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Search Results: 1 - 10 of 32861 matches for " John Reich "
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Caprin Controls Follicle Stem Cell Fate in the Drosophila Ovary
John Reich, Ophelia Papoulas
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035365
Abstract: Adult stem cells must balance self-renewal and differentiation for tissue homeostasis. The Drosophila ovary has provided a wealth of information about the extrinsic niche signals and intrinsic molecular processes required to ensure appropriate germline stem cell renewal and differentiation. The factors controlling behavior of the more recently identified follicle stem cells of the ovary are less well-understood but equally important for fertility. Here we report that translational regulators play a critical role in controlling these cells. Specifically, the translational regulator Caprin (Capr) is required in the follicle stem cell lineage to ensure maintenance of this stem cell population and proper encapsulation of developing germ cells by follicle stem cell progeny. In addition, reduction of one copy of the gene fmr1, encoding the translational regulator Fragile X Mental Retardation Protein, exacerbates the Capr encapsulation phenotype, suggesting Capr and fmr1 are regulating a common process. Caprin was previously characterized in vertebrates as Cytoplasmic Activation/Proliferation-Associated Protein. Significantly, we find that loss of Caprin alters the dynamics of the cell cycle, and we present evidence that misregulation of CycB contributes to the disruption in behavior of follicle stem cell progeny. Our findings support the idea that translational regulators may provide a conserved mechanism for oversight of developmentally critical cell cycles such as those in stem cell populations.
Exciton resonances quench the photoluminescence of zigzag carbon nanotubes
Stephanie Reich,Christian Thomsen,John Robertson
Physics , 2005, DOI: 10.1103/PhysRevLett.95.077402
Abstract: We show that the photoluminescence intensity of single-walled carbon nanotubes is much stronger in tubes with large chiral angles - armchair tubes - because exciton resonances make the luminescence of zigzag tubes intrinsically weak. This exciton-exciton resonance depends on the electronic structure of the tubes and is found more often in nanotubes of the +1 family. Armchair tubes do not necessarily grow preferentially with present growth techniques; they just have stronger luminescence. Our analysis allows to normalize photoluminescence intensities and find the abundance of nanotube chiralities in macroscopic samples.
Nanotube caps on Ni, Fe, and NiFe nano particles: A path to chirality selective growth
Heiko Dumlich,John Robertson,Stephanie Reich
Physics , 2013,
Abstract: Carbon nanotubes have properties depending on the arrangement of carbon atoms on the tube walls, called chirality. Also it has been tried to grow nanotubes of only one chirality for more than a decade it is still not possible today. A narrowing of the distribution of chiralities, however, which is a first step towards chirality control, has been observed for the growth of nanotubes on catalysts composed of nickel and iron. In this paper, we have calculated carbon-metal bond energies, adhesion energies and charge distributions of carbon nanotube caps on Ni, Fe and NiFe alloy clusters using density functional theory. A growth model using the calculated energies was able to reproduce the experimental data of the nanotube growth on the alloy catalysts. The electronic charge was found to be redistributed from the catalyst particles to the edges of the nanotube caps in dependence of the chiral angles of the caps increasing the reactivity of the edge atoms. Our study develops an explanation for the chirality enrichment in the carbon nanotube growth on alloy catalyst particles.
miRNA-Dependent Translational Repression in the Drosophila Ovary
John Reich, Mark J. Snee, Paul M. Macdonald
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004669
Abstract: Background The Drosophila ovary is a tissue rich in post-transcriptional regulation of gene expression. Many of the regulatory factors are proteins identified via genetic screens. The more recent discovery of microRNAs, which in other animals and tissues appear to regulate translation of a large fraction of all mRNAs, raised the possibility that they too might act during oogenesis. However, there has been no direct demonstration of microRNA-dependent translational repression in the ovary. Methodology/Principal Findings Here, quantitative analyses of transcript and protein levels of transgenes with or without synthetic miR-312 binding sites show that the binding sites do confer translational repression. This effect is dependent on the ability of the cells to produce microRNAs. By comparison with microRNA-dependent translational repression in other cell types, the regulated mRNAs and the protein factors that mediate repression were expected to be enriched in sponge bodies, subcellular structures with extensive similarities to the P bodies found in other cells. However, no such enrichment was observed. Conclusions/Significance Our results reveal the variety of post-transcriptional regulatory mechanisms that operate in the Drosophila ovary, and have implications for the mechanisms of miRNA-dependent translational control used in the ovary.
