The mean-variance model from the inverse of the variance-covariance matrix

In this paper we obtain the main results of the Markowitz mean-variance model from the inverse of the covariance matrix, following a shorter and mathematically rigorous path. We also obtain the equilibrium expression of Sharpes capital asset pricing model (CAPM).capm, beta, portfolio composition

Citações de livros: influência do pensamento epidemiológico na comunidade acadêmica

Whilst their 'death' has often been certified, books remain highly important to most professions and academic disciplines. Analyses of citations received by epidemiologic texts may complement other views on epidemiology. The objective was to assess the number of citations received by some books of epidemiology and public health, as a first step towards studying the influence of epidemiological thought and thinking in academia. For this purpose, Institute for Scientific Information/ Thomson Scientific - Web of Science/ Web of Knowledgedatabase was consulted, in May 2006. The book by Rothman & Greenland appeared to have received the highest number of citations overall (over 8,000) and per year. The books by Kleinbaum et al, and by Breslow & Day received around 5,000 citations. In terms of citations per year the book by Sackett et al ranks 3rd, and the one by Rose, 4th of those included in this preliminary study. Other books which were influential in the classrooms collected comparatively less citations. Results offer a rich picture of the academic influences and trends of epidemiologic methods and reasoning on public health, clinical medicine and the other health, life and social sciences. They may contribute to assess epidemiologists' efforts to demarcate epidemiology and to assert epistemic authority, and to analyze some historical influences of economic, social and political forces on epidemiological research.Ainda que sua 'morte' tenha sido freqüentemente certificada, os livros continuam sendo relevantes para muitas profissões e disciplinas acadêmicas. Análises de citações recebidas por textos epidemiológicos podem complementar outras visões em epidemiologia. O objetivo do estudo foi avaliar o número de citações recebidas por alguns livros de epidemiologia e saúde pública, como um primeiro passo para estudar a influência do pensamento epidemiológico e o pensar da academia. Para este propósito, a base de dados do Institute for Scientific Information/ Thomson Scientific - Web of Science/ Web of Knowledge foi consultada em maio de 2006. O livro de Rothman & Greenland recebeu o maior número de citações no total (mais de 8.000) e por ano. Os livros de Kleinbaum et al, e de Breslow & Day tiveram em torno de 5.000 citações. Em termos de citações por ano, o livro de Sackett et al ocupou o terceiro lugar, e o de Rose, o quarto entre os incluídos no estudo. Outros livros que tiveram influência em salas de aula, comparativamente, tiveram menos citações. Os achados oferecem um rico retrato das influências acadêmicas e tendências de métodos epidemiológicos e interpretação em saúde pública, medicina clínica e outras ciências da saúde, da vida, e sociais. Eles podem contribuir para avaliar os esforços dos epidemiologistas para demarcar a epidemiologia e afirmar sua autoridade epistemológica, e para analisar algumas influências históricas de forças econômicas, sociais e políticas sobre as pesquisas epidemiológicas

Aproximació al coneixement de la flora liquènica i dels fongs liquenícoles dels altiplans i conques centrals de Catalunya: el sector segàrric

