Strain specific motility patterns and surface adhesion of virulent and probiotic Escherichia coli

Bacterial motility provides the ability for bacterial dissemination and surface exploration, apart from a choice between surface colonisation and further motion. In this study, we characterised the movement trajectories of pathogenic and probiotic Escherichia coli strains (ATCC43890 and M17, respectively) at the landing stage (i.e., leaving the bulk and approaching the surface) and its correlation with adhesion patterns and efficiency. A poorly motile strain JM109 was used as a control. Using specially designed and manufactured microfluidic chambers, we found that the motion behaviour near surfaces drastically varied between the strains, correlating with adhesion patterns. We consider two bacterial strategies for effective surface colonisation: horizontal and vertical, based on the obtained results. The horizontal strategy demonstrated by the M17 strain is characterised by collective directed movements within the horizontal layer during a relatively long period and non-uniform adhesion patterns, suggesting co-dependence of bacteria in the course of adhesion. The vertical strategy demonstrated by the pathogenic ATCC43890 strain implies the individual movement of bacteria mainly in the vertical direction, a faster transition from bulk to near-surface swimming, and independent bacterial behaviour during adhesion, providing a uniform distribution over the surface.

Toward Long-Term Sailing Robots: State of the Art From Energy Perspectives

Sailing robots can contribute significantly to maritime surface exploration, due to its potential for long-range and long-duration motions in the environment with abundant wind. However, energy, the critical factor for their long-term missions, shall be carefully investigated, so as to achieve sustainability in distance and time. In this survey, we have conducted a comprehensive investigation on numerous sailing robots, developed in academia and industry. Some of them have achieved long-term operation, and some are motivated by, but still on the way to this ambitious goal. Prototypes are grouped in each team, so as to view the development path. We further investigate the existing design and control strategies for energy sufficiency from three perspectives: actuation, harvesting, and energy management. In propulsion and steering, i.e., two major actuations, researchers have accumulated effective sail and rudder designs. The motorized propeller and wave-glider–inspired mechanism also contribute as compliments for propulsion. Electricity harvesting based on solar or wind energies is also discussed to gather more power from nature. Pros and cons in strategies of energy management, which are valuable tools to enhance power utilization efficiency, are elaborated. This article is hoped to provide researchers in long-term robotic sailing with a comprehensive reference from the perspectives of energy.

Acoustic monitoring of laser-induced phase transitions in minerals: implication for Mars exploration with SuperCam

The SuperCam instrument suite onboard the Mars 2020 Perseverance rover uses the laser-induced breakdown spectroscopy (LIBS) technique to determine the elemental composition of rocks and soils of the Mars surface. It is associated with a microphone to retrieve the physical properties of the ablated targets when listening to the laser-induced acoustic signal. In this study, we report the monitoring of laser-induced mineral phase transitions in acoustic data. Sound data recorded during the laser ablation of hematite, goethite and diamond showed a sharp increase of the acoustic signal amplitude over the first laser shots. Analyses of the laser-induced craters with Raman spectroscopy and scanning electron microscopy indicate that both hematite and goethite have been transformed into magnetite and that diamond has been transformed into amorphous-like carbon over the first laser shots. It is shown that these transitions are the root cause of the increase in acoustic signal, likely due to a change in target’s physical properties as the material is transformed. These results give insights into the influence of the target’s optical and thermal properties over the acoustic signal. But most importantly, in the context of the Mars surface exploration with SuperCam, as this behavior occurs only for specific phases, it demonstrates that the microphone data may help discriminating mineral phases whereas LIBS data only have limited capabilities.

