Alternative Topologies Research Articles

Sychnotylenchus kulinichi sp. n. (Nematoda: Anguinoidea) from the Primorsky Krai of Russia with a tabular key to the genus Sychnotylenchus Rühm, 1956

Summary A new species of the genus Sychnotylenchus Rühm, 1956, S. kulinchi sp. n., inhabiting the bark beetle galleries of Pityogenes chalcographus in Pinus koraiensis was found in the Primorsky Krai of Russia. The new species differs morphologically from the closely related species S. yasinskii and S. mayor in having a shorter body length (626-1030 vs 1250-1280 and 1935-1455 μm, respectively) and from S. sparnugus in having a greater value of the ratio between spicule length and tail length (0.9-11 vs less than 0.7). Phylogenetic analysis of the partial 18S rRNA, D2-D3 expansion segments of the 28S rRNA, the ITS rRNA and COI gene sequences showed that the Russian S. kulinichi sp. n. population grouped with populations from Israel and an unspecified locality that were identified incorrectly as Ditylenchus forepolitor, which are considered conspecific with S. kulinichi sp. n. in this study. Phylogenetic analyses aiming to clarify the controversial taxonomic status of Neoditylenchus and Sychnotylenchus species indicated that, although the genus Sychnotylenchus was paraphyletic in some phylogenetic trees, testing of alternative topologies for the 18S rRNA, D2-D3 of 28S rRNA and ITS rRNA gene trees and datasets using the maximum likelihood method did not exclude the monophyly of this genus and did not justify the validity of the genus Neoditylenchus, which should be considered a junior synonym of Sychnotylenchus as proposed by Fortuner & Maggenti (1987). Molecular phylogeny showed close relationships of Sychnotylenchus with plant-parasitic nematodes from the genera Ficotylus, Orrina and Pterotylenchus, and also with the insect-associated genus Neomisticius. A polytomous key listing 24 morphological diagnostic characters for the identification of 33 species of Sychnotylenchus is provided, along with a table listing associated bark beetle species.

Revisiting the four Hexapoda classes: Protura as the sister group to all other hexapods

Insects represent the most diverse animal group, yet previous phylogenetic analyses based on morphological and molecular data have failed to agree on the evolutionary relationships of early insects and their six-legged relatives (together constituting the clade Hexapoda). In particular, the phylogenetic positions of the three early-diverging hexapod lineages-the coneheads (Protura), springtails (Collembola), and two-pronged bristletails (Diplura)-have been debated for over a century, with alternative topologies implying drastically different scenarios of the evolution of the insect body plan and hexapod terrestrialization. We addressed this issue by sampling all hexapod orders and experimenting with a broad range of across-site compositional heterogeneous models designed to tackle ancient divergences. Our analyses support Protura as the earliest-diverging hexapod lineage ("Protura-sister") and Collembola as a sister group to Diplura, a clade corresponding to the original composition of Entognatha, and characterized by the shared possession of internal muscles in the antennal flagellum. The previously recognized 'Elliplura' hypothesis is recovered only under the site-homogeneous substitution models with partial supermatrices. Our cross-validation analysis shows that the site-heterogeneous CAT-GTR model, which recovers "Protura-sister," fits significantly better than homogeneous models. Furthermore, the morphologically unusual Protura are also supported as the earliest-diverging hexapod lineage by other lines of evidence, such as mitogenomes, comparative embryology, and sperm morphology, which produced results similar to those in this study. Our backbone phylogeny of hexapods will facilitate the exploration of the underpinnings of hexapod terrestrialization and megadiversity.

Improving the performance of mutation-based evolving artificial neural networks with self-adaptive mutations.

