A model of host response to a multi-stage pathogen

We model the immune surveillance of a pathogen which passes through $n$ immunologically distinct stages. The biological parameters of this system induce a partial order on the stages, and this, in turn, determines which stages will be subject to immune regulation. This corresponds to the system's unique asymptotically stable fixed point.Comment: 22 pages, no figure

Preliminary Checklist of the Fishes of the Illinois River, Arkansas

A survey of the fishes of the mainstream of the Illinois River in northwestern Arkansas produced 51 species representing 11 families. Four of these species, Ictiobus bubalus, smallmouth buffalo; Moxostoma carinatum, river redhorse; Lepomis gulosus, warmouth; and Percina phoxocephala, slenderhead darter, have not been recorded previously from the Arkansas part of the Illinois. Eleven additional species have been reported previously that were not collected during this survey, for a total of 62 species known in the Illinois River

Dynamics of alliance formation and the egalitarian revolution

Arguably the most influential force in human history is the formation of social coalitions and alliances (i.e., long-lasting coalitions) and their impact on individual power. In most great ape species, coalitions occur at individual and group levels and among both kin and non-kin. Nonetheless, ape societies remain essentially hierarchical, and coalitions rarely weaken social inequality. In contrast, human hunter-gatherers show a remarkable tendency to egalitarianism, and human coalitions and alliances occur not only among individuals and groups, but also among groups of groups. Here, we develop a stochastic model describing the emergence of networks of allies resulting from within-group competition for status or mates between individuals utilizing dyadic information. The model shows that alliances often emerge in a phase transition-like fashion if the group size, awareness, aggressiveness, and persuasiveness of individuals are large and the decay rate of individual affinities is small. With cultural inheritance of social networks, a single leveling alliance including all group members can emerge in several generations. Our results suggest that a rapid transition from a hierarchical society of great apes to an egalitarian society of hunter-gatherers (often referred to as "egalitarian revolution") could indeed follow an increase in human cognitive abilities. The establishment of stable group-wide egalitarian alliances creates conditions promoting the origin of cultural norms favoring the group interests over those of individuals.Comment: 37 pages, 15 figure

Static Analysis for Ruby in the Presence of Gradual Typing

Dynamic languages provide new challenges to traditional static analysis techniques, leaving most errors to be detected at runtime and making many properties of code difficult to infer. Ruby code usually takes advantage of both dynamic typing and metaprogramming to produce elegant yet difficult-to-analyze programs. Function evalpq and its variants, which usually foil static analysis, are used frequently as a primitive runtime macro system. The goal of this thesis is to answer the question: What useful information about real-world Ruby programs can be determined statically with a high degree of accuracy? Two observations lead to a number of statically-discoverable errors and properties in parseable Ruby programs. The first is that many interesting properties of a program can be discovered through traditional static analysis techniques despite the presence of dynamic typing. The second is that most metaprogramming occurs when the program files are loaded and not during the execution of the main program. Traditional techniques, such as flow analysis and Static Single Assignment transformations aid extraction of program invariants, including both explicitly programmed constants and those implicitly defined by Ruby\u27s semantics. A meaningful, well-defined distinction between load time and run time in Ruby is developed and addresses the second observation. This distinction allows us to statically discern properties of a Ruby program despite many idioms that require dynamic evaluation of code. Lastly, gradual typing through optional annotations improves the quality of error discovery and other statically-inferred properties

A high performance, microchannel plate based, photon counting detector for space use

This thesis describes the development of a microchannel plate (MCP) based photon counting detector using the Spiral Anode (SPAN) as a readout. This detector was one of two being evaluated for use in the Optical Monitor for ESA's X-ray Multi Mirror satellite. Throughout this thesis, where possible, the underlying physical processes, particularly those of the MCP, have been identified and studied separately. The first chapter is an introduction to photon counting detectors and includes a review of the various readouts used with MCPs. The second chapter provides a more detailed review and analysis of cyclic, continuous-electrode, charge-division readouts, of which SPAN is an example. The next two chapters describe the technique for measuring the radial distribution of the MCP charge cloud, which can significantly affect detector imaging performance. Results are presented for various operating conditions. The distribution consists of two parts and the size is dependent on the operating voltages of the MCP stack. The fifth and sixth chapters describe the procedure for operating a SPAN readout and the decoding necessary for converting the ADC readings into a two dimensional coordinate. Various methods are described and their limitations evaluated. The cause of problems associated with the SPAN readout, such as "ghosting" and fixed patterning and methods of reducing them are discussed in detail. Results are presented which demonstrate the performance of the anode. The seventh chapter discusses and evaluates the interaction between channels in MCPs and the long range effects an active pore has on the surrounding quiescent pores. This represents the first time that these effects have been measured. The importance of this phenomenon for imaging detectors is discussed and possible mechanisms evaluated. The last chapter presents the conclusions of this work and discusses the suitability of SPAN detectors for use on satellites

A Cost Study For An Alternative Source Of Water For The City Of Fairbanks, Alaska, 1968

Thesis (M.B.A.) University of Alaska Fairbanks, 196

Development of a test system to analyze different hip fracture osteosyntheses under simulated walking

The mechanical complications of osteosyntheses after hip fractures are previously investigated by mostly static or dynamic uniaxial loading test systems. However, the physiologic loading of the hip joint during a normal gait is a multiplanar, dynamic movement. Therefore, we constructed a system to test osteosyntheses for hip fractures under physiologic multiplanar loading representative of normal gait. To evaluate the testing system, 12 femora pairs were tested under 25,000 cycles with two standard osteosyntheses (Proximal Femoral Nail Antirotation/Gamma3 Nail). For angular movement, the varus collapse to cut out (proportional to(CO)) (proportional to(CO) = 4.8 degrees +/- 2.1 degrees for blade and proportional to(CO) = 7.8 degrees +/- 3.8 degrees for screw) was the dominant failure mode, and only slight rotational angle shifts (proportional to(Rot)) (proportional to(Rot) = 1.7 degrees +/- 0.4 degrees for blade and proportional to(Rot) = 2.4 degrees +/- 0.3 degrees for screw) of the femoral head around the implant axis were observed. Angular displacements in varus direction and rotation were higher in specimens reinforced with screws. Hence, the cut out model and the migration directions showed a distinction between helical blade and hip screw. However, there were no significant differences between the different implants. The new setup is able to create clinical failures and allows to give evidence about the anchorage stability of different implant types under dynamic gait motion pattern

CASIMIR: a submillimeter heterodyne spectrometer for SOFIA

The CAltech Submillimeter Interstellar Medium Investigations Receiver (CASIMIR) is a multichannel, heterodyne spectrometer being developed for the Stratospheric Observatory for Infrared Astronomy (SOFIA). It has a very high resolution, up to a million, over the submillimeter and far-infrared wavelength range of 150 to 600 micrometers , or 2.0 to 0.5 THz. CASIMIR is extremely well suited to the investigation of both the galactic and extragalactic warm, approximately 100 K, interstellar medium. A combination of advanced SIS and Hot Electron Bolometers receivers will be used to cover this frequency range with very high sensitivity. CASIMIR will use only solid state local oscillators, with quasioptical coupling to the mixers. We present a description of the instrument and its capabilities, including detailed discussions of the receivers, local oscillators and IF systems