Preparation and application of highly porous aerogel-based bioactive materials in dentistry

In this study, the possibility of preparation and application of highly porous silica aerogel-based bioactive materials are presented. The aerogel was combined with hydroxyapatite and p.tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in themesoporous region with a maximum pore diameter of 7,4 and 12.7 nm for the composite materials. The newly developed bioactive materials were characterized by scant electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.     

Module-Based Reinforcement Learning: Experiments with a Real Robot

The behavior of reinforcement learning (RL) algorithms is best understood in completely observable, discrete-time controlled Markov chains with finite state and action spaces. In contrast, robot-learning domains are inherently continuous both in time and space, and moreover are partially observable. Here we suggest a systematic approach to solve such problems in which the available qualitative and quantitative knowledge is used to reduce the complexity of learning task. The steps of the design process are to:i) decompose the task into subtasks using the qualitative knowledge at hand; ii) design local controllers to solve the subtasks using the available quantitative knowledge and iii) learn a coordination of these controllers by means of reinforcement learning. It is argued that the approach enables fast, semi-automatic, but still high quality robot-control as no fine-tuning of the local controllers is needed. The approach was verified on a non-trivial real-life robot task. Several RL algorithms were compared by ANOVA and it was found that the model-based approach worked significantly better than the model-free approach. The learnt switching strategy performed comparably to a handcrafted version. Moreover, the learnt strategy seemed to exploit certain properties of the environment which were not foreseen in advance, thus supporting the view that adaptive algorithms are advantageous to non-adaptive ones in complex environments.     

Time- and concentration-dependence of the growth-promoting activity of insulin and histamine in Tetrahymena. Application of the MTT-method for the determination of cell proliferation in a protozoan model

The unicellular ciliate Tetrahymena pyriformis was treated with different concentrations of insulin or histamine and at different time points the cell density was measured, using a tetrazolium-based semiautomated colorimetric assay (MTT). The assay was suitable to determine the rate of cell proliferation of Tetrahymena. Insulin in each concentration significantly elevated the cell count up to 3 h. After that, it was neutral or its effect was insignificant. Histamine at 10(-5) M concentration diminished cell count at 3, 5, 7 and 24 h. At 10(-6) M concentration there was no difference and at 10(-7) M concentration it enhanced cell division up to 5 h, after that there being no difference. The two hormones have cell division promoting activity for cells of higher animals and the experiments demonstrate this effect already at a unicellular level.     

The effects of ceramide and its analogues on the secretion of the mucocyst content of Tetrahymena

Monoclonal antibody to Geodia lectin is bound by the mucocyst content of Tetrahymena. By using this (fluorescent-labelled) antibody and confocal microscopy, the actual state of the mucocyst (position, resting, filling or extruding) can be studied. Treatment with C2 ceramide and non-hydroxy fatty acid caused a rapid depletion of mucocyst material. Another ceramide analogue, psychosine caused fusion of mucocysts. In these cases--in contrast to the controls--the contractile vacuole was filled with mucocyst material and this was seen in the tubules in contact with the contractile vacuoles. Hydroxy fatty acid ceramide, sphingomyelin and sphingosine-1-phosphate were ineffective. As the former materials influence also the cytoskeleton, while the latter do not, the cytoskeleton is presumed to have a mediatory effect. Neither the connection of contractile vacuoles with tubular structures nor mucocyst fusion have been described before.     

Nanocomputing by field-coupled nanomagnets

Demonstrates through simulations the feasibility of using magnetically coupled nanometer-scale ferromagnetic dots for digital information processing. Microelectronic circuits provide the input and output of the magnetic nanostructure, but the signal is processed via magnetic dot-dot interactions. Logic functions can be defined by the proper placements of dots. We introduce a SPICE macromodel of interacting nanomagnets and use this tool to design and simulate the proposed nanomagnet logic units. This SPICE model allows us to simulate such magnetic information processing devices within the same framework as conventional electronic circuits.     

Selecting the nozzle assortment for a Gantry-type placement machine

Electronics manufacturing systems employ increasingly multi-head gantry machines, where several vacuum nozzles are used simultaneously in pick-and-place operations to insert components on bare PCBs. Their use includes several options that have an impact on the overall manufacturing speed of the machine. In the present paper we address the problem of selecting the nozzles for this kind of a gantry machine, which is an important subproblem of the larger scheduling problem of multi-head gantry machines. Nozzles come in different types, and different types of components may require different types of nozzles in their placing. We address first a case where a single PCB type is manufactured and the only limitation on the number of nozzles is given by the capacity of the placement head. Then we discuss the case where there is a budget limitation on the total cost of the nozzles we can buy. We show that both of these problems can be solved optimally by the means of efficient greedy algorithms. We also discuss the case of selecting nozzles when manufacturing multiple different PCB types.     

