Nonlinear vibration energy harvesting by intentional excitation of high-frequency dynamical instability

In this thesis, a vibration-based energy harvesting system utilizing essential (nonlinearizable) nonlinearities and various electromechanical coupling elements is investigated. These elements include electromagnetic and piezoelectric methods of energy conversion. The mechanical system of interest consists of a grounded, weakly damped linear oscillator (primary system) subjected impulsive loading. This primary system is coupled to a lightweight, damped oscillating attachment (nonlinear energy sink, NES) via a thin wire, which generates an essential geometric cubic sti ness nonlinearity. Various electromechanical coupling elements are included within the oscillator coupling in various con gurations depending on the system being studied. Under single or repeated impulsive input, the damped dynamics of this system exhibit transient resonance captures (TRCs) causing large-amplitude, high-frequency instabilities in the response of the NES. These TRCs result in strong energy transfer from the directly excited primary system to the light-weight attachment. The energy is harvested by the electromechanical elements in the coupling and, in this present case, dissipated across a resistive element in the electrical circuit. The primary goal of this work is to numerically, analytically, and experimentally demonstrate the e cacy of employing this type of high-frequency dynamic instability to achieve enhanced vibration energy harvesting under single or repeated impulsive excitation

Interleukin-8 levels and activity in delayed-healing human thermal wounds

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72020/1/j.1524-475x.2000.00216.x.pd

Rhesus Macaque Theta Defensins Suppress Inflammatory Cytokines and Enhance Survival in Mouse Models of Bacteremic Sepsis

Theta-defensins (θ-defensins) are macrocyclic antimicrobial peptides expressed in leukocytes of Old World monkeys. The peptides are broad spectrum microbicides in vitro and numerous θ-defensin isoforms have been identified in granulocytes of rhesus macaques and Olive baboons. Several mammalian α- and β-defensins, genetically related to θ-defensins, have proinflammatory and immune-activating properties that bridge innate and acquired immunity. In the current study we analyzed the immunoregulatory properties of rhesus θ-defensins 1–5 (RTDs 1–5). RTD-1, the most abundant θ-defensin in macaques, reduced the levels of TNF, IL-1α, IL-1β, IL-6, and IL-8 secreted by blood leukocytes stimulated by several TLR agonists. RTDs 1–5 suppressed levels of soluble TNF released by bacteria- or LPS-stimulated blood leukocytes and THP-1 monocytes. Despite their highly conserved conformation and amino acid sequences, the anti-TNF activities of RTDs 1–5 varied by as much as 10-fold. Systemically administered RTD-1 was non-toxic for BALB/c mice, and escalating intravenous doses were well tolerated and non-immunogenic in adult chimpanzees. The peptide was highly stable in serum and plasma. Single dose administration of RTD-1 at 5 mg/kg significantly improved survival of BALB/c mice with E. coli peritonitis and cecal ligation-and-puncture induced polymicrobial sepsis. Peptide treatment reduced serum levels of several inflammatory cytokines/chemokines in bacteremic animals. Collectively, these results indicate that the anti-inflammatory properties of θ-defensins in vitro and in vivo are mediated by the suppression of numerous proinflammatory cytokines and blockade of TNF release may be a primary effect