Synthesis of novel ZnO/carbon xerogel composites: Effect of carbon content and calcination temperature on their structural and photocatalytic properties

This paper reports the development of new ZnO/carbon xerogel composites (XZn w) for photocatalytic applications. The use of black wattle tannin as a precursor to the carbon xerogel aimed at reducing costs and environmental impacts. The composites were characterized by diffuse reflectance spectroscopy (DRS), BET surface area, scanning electron microscopy (FEG-SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and X-ray diffraction (XRD). The photocatalytic performance of the materials was evaluated in the decomposition process of methylene blue, a known toxic pollutant. The impacts of the catalyst dosage and calcination temperature on the photocatalytic process were also examined systematically. The X-ray profiles of the XZn w evidenced the existence of the hexagonal structure of the zinc oxide (wurtzite) in the composites. The XPS and XRD analyses confirmed the incorporation of carbon in the zinc oxide crystalline structure. The higher carbon content resulted in a larger surface area. All composites presented the ability to absorb radiation in less energetic wavelengths, contrary to pure zinc oxide that only absorbs radiation of wavelengths below 420?nm. The optimal dosage and calcination temperature were found to be 0.2?g?L^?1 and 300?°C. All the developed composites displayed significant photocatalytic activities in the decomposition of methylene blue under both visible and solar light. The composites had superior photocatalytic efficiency under visible light when compared to pure zinc oxide. The XZn 0.5 presented the best degradation efficiency under visible radiation. All materials presented similar photocatalytic responses under solar light, evidencing the synergy between the carbon xerogel and the zinc oxide. The photocatalytic mechanism was evaluated by trapping experiments to be mainly controlled by the electron vacancies that are generated during the photoexcitation of the composites.     

Carbonate binders by “cold sintering” of calcium carbonate

The solubility of calcium carbonate (limestone) particles depends on the amount of CO₂ dissolved in the water, which is a function of temperature and the pressure of CO₂ that is in equilibrium with water. At a constant temperature, increasing CO₂ pressure increases the solubility of CaCO₃, and decreasing CO₂ pressure favours the crystallisation of CaCO₃. This dissolution–crystallisation behaviour of CaCO₃ can be used in the development of carbonate binders—a process called “cold sintering”—of limestone. This paper examines the effect of a range of parameters on the cold sintering process of limestone powder. The parameters studied are CO₂ gas pressure (atmospheric, 10 atm and 35 atm), exposure time (0–90 min), post-compaction pressure (10 and 15 MPa) and compact pressing time (10–60 min). The water/limestone powder ratio was kept constant at 0.2 (by weight). The compressive strength of the limestone compacts was used as a measure of the efficiency of the carbonate binder formation process, and scanning electron microscopy was used to study the microstructural developments. The results show that carbonate binders can be produced by cold sintering of limestone powder. Exposure of limestone compacts to high CO₂ pressure followed by post-compaction at high mechanical pressure, enhances the strength of the compact. From the microstructural data, it is evident that newly formed calcium carbonate crystal growths are responsible for the strength improvements observed. The amount of water that is used in the limestone powder mixture is one factor that controls the quantity of the cementing phase. Future work has to be focussed on the application of methods to further increase the solubility of calcium carbonate, as the amount of calcium carbonate available for recrystallisation is important in producing a strong binder.     

ONTOLOGY-BASED USER MODELING AND E-PORTFOLIO GRID LEARNING SERVICES

Several challenges need to be met by a new generation of learning services. On one hand, they need to fit into a ubiquitous and serendipitous learning vision, to adapt to different types of users with different backgrounds and needs. On the other hand, they need to integrate modern pedagogical approaches of learning. These services will probably rely on the cooperation of different distributed, autonomous, goal-oriented entities, and they can be Grid- or Web-Oriented. In this paper, we show how core technologies can contribute to the development of a next generation of learning services. In particular, we focus our attention on personalized services delivery for learning by employing an ontological perspective and user modeling techniques. This paper presents some preliminary results obtained within Elegi FP6 project.     

3-D Interpolation in Object Perception: Evidence From an Objective Performance Paradigm.

