This paper presents a novel integrated approach for efficient optimization based online trajectory planning of topologically distinctive mobile robot trajectories. Online trajectory optimization ...deforms an initial coarse path generated by a global planner by minimizing objectives such as path length, transition time or control effort. Kinodynamic motion properties of mobile robots and clearance from obstacles impose additional equality and inequality constraints on the trajectory optimization. Local planners account for efficiency by restricting the search space to locally optimal solutions only. However, the objective function is usually non-convex as the presence of obstacles generates multiple distinctive local optima.
The proposed method maintains and simultaneously optimizes a subset of admissible candidate trajectories of distinctive topologies and thus seeking the overall best candidate among the set of alternative local solutions. Time-optimal trajectories for differential-drive and carlike robots are obtained efficiently by adopting the Timed-Elastic-Band approach for the underlying trajectory optimization problem. The investigation of various example scenarios and a comparative analysis with conventional local planners confirm the advantages of integrated exploration, maintenance and optimization of topologically distinctive trajectories.
•An integrated online trajectory optimization approach is proposed.•Maintaining and optimization of admissible candidate trajectories of distinctive topologies in order to seek the overall best solution.•An exploration strategy based on Voronoi diagrams provides the complete set of alternative trajectories.•An alternative proposed sampling based strategy generates a sufficient subset for small to medium sized environments under limited computational budgets.•The Timed-Elastic-Band trajectory optimization method complies with non-holonomic kinematics of differential-drive and carlike robots.
Mesoporous organic–inorganic hybrid materials, a new class of materials characterized by large specific surface areas and pore sizes between 2 and 15 nm, have been obtained through the coupling of ...inorganic and organic components by template synthesis. The incorporation of functionalities can be achieved in three ways: by subsequent attachment of organic components onto a pure silica matrix (grafting), by simultaneous reaction of condensable inorganic silica species and silylated organic compounds (co‐condensation, one‐pot synthesis), and by the use of bissilylated organic precursors that lead to periodic mesoporous organosilicas (PMOs). This Review gives an overview of the preparation, properties, and potential applications of these materials in the areas of catalysis, sorption, chromatography, and the construction of systems for controlled release of active compounds, as well as molecular switches, with the main focus being on PMOs.
Pores for thought: The modification of mesoporous silica phases with organic components extends this class of materials and their potential application in areas such as the production of insulators in the chip industry. Periodic mesoporous organosilicas (PMOs) occupy a special position in this respect, as the organic component is an integral part of the framework. The figure shows a PMO with a crystal‐like structure of the pore wall.
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•Combination of semi-carbonization and KOH activation leads to carbons with higher surface areas and pore volumes.•High specific capacitance in standard organic electrolytes.•Superior ...current response with 97.8% capacitance retention and low time relaxation constants.
A series of porous carbon samples were prepared by combining a semi-carbonization process of acidic polymerized phenol-formaldehyde resins and a following chemical activation with KOH used in different ratios to increase specific surface area, micropore content and pore sizes of the carbons which is favourable for supercapacitor applications. Samples were characterized by nitrogen physisorption, powder X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The results show that the amount of KOH, combined with the semi-carbonization step had a remarkable effect on the specific surface area (up to SBET: 3595m2g−1 and SDFT: 2551m2g−1), pore volume (0.60–2.62cm3g−1) and pore sizes (up to 3.5nm). The carbons were tested as electrode materials for electrochemical double layer capacitors (EDLC) in a two electrode setup with tetraethylammonium tetrafluoroborate in acetonitrile as electrolyte. The prepared carbon material with the largest surface area, pore volume and pore sizes exhibits a high specific capacitance of 145.1Fg−1 at a current density of 1Ag−1. With a high specific energy of 31Whkg−1 at a power density of 33028Wkg−1 and a short time relaxation constant of 0.29s, the carbon showed high power capability as an EDLC electrode material.
