Large Differences In Amplitude Research Articles

Influence of Temperature and Incidence Angle on the Irradiation Cascade Effect of 6H-SiC: Molecular Dynamics Simulations.

SiC devices have been typically subjected to extreme environments and complex stresses during operation, such as intense radiation and large diurnal amplitude differences on the lunar surface. Radiation displacement damage may lead to degradation or failure of the performance of semiconductor devices. In this paper, the effects of temperature and incidence angle on the irradiation cascade effect of 6H-SiC were investigated separately using the principles of molecular dynamics. Temperatures were set to 100 K, 150 K, 200 K, 250 K, 300 K, 350 K, 400 K and 450 K. The incidence direction was parallel to the specified crystal plane, with angles of 8°, 15°, 30°, 45°, 60° and 75° to the negative direction of the Z-axis. In this paper, the six types of defects were counted, and the microscopic distribution images and trajectories of each type of defect were extracted. The results show a linear relationship between the peak of the Frenkel pair and temperature. The recombination rate of Frenkel pairs depends on the local temperature and degree of aggregation at the center of the cascade collision. Increasing the angle of incidence first inhibits and then promotes the production of total defects and Frenkel pairs. The lowest number of total defects, Frenkel pairs and antisite defects are produced at a 45° incident angle. At an incidence angle of 75°, larger size hollow clusters and anti-clusters are more likely to appear in the 6H-SiC.

Investigation of Low Order Parameters Affecting Tidal Stream Energy Resource Assessments

Tidal stream energy may have the potential to contribute to the baseline energy needs of the UK. There is a significant difference between the existing assessments of the UK’s resource, highlighting the need for a standardised model. The paper investigates some challenges of quantifying tidal stream energy. This study examines the sensitivity of resource assessments to low-order parameters, in order to inform higher order modelling and contribute to defining a standardised model. A combination of channel characteristics, turbine parameters and simulation settings formed the basis of 96+ cases to determine key parameters affecting resource assessments. Two 0-dimensional, idealised channels were modelled using 2-8 constituents from four UK sites spanning the semi-diurnal form factor range. Blockage-corrected blade element momentum theory was used to represent variable-speed, variable-pitch turbines. Three blockage designed rotors and one rotor designed for an unspecified blockage were simulated. Power capping and combined power and thrust capping were implemented.
 
 The study indicates dynamic balance is a key parameter affecting tidal dynamics when turbines are present in a channel. Variability of annual energy production due to the nodal cycle was most significant in the drag dominated channel with increasing blockage. Constituents with large amplitude and phase differences led to greater variability of the resource across the nodal cycle. Results indicate that the maximum deviation from the average annual energy production over the 18.6-year nodal cycle is +/- 8.8%. At a low form factor site, the difference between using 2 or 4 constituents was insignificant. However, for a higher form factor site, that is still semi-diurnal, the peak velocity increases by 0.32 m/s with 8 constituents compared to 2. Random Forest modelling indicates that the most important characteristic point on a variable-speed, variable-pitch turbine performance curve is the rated speed. Comparison of capping strategies highlights that combined power and thrust capping leads to an increase in energy per swept area. Combined capping decreased the variability of the resource over the nodal cycle, which is helpful to maintain a steady supply to the grid and sizing energy storage systems.

ATFormer: Advanced transformer for medical image segmentation

Combining transformers and convolutional neural networks is considered one of the most important directions for tackling medical image segmentation problems. To learn the long-range dependencies and local contexts, previous approaches embedded a convolutional layer into feedforward neural network inside the transformer block. However, a common issue is the instability during training since large differences in amplitude across layers by pre-layer normalization. Furthermore, multi-scale features were directly fused using the transformer from the encoder to decoder, which could disrupt valuable information for segmentation. To address these concerns, we propose Advanced TransFormer (ATFormer), a novel hybrid architecture that combines convolutional neural networks and transformers for medical image segmentation. First, the traditional transformer block has been refined into an Advanced Transformer Block, which adopts post-layer normalization to obtain mild activation values and employs the scaled cosine attention with shifted window for accurate spatial information. Second, the Progressive Guided Fusion module is introduced to make multi-scale features more discriminative while reducing the computational complexity. Experimental results on the ACDC, COVID-19 CT-Seg, and Tumor datasets demonstrate the significant advantage of ATFormer over existing methods that rely solely on convolutional neural networks, transformers, or their combination.

