Stoic unformed substance and old academic ontology

This thesis examines the influences on the Stoics' development of their material principle. The thesis argues that the reasons for the Stoics' conceiving of a material principle as they did actually have their origins in metaphysical speculation rather than physics. While the natural philosophy of the Ionians, as interpreted by Aristotle and his followers, no doubt furnished the intellectual background for a persisting material substrate of all sensible change, it is in fact the concerns of Plato and his early followers with the non-sensible that exert the strongest influence on the Stoics. The thesis examines the concepts of space and matter in the Timaeus ultimately rejecting this work of physics as central to the development of Stoic thought on matter. Rather it is the metaphysical doctrines of Plato and his successors, and the use they make of an incorporeal matter, that exerted the greatest influence on the Stoics and their material principle. The interpretation of Platonic metaphysics argued for in the thesis, based on the Unwritten Doctrines and the Old Academy's teachings, challenges the majority opinion of the English speaking community; and as a result offers a novel understanding of the relationship of Stoicism to Platonic metaphysics. The thesis concludes that it is likely that the early Stoics developed their doctrine of a material substrate in the particular way they did because of the tendency in the Old Academy to simplify the doctrines of Plato. This simplifying tendency comes to a head in the early Stoics with the ultimate reduction of the Old Academic system of hypostases, making use of active and passive principles at various levels of reality, finally ending in one level of reality and a simple two principle system

Very fast X-ray spectral variability in Cygnus X-1: Origin of the hard and soft-state emission components

The way in which the X-ray photon index, {\Gamma}, varies as a function of count rate is a strong diagnostic of the emission processes and emission geometry around accreting compact objects. Here we present the results from a study using a new, and simple, method designed to improve sensitivity to the measurement of the variability of {\Gamma} on very short time-scales. We have measured {\Gamma} in ~2 million spectra, extracted from observations with a variety of different accretion rates and spectral states, on time-scales as short as 16 ms for the high mass X-ray binary Cygnus X-1, and have cross-correlated these measurements with the source count rate. In the soft-state cross-correlation functions (CCFs) we find a positive peak at zero lag, stronger and narrower in the softer observations. Assuming that the X-rays are produced by Compton scattering of soft seed photons by high energy electrons in a corona, these results are consistent with Compton cooling of the corona by seed photons from the inner edge of the accretion disc, the truncation radius of which increases with increasing hardness ratio. The CCFs produced from the hard-state observations, however, show an anti-correlation which is most easily explained by variation in the energy of the electrons in the corona rather than in variation of the seed photon flux. The hard-state CCFs can be decomposed into a narrow anti-correlation at zero lag, which we tentatively associate with the effects of self-Comptonisation of cyclo-synchrotron seed photons in either a hot, optically thin accretion flow or the base of the jet, and a second, asymmetric component which we suggest is produced as a consequence of a lag between the soft and hard X-ray emission. The lag may be caused by a radial temperature/energy gradient in the Comptonising electrons combined with the inward propagation of accretion rate perturbations.Comment: 12 pages, 14 figures; accepted for publication in Monthly Notices of the Royal Astronomical Society, 2013 June

Pressure dependence of the superconducting transition temperature in C6_6Yb and C6_6Ca

We have studied the evolution, with hydrostatic pressure, of the recently discovered superconductivity in the graphite intercalation compounds C$_6$Yb and C$_6$Ca. We present pressure-temperature phase diagrams, for both superconductors, established by electrical transport and magnetization measurements. In the range 0-1.2 GPa the superconducting transition temperature increases linearly with pressure in both materials with $dT_c/dP = +0.39 K/GPa$ and $dT_c/dP = +0.50 K/GPa$ for C$_6$Yb and C$_6$Ca respectively. The transition temperature in C$_6$Yb, which has beenmeasured up to 2.3 GPa, reaches a peak at around 1.8 GPa and then starts to drop. We also discuss how this pressure dependence may be explained within a plasmon pairing mechanism.Comment: 4 pages, 3 figure