Neuroevolution is a promising approach for designing artificial neural networks using an evolutionary algorithm. Unlike recent trending methods that rely on gradient-based algorithms, neuroevolution can simultaneously evolve the topology and weights of neural networks. In neuroevolution with topological evolution, handling crossover is challenging because of the competing conventions problem. Mutation-based evolving artificial neural network is an alternative topology and weights neuroevolution approach that omits crossover and uses only mutations for genetic variation. This study enhances the performance of mutation-based evolving artificial neural network in two ways. First, the mutation step size controlling the magnitude of the parameter perturbation is automatically adjusted by a self-adaptive mutation mechanism, enabling a balance between exploration and exploitation during the evolution process. Second, the structural mutation probabilities are automatically adjusted depending on the network size, preventing excessive expansion of the topology. The proposed methods are compared with conventional neuroevolution algorithms using locomotion tasks provided in the OpenAI Gym benchmarks. The results demonstrate that the proposed methods with the self-adaptive mutation mechanism can achieve better performance. In addition, the adjustment of structural mutation probabilities can mitigate topological bloat while maintaining performance.

Radical-Induced Photochromic Silver(I) Metal-Organic Frameworks: Alternative Topology, Dynamic Photoluminescence and Efficient Photothermal Conversion Modulated by Anionic Guests.

Photogenerated radicals are an indispensable member of the state-of-the-art photochromic material family, as they can effectively modulate the photoluminescence and photothermal conversion performance of radical-induced photochromic complexes. Herein, two novel radical-induced photochromic metal-organic frameworks (MOFs), [Ag(TEPE)](AC) ⋅ 7/4H2O ⋅ 5/4EtOH (1) and [Ag(TEPE)](NC) ⋅ 3H2O ⋅ EtOH (2), are reported. Distinctly different topological networks can be obtained by judiciously introducing alternative π-conjugated anionic guests, including a new topological structure (named as sfm) first reported in this work, describing as 4,4,4,4-c net. EPR data and UV-Vis spectra prove the radical-induced photochromic mechanism. Dynamic photochromism exhibits tunability in a wide CIE color space, with a linear segment from yellow to red for 1, while a curved coordinate line for 2, resulting in colorful emission from blue to orange. Moreover, photogenerated TEPE* radicals effectively activate the near-infrared (NIR) photothermal conversion effect of MOFs. Under 1 W cm-2 808 nm laser irradiation, the surface temperatures of photoproducts 1* and 2* can reach ~160 °C and ~120 °C, respectively, with competitive NIR photothermal conversion efficiencies η=51.8 % (1*) and 36.2 % (2*). This work develops a feasible electrostatic compensation strategy to accurately introduce photoactive anionic guests into MOFs to construct multifunctional radical-induced photothermal conversion materials with tunable photoluminescence behavior.

Radical‐Induced Photochromic Silver(I) Metal–Organic Frameworks: Alternative Topology, Dynamic Photoluminescence and Efficient Photothermal Conversion Modulated by Anionic Guests

AbstractPhotogenerated radicals are an indispensable member of the state‐of‐the‐art photochromic material family, as they can effectively modulate the photoluminescence and photothermal conversion performance of radical‐induced photochromic complexes. Herein, two novel radical‐induced photochromic metal–organic frameworks (MOFs), [Ag(TEPE)](AC) ⋅ 7/4H2O ⋅ 5/4EtOH (1) and [Ag(TEPE)](NC) ⋅ 3H2O ⋅ EtOH (2), are reported. Distinctly different topological networks can be obtained by judiciously introducing alternative π‐conjugated anionic guests, including a new topological structure (named as sfm) first reported in this work, describing as 4,4,4,4‐c net. EPR data and UV–Vis spectra prove the radical‐induced photochromic mechanism. Dynamic photochromism exhibits tunability in a wide CIE color space, with a linear segment from yellow to red for 1, while a curved coordinate line for 2, resulting in colorful emission from blue to orange. Moreover, photogenerated TEPE* radicals effectively activate the near‐infrared (NIR) photothermal conversion effect of MOFs. Under 1 W cm−2 808 nm laser irradiation, the surface temperatures of photoproducts 1* and 2* can reach ~160 °C and ~120 °C, respectively, with competitive NIR photothermal conversion efficiencies η=51.8 % (1*) and 36.2 % (2*). This work develops a feasible electrostatic compensation strategy to accurately introduce photoactive anionic guests into MOFs to construct multifunctional radical‐induced photothermal conversion materials with tunable photoluminescence behavior.

