2,264 research outputs found

    Cooperative Simultaneous Localization and Synchronization in Mobile Agent Networks

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    Cooperative localization in agent networks based on interagent time-of-flight measurements is closely related to synchronization. To leverage this relation, we propose a Bayesian factor graph framework for cooperative simultaneous localization and synchronization (CoSLAS). This framework is suited to mobile agents and time-varying local clock parameters. Building on the CoSLAS factor graph, we develop a distributed (decentralized) belief propagation algorithm for CoSLAS in the practically important case of an affine clock model and asymmetric time stamping. Our algorithm allows for real-time operation and is suitable for a time-varying network connectivity. To achieve high accuracy at reduced complexity and communication cost, the algorithm combines particle implementations with parametric message representations and takes advantage of a conditional independence property. Simulation results demonstrate the good performance of the proposed algorithm in a challenging scenario with time-varying network connectivity.Comment: 13 pages, 6 figures, 3 tables; manuscript submitted to IEEE Transaction on Signal Processin

    Equal Efficacy of Glucoprotamin and an Aldehyde Product for Environmental Disinfection in a Hematologic Transplant Unit: A Prospective Crossover Trial

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    Background. The inanimate hospital environment has emerged as an important reservoir of nosocomial pathogens. In particular, multidrug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus, Acinetobacter species, and Clostridium difficile, play a major role in the transmission of hospital-acquired infections. In Europe, aldehydes, chlorine, and quaternary ammonium compounds have been commonly used for environmental disinfection. Glucoprotamin, a newer active compound for disinfectants, has been clinically tested for disinfection of instruments but not for environmental disinfection. Objective. This study evaluated the antimicrobial effectiveness of a glucoprotamin-containing product (Incidin) compared with that of an aldehyde-containing product (Deconex), the current standard at our institution. Methods. This prospective crossover study was conducted in our access-restricted hematologic transplant unit. A total of 3,086 samples from the environment were processed and examined for overall bacterial burden as well as selectively for S. aureus, C. difficile, and gram-negative bacteria. Results. There was no significant difference in residual bacteria after disinfection between the 2 products in terms of overall burden and selected pathogens. Enterococci were the predominant pathogens recovered from surfaces, but no vancomycin-resistant enterococci were recovered. Similarly, C. difficile could not be found in the patients' environment, even in rooms, despite the use of selective media. Conclusion. The aldehyde-containing product (Deconex) and the glucoprotamin-containing product (Incidin) demonstrated similar efficacy against environmental contamination in a hematologic transplant unit with the application of selective media for C. difficile, S. aureus, and gram-negative bacteria in addition to standard mediu

    Incidence and predictors of immediate complications following perioperative non-obstetric epidural punctures

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    Background: Epidural Anesthesia (EA) is a well-established procedure. The aim of the present study was to evaluate the incidence of immediate complications following epidural puncture, such as sanguineous puncture, accidental dural perforation, unsuccessful catheter placement or insufficient analgesia and to identify patient and maneuver related risk factors. Methods: A total of 7958 non-obstetrical EA were analyzed. The risk of each complication was calculated according to the preconditions and the level of puncture. For probabilistic evaluation we used a logistic regression model with forward selection. Results: The risk of sanguineous puncture (n = 247, 3.1%) increases with both the patient's age (P = 0.013) and the more caudal the approach (P &lt; 0.01). Dural perforation (n = 123, 1.6%) was found to be influenced only by advanced age (P = 0.019). Unsuccessful catheter placement (n = 68, 0.94%) occurred more often in smaller individuals (P < 0.001) and at lower lumbar sites (P < 0.01). Amongst all cases with successful catheter placement a (partial) insufficient analgesia was found in 692 cases (8.8%). This risk of insufficient analgesia decreased with patient's age (P < 0.01), being least likely for punctures of the lower thoracic spine (P < 0.001). Conclusions: Compared to more cranial levels, EA of the lower spine is associated with an increased risk of sanguineous and unsuccessful puncture. Insufficient analgesia more often accompanies high thoracic and low lumbar approaches. The risk of a sanguineous puncture increases in elderly patients. Gender, weight and body mass index seem to have no influence on the investigated complications

