325,552 research outputs found
Multi-objective optimisation on motorized momentum exchange tether for payload orbital transfer
No full textThe symmetrical motorised momentum exchange tether, is intended to be excited by a continuous torque, so that, it can be applied as an orbital transfer system. The motor drive accelerates the tether, and increases the relative velocity of payloads fitted to each end. In order to access better tether performance, a higher efficiency index needs to be achieved. Meanwhile, the stress in each tether sub-span should stay within the stress limitations. The multi-objective optimisation methods of Genetic Algorithms can be applied for tether performance enhancement. The tether's efficiency index and stress are used as multi-objectives, and the analysis of the resulting Pareto front suggests a set of solutions for the parameters of the motorised momentum exchange tether when used for payload transfer, in order to achieve relative high transfer performance, and safe tether strength
Hybrid fuzzy and sliding-mode control for motorised tether spin-up when coupled with axial vibration
No full textA hybrid fuzzy sliding mode controller is applied to the control of motorised tether spin-up coupled with an axial oscillation phenomenon. A six degree of freedom dynamic model of a motorised momentum exchange tether is used as a basis for interplanetary payload exchange. The tether comprises a symmetrical double payload configuration, with an outrigger counter inertia and massive central facility. It is shown that including axial elasticity permits an enhanced level of performance prediction accuracy and a useful departure from the usual rigid body representations, particularly for accurate payload positioning at strategic points. A special simulation program has been devised in MATLAB and MATHEMATICA for a given initial condition data case
Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere
No full textThe dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy
Expression of <i>OSH</i>, tether, and high-copy suppressors genes in Δ-s-tether, <i>osh4-1</i><sup>ts</sup> <i>oshΔ</i>, <i>and osh4-1</i><sup>ts</sup> Δ-s-tether cells.
No full text(A) Transcriptional expression of OSH1-OSH7 in Δ-s-tether (CBY5838) cells relative to WT (SEY6210) cells cultured with or without 75 μM inositol. (B) Transcriptional expression of genes encoding primary tether proteins in osh4-1ts oshΔ (CBY926) cells relative to WT cells cultured with or without inositol. (C) DGK1 expression in osh4-1ts oshΔ, Δ-s-tether, and osh4-1ts Δ-s-tether (CBY6031) cells relative to WT. (D) Transcriptional expression of ER-PM tether genes in osh4-1 (CBY7177) and osh4-1ts oshΔ cells relative to WT. (TIFF)</p
Slow growth of Δ-s-tether cells is rescued by expression of an artificial ER-PM tether or choline.
No full textA. The “ER-PM staple" has a modular architecture consisting of an N-terminal GFP, an ER anchor comprising two transmembrane domains and a lumenal loop from herpes virus (MVH68) mK3 E3 ubiquitin ligase, two helices from mitofusin 2 that are predicted to adopt an antiparallel arrangement about 9 nm long, and the polybasic domain from RitC that targets the PM. B. Tenfold serial dilutions of WT (SEY6210) and Δ-s-tether (CBY5838) cells, transformed with either the vector control (YCplac111) or a plasmid expressing the artificial staple (pCB1185), spotted on solid growth medium, and incubated for 2 d at 30 °C. C. DIC images of WT and Δ-s-tether cells and the corresponding spinning disc confocal fluorescence microscopy images showing the colocalization of RFP-ER (pCB1024) and the GFP-marked artificial staple (pCB1185) at three different optical focal planes. Scale bar = 5 μm. D. Quantification of the staple distribution within mother and buds and at cER versus internal cytoplasmic ER. E. Choline-dependent growth of Δ-s-tether cells. WT, Δtether (ANDY198), and Δ-s-tether (CBY5838) cells were streaked onto solid growth medium supplemented with 1 mM choline chloride, as indicated, and incubated for 3 d at 30 °C. F. Quantification of ER-RFP localization in WT and Δ-s-tether cells, with and without 1 mM choline, represented as a ratio of the length of PM-associated ER per circumference of PM in each cell (n > 50 cells; error bars represent SEM). G. Lipid composition of WT, Δtether, and Δ-s-tether cells represented as a normalized mole percentage relative to WT (set to 1.0). The data represent the mean ± SEM derived from the analysis of five independent samples. Numerical data presented in this figure may be found in S1 Data. Δ-s-tether, Δ-super-tether; cER, cortical ER; DAG, diacylglycerol; DIC, differential interference contrast; ER, endoplasmic reticulum; GFP, green fluorescent protein; IPC, inositol-phosphoceramide; MIPC, mannosylinositol phosphoceramide; mmPE, dimethyl PE; mPE, monomethyl PE; PA, phosphatidic acid; PC, phosphatidylcholine; PCe, ether phosphatidylcholine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; PI, phosphatidylinositol; PM, plasma membrane; PS, phosphatidylserine; RFP, red fluorescent protein, RitC; C-terminal polybasic region from mammalian Rit1; WT, wild type.</p
KEGG pathway and heatmap analysis of <i>osh4-1</i><sup>ts</sup> Δ-s-tether, Δ-s-tether, and <i>osh4-1</i><sup><i>ts</i></sup> <i>osh</i>Δ genomic expression.
No full text(A) Gene expression relative to WT (SEY6210) in osh4-1ts Δ-s-tether (CBY6031), Δ-s-tether (CBY5838), and osh4-1ts oshΔ (CBY926) cells listed by KEGG category. (B) Relative to WT, heatmap analyses of transcriptional responses in osh4-1ts Δ-s-tether, Δ-s-tether, and osh4-1ts oshΔ cells affecting inositol metabolism and regulation, lipid metabolism, and ERAD gene expression. Blue bars indicate transcriptional induction and red indicates repression. (TIFF)</p
<i>OSH2</i> deletion in Δ-s-tether cells does not impact growth.