Section 14 StandAG – Identification of siting regions and associated challenges

With the publication of the subarea interim report on sub-regions on 28 September 2020, the Federal Company for Radioactive Waste Disposal (BGE), as the implementer of the German site selection procedure, has completed the first step of phase I in due time. The second step of phase I is the identification of siting regions for surface exploration. In the following step 2 of phase I, the determination of siting regions for surface exploration will be carried out based on the interim results of the first step of phase I in accordance with section 14 of the regulating law (StandAG). A central component of this second step of phase I is the representative preliminary safety assessments pursuant to section 27 StandAG, the ordinances on “Safety Requirements” (EndlSiAnfV) and “Preliminary Safety Assessments” (EndlSiUntV), which are carried out for each of the sub-regions. Based on the results of the preliminary safety assessments and the renewed application of the geoscientific weighting criteria (section 24 StandAG), siting regions will be identified that have the potential to become the site with the best possible safety for a repository for high-level radioactive waste. During the second step of phase I, the planning scientific consideration criteria (section 25 StandAG) can be applied for the first time. The path to the siting regions for surface exploration can be accompanied by various challenges related to geoscientific, methodological and also societal questions. For example, the application of the representative preliminary safety assessments may be more challenging in larger subareas compared to smaller ones as subsurface properties are likely to be more variable. In this context, areas with little data coverage for example, and the treatment of these areas in the procedure may pose another challenge. Therefore, sound methodological concepts must be developed for performing the representative preliminary safety assessments as well as for applying the geoscientific weighting criteria. Furthermore, the German site selection procedure defines special requirements (section 1 StandAG): the implementation of the participatory, science-based, transparent, self-questioning and learning procedure poses challenges to all stakeholders of the procedure on the way to the best possible disposal of high-level radioactive waste.

A systematic approach for surface exploration of sites – analysis of international exploration programs

The site selection procedure for a high-level radioactive waste repository in Germany is based on the Repository Site Selection Act (StandAG, 2017), which comprises three phases. In phase 2 the Federal Company for Radioactive Waste Disposal (BGE) will conduct surface exploration. Based on the exploratory findings, the further developed preliminary safety analyses, the common requirements and criteria, and potential socioeconomic analyses will be applied feeding into proposed sites for underground exploration. Commissioned by the BGE, the Federal Institute for Geosciences and Natural Resources (BGR) contributes to this procedure with the projects GeoMePS and ZuBeMErk, which collate and assess geoscientific and geophysical methods and programs for surface exploration. Their common goal is to develop recommendations for surface exploration of siting regions. For this purpose, the BGR has developed a systematic approach that includes (1) deducing exploration targets, (2) compilation of geoscientific and geophysical exploration methods in a database structure, and (3) analysis of case studies of national and international exploration programs for high-level radioactive waste disposal. Exploration targets are based on the common criteria and requirements as defined by the StandAG. The identified exploration targets (Kneuker et al., 2020) together with a large number of geoscientific and geophysical exploration methods were integrated and linked within the BGR database “GeM-DB”. All methods were evaluated according to their suitability and applicability for (a) the three defined host rocks (crystalline rock, claystone, rock salt) and (b) the previously defined exploration targets. In step (3) the BGR reviews national and international waste disposal programs exploring for crystalline rock, claystone, and rock salt. Here, the focus is on nondestructive and minimally invasive surface exploration techniques, such as geophysical airborne and ground-based methods or investigations in drill holes and on drill cores. The aims are to identify gaps in the method catalogue of the GeM-DB and to infer exploration directives for surface exploration during phase 2. An example is the analysis of the Swedish site selection process, especially the site investigation program. There, the site investigations are, e.g. the basis for the discipline-specific site descriptive models, which were applied for design and safety assessments (SKB, 2001). The Swedish site investigation program along with programs of other countries considering crystalline host rocks, such as Finland and Canada, show a common ground, which could be adapted for surface exploration of crystalline host rock regions in Germany. The assessment and evaluation of selected programs exploring for rock salt and claystone is currently in progress. The entire systematic approach of the projects GeoMePS and ZuBeMErk aims to develop recommendations for a nondestructive and minimally invasive surface exploration program of siting regions in Germany, regarding the lithological, structural, mechanical, and hydrogeological characterization of the different host rock formations.