An Iterative OLA Method for Inversion of Solar Spectropolarimetric Data. I. Single- and Multiple-variable Inversions of Thermodynamic Quantities

This paper describes an adaptation of the Optimally Localized Averaging (OLA) inversion technique, originally developed for geo- and helioseismological applications, to the interpretation of solar spectroscopic data. It focuses on inverting the thermodynamical properties of the solar atmosphere, assuming that the atmosphere and radiation field are in local thermodynamic equilibrium (LTE). We leave inversions of magnetic field and non-LTE inversions for future work. The advantage with the OLA method is that it computes solutions that are optimally depth resolved with minimal crosstalk error between variables. Additionally, the method allows for direct assessment of the vertical resolution of the inverted solutions. The primary challenges faced when adapting the method to spectroscopic inversions originate with the possible large-amplitude differences between the atmospheric model used to initiate the inversion and the underlying atmosphere it aims to recover, necessitating the development of an iterative scheme. Here, we describe the iterative OLA method we have developed for both single and multivariable inversions and demonstrate its performance on simulated data and synthesized spectra. We note that, when carrying out multivariable inversions, employing response function amplification factors can address the inherent spectral sensitivity bias that makes it hard to invert for less spectrally sensitive variables. The OLA method can, in most cases, reliably invert as well as or better than the frequently employed Stokes Inversion based on Response functions (SIR) scheme, but some difficulties remain. In particular, the method struggles to recover large-scale offsets in the atmospheric stratification. We propose future strategies to improve this aspect.

High-fidelity fluid structure interaction simulations of turbulent-like aneurysm flows reveals high-frequency narrowband wall vibrations: A stimulus of mechanobiological relevance?

Recent high-fidelity/resolution computational fluid dynamics simulations of intracranial aneurysm hemodynamics have revealed turbulent-like flows. We hypothesized that the associated high-frequency pressure fluctuations could promote aneurysm wall vibrations. We performed fully coupled high-fidelity transient fluid structure interaction simulations between the blood flow and compliant aneurysm sac wall taking 5,000 time steps per second using a 3D patient-specific model previously shown to harbour turbulent-like flow. Our results show that the flow velocity contained fluctuations with a smooth and continuously decaying energy up to ∼160Hz, and fluctuating pressures with characteristic frequency peaks at approximately 30, 130 and 210Hz. There was a strong two-way coupling between the pressure and the wall deformation, for which the frequency spectrum showed similar characteristics, but with a narrow band peak at ∼120Hz with large regional differences in amplitude up to 80μm. The physics of the flow is broadly consistent with clinical reports of turbulent-like flows, while the physics of the wall is consistent with reports of spectral peaks in aneurysm patients. As many aneurysms are known to harbour turbulent-like flows, wall vibrations could be a widespread phenomenon. Finally, since aneurysms are vascular pathologies by definition and many/most aneurysms do not have endothelial cells but still display a focal remodeling, we hypothesize that vibrations and stresses within the wall itself might play a role in the mechanobiological processes of vessel wall pathology.

