Biotic carbon feedbacks in a materially-closed soil-vegetation-atmosphere system

The magnitude and direction of the coupled feedbacks between the biotic and abiotic components of the terrestrial carbon cycle is a major source of uncertainty in coupled climate–carbon-cycle models1, 2, 3. Materially closed, energetically open biological systems continuously and simultaneously allow the two-way feedback loop between the biotic and abiotic components to take place4, 5, 6, 7, but so far have not been used to their full potential in ecological research, owing to the challenge of achieving sustainable model systems6, 7. We show that using materially closed soil–vegetation–atmosphere systems with pro rata carbon amounts for the main terrestrial carbon pools enables the establishment of conditions that balance plant carbon assimilation, and autotrophic and heterotrophic respiration fluxes over periods suitable to investigate short-term biotic carbon feedbacks. Using this approach, we tested an alternative way of assessing the impact of increased CO2 and temperature on biotic carbon feedbacks. The results show that without nutrient and water limitations, the short-term biotic responses could potentially buffer a temperature increase of 2.3 °C without significant positive feedbacks to atmospheric CO2. We argue that such closed-system research represents an important test-bed platform for model validation and parameterization of plant and soil biotic responses to environmental changes.

Dynamic simulation for closed loops in heating systems with decision-making support

Nowadays utilising the proper HVAC system is essential both in extreme weather conditions and dense buildings design. Hydraulic loops are the most common parts in all air conditioning systems. This article aims to investigate the performance of different hydraulic loop arrangements in variable flow systems. Technical, economic and environmental assessments have been considered in this process. A dynamic system simulation is generated to evaluate the system performance and an economic evaluation is conducted by whole life cost assessment. Moreover, environmental impacts have been studied by considering the whole life energy consumption, CO2 emission, the embodied energy and embodied CO2 of the system components. Finally, decision-making in choosing the most suitable hydraulic system among five well-known alternatives has been proposed.

The long wavelength limit of hard thermal loop effective actions

We derive a closed form expression for the long wavelength limit of the effective action for hard thermal loops in an external gravitational field. It is a function of the metric, independent of time derivatives. It is compared and contrasted with the static limit, and with the corresponding limits in an external Yang-Mills field. (C) 2009 Elsevier B.V. All rights reserved.

Conformation analysis of a surface loop that controls active site access in the GH11 xylanase A from Bacillus subtilis

Xylanases (EC 3.2.1.8 endo-1,4-glycosyl hydrolase) catalyze the hydrolysis of xylan, an abundant hemicellulose of plant cell walls. Access to the catalytic site of GH11 xylanases is regulated by movement of a short beta-hairpin, the so-called thumb region, which can adopt open or closed conformations. A crystallographic study has shown that the D11F/R122D mutant of the GH11 xylanase A from Bacillus subtilis (BsXA) displays a stable "open" conformation, and here we report a molecular dynamics simulation study comparing this mutant with the native enzyme over a range of temperatures. The mutant open conformation was stable at 300 and 328 K, however it showed a transition to the closed state at 338 K. Analysis of dihedral angles identified thumb region residues Y113 and T123 as key hinge points which determine the open-closed transition at 338 K. Although the D11F/R122D mutations result in a reduction in local inter-intramolecular hydrogen bonding, the global energies of the open and closed conformations in the native enzyme are equivalent, suggesting that the two conformations are equally accessible. These results indicate that the thumb region shows a broader degree of energetically permissible conformations which regulate the access to the active site region. The R122D mutation contributes to the stability of the open conformation, but is not essential for thumb dynamics, i.e., the wild type enzyme can also adapt to the open conformation.

