A very special EPW sextic and two IHS fourfolds

We show that the Hilbert scheme of two points on the Vinberg $K3$ surface has a 2:1 map onto a very symmetric EPW sextic $Y$ in $\mathbb{P}^5$. The fourfold $Y$ is singular along $60$ planes, $20$ of which form a complete family of incident planes. This solves a problem of Morin and O'Grady and establishes that $20$ is the maximal cardinality of such a family of planes. Next, we show that this Hilbert scheme is birationally isomorphic to the Kummer type IHS fourfold $X_0$ constructed in [DW]. We find that $X_0$ is also related to the Debarre-Varley abelian fourfold.Comment: 32 page

Pierwsze stwierdzenie modraszka wikramy Pseudophilotes vicrama (Moore, 1865) (Lepidoptera: Lycaenidae) w Bieszczadach Zachodnich

First record of Eastern Baton Blue Pseudophilotes vicrama (Moore, 1865) (Lepidoptera: Lycaenidae) in the Western Bieszczady Mts. The paper presents first observation of Eastern Baton Blue Pseudophilotes vicrama (Moore, 1865) in the Western Bieszczady Mts. A single individual was observed on the top of Połonina Wetlińska Range. This site is located approx. 30 km north-east of the known sites in Slovakia and approx. 35 km north of the sites in Ukraine. At the only two known and historical sites in the Podkarpacie Region, near Pruchnik and Jarosław, the species was last observed before 1960

Satellite laser ranging to GNSS-based Swarm orbits with handling of systematic errors

Satellite laser ranging (SLR) retroreflectors along with GNSS receivers are installed onboard numerous active low earth orbiters (LEOs) for the independent validation of GNSS-based precise orbit determination (POD) products. SLR validation results still contain many systematic errors that require special handling of various biases. For this purpose, we derive methods of reducing systematic effects affecting the SLR residuals to LEO Swarm satellites. We test solutions incorporating the estimation of range biases, station coordinate corrections, tropospheric biases, and horizontal gradients of the troposphere delays. When estimating range biases once per day, the standard deviation (STD) of Swarm-B SLR residuals is reduced from 10 to 8 mm for the group of high-performing SLR stations. The tropospheric biases estimated once per day, instead of range biases, further reduce the STD of residuals to the level of 6 mm. The systematic errors that manifest as dependencies of SLR residuals under different measurement conditions, e.g., elevation angle, are remarkably diminished. Furthermore, introducing troposphere biases allows for the comparison of the orbit quality between kinematic and reduced-dynamic orbits as the GPS-based orbit errors become more pronounced when SLR observations are freed from elevation-dependent errors. Applying tropospheric biases in SLR allows obtaining the consistency between the POD solution and SLR observations that are two times better than when neglecting to model of systematic effects and by 29% better when compared with solutions considering present methods of range bias handling

Realization of the terrestrial reference frame based on integrated SLR measurements to LEO, geodetic,and Galileo satellites

Numerous active low Earth orbiters (LEOs) and Global Navigation Satellite System (GNSS) satellites, including the Galileo constellation,are equipped with laser retroreflectors used for Satellite Laser Ranging (SLR). Moreover, most LEOs are equipped with GNSS receivers for precise orbit determination. SLR measurements to LEOs, GNSS, and geodetic satellites vary in terms of registered numbers of the normal points (NPs) or registered satellite passes. In 2016-2018, SLR measurements to LEOs constituted 81% of all NPs and 59% of all registered satellite passes, whereas 10% of NPs and 30% of satellite passes, respectively,were assigned to GNSS. The remaining SLR measurements, 9% of NPs and 11% of passes, were completed by geodetic satellites, including LAGEOS-1 and LAGEOS-2. In this study, we show that the SLR observations to Galileo, passive geodetic and active LEO satellites together with precise GNSS-based orbits of LEOs and Galileocan be used for the determination of SLR station coordinates.Station coordinates, as well as the realization of the ITRF, are typically determined using SLR observations to passive geodetic satellites, such as LAGEOS-1/2. Here, we use SLR observations to Galileo, LAGEOS-1/2, LARES, Sentinel-3A, SWARM-A/B/C, TerraSAR, Jason-2, GRACE-A/B satellites to investigate whether they can be applied for the reference frame realization and for deriving high-quality station coordinates. We present various types of solutions based on different solution lengths, different SLR ground network constraining, and the combination of different sets of satellites to investigate the best solution set-up and the relative weights for the variance scaling factors of normal equations. We compare our results with the standard LAGEOS-based solutions and show the consistency level of the results with respect to the classical SLR solutions. Combination of observations improves the station coordinates especially for those stations which provide more SLR observations to LEOs, and Galileo satellites than to LAGEOS