016 Associations between Circadian Melatonin and Temperature Amplitudes during Constant Routine

Abstract Introduction Circadian amplitude measures the strength or robustness of a rhythm and changes in amplitude may have implications for health. Large individual differences in melatonin amplitude are recognized. Here we aimed to determine the strength of relationships between melatonin and the core body (CBT) and distal-proximal skin temperature gradient (DPG) amplitudes during a constant routine protocol. Additionally, we determined the best fitting harmonic model for the DPG circadian rhythm. Methods 17 young healthy adults [13 males (22.3±3.9yr;mean±SD)] completed a 28-hr constant routine protocol after maintaining 8h habitual sleep schedules for one week at home. Endogenous circadian amplitudes of melatonin and CBT were fit with standard three- and dual-harmonic linear regression models, respectively. The DPG amplitude was analyzed with both dual and three-harmonic regression models to determine which model produced the best fit. Results The DPG was best fit by a three-harmonic regression model with significantly lower standard deviation and higher signal-to-noise ratio compared to the 2-harmonic model (both p<0.05) as well as by visualization of the fitted curves. Melatonin, CBT and DPG amplitudes were not found to be associated with each other during constant routine (all r<0.37; all p>0.10). Conclusion While it is common for melatonin and body temperature circadian phase estimates to be used interchangeably, non-significant findings for associations between circadian amplitudes of melatonin, CBT and DPG indicate that these markers may not provide similar information about circadian amplitude. Further, research is needed to explore possible associations between individual differences in melatonin, CBT and DPG amplitudes with other physiological and behavioral outcomes to determine which measure(s) of circadian amplitude may be functionally relevant. Support (if any) NIH R01 HL081761

Effects of Dispositional Affect on the N400: Language Processing and Socially Situated Context.

We examined whether the N400 Event-Related Potential (ERP) component would be modulated by dispositional affect during sentence processing. In this study, 33 participants read sentences manipulated by direct object type (congruent vs. incongruent) and object determiner type (definite vs. demonstrative). We were particularly interested in sentences of the form: (i) The connoisseur tasted the wine on the tour vs. (ii) The connoisseur tasted the # roof … We expected that processing incongruent direct objects (#roof) vs. congruent objects (wine) would elicit N400 effects. Previous ERP language experiments have shown that participants in (induced) positive and negative moods were differentially sensitive to semantic anomaly, resulting in different N400 effects. Presently, we ask whether individual dispositional affect scores (as measured by the Positive and Negative Affect Schedule; PANAS) would modulate N400 effects as shown previously. Namely, previous results showed larger N400 effects associated with happy moods and attenuated amplitudes associated with sad moods. Results revealed significant N400 effects, driven by the #roof vs. the wine, where larger amplitude differences were found for individuals showing smaller negative affect (NA) scores, thus partially replicating previous findings. We discuss our results in terms of theories of local (lexical) inhibition, such that low NA promotes stronger lexico-semantic links in sentences. Finally, our results support accounts of language processing that include social and biological characteristics of individuals during real-time sentence comprehension.

Large EEG amplitude effects are highly similar across Necker cube, smiley, and abstract stimuli.

The information available through our senses is noisy, incomplete, and ambiguous. Our perceptual systems have to resolve this ambiguity to construct stable and reliable percepts. Previous EEG studies found large amplitude differences in two event-related potential (ERP) components 200 and 400 ms after stimulus onset when comparing ambiguous with disambiguated visual information ("ERP Ambiguity Effects"). These effects so far generalized across classical ambiguous figures from different visual categories at lower (geometry, motion) and intermediate (Gestalt perception) levels. The present study aimed to examine whether these ERP Effects are restricted to ambiguous figures or whether they also occur for different degrees of visibility. Smiley faces with low and high visibility of emotional expressions, as well as abstract figures with low and high visibility of a target curvature were presented. We thus compared ambiguity effects in geometric cube stimuli with visibility in emotional faces, and with visibility in abstract figures. ERP Effects were replicated for the geometric stimuli and very similar ERP Effects were found for stimuli with emotional face expressions but also for abstract figures. Conclusively, the ERP amplitude effects generalize across fundamentally different stimulus categories and show highly similar effects for different degrees of stimulus ambiguity and stimulus visibility. We postulate the existence of a high-level/meta-perceptual evaluation instance, beyond sensory details, that estimates the certainty of a perceptual decision. The ERP Effects may reflect differences in evaluation results.