Hunting for warped extra dimensions via loop-induced processes

This thesis is on loop-induced processes in theories with warped extra dimensions where the fermions and gauge bosons are allowed to propagate in the bulk, while the Higgs sector is localized on or near the infra-red brane. These so-called Randall-Sundrum (RS) models have the potential to simultaneously explain the hierarchy problem and address the question of what causes the large hierarchies in the fermion sector of the Standard Model (SM). The Kaluza-Klein (KK) excitations of the bulk fields can significantly affect the loop-level processes considered in this thesis and, hence, could indirectly indicate the existence of warped extra dimensions. The analytical part of this thesis deals with the detailed calculation of three loop-induced processes in the RS models in question: the Higgs production process via gluon fusion, the Higgs decay into two photons, and the flavor-changing neutral current b → sγ. A comprehensive, five-dimensional (5D) analysis will show that the amplitudes of the Higgs processes can be expressed in terms of integrals over 5D propagators with the Higgs-boson profile along the extra dimension, which can be used for arbitrary models with a compact extra dimension. To this end, both the boson and fermion propagators in a warped 5D background are derived. It will be shown that the seemingly contradictory results for the gluon fusion amplitude in the literature can be traced back to two distinguishable, not smoothly-connected incarnations of the RS model. The investigation of the b → sγ transition is performed in the KK decomposed theory. It will be argued that summing up the entire KK tower leads to a finite result, which can be well approximated by a closed, analytical expression.rnIn the phenomenological part of this thesis, the analytic results of all relevant Higgs couplings in the RS models in question are compared with current and in particular future sensitivities of the Large Hadron Collider (LHC) and the planned International Linear Collider. The latest LHC Higgs data is then used to exclude significant portions of the parameter space of each RS scenario. The analysis will demonstrate that especially the loop-induced Higgs couplings are sensitive to KK particles of the custodial RS model with masses in the multi tera-electronvolt range. Finally, the effect of the RS model on three flavor observables associated with the b → sγ transition are examined. In particular, we study the branching ratio of the inclusive decay B → X_s γ

Loop formulation of the supersymmetric nonlinear O(N) sigma model

We derive the fermion loop formulation for the supersymmetric nonlinear O(N) sigma model by performing a hopping expansion using Wilson fermions. In this formulation the fermionic contribution to the partition function becomes a sum over all possible closed non-oriented fermion loop configurations. The interaction between the bosonic and fermionic degrees of freedom is encoded in the constraints arising from the supersymmetry and induces flavour changing fermion loops. For N ≥ 3 this leads to fermion loops which are no longer self-avoiding and hence to a potential sign problem. Since we use Wilson fermions the bare mass needs to be tuned to the chiral point. For N = 2 we determine the critical point and present boson and fermion masses in the critical regime.

A picrotoxin-specific conformational change in the glycine receptor M2-M3 loop.

The external loop linking the M2 and M3 transmembrane domains is crucial for coupling agonist binding to channel gating in the glycine receptor chloride channel (GlyR). A substituted cysteine accessibility scan previously showed that glycine activation increased the surface accessibility of 6 contiguous residues (Arg(271) Lys(276)) toward the N-terminal end of the homomeric alpha 1 GlyR M2 - M3 loop. In the present study we used a similar approach to determine whether the allosteric antagonist, picrotoxin, could impose conformational changes to this domain that cannot be induced by varying agonist concentrations alone. Picrotoxin slowed the reaction rate of a sulfhydryl-containing compound ( MTSET) with A272C, S273C, and L274C. Before interpreting this as a picrotoxin-specific conformational change, it was necessary to eliminate the possibility of steric competition between picrotoxin and MTSET. Accordingly, we showed that picrotoxin and the structurally unrelated blocker, bilobalide, were both trapped in the R271C GlyR in the closed state and that a point mutation to the pore-lining Thr(6') residue abolished inhibition by both compounds. We also demonstrated that the picrotoxin dissociation rate was linearly related to the channel open probability. These observations constitute a strong case for picrotoxin binding in the pore. We thus conclude that the picrotoxin-specific effects on the M2 - M3 loop are mediated allosterically. This suggests that the M2 - M3 loop responds differently to the occupation of different binding sites.

