Collision Avoidance Algorithm for USV Based on Rolling Obstacle Classification and Fuzzy Rules

Dynamic collision avoidance between multiple vessels is a task full of challenges for unmanned surface vehicle (USV) movement, which has high requirements on real-time performance and safety. The difficulty of multi-obstacle collision avoidance is that it is hard to formulate the optimal obstacle avoidance strategy when encountering more than one obstacle threat at the same time; a good strategy to avoid one obstacle sometimes leads to threats from other obstacles. This paper presents a dynamic collision avoidance algorithm for USVs based on rolling obstacle classification and fuzzy rules. Firstly, potential collision probabilities between a USV and obstacles are calculated based on the time to the closest point of approach (TCPA). All obstacles are given different priorities based on potential collision probability, and the most urgent and secondary urgent ones will then be dynamically determined. Based on the velocity obstacle algorithm, four possible actions are defined to determine the basic domain in the collision avoidance strategy. After that, the Safety of Avoidance Strategy and Feasibility of Strategy Adjustment are calculated to determine the additional domain based on fuzzy rules. Fuzzy rules are used here to comprehensively consider the situation composed of multiple motion obstacles and the USV. Within the limited range of the basic domain and the additional domain, the optimal collision avoidance parameters of the USV can be calculated by the particle swarm optimization (PSO) algorithm. The PSO algorithm utilizes both the characteristic of pursuance for the population optimal and the characteristic of exploration for the individual optimal to avoid falling into the local optimal solution. Finally, numerical simulations are performed to certify the validity of the proposed method in complex traffic scenarios. The results illustrated that the proposed method could provide efficient collision avoidance actions.

Molecular coevolution of nuclear and nucleolar localization signals inside basic domain of HIV-1 Tat

During evolution, viruses had to adapt to an increasingly complex environment of eukaryotic cells. Viral proteins that need to enter the cell nucleus or associate with nucleoli possess nuclear localization signals (NLSs) and nucleolar localization signals (NoLSs) for nuclear and nucleolar accumulation, respectively. As viral proteins are relatively small, acquisition of novel sequences seems to be a more complicated task for viruses than for eukaryotes. Here, we carried out a comprehensive analysis of the basic domain (BD) of HIV-1 Tat to show how viral proteins might evolve with NLSs and NoLSs without an increase in protein size. The HIV-1 Tat BD is involved in several functions, the most important being the transactivation of viral transcription. The BD also functions as an NLS, although it is substantially longer than a typical NLS. It seems that different regions in the BD could function as NLSs due to its enrichment with positively charged amino acids. Additionally, the high positive net charge inevitably causes the BD to function as an NoLS through a charge-specific mechanism. The integration of NLSs and NoLSs into functional domains enriched with positively charged amino acids might be a mechanism that allows the condensation of different functional sequences in small protein regions and, as a result, to reduce protein size, influencing the origin and evolution of NLSs and NoLSs in viruses. IMPORTANCE Here, we investigated the molecular mechanism of NLS and NoLS integration into the basic domain of HIV-1 Tat ( 49 RKKRRQRRR 57 ), and found that these two supplementary functions (i.e., function of NLS and NoLS) are embedded in the basic domain amino acid sequence. The integration of NLSs and NoLSs into functional domains of viral proteins enriched with positively charged amino acids is a mechanism that allows the concentration of different functions within small protein regions. Integration of NLS and NoLS into functional protein domains might have influenced the viral evolution, as this could prevent an increase in the protein size.

Validation of interventions for risk of impaired skin integrity in adult and aged patients

ABSTRACT Objectives: to validate nursing interventions for the diagnosis Risk for Impaired Skin Integrity in adult and aged hospitalized patients. Methods: descriptive, quantitative study, using the content validity of interventions done by 14 specialist nurses. Results: the specialist nurses had worked in the area for more than five years. Four (28.5%) used NANDA-I and CIPE®, three (21.4%) used NANDA-I, NIC and CIPE®, three (21.4%) used NANDA-I, NIC, NOC and CIPE® and four (28.5%) were currently working only with CIPE®. The validation analyzed 32 NIC interventions, of which 11 were priority and 21 were suggested. Of the priority interventions, five belonged to the Physiological/Complex domain, five to the Physiological/Basic domain and one to the Safety Domain. Final Considerations: nursing interventions are essential for planning and support good practices in teaching, research and care.

