Shell Distribution Research Articles

Simultaneous Generation of EMIC and MS Waves During the Magnetic Dip in the Inner Magnetosphere

AbstractThe Van Allen Probe B satellite simultaneously observed electromagnetic ion cyclotron (EMIC) and fast magnetosonic (MS) waves in a magnetic dip on April 29, 2017. During the magnetic dip, we found the coexistence of flux enhancements of ring current protons (∼11.2–∼51.7 keV) and flux reductions of relativistic electrons (∼1 MeV), which are identified as typical signatures of a magnetic dip in the inner magnetosphere. Based on linear theoretical calculations and observational analysis, the observed ring current protons show an anisotropic temperature distribution and partial shell distribution for different energies during the magnetic dip to provide free energies for the generation of EMIC and MS waves, respectively. Our findings indicate that the complex unstable distribution in the velocity phase space of ring current protons during the magnetic dip can trigger the simultaneous generation of EMIC and MS waves in the inner magnetosphere.

Expanding Alternating Spherical and Cylindrical Regions by Tailoring Binary Symmetric ABC/ABC Blends

The self-assembly of a binary blend composed of two different symmetric ABC triblock copolymers has been investigated using self-consistent field theory in the grand canonical ensemble, aiming to expand the phase regions of alternating spherical and cylindrical phases by tailoring the molecular parameters. Our study confirms that the region of the spherical phase is expanded by the effect of bidispersity in which the long and short A-blocks (or C-blocks) form a core–shell distribution within the spherical domain to increase the spontaneous curvature. The bidispersity effect also expands the phase region of the alternating cylinders. In contrast to the spherical phase, the cylindrical region can be expanded by another effect of bidisperse B-blocks to release the high packing frustration of the low-coordinated tetragonal array of alternating A/C cylinders. With optimized parameters, the regions of both the spherical and cylindrical phases are tremendously expanded to such large volume fractions that the spheres and cylinders are remarkably deformed. Our work not only deepens the understanding on the self-assembly mechanism of ABC/ABC blends but also provides a valuable guide for the fabrication of alternating spherical and cylindrical morphologies with large volume fractions.

A novel analytical study on the buckling of cylindrical shells subjected to arbitrarily distributed external pressure

A completely new analytical method to solve the fourth-order governing partial differential equations with variable coefficients is proposed for the buckling of cylindrical shells subjected to distributed external pressure. Unlike the present energy method in literatures, pressure distribution needs not be assumed beforehand and be simple, which is arbitrary in this manuscript. The present novel method makes the buckling analysis for the complicated external pressure distributions (including discontinuous loads) possible. Furthermore, general buckling load formulas related to geometrical sizes of the shell and pressure distribution functions are obtained by the combined perturbation method and Fourier series expansion for the first time. The first and second order asymptotic terms of buckling loads are directly given for the purpose of engineering application. Based on the presented method, three types of external pressure loads (namely, linear liquid pressure, wind type pressure and discontinuous stepwise external pressure)are considered. Validity and accuracy are demonstrated by comparing with the results in published literatures for linear liquid pressure and wind type pressure, and it is also the first time to derive the buckling load for a shell under discontinuous stepwise external pressure. Parametric discussion is also performed to investigate the effects of load distribution types and parameters on buckling resistance capacity.

Design of Highly Durable Core-Shell Catalysts by Controlling Shell Distribution Guided by In-Situ Corrosion Study.

Most degradations in electrocatalysis are caused by corrosion in operation, for example the corrosion of the core in a core-shell electrocatalyst during the oxygen reduction reaction (ORR). Herein, according to the in-situ study on nanoscale corrosion kinetics via liquid cell transmission electron microscopy (LC-TEM) in the authors' previous work, they sequentially designed an optimized nanocube with the protection of more layers on the corners by adjusting the Pt atom distribution on corners and terraces. This modified nanocube (MNC) is much more corrosion resistant in the in-situ observation. Furthermore, in the practical electrochemical stability testing, the MNC catalyst also showed the best stability performance with the 0.37% and 9.01% loss in specific and mass activity after 30 000 cycles accelerated durability test (ADT). This work also demonstrates that how an in-situ study can guide the design of desired materials with improved properties and build a bridge between in-situ study and practical application.

