677 research outputs found

    The Independent Counsel Statute: A Legal History

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    Priester et al provide a comprehensive legal history of the independent counsel statute from its inception in 1978 until its apparent last hurrah in 1999. They also explore the role of the independent counsel in the history and practice of the government\u27s evidentiary privileges

    Artifact or Meaningful Theoretical Constructs?: Examining Evidence for Nonbelief‐ and Belief‐Based Attitude Change Processes

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142140/1/jcpy67.pd

    Modeling Physiological Processes That Relate Toxicant Exposure and Bacterial Population Dynamics

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    Quantifying effects of toxicant exposure on metabolic processes is crucial to predicting microbial growth patterns in different environments. Mechanistic models, such as those based on Dynamic Energy Budget (DEB) theory, can link physiological processes to microbial growth. Here we expand the DEB framework to include explicit consideration of the role of reactive oxygen species (ROS). Extensions considered are: (i) additional terms in the equation for the ‘‘hazard rate’’ that quantifies mortality risk ; (ii) a variable representing environmental degradation ; (iii) a mechanistic description of toxic effects linked to increase in ROS production and aging acceleration, and to non-competitive inhibition of transport channels ; (iv) a new representation of the ‘‘lag time’’ based on energy required for acclimation. We estimate model parameters using calibrated Pseudomonas aeruginosa optical density growth data for seven levels of cadmium exposure. The model reproduces growth patterns for all treatments with a single common parameter set, and bacterial growth for treatments of up to 150 mg(Cd)/L can be predicted reasonably well using parameters estimated from cadmium treatments of 20 mg(Cd)/L and lower. Our approach is an important step towards connecting levels of biological organization in ecotoxicology. The presented model reveals possible connections between processes that are not obvious from purely empirical considerations, enables validation and hypothesis testing by creating testable predictions, and identifies research required to further develop the theory

    Optimized gadolinium-DO3A loading in RAFTpolymerized copolymers for superior MR imaging of aging blood–brain barrier

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    The development of gadolinium-based contrast agents (GBCAs) has been pivotal in advancing magnetic resonance imaging (MRI), offering enhanced soft tissue contrast without ionizing radiation exposure. Despite their widespread clinical use, the need for improved GBCAs has led to innovations in ligand chemistry and polymer science. We report a novel approach using methacrylate-functionalized DO3A ligands to synthesize a series of copolymers through direct reversible addition-fragmentation chain transfer (RAFT) polymerization. This technique enables precise control over the gadolinium content within the polymers, circumventing the need for subsequent conjugation and purification steps, and facilitates the addition of other components such as targeting ligands. The resulting copolymers were analysed for their relaxivity properties, indicating that specific gadolinium-DO3A loading contents between 12–30 mole percent yield optimal MRI contrast enhancement. Inductively coupled plasma (ICP) measurements corroborated these findings, revealing a non-linear relationship between gadolinium content and relaxivity. Optimized copolymers were synthesized with the claudin-1 targeting peptide, C1C2, to image BBB targeting in aged mice to show imaging utility. This study presents a promising pathway for the development of more efficient GBCA addition to copolymers for targeted drug delivery and bioimaging application

    An Endothelial Storage Granule for Tissue-Type Plasminogen Activator

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    In previous studies we have shown that, after stimulation by a receptor ligand such as thrombin, tissue-type plasminogen activator (tPA) and von Willebrand factor (vWf) will be acutely released from human umbilical vein endothelial cells (HUVEC). However, the mechanisms involved in the secretion of these two proteins differ in some respects, suggesting that the two proteins may be stored in different secretory granules

    Conformally coupled dark matter

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    Dark matter is obtained from a scalar field coupled conformally to gravitation; the scalar being a relict of Dirac's gauge function. This conformally coupled dark matter includes a gas of very light (m2.25×1034eVm\approx 2.25\times 10^{-34} eV) neutral bosons having spin 0, as well as a time-dependent global scalar field, both pervading all of the cosmic space. The time-development of this dark matter in the expanding F-R-W universe is investigated, and an acceptable cosmological behaviour is obtained.Comment: LaTEX File 10 pages, no figure

    Hippocampal vascular reserve associated with cognitive performance and hippocampal volume

