Complex Coupling Mechanisms Research Articles

The Skin as a Neurodevelopmental Interface

After completing this article, readers should be able to: 1. Characterize the incidence of severe neurodevelopmental handicaps in very low-birthweight infants over the past decade. 2. Define severe neurodevelopmental deficits. 3. Characterize the derivation of the brain and the epidermis. 4. Describe the possibilities of evoked potential testing for evaluation of brain function in asphyxiated and very low-birthweight preterm infants. 5. Characterize in utero development of the high electrical resistance of skin. “Compared with newborns of other species, the human neonate is relatively helpless in motor capabilities and relatively precocious in sensory capabilities.” —T. Berry Brazelton Behavioral Competence Avery’s Neonatology . 5th ed. 1999 Accumulating evidence suggests a connection between the developing brain and the developing skin. In this view, the skin, broadly considered, functions as a neurodevelopmental boundary in the very low-birthweight (VLBW) preterm infant. The epidermis, for example, plays a role as a specialized ectodermal derivative closely linked to both neuroperception and noninvasive monitoring in intensive care environments. The terminal differentiation product of the epidermis, the stratum corneum, is considered a prototypical smart material. The concept of the skin as a neurodevelopmental interface may be broadened to include its role as an interface with the caregiver and a boundary for primary care delivery in the neonatal intensive care unit. Recent reviews have demonstrated the persistence of a high incidence of severe neurodevelopmental disability in VLBW preterm infants (Fig 1⇓ ). (1) Severe neurodevelopmental disability generally is defined as subnormal cognitive function, cerebral palsy, blindness, deafness, or a combination of these factors. The continuing high incidence of neurodevelopmental handicap raises several questions: 1) Given the complexity and relative inaccessibility of the central nervous system (CNS), is it advantageous to consider alternative viewpoints for the etiology and therapy of neurodevelopmental handicaps? 2) Given the close embryologic connection between brain and skin, should cognition be …

Quantifying the coupling degree between land surface and the atmospheric boundary layer with the coupled vegetation-atmosphere model HIRVAC

Abstract. In the present study, the ability of different indices to quantify the coupling degree between a vegetated surface and the atmospheric boundary layer is tested. For this purpose, a one-and-a-half dimensional atmospheric boundary layer model, including a high resolved vegetation canopy, was applied (HIRVAC) and indices, such as the decoupling factor Ω, as well as other measures derived from model out-put were used. The aim of the study was to show that the quite complex coupling and feedback mechanisms can be described with these relatively simple measures. Model results illustrate that the vegetation and the atmosphere are well coupled (expressed by a lower Ω) under conditions of a tall and dense canopy, as well as under strong dynamic forcing. This better aerodynamic coupling leads to an increase in evapotranspiration, as well as an increase in the evaporative fraction. This fact was also shown by the second coupling measure: the relative changes in daily model evapotranspiration. This measure was inspired by the assumption that these changes are primarily dependent on the coupling degree between the surface and the atmosphere, if the other boundary conditions in the model are fixed. A third sensitivity measure was used according to Jacobs and de Bruin (1992). It shows that the sensitivity of evaporative fraction to stomata resistance is much higher with a better aerodynamic coupling. The results of the factor Ω; are in a good agreement with the findings of Jacobs and de Bruin: they stress that it is a valuable strategy to group vegetation into two simple categories (smooth and rough) for the understanding of vegetation-atmosphere coupling.Key words. Atmospheric composition and structure (biosphere- atmosphere interactions) – Hydrology (evapotranspiration; hydroclimatology)

Binding mode of 1,4-naphthoquinones at the QA-site of the reaction centre from Rhodobacter sphaeroides investigated by light-induced FTIR difference spectroscopy