Object perception requires interpolation processes that connect visible regions despite spatial gaps. Some research has suggested that interpolation may be a 3-D process, but objective performance data and evidence about the conditions leading to interpolation are needed. The authors developed an objective performance paradigm for testing 3-D interpolation and tested a new theory of 3-D contour interpolation, termed 3-D relatability. The theory indicates for a given edge which orientations and positions of other edges in space may be connected to it by interpolation. Results of 5 experiments showed that processing of orientation relations in 3-D relatable displays was superior to processing in 3-D nonrelatable displays and that these effects depended on object formation. 3-D interpolation and 3-D relatabilty are discussed in terms of their implications for computational and neural models of object perception, which have typically been based on 2-D-orientation-sensitive units. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of Antidepressant-like Effects and Action Mechanisms of GSB-106, a Small Molecule,Affecting the TrkB Signaling

Induction of BDNF-TrkB signaling is associated with the action mechanisms of conventional and fast-acting antidepressants. GSB-106, developed as a small dimeric dipeptide mimetic of BDNF, was previously shown to produce antidepressant-like effects in the mouse Porsolt test, tail suspension test, Nomura water wheel test, in the chronic social defeat stress model and in the inflammation-induced model of depression. In the present study, we evaluated the effect of chronic per os administration of GSB-106 to Balb/c mice under unpredictable chronic mild stress (UCMS). It was observed for the first time that long term GSB-106 treatment (1 mg/kg, 26 days) during ongoing UCMS procedure ameliorated the depressive-like behaviors in mice as indicated by the Porsolt test. In addition, chronic per os administration of GSB-106 resulted in an increase in BDNF levels, which were found to be decreased in the prefrontal cortex and hippocampus of mice after UCMS. Furthermore, prolonged GSB-106 treatment was accompanied by an increase in the content of pTrkB^706/707 in the prefrontal cortex and by a pronounced increase in the level of pTrkB⁸¹⁶ in both studied brain structures of mice subjected to UCMS procedure. In summary, the present data show that chronic GSB-106 treatment produces an antidepressant-like effect in the unpredictable chronic mild stress model, which is likely to be associated with the regulation of the BDNF-TrkB signaling.     

Neuroprotective Properties of Quinone Reductase 2 Inhibitor M-11, a 2-Mercaptobenzimidazole Derivative

The ability of NQO2 to increase the production of free radicals under enhanced generation of quinone derivatives of catecholamines is considered to be a component of neurodegenerative disease pathogenesis. The present study aimed to investigate the neuroprotective mechanisms of original NQO2 inhibitor M-11 (2-[2-(3-oxomorpholin-4-il)-ethylthio]-5-ethoxybenzimidazole hydrochloride) in a cellular damage model using NQO2 endogenous substrate adrenochrome (125 µM) and co-substrate BNAH (100 µM). The effects of M-11 (10–100 µM) on the reactive oxygen species (ROS) generation, apoptosis and lesion of nuclear DNA were evaluated using flow cytometry and single-cell gel electrophoresis assay (comet assay). Results were compared with S29434, the reference inhibitor of NQO2. It was found that treatment of HT-22 cells with M-11 results in a decline of ROS production triggered by incubation of cells with NQO2 substrate and co-substrate. Pre-incubation of HT-22 cells with compounds M-11 or S29434 results in a decrease of DNA damage and late apoptotic cell percentage reduction. The obtained results provide a rationale for further development of the M-11 compound as a potential neuroprotective agent.     

Study on Lake Izvorul Muntelui rehabilitation

In the actual economical and ecological context the rehabilitation of aquatic ecosystems represents one of the most important concerns all over the world. The physical, chemical and biological processes that take place inside a lake are very complex. A simple analysis of the field data is not enough. Even if those dates offers an appreciation of the global functioning of the ecosystem under the influence of certain factors, it does not allow to predict the system evolution, the optimization of the water arrangement, in order to respect and to assure the water quality criteria or to propose solutions for diminishing the lakes eutrophication.In the recent years, Lake Izvorul Muntelui, which is the largest artificial lake on the interior waters of Romania, experienced eutrophication problems. This paper analyzes the apparition condition, its effects onto water quality in the lake and the solutions for the rehabilitation of the ecosystem. Since systematic measured data are not available for this ecosystem, the mathematical modelling it is used.The simulation is done by considering the ecosystem dynamic and the stipulation of the spatial and temporal variation domains for the natural processes to appear and act onto perturbation factors to modify the ecological succession.Thus, different scenarios will be created allowing us to offer solutions for the eutrophication phenomenon and, in the same time, to identify solutions for the rehabilitation of the Izvorul Muntelui Lake.     

