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PubMed2006

Emergent magnetic moments produced by self-damage in plutonium.

Plutonium possesses the most complicated phase diagram in the periodic table, driven by the complexities of overlapping 5f electron orbitals. Despite the importance of the 5f electrons in defining the structure and physical properties, there is no experimental evidence that these electrons localize to form magnetic moments in pure Pu. Instead, a large temperature-independent Pauli susceptibility indicates that they form narrow conduction bands. Radiation damage from the alpha-particle decay of Pu creates numerous defects in the crystal structure, which produce a significant temperature-dependent magnetic susceptibility, chi(T), in both alpha-Pu and delta-Pu (stabilized by 4.3 atomic percent Ga). This effect can be removed by thermal annealing above room temperature. By contrast, below 35 K the radiation damage is frozen in place, permitting the evolution in chi(T) with increasing damage to be studied systematically. This result leads to a two-component model consisting of a Curie-Weiss term and a short-ranged interaction term consistent with disorder-induced local moment models. Thus, it is shown that self-damage creates localized magnetic moments in previously nonmagnetic plutonium.

Journal Article↗

PubMed2003

Relaxation and metastability in a local search procedure for the random satisfiability problem.

An analysis of the average properties of a local search procedure (RandomWalkSAT) for the satisfaction of random Boolean constraints is presented. Depending on the ratio alpha of constraints per variable, reaching a solution takes a time T(res) growing linearly [T(res) approximately tau(res)(alpha)N, alpha alpha(d)) with the size N of the instance. The relaxation time tau(res)(alpha) in the linear phase is calculated through a systematic expansion scheme based on a quantum formulation of the evolution operator. For alpha>alpha(d), the system is trapped in some metastable state, and resolution occurs from escape from this state through crossing of a large barrier. An annealed calculation of the height zeta(alpha) of this barrier is proposed. The polynomial to exponential cross-over alpha(d) approximately =2.7 is not related to the onset of clustering among solutions occurring at alpha approximately =3.86.

Journal Article↗

PubMed1982

Training supervision as a separate faculty role.

Training supervision is a longitudinal, nonclinically focused personal relationship between a faculty member and a resident for exploring the latter's professional development. In the authors' program the training supervisor meets with the supervisee monthly over the 3-year residency. The training supervisor's role is that of a nonevaluative senior colleague who orients and advises the resident and systematically reviews training progress and problems. The authors discuss the evolution of the training supervision concept, explore potential role conflicts for the training supervisor, who may serve other functions in the residency of the supervisee, and present positive and negative resident and faculty evaluations of their program.

Adult↗

PubMed2006

A statewide public health approach to improving organ donation: the Massachusetts Organ Donation Initiative.

Despite the growing disparity between organ supply and demand in the United States, few initiatives have attempted to close the gap through systematic population-based public health endeavors. We examined the evolution, implementation, and outcomes of the Massachusetts Organ Donation Initiative, a statewide effort that included a unique partnership among organ procurement organizations, major teaching hospitals, and the state's department of public health. Lessons from this initiative have contributed to growing national efforts for increasing organ supply and have provided insights for addressing this continuing public health challenge.

Cooperative Behavior↗

PubMed1977

Humoral and cellular immune response during the growth of an SV40 induced tumour in hamsters.

Hamster fibroblasts transformed in vivo by the SV40 virus (TSV5Cl2) induce tumours when injected into adult hamsters and antibodies present in sera of tumour-bearing animals are used to demonstrate the presence of the antigens specific for the viral transformation. These tumours are a very useful tool in studying the evolution of the immune response during the tumour growth. A systematic histological examination of the spleen, thymus and lymph nodes was undertaken and the results thus obtained were correlated with a parallel study of the cells of the peritumoral region, the thymus and the spleen by immunofluorescence using antisera of different specificities. We were able to show that the plasma cells which make up the early peritumoral reaction and the lymphoblasts found later in spleen and thymus both synthesize antibodies directed against virus induced antigens. Circulating antibody directed against the same antigens is first detected at/or about the time that the peritumoral plasma cell reaction disappears and increases progressively as tumour weight increases.

Animals↗

PubMed1979

[A case of thymolipoma in a child (author's transl)].

