Gravitropic bending of fruiting bodies--a model based on hyphal gravisensing and cooperativity.

Gravitropic bending of the winter mushroom Flammulina velutipes is achieved by differential growth of the apical part of the stem, the transition zone. Ultrastructural analysis revealed that bending is due to the relaxation of tissue tensions at the lower flank of the stem where hyphal extension growth is promoted in contrast to the upper flank. Extension of lower flank hyphae is preceded by a conspicuous accumulation of microvesicles in the cytosol and their subsequent fusion with the vacuolar compartment, leading to a large volume increase. The hypothesis is put forward that all hyphae in the transition zone are capable of gravisensing. It is derived from experiments with transition zone segments, which exhibit negative gravitropic response independent from their origin within the stem. A model is presented which connects individual gravisensing of the hyphae with a cooperative response within the stem or small segments of the stem. An essential step is the transmission of positional information, by each hypha with respect to the gravitational vector, to the surroundings. The existence of a soluble growth regulator, which is enriched at the lower flank of the stem, is discussed. A gradient could be formed which precedes the gradient of microvesicle formation, and thereby determines the change of growth direction.     

Interannual variability

The new Reference Atmosphere presented here is based on global satellite data and forms a very useful basis for climatological studies. When using such climatologies it is important to be aware of the well known interannual variability which in the middle atmosphere is particularly large during the northern winters and southern springs.     

The exact Cramer-Rao bound for Gaussian autoregressive processes

An explicit expression is derived for the Cramer-Rao bound (CRB) on unbiased estimates of the parameters of autoregressive (AR) processes, given a finite number of measurements. The expression converges to the well-known asymptotic form of the CRB when the number of measurements tends to infinity. The behavior of the bound is illustrated by some numerical examples     

Lunar Exploration Neutron Detector for the NASA Lunar Reconnaissance Orbiter

The design of the Lunar Exploration Neutron Detector (LEND) experiment is presented, which was optimized to address several of the primary measurement requirements of NASA’s Lunar Reconnaissance Orbiter (LRO): high spatial resolution hydrogen mapping of the Moon’s upper-most surface, identification of putative deposits of appreciable near-surface water ice in the Moon’s polar cold traps, and characterization of the human-relevant space radiation environment in lunar orbit. A comprehensive program of LEND instrument physical calibrations is discussed and the baseline scenario of LEND observations from the primary LRO lunar orbit is presented. LEND data products will be useful for determining the next stages of the emerging global lunar exploration program, and they will facilitate the study of the physics of hydrogen implantation and diffusion in the regolith, test the presence of water ice deposits in lunar cold polar traps, and investigate the role of neutrons within the radiation environment of the shallow lunar surface.     

Sikkim's Teesta River fog, mist and dust particle monitoring using monostatic LIDAR

Fog, mist, and atmospheric dust particles, having the dimension of one micrometer or less, play an important role in the deterioration of visibility, as well as in causing local warming in the atmosphere. With an attempt to reduce the deterioration, a scientific approach has to be taken to determine their origins. A monostatic LIDAR may be one of the best instruments for such work. The authors are tempted to develop such a LIDAR for fog, mist, and dust particle monitoring over River Teesta at Sikkim. LIDAR is an acronym for Light Detection And Ranging. What can we do with LIDAR? Measure distance, measure speed, measure rotation, measure chemical composition and concentration, and measure cross-sections of the targets. The digital technique is always utilized for its development which results in better security, lower power consumption, higher power efficiency, higher reliability, lower transmitter power, lower multipath effect, higher interference suppression as compared to an analog system. The commercial systems like disdometer, rain radar, mobile robot, etc., utilizing LIDAR principles are operational in different parts of the world. The authors are highly motivated for such LIDAR development and their development effort follows.     

The elemental composition in energetic particle events at high heliospheric latitudes

The relative abundances of low energy ions (0.6–2.0 MeV/n) in solar energetic particle (SEP) and corotating interaction region (CIR) events have been measured by the EPAC experiment aboard Ulysses since launch in October 1990 until the present time. We give an overview of the abundances of heavy ions (He, C, Ne, Fe) relative to oxygen during energetic particle events lasting longer than 5 days during the in- and out-of-ecliptic phase of the mission. While the period Oct. 1990 to Aug. 1992 was dominated by high solar activity the Ulysses out of ecliptic passage at solar latitudes up to 45° went parallel to the declining phase of solar activity. Thus a very clear structure of corotating interaction regions was observed. While the in-ecliptic composition is in general agreement with measurements made near the Earth, the development of the CIR-composition shows two phases: From Aug. 1992 to May 1993 the C/O-ratio is 0.55–0.70, afterwards it increases to 0.8–0.9. This increase is correlated to the disappearance of the current sheet at 30° solar latitude reported by Smithet al. (1993).