Propagation of sound from aircraft ground operations

Atmospheric absorption effects on sound propagation losses during aircraft ground operation

The propagation of sound from airport ground operations

Noise measurements of sound propagation related to jet aircraft takeoff

Wetting criteria for the applicability of membrane distillation

Membrane distillation can only be applied on liquid mixtures which do not wet a microporous hydrophobic membrane. Solutions of inorganic material in water have such high values of surface tension (γLgreater-or-equal, slanted72x10−3 N/m) that the non-wetting condition is fulfilled for a number of hydrophobic membranes. As soon as organic solutes are present in the solution, the surface tensionγL will be lowered, and if the concentration of organic material becomes too high, wetting of the membrane will occur. By means of theoretical considerations a critical solute concentration or surface tension at which a homogeneous smooth material will be wetted (gq < 90/deg) can be calculated. For a (micro)porous membranes no such theoretical relation can be derived. Therefore, a simple experimental method is described to measure the maximum allowable concentration for a (micro)porous membrane. On the basis of these measurements, the maximum allowable concentration under process conditions can be determined

The minimal primary structures of RNA aptamers selected to bind HIV-1 reverse transcriptase

Title from PDF of title page (University of Missouri--Columbia, viewed on June 7, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Thesis advisor: Dr. Donald Burke.Vita.M.S. University of Missouri--Columbia 2010.Human Immunodeficiency Virus (HIV) reverse transcriptase (RT) is the most common molecular target of current HIV treatments. Oligonucleotide aptamers bind and inhibit the RNA- and DNA-dependent polymerization activities of HIV RT. Libraries consisting of aptamers including 32, 70 or 80 nucleotide variable regions were previously screened by Systematic Evolution of Ligands by Exponential Enrichment (SELEX) against RT. Roughly half of the resulting aptamers were represented by pseudoknots with well defined signature sequences (the Family I), but also additional pseudoknots with little sequence convergence (Family II), and non-pseudoknot aptamers (Family III). Nucleic acid aptamers bind RT in the primer/template binding site. Aptamers are generally non-toxic and non-immunogenic molecules making them enticing drug prospects. Many aptamers inhibit DNA dependent DNA polymerization by RT from several phenotypically different recombinant viruses, but inhibition depends on a single amino acid mutation at position 277 for other aptamers. Aptamers that are un-reactive to the identity of this amino acid represent a group which may inhibit RT from other viruses as well. In this work I present a set of aptamers with unknown secondary structure which in some cases inhibit polymerization activity by RT from two HIV subtypes with different polymorphisms at position 277. I identify the minimal primary structure containing a pseudoknot in many of these aptamers sequences. I present evidence that in at least one aptamer, the structure responsible for binding RT is not a pseudoknot, which is highly uncommon in RNA anti-RT aptamers. For at least one other aptamer I show that a pseudoknot is the important binding element, but binding is increased in the presence of additional flanking sequence.Includes bibliographical reference

Multiband Flanger

Architecture & Allied Art

Twist1 Is a TNF-Inducible Inhibitor of Clock Mediated Activation of Period Genes.

BACKGROUND: Activation of the immune system affects the circadian clock. Tumor necrosis factor (TNF) and Interleukin (IL)-1β inhibit the expression of clock genes including Period (Per) genes and the PAR-bZip clock-controlled gene D-site albumin promoter-binding protein (Dbp). These effects are due to cytokine-induced interference of E-box mediated transcription of clock genes. In the present study we have assessed the two E-box binding transcriptional regulators Twist1 and Twist2 for their role in cytokine induced inhibition of clock genes. METHODS: The expression of the clock genes Per1, Per2, Per3 and of Dbp was assessed in NIH-3T3 mouse fibroblasts and the mouse hippocampal neuronal cell line HT22. Cells were treated for 4h with TNF and IL-1β. The functional role of Twist1 and Twist2 was assessed by siRNAs against the Twist genes and by overexpression of TWIST proteins. In luciferase (luc) assays NIH-3T3 cells were transfected with reporter gene constructs, which contain a 3xPer1 E-box or a Dbp E-box. Quantitative chromatin immunoprecipitation (ChIP) was performed using antibodies to TWIST1 and CLOCK, and the E-box consensus sequences of Dbp (CATGTG) and Per1 E-box (CACGTG). RESULTS: We report here that siRNA against Twist1 protects NIH-3T3 cells and HT22 cells from down-regulation of Period and Dbp by TNF and IL-1β. Overexpression of Twist1, but not of Twist2, mimics the effect of the cytokines. TNF down-regulates the activation of Per1-3xE-box-luc, the effect being prevented by siRNA against Twist1. Overexpression of Twist1, but not of Twist2, inhibits Per1-3xE-box-luc or Dbp-E-Box-luc activity. ChIP experiments show TWIST1 induction by TNF to compete with CLOCK binding to the E-box of Period genes and Dbp. CONCLUSION: Twist1 plays a pivotal role in the TNF mediated suppression of E-box dependent transactivation of Period genes and Dbp. Thereby Twist1 may provide a link between the immune system and the circadian timing system

Refractory nerve agent induced seizures: the role of GABA(A) receptors and oxidative stress

