Direct activation of RNA polymerase III transcription by c-Myc

The proto-oncogene product c-Myc has a direct role in both metazoan cell growth and division. RNA polymerase III (pol III) is involved in the generation of transfer RNA and 5S ribosomal RNA, and these molecules must be produced in bulk to meet the need for protein synthesis in growing cells. We demonstrate here that c-Myc binds to TFIIIB, a pol III-specific general transcription factor, and directly activates pol III transcription. Chromatin immunoprecipitation reveals that endogenous c-Myc is present at tRNA and 5S rRNA genes in cultured mammalian cells. These results suggest that activation of pol III may have a role in the ability of c-Myc to stimulate cell growt

Impact of pirimiphos-methyl and cold temperatures on arthropod populations in stored wheat

Appliqué à une concentration moyenne de 6,4 mg m.a. kg-1 à 5 t de ble (Triticum aestivum) dans un grenier du sud du Manitoba, l'insecticide pyrimiphos-méthyl est resté actif pendant plus de 24 mo. La plupart des insectes et des acariens qui vivaient dans le grain traité n'ont pu survivre, à l'exception d'un psoque, Liposcelis sp., ainsi que les acariens Tarsonemus granarius et Aeroglyphus robustus, dont les populations ont été considérablement réduites par rapport à celles qui vivaient dans du blé non traité. À 1 m de profondeur, la concentration en résidus de l'insecticide a diminué de 52% en 12 mo, passant de 8,1 mg kg-1 à 4,0 mg kg-1 puis est restée stable jusqu'à la fin de la période de 24 mo. La teneur en humidité du grain à cette profondeur était constamment supérieure (plus de 14%) à celle mesurée en surface du blé, où les résidus sont demeurés à une concentration voisine de 4,5 mg kg-1 pendant les 24 mo. La température du blé fluctuait entre des maximums estivaux voisins de 23°C et des minimums hivernaux de près de -40°C à la surface du blé. Après 24 mo d'entreposage, du blé traité a été contaminé avec des adultes du Tribolium castaneum; le taux de mortalité observé a été d'environ 80%. Des populations de T. castaneum ou de Rhyzopertha dominica introduites dans 5 t de blé non traité ne se sont pas établies; de petites populations de Cryptolestes ferrugineus se sont établies, mais elles ont été éliminées par le froid. Les populations de Liposcelis sp. et des acariens A robustus, T. granarius, Blattisocius keegani et de Cheyletus eruditus étaient les plus élevées à la fin de l'été et en automne. La germination des grains et la microflore n'ont pas été directement affectées par le pyrimiphos-méthyl. La lente décomposition de cet insecticide dans le grain empêcherait des communautés d'arthropodes de se développer autant que dans un écosystème constitué de blé entreposé et non traité sur une période de 24 mo.The insecticide pirimiphos-methyl applied at a mean concentration of 6.4 mg a.i. kg 1 to 5t of wheat (Triticum aestivum) in a farm granary in southern Manitoba remained active over 24 mo. Most insects and mites in the treated grain could not survive except a psocid, Liposcelis sp., and the mites Tarsonemus granarius and Aeroglyphus robustus, and their populations were sharply reduced relative to those in a bulk of untreated wheat. Insecticide residues at a 1-m depth decreased ca. 52% in 12 mo from 8.1 mg kg-1 to 4.0 mg kg-1, then remained constant until 24 mo. Grain moisture content (MC) at this depth was consistently higher (over 14% MC) than at the top of the wheat bulk where residues remained near 4.5 mg kg-1 over 24 mo. Grain temperatures fluctuated from summer maxima near 23°C to winter minima near -40°C at the bulk surface. Bioassay of treated wheat with adult Tribolium castaneum after 24 mo of storage resulted in about 80% mortality. Populations of T castaneum or Rhyzopertha dominica introduced into 5 t of untreated wheat did not become established; small populations of Cryptolestes ferrugineus were established but were eliminated by winter cold. Populations of Liposcelis sp. and the mites A. robustus, T. granarius, Blattisocius keegani and Cheyletus eruditus were highest in late summer and autumn. Seed germination and microflora were not directly affected by pirimiphos-methyl. The slow rate of degradation of this insecticide in grain would prevent communities of arthropods from developing to the same extent as in an untreated stored-wheat ecosystem over 24 mo

