COMPARISON OF THE VELOCITIES AND THE WALL EFFECT BETWEEN SPHERES AND CUBES IN THE ACCELERATING REGION

The velocities and the wall effect for spheres and cubes in the accelerating region were compared experimentally for very high Reynolds number (18000 < N _Re  < 77000 for spheres and 12000 < N _Re  < 49000 for cubes). Experiments were conducted with 0.012, 0.015, 0.018, 0.021, 0.025, and 0.03175 m spheres and their respective cubes of equal volume falling in water inside cylinders of diameters equal to 0.034, 0.049, 0.07, 0.10, 0.14, and 0.19 m. The velocities of the spheres were always greater than the velocities for the respective cubes of equal volume. The wall effect increases with the particle size and fall distance. The relative wall effect between the spheres and the cubes varies with the fall distance and the ratio of the particle to tube diameter. The wall factor as a function of particle-to-tube ratio for the spheres is described well by the Munroe equation (5.7% absolute error), while for the cubes the points are more dispersed.     

Link adaptation for Ka band low Earth orbit Earth Observation systems: A realistic performance assessment

In this paper, a proposal is sketched for realizing high data rate downlinks in next‐generation Ka band low Earth orbit (LEO) Earth Observation (EO) systems. The work aims at realistically assessing the throughput advantage stemming from link adaptation strategies—embraced by most wireless and satellite communication standards—compared with non‐adaptive transmission, which is the approach followed in conventional X band EO systems. The transmission strategies examined include constant, (static and dynamic) variable, and adaptive flavors of coding and modulation, each representing a different performance/system complexity trade‐off. Practicality is pursued to the extent possible by incorporating state‐of‐the‐art orbital, ground station, spacecraft, propagation, physical layer, and system implementation characteristics. The results manifest that under particular conditions, link adaptation offers throughput improvements of up to 100% against non‐adaptive transmission schemes in Ka band LEO EO systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Practical MIMO aspects in dual polarization per beam mobile satellite broadcasting

Building upon a number of recent publications promoting the use of multiple‐input multiple‐output (MIMO) over dual polarization per beam mobile satellite broadcasting (MSB), the present paper sets MIMO well on its way for practical implementation in next‐generation MSB by analyzing critical aspects of this novel architecture. Specifically, it carries out a sensitivity analysis of various system parameters including how time interleaving, terminal antenna cross‐polarization discrimination and intrasytem interference impact MIMO performance. Next, the paper proposes a channel estimation approach compatible with the latest digital video broadcasting‐satellite to handheld (DVB‐SH) standard for MIMO land mobile satellite (LMS) channel estimation. Finally, the impact of non‐linear distortion on the most prominent space–time coding alternatives is investigated. Copyright © 2012 John Wiley & Sons, Ltd.     

Oxidative stress due to anesthesia and surgical trauma: Importance of early enteral nutrition

Anesthesia and surgical trauma are considered major oxidative and nitrosative stress effectors resulting in the development of SIRS. In this study we evaluated the usefulness of early enteral nutrition after surgical trauma. Sixty male Wistar rats were subjected to midline laparotomy and feeding‐gastrostomy. Twenty of these rats served as controls after recovering from the operation stress. The remaining rats received, through gastrostomy, enteral nutrition or placebo‐feeding for 24 h. Oxidative stress markers and CC chemokine production were evaluated in rat serum and liver tissue. The operation itself was found to increase nitric oxide (NO) and malondialdehyde (MDA) and to decrease superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px), as well as liver tissue energy charge (EC) in relation to controls. The rats receiving enteral feeding exhibited statistically significantly lower levels of NO and MDA, and higher levels of SOD, GSH‐Px, and liver EC, in relation to placebo feeding rats. The operation significantly increased the chemokines monocyte chemoattractant protein (MCP)‐1 and regulated upon activation, normal T‐cell expressed, and secreted (RANTES) in rat serum, while enteral nutrition caused a further significant increase in chemokine levels in serum. mRNA chemokine expression in liver was increased in a similar pattern. These findings indicate that early enteral feeding might play an important role after surgery ameliorating oxidative stress, affecting positively the hepatic EC and regulating, via chemokine production, cell trafficking, and healing process.     

Frontostriatal deficits in unipolar major depression

Recent accounts of major depression have tended to focus on dysfunction of frontothalamic-striatal reentrant circuits as a possible source of the disorder. Evidence of frontostriatal involvement in unipolar major depression from lesion and neuropsychological studies, and functional and structural imaging studies is examined. The high incidence of depressive symptomatology following left frontal and basal ganglia lesions implicate these as possible sites of dysfunction. Neuropsychological evidence indicates similar deficits in patients with major depression, perhaps with dorsolateral prefrontal deficits most prominent. Structural imaging studies report frontal and basal ganglia (BG) abnormalities particularly in cases of late-age onset depression. Resting state functional imaging studies show deficits in dorsolateral, anterior cingulate (medial frontal), and BG structures. Activation imaging studies show less consistent evidence of dorsolateral deficit, while anterior cingulate deficit is more consistently demonstrated. Variability in findings across studies may reflect differences between subtypes of depression and differences in methodology. Possible involvement of the BG in the psychomotor retardation of depression is examined. It is concluded that, while there is evidence of frontostriatal deficit in major depression, the exact nature of such deficits is uncertain. Issues such as component vs. system dysfunction need to be addressed.     

Dual polarization MIMO in LMS broadcasting systems: Possible benefits and challenges

The benefits of employing dual polarization in wireless multiple‐input multiple‐output (MIMO) communication systems are only recently becoming apparent due to the continuous measurement and modeling efforts by the terrestrial research community. Land mobile satellite (LMS) broadcasting systems exhibit distinct channel, system and geometrical characteristics and are subjected to stringent spatial limitations compared to terrestrial wireless. Therefore, it remains to be investigated which operating conditions favor the joint instead of the independent encoding/decoding over the two polarizations of satellite beams. After outlining the relevant progress made in wireless dual polarization MIMO systems, the present work carries out a thorough comparison between the joint and independent encoding/decoding approaches in typical single‐satellite LMS systems exploiting state‐of‐the‐art building blocks. This comparative analysis investigates both the capacity and error performance under a fair framework between systems occupying the same resources. Since the same analytical tools are used for both terrestrial and satellite dual polarization systems, the present paper may also serve as an analytical bridge between the two. Copyright © 2010 John Wiley & Sons, Ltd.     

Group contribution-based LCA models to enable screening for environmentally benign novel chemicals in CAMD applications

This study considers the development of suitable models for the estimation of life cycle assessment (LCA) indices of organic chemicals. Unlike state-of-the-art models, the tools developed here correlate LCA indices with the molecular composition according to the well-established group contribution (GC) approach. The LCA indices considered here are global warming potential, cumulative energy demand, and Eco-Indicator 99. The model development uses data from existing LCA databases, where each material is associated with its cradle-to-gate LCA metrics. A variety of regression and nonregression methodologies are recruited to achieve the optimum correlation. GC models can be used to screen for molecules with optimal and/or desirable properties, using appropriate molecular design synthesis algorithms. In this framework, the models developed here are linked to the design algorithm to enable the consideration of LCA features together with other properties, for the design of environmentally benign liquid–liquid extraction solvents.