Este trabajo analiza la segregación de la población escolar en Chile en dos dimensiones: la segregación socioeconómica y la segregación académica, materia de enorme interés dado la fuerte ...configuración de mercado del sistema educacional chileno. El texto sitúa el análisis de la segregación en el marco de la creciente preocupación por la equidad educacional y propone una conceptualización que vincula la segregación escolar con la investigación acerca del "efecto de los compañeros" en educación (peer effects). A continuación, se revisa y discute la evidencia empírica disponible acerca de la magnitud, causas y efectos de la segregación socioeconómica y la segregación académica de la educación chilena. El trabajo concluye identificando algunos de los desafíos que este campo de estudio presenta a la investigación científica y proponiendo líneas de investigación futura que permitan avanzar en el conocimiento de un tema relevante pero comparativamente poco estudiado. Palabras clave: segregación escolar, efecto de los compañeros, equidad educacional, sociología de la educación. This paper analyzes school segregation in Chile in two dimensions: socioeconomic segregation and academic segregation; a matter of great interest given the radical market oriented organization of the Chilean education. The analysis is situated in the context of the growing concern about the educational equity and proposes a conceptualization that links school segregation to the study of the peer-effect in education (i.e. the effect caused by school peers). Additionally, the paper reviews and discusses the available empirical evidence about the magnitude, causes and effects of the socioeconomic and academic segregation in Chile. Finally, the paper identifies some of the challenges that school segregation poses to the scientific research and proposes some research branches for additional studies, in order to advance in the academic knowledge of this relevant but poorly studied issue. Key words: school segregation, peer effect, equity in education, sociology of education. Analisa-se a segregacáo da populacáo escolar no Chile em duas dimensoes: a segregacáo socioeconómica e a académica, tema de grande interesse, dada a forte configuracáo do mercado do sistema educacional chileno. Situa-se a análise da segregacáo no contexto da crescente preocupacáo com a equidade educacional e propoe-se uma conceituacáo que liga a segregacáo escolar á pesquisa sobre o "efeito de pares" na educacáo (peer effects). Revisa-se e situa-se a evidéncia empírica sobre a magnitude, causas e efeitos da segregacáo socioeconómica e da segregacáo académica na educacáo chilena. Conclui-se identificando alguns dos desafios que este campo de estudo apresenta á pesquisa científica, propondo linhas para futura pesquisa que permita avancar no conhecimento de um tema relevante, porém pouco estudado. Palavras chave: segregacáo escolar, efeito dos pares, equidade educacional, sociologia da educacáo.
Each successive generation of X-ray machines has opened up new frontiers in science, such as the first radiographs and the determination of the structure of DNA. State-of-the-art X-ray sources can ...now produce coherent high-brightness X-rays of greater than kiloelectronvolt energy and promise a new revolution in imaging complex systems on nanometre and femtosecond scales. Despite the demand, only a few dedicated synchrotron facilities exist worldwide, in part because of the size and cost of conventional (accelerator) technology. Here we demonstrate the use of a new generation of laser-driven plasma accelerators, which accelerate high-charge electron beams to high energy in short distances, to produce directional, spatially coherent, intrinsically ultrafast beams of hard X-rays. This reduces the size of the synchrotron source from the tens of metres to the centimetre scale, simultaneously accelerating and wiggling the electron beam. The resulting X-ray source is 1,000 times brighter than previously reported plasma wigglers and thus has the potential to facilitate a myriad of uses across the whole spectrum of light-source applications.
The acceleration of electrons to approximately 0.8 GeV has been observed in a self-injecting laser wakefield accelerator driven at a plasma density of 5.5x10(18) cm(-3) by a 10 J, 55 fs, 800 nm laser ...pulse in the blowout regime. The laser pulse is found to be self-guided for 1 cm (>10zR), by measurement of a single filament containing >30% of the initial laser energy at this distance. Three-dimensional particle in cell simulations show that the intensity within the guided filament is amplified beyond its initial focused value to a normalized vector potential of a0>6, thus driving a highly nonlinear plasma wave.