Description and Evaluation of the specified-dynamics experiment in the Chemistry-Climate Model Initiative

Abstract. We provide an overview of the REF-C1SD specified-dynamics experiment that was conducted as part of phase 1 of the Chemistry-Climate Model Initiative (CCMI). The REF-C1SD experiment, which consisted of mainly nudged general circulation models (GCMs) constrained with (re)analysis fields, was designed to examine the influence of the large-scale circulation on past trends in atmospheric composition. The REF-C1SD simulations were produced across various model frameworks and are evaluated in terms of how well they represent different measures of the dynamical and transport circulations. In the troposphere there are large (∼40 %) differences in the climatological mean distributions, seasonal cycle amplitude, and trends of the meridional and vertical winds. In the stratosphere there are similarly large (∼50 %) differences in the magnitude, trends and seasonal cycle amplitude of the transformed Eulerian mean circulation and among various chemical and idealized tracers. At the same time, interannual variations in nearly all quantities are very well represented, compared to the underlying reanalyses. We show that the differences in magnitude, trends and seasonal cycle are not related to the use of different reanalysis products; rather, we show they are associated with how the simulations were implemented, by which we refer both to how the large-scale flow was prescribed and to biases in the underlying free-running models. In most cases these differences are shown to be as large or even larger than the differences exhibited by free-running simulations produced using the exact same models, which are also shown to be more dynamically consistent. Overall, our results suggest that care must be taken when using specified-dynamics simulations to examine the influence of large-scale dynamics on composition.

An Ultrasonic Object Detection Applying the ID Based on Spread Spectrum Technique for a Vehicle.

When an ultrasonic sensor generates an ultrasonic wave and detects an obstacle from a reflected wave, a signal transmitted by other ultrasonic sensors would be interference. In this paper, to overcome the interference, a transducer transmits a signal with a unique ID modulated. The interference is ignored by verifying that the reflected signal includes its ID. The ID verification process uses a correlation between the received signal and the ID. Therefore, the ID is selected from orthogonal codes with good cross-correlation. Long code has the advantage of being more robust to interference. However, the reflected wave from nearby obstacles might return before the transmission ends. Therefore, the 7-bit Barker code is applied for near obstacle detection and a 31-bit Gold code is used for distant obstacle detection. The modulation technique is DQPSK, which is available in a narrow bandwidth and has a simple receiver structure. In ID recognition based on correlation, a near–far problem occurs due to a large amplitude difference between the received wave and interference. The addition of a zero-crossing detector solves this problem. The hardware is implemented based on the algorithm proposed in this paper. The simulation showed a detection rate of at least 90% and the the result of the real measurement represented a detection rate of 97.3% at 0.5 m and 94.5% at 2 m.

Monitoring Land-Use/Land-Cover Changes at a Provincial Large Scale Using an Object-Oriented Technique and Medium-Resolution Remote-Sensing Images

An object-based image analysis (OBIA) technique is replacing traditional pixel-based methods and setting a new standard for monitoring land-use/land-cover changes (LUCC). To date, however, studies have focused mainly on small-scale exploratory experiments and high-resolution remote-sensing images. Therefore, this study used OBIA techniques and medium-resolution Chinese HJ-CCD images to monitor LUCC at the provincial scale. The results showed that while woodland was mainly distributed in the west, south, and east mountain areas of Hunan Province, the west had the largest area and most continuous distribution. Wetland was distributed mainly in the northern plain area, and cultivated land was distributed mainly in the central and northern plains and mountain valleys. The largest impervious surface was the Changzhutan urban agglomerate in the northeast plain area. The spatial distribution of land cover in Hunan Province was closely related to topography, government policy, and economic development. For the period 2000–2010, the areas of cultivated land transformed into woodland, grassland, and wetland were 183.87 km2, 5.57 km2, and 70.02 km2, respectively, indicating that the government-promoted ecologically engineered construction was yielding some results. The rapid economic growth and urbanization, high resource development intensity, and other natural factors offset the gains made in ecologically engineered construction and in increasing forest and wetland areas, respectively, by 229.82 km2 and 132.12 km2 from 2000 to 2010 in Hunan Province. The results also showed large spatial differences in change amplitude (LUCCA), change speed (LUCCS), and transformation processes in Hunan Province. The Changzhutan urban agglomerate and the surrounding prefectures had the largest LUCCA and LUCCS, where the dominant land cover accounted for the conversion of some 189.76 km2 of cultivated land, 129.30 km2 of woodland, and 6.12 km2 of wetland into impervious surfaces in 2000–2010. This conversion was attributed to accelerated urbanization and rapid economic growth in this region.

