Spore dosimetry of solar UV radiation: applications to monitoring of daily irradiance and personal exposure.

Environmental UV radiation can be quantified using spore dosimetry, which measures the inactivation of repair-deficient Bacillus subtilis spores dried on a membrane filter. The system exhibits highly selective sensitivity to UV radiation, not being affected by various environmental adversities, such as high and low temperature and humidity. Biologically-effective dose rate and cumulative dose of ambient radiation are measurable under various conditions at various places on the earth, including tropical, temperate, and polar sites. Applications to monitor the exposure at the surface of organisms including humans and plants have also been advanced.     

Six-impulse maneuvers for rendezvous of spacecraft in near-circular noncoplanar orbits

The problem of a rendezvous of two spacecraft in close near-circular noncoplanar orbits is considered. The angles of applying velocity impulses and their orientation are determined from necessary conditions of optimality derived using the basis vector theory. For non-degenerate six-impulse solutions the analytical formulas are found that approximate the dependence of moments of applying velocity impulses and angles determining their orientation on the rendezvous duration. The total characteristic velocity of six-impulse solutions (or five-impulse solutions derived from them) is compared to the total characteristic velocity obtained when solving the Lambert problem.     

On the modular approach of a 3D model of the system magnetosheath–magnetosphere

This article presents some preliminary features of a new self consistent model of the system magnetosheath–magnetosphere, recently developed in the Institute of Mechanics, Sofia, Bulgaria. The flow in the magnetosheath is governed by 3D ideal gas-dynamic equations. The positions and the shapes of the bow shock and the magnetopause are calculated iteratively as a part of the solution. These surfaces are essentially three-dimensional (generally non-axially-symmetric). The self-consistency between the regions is ensured via the boundary conditions. The magnetopause cusp indentations are formed, influencing essentially the magnetosheath flow. Prediction of the position and the shape of the bow shock for different values of the sonic Mach number are derived. Distribution of some flow parameters in the magnetosheath is presented. 3D numerical finite element model, calculating the field due to the magnetopause currents for an arbitrary magnetopause geometry, is used in the magnetosphere. The fields due to the current systems inside the magnetosphere(cross-tail current, ring current, and Birkeland current) are taken from the Tsyganenko empirical model. The magnetopause surface is calculated from the requirement the outside gas-dynamic pressure to be balanced by the magnetic pressure inside. The magnetosphere model can be viewed as an improved version of the empirical model but with more realistic magnetopause form and shielding field. Not a final but a beta version is used in this approach. The final model version as well the model details will be presented elsewhere.     

A system of flight data acquisition,processing, and recording

A system for recording and analysis of flight information including the technical condition of a control object and the state of its controller’s health in real time aboard a flight vehicle and in ground-based air traffic control centers is described.     

The effect of the longitudinal propagating waves on the electron acceleration in the reconnecting current sheet

Based upon the most efficient electron acceleration near the midplane of 3D non-neutral driven reconnecting current sheet (RCS) and the electrostatic wave excitation by the drift Maxwellian distribution of electrons in Vlasov simulation, we assume that the electrostatic waves mainly propagate opposite to the reconnecting electric field and investigated how these waves affect the electron acceleration. The main results are: (1) when the electron’s velocity equals to the phase speed of the waves, they will be trapped and have the different accelerating characteristics from the untrapped electrons through solving the momentum equations of electrons analytically; (2) the test particle simulations further prove that the number of the energetic electrons decreases with the increasing intensity of unstable waves, and the distribution of the energetic electrons takes on the double power-law.     

Exposure to altered gravity affects all stages of endochondral cartilage differentiation.

Chondrogenesis has a number of well-defined steps: (1) condensation, which involves cell aggregation, adhesion and communication; (2) activation of cartilage genes, which is accompanied by rounding up of the cells and intracellular differentiation; and (3) production and secretion of cartilage specific matrix molecules. Our studies show that each of these steps is affected by exposure to gravitational changes. Clinorotation and centrifugation affected initial aggregation and condensation. In the CELLS experiment, where cells were exposed to microgravity after some condensation occurred preflight, intracellular differentiation and matrix production were delayed relative to controls. Once cartilage has developed, in rats, further differentiation (hypertrophy, matrix production) was also affected by spaceflight and hind limb suspension. For the process of chondrogenesis to proceed as we know it, loading and other factors present at 1g are required at each step of the process. This requirement means that not only will skeletal development and bone healing, processes involving chondrogenesis, be altered by long term exposure to microgravity, but that continuous intervention will be necessary to correct any defects produced by altered gravity environments.     

Comparative Utilization of Limited Energy for Continuous and Pulse Operations

Comparative utilization of a limited amount of energy for continuous and pulse operations was investigated. Under a restriction that the amount of available energy was limited, general equations for operational hours of the energy source for given power output were derived for both continuous and pulse mode operations. This paper points out that due to various adjustable parameters available for pulse mode operation, if properly designed pulse mode operation produces longer utilization of available energy for required output power than continuous mode operation.     

The STEREO/IMPACT Magnetic Field Experiment

The magnetometer on the STEREO mission is one of the sensors in the IMPACT instrument suite. A single, triaxial, wide-range, low-power and noise fluxgate magnetometer of traditional design—and reduced volume configuration—has been implemented in each spacecraft. The sensors are mounted on the IMPACT telescoping booms at a distance of ～3 m from the spacecraft body to reduce magnetic contamination. The electronics have been designed as an integral part of the IMPACT Data Processing Unit, sharing a common power converter and data/command interfaces. The instruments cover the range ±65,536 nT in two intervals controlled by the IDPU (±512 nT; ±65,536 nT). This very wide range allows operation of the instruments during all phases of the mission, including Earth flybys as well as during spacecraft test and integration in the geomagnetic field. The primary STEREO/IMPACT science objectives addressed by the magnetometer are the study of the interplanetary magnetic field (IMF), its response to solar activity, and its relationship to solar wind structure. The instruments were powered on and the booms deployed on November 1, 2006, seven days after the spacecraft were launched, and are operating nominally. A magnetic cleanliness program was implemented to minimize variable spacecraft fields and to ensure that the static spacecraft-generated magnetic field does not interfere with the measurements.     

Computer-aided simulation of the AMg6 alloy rolling process with allowance for its anisotropy

Some data obtained in the course of computer-aided simulation of a process of plane AMg6 alloy specimen rolling in the CAE-system MSC.SuperForm are presented. The influence of a real material structure upon the stress-strain state and the flow pattern of layers throughout the specimen height is taken into account. Also determined are the values of total pressure of metal on the rolls and a moment of rolling with the use of the isotropic and anisotropic finite element models (FEM) of specimens.