157 research outputs found
Characteristics of Spinach Chloroplast Envelope, Thylakoid and Stroma Polypeptides as Revealed by Triton X-114 Phase Partition
Comparison of the SDS-PAGE profiles of the spinach chloroplast stroma, thylakoid and envelope membranes shows that several polypeptides have the same electrophoretic mobility. To simplify these somewhat complex electrophoretic profiles and to verify whether the polypeptides having similar electrophoretic mobility are identical, we used Triton X-114 phase partition to obtain a separation of the polypeptides according to their relative hydrophobicity. The stroma polypeptides partitioned essentially in the aqueous phase. About half of the thylakoid and envelope membrane polypeptides were exclusively recovered in either one of the two phases. Therefore, the phase partitioning of membrane polypeptides proved to be useful, as the organic phase contained true intrinsic polypeptides, while the aqueous phase was composed of peripheral ones and stroma components. Particularly interesting was the release of the RubisCO large subunit known to copurify with the envelope membranes. Additional experimental approaches were used (immunology, proteosynthesis in organello) to further characterize proteins which had apparent ambiguous phase partitioning. Here, we show that Triton X-l 14 is an excellent tool to unmask polypeptides having identical electrophoretic mobility but different behaviour towards this detergent; its use leads to a clarification of the polypeptide SDS-PAGE profiles of chloroplast membrane
High-Thrust in-Space Liquid Propulsion Stage: Storable Propellants
In the frame of a project funded by ESA, a consortium led by Avio in cooperation with Snecma, Cira, and DLR is performing the preliminary design of a High-Thrust in-Space Liquid Propulsion Stage for two different types of manned missions beyond Earth orbit. For these missions, one or two 100 ton stages are to be used to propel a manned vehicle. Three different propellant combinations; LOx/LH2, LOx/CH4 and MON-3/MMH are being compared.
The preliminary design of the storable variant (MON-3/MMH) has been performed by DLR. The Aestus II engine with a large nozzle expansion ratio has been chosen as baseline. A first iteration has demonstrated, that it indeed provides the best performance for the storable propellant combination, when considering all engines available today or which may be available in a short- to medium term. The RD-861 K engine has been proposed as alternative to reduce the development duration of the high-thrust stage. Structure analyses and optimisations have converged towards a common bulkhead architecture with a Whipple shield, similar to the one used on the ATV, to protect the main propellant tanks against perforations caused by meteoroids and space debris. The propulsion system has been built around six Aestus II engines equipped with TVC and placed on a circular engine thrust frame. The RCS, the thermal system, and the power system have also been included in the preliminary design, and they have been sized for the most demanding mission. The performance of the high-thrust stage, resulting from the preliminary design, has been assessed for both missions taken into consideration
Exploiting semantic information in a spiking neural SLAM system
To navigate in new environments, an animal must be able to keep track of its position while simultaneously creating and updating an internal map of features in the environment, a problem formulated as simultaneous localization and mapping (SLAM) in the field of robotics. This requires integrating information from different domains, including self-motion cues, sensory, and semantic information. Several specialized neuron classes have been identified in the mammalian brain as being involved in solving SLAM. While biology has inspired a whole class of SLAM algorithms, the use of semantic information has not been explored in such work. We present a novel, biologically plausible SLAM model called SSP-SLAMâa spiking neural network designed using tools for large scale cognitive modeling. Our model uses a vector representation of continuous spatial maps, which can be encoded via spiking neural activity and bound with other features (continuous and discrete) to create compressed structures containing semantic information from multiple domains (e.g., spatial, temporal, visual, conceptual). We demonstrate that the dynamics of these representations can be implemented with a hybrid oscillatory-interference and continuous attractor network of head direction cells. The estimated self-position from this network is used to learn an associative memory between semantically encoded landmarks and their positions, i.e., an environment map, which is used for loop closure. Our experiments demonstrate that environment maps can be learned accurately and their use greatly improves self-position estimation. Furthermore, grid cells, place cells, and object vector cells are observed by this model. We also run our path integrator network on the NengoLoihi neuromorphic emulator to demonstrate feasibility for a full neuromorphic implementation for energy efficient SLAM
Gepotidacin for the Treatment of Uncomplicated Urogenital Gonorrhea: A Phase 2, Randomized, Dose-Ranging, Single-Oral Dose Evaluation
Background:
In this phase 2 study, we evaluated the efficacy and safety of oral gepotidacin, a novel triazaacenaphthylene bacterial type II topoisomerase inhibitor, for the treatment of uncomplicated urogenital gonorrhea.
