Search

This paper presents a robotic capture concept that was developed as part of the e.deorbit study by ESA. The defective and tumbling satellite ENVISAT was chosen as a potential target to be captured, stabilized, and subsequently de-orbited in a controlled manner. A robotic capture concept was developed that is based on a chaser satellite equipped with a seven degrees-of-freedom dexterous robotic manipulator, holding a dedicated linear two-bracket gripper. The satellite is also equipped with a clamping mechanism for achieving a stiff fixation with the grasped target, following their combined satellite-stack de-tumbling and prior to the execution of the de-orbit maneuver. Driving elements of the robotic design, operations and control are described and analyzed. These include pre and post-capture operations, the task-specific kinematics of the manipulator, the intrinsic mechanical arm flexibility and its effect on the arm's positioning accuracy, visual tracking, as well as the interaction between the manipulator controller and that of the chaser satellite. The kinematics analysis yielded robust reachability of the grasp point. The effects of intrinsic arm flexibility turned out to be noticeable but also effectively scalable through robot joint speed adaption throughout the maneuvers. During most of the critical robot arm operations, the internal robot joint torques are shown to be within the design limits. These limits are only reached for a limiting scenario of tumbling motion of ENVISAT, consisting of an initial pure spin of 5 deg/s about its unstable intermediate axis of inertia. The computer vision performance was found to be satisfactory with respect to positioning accuracy requirements. Further developments are necessary and are being pursued to meet the stringent mission-related robustness requirements. Overall, the analyses conducted in this study showed that the capture and de-orbiting of ENVISAT using the proposed robotic concept is feasible with respect to relevant mission requirements and for most of the operational scenarios considered. Future work aims at developing a combined chaser-robot system controller. This will include a visual servo to minimize the positioning errors during the contact phases of the mission (grasping and clamping). Further validation of the visual tracking in orbital lighting conditions will be pursued., (Copyright © 2018 Jaekel, Lampariello, Rackl, De Stefano, Oumer, Giordano, Porges, Pietras, Brunner, Ratti, Muehlbauer, Thiel, Estable, Biesbroek and Albu-Schaeffer.)

The effect of eliminating D-lactate synthesis in poly(3-hydroxybutyrate) (PHB)-accumulating recombinant Escherichia coli (K24K) was analyzed using glycerol as a substrate. K24KL, an ldhA derivative, produced more biomass and had altered carbon partitioning among the metabolic products, probably due to the increased availability of carbon precursors and reducing power. This resulted in a significant increase of PHB and ethanol synthesis and a decrease in acetate production. Cofactor measurements revealed that cultures of K24K and K24KL had a high intracellular NADPH content and that the NADPH/NADP(+) ratio was higher than the NADH/NAD(+) ratio. The ldhA mutation affected cofactor distribution, resulting in a more reduced intracellular state, mainly due to a further increase in NADPH/NADP(+). In 60-h fed-batch cultures, K24KL reached 41.9 g·liter⁻¹ biomass and accumulated PHB up to 63% ± 1% (wt/wt), with a PHB yield on glycerol of 0.41 ± 0.03 g·g⁻¹, the highest reported using this substrate.

Growth and polymer synthesis were studied in a recombinant E. coli strain carrying phaBAC and phaP of Azotobacter sp. strain FA8 using different carbon sources and oxygen availability conditions. The results obtained with glucose or glycerol were completely different, demonstrating that the metabolic routes leading to the synthesis of the polymer when using glycerol do not respond to environmental conditions such as oxygen availability in the same way as they do when other substrates, such as glucose, are used. When cells were grown in a bioreactor using glucose the amount of polymer accumulated at low aeration was reduced by half when compared to high aeration, while glycerol cultures produced at low aeration almost twice the amount of polymer synthesized at the higher aeration condition. The synthesis of other metabolic products, such as ethanol, lactate, formate and acetate, were also affected by both the carbon source used and aeration conditions. In glucose cultures, lactate and formate production increased in low agitation compared to high agitation, while poly(3-hydroxybutyrate) synthesis decreased. In glycerol cultures, the amount of acids produced also increased when agitation was lowered, but carbon flow was mostly redirected towards ethanol and poly(3-hydroxybutyrate). These results indicated that carbon partitioning differed depending on both carbon source and oxygen availability, and that aeration conditions had different effects on the synthesis of the polymer and other metabolic products when glucose or glycerol were used., (© 2010 Landes Bioscience)

Bioreactor cultures of Escherichia coli recombinants carrying phaBAC and phaP of Azotobacter sp. FA8 grown on glycerol under low-agitation conditions accumulated more poly(3-hydroxybutyrate) (PHB) and ethanol than at high agitation, while in glucose cultures, low agitation led to a decrease in PHB formation. Cells produced smaller amounts of acids from glycerol than from glucose. Glycerol batch cultures stirred at 125 rpm accumulated, in 24 h, 30.1% (wt/wt) PHB with a relative molecular mass of 1.9 MDa, close to that of PHB obtained using glucose.

