Seismic hazard assessment in active fault zones can benefit of strain rate measurements derived from geodetic data. Producing a continuous strain rate map from discrete data is an inverse problem ...traditionally tackled with standard interpolation schemes. Most algorithms require user‐defined regression parameters that determine the smoothness of the recovered velocity field and the amplitude of its spatial derivatives. This may lead to biases in the strain rates estimation which could eventually impact studies on earthquake hazard. Here we propose a transdimensional Bayesian method to estimate surface strain rates from Global Navigation Satellite System (GNSS) velocities. We parameterize the velocity field with a variable number of Delaunay triangles and use a reversible‐jump Monte‐Carlo Markov Chain algorithm to sample the probability distribution of surface velocities and spatial derivatives. The solution is a complete probability distribution function for each component of the strain rate field. We conduct synthetic tests and compare our approach to a standard b‐spline interpolation scheme. Our method is more resilient to data errors and uneven data distribution, while providing uncertainties associated with recovered velocities and strain rates. We apply our method to the Southwestern United States, an extensively studied and monitored area and infer probabilistic strain rates along the main fault systems, including the San Andreas one, from the inversion of interseismic GNSS velocities. Our approach provides a full description of the strain rate tensor for zones where strain rates are highly contrasted, with no need to manually tune user‐defined parameters. We recover sharp velocity gradients, without systematic artifacts.
Plain Language Summary
Mapping the amplitude, type and direction of crustal deformation is of great help to detect active faults and ultimately estimate seismic hazard. However, systematic biases remain in the standard methods used to produce continuous maps of the strain rate components from discrete observations such as Global Navigation Satellite System (GNSS) long‐term velocities. It is notably difficult to properly assert the uncertainties on the results. We propose a new method based on Bayesian inference to get the full probability distribution on the strain rate components. Proper uncertainties can therefore be attributed to these values that can be included correctly in seismic hazard assessment studies. We perform a synthetic test to compare this Bayesian method to a bicubic spline interpolation. We apply successfully this method to the California highly straining San Andreas system and neighboring Basin and Range.
Key Points
A Bayesian interpolation scheme is applied to derive strain rates from discrete geodetic horizontal velocities
Full probability density functions are provided for spatial derivatives of the 2D velocity field
Consistent estimates of strain rates are obtained without underlying physical model nor ad hoc smoothing parameter
Aims. We present a new measurement of the cosmic X-ray background (CXRB) in the 1.5-7 keV energy band, performed by exploiting the Swift X-ray telescope (XRT) data archive. We also present a ...CXRB spectral model in a wider energy band (1.5-200 keV), obtained by combining these data with the recently published Swift-BAT measurement. Methods. From the XRT archive we collect a complete sample of 126 high Galactic latitude gamma-ray burst (GRB) follow-up observations. This provides a total exposure of 7.5 Ms and a sky-coverage of ~7 square degrees which represents a serendipitous survey, well suited for a direct measurement of the CXRB in the 1.5-10 keV interval. Our work is based on a complete characterization of the instrumental background and an accurate measurement of the stray-light contamination and vignetting calibration. Results. We find that the CXRB spectrum in the 1.5-7 keV energy band can be equally well fitted by a single power-law with photon index $\Gamma=1.47\pm0.07$ or a single power-law with photon index $\Gamma=1.41\pm0.06$ and an exponential roll-off at 41 keV. The measured flux in the 2-10 keV energy band is $2.18 \pm0.13 \times10^{-11}$ erg cm-2 s-1 deg-2 in the 2-10 keV band. Combining Swift-XRT with Swift-BAT (15-200 keV) we find that, in the 1.5-200 keV band, the CXRB spectrum can be well described by two smoothly-joined power laws with the energy break at $29.0\pm0.5$ keV corresponding to a $\nu F_{\nu}$ peak located at $22.4\pm0.4$ keV. Conclusions. Taking advantage of both the Swift high energy instruments (XRT and BAT), we produce an analytical description of the CXRB spectrum over a wide (1.5-200 keV) energy band. This model is marginally consistent with the HEAO1 measurement (~10% higher) at energies higher than 20 keV, while it is significantly (30%) higher at low energies (2-10 keV).
Abstract
The ability of patients with hematologic malignancies (HM) to develop an effective humoral immune response after COVID-19 is unknown. A prospective study was performed to monitor the immune ...response to SARS-CoV-2 of patients with follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), chronic lymphoproliferative disorders (CLD), multiple myeloma (MM), or myelodysplastic/myeloproliferative syndromes (MDS/MPN). Antibody (Ab) levels to the SARS-CoV-2 nucleocapsid (N) and spike (S) protein were measured at +1, +3, +6 months after nasal swabs became PCR-negative. Forty-five patients (9 FL, 8 DLBCL, 8 CLD, 10 MM, 10 MDS/MPS) and 18 controls were studied. Mean anti-N and anti-S-Ab levels were similar between HM patients and controls, and shared the same behavior, with anti-N Ab levels declining at +6 months and anti-S-Ab remaining stable. Seroconversion rates were lower in HM patients than in controls. In lymphoma patients mean Ab levels and seroconversion rates were lower than in other HM patients, primarily because all nine patients who had received rituximab within 6 months before COVID-19 failed to produce anti-N and anti-S-Ab. Only one patient requiring hematological treatment after COVID-19 lost seropositivity after 6 months. No reinfections were observed. These results may inform vaccination policies and clinical management of HM patients.
