Publications by authors named "Brian Mace"

The sound transmission loss (STL) of wall partitions, especially in the coincidence region, is investigated. A Mindlin plate with periodically attached masses in a periodic "supercell" pattern is analyzed theoretically and experimentally for sound attenuation. Modeling the masses as points, analytical expressions for predicting the dispersion relation and frequency bandgaps of the plate are developed.

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Traumatic brain injury (TBI) from closed-head trauma is a leading cause of disability, with limited effective interventions. Many TBI models impact brain parenchyma directly, and are limited by the fact that these forces do not recapitulate clinically relevant closed head injury. However, applying clinically relevant injury mechanics to the intact skull may lead to variability and as a result, preclinical modeling TBI remains a challenge.

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The underlying etiologies of seizures are highly heterogeneous and remain incompletely understood. While studying the unfolded protein response (UPR) pathways in the brain, we unexpectedly discovered that transgenic mice (XBP1s-TG) expressing spliced X-box-binding protein-1 (Xbp1s), a key effector of UPR signaling, in forebrain excitatory neurons, rapidly develop neurologic deficits, most notably recurrent spontaneous seizures. This seizure phenotype begins around 8 days after Xbp1s transgene expression is induced in XBP1s-TG mice, and by approximately 14 days post induction, the seizures evolve into status epilepticus with nearly continuous seizure activity followed by sudden death.

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Traumatic brain injury (TBI) is a global cause of morbidity and mortality. Initial management and risk stratification of patients with TBI is made difficult by the relative insensitivity of screening radiographic studies as well as by the absence of a widely available, noninvasive diagnostic biomarker. In particular, a blood-based biomarker assay could provide a quick and minimally invasive process to stratify risk and guide early management strategies in patients with mild TBI (mTBI).

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Unlabelled: Acute spinal cord injury is a devastating injury that may lead to loss of independent function. Stem-cell therapies have shown promise; however, a clinically efficacious stem-cell therapy has yet to be developed. Functionally, endothelial progenitor cells induce angiogenesis, and neural stem cells induce neurogenesis.

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Alzheimer's disease (AD) is the most common form of dementia and is characterized pathologically by Aβ plaques. Current treatments are purely symptomatic despite decades of intensive research interest. Notably, patients with the APOE4 allele are at increased risk for developing AD.

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Background: Despite data indicating the importance of continuous video-electroencephalography (cvEEG) monitoring, adoption has been slow outside major academic centers. Barriers to adoption include the need for technologists, equipment, and cvEEG readers. Advancements in lower-cost lead placement templates and commercial systems with remote review may reduce barriers to allow community centers to implement cvEEG.

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This paper describes the extension of a wave and finite element (WFE) method to the prediction of noise transmission through, and radiation from, infinite panels. The WFE method starts with a conventional finite element model of a small segment of the panel. For a given frequency, the mass and stiffness matrices of the segment are used to form the structural dynamic stiffness matrix.

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Purpose: To evaluate the sensitivity and specificity of a panel of quantitative EEG (qEEG) trends for seizure detection in adult intensive care unit (ICU) patients when reviewed by neurophysiologists and non-neurophysiologists.

Methods: One hour qEEG panels (n = 180) were collected retrospectively from 45 ICU patients and were distributed to 5 neurophysiologists, 7 EEG technologists, and 5 Neuroscience ICU nurses for evaluation of seizures. Each panel consisted of the following qEEG tools, displayed separately for left and right hemisphere electrodes: rhythmicity spectrogram (rhythmic run detection and display; Persyst Inc), color density spectral array, EEG asymmetry index, and amplitude integrated EEG.

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Female sex is associated with improved outcome in experimental brain injury models, such as traumatic brain injury, ischemic stroke, and intracerebral hemorrhage. This implies female gonadal steroids may be neuroprotective. A mechanism for this may involve modulation of post-injury neuroinflammation.

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The human APOE4 allele is associated with an early age of onset and increased risk of Alzheimer's disease (AD). Apolipoprotein E is secreted as part of a high-density lipoprotein-like particle by glial cells in the brain for the primary purpose of transport of lipophilic compounds involved in the maintenance of synapses. Previous studies examining synaptic integrity in the amygdala of human apoE targeted replacement (TR) mice showed a decrease in spontaneous excitatory synaptic activity, dendritic arbor, and spine density associated with apoE4 compared with apoE3 and apoE2 in adult male mice.

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Emerging evidence suggests sex and apolipoprotein E (APOE) genotype separately modify outcomes after intracerebral hemorrhage (ICH). We test the hypothesis that an interaction exists between sex and APOE polymorphism in modifying outcomes after ICH and is altered by administration of exogenous apoE-mimetic peptide. To define the effects of sex and APOE polymorphism in ICH, we created collagenase-induced ICH in male and female APOETR mice (targeted replacement mice homozygous for APOE3 or APOE4 alleles; n=12/group) and assessed performance on Rotarod (RR) and Morris water maze (MWM).

