Admission Control and Scheduling for High-Performance WWW Servers

In this paper we examine a number of admission control and scheduling protocols for high-performance web servers based on a 2-phase policy for serving HTTP requests. The first "registration" phase involves establishing the TCP connection for the HTTP request and parsing/interpreting its arguments, whereas the second "service" phase involves the service/transmission of data in response to the HTTP request. By introducing a delay between these two phases, we show that the performance of a web server could be potentially improved through the adoption of a number of scheduling policies that optimize the utilization of various system components (e.g. memory cache and I/O). In addition, to its premise for improving the performance of a single web server, the delineation between the registration and service phases of an HTTP request may be useful for load balancing purposes on clusters of web servers. We are investigating the use of such a mechanism as part of the Commonwealth testbed being developed at Boston University

Differentiation of Andean and Mesoamerican accessions in a proposed core collection of grain amaranths

Grain amaranths are made up of three New World species of pseudo-cereals with C4 photosynthesis from the dicotyledonous family Amaranthaceae and the genus Amaranthus. They originate in two ecoregions of the Americas, namely, the inter-Andean valleys of South America and the volcanic axis and lowlands of Mexico and Central America. These correspond to two centers of domestications for Andean and Mesoamerican crops, with one cultivated species found in the first region and two found in the latter region. To date, no core collection has been made for the grain amaranths in the United States Department of Agriculture (USDA) germplasm system. In this study, our objective was to create a core for the 2,899 gene bank accessions with collection site data by town or farm site of which 1,090 have current geo-referencing of latitude and longitude coordinates. We constituted the core with 260 genotypes of Amaranthus, which we evaluated with 90 single-nucleotide polymorphism markers. Our goal was to distinguish between Andean and Mesoamerican gene pools of amaranths, including the cultivated species and three possible progenitor or wild relative ancestors along with two more species in an outgroup. Population structure, clustering, and discriminant analysis for principal components showed that Andean species Amaranthus caudatus and Amaranthus quitensis shared fewer alleles with Mesoamerican species Amaranthus cruentus and Amaranthus hypochondriacus, compared to each group individually. Amaranthus hybridus was a bridge species that shared alleles with both regions. Molecular markers have the advantage over morphological traits at quickly distinguishing the Andean and Mesoamerican cultivars and have the added benefit of being useful for following inter-species crosses and introgression

Grinding methods effects on the synthesis of Potassium-Sodium Niobate powders by oxide mixing

Los materiales piezoeléctricos son ampliamente utilizados en dispositivos electrónicos. Tradicionalmente, para tales aplicaciones, se han utilizado diversos materiales a base de plomo; sin embargo, debido al daño causado por este elemento, se han desarrollado materias primas con características similares que no causen un impacto negativo a la sociedad o al medio ambiente. Un material con estas características es el niobato de potasio y sodio K0.5Na0.5 Nbo3. En este artículo, se realizaron análisis termogravimétricos, estructurales y microestructurales para los polvos del sistema K0.5Na0.5 Nbo3 obtenidos mediante mezcla de óxido, con el objetivo de determinar el efecto y la eficiencia de la molienda utilizando molinos de bolas, planetario y horizontal en la etapa de mezcla de los reactivos, para la producción del polvo final. Se determinó que el uso de la molienda horizontal y la calcinación a 900 °C crean las condiciones óptimas para obtener polvos  con una estructura y microestructura adecuadas para continuar los procesos de densificación y/o dopaje.Piezoelectric materials are widely used in electronic devices and, traditionally, various lead-based materials have been implemented in such applications. However, because of the damage caused by lead, other materials with similar characteristics that do not cause a negative impact on human health and the environment have been developed. A material with those characteristics is potassium-sodium niobite K0.5Na0.5 Nbo3. In this study, we investigate the thermogravimetric, structural, and microstructural properties of powders of such system obtained through oxide mixing with the aim of establishing the effect and efficiency of grinding (using a horizontal and a planetary ball mill grinder) on the production of the final material. It was determined that horizontal grinding and calcination at 900°C create the optimal conditions for obtaining K0.5Na0.5 Nbo3 powders, by oxide mixing, with the adequate structure and microstructure to continue the densification and/or doping processes

Allelic Diversity at Abiotic Stress Responsive Genes in Relationship to Ecological Drought Indices for Cultivated Tepary Bean, Phaseolus acutifolius A. Gray, and Its Wild Relatives

Some of the major impacts of climate change are expected in regions where drought stress is already an issue. Grain legumes are generally drought susceptible. However, tepary bean and its wild relatives within Phaseolus acutifolius or P. parvifolius are from arid areas between Mexico and the United States. Therefore, we hypothesize that these bean accessions have diversity signals indicative of adaptation to drought at key candidate genes such as: Asr2, Dreb2B, and ERECTA. By sequencing alleles of these genes and comparing to estimates of drought tolerance indices from climate data for the collection site of geo-referenced, tepary bean accessions, we determined the genotype x environmental association (GEA) of each gene. Diversity analysis found that cultivated and wild P. acutifolius were intermingled with var. tenuifolius and P. parvifolius, signifying that allele diversity was ample in the wild and cultivated clade over a broad sense (sensu lato) evaluation. Genes Dreb2B and ERECTA harbored signatures of directional selection, represented by six SNPs correlated with the environmental drought indices. This suggests that wild tepary bean is a reservoir of novel alleles at genes for drought tolerance, as expected for a species that originated in arid environments. Our study corroborated that candidate gene approach was effective for marker validation across a broad genetic base of wild tepary accessions

