Quantum simulation of frustrated magnetism in triangular optical lattices

Magnetism plays a key role in modern technology as essential building block of many devices used in daily life. Rich future prospects connected to spintronics, next generation storage devices or superconductivity make it a highly dynamical field of research. Despite those ongoing efforts, the many-body dynamics of complex magnetism is far from being well understood on a fundamental level. Especially the study of geometrically frustrated configurations is challenging both theoretically and experimentally. Here we present the first realization of a large scale quantum simulator for magnetism including frustration. We use the motional degrees of freedom of atoms to comprehensively simulate a magnetic system in a triangular lattice. Via a specific modulation of the optical lattice, we can tune the couplings in different directions independently, even from ferromagnetic to antiferromagnetic. A major advantage of our approach is that standard Bose-Einstein-condensate temperatures are sufficient to observe magnetic phenomena like N\'eel order and spin frustration. We are able to study a very rich phase diagram and even to observe spontaneous symmetry breaking caused by frustration. In addition, the quantum states realized in our spin simulator are yet unobserved superfluid phases with non-trivial long-range order and staggered circulating plaquette currents, which break time reversal symmetry. These findings open the route towards highly debated phases like spin-liquids and the study of the dynamics of quantum phase transitions.Comment: 5 pages, 4 figure

Alteration of NF-κB activity leads to mitochondrial apoptosis after infection with pathological prion protein

Nuclear factor kappa B (NF-κB) is a key regulator of the immune response, but in almost the same manner it is involved in induction of inflammation, proliferation and regulation of apoptosis. In the central nervous system activated NF-κB plays a neuroprotective role. While in some neurodegenerative disorders the role of NF-κB is well characterized, there is poor knowledge on the role of NF-κB in prion disease. We found binding but no transcriptional activity of the transcription factor in vitro. Characterizing the mechanism of cell death after infection with pathological prion protein increased caspase-9 and caspase-3 activity was detected and the lack of NF-κB activity resulted in the inability to activate target genes that usually play an important role in neuroprotection. Additionally, we investigated the role of NF-κB after prion infection of Nfkb1–/–, Nfkb2–/– and Bcl3–/– mice and central nervous system-specific p65-deleted mice revealing an accelerated prion disease in NF-κB2- and Bcl-3-deficient mice, which is in line with a reduced neuroprotective activity in prion infection. Based on our findings, we propose a model whereby the alteration of NF-κB activity at the early stages of infection with pathological prion protein leads to neuronal cell death mediated by mitochondrial apoptosis

Inhibition of MLC Phosphorylation Restricts Replication of Influenza Virus—A Mechanism of Action for Anti-Influenza Agents

Influenza A viruses are a severe threat worldwide, causing large epidemics that kill thousands every year. Prevention of influenza infection is complicated by continuous viral antigenic changes. Newer anti-influenza agents include MEK/ERK and protein kinase C inhibitors; however, the downstream effectors of these pathways have not been determined. In this study, we identified a common mechanism for the inhibitory effects of a significant group of anti-influenza agents. Our studies showed that influenza infection activates a series of signaling pathways that converge to induce myosin light chain (MLC) phosphorylation and remodeling of the actin cytoskeleton. Inhibiting MLC phosphorylation by blocking RhoA/Rho kinase, phospholipase C/protein kinase C, and HRas/Raf/MEK/ERK pathways with the use of genetic or chemical manipulation leads to the inhibition of influenza proliferation. In contrast, the induction of MLC phosphorylation enhances influenza proliferation, as does activation of the HRas/Raf/MEK/ERK signaling pathway. This effect is attenuated by inhibiting MLC phosphorylation. Additionally, in intracellular trafficking studies, we found that the nuclear export of influenza ribonucleoprotein depends on MLC phosphorylation. Our studies provide evidence that modulation of MLC phosphorylation is an underlying mechanism for the inhibitory effects of many anti-influenza compounds

Ephrin-A5 Suppresses Neurotrophin Evoked Neuronal Motility, ERK Activation and Gene Expression

