Trastornos del sueño y seguridad vial : un tema no resuelto

Fil: Cardinali, Daniel P. Universidad de Buenos Aires. Facultad de Medicina; Argentina.Fil: Pérez Chada, Daniel. Hospital Universitario Austral. Departamento de Medicina Interna; ArgentinaLos mayores accidentes industriales y vehiculares de nuestros días pueden vincularse a la utilización de\n"las máquinas humanas" más allá de sus especificaciones naturales. En nuestro país, y a pesar de la\ncreciente preocupación pública por la seguridad vial, se presta poco interés al hecho de que la influencia\ndel sueño insuficiente es causa en una importante proporción de accidentes vehiculares

The hessian blob algorithm : precise particle detection in atomic force microscopy imagery

"Received: 20 October 2017; Accepted: 29 December 2017; Published online: 17 January 2018."Imaging by atomic force microscopy (AFM) offers high-resolution descriptions of many biological systems; however, regardless of resolution, conclusions drawn from AFM images are only as robust as the analysis leading to those conclusions. Vital to the analysis of biomolecules in AFM imagery is the initial detection of individual particles from large-scale images. Threshold and watershed algorithms are conventional for automatic particle detection but demand manual image preprocessing and produce particle boundaries which deform as a function of user-defined parameters, producing imprecise results subject to bias. Here, we introduce the Hessian blob to address these shortcomings. Combining a scalespace framework with measures of local image curvature, the Hessian blob formally defines particle centers and their boundaries, both to subpixel precision. Resulting particle boundaries are independent of user defined parameters, with no image preprocessing required. We demonstrate through direct comparison that the Hessian blob algorithm more accurately detects biomolecules than conventional AFM particle detection techniques. Furthermore, the algorithm proves largely insensitive to common imaging artifacts and noise, delivering a stable framework for particle analysis in AFM

Single-molecule observation of nucleotide induced conformational changes in basal SecA-ATP hydrolysis

11 pages ; illustrationsSecA is the critical adenosine triphosphatase that drives preprotein transport through the translocon, SecYEG, in Escherichia coli. This process is thought to be regulated by conformational changes of specific domains of SecA, but real-time, real-space measurement of these changes is lacking. We use single-molecule atomic force microscopy (AFM) to visualize nucleotide-dependent conformations and conformational dynamics of SecA. Distinct topographical populations were observed in the presence of specific nucleotides. AFM investigations during basal adenosine triphosphate (ATP) hydrolysis revealed rapid, reversible transitions between a compact and an extended state at the ~100-ms time scale. A SecA mutant lacking the precursor-binding domain (PBD) aided interpretation. Further, the biochemical activity of SecA prepared for AFM was confirmed by tracking inorganic phosphate release. We conclude that ATP-driven dynamics are largely due to PBD motion but that other segments of SecA contribute to this motion during the transition state of the ATP hydrolysis cycle.Funding: This work was supported by the National Science Foundation (CAREER award number 1054832 to G.M.K.) and a Burroughs Wellcome Fund Career Award at the Scientific Interface (to G.M.K.)Nagaraju Chada1*, Kanokporn Chattrakun1, Brendan P. Marsh1†, Chunfeng Mao2, Priya Bariya2, Gavin M. King1,2‡: 1Department of Physics and Astronomy, University of Missouri–Columbia, Columbia, MO 65211, USA. 2Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA. *Present address: Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA. †Present address: Department of Applied Physics, Stanford University, Stanford, CA 94305 USA. ‡Corresponding author.Nagaraju Chada (1*), Kanokporn Chattrakun (1), Brendan P. Marsh (1†), Chunfeng Mao (2), Priya Bariya (2), Gavin M. King (1,2‡) -- References: 1) Department of Physics and Astronomy, University of Missouri–Columbia, Columbia,MO 65211, USA ; 2) Department of Biochemistry, University of Missouri–Columbia, Columbia, MO 65211, USA ; *) Present address: Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA ; †) Present address: Department of Applied Physics, Stanford University, Stanford, CA 94305 USA ; ‡) Corresponding author

