Shell tile thermal protection system

A reusable, externally applied thermal protection system for use on aerospace vehicles subject to high thermal and mechanical stresses utilizes a shell tile structure which effectively separates its primary functions as an insulator and load absorber. The tile consists of structurally strong upper and lower metallic shells manufactured from materials meeting the thermal and structural requirements incident to tile placement on the spacecraft. A lightweight, high temperature package of insulation is utilized in the upper shell while a lightweight, low temperature insulation is utilized in the lower shell. Assembly of the tile which is facilitated by a self-locking mechanism, may occur subsequent to installation of the lower shell on the spacecraft structural skin

A search for massive particles in the cosmic radiation

Two large area (l.29m.(^2))thin water Cerenkov counters have been developed and their properties investigated when amino G acid (a wavelength shifter) is added to the water. With a concentration of I6mg./litre of the acid an increased response of'~5 is achieved, as well as the uniformity improving by a factor of 2, compared with that of a pure water counter. The efficiency of the acid, however, has been found to deteriorate at a rate of 3.5%/month. The velocity response of the counters has been studied and it is found that, for counters of the present geometry, the addition of the acid is essential to maintain the inherent property of Cerenkov counters: that of a sharp velocity cut off. The counters, together with plastic scintillators, neon flash tubes and suitable amounts of absorber have been combined to form a large aperture (~ 0,1 m.(^2)sterad.) telescope capable of mass discrimination over a range of several Gev/c(^2). The properties of, and mass resolution attainable with such a system have been investigated by selecting sub-relativistic sea level cosmic ray protons to traverse the telescope. The mass resolution achieved for protons was a full width at half height of 350 Mev/c(^2), and the intensities of observed protons were found to be in good agreement with measurements of other workers in the same energy region. The telescope has been operated in a search for sub-relativistic massive particles, having integral or fractional charge ('quarks'), in the sea level cosmic radiation (typically M> 1.3 Gev/c(^2)for z = 1; a lower value applying for z 4 Gev/c(^2)), weakly interacting and to comprise ~10(^-3) of the primary radiation). Deuterons have been detected at various stages of the work and their, intensity in the sea level cosmic radiation has been evaluated as (DIAGRAM FORMULA)The measured intensities have been shown to be an order of magnitude too large to be consistent with the bulk of production coming through reactions such as NN→dTT, but they are apparently consistent with what would be expected from 'pick-up' reactions. The 'heavy mass telescope" has been modified to investigate the possibility of the direct production of muons, from the interactions of neutral primaries, at a rate much greater than that expected from neutrinos having their 'noimal' cross section. The results of a series of experiments that were performed were suggestive of a very high pion and proton background, and within the uncertainties in the sea level neutron spectrum the observed rates of events were not inconsistent with all of them having been neutron induced. It is concluded that there is no evidence for an excess of muons induced by neutral primaries as has repeatedly been reported by Cowan et al., (l964 - 1969)

Modification of an impulse-factoring orbital transfer technique to account for orbit determination and maneuver execution errors

A method has previously been developed to satisfy terminal rendezvous and intermediate timing constraints for planetary missions involving orbital operations. The method uses impulse factoring in which a two-impulse transfer is divided into three or four impulses which add one or two intermediate orbits. The periods of the intermediate orbits and the number of revolutions in each orbit are varied to satisfy timing constraints. Techniques are developed to retarget the orbital transfer in the presence of orbit-determination and maneuver-execution errors. Sample results indicate that the nominal transfer can be retargeted with little change in either the magnitude (Delta V) or location of the individual impulses. Additonally, the total Delta V required for the retargeted transfer is little different from that required for the nominal transfer. A digital computer program developed to implement the techniques is described

Monetary costs of agitation in older adults with Alzheimer's disease in the UK: prospective cohort study

While nearly half of all people with Alzheimer's disease (AD) have agitation symptoms every month, little is known about the costs of agitation in AD. We calculated the monetary costs associated with agitation in older adults with AD in the UK from a National Health Service and personal social services perspective

Organizational learning and emotion: constructing collective meaning in support of strategic themes

