| 1. |
- Ben-Shabat, Ilan, et al.
(författare)
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Isolated hepatic perfusion as a treatment for liver metastases of uveal melanoma.
- 2015
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Ingår i: Journal of visualized experiments : JoVE. - : MyJove Corporation. - 1940-087X. ; :95
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Tidskriftsartikel (refereegranskat)abstract
- Isolated hepatic perfusion (IHP) is a procedure where the liver is surgically isolated and perfused with a high concentration of the chemotherapeutic agent melphalan. Briefly, the procedure starts with the setup of a percutaneous veno-venous bypass from the femoral vein to the external jugular vein. Via a laparotomy, catheters are then inserted into the proper hepatic artery and the caval vein. The portal vein and the caval vein, both supra- and infrahepatically, are then clamped. The arterial and venous catheters are connected to a heart lung machine and the liver is perfused with melphalan (1 mg/kg body weight) for 60 min. This way it is possible to locally perfuse the liver with a high dose of a chemotherapeutic agent, without leakage to the systemic circulation. In previous studies including patients with isolated liver metastases of uveal melanoma, an overall response rate of 33-100% and a median survival between 9 and 13 months, have been reported. The aim of this protocol is to give a clear description of how to perform the procedure and to discuss IHP as a treatment option for liver metastases of uveal melanoma.
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| 2. |
- Broman, Marcus, et al.
(författare)
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Simplified citrate anticoagulation for CRRT without calcium replacement.
- 2015
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Ingår i: ASAIO Journal. - 1538-943X. ; 61:4, s. 437-442
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Tidskriftsartikel (refereegranskat)abstract
- Since 2012 citrate anticoagulation is the recommended anticoagulation strategy for CRRT. The main drawback using citrate compared with heparin as anticoagulant is the need for calcium replacement and the rigorous control of calcium levels. This study investigated the possibility to achieve anticoagulation while eliminating the need for calcium replacement. This was successfully achieved by including citrate and calcium in all CRRT solutions. Thereby the total calcium concentration was kept constant throughout the extracorporeal circuit while the ionized calcium was kept at levels low enough to avoid clotting. Being a completely new concept, only five patients with acute renal failure were included in a short, prospective, intensely supervised non-randomized pilot study.Systemic electrolyte levels and acid-base parameters were stable and remained within physiological levels. Ionized calcium levels declined slightly initially, but stabilized at 1.1 mmol/l. Plasma citrate concentrations stabilized at around 0.6 mmol/l. All post-filter ionized calcium levels were <0.5 mmol/l, i.e. an anticoagulation effect was reached. All filter pressures were normal indicating no clotting problems, and no visible clotting was observed. No calcium replacement was needed.This pilot study suggests that it is possible to perform regional citrate anticoagulation without the need for separate calcium infusion during CRRT.
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| 3. |
- Duan, R D, et al.
(författare)
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Distribution of alkaline sphingomyelinase activity in human beings and animals. Tissue and species differences
- 1996
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Ingår i: Digestive Diseases and Sciences. - 1573-2568. ; 41:9, s. 1801-1806
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Tidskriftsartikel (refereegranskat)abstract
- The alkaline sphingomyelinase (SMase) was first found in rat intestinal brush border. The important roles of this enzyme in digestion of sphingomyelin and in mucosal cell proliferation have been suggested. In the present work, the distribution of the alkaline SMase in the tissues of human beings and animals have been studied. By assaying the enzyme activity in human biopsy samples, we found that the alkaline SMase activity was absent in the stomach, increased in the duodenum, present at high levels in the small intestine, and slightly declined in the colon and rectum. High activities were found similarly in the intestinal contents of the healthy adults and infants. The activities were also found in the intestinal mucosa of rats, normal and germ-free mice, and hamsters with the same distribution pattern as in humans, but not in the intestinal mucosa of guinea pigs. Apart from the intestinal tract, a SMase activity preferring alkaline pH was identified in human and guinea pig bile, but not in the bile of rat, pig, sheep, and cow. No activity was found in either pancreatic tissue or pancreatic juice in all species tested, and none was detected in human urine and milk. In conclusion, alkaline SMase exists predominantly in the digestive system with considerable tissue and species differences.