Glass is a viable substrate for precision force microscopy of membrane proteins

Scientific Reports ; 5:12550 ; DOI: 10.1038/srep12550.Chada, N. et al. Glass is a Viable Substrate for Precision Force Microscopy of Membrane Proteins. Sci. Rep. 5, 12550; doi: 10.1038/srep12550 (2015).8 pages.Received: 01 April 2015 ; Accepted: 02 July 2015 ; Published: 31 July 2015.Though ubiquitous in optical microscopy, glass has long been overlooked as a specimen supporting surface for high resolution atomic force microscopy (AFM) investigations due to its roughness. Using bacteriorhodopsin from Halobacterium salinarum and the translocon SecYEG from Escherichia coli, we demonstrate that faithful images of 2D crystalline and non-crystalline membrane proteins in lipid bilayers can be obtained on microscope cover glass following a straight-forward cleaning procedure. Direct comparison between AFM data obtained on glass and on mica substrates show no major differences in image fidelity. Repeated association of the ATPase SecA with the cytoplasmic protrusion of SecYEG demonstrates that the translocon remains competent for binding after tens of minutes of continuous AFM imaging. This opens the door for precision long-timescale investigations of the active translocase in near-native conditions and, more generally, for integration of high resolution biological AFM with many powerful optical techniques that require non-birefringent substrates.Includes bibliographical references

Glass is a viable substrate for atomic force microscopy of membrane proteins : [abstract]

Abstract only."2314-Pos Board B6.""Page 458a, Tuesday, February 18, 2014."--At top of page.Abstract in program book: Since its invention in the mid-1980s, the atomic force microscope (AFM) has become an invaluable complementary tool for studying membrane proteins in near-native environments. Historically, mica is the most common substrate utilized for biological AFM. Glass being amorphous, transparent, and optically homogeneous has its own set of advantages over mica and has the potential to broaden the use the AFM into fields that require high quality non-birefringent optical access. The use of silanized glass as AFM substrates has been reported as a means to fine tune surface chemistry. However, such coatings usually require hours of additional preparation time and can lead to increased surface roughness. In this work, we present a simple technique for preparing borosilicate glass as a substrate for two membrane systems: non-crystalline translocons (SecYEG) of the general secretary system from E. coli, and bacteriorhodopsin (BR) from H. salinarum. For both these membrane proteins, quantitative comparisons of the measured protein structures on glass versus mica substrates show agreement. An additional advantage of glass is that lipid coverage is rapid (< 10 minutes) and complete (occupying the entire surface). A goal is to study the bacterial export system using recently developed precision measurement techniques such as ultra-stable AFM

Glass is a viable substrate for atomic force microscopy of membrane proteins : [abstract]

Abstract only."2314-Pos Board B6.""Page 458a, Tuesday, February 18, 2014."--At top of page.Abstract in program book: Since its invention in the mid-1980s, the atomic force microscope (AFM) has become an invaluable complementary tool for studying membrane proteins in near-native environments. Historically, mica is the most common substrate utilized for biological AFM. Glass being amorphous, transparent, and optically homogeneous has its own set of advantages over mica and has the potential to broaden the use the AFM into fields that require high quality non-birefringent optical access. The use of silanized glass as AFM substrates has been reported as a means to fine tune surface chemistry. However, such coatings usually require hours of additional preparation time and can lead to increased surface roughness. In this work, we present a simple technique for preparing borosilicate glass as a substrate for two membrane systems: non-crystalline translocons (SecYEG) of the general secretary system from E. coli, and bacteriorhodopsin (BR) from H. salinarum. For both these membrane proteins, quantitative comparisons of the measured protein structures on glass versus mica substrates show agreement. An additional advantage of glass is that lipid coverage is rapid (< 10 minutes) and complete (occupying the entire surface). A goal is to study the bacterial export system using recently developed precision measurement techniques such as ultra-stable AFM

Glass : a multi-platform specimen supporting substrate for precision single molecule studies of membrane proteins : [abstract]

