Angular motion of a PAH molecule in interstellar environment

Polycyclic aromatic hydrocarbon (PAH) molecules have recently been proposed as an important and hitherto undetected component of the Interstellar Medium (ISM). The theory was based on an explanation of the Unidentified IR Emission Bands by Leger et al. It has already led to a verified prediction on extended galactic and extragalactic emissions measured by IRAS, or by a recent balloon borne experiment. The physics that rules the motion of such molecules in the ISM was studied, taking into account their coupling with the ambient gas, the radiation field (absorption and emission) and the static magnetic field. This is important for many implications of the PAH theory such as the radio emission by these molecules or the expected polarization of their IR emission. A reflection nebulae is considered where the situation is rather well known. Every day life of a mean PAH molecule in such a region is as follows: every 3 hrs a UV photon is absorbed heating the molecule to a thousand degs; the temperature decay due to cooling by IR emission follows then within a few seconds. A collision with a molecule of gas occurs typically once a week, while an H atom is ejected or captured at the same rate. A typical cooling cycle after a heat impulse is given. The PAH molecules studied as representative of the family has typically 50 atoms, a radius of 4.5 A, is circular and has a molecular mass of M = 300; its permanent dipole moment is 3 Debye

Refuge Management: Committed to the Future

The Back Bay National Wildlife Refuge was established on June 6, 1938, ... as a refuge and breeding ground for migratory birds and other wildlife. During its first 30 years, the Refuge was managed similar to other areas of the National Wildlife Refuge System. Dikes were constructed, facilities were built, and wildlife management programs were initiated. In the late 1960\u27s, the emphasis of the area changed, as increasing numbers of beach oriented visitors, primarily using 4 wheel drive vehicles, began using the area. By 1971 public use reached 348,000 visits per year. Throughout the 1970\u27s and early 1980\u27s Refuge Management focused primarily on administration of a Motor Vehicle Access Permit Program that was designed to control this use and preserve wildlife habitat. By the mid-1980\u27s the vehicle access situation was brought under control, and the Refuge began to turn its attention to more traditional management activities. From 1986-1990 major strides were made in the areas of environmental education, impoundment rehabilitation, fire management, land acquisition, and cooperation with other agencies and private groups. As the 1990\u27s begin, the Refuge is committed to providing leadership in habitat protection, progressive land management, environmental education, restoration of the Back Bay watershed, and establishing and continuing partnerships between the public and private sectors

Alien Registration- Leger, Emil D. (Bangor, Penobscot County)

https://digitalmaine.com/alien_docs/11890/thumbnail.jp

PAHs molecules and heating of the interstellar gas

Until now it has remained difficult to account for the rather high temperatures seen in many diffuse interstellar clouds. Various heating mechanisms have been considered: photoionization of minor species, ionization of H by cosmic rays, and photoelectric effect on small grains. Yet all these processes are either too weak or efficient under too restricting conditions to balance the observed cooling rates. A major heat source is thus still missing in the thermal balance of the diffuse gas. Using photoionization cross sections measured in the lab, it was shown that in order to balance the observed cooling rates in cold diffuse clouds (T approx. 80 K) the PAHs would have to contain 15 percent of the cosmic abundance of carbon. This value does not contradict the former estimation of 6 percent deduced from the IR emission bands since this latter is to be taken as a lower limit. Further, it was estimated that the contribution to the heating rate due to PAH's in a warm HI cloud, assuming the same PAH abundance as for a cold HI cloud, would represent a significant fraction of the value required to keep the medium in thermal balance. Thus, photoionization of PAHs might well be a major heat source for the cold and warm HI media

Vireo song repertoires and migratory distance: Three sexual selection hypotheses fail to explain the correlation

Previous studies have found a relationship between migration and the degree of elaboration of sexually selected traits, but investigators have differed in the mechanisms they proposed to account for this association. We examined the relationship between song repertoire size and distance migrated among birds in the genus Vireo. There is a strong positive relationship between migratory distance and repertoire size in this genus, but our data do not support the specific predictions of any of the three proposed mechanisms (the “rapid pairing,” “good migrations,” and “territory lottery” hypotheses). Migration distance is presumably correlated with other life-history characteristics that influence the development of sexually selected traits

Vireo song repertoires and migratory distance: Three sexual selection hypotheses fail to explain the correlation

Previous studies have found a relationship between migration and the degree of elaboration of sexually selected traits, but investigators have differed in the mechanisms they proposed to account for this association. We examined the relationship between song repertoire size and distance migrated among birds in the genus Vireo. There is a strong positive relationship between migratory distance and repertoire size in this genus, but our data do not support the specific predictions of any of the three proposed mechanisms (the “rapid pairing,” “good migrations,” and “territory lottery” hypotheses). Migration distance is presumably correlated with other life-history characteristics that influence the development of sexually selected traits

Contamination of spacecraft by recontact of dumped liquids

Liquids partially freeze when dumped from spacecraft producing particles which are released into free space at various velocities. Recontact of these particles with the spacecraft is possible for specific particle sizes and velocities and, therefore, can become contamination for experiments within the spacecraft or released experiments as a result of waste and potable water dumped from Space Shuttle. An examination of dump characteristics was conducted on STS-29 using both on-board video records and ground based measurements. A preliminary analysis of data from this flight indicates particle velocities are in the range of 30 to 75 ft/sec and recontact is possible for limited particle sizes