Search

Introduction: Central venous access plays a crucial role in various clinical settings, and ultrasound guidance has become increasingly popular for improving its safety and success rates. The aim of this meta‐analysis was to compare the short‐axis (SAX) and long‐axis (LAX) ultrasound‐guided techniques for internal jugular vein (IJV) cannulation in terms of first needle pass success rate, number of cannulation attempts, access time, guidewire insertion time, posterior IJV wall puncture, arterial puncture, haematoma and catheter‐related bloodstream infection. Methods: A comprehensive literature search was conducted, and randomised controlled trials (RCTs) comparing SAX and LAX techniques for IJV cannulation on adults were included. Results: A total of 11 RCTs involving 1183 patients were included in the meta‐analysis. The SAX technique demonstrated a significantly greater first needle pass success rate and faster IJV access time compared to the LAX technique. However, more posterior IJV wall puncture was significantly associated with the SAX technique. There was no significant difference between the two techniques in terms of number of cannulation attempts, guidewire insertion time, arterial puncture, haematoma and catheter‐related bloodstream infection. Conclusion: This meta‐analysis suggests that the SAX technique may have advantages over the LAX technique in terms of first needle pass success rate and potentially reducing cannulation attempts and access time. However, the occurrence of posterior IJV wall puncture raises concerns. The decision on the choice of technique should be based on individual patient factors and operator proficiency. [ABSTRACT FROM AUTHOR]

Approximate images of the earth's subsurface structures are usually obtained by migrating surface seismic data. Least-squares migration, under the single-scattering assumption, is used as an iterative linearized inversion scheme to suppress migration artifacts, deconvolve the source signature, mitigate the acquisition fingerprint, and enhance the spatial resolution of migrated images. The problem with least-squares migration of primaries, however, is that it may not be able to enhance events that are mainly illuminated by internal multiples, such as vertical and nearly vertical faults or salt flanks. To alleviate this problem, we adopted a linearized inversion framework to migrate internally scattered energy. We apply the least-squares migration of first-order internal multiples to image subsurface vertical fault planes. Tests on synthetic data demonstrated the ability of the proposed method to resolve vertical fault planes, which are poorly illuminated by the least-squares migration of primaries only. The proposed scheme is robust in the presence of white Gaussian observational noise and in the case of imaging the fault planes using inaccurate migration velocities. Our results suggested that the proposed least-squares imaging, under the double-scattering assumption, still retrieved the vertical fault planes when imaging the scattered data despite a slight defocusing of these events due to the presence of noise or velocity errors. [ABSTRACT FROM AUTHOR]

Vimentin is a major intermediate filament protein in vascular endothelial cells which might be involved in their function as a barrier tissue. It is proposed to dynamically maintain integrity of the endothelium as a tightly regulated permeability barrier that is subjected to a variety of shear and contractile forces. The results described in this report demonstrate that vimentin plays that role through mechanisms that are dependent on its phosphorylation state. Withaferin A (WFA), a vimentin targeting drug is shown to disrupt endothelial barrier function through its effects on vimentin filament distribution and physical properties. These effects are related to WFA's ability to increase vimentin phosphorylation. Through overexpressing a non-phosphorylatable vimentin mutant we can block the effects of WFA on vimentin distribution and barrier permeability. The barrier augmentation effect appears to extend to endothelial cells that do not express detectable mutant vimentin which might suggest transmissible effects across cells. Blocking vimentin phosphorylation also protects the endothelial barrier against LPS endotoxin, implicating it as a target for drug development against pulmonary edema and acute respiratory distress syndrome (ARDS). J. Cell. Physiol. 229: 1484-1493, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

An approximate subsurface reflectivity distribution of the earth is usually obtained through the migration process. However, conventional migration algorithms, including those based on the least-squares approach, yield structure descriptions that are slightly smeared and of low resolution caused by the common migration artifacts due to limited aperture, coarse sampling, band-limited source, and low subsurface illumination. To alleviate this problem, we use the fact that minimizing the L1-norm of a signal promotes its sparsity. Thus, we formulated the Kirchhoff migration problem as a compressed-sensing (CS) basis pursuit denoise problem to solve for highly focused migrated images compared with those obtained by standard and least-squares migration algorithms. The results of various subsurface reflectivity models revealed that solutions computed using the CS based migration provide a more accurate subsurface reflectivity location and amplitude. We applied the CS algorithm to image synthetic data from a fault model using dense and sparse acquisition geometries. Our results suggest that the proposed approach may still provide highly resolved images with a relatively small number of measurements. We also evaluated the robustness of the basis pursuit denoise algorithm in the presence of Gaussian random observational noise and in the case of imaging the recorded data with inaccurate migration velocities. [ABSTRACT FROM AUTHOR]

The initial quantification of data quality is an important step in seismic data acquisition design, including the choice of sensing strategy. The signal-to-noise ratio (SNR) often drives the choice of distributed acoustic sensing (DAS) parameters in vertical seismic profiling (VSP). We compare this established approach for data quality assessment with metrics comparing DAS data products to available well logs. First, we create kinematic and dynamic data products derived from original seismic data, such as the interval velocity and amplitude of P-wave arrivals. Next, we quantify the quality of derived data products using well log data by calculating various statistical metrics. Using a large dataset of 220 different VSP experiments with a fixed source location and various DAS acquisition parameters, such as gauge length (GL), conveyance type, and lead-in length, we analyzed the statistical distribution of various metrics. The results indicate the decoupling between seismic-based and log-based metrics as well as between the quality of dynamic and kinematic data-products for the same record. Therefore, we propose using fit-for-purpose metrics to optimize the acquisition cost. In particular, for ray-based tomographic processing, it is sufficient to use traveltime-based metrics. On the other hand, for advanced dynamic analysis, amplitude-based metrics define the quality of final processing products. Hence, it is crucial to use fit-for-purpose metrics to optimize DAS VSP acquisition. [ABSTRACT FROM AUTHOR]

A storage/retrieval scheme has been implemented for a Stochastic Reactor Model (SRM) for Homogeneous Charge Compression Ignition (HCCI) engines which enables fast evaluation in transient multi-cycle simulations. The SRM models combustion, turbulent mixing, and convective heat transfer during the closed-volume part of the engine cycle employing detailed chemical kinetics. In contrast to previously developed storage/retrieval techniques which tabulate chemistry only, our method stores, retrieves, and interpolates output quantities of the entire internal combustion engine model, i.e. the SRM. These quantities include ignition timing, cumulative heat release, maximum pressure rise rate, and emissions of CO, CO2, unburnt hydrocarbons, and NOx, as functions of equivalence ratio, octane number, and inlet temperature for instance. The new tool is intended to be used for performing a variety of otherwise exceedingly expensive computational tasks such as multi-cycle multi-cylinder simulations, transient operation and control, optimization of engine operating parameters, design of experiments, and identification of parameters for achieving stable HCCI operation over a wide range of conditions. Using transient control as an example, we show that, when coupled to a commercial 1D CFD engine modelling package, the tabulation scheme makes such simulations feasible and convenient. [ABSTRACT FROM AUTHOR]