Phytochrome A mediates blue-light enhancement of second-positive phototropism in Arabidopsis

Hypocotyl phototropism of etiolated Arabidopsis seedlings is primarily mediated by the blue-light receptor kinase phototropin 1 (phot1). Phot1-mediated curvature to continuous unilateral blue light irradiation (0.5 µmol m-2 s-1) is enhanced by overhead pre-treatment with red light (20 µmol m-2 s-1 for 15 min) through the action of phytochrome (phyA). Here, we show that pre-treatment with blue light is equally as effective in eliciting phototropic enhancement and is dependent on phyA. Although blue pre-treatment was sufficient to activate early phot1 signalling events, phot1 autophosphorylation in vivo was not found to be saturated, as assessed by subsequently measuring phot1 kinase activity in vitro. However, enhancement effects to red and blue pre-treatment were not observed at higher intensities of phototropic stimulation (10 µmol m-2 s-1). Phototropic enhancement to red and blue pre-treatments to 0.5 µmol m-2 s-1 unilateral blue light irradiation was also lacking in transgenic Arabidopsis where PHOT1 expression was restricted to the epidermis. Together, these findings indicate that phyA-mediated effects on phot1 signalling are restricted to low intensities of phototropic stimulation and originate from tissues other than the epidermis

The Construction Wage Determination Process in the 1970's

This Technical Report was published by the School of Business at the University of Kansas.Review of wage determination in the US construction industry in the 1970's with regression estimation of various effects

Large thermomagnetic effects in weakly disordered Heisenberg chains

The interplay of different scattering mechanisms can lead to novel effects in transport. We show theoretically that the interplay of weak impurity and Umklapp scattering in spin-1/2 chains leads to a pronounced dip in the magnetic field dependence of the thermal conductivity $\kappa$ at a magnetic field $B \sim T$. In sufficiently clean samples, the reduction of the magnetic contribution to heat transport can easily become larger than 50% and the effect is predicted to exist even in samples with a large exchange coupling, J >> B, where the field-induced magnetization is small. Qualitatively, our theory might explain dips at $B \sim T$ observed in recent heat transport measurements on copper pyrazine dinitrate, but a fully quantitative description is not possible within our model.Comment: 5 pages, 2 figure

CISC controls and the union/non-union wage ratio

This article was published in the Journal of Behavioral Economics, Vol 13: David Shulenburger, Robert A. McLean, Sara B. Rasch, CISC controls and the union/non-union wage ratio, Pages 57-66. Copyright Elsevier (1984)

Simulating Ability: Representing Skills in Games

Throughout the history of games, representing the abilities of the various agents acting on behalf of the players has been a central concern. With increasingly sophisticated games emerging, these simulations have become more realistic, but the underlying mechanisms are still, to a large extent, of an ad hoc nature. This paper proposes using a logistic model from psychometrics as a unified mechanism for task resolution in simulation-oriented games

Simple model of the rf noise generated by multipacting electrons

A simplified analytical model is developed to predict the spectrum of electric current induced by the multipacting electrons between two parallel electrodes exposed to an rf voltage of fixed amplitude. The model is based on the resonant multipactor theory and makes it possible to calculate the relative spectral amplitudes of electric current at different harmonics and sub-harmonics of the applied rf frequency. The theoretical predictions are confirmed by numerical simulations of multipactor inside a rectangular waveguide. Specifically it is seen that the relative height of the spectral peaks decreases with increasing gap height

Magnetoelastic coupling in triangular lattice antiferromagnet CuCrS2

CuCrS2 is a triangular lattice Heisenberg antiferromagnet with a rhombohedral crystal structure. We report on neutron and synchrotron powder diffraction results which reveal a monoclinic lattice distortion at the magnetic transition and verify a magnetoelastic coupling. CuCrS2 is therefore an interesting material to study the influence of magnetism on the relief of geometrical frustration.Comment: 6 pages, 6 figures, 1 tabl

The Effect of AICAR-Induced AMPK Activation on Gene Expression in Sarcopenic Muscle

The loss of muscle mass and function (sarcopenia) afflicts 11-74% of all aging adults, with prevalence increasing with age. Exercise training is clearly effective in preventing or attenuating sarcopenia. The cellular mechanisms of exercise’s protective effects are not entirely clear, but AMP-activated protein kinase (AMPK) is thought to play an important role, in part by regulating gene expression. PURPOSE: To determine the effect of chronic pharmacological AMPK activation on skeletal muscle gene expression in sarcopenic muscle. METHODS: 24-month-old C57Bl/6J mice received either one acute injection or chronic daily saline injections of the AMPK-activating drug AICAR for 31 days. 5-month-old saline-injected mice served as young controls for reference. Treadmill running capacity was measured before and after treatment. Expression of genes relating to mitochondria, muscle size regulation, and inflammation was measured by real-time polymerase chain reaction (RT-PCR). RESULTS: One hour after a single injection of AICAR, raptor phosphorylation was increased in both young and old mice, indicating AMPK activation. Phosphorylation of the mTORC1 targets 4EBP1, and S6k were both elevated in old muscle, consistent with previous reports of hyperactivated mTORC1 in aged muscle. Acute AICAR injection returned 4EBP1 and S6k phosphorylation to young levels. RNA sequencing demonstrated that chronic AICAR injections restored the expression of many genes in old muscle to the levels observed in young muscle. Among these, mitochondrial splicing suppressor 51 (Mss51) expression, which is associated with impaired mitochondrial function and muscle loss, was elevated in sarcopenic muscle but attenuated by AICAR treatment, and this was confirmed by RT-PCR analysis. CONCLUSION: AICAR treatment reverses several critical age-related changes in gene expression and mTORC1 activity. Our findings support further investigation of AMPK activation and Mss51 repression as targets for therapeutic interventions in sarcopenia