Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.     

Thermal and nonthermal flare emission observed with the Nobeyama Radio Heliograph

The early phases of three flares, observed by the Nobeyama Radio Heliograph, are studied. Nonthermal and thermal radio sources are identified by comparison with soft X-ray images taken by the Soft X-ray Telescope onboard the Yohkoh satellite. Two of the flares are mainly of nonthermal origin and their location coincides with one of the footpoints of soft X-ray loops. Another flare has both thermal and nonthermal components which start to brighten simultaneously. This suggests that particle acceleration and plasma compression develop simultaneously.     

Processing requirements for multisensor low-cost brilliantmunitions

A generic mission for an autonomous brilliant munition is presented and used to identify the functions that embedded signal processors must perform. Based on these functions and other operational factors such as weather, countermeasures, larger search areas, reduced false alarm rates, and increased munition maneuverability, the processing loads in bits/second messages/second, operations/second, and instructions/second are derived. An evaluation of general implementation issues such as the requirements for data fusion, distributed and parallel processing architectures, reliable software, and low-cost hardware is presented     

Occurrence of brain tumors in rhesus monkeys exposed to 55-MeV protons.

Twenty-year observation of monkeys exposed to single doses of high energy protons simulating solar particles revealed that the most prevalent fatal cancers were brain tumors in the group of animals exposed to 55-MeV protons. Of 72 animals (50 males and 22 females) receiving 0.25 to 8.0 Gy total body surface dose, nine developed fatal tumors classified as grade IV astrocytoma or glioblastoma multiforme. The latent period for tumor development ranged from 14 months to 20 years, with a median of 5 years. Doses associated with the tumors were 4.0 to 8.0 Gy. Eight males and one female were affected. Depth-dose determinations suggest that the high incidence of cerebral neoplasia is associated with the Bragg Peak energy distribution of the 55-MeV protons. Comparison of the tumor incidence with that in humans with brain exposures incidental to radiotherapy indicates a high biological effectiveness compared with gamma radiation. Studies are in progress to attempt to replicate the results in rodents and establish a dose-response curve for proton-induced brain tumors.     

非齐次Poisson过程的若干新性质

本文在一些文献的基础上,进一步讨论非齐次Poisson过程的某些性质,给出了若干新性质。 设{N(t),t≥0}是累积强度为的非齐次Poisson过程。迄今的文献(如[1][2]等)指出,(?)n≥1,前n个到达时刻τ_1,τ_2,…,τ_n的联合概率密度为 本文定理1指出,上式不仅是必要的,而且是充分的,并给出了充分性的证明。从而,得到了描写过程统计规律的一个刻画。然后,在N(t_i)=n_i(i=1,…,k,0相似文献   

Chronic hyperhydration and hematological changes in trained subjects during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the hemoglobin content of endurance trained athletes during hypokinesia (decreased number of steps from 10,000 to 3000 steps per day). The studies were performed on 30 long-distance runners who had a VO2max average of 66 ml kg-1 min-1 and were in the age range of 19-24 years. Prior to their exposure to hypokinesia (HK) of 364 days, all volunteers were on an average of 10,000 steps per day. All volunteers were divided into three equal groups: the first group underwent normal ambulatory life (control subjects), the second group was kept under continuous restriction of motor activity (hypokinetic subjects), and the third group was placed under continuous restriction of motor activity and consumed 26 ml water kg-1 body weight daily and 0.1 g sodium chloride kg-1 body weight in the form of supplementation (hyperhydrated subjects). For simulation of the hypokinetic effect, the number of steps taken per day by the second and third groups of volunteers was restricted to an average of 3000. During the hypokinetic period we determined reticulocytes (Rt), hemoglobin (Hb), hematocrit (Hct), plasma volume (PV), red blood cell (RBC) mass and VO2max. In hyperhydrated volunteers the content of Hb and Hct decreased significantly, while PV, RBC mass and Rt count increased significantly. In hypokinetic volunteers Hb and Hct increased, while PV, RBC and Rt decreased significantly. It was concluded that chronic hyperhydration may be used to attentuate an increase in the Hb content of physically conditioned subjects during prolonged restriction of motor activity.     

Latitude and solar-cycle dependence of radial IMF intensity

I describe a simple procedure for extrapolating the observed solar magnetic field into the heliosphere, which averages the asymptotic fields computed using the standard source surface and current sheet models. The resultant field is characterized by strong latitudinal gradients (maintained by volume currents outside the source surface) and by abrupt reversals in direction at the current sheets. The model yields good agreement with the observed long-term variation of the radial IMF component in the ecliptic, and is used to predict the variation of |B _r | along the latitudinal trajectory of Ulysses during 1990–1994. As found in earlier studies, the magnitude ofB _r at any latitude is determined largely by the strength and relative orientation of the Sun's dipole moment.     

液氧/煤油发动机地面试验故障紧急关机系统研制

论述了液氧／煤油发动机研制地面试车中，出现故障时所采用的紧急关机系统的原理和系统结构、设计程序、设计指标、关机判断准则、验证及应用等。     

Study of water-salt metabolism and renal function in cosmonauts

In manned space flights the renal function and water-salt metabolism undergo substantial changes. With the reserve capabilities of kidneys in mind, their function and regulation of the water-salt balance were investigated in cosmonauts postflight and in Earth-bound simulation experiments with the aid of water loading, hormonal injections (pituitrin, engiotensin, DOCA, ACTH); water- and ion-release were also studied during LBNP and physical exercises. The cosmonauts who performed space flights of 2 to 5 days showed water retention and increased urine excretion of salts during the first postflight days in response to a water load. After the 18-day flight water excretion remained unchanged whereas salt excretion increased. The capacity for osmotic concentration and urine dilution did not alter. The study of the hormonal effect in simulation experiments of different duration demonstrated a normal renal response to the hormonal excretion. After the LBNP tests and physical exercises the water- and salt-excretion declined; a correlation between the level of water- and salt-excretion and the level of these loads was established. The data on the blood- and urine-ionic composition, excretion of nitrogen metabolites, and hormones postflight as well as the results of load and functional tests suggest that changes in the renal function of cosmonauts in weightlessness are associated with regulatory effects on the kidney rather than disturbances in the function of nephron cells.