COMPARATIVE ANALYSIS OF FIVE COMPLETE AMBYSTOMATID SALAMANDER MITOCHONDRIAL GENOMES

In this study, mitochondrial transcript information from a recent EST project wasextended to obtain complete mitochondrial genome sequence for 5 tiger salamandercomplex species (Ambystoma mexicanum, A. t. tigrinum, A. andersoni, A. californiense,and A. dumerilii). For the first time, aspects of mitochondrial transcription in arepresentative amphibian are described, and then complete mitochondrial sequencedata are used to examine salamander phylogeny at both deep and shallow levels ofevolutionary divergence. The available mitochondrial ESTs for A. mexicanum (N=2481)and A. t. tigrinum (N=1205) provided 92% and 87% coverage of the mitochondrialgenome, respectively. Complete mitochondrial sequences for all species were rapidlyobtained by using long distance PCR and DNA sequencing. A number of genomestructural characteristics (base pair length, base composition, gene number, geneboundaries, codon usage) were highly similar among all species and to other distantlyrelated salamanders. Overall, mitochondrial transcription in Ambystoma approximatedthe pattern observed in other vertebrates. From the mapping of ESTs onto mtDNA it wasinferred that transcription occurs from both heavy and light strand promoters andcontinues around the entire length of the mtDNA, followed by post-transcriptionalprocessing. However, the observation of many short transcripts corresponding to rRNAgenes indicates that transcription may often terminate prematurely to bias transcriptionof rRNA genes; indeed an rRNA transcription termination signal sequence was observedimmediately following the 16S rRNA gene. Phylogenetic analyses of salamander familyrelationships consistently grouped Ambystomatidae in a clade containingCryptobranchidae and Hynobiidae, to the exclusion of Salamandridae. This robust resultsuggests a novel alternative hypothesis because previous studies have consistentlyidentified Ambystomatidae and Salamandridae as closely related taxa. Phylogeneticanalyses of tiger salamander complex species also produced robustly supported trees.The D-loop, used in previous molecular phylogenetic studies of the complex, was foundto contain a relatively low level of variation and we identified mitochondrial regions withhigher rates of molecular evolution that are more useful in resolving relationships amongspecies. Our results show the benefit of using complete mitochondrial genomeinformation in studies of recently and rapidly diverged taxa

A SCHOLARLY CONSIDERATION ON THE THEORIES AND LITERATURE OF TAX REFORMS IN SIERRA LEONE

This study examines how tax reforms have been implemented and how it has influenced Sierra Leone's ability to streamline fiscal structures. The topic of tax revenue mobilization is becoming more and more popular and crucial for emerging nations. The fiscal arrangement that exists between taxpayers and the current political administration is a fiduciary relationship that binds both parties to the right and obligation to effectively and efficiently mobilize revenues. The tax system in use has had a significant impact on government revenue since it allows for loopholes, dishonest tax authorities, inadequate data, and many other issues. This study also applauds the government for strengthening corporate tax authority plans and putting local restrictions on large corporations and foreign governments who conduct business in Sierra Leone. By doing this, taxpayers and tax authorities will be encouraged to be accountable, transparent, and compliant. Additionally, Sierra Leone's tax administration underwent a number of modifications between 2014 and 2019, although nothing is known about how well those reforms fared in terms of raising tax revenue. In fact, reform as a factor affecting tax collection has received little attention in the research on what motivates domestic resource mobilization. The paper evaluates whether reforms are crucial for raising tax revenue by taking into account various aspects of reforms in the tax administration, including tax-related reforms and reforms related to institutions, and using various econometric methods based on ordinary least squares, instrumental variable two-stage least squares, and iteratively reweighted least squares. According to the findings, tax reforms, institutional reforms, and all other reforms put together have greatly improved tax revenue performance. The main takeaway is that greater institutional and tax-related reforms are essential for sustainingly increasing tax revenue collection. JEL: E61, E62, P35  Article visualizations

Dynamics of vortex tangle without mutual friction in superfluid 4^4He

A recent experiment has shown that a tangle of quantized vortices in superfluid $^4$He decayed even at mK temperatures where the normal fluid was negligible and no mutual friction worked. Motivated by this experiment, this work studies numerically the dynamics of the vortex tangle without the mutual friction, thus showing that a self-similar cascade process, whereby large vortex loops break up to smaller ones, proceeds in the vortex tangle and is closely related with its free decay. This cascade process which may be covered with the mutual friction at higher temperatures is just the one at zero temperature Feynman proposed long ago. The full Biot-Savart calculation is made for dilute vortices, while the localized induction approximation is used for a dense tangle. The former finds the elementary scenario: the reconnection of the vortices excites vortex waves along them and makes them kinked, which could be suppressed if the mutual friction worked. The kinked parts reconnect with the vortex they belong to, dividing into small loops. The latter simulation under the localized induction approximation shows that such cascade process actually proceeds self-similarly in a dense tangle and continues to make small vortices. Considering that the vortices of the interatomic size no longer keep the picture of vortex, the cascade process leads to the decay of the vortex line density. The presence of the cascade process is supported also by investigating the classification of the reconnection type and the size distribution of vortices. The decay of the vortex line density is consistent with the solution of the Vinen's equation which was originally derived on the basis of the idea of homogeneous turbulence with the cascade process. The obtained result is compared with the recent Vinen's theory.Comment: 16 pages, 16 figures, submitted to PR

Evaporation of a packet of quantized vorticity

A recent experiment has confirmed the existence of quantized turbulence in superfluid He3-B and suggested that turbulence is inhomogenous and spreads away from the region around the vibrating wire where it is created. To interpret the experiment we study numerically the diffusion of a packet of quantized vortex lines which is initially confined inside a small region of space. We find that reconnections fragment the packet into a gas of small vortex loops which fly away. We determine the time scale of the process and find that it is in order of magnitude agreement with the experiment.Comment: figure 1a,b,c and d, figure2, figure