GNSS Visibility and Performance Implications for the GENESIS Mission

The GENESIS mission prepared for launch in 2027 integrates the four space-geodetic techniques on a single spaceborne platform in medium Earth orbit. With its unique observations and alternative tie concepts, the mission aims to contribute to an improved accuracy and homogeneity of future terrestrial reference system realizations. To assess the expected contribution of Global Navigation Satellite System (GNSS) tracking, a comprehensive GNSS coverage analysis is performed based on detailed link-budget simulations, taking into account the best available gain patterns and signal-specific transmit power estimates derived for this work from measurements of a high-gain dish antenna. The benefit of different receiver antenna concepts for the GENESIS spacecraft is assessed and it is demonstrated that a single-antenna system with either a nadir-looking or side-looking boresight is a viable alternative to the dual-antenna configuration considered in initial mission studies. Compared to terrestrial users and missions in low Earth orbit, GENESIS will collect GNSS signals transmitted at up to two times larger off-boresight angles. Only limited information on the actual transmit antenna phase patterns is presently available in this region, which hampers a quantitative assessment of the expected measurement and orbit determination accuracy. As such, a comprehensive release of manufacturer calibrations is encouraged for all blocks of GPS and Galileo satellites. In parallel, a need for in-flight characterization and calibration of the GNSS transmit antennas for off-boresight angles of up to 30 deg using observations of the GENESIS mission itself is expected. The impact of such calibrations on the overall quality of terrestrial reference frame parameters will need to be assessed in comprehensive simulations of global GNSS network solutions with joint processing of terrestrial and GENESIS GNSS observations

What has happened to the females? : population trends in the Aesculapian snake at its northern range limit

Populations at the edge of their main range of distribution are often exposed to suboptimal environments. They therefore exhibit a greater susceptibility towards habitat changes and often clearly differ in their structure and dynamics from populations in the main range. Here we define population parameters of the Aesculapian snake Zamenis longissimus, a species endangered in Europe, at its northern range limit based on data obtained in the valley of the River San (Bieszczady Mts., SE Poland) in 2009-2013. We focus on the spatial and temporal sex ratio patterns by comparing data obtained in 2009-2013 with published records from 1990 to 1998 and five other northern populations (1 from the main range, 1 at the northern edge of its contiguous range, and 3 entirely isolated ones). Using the capture-mark-recapture (CMR) method, we estimated the population size to be about 230 snakes. Our data show that among adults the percentage of females (17.74%) in the San valley population was significantly lower than in those other five populations and the same population studied two decades earlier. Because of the male-biased sex ratio, we estimated the effective population size to be about 74 snakes. This disproportion between the sexes in adults may be interpreted as an early stage of the population extinction process at the northern range limit of this species’ distribution. It is probably due to the limited availability of egg-laying sites, compelling females to undertake longer movements, which may heighten the risk of mortality. Keywords: Zamenis longissimus, Population size, Sex ratio, Northern range limit, Extinctio

Validation of Galileo orbits using SLR with a focus on satellites launched into incorrect orbital planes

