Guidance methods for low-thrust space vehicles Cumulative progress report, 1 Jan. 1969 - 31 Jan. 1970

Guidance and control schemes for optimal low-thrust Earth-Mars transfer mission

Simple models for the shuttle remote manipulator system

The investigation is aimed at establishing a series of simple models which can be used to study the forces and moments which occur due to the reaction control system (RCS) jet plume firings during a deployment or retrieval of an IUS type payload. The models considered in this investigation are primarily planar in nature. In this study primary attention is given to the roles the payload play in determining the overall moments on the remote manipulator system arm

WHIRLAWAY--A THREE-DIMENSIONAL, TWO-GROUP NEUTRON DIFFUSION CODE FOR THE IBM 7090 COMPUTER

WHIRLAWAY is an IBM 7090 FORTRAN programmed code for the solution of two- group neutron diffusion equations in xyz geometry. The code was designed to run under control of the IBM 7090 FORTRAN Monitor System on a machine with at least six tape units. The maximum number of mesh points is limited to 12,750. Arbitrary distributions of materials and mesh spacing are permitted. The boundary conditions are either zero flux or zero current at each of the six faces of the reactor, and the code will, if desired, compute the adjoint-flux and associated flux-adjoint-flux region integrals that are necessary for perturbation calculations. Computation time is approximately 0.006 sec per point iteration. Normally, running times are about 2 to 3 hr for a 10,000-point problem. (auth

Phase Coexistence in Driven One Dimensional Transport

We study a one-dimensional totally asymmetric exclusion process with random particle attachments and detachments in the bulk. The resulting dynamics leads to unexpected stationary regimes for large but finite systems. Such regimes are characterized by a phase coexistence of low and high density regions separated by domain walls. We use a mean-field approach to interpret the numerical results obtained by Monte-Carlo simulations and we predict the phase diagram of this non-conserved dynamics in the thermodynamic limit.Comment: 4 pages, 3 figures. Accepted for publication on Phys. Rev. Let

Bone marrow transplantation alters the tremor phenotype in the murine model of globoid-cell leukodystrophy

Tremor is a prominent phenotype of the twitcher mouse, an authentic genetic model of Globoid-Cell Leukodystrophy (GLD, Krabbe’s disease). In the current study, the tremor was quantified using a force-plate actometer designed to accommodate low-weight mice. The actometer records the force oscillations caused by a mouse’s movements, and the rhythmic structure of the force variations can be revealed. Results showed that twitcher mice had significantly increased power across a broad band of higher frequencies compared to wildtype mice. Bone marrow transplantation (BMT), the only available therapy for GLD, worsened the tremor in the twitcher mice and induced a measureable alteration of movement phenotype in the wildtype mice. These data highlight the damaging effects of conditioning radiation and BMT in the neonatal period. The behavioral methodology used herein provides a quantitative approach for assessing the efficacy of potential therapeutic interventions for Krabbe’s disease

PS2 Beam Transfer Systems: Conceptual Design Considerations

The replacement of CERN's existing 26 GeV Proton Synchrotron (PS) machine with a separated function synchrotron PS2 has been identified as an important part of the future upgrade of the CERN accelerator complex [1,2]. The PS2 will require the design of a number of beam transfer systems associated with injection, extraction, beam dumping and transfer. The different requirements are briefly presented. A first iteration of the conceptual design aspects of these systems is presented, based on the initial PS2 parameter set [3] and assuming a simple 90-degree phase advance FODO lattice. The required equipment sub-system performance is derived and discussed, and possible limitations are analysed. The impact on the overall design and parameter set is discussed, together with some recommendations for the direction of the continuing studies

Gene identification for the cblD defect of vitamin B12 metabolism

Background Vitamin B12 (cobalamin) is an essential cofactor in several metabolic pathways. Intracellular conversion of cobalamin to its two coenzymes, adenosylcobalamin in mitochondria and methylcobalamin in the cytoplasm, is necessary for the homeostasis of methylmalonic acid and homocysteine. Nine defects of intracellular cobalamin metabolism have been defined by means of somatic complementation analysis. One of these defects, the cblD defect, can cause isolated methylmalonic aciduria, isolated homocystinuria, or both. Affected persons present with multisystem clinical abnormalities, including developmental, hematologic, neurologic, and metabolic findings. The gene responsible for the cblD defect has not been identified. Methods We studied seven patients with the cblD defect, and skin fibroblasts from each were investigated in cell culture. Microcell-mediated chromosome transfer and refined genetic mapping were used to localize the responsible gene. This gene was transfected into cblD fibroblasts to test for the rescue of adenosylcobalamin and methylcobalamin synthesis. Results The cblD gene was localized to human chromosome 2q23.2, and a candidate gene, designated MMADHC (methylmalonic aciduria, cblD type, and homocystinuria), was identified in this region. Transfection of wild-type MMADHC rescued the cellular phenotype, and the functional importance of mutant alleles was shown by means of transfection with mutant constructs. The predicted MMADHC protein has sequence homology with a bacterial ATP-binding cassette transporter and contains a putative cobalamin binding motif and a putative mitochondrial targeting sequence. Conclusions Mutations in a gene we designated MMADHC are responsible for the cblD defect in vitamin B12 metabolism. Various mutations are associated with each of the three biochemical phenotypes of the disorder