Practical guidance and workflows for identifying fast evolving non-coding genomic elements using PhyloAcc.

Comparative genomics provides ample ways to study genome evolution and its relationship to phenotypic traits. By developing and testing alternate models of evolution throughout a phylogeny, one can estimate rates of molecular evolution along different lineages in a phylogeny and link these rates with observations in extant species, such as convergent phenotypes. Pipelines for such work can help identify when and where genomic changes may be associated with, or possibly influence, phenotypic traits. We recently developed a set of models called PhyloAcc, using a Bayesian framework to estimate rates of nucleotide substitution on different branches a phylogenetic tree and evaluate their association with pre-defined or estimated phenotypic traits PhyloAcc-ST and PhyloAcc-GT both allow users to define a priori a set of target lineages and then compare different models to identify loci accelerating in one or more target lineages. Whereas ST considers only one species tree across all input loci, GT considers alternate topologies for every locus. PhyloAcc-C simultaneously models molecular rates and rates of continuous trait evolution,allowing the user to ask whether the two are associated. Here we describe these models and provide tips and workflows on how to prepare the input data and run PhyloAcc.

A revised tribal classification of Papaveraceae (poppy family) based on molecular and morphological data

AbstractPapaveraceae, commonly known as the poppy family, contains many species with horticultural and/or pharmaceutical importance and has been the subject of various molecular studies. However, a widely accepted tribal classification for Papaveraceae remains lacking. In this study, we used a sampling covering all 48 of the currently recognized genera of Papaveraceae. Our study is to employ broad morphological data in combination with sequence data from two nuclear and seven plastid DNA regions to reconstruct phylogenetic relationships within the family. Our analyses indicate that Pteridophylloideae is sister to the clade containing Hypecooideae and Fumarioideae, and these three lineages are in turn sister to Papaveroideae. The alternative topologies constraining Pteridophylloideae as sister to the other poppy species, to Papaveroideae or to Hypecooideae, as recovered in previous studies, are all rejected. Fumarioideae contains nine main clades, and Fumarieae is nested in traditional Corydaleae. Within Papaveroideae, three main clades are recovered and Platystemoneae is embedded within traditional Papavereae. Both topologies constraining traditional Corydaleae or Papavereae as monophyletic are significantly rejected. Within this phylogenetic framework, the evolution of selected characters is inferred and diagnostic morphological characters at different taxonomic levels are identified and discussed. Based on morphological and molecular evidence, a new tribal classification of Papaveraceae is presented, in which 4 subfamilies, 14 tribes (including 7 newly described tribes), and 43 genera are recognized.

Performance evaluation of multilevel multiphase inverters by piece-wised linearized simulation models

The paper deals with the design issue of the computer simulation models of the traction inverter reflecting request on the rapid investigation of the efficiency performance under various operational conditions. According to this, a piece-wised linearized simulation tool PLECS is selected for model development, which considers the relevant loss behaviour of the main power circuit semiconductor components. The topologies, for which the simulation models are created, are topologies, one of which is commonly used across the automotive industry as the heart of the traction drive (VSI – Voltage Source Inverter), and its perspective alternative three-level traction inverter topology T-NPC – T-type Neutral Point Clamped. The simulation models created in the given simulation tool are thus subjected to the analysis of power parameters, which also include the calculated power losses of the entire system of semiconductor devices for both topologies of the traction inverter. Based on the obtained power parameters, the efficiency performance under various operational conditions of both topologies is evaluated. The presented methodology enables rapid investigation of operational performance enabling fast optimization methods. Any design of linearized simulation models in the PLECS simulation tool, whose core consists of semiconductor elements, can be analyzed by the proposed methodology.