    Incidence and predictors of immediate complications following perioperative non-obstetric epidural punctures

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    Background: Epidural Anesthesia (EA) is a well-established procedure. The aim of the present study was to evaluate the incidence of immediate complications following epidural puncture, such as sanguineous puncture, accidental dural perforation, unsuccessful catheter placement or insufficient analgesia and to identify patient and maneuver related risk factors. Methods: A total of 7958 non-obstetrical EA were analyzed. The risk of each complication was calculated according to the preconditions and the level of puncture. For probabilistic evaluation we used a logistic regression model with forward selection. Results: The risk of sanguineous puncture (n = 247, 3.1%) increases with both the patient's age (P = 0.013) and the more caudal the approach (P &lt; 0.01). Dural perforation (n = 123, 1.6%) was found to be influenced only by advanced age (P = 0.019). Unsuccessful catheter placement (n = 68, 0.94%) occurred more often in smaller individuals (P < 0.001) and at lower lumbar sites (P < 0.01). Amongst all cases with successful catheter placement a (partial) insufficient analgesia was found in 692 cases (8.8%). This risk of insufficient analgesia decreased with patient's age (P < 0.01), being least likely for punctures of the lower thoracic spine (P < 0.001). Conclusions: Compared to more cranial levels, EA of the lower spine is associated with an increased risk of sanguineous and unsuccessful puncture. Insufficient analgesia more often accompanies high thoracic and low lumbar approaches. The risk of a sanguineous puncture increases in elderly patients. Gender, weight and body mass index seem to have no influence on the investigated complications

    Noise Reduction for Single-Shot Grating-Based Phase-Contrast Imaging at an X-ray Backlighter

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    X-ray backlighters allow the capture of sharp images of fast dynamic processes due to extremely short exposure times. Moiré imaging enables simultaneously measuring the absorption and differential phase-contrast (DPC) of these processes. Acquiring images with one single shot limits the X-ray photon flux, which can result in noisy images. Increasing the photon statistics by repeating the experiment to gain the same image is not possible if the investigated processes are dynamic and chaotic. Furthermore, to reconstruct the DPC and transmission image, an additional measurement captured in absence of the object is required. For these reference measurements, shot-to-shot fluctuations in X-ray spectra and a source position complicate the averaging of several reference images for noise reduction. Here, two approaches of processing multiple reference images in combination with one single object image are evaluated regarding the image quality. We found that with only five reference images, the contrast-to-noise ratio can be improved by approximately 13% in the DPC image. This promises improvements for short-exposure single-shot acquisitions of rapid processes, such as laser-produced plasma shock-waves in high-energy density experiments at backlighter X-ray sources such as the PHELIX high-power laser facility

    Conservative or surgical treatment of pyogenic spinal infection: a retrospective multicenter binational retrospective cohort study [Abstract]

