CPT symmetry and antimatter gravity in general relativity

The gravitational behavior of antimatter is still unknown. While we may be confident that antimatter is self-attractive, the interaction between matter and antimatter might be either attractive or repulsive. We investigate this issue on theoretical grounds. Starting from the CPT invariance of physical laws, we transform matter into antimatter in the equations of both electrodynamics and gravitation. In the former case, the result is the well-known change of sign of the electric charge. In the latter, we find that the gravitational interaction between matter and antimatter is a mutual repulsion, i.e. antigravity appears as a prediction of general relativity when CPT is applied. This result supports cosmological models attempting to explain the Universe accelerated expansion in terms of a matter-antimatter repulsive interaction.Comment: 6 pages, to be published in EPL (http://epljournal.edpsciences.org/

Trasplante meniscal. Estudio experimental en corderos

El menisco es una unidad funcional que absorbe y distribuye las solicitaciones de la articulación de la rodilla. El trasplante de menis- co pretende la restitución anatómica, la recuperación de la mecánica articular y evitar la degeneración del cartílago articular, en pacientes jóvenes cuando se extirpa el menisco. Material y Métodos: Se han estudiado dos grupos, de ocho corderos cada uno, Grupo I: meniscectomía; Grupo II: meniscectomía y tras- plante de aloinjerto meniscal, se analizó la morfología del cartílago articular y del menisco trasplantado a los 6 meses de la intervención. Resultados: El grupo meniscectomizado presentó alteraciones radiológicas y macroscópicas de la superficie articular que no se vieron en el grupo trasplantado. En ambos grupos se encontraron cambios estructurales y celulares, más evidentes en los animales meniscectomizados. Los injertos mostraron una buena revascularización e infiltrado ce- lular desde la sinovial del menisco con importante desorganización fibrilar. Conclusión: El trasplante meniscal no protege completamente al car- tílago articular y el menisco, aunque presenta una adecuada integra- ción, no recupera su estructura.The meniscus is a functional structure which absorbs and distributes the knee stresses. The aim of meniscus allograft transplantation is anatomic restitution, the recuperation of the articular biomechanics and prevention of articular degeneration in young patients in whom meniscectomy is necessary. Material and Methods: We studied two groups, with 8 animals in each. Group I: meniscectomy; Group II: meniscectomy plus transplantation of fresh frozen meniscus allograft. We analyzed the morphology of the articular cartilage and the meniscus allograft six months after the operation. Results: The meniscectomized group showed radiographic and macroscopic alterations that were not observed in the transplanted group. In both meniscectomized and meniscus allograft group we found structural and cellular changes, but these were more evident in the meniscectomized group. The allografts showed adequate revascularization, with cellular repopulation of the allograft menisci by cells predominantly from the host synovium, and disordered fibers. Conclusion: Meniscus allograft transplantation does not protect the articular cartilage, and even where the meniscus is adequately integrated it does not recover its structure

Mechanical barriers and transforming growth factor beta inhibitor on epidural fibrosis in a rabbit laminectomy model

Background: TGF-β has been described as a mediator of fibrosis and scarring. Several studies achieved reduction in experimental scarring through the inhibition of TGF-β. Fibroblasts have been defined as the cell population originating fibrosis, blocking fibroblast invasion may impair epidural fibrosis appearance. For this purpose, biocompatible materials used as mechanical barriers and a TGF-β inhibitor peptide were evaluated in the reduction of epidural fibrosis. Methods: A L6 laminectomy was performed in 40 New Zealand white rabbits. Divided into four groups, each rabbit was assigned to receive either collagen sponge scaffold (CS group), gelatin-based gel (GCP group), P144® (iTGFβ group), or left untreated (control group). Four weeks after surgery, cell density, collagen content, and new bone formation of the scar area were determined by histomorphometry. Two experienced pathologists scored dura mater adhesion, scar density, and inflammatory infiltrate in a blinded manner. Results: In all groups, laminectomy site was filled with fibrous tissue and the dura mater presented adhesions. Only GCP group presented a significant reduction in collagen content and scar density. Conclusion: GCP treatment reduces epidural fibrosis although did not prevent dura mater adhesion completely

Compositional mapping by Z-contrast imaging

This research was sponsored by the Office of Basic Energy Sciences, Materials Sciences and Engineering Division, U.S. Department of Energy (SJP, MV), by the Spanish MCI (projects CONSOLIDER INGENIO 2010 CSD2009-00013 andTEC2008-06756-C03-02/TEC,) and the Junta de Andalucía (PAI research’s groups TEP-120 and TIC-145; project P08-TEP-03516).Peer Reviewe

