The Cardiovascular Benefits of Regular Exercise in Type 1 Diabetes Mellitus and the Risk of Exercise-induced Hypoglycemia

Type 1 diabetes mellitus (T1DM) is associated with compromised glycemic control and a heightened risk for cardiovascular disease. The common treatment of T1DM with strict glycemic control through intensive insulin therapy can be problematic (weight gain, insulin resistance, hypoglycemia). Regular exercise is known to improve cardiovascular health, yet most individuals with T1DM remain sedentary, and identify the risk of exercise-induced hypoglycemia as a significant barrier. The investigation into the use of different forms of exercise (higher intensity, resistance) for preventing exercise-induced hypoglycemia in populations with T1DM has been promising, however, little work has investigated their cardiovascular benefit or whether the risk of exercise-induced hypoglycemia changes over the course of exercise training. As such, using a novel insulin-treated rat model of T1DM the objectives of this dissertation were: (1) to determine whether the risk of hypoglycemia in response to different exercise modalities changes over the course of training in T1DM, (2) to characterize which exercise modality provides the largest amount of cardiovascular protection (as determined by recovery from an ischemia-reperfusion injury and fine-wire vascular myography), while assessing risk for exercise-induced hypoglycemia, and (3) to explore whether exercise training, when paired with modest glycemic control, results in larger cardiovascular protection than stringent glycemic control alone. The main findings of these collective studies were as follows; (1) the magnitude of the abrupt decline in blood glucose in response to different exercise modalities remains consistent after exercise training and infrequently reaches hypoglycemic concentrations if blood glucose concentrations are elevated prior to exercise in T1DM rats, (2) both exercise-induced fluctuations in blood glucose and the amount of cardiovascular protection obtained from regular exercise training appears to be modality-specific; however, results suggest that high intensity aerobic exercise provides the largest amount of cardiovascular protection (increased recovery from ischemia-reperfusion injury, vascular insulin sensitivity, and glycemic control), and (3) maintaining more modest glycemic control may provide similar cardiovascular benefits as stricter glycemic control when combined with regular exercise. Overall, less of a reliance on strict glycemic could allow for exercise to be performed safely (and providing cardiovascular benefits), while preventing complications associated with intensive insulin therapy

High-speed plasma measurements with a plasma impedance probe

Plasma impedance probes (PIPs) are a type of RF probe that primarily measure electron density. This work introduces two advancements: a streamlined analytical model for interpreting PIP-monopole measurements and techniques for achieving $\geq 1$ MHz time-resolved PIP measurements. The model's improvements include introducing sheath thickness as a measurement and providing a more accurate method for measuring electron density and damping. The model is validated by a quasi-static numerical simulation which compares the simulation with measurements, identifies sources of error, and provides probe design criteria for minimizing uncertainty. The improved time resolution is achieved by introducing higher-frequency hardware, updated analysis algorithms, and a more rigorous approach to RF calibration. Finally, the new model and high-speed techniques are applied to two datasets: a 4 kHz plasma density oscillation resolved at 100 kHz with densities ranging between $2 \times 10^{14}$ to $3 \times 10^{15}$ m$^{-3}$ and a 150 kHz oscillation resolved at 4 MHz with densities ranging between $4 \times 10^{14}$ to $6 \times 10^{14}$ m$^{-3}$

High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 1, data analysis and results

High-resolution broadband spectroscopy at near-infrared wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar. Observations of stars were performed with the “TEDI” interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec near-infrared echelle spectrograph. These are the first multidelay EDI demonstrations on starlight, as earlier measurements used a single delay or laboratory sources. We demonstrate very high (10×) resolution boost, from original 2700 to 27,000 with current set of delays (up to 3 cm), well beyond the classical limits enforced by the slit width and detector pixel Nyquist limit. Significantly, the EDI used with multiple delays rather than a single delay as used previously yields an order of magnitude or more improvement in the stability against native spectrograph point spread function (PSF) drifts along the dispersion direction. We observe a dramatic (20×) reduction in sensitivity to PSF shift using our standard processing. A recently realized method of further reducing the PSF shift sensitivity to zero is described theoretically and demonstrated in a simple simulation which produces a 350× times reduction. We demonstrate superb rejection of fixed pattern noise due to bad detector pixels—EDI only responds to changes in pixel intensity synchronous to applied dithering. This part 1 describes data analysis, results, and instrument noise. A section on theoretical photon limited sensitivity is in a companion paper, part 2

New ADS Functionality for the Curator

In this paper we provide an update concerning the operations of the NASA Astrophysics Data System (ADS), its services and user interface, and the content currently indexed in its database. As the primary information system used by researchers in Astronomy, the ADS aims to provide a comprehensive index of all scholarly resources appearing in the literature. With the current effort in our community to support data and software citations, we discuss what steps the ADS is taking to provide the needed infrastructure in collaboration with publishers and data providers. A new API provides access to the ADS search interface, metrics, and libraries allowing users to programmatically automate discovery and curation tasks. The new ADS interface supports a greater integration of content and services with a variety of partners, including ORCID claiming, indexing of SIMBAD objects, and article graphics from a variety of publishers. Finally, we highlight how librarians can facilitate the ingest of gray literature that they curate into our system.Comment: Submitted to the Proceedings of Library and Information Services in Astronomy VIII, Strasbourg, Franc

Is Environmental Enrichment Ready for Clinical Application in Human Post-stroke Rehabilitation?