Geoscientific Characterization and Interpretation (Geosynthesis) within the Preliminary Safety Assessment in the German Site-Selection Procedure for a High-level Nuclear Waste Repository

After implementation of the Repository Site Selection Act (StandAG) in 2017, the Federal Company for Radioactive Waste Disposal (BGE), as the German waste management organization, started the site selection procedure for a nuclear repository for high-level radioactive waste in Germany. On the way towards the repository site with the best possible safety, the site selection procedure is required to be a participatory, transparent, learning and self-questioning process based on scientific expertise. With the Subareas Interim Report published in 2020, first results were presented outlining subareas with favourable geological conditions in preparation for defining the siting regions for surface exploration. Currently, one of the main tasks in the site selection procedure is to establish a detailed geoscientific synthesis (Geosynthesis) for each subarea. The Geosynthesis contains all geological information for the characterization of each subarea and hence serves as the foundation for the subsequent analysis within the representative preliminary safety assessments (rvSU) and the geoscientific consideration criteria. Based on this information, all areas within the subareas will be evaluated to find the siting regions for surface exploration. The Geosynthesis includes a description of the regional geology focusing on the host rock, the overburden and relevant geological processes that may affect the potential nuclear waste repository in the next 1 million years. The data for the Geosynthesis are mostly compiled from state authorities and include 3-D geologic models, regional maps and cross-sections, bore hole data (e.g. geophysical logs) and seismic data. Furthermore, it is necessary to digitize, process, interpret and evaluate the aforementioned data using the available knowledge from the scientific literature in the context of the site selection procedure.

Investigation of Surface Exploration Programs for Hydrological, Hydrogeological and Hydrogeochemical Issues in the Site Selection Procedure

The project “Investigation of Surface Exploration Programmes for Hydrological, Hydrogeological and Hydrogeochemical Issues in the Site Selection Procedure” summarizes the measurement methods that can be used for surface exploration of site regions and compares them with the measurement parameters as given in the Repository Site Selection Act (StandAG). Based on this, an orientation framework was developed that can support the evaluation of actual exploration programs. This project is limited to those measurement parameters that result from §§ 22–24 in conjunction with the Annexes 1–11 of the StandAG for the surface exploration of hydrological, hydrogeological and hydrogeochemical characteristics of site regions. In a first step, definitions of terms which are subject to interpretation were identified in the StandAG and advice was provided on how to deal with them and, in some cases, justified proposals for interpretation within the framework of this project were given. As a result, hydrological, hydrogeological and hydrogeochemical parameters were presented that were derived directly from the StandAG, as well as those that are not explicitly mentioned in the StandAG but are necessary for a detailed characterization of the rock formations in a site region. The next step was to identify measurement methods to be used for surface exploration of hydrological, hydrogeological and hydrogeochemical parameters. In particular, hydrogeologic and (borehole) geophysical methods were considered in the context of field measurements and laboratory investigations as well as field and laboratory tests for the determination of hydrogeochemical parameters. These measuring methods were described with respect to their measuring principle, the respective limits, the technical effort as well as the advantages and disadvantages of their application. Possible combinations with other measuring methods as well as a potential need for additional research and development for use in surface exploration programs were also presented. Considering the boundary conditions and dependencies for different rock types and necessary exploration depths, the measuring methods were assigned to the relevant parameters with respect to their applicability. In most cases, several methods are suitable for the determination of a specific parameter. Combining different physically independent methods can limit the range of variation of the measured variables and significantly increase the reliability of the results. The resulting compilation of measurement methods was used in the last step to establish an orientation framework. This framework contains the essential requirements for a complete documentation and quality assurance of the measurements and sampling and derives fundamental factors influencing the quality and quantity of the parameters. The orientation framework also refers to various factors that may influence the selection of suitable measuring methods for the surface exploration of the parameters as well as the determination of appropriate measuring network densities and measurement intervals. The measurement network densities selected at the beginning of the exploration are usually adjusted based on increasing knowledge of the site-specific geological conditions. This step-by-step procedure, which has proven successful in geological exploration programs, was also emphasized in the orientation framework, as it gradually increases the level of knowledge, the level of detail and thus the reliability of the measurement results.

