Correcting surface wave bias in structure function estimates of turbulent kinetic energy dissipation rate

The combination of acoustic Doppler current profilers and the structure function methodology provides an attractive approach to making extended time series measurements of oceanic turbulence (the rate of turbulent kinetic energy dissipation ε) from moorings. However, this study shows that for deployments in the upper part of the water column, estimates of ε will be biased by the vertical gradient in wave orbital velocities. To remove this bias, a modified structure function methodology is developed that exploits the differing length scale dependencies of the contributions to the structure function resulting from turbulent and wave orbital motions. The success of the modified method is demonstrated through a comparison of ε estimates based on data from instruments at three depths over a 3-month period under a wide range of conditions, with appropriate scalings for wind stress and convective forcing

Rapid injection of near-inertial shear into the stratified upper ocean at an Antarctic Circumpolar Current front

The impact on the upper ocean of the passage of a short, intense storm over a Southern Ocean site, in proximity to an Antarctic Circumpolar Current front, is characterized. The storm causes a wind-induced deepening of the mixed layer and generates an inertial current. Immediate post-storm observations indicate a mixed layer extending to approximately 50 m depth. Subsequent measurements show the upper-ocean to have re-stratified, injecting near-inertial shear in stratified waters within 1 day of the storm's passage. This time scale for the development of near-inertial shear is one order of magnitude shorter than that predicted by the ?-dispersion paradigm. The observed rapid changes in upper-ocean stratification point to the existence of an as yet undocumented, efficient mechanism for injection of near-inertial shear into the stratified ocean that is in turn associated with enhanced turbulence and mixing

Plasma Proteomic Profiling in HIV-1 Infected Methamphetamine Abusers

We wanted to determine whether methamphetamine use affects a subset of plasma proteins in HIV-infected persons. Plasma samples from two visits were identified for subjects from four groups: HIV+, ongoing, persistent METH use; HIV+, short-term METH abstinent; HIV+, long term METH abstinence; HIV negative, no history of METH use. Among 390 proteins identified, 28 showed significant changes in expression in the HIV+/persistent METH+ group over the two visits, which were not attributable to HIV itself. These proteins were involved in complement, coagulation pathways and oxidative stress. Continuous METH use is an unstable condition, altering levels of a number of plasma proteins

Opportunities for the Development of Neuroimmune Therapies in Addiction

Studies have implicated neuroinflammatory processes in the pathophysiology of various psychiatric conditions, including addictive disorders. Neuroimmune signaling represents an important and relatively poorly understood biological process in drug addiction. The objective of this review is to update the field on recent developments in neuroimmune therapies for addiction. First, we review studies of neuroinflammation in relation to alcohol and methamphetamine dependence followed by a section on neuroinflammation and accompanying neurocognitive dysfunction in HIV infection and concomitant substance abuse. Second, we provide a review of pharmacotherapies with neuroimmune properties and their potential development for the treatment of addictions. Pharmacotherapies covered in this review include ibudilast, minocycline, doxycycline, topiramate, indomethacin, rolipram, anakinra (IL-1Ra), peroxisome proliferator-activated receptor agonists, naltrexone, and naloxone. Lastly, summary and future directions are provided with recommendations for how to efficiently translate preclinical findings into clinical studies that can ultimately lead to novel and more effective pharmacotherapies for addiction

Down-welling circulation of the northwest European continental shelf: A driving mechanism for the continental shelf carbon pump

Annually integrated measurements of pCO(2) have demonstrated that seasonally stratified regions of temperate shelf seas can be an important sink of atmospheric CO2. A key process to support this sink is the transport of carbon from shelf seas to below the permanent pycnocline of the deep ocean. Using a hydrodynamic model simulation of the northwest European Continental shelf, we find that both the large scale circulation and frictional processes support the off-shelf transport of carbon sufficiently quickly to remove similar to 40% of the carbon sequestered by one growing season before the onset of the next. This transport is highly heterogeneous, with some regions being only weakly flushed. Only 52% of this exported carbon is transported below the permanent pycnocline, hence the shelf sea and open ocean carbon cycles are intrinsically coupled. Citation: Holt, J., S. Wakelin, and J. Huthnance (2009), Down-welling circulation of the northwest European continental shelf: A driving mechanism for the continental shelf carbon pump

Variable behavior in pycnocline mixing over shelf seas

Vertical mixing, driven by turbulence in the ocean, underpins many of the critical interactions that allow life on earth to flourish since vertical buoyancy flux maintains global overturning circulation and vertical nutrient fluxes are critical to primary production. Prediction of the ocean system is therefore dependent on accurate simulation of turbulent processes that, by their very nature, are chaotic. A growing evidence base exists that provides insight into these complex processes and permits investigation of turbulence relative to better determined, and therefore predictable, parameters. Here we examine three time series of the dissipation rate of turbulent kinetic energy (ε) in “stability space”. We reveal an ordered structure within the mean distribution of ε that compares well to a variety of proposed models of oceanic turbulence. The requirement for differing site-specific tuning and only partial success however raises questions over “missing physics” within such models and the validity of measurement techniques

