| 1. |
- Andersson, Kennet, et al.
(författare)
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Effect of resting pressure on the estimate of cerebrospinal fluid outflow conductance
- 2011
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Ingår i: Fluids and barriers of the CNS. - : Springer Science and Business Media LLC. - 2045-8118. ; 8:1, s. 15-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A lumbar infusion test is commonly used as a predictive test for patients with normal pressure hydrocephalus and for evaluation of cerebrospinal fluid (CSF) shunt function. Different infusion protocols can be used to estimate the outflow conductance (Cout) or its reciprocal the outflow resistance, (Rout) with or without using the baseline resting pressure, Pr. Both from a basic physiological research and a clinical perspective, it is important to understand the limitations of the model on which infusion tests are based. By estimating Cout using two different analyses, with or without Pr, the limitations could be explored. The aim of this study was to compare the Cout estimates, and investigate what effect Pr had on the results. METHODS: Sixty-three patients that underwent a constant pressure infusion protocol as part of their preoperative evaluation for normal pressure hydrocephalus, were included (age 70.3+/-10.8 years (mean +/-SD). The analysis was performed without (Cexcl Pr) and with (Cincl Pr) Pr. The estimates were compared using Bland-Altman plots and paired sample t-tests (p<0.05 considered significant). RESULTS: Mean Cout for the 63 patients was: Cexcl Pr = 7.0+/-4.0 (mean +/-SD) ul/(s kPa) and Cincl Pr = 9.1+/-4.3 ul/(s kPa) and Rout was 19.0+/-9.2 and 17.7+/-11.3 mmHg/ml/min, respectively. There was a positive correlation between methods (r=0.79, n=63, p<0.01). The difference, DeltaCout, -2.1+/-2.7 ul/(s kPa) between methods was significant (p<0.01) and DeltaRout was 1.2 +/- 8.8 mmHg/ml/min). The Bland-Altman plot visualized that the variation around the mean difference was similar all through the range of measured values and there was no correlation between DeltaCout and Cout. CONCLUSIONS: The difference between Cout estimates, obtained from analyses with or without Pr, needs to be taken into consideration when comparing results from studies using different infusion test protocols. The study suggests variation in CSF formation rate, variation in venous pressure or a pressure dependent Cout as possible causes for the deviation from the CSF absorption model seen in some patients.
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| 2. |
- Fällmar, Helena, 1980-, et al.
(författare)
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Neuropeptide Y/peptide YY receptor Y2 duplicate in zebrafish with unique introns displays distinct peptide binding properties
- 2011
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Ingår i: Comparative Biochemistry and Physiology - Part B. - : Elsevier BV. - 1096-4959 .- 1879-1107. ; 160:4, s. 166-173
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The neuropeptide Y-family peptides and receptors are involved in a broad range of functions including appetite regulation. Both the peptide genes and the receptor genes are known to have duplicated in early vertebrate evolution. The ancestral jawed vertebrate had 7 NPY receptors but the number varies between 4 and 7 in extant vertebrates. Herein we describe the identification of an additional NPY receptor in two fish species, zebrafish and medaka. They cluster together with the Y2 receptors in phylogenetic analyses and seem to be orthologous to each other that is why we have named them Y2-2. Their genes differ from Y2 in having introns in the coding region. Binding studies with zebrafish Y2-2 receptors show that the three endogenous peptides NPY, PYYa and PYYb have similar affinities, 0.15-0.66nM. This is in contrast to the Y2 receptor where they differed considerably from one another. N-terminally truncated NPY binds poorly and the Y2 antagonist BIIE0246 binds well to Y2-2, results that are reversed in comparison to Y2. Zebrafish Y2-2 mRNA was detected by PCR in the intestine and the eye, but not in the brain. In conclusion, we have found a novel Y2-like NPY/PYY receptor that probably arose in early teleost fish evolution.
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| 3. |
- Magnusson, Patrik, 1984, et al.