Narrowband Magnetosonic Waves Near the Lower Hybrid Resonance Frequency in the Inner Magnetosphere: Wave Properties and Excitation Conditions

AbstractIn this study, the excitation of narrowband fast magnetosonic (MS) waves near the lower hybrid resonance frequency (fLHR) has been investigated with observations from Van Allen Probes mission and linear growth theory. A typical wave event is first examined to show that these waves can be excited through linear instabilities driven by partial shell distributions of protons. Then it is found that these narrowband MS waves from 188 wave events observed by the Van Allen Probe A between January 1, 2013 to December 31, 2015 have central frequencies around 0.7fLHR with a bandwidth of 0.2fLHR. In addition, these waves are observed mainly in the dayside and dusk sectors outside the plasmapause, which is different from previously reported results. Moreover, the simultaneously observed energetic protons during wave activities show that the ratios of the ring speed Vr to the Alfvén speed VA mainly fall into the range of 0.8 < Vr/VA < 1, and this preferred condition for excitations of narrowband MS waves near fLHR is also verified by a parameter analysis of calculating linear wave growth rates combined with wave observations.

Plasma Density and Magnetic Field Fluctuations in the Ion Gyro‐Frequency Range Near the Diamagnetic Cavity of Comet 67P

AbstractWe report the detection of large‐amplitude, quasi‐harmonic density fluctuations with associated magnetic field oscillations in the region surrounding the diamagnetic cavity of comet 67P. Typical frequencies are ∼0.1 Hz, corresponding to ∼10 times the water and times the proton gyro‐frequencies, respectively. Magnetic field oscillations are not always clearly observed in association with these density fluctuations, but when they are, they consistently have wave vectors perpendicular to the background magnetic field, with the principal axis of polarization close to field‐aligned and with a ∼90° phase shift with respect to the density fluctuations. The fluctuations are observed in association with asymmetric plasma density and magnetic field enhancements previously found in the region surrounding the diamagnetic cavity, occurring predominantly on their descending slopes. This is a new type of waves not previously observed at comets. They are likely ion Bernstein waves, and we propose that they are excited by unstable ring, ring‐beam, or spherical shell distributions of cometary ions just outside the cavity boundary. These waves may play an important role in redistributing energy between different particle populations and reshape the plasma environment of the comet.

Remote set of oyster (Crassostrea virginica) in various aquaculture gear

Remote-setting of oyster, Crassostrea virginica, larvae from the disease-resistant Haskin NEH line is performed every other year in Delaware to supply small-scale oyster enhancement efforts, citizen oyster gardening program. Over the past four remote sets (2009, 2011, 2013, 2015), three types of shell containment gear were utilized to monitor and compare the setting efficiency rate and post-set survival. Shell containment gears included diamond, plastic mesh bags (2009, 2011), wire baskets (2011, 2015), and plastic aquaculture trays (2013, 2015). Average setting efficiency was estimated at 28%, 23%, 17%, and 29% in the respective 2009, 2011, 2013, and 2015 remote sets while gear specific settling efficiency (%) include 28% for mesh bags in 2009, 22% for mesh bags and 33% for wire baskets in 2011, 17% for aquaculture trays in 2013, and 30% for aquaculture trays and 22% for wire baskets in 2015. Settling efficiency was lowest in 2013 using aquaculture trays compared to other years while aquaculture trays in 2015 and wire baskets in 2011 resulted equally higher settling efficiency. For small-scale growers, the stacked aquaculture trays are advantageous for several reasons: reducing handling time, uniform shell distribution within tanks, environmentally friendly alternative, and ease of cleaning detritus between shell layers.

Thermoacoustic response of porous FGM cylindrical shell surround by elastic foundation subjected to nonlinear thermal loading

Due to defects in processing, there are some voids or pores inside the functionally graded material during the production progress. It has been proved that porosity has been shown to have a large influence on the mechanical response of the structure, but the effect of porosity on the acoustic performance is still worth studying. To reveal these effects, the thermoacoustic response of porous functionally graded material (PFGM) cylindrical shell on elastic foundation under nonlinear thermal environment are investigated analytically. In the analysis, three common types of PFGM cylindrical shell, namely, uniform, symmetric and asymmetric distribution are considered. Assuming that material properites are related to temperature, and the thermomechanical stresses are obtained according to the nonlinear heat conduction equation. The Pasternak model is used to describe elastic foundation, and the cylindrical shell dynamic equation based on the first-order shear deformation shell theory is established by Hamilton's principle. By using the velocity continuity condition at fluid-structure interfaces to consider the fluid-structure coupling. By comparing the numerical results with the existing solutions in open literature, the validity of the proposed theoretical model is verified. Finally, the influences of porosity distribution type, gradient index, porosity volume fraction, material properties, elastic foundations and nonlinear temperature fields on the acoustic characteristics of PFGM cylindrical shell have been investigated.