Factores asociados a la elección de carrera y universidad

RESUMEN: Con el fin de identificar factores asociados a la elección de carrera y universidad, se realizó un estudio, mediante una encuesta, a los estudiantes de undécimo grado de establecimientos educativos ubicados en la zona urbana de los municipios de Santas Bárbara, La Pintada, Fredonia y Barbosa en el departamento de Antioquia. Los resultados muestran que el 28% de los estudiantes se inclinan por carreras del área de salud tales como medicina, veterinaria, enfermería y odontología. Además, se detectó que en la elección del estudiante ejercen influencia los padres, familiares más cercanos y amigos. Esta influencia se ejerce, muchas veces, de manera indirecta, ya que tanto los padres como los hijos no reconocen conscientemente la influencia que está en juego. Por otro lado, se halló que el 80% de los estudiantes prefieren estudiar en las universidades públicas como la Universidad de Antioquia y la Universidad Nacional, pues consideran que "son favorables económicamente" y "tienen calidad académica”. El proceso de elección de carrera y universidad, al margen de los determinantes externos, se encuentra regulado por las elecciones particulares de cada individuo, las cuales se reflejan en los imaginarios en los que basa el estudiante para hacer su elección

Una arquitectura para el diseño conceptual de vehículos para exploración subacuática

Este artículo presenta una arquitectura para el diseño conceptual de vehículos subacuáticos operados remotamente (ROV) -- La arquitectura propuesta está basada en una revisión extensa de literatura y la experiencia obtenida durante 20 años con el desarrollo de tres sistemas ROV diseñados para misiones de inspección subacuática -- El ROV se divide en cinco subsistemas: vehículo, estación en superficie, interfaz superficie/vehículo, sistema de control y software -- Para cada uno de estos subsistemas se definen funciones y tareas, se enuncian componentes, se establecen interrelaciones con otros subsistemas y se plantean alternativas comúnmente utilizadas -- La delimitación de los subsistemas desde el diseño conceptual busca evitar problemas en las fases avanzadas del desarrollo del sistema robótico de exploraciónThis paper addresses an architecture for the conceptual design of remotely operated vehicles (ROV) -- The proposed architecture is based in an extensive literature review and the experience acquired during 20 years with the development of three ROV systems that where designed for underwater inspection -- The ROV is divided into five subsystems: vehicle, surface station, surface/vehicle interface, control system, and software -- For each subsystem, functions and tasks are defined, components are listed, interrelations with other subsystems are established, and commonly used alternatives are proposed -- The subsystem's division used for the conceptual design process allows one to avoid problems in the advanced stages of the robotic exploration system developmen

High-throughput phenotyping and improvements in breeding cassava for increased carotenoids in the roots

Past research developed reliable equations to base selections for high β-carotene on near-infrared spectroscopy (NIR) predictions (100 genotypes d−1) rather than with high-performance liquid chromatography (HPLC) (<10 samples d−1). During recent harvest, CIAT made selections based on NIR predictions for the first time. This innovation produced valuable information that will help other cassava (Manihot esculenta Crantz) breeding programs. A total of 284 samples were analyzed with NIR and HPLC for total β-carotene (TBC) and by the oven method for dry matter content (DMC). Results indicated that NIR reliably predicted TBC and DMC. In addition, 232 genotypes grown in preliminary yield trials (PYTs) were harvested at 8.5 and 10.5 mo after planting (one plant per genotype and age) and root quality traits analyzed (by NIR only). Repeatability of results at the two ages was excellent, suggesting reliable results from NIR. In contrast to previous reports, age of the plant did not influence carotenoids content in the roots. The availability of a high-throughput NIR protocol allowed comparing results (for the first time) from seedling and cloned plants from the same genotype. Results showed very little relationship for DMC between seedling and cloned plants (R2 = 0.09). There was a much better association for TBC (R2 = 0.48) between seedling and cloned plants. It is postulated that variation in the environmental conditions when seedling and cloned plants (from the same genotype) may be responsible for these weak associations. Important changes in selection strategies have been implemented to overcome problems related to a lengthy harvesting season. (Résumé d'auteur

Lovastatin delays infection and increases survival rates in AG129 mice infected with dengue virus serotype 2

ABSTARCT: It has been reported that treatment of DENV-infected cultures with Lovastatin (LOV), can affect viral assembly. The objective of this study was to evaluate the effect of LOV on the survival rate and viremia levels of DENV-2-infected AG129 mice. Methodology/Principal Findings: Mice were inoculated with 16106 plaque-forming units (PFU/ml) of DENV-2 and treated with LOV (200 mg/kg/day). Pre-treatment with one or three doses of LOV increased the survival rate compared to untreated mice (7.3 and 7.1 days, respectively, compared to 4.8 days). Viremia levels also decreased by 21.8% compared to untreated mice, but only in the group administered three doses prior to inoculation. When LOV was administered after viral inoculation, the survival rate increased (7.3 days in the group treated at 24 hpi, 6.8 days in the group treated at 48 hpi and 6.5 days in the group treated with two doses) compared to the untreated group (4.8 days). Interestingly, the serum viral titer increased by 24.6% in mice treated at 48 hpi with a single dose of LOV and by 21.7% in mice treated with two doses (at 24 and 48 hpi) of LOV compared to untreated mice. Finally histopathological changes in the liver and spleen in infected and untreated mice included massive extramedullary erythropoiesis foci and inflammatory filtration, and these characteristics were decreased or absent in LOV-treated mice. Conclusions/Significance: Our results suggest that the effect of LOV on viremia depends on the timing of treatment and on the number of doses administered. We observed a significant increase in the survival rate in both schemes due to a delay in the progression of the disease. However, the results obtained in the post-treatment scheme must be handled carefully because this treatment scheme increases viremia and we do not know how this increase could affect disease progression in humans

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection