To Keep on Knowing More(?): Seminar XVILL, The Other Side of Psychoanalysis

This is an explication of Lacan’s Seminar XVII. The introduction situates the Seminar in its time and in relation to other theories of discourse. In part one I examine the changes which it brings to a variety of ideas already known in Lacan’s oeuvre such as Jouissance, Master Signifier(s) and Oedipus. Part two looks the four discourses in detail after considering the positions common to each. I provide accounts of each discourse as taking place internally to a subject and between subjects. The coda examines areas where further research is possible, reviews and critiques some scholarship on this seminar and inquires into the use value of the discourse theory, both generally and as a means of getting beyond Lacan

A New Literature for the Space Age

Technological developments, just as social changes, economic processes, or political events, make their impact on the literature of a nation, a culture or an era. The reverse, of course, is also true: man\u27s many and diverse activities are influenced and shaped by what is said about them. This paper attempts to project the trend, as well as some of the developments, of this culture-technology interaction in the forseeable future

Non-invasive cardiac radiosurgery with MRI guidance: a ground-truth for real-time target localisation using the XCAT phantom

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia. The growing epidemic of AF already affects millions of patients around the world and millions more are forecast to develop the condition in coming decades. The standard non-pharmacological treatment for AF is catheter ablation, an invasive and time consuming procedure. Non-invasive treatment of AF with radiosurgery has recently been put forward but is challenged by complex cardiac and respiratory motion. Compensating for target motion and treating in real-time could be realised with a MRI linear accelerator (MRI-Linac). A recent study developed methodology to track cardiac targets for this purpose but until now no measure of its accuracy has been accessible. In this investigation, the existing real-time cardiac tracking is quantified and developed on a digital phantom platform. It is first tested within a perfect digital scenario and then extended to a realistic anthropomorphic simulation. In a final experiment, developed tracking methods are applied to real-world anatomical data. A total number of twenty-one virtual patients were generated with the 4 dimensional extended cardiac-torso (XCAT) phantom software and received magnetic resonance imaging (MRI) simulated cardiac scans. A 3D volume representing a distinct cardiac phase is comprised of 2D slices which cover the entire target area. These template volumes are matched through pixel similarity to 2D orthogonal real-time MRI planes to localise the target volume in real-time. One virtual patient represented ideal and thus unrealistic MRI scans to initially test the cardiac tracking. Twenty virtual patients were subjected to MRI scans that closely model the proposed real-world scenario. An available ground-truth is compared to target motion trajectories output from the cardiac tracking algorithm for the twenty-one virtual patients. The cardiac tracking methodology is simultaneously developed as a result of the quantitative measures. Additionally, the correlation and significance of the virtual patients’ physiological parameters with tracking accuracy is investigated. Finally, the best performing tracking function is qualitatively assessed on a single patient’s real-world MRI scans. Employing a tracking method with the same basic methodology as the original tracking on the twenty virtual patient cohort resulted in a mean 3D tracking error of 3.2 ± 1.7 mm. The three anatomical plane constituent errors were 1.3 ± 0.9 mm in the superior inferior (SI) plane, 1.4 ± 0.9 mm in the anterior posterior (AP) plane and 2.2 ± 1.8 mm in the left right (LR) plane. This result is in strong agreement with the inferred error of 3 - 4 mm from the previous study that was based on 2D quantification. After tracking developments were implemented, the best performing mean 3D tracking error of 2.9 ± 1.6 mm was ascertained. A patient’s heart rate is the only anatomical parameter to show a significant linear relationship with tracking error (r=0.65, p-value = 0.0018). Comparing best performing tracking functions across the virtual patients show that the optimal tracking function is patient-specific. When the developed methods were reintroduced to a patient’s MRI data the tracking accuracy was qualitatively assessed to have improved. The results of the previous single patient treatment planning indicate that high-dose cardiac radiosurgery can be administered for the treatment of AF when safety margins are below 5 mm. The quantitative measures presented here demonstrate that real-time target localisation and motion compensation could successfully be implemented with an MRI-Linac. The conclusions of this work strongly encourage further development of the proposed AF treatment with non-invasive radiosurgery

Environmental Aging of Scotch-Weld(TradeMark) AF-555M Structural Adhesive in Composite to Composite Bonds

Fiber reinforced resin matrix composites have found increased usage in recent years. Due to the lack of service history of these relatively new material systems, their long-term aging performance is not well established. In this study, adhesive bonds were prepared by the secondary bonding of Scotch-Weld(TradeMark) AF-555M between pre-cured adherends comprised of T800H/3900-2 uni-directional laminate. The adherends were co-cured with wet peel-ply for surface preparation. Each bond-line of single-lap-shear (SLS) specimen was measured to determine thickness and inspected visually for voids. A three-year environmental aging plan for the SLS specimens at 82 C and 85% relative humidity was initiated. SLS strengths were measured for both controls and aged specimens at room temperature and 82 C. The aging results of strength retention and failure modes to date are reported

The Effects of Temperature, Humidity and Aircraft Fluid Exposure on T800H/3900-2 Composites Bonded with AF-555M Adhesive