Null Beamsteering Using Distributed Arrays and Shared Aperture Distributions

In this work, a novel technique using closed-form expressions is rigorously surveyed to collaboratively nullsteer uniformly distributed, planar ring, and volumetric shell distributions. To assess the radiation behavior of these geometries circular tapers is of interest for their attractiveness in derivation, design, application, and mathematical simplicity. A rigorous mathematical derivation is used for the generation of closed-form expressions of the mean-valued radiation characteristics. The numerical simulations are performed using both ANSYS HFSS and MATLAB using a finite-element distribution. To validate the analytical models, we include the measured results of a uniformly distributed ring array topology, constrained to a set of 18 elements and a uniformly distributed shell array topology constrained to 16 elements. The results of all methods are compared to demonstrate exceptional agreement in the recommended theoretical analysis. This process follows differently from traditional phased array nulling methods, which apply the unique amplitude tapers along individual phased array elements. Unlike typical adaptive beamforming algorithms, this process does not require the estimation of second-order statistical metrics and avoids expansions of large polynomial equations. It uses shared aperture characteristics in order to generate null beams simultaneously. This can also be extended to widen null widths from the compounding of these shared aperture distributions, which is shown in simulation.

Sustaining Saturn's Electron Radiation Belts Through Episodic, Global‐Scale Relativistic Electron Flux Enhancements

AbstractThe L shell distributions of MeV electrons in Saturn's radiation belt are investigated orbit by orbit for the 13‐year exploration of Cassini. It is found that in addition to the monotonic decrease profiles, there are orbits showing superimposed transient extensions. The extensions are found to stand out above the background population during 50% of belt crossings. We estimate that there is high probability (>72%) that transient extensions contribute more than 10% electron content in the radiation belt. The high occurrence frequency of one extension every 2–3 weeks, together with the relative content, demonstrate that the extensions constitute a regular and fundamental process populating and sustaining the electron belts of Saturn. The transients regularity excludes interplanetary coronal mass ejections as dominant trigger and implies corotation interaction regions and/or internal processes as candidates. Statistical results suggest that the communication of electrons between the middle magnetosphere and the radiation belts is largely through convective radial transport, which produces transient radiation belt extensions.

Comparing theory and simulation of ion cyclotron emission from energetic ion populations with spherical shell and ring-beam distributions in velocity-space

Observations have recently been made of ion cyclotron emission (ICE) that originates from the core plasma in the DIII-D (Thome et al 2018 Rev. Sci. Instrum. 89 10I102, Thome et al 2019 Nucl. Fusion http://iopscience.iop.org/10.1088/1741-4326/ab20e7) and ASDEX-Upgrade (Ochoukov et al 2018 Rev. Sci. Instrum. 89 10J101, Ochoukov et al 2019 Nucl. Fusion 59 014001) tokamaks. The ICE spectral peaks correspond to the local cyclotron harmonic frequencies of fusion-born ions close to the magnetic axis, in contrast to the hitherto usual spatial localisation of the ICE source to the outer midplane edge in tokamak and stellarator plasmas. Core ICE is temporally transient, and may sometimes be caused by the rapid onset and increase of local fusion reactivity. This would give rise to a highly non-Maxwellian population of fusion-born ions near their birth energy. In an idealised deuterium-tritium plasma, this distribution would initially be a thin spherical shell in velocity-space. For as long as it persists, as pointed out in (D’Inca 2014 Ion Cyclotron Emission on ASDEX Upgrade PhD Thesis Ludwig-Maximilians-Universitat), the shell might drive the magnetoacoustic cyclotron instability (MCI), which is the excitation process which underlies ICE. Here we present, under core plasma conditions, direct numerical simulations of ICE generation by a spherical shell distribution of fusion-born ions in velocity-space. These energetic minority ions are found to relax collectively in particle-in-cell (PIC) computations which follow their self-consistent gyro-orbit-resolved dynamics, together with that of the majority thermal ions and electrons, under the Maxwell–Lorentz system of equations. We relate the computational outputs, which extend into the nonlinearly saturated regime of the MCI, to the analytical theory of the linear MCI for shell-type energetic ion distributions, and to fully nonlinear simulations of related ring-beam energetic ion distributions relaxing under the MCI. We find that the MCI is excited in all cases, and that the linear growth phase of the shell simulations typically takes almost twice as long to reach saturation than in the ring-beam simulations. It is shown that for both types of velocity distribution, nonlinear wave-wave interactions play a vital role in the excitation of the ICE spectral peaks at lower cyclotron harmonics which are typically detected in experiments. We conclude that in future simulations for ICE interpretation, ring-beam distributions may provide an acceptable proxy for shell distributions, while using significantly fewer computational particles and still maintaining a satisfactory signal-to-noise ratio.