Methods:
Adult participants with suspected urogenital gonorrhea were enrolled and completed baseline (day 1) and test-of-cure (days 4-8) visits. Pretreatment and posttreatment urogenital swabs were collected for Neisseria gonorrhoeae (NG) culture and susceptibility testing. Pharyngeal and rectal swab specimens were collected if there were known exposures. Participants were stratified by gender and randomized 1:1 to receive a 1500-mg or 3000-mg single oral dose of gepotidacin.
Results:
The microbiologically evaluable population consisted of 69 participants, with NG isolated from 69 (100%) urogenital, 2 (3%) pharyngeal, and 3 (4%) rectal specimens. Microbiological eradication of NG was achieved by 97%, 95%, and 96% of participants (lower 1-sided exact 95% confidence interval bound, 85.1%, 84.7%, and 89.1%, respectively) for the 1500-mg, 3000-mg, and combined dose groups, respectively. Microbiological cure was achieved in 66/69 (96%) urogenital infections. All 3 failures were NG isolates that demonstrated the highest observed gepotidacin minimum inhibitory concentration of 1 ”g/mL and a common gene mutation. At the pharyngeal and rectal sites, 1/2 and 3/3 NG isolates, respectively, demonstrated microbiological cure. There were no treatment-limiting adverse events for either dose.
Conclusions:
This study demonstrated that single, oral doses of gepotidacin were â„95% effective for bacterial eradication of NG in adult participants with uncomplicated urogenital gonorrhea
Using rapid point-of-care tests to inform antibiotic choice to mitigate drug resistance in gonorrhoea
Background:
The first cases of extensively drug resistant gonorrhoea were recorded in the United Kingdom in 2018. There is a public health need for strategies on how to deploy existing and novel antibiotics to minimise the risk of resistance development. As rapid point-of-care tests (POCTs) to predict susceptibility are coming to clinical use, coupling the introduction of an antibiotic with diagnostics that can slow resistance emergence may offer a novel paradigm for maximising antibiotic benefits. Gepotidacin is a novel antibiotic with known resistance and resistance-predisposing mutations. In particular, a mutation that confers resistance to ciprofloxacin acts as the âstepping-stoneâ mutation to gepotidacin resistance.
Aim:
To investigate how POCTs detecting Neisseria gonorrhoeae resistance mutations for ciprofloxacin and gepotidacin can be used to minimise the risk of resistance development to gepotidacin.
Methods:
We use individual-based stochastic simulations to formally investigate the aim.
Results:
The level of testing needed to reduce the risk of resistance development depends on the mutation rate under treatment and the prevalence of stepping-stone mutations. A POCT is most effective if the mutation rate under antibiotic treatment is no more than two orders of magnitude above the mutation rate without treatment and the prevalence of stepping-stone mutations is 1â13%.
Conclusion:
Mutation frequencies and rates should be considered when estimating the POCT usage required to reduce the risk of resistance development in a given population. Molecular POCTs for resistance mutations and stepping-stone mutations to resistance are likely to become important tools in antibiotic stewardship
Capabilities of Gossamer-1 derived small spacecraft solar sails carrying MASCOT-derived nanolanders for in-situ surveying of NEAs
Any effort which intends to physically interact with specific asteroids requires understanding at least of the composition and multi-scale structure of the surface layers, sometimes also of the interior. Therefore, it is necessary first to characterize each target object sufficiently by a precursor mission to design the mission which then interacts with the object. In small solar system body (SSSB) science missions, this trend towards landing and sample-return missions is most apparent. It also has led to much interest in MASCOT-like landing modules and instrument carriers. They integrate at the instrument level to their mothership and by their size are compatible even with small interplanetary missions.
The DLR-ESTEC Gossamer Roadmap NEA Science Working Groupsâ studies identified Multiple NEA Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. Parallel studies of Solar Polar Orbiter (SPO) and Displaced L1 (DL1) space weather early warning missions studies outlined very lightweight sailcraft and the use of separable payload modules for operations close to Earth as well as the ability to access any inclination and a wide range of heliocentric distances.
These and many other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter. Since the original MNR study, significant progress has been made to explore the performance envelope of near-term solar sails for multiple NEA rendezvous.
However, although it is comparatively easy for solar sails to reach and rendezvous with objects in any inclination and in the complete range of semi-major axis and eccentricity relevant to NEOs and PHOs, it remains notoriously difficult for sailcraft to interact physically with a SSSB target object as e.g. the Hayabusa missions do.