A systematic approach for surface exploration of sites – a database to research and evaluate suitable methods

The site selection procedure for a high-level radioactive waste repository in Germany is based on the Repository Site Selection Act (StandAG, 2017), which comprises three phases. In phase 2, the Federal Company for Radioactive Waste Disposal (BGE) will conduct surface exploration. Based on the exploratory findings, the further developed preliminary safety analyses, the common requirements and criteria, and socioeconomic potential analyses will be applied feeding into proposed sites for underground exploration. Commissioned by the BGE, the Federal Institute for Geosciences and Natural Resources (BGR) contributes to this procedure with the projects “GeoMePS” and “ZuBeMErk”, which compile and assess geoscientific and geophysical methods and programs for surface exploration. Their common goal is to develop recommendations for surface exploration of siting regions. For this purpose, the BGR has developed a systematic approach that includes (1) deducing 186 exploration targets (Kneuker, 2020) based on the requirements defined by StandAG, (2) compilation of geoscientific and geophysical exploration methods in a database structure, and (3) analysis of case studies of national and international exploration programs for high-level radioactive waste disposal. During step (2) the BGR developed the database “GeM-DB” which utilizes MS SQL Server 2017 and PHP scripts for a browser-based interface (Beilecke, 2021). Both lead to a highly customizable, user-friendly database enabling further adaptations, expansions and analyses of the contents. Merging the knowledge of about 100 BGR experts, the database currently comprises approx. 140 geoscientific and geophysical exploration methods, including basic information and essential metadata to evaluate the general applicability of the methods for surface exploration of the three defined host rocks (crystalline rock, claystone, rock salt). Additionally, the methods are rated according to their suitability for the previously defined exploration targets. An example for a method selection, which is suitable to target fault zones (exclusion criterion 2, StandAG) is given in Fig. 1. In step (3) the BGR screens national and international waste disposal programs exploring for crystalline rock, claystone, and rock salt and feeds the obtained information back into “GeM-DB”. The entire systematic approach of the projects “GeoMePS” and “ZuBeMErk” aims to develop recommendations for a non-destructive and minimally invasive surface exploration program of siting regions in Germany, regarding the lithological, structural, mechanical, and hydrogeological characterization of the different host rock formations.

Nut Unfastening by Robotic Surface Exploration

In this paper, we present a novel concept and primary investigations regarding automated unfastening of hexagonal nuts by means of surface exploration with a compliant robot. In contrast to the conventional industrial approaches that rely on custom-designed motorised tools and mechanical tool changers, we propose to use robot fingers to position, grasp and unfasten unknown random-sized hexagonal nuts, which are arbitrarily positioned in the robot’s task space. Inspired by how visually impaired people handle unknown objects, in this work, we use information observed from surface exploration to devise the unfastening strategy. It combines torque monitoring with active compliance for the robot fingers to smoothly explore the object’s surface. We implement a shape estimation technique combining scaled iterative closest point and hypotrochoid approximation to estimate the location as well as contour profile of the hexagonal nut so as to accurately position the gripper fingers. We demonstrate this work in the context of dismantling an electrically driven vehicle battery pack. The experiments are conducted using a seven degrees of freedom (DoF)–compliant robot fitted with a two-finger gripper to unfasten four different sized randomly positioned hexagonal nuts. The obtained results suggest an overall exploration and unfastening success rate of 95% over an average of ten trials for each nut.

Rolling controls sperm navigation in response to the dynamic rheological properties of the environment

Mammalian sperm rolling around their longitudinal axes is a long-observed component of motility, but its function in the fertilization process, and more specifically in sperm migration within the female reproductive tract, remains elusive. While investigating bovine sperm motion under simple shear flow and in a quiescent microfluidic reservoir and developing theoretical and computational models, we found that rolling regulates sperm navigation in response to the rheological properties of the sperm environment. In other words, rolling enables a sperm to swim progressively even if the flagellum beats asymmetrically. Therefore, a rolling sperm swims stably along the nearby walls (wall-dependent navigation) and efficiently upstream under an external fluid flow (rheotaxis). By contrast, an increase in ambient viscosity and viscoelasticity suppresses rolling, consequently, non-rolling sperm are less susceptible to nearby walls and external fluid flow and swim in two-dimensional diffusive circular paths (surface exploration). This surface exploration mode of swimming is caused by the intrinsic asymmetry in flagellar beating such that the curvature of a sperm’s circular path is proportional to the level of asymmetry. We found that the suppression of rolling is reversible and occurs in sperm with lower asymmetry in their beating pattern at higher ambient viscosity and viscoelasticity. Consequently, the rolling component of motility may function as a regulatory tool allowing sperm to navigate according to the rheological properties of the functional region within the female reproductive tract.