Synthesis and characterization of chemically and electrochemically prepared conducting polymer/iron oxalate composites

Poly(3-octyl-thiophene) (POT) and polypyrrole (PPy) iron oxalate composites were synthesized through a post-polymerization oxidative treatment. The composite of the latter has been prepared also by electrochemical polymerization. The samples have been characterized by X-ray diffraction (XRD), impedance spectroscopy, scanning electron microscope (SEM) combined with energy dispersive X-ray (EDX) spectroscopy, Mössbauer spectroscopy, cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). In case of PPy, two peaks in the XRD spectra show the presence of iron containing composite, while with POT only the layered structure originating from the octyl side-chain interactions was modified by the composite formation. The assumption of the weakening of short- and long-range interactions was proven by the decrease in conductivity of the composite. The successful electrochemical synthesis resulted a composite of ∼5% iron content, determined by EDX. Mössbauer spectroscopy measurements evidenced a composite containing mixed valence iron oxalate doping ions, which supports the indirect EQCM data.     

On sparse matrix orderings in interior point methods

The major computational task of most interior point implementations is solving systems of equations with symmetric coefficient matrix by direct factorization methods, therefore, the performance of Cholesky-like factorizations is a critical issue. In the case of sparse and large problems the efficiency of the factorizations is closely related to the exploitation of the nonzero structure of the problem. A number of techniques were developed for fill-reducing sparse matrix orderings which make Cholesky factorizations more efficient by reducing the necessary floating point computations. We present a variant of the nested dissection algorithm incorporating special techniques that are beneficial for graph partitioning problems arising in the ordering step of interior point implementations. We illustrate the behavior of our algorithm and provide numerical results and comparisons with other sparse matrix ordering algorithms.     

Research progress of electrode suspensions of lithium-ion flow batteries

锂离子液流电池将锂离子电池的工作原理与传统液流电池的结构特点相结合,是一种正处于基础技术开发阶段的新型电化学储能电池技术,具有输出功率和储能容量彼此独立、成本较低等特点,适用于未来电网储能领域。电极悬浮液作为实现锂离子液流电池充放电功能的主体材料,其导电性能和流动性能是影响锂离子液流电池倍率特性和能量密度的重要因素。论文结合实验数据对该方向面临的主要技术问题及研究重点进行了分析,认为电极悬浮液的研究需要从导电机理、质量比容量、流变性能等方面进一步深入研究,并建立标准评价体系。     

Electrophysiological Effects of the Transient Receptor Potential Melastatin 4 Channel Inhibitor (4-Chloro-2-(2-chlorophenoxy)acetamido) Benzoic Acid (CBA) in Canine Left Ventricular Cardiomyocytes

Transient receptor potential melastatin 4 (TRPM4) plays an important role in many tissues, including pacemaker and conductive tissues of the heart, but much less is known about its electrophysiological role in ventricular myocytes. Our earlier results showed the lack of selectivity of 9-phenanthrol, so CBA ((4-chloro-2-(2-chlorophenoxy)acetamido) benzoic acid) was chosen as a new, potentially selective inhibitor. Goal: Our aim was to elucidate the effect and selectivity of CBA in canine left ventricular cardiomyocytes and to study the expression of TRPM4 in the canine heart. Experiments were carried out in enzymatically isolated canine left ventricular cardiomyocytes. Ionic currents were recorded with an action potential (AP) voltage-clamp technique in whole-cell configuration at 37 °C. An amount of 10 mM BAPTA was used in the pipette solution to exclude the potential activation of TRPM4 channels. AP was recorded with conventional sharp microelectrodes. CBA was used in 10 µM concentrations. Expression of TRPM4 protein in the heart was studied by Western blot. TRPM4 protein was expressed in the wall of all four chambers of the canine heart as well as in samples prepared from isolated left ventricular cells. CBA induced an approximately 9% reduction in AP duration measured at 75% and 90% of repolarization and decreased the short-term variability of APD₉₀. Moreover, AP amplitude was increased and the maximal rates of phase 0 and 1 were reduced by the drug. In AP clamp measurements, CBA-sensitive current contained a short, early outward and mainly a long, inward current. Transient outward potassium current (I_to) and late sodium current (I_Na,L) were reduced by approximately 20% and 47%, respectively, in the presence of CBA, while L-type calcium and inward rectifier potassium currents were not affected. These effects of CBA were largely reversible upon washout. Based on our results, the CBA induced reduction of phase-1 slope and the slight increase of AP amplitude could have been due to the inhibition of I_to. The tendency for AP shortening can be explained by the inhibition of inward currents seen in AP-clamp recordings during the plateau phase. This inward current reduced by CBA is possibly I_Na,L, therefore, CBA is not entirely selective for TRPM4 channels. As a consequence, similarly to 9-phenanthrol, it cannot be used to test the contribution of TRPM4 channels to cardiac electrophysiology in ventricular cells, or at least caution must be applied.