Performance comparison of an alternative converter for wind powered switched reluctance generators

The subject of this paper is a comparison of the performances of two converter topologies for Switched Reluctance Generators – SRG. It deals with this special electrical generator excited through a rectified DC link. The prime mover is a wind turbine. Mathematical model and simulation results are presented. Both the power converters topologies implemented work well but the alternative one is cheaper and more efficient than the conventional half-bridge one. Furthermore, only the alternative converter allows to feed the load from the grid even when the SRG is not running. This is good for complementary wind power. Experimental results are presented. It was shown that the SRG worked as expected and that the alternative topology reached expectations.

A genomic hotspot of diversifying selection and structural change in the hoary bat (Lasiurus cinereus).

Previous work found that numerous genes positively selected within the hoary bat (Lasiurus cinereus) lineage are physically clustered in regions of conserved synteny. Here I further validate and expand on those finding utilizing an updated L. cinereus genome assembly and additional bat species as well as other tetrapod outgroups. A chromosome-level assembly was generated by chromatin-contact mapping and made available by DNAZoo (www.dnazoo.org). The genomic organization of orthologous genes was extracted from annotation data for multiple additional bat species as well as other tetrapod clades for which chromosome-level assemblies were available from the National Center for Biotechnology Information (NCBI). Tests of branch-specific positive selection were performed for L. cinereus using PAML as well as with the HyPhy package for comparison. Twelve genes exhibiting significant diversifying selection in the L. cinereus lineage were clustered within a 12-Mb genomic window; one of these (Trpc4) also exhibited diversifying selection in bats generally. Ten of the 12 genes are landmarks of two distinct blocks of ancient synteny that are not linked in other tetrapod clades. Bats are further distinguished by frequent structural rearrangements within these synteny blocks, which are rarely observed in other Tetrapoda. Patterns of gene order and orientation among bat taxa are incompatible with phylogeny as presently understood, implying parallel evolution or subsequent reversals. Inferences of positive selection were found to be robust to alternative phylogenetic topologies as well as a strong shift in background nucleotide composition in some taxa. This study confirms and further localizes a genomic hotspot of protein-coding divergence in the hoary bat, one that also exhibits an increased tempo of structural change in bats compared with other mammals. Most genes in the two synteny blocks have elevated expression in brain tissue in humans and model organisms, and genetic studies implicate the selected genes in cranial and neurological development, among other functions.

Testing the Advanced Single Phase Asymmetric Cascaded Multilevel Inverter Topology using RES

This paper works on developing a model of single phase asymmetrical cascaded multilevel inverter (MLI) which couples’ renewable energy sources (RES) to the electrical or electronic loads of the AC powered transport system applications (e.g., Locomotives, Vehicles). MLI is the most important device as it is the main adaptation stage between the source and the load. Researchers are now more focused on multilevel inverters because of its numerous advantages. The prime benefit of a multilevel inverter is obtaining more output voltage levels using a smaller number of DC sources. The proposed topology for this work is asymmetric and produces 31-Levels of output which consists of 12 IGBT switches and 4 isolated dc voltage supplies V dc1 , V dc2 , V dc3 and V dc4 (Ratio of 2:4:8:16). The proposed topology has been processed by using PWM (Pulse Width Modulation) technique. Fundamental switching frequency (50HZ) has been used to achieve better quality of output voltage waveform with low harmonic distortion. The proposed topology has been explicitly and thoroughly analyzed throughout the study to demonstrate its superiority over alternative MLI topologies. Power loss analysis of the chosen MLI topology is also shown. An adequate comparison is also carried out between traditional and the proposed topologies. The comparative analysis shows that the chosen existing topology is better performed than others. According to the theoretical analysis conducted, the maximum efficiency obtained is 92.91% along with THD of 4.44% and TSV of 60 V dc . The accuracy of the proposed topology is verified through simulating the entire model in MATLAB-Simulink software.

