A 300-800MHz Tunable Filter and Linearized LNA applied in a Low-Noise Harmonic-Rejection RF-Sampling Receiver

A multiband flexible RF-sampling receiver aimed at software-defined radio is presented. The wideband RF sampling function is enabled by a recently proposed discrete-time mixing downconverter. This work exploits a voltage-sensing LNA preceded by a tunable LC pre-filter with one external coil to demonstrate an RF-sampling receiver with low noise figure (NF) and high harmonic rejection (HR). The second-order LC filter provides voltage pre-gain and attenuates the source noise aliasing, and it also improves the HR ratio of the sampling downconverter. The LNA consists of a simple amplifier topology built from inverters and resistors to improve the third-order nonlinearity via an enhanced voltage mirror technique. The RF-sampling receiver employs 8 times oversampling covering 300 to 800 MHz in two RF sub-bands. The chip is realized in 65 nm CMOS and the measured gain across the band is between 22 and 28 dB, while achieving a NF between 0.8 to 4.3 dB. The IIP2 varies between +38 and +49 dBm and the IIP3 between -14 dBm and -9 dBm, and the third and fifth order HR ratios are more than 60 dB. The LNA and downconverter consumes 6 mW, and the clock generator takes 12 mW at 800 MHz RF.\ud \u

Bringing Math teachers to ICT for teaching and learning

En este documento se presenta una primera fase de un proceso de introducción de tecnologías digitales de la información y comunicación (TICS) en formación de profesores de matemáticas en ejercicio del Departamento del Tolima en Colombia. Se han indagado los procesos cognitivos de representación en conexión con los tipos de procesos y pensamiento matemáticos definidos en los Lineamientos Curriculares para el área de Matemáticas en Colombia. Se han empleado 10 software libres en la red de Internet y se han encontrado índices de dificultad en la resolución de problemas y en el empleo de representaciones.This paper presents a first phase of a process of introducing digital technologies of information and communication (ICT) into mathematics teacher training in exercise of the Department of Tolima in Colombia. The inquiry explores the cognitive processes of representation in connection with the types of mathematical thinking and processes defined in the Curriculum Guidelines for Mathematics area in Colombia. Have been used 10 software free in the Internet and found rates of difficulty in problem solving and the use of representations

A model for the electromagnetic spectrum of the inner jets of Cen A

Centaurus A, the closest active galaxy, has been detected from radio to high-energy gamma-rays. The synchrotron radiation by extremely high energy protons may be a suitable mechanism to explain the MeV to GeV emission detected by the instruments of the Compton Gamma-Ray Observatory, as coming from the inner jets. This scenario requires a relatively large magnetic field of about 10^4 G that could be present only close to the central black hole. We investigate the spectral energy distribution (SED) resulting from a one-zone compact acceleration region, where both leptonic and hadronic relativistic populations arise. We present here results of such a model, where we have considered synchrotron radiation by primary electrons and protons, inverse Compton interactions, and gamma-ray emission originated by the inelastic hadronic interactions between relativistic protons and cold nuclei within the jets themselves. Photo-meson production by relativistic hadrons were also taken into account, as well as the effects of secondary particles injected by all interactions. The internal and external absorption of gamma rays is shown to be of great relevance to shape the observable SED, which was also recently constrained by the results of HESS.Comment: 13 pages (ref. style), submitted to MNRAS on December 04, 2008. Waiting for revie

A Frequency Tripler Using a Subharmonic Mixer and Fundamental Cancellation

A new odd-order frequency multiplier topology is demonstrated in this work that uses a subharmonic mixer to realize a frequency tripler. A feedforward circuit is used for fundamental cancellation at the output and eliminates the need for filtering structures. For demonstrative purposes, and to validate the concept, a 1-3-GHz proof-of-concept frequency tripler circuit was fabricated. The tripler circuit achieved a measured output fundamental suppression of up to 30 dB below the third harmonic and a conversion gain of up to 3 dB. The circuit was implemented in CMOS 0.18-mu m technology and the chip area was 0.8 mm(2) including bonding pads