A stereoselective synthesis of functionalized hexahydrocarbazoles was developed based on an unprecedented photoredox‐induced dearomative radical (4+2)‐cyclization/1,4‐addition cascade between ...3‐(2‐iodoethyl)indoles and acceptor‐substituted alkenes. The title reaction simultaneously generates three C−C bonds and one C−H bond, along with three contiguous stereogenic centers. The hexahydro‐1H‐carbazole products are highly valuable intermediates for the synthesis of novel antibiotics, as well as unnatural ring homologues of polycyclic indoline alkaloids.
One photon, four bonds: A photoredox‐induced dearomative radical (4+2)‐cyclization/1,4‐addition cascade with 3‐(2‐iodoethyl)indoles and acceptor‐substituted alkenes enables the synthesis of highly substituted hexahydro‐1H‐carbazoles. This method involves the simultaneous formation of four bonds and three contiguous stereocenters with high stereoselectivity. PC=photocatalyst.
Force‐field based grand‐canonical Monte Carlo simulations are used to investigate the acetylene and carbon dioxide uptake capacity, as well as the C2H2/CO2 adsorption selectivity of three novel ...microporous materials: Magnesium formate, Cu3(btc)2, and cucurbit6uril. Because no comparable computational studies of acetylene adsorption have been reported so far, the study focuses on systems for which experimental data are available to permit a thorough validation of the simulation results. The results for magnesium formate are in excellent agreement with experiment. The simulation predicts a high selectivity for acetylene over CO2, which can be understood from a detailed analysis of the structural features that determine the affinity of Mg‐formate towards C2H2. For Cu3(btc)2, preliminary calculations reveal the necessity to include the interaction of the sorbate molecules with the unsaturated metal sites, which is done by means of a parameter adjustment based on ab‐initio calculations. In spite of the high C2H2 storage capacity, the C2H2/CO2 selectivity of this material is very modest. The simulation results for the porous organic crystal cucurbit6uril show that the adsorption characteristics that have been observed experimentally, particularly the very high isosteric heat of adsorption, cannot be understood when an ideal structure is assumed. It is postulated that structural imperfections play a key role in determining the C2H2 adsorption behavior of this material, and this proposition is supported by additional calculations.
Separating the similar: Force‐field‐based simulations are used to calculate the C2H2 storage capacity of two MOFs and one organic porous crystal (see picture). The C2H2/CO2 adsorption selectivity of these systems is predicted from additional computations. The structural features determining the adsorption and separation properties are analyzed in detail.
Quantum computing and quantum information processing (QC/QIP) crucially depend on the availability of suitable quantum bits (qubits) and methods of their manipulation. Most qubit candidates known to ...date are not applicable at ambient conditions. Herein, we propose radical‐grafted mesoporous silica as a versatile and prospective nanoplatform for spin‐based QC/QIP. Extremely stable Blatter‐type organic radicals are used, whose electron spin decoherence time is profoundly long even at room temperature (up to Tm≈2.3 μs), thus allowing efficient spin manipulation by microwave pulses. The mesoporous structure of such composites is nuclear‐spin free and provides additional opportunities of embedding guest molecules into the channels. Robustness and tunability of these materials promotes them as highly promising nanoplatforms for future QC/QIP developments.
Extremely stable Blatter's type organic radicals grafted into the mesoporous silica show advanced relaxation properties at room temperature. Electron spin decoherence time exceeds that in many other qubit candidates, allowing efficient spin manipulation at ambient conditions. The tuneable multifunctional nature of such composite materials promotes them as promising nanoplatforms for developing new spin‐based quantum bits.
Few natural oxindole alkaloids possess an exceptional spiro‐(1,3)oxazinan‐3,6′‐oxindole core structure, which results from an unusual oxidative indole rearrangement. The Rauvolfia alkaloid reserpine ...can be converted into the spirooxindole‐1,3‐oxazines dioxyreserpine and trioxyreserpine through efficient visible‐light catalytic photooxygenation with anthraquinone photocatalysts. A mechanistic investigation sheds new light on the photooxidative rearrangement of reserpine and related monoterpene indole alkaloids, and the spirooxindole‐1,3‐oxazine products can be valorized by reductive ring opening, to obtain cis‐decahydroisoquinolines as new enantiopure synthetic building blocks, as demonstrated for dioxyreserpine.
