186 research outputs found
The Early Modern Debate on the Problem of Matter's Divisibility: A Neo-Aristotelian Solution
Thesis advisor: Jean-Luc SolèreThesis advisor: Marius StanMy dissertation focuses on the problem of matter's divisibility in the 17th-18th centuries. The problem of material divisibility is a focal point at which the metaphysical principle of simplicity and the mathematical principle of space's infinite divisibility conflict. The principle of simplicity is the metaphysical requirement that there must be a simple or indivisible being that is the constitutive foundation of all composite things in nature. Without simple beings, there cannot be composite beings. The mathematical principle of space's infinite divisibility is a staple of Euclidean geometry: space must be divisible into infinitely smaller parts because indivisibles or points cannot compose extension. Without reconciling these metaphysical and mathematical principles, one can call into question the integrity of mathematics and metaphysics. Metaphysical contradiction results from the application of metaphysical simplicity to the composition of material bodies that occupy infinitely divisible space. How can a simple being constitute a material object while occupying a space that lacks a smallest part? Should we assume that a composite material object (such as the paper in front of the reader) exists in an infinitely divisible space, then the simple beings must occupy a space that consists of ever smaller spaces. The simple being thereby appears to consist of parts simpler than itself--a metaphysical contradiction. Philosophers resolve this contradiction by either modifying the metaphysical principle of simplicity to allow for the occupation of infinitely divisible space, or have simply dismissed one principle for the sake of preserving the other principle. The rejection of one principle for preserving the other principle is an undesirable path. Philosophers would either forfeit any attempt to account for the composition of material reality by rejecting simplicity or deny understanding of geometry heretofore via the rejection of space's infinite divisibility. My objective in this dissertation is two-fold: 1.) to provide an historical analysis of various philosophers' attempts to reconcile simplicity and infinite divisibility or to argue for the exclusive nature of the said principles; 2.) to articulate a reconciliation between simplicity and infinite divisibility. Underlying both objectives is my attempt to draw a connection between the metaphysical principle of simplicity and the metaphysical principle of sufficient reason. Having shown in the historical section that each philosopher implicitly references a modified version of the principle of sufficient reason when articulating their theories of metaphysical simplicity, I will use this common principle to develop a Neo-Aristotelian solution to the problem of material divisibility. This Neo-Aristotelian solution differs from other accounts in the historical section by including a potential parts theory of material divisibility while modifying the principle of simplicity: simple beings are no longer conceived as constitutive parts of a material thing, but as the sources of unity for a natural composite being.Thesis (PhD) — Boston College, 2014.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Philosophy
Synthesis and NMR Characterization of a New Series of Thiazole-2-Carboxaldehyde Thiosemicarbozone Compounds
This work will be the synthesis of a series of thiazole-carboxaldehyde-thiosemicarbazone ligands. After the synthesis and purification of these ligands, the new compounds went through analysis using the NMR spectrometer and obtaining data on +H NMR, 13C NMR, HSQC (heteronuclear single quantum coherence) 1H-13C NMR and HSQC 1H-15N NMR, to obtain evidence for our predicted structures. After the analysis was complete, we reacted the new ligands with palladium to form their metal complexes
Where Did The Moon Come From?
The current standard theory of the origin of the Moon is that the Earth was
hit by a giant impactor the size of Mars causing ejection of iron poor impactor
mantle debris that coalesced to form the Moon. But where did this Mars-sized
impactor come from? Isotopic evidence suggests that it came from 1AU radius in
the solar nebula and computer simulations are consistent with it approaching
Earth on a zero-energy parabolic trajectory. But how could such a large object
form in the disk of planetesimals at 1AU without colliding with the Earth
early-on before having a chance to grow large or before its or the Earth's iron
core had formed? We propose that the giant impactor could have formed in a
stable orbit among debris at the Earth's Lagrange point (or ). We
show such a configuration is stable, even for a Mars-sized impactor. It could
grow gradually by accretion at (or ), but eventually gravitational
interactions with other growing planetesimals could kick it out into a chaotic
creeping orbit which we show would likely cause it to hit the Earth on a
zero-energy parabolic trajectory. This paper argues that this scenario is
possible and should be further studied.Comment: 64 pages, 27 figures, accepted for publication in A
Disk, Corona, Jet Connection in the Intermediate State of MAXI J1820+070 Revealed by NICER Spectral-timing Analysis
We analyze five epochs of Neutron star Interior Composition Explorer (NICER) data of the black hole X-ray binary MAXI J1820+070 during the bright hard-to-soft state transition in its 2018 outburst with both reflection spectroscopy and Fourier-resolved timing analysis. We confirm the previous discovery of reverberation lags in the hard state, and find that the frequency range where the (soft) reverberation lag dominates decreases with the reverberation lag amplitude increasing during the transition, suggesting an increasing X-ray emitting region, possibly due to an expanding corona. By jointly fitting the lag-energy spectra in a number of broad frequency ranges with the reverberation model reltrans, we find the increase in reverberation lag is best described by an increase in the X-ray coronal height. This result, along with the finding that the corona contracts in the hard state, suggests a close relationship between spatial extent of the X-ray corona and the radio jet. We find the corona expansion (as probed by reverberation) precedes a radio flare by ~5 days, which may suggest that the hard-to-soft transition is marked by the corona expanding vertically and launching a jet knot that propagates along the jet stream at relativistic velocities
A Regional Initiative to Reduce Skin Infections amongst Aboriginal Children Living in Remote Communities of the Northern Territory, Australia
Skin infections are endemic in many in remote Australian Aboriginal communities and have been linked to very high rates of chronic heart and kidney disease in this population. We report the results of a regional collaboration that aimed to reduce skin infections amongst children aged less than 15 years in five remote communities. The program included annual mass scabies treatment days offered to all residents and routine screening/follow-up of children. Trained community workers helped conduct over 6000 skin assessments on 2329 children over a three year period. Of every 100 children seen at the commencement of the study, 47 were found to have skin sores and many had multiple sores. We demonstrate a reduction both in the number of children with skin sores and in the severity of those sores. On average, of every 100 children seen per month, there were 14 fewer children with skin sores and seven fewer children with multiple sores. Overall improvement in treatment uptake was a critical factor. We found no discernible impact against scabies. While the burden of skin infections remains unacceptably high, we believe the results presented here are a good news story for local action to address a serious public health problem
Developing a New Generation of Integrated Micro-Spec Far Infrared Spectrometers for the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)
The current state of far-infrared astronomy drives the need to develop
compact, sensitive spectrometers for future space and ground-based instruments.