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    Spinal Tumors / Infections (Spine Parallel Session v.3), September 27, 2023, 8:30 AM - 10:00 AM Background: The optimal treatment of patients with spinal infections remains a controversial topic. While there is some consensus regarding the indication for surgical intervention in infections with neurologic deficit, significant deformity or progressive disease, other situations remain controversial. Within Europe, fundamentally different therapeutic concepts are found. Therefore, the aim of this study was to compare the outcome of patients who received surgical vs. antibiotic treatment alone for primary pyogenic spondylodiscitis in an international cohort analysis. Methods: The retrospectively compiled databases of tertiary high-volume spine centers served as the baseline for this study. All documented cases of primary spondylodiscitis treated surgically and conservatively in the period of 2017-2022 were included and grouped according to the therapeutic concept: conservative vs. surgical treatment. Independent investigators collected the relevant clinical and radiological data. The primary endpoint of this study was mortality rate; secondary endpoints were relapse rate and persisting neurological deficit. Results: A total of 392 patients were included in the analysis (155 females and 237 males with a mean age of 68 years). Of these, 95 cases were treated conservatively (CoT) and 297 cases were treated surgically (SuT). Most of conservatively treated patients were treated in the United Kingdom (CoT 81/ SuT 7), while most of the surgically treated cases were treated in Germany (CoT 14/ SuT 290). There was no significant difference (p<0.01) related to patient’s disease characteristics: Lumbar was the main location (n=240, CoT 58/ SuT 182, p=0.97) followed by thoracic (n=70, CoT 24/ SuT 46, p=0,03) and cervical (n=47, CoT 7/ SuT 40, p=0.11) region. A multilocular spinal infection was present in 32 patients (CoT 3/ SuT 29, p=0.04). 181 cases (CoT 36/ SuT 145, p=0.06) presented with an epidural abscess. Neurological deficits were recorded in 100 cases (CoT 26/ SuT 74, p=0.63), and septic conditions in 88 cases (CoT 26/ SuT 62, p=0.19). Pre-existing conditions like Diabetes (CoT 20/, SuT 71, p=0.57), renal failure (CoT 19/ SuT 60, p= 0.97), hepatopathy (CoT 4/ SuT 26, p= 0.15), malignoma (CoT 9/ SuT 38, p=0.39) or i.v. drug abuse (CoT 5/, SuT 15, p=0.93) did also not differ between the groups. The mortality rate of all conservatively treated was 24.2% (23 cases) and 6.7% (20 cases) in all surgically treated patients (p<0.001). A follow-up of ≥ 6 weeks was available in 289 cases (CoT 83, SuT 206 ). In this subset of patients relapse of infection occurred in six (7.2%) and 23 (11.2%) cases in the conservative and early surgical treatment group, respectively (p=0.69). Persisting neurological deficit was recorded in 21 (25.3%) of conservatively treated and 51 (24.8%) of surgically treated cases (p=0.92). Conclusions: Whereas relapse rates and persisting neurological deficit were not found to differ significantly, the results of this international data analyses, with their respective limitations, clearly support the growing evidence of a significantly reduced mortality rate after surgical therapy for primary pyogenic spondylodiscitis when compared to conservative treatment regimen

    Single-exposure X-ray phase imaging microscopy with a grating interferometer

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    The advent of hard X-ray free-electron lasers enables nanoscopic X-ray imaging with sub-picosecond temporal resolution. X-ray grating interferometry offers a phase-sensitive full-field imaging technique where the phase retrieval can be carried out from a single exposure alone. Thus, the method is attractive for imaging applications at X-ray free-electron lasers where intrinsic pulse-to-pulse fluctuations pose a major challenge. In this work, the single-exposure phase imaging capabilities of grating interferometry are characterized by an implementation at the I13-1 beamline of Diamond Light Source (Oxfordshire, UK). For comparison purposes, propagation-based phase contrast imaging was also performed at the same instrument. The characterization is carried out in terms of the quantitativeness and the contrast-to-noise ratio of the phase reconstructions as well as via the achievable spatial resolution. By using a statistical image reconstruction scheme, previous limitations of grating interferometry regarding the spatial resolution can be mitigated as well as the experimental applicability of the technique

    Opportunities and Alternatives of Modern Radiation Oncology and Surgery for the Management of Resectable Brain Metastases.

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    Postsurgical radiotherapy (RT) has been early proven to prevent local tumor recurrence, initially performed with whole brain RT (WBRT). Subsequent to disadvantageous cognitive sequalae for the patient and the broad distribution of modern linear accelerators, focal irradiation of the tumor has omitted WBRT in most cases. In many studies, the effectiveness of local RT of the resection cavity, either as single-fraction stereotactic radiosurgery (SRS) or hypo-fractionated stereotactic RT (hFSRT), has been demonstrated to be effective and safe. However, whereas prospective high-level incidence is still lacking on which dose and fractionation scheme is the best choice for the patient, further ablative techniques have come into play. Neoadjuvant SRS (N-SRS) prior to resection combines straightforward target delineation with an accelerated post-surgical phase, allowing an earlier start of systemic treatment or rehabilitation as indicated. In addition, low-energy intraoperative RT (IORT) on the surgical bed has been introduced as another alternative to external beam RT, offering sterilization of the cavity surface with steep dose gradients towards the healthy brain. This consensus paper summarizes current local treatment strategies for resectable brain metastases regarding available data and patient-centered decision-making
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