An efficient microwave outphasing transmitter based on class-E power amplifiers

This article presents two alternative topologies combining lumped and distributed elements for designing class-E power amplifiers (PAs) for the 3.5 GHz frequency band, that differ in their approach to terminating the second harmonic. The first design employs a transmission line with a capacitor to create a short-circuit, while the second design uses a simple stub. The first design outperforms the second one in terms of efficiency enhancement. Accordingly, an outphasing transmitter based on a surface mount hybrid coupler combiner is designed using the first topology, achieving peak value results of 78% drain efficiency and 44.3 dBm output power. At a 6 dB back-off point, the simulation results show that the proposed architecture achieves 67.6% drain efficiency.

Phylogenomic analyses support a new infrageneric classification of Pourthiaea (Maleae, Rosaceae) using multiple inference methods and extensive taxon sampling

AbstractIn this comprehensive study, based on extensive taxon sampling, we performed phylogenomic analyses of plastome and nuclear ribosomal DNA (nrDNA) datasets. We employed multiple inference methods, including concatenated and coalescent‐based strategies, to generate an accurate phylogeny of the woody Rosaceae genus Pourthiaea. The nrDNA phylogeny of Pourthiaea strongly supports three major clades, which are consistent with morphology. However, the plastid tree provides an alternative phylogenetic topology, indicating cytonuclear discordance which could be explained by frequent hybridizations between and among the species of Pourthiaea. Considering evidence from morphology and phylogenomic data, we propose a new infrageneric classification for Pourthiaea, consisting of three sections: P. sect. Pourthiaea, P. sect. Amphidoxae sect. nov., and P. sect. Impressivenae sect. nov.

Genome evolution of Buchnera aphidicola (Gammaproteobacteria): Insights into strand compositional asymmetry, codon usage bias, and phylogenetic implications

Taxa of Buchnera aphidicola (hereafter “Buchnera”) are mutualistic intracellular symbionts of aphids, known for their remarkable biological traits such as genome reduction, strand compositional asymmetry, and symbiont-host coevolution. With the growing availability of genomic data, we performed a comprehensive analysis of 103 genomes of Buchnera strains from 12 host subfamilies, focusing on the genomic characterizations, codon usage patterns, and phylogenetic implications. Our findings revealed consistent features among all genomes, including small genome sizes, low GC contents, and gene losses. We also identified strong strand compositional asymmetries in all strains at the genome level. Further investigation suggested that mutation pressure may have played a crucial role in shaping codon usage of Buchnera. Moreover, the genomic asymmetries were reflected in asymmetric codon usage preferences within chromosomal genes. Notably, the levels of these asymmetries were varied among strains and were significantly influenced by the degrees of genome shrinkages. Lastly, our phylogenetic analyses presented an alternative topology of Aphididae, based on the Buchnera symbionts, providing robust confirmation of the paraphylies of Eriosomatinae, and Macrosiphini. Our objectives are to further understand the strand compositional asymmetry and codon usage bias of Buchnera taxa, and provide new perspectives for phylogenetic studies of Aphididae.

Chromosome-aware phylogenomics of Assassin Bugs (Hemiptera: Reduvioidea) elucidates ancient gene conflict.

Though the phylogenetic signal of loci on sex chromosomes can differ from those on autosomes, chromosomal-level genome assemblies for non-vertebrates are still relatively scarce and conservation of chromosomal gene content across deep phylogenetic scales has therefore remained largely unexplored. We here assemble a uniquely large and diverse set of samples (17 Anchored Hybrid Enrichment [AHE], 24 RNA-Seq, and 70 whole-genome sequencing [WGS] samples of variable depth) for the medically important assassin bugs (Reduvioidea). We assess the performance of genes based on multiple features (e.g., nucleotide vs. amino acid, nuclear vs. mitochondrial, and autosomal vs. X chromosomal) and employ different methods (concatenation and coalescence analyses) to reconstruct the unresolved phylogeny of this diverse (∼7,000 spp.) and old (>180 MYA) group. Our results show that genes on the X chromosome are more likely to have discordant phylogenies than those on autosomes. We find that the X chromosome conflict is driven by high gene substitution rates that impact accuracy of phylogenetic inference. However, gene tree clustering showed strong conflict even after discounting variable third codon positions. Alternative topologies were not particularly enriched for sex chromosome loci, but spread across the genome. We conclude that binning genes to autosomal or sex chromosomes may result in a more accurate picture of the complex evolutionary history of a clade.

