Universal Minimum Heat Leak on Low-Temperature Metallic Electrical Leads

Low-temperature electronic systems require electrical leads which have low electrical resistance to provide bias current I without excessive voltage drop V. But proper cryogenic design also requires high thermal resistance to maintain a minimum heat leak Q from the hot temperature T[hot] to the cold temperature T[cold]. By the Wiedemann-Franz law, these requirements are in direct conflict, and the optimal configuration takes a particularly simple universal approximate form for the common case that T[cold] << T[hot]: Q/I = V = 3.6 kT[hot]/e. This is applied here to the cryopackaging of RSFQ superconducting circuits on a 4K cryocooler, but is equally applicable to other cryogenic systems such as a superconducting sensor array at low and ultra-low temperatures.Comment: Proc. Int. Low Temp. Phys. Conf. (LT24), held in Orlando, FL, Aug. 2005. 2 pages. Minor changes in notation and references in response to reviewer

The Economical Impact of Mountain Bicycle Events in Oregon

The current project aimed to quantify the economic impact of several mountain biking events and one tour operator in Oregon during 2012. Participants from three events and customers of one mountain bike tour company (Cog Wild) were surveyed in 2012 using an online survey. Our work summarizes the initial data analysis of participant responses to the survey questions. Specifically, we outlined the county level economic impact travel estimates, participant demographics, travel party size and spending averages across the four events. Only data from non-local participants (i.e., participants living outside of the event host county) were used for the economic impact analysis

The Effect of Vincristine Sulphate on the Axoplasmic Flow of Proteins in Cultured Sympathetic Neurons

The effect of vincristine sulphate on the axoplasmic flow of labelled proteins in neurites of chick embryo sympathetic neurons growing in tissue culture was studied by autoradiography. In control neurons most of the 3H-proteins synthesized during a 90-min pulse with a 3H-amino acid were localized in cell bodies. There was a diminishing gradient of labelled proteins in the neurites which was highest in portions adjacent to the cell bodies and lowest at the periphery. During a physiological chase there was a gradual increase in the amount of label in the neurites, so that after a 15-h chase even the most peripheral portions were well labelled. This indicates that a portion of the labelled proteins synthesized in the cell bodies are transported peripherally into the neurites. The centrifugal movement of labelled proteins in neurites was markedly decreased when cells were grown in medium containing 10 µg/ml vincristine sulphate. After a 15-h chase in the presence of drug only a small amount of label was in the peripheral portion of the neurites. Treatment with vincristine did not decrease the rate of amino acid incorporation or alter the rate of protein turnover during the course of the experiment. Thus an explanation of the results based on an altered rate of total cell protein synthesis or degradation is unlikely. The capacity of sympathetic neurons to take up and concentrate exogenous [3H]norepinephrine in their neurites was only slightly reduced by vincristine. This indicates that at least some cellular activities requiring metabolic energy are relatively unaffected by the interruption in axoplasmic flow caused by vincristine and that the mechanism by which vincristine interferes with axoplasmic flow does not involve general cellular toxicity. The major morphological differences between control and vincristine-treated neurons were the absence of microtubules and the presence of crystal-like structures within the cells. The relationship between the effect of vincristine on the axoplasmic flow of proteins and the arrangement of the microtubule system is discussed

Making Mary Ann Waters is a Free Black Woman: Critical Fabrication as Bibliographic Method

This article discusses the process of creating an artist’s book on Mary Ann Waters, a Black trans woman and sex worker in Antebellum Baltimore. In addition, informed by the author’s experience of making the artist’s book, he proposes a process of critical fabrication—which brings together Saidiya Hartman’s method of “critical fabulation” with Natalie Loveless’s articulation of “research-creation”—as a method for critical bibliography. (In the issue section Bibliographic Knowledge(s)

Nonlinear coupling of nano mechanical resonators to Josephson quantum circuits

We propose a technique to couple the position operator of a nano mechanical resonator to a SQUID device by modulating its magnetic flux bias. By tuning the magnetic field properly, either linear or quadratic couplings can be realized, with a discretely adjustable coupling strength. This provides a way to realize coherent nonlinear effects in a nano mechanical resonator by coupling it to a Josephson quantum circuit. As an example, we show how squeezing of the nano mechanical resonator state can be realized with this technique. We also propose a simple method to measure the uncertainty in the position of the nano mechanical resonator without quantum state tomography