AN ANALYSIS ON THE EFFECTS OF ADDITIVE MANUFACTURING (AM) ON F/A-18E/F READINESS

This research paper focuses on the Boeing F/A-18E and the F/A-18F Super Hornet aviation depot level repairable (AVDLR) parts process and the potential effects of additive manufacturing (AM) on that process. The motivation for study was spurred by recent reports indicating that the F/A-18E/F is experiencing decreased operational readiness due to increases in maintenance-related impacts related to parts availability, long lead times, and increased parts failure frequency. This study aimed to determine the requirements for interjecting AM into the Intermediate level repair process in order to make a significant impact on  F/A-18E/F depot-level repairable part lead times. More specifically, this research analyzes the potential impact of various AM production levels on overall lead times. Facilitation of this research project was accomplished through mathematical modeling and by conducting simulations based on various assumptions and probability distributions. Eight simulations were conducted, each with different AM production time assumptions. Resultant outputs reflected 19 different scenarios simulating 0%–90% production of AM at the Intermediate Maintenance level. Results indicate that AM has the potential to decrease overall expected lead time averages if AM production can be kept to less than approximately 30 days.Lieutenant, United States NavyLieutenant, United States NavyLieutenant Commander, United States NavyApproved for public release. Distribution is unlimited

Towards Hydrazine Based Hydrogen Storage Materials Incorporating Late Transition Metals: a DFT Study

AbstractOur established method of modeling transition metal based H2 storage materials is extended to include the desirable and achievable targets of hydrazine linked Cu(I), Cu(II) and Ni(II). Two coordinate Cu(I) H2 binding site representations bind two H2 molecules through the reversible Kubas interaction with a theoretical maximum storage capacity of 4.27%wt

Separating Stimulus-Induced and Background Components of Dynamic Functional Connectivity in Naturalistic fMRI

We consider the challenges in extracting stimulus-related neural dynamics from other intrinsic processes and noise in naturalistic functional magnetic resonance imaging (fMRI). Most studies rely on inter-subject correlations (ISC) of low-level regional activity and neglect varying responses in individuals. We propose a novel, data-driven approach based on low-rank plus sparse (L+S) decomposition to isolate stimulus-driven dynamic changes in brain functional connectivity (FC) from the background noise, by exploiting shared network structure among subjects receiving the same naturalistic stimuli. The time-resolved multi-subject FC matrices are modeled as a sum of a low-rank component of correlated FC patterns across subjects, and a sparse component of subject-specific, idiosyncratic background activities. To recover the shared low-rank subspace, we introduce a fused version of principal component pursuit (PCP) by adding a fusion-type penalty on the differences between the columns of the low-rank matrix. The method improves the detection of stimulus-induced group-level homogeneity in the FC profile while capturing inter-subject variability. We develop an efficient algorithm via a linearized alternating direction method of multipliers to solve the fused-PCP. Simulations show accurate recovery by the fused-PCP even when a large fraction of FC edges are severely corrupted. When applied to natural fMRI data, our method reveals FC changes that were time-locked to auditory processing during movie watching, with dynamic engagement of sensorimotor systems for speech-in-noise. It also provides a better mapping to auditory content in the movie than ISC

Acute COVID-19, the Lived Experience, and Lessons to Learn for Future Pandemics

Objectives: The study aimed to increase the understanding of the lived experience of patients during the acute phase of a coronavirus disease 2019 (COVID-19) infection. Method: A Web-based survey was distributed through established patient and public engagement and involvement groups and networks, social media, and by means of word of mouth. The survey covered questions relating to patient demographics, COVID-19 diagnosis, symptom profile, and patient experience during acute COVID-19. Results: The findings demonstrate the varying symptom profiles experienced by people in the acute stage of COVID-19 infection, with participants sharing how they managed care at home, and/or accessed medical advice. Findings: also highlight themes that people were concerned with being unable to receive care and believed they needed to rely heavily on family, with extreme thoughts of death. Conclusions Although the urgent threat to public health has been negated by efficacious vaccines and enhanced treatment strategies, there are key lessons from the lived experience of COVID-19 that should be used to prepare for future pandemics and public health emergencies