No full textWT (SEY6210), osh4Δ Δ-s-tether (CBY5988) and osh2Δ Δ-s-tether (CBY6734) cells that contain SCS2 on a URA3-marked plasmid (pSCS2) were streaked onto solid growth medium. Cells were cultured for 4 days at 30°C on growth medium (containing 5’-FOA) to select against the SCS2-containing plasmid (-SCS2). As compared to growth on standard synthetic medium (+SCS2), osh4Δ Δ-s-tether cells do not growth in the absence of SCS2, whereas growth of osh2Δ Δ-s-tether cells is not dependent on SCS2. (TIF)</p
Correlative analysis of <i>osh4-1</i><sup><i>ts</i></sup> Δ-s-tether, Δ-s-tether, and <i>osh4-1</i><sup><i>ts</i></sup> <i>osh</i>Δ transcriptomic profiles.
No full textCorrelation matrix of relative transcript abundance in osh4-1ts Δ-s-tether (CBY6031), Δ-s-tether (CBY5898), and osh4-1ts oshΔ (CBY926) cells relative to WT (SEY6210) grown in synthetic minimal medium at 30°C; osh4-1ts Δ-s-tether and osh4-1ts oshΔ cells were then incubated at 37°C for 1 h, as was their comparative WT control. Pearson correlations of corresponding genotypes as shown. (TIF)</p
Transcriptomic profiles of <i>osh4-1</i><sup><i>ts</i></sup> Δ-s-tether, Δ-s-tether and <i>osh4-1</i><sup><i>ts</i></sup> <i>osh</i>Δ cells.
No full textVolcano plots showing relative transcript abundance in (A) osh4-1ts Δ-s-tether (CBY6031), (B) Δ-s-tether (CBY5898) and (C) osh4-1ts oshΔ (CBY926) cells grown in synthetic minimal media at 37°C. Plots show log2-fold expression change relative to WT (SEY6210) versus the negative log10-P value (y-axis). Transcript changes log2 ≥ or ≤ 1 are shown in black whereas representative stress pathway genes are blue and red, corresponding to induction or repression, respectively. (D) Venn Diagram showing overlapping subsets of upregulated (blue) or downregulated genes (red) in osh4-1ts Δ-s-tether, Δ-s-tether and osh4-1ts oshΔ cells.</p
Alterations in ergosterol pools and dynamics at the PM in Δ-s-tether cells.
No full textA. Sensitivity of Δ-s-tether cells to nystatin. Tenfold serial dilutions of WT (SEY6210), osh4Δ (HAB821), Δtether (ANDY198), and Δ-s-tether (CBY5838) cultures spotted onto solid rich medium containing no nystatin, 1.25 μM (+) nystatin, or 2.5 μM (++) nystatin and incubated for 3 d at 30 °C. B. Tenfold serial dilutions of WT, Δtether, and Δ-s-tether, lem3Δ (CBY5194) cultures were spotted onto solid rich media containing no drug, 5 μM duramycin, or 60 μM edelfosine and incubated for 2 d at 25 °C and 30 °C. The lem3Δ strain is known to be duramycin-sensitive and was used as a positive control. C. Tenfold serial dilutions of WT, Δtether, Δ-s-tether, and osh3Δ (JRY6202) cultures were spotted onto solid rich media containing no drug or 0.5 μg/mL myriocin and incubated for 2 d at 30 °C. The osh3Δ strain is known to be myriocin resistant and was used as a positive control. D. Assay to measure the proportion of cellular ergosterol that is extracted by MβCD. The PM of a yeast cell is shown, with outer (green) and inner (blue) leaflets delineated. Incubation of cells with MβCD on ice results in extraction of ergosterol from the outer leaflet. The sample is centrifuged to recover MβCD-ergosterol complexes in the supernatant. Ergosterol is extracted from the cell pellet and supernatant with hexane/isopropanol and quantified by HPLC (UV detection). E. The MβCD-accessible pool of ergosterol (quantified as in panel D) is about 20-fold greater in Δ-s-tether cells versus WT cells, and partially restored to WT levels in cells expressing the “ER-PM staple.” The statistical significance of the difference between the measurement of WT cells and each of the different Δ-s-tether samples is p p = 0.0205 (*) and 0.436 (ns). F. Assay to measure transport of newly synthesized ergosterol from the ER to the MβCD-accessible pool. Cells are pulse-labeled with [3H]methyl-methionine to generate [3H]ergosterol in the ER, and chased as described in Fig 3. After a 30 min chase period, energy poisons are added and cells are placed on ice and incubated with MβCD. The ratio of the specific radioactivity of ergosterol in MβCD-ergosterol complexes versus that of the cell homogenate (RSR) provides a measure of transport. G. Transport of newly synthesized ergosterol from the ER to the MβCD-accessible pool. The bar chart shows RSR values for the different samples. The dotted line indicates the average RSR (about 0.82, averaged over both WT and Δ-s-tether samples) after 30 min of chase for the PM fraction, as described in Fig 3. The statistical significance was determined by one-way ANOVA (***p = 0.0003, **p = 0.0027, *p = 0.043). Numerical data presented in this figure may be found in S1 Data. Δ-s-tether, Δ-super-tether; ER, endoplasmic reticulum; HPLC, high-performance liquid chromatography; MβCD, methyl-β-cyclodextrin; ns, not significant; PM, plasma membrane; RSR, relative specific radioactivity; UV, ultraviolet; WT, wild type.</p
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