(författare)
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Planning transport sequences for flexible manufacturing systems
- 2011
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902661937 ; 18:PART 1, s. 9494-9499
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Konferensbidrag (refereegranskat)abstract
- When designing a manufacturing system it is important to plan what the systemshould do. One important activity in most manufacturing systems is to transport products orresources between different positions. In a flexible manufacturing system it can be challengingto design and plan these transport operations due to their complex logical behavior. This paperpresents a method that identifies, creates and visualizes these transport operations based oninputs from a standard virtual manufacturing tool and a high level product operation recipe.The planning of the created transport operations is transformed into a problem of finding anon-blocking solution for a discrete model of the product refinement.
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| 4. |
- Malm, Jan, et al.
(författare)
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Implementation of a new CSF dynamic device: a multicenter feasibility study in 562 patients
- 2012
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Ingår i: Acta Neurologica Scandinavica. - : John Wiley and Sons. - 0001-6314 .- 1600-0404. ; 125:3, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- Objectives - The cerebrospinal fluid (CSF) infusion test is frequently used when selecting hydrocephalus patients for shunt surgery. Very little has been reported regarding adverse events. We present a prospective feasibility study. Methods -Standardized devices for measuring CSF dynamics were built and 562 patients investigated: Needles were placed by lumbar puncture (LP). An automatic CSF infusion protocol was performed. Course of events during the investigation as well as adverse events were registered. Results Preoperative evaluation of normal-pressure hydrocephalus was the most common indication (63%), followed by evaluation of shunt function (23%) and intracranial pressure recordings (14%). The LP was successfully performed in all but nine cases with 24 patients (4.3%) reporting major discomfort. Ringer infusion was performed in 474 investigations, and a valid measurement of the outflow resistance was received in 439 (93%). During the infusion phase, 17 (4%) patients reported severe headache. Infusion volume was significantly higher in patients having subjective symptoms during the infusion phase compared with those without adverse events. During 269 preoperative CSF tap tests, six (2%) patients had severe headache. Postinvestigational headache was reported by 83 (15%) patients at the 24-h follow-up. No serious adverse events were observed. Conclusion Infusion testing was safe and without serious adverse events with a high rate of successful procedures. The investigation was associated with expected mild to moderate discomfort.
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| 5. |
- Qvarlander, Sara, 1982-, et al.
(författare)
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Postural effects on intracranial pressure : modeling and clinical evaluation
- 2013
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 115:10, s. 1474-1480
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Tidskriftsartikel (refereegranskat)abstract
- Introduction The physiological effect of posture on intracranial pressure (ICP) is not well described. This study defined and evaluated three mathematical models describing the postural effects on ICP, designed to predict ICP at different head-up tilt-angles from the supine ICP value.Methods Model I was based on a hydrostatic indifference point for the cerebrospinal fluid (CSF) system, i.e. the existence of a point in the system where pressure is independent of body position. Models II and III were based on Davson's equation for CSF absorption, which relates ICP to venous pressure, and postulated that gravitational effects within the venous system are transferred to the CSF system. Model II assumed a fully communicating venous system and model III that collapse of the jugular veins at higher tilt-angles creates two separate hydrostatic compartments. Evaluation of the models was based on ICP measurements at seven tilt-angles (0-71°)in 27 normal pressure hydrocephalus patients.Results ICP decreased with tilt-angle (ANOVA, p<0.01). The reduction was well predicted by model III (ANOVA lack-of-fit: p=0.65), which showed excellent fit against measured ICP. Neither model I nor II adequately described the reduction in ICP (ANOVA lack-of-fit: p<0.01).Conclusion Postural changes in ICP could not be predicted based on the currently accepted theory of a hydrostatic indifference point for the CSF system, but a new model combining Davson's equation for CSF absorption and hydrostatic gradients in a collapsible venous system performed well and can be useful in future research on gravity and CSF physiology.
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| 6. |
- Sundström, Nina, et al.
