Gravitational shock waves and vacuum fluctuations

We show that the vacuum expectation value of the stress-energy tensor of a scalar particle on the background of a spherical gravitational shock wave does not give a finite expression in second order perturbation theory, contrary to the case seen for the impulsive wave. No infrared divergences appear at this order. This result shows that there is a qualitative difference between the shock and impulsive wave solutions which is not exhibited in first order.Comment: Submitted to Class. and Quant. Grav.,7 pages, no figure

N=2 SYM Action as a BRST Exact Term, Topological Yang Mills and Instantons

By constructing a nilpotent extended BRST operator \bs that involves the N=2 global supersymmetry transformations of one chirality, we show that the standard N=2 off-shell Super Yang Mills Action can be represented as an exact BRST term \bs \Psi, if the gauge fermion $\Psi$ is allowed to depend on the inverse powers of supersymmetry ghosts. By using this nonanalytical structure of the gauge fermion (via inverse powers of supersymmetry ghosts), we give field redefinitions in terms of composite fields of supersymmetry ghosts and N=2 fields and we show that Witten's topological Yang Mills theory can be obtained from the ordinary Euclidean N=2 Super Yang Mills theory directly by using such field redefinitions. In other words, TYM theory is obtained as a change of variables (without twisting). As a consequence it is found that physical and topological interpretations of N=2 SYM are intertwined together due to the requirement of analyticity of global SUSY ghosts. Moreover, when after an instanton inspired truncation of the model is used, we show that the given field redefinitions yield the Baulieu-Singer formulation of Topological Yang Mills.Comment: Latex, 1+15 pages. Published versio

Sense and Antisense Transcripts of Convergent Gene Pairs in Arabidopsis thaliana Can Share a Common Polyadenylation Region

The Arabidopsis genome contains a large number of gene pairs that encode sense and antisense transcripts with overlapping 3′ regions, indicative for a potential role of natural antisense transcription in regulating sense gene expression or transcript processing. When we mapped poly(A) transcripts of three plant gene pairs with long overlapping antisense transcripts, we identified an unusual transcript composition for two of the three gene pairs. Both genes pairs encoded a class of long sense transcripts and a class of short sense transcripts that terminate within the same polyadenylation region as the antisense transcripts encoded by the opposite strand. We find that the presence of the short sense transcript was not dependent on the expression of an antisense transcript. This argues against the assumption that the common termination region for sense and antisense poly(A) transcripts is the result of antisense-specific regulation. We speculate that for some genes evolution may have especially favoured alternative polyadenylation events that shorten transcript length for gene pairs with overlapping sense/antisense transcription, if this reduces the likelihood for dsRNA formation and transcript degradation

Distinct expression patterns of two Arabidopsis phytocystatin genes, AtCYS1 and AtCYS2, during development and abiotic stresses

The phytocystatins of plants are members of the cystatin superfamily of proteins, which are potent inhibitors of cysteine proteases. The Arabidopsis genome encodes seven phytocystatin isoforms (AtCYSs) in two distantly related AtCYS gene clusters. We selected AtCYS1 and AtCYS2 as representatives for each cluster and then generated transgenic plants expressing the GUS reporter gene under the control of each gene promoter. These plants were used to examine AtCYS expression at various stages of plant development and in response to abiotic stresses. Histochemical analysis of AtCYS1 promoter- and AtCYS2 promoter-GUS transgenic plants revealed that these genes have similar but distinct spatial and temporal expression patterns during normal development. In particular, AtCYS1 was preferentially expressed in the vascular tissue of all organs, whereas AtCYS2 was expressed in trichomes and guard cells in young leaves, caps of roots, and in connecting regions of the immature anthers and filaments and the style and stigma in flowers. In addition, each AtCYS gene has a unique expression profile during abiotic stresses. High temperature and wounding stress enhanced the expression of both AtCYS1 and AtCYS2, but the temporal and spatial patterns of induction differed. From these data, we propose that these two AtCYS genes play important, but distinct, roles in plant development and stress responses

Phylogenetic Analysis of Seven WRKY Genes across the Palm Subtribe Attaleinae (Arecaceae) Identifies Syagrus as Sister Group of the Coconut

