434 research outputs found
The effects of localized damping on structural response
The effect of localized structural damping on the excitability of higher order normal modes of the large space telescope was investigated. A preprocessor computer program was developed to incorporate Voigt structural joint damping models in a NASTRAN finite-element dynamic model. A postprocessor computer program was developed to select critical modes for low-frequency attitude control problems and for higher frequency fine-stabilization problems. The mode selection is accomplished by ranking the flexible modes based on coefficients for rate gyro, position gyro, and optical sensors, and on image-plane motions due to sinusoidal or random power spectral density force and torque inputs
Calibración de sensores de humedad capacitivos usando redes neuronales
X Jornadas de Investigación de la Zona no Saturada del Suelo, Salamanca (España), 2011El estudio de la variabilidad espacial de la
humedad del suelo a escala de parcela o cuenca agrícola
requiere el uso de redes de sensores de humedad de bajo
coste, que suelen mostrar una fiabilidad limitada y requieren
de calibraciones específicas, especialmente en suelos con
elevados contenidos en arcilla. El presente trabajo pretende
plantear una calibración más fiable de sondas de humedad
mediante un análisis mixto campo-laboratorio. Para la
calibración de campo se dispone de datos gravimétricos;
para la calibración en laboratorio se han usado columnas de
suelo inalterado que tras ser saturadas fueron desecadas en
un entorno controlado mientras se monitorizaba la
evolución de su peso y la de su humedad volumétrica,
medida con diferentes sondas capacitivas Decagon. Tras
obtener curvas de secado y la relación entre la humedad
gravimétrica y la volumétrica es posible realizar una
calibración mejorada específica para cada tipo de suelo. Las
redes neuronales son particularmente útiles para el
modelado de procesos físicos y el ajuste de modelos. En
este trabajo se propone el empleo de dichas herramientas
para obtener calibraciones para las sondas analizadas en el
tipo de suelo objeto de estudio. Los resultados muestran que
dichas calibraciones permiten mejorar la precisión de las
mediciones de humedad realizadas.The study of the spatial variability of soil
water content at agricultural plot or catchment scales
requires the use of low-cost soil water content sensor
networks, which usually show a limited reliability and
require specific calibrations, specially for soils with a high
clay content. This work proposes a more reliable calibration
of soil water content probes with a laboratory analysis.
Minimally disturbed soil columns were saturated with water
and dried in a controlled environment while monitorizing
the evolution of their volumetric soil water content (with
different capacitive Decagon Probes) and weights. After
obtaining the drying curves and the relation between the
volumetric and the measured gravimetric soil water contents
it is possible to achieve an improved calibration specific for
different kinds of soil. Neural networks are especially
interesting for the modeling of physical processes and
model adjustment. In this work, these tools were used in
order to obtain improved calibrations for the analyzed
probes in the studied soil type. Results show that this
calibration improves the accuracy and pMinisterio de Ciencia e Innovación AGL2009 C03-03Junta de Andalucía AGR-478
The free energy landscape of retroviral integration
Retroviral integration, the process of covalently inserting viral DNA into the host genome, is a point of no return in the replication cycle. Yet, strand transfer is intrinsically iso-energetic and it is not clear how efficient integration can be achieved. Here we investigate the dynamics of strand transfer and demonstrate that consecutive nucleoprotein intermediates interacting with a supercoiled target are increasingly stable, resulting in a net forward rate. Multivalent target interactions at discrete auxiliary interfaces render target capture irreversible, while allowing dynamic site selection. Active site binding is transient but rapidly results in strand transfer, which in turn rearranges and stabilizes the intasome in an allosteric manner. We find the resulting strand transfer complex to be mechanically stable and extremely long-lived, suggesting that a resolving agent is required in vivo
DNA fluctuations reveal the size and dynamics of topological domains
DNA supercoiling is a key regulatory mechanism that orchestrates DNA readout, recombination, and genome maintenance. DNA-binding proteins often mediate these processes by bringing two distant DNA sites together, thereby inducing (transient) topological domains. In order to understand the dynamics and molecular architecture of protein-induced topological domains in DNA, quantitative and time-resolved approaches are required. Here, we present a methodology to determine the size and dynamics of topological domains in supercoiled DNA in real time and at the single-molecule level. Our approach is based on quantifying the extension fluctuations—in addition to the mean extension—of supercoiled DNA in magnetic tweezers (MT). Using a combination of high-speed MT experiments, Monte Carlo simulations, and analytical theory, we map out the dependence of DNA extension fluctuations as a function of supercoiling density and external force. We find that in the plectonemic regime, the extension variance increases linearly with increasing supercoiling density and show how this enables us to determine the formation and size of topological domains. In addition, we demonstrate how the transient (partial) dissociation of DNA-bridging proteins results in the dynamic sampling of different topological states, which allows us to deduce the torsional stiffness of the plectonemic state and the kinetics of protein-plectoneme interactions. We expect our results to further the understanding and optimization of magnetic tweezer measurements and to enable quantification of the dynamics and reaction pathways of DNA processing enzymes in the context of physiologically relevant forces and supercoiling densities
Parametric expressions for the adjusted Hargreaves coefficient in Eastern Spain
The application of simple empirical equations for estimating reference evapotranspiration (ETo) is the
only alternative in many cases to robust approaches with high input requirements, especially at the local
scale. In particular, temperature-based approaches present a high potential applicability, among others,
because temperature might explain a high amount of ETo variability, and also because it can be measured
easily and is one of the most available climatic inputs. One of the most well-known temperature-based
approaches, the Hargreaves (HG) equation, requires a preliminary local calibration that is usually performed
through an adjustment of the HG coefficient (AHC). Nevertheless, these calibrations are sitespecific,
and cannot be extrapolated to other locations. So, they become useless in many situations,
because they are derived from already available benchmarks based on more robust methods, which will
be applied in practice. Therefore, the development of accurate equations for estimating AHC at local scale
becomes a relevant task. This paper analyses the performance of calibrated and non-calibrated HG equations
at 30 stations in Eastern Spain at daily, weekly, fortnightly and monthly scales. Moreover, multiple
linear regression was applied for estimating AHC based on different inputs, and the resulting equations
yielded higher performance accuracy than the non-calibrated HG estimates. The approach relying on the
ratio mean temperature to temperature range did not provide suitable AHC estimations, and was highly
improved by splitting it into two independent predictors. Temperature-based equations were improved
by incorporating geographical inputs. Finally, the model relying on temperature and geographic inputs
was further improved by incorporating wind speed, even just with simple qualitative information about
wind category (e.g. poorly vs. highly windy). The accuracy of the calibrated and non-calibrated HG estimates
increased for longer time steps (daily < weekly < fortnightly < monthly), although with a decreasing
accuracy improvement rate. The variability of goodness-of-fit between AHC models was translated
into lower variability of accuracy between the corresponding HG calibrated ETo estimates, because a single
AHC was applied per station. The AHC fluctuations throughout the year suggest the convenience of
using monthly or, at least, seasonal models.
