Current-Mode Temperature Compensated Continuous-Time CMOS Transconductance-C Filter

In this paper a low voltage low power current-mode continuous-timelow-pass filter is presented. The current-integrator is constructedof a multi-output linearized transconductance element drivenby a balanced transimpedance amplifier. A 1 MHz third order ellipticlow pass filter is designed and fabricated with the proposedcurrent-mode integrator. The measurements show capability ofoperation with down to a 3 V supply voltage. The measured currentconsumption is 850 µA at room temperature andthe dynamic range is 66 dB. The distortion of the filter is below50 dBc with peak signal levels up to twice the quiescent currentlevel and with the refined designs even lower distortion is expected.The filter uses a CMOS-current reference for temperature andprocess variation stabilization with a measured corner frequencytemperature coefficient of –100 ppm/K.     

Tetrahedral mesh generation in convex primitives

This paper presents a method for generating tetrahedral meshes in three-dimensional primitives. Given a set of closed and convex polyhedra having non-zero volume and some mesh controlling parameters, the polyhedra are automatically split to tetrahedra satisfying the criteria of standard finite element meshes. The algorithm tries to generate elements close to regular tetrahedra by maximizing locally the minimum solid angles associated to a set of a few neighbouring tetrahedra. The input parameters define the size of the tetrahedra and they can be used to increase or decrease the discretization locally. All the new nodes, which are not needed to describe the geometry, are generated automatically.     

Electrical Resistance Tomography imaging of concrete

We apply Electrical Resistance Tomography (ERT) for three dimensional imaging of concrete. In ERT, alternating currents are injected into the target using an array of electrodes attached to the target surface, and the resulting voltages are measured using the same electrodes. These boundary measurements are used for reconstructing the internal (3D) conductivity distribution of the target. In reinforced concrete, the metallic phases (reinforcing bars and fibers), cracks and air voids, moisture gradients, and the chloride distribution in the matrix carry contrast with respect to conductivity. While electrical measurements have been widely used to characterize the properties of concrete, only preliminary results of applying ERT to concrete imaging have been published so far. The aim of this paper is to carry out a feasibility evaluation with specifically cast samples. The results indicate that ERT may be a feasible modality for non-destructive evaluation of concrete.     

Antiproliferative effects of sea buckthorn (Hippophae rhamnoides L.) extracts on human colon and liver cancer cell lines

Sea buckthorn berries contain many bioactive compounds that have anticancer properties. To investigate whether the antiproliferative effects could be associated with the presence of certain compounds, a sequential extraction was performed. The extraction started with heptane followed by ethyl acetate, ethanol, and water. A second protocol using ethanol:water (1:1) was also used. The contents of the extracts were determined and their effects on cell proliferation were investigated in both Caco-2 and Hep G2 cells. The ethyl acetate fraction was exclusively found to contain high levels of ursolic acid, together with low amounts of phenolics. The ethanol:water extracts contained high levels of phenolic compounds and proanthyocyanidin, but little ursolic acid. When the antiproliferative effects were examined, the strongest inhibitory effect was found in the ethyl acetate extract for the Caco-2 cells and in the ethanol:water extract for the Hep G2 cells. The antiproliferative effects were in both cases dose-dependent and were in the case of the ethyl acetate extract associated with an increase in apoptosis. The results obtained show that the choice of extraction solvent is of considerable importance and that ursolic acid might be more important than the polyphenols in inhibiting the cancer cell proliferation.     

PRODUCTION OF NICOTINIC ACID BY BAKER'S YEAST GROWING IN NITROGEN-RICH AND NITROGEN-POOR MEDIA

The biosynthesis of nicotinic acid by baker's yeast was investigated in laboratory-scale aerobic batch cultivation in nitrogen-rich and nitrogen-poor nutrient solutions. Biosynthesis, which occurred parallel with yeast growth, was vigorous during the exponential growth phase and almost ceased during the retardation phase. The amount of nicotinic acid synthesized per batch was dependent on the nitrogen content of the solution. When a small inoculation of seed yeast was used, the amount of nicotinic acid synthesized per unit weight of yeast formed and the nicotinic acid content of the yeast did not depend on the nitrogen concentration of the nutrient solution. With a large inoculum, both the amount of nicotinic acid synthesized per unit weight of yeast produced and the nicotinic acid concentration of the yeast decreased with the nitrogen concentration of the nutrient solution. Calculated as μg. per g. of protein formed, the amount of nicotinic acid synthesized and the nicotinic acid concentration in the yeast were higher in the nitrogen-poor medium than in the nitrogen-rich medium when a small inoculum was used, but lower when large amounts of seed yeast were used.     

