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Search Results: 1 - 10 of 14773 matches for " Christian Rabeling "
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Thelytokous Parthenogenesis in the Fungus-Gardening Ant Mycocepurus smithii (Hymenoptera: Formicidae)
Christian Rabeling, José Lino-Neto, Simone C. Cappellari, Iracenir A. Dos-Santos, Ulrich G. Mueller, Maurício Bacci
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006781
Abstract: The general prevalence of sexual reproduction over asexual reproduction among organisms testifies to the evolutionary benefits of recombination, such as accelerated adaptation to changing environments and elimination of deleterious mutations. Documented instances of asexual reproduction in groups otherwise dominated by sexual reproduction challenge evolutionary biologists to understand the special circumstances that might confer an advantage to asexual reproductive strategies. Here we report one such instance of asexual reproduction in the ants. We present evidence for obligate thelytoky in the asexual fungus-gardening ant, Mycocepurus smithii, in which queens produce female offspring from unfertilized eggs, workers are sterile, and males appear to be completely absent. Obligate thelytoky is implicated by reproductive physiology of queens, lack of males, absence of mating behavior, and natural history observations. An obligate thelytoky hypothesis is further supported by the absence of evidence indicating sexual reproduction or genetic recombination across the species' extensive distribution range (Mexico-Argentina). Potential conflicting evidence for sexual reproduction in this species derives from three Mycocepurus males reported in the literature, previously regarded as possible males of M. smithii. However, we show here that these specimens represent males of the congeneric species M. obsoletus, and not males of M. smithii. Mycocepurus smithii is unique among ants and among eusocial Hymenoptera, in that males seem to be completely absent and only queens (and not workers) produce diploid offspring via thelytoky. Because colonies consisting only of females can be propagated consecutively in the laboratory, M. smithii could be an adequate study organism a) to test hypotheses of the population-genetic advantages and disadvantages of asexual reproduction in a social organism and b) inform kin conflict theory. For a Portuguese translation of the abstract, please see S1.
Cyatta abscondita: Taxonomy, Evolution, and Natural History of a New Fungus-Farming Ant Genus from Brazil
Jeffrey Sosa-Calvo, Ted R. Schultz, Carlos R. F. Brand?o, Christiana Klingenberg, Rodrigo M. Feitosa, Christian Rabeling, Maurício Bacci, Cauê T. Lopes, Heraldo L. Vasconcelos
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080498
Abstract: Cyatta abscondita, a new genus and species of fungus-farming ant from Brazil, is described based on morphological study of more than 20 workers, two dealate gynes, one male, and two larvae. Ecological field data are summarized, including natural history, nest architecture, and foraging behavior. Phylogenetic analyses of DNA sequence data from four nuclear genes indicate that Cyatta abscondita is the distant sister taxon of the genus Kalathomyrmex, and that together they comprise the sister group of the remaining neoattine ants, an informal clade that includes the conspicuous and well-known leaf-cutter ants. Morphologically, Cyatta abscondita shares very few obvious character states with Kalathomyrmex. It does, however, possess a number of striking morphological features unique within the fungus-farming tribe Attini. It also shares morphological character states with taxa that span the ancestral node of the Attini. The morphology, behavior, and other biological characters of Cyatta abscondita are potentially informative about plesiomorphic character states within the fungus-farming ants and about the early evolution of ant agriculture.
Role of Estradiol, Progestins, Insulines and Adipocytokines in Breast Cancer Promotion in Post-Menopausal Women  [PDF]
Christian Jamin
Journal of Cancer Therapy (JCT) , 2010, DOI: 10.4236/jct.2010.11007
Abstract: Estrogens and artificial progestins used in hormone replacement therapy increase breast cancer risk. This seems to bedue to a promoting and not initiating effect. A synergic effect of estradiol and hyperinsulinism has been shown. Insulinplays a role in the increase of breast cancer risk when associated with android obesity, sedentariness, type II diabetes,and high glycemic index food, alcohol and trans fatty acids intake. Natural menopause induces insulin resistance anddoes not induce a risk decrease. The role of insulin gives a new outlook on the influence of HRT in breast cancer promotion:estradiol alone, which improves insulin-sensitivity, does not increase breast cancer risk. Artificial progestinsassociated with estrogens increase the risk, whereas estrogens associated with progesterone do not. This could be dueto the fact that artificial progestins increase insulin resistance, whereas natural progesterone does not. Adipose tissue,which is an endocrine gland, is insulin dependant. Breast cancer and its seriousness are correlated to adipocytokincirculating levels such as resistin, leptin, interleukin 1, adipocyte fatty acid-binding protein, and are inversely correlatedto the level of adiponectin. Insulin could play a synergic role with sexual steroids by a direct effect and by increasingadipose tissue secretions.
The Timeliness of Direct Democracy in the EU—The Example of Nuclear Energy in the EU and the Institutionalisation of the European Citizens’ Initiative in the Lisbon Treaty  [PDF]
Christian Joerges
Beijing Law Review (BLR) , 2012, DOI: 10.4236/blr.2012.31001
Abstract: The catastrophic nuclear incident in Fukushima in March 2011 has shocked Europe. Its impact was particularly strong in Germany with its decade-old anti-nuclear movements. Political and technological re-orientations were initiated in that country without considering at any depth the potential of European law and politics to control or obstruct such moves. Somewhat paradoxically, the Euratom Treaty of 1957 and also the new Treaty of Lisbon confirm the right of each Member State to decide upon the use of nuclear energy autonomously. This means that European citizens remain exposed to the risks of that technology until the highly unlikely consent of all Member States to abstain from its further use. That constellation poses a dilemma for democracy because it implies that each political decision taken within parts of the Union exerts external pan-European effects. The article considers the chances for an inclusive democratic process which would lead to a legitimated European decision. It examines the possibilities offered by the new European Citizens Initiative which the Lisbon Treaty has institutionalized in its Article 12 and concludes that this instrument could indeed be used to instigate a European-wide debate which may eventually lead to pertinent changes in the Treaties.
The Methodological Implications of the Schutz-Parsons Debate  [PDF]
Christian Etzrodt
Open Journal of Philosophy (OJPP) , 2013, DOI: 10.4236/ojpp.2013.31006
Abstract:

The aim of this paper is an analysis of the different standpoints of Parsons and Schutz concerning Weber’s suggestion that sociological explanations have to include the subjective point of view of the actors, the Cartesian Dilemma that the actor’s consciousness is not accessible to the researcher, and the Kantian Problem that theories are necessary in order to interpret sensory data, but that there is no guarantee that these theories are true. The comparison of Schutz’s and Parsons’s positions shows that Parsons’s methodology is na?ve and unsuitable for a sociological analysis. But although Schutz’s methodological standpoint is much more reasonable, it is also problematic, because it excludes highly abstract social “facts” such as social systems from the research agenda. Parsons can deal with such highly abstract facts, despite the drawback that with his methodology the truth content of theories cannot be judged.

Psychodynamic Positive Psychotherapy Emphasizes the Impact of Culture in the Time of Globalization  [PDF]
Christian Henrichs
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.312A169
Abstract:

The emphasis of Positive Psychotherapy on culture is a specific contribution to psychodynamic psycho- therapy and to contemporary psychological reasoning and intervention in general. In this article, it is argued that a consistent psycho-cultural perspective as introduced by the founder of Positive Psychotherapy, the Persian-German psychiatrist and psychotherapist Nossrat Peseschkian (1933-2010), is beneficial for humanity’s psychological needs in the time of globalization. Also elementary concepts and the style of intervention in Positive Psychotherapy are described.