Exogenous covert attention improves discriminability and accelerates the rate of visual information processing (M. Carrasco & B. McElree, 2001). Here we investigated and compared the effects of both endogenous (sustained) and exogenous (transient) covert attention. Specifically, we directed attention via spatial cues and evaluated the automaticity and flexibility of exogenous and endogenous attention by manipulating cue validity in conjunction with a response-signal speed-accuracy trade-off (SAT) procedure, which provides conjoint measures of discriminability and information accrual. To investigate whether discriminability and rate of information processing differ as a function of cue validity (chance to 100%), we compared how both types of attention affect performance while keeping experimental conditions constant. With endogenous attention, both the observed benefits (valid-cue) and the costs (invalid-cue) increased with cue validity. However, with exogenous attention, the benefits and costs in both discriminability and processing speed were similar across cue validity conditions. These results provide compelling time-course evidence that whereas endogenous attention can be flexibly allocated according to cue validity, exogenous attention is automatic and unaffected by cue validity.

Polyhydroxyalkanoates (PHAs) are accumulated as intracellular granules by many bacteria under unfavorable conditions, enhancing their fitness and stress resistance. Poly(3-hydroxybutyrate) (PHB) is the most widespread and best-known PHA. Apart from the genes that catalyze polymer biosynthesis, natural PHA producers have several genes for proteins involved in granule formation and/or with regulatory functions, such as phasins, that have been shown to affect polymer synthesis. This study evaluates the effect of PhaP, a phasin, on bacterial growth and PHB accumulation from glycerol in bioreactor cultures of recombinant Escherichia coli carrying phaBAC from Azotobacter sp. strain FA8. Cells expressing phaP grew more, and accumulated more PHB, both using glucose and using glycerol as carbon sources. When cultures were grown in a bioreactor using glycerol, PhaP-bearing cells produced more polymer (2.6 times) and more biomass (1.9 times) than did those without the phasin. The effect of this protein on growth promotion and polymer accumulation is expected to be even greater in high-density cultures, such as those used in the industrial production of the polymer. The recombinant strain presented in this work has been successfully used for the production of PHB from glycerol in bioreactor studies, allowing the production of 7.9 g/liter of the polymer in a semisynthetic medium in 48-h batch cultures. The development of bacterial strains that can efficiently use this substrate can help to make the industrial production of PHAs economically feasible.

We investigated whether the effect of covert attention on information accrual varies with eccentricity (4 degrees vs 9 degrees) and the complexity of the visual search task (feature vs conjunction). We used speed-accuracy tradeoff procedures to derive conjoint measures of the speed of information processing and accuracy in each search task. Information processing was slower with more complex conjunction searches than with simpler feature searches, and overall it was faster at peripheral (9 degrees) than parafoveal (4 degrees) locations in both search types. Covert attention increased discriminability and accelerated information accrual at both eccentricities, and the magnitude of this attentional effect was the same for both feature (simple) and conjunction (complex) searches. Interestingly, in contrast to the compensatory effect of covert attention on information processing at iso-eccentric locations (temporal performance fields), covert attention did not eliminate speed differences across eccentricity.

This study is the first to investigate: (a) 'temporal performance fields,' whether the speed of information accrual differs for different locations at a fixed eccentricity, and (b) whether covert attention modulates temporal dynamics differentially at isoeccentric locations. Using the speed accuracy tradeoff (SAT) procedure, we derived conjoint measures of how isoeccentric locations and precueing targets location affect speed and accuracy in a search task. The results demonstrate the existence of temporal performance fields, analogous to spatial performance fields: information accrual was fastest for target on the horizontal meridian, intermediate for targets at the intercardinal locations, slow for targets on the vertical meridian, and slowest for targets at the North (N) location (accrual time pattern: E&WS>intercardinal>E&W). Hence, the compensatory effect of attention eliminated the temporal asymmetries across isoeccentric locations.

The visual system has a duplex design to meet conflicting environmental demands: the fovea has the resolution required to process fine spatial information, but the periphery is more sensitive to temporal properties. To investigate whether the periphery's sensitivity is partly due to the speed with which information is processed, we measured the full timecourse of visual information processing by deriving joint measures of discriminability and speed, and found that speed of information processing varies with eccentricity: processing was faster when same-size stimuli appeared at 9 degrees than 4 degrees eccentricity, and this difference was attenuated when the 9 degrees stimuli were magnified to equate cortical representation size. At the same eccentricity, larger stimuli are processed more slowly. These temporal differences are greater than expected from neurophysiological constraints.