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| 4. |
- Fan, Bo-Guang, et al.
(författare)
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Total parenteral nutrition influences both endocrine and exocrine function of rat pancreas
- 1997
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Ingår i: Pancreas. - 0885-3177. ; 15:2, s. 147-153
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine the effect of total parenteral nutrition (TPN) on the endocrine and exocine function of the pancreas. Endocrine function was investigated using an intravenous glucose tolerance test (IGTT) in rats with TPN for 7 or 14 days. Exocrine function was evaluated by measuring amylase secretion from isolated acini as well as pancreatic weight, water content, protein, and enzymes after 7 days of TPN. When the TPN rats were compared with the controls, the glucose tolerance curve after an IGTT was unchanged, the basal plasma insulin levels were slightly lower and the insulin secretory response to intravenous glucose was markedly impaired. No differences could be seen between the insulin response after 7 days and that after 14 days of TPN. The weight of pancreas, the total content and concentration of pancreatic protein, and the total amylase content of the pancreas were lower, whereas the total content of both chymotrypsin and trypsin was higher. The concentration of DNA remained intact, whereas the total DNA content decreased. The levels of lipolytic enzymes, except for carboxylesterlipase, were unaffected. After TPN treatment, the insulin secretory response to glucose is impaired, the exocrine pancreas is hypoplastic and the storage pattern of pancreatic exocrine enzymes is altered.
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| 5. |
- Hillerström, Gunnar, et al.
(författare)
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Adaptive rejection of periodic disturbances with unknown period
- 1996
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Ingår i: Journal of Dynamic Systems Measurement, and Control. - : ASME International. - 0022-0434 .- 1528-9028. ; 118:3, s. 606-610
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Tidskriftsartikel (refereegranskat)abstract
- A disturbance cancellation extension by means of Youla parametrization to a stabilizing nominal controller is investigated. In the case of known disturbance model, disturbance frequencies or period time, it may be implemented directly as an add-on device to the existing control system. The nominal control system may be designed without consideration of the deterministic disturbances. This way it may suffice with a PID controller. It may also be a more complex one e.g., designed to obtain certain robustness properties. For known relation between the disturbance frequencies (one or more periodic signals) but unknown fundamental frequency, a frequency shaped disturbance model estimarion scheme is utilized. This makes it possible to e.g., adapt the disturbance model to minimize the error directly with respect to the output. For periodic disturbances the scheme implements a self-tuning discrete time repetitive controller. To illustrate the feasibility of the approach taken it is used for rejecting a periodic disturbance acting on a nonminimum-phase plant.
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| 6. |
- Hillerström, Gunnar, et al.
(författare)
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Application of repetitive control to a peristaltic pump
- 1993
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Ingår i: Proceedings. - : IEEE Communications Society. - 0780308611 ; , s. 136-140
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Konferensbidrag (refereegranskat)abstract
- In many machinery there are rotating axis, which sometimes give problems with mechanically coupled disturbances from e.g. imperfect roundness or loads. These disturbance can be modeled as a nonlinear feedback, and treated under the framework of repetitive control.
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| 7. |
- Hillerström, Gunnar, et al.
(författare)
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Application of repetitive control to a peristaltic pump
- 1994
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Ingår i: Journal of Dynamic Systems Measurement, and Control. - : ASME International. - 0022-0434 .- 1528-9028. ; 116:4, s. 786-789
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to study angular velocity control of a rotating axis, a peristaltic pump where the disturbance is associated with certain angular positions. The use of constant sampling rate then implies varying disturbance period. A discrete repetitive control scheme based on a reduced order disturbance model tuned to the setpoint of the angular velocity is shown to reject the modeled disturbance with asymptotically zero error. With axis angle synchronization of sampling, the plant model is time-varying but it gives a static discrete disturbance model independent of the angular velocity. If the deviation from the nominal working point is not too large this is to prefer while it gives faster convergence
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| 8. |
- Hillerström, Gunnar, et al.