Conservation of Gravitational Energy-Momentum and Inner Diffeomorphism Group Gauge Invariance  [PDF]
Christian Wiesendanger
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.48A006
Abstract:

Viewing gravitational energy momentum \"\" as equal by observation, but different in essence from inertial energy-momentum \"\" requires two different symmetries to account for their independent conservations—spacetime and inner translation invariance. Gauging the latter a generalization of non-Abelian gauge theories of compact Lie groups is developed resulting in the gauge theory of the non-compact group of volume-preserving diffeomorphisms of an inner Minkowski space M4. As usual the gauging requires the introduction of a covariant derivative, a gauge field and a field strength operator. An invariant and minimal gauge field Lagrangian is derived. The classical field dynamics and the conservation laws for the new gauge theory are developed. Finally, the theorys Hamiltonian in the axial gauge is expressed by two times six unconstrained independent canonical variables obeying the usual Poisson brackets and the positivity of the Hamiltonian is related to a condition on the support of the gauge fields.

Conservation of Gravitational Energy Momentum and Renormalizable Quantum Theory of Gravitation  [PDF]
Christian Wiesendanger
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.48A013
Abstract:

Viewing gravitational energy-momentum as equal by observation, but different in essence from inertial energymomentum \"\" naturally leads to the gauge theory of volume-preserving diffeomorphisms of an inner Minkowski space \"\" which can describe gravitation at the classical level. This theory is quantized in the path integral formalism starting with a non-covariant Hamiltonian formulation with unconstrained canonical field variables and a manifestly positive Hamiltonian. The relevant path integral measure and weight are then brought into a Lorentz- and gauge-covariant form allowing to express correlation functions—applying the De Witt-Faddeev-Popov approach—in any meaningful gauge. Next the Feynman rules are developed and the quantum effective action at one loop in a background field approach is renormalized which results in an asymptotically free theory without presence of other fields and in a theory without asymptotic freedom including the Standard Model (SM) fields. Finally the BRST apparatus is developed as preparation for the renormalizability proof to all orders and a sketch of this proof is given.

General Relativity as the Classical Limit of the Renormalizable Gauge Theory of Volume Preserving Diffeomorphisms  [PDF]
Christian Wiesendanger
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.510098
Abstract:

The different roles and natures of spacetime appearing in a quantum field theory and in classical physics are analyzed implying that a quantum theory of gravitation is not necessarily a quantum theory of curved spacetime. Developing an alternative approach to quantum gravity starts with the postulate that inertial energy-momentum and gravitational energy-momentum need not be the same for virtual quantum states. Separating their roles naturally leads to the quantum gauge field theory of volume-preserving diffeomorphisms of an inner four-dimensional space. The classical limit of this theory coupled to a quantized scalar field is derived for an on-shell particle where inertial energy-momentum and gravitational energy-momentum coincide. In that process the symmetry under volume-preserving diffeomorphisms disappears and a new symmetry group emerges: the group of coordinate transformations of four-dimensional spacetime and with it General Relativity coupled to a classical relativistic point particle.

A Renormalizable Theory of Quantum Gravity: Renormalization Proof of the Gauge Theory of Volume Preserving Diffeomorphisms  [PDF]
Christian Wiesendanger
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.510099
Abstract:

Inertial and gravitational mass or energy momentum need not be the same for virtual quantum states. Separating their roles naturally leads to the gauge theory of volume-preserving diffeomorphisms of an inner four-dimensional space. The gauge-fixed action and the path integral measure occurring in the generating functional for the quantum Green functions of the theory are shown to obey a BRST-type symmetry. The related Zinn-Justin-type equation restricting the corresponding quantum effective action is established. This equation limits the infinite parts of the quantum effective action to have the same form as the gauge-fixed Lagrangian of the theory proving its spacetime renormalizability. The inner space integrals occurring in the quantum effective action which are divergent due to the gauge group’s infinite volume are shown to be regularizable in a way consistent with the symmetries of the theory demonstrating as a byproduct that viable quantum gauge field theories are not limited to finite-dimensional compact gauge groups as is commonly assumed.

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