Multimode Hong-Ou-Mandel Interferometry

We review some recent experiments based upon multimode two-photon interference of photon pairs created by spontaneous parametric down-conversion. The new element provided by these experiments is the inclusion of the transverse spatial profiles of the pump, signal and idler fields. We discuss multimode Hong-Ou-Mandel interference, and show that the transverse profile of the pump beam can be manipulated in order to control two-photon interference. We present the basic theory and experimental results as well as several applications to the field of quantum information.Comment: 20 pages, 14 figures, Brief Review to be published in Modern Physics Letters

Quantum field theory approach to the optical conductivity of strained and deformed graphene

The computation of the optical conductivity of strained and deformed graphene is discussed within the framework of quantum field theory in curved spaces. The analytical solutions of the Dirac equation in an arbitrary static background geometry for one dimensional periodic deformations are computed, together with the corresponding Dirac propagator. Analytical expressions are given for the optical conductivity of strained and deformed graphene associated with both intra and interbrand transitions. The special case of small deformations is discussed and the result compared to the prediction of the tight-binding model.The authors acknowledge financial supportfrom the Brazilian agencies FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico)

Long-term concentration of tropical forest nutrient hotspots is generated by a central-place apex predator

Apex predators typically affect the distribution of key soil and vegetation nutrients through the heterogeneous deposition of prey carcasses and excreta, leading to a nutrient concentration in a hotspot. The exact role of central-place foragers, such as tropical raptors, in nutrient deposition and cycling, is not yet known. We investigated whether harpy eagles (Harpia harpyja) in Amazonian Forests—a typically low soil fertility ecosystem—affect soil nutrient profiles and the phytochemistry around their nest-trees through cumulative deposition of prey carcasses and excreta. Nest-trees occurred at densities of 1.5–5.0/100 km2, and each nest received ~ 102.3 kg of undressed carcasses each year. Effects of nests were surprisingly negative over local soil nutrient profiles, with soils underneath nest-trees showing reductions in nutrients compared with controls. Conversely, canopy tree leaves around nests showed significant 99%, 154% and 50% increases in nitrogen, phosphorus and potassium, respectively. Harpy eagles have experienced a 41% decline in their range, and many raptor species are becoming locally extirpated. These are general examples of disruption in biogeochemical cycles and nutrient heterogeneity caused by population declines in a central-place apex predator. This form of carrion deposition is by no means an exception since several large raptors have similar habits

Comparative assessment of skin reactivity to thimerosal- or phenol-preserved Imunoleish® antigen in dogs with suspected American Tegumentary Leishmaniasis in an endemic area of the state of Rio de Janeiro, Brazil

The leishmanin skin test (LST), which is an in vivo test that assesses the cellular immune responses to Leishmania-derived antigens, is an important tool in the laboratory diagnosis of American tegumentary leishmaniasis (ATL). This study aimed to compare the results obtained in LST employing the Imunoleish® antigen preserved with thimerosal (AgT) or phenol (AgP) and serological techniques to detect a possible infection caused by Leishmania (Viannia) braziliensis in dogs. The study included 172 dogs from an area endemic for ATL in the municipality of Paracambi, state of Rio de Janeiro, Brazil. The results obtained with Imunoleish® antigen preserved with thimerosal (AgT) or phenol (AgP) and serological tests were compared. Each dog received, intradermally, 0.1 mL of each antigen on the inner side of the right (AgT) and left (AgP) thighs. Five (2.7%) dogs presented ATL lesions. Of these, two were reactive to both formulations and three were reactive only to AgT. Among the 172 dogs, 68 (39.5%) were reactive only to AgT, 16 (9.3%)  only to AgP, and 11 (6.4%) to both formulations. Twenty-one (12.2%) sera samples were reactive by immunofluorescent antibody test (IFAT) and 21 enzyme-linked immunosorbent assay (ELISA). However, in only two dogs out of the five which Leishmania was isolated from, serological tests were positive. The LST and serological tests could be a useful tool in the diagnosis of L. (V.) braziliensis infection in dogs. Standardization of the techniques and reagents used could allow comparative studies on sensitivity, specificity, and positive and negative predictive values in dogs from different regions.Keywords: American Tegumentary Leishmaniasis, Leishmanin skin test, Diagnosis, Dogs, Host

Quantum systems in weak gravitational fields

Fully covariant wave equations predict the existence of a class of inertial-gravitational effects that can be tested experimentally. In these equations inertia and gravity appear as external classical fields, but, by conforming to general relativity, provide very valuable information on how Einstein's views carry through in the world of the quantum.Comment: 22 pages. To be published in Proceedings of the 17th Course of the International School of Cosmology and Gravitation "Advances in the interplay between quantum and gravity physics" edited by V. De Sabbata and A. Zheltukhin, Kluwer Academic Publishers, Dordrech

Spin, gravity, and inertia

The gravitational effects in the relativistic quantum mechanics are investigated. The exact Foldy-Wouthuysen transformation is constructed for the Dirac particle coupled to the static spacetime metric. As a direct application, we analyze the non-relativistic limit of the theory. The new term describing the specific spin (gravitational moment) interaction effect is recovered in the Hamiltonian. The comparison of the true gravitational coupling with the purely inertial case demonstrates that the spin relativistic effects do not violate the equivalence principle for the Dirac fermions.Comment: Revtex, 12 pages, no figures, accepted in Phys. Rev. Let

Use of DNA technology in forensic dentistry

The established importance of Forensic Dentistry for human identification, mainly when there is little remaining material to perform such identification (e.g., in fires, explosions, decomposing bodies or skeletonized bodies), has led dentists working with forensic investigation to become more familiar with the new molecular biology techniques. The currently available DNA tests have high reliability and are accepted as legal proofs in courts. This article presents a literature review referring to the main studies on Forensic Dentistry that involve the use of DNA for human identification, and makes an overview of the evolution of this technology in the last years, highlighting the importance of molecular biology in forensic sciences