HIT and brain reward function: a case of mistaken identity (theory)

This paper employs a case study from the history of neuroscience—brain reward function—to scrutinize the inductive argument for the so-called ‘Heuristic Identity Theory’ (HIT). The case fails to support HIT, illustrating why other case studies previously thought to provide empirical support for HIT also fold under scrutiny. After distinguishing two different ways of understanding the types of identity claims presupposed by HIT and considering other conceptual problems, we conclude that HIT is not an alternative to the traditional identity theory so much as a relabeling of previously discussed strategies for mechanistic discovery

Thermo-Mechanical System Identification of a Shape Memory Alloy Actuated Mechanism

Shape memory alloy (SMA) actuators paired in an antagonistic arrangement can be used to produce mechanisms that replicate human biomechanics. To investigate this proposal, the biomechanical articulation of the elbow by means of the biceps brachii muscle is compared with that of a SMA actuated arm. This is accomplished by parametric analysis of a crank-slider kinematic mechanism actuated, first, with an experimentally characterized SMA wire and then an idealized musculotendon actuator based on actuation properties of muscles published in the literature. Next, equations of motion for the system dynamics of the SMA actuated mechanism are derived and phase portrait analysis is conducted varying system parameters around different operating points. The eigenvalues of the differential equation are examined around equilibrium points and a stiffness ratio metric is proposed to characterize dynamic stability based on system parameters. Next, a heat transfer model is proposed and energy analysis is conducted on each stage of phase transformation for the SMA wire. The unknown parameters in the heat transfer model are theoretically derived and an experimental system identification is conducted. A proof of concept antagonistic SMA actuated mechanism is designed and kinematic analysis is conducted on an experimental prototype

Geochemical tracers of crustal thickness and their applicability to the Tibetan-Himalayan Orogen

Tectonic models of continental orogens seek to reconstruct the deformation processes associated with large-scale continental collision events. Geographically broad field surveys provide two spatial dimensions, and geochronology provides a third temporal dimension. The missing fourth dimension, most critical to understanding crustal evolution throughout collision, is the crustal thickening history of the orogen. Over the past few decades, however, accurate methods for estimating crustal thickness from the rock record have not fully emerged. Recently, indirect proxies for Moho depth have been developed using whole rock composition: trace element ratios Sr/Y, La/Yb, and Gd/Yb, and stable Nd isotopes. While these proxies can show changes in apparent depth based on transitions in whole-rock chemistry, these proxies are not immune to unconstrained effects on composition, including source melt composition and phase relations, or systematic changes in the intensive variables controlling the proxy. The application of an accurate and precise empirical thermobarometer to plutonic rocks can provide the depth of magma generation and assimilation, and thus the minimum depth of the Moho and thickness of the crust. The Gangdese batholith in southern Tibet, spanning ca. 200 Ma of pre- and syn-orogenic history, provides a continuous record of silicic magmatism associated with the subduction and collision history of southern Tibet. This work reconstructs whole-rock and zircon P-T-X-t histories of Gangdese granitoids spanning 225 Ma – 18 Ma from a transect of plutons 0 – 110km north of the Indus-Tsangpo Suture, the southern margin of Eurasia, near Lhasa, Tibet at 92�E. I compare the utility of indirect geochemical proxies and thermobarometry, and discuss the relationship between the thermo-chemical histories of complex plutonic growth processes, and crustal thickening during orogenesis. High-resolution in-situ thermobarometry of quartz inclusions in zircon suggest rapid crustal thickening began ca. 25 Ma earlier than indicated by indirect isotopic and geochemical proxies. Pluton formation occurred throughout the lower three-quarters of the Tibetan Crust, representing a large zone of plutonic activity that weakened the lower crust and contributed significantly to total orogenic heat budget. These results provide constraints for geodynamic models of intracontinental deformation and reveal the limitations and utility of various barometers and pseudobarometers in granites

Applications of Band Ratioing at Fort Irwin, California.

This dissertation describes the results of two projects that demonstrate the power of band ratioing of remote sensing data. The first method, Band Ratio Differencing (BRD), challenges the more traditional techniques for detecting environmental disturbance of the surface in and terrains. These traditional techniques are inadequate because they cannot identify the nature of the change (physical, chemical, biological) or the processes (natural, anthropogenic) involved in causing the change. In contrast, BRD of Landsat TM data has the advantage of providing information about changes in the composition of alluvial surfaces. These compositional changes, when combined with empirical field data provides insight into the specific causes and effects of environmental change. BRD was applied at Fort Irwin, California, the U.S. Army\u27s National Training Center (NTC) for desert warfare. Two dates of Landsat TM imagery (1985 and 1995) were acquired and BRD applied. A total of 514.5 square kilometers, or 42% of the alluvial surface at Fort Irwin has been affected by off road vehicular traffic. Two major types of change were identified: Disturbed Alluvial Surface and Continuous Dust Mantle, which can be further subdivided into six separate classes of change, related to either the cause or the effect of the disturbance. Hyperspectral Assisted Mapping (HAM) was developed as an alternative to Spectral Signature Mapping (SSM) techniques typically applied to AVIRIS hyperspectral data. Our analysis suggests that SSM-based techniques when applied to AVIRIS provide little to no additional information about sedimentary and igneous rocks. This is because many rock forming minerals of sedimentary and igneous rocks possess little to no diagnostic spectral absorption features in the range measured by the AVIRIS sensor. The HAM method integrates the geornorphic information provided by a Digital Elevation Model (DEM) and the lithologic discrimination, but not identification, provided by hyperspectral data to produce a surface materials map. HAM was successfully applied at the North Alvord Slope study area, on the southern margin of Fort Irwin, California. Nine distinct surface materials classes were identified by the technique. All nine classes were discriminated on the basis of minor mineral constituents in the materials, such as micas and clays