Forty-five patients were evaluated for reconstruction of the mandible. Thirty-four patients had a particulate cancellous bone and marrow (PCM) crib graft placed. Thirty of 34 were successful at the primary operation producing a success rate of 88%. By using secondary procedures all 33 patients repaired to date have been rehabilitated. A dynamic bendable defect bridging plate with cancellous cortical graft (DBDB plate with CCG) was used in 7 patients, 4 of whom had tumor surgery and 3 of whom were operated on after trauma to the anterior mandible. All 7 cases were successfully rehabilitated in achieving a stable, functioning mandibular arch. An osteomyocutaneous flap was planned to reconstruct the anterior mandible in 4 cases; 1 in this group was not reconstructed. The PCM graft has been our first line approach to the mandibular non-union but with experience we are beginning to rely on the DBDB plate with CCG for large bony defects after both trauma and secondarily after tumor surgery. When indicated, the osteomyocutaneous flap has been eminently successful in restoring function and form in the tumor patient.

Tracheal mucociliary clearance studies, mucus collections, and rheologic studies were performed on a weekly basis in 7 adult purebred beagles in an attempt to correlate clearance rate with rheology of mucus. Clearance rates were determined by a percutaneous transtracheal, radioisotope injection technique. Mucus was collected from dogs equipped with a tracheal pouch, and rheologic determinations were performed on a dynamic microrheometer. Individual analysis of data for each dog failed to reveal any significant relationship between clearance rate and any parameter of elasticity or viscosity. However, when data from all 7 dogs were pooled, covering a much wider range of the measured variables, it was seen that as the elastic modulus increased, the rate of clearance decreased. The mucociliary clearance rate was halved by an approximate ten-fold increase in elastic modulus of mucus.

In the past laryngeal pseudosarcomas have been diagnosed as a. carcinosarcomas, b. pleomorphic or spindle cell carcinomas, or c. squamous cell carcinomas with pseudosarcomatous reactive stroma. Arguments have centered around the nature of the sarcomatous stroma. Because of this confusion there is disagreement as to the treatment and prognosis of these tumors. Seven pseudosarcomas were treated between 1969-1979, 4 were pedunculated and 3 exophytic. Treatment consisted of primary CO60 irradiation in 2 patients, surgery in 3 cases and combined therapy in 2 cases with no recurrences. Three of the 7 have died, 1 of a poorly differentiated adenosquamous carcinoma of the right main stem bronchus and the other 2 of natural causes at ages 77 and 85. From a review of the literature as well as our experience, we have reached the following conclusions. 1. Stromal cells are a malignant morphologic variant of the squamous cell and are best termed spindled cells. 2. Neck metastasis at any time is a poor prognostic sign. 3. The pattern of metastasis and survival seems to parallel laryngeal squamous cell carcinoma, and thus treatment should be similar for given stages.

In a review of 350 patients with mandibular fractures between 1976 and 1978, eight cases of chronic mandibular osteomyelitis were found. Treatment in all cases consisted of intravenous antibiotics and debridement. In addition, in some cases a suction-irrigation system was used after debridement. From this study, the following can be stated: (1) Osteomyelitis following mandibular fractures is uncommon. (2) Once chronic osteomyelitis has developed, aggressive antibiotic and surgical treatment is needed. (3) The use of the suction-irrigation system after debridement is an effective adjunctive aid in treating osteomyelitis. Cosmesis is superior to that obtained with older techniques because wounds are closed primarily.

Pharyngocutaneous fistula is one of the major complications following laryngeal surgery. Prior to 1979, patients undergoing laryngectomy at the University of Minnesota were not fed until 9 or 10 days postoperatively if unirradiated and 12 to 14 days if irradiated. Most fistulas were apparent by 14 days postoperatively, but occasionally a patient would develop a fistula as late as a month postoperatively. Starting in 1979, in an attempt to decrease the length of hospitalization as well as prevent fistula formation, routine barium-swallow videoesophagograms were obtained 7 days postoperatively in all laryngectomy patients. If the results were considered normal, the nasogastric tube was removed and oral feedings were started. Of a total of 45 patients undergoing wide-field laryngectomy, there were three clinical fistulas and three radiologic fistulas. Following this protocol, we shortened the average postoperative hospitalization by 2 days without an increase in the rate of fistulization.