Evaluation of low cost, high sensitivity GNSS receivers based on the ISO RTK standards

ABSTRACT The emergence of single-frequency, navigation-type receivers capable to provide carrier phase data (the so-called high sensitivity carrier phase positioning) has been steadily growing over the recent years. The level of positioning accuracy obtained with navigation-type receivers has raised interest to various communities that use positioning information. Over the last years, various researchers have investigated the potential of high-sensitivity navigation-type receivers and antennas with analysis on their positioning performance in post-processing and RTK modes. Although the above efforts express valuable guidelines for the practical use of navigation-type receivers, they lack standardized test procedures. In addition, these procedures are not always easily tractable and the time and effort required to perform these are not insignificant. The main purpose of this study is evaluate the positioning performance of high-sensitivity carrier phase-based navigation receivers based on the official International Standards Organisation (ISO) specifications for real-time kinematic (RTK) GNSS geodetic receivers. A number of standardised experiments are described using as rover receiver the u-blox NEO-7P XXL bundle package that contains the NEO-7P module and the low-cost antenna Tallysman TW2410. Based on the ISO 17123 part 8 GNSS RTK standards, the experiments include a number of simplified and full test procedures in different observation periods and under varying satellite geometry. The results demonstrate the suitability of the u-blox NEO-7P XXL bundle package with the NEO-7P module for different accuracy levels of RTK positioning applications

Intradialytic Complement Activation Precedes the Development of Cardiovascular Events in Hemodialysis Patients

Background: Hemodialysis (HD) is a life-saving treatment for patients with end stage renal disease. However, HD patients have markedly increased rates of cardiovascular morbidity and mortality. Previously, a link between the complement system and cardiovascular events (CV-events) has been reported. In HD, systemic complement activation occurs due to blood-to-membrane interaction. We hypothesize that HD-induced complement activation together with inflammation and thrombosis are involved in the development of CV-events in these patients. Methods: HD patients were followed for the occurrence of CV-events during a maximum follow-up of 45 months. Plasma samples were collected from 55 patients at different time points during one HD session prior to follow-up. Plasma levels of mannose-binding lectin, properdin and C3d/C3 ratios were assessed by ELISA. In addition, levels of von Willebrand factor, TNF-α and IL-6/IL-10 ratios were determined. An ex-vivo model of HD was used to assess the effect of complement inhibition. Results: During median follow-up of 32 months, 17 participants developed CV-events. In the CV-event group, the C3d/C3-ratio sharply increased 30 min after the start of the HD session, while in the event-free group the ratio did not increase. In accordance, HD patients that developed a CV-event also had a sustained higher IL-6/IL-10-ratio during the first 60 min of the HD session, followed by a greater rise in TNF-α levels and von Willebrand factor at the end of the session. In the ex-vivo HD model, we found that complement activation contributed to the induction of TNF-α levels, IL-6/IL-10-ratio and levels of von Willebrand factor. Conclusions: In conclusion, these findings suggest that early intradialytic complement activation predominantly occurred in HD patients who develop a CV-event during follow-up. In addition, in these patients complement activation was accompanied by a pro-inflammatory and pro-thrombotic response. Experimental complement inhibition revealed that this reaction is secondary to complement activation. Therefore, our data suggests that HD-induced complement, inflammation and coagulation are involved in the increased CV risk of HD patients.info:eu-repo/semantics/publishedVersio

Characteristics of Nondisabled Older Patients Developing New Disability Associated with Medical Illnesses and Hospitalization

OBJECTIVE: To identify demographic, clinical, and biological characteristics of older nondisabled patients who develop new disability in basic activities of daily living (BADL) during medical illnesses requiring hospitalization. DESIGN: Longitudinal observational study. SETTING: Geriatric and Internal Medicine acute care units. PARTICIPANTS: Data are from 1,686 patients aged 65 and older who independent in BADL 2 weeks before hospital admission, enrolled in the 1998 survey of the Italian Group of Pharmacoepidemiology in the Elderly Study. MEASUREMENTS: Study outcome was new BADL disability at time of hospital discharge. Sociodemographic, functional status, and clinical characteristics were collected at hospital admission; acute and chronic conditions were classified according to the International Classification of Disease, ninth revision; fasting blood samples were obtained and processed with standard methods. RESULTS: At the time of hospital discharge 113 patients (6.7%) presented new BADL disability. Functional decline was strongly related to patients’ age and preadmission instrumental activities of daily living status. In a multivariate analysis, older age, nursing home residency, low body mass index, elevated erythrocyte sedimentation rate, acute stroke, high level of comorbidity expressed as Cumulative Illness Rating Scale score, polypharmacotherapy, cognitive decline, and history of fall in the previous year were independent and significant predictors of BADL disability. CONCLUSION: Several factors might contribute to loss of physical independence in hospitalized older persons. Preexisting conditions associated with the frailty syndrome, including physical and cognitive function, comorbidity, body composition, and inflammatory markers, characterize patients at high risk of functional decline

Geospatial techniques of determination of foreshore zone - backshore zone and old foreshore zone

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Γεωπληροφορική

Endothelial role in cardiovascular instability in patients undergoing chronic hemodialysis treatment

