Detection of Spatial and Temporal Interactions in Renal Autoregulation Dynamics

Renal autoregulation stabilizes renal blood flow to protect the glomerular capillaries and maintain glomerular filtration rates through two mechanisms: tubuloglomerular feedback (TGF) and the myogenic response (MR). It is considered that the feedback mechanisms operate independently in each nephron (the functional unit of the kidney) within a kidney, but renal autoregulation dynamics can be coupled between vascular connected nephrons. It has also been shown that the mechanisms are time-varying and interact with each other. Understanding of the significance of such complex behavior has been limited by absence of techniques capable of monitoring renal flow signals among more than 2 or 3 nephrons simultaneously. The purpose of this thesis was to develop approaches to allow the identification and characterization of spatial and temporal properties of renal autoregulation dynamics. We present evidence that laser speckle perfusion imaging (LSPI) effectively captures renal autoregulation dynamics in perfusion signals across the renal cortex of anaesthetized rats and that spatial heterogeneity of the dynamics is present and can be investigated using LSPI. Next, we present a novel approach to segment LSPI of the renal surface into phase synchronized clusters representing areas with coupled renal autoregulation dynamics. Results are shown for the MR and demonstrate that when a signal is present phase synchronized regions can be identified. We then describe an approach to identify quadratic phase coupling between the TGF and MR mechanisms in time and space. Using this approach we can identify locations across the renal surface where both mechanisms are operating cooperatively. Finally, we show how synchronization between nephrons can be investigated in relation to renal autoregulation effectiveness by comparing phase synchronization estimates from LSPI with renal autoregulation system properties estimated from renal blood flow and blood pressure measurements. Overall, we have developed approaches to 1) capture renal autoregulation dynamics across the renal surface, 2) identify regions with phase synchronized renal autoregulation dynamics, 3) quantify the presence of the TGF-MR interaction across the renal surface, and 4) determine how the above vary over time. The described tools allow for investigations of the significance and mechanisms behind the complex spatial interactions and time-varying properties of renal autoregulation dynamics

From alliance to enmity: Anglo-Japanese relations, 1930 to 1939

During the early twentieth century, Anglo-Japanese relations declined dramatically, and disintegrated altogether during the 1940s. The purpose of the thesis was to examine relations between Britain and Japan from 1930 to 1939. Numerous archival and secondary sources concerning diplomatic relations, contemporary domestic politics, economic constraints, and public opinion were consulted. The principal conclusions were that the decline of the Anglo-Japanese alliance was all but inevitable in light of the altered diplomatic environment following the First World War, that Britain lacked any practical means of stopping Japanese aggression in Manchuria, and that while numerous Britons recognised the threat posed by Japan, few could see any practical way of stopping her

Sideband generation of transient lasing without population inversion

We suggest a method to generate coherent short pulses by generating a frequency comb using lasing without inversion in the transient regime. We use a universal method to study the propagation of a pulse in various spectral regions through an active medium that is strongly driven on a low-frequency transition on a time scale shorter than the decoherence time. The results show gain on the sidebands at different modes can be produced even if there is no initial population inversion prepared. Besides the production of ultra-short pulse this frequency comb may have applications towards making short-wavelength or Tera-hertz lasers

The effect of hydrocarbon exposure and temperature on the behaviour of elastomeric seals

