Dynamic behavior of wood strip over elastic underlayment composite flooring subjected to light impact loads

Summary The dynamic behavior of composites consisting of wood flooring strips placed over rubber sheeting was investigated. A light impact load was applied to the center of the strips and impact force, contact duration and contact area were measured. The energy transfer from the impacting mass to the composite was estimated by measuring the restitution coefficient. Frequency analysis was conducted in order to examine the vibration characteristics of the composites.This study was carried out at the Forest Products Laboratory, University of California at Berkeley while the first author was a visiting scholar supported by the Science and Technology Agency, Japan     

Durability evaluation of particleboards by accelerated aging tests

Summary Specimens of four commercially produced particleboards were exposed to various accelerated aging treatments: 1) 6-cycle ASTM D-1037 exposure, 2) 6-cycle WCAMA exposure, 3) BS 5669 test, 4) cyclic soak-dry test, and 5) cyclic boil-dry test. Thickness swelling (TS) and internal bond strength (IB) were measured after each step of each cycle. Phenol and phenol (face)/isocyanate (core)bonded boards are more durable than urea and melamine urea bonded boards. The effect of treatment 1) is most severe on TS and IB retention, followed in order by treatments 2), 5), 4) and 3). When the value of springback reached about 35%, IB became equal to zero.     

Der Einfluß von Außenfaktoren auf das Wanderverhalten der Deutschen Schabe,Blattella germanica (L.) (Blattodea,Blattellidae), in einer Mülldeponie

Mass propagation of the German cockroach in refuse tips may result in an increased emigration of this species into the surrounding area of the tip and thus in a heavy infestation of nearby buildings. Therefore, knowledges about the migration behavior are important when refuse tips are managed or projected. The influence of several environmental factors (as sun, day time, wind, temperature, season, light intensity) on the running behavior of the German cockroach was investigated under outdoor conditions. The most important results are as follows:

1. The reaction of young larvae (especially of L₁ and L₂) on the investigated factors differs considerably from that of older larvae and adults. As the young larvae do not emigrate, their behavior can be neglected in respect to the questions discussed here.
2. During sunshine, the position of the sun is primarily responsible for the direction of the migration. The highest percentage of the cockroaches walks directly towards the sun or a few grade right and left from the sun. When the sun is covered by clouds, the variation in the running direction is very high and many cockroaches migrate even into the direction opposite to the sun.
3. From morning to evening, the main migration direction is shifting from east to west, following the position of the sun.
4. Wind direction (at speeds of less than 5 m/sec.) and temperature (within the activity range of the cockroaches from approximately 18 to more than 30°C) have no recognizable influence upon the migration direction.
5. The clearest reaction of the running cockroaches towards the position of the sun was noticed during the main migration-time in the year (June and July).
6. The results of these investigations confirm former findings made in the field during a mass emigration of the German cockroach from a refuse tip.

     

On the distribution of tree growth stresses

Summary A plane strain pure bending elastic model is used to predict stress states in a cylindrically orthotropic cylinder due to asymmetric strain distributions continously induced at the periphery. A general solution for the stress states related to each component of the strain distribution expanded in a Fourier series is given. Details of solutions for eleven representative tree species are given. Also the change of curvature of a stem caused by a measured peripheral strain distribution is computed for a given period of growth.     

Kleiderläuse (Pediculus humanus Linnaeus, 1758) (Anoplura) im Soldatenalltag im Ersten Weltkrieg Zum Gedenken an Professor Dr. Albrecht Hase anläßlich seines 100. Geburtstages

A short review on infection of the army by body lice and on the development of lice control in the World War I is given principally regarding the work of late professor Dr.Albrecht Hase, the first military entomologist in Germany. Based on historical documents (postal cards, sentences our of letters, anedotes, drawings) is described, how the soldiers have met with lice and their control.     

Occurrence of anholocylic strains of pest aphids on winter barley and wheat in South Moravia,Czech Republic

Anholocyclic strains ofSitobion avenae (F.),Rhopalosiphum padi (L.) andRhopalosiphum maidis (Fitch) were detected on winter barley and wheat in autumn, 1995 in South Moravia, the Czech Republic. Anholocycly was proved by samples docummenting the species composition and population structure of aphids in 20 localities throughout the area. Natural enemy presence was also determined and the species are listed. Anholocycly established in the cereal aphids in the target area is discussed in relation to a similar evidence known from the north-west Europe and some parts of the Mediterranean.     

Bending strength adjustments for moisture content for structural lumber

Summary Effects of moisture content on bending strength and section capacity have been studied assuming that strength properties are linearly related to moisture content below the fiber saturation point. The models developed using the linear strength vs. moisture content relationships are compared with quadratic models developed earlier. The linear representation of strength variation with moisture content leads to predicted member bending capacity relationships which show that increases in member bending strength with moisture content will compensate for section property decreases at all bending strength property levels. Comparisons of bending strength and bending capacity models show that the two modelling approaches lead to similar predicted member performance. Simplified procedures are provided for adjusting member bending strength for moisture content which are suitable for materials properties codes or standards.     

Suitability of the Citrus Brown Mite,Eutetranychus orientalis (Acari, Tetranychidae) as prey for nine species of phytoseiid mites

Nine phytoseiid species were tested to evaluate their potential as predators ofEutetranychus orientalis (Klein).Typhlodromus atbiasae Porath and Swirski,Amblyseius barkeri (Hughes) andAmblyseius olivi Nasr and Abou-Awad had a shorter developmental period thanTyphlodromus transvalensis (Nesbitt).Typhlodromus athiasae andAmblyseius barkeri showed the highest oviposition rates.Amblyseius olivi showed a low rate of oviposition althoughTyphlodromus transvalensis has not able to lay any eggs. Immatures survival ofTyphlodromus talbii Athias Henriot,Typhlodromus balanites El-Badry,Amblyseius badryi. Yousef and El-Borolossy,Amblyseius cabonus (Schicha) andAmblyseius lindquisti Schuster and Pritchard were very low onEutetranychus orientalis and all failed to develop to adulthood.     

Sekrete und Delta-16-Steroide als Lockmittel für die Rötelmaus (Clethrionomys glareolus)

Zusammenfassung Lebendfallen, die Nestmaterial oder Ausscheidungen von Rötelmäusen enthielten, wurden im Freiland von Artgenossen signifikant häufiger besucht als nicht-kontaminierte Fallen. Die Untersuchungen wurden im Spätsommer und Herbst in den Jahren 1986 und 1987 in Forstkulturen durchgeführt. In den Monaten August bis Oktober wurden Fallen, die kontaminierte Einstreu von Artgenossen enthielten, bevorzugt, in den Monaten November und Dezember Fallen mit Nestgeruch.Von den beiden Verbindungen 16-(5-alpha)-androsten-3-on (Androsten-on) und 16-(5-alpha)-androsten-3-alpha-ol (Androsten-ol) wurde die letztere signifikant von der Rötelmaus bevorzugt.

---

Secretions and Delta-16-steroids as attractants for Bank Voles (Clethrionomys glareolus)

Bank Voles (Clethrionomys glareolus) preferred significantly live traps containing bedding or nesting material contaminated by conspecifics in comparision to clean traps (=control). The tests were conducted in forest cultivations in late summer and autumn of 1986 and 1987. In both years at the begin in August the traps contaminated with urin of conspecifics were most attractive. Females were significantly more frequently caught in traps contaminated by conspecific males and vice versa males visited preferably traps with bedding material of females. Later during October and November traps with nest odour were preferred by both sexes.It was assumed that derivatives of hormones could act as pheromones. Both compounds 16-(5-alpha)-androsten-3-one and 16-(5-alpha)-androsten-3-alpha-ol were tested in field plots. The latter was significantly preferred by Bank Voles but not by other species.

---

---

Mit 7 Abbildungen und einer Tabelle