Timothy McDevitt

The Effect of Catheter to Vein Ratio on Blood Flow Rates in a Simulated Model of Peripherally Inserted Central Venous Catheters

BACKGROUND Catheter-related thrombosis is a common complication in all anatomic sites, especially when smaller veins of the upper extremity are considered. It is presumed that the presence of a catheter within the lumen of a vein will decrease flow and potentially create stasis, and clinical data suggest that the size of the catheter impacts thrombosis rates. We sought to determine, both mathematically and experimentally, the impact of catheters on fluid flow rates. METHODS We used fluid mechanics to calculate relative flow rates as a function of the ratio of the catheter to vein diameters. We also measured the flow rate of a blood analyte solution in an annular flow model using diameters that simulate the size of upper extremity veins and commonly used peripherally inserted central catheters (PICCs). RESULTS We compared each of the derived relative flow rates to the experimentally determined ones for three cylinder sizes and found a correlation of r(2) = 0.90. We also confirmed that the decrease in fluid flow rate with each successive catheter size is statistically significant (P < .0001). CONCLUSIONS Our results demonstrate that fluid flow is dramatically decreased by the insertion of a centrally located obstruction. Assuming that blood flow in veins behaves in a similar manner to our models, PICCs, in particular, may substantially decrease venous flow rates by as much as 93%.

Being, Becoming and the Undivided Universe: A Dialogue Between Relational Blockworld and the Implicate Order Concerning the Unification of Relativity and Quantum Theory

In this paper two different approaches to unification will be compared, Relational Blockworld (RBW) and Hiley’s implicate order. Both approaches are monistic in that they attempt to derive matter and spacetime geometry ‘at once’ in an interdependent and background independent fashion from something underneath both quantum theory and relativity. Hiley’s monism resides in the implicate order via Clifford algebras and is based on process as fundamental while RBW’s monism resides in spacetimematter via path integrals over graphs whereby space, time and matter are co-constructed per a global constraint equation. RBW’s monism therefore resides in being (relational blockworld) while that of Hiley’s resides in becoming (elementary processes). Regarding the derivation of quantum theory and relativity, the promises and pitfalls of both approaches will be elaborated. Finally, special attention will be paid as to how Hiley’s process account might avoid the blockworld implications of relativity and the frozen time problem of canonical quantum gravity.

End of a dark age

We argue that dark matter and dark energy phenomena associated with galactic rotation curves, X-ray cluster mass profiles, and type Ia supernova data can be accounted for via small corrections to idealized general relativistic spacetime geometries due to disordered locality. Accordingly, we fit THINGS rotation curve data rivaling modified Newtonian dynamics, ROSAT/ASCA X-ray cluster mass profile data rivaling metric-skew-tensor gravity, and SCP Union2.1 SN Ia data rivaling

Discrete Lanczos derivatives of noisy data

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Space, Time, and Adynamical Explanation in the Relational Blockworld

CDM without non-baryonic dark matter or a cosmological constant. In the case of dark matter, we geometrically modify proper mass interior to the Schwarzschild solution. In the case of dark energy, we modify proper distance in Einstein-deSitter cosmology. Therefore, the phenomena of dark matter and dark energy may be chimeras created by an errant belief that spacetime is a differentiable manifold rather than a disordered graph.

Underwriting information-theoretic accounts of quantum mechanics with a realist, psi-epistemic model

Finite differences are frequently used to differentiate empirical functions, but standard differences tend to amplify the random error that is present in almost all empirical data. This paper uses higher-order Lanczos derivatives and discretized Legendre polynomials to generate minimum variance finite differences to approximate ordinary derivatives of all orders for a fixed discretization error magnitude. The resulting differences can be implemented as finite impulse response filters and are therefore very fast on a computer.

Modified Regge calculus as an explanation of dark energy

Relational Blockworld (RBW) is an interpretation of quantum mechanics based on the path integral approach to physics. In the path integral approach, quantum mechanics is couched in spacetime rather than 3N-dimensional configuration space, since the path integral computation of a probability amplitude is based on a particular outcome in spacetime. That is, instead of using Schrӧdinger’s equation to time-evolve the wave function in the 3N-dimensional configuration space of all possible outcomes, one uses the Feynman path integral to compute the probability amplitude for a specific outcome in spactime. In such a spatiotemporal or least action approach, time-evolved dynamical explanation is replaced with a spatiotemporally global constraint, e.g., Fermat’s principle says that a light ray takes the path of least time from source to sink. The mysteries of quantum nonlocality are resolved by simply assuming this adynamical explanation in the blockworld is fundamental to dynamical explanation in the mechanical universe. Herein we introduce RBW’s form of adynamical explanation based on spatiotemporal ontological contextuality.

Explaining the Supernova Data without Accelerating Expansion

We propose an adynamical interpretation of quantum theory called Relational Blockworld (RBW) where the fundamental ontological element is a 4D graphical amalgam of space, time and sources called a “spacetimesource element.” These are fundamental elements of space, time and sources, not source elements in space and time. The transition amplitude for a spacetimesource element is computed using a path integral with discrete graphical action. The action for a spacetimesource element is constructed from a difference matrix K and source vector J on the graph, as in lattice gauge theory. K is constructed from graphical field gradients so that it contains a non-trivial null space and J is then restricted to the row space of K, so that it is divergence-free and represents a conserved exchange of energy–momentum. This construct of K and J represents an adynamical global constraint between sources, the spacetime metric and the energy–momentum content of the spacetimesource element, rather than a dynamical law for time-evolved entities. To illustrate this interpretation, we explain the simple EPR-Bell and twin-slit experiments. This interpretation of quantum mechanics constitutes a realist, psi-epistemic model that might underwrite certain information-theoretic accounts of the quantum.