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    Medial temporal lobe dependent cognitive functions are highly vulnerable to hypoxia in the hippocampal region, yet little is known about the relationship between the richness of hippocampal vascular supply and cognition. Hippocampal vascularization patterns have been categorized into a mixed supply from both the posterior cerebral artery and the anterior choroidal artery or a single supply by the posterior cerebral artery only. Hippocampal arteries are small and affected by pathological changes when cerebral small vessel disease is present. We hypothesized, that hippocampal vascularization patterns may be important trait markers for vascular reserve and modulate (i) cognitive performance; (ii) structural hippocampal integrity; and (iii) the effect of cerebral small vessel disease on cognition. Using high-resolution 7 T time-of-flight angiography we manually classified hippocampal vascularization patterns in older adults with and without cerebral small vessel disease in vivo. The presence of a mixed supplied hippocampus was an advantage in several cognitive domains, including verbal list learning and global cognition. A mixed supplied hippocampus also was an advantage for verbal memory performance in cerebral small vessel disease. Voxel-based morphometry showed higher anterior hippocampal grey matter volume in mixed, compared to single supply. We discuss that a mixed hippocampal supply, as opposed to a single one, may increase the reliability of hippocampal blood supply and thereby provide a hippocampal vascular reserve that protects against cognitive impairment

    On the exciton binding energy in a quantum well

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    We consider a model describing the one-dimensional confinement of an exciton in a symmetrical, rectangular quantum-well structure and derive upper and lower bounds for the binding energy EbE_b of the exciton. Based on these bounds, we study the dependence of EbE_b on the width of the confining potential with a higher accuracy than previous reports. For an infinitely deep potential the binding energy varies as expected from 1Ry1 Ry at large widths to 4Ry4 Ry at small widths. For a finite potential, but without consideration of a mass mismatch or a dielectric mismatch, we substantiate earlier results that the binding energy approaches the value 1Ry1 Ry for both small and large widths, having a characteristic peak for some intermediate size of the slab. Taking the mismatch into account, this result will in general no longer be true. For the specific case of a Ga1xAlxAs/GaAs/Ga1xAlxAsGa_{1-x}Al_{x}As/GaAs/Ga_{1-x}Al_{x}As quantum-well structure, however, and in contrast to previous findings, the peak structure is shown to survive.Comment: 32 pages, ReVTeX, including 9 figure

    Hippocampal vascularization patterns exert local and distant effects on brain structure but not vascular pathology in old age

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    The hippocampus within the medial temporal lobe is highly vulnerable to age-related pathology such as vascular disease. We examined hippocampal vascularization patterns by harnessing the ultra-high resolution of 7 Tesla magnetic resonance angiography. Dual-supply hemispheres with a contribution of the anterior choroidal artery to hippocampal blood supply were distinguished from single-supply ones with a sole dependence on the posterior cerebral artery. A recent study indicated that a dual vascular supply is related to preserved cognition and structural hippocampal integrity in old age and vascular disease. Here, we examined the regional specificity of these structural benefits at the level of medial temporal lobe sub-regions and hemispheres. In a cross-sectional study with an older cohort of 17 patients with cerebral small vessel disease (70.7 ±  9.0 years, 35.5% female) and 27 controls (71.1 ±  8.2 years, 44.4% female), we demonstrate that differences in grey matter volumes related to the hippocampal vascularization pattern were specifically observed in the anterior hippocampus and entorhinal cortex. These regions were especially bigger in dual-supply hemispheres, but also seemed to benefit from a contralateral dual supply. We further show that total grey matter volumes were greater in people with at least one dual-supply hemisphere, indicating that the hippocampal vascularization pattern has more far-reaching structural implications beyond the medial temporal lobe. A mediation analysis identified total grey matter as a mediator of differences in global cognition. However, our analyses on multiple neuroimaging markers for cerebral small vessel disease did not reveal any evidence that an augmented hippocampal vascularization conveys resistance nor resilience against vascular pathology. We propose that an augmented hippocampal vascularization might contribute to maintaining structural integrity in the brain and preserving cognition despite age-related degeneration. As such, the binary hippocampal vascularization pattern could have major implications for brain structure and function in ageing and dementia independent of vascular pathology, while presenting a simple framework with potential applicability to the clinical setting
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