2015 Elsevier B.V. All rights reserved.P. Marti acknowledges the financial support of the research grant Juan de la Cierva JCI-2012-13513 (Spanish Ministry of Economy and Competitiveness).Martí Pérez, PC.; Zarzo Castelló, M.; Vanderlinden, K.; Girona, J. (2015). Parametric expressions for the adjusted Hargreaves coefficient in Eastern Spain. Journal of Hydrology. 529(3):1713-1724. https://doi.org/10.1016/j.jhydrol.2015.07.054S17131724529
Molecular structure, DNA binding mode, photophysical properties and recommendations for use of SYBR Gold
SYBR Gold is a commonly used and particularly bright fluorescent DNA stain, however, its chemical structure is unknown and its binding mode to DNA remains controversial. Here, we solve the structure of SYBR Gold by NMR and mass spectrometry to be 2-N-(3-dimethylaminopropyl)-N-propylamino]-4-2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene-1-phenyl-quinolinium and determine its extinction coefficient. We quantitate SYBR Gold binding to DNA using two complementary approaches. First, we use single-molecule magnetic tweezers (MT) to determine the effects of SYBR Gold binding on DNA length and twist. The MT assay reveals systematic lengthening and unwinding of DNA by 19.1° ± 0.7° per molecule upon binding, consistent with intercalation, similar to the related dye SYBR Green I. We complement the MT data with spectroscopic characterization of SYBR Gold. The data are well described by a global binding model for dye concentrations ≤2.5~μM, with parameters that quantitatively agree with the MT results. The fluorescence increases linearly with the number of intercalated SYBR Gold molecules up to dye concentrations of ∼2.5~μM, where quenching and inner filter effects become relevant. In summary, we provide a mechanistic understanding of DNA-SYBR Gold interactions and present practical guidelines for optimal DNA detection and quantitative DNA sensing applications using SYBR Gold
Mechanism of polyubiquitination by human anaphase-promoting complex: RING repurposing for ubiquitin chain assembly.
Polyubiquitination by E2 and E3 enzymes is a predominant mechanism regulating protein function. Some RINGE3s, including anaphase-promoting complex/cyclosome (APC), catalyze polyubiquitination by sequential reactions with two different E2s. An initiating E2 ligates ubiquitin to an E3-bound substrate. Another E2 grows a polyubiquitin chain on the ubiquitin-primed substrate through poorly defined mechanisms. Here we show that human APC's RING domain is repurposed for dual functions in polyubiquitination. The canonical RING surface activates an initiating E2-ubiquitin intermediate for substrate modification. However, APC engages and activates its specialized ubiquitin chain-elongating E2 UBE2S in ways that differ from current paradigms. During chain assembly, a distinct APC11 RING surface helps deliver a substrate-linked ubiquitin to accept another ubiquitin from UBE2S. Our data define mechanisms of APC/UBE2S-mediated polyubiquitination, reveal diverse functions of RING E3s and E2s, and provide a framework for understanding distinctive RING E3 features specifying ubiquitin chain elongation
Tests at 2K of the beta 0.35 spoke cryomodule prototype with the MTCA.4-based Low Level RF system prototype for the MYRRHA R&D
Within the framework of the first phase of MYRRHA (Multi-purpose hYbrid
Research Reactor for High-tech Applications) project, called MINERVA, IJCLab
was in charge of a fully equipped Spoke cryomodule prototype development,
tested at 2K. It integrates two superconducting single spoke cavities, the RF
power couplers and the Cold Tuning Systems associated. On the control side, a
MTCA.4-based Low Level Radio Frequency (LLRF) system prototype and the
Software/EPICS developments has been realized by IJCLab and the SCK CEN in
collaboration with the company IOxOS Technologies. The final version of the
global system and the results of the tests at 2K will show with some
perspectives.Comment: Poster pr\'esent\'e au LLRF Workshop 2023 (LLRF2023, arXiv :
2310.03199
Correction to ‘Molecular structure, DNA binding mode, photophysical properties and recommendations for use of SYBR Gold’
This is a correction to: Nucleic Acids Research, Volume 49, Issue 9, 21 May 2021, Pages 5143–5158, https://doi.org/10.1093/nar/gkab26
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