Two-dimensional scour hole problem: Role of fluid structures

An experimental program was carried out to further understand the scour caused by a plane wall jet. To this end, a two-dimensional laser Doppler anemometer was used to characterize the velocity field at various stations in the scour hole region. Present observations indicate that different types of flow structures influence scour at different time periods. Following vigorous digging caused principally by jet shear forces and impingement at the start of the test, the flow was characterized by the presence of longitudinal axial vortices, turbulent bursts and movement of the jet impingement point during the later stages. Attempts have been made to identify the role of these structures at near asymptotic conditions. The scour hole region was characterized by the presence of randomly forming and disappearing streaks, longitudinally located concave shaped depressions, rolling and ejection of sand grains. Through analysis of higher order moments and quadrant decomposition, sweep and ejection type events were observed. Such events contribute to scour and need to be incorporated in future modeling work.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .B49. Source: Masters Abstracts International, Volume: 44-03, page: 1434. Thesis (M.A.Sc.)--University of Windsor (Canada), 2005

Seasonal and interannual variability of North American isoprene emissions as determined by formaldehyde column measurements from space

Formaldehyde (HCHO) columns measured from space by solar UV backscatter allow mapping of reactive hydrocarbon emissions. The principal contributor to these emissions during the growing season is the biogenic hydrocarbon isoprene, which is of great importance for driving regional and global tropospheric chemistry. We present seven years (1995-2001) of HCHO column data for North America from the Global Ozone Monitoring Experiment (GOME), and show that the general seasonal and interannual variability of these data is consistent with knowledge of isoprene emission. There are some significant regional discrepancies with the seasonal patterns predicted from current isoprene emission models, and we suggest that these may reflect flaws in the models. The interannual variability of HCHO columns observed by GOME appears to follow the interannual variability of surface temperature, as expected from current isoprene emission models

Can a “state of the art” chemistry transport model simulate Amazonian tropospheric chemistry?

We present an evaluation of a nested high-resolution Goddard Earth Observing System (GEOS)-Chem chemistry transport model simulation of tropospheric chemistry over tropical South America. The model has been constrained with two isoprene emission inventories: (1) the canopy-scale Model of Emissions of Gases and Aerosols from Nature (MEGAN) and (2) a leaf-scale algorithm coupled to the Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) dynamic vegetation model, and the model has been run using two different chemical mechanisms that contain alternative treatments of isoprene photo-oxidation. Large differences of up to 100 Tg C yr^(−1) exist between the isoprene emissions predicted by each inventory, with MEGAN emissions generally higher. Based on our simulations we estimate that tropical South America (30–85°W, 14°N–25°S) contributes about 15–35% of total global isoprene emissions. We have quantified the model sensitivity to changes in isoprene emissions, chemistry, boundary layer mixing, and soil NO_x emissions using ground-based and airborne observations. We find GEOS-Chem has difficulty reproducing several observed chemical species; typically hydroxyl concentrations are underestimated, whilst mixing ratios of isoprene and its oxidation products are overestimated. The magnitude of model formaldehyde (HCHO) columns are most sensitive to the choice of chemical mechanism and isoprene emission inventory. We find GEOS-Chem exhibits a significant positive bias (10–100%) when compared with HCHO columns from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and Ozone Monitoring Instrument (OMI) for the study year 2006. Simulations that use the more detailed chemical mechanism and/or lowest isoprene emissions provide the best agreement to the satellite data, since they result in lower-HCHO columns

Prospective approach of Swietenia macrophylla as a neuroprotective agent for Alzheimer’s Disease: Emphasis on ameliorative mechanism

Alzheimer's disease (AD) poses a significant challenge to healthcare systems and economics worldwide in the 21st century. It is characterised by progressive memory dysfunction and is a leading cause of dementia. Literature suggests that the involvement of neuroinflammation plays a critical role in the progression of neuropathological changes in AD. Currently, available drugs for AD management primarily focus on symptomatic treatment. There is a need for safe adjunctive agents with a specific target and explicit mechanism of action. Swietenia macrophylla (SM) has been traditionally used as a food source and for pain relief in folk medicine. Recent studies have highlighted the neuroprotective properties of SM, including its anti-inflammatory, antioxidant, anti-acetylcholinesterase, and anti-mitochondrial dysfunction effects. In light of these considerations, this review aims to explore the potential neuroprotective role of SM by examining the existing literature to elucidate its potential mechanisms of action in addressing the complex challenges presented by AD

Treatment patterns and characteristics of European patients with castration-resistant prostate cancer.

Results from this analysis highlight inconsistencies in common hormonal therapy treatment patterns for CRPC and hormonal therapy across the EU

Cannabinoids: Emerging sleep modulator

Sleep is an essential biological phase of our daily life cycle and is necessary for maintaining homeostasis, alertness, metabolism, cognition, and other key functions across the animal kingdom. Dysfunctional sleep leads to deleterious effects on health, mood, and cognition, including memory deficits and an increased risk of diabetes, stroke, and neurological disorders. Sleep is regulated by several brain neuronal circuits, neuromodulators, and neurotransmitters, where cannabinoids have been increasingly found to play a part in its modulation. Cannabinoids, a group of lipid metabolites, are regulatory molecules that bind mainly to cannabinoid receptors (CB1 and CB2). Much evidence supports the role of cannabinoid receptors in the modulation of sleep, where their alteration exhibits sleep-promoting effects, including an increase in non-rapid-eye movement sleep and a reduction in sleep latency. However, the pharmacological alteration of CB1 receptors is associated with adverse psychotropic effects, which are not exhibited in CB2 receptor alteration. Hence, selective alteration of CB2 receptors is also of clinical importance, where it could potentially be used in treating sleep disorders. Thus, it is crucial to understand the neurobiological basis of cannabinoids in sleep physiology. In this review article, the alteration of the endocannabinoid system by various cannabinoids and their respective effects on the sleep-wake cycle are discussed based on recent findings. The mechanisms of the cannabinoid receptors on sleep and wakefulness are also explored for their clinical implications and potential therapeutic use on sleep disorders

Are plant emissions green?

Hydrocarbon emissions from living vegetation are thought to be harmful to the atmosphere. But the latest study suggests that the negative impact of these emissions in pristine environments is less than expected. ©2008 Nature Publishing Group