The structure of porin from Rhodobacter capsulatus at 1.8 Å resolution

AbstractThe structure of the porin from Rhodobacter capsulanus was determined at a resolution of 1.8 Å. The analysis started from a closely related crystal structure that had been solved at a medium resolution of 3 Å using multiple isomorphous replacement and solvent flattening. The new structure contains the complete sequence of 301 amino acid residues. Refinement of the model is under way: the present R-factor is 22% with good geometry. Except for the lengths of several loops, the resulting chain fold corresponds to the medium resolution model. The membrane channel is lined by a large number of ionogenic side chains with characteristic segregation of differently charged groups

Dynamics of surface migration in the weak corrugation regime

We report a systematic study for metal-on-metal surface migration in the weak corrugation regime, i.e., with migration barriers falling below approximate to 100 meV. The migration characteristics are elucidated by variable-temperature scanning tunneling microscopy observations in the 50-200 K temperature range, which are analyzed by means of nucleation theory. The results demonstrate that, upon entering the weak corrugation regime, the dynamics of the systems are characterized by increasingly reduced effective preexponential factors, while Arrhenius behavior prevails

PEPTIDOS TOXICOS Y NO TOXICOS DE CIANOBACTERIAS EN CUERPOS DE AGUA DULCE DE LA V REGION, CHILE

En Chile se ha detectado la presencia de algunos géneros de cianobacterias que pueden producir potentes hepatotoxinas y neurotoxinas, las que pueden ser letales para humanos y animales. En el presente trabajo se determinó la presencia de dos géneros de cianobacterias no tóxicos: Chroococcus y Spirulina; y cuatro génerosde cianobacterias productores de toxina, Anabaena, Anabaenopsis, Microcystis y Oscillatoria en tres diferentes cuerpos de agua de la V Región: Lago Peñuelas (Valparaíso), Tranque Recreo (Villa Alemana) y Embalse Los Aromos (Limache). Además se detectó la presenciade hepatotoxinas por MALDI-TOF MS encontrándose microcistina-RR, -LA, -YR y nodularina en Embalse Los Aromos, microcistina-LA en Tranque Recreo y microcistina- RR y LA en Lago Peñuelas. Adicionalmente enalgunas de las muestras se detectó la presencia de péptidos no tóxicos, que presentan actividad biológica tales como aeruginosinas, cianopeptolinas y microgininas. Como estos cuerpos de agua dulce sonutilizados para abastecimiento público y para la recreación, es importante diseñar planes de tratamiento y monitoreo para detectar y evitar los riesgos a la salud  humana y animal provocado por estos microorganismos

An Improved On-line Contingency Screening for Power System Transient Stability Assessment

peer reviewedThis paper presents a contingency screening method and a framework for its on-line implementation. The proposed method carries out contingency screening and on-line stability assessment with respect to first-swing transient stability. For that purpose, it utilizes the single machine equivalent method and aims at improving the prior developed contingency screening approaches. In order to determine vulnerability of the system with respect to a particular contingency, only one time-domain simulation needs to be performed. An early stop criteria is proposed so that in a majority of the cases the simulation can be terminated after a few hundred milliseconds of simulated system response. The method’s outcome is an assessment of the system’s stability and a classification of each considered contingency. The contingencies are categorized by exploiting parameters of an equivalent one machine infinite bus system. A novel island detection approach, appropriate for an on-line application since it utilizes efficient algorithms from graph theory and enables stability assessment of individual islands, is also introduced. The New England and New York system as well as the large-scale model of the Continental-European interconnected system are used to test the proposed method with respect to assessment accuracy and computation time

Quantitative analysis by renormalized entropy of invasive electroencephalograph recordings in focal epilepsy

Invasive electroencephalograph (EEG) recordings of ten patients suffering from focal epilepsy were analyzed using the method of renormalized entropy. Introduced as a complexity measure for the different regimes of a dynamical system, the feature was tested here for its spatio-temporal behavior in epileptic seizures. In all patients a decrease of renormalized entropy within the ictal phase of seizure was found. Furthermore, the strength of this decrease is monotonically related to the distance of the recording location to the focus. The results suggest that the method of renormalized entropy is a useful procedure for clinical applications like seizure detection and localization of epileptic foci.Comment: 10 pages, 5 figure

Realizing distance-selective interactions in a Rydberg-dressed atom array

Measurement-based quantum computing relies on the rapid creation of large-scale entanglement in a register of stable qubits. Atomic arrays are well suited to store quantum information, and entanglement can be created using highly-excited Rydberg states. Typically, isolating pairs during gate operation is difficult because Rydberg interactions feature long tails at large distances. Here, we engineer distance-selective interactions that are strongly peaked in distance through off-resonant laser coupling of molecular potentials between Rydberg atom pairs. Employing quantum gas microscopy, we verify the dressed interactions by observing correlated phase evolution using many-body Ramsey interferometry. We identify atom loss and coupling to continuum modes as a limitation of our present scheme and outline paths to mitigate these effects, paving the way towards the creation of large-scale entanglement.Comment: 5 pages, 4 figures + supplementary informatio