Prevalence of pathological Internet use among university students and correlations with self-esteem, the general health questionnaire (GHQ), and disinhibition

Over the last few years, there has been increased interest in the addictive potential of the Internet. The current study was an attempt to replicate common findings in the literature and provide more evidence for the existence of Internet addiction among students—a population considered to be especially vulnerable. A total of 371 British students responded to the questionnaire, which included the Pathological Internet Use (PIU) scale, the General Health Questionnaire (GHQ-12), a self-esteem scale, and two measures of disinhibition. Results showed that 18.3% of the sample were considered to be pathological Internet users, whose excessive use of the Internet was causing academic, social, and interpersonal problems. Other results showed that pathological Internet users had lower self-esteem and were more socially disinhibited. However, there was no significant difference in GHQ scores. These results are discussed in relation to the methodological shortcomings of research in the area as a whole

Thermal and moisture flux in soft fibreboards

The thermal conductivity of several wet and dry processed industrial soft fibreboards was determined at temperatures between10°C and30°C. Additionally, the thermal conductivity was tested relative to the moisture content ranging from an oven-dry sample to a moisture content of 85% relative humidity. Furthermore, the water vapour diffusion was investigated to determine the resistance factor and the diffusion coefficient under ‘dry cup' and ‘wet cup' conditions and the sorptions were tested by means of the sorption isotherms. The thermal conductivity increases with increasing temperature at about 0.45% per Kelvin and with increasing moisture at about 0.17×10−2W/mK per percent volumetric moisture content. Furthermore, the thermal conductivity depends on the manufacture (dry or wet process) and is influenced by density. The water vapour resistance factor increases and the diffusion coefficient decreases with increasing density. Both factors decrease with increasing moisture content and they are dependant on board thickness, composition and manufacturing. The sorption isotherm is similar to solid wood below about 80% relative humidity but strongly increases for soft fibreboards with binding fibres and additives of ammonium phosphate or sodium borate and boric acid when above 80% relative humidit

Untersuchungen zur Bestimmung der Poissonschen Konstanten an Fichtenholz

Zusammenfassung: An Fichtenholz wurden mittels inkrementaler Wegaufnehmer die E-Moduln in den drei Hauptschnittrichtungen (längs, radial, tangential) und die sechs Poissonschen Konstanten nach Klimatisierung im Normalklima bestimmt. Das Verhältnis der E-Moduln ET:ER:EL wurde mit 1:2,43:25,4 ermittelt. Es wurden folgende Poissonsche Konstanten bestimmt: μRL= 0,022, μTL=0,015, μLR=0,376, μLT= 0,420, μTR=0,335, μRT=0,64

Thermal conductivity and water vapour transmission properties of wood-based materials

For several wood-based materials (plywood, OSB, melamine faced board (MFB), particle board and fibre board), the thermal conductivity was determined as afunction of the temperature (ranging between 10 and 30°C) and also the moisture content (from an oven-dry sample up to amoisture content at 80% RH). Furthermore, the water vapour resistance factor of these materials as well as of the coating (at MFB) and the diffusion coefficient were determined under dry cup (performance at low humidity dominated by vapour diffusion) and wet cup (performance at high humidity with liquid water and vapour transport) conditions. Thermal conductivity increases with rising temperature, moisture content and density. Moreover, aclear decrease of thermal conductivity was found with decreasing particle size at the same density level, from solid wood over plywood and particle board to fibre board. The water vapour resistance factor of the wood-based materials increases with rising density and decreases with increasing moisture content. An influence of the particle and fibre board thickness was also revealed. In contrast to the remaining materials, an increase of the water vapour resistance factor with increasing moisture content was measured for the coating. The diffusion coefficient decreases with rising density and moisture conten

Porosity and pore size distribution of different wood types asdetermined by mercury intrusion porosimetry

In this work, densities and porosity parameters are determined on domestic and overseas soft- and hardwoods by application of pycnometric methods and mercury intrusion porosimetry (MIP). Great variability was found in bulk density, porosity and in the specific surface area. According to the pore size distribution, four pore size classes could be distinguished: macropores (radius 58-2μm and 2-0.5μm), mesopores (500-80nm), and micropores (80-1.8nm). The pore size distribution can vary even in the case of comparable pore volumes. The hardwoods, particularly the European diffuse-porous ones, show a higher amount of micropores, which represent the microvoids or cell wall capillaries. Ahigh cumulative pore volume can also be the result of a high content of micropores with poorer accessibility. The value of the total specific surface area from MIP measurements is, generally, below those values obtained by the water vapour adsorption technique. These results can provide information for further investigations on the sorption behaviour and the fluid intake as technological characteristics in industrial processes of impregnation and penetration of coating materials or adhesive

The influence of compression failure on the bending, impact bending and tensile strength of spruce wood and the evaluation of non-destructive methods for early detection

Bending strength (MOR) and bending Young's modulus (MOE) according to DIN 52186 and MOE calculated on the basis of eigenfrequency and sound velocity were tested on small clear wood specimens of Norway spruce wood with and without compression failure. One group of specimens was climatised in a normal climate of 20°C and 65% relative humidity, while the other group was stored for one month under water before testing. The MOR of specimens with compression failure decreased about 20% on average (normal climate and wet) compared with the specimens without compression failure. The MOE of the specimens with compression failure was reduced only minimally compared with the specimens without compression failure stored in a normal climate, but very distinct differences (more then 30%) were found under wet conditions. The MOE of the specimens with compression failure calculated on the basis of eigenfrequency and sound velocity were not reduced or only minimally compared with the specimens without compression failure. It is therefore not possible to detect compression failure and to determine reduction in MOR using eigenfrequency or sound velocity. In addition, impact bending (DIN 52189), tensile strength and tensile MOE (DIN 52188) were tested on small clear wood specimens of Norway spruce wood with and without compression failure. The specimens with compression failure revealed an average reduction in impact strength of about 40% and an average reduction in tensile strength of about 20% compared with the specimens without compression failure, whereas tensile MOE of the specimens with compression failure was not reduced compared with the specimens without compression failure. The detection of compression failure by computer tomography (CT) was tested on Norway spruce wood boards 10cm in thickness, and detection by optical scanner was tested on planed Norway spruce wood boards. CT recognised large compression failures easily, whereas the scanner was not able to detect the

Moisture-dependent, viscoelastic creep of European beech wood in longitudinal direction

In the present study, the pure viscoelastic behaviour of European beech wood is analysed in the longitudinal direction at three different moisture contents. The moisture-dependent creep compliance is identified using a four-point bending test device. The viscoelastic behaviour is ascertained to be linear with moisture content and quantified by means of a Kelvin-Voigt model approac