Granuloma reparativo de células gigantes en el escafoides tarsiano: a propósito de 1 caso

Se presenta el caso de una mujer de 22 años con dolor en la región medialarsiana del pie izquierdo de 1 año de evolución sin antecedente traumático. La paciente presentaba una tumoración dolorosa en la cara medial de escafoides. La movilidad del tobillo era completa. La radiología mostraba una lesión radiolucente insuflante en el escafoides. En la TAC se apreciaba una ruptura de la cortical y la ausencia de afectación de partes blandas. La captación con 99Tc mostraba una alta concentración de radioisótopo en la lesión. El tratamiento quirúrgico incluyó curetaje e injerto óseo. La microscopía de la muestra quirúrgica ofreció el diagnóstico de granuloma reparativo de células gigantes. Se discute el diagnóstico diferencial de esta lesión.A 22-year-old women with pain in her left midle foot since one year before the first visit to the hospital, without any previous trauma is presented. At physical examination there was a tender point and tumor at the medial aspect of the foot, over the navicular bone. Complete range of motion was present. Plain X-rays showed a radiolucent lesion in the navicular. Computed tomography showed cortical bone disruption and no soft tissue involvement. The tecnetium-99 bone scan disclosed a high concentration of radioisotope at the lesion. Surgical treatment included curetagge and bone grafting. Microscopic assesment of the resected tissue was compatible with giant cell reparative granuloma. The differential diagnosis is discussed

Coherent transport in graphene nanoconstrictions

We study the effect of a structural nanoconstriction on the coherent transport properties of otherwise ideal zig-zag-edged infinitely long graphene ribbons. The electronic structure is calculated with the standard one-orbital tight-binding model and the linear conductance is obtained using the Landauer formula. We find that, since the zero-bias current is carried in the bulk of the ribbon, this is very robust with respect to a variety of constriction geometries and edge defects. In contrast, the curve of zero-bias conductance versus gate voltage departs from the $(2n+1) e^2/h$ staircase of the ideal case as soon as a single atom is removed from the sample. We also find that wedge-shaped constrictions can present non-conducting states fully localized in the constriction close to the Fermi energy. The interest of these localized states in regards the formation of quantum dots in graphene is discussed.Comment: 9 pages, 9 figure

Coherent optical focal plane array receiver for PPM signals: investigation and applications

The performance of a coherent optical focal plane array receiver for PPM signals under atmospheric turbulence is investigated and applications of this system are addressed. The experimental demonstration of this project has already been explained in previous publications. This article shows a more exhaustive analysis of the expressions needed to obtain the Bit Error Rate (BER) for the real system under study in the laboratory, specifically an approach using the Saddle-Point approximation of the Marcum-Q function. Selected experimental results of this system are described and compared with theoretical BER expressions, and array combining gains are presented. Receiver sensitivity in terms of photons per bit (PPB) is examined; BER results are shown as a function of signal to noise ratios (SNR) as well as a function of photons per bit

HIV-1 and Alzheimer: a real conection?

La infección por el virus de inmunodeficiencia humana (VIH) causa alteraciones neurológicas que son más graves y frecuentes como consecuenia del envejecimieno de la población. Este daño se asocia a la disfunción neuronal, que patológicamente se caracteriza como una pérdida de sinapsis, acortamiento de neuritas, anormalidades dendríticas, así comon pérdida neuronal. A este respecto, varios estudios han observado un aumento significativo de placas amiloides en cerebros de individuos infectados por el VIH en comparación con controles sanos, así como en individuos VIH positivos que habían estado expuestos a la terapia antirretroviral. En este trabajo se ha investigado el efecto de la combinación del péptido β-amiloide e infección por VIH-1 en diferentes células del sistema nervioso. El pretratamiento de las células gliales y neuronales provoca un incremento en la replicación viral, así como el tratamiento combinado virus y formas de oligómeros y fibrillas producen un incremento en las especies reactivas de oxígeno y de la forma activa de la enzima proapoptótica caspasa-3, en astrocitos. Lo que podría traducirse como un incremento de neurotoxicidad y depositos de β-amiloide en el cerebro infectado.Infection by human immunodeficiency virus (HIV) promotes neurological alterations which are more severe and frequents, due to the aging of the population. This dementia is associated to neuronal disfunction, and is pathologicaly characterized as sinapse lose, dendritic abnormalities and neuronal death. Supporting this, several studies have shown a significant increase of the amyloid plaques in infected HIV brains compared to healthy controls as well as HIV positive individuals which were exposed to antiretroviral therapy. In the present study we have investigated the combined effect of amyloid-β and HIV-1 infection in diferent nervous cells. When we pretreated glial cells and neurons we found an increased viral replication, as well as the combined treatment of HIV and oligomeric and fibrils forms of amyloid-β which produce glial increased levels of oxygen reactive species and the proapoptotic enzyme caspase-3. These observations could be traduced in an increased neurotoxicity and amyloid-β deposits in infected brains