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Modern satellites of Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflector arrays for Satellite Laser Ranging (SLR). Laser range observations to GNSS satellites allow for the co‐location of two space geodetic techniques onboard navigation satellites. We search for the best network constraining strategy for the SLR and GNSS stations to realize the geodetic datum using combined microwave‐GNSS and SLR‐to‐GNSS measurements. We find that consistent imposing of no‐net‐translation and no‐net‐rotation for the unified GNSS and SLR network provides the best quality of station coordinates and the best common realization of the terrestrial reference frame (TRF). We employ the space ties using solely space geodetic techniques for the SLR and GNSS station coordinates and confront them with the ground‐based measurements, that is, local ties, conducted at the SLR‐GNSS co‐located sites. The common processing of the GNSS and SLR observations allows for the realization of the TRF using space ties that are independent of the a priori coordinates and independent of the errors in local tie measurements. The agreement of space ties with ground measurements is at the level of 1 mm in terms of long‐term mean values for the co‐located station in Zimmerwald, Switzerland. We also revise the approach for handling the SLR range biases which now considers the impact of the SLR observations to GNSS and LAGEOS satellites. The updated SLR range biases improve the agreement between space ties and local ties from 4.4 to 2.4 mm for the co‐located station in Wettzell, Germany. Plain Language Summary: Every natural phenomenon observed in the Earth system demands a stable and accurate terrestrial reference frame (TRF). Currently, TRF is resolved by a combination of observations provided solely by space techniques, that is, Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). All the techniques are treated separately in the current realization of the International Terrestrial Reference Frame (ITRF2014), and a linkage between the observing stations of each technique is resolved by ground measurements as the so‐called "local ties" which cannot be obtained operationally. However, newly developed satellites of GNSS systems are equipped with laser retroreflectors for the SLR technique. As a result, the GNSS satellites comprise a platform for the integration of two techniques onboard navigation spacecraft in space. This study provides the first‐ever results of co‐location onboard navigation satellites of the Galileo and GLONASS systems. The new linkage between the GNSS and SLR techniques called "space tie" is consistent with local ties at the level of 1 mm and can be provided whenever GNSS and SLR data are available enabling, therefore, the realization of TRF in space on the operational basis. Key Points: Co‐location of Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS) space techniques onboard navigation satellites enables the realization of a terrestrial reference frame in spaceSpace ties computed using GNSS and SLR observations indicate a 1‐mm consistency with local ties for co‐located SLR and GNSS stationsDifferent methods of the handling of SLR range biases lead to different realizations of the terrestrial reference frame origin and scale [ABSTRACT FROM AUTHOR]

The first pair of satellites belonging to the European Global Navigation Satellite System (GNSS)—Galileo—has been accidentally launched into highly eccentric, instead of circular, orbits. The final height of these two satellites varies between 17,180 and 26,020 km, making these satellites very suitable for the verification of the effects emerging from general relativity. We employ the post-Newtonian parameterization (PPN) for describing the perturbations acting on Keplerian orbit parameters of artificial Earth satellites caused by the Schwarzschild, Lense–Thirring, and de Sitter general relativity effects. The values emerging from PPN numerical simulations are compared with the approximations based on the Gaussian perturbations for the temporal variations of the Keplerian elements of Galileo satellites in nominal, near-circular orbits, as well as in the highly elliptical orbits. We discuss what kinds of perturbations are detectable using the current accuracy of precise orbit determination of artificial Earth satellites, including the expected secular and periodic variations, as well as the constant offsets of Keplerian parameters. We found that not only secular but also periodic variations of orbit parameters caused by general relativity effects exceed the value of 1 cm within 24 h; thus, they should be fully detectable using the current GNSS precise orbit determination methods. Many of the 1-PPN effects are detectable using the Galileo satellite system, but the Lense–Thirring effect is not. [ABSTRACT FROM AUTHOR]

The Satellite Laser Ranging (SLR) network struggles with some major limitations including an inhomogeneous global station distribution and uneven performance of SLR sites. The International Laser Ranging Service (ILRS) prepares the time-variable list of the most well-performing stations denoted as 'core sites' and recommends using them for the terrestrial reference frame (TRF) datum realization in SLR processing. Here, we check how different approaches of the TRF datum realization using minimum constraint conditions (MCs) and the selection of datum-defining stations affect the estimated SLR station coordinates, the terrestrial scale, Earth rotation parameters (ERPs), and geocenter coordinates (GCC). The analyses are based on the processing of the SLR observations to LAGEOS-1/-2 collected between 2010 and 2018. We show that it is essential to reject outlying stations from the reference frame realization to maintain a high quality of SLR-based products. We test station selection criteria based on the Helmert transformation of the network w.r.t. the a priori SLRF2014 coordinates to reject misbehaving stations from the list of datum-defining stations. The 25 mm threshold is optimal to eliminate the epoch-wise temporal deviations and to provide a proper number of datum-defining stations. According to the station selection algorithm, we found that some of the stations that are not included in the list of ILRS core sites could be taken into account as potential core stations in the TRF datum realization. When using a robust station selection for the datum definition, we can improve the station coordinate repeatability by 8%, 4%, and 6%, for the North, East and Up components, respectively. The global distribution of datum-defining stations is also crucial for the estimation of ERPs and GCC. When excluding just two core stations from the SLR network, the amplitude of the annual signal in the GCC estimates is changed by up to 2.2 mm, and the noise of the estimated pole coordinates is substantially increased. [ABSTRACT FROM AUTHOR]

