The effect of low-intensity pulsed ultrasound on bone healing in SR-PLLA rod fixed experimental distal femur osteotomy in rat

The effects of low-intensity pulsed ultrasound (30 mW/cm²) were investigated in experimental cancellous bone fracture healing in bioabsorbable self-reinforced poly-l-lactide (SR-PLLA) rod fixed distal femur osteotomy in rats. A transverse transcondylar osteotomy was fixed with one SR-PLLA rod in 32 male Wistar rats of the age of 20 weeks. Half of the rats had a daily 20-min ultrasound exposure for three weeks. The follow-up times were three, six, and 12 weeks. Radiographical, histological, microradiographical, oxytetracycline labeling, and histomorphometrical analyses were performed. No foreign-body reactions were noted. The biocompatibility of SR-PLLA and ultrasound was found to be good. In the radiological and histological assessments there was a slight tendency for enhanced healing in the ultrasound group at three weeks, but at six and 12 weeks no differences were observed. The histomorphometrical and oxytetracycline labeling analyses showed that ultrasound exposure had no significant effects on bone healing. The present study shows that there were no obvious findings to support the hypothesis that low-intensity pulsed ultrasound enhances bone healing in self-reinforced poly-l-lactide (SR-PLLA) rod fixed experimental metaphyseal distal femur osteotomy in rats. The observed good biocompatibility provides a safe starting-point for clinical trials on bioabsorbable fixation combined with low-intensity ultrasound.     

Characterization of porous glass fiber-reinforced composite (FRC) implant structures: porosity and mechanical properties

The aim of this study was to characterize the microstructure and mechanical properties of porous fiber-reinforced composites (FRC). Implants made of the FRC structures are intended for cranial applications. The FRC specimens were prepared by impregnating E-glass fiber sheet with non-resorbable bifunctional bis-phenyl glycidyl dimethacrylate and triethylene glycol dimethacrylate resin matrix. Four groups of porous FRC specimens were prepared with a different amount of resin matrix. Control group contained specimens of fibers, which were bound together with sizing only. Microstructure of the specimens was analyzed using a micro computed tomography (micro-CT) based method. Mechanical properties of the specimens were measured with a tensile test. The amount of resin matrix in the specimens had an effect on the microstructure. Total porosity was 59.5 % (median) in the group with the lowest resin content and 11.2 % (median) in the group with the highest resin content. In control group, total porosity was 94.2 % (median). Correlations with resin content were obtained for all micro-CT based parameters except TbPf. The tensile strength of the composites was 21.3 MPa (median) in the group with the highest resin content and 43.4 MPa (median) in the group with the highest resin content. The tensile strength in control group was 18.9 MPa (median). There were strong correlations between the tensile strength of the specimens and most of the micro-CT based parameters. This experiment suggests that porous FRC structures may have the potential for use in implants for cranial bone reconstructions, provided further relevant in vitro and in vivo tests are performed.     

A simple method to estimate the maximum nontrivial correlation of some sets of sequences

Code division multiple access and many other applications require large families of sequences with good correlation properties. In this paper we show that the moduli of certain character sums can be estimated in an easy way by using a method of Sidelnikov. These results yield a simple method to estimate the maximum nontrivial correlations of several well-known sets of sequences.Supported by the Technology Development Center of Finland, Elektrobit Company, Finnish Air Force, Nokia Mobile Phones Inc. and Nokia Cellular Systems Inc.Partially supported by the Academy of Finland     

Lightweight porous silica foams with extreme-low dielectric permittivity and loss for future 6G wireless communication technologies

In the next generation wireless communication systems operating at near terahertz frequencies, dielectric substrates with the lowest possible permittivity and loss factor are becoming essential. In this work, highly porous (98.9% ± 0.1%) and lightweight silica foams (0.025 ± 0.005 g/cm3), that have extremely low relative permittivity (εr = 1.018 ± 0.003 at 300 GHz) and corresponding loss factor (tan δ< 3 × 10?4 at 300 GHz) are synthetized by a template-assisted sol-gel method. After dip-coating the slabs of foams with a thin film of cellulose nanofibers, sufficiently smooth surfaces are obtained, on which it is convenient to deposit electrically conductive planar thin films of metals important for applications in electronics and telecommunication devices. Here, micropatterns of Ag thin films are sputtered on the substrates through a shadow mask to demonstrate double split-ring resonator metamaterial structures as radio frequency filters operating in the sub-THz band.     