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Current models of the cochlea can be characterized as being either based on the assumed propagation of a single slow wave, which provides good insight, or involve the solution of a numerical model, such as in the finite element method, which allows the incorporation of more detailed anatomical features. In this paper it is shown how the wave finite element method can be used to decompose the results of a finite element calculation in terms of wave components, which allows the insight of the wave approach to be brought to bear on more complicated numerical models. In order to illustrate the method, a simple box model is considered, of a passive, locally reacting, basilar membrane interacting via three-dimensional fluid coupling.

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Although estrogen and the enzymes responsible for its metabolism have been detected within the lung, the ability of this tissue to metabolize estrogen has not been demonstrated previously. The goal of this study was to characterize the profile of estrogen metabolites within the murine lung and to determine the effect of tobacco smoke exposure on metabolite levels. Use of liquid chromatography-tandem mass spectrometry led to the detection of three estrogens (E1, E2 and E3) and five estrogen metabolites (2-OHE1, 4-OHE1, 4-OHE2, 2-OMeE1 and 2-OMeE2) within the perfused lung, with 4-OHE1 being the most abundant species.

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The isometric force response of the locust hind leg extensor tibia muscle to stimulation of a slow extensor tibia motor neuron is experimentally investigated, and a mathematical model describing the response presented. The measured force response was modelled by considering the ability of an existing model, developed to describe the response to the stimulation of a fast extensor tibia motor neuron and to also model the response to slow motor neuron stimulation. It is found that despite large differences in the force response to slow and fast motor neuron stimulation, which could be accounted for by the differing physiology of the fibres they innervate, the model is able to describe the response to both fast and slow motor neuron stimulation.

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The dispersion curves describe wave propagation in a structure, each branch representing a wave mode. As frequency varies the wavenumbers change and a number of dispersion phenomena may occur. This paper characterizes, analyzes, and quantifies these phenomena in general terms and illustrates them with examples.

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An EMG-driven musculoskeletal model is implemented to estimate subject-specific musculoskeletal parameters such as the optimal physiological muscle length, the tendon slack length and the maximum isometric muscle force of flexor and extensor muscle groups crossing the wrist, as well as biomechanical indexes to quantify the muscle operating range, the stiffness of the musculotendon actuators, and the contribution of the muscle fibres to the joint moment. Twelve healthy subjects (11 males and 1 female, mean age 31.1±8.

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Muscle models are an important tool in the development of new rehabilitation and diagnostic techniques. Many models have been proposed in the past, but little work has been done on comparing the performance of models. In this paper, seven models that describe the isometric force response to pulse train inputs are investigated.

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Age-related macular degeneration (AMD) is a leading cause of visual dysfunction worldwide. Amyloid β (Aβ) peptides, Aβ1-40 (Aβ40) and Aβ1-42 (Aβ42), have been implicated previously in the AMD disease process. Consistent with a pathogenic role for Aβ, we show here that a mouse model of AMD that invokes multiple factors that are known to modify AMD risk (aged human apolipoprotein E 4 targeted replacement mice on a high-fat, cholesterol-enriched diet) presents with Aβ-containing deposits basal to the retinal pigmented epithelium (RPE), histopathologic changes in the RPE, and a deficit in scotopic electroretinographic response, which is reflective of impaired visual function.

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An improved model of locust skeletal muscle will inform on the general behaviour of invertebrate and mammalian muscle with the eventual aim of improving biomedical models of human muscles, embracing prosthetic construction and muscle therapy. In this article, the isometric response of the locust hind leg extensor muscle to input pulse trains is investigated. Experimental data was collected by stimulating the muscle directly and measuring the force at the tibia.

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A musculoskeletal model of wrist flexors comprising musculoskeletal dynamics and limb anatomy was experimentally validated with healthy subjects during maximum voluntary contractions. Electromyography signals recorded from flexors were used as input, while measured torques exerted by the hand were compared to the torques predicted by the model. The root mean square error and the normalized root mean square error calculated during estimation and validation phases were compared.

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A predictive model that can be used to estimate the isometric force response of the locust hind leg extensor muscle is presented. The model consists of two first order coupled differential equations. The first of these equations is linear and relates an input pulse train to the calcium concentration in muscle filaments.

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Cognitive impairment is common following traumatic brain injury (TBI), and neuroinflammatory mechanisms may predispose to the development of neurodegenerative disease. Apolipoprotein E (apoE) polymorphisms modify neuroinflammatory responses, and influence both outcome from acute brain injury and the risk of developing neurodegenerative disease. We demonstrate that TBI accelerates neurodegenerative pathology in double-transgenic animals expressing the common human apoE alleles and mutated amyloid precursor protein, and that pathology is exacerbated in the presence of the apoE4 allele.

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This study concerns the influence of visuomotor rotating disturbance on motion dynamics and brain activity. It involves using a PC-mouse and introducing a predefined bias angle between the direction of motion of the mouse pointer and that of the screen cursor. Subjects were asked to execute three different tasks, designed to study the effect of visuomotor rotation on direction control, extent control or the two together.

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A mathematical model of the locust hind leg extensor muscle is described. The model accounts for the force response of the muscle to well-separated input stimuli under isometric conditions. Experimental data was collected by stimulating the extensor muscle and measuring the force generated at the tibia.

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