L'estudi del sector segàrric dels altiplans i conques centrals catalanes, una àrea poc explorada des d'un punt de vista liquènic, ha aportat un catàleg de 334 tàxons, dels quals 301 són fongs liquenificats, i 33, fongs liquenícoles. Cal destacar l'aportació de sis nous tàxons per a la península Ibèrica (Acarospora chrysocardia, Diplotomma hedinii, Lecanora barkmanniana, L. farinaria, Lichenostigma subradians i Skyttea hawksworthii). A més, s'incrementa en 14 tàxons la llista de líquens i fongs liquenícoles de Catalunya (Caloplaca lucifuga, Candelariella faginea, Catapyrenium daedalum, Chaenothecopsis viridireagens, Collema fragrans, Lecania spadicea, Lepraria elobata, Lichenostigma gracilis, Lichinella jodopulchra, Muellerella hospitans, Placidium semaforonense, Solenopsora cesatii, Trapeliopsis pseudogranulosa i Xanthoparmelia pokornyi) i 96 tàxons són citacions noves per a les comarques lleidatanes. La composició florística de la zona estudiada se situa a mig camí entre la flora de les zones muntanyoses i de la regió mediterrània, sobretot pel que fa a les formes vitals i al tipus de fotobiont.A lichenological survey of the plateaus and basins of the central part of Catalonia has yielded a catalogue of 334 taxa, 301 of which are lichenized fungi and 33 lichenicolous fungi. Among the quoted species, six taxa are newly reported for the Iberian Peninsula (Acarospora chrysocardia, Diplotomma hedinii, Lecanora barkmanniana, L. farinaria, Lichenostigma subradians and Skyttea hawksworthii). In addition, 14 taxa are added to the current biota of Catalonia (Caloplaca lucifuga, Candelariella faginea, Catapyrenium daedalum, Chaenothecopsis viridireagens, Collema fragrans, Lecania spadicea, Lepraria elobata, Lichenostigma gracilis, Lichinella jodopulchra, Muellerella hospitans, Placidium semaforonense, Solenopsora cesatii, Trapeliopsis pseudogranulosa and Xanthoparmelia pokornyi). 96 taxa are newly reported for the province of Lleida. The floristic analysis of the area reveals that the lichen biota of the area shows a distribution of life forms and type of photobiont with an intermediate position between montane areas and the Mediterranean region.El estudio del sector segárrico de los altiplanos y cuencas centrales catalanas, un área poco explorada desde un punto de vista liquénico, ha aportado un catálogo de 334 taxones, de los que 301 son hongos liquenificados, y 33, hongos liquenícolas. Se destaca la aportación de seis nuevos taxones para la Península Ibérica (Acarospora chrysocardia, Diplotomma hedinii, Lecanora barkmanniana, L. farinaria, Lichenostigma subradians y Skyttea hawksworthii). Además, 14 taxones son nuevas citas para la biota liquènica y fúngica de Cataluña (Caloplaca lucifuga, Candelariella faginea, Catapyrenium daedalum, Chaenothecopsis viridireagens, Collema fragrans, Lecania spadicea, Lepraria elobata, Lichenostigma gracilis, Lichinella jodopulchra, Muellerella hospitans, Placidium semaforonense, Solenopsora cesatii, Trapeliopsis pseudogranulosa y Xanthoparmelia pokornyi) y 96 taxones son nuevas citas para las comarcas leridanas. El análisis de la composición florística sitúa a la flora liquénica de la zona a caballo entre la flora de las zonas de montaña y la región mediterránea, sobretodo por las formas vitales y el tipo de fotobionte presente

Novel tobacco and nicotine products and youth in the European Union

In recent years, there has been a rapid proliferation of novel tobacco and nicotine products in the market, which have gained in popularity among adolescents. The prevalence of ever users of electronic cigarettes (e-cigs) in Europe among those aged 10–24 ranges from 5.5% to 56.6%, with significant variations across countries. Adolescents have reported several reasons for e-cig use initiation, including low harm perception, social acceptability, novelty, and peer influence. Despite being marketed as safe alternatives, e-cigs are not risk-free and have already been associated with respiratory diseases. A major concern is their potential to renormalize smoking among non-smokers and to foster nicotine dependence, leading to the initiation of conventional cigarette smoking, which would reverse actual declining trends in tobacco consumption. Hence, to prevent a setback on the progress made in tobacco control, there is a pressing need for more comprehensive regulation, with a particular focus on adolescents, given that the teenage years are pivotal in determining future smoking behavior

Novel tobacco and nicotine products and youth in the European Union

In recent years, there has been a rapid proliferation of novel tobacco and nicotine products in the market, which have gained in popularity among adolescents. The prevalence of ever user of electronic cigarettes (e-cigs) in Europe among those aged 10–24 ranges from 5.5% to 56.6%, with significant variations across countries. Adolescents have reported several reasons for e-cigs use initiation, including low harm perception, social acceptability, novelty, and peer influence. Despite being marketed as safe alternatives, e-cigs are not risk-free and have already been associated with respiratory diseases. A major concern is their potential to renormalize smoking among non-smokers and to foster nicotine dependence, leading to initiation of conventional cigarette smoking, which would revert actual declining trends in tobacco consumption. Hence, to prevent a setback in the progress made in tobacco control, there is a pressing need for more comprehensive regulation, with a particular focus on adolescents, given that teenage years are key in determining future smoking behaviors

Development of a three-dimensional cell culture system based on microfluidics for nuclear magnetic resonance and optical monitoring.

A new microfluidic cell culture device compatible with real-time nuclear magnetic resonance (NMR) is presented here. The intended application is the long-term monitoring of 3D cell cultures by several techniques. The system has been designed to fit inside commercially available NMR equipment to obtain maximum readout resolution when working with small samples. Moreover, the microfluidic device integrates a fibre-optic-based sensor to monitor parameters such as oxygen, pH, or temperature during NMR monitoring, and it also allows the use of optical microscopy techniques such as confocal fluorescence microscopy. This manuscript reports the initial trials culturing neurospheres inside the microchamber of this device and the preliminary images and spatially localised spectra obtained by NMR. The images show the presence of a necrotic area in the interior of the neurospheres, as is frequently observed in histological preparations; this phenomenon appears whenever the distance between the cells and fresh nutrients impairs the diffusion of oxygen. Moreover, the spectra acquired in a volume of 8 nl inside the neurosphereshow an accumulation of lactate and lipids, which are indicative of anoxic condi-tions. Additionally, a basis for general temperature control and monitoring and a graphical control software have been developed and are also described. The complete platform will allow biomedical assays of therapeutic agents to be performed in the early phases of therapeutic development. Thus, small quantities of drugs or advanced nanodevices may be studied long-term under simulated living conditions that mimic the flow and distribution of nutrient

Comparative study of extracellular recording methods for analysis of afferent sensory information: Empirical modeling, data analysis and interpretation

Background: Physiological studies of sensorial systems often require the acquisition and processing of data extracted from their multiple components to evaluate how the neural information changes in relation to the environment changes. In this work, a comparative study about methodological aspects of two electrophysiological approaches is described. New method: Extracellular recordings from deep vibrissal nerves were obtained by using a customized microelectrode Utah array during passive mechanical stimulation of rat´s whiskers. These recordings were compared with those obtained with bipolar electrodes. We also propose here a simplified empirical model of the electrophysiological activity obtained from a bundle of myelinated nerve fibers. Results: The peripheral activity of the vibrissal system was characterized through the temporal and spectral features obtained with both recording methods. The empirical model not only allows the correlation between anatomical structures and functional features, but also allows to predict changes in the CAPs morphology when the arrangement and the geometry of the electrodes changes. Comparison with existing method(s): This study compares two extracellular recording methods based on analysis techniques, empirical modeling and data processing of vibrissal sensory information. Conclusions: This comparative study reveals a close relationship between the electrophysiological techniques and the processing methods necessary to extract sensory information. This relationship is the result of maximizing the extraction of information from recordings of sensory activity.Fil: Farfan, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Soto Sanchez, Cristina. Universidad de Miguel Hernández; España. Consorcio Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina; EspañaFil: Pizá, Alvaro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Albarracin, Ana Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Soletta, Jorge Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Lucianna, Facundo Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Bioingeniería. Laboratorio de Medios e Interfases; ArgentinaFil: Fernandez, Esteve. Universidad de Miguel Hernández; España. Consorcio Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina; Españ

Lysyl oxidase-dependent extracellular matrix crosslinking modulates calcification in atherosclerosis and aortic valve disease

Atherosclerosis; Cardiovascular calcification; Lysyl oxidaseAterosclerosis; Calcificación cardiovascular; Lisil oxidasaAterosclerosi; Calcificació cardiovascular; Lisil oxidasaExtracellular matrix (ECM) is an active player in cardiovascular calcification (CVC), a major public health issue with an unmet need for effective therapies. Lysyl oxidase (LOX) conditions ECM biomechanical properties; thus, we hypothesized that LOX might impact on mineral deposition in calcific aortic valve disease (CAVD) and atherosclerosis. LOX was upregulated in calcified valves from two cohorts of CAVD patients. Strong LOX immunostaining was detected surrounding calcified foci in calcified human valves and atherosclerotic lesions colocalizing with RUNX2 on valvular interstitial cells (VICs) or vascular smooth muscle cells (VSMCs). Both LOX secretion and organized collagen deposition were enhanced in calcifying VICs exposed to osteogenic media. β-aminopropionitrile (BAPN), an inhibitor of LOX, attenuated collagen deposition and calcification. VICs seeded onto decellularized matrices from BAPN-treated VICs calcified less than cells cultured onto control scaffolds; instead, VICs exposed to conditioned media from cells over-expressing LOX or cultured onto LOX-crosslinked matrices calcified more. Atherosclerosis was induced in WT and transgenic mice that overexpress LOX in VSMC (TgLOXVSMC) by AAV-PCSK9D374Y injection and high-fat feeding. In atherosclerosis-challenged TgLOXVSMC mice both atherosclerosis burden and calcification assessed by near-infrared fluorescence (NIRF) imaging were higher than in WT mice. These animals also exhibited larger calcified areas in atherosclerotic lesions from aortic arches and brachiocephalic arteries. Moreover, LOX transgenesis exacerbated plaque inflammation, and increased VSMC cellularity, the rate of RUNX2-positive cells and both connective tissue content and collagen cross-linking. Our findings highlight the relevance of LOX in CVC and postulate this enzyme as a potential therapeutic target for CVC.We thank the technical support provided by Silvia Aguiló. This work was supported by the Spanish Ministerio de Ciencia e Innovación (RTI2018-094727-B-100 and PID2021-122509OB-I00 funded by MCIN/ AEI/10.13039/501100011033 and by “ERDF A way of making Europe”), Instituto de Salud Carlos III (ISCIII; Spain; PI21/01048), and Fundación Española de Arteriosclerosis (FEA-2022). C.B-S and L.P-U were supported by a FPU (Ministerio de Universidades; Spain), and PFIS (ISCIII) fellowships, respectively and N.L-A by a Miguel Servet contract (ISCIII). There is no financial or personal relationship with organizations that could potentially influence the described research