Length, lexicality, and articulatory suppression in immediate recall:evidence against the articulatory loop

Influential models of short-term memory have attributed the fact that short words are recalled better than longer words in serial recall (the length effect) to articulatory rehearsal. Crucial for this link is the finding that the length effect disappears under articulatory suppression. We show, instead, that, under suppression, the length effect is abolished or reversed for real words but remains robust for nonwords. The latter finding is demonstrated in a variety of conditions: with lists of three and four nonwords, with nonwords drawn from closed and open sets, with spoken and written presentation, and with written and spoken output. Our interpretation is that the standard length effect derives from the number of phonological units to be retained. The length effect is abolished or reversed under suppression because this condition encourages reliance on lexical-semantic representations. Using these representations, longer words can more easily be reconstructed from degraded phonology than shorter words. © 2005 Elsevier Inc. All rights reserved.

Evaluation of recycled tiles and OSB ceiling materials in closed broiler house prototypes

This study aimed at evaluating the thermal performance of a modular ceiling system for poultry houses. The reduced- and distorted-scale prototypes used ceiling modules made of reforested wood and were covered with recycled long-life package tiles. The following parameters were measured for 21 days: tile internal surface temperature (ST), globe temperature and humidity index (WBGT), and radiant heat load (RHL). Measurements were made at times of highest heat load (11:00 am, 13:00 pm, and 03:00 pm). Collected data were analyzed by "R" statistics software. Means were compared by multiple comparison test (Tukey) and linear regression was performed, both at 5% significance level. The results showed that the prototype with the ceiling was more efficient to reduce internal tile surface temperature; however, this was not sufficient to provide a comfortable environment for broilers during the growout. Therefore, other techniques to provide proper cooling are required in addition to the ceiling.

Estudo fotoelástico do controle vertical com o arco de dupla chave na técnica Straight wire

INTRODUÇÃO: em alguns casos, a extração de pré-molares torna-se necessária e nem sempre os espaços são completamente fechados após o alinhamento e nivelamento. O arco de dupla chave, ou Double Key Loop (DKL), é um arco retangular de aço para retração, com duas alças - uma mesial e outra distal ao canino. OBJETIVOS: este trabalho propôs-se a estudar o local onde a força é exercida, após a ativação desse arco, utilizando ativação na alça distal, ativação entre as alças e na alça distal, e ativação com Gurin®. MÉTODOS: foram montados nove modelos fotoelásticos de um arco dentário inferior, sem os primeiros pré-molares e os terceiros molares, com braquetes In-Ovation e arco DKL. O arco foi ativado e a região de incisivos, caninos e dentes posteriores foi fotografada, com interposição de filtros polarizadores de luz. RESULTADOS E CONCLUSÕES: após a análise do modelo fotoelástico, concluiu-se que a ativação com Gurin® pode produzir movimento de retração anterior com componente extrusivo; a ativação na alça distal pode produzir movimento de retração anterior sem componente extrusivo; e a ativação entre as alças e na alça distal pode produzir movimento de retração anterior com componente intrusivo.

Design and characterization of bridged loop-gap resonators for use in electron paramagnetic resonance measurements

This paper revisits the design of L and S band bridged loop-gap resonators (BLGRs) for electron paramagnetic resonance applications. A novel configuration is described and extensively characterized for resonance frequency and quality factor as a function of the geometrical parameters of the device. The obtained experimental results indicate higher values of the quality factor (Q) than previously reported in the literature, and the experimental analysis data should provide useful guidelines for BLGR design.