Nonlinear dynamics of micromechanical resonator arrays for mass sensing

This paper investigates the mass sensing capability of an array of a few identical electrostatically actuated microbeams, as a first step toward the implementation of arrays of thousands of such resonant sensors. A reduced-order model is considered, and Taylor series are used to simplify the nonlinear electrostatic force. Then, the harmonic balance method associated with the asymptotic numerical method, as well as time integration or averaging methods, is applied to this model, and its results are compared. In this paper, two- and three-beam arrays are studied. The predicted responses exhibit complex branches of solutions with additional loops due to the influence of adjacent beams. Moreover, depending on the applied voltages, the solutions with and without added mass exhibit large differences in amplitude which can be used for detection. For symmetric configurations, the symmetry breaking induced by an added mass is exploited to improve mass sensing.

High sensitivity label-free refractometer based biosensor applicable to glycated hemoglobin detection in human blood using all-circular photonic crystal ring resonators

Abstract Lab-on-a-chip integrated optical biosensors have shown useful in non-invasive detection of biomaterials. Furthermore they are immune to electromagnetic interference rather than their electronic counterparts. In this paper, an all-optical photonic crystal (PhC)-based biosensor is presented. The biosensor is made up of two PhC-based W 1 waveguides which are critically coupled to a PhC-based ring-resonator (RR). The hub of the ring is designed in an all-circular quasi-crystal fashion to enhance output efficiency as well as easy injection of analyte. This PhCRR can distinguish 85 ± 15% of amplitude change via resonant wavelength shift of 0.75 ± 0.15 nm, or equally a 0.005 change in the refractive index unit (RIU). By introducing any change in the optical characteristics of desired biomaterials (i.e. refractive index of glycated hemoglobin), the resonance frequency of resonator changes and due to its high quality factor and sensitivity, a large amplitude difference appears in the output. The proposed glycated hemoglobin biosensor works in the wavelength interval of 1.545–1. 565 μ m , and its quality factor, figure of merit (FOM) and sensitivity are calculated to be 2500 ± 500 , 1400 ± 200 RIU−1 and 690 ± 50 nm/RIU, respectively. The simulations are performed in two-dimensional and finite difference time domain (FDTD) algorithm is used to numerically solve time-dependent Maxwell-equations within propagation domain.

Effect of Dynamical Phase on the Resonant Interaction Among Tsunami Edge Wave Modes

Different modes of tsunami edge waves can interact through nonlinear resonance. During this process, edge waves that have very small initial amplitude can grow to be as large or larger than the initially dominant edge wave modes. In this study, the effects of dynamical phase are established for a single triad of edge waves that participate in resonant interactions. In previous studies, Jacobi elliptic functions were used to describe the slow variation in amplitude associated with the interaction. This analytical approach assumes that one of the edge waves in the triad has zero initial amplitude and that the combined phase of the three waves φ = θ1 + θ2 − θ3 is constant at the value for maximum energy exchange (φ = 0). To obtain a more general solution, dynamical phase effects and non-zero initial amplitudes for all three waves are incorporated using numerical methods for the governing differential equations. Results were obtained using initial conditions calculated from a subduction zone, inter-plate thrust fault geometry and a stochastic earthquake slip model. The effect of dynamical phase is most apparent when the initial amplitudes and frequencies of the three waves are within an order of magnitude. In this case, non-zero initial phase results in a marked decrease in energy exchange and a slight decrease in the period of the interaction. When there are large differences in frequency and/or initial amplitude, dynamical phase has less of an effect and typically one wave of the triad has very little energy exchange with the other two waves. Results from this study help elucidate under what conditions edge waves might be implicated in late, large-amplitude arrivals.

