A bead on a hoop rotating about a horizontal axis: a 1-D ponderomotive trap

We describe a simple mechanical system that operates as a ponderomotive particle trap, consisting of a circular hoop and a frictionless bead, with the hoop rotating about a horizontal axis lying in the plane of the hoop. The bead in the frame of the hoop is thus exposed to an effective sinusoidally-varying gravitational field. This field's component along the hoop is a zero at the top and bottom. In the same frame, the bead experiences a time-independent centrifugal force that is zero at the top and bottom as well. The system is analyzed in the ideal case of small displacements from the minimum, and the motion of the particle is shown to satisfy the Mathieu equation. In the particular case that the axis of rotation is tangential to the hoop, the system is an exact analog for the rf Paul ion trap. Various complicating factors such as anharmonic terms, friction and noise are considered. A working model of the proposed system has been constructed, using a ball-bearing rolling in a tube along the outside of a section of a bicycle rim. The apparatus demonstrates in detail the operation of an rf Paul trap by reproducing the dynamics of trapped atomic ions and illustrating the manner in which the electric potential varies with time.Comment: Second external review for AJP, 28 pages double spaced, 11 figure

Palmitoylation of Desmoglein 2 Is a Regulator of Assembly Dynamics and Protein Turnover.

Desmosomes are prominent adhesive junctions present between many epithelial cells as well as cardiomyocytes. The mechanisms controlling desmosome assembly and remodeling in epithelial and cardiac tissue are poorly understood. We recently identified protein palmitoylation as a mechanism regulating desmosome dynamics. In this study, we have focused on the palmitoylation of the desmosomal cadherin desmoglein-2 (Dsg2) and characterized the role that palmitoylation of Dsg2 plays in its localization and stability in cultured cells. We identified two cysteine residues in the juxtamembrane (intracellular anchor) domain of Dsg2 that, when mutated, eliminate its palmitoylation. These cysteine residues are conserved in all four desmoglein family members. Although mutant Dsg2 localizes to endogenous desmosomes, there is a significant delay in its incorporation into junctions, and the mutant is also present in a cytoplasmic pool. Triton X-100 solubility assays demonstrate that mutant Dsg2 is more soluble than wild-type protein. Interestingly, trafficking of the mutant Dsg2 to the cell surface was delayed, and a pool of the non-palmitoylated Dsg2 co-localized with lysosomal markers. Taken together, these data suggest that palmitoylation of Dsg2 regulates protein transport to the plasma membrane. Modulation of the palmitoylation status of desmosomal cadherins can affect desmosome dynamics

SHORTFALLS IN 1997 NET FARM INCOME IN NORTH DAKOTA (Prepared for Senators Byron Dorgan and Kent Conrad)

North Dakota net farm income declined in 1997 due to adverse weather conditions and low prices. The total income loss in 1997 was estimated to be $394 million, which was divided into$290 million due to weather and diseases, and $104 million due to lower-than-average prices. Net farm income losses were largest in Region 3 (Northeast), followed by Regions 1 (Northwest) and 6 (East Central). HRS wheat accounted for the largest income loss, followed by durum and barley.Net farm income, crop losses, weather conditions, North Dakota input output model, Agricultural Finance,

Chewing gum and impasse-induced self-reported stress

An insoluble anagram task (Zellner et al., 2006) was used to investigate the proposition that chewing gum reduces self-rated stress (Scholey et al., 2009). Using a between-participants design, forty participants performed an insoluble anagram task followed by a soluble anagram task. These tasks were performed with or without chewing gum. Self-rated measures were taken at baseline, post-stressor, and post-recovery task. The insoluble anagram task was found to amplify stress in terms of increases in self-rated stress and reductions in both self-rated calmness and contentedness. However, chewing gum was found not to mediate the level of stress experienced. Furthermore, chewing gum did not result in superior performance on the soluble anagram task. The present study fails to generalise the findings of Scholey et al. to an impasse induced stress that has social components. The explanation for the discrepancy with Scholey et al. is unclear; however, it is suggested that the impossibility of the insoluble anagram task may negate any secondary stress reducing benefits arising from chewing gum-induced task improvement

Least Squares Estimation of a Monotone Quasiconvex Regression Function

We develop a new approach for the estimation of a multivariate function based on the economic axioms of monotonicity and quasiconvexity. We prove the existence of the nonparametric least squares estimator (LSE) for a monotone and quasiconvex function and provide two characterizations for it. One of these characterizations is useful from the theoretical point of view, while the other helps in the computation of the estimator. We show that the LSE is almost surely unique and is the solution to a mixed-integer quadratic optimization problem. We prove consistency and find finite sample risk bounds for the LSE under both fixed lattice and random design settings for the covariates. We illustrate the superior performance of the LSE against existing estimators via simulation. Finally, we use the LSE to estimate the production function for the Japanese plywood industry and the cost function for hospitals across the US.Comment: 34 pages, 8 figure

Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

The feasibility of using carbon-carbon (C-C) recuperators in conceptual closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance expectations were forecast based on notional thermodynamic cycle state values for potential planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 30 to 60 percent were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25 to 1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, 60 percent savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed

Decentralized Task Allocation with Coupled Constraints in Complex Missions

This paper presents a decentralized algorithm that creates feasible assignments for a network of autonomous agents in the presence of coupled constraints. The coupled constraints address complex mission characteristics that include assignment relationships, where the value of a task is conditioned on whether or not another task has been assigned, and temporal relationships, where the value of a task is conditioned on when it is performed relative to other tasks. The new algorithm is developed as an extension to the Consensus-Based Bundle Algorithm (CBBA), introducing the notion of pessimistic or optimistic bidding strategies and the relative timing constraints between tasks. This extension, called Coupled-Constraint CBBA (CCBBA), is compared to the baseline in a complex mission simulation and is found to outperform the baseline, particularly for task-rich scenarios.United States. Air Force Office of Scientific Research (Grant FA9550-08-1-0086)United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Grant FA9550-08-1-0356

Sexual Dimorphisms in Habitat-Specific Morphology and Behavior in the Green Anole Lizard

Species that occur in variable environments often exhibit morphological and behavioral traits that are specific to local habitats. Because the ability to move effectively is closely associated with structural habitat, locomotor traits may be particularly sensitive to fine-scale habitat differences. Anolis lizards provide an excellent opportunity to study the relationship between locomotion and natural perch use in the field, as laboratory studies have demonstrated that lizards that use broader perches develop longer limbs and have higher sprint speeds. We examined Anolis carolinensis (the green anole) in three habitats in close proximity. Our goals were to determine whether habitat-specific differences in hindlimb and toe morphologies occurred in a population in which perch size was variable but not manipulated, whether locomotor behaviors were associated with these morphologies, and whether habitat-specific traits differed between the sexes. We found that while juveniles in the three habitats did not differ in limb or toe morphology, adult females using broader perches had relatively longer limbs than females using narrower perches. Females also differed in toe length across habitats, but not in relation to perch diameter. Males, in contrast, exhibited differing growth patterns (allometry) in these traits, and marginal differences in locomotor behavior. Together, these results suggest that sex-specific responses in morphology and behavior, consistent with experimental observations of phenotypic plasticity, provide a mechanism for refining local habitat use