Hierarchical Up/Down Routing Architecture for Ethernet backbones and campus networks

We describe a new layer two distributed and scalable routing architecture. It uses an automatic hierarchical node identifier assignment mechanism associated to the rapid spanning tree protocol. Enhanced up/down mechanisms are used to prohibit some turns at nodes to break cycles, instead of blocking links like the spannning tree protocol does. The protocol performance is similar or better than other turn prohibition algorithms recently proposed with lower complexity O(Nd) and better scalability. Simulations show that the fraction of prohibited turns over random networks is less than 0.2. The effect of root bridge election on the performance of the protocol is limited both in the random and regular networks studied. The use of hierarchical, tree-descriptive addresses simplifies the routing, and avoids the need of all nodes having a global knowleddge of the network topology. Routing frames through the hierarchical tree at very high speed is possible by progressive decoding of frame destination address, without routing tables or port address learning. Coexistence with standard bridges is achieved using combined devices: bridges that forward the frames having global destination MAC addresses as standard bridges and frames with local MAC frames with the proposed protocol.Publicad

La tendencia a restar en la resolución de problemas de m.c.d. en alumnos de primaria

En esta comunicación se presentan resultados de una investigación con alumnos de primaria sobre la resolución de problemas verbales ligados al concepto de máximo común divisor (m.c.d.) y mínimo común múltiplo (m.c.m.). Los principales objetivos de la investigación eran evaluar la competencia de los estudiantes en la resolución de este tipo de problemas y analizar los distintos patrones o procesos de resolución empleados. En particular, esta comunicación se centra en una dificultad que presentan los estudiantes en problemas cuya solución se correspondería con el m.c.d. de dos cantidades dadas en el enunciado. En este sentido, resultados, tanto cuantitativos como cualitativos, apuntan a que el origen de la dificultad podría deberse a que los estudiantes intentan relacionar las cantidades intervinientes en el enunciado mediante la sustracción atendiendo al tamaño de las cantidades conocidas y de la solución, sin involucrar en la resolución del problema las ideas de múltiplo y divisor

High-Performance Concrete and Fiber-Reinforced High- Performance Concrete under Fatigue Efforts

Fatigue is the process of mechanical degradation of a material, which leads to its collapse. Repeated load applications with a maximum value lower than the one that provokes the static failure of the material, causes internal damage in the material that, progressively, reduces its mechanical capacity until it finally collapses. The increasingly widespread use of high-strength concretes permits the construction of more lightweight structures. This implies that the variable loads (which are the causes of fatigue) represent an ever larger percentage of the total load. In consequence, fatigue is an increasingly important factor in concrete structures. In some cases, it even begins to be the dimensioning load of the structure. In addition, the presence of fibers within the concrete modifies the fatigue response of the concrete. In this chapter, the classic theory of fatigue is presented in detail and the most recent developments in the study of concrete fatigue are discussed

Tratamiento quirúrgico de fracturas toracolumbares por vía posterior con instrumentación y fusión bisegmentaria

Analizamos de forma retrospectiva, los resultados clínico-radiológicos y funcionales de pacientes con fracturas vertebrales con y sin afección neurológica, intervenidos quirúrgicamente mediante instrumentación vertebral pedicular de los dos segmentos adyacentes a la vértebra fracturada. Se estudian 30 pacientes que presentan fractura vertebral inestable del segmento toracolumbar, intervenidos desde enero de 1993 hasta diciembre de 2000. En todos los casos se realizó abordaje posterior, con inclusión en 8 casos de la vértebra fracturada y artrodesis posterolateral en todos los casos con injerto antólogo córtico-esponjoso. En dos casos con déficit neurológico se asoció laminectomía con descompresión posterolateral. El resultado clínico-funcional lo valoramos según la escala de Smiley-Webster con resultados excelentes en 22 pacientes. El índice sagital preoperatorio fue de 14,4 grados y postoperatorio de 4,2 grados. La altura media del cuerpo vertebral preoperatorio fue de 46% y postoperatoria de 78%. Los resultados obtenidos con esta fijación son similares a los obtenidos con otras técnicas, que requieren instrumentaciones y fusiones más largas o segundas intervenciones para retirar la fijación.We evaluate retrospectively the clinical, radiologic and functional outcomes of patients admitted to our hospital with unstable vertebral fractures with or without neurologic lesion treated with posterior fusion and transpedicular instrumentation of the upper and lower segment to the fractured vertebra. Thirty patients with unstable vertebral fracture of the thoracolumbar segment surgically managed between January 1993 and December 2000 are studied. The surgical approach was posterior in all cases, with posterolateral fusion with autologous corticocancellous graft. In 8 patients the fractured vertebra was also included. In two cases with neurologic impairment, a posterolateral decompression and laminectomy were associated. The Smiley-Webster score was used for the clinical and functional outcome with excellent results in 22 patients. The preoperative sagittal index was 14,4 degrees and improved to 4,2 degrees after surgery. The mean of vertebral body height was 46% preoperatively, and 78% postoperatively. The results obtained with this fixation are similar to other devices which require longer fusion and instrumentation or a second procedure to remove the hardware