Hemodynamic instability observed in patients undergoing chronic hemodialysis treatment is characterized by inadequate control of arterial hypertension, whilst hypotensive episodes are very common, appearing in 30-40% of these patients. The role of substances, like NO and ET-1, is to ensure that vascular tone can be preserved and arterial pressure variations, frequently seen in hemodialysis session. Based in our findings, we conclude that: 1) patients with pre-dialysis renal disease endothelial dysfunction 2) alteration of endothelial normal activity in the regulation of vascular tone, by the production of vasoactive agents, is accompanied by hemodynamic disorders during and after hemodialysis session expressed by symptomatic hypotensive episodes 3) endothelial dysfunction due to alteration of hemostatic factors, expressed by the appearance of various vascular incidents, more often by thrombotic episodes.Η αιμοδυναμική αστάθεια των ασθενών που υποβάλλονται σε χρόνια αιμοκάθαρση χαρακτηρίζεται από τον ανεπαρκή έλεγχο της αρτηριακής υπέρτασης, ενώ τα υποτασικά επεισόδια φτάνουν στο 30-40% των αιμοκαθαιρόμενων ασθενών. Ο ρόλος του ενδοθηλίου στην αιμοδυναμική συμπεριφορά των ασθενών αυτών είναι πολύ σημαντικός και συμβάλλει καθοριστικά στην καρδιοαγγειακή ομοιόσταση με τη σύνθεση ισχυρών αγγειοδραστικών ουσιών. Ο ρόλος του μονοξειδίου του αζώτου και της ενδοθηλίνης είναι να διασφαλίζεται η ομαλή αγγειοκινητική λειτουργία του οργανισμού, ώστε να δύναται να ανταποκριθεί στη διατήρηση του αγγειακού τόνου στην αποκατάσταση των αυξομειώσεων της αρτηριακής πίεσης. Συμπερασματικά: 1) ασθενείς με ΧΝΑ προτελικού ή τελικού-αιμοκαθαιρόμενοι εμφανίζουν δυσλειτουργία του ενδοθηλίου 2) η μεταβολή της φυσιολογικής δραστηριότητας του ενδοθηλίου στη ρύθμιση του αγγειακού τόνου συνοδεύεται από αιμοδυναμικές μεταβολές με συμπτωματικά επεισόδια υπότασης 3) η δυσλειτουργία του ενδοθηλίου διαταράσσει και το μηχανισμό αιμόστασης

Synchronous Surgical Treatment of Lower Eyelid Involutional Entropion and Ptosis

Background. Involutional entropion and upper eyelid ptosis are common eyelid diseases in the elderly population. They represent a frequent cause of discomfort and often result in significant visual and functional impairment. The surgical management of these disorders includes various treatment options and techniques and is usually carried out in multiple time sessions. Case Report. We report the case of a 72 year old female patient, suffering from right eye involutional lower eyelid entropion and ptosis, who was treated synchronously for both conditions, by applying the lateral tarsal strip procedure and the levator resection technique. Conclusion. The synchronous treatment of involutional entropion and ptosis is an alternative treatment strategy, which could potentially improve surgical outcome, while reducing postoperative recovery time and treatment costs

Compliance of low-cost, single-frequency GNSS receivers to standards consistent with ISO for control surveying

The emergence of single-frequency, navigation-type Global Navigation Satellite System receivers capable to provide carrier phase data [the so-called high sensitivity (HS) carrier phase positioning] has been steadily growing over the recent years. The main purpose of this study is to metrologically evaluate two low-cost, HS receivers, namely the u-blox LEA-6T and NEO-7P, in control surveying specifications. The evaluation was carried out within a published framework of standards and associated guidelines that are consistent with  standards from the International Standards Organisation. The survey results were obtained from sufficient independent testing and proof and achieved an accuracy classification of ‘1 cm’ at 95% confidence level. This indicates that the particular type of receiver used with geodetic antennas can provide positioning results for general purpose control surveying applications that are comparable to using geodetic receivers and with a significantly lower cost

Evaluation of low cost GNSS receivers based on the ISO RTK standards Evaluation of low cost GNSS receivers based on ISO RTK standards

SUMMARY The emergence of single-frequency, navigation-type receivers capable to provide carrier phase data (the so-called high sensitivity carrier phase positioning) has been steadily growing over the recent years. The level of positioning accuracy obtained with navigation-type receivers has raised interest to various communities that use positioning information. Over the last years, various researchers have investigated the potential of high-sensitivity navigation-type receivers and antennas with analysis on their positioning performance in postprocessing and RTK modes. Although the above efforts express valuable guidelines for the practical use of navigation-type receivers, they lack standardized test procedures. In addition, these procedures are not always easily tractable and the time and effort required to perform these are not insignificant. The main purpose of this study is evaluate the performance of high-sensitivity carrier phasebased positioning using navigation-type equipment based on the official International Standards Organisation (ISO) specifications for real-time kinematic (RTK) GNSS receivers. A number of standardised experiments will be described using as rover receiver the u-blox NEO-7P XXL bundle package that contains the NEO-7P module and the low-cost antenna Tallysman TW2410. Based on the ISO 17123 part 8 GNSS RTK standards, the experiments include a number of simplified and full test procedures in different observation periods and under varying satellite geometry. The results demonstrate the suitability of the u-blox NEO-7P XXL bundle package with the NEO-7P module for different type positioning applications