Abstract only."852-Pos Board B632.""Page 170a, Sunday, February 8, 2015."--At top of page.Abstract in program book: High resolution (~ 1 nm lateral resolution) biological AFM imaging has been carried out almost exclusively using freshly cleaved mica as a specimen supporting surface, but mica suffers from a fundamental limitation that has hindered AFM’s broader integration with many modern optical methods. Mica exhibits biaxial birefringence; indeed, this naturally occurring material is used commercially for constructing optical wave plates. In general, propagation through birefringent material alters the polarization state and bifurcates the propagation direction of light in a manner which varies with thickness. This makes it challenging to incorporate freshly cleaved mica substrates with modern optical methods, many of which employ highly focused and polarized laser beams passing through then specimen plane. Using bacteriorhodopsin from Halobacterium salinarum and the translocon SecYEG from Escherichia coli, we demonstrate that faithful images of 2D crystalline and non-crystalline membrane proteins in lipid bilayers can be obtained on common microscope cover glass following a straight-forward cleaning procedure. Direct comparison between data obtained on glass and on mica show no significant differences in AFM image fidelity. This work opens the door for combining high resolution biological AFM with powerful optical methods that require optically isotropic substrates such as ultra-stable1 and direct 3D AFM2. In turn, this capability should enable long timescale conformational dynamics measurements of membrane proteins in near-native conditions

Sleep and quality of life in urban poverty : the effect of a slum housing upgrading program

Study Objectives : To evaluate the effect of a housing transition on sleep quality and quality of life in slum dwellers, participating in a slum housing upgrading program. Design : Observational before-and-after study with a convergent-parallel mixed method design. Setting : Five slums located in the metropolitan area of Buenos Aires, Argentina. Participants : A total of 150 slum dwellers benefited by a housing program of the nonprofit organization TECHO (spanish word for “roof”). Interventions : Participants moved from their very low-quality house to a basic prefabricated 18 m2 modular house provided by TECHO. Measurements and Results : The Pittsburgh Sleep Quality Index (PSQI) and World Health Organization Quality of Life brief scale (WHOQOL-BREF) were administered before and after housing upgrading. Data about housing conditions, income, education, sleeping conditions, and cardiovascular risk were also collected. Semistructured interviews were used to expand and nuance quantitative data obtained from a poorly educated sample. Results showed that sleep quality significantly increased after the housing program (z = -6.57, P < 0.001). Overall quality of life (z = -6.85, P < 0.001), physical health domain (z = -4.35, P < 0.001), psychological well-being domain (z = -3.72, P < 0.001) and environmental domain (z = -7.10, P < 0.001) of WHOQOL-BREF were also improved. Interviews demonstrated the importance of serenity for improving quality of life. Conclusions : A minimal improvement in the quality of basic housing can significantly increase sleep quality and quality of life among slum dwellers. Understanding sleep and daily life conditions in informal urban settlements could help to define what kind of low-cost intervention may improve sleep quality, quality of life, and reduce existent sleep disparity

The Emergence of Miller's Magic Number on a Sparse Distributed Memory

Human memory is limited in the number of items held in one's mind—a limit known as “Miller's magic number”. We study the emergence of such limits as a result of the statistics of large bitvectors used to represent items in memory, given two postulates: i) the Sparse Distributed Memory; and ii) chunking through averaging. Potential implications for theoretical neuroscience are discussed

Management and resistance in the digital newsroom

What happens when there is conflict between the profit motivations of a news outlet and the professional values of its journalists? Questions of managerial influence and journalistic autonomy have interested media scholars from the seminal work of Warren Breed onwards. However, there have only been a handful of studies since the introduction of audience metrics which, this research suggests, allow managers to more efficiently monitor and discipline their journalists. This article presents an ethnographic case study of a Reuters newswire bureau during a time of conflict between the management and journalists. The article outlines the strategies that management used to incentivize their journalists to change their reporting priorities. These included the strategic dissemination of audience metrics and praise, and the hiring and promotion of ‘appropriate’ journalists to positions of influence. These interventions changed who was considered a ‘good journalist’ at the newswire, disrupting existing hierarchies, and eventually changing the culture of the newsroom. The article draws on the insights of Pierre Bourdieu’s field theory to help explain how managerial power operates, and the role that individual journalists play producing and reinforcing newsroom norms