Energy Power Spectra Measured at an Interplanetary Shock by the New Horizon's SWAP Experiment: 1D Full Particle Simulations versus Observations

Abstract One-dimensional particle-in-cell (PIC) simulations are used to analyze the energy spectra measured by the New Horizons’ Solar Wind Around Pluto (SWAP) instrument in the upstream region of an interplanetary shock observed at a distance of ∼34 au from the Sun. The use of individual populations simulating the different solar wind ion and pick-up ion (PUI) populations allows us to clearly identify the contribution of each population to the global energy spectra. The important role of shock front obliquity is stressed in the formation of PUIs streaming back along the magnetic field into the upstream region far from the front. Energy spectra measured by the SWAP experiment are well reproduced in the present simulations. A detailed analysis shows that (1) the highest-energy part of the spectrum is formed primarily by both backstreaming PUI–H+ and PUI–He+; (2) the middle-energy part of the energy spectrum is composed of both solar wind SW–H+ and SW–He2+ incoming ions that are superimposed on the PUI–H+ population; and (3) the low-energy range is composed of incoming PUI–H+. The agreement between experimental and simulation results is improved by using an initially filled-shell distribution for the PUI–H+ population (instead of a zero-thickness shell), as this affects the low-energy part of the spectrum strongly. This means that PUI–H+ ions have sufficient time to diffuse onto and fill out a shell distribution after their initial pick-up in the heliosphere, indicating that the subsequent cooling has an important impact on the global energy spectrum.

Micromagnetic simulations of reversal magnetization in core ((Nd<sub>0.7</sub>, Ce<sub>0.3</sub>)<sub>2</sub>Fe<sub>14</sub>B)-shell (Nd<sub>2</sub>Fe<sub>14</sub>B) type

The effects of core size, shell thickness and shell distribution on the coercivity of single-grain core ((Nd<sub>0.7</sub>,Ce<sub>0.3</sub>)<sub>2</sub>Fe<sub>14</sub>B)-shell (Nd<sub>2</sub>Fe<sub>14</sub>B) magnets are studied by programming and modeling them through using the C++ language. All the micromagnetic simulations are carried out via object oriented micro magnetic framework (OOMMF). The results show that the coercivity decreases with the increase of core size when the shell thickness is constant. It is considered that for the grain, the increase in the size of the core leads the average magnetocrystalline anisotropy field to increase and the total demagnetization energy to increase, thereby contributing to the magnetization reversal occurring under a smaller external field. When the core size is unchanged, as the shell thickness increases gradually, the coercivity first increases and then decreases. The analysis of the position of the nucleation point shows that the reason why the coercivity increases in the early period is mainly that the nucleation point is located at the core-shell junction and belongs to the core. As the thickness of the shell increases, the exchange interaction effect between the magnetic moment of the shell and the one of the nucleation point is strengthened, so a larger external field is needed in the nucleation process. As for the decrease of the coercivity in the later period, the main reason is that the nucleation points are exactly the vertices of the shell (also the vertices of the grain), and the increase of the shell thickness conduces to increasing the total demagnetization energy, so the nucleation points can be formed under a smaller external magnetic field. With core size and shell volume kept unchanged, when the shell is distributed on the two easy-axis planes (i.e. the planes perpendicular to the easy axis) of the core, the coercivity of the magnet reaches a largest value. It is because that the nucleation points are located at the vertices of the shell (also the vertices of the grain), of which the magnetocrystalline anisotropy field is larger, and the demagnetization field is smaller. Via magnetocrystalline anisotropy field, the demagnetization energy, nucleation point, etc, the changes of coercivity in above cases can be explained.