Here we present details of the -Spec spectrometers currently in
development for the far-infrared balloon mission EXCLAIM. The spectrometers are
designed to cover the m range with a resolution of $\rm R\
=\ \lambda / \Delta\lambda\ =\ 512\rm 638\ \mu\rm \mu\rm R = 64\ \muM{=}2{\sim}8\times10^{-19}\rm W/\sqrt{Hz}\rm \mu$-Spec
spectrometers for EXCLAIM.Comment: 9 pages, 5 figures, to appear in the Proceedings of the SPIE
Astronomical Telescopes + Instrumentation (2022
Overview and status of EXCLAIM, the experiment for cryogenic large-aperture intensity mapping
The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a
balloon-borne far-infrared telescope that will survey star formation history
over cosmological time scales to improve our understanding of why the star
formation rate declined at redshift z < 2, despite continued clustering of dark
matter. Specifically,EXCLAIM will map the emission of redshifted carbon
monoxide and singly-ionized carbon lines in windows over a redshift range 0 < z
< 3.5, following an innovative approach known as intensity mapping. Intensity
mapping measures the statistics of brightness fluctuations of cumulative line
emissions instead of detecting individual galaxies, thus enabling a blind,
complete census of the emitting gas. To detect this emission unambiguously,
EXCLAIM will cross-correlate with a spectroscopic galaxy catalog. The EXCLAIM
mission uses a cryogenic design to cool the telescope optics to approximately
1.7 K. The telescope features a 90-cm primary mirror to probe spatial scales on
the sky from the linear regime up to shot noise-dominated scales. The telescope
optical elements couple to six {\mu}-Spec spectrometer modules, operating over
a 420-540 GHz frequency band with a spectral resolution of 512 and featuring
microwave kinetic inductance detectors. A Radio Frequency System-on-Chip
(RFSoC) reads out the detectors in the baseline design. The cryogenic telescope
and the sensitive detectors allow EXCLAIM to reach high sensitivity in spectral
windows of low emission in the upper atmosphere. Here, an overview of the
mission design and development status since the start of the EXCLAIM project in
early 2019 is presented.Comment: SPIE Astronomical Telescopes + Instrumentation. arXiv admin note:
substantial text overlap with arXiv:1912.0711
Avalanches in a Stochastic Model of Spiking Neurons
Neuronal avalanches are a form of spontaneous activity widely observed in cortical slices and other types of nervous tissue, both in vivo and in vitro. They are characterized by irregular, isolated population bursts when many neurons fire together, where the number of spikes per burst obeys a power law distribution. We simulate, using the Gillespie algorithm, a model of neuronal avalanches based on stochastic single neurons. The network consists of excitatory and inhibitory neurons, first with all-to-all connectivity and later with random sparse connectivity. Analyzing our model using the system size expansion, we show that the model obeys the standard Wilson-Cowan equations for large network sizes ( neurons). When excitation and inhibition are closely balanced, networks of thousands of neurons exhibit irregular synchronous activity, including the characteristic power law distribution of avalanche size. We show that these avalanches are due to the balanced network having weakly stable functionally feedforward dynamics, which amplifies some small fluctuations into the large population bursts. Balanced networks are thought to underlie a variety of observed network behaviours and have useful computational properties, such as responding quickly to changes in input. Thus, the appearance of avalanches in such functionally feedforward networks indicates that avalanches may be a simple consequence of a widely present network structure, when neuron dynamics are noisy. An important implication is that a network need not be “critical” for the production of avalanches, so experimentally observed power laws in burst size may be a signature of noisy functionally feedforward structure rather than of, for example, self-organized criticality
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