New symbiotic hypothesis on the origin of eukaryotic flagella

The origin of eukaryotic flagella has long been a mystery. Here we review the possibility that flagella sprouted evolutionarily from the eukaryotic cell proper seems very unlikely because it is hard to imagine what function and benefit in natural selection the flagella would have provided to the cells when they first emerged as simple buds. Lynn Margulis' 1970 spirochete hypothesis, though popular still, has never been confirmed. Moreover, the absence of tubulin and axonemal dynein in the spirochetes and the incapability of the bacterial and eukaryotic membranes' making a continuum now suggest that the hypothesis is outdated. Tubulin genes were recently identified in a new bacteria division, verrucomicrobia, and microtubules have also been found in one of these species, epixenosomes, the defensive ectosymbionts. On the basis of these data, we propose a new symbiotic hypothesis: that the mid-ancestor of eukaryotic cells obtained epixenosomelike verrucomicrobia as defensive ectosymbionts and the ectosymbionts later became endosymbiotic. They still, however, protruded from the surface of their host to play their role. Later, many genes were lost or incorporated into the host genome. Finally, the genome, the bacterial membrane, and the endosymbiotic vesicle membrane were totally lost, and fingerlike protrusions with microtubules formed. As the cells grew larger, the defensive function of the protrusions eventually weakened and then vanished. Some of the protrusions took on a new role in cell movement, which led them to evolve into flagella. The key step in this process was that the dynein obtained from the host evolved into axonemal dyneins, attaching onto the microtubules and forming motile axonemes. Our hypothesis is unproven, but it offers a possible explanation that is consistent with current scientific thought. We hope that our ideas will stimulate additional studies on the origin of eukaryotic flagella and on investigations of verrucomicrobia. Whether such studies confirm, refine, or replace our hypothesis, they should nevertheless further our understanding of the origin of eukaryotic cells.

Corpus design for a unit selection TtS system with application to Bulgarian

In this paper we present the process of designing an efficient speech corpus for the first unit selection speech synthesis system for Bulgarian, along with some significant preliminary results regarding the quality of the resulted system. As the initial corpus is a crucial factor for the quality delivered by the Text-to-Speech system, special effort has been given in designing a complete and efficient corpus for use in a unit selection TTS system. The targeted domain of the TTS system and hence that of the corpus is the news reports, and although it is a restricted one, it is characterized by an unlimited vocabulary. The paper focuses on issues regarding the design of an optimal corpus for such a framework and the ideas on which our approach was based on. A novel multi-stage approach is presented, with special attention given to language and speaker dependent issues, as they affect the entire process. The paper concludes with the presentation of our results and the evaluation experiments, which provide clear evidence of the quality level achieved. © 2011 Springer-Verlag.

Short- and long-term changes in joint co-contraction associated with motor learning as revealed from surface EMG.

In the field of motor control, two hypotheses have been controversial: whether the brain acquires internal models that generate accurate motor commands, or whether the brain avoids this by using the viscoelasticity of musculoskeletal system. Recent observations on relatively low stiffness during trained movements support the existence of internal models. However, no study has revealed the decrease in viscoelasticity associated with learning that would imply improvement of internal models as well as synergy between the two hypothetical mechanisms. Previously observed decreases in electromyogram (EMG) might have other explanations, such as trajectory modifications that reduce joint torques. To circumvent such complications, we required strict trajectory control and examined only successful trials having identical trajectory and torque profiles. Subjects were asked to perform a hand movement in unison with a target moving along a specified and unusual trajectory, with shoulder and elbow in the horizontal plane at the shoulder level. To evaluate joint viscoelasticity during the learning of this movement, we proposed an index of muscle co-contraction around the joint (IMCJ). The IMCJ was defined as the summation of the absolute values of antagonistic muscle torques around the joint and computed from the linear relation between surface EMG and joint torque. The IMCJ during isometric contraction, as well as during movements, was confirmed to correlate well with joint stiffness estimated using the conventional method, i.e., applying mechanical perturbations. Accordingly, the IMCJ during the learning of the movement was computed for each joint of each trial using estimated EMG-torque relationship. At the same time, the performance error for each trial was specified as the root mean square of the distance between the target and hand at each time step over the entire trajectory. The time-series data of IMCJ and performance error were decomposed into long-term components that showed decreases in IMCJ in accordance with learning with little change in the trajectory and short-term interactions between the IMCJ and performance error. A cross-correlation analysis and impulse responses both suggested that higher IMCJs follow poor performances, and lower IMCJs follow good performances within a few successive trials. Our results support the hypothesis that viscoelasticity contributes more when internal models are inaccurate, while internal models contribute more after the completion of learning. It is demonstrated that the CNS regulates viscoelasticity on a short- and long-term basis depending on performance error and finally acquires smooth and accurate movements while maintaining stability during the entire learning process.

Transboundary diagnostic analysis. Vol. 1. Issues, proximate and root causes

The Transboundary Diagnostic Analysis(TDA) quantifies and ranks water-related environmental transboundary issues and their causes according to the severity of environmental and/or socio-economic impacts. The three main issues in BOBLME are; overexploitation of marine living resources; degradation of mangroves, coral reefs and seagrasses; pollution and water quality. Volume 1 describes the transboundary issues in BOBLME and their proximate and underlying root causes. These will be used to develop a Strategic Action Plan (SAP)

A study of capacitance-voltage characteristics of lead zirconate titanate ferroelectric thin films and their usage to investigate polarization and coercive field.

Capacitance-voltage (C-V) characteristics of lead zirconate titanate (PZT) thin films with a thickness of 130 nm were measured between 300 and 533 K. The transition between ferroelectric and paraelectric phases was revealed to be of second order in our case, with a Curie temperature at around 450 K. A linear relationship was found between the measured capacitance and the inverse square root of the applied voltage. It was shown that such a relationship could be fitted well by a universal expression of C/A = k(V+V(0))(-1/2) and that this expression could be derived by expanding the Landau-Devonshire free energy at an effective equilibrium position of the Ti/Zr ion in a PZT unit cell. By using the derived equations in this work, the free energy parameters for an individual material can be obtained solely from the corresponding C-V data, and the temperature dependences of both remnant polarization and coercive voltage are shown to be in quantitative agreement with the experimental data.