Carlos Vega

Ultrastructural detection of kinetochores by silver impregnation

We describe a simple silver impregnation method for the ultrastructural detection of kinetochores on meiotic chromosomes of the grasshopperEyprepocnemis plorans. Testes were fixed with glutaraldehyde and silver-impregnated. After Epon 812 embedding, ultrathin cutting and counterstaining with uranyl acetate, sections were studied by transmission electron microscopy. The meiotic chromosomes showed differentially silver-impregnated ‘ball and cup’ kinetochores. Some pericentriolar material also showed silver deposits. These observations are discussed in the light of previous results obtained by light microscopy of silver-stained spermatocytes in which both kinetochores and pericentriolar material were also preferentially stained. These results suggest a role for acidic proteins in the composition of these structures.

Supernumerary chromosome segments and intrabivalent chiasma redistribution in Pyrgomorpha conica (Orthoptera)

Two kinds of supernumerary chromosome segments have been found on the megameric chromosome of the grasshopper Pyrgomorpha conica. One of them is euchromatic and distally located while the other one is heterochromatic and proximally located. Their effects on chiasma distribution in heterozygous, homozygous and doubly heterozygous bivalents for these segments have been analyzed. Both segments distort chiasma distribution so that the single chiasma is preferentially formed far from the location of each supernumerary segment. This effect is more pronounced in bivalents that are homozygous for the presence of the proximal heterochromatic segment. In doubly heterozygous bivalents that possess both segments on the same chromosome the chiasma distribution is significantly different from that observed in heterozygous bivalents for each segment and a significant frequency of univalents was scored.

Unstable B-Chromosomes in Gomphocerus Sibiricus (Orthoptera)

SUMMARYThe cytogenetic analysis of a Pyrenean population of Gomphocerus sibiricus has uncovered the existence of an unstable system of B-chromosomes. Some aspects related to their behaviour, size and pycnosis through meiosis are discussed. The presence of extra material in the genome increases the production of abnormal spermatid nuclei including both microspermatids and macrospermatids. The possible influence on the offspring of these abnormal nuclei is discussed.

Multi-Gbps HTTP traffic analysis in commodity hardware based on local knowledge of TCP streams

In this paper we propose and implement novel techniques for performance evaluation of web traffic (response time, response code, etc.), with no reassembly of the underlying TCP connection, which severely restricts the traffic analysis throughput. Furthermore, our proposed software for HTTP traffic analysis runs in standard hardware, which is very cost-effective. Besides, we present sub-TCP connection load balancing techniques that significantly increase throughput at the expense of losing very few HTTP transactions. Such techniques provide performance evaluation statistics which are indistinguishable from the single-threaded alternative with full TCP connection reassembly.

Scaffold-like structures in mouse chromosomes revealed by restriction endonuclease digestion and electron microscopy

Summary— A scaffold‐like structure is observed under the electron microscope when mouse chromosomes are digested with the restriction endonuclease Hae III. This structure, located in the inner part of chromatids, may correspond to those fragments of chromatin loops anchored to the chromosome scaffold and is obtained when chromosomes are treated either in suspension or attached to grids. The width of the structure is correlated with the extent of digestion in chromosomes treated in suspension. Those treated on grids show this structure whenever chromatids do not collapse. These results agree with the model of chromosome organization based on a non‐histone protein scaffold.

Diluting the Scalability Boundaries: Exploring the Use of Disaggregated Architectures for High-Level Network Data Analysis

Traditional data centers are designed with a rigid architecture of fit-for-purpose servers that provision resources beyond the average workload in order to deal with occasional peaks of data. Heterogeneous data centers are pushing towards more cost-efficient architectures with better resource provisioning. In this paper we study the feasibility of using disaggregated architectures for intensive data applications, in contrast to the monolithic approach of server-oriented architectures. Particularly, we have tested a proactive network analysis system in which the workload demands are highly variable. In the context of the dReDBox disaggregated architecture, the results show that the overhead caused by using remote memory resources is significant, between 66% and 80%, but we have also observed that the memory usage is one order of magnitude higher for the stress case with respect to average workloads. Therefore, dimensioning memory for the worst case in conventional systems will result in a notable waste of resources. Finally, we found that, for the selected use case, parallelism is limited by memory. Therefore, using a disaggregated architecture will allow for increased parallelism, which, at the same time, will mitigate the overhead caused by remote memory.

FlexiTop: a flexible and scalable network monitoring system for Over-The-Top services

Nowadays, the demand of Over-The-Top (OTT) services such as multimedia streaming, web services or social networking is rapidly increasing. Consequently, there is a wide interest in studying the quality of these services so that Internet Service Providers (ISP) can deliver the best experience to their clients. For this purpose, we present FlexiTop, a flexible and scalable system to actively monitor these OTT services, which allows an operator to obtain metrics with a limited resource usage. Due to the continuous evolution of OTT services, this system was designed with different approaches that can be extrapolated to future situations. By looking at the results, the proposal meets all the expectations and requirements and therefore it proves its success. The proposed design was implemented and validated with different alternatives whenever it was possible, both in wired and wireless networks. Moreover, long-time testing was performed to both ensure its stability and analyze the obtained data.

FlexiTop: sistema de medidas de calidad de servicio escalable y flexible para servicios OTT

Hoy en dia, el uso de los servicios Over-The-Top tales como streaming de video, servicios web y redes sociales es dominante en el trafico de Internet. En consecuencia, existe un amplio interes por parte de los proveedores de servicios de Internet ( Internet Service Providers , ISP) en conocer la calidad de este tipo de comunicaciones para poder proporcionar el mejor servicio y por tanto la mejor experiencia a los usuarios. Para este proposito, se propone FlexiTop , un sistema flexible y escalable de medidas activas de calidad para este tipo de servicios, que permite obtener metricas con un consumo de recursos contenido. El diseno propuesto ha sido implementado y validado mediante pruebas. Asi mismo se ha realizado una campana de medidas durante varios meses en diferentes equipos, pudiendose concluir que el sistema cumple con las expectativas de los actores incumbentes

Loginson: a transform and load system for very large-scale log analysis in large IT infrastructures

Nowadays, most systems and applications produce log records that are useful for security and monitoring purposes such as debugging programming errors, checking system status, and detecting configuration problems or even attacks. To this end, a log repository becomes necessary whereby logs can be accessed and visualized in a timely manner. This paper presents Loginson, a high-performance log centralization system for large-scale log collection and processing in large IT infrastructures. Besides log collection, Loginson provides high-level analytics through a visual interface for the purpose of troubleshooting critical incidents. We note that Loginson outperforms all of the other log centralization solutions by taking full advantage of the vertical scalability, and therefore decreasing Capital Expenditure (CAPEX) and Operating Expense (OPEX) costs for deployment scenarios with a huge volume of log data.