Fiber reinforced resin matrix composites and structural adhesives have found increased usage on commercial and military aircraft in recent years. Due to the lack of service history of these relatively new material systems, their long-term aging performance has not been well established. In this study, single lap shear specimens (SLS) were fabricated by secondary bonding of Scotch-Weld(TradeMark) AF-555M between pre-cured adherends comprised of T800H/3900-2 uni-directional laminates. The adherends were co-cured with wet peel-ply for surface preparation. Each bond-line of the SLS specimen was measured to determine thickness and inspected visually using an optical microscope for voids. A three-year environmental aging plan for the SLS specimens at 82 C (180 F) and 85% relative humidity was initiated. SLS strengths were measured for both controls and aged specimens at room temperature and 82 C. The effect of this exposure on lap shear strength and failure modes to date is reported. In addition, the effects of water, saline water, deicing fluid, JP-5 jet fuel and hydraulic fluid on both the composite material and the adhesive bonds were investigated. The up to date results on the effects of these exposures will be discussed

Structural and Biochemical Studies of Human 4-hydroxy-2-oxoglutarate Aldolase: Implications for Hydroxyproline Metabolism in Primary Hyperoxaluria

4-hydroxy-2-oxoglutarate (HOG) aldolase is a unique enzyme in the hydroxyproline degradation pathway catalyzing the cleavage of HOG to pyruvate and glyoxylate. Mutations in this enzyme are believed to be associated with the excessive production of oxalate in primary hyperoxaluria type 3 (PH3), although no experimental data is available to support this hypothesis. Moreover, the identity, oligomeric state, enzymatic activity, and crystal structure of human HOGA have not been experimentally determined.In this study human HOGA (hHOGA) was identified by mass spectrometry of the mitochondrial enzyme purified from bovine kidney. hHOGA performs a retro-aldol cleavage reaction reminiscent of the trimeric 2-keto-3-deoxy-6-phosphogluconate aldolases. Sequence comparisons, however, show that HOGA is related to the tetrameric, bacterial dihydrodipicolinate synthases, but the reaction direction is reversed. The 1.97 Å resolution crystal structure of hHOGA bound to pyruvate was determined and enabled the modeling of the HOG-Schiff base intermediate and the identification of active site residues. Kinetic analyses of site-directed mutants support the importance of Lys196 as the nucleophile, Tyr168 and Ser77 as components of a proton relay, and Asn78 and Ser198 as unique residues that facilitate substrate binding.The biochemical and structural data presented support that hHOGA utilizes a type I aldolase reaction mechanism, but employs novel residue interactions for substrate binding. A mapping of the PH3 mutations identifies potential rearrangements in either the active site or the tetrameric assembly that would likely cause a loss in activity. Altogether, these data establish a foundation to assess mutant forms of hHOGA and how their activity could be pharmacologically restored

Intra-season variations in distribution and abundance of humpback whales in the West Antarctic Peninsula using cruise vessels as opportunistic platforms

Fine-scale knowledge of spatiotemporal dynamics in cetacean distribution and abundance throughout the Western Antarctic Peninsula (WAP) is sparse yet essential for effective ecosystem-based management (EBM). Cruise vessels were used as platforms of opportunity to collect data on the distribution and abundance of humpback whales (Megaptera novaeangliae) during the austral summer of 2019/2020 in a region that is also important for the Antarctic krill (Euphausia superba) fishery, to assess potential spatiotemporal interactions for future use in EBM. Data were analyzed using traditional design-based line transect methodology and spatial density surface hurdle models fitted using a set of physical environmental covariates to estimate the abundance and distribution of whales in the area, and to describe their temporal dynamics. Our results indicate a rapid increase in humpback whale abundance in the Bransfield and Gerlache Straits through December, reaching a stable abundance by mid-January. The distribution of humpback whales appeared to change from a patchier distribution in the northern Gerlache Strait to a significantly concentrated presence in the central Gerlache and southern Bransfield Straits, followed by a subsequent dispersion throughout the area. Abundance estimates agreed well with previous literature, increasing from approximately 7000 individuals in 2000 to a peak of 19,107 in 2020. Based on these estimates, we project a total krill consumption of between 1.4 and 3.7 million tons based on traditional and contemporary literature on per capita krill consumption of whales, respectively. When taken in the context of krill fishery catch data in the study area, we conclude that there is minimal spatiotemporal overlap between humpback whales and fishery activity during our study period of November-January. However, there is potential for significant interaction between the two later in the feeding season, but cetacean survey efforts need to be extended into late season in order to fully characterize this potential overlap.Publisher PDFPeer reviewe

Ion acceleration with radiation pressure in quantum electrodynamic regimes

The radiation pressure of next generation high-intensity lasers could efficiently accelerate ions to GeV energies. However, nonlinear quantum-electrodynamic effects play an important role in the interaction of these lasers with matter. We show that these quantum-electrodynamic effects lead to the production of a critical density pair-plasma which completely absorbs the laser pulse and consequently reduces the accelerated ion energy and efficiency by 30-50%