Implications of shunt morphology for the surgical management of extrahepatic portosystemic shunts

Objectives: To describe the implications of extrahepatic portosystemic shunt morphology for 14 the chosen site of shunt closure in dogs and cats. Methods: A retrospective review of a consecutive series of dogs and cats managed for 16 congenital extrahepatic portosystemic shunts was used. Results: In total 54 dogs and 10 cats met the inclusion criteria revealing five distinct shunt 18 types; left gastro-phrenic, right gastro-caval (types Ai, Aii and Aiii), spleno-caval, colo-caval 19 and left gastro-azygos. Without exception, findings of computed tomography angiography and 20 direct gross observations at the time of surgery confirmed four consistent sites of 21 communication between the anomalous shunting vessel and the systemic venous system; the 22 caudal vena cava at the level of the epiploic foramen, the left phrenic vein at the level of the 23 oesophageal hiatus, the azygos vein at the level of the aortic hiatus and the caudal vena cava 24 or iliac vein at the level of the sixth or seventh lumbar vertebrae. The use of intra-operative mesenteric portography was effective in confirming that at the time of surgery all portal 26 tributary vessels were proximal to the point of shunt attenuation. Conclusions: Findings confirmed that for the common types of extrahepatic portosystemic 28 shunts seen there were only four consistent sites of communication between the shunt and the 29 systemic venous system. This information supports the use of a systematic approach for 30 location and attenuation of shunts in dogs and cats

Implications of shunt morphology for the surgical management of extrahepatic portosystemic shunts

Objectives: To describe the implications of extrahepatic portosystemic shunt morphology for 14 the chosen site of shunt closure in dogs and cats. Methods: A retrospective review of a consecutive series of dogs and cats managed for 16 congenital extrahepatic portosystemic shunts was used. Results: In total 54 dogs and 10 cats met the inclusion criteria revealing five distinct shunt 18 types; left gastro-phrenic, right gastro-caval (types Ai, Aii and Aiii), spleno-caval, colo-caval 19 and left gastro-azygos. Without exception, findings of computed tomography angiography and 20 direct gross observations at the time of surgery confirmed four consistent sites of 21 communication between the anomalous shunting vessel and the systemic venous system; the 22 caudal vena cava at the level of the epiploic foramen, the left phrenic vein at the level of the 23 oesophageal hiatus, the azygos vein at the level of the aortic hiatus and the caudal vena cava 24 or iliac vein at the level of the sixth or seventh lumbar vertebrae. The use of intra-operative mesenteric portography was effective in confirming that at the time of surgery all portal 26 tributary vessels were proximal to the point of shunt attenuation. Conclusions: Findings confirmed that for the common types of extrahepatic portosystemic 28 shunts seen there were only four consistent sites of communication between the shunt and the 29 systemic venous system. This information supports the use of a systematic approach for 30 location and attenuation of shunts in dogs and cats

Comparison of the density-matrix renormalization group method applied to fractional quantum Hall systems in different geometries

We report a systematic study of the fractional quantum Hall effect (FQHE) using the density-matrix renormalization group (DMRG) method on two different geometries: the sphere and the cylinder. We provide convergence benchmarks based on model Hamiltonians known to possess exact zero-energy ground states, as well as an analysis of the number of sweeps and basis elements that need to be kept in order to achieve the desired accuracy.The ground state energies of the Coulomb Hamiltonian at $\nu=1/3$ and $\nu=5/2$ filling are extracted and compared with the results obtained by previous DMRG implementations in the literature. A remarkably rapid convergence in the cylinder geometry is noted and suggests that this boundary condition is particularly suited for the application of the DMRG method to the FQHE.Comment: 5 pages, 7 figure

Classification of portosystemic shunts entering the caudal vena cava at the omental foramen in dogs

