The world wide spread of space technology

Space technological capabilities and developments in US, USSR, Western Europe, Japan, China, and developing nation

Solid state, CCD-buried channel, television camera study and design

An investigation of an all solid state television camera design, which uses a buried channel charge-coupled device (CCD) as the image sensor, was undertaken. A 380 x 488 element CCD array was utilized to ensure compatibility with 525 line transmission and display monitor equipment. Specific camera design approaches selected for study and analysis included (a) optional clocking modes for either fast (1/60 second) or normal (1/30 second) frame readout, (b) techniques for the elimination or suppression of CCD blemish effects, and (c) automatic light control and video gain control techniques to eliminate or minimize sensor overload due to bright objects in the scene. Preferred approaches were determined and integrated into a design which addresses the program requirements for a deliverable solid state TV camera

Mechanisms of Surviving Burial: Dune Grass Interspecific Differences Drive Resource Allocation After Sand Deposition

Sand dunes are important geomorphic formations of coastal ecosystems that are critical in protecting human populations that live in coastal areas. Dune formation is driven by ecomorphodynamic interactions between vegetation and sediment deposition. While there has been extensive research on responses of dune grasses to sand burial, there is a knowledge gap in understanding mechanisms of acclimation between similar, coexistent, dune-building grasses such as Ammophila breviligulata (C3), Spartina patens (C4), and Uniola paniculata (C4). Our goal was to determine how physiological mechanisms of acclimation to sand burial vary between species. We hypothesize that (1) in the presence of burial, resource allocation will be predicated on photosynthetic pathway and that we will be able to characterize the C3 species as a root allocator and the C4 species as leaf allocators. We also hypothesize that (2) despite similarities between these species in habitat, growth form, and life history, leaf, root, and whole plant traits will vary between species when burial is not present. Furthermore, when burial is present, the existing variability in physiological strategy will drive species-specific mechanisms of survival. In a greenhouse experiment, we exposed three dune grass species to different burial treatments: 0 cm (control) and a one-time 25-cm burial to mimic sediment deposition during a storm. At the conclusion of our study, we collected a suite of physiological and morphological functional traits. Results showed that Ammophila decreased allocation to aboveground biomass to maintain root biomass, preserving photosynthesis by allocating nitrogen (N) into light-exposed leaves. Conversely, Uniola and Spartina decreased allocation to belowground production to increase elongation and maintain aboveground biomass. Interestingly, we found that species were functionally distinct when burial was absent; however, all species became more similar when treated with burial. In the presence of burial, species utilized functional traits of rapid growth strategy, although mechanisms of change were interspecifically variable

Population of bound excited states in intermediate-energy fragmentation reactions

Fragmentation reactions with intermediate-energy heavy-ion beams exhibit a wide range of reaction mechanisms, ranging from direct reactions to statistical processes. We examine this transition by measuring the relative population of excited states in several sd-shell nuclei produced by fragmentation with the number of removed nucleons ranging from two to sixteen. The two-nucleon removal is consistent with a non-dissipative process whereas the removal of more than five nucleons appears to be mainly statistical.Comment: 5 pages, 6 figure

Organizational learning in development assistance: a comparative analysis of six tree-planting projects in Kenya

Most community-level development assistance projects fail to achieve their stated objectives. With frustrating regularity, new projects repeat the mistakes that defeated their predecessors. If development assistance organizations are to become effective, they must develop the capacity to learn from their experiences and the experiences of others. There is evidence that community-level forestry projects sponsored by several national and international organisations in Kenya have begun to develop this capacity. I propose to undertake a comparative analysis of six Kenyan efforts (Kenya Wood fuel Development Program, Kenya Renewable Energy Development Project, Rural Afforestation Extension Scheme, CARE Agro-forestry Extension Project, the Greenbelt Movement, and the Kenya Energy Non-Governmental Organization Association), to determine what, these organizations have learned about the design and implementation of sustainable projects and how they learned it

Cross-pollination: inter-organizational learning in Kenyan tree-planting programs

Development assistance organizations working on the same problems in the same region have much to learn from each other's experiences. This preliminary analysis examines inter-organizational learning, as part of a larger study of organizational learning in development assistance. A comparative analysis of tree-planting programs in Kenya found that most formal mechanisms to foster inter-organizational learning achieved only limited success. It is argued that the failures of these mechanisms can be ascribed to their reliance on the participation of program managers, who lack the time, resources, or incentives to participate beyond a superficial level. However, the analysis also reveals that a great deal of information and expertise is shared among these organizations in informal ways, through collegial networks and cooperation among extension staffs. It is recommended that formal mechanisms for inter-organizational learning be adjusted to reflect their limitations, and that informal mechanisms be recognized and encouraged

Anomalous Dynamics of Translocation

We study the dynamics of the passage of a polymer through a membrane pore (translocation), focusing on the scaling properties with the number of monomers $N$. The natural coordinate for translocation is the number of monomers on one side of the hole at a given time. Commonly used models which assume Brownian dynamics for this variable predict a mean (unforced) passage time $\tau$ that scales as $N^2$, even in the presence of an entropic barrier. However, the time it takes for a free polymer to diffuse a distance of the order of its radius by Rouse dynamics scales with an exponent larger than 2, and this should provide a lower bound to the translocation time. To resolve this discrepancy, we perform numerical simulations with Rouse dynamics for both phantom (in space dimensions $d=1$ and 2), and self-avoiding (in $d=2$) chains. The results indicate that for large $N$, translocation times scale in the same manner as diffusion times, but with a larger prefactor that depends on the size of the hole. Such scaling implies anomalous dynamics for the translocation process. In particular, the fluctuations in the monomer number at the hole are predicted to be non-diffusive at short times, while the average pulling velocity of the polymer in the presence of a chemical potential difference is predicted to depend on $N$.Comment: 9 pages, 9 figures. Submitted to Physical Review

Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag

We study the electrophoretic separation of polyelectrolytes of varying lengths by means of end-labeled free-solution electrophoresis (ELFSE). A coarse-grained molecular dynamics simulation model, using full electrostatic interactions and a mesoscopic Lattice Boltzmann fluid to account for hydrodynamic interactions, is used to characterize the drag coefficients of different label types: linear and branched polymeric labels, as well as transiently bound micelles. It is specifically shown that the label's drag coefficient is determined by its hydrodynamic size, and that the drag per label monomer is largest for linear labels. However, the addition of side chains to a linear label offers the possibility to increase the hydrodynamic size, and therefore the label efficiency, without having to increase the linear length of the label, thereby simplifying synthesis. The third class of labels investigated, transiently bound micelles, seems very promising for the usage in ELFSE, as they provide a significant higher hydrodynamic drag than the other label types. The results are compared to theoretical predictions, and we investigate how the efficiency of the ELFSE method can be improved by using smartly designed drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule

Two-neutron knockout from neutron-deficient 34^{34}Ar, 30^{30}S, and 26^{26}Si

Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have been studied using intermediate-energy beams of neutron-deficient $^{34}$Ar, $^{30}$S, and $^{26}$Si. The inclusive cross sections, and also the partial cross sections for the population of individual bound final states of the $^{32}$Ar, $^{28}$S and $^{24}$Si knockout residues, have been determined using the combination of particle and $\gamma$-ray spectroscopy. Similar to the two-proton knockout mechanism on the neutron-rich side of the nuclear chart, these two-neutron removal reactions from already neutron-deficient nuclei are also shown to be consistent with a direct reaction mechanism.Comment: Phys. Rev. C, rapid communication, in pres