A comparison of wealth inequality in humans and non-humans

Inequality in the distribution of material resources (wealth) occurs widely across human groups. The extent of inequality, as measured by the Gini coefficient, is less in small-scale societies, such as hunter-gatherers and pastoralists, and greater in large-scale ones like current nation states. In many societies, the statistical distribution of wealth takes a characteristic form: unimodal, skewed to the right, and fat-tailed. However, we have relatively little systematic information about the distribution of material resources in nonhuman animals even though such resources are vital to their survival and fitness. Here we present the first description of inequality in material resources in an animal population: the distribution of gastropod (snail) shells inhabited by the hermit crab Pagurus longicarpus. We find that the shell distribution for the crabs strongly resembles the characteristic form of wealth distribution in human groups. The amount of inequality in the crabs is more than that in some small-scale human groups but less than that in nations. We argue that the shell distribution in the crabs is not simply generated by biological factors such as survival and growth of either crabs or gastropods. Instead, the strong resemblance in the human and hermit crab distributions suggests that comparable factors, not dependent upon culture or social institutions, could shape the patterns of inequality in both groups. In addition to the similarity in their inequality distributions, human and hermit crabs share other features of resource distribution, including the use of vacancy chains, not seen in other species. Based upon these parallels, we propose that P. longicarpus could be used as an animal model to test two factors – individual differences and intergenerational property transfers – that some economists theorize as major factors influencing the form of wealth distributions in humans. We also propose that inequality in hermit crabs could provide a baseline for examining human inequality.

Influences of element distribution on the magnetic properties in the (PrNd)–(YCe)–Fe–B sintered magnets

In this work, the effects of rare earth(RE) elements distribution on the magnetic properties and the microstructure of the (PrNd)–(Y10-xCex)–Fe–B sintered magnets have been studied. A remarkable increase has been achieved in coercivity from 8.85 kOe to 10.39 kOe for x = 2. Microstructure studies show that the recognizable core–shell distribution characteristics are maintained in the matrix phase with x increasing. In addition, high abundance rare earths(HARE) content in the matrix phase is restrained because of amount of Ce-rich intergranular phase forming in the triple junction areas. Combining the merit of the core–shell distribution of Y and reduced HARE content in 2:14:1 phase, a higher magnetocrystalline anisotropy field is obtained. The formation of Ce-rich intergranular phase is also beneficial for the (PrNd)–(YCe)–Fe–B sintered magnets to maintain high Curie temperature. This work suggests that Y-Ce co-substitution can tune the distribution of HARE elements to effectively improve the magnetic properties of the (PrNd)-(YCe)-Fe-B sintered magnets and promote the efficient utilization of RE elements.

Dynamic Reorganization of Bimetallic Nanoparticles under Reaction Depending on the Support Nanoshape: The Case of RhPd over Ceria Nanocubes and Nanorods under Ethanol Steam Reforming

Bimetallic catalysts exhibit high performance compared to that of their monometallic counterparts in a wide range of catalytic reactions. Both geometric and electronic phenomena yield unique properties that cannot be reproduced by other means. Bimetallic nanoparticles reorganize dynamically under reaction conditions, usually forming complex core–shell distributions of metals and oxidation states. This reorganization is even more complex in the presence of a reducible support. Here we show by operando ambient pressure X-ray photoelectron spectroscopy (AP-XPS) that the shape of the support also plays a crucial role in the reorganization of bimetallic nanoparticles, which has important consequences for catalytic performance. We have monitored the surface composition and oxidation states of preformed Rh0.5Pd0.5 model nanoparticles of 4 nm in size supported over CeO2 nanocubes and CeO2 nanorods during the catalytic steam reforming of ethanol (ESR) at 823 K. Over Rh0.5Pd0.5/CeO2-nanocubes, both rhodium and pall...

Constraining the IMF at Pluto Using New Horizons SWAP Data and Hybrid Simulations

AbstractNew Horizons did not carry a magnetometer, so there is no direct way to know the strength of the Interplanetary Magnetic Field (IMF) at the time of the flyby. Using a hybrid model together with a detailed model of the Solar Wind Around Pluto (SWAP) instrument (McComas et al., 2007, https://doi.org/10.1007/s11214-007-9205-3) we have identified three observables that are sensitive to IMF strength: the width of Pluto's heavy ion tail, the energy of heavy ions, and the profile of thermal pressure along the New Horizons trajectory. By comparing simulation to data we infer that the IMF strength was most likely near or below ∼0.1 nT. We also show that the shell distribution of Interstellar Pickup Ions is important for reproducing these observations due to its effect on global pressure balance.