During brain development, growth cones respond to attractive and repulsive axon guidance cues. How growth cones integrate guidance instructions is poorly understood. Here, we demonstrate a link between BDNF (brain derived neurotrophic factor), promoting axonal branching and ephrin-A5, mediating axonal repulsion via Eph receptor tyrosine kinase activation. BDNF enhanced growth cone filopodial dynamics and neurite branching of primary neurons. We show that ephrin-A5 antagonized this BDNF-evoked neuronal motility. BDNF increased ERK phosphorylation (P-ERK) and nuclear ERK entry. Ephrin-A5 suppressed BDNF-induced ERK activity and might sequester P-ERK in the cytoplasm. Neurotrophins are well established stimulators of a neuronal immediate early gene (IEG) response. This is confirmed in this study by e.g. c-fos, Egr1 and Arc upregulation upon BDNF application. This BDNF-evoked IEG response required the transcription factor SRF (serum response factor). Notably, ephrin-A5 suppressed a BDNF-evoked neuronal IEG response, suggesting a role of Eph receptors in modulating gene expression. In opposite to IEGs, long-term ephrin-A5 application induced cytoskeletal gene expression of tropomyosin and actinin. To uncover specific Eph receptors mediating ephrin-As impact on neurotrophin signaling, EphA7 deficient mice were analyzed. In EphA7 deficient neurons alterations in growth cone morphology were observed. However, ephrin-A5 still counteracted neurotrophin signaling suggesting that EphA7 is not required for ephrin and BDNF crosstalk. In sum, our data suggest an interaction of ephrin-As and neurotrophin signaling pathways converging at ERK signaling and nuclear gene activity. As ephrins are involved in development and function of many organs, such modulation of receptor tyrosine kinase signaling and gene expression by Ephs might not be limited to the nervous system

Gateway Centre - Minneapolis, Minnesota

This synopsis of the original thesis completed in 1978, no longer in existence, was prepared in 2013 by the author

Educational Needs of North Dakota Agribusiness Managers

The author reviews a study which was conducted to determine the importance and value of various management skills as they relate to agribusiness managers. Also, to determine areas where these managers felt they needed the most assistance in the improvement of their management skills. The method chosen was a survey. It appeared that managers in all five categories would benefit from a common training program. The majority of the skills included on the survey could be used to form a core for the curriculum for agribusiness management training courses

Innovative Milieux and Regional Competitiveness: The Role of Associations and Chambers of Commerce and Industry in Germany

Maennig W. and Olschlager M. Innovative milieux and regional competitiveness: the role of associations and chambers of commerce and industry in Germany, Regional Studies. Innovation is regarded as a spatially embedded process in which the social and economic interactive relationships of the actors are an important factor for success. This paper is one of the first to examine empirically the role of organizations such as associations, clubs, societies, and chambers of commerce and industry in innovative milieux. A limited effect of these actors on the regional competitiveness of the sixty largest German cities is found. [image omitted] Maennig W. et Olschlager M. Les milieux innovateurs et la competitivite regionale: le role des associations et des chambres de commerce et d'industrie en Allemagne, Regional Studies. L'innovation est consideree comme un processus qui est ancre dans l'espace et dans lequel l'interaction sociale et economqiue des agents est un prealable a la reussite. Cet article est l'un des premiers a examiner empiriquement le role des organisations, telles les associations, les clubs, les societes, et les chambres de commerce et d'industrie situes dans des milieux innovateurs. L'impact de ces agents sur la competitivite regionale des soixante villes les plus grandes d'Allemagne s'avere mitige. Innovation Milieux innovateurs Organisations Capital social Competitivite regionale Maennig W. und Olschlager M. Innovative Milieus und regionale Wettbewerbsfahigkeit: die Rolle von Vereinen und Industrie- und Handelskammern in Deutschland, Regional Studies. Innovation wird als ein raumlich eingebetteter Prozess verstanden, wobei interaktive soziale und okonomische Beziehungen der Akteure ein wichtiger Erfolgsfaktor sind. Dieser Beitrag ist dabei einer der ersten, der die Rolle von Organisationen wie Vereinen oder Industrie- und Handelskammern im innovativen Milieu empirisch untersucht. Wir kommen zu dem Ergebnis, dass die untersuchten Akteure teilweise einen Einfluss auf die regionale Wettbewerbsfahigkeit der 60 grossten Stadte in Deutschland haben. Innovation Innovative Milieus Organisationen Sozialkapital Regionale Wettbewerbsfahigkeit Maennig W. y Olschlager M. Circulos innovadores y la competitividad regional: el papel de asociaciones y camaras de comercio e industria en Alemania, Regional Studies. La innovacion se considera un proceso arraigado en el espacio en el que las relaciones interactivas de los actores desde el punto de vista social y economico representan un factor importante para lograr el exito. Este articulo es uno de los primeros en analizar empiricamente el papel de las organizaciones, tales como asociaciones, clubes, sociedades y camaras de comercio y la industria en circulos innovadores. Llegamos a la conclusion de que estos actores influyen de modo limitado en la competitividad regional de las sesenta ciudades mas grandes de Alemania. Innovacion Circulos innovadores Organizaciones Capital social Competitividad regionalInnovation, Innovative milieux, Organizations, Social capital, Regional competitiveness,