Algebraic K-theory of group rings and the cyclotomic trace map
Wolfgang Lueck,Holger Reich,John Rognes,Marco Varisco
Mathematics , 2015,
Abstract: We prove that the Farrell-Jones assembly map for connective algebraic K-theory is rationally injective, under mild homological finiteness conditions on the group and assuming that a weak version of the Leopoldt-Schneider conjecture holds for cyclotomic fields. This generalizes a result of B\"okstedt, Hsiang, and Madsen, and leads to a concrete description of a large direct summand of $K_n(\mathbb{Z}[G])\otimes_{\mathbb{Z}}\mathbb{Q}$ in terms of group homology. In many cases the number theoretic conjectures are true, so we obtain rational injectivity results about assembly maps, in particular for Whitehead groups, under finiteness assumptions on the group only. The proof uses the cyclotomic trace map to topological cyclic homology, B\"okstedt-Hsiang-Madsen's functor C, and new general injectivity results about the assembly maps for topological Hochschild homology and C.
Zaparcie czynno ciowe imituj ce nieswoiste zapalenie jelit u 12-letniej dziewczynki - opis przypadku
Magdalena Reich
Pediatria Wspó?czesna , 2011,
Abstract: W obecnej pracy prezentowana jest 12-letnia dziewczynka, która zg asza a silne bóle brzucha, oddawa a zaparte stolce co 2-4 dni, z czasem zaobserwowa a brudzenie bielizny, które mylnie zosta o rozpoznane jako biegunka. Dziecko straci o apetyt, a w okresie 6 mies. jego masa zmniejszy a si o 4 kg. Wysuni to podejrzenie nieswoistego zapalenia jelit i dziewczynk skierowano do oddzia u gastroenterologicznego celem dalszej diagnostyki i leczenia. W trakcie badania fizykalnego stwierdzono obecno zalegaj cych mas ka owych w odbytnicy, okolica odbytu by a zanieczyszczona ka em, a w badaniu manometrycznym wykazano zaburzenia aktu defekacji. Przy braku innej patologii rozpoznano zaparcia czynno ciowe jako pierwotn przyczyn zg aszanych dolegliwo ci i rozpocz to odpowiedni terapi . U dzieci kilkudniowy brak wypró nień powoduje bóle brzucha, brak aknienia, a z czasem ubytek masy cia a i zahamowanie rozwoju somatycznego. W wyniku rozci gania ciany odbytnicy przez zalegaj ce masy ka owe mo e pojawi si brudzenie bielizny i popuszczanie stolca. To mimowolne nietrzymanie ka u mo e by mylone z biegunk i utrudnia postawienie w a ciwego rozpoznania choroby.
A case of inbreeding in the African Wild Dog Lycaon pictus in the Kruger National Park
A. Reich
Koedoe : African Protected Area Conservation and Science , 1978, DOI: 10.4102/koedoe.v21i1.967
Abstract: An observed case of inbreeding in a pack ot wild dogs Lycaon pictus in the Kruger National Park, Republic of South Africa, provides evidence for the phenomenon of dominance reversal in this species. This is believed to be the first recorded instance of inbreeding in Lycaon. Emigration of subordinate females from established packs of wild dogs has been documented in the Serengeti National Park and Ngorongoro Conservation Area in northern Tanzania, as well as in the Kruger National Park. However, the newly subordinate (ex-dominant) female in the pack in which inbreeding has occurred has not emigrated in the 16 months since the change in her status. A possible explanation for this behaviour is given. As a result of this reversal, the pack contains at least two females capable of breeding, the subordinate of which is at least two years older than the dominant. This is considered the first record of such a breeding structure in Lycaon.
Die Kassation in Zivilsachen [in der DDR] - Ma nahmeakt oder Rechtsinstitut?
