GNSS technology holds significant importance across wide applications, ranging from mapping, surveying, and precise timekeeping to ship navigation. Its operational principle hinges on the accurate ...measurement of signal travel time, which is crucial for determining the distance between the GNSS satellite and the receiving device. However, the precision of GNSS positioning is often compromised due to various error sources that impact GNSS measurements. Among these sources, atmospheric effects are widely acknowledged as the primary contributors to spatially correlated inaccuracies in GNSS (Global Navigation Satellite System) measurements. The accuracy of zenith tropospheric delay (ZTD) and zenith wet delay (ZWD) prediction using an artificial neural network model was successfully demonstrated in this study. By combining data from GNSS observations and in-situ meteorological measurements, high-resolution water vapour data can be produced for reliable and accurate weather forecasting. The validation of the predictions revealed a mean standard deviation error of 5 mm and 3.6 mm for ZTD and ZWD, respectively. This study emphasizes the significance of estimating tropospheric wet delay in real-time weather forecasting applications.
Low-Cost Positioning Single Frequency Receivers (SFR) using Global Positioning Systems (GPS) can become a precise alternative to Dual Frequency Receivers (DFRs) in different applications. Ionospheric ...delay is one of the significant provenances of errors in GPS navigation and positioning. These blunders in both Phase range and pseudo range can differ according to the receiver location, solar cycle, time, and geomagnetic activity.
Some ground receivers over Egypt and Europe were regarded in This publication to examine various ionosphere correction products' capability. Data from IGS stations spanning various latitudes and solar activity times (high, medium, or small) are taken into account. The findings demonstrate that the sub-meter level's precision is obtainable using single-frequency data using suitable mitigation approaches for ionospheric impacts.
The implications for GNSS positioning (especially on horizontal precision) of ionospheric corrections have been studied. The findings demonstrate that all ionosphere corrections clearly enhance the accuracy of the vertical positions where the absolute vertical error is about 30 cm, 32.3 cm, and 57.2 cm for LIMs (Local Ionosphere Maps), GIMs (Global Ionosphere Maps), and BKP (Broadcasted Klobuchar Parameter). However, the horizontal enhancement is lower than the vertical, and even worse, the horizontal error can be increased with ionosphere correction. The horizontal error ranges from 2.7 to 51.8 cm by using LIMs, while ranges from 4.5 to 47.2 cm by using GIMs but the maximum horizontal error obtained by applying BKP, which ranges from 20.7 to 100.2 cm. In comparison, the north bias plays a vital role in reducing horizontal precision. If north bias were not resolved correctly with ionosphere corrections, the horizontal positioning efficiency would deteriorate.
The significant efficiency of mid-latitude Egyptian ionosphere correction (estimated by LIMs) in stormy and quiet geomagnetic environments rather than GIMs and BKP, 3D RMS error improved by 16 %, and GIMs up 63 %. Furthermore, in low solar activity, 3D RMS error improved 6% compared to GIMs and 87% compared to BKP.
This study directly compared outcomes of transcatheter aortic valve-in-valve insertion (TAVI-in-valve) with repeat surgical aortic valve replacement (SAVR) for failing stented aortic biological ...prostheses.
We retrospectively reviewed the records of 350 consecutive patients who underwent repeat aortic valve replacement of failing stented aortic biological valve prostheses at our institution between November 2008 and May 2018. Operations included TAVI-in-valve in 90 patients (26%) and repeat SAVR in 260 patients (74%).