Switching the core: Few natural oxindole alkaloids possess the exceptional spirooxindole‐1,3‐oxazine core structure, which results from an unusual oxidative indole rearrangement. The Rauvolfia alkaloid reserpine can be converted into the photoproducts dioxyreserpine and trioxyreserpine through efficient visible‐light catalytic photooxygenation with anthraquinone photocatalysts (see scheme).
For decades, the headache was not considered a typical symptom of multiple sclerosis (MS) and was construed as a "red flag" for important differential diagnoses such as cerebral vasculitis. ...Meanwhile, several studies have demonstrated an increased prevalence of headaches in MS compared to the general population. This is due to the heterogeneity of headache genesis with frequent occurrence of both primary and secondary headaches in MS. On the one hand, MS and migraine are often comorbid. On the other hand, secondary headaches frequently occur, especially in the course of MS relapses. These are often migraine-like headaches caused by inflammation, which can improve as a result of MS-specific therapy. Headaches are particularly common in the early stages of chronic inflammatory CNS disease, where inflammatory activity is the greatest. In addition, headaches can also occur as a side effect of disease-modifying drugs (DMDs). Headache can occur with most DMDs and is most frequently described with interferon-beta therapy. The aim of this work is to present the prevalence of headaches and describe the heterogeneity of possible causes of headaches in MS. In addition, important therapeutic aspects in the treatment of MS patients, in general, will be presented as well as different approaches to the treatment of headaches in MS depending on the etiological classification.
The diagnostic and pathophysiological relevance of antibodies to aquaporin-4 (AQP4-Ab) in patients with neuromyelitis optica spectrum disorders (NMOSD) has been intensively studied. However, little ...is known so far about the clinical impact of AQP4-Ab seropositivity.
To analyse systematically the clinical and paraclinical features associated with NMO spectrum disorders in Caucasians in a stratified fashion according to the patients' AQP4-Ab serostatus.
Retrospective study of 175 Caucasian patients (AQP4-Ab positive in 78.3%).
Seropositive patients were found to be predominantly female (p < 0.0003), to more often have signs of co-existing autoimmunity (p < 0.00001), and to experience more severe clinical attacks. A visual acuity of ≤ 0.1 during acute optic neuritis (ON) attacks was more frequent among seropositives (p < 0.002). Similarly, motor symptoms were more common in seropositive patients, the median Medical Research Council scale (MRC) grade worse, and MRC grades ≤ 2 more frequent, in particular if patients met the 2006 revised criteria (p < 0.005, p < 0.006 and p < 0.01, respectively), the total spinal cord lesion load was higher (p < 0.006), and lesions ≥ 6 vertebral segments as well as entire spinal cord involvement more frequent (p < 0.003 and p < 0.043). By contrast, bilateral ON at onset was more common in seronegatives (p < 0.007), as was simultaneous ON and myelitis (p < 0.001); accordingly, the time to diagnosis of NMO was shorter in the seronegative group (p < 0.029). The course of disease was more often monophasic in seronegatives (p < 0.008). Seropositives and seronegatives did not differ significantly with regard to age at onset, time to relapse, annualized relapse rates, outcome from relapse (complete, partial, no recovery), annualized EDSS increase, mortality rate, supratentorial brain lesions, brainstem lesions, history of carcinoma, frequency of preceding infections, oligoclonal bands, or CSF pleocytosis. Both the time to relapse and the time to diagnosis was longer if the disease started with ON (p < 0.002 and p < 0.013). Motor symptoms or tetraparesis at first myelitis and > 1 myelitis attacks in the first year were identified as possible predictors of a worse outcome.
This study provides an overview of the clinical and paraclinical features of NMOSD in Caucasians and demonstrates a number of distinct disease characteristics in seropositive and seronegative patients.
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