Fluid identification method and application of pre-stack and post-stack integration based on seismic low-frequency

Seismic low-frequency component included more fluid information, which was still a focus in geophysics. Seismic pre-stack data contained more fluid information, but signal to noise ratio (SNR) was low. By comparison, seismic post-stack data had a high SNR, but some fluid information was lost during data processing. Different angel stacks reflected different fluid seismic amplitude, compared with near-angle stacks. Far angle stacks had more low frequency components, which were more benefit for fluid identification. Based on this principle, combined with the pre-stacks and post-stacks seismic data, more fluid information would be included. In this study, a new fluid identification method was proposed. This method combined the post-stack seismic and pre-stack seismic data, it took into consideration high SNR of the post-stack seismic data and the large fluid amplitude differences of the pre-stack different angles. Field testing indicated this method was quite effective in detecting fluids.

Neural Correlates of the Binaural Masking Level Difference in Human Frequency-Following Responses.

The binaural masking level difference (BMLD) is an auditory phenomenon where binaural tone-in-noise detection is improved when the phase of either signal or noise is inverted in one of the ears (SπNo or SoNπ, respectively), relative to detection when signal and noise are in identical phase at each ear (SoNo). Processing related to BMLDs and interaural time differences has been confirmed in the auditory brainstem of non-human mammals; in the human auditory brainstem, phase-locked neural responses elicited by BMLD stimuli have not been systematically examined across signal-to-noise ratio. Behavioral and physiological testing was performed in three binaural stimulus conditions: SoNo, SπNo, and SoNπ. BMLDs at 500Hz were obtained from 14 young, normal-hearing adults (ages 21-26). Physiological BMLDs used the frequency-following response (FFR), a scalp-recorded auditory evoked potential dependent on sustained phase-locked neural activity; FFR tone-in-noise detection thresholds were used to calculate physiological BMLDs. FFR BMLDs were significantly smaller (poorer) than behavioral BMLDs, and FFR BMLDs did not reflect a physiological release from masking, on average. Raw FFR amplitude showed substantial reductions in the SπNo condition relative to SoNo and SoNπ conditions, consistent with negative effects of phase summation from left and right ear FFRs. FFR amplitude differences between stimulus conditions (e.g., SoNo amplitude-SπNo amplitude) were significantly predictive of behavioral SπNo BMLDs; individuals with larger amplitude differences had larger (better) behavioral B MLDs and individuals with smaller amplitude differences had smaller (poorer) behavioral B MLDs. These data indicate a role for sustained phase-locked neural activity in BMLDs of humans and are the first to show predictive relationships between behavioral BMLDs and human brainstem responses.

The 492 GHz emission of Sgr A* constrained by ALMA

We report linearly polarized continuum emission properties of Sgr A* at $\sim$492 GHz, based on the Atacama Large Millimeter Array (ALMA) observations. We used the observations of the likely unpolarized continuum emission of Titan, and the observations of C\textsc{i} line emission, to gauge the degree of spurious polarization. The Stokes I flux of 3.6$\pm$0.72 Jy during our run is consistent with extrapolations from the previous, lower frequency observations. We found that the continuum emission of Sgr A* at $\sim$492 GHz shows large amplitude differences between the XX and the YY correlations. The observed intensity ratio between the XX and YY correlations as a function of parallactic angle may be explained by a constant polarization position angle of $\sim$158$^{\circ}$$\pm$3$^{\circ}$. The fitted polarization percentage of Sgr A* during our observational period is 14\%$\pm$1.2\%. The calibrator quasar J1744-3116 we observed at the same night can be fitted to Stokes I = 252 mJy, with 7.9\%$\pm$0.9\% polarization in position angle P.A. = 4.1$^{\circ}$$\pm$4.2$^{\circ}$. The observed polarization percentage and polarization position angle in the present work appear consistent with those expected from longer wavelength observations in the period of 1999-2005. In particular, the polarization position angle at 492 GHz, expected from the previously fitted 167$^{\circ}$$\pm$7$^{\circ}$ intrinsic polarization position angle and (-5.6$\pm$0.7)$\times$10$^{5}$ rotation measure, is 155$^{+9}_{-8}$, which is consistent with our new measurement of polarization position angle within 1$\sigma$. The polarization percentage and the polarization position angle may be varying over the period of our ALMA 12m Array observations, which demands further investigation with future polarization observations.