A new case of asymptomatic thymolipoma in a 4.5 years old girl is reported. It was discovered during systematic medical investigation. Its radiological characteristics and the lack of evolutivity made the authors suspect the diagnosis before operating. A total surgical extraction of the 300 g weighing tumor was performed through a right thoracotomy. No complication occurred in the post-operative time. Others authors already indicated the scarcity of this affection (less than 10 cases in children) as well as the special radiological characteristics of this tumor and the noticeable clinical tolerance often despite a large bulk. Histologically the tumor is made of an infiltrating of the normal thymic tissue by proliferating adipose adulte cells, the benignity of which is demonstrated by the evolution. In this study a differential diagnosis between thymolipoma and other mediastinal tumors is made and also some pathogenic assessments. Surgery always is required for treatment.

Child, Preschool↗

PubMed2001

The molecular systematics and biogeography of the European cobitids based on mitochondrial DNA sequences.

Phylogenetic inference regarding the biogeography and evolution of the family Cobitidae depends in large part on the correct interpretation of transitions between the morphological states of secondary sexual characters (e.g., the scale of Canestrini or lamina circularis). Here, we use the complete mitochondrial ATP synthase 8 and 6 and cytochrome b genes to provide an independent assessment of systematics and biogeographic relationships of species in the genus Cobitis, including geographic and subgeneric sampling of species with Canestrini's scale present, duplicated, or absent. The mtDNA-based phylogeny for the genus Cobitis provides the first formal hypothesis for the group and permits a phylogenetic-based assessment of the morphological transitions demonstrated by Canestrini's scale. Our data confirm the monophyly of the genus Cobitis and indicate that European Cobitis comprise six evolutionarily independent lineages. These lineages were defined by nucleotide synapomorphies permitting bootstrapped confidence estimates of 95% or greater and mtDNA genetic distances greater than 4.5% and correspond with moderate fidelity to the Cobitis groups defined by Bacescu (1962, Rev. Roum. Biol. 4, 435-448). The Caucasian lineage, C. cf. sibirica, represents the basal sister species of the genus Cobitis, supporting an eastern Asiatic origin of the European Cobitis: Cobitis sensu stricto, Acanestrinia, Bicanestrinia, Iberocobitis, and Cobitis calderoni. Phylogenetic relationships among Cobitis subgenera and species indicate that the ancestral condition of one scale of Canestrini was duplicated once at the origin of the Bicanestrinia lineage and has been independently lost by C. calderoni and C. elongata. The absence of the scale of Canestrini is the synapomorphy defining the subgenus Acanestrinia, but the mtDNA phylogeny indicates that Acanestrinia is not a natural group and places C. calderoni as the sister lineage to the subgenus Iberocobitis, a finding that is also geographically parsimonius.

Animals↗

PubMed2026

Toward real-time quantification of driving risks: a systematic review and research agenda of risk field theory.

In complex traffic systems, driving risk often evolves in a continuous and progressive manner prior to crash occurrence. How to effectively represent and analyze such latent risk states remains a central challenge in traffic safety research. In recent years, risk field-based approaches have introduced spatial and spatiotemporal continuous modeling paradigms, providing new perspectives for characterizing the distribution of traffic risk and its dynamic evolution. Motivated by the rapid growth of this research area and the lack of a systematic synthesis, this paper presents a comprehensive review of studies applying risk field theory to driving safety and traffic risk analysis. Following the PRISMA guidelines, relevant literature was collected through multi-database searches and analyzed using a combination of bibliometric analysis and qualitative review. The review systematically summarizes the theoretical foundations, modeling elements, data sources, analytical methods, and application domains of risk field-related research. Particular attention is given to studies that conceptualize traffic risk as a continuous field, complemented by a broader review of traffic risk factor literature to identify key elements and analytical dimensions involved in risk field modeling. On this basis, the paper synthesizes research progress in major application areas, including traffic safety state representation, driving behavior analysis, traffic conflict assessment, and autonomous driving and human-machine cooperative systems. Differences and commonalities among existing studies are compared in terms of modeling strategies, data support, and application scenarios. Through this systematic review, the paper clarifies the main research themes and methodological trends of risk field-based studies, providing a structured framework for understanding the evolution and application of this approach and offering methodological insights for risk perception modeling and safety-oriented decision support in intelligent transportation systems (ITS).

Humans↗

PubMed2004

Multiple origin of viviparity in Southeast Asian gastropods (Cerithioidea: Pachychilidae) and its evolutionary implications.