Both, the network configuration and the way of terrestrial reference frame (TRF) realization, affect the global geodetic products delivered from the Global Navigation Satellite Systems (GNSS) data processing. The purpose of this study is to analyze the differences in GNSS products, such as station coordinates, Earth rotation parameters, geocenter coordinates (GCC), and satellite orbits delivered from the double‐difference multi‐GNSS (GPS, GLONASS, and Galileo) processing, which may arise from (1) using a homogeneous and inhomogeneous network of multi‐GNSS stations, (2) different approaches to the TRF realization using minimum constraint conditions, and (3) different approaches to handling of GCC in GNSS global processing. The questionable quality of GCC delivered from the global GNSS solutions is described with a special attention to network effects and system‐specific parameters. We found that Galileo can provide GCC, whose quality corresponds to the GPS series. Moreover, the GCC from Galileo is of a better quality than those based on GLONASS data, despite the same number of nominal orbital planes and a much lower number of active satellites. When the No‐Net‐Translation constraint is not applied on the GNSS network, the station coordinate repeatability is worsened by about 70%, 55%, and 25% for the north, east, and up components, respectively, compared to the solution when applying No‐Net‐Translation and when having the network origin consistent with the international TRF. We thus infer that the No‐Net‐Translation condition is mandatory in global GNSS solutions. Key Points: Using the No‐Net‐Translation constraint in global multi‐GNSS processing is beneficial for station coordinate estimatesGalileo constellation can provide geocenter coordinates whose quality corresponds to that from GPSInhomogeneous distribution of GNSS stations leads to systematic effects in geocenter coordinates delivered from GNSS [ABSTRACT FROM AUTHOR]

Abstract: All satellites of new Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflectors dedicated to Satellite Laser Ranging (SLR). This paper demonstrates the contribution of SLR tracking of multi‐GNSS constellations to the improved SLR‐derived reference frame and scientific products. We show a solution strategy with estimating satellite orbits, SLR station coordinates, geocenter coordinates, and Earth rotation parameters using SLR observations to 2 Laser Geodynamics Satellites (LAGEOS) and 55 GNSS satellites: 1 GPS, 31 Globalnaya Navigatsionnaya Sputnikovaya Sistema, 18 Galileo, 3 BeiDou Inclined Geosynchronous Orbit, 1 BeiDou Medium Earth Orbit, and 1 Quasi‐Zenith Satellite System satellite for the period 2014.0–2017.4. Due to a substantial number of GNSS observations, the number of weekly solutions for some SLR stations, for example, Arkhyz, Komsomolsk, Altay, and Brasilia, is larger up to 41% in the combined LAGEOS + GNSS solution when compared to the LAGEOS‐only solution. The SLR observations to GNSS can transfer the orientation of the reference frame from GNSS to SLR solutions. As a result, the SLR‐derived pole coordinates and length‐of‐day estimates become more consistent with GNSS microwave‐based results. The root‐mean‐square errors of length‐of‐day are reduced from 122.5 μs/d to 43.0 μs/d, whereas mean offsets are reduced from −81.6 μs/d to 0.5 μs/d in LAGEOS only and in the combined LAGEOS + GNSS solutions, respectively. [ABSTRACT FROM AUTHOR]

Objective The aim of this paper was to analyse the results of treatment of anal fistulas retrospectively. Methods Between 1992 and 2004, 407 patients were operated on for perianal fistula. In the follow-up period, 107 patients were lost, so 300 patients were analysed in the study. The mean follow-up time was 4.2 years. Analysed parameters included: types of surgical procedures in different kinds of fistulas and postoperative complications. Various types of surgical procedures and their effectiveness were described. Late results were assessed taking into account healing time, duration of sick leave, recurrence rate and incidence of anal sphincter dysfunction. Severity of gas and stool incontinence was assessed according to the Cleveland Clinic Incontinence Score. Results In our study, subcutaneous fistula was diagnosed in 23.3%, inter-sphincteric in 18%, trans-sphincteric in 37.7%, supra-sphincteric in 16% and extra-sphincteric in 5% of patients. Single-tract fistulas were present in 88.7% and multi-tract fistulas were present in 11.3%. Overall, 242 patients had primary fistulas and 58 patients had recurrent fistulas. The most frequently performed procedures were cutting seton (139 patients) and radical fistulectomy (104 patients). Recurrent fistulas developed in 14.3%. Postoperative gas and/or stool incontinence was noticed in 10.7%. The recurrence rate was 5.4% in patients with primary fistula and in 51.7% patients presenting with a recurrent fistula. Gas and stool incontinence developed in 3.7% of patients with primary fistulas and in 39.7% of patients presenting with recurrent fistulas. Recurrence rate was 12% in the patients of single-tract fistulas and 32.4% in the patients of multi-tract fistulas. Postoperative gas and/or stool incontinence occurred in 8.3% of patients of single-tract fistulas and in 29.4% of patients of multi-tract fistulas. Conclusions The complication rate was 10-fold higher in patients presenting with a recurrent fistula than in those with primary fistulas and threefold higher in patients with multi-tract fistulas than in those with single-tract fistulas. [ABSTRACT FROM AUTHOR]

