Surface reactions of bioactive glasses in buffered solutions

In vitro bioactivity of glasses is usually measured in buffered solutions whereby a formation of a hydroxyapatite layer on the surface is taken as an indication of the bioactivity. In this work we compare the layer formation on three glasses in simulated body fluid, Tris buffer solution, sodium phosphate buffered saline and osteoblast medium. Two of the glasses are known bioactive glasses, 45S5 (45 wt.% SiO₂) and S53P4 (53 wt.% SiO₂), while the third is an experimental composition with a higher silica content (68 wt.% SiO₂). Plates of the glasses were immersed in the solutions at 37 °C for different times up to two weeks. The results showed clear differences between the layer developments on the three glasses in the different solutions. The results indicated that the relative order of the reactivity depended on the solution. Thus, results gained in different solutions for different glasses cannot be directly compared.     

Impacts of distributed photovoltaics on network voltages: Stochastic simulations of three Swedish low-voltage distribution grids

The continuously increasing application of distributed photovoltaics (PV-DG) in residential areas around the world calls for detailed assessment of distribution grid impacts. Both photovoltaic generation and domestic electricity demand exhibit characteristic variations on short and long time scales and are to a large extent negatively correlated, especially at high latitudes. This paper presents a stochastic methodology for simulation of PV-DG impacts on low-voltage (LV) distribution grids, using detailed generation and demand models. The methodology is applied to case studies of power flow in three existing Swedish LV grids to determine load matching, voltage levels and network losses at different PV-DG penetration levels. All studied LV grids can handle significant amounts of PV-DG, up to the highest studied level of 5 kW_p PV per household. However, the benefits of PV-DG in terms of relative improvement of on-site reduction of demand, mitigated voltage drops and reduced losses were most significant at a penetration level of 1 kW_p PV per household.     

Roughened glass slides and a spectrophotometer for the detection of the wavelength-dependent refractive index of transparent liquids

We describe a method to determine the wavelength-dependent refractive index of liquids by measurement of light transmittance with a spectrophotometer. The method is based on using roughened glass slides with different a priori known refractive indices and immersing the slides into the transparent liquid with unknown refractive index. Using the dispersion data on the glass material it is possible to find the index match between the liquid and the glass slide, and hence the refractive index of the liquid.     

Energy-efficient neighbor discovery protocol for mobile wireless sensor networks

Low energy consumption is a critical design requirement for most wireless sensor network (WSN) applications. Due to minimal transmission power levels, time-varying environmental factors and mobility of nodes, network neighborhood changes frequently. In these conditions, the most critical issue for energy is to minimize the transactions and time consumed for neighbor discovery operations. In this paper, we present an energy-efficient neighbor discovery protocol targeted at synchronized low duty-cycle medium access control (MAC) schemes such as IEEE 802.15.4 and S-MAC. The protocol effectively reduces the need for costly network scans by proactively distributing node schedule information in MAC protocol beacons and by using this information for establishing new communication links. Energy consumption is further reduced by optimizing the beacon transmission rate. The protocol is validated by performance analysis and experimental measurements with physical WSN prototypes. Experimental results show that the protocol can reduce node energy consumption up to 80% at 1–3 m/s node mobility.     

Note — Preliminary Applications of Response Surface Modelling to the Evaluation of Optimal Growth Conditions for Beer‐spoiling Pediococcus damnosus

Beer‐spoiling lactic acid bacteria (LAB) belong to the most harmful contaminants in the brewing industry and various rapid molecular detection methods have been introduced for the detection of these organisms. However, the enrichment cultivation steps needed prior to detection by molecular methods can extend the duration of the analytical procedure by up to several days. The use of brewery‐specific enrichment cultivation media has been recommended due to the large variety within the group of LAB, as well as differences in the microbes encountered at the breweries. In contrast to using a general medium that may support only the growth of some LAB, the combination of several media could allow detection of all relevant LAB. The aim of the present study was to show the effects of shifts in the cultivation conditions and media on the growth of beer‐spoiling LAB using one of the most frequently encountered species, Pediococcus damnosus, as an example. Based on the variable analysis, significant factors could be recognized and their effects on lag‐times and growth rates were compared by means of response surface modelling.     

Design of integrated 1.6 GHz, 2 W tuned RF power amplifier

This paper describes the design of an integrated tuned power amplifier specified to operate at Inmarsat satellite uplink frequencies from 1626.5 to 1660.5 MHz. The basic topology of the amplifier lies on the parallel tuned inverse class E amplifier that is modified by placing the DC-blocking capacitor into a new position and by adjusting the size of the capacitor to improve stability below the desired band. Further, the new positioning reduces losses between drain and load. The high currents flowing in the circuit made it necessary to use wide inductor width and high-Q finger capacitors in the on-chip resonator. The amplifier was implemented as a Gallium Arsenide (GaAs) integrated circuit (IC) that delivered 2 W of output power while the drain efficiency was ca. 56%. Measurements included source and load pulls to further improve the performance of the amplifier and to investigate the stability at small input drive levels.     

Indirect energy input of agricultural machinery in bioenergy production

Sustainability of bioenergy products should be evaluated by means of an energy analysis that takes into account all relevant direct and indirect energy inputs. Direct energy input is viewed as the major energy consuming factor, and is quite easy to measure. Indirect energy input, however, has received relatively scant attention, so it is likely to be insufficiently analysed and possibly underestimated. This paper reviews the data available and suggests the type of research that would be needed to get a better understanding of the indirect energy input. The analysis addresses questions about the use of energy to produce and maintain agricultural machinery, the allocation of energy to different bioenergy products, and the real use and lifetime of machinery.     

URTHER DEVELOPMENT OF A COMPUTER PROGRAM SIMULATING HEAT PIPE FUNCTIONING IN CONDEBELT PAPER DRYING

ABSTRACT

A previously developed computer program for depicting the heat and mass transfer behavior of heat pipe conduits, slightly open to a large ambient at their far ends, inside moist paper webs is developed further. The addition consists of accounting for the thermal dynamics of a hot metal slab from which the latent heat of evaporation corresponding to vapor generation in the hot end of the heat pipe is drawn. Values are used for the input parameters representing as closely as possible an approximately 40 % dry (by total weight) printing paper sheet being suddenly pressed against a hot steel or iron slab at l50°C or 200°C. These are conditions that could occur in Condebelt drying. Temperature distributions in the metal and inside the web, as well as the pressure distribution inside the web, are determined as functions of the distance from the hot surface and time. Important parameters are the initial metal and web temperatures, the interface Biot number, the structural geometry of the web, and the metal Fourier number. It is shown that there is a S to 25°C metal surface temperature drop in the first 100 μs after contact with the web. This can be significant in reducing possible web surface damage.     

Quantification of metabolites from single-voxelin vivo 1H NMR data of normal human brain by means of time-domain data analysis

We present here a combination of time-domain signal analysis procedures for quantification of human brainin vivo ¹H NMR spectroscopy (MRS) data. The method is based on a separate removal of a residual water resonance followed by a frequency-selective time-domain line-shape fitting analysis of metabolite signals. Calculation of absolute metabolite concentrations was based on the internal water concentration as a reference. The estimated average metabolite concentrations acquired from six regions of normal human brain with a single-voxel spin-echo technique for theN-acetylaspartate, creatine, and choline-containing compounds were 11.4±1.0,6.5±0.5, and 1.7±0.2 mmol kg^–1 wet weight, respectively. The time-domain analyses ofin vivo ¹H MRS data from different brain regions with their specific characteristics demonstrate a case in which the use of frequency-domain methods pose serious difficulties.