Patient age was 74 years (interquartile range IQR, 65-79 years), 100 patients (29%) were women, aortic valve internal diameter was 21 mm (IQR, 19-22), Society of Thoracic Surgeons predicted operative mortality risk was 4.1% (IQR, 2.3%-6.8%), and the interval to repeat operation was 7 years (IQR, 5-11 years). A 23-mm or smaller valve was inserted in 57 patients (63%) in the TAVI-in-valve group and in 170 (65%) in the SAVR group (P = .725). Aortic root enlargement was done in 45 patients (17%) in the SAVR group. Procedure-related complications were less in the TAVI-in-valve group (23% vs SAVR 59%, P < .001), whereas operative mortality was similar in both groups (2.2% vs SAVR 2.6%, P = 1.000). Severe patient-to-prosthesis mismatch was more common after TAVI-in-valve (44% vs SAVR 12%, P < .001). Median duration of follow-up was 2.1 years (IQR, 1.2-4.2 years). Multivariable analysis demonstrated no association between TAVI-in-valve and intermediate-term mortality (hazard ratio, 1.18; 95% confidence interval, 0.62 to 2.22; P = .612).
TAVI-in-valve and repeat SAVR can be done with similar operative and intermediate-term mortality. SAVR results in better hemodynamic function and thus appears the preferred option.
Andexanet alfa was employed to reverse the anticoagulant effect of direct oral anticoagulants in 3 patients who required emergent surgery for repair of type A aortic dissection. Its use was ...instrumental in securing haemostasis. However, we caution against the administration of Andexanet alfa prior to cardiopulmonary bypass as it can induce heparin resistance and complicate the perioperative monitoring of anticoagulation during cardiopulmonary bypass.
Precise total electron content (TEC) is required to produce accurate spatial and temporal resolution of global ionosphere maps (GIMs). Receivers and satellite differential code biases (DCBs) are one ...of the main error sources in estimating precise TEC from Global Positioning System (GPS) data. Recently, researchers have been interested in developing models and algorithms to compute DCBs of receivers and satellites close to those computed from the Ionosphere Associated Analysis Centers (IAACs). Here we introduce a MATLAB code called Multi Station DCB Estimation (MSDCBE) to calculate satellite and receiver DCBs from GPS data. MSDCBE based on a spherical harmonic function and a geometry-free combination of GPS carrier-phase, pseudo-range code observations, and weighted least squares was applied to solve observation equations and to improve estimation of DCB values. There are many factors affecting the estimated values of DCBs. The first one is the observation weighting function which depends on the satellite elevation angle. The second factor is concerned with estimating DCBs using a single GPS station using the Zero Difference DCB Estimation (ZDDCBE) code or using the GPS network used by the MSDCBE code. The third factor is the number of GPS receivers in the network. Results from MSDCBE were evaluated and compared with data from IAACs and other codes like M_DCB and ZDDCBE. The results of weighted (MSDCBE) least squares show an improvement for estimated DCBs, where mean differences from the Center for Orbit Determination in Europe (CODE) (University of Bern, Switzerland) are less than 0.746 ns. DCBs estimated from the GPS network show better agreement with IAAC than DCBs estimated from precise point positioning (PPP), where the mean differences are less than 0.1477 and 1.1866 ns, respectively. The mean differences of computed DCBs improved by increasing the number of GPS stations in the network.
Published data are limited in comparison of transcatheter aortic valve replacement with surgical aortic valve replacement for the failing aortic root homograft. We reviewed our experience with repeat ...aortic valve replacement in failing aortic root homografts to compare outcomes of transcatheter aortic valve replacement and surgical aortic valve replacement.
We retrospectively reviewed the records of 51 patients with failing aortic root homografts who received repeat aortic valve replacement between October 2000 and May 2018. Operation included transcatheter aortic valve replacement in 11 patients between June 2014 and May 2018. Surgical aortic valve replacement was performed in 40 patients between October 2000 and January 2018, and operation included repeat composite aortic valve/root replacement in 30 patients (75%).
Patient age was 59 years (interquartile range, 50-72 years), sex was female in 9 patients (18%), and time to repeat aortic valve replacement was 12 years (interquartile range, 8-13). Procedure-related complications occurred in 37 patients (73%): vascular injury (any) more commonly in the transcatheter aortic valve replacement group (36% vs 5%; P = .015), bleeding (major or life-threatening) more commonly in the surgical aortic valve replacement group (58% vs 0%; P < .001), and sternal reentry injury only in the surgical aortic valve replacement group (n = 6, 15%). There were 3 procedure-related deaths in the surgical aortic valve replacement group (8%) and 1 (9%) in the transcatheter aortic valve replacement group (P = 1.000). Subsequent cardiac operation occurred in no patients in the transcatheter aortic valve replacement group and in 5 patients in the surgical aortic valve replacement group.