Minimization of measuring points for the electric field exposure map generation in indoor environments by means of Kriging interpolation and selective sampling

In a world with increasing systems accessing to radio spectrum, the concern for exposure to electromagnetic fields is growing and therefore it is necessary to check limits in those areas where electromagnetic sources are working. Therefore, radio and exposure maps are continuously being generated, mainly in outdoor areas, by using many interpolation techniques. In this work, Surfer software and Kriging interpolation have been used for the first time to generate an indoor exposure map. A regular measuring mesh has been generated. Elimination of Less Significant Points (ELSP) and Geometrical Elimination of Neighbors (GEN) strategies to reduce the measuring points have been presented and evaluated. Both strategies have been compared to the map generated with all the measurements by calculating the root mean square and mean absolute errors. Results indicate that ELSP method can reduce up to 70% of the mesh measuring points while producing similar exposure maps to the one generated with all the measuring points. GEN, however, produces distorted maps and much higher error indicators even for 50% of eliminated measuring points. As a conclusion, a procedure for reducing the measuring points to generate radio and exposure maps is proposed based on the ELSP method and the Kriging interpolation.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors

PLK1 regulates centrosome migration and spindle dynamics in male mouse meiosis

Cell division requires the regulation of karyokinesis and cytokinesis, which includes an essential role of the achromatic spindle. Although the functions of centrosomes are well characterised in somatic cells, their role during vertebrate spermatogenesis remains elusive. We have studied the dynamics of the meiotic centrosomes in male mouse during both meiotic divisions. Results show that meiotic centrosomes duplicate twice: first duplication occurs in the leptotene/zygotene transition, while the second occurs in interkinesis. The maturation of duplicated centrosomes during the early stages of prophase I and II are followed by their separation and migration to opposite poles to form bipolar spindles I and II. The study of the genetic mouse model Plk1(Δ/Δ) indicates a central role of Polo-like kinase 1 in pericentriolar matrix assembly, in centrosome maturation and migration, and in the formation of the bipolar spindles during spermatogenesis. In addition, in vitro inhibition of Polo-like kinase 1 and Aurora A in organotypic cultures of seminiferous tubules points out to a prominent role of both kinases in the regulation of the formation of meiotic bipolar spindlesThis work was supported by funding from Ministerio de Economía, Industria y Competitividad, Gobierno de España (MINECO) (Spain) [grant number BFU2014-53681-P and MEIONET (BFU2015-71786-REDT) to J. A. S. and grant number RTI2018-095582-B-I00 to M. M.]

¿Pueden los factores clínicopatológicos mejorar la predicción de metástasis en ganglios linfáticos no centinelas en pacientes con cáncer de mama?

Introduction: To determine whether clinicopathological characteristics can improve the prediction of metastasis to nonsentinel lymph nodes (NSLNs) over the use of only mRNA copy number in sentinel lymph node (SLN) biopsies. Methods: This was a retrospective, observational study that included a total of 824 patients with T1-3 breast cancer who had clinically negative, ultrasound-negative axilla without evidence of metastasis and who underwent one-step nucleic acid amplification in SLN biop-sies. Results: 118 required a complete axillary lymph node dissection (ALNhD). About 35.6% (42/118) had metastases to a NSLN, and 64.4% (76/118) had no metastasis to a NSLN. The ROC curve of the total tumor load (TTL) presented an area under the curve (AUC) of 0.651 (95%; CI: 0.552-0.751). The 7294 copies of CK19 mRNA were established as the optimal cutoff point, with sensitivity: 93%, specificity: 63%, positive predictive value: 44%, and negative predictive value: 91%. By as-sociating the clinicopathological parameters (multicentricity, pooled immunohistochemistry [IHC], and progesterone receptors), the AUC went up to 0.752 (95% CI: 0.663-0.841). Conclusions: Clinicopathological factors should be considered together with the total CK19 mRNA copy number (the TTL) of the SLNs to improve the predictive capacity of metastatic involvement of the NSLNs