Macrophages come to mind as keys to cognitive decline

Cognitive impairment, an underappreciated consequence of hypertension, is linked to cerebral arteriolar disease through poorly defined mechanisms. A study by Faraco et al. in this issue of the JCI points to perturbations of neurovascular unit coupling caused by perivascular macrophages (PVMs) as a cause of hypertension-related cognitive impairment. Angiotensin II (Ang II) was shown to activate PVMs, causing them to produce superoxide and thereby alter the proper functioning of the adjacent arterioles. Faraco and colleagues also show that disruption of the blood-brain barrier occurs in hypertension, allowing circulating Ang II to access PVMs. This study provides important new insight into the role of inflammatory cells in the genesis of vascular dementia

Springs–neaps cycles in daily total seabed light: Daylength-induced changes

AbstractIn shallow, tidal seas, daily total seabed light is determined largely by the interaction of the solar elevation cycle, the tidal cycle in water depth, and any temporal variability in turbidity. Since tidal range, times of low water, and often turbidity vary in regular ways over the springs–neaps cycle, daily total seabed light exhibits cycles of the same periodicity. Corresponding cycles are likely to be induced in the daily total primary production of benthic algae and plants, particularly those light-limited specimens occupying the lower reaches of a sub-tidal population. Consequently, this effect is an important control on the growth patterns, depth distribution and survival of, for example, macroalgal forests and seagrass meadows.Seasonal changes in daylength exert an important additional control on these cycles, as they alter the fraction of the tidal and turbidity cycles occurring within daylight hours. Bowers et al. (1997) modelled this phenomenon numerically and predicted that for a site with low water at about midday and midnight at neaps tides, 6am and 6pm at springs, daily total seabed light peaks at neaps in winter, but the ‘sense’ of the cycle ‘switches’ so that it peaks at springs in summer — the longer daylength permits the morning and evening low water springs to contribute substantially to the daily total. Observations for such a site in North Wales (UK), presented in this paper, show that no such ‘switch’ occurs, and neaps tides host the largest daily totals throughout the year. The predicted ‘switch’ is not observed because turbidity increases generally at spring tides, and specifically at low water springs, both of which were not accounted for in the model. Observations at a second site in Brittany (France), diametrically opposite in terms of the times of low water at neaps and at springs, indicate a peak at springs throughout the year.Analytical tools are developed to calculate the percentage of daily total sea surface irradiance reaching the bed at a site of interest on any given day, and to determine the sense of any springs–neaps cycle thereof for a given season. The conditions required for a ‘switch’ are explored graphically, resulting in the identification of criteria (and a useful parameter) for predicting their occurrence. Consequences for the growth patterns, depth limits and long-term survival of benthic algae and plants are discussed

Improved Landau Gauge Fixing and Discretisation Errors

Lattice discretisation errors in the Landau gauge condition are examined. An improved gauge fixing algorithm in which order a^2 errors are removed is presented. Order a^2 improvement of the gauge fixing condition displays the secondary benefit of reducing the size of higher-order errors. These results emphasise the importance of implementing an improved gauge fixing condition.Comment: LATTICE99 (Improvement and Renormalization), 3 pages, 1 figur

Functional correlates of positional and gender-specific renal asymmetry in drosophila

Accordingly, the physical asymmetry of the tubules in the body cavity is directly adaptive. Now that the detailed machinery underlying internal asymmetry is starting to be delineated, our work invites the investigation, not just of tissues in isolation, but in the context of their unique physical locations and milieux

A comparative assessment of waste incinerators in the UK

The uptake in Europe of Energy from Waste (EfW) incinerator plants has increased rapidly in recent years. In the UK, 25 municipal waste incinerators with energy recovery are now in operation; however, their waste supply chains and business practices vary significantly. With over a hundred more plant developments being considered it is important to establish best business practices for ensuring efficient environmental and operational performance. By reviewing the 25 plants we identify four suitable case study plants to compare technologies (moving grate, fluidised bed and rotary kiln), plant economics and operations. Using data collected from annual reports and through interviews and site visits we provide recommendations for improving the supply chain for waste incinerators and highlight the current issues and challenges faced by the industry. We find that plants using moving grate have a high availability of 87-92%. However, compared to the fluidised bed and rotary kiln, quantities of bottom ash and emissions of hydrogen chloride and carbon monoxide are high. The uptake of integrated recycling practices, combined heat and power, and post incineration non-ferrous metal collections needs to be increased among EfW incinerators in the UK. We conclude that one of the major difficulties encountered by waste facilities is the appropriate selection of technology, capacity, site, waste suppliers and heat consumers. This study will be of particular value to EfW plant developers, government authorities and researchers working within the sector of waste management