Fe2O3–TiO2 Nano‐heterostructure Photoanodes for Highly Efficient Solar Water Oxidation

Harnessing solar energy for the production of clean hydrogen by photo­electrochemical water splitting represents a very attractive, but challenging approach for sustainable energy generation. In this regard, the fabrication of Fe₂O₃–TiO₂ photoanodes is reported, showing attractive performances [≈2.0 mA cm⁻² at 1.23 V vs. the reversible hydrogen electrode in 1 M NaOH] under simulated one‐sun illumination. This goal, corresponding to a tenfold photoactivity enhancement with respect to bare Fe₂O₃, is achieved by atomic layer deposition of TiO₂ over hematite (α‐Fe₂O₃) nanostructures fabricated by plasma enhanced‐chemical vapor deposition and final annealing at 650 °C. The adopted approach enables an intimate Fe₂O₃–TiO₂ coupling, resulting in an electronic interplay at the Fe₂O₃/TiO₂ interface. The reasons for the photocurrent enhancement determined by TiO₂ overlayers with increasing thickness are unraveled by a detailed chemico‐physical investigation, as well as by the study of photo­generated charge carrier dynamics. Transient absorption spectroscopy shows that the increased photoelectrochemical response of heterostructured photoanodes compared to bare hematite is due to an enhanced separation of photogenerated charge carriers and more favorable hole dynamics for water oxidation. The stable responses obtained even in simulated seawater provides a feasible route in view of the eventual large‐scale generation of renewable energy.     

Synthesis of ZnO tetrapods for flexible and transparent UV sensors

ZnO tetrapods (ZnO-Ts) were synthesized in a vertical flow reactor by gas phase oxidation of Zn vapor in an air atmosphere. The morphology of the product was varied from nearly spherical nanoparticles to ZnO-Ts, together with the partial pressure of Zn and reaction temperature. MgO introduced during synthesis, increased the band gap, the optical transparency in the visible range, and also changed the ZnO-T structure. Fabricated flexible transparent UV sensors showed a 45-fold current increase under UV irradiation with an intensity of 30 μW cm(-2) at a wavelength of 365 nm and response time of 0.9 s.     

Synthesis of nitrogen-functionalized polyolefins with metallocene/methylaluminoxane catalysts

Summary Thirteen differently substituted long-chain amide- and amine-functional alkenes were synthesised and used as comonomers in zirconocene/methylaluminoxane-catalysed copolymerizations with ethylene and propylene. Characterization of the prepared copolymers showed the formation of functionalized copolymers with isolated comonomer units. The incorporation level of the comonomers ranged from 0.24 to 1.3 mol % with ethylene and from 0.04 to 0.96 mol % with propylene. The molar masses of the copolymers were lower than those of the corresponding homopolymers. End group analysis of the copolymers by NMR suggested that the dominant chain termination mechanism was chain transfer to aluminium. Received: 8 December 2000/Accepted: 12 February 2001     

Great differences in the ways of implementing the new EIA Directive – the offerings of the EIALAW 2018 conference

On the 23 March 2018, the most recent developments of the environmental impact assessment (EIA) law were examined by experts in Helsinki. The main theme of the conference was the comparison of the implementation experiences of various countries concerning the reformed EU EIA Directive. The European EIA debate was reflected against experiences in Canada. This paper examines the key points of the conference presentations and the lessons of the event.     

Photon‐Pair Generation with a 100 nm Thick Carbon Nanotube Film

Nonlinear optics based on bulk materials is the current technique of choice for quantum‐state generation and information processing. Scaling of nonlinear optical quantum devices is of significant interest to enable quantum devices with high performance. However, it is challenging to scale the nonlinear optical devices down to the nanoscale dimension due to relatively small nonlinear optical response of traditional bulk materials. Here, correlated photon pairs are generated in the nanometer scale using a nonlinear optical device for the first time. The approach uses spontaneous four‐wave mixing in a carbon nanotube film with extremely large Kerr‐nonlinearity (≈100 000 times larger than that of the widely used silica), which is achieved through careful control of the tube diameter during the carbon nanotube growth. Photon pairs with a coincidence to accidental ratio of 18 at the telecom wavelength of 1.5 µm are generated at room temperature in a ≈100 nm thick carbon nanotube film device, i.e., 1000 times thinner than the smallest existing devices. These results are promising for future integrated nonlinear quantum devices (e.g., quantum emission and processing devices).