A Stochastic Compartmental Model for Fast Axonal Transport

In this paper we develop a probabilistic micro-scale compartmental model and use it to study macro-scale properties of axonal transport, the process by which intracellular cargo is moved in the axons of neurons. By directly modeling the smallest scale interactions, we can use recent microscopic experimental observations to infer all the parameters of the model. Then, using techniques from probability theory, we compute asymptotic limits of the stochastic behavior of individual motor-cargo complexes, while also characterizing both equilibrium and non-equilibrium ensemble behavior. We use these results in order to investigate three important biological questions: (1) How homogeneous are axons at stochastic equilibrium? (2) How quickly can axons return to stochastic equilibrium after large local perturbations? (3) How is our understanding of delivery time to a depleted target region changed by taking the whole cell point-of-view

Control of Protoporphyrinogen Oxidase-resistant Palmer amaranth

Already one of the most troublesome weeds in row crop production in the southern U.S., protoporphyrinogen oxidase (PPO)-resistant Palmer amaranth [Amaranthus palmeri (S.) Wats.] was first documented in Arkansas in 2015. Since this confirmation, PPO-resistant Palmer amaranth has been identified throughout the Midsouth. The following research evaluated both current and future herbicide programs for controlling PPO-resistant Palmer amaranth and quantified field-level resistance to PPO-inhibiting herbicides. On-farm research, located in fields with confirmed PPO-resistant Palmer amaranth, was conducted in 2016 and 2017. In preemergence (PRE) herbicide experiments, PPO-inhibiting herbicides still proved useful when combined with herbicides such as metribuzin and/or pyroxasulfone. Interestingly, a decline in control from S-metolachlor (\u3c78%) was observed in PRE experiments, suggesting heavy reliance on this herbicide alone may lead to control failures. In fact, no PRE herbicide program utilizing only one site of action (SOA) provided effective, sustained control of PPO-resistant Palmer amaranth, regardless of their chemistry. No PPO-inhibiting herbicide applied postemergence (POST) provided effective control of PPO-resistant Palmer amaranth (\u3c40%). Postemergence experiments also highlighted the lack of achievable control in glyphosate-resistant soybean [Glycine max (L.) Merr.] vastly in contrast to control provided by options in glufosinate-, 2,4-D-, and dicamba-resistant soybean. Control of PPO-resistant Palmer amaranth in soybean was possible and achieved by multiple effective SOAs PRE followed by a timely POST program containing glufosinate, 2,4-D, or dicamba

Reduction of the Effective Electron Temperature in a Cryogen-Free Dilution Refrigerator via Electronic Filtering and Vibration Dampening

Cryogen-free dilution refrigerators (dry fridges) have become an increasingly popular solution to researchers’ cryogenic measurement needs due to their user friendliness and long term use cost savings (4He does not need to be replenished). However, commercially available dry fridges frequently have an effective electron temperatures much warmer than the base temperature of the mixing chamber of the dry fridge. This thesis documents efforts taken to reduce the electron temperature in a dry fridge and the direct probing of the electron temperature via Coulomb blockade thermometry in a 500 nm wide quantum dot

Remote vibrometry recognition of nonlinear eigen-states for object coverage of randomly large size

For objects of “large” vibration size such as waves on the sea surface, the choice of measurement method can create different understandings of system behavior. In one case, laser vibrometry measurements of a vibrating bar in a controlled laboratory setting, variation in probe spot size can omit or uncover crucial structural vibration mode coupling data. In another case, a finite element simulation of laser vibrometry measures a nonlinearly clattering armor plate system of a ground vehicle. The simulation shows that sensing the system dynamics simultaneously over the entire structure reveals more vibration data than point measurements using a small diameter laser beam spot, regardless of the variation of footprint (coverage) boundaries. Furthermore, a simulation method described herein allows calculation of transition probabilities between modes (change-of-state). Wideband results of both cases demonstrate the 1/f trend explained within – that the energy of discrete structural vibration modes tends to decrease with increasing mode number (and frequency), and why. These results quantify the use of less expensive non-imaging classification systems for vehicle identification using the remote sensing of surface vibrations while mitigating spectral response distortion due to coverage variation on the order of the structural wavelength (spectral reduction or elimination)

Wolfgang von Ohnesorge

This manuscript got started when one of us (G.H.M.) presented a lecture at the Institute of Mathematics and its Applications at the University of Minnesota. The presentation included a photograph of Rayleigh and made frequent mention of the Ohnesorge number. When the other of us (M.R.) enquired about a picture of Ohnesorge, we found out that none were readily available on the web. Indeed, little about Ohnesorge is available from easily accessible public sources. A good part of the reason is certainly that, unlike other “numbermen” of fluid mechanics, Ohnesorge did not pursue an academic career. The purpose of this article is to fill the gap and shed some light on the life of Wolfgang von Ohnesorge. We shall discuss the highlights of his biography, his scientific contributions, their physical significance, and their impact today