Theoretical modelling of quaternary GaInAsSb/GaAs self-assembled quantum dots

Trabajo presentado al "Quantum Dot", celebrado en Nottingham (UK) del 26 al 30 de Abril de 2010.InAs/GaAs quantum dots exposed to Sb after growth exhibit spectral changes. We study in the present paper an idealized nanostructure consisting of a homogeneous distribution of the quaternary GaInAsSb surrounded by a barrier of GaAs. We nd that the valence band o set is a critical parameter in modelling its electronic structure. Depending on this value, we predict a transition from type-I to type-II band alignment at a di erent Sb concentration. The addition of Sb to reduce the transition energy while keeping a type-I alignment is only of bene t at low Sb concentrationThis work was supported by the Spanish MICINN (projects TEC2008-06756-C03-01/02/TEC, CONSOLIDER INGENIO 2010 CSD2006-0019 and CSD2009-00013), the Junta de Andalucía (PAI research groups TEP-120 and TIC-145; project P08-TEP-03516) and Comunidad Autónoma de Madrid S2009ESP-1503.Peer reviewe

Molecular and Cellular Mechanisms of Delayed Fracture Healing in Mmp10 (Stromelysin 2) Knockout Mice

The remodeling of the extracellular matrix is a central function in endochondral ossification and bone homeostasis. During secondary fracture healing, vascular invasion and bone growth requires the removal of the cartilage intermediate and the coordinate action of the collagenase matrix metalloproteinase (MMP)-13, produced by hypertrophic chondrocytes, and the gelatinase MMP-9, produced by cells of hematopoietic lineage. Interfering with these MMP activities results in impaired fracture healing characterized by cartilage accumulation and delayed vascularization. MMP-10, Stromelysin 2, a matrix metalloproteinase with high homology to MMP-3 (Stromelysin 1), presents a wide range of putative substrates identified in vitro, but its targets and functions in vivo and especially during fracture healing and bone homeostasis are not well defined. Here, we investigated the role of MMP-10 through bone regeneration in C57BL/6 mice. During secondary fracture healing, MMP-10 is expressed by hematopoietic cells and its maximum expression peak is associated with cartilage resorption at 14 days post fracture (dpf). In accordance with this expression pattern, when Mmp10 is globally silenced, we observed an impaired fracture-healing phenotype at 14 dpf, characterized by delayed cartilage resorption and TRAP-positive cell accumulation. This phenotype can be rescued by a non-competitive transplant of wild-type bone marrow, indicating that MMP-10 functions are required only in cells of hematopoietic linage. In addition, we found that this phenotype is a consequence of reduced gelatinase activity and the lack of proMMP-9 processing in macrophages. Our data provide evidence of the in vivo function of MMP-10 during endochondral ossification and defines the macrophages as the lead cell population in cartilage removal and vascular invasio

1.55 µm InAs/GaAs Quantum Dots and High Repetition Rate Quantum Dot SESAM Mode-locked Laser

High pulse repetition rate (≥10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.55 µm In(Ga)As QDs on GaAs substrates, their incorporation into a SESAM, and the realization of the first 10 GHz repetition rate QD-SESAM modelocked laser at 1.55 µm, exhibiting ∼2 ps pulse width from an Er-doped glass oscillator (ERGO). With a high areal dot density and strong light emission, this QD structure is a very promising candidate for many other applications, such as laser diodes, optical amplifiers, non-linear and photonic crystal based devices

Interfaz periprotésica en vástagos y cotilos, cementados y no cementados, de prótesis totales de cadera revisadas: II. Contenido de partículas metálicas

Se midieron la cantidad y tipo de las partículas metálicas obtenidas en 92 muetras de interfaces de cotilos y vástagos femorales durante los procedimientos de revisión de artroplastias no sépticas y su relación con la clínica y la radiología. En cada muestra se correlacionaron los datos clínicos y radiológicos de los pacientes con la cantidad de elementos metálicos medidos mediante digestión y espectrofotometría de absorción atómica. Las interfaces correspondían a 47 varones y 45 mujeres, con edades comprendidas entre 19 y 93 años (edad media 66 años). El tiempo medio de duración de las prótesis estudaiadas fue de diez años (rango: 1-28 años). Se estudiaron las membranas de 48 vástagos, 27 cementados y 21 no cementados, y 44 cotilos, 16 cementados y 28 no. Recogimos interfaces de 44 implantes de titanio, 33 de aleaciones de cromo-cobalto y 15 de polietileno que se utilizaron como control. Se apreció osteolisis en el 88% de los casos viendo mayor número de zonas de osteolisis cuando había grandes cantidades de níquel (p=0,003) en la membrana fibrosa. Las prótesis no cementadas presentaron mayor cantidad de cromo (p=0,014), titanio (p=0,000) y aluminio (p=0,003). El titanio guardó una relación altamente significativa con la duración de la prótesis (p=0,001) encontrando mayor cantidad de titanio en las prótesis retiradas en los diez primeros año