An Integrated Approach to Orbital Debris Research and Management

A viable space traffic management program faces a great barrier caused by the ever-increasing number and variety of orbiting objects ranging in size from a few microns to several meters. Although several international agreements to limit the growth rate of orbital debris are in place, the risk of damage and destruction to active satellites is continually rising. The urgency of this situation was highlighted by the 2007 Chinese ASAT test and the collision of Iridium and Cosmos satellites in 2009. Although many debris removal techniques have been posited none have been implemented. Unless a space debris reduction program is undertaken in the near future, continued access to space and use of space for applications and exploration may be extremely compromised. The growing collision threat will continue to complicate any future space traffic management program. Space junk is a man-made, growing threat to space-based applications such as communications, weather forecasting and Earth observation among many others. Space commerce is expanding and as this industry grows the need for an effective traffic management system will become critical to commercial growth and exploration of space. An integrated approach to resolving the debris issues through a carefully designed research program is described. Such a program could facilitate resolution of orbital debris impediments to a controlled space environment

Evaluation of Spacecraft Technology Programs (Effects on Communication Satellite Business Ventures), Volume 2

The computational procedures used in the evaluation of spacecraft technology programs that impact upon commercial communication satellite operations are discussed. Computer programs and data bases are described

The Measurement of Information Transmitted by a Neural Population: Promises and Challenges

All brain functions require the coordinated activity of many neurons, and therefore there is considerable interest in estimating the amount of information that the discharge of a neural population transmits to its targets. In the past, such estimates had presented a significant challenge for populations of more than a few neurons, but we have recently described a novel method for providing such estimates for populations of essentially arbitrary size. Here, we explore the influence of some important aspects of the neuronal population discharge on such estimates. In particular, we investigate the roles of mean firing rate and of the degree and nature of correlations among neurons. The results provide constraints on the applicability of our new method and should help neuroscientists determine whether such an application is appropriate for their data

An analysis of the organization of the Boston Planning Agency

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of City and Regional Planning, 1960.Includes bibliographical references (leaves [156]-[162]).by Marshall Kaplan.M.C.P

Estimating the Amount of Information Carried by a Neuronal Population

Although all brain functions require coordinated activity of many neurons, it has been difficult to estimate the amount of information carried by a population of spiking neurons. We present here a Fourier-based method for estimating the information delivery rate from a population of neurons, which allows us to measure the redundancy of information within and between functional neuronal classes. We illustrate the use of the method on some artificial spike trains and on simultaneous recordings from a small population of neurons from the lateral geniculate nucleus of an anesthetized macaque monkey

The Nearby Neutron Star RX J0720.4-3125 from Radio to X-rays

We present radio, optical, ultraviolet, and X-ray observations of the isolated, thermally-emitting neutron star RX J0720.4-3125 using the Parkes radio telescope, the Very Large Array, the Hubble Space Telescope, and the Chandra X-ray Observatory. From these data we show that the optical/UV spectrum of RX J0720.4-3125 is not well fit by a Rayleigh-Jeans tail as previously thought, but is instead best fit by either a single non-thermal power-law or a combination of a Rayleigh-Jeans tail and a non-thermal power-law. Taken together with the X-ray spectrum, we find the best model for RX J0720.4-3125 to be two blackbodies plus a power-law, with the cool blackbody implying a radius of 11-13 km at an assumed distance of 300 pc. This is similar to many middle aged (10^{5-6} yr) radio pulsars such as PSR B0656+14, evidence supporting the hypothesis that RX J0720.4-3125 is likely to be an off-beam radio pulsar. The radio data limit the flux at 1.4 GHz to be <0.24 mJy, or a luminosity limit of 4*pi*d^2*F < 3e25*d_300^2 ergs/s, and we see no sign of extended nebulosity, consistent with expectations for a pulsar like RX J0720.4-3125.Comment: 13 pages, 9 figures. Uses emulateapj5.sty and onecolfloat5.sty. Accepted for publication in Ap

Differences in the localization and morphology of chromosomes in the human nucleus

Using fluorescence in situ hybridization we show striking differences in nuclear position, chromosome morphology, and interactions with nuclear substructure for human chromosomes 18 and 19. Human chromosome 19 is shown to adopt a more internal position in the nucleus than chromosome 18 and to be more extensively associated with the nuclear matrix. The more peripheral localization of chromosome 18 is established early in the cell cycle and is maintained thereafter. We show that the preferential localization of chromosomes 18 and 19 in the nucleus is reflected in the orientation of translocation chromosomes in the nucleus. Lastly, we show that the inhibition of transcription can have gross, but reversible, effects on chromosome architecture. Our data demonstrate that the distribution of genomic sequences between chromosomes has implications for nuclear structure and we discuss our findings in relation to a model of the human nucleus that is functionally compartmentalized

Global analysis of night marine air temperature and its uncertainty since 1880: the HadNMAT2 Dataset

An updated version of the Met Office Hadley Centre’s monthly night marine air temperature dataset is presented. It is available on a 5? latitude-longitude grid from 1880 as anomalies relative to 1961-1990 calendar-monthly climatological average night marine air temperature (NMAT). Adjustments are made for changes in observation height; these depend on estimates of the stability of the near surface atmospheric boundary layer. In previous versions of the dataset, ad hoc adjustments were also made for three periods and regions where poor observational practice was prevalent. These adjustments are re-examined. Estimates of uncertainty are calculated for every grid box and result from: measurement errors; uncertainty in adjustments applied to the observations; uncertainty in the measurement height and under-sampling. The new dataset is a clear improvement over previous versions in terms of coverage because of the recent digitization of historical observations from ships' logbooks. However, the periods prior to about 1890 and around World War 2 remain particularly uncertain and sampling is still sparse in some regions in other periods. A further improvement is the availability of uncertainty estimates for every grid box and every month. Previous versions required adjustments that were dependent on contemporary measurements of sea surface temperature (SST); to avoid these, the new dataset starts in 1880 rather than 1856. Overall agreement with variations of SST is better for the updated dataset than for previous versions, maintaining existing estimates of global warming and increasing confidence in the global record of temperature variability and change