A history of Proterozoic terranes in southern South America: From Rodinia to Gondwana

The role played by Paleoproterozoic cratons in southern South America from the Mesoproterozoic to the Early Cambrian is reconsidered here. This period involved protracted continental amalgamation that led to formation of the supercontinent Rodinia, followed by Neoproterozoic continental break-up, with the consequent opening of Clymene and Iapetus oceans, and finally continental re-assembly as Gondwana through complex oblique collisions in the Late Neoproterozoic to Early Cambrian. The evidence for this is based mainly on a combination of precise U-Pb SHRMP dating and radiogenic isotope data for igneous and metamorphic rocks from a large area extending from the Rio de la Plata craton in the east to the Argentine Precordillera in the west and as far north as Arequipa in Peru. Our interpretation of the paleogeographical and geodynamic evolution invokes a hypothetical Paleoproterozoic block (MARA) embracing basement ultimately older than 1.7 Ga in the Western Sierras Pampeanas (Argentina), the Arequipa block (Peru), the Rio Apa block (Brazil), and probably also the Paraguaia block (Bolivia).Centro de Investigaciones Geológica

Lower Paleozoic Orogenies at the proto-andean margin of South America, Sierras Pampeanas, Argentina

El margen proto-andino de Gondwana ha sido el escenario de al menos dos orogénesis desde el desmembramiento del supercontinente Rodinia al final del Neoprotrozoico, hasta el reagrupamiento de las masas continentales en Pangea al final del Carbonifero. Ambas orogénesis van precedidas de un periodo de apertura oceánica y sedimentación en márgenes pasivos y culminan en subducción oceánica con desarrollo de arcos-magmáticos de tipo cordillerano y colision de tipo continente-continente. La primera, orogénesis Pampeana, tiene lugar en el Cámbrico, en un intervalo de tiempo relativamente pequeño (535-520 Ma: etapas de subducción-arco magmático y colisión), y culmina con la acreción ortogonal de un pequeño terreno continental (terreno Pampeano) de naturaleza semiautóctona. Por el contrario, la orogénesis Famatiniana, tiene lugar en un periodo de tiempo más dilatado, durante el Ordovícico y Silúrico (499-435 Ma). Durante esta orogénesis tuvo lugar la acreción de un terreno exótico a Gondwana, el terreno Precordillera (460 Ma). Este terreno está constituido por un basamento grenvilliano (aprox. 1.1Ga) y una cubierta sedimentaria de plataforma carbonatada de edad Cámbrico-Ordovícico. La acreción al margen de Gondwana fue probablemente oblicua, y el margen oriental del terreno Precordillera fue afectado por fuerte deformación y metamorfismo regional. El basamento de los cinturones andinos del Paleozoico Superior y Mesozoico situados al oeste de la Precordillera, parece estar constituido también por rocas metamórficas grenvillianas; con lo cual, gran parte de los Andes centrales entre los 26ºS y 34ºS se encuentra asentado sobre terrenos alóctonos. En cualquier caso, la paleogeografía de las masas continentales involucradas en la colisión de los terrenos exóticos durante el Paleozoico Inferior no se conoce bien todavía.The proto-Andean margin of Gondwana was the site of at least two orogenies between the break-up of the Rodinia supercontinent, at the end of the Neoproterozoic, and the new continental amalgamation of Pangea at the end of the Carboniferous. Both orogenies were preceded by a period of ocean opening and passive margin sedimentation and ended with ocean subduction, development of cordilleran-type magmatic arcs and continent-continent collision. The Pampean orogeny took place in a relatively short period of time in the early Cambrian (535- 520 Ma; subduction – magmatic arc stage and continental collision), and ended with the orthogonal accretion of a semiautochthonous microcontinental fragment - the Pampean Terrane- to the Gondwana margin. On the other hand, the Famatinian orogeny spanned a longer period of time in the Ordovician and Silurian (499-435 Ma). During this orogeny the exotic Precordillera Terrane was accreted to the margin of Gondwana (460 Ma). This terrane, probably of Laurentian provenance, consists of a Grenvillian basement (1.1 Ga) and a Lower Paleozoic sedimentary cover of the carbonate platform type. Accretion was probably oblique to the Gondwana margin, and the eastern margin of the Precordillera Terrane was thoroughly affected by Famatinian deformation and regional metamorphism. The basement to the Upper Paleozoic and Mesozoic Andean belts, situated to the west of the Precordillera, also appears to be formed by Grenvillian metamorphic rocks, so that the greater part of the Central Andes between 26ºS and 34ºS are established upon allocthonous terranes. The Lower Paleozoic paleogeography of continental masses involved in the collision is not still fully understood.Centro de Investigaciones Geológica