This study aims at a better understanding of the evolutionary significance of viviparity in some freshwater gastropods. We use a phylogeny based on partial sequences of the mitochondrial 16S gene of representatives of the limnetic and pantropical Pachychilidae to infer the relationships within this particular group of cerithioideans and the evolution of reproductive strategies. The phylogeny presented herein implies a new systematization and suggests that viviparity has appeared three times among the Pachychilidae. This is supported by the finding of very distinct reproductive morphologies in different lineages of viviparous taxa that are exclusively found in Southeast Asia. Based on the observation that oviparity is the ancestral character state in this freshwater family, we conclude that viviparity has evolved subsequent to the exploration of freshwater. We present data showing that all Pachychilidae produce considerably larger but fewer egg capsules compared to most marine snails. In other studies on freshwater gastropods, this has been discussed as an adaptation to freshwater environments. In this context we hypothesize that the increased parental investment involved in the enlargement of eggs in concert with the reduction of clutch sizes was the driving factor that ultimately lead to the evolution of viviparity in the Asian taxa. Consequently, although not directly correlated with the colonization of the new adaptive zone, viviparity is strongly favored by other consequences of this step. Hence, we hypothesize that the production of large eggs, which is necessitated by the exploration of freshwater, represents a preadaptation existing in those ancestors from which viviparous pachychilid lineages eventually evolved in Southeast Asia.

Animals↗

PubMed1988

Free fitness that always increases in evolution.

I here introduce a free fitness function in population biology, which monotonically increases with time and takes its maximum at the evolutionary equilibrium. By suitably defining an "index" for each state, the free fitness is expressed as the average index plus an entropy term. In many cases, the index has a biologically clear meaning, such as the logarithmic population mean fitness. The technique is applicable to any Markov process model (either continuous or discrete) with a positive steady state. I discuss four examples from various branches of population biology: (1) one-locus-two-allele system of population genetics with mutation, selection, and random genetic drift; (2) evolutionary dynamics of quantitative characters; (3) a molecular evolution model; and (4) an ecological succession model. Introducing free fitness clarifies the balance between systematic forces (e.g. natural selection or successional trend toward the climax) and disturbing processes (e.g. random drift).

Animals↗

PubMed1995

Saltationist and punctuated equilibrium models for the evolution of viviparity and placentation.

Vertebrate viviparity (live-bearing reproduction), placentation, and placentotrophy are widely assumed to have evolved as three successive, gradualistic transformations. From empirical data and predictive tests on lizards and snakes, this paper indicates that placentae and a degree of placentotrophy have evolved repeatedly as necessary correlates of viviparity, not as subsequent modifications. In addition, information derived from studies of anatomy, physiology, biogeography and systematics is used to evaluate new saltationist and punctuated equilibrium models for the evolution of viviparity. Phylogenetic reconstruction reveals that more than 100 squamate clades have made the transition to viviparity and placentation. However, various phenotypic intermediates postulated by the gradualistic model are either scarce or unrepresented among known forms, including those in which viviparity has evolved at specific and subspecific levels. Evolution in squamates seems to have produced a dichotomy between two evolutionarily stable patterns: (i) retention of weakly shelled or shell-free eggs to term (viviparity), with development of fully functional placentae; and (ii) deposition of shelled eggs at or near the limb bud stage of development (typical oviparity). Conflicting functional demands placed on eggshell morphology may constrain establishment of prolonged, oviparous egg-retention as a viable, historically stable pattern. Alternatively, the costs of prolonged egg-retention associated with decreased female mobility or decreased fecundity may exceed the benefits in oviparous forms.

Animals↗

PubMed2004

The evolutionary gain of spliceosomal introns: sequence and phase preferences.

Theories regarding the evolution of spliceosomal introns differ in the extent to which the distribution of introns reflects either a formative role in the evolution of protein-coding genes or the adventitious gain of genetic elements. Here, systematic methods are used to assess the causes of the present-day distribution of introns in 10 families of eukaryotic protein-coding genes comprising 1,868 introns in 488 distinct alignment positions. The history of intron evolution inferred using a probabilistic model that allows ancestral inheritance of introns, gain of introns, and loss of introns reveals that the vast majority of introns in these eukaryotic gene families were not inherited from the most recent common ancestral genes, but were gained subsequently. Furthermore, among inferred events of intron gain that meet strict criteria of reliability, the distribution of sites of gain with respect to reading-frame phase shows a 5:3:2 ratio of phases 0, 1 and 2, respectively, and exhibits a nucleotide preference for MAG GT (positions -3 to +2 relative to the site of gain). The nucleotide preferences of intron gain may prove to be the ultimate cause for the phase bias. The phase bias of intron gain is sufficient to account quantitatively for the well-known 5:3:2 bias in phase frequencies among extant introns, a conclusion that holds even when taxonomic heterogeneity in phase patterns is considered. Thus, intron gain accounts for the vast majority of extant introns and for the bias toward phase 0 introns that previously was interpreted as evidence for ancient formative introns.