Synthetic jet fuels have been proposed as alternatives to petroleum Jet A-1. Compatibility issues, however, are of concern; specifically the interaction of synthetic fuels with polymeric materials which are commonly used to seal fuel systems. This is because of differences between the composition of synthetic fuels and petroleum-derived fuels. Synthetic fuel streams contain no or very low aromatics, unlike petroleum-derived fuels. This investigation was consequently initiated to gain a greater understanding of the factors affecting seal swell in the aviation industry. The study focussed interactions between fuel components from various fuel classes and nitrile rubber (NBR) as well as a restricted set of investigations on fluorocarbon (FKM) rubber. No comprehensive study of the temperature sensitivity of fuel composition on swelling has been attempted prior to this study. NBR and FKM were swollen in petroleum Jet A-1, synthesised paraffinic kerosene (SPK) and a variety of blends of pure components with SPK. These components were selected from aromatic species (monoaromatic, diaromatic and heterocyclic), cycloparaffins, aromatic oxygenates and other oxygenates. Aromatic species were blended at 8% (v/v) while all other species were blended at 15% (v/v). Within the class of aromatic hydrocarbon components, it was found that decreasing molecular size, increasing the number of ring structures (particular aromatic rings) as well as increasing all Hansen solubility parameters increased swelling. Of the Hansen solubility parameters, the greatest correlation was found with the hydrogen-bonding (electron exchange) parameter. Nonetheless the dispersion parameter which is strongly affected by the number of aromatic rings and length of any aliphatic side-chain was also important. A very good correlation was found between swelling and the density of the aromatic species. It was found furthermore that introducing oxygen atoms increased swelling. The introduction of cycloparaffins also increase swelling although to a much lesser extent than aromatics. Cyclisation together with a polar moiety was observed to increase swell significantly. With FKM elastomers, fuel composition had less influence. Temperature sensitivity was explored by performing swelling at 20oC, 35 oC and 50 oC. Van't Hoff plots were used to obtain enthalpies of mixing. It was found that all hydrocarbons swelled more as temperature rose. This is indicative of endothermic interactions between these species and polar NBR. However, it was observed that species with high polar and hydrogenbonding Hansen solubility parameters had lower sensitivity to temperature. It is postulated that in these species, less aromatic concentration in the NBR occurs at elevated temperatures, contributing to lower sensitivities. Aromatic oxygenates were observed to decrease in swelling with temperature. This is ascribed to a strong exothermic interaction. This behaviour was in contrast to non-aromatic oxygenates. It is possible that blends of these non-aromatic oxygenates with SPK are less stable at elevated temperatures leading to component separation into the NBR and thus more swelling. Similar trends were observed with fluorocarbon elastomers (FKM). Physical property measurements were made on swollen NBR O-rings. A distinct relationship between decreased glass transition temperature and the extent of swelling was observed. Fuel which had adsorbed into the elastomer was observed to act as an effective plasticiser. Not only did increased swelling lower the glass transition temperature but it reduced the modulus of NBR O-rings in a predictable fashion. A significant decrease in storage modulus was associated with increased swelling. Increased swelling was found to be associated with increased compression set although the mechanism by which this manifests itself is unclear

Observability of flashes from ejecta crashes in aspherical supernovae, with application to SN 2008D

A new class of transient, which has been hypothesized to accompany the explosion of an aspherical compact supernova, would arise when streams of ejecta collide outside the star. However, conditions that favour the prompt release of radiation from the collision, such as a diffuse stellar envelope, disfavour the creation of non-radial ejecta in the first place. To determine whether the collision can both occur and be visible, we simulate aspherical explosions using the HUJI-RICH moving-mesh hydrodynamics code and analyze them in terms of diffusion measures defined for individual fluid elements. While our simulations are highly idealized, they connect to realistic explosions via a single dimensionless parameter. Defining two measures of the importance of diffusivity (two versions of the inverse P'eclet number), we find that one varies in a way that indicates colliding ejecta can release a photon flash, while the other does not. Examining the x-ray transient XT 080109 associated with supernova SN 2008D, we find that its fluence and duration are consistent with the properties of an ejecta collision in the aspherical model that is most likely to emit a flash. Our results give tentative evidence for the possibility of collision-induced flashes for a narrow and radius-dependent range of asphericity, and motivate future radiation hydrodynamics simulations.Comment: 8 pages, 3 figures, submitted to MNRA

The cospectrum of stress-carrying turbulence in the presence of surface gravity waves

Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 29-44, doi:10.1175/JPO-D-17-0016.1.The cospectrum of the horizontal and vertical turbulent velocity fluctuations, an essential tool for understanding measurements of the turbulent Reynolds shear stress, often departs in the ocean from the shape that has been established in the atmospheric surface layer. Here, we test the hypothesis that this departure is caused by advection of standard boundary layer turbulence by the random oscillatory velocities produced by surface gravity waves. The test is based on a model with two elements. The first is a representation of the spatial structure of the turbulence, guided by rapid distortion theory, and consistent with the one-dimensional cospectra that have been measured in the atmosphere. The second model element is a map of the spatial structure of the turbulence to the temporal fluctuations measured at fixed sensors, assuming advection of frozen turbulence by the velocities associated with surface waves. The model is adapted to removal of the wave velocities from the turbulent fluctuations using spatial filtering. The model is tested against previously published laboratory measurements under wave-free conditions and two new sets of measurements near the seafloor in the coastal ocean in the presence of waves. Although quantitative discrepancies exist, the model captures the dominant features of the laboratory and field measurements, suggesting that the underlying model physics are sound.This research was supported by National Science Foundation Ocean Sciences Division Award 1356060 and the U.S. Geological Survey Coastal and Marine Geology Program