BACKGROUND:The Cocoseae is one of 13 tribes of Arecaceae subfam. Arecoideae, and contains a number of palms with significant economic importance, including the monotypic and pantropical Cocos nucifera L., the coconut, the origins of which have been one of the "abominable mysteries" of palm systematics for decades. Previous studies with predominantly plastid genes weakly supported American ancestry for the coconut but ambiguous sister relationships. In this paper, we use multiple single copy nuclear loci to address the phylogeny of the Cocoseae subtribe Attaleinae, and resolve the closest extant relative of the coconut. METHODOLOGY/PRINCIPAL FINDINGS:We present the results of combined analysis of DNA sequences of seven WRKY transcription factor loci across 72 samples of Arecaceae tribe Cocoseae subtribe Attaleinae, representing all genera classified within the subtribe, and three outgroup taxa with maximum parsimony, maximum likelihood, and Bayesian approaches, producing highly congruent and well-resolved trees that robustly identify the genus Syagrus as sister to Cocos and resolve novel and well-supported relationships among the other genera of the Attaleinae. We also address incongruence among the gene trees with gene tree reconciliation analysis, and assign estimated ages to the nodes of our tree. CONCLUSIONS/SIGNIFICANCE:This study represents the as yet most extensive phylogenetic analyses of Cocoseae subtribe Attaleinae. We present a well-resolved and supported phylogeny of the subtribe that robustly indicates a sister relationship between Cocos and Syagrus. This is not only of biogeographic interest, but will also open fruitful avenues of inquiry regarding evolution of functional genes useful for crop improvement. Establishment of two major clades of American Attaleinae occurred in the Oligocene (ca. 37 MYBP) in Eastern Brazil. The divergence of Cocos from Syagrus is estimated at 35 MYBP. The biogeographic and morphological congruence that we see for clades resolved in the Attaleinae suggests that WRKY loci are informative markers for investigating the phylogenetic relationships of the palm family

The Universality of human adventure in dream plays of Thornton Wilder: Our Town and The Skin of Our Teeth

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.59 İNGİLİZCE ABSTRAKT (en fazla 250 sözcük): ABSTRACT This study is about the universality of human adventure in Thornton Wilder's dream plays which are Our Town and The Skin of Our Teeth. The focus is on both of Wilder's plays which are representatives of universality of human adventure by using dream play technique. The first chapter covers Wilder's career in American drama with short introduction of his plays which are considered to be reflection of his life and our thesis subject plays. Chapter two concentrates on the dream play technique. The innovator of this technique, Strindberg, is presented with some examples from his plays in order to supply a better understanding of the subject we work on. Chapter three deals with the analysis of the thesis subject in both plays. Our Town seems to contain. in a New England small town and ordinariness is presented by everyday occurences in the town. The Skin of Our Teeth covers humanity in fanciful adventures of a family who lives in New Jersey. Wilder, in both of the plays, brought new touches to American theatre by using dream play technique in order to emphasize the universal.58 TÜRKÇE ABSTRAKT (en fazla 250 sözcük ): (TUBİT TURDÖK'un Abstrakt Hazırlama Kılavuzunu kullanınız.) TÜRKÇE ABSTRAKT Bu çalışma, Thornton Wilder'ın rüya oyunlarından olan Our Town ve The Skin of Our Teeth eserlerindeki insanlık macerasının evrenselliği ile ilgilidir. Ortaya koyduğumuz tez, rüya oyun tekniğini kullanarak insanlık macerasının evrenselliğinin temsilcisi olan Wilder'ın iki oyunu üzerine odaklanmaktadır. ilk bölüm, Wilder 'ın Amerikan dramasındaki kariyerini, bizim tez konumuz olan oyunlarının ve kendi hayatının yansıması olarak düşünülen oyunlarının kısa bir sunuşunu kapsar. İkinci bölüm, rüya oyun tekniğinde merkezlenmektedir. Bu tekniğin kurucusu olan Strindberg'in oyunlarından bazı örnekler, üzerinde çalıştığımız konunun daha iyi anlaşılması açısından verilmiştir. Üçüncü bölüm, her iki oyunda işlenen temanın analizi ile ilgilidir. Our Town 'nun Yeni İngiltere'deki küçük bir kasabada geçtiği görünür ve sıradanlık kasabadaki günlük olaylar ile birlikte sunulur. The Skin of Our Teeth insaniliği, New Jersey'de fantazi maceralarla yaşayan bir aile olarak sunar. Wilder, her iki oyunda da evrenselliği vurgulamak için kullandığı rüya oyun tekniği Amerikan tiyatrosuna yeni bir anlayış getirmişti