The German Aerospace Center, DLR, recently brought the Gossamer solar sail deployment technology to qualification status in the Gossamer-1 project. Development of closely related technologies is continued for very large deployable membrane-based photovoltaic arrays in the GoSolAr project.
We expand the philosophy of the Gossamer solar sail concept of efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions. These are equally useful for planetary defence scenarios, SSSB science and NEO utilization. We outline the technological concept used to complete such missions and the synergetic integration and operation of sail and lander.
We similarly extend the philosophy of MASCOT and use its characteristic features as well as the concept of Constraints-Driven Engineering for a wider range of operations
Small Spacecraft Based Multiple Near-Earth Asteroid Rendezvous and Landing with Near-Term Solar Sails and âNow-Termâ Technologies
Physical interaction with small solar system bodies (SSSB) is the next step in planetary science, planetary in-situ resource utilization (ISRU), and planetary defense (PD). It requires a broader understanding of the surface properties of the target objects, with particular interest focused on those near Earth. Knowledge of composition, multi-scale surface structure, thermal response, and interior structure is required to design, validate and operate missions addressing these three fields. The current level of understanding is occasionally simplified into the phrase, âIf youâve seen one asteroid, youâve seen one asteroidâ, meaning that the in-situ characterization of SSSBs has yet to cross the threshold towards a robust and stable scheme of classification. This would enable generic features in spacecraft design, particularly for ISRU and science missions. Currently, it is necessary to characterize any potential target object sufficiently by a dedicated pre-cursor mission to design the mission which then interacts with the object in a complex fashion. To open up strategic approaches, much broader in-depth characterization of potential target objects would be highly desirable. In SSSB science missions, MASCOT-like nano-landers and instrument carriers which integrate at the instrument level to their mothership have met interest. By its size, MASCOT is compatible with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap Science Working Groupsâ studies identified Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. The Solar Polar Orbiter (SPO) study showed the ability to access any inclination, theDisplaced-L1 (DL1) mission operates close to Earth, where objects of interest to PD and for ISRU reside. Other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter, and significant progress has been made to explore the performance envelope of near-term solar sails for MNR. However, it is difficult for sailcraft to interact physically with a SSSB. We expand and extend the philosophy of the recently qualified DLR Gossamer solar sail deployment technology using efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions by synergetic integration and operation of sail and lander. The MASCOT design concept and its characteristic features have created an ideal counterpart for thisand has already been adapted to the needs of the AIM spacecraft, former part of the NASA-ESA AIDA mission. Designing the combined spacecraft for piggy-back launch accommodation enables low-cost massively parallel access to the NEA population
Solar Sails for Planetary Defense and High-Energy Missions
20 years after the successful ground deployment test of a (20 m)ÂČ solar sail at DLR Cologne, and in the light of the upcoming U.S. NEAscout mission, we provide an overview of the progress made since in our mission and hardware design studies as well as the hardware built in the course of our solar sail technology development. We outline the most likely and most efficient routes to develop solar sails for useful missions in science and applications, based on our developed ânow-termâ and near-term hardware as well as the many practical and managerial lessons learned from the DLR-ESTEC GOSSAMER Roadmap. Mission types directly applicable to planetary defense include single and Multiple NEA Rendezvous ((M)NR) for precursor, monitoring and follow-up scenarios as well as sail-propelled head-on retrograde kinetic impactors (RKI) for mitigation. Other mission types such as the Displaced L1 (DL1) space weather advance warning and monitoring or Solar Polar Orbiter (SPO) types demonstrate the capability of near-term solar sails to achieve asteroid rendezvous in any kind of orbit, from Earth-coorbital to extremely inclined and even retrograde orbits. Some of these mission types such as SPO, (M)NR and RKI include separable payloads. For one-way access to the asteroid surface, nanolanders like MASCOT are an ideal match for solar sails in micro-spacecraft format, i.e. in launch configurations compatible with ESPA and ASAP secondary payload platforms. Larger landers similar to the JAXA-DLR study of a Jupiter Trojan asteroid lander for the OKEANOS mission can shuttle from the sail to the asteroids visited and enable multiple NEA sample-return missions. The high impact velocities and re-try capability achieved by the RKI mission type on a final orbit identical to the target asteroidâs but retrograde to its motion enables small spacecraft size impactors to carry sufficient kinetic energy for deflection
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