ObjectiveTo re‐evaluate the anatomy and classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen.Material and MethodsA retrospective review of a consecutive series of dogs undergoing CT angiography as part of the diagnostic work‐up for a congenital extrahepatic portosystemic shunt.ResultsIn total, 53 dogs met the inclusion criteria revealing four anatomically distinct omental foramen shunt types; one of which (32 of 53 dogs) showed no shunting blood flow through the right gastric vein and three of which (21 of 53 dogs) involved shunting flow through this vessel. The anatomy of these four distinct shunt types, as defined by CT angiography, was found to be highly consistent. In all cases, regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava. Using these findings, a more accurate naming classification for congenital portosystemic shunts entering the caudal vena cava at the level of the omental foramen was proposed.Clinical SignificanceA precise pre‐treatment anatomical classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen is important for a more complete understanding of the severity of clinical signs and prognosis, and for the better communication between clinicians and researchers in this clinical field

Dynamical Properties of Two Coupled Hubbard Chains at Half-filling

Using grand canonical Quantum Monte Carlo (QMC) simulations combined with Maximum Entropy analytic continuation, as well as analytical methods, we examine the one- and two-particle dynamical properties of the Hubbard model on two coupled chains at half-filling. The one-particle spectral weight function, $A({\bf k},\omega)$, undergoes a qualitative change with interchain hopping $t_\perp$ associated with a transition from a four-band insulator to a two-band insulator. A simple analytical model based on the propagation of exact rung singlet states gives a good description of the features at large $t_\perp$. For smaller $t_\perp$, $A({\bf k}, \omega)$ is similar to that of the one-dimensional model, with a coherent band of width the effective antiferromagnetic exchange $J$ reasonably well-described by renormalized spin-wave theory. The coherent band rides on a broad background of width several times the parallel hopping integral $t$, an incoherent structure similar to that found in calculations on both the one- and two-dimensional models. We also present QMC results for the two-particle spin and charge excitation spectra, and relate their behavior to the rung singlet picture for large $t_\perp$ and to the results of spin-wave theory for small $t_\perp$.Comment: 9 pages + 10 postscript figures, submitted to Phys.Rev.B, revised version with isotropic t_perp=t data include

Spin-fluctuations in the quarter-filled Hubbard ring : significances to LiV2_2O4_4

Using the quantum Monte Carlo method, we investigate the spin dynamics of itinerant electrons in the one-dimensional Hubbard system. Based on the model calculation, we have studied the spin-fluctuations in the quarter-filled metallic Hubbard ring, which is aimed at the vanadium ring or chain defined along corner-sharing tetrahedra of LiV$_2$O$_4$, and found the dramatic changes of magnetic responses and spin-fluctuation characteristics with the temperature. Such results can explain the central findings in the recent neutron scattering experiment for LiV$_2$O$_4$.Comment: 5 pages, 3 figure

Tuned mass damper effects on the response of multi-storied structures observed in geotechnical centrifuge tests

Tuned mass dampers (TMDs) are widely used to reduce vibrations in structures. However, very little research is available on the experimental investigation of TMDs and their performance in soilstructure systems. In this paper, a series of geotechnical centrifuge tests was conducted to investigate the effects of TMDs on the response of a multiple-storey sway frame structure undergoing dynamic soil-structure interaction (SSI). Structural responses were recorded for a wide range of input motion characteristics, damper configurations and soil profiles. The practicality associated with the use of TMDs in the damping of resonant structures in light of unexpected earthquake characteristics different from design earthquakes was experimentally demonstrated. Tuning a TMD to soil-structure system properties rather than fixed-base structural properties was found to double the improvement in damping and reduce the original peak response by nearly half. The potential effectiveness of a detuned mass damper in light of significant SSI was also demonstrated.The financial help during the course of the study was extended by the Engineering and Physical Sciences Research Council (EPSRC).This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.soildyn.2015.06.01

Quantum lattice dynamical effects on the single-particle excitations in 1D Mott and Peierls insulators

As a generic model describing quasi-one-dimensional Mott and Peierls insulators, we investigate the Holstein-Hubbard model for half-filled bands using numerical techniques. Combining Lanczos diagonalization with Chebyshev moment expansion we calculate exactly the photoemission and inverse photoemission spectra and use these to establish the phase diagram of the model. While polaronic features emerge only at strong electron-phonon couplings, pronounced phonon signatures, such as multi-quanta band states, can be found in the Mott insulating regime as well. In order to corroborate the Mott to Peierls transition scenario, we determine the spin and charge excitation gaps by a finite-size scaling analysis based on density-matrix renormalization group calculations.Comment: 5 pages, 5 figure