Introduction: Organophosphate nerve agents act as potent acetylcholinesterase inhibitors which can cause refractory seizure activity in exposed casualties. The mechanism of these refractory seizures is poorly understood, thus creating a treatment challenge when selecting the appropriate anticonvulsant and neuroprotection, as survivors tend to show neurological deficits. Oxidative stress may play a role in neuropathology of nerve agent exposures, specifically via free radical production by NADPH oxidases (NOX2 and NOX4) and saturation of endogenous antioxidant mechanisms. Furthermore, previous research indicates GABA(A) receptor trafficking has a role in refractory seizure activity and that GABA neurotransmission may be modulated by oxidative stress. N-acetylcysteine (NAC) is a well characterized, effective, and widely available antioxidant compound. The first aim of this study assessed the role of oxidative stress in nerve agent, specifically soman, induced brain injury and its effect on GABA(A) receptor distribution. The second aim of this study was to investigate the effect of antioxidant NAC on seizure activity, oxidative markers and GABA(A) receptor levels. Methods: Rats were pre-treated with HI-6 and atropine to ensure survival 30 minutes prior to an 85 µg/kg soman injection or saline control, end points for brain dissection and collection were at 3, 24, and 48 hours. The second objective of this study used the same methods with the addition of 100 mg/kg and 300 mg/kg NAC pre-treatment 60 minutes prior to exposure. Western blot was used to analyze hippocampus and cortex samples prepared as homogenates and synaptoneurosomes to assess GABA(A)α1 subunit levels, NOX changes, and brain injury biomarkers. Confocal imaging was used to qualitatively assess gliosis and brain damage in the hippocampus CA1 and dentate gyrus regions. Biochemical assays were used to quantify oxidative stress and antioxidant function. Results: Rats exhibited either convulsive or nonconvulsive seizures induced by soman. GABA(A)α1 subunit densities decreased at 3 hours in synaptoneurosomes but not in homogenates, indicating decreased GABA(A) receptor availability on post-synaptic membranes. At 24 and 48 hours, GABA(A)α1 returned to control levels in the hippocampus and cortex. Oxidative stress parameters do not change significantly in any of the six biochemical assays used and Western blot brain injury markers were not significantly elevated. Gliosis appeared as early as 3 hours in severe seizure brains and persisted until at least 48 hours. NAC preserves GABA(A)α1 expression at the post-synaptic density at 100 mg/kg doses but does not reduce seizure severity. Conclusions: Oxidative stress is insignificant to neurological damage observed at the end points analyzed. This study provides the first in vivo evidence that GABA(A) receptor internalization occurs following soman exposure independently of oxidative stress and supports the hypothesis for the role of GABA(A) receptor downregulation as an important mechanism for refractory nerve agent induced seizures. Although oxidative stress was not observed in exposed animals, the administration of NAC prevented the downregulation of synaptic GABA(A) receptors which could provide an improvement of seizure arrest using diazepam. Further studies determining the adjunct efficacy of NAC and the mechanism of action will have to be conducted

Effects of auditory feedback consistency on vowel production

In investigations of feedback control during speech production, researchers have focused on two different kinds of responses to erroneous or unexpected auditory feedback. Compensation refers to online, feedback-based corrections of articulations. In contrast, adaptation refers to long-term changes in the speech production system after exposure to erroneous/unexpected feedback, which may last even after feedback is normal again. In the current study, we aimed to compare both types of feedback responses by investigating the conditions under which the system starts adapting in addition to merely compensating. Participants vocalized long vowels while they were exposed to either consistently altered auditory feedback, or to feedback that was unpredictably either altered or normal. Participants were not aware of the manipulation of auditory feedback. We predicted that both conditions would elicit compensation, whereas adaptation would be stronger when the altered feedback was consistent across trials. The results show that although there seems to be somewhat more adaptation for the consistently altered feedback condition, a substantial amount of individual variability led to statistically unreliable effects at the group level. The results stress the importance of taking into account individual differences and show that people vary widely in how they respond to altered auditory feedback

Examining associations between brain morphology in late childhood and early alcohol or tobacco use initiation in adolescence:findings from a large prospective cohort

A prominent challenge in understanding neural consequences of substance use involves disentangling predispositional risk factors from resulting consequences of substance use. Existing literature has identified pre-existing brain variations as vulnerability markers for substance use throughout adolescence. As early initiation of use is an important predictor for later substance use problems, we examined whether pre-existing brain variations are associated with early initiation of use. In the Generation R Study, a prospective population-based cohort, brain morphology (gray matter volume, cortical thickness and surface area) was assessed at ages 10 and 14 using neuroimaging. In the second wave, participants reported on alcohol and tobacco use initiation. From a base study population (N = 3019), we examined the longitudinal (N = 2218) and cross-sectional (N = 1817) association between brain morphology of frontolimbic regions of interest known to be associated with substance use risk, and very early (age &lt; 13) alcohol/tobacco use initiation. Additionally, longitudinal and cross-sectional associations were examined with a brain surface-based approach. Models were adjusted for age at neuroimaging, sex and relevant sociodemographic factors. No associations were found between brain morphology (ages 10 and 14) and early alcohol/tobacco use initiation (&lt;13 years). Sex-specific analyses suggested a cross-sectional association between smaller brain volume and early initiated tobacco use in girls. Our findings are important for interpreting studies examining neural consequences of substance use in the general population. Future longitudinal studies are needed to specify whether these findings can be extended to initiation and continuation of alcohol/tobacco use in later stages of adolescence.</p