(författare)
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Comparison between 3 infusion methods to measure cerebrospinal fluid outflow conductance
- 2010
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Ingår i: Journal of Neurosurgery. - : American Association of Neurological Surgeons. - 0022-3085 .- 1933-0693. ; 113:6, s. 1294-1303
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Tidskriftsartikel (refereegranskat)abstract
- Object There are several infusion methods available to estimate the outflow conductance (Cout) or outflow resistance (Rout = 1/Cout) of the CSF system. It has been stated that for unknown reasons, the bolus infusion method estimates a higher Cout than steady-state infusion methods. The aim of this study was to compare different infusion methods for estimation of Cout.Methods The following 3 different infusion methods were used: the bolus infusion method (Cout bol); the constant flow infusion method, both static (Cout stat) and dynamic (Cout dyn) analyses; and the constant pressure infusion method (Cout cpi). Repeated investigations were performed on an experimental model with well-known characteristics, with and without physiological pressure variations (B-waves, breathing, and so on). All 3 methods were also performed in a randomized order during the same investigation in 20 patients with probable or possible idiopathic normal-pressure hydrocephalus; 6 of these patients had a shunt and 14 did not.Results Without the presence of physiological pressure variations, the concordance in the experimental model was good between all methods. When they were added, the repeatability was better for the steady-state methods and a significantly higher Cout was found with the bolus method in the region of clinically relevant Cout (p < 0.05). The visual fit for the bolus infusion was dependent on subjective assessment by the operator. This experimental finding was confirmed by the clinical results, where significant differences were found in the investigations in patients without shunts between Cout of the visual bolus method and Cout stat, Cout dyn, and Cout cpi (4.58, 4.18, and 6.12 μl/[second × kPa], respectively).Conclusions This study emphasized the necessity for standardization of Cout measurements. An experienced operator could partly compensate for difficulties in correctly estimating the pressure parameters for the bolus infusion method, but for the general user this study suggests a steady-state method for estimating Cout.
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| 7. |
- Sundström, Nina, 1980, et al.
(författare)
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Event- and time-based design of operation sequences with uncertainties in execution times
- 2013
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Ingår i: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA. - 1946-0759 .- 1946-0740. - 9781479908646 ; 18
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Konferensbidrag (refereegranskat)abstract
- In this paper, we introduce a complete framework for integrating the design of the manufacturing process and control system. We show how operation sequences can be designed in a modeling tool, Sequence Planner (SP), and how relations between operations may be expressed using logical conditions. An approach to convert the SP model into a constraint programming model for optimization is presented. The time-based solution is transformed to an event-based description. Due to uncertainties in execution times, some logical restrictions based on the optimal schedule are relaxed to avoid unnecessary delays. The control logics to achieve the desired operation sequences are added to the SP model. Hence, the process designer can revise the sequences if necessary, and the control designer retrieves a logical description of the optimized process that can be automatically converted to control code.
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| 8. |
- Sundström, Nina, 1980, et al.
(författare)
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Optimization of operation sequences using constraint programming
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902661982 ; 14:1, s. 1580-1585
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Konferensbidrag (refereegranskat)abstract
- In this paper, we connect the dots: design and optimization of production systems. A possible link between these two areas, is a previously presented modeling language, Sequence Planner Language (SPL). It has been demonstrated how relevant information can be extracted from production systems modeling applications, and converted into SPL. We show how the SPL model can be converted into a constraint programming model for optimization. Also, a useful abstraction concept, work-equivalence, is introduced to enable alternative model formulations. A case study consisting of an aero engine structure assembly plant is presented, in which the efficiency of the resulting constraint programs is investigated. The formulations enabled by abstraction are shown to perform better than the standard formulation.
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| 9. |
- Wigström, Oskar, 1986, et al.
(författare)
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Optimization of Hybrid Systems with Known Paths
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. ; 45:9, s. 39-45
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Konferensbidrag (refereegranskat)abstract
- In this paper we study a subset of hybrid systems and present a generalized method for their optimization. We outline Hybrid Cost Automata (HCA), an extension to Hybrid Automata, where discrete and continuous cost expressions are added. The class of hybrid systems with known spatial paths is dened in the context of HCA. This type of system is common in industry where for example AGVs transport goods from one location to another, or manipulators move between joint coordinates. The optimization is performed using Dynamic Programming as a preprocessing step, whereafter Mixed Integer Nonlinear Programming is used for scheduling. A case study of a four robot cell is presented with energy consumption used as a minimization criterion.
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