Animals↗

PubMed2003

Evolution of the APETALA3 and PISTILLATA lineages of MADS-box-containing genes in the basal angiosperms.

The B class genes, including homologs of the Arabidopsis loci APETALA3 (AP3) and PISTILLATA (PI ), appear to play a conserved role in the determination of petal and stamen identity across core eudicot angiosperms. Understanding how and when these functions evolved is a critical component of elucidating the evolution of flowers, particularly the appearance of petaloid perianth organs. Before comparisons of gene expression patterns or functions can be made, however, it is necessary to establish the orthology of AP3 and PI homologs from basal angiosperms. Here, we report the identification and analysis of 29 new representatives of the B gene lineage from basal ANITA and magnoliid dicot angiosperms. These studies indicate that gene duplications have occurred at every phylogenetic level, both before and after the duplication that produced the separate AP3 and PI lineages. Comparison of genomic structure among PI homologs indicates that a 12-nucleotide deletion that had been considered synapomorphic for the whole PI lineage actually arose within the ANITA grade, after the split of the Nymphaeales but before the separation of the Austrobaileyales. Evidence for alternative splicing of the Nymphaea AP3 homolog is also presented. The implications of these findings for angiosperm systematics, the conservation of AP3 and PI gene function, and the evolution of the ABC program are discussed.

Alternative Splicing↗

PubMed2006

Systematic analysis of embryonic expression profiles of zinc finger genes in Ciona intestinalis.

The recent decoding of a number of animal genomes has provided unprecedented information regarding evolution and gene structures, but this information must be supplemented with precise gene annotations and the temporal and spatial expression patterns of individual genes. In the present study, we systematically identified and characterized 566 zinc finger genes in the genome of Ciona intestinalis, an emerging model system for genome-wide studies of development and evolution. Of these genes, 356 genes encoded a potential transcription factor based on putative nucleic acid binding activity or domains of unknown function. We further examined the expression patterns of 225 genes during embryogenesis, and, when considered with a previous study [Imai, K.S., Hino, K., Yagi, K., Satoh, N., Satou, Y., 2004. Gene expression profiles of transcription factors and signaling molecules in the ascidian embryo: towards a comprehensive understanding of gene networks. Development 131, 4047-4058], we have characterized the developmental expression patterns of nearly 85% of the potential zinc finger-containing transcription factors. Overall, zinc finger genes are preferentially maternally expressed with little larval expression during development. The present study provides a valuable reference for genome-wide studies in this species and for future studies wishing to examine zinc finger gene expression patterns in other animals.

Animals↗

PubMed1996

The systematics of North American Daphnia (Crustacea: Anomopoda): a molecular phylogenetic approach.

Despite extensive studies on the ecology and evolution of the freshwater microcrustacean Daphnia, there is little understanding of the evolutionary history of the genus. Past attempts at reconstructing phylogenetic relationships among Daphnia species have been highly controversial, mainly because of the poor taxonomy of the genus. However, following a revised taxonomy of the daphniid fauna of North America, we conducted a comprehensive appraisal of systematic relationships within the genus through the analysis of sequence diversity in 503 b.p. of the 12S rRNA gene of the mtDNA. The large sequence divergence among its 34 North American members indicates that the genus Daphnia originated during the Mesozoic, even though many lineages exhibit extreme morphological stasis. Results from both cladistic and phenetic analyses indicate the presence of three subgenera comprised of 15 species complexes. Only four of these lineages have shown active speciation over the past 3 Ma, suggesting that cladogenesis in the genus has been constrained. Our study also reveals that interspecific hybridization occurs between taxa which show very large sequence divergence (up to 14%), suggesting that reproductive isolation within the genus evolves slowly.

Animals↗

PubMed2005

The testate lobose amoebae (order Arcellinida Kent, 1880) finally find their home within Amoebozoa.