Sharp two-sided heat kernel estimates for critical Schr\"odinger operators on bounded domains

On a smooth bounded domain \Omega \subset R^N we consider the Schr\"odinger operators -\Delta -V, with V being either the critical borderline potential V(x)=(N-2)^2/4 |x|^{-2} or V(x)=(1/4) dist (x,\partial\Omega)^{-2}, under Dirichlet boundary conditions. In this work we obtain sharp two-sided estimates on the corresponding heat kernels. To this end we transform the Scr\"odinger operators into suitable degenerate operators, for which we prove a new parabolic Harnack inequality up to the boundary. To derive the Harnack inequality we have established a serier of new inequalities such as improved Hardy, logarithmic Hardy Sobolev, Hardy-Moser and weighted Poincar\'e. As a byproduct of our technique we are able to answer positively to a conjecture of E.B.Davies.Comment: 40 page

The Landshoff-Nachtmann Pomeron on the Lattice

We investigate the Landshoff-Nachtmann two-gluon-exchange model of the Pomeron using gluon propagators computed in the Landau gauge within quenched lattice QCD calculations. We first determine an effective gluon-quark coupling by constraining the Pomeron-quark coupling to its phenomenological value \beta_0 = 2\, \gev^{-1}. We then provide predictions for a variety of diffractive processes. As the propagators have been evaluated entirely from QCD first principles (although in the quenched approximation), our results provide a consistency check of the Landshoff-Nachtmann model. We address the issue of the possible gauge-dependence of our results, which will be the object of a future study.Comment: uuencoded, compressed tar file, 13 pages latex, 4 Postscript figures, requires epsf.st

Do static sources respond to massive scalar particles from the Hawking radiation as uniformly accelerated ones do in the inertial vacuum?

We revisit the recently found equivalence for the response of a static scalar source interacting with a {\em massless} Klein-Gordon field when the source is (i) static in Schwarzschild spacetime, in the Unruh vacuum associated with the Hawking radiation and (ii) uniformly accelerated in Minkowski spacetime, in the inertial vacuum, provided that the source's proper acceleration is the same in both cases. It is shown that this equivalence is broken when the massless Klein-Gordon field is replaced by a {\em massive} one.Comment: 4 pages, 2 figure

A Study of Phase Transition in Black Hole Thermodynamics

This paper deals with five-dimensional black hole solutions in (a) Einstein-Maxwell-Gauss-Bonnet theory with a cosmological constant and (b)Einstein-Yang-Mills-Gauss-Bonnet theory for spherically symmetric space time. In both the cases the possibility of phase transition is examined and it is analyzed whether the phase transition is a Hawking-Page type phase transition or not.Comment: 16 figure

Quantum Stability of Accelerated Black Holes

We study quantum aspects of the accelerated black holes in some detail. Explicitly shown is the fact that a uniform acceleration stabilizes certain charged black holes against the well-known thermal evaporation. Furthermore, a close inspection of the geometry reveals that this is possible only for near-extremal black holes and that most nonextremal varieties continue to evaporate with a modified spectrum under the acceleration. We also introduce a two-dimensional toy model where the energy-momentum flow is easily obtained for general accelerations, and find the behavior to be in accordance with the four-dimensional results. After a brief comparison to the classical system of a uniformly accelerated charge, we close by pointing out the importance of this result in the WKB expansion of the black hole pair-creation rate.Comment: LaTeX, 22 pages, 5 uuencoded figures (minor errors corrected, more discussions on the case with black holes formed by gravitational collapse.