Quantum control of EIT dispersion via atomic tunneling in a double-well Bose-Einstein condensate

Electromagnetically induced transparency (EIT) is an important tool for controlling light propagation and nonlinear wave mixing in atomic gases with potential applications ranging from quantum computing to table top tests of general relativity. Here we consider EIT in an atomic Bose-Einstein Condensate (BEC) trapped in a double well potential. A weak probe laser propagates through one of the wells and interacts with atoms in a three-level $\Lambda$ configuration. The well through which the probe propagates is dressed by a strong control laser with Rabi frequency $\Omega_{\mu}$, as in standard EIT systems. Tunneling between the wells at the frequency $g$ provides a coherent coupling between identical electronic states in the two wells, which leads to the formation of inter-well dressed states. The tunneling in conjunction with the macroscopic interwell coherence of the BEC wave function, results in the formation of two ultra-narrow absorption resonances for the probe field that are inside of the ordinary EIT transparency window. We show that these new resonances can be interpreted in terms of the inter-well dressed states and the formation of a novel type of dark state involving the control laser and the inter-well tunneling. To either side of these ultra-narrow resonances there is normal dispersion with very large slope controlled by $g$. For realistic values of $g$, the large slope of this dispersion yields group velocities for the probe field that are two orders of magnitude slower than standard EIT systems. We discuss prospects for observing these ultra-narrow resonances and the corresponding regions of high dispersion experimentally

Molecular Response in One-Photon Absorption via Natural Thermal Light vs Pulsed Laser Excitation

Photoinduced biological processes occur via one photon absorption in natural light, which is weak, CW and incoherent, but are often studied in the laboratory using pulsed coherent light. Here we compare the response of a molecule to these two very different sources within a quantized radiation field picture. The latter is shown to induce coherent time evolution in the molecule, whereas the former does not. As a result, the coherent time dependence observed in the laboratory experiments will not be relevant to the natural biological process. Emphasis is placed on resolving confusions regarding this issue that are shown to arise from aspects of quantum measurement and from a lack of appreciation of the proper description of the absorbed photon.Comment: Revised (now published) manuscript: Replaces ArXiv:1109.002

Direct measurements of mean Reynolds stress and ripple roughness in the presence of energetic forcing by surface waves

Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 123 (2018): 2494-2512, doi:10.1002/2017JC013252.Direct covariance observations of the mean flow Reynolds stress and sonar images of the seafloor collected on a wave‐exposed inner continental shelf demonstrate that the drag exerted by the seabed on the overlying flow is consistent with boundary layer models for wave‐current interaction, provided that the orientation and anisotropy of the bed roughness are appropriately quantified. Large spatial and temporal variations in drag result from nonequilibrium ripple dynamics, ripple anisotropy, and the orientation of the ripples relative to the current. At a location in coarse sand characterized by large two‐dimensional orbital ripples, the observed drag shows a strong dependence on the relative orientation of the mean current to the ripple crests. At a contrasting location in fine sand, where more isotropic sub‐orbital ripples are observed, the sensitivity of the current to the orientation of the ripples is reduced. Further, at the coarse site under conditions when the currents are parallel to the ripple crests and the wave orbital diameter is smaller than the wavelength of the relic orbital ripples, the flow becomes hydraulically smooth. This transition is not observed at the fine site, where the observed wave orbital diameter is always greater than the wavelength of the observed sub‐orbital ripples. Paradoxically, the dominant along‐shelf flows often experience lower drag at the coarse site than at the fine site, despite the larger ripples, highlighting the complex dynamics controlling drag in wave‐exposed environments with heterogeneous roughness.National Science Foundation Ocean Sciences Division Award Grant Number: 1356060; U.S. Geological Survey Coastal and Marine Geology Program2018-09-2