Geophone-seabed coupling effect and its correction

By summing geophone and hydrophone data with opposite polarity responses to water layer reverberation, the ocean bottom cable dual-sensor acquisition technique can effectively eliminate reverberation, broaden the frequency bandwidth, and improve both the resolution and fidelity of the seismic data. It is thus widely used in industry. However, it is difficult to ensure good coupling of the geophones with the seabed because of the impact of ocean flow, seafloor topography, and field operations; therefore, geophone data are seriously affected by the transfer function of the geophone-seabed coupling system. As a result, geophone data frequently have low signal-to-noise ratios (S/N), which causes large differences in amplitude, frequency, and phases between geophone and hydrophone data that severely affect dual-sensor summation. In contrast, the hydrophone detects changes in brine pressure and has no coupling issues with the seabed; thus, hydrophone data always have good S/N. First, in this paper, the mathematical expression of the transfer function between geophone and seabed is presented. Second, the transfer function of the geophone-seabed is estimated using hydrophone data as reference traces, and finally, the coupling correction based on the estimated transfer function is implemented. Using this processing, the amplitude and phase differences between geophone and hydrophone data are removed, and the S/N of the geophone data are improved. Synthetic and real data examples then show that our method is feasible and practical.

Kinetic Mechanism of DNA Polymerization Catalyzed by Human DNA Polymerase ε

Eukaryotes require highly accurate and processive DNA polymerases to ensure faithful and efficient replication of their genomes. DNA polymerase ε (Polε) has been shown to catalyze leading-strand DNA synthesis during replication in vivo, but little is known about the kinetic mechanism of polymerization catalyzed by this replicative enzyme. To elucidate this mechanism, we have generated a truncated, exonuclease-deficient mutant of the catalytic subunit of human Polε (Polε exo-) and carried out pre-steady-state kinetic analysis of this enzyme. Our results show that Polε exo-, as other DNA polymerases, follows an induced-fit mechanism when catalyzing correct nucleotide incorporation. Polε exo- binds DNA with a Kd(DNA) of 79 nM and dissociates from the E·DNA binary complex with a rate constant of 0.021 s(-1). Although Polε exo- binds a correct incoming nucleotide weakly with a Kd(dTTP) of 31 μM, it catalyzes correct nucleotide incorporation at a fast rate constant of 248 s(-1) at 20 °C. Both a large reaction amplitude difference (42%) between pulse-chase and pulse-quench assays and a small elemental effect (0.9) for correct dTTP incorporation suggest that a slow conformational change preceding the chemistry step limits the rate of correct nucleotide incorporation. In addition, our kinetic analysis shows that Polε exo- exhibits low processivity during polymerization. To catalyze leading-strand synthesis in vivo, Polε likely interacts with its three smaller subunits and additional replication factors in order to assemble a replication complex and significantly enhance its polymerization processivity.

Characteristics of observed strong motion accelerograms from the 2011 Lorca (Spain) Earthquake

The Lorca earthquake (southeast Spain) on May 11, 2011; Mw 5.1, and its aftershocks, have provided an important set of accelerograms recorded by the strong motion network of the Instituto Geografico Nacional of Spain. It is particularly noticeable that the record obtained in Lorca town, very near of the fault rupture, presents a PGA value close to 0.37 g in the N30W component. This paper provides an overview of the strong motion data recorded during the Lorca seismic series, with particular attention to the accelerograms from the mainshock and foreshock and its characteristics. Due to the special circumstances of these two records, a more detailed processing has been required, in which various alternatives to adjust the baseline have been considered and analyzed. Based on this special processing, small residual displacements were obtained and reported in some of these cases. However, given the sensitivity of the process and the small obtained values, these findings should be taken with caution. Besides, response spectra have been analyzed and compared with design spectra proposed by the Spanish Seismic Code (NCSE-02) for the towns of Lorca, Alhama de Murcia and Mula. Large amplitude differences were observed in these spectra if compared to those recorded in Lorca. Also noteworthy is that the design spectra proposed for this town were exceeded by some horizontal directions of the response spectra.