Missing in the organizational learning literature is an integrative framework that reflects the emotional as well as the cognitive dynamics involved. Here, we take a step in this direction by focusing in depth over time (five years) on a selected organization which manufactures electronic equipment for the office industry. Drawing on personal construct theory, we define organizational learning as the collective re-construal of meaning in the direction of strategically significant themes. We suggest that emotions arise as members reflect on progress or lack of progress in achieving organizational learning. Our evidence suggests that invalidation – where organizational learning fails to correspond with expectations – gives rise to anxiety and frustration, while validation – where organizational learning is aligned with or exceeds expectations – evokes comfort or excitement. Our work aims to capture the key emotions involved as organizational learning proceeds

Self-organized patterns of coexistence out of a predator-prey cellular automaton

We present a stochastic approach to modeling the dynamics of coexistence of prey and predator populations. It is assumed that the space of coexistence is explicitly subdivided in a grid of cells. Each cell can be occupied by only one individual of each species or can be empty. The system evolves in time according to a probabilistic cellular automaton composed by a set of local rules which describe interactions between species individuals and mimic the process of birth, death and predation. By performing computational simulations, we found that, depending on the values of the parameters of the model, the following states can be reached: a prey absorbing state and active states of two types. In one of them both species coexist in a stationary regime with population densities constant in time. The other kind of active state is characterized by local coupled time oscillations of prey and predator populations. We focus on the self-organized structures arising from spatio-temporal dynamics of the coexistence. We identify distinct spatial patterns of prey and predators and verify that they are intimally connected to the time coexistence behavior of the species. The occurrence of a prey percolating cluster on the spatial patterns of the active states is also examined.Comment: 19 pages, 11 figure

On the use of a sunward-libration-point orbiting spacecraft as an IMF monitor for magnetospheric studies

Magnetospheric studies often require knowledge of the orientation of the IMF. In order to test the accuracy of using magnetometer data from a spacecraft orbiting the sunward libration point for this purpose, the angle between the IMF at ISEE 3, when it was positioned around the libration point, and at ISEE 1, orbiting Earth, has been calculated for a data set of two-hour periods covering four months. For each period, a ten-minute average of ISEE 1 data is compared with ten-minute averages of ISEE 3 data at successively lagged intervals. At the lag time equal to the time required for the solar wind to convect from ISEE 3 to ISEE 1, the median angle between the IMF orientation at the two spacecraft is 20 deg, and 80% of the cases have angles less than 38 deg. The results for the angles projected on the y-z plane are essentially the same

Lower limb biomechanics and muscle function

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recor

Reversibility, heat dissipation and the importance of the thermal environment in stochastic models of nonequilibrium steady states

We examine stochastic processes that are used to model nonequilibrium processes (e.g, pulling RNA or dragging colloids) and so deliberately violate detailed balance. We argue that by combining an information-theoretic measure of irreversibility with nonequilibrium work theorems, the thermal physics implied by abstract dynamics can be determined. This measure is bounded above by thermodynamic entropy production and so may quantify how well a stochastic dynamics models reality. We also use our findings to critique various modeling approaches and notions arising in steady-state thermodynamics.Comment: 8 pages, 2 figures, easy-to-read, single-column, large-print RevTeX4 format; version with modified abstract and additional discussion, references to appear in Phys Rev Let

Synthesis and antibacterial effects of cobalt–cellulose magnetic nanocomposites

© The Royal Society of Chemistry. Green synthesis is employed to prepare cobalt/cellulose nanocomposites with cubic (α-cobalt) cobalt as a main component with antibacterial and magnetic properties. An in situ reduction of aqueous solutions of cobalt ions on a model cellulose substrate surface using hydrogen gas affords spherical, cellulose-stabilised cobalt nanoclusters with magnetic properties and an average diameter of 7 nm that are distributed evenly over the surface of the cellulose fibres. These cobalt/cellulose nanocomposites exhibit good antibacterial action against opportunistic pathogens both Gram-positive (S. aureus) and Gram-negative (E. coli, A. baumannii and P. aeruginosa), with zones of inhibition up to 15 mm, thereby encouraging the deployment of these advanced materials for the treatment of wastewater or within medical dressings. This method of preparation is compared with the analogous in situ reduction of cobalt ions on a cellulose surface using sodium borohydride as reducing agent