Physical Roles of Interstellar-origin Pickup Ions at Heliospheric Termination Shock. II. Impact of the Front Nonstationary on the Energy Partition and Particle Velocity Distribution

Abstract The impact of the nonstationarity of the heliospheric termination shock in the presence of pickup ions (PUIs) on the energy partition between different plasma components is analyzed self-consistently by using a one-dimensional particle-in-cell simulation code. Solar wind ions (SWIs) and PUIs are introduced as Maxwellian and shell distributions, respectively. For a fixed time, (a) with a percentage of 25% PUIs, a large part of the downstream thermal pressure is carried by reflected PUIs, in agreement with previous hybrid simulations; (b) the total downstream distribution includes three main components: (i) a low-energy component dominated by directly transmitted (DT) SWIs, (ii) a high-energy component dominated by reflected PUIs, and (iii) an intermediate-energy component dominated by reflected SWIs and DT PUIs. Moreover, results show that the front nonstationarity (self-reformation) persists even in presence of 25% PUIs, and has some impacts on both SWIs and PUIs: (a) the rate of reflected ions suffers some time fluctuations for both SWIs and PUIs; (b) the relative percentage of downstream thermal pressure transfered to PUIs and SWIs also suffers some time fluctuations, but depends on the relative distance from the front; (c) the three components within the total downstream heliosheath distribution persist in time, but the contribution of the ion subpopulations to the low- and intermediate-energy components are redistributed by the front nonstationarity. Our results allow clarifying the respective roles of SWIs and PUIs as a viable production source of energetic neutral atoms and are compared with previous results.

Programming of Multicomponent Temporal Release Profiles in 3D Printed Polypills via Core-Shell, Multilayer, and Gradient Concentration Profiles.

Additive manufacturing (AM) appears poised to provide novel pharmaceutical technology and controlled release systems, yet understanding the effects of processing and post-processing operations on pill design, quality, and performance remains a significant barrier. This paper reports a study of the relationship between programmed concentration profile and resultant temporal release profile using a 3D printed polypill system consisting of a Food and Drug Administration (FDA) approved excipient (Pluronic F-127) and therapeutically relevant dosages of three commonly used oral agents for treatment of type 2 diabetes (300-500 mg per pill). A dual-extrusion hydrogel microextrusion process enables the programming of three unique concentration profiles, including core-shell, multilayer, and gradient structures. Experimental and computational studies of diffusive mass transfer processes reveal that programmed concentration profiles are dynamic throughout both pill 3D printing and solidification. Spectrophotometric assays show that the temporal release profiles could be selectively programmed to exhibit delayed, pulsed, or constant profiles over a 5 h release period by utilizing the core-shell, multilayer, and gradient distributions, respectively. Ultimately, this work provides new insights into the mass transfer processes that affect design, quality, and performance of spatially graded controlled release systems, as well as demonstrating the potential to create disease-specific polypill technology with programmable temporal release profiles.

A case of biodiversity overestimation in the Balkan Belgrandiella A. J. Wagner, 1927 (Caenogastropoda: Hydrobiidae): molecular divergence not paralleled by high morphological variation

ABSTRACTBelgrandiella A. J. Wagner, 1927 is a genus comprising minute snails with conic or turriform shells that are facultative stygobionts, inhabiting subterranean waters and springs. Few specimens or even empty shells of this taxon can be found, so the taxonomy is based mostly on the shell morphology and geographic distribution. Anatomy is known for a few taxa, and its usefulness is restricted. This, coupled with a popular idea that isolation is the first factor shaping divergence and speciation of the spring/cave fauna, resulted in dozens of nominal species of Belgrandiella, known from shells at a given locality. Herein we present shells, anatomy and four molecular markers (nuclear H3, 18S and 28S and mitochondrial cytochrome oxidase subunit I) in Belgrandiella from 16 localities in Slovenia, northern Croatia, and Bosnia and Herzegovina. Five sites are type localities of Boleana umbilicata, Belgrandiella kusceri, Belgrandiella krupensis, Belgrandiella zermanica and Belgrandiella robusta, respectively. Considering the shell and geographic distribution, we have determined B. cf. robusta Belgrandiella cf. croatica, Belgrandiella cf. fontinalis, Belgrandiella cf. kuesteri, Belgrandiella cf. pageti and Belgrandiella cf. koprivnensis The shells of all, as well as penes and female reproductive organs of two putative, species have been illustrated. Molecular analysis indicates four distinct clades, most probably of species rank for B. kusceri, B. cf. kuesteri, B. cf. fontinalis and B. cf. koprivnensis. Four nominal species (B. krupensis, B. robusta, B. umbilicata and B. zermanica) and one genus (Boleana) must be synonymised with Belgrandiella kusceri, and there are no more than four valid, biological species in the studied Belgrandiella. The molecular divergence is completely unmirrored by high morphological variability. Hence the level of endemism is markedly overestimated in these snails.