Complex networks: new trends for the analysis of brain connectivity

Today, the human brain can be studied as a whole. Electroencephalography, magnetoencephalography, or functional magnetic resonance imaging techniques provide functional connectivity patterns between different brain areas, and during different pathological and cognitive neuro-dynamical states. In this Tutorial we review novel complex networks approaches to unveil how brain networks can efficiently manage local processing and global integration for the transfer of information, while being at the same time capable of adapting to satisfy changing neural demands.Comment: Tutorial paper to appear in the Int. J. Bif. Chao

Problemas cafeteros

El sensible decaimiento de numerosos cafetales, en municipios considerados desde hace cuarenta años como verdaderos baluartes de la industria, decaimiento que se hace más ostensible si se analiza el rendimiento de la producción por unidad, nos hace pensar que para el cultivador ha de llegar una hora, en que vuelto sobre sí mismo, tratará de alejarse de sus viejas tácticas, para enrutarse hacia nuevos sistemas que ante todo, se acomoden a la realidad económica y al avance técnico, que en materia de explotaciones agrícolas ya se vislumbra. En Antioquia, de manera especial, las empresas cafeteras sufren las terribles consecuencias de la erosión, disminuyéndose diariamente el espesor de la zona del suelo penetrable a las raíces del cafeto y restringiéndose funestamente la absorción de los nutrientes, que aquél necesita para sus funciones biológicas. Se hace para estas nuestras tierras, indispensable una campaña que por fortuna ya se inicia que tienda a mantener en el suelo, el juego continuo de las bacterias tan decisivas en la descomposición, aprovechando los troncos de plátano, las hojas que naturalmente deja caer el sombrío y que a veces forman un verdadero acolchonamiento con muy lejanas probabilidades de incorporarse al suelo, y la pulpa de café, en los hoyos o cajuelas que se abren en el suelo entre los árboles, con una profundidad que afecte el subsuelo siquiera en veinte centímetros

A microfluidic platform for combinatorial synthesis and optimization of targeted polymeric nanoparticles for cancer therapy

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2013."November 2012." Cataloged from PDF version of thesis.Includes bibliographical references.The use of nanotechnology to engineer drug delivery vehicles comprised of controlled release polymers with targeting molecules has the potential to revolutionize cancer therapy, among other diseases. Although a myriad of nanotherapeutics have been developed at the bench side, many of them stay at the research stage due to their complexity and difficulty in their optimization. A key challenge for optimization of nanoparticles (NPs) for drug delivery is the ability to systematically and combinatorially create and screen libraries of NPs with distinct physicochemical properties, from which promising formulations can be moved forward to preclinical and clinical studies. In this work, the development of a controlled method to synthesize libraries of NPs with distinct properties is described. The procedure uses a microfluidic platform that rapidly mixes reagents and provides homogeneous reaction environments, resulting in the reproducible, single-step synthesis of NPs with well-defined properties and narrow size distributions. The microfluidic system is composed of a mixing unit and a NP assembly unit. The mixing unit consists of a multi-inlet, 2-layer mixer where different precursors such as polymers of different MW and charge, ligand- and drug-conjugated polymers, free drugs, and solvents are mixed at different ratios into a homogenous solution. In the assembly unit, the precursor solution is quickly mixed with an anti-solvent (i.e. water) using 3D hydrodynamic flow focusing where NPs self-assemble after complete mixing. With the microfluidic platform, a library of 100 NPs with different sizes (15-200nm), charge (-30 to +30mV), surface chemistry (i.e. PEG coverage), surface ligand density (0-2.510⁵ ligands/[mu]m²), and drug loading (0-5 w/w%) was producedd in a high-throughput manner by simply varying the flow ratios of precursors entering the system. This library was implemented for (i) screening for formulations (in vitro and in vivo) with optimal clinical properties for cancer treatment and (ii) deepening the understanding of how NP properties affect their biological behavior. The platform developed in this work would likely lead to better understanding of the design parameters for polymeric NPs and their smoother transition to the clinic.by Pedro M. Valencia.Ph.D

Topography of Cortical Activation Differs for Fundamental and Harmonic Frequencies of the Steady-State Visual-Evoked Responses. An EEG and PET H15 2 O Study

In humans, visual flicker stimuli of graded frequency (2--90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-H15 2 O at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parietooccipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with lowresolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the procparieto-occipital sulcus

Human Cerebral Activation during Steady-State Visual-Evoked Responses

Flicker stimuli of variable frequency (2-90 Hz) elicit a steady-state visual-evoked response (SSVER) in the electroencephalogram (EEG) with the same frequency as the stimulus. In humans, the amplitude of this response peaks at approximately 15 Hz, decreasing at higher stimulation frequencies. It was not known whether this peak response corresponds to increased synaptic activity in the visual cortex or to other mechanisms [for instance, the temporal coherence (phase summation) of evoked responses]. We studied the SSVER in 16 normal volunteers by means of visual stimulation at 14 different frequencies (from 5 to 60 Hz) while recording the EEG. In nine subjects of the group, we measured regional cerebral blood flow (rCBF) with positron emission tomography (PET)-H2(15)O at rest and during visual stimulation at five different frequencies: 5, 10, 15, 25, and 40 Hz. We confirmed that the amplitude of the SSVER in occipital regions peaks at 15 Hz stimulation. Applying to the PET rCBF data a contrast weighted by the amplitude of the SSVER, we determined that the primary visual cortex rCBF follows an activation pattern similar to the SSVER. This finding suggests that the amplitude of the SSVER corresponds to increased synaptic activity, specifically in Brodmann's area 17. Additionally, this study showed that visual stimulation at 40 Hz causes selective activation of the macular region of the visual cortex, and that a region in the dorsal aspect of the Crus I lobule of the left cerebellar hemisphere is activated during repetitive visual stimulation

Paratuberculosis control strategies in dairy cattle: A systematic review

Background: Mycobacterium avium subsp. paratuberculosis is the causative agent of paratuberculosis (PTB), incurable enterocolitis, affecting domestic and wild ruminants. Economic losses, impacts on animal health and welfare, and public health concerns justify its herd-level control.Aim: To systematically collect information to answer: What are the control and eradication strategies of PTB in dairy cattle worldwide?Methods: The search procedure was carried out on October 2nd, 2019, and updated on August 3rd, 2021, using OVID®, SciELO, and Redalyc databases, and the registers from the International Colloquium on Paratuberculosis (1991–2018). The inclusion criteria considered articles published in English, Portuguese, and Spanish and in peerreviewed journals. The exclusion criteria included irrelevant topics, species other-than bovines, and not original articles. Definitive studies were obtained through the consensus of the authors on eligibility and quality. Data extraction was performed, considering bibliographic information, control and outcome strategies, follow-up time, and results.Results: Twenty-six relevant studies were found, reporting the use of three grouped control strategies: hygiene and management strategy (HMS), test-and-cull strategy (TCS), and vaccination strategy (VS). The HMS was the most common one (20/26), followed by TCS (17/26) and VS (7/26). Combined control strategies such as TCS-HMS (12/26), TCS-VS (1/26), and HMS-VS (1/26) were also described, and the consideration of the three control strategies (TCSHMS-VS) was reported in two articles. The HMS included practices such as neonates/juvenile livestock hygiene, biosecurity, prevention of infection introduction into the herd, and environmental management. Within HMS, the most frequent practices were to remove calves from their dams as soon as possible after birth and to keep the minimal exposure of calves and heifers to adult cattle. As limitations, within the HMS, it is considered that some strategies cannot be included due to lack of compliance, or the application of the same strategy among one study and another may have a different degree of interpretation; publication bias was not controlled since the results of the control programs in endemic countries may be not available.Conclusion: The main PTB control strategies in dairy cattle worldwide are HMS, TCS, and VS. The use of one or several combined strategies has been found to succeed in controlling the disease at the herd-level

The Mediterranean diet and incidence of hypertension: the Seguimiento Universidad de Navarra (SUN) Study

The Mediterranean diet is receiving increasing attention in cardiovascular epidemiology. The association of adherence to the Mediterranean diet with the incidence of hypertension was evaluated among 9,408 men and women enrolled in a dynamic Spanish prospective cohort study during 1999–2005. Dietary intake was assessed at baseline with a validated semiquantitative food frequency questionnaire, and a 9-point Mediterranean diet score was constructed. During a median follow-up period of 4.2 years (range, 1.9–7.9), 501 incident cases of hypertension were identified. After adjustment for major hypertension risk factors and nutritional covariates, adherence to the Mediterranean diet was not associated with hypertension (the hazard ratio was 1.10 (95% confidence interval (CI): 0.81, 1.41) for moderate adherence and 1.12 (95% CI: 0.79, 1.60) for high adherence). However, it was associated with reduced changes in mean levels of systolic blood pressure (moderate adherence, 2.4 mm Hg (95% CI: 4.0, 0.8); high adherence, 3.1 mm Hg (95% CI: 5.4, 0.8)) and diastolic blood pressure (moderate adherence, 1.3 mm Hg (95% CI: 2.5, 0.1); high adherence, 1.9 mm Hg (95% CI: 3.6, 0.1)) after 6 years of follow-up. These results suggest that adhering to a Mediterranean-type diet could contribute to the prevention of age-related changes in blood pressure

ACME Stellar Spectra. I. Absolutely Calibrated, Mostly Empirical Flux Densities of 55 Cancri and its Transiting Planet 55 Cancri e

The ACME Spectra project provides absolutely calibrated, mostly empirical spectra of exoplanet host stars for use in analysis of the stars and their planets. Spectra are obtained from ground-based telescopes and are tied directly to calibrated ground- and space-based photometry. The spectra remain only "mostly" empirical because of telluric absorption, but interpolation of stellar models over the gaps in wavelength coverage provides continuous stellar spectra. Among other uses, the spectra are suitable for precisely converting observed secondary eclipses (occultations) into absolute flux units with minimal recourse to models. In this letter I introduce ACME's methods and present a calibrated spectrum of the nearby, super-Earth hosting star 55 Cancri that spans the range from 0.81-5.05 micron. This spectrum is well-suited for interpreting near- and thermal-infrared eclipse observations. With this spectrum I show that the brightness temperature of the small, low-mass transiting planet 55 Cnc e is 1950 +260/-190 K at 4.5 micron (cooler than previously reported), which corresponds to a planetary flux of 0.44 +0.12/-0.08 mJy. This result suggests the planet has some combination of a nonzero albedo, a moderately efficient redistribution of absorbed stellar irradiation, and/or an optically thick atmosphere, but more precise eclipse measurements are required to distinguish between these scenarii.Comment: Accepted to A&A. 6 pages, 1 figure, 1 electronic table. See http://irtfweb.ifa.hawaii.edu/~spex/IRTF_Spectral_Library/ for an alternative spectru

Slow oscillatory activity and levodopa-induced dyskinesias in Parkinson’s disease

The pathophysiology of levodopa-induced dyskinesias (LID) in Parkinson’s disease is not well understood. We have recorded local field potentials (LFP) from macroelectrodes implanted in the subthalamic nucleus (STN) of 14 patients with Parkinson’s disease following surgical treatment with deep brain stimulation. Patients were studied in the ‘Off’ medication state and in the ‘On’ motor state after administration of levodopa– carbidopa (po) or apomorphine (sc) that elicited dyskinesias in 11 patients. The logarithm of the power spectrum of the LFP in selected frequency bands (4–10, 11–30 and 60–80 Hz) was compared between the ‘Off’ and ‘On’ medication states. A peak in the 11–30 Hz band was recorded in the ‘Off’ medication state and reduced by 45.2% (P < 0.001) in the ‘On’ state. The ‘On’ was also associated with an increment of 77. 6% (P < 0.001) in the 4–10 Hz band in all patients who showed dyskinesias and of 17.8% (P < 0.001) in the 60–80 Hz band in the majority of patients. When dyskinesias were only present in one limb (n = 2), the 4–10 Hz peak was only recorded in the contralateralSTN. These findings suggest that the 4–10 Hz oscillation is associated with the expression of LID in Parkinson’s disease

Diseño e implementación de un sistema de detección e identificación de aficionados violentos en estadios de futbol

In this paper, we describe the design process and implementation of an avocado system to detect and identify hooligans in football stadiums. Same describing the need to implement this technology in crowded areas, is to establish a system that when combined with various technology tools, allows to have the most complete system identifier applied faces football stadiums.En este documento, se describe el proceso de diseño e implementación de un sistema avocado a la detección e identificación de aficionados violentos en estadios de futbol. Misma que describe la necesidad de implementar este tipo de tecnología en sectores concurridos, se pretende establecer un sistema que al ser combinado con diversas herramientas tecnológicas, permita tener el más completo sistema de identificador de rostros  aplicado en estadios de futbol