Testate lobose amoebae (order Arcellinida Kent, 1880) are common in all aquatic and terrestrial habitats, yet they are one of the last higher taxa of unicellular eukaryotes that has not found its place in the tree of life. The morphological approach did not allow to ascertain the evolutionary origin of the group or to prove its monophyly. To solve these challenging problems, we analyzed partial small-subunit ribosomal RNA (SSU rRNA) genes of seven testate lobose amoebae from two out of the three suborders and seven out of the 13 families belonging to the Arcellinida. Our data support the monophyly of the order and clearly establish its position among Amoebozoa, as a sister-group to the clade comprising families Amoebidae and Hartmannellidae. Complete SSU rRNA gene sequences from two species and a partial actin sequence from one species confirm this position. Our phylogenetic analyses including representatives of all sequenced lineages of lobose amoebae suggest that a rigid test appeared only once during the evolution of the Amoebozoa, and allow reinterpretation of some morphological characters used in the systematics of Arcellinida.

Amoeba↗

PubMed2005

Genome plasticity and ori-ter rebalancing in Salmonella typhi.

Genome plasticity resulting from frequent rearrangement of the bacterial genome is a fascinating but poorly understood phenomenon. First reported in Salmonella typhi, it has been observed only in a small number of Salmonella serovars, although the over 2,500 known Salmonella serovars are all very closely related. To gain insights into this phenomenon and elucidate its roles in bacterial evolution, especially those involved in the formation of particular pathogens, we systematically analyzed the genomes of 127 wild-type S. typhi strains isolated from many places of the world and compared them with the two sequenced strains, Ty2 and CT18, attempting to find possible associations between genome rearrangement and other significant genomic features. Like other host-adapted Salmonella serovars, S. typhi contained large genome insertions, including the 134 kb Salmonella pathogenicity island, SPI7. Our analyses showed that SPI7 disrupted the physical balance of the bacterial genome between the replication origin (ori) and terminus (ter) when this DNA segment was inserted into the genome, and rearrangement in individual strains further changed the genome balance status, with a general tendency toward a better balanced genome structure. In a given S. typhi strain, genome diversification occurred and resulted in different structures among cells in the culture. Under a stressed condition, bacterial cells with better balanced genome structures were selected to greatly increase in proportion; in such cases, bacteria with better balanced genomes formed larger colonies and grew with shorter generation times. Our results support the hypothesis that genome plasticity as a result of frequent rearrangement provides the opportunity for the bacterial genome to adopt a better balanced structure and thus eventually stabilizes the genome during evolution.

Evolution, Molecular↗

PubMed2003

"Decoking" of a "coked" zeolite catalyst in a glow discharge.

"Decoking" of a "coked" zeolite catalyst in a glow discharge in oxygen is investigated. The "decoking" process involves reactions of atomic oxygen (O atoms) with "coke" and yields gases such as CO, CO(2) as well as other gaseous products that could be easily pumped out. Three different modes of discharge were investigated including a static mode, a flowing-gas mode, and a periodic-purge mode where the oxygen and other gaseous products of the discharge were replaced by fresh O(2)gas after short but regular intervals of time. In some cases, additional heating was also used to provide base temperatures of the order of 100 degrees C to facilitate penetration of oxygen atoms into the inner layers and cages of the zeolite catalyst. This paper presents some results of spectroscopic analytical techniques used to monitor the atomization of oxygen, oxidation of "coke", and to confirm the process of "decoking". More specifically, radiation emission on the 3 s (5)S- 3p (5)P transitions of O around 777.2-777.5 nm were selected for monitoring the atomization of O(2). On the other hand, X-ray photo-electron spectroscopy (XPS) was used to determine the amount of residual carbon and extent of "decoking". Furthermore, evolution of CO and CO(2) gases as a function of time was systematically monitored in real time. For CO, the 451.1 nm band head belonging to the B(1) Sigma - A(1) Pi bands of the Angstrom system of the CO spectrum was used, while for CO(2), the band head at 353.4 nm belonging to the CO(2)(+) spectrum was used. The rates of evolution of CO and CO(2) were related to the rate of "decoking" of the catalyst. It is noted that in the periodic-purge mode, about 63% of the total yield of CO from a given sample of the catalyst appears in the first 3-min exposure to discharge whereas it takes up to 15 min to remove nearly 94% of the removable carbon under our experimental conditions.

Journal Article↗