The Ulster question in international politics, 1968-1978

This thesis has three general concerns. They relate to the processes by which the Ulster Question became 'internationalised'; the extent to which it became an international issue; and, the extent to which it was subject to international influences. In 1968, the island of Ireland had been partitioned for some forty-seven years into two states: a twenty-six county, predominantly Catholic, Republic; and a six county, mainly Protestant, state — Northern Ireland — which was constitutionally subordinate to the United Kingdom Parliament at Westminster. Within the latter, the minority Catholic community had been subjected to various forms of discrimination, including infringements and deprivations of their civil rights. As a result, a campaign was mounted to remedy their grievances. In these terms, therefore, the issue at stake was essentially within the domestic jurisdiction of the United Kingdom Government. The civil rights campaign, however, provoked extreme Unionists (also known as Loyalists) to respond violently. Civil disturbances thus became common, and on such a scale that it was only a short period before the real questions were not of civil rights, but of the continued existence of the state of Northern Ireland and the political re-integration of the island itself. In this transformation, the central roles were played by the governments of Britain and the Republic of Ireland. Through the years 1968 — 1978, both made approaches to the 'national' question and failed. Yet they failed, not because the problem was demonstrably insoluble, but because neither individually nor together did they adopt the type of policies which may have brought success, albeit limited. The conduct of Anglo-Irish relations, therefore, was one of the great sadnesses of modern Ireland. Outside of the politics between these two countries, the Ulster Question diminished in importance. Despite occasions when the world seemed genuinely shocked or revolted by what was happening in the North and despite attempts by the Irish Government to win international support for various of its objectives there, the community of states simply did not regard the Ulster Question as an issue which required anything approaching a sustained attention and activity. The 'troubles', evidently, were such a morass that it had no wish to enter — besides which, to have done so was to risk offending one of the central parties. Even in the area of international organisation this was true, except that here, the question proved more amenable to atomisation, and so pressing aspects of it frequently gained a currency, particularly in the forums of Europe. Notwithstanding the overall response of states to the Ulster Question in its entirety, there were instances of quite sustained interest being shown in the conflict it gave rise to. Libya was thus prominent for a period, for the financial and other assistance it provided to the Provisional Irish Republican Army. So, too, were several non-state actors who were similarly inclined, such as the Irish- American support network in the United States, and the Palestine Liberation Organisation. Their contributions, however, substantial as they might have been in terms of cash and arms, did not change in any major way the direction or the magnitude of the unique war being waged within (and sometimes without) the Six Counties. It is, therefore, a central conclusion of this thesis that the Ulster Question was an issue of but limited international significance. As long as Ireland is partitioned it is certain to remain as an outstanding question for only two countries, Britain and Ireland. But as long as Northern Ireland continues to provide a situation within its recent and current dimensions — i.e. one that can, for all practical purposes, be kept at some distance by its European neighbours — it will also remain on the periphery of international concern. Hence, it may be Ireland's misfortune to compare unfavourably with various contemporary misfortunes — such as Vietnam or the Middle East — and to be deprived of urgent considerations and initiatives. But this at least throws the Ulster Question back upon those who are most intimately concerned with it. In the final analysis it is a question which requires both an Irish and, perhaps inappropriately and perversely, a British answer

Interannual variability of the air-sea flux of oxygen in the North Atlantic

In studies using timeseries observations of atmospheric O[subscript 2]/N[subscript 2] to infer the fate of fossil fuel CO[subscript 2], it has been assumed that multi-year trends in observed O[subscript 2]/N[subscript 2] are insensitive to interannual variability in air-sea fluxes of oxygen. We begin to address the validity of this assumption by investigating the magnitude and mechanisms of interannual variability in the flux of oxygen across the sea surface using a North Atlantic biogeochemical model. The model, based on the MIT ocean general circulation model, captures the gross patterns and seasonal cycle of nutrients and oxygen within the basin. The air-sea oxygen flux exhibits significant interannual variability in the North Atlantic, with a standard deviation (0.36 mol m[superscript −2] y[superscript −1]) that is a large fraction of the mean (0.85 mol m[superscript −2] y[subscript −1]). This is primarily a consequence of variability in winter convection in the subpolar gyre.Goddard Space Flight Center (Grants NGTS-30189 and NCC5-244