Environmental enrichment (EE) has been widely used as a means to enhance brain plasticity mechanisms (e.g., increased dendritic branching, synaptogenesis, etc.) and improve behavioral function in both normal and brain-damaged animals. In spite of the demonstrated efficacy of EE for enhancing brain plasticity, it has largely remained a laboratory phenomenon with little translation to the clinical setting. Impediments to the implementation of enrichment as an intervention for human stroke rehabilitation and a lack of clinical translation can be attributed to a number of factors not limited to: (i) concerns that EE is actually the “normal state” for animals, whereas standard housing is a form of impoverishment; (ii) difficulty in standardizing EE conditions across clinical sites; (iii) the exact mechanisms underlying the beneficial actions of enrichment are largely correlative in nature; (iv) a lack of knowledge concerning what aspects of enrichment (e.g., exercise, socialization, cognitive stimulation) represent the critical or active ingredients for enhancing brain plasticity; and (v) the required “dose” of enrichment is unknown, since most laboratory studies employ continuous periods of enrichment, a condition that most clinicians view as impractical. In this review article, we summarize preclinical stroke recovery studies that have successfully utilized EE to promote functional recovery and highlight the potential underlying mechanisms. Subsequently, we discuss how EE is being applied in a clinical setting and address differences in preclinical and clinical EE work to date. It is argued that the best way forward is through the careful alignment of preclinical and clinical rehabilitation research. A combination of both approaches will allow research to fully address gaps in knowledge and facilitate the implementation of EE to the clinical setting

An overview of the extratropical storm tracks in CMIP6 historical simulations

The representation of the winter and summer extratropical storm tracks in both hemispheres is evaluated in detail for the available models in the 6th phase of the Coupled Model Intercomparison Project (CMIP6). The state of the storm tracks from 1979-2014 is compared to that in ERA5 using a Lagrangian objective cyclone tracking algorithm. It is found that the main biases present in the previous generation of models (CMIP5) still persist, albeit to a lesser extent. The equatorward bias around the SH is much reduced and there appears to be some improvement in mean biases with the higher resolution models, such as the zonal tilt of the North Atlantic storm track. Low resolution models have a tendency to under-estimate the frequency of high intensity cyclones with all models simulating a peak intensity that is too low for cyclones in the SH. Explosively developing cyclones are under-estimated across all ocean basins and in both hemispheres. In particular the models struggle to capture the rapid deepening required for these cyclones. For all measures, the CMIP6 models exhibit an overall improvement compared to the previous generation of CMIP5 models. In the NH most improvements can be attributed to increased horizontal resolution, whereas in the SH the impact of resolution is less apparent and any improvements are likely a result of improved model physics

Buoyancy Instabilities in a Weakly Collisional Intracluster Medium

The intracluster medium of galaxy clusters is a weakly collisional, high-beta plasma in which the transport of heat and momentum occurs primarily along magnetic-field lines. Anisotropic heat conduction allows convective instabilities to be driven by temperature gradients of either sign, the magnetothermal instability (MTI) in the outskirts of non-isothermal clusters and the heat-flux buoyancy-driven instability (HBI) in their cooling cores. We employ the Athena MHD code to investigate the nonlinear evolution of these instabilities, self-consistently including the effects of anisotropic viscosity (i.e. Braginskii pressure anisotropy), anisotropic conduction, and radiative cooling. We highlight the importance of the microscale instabilities that inevitably accompany and regulate the pressure anisotropies generated by the HBI and MTI. We find that, in all but the innermost regions of cool-core clusters, anisotropic viscosity significantly impairs the ability of the HBI to reorient magnetic-field lines orthogonal to the temperature gradient. Thus, while radio-mode feedback appears necessary in the central few tens of kpc, conduction may be capable of offsetting radiative losses throughout most of a cool core over a significant fraction of the Hubble time. Magnetically-aligned cold filaments are then able to form by local thermal instability. Viscous dissipation during the formation of a cold filament produces accompanying hot filaments, which can be searched for in deep Chandra observations of nearby cool-core clusters. In the case of the MTI, anisotropic viscosity maintains the coherence of magnetic-field lines over larger distances than in the inviscid case, providing a natural lower limit for the scale on which the field can fluctuate freely. In the nonlinear state, the magnetic field exhibits a folded structure in which the field-line curvature and field strength are anti-correlated.Comment: 20 pages, 20 figures, submitted to ApJ; Abstract abridge