Age, Sr and Nd-Isotope Systematics, and Origin of Two Fluorite Lodes, Sierras Pampeanas, Argentina

Fluorite mineralization at the La Nueva and Bubu mines yields Sm-Nd ages of 131 ± 22 and 117 ± 26 Ma, respectively. Thus, the mineralization most probably is related to a late Gondwanian (Lower Cretaceous) extensional and magmatic event that affected the Sierras Pampeanas basement during the opening of the Atlantic Ocean. Hydrothermal fluids involved in the formation of the fluorite probably were of meteoric origin, their isotopic composition (Sr and Nd) resulting largely from the incongruent dissolution of feldspars in the host porphyritic granites.Facultad de Ciencias Naturales y Muse

Prevalence and serotypes of Shiga toxin-producing Escherichia coli (STEC) in dairy cattle from Northern Portugal

The prevalence of Shiga toxin (Stx)-producing Escherichia coli (STEC) was determined by evaluating its presence in faecal samples from 155 heifers, and 254 dairy cows in 21 farms at North of Portugal sampled between December 2017 and June 2019. The prevalence of STEC in heifers (45%) was significantly higher than in lactating cows (16%) (p<0.05, Fisher exact test statistic value is <0.00001). A total of 133 STEC were isolated, 24 (13.8%) carried Shiga-toxin 1 (stx1) genes, 69 (39.7%) carried Shiga-toxin 2 (stx2) genes, and 40 (23%) carried both stx1 and stx2. Intimin (eae) virulence gene was detected in 29 (21.8%) of the isolates. STEC isolates belonged to 72 different O:H serotypes, comprising 40 O serogroups and 23 H types. The most frequent serotypes were O29:H12 (15%) and O113:H21 (5.2%), found in a large number of farms. Two isolates belonged to the highly virulent serotypes associated with human disease O157:H7 and O26:H11. Many other bovine STEC serotypes founded in this work belonged to serotypes previously described as pathogenic to humans. Thus, this study highlights the need for control strategies that can reduce STEC prevalence at the farm level and, thus, prevent food and environmental contamination.This study was financially supported by: i) project PhageSTEC (POCI-01-0145 -FEDER 029628) funded by FEDER through COMPETE2020 (Programa Operacional Competitividade e Internacionalizac¸ão) and by National Funds thought FCT (Fundac¸ão para a Ciência e a Tecnologia); ii) strategic project UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER 000004) funded by FCT under the scope of the European Regional Development Fund (Norte2020 - Programa Operacional Regional do Norte); iii) project PI16/01477 from Plan Estatal de I+D+I 2013-2016, Instituto de Salud Carlos III (ISCIII), Subdireccio´n General de Evaluacio´n y Fomento de la Investigacio´n, Ministerio de Economı´a y Competitividad (Gobierno de España) and FEDER; and iv) grant ED431C2017/57 from the Consellerı´a de Cultura, Educacio´n e Ordenación Universitaria, (Xunta de Galicia) and FEDER; UIDB/AGR/04033/2020 by National Funds thought FCT. Author IGM acknowledges the Consellerı´a de Cultura, Educacio´n e Ordenacio´n Universitaria, Xunta de Galicia for the individual grant ED481A-2015/149 and and author SCFS acknowledges the FPU programme for the individual grant FPU15/02644 from the Secretarı´a General de Universidades, Spanish Ministerio de Educacio´n, Cultura y Deporte. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