GRB 090618 was an extremely bright burst, detected across the electromagnetic spectrum. It has a redshift of 0.54 and a supernova (SN) was identified in ground-based photometry. We present a thorough ...analysis of the prompt and early afterglow emission using data from Swift, Fermi Gamma-ray Burst Monitor and ROTSE, in which we track the evolution of the synchrotron spectral peak during the prompt emission and through the steep decay phase. We find evidence of a thermal X-ray component alongside the expected non-thermal power-law continuum. Such a component is rare among gamma-ray bursts (GRBs), with firm data for only GRBs 060218 and 100316D so far, and could potentially originate from an SN shock breakout, although there remains doubt regarding this explanation for any of the bursts. However, in contrast to these other Swift GRB-SNe with similar thermal signatures, GRB 090618 is a much more 'typical' burst: GRB-SNe 060218 and 100316D were both low-luminosity events, with long durations and low peak energies, while GRB 090618 was more representative of the wider population of long GRBs in all of these areas. It has been argued, based both on theory and observations, that most long GRBs should be accompanied by SNe. If this thermal X-ray component is related to the SN, its detection in GRB 090618, a fairly typical burst in many ways, may prove an important development in the study of the GRB-SN connection.
Abstract
We discuss a general method of constructing the products of composite operators using the exact renormalization group formalism. Considering mainly the Wilson action at a generic fixed point ...of the renormalization group, we give an argument for the validity of short-distance expansions of operator products. We show how to compute the expansion coefficients by solving differential equations, and test our method with some simple examples.
Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome of the collapse of massive stars and are typically found in the distant universe. Because of its intrinsic luminosity (L ~ 3 × 10⁵³ ...ergs per second) and its relative proximity (z = 0.34), GRB 130427A reached the highest fluence observed in the γ-ray band. Here, we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early universe and over the full range of GRB isotropie energies.
As the SARS-CoV-2 pandemic continues to rage worldwide, the emergence of numerous variants of concern (VOC) represents a challenge for the vaccinal protective efficacy and the reliability of ...commercially available high-throughput immunoassays. Our study demonstrates the administration of two doses of the BNT162b2 vaccine that elicited a robust SARS-CoV-2-specific immune response which was assessed up to 3 months after full vaccination in a cohort of 37 health care workers (HCWs). SARS-CoV-2-specific antibody response, evaluated by four commercially available chemiluminescence immunoassays (CLIA), was qualitatively consistent with the results provided by the gold-standard in vitro neutralization assay (NTA). However, we could not observe a correlation between the quantity of the antibody detected by CLIA assays and their neutralizing activity tested by NTA. Almost all subjects developed a SARS-CoV-2-specific T-cell response. Moreover, vaccinated HCWs developed a similar protective neutralizing antibodies response against the EU (B.1), Alpha (B.1.1.7), Gamma (P.1), and Eta (B.1.525) SARS-CoV-2 variants, while Beta (B.1.351) and Delta (B.1.617.2) strains displayed a consistent partial immune evasion. These results underline the importance of a solid vaccine-elicited immune response and a robust antibody titre. We believe that these relevant results should be taken into consideration in the definition of future vaccinal strategies.
Modal sensors and actuators working in closed loop enable to observe and control independently specific vibration modes, reducing the apparent dynamical complexity of the system and the necessary ...energy to control them. Modal sensors may be obtained by a properly designed weighted sum of the output signals of an array of sensors distributed on the host structure. Although some works found in the literature present techniques for designing and implementing modal filters based on a given array of sensors, the effect of the sensors’ distribution on the modal filter performance has received little attention. Recent studies have shown that some parameters, such as size, shape and location of the sensors, are very important for the performance of the resulting modal filters. This work presents a methodology for the design of semi-modal active vibration control of a rectangular plate using modal filters based on arrays of piezoelectric sensors. The geometric distribution of the array of piezoelectric sensors bonded to a rectangular plate is numerically optimized to improve the effectiveness and frequency range of a set of modal filters. An experimental implementation of the modal filters is carried out in order to validate their performance. It is shown that proper setup of weighting coefficients is an important requirement. Then, two simple control laws, namely direct velocity feedback and positive position feedback, using the modal filter output are designed and implemented. It is shown that modal filtering allows to effectively control selected vibration modes with quite simple signal processing requirements.
The 22 Month Swift-BAT All-Sky Hard X-ray Survey Tueller, J; Baumgartner, W. H; Markwardt, C. B ...
The Astrophysical journal. Supplement series,
02/2010, Volume:
186, Issue:
2
Journal Article
Abstract
Niobium superconductive radio frequency cavities (SRF cavities) are commonly employed in linear accelerator; very pure, clean, and smooth internal walls are required to make the cavity ...working properly and with a high Q factor. Typically, to achieve a suitable surface quality the SRF cavities are subjected to a surface treatment called Buffered Chemical Polish (BCP), the latter uses a strong concentrated acids mixture flowing through the cavity to chemically etch a thin niobium layer (∼250 μm). A viable way to understand and optimize the BCP process is by using computational fluid dynamic (CFD); however, the experimental validation of the numerical and physical models is required to confidently use CFD results. The aim of our work is to investigate the fluid dynamics of the BCP process by using the Particle Image Velocimetry (PIV) and the refractive index matching (RIM) techniques, and to provide data to validate CFD simulations. The paper describes and briefly analyse the experimental setup and the preliminary results achieved so far.
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