Control of Fixation and Saccades in Humans With Chronic Lesions of Oculomotor Cortex.

To elucidate the dynamic interactions of cortical and subcortical oculomotor systems, the authors investigated reflexive and strategic control over fixation and saccades in patients with chronic unilateral lesions that involved either frontal or parietal cortex. They measured the effects of indicating the location of the forthcoming target and removing the fixation stimulus on the latencies of eye movements toward a peripheral visual target in 12 patients with frontal eye field (FEF) lesions, 9 patients with lesions restricted to parietal cortex, and 12 neurologically healthy controls. They found that chronic damage to FEF cortex disrupts cortico-collicular interactions, resulting in hypoactivity in the contralesional superior colliculus and a loss of strategic control over the intrinsic collicular circuits that regulate fixation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Effect of Low-Energy Laser-Driven Ultrashort Pulsed Electron Beam Irradiation on Erythropoiesis and Oxidative Stress in Rats

Anemia is a commonly observed consequence of whole-body exposure to a dose of X-ray or gamma irradiation of the order of the mean lethal dose in mammals, and it is an important factor for the determination of the survival of animals. The aim of this study was to unravel the effect of laser-driven ultrashort pulsed electron beam (UPEB) irradiation on the process of erythropoiesis and the redox state in the organism. Wistar rats were exposed to laser-driven UPEB irradiation, after which the level of oxidative stress and the activities of different antioxidant enzymes, as well as blood smears, bone marrow imprints and sections, erythroblastic islets, hemoglobin and hematocrit, hepatic iron, DNA, and erythropoietin levels, were assessed on the 1st, 3rd, 7th, 14th, and 28th days after irradiation. Despite the fact that laser-driven UPEB irradiation requires quite low doses and repetition rates to achieve the LD₅₀ in rats, our findings suggest that whole-body exposure with this new type of irradiation causes relatively mild anemia in rats, with subsequent fast recovery up to the 28th day. Moreover, this novel type of irradiation causes highly intense processes of oxidative stress, which, despite being relatively extinguished, did not reach the physiologically stable level even at the 28th day after irradiation due to the violations in the antioxidant system of the organism.     

Investigation of chemical transformations of thiophenylglycoside of muramyl dipeptide on the fumed silica surface using TPD-MS,FTIR spectroscopy and ES IT MS

In this study, chemical transformations of benzyl ester of О-(phenyl-2-acetamido-2,3-dideoxy-1-thio-β-d-glucopyranoside-3-yl)-d-lactoyl-l-alanyl-d-isoglutamine (SPhMDPOBn) on the fumed silica surface were examined, and the surface complex structure was characterized by temperature-programmed desorption mass spectrometry (TPD-MS), infrared spectroscopy (FTIR) and electrospray ion trap mass spectrometry (ES IT MS). Stages of pyrolysis of SPhMDPOBn in pristine state and on the silica surface have been determined. Probably, hydrogen-bonded complex forms between silanol surface groups and the C = O group of the acetamide moiety NH-(CH₃)-C = O…H-O-Si≡. The thermal transformations of such hydrogen-bonded complex result in pyrolysis of SPhMDPOBn immobilized on the silica surface under TPD-MS conditions. The shifts ∆ν of amide I band (measured from 1,626 to 1,639 cm^−l for SPhMDPOBn in pristine state) of 33 and 35 cm^−l which occurred when SPhMDPOBn was immobilized on the silica surface may be caused by a weakening of the intramolecular hydrogen bonding of the SPhMDPOBn because the interaction with the silica surface as hydrogen bond with silanol groups is weaker than that in associates.