The Mexican axolotl (Ambystoma mexicanum) provides an excellent model for studying heart development since it carries a cardiac lethal mutation in gene c that results in failure of contraction of mutant embryonic myocardium. In cardiac mutant axolotls (c/c) the hearts do not beat, apparently because of an absence of organized myofibrils. To date, there has been no way to analyze the genotypes of embryos from heterozygous spawnings (+/c×+/c) until stage 35 when the normal (+/c or +/+) embryos first begin to have beating hearts; mutant (c/c) embryos fail to develop normal heartbeats. In the present study, we created chimeric axolotls by using microsurgical techniques. The general approach was to transect tailbud embryos and join the anterior and posterior halves of two different individuals. The chimeric axolotl is composed of a normal head and heart region (+/+), permitting survival and a mutant body containing mutant gonads (c/c) that permits the production of c/c mutant offspring: 100% c/c offspring were obtained by mating c/c chimeras (c/c×c/c). The mutant phenotypes were confirmed by the absence of beating hearts and death at stage 41 in 100% of the embryos. Examination of the mutant hearts with electron microscopy and comfocal microscopy after immunofluorescent staining for tropomyosin showed identical images to those described previously in naturally-occurring c/c mutant axolotls (i.e., lacking organized sarcomeric myofibrils). These ”c/c chimeric” axolotls provide a useful and unique way to investigate early embryonic heart development in cardiac mutant Mexican axolotls. [ABSTRACT FROM AUTHOR]

A precise organization of contractile proteins is essential for contraction of heart muscle. Without a necessary stoichiometry of proteins, beating is not possible. Disruption of this organization can be seen in diseases such as familial hypertrophic cardiomyopathy and also in acquired diseases. In addition, isoform diversity may affect contractile properties in such functional adaptations as cardiac hypertrophy. The Mexican axolotl provides an uncommon model in which to examine specific proteins involved with myofibril formation in the heart. Cardiac mutant embryos lack organized myofibrils and have altered expression of contractile proteins. In order to replicate the disruption of myofibril formation seen in mutant hearts, we have developed procedures for the introduction of contractile protein antibodies into normal hearts. Oligonucleotides specific to axolotl tropomyosin isoforms (ATmC-1 and ATmC-3), were also successfully introduced into the normal hearts. The antisense ATmC-3 oligonucleotide disrupted myofibril formation and beating, while the sense strands did not. A fluorescein-tagged sense oligonucleotide clearly showed that the oligonucleotide is introduced within the cells of the intact hearts. In contrast, ATmC-1 anti-sense oligonucleotide did not cause a disruption of the myofibrillar organization. Specifically, tropomyosin expression can be disrupted in normal hearts with a lack of organized myofibrils. In a broader approach, these procedures for whole hearts are important for studying myofibril formation in normal hearts at the DNA, RNA, and/or protein levels and can complement the studies of the cardiac mutant phenotype. All of these tools taken together present a powerful approach to the elucidation of myofibrillogenesis and show that embryonic heart cells can incorporate a wide variety of molecules with cationic liposomes. [ABSTRACT FROM AUTHOR]

All Galileo, GLONASS, QZSS, and BeiDou satellites are equipped with laser retroreflector arrays dedicated to satellite laser ranging (SLR). Using SLR data to new GNSS systems allows for estimating global geodetic parameters, such as Earth rotation parameters, global scale, and geocenter coordinates. In this study, we evaluate the quality of global geodetic parameters estimated on a basis of SLR tracking of new GNSS satellites and the combined solution based on SLR observations to GNSS and LAGEOS. We show that along with a progressive populating of Galileo orbital planes, the quality of geocenter components based on SLR-GNSS data has been improved to the level of 6 and 15 mm for equatorial and polar geocenter components, respectively. The scale of the reference frame and the geocenter coordinates in the combined LAGEOS + GNSS solutions are dominated by the LAGEOS data. Some noncore SLR stations provide by far more observations to GNSS than to LAGEOS, e.g., Russian and Chinese stations dedicated to supporting GLONASS and BeiDou constellations. The number of solutions for these stations can be increased by up to 40%, whereas the station coordinate repeatability can be improved from about 20-30 mm to the level of 15-20 mm when considering both SLR to LAGEOS and SLR to GNSS. [ABSTRACT FROM AUTHOR]