Recently, methyl substituted 1,4-naphthoquinone compounds have gained substantial interest since those compounds bind tightly to the QA site of the bacterial reaction center (RC) from Rhodobacter sphaeroides enabling its functional reconstitution while retaining the native ubiquinone at QB. We reported the synthesis of 29 naphthoquinone derivatives containing different numbers of methyl groups in various positions of the ring system and a systematically altered tail structure. To investigate the binding mode of these quinones at QA we measured QA-/QA-FTIR difference spectra. In the non quinonic regions the band shapes and vibrational frequencies exhibited a high similarity for all quinones. This indicates that no larger structural changes of the binding site occur upon quinone binding. Based on the well characterized QA-/QA-FTIR difference spectra for vitamin K1 some of the quinone signals were tentatively assigned to specific vibrational modes. Accordingly, those quinones carrying methyl groups in position 6 and/or 7 exhibit asymmetric hydrogen bonds between the two quinone oxygens and the protein binding pocket in both the oxidized and the reduced form, whereas in case of vitamin K1 these hydrogen bonds become symmetric upon photoreduction. Work is in progress to assign all relevant vibrational modes of the quinones by means of isotopically labelled compounds. A detailed knowledge of the quinone spectral contributions is a prerequisite for using these naphthoquinones to elucidate the complex coupling mechanism of electron transfer, proton transfer and conformational changes in the RC protein.

A simple greenhouse climate control model incorporating effects of ventilation and evaporative cooling

A greenhouse climate model, incorporating the effects of natural ventilation and evaporative cooling (fog-system), is proposed and discussed. Linearization of the greenhouse heat and water balance equations leads to a simple system of two equations with two unknowns (the temperature and humidity differences between inside and outside air) which represent quite well the complex coupling mechanisms between ventilation and fog observed in situ. The model predicts that a minimum inside temperature can be reached for a certain combination of these cooling processes. Crop temperature and transpiration were also estimated using the Penman-Monteith approach and the energy balance of the crop. Good agreement between measured and computed values of air temperature, air humidity, crop temperature and transpiration was observed. From a practical point of view this approach may permit improvement in on-line climate control.

Heat transfer in thermal insulations?Recent progress in analysis

Thermal insulations made of fibers, powders, or porous gels are characterized best with respect to their infrared optical thickness, (i) In optically thick insulations, where diffusion of infrared radiation occurs, the contributions from solid conduction and radiative transport are superimposed additively. (ii) For optically thin insulations a complex coupling mechanism causes the total heat transfer to be larger than the sum of the components; this holds especially for low emissivity boundaries. In this paper recent progress in the investigation of evacuated thermal insulations is reviewed.

Cell cycle changes in the adenylate cyclase of C6 glioma cells.

The adenylate cyclase of C6 glioma cell cultures was characterized for sensitivity to the beta-adrenergic agonist isoproterenol, as well as fluoride, and GTP as a function of the cell cycle. The mitotic phase of the cell cycle was emphasized because both the basal cellular cyclic AMP level and the intact C6 cell's capacity to accumulate cyclic AMP in response to isoproterenol decreased during mitosis. Basal and stimulated adenylate cyclase activities in mitotic cells were decreased relative to the enzyme activities in the G1, S, and G2 phases of the cell cycle. Analysis of the beta-adrenergic receptor using the radioligand(-)[3H]dihydroalprenolol showed that neither ligand affinity nor receptor density changed during the cell cycle, indicating that the reduced adenylate cyclase activity of the mitotic C6 cell was not caused by alterations in this hormone receptor. The reduction in the mitotic cell's basal adenylate cyclase activity was more prominent than the decrease in isoproterenol-, fluoride, or GTP-stimulated activities suggesting that the effectiveness of these enzymes activators (i.e., the efficiency of the coupling mechanism) was not attenuated during mitosis. These studies indicate that the intrinsic catalytic capacity (not the beta-adrenergic receptor or the coupling mechanism) of the C6 adenylate cyclase complex is reduced during mitosis and contributes to the mitotic cell's inability to accumulate and maintain the cyclic AMP concentration at the interphase level.