How do microorganisms reach the stratosphere?

A number of studies have demonstrated that bacteria and fungi are present in the stratosphere. Since the tropopause is generally regarded as a barrier to the upward movement of particles it is difficult to see how such microorganisms can reach heights above 17 km. Volcanoes provide an obvious means by which this could be achieved, but these occur infrequently and any microorganisms entering the stratosphere from this source will rapidly fall out of the stratosphere. Here, we suggest mechanisms by which microorganisms might reach the stratosphere on a more regular basis; such mechanisms are, however, likely only to explain how micrometre to submicrometre particles could be elevated into the stratosphere. Intriguingly, clumps of bacteria of size in excess of 10 μm have been found in stratospheric samples. It is difficult to understand how such clumps could be ejected from the Earth to this height, suggesting that such bacterial masses may be incoming to Earth. We suggest that the stratospheric microflora is made up of two components: (a) a mixed population of bacteria and fungi derived from Earth, which can occasionally be cultured; and (b) a population made up of clumps of, viable but non-culturable, bacteria which are too large to have originated from Earth; these, we suggest, have arrived in the stratosphere from space. Finally, we speculate on the possibility that the transfer of bacteria from the Earth to the highly mutagenic stratosphere may have played a role in bacterial evolution

Level correlations in integrable systems

We derive a simple analytical expression for the level correlation function of an integrable system. It accounts for both the lack of correlations at smaller energy scales and for global rigidity (level number conservation) at larger scales. We apply our results to a rectangle with incommensurate sides and show that they are in excellent agreement with the limiting cases established in the semiclassical theory of level rigidity.Comment: 5 page

The True Incidence of Magnetism among Field White Dwarfs

We study the incidence of magnetism in white dwarfs from three large and well-observed samples of hot, cool, and nearby white dwarfs in order to test whether the fraction of magnetic degenerates is biased, and whether it varies with effective temperature, cooling age, or distance. The magnetic fraction is considerably higher for the cool sample of Bergeron, Ruiz, and Leggett, and the Holberg, Oswalt, and Sion sample of local white dwarfs that it is for the generally-hotter white dwarfs of the Palomar Green Survey. We show that the mean mass of magnetic white dwarfs in this survey is 0.93 solar masses or more, so there may be a strong bias against their selection in the magnitude-limited Palomar Green Survey. We argue that this bias is not as important in the samples of cool and nearby white dwarfs. However, this bias may not account for all of the difference in the magnetic fractions of these samples. It is not clear that the magnetic white dwarfs in the cool and local samples are drawn from the same population as the hotter PG stars. In particular, two or threee of the cool sample are low-mass white dwarfs in unresolved binary systems. Moreover, there is a suggestion from the local sample that the fractional incidence may increase with decreasing temperature, luminosity, and/or cooling age. Overall, the true incidence of magnetism at the level of 2 megagauss or greater is at least 10%, and could be higher. Limited studies capable of detecting lower field strengths down to 10 kilogauss suggest by implication that the total fraction may be substantially higher than 10%.Comment: 16 pages, 2 figures, Astronomical Journal in press -- Jan 2003 issu

Heterogeneous processor pipeline for a product cipher application

Processing data received as a stream is a task commonly performed by modern embedded devices, in a wide range of applications such as multimedia (encoding/decoding/ playing media), networking (switching and routing), digital security, scientific data processing, etc. Such processing normally tends to be calculation intensive and therefore requiring significant processing power. Therefore, hardware acceleration methods to increase the performance of such applications constitute an important area of study. In this paper, we present an evaluation of one such method to process streaming data, namely multi-processor pipeline architecture. The hardware is based on a Multiple-Processor System on Chip (MPSoC), using a data encryption algorithm as a case study. The algorithm is partitioned on a coarse grained level and mapped on to an MPSoC with five processor cores in a pipeline, using specifically configured Xtensa LX3 cores. The system is then selectively optimized by strengthening and pruning the resources of each processor core. The optimized system is evaluated and compared against an optimal single-processor System on Chip (SoC) for the same application. The multiple-processor pipeline system for data encryption algorithms used was observed to provide significant speed ups, up to 4.45 times that of the single-processor system, which is close to the ideal speed up from a five-stage pipeline

Activity Budget and Drey Building of Free-Ranging Grizzled Giant Squirrel

Ratufa macroura dandolena is one of the three distinct sub-species of Giant Squirrels presentin Sri Lanka and it is the smallest of the Giant Squirrels in the world. They are beingthreatened due to habitat loss from deforestation for agricultural, residential and commercialpurposes. Activity budgeting is an essential component to form an effective conservation andmanagement system. We conducted six months of study between June and September 2014and between December 2014 and March 2015 using focal animal sampling techniques togather behavioral data. Field visits were made three days per week, during the study periodand point samples on an individual were recorded at five-minute intervals. Observations ondreys were opportunistically conducted during field visits. The study took place in areas ofdisturbed regenerating forest within the premises of the Rajarata University in Mihintale.Data collection was done between 07:00 and 17:00 hrs. Grizzled Giant Squirrels were mostlyinvolved in feeding during the period of observation (45.58%) and was least engaged in otheractivities (0.17%) namely branch shaking and watching the observer. They spent 29.57% inresting, 14.34% in locomotion, 3.73% in intraspecific activities, 1.53% in grooming, 0.73%in communicatory behavior and 4.32% in drey related activities. Feeding mostly occurredfrom 07:00 to 10:00 hrs and 15:00 to 16:00 hrs according to the diurnal time budget. Majorityof the resting was between 11:00 to 15:00 hrs. The walls of the dreys were made by Grewiasp. twigs and the inner floor using leaves of Mangifera indica. Dreys were about 45.95±0.35cm in length, 30.9±0.56 cm in width, 14.85±0.21 cm in depth and 412.5±3.5 g in weight. Werecommend further study of this species at other sites with different forest types to betterunderstand its behavioral ecology and conservation needs. Particular emphasis should begiven to studying this species at different altitudes.Keywords: Mammal, Rodent, Behavior, Giant Squirrel, Sri Lank