Repeat aortic valve replacement for failing aortic root homograft is associated with notable risk of morbidity and mortality regardless of replacement technique. Avoidance of vascular injury could lead to improved outcomes in the transcatheter aortic valve replacement group.
Various factors can increase ionosphere activity, such as the geomagnetic latitude, altitude, and geomagnetic storms. These storms can result in a significant disruption of the Earth’s atmosphere due ...to the interchange of solar wind energy into the milieu encompassing the Earth. The principal reason for this research is investigating the geomagnetic activity effect on ionospheric delays over Egypt using GPS (Global Positioning System) multi-frequency (
L
2
and
L
1
) measurements. In this contribution, a GPS network spread over Egypt was utilized to figure ionosphere errors over Egypt, utilizing two models that rely upon GPS observable linear combination and smoothed phase observables. An algorithm was coded in MATLAB® environment and was called the Ionosphere Error Estimation (IEE) program. GPS phase observables were considered in this investigation to avoid blunders from pseudo-range measurements. Data from six ground-based multi-frequency GPS receivers located over Egypt have been chosen to study the impact of geomagnetic storms on ionospheric blunders. This paper presents the consequences of ionospheric blunders during disturbed and quiet days throughout the years of 2013 and 2014. Results clarify that the applied models using unsmoothed and smoothed phase observables show a good agreement in estimating ionospheric blunders, especially in quiet days. Ionospheric blunder standard deviation of mean (SDM) results from using smoothed phase observables that ranges from 16 to 3 cm in quiet conditions and ranges from 21 to 8 cm in stormy conditions. While ionospheric blunder SDM ranges from 17 to 5 cm in quiet days and from 23 to 8 cm in stormy days using unsmoothed phase observables. In The maximum ionosphere delay estimated over stormy days using the unsmoothed phase observables, its magnitude was 13.19 m at ASWN while the highest ionosphere error at ASWN station in quiet days was 6.83 m. In the maximum ionosphere delay estimated over stormy days using the smoothed phase observables, its magnitude was 13.34 m at ALAM while the highest ionosphere error at ALAM station in quiet days was 4.94 m. Finally, geomagnetic storms represent a real problem in equatorial and high-latitude zones, which causes a significant influence on the ionosphere blunder, and they have the capability of upsetting the results.
This study aimed to measure and validate altitudes from existing sources with direct GNSS measurements and airborne lidar data. For this purpose, 12 mountain peaks located in the south part of Polish ...territory were selected. Measurements were performed using a GNSS receiver using the Real-Time Kinematic (RTK) or static techniques enabling altitude measurements with accuracy of 10 cm. GNSS was treated as the primary data source, as the direct field measurements can determine the highest point on each peak. The obtained results were confronted with historical, internet sources, and official altitude data. Moreover, each altitude was determined using lidar data from an airborne lidar dataset of Poland from the ISOK program and provided by the national agency. Significant discrepancies in data were already detected during the analysis of internet materials and traditional maps, up to a few meters. The differences between measured and internet sources in altitude of mountain peak range from 27 cm to 504 cm. This study has shown the need to re-measure the altitudes of the mountain peaks and determine the highest point correctly.