The space segment of the European Global Navigation Satellite System (GNSS) Galileo consists of In-Orbit Validation (IOV) and Full Operational Capability (FOC) spacecraft. The first pair of FOC satellites was launched into an incorrect, highly eccentric orbital plane with a lower than nominal inclination angle. All Galileo satellites are equipped with satellite laser ranging (SLR) retroreflectors which allow, for example, for the assessment of the orbit quality or for the SLR–GNSS co-location in space. The number of SLR observations to Galileo satellites has been continuously increasing thanks to a series of intensive campaigns devoted to SLR tracking of GNSS satellites initiated by the International Laser Ranging Service. This paper assesses systematic effects and quality of Galileo orbits using SLR data with a main focus on Galileo satellites launched into incorrect orbits. We compare the SLR observations with respect to microwave-based Galileo orbits generated by the Center for Orbit Determination in Europe (CODE) in the framework of the International GNSS Service Multi-GNSS Experiment for the period 2014.0–2016.5. We analyze the SLR signature effect, which is characterized by the dependency of SLR residuals with respect to various incidence angles of laser beams for stations equipped with single-photon and multi-photon detectors. Surprisingly, the CODE orbit quality of satellites in the incorrect orbital planes is not worse than that of nominal FOC and IOV orbits. The RMS of SLR residuals is even lower by 5.0 and 1.5 mm for satellites in the incorrect orbital planes than for FOC and IOV satellites, respectively. The mean SLR offsets equal −44.9,−35.0, and −22.4 mm for IOV, FOC, and satellites in the incorrect orbital plane. Finally, we found that the empirical orbit models, which were originally designed for precise orbit determination of GNSS satellites in circular orbits, provide fully appropriate results also for highly eccentric orbits with variable linear and angular velocities

Zirconium-based metal–organic frameworks as acriflavine cargos in the battle against coronaviruses : a theoretical and experimental approach

[Image: see text] In this study, we present a complementary approach for obtaining an effective drug, based on acriflavine (ACF) and zirconium-based metal–organic frameworks (MOFs), against SARS-CoV-2. The experimental results showed that acriflavine inhibits the interaction between viral receptor-binding domain (RBD) of spike protein and angiotensin converting enzyme-2 (ACE2) host receptor driving viral cell entry. The prepared ACF@MOF composites exhibited low (MOF-808 and UiO-66) and high (UiO-67 and NU-1000) ACF loadings. The drug release profiles from prepared composites showed different release kinetics depending on the local pore environment. The long-term ACF release with the effective antiviral ACF concentration was observed for all studied ACF@MOF composites. The density functional theory (DFT) calculations allowed us to determine that π–π stacking together with electrostatic interaction plays an important role in acriflavine adsorption and release from ACF@MOF composites. The molecular docking results have shown that acriflavine interacts with several possible binding sites within the RBD and binding site at the RBD/ACE2 interface. The cytotoxicity and ecotoxicity results have confirmed that the prepared ACF@MOF composites may be considered potentially safe for living organisms. The complementary experimental and theoretical results presented in this study have confirmed that the ACF@MOF composites may be considered a potential candidate for the COVID-19 treatment, which makes them good candidates for clinical trials

Utilization of the out of hours service in Poland: an observational study from Krakow

<p>Abstract</p> <p>Background</p> <p>In 2000 a new GP contract was introduced in Poland. It allowed GPs to subcontract out of hours care to specialized deputizing services. One such service in Kraków provides care to 61 GP practices with a population of 420 000 inhabitants. The aim of this study is to analyze seasonal and geographical variation in out of hours care use and to find the most important factors influencing it.</p> <p>Methods</p> <p>Routinely collected data for 24 months (2003–2004) containing type, date and time of the contacts were used.</p> <p>Results</p> <p>During the study period 238 072 contacts were recorded: 149 911 ambulatory doctor visits, 23 434 home visits and 64 727 nurse procedures. The mean rate of out of hours contacts was: for ambulatory visits 178 per 1000 inhabitants/year (varied between practices from 9 to 696), for home visits 28 (from 1 to 36) and for nurse procedures 77 (from 3 to 327). The highest rate of ambulatory visits was 739 in the age group 0–4, the lowest – 104 in the age group 45–49. The highest rate of home visits was 221 in the age group over 85. The rate of ambulatory GP visits and nurse procedures was negatively correlated with the distance between the location of GP practice and the nearest out of hours clinic. The rate of home visits was positively correlated with the age of the patient.</p> <p>Conclusion</p> <p>Significant differences between practices suggest that non medical factors may play an important role in the patient's decision to see a GP when the surgery is closed. Their influence should be limited to make the system more efficient.</p

GENESIS: Co-location of Geodetic Techniques in Space

Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.Comment: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS