Aspects of red squirrel (Tamiasciurus Hudsonicus) population ecology in interior Alaska

Thesis (M.S.) University of Alaska Fairbanks, 1969Red squirrel (Tamiasciurus hudsonicus preblei) population ecology was investigated in a field study conducted between 21 September 1967 and 30 October 1968 near College, Alaska. Population density on the 21 ha study area was one squirrel per 1.1 ha during the spring 1968 and one per 1.2 ha during the fall 1968. Territoriality appears to be somewhat relaxed during the spring, and there are non-territorial squirrels present at that time. Young of the year squirrels can be distinguished from adults, at least through October, according to the degree of closure of the epiphyses of the radius and ulna. Immature males can be distinguished from adults on the basis of testis weight during the fall. Immature squirrels constituted 57.1% of the population sample during the fall 1967 and 51.3% during the fall 1968. Males formed 66.7% of the sample of adults and 64.0% of the sample of immature squirrels. Males were not significantly heavier or larger than females. Mean tail length of immature squirrels exceeded that of adults. Fall molt commences for all red squirrels during late August and September. The spring molt commences for females during March, whereas males do not molt until May. Testes measurements and female reproductive condition indicate that there is a single annual reproductive season, from late February through April. Squirrels breed during their first spring at about 10 to 11 months of age. Estimated mean litter size was 4.20 based on embryo counts and 3.92 based on placental scars. The most frequent litter size was four

Effect of Original Layer Thicknesses on the Interface Bonding and Mechanical Properties of Ti-Al Laminate Composites

It is of great significance in high-temperature aeroengine applications for large-surface-area TiAl laminate composites to be fabricated into Ti-Al3Ti parts by plastic forming and subsequent vacuum hot pressing. Then the original layer thicknesses have an important influence on the interface bonding and mechanical properties of TiAl laminate composites, but only few reports about it have been published so far. In the present study, vacuum hot pressing was employed to fabricate TiAl laminate composites using Ti and Al foils of different thickness. The resulting interface bond and mechanical properties of TiAl laminate composites were then studied to determine the optimum sheet configuration and thickness. To further assess their formability and develop a forming limit diagram (FLD), 0.1/0.15 TiAl laminate composites were operated on bending and forming tests to provide guidance for subsequent plastic forming of complex geometries. The results indicated that hot pressed laminates composed of alternating 0.1 (Al) and 0.15 (Ti) mm thick sheets exhibited enhanced superior interface bonding and mechanical properties compared with 0.2/0.25 and 0.4/0.4 sheets. The 0.1/0.15 TiAl laminate composites had excellent bending characteristics and reasonable formability. Fabrication of a drawn cup further confirms the potential for hot pressed TiAl laminate composites to be fabricated into complex shapes

PF191012 Myszyniec - highest Orionid meteor ever recorded

On the night of Oct 18/19, 2012 at 00:23 UT a -14.7 mag Orionid fireball occurred over northeastern Poland. The precise orbit and atmospheric trajectory of the event is presented, based on the data collected by five video and one photographic Polish Fireball Network (PFN) stations. The beginning height of the meteor is 168.4 +\- 0.6 km which makes the PF191012 Myszyniec fireball the highest ever observed, well documented meteor not belonging to the Leonid shower. The ablation became the dominant source of light of the meteor at a height of around 115 km. The thermalization of sputtered particles is suggested to be the source of radiation above that value. The transition height of 115 km is 10-15 km below the transition heights derived for Leonids and it might suggest that the material of Leonids should be more fragile and have probably smaller bulk density than in case of Orionids.Comment: 5 pages, 5 figures, accpeted for publication in Astronomy & Astrophysic

Structure and magnetic properties of Fe–Nb–B amorphous/nanocrystalline alloys produced by compaction of mechanically alloyed powders

Mechanical alloying of Fe75Nb10B15 and Fe85Nb5B10 systems has been performed from an initial mixture of elemental powders. A bcc supersaturated solid solution is developed during milling for both alloys. However, Fe75Nb10B15 alloy also develops an amorphous phase, which amount increases with milling time. Milled powder samples were compacted at 7.7 GPa at different temperatures. Scanning electron microscopy images show that the presence of amorphous phase enhances the quality of compaction. Compaction at 823 K preserves both microstructure and magnetic properties of as-milled powders in both alloys. Compaction at 973 K affects mainly the crystalline fraction of the alloy with 10 at. % Nb. Compaction at 1273 K yields the formation of bcc Nb and fcc Fe23B6 phases, which magnetically harden the material

Crack path and fracture analysis in FSW of small diameter 6082-T6 aluminium tubes under tension-torsion loading

This paper reports part of the work done in a research project aimed at developing an optimised process to join 38. mm diameter tubes of 6082-T6 aluminium alloy using friction stir welding (FSW), and then to determine the fatigue performance under tension, torsion and tension-torsion loading conditions. The final outcome of the project is intended to be guidance for fatigue design of small diameter aluminium tubes joined by FSW, and this paper presents information on crack path and defects under the various loading conditions. Crack path analysis was performed using both low magnification stereo microscopy and scanning electron microscopy, in order to identify crack initiation sites, the direction of crack propagation and the interrelated influence of microstructure and weld geometry on the crack initiation path

Multiaxial Fatigue Assessment of Friction Stir Welded Tubular Joints of Al 6082-T6

The present paper addresses the problem of designing aluminium friction stir (FS) welded joints against multiaxial fatigue. After developing a bespoke FS welding technology suitable for joining aluminium tubes, some one hundred welded tubular specimens of Al 6082-T6 were tested under pure axial, pure torsional and biaxial tension-torsion loading. The influence was explored of two independent variables, namely the proportional or nonproportional nature of the biaxial loading and the effect of axial and torsional non-zero mean stresses. The experimental results were re-analysed using the Modified Wöhler Curve Method (MWCM), with this bi-parametrical critical plane approach being applied in terms of nominal stresses, notch stresses, and also the Point Method. The validation exercise carried out using these experimental data demonstrated that the MWCM is applicable to prediction of the fatigue lives for these FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands. The approach proposed in the present paper offers, for the first time, a complete solution to the problem of designing tubular FS welded joints against multiaxial fatigue loading

Strong Host-Feeding Preferences of the Vector Triatoma infestans Modified by Vector Density: Implications for the Epidemiology of Chagas Disease

Chagas disease is a complex zoonosis with more than 150 mammalian host species, nearly a dozen blood-sucking triatomine species as main vectors, and 9–11 million people infected with Trypanosoma cruzi (its causal agent) in the Americas. Triatoma infestans, a highly domesticated species and one of the main vectors, feeds more often on domestic animals than on humans in northern Argentina. The question of whether there are host-feeding preferences among dogs, cats, and chickens is crucial to estimating transmission risks and predicting the effects of control tactics targeting them. This article reports the first host choice experiments of triatomine bugs conducted in small huts under natural conditions. The results demonstrate that T. infestans consistently preferred dogs to chickens or cats, with host shifts occurring more frequently at higher vector densities. Combined with earlier findings showing that dogs have high infection rates, are highly infectious, and have high contact rates with humans and domestic bugs, our results reinforce the role of dogs as the key reservoirs of T. cruzi. The strong bug preference for dogs can be exploited to target dogs with topical lotions or insecticide-impregnated collars to turn them into baited lethal traps or use them as transmission or infestation sentinels