Conformational Flexibility of p150Glued(1-191) Subunit of Dynactin Assembled with Microtubules

ABSTRACTMicrotubule-associated proteins (MAPs) perform diverse functions in cells. These functions are dependent on their interactions with microtubules. Dynactin, a cofactor of dynein motor, assists the binding of dynein to various organelles and is crucial to the long-distance processivity of dynein-based complexes. The largest subunit of dynactin, the p150glued, contains a N-terminus segment that is responsible for the microtubule-binding interactions and long-range processivity of dynactin. We employed solution and magic angle spinning NMR spectroscopy to characterize the structure and dynamics of the p150glued N-terminal region, both free and in complex with polymerized microtubules. This 191-residue region encompasses the CAP-Gly domain, the basic domain and serine-proline-rich (SP-rich) domain. We demonstrate that the basic and SP-rich domains are intrinsically disordered in solution and significantly enhance the binding affinity to microtubules as these regions contain the second microtubule-binding site on the p150Glued subunit. The majority of the basic and SP-rich domains are predicted to be random-coil, while the segments S111–I116, A124–R132 and K144–T146 in the basic domain contain short α-helical or β-sheet structures. These three segments possibly encompass the microtubule binding site. Surprisingly, the protein retains high degree of flexibility upon binding to microtubules except for the regions that are directly involved in the binding interactions with microtubules. This conformational flexibility may be essential for the biological functions of the p150Glued subunit.STATEMENT OF SIGNIFICANCEMicrotubule-associated proteins (MAPs) perform diverse functions in cells. Many of them comprises intrinsically disordered regions, whose structural flexibility are central to microtubule-based cellular functions of MAPs. We employed solution and magic angle spinning NMR spectroscopy to characterize the structure and dynamics of the p150glued N-terminal region encompassing the CAP-Gly domain, the basic domain and serine-proline-rich (SP-rich) domain, both free and in complex with polymerized microtubules. The results reveal that the basic and SP-rich domains are largely unstructured and retains high degree of flexibility upon binding to microtubules except for the regions that are possibly involved in the binding interactions with microtubules. This approach is informative for dynamics studies of intrinsically disordered MAPs and other disordered proteins in large biological assemblies.

Didehydro-Cortistatin A Inhibits HIV-1 by Specifically Binding to the Unstructured Basic Region of Tat

ABSTRACTThe intrinsically disordered HIV-1 Tat protein binds the viral RNA transactivation response structure (TAR), which recruits transcriptional cofactors, amplifying viral mRNA expression. Limited Tat transactivation correlates with HIV-1 latency. Unfortunately, Tat inhibitors are not clinically available. The small molecule didehydro-cortistatin A (dCA) inhibits Tat, locking HIV-1 in persistent latency, blocking viral rebound. We generated chemical derivatives of dCA that rationalized molecular docking of dCA to an active and specific Tat conformer. These revealed the importance of the cycloheptene ring and the isoquinoline nitrogen’s positioning in the interaction with specific residues of Tat’s basic domain. These features are distinct from the ones required for inhibition of cyclin-dependent kinase 8 (CDK8), the only other known ligand of dCA. Besides, we demonstrated that dCA activity on HIV-1 transcription is independent of CDK8. The binding of dCA to Tat with nanomolar affinity alters the local protein environment, rendering Tat more resistant to proteolytic digestion. dCA thus locks a transient conformer of Tat, specifically blocking functions dependent of its basic domain, namely the Tat-TAR interaction; while proteins with similar basic patches are unaffected by dCA. Our results improve our knowledge of the mode of action of dCA and support structure-based design strategies targeting Tat, to help advance development of dCA, as well as novel Tat inhibitors.IMPORTANCETat activates virus production, and limited Tat transactivation correlates with HIV-1 latency. The Tat inhibitor dCA locks HIV in persistent latency. This drug class enables block-and-lock functional cure approaches, aimed at reducing residual viremia during therapy and limiting viral rebound. dCA may also have additional therapeutic benefits since Tat is also neurotoxic. Unfortunately, Tat inhibitors are not clinically available. We generated chemical derivatives and rationalized binding to an active and specific Tat conformer. dCA features required for Tat inhibition are distinct from features needed for inhibition of cyclin-dependent kinase 8 (CDK8), the only other known target of dCA. Furthermore, knockdown of CDK8 did not impact dCA’s activity on HIV-1 transcription. Binding of dCA to Tat’s basic domain altered the local protein environment and rendered Tat more resistant to proteolytic digestion. dCA locks a transient conformer of Tat, blocking functions dependent on its basic domain, namely its ability to amplify viral transcription. Our results define dCA’s mode of action, support structure-based-design strategies targeting Tat, and provide valuable information for drug development around the dCA pharmacophore.