain finite, separation-dependent mass corrections resulting from the combined effect of the two plates. The global mass correction is proportional to the static Casimir energy, in agreement with Einstein's law of equivalence between mass and energy for stressed rigid bodies.Comment: 9 pages, 1 figure; title and abstract changed; to appear in Physical Review

Ideally embedded space-times

Due to the growing interest in embeddings of space-time in higher-dimensional spaces we consider a specific type of embedding. After proving an inequality between intrinsically defined curvature invariants and the squared mean curvature, we extend the notion of ideal embeddings from Riemannian geometry to the indefinite case. Ideal embeddings are such that the embedded manifold receives the least amount of tension from the surrounding space. Then it is shown that the de Sitter spaces, a Robertson-Walker space-time and some anisotropic perfect fluid metrics can be ideally embedded in a five-dimensional pseudo-Euclidean space.Comment: layout changed and typos corrected; uses revtex

Dust Emission from Active Galactic Nuclei

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central source, giving rise to Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the observed IR is in broad agreement with this scheme, the behavior of the 10 micron silicate feature and the width of the far-IR emission peak remained serious problems in all previous modeling efforts. We show that these problems find a natural explanation if the dust is contained in about 5-10 clouds along radial rays through the torus. The spectral energy distributions (SED) of both type 1 and type 2 sources are properly reproduced from different viewpoints of the same object if the visual optical depth of each cloud is larger than about 60 and the clouds' mean free path increases roughly in proportion to radial distance.Comment: 11 pages, submitted to ApJ Letter

Lateral Casimir-Polder force with corrugated surfaces

We derive the lateral Casimir-Polder force on a ground state atom on top of a corrugated surface, up to first order in the corrugation amplitude. Our calculation is based on the scattering approach, which takes into account nonspecular reflections and polarization mixing for electromagnetic quantum fluctuations impinging on real materials. We compare our first order exact result with two commonly used approximation methods. We show that the proximity force approximation (large corrugation wavelengths) overestimates the lateral force, while the pairwise summation approach underestimates it due to the non-additivity of dispersion forces. We argue that a frequency shift measurement for the dipolar lateral oscillations of cold atoms could provide a striking demonstration of nontrivial geometrical effects on the quantum vacuum.Comment: 12 pages, 6 figures, contribution to QFEXT07 proceeding

Traumatologia renal nos HUC: experiência de treze anos

Os autores fazem uma revisão da casuística de traumatologia renal da sua instituição. Analisam-se 152 traumatismos renais ocorridos em 13 anos avaliando-se a classificação, mecanismo causal, etiologia, sintomatologia, estudo imagiológico, lesões associadas, tratamento, complicações e evolução

Expression Of Mcl-1 And Ki-67 In Papillary Thyroid Carcinomas

Studying molecules that are differentially expressed in cancers as well as benign and normal tissues is crucial for identifying novel bio-markers for cancer immunotherapy. This study aimed to investigate the clinical utility of the immunochemical expression of the proliferative cell marker Ki-67 and the apoptotic blocker Mcl-1 in papillary thyroid carcinoma (PTC). Methods: We built a tissue microarray with 282 thyroid specimens. There were 59 PTCs including 35 classic (CPTC), 3 tall cell (TCPTC) and 21 follicular variants (FVPTC); 79 benign thyroid diseases (22 follicular adenomas; 57 adenomatoid hyperplasia); 33 Hashimoto's thyroiditis (HT) specimens; and 111 normal thyroid tissues. Clinical history and ultrasound data were retrospectively obtained by chart review. Results: Mcl-1 overexpression was evident in 66.7% of the PTC tissues compared to 32% of the benign thyroid diseases. Mcl-1 strong staining distinguished benign from malignant thyroid lesions (sensitivity = 61.3%; specificity = 72.8%; negative predictive value, NPV = 68%; positive predictive value, PPV = 66.7% and 67.5% accuracy). Positive nuclear Ki-67 staining was observed in 34% of PTCs vs. 19% of thyroid adenomas (P = 0.031). Strong Mcl-1 and Ki-67 co-expression was identified in 57.5% of PTCs with a higher PPV (75.8%). Mcl-1 and Ki-67 expression was not associated with any clinicopathological feature of malignancy. No deaths occurred during the follow-up. Conclusions: Mcl-1 immunochemical overexpression allowed differentiating low-risk PTC from the benign thyroid lesions. We suggest that Mcl-1 expression may help differentiate follicular patterned thyroid lesions. The influence of the Mcl-1 expression on several features of tumor aggressiveness has to be studied in large series of high-risk thyroid carcinomas.124420921