(författare)
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Rejection of periodic disturbances with unknown period : a frequency domain approach
- 1994
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Ingår i: Proceedings of the 1994 American Control Conference. - Piscataway, NJ : IEEE Communications Society. - 0780317831 ; , s. 1626-1631
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Konferensbidrag (refereegranskat)abstract
- A self-tuning discrete time repetitive controller comprising a gradient descent disturbance model estimation and a pseudo feedforward controller is investigated. To illustrate the feasibility of the approach considered an example is given for rejecting a periodic disturbance acting on a nonminimum-phase plant.
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| 9. |
- Hillerström, Gunnar, et al.
(författare)
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Repetitive control using low order models
- 1994
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Ingår i: Proceedings of 1994 American Control Conference. - Piscataway, NJ : IEEE Communications Society. - 0780317831 ; , s. 1873-1878
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Konferensbidrag (refereegranskat)abstract
- In repetitive control based on the internal model principle of Francis and Wonham (1976) much interest has been focused around the model comprising a time delay with a memoryless positive feedback around it. A definite merit of this model is that, when used in the closed loop, it will generate an arbitrary periodic signal. In discrete-time the model order increases proportionally to the rise in sampling rate, giving a high order model. The input (disturbance or reference) signal may however be concentrated to some frequencies rather than the whole band up to the Nyquist frequency. Then the model is too large in the sense that it models frequencies that are not present in the input. The inactive part of the model can produce oscillations in the closed loop. Oscillations can be reduced by introducing a lowpass filter (or Q-filter) in the feedback path of the model, but thereby the asymptotic zero error property is lost. A lower order model is shown to overcome this problem and feasibility illustrated by a simulation example.
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| 10. |
- Hillerström, Gunnar, et al.
(författare)
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Robustness properties of repetitive controllers
- 1996
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Ingår i: International Journal of Control. - : Informa UK Limited. - 0020-7179 .- 1366-5820. ; 65:6, s. 939-961
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Tidskriftsartikel (refereegranskat)abstract
- Stability robustness properties of sampled data repetitive control systems are examined. Due to the infinite loop gain at periodic frequencies originating from the included internal model (Internal Model Principle), repetitive systems are, if properly designed, not very sensitive towards possibly time-varying gains. Uncertainty in plant delay is, however, a problem. Controller action timing becomes more or less out of order and may result in severe performance degradation, depending on model type and the number of frequencies included in the design. With a Linear Time-Invariant (LTI) controller comprising the commonly used time delay internal model, the closed loop system is stable for nominal time delay plus/minus at most one sampling interval. A controller based on a reduced order model, perhaps not modelling all harmonics, is utilized to enhance robustness properties. Simulation runs with different controllers show how different models work in the closed loop, and also that synchronization in time is of utmost importance in order to utilize the delay internal model.Stability robustness properties of sampled data repetitive control systems are examined. Due to the infinite loop gain at periodic frequencies originating from the included internal model (Internal Model Principle), repetitive systems are, if properly designed, not very sensitive towards possibly time-varying gains. Uncertainty in plant delay is, however, a problem. Controller action timing becomes more or less out of order and may result in severe performance degradation, depending on model type and the number of frequencies included in the design. With a Linear Time-Invariant (LTI) controller comprising the commonly used time delay internal model, the closed loop system is stable for nominal time delay plus/minus at most one sampling interval. A controller based on a reduced order model, perhaps not modelling all harmonics, is utilized to enhance robustness properties. Simulation runs with different controllers show how different models work in the closed loop, and also that synchronization in time is of utmost importance in order to utilize the delay internal model.
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