From physics to fishing over a shelf sea bank

The research presented in this Special Issue focuses on how seabed topography can drive horizontal patchiness in physical and biogeochemical processes, and organism distributions in a temperate shelf sea during the period of established stratification in summer. The work is based upon data collected during a research cruise aboard the RRS James Cook over Jones Bank in the Celtic Sea in summer 2008. Jones Bank was chosen because of its well-defined topography within an otherwise flat region of shelf. The project arose following observations of patchiness in the chlorophyll concentration within the summer sub-surface chlorophyll maximum (SCM) of the Celtic Sea associated with marked increases in internal turbulent mixing over large bank features such as Jones Bank. These sub-surface chlorophyll patches are not apparent at the sea surface and so cannot be detected in satellite imagery. Similar structures in sub-surface chlorophyll have been found to correlate with the distributions of foraging seabirds in the North Sea (Scott et al., 2010). Our aim was to make measurements from the scale of turbulent microstructure, through the biogeochemical rates and phytoplankton distributions, up to the distributions of fish and seabirds. We were motivated to determine what aspects of the shelf system responded to the bank, and what causitive links there may be between the physical perturbation caused by the bank and the attraction of the bank for marine top predators, including fishing fleets. In this preface to the Special Issue we will describe the physical and biological environment of the Celtic Sea, using earlier data to highlight the likely effects of a bank on shelf sea structure, and set the context and pose the questions addressed by the papers in this issue. We then summarise the findings of the research, and provide a synthesis describing why banks in a stratified shelf sea may attract mobile marine predators

Statistical power of studies examining the cognitive effects of subthalamic nucleus deep brain stimulation in Parkinson\u27s disease

It has been argued that neuropsychological studies generally possess adequate statistical power to detect large effect sizes. However, low statistical power is problematic in neuropsychological research involving clinical populations and novel interventions for which available sample sizes are often limited. One notable example of this problem is evident in the literature regarding the cognitive sequelae of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in persons with Parkinson\u27s disease (PD). In the current review, a post hoc estimate of the statistical power of 30 studies examining cognitive effects of STN DBS in PD revealed adequate power to detect substantial cognitive declines (i.e., very large effect sizes), but surprisingly low estimated power to detect cognitive changes associated with conventionally small, medium, and large effect sizes. Such wide spread Type II error risk in the STN DBS cognitive outcomes literature may affect the clinical decision-making process as concerns the possible risk of postsurgical cognitive morbidity, as well as conceptual inferences to be drawn regarding the role of the STN in higher-level cognitive functions. Statistical and methodological recommendations (e.g., meta-analysis) are offered to enhance the power of current and future studies examining the neuropsychological sequelae of STN DBS in PD

Periodic Stratification in the Rhine ROFI in the North Sea

The nature of the physical regime in the vicinity of the Rhine ROFI (Region Of Freshwater Influence) has been determined in a series of collaborative observations. Extensive surveys with shipboard CTD/rosette systems have been used to complement time series observations by an array of moorings instrumented with currentmeters, transmissometers and fluorimeters. The observations reveal a highly variable system in which the influence of the freshwater input from the Rhine extends northeastwards from the source and out to 30 km from the coast. The mean flow within this region is generally parallel to the coast (northeastwards) and with surface speeds, determined by the HF radar, of 15-20 cm/s. The residual current at sub-tidal frequencies was strongly correlated with windstress-forcing with a transfer factor of ca. 1%. Water column structure exhibits marked periodic variations particulary on semidiurnal and semi-monthly time scales, the latter highlighted by contrasting post-springs and post-neaps surveys of the ROFI region. Springs tidal stirring was reinforced by strong wind (and wave) mixing which brought about complete vertical homogeneity everywhere except at the Rhine mouth. After the following neaps, and a period of light winds, the water column was observed to have re-stratified over the whole inshore region through the relaxation of the horizontal gradients under gravity and with the influence of rotation as in the model of Ou (1983). The switching of the water column regime between stratified and mixed conditions was observed to markedly change the coupling between low frequency surface and bottom currents and is also reflected in the suspended sediment variations. Generally high levels of seston throughout the coastal boundary layer in the post-springs period were followed by a dramatic reduction especially in the region which re-stratified. An interesting exception was combined occurrence of high turbidity and low salinity in surface waters due to the immediate influence of the Rhine outflow near the source