Studies on the body composition of beef cows

Suckler cow management systems generally require cows to be dependent on their body reserves of energy and protein at some stage of the production cycle. In nutritional studies with suckler cows it is therefore important that the rate of use or replenishment of body reserves be considered with contemporary nutrition. This requires the quantification of body reserves and hence a means of measuring body composition in the live animal.The methods available for the estimation of in vivo body composition in animals are reviewed and a number of techniques (live weight, skeletal size, total body water as estimated by deuterium oxide dilution, blood and red cell volumes as estimated by Evans Blue dilution, ultrasonic measurement of subcutaneous fat depth and eye-muscle area, and body condition scoring) were examined using 73 non-pregnant, non-lactating cows of five genotypes (Hereford x Friesian, Blue-Grey, Galloway, Luing and British Friesian) ranging in body condition score from 0.75-4.5. Direct measurement of body composition in terms of water, fat, protein and ash were made following slaughter.Live weight, deuterium oxide dilution, ultrasonic measurement of subcutaneous fat depth and eye-muscle area, and body condition scoring were all considered to be potentially useful predictors of body composition, but a combination of techniques offered a better prediction than did any single index. Using a combination of techniques it was possible to predict body fat and protein with residual standard deviations of 13.1 kg and 3.15 kg respectively.Body composition changes were also examined, and it was calculated that the composition of empty body-weight change was dependent upon empty body weight, containing more fat and less water, protein and ash at higher empty body weights.Important breed differences were found in the partition of fat among the main adipose tissue depots, with the Friesian cows having a greater proportion of fat in the internal depots and a lower proportion in the subcutaneous depot. The implications of breed differences in fat partition are discussed in relation to in vivo body composition measurement.An ancillary study was carried out into the effects of body condition on maintenance requirements and on the use of blood metabolites to measure energy status in suckler cows. This indicated that body condition affected maintenance requirements to the extent that at 500 kg live weight, maintenance requirements were 8 MJ ME/day less for each unit increase in condition score. Plasma free fatty acids were shown to be particularly useful in assessing energy status in cows, but 3-hydroxybutyrate concentrations were of little value in non-pregnant, non-lactating animals.Finally, the conclusions of the two studies are discussed in relation to areas of study likely to prove useful in the development of efficient systems of suckled calf production

Plasticizer degradation by marine bacterial isolates : a proteogenomic and metabolomic characterization

Many commercial plasticizers are toxic endocrine-disrupting chemicals that are added to plastics during manufacturing and may leach out once they reach the environment. Traditional phthalic acid ester plasticizers (PAEs), such as dibutyl phthalate (DBP) and bis(2-ethyl hexyl) phthalate (DEHP), are now increasingly being replaced with more environmentally friendly alternatives, such as acetyl tributyl citrate (ATBC). While the metabolic pathways for PAE degradation have been established in the terrestrial environment, to our knowledge, the mechanisms for ATBC biodegradation have not been identified previously and plasticizer degradation in the marine environment remains underexplored. From marine plastic debris, we enriched and isolated microbes able to grow using a range of plasticizers and, for the first time, identified the pathways used by two phylogenetically distinct bacteria to degrade three different plasticizers (i.e., DBP, DEHP, and ATBC) via a comprehensive proteogenomic and metabolomic approach. This integrated multi-OMIC study also revealed the different mechanisms used for ester side-chain removal from the different plasticizers (esterases and enzymes involved in the β-oxidation pathway) as well as the molecular response to deal with toxic intermediates, that is, phthalate, and the lower biodegrading potential detected for ATBC than for PAE plasticizers. This study highlights the metabolic potential that exists in the biofilms that colonize plastics-the Plastisphere-to effectively biodegrade plastic additives and flags the inherent importance of microbes in reducing plastic toxicity in the environment

Deserts and pile-ups in the distribution of exoplanets due to photoevaporative disc clearing

We present models of giant planet migration in evolving protoplanetary discs. We show that disc clearing by EUV photoevaporation can have a strong effect on the distribution of giant planet semi-major axes. During disc clearing planet migration is slowed or accelerated in the region where photoevaporation opens a gap in the disc, resulting in "deserts" where few giant planets are found and corresponding "pile-ups" at smaller and larger radii. However, the precise locations and sizes of these features are strong functions of the efficiency of planetary accretion, and therefore also strongly dependent on planet mass. We suggest that photoevaporative disc clearing may be responsible for the pile-up of ~Jupiter-mass planets at ~1AU seen in exoplanet surveys, and show that observations of the distribution of exoplanet semi-major axes can be used to test models of both planet migration and disc clearing.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letter