Coactivation of the shoulder and arm muscles during closed kinetic chain exercises on an unstable surface

Introduction: The purpose of this study was to compare the electromyography index of muscle coactivation of the following muscle pairs: posterior deltoid and pectoralis major (PD/PM); triceps brachii and biceps brachii (TB/BB); and serratus anterior and upper trapezius (SA/UT) during three different closed kinetic chain exercises (wall-press, bench-press and push-up) on an unstable surface at the maximal load. Methods: A total of 20 healthy sedentary men participated in the study. Integral linear values were obtained from three sustained contractions of six seconds each for the three proposed exercises. Mean coactivation index values were compared using the mixed-effects linear model, with a five percent significance level. Results: Electromyography indexes of muscle coactivation showed significant differences for the PD/PM and TB/BB muscle pairs. No differences were found between exercises for the SA/UT muscle pair. Conclusion: Our results seem to differ from those of previous studies, which reported that the similarity in exercises performed is responsible for the comparable muscle activation levels.

Evaluating Patellar Kinematics Through Magnetic Resonance Imaging During Open- and Closed-Kinetic-Chain Exercises

Purpose: To evaluate patellar kinematics of volunteers Without knee pain at rest and during isometric contraction in open- and closed-kinetic-chain exercises. Methods: Twenty individuals took part in this study. All were submitted to magnetic resonance imaging (MRI) during rest and voluntary isometric contraction (VIC) in the open anti closed kinetic chain at 15 degrees, 30 degrees, and 45 degrees of knee flexion. Through MRI and using medical e-film software, the following measurements were evaluated: sulcus angle, patellar-tilt angle, and bisect offset. The mixed-effects linear model was used for comparison between knee positions, between rest and isometric contractions, and between (he exercises. Results: Data analysis revealed that the sulcus angle decreased as knee flexion increased and revealed increases with isometric contractions in both the open and closed kinetic chain for all knee-flexion angles. The patellar-tilt angle decreased with isometric contractions in both the open and closed kinetic chain for every knee position. However, in the closed kinetic chain, patellar tilt increased significantly with the knee flexed at 15 degrees. The bisect offset increased with the knee flexed at 15 degrees during isometric contractions and decreased as knee flexion increased during both exercises. Conclusion: VIC in the last degrees of knee extension may compromise patellar dynamics. On the other hand, it is possible to favor patellar stability by performing muscle contractions with the knee flexed at 30 degrees and 45 degrees in either the open or closed kinetic chain.

Effective actions at finite temperature

This is a more detailed version of our recent paper where we proposed, from first principles, a direct method for evaluating the exact fermion propagator in the presence of a general background field at finite temperature. This can, in turn, be used to determine the finite temperature effective action for the system. As applications, we discuss the complete one loop finite temperature effective actions for 0+1 dimensional QED as well as for the Schwinger model in detail. These effective actions, which are derived in the real time (closed time path) formalism, generate systematically all the Feynman amplitudes calculated in thermal perturbation theory and also show that the retarded (advanced) amplitudes vanish in these theories. Various other aspects of the problem are also discussed in detail.

One-loop energy-momentum tensor in QED with electriclike background

We have obtained nonperturbative one-loop expressions for the mean-energy-momentum tensor and current density of Dirac's field on a constant electriclike back-round. One of the goals of this calculation is to give a consistent description of backreaction in such a theory. Two cases of initial states are considered: the vacuum state and the thermal equilibrium state. First, we perform calculations for the vacuum initial state. In the obtained expressions, we separate the contributions due to particle creation and vacuum polarization. The latter contribution,, are related to the Heisenberg-Euler Lagrangian. Then, we Study the case of the thermal initial state. Here, we separate the contributions due to particle creation, vacuum polarization, and the contributions due to the work of the external field on the particles at the initial state. All these contributions are studied in detail, in different regimes of weak and strong fields and low and high temperatures. The obtained results allow us to establish restrictions on the electric field and its duration under which QED with a strong constant electric field is consistent. Under such restrictions, one can neglect the backreaction of particles created by the electric field. Some of the obtained results generalize the calculations of Heisenberg-Euler for energy density to the case of arbitrary strong electric fields.