This is not classified: everyday information seeking and encountering in smart urban spaces

We present a multipronged comparative study of citizens’ self-proclaimed information needs and actual information seeking behavior in smart urban spaces. We first conducted several user studies to identify the types of information services that citizens believed to be useful in urban setting utilizing methods ranging from contextual inquiry with lo-fi prototypes to “card sorting” exercise with a separate set of participants, and finally to implementing selected services. We then made a sizeable constructive intervention into the urban space by deploying in a city center 12 large, interactive public displays called “hotspots” to offer a wide range of previously identified information services. We collected comprehensive qualitative and quantitative data on the usage of the hotspots and their services by the general public during 13 months. Our study reveals discrepancies between a priori and a posteriori information seeking strategies extracted from the self-proclaimed information needs and the actual usage of the hotspots.     

Pleasantness in relation to difference threshold of NaCl in mashed potato

Difference threshold values for sodium chloride were determined to investigate to what extent just noticeable differences (jnd) affect preferences. Samples were unflavored, garlic-flavored and pepper-flavored mashed potato. At the reference concentration of 0.60% NaCl, the jnd value for unflavored and garlic-flavored samples was 0.07% NaCl, and for the pepper-flavored sample, 0.08% NaCl. The pleasantness of seven samples between ±9 jnds from the reference (0.60% NaCl), was rated on a graphic scale ranging from less pleasant to more pleasant (reference at the midpoint). Forty-one subjects participated in the test. For unflavored and garlic-flavored mashed potato, concentrations below 0.36% NaCl and above 0.82% NaCl, and for pepper-flavored, below 0.31% NaCl and above 0.83% NaCl, were required to obtain statistically significant differences in hedonic responses compared to the reference concentration.     

Factors affecting the development of biodeterioration in wooden constructions

Water leakages are the general cause of moisture stress exceeding the moisture tolerances of constructions. Moisture stress causes biodeterioration (mould, rot and insect damage) in wooden constructions. The degree of damage is affected by the severity and duration of moisture exposure and temperature, together with the sensitivity of the wooden construction to environmental stress. The growth of mould fungi on wooden materials depends mainly on the air humidity, temperature and the surface quality of wood. Long term humidity conditions above a relative humidity (RH) of 80% are a risk for mould growth in pine and spruce sapwood when the temperature is between +5°C and +50°C. Between −5°C and +5°C the growth of mould fungi is slow, and possible only when the relative humidity is above 90%. High nutrient content of the surface can stimulate the mould growth. In fluctuating humidity conditions, the severity and cumulative time of conditions suitable for mould growth are critical factors for the development of mould fungi in constructions. Humidity conditions must be above RH 95% (around the fibre saturation point of wood, wood moisture content about 25–30%) for the spore germination and mycelium activation of brown rot fungi. Under unsuitable conditions, fungi are inactive, but they can become active quickly under suitable conditions. The degree of decay in wood depends on the total time the decay organism is active. The natural durability of wood varies with the environmental conditions, wood characteristics (wood species, sapwood or heartwood, etc.) and the decay organisms. The service time of wooden materials can be extended by modification of the wood.

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Resume Les eaux d'infiltration sont, en général, responsables de la contrainte due à l'humidité dépassant le seuil de tolérance des constructions en bois. Le degré de détérioration est affecté par la sévérité et la durée de l'exposition à l'humidité et la température, ainsi que par la sensibilité de la construction en bois à la contrainte ambiante. Le développment de moisissures sur des matériaux en bois dépend surtout de l'humidité de l'air, de la température et de la qualité de la surface. Dans des conditions d'humidité à long terme supérieure à une humidité relative de 80%, des moisissures risquent de se développer dans le pin et l'aubier de sapin quand la température se situe entre +5°C et +50°C. Entre −5°C et +5°C, la croissance de champignons est lente et possible seulement si l'humidité relative dépasse 90%. Une teneur importante d'éléments nutritifs à la surface peut stimuler le développement de moisissures. Dans des conditions d'humidité fluctuantes, la réunion et l'accumulation dans le temps de conditions favorables à la croissance de champignons constitute un facteur critique de développement de moisissures. Les conditions d'humidité doivent dépasser une humidité relative de 95% (autour du point de saturation de la fibre, une teneur en humidité d'environ 25 à 30%) pour la germination du spore et l'activation du mycélium de champignons brun rouge. Dans des conditions défavorables, les champignons sont inactifs mais ils peuvent devenir rapidement actifs dans des conditions favorables. Le degré de détérioration du bois dépend de la vie active totale de l'organisme de décomposition. La durabilité naturelle du bois varie avec les conditions ambiantes, les caractéristiques du bois (espèce, aubier ou coeur) et les organismes de décomposition. La durée de vie du bois peut être allongée en le traitant.