We report experimental evidence for a Rayleigh-Taylor-like instability driven by radiation pressure of an ultraintense (10(21) W/cm(2)) laser pulse. The instability is witnessed by the highly ...modulated profile of the accelerated proton beam produced when the laser irradiates a 5 nm diamondlike carbon (90% C, 10% H) target. Clear anticorrelation between bubblelike modulations of the proton beam and transmitted laser profile further demonstrate the role of the radiation pressure in modulating the foil. Measurements of the modulation wavelength, and of the acceleration from Doppler-broadening of back-reflected light, agree quantitatively with particle-in-cell simulations performed for our experimental parameters and which confirm the existence of this instability.
COVID-19's severity has been associated with a possible imbalance in the cross-regulation of cytokines and vascular mediators. Since the beginning of the pandemic, kidney transplant recipients (KTRs) ...have been identified as patients of high vulnerability to more severe diseases. Thus, aiming to describe the patterns of cytokines and vascular mediators and to trace patients' differences according to their KTR status, this prospective study enrolled 67 COVID-19 patients (20 KTRs) and 29 non-COVID-19 controls before vaccination. A panel comprising 17 circulating cytokines and vascular mediators was run on samples collected at different time points. The cytokine and mediator patterns were investigated via principal component analysis (PCA) and correlation-based network (CBN). In both groups, compared to their respective controls, COVID-19 was associated with higher levels of cytokines and vascular mediators. Differentiating between the KTRs and non-KTRs, the number of correlations was much higher in the non-KTRs (44 vs. 14), and the node analysis showed the highest interactions of NGAL and sVCAM-1 in the non-KTRs and KTRs (9 vs. 4), respectively. In the PCA, while the non-KTRs with COVID-19 were differentiated from their controls in their IL-10, IFN-α, and TNF-α, this pattern was marked in the NGAL, sVCAM-1, and IL-8 of the KTRs.
This review aims to explore the role and value of serology testing in the context of COVID-19 immunization policies in Latin American countries and the barriers and challenges to the adequate use and ...uptake of this tool. It builds on a review of the academic literature, evidence, and existing policies, and includes a multistage process of discussion and feedback by a group of five experts. Regional and country-level evidence and resources from five focus countries-Argentina, Brazil, Chile, Colombia, and Mexico-were collected and analyzed. This review contains an overview of (1) the impact of the SARS-CoV-2 pandemic, the variants of concern and current testing strategies, (2) the introduction of COVID-19 vaccination, (3) the potential use of serology testing to support immunization initiatives, (4) the current frameworks for the use of serology testing in the region, and (5) the barriers and challenges to implementing serology testing in the context of COVID-19 immunization policies, including a discussion on the potential actions required to address these barriers and facilitate the uptake of this strategy in the region. Stakeholders can use elements of this document to guide timely decision-making, raise awareness, and inspire further studies.
Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy ...coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser-plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations. Such an improvement of energy-density flux through dense matter paves the ground for advances in laser-driven intense sources of energetic particles and radiation, driving matter to extreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessible at the laboratory scale and achieving high-gain laser-driven thermonuclear fusion.
The first evidence of x-ray harmonic radiation extending to 3.3 A, 3.8 keV (order n>3200) from petawatt class laser-solid interactions is presented, exhibiting relativistic limit efficiency scaling ...(eta approximately n{-2.5}-n{-3}) at multi-keV energies. This scaling holds up to a maximum order, n{RO} approximately 8{1/2}gamma;{3}, where gamma is the relativistic Lorentz factor, above which the first evidence of an intensity dependent efficiency rollover is observed. The coherent nature of the generated harmonics is demonstrated by the highly directional beamed emission, which for photon energy hnu>1 keV is found to be into a cone angle approximately 4 degrees , significantly less than that of the incident laser cone (20 degrees ).
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