Torsten Reich
Forum Historiae Iuris , 1997,
Alexander von Humboldt und Carl Friedrich Gau als Wegbereiter der neuen Disziplin Erdmagnetismus
Karin Reich
HiN. Alexander von Humboldt im Netz , 2011,
Abstract: Though Alexander von Humboldt was motivated for the first time to deal with earthmagnetism during his stay in Freiberg, it was in France that he really became a specialist in this respect. During most of his journeys he made earthmagnetic measurements. His collaboration with Arago was of great importance, it was in Paris that the first magnetic observatory was built. Humboldt rendered outstanding services to the investigation of earth magnetism by two major achievements: 1. He emphasized intensity measurements and 2. he put forward the law that the magnetic intensity is increasing from the magnetic equator toward the magnetic poles. At least since 1803 Carl Friedrich Gauss was interested in earthmagnetism and especially in Humboldt’s early published data. That Wilhelm Weber became professor of physics at the University of G ttingen in 1831 was a turning point for Gauss. In 1833 G ttingen was the centre of investigating earthmagnetism, a new era began which lasted only until 1843. Gauss’ main contributions were more or less theoretical, in 1832/3 he transformed Humboldt’s relative intensity measurements into absolute ones which were independent of the instrument’s needle. A new epoch began with Gauss’ publication Allgemeine Theorie des Erdmagnetismus” (1839). The main point was the newly defined notion of potential“. Gauss was the first to present the surface of the earth with equipotential lines. ZusammenfassungAlexander von Humboldt hatte sich bereits in Freiberg mit dem Erdmagnetismus besch ftigt; jedoch erst in Frankreich lernte er die entsprechenden Beobachtungsmethoden kennen. Auf allen seinen Reisen machte er erdmagnetische Messungen. Seine Zusammenarbeit mit Arago in Paris war besonders fruchtbar, hier wurde das erste magnetische Observatorium gebaut. Humboldt besch ftigte sich vor allem mit Intensit tsmessungen; sein wichtigster Beitrag war die Feststellung, dass die magnetische Intensit t vom magnetischen quator bis hin zu den Polen zunimmt. Carl Friedrich Gau interessierte sich seit mindestens 1803 für den Erdmagnetismus; vor allem trachtete er danach, die Humboldtschen Messergebnisse zu bekommen. Als im Jahre 1831 Wilhelm Weber als Professor der Physik nach G ttingen berufen worden war, war dies ein Wendepunkt für Gau . Bereits 1833 war G ttingen zum Zentrum für erdmagnetische Forschungen geworden; eine neue ra begann, welche allerdings nur bis 1843 w hrte. Gau ’ wichtigste Beitr ge waren theoretischer Natur; zun chst stellte er Humboldts relative Intensit tsmessungen auf absolute Messungen um, die unabh ngig von der jeweils gebr
Sternschnuppen und Erdmagnetismus, ein von Alexander von Humboldt und Carl Friedrich Gau w hrend der Universit tsfeierlichkeiten in G ttingen im September 1837 initiiertes Projekt
Karin Reich
HiN. Alexander von Humboldt im Netz , 2011,
Abstract: In September 1837 the centennial celebrations of G ttingen university took place; Alexander von Humboldt, who visited G ttingen for this purpose, and Carl Friedrich Gauss created the project: Do showers of meteors influence the terrestrial magnetic phaenomena, comparable to the aurora borealis? The investigation should take place in November 1837, when strong meteor showers were once again expected. In this context the letter of Humboldt to Gauss from November 30, 1837 is of great importance; in this letter two enclosures were mentioned which still exist, but which were not presented in the edition of the letters between Humboldt and Gauss.One of these enclosures is a letter from Boguslawski to Humboldt from November 15, 1837, on which Humboldt made several remarks. Boguslawski was astronomer at the observatory of Breslau. The other enclosure was a document, containing the observation data of Humboldt and Herter, which were made in Berlin during November 12 to 15 and 21. These two documents together with the historical context are presented here for the first time, accompanied by the report by Gerling on meteor showers observed in Marburg from November 12 to 14.ZusammenfassungW hrend der im September 1837 in G ttingen stattfindenden Universit tsfeierlichkeiten initiierten Alexander von Humboldt und Carl Friedrich Gau gemeinsam ein Projekt; es ging dabei um die Frage, ob Sternschnuppen die erdmagnetischen Erscheinungen beeinflussen würden, dem Nordlicht vergleichbar. Dies sollte im folgenden November, anl sslich des zu erwartenden gro en Sternschnuppenschauers, überprüft werden.Im Zentrum dieser Untersuchung steht der Brief von Alexander von Humboldt an Gau vom 30. November 1837 (Briefwechsel Humboldt-Gau , S. 63–65); in diesem wurden zwei Beilagen bzw. Anlagen angesprochen, die zwar noch existieren, die aber bei der Ausgabe des Humboldt-Gau schen Briefwechsels fast ganz unberücksichtigt blieben. Es handelt sich erstens um einen Brief von dem in Breslau wirkenden Astronomen Boguslawski an Humboldt vom 15. November 1837, den Humboldt, versehen mit eigenen Anmerkungen, Gau zukommen lie , und zweitens um ein Dokument, enthaltend die von Humboldt und Herter in Berlin w hrend der Zeit vom 12. bis 21. November angestellten erdmagnetischen Beobachtungen. Diese Dokumente sollen hier erstmals in den historischen Kontext eingebettet, vorgestellt werden, zusammen mit dem Bericht über die in Marburg gemachten Sternschnuppenbeobachtungen vom 12. bis 14. November, die Gerling veranlasst hatte.
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