Detachment fronts and the onset of dynamic friction

The dynamics of friction have been studied for hundreds of years, yet many aspects of these everyday processes are not understood. One such aspect is the onset of frictional motion (slip). First described more than 200 years ago as the transition from static to dynamic friction, the onset of slip is central to fields as diverse as physics, tribology, mechanics of earthquakes and fracture. Here we show that the onset of frictional slip is governed by three different types of coherent crack-like fronts: these are observed by real-time visualization of the net contact area that forms the interface separating two blocks of like material. Two of these fronts, which propagate at subsonic and intersonic velocities, have been the subject of intensive recent interest. We show that a third type of front, which propagates an order of magnitude more slowly, is the dominant mechanism for the rupture of the interface. No overall motion (sliding) of the blocks occurs until either of the slower two fronts traverses the entire interface.     

Inverse Perturbation Method for Inverse Eigenvalue Problem Based on Finite Element Analysis

An inverse perturbation method is described for solving the general inverse eigenvalne problem. By taking the analysis of the rotor system as example based upon FEM,the new inverse perturbation method for structural design with specified low-order natural freqneneies or frequency constraint bands is detailed as well as its complete theoretical basis. Moreover, formulations to calculate the inverse perturbation parameter ε and method to select thecorresponding ε‘s value properly are also proposed. Theproposed method is characterized in reducing frequencyanalysis and suitable for large and small structural changesalike. Finally, several different numerical examples forinverse eigenvalue problem are discussed to illustrate themethod, which show that this inverse perturbation methotis general and can be applied to other type of structure orelement.     

Effect of rearing method on chukar survival

Survival of adult chukar-imprinted, game farm (sibling/human-imprinted), and wild chudkars was compared in three releases (two sites). Combined results indicate similar ( P P < .05) for game farm chukars. With early behavioral conditioning, some potential exists for using captive-reared chukars to establish new populations.     

Density, distribution, and habitat of Flammulated Owls in Idaho

From 1990 to 1992 we surveyed for Flammulated Owls ( Otus flammeolus ) in 3 areas in Idaho: Salmon National Forest (SNF), Payette National Forest and adjacent Hells Canyon National Recreation Area (PNF-HCNRA), and Nez Perce National Forest (NPNF). We also collected and summarized information on all historic and modern records of Flammulated Owls in Idaho. Flammulated Owls were detected on 65% of 68 routes (2-16 km in length) surveyed at densities ranging from 0.04 to 1.25 singing males/40 ha. Owls were detected on survey routes as early as 10 May and as late as 23 July. Mean percent canopy cover estimated at owl locations on the PNF-HCNRA and NPNF study sites ranged from 52% to 64%, while shrub cover ranged from 16% to 21% and ground cover was 39% to 49%. Our surveys and summary of distributional records indicated that Flammulated Owls occur throughout the montane forests of Idaho in old or mature stands of open ponderosa pine ( Pinus ponderosa ), Douglas-fir ( Pseudotsuga menziesii ), and stands co-dominated by those 2 species. Fire suppression and timber harvest activity in ponderosa pine forests represent 2 main threats to the species' future security in Idaho. More research on the effects of various silvicultural treatments on Flammulated Owl populations is warranted.     

Radio transmitter attachment for chukars

Thirty-seven chukars ( Alectoris chukar ), fitted with conventional poncho-type radio transmitters, were released on Antelope Island in Utah's Great Salt Lake. Twenty-seven removed their radios, averaging three days after release. The remaining 10 died from predation (average 15 days). Twenty-two chukars with pleated and six with harness ponchos were then released. Five of the pleated ponchos were removed (average four days), and 17 resulted in mortality (average two days). All six harness poncho-equipped birds were dead the following day. A consequential laboratory study comparing various attachment methods (conventional, pleated, harness, and ""irreversible"" flange poncho vs. bellystrap and wingstrap backpack) favored the wingstrap backpack. The effectiveness of 30 conventional ponchos and 30 wingstrap backpacks was compared on game farm chukars. Twenty-nine removed their ponchos within one day. One remained attached throughout the 30-day trial. All of the wingstrap backpacks remained attached with no apparent problems.     

The oak leaf roller (Archips semiferanus Walker) sex pheromone complex: Field and laboratory evaluation of requisite behavioral stimuli

Zusammenfassung Die früher als Bestandteile der von Abdominalextrakten des weiblichen Eichenblattrollers,Archips semiferanus Walker, festgestellten 21 Isomeren von Tetradecenyl-Acetat wurden mit der Elektroantennogram-(EAG) und der Fallenfang-Methode auf ihre Wirkung bei Männchen vonA. semiferanus geprüft. Während alle 21 Isomere sich als EAG-aktiv erwiesen, vermochten nur 17 Männchen anzulocken. Aktivitätsvergleiche der Isomeren haben gezeigt, dass zwischen den Resultaten der beiden Test-Methoden nur eine geringe Beziehung existiert.

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The Pennsylvania State University, Department of Entomology and Pesticide Research Laboratory, University Park, Penna 16802, USA.

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Note added in proof: For a possible explanation of these results seeL. B. Hendry, J. K. Wichmann, D. M. Hindenlang, R. O. Mumma andM. E. Anderson, Science188, 59 (1975).