Colombian consensus on the diagnosis, treatment, and prevention of candida Spp. disease in children and adults

La Candidiasis Invasora (CI) y la candidemia, como su manifestación más frecuente, se ha convertido en la principal causa de micosis oportunista a nivel hospitalario. Este manuscrito realizado por miembros de la Asociación Colombiana de Infectología (ACIN), tuvo como objetivo proporcionar un conjunto de recomendaciones para manejo, seguimiento y prevención de la CI/candidemia y de la infección candidiásica de mucosas, en población adulta, pediátrica y neonatal, en un entorno hospitalario, incluyendo las unidades hemato-oncológicas y unidades de cuidado crítico. Todos los datos obtenidos mediante una búsqueda exhaustiva, fueron revisados y analizados de manera amplia por todos los miembros del grupo, y las recomendaciones emitidas se elaboraron luego de la evaluación de la literatura científica disponible, y el consenso de todos los especialistas involucrados, reconociendo el problema de la emergencia de las infecciones por Candida Spp. y brindando una correcta orientación a los profesionales de la salud sobre el manejo de pacientes con enfermedad candidiásica, de una forma racional y práctica, enfatizando en la evaluación del paciente, estrategias de diagnóstico, profilaxis, tratamiento empírico, tratamiento dirigido y terapia preventiva.Invasive Candidiasis (IC) and candidemia (as its most frequent manifestation) have become the main cause of opportunistic mycosis at hospital settings. This study, made by members of the Colombian Association of Infectious Diseases (ACIN), was aimed at providing a set of recommendations for the management, follow-up and prevention of IC / candidemia and mucous membrane candida infection in adult, pediatric and neonatal patients in a hospital setting, including the hemato-oncological and critical care units. All the data obtained through an exhaustive search were reviewed and analyzed in a comprehensive manner by all the members of the group, and the recommendations issued are being made after a careful review of the scientific literature available and the consensus of all specialists involved; the emergence of Candida Spp. problem is highlighted and a correct orientation to health professionals regarding the management of patients with candidiasis is provided in a rational and practical way, emphasizing patient evaluation, diagnostic strategies, prophylaxis, empirical treatment, directed treatment and preventative therap

Hydrolytic Reactivity Trends among Potential Prodrugs of the O2-Glycosylated Diazeniumdiolate Family. Targeting Nitric Oxide to Macrophages for Antileishmanial Activity

Glycosylated diazeniumdiolates of structure R2NN(O)dNO-R ′ (R ′ ) a saccharide residue) are potential prodrugs of the nitric oxide (NO)-releasing but acid-sensitive R2NN(O)dNO- ion. Moreover, cleaving the acid-stable glycosides under alkaline conditions provides a convenient protecting group strategy for diazeniumdiolate ions. Here, we report comparative hydrolysis rate data for five representative glycosylated diazeniumdiolates at pH 14, 7.4, and 3.8-4.6 as background for further developing both the protecting group application and the ability to target NO pharmacologically to macrophages harboring intracellular pathogens. Confirming the potential in the latter application, adding R2NN(O)dNO-GlcNAc (where R2N) diethylamino or pyrrolidin-l-yl and GlcNAc) N-acetylglucosamin-l-yl) to cultures of infected mouse macrophages that were deficient in inducible NO synthase caused rapid death of the intracellular protozoan parasite Leishmania major with no host cell toxicity