Low pathogenic avian influenza (LPAI) H9N2 virus is one of the major poultry pathogens associated with severe economic losses in the poultry industry (broiler, layers, breeders, and grandparents' ...flocks), especially in endemic regions including the Middle East, North Africa, and Asian countries. This work is an attempt to evaluate the efficacy of whole inactivated H9N2 vaccine (MEFLUVAC
H9) in turkey poults kept under laboratory and commercial farm conditions. Here, 10,000 white turkey poults (1-day old) free from maternally derived immunity against H9N2 virus were divided into four groups; G1 involved 10 vaccinated birds kept under biosafety level-3 (BLS-3) as a laboratory vaccinated and challenged group, while G2 had 9970 vaccinated turkeys raised on a commercial farm. Ten of those birds were moved to BLS-3 for daily cloacal and tracheal swabbing to check for the absence of any life-threating disease, before conducting analyses. G3 (10 birds) served as a non-vaccinated challenged control under BSL-3 conditions, while G4 (10 birds) was used as a non-vaccinated and non-challenged control under BSL-3 conditions. Sera were collected on days 7-, 14-, 21-, and 28-post-vaccinations to monitor the humoral immune response using a hemagglutination-inhibition (HI) test. At these same intervals, cloacal and tracheal swabs were also checked for any viral infection. The challenge was conducted 28 days post-vaccination (PV) using AI-H9N2 in BSL-3 by intranasal inoculation of 6-log10 embryo infective dose
(EID
). At 3-, 6-, and 10-days post-challenge, oropharyngeal swabs were taken from challenged birds to quantify viral shedding by quantitative polymerase chain reaction (qRT-PCR). The results of this study showed that vaccinated groups (G1/2) developed HI titers of 1.38, 4.38, 5.88, and 7.25 log
in G1 vs. 1.2, 3.8, 4.9 and 6.2 log
in G2 when measured at 7-, 14-, 21- and 28-days PV, respectively, while undetectable levels were recorded in non-vaccinated groups (G3/4). Birds in G3 showed 90% clinical sickness vs. 10% and 20% in G1/2, respectively, over a 10-day monitoring period following challenge. Vaccinated birds showed a significant reduction in virus shedding in terms of the number of shedders, amount of shed virus and shedding interval over the non-vaccinated challenged birds. Regarding mortality, all groups did not show any mortality, which confirms that the circulating H9N2 virus still has low pathogenicity and cannot cause mortality. However, the virus may cause up to 90% clinical sickness in non-vaccinated birds vs. 10% and 20% in laboratory- and farm-vaccinated birds, respectively, highlighting the role of the vaccine in limiting clinical sickness cases. In conclusion, under the current trial circumstances, MEFLUVAC
-H9 provided protective seroconversion titers, significant clinical sickness protection and significant reduction in virus shedding either in laboratory- or farm-vaccinated groups after a single vaccine dose.
Global Navigation Satellite Systems (GNSS) have many applications in surveying, geodesy, and everyday life, so the accuracy of observations is very important. To have accurate results, many errors ...should be corrected, including ionospheric errors. Estimating the Differential Code Bias (DCB) and Total Electron Content (TEC) is essential to reduce ionospheric errors. This study's main aim is to determine how the combination of GPS (Global Positioning System) and GLONASS (GLObal NAvigation Satellite System) observations affect the estimation of DCB of satellites (SDCB) and receivers (RDCB) under the effects of geomagnetic storms and seasonal changes. The MATLAB-based software GR_DCB (GPS and GLONASS DCB estimation) was developed to estimate the SDCB and RDCB based on GPS and GLONASS observations. Theresults were tested using data from the International GNSS Service (IGS) network from nine stations and compared to previous studies to assess the effectiveness of the developed code. The findings are consistent with IGS products and more precise than previous studies that relied solely on GPS observations. An analysis of the effects of the geomagnetic storm on DCB variance is considered for June 22–23, 2015. During the geomagnetic storm, all GPS and GLONASS stations exhibited a fall in RDCB, led by a modest increase in some stations. The SDCB had no observed change on storm days compared with quiet days. The seasonal change affected GPS and GLONASS stations RDCB. Winter, which has the highest RDCB mean values, is also the season when a deviation in RDCB is the greatest. Autumn and Summer had the lowest dispersion in RDCB over the season and the lowest RDCB values.
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