More than a spiny morphology: plastome variation in the prickly pear cacti (Opuntieae).

Plastid genomes (plastomes) have long been recognized as highly conserved in their overall structure, size, gene arrangement and content among land plants. However, recent studies have shown that some lineages present unusual variations in some of these features. Members of the cactus family are one of these lineages, with distinct plastome structures reported across disparate lineages, including gene losses, inversions, boundary movements or loss of the canonical inverted repeat (IR) region. However, only a small fraction of cactus diversity has been analysed so far. Here, we investigated plastome features of the tribe Opuntieae, the remarkable prickly pear cacti, which represent one of the most diverse and important lineages of Cactaceae. We assembled de novo the plastome of 43 species, representing a comprehensive sampling of the tribe, including all seven genera, and analysed their evolution in a phylogenetic comparative framework. Phylogenomic analyses with different datasets (full plastome sequences and genes only) were performed, followed by congruence analyses to assess signals underlying contentious nodes. Plastomes varied considerably in length, from 121 to 162 kbp, with striking differences in the content and size of the IR region (contraction and expansion events), including a lack of the canonical IR in some lineages and the pseudogenization or loss of some genes. Overall, nine different types of plastomes were reported, deviating in the presence of the IR region or the genes contained in the IR. Overall, plastome sequences resolved phylogenetic relationships within major clades of Opuntieae with high bootstrap values but presented some contentious nodes depending on the dataset analysed (e.g. whole plastome vs. genes only). Congruence analyses revealed that most plastidial regions lack phylogenetic resolution, while few markers are supporting the most likely topology. Likewise, alternative topologies are driven by a handful of plastome markers, suggesting recalcitrant nodes in the phylogeny. Our study reveals a dynamic nature of plastome evolution across closely related lineages, shedding light on peculiar features of plastomes. Variation of plastome types across Opuntieae is remarkable in size, structure and content and can be important for the recognition of species in some major clades. Unravelling connections between the causes of plastome variation and the consequences for species biology, physiology, ecology, diversification and adaptation is a promising and ambitious endeavour in cactus research. Although plastome data resolved major phylogenetic relationships, the generation of nuclear genomic data is necessary to confront these hypotheses and assess the recalcitrant nodes further.

The Enhanced Modular Multilevel Converter With DC Fault Blocking Capability

The large energy-storage requirement and lack of dc-fault tolerant capability are the major drawbacks of modular multilevel converter (MMC). To address these issues, alternate hybrid topologies have been developed, but these are all non-modular and hence MMC remains the most preferred topology for high-power applications. In this paper, a new submodule (SM) structure is proposed that consists of five switches and a capacitor. Based on this SM, a novel Enhanced Modular Multilevel Converter (EMMC) is developed, which is fully modular, scalable and requires fewer switches and capacitors. It also possesses the features of reduced energy-storage requirement and dc-fault tolerant capability. The structures and operating principles of proposed SM and EMMC topology are presented. The proposed topology is compared with state-of-the-art topologies in terms of the switch counts, SM capacitors and isolated power-supplies requirements to highlight the main features of EMMC. The proposed EMMC is an effective and more efficient converter solution compared to the major existing high-power hybrid converters. Moreover, it has fully modular structure. A 21-level, grid-connected EMMC simulation model is developed to validate its working principles and dc-fault tolerant capability. The working principles and dc-fault tolerant capability are further validated using a scaled-down, 5-level EMMC experimental prototype.

Alternative Surface-Mounted Permanent Magnet Topology for Reducing Voltage and Torque Harmonics in Shaft Generators

Traditional diesel generators on a merchant ship, composed of a wound rotor synchronous generator and a four-stroke diesel engine, supply electrical power for various loads. Recently, shaft generators for merchant ships have been increasingly replacing diesel generators to reduce CO2 emissions through fuel efficiency improvement. In particular, permanent magnet synchronous generators have replaced induction generators due to their high-efficiency characteristics at light loads. The surface-mounted permanent magnet rotor can be a suitable topology owing to the relatively short constant power range. This generator can also operate as a motor according to the propulsion mode, so minimizing the harmonics of the induced voltage with the torque pulsation being essential. This paper proposes an alternative surface permanent magnet topology. Three magnets comprise one pole, with one bread-loaf magnet and two rectangular magnets. It helps to simplify the magnetization and assembly of the rotor because of the flat bottom shape of the magnet. Due to the low remanence of two rectangular magnets at the pole edge, this rotor structure effectively makes the air-gap magnetic flux density sinusoidal with production costs reduced. The step-skew suppresses higher-order harmonics. The total harmonic distortion comparison of the two-dimensional finite element analysis and the no-load test result shows under 6% difference from the interior permanent magnet prototype machine. A comparison of harmonic characteristics with other rotors shows that the proposed modular pole has sufficient competitiveness compared to the tapered bread-loaf type. It can be applied as a substitute for the tapered bread-loaf magnet in direct-drive ship propulsion systems and is expected to shorten the manufacturing process and time.

Statistical evaluation of character support reveals the instability of higher-level dinosaur phylogeny

The interrelationships of the three major dinosaur clades (Theropoda, Sauropodomorpha, and Ornithischia) have come under increased scrutiny following the recovery of conflicting phylogenies by a large new character matrix and its extensively modified revision. Here, we use tools derived from recent phylogenomic studies to investigate the strength and causes of this conflict. Using maximum likelihood as an overarching framework, we examine the global support for alternative hypotheses as well as the distribution of phylogenetic signal among individual characters in both the original and rescored dataset. We find the three possible ways of resolving the relationships among the main dinosaur lineages (Saurischia, Ornithischiformes, and Ornithoscelida) to be statistically indistinguishable and supported by nearly equal numbers of characters in both matrices. While the changes made to the revised matrix increased the mean phylogenetic signal of individual characters, this amplified rather than reduced their conflict, resulting in greater sensitivity to character removal or coding changes and little overall improvement in the ability to discriminate between alternative topologies. We conclude that early dinosaur relationships are unlikely to be resolved without fundamental changes to both the quality of available datasets and the techniques used to analyze them.

A Switched Mid-Point Modular Multilevel Converter for HVDC Applications

The modular multilevel converter (MMC) has emerged as the industry standard for voltage source converters (VSC) based high voltage direct-current (HVDC) applications since its benefits of scalability, modularity, high efficiency and better output quality outweigh its drawback of large energy storage. However, with a growing number of offshore HVDC installations, the volume and footprint of the converter, which are largely influenced by its energy storage, are becoming increasingly critical. This has led to a rising interest in alternative converter topologies that reduce the energy storage while maintaining the benefits of the MMC. This paper introduces a switched mid-point modular multilevel converter (SMPC), that is able to generate the desired AC-side waveforms with significantly less energy storage (around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$50\%$</tex-math></inline-formula> ) than the MMC. The DC-side is free from any distortion that requires additional filtering. Reduced energy storage and the associated reduction in volume is achieved at the expense of requiring more switches and slightly lower efficiency when compared to the MMC. Like many other MMC-style circuits, except when operating at a ‘sweet-spot’, active control of the energy balance is needed, for which a technique based on second harmonic injection is proposed. The converter